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  • Wael Abdelraheem added an answer in Benzamidines:
    Polar compounds separation by HPLC - any thoughts?

    I have a polar compound (Benzamidine) and want to retain/analyze it by HPLC using Discovery C18 or C8 column. I tried many eluents (e.g., ACN, MeOH, EtOH, phsphate buffer pH 7, water) with these columns but could not seperate it. Is there any suggestions? Provided that polar compounds are difficult to retain by these conventional columns because they make an electrostatic bond with the stationary phase of the column.

    Wael Abdelraheem · University of Cincinnati

    Thank you for the responses.

    I did not use amm.acetate as a mobile phase but if you believe it will work then I can try.

    Actually I have these two types of columns I mentioned beside a C8 amide column. I have many solvents to use beside those ones I mentioned. 

  • Saso Tomazic added an answer in Microsoft Windows:
    How can I make (in a program) a virtual disk on MS Windows?

    Does anybody know how to program a virtual disk (a file which acts as disk) in Windows. For example, program TRueCrypt installs virtual local disk, which looks like a real disk although the content is encrypted and stored in a file.

    Saso Tomazic · University of Ljubljana

    Nicolae , I've sent you an e-mail. Hope you'll answer

  • Gary Hurd added an answer in Pottery:
    In TL dating of ancient potteries, is it necessary, or even recommended, to take into account the moisture content of the sample?

    I come from OSL dating of geological samples, where the moisture content of the sample is very important. I've read several papers about thermoluminescence dating, but none of them is specific about the significance of moisture content when it comes to archaeology.

    Gary Hurd · Retired

    Soil humidity modifies the retention of radon, and in occasionally saturated matrix you could also have dissolved uranium, and thorium oxides. Thorium could actually be removed in very wet conditions. However, if you use single grain methods, the native gamma dose will be much higher than any occasional one external to the mineral grain.

    This is fairly old information. You might still find “Chronometric Dating in Archaeology” by Taylor, and Aitken (1997New York: Plenum Press).

  • How to use R language for larger datasets of size more than a machine RAM size?

    I am implementing statistical models for my project having very large data with me. I have used R language for implementing this and now i want to use machine learning model on it. But it creates problem while loading the data into RAM or sometimes performs operation for some data and throws error and stops working. I need solution for this problem so that it should carry its operation automatically. I have tried bigmemory and ff packages also but its not working. Is there any solution for this problem?

    Amir B K Foroushani · Simon Fraser University

    Hi Mayur,

    As Mathias mentioned, RMySQL or RSQLite  could be useful in your case.

    Here a couple of  additional "pure R" solutions:

    A) If you have a lot of columns and can preform your analysis in a column-by- column fashion, you can use the colClasses argument of read.table()  in a loop that skips certain columns in each step:

    http://stackoverflow.com/questions/5788117/only-read-limited-number-of-columns-in-r

    B) Similarly, if  you have too many rows and and can preform a row-by-row analysis, you should take a look at the skip an nrows arguments of read.table()

    C) If your data is relatively sparse,  the functionality in package Matrix might be helpful:

    http://www.johnmyleswhite.com/notebook/2011/10/31/using-sparse-matrices-in-r/

    Good Luck,

    Amir

  • Tameika Bartley added an answer in Reductionism:
    Why did quantitative analysis of total flavonoid content with AlCl3 in plant extract give positive result but qualitative tests gave negative results?

    I have estimated flevonoids content qualitatively with Zn-HCl reduction method, Lead acetate, shinoda's test and alkaline reagent test. these tests give negative results but the quantitative estimation of total flavonoids content with AlCl3 method showed the presence of flavonoids. what is the reason behind this? 

    Tameika Bartley · The University of the West Indies at Mona

    The extract may contain a larger number of flavonoids than what was detected by the qualitative tests. The level/concentration of the compounds detected quantitatively may not be sensitive to the qualitative method that was used.

  • Hugh Buckingham added an answer in Phonology:
    Are minimal pairs and auditory discrimination grouped within phonological awareness?

