Категорія двоїни і становлення морфологічної норми української мови

У статті простежено вплив граматичної категорії двоїни на становлення морфологічної норми сучасної української літературної мови.The research presents an analysis of grammatical category of plural number with pair meaning. The main trends of morphological norm in literary Ukrainian have been generalised

Cross-linked polyimide membranes

The present invention relates to a process for cross-linking a membrane comprising a polyimide, wherein the polyimide is cross-linked with a cross-linking agent comprising two or more isocyanate groups. The present invention also relates to a membrane obtainable by this process and to the use of the membrane in a separation process. The present invention also relates to a process for separating a dissolved component having a molecular weight of about 100 to about10000 Dalton from a solution, said process comprising: (a) contacting the solution with the membrane, and (b) isolating or concentrating the component

Crosslinked polyimide membrane

The present invention relates to a process for cross-linking a membrane comprising a polyimide, wherein the polyimide is cross-linked with a cross-linking agent comprising two or more isocyanate groups. The present invention also relates to a membrane obtainable by this process and to the use of the membrane in a separation process. The present invention also relates to a process for separating a dissolved component having a molecular weight of about 100 to about10000 Dalton from a solution, said process comprising: (a) contacting the solution with the membrane, and (b) isolating or concentrating the component

Facile method of building hydroxyapatite 3D scaffolds assembled from porous hollow fibers enabling nutrient delivery

Nowadays, diffusion through scaffold and tissue usually limits transport, and forms potentially hypoxic regions. Several methods are used for preparation of 3D hydroxyapatite scaffolds, however, production of a scaffold including porous hollow fibers for nutrition delivery is difficult and expensive. In this study, we describe an easy and inexpensive method to create 3D hydroxyapatite structure containing porous hollow fibers via microtemplating. The fibers which are assembled into 3D scaffold and sintered, contain asymmetric membrane walls with flux suitable for nutrient delivery. These hollow fibers have good mesenchymal stem cell adhesion showing that the presented method has no negative influence on cell cytocompatibility. The proposed straightforward method for building 3D structures containing porous hollow fibers for nutritions can be suitable for in vitro bioreactors studies as well as for production tissue engineered or in vivo prepared bone graft

"Chemistry in a spinneret" to fabricate hollow fibers for organic solvent filtration

Organic solvent filtration (OSF) is a very efficient separation technique with high potential in many branches of industry. Currently the choice of the commercial membranes is limited only to a few flat sheet membranes and spiral wound modules. It is generally known that a membrane in hollow fiber form has several advantages, over a flat configuration, such as high surface to volume ratio and no need of spacers. Consequently more compact and simpler modules and easy to scale up can be built.\ud \ud In this work we explore a new technique called “chemistry in a spinneret”, to fabricate a hollow fiber (HF) for OSF. This technique combines the membrane formation and crosslinking reaction into a single step process. P84 polyimide was chosen as a membrane forming polymer and poly(ethylene imine) (PEI), dissolved in the bore liquid, as a crosslinking agent. In order to obtain a membrane with the best stability and low membrane MWCO, the composition of the bore liquid was systematically varied, including solvent/non-solvent ratio and PEI concentration.\ud \ud The crosslinked membranes have MWCO in the range of 2500–3500 g mol−1 and toluene permeance in the range of 0.2–1.1 l m−2 h−1 bar−1. The most stable crosslinked membrane maintains 80% of its mass after 11 days immersion in N-methyl-2-pyrrolidinone. Due to crosslinking, the HFs become more hydrophilic and therefore attractive for separations in alcohol systems. Preliminary results are in fact presented here using an ethanol/polyethylene glycol model system\u

Important factors influencing molecular weight cut-off determination of membranes in organic solvents

In solvent resistant nanofiltration (SRNF), sensible selection of a membrane for a particular solvent/solute system is recognized as challenging. Prospective methods for suitability analysis of membranes include molecular weight cut off (MWCO) characterization. However, insufficient understanding of the interrelated effects of solvent, solute, membrane properties, and the applied process conditions often complicates interpretation of MWCO data. This study demonstrates and discusses such effects with respect to transport mechanism. To this end very different SRNF systems have been selected: a rigid porous membrane (hydrophobized zirconia) versus a rubbery dense membrane (polydimethylsiloxane); a low flux solvent (toluene) versus high flux solvent (n-hexane); and a stiff solute (polystyrene) versus a flexible solute (polyisobutylene). The results indicate that, for the applied conditions, the MWCO of the dense membrane is predominantly affected by solute–membrane and solvent–membrane interactions. For the rigid porous membrane a significant effect of applied pressure is observed, in particular for the flexible solute. The non-linear relation between flux and pressure and the variations in MWCO with pressure indicate combined effects of concentration polarization and shear induced deformation of the flexible solute. The results unmistakably show that the interpretation of MWCO is heavily dependent on the system under stud

Composite capillary membrane for solvent resistant nanofiltration

Solvent resistant nanofiltration (SRNF) is a membrane separation process allowing for an efficient separation of small molecules of 200–1000 g mol−1 from organic solvents. The application of SRNF in industry applications is currently hindered by a limited choice of SRNF membranes and configurations. Despite clear advantages of capillary membranes (high surface to volume ratio, no spacers required and therefore more compact and simpler modules can be built), commercial SRNF membranes are almost exclusively produced in a spiral wound form. In this work, we prepare and study SRNF composite capillary membranes made of an α-alumina support and a selective poly (dimethylsiloxane) (PDMS) top layer. We combine the advantages of a ceramic support such as high mechanical, thermal and chemical stability with very good separation properties of the PDMS coating. All composite membranes are systematically investigated including: permeation experiments (permeance/molecular weight cut-off, MWCO) using a high pressure set-up and study of morphology using SEM imaging. The prepared composite capillary membranes are stable for at least 40 h in toluene and have MWCO of 500 Da

Predictors of the Onset of Cigarette Smoking: A Systematic Review of Longitudinal Population-Based Studies in Youth

CONTEXT: The onset of cigarette smoking typically occurs during childhood or early adolescence. Nicotine dependence symptoms can manifest soon after onset, contributing to sustained, long-term smoking. Previous reviews have not clarified the determinants of onset. EVIDENCE ACQUISITION: In 2015, a systematic review of the literature in PubMed and EMBASE was undertaken to identify peer-reviewed prospective longitudinal studies published between January 1984 and August 2015 that investigated predictors of cigarette smoking onset among youth aged \u3c 18 years who had never smoked. EVIDENCE SYNTHESIS: Ninety-eight conceptually different potential predictors were identified in 53 studies. An increased risk of smoking onset was consistently (i.e., in four or more studies) associated with increased age/grade, lower SES, poor academic performance, sensation seeking or rebelliousness, intention to smoke in the future, receptivity to tobacco promotion efforts, susceptibility to smoking, family members\u27 smoking, having friends who smoke, and exposure to films, whereas higher self-esteem and high parental monitoring/supervision of the child appeared to protect against smoking onset. Methodologic weaknesses were identified in numerous studies, including failure to account for attrition or for clustering in samples, and misidentification of potential confounders, which may have led to biased estimates of associations. CONCLUSIONS: Predictors of smoking onset for which there is robust evidence should be considered in the design of interventions to prevent first puff in order to optimize their effectiveness. Future research should seek to define onset clearly as the transition from never use to first use (e.g., first few puffs)