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.

Browse Topics

  • Tyrone LuGarde Talbot asked a question in Presidentialism:
    Can anyone direct me to a database that has statistics on naturalized US citizens for presidential election years 04 to 2012?

    I am trying to find statistics for US Presidential election years 2004, 2008, and 2012. In particular I am looking for voter turnout numbers of Naturalized US citizens which is my dependent variable. My independent variable is married two family household of naturalized citizens. 

  • Haroon Rashid added an answer in Tissue Engineering:
    Can anyone suggest or send me a paper related to tissue engineering?

    I am searching for  limitations caused by donor variability and considerations about donor site morbidity for applying Tissue eng constructs?

    Haroon Rashid


  • Shanshan Wu Howland added an answer in Transgenes:
    Can someone help with the deterioration and unpredictability of lentiviruses?

    About 5 months ago I made batches of 2nd generation lentiviruses, all with different modifications of a single transgene in. The transgene was either tagged to a GFP under a CMV promoter, or under an EF1alpha promoter with an IRES controlling transcription of the transgene and then a GFP. Initially I had great success transducing HEK and SHSY5Y cells and around 90% would go green.I had viral titres around 1x10^7or8 TU/ml. But now I transduce the same cell types and I hardly get any good green signals with some viral aliquots but others are fine, and I think my CMV promoter is being silenced after about 3 days as no transduced cells are green after this time point. I have heard lentiviruses can be very sensitive to repeated freeze/thawing, so have kept aliquots at -80 and been careful not to repeatedly freeze/thaw. I also read their shelf life is only about 6 months. Could this be why I am getting so much variability?

    Shanshan Wu Howland

    Lentivirus titres can drop by 50% with just one freeze-thaw, so for me, each aliquot is used once only. However, I have not seen drastic drops in titre even after a couple of years at -80oC. If I understand you correctly, this may not be a storage issue, but rather some of your lentiviral constructs just don't work as well as others. This is common; for example, larger constructs will generally give you poorer titres. Also, CMV silencing is often a problem with primary cell lines and cell lines that are more differentiated/difficult (like SHSY5Y?). I prefer EF1a. I also prefer using a 2A self-cleaving peptide to separate my gene-of-interest from GFP, rather than IRES.

  • Carolyn Bonquin added an answer in ASEAN:
    Who would gain the most (or lose the most) from the intra-ASEAN mobility of professionals brought about by ASEAN economic integration?

    Among the anticipated outcomes of ASEAN Integration is intra-regional mobility among professionals. ASEAN professionals may soon be able to practice anywhere within the region. What does the current discourse say on who would stand to gain or lose from this eventuality? We are not referring to countries or nationalities but to sectors or groups with specific descriptors or circumstances. What does the literature say?

    Carolyn Bonquin

    By next year, 2016, professionals from ASEAN member-states will have better mobility within the ASEAN Economic community. According to a study of the Asian Development Bank and the International Labour Organization, the mobility will focus on the exchange of expertise. Currently,  “business visitors for sales, negotiations, natural persons on a temporary basis and intra-company transfers of executives, managers and high skilled professionals” are among to those who  benefit on the inter-regional mobility. The ASEAN Mutual Recognition Agreements just cover the following careers: engineering services, nursing services, architectural services and surveying qualifications, medical practitioners, dental practitioners, and accountancy services and tourism professionals.

    Although the flow of low skilled workers will continue to flow, workers form this sectors will not directly benefit from the regional mobility. Low skilled workers are not addressed by the AEC upon the arguments that the "closer economic integration" will lead to a production improvement. Low skilled workers will indirectly benefit from the development on the economic activity which will later demand for low skilled workers in various sectors, causing a temporary "migration hump".

    Asian Development Bank and International Labour Organization. (2014). ASEAN Community 2015: Managing Integration for Better Jobs and Shared Prosperity. Retrieved from: http://www.adb.org/sites/default/files/publication/42818/asean-community-2015-managing-integration.pdf

  • Haroon Rashid added an answer in Complete Denture:
    ICP or RCP: Is is always necessary to record the jaw relationship in retruded contact position for complete dentures ?

    Is is always necessary to record the jaw relationship in retruded contact position for complete dentures ?

    Haroon Rashid

    Mr Lawrence .... thanks for the input but sometimes it is impossible to achieve an RCP. What do we do then ?

