Deformation behaviour of electrodeposited nanocrystalline Ni with broad grain size distribution

In the present work, nanocrystalline Ni (nc-Ni) with a broad grain size distribution (BGSD) of 5-120 nm and an average grain size of 27.2 nm was prepared. The BGSD nc-Ni sample shows a similar strength and good ductility in comparison with electrodeposited nc-Ni with a narrow grain size distribution. The intracrystalline dislocation network was observed in the post-deformed microstructure confirming the conventional intracrystalline dislocation sliding mechanism in BGSD nc-Ni. The uniaxial tensile loading-unloading-loading deformation shows BGSD nc-Ni has the capability to store dislocations in the grain interior, which is very limited compared with that of coarse grained metals. For BGSD nc-Ni, the strain rate sensitivity of flow stress m enhances with decreasing strain rate. At the strain rate of 5 x 10(-6) s(-1), m was estimated to be 0.055. At the corresponding strain rate, the enhanced ductility along with the decreased strength was achievable, indicating activation of other deformation mechanisms, e. g. grain boundary sliding or diffusion.

黄土塬区三种豆科牧草的竞争生长

通过田间试验研究了沙打旺、紫花苜蓿和达乌里胡枝子3种豆科牧草在黄土旱塬以不同密度单播、混播时的竞争生长能力及水分利用效率。单播时苜蓿生长次年3个密度的生产力分别为15349kg·hm-2、20582kg·hm-2、21531kg·hm-2,沙打旺和胡枝子3个密度的生产力分别为7979kg·hm-2、16 440 kg·hm-2、21055kg·hm-2和2412kg·hm-2、5270kg·hm-2、7102kg·hm-2。混播草地生产力以苜蓿+胡枝子最高(平均19227kg·hm-2),沙打旺与胡枝子混播的生产力最低(平均11977kg·hm-2)。和生产力较高的参混种苜蓿、沙打旺单播相比,苜蓿与沙打旺混播及沙打旺与胡枝子混播的生产力在3种密度下均有不同程度的降低。苜蓿主根下扎深度2m,0~60cm根系占总根量的66%,沙打旺和胡枝子根系最大下扎深度分别为1.8 m和1.5m,0~60cm根系占总根量比例分别是80%、91%。3种牧草中苜蓿的平均水分利用效率最高,为25.75kg·mm-1·hm-2,胡枝子最低为7.71kg·mm-1·hm-2,沙打旺居中。苜蓿群体种内个体间竞争强度高于沙打旺和胡枝子。结果...

