Effect of aqueous comonomer solubility on the surfactant-free emulsion copolymerization of methyl methacrylate

Surfactant-free emulsion copolymerization was used to prepare methyl methacrylate-hydroxyethyl methacrylate (MMA-HEA) and methyl methacrylate-hydroxypropyl methacrylate (MMA-HPMA) latex particles. Also, glycidyl methacrylate (GMA) was grafted onto the surface of the preformed MMA-HPMA latex particles by seeded surfactant-free emulsion copolymerization. The copolymerization reactions were conducted at 75 °C using a water-soluble initiator, potassium persulfate (KPS). The morphologies of copolymer latex particles were observed using Scanning electron microscopy (SEM). The influence of different reactions parameters (the MMA saturation concentration (Sr), the KPS concentration and the aqueous solubility of the comonomers (HEA or HPMA)) on the particles average diameter and particles size dispersity was investigated. The experimental results showed that the increase of initiator concentration induces in all investigated cases the increase of particles average diameter, while the presence of HEA or HPMA as comonomers in the copolymerization reaction of MMA (1,000% Sr) lead to a decrease of particles average diameter. At small KPS concentration the latex is monodisperse, the increase of the initiator concentration leading to the formation of polydisperse latex. In the case of grafting reaction of GMA onto the monodisperse preformed MMA-HEA latex particles, although the average diameter of the final particles doubles the latex remains quasi-monodisperse.     

The effect of arginine on gold nanoparticles in colloidal solutions and in thin films

Gold nanoparticles were prepared in aqueous colloidal solutions and their interaction with L-arginine solutions at different concentrations was investigated by UV-vis spectroscopy, transmission electron microscopy (TEM) and atomic force microscopy (AFM). The shift towards red of the absorption maximum of gold nanoparticles with increasing L-arginine concentration and in time, and the apparition of a new large band at higher wavelength evidence the formation of assemblies of gold nanoparticles, mediated by the amino acid. TEM images present the progress in the building process of supermolecular structures. Further, the AFM images show the self assemblies of gold nanoparticles capped with L-arginine well ordered in large domains on silanized glass. As a model for the process, we suggest that the positively charged guanidinium group of L-arginine is anchored on the negative citrate capped gold nanoparticles, while the other two functionalities of L-arginine are involved in the bonding between gold nanoparticles. The ability of arginine to specifically bind gold nanoparticles could lead to an increased ability of proteins, containing arginine, to specifically bind to nanogold. Then, they bind other target proteins or different ligands underlying numerous biological and medical applications that range from nanoscale biosensors, cell-cell communications to targeted delivery of drugs to cancer cells.     

Applications of Nanomaterials in Cell Stem Therapies and the Onset of Nanomedicine

Stem cells hold enormous potential in the treatment of diseases such as diabetes, arthritis, cirrhosis, spinal cord injury, and Alzheimer's disease, due to their unique ability to differentiate into various cell lines and tissues and integrate seamlessly into damaged or diseased tissue. The use of nanoparticles as bioactive molecules is still considered a nascent science, but their unique physical and chemical properties hold great hopes for drug delivery, cancer targeting, and bioimaging. There is active worldwide ongoing research to generate advanced therapeutic compounds for incurable diseases, combining the unique properties of nanomaterials and stem cells. The present review will cover emerging areas of nanotechnology applications in stem cell therapy, one of the next frontiers of medical science.     

Bioactive cotton fabrics containing chitosan and biologically active substances extracted from plants

The paper studies the obtaining of bioactive textiles using chitosan-coated fabrics, in which biologically active substances contained by Viola Tricolor (VT) – an extract of three Viola species (Violaceae) – were immobilized. Chitosan was applied on cotton fabric or on chemically modified cotton (having reactive –CHO or carboxymethyl groups), as tripolyphosphate (TPP) crosslinked fine particles, or by use of glutaraldehyde crosslinking agent. The amount of VT retained on the fabrics was found to depend on the procedure of chitosan application on the cotton. The obtained bioactive textiles are expected to have antioxidant activity due to the biologically active substances from VT; they can be used for obtaining clothes for people with allergies or other skin problems, assuring a controlled release of biomolecules. The study focuses on the in vitro release of VT retained on the fabrics, as well as on its antioxidant activity.     

