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A protective effect of two herbs, Glycyrrhiza glabra and Tinospora cordifolia, given as feed additives was observed against the growth inhibitory effect of ochratoxin A (OTA) and associated immunosuppression and biochemical or pathomorphological changes. The feed levels of 3 mg/kg OTA and fine powder of one of both herbs were given during a period of 32 days to female broiler chicks divided into 3 experimental and 1 control groups (14 chicks per group). The observed pathological and biochemical changes, the changes in relative organs’ weight and body weight, and the decrease of antibody titer against Newcastle disease were more pronounced in the OTA-treated chicks without herbal supplementation, and less pronounced in the chicks treated additionally with G. glabra or T. cordifolia as was shown by the better feed performance and the higher body weight in the chicks treated with the herbs. The higher relative weight of lymphoid organs of the chicks supplemented with both herbs revealed their beneficial effects on the immune system. The hepatoprotective effect of both herbs was evident, being stronger in the chicks additionally supplemented with G. glabra shown by the pathomorphological findings and by the lower levels of aspartate transaminase (131.1 U/l) compared to chicks given only OTA (156.0 U/l). A protective effect of T. cordifolia on the bone marrow and kidneys was found as was shown by the lower levels of uric acid (382.9 μmol/l) compared to chicks given only OTA (466.9 μmol/l).

The aim of this work was to investigate the effect of Ochratoxin A (OTA) and Silymarin on serum lysozyme concentrations, complement and betalysin activity in broiler chickens. In this experiment 144 one-day-old Ross 308 male broiler chicks were used. All chicks were divided in four groups of 36 birds each: Group 1: Basal diet (BD) with no supplementation of Ochratoxin A (OTA) and Silymarin; Group 2: BD with 1.0% Silymarin; Group 3: BD with 3.0 mg/kg OTA; Group 4: BD with 3.0 mg/kg OTA plus 1.0% Silymarin. It was found that lysozyme concentration in the 2nd group there is a significant difference to groups 3 and 4. The immunosuppressive effect of Ochratoxin A is underlined but no protective effect of Silymarin in the group 4 was found. The alternative pathway of complement activation (APCA) is affected in the group 4. Betalysine there is a significant decreasing in the group 3 but slightly increasing of Betalysine in 4th group. Based on these results it can be concluded that OTA there is an immunosuppressive effect on the studied traits and there is a positive effect of Silymarin only on serum betalysine.

The protective effects of herbal feed additives Silybum marianum, Withania somnifera and Centella asiatica against the toxic effects of ochratoxin A (OTA) were studied in 70 broiler chicks aged from 11 to 42 days. OTA was given with the feed at levels 5 mg/kg, whereas S. marianum, W. somnifera and C. asiatica were given at levels of 1,100, 4,000 and 4,600 mg/kg, respectively. All chicks were immunised at the age of 14 days against Newcastle disease. A protective effect of all studied herbal additives against the immunosuppressive effect of OTA and associated biochemical or pathomorphological changes was seen. The intensity of macroscopical and histopathological changes, the deviations in relative organs’ weight or body weight, the biochemical changes and the decrease of antibody titer were strongest in the OTA-exposed chicks without herbal supplementation; followed by chicks treated additionally with C. asiatica, whereas the same changes were significantly slighter or not seen in chicks additionally treated with the herbal additives W. somnifera or S. marianum. The slight increase in the serum levels of uric acid and the enzyme activity of aspartate transaminase and alanine transaminase also supported the protective effects of both herbs on the kidneys and/or liver. The strong immunosuppressive effect of OTA on humoral immune response against Newcastle disease was completely prevented in the chicks taking the herbal additives W. somnifera or S. marianum, which was supported by the higher relative weight of immunocompetent (lymphoid) organs in the same chicks. A hepatoprotective effect was found in OTA-exposed chicks treated additionally with W. somnifera and S. marianum, whereas a nephroprotective effect was only found in the chicks additionally treated with S. marianum as observed from the biochemical and pathomorphological findings. The same herbs could be used as a practical approach for safely utilising of OTA-contaminated feed.