吗啡给药及戒断期间大鼠眶额叶脑区功能活动特征户外环境下自由活动猕猴顶叶及海马神经元单位放电的胞外记录方法

已有的研究表明，眶额叶在解剖上与现在已知的药物滥用相关的脑区是紧密联系在一起的。例如，眶额叶在药物滥用和强迫性重复行为中起作用，且随着脑成像技术的应用，越来越多的证据表明眶额叶参与了药物滥用。但是我们并不了解在阿片给药和戒断期间眶额叶脑区活动是如何变化的。因此，我们在实验中采用了Mn2+增强的核磁共振成像（Manganese-enhanced magnetic resonance　imaging，MEMRI，4.7T）技术和脑电（EEG）记录的方法，以研究大鼠眶额叶在给与阿片类药物（盐酸吗啡）以及戒断过程中的动态变化。 MEMRI是一种近年才发展起来的新型技术。研究表明，Mn2+是Ca2+的类似物，可以通过Ca2+通道进入兴奋性的神经元里面并结合到胞内的蛋白质和核酸上的Ca2+和Mg2+结合位点上 (MILDVAN and COHN, 1963; EISINGER et al., 1965)。另外，Mn2+的顺磁性也为它成为核磁共振成像的造影剂提供了前提条件。可是成功应用MEMRI的前提就是要在适当的时间把合适剂量的Mn2+传递到靶点上。因此，Mn2+在注射到靶点后，是否能够在有效的时间内反映大脑活动的变化就成为一个非常重要并且在技术上较为棘手的问题。在给实验大鼠脑区微量注射Mn2+（80mMol/L，200nl）的同时，通过微量注射兴奋性神经递质谷氨酸（Glu 0.5mM/L）或抑制性递质γ-aminobutyric acid（GABA 0.5M/L）以改变靶点神经元兴奋性的方法，检测Mn2+能否反映脑区的活动变化。另外，我们随机选取实验动物，分别在注射Mn2+ 3小时、5小时和8小时后对三组大鼠（n=5）进行10％福尔马林灌流，并且通过观察大鼠眶额叶脑区Mn2+强度的变化来研究最佳的灌流时间。我们的实验结果表明，Mn2++Glu组的右侧脑区/左侧脑区的Mn2+亮度比Mn2+空白对照组增加了20％（p=0.016, student t-test, *p <0.05），也远大于Mn2++GABA组（p=0.047, *p<0.05）。结果表明，当神经元被兴奋的时候，较多的Mn2+可以通过Ca2+通道进入兴奋的神经元内，使得Mn2+的成像亮度增加。由于Mn2+成像亮度的增加可以反映神经元的兴奋活动，因此可以显示出靶点区的脑活动。另外，在研究灌流时间对Mn2+亮度影响的实验中发现，注射Mn2+ 5小时后灌流得到的信噪比分别比注射Mn2+3小时（p＝0.055）和8小时（p=0.004，*p<0.05）高出24％和32％。总之，我们采用微量注射Mn2+（80mM/L,200nl）后5小时用10%福尔马林心脏灌流的方法获得了较好的结果。另外在试验中我们首先观测了大鼠吗啡戒断后的行为学指标和检测大鼠戒断后条件化位置偏好的程度。实验结果表明大鼠可以建立非常明显的条件化位置偏好，但在湿狗抖等行为学指标上无明显症状。这说明大鼠对于吗啡(10mg/kg, 一天两次，持续12天)形成了明显的心理依赖而无明显的生理依赖。此外，MEMRI的结果表明，在吗啡给药的第1天和第6天，大鼠眶额叶的Mn2+强度与空白对照组相比有显著的降低( one-way ANOVA, Post Hoc Dunnett’s C Tests), F (6,28)=7.242, P<0.001)；而在戒断第3天又恢复到正常水平，在戒断第5天和第7天Mn2+强度跟空白对照组相比没有显著性差别(one-way ANOVA, *p<0.05)。脑电（EEG）的结果表明，急性吗啡诱导的gamma波段的EEG显著降低(Two-way ANOVA, F(1,10)=13.626,p=0.006)。然而在戒断第1天gamma波段的EEG与空白对照组相比是增加的。在戒断第3天和戒断第5天，gamma波段的EEG与空白对照组相比也有显著性增强。以上研究结果表明：大鼠眶额叶脑区的动态变化与整个吗啡给药和戒断过程是密切相关的；此外，MEMRI在探讨药物滥用以及成瘾等机制上有很大的应用前景。

3D 异金属Bi(III)-Pr(III)配位聚合物的合成、晶体结构和热稳定性

在水溶液中合成了双金属配位聚合物({[(NO3)(H2O)3Pr(μ4-Hedta)Bi-(NO3)2].2H2O}2)n,并通过元素分析、红外光谱和X射线单晶衍射等手段进行了表征.该配合物为单斜晶系,P2(1)/n空间群,a=1.26831(18)nm,b=0.82189(12)nm,c=2.3755(3)nm,β=105.055(2)°,R=0.0429,V=2.3913(6)nm3,Z=4.Bi(Ⅲ)-Pr(Ⅲ)间通过配阴离子Hedta3-中4个羧基的桥联作用构建配合物的3D结构.TG-DSC结果表明,该配合物热分解经历脱水、配体分解以及盐分解过程,残余物为Bi-Pr-O的三元复合氧化物.