  • Bibhuti B Sahu added an answer in Magnetron Sputtering:
    Is it possible to sputter Aluminium alloy by nickel target using D.C. unbalanced magnetron Sputtering? If so, what are the parameters?

    Is it possible to sputter Aluminium alloy by nickel target using D.C. unbalanced magnetron Sputtering? If so, what are the parameters is should go for?

    Bibhuti B Sahu

    Use target Ni and Al. Use Ar and N2 as process gas. Study the effect of N2 addition also.

  • Raveendra Nath Yasarapu added an answer in Climate Change:
    Is it time we shift emphasis from technological solutions to climate change & focus on the 'Human Dimension'?

    Isn't the obvious solution and the elephant-in-the-room 'BETTER HUMAN BEINGS'? Shouldn't the focus be on better human beings rather than better technology? Why is it that everyone wants to develop better technology rather than focus on better humanity? Because no one has the answers and no one wants to change themselves? In environmental degradation, is it not obvious that nature can heal itself, if only left alone, and it is we humans who need regulation? Many natural parks managers do just that; seal off the area from human interference to let nature heal and recover. It is classified as 'Strict Nature Reserve"by IUCN. Complacency and inaction are not advocated here, as many have misunderstood, but the shifting of focus from technology to the human being. As technology is no match for human greed, isn't introspection & restraining ourselves more relevant than developing more technology, which caused the mess in the first place, by making it easy for a few to consume more? Since technology is only a short term quick fix which fails after a short time, isn't the real problem our addiction to material consumption & our lack of understanding about human nature? Isn't developing more technology sustaining the addiction instead of correcting it, leading to more complex problems later on, needing more complex technological quick fixes like higher drug dosages, more ground troops & equipment, (along with their debilitating side effects) in the future? Isn't this the vicious addiction circle we are trapped in? As researchers, do we merely buy more time with technology OR go to the very root of the problem, the human being?

    A lot of hue and cry is made about climate change and the environment in general. Public and private money is poured into research to study its effects on the environment, sustainability etc. Should we study nature or ourselves?

    " Our studies must begin with our selves and not with the heavens. "-Ouspensky

    Human activities have been found to have a direct correlation to climate change and its impact on the environment(I=P x A x T, the Ehrlich and Holdren equation), in spite of what some complacent sections say to protect their own self interests.

    We hardly know about Human nature. We can scarcely predict human behavior. We need to find out why we think like we do and why we do what we do and why, in spite of all knowledge and wisdom, consume more than what we need, in the form of addictions to consumption and imbalance not only ourselves but also the family, society and environment around us..
    Humanity is directly responsible for all the unnatural imbalances occurring on the planet. Yet we refuse to take responsibility and instead focus on climate change, or fool the public exchequer with a 'breakthrough in renewable energy just around the corner'. We scarcely know what drives human beings. If we had known, all the imbalances around us would have had solutions by now, given the amount of money plowed into finding such solutions. Are we blindly groping in the dark of climate change because we don't know the answers to our own nature?
    Is it not high time we focus on what makes us human, correct our consumptive behavior and leave nature to take care of climate change? Why focus effort on 'externals' when the problem is 'internal'- 'me'?
    Aren't we addicts denying our addiction and blaming everything else but ourselves?

    " We are what we Think.

    All that we are arises with our thoughts.

    With our thoughts, we make the world." - Buddha 

    IMHO, We don't need to save the World. It is enough if we save ourselves from ourselves. The need of the hour is not vain glorious interventions, but self-restraint and self-correction!

    The Mind is the Final frontier.

    + 2 more attachments

    Raveendra Nath Yasarapu

    To All our Brothers and Sisters in the US,

    Happy Thanksgiving!

    Thank you Mother Nature for all your Wonderful Gifts!

  • Mosfera Chowdury asked a question in Chromatography:
    Is there any protocol for washing chromatography paper (1 CHR) with HPLC water?

    I have to wash chromatography (1 CHR) paper with HPLC water but  I am not sure what should be the amount of water i need. I am dealing with with 200 mm x 200 mm size of paper. I don't have idea what should be the proportion of wate and paper, time period for washing and procedure of washing.

  • Mohammed Aboajmaa asked a question in MATLAB:
    Could you please help me to simulate PAPR reduction using SLM or Precoding-DHT?

    I'm working on PAPR reduction in OFDM and I want any one help me to simulate SLM or precoding DHT using Matlab.


