Microstructure and mechanical properties of a novel Zr-based bulk metallic glass composite

Zr48.5Cu46.5Al5 bulk metallic glass (BMG) composites with diameters of 3 and,4 mm were prepared through suction casting in an arc melting furnace by modulating the alloy composition around the monothetic BMG composition of the high glass forming ability. Microstructural characterization reveals that the composites contain micron-sized CuZr phase with martensite structure, as well as nano-sized Zr2Cu crystalline particles and Cu10Zr7 plate-like phase embedded in an amorphous matrix. Room temperature compression tests showed that the composites exhibited significant strain hardening and obvious plastic strain of 7.7% for 3 nun and 6.4% for 4 nun diameter samples, respectively.

Enhanced cycling performance and high energy density of LiFePO4 based lithium ion batteries

LiFePO4 attracts a lot of attention as cathode materials for the next generation of lithium ion batteries. However, LiFePO4 has a poor rate capability attributed to low electronic conductivity and low density. There is seldom data reported on lithium ion batteries with LiFePO4 as cathode and graphite as anode. According to our experimental results, the capacity fading on cycling is surprisingly negligible at 1664 cycles for the cell type 042040. It delivers a capacity of 1170 mAh for 18650 cell type at 4.5C discharge rate. It is confirmed that lithium ion batteries with LiFePO4 as cathode are suitable for electric vehicle application. (c) 2007 Elsevier B.V. All rights reserved.

Fertilidad y fertilización de suelos

Estas notas han sido escritas con el fin de que los estudiantes de agronomia orientados en el uso y manejo de suelos y agua tengan un texto adaptado a su plan de estudio. Este ha sido un compromiso del colectivo de fertilidad de suelos de la Escuela de Suelos para con nuestros estudiantes en aras de la excelencia académica de nuestra alta casa de estudios del agro en Nicaragua. La presentación de los temas se ha hecho en forma sencilla a través de doce capitulos, cuyo objetivo principal, es el de presentar los principios generales del manejo de la fertilidad y fertilización de los suelos en la agricultura. Publicar un texto, aún sencillo como éste, es una tarea dificil pues es de esperar, que no se puede contemplar todos los conocimientos sobre los tópicos relacionados con la fertilidad de los suelos, por lo que las sugerencias, aportes y criticas de los lectores nos será de mucha ayuda y estimulo para mejorarlo en el futuro, por lo que de antemano lo agradecemos. Nuestro reconoc.imiento, al asesor del Proyecto UNA/LUW/SUELOS Ir. Pedro Manzanares, por sus fundamentales aportes técnicos a este texto, el cual, junto con profesionales jóvenes como el Ing. Félix Vega y los autores, elaboraron los primeros manuscritos de este texto allá por 1988. Asi también la valiosa colaboración del Dr. Espinoza del Instituto Internacional de la Potasa y el Fósforo por sus aportes a la actualización de nuestra literatura. Agradecemos también, a todas aquellas personas que de una u otra forma contribuyeron directa o indirectamente en este esfuerzo

A temporal and spatial study of invertebrate communities associated with hard-bottom habitats in the South Atlantic Bight

Species composition, biomass, density, and diversity of benthic invertebrates from six bard-bottom areas were evaluated. Seasonal collections using a dredge, trawl, and suction and grab samplers yielded 432, 525, and 845 taxa, respectively. Based on collections wltb the different gear types, species composition of invertebrates was found to change bathymetrically. Inner- and mlddle-shelf sites were more similar to each other in terms of invertebrate species composition than they were to outer-shelf sites, regardless of season. Sites on the inner and outer shelf were grouped according to latitude; however, results suggest that depth is apparently a more important determinant of invertebrate species composition than either season or latitude. Sponges generally dominated dredge and trawl collections in terms of biomass. Generally, cnidarians, bryozoans, and sponges dominated at sites In terms of number of taxa collected. The most abundant smaller macrofauna collected in suction and grab samples were polychaetes, amphipods, and mollusks. Densities of the numerically dominant species changed botb seasonally and bathymetrically, with very few of these species restricted to a specific bathymetrlc zone. The high diversity of invertebrates from hard-bottom sites is attributed to the large number of rare species. No consistent seasonal changes in diversity or number of species were noted for individual stations or depth zones. In addition, H and its components showed no definite patterns related to depth or latitude. However, more species were collected at middle-shelf sites than at inner- or outer-shelf sites, which may be related to more stable bottom temperature or greater habitat complexity in that area. (PDF file contains 110 pages.)