The aim of the survey was to determine the prevalence of all types of lesions associated with contact dermatitis in commercial broiler chickens using pathomorphological methods. Contact dermatitis in commercial broiler chickens was monitored for a period of one year. The samples were taken from a fattening Ross 308 hybrid farm. The annual production cycle was 696,000 birds. The investigations were performed by clinical examination of chickens which showed obvious signs of contact dermatitis on their carcasses in the slaughterhouse. The number and type of contact dermatitis lesions in the different flocks were determined through a meat inspection process. In addition to the gross examination, a histological study on a predetermined proportion of tissue samples was conducted. The total number of contact dermatitis lesions was 152,215 (21.87%). The occurrence was most prevalent during the winter-spring and autumn seasons – 88,932 (12.77%), as opposed to 63,283 (9.1%) during the summer period. Lesions on the plantar skin surface of the foot were predominant – 109,272 (15.7%). This was followed by contact dermatitis lesions on the breast, affecting the sternal bursa – 36,888 (5.3%). The contact dermatitis lesions in the tarsometatarsal joint region were the least prevalent – 6,055 (0.87%).

The present study aims to determine the levels of the heavy metals manganese (Mn) and zinc (Zn) contained in the fungicide Mancozeb in the eggs and musculature of the rainbow trout (Oncorhynchus mykiss W.) which have grown in an environment, containing a permissible amount of Mancozeb and fed with or without the carotenoid pigment astaxanthin. The study follows the feeding, then the analysis of the level of Mn and Zn in the eggs and musculature of the rainbow trout, treated with and without the pigment astaxanthin and the fungicide Mancozeb. The determination of Mn and Zn concentrations is performed using a modern method for measuring macro- and microelements with an atomic absorption spectrometer, which is characterized by high selectivity, swiftness and sensitivity. Experimental data show accumulation of Mn and Zn, contained in the fungicide Mancozeb even when its concentration in the habitat does not exceed the maximum permissible levels in the normative documents. As a result, the analysis of the eggs and musculature shows the same trend regarding the accumulation of Mn and Zn. In non-fertilized, as well as in fertilized rainbow trout eggs and musculature, the experimental data show a slight increase of Mn and Zn in the presence of only astaxanthin in the added feed and a significant decrease in these metals in the presence of both astaxanthin and Mancozeb. The supplementation of astaxanthin in the diet can significantly reduce the rate of heavy metals accumulation in fish tissues and eggs, but high concentrations of these pollutants in the aquatic environment over a longer period of time would certainly result in metabolic disturbances in the fish body and reduction of their eggs’ hatchability.

The aim of the present study was to follow up the erythrocyte sedimentation rate (ESR) in healthy female goats during and after 5-day parenteral treatment with amikacin (10 mg/kg), tobramycin (5 mg/kg), apramycin (20 mg/kg), gentamicin (4 mg/kg), kanamycin (10 mg/kg) and spectinomycin (20 mg/kg). Gentamicin and tobramycin caused an initial increase followed by a significant decrease of ESR on the 5th day for gentamicin and the 10th day for tobramycin, respectively, followed by recovery after the treatment. Reversely, amikacin and especially spectinomycin produced an increase of ESR without recovery several days post treatment. Kanamycin caused decrease of ESR on the 5th day without recovery in the subsequent days. Only apramycin did not give rise to increasing of ESR. In conclusion the aminoglycosides, especially tobramycin and gentamicin, caused more severe alterations of ESR than the aminocyclitols.

The experiments for evaluation of the effect of Immunobeta® were performed with turkeys and organically reared layer hens. Turkeys received Immunobeta® at a dose of 4 g/kg feed during the beginning of lay (cold period), thermoneutral period and hot summer period. In hens, two dietary levels of Immunobeta® were tested: 2 g/kg and 4 g/kg. Blood serum and egg white lysozyme levels, alternative pathway of complement activation (APCA) and beta-lysins concentrations were determined. It was found out that Immunobeta® had a beneficial effect on serum lysozyme, APCA activity and beta-lysins in turkeys and hens. The lysozyme concentration in egg white was significantly higher in eggs produced by birds treated with both doses of the immunomodulator. Immunobeta®, offered at a dose of 4.0 g/kg feed had a beneficial effect on natural humoral immunity factors. Applied at a dose of 4.0 g/kg, the tested immunomodulator increased significantly egg white lysozyme concentrations in hens, presuming a higher shelf life of eggs and possibly, better protection of chick embryos.

