OXYGEN LIMITATION IN MICROFLUIDIC BIOFUEL CELLS

Biofuel cells are devices that use biocatalysts (enzymes or microbes) to convert biochemical energy directly into electrical energy. Microfluidic biofuel cells exploit the lack of active mixing at microscale dimensions to eliminate the use of proton exchange membranes that separate anolyte and catholyte streams. Simulation of this system, by solving the governing 3-D conservation equations (flow, species transport), reveals that oxygen availability limits the performance of the cathode. An exponential decay in the availability of oxygen at the cathode is observed along the length of the microchannel, indicating that increasing the number of electrode pairs reduces the overall current density. This conclusion is consistent with experimental observations. Increasing electrolyte flow rates can reduce the mass transport limitations by decreasing the diffusion boundary-layer thickness, but disparity between the flow rates of the anolyte and catholyte can induce wastage of dissolved oxygen.     

N,7,7‐Tricyanoquinomethanimine (TCQMI) Based Organic Magnetic Materials

The synthesis and characterization of a new family of magnetic materials based on the electron accepting cyanocarbon N,7,7‐tricyanoquinomethanimine, TCQMI, its radical anion [TCQMI], and its σ‐dimer, σ‐[TCQMI]₂^2?, are reported. [Fe^IIICp*₂][TCQMI] (where Cp* is pentamethylcyclopentadienide) forms parallel chains of alternating [TCQMI]^?? and [FeCp*₂]^?+ and magnetically orders at 3.4 K as a weak ferromagnet. M[TCQMI]₂?zCH₂Cl₂ (M = V, Fe) are amorphous solids with [TCQMI]^?? coordinated to metal centers through the nitrile groups. The Fe compound magnetically orders as a weak ferromagnet at ≈4 K, whereas the V compound shows no evidence of magnetic ordering. {[Mn^IIITPP]⁺}₂[TCQMI]₂^2? (TPP = tetraphenylporphyrin) results from the reaction of TCQMI with Mn^IITPP(py) due to the formation of the [TCQMI]₂^2? σ‐dimer in situ, and is a weak ferromagnet below 3.7 K. The lack of magnetic ordering in V[TCQMI]₂?zCH₂Cl₂ is not currently understood, and is in strong contrast to V[TCNE]₂?zCH₂Cl₂, which magnetically orders above room temperature.     

Comparison of antioxidant activities and bioactive compounds between Bokbunja (Rubus coreanus Miq.) and other berries

The physicochemical properties and antioxidant properties of bokbunja, a Korean black raspberry, were clarified and compared with blueberry, cranberry, raspberry, and strawberry. The amount of soluble solids was significantly (p<0.05) lower in bokbunja than in other berries, whereas the pH of bokbunja was significantly (p<0.05) higher. Analysis of the total phenolic, flavonoid, and anthocyanin contents found that bokbunja had the highest, while the others were ranked in the order of raspberry>blueberry>cranberry>strawberry. The content of ellagic acid (147.3 mg/100 g of FW) also was highest in bokbunja. The antioxidant activities of bokbunja, assessed based on DPPH, ABTS, and ferric reducing antioxidant power (FRAP) assays, were higher than for other berries. Bokbunja is a healthier antioxidant source than other berries.     

电子束表面工程的技术发展水平（下）

四、第一代表面工程方法 １．固态淬火（硬化） 加热的各项工艺参数、材料的初始组织和机件的具体几何形状,都对材料的组织和性能、淬硬的深度和机件的表面质量有很大的影响。在我们的试验研究中,对各种不同的结构钢和工具钢以及某些铁进行了研究,采用的加热方式为将需要淬硬的整个表面同时加热等。对于退火状态的和整体淬硬的多,硬化度分别达到３．６～３．７和１．５～１．７。钢的硬度达到ＨＲＣ６５～６８,显微硬度为１０～１１ＧＰａ,硬化的深度为 １．５－２．０ｍｍ。 在各种钢中,会产生残余的压缩应力,还会形成细粒组织,并…     

