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Ionizing Radiation - Science topic

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I've read many posts and articles touting the use of externally applied low dose radiation to the lungs to address the inflammation brought on by COVID.
Since, as pointed out in our paper on the possibility of a direct anti-viral impact from xenon-133, nuclear medicine lung ventilation has the unique ability to bring ionizing radiation to the entire respiratory system, shouldn't it be explored as a means to provide a more targeted low dose therapy than available from an external beam approach?
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You raise a very interesting idea. I have heard that Xe-133 is much more common in USA and less in some places. For example, for V/Qs in Europe, there are a lot of places and practices that use Technegas. Does your suggestion also apply to Technegas?
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I'm trying to pass through characterization into normalization for a product which I found on literatture in an excel sheet.
The method I'm using is IMPACT 2002+.
I considered putting my impact categories as follows:
  • Human health: human toxicity + respiratory effects + ionizing radiation + ozone layer depletion + photochemical oxidation
  • Ecosystem quality: Aquatic ecotoxicity + terrestrial ecotoxicity + Terrestrial Acid/nutria + land occupation + aquatic acidification + aquatic eutrophication
  • Climate change: global warming
  • Resources : Nonrenewable resources + mineral resources
However, this calculation is incorrect according to the prior example, which was created entirely in SimaPro. I believe there are several factors that are missing.
Anyone could help me ?
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maybe before checking 2002+ which is EU focused you could take a look at the new method they developed IMPACT world https://www.impactworldplus.org/en/methodology.php
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the use of CT scan in addition to abdominal ultrasound to diagnose and to conform diagnosis of acute appendicitis has the hazard of exposure to ionizing radiation, so can we depend only on ultrasound with clinical correlation to make and conform the diagnosis ?
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Dear Dalya Al-Falaki, we use ultrasonography methods visualizations to conform appendicitis, without MR and KT investigations. We made abdomen ultrasound to all patients with symptoms acute abdomen. If we don't see appendix , we send patients to surgical department and watching him after 6-12 hours
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Hello every one
my question is about in vitro exposure of blood samples (blast cells) with ionization radiation to repair DNA damage.
The best
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In some research show about this study that the peak value of DNA effects in human
leukocytes appeared 15 to 30 min after tourniquet release. Animal works
revealed showed that postischemic effects on DNA peaked
at 1 to 6 h after tourniquet release and declined gradually
afterward to the baseline level after 4 to 24 h.
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Hello all,
What is the best housekeeping gene to use on real-time PCR using cells cultured and subjected to different doses of ionizing radiation?
Thank you.
Elisa
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The selection of housekeeipng gene depends on your gene of interest, if it is organelle specific or cytosolic or membrane proetein or nuclear protein. For the cellular or cytosolic protein, 16S rRNA or GAPDH or tubulin or beta-actin can be suitable option; for nuclear protein, you can use TBP or Histone (H2B or H3)or laminin B1; depends on the type of your experimental gene of interest. Find out the attachments.
Best regards.
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I am ready to submit the thesis entitled "Study on the effect of MMP-2 gene silencing in the protection of human normal dermal fibroblasts and sensitization of MCF-7 human breast cancer cells from Ionizing Radiation"
Can anyone suggest foreign adjudicators for evaluation of Ph.D. thesis relevant to this area of research
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You must have done extensive review of literature in your thesis and made intellectual/scientific connections of your work. Best will be to find few relevant papers from your review and figure out who are leaders in that area. That will be right thing to do. If your thesis end up in the hand of someone slightly irrelevant person, he/she may blow it up. And your PhD may be in jeopardy.
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All organs are not equally damaged by same amount of radiation dosage. But, on which basis equivalency is measured? (i..e 1 gray in this organ equals 10 sievert) Is it arbitrarily qualitative or quantitative as well? Then what is the quantity? ( concentration of reactive oxygen species, DNA mutation frequency, Radiative cellular apoptosis..., percent Coagulation of biomolecules). But all humans are not equally affected by same amount of radiation energy applied on same organ. Then, does the equivalency chart vary from person-to-person, species-to-species, or year to year ?(i.e. refining of values with increasing precision) I f so, thaen how the equivalency are standardized?
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For derivation of dose limits, radiation weighting factors, tissue weighting factors etc, you may be interested in
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The worldwide average natural dose to humans is about 2.4 mSv per year. Some areas with sizable populations have much higher than average background radiation levels. The highest are found primarily in (Guarapari, Brazil; Kerala, India; Ramsar, Iran; Yangjiang, China) and are due to high concentrations of radioactive minerals in the soil. What technique should be used to determine the possible long term health effects for the people living in these high natural background area ?
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The impact of low dose radiation has been studied for many years and I would recommend you look up all the work that has been generated by the "low dose program" led the Department of Energy (DOE) in the US. The Europeans have been doing a lot of work on low-dose research (http://www.melodi-online.eu/).
The ideal monitoring should involve not only a good dosimetry on site, but a population follow-up for epidemiology. As you search the literature, you will find two different philosophies:
1. the LNT model (Linear No Threshold), which assumes there are no safe level of Ionizing Radiation and cancer risk is proportional to the accumulated dose
2. the threshold model, setting a value below which radiation is fully repaired and harmless for normal individual. In this latter model, the dose rate becomes a difficult parameter to track and regulatory agencies have used the LNT mainly for practical reasons, but it can lead to unnecessary and costly regulations.
The threshold idea (point 2 above) has gained momentum over the past decade and various studies suggest there is a strong genetic factor predicting the response in the dose rate range, with some individual benefiting from low dose rate whereas other suffering from hypersensitivity. Therefore, I would argue a good epidemiologic data should be done in conjunction with genotyping the population exposed in these high background area and tracked as a function of dose rate and accumulated dose. Of course, nutrition and life style are other confounding factors that must be tracked as well. As you can guess, such experimental design would be highly costly and probably require the cooperation of local government to help. There is still so much to learn from ionizing radiation...
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Hi. Anyone can give answer for my question?For your information I am not doing experimental works, as i am a mathematician. i am just developing a mathematical model of the effect or ionizing radiation by direct and indirect action. Thanks
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Hello sir
Rajaguru Arivuselvam
. Thanks a lot for helping me to get the informations. Really appreciate it. Many thanks sir
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I am searching about a software for analyzing of electronic and communication boards viewpoint of radiation tolerance. for example the output of this software is 40 krad. it means this boards can tolerate 40 krad in radiation environments.
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If what you are searching for is the capacity to simulate the damage in boards when irradiated, you could use TCAD for that (through the Sentaurus Workbench). Once the electronics is designed, it allows for a radiation damage model.
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I want to evaluate the ionizing radiation effects on miRNA expression level in mice.
Some paper used  PBMCs  and others used whole blood ( WBC ) for RNA extraction . 
is there difference between these two source or which of them  is better for this aim .
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Thank you.
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hi
I want to study the expression of XRCC2 gene (involve in HR) and XRCC4 gene (involve in NHEJ) after irradiation to ionizing radiation. These genes are involved in DNA double-strand break repair pathways of HR and NHEJ respectively.
what is the best time after irradiation to assess their expressions?
i studied some literature but I did not get a clear result
Is there an optimal time to express these genes at high levels?
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На жаль я не фахівець з цього напрямку
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Hello
there is a p-type of HpGe detectors, this kind is characterized by the litium dead layer wich existe in the outer side of the detector cristal and it is increased with the passage of time ( dead layer= 0,7 mm if the detector is new ).
