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51.
It is well known that the phenomenon of Ag-photodoping into amorphous (a-) chalcogenide film depends on film thickness (d). Herein, we report that the effects of Ag-photodoping into a-GeSe thin films exhibit a systematical change dependent on d using a holographic exposure (HeCd laser) and the measurement of diffraction efficiency (η) in real time. The η-kinetics of Ag-photodoping in the sample structure of an a-GeSe/Ag/p-type Si substrate is divided into two steps. A photodarkening-dominant process related to the generation of valence-alternation pairs (VAPs) in the chalcogenide explains the first step while a doping-dominant process accounts for the second step. In particular, we confirmed that the d-dependencies of the η-kinetics are classified into 3 groups: (A) d < 2dP; (B) 2dP ? d < 4dP; (C) d > 4dP, where dP indicates the penetration depth of the HeCd laser. In group A, the Ag-doping process occurs simultaneously with the darkening process. In group C, the η-kinetics results from the darkening process only. Contrarily, in group B, the η-kinetics exhibits a sharp distinction between the photodarkening process and the Ag-doping process, and in particular, ηM increases almost linearly with an increase in d. 相似文献
52.
We have constructed a number of benzamidine- and butylamine-based hydantoin compounds by means of an efficient route using
solid phase synthesis in which neat diisopropylamine was employed for a novel cyclization/traceless cleavage step. All library
compounds were obtained in excellent yield and high purity.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
53.
Cleaning the surfaces of the as-deposited Ge2Sb2Te5 was studied by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and X-ray diffraction (XRD). The mixed native oxides on the as-deposited Ge2Sb2Te5 surface can be easily removed by dipping Ge2Sb2Te5 in de-ionized water for 1 min, while the surface morphology remains unchanged after cleaning. Native oxides only re-grow after exposure to air for more than 4 min. Although dipping in water leads to a surface layer deficient in Ge and Sb, the surface composition of Ge2Sb2Te5 can recover to its stoichiometric value after annealing at 200 °C in vacuum. The phase remains amorphous at room temperature after dipping in water, and changes to fcc and hcp after annealing at 100 and 220 °C, respectively. 相似文献
54.
55.
C. elegans is a popular model organism with a well‐developed neural network. Approximately 60% of the genes in C. elegans have genomic counterparts in humans, including those involved in building neural circuits. Therefore, we can extend the study of human neural network mechanisms to C. elegans which is easy to genetically manipulate. C. elegans shows behavioural responses to various external physical and chemical stimuli. Electrotaxis is one of its distinct behavioural responses, which is defined as movement towards the cathode in an electric field. In this study, we developed an effective microfluidic trap system for analysing electrotaxis in C. elegans. In addition, two mutant strains (unc‐54(s74) and unc‐6(e78)) from wild‐type (N2) worms were screened using the system. Wild‐type (N2) worms and the two mutant strains clearly showed different behavioural responses to the applied electric field, thus enabling the effective screening of the mutant worms from the wild type (N2). This microfluidic system can be utilized as a platform for the study of behavioural responses, and for the sorting and mutant screening of C. elegans. 相似文献
56.
An all-fibre Tm:Ho laser system is reported, using a 1600 nm Er fibre pump laser and 0.3 m length of the fibre through a two-stage optimization of both the pump source and laser configuration to achieve a low threshold operation. As a result a low threshold power of 33 mW and a slope efficiency of 0.6% have been achieved, in laser operation at a wavelength of 1870 nm and a cross-comparison with 785 nm laser diode pumping has been made. 相似文献
57.
The accuracy of measuring voxel intensity changes between stimulus and rest images in fMRI echo-planar imaging (EPI) data is severely degraded in the presence of head motion. In addition, EPI is sensitive to susceptibility-induced geometric distortions. Head motion causes image shifts and associated field map changes that induce different geometric distortion at different time points. Conventionally, geometric distortion is "corrected" with a static field map independently of image registration. That approach ignores all field map changes induced by head motion. This work evaluates the improved motion correction capability of mapping slice to volume with concurrent iterative field corrected reconstruction using updated field maps derived from an initial static field map that has been spatially transformed and resampled. It accounts for motion-induced field map changes for translational and in-plane rotation motion. The results from simulated EPI time series data, in which motion, image intensity and activation ground truths are available, show improved accuracy in image registration, field corrected image reconstruction and activation detection. 相似文献
58.
59.
Hydrophobic‐Force‐Driven Removal of Organic Compounds from Water by Reduced Graphene Oxides Generated in Agarose Hydrogels 下载免费PDF全文
Chongling Cheng Dr. Yongqing Cai Dr. Guijian Guan Prof. Leslie Yeo Prof. Dayang Wang 《Angewandte Chemie (International ed. in English)》2018,57(35):11177-11181
Hydrophobic reduced graphene oxides (rGOs) were generated in agarose hydrogel beads (AgarBs) by NaBH4 reduction of graphene oxides (GOs) initially loaded in the AgarBs. The resulting rGO‐loaded AgarBs were able to effectively adsorb organic compounds in water as a result of the attractive hydrophobic force between the rGOs in the AgarBs and the organic compounds dissolved in aqueous media. The adsorption capacity of the rGOs was fairly high even toward reasonably water‐soluble organic compounds such as rhodamine B (321.7 mg g?1) and aspirin (196.4 mg g?1). Yet they exhibited salinity‐enhanced adsorption capacity and preferential adsorption of organic compounds with lower solubility in water. Such peculiar adsorption behavior highlights the exciting possibility for adopting an adsorption strategy, driven by hydrophobic forces, in practical wastewater treatment processes. 相似文献
60.
Towards chemical analysis of nanostructures in biofilms II: tip-enhanced Raman spectroscopy of alginates 总被引:1,自引:1,他引:0
Schmid T Messmer A Yeo BS Zhang W Zenobi R 《Analytical and bioanalytical chemistry》2008,391(5):1907-1916
This study examines the feasibility of using tip-enhanced Raman spectroscopy (TERS) for label-free chemical characterization
of nanostructures in biological systems. For this purpose, a well-defined model system consisting of calcium alginate fibers
is studied. In a companion paper, calcium alginate fibers and their network structures were shown to be a good model for the
extracellular polysaccharides of biofilms at the nanoscale. TERS analysis of biological macromolecules, such as alginates,
is complicated by heterogeneity in their sequence, molecular weight, and conformations, their small Raman cross-section, and
the large number of functional groups, which can chemically interact with the silver surface of the tip and cause significant
band shifts. Due to these effects, Raman frequencies in TERS spectra of biopolymers do not necessarily resemble band positions
in the normal Raman spectrum of the bulk material, as is the case for less complex samples (e.g., dye molecules) studied so
far. Additionally, analyte decomposition due to laser heating can have a significant influence, and carbon contamination signals
can sometimes even overwhelm the weak analyte signals. Based on the investigation of alginates, strategies for spectra correction,
choice of appropriate reference samples, and data interpretation are presented. With this approach, characteristic frequency
ranges and specific marker bands can be found for biological macromolecules that can be employed for their identification
in complex environments.
Figure TERS spectrum of a calcium alginate fiber bundle 相似文献