  • Fernando Medrano asked a question in Dreams:
    Are dreams studied as an adaptative trait?

    Hi everyone,

    I want to know if there are some studies about the adaptative advantage of dreams on human fitness,

    Thanks in advice


  • Sebastian Freeman asked a question in Paraformaldehyde:
    Why might paraformaldehyde destroy cells?

    Hello everyone,

    I was culturing a cancer cell line and primary HUVECs for an experiment for immunofluorescence. I had treated the plastic surface with poly-L-lysine for improved adhesion since in the past I know I lose many cells during the protocol steps and I wanted to see if it would help. At the end of their culture period, I briefly rinsed with 1X PBS and then fixed with 4% neutral buffered paraformaldehyde (PFA). Since I have such a problem with losing cells in plastic wells, I check the cells after each wash or treatment under the microscope. I added the PFA and checked under the microscope directly under the microscope, and much to my dismay almost all my cells appeared destroy. Their membranes looked destroyed and many were now floating. I let them fix for 15 minutes anyways and then rinse. Only a few cells remained.

    I had concerns about the pH of the solution, so I shortly after when to check it. It read at 6.95. Should the pH be higher?

    Does anyone know why this happened? How important is it that PFA be as fresh as possible? I prepared this PFA in 1X PBS, and had to use a couple hundred microliters of HCl to fix the pH (in a total volume of 100 mL). Could this through off tonicity of the solution and made my cells rupture? I used the PFA cold from the fridge. Could this be a problem? Also, why didn't all the cells rupture?

    Thank you

  • André Michaud added an answer in Quantum Physics:
    Why has the classical electron radius generally been rejected in quantum physics?

    There is a very close and accurate agreement between the classical electron radius, alpha, the electron Compton wavelength and the Bohr radius. such that:

    re = alpha. lambdae /2pi = alpha2 a0

    Given the great accuracy ascribed to alpha in particular, this would suggest that the classical electron  radius is valid.  

    André Michaud

    Dear Jacques

    Interesting paper indeed.

    Note that in Gauss's time the notion of acceleration induced kinetic energy in charged elementary particles by the Coulomb force was not yet around since the electron was discovered 11 years after he described this idea of "action at a distance that would propagate with a finite velocity" (1856 by Joseph Thompson),. Even such a finite velocity of free energy was established even later by Maxwell as being c.

    So Gauss did not have a full hand of cards at his disposal. He did the best with what he had. Quite remarkable in fact that he could come up with this concept at that moment.

    But we know much more now about kinetic energy induction.

    I note also that the paper is fields-oriented and, unless I missed it somehow, it does not directly address the energy induction process in elementary particles. As far as I can see it does not directly address calculation of energy per se either of that making up the rest mass of the electron or that which is induced in accelerating charged elementary particles.

    The whole concept of radiation source versus absorber being described with its advanced and retarded fields concept due to the assumed limited velocity of the message propagation between source and absorber appears to be self-consistant. All the more so since from Wheeler/Feynman's own admission, at the limit it provides the same end results as what they name "the theory of action at a distance", but with much more complex math development to account for the advance/retarded fields that need to be involved and the associated notion of pre-acceleration.

    Even in Wheeler and Feynman's time of publication (1945), it was not yet known that neutrons and protons are not elementary but composite particles made up of triads of scatterable, charged and massive elementary particles (up and down quarks). This is why he speaks of and takes into account the possible existence of "uncharged particles (page 158)". This was clarified much later in 1968 from SLAC experiments that the only massive stable elementary electromagnetic particles in existence are electron, positron, up quark and down quark.

    So we know now that in physical reality, all elementary particles making up all atoms in existence are charged. No exception.

    This means that in physical reality the only "accelerated" particles in existence are those that are captive of various stable states of least action electromagnetic equilibrium. All other particles are in the process of accelerating and will be until they stabilize in some electromagnetic least action states.

    Regarding the so-called action at a distance that supposedly can only propagate at a finite velocity. As I mentioned, at the time of conception of the idea, the clear distinction that needs to be made between electrostatic force (Coulomb force) per se and the kinetic energy that this force induces in accelerating charged particles seemed not to have been yet completely addressed, from what I could gather.

    All being considered, the Coulomb force acting between two charged particles, a force whose nature and origin are still a mystery, is known to be in permanent infinitesimally progressive decreasing or increasing action as a function of the inverse square of the distance between the particles involved, irrespective of the distance between them, which means that it is permanently present by structure and does not "travel" or "move" between the particles.

