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  • Vladimir Mikhailovskii added an answer in Detectors:
    How could SEM detectors discriminate between SE and BSE ?

    hello everyone
    I just wondered , what is the theory behind the ability of different SEM detector to collect and detect a specific type of electrons .
    for example: there is a secondary electron detector (SED) which detect only secondary electrons , and on the other hand there is the backscattered electrons detector (BSE) which detect only BSE .

    Vladimir Mikhailovskii

    In addition: many BSE detectors are semiconductor detectors. Sensitivity of sc detectors depends on electron energy, therefore low-energy SE make negligible signal corresponding to high-energy BSE.

    Most SE detectors are scintillation detectors with photoelectronic multiplier, so they are able to collect each type of electron signal. But their angular size is relatively small, so they collect only small portion of BSE. To increse SE collection ability, there is a collecting grid in front of detector(Everhat-Thornley detector). If you apply 200-500 V on this grid, you can collect all SE emmited by the sample(if working distance is enough), but this voltage doesn't affect high-energy BSE, so you can separate signals again.

    There is an effect of BSE to SE conversion: BSE from sample surface hit the chamber walls and generate SE3 signal. SE detector collects this SE3 signal, so some BSE contrast may present in SE images(fpr more information see here: Reimer L., Volber B. // SCANNING, 1979, V. 2, p. 238).

    Also there are some types of SE and BSE detectors inside electron column. They separate SE and BSE by lower electron optics. 

  • Shachinthaka Dissanayaka added an answer in His-Tag:
    How can I identify proteins at 280 nm when I'm using immidazole in affinity chromatography?

    Due to the high absorbance of immidazole at 280nm, it's  difficult to identify proteins. Even I used high quality immidazole (sigma, molecular grade) I was not able to identify any peaks during  the elution step (con of immidazole 250 mM). Therefore, I have to purifiy the his tag proteins manually.Is there any suggestions to get rid of this high absorbance of immidazole

    Shachinthaka Dissanayaka

    Dear sir,normally I, purified his tag proteins with the same procedure you described. first I wash the equilibrate the Ni-Nta column with 5 mM immidazole containing buffer and wash non specifically bound protein with 70 mM immidazole and finally elute with 250mM immidazole. During each steps I was not able observe any peaks at 280 nm. But proteins were there when I cheked with SDS-PAGE. Here with I have attached chromatogram ( greenline indicates absorbance at 280 nm)

  • Peter Suber added an answer in Open Access Publishing:
    Any affordable open access journal for Humanties and Social Science?

    Scientists are spoilt for choice in open access publishing - BioMed Central, eLife, F1000Research, Frontiers, Hindawi, Libertas Academica, MDPI, PeerJ, Pensoft Publishers, PLOS, Any affordable open access journal for Humanties and Social Science

    Peter Suber

    Most peer-reviewed OA journals (70%) are free for authors, and the percentage is even higher in the humanities and social sciences. Browse the Directory of Open Access Journals (DOAJ) [ www.doaj.org ] for OA journals in your field. Click on any one that looks promising and DOAJ will tell you whether it charges an article processing charge or APC.

    Don't assume from certain prominent fee-based journals that all or even most OA journals charge fees. Don't assume that all the *good* OA journals charge fees. Don't assume that the ratio of fee-based to no-fee OA journals is the same in the humanities and social sciences as it is in the STEM fields.

  • Vikash Pandey added an answer in Mathematical Concepts:
    Do we really understands the ripples of space time?

    Ripples of space time what we call gravitational waves, even after the discovery of these ripples , do we really understands the physical origin of these ripples?

    I am asking it because, I even don't understand the physics of mass energy tensor to space time curvature ( a mere mathematical concept for me).

    Vikash Pandey

    If you derive the field equations as I suggested earlier, you will see the connection between mass energy tensor and space time curvature, as it is often said 

    "matter tells space-time how to curve, and curved space-time tells matter how to move".

  • Katarzyna Dziedzic added an answer in HEK Cells:
    Why Hek cells does not grow well after thawing ?

