Photogalvanic cells

An analysis of photogalvanic cells is carried out and applied to a specific system, iron-thionine, with only slight simplifications. The criteria for successful cell design are given and discussed. It is concluded that many formidable obstacles to practical application exist. The principal difficulties are the following: (1) Diffusion to the electrodes and reaction there must be sufficiently rapid to make bulk back reactions unimportant. (2) A means for keeping at least one active species from reaching one electrode must be found. (3) A sufficient range of the solar spectrum must be exploited without increasing the rate of photon absorption to the point where bulk back reaction becomes important. These problems are discussed in some detail and quantitative criteria are presented in terms of absorbed photon flux, cell size parameters, chemical rate constants, exchange current densities, overvoltages and diffusion coefficients.     

Modification of diaphragm-type chlor-alkali cells to ion exchange membrane cells

Ion exchange membrane cell technology, recently developed for producing chlorine and caustic soda, has been applied to the modification of existing diaphragm cells into special IEM cells, termed the MBC^®, which offer a higher energy (electricity and steam) efficiency and a higher product quality than those of diaphragm cells with only a small amount of additional modification cost.     

Modelling microbial fuel cells with suspended cells and added electron transfer mediator

Derivation of a mathematical model for microbial fuel cells (MFC) with suspended biomass and added electron-transfer mediator is described. The model is based on mass balances for several dissolved chemical species such as substrate, oxidized mediator and reduced mediator. Biological, chemical and electrochemical reactions can occur in the bulk liquid and at the electrode surface, respectively. Model outputs include time-dependent production of current and electrical charge, current–voltage and current–power curves, and the evolution of concentrations of chemical species. The model behaviour is illustrated using a test case based on detailed experimental observations reported in the literature for a microbial fuel cell operated in batch mode and repeatedly fed with a single substrate. A detailed model parameter estimation procedure is presented. The model simulates the current–time evolution and voltage–current curves in the MFC with glucose as anode substrate and the ferrocyanide/ferricyanide redox couple as the oxidation reaction at the cathode. Simulations show the effect of different parameters (electrical resistance, mass transfer resistance, exchange current, coulombic yields and biomass, substrate and mediator concentrations) on the MFC characteristics. The model explains how the endogenous metabolism or intracellular substrate storage could lead to a non-zero background current even when the added substrate has been depleted. Different trends (increasing or decreasing) in the initial current are explained by the initial oxidation state of the mediator (oxidized or reduced, respectively). The model has potential applications for other bioelectrochemical systems.     

Liver parenchymal cells differ from the fat-storing cells in their lipid composition

The neutral lipid and phospholipid compositions of purified sinusoidal (fat-storing, endothelial and Kupffer) cells, parenchymal cells and liver homogenates were determined by thin layer chromatography. In addition, the retinoid content of the same purified cell populations was determined by high performance liquid chromatography. From each cell type, both a lipid droplet fraction and a pellet fraction (containing the majority of the remaining cell organelles) were prepared by differential centrifugation. Electron microscopic analysis showed that lipid droplets isolated from fat-storing cells were larger (up to 8 μm) than those isolated from parenchymal cells (up to 2.5 μm). Moreover, the parenchymal lipid droplets seemed to be surrounded by a membranous structure, while the fat-storing lipid droplets seemed not to be. Both fat-storing and parenchymal cells contained high concentrations of neutral lipids, 57.9 μg and 71.0 μg/10⁶ cells, respectively, while endothelial and Kupffer cells contained only 8.6 μg and 13.8 μg/10⁶ cells of neutral lipids, respectively. Sixty-five percent of fat-storing cell lipid droplet fractions comprised esters of retinol and cholesterol. This combined ester fraction contained mainly retinyl esters. In addition, considerable quantities (20%) of triglycerides were present. Parenchymal cell lipid droplet fractions comprised triglycerides (62%) and cholesteryl esters (up to 30%). The pellet fractions prepared from all four cell types consisted mainly of cholesterol (41–67%) and free fatt acids (20–28%). The phospholipid content was much higher in parenchymal cells than in the sinusoidal liver cell types. The relative proportions of the four major phospholipid classes were comparable in all liver cell types analyzed. It is concluded that parenchymal cell lipid droplets comprised mainly triglycerides and cholesteryl esters, which is in agreement with the function of parenchymal cells in lipid metabolism. Fat-storing cell lipid droplets consisted of retinyl esters and triglycerides, which correlates well with their function in retionid storage and metabolism.     

