Functionalization of Quinazolin‐4‐Ones Part 2#: Reactivity of 2‐Amino‐3, 4, 5, or 6‐Nitrobenzoic Acids with Triphenylphosphine Thiocyanate,Alkyl Isothiocyanates,and Further Derivatization Reactions

2‐amino‐3, 4, 5, or 6‐nitrobenzoic acids were reacted with PPh₃(SCN)₂ and alkyl isothiocyanates to give 5, 6, 7, or 8‐nitro‐2‐thioxo‐3‐substituted quinazolin‐4‐ones, respectively. The position of the nitro group was found to have significant influence on the outcome of the reactions. Similarly, the nature of the substituent at position 8 (NO₂, NH₂, NH(C═O)CH₃) in 8‐substituted‐2‐methylthio quinazolin‐4‐ones was also found to significantly influence their reactivity towards morpholine. A selection of the products were also tested for in vitro antibacterial activity but little activity was observed.     

A distributed‐memory parallel lattice Kinetic Monte Carlo algorithm for crystal growth applied to barite (001) face

This work presents a parallel approach of the Kinetic Monte Carlo (KMC) algorithm using a distributed memory architecture. The resulting computer software was tested by conducting crystal growth simulations on barite (001) face. Execution times, simulated times and crystallization velocities are compared with a shared memory parallel KMC software (MMonCa). Finally, a ≈ 1 μm² crystal growth simulation is performed and compared with atomic force microscopy crystal growth experiments. The capability of this approach is demonstrated: a) a significant reduction of parallel overhead is achieved when comparing to the shared memory parallel version of the software, b) a distributed memory approach achieves an increase in memory resources enough to perform simulations with lattice sizes about 1 μm², allowing the study of larger structures than those in shared memory or sequential implementations, c) this approach should be used only with large scale simulations to take advantage of the distributed memory architecture, d) further improvements are needed for parallel KMC to be faster than serial KMC in small scale simulations, e) the KMC algorithm used is able to adequately simulate two‐dimensional nucleation on large areas of barite (001) faces.     

MCM-48介孔材料相转化合成的形成机制

利用水热合成的方法,使用新型的表面活性剂十六烷基三甲基对苯磺酸盐作为模板剂合成了高质量的MCM-48介孔分子筛,并用X-射线衍射(XRD)、扫描电镜(SEM)、高分辨透射电镜(HRTEM)以及N₂吸附-脱附进行了表征。合成过程的研究表明该合成体系经历了三相,起始相为具有六方对称性的MCM-41,随着加热时间的延长,生成了具有立方对称性的MCM-48,进一步延长加热时间则生成了层状相MCM-50。三相转变发生的核心驱动力来自于表面活性剂有效堆积参数g因子的改变,随着反应时间的延长,由于对甲基苯磺酸根离子（Tos^-）的流失,表面活性剂极性头所占的有效面积（a₀）明显减小,g值变大。另外,XRD、傅立叶变换的红外光谱(FT-IR)以及固体魔角自旋核磁共振(²⁹Si MAS NMR)的表征结果证明：随着晶化时间的延长,相转变的同时伴随着介孔材料的孔壁逐渐由原子无序的非晶态向原子有序的晶态结构转变。最终形成的原子有序层状介孔分子筛可以作为扩孔型微孔分子筛合成的有效前驱体。     

Synthesis and thermoluminescence characterization of MgB4O7:Gd,Li

Magnesium tetraborate (MTB) doped with rare earth elements were synthesized by solid state sintering technique. Among the different rare earth dopants studied in this phosphor, gadolinium doped phosphors resulted in a single intense dosimetric peak at 250 °C and this is the first report in rare earth-doped MgB₄O₇ with a glow peak above 200 °C Photoluminescence (PL) and thermoluminescence (TL) studies were performed with this phosphor after exposing the powder samples to ionizing radiation. Monovalent dopants, including Na, Li and Ag, were found to increase the TL sensitivity of the MgB₄O₇:Gd phosphor without a shift in the TL peak temperature. The TL emission spectra showed characteristic emission of the host lattice, which showed an increase on doping with rare earth or monovalent codopants. The TL sensitivity, dose response curve, and post-irradiation storage stability were studied for the possible use of this material in radiation dosimetry applications. The TL parameters, such as the activation energy, the frequency factor, and the order of kinetics were determined for the Gd-doped MgB₄O₇ phosphor. The phosphor was found to be reusable after a few cycles of irradiation and annealing. The post-irradiation storage stability studies showed that this near tissue-equivalent phosphor, which has a gamma sensitivity five times that of TLD-100, is suitable for medical dosimetry applications.     