    I want to know if I can group minimal pairs and auditory discrimination in phonological awareness category or these three are totally different?

    Hugh Buckingham · Louisiana State University

    First, auditory discrimination is the job of the hearer.  The speaker must  have the productive knowledge to produce phonemic targets WITHIN ranges whose quanta are within the acoustic realm such that the hearer can perceive the correct intented phoneme of the speaker.  Neither the speaker nor the hearer can afford to be "off target" with any of the major distinctive features that uniquely provide the phoneme in question.  Now, this is PART of what some call "phonological awareness."  Three other aspects of this "awareness" deal with phoneme - grapheme mapping as well as the segmentation of phonemic and/or graphemic strings into their  constituent parts, and the appreciation of the  basic syllable constituents and the templatic hierarchy of that syllable.

    Be aware (no pun!) that this "awareness" is platonic in the sense that it is NOT at all "out of awares" in the explicit.  No.  The awareness here is in the "implicit" realm, and therefore in an important sense, the childre3n are not consciously aware of any of this, and surely cannot comment on what it us that they are "aware" of.  The actual structural patterns that constitute their "phonological awareness" must be drawn out by elicitation or experimentation or by engaging them in conversation - with a recorder turned on.

  • Andrea Manconi added an answer in SAR:
    Are SAR images the best solution for ground monitoring?

    Do you think that the best solutions for ground monitoring and maps updating in the areas of high clouds cover, most months of the year are the use of SAR Images?

    Andrea Manconi · National Research Council

    I think that space-borne SAR is a very powerful tool to monitor ground surface. However, effects as foreshortening and shadowing might introduce some difficulties in the visual interpretation of ground features. Regarding deformation, DInSAR has demonstrated in the last two decades its potential in several conditions. I agree that standard approaches are well suited for slow deformation processes. However, emerging techniques combining phase and amplitude analysis of the SAR signal can be used to monitor also rapid and large displacement. Regarding the high costs, well this is true at the moment. However, new generation missions as the ESA SENTINEL-1 will provide open access to data. In addition, for research purposes data can be usually gathered at lower rates than for commercial use.

  • Tameika Bartley added an answer in Hydration:
    Do aqueous solutions of strongly hygroscopic salts continue to hydrate over time?

    For example, our lab has been experiencing problems with dry Lithium Bromide taking on water mass when we work with it. If we make a highly concentrated solution of this salt as a stock solution, will it continue to attract water from the atmosphere and thus become more dilute over time? 

    Tameika Bartley · The University of the West Indies at Mona

    The hygroscopic salt will absorb water from the atmosphere even if it is already in solution. Basically, solution is the interaction of solute particles with the solvent (water in this case). So if the solute is hygroscopic, it will absorb water vapour even if it is in a concentrated solution to attain equilibrium of water to solute particles. Keep the solution in a tightly closed container. Alternatively, you could keep the anhydrous salt in a tightly closed container and prepare smaller stock volumes of solutions only when needed instead of preparing a stock to use over a time period.

  • Imre Tóth added an answer in Phosphines:
    How does one remove triphenylphosphine oxide from product?

    I am synthesizing 1,3-bis(1-phenylethenyl)benzene using Wittig reaction. My crude product contains TPPO (triphenyl phosphine oxide) as an impurity and the product and TPPO both are soluble in ether and most of the solvents. Can anyone suggest how to remove this TPPO from my product and recrystallize my product to get pure crystals?

    Imre Tóth · University of Pannonia, Veszprém

    The synthesis of NiCl2(OPPh3)2 was among the references I've sent above.

  • Andreas Hemming added an answer in Ethnography:
    Justifications for using covert participant ethnography?

    What are the main reasons for using covert participant ethnography (i.e. undercover as an employee within a workplace, in order to observe management practises/HR relationships)? Or indeed, not?

  • Emre Erturk added an answer in Systems Thinking:
    What kind of systematic inputs or triggers are needed for a knowledge building community or class?

