ResearchGate Q&A lets scientists and researchers exchange questions and answers relating to their research expertise, including areas such as techniques and methodologies.
Browse by research topic to find out what others in your field are discussing.
- How the performance of an optical detector is independent of temperature?
( of course other than the method of, "using a polymer layer with an opposite temperature coefficient .")
I want to decrease the effect of temperature non-linearity on refractive index and so on some properties of ring resonator based photodetectors, such as " Quantum Efficiency", " Responsivity", " Dark Current", "BEP" and so on....
the use of polymer cladding layer with opposite temperature coefficient , has been studied in previous works.
Another approach would be to use the material with gradual dependance of its characteristics on temperature. Some materials are more sensitive to temperature than others.
If you are speaking about large-scale temperature changes, then you can add a temperature sensor to your detector, carefully calibrate all parameters of your detector based on temperature, and then adjust the output in software.
Some effects such as black-body-radiation at higher temperatures will be impossible to avoid regardless of the material used.Following
- Statistical Software Opinion?
I know there are a lot of statistical software on the market both paid and free. What is your opinion on choosing the best considering all of value, ease-of-use, flexibility, reliability, brand name, quality, etc.? What kind of analysis do you often perform with the software in which field? In your experience, please rank from the best to the least.
For me,SmartPLS is useful for the market research.Following
- How can one induce diabetes in hamsters by STZ injection?
I tried to induce diabetes in hamsters with high cholesterol diet by STZ injection. I used a dose of 50mg/kg BW for 3 consecutive days at non-fasting status. My hamsters died in the following 2 weeks. The remaining were high in plasma lipids and glucose with very bad health condition. How can I improve my protocol and decrease the mortality? Thank you
Actually it depend on what type of diabetes u want to develop. In my case i want to develop type 2 so i hv tried 40-45mg/kg bw of STZ. In my opinion and experience, 60mg/kg bw might cause greater effect towards the subjects (maybe it seems to develop late-onset of diabetes characteristics)Following
- Is censoring in WSN's the best/state-of-the-art mechanism to achieve energy-efficiency in WSN's?
As I go through the literature on censoring, I have a feeling that, apart from having to deploy sensors that are smart and expensive, I do not see any other disadvantages with censoring. Can any one point out possible disadvantages associated with censoring?
WSN stands for Wireless Sensor Network. My apologies for not writing the expansion.Following
- How can I select solid45 elements in ANSYS (mechanical APDL)?
I can only find a limited number of solid elements but while reading the options in the ''help'' of ansys, many other elements are available.
Thank you so much sir.
How can we assign ''elements attribute'' selecting one solid elements at a time since i m using three solid elements,is there any option to hide one volume and select other volumes???Following
- Does anyone know of any studies that pertain to the effects of eccentric resistance training, more specifically the effects on flexibility?
Looking for a study that focuses on or at least includes data on the effects of eccentric resistance training on flexibility.Following
- Does anyone know how to convert IU/mg to ug/ml?
I have a EU monograph reference standard gentamicin sulfate which stated 660 IU/mg, how can I convert it to ug/mg for test?
I found that some people said 0.01mg = 1 IU
However, from online converter stated 660 IU/mg = 1030 ug/mg
It makes me so confused, is there anyone have idea?
Thanks all of your comments and refereed linkFollowing
- What is the difference between additive layer manufacturing and welding?
Is there any logical difference between ALM and welding?Following
- Is there any difference between Optics and Photonics ?
As we know, BASIC terminologies and their meanings in science are not something used randomly because they represent some particular or specific ideas! Since I study Optics I tried to understand the clear-cut difference between Optics and Photonics ! Some scholars use them interchangeably. Where as others think that they are two separate entities that Optics represents classical concepts of light while Photonics is for quantum aspects. For example, in this article,which I found reasonable,( http://optics.org/article/32348 ), we can see that there is no convention among exerts regarding the two terms! Thus, I perceived that there is no clear-cut difference or we can use them interchangeably! However, I am still not satisfied and want to know more if there is some scientific definition or method to differentiate them clearly! Besides, as fields of study, Optics and Photonics should have clearly defined meanings if they are two different things.
