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Close galaxy flybys, interactions during which two galaxies inter-penetrate, are frequent and can significantly affect the evolution of individual galaxies. Equal-mass flybys are extremely rare and almost exclusively distant, while frequent flybys have mass ratios 0.1 or lower, with a secondary galaxy penetrating deep into the primary. This can result in comparable strengths of interaction S between the two classes of flybys and lead to essentially the same effects. To demonstrate this, emphasize and explore the role of the impact parameter $b$, we performed a series of N-body simulations of flybys with varying relative $b$ ranging from 0.114 to 0.272 of the virial radius of the primary. Two-armed spirals form during flybys, with radii of origin correlated with $b$ and strengths well approximated with an inverted S-curve. The impact parameter does not affect the shape of induced spirals, and the lifetimes of a distinguished spiral structure appear to be constant, 2 Gyr. Bars, with strengths anti-correlated with $b$, form after the encounter is over in simulations with interaction strengths $S\geq0.076$, but they are short-lived except for the stronger ones with $S\geq0.129$. We showcase an occurrence of double bar that survives for a long time in one of the simulations. Effects on the pre-existing bar instability are diverse. There is no uniform correlation between these effects and $b$, as they are secondary effects, happening later in a post-flyby stage. Bulges are resilient to flybys, while dark matter halos can significantly spin up in the amount anti-correlated with $b$. There is an offset angle between the angular momentum vector of the dark matter halo and that of a disc, and it correlates linearly with b. Flybys remain an important pathway for structural evolution within galaxies in the local Universe., Comment: 21 pages, 13 figures, accepted for publication in PASA

The oligo(ethylene glycol) dimethacrylate (OEGDMA), one of the most commonly utilized crosslinking monomers, was used to tailor thermoresponsive POEGDMA hydrogels by varying the monomer/solvent feed ratio (from 10 to 100 wt% of monomer). For the first time, synthesis of different POEGDMA homopolymeric networks was performed by gamma radiation, and due to the expected thermoresponsiveness their temperature-dependent properties were extensively analysed. The sol-gel study was performed as the first step after radiation-induced synthesis. The swelling properties were investigated over the wide pH (2.2–9.0) and temperature (5–80 °C) range. Characterization of structure and properties was additionally conducted by SEM, DSC, FTIR, and UV–Vis spectroscopy. The results indicated that all POEGDMA hydrogels showed a high gel content, inverse thermoresponse and volume phase transition temperature (VPTT) with no respect to initial preparation. On the other hand, by altering the monomer/solvent ratio in the prepolymerisation mixture a large diversity in the microstructure, swelling capacity and VPTT was obtained. © 2019 Elsevier Ltd This is the peer-reviewed version of the following article: Suljovrujic, Edin, Zorana Rogic Miladinovic, Maja Micic, Denis Suljovrujic, and Dejan Milicevic. "The influence of monomer/solvent feed ratio on POEGDMA thermoresponsive hydrogels: Radiation-induced synthesis, swelling properties and VPTT." Radiation Physics and Chemistry 158 (2019): 37-45. [http://dx.doi.org/10.1016/j.radphyschem.2018.12.034] Published version available at: [http://vinar.vin.bg.ac.rs/handle/123456789/8048]

We present an isolated Milky Way-like simulation in GADGET2 N-body SPH code. The Galactic disk star formation rate (SFR) surface densities and stellar mass indicative of Solar neighbourhood are used as thresholds to model the distribution of stellar mass in life friendly environments. SFR and stellar component density are calculated averaging the GADGET2 particle properties on a 2D grid mapped on the Galactic plane. The peak values for possibly habitable stellar mass surface density move from $10$ to $15$ kpc cylindrical galactocentric distance in $10$ Gyr simulated time span. At $10$ Gyr the simulation results imply the following. Stellar particles which have spent almost all of their life time in habitable friendly conditions reside typically at $\sim16$ kpc from Galactic centre and are $\sim 3$ Gyr old. Stellar particles that have spent $\ge 90 \%$ of their $4-5$ Gyr long life time in habitable friendly conditions, are also predominantly found in the outskirts of the Galactic disk. Less then $1 \%$ of these particles can be found at a typical Solar system galactocentric distance of $8-10$ kpc. Our results imply that the evolution of an isolated spiral galaxy is likely to result in galactic civilizations emerging at the outskirts of the galactic disk around stellar hosts younger than the Sun., Published in MNRAS, no changes, metadata update

Gamma radiation was used to prepare copolymer hydrogel libraries based on oligo(propylene glycol) methacrylate (OPGMA) and 2-hydroxyethyl methacrylate (HEMA); a complete screening in composition of P(OPGMA/HEMA) copolymers was elaborated from 0% to 100% of OPGMA. Determination of gel fraction was performed as the first step after radiation induced synthesis. Tuning of the volume phase transition temperature (VPTT) of P(OPGMA/HEMA) copolymeric hydrogels was investigated by swelling study. Additional characterization of structure and properties was conducted by FTIR, DSC, and UV-Vis spectroscopy. All results indicate that new P(OPGMA/HEMA) copolymeric hydrogels have wide diversity in thermoresponsive properties which strongly depend on their composition. [GRAPHICS] .