    From the perspective of systems thinking, we can view a classroom as a system: composed of dynamic units or actors, autonomous, and part of a larger system. A system also gets inputs. For an actively engaged and knowledge building classroom, what initial inputs or preparation is necessary? In addition to a certain level of maturity and prior knowledge, does this system require some initial "knowledge transfer" from a teacher, mentor, or supervisor? What form does this come in (e.g. establishing rules, providing effective reading or learning tips, teaching a certain amount of background theory, and so on)?  What do you think? Any concrete examples of initial preparation, inputs, or direct transfers in your face-to-face or online classes, or at the institutions you have studied or worked in, that helped achieve heutagogy and knowledge building? 

    Emre Erturk · Eastern Institute of Technology

    Hi James, That makes sense. For heutagogy and knowledge building to become more effective, social skills, literacy skills, and communication skills may act as inputs or prerequisites. These are some of the things we can foster in our students as we expect them to become more independent, work with each other, and learn together. In one of our courses that has a major group project, we do a team building session early in the course. Although we expect them to bring a sufficient level of literacy and communication from their high school education;.. in higher education, we can still continue to inform our students and continue to help them become better learners. 

  • Can pseudotachylites be related to mineralization trigger events?

    It's understood that earthquakes can be triggers of mineralizing events, but there is no evidence of a direct relationship between these events and the generation of pseudotachylites

  • Sergei Turanov added an answer in Fish:
    Can anyone provide reliable information on species pairs (fishes are preferable) that have clear differences in morphological characters?

    Can anyone provide reliable information on species pairs (fishes are preferable) that have clear differences in morphological characters but show a little or no difference on the DNA level?

    Species names in Latin would be nice.
    References would be great.

    Thank you!

    Sergei Turanov · Institute of Marine Biology

    Thank you all!

    Finally, my case.

    In my study on DNA barcoding one can  find results on variation analysis of the gene COI in Stichaeus grigorjewi and S. nozawae. Their values have low variation and overlap. But they are really different species with distinct features on morphology, behaviour , feeding, etc. However, they are found in the area of ​​sympatry and have a narrow area, and as well are considered the most primitive members of the family Stichaeidae.

  • Janos Mink added an answer in Molecular Geometry:
    What will be the molecular geometry of TICl4 molecule in magnesium dichloride supported Ziegler Natta catalyst?
    Can it be explained by any theory?
    Janos Mink · Hungarian Academy of Sciences

    If you can measure IR and Raman spectra . the extent of distortion from regular tetrahedron can be estimated with good approximation.

  • How can we increase the awareness of the need for innovative solutions to the world's water problems?

    This year, Iran is facing dangerous water crisis as arid temperatures rise with the encroaching summer season. As summer presses and temperatures rise, water scarcity in Iran is becoming a national emergency.
    Who to blame? It is said that the water crisis in Iran is a two pronged problem. Global climate change (arguably helped along by the country's heavy GHG emissions) is intensifying the region's already arid climate. The other problem, and what many experts say is the most immediate problem, is the people of Iran themselves.Despite imminent shortages, water use in Iran remains inefficient, with domestic use 70% higher than the global average. Accordingly, experts say the Iranian people are to blame for this problem (with GHG emissions helping the crisis worsen).
    Other countries may be experiencing similar problems to my country. Remember that "as the world's population is expected to reach 9 billion by year 2050 and at the rate we are going there won't be nearly enough water for that many of us". Therefore, We must raise awareness and groom the scientists and professionals that we need for both today and tomorrow. Students in today's classrooms are the scientists and technologists of the future that we will need to meet this challenge. How can we inspire them? Overcoming fear of failure is a necessity to overcome crises and for success on any level.

    António Manuel Abreu Freire Diogo · University of Coimbra

    Raining water is for free! So why desalinization, treatment and reuse, or Inter-basin transfer? You have just to catch the water from your roof to a tank and wait for the rain. In a larger scale, you just have built a dam to retain the water as superficial water in a pond or in an aquifer after infiltration. That will work excellently if you have good topographic conditions for the pond and if there is enough rain.