One of the most important properties of probiotic bacteria is their antimicrobial activity against many species of microorganisms which could be useful to prevent food spoilage caused by certain sensitive bacteria and fungi as well as to control the speed of propagation of potentially pathogenic bacteria by probiotic application. Lactobacillus plantarum is considered one of the probiotic bacteria with broad-est spectrum of antibacterial activity which makes it useful in veterinary, human medicine and food industry. According to a number of studies Lactobacillus plantarum exerts inhibitory activity against ma¬ny Gram-positive and Gram-negative bacteria – Escherichia coli (including E. coli 0157:H7), Pseudomonas aeruginosa, Helicobacter pylori, Yersinia enterocolitica, Campylobacter jejuni, Lis-teria monocytogenes, Staphylococcus aureus, Klebsiella, Salmonella, Shigella, Bacillus, Clostridium, Enterococcus, Lactobacillus spp., etc. as well as a number of moulds and yeasts – Aspergillus, Fusa-rium, Mucor, Candida spp., etc. The main antibacterial compounds of Lactobacillus plantarum are the bacteriocins and organic acids whereas the antifungal compounds are the organic acids, hydroxy fatty acids and cyclic dipeptides. Because of the high antifungal activity of some L. plantarum strains against food spoilage microorganisms they can be used as effective biopreservatives in food industry. Also, some L. plantarum strains could be applied as supporting therapeutic agents in treatment of infections caused by the corresponding susceptible microorganisms.

The purpose of this review is to summarize the information regarding the antimicrobial activity of Lactobacillus acidophilus, an important species of lactic acid bacteria. Lactic acid bacteria are constituents of many beneficent for the consumer's health food products. They are considered potentially promising in the strategy to combat infections and prevent the growth of spoilage microorganisms, and also have antimutagenic, anticarcinogenic, hypolipidemic and hypocholesterolemic properties, improve the lactose metabolism, stimulate the immune system, etc. In the resent years Lactobacillus acidophilus is considered the main probiotic species in the intestinal tract of healthy humans and is widely used in functional dairy foods. It produces a variety of metabolic products with antimicrobial properties, including organic acids and bacteriocins, such as lactacins B and F, acidophilin, acidocin, acidophilucin, acidophilicin, which are active against many pathogenic and spoilage microorganisms - Escherichia coli (including Escherichi coli 0157:H7), Staphylococcus aureus, Pseudomonas aeruginosa, Listeria monocytogenes, Vibrio parahaemolyticus, Vibrio cholerae, Helicobacter pylori, Klebsiella, Salmonella, Shigella, Bacillus, Clostridium, Mucor, Aspergillus, Fusarium, Trichoderma and Candida spp., etc. Because of the above mentioned reasons Lactobacillus acidophilus could be used as an alternative therapeutic agent against infections caused by susceptible microorganisms. On the other hand Lactobacillus acidophilus based antimicrobial products (mainly bacteriocins and pure cultures) could also be applied to food products to prevent the growth of spoilage microorganisms and food-borne pathogens. To better understand the mode of action and the spectrum of antifungal activity more clinical and laboratory studies of different Lactobacillus acidophilus strains are required.