On the other hand, the n-ype of these detectors is characterized by a very thin dead layer ( in order of 10E-4 mm ) in the outer side and gross daed layer in the detector cavity.
Flowing our monte simulation of the n-type HpGE using MCNP gives a clair contrast with the expiremental results. where :
MCNP effeciency /Experemental effeciency <1 .
The insertion of the a dead layer ( dead layer depth= 0,08 mm) in the simulation improve the results especially in the <100 keV energy range.
My quation is, do what i did is correct ? and this value of the dead layer is reasonable after 20 years of functioning ? especially that in the leterature, the study of the dead layer of the n-type detector is rare and it is limited for the dead layer existing in the inere part (the cavity).
Regards
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If we irradiate MOSFETS by any ionizing radiation, change in interface trap charges is observed which varies surface potential. How can I relate these all with radiation dose --> then surface potential variation to get change in threshold voltage>?
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I am interested in observing change in threshold voltage from transfer characteristics . How to relate this with surface potential and radiation dose?
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I would like to know from your experience where the mistake is
Experimental steps include the use of sodium salt calf thumus and was diluted in TE buffer size 50 ml  and at a concentration of 2 mg / ml l . After dissolving DNA for 24 hours at 4 ° C was exposed to eletctron beam 6 Mev from elekta preise linac (dose = 80 Gy and dose rate = 5 G / min, field size 20 * 20)
 Then 50 mL DNA  was divided into two glass petri dishes and a depth of each DNA solution in petri dish was ~ 1.6 cm and 1.5 cm water equivalent material was placed directly above the two plates without placing the cap petri dish. Gel eletrophorsis were then performed after a week of exposure and the sample in that period was reserved for the refrigerator at 4 ° C
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do you expect to see visible degradation?. If one of those samples is a control then it is already quite degraded so any degradation of other samples will simply move already degraded dna a little lower down the gel but looking very like the control. Ionising radiation will cause single stranded nicks but dna is very long and double stranded nicking causing breakages will be quite rare. I think that you need a more sensitive technique than agarose gel to measure degradation. Possibly some of the bright signal in the well might be very large dna but could also be protein like histones.
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Have a nice day everyone,
How does a Si/Ge photon detector discern energy from intensity, when both the energy of a photon and intensity of photons would proportionally contribute to the signal?
(The following is optional to read)
The working principles of energy-dispersive x-ray spectroscopy (EDXS) include the use of a semiconductor detector. The semiconductor is induced electron-hole pairs upon incident ionizing radiation. The number of induced electron pairs is proportional to the energy of the incident photon.
Ehv = N Eeh
where Ehv is the energy of an incident photon; Eeh is the electron-hole pair formation energy and N is the number of induced electron-hole pairs.
It is said that the detector use this proportionality to discern the energy of incident x-rays.
However, the number of induced electron-hole pairs is also proportional to the incident photon intensity/flux/number. Then we should also have
NhvEhv = Nt Eeh (I added this one. It was not written in the textbook.)
where Nhv is the incident photon number and Nt is the total electron-hole pair number induced: Nt = Nhv N
The question is: How does a semiconductor detector discern photon energy from photon intensity, if two of them both contribute to the number of electron-hole pair induced?
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adding to Erik's answer. The electronics of the detector must be designed to collect the electrons from a single photon. The detector and electronic system has a rate limit on collecting and forming the electron pulse. The photon rate striking the detector must be lower than the rate limit of the detector and electronics. The higher the photon rate the more pulse pile up and summing. A too high photon rate will render the system useless for both energy and intensity.
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Have a nice day everyone,
The working principles of energy-dispersive x-ray spectroscopy (EDXS) include the use of a semiconductor detector. The semiconductor is induced electron-hole pairs upon incident ionizing radiation. The number of induced electron pairs is proportional to the energy of the incident photon.
Ehv = N Eeh
where Ehv is the energy of an incident photon; Eeh is the electron-hole pair formation energy and N is the number of induced electron-hole pairs.
It is said that the detector use this proportionality to discern the energy of incident x-rays.
However, the number of induced electron-hole pairs is also proportional to the incident photon intensity/flux/number. Then we should also have
NhvEhv = Nt Eeh (I added this one. It was not written in the textbook.)
where Nhv is the incident photon number and Nt is the total electron-hole pair number induced: Nt = Nhv N
The question is: How does a semiconductor detector discern photon energy from photon intensity, if two of them both contribute to the number of electron-hole pair induced?
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Dear Yen-Chun Chen,
your issue is a matter of the time scale of the incoming photons.
Imagine that you have got ‚only‘ 1 photon for example in 1 sec.
Here the detector has enough time to collect the charges and to provide a voltage signal in the form of a voltage peak. The shaping time of the detector’s circuitry governs the width of the peak. Its height is proportional to your number N = Ehv / Eeh given above by you.
So far all things are ok.
But now the intensity comes into play.
Having increasing photon intensity falling onto the detector the time distance between two successive photons more and more decreases down to that point when two photons interact with the detector within the shaping time of the detector.
In the worst case now the electric charges arising from absorption of two photon are collected and the voltage peak height will be proportional to the sum N1+N2 of the two charge clouds. This effect is called ‚pile-up‘. However due to the statistical distribution of the photon time distances in the x-ray beam the fraction of voltage peaks suffering from pile-up is quite small. But for increasing intensity the amount of pile-up events increases nonlinearily.
For sufficient ‚high‘ photon intensity even three-photon pile-up events may show up.
In a peaky x-ray spectrum (e. g. from x-ray fluorescence or gammas from radio nuclides) pile-up shows up when sum peaks in addition to XRF or gamma peaks are popping up. Sum peaks have got the an energy position which is equal to the sum of the photon energies of the involved photons (double or even triple photon coincidence).
In countinous x-ray spectra arising from an x-ray tube, pile-up artifacts are seen as an up-coming photon background beyond the kV limit of the x-ray spectrum. In the ideal case(i.e. no pile up) only a very few counts are showing up from surrounding radio-activity and radiation from space.
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Ruby (Al2O3 doped with Cr3+ ions), when exposed to ionizing radiation (for e.g. X-rays), emits luminescence. What is the mechanism that causes this 'Radio-luminescence? Does Cr3+ accept electrons or give up?
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@Raju: It may happen that we use such conversion for understanding but possibly no such experimental evidences are available in many cases. Even if conversion is there, it may be well below detection limit and negligible. See sizes of different states, they may find difficult to adjust in lattice etc.In CaSO4:Dy we assume Reduction as per Nambi Model, but experimental evidence is not there. There is no change in colour evan after huge irradiation for CaSO4:Dy, if reduction holds, colour should change. You may contact Dr. B. C. Bhatt, who is also on ResearchGate and has done pioneering work in these fields. I am also sharing the question with him.
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We are using gammaH2Ax as a biomarker for DNA damage in HeLa cells after exposim them to different doses of ionizing radiation.
Samples at 0 and 0.5 h from irradiation look normal, however, samples at 24 h from irradiation (both 0 and 4 Gy) display a strong signal from the whole nuclei for the filter corresponding to gammaH2Ax.
Anyone had similar experience or any idea about what could be wrong?
The protocol works for other cell lines- glioblastoma, fibroblasts.
And we had very high reproducibility (4 experiements in total).
