Reactive Laser Ablation Synthesis of Nanosize Aluminum Nitride

An aluminum (Al) target was laser ablated in a nitrogen (N₂) atmosphere, producing aluminum nitride (AlN) powder. These powders were calcined at 900°C for 2 h. Powders were produced at various nitrogen pressures, and the calcined powders were tested for unreacted aluminum content, using differential thermal analysis (DTA). The AlN powder, produced at a laser fluence of 12 J/cm² and a nitrogen pressure of 10.0 kPa (75 torr), showed no evidence of unreacted aluminum by DTA and was phase-pure AlN by X-ray diffraction (XRD). The surface area of this powder is 82 m²/g, corresponding to a particle size of ∼11 nm, which is in good agreement with TEM observations.     

Molecular design and characterization of catalysts for NO x selective reduction by hydrocarbons in the oxygen excess based upon ultramicroporous zirconia pillared clays

Approaches to design of zirconia pillared clays via control of the properties of pillaring species in solutions were elaborated. Structural features of pillars and Pt + Cu active components fixed at these nanoparticles were shown to determine catalytic properties of pillared clays in NO_x selective reduction by hydrocarbons in the oxygen excess.     

Confinement, composition, and spin-coating effects on the glass transition and stress relaxation of thin films of polystyrene and styrene-containing random copolymers: Sensing by intrinsic fluorescence

The glass transition temperatures (T_gs) of polystyrene (PS) and styrene/methyl methacrylate (S/MMA) random copolymer films are characterized by intrinsic fluorescence, i.e., monomer fluorescence from an excited-state phenyl ring and excimer fluorescence from an excited-state dimer of two phenyl rings. The T_g is determined from the intersection of the rubbery- and glassy-state temperature dependences of the integrated fluorescence intensity measured upon cooling from an equilibrated state. With PS, the effects of nanoconfinement on T_g and the transition strength agree with results from studies using probe fluorescence and ellipsometry. The T_g-nanoconfinement effect is “tuned” by copolymer composition. As S-content is reduced from 100 mol% to 22 mol%, the confinement effect changes from a reduction to an enhancement of T_g relative to bulk T_g. Intrinsic fluorescence is also a powerful tool for characterizing relaxation of residual stresses. Stresses induced by spin coating affect local conformations, which in turn affect excimer and monomer fluorescence and thereby integrated intensity. The heating protocol needed to achieve apparently equilibrated local conformations is determined by equivalence in the integrated intensities obtained upon heating and subsequent cooling. While partial stress relaxation occurs upon heating in the glassy state, full relaxation of local conformations requires that a film be heated above T_g for times that are long relative to the average cooperative segmental relaxation time. For example, in thin and ultrathin films, equilibration is achieved by heating slowly (∼1 K/min) to 15-20 K above T_g. Dilute solution fluorescence of PS and S/MMA copolymers is also characterized and compared to reports in the literature.     

Altered arachidonic acid content in polymorphonuclear and mononuclear cells from patients with allergic rhinitis and/or asthma

We previously have found that monocytes from patients with allergic rhinitis and/or asthma produce less PGE₂ than cells from normal subjects in response to a histamine-induced lymphokine. In order to investigate this observation further, we measured the fatty acid content in the total phospholipids derived from the plasma, red cells, buffy coat cells, neutrophils, monocytes and lymphocytes of 27 allergic patients and 21 normal controls. There were no substantial differences between atopics and normals in the fatty acid analyses carried out for plasma and red cells. However, linoleic acid (18∶2n−6) levels were elevated significantly in the buffy coat fraction, while arachidonic acid (20∶4n−6) levels were reduced. Measurement of fatty acid levels after fractionation of the buffy coat population into neutrophils and monocytes yielded similar elevations in 18∶2n−6 and reduced 20∶4n−6. In contrast, lymphocytes appeared to have the reverse pattern, i.e., significantly reduced 18∶2n−6 and elevated 20∶4n−6 levels. These data suggest that atopic leukocytes may have altered essential fatty acid metabolism.     

时尚

时尚是有规律的.它不是以进步的形式运动,而是在循环中运动.外在的一致性通常会破坏内在的一致性.本文就时尚的规律、时尚的产生与运动过程、时尚与限制性规则、现代时尚的新变革等方面展开讨论.     

Sulfur-Tolerant NOx Storage Traps: An Infrared and Thermodynamic Study of the Reactions of Alkali and Alkaline-Earth Metal Sulfates

The sulfur tolerance of a barium-containing NO_x storage/reduction trap was investigated using infrared analysis. It was confirmed that barium carbonate could be replaced by barium sulfate by reaction with low concentrations of sulfur dioxide (50 ppm) in the presence of large concentrations of carbon dioxide (10%) at temperatures up to 700 °C. These sulfates could at least be partially removed by switching to hydrogen-rich conditions at elevated temperatures. Thermodynamic calculations were used to evaluate the effects of gas composition and temperature on the various reactions of barium sulfate and carbonate under oxidizing and reducing conditions. These calculations clearly showed that if, under a hydrogen-rich atmosphere, carbon dioxide is included as a reactant and barium carbonate as a product then barium sulfate can be removed by reaction with carbon dioxide at a much lower temperature than is possible by decomposition to barium oxide. It was also found that if hydrogen sulfide was included as a product of decomposition of barium sulfate instead of sulfur dioxide then the temperature of reaction could be significantly lowered. Similar calculations were conducted using a selection of other alkaline-earth and alkali metals. In this case calculations were simulated in a gas mixture containing carbon monoxide, hydrogen and carbon dioxide with partial pressures similar to those encountered in real exhausts during switches to rich conditions. The results indicated that there are metals such as lithium and strontium with less stable sulfates than barium, which may also possess sufficient NO_x storage capacity to give sulfur-tolerant NO_x traps.     

