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Now showing items 145 - 160 of 86128

  • A GC-FID method for quantitative analysis of N,N-carbonyldiimidazole

    Lee, Claire   Mangion, Ian  

    N,N-Carbonyldiimidazole (CDI), a common synthetic reagent used in commercial scale pharmaceutical synthesis, is known to be sensitive to hydrolysis from ambient moisture. This liability demands a simple, robust analytical method to quantitatively determine reagent quality to ensure reproducible performance in chemical reactions. This work describes a protocol for a rapid GC-FID based analysis of CDI. (C) 2016 Published by Elsevier B.V.
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  • A Tutorial on Hunting Statistical Significance by Chasing N

    Denes Szucs  

    There is increasing concern about the replicability of studies in psychology and cognitive neuroscience. Hidden data dredging (also called p-hacking) is a major contributor to this crisis because it substantially increases Type I error resulting in a much larger proportion of false positive findings than the usually expected 5%. In order to build better intuition to avoid, detect and criticize some typical problems, here I systematically illustrate the large impact of some easy to implement and so, perhaps frequent data dredging techniques on boosting false positive findings. I illustrate several forms of two special cases of data dredging. First, researchers may violate the data collection stopping rules of null hypothesis significance testing by repeatedly checking for statistical significance with various numbers of participants. Second, researchers may group participants post hoc along potential but unplanned independent grouping variables. The first approach ‘hacks’ the number of participants in studies, the second approach ‘hacks’ the number of variables in the analysis. I demonstrate the high amount of false positive findings generated by these techniques with data from true null distributions. I also illustrate that it is extremely easy to introduce strong bias into data by very mild selection and re-testing. Similar, usually undocumented data dredging steps can easily lead to having 20–50%, or more false positives.
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  • A (t,m,n)-Group Oriented Secret Sharing Scheme

    Miao Fuyou   Fan Yuanyuan   Wang Xingfu   Xiong Yan   Badawy, Moaman  

    Basic (t,n)-Secret sharing (SS) schemes share a secret among n shareholders by allocating each a share. The secret can be reconstructed only if at least t shares are available. An adversary without a valid share may obtain the secret when more than t shareholders participate in the secret reconstruction. To address this problem, the paper introduces the notion and gives the formal definition of (t, m, n)-Group oriented secret sharing (GOSS); and proposes a (t,m,n)-GOSS scheme based on Chinese remainder theorem. Without any share verification or user authentication, the scheme uses Randomized components (RC) to bind all participants into a tightly coupled group, and ensures that the secret can be recovered only if all m (m >=3D t) participants in the group have valid shares and release valid RCs honestly. Analysis shows that the proposed scheme can guarantee the security of the secret even though up to m-1 RCs or t-1 shares are available for adversaries. Our scheme does not depend on any assumption of hard problems or one way functions.
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  • A Convenient Synthesis of N,N-Dimethylformamidines from Sulfonamides

    Chen, Yantao; Gradén, Henrik; Aurell, Carl-Johan; Gibson, James  

    N,N-Dimethylformamidines were synthesized from sulfonamides using the Vilsmeier reagent as a cleavage activator. The reactions were performed under mild conditions achieving good to excellent yields. The chemistry presented can also be used as a deprotection strategy when amines or anilines are protected with sulfonyl groups, such as the tosyl group.
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  • A queueing system with vacations after N services

    Boxma, Onno   Claeys, Dieter   Gulikers, Lennart   Kella, Offer  

    This article is devoted to the study of an M/G/1 queue with a particular vacation discipline. The server is due to take a vacation as soon as it has served exactly N customers since the end of the previous vacation. N may be either a constant or a random variable. If the system becomes empty before the server has served N customers, then it stays idle until the next customer arrival. Such a vacation discipline arises, for example, in production systems and in order picking in warehouses. We determine the joint transform of the length of a visit period and the number of customers in the system at the end of that period. We also derive the generating function of the number of customers at a random instant, and the Laplace-Stieltjes transform of the delay of a customer. (c) 2015 Wiley Periodicals, Inc. Naval Research Logistics 62: 646-658, 2015
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  • Large N matrices from a nonlocal spin system

    Anninos, Dionysios   Hartnoll, Sean A.   Huijse, Liza   Martin, Victoria L.  

    Large N matrices underpin the best understood models of emergent spacetime. We suggest that large N matrices can themselves be emergent from simple quantum mechanical spin models with finite dimensional Hilbert spaces. We exhibit the emergence of large N matrices in a nonlocal statistical physics model of order N-2 Ising spins. The spin partition function is shown to admit a large N saddle described by a matrix integral, which we solve. The matrix saddle is dominant at high temperatures, metastable at intermediate temperatures and ceases to exist below a critical order one temperature. The matrix saddle is disordered in a sense we make precise and competes with ordered low energy states. We verify our analytic results by Monte Carlo simulation of the spin system.
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  • Thermal decomposition of metal N, N-dialkylcarbamates A TG-FTIR study

    Duce, Celia   Spepi, Alessio   Pampaloni, Guido   Piccinelli, Fabio   Tine, Maria Rosaria  

    Thermogravimetric analysis coupled with IR spectroscopy was used to investigate the thermal stability and decomposition products of N,N-dialkylcarbamates of zirconium(IV), hafnium(IV), and niobium(IV), M(O2CNR2)(4). The niobium derivatives were less stable than the corresponding Zr(IV) and Hf(IV) derivatives, and the thermal stability was in the order of R =3D Et > Pr-i > Me. XRD analysis of the residue showed the formation of the oxides ZrO2 (tetragonal, P4 (2) /nmc), HfO2, (monoclinic, P2 (1)/c), and Nb2O5 (orthorhombic, Pbam). TEM analysis showed that all the oxides were obtained as nanopowders with a crystal size below 30 nm.
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  • Thermal properties of a string bit model at large N

