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11.
Tamar Shamai Yamin Hagit Prihed Moran Madmon Merav Blanca Avi Weissberg 《Journal of mass spectrometry : JMS》2020,55(10)
V‐nerve agents present information‐poor spectra, both in GC‐EI‐MS and LC‐ESI‐MS/MS, with dominant fragments/product ions corresponding to the amine‐containing residue. Hence, derivatives/isomers with the same amine residue exhibit similar mass spectral patterns, leading to ambiguity in the phosphonate structure. We present a simple approach for their structural elucidation based on two complementary experiments: ESI‐MS/MS of the original compound, which provides information about the amine moiety, and ESI‐MS/MS of the phosphonic acid hydrolysis products generated by N‐iodosuccinimide, which provides ions' characteristic of the phosphonate structure. This approach enables the structural elucidation of the original V‐agents with a higher degree of certainty. 相似文献
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Ericka Santacruz Gabriela Huelgas Sandra K. Angulo Virginia M. Mastranzo Simón Hernández-Ortega Judit A. Aviña Eusebio Juaristi Cecilia Anaya de Parrodi Patrick J. Walsh 《Tetrahedron: Asymmetry》2009,20(24):2788-2794
New chiral thioureas 1–8 containing 1,2-ethylendiamine or trans-1,2-diaminocyclohexane as the carbon skeleton, and containing an (S)-α-phenylethyl group have been prepared (79–98% yield). Thioureas 1–8 were used as ligands for the zinc-based catalyzed asymmetric hydrosilylation of acetophenone with polymethylhydrosiloxane (PMHS). The best result was achieved with monothiourea 1 (up to 75% ee), in toluene and a catalyst load of 5 mol %. 相似文献
14.
This paper focuses on dynamic, continuous-time production control problems in the fashion industry. Similar to the classical news-vendor problem, we consider a single product-type and the cumulative demand for items is not known until the end of the production horizon and therefore must be forecasted. Since there are periodic updates before a single selling season, actual demand during a period of time can only be determined by the end of the period. If the overall demand is overestimated, excessive inventory holding and production costs are paid and surpluses are sold at low prices at the end of the production horizon. If it is under-estimated, then sales are lost. The objective is to dynamically determine production orders which minimize overall expected costs. Since the optimal feedback for such a problem is characterized by thresholds evolving with time and system states, there is a significant computational burden in determining them. With the aid of the variational analysis and a decomposition, we derive a closed-form solution for the thresholds. A numerical study carried out to compare the decomposition and straightforward simulation-based solutions indicates the high accuracy of the suggested approach while the computational burden is dramatically reduced. 相似文献
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This paper concerns the open problem of Lovász and Saks regarding the relationship between the communication complexity of a boolean function and the rank of the associated matrix. We first give an example exhibiting the largest gap known. We then prove two related theorems.A preliminary version of this paper appeared in [10].This work was supported by USA-Israel BSF grant 92-00043 and by a Wolfeson research award administered by the Israeli Academy of Sciences.This work was supported by USA-Israel BSF grant 92-00106 and by a Wolfeson research award administered by the Israeli Academy of Sciences. 相似文献
18.
Avi Sigler 《International Journal of Mathematical Education in Science & Technology》2017,48(5):782-793
Students use GeoGebra to explore the mathematical relations among different radii of circles in a triangle (circumcircle, incircle, excircles) and the sides and other segments in the triangle. The more formal mathematical development of the relations that follows the explorations is based on known geometrical properties, different formulas relating the radii to the sides and the inequalities between the different averages. The activities described were conducted with pre-service teachers of mathematics, with empirical investigation of the relations using dynamical geometry software, and formal presentation of proofs. 相似文献
19.
Moshe Stupel Victor Oxman Avi Sigler 《International Journal of Mathematical Education in Science & Technology》2017,48(1):149-161
We present a geometrical investigation of the process of creating an infinite sequence of triangles inscribed in a circle, whose areas, perimeters and lengths of radii of the inscribed circles tend to a limit in a monotonous manner.First, using geometrical software, we investigate four theorems that represent interesting geometrical properties, after which we present formal proofs that rest on a combination between different fields of mathematics: trigonometry, algebra and geometry, and the use of the concept of standard deviation that is taken from statistics. 相似文献
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The baseline and forced flow around a bluff body with semi-elliptical D-shape was investigated by solving the 2D Navier–Stokes
equations at low Reynolds numbers. A D-shape rather than the canonic circular-cylinder was selected due to the fixed separation
points in the latter, enabling to study a pure wake rather than boundary-layer control. The correlation between Strouhal and
Reynolds numbers, the mean drag, the lift and drag oscillations vs. the Reynolds number and wake structure were investigated
and compared to experimental and numerical data. Effects of open-loop forcing, resulting from the influence of zero-mass-flux
actuators located at the fixed separation points, were studied at a Reynolds number of 150. Fluidic rather than body motion
or volume forcing was selected due to applicability considerations. The motivation for the study was to quantify the changes
in the flow field features, as captured by Proper Orthogonal Decomposition (POD) analysis, due to open-loop forcing, inside
and outside the “lock-in” regime. This is done in order to evaluate the suitability of low-order-models based on POD modes
of this changing flow field, for future feed-back flow control studies. The evolution of the natural and the excited vortices
in the Kármán wake were also investigated. The formation and convection regions of the vortex evolution were documented. It
was found that the forcing causes an earlier detachment of the vortices from the boundary-layers, but does not affect their
circulation or convection speeds. The results of the POD analysis of the near-wake flow show that the influence of the bluff
body shape (“D”-shaped versus circular cylinder) on the baseline POD wake modes is small. It was found that the eigenfunctions
(mode-shapes) of the POD velocity modes are less sensitive to slot excitation than the vorticity modes. As a result of the
open-loop excitation, two types of mode-shape-change were observed: a mode can be exchanged with a lower-energy mode or shifted
to a low energy level. In the latter case, the most energetic mode becomes the “actuator” mode. The evolution of one-slot
excitation on still fluid (“Synthetic jet”) was studied and compared to published data and to “actuator” modes with external
flow present. Based on the current findings, it is hypothesized that the cross-flow velocity POD modes are suitable for feedback
control of wake flow using periodic excitation, due to their low sensitivity to the excitation as compared to the streamwise
velocity or vorticity modes. 相似文献