Q&A

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27
A particular Riemannian metric on R^n?

What is  an explicit formula for  a Riemannian metric on R^n such that the restriction of this metric to the unit sphere gives us the standard Euclidean distance $\sqrt \sum (x_{i}-y_{i})^2$  on S^(n-1)?

Note that the standard Riemannian metric does not satisfies this property!

For such metric, how is the shape of geodesics of S^{n-1}?

Dear Ali:

The metric  d(x,y) = |x-y|  for  x,y \in S^{n-1}  does not come from any Riemannian metric on S^{n-1}; in particular it is not induced by any Riemannian metric on R^n. The reason is that S^{m-1} with that metric is not a length space. A metric space (X,d) is called length space if for any x,y\in X the distance d(x,y) is the infimum of the length of all rectifiable curves from x to y. It means that the distance  d(x,y)  adds up as the sum of distances of "neighbouring points" between x and y. Aparently, d(x,y) = |x-y| does not have this property: Adding up the distances of very close points on a great circle between x and y one obtains the euclidean length of the great circle segment which is bigger than |x-y|.

Concerning your later question: "Let (M,g) be  a  Riemannian manifold and N is  a  submanifold of M such that the metric induced from restriction g to N coincide to the original metric induced from (M,g). Does this imply that N is  a  totally geodesic submanifold of M?" The answer is yes (the Riemannian metric is just the infinitesimal version of the distance function), but the converse statement does not hold in general: A totally geodesic submanifold need not have the same induced distance function as the ambient manifold since the shortest geodesic in M between two points in N need not be contained in N. If this stronger property holds, the submanifold  N is called convex in M; convex is stronger than totally geodesid. Here is an example of a submanifold which is totally geodesic but not convex: Let M be a flat 2-torus whose fundamental domain is a rhombus with a short and a long diagonal, and let N be the long diagonal. Let p be the center of the rhombus (the intersection of the two diagonals) and q the vertices of the rhombus which are identified to one point in M. The distance between p and q in M is the half length of the short diagonal, but the distance in N is the half length of the long diagonal.

Best regards

Jost

5
How do you measure IPCE of DSCs (DSSC)?

Dear colleagues, do you often measure IPCE of DSCs (dye sensitized solar cells)? What equipment do you use? If you use lock-in signal detection what frequency do you usually use? Recently a setup for IPCE measurement was assembled in the lab, so I would like to share my experience and to discuss some details with you.

So, what parameters do you use?

11
What should be the minimum duration for conducting a cohort study?? is there any specific guideline??

can cohort can be followed up for 1 month...

8
Has anyone worked on predicting the thermal conductivity of bio-molecules using LAMMPS?

I am working on topic to predict thermal conductivity of bio-molecule using Lammps. I have got read_data file with all angles and dihedrals. If somebody can provide the Lammps code for worked out problems like this that would be more helpful (apart from Lammps website examples).

Dear Jamie, I have also used something similar to this. Do you have any published reference for this? Thanks

Alex

9
How can nodes be found in resting state functional connectivity?

in resting state ,for graph theory , how can voxel  define  as nodes and how can extract them from FMRI data?

Functional connectivity toolbox is the best I guess for graph theory and to determine the nodes involved for a particular task- here is the link: https://www.nitrc.org/projects/conn

7
How can we identify drug interactions in vitro?

If I am treating cancer cells with the more than two drug. Then would it be possible that one drug react with another drug. So what would be possible methods to study drug interaction.

Try to use the following paper and link.

Best wishes

+ 1 more attachment

• Vaijanath Chinchane asked a question in Integral Equations:
New
How to solve voterra integral equation by any software ?

Is there any book for the programming for such problem?

1
What is the relationship between amplitude ;level of a signal in the time domain and the magnitude of the frequency spectrum?

I applied spectral subtraction technique to AE signal by subtracting the recorded noise spectrum from the acquired AE spectrum (NB: AE data contains both AE and spindle noise influence). the ifft of the residual in the time domain indicates higher amplitudes in the result compared to the time domain amplitude of the signal + noise. why is that so? does it mean that lower frequency content results in high amplitudes in the time domain, is there any explanation to support this inverse proportionality

I'm not sure about your specific application or if this answers your question, but you may want to consider multiplying your FFT output by the sample period (1/sample rate).  This will give you a more consistent scaling for your FFT output for different sample rates.  Otherwise, consider using a unitary DFT, which is usually just an additional scaling of 1/sqrt(N) that you apply to your FFT output (or input), where N is the length of the input signal in samples.  You may also have to consider other rescalings if zero-padding is applied..