    So it seems to me that the force proper does not move, but is the cause of the acceleration of charged particles towards or away from each other, or rather, it is the cause of the induction of kinetic energy in the particles, an energy that will be vectorially directed towards the other particle in case of attraction or in the opposite direction in case of repulsion, and that naturally manifests its presence by a change in velocity of particles when external electromagnetic constraints do not partially or even completely prevents such a change in velocity.

    This is why the energy that progressively accumulates in an electron accelerating towards a proton, for example, can always be calculated by integrating the energy of the Coulomb equation from infinity to a0 (radius of the mean rest orbital of an electron in a hydrogen atom), where it will be captured in this well known state of electromagnetic equilibrium, a sudden stop that will force the emission of a 13.6 eV bremmsstrahlung photon of translational energy now in excess.

  • Huda Almaarofi added an answer in Water Quality Management:
    What is the suitable method to evaluate "multiple management options" against multiple criteria/sub-criteria?

    I am working on a framework to optimize surface water quality management strategies in catchments. I am looking for a suitable (simple as possible) method to evaluate the management options and rank them against fix cost/budget.

    Huda Almaarofi

    Dear all,

    Thank you so much for your support. I really appreciate all answers.

    I have 4 categories (Water quality, Environmental, Economic, and Social). These categories are divided into several Criteria, and each criteria divided into several sub-criteria. Management options such as (Nutrients control, Riparian filter strips, Wetland filters, ..). I want to reach which best 3 management options that together when applied we receive the excellent catchment score, good score, or acceptable. in most situations the budget will be fixed (let's say either between $100M-50M, 50M-10M, or less than 10M). The "Goal" will be $/ changing score. 

    I am thinking of Fuzzy Goal methodology, but still can't imagine the rules! I believe that each category need different rules. for Water quality, I think Max of possibilities is applicable. but for the other categories (Environmental, Economical, and Social) still I am not sure!

  • Xingjian Xu added an answer in Sterilization:
    What is the most suitable approach for sterilizing sulphur?

    Hei, I want to sterilize sulphur.  UV irradiation sterilization or  high pressure of steam sterilization, which one is the most appropriate? 

    Xingjian Xu
    • Thank you for your valuable suggestion.
  • Jie Yin Yee asked a question in Baseline:
    How to I calculate changes in biomarkers?
    1. Follow-up minus baseline
    2. (Follow-up minus baseline)/ Baseline
  • Bibhuti B Sahu added an answer in PEDOT:PSS:
    What is the typical RF power and time used for plasma cleaning of ITO substrates for spin coating PEDOT PSS layer?

    I am trying to deposit PEDOT PSS on ITO for polymer solar cell application.

    Bibhuti B Sahu

    You can make N2 plasma treatment for 10-15 Second as pretreatment with low RF power of 40-50 W.

    It depends on plasma condition (operating pressure, power, electrode separation, substrate position) and deposition method like sputtering or PECVD.

    Anyway you can make N2 pre cleaning. Altrenatively, you can use 2-5 nm SiO2 coating substrate by PECVD for better film quality.

  • Fouad Mohave added an answer in Crystalline Structures:
    Can anybody explain the crystalline structure of MCM-41?

    I have always wondered how to visualize MCM-41 crystal structure. The literature says that MCM-41 is an arrangement of cilyndrical pores in a hexagonal shape, builded by amorphous silica. Nevertheless, MCM-41 does have a well-defined XRD pattern (peaks related with 100, 110 and 200 planes).

    Sincerely, I have not been able to visualize this. How can MCM-41 have a crystaline structure when silica building blocks are suposed to be amorphously packed? How can I visualize the unit cell of MCM-41?

    On the other hand, if the unit cell is hexagonal, Miller-Bravais (hkil) indices should be used instead of Miller (hkl) indices, but all literature I have found so far uses Miller indices.

    Fouad Mohave

    Dear Casas-Orozco 

    A typical X-ray diffraction pattern of MCM-41 shows the hexagonal symmetry of the pore ordering (space group: p6m) and it typically contains four main reflection lines (d100, d110, d200 and d210) or more at low angles (2theta = 10). Since MCM-41 consists of amorphous silica, it has no crystallinity at the atomic level. Therefore, no reflections can be observed at higher degrees 2theta and as Dr.Jadhav mentioned these diffraction are due to the hexagonal pores. 