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The following papers report the data on gammaH2AX foci in HeLa cells at 24 h after exposure to 4 Gy of X-rays (and energetic carbon ions as well in the first paper).
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For example, ionizing radiation induces multiple types of cell death such as apoptosis, necrosis, mitotic and autophagic. If, we can drive multiple into a single one, targetting the death can be realistic.
I mean how cell decides that which path they have to choose?whether it is "Karma" or "Destiny" ?
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This is a very difficult question. Multiple cell death pathways are currently acknowledged, and the circumstances surrounding each ‘type’ or ‘mode’ are quite variable. I suggest you try to frame your question on more specific terms based on the current recommendations described by a knowledgeable panel in
Cell Death Differ. 2018 Mar;25(3):486-541. doi: 10.1038/s41418-017-0012-4. Epub 2018 Jan 23.
Molecular mechanisms of cell death: recommendations of the Nomenclature Committee on Cell Death 2018.
Galluzzi L et al...
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Hi, in the late '90s I used a software package from AIC Software Inc., called Photcoef, to calculate the ionizing  dose / energy deposited and attenuation of x-rays and gamma rays through material stacks.  This was very useful but the DOS software no longer functions and AIC no longer exists.  Do you know any alternative that includes dose build-up due to generated electrons etc?  I know I could use GEANT but this is rather too complex for my needs.  Thanks  Mark
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Hi! Are there any available analogues of these programs? On the Internet, I did not know anything about them. I need to calculate the dose from ultra-soft (<2 keV) X-rays in different materials. For what minimum energy limit can program data be calculated?
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Why organic materials were not used as bio-polymers, to protect against ionizing radiation. And why there are no studies and research on this subject
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Your result of not effective for beta, but effective for gamma is curious, as other answers have noted. You did not provide energy information for the radiations, nor what you consider effective.
What thicknesses of shielding material were used?
What radiation energies were used?
What do you consider effective?
Intensity of radiation and time of use is important for organic materials. Organic materials degrade in a radiation field with a change in physical characteristics.
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The most common way that conventional doctors look for the first signs of breast cancer in women is to identify lumps in the breast. They most often do this with mammogram x-rays. This offer physicians a basic road map for navigating the terrain of breast tissue, which they believe allows them to pinpoint any lumps, masses, or other warning signs of breast cancer that might point to a malignancy.
But mammograms can be a potential cause of cancer due to the ionizing radiation they send into breast tissue. They also aren’t accurate 100 percent of the time, despite what you may have been told. Lumps and masses in breast tissue can be either benign (harmless) or malignant (cancerous), and mammograms don’t differentiate between the two. This often leads to false diagnoses and unnecessary treatments with chemotherapy and radiation
is there any information about Is there any information about the diagnosis or early signs of this disease? share with me ...
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  • retraction, or inward turning of the nipple
  • enlargement of one breast
  • dimpling of the breast surface
  • an existing lump that gets bigger
  • an “orange peel” texture to the skin
  • vaginal pain
  • unintentional weight loss
  • enlarged lymph nodes in the armpit
  • visible veins on the breast
Having one or more of these symptoms doesn’t necessarily mean you have breast cancer. Nipple discharge, for example, can also be caused by an infection. See your doctor for a complete evaluation if you experience any of these signs and symptoms.
FIND A DOCTORCost of a mammogram near you
Where you live might affect how much you’ll pay for a screening mammogram. Explore the range of costs for screening mammograms in your region using the cost research tool below, powered by our partner Amino. Click on the cities to see nearby doctors. You can also start a new doctor search and book an appointment for free using this tool.
SIGNS IN MENMen and breast cancer
Breast cancer isn’t typically associated with men. However, male breast cancer can occur in rare instances at any age, although it’s more common in older men. Many people don’t realizethat men have breast tissue too, and those cells can undergo cancerous changes. Because male breast cells are much less developed than women’s breast cells, breast cancer in men isn’t as common.
The most common symptom of breast cancer in men is a lump in the breast tissue.
Other than a lump, symptoms of breast cancer in men include:
  • thickening of the breast tissue
  • nipple discharge
  • redness or scaling of the nipple
  • a nipple that retracts or turns inward
  • unexplained redness, swelling, skin irritation, itchiness, or rash on the breast
Most men don’t regularly check their breast tissue for signs of lumps, so male breast cancer is often diagnosed much later.
EXAMSBreast exams
When you visit your doctor with concerns about breast pain, tenderness, or a lump, there are common tests they might perform.
Physical examination
Your doctor will examine your breasts and the skin on your breasts, as well as check for nipple problems and discharge. They may also feel your breasts and armpits to look for lumps.
Medical history
Your doctor will ask you questions about your health history, including any medications you might be taking, as well as the medical history of immediate family members. Because breast cancer can sometimes be related to your genes, it’s important to tell your doctor about any family history of breast cancer. Your doctor will also ask you about your symptoms, including when you first noticed them.
Mammogram
Your doctor may request a mammogram, which is an X-ray of the breast, to help distinguish between a benign and malignant mass.
Ultrasound
Ultrasonic sound waves can be used to produce an image of breast tissue.
MRI
Your doctor may suggest an MRI scan in conjunction with other tests. This is another noninvasive imaging test used to examine breast tissue.
Biopsy
This involves removing a small amount of breast tissue to be used for testing.
Read on to learn more about breast cancer tests.
TYPESTypes of breast cancer
There are two categories that reflect the nature of breast cancer:
  • Noninvasive (in situ) cancer is cancer that hasn’t spread from the original tissue. This is referred to as stage 0.
  • Invasive (infiltrating) cancer is cancer that has spread to surrounding tissues. These are categorized as stages 1, 2, 3, or 4.
The tissue affected determines the type of cancer:
  • Ductal carcinoma is a cancer that forms in the lining of the milk ducts. This is the most common type of breast cancer.
  • Lobular carcinoma is cancer in the lobules of the breast. The lobules are where milk is produced.
  • Sarcoma is cancer in the breast’s connective tissue. This is a rare type of breast cancer.
GROWTHGenes and hormones affect cancer growth
Geneticists are starting to learn how genes affect the growth of cancer and have even identified one: the HER2 gene. This gene fuels growth of breast cancer cells. Medications can help shut this gene down.
Like genes, hormones may also speed up the growth of some types of breast cancers that have hormone receptors.
  • If a cancer is estrogen receptor-positive, it responds to estrogen.
  • If a cancer is progesterone receptor-positive, it responds to progesterone.
  • If a cancer is hormone receptor-negative, it has no hormone receptors.
TREATMENTSTreatments for breast cancer
Depending on the type and stage of cancer, treatments can vary. However, there are some common practices doctors and specialists use to combat breast cancer:
  • A lumpectomy is when your doctor removes the tumor while leaving your breast intact.
  • A mastectomy is when your doctor surgically removes all of your breast tissue including the tumor and connecting tissue.
  • Chemotherapy is the most common cancer treatment, and it involves the use of anticancer drugs. These drugs interfere with cells’ ability to reproduce.
  • Radiation uses X-rays to treat cancer directly.
  • Hormone and targeted therapy can be used when either genes or hormones play a part in the cancer’s growth.
RECURRENCESigns of recurrence
Despite initial treatment and success, breast cancer can sometimes come back. This is called recurrence, which happens when a small number of cells escape the initial treatment.