    Any idea about how many days i should give to my newly thawed Hek cells to grow ?

    I usually just change the medium after the day i thaw them and then i wait for them to reach 80% confluency but sometimes they just don't attach at all...

    Katarzyna Dziedzic

    Maybe your thawing procedure is too harsh? I usually add thawed cell suspension to pre-warmed culture medium and spin (typicall cell spinning conditions). After that suspend in fresh culture medium with 20% of FBS. Sometimes this is too harsh for vulnerable cells and instead of spinning I just add droplets of thawed cell suspension to new flask with culture medium (very slowly, drop by drop) and change the medium after cell attachment (usually after few hours). With this procedure you will have DMSO remaining in culture medium till you change it but you are avoiding spinning of cells.

  • Parag Sen asked a question in Vehicles:
    Why idling condition requires more power (because the vehicle is not moving)?

    Why idling condition requires more power because the vehicle is not moving?

  • Victor Mark Kolombus asked a question in Invasive:
    I need articles about Non-discogenic Piriformis Syndrome and its management, both conservative and invasive?

    I am writing a brief review of Non-Discogenic Piriformis Syndrome: aetiology, diagnosis and treatment, conservative and invasive.

  • Maria Bettencourt Pires added an answer in Wisdom:
    What is wisdom?

    Philosophic, religious, and opinion responses are acceptable.

    Maria Bettencourt Pires

     What wonderful thought, dear Dr. Tajudeen ! Thank you !!!

    I might not think of being fearful of conscience... ( I usually tend to think that drug addiction comes from the fear of reality, and consciousness ... unwise, to do so ! )

  • Robert Kiss added an answer in Cancer:
    Can anyone describe the mechanism of action of cancer?

    Just give a general overview for this question.

    Robert Kiss

    The two reviews provided by Karoly are the best ones.

    I attach here some more "unusual" reviews on this subject.

    I have these articles thanks to the RG community. Warm thanks to you!

    Best regards


    + 2 more attachments

  • Jean-Marc Vifquin asked a question in Vision:
    Do you know researches about the impact of devices of professional vision 's development for future teachers about the skill to notice ?

    As we use videoformation, we are interested by the researches wich show the impact of special conditions used in the training of professional vision on the skill to notice, and if it's possible to asses the effects on the practices in the classroom.

  • Ivo Carneiro de Sousa added an answer in Tamil:
    Why is there an interval of more than 30.000 years between the first visible traces of art and writing?

    The first signs of art date from more than 30.000 years ago (e.g. cave art) whereas the first signs of writing (e.g. Tamil) appeared let say ca. 5000 years ago?

    Any idea why artistic humans waited such a long period before they decided to start writing?

    Ivo Carneiro de Sousa

    Dear Marcel, I don't really know if the Lesser Sunda islands, Timor and Australia were as isolated as one can think before the end of the last so-called "Ice Age", roughly 110.000 to 12.000 years ago. I have never studied the subject, but when I was collecting myths in Timor, I went to the neighboring island of Atauro and I collected there a very arcane myth of the Atauro eel, which still is the main local taboo. The myth recalls a giant eel that with her powerful tail has separated Timor from the great island (Australia), then the small islands, Atauro, Wetare and the rest of the eastern part of the Sunda islands. Thereafter, when one compares myths, old rock paintings, main anthropomorphic, zoomorphic and cosmological symbols between the remote populations of Timor and adjacent islands that are not Australasian one finds a huge constellation of similar themes among the Australian aborigines. I have never researched the subject by myself but one of my East-Timorese PhD students did compared Makassae (a melanesian language in the East of East Timor) and the Australian aborigines anthropology and concluded that they shared the same affilial system and plenty of old cultural productions. 

  • Esther De Ru added an answer in Bone Remodeling:
    What causes osteoporosis? What is the mechanism of bone loss?

    Is there any relation between age, food habits, hormones, physical activity? Bone remodeling is a complex process and it depends on so many things, so what is the exact cause of it? Please help to understand it deeply.

