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  • How can I determine the exact Hg(II) ion concentration from a unknown Hg solution by 1,5 diphenyl carbazide test?

    Wan to know the calibration curve?


    As Stefan has well said, optical or spectrophotometric methods are the best choice for Hg determination in these matrix.

    I have experience in HG-AAS determination. it is simple and not so expensive.


  • Luis R. Concepcion added an answer in E-Learning:
    How would you validate an e-learning degree as an employer?

    Would you hire a person if he would be self-taught by e-learning courses. How would you perceive his accreditation if he states that he has conducted the same research and had the same level of education but by utilizing e-learning instead of attending an official university. Would that be depending on the source of the e-learning? In that case could you name any e-learning suppliers that you feel are valid for stating that you have gained sufficient knowledge towards a certain field?

    Luis R. Concepcion · Universidade Internacional Iberoamericana

    Nienke, I have studied in both traditional (also known as brick-and-mortar) schools as well as online ones and can tell you that, as a general rule, and as long as the school that your candidate comes from is an accredited one, there should be no difference between the level of training and/or expertise between your candidate coming from an e-learning background, and a different one coming from a traditional school. I think that one glaring exception to this rule comes from the IT world where non-traditional education seems to be the rule, and candidates must show skills up-front in the form of a catalog of work done in the past.

  • Ahmed M. Abdo added an answer in Absorbance:
    Why do we use a positive control (eg quercetin) and a negative control (methanol) while calculating the DPPH free radical scavenging activity?

    Can anyone explain the importance of using a positive control (eg quercetin) and a negative control (methanol) while calculating the DPPH free radical scavenging activity?

    The formula that I am using for my extracts is as follows:

    % Inhibition = [(A0-A1)/A0] × 100
    Where A0 is the absorbance of the control; A1 is the absorbance of test samples.

  • Eddie Seva See added an answer in Joining:
    Do You think that inter-disciplinary collaboration can give multiple colors to researches?

    Time has come to break the walls of subjects. We must join hands to form an inter-disciplinary team.

    Eddie Seva See · Bicol University

    I agree. But this is not a very simple matter. We have to develop a strategy so that in our coordination efforts, "Our whole will be greater than the sum of its parts- synergy".

  • Ahmad Hussain added an answer in Higher Education:
    How do you deal with colleagues that try to hold you back and bring you down?
    While you try to do your work and "go the extra mile" in teaching and research, some of your colleagues try to hold you back and bring you down. This may be due to their complex of inferiority, unethical upbringing, jealousy, etc. How can you convince them that if you succeed in some endeavor, then the whole department/faculty/university succeeds? While you always try to be a good team player and try a constructive approach always keeping in mind how to get to a win-win situation, all the politics they do is a destructive practice where they only think about themselves and their personal benefits! How do you deal with this type of colleagues?
    Ahmad Hussain · King Abdulaziz University

    Dear Michel you have posted a very important question as we all experience this in our professional life. One has to handle his difference intelligently and efficiently so that you have minimum friction with your colleagues. Respect others and get their respect ! the simple principle.

  • Ashraf E. Sayour added an answer in Identification of Bacteria:
    Could MALDI TOF - MS be used as a specific and sensitive strain- level identification tool for Staphylococcus aureus ?

    i want to use MALDI -TOF biotyper  to confirm the identity of a number of  staph.aureus clinical isolates and i read a review that claimed its ability to provide a strain-level identification of bacteria , but when i contacted the responsible technician he seemed to have no idea about such thing , so i want to know if anyone has experienced this technology ?  

    another question , does MALDI-TOF differentiate between MRSA and MSSA ? 

    Ashraf E. Sayour · Animal Health Research Institute

    I tried the MALDI-TOF Microflex Biotyper from Bruker on Brucella.  Unlike, staphylococci, brucellae have a very high genetic and phenotypic homology, thus constitute a real challenge to the resolution of the technique.  The technique managed to differentiate brucellae at least to the biovar level.  MALDI-TOF MS is a very promising tool and a real revolution in the field of microbial biotyping.  The main challenge scientists are currently working on is to use samples directly without the need of a pure culture and proteome extraction.  Scientists are also struggling to include viruses as well.