Naphthyl and thionaphthyl end-capped oligothiophenes as organic semiconductors: Effect of chain length and end-capping groups

Two series of oligothiophenes (OThs), NaTn and TNTn (n = 2-6 represents the number of thiophene rings), end-capped with naphthyl and thionaphthyl units have been synthesized by means of Stille coupling. Their thermal properties, optical properties, single crystal structures, and organic field-effect transistor performance have been characterized. All oligomers display great thermal stability and crystallinity. ne crystallographic structures of NaT2, NaT3, TNT2, and TNT3 have been determined. The crystals of NaT2 and NaT3 are monoclinic with space group P2(1)/C, while those of TNT2 and TNT3 are triclinic and orthorhombic with space groups P-1(-) and P2(1)2(1)2(1), respectively. All oligomers adopt the well-known herringbone packing-mode in crystals with packing parameters dependent on the structure of the end-capping units and the number of thiophene rings. The shorter intermolecular distance in NaT3 compared to NaT2 indicates that the intermolecular interaction principally increases with increasing molecular length. X-ray diffraction and atomic force microscopy (AFM) characterization indicate that the NaTn oligomers can form films with better morphology and high molecular order than TNTn oligomers with the same number of thiophene rings. The NaTn oligomers exhibit mobilities that are much higher than those for TNTn oligomers (0.028-0.39 cm(2) V-1 s(-1) versus 0.010-0.055 cm(2) V-1 s(-1), respectively).

Hydrothermal synthesis and structural characterization of a novel P-V-O layered compound [H(2)en](2)[H3O](6)[Co(H2O)(2)(VO)(8)(OH)(4)(PO4)8]

A new compound [H(2)en](2)[H3O](6)[Co(H2O)(2)(VO)(8)(OH)(4)(PO4)(8)] has been hydrothermally synthesized. Single crystal X-ray analysis indicates that this compound crystallizes in a monoclinic system, space group P2(1)/n with a=1.438 5(3) nm, b=1.012 2(2) nm, c=1.832 5(4) nm, beta=90.21degrees, V=2.668 2 (9) nm(3), Z = 2, D-c = 2.112 g/cm(3), R = 0.055, wR = 0.149 7, S = 1.037. The structure of [H(2)en](2)[H3O](6)[Co(H2O)(2)(VO)(8)(OH)(4)(PO4)(8)] is characterized by P-V-O layers constructed by [(VO)4 (OH)(2)(PO4)(4)](6-) non-symmetric units. The P-V-O layers are pillared by [Co(H2O)(2)](2+) group, resulting in the channels within which the protonated diaminoethane and H3O+ are located.

水合二高碘酸氢合铜(Ⅲ)酸钾钠配合物的合成、结构与光谱性质

本文报道了碱溶液中获得组份为Na_4K[Cu(HIO_6)_2]·12H_2O晶体配合物.用X-射线衍射法测定了晶体结构.晶体属单斜晶系,P2_1/c空间群,a=6.108(2)(?),b=25.055(10)(?),c=14.716(7)(?),β=97.77(3)°,V=2231(2)(?)~3,D_c=2.555g/cm~3,Z=4.晶体中二个畸变的IO_5(OH)八面体与中心铜原子螯合,构成CuO_4平面;Cu—O平均键长为1.83(?);加上CuO_4平面上侧与铜原子形成弱配位的氧原子;共有五个氧原子与铜原子构成近似为C_(2v)点群对称的四方单锥多面体.在碱性水溶液中,配合物的紫外吸收峰的衰减表明,[Cu(HIO_6)_2]~(5-)还原为一级反应.

Gastroprotective potential of Buddleja scordioides Kunth: Effects into the modulation of antioxidant enzymes and inflammation markers in an in vivo model

Ethnopharmacological relevance: A common plant used to treat several gastric disorders is Buddleja scordioides Kunth,commonly known as salvilla. Aim of thes tudy: To detect inflammatory markers,in order to evaluate the gastroprotective potential of salvilla infusions,as this could have beneficial impact on the population exposed to gastric ulcers and colitis. Materials and methods: The present work attempted infusions were prepared with B. scordioides (1% w/w) lyophilized and stored.Total phenolic content and GC–MS analysis were performed. Wistar rats were divided into five groups a negative vehicle control,an indomethacin group,and three experimental groups,named preventive,curative,and suppressive. All rats were sacrificed under deep ether anesthesia(6h)after the last oral administration of indomethacin/infusion.The rat stomachs were promptly excised,weighed,and chilled in ice-cold and 0.9%NaCl.Histological analysis,nitrites quantification and immunodetection assays were done. Results: B.scordioides infusions markedly reduced the visible hemorrhagic lesions induced byindomethacin in rat stomachs,also showed down-regulation of COX2, IL-8 and TNFα and up-regulation of COX-1with a moderate down-regulation of NFkB and lower amount of nitrites.However,this behavior was dependent on the treatment,showing most down-regulation of COX-2,TNFα and IL-8 in the curative treatment;more down-regulation of NF-kB in the preventive treatment;and more up-regulation of COX-1 for the suppressor and preventive treatments. Conclusion: The anti-inflammatory potential of B. scordioides infusions could be related with the presence of polyphenols as quercetin in the infusion and how this one is consumed.