The aim of the present investigation is to report the prevalence of spontaneous fractures associated with leg skeletal pathology and compromised welfare in commercial broiler chickens. Our studies focused on fractures of different leg segments (femur, tibiotarsus, tarsometatarsus) detected as incidental findings during pathoanatomic examinations in cases of rickets, tibial dyschondroplasia (TD), and femoral head necrosis (FHN). The morphogenetic and etiopathogenetic aspects of the findings were further investigated through histopathologic, bacteriologic, and bone mineral analyses. The gross anatomy study showed that in about 10% of bones affected by rickets-specific lesions, fractures of the proximal tibiotarsus were present. A relatively low percentage (6.5%) of fractures of the same anatomic location could be attributed to TD lesions. The highest prevalence of fractures (68.5%), mainly of the proximal femur, was associated with FHN and osteomyelites. The results from the large-scale field surveys allowed us to confirm that the prevalence of spontaneous bone fractures of the legs in broiler chickens was largely associated with FHN, rickets, and TD. The poor vascularization of the grown prehypertrophic cartilage in cases of rickets and TD, as well as the osteolytic lesions in FHN, resulted in degenerative, necrobiotic processes which may entail bone fractures.Estudios anatomopatológicos comparativos sobre la incidencia de fracturas asociadas con patologías esqueléticas de la pierna en pollos de engorde comerciales. El objetivo de la presente investigación es informar sobre la prevalencia de fracturas espontáneas asociadas con patologías esqueléticas de la pierna y con problemas de bienestar en pollos de engorde comerciales. Estos estudios se centraron en fracturas de diferentes segmentos de la pierna (fémur, tibiotarso, tarsometatarso) detectados como hallazgos incidentales durante los exámenes anatomopatológicos en casos de raquitismo, discondroplasia tibial (TD) y necrosis de la cabeza de fémur (FHN). Los aspectos morfogenéticos y etiológico-patogenéticos de los hallazgos se investigaron más a fondo mediante análisis histopatológicos, bacteriológicos y por determinaciones de minerales óseos. El estudio de anatomía macroscópica mostró que en aproximadamente el 10% de los huesos afectados por lesiones específicas de raquitismo, se presentaban fracturas del tibiotarso proximal. Un porcentaje relativamente bajo (6.5%) de fracturas de la misma ubicación anatómica podrían atribuirse a las lesiones por discondroplasia tibial. La mayor prevalencia de las fracturas (68.5%), principalmente del fémur proximal, se asociaron con necrosis de la cabeza del fémur y osteomielitis. Los resultados de los muestreos de campo a gran escala permitieron confirmar que la prevalencia de fracturas óseas espontáneas de las patas de pollos de engorde se asociaba en gran medida con necrosis de la cabeza del fémur, raquitismo y discondroplasia tibial. La pobre vascularización del cartílago prehipertrófico con crecimiento en casos de raquitismo y discondroplasia tibial, así como las lesiones osteolíticas en la necrosis de la cabeza del fémur resultaron en procesos degenerativos y necrobióticos que pueden estar asociados con fracturas óseas.

A survey was made of the literature concerning the occurrence and incidence of mycotoxic nephropathy in pigs and chicks in different countries. Various etiological factors contributing to the development of the disease were considered. The main nephrotoxic fungi as well as the specific conditions for their growth and toxins production were briefly described. A survey was made about the most frequent nephrotoxic fungal contaminants in various feedstuffs from plant origin. In addition, their natural quantities and importance for development of mycotoxic porcine/chick nephropathy (MPN/MCN) are also explored. In addition, a survey was made of the feedstuffs representing the most favorable environment for nephrotoxic fungal growth as well as the most favorable storehouse conditions for this fungal growth were shortly described. The significance of some underestimated fungal species, which can provoke kidney damage, was studied. The importance of joint mycotoxin interaction and newly identified fungal metabolites in the complex etiology of mycotoxic nephropathy ranged in some countries is deeply investigated. The toxicity of the low contamination levels of some combinations of mycotoxins often administered by pigs and chicks in the practice was carefully studied.

We found that a novel optically-induced in-plane separation of plasmas of opposite charge is responsible for the large ring emission pattern around a laser excitation spot observed in modulation doped quantum well (QW) structures. The charge separation is a result of an interplay between the electrical field applied perpendicular to the QW and the diffusion of optically generated carriers in the QW plane. Excitonic emission at the sharp boundary between the positive and negative charges forms the ring. The initially hot carriers that are generated optically, cool as they diffuse and are therefore cold before they recombine at the ring. Such separation of charges was only observed when the excitation energy is above the barrier height of the QW. The effect of the lower energy excitation is found to be dramatically different, resulting in a shrinkage and even a total collapse of an existing ring pattern. © 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim.

