ACu9X4 ‐ Neue Verbindungen mit der CeNi8, 5Si4, 5‐Struktur (A: Sr,Ba; X: Si,Ge)

ACu₉X₄ ‐ New Compounds with CeNi_{8, 5}Si_{4, 5} Structure (A: Sr, Ba; X: Si, Ge) The new compounds SrCu₉Si₄ (a = 8.146(1), c = 11.629(2)Å), BaCu₉Si₄ (a = 8.198(2), c = 11.735(2)Å), SrCu₉Ge₄ (a = 8.273(2), c = 11.909(5)Å), and BaCu₉Ge₄ (a = 8.338(4), c = 12.011(7)Å) are formed by reaction of the elements at 1000° ‐ 1100 °C. They are isotypic (I4/mcm, Z = 4) and crystallize in an ordered variant of the cubic NaZn₁₃ type structure, also built up by the binary phase BaCu₁₃. In the ternary compounds the positions of Cu2 are orderly occupied by copper and silicon and germanium, respectively. This results in a lowering of symmetry and a distortion of the polyhedra. The metallic conductivity of the compounds was confirmed by measurements on BaCu₉Si₄.     

Effect of polarization on the electrode behavior and microstructure of (La,Sr)MnO<Subscript>3</Subscript> electrodes of solid oxide fuel cells

The electrode behavior and microstructure of freshly prepared (La_0.8Sr_0.2)_0.9MnO₃ (LSM) electrodes were investigated under various polarization conditions. The original, large agglomerates in freshly prepared LSM electrodes were broken down into sphere-shaped grains when exposed to cathodic or anodic current passage of 200 mA cm^–2 at 800 °C in air for 3 h. Microstructural changes under cathodic polarization could be related to the pronounced diffusion and migration of oxygen vacancies and Mn ions on the LSM surface and lattice expansion, while lattice shrinkage under oxidation conditions most likely contributes to the structural changes under anodic polarization. Such morphological changes were irreversible and were found to be beneficial to the performance of freshly prepared LSM electrodes. Freshly prepared LSM electrodes behaved very differently with respect to the cathodic and anodic current passage treatment.     

Biofuel cell anode based on the Gluconobacter oxydans bacteria cells and 2,6-dichlorophenolindophenol as an electron transport mediator

A basic scheme of the use of the Gluconobacter oxydans bacteria cells as a biocatalyst at an anode of a biofuel cell with air-based cathode is raised up. The anode and cathode of the cell are made of graphite; 2,6-dichlorophenolindophenol serves as an electron transport mediator; and glucose is the substrate to be oxidized. The open-circuit voltage is 55 mV, for the bacteria cell, the mediator, and glucose concentrations of 3 mg/ml (raw weight), 34 mM, and 10 mM, respectively. The voltage and current of the biofuel cell loaded with an external resistance of 10 kohm are 5.6 mV and 0.56 mA. The cell’s internal resistance is 88 kohm.     

A Procedure for Transforming Impedance Spectra for the Determination of Mechanism of Electrochemical Reactions

Transformation of impedance spectra into relaxation time spectra (RTS) is used for determining contributions of individual processes of the oxygen electroreduction reaction (OER) to the polarization resistance of the electrochemical cell. The transformation technique involves the solution of the convolution equation found with the aid of a modified Van Cittert iteration algorithm checked on model impedance spectra. The technique, when used to analyze impedance spectra of electrochemical cells air|Pt|YSZ|YSZ + Pt|air, shows that the conversion of a globular structure of the YSZ + Pt cermet layer to a columnar one is accompanied by a change of peak amplitudes in RTS. The revealed RTS dynamics when heated to 750°C is compared with peculiarities of individual processes in OER.     

Production of α-keto acids Part I. Immobilized cells ofTrigonopsis variabilis containing D-amino acid oxidase

Whole cells ofTrigonopsis variabilis were immobilized by entrapment in Ca²⁺-alginate and used for the production of α-keto acids from the corresponding D-amino acids. The D-amino acid oxidase within the immobilized cells has a broad substrate specificity. Hydrogen peroxide formed in the enzymatic reaction was efficiently hydrolyzed by manganese oxide co-immobilized with the cells. The amino acid oxidase activity was assayed with a new method based on reversed-phase HPLC. Oxygen requirements, bead size, concentration of cells in the beads, flow rate, and other factors were investigated in a “ trickle-bed ” reactor.     