A Network for Learning Kinematics with Application to Human Reaching Models

A model for self-organization of the coordinate transformations required for spatial reaching is presented. During a motor babbling phase, a mapping from spatial coordinate directions to joint motion directions is learned. After learning, the model is able to produce straight-line spatial velocity trajectories with characteristic bell-shaped spatial velocity profiles, as observed in human reaches. Simulation results are presented for transverse plane reaching using a two degree-of-freedom arm.

Comparative performance of multiview stereoscopic and mammographic display modalities for breast lesion detection.

PURPOSE: Mammography is known to be one of the most difficult radiographic exams to interpret. Mammography has important limitations, including the superposition of normal tissue that can obscure a mass, chance alignment of normal tissue to mimic a true lesion and the inability to derive volumetric information. It has been shown that stereomammography can overcome these deficiencies by showing that layers of normal tissue lay at different depths. If standard stereomammography (i.e., a single stereoscopic pair consisting of two projection images) can significantly improve lesion detection, how will multiview stereoscopy (MVS), where many projection images are used, compare to mammography? The aim of this study was to assess the relative performance of MVS compared to mammography for breast mass detection. METHODS: The MVS image sets consisted of the 25 raw projection images acquired over an arc of approximately 45 degrees using a Siemens prototype breast tomosynthesis system. The mammograms were acquired using a commercial Siemens FFDM system. The raw data were taken from both of these systems for 27 cases and realistic simulated mass lesions were added to duplicates of the 27 images at the same local contrast. The images with lesions (27 mammography and 27 MVS) and the images without lesions (27 mammography and 27 MVS) were then postprocessed to provide comparable and representative image appearance across the two modalities. All 108 image sets were shown to five full-time breast imaging radiologists in random order on a state-of-the-art stereoscopic display. The observers were asked to give a confidence rating for each image (0 for lesion definitely not present, 100 for lesion definitely present). The ratings were then compiled and processed using ROC and variance analysis. RESULTS: The mean AUC for the five observers was 0.614 +/- 0.055 for mammography and 0.778 +/- 0.052 for multiview stereoscopy. The difference of 0.164 +/- 0.065 was statistically significant with a p-value of 0.0148. CONCLUSIONS: The differences in the AUCs and the p-value suggest that multiview stereoscopy has a statistically significant advantage over mammography in the detection of simulated breast masses. This highlights the dominance of anatomical noise compared to quantum noise for breast mass detection. It also shows that significant lesion detection can be achieved with MVS without any of the artifacts associated with tomosynthesis.

A neural biomarker of psychological vulnerability to future life stress.

We all experience a host of common life stressors such as the death of a family member, medical illness, and financial uncertainty. While most of us are resilient to such stressors, continuing to function normally, for a subset of individuals, experiencing these stressors increases the likelihood of developing treatment-resistant, chronic psychological problems, including depression and anxiety. It is thus paramount to identify predictive markers of risk, particularly those reflecting fundamental biological processes that can be targets for intervention and prevention. Using data from a longitudinal study of 340 healthy young adults, we demonstrate that individual differences in threat-related amygdala reactivity predict psychological vulnerability to life stress occurring as much as 1 to 4 years later. These results highlight a readily assayed biomarker, threat-related amygdala reactivity, which predicts psychological vulnerability to commonly experienced stressors and represents a discrete target for intervention and prevention.