    Esther De Ru

    Dear Max, Thanks for the information given so far. Which foods help keep the Ph at a normal level? Any list available?

  • Vincent Amelot asked a question in Publications:
    Publications about differences between answers to auto-questionnaires and answers to hetero-questionnaires ?

    I'm looking for publications about differences between auto and hetero-questionnaires, about the impact on the answers of the participant. Any ideas ?

  • Mostafa Kadi asked a question in CDS:
    How can synthesis ploysulphide electrolyte for CdSe and CdS Quantum dot-sensitized solar cells ?

    i need procedure to synthesis sodium polysulphide electrolyte !

  • Marianne Levon Shahsuvaryan added an answer in Polycystic Ovary Syndrome (PCOS):
    Where can I find PCOS occurrence yearly data?

    I want to compare the yearly occurrence of PCOS with other diseases.  If you know of websites that have this data, I would really appreciate it.

    Marianne Levon Shahsuvaryan

    I think that required figures could be presented at the www.medscape.com

  • Metwally Bekhit added an answer in Plant Tissue Culture:
    How to avoid water vapour in plant tissue culture media?

    Repeatedly I am getting contamination from the bottom of the tissue culture container. How to avoid this one?

    Metwally Bekhit

    I agree with all mentioned above. In addition, there is another factor such as internal infection by endophytic bacteria, so you have to identify kind of this bacteria, since the presence of water vapor inside the cultivation vessel-contaminated, no evidence that it's the only cause. But if so, Simon state many important factors that are affected water vapor formation, the most important one to avoid contamination resulting from water vapor is wrapping around the closure with parafilm after culturing directly under completely aseptic conditions.............................best regards

  • Michala Jakubcová added an answer in Hydrological Modeling:
    Tutorial on winSRM?

    I want to do in my simulation of snow runoff Can someone give me a step by step tutorial to photos? What is needed to start? 

    Michala Jakubcová


    you can try the official SRM user manual from http://aces.nmsu.edu/pubs/research/weather_climate/SRMSpecRep100.pdf I find it very helpful.

  • Bartosz Trzaskowski added an answer in Autodock:
    How can I run autodock calculation in a protein with molybdopterin cofactor?

    I want to check the antioxidant activity of a organic derivative on xanthine oxidase enzyme using molecular docking . For this I have downloaded the Bovine milk XO enzyme from PDB. The active site of the enzyme contains molybdopterin cofactor. Autodock4 shows some errors when I try to run it. I think this may be due to the Mo atom. Anyone please help me to resolve this problem.

    Bartosz Trzaskowski

    Mo is not parametrized in Autodock, hence the problem.

    See: http://autodock.scripps.edu/faqs-help/how-to/adding-new-atom-parameters-to-autodock how to deal with this problem. In general it's not easy since you will have to parametrize it on your own, unless you'll find some reasonable parameters for Mo or the entire cofactor.

  • Viral Mevcha added an answer in Applied Mechanics:
    How can one find the deflection of a non-prismatic cantilever beam ?

    The beam has a varying cross section. Also one of the sides is loaded uniformly by a force. See attached file for more clarification.

    Viral Mevcha

    You may find answer in below attached file.

    + 1 more attachment

  • Cristina Domenech added an answer in Elemental Speciation:
    Rare earth elements speciation by PHREEQC?

    How can we model the rare earth elements and extract the Lnco3+ from phreeqc software?

    Cristina Domenech

    You can take a look at https://www.thermochimie-tdb.com/

    maybe this database, that can be extracted with PHREEQC format, has the complexes you need.



  • Mohamed Darwish asked a question in Limestone:
    Does anyone have a reference for the Modulus of Elasticity and the unit weight of Egyptian limestone?

    Does anyone have a reference for the Modulus of Elasticity and the unit weight of Egyptian limestone?

  • Faris Alshubiri added an answer in Money:
    What are the determinats of broad money supply in ghana?

    the constitutes of broad money and the periodical sources of it.