    Beccaria, Matteo  

    We study the finite temperature properties of a recently introduced string bit model designed to capture some features of the emergent string in the tensionless limit. The model consists of a pair of bosonic and fermionic bit operators transforming in the adjoint representation of the color group SU(N). Color confinement is not achieved as a dynamical effect, but instead is enforced by an explicit singlet projection. At large N and finite temperature, the model has a non trivial thermodynamics. In particular, there is a Hagedorn type transition at a finite temperature T =3D T-H where the string degrees of freedom are liberated and the free energy gets a large contribution similar to N-2 that plays the role of an order parameter. For T > T-H, the low temperature phase becomes unstable. In the new phase, the thermodynamically favoured configurations are characterized by a non-trivial gapped density of the SU(N) angles associated with the singlet projection. We present an accurate algorithm for the determination of the density pro file at N =3D infinity. In particular, we determine the gap endpoint at generic temperature and analytical expansions valid near the Hagedorn transition as well as at high temperature. The leading order corrections are characterized by non-trivial exponents that are determined analytically and compared with explicit numerical calculations.
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  • Annual agricultural N surplus in France over a 70-year period

    Poisvert, C.   Curie, F.   Moatar, F.  

    High levels of nitrogen (N) contamination of ground and surface water are still detected at European and national scales, despite the implementation of Directives, highlighting the need to improve understanding of changes in N pressure. Soil surface nitrogen balance was investigated at the county level in France over a 70-year period to identify areas with high N surpluses and trends in N pressure. Soil surface nitrogen balances were calculated for 90 NUTS3 (Nomenclature of Territorial Units for Statistics in the EU) called 'departments' (ranging from 611 to 10,145 km(2), median surface area 6032 km(2)) and one NUTS2 entity. Over the whole period, the N surplus calculated for France as a whole averaged 37 kgN per ha of utilized agricultural area (UAA) and departmental N surpluses mean ranged from 10 to 86 kgN ha UAA(-1). Imprecision, i.e. an 80% confidence interval in N surpluses, was calculated using Monte Carlo simulation. Average imprecision for the whole period ranged from 6 to 45 kgN ha UAA(-1) across different departments. Analysis revealed that yearly and departmental imprecision values were mainly correlated with N export (R-2 =3D 0.46). Despite this imprecision, the soil surface nitrogen balance was found to be a consistent and suitable tool to determine trends in N pressure at the department level. The model revealed an upward trend in N surplus until the 1990s for 82% of the area studied, and a downward or stable trend for more than 90% of the area since the European Nitrates Directive has been implemented.
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  • Multi-centered N=3D2 BPS black holes: a double copy description

    Cardoso, G. L.   Nagy, S.   Nampuri, S.  

    We present the on-shell double copy dictionary for linearised N =3D 2 supergravity coupled to an arbitrary number of vector multiplets in four dimensions. Subsequently, we use it to construct a double copy description of multi-centered BPS black hole solutions in these theories in the weak-field approximation.
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  • A. N. Doane (ed.). Genesis A: A New Edition, Revised

    Neidorf, Leonard  

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  • O4-04-01: WHAT CAN STRUCTURAL MRI TELL ABOUT A/T/N STAGING?

    Lang, Alexander; Weiner, Michael W.; Tosun, Duygu  

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  • A binomial N‐mixture model for estimating arrival and departure timing

    Mizel, Jeremy D.   Schmidt, Joshua H.   Phillips, Laura M.   Mcintyre, Carol L.  

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  • ALMOST PARTITIONING A 3-EDGE-COLORED Kn,n INTO FIVE MONOCHROMATIC CYCLES

    Lang, Richard   Schaudt, Oliver   Stein, Maya  

    We show that for any coloring of the edges of the complete bipartite graph K-n,K-n with three colors there are five disjoint monochromatic cycles which together cover all but o(n) of the vertices. In the same situation, 18 disjoint monochromatic cycles together cover all vertices.
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  • Example of a Smooth Homeomorphism Violating the Luzin N−1 Property

    Kleprlík, L.   Molchanova, A. O.   Roskovec, T.  

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  • A Seven-Membered N,N '-Diamidocarbene

    Hudnall, Todd W.   Tennyson, Andrew G.   Bielawski, Christopher W.  

    Condensation of N,N'-dimesitylformamidine with phthaloyl chloride afforded 1 center dot HCl, which, upon treatment with base, afforded 2,4-dimesitylbenzo[e][1,3]diazepin-1,5-dione-2-ylidene (1), a seven-membered N,N'-diamidocarbene (DAC), in high yield (85%). The free DAC was used to synthesize four new, late transition metal complexes: [Rh(cod)(1)Cl] (2a) (cod = 1,5-cyclooctadiene), [Ir(cod)(1)Cl] (2b), [Rh(CO)(2)(1)Cl] (3a), and [1-AuCl] (5). The Tolman electronic parameter (TEP) of 1 was calculated to be 2047 cm(-1) from the IR spectrum of 3a. This TEP value is approximately 10 cm(-1) than known DACs and 5 cm(-1) lower than known imidazol-2-ylidenes, indicating that DAC 1 is a relatively strong electron donor. Additionally, electrochemical analyses of 2a and 2b corroborated the IR data obtained on 3a and revealed E(1/2) values that were shifted cathodically by ca. 0.16 V when compared to analogous complexes supported by N-heterocyclic carbenes. The gold complex 5 was found to catalyze the hydration of phenylacetylene, affording acetophenone in yields up to 78% after 12 h at 80 C at a catalyst loading of 2 mol %. Treatment of 1 with 2,6-dimethylphenylisocyanide afforded N, N'-diamidoketenimine 4 as a thermally robust, crystalline solid.
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