Electrochemical impedance spectra of solid-oxide fuel cells and polymer membrane fuel cells

Electrochemical impedance spectroscopy (EIS) is a very useful method for the characterization of fuel cells. The anode and cathode transfer functions have been determined independently without a reference electrode using symmetric gas supply of hydrogen or oxygen on both electrodes of the fuel cell at open circuit potential (OCP). EIS are given for both polymer electrolyte fuel cells (PEFC) and solid oxide fuel cells (SOFC) at current densities up to 0.76 A cm⁻² (PEFC) and 0.22 A cm⁻² (SOFC). With increasing current density the PEFC-impedance decreases significantly in the low frequency range reaching a minimum at 0.4 A cm⁻². At even higher current densities an increasing contribution of water diffusion is observed: the cell impedance increases again. From EIS of SOFC a finite diffusion behavior is observed even at OCP, depending on water partial pressure of the anodic gas supply. This additional element reflects the influence of water partial pressure on the cell potential. The simulation of the measured EIS with an equivalent circuit enables the calculation of the individual voltage losses in the fuel cell.     

Reconsidering differential aeration cells

The differential aeration cells are responsible in practice for multiple corrosion forms. The established tension gradients between the cathodic and anodic areas are quite reduced, and consequently both electrodes stay submitted also to corrosion phenomena due to local-action cells. By analysing the theoretical current-potential curves it is shown that differential aeration cells are not responsible for an increase of the electrode corrosion in the oxygen-starved electrolyte in the absence of secondary effects.Differential aeration cells developed on normal carbon steel were investigated in H₂CO₃/HCO₃⁻/CO₃²⁻ solutions of different pH values. The results from polarization data and immersion corrosion tests of coupling indicated have shown the following: (1) the electrode in the aerated zone, for each one of the chosen pH, tends to attain the same potential of the electrode in the deaerated zone; (2) an alkalization of the electrolyte in the aerated and deaerated zones for initial pH 5 and 7.5 in the system; (3) the current density that cross the macrocell is little, of the same order for all pH, and does not justify the observed corrosion rate in both electrodes; (4) there is a polarity inversion of the electrodes for the pH 5 and 7.5; (4) the observed corrosion rate in each one of the tested solutions was practically the same for the aerated and deaerated electrodes. An explanation for this behaviour is given.     

Cupric oxalate-magnesium seawater cells

Cells with cupric oxalate cathodes bonded with polystyrene and magnesium alloy AZ61 anodes were discharged at room temperature. The cathode current efficiency was approximately 75% to a 0.8 V cut-off at an apparent current density of 10 mA cm^–2. Cells with sulphur-cupric oxalate cathodes showed discharge performance at higher voltages with higher efficiences than those without sulphur. The use of different oxalate samples appeared to result in no significant difference in performance. The samples were either obtained commercially or prepared by precipitation. The cathodic behaviour of cupric oxalate was also investigated by potential sweep voltammetry with a slow sweep rate. In sodium chloride solutions a double peak was obtained on the voltammogram. When the stoichiometric quantity of sulphur was added to the cupric oxalate active material, it gave a main and two smaller peaks. The possible reactions are discussed.     

Upconversion in solar cells

The possibility to tune chemical and physical properties in nanosized materials has a strong impact on a variety of technologies, including photovoltaics. One of the prominent research areas of nanomaterials for photovoltaics involves spectral conversion. Modification of the spectrum requires down- and/or upconversion or downshifting of the spectrum, meaning that the energy of photons is modified to either lower (down) or higher (up) energy. Nanostructures such as quantum dots, luminescent dye molecules, and lanthanide-doped glasses are capable of absorbing photons at a certain wavelength and emitting photons at a different (shorter or longer) wavelength. We will discuss upconversion by lanthanide compounds in various host materials and will further demonstrate upconversion to work for thin-film silicon solar cells.     