    Faris Alshubiri

    Dear Frimpong Ofori


    Please find the attached file about your topic may be useful for you

    Best Regards

  • Qahtan Qasem added an answer in Theoretical:
    What is the main difference between theoretical framework and theoretical concept?

    I want to make a research study.

    Qahtan Qasem

    Dear Ambika, here are the main differences. with all respect

  • Ulrich Schmitt added an answer in Technological Change:
    What do you think will be the major challenges for today's children when they become adults in a few years?

    Many technological changes happening this days will have societal impact and will provide opportunities and risks. Those of us in science and technology are already following and previewing what will be the future. Young people will have to learn fast and cope with such challenges. What will be the major challenges?

    Ulrich Schmitt

    Thank you for your speedy feedback, Arturo and Fernando, your concerns are also mine. Hence, my approach favors meme-based repositories stored with their relationships rather than traditional document-centric systems. People capture the memes they feel relevant, are able to combine it with whatever they already know, re-purpose it with own ideas for their own creative authorship, and share it with acquaintances close to them. As a result, the concept/system is closing in on Vannevar Bush’s still unfulfilled vision of the ‘Memex’ celebrating its 70th anniversary as an inspiring idea never realized. It also addresses the scenario recently put forward by Levy which foresees a decentralizing revolution of knowledge management that gives more power and autonomy to individuals and self-organized groups. The suggested solution also addresses the diverse opportunity divides, rightfully prioritized by Arturo.

    + 1 more attachment

  • Michael F. Cassidy added an answer in Semantic Differential:
    I'm not familiar with semantic differential scale. Please help?

    How to present data using semantic differential scale?

    What type of statistical test is applicable for questionnaire in semantic scale form?

    Michael F. Cassidy

    The answers already given should be quite helpful. Rooted in marketing research, I have found the scale to be helpful segmenting "market" segments. For example, I once conducted a survey of psychiatrists specializing in geriatrics. The client, a professional association, wanted input on planning upcoming meetings. Using Osgood's scale I found a strong preference for ski locations for relatively younger doctors and "sunny", warm spots for those relatively older. Not a terrible surprise, but the preferences for different sets of attributes were helpful to the client.

  • Sachin A. More added an answer in Ligation:
    Why I get wrong sized band after heat shock transformation?

    Hi dear scientists

    I really need your advice. I want to clone my gene by length of 750 bp in pET 22 But I faced a trouble.

    I’ve digested cloning plasmid(pGH 8) then extracted my gene using bioron gel extraction kit. After that I’ve done similar process for digested pET 22. Then I’ve read 260 od for each one and then perform ligation according to Neb formula for 2 hours at 22® C. In addition to check if ligation was successful I’ve done a PCR. PCR product size shows that ligation is done correctly. Then I transformed 15uL of my ligation product to 50uL of BL21 competent cell using EMBL heat shock transformation protocol. After that I want to screen correct colonies using pcr but unfortunately all colonies give bands with wrong size. Our pcr product size should be 939bp but as you can see no band at this region are available.(fig 1)

    In addition pcr condition are set up as you can see its performance in detecting intact pET 22 in BL21(fig 3)

    I repeat this process with another vector called pET26(fig 2)

    + 2 more attachments

    Sachin A. More

    Isolate the plasmid from transformed colony try to do restriction digestion to confirm your desired insert and vector. It will resolve the problem of contamination or wrong insert during ligation. 

  • Eric B. Brennan asked a question in Hoverflies:
    What are some good studies showing that the abundance of food resources for beneficial insects do not always increase biocontrol of target pest?