  • Mehdi Lima added an answer in Abaqus:
    How can i model nonlinear torsional vibration in Abaqus?

    I can do linear analysis. But i dont know how do nonlinear analysis.

    Mehdi Lima · Griffith University

    Non-linearity can be in geometry or material. You can activate NLgeom  to consider nonlinear geometry. 

  • Which is the most efficient algorithm/package to solve delay differential equations?

    I wish to know the methods of solving a system of equations that require, and those which don't require computer algebra. Is there a method, which is both theoretically and computationally efficient?

    Sonam Kumar · Tezpur University

    Thanks Hans. I think I should now move to the next level of what i am doing. :)

  • M. Laura Angelini added an answer in Teaching:
    What are your best personal, innovative, and successful experiences in language teaching skills?
    Could you please share your effective and successful experiences in teaching language skills (speaking, writing, reading, listening, even grammar) to your students? It is the post-methods era and each teacher has their own particular and innovative methods or techniques to convey the intended messages to their students. What are yours?
    M. Laura Angelini · Catholic University of Valencia "San Vicente Martir"

    Hi Bahram,

    So glad you asked this question. My answer may sound simple, though the practice is quite complex. I believe one of the most important qualities a teacher must have is flexibility (apart from generosity). Teachers must be capable of integrating methods and classroom techniques to get the most of their students. In my case, I promote active learning through the integration of flipped learning and collaborative/cooperative learning. I implement simulations and games to provide my students with a worry-free context in which they can interact and develop the language skills. 

    I attach some of my research below.



  • Dear Scientists, yours suggestions about lanthanium analysis, others techniques than emission spectroscopy or arsenazoIII complexation?

    interferences of rare earth elements should be considered. Many thanks

    Please, in order to be more specific, you should give more details. What matrix? what is the content you will determine??

    I guess ICP-OES or ICP-MS may be the best choice, if the matrix is aqueous or mineral.


  • Luis R. Concepcion asked a question in Flow:
    Has anyone done any work on flow theory?

    Trying to see if anyone has done any work on flow theory that I can ask some questions. Thanks in advance for any help.

  • "Organisation of the Future" - really would appreciate if anybody can recommend some literature about these topic to me?

    Journals, papers, PhDs, Peer-to-Peer

    Olivier Serrat · Asian Development Bank

    An article titled On Networked Organizations, available at http://digitalcommons.ilr.cornell.edu/intl/268/, is on that very subject. Strangely enough, its original working title was Organizations of the Future.

  • Ahmed Najar added an answer in Allelopathy:
    Can anyone suggest publications examining dual direction allelopathy (i.e. both species interfere with each other)?

    I want to examine the allelopathy (through root exudation) of two species to determine and compare the relative allelopathic potential of both species. 

    Ahmed Najar · University of Alberta

    Dr. Inderjit Singh is your guy!

  • How to introduce mathematics in psychology?

    I was in a meeting and a man said samothing about that, so now I'm interested in that.

    George Stoica · University of New Brunswick

    Dear Marcelo,

    I would answer your question by saying that "Mathematics should be introduced to Psychology together with Statistics". It seems that, lately, the latter applies better to Psychology than the former. As for how to do it, there are short courses targeted to Psychology, as well as extended versions for those interested in details.



  • Daniel E Croker added an answer in Cell Culture:
    How long the human primary macrophages survive in cell culture?


    I would like to know how long the human primary macrophages (isolated from PCMB and differentiated) survive in culture?

    Thank you very much,


    Daniel E Croker · University of Queensland

    Hi Roberto,

    In my experience they usually last about 3 days after the 7 days of differentiation.



  • Eddie Seva See asked a question in Causality:
    Is a strong, significant relationship between variables sufficient to assume causality?

    ..even if our design is ex-post facto, non-experimental?

    I have observed in many papers where researchers make recommendations of intervention (e.g. increase salary of employees to improve their performance) on the basis of strong positive relationships arising from non-experiments.

  • Which is the correct method for N2O determination using N2 as carrier gas?

    I am working with gas chromatography using a HP 5890 series II chromatograph, for determining N2O emissions. Moreover, i am wondering which would be the best way to build the calibration curve.

