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51.
Nanosized diamond (UDD), obtained by a detonation procedure, was modified with iron from the corresponding acetylacetonate precursor under various pretreatment conditions. Nitrogen physisorption, X-ray diffraction, temperature-programmed reduction, and FTIR and M?ssbauer spectroscopy were used for their characterization. The samples' catalytic behavior in methanol decomposition was also studied. The physicochemical and catalytic properties of the obtained materials (Fe/UDD) were compared with those of other iron-oxide-modified mesoporous supports with different nature and functionality (MCM-48 silica and CMK-1 carbon). The highest catalytic activity and stability was achieved with air-pretreated Fe/UDD.  相似文献   
52.
Numerous forms of the neurotransmitter GnRH have been discovered in vertebrates and invertebrates. Methods used for identification of these peptides are laborious and often require the application of multiple, confirmatory techniques. In this study, we investigate whether HPLC-MS/MS and de novo sequencing techniques applied to whole peptide analysis can provide a simpler approach to GnRH characterization. Experiments were performed with six GnRH forms (chicken I, chicken II, lamprey III, mammalian, salmon and seabream) to determine whether MS/MS spectra would be dominated by proline-directed fragmentation to the detriment of obtaining sufficient fragmentation for sequencing. While the expected b8 fragment was prominent, sufficient ion series were obtained for the six GnRH peptides to provide sequence identification. On the basis of the patterns observed for six model peptides, similar fragmentation patterns are expected for other GnRH forms. To confirm the applicability of the method, extracts from Sprague-Dawley rat brains were examined. These experiments confirm the presence of mammalian GnRH and a posttranslationally modified form of mammalian GnRH, hydroxyproline9 GnRH, in Sprague-Dawley rat brains and demonstrate that ESI-MS/MS techniques provide a valuable addition to existing qualitative methods.  相似文献   
53.
制造技术与复杂模型、设计工具的进步使微纳结构光学器件的实现成为可能。微纳结构光学器件可用于导光与光的相互作用,液态或气态新型光源和传感器件。IPAS致力于新型光学材料研究与开发,将玻璃工艺和光纤开发有机结合,重点研究微纳结构光纤,光纤表面功能处理和器件开发。介绍了IPAS的研究实力和近年的发展概况,其中包括中红外光学材料、纳米粒子嵌入玻璃材料、新型化学和生物传感器(适用于超低量样本及/或体内样本)、激光器件,以及用于光数据处理的新型高非线性光纤。  相似文献   
54.
The epitaxy optimization studies of high-quality n-type AlInN alloys with different indium contents grown on two types of substrates by metalorganic vapor phase epitaxy (MOVPE) were carried out. The effect of growth pressure and V/III molar ratio on growth rate, indium content, and surface morphology of these MOVPE-grown AlInN thin films were examined. The surface morphologies of the samples were characterized by scanning electron microscopy and atomic force microscopy. By varying the growth temperatures from 860 °C to 750 °C, the indium contents in AlInN alloys were increased from 0.37% up to 21.4% as determined by X-ray diffraction (XRD) measurements. The optimization studies on the growth conditions for achieving nearly-lattice-matched AlInN on GaN templates residing on sapphire and free-standing GaN substrates were performed, and the results were analyzed in a comparative way. Several applications of AlInN alloy for thermoelectric and light-emitting diodes are also discussed.  相似文献   
55.
The reactions of N-alkylaryl-and N, N′-dialkylarylureas with aldehydes in acidic medium leads to the synthesis of N-carbamoyltetrahydro-isoquinolines and tetrahydro-1,3,5-oxadiazin-4-ones (urons) depending on the structure of starting compounds and the reaction conditions.  相似文献   
56.
This paper describes students’ perspectives of a one-off flipped lecture in a large undergraduate mathematics service course. The focus was on calculating matrix determinants and was designed specifically to introduce debate and argumentation into a mathematics lecture. The intention was to promote a deeper learning and understanding through engagement with the added hope of instilling some passion for the subject. During the lecture, students were asked to vote with their feet, literally moving around the lecture theatre to form groups according to their shared favourite technique for calculating matrix determinants. Group discussions were then followed by a whole class debate facilitated by the lecturers, before they wrapped up the lecture by resolving the professional disagreements that had come to light during the debate. Following the lecture, data on student perspectives was gathered using both surveys and focus groups. Within this paper, we share the data and reveal the interesting results that emerged from our analysis. Despite remaining unconvinced as to whether flipped lectures are better for learning, students reported greater engagement and increased understanding of the material covered.  相似文献   
57.