深圳湾浮游生物和底栖动物现状调查研究

对深圳湾浮游植物、浮游动物和底栖动物的种类、数量及分布现状进行了研究。结果表明 ,淡水种类占绝对优势 ,藻类5门32属45种 ,其中硅藻12属18种 ,绿藻1属15种 ,蓝藻7属10种 ,裸藻、金藻各1属1种 ;浮游动物共计37种 ,其中原生动物9种,轮虫14种 ,枝角类2种 ,桡足类8种 ,浮游幼虫及其它4种 ;底栖动物20种 ,分别为环节动物的多毛类7种 ,寡毛类2种 ,软体动物8种 ,甲壳动物2种 ,鱼类1种。浮游生物和底栖动物数量和分布的特征是 :藻类细胞密度为2.4×106～1.4×107个/L

A method of Biomimetic Pattern Recognition for face recognition

A new method of face recognition, based on Biomimetic Pattern Recognition and Multi-Weights Neuron Network, had been proposed. A model for face recognition that is based on Biomimetic Pattern Recognition had been discussed, and a new method of facial feature extraction also had been introduced. The results of experiments with BPR and K-Nearest Neighbor Rules showed that the method based on BPR can eliminate the error recognition of the samples of the types that not be trained, the correct rate is also enhanced.

一种硅改性钇-铝石榴石纤维的制备方法

本发明公开了一种硅改性多晶铝酸钇纤维的制备方法，采用无机钇盐和铝为基本原料，以水作溶剂，在一定量有机酸的催化下，制得均匀稳定的钇氧铝溶胶，然后将有机硅的醇溶液加入到该溶胶中，再加入适当高分子助纺剂并浓缩成具有一定流变性能的纺丝原液，最后经喷吹法得到凝胶纤维。凝胶纤维经低温干燥、中温水、热处理和高温焙烧，最终制得多晶铝酸钇纤维。该方法原料价廉易得，纺丝液配制及纤维喷吹工艺简单，制得的纤维无渣球，直径均匀且柔软亮泽。

真鲷（Pagrus major）胚胎超低温损伤机理研究

鱼类胚胎由于其自身结构特征：体积大、含水量高、多室结构等，迄今超低温保存尚未成功。超低温保存过程中所造成的冷冻损伤是制约鱼类胚胎超低温保存成功与否的关键，具体表现为渗透压影响、抗冻剂毒性、冰晶损伤等。系统研究并阐明鱼类胚胎冷冻损伤机理，是成功建立鱼类胚胎超低温保存技术的基础。本论文主要针对胚胎对渗透压的耐受性、抗冻剂对胚胎的渗透性、降温速率对胚胎内外冰晶形成温度的影响等冷冻损伤机理进行了系统研究，主要研究结果如下： 1.通过检测胚胎在不同浓度人工海水（0%、25%、50%、75%、1×、2×、3×、4×，渗透压范围0~3740 mOsm/kg）中的孵化率，确定了真鲷不同发育时期胚胎对渗透压的耐受范围，以及心跳期胚胎浸泡不同时间对渗透压的耐受范围。结果显示：①真鲷2-4细胞期、原肠期、10-14体节期胚胎、心跳期和出膜前期胚胎孵化率>50%时渗透压的范围依次为：919~1391 mOsm/kg、919~1391 mOsm/kg、462 ~1391 mOsm/kg、232~1878 mOsm/kg和692~1391 mOsm/kg，表明心跳期胚胎对渗透压变化的耐受范围最广；②在不同浓度人工海水中分别浸泡10 min、30 min、1 h、5 h和10 h后，真鲷胚胎孵化率无显著变化的渗透压范围分别为0~2804 mOsm/kg、0~1878 mOsm/kg、232~1391 mOsm/kg、232~1391 mOsm/kg和919~1391 mOsm/kg；结果表明心跳期胚胎对渗透压的耐受范围随浸泡时间的延长而减小。 2.采用毛细管电泳技术检测胚胎内部DMSO的浓度，并且分析了胚胎孵化率和胚胎内部DMSO的浓度随浸泡时间变化与外部抗冻剂的关系。结果表明胚胎孵化率随胚胎外部抗冻剂溶液浓度和浸泡时间的增加而降低；胚胎内部DMSO浓度随胚胎外部抗冻剂溶液浓度和浸泡时间的增加而增加。对胚胎孵化率（y1）随抗冻剂溶液浓度（x）的变化进行一元三次多项式回归，当浸泡时间分别为10 min、30 min和60 min时，回归方程依次为：y1 = -2832.7x3 + 575.01x2 - 37.011x + 99.641（R2 = 0.9722）；y1 = 30288x3 - 16322x2 + 2077.3x + 27.603（R2 = 0.9876）；y1 = 16052x3 - 5985.2x2 - 32.696x + 119.6（R2 = 0.9124）。对胚胎内部DMSO浓度（y2）随抗冻剂溶液浓度（x）的变化进行回归，当浸泡时间分别为10 min、30 min和60 min时，回归方程依次为：y2 = 0.2584e6.7294x（R2 = 0.9876）；y2 = 0.2521e10.964x（R2 = 0.9644）；y2 = 0.4054e10.95x（R2 = 0.8954）。 3. 利用低温显微镜观察了不同降温速率（20、40、60、80、100、120℃/min）对胚胎内外冰晶形成温度的影响。胚胎外部冰晶形成温度（TEIF）随降温速率的增加显著下降，在降温速率大于80℃/min之后，TEIF随降温速率增加而降低的幅度减小；胚胎内部冰晶形成温度（TIIF）在降温速率小于80℃/min 时随降温速率的升高而降低，在降温速率大于80℃/min 时随降温速率的升高而升高；胚胎内外冰晶形成温度差值（TEIF - TIIF）在降温速率小于80℃/min时随降温速率的升高而增大，在降温速率大于80℃/min时随降温速率的升高而减小。 4. 在低温显微镜下观察了真鲷胚胎低温保存中有复活胚胎记录的保存方法在冷冻解冻过程中的冰晶形成过程，结果表明：①在冷冻过程中，玻璃化法冷冻的胚胎的内部冰晶形成温度（-53.70，-64.33℃）显著低于程序降温法（-17.51，-21.40℃）；而且在玻璃化法冷冻的胚胎内部冰晶形成温度高于外部冰晶后形成（-70.30℃），程序降温法中则相反，胚胎内部冰晶形成温度显著低于外部冰晶形成温度（-4.93，-5.00℃）；玻璃化法中，40%PG冷冻的胚胎外部溶液出现玻璃化现象，其他组均未出现；②在解冻过程中，各组均出现重结晶现象；解冻后，玻璃化法的胚胎完整率（62.82%）远高于程序降温法（9.21%）。

