Ionizing Radiation - Science topic

Here are a few features that could enhance dosimetry equipment for dose calibration or personal protection:

Excellent! Thanks a lot Gerhard!

Ok sir, thank you very much

It is done by usual photodetectors which have to be calibrated. Also, one needs to take into account light coupling losses. E.g.

It depends on medical managment inclding triage is high throughout assesment of radiation recivied should be cosidered .for more detailed read the attached ref.

http;//ncbi.nlm.gov>pmc

Hello Frank P. Dawry

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?

Dear Moez,

I think you might want to use the ReCiPe 2016 method instead. Would you be able to do that? ReCiPe calculates 18 midpoint indicators and 3 endpoint indicators.

Here, endpoint indicators show the environmental impact at three higher levels of aggregation, being the effect on human health, the biodiversity, and the resource scarcity. With each aggregation step, uncertainty in the results increases !! I'm using GaBi software not SimaPro, so it came to my mind suddenly now.

Best wishes,

Viktoria

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.

Hello Elisa E. Córdoba

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.

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.

For derivation of dose limits, radiation weighting factors, tissue weighting factors etc, you may be interested in

Hello sir . Thanks a lot for helping me to get the informations. Really appreciate it. Many thanks sir

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.

Thank you.

На жаль я не фахівець з цього напрямку

Can anybody answer this Q

I am interested in observing change in threshold voltage from transfer characteristics . How to relate this with surface potential and radiation dose?

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.

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.

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 = E_hv / E_eh 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.

@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.

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).

http://cancerres.aacrjournals.org/content/70/7/2984.long

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...

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?

@All. It appears that the bio materials contain high Z element mixed or embedded while preparation. It may be Bismuth etc. In such cases, bio materials etc may be useful and a substitute to lead based Aprons. I think vendors do not reveal the formala or recipe due to commercial and trade secret aspects.

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:

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.

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.

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.

Your doctor may request a mammogram, which is an X-ray of the breast, to help distinguish between a benign and malignant mass.

Ultrasonic sound waves can be used to produce an image of breast tissue.

Your doctor may suggest an MRI scan in conjunction with other tests. This is another noninvasive imaging test used to examine breast tissue.

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:

The tissue affected determines the type of 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.

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:

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:

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:

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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@Abubakar: For trainees the dose limits are 1/3 of the dose limits for occupational workers in India. These are specified by National Regulatory Authorities. The number may vary from country to country but the dose limits for students/Trainees (>16 years) are lower than that of occupational radiation workers.

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.

Dear Sir, 

I think you can get benefit from the document below.  

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.

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.

You may further refer to n/p versus Z or A in standard nuclear physics text books.

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.

Hi Shrikant,

I published a comprehensive review article on the subject several years ago. Here are the links to my paper:

and

I hope that helps.

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.

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. 

https://www.ncbi.nlm.nih.gov/pubmed/10220401 

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.

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.

 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

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!

My pleasure, Ms Nkiruka Adesiji

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.

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

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.

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.

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. 

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).

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).

You can also use IR and near-IR spectra. These methods are cheaper and often more easily applied to such samples.

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.

Yes, it is very helpful. Thank you very much.

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.

Thou

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.

I believe ICRP Publication 123 has the correct information. For simulations, I recommend using SPENVIS.  https://www.spenvis.oma.be

Jupiter specific information:

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.

I should thank members for their opinion.

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.

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.

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.

Yes, but the journals ask for the use of SI!

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.

Thank you Dr Roman V. Gulyaev. The article u mentioned is very helpful.

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

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.

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.

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. 

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

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

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.

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.

No. But air ionization can be induced by high voltage, applied to the tube.

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.

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.

Thank you very much Dr. Dimitrios for your answer. 

Thank you 

for your additions. 

Regards 

Hi Brenton,

It was nice meeting you recently and chatting a bit.

Dan's answers are right on. I'd only add that typically it takes between 1 minute (Quaternary samples) and 2 days (Archean samples) of irradiation to build up the necessary amounts of 39Ar.

After irradiation, it typically takes between 4 and 6 weeks for the samples (and their wrapping) to "cool off" before they can be safely handled.

Hope this helps.

Paul.

Dear Mahomar. Please use well defined terms in your statements. "to dissociate it" means in the discussed reaction the photoinduced dissociation of H2N-H bond, This requires energy of 435 kJ/mol. The Hess's Law is thermodynamically correct. The reaction 2 NH3 -> N2 + 3 H2  is NOT the dissociation! According to IUPAC 

The dissociation is 

1. The separation of a molecular entity into two or more molecular entities (or any similar separation within a polyatomic molecular entity). Examples include unimolecular heterolysis and homolysis, and the separation of the constituents of an ion pair into free ions.

2. The separation of the constituents of any aggregate of molecular entities.

In both senses dissociation is the reverse of association.