The synthesis of poly(oligo(propylene glycol) methacrylate) (POPGMA) from functionalised oligo(propylene glycol) methacrylate (OPGMA) monomers by gamma radiation-induced radical polymerisation is reported for the first time; POPGMA homopolymeric hydrogel with oligo(propylene glycol) (OPG) pendant chains, as a non-linear PPGMA-analogue, was synthesised from an monomer-solvent (OPGMA(375)-water/ethanol) mixture at different irradiation doses (5, 10, 25, and 40 kGy). Determination of the gel fraction was conducted after synthesis. The swelling properties of the POPGMA hydrogel were preliminarily investigated over wide pH (2.2-9.0) and temperature (4-70 degrees C) ranges. Additional characterisation of structure and properties was conducted by UV-vis and Fourier transform infrared (FTIR) spectroscopy as well as by differential scanning calorimetry (DSC). In order to evaluate the potential for biomedical applications, biocompatibility (cytocompatibility and haemolytic activity) studies were performed as well. Sol-gel conversion was relatively high for all irradiation doses, indicating radiation-induced synthesis as a good method for fabricating this hydrogel. Thermoresponsiveness and variations in swelling capacity as a result of thermosensitive OPG pendant chains with a lower critical solution temperature (LCST) were mainly observed below room temperature; thus, the volume phase transition temperature (VPTT) of POPGMA homopolymeric hydrogel is about 15 degrees C. Furthermore, POPGMA has satisfactory biocompatibility. The results indicate that the hydrogels with propylene glycol pendant chains can be easily prepared by gamma radiation and have potential for different applications as smart and biocompatible polymers. (C) 2014 Elsevier B.V. All rights reserved.

New hydrogels based on different oligo(alkylene glycol) methacrylate (OAGMA) with inverse thermoresponse and volume phase transition temperature (VPTT) were obtained and characterised in this paper. Synthesis was performed from monomer-solvent (OAGMA-water/ethanol) mixture by simultaneous radiation-induced polymerisation and crosslinking; three different OAGMA (EG(6)MA, EG(6)PG(3)MA, and PG(5)MA) were used. The main focus was made on PEG(6)PG(3)MA hydrogel based on ethylene glycol (EG) propylene glycol (PG) pendant chains with EG (6) and PG (3) block units, since in the case of POPGMA and POEGMA homopolymers (i.e. hydrogels with pure PG and EG pendant chains) the VPTTs were observed far below and far above the human body temperature, respectively. Characterisation of the hydrogels was performed by swelling, UV-Vis, FTIR, SEM, DSC and in vitro biocompatibility (cytocompatibility and haemolytic activity) investigations. Due to the possibility to combine VPTT close to human body temperature with good biocompatibility, new hydrogel based on EGPG block pendant chains showed promising potential for different biomedical applications.

Changes in the structure and dielectric properties of low-density polyethylene were created by gamma irradiation in air, deionised water and nitrogen. Role of irradiation media on dielectric and charge trapping behaviour was studied through dielectric loss and thermally stimulated discharge current measurements. Changes in magnitude, position and activation energy of all dielectric relaxations (gamma, beta and alpha) were found to be dependent on crosslinking and oxidative degradation, two competitive processes which can be tuned by radiation dose and media. Largest changes in the position and activation energy were found for the beta relaxation due to its cooperative nature.

A series of copolymeric hydrogels with different mole ratios of 2-hydroxyethyl methacrylate (HEMA), itaconic acid (IA) and oligo(ethylene glycol) acrylate (OEGA) was synthesised by gamma radiation. In our previous paper, the swelling properties of P(HEMA/IA/OEGA) terpolymeric hydrogels were preliminary investigated, showing dual (pH and thermo) responsiveness and large variation in the swelling capacity. In this study, the basic structural parameters of the P(HEMA/IA/OEGA) networks such as the average molecular weight between cross-links ((M) over bar (c),), effective cross-linking density (nu(e)), polymer-solvent interaction parameter (chi) and mesh size (xi) were determined by using swelling and mechanical measurements. Cytocompatibility and hemolytic activity measurements were used to investigate the influence of hydrogel composition (i.e. the influence of different fractions of IA and OEGA) on the biocompatibility of the hydrogels obtained. The microbe penetration test against Staphylococcus aureus and Escherichia coli was performed, too. It was observed that variation in hydrogel composition strongly influenced the smart swelling behaviour and introduced some changes in biocompatibility. The results indicate that P(HEMA/IA/OEGA) terpolymers, as smart and biocompatible hydrogels, have wide diversity and great potential for different biomedical applications, but their optimisation study can give the best candidate for certain biomedical applications. (C) 2013 Elsevier Ltd. All rights reserved.