Thanks in advance!
In addition to the answers provided above, photonics is often used to describe fiber-based or on-chip-integrated systems, while optics applies to free-space experiments using large standalone optical elements, i.e. integrated photonics and bulk optics respectively.Following
- What is the best weight percent for making successful metal oxide doping?
What is the best weight percent for making successful doping? Should I use 0.1, 0.3, 0.5..... molar ratios?. or 0.01,.0.02...or 0.001, 0.002..0.003 molar ratios?
Dear Dr. Wahba:
Please, considere another way to measure the amount of cation that not weight percent. Due the great difference of densities between compounds to attain stoichiometric calculus seems important to count each cation present, then atom percent or mol percent should be mandatory in a doping...
There is not a specific number. It is necessary to consult the "phase diagram" of mixture but effects on the color, electric conductivity, dielectric behaviour etc,...etc are expected be intense with low amount of dopant. Also, typically, anomalies are expected during analysis at great intervals of doping. Typically, the property monitored in non linear with dopant concentration. At cromophores dopant, the emission effect is only observed at low concentrations, high concentration of dopant cromophores induces a kind of phenomenon called "quenching". As a general approach, the doping can be carried out up to limit of solubility, while a solid solution exist (nor segregation or secondary phase is observed).
Values of order of 0.001 % or 0.1 % are every possible of dissolve in the host, in a broad sense. A priori, should exist a international Table or paper or Synposium that report the limit of solubility of solute (doping agent).
Typically metal transition oxide supports to dissolve a great amount of doping, as an example, in ZnO a great amount of cation cobalt or manganese, more cobalt. It is possible a solid solution ZnO with cobalt at 3% in mol, the solid soltion ZnO.Co is a pale green, while ZnO is white. Also, ZnO.Mn is possible at large amount, low Mn doping gives a yellow-redish and high Mn amount gives a solid solution brown-redish.
See, ternary systhem (Zn/Co/O) type 97% ZnO + 3% CoO, ( 0,97ZnO + 0,03CoO), in a general way exhibit a simple behaviour. But it is possible complex phenomenon, type synergetic effects, as in the quaternary (Zn/Co/Mn/O): ZnO + CoO + MnO4/Mn2Ox. In this mixtures, the solubilty limit of a dopant is increased by the presence of another and vice-versa.
In cases where consult of the phase-diagram of the mixture is not possible, similarities of ionic radi and valence between cation of the host structure and dopant cation can mean a good solubility. Conterclockwise, the limit of solubility tend to decreasing or in not possible.
Marcos Nobre (M. A. L. Nobre)Following
- What is the physical cause of photoluminescence in a plasmonic nanocomposite?
Specifically, I'm referring to spherical noble metal nanoparticles within an optically transparent glass. The papers I have read seem to gloss over the underlying physics. This is really a two-part question:
1) Since the wavenumbers of light and the plasmon must be equal (dependent on the plasma frequency) for plasmon/polariton coupling, why is absorption observed over a range of wavelengths, rather than a narrow band?
2) If I am understanding correctly, the plasma frequency is constant (dependent on electron density, particle size, etc). In the case of the nanocomposite, how is the absorbed wavelength different from the emitted wavelength? Where does the energy go? Is it lost as heat in the metal nanoparticle? If that is the case, how can the frequency of oscillation of the plasmon be less than the plasma frequency?
Any help is appreciated.Following
- What is the best approach to obtaining competition in construction alliance bids?
Construction alliances are a form of procurement that seeks to reduce adversarial approaches to the construction process, while improving innovation. How can alliance firms be identified that will also be market competitive?Following
- How do you send a beacon message in ns-2?
How do you send a beacon message containing informations like position, and how do you extract this information and signal strength by a second node?
Thank you for your response, bu I work on WSN . I dont think it is the same case as VANETFollowing
- Is there a role of Geriatric Colorectal Surgery as a special service?