Strain and dimensional confinement can be used to tune magnetic and ferroelectric properties or enhance device performance. In epitaxial films, the different lattice spacing of an underlying substrate can be used to impose a biaxial strain. We have studied the effect of the substrate-induced biaxial strain on the electrical conductivity and magnetic properties of manganite compounds. Epitaxial (001) La0.7Sr0.3MnO3 thin films have been grown by reactive molecular-beam epitaxy (MBE) on single crystalline substrates, varying the substrate-induced biaxial strain from −2.3% to +3.2%. The strain caused the Curie temperature to decrease by up to 100 K in very good agreement with the predictions of Millis et al. [A. J. Millis, T. Darling, and A. Migliori, J. Appl. Phys. 83, 1588 (1998)]. The effect of dimensional confinement on manganites was also investigated in thin films by synthesizing a superlattice of two formula-unit-thick layers of CaMnO3 separated by CaO double layers, i.e., the n=2 Ruddlesden-Popper phase Ca3Mn2O7. Magnetization measurements on 30 nm thick (001)-oriented Ca3Mn2O7 thin films grown on (110) YAlO3 substrates by MBE reveal a Neél transition temperature of TN=115 K, similar to bulk Ca3Mn2O7, but 10 K lower than thick CaMnO3 films grown on this same substrate.

The objective of these experimental trials was to determine the effect of a mannan oligosaccharide (MOS) derived from the outer cell wall of Saccharomyces cerevisiae strain 1026 on the growth performance and immune status of rainbow trout. Two experiments were conducted, one with eight net cages and the other with eight raceways. The net cage experiment (42 days) involved 14,400 fish with an initial average weight of 30 g. The raceway experiment (90 days) was conduced with 40,000 fish with an initial average weight of 101 g. Both experiments compared a commercial extruded diet with and without 2,000 ppm MOS supplementation. The calculated daily feed was supplied in six equal rations. Body weight, feed intake, and mortality were recorded and samples were taken for analysis of indicators of immune status. All data were subjected to ANOVA, with a net cage or raceway regarded as an experimental unit. Significantly improved performance and immune status were observed in the net cage trial—improved weight gain of 13.7% (P

During the past ten years, coupled quantum wells have emerged as a promising system for experiments on Bose condensation of excitons, with numerous theoretical1,2,3,4,5,6 and experimental7,8,9,10,11,12 studies aimed at the demonstration of this effect. One of the issues driving these studies is the possibility of long-range coherent transport of excitons. Excitons in quantum wells typically diffuse only a few micrometres from the spot where they are generated by a laser pulse; their diffusion is limited by their lifetime (typically a few nanoseconds) and by scattering due to disorder in the well structure. Here we report photoluminescence measurements of InGaAs quantum wells and the observation of an effect by which luminescence from excitons appears hundreds of micrometres away from the laser excitation spot. This luminescence appears as a ring around the laser spot; almost none appears in the region between the laser spot and the ring. This implies that the excitons must travel in a dark state until they reach some critical distance, at which they collectively revert to luminescing states. It is unclear whether this effect is related to macroscopic coherence caused by Bose condensation of excitons.

The adsorption of acetic acid on the Cu(110) surface has been investigated by the time-of-flight electron stimulated desorption ion angular distribution technique by observing H+(D+) ions from the methyl groups. The activated conversion of acetic acid to acetate has been witnessed by observing the formation of oriented acetate species. It has been found that the activation energy for acetate formation varies from 0.39±0.06 eV at low coverage to 1.1±0.1 eV at high coverage, possibly because of acetic acid stabilization at high coverage by hydrogen bonding. Methyl groups are oriented with one C–H bond azimuthally directed in the 〈110〉 direction. At high coverage, the methyl groups are tilted slightly in the 〈110〉 direction due to repulsive acetate–acetate interactions. The activated rotation of the methyl groups on adsorbed acetate is clearly observed by the electron stimulated desorption ion angular distribution method and the barrier height for CH3 rotation is estimated to be 12±6 meV, and for CD3 group...