Inhibition of lead solubilization during the leaching of gold and silver in ammoniacal thiosulfate solutions (effect of phosphate addition)

The chemistry of precious metal ammoniacal thiosulfate leaching is very complex, especially with additives, such as EDTA, which are used to stabilize the major reactants in this system. Lead, which is co-extracted in these solutions, can be a large consumer of both EDTA and thiosulfate, decreasing the leaching capacity for gold and silver. In this research, thermodynamic analyses for different compositions of the leaching solution are performed to determine their ability to extract lead, silver and gold. These are used to explain the leaching behavior observed for a sulfide concentrate and for a mineral, both with high silver and lead contents and the latter, with an elevated concentration of gold.     

提高力反馈速率陀螺动态特性的优化设计

陀螺带宽窄将影响系统的动态特性.本文采用比例-积分控制和迟后-超前网络相结合的校正方法,通过优化校正网络的参数、合理配置零极点、设计控制回路,使陀螺系统的带宽提高到150 Hz、输出噪声小于10 mV.并通过仿真验证了控制回路设计的合理性.     

Root caries in a sample of elderly persons

With the anticipated increase in the aged adult population and the associated gingival recession, the prevalence of root caries is expected to increase. The purpose of this study was to determine the experience and distribution of root caries in a group of aged adults living in Kayelitsha. All non-institutionalized elderly black adults participating in a community geriatric programme were examined. Root caries was recorded using visual and tactile criteria and expressed as the root caries index (RCI) rate. The mean age of the subjects was 65.2 years, the mean number of teeth present was 17.3 and the mean RCI rate was 2.2 per cent. All subjects had gingival recession while only 23.8 per cent had root caries. No surfaces with restored root caries lesions were found. In the maxilla the highest RCI rate was observed on the interproximal surfaces of the posterior teeth (4.4 per cent) but in the mandible the buccal surfaces of the posterior teeth had the highest RCI rate (4.2 per cent). In both the maxilla and the mandible the lingual surfaces of the anterior teeth showed no root caries. Maxillary teeth did not have a significantly higher root caries attack rate than mandibular teeth. Root caries does not appear to be a public health problem in the sampled population.     

Albuminuria and overall capillary permeability of albumin in acute altitude hypoxia

The mechanism of proteinuria at high altitude is unclear. Renal function and urinary excretion rate of albumin (Ualb) at rest and during submaximal exercise and transcapillary escape rate of 125I-labeled albumin (TERalb) were investigated in 12 normal volunteers at sea level and after rapid and passive ascent to 4,350 m. The calcium antagonist isradipine (5 mg/day; n = 6) or placebo (n = 6) was administered to abolish hypoxia-induced rises in blood pressure. Lithium clearance and urinary excretion of beta 2-microglobulin were used to evaluate renal tubular function. High altitude increased Ualb from 2.8 to > 5.0 micrograms/min in both groups (P < 0.05). In the placebo group, high altitude significantly increased filtration fraction (P < 0.05), but this response was abolished by isradipine. Lithium clearance and urinary excretion of beta 2-microglobulin remained unchanged by hypoxia in both groups. Exercise did not reveal any further renal dysfunction. In both groups, high altitude increased TERalb from 4.8 to > 6.7%/h (P < 0.05). In conclusion, acute altitude hypoxia increases Ualb despite unchanged tubular function and independent of effects of isradipine on filtration fraction. The elevated TERalb suggests an overall increase in capillary permeability, including the glomerular endothelium, as the critical factor in high-altitude induced albuminuria.     

Development of the enhanced neural response to NaCl in Fischer 344 rats

Duplications of the esophagus or stomach alone are infrequent, and complete foregut duplication has only rarely been described. Most combined esophagogastric duplications present within the first year of life, and if communication with the normal alimentary tract does occur, it does so only either above or below the diaphragm. This report illustrates a case of continuous duplication of the esophagus and stomach with communication to the normal alimentary tract at both proximal and distal ends. Operative management and a review of the literature and embryology are described.