    However, we are speaking about arid climates. If it rains in average less than 100 or 200 mm in a year, and the rains are scarce, erratic and intense (it may not practically rain during several consecutive years) you cannot wait a year to drink your cup of water or have your bath. Other interesting alternatives had been tested and abandoned, for example trying to interfere with the clouds or condensation of fog.

    If you have a big flood, short and intense, in two or three days in a year in an arid climate it does not mean that you can solve the problem catching that water. With the current climate change, we have too much water in some places (really huge floods) and to less in others (really dry climate). Globally speaking we have really many, many, many water for the 9 (American) billions (do not worry). The problem is just where, when and with what quality (we just have to work on that). I hope this can helps.

  • Do you have SEO with your academic papers?
    Getting citations is becoming increasingly important to the academic career of a researcher or professor, so worrying about them is logical.

    SEO is a marketing methodology that improves network positioning on search engines like Google, and if applied to your papers makes them more easily found, and thus most frequently cited.

    If you get published in indexed journals, you're doing almost everything right with your article, when writing and rounding it. You just have to review the SEO recommendations to display your articles in search engines in a more relevant way.
    Maria-Teresa Soria-Trastoy · Universidad de Cádiz

    Being a Senior SEO Consultant and a Researcher in Archaeology, I hope that most of the tecniques and practices used to reach the best position in Google, for example, through SEO never will be used in ASEO.

    As pointed above, it is not the same if you have your own website to promote your papers or if you are using a external platform (Social Network) like this one (ResearchGate, Acaemia.edu,...). Neither is the same to optimize your papers for a given group of scholars with a given interest or if your target is all the scholars or the public in general. You have to use either different SEO techniques taking in mind where you want to be found.

    Generally speaking, if you write your paper scientifically centered on a subjetc in which the title is a description of its content and the abstract is its summary, the SEO work is done inside the paper. That way you don´t need to count your keywords or measure the keyword density: if you write an article on "fish gorges" that keyword will appear enough times in the body if your article is consistent; moreover taking into account the new algorithm of Google where you can use synonims, plurals, singulars, masculine femenine genders being the same to Google. If you have your own website to promote it, take care with metadata and use structured data (this is a must: http://schema.org/Article); if not, take care with tags and description. Use Academic Social Networkings, etc, etc. Optimization is not the same now when your target are mobile devices or a desktop platform.

    This is a complex matter with a lot of variables to take into consideration before giving a non exist magical recipe. And please, never forget why you write an article, what are you writing for and who are you writing for. The aim of research is not to be at the first position in the first page of Google Scholar.

    This article must be useful for you, although I do not share some of its statements and it is a little bit outdated (2010): http://www.sciplore.org/publications/2010-ASEO--preprint.pdf

    Best,

  • Christopher J Brown added an answer in Waste Water:
    When can Potassium, Chloride and Bromide be a good indicator for leakage from waste water?

    How we can know that increasing Potassium, Chloride and Bromide concentration can be an indicator about leakage from waste water into groundwater.

    Christopher J Brown · University of North Florida

    You may also want to look at the ratio of various compounds in the wastewater and groundwater.  Also, as noted by my peers, identifying some tracer compounds in the wastewater that are not in the groundwater in appreciable quantities would provide a means to track wastewater leakage into ambient groundwater.  Another interesting tracer would be caffeine as that has been found in wastewater since the 1970s.

  • Do you agree that the digital revolution can fix scientific publishing and speed-up discoveries?

    There are several Q&A threads on RG about this issue; here is an additional perspective worthy of consideration by the RG community.  Do you agree with the problems and solutions outlined in the attached article?  Do you have any other suggestions that would improve the scientific publishing paradigm? 

  • Nima Nezafati added an answer in Minerals:
    What mineral is this?

