The effect of colloidal solution of molybdenum nanoparticles on the microbial composition in rhizosphere of Cicer arietinum L.

The use of colloidal solutions of metals as micronutrients enhances plant resistance to unfavorable environmental conditions and ensures high yields of food crops due to the active penetration of nanoelements into the plant cells.Microbiological examination of rhizosphere soil have revealed that combined use of colloidal solution of nanoparticles of molybdenum (CSNM, 8 mg/l), and microbial preparation for pre-sowing inoculation of chickpea seeds stimulates the development of ‘agronomically valuable’ microflora. It was shown that combined seed treatment with colloidal solution of Mo nanoparticles with microbial preparation have stimulated nodule formation per plant by four times compared to controls. Single treatment with CSNM increased the number of nodules by two times, while the treatment of microbial preparation have not significantly affected the number of nodules per plant.

PACS

Colloids, 82.70.Dd; Ecology, 87.23.-n     

Dependence of the efficiency of Raman scattering in silicon nanowire arrays on the excitation wavelength

The features of Raman scattering in layers of silicon nanowires from 50 to 350 nm in diameter, obtained by the chemical etching of crystalline silicon (c-Si) wafers with preliminarily deposited silver nanoparticles in fluoric acid solutions are studied. c-Si wafers with various crystallographic orientations and doping levels are used, which is conditioned by the different sizes and degrees of ordering of the formed nanostructures. It is found that the radiation of the Raman scattering of samples is depolarized, and its efficiency depends strongly on the excitation wavelength. Upon excitation by light with a wavelength of 1064 nm, the ratio of Raman-scattering intensities of silicon nanowire samples and c-Si is 2 to 5; as the wavelength decreases, this ratio increases for structures with larger silicon-nanowire diameters and higher degrees of ordering and decreases for less ordered structures. The results obtained are explained by the effect of partial light localization in silicon nanowire arrays.     

Microbial O2- and H2O2-electrode sensors for alcohol assays based on the use of permeabilized mutant yeast cells as the sensitive bioelements

Two types of alcohol-specific microbial/electrochemical biosensors have been developed using specially constructed mutant cells of the methylotrophic yeast Hansenula polymorpha. The cells were immobilized in a calcium alginate gel, and placed between two membranes on the surface of oxygen or hydrogen peroxide-electrodes. The O2 electrode based biosensor contained mutant cells with strongly elevated alcohol oxidase activity. The peroxide electrode based biosensor consisted of catalase-defective mutant cells which produce hydrogen peroxide in the presence of alcohol. Both types of mutant cells were used in permeabilized form in order to release some components of the cellular respiration system, thus increasing the selectivity of the cellular respiration response to alcohol (cell/O2-biosensor) Permeabilization also increased sensitivity of the signal and shortened the response time (cell/H2O2-biosensor). Cell/O2 biosensors were linear up to 1.2 mM for ethanol and 0.35 mM for methanol, cell/H2O2 biosensors were linear up to 4.0 mM for ethanol, and 1.2 mM for methanol. Results were reproducible, sample pretreatment was not required, and the sensors exhibited good operational and storage stability. The use of sucrose, dulcitol or inositol during the preparation of the sensors resulted in increased stability of cells during their liophilization and storage in the dried state. Both biosensors had similar selectivity towards alcohols in the order of methanol (100%), ethanol (21%), and formaldehyde (12%). No signal was observed with glucose or glycerol as substrates.     

A Novel Enzyme Biosensor Specific for Formaldehyde Based on pH-Sensitive Field Effect Transistors

An enzyme biosensor specific for formaldehyde has been developed using pH-sensitive field effect transistors (FET) as a transducer and alcohol oxidase (AOX) from Hansenula polymorpha as a sensitive element. The steady-state response time of the developed biosensor was 10–60 s. The linear dynamic range (in semi-logarithmic scale) of the sensor output signal corresponded to 10–300 mmol dm⁻³ formaldehyde concentration. The operational stability of the biosensor was not less than 7 h and the relative standard deviation approximately 1–3%. When stored at +4°C, the response was stable for more than 30 days. The biosensor demonstrated high specificity to formaldehyde with no potentiometric response to primary alcohols. The influence of buffer concentration and enzyme concentration in the biomembrane on the sensor signal was investigated. The specific biosensor could also be successfully used for highly selective, quantitative estimation of mercury ion in an aqueous solution. © 1997 SCI.     

Solubility limit and thermoelectric properties of bismuth-supersaturated tellurium

Charge carrier density in bismuth-doped tellurium has been studied as a function of the dopant concentration in order to determine the boundary of the second phase formation in the Bi-Te system. All bismuthdoped tellurium samples, in contrast to the initial undoped material, exhibit hole conductivity. The hole density significantly increases with the dopant content and reaches a maximum value (2.1 × 10¹⁸ cm^?3) at a bismuth concentration of 0.1 at. %, which corresponds to the limiting solubility. This conclusion fully agrees with the character of transformation of the temperature dependence of the thermo emf α of bismuth-doped tellurium, which shows a decrease in α for Y ^Bi > 0.1 at. % as a result of increasing contribution of the second phase (Bi₂Te₃) inclusions possessing electron conductivity.     

Hydrogas dynamics of metal refining in intermediate ladles

A three-dimensional model is proposed for the hydrogas-dynamic phenomena within the intermediate ladle of a continuous-casting machine. The results—the distribution of the current function and the velocity field—permit quantitative estimation of the increase in the transfer coefficient at the slag-metal boundary. These data may be used in intermediate-ladle design. By this means, the content of nonmetallic inclusions in continuous-cast billet may be significantly reduced.     

细菌和真菌蛋白酶在生皮脱毛中的应用研究

利用不同来源的微生物酶制剂(中俄两国)进行生皮脱毛试验与研究。对脱毛用微生物酶的来源及其各组成成分的作用,以及传统制革脱毛工艺与微生物酶制剂脱毛工艺显现的不同污染指数进行了详细的论述。结果表明,微生物酶制剂脱毛方法能够有效改善制革工艺,降低制革污染,提高成品革的品质,有利于制革者和皮革消费者的健康。