Biomimetic mineralization synthesis of calcium‐deficient carbonate‐containing hydroxyapatite in a three‐dimensional network of bacterial cellulose

BACKGROUND: Both hydroxyapatites (HAp) and bacterial cellulose (BC) are excellent biomaterials. The former has outstanding osteoconductivity and bioactivity, while the latter has been proven to be a remarkably versatile biomaterial. By alkaline treatment, Ca²⁺ activation, and biomimetic mineralization, the nanocomposites (CaDHCAp/BC) consisting of calcium‐deficient carbonate‐containing hydroxyapatite (CaDHCAp) in the three‐dimensional (3D) network of BC nanofibers were synthesized. RESULTS: The CaDHCAp/BC nanocomposites obtained were characterized by inductively coupled plasma atomic emission spectroscopy (ICP‐AES), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X‐ray diffraction spectroscopy (XRD). The results indicated that alkaline treatment improved the apatite nucleation ability of BC, and the apatite crystals deposited along BC nanofibers were partially substituted with calcium carbonate and the uniform spherical apatite particles were composed of squama‐shaped nano‐sized apatite crystals. The crystallite sizes of apatite crystals are below 10 nm and the crystallinities are below 1%. The formation mechanism of CaDHCAp crystals along the BC fibers was described. CONCLUSION: Alkaline treatment was introduced before the biomimetic mineralization process. Compared with the results without alkaline treatment, the mineralization efficiency was obviously improved. The nanocomposites obtained may have potential application as an orthopedic biomaterial. Copyright © 2008 Society of Chemical Industry     

Steady state thermal-hydraulic analysis of hydride-fueled grid-supported BWRs

A steady state thermal-hydraulic analysis was performed to estimate the power density attainable with hydride-fueled boiling water reactor (BWR) cores with respect to that of an existing oxide BWR core chosen as reference. The power-limiting constraints taken into account were the minimum critical power ratio (MCPR), core pressure drop, fuel average and centerline temperature, cladding outer temperature, flow-induced vibrations and power/flow ratio.The study consisted of two independent analyses: a whole core analysis and a single bundle analysis. The whole core analysis was performed, with a fixed core volume, for both hydride and oxide fuel over hundreds of combinations of rod diameter-rod pitch, referred to as “geometries”, in the ranges 0.6 ≤ D ≤ 1.6 cm and 1.1 ≤ P/D ≤ 1.6. For each geometry, the maximum achievable steady state core power was calculated. Preliminary neutronics results derived from a companion neutronic study were then overlaid on the whole-core thermal-hydraulic results to estimate the reduction in maximum achievable power caused by the application of neutronic constraints. The single bundle analysis was performed to compare in greater detail the thermal-hydraulic performance of a limited number of hydride and oxide fuel bundles having D and P values similar to those of the reference oxide bundle, and for which the compliance with neutronic constraints was demonstrated in a companion neutronic study.The study concluded that, if the core pressure drop is not allowed to increase above the reference core value, the power density increase attainable with hydride fuel is estimated to be in the range 0-15%. If the pressure drop is allowed to increase up to a value 50% higher than the reference core value, the power density increase is estimated to be in the range 25-45%. These power density increases, which are defined with respect to the reference oxide core, decrease about 10% if the comparison is made with respect to oxide designs resembling the most recent commercial high-performance oxide cores.The power gain capability of hydride fuel is primarily due to the possibility of: (1) replacing volumes occupied by water rods and water gaps in oxide fuel cores with fuel rods, thus increasing the heat transfer area per core volume, and (2) flattening the bundle pin-by-pin power distribution.The actual achievement of the above-mentioned power density increase is however conditioned to the compliance of hydride-fueled cores to safety requirements related to core behavior during transients, hydrodynamic stability and steam dryer performance, which are fields of study not addressed in this work. A potential 25-45% power density increase justifies however interest for further investigation on this alternative fuel.     

PTT织物还原染料隐色酸染色

用还原蓝BC染PTT纤维织物,探讨了染浴的pH值、染色温度、时间、尿素的用量对染色深度的影响。结果表明,在pH值为6,110℃下染60min可得到很好的染色效果,尿素的加入可以提高得色深度。各个浓度下,还原蓝BC对PTT纤维织物染色后都具有很好的摩擦色牢度、皂洗色牢度。     

Determination of the time resolution for neutron scintillation detectors by multi-coincidence measurement

Based on the multi-coincidence measurement, the time resolution of three liquid scintillation detectors （BC501A） were determined strictly by solving the coincidence equations, where the influence from electronics estimated by self coincidence measurement     

Design and optimization of hydrogen storage units using advanced solid materials: General mathematical framework and recent developments

This review presents the general mathematical framework of modeling, design and optimization of hydrogen storage using advanced solid materials. The emphasis is given on metal hydride storage tanks, since these systems have been well studied in the literature, both theoretically and experimentally, and are expected to offer significant advantages when current research and development efforts succeed in commercializing the required technology. Enhanced cooling during hydrogen filling of the storage tank is found to be essential to improve hydrogen storage time requirements. For this reason several innovative design strategies for heat exchanger configurations are presented and evaluated in terms of process design and performance improvement. Finally, control and optimization of certain operating conditions can also have a significant impact in hydrogen storage operation.     