Ecological And Metabolic Studies On Free-Living Nematodes From An Estuarine Mud-Flat

Nematodes from a mud-flat in the river Lynher estuary, Cornwall, U.K., have a population density ranging between 8 and 9 × 106 m−2 in the winter months, corresponding to a dry weight of 1·4 and 1·6 g m−2. They reach a peak abundance of 22·86 × 106 m−2 (3·4 g) in May. About 40 species are present, and the species composition remained seasonally stable over the period of study. Analysis of age-structure suggests that the major species have continuous asynchronous reproduction. Respiration rates of 16 species have been determined at 20 °C using Cartesian diver respirometry. For five species, respiration/body size regressions were obtained in the form log10R = log10a+b log10V, where R = respiration in nl O2 ind−1 h−1 and V = body volume in nl: Mesotheristus setosus (log10a = −0·04,b = 0·74), Sphaerolaimus hirsutus (log10a = 0·11, b = 0·68), Axonolaimus paraspinosus (log10a = 0·00, b = 0·79), Metachromadora vivipara (log10a = −0·59, b = 1·07), Praeacanthonchus punctatus (log10a = 0·00, b = 0·55). For the remaining 11 species, several animals were used in each diver and, by assuming b = 0·75, log10a′ values were calculated: Viscosia viscosa (log10a′ = 0·188), Innocuonema tentabundum (−0·012), Ptycholaimellus ponticus (−0·081), Odontophora setosa (−0·092), Sphaerolaimus balticus (−0·112), Dichromadora cephalata (−0·133), Atrochromadora microlaima (−0·142), Cylindrotheristus normandicus (−0·150), Terschellingialongicaudata (−0·170), Sabatieria pulchra (−0·197), Terschellingia communis (−0·277). These values are compared with recalculated values for other species from the literature. Annual respiration of the nematode community is 28·01 O2 m−2, equivalent to 11·2 g carbon metabolised. Community respiration is compared with figures from N. American saltmarshes. At 20 °C, a respiration of about 61 O2 m−2 year−1 g−1 wet weight of nematodes appears to be typical. Annual production is estimated to be 6·6 g C m−2. The correlation between feeding-group, body-size, habitat and the repiration rate of individual species is discussed.

Relationship between biomedical catheter surface properties and lubricity as determined using textural analysis and multiple regression analysis

In this study, the surface properties of and work required to remove 12 commercially available and developmental catheters from a model biological medium (agar), a measure of catheter lubricity, were characterised and the relationships between these properties were examined using multiple regression and correlation analysis. The work required for removal of catheter sections (7 cm) from a model biological medium (1% w/w agar) were examined using tensile analysis. The water wettability of the catheters were characterised using dynamic contact angle analysis, whereas surface roughness was determined using atomic force microscopy. Significant differences in the ease of removal were observed between the various catheters, with the silicone-based materials generally exhibiting the greatest ease of removal. Similarly, the catheters exhibited a range of advancing and receding contact angles that were dependent on the chemical nature of each catheter. Finally, whilst the microrugosities of the various catheters differed, no specific relationship to the chemical nature of the biomaterial was apparent. Using multiple regression analysis, the relationship between ease of removal, receding contact angle and surface roughness was defined as: Work done (N mm) 17.18 + 0.055 Rugosity (nm)-0.52 Receding contact angle (degrees) (r = 0.49). Interestingly, whilst the relationship between ease of removal and surface roughness was significant (r = 0.48, p = 0.0005), in which catheter lubricity increased as the surface roughness decreased, this was not the case with the relationship between ease of removal and receding contact angle (r = -0.18, p > 0.05). This study has therefore uniquely defined the contributions of each of these surface properties to catheter lubricity. Accordingly, in the design of urethral catheters. it is recommended that due consideration should be directed towards biomaterial surface roughness to ensure maximal ease of catheter removal. Furthermore, using the method described in this study, differences in the lubricity of the various catheters were observed that may be apparent in their clinical use. (C) 2003 Elsevier Ltd. All rights reserved.

Non-agrocultural co-peratives and economy transformation in Cuba: politic processes and strategies

Contribution of co-operatives has been demonstrated since the 1970s as the main development line in agricultural production in Cuba. In contrast, there has been a late recognition of urban co-operatives, even if the need of transformations based on the realization of property in different territorial scenarios had been identified. The article analyses the reform processes launched since the first decade of the 21st century focusing on the nature of the initiatives fostering formation and promotion of nonagricultural co-operatives including follow up of their performance. The potential and limitations of the recent experiences are examined in order to reflect on the organizational processes and transformations from the point of view of their members. To conclude, some questions are posed about whether these co-operatives are capable of avoiding the impact of earlier employment circumstances and of developing strategies aimed at reinforcing voluntary membership and autonomy on which they are founded.