4
Aspergers 'Fountain of Youth'?

People diagnosed with Aspergers Syndrome, ASDs and ADHD are often reported as appearing much younger than their real age, can any research indicate this?

Thank you Alan :)

Ok, my search for literature to explore the notion let alone support it has also been fruitless, so I needed to ask this question to try and see if a gap exists.

I can find and furnish the blogs, posts on community chat rooms, forums etc.. and non academic online articles that mention it, if what is occurring here in responses is an actual skepticism over where my idea has originated. Further, I accept at this point fully that even those sources are sporadic and inconsistent. They would not constitute a legitimate body of evidence even for exploratory research.. but I can certainly show some form of community-led basis outside of my own imagination, to explain my curiosity for academic feedback If anyone is interested?

I'm on the spectrum.. ergo, it has not been overlooked on my part that my own observations with those I have met, informal disclosures from other Aspies and ADHD patients telling me they receive this feedback on their appearance, along with consistent responses over reactions to my own age disclosure as I reach middle-adulthood... are hardly scientifically valid.... and could easily be a result from contaminating effects of a 'leading' or unintended 'coaching'  style to my own discourse. Perhaps inherently biased reactions to all of the above examples on my part, is merely support for my own potential traitwise display of a Theory of Mind deficit.

This is exactly why I have put the question to this forum. I am still curious as to whether I have stumbled upon potential phenomenological evidence of a folk theory.

If it has not occurred to relevant industry practitioners and professionals and academics researching with their participants to explore the question with those on the spectrum - and I fully understand it seems there is simply not sufficient exposure of the concept in general for this to seem relevant or worthwhile... i'd like to raise the possibility that it would equally not occur to many of us on the spectrum to ever raise our experiences with this in our contact with interviews and surveys - as a pragmatic or literal outcome of how many of us generate ideas in discussions.

I had to ask because (if something real OR imagined is occurring 'out there') of the potential for; genetic research implications, cultural origins and impact of behavioral interpretations upon age perception, what it might contribute around knowledge of cultural, social and cognitive biases, lifestyle factors in aging research and even the diagnostic angle. Implications and applications that could be generated.

I'm not attempting a hoax, i'm not deluded or misinterpreting the discourses I refer to.. nor the contexts that frame them, and this would be a terrible way to attempt to establish a profile for myself in the academic world! My question was genuine, if ultimately a waste of time for science. I can at least find and furnish links to the invalid sources that do persist online, to support my entirely genuine intention here.

I'm still interested to research how to formulate an exploratory survey, or other forms of methodology that can load sufficient controls around establishing some kind of hypothesis or finding on the matter to resolve my genuine curiosity as to why this belief and perception occurs at all, due to my own informal experiences as described. It's not an isolated occurrence just with me, as mentioned other independently have put this observation in online discourse with no prior influence or contact on my part.

I ask the question because the idea keeps turning up, for years now, as I pursue my own special interest over the Autistic phenotype in all of it's myriad manifestations.

Perhaps I should think of this in a similar light to another example of potential folk theory generated in online circles frequented by people on the spectrum; the persistent (yet scientifically unfounded) community-led belief that Autism is a 'revolutionary' evolutionary process... seemingly founded on unscientific notions, extrapolations from non-general evidence of cultural and functional advantages to some autistic traits in some arenas of daily life, misconstrued, conflated and misinterpreted data correlations, and plain old logical fallacy. Scientific contention and a lack of basis in validity, reliability, replicability does not prevent the increasing spread of many more popular concepts over Autism, that I understand.

So I certainly thank you for the response. You might just have saved me a great deal of time. I have covered all of my thoughts over this to clarify my contact here.

I am a verbose 'Aspie' with much to say over this topic - but any other responses i give can now be more sufficiently brief and appropriate to the purpose and format of this site.