Semitransparent polymer solar cells

Bulk heterojunction based polymer:fullerene solar cells have attracted intensive research interest both in academic and industrial communities in the last two decades, mainly related to their potential low‐cost production process. A power conversion efficiency of over 10% has been reported recently, making the commercialization of this clean and cheap solar energy convertor a realistic prospect for the near future. The intrinsic features of semitransparency and color tunability of the thin polymeric photoactive films are the greatest asset for polymer solar cells. Recently, aesthetic semitransparent polymer solar cells (ST‐PSCs) that can be integrated into transparent windows, roofs, glass and other semitransparent architectural elements have received much attention. In this perspective paper, we present the progress in achieving high performance ST‐PSCs, discuss the requirements for transparent electrodes, focusing on alternatives to tin‐doped indium oxide, and address the challenges ahead to make ST‐PSC viable for real applications. © 2013 Society of Chemical Industry     

Non aqueous lithium cells

Recent developments of lithium organic and inorganic electrolyte batteries are reviewed and discussed. Particular attention is dedicated to the role of anode passivation phenomena in the performance of both primary and secondary lithium cells.     

Feeding PEM fuel cells

This paper discusses the laws of the fuel consumption in a polymer electrolyte fuel cell and its related performance. Based on simplifying but realistic approximations these laws are presented in analytical form. We verify these laws with space resolved current-voltage measurements in a single channel fuel cell. The results give a clear picture of the inside-the-cell distribution of performance associated with reactant consumption. This picture helps to rationalize the modes of optimal fuelling and is lessening for design of the flow-fields.     

人胎盘来源的造血干细胞和间充质干细胞的分离及鉴定

目的建立人胎盘来源的造血干细胞(placenta hematopoietic stem cells,hP-HSCs)和间充质干细胞(placentaderived mesenchymal stem cells,hP-MSCs)的分离方法,并进行鉴定和组分分析。方法选取10份新生健康婴儿胎盘组织,采用机械破碎法联合磁珠分选法分离h P-HSCs,胎盘绒毛膜组织块贴壁法分离hP-MSCs,利用形态学观察、集落培养、流式细胞术等进行鉴定。结果 hP-HSCs:分离后有核细胞数(total nucleated cell number,TNC)为(11. 82±2. 46)×10~8个,TNC回收率≥80%;细胞活性为(99. 7±0. 3)%;细胞表面抗体CD34~+CD45dim表达率为(8. 69±0. 36)%,CD34~+总数为(108. 0±6. 48)×10~6个;集落形成总数为(1. 88±1. 07)×10~6。hP-MSCs:冻存细胞总数为(40. 78±9. 35)×10~7个;细胞活性为(99. 0±1. 5)%;细胞表面抗体CD34~+CD45~+表达率为(0. 1±0. 1)%,CD44~+CD105~+为(99. 6±0. 2)%,CD14~+CD19~+为(0. 1±0. 1)%,CD90~+CD73+为(98. 9±0. 2)%;且具有良好成脂、成骨分化潜能。结论成功建立了hP-HSCs和hP-MSCs体外分离培养方法,为胎盘的临床应用奠定了基础,并提供了细胞种子资源。     

不同尿细胞诱导多能干细胞效率的比较

目的比较不同来源及不同批次尿细胞诱导多功能干细胞的效率。方法收集夜尿样本25份及非夜尿样本81份(其中31份来自男性,50份来自女性),采用非整合、无血清、无饲养层细胞、无致癌基因c-MYC的重编程法诱导获得诱导多能干细胞(induced pluripotent stem cells,i PSCs)。经碱性磷酸酶(alkaline phosphatase,AP)染色估算尿细胞重编程效率。结果夜尿与非夜尿中尿细胞分离的成功率分别为8%和44%,差异有统计学意义(P0.05);同一来源不同批次尿细胞间及不同尿液来源尿细胞间的重编程效率的差异均有统计学意义(P0.05)。结论夜尿不适宜作为收集尿细胞的来源。不同的尿细胞会影响重编程的效率,本实验为提高诱导效率的研究奠定了基础。