Currently, the most efficient passive attack on the NTRU public-key cryptosystem, proposed by Coppersmith and Shamir [1], is based on finding a short enough vector in an integral lattice. An NTRU lattice possesses a cyclic automorphism group whose symmetry may be exploited. We have designed methods for reducing bases of NTRU integral lattices based on this symmetry. In addition to these methods, we use hill-descending techniques to combine new and proposed lattice-reduction algorithms. This approach includes deterministic and non-deterministic components which may be efficiently parallelized.  相似文献   
58.
FeII4L6 tetrahedral cage 1 was prepared from a redox-active dicationic naphthalenediimide (NDI) ligand. The +20 charge of the cage makes it a good host for anionic guests, with no binding observed for neutral aromatic molecules. Following reduction by Cp2Co, the cage released anionic guests; subsequent oxidation by AgNTf2 led to re-uptake of anions. In its reduced form, however, 1 was observed to bind neutral C60. The fullerene guest was subsequently ejected following cage re-oxidation. The guest release process was found to be facilitated by anion-mediated transport from organic to aqueous solution. Cage 1 thus employs electron transfer as a stimulus to control the uptake and release of both neutral and charged guests, through distinct pathways.

FeII4L6 cage 1 binds anionic guests but not neutral guests. In its reduced form, the cage can bind neutral C60. Reduction and oxidation of the cage could thus be used as a stimulus to control the uptake and release of both neutral and charged guests.  相似文献   
59.
Titanium dioxide (TiO2) is one of the best semiconductor photocatalysts with optical band gap of 3.2 eV. The optical band gap and photocatalytic properties could be further tuned by tailoring shape, size, composition, and morphology of the nanostructures. Hydrothermal synthesis methods have been applied to produce well-controlled nanostructured TiO2 materials with different morphologies and improved optoelectronic properties. Among various morphologies, one-dimensional (1D) TiO2 nanostructures are of great importance in the field of energy, environmental, and biomedical because of the directional transmission properties resulting from their 1D geometry. Particularly, TiO2 nanorods (NRs) have gained special attention because of their densely packed structure, quantum confinement effect, high aspect ratio, and large specific surface area that could specially improve the directional charge transmission efficiency. This results in the effective photogenerated charge separation and light absorption, which are really important for potential applications of TiO2-based materials for photocatalytic and other important applications. In this review, hydrothermal syntheses of TiO2 NRs including the formation chemistry and the growth mechanism of NRs under different chemical environments and effects of various synthesis parameters (pH, reaction temperature, reaction time, precursors, solvents etc.) on morphology and optoelectronic properties have been discussed. Recent developments in the hydrothermal synthesis of TiO2 NRs and tailoring of their surface properties through various modification strategies such as defect creation, doping, sensitization, surface coating, and heterojunction formation with various functional nanomaterials (plasmonic, oxide, quantum dots, graphene-based nanomaterials, etc.) have been reported to improve the photocatalytic activities. Furthermore, applications of TiO2 NRs/tailored TiO2 NRs as superior photocatalysts in degradation of organic pollutants and bacterial disinfection have been discussed with emphasis on mechanisms of action and recent advances in the fields.  相似文献   
60.
Product distribution studies of the OH radical and Cl atom initiated oxidation of CF3CH2CH2OH in air at 1 atm and 298 +/- 5 K have been carried out in laboratory and outdoor atmospheric simulation chambers in the presence and absence of NOx. The results show that CF3CH2CHO is the only primary product and that the aldehyde is fairly rapidly removed from the system. In the absence of NOx the major degradation product of CF3CH2CHO is CF3CHO, and the combined yields of the two aldehydes formed from CF3CH2CH2OH are close to unity (0.95 +/- 0.05). In the presence of NOx small amounts of CF3CH2C(O)O2NO2 were also observed (<15%). At longer reaction times CF3CHO is removed from the system to give mainly CF2O. The laser photolysis-laser induced fluorescence technique was used to determine values of k(OH + CF3CH2CH2OH) = (0.89 +/- 0.03) x 10(-12) and k(OH + CF3CH2CHO) = (2.96 +/- 0.04) x 10(-12) cm3 molecule(-1) s(-1). A relative rate method has been employed to measure the rate coefficients k(OH + CF3CH2CH2OH) = (1.08 +/- 0.05) x 10(-12), k(OH + C6F13CH2CH2OH) = (0.79 +/- 0.08) x 10(-12), k(Cl + CF3CH2CH2OH) = (22.4 +/- 0.4) x 10(-12), and k(Cl + CF3CH2CHO) = (25.7 +/- 0.4) x 10(-12) cm3 molecule(-1) s(-1). The results from this investigation are discussed in terms of the possible importance of emissions of fluorinated alcohols as a source of fluorinated carboxylic acids in the environment.  相似文献   
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