Thanks again, I am confident the responses so far clearly reflect a professional and authentic reflection of those established across relevant disciplinary fields in general.  Still happy to receive further feedback to further consolidate the response outcome, and would be grateful for any other ideas as to what has happened for the concept to emerge at all, informally in community circles where autism is discussed.

If so, i'll make any further contact on my part brief and simply relevant to your response. If the responses remain substantially consistent that simply mean's i'll thank you for taking time to support a clarification for my understanding. From here i'd just be interested to collect responses as a reflection of scientific opinion I can introduce where applicable in any further discussions accessed, if this concept is raised or come across again.

Gram

2
Does anyone have an idea on why qPCR would stop working (amplifying) for a non-model organism?

I have been working on a species of deep sea coral and trying to determine the primer efficiency for two potential control genes or HKG. The samples were amplifying and I was able to narrow down optimal annealing temperatures to get the primer efficiency for both in the range of 95-100%.

When I ran out of cDNA for the two samples I was using, more was made but the samples were not amplifying as they were before, some not even at all. I tried cDNA from those same samples and from different samples of the same species with no luck. I would occasionally get amplification in a 1:10 dilution only, or a 1:1 and 1:100 but not the 1:10 or 1:1000 dilution- which makes no sense to me. [Annealing temp. 59C and 10uM primer concentrations]

I also tried re-running a temperature gradient to include the temperature that was originally thought to be optimal (59C) to 63C and only one sample amplified at 63C with a high Ct value (~38). The other sample did not even amplify at that temperature.

I have tried new primer dilutions (from stock) and also ran one of the primers on a different coral species and the amplification was fairly normal.

I tried troubleshooting the RNA extractions, but the 260/260's are ~2 and 260/230 are >1. The 28S and 18S ribosomal bands also appear clear on the gel and no clear sign of degradation is present.

I then tried troubleshooting the cDNA synthesis (SuperScript III First strand kit) thinking there may be contamination, bought a new kit and got similar results.

Any ideas or suggestions are greatly appreciated!

In retrospect now not sure if my prior answer goes to the heart of the problem. Have you tried testing primers by RT PCR using agarose gels ?

New
Who is a real nurse?

Nursing is a profession within the health care sector focused on the care of individuals, families, and communities so they may attain, maintain, or recover optimal health and quality of life. There are many definition about a nurse.

OK.

What is your definition about a real nurse? Is it a profession, job or work?

Who is a real nurse? What is his/her characteristics?

4
How to select a good, small sample?

This is a sampling question. We are interested in interviewing only 15-18 patients out of, say, 500 sampling frame. What method could we use that would give us the most valid sample? For instance, would you select within a certain age range, or just random sample? Thanks!

For quantitative purposes for continuous data, purposive sampling can be used if you have regressor data, and can separate data into groups for modeling purposes.

Here, using the link below, are examples of looking at one modeling group and category at a time, to determine sample size needs.  It is written with skewed data, an establishment survey, in mind, but works the same way in your case, except your x would be administrative data on all 500 cases (well, the part of the 500 within a given modeling group) in the population.

https://www.researchgate.net/publication/261947825_Projected_Variance_for_the_Model-based_Classical_Ratio_Estimator_Estimating_Sample_Size_Requirements

........

However, you could just do a simple random sample first, and see what kind of estimated standard error results you obtain, for each variable of interest.  This is especially true as I do not know what kind of data you are collecting, but I am still assuming that you are collecting some kind of numerical data.

Standard errors, bias, sampling and nonsampling errors are all important considerations for quantitative data, and one should generally at least estimate standard errors.  For continuous data (my expertise), and yes/no data, it is essential.