Symptoms of a recurrence in the same place as the first breast cancer are very similar to symptoms of the first breast cancer. They include:
  • a new breast lump
  • changes to the nipple
  • redness or swelling of the breast
  • a new thickening near the mastectomy scar
If breast cancer comes back regionally, it means that the cancer has returned to the lymph nodes or close by the original cancer but not exactly the same place. The symptoms may be slightly different.
Symptoms of a regional recurrence may include:
  • lumps in your lymph nodes or near the collarbone
  • chest pain
  • pain or loss of sensation in your arm or shoulder
  • swelling in your arm on the same side as the original breast cancer
If you’ve had a mastectomy or other surgery related to breast cancer, you might get lumps or bumps caused by scar tissue in the reconstructed breast. This isn’t cancer, but you should let your doctor know about them so they can be monitored.
As with any cancer, early detection and treatment are major factors in determining the outcome. Breast cancer is easily treated and usually curable when detected in the earliest of stages.
The American Cancer Society says the five-year survival rate for breast cancer that is stage 0 to stage 2 is more than 90 percent. The five-year survival rate for stage 3 cancer is more than 70 percent.
Breast cancer is the most common cancer in women, according to the World Health Organization. Whether you’re concerned about breast pain or tenderness, it’s important to stay informed on risk factors and warning signs of breast cancer.
The best way to fight breast cancer is early detection, whether that includes self-examinations, annual breast exams at your doctor’s office, or regular mammograms. If you’re worried that your breast pain or tenderness could be something serious, make an appointment with your doctor today. If you find a lump in your breast (even if your most recent mammogram was normal), see your doctor.
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ICRP-118-2011) Published new version decreased dose limit for occupational workers from 150 mSv to 20 mSv but i did not find any publication concerning any change in eye lens dose limit for public. 
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Situations should be different among countries each with different national regulation and policy, but all people who enter radiation control area (regardless of whether routinely or occasionally) should wear dosimeter.
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I am part of the scientific team of a mission of young researchers to send a biological mini-lab to the Moon thanks to the company Team Indus. Our experiment requires real-time measurement of ionizing radiation on the Moon. Thanks to data from the NASA mission Crater we can see that the range of radiation intensities are in the range of 0.001 to 0.01 cGy / day and during solar events can reach values of 100 cGy / day.
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Dear Romulo , use p-channel MOSFET , its sensitive to radiation, with low DC bias voltage in the range of 0.5 to 4V. in which the critical region affect by radiation its oxide gate.
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Just wondering if anybody has ever done this. I would suppose the oligos could suffer, since they´ll be exposed to ionizing radiation for a brief period... but i´m not quite sure if enough to destroy them.
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Unique Response of Double-Stranded Oligonucleotides Containing a Single 8-Oxo-7,8-Dihydroguanine to Gamma Rays in the Frozen Aqueous State at 77 K
may be useful
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I want to determine the absorbed dose of x-ray and Gamma ray of human body when it's ionized radiations are used in medical application    
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Dear Sir, 
I think you can get benefit from the document below.  
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Why are some isotopes radioactive and others not? Can you predict which ones will be radioactive?
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Of course the answer is indeed related to the n/p ratio and to the atomic number. But the simple quantitative rule is:
a nuclide is radioactive if its mass is higher than the mass of its decay products
or in other words
a nuclide is radioactive if its decay liberates energy.
However when considering alpha decay and spontaneous fission (as well as other rare decay modes like p or 14C decay), the decay which is theoretically possible can be so strongly hindered by the Coulomb barrier that it cannot be observed.
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Why Ionizing Radiation is known as a double edged sword?
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Ionizing Radiation is of great benefit in detecting cancer, eliminating cancer and improving survival. But as valuable as it is in cancer diagnosis and treatment, ionizing radiation must be used carefully, because it can cause side effects such as burns and hair loss that become apparent soon after the exposure, or arise many years later in the form of secondary cancers.
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What is meant by RBE (Relative Biological Effectiveness)? Does RBE varies with increasing LET?
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The US National Aeronautics and Space Administration (NASA) uses the relative biological effectiveness (RBE) to calculate gray equivalent (Gy-Eq). RBE values commonly recommended for the lens of the eye, skin, blood forming organs, and circulatory systems are 6.0 in a range between 4 and 8 for 1–5 MeV neutrons, 3.5 (2-5) for 5-50 MeV neutrons, 2.5 (1-4) for heavy ions, and 1.5 for >2 MeV protons. There have not been sufficient data for <1 MeV or >25 MeV neutrons and heavy ions (Z >18) to derive RBE. RBE for late tissue reactions is higher than that for early tissue reactions in some tissues.
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What is meant by prodromal syndrome? At what total-body absorbed dose range this syndrome resulted? 
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5-hydroxytryptamine-3 receptor antagonists (5HT3 RAs), dexamethasone, metoclopramide, haloperidol, metoclopramide, dexamethasone and lorazepam have been used for prophylaxis of radiation-induced nausea and vomiting (RINV) following radiation therapy. Aprepitant (substance P neurokinin 1 receptor antagonist) is the newer antiemetic agent.
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Do you have any information about Dr. Luckey's work and where can you get more info on "Hormesis".
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Why and How does Fractionation introduces a "waste in dose", which is more pronounced for beams with a wide shoulder than for beams with a narrow shoulder in the survival curve??
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In addition to tumors refractory to conventional photons, carbon ion radiotherapy utilizes hypofractionation regimens for radioresponsive tumors, e.g., delivery of 40 or 50 Gy in 2 to 16 fractions for lung cancer, prostate cancer, and hepatocellular carcinoma.
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What is meant by "Oxygen Enhancement Ratio"?
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The mechanistic underpinnings of the oxygen effects remain incompletely understood, but indirect effects to nuclear DNA are explained above by others. Here I wish to highlight two other potential mechanisms.
A recent study attributed the oxygen effect to radiation-induced effects in mitochondria, such that reactive oxygen species generated in mitochondria target nuclear DNA indirectly.
Targeted cyctoplasmic irradiation induces DNA damage, inactivates clonogenic potential and causes mitochondrial dysfunction leading to increased oxidative stress. These suggest extranuclear target for radiation effects. 
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How safe is a non ionizing radiation dose?
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According to US Department of Labor, non-ionizing radiation is described as a series of energy waves composed of oscillating electric and magnetic fields traveling at the speed of light. Non-ionizing radiation includes the spectrum of ultraviolet (UV), visible light, infrared (IR), microwave (MW), radio frequency (RF), and extremely low frequency (ELF). Lasers commonly operate in the UV, visible, and IR frequencies. Non-ionizing radiation is found in a wide range of occupational settings and can pose a considerable health risk to potentially exposed workers if not properly controlled.
Extremely Low Frequency Radiation (ELF)
Extremely Low Frequency (ELF) radiation at 60 HZ is produced by power lines, electrical wiring, and electrical equipment. Common sources of intense exposure include ELF induction furnaces and high-voltage power lines.
Radiofrequency and Microwave Radiation
Microwave radiation (MW) is absorbed near the skin, while Radiofrequency (RF) radiation may be absorbed throughout the body. At high enough intensities both will damage tissue through heating. Sources of RF and MW radiation include radio emitters and cell phones.
Infrared Radiation (IR)
The skin and eyes absorb infrared radiation (IR) as heat. Workers normally notice excessive exposure through heat sensation and pain. Sources of IR radiation include furnaces, heat lamps, and IR lasers.
