EVALUATION OF BIOGENIC AMINES FORMATION BY PROTEOLYTIC ENTEROCOCCI STRAINS ISOLATED FROM RAW DROMEDARY MILKS FROM SOUTHERN ALGERIA

Twenty-three strains of lactic acid enterococci isolated from dromedary raw milks in Southern Algeria were investigated for their proteolytic activity and ability to produce biogenic amines by decarboxylating amino acids: histidine, tyrosine and ornithine. All strains tested displayed proteolytic activities, but none of them were able to produce detectable biogenic amines in the usual adequate laboratory media, namely, Joosten and Northolt medium and Leuschner medium. Polymerase chain reaction experiments indicate a positive correlation between the absence of the hdc and odc genes and the lack of histamine and putrescine production for all tested strains. By contrast, all strains appeared to possess tdc gene, but no correlation was found with a negative expression of tyrosine decarboxylase.

PRACTICAL APPLICATIONS

In foods, biogenic amines are mainly generated by decarboxylation of the corresponding amino acids through substrate-specific enzymes of the microorganisms present in this environment, particularly histidine, tyrosine, lysine, ornithine and arginine, and the capability of enterococci and some other lactic acid bacteria to produce biogenic amines has been described. For this purpose, several qualitative and quantitative methods to determine biogenic amines production by these microorganisms have been developed. There is great interest to identify and to characterize the bacteria strains intended for an industrial use and to verify if they are potentially able to produce biogenic amines in order to prevent it's synthesis and limit the poisoning risk.     

Power-efficient smooth-start devices in alternating-current engines

A nonstandard approach is considered to constructing smooth-start devices in asynchronous engines that allows one to improve the quality of the starting current and to decrease or even reduce to zero the additional consumption of reactive network power. Moreover, the use of thyristor rectifiers on the voltage improves.     

Improving the reliability of electric drives of exhausters of the oxygen-converter process

This paper deals with increasing the reliability of electric drives of exhausters of the oxygen-converter process. The dependences of the reliability parameters in the electrical converter–electric motor system on the power reserve were obtained. The costs for the installed equipment were taken as an optimization criterion. It is noted that improving the reliability of an electric drive is possible both by increasing the overall power of the power unit and by changing the number of phases. It is shown that the reliability of the system can be improved in a synchronous electric drive with pulse-vector control at the reservation of a semiconductor converter. A mathematical model of the electrical converter–reluctance motor with a field-regulated machine complex is proposed. The results of the mathematical modeling of the synchronous electric drive with pulse-vector control are considered. The dependence of the specific electric parameters on the number of phases is determined.     

A traction electric drive for electric cars

It is advisable to use a controlled electric drive in electric drives of electric off-road vehicles due to its significant multiplicity of the supported torque (5: 1 and higher) in a low-power mode. Such overloads can be achieved, for example, in electric drives with a field-regulated reluctance machine, not only because of the capacity of the electric machines, but also due to the choice of the drive control system. Analysis of requirements for the electric drive of an electric vehicle is performed, and the influence of the control method on the specific parameters is considered. Analysis of the number of independent control actions in synchronous reluctance electric drives is provided. The possibility of increasing the overload multiplicity of the torque by abandoning the vector control in favor of structures similar to dc drive systems is shown.     

The Effect of a Nanosize TiO<Subscript> <Emphasis Type="Italic">x</Emphasis> </Subscript> Layer on the Performance of an Organic Solar Cell

This work studies the role of a cathodic TiO_x buffer layer in operation of a photovoltaic organic solar cell (OSC) based on a photoactive layer with a bulk heterojunction. Using a liquid solution to obtain a TiO_x layer is of current interest for simplification of process technologies of successive formation of OSC layers. It is found that the optimum thickness of the TiO_x layer is 10 nm; at this thickness, the efficiency of the OSC reaches the value of 4.36%. The effect of air oxygen on the OSC samples is studied and it is found that samples with a TiO_x buffer layer undergo degradation to a lesser extent as compared to the samples with no such layer. The effect of oxygen on operation of the photovoltaic device is discussed.     

Investigation of 12 – 15 Kev Electron Transmission Through Tapered Glass Capillaries

Glass and Ceramics - The results of experimental studies of the transmission of 12 and 15 keV electron beams through tapered glass macro-capillaries are presented. Measurements showed that there is...     

Correlation of Vibroacoustic Signal with Ceramic Component Wear During Frictional Interaction with a Steel Disc

Refractories and Industrial Ceramics - Complete correlation between dimensions of the wear area on specimens made of oxide-carbide ceramics and the root-mean-square value of vibration acceleration...     

Catalytic Sulfation of Betulin with Sulfamic Acid: Experiment and DFT Calculation

Betulin is an important triterpenoid substance isolated from birch bark, which, together with its sulfates, exhibits important bioactive properties. We report on a newly developed method of betulin sulfation with sulfamic acid in pyridine in the presence of an Amberlyst^®15 solid acid catalyst. It has been shown that this catalyst remains stable when being repeatedly (up to four cycles) used and ensures obtaining of sulfated betulin with a sulfur content of ~10%. The introduction of the sulfate group into the betulin molecule has been proven by Fourier-transform infrared, ultraviolet-visible, and nuclear magnetic resonance spectroscopy. The Fourier-transform infrared (FTIR) spectra contain absorption bands at 1249 and 835–841 cm⁻¹; in the UV spectra, the peak intensity decreases; and, in the nuclear magnetic resonance (NMR) spectra, of betulin disulfate, carbons С3 and С28 are completely shifted to the weak-field region (to 88.21 and 67.32 ppm, respectively) with respect to betulin. Using the potentiometric titration method, the product of acidity constants K₁ and K₂ of a solution of the betulin disulfate H⁺ form has been found to be 3.86 × 10^–6 ± 0.004. It has been demonstrated by the thermal analysis that betulin and the betulin disulfate sodium salt are stable at temperatures of up to 240 and 220 °C, respectively. The density functional theory method has been used to obtain data on the most stable conformations, molecular electrostatic potential, frontier molecular orbitals, and mulliken atomic charges of betulin and betulin disulfate and to calculate the spectral characteristics of initial and sulfated betulin, which agree well with the experimental data.     

Effect of Continuous Extrusion Parameters on Alloy M1 Round Section Bar Microstructure and Mechanical Property Formation

Metallurgist - Results are provided for microstructural evolution and mechanical property formation in a deformation zone during continuous extrusion, and the effect of extrusion rate parameters on...     

Malfunctioning of Microcontroller Irradiated with Ultrashort Ultrabroadband Pulse Trains

Effect of the number of ultrashort ultrabroadband pulses with a repetition rate of 1 kHz on malfunctioning of microcontroller in radio transparent housing is studied when the device is irradiated using pulse trains at a pulse duration of about 10^–10 s and radiation frequencies ranging from 1 to 30 GHz. The radiation is received by internal conducting stripes that connect the electronic circuit and external outputs. The malfunction probability is determined by the number of pulses in the pulse train, pulse number, and electric field strength. It is shown that malfunctioning is predominantly caused by the leading pulses in the pulse train.