• Source
##### Conference Paper: Projected Variance for the Model-based Classical Ratio Estimator: Estimating Sample Size Requirements
[Hide abstract]
ABSTRACT: to be found at http://www.amstat.org/sections/SRMS/Proceedings/ Joint Statistical Meetings (JSM) 2013 - Session 89 Projected Variance for the Model-based Classical Ratio Estimator: Estimating Sample Size Requirements Sponsor: Survey Research Methods Section Keywords: Model-based Estimation, Classical Ratio Estimator, Official Statistics, Resource Allocation Planning, Volume Coverage, Sample Size Requirements James Knaub U.S. Energy Information Administration. Also, please see: https://www.researchgate.net/publication/263235800_Example_-_Use_of_Appendix_A_Data_-_Projected_Variance_for_the_Model-Based_CRE_in_JSM2013_-_Spreadsheet_Tool Here we explore planning for the allocation of resources for use in obtaining official statistics through model-based estimation. Concentration is on the model-based variance for the classical ratio estimator (CRE). This has application to quasi-cutoff sampling (simply cutoff sampling when there is only one attribute), balanced sampling, econometrics applications, and perhaps others. Multiple regression for a given attribute can occasionally be important, but is only considered briefly here. Nonsampling error always has an impact. Allocation of resources to given strata should be considered as well. Here, however, we explore the projected variance for a given attribute in a given stratum, for resource planning at that base level. Typically one may consider the volume coverage for an attribute of interest, or related size data, say regressor data, to be important, but standard errors for estimated totals are needed to judge the adequacy of a sample. Thus the focus here is on a 'formula' for estimating sampling requirements for a model-based CRE, analogous to estimating the number of observations needed for simple random sampling. Balanced and cutoff sampling are considered. - (When estimating the WLS version of MSE (random factors of residuals only), the smallest observations in previous data test sets may sometimes best be ignored due to their sometimes relatively lower data quality in highly skewed establishment survey data, when samples are frequently collected, as noted by myself and other colleagues. - JRK - October 2014.) ----- For multiple attributes (variables of current interest), this may be applied iteratively, as a change in sample for one attribute impacts the sample size for another. Please see the definitions section in https://www.researchgate.net/publication/261472614_Efficacy_of_Quasi-Cutoff_Sampling_and_Model-Based_Estimation_For_Establishment_Surveys_and_Related_Considerations?ev=prf_pub.
Joint Statistical Meetings, Montreal, Quebec, Canada; 08/2013
40
In GR, can we always choose the local speed of light to be everywhere smaller that the coordinate speed of light? Can this be used in a theory?

It seems that many, if not all, solutions of Einstein's equations, such as black holes and grav. waves, can be given coordinates x\mu in such a way that the local speed of light is always slower than the coordinate speed of light. Think of gravitational lensing: the index of refraction of a gravitational potential always seems to be >1, in practical examples, so a gravitational potential slows light down, and never speeds it up (if coordinates are chosen carefully). This wouldn't be true for a negative-mass Schwarzschild solution, but that seems to be outlawed in nature.

Now this was only a conjecture, I have not attempted to prove it. How would a rigorous mathematical theorem be formulated? And did anybody - and here I mean a wise person, not the average blogger - ever try to do something interesting with this observation? Like constructing a “hidden medium” for curved space-time?

@Amrit Sorli could you please explain why at a stronger gravitational field the vacuum thins out? for slowing light wouldn't you expect the dielectric constant to grow? shouldn't the strain-tensor depend on the vacuum and thereby affect the field? Consider the Unruh effect, since acceleration is equivalent to gravitational field for  larger acceleration you'd expect higher temperature ergo denser vacuua...

11
What are the constraints when we talk about urban development?

What I am trying to question here is, is it the mindset of the people that restricts the development or there is something else which does not support?

Specifically in India, people do not respond the way they respond in the other countries towards different kinds of spaces and towards all kind of development.

Are the decison-makers permanently living in the urban environments they wish to develop, as is the case for most of the citizens that live in urban environments?

87
Are there authentic published work confidently pinpointing the sole anthropogenic factors contributing to Climate Change?

Combined natural and anthropogenic factors (geologically recent phenomenon) govern Climate Change. It is, therefore, of paramount importance to discretely recognize the role of humans in Climate Change and to plan efficient strategy to mitigate it.

Ken

I am talking about science which means that there is a why involvd and thus a a "theory" not just observations like the questioner thinks: there is a moon

The science is why is there a moon, why it moving around the earth why at that disctance etc

As for the weather the plain remark tomorrow is different from today is pseudo science in the sense that is based on milennia of knowledge but what has science to do with this; the science is to project with a theory on meteorology what is coming tomorrow on the basis of what there is today

• Arezou Dilmaghani asked a question in Oil:
New
Could we use n-hexane instead of tetra-decane for creating biphasic system (aqueous and organic) to simulate diesel oil ??
2
Integration of BIM and building energy simulaiton?

