The ability of a femtosecond laser pulse to manipulate and reverse the magnetization in a ferrimagnetic Gd24Fe66.5Co9.5 thin film was studied experimentally as a function of temperature. For a fixed energy of the laser pulse, the dynamics of magnetization showed different behavior depending on whether the sample temperature was below or above the magnetization compensation point (TM). The conditions for full ultrafast demagnetization and magnetization reversal were easily achieved below TM, while the same laser excitation caused just 50% demagnetization above TM. This interesting change in magnetization dynamics is qualitatively explained in terms of effective changes in the magnitudes of magnetizations of atomic sublattices. 相似文献
A series of mono imine (C=N) group that contained Wittig-based Schiff-Base ligands was optimized using the DFT-based computational method and Gaussian 09 program package. These optimized molecules were docked with Quadruplex DNA (PDB ID: 1KF1) and duplex DNA (PDB ID: 1BNA) using AutoDock Vina program along with the reference molecules. Schiff-Base ligands derived from fused aromatic rings contained amines and precursor aldehyde (PA-5 both Z and E isomers) showed lower binding energy for G-quadruplex DNA among all and N-5 category both Z and E isomer Schiff-Base ligands have shown high selectivity for G-quadruplex DNA over duplex DNA which is a very important phenomenon to develop the G-quadruplex DNA stabilizers. For a few Schiff-Base molecules like Ligand-6 (1-{[2-Hydroxy-5-(2-pyren-1-yl-vinyl)-benzylidene]-amino}-naphthalen-2-ol) of N-5 category both Z and E isomers with groove binding and end stacking modes, molecular dynamic calculations were carried out. The study revealed that Ligand-6 of N-5 category E isomer with groove binding mode has higher stabilizing effect on G-quadruplex DNA in spite of having the higher binding energy value. Among Schiff-Base copper(II) complexes, Complex-3 (E-(1-{[2-Hydroxy-5-(2-pyren-1-yl-vinyl)-benzylidene]-amino}-naphthalen-2-ol)Cu) is having high binding affinity for G-quadruplex DNA as compared to others.
A simple and rapid liquid-phase microextraction (LPME) method using a hollow fiber membrane (HFM) in conjunction with gas chromatography-mass spectrometry (GC-MS) is presented for the quantitative determination of 16 polycyclic aromatic hydrocarbons (PAHs) and 12 organochlorine pesticides (OCPs) in rainwater samples. The LPME conditions were optimized for achieving high enrichment of the analytes from aqueous samples, in terms of hollow fiber exposure time, stirring rate, sample pH, and composition. Enrichment factors of more than 100 could be achieved within 35 min of extraction with relative standard deviations (R.S.D.s) 1.3-13.6% for PAHs and 1.7-13.8% for OCPs, respectively, over a wide range of analyte concentrations. Detection limits ranged from 0.002 to 0.047 microg l(-1) for PAHs, and from 0.013 to 0.059 microg l(-1) for OCPs, respectively. The newly developed LPME-GC-MS method has been validated for the analysis of PAHs and OCPs in rainwater samples. Extraction recoveries from spiked synthetic rainwater samples varied from 73 to 115% for PAHs and from 75 to 113% for OCPs, respectively. Real rainwater samples were analyzed using the optimized method. The concentrations of PAHs and OCPs in real rainwater samples were between 0.005-0.162, and 0.063 microg l(-1), respectively. 相似文献
An unprecedented enantioselective oxa‐Michael reaction of α‐tertiary alcohols using cinchona‐alkaloid‐based chiral bifunctional squaramide catalysts is reported. An oxidative dearomatization of phenol followed by an enantioselective oxa‐Michael addition sequence provided a broad array of chiral sterically hindered tetrahydrofurans and tetrahydropyrans attached to a cyclohexadienone moiety in spiro fashion. In general, good yields and excellent enantioselectivities (up to 99 %) were observed. The chiral oxo‐cycles obtained have easily been transformed into chromans without disturbing the enantioselectivity. 相似文献
Aziridines undergo ring opening readily with various thiols in the presence of polyethylene glycol (PEG) to afford the corresponding β-amino sulfides in high yields with good regioselectivity under mild and neutral conditions. The PEG can be recovered and reused. 相似文献
An unprecedented enantioselective oxa‐Michael reaction of α‐tertiary alcohols using cinchona‐alkaloid‐based chiral bifunctional squaramide catalysts is reported. An oxidative dearomatization of phenol followed by an enantioselective oxa‐Michael addition sequence provided a broad array of chiral sterically hindered tetrahydrofurans and tetrahydropyrans attached to a cyclohexadienone moiety in spiro fashion. In general, good yields and excellent enantioselectivities (up to 99 %) were observed. The chiral oxo‐cycles obtained have easily been transformed into chromans without disturbing the enantioselectivity. 相似文献
Research on Chemical Intermediates - A simple and effective green method has been developed for the synthesis of a series of novel bis α-aminophosphonate derivatives (4a–j) by the... 相似文献
Heterocyclic cadmium dithiocarbamates, [Cd(S2CNC5H10)2] and [Cd(S2CNC9H10)2] were synthesized. The complexes were thermolysed in hexadecylamine (HDA) to give HDA capped CdS nanoparticles. A combination of close to spherical, rod, bipods and tripods was obtained by varying the reaction parameters such as precursor concentration and temperature. The optical properties and X-ray diffraction studies of the particles are also reported. 相似文献
Reverse-micelle forming amphiphilic homopolymers with carboxylic acid and quaternary amine substituents are used to selectively enrich biomarker peptides and protein fragments from human serum prior to matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS) analysis. After depletion of human serum albumin (HSA) and immunoglobulin G (IgG), low abundance peptide biomarkers can be selectively enriched and detected by MALDI-MS at clinically relevant concentrations by using the appropriate homopolymer(s) and extraction pH value(s). Three breast cancer peptide biomarkers, bradykinin, C4a, and ITIH(4), were chosen to test this new approach, and detection limits of 0.5 ng mL(-1), 0.08 ng mL(-1), and 0.2 ng mL(-1), respectively, were obtained. In addition, the amphiphilic homopolymers were used to detect prostate specific antigen (PSA) at concentrations as low as 0.5 ng mL(-1) by targeting a surrogate peptide fragment of this protein biomarker. Selective enrichment and sensitive MS detection of low abundance peptide/protein biomarkers by these polymeric reverse micelles should be a sensitive and straightforward approach for biomarker screening in human serum. 相似文献