Sunflower as a biofuels crop: An analysis of lignocellulosic chemical properties

Four accessions of cultivated sunflower (Helianthus annuus) and silverleaf sunflower (Helianthus argophyllus), were each grown in three locations (Georgia, British Columbia, and Iowa) at different planting densities and phenotyped for biomass-related traits and wood biochemistry. In most environments, H. argophyllus produced significantly more biomass than H. annuus. Cell wall chemistry for a subset of plants grown in Georgia and Iowa was assessed using analytical wet chemistry methods to measure lignin and sugar content/composition. The analysis of lignin and the S/G-lignin ratios for a larger number of samples (n > 250) was also assessed by high-throughput pyrolysis Molecular Beam Mass Spectrometry. Average pyMBMS estimated lignin content (i.e., dry weight fraction) for 60 °C dried basal stem samples of H. annuus and H. argophyllus was 29.6% (range, 24.0%–34.6%) and 28.6% (range, 24.6%–33.3%), respectively when averaged across all environments. The average S/G lignin mass ratio was 1.5 (range, 1.0–2.0) for H. annuus and 1.7 (range, 1.0–2.4) in H. argophyllus. Stem samples from these two species only differed statistically for a few cell wall chemistry traits; however, accession level differences within each species were apparent. Cell wall chemistry in both species was significantly affected by both location and planting density, thus demonstrating the need to select for these traits in the environment for which the crop will be produced. Overall, these results show that cultivated sunflower and silverleaf sunflower both possess the necessary phenotypic diversity to facilitate the development of a hybrid sunflower with improved lignocellulosic biofuels traits, namely increased biomass, decreased lignin, and increased glucan.     

和速率约束下衰落高斯MIMO广播信道的和功率优化

 本文研究了在系统和速率一定的条件下有着高斯噪声的衰落MIMO广播信道和功率最小化问题.该问题通常存在于无线通信系统动态资源分配中,是和功率约束下衰落MIMO下行链路和速率最大化的互补问题.首先利用MIMO MAC和MIMO BC的对偶性,将问题描述和转化为凸最优化问题,在此基础上,利用子梯度法和二分法,设计了相应的快速迭代的多用户注水算法,用于计算基站的发射功率.理论分析和数值仿真结果表明,该算法全局有效地收敛于最小的和功率.     

BC728IA串行通讯的解决方案

本文重点阐述数码管显示及键盘接口专用控制芯片BC7281A与MCU串行通讯中应注意的几个问题,给出了有效的解决方法,并提出了改进建议.     

Dentinal tubule penetration of endodontic sealers after nonthermal plasma treatment: A confocal laser scanning microscopy study

One of the factors affecting the success of endodontic treatment is to fill the root canal system hermetically. The aim of this in vitro study was to evaluate the effect of nonthermal plasma (NP) on dentinal tubule penetration of root canal sealers using confocal laser scanning microscopy. Forty mandibular premolar teeth were selected and the root canals were prepared with large‐Waveone‐Gold rotary‐files. Specimens were divided into four experimental groups according to sealer and NP treatment (n = 10). G1: AH‐Plus (AH) G2: nonthermal plasma application + AH‐Plus(AH‐P) G3: Endosequence‐BC(BC) G4: nonthermal plasma application + Endosequence‐BC(BC‐P). Cold lateral‐condensation technique was used for the obturation of root canals. The roots were sectioned horizontally and the sections were examined under confocal laser scanning microscopy. The maximum tubule penetration and percentage of penetration values were obtained from the microscopy images and were statistically analyzed with repeated measurements‐ANOVA and the Tukey (HSD) test (p < 0.05). The percentages of dentinal tubule penetration of the groups were not statistically different. The maximum tubule penetration of the AH‐P was statistically lower than that of the BC‐P (p < 0.05). Plasma application had no affect on the percentage of dentinal tubule penetration. Under the conditions of this in vitro Endosequence‐BC sealer showed higher maximum tubule penetration values than AH‐Plus after NP treatment. Percentage of dentinal tubule penetration values of experimental groups was similar.