Effects of sintering temperature on structure of hydroxyapatite studied with Rietveld method

It is obvious that the sintering temperature of hydroxyapatite (HA) ceramics significantly affects their biological responses in vitro or in vivo. The HA ceramics sintered at different temperatures exhibite a wide variation of biological response, but the correlation of this variation with the parameters of HA crystalline structure is not fully investigated. In present study, the crystalline structure of HA powders sintered at different temperatures at 600, 800, 1000, 1200 °C, was characterized using X-ray diffraction (XRD), and then refined with Rietveld method. A series of structure parameters, such as, cell lattice parameters (a and c) and bond length, distances of special atoms on surface to nearest atom, a numerical index of distortion for PO₄ tetrahedron, as well as internal energy and density of HA cell, were calculated to characterize the crystalline structure of HA at atom level. The broadening effect of XRD reflections was also separated to calculate the micro-strain/crystalline size, respectively. These parameters of HA crystalline structure and cell demonstrated that with rising of the sintered temperature, the internal energy and micro-strain of HA cell decreased, but the crystalline size increased. The regularity of PO₄ tetrahedron and distance between Ca₁ and O₃ in HA cell showed the same tendency as the internal energy and micro-strain with sintering temperature. All of these parameters indicated that HA became more stable with the rising of sintering temperature.     

Adaptive eigendecomposition of data covariance matrices based onfirst-order perturbations

In this paper, new algorithms for adaptive eigendecomposition of time-varying data covariance matrices are presented. The algorithms are based on a first-order perturbation analysis of the rank-one update for covariance matrix estimates with exponential windows. Different assumptions on the eigenvalue structure lead to three distinct algorithms with varying degrees of complexity. A stabilization technique is presented and both issues of initialization and computational complexity are discussed. Computer simulations indicate that the new algorithms can achieve the same performance as a direct approach in which the exact eigendecomposition of the updated sample covariance matrix is obtained at each iteration. Previous algorithms with similar performance require O(LM²) complex operations per iteration, where L and M respectively denote the data vector and signal-subspace dimensions, and involve either some form of Gram-Schmidt orthogonalization or a nonlinear eigenvalue search. The new algorithms have parallel structures, sequential operation counts of order O(LM) or less, and do not involve any of the above steps. One particular algorithm can be used to update the complete signal-subspace eigenstructure in 5LM complex operations. This represents an order of magnitude improvement in computational complexity over existing algorithms with similar performance. Finally, a simplified local convergence analysis of one of the algorithms shows that it is stable and converges in the mean to the true eigendecomposition. The convergence is geometrical and is characterized by a single time constant     

室内热湿环境仿真软件开发

建筑室内热环境仿真软件已成为室内环境研究的重要手段之一.在VB.NET开发平台下,采用高效的计算语言Visual Fortran与Visual Basic混合编程,开发了一套界面友好、计算速度较快、计算结果可视化的建筑室内热环境仿真软件Indoor Thermal Environment Simulation (ITES),并在重庆大学热环境实验室进行了实验,对特定热湿环境下的室内温度分布进行测试,其测试结果与ITES软件的模拟结果相一致.验证了ITES软件对建筑室内热环境仿真模拟的可信性.     

Review of Bioretention System Research and Design: Past, Present, and Future

This paper reviews the evolution of bioretention systems, a promising at-source storm-water best management practice. The introduction of bioretention systems in the 1990s by Prince George’s County, Md. is examined along with the motivations behind the development of the systems. A summary of the research findings on the performance of bioretention systems is provided including proposed design modifications to improve the field performance. Also included is an overview of past and current bioretention design guidelines in North America, as well as a discussion of issues surrounding the public adoption and implementation of bioretention systems. Potential alternative uses for the systems are highlighted and a review of bioretention modeling work is provided. Finally, the paper outlines research needs and anticipated future work necessary to bring about the widespread use of bioretention systems.     

Timing During Interruptions in Timing.

Duration and location of breaks in time interval production were manipulated in various conditions of stimulus presentation (Experiments 1-4). Produced intervals shortened and then stabilized as break duration lengthened, suggesting that participants used the break as a preparatory period to restart timing as quickly as possible at the end of the break. This interpretation was supported in Experiment 5, in which similar results were obtained with a reaction time response executed at the end of the break. In all experiments, produced intervals lengthened as the break occurred later during the interval. The authors conclude that varying break location and duration reveal, respectively, the influence of attentional time-sharing before the interruption and of preparatory processes taking place during the break. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

