The crystal-like anatomical uniformity of the striate cortex

The visual field is topographically mapped onto the primary visual cortex (V1), forming a retinotopic map which is far more detailed for the foveal regions than for the periphery. We found that receptive field (RF) size in monkey V1 increases with eccentricity, and that a 1—2 m² V1 region contains roughly a complete set of machinery necessary to analyze a visual-field area whose size is about that of the RFs of the cells. This allows V1 to be anatomically uniform, and is in sharp contrast with the retina.     

Elaboration and Properties of Nanocomposite Structures Based on Crown Modified Platinum Nanoparticles

1 Results This paper presents the development of platinum nanocomposites structures based on organically modified c.a.2 nm core platinum nanoparticles.The chemical modification of the 4-mercaptoaniline functionalized particles by various in coming molecules is evidenced and precisely quantified.The particles can be dissolved like molecules in various solvents depending on the features of the new crown and X-rays shows that the interparticle distance is affected by the crown modification.These platinum n...     

浅谈新型墙体材料——煤矸石空心砖

煤矸石空心砖是一种新型环保墙体材料，符合国家及山西省出台的限制生产和使用实心黏土砖，鼓励发展新型建筑材料的政策。利用煤矸石制造的空心砖可以作为保温材料，既可节约建筑能耗，又可节约土地资源，减少环境污染。煤矸石空心砖同黏土实心砖相比，具有高强、轻质、隔音、隔热、保温、防震等优点，市场前景良好。     

Timed bromocriptine administration reduces body fat stores in obese subjects and hyperglycemia in type II diabetics.

Obese postmenopausal female volunteers were given timed daily oral dosages of bromocriptine, and tested for reduction of body fat stores. This dopamine agonist has been shown to reset circadian rhythms that are altered in obese animals and to reduce body fat levels in several animal models. The participants were instructed not to alter their existing exercise and eating behavior during treatment. Skinfold measurements were taken on 33 subjects as indices of body fat. The measurements (e.g., suprailiac) were reduced after six weeks by about 25%, which represents a reduction of 11.7% of the total body fat. These dramatic decreases in body fat, which are equivalent to that produced by severe caloric restriction, were accompanied by more modest reductions of body weight (2.5%), indicating a possible conservation of protein that is usually lost as a consequence of such caloric restriction. The effects of bromocriptine treatment on body fat and hyperglycemia were also examined in non-insulin dependent diabetics being treated with oral hypoglycemics (7 subjects) or insulin (7 subjects). Total body fat was reduced by 10.7% and 5.1% in diabetics on oral hypoglycemics and insulin, respectively, without any significant reductions in body weight. Hyperglycemia was reduced in most of the 15 diabetic subjects treated leading to euglycemia and even cessation of hypoglycemic drugs in 3 of the 7 subjects during 4-8 weeks of bromocriptine treatment. These findings support the hypothesis that obesity and type II diabetes may be treated effectively with bromocriptine when administered at the proper times and dosages.     

Quantal transmitter secretion from myocytes loaded with acetylcholine.

It is well known that transmitter secretion requires specialized secretory organelles, the synaptic vesicles, for the packaging, storage and exocytotic release of the transmitter. Here we report that when acetylcholine (ACh) is loaded into an isolated Xenopus myocyte, there is spontaneous quantal release of ACh from the myocyte which results in activation of its own surface ACh channels and the appearance of membrane currents resembling miniature endplate currents. This myocyte secretion probably reflects Ca(2+)-regulated exocytosis of ACh-filled cytoplasmic compartments. Furthermore, step depolarization of the myocyte membrane triggers evoked ACh release from the myocyte with a weak excitation-secretion coupling. These findings suggest that quantal transmitter secretion does not require secretory pathways unique to neurons and that the essence of presynaptic differentiation may reside in the provision of transmitter supply and modification of the preexisting secretion pathway.     

国际发展趋势下实验力学的未来作用

考察了分析结构、结构构件以及技术系统中的位移、应变与应力的测量和实验方法在目前和未来的作用。现在,比以往任何时候都更有理由和有更广阔的领域需要用到实验力学方法;许多先进、现代化技术,新型测量设备,测量和赋值过程自动化系统可供使用;以先进的测量技术和计算机技术相结合而形成的各种杂交法已被提出来。利用这些方法,可以优化结构和产品,节约能源和原材料,提高产品质量,增强结构、技术系统的可靠、安全性,控制生产过程以及监督操作系统的安全性;利用这些方法,能够并且应当使技术系统可能发生的危险以及对环境的毁损降至最低程度。     

Clustering of voltage-dependent sodium channels on axons depends on Schwann cell contact.