    In my microscopic investigations on an andesite, I find a rather frequent mineral (please see the attached image), scattered as hypidiomorphic grains (size: 1 to >50 micrometer) with the following general composition (measured by SEM/EDS):

    Fe: 20 to 37%,

    Cr: 9 to 12%,

    O: 29 to 48%,

    Al: 4.5 to 12.5% 

    + variable amounts of Ti, Mg, Zn, Si, Ca

    I can not figure out a name for the mineral (although have already checked webmineral.com).

    I would be grateful for any help in this regard.

    Nima Nezafati · Deutsches Bergbau-Museum Bochum

    Dear Jason,

    Many thanks for your answer. Unfortunately I have no access to EPMA for the time being.

    Concerning your questions, yes the andesite is an amigdaloidal andesite and has born a low grade metamorphism (prehnite, pompleite, chlorite facies). The grains are not big enough to be examined in hand speciemen. I did not recognize any zonation in the mineral (using SEM).

    Anyhow, I think the grains should be a kind of "chromian-zincian hercynite or magnetite". But hercynite seems to be more likely.

    Best regards

  • Jumana Baaj added an answer in Epidural Anesthesia:
    When would you administer an epidural analgesia?
    What is your opinion regarding a request for epidural labor analgesia for a parturient woman with fever (38 º Celsius) and leukocytosis plus neutrophilia and no focal infectious signs? Would you use it or refuse?
    Jumana Baaj · King Saud University

    I prefer to avoid epidural  catherinsertion in   such this patient 

    the fever could be related to chorioamnitis or the patient has prolong rupture membrane with multiple vaginal examination 

    epidural it self may induce fever which exagerate the effect of this hyperthermia on the mother and baby 

  • Dr. Godfred A. Menezes added an answer in PCR:
    Can PCR identify all strains of E. Coli in water sample?

    I would identify all strains of E. coli in groundwater and surface water samples. I am not sure if PCR can help me to do this, and what do I need?

    Thanks

    Dr. Godfred A. Menezes · Jawaharlal Institute of Postgraduate Medical Education & Research- JIPMER, India (past), Erasmus MC, Holland (past), Sree Balaji Medical College & Hospital (Current)

    You have to try out a multiplex PCR, sets of primers depends on how many serotypes you would like to target, such as ETEC, EPEC etc., 

    You can use upto 4 to 5 sets of primers easily in multIplex PCR. 

    Initially you have to take the pain of finding out the primer sets (from existing publications/ or by primer designing).

    Please check this paper as an example of multiplex PCR. 

    Simultaneous Identification of Strains of Escherichia coli Serotype
    O157:H7 and Their Shiga-Like Toxin Type by Mismatch
    Amplification Mutation Assay-Multiplex PCR. JOURNAL OF CLINICAL MICROBIOLOGY, Jan. 1995, p. 248–250

  • Does anyone know of a conceptual model for reclamation of wastelands, simulation and integrated modelling for agricultural development?

    I believe that we can make a conceptual model for watershed reclamation projects driven from wasteland reclamation and integration of reclaimed lands into a basin. does anyone know of such a model or have published any relevant reports?

    Christopher J Brown · University of North Florida

    There are conceptual models for reclamation of landfills, mine tailing wastes, and abandoned mine areas.  I would search the literature in those areas.  Good luck with your interesting question.

  • Emilio José Chaves added an answer in Randomized:
    Can a bivariate random dataset be nonlinear and polysemic at the same time?

    Variables are Q,Y and dataset N=11. As expected the graph Yvs.Q is non linear, but for the same Q it shows two different Y values. Dataset is  down:

    I ask: 1) Are these cases frequent in natural sciences?, and 2) Can the ambiguity results be worked with traditional statistics of linear correlations, predictors, etc.? Thanks in advance for your answer and reasons.

