Search results for "PLASTICS"

Spatial heterogeneity in glassy polystyrene detected by deuteron NMR relaxation

1999

Using deuteron NMR, the dynamics of supercooled polystyrene-d 3 was investigated near the calorimetric glass transition. At these temperatures non-exponential spin lattice relaxation is found, indicating the presence of spatial heterogeneity. With increasing temperature, structural relaxation becomes fast enough to average efficiently over different spatial environments, leading to exponential magnetization decays. A qualitative comparison with toluene as a representative of a low molecular weight glass former is carried out. Indications are found that in polystyrene the observed averaging process is more effective at T g than it is in toluene.

Polyaspartamide based hydrogel with cell recruitment properties for the local administration of hydrophobic anticancer drugs

2019

Abstract By exploiting the chemical versatility and the high water dispersibility of α,β-poly(N-2-hydroxyethyl)D,L-aspartamide, in this work, two different polymer derivatives were synthesized for the first time. Obtained macromolecules were characterized and used to produce hydrogels exploitable for the local release of hydrophobic anticancer drugs. The first derivative, bearing pendant β-cyclodextrins, was employed to solubilize tamoxifen, chosen as a model drug, and to produce a water soluble supramolecular complex, as evidenced through tamoxifen phase solubility studies. The second derivative, bearing pendant Cyclo(Arginine-Glyicine-Asparagine-D-Phenilyalanine-Cysteine) peptide moieties…

1997

We have determined by forced Rayleigh scattering the diffusion coefficients of photo-labeled polystyrene micronetwork spheres (radii ≤ 10 nm) in melts of linear polyvinylmethylether (M W ≤ 40000 g/mol) at temperatures of 20-80°C. An expected slippage of the spheres through the meshes of the entanglement network appears possible but is still within the experimental uncertainty of our results.

Hydrogen Production from Methanol-Water Solution and Pure Water Electrolysis Using Nanocomposite Perfluorinated Sulfocationic Membranes Modified by P…

2022

In this work, we report the preparation of Nafion membranes containing two different nanocomposite MF-4SC membranes, modified with polyaniline (PANI) by the casting method through two different polyaniline infiltration procedures. These membranes were evaluated as a polymer electrolyte membrane for water electrolysis. Operating conditions were optimized in terms of current density, stability, and methanol concentration. A study was made on the effects on the cell performance of various parameters, such as methanol concentration, water, and cell voltage. The energy required for pure water electrolysis was analyzed at different temperatures for the different membranes. Our experiments showed …

Роль международного медицинского сотрудничества в развитии здравоохранения Бурятии (1923–1928 гг.)

2019

The article presents the analysis of the role of international medical cooperation in the development of healthcare in the Buryat-Mongolian ASSR in its early years. Prevalence of venereal diseases and tuberculosis in the Buryats was the main problem in the 1920s. At the same time, Buryat-Mongolia played an important role in the geopolitical plans to export revolution eastwards. Thus, the Bolsheviks paid much attention to the improvement of health of the Buryat people directing the incoming international aid toward these purposes. The authors expose causal relationships leading to the organization of one of the best known international joint projects of the 1920s in medicine – the 1928 Sovie…

Институализация социальной гигиены в Советской России в 1920-1930-х годах в международном контексте

2020

This article is devoted to the emergence, development and liquidation of organizations and units of social hygiene in Soviet Russia in 1918–1934, as well as the analysis of this process in the international context. The first social-hygienic institution in the country was the State Museum of Social Hygiene of the People's Commissariat of Health of the Soviet Russia. The first department of social hygiene was organized only in 1922 in the 1st Moscow State University. By the end of the 1920s there were already 18 such departments. In 1929, the country entered a new period of collectivization of agriculture and industrialization of industry. In the early 1930s all social hygiene institutes in th…

A Study on the Propagation of Plane Stress Waves across the Thickness of a Plate by the Method of Analytic Continuation in Time

2004

The interaction of plane tension/compression waves propagating within a plate perpendicularly to its surface is considered. The analytic solution is obtained by a modified method of characteristics for the one-dimensional wave equation used in problems on an impact of a rigid body on the surface of a plate. The displacements, velocities, and stresses in the plate are determined by the edge disturbance caused by the initial velocity and the stationary force field of masses of the striker and the plate. The method of analytic continuation in time put forward allows a stress analysis for an arbitrary time interval by using finite expressions. Contrary to a stress analysis in the frequency doma…

Poly(methyl ethylene phosphate) hydrogels

2020

Abstract A degradable and water-soluble polyphosphoester (PPE), namely poly(methyl ethylene phosphate)-dimethacrylate (PMEP-DMA), was synthesized and crosslinked by UV irradiation to prepare PPE-hydrogels. Hydrogels with 10 and 15 wt% of PMEP were prepared after UV-irradiation with an additional 0.2 wt% of photoinitiator. The colorless and transparent PPE hydrogels were studied for their swelling and water uptake. The rheological analysis demonstrated their viscoelastic behavior. The PPE hydrogels were compared to poly(ethylene glycol) (PEG) hydrogels prepared from PEG-macromonomers of similar degrees of polymerization. Hydrolysis experiments proved a successful disintegration of the PPE hy…

Self-reporting hydrogels rapidly differentiate among enterohemorrhagic Escherichia coli (EHEC) and non-virulent Escherichia coli (K12)

2016

Abstract We report on the development of an autonomously reporting indicator hydrogel for the rapid and selective detection of enzymes secreted by the food-borne biosafety level 3 pathogen enterohemorrhagic Escherichia coli (E. coli) O157:H7 (EHEC) and the differentiation of this pathogen from the non-virulent E. coli strain K12. To introduce the sensing functionality, chitosan hydrogel films were equipped with fluorogenic substrates for the detection of α-galactosidase (α-Gal) and β-galactosidase (β-Gal), which are secreted by E. coli O157:H7, and β-glucuronidase (β-GUS), which is produced by the non-virulent E. coli K12 strain, but not by E. coli O157:H7, respectively. In the presence of …

An assembly of organic-inorganic composites using halloysite clay nanotubes

2018

Halloysite is natural tubular clay suitable as a component of biocompatible nanosystems with specific functionalities. The selective modification of halloysite inner/outer surfaces can be achieved by exploiting supramolecular and covalent interactions resulting in controlled colloidal stability adjusted to the solvent polarity. The functionalized halloysite nanotubes can be employed as reinforcing filler for polymers as well as carriers for the sustained release of active molecules, such as antioxidants, flame-retardants, corrosion inhibitors, biocides and drugs. The tubular morphology makes halloysite a perspective template for core-shell metal supports for mesoporous catalysts. The cataly…