基于水文控制目标的中小尺度海绵城市改造方案评价

为正确评价中小尺度低影响开发(LID)措施改造方案的水文控制效能,以重庆市秀山县海绵城市建设试点为例,将LID措施的生态、经济和社会效应具体量化为径流量控制、径流污染控制、建设成本、维护管理成本和径流利用效益等5个指标,构建了基于水文控制目标的LID措施评价体系,并利用暴雨管理模型(SWMM)对不同LID设施改造方案的暴雨径流水文过程进行了验证模拟。研究结果表明:现有LID措施因其规模占比过小且组合方式不合理而对暴雨径流的水文控制效果不佳,不满足75%年径流总量控制率目标,需进行扩容和组合优化;LID设施改造方案综合评价结果显示综合评分与径流总量控制率、峰值流量削减率等水文控制指标呈显著正相关,可直接作为中小尺度海绵城市改造方案评价。     

Study of oxidation after monoacrylate grafting on polyethylene

BACKGROUND: The surface properties of high‐density polyethylene and linear low‐density polyethylene were modified by grafting urethane monoacrylate monomer under UV irradiation. This graft polymerization was carried out on native substrates and on substrates pre‐treated by wet oxidation, for different oxidation times. RESULTS: As the urethane monacrylate layer is crosslinked, its grafting efficiency was checked by dissolving the polyethylene substrates in hot toluene. Grafting was evidenced by Fourier transform infrared spectroscopy of the obtained residues, which showed that both the characteristic urethane acrylate (3350 cm^?1) and polyethylene (2920, 730 and 720 cm^?1) bands were observable for any polyethylene oxidation time. For an oxidation time longer than 10 hours, acrylate grafting was homogeneous and the grafted surface was smooth with a roughness of less than 10 nm. In addition, X‐ray photoelectron spectroscopy analysis of the residues revealed that O/C had an average value of 0.19, which is lower than the value corresponding to pure acrylate (0.42), whereas N/C had an average value of 0.068, also lower than that of pure acrylate (0.09), thus confirming the grafting. CONCLUSION: A urethane monoacrylate layer was grafted on native and oxidized polyethylene films. For highly oxidized films, the grafted surfaces are smooth and homogeneous. Copyright © 2008 Society of Chemical Industry     

Identification of a steroidogenic neurohormone in female mosquitoes

In the female mosquito, Aedes aegypti, neurohormones are released from the brain in response to a blood meal and stimulate the ovaries to secrete ecdysteroid hormones, which modulate yolk protein synthesis in the fat body. Neuropeptides with this bioactivity were isolated from head extracts, and partial sequences from these peptides when aligned gave a 31-residue sequence at the amino terminus. Oligonucleotide primers for this sequence were used to amplify with the polymerase chain reaction a genomic DNA product that hybridized to a clone from a head cDNA library. The cDNA encodes a 149-residue preprohormone that is processed into an 86-residue peptide, as indicated by the mass value obtained from the native peptide, with the expected amino-terminal sequence. After modification, the cDNA for the putative neurohormone was expressed in a bacterial system, and the purified peptide had high specific activity in bioassays, thus confirming that it is a steroidogenic gonadotropin, the first to be identified for invertebrates.     

Diet design for a multicenter controlled feeding trial: the DELTA program. Delta Research Group

OBJECTIVE: To describe the process and results of diet standardization, diet validation, and monitoring of diet composition, which were key components of protocol 1 of Dietary Effects on Lipoproteins and Thrombogenic Activity (DELTA-1), the initial protocol in a program of multicenter human feeding studies designed to evaluate the effects of amount and type of fat on lipoproteins and hemostasis parameters in various demographic groups. DESIGN: DELTA-1 was based on a randomized, blinded, crossover experimental design. Three diets were fed for 8 weeks to 103 healthy men and women aged 22 to 67 years at 4 field centers. Diet A, an average American diet, was designed to provide 37% of energy from fat, 16% of energy from saturated fatty acids (SFAs); diet B (step 1 diet) was designed to provide 30% of energy from fat, 9% of energy from SFA; and diet C (low SFA diet) was designed to provide 26% of energy from fat, 5% of energy from SFA. Key features of diet standardization included central procurement of fat-containing foods, inclusion of standard ingredients, precision weighing of foods--especially sources of fat and cholesterol--and use of standardized written procedures. SETTING: For menu validation, a set of 12 menus for each diet was prepared in duplicate and chemically assayed. For monitoring of diet composition during the study, an 8-day diet cycle (6 weekday and 2 weekend menus) was sampled by every field center twice during each of 3 feeding periods. STATISTICAL ANALYSES: Means (+/- standard error) were calculated and compared with target nutrient specifications. RESULTS: DELTA-1 was able to provide a standardized diet that met nutrient specifications across 4 field centers over 24 weeks of participant feeding spanning a total of 8 months. APPLICATIONS: Prestudy chemical validation of menus and continuous sampling and assay of diets throughout the study are essential to standardize experimental diets and to ensure that nutrient target goals are met and maintained throughout a controlled multicenter feeding study.