    Q      Y
    3      5
    2,84 4,88
    2,76 4,72
    2,76 4,52
    2,84 4,28
    3      4
    3,24 3,68
    3,56 3,32
    3,96 2,92
    4,44 2,48
    5      2

    Emilio José Chaves · University of Nariño

    Henry, indeed I used the computer as a lab, but the generated data is non parametric because it does not contain parameters, but only coefficients and exponents on variable x; it is made of polynomic expressions. They are linked through X, the receptor cummulative population. Q is related to Y, Y to Q, and both to X. None of them is an independent variable that makes the other dependent; they are simply related because in the moment I declare the table is the dataset, we may graph X vs Q, Q vs. Y, Y vs. Q, etc. With Q,Y data we may graph them and observe their curved retalionship at once, with some polysemic interval. These cases only admits nonparametric analysis. You may design many examples made of more complex shapes and declare them as your data.

    In nature we observe winds with positive velocities and diferent orientation, with their own temperature, humidity, pressure, sunlight, etc. When they meet they create an unsteady situation that must be solved someway. Many times they dissipate, other times they resolve as rain, as a thunder, as a tornado, as snow, etc.. This is a polysemic situation for us, not for nature that finds something to grasp itself and discharge its energy getting a new more quiet balance. Those events contain a natural random component with several options and non-linear behaviour, that we hardly understand.

    I have strong doubts about linear models and correlations to solve  simpler cases. So I seek some help and new ideas about it. This motivated my question. OK, my regards.emilio

  • Janos Mink added an answer in Solvents:
    Are there any organic solvents that can dissolve K2PtCl4?

    K2PtCl4 solubility.

    Janos Mink · Hungarian Academy of Sciences

    According to our opinion  H2O is the best solvent, but [NEt4]2PtCl4 is soluble in many organic solvents.It is true for other tetraalkyl ammonium derivatives.

  • István Nagy added an answer in FASTA:
    How does one join two text files with using their shared sequence identifier?

    I am working on Sequence Read Archive (SRA) datasets. I have one fasta file containing the SRA identifier and the sequence (atcagtt..) and one blast output file including sequence identifier, gi number and the rest of the details. Both of them are in csv format.

    I want to use the common sequence identifier to combine my files. Eventually I would like to have one file with all the sequence information as well as the sequence itself.

    Attached is link for a possible solution, however the sort function does only give me the sequence (as in aaccgttc...), but no identifiers.

    István Nagy · Aarhus University

    I had problems by attaching the Perl script as a file.

    You find the script below. Copy the content between the  xxxxxxx lines, save it as

    <replace_fasta_headers.pl>

    and make it executable.

    xxxxxxxxxxxxxxxx

    #!/usr/bin/perl

    # Found in old times on Internet. Don't remember where.
    #Made little modifications on it. IN

    use strict;
    use warnings;

    @ARGV == 2 or die "usage: $0 <multifasta file> <header replacement file>\n";

    my ( $fasta_file, $header_file ) = @ARGV;
    my $destination = $fasta_file . 'headers-replaced.fasta';

    open IN2, '<', $header_file or die "Can't read from tab-delimited header replacement file $header_file: $!\n";

    my %head_seqs;
    while ( <IN2> ) {
    chomp;
    my ( $old, $new ) = split /\t/;
    $head_seqs{ $old } = $new;
    }
    close IN2;

    open IN1, '<', $fasta_file or die "Can't read from multifasta file with alternating lines of headers and sequences $fasta_file: $!\n";

    open OUT, '>', $destination or die "Can't write to file $destination:
    +$!\n";

    while ( <IN1> ) {

    if ( /^>(.+)$/ && exists $head_seqs{ $1 } ) {
    $_ = ">$head_seqs{ $1 }\n";
    }
    print OUT $_;
    }
    close IN1;
    close OUT;

    xxxxxxxxxxxxxxxxx

  • Why does Feynman not discuss the electrical conductivity of metals?

    I was surprised by the fact that Drude’s formula for the electrical conductivity of metals does not appear in the famous textbook: “The Feynman Lectures on Physics”.

    Kai Fauth · University of Wuerzburg

    Ashcroft & Mermin in their first chapters give an excellent exposition on merits and problems of Drude & Co.