An International Collaborative Study on Trypsin Inhibitor Assay for Legumes,Cereals, and Related Products

For determining trypsin inhibitor activity (TIA) in soy products, the American Oil Chemists' Society (AOCS) Method Ba 12-75 has been used. It measures differences in absorbance at 410 nm of bovine trypsin activity toward a synthetic substrate (Nα-benzoyl-DL-arginine-p-nitroanilide) in the absence and presence of an inhibitor. Recently, a significantly improved method was developed (JAOCS, 2019, 96:635–645), featuring 5 mL of total assay volume, enzyme-last sequence, and single inhibitor level in duplicate. It is proposed as the AOCS Method Ba 12a-2020. As a part of the AOCS method approval process, a collaborative study involving 12 international laboratories was conducted to evaluate the performance of the proposed method. The study involved measuring TIA in 10 selected test samples plus a blind duplicate. They included soybeans, pulses, cereals, and their processed products (flours, concentrates, and isolates). After rigorous statistical treatment of the data, only three outliers were removed from the data of two samples. Repeatability relative standard deviations (RSDr) for the 11 samples ranged from 0.99% to 5.52%. Reproducibility RSD (RSD_R) ranged from 7.07% to 22.92%, with seven samples having RSD_R around 10% or less. The remaining four samples had very low TIA, and their RSD_R values ranged from 13.34% to 22.92%. The study has demonstrated reliable performance of the proposed AOCS method. Several collaborators carried out additional experiments addressing some aspects of the method, leading to further refinements. The proposed method is undergoing evaluation by the AOCS Uniform Methods Committee for adoption as an Official Method for measuring TIA in various legume and grain products.     

Exploiting SSDs in operational multiversion databases

Multiversion databases store both current and historical data. Rows are typically annotated with timestamps representing the period when the row is/was valid. We develop novel techniques to reduce index maintenance in multiversion databases, so that indexes can be used effectively for analytical queries over current data without being a heavy burden on transaction throughput. To achieve this end, we re-design persistent index data structures in the storage hierarchy to employ an extra level of indirection. The indirection level is stored on solid-state disks that can support very fast random I/Os, so that traversing the extra level of indirection incurs a relatively small overhead. The extra level of indirection dramatically reduces the number of magnetic disk I/Os that are needed for index updates and localizes maintenance to indexes on updated attributes. Additionally, we batch insertions within the indirection layer in order to reduce physical disk I/Os for indexing new records. In this work, we further exploit SSDs by introducing novel DeltaBlock techniques for storing the recent changes to data on SSDs. Using our DeltaBlock, we propose an efficient method to periodically flush the recently changed data from SSDs to HDDs such that, on the one hand, we keep track of every change (or delta) for every record, and, on the other hand, we avoid redundantly storing the unchanged portion of updated records. By reducing the index maintenance overhead on transactions, we enable operational data stores to create more indexes to support queries. We have developed a prototype of our indirection proposal by extending the widely used generalized search tree open-source project, which is also employed in PostgreSQL. Our working implementation demonstrates that we can significantly reduce index maintenance and/or query processing cost by a factor of 3. For the insertion of new records, our novel batching technique can save up to 90 % of the insertion time. For updates, our prototype demonstrates that we can significantly reduce the database size by up to 80 % even with a modest space allocated for DeltaBlocks on SSDs.     

Sensitivity analysis for biometric systems: A methodology based on orthogonal experiment designs

The purpose of this paper is to introduce an effective and structured methodology for carrying out a biometric system sensitivity analysis. The goal of sensitivity analysis is to provide the researcher/developer with insight and understanding of the key factors—algorithmic, subject-based, procedural, image quality, environmental, among others—that affect the matching performance of the biometric system under study. This proposed methodology consists of two steps: (1) the design and execution of orthogonal fractional factorial experiment designs which allow the scientist to efficiently investigate the effect of a large number of factors—and interactions—simultaneously, and (2) the use of a select set of statistical data analysis graphical procedures which are fine-tuned to unambiguously highlight important factors, important interactions, and locally-optimal settings. We illustrate this methodology by application to a study of VASIR (Video-based Automated System for Iris Recognition)—NIST iris-based biometric system. In particular, we investigated k = 8 algorithmic factors from the VASIR system by constructing a (2^6?1 × 3¹  × 4¹) orthogonal fractional factorial design, generating the corresponding performance data, and applying an appropriate set of analysis graphics to determine the relative importance of the eight factors, the relative importance of the 28 two-term interactions, and the local best settings of the eight algorithms. The results showed that VASIR’s performance was primarily driven by six factors out of the eight, along with four two-term interactions. A virtue of our two-step methodology is that it is systematic and general, and hence may be applied with equal rigor and effectiveness to other biometric systems, such as fingerprints, face, voice, and DNA.     

Development of an operational fitness test for the Royal Air Force

Since 2002, the Royal Air Force (RAF) has been working towards developing role-related physical tests for use as an operational fitness test (OFT). The purpose of this study was to establish reliability of the OFT (comprising four tests), investigate gym-based tests as predictors of performance and establish performance standards. Fifty-eight RAF personnel performed the OFT on three occasions. A separate cohort carried out fitness and anthropometric tests before performing the OFT, by way of establishing performance predictors. Documented evidence and views of an expert panel were used to determine OFT standards. Reliability ranged from moderate to good for three tests, with one test (Dig) showing poor reliability. The 95% limits of agreement for the prediction models ranged from good to poor (6.7-34.2%). The prediction models were not sufficiently accurate to estimate confidently OFT performance, but could be used as a guide to quantify likely outcome and training needs.