This review attempts to present most recent findings related to the very controversial question of which processes guide the flow of gas to the galactic centers where the accretion and growth of supermassive black holes occurs. Also, we put this question in the context of influence of the environment (galaxy clusters versus field) onto these processes. [Projekat Ministarstva nauke Republike Srbije, br. 176021: Visible and Invisible Matter in Nearby Galaxies: Theory and Observations. The author acknowledges the financial support provided by the European Commission through project BELISSIMA (BELgrade Initiative for Space Science, Instrumentation and Modelling in Astrophysics, call FP7-REGPOT-2010-5, contract no. 256772]

The purpose of this study was to attain oligo(propylene glycol) methacrylate (OPGMA) based hydrogels for different biomedical applications. Since the volume phase transition temperature (VPTT) of poly(oligo(propylene glycol) methacrylate) (POPGMA) homopolymer was below room temperature, it was necessary to tune the thermoresponsiveness and the VPTT to higher temperatures; radical copolymerisation of OPGMA with more hydrophilic and/or pH responsive monomers was used to adjust these values. A series of copolymeric hydrogels with different ratios of OPGMA, 2-hydroxyethyl methacrylate (HEMA) and itaconic acid (IA) was synthesised by gamma radiation. The swelling properties were preliminarily investigated over a wide pH (2.2-9.0) and temperature (4-80 degrees C) ranges. Additional characterization of their structure and properties was conducted by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The presented results revealed temperature/pH dual responsive P(OPGMA/IA) and P(OPGMA/HEMA/IA) copolymers with large diversity in swelling properties, as a result of the addition of OPGMA thermoresponsive units with a lower critical solution temperature (LCST) and IA pH responsive units. It was demonstrated that VPTT can be significantly shifted to higher (e. g. body) temperatures at higher pH values (pH = 4) by increasing the IA content in the hydrogel composition. Due to the possibility of making dual responsive copolymers in the manner explained in this paper, OPGMA based hydrogels show potential for different biomedical applications.

To explore the potential usage of recombinant banana lectin as an immunostimulator it was of interest to analyze the effect it exerted in vivo in mice, upon two different routes of exposure. By Western blotting analysis of the gastric and intestinal luminal content it was found that recombinant banana lectin is stable in vivo in the mouse digestive tract, where it specifically interacts with the mucosal surfaces which can be inhibited by the addition of glucose. Its attachment to mice jejunum has been confirmed by immunofluorescence. In addition, it was able to induce systemic immunity, evidenced by specific antibody production, by oral application, a property that might be exploited for the induction of systemic immune responses. (c) 2012 Elsevier Ltd. All rights reserved.

This paper presents the influence of ageing on the morphological and optical properties of TPD (N, N’ - Bis (3 - methylphenil) - N, N’ diphenylbenzidine) thin films. Understanding of the nucleation mechanism and growth dynamics of molecular thin films is pivotal for controlling their morphology and the film interfacial properties, while the influence of ageing is essential for the potential commercial utilization. Initially, thin films were prepared using a combinatorial physical vapour deposition (CPVD) method, following a cosine-like distribution profile of thickness along monocrystal silica substrate. Morphology of thin films was investigated by using optical (OM) and atomic force microscopy (AFM). The link between optical properties and the resulting thin film morphology was made by spatially correlated morphological (AFM and OM) and optical (absorption and photoluminescence) measurements. The changes in the absorption and photoluminescence spectra are strongly connected to the ageing-induced changes in the microstructure of thin films. Regardless of morphological and differences in the film thickness (two orders of magnitude), all films show amorphous arrangement just after the deposition. Ageing of these films in regular atmosphere conditions results in morphological and changes in optical properties induced by the crystallization. The crystallization of initially amorphous samples was also confirmed by the differentional scanning calorimetry (DSC) measurements. All results indicate the limited possibility of using TPD films in organic electroluminescent devices.

The copolymeric hydrogels based on 2-hydroxyethyl methacrylate (HEMA) and itaconic acid (IA) were synthesized by gamma radiation induced radical polymerization. Swelling and thermodynamic properties of PHEMA and copolymeric P(HEMA/IA) hydrogels with different IA contents (2, 3.5 and 5 mol%) were studied in a wide pH and temperature range. Initial studies of so-prepared hydrogels show interesting pH and temperature sensitivity in swelling and drug release behavior. Special attention was devoted to temperature investigations around physiological temperature (37 degrees C), where small changes in temperature significantly influence swelling and drug release of these hydrogels. Due to maximum swelling of hydrogels around 40 degrees C, the P(HEMA/IA) hydrogel containing 5mol% of IA without and with drug-antibiotic (gentamicin) were investigated at pH 7.40 and in the temperature range 25-42 degrees C, in order to evaluate their potential for medical applications. (c) 2007 Elsevier Ltd. All rights reserved. 11th Tihany Symposium on Radiation Chemistry, Aug 26-31, 2006, Eger, Hungary