    As soon as you decide to drop that idea for good, you're in to solid state physics, crystals, k-space etc until you comme back to the point where you have a representation of what a current carrynig state may look like. Its not whithin the scope of Feynman's books... (not explicitely, at least)

  • Masa Radulovic added an answer in Co-authorship:
    Does co-authorship lead to more scientific researches?

    Co-authorship aimed at inducing collaboration between authors, increasing their productivity, and improving the researches quality. What is your opinion?

    Masa Radulovic · University of Novi Sad

    It depends. 

    I  prefer to be independent in my research, but I have had experienced co - authorship as well, and it was interesting process. If your co - author / is / are productive and can contribute , be responsible for the work, and if you all make good team, then why not? 

  • Can anyone suggest a 3D adult spine ultrasound image database?

    For research purpose .

    Francesco Prada · Fondazione I.R.C.C.S. Istituto Neurologico Carlo Besta

    Hello. I am not aware of such a database. But in order to obtain such imaging, given the paucity of the imaging and the objective difficulty in obtaining a 360°US evaluation (chest-abdomen), it would be useful to link the US probe with a navigation system and fuse the US with a pre-aquired CT and or MRI, to enhance orientation.

  • Ulrich Kueppers added an answer in Sediments:
    Who can identify these sediments? Which sedimentary environment is appropriate for deposite of these sediments?

    This sediments belong to Sahand volcano (Tabriz, Azerbaijan) in the Late Miocene.Pliocene and are appear alternating with clastic sediments.

    Ulrich Kueppers · Ludwig-Maximilian-University of Munich

    Hi all, what I see in pictures 2 and 3 of Mobin are massive ash-lapilli tuffs that were deposited from pyroclastic density currents (PDC). The massive nature shows that the depositional conditions did not vary significantly over the course of time required to deposit this unit (looks like many hours to days to me). The current itself may have been fast but deposition took place without significant shearing at the base. The amazingly homogeneous grain size distribution of the deposit should not be taken as proxy of the composition of the travelling current and clearly does not indicate a non-stratified PDC. The deposit does not represent thickness of moving PDCs!  The brownish colour of the top of the underlying unit (figures 2 and 3) proves that the PDC emplacement was the first depositional process after a long hiatus exposing the underlying units to erosion and weathering. PDC deposits that are deposited below the temperatures required for thermal sintering are easily subject to erosion (rain, wind) and the rounded pumices are a good indicator for me for local reworking in a dense (= frequent particle interaction) medium. Abrasion of pumice clasts may also take place in PDCs (http://www.sciencedirect.com/science/article/pii/S1474706511002580) but they usually have a significantly lower concentration than suspensions in water.

  • Species distribution modelling for dummies

    Over the years I have been working, I have been compiling a presence only list (coordinates) of a rare tree species from my area. I have good reason to believe (from industry experts and the literature) that my list may be one of the most comprehensive that exists. As well as compiling this info for submission to flora databases, I wanted to put in some time to help develop the knowledge of the species, as well as learn some skills myself. I was hoping to undertake some form of species modelling to determine the species original extent (prior to european settlement which resulted in extensive clearing) and combining that with extant layers of native vegetation to get an idea on how many may still be present in remnant populations (I believe the number of trees left is far different to that commonly stated). I may even try and field truth the predictions. The species occupies a relatively narrow area of (approximately) 300x100 kilometers. 

    When I browse through the literature in this topic, I am overwhelmed. I am hoping to get some direction on the type of modelling I should do with some good guidance on how to go about it (seeing as I have limited experience in the field). Software suggestions (I am an independent researcher so free would be ideal), type of analysis to run, and guides on using the software would be ideal. I have a moderate skill set with ESRI products but again, because I am not affiliated with a university, i can not afford extensions. I know I am probably underestimating the difficulty of this task but I am willing to treat this as a learning exercise and put in the time.

    Harley Schinagl · Indigenous Design

    Thank you. I have read about maxent and thought it sounded like the most appropriate software.