132,754 research outputs found
Formal Computations and Methods
No full textWe present formal verification methods and procedures for finding bounds of linear programs and proving nonlinear inequalities. An efficient implementation of formal arithmetic computations is also described. Our work is an integral part of the Flyspeck project (a formal proof of the Kepler conjecture) and we show how developed formal procedures solve formal computational problems in this project. We also introduce our implementation of SSReflect language (originally developed by G. Gonthier in Coq) in HOL Light
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
CHEMISTRY OF N-HETEROCYCLIC CARBENE–BORANE COMPLEXES
No full textStudies on chemistry of N-heterocyclic carbene-borane complexes (NHC-boranes), a new class of organic reagents, are reported. The radical chain mechanism of xanthate reduction with NHC-boranes has been established by the evaluation of rate constants of hydrogen abstraction, the isolation of boron-derived by-products, and EPR spectroscopic studies.
NHC-BH3 complexes have been found to react with many electrophilic compounds. They reduce alkyl halides and sulfonates by an ionic mechanism. The boron products of their reactions with halogenation agents, Brønsted and Lewis acids were isolated and characterized.
NHC-boryl iodide and triflate complexes undergo nucleophilic substitutions at the boron atom. In this way, a variety of substituted boranes with unusual and unprecedented structural motifs were prepared, including boryl azides, nitrosooxyborane, and nitroborane. The reaction with phenoxides in tetrahydrofuran (THF) afforded unexpected products of THF ring opening. A compound with a novel dihydroxyborenium cation was obtained from certain disubstituted NHC-boranes under acidic conditions.
Reduction of NHC-boryl iodide complex with lithium di-tert-butylbiphenylide (LDDB) gave a reactive NHC-boryl anion. This was trapped with several electrophiles to obtain boron-substituted complexes, including acyl boranes. Deprotonation of imidazol-2-ylidene-boranes with BuLi and subsequent reactions with electrophiles allowed us to prepare ring-functionalized NHC-borane complexes. The resulting complexes of substituted NHC and BH3 can be converted to corresponding substituted imidazolium salts by a simple deboronation protocol
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
IRMS, SNIF-NMR and proton NMR in wine analysis
No full textWine is an important element of world food industry; last year the wine production in EU was over 180 million hl (over 60% share of the world) and contributed over € 7 billion to EU trade balance. Such large markets always attract fraudulency and wine is no exception: in 2012 to 2015 counterfeit goods have cost € 59 billion, of these spirits and wine being € 2.7 billion. Therefore, effective control of such adulterations requires use of robust and reliable analytical methods for authentication of wines. One of these is isotope ratio mass spectrometry (IRMS), via which it is possible to measure ratios of nature stable isotopes of carbon, hydrogen and oxygen in wine. They depend on the origin of the compounds containing them and, therefore, allow for determining geographical origin of the samples and addition of water and exogenous sugar. Another approach is Site-specific Natural Isotopic Fractionation Nuclear Magnetic Resonance Spectroscopy (SNIF-NMR). By this method, the site-specific D/H isotope ratio in methylic and methylenic sites of ethanol is measured, and the values aid in determining the origin of ethyl alcohol in wine. In 1990s European Commission and International Organization of Vine and Wine (OIV) has adopted this method as a certified official method for analysis of wines. It is the only method based on NMR recognized as official standard. IRMS and SNIF-NMR methods are robust and reliable, but have some disadvantages, such as use of expensive standards, prolonged sample preparation, expensive equipment maintenance; also, the analysis is destructive in many cases. Over the recent years, a new approach for wine analysis emerged: proton NMR spectroscopy, which can be used for either targeted analysis, or non-targeted profiling. Compared to classical methods, proton NMR requires less sample preparation, less time to record the spectrum and has cheaper equipment maintenance costs. However, it has not yet been officially approved for food authentication
Se-speciation investigations at neural barrier (NB)
No full textIntroduction: Se-speciation helps for deeper insight into Se-metabolism and transport, important at NB or under
neurological diseases. Analytical set-up of hyphenated speciation techniques with 2-D-identification of Se-compounds
is described. Then applications at NB in paired serum and cerebrospinal fluid (CSF) samples are reported, finishing
with comparison of Se-speciation of neurologically diseased persons vs. controls.
Method: Serum and CSF samples were subject to speciation analysis by HPLC-ICP-DRC-MS. For improved species
identification Se-species were analysed serially after HPLC by CE-ICP-DRC-MS (2D approach).
Result: Paired samples had 58.39 (serum) or 0.86 (CSF , each μg Se/L). Prominent Se-species were selenoprotein-P
(SePP), glutathione-peroxidase (GPx), thioredoxinreductase (TrxR), Se(IV) and Se-albumin (Se-HSA).
Relationships between Se-species from serum and CSF allowed evaluating Se-species passage across NB: SePP-serum
correlated with total Se-serum when > 65 μg/L. SePP-CSF appeared independent from SePP-serum. For anti-oxidative Seenzymes
higher correlation factors (r2) were calculated: GPx-serum/GPx-CSF: r2=0.3837 and TrxR-serum/TrxR-CSF:
r2=0.6293. No correlation for inorganic Se-compounds was found proving limited representativeness of their circulating
levels beyond NB[1].
Se-species-ratios (CSF/serum) were 21.4*10-3 (TrxR) or 8.3*10-3 (GPx), being significantly elevated compared to NB
permeability factor 3.8*10-3 (HSA).
In a hospital-referred cases-control we investigated Se-species in CSF of patients with amyotrophic lateral sclerosis,
compared to reference neurological patients. We found an excess concentration of inorganic Se(IV) and reduced levels
of organic Se-compounds among ALS patients[2].
Discussion: ROS-protecting enzymes GPx and TrxR seem to be shuttled across NB to brain/CSF. In ALS etiology
overexposure of inorganic Se(IV) together with decreased organic Se-species may be involved in ALS etiology
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Scholarly Communication and Publishing Lunch and Learn Talk #11: The ULS Open Access Author Fee Fund
No full textAt the May 2014 talk, you will learn about the ULS Open Access Author Fee Fund--what it is, why we do it, how it works, and how the program is going so far
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