There is an increasing trend in the number of elderly patients with colorectal pathologies.
I request all to explain the reasoning to support thier answer/view.Following
- Does anyone have experience with blotting proteins from Agarose gel to nitrocellulose membrane?
I am separating multiprotein complexes with DNA on agarose gel (sort of gel shift assay). I use DNA loading dye and TAE buffer for separation (without SDS)and I want to transfer it on nitrocellulose membrane to detect proteins in complex. Does anyone have prior experience with this ? suggestion will be appreciable.
I did tons of Western blots with SDS-PAGE onto membrane but never agarose gel. How thick is your agarose gel? Maybe you could give semi-dry a go?Following
- How to create a pdb file of the standard RNA triplex?
I need a pdb file of RNA triplex to do Molecular dynamics simulations. Do you know what software or method can be used to create structures of a (the) standard RNA triplex? Thanks a lot.
To Danish Jasnaik ,
Thank you, Danish. Yes, the Open Babel software is powerful and useful in creating chemical data file. However, my problem is that I have nothing information about triplex except their sequences. So, I hope there are some tools, which can be used to produce RNA triplex from a sequence. Thank you all the same.Following
- What are the reasons for the difficulties in achieving the same cell density in an embryogenic cell culture of the same genotype when repeated?
When I first started a cell culture from leaf explants, it produced a very high density dispersed cell culture and I could produce large amounts of somatic embryos. When I tried to repeat it, the cell density is less and the culture is growing much slower than before. We used the same media, same culture conditions and same genotype.
As it is pointed out the physiological age is crucial in cell culture or in any other tissue culture for that matter. However once you obtained high regenerating cells you could use the same reserved cells for repeated culture to certain extent since it is same genotype species etc. I used to monitor the physiological age by noting down the germination time or for axillary buds, the bud break time and the explant position in case of leaf.Following
- What the impact of resource allocation in social media ?
here i mean by the impact the challenges of resource allocation in social media
The first question to ask is what type of social media strategy are you trying to adopt and for what type of organization? Depending on the strategy an assessment can then be made about resource allocation-ie how much in terms of people, hours to be devoted to the activity, tools that are required and so on. This can be costed. ROI is calculated in terms of measurable impacts-which may include hits on web sites, mentions made, new customers, and product sold as a result of social media marketing campaings.Following
- One possible misunderstanding about p-values in multiple testing?
Here is one example of an analysis and reviewer response I've seen a few times, and I'm wondering what you all thing about it. I want to see if I can find a good way to explain it to people, to respond to reviewers, and to avoid it in the future.
Example: Say we do an analysis reporting randomized experiment results for a basic 2-condition design (control v. experimental condition). We test differences between condition means for 20 variables. All variables are "independent" outcomes based on different questions in the survey. I say "independent" in quotes because while they may be related by being from the same respondents, and may have an objective correlation, they are not mathematical combinations of each other (i.e., they are not re-codes from the same survey item). Some are categorical and some continuous so we use a combination of independent samples t-tests and chi-square tests. No multiple testing adjustments are done. All variables are conceptually-relevant, so we're not just fishing here, although the work is exploratory.
Results: We find one significant difference at the alpha = 0.05 level.
The reviewer responds with something like "You have tested 20 items and only found one to be significant, which is the number expected by change at alpha = 0.05. I don't think these findings are very strong or reliable."
Here are my questions.
Q1: Check my knowledge/reasoning
To me this seems like a misunderstanding of p-values. This is always hard to say in words, but here goes...I understand p-values (and alpha-level) as reflecting the risk of rejecting the null when it's true (the probability of a Type 1 error). However, they apply only to individual tests, not the cumulative number of tests you do in an analysis. Reviewer comments like the one above seem to reflect a notion of "study-wise error rate" (i.e., the probability of finding any statistically-significant difference where there truly is none in the population), but that's not what p-values are about in my understanding. My statistical training is mostly applied, so I'll admit I may be missing something here.
Q2: Should multiple comparison adjustments be done in situations like this?