    Manjula Premaratne · Lincoln University New Zealand

    Please check  our publication regarding above question. GC-ECD with 310C and alpha or beta standards up to 100ppm could be used as standard gasses.  Column temperature between 45-60C, depends on the column length. Can use sub ambient concentration such as 0.2 ppm and atmospheric concentration 0.325 ppm as low standards. Using  glass syringes, high concentration such as 100ppm can dilute with N2 to make series of standard curve.  The ECD responses to N2O polynomially.

  • Germán Bautista asked a question in Permaculture:
    How to determine a type of study in tropical home gardens?

    How to determine a type of study in tropical home gardens ?, I am interested in applying the principles of permaculture. Thank You

  • Mehdi Lima added an answer in Abaqus:
    I got an error in ABAQUS"Detected lock file Job-1.lok" please I need assistance to figerout this error?

    When I try to analyse any model even a simple model by ABAQUS software I got the same error that I mentioned please could assist me? 

    Mehdi Lima · Griffith University

    Try to run another job with different name. 

  • Jing Yang Tee added an answer in HEK293 Cells:
    Why aren't my cells migrating to serum (my positive control)?

    I'm transfecting HEK293 cells with GFP and a chemokine receptor for 16-24H in serum free media and plating 200K cells in 1% FBS Media in a transwell chamber to assess motility.  More cells migrate to my serum free media (negative control) and my chemokine than to my positive control (10% FBS Media).  I've even done an experiment with just GFP transfected cells and 0%, 1%, 2% 5% and 10% Serum Media.  There was clear migration to the 0%/Serum Free condition, and just a few cells to the other conditions.  One concern is the health of my cells after a 24H transfection with a lot of DNA...  Are there any other factors I should be considering?

    Jing Yang Tee · Griffith University

    Just to add another thought to the great conversation in this thread, FBS could potentially contain chemorepellents (i.e. doing the opposite of what an attractant will do to lead to reduced directional migration). So, the reasonable way to go about this is to use serum-free medium and supplement known chemoattractants.

  • Can you help me to find Cost effective microplate readers?

    We have planned to buy a microplate reader (absorbance) for our laboratory. The available funding is Rs.4,50,000 (7000 dollars). While enquiry, we came to know that filter based readers are comparatively cheaper than monochromatic based readers. Please suggest us to find the ideal microplate reader with this available funds.

    Thanking you in advance for your replies. 

  • Where can I find articles that describe the psychological mechanisms of activity of inventors?

    Interested in articles which describe psychological research in the area of design and invention.What diagnostic procedures should be employed for the analysis of creative thinking in this case?

    Alexander Kushch · Kremenchuk Mykhailo Ostrohradskyi National University

    Thanks, I will look at the proposed publication.But I'm more interested in the psychology of invention in the industry than the psychology of art.

  • In elderly patients more than 70 years old, do you recommend laparoscopic or open cholecystectomy?

    In elderly patients more than 70 years old with gall bladder stones, do you recommend laparoscopic or open cholecystectomy?

    Or , no surgery at all except in emergency or profound complaint?

    José Gustavo Olijnyk · Hospital Militar de Área de Porto Alegre, Brasil

    My service recommends laparoschopic approach for symptomatic disease.

  • Stephen Debus added an answer in Bioluminescence:
    Is anyone in Australia interested in researching possible bioluminescence in Barn Owls in the lab?

    If so, a contact of mine is very keen to hear from you. He proposes injecting adrenaline, under anaesthesia on captive birds in controlled conditions, into possible photophore-like structures on the breast skin, but needs an academic collaborator with facilities etc. Comments also welcome. Thanks.

    Stephen Debus · University of New England (Australia)

    Dear Mahmoud, thanks for your answer.  I was aware of the work of GLOW.  Regards, Stephen

  • Stephen Fargo asked a question in Urban Design:
    Are there any residents of Sao Paulo who can recommend a good english language source on the history and development of the city?

    I am an urban design PhD research student primarily interested in 21st century development but recognise the importance of historical information dating back up to 150 years.

  • After storage of histopathology slides for few months, we find development of minute vacuoles throughout rendering them useless, can anybody help?

    We have been facing this problem for couple of years. We have changed DPT mountant but the problem persists. The slides we have prepared in the past are good even after one and a half decades. We follow the same paraffin embedding technique now but the slides does not last long (a few months).