具有三维力反馈的原子力显微镜纳米操作系统

在基于原子力显微镜的纳米操作过程中,由于缺乏实时反馈信息,造成纳米操作效率低下且灵活性差,同时探针因受力过大而损坏。为此,本文通过对探针受力-悬臂变形进行建模,并根据实时检测到的悬臂变形信号、新的参数获取与校准方法,从而获取探针所受的实时三维纳米力。将此三力经比例放大后送入力/触觉设备进行感知,操作者就可以实时调节施加在探针上力的大小及探针的运动轨迹,使得操作的效率及灵活性明显提高,且可以避免探针因受力过大而造成损坏。纳米刻画和多壁碳纳米管的操作实验验证了系统的有效性。

Identification of the region of non-A beta component (NAC) of alzheimer's disease amyloid responsible for its aggregation and toxicity

The non-beta-amyloid (Aß) component of Alzheimer's disease amyloid (NAC) and its precursor a-synuclein have been linked to amyloidogenesis in several neurodegenerative diseases. NAC and a-synuclein both form ß-sheet structures upon ageing, aggregate to form fibrils, and are neurotoxic. We recently established that a peptide comprising residues 3±18 of NAC retains these properties. To pinpoint the exact region responsible we have carried out assays of toxicity and physicochemical properties on smaller fragments of NAC. Toxicity was measured by the ability of fresh and aged peptides to inhibit the reduction of the redox dye 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide (MTT) by rat pheochromocytoma PC12 cells and human neuroblastoma SHSY-5Y cells. On immediate dissolution, or after ageing, the fragments NAC(8±18) and NAC(8±16) are toxic, whereas NAC(12±18), NAC(9±16) and NAC(8±15) are not. Circular dichroism indicates that none of the peptides displays ß-sheet structure; rather all remain random coil throughout 24 h. However, in acetonitrile, an organic solvent known to induce ß sheet, fragments NAC(8±18) and NAC(8±16) both form ß-sheet structure. Only NAC(8±18) aggregates, as indicated by concentration of peptide remaining in solution after 3 days, and forms fibrils, as determined by electron microscopy. These findings indicate that residues 8±16 of NAC, equivalent to residues 68±76 in a-synuclein, comprise the region crucial for toxicity.

Activation of Akt/PKB, increased phosphorylation of Akt substrates and loss and altered distribution of Akt and PTEN are features of Alzheimer's disease pathology

Studies suggest that activation of phosphoinositide 3-kinase-Akt may protect against neuronal cell death in Alzheimer's disease (AD). Here, however, we provide evidence of increased Akt activation, and hyperphosphorylation of critical Akt substrates in AD brain, which link to AD pathogenesis, suggesting that treatments aiming to activate the pathway in AD need to be considered carefully. A different distribution of Akt and phospho-Akt was detected in AD temporal cortex neurons compared with control neurons, with increased levels of active phosphorylated-Akt in particulate fractions, and significant decreases in Akt levels in AD cytosolic fractions, causing increased activation of Akt (phosphorylated-Akt/total Akt ratio) in AD. In concordance, significant increases in the levels of phosphorylation of total Akt substrates, including: GSK3ßSer9, tauSer214, mTORSer2448, and decreased levels of the Akt target, p27kip1, were found in AD temporal cortex compared with controls. A significant loss and altered distribution of the major negative regulator of Akt, PTEN (phosphatase and tensin homologue deleted on chromosome 10), was also detected in AD neurons. Loss of phosphorylated-Akt and PTEN-containing neurons were found in hippocampal CA1 at end stages of AD. Taken together, these results support a potential role for aberrant control of Akt and PTEN signalling in AD.