The new copolymeric hydrogels based on 2-hydroxyethyl methacrylate (HEMA) and itaconic acid (IA) were prepared by gamma irradiation, in order to examine the potential use of these hydrogels in controlled drug release systems. The influence of IA content in the gel on the swelling characteristics and the releasing behavior of hydrogels, and the effect of different drugs, theophylline (TPH) and fenethylline hydrochloride (FE), on the releasing behavior of P(HEMA/IA) matrix were investigated in vitro. The diffusion exponents for swelling and drug release indicate that the mechanisms of buffer uptake and drug release are governed by Fickian diffusion. The swelling kinetics and, therefore, the release rate depends on the matrix swelling degree. The drug release was faster for copolymeric hydrogels with a higher content of itaconic acid. Furthermore, the drug release for TPH as model drug was faster due to a smaller molecular size and a weaker interaction of the TPH molecules with(in) the P(HEMA/IA) copolymeric networks. (C) 2006 Elsevier Ltd. All rights reserved.

New types of hydrogels were prepared by the radical copolymerization of 2-hydroxyethyl methacrylate, itaconic acid and four different poly(alkylene glycol) (meth)acrylate components (Bisomers) in a water/ethanol mixture as solvent. The polymers swell in water at 25°C to yield homogeneous transparent hydrogels. All the hydrogels displayed pH sensitive behavior in buffers of the pH range from 2.20 to 7.40, under conditions similar to those of biological fluids. The presence of these two comonomers, which were added to HEMA, increased the swelling degree of the hydrogels and gave gels with better elasticity. The hydrogels were thermally stable in the vicinity of the physiological temperature (37°C). The copolymer containing pure poly(ethylene glycol) acrylate units generally had the best properties. The tests performed on the hydrogels confirmed that they were neither hemolytic nor cytotoxic. The copolymer samples showed better cell viability and less hemolytic activity than the PHEMA sample, confirming the assumption that poly(alkylene glycols) improve the biocompatibility of hydrogels. Due to their swelling and mechanical characteristics, as well as the very good biocompatibility and bioadhesive properties, poly(Bisomer/HEMA/IA) hydrogels are promising for utilization in the field of biomedicals, especially for the controlled release of drugs. Radikalnom kopolimerizacijom 2-hidroksietil metakrilata (HEMA), itakonske kiseline (IK) i četiri tipa poli(alkilen glikol) (met)akrilata (Bisomera-BIS) dobijeni su novi poli(BIS/HEMA/IK) hidrogelovi, u smeši voda/etanol kao rastvaraču. Ispitan je uticaj tipa Bisomera na bubrenje u puferima pH 2,20-7,40, u uslovima sličnim biološkim fluidima. Takođe, praćenje i uticaj na mehanička svojstva, morfologiju i termičko ponašanje dobijenih gelova. Testiranje biokompatibilnosti in vitro napoli (BIS/HEMA/IK) hidrogelovima pokazuje da nema ćelijske toksičnosti, niti hemolitičke aktivnosti. Gelovi poseduju zadovoljavajuću bioadhezivnost.

Hydrogels based on 2-hydroxyethyl methacrylate and different types of poly(alkylene glycol) acrylates and methacrylates, with a small percent of itaconic acid, have been prepared by solution copolymerization using gamma irradiation. In this study, the swelling behavior and network parameters of these hydrogels as a function of poly(alkylene glycol) acrylate type are reported for the first time. Morphology of the obtained hydrogels was characterized using scanning electron microscopy (SEM) technique. Current Research in Advanced Materials and Processes, 6th Conference of the Yugoslav-Materials-Research-Society, Sep 13-17, 2004, Herceg Novi, Montenegro

Silver nanoparticles were fabricated via in situ reduction of silver nitrate embedded in swollen P(HEMA/IA) hydrogel, using gamma radiolysis method. Copolymeric hydrogels based on 2-hydroxyethyl methacrylate (HEMA) and itaconic acid (IA), previously synthesised by gamma radiation for wound dressing application, were used as a carrier and a stabilising agent, while ethyl alcohol was used as a free radical scavenger. The influence of different P(HEMA/IA) hydrogels and silver salt concentrations on the size and distribution of nanoparticles was investigated. The Ag/P(HEMA/IA) nanocomposites were characterised by high resolution scanning electron microscopy, energy dispersive spectroscopy, wide-angle X-ray diffraction, UV-Vis spectroscopy and swelling measurements. Escherichia coli (Gram-negative bacterium), Staphylococcus aureus (Gram-positive bacterium) and Candida albicans (fungus) were used to prove the antimicrobial properties of Ag/P(HEMA/IA) nanocomposites. The inhibition kinetics of bacteria growth was investigated by measuring the colony-forming unit. The antimicrobial effectiveness of the Ag/P(HEMA/IA) hydrogel nanocomposite was demonstrated even at small silver concentrations. P(HEMA/IA) hydrogels containing nanosilver particles was found suitable to be used as wound dressing.