    Fidel Fernandez · SEGi University College

    I agree with Tony George Jacob, by principle I believe it is basically due to moisture.  where the moisture is from? only one source, which is the incomplete dehydration of the tissue that is mounted. So check the processing specially the dehydration with alcohol.  check the quality of alcohol, this could have been diluted so a 95%label could not actually be 95% etc...

  • Perikles Karipidis added an answer in Leadership:
    Culture and leadership are two sides of the same coin?

    Edgar Schein claims that: "Culture and leadership are two sides of the same coin. When organizations start or when groups start there is always a leader who has a preferred way of doing things, and those preferences by definition are going to be imposed on the group members. If you don’t like the way I run this group, I’ll replace you. The leader’s values and preferences are the first ways that a group or organization does things and if that works it becomes eventually the culture of that group. So in a very real sense, founders and leaders create culture.

    Can the same be true for an organization within business ecosystem?

    Perikles Karipidis · Technical University Darmstadt

    its debatable whether a "great man" in the beginning of an organisation shapes it indefinetly. fact is that organisazional culture is very heavily indebted to the founders of an organisation. this is very true for older organisations of medium size, which are often run by relatives of the inaugural founder.

    But I highly doubt that big multinational coorporations like Daimler are still run the way they were run at the beginning by their original founders. 

    (Daimler has changed its formal corporate structure at least 3 times in the last 20 years).

    organisational culture set by the original leader mainly survives in the way things are run informally (even in big corporations like the afore mentioned Daimler) and leadership may be exerted within this boundaries by successors. So please dont take Edgar Schein´s ideas at face value since there are several factors which have to be taken into the equation. (just study the case of german software firm SAP and its revolving door of ever changing CEOs which seemingly change organisational culture on the fly every 6-12 months :D)

    within the business ecosystem organisations need to be able to change very quickly if they want to survive. Feeling obliged to follow rules set maybe 150 years by long deceased people, who ran things differently in a way slower moving and smaller world wont help much...

  • Robert L Baxter added an answer in Evaporation:
    Is there a colorant that evaporates with the gasphase of Ethanol?

    We have a leak in our application system (bottle with spray head) and there are 4 possible ways that Ethanol (80% solution) evaporate through one or more. We hope to identify the leaking spot by passivly colouring it. Any ideas? Thanks a lot!!

    Robert L Baxter · The University of Edinburgh

    Maybe a dye isn't the best idea. I can't think of any that would co-evaporate with EtOH. If it were my project (and given a well equipped lab -or access to a reasonable University facility) I'd spike the sample with about 0.1uC of 14C-labelled ethanol ... and then spray it in a contained box, swab the area and then scan the surface of the container with a Geiger counter. Narrow area swabbing and scintillation counting of the swabs would provide definite results. OK this is drastic.

    The problem might be able to be turned round. Have you thought of putting a dye on the OUTSIDE of the container to detect the leak? 

  • Ramesh Sivanpillai added an answer in ERDAS Imagine:
    How can I remove/change the misclassified pixels during unsupervised image classification in ERDAS imagine?

    I have done unsupervise image classification and in that image the pixels of Barren area and settlement area are not get classified separately. so how to seperate them to show these two different classes.

    Thanks in advance.

    Ramesh Sivanpillai · University of Wyoming

    It will be worthwhile to read Cihlar (2000) where supervised and unsupervised classification methods are compared (section 3.2 pages 1101 - 1104). Though this paper is focused on regional scale mapping, some principles are applicable at other scales as well. 

    Cihlar J (2000). Land cover mapping of large areas from satellites: Status and research priorities, International Journal of Remote Sensing, 21:6-7, 1093-1114

    URL: http://dx.doi.org/10.1080/014311600210092

    B) As others have suggested, one way to resolve the problem you are facing is by generating large number of clusters. Another possible approach is through multi-stage iterative classification methods. Wyman et al. (2001) has provided a good description of an iterative classification method (p. 1156-1157).

    Wayman et al. 2001. Landsat TM-based forest area estimation using iterative guided spectral class rejection. PE&RS 67(10): 1155-1166.

    URL: http://info.asprs.org/publications/pers/2001journal/october/2001_oct_1155-1166.pdf