Перинатология. Настоящее и будущее

На основании обобщения многолетнего собственного опыта автора, данных литературы и результатов работы Московского центра планирования семьи и репродукции освещены актуальные проблемы перинатологии от пренатального периода до постнатальной охраны здоровья плода. Сделано заключение о необходимости и возможности создания стандартов в области лечебных мероприятий и тактики ведения родов при осложнениях.Basing on the generalization of many−year experience as well as the data of the literature and results of the work of Moscow Center for Family Planning and Reproduction, the author features the urgent issues of perinatology from prenatal period to postnatal health protection. The author concludes about the necessity and possibility to create the standards in the field of therapeutic measures and management tactics in complicated delivery

The influence of the mode of plasma generation on the plasma nitriding behaviour of a micoralloyed [i.e. microalloyed] steel

It is well understood that the introduction of nitrogen into metallic surfaces improves the mechanical properties of engineering components, such as hardness, wear and fatigue as well as the corrosion resistance. In addition to conventional techniques such as salt bath and gas nitriding there are currently several methods which utilise plasma environments for mass transfer, e.g. D C plasma nitriding, R F plasma nitriding and plasma immersionion implantation (PI3). It was the main aim of this investigation to study the plasma nitriding behaviour of a commercially available chromium bearing microalloyed steel, MAXIMA™ , in the hot rolled and air cooled condition. The ultimate goal was to assess the possibility of using it as an alternative to conventional quenched and tempered nitriding steels, such as En19(AISI 4140) which was used as a reference in this investigation. In order to identify themost suitable gas mixture for the nitriding of MAXIMA™ , a comprehensive investigation of DC plasma nitriding at 450°C was performed by varying the hydrogen concentration in the nitriding atmosphere and examining the structure and the properties of the surface layers. A detailed study of RF plasma nitriding and PI3 was undertaken using MAXIMA™ steel. In order to gain an insight into the influence of different modes of plasma generation on the formation of the hardened layer and the mass transfer mechanisms involved, a comparison was also made with DC plasma nitriding. All the experiments were conducted on MAXIMA™ steel for five hours at the temperatures of 350, 400,450, 500 and 550°C. Optical, scanning electron and atomic force microscopy, in conjunction with microhardness and surface roughness measurements were employed to characterise the nitrided surfaces. X-ray diffraction, both in normal and glancing angle configurations and glow discharge optical emission spectroscopy were also utilised to identify the phases that formed on the surface of nitrided specimens and the concentration profiles of different elements. It was found that DC plasma nitriding of MAXIMA™ at all temperatures developed cases with higher surface hardness and roughness, and a slightly thinner compound layer and diffusion zone than those obtained from Enl9 steel. A comparative study between PI3 and RF plasma nitriding revealed that the PI3 process produced surface layers with more favourable properties, such as higher hardnesses and thicker cases, than RF plasma nitriding. Unlike DC plasma nitriding, for the conditions employed no compound layer was formed on the surface of the samples treated by either PI3 or RF plasma nitriding. The best case, in terms of hardness and depth, was produced by PI3 at 350°C and by DC plasma nitriding at higher temperatures. At all temperatures, RF plasma nitriding produced the shallowest cases with the lowest hardnesses. It has been argued that the mode of plasma generation plays a critical role in nitrogen mass transfer. More specifically, the operating pressure and ion energy have been found to be the key parameters in determining the total nitrogen adsorption on the surface. In DC plasma nitriding mass transfer is primarily controlled by sputtering and re-deposition.The moderate ion energy in DC plasma nitriding causes sputtering of the cathodic surfaces. Sputtered species undergo collision with the nitrogen in the vicinity of the surface because of low mean free path for collision (few millimetres) which is a direct result of the relatively high operating pressure of a DC plasma. In stark contrast, in PI3 and RF plasma nitriding, the mean free path for collision of the ions and atoms is in the order of several centimetres because of low operating pressure, hence there will be no collisions near the sample and no re-deposition of sputtered material will take place. Owing to extremely high ion energies involved in PI3, ion implantation is the dominant mass transfer mechanism and sputtering of surface atoms is considerably lower than DC plasma nitriding. The lack of significantly energised ions in RF plasma nitriding eliminates the possibility of implantation and the main mass transfer mechanism is due to the adsorption of low energy neutral species which are incapable of inducing and sputtering