Different polyolefines (low density polyethylene (LDPE), linear low density polyethylene (LLDPE), high density polyethylene (HDPE) and isotactic polypropylene (iPP)) were oriented via solid-state stretching at an elevated temperature. In order to investigate orientation-induced changes in microstructure and crystallinity, optical microscopy (OM), scanning electron microscopy (SEM), wide angle X-ray scattering (WAXS) and differential scanning calorimetry (DSC) were employed. To quantify the degree of molecular orientation WAXS data were used to calculate Herman’s orientation function (f c ); the results reinforce the morphological picture obtained from OM and SEM confirming Peterlin’s molecular model of drawing. Furthermore, orientation-induced changes in the crystalline phase, especially in its volume and perfection, were observed by DSC and WAXS. Comparison between these data showed that the biggest change in the degree of crystallinity was achieved during the transformation of the initial lamellar into fibrillar structure. After completion of this transformation further orientation, which occurs through plastic deformation of fibre structure, introduces only minor changes in crystallinity. The overall orientation-induced behaviour hasn’t been considerably influenced by the structural differences amongst polyolefins.

Since it is presumed that by incorporation of pH-responsive (IA) and temperature-responsive (OEGA) co-monomers, it is possible to prepare P(HEMA/IA/OEGA) hydrogels with dual (pH and thermo) responsiveness, the main purpose of our study is to investigate the influence of different mole fractions of IA and especially OEGA on the diversity of the swelling properties of the obtained hydrogels. For that reason, a series of terpolymeric hydrogels with different mole ratios of 2-hydroxyethyl methacrylate (HEMA), itaconic acid (IA) and oligo(ethylene glycol) acrylates (OEGA) was synthesised by gamma radiation. The obtained hydrogels were characterised by swelling studies in the wide pH (2.2-9.0) and temperature range (20-70 degrees C), confirming dual (pH and thermo) responsiveness and a large variation in the swelling capability. It was observed that the equilibrium swelling of P(HEMA/IA/OEGA) hydrogels, for a constant amount of IA, increased progressively with an increase in OEGA share. On the other hand, the dissociation of carboxyl groups from IA occurs at pH GT 4; therefore, small mole fractions of IA render good pH sensitivity and a large increase in the swelling capacity of these hydrogels at higher pH values. Additional characterisation of structure and properties was conducted by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and mechanical measurements, confirming that the inherent properties of P(HEMA/IA/OEGA) hydrogels can be significantly tuned by variation in their composition. According to all presented, it seems that the obtained hydrogels can be a beneficial synergetic combination for controlled delivery of bioactive molecules such as drugs, peptides, proteins, etc. (C) 2011 Elsevier Ltd. All rights reserved. 12th Tihany Symposium on Radiation Chemistry, Aug 27-Sep 01, 2011, Zalakaros, Hungary

pH- and temperature-sensitive hydrogels, based on 2-hydroxyethyl methacrylate (HEMA) and itaconic acid (IA) copolymers, were prepared by gamma-irradiation and characterized in order to examine their potential use in biomedical applications. The influence of comonomer ratio in these smart copolymers on their morphology, mechanical and thermal properties, biocompatibility and microbe penetration capability was investigated. The mechanical properties of copolymers were investigated using the dynamic mechanical analysis (DMA), while their thermal properties and morphology were examined by thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The morphology, mechanical and thermal properties of these hydrogels were found to be suitable for most requirements of biomedical applications. The in vitro study of P(HEMA/IA) biocompatibility showed no evidence of cell toxicity nor any considerable hemolytic activity. Furthermore, the microbe penetration test showed that neither Staphylococcus aureus nor Escherichia coli passed through the hydogel dressing; thus the P(HEMA/IA) dressing could be considered a good barrier against microbes. All results indicate that stimuli-responsive P(HEMA/IA) hydrogels have great potential for biomedical applications, especially for skin treatment and wound dressings. (C) 2009 Elsevier Ltd. All rights reserved.