Reassessment of the classical closures for scalar turbulence

In deducing the consequences of the Direct Interaction Approximation, Kraichnan was sometimes led to consider the properties of special classes of nonlinear interactions in degenerate triads in which one wavevector is very small. Such interactions can be described by simplified models closely related to elementary closures for homogeneous isotropic turbulence such as the Heisenberg and Leith models. These connections can be exploited to derive considerably improved versions of the Heisenberg and Leith models that are only slightly more complicated analytically. This paper applies this approach to derive some new simplified closure models for passive scalar advection and investigates the consistency of these models with fundamental properties of scalar turbulence. Whereas some properties, such as the existence of the Kolmogorov–Obukhov range and the existence of thermal equilibrium ensembles, follow the velocity case closely, phenomena special to the scalar case arise when the diffusive and viscous effects become important at different scales of motion. These include the Batchelor and Batchelor–Howells–Townsend ranges pertaining, respectively, to high and low molecular Schmidt number. We also consider the spectrum in the diffusive range that follows the Batchelor range. We conclude that improved elementary models can be made consistent with many nontrivial properties of scalar turbulence, but that such models have unavoidable limitations.     

Pancharatnam phase of two Cooper-pair boxes in a dissipative cavity

The time evolution of a single Cooper pair in the presence of another Cooper pair interacting with an electromagnetic field in a dissipative cavity is presented. The strong dependence of the dynamics of two superconducting charge qubits interacting with the microcavity field on the instantaneous phase shift experienced by the second qubit is demonstrated. The Pancharatnam phase is found to be more sensitive than the population dynamics to the phase shift. This leads us to suggest a new technique for controlling the system dynamics. Furthermore, although the atom is not directly coupled to the cavity modes, its coherent properties are found to be strongly influenced by dissipation, both qualitatively and quantitatively.     

Two-point method for kinetic analysis of a thermoluminescence glow peak

We present a method for the estimation of defect (trap) physical parameters from thermoluminescence (TL) glow peaks. In this method, the order of kinetics b is determined using two values of TL intensity each of which corresponds to the same temperature (T ₁) on two separate glow peaks of a phosphor. The two glow peaks are obtained from two aliquots of the phosphor irradiated to same dose but read out at different heating rates. The proposed method requires a minimum of only two data points in contrast to standard peak shape (PS) methods that require three points corresponding to three different temperatures on the same glow peak. Once the order of kinetics b is determined, the activation energy E is calculated by taking a second point (T ₂) on any one of the two glow peaks. The values of b and E thus obtained are used to evaluate the frequency factor S ^′′ and the number of trapped electrons before the heating begins n _o. The validity of the method was checked using two numerically generated glow peaks. For the two cases, the method reproduced the input values reasonably well. The method was also used to analyse two experimental glow peaks. The results obtained provide a reasonably good fit to the experimental data. The kinetic parameters calculated using the present technique are comparable to those calculated using PS and initial rise methods. Initial guesses can easily be obtained for E and S ^′′ using the present technique when a glow curve is to be deconvoluted with a model consisting of many unknown parameters with E and S″ inclusive.     

Improvement of Acoustic Doppler Velocimetry in bubbly flow measurements as applied to river characterization for kinetic turbines

Acoustic Doppler Velocimetry (ADV) can measure flow velocities in three directions in experimental facilities and field applications. Based on the Doppler shift effect, ADV can accurately resolve the quasi-instantaneous flow field at frequencies of up to approximately 200 Hz. However, this technique is sensitive to operating conditions that can lead to contaminated signals containing large amplitude spikes, a disadvantage of ADV. Aliasing of the Doppler signal creates these spikes. Such a situation occurs when large particles intersect the sampling volume or acoustic waves. For example during the characterization of river velocities, sediments floating near the riverbed cause aliasing from particles, and more importantly, surface entrained air bubbles contaminate the ADV signal. Spikes due to air bubbles not only increase the standard deviation of the velocity, but also corrupt the autocorrelation and power spectra. As some of these spikes appear like velocity fluctuations, developing accurate despiking procedures is an important requirement during post-processing of ADV velocity measurements in bubbly flow applications. A new hybrid method is introduced which has advantages over conventional despiking methods such as the acceleration thresholding method and the phase-space thresholding method when using ADV in bubbly flow. ADV river velocity measurements near kinetic turbines demonstrate the proposed method. This method is applicable to other bubbly flow applications to characterize the liquid phase using ADV.     

A station-keeping strategy for collinear libration point orbits

Spacecrafts in periodic or quasi-periodic orbits near the collinear libration points are proved to be excellent platforms for scientific investigations of various phenomena. Since such periodic or quasi-periodic orbits are exponentially unstable, the station-keeping maneuver is needed. A station-keeping strategy which is found by an analytical method is presented to eradicate the dominant unstable component of the libration point trajectories. The inhibit force transforms the unstable component to a stable component. In this method, it is not necessary to determine a nominal orbit as a reference path.