Visible Light Radiation
The different visible frequencies of the electromagnetic (EM) spectrum are "seen" by our eyes as different colors. Good lighting is conducive to increased production, and may help prevent incidents related to poor lighting conditions. Excessive visible radiation can damage the eyes and skin.
Ultraviolet Radiation (UV)
Ultraviolet radiation (UV) has a high photon energy range and is particularly hazardous because there are usually no immediate symptoms of excessive exposure. Sources of UV radiation include the sun, black lights, welding arcs, and UV lasers.
Laser Hazards
Lasers typically emit optical (UV, visible light, IR) radiations and are primarily an eye and skin hazard. Common lasers include CO2 IR laser; helium - neon, neodymium YAG, and ruby visible lasers, and the Nitrogen UV laser.
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How oxygen plays role in lethality of ionizing radiation?
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The pathogenesis of ionizing radiation damage starts at with the physicochemical processes. These processes give origin to reactive compounds that act on molecular level and cause radiation cellular changes. This causes cells to losing their specific properties. At the subcellular level there are irregularities happening to the biochemical processes:
The activity of enzymes changes
phosphorylation mechanisms are disrupted
the synthesis of nucleic acid
specific proteins do no longer work.
The cellular level of damage first manifests itself with a decrease in the number of proliferating cellular populations. The loss of specialized cells causes the biochemical changes to intensify. The changes starts to interfere with the functions of vitally important organs such as hematopoietic tissues, intestinal epithelium etc. The resulting organ and systemic changes to the whole organism initiates the development of radiation sickness. There are also latent somatic and genetic damages, which can be seen on a population level.
Biological effects of the same doses of ionizing radiation can differ greatly. These effects depend on the linear energy transfer and on the spatial distribution of a given dose. DNA molecules are the most critical cellular structures that can be affected by ionizing radiation. Ionizing radiation can induce a number of changes in the size, structure and shape of these molecules.
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Background radiation is the ionizing radiation present in the environment. Background radiationoriginates from a variety of sources, both natural and artificial.
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 Source or mode                  Annual average dose (mSv)
Inhalation (radon gas)                   1.26
External terrestrial                         0.48
Ingestion                                        0.29
Cosmic radiation                           0.39
Total natural                                  2.4
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I am looking for a measure of the time scale between direct irradiation, and bystander effects being observed in vitro. I have a mathematical model that predicts this, and would like some validation.
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it depends on different things : your cell line, LET of photons, and maybe the issues that we do not now yet. but based on Mothersill and Seymour, 1997 it is around 30 min to see bystander effect ( cell death ), definitely  in molecular level like gene expression it would be lower!
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What is the latest on radiation hormesis?
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My pleasure, Ms Nkiruka Adesiji
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I am trying to have human fibroblast irradiated by Ionizing radiation(Cobalt 60).
I encounter some problem during the experiment.
I tried to use 10/30/100 Gy of IR on fibroblast cells, and after 24 and 48 hr incubation, I couldn't see any floating cells(dead cells). All of cells were attached, and I assumed all of them were live cells. This seems very weird, according to most of papers which use dose of 5-20 Gy for measuring apoptosis of cells.
I am wondering in your experience whether after radiation and incubation, the cells had some portion of floating cells, or there were no any floating cells and apoptosis assay could recognize those apoptotic cells. 
I hope to have some suggestion from your response.
Thank you very much.
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FYI, even in vivo, there is the case where removal of apoptosed cells by phagocytes does not occur: the ocular lens is enclosed with the lens capsule inside which phagocytes cannot access, so that apoptosed cells remain in the tissue.
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I have access to a x-ray irradiator but not a gamma ray irradiator.
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Dear Julia,
without knowing your irradiator, a correct answer is hard to give. Maybe you can list some parameters of your X-ray irradiator, such as kVp (range of adjustable kVp), filtration and dose rate (range of possible dose rate).
As other researchers mentioned before, gammas and X-rays are in principle the same: they are photons with different origin (electron shell vs. nucleus). But, depending on energy and dose rate, the biological effect due to irradiation can vary. For example, gamma irradiators are mostly equipped with Co-60 or Cs-137, producing "high" energy photons (1173/1332 keV or 662 keV). So, substitution with "high" energy X-rays (150-300 kVp with thick filtration) should result in approx. the same biological effect using the same dose (keyword: RBE = relative biological effectiveness). However, substitution with "low" energy X-rays (<= 50 kVp) will not be appropriate, in my opinion, due to an increased RBE. Variation of dose rate can also result in different biological outcome because of time-dependent cell repair mechanisms.
Best regards
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Due to the interaction of such radiation with matter, a small charge will be formed on the material surface. This charge must be safely leak out; therefore such shielding material must have good electrical properties.
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Materials become charged when electrons leave the surface of the material and when electrons from photo and Compton reactions enter the material. These external photons can be substantial for photons above 1 MeV. Hot cell windows irradiated with gamma only can shatter if no leakage method is provided.
Most counting laboratories do not have a problem with shield charging when non-conductive materials are included. Charge build up is easily leaked away as dose to the material is usually low. Nevertheless, surprises do occur in experimental configurations, particularly when there is low humidity. 
Most charging problems are seen in accelerators when targets build up substantial charges. See attached from an electron accelerator.
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Use of dicentric counting Chromosomal aberration test for biodosimety for ionizing radiation is very common technique. How much reliable method is this ? i m worried about this because of limited number of dicentrics formations in the exposed person.
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The Special Issue on the European RENEB project guest edited by Drs Ulrike Kulka and Andrzej Wojcik has just become available online as the January 2017 issue of International Journal of Radiation Biology. All papers in this special issue are freely downloadable.
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Hi all, this is Wen. I am working on an ion beam irradiation program. Now I have calculated the dpa (displacement per atom) of the beam on the target, but I don't know how to evaluate the total dose needed to fail the target. This is essential to my program but I have never worked on such problems before. Can anyone teach me?
Thank you so much.
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If you worked with SRIM, than the number (N_i) and energy (E_i) of projectiles have been input parameters. If the projectiles are not stopped in the medium, you can get the number of no-stopped projectiles (N_o) and their average energy (E_o)  as output.
In any case, the applied dose (unit: J/kg) can be calculated from (N_i *E_i)-(N_o*E_o), normalized to the affected mass. 
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D. robiginosus was isolated from a sterilization dose audit. Have you performed any D10 assessments following exposure to ionizing (gamma) radiation?
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It is unlikely that tolerance of Domibacillus (not only D. robiginosus but also other bacteria belonging to the genus Domibacillus) to ionizing radiation has been reported in the literature (at least which is searchable in PubMed).
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Numerous papers have reported increased invasion of cancer cells after treatment with high doses of ionizing radiation. I have seen this in my work with lung cancer cells as well. Is there a common biological explanation for this observation or do different cell lines activate different pathways that increase invasion of the cells?
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Whether ionizing irradiation augments or alleviates invasion depends on various factors (e.g., please see discussion in http://dx.doi.org/10.1016/j.semcancer.2015.09.003, from which PDF is freely downloadable).
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Dear All,
I was wondering what analytical method I should utilize in order to detect any chemical alteration in an organic sample that is irradiated by X-ray radiation?
Note: The color change was observed as a result of irradiation.
Best,
Sevan
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You can also use IR and near-IR spectra. These methods are cheaper and often more easily applied to such samples.