Does anyone has experiences in combining a BIM software with building enery simulation and other building physics simulations? How does the IFC works in transporting models?

BIM has many possibilities. Please check: http://aceee.org/files/proceedings/2012/data/papers/0193-000367.pdf

2
Can you suggest a fluorescent dye soluble in polar aprotic solvents?

Hello,

I would like to find a fluorescent dye with absorption in near to mid UV range (≈200-400nm) and maximum emission in the visible, which could be dissolved in organic solvents such as propylene carbonate or other carbonate esters.

I would also be interested in non-fluorescent dyes with similar solubility.

@ Jean Rene: sorry to say, but there is nothing wrong with the question. Polar aprotic solvents are a solvent class of their own: https://en.wikipedia.org/wiki/Protic_solvent#Polar_aprotic_solvents

I would have a look for dyes that are soluble in methanol/ ethanol, these should have similar solubility in polar aprotic solvents ( acetonitrile comes into my mind first).

Perhaps coumarines are a good choice, as they are quite stable, absorb in the UV and emit in the visible...

A short overview on several dye classes with spectra can be found here:

17
Can someone advise on how to use X'pert highscore plus for Rietveld refinement of XRD pattern?
How to use X'pert highscore plus for Rietveld refinement of XRD pattern?

Can anyone advise on how to use quantification icon or quantify a mineral in x'pert high score plus v.2.0 ?

1
Any research work on Quality of Management model by Sumantra Ghoshal and Christopher Bartlett?
Ghoshal and Bartlett in their 1994 Quality of Management (QoM) model posited that the old command and control management model was demotivating and dysfunctional and that leaders in firms should manage with the aim to encourage individual initiative, creativity, engagement, collaboration, learning and development. Birkinshaw and Gibson used this model in their organisational ambidexterity frameworks. Has any further empirical work been done on the QoM?

In my opinion, the quality of management (QoM) of command and control management is inadequate not only for lack of individual initiative, creativity, engagement, collaboration, learning and development but above all for lack of understanding of original discovery of individual researcher.

I have discovered original patent procedure very useful for whole humanity applications.

See:

http://marcolarosa.blogspot.it/2013/04/il-genio-italiano-nonostante-tuttonon-e.html

I have many difficulties for practical applications attainment based on patent procedure.

I thank Krishnan Umachandran for his precious help to me for sharing this information.

Best regards.

Giuseppe Cotellessa

• Phillip Munson asked a question in Exosomes:
New
PKH labeling of exosomes: why do some investigators resuspend their exosome pellet in PBS rather than Diluent C?

Is Diluent C alone, harmful to exosome stability perhaps? Salts present in PBS reduce the staining efficiency of the dye so am curious why people do this step. Just want to clarify, if anyone can help with this question.

Also, has anyone else noticed that PKH67 dye in diluent C (control) has little to no fluorescence signal (Exc. 485/20nm, Emm. 528/20nm), yet has a substantial fluorescence signal when diluted in serum or complete medium? This seems strange, does the dye only fluoresce in certain conditions?

3
Does anybody have a good review article about lack of appetite in inflammatory states?

I would like to know the mechanisms which chronic diseases cause lack of appetite

Dear Luiz,

Cancer and lack of appetite:

• ##### Article: Appetite and Cancer-Associated Anorexia: A Review
[Hide abstract]
ABSTRACT: Appetite is governed by peripheral hormones and central neurotransmitters that act on the arcuate nucleus of the hypothalamus and nucleus tactus solitarius of the brainstem. Cancer anorexia appears to be the result of an imbalance between neuropeptide-Y and pro-opiomelanocortin signals favoring pro-opiomelanocortin. Many of the appetite stimulants redress this imbalance. Most of our understanding of appetite neurophysiology and tumor-associated anorexia is derived from animals and has not been verified in humans. There have been few clinical trials and very little translational research on anorexia despite its prevalence in cancer.
Journal of Clinical Oncology 05/2004; 22(8):1510-7. DOI:10.1200/JCO.2004.03.103
13
Why do we need continuous time signal processing nowadays?

I normally perform discrete-time signal processing and recently I have been finding several research works in continuous-time processing, e.g. : Applications of Kalman-Bucy Filter.