New electromagnetic shielding materials based on viscose‐carbon nanotubes composites

A convenient approach for the preparation of cellulose ‐ carbon nanotubes (CNT) hybrid materials owning electromagnetic shielding properties, based on viscose (V) and TEMPO‐oxidized viscose fibers (VO) is proposed. Viscose ‐ carbon nanotubes (V‐CNT) and TEMPO‐oxidized viscose ‐ carbon nanotubes (VO‐CNT) composites were prepared by embedding carbon nanotubes on the surface of two types of cellulose fibers, that is, viscose and its C₆‐oxidized derivative. The chemical composition, morphology, and thermal stability of the prepared hybrid materials were thoroughly investigated by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermogravimetric analyses. Moreover, electrical properties of the original and composite fibers were assessed. POLYM. ENG. SCI., 59:1499–1506 2019. © 2019 Society of Plastics Engineers     

Short-Term Blockade of Pro-Inflammatory Alarmin S100A9 Favorably Modulates Left Ventricle Proteome and Related Signaling Pathways Involved in Post-Myocardial Infarction Recovery

Prognosis after myocardial infarction (MI) varies greatly depending on the extent of damaged area and the management of biological processes during recovery. Reportedly, the inhibition of the pro-inflammatory S100A9 reduces myocardial damage after MI. We hypothesize that a S100A9 blockade induces changes of major signaling pathways implicated in post-MI healing. Mass spectrometry-based proteomics and gene analyses of infarcted mice left ventricle were performed. The S100A9 blocker (ABR-23890) was given for 3 days after coronary ligation. At 3 and 7 days post-MI, ventricle samples were analyzed versus control and Sham-operated mice. Blockade of S100A9 modulated the expressed proteins involved in five biological processes: leukocyte cell–cell adhesion, regulation of the muscle cell apoptotic process, regulation of the intrinsic apoptotic signaling pathway, sarcomere organization and cardiac muscle hypertrophy. The blocker induced regulation of 36 proteins interacting with or targeted by the cellular tumor antigen p53, prevented myocardial compensatory hypertrophy, and reduced cardiac markers of post-ischemic stress. The blockade effect was prominent at day 7 post-MI when the quantitative features of the ventricle proteome were closer to controls. Blockade of S100A9 restores key biological processes altered post-MI. These processes could be valuable new pharmacological targets for the treatment of ischemic heart. Mass spectrometry data are available via ProteomeXchange with identifier PXD033683.     

Robust Control of Permanent Magnet Synchronous Machine Based on Passivity Theory

This paper presents a robust control strategy for a Permanent Magnet Synchronous Machine (PMSM) based on passivity theory. Pre‐control terms ensure robustness to variation of parameters. The nominal electrical and mechanical dynamics are treated separately and a cascade structure is obtained. A comparative analysis is done in Matlab‐Simulink with a Simple Adaptive Control (SAC) strategy in terms of settling time, stationary error, time response and energy efficiency. Improvements of the proposed Passivity Based Control (PBC) strategy are shown in comparison with some other PBC controllers.     

Improved Physico-chemical Properties of Mesoporous Carbon by Functionalization with Aminopropyl-polydimethylsiloxane (AP-PDMS)

The present research reports on the synthesis and properties of mesoporous carbon (MC) surface with functionalized aminopropyl-polydimethylsiloxane (AP-PDMS). The aim of MC surface modification was focused on the improvement of its electrical properties (EC electric conductivity), as well as its sorption capacity for cesium ions. In order to anchor AP-PDMS molecules, an intermediate functionalization step of the MC surface with carboxylic groups was carried out. In this respect, two different methods, namely: (i) sonication in the presence of the hydrogen peroxide (MC-COOH) and (ii) gas-plasma activation (MCA) have been considered for carbon surface oxidation. Further, AP-PDMS component was crosslinked to the COOH-reached carbon surface. Fourier transform infrared spectroscopy (FT-IR) and energy dispersion spectroscopy (EDX) were used to confirm the presence of AP-PDMS molecules on MC surface. Morphological and textural properties of the obtained composites have been investigated by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and nitrogen adsorption–desorption measurements, as well as their electrical properties (EC). The obtained results reveal the grafting of silane-containing component onto MC surface, an improved electrical conductivity of the synthesized composites toward MC sample. Also, the functionalization proved to be efficient in the sorption process of the cesium ions from aqueous solutions, despite the fact that the materials surface became hydrophobic.     

Access to RF White Spaces in Romania: Present and Future

As the demand for frequency resources increases because of the great number of new wireless technologies, the frequency spectrum becomes overcrowded and solutions have to be found in order to solve this problem. One possible solution would be to take advantage of the so called white spaces (WS), frequency bands that are actually not used by the primary (licensed) radio communication systems, by using a dynamic spectrum access (DSA) approach. In order to take advantage of these spaces, secondary (unlicensed) users have to perform a spectrum sensing process in order to accurately detect the presence of a primary system and avoid unwanted interference with it. This paper provides an overview of the status of WS in Romania by analysing the current regulations and the analogue switch-off that is planned to take place in the near future (2015). The current state of the art regarding several standards that incorporate DSA elements is being made, emphasizing the high interest in using this WS in upcoming communication systems. In order to prove the low degree in which the RF spectrum is currently used, the results of a measurement campaign performed in both urban and rural locations of Romania are discussed. A comparison with the results of other similar measurement campaigns conducted in several locations worldwide is performed as well. Several frequency bands are identified as possible WS for future opportunistic use.