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The biological dosimetry estimates the absorbed dose in living tissues by studying certain biomarkers (e.g. chromosome mutations). Are these alterations totally specific of ionizing radiations or could they be caused by other agents as well?
Is it possible to use biological dosimetry long after the irradiation or is it necessary to take the samples shortly after the exposure?
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Specificity and time dependency is different for various endpoints. It also has to be considered that, in case of a dose estimation after an accident, we don't have a (non exposed) control value. In such situations the marker needs to be very robust, especially with regard to age and lifestyle of the person and time span between exposure and sample taking.
Most specific is the dicentric chromosome (dic). There are some chemicals which also can cause dics but they are not very common. The background in non exposed persons is very low (about 1 dic in 1000 lymphocytes), they show low age dependency  and are stable in  the exposed blood lymphocytes as long as the  cell is alive (several years, depending on the age of the exposed lymphocyte).  Usually dics are used to estimate the dose after an acute exposure, that happend not long ago (ca 6 month). Symmetric translocation (FISH assay)  are still detectable  for a longer time period after an irradiation but they can be influenced by age and lifestyle. The background and variation between individuals  is higher compared to dics. They are used to estimate an irradiation, that dates back up to several years or a protracted irradiation. Micronuclei are also suitable for dose estimation but are less specific and also show interindividual variation. Repair points of double strand breaks (Gamma H2AX)  are not specific  and are detectable for a very short time span but this method is quite fast and can be applied on many persons. So each of these endpoints have their optimal field of application. Optimal is to have a panel of methods, including biological and  physical retrospective techniques and to receive the information from  more than 1 endpoint. In this case the irradiation scenario can be reconstructed. More information  and references to each of the  different methods are found here:  RENEB – Running the European Network of biological dosimetry and physical retrospective dosimetry ( http://dx.doi.org/10.108/09553002.2016.1230239 ).
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There are many dosimeter available in the market especially online. How do one ascertain if a particular dosimeter one should use for measuring the quantity of ionizing radiation of a device e.g mobile phones is effective and accurate particularly when it is to be purchased from online store and there is no sample?
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This question does not make any scientific sense. Cell phones (aka: mobile phones) do not emit any ionizing radiation so you would not use an ionization radiation dosimeter to measure and/or record any accumulation or dose. Cell phones emit non-ionizing (aka: radio-frequency) energy. From a clinical and scientific point of view, radio-frequency energy has thus far only been shown to heat things up, not break DNA or cause mutations. More research is needed and underway on this topic and you can do a keyword search to find additional research.
If you would like to measure the amount of radio-frequency energy emitted by a cell phone, then you should acquire a RF Meter which can measure it within the appropriate frequency ranges used. That information can then be recorded in SAR (specific absorption rate) to find the equivalent of dose.
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In the literature it is said that the grainless nature of radiochromic films is responsible for their high resolution. What exactly does this mean?
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Yes, it is very helpful. Thank you very much.
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I am planning to perform double strand break (DSB) assay to test how cells response to DSB (patients vs controls) (general design: induce DSB and measure the level of  γ-H2AX foci). I could see that there are 2 main options to induce DSB: ionizing radiation or agents (e.g. ETOP). Can I choose either option or should I need to consider some factors to choose the appropriate option? If it's the latter, what factors are they?
(I'm plannning to test on primary human peripheral mononuclear cells (PBMC) extracted from blood as well as EBV-transformed PBMC.)
Thanks.
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With the X-ray generator, you can irradiate X-rays, e.g., at 0.5 Gy/min. 1 Gy produces about 30-40 DSBs for which the number of gamma-H2AX foci reaches a maximum at 30 min post-irradiation. When you compare the repair capacity of different cell types (here, patient and non-patient cells), it will be intriguing/important to look at the time course, especially a later time, as the cellular response is affected by the residual DNA damage.
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One of the ways through which Crystalline materials turning amorphous is under swift ion irradiation. Crystalline materials can also be amorphized via ball milling, owing to impact-induced crystal attrition. Now, considering the final state of the material being same (amorphous), can we draw any similarities between the two processes in terms of its path or mechanism to reach amorphous state ? 
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Thou
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We want to determine/understand DNA damage/mutation caused by different doses of gamma irradiation on different organisms. However, although I have performed DNA sequencing using Genetic Analyzer 3500, but I don't have any experience on determining DNA damage/mutation caused by ionizing radiation. Those who have experience on this field, please provide your insightful guidelines on this issue.
Thank you very much.
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The best biomarker of DNA damage by gamma-irradiation is the detection of the phosphorylated form of variant histone H2AX (γ-H2AX), which occurs specifically at sites of DNA double-strand breaks (DSBs). There  are many protocol that can be used. Check for example this paper:
γ-H2AX as a biomarker of DNA damage induced by ionizing radiation in human peripheral blood lymphocytes and artificial skin.
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I tried searching it in google indeed, but just found some old and new articles on modeling of radiation environment that were of no use to my problem. What I'm exactly looking for is a set of information like what we have for gravitational field (Spherical harmonic coefficients) that describes the magnetic field strength and charge densities in proportion to solar activity.
Let's put it this way: I want a model to use it to calculate the amount of radiation dosage absorbed by spacecraft in a trajectory around Jupiter (or Earth) for a certain amount of time.
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I believe ICRP Publication 123 has the correct information. For simulations, I recommend using SPENVIS.  https://www.spenvis.oma.be
Jupiter specific information:
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Dear Colleagues,
in order to shield a dose rate (NORM in drums) from about 250 micro Sievert per hour, down to about 5 micro Sievert per hour, I have calculated a lead sheet shielding of about 17 mm thickness. Is there anybody to confirm this result, respectively giving a more detailed input on this topic such as literature or examples, standards etc.
Your kind support is highly appreciated
Ruediger
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Ruediger
The majority of the dose comes from the higher energy gammas from the Ra progeny. Calculation is difficult. Dose rate depends upon shape, size, the matrix containing the Ra and distribution of Ra in material. The HVL of 4 mm is for a point source. Many medical sources have a listed HVL of 12 - 14 mm. See attached.
What type instrument are you using for measuring dose rate? Some instruments over respond to low energy gammas making the measurement too high. Check with simple shielding. If the dose rate is easily reduced by shielding you have over response.
Consider repackaging. Is the Ra uniformly distributed? If not, place higher dose rate material in the center. Can you add filler, for example, wet soil? If uniformly distributed place material in smaller containers and then filler in the 200 L drums to hold them in the center.
How you shield will come down to cost.
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Exposure of the heart to ionizing radiation during radiotherapy for breast cancer  may increases the subsequent rate of ischemic heart disease.
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I should thank members for their opinion.
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As the biological effect of radiation is measured in Sievert, I would
like to know if and how one can convert W/meter square or dBM of a
non-ionizing radiation into the unit Sievert?
Under ICD-10, a new entity has been recommended [Z58.4] for disease due to exposure to radiation, or EMF syndrome. Though safer than ionizing radiation, too much of non-ionizing radiation can be unsafe, but requires lot of efforts to demystify the reality.
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I also mostly agree with Joseph. However, depending on the penetration depth of the radiation (which, of course, is dependent on its wavelength) it might not be meaningful to try to convert these units into the Gray/Sv systems (J/kg) but maybe more promising to take the W/m2 as the measure and to define effectiveness/quality factors to arrive at a quantitiy analogous to Sv.
