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排序方式: 共有308条查询结果,搜索用时 31 毫秒
111.
In this paper, we prove the existence and uniqueness of solutions for an anti-periodic boundary value problem of nonlinear impulsive differential equations of fractional order α∈(2,3] by applying some well-known fixed point theorems. Some examples are presented to illustrate the main results. 相似文献
112.
Liu DJ Credo GM Su X Wu K Lim HC Elibol OH Bashir R Varma M 《Chemical communications (Cambridge, England)》2011,47(29):8310-8312
A new pyrophosphate (PPi) chelator was designed for surface-sensitive electrical detection of biomolecular reactions. This article describes the synthesis of the PPi-selective receptor, its surface immobilization and application to label-free electrical detection on a silicon-based field-effect transistor (FET) sensor. 相似文献
113.
Background
The heterocyclic hydrazones constitute an important class of biologically active drug molecules. The hydrazones have also been used as herbicides, insecticides, nematocides, redenticides, and plant growth regulators as well as plasticizers and stabilizers for polymers. The importance of the phenolic quinolyl hydrazones arises from incorporating the quinoline ring with the phenolic compound; 2,4-dihydroxy benzaldehyde. Quinoline ring has therapeutic and biological activities whereas, phenols have antiseptic and disinfectants activities and are used in the preparation of dyes, bakelite and drugs. The present study is planned to check the effect of the counter anions on the type and geometry of the isolated copper(II)- complexes as well as the ligational behavior of the phenolic hydrazone; 4-[(2-(4,8-dimethylquinolin-2-yl)hydrazono)methyl] benzene-1,3-diol; (H2L). 相似文献114.
Saeed Ahmad Haseeba Sadaf Muhammad Altaf Helen Stoeckli-Evans Seerat-ur-Rehman Sarfaraz Ahmed Bashir 《Crystallography Reports》2013,58(5):692-696
Two mercury(II) complexes containing cyanide and, N,N′-diethylthiourea (detu) and N,N′-dipropylthiourea (dprtu) ligands, [(detu)2Hg(CN)2] (1) and [(dprtu)2Hg(CN)2] (2), respectively, have been prepared and characterized by X-ray crystallography. In the both complexes Hg atom lies on a 2-fold rotation axis, and is coordinated to the sulfur atoms of two thiourea ligands and to two cyanide carbon atoms. Both have a distorted tetrahedral environment with bond angles about the Hg atoms in the range of 93.41(4)°–146.75(19)°. In the crystal structures symmetry related molecules are linked via N-H-N hydrogen bonds resulting in the formation of a two-dimensional network in 1, while in 2 a double stranded one-dimensional chain is formed. 相似文献
115.
Bashir Ahmed Tahir Rashid Ahmed M. G. B. Ashiq Afaq Ahmed M. A. Saeed 《中国物理 B》2012,21(4):44201-044201
This study deals with Nd:YAG laser cutting nonmetallic materials, which is one of the most important and popular industrial applications of laser. The main theme is to evaluate the effects of Nd:YAG laser beam power besides work piece scanning speed. For approximate cutting depth, a theoretical study is conducted in terms of material property and cutting speed. Results show a nonlinear relation between the cutting depth and input energy. There is no significant effect of speed on cutting depth with the speed being larger than 30 mm/s. An extra energy is utilized in the deep cutting. It is inferred that as the laser power increases, cutting depth increases. The experimental outcomes are in good agreement with theoretical results. This analysis will provide a guideline for laser-based industry to select a suitable laser for cutting, scribing, trimming, engraving, and marking nonmetallic materials. 相似文献
116.
Shazia Bashir Nazar Farid Khaliq Mahmood M. Shahid Rafique 《Applied Physics A: Materials Science & Processing》2012,107(1):203-212
The ablation of Cd has been performed by employing Q-switched Nd: YAG 10 ns laser pulses with a central wavelength of 1064 nm
for a pulsed energy of 200 mJ under various ambient environments of argon, air and helium. The optical emission spectroscopy
of Cd plasma has been studied under different filling pressures of shield gases ranging from 5 torr to 760 torr using LIBS
spectrometer system. The effect of different gases and their pressures on the intensity of spectral emission, electron temperature
and density of the laser-produced plasma has been investigated. SEM analysis has been performed to investigate the dependence
of surface morphological changes of an irradiated target on the nature and pressure of an ambient gas. A strong correlation
has revealed the vital role of electron temperature and density of laser-induced plasma for the surface modification of Cd.
These results strongly indicate that the nature and pressure of the ambient atmosphere is one of the controlling factors of
the plasma characteristics, as well as the factors related to the laser energy absorption for surface modification. 相似文献
117.