    Biological control of insect pests like aphids in vegetable production is widely used in organic production systems in the Salinas Valley of California where I enjoy working.  In these systems, we typically use flowering plants like alyssum, dill, and coriander interplanted with vegetables.  This works especially well for aphid control in lettuce, and somewhat for long season crucifer crops (i.e., broccoli, cabbage, brussels sprout).  We'd like to develop more reliable and land-efficient systems for biological control of aphids in these crucifers and to help with this I need to learn more about how floral resource abundance affects biological control in positive, neutral, or negative ways.  Specifically, I’d appreciate being directed to studies showing that increasing the abundance of floral resources (i.e. pollen and nectar) for natural enemies of aphids (i.e., hoverflies or parasitoids) may not increase aphid control.  I’m also interested in studies that look at how biological control may increase as floral resources increase to a certain point, and then levels off.  Below are a few studies that seem relevant, but I’m sure that scientist with more experience in this area will have other suggestions for further reading for myself and others.  Thanks, Eric

    -Smith, J.G., 1976. Influence of crop background on natural enemies of aphids on brussels-sprouts. Ann. Appl. Biol. 83:15-29.

    -Costello, M.J. and M.A. Altieri, 1995. Abundance, growth-rate and parasitism of Brevicoryne-brassicae and Myzus-persicae (Homoptera, Aphididae) on broccoli grown in living mulches. Agric. Ecosyst. Environ. 52:187-196.

    -Gillespie, M., S. Wratten, R. Sedcole, and R. Colfer, 2011. Manipulating floral resources dispersion for hoverflies (Diptera: Syrphidae) in a California lettuce agro-ecosystem. Biol. Control 59:215-220.

  • Bartosz Trzaskowski added an answer in GaussView:
    How can I simulate a gold (111) cluster?

    I am using Gaussian 09W and Gaussview 05 and trying to simulate a gold (111) cluster. But optimisation failed and the output file is not a cluster. Can anyone help me to resolve the issue?

    Bartosz Trzaskowski

    Could we get at least the entire input line? Or, better, with the starting geometry? There are too many mistakes one can make when preparing the input to list all of the here...

  • Rafik Karaman added an answer in Mycobacterium Smegmatis:
    Relation between OD600 and CFU/ml of Mycobacterium smegmatis?

    I am working on M. smegmatis, and i want to calculate the CFU/ml concentration for the cell growth i obtain using the OD at 600 nm. Kindly tell me what is the corresponding value of CFU/ml for 0.1 OD at 600 nm

    Rafik Karaman

    Dear Pritish,

    Please read the following and examine Figure 2 in page 289 (attached file):

    In quantifying cfu/mL by colony counting, colonies were not observed until the 9th day of incubation. During log phase, the generation time was calculated in 24.91 h. Figure 2 shows the correlation of the growth curves generated from the different methods. The correlation between cfu/mL quantification and OD600 measurement was the lowest (R2 = 0.8913, Figure 2A), followed by the correlation between cfu/mL quantification and turbidity measurement (R2 = 0.9252, Figure 2B). OD600 and turbidity measurements were highly correlated (R2 = 0.9823, Figure 2C). We determined in M. tuberculosis H37Rv ATCC 27294 that 1 McFarland unit is equivalent to either 1.97 × 106 cfu/mL or 0.39 OD600, and an OD600 measurement of 1 is equivalent to either 3.13 × 107 cfu/mL or 3.66 McFarland units.

    Braz J Microbiol. 2013; 44(1): 287–289.
    Published online 2013 May 31. doi:  10.1590/S1517-83822013000100042
    PMCID: PMC3804212
    Measuring of Mycobacterium tuberculosis growth. A correlation of the optical measurements with colony forming units
    Katia Peñuelas-Urquides,1,2 Licet Villarreal-Treviño,2 Beatriz Silva-Ramírez,3 Liliana Rivadeneyra-Espinoza,4 Salvador Said-Fernández,5 and Mario Bermúdez de León1
    Author information ► Article notes ► Copyright and License information ►
    This article has been cited by other articles in PMC.
    Go to:
    The quantification of colony forming units (cfu), turbidity, and optical density at 600 nm (OD600) measurements were used to evaluate Mycobacterium tuberculosis growth. Turbidity and OD600measurements displayed similar growth curves, while cfu quantification showed a continuous growth curve. We determined the cfu equivalents to McFarland and OD600 units.
    Keywords: bacterial growth, colony forming units, McFarland, Mycobacterium tuberculosis, optical density

    Hoping this will be helpful,