I understand the need for doing multiple comparison adjustments in post-hoc ANOVA tests (and similar) where the various comparisons are known to be correlated because they come from the same items and have the same statistical information, but situations like the one I'm asking about here are less clear. It seems to be pretty arbitrary how you group all the various tests you might do on a single data set for different purposes (i.e., how would you decide whether 20 or some other number goes in the denominator of the adjustment).
It seems to me that if the survey items are correlated, then adjustments should be made, but if the are not (i.e., are truly independent), then no adjustments are needed. What do you think? Are there more formal ways to think about this? Is this "study-wise error rate" something I should be thinking about and adjusting for?
Thanks in advance.
This is a tricky one, and I am not sure that there is any consensus yet among statisticians. There have been a couple of good papers that discuss the issue, and based on these I usually advise researchers to NOT undertake adjustment for multiple testing, but instead discuss the issue in the Discussion section.
Here are the papers:
Ronald J Feise. Do multiple outcome measures require p-value adjustment? BMC Medical Research Methodology 2002, 2:8.
Rothman KJ. No adjustments are needed for multiple comparisons. Epidemiology. 1990 Jan;1(1):43-6.
- What is Mixed research?
I recently read about Mixed research method and i want to read more details about this method. Is there any references that i can begin with?
A mixed research method can be understood as using more than one method, normally a quantitative plus a qualitative, in different stages of a study to make full use of the advantages (and avoid the disadvantages) of each method.
Following links to Sage Publications may be useful to you:
If you want to know more, you may read articles in Journal of Mixed Methods Research.Following
- What is the difference in your solution?
Please see this paper:
The solution for linear programming problems with bounded variables and a single linear combination constraint is given. Necessary and sufficient conditions for the existence of a feasible solution and for a bounded optimum are derived. This solution is used for constructing a simple 0(n) space and 0(n log n) time algorithm where n is the number of variables. The algorithm has been implemented successfully on a personal computer for problems with thousands of variables.
- Can anyone tell me what is the proper procedure for taking HEK293T cells out of cryovial without them undergoing apoptosis?
I am working with HEK293T cells. Unfortunately, I have run into the problem of my cells dying after preserving them in the deep freezer. After adding DMEM, 20% FBS, and 10% DMSO the cells are then placed in cryovials which are then placed in an isopropanol chamber to be stored in the deep freezer. However, I have taken the cells out and placed them into 10mm petri dishes to grow them again but the cells aren't happy and seem to undergo apoptosis. I have tried adding the cells from the cryovial to a 15ml falcon tube with 4 ml of fresh DMEM complete media containing 10% FBS and 1% PenStrep, spun them down, removed the supernatant and added 1ml of fresh new media to resuspend the cells and place them in the 10mm dish to try and fix the problem. Yet the problem continues and the cells still seem to be dying. If anyone knows how to alleviate this problem please let me know. Thank you.
Hi, I work with HEK239 and 239T cells for many years, and never had any problem with bringing them up from -80. I would suggest freezing your healthy cells in growth media + 10% DMSO when they are at 80% confluency (you should never leave them reaching 100%). Minimise the DMSO exposure time by pre cool your freezing media, and when bringing them up, wash off the DMSO as soon as the cell thaw in 10 ml of pre warmed growth media. If you have low cell density, grow them up in a smaller plate/flask first, once reach 80% seed into bigger flask. Hope that helpFollowing
- Does anyone know any paper where the primer purity or supplier source has been compared in saturation mutagenesis experiments?
I need to know if desalted primers can be better than HPLC...
I have tried several mutations myself as well as for my labmates. My understanding indicates, there is not much difference in two categories of primers as anyway you are going to do selection and sequencing studies later.
Start with anyone category, select multiple colonies, purify and get your DNA sequenced. I am sure you will find few sequences of your desired mutation if you select 3-5 colonies during selection.Following
- How can I calculate the effect-size for a repeated measures t-test?