Shazia Bashir M. Shahid Rafique Wolfgang Husinsky 《Applied Physics A: Materials Science & Processing》2012,109(2):421-429
Ultra-fast electronic and thermal processes for the energy deposition mechanism during femtosecond laser ablation of Si have been identified by means of atomic force microscopy and Raman scattering techniques. For this purpose, Si targets were exposed with 800-nm, 25-fs Ti:sapphire laser pulses for different laser fluencies in air and under UHV (ultra high vacuum) conditions. Various nano- and microstructures on the surface of the irradiated samples are revealed by a detailed surface topography analysis. Ultra-fast electronic processes are dominant in the lower-fluence regime. Therefore, by starting from the ablation threshold three different fluence regimes have been chosen: a lower-fluence regime (0.06–0.5 J?cm?2 single-shot irradiation under UHV condition and 0.25–2.5 J?cm?2 single-shot irradiation in ambient condition), a moderate-fluence regime (0.25–1.5 J?cm?2 multiple-shot irradiation), and a higher-fluence regime (2.5–3.5 J?cm?2 multiple-shot irradiation). Around the ablation threshold fluence, most significant features identified at the Si surface are nanohillock-like structures. The appearance of these nanohillocks is regarded as typical features for fast electronic processes (correlated with existence of hot electrons) and is explained on the basis of Coulomb explosion. The growth of these typical features (nanohillocks) by femtosecond laser irradiation is an element of novelty. At moderate irradiation fluence, a ring-shaped ablation with larger bumps and periodic surface structures is observed and is considered as a footprint of ultra-fast melting. Further increase in the laser fluence, i.e. a higher-fluence regime, resulted in strong enhancement of the thermal process with the appearance of larger islands. The change in surface topography provides an innovative clue to differentiate between ultra-fast electronic processes, i.e. Coulomb explosion (sub-100 fs) at a lower-fluence regime and ultra-fast melting (hundreds of fs) at a moderate-fluence regime, and slow thermal processes (ps time scale) at a higher-fluence regime. These fast electronic and thermal processes are well correlated to structural and crystallographic alterations, inferred from Raman spectroscopy. 相似文献
118.
Adnan Bashir CHANG Lei Ian C. Cloet Bruno El-Bennich LIU Yu-Xin Craig D. Roberts Peter C. Tandy 《理论物理通讯》2012,58(1):79-134
We survey contemporary studies of hadrons and strongly interacting quarks using QCD's Dyson-Schwinger equations, addressing the following aspects: confinement and dynamical chiral symmetry breaking; the hadron spectrum; hadron elastic and transition form factors, from small- to large-Q2; parton distribution functions; the physics of hadrons containing one or more heavy quarks; and properties of the quark gluon plasma. 相似文献
119.
Khashayar Rajabimoghadam Yousef Darwish Umyeena Bashir Dylan Pitman Sidney Eichelberger Maxime A. Siegler 《Journal of Coordination Chemistry》2019,72(8):1346-1357
AbstractIn this research article, we report the synthesis and structural characterization of a family of first-row metal complexes bearing redox-active ligands with tunable H-bonding donors. We observed that these coordination complexes can adopt three different geometries and that they are stabilized by intramolecular multicenter H-bonding interactions, which are systematically modified by changing the metal ion (Co, Ni, Cu, Zn), the ligand scaffold (variations in the diamine and ureanyl substituents used) and the solvent of crystallization. 相似文献
120.
Bashir A. Mansoori Edward W. Dyer Christopher M. Lock Kevin Bateman Robert K. Boyd Bruce A. Thomson 《Journal of the American Society for Mass Spectrometry》1998,9(8):775-788
The effect on triple-quadrupole performance of applying an axial field, in an rf-only quadrupole collision cell operated at pressures sufficiently high that collisional focusing is operating, has been investigated. The advantages of such cells have been shown previously to include increased transmission and much improved resolution in fragment ion spectra relative to the performance of collision cells operating at lower gas pressures. The disadvantages of high-pressure collision cells all derive from the relatively long transit times for the ions, which can be long relative to characteristic times for scanning the first mass filter (precursor ion selector) or for switching its setting in multiple reaction monitoring (MRM) cycles. The present work describes experiments on a high-pressure cell in which an axial field is created through use of conical rather than cylindrical or hyperbolic rods. In addition, results of computations of the electric fields within such a cell, and of ion trajectories through it, are presented. It is shown that application of axial fields of the order of 0. 1 V/cm can remove all hysteresis effects associated with the long ion transit times, and thus provide excellent performance in quantitation work using MRM, as well as in other scan modes. Furthermore, the advantages of collisional focusing in quadrupole collision cells are shown to be unimpaired by these low axial fields. 相似文献