I wonder if these techniques make sense anymore as most signals and time series are discrete registers in computers, which are already sampled.

Does anybody have any application domain where they are relevant?

.

Jesus:

.

Yes, Optics is certainly the domain. The

element I have in mind is a simple prism.

.

Barrie

8
Can anyone recommend good papers on market making and finance?

Hello,

I'm trying to learn the theory of market making strategy (eg. what strategies are employed in exchanges such as NASDAQ, NYSE etc...), but am very new to the field of finance.  Can anyone recommend some good papers on market making strategies, as well as more general papers on quantitative finance?

Sorry, I know this is a broad question, but it would be very helpful!

Ok, awesome thanks

1
How does the presence of different solvents can affect on photo-luminescence of photo catalyst?

I like to know about the effect of different solvent on photo-luminescence of semiconductor photo catalyst. some solvent can act as sacrificial electron donor in  photo catalysis process. I want to how they can affect photo-luminescence.

you can see these papers

Chen S Y, Yang C C, Cheng S Y, Lee H Y. Effects of
phase transformation on photoluminescence behavior of
ZnO:Eu prepared in different solvents. Ceram. Int., 2006,
32: 37.

2
How can a teacher education institution in a developing country institutionalize education for sustainable development?

Difficulties/ barriers

How to sustain this institutionalization?

Dear Kinh,

Education for sustainable development in developing countries comes up against a number of problems:

1. Sustainable development is rarely a requirement in national and provincial programs studies.

2. The teacher certification at the guidelines do not mention sustainable development.

3. There is little or no properly trained specialists familiar with Education for sustainable development.

4. Financial and material resources are lacking or insufficient.

5. There is little or no support for Education for Sustainable development measures in national, provincial and local policies.

6. The institutional climate does not favor - or too little - creativity, innovation, and taking the risks necessary to support efforts to transform education for the shift to sustainable development.

7. Establishments or teachers who set off programs Education for sustainable development are not rewarded, or not at all.

To institutionalize education for sustainable development, the following proposals are necessary in my humble opinion:

1. Creation of institutes and centers of education for sustainable development.

2. Establishment of committees and focus groups on Education for Sustainable Development at the level of institutions.

3. Launch of an environmental education cyberinstitut.

4. Establishment of partnerships with governments and local and regional NGOs.

5. Launch Research on inclusion of education for sustainable development in teacher training at national level.

6. Organization of Schools Recognition programs and institutions that promote education for sustainable development (as, for example, the movement of eco-schools).

7. Building Trade Partnerships conscious development sustainable in order to promote ESD.

8. Development of extramural training projects for teachers set implemented with the support of the local community in disadvantaged neighborhoods to better educate young people whose educational level is insufficient.

9. Establishment of regional teams responsible for drafting programs Studies of ESD.

10. Establishing a link between the educational and training center business school to develop joint programs professional development on ESD for senior officials administrative educational.

11. Manual Production, texts, websites and other educational materials on sustainable development for primary and secondary schools.

12. Use of geographic information systems and other approaches based on information technology to monitor the issues related to sustainable development at the community level.

With my best regards

Prof. Bachir ACHOUR

1
Have you experience with acute renal failure in Visceral Leishmaniasis treated with liposomal amphotericine?

Do you know if is enough a single dose of Ambisome (250 mg, 2 hrs of infusion) to double creatinine level (1,3 to 2,8)?  or is more probable that there's another cause behind it?

I hope that attached paper and link are helpful, PLZ check out.

Regards

+ 1 more attachment

7
Are there abjective functions with shared variables?

If a firm has two objective functions.

1) Minimize (K), where K = A + B, B = M/N

2) Maximize (L), where L = P - zB

Here in both objective functions there is a shared variable B, How to find the optimal solutions to these two optimization problems simultaneously?Any suggestions?

Thanks everyone.

Eq. (1) Minimize (K), where K = A + B, B = M/N

Eq. (2) Maximize (L), where L = P - zB

If we apply multi-objective, Epsilon constraints method:

Using Epsilon constraints method, objective function 2 can be considered as constraint. The objective functions can be transformed as follows:

Minimize Eq. (1)

Subjected to Eq. (2) < Epsilon

Constraints: B>0, A>0

There is still a shared variable B, How to find the value of Epsilon? Any idea?