In this work, novel hydrogels based on 2-hydroxyethyl methacrylate (HEMA) and different poly(alkylene glycol)(meth)acrylates (BIS) were prepared by radiation-induced copolymerization. The influence of different BIS types with variation in chain length, based on ethylene glycol (EG) and/or propylene glycol (PG) pendant units, on the nature and inherent properties of P(HEMA/BIS) copolymeric hydrogels was the main idea of this paper. Swelling studies were conducted for all types of P(HEMA/BIS) copolymeric hydrogels in a wide pH and temperature range. Additional characterization of structure, morphology and thermal behaviour of the obtained hydrogels was conducted by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and thermogravimetric (TG) analysis. The modelling of drug release and diffusion characteristics was tested using cephalexin (CEX). The results indicate that P(HEMA/BIS) hydrogels properties are significantly dependent on the type of BIS. The hydrogels with ethylene glycol (EG) pendant chains show a noticeable pH and/or temperature sensitivity and can be considered smart hydrogels. The introduction of propylene glycol (PG) units, pure and mixed with ethylene glycol (EG) pendant chains, can additionally tune the characteristics of such gels. Furthermore, drug release studies indicate that these types of P(HEMA/BIS) copolymeric hydrogels are suitable candidates for controlled drug release systems. (C) 2010 Elsevier B.V. All rights reserved.

In this work new hybrid hydrogels were prepared by radical copolymerization of 2-hydroxyethyl methacrylate, itaconic acid, poly(vinylpyrrolidone) and silver particles. FTIR spectroscopy has confirmed binding of silver particels in hydrogels. Swelling studies performed in in vitro conditions showed dependence on PVP content and temperature. It can be seen that the antimicrobial activity of the Ag/P(HEMA/IA)PVP hybrid hydrogels depends on the PVP moiety and with the increase of PVP content the microbial contamination is more efficiently reduced. The best sensitivity was obtained for the polymers tested for antimicrobial activity against the yeast C. albicans, one of the most commonly encountered human pathogens, causing a wide variety of infections ranging from mucosal infections in generally healthy persons to life-threatening systemic infections in individuals with impaired immunity. A slightly less susceptible to antimicrobial effect of hydrogels was obtained for the Gram-positive bacteria S. aureus, where the reduction of cells was about 70 % after two hours of exposure, for the sample with the highest PVP content. The least susceptible to the antimicrobial activity of hydrogels examined was the Gram-negative bacteria E. coli, where the percent of cell reduction was below 20 %. Bearing in mind the influence of the time of exposure of microbes to the Ag/P(HEMA/IA)/PVP hybrid hydrogels, it was observed that the reduction of the number of cells depends on time, microbial culture and type of hybrid hydrogel sample. Due to their swelling and antimicrobial properties, silver/poly(2-hydroxyethyl methacrylate/itaconic acid)/poly(vinylpyrrolidone) hybrid hydrogles show potential to use in the field of biomedicine, especially for treatment of skin and burns in dermocosmetics.

Silver(I) itaconic acid-based hydrogel complexes were synthesized and characterized in order to examine the potential use of these systems; FTIR, AFM, in vitro fluid-uptake, metal sorption and antibacterial activity assay measurements were used for the characterization. Metal (silver(I)) ion uptaken by IA-based hydrogels was determined by inductively coupled plasma mass spectrometry. The coordination sites for metal ions were identified and the stability in in vitro condition was determined. Incorporation of silver(I) ions into hydrogels and the influence of these ions on the diffusion properties of hydrogels were analyzed and discussed, too; it was found that the itaconic acid moiety in hydrogels is the determining factor which influences metal ion binding and therefore fluid uptake inside the polymeric network. Furthermore, silver(I) itaconic acid-based hydrogel showed a satisfactory antibacterial activity. The most advanced feature of these materials is that the silver ions embedded throughout the networks leaches out via controlled manner with time in aqueous media. Therefore, the ions escape from the swollen networks with time and interact with the bacteria. Because of a good dispersion of silver ions in Ag(I)-P(HEMA/2IA) hydrogel complex, we have evaluated the antibacterial activity for this sample. As expected, the number of colonies grown surrounding the Ag(I)-P(HEMA/2IA) hydrogel complex was found to be almost nil, whereas the pure P(HEMA/2IA) hydrogel did not show any effect on Escherichia coli. Therefore, we conclude that the Ag(I)-P(HEMA/IA) hydrogel complexes are excellent antibacterial materials. Due to these facts, the silver ion IA-based hydrogel complexes reported here might be used as smart materials in the range of biomedical applications, including drug-delivery devices, biosensors, wound healing dressings, tissue reconstruction and organ repair. Sintetisani su kompleksi srebra(I) sa kopolimernim hidrogelovima 2-hidroksietil metakrilata (HEMA) i itakonske kiseline (IK) (Ag(I)-P(HEMA/IK)) u cilju ispitivanja primene ovih sistema kao biomaterijala. Uzorci su karakterisani sledećim metodama: FTIR, AFM, analiza bubrenja u in vitro uslovima, apsorpcija metala i analiza antibakterijske aktivnosti. Apsorpcija srebra(I) u hidrogelove na bazi IK je određena metodom indukovano spregnutne plazma-masene spektrometrije (ICP-MS). Analiziran je uticaj ugrađenih jona Ag na difuziona svojstva komplesiranih hidrogelova. Udeo IK u hidrogelu je preovlađujući faktor koji utiče na vezivanje Ag jona, pa otuda i na apsorpciju fluida u polimernoj mreži. Testovi antibakterijske aktivnosti su pokazali zadovoljavajuća antibakterijska svojstva biomaterijala u odnosu na soj bakterija Escherichia coli.