    Useful review: Microporous and Mesoporous Materials 125 (2009) 170–223.

  • Jacques Lavau added an answer in Electromagnetic Waves:
    How do you visualize a photon?

    I am writing a paper for a conference titled: The Nature of Light: What are Photons? It would be very helpful to obtain an idea about how this group of scientists visualize a photon propagating in a vacuum. There are no right or wrong answers. You can give either a detailed answer or merely choose one of the following four photon descriptions. A) The Copenhagen interpretation where a packet of energy discontinuously jumps to form waves of probability. B) The de Broglie model where a packet of energy has a pilot wave which steers the packet of energy. C) A distributed electromagnetic wave which propagates in an empty vacuum. The particle property appears because the energy collapses to a point when absorbed. D) A distributed electromagnetic wave propagating like a quantized transverse sound wave in the quantum mechanical medium of highly energetic vacuum (zero point energy). The particle property appears because the energy collapses to a point when absorbed.

    Jacques Lavau

    No "Probability waves" at all in the writings of Schrödinger and Dirac themselves. Only waves.

    Simply the hegemonic teaching heavily "Un-Schrödinger-izes" the works of Erwing Schrödinger. For 1926, it is war, a fight to the death against waves, de Broglie, Schrödinger, and more discretely, against Dirac too... Since 1986, against John Cramer, too.

    I have scanned the paper from La Taena and de Maria :

    Schrödinger's and Dirac's Unorthodoxy in Quantum Mechanics

    20 pages, Fundamenta Scientiae, Vol. 3, No. 2, pp. 129-148, 1982.

    Text "as is", is at http://deonto-ethics.org/resources/physique/Unorthodoxy.odt

    Still needs work for corrections.

    For 1930, the "lights" in the Göttingen-København sect behave in front of the Zitterbewegung like a hen who has found a knife. Dirac was far mor cute. See his Nobel lecture, 1933.

  • Ma'en Zaid Abu-Qamar added an answer in Quality of Health Care:
    How do I measure the quality of health care in hospitals?

    Many of the avialble studies on patients satisfaction with health care in hospitals do not reflect the correct picture! mostly overestimate the quality. 

    When we study the health care quality in hospitlas, what dimension should we include? whom to ask {Which sample, what characteristics}? to study QoC in qualitative or Quantitative approach?

    Ma'en Zaid Abu-Qamar

    Hi Professor Muayyad,

    This is not filed of research. But, I touched on this during my doctoral studies. The quality of healthcare can be measured by assessing outcomes of healthcare.  There are indicators of healthcare that can be assessed. Examples of these include the duration of hospitalisation. Patient satisfaction is one aspect. The indicators are complex and varied. This paper could give an idea.


     I hope this could help

  • Chen Liu added an answer in Bioceramics:
    How often should I change SBF solution during degradation test?

    I'm doing a degradation test for electrospun scaffolds (composed of polymers and bioceramics) using SBF (simulated body fluid). How often should I change the solution for my samples to keep the results accurate?

    P.s: I'm planning to keep my samples in it for 2 or 3 weeks

    Chen Liu

    During the early period, change every day. With the time goes long,change every two days. 

  • Bibhuti B Sahu added an answer in Waveguides:
    Is anyone familiar with P-Band circular waveguide?

    Are there any comapnies manufacuring such kind of waveguides

    Bibhuti B Sahu

    Microwave frequency bands

    Frequency range
    P Band
    300 MHz-1GHz
    L band
    1 to 2 GHz
    S band
    2 to 4 GHz
    C band
    4 to 8 GHz
    X band
    8 to 12 GHz
     "P band" is used for ultra high frequencies below the L-band.

    You can design and fabricate by your self once you fix up your operating frequency range and then estimate the waveguide dimention.

    May be following link would be helpful for you.


    Additionally: You may try the company (I am not sure)

    Contact Us
    Microwave Communications Laboratories, Incorporated
    7255 30th Avenue North
    Saint Petersburg, FL 33710.


    Toll Free Number



  • Akhila Vijaykumar added an answer in Flip Teaching:
    How do I make the students more participative and interactive through the online live lectures?

    For flipped classrooms and pedagogical approaches

    Akhila Vijaykumar

    Thank you all for varied and valuable inputs.

  • Igor Brown added an answer in Algae:
    Can I store Oxygen which is produced by algae production?