The striped structure of the partially oxidized Cu(110) surface has been studied using a novel technique, momentum-resolved electron stimulated desorption ion angular distribution (ESDIAD) Long …O–Cu–O… strings oriented in the 〈001〉 direction and exhibiting attractive interactions with each other form periodically arranged stripes with widths in the nanometer range [D. J. Coulman et al., Phys. Rev. Lett. 64, 1761 (1990); K. Kern et al., ibid. 67, 855 (1991)]. Two different oxygen sites were detected, leading to a twofold symmetrical four-beam O+ ESDIAD pattern with 22° tilting of the beams in the 〈110〉 azimuth (A) direction and 8° in the 〈001〉 azimuth (B) direction. The relative intensities of the four beams have been compared for a wide range of oxygen coverages leading to a model in which the A beams correspond to O+ ions desorbing from the edges of the stripes and the B beams from the internal regions of the stripes. This model is confirmed by studying the effect of the coadsorption of Ar at 32 K on t...

Mycotoxic nephropathy was induced in eighteen young pigs by mouldy diets containing 0.5 ppm ochratoxin A (OTA) and/or 10 ppm fumonisin B1 (FB1) for three months. While the most obvious damages provoked by OTA were seen in the kidneys as expressed by the strong degenerative changes in proximal tubules and fibrosis in kidneys, FB1 was found to induce an increase in permeability of vessels mainly in lung, brain, cerebellum or kidneys and slight to moderate degenerative changes in kidneys. Pathomorphological damages in pigs exposed to both mycotoxins simultaneously present a combination of the main lesions provoked by each mycotoxin alone being stronger in their expression. Biochemical investigations as expressed by the increase of serum creatinine, urea and enzyme activity of ASAT/ALAT and by the decrease of serum cholesterol, total protein, albumin and glucose were strongest in pigs exposed to both mycotoxins simultaneously as can be anticipated form the strongest lesions in the kidneys. Both mycotoxins and their combination were found to disturb powerfully humoral immune response in all experimental pigs as expressed by the strong decrease in antibody titer against Morbus Aujesky at days 21 and 35 after vaccination. Having in mind that the feed levels of the both mycotoxins as well as the exposure time and the pathological findings corresponded to those in some spontaneous cases of porcine nephropathy in Bulgaria and South Africa, it can be concluded that the same mycotoxins are involved in the observed field cases of that nephropathy.

Spontaneous nephropathy in pigs seen in South Africa was found to have multi-mycotoxic etiology involving several mycotoxins such as ochratoxin A (OTA), penicillic acid (PA) and fumonisin B1 (FB1) in addition to a not yet identified mycotoxin. Contamination levels of OTA were comparatively low (67–75 μg/kg) in contrast to high contamination levels of FB1 (5,289–5,021 μg/kg) and PA (149–251 μg/kg). A heavy contamination with Gibberella fujikuroi var. moniliformis and Penicillium aurantiogriseum complex (mainly P. polonicum) was observed in the fed forages in contrast to the light contamination with Aspergillus ochraceus, P. verrucosum and P. citrinum. The pathomorphological picture of this nephropathy was found to differ from the classical description of mycotoxic porcine nephropathy as originally made in Scandinavia by the extensive vascular changes.

We report the magnetic and electrical characteristics of polycrystalline ${\mathrm{FeTiO}}_{3}$ synthesized at high pressure that is isostructural with acentric ${\mathrm{LiNbO}}_{3}$ (LBO). Piezoresponse force microscopy, optical second harmonic generation, and magnetometry demonstrate ferroelectricity at and below room temperature and weak ferromagnetism below $\ensuremath{\sim}120\text{ }\text{ }\mathrm{K}$. These results validate symmetry-based criteria and first-principles calculations of the coexistence of ferroelectricity and weak ferromagnetism in a series of transition metal titanates crystallizing in the LBO structure.