In myelinated nerves, segregation of voltage-dependent sodium channels to nodes of Ranvier is crucial for saltatory conduction along axons. As sodium channels associate and colocalize with ankyrin at nodes of Ranvier, one possibility is that sodium channels are recruited and immobilized at axonal sites which are specified by the subaxolemmal cytoskeleton, independent of glial cell contact. Alternatively, segregation of channels at distinct sites along the axon may depend on glial cell contact. To resolve this question, we have examined the distribution of sodium channels, ankyrin and spectrin in myelination-competent cocultures of sensory neurons and Schwann cells by immunofluorescence, using sodium channel-, ankyrin- and spectrin-specific antibodies. In the absence of Schwann cells, sodium channels, ankyrin and spectrin are homogeneously distributed on sensory axons. When Schwann cells are introduced into these cultures, the distribution of sodium channels dramatically changes so that channel clusters on axons are abundant, but ankyrin and spectrin remain homogeneously distributed. Addition of latex beads or Schwann cell membranes does not induce channel clustering. Our results suggest that segregation of sodium channels on axons is highly dependent on interactions with active Schwann cells and that continuing axon-glial interactions are necessary to organize and maintain channel distribution during differentiation of myelinated axons.     

A ground‐level ozone forecasting model for Santiago,Chile

A physically based model for ground‐level ozone forecasting is evaluated for Santiago, Chile. The model predicts the daily peak ozone concentration, with the daily rise of air temperature as input variable; weekends and rainy days appear as interventions. This model was used to analyse historical data, using the Linear Transfer Function/Finite Impulse Response (LTF/FIR) formalism; the Simultaneous Transfer Function (STF) method was used to analyse several monitoring stations together. Model evaluation showed a good forecasting performance across stations—for low and high ozone impacts—with power of detection (POD) values between 70 and 100%, Heidke's Skill Scores between 40% and 70% and low false alarm rates (FAR). The model consistently outperforms a pure persistence forecast. Model performance was not sensitive to different implementation options. The model performance degrades for two‐ and three‐days ahead forecast, but is still acceptable for the purpose of developing an environmental warning system at Santiago. Copyright © 2002 John Wiley & Sons, Ltd.     

Mechanism for the learning deficits in a mouse model of neurofibromatosis type 1.

Neurofibromatosis type I (NF1) is one of the most common single-gene disorders that causes learning deficits in humans. Mice carrying a heterozygous null mutation of the Nfl gene (Nfl(+/-) show important features of the learning deficits associated with NF1 (ref. 2). Although neurofibromin has several known properties and functions, including Ras GTPase-activating protein activity, adenylyl cyclase modulation and microtubule binding, it is unclear which of these are essential for learning in mice and humans. Here we show that the learning deficits of Nf1(+/-) mice can be rescued by genetic and pharmacological manipulations that decrease Ras function. We also show that the Nf1(+/-) mice have increased GABA (gamma-amino butyric acid)-mediated inhibition and specific deficits in long-term potentiation, both of which can be reversed by decreasing Ras function. Our results indicate that the learning deficits associated with NF1 may be caused by excessive Ras activity, which leads to impairments in long-term potentiation caused by increased GABA-mediated inhibition. Our findings have implications for the development of treatments for learning deficits associated with NF1.     

新型全固态铁离子敏感电极研究

采用稀土电极材料六硼化镧制备了一种新的全固态铁离子敏感电极。研究了该敏感电极在常见介质中对Ｆｅ３＋的响应行为。结果表明，该铁离子敏感电极在１．５ｍｏｌ／ＬＨ３ＰＯ４介质中的线性响应范围、检测下限和响应斜率分别为１．０×１０－５～１．０×１０－１ｍｏｌ／ＬＦｅ３＋，６．０×１０－６ｍｏｌ／ＬＦｅ３＋和６０ｍＶ／ｐＣ，且具有较好的选择性。