The electric field in porous materials calculated with the grainconsolidation model

We have used the grain consolidation model (GCM) to study the spatial variation of the electric field inside a porous medium such as oil impregnated cellulose. The calculations were primarily performed in order to determine the maximum electric field within the composite, which is important for the overall dielectric strength of the material. In the composite as a whole, the maximum field may be considerably higher than in a homogeneous medium under the same applied external field. The contacts between the solid particles in the composite material are more realistically described in the GCM than in effective-medium models, and a comparison shows that the GCM yields higher maximum fields than effective-medium theory. Two different 3-dimensional geometries have been used in the GCM calculations and the results indicate that the exact geometry is of minor importance. These models are isotropic, while many important insulation materials are highly anisotropic. In order to illustrate the effects of different geometries, we have also performed calculations on a 2-dimensional geometry. In this case, it appears as if the lack of contacts between the solid particles mainly influences the maximum field in the phase which has the highest complex conductivity. If the conductivities of both phases are almost equal, the maximum field is close to the applied field. Increasing the difference in conductivity between the oil and the solid increases the maximum electric field. We have also shown that the GCM can be used to estimate the electric field in the presence of interface effects     

中温燃料电池的新固体电解质LiNaSO4-Al2O3

本文讨论了三相复合陶瓷电解质材料的制备和研究，ＸＲＤ谱图表明了存在ＬｉＮａＳＯ４和γ－Ａｌ２Ｏ３相，５００℃时的电导率达到１０＾－２－１０＾－１Ｓ／ｃｍ在４９９℃出现六万到体心立方的相变，氧化铝使得样品在６００℃以上能保持良好的机械强度，并且提高了电导率，高温质子迁移数为０．９－１．０。     

Efficiency enhancement in dye sensitized solar cells based on PAN gel electrolyte with Pr4NI + MgI2 binary iodide salt mixture

The effect of using a binary iodide salt mixture in N719 dye-sensitized TiO₂ solar cells (DSSCs) is investigated. The cells use tetrapropylammonium iodide (Pr₄NI) and magnesium iodide (MgI₂) in a plasticized polyacrylonitrile gel in glass/FTO/nano-porous TiO₂/gel, I₂/Pt/FTO/glass solar cell structure. The salt composition in the gel electrolyte is varied to optimize the efficiency of DSSCs. The DSSCs with MgI₂ or Pr₄NI as the only iodide salt showed the efficiencies 2.56 and 4.16 %, respectively, under AM 1.5 (100 mW cm^?2) illumination while the DSSC with mixed cations with 18.4:81.6 MgI₂:Pr₄NI molar ratio shows the highest efficiency of 5.18 %. Thus the efficiency enhancement, relative to the high efficiency end member is about 25 %. DC polarization measurements establish the predominantly ionic behavior of the electrolytes, and show that the variation of efficiency with salt composition correlates with the change in short circuit photocurrent density (J _sc), which appears to be governed by the iodide ion conductivity. It is also found that J _sc correlates with the iodide ion transference number estimated from DC polarization data taken with non-blocking iodine electrodes. This study suggests that binary iodide mixtures may be used to obtain efficiency enhancement in different types of DSSCs based on polymeric, gel, or solvent electrolytes.     

Electrogenic ion transport along the human duodenum in childhood

BACKGROUND: To find reliable sites to study the effects of different secretagogues on electrogenic ion secretion, we investigated the secretion pattern in different parts of duodenum. METHODS: Histologically normal routine intestinal biopsy specimens from children were mounted in a modified Ussing chamber. The secretory responses to prostaglandin E2 (PGE2), aminophylline, dibutyryl cyclic adenosine 5'-monophosphate (cAMP), and acetylcholine (ACh) were studied with continuous measurements of the potential difference. Tissue resistance and generated current were calculated. RESULTS: ACh induced secretion in the whole of duodenum, although the secretory response was augmented distally. PGE2 and cAMP induced significant secretion only in the distal duodenum. CONCLUSIONS: The ACh-induced, calcium-mediated, electrogenic secretion was expressed along the whole duodenum, whereas the cAMP-mediated secretion was only seen in the distal part. The fully expressed electrogenic chloride secretion was only seen at or distal to the duodenojejunal flexure. Our study shows that it is important to carefully define the localization of physiologic studies performed in the duodenum.     