    As algae photosyntetic organism, they produce oxygen and i am wondering if this is possible to store this produced oxygen in order to use fish production (RAS system). Any idea? Papers? Company?
    Thanks :-)

    Igor Brown

    You can store O2 produced by an alga  as O2/N2 mix but not as pure O2. For this end you will have to flush the out-flowing  gas mix from a bioreactor through a hydroxide solution to bind CO2. Perhaps Ca(OH)2 will be most effective. Most likely the removal of CO2 may require several cycles.

    I am very curious whether some one can propose a simple method to fraction O2/N2 mix without application of cryogenic technique. IB

  • Harrison Andeko asked a question in Toxicology:
    Explaining various toxicological tests?

    i need a brief explanation of toxicological test performed in a biotechnology laboratory

  • Shin Wei Tie asked a question in Human Cell Lines:
    Is gene expression real time RT-PCR study having a big biological replicate differences?

    I am doing real time RT-PCR of human cell line. May I know if the gene expression in different biological replicates will be different or almost the same?

  • Ted Dunning added an answer in Data Mining:
    How to Avoid Overfitting?
    Overfitting is a phenomena in data mining. Many methods are reported in the literature but not many working examples. I need some good reference on the topic.
    Ted Dunning

    Actually Tshilidzi's idea of introducing noise is a really excellent one.  If you extend it to the concept of not only adding noise, but also adding small transformations of the inputs, you have one of the more important methods of getting really excellent models out of simple learning algorithms.

    Check out this paper for an example: http://arxiv.org/pdf/1003.0358.pdf

    This method of training on deformations of the input was able to set a record (at the time) for isolated hand-written digit recognition.

  • Tarek Abdellatif added an answer in Quantitative Analysis:
    How can I do the species delimitation test?

    I need to differentiate the two species sequences by any DNA quantitative analysis. morphologically those species was identified but genetic variation very is  less. what method i should follow?.

    Tarek Abdellatif

    I adice you to read these papers

    - http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0097556

    - http://sysbio.oxfordjournals.org/content/63/4/534.short

    - http://sysbio.oxfordjournals.org/content/63/2/119.short

  • Jose William Porras added an answer in Algebraic Number Theory:
    What is the minimum gap between algebraic numbers?

    Dear searchers,

    The set of all algebraic numbers is countable. I wish if someone can help by giving the smallest gap between algebraic numbers in general, or between the conjugates in particular, or if that gap depends on the degree or the wight or the height of the minimal polynomial of them. 

    Recall that the conjugates are the roots (zeros) of a minimal polynomial

    Jose William Porras

    According to what is expressed in the previous answers, I think that the smallest gap does not exist because the gap tends to zero when n tends to infinity. 

    There is something more interesting and is related with the primes:  which is the lower boundary of P (k + 1) - P (k) being both primes when k tends to infinity?

    This is my answer:

    Dirichlet, demonstrated that:

    For any two positive coprime integers a  and b  , there are infinite primes of the form  a+bm, where  n is a non-negative integer (n=1,2,... ). In other words, there are infinite primes which are congruent to a mod b . The numbers of the form  a+bn is an arithmetic progression.

    Actually, Dirichlet checks a result somewhat more interesting than the previous claim, since he demonstrated that:

    ∑_(p=a mod b) [lnp/p]→∞

    Which implies that there are infinite primes p≡a mod b.


    H_1:=〖lim⁡inf〗┬(k→∞)⁡(p_(k+1)-p_k )=2

    Becasue according with Dirichlet's theorem:

    p_(k+1) when k→∞)=[(a+bn when n→∞)] and

    p_(k) when k→∞)=[(b+bn when n→∞)]

    Then the smallest gap will be a-b=2, since primes.2 are odd.

    This solved the conjecture of twin primes. Zhang came to 246 in  2014 by other form.

  • Nazat Fahmi asked a question in MALDI:
    A peptide has one chlorine in the structure, but in MALDI, it only shows the m/z peak from the primary isotope, how to explain that?

    3 peptides (MW- 741g/mol, 798 g/mol) was synthesised via SPPS ad were analysed by using MALDI. Although each of them contains one chlorine in their structure, the MALDI trace only shows one [M+H]+ peak;  i.e. for the peptide with MW 741, the m/z peaks are at 742.33 and 743.33 (instead of 742 and 744). How can it be explained?
    Thanks :)