Silver(I) complexes based on itaconic acid hydrogel were prepared and characterized in order to examine the potential use of these materials. FTIR, AFM, in vitro fluid-uptake, metal sorption, and antibacterial activity assay measurements were used for the characterization. Silver(I) ion uptake by hydrogels based on 2-hydroxyethyl methacrylate (HEMA), ethylene glycol dimethacrylate (EGDMA), and different content of itaconic acid (2; 3.5; 5 mol%) were determined by inductively coupled plasma mass spectrometry. The coordination sites for metal ions were identified, and the stability in in-vitro condition was determined. Incorporation of silver(I) ions into hydrogels and the influence of these ions on material diffusion properties were analyzed. It was found that the itaconic acid moiety is the determining factor which influences metal ion binding and, therefore, fluid uptake inside the polymer network. Furthermore, obtained hydrogels showed a satisfactory antibacterial activity.

pH and temperature sensitive hydrogels, based on 2-hydroxyethyl methacrylate (HEMA) and itaconic acid (IA) copolymers, were prepared by gamma irradiation and characterized in order to examine their potential use in biomedical applications. The influence of comonomer ratio in these smart copolymers on their morphology, mechanical properties, biocompatibility and microbe penetration capability was investigated. The mechanical properties of copolymers were investigated using the dynamic mechanical analysis (DMA), while their morphology was examined by scanning electron microscopy (SEM). The morphology and mechanical properties of these hydrogels were found to be suitable for most requirements of biomedical applications. The in vitro study of P(HEMA/IA) biocompatibility showed no evidence of cell toxicity nor any considerable hemolytic activity. Furthermore, the microbe penetration test showed that neither Staphylococcus aureus nor Escherichia coli passed through the hydogel dressing; thus the P(HEMA/IA) dressing could be considered a good barrier against microbes. All results indicate that stimuli-responsive P(HEMA/IA) hydrogels have great potential for biomedical applications, especially for skin treatment and wound dressings. pH i temperaturno osetljivi hidrogelovi na bazi kopolimera 2-hidroksietilmetakrilata (HEMA) i itakonske kiseline (IK) sintetisani su upotrebom gama zračenja i karakterisani s ciljem ispitivanja njihove potencijalne primene kao biomaterijala. Ispitivan je uticaj odnosa komonomera u ovim inteligentnim polimernim biomaterijalima na morfologiju, mehanička svojstva, biokompatibilnost i penetraciju mikroba. Mehanička svojstva kopolimera su ispitivana dinamičko-mehaničkom analizom (DMA), dok je morfologija karakterisana skenirajućom elektronskom mikroskopijom (SEM). Pokazalo se da su morfologija i mehanička svojstva ovih hidrogelova odgovarajući za većinu biomedicinskih primena. In vitro analizom biokompatibilnosti P(HEMA/IK) hidrogelova potvrđeno je da nisu toksični za ćelije niti izazivaju značajnu hemolitičku aktivnost. Takođe, test mikrobne penetracije pokazao je da ni Staphylococcus aureus ni Escherichia coli ne prolaze kroz hidrogelne obloge; stoga se P(HEMA/IK) obloge mogu smatrati dobrom barijerom protiv mikroba, a radi održavanja sterilnosti okolne sredine. Svi rezultati pokazuju da P(HEMA/IK) hidrogelovi imaju veliku mogućnost primene u biomedicini, posebno kod tretmana kože i kao obloge za opekotine.

Controlled release studies of drugs (theophylline (TH), fenethylline hydrochloride (FE) and gentamicin sulphate (GS)) from pH sensitive poly(2-hydroxyethyl methacrylate/itaconic acid) (P(HEMA/IA)) hydrogels obtained by gamma irradiation were carried out to investigate transport phenomena. Drug behavior and release profiles were analyzed using the restriction coefficient combining the influence of network structure and the size of the drug on release and transport properties. The results demonstrated that the ratio of drug radius to polymer pore size and drugpolymer interactions were dominant factors in hindering the diffusion process. The diffusivity of a drug through the hydrogels decreases with the size of the drug molecules and with the decrease in gel pore size. The diffusion equations for used drugs explain drug transport in hydrogels. Research Trends in Contemporary Materials Science, 8th Conference of the Yugoslav-Materials-Research-Society (Yu-MRS), Sep 04-08, 2006, Herceg Novi, Montenegro