We report the magnetic and electrical characteristics of polycrystalline FeTiO_{3} synthesized at high pressure that is isostructural with acentric LiNbO_{3} (LBO). Piezoresponse force microscopy, optical second harmonic generation, and magnetometry demonstrate ferroelectricity at and below room temperature and weak ferromagnetism below approximately 120 K. These results validate symmetry-based criteria and first-principles calculations of the coexistence of ferroelectricity and weak ferromagnetism in a series of transition metal titanates crystallizing in the LBO structure.

We show that amorphous alloy powders of TiSi can be produced over a broad compositional range by mechanical alloying of the elemental powders in a vibro mill. The mechanism of amorphous phase formation and the glass-forming range are investigated by means of X-ray diffraction, differential thermal analysis and scanning electron microscopy. To our best knowledge amorphous TiSi alloy has not until now been produced by mechanical alloying.

IT has been observed that an androgenic effect can be induced in broiler chickens by supplementing their diet with finely ground wood shavings from the African tree Funtumia latifolia ([Smith and Wells 1978][1]). That study was motivated by the observation that female chicks adopted a male

The appearance of a luminescence ring around a central illumination spot in quantum well structures is now well understood in terms of charge separation between the electron and hole gasses in the quantum well region with the ring appearing at their boundary. We propose a slightly modified model including Coulomb interaction between the electron and hole gas and their image charge. © 2005 Elsevier Ltd. All rights reserved.

The dramatic appearance of luminescence rings with radius of several hundred microns in quantum well structures can be understood through a fairly simple nonlinear model of the diffusion and recombination of electrons and holes in a driven nonequilibrium system. The ring corresponds to the boundary between a positive hole gas and a negative electron gas in steady state. While this basic effect is now well understood, we discuss several other experimental results which can not be explained by this simple model., Comment: 8 pages, 5 figures

We report on new experiments and theory that unambiguously resolve the recent puzzling observation of large diameter exciton emission halos around a laser excitation spot in two dimensional systems. We find a novel separation of plasmas of opposite charge with emission from the sharp circular boundary between these two regions. This charge separation allows for cooling of initially hot optically generated carriers as they dwell in the charge reservoirs for very long times.

The combined toxic effect of ochratoxin A (OTA) and penicillic acid (PA) on the body mass, the weight and pathomorphology of some internal organs was studied in 85 broiler chickens fed a mouldy diet containing 130, 300 or 800 ppb OTA and 1000-2000 ppb PA. The main pathomorphological changes were cloudy swelling and granular degeneration in the epithelium and mononuclear cell proliferation and activation of capillary endothelium in the kidney and liver; degenerative changes and depletion of lymphoid cells in lymphoid organs (bursa of Fabricius, thymus and spleen) were also seen. Protective effects of 5% total water extract of artichoke and a new natural phytosubstance Rosallsat against these pathomorphological changes were observed. A significant decrease in body mass and relative weight of lymphoid organs was found after 6 weeks of exposure and a greater decrease after 10 weeks of exposure to OTA and PA, and a protective effect of artichoke extract and a slight effect of Rosallsat against that decrease was observed. A significant increase in relative weight of liver and kidneys was also observed as well as a protective effect of artichoke extract against that increase. The quantity of OTA and the percentage of positive samples were significantly lower in tissues of chickens treated with artichoke extract or Rosallsat in addition to OTA than in those treated with only OTA.

We show that undoped coupled quantum well structures of GaAs and InGaAs have a magnetoresistance effect which leads to a wavelength shift of the optical spectrum. This effect allows the optical emission to be used to detect magnetic field in the range 0-0.5 T.

A comprehensive study of the exciton relaxation processes in Cu2O has led to some surprises. We find that the ortho-para conversion rate becomes slower at high stress, and that the Auger nonradiative recombination rate increases with stress, with apparently no Auger recombination at zero stress. These results have important consequences for the pursuit of Bose-Einstein condensation of excitons in a harmonic potential., 10 figures, 1 table

not Available.

A novel optically induced, in-plane separation of electrons and holes in modulation doped quantum wells leads to a long-lifetime supply of dense gas of thermalized cold excitons, forming ring emission patterns with large diameters