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Consider a solid sphere of some material and a spherical shell of the same material with both having the same thickness in the sense that a straight-line path from outside to the center travels through the same thickness of material. These are intended to be used as radiation shields in a given external electron environment. The interest here is the ionizing radiation dose at the center of each. Because electrons do not follow straight-line paths when going through a shield, I am not surprised that the solid sphere and spherical shell will not produce identical doses at the center, but how much different should they be? And why? Is there some simple analytical argument (not Monte Carlo) that can roughly account for this difference?
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Thank you for the help but my question is not whether the spherical shell is the worst case. My question is whether there is a simple qualitative explanation as to why it is the worst case.
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Dear engineer Why win-q disconnected to quantulus 1220?.what can i do to solve this problem.I turn on and off system and counter but win-q display disconnected massage in application.I reinstalled app. But win-q is disconnect .at first its error was conveyor clearing but after turn off & on it shows disconnected. we check the plates and remove trays and check them.they dont have any problem. please answer my question. I need to answer .best regard((when counter time was over the elevator took vial at tray and after that we hearing the pneumatic pomp tone(Eu-152,STD capsule) more and more.after that we turn on & off several times.but after that application showed disconnected))
best regard.
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برای کاهش دماتا این اندازه ای که مد نظرتون باید با استفاده از دو لوله مسی که در پشت قسمت خنک کننده تعبیه شده جریان آب برقرار کنید چون همنطور ک می دوندی قسمت خنک کننده فقط از جریان هما استفاده می کنه و رسیدن به دمای 5 با برقراری فقط جریان هوا فکر نمی کنم ممکن باشه.
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I have been using the unit: umol m-2 s-1 to talk about photosynthetically active radiation, but is it wrong in the International System of Units?
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Yes, but the journals ask for the use of SI!
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In gamma irradiation of polymer experiment, which surface is more influenced, the entry or the exit surface and why?
and when the film thickness is in micro range, is that make difference? or is there a difference between the entry and exit for small thickness samples? 
what about gamma attenuation in polymers is it effective to use polymers as a shielding material since it is rich of hydrogen.
please give some details in your answer??
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What are you reporting that requires units? If you are reporting the gamma beam energy it is kerma, free-in-air. The unit is Gy. If you are reporting the dose to the polymer it is energy deposited and the unit is Gy.  To report dose to the polymer you will have to calculate the energy deposited using assumptions on the kerma distribution in the polymer or you will need a method to measure it. Sv is inappropriate as it is a unit of risk. 
Ion fluence assumes you have a measurement or estimate. The unit should be that used to measure or estimate. The unit cm-2 seems appropriate.
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During XPS / ESCA Analysis
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Thank you Dr Roman V. Gulyaev. The article u mentioned is very helpful.
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Dose the charge effect of irradiating ions play a part in the radiation damage build-up in materials? e.g., the Xe+ and Xe26+ ions induced damages in a specific kind of material are due to the same or different mechanism?
Thanks in advance!
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Many thanks to everyone! I benefit a lot from you.
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OR, does the use of these radionuclide tracers, themselves, add a significant risk of causing cancer in patients?
The dose of ionizing-radiation from the tracer used in one PET scan, for example, typically exposes the patient to about 25% of the maximum allowable annual radiation exposure permitted for nuclear workers (which is a VERY high limit = to over 200 standard/modern medical chest xrays, meaning a patient is getting exposed to the equivalent of about 50x chest xrays ALL AT ONCE for each PET test).
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Dear Bob,
Actually, some of them appear to be not quite safe. For example, there are risks of a Gallbladder Radionuclide Scan.
The Risks of a Gallbladder Radionuclide Scan
There is a risk of exposure to radiation with this test. The gallbladder radionuclide scan uses small amounts of radioactive tracers. However, this test has been used for over 50 years and there are no known long-term side effects from such low doses of radiation. The benefits of the tests outweigh the risk of radiation exposure (Radiology, 2012).
There is, however, a rare chance of an allergic reaction, which is typically mild.
On the other hand, others were proved to be safe. For example, in the bone scan:
The amount of the radionuclide injected into your vein for the procedure is small enough that there is no need for precautions against radioactive exposure. The injection of the tracer may cause some slight discomfort. Allergic reactions to the tracer are rare, but may occur.
Hoping this will be helpful,
Rafik
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We have small diffusion chambers from aluminum, inside this chamber a Ra-226 source is installed with a normal emanation coefficient. Do we need to isolate this box with a roof using a good isolation glue? 
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To seal my samples, I use high density polyethylene (HDPE) bottles with screw cap of the same material. You can see this in the attached presentation (page 6) to work: "NATURAL OCCURRING RADIONUCLIDES IN NOVEL SAND BEACHES FROM ESPÍRITO SANTO, STATE, BRAZIL" on my profile. In a similar to your experiment, I used a PVC tape on the threads and, after threaded, sealed with silicone. For more information, contact me at raquino@ipen.br
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Is it possible that XRD peak intensity decresing with increasing ion irradiation ?
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The mechanism is likely to be a bit too complex to explain in detail, but the radiation is ionising radiation (X-rays), they will certainly produce what would be ionisations if they were produced in a gas.  The relaxationof such energy could produce dislocations, imperfections in the lattice, vacancies or other crystalographic faults.  This will disturb the coherency of the diffdraction peaks.  It requires quite a length of ordered crystal to produce a distinct diffraction peak.  For example, powder diffraction can only be done fi the powdered aprticles have a certain size, of the order of some tens or hundreds of nanometres.  Without that size, you just don't get clear diffraction peaks.
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Although, senescence and mitotic catastrophe are 2 independent processes, I have observed cells with enlarged appearance, highly polyunucleated and with micro-nuceli that stain positive for beta-galactosidase activity.
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Very fascinating phenomenon, I think. . Mitotic catastrophe is defined as the failure to cell cycle arrest during the mitosis, which triggers the aberrant chromosome segregation. Further, SA-β-gal(senescence-associated beta-galactosidase) is not necessarily derived from cellular senescence, and this molecule is induced by cellular stress response. That is why caspase2-dependent stress response is likely the co-existence of mitotic catastrophe and SA-β-gal.
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I'm using the Quantulus Liquid Scintillation Spectrometer with the Perkin Elmer Filter Count scintillation cocktail in a plastic vial to measure the activity of Am243 and Am241 (separately) in two different conditions: radionuclide dissolved in an homogeneous solution and radionuclide deposited on a borosilicate glass filter immersed into the scintillation cocktail into the vial.
When I measure the Am243's CPM (counts per minute) I always obtain a 180-200% efficiency (CPM/activity[Bq/min]). When I measure the Am241's CPM, instead, I have an averaged efficiency of 86% in the homogeneous solution and an averaged efficiency of 120% with the radionuclide deposited on a borosilicate glass filter.
With respect to the Am243 I know that the Am243 (100 % alpha emitter - Qalfa=5.438 MeV - Half life= 7370 years) decays in Np239 (100% beta emitter - Qbeta=722 keV - Half life=2.3days) so I thought that the 200% efficiency was due to the secular equilibrium of the Np239 even if the Quantulus should discriminate the beta emissions and the alpha emissions. The problem is that the instrument doesn't show the presence of Np239 in the scintillation spectrum. Is this consideration acceptable in your opinion?