Graphene oxide nanoribbons and their applications in supercapacitors

We report the enhanced capacitance of the Multi-Walled Carbon NanoTubes (MWCNTs) after a chemical unzipping process in concentrated sulfuric acid (H2SO4) and potassium permanganate (KMnO4). The effects of the test duration and temperature were investigated on the unzipping process of the MWCNTs to synthesize the graphene oxide nanoribbons. The SEM and TEM studies were carried out on untreated and unzipped MWCNTs samples to investigate the cutting and unzipping of the MWCNTs. The results confirmed that the efficient tube unzipping with improved effective surface area was obtained from the 1h treatment at 60°C, at which most of the tubes were opened without any tube annihilation. The graphite plate deposited with the untreated and unzipped MWCNTs samples was investigated by electrochemical studies. Cyclic voltammetry studies showed that the MWCNTs after 1h unzipping at 60°C had better electrochemical behavior than the other samples. Galvanostatic charging/discharging measurements were carried out on the untreated and unzipped MWCNTs samples. A remarkable specific capacitance of 33 Fg-1 was obtained for the unzipped MWCNTs at a current density of 1 Ag-1 in 0.5 M KCl solution compared with 8 Fg-1 for pristine MWCNTs, again confirming the enhanced effective surface area and increased defect density in the tube surfaces after the unzipping process. These results make the unzipped MWCNTs a promising electrode material for all energy storage applications

Structure and tribological behavior of diamond-like carbon coatings deposited on the martensitic stainless steel: the influence of gas composition and temperature

The relationship between the tribological behavior and inherent features of the DLC coatings (i.e. structural and mechanical properties) as a consequence of deposition conditions was investigated. Hence, a plasma nitrocarburising process as pretreatment followed by Diamond-Like Carbon (DLC) deposition by pulsed DC Plasma Assisted Chemical Vapor Deposition (PACVD) method, was utilized. Although a remarkable reduction in the friction coefficient of coated samples was observed, almost the same friction coefficient was measured for the DLC coatings (i.e. 0.2), regardless of their diverse intrinsic properties. As the H/C ratio in feeding gas and temperature increased up to certain values, the hardness and elastic modulus increased while the wear rate decreased. Therefore, the DLC coating deposited with the highest Hydrogen fraction at 160 degrees C, exhibited the highest hardness and elastic modulus (i.e. 25.4 GPa and 177.4 GPa, respectively), as well as the lowest wear rate of 5.9 x 10(-6) mm(3)/N.m

Isotopic signatures and patterns of volatile compounds for discrimination of genuine lemon, genuine lime and adulterated lime juices

Isotopic signatures and patterns of volatile organic compounds (VOCs) are a useful set of markers for the authenticity assessment of fruit juices. In the present study, the carbon and nitrogen stable isotopes and VOCs fingerprinting of 16 genuine lemon and 16 genuine lime juices as well as 28 citric acid-adulterated lime juices were investigated to discriminate them and reveal the underlying mechanism for their differences. Samples were subjected to isotope ratio mass spectrometry (IRMS) and proton transfer reaction time of flight mass spectrometry (PTR-ToF-MS). Following δ13C and δ15N analysis, no significant difference between genuine lemon (δ13C: -24.50 ± 1.29; δ15N: 5.40 ± 2.06) and genuine lime juices (δ13C: -25.17 ± 0.7; δ15N: 5.30 ± 0.97) was observed due to the same photosynthetic pathway (C3 photosynthetic pathway) of lemon and lime trees. However, Adulterated lime juice samples had higher δ13C values (-14.99 ± 2.79) and lower δ15N (1.23 ± 2.36) values compared to the genuine lemon and genuine lime juices which could be related to the added exogenous commercially available citric acid manufactured by fermenting sugars that follow the C4 photosynthetic pathway. Besides, a positive correlation (r2 = 0.941) between citric acid to iso-citric acid ratios and δ13C values was found in the adulterated samples. No significant difference was observed in the total concentration of VOCs among the analyzed samples. However, for all samples, ions m/z 81 and 137 had the highest concentrations. Exploratory VOC pattern analysis by principal component analysis (PCA) and hierarchical cluster analysis (HCA) revealed the clustering of samples in different groups according to their nature. Besides, extremely adulterated samples were well distinguished from slightly adulterated samples following HCA analysis. The current study provided empirical evidence on the capability of IRMS and PTR-ToF-MS in the discrimination of lemon juice, lime juice, and adulterated lime juices. However, further investigation is required to confirm the promising results of this study