Artificial red cells with crosslinked hemoglobin membranes

Artificial cells containing concentrated hemoglobin (Hb) solution were prepared by interfacial polymerization of Hb with glutaraldehyde (GA) in liquid membrane capsules (LMC). A solution containing 30% of Hb was emulsified in mineral oil as red cell-size microdroplets, and this emulsion was dispersed in an aqueous phase containing glutaraldehyde to form LMC. The LMC were semipermeable templates that held the microdroplets of Hb in suspension while GA diffused through the oil to the microdroplet surfaces. The GA crosslinked Hb at the surface of each microdroplet to form an artificial red-cell membrane encapsulating Hb solution. A water-soluble surfactant was used to eject the cells from the LMC and suspend them in saline. Several surfactants were evaluated. Cell size was controlled by agitation speed during preparation of the original emulsion. Cells of 2.52 = ±1.69 μm were prepared. The encapsulated Hb retained capacity to bind and release O₂. The cells had aP ₅₀ of 8.9 torr (1200 Pa) and a capacity of 0.55 cc O₂/g of total Hb, indicating that the crosslinked portion of the Hb did not contribute to O₂ transport.     

Toward a new generation of therapeutics

Scientific evidence in the prevention and treatment of various disorders is accumulating regarding probiotics. The health benefits supported by adequate clinical data include increased resistance to infectious disease, decreased duration of diarrhea, management of inflammatory bowel disease, reduction of serum cholesterol, prevention of allergy, modulation of cytokine gene expression, and suppression of carcinogen production. Recent ventures in metabolic engineering and heterologous protein expression have enhanced the enzymatic and immunomodulatory effects of probiotics and, with time, may allow more active intervention among critical care patients. In addition, a number of approaches are currently being explored, including the physical and chemical protection of cells, to increase probiotic viability and its health benefits. Traditional immobilization of probiotics in gel matrices, most notably calcium alginate and κ-carrageenan, has frequently been employed, with noted improvements in viability during freezing and storage. Conflicting reports exist, however, on the protection offered by immobilization from harsh physiologic environments. An alternative approach, microencapsulation in “artificial cells,” builds on immobilization technologies by combining enhanced mechanical stability of the capsule membrane with improved mass transport, increased cell loading, and greater control of parameters. This review summarizes the current clinical status of probiotics, examines the promises and challenges of current immobilization technologies, and presents the concept of artificial cells for effective delivery of therapeutic bacterial cells.     

不同分子量N-琥珀酰壳聚糖的制备及其与K562肿瘤细胞间亲和性的初步探讨

用化学降解法制备不同分子量的壳聚糖 ,以其为原料合成了系列N 琥珀酰壳聚糖 ,然后用异硫氰酸荧光素进行荧光标记 ,再与K5 6 2肿瘤细胞共孵育 ,通过流式细胞仪检测细胞的荧光强度来确定不同分子量N 琥珀酰壳聚糖与K5 6 2肿瘤细胞间亲和性的强弱 ,为靶向抗肿瘤药物载体的研究提供初步的参考 .结果表明N 琥珀酰壳聚糖和K5 6 2肿瘤细胞间有较强的亲和性 ,随着分子量的增加 ,其亲和性逐渐减弱 .     

Microcalorimetric investigation of influence of cancerogenic and anticancerogenic compounds on nuclear chromatin of tumor cells

The influence of mitoxantron (M) and benz(a)pyrene (BP) on chromatin DNA in composition of spleen and liver tissues and cells of BALB/c mice were studied using a high-sensitive differential scanning microcalorimeter. It was established that BP can cause a) the specific breaks in inactive chromatin DNA chain and unfolding of the whole domain (a loop of chromatin) which should lead to uncontrolled genome activation; b) the breaks in the DNA double-helix creating short duplexes.M at low doses, interacting with naked linker DNA of tumor restores the chromatin structure, at high doses or at repeated injections,M causes the disturbance of chromatin structure.