Regarding the Am241(alpha emitter - Qalfa=5.958 MeV - Half life= 432 years), it decays (alpha) in Np237 (100 % alpha emitter - Qalfa=5.438 MeV - Half life= 2.144*10^6 years) that is in transient equilibrium with the parent element. So I think that the presence of Np237 in the scintillation spectrum is negligible. In this case I can't explain the averaged efficiency of 86% in the homogeneous solution and the averaged efficiency of 120% with the radionuclide deposited on a borosilicate glass filter. Could anyone help me with this?
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In order to receive suggestions to the problems you are seeing, you should first define the following:
1) region of interest you are using to assess your instrument response
2) volume and reagent of your Am source added to what volume of scintillation cocktail.  E.g., is a portion of your aqueous solution spike insoluble in the cocktail volume and settling to the bottom over time?
3) how far above the instrument background are your samples?
4) by what means are your standards' activities quantified or externally calibrated?
5) what are you seeing on the pulse height spectra?
This information should aide in getting answers to your questions. 
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It is easy to produce linearized ends with sticky ends using restriction enzymes and these sticky ends are readily ligated by DNA ligase enzyme alone without the need for DNA end-processing. 
How do I make such linearized DNA behave like the DNA breaks created by ionizing radiation where DNA breaks need end-processing before DNA ligation can proceed. 
In simple words, how do I create a linearized DNA with sticky ends resembling radio damaged 'non-ligatable' ends. 
Not interested in 'dephosphorylation'. 
Can someone direct me to one such method, if it exists, please.
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Hi,
following article mentions synthetic oligonucleotide models for DSB ends in the introduction and give references (no 5 and 35):
Nucleic Acids Res. 2012 Nov;40(21):10821-31. doi: 10.1093/nar/gks879. Epub 2012 Sep 24.
The dynamics of Ku70/80 and DNA-PKcs at DSBs induced by ionizing radiation is dependent on the complexity of damage.
Reynolds P1, Anderson JA, Harper JV, Hill MA, Botchway SW, Parker AW, O'Neill P.
Maybe this is what you are looking for.
Best wishes,
GAD
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There are various methods available in the literature (Initial Rise, Peak Shape, Glow curve deconvolution etc.) which are used to analyse a thermoluminescence glow curve that recorded at a linear heating rate. But if the heating rate is not linear is there any method to accurately estimate the trapping parameters from the glow curve? 
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You are right that thermal quenching has to do with increasing temperature. The relation to heating rate is the following. Since an increase in the heating rate shifts the peak to higher temperature, at a higher heating rate the thermal quenching is in effect due to the higher temperature. Thus, at a higher heating rate, if thermal quenching takes place, the total area diminishes
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The International Commission on Radiation Protection (ICRP) proposed a set of operational quantities defined to allow for calibration of ionizing radiation protection instruments for measurements to show compliance with the system of protection quantities. These measurable quantities are the ambient dose equivalent, the directional dose equivalent, and the personal dose equivalent.
An earlier question "What is the difference between Sievert and Gray? A practical question concerning the SI units for ionizing radiation?" addressed the confusion of Sievert and Gray and its use in radiation protection programs. This question is a continuation and addresses the practical aspects of calibrating and interpreting instruments used for radiation protection.
The ICRP asserts it has proposed measurable quantities, but have defined them by calculation. The calculation is ideal and impractical for measurement as a parallel expanded beam of a single energy is not possible to produce. The point of dose is at a depth in a sphere or slab, a location not accessible to an instrument. Actual calibration must be performed free-in-air with a non-uniform beam and with physical constraints that may not be negligible. Calibration is to an instrument that is energy dependent and does not have the backscatter characteristics of a sphere, slab, or human body.
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Dear Joseph,
I first read our old discussion again, in order not to repeat to much.
I think you had a look at my chapter about doses and dose units. The central point there is, you can calibrate a dose meter using exaggerating geometries like enlarged and adjusted fields in special phantoms. That means that your calibration factors contain  attenuation and scattering from the phantom and maximal enlarged fields. If you now add the radiation quality factors Q you indeed can factor in the kind of radiation (light or dense ionizing).
I have strange problems to use the unit Sievert (Sv) for "physical" operational doses used for measurements and body doses like organ dose and effective dose which are used to estimate risks.
For the information of other participants in this question I add again my textbook chapter, where you can find the calibration geometries, phantoms and dose definitions etc.
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In theory an alpha particle has 2 electron holes giving the particle its ionic charge. With the alpha particles' velocity, could a series of dropleton like phenomena be formed in its wake until enough energy is transferred away from its velocity for electrons to achieve a stable orbit around the emitted nuclei? I'm currently looking at radiation effects on lung tissue in mice and would love to be able to apply these observations with some confidence in my write ups.
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My first though is that you are trying to make things too complicated. An alpha particle is best thought of as a cannon ball loosing its kinetic energy by impact. Electron holes are a lattice phenomena; the alpha particle has two positive charges not electron holes. There is no evidence that an alpha particle experiences drag in free space.
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Can a He-Ne laser emit ionizing radiation?
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No. But air ionization can be induced by high voltage, applied to the tube.
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Since unpolarized light becomes polarized by Rayleigh scattering (specially if the scattering angle is 90º), one may think that the same happens with X or gamma rays in the Compton scattering. And if this scattered radiation undergoes a second scattering, the angular distribution (differential cross section) will not have azimuthal symetry any more as ussually assumed, due to the polarization. Am I right?
If that is true, it is not mentioned at all in the context of radiation transport in medical physics or other practical applications of X- or gamma radiations. I suppose in the worst scenario it would lead to very small changes in the absorbed dose distribution, but may there be any situation in which the effect is not negligible? Do Monte Carlo simulations ( with EGSnrc, MCNP, PENELOPE, GEANT, etc) take this into account?
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Compton Scattering is sensitive to linear polarization of gamma rays and x-rays. 
This sensitivity is governed by the KELIN-NISHINA formula which gives the differential scattering cross section for Compton scattering of polarized radiation. Because of this property, several Compton polarimetres were constructed and used for measuring the degree of linear polarization of photon beams. The sensitivity of such polarimeters are relatively high below 4 MeV photons.  One such Compton polarimeter is described in the literature (see e.g. Nuc. Inst. Meth. 98 (1972) 13-20 ).which also contains relevant literature concerning your question.
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Oxygen metabolism is key to eukaryotic life and important for signaling as well as metabolism. Yet, ROS are linked to cancer and aging as well as inflammation. There is also a possible link between stem cells and levels of ROS. With new in vivo imaging, and other methods ROS levels may be more evident at the individual cell level and in response to environmental stresses. 
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Another interesting point is that both tumor microenvironments and stem cell niches tend to be hypoxic. Depending on the metabolic rate of the cells this can lead to more or less ROS. A stem cell niche might be preserving itself from ROS during quiescence, conversely tumor stem cells might be driven to death while dividing in a hypoxic environment created by antiangiogenic drugs. It seems important to gauge the level of hypoxia, metabolic rate, and ROS buildup of a given niche or tumor model to get a real sense of what is going on.
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I want to treat the soybean seeds with an electron beam to enhance the overall food quality.
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This depends on the type of microorganisms and degree of contamination: First you have to check existing microorganism variety on your product (e.g. PCR analyses) and find the most harmful ones. Get the inactivation resistance against electron beam treatment to find the right dose for the required inactivation. With low energy electrons about 12 kGy should work, but it can be tricky to reach the microorganisms in the shady areas of the soybean.
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