I use an online calculator for between subjects t-tests, as my version of SPSS doesn't seem to offer effect sizes. I recollect checking what it did many years ago and it seemed to be accurate. So if anyone can point me to an online calculator for repeated measures effect sizes, I'd be most grateful.
I see several approaches here.
Online calculator paired t-test
If you are working from a t-test output, Lenhard & Lenhard's calculators help. Subheading number 4 provides a calculator for both paired and independent t-tests. You need to also know the correlation between the paired groups in order to calculate the effect size (I'm not sure if it returns Cohen's d or Cohen's dz, though).
Online calculator paired groups
If you have descriptive statistics for each group, you can plug them in Wiseheart's calculator. You need to also know the correlation between the paired groups in order to calculate the effect size (I'm not sure if it returns Cohen's d or Cohen's d4, though).
Hand calculation of Cohen's dz
An alternative approach, if you own the database, is to calculate the effect size by hand. The simplest way seems to be that provided by Cohen (eg, 1988), which chiefly ignores the correlation between paired groups but suffix for the case when such correlation is not known:
1) create a new variable of the differences between both groups (z = Time1 - Time2),
2) obtain the mean (Mz) and standard deviation (SDz) for this new variable,
3) divide Mz by SDz, which will give you the effect size for dependent groups (dz = Mz / SDz)
4) (Optional) For comparability purposes, Cohen's d = dz √2
Hand calculation of Cohen's d4
If the correlation between groups is known, then another alternative provided by Cohen (eg, 1988) is to calculate the effect size using the formula for d but correcting it by r.
1) d4 = (M1 - M2) / SD
2) Cohen's d = d4 / ( √1 - r )
COHEN Jacob (1988). Statistical power analysis for the behavioral sciences (2nd ed). Psychology Press (New York, USA). ISBN 9780805802832.
LENHARD Wolfgang & Alexandra LENHARD (2014). Calculation of Effect Sizes. Retrieved from http://www.psychometrica.de/effect_size.html on 24 November 2014.
WISEHEART Melody (2013). Effect size calculator. Retrieved from http://www.cognitiveflexibility.org/effectsize/ on 24 November 2014.Following
- What are typical ranges of aerobic and anaerobic biomass (sludge) yield?
I want to know about typical ranges of aerobic and anaerobic processes' biomass (sludge) yield in wastewater field. I already searched some references, but I couldn't find the typical range of above two processes. can you tell me the typical range and references?
- How can I plot/determine ROC/AUC for SVM?
ROC: Receiver Operator Curve
AUC: Area Under Curve.
I don't totally understand your question, but I suppose having a look at the following links may be of some assistance:Following
- Can light evoke feelings/experiences to define a type or function of space?
If so, how does it work?
I'm currently doing research regarding architectural atmospheres which I'm focusing on light where I found this quite interesting after I read a couple of articles about "Church of Light" designed by Tadao Ando, where he uses light to increase the occupants' awareness/feeling of the spiritual and secular within themselves.
I'm planning to dig deeper into this topic.
Thank you for your prompt response to the question. I really appreciate your help for giving me the information and suggestions about lighting that helped me a lot with my research.
By the way, I want to know your opinion regarding emotions/feeling: Is emotions important in architecture? what I see nowadays they prefer to focus on aesthetic and functional but often forget to trigger an emotionFollowing
- Why I am getting multiple bands in PCR?
I set up PCR reaction volume of 50ul with Taq polymerase and I found distinct band of amplicon but when I double the reaction volume to 100ul to get higher volume of amplicon I found multiple bands of different sizes!
Can anyone help me to sort out the issue.
As pointed out above, either your primers are not annealing properly because of the temperature, PCR conditions or poor primer design, so you need to try changes in temperature and conditions to see if that makes any difference, if not, you may want to try new primers.Following
- What is the best procedure to activate monocyte macrophage and drug treatment?
Hello everyone. I want to check some protein expression in activated THP1 macrophage by treating PMA. What should be the best procedure for adding drug (for example rifampin)? Should add the drug with PMA solution or after activating with certain periods (48 hours or 72 hours with PMA treatment)?Following