Ag-poy(BIS-co-HEMA-co-IA) nanocomposites are prepared via in situ reduction of silver salt embedded in swollen polymer gels by employing gamma irradiation. Hydrogels based on 2-hydroxyethyl methacrylate, itaconic acid and four types of poly(alkylene glycol) acrylate or methacrylate (Bisomers) were previously prepared using gamma irradiation. The nanocomposites are characterized by using UV-vis, swelling measurements and thermal analysis. Evolution of plasmon absorption detected by UV-vis spectro photometry indicated generation of Ag nanoparticles in polymer hydrogels. Altering the structure of the hydrogels did not lead to alternation of the position of the absorption maximum. The bulk property of equilibrium swelling is dependent on the presence of the Ag nanostructures. The initial thermal stability of the polymer is slightly increased due to presence of silver as nanofiller. (c) 2007 Elsevier Ltd. All rights reserved. 11th Tihany Symposium on Radiation Chemistry, Aug 26-31, 2006, Eger, Hungary

Described is the application of a combinatorial physical vapor deposition (CPVD) method for studying the growth dynamics of epitaxial films. The CPVD method takes advantage of the angle-dependent evaporation rate from a point source to produce thin film libraries whose deposition rate changes continuously for a factor of 50 across a 70-mm long-substrate. The link between the deposition rate and the resulting thin film morphology was made by spatially correlated absorption and atomic force microscopy measurements. It is shown that the growth of tryphenyldiamine derivate on a silica surface proceeds by three-dimensional growth of isolated islands which, at some critical coverage, coalesce to form uniform amorphous film. While the critical coverage of such films depends on the deposition rate in the 0.015-0.4 nm/s region, the particle size distribution function does not.

Protein-functionalized atomic force microscopy (AFM) tips have been used to investigate the interaction of individual ligand-receptor complexes. Herein we present results from scanning electron microscopy (SEM) studies of protein-functionalized AFM cantilever tips. The goals of this study were (1) to examine the surface morphology of protein-coated AFM tips and (2) to determine the stability of the coated tips. Based on SEM images, we found that bovine serum albumin (BSA) in solution spontaneously adsorbed onto the surface of silicon nitride cantilevers, forming a uniform protein layer over the surface. Additional protein layers deposited over the initial BSA-coated surface did not significantly alter the surface morphology. However, we found that avidin-functionalized tips were contaminated with debris after a series of force measurements with biotinylated agarose beads. The bound debris presumably originated from the transfer of material from the agarose bead. This observation is consistent with the observed deterioration of functional activity as measured in ligand-receptor binding force experiments.

To assess the significance of gonadal function in the maintenance of thymic structure, male, sexually mature, 60 days old rats were bilaterally orchidectomized and the volumes of both the thymic compartments, total cellularity of each of them, as well as density (Nv) and mean diameter (D) of thymocytes within the specific thymic regions were stereologically analyzed 3, 7 and 15 days later. Three days after the orchidectomy a decrease in the thymic weight, and a reduction of both the cortical and medullary volumes, were observed. The reduction in cortical volume was followed by a decrease in overall number of the cortical thymocytes, suggesting an enhanced process of thymocyte death. In the same animals, the total number of the medullary thymocytes as well as D remained unchanged. Seven days after orchidectomy both volume of the cortex and total number of the cortical thymocytes reached the control values, while all the changes observed in the medulla of rats 3 days post castration, persisted. In addition, 7 days post castration, the volume of the interlobular connective tissue was increased and this persisted at day 15 post castration. The results indicate that orchidectomy can affect the thymic structure, and possibly the process of intrathymic T cell maturation; the extent of changes depending on the duration of the gonadal deprivation.

The molecular relaxation behavior of an ice-quenched high density polyethylene (HDPE) subjected to solid-state stretching at elevated temperature (100 °C) to various draw ratios (up to Λ=13.7) was examined by means of dielectric spectroscopy. All relaxation zones (α, β and γ, in order of decreasing temperature) between 25 K and melting temperature were studied in the frequency range from 1 kHz to 1 MHz. The changes observed in different dielectric relaxations were related to the orientation-induced modifications of the structural and morphological parameters. In order to investigate orientation-induced structural changes, optical microscopy (OM), scanning electron microscopy (SEM), wide angle X-ray scattering (WAXS), and differential scanning calorimetry (DSC) were employed. Herman's orientation function (fc) was used to quantify the degree of crystal orientation. Complete disappearance of the already weak β relaxation with orientation is attributed to the increase in crystallinity, but the contribution due to a more restricted chain segment mobility in the interlamellar regions of oriented specimens should also be taken into account. Presented results also reveal two different orientation-induced dynamics in the evolution of the dielectric α and γ relaxations connected with the main transformation stages in the drawing of crystalline polymers. The transformation of the initial isotropic into a fully oriented fibrillar structure introduces large changes in the dielectric relaxation spectra of HDPE, especially in the α relaxation zone; by contrast, with further increase in the draw ratio much smaller changes are observed due to the deformation of the fiber structure by longitudinal sliding motions of microfibrils and/or by fibrils slipping past each other.