Creating low-impedance tetrodes by electroplating with additives

A tetrode is a bundle of four microwires that can record from multiple neurons simultaneously in the brain of a freely moving animal. Tetrodes are usually electroplated to reduce impedances from 2-3 MΩ to 200-500 kΩ (measured at 1 kHz), which increases the signal-to-noise ratio and allows for the recording of small amplitude signals. Tetrodes with even lower impedances could improve neural recordings but cannot be made using standard electroplating methods without shorting. We were able to electroplate tetrodes to 30-70 kΩ by adding polyethylene glycol (PEG) or multi-walled carbon nanotube (MWCNT) solutions to a commercial gold-plating solution. The MWCNTs and PEG acted as inhibitors in the electroplating process and created large-surface-area, low-impedance coatings on the tetrode tips.     

毛里求斯水电可持续发展的整体优化

虽然毛里求斯的水电蕴藏量已得到充分开发,但从满足高峰用电需求,增加蓄水、居民生活用水及其他用途的供水方面看,还要进一步提高水资源利用效率。分析认为,该国能源领域具有良好的发展前景,优化水电利用可以实现可持续发展的最终目标。     

认识中国的十大误区

所谓“误区”，大略是美国国内最流行的一些关于中国的印象。成立于1973年的传统基金会，是美国最大、影响力最强的保守派公共政策研究机构之一。其在美国的世界政策制定中拥有举足轻重的作用。比如，美国的战区导弹防御计划就是由该机构提出的。     

钨和钼的杂多化合物及其应用

本文介绍了钨和钼的杂多化合物的合成、结构、性质以及杂多化合物在固体化学、化学工业、临床化学和医学等方面的应用．     

解非线性有限元问题的组合弧长法

用有限元法解非线性力学问题时有效的解法显得很重要。本文介绍伴有线性搜索和各种牛顿型步骤的组合弧长法。此法可用于描述具有极值点的载荷——位移曲线,同时改善解的性能。在本文里,首先回顾一下早期的工作,然后介绍组合弧长法。此法已插入一个非线性壳结构分析程序中,涉及几何与材料非线性壳结构分析例题结果表明,组合弧长法值得推荐。     

Natural organic matter affects arsenic speciation and sorption onto hematite

Arsenic mobility in natural environments is controlled primarily by sorption onto metal oxide surfaces, and the extent of this sorption may be influenced strongly by the presence of other dissolved substances that interact with surfaces or with arsenic itself. Natural organic matter (NOM), a prevalent constituent of natural waters, is highly reactive toward both metals and surfaces and is thus a clear candidate to influence arsenic mobility. The objectives of this study were therefore to reveal the influences of diverse NOM samples on the sorption of arsenic onto hematite, a model metal oxide, as well as to reveal influences of arsenic on the sorption of NOM, using conditions and concentrations relevant to natural freshwater environments. Of the six NOM samples tested, four formed aqueous complexes with arsenate and arsenite. The extent of complexation varied with the NOM origin and, in particular, increased with the cationic metal (primarily Fe) content of the NOM sample. In addition, every NOM sample showed active redox behavior toward arsenic species, indicating that NOM may greatly influence redox as well as complexation speciation of arsenic in freshwater environments. When NOM and As were incubated together with hematite, NOM dramatically delayed the attainment of sorption equilibrium and diminished the extent of sorption of both arsenate and arsenite. Consistent with this result, when NOM and As were introduced sequentially, all NOM samples displaced sorbed arsenate and arsenite from hematite surfaces, and arsenic species similarly displaced sorbed NOM from hematite in significant quantities. Competition between NOM and As for sorption thus appears to be a potentially important process in natural waters, suggesting that NOM may play a greater role in arsenic mobility than previously recognized. In addition, in all sorption experiments, arsenite was consistently desorbed or prevented from sorbing to a greater extent than arsenate, indicating that interactions with NOM may also partially explain the generally greater mobility of arsenite in natural environments.     

Physiological and production responses to feeding schedule in lactating dairy cows exposed to short-term,moderate heat stress

The objective of this research was to characterize the production responses of lactating dairy cows during and after short-term, moderate heat exposure, and to determine whether evening (p.m.) feeding would alleviate the associated production losses. In a two-period, cross-over design, eight mature lactating cows were fed a total mixed ration at either 0830 or 2030 h. Each 15-d period consisted of a 5-d thermoneutral phase, a 5-d heat stress phase and a 5-d thermoneutral recovery phase. Mean daily vaginal temperature and respiration rate increased by 0.6 +/- 0.04 degrees C and 27 +/- 1.3 breaths/min, respectively, during short-term heat exposure. Daily dry matter intake, milk yield and solids-not-fat were depressed by 1.4 +/- 0.13 kg, 1.7 +/- 0.32 kg and 0.07 +/- 0.023%, respectively, during heat exposure. During the recovery phase, dry matter intake remained depressed, milk protein declined by 0.05 +/- 0.020%, and daily milk yield exhibited a further decline of 1.2 +/- 0.32 kg. Time of feeding had no effect on vaginal temperature, respiration rate, dry matter intake, water intake, milk yield, fat-corrected milk, protein percent, solids-non-fat percent or somatic cell count during heat exposure or during the recovery period that followed. Fat percent was, however, significantly lower in p.m.-fed animals. These data indicate that short-term, moderate heat stress, which occurs during the spring and summer months in Canada and the Northern United States, will significantly decrease production in the lactating cow. Shifting from morning to evening feeding did not alleviate production losses associated with this type of heat stress.     

SPIFI: a direct-detection imaging spectrometer for submillimeter wavelengths

The South Pole Imaging Fabry-Perot Interferometer (SPIFI) is the first instrument of its kind-a direct-detection imaging spectrometer for astronomy in the submillimeter band. SPIFI's focal plane is a square array of 25 silicon bolometers cooled to 60 mK; the spectrometer consists of two cryogenic scanning Fabry-Perot interferometers in series with a 60-mK bandpass filter. The instrument operates in the short submillimeter windows (350 and 450 microm) available from the ground, with spectral resolving power selectable between 500 and 10,000. At present, SPIFI's sensitivity is within a factor of 1.5-3 of the photon background limit, comparable with the best heterodyne spectrometers. The instrument's large bandwidth and mapping capability provide substantial advantages for specific astrophysical projects, including deep extragalactic observations. We present the motivation for and design of SPIFI and its operational characteristics on the telescope.