SDC–LiNa carbonate composite and nanocomposite electrolytes

Structural and A.C. impedance analyses were conducted for various ceria-based composite systems. Structural studies showed that the ceria–carbonate composites are two-phase materials, where carbonates were often amorphous. Two phases of ceria and carbonates are mixed at different particle size levels depending on the preparation techniques, especially, employing the NANOCOFC (nanocomposites for advanced fuel cell technology) approach to prepare ceria–LiNaCO₃ nanocomposites. General observations from structural analyses are that different preparation techniques resulted in two-phase composite particles in different particle sizes varying from micrometer level to nano-level accompanying also different homogeneity. General observations from impedance analyses are that for the nanocomposites (particle size at nano-scale) more complex grain boundary interface effects are observed compared to that for samples with grains of the micrometer level, but nanocomposites showed enhanced conductivities at the low temperatures. Interfaces and interfacial conduction mechanism can be concluded for such conductivity enhancement.     

Quasi solid state polymer electrolyte with binary iodide salts for photo-electrochemical solar cells

Quasi-solid-state polymer electrolytes can be used in dye sensitized solar cells (DSSCs) in order to overcome various problems associated with liquid electrolytes. Prior to fabricating commercially viable solar cells, the efficiency of quasi solid state DSSCs needs to be improved. Using electrolytes with a binary iodide mixture is a novel technique used to obtain such efficiency enhancement. In this work we report both conductivity and solar cell performance enhancements due to incorporation of a mixture containing LiI and tetrahexylammonium iodide in a quasi-solid-state electrolyte. The conductivity of the electrolyte increases with added amounts of LiI and thus the highest conductivity, 3.15 × 10⁻³ S cm⁻¹ at 25 °C, is obtained for the electrolyte 100 wt% LiI. The predominantly ionic behavior of the electrolytes was established from dc polarization measurements. The iodide ion conductivity, measured using iodine pellet electrodes decreased somewhat with increasing amount of LiI even though the overall conductivity increased. However, the highest efficiency was obtained for the DSSC containing a polymer electrolyte with Hex₄N⁺I^¯:LiI = 1:2 mass ratio. This cell had the largest short circuit current density of about 13 mA cm⁻² and more than 4% overall energy conversion efficiency. The results thus show that electrolytes with Hex₄N⁺I^¯/LiI mixed iodide system show better DSSC performance than single iodide systems.     

Symptoms, complaints, ocular and nasal physiological signs in university staff in relation to indoor environment - temperature and gender interactions

Symptoms, signs, perceptions, and objective measures were studied in university buildings. Two problem buildings with a history of dampness and complaints were compared with two control buildings. Health investigations among university staff were performed at the workplace (n = 173) including tear film stability [non-invasive break-up time (NIBUT) and self-reported break-up time (SBUT)], nasal patency (acoustic rhinometry), nasal lavage fluid analysis [NAL: eosinophil cationic protein (ECP), myeloperoxidase (MPO), lysozyme and albumin] and atopy by total serum IgE and IgE antibodies (Phadiatop). Exposure assessment included inspections, thermal and atmospheric climate at 56 points modelled for all work sites. Multiple regressions were applied, controlling for age and gender. Exposure differences between problem buildings and controls were small, and variations between rooms were greater. Workers in the problem buildings had more general and dermal symptoms, but not more objective signs than the others. Adjusted day NIBUT and SBUT increased at higher night air temperatures, with B (95% CI) 0.6 (0.04-1.2) and 1.3 (-0.02 to 2.5), respectively. Higher relative humidity at mean day air temperature <22.1 degrees C was associated with adjusted NIBUT and SBUT, with B (95% CI) 0.16 (0.03-0.29) and 0.37 (-0.01 to 0.75), respectively. Air velocity below recommended winter values and reduced relative humidity in the range of 15-30% were associated with dry air and too low temperature. PRACTICAL IMPLICATIONS: Thermal climate in university buildings may be associated with both perceptions and physiological signs. Reduced night time air temperature, increased difference in air temperature between day and night, and fast changes in air temperature might impair indoor environment. This may have implication for energy-saving policies. It might be difficult to identify the exposure behind, and find the reason why, some buildings are defined as 'problem buildings'.