Histopatološka analiza jetre riba (Barbus meridionalis petenyi Heckel) iz akumulacije Trebeništa

The Barbus meridionalis petenyi Heck. is a typical benthophagous fish, feeding on the zoobenthos and plant components and thanks to its sensitivity to the changes in surrounding medium is an ideal object for indication of the health of aquatic ecosystems. The Teleostei fish liver is susceptible to numerous, both toxic and metabolic, disturbances. Liver pieces of 40 individuals collected from Trebeništa Reservoir in July 1999, were excised and processed for standard histopathological analysis. The obtained results revealed pathological changes in the liver tissue including parenchyme cell necrosis associated with hemorragia.Barbus meridionalis petenyi Heck. tipična je bentofagna riba koja se hrani zoobentosom i dijelovima biljaka, a zbog svoje osjetljivosti na promjene u okolišu idealan je objekt za određivanje zdravlja vodenih ekosustava. Jetra riba koštunjača podložna je mnogobrojnim toksičnim i metaboličkim promjenama. U srpnju 1999. prikupljeni su iz akumulacije Trebeništa uzorci jetre 40 riba koji su obrađeni standardnom histopatološkom analizom. Prikupljeni podaci otkrili su patološke promjene u tkivu jetre, uključujući nekrozu parenhimskih stanica povezanu s hemoragijom

Dielectric relaxation study of gamma irradiated oriented low-density polyethylene

The influence of drawing, gamma irradiation and accelerated aging on the dielectric relaxation of low-density polyethylene has been studied using dielectric loss tangent measurements in the temperature range from 25 to 325 K and in the frequency range from 10(3) to 10(6) Hz. The intensity, position and activation energy of the gamma- and beta-dielectric relaxations were found to be strongly dependent upon the changes in the microstructure of the amorphous phase induced by uniaxial orientation, oxidation and crosslinking. (C) 2003 Elsevier Science Ltd. All rights reserved

Thermal wave propagation in media with thermal memory induced by pulsed laser irradiation

If a sample is exposed to the influence of laser radiation the part of its energy is absorbed and converted into heat. The heat, generated in this way, is transferred through the sample as heat waves, resulting in various effects (for example, photothermal effects). A large number of nondestructive diagnostic methods are based on recording of these effects. In a certain number of materials excited by laser pulses, such as complex biological materials, polymers, metal excited by very short laser pulses, etc., the property of thermal memory become significant. Starting with the hyperbolic equation that describes heat transfer processes of such media, we have developed a model of laser pulse-excited heat waves propagation in order to enable application of photothermal techniques in characterization of these media. The cases of optically opaque and transparent samples are considered. The influence of various backings on photothermal waves has also been analyzed. The results are compared to the previous models. (C) 2003 Elsevier Science Ltd. All rights reserved.10th Tihany Symposium on Radiation Chemistry, Aug 31-Sep 05, 2002, Sopron, Hungar

Ancient civilizations already had an impact on cladoceran assemblages in Europe's oldest lake

Lake Ohrid (Republic of North Macedonia) is the oldest and most biodiverse freshwater lake in Europe. While the lake has recently been under severe anthropogenic pressure, historical impacts are poorly studied. We used paleolimnological information, particularly from cladoceran assemblages, to describe the long-term anthropogenic impacts that the lake has experienced over the last 6650 years. Multivariate analyses of cladoceran abundances together with selected environmental indicators were used to distinguish natural from human impacts and to track the direction and causes of observed changes. In addition, morphological analyses of planktonic Bosmina allowed us to assess the effects of fisheries and aquaculture on cladoceran phenotypic plasticity. Our findings reveal that the lake has been regularly exposed to anthropogenic impacts during the last millennia, including habitat deterioration, shifts in the food web and species introductions. Before 2400 cal yr BP, cladocerans showed the highest diversity values, and the relatively larger size of Bosmina longirostris indicated limited zooplanktivory. Since 2400 cal yr BP, coinciding with the foundation of the town of Ohrid and elevated erosion and deforestation, there has been a progressive loss of littoral taxa. Since 1700 cal yr BP, fish introductions have increased, inducing morphological changes in Bosmina, which resulted in a significant decrease in body size and antennule length and an increase in mucro and antennule angle. We also show that the present-day cladoceran community differs from the prehistoric community due to the invasion of Diaphanosoma. Overall, our results highlight the sensitivity of this unique ecosystem to human alterations, which began before the Anthropocene

Heat flow in thermoplastics with thermal history effects

In thermosets and semicrystalline and/or amorphous thermoplastics, processing can result in internal molecular stress, which relieves on reheating (thermal history effects). The relief of these stresses appears as a small endothermic relaxation even after glass transition. Non reversing transitions in polymers also indicate the existence of thermal history effects. These effects can be modeled thereby improving interpretation of many experimental results. In this paper, a mathematical model for thermal history effects and heat flow in thermoplastics has been developed.4th Yugoslav-Materials-Research-Society Conference, Sep 10-14, 2001, Herceg Novi, Yugoslavi

Heat flow in thermoplastics with thermal history effects

In thermosets and semicrystalline and/or amorphous thermoplastics, processing can result in internal molecular stress, which relieves on reheating (thermal history effects). The relief of these stresses appears as a small endothermic relaxation even after glass transition. Non reversing transitions in polymers also indicate the existence of thermal history effects. These effects can be modeled thereby improving interpretation of many experimental results. In this paper, a mathematical model for thermal history effects and heat flow in thermoplastics has been developed.4th Yugoslav-Materials-Research-Society Conference, Sep 10-14, 2001, Herceg Novi, Yugoslavi