Impact of defects on photoexcited carrier relaxation dynamics in GeSn thin films.

We report the results of a study that was conducted to investigate the recombination paths of photoexcited charge carriers in GeSn thin films. The charge carrier lifetime was predicted as a function of temperature from a description of photoconductivity transients, assuming co-influence of Shockley-Read-Hall and radiative carrier recombination paths. We identify that dislocations are the source of a band of electronic states with the highest occupied state at E V + (85÷90) meV that acts as Shockley-Read-Hall centers determining the charge carrier lifetime. The photoluminescence (PL) and photoconductivity spectroscopy have been applied to distinguish between the contribution of both band-to-band and dislocation-related electron transitions. The PL band was found to demonstrate a low-energy shift of about 80 ± 20 meV relative to the edge of the photoconductivity spectra in the indirect bandgap GeSn films with dislocations. The role of a different nature deeper acceptor level at E V + (140 ÷ 160) meV in the recombination processes of the GeSn layers with better structural quality and the Sn content higher than 4% was discussed. This detailed understanding of the recombination processes is of critical importance for developing GeSn/Ge-based optoelectronic devices.

Formation and Luminescent Properties of Al2O3:SiOC Nanocomposites on the Base of Alumina Nanoparticles Modified by Phenyltrimethoxysilane.

Al2O3:SiOC nanocomposites were synthesized by thermal treatment of fumed alumina nanoparticles modified by phenyltrimethoxysilane. The effect of annealing temperature in inert ambient on structure and photoluminescence of modified alumina powder was studied by IR spectroscopy as well as photoluminescence spectroscopy with ultraviolet and X-ray excitation. It is demonstrated that increase of annealing temperature results in formation of silica precipitates on the surface of alumina particles that is accompanied by development and spectral evolution of visible photoluminescence. These observations are discussed in terms of structural transformation of the surface of Al2O3 particles.

[Differential diagnosis of early central choroidal melanoma and late stage age-related macula degeneration].

Clinical signs characteristic for early central choroidal melanoma (42 patients) and late stage age-related macula degeneration according to AREDS (47 patients) were determined in 89 patients. These signs allow to differentiate between tumor and degenerative process thus providing appropriate treatment.

[Assessment of the clinical and functional results of laser coagulation of retinal drusen in the central zone of the eye grounds].

Macular drusen are known to be a major risk factor of age-related macular degeneration (ARMD) of the retina. The use of laser coagulation of macular drusen to prevent the progression of a dystrophic process remains to be disputable question so far. This paper presents the clinical and functional results of laser coagulation of macular drusen in 30 patients with bilateral retinal ARMD. The routine ophthalmological study, photorecording, fluorescence angiography of the fundus of the eye, optic coherent tomography, and electrophysiological studies indicated macular drusen regression, increased visual acuity, and better electrophysiological parameters. Choriodal neovascularization and exudative complications did not develop in both the early and late follow-up periods.

[Modern understanding of the pathogenesis of pre-proliferative diabetic retinopathy]. / Sovremennye predstavleniia o patogeneze proproliferativnoi diabeticheskoi retinopatii.

Diabetic retinopathy (DR) is a severe and late complication of diabetes mellitus leading, in a majority of cases, to poor vision and blindness. The pathogenesis of DR and of the main diseases is complicated; many of its chains are not explained until now. Hyperglycemia is the key reason of many metabolic disorders in diabetes mellitus resulting in vascular complications. An irreversible glycosylation of proteins and activation of free-radical lipid peroxidation occur under the conditions of a long-term hyperglycemia; it brings about structural changes in the retinal microvessel walls, disorders of hematoretinal barrier and transcapillary metabolism as well as hemodynamic and vasoocclusive changes provoking the development of retinal ischemia.

A review of riverine fluxes of hexachlorocyclohexane and DDT to the Azov and Black seas from the former USSR and Russian Federation.

While the Azov and Black seas are subject to anthropogenic pollution to a much higher extent than any other seas, this has been little studied with only a few critical reviews of contaminant fluxes to these seas. Riverine fluxes of the organochlorine pesticides (OCPs) hexachlorocyclohexane (HCH) and DDT to the Azov and Black seas from the former Soviet Union and Russian Federation were thus reviewed for 1986 to 1996. The review was based on official data and data obtained by independent specialists. The amount of HCH used, and the intensity of usage, in these river catchments decreased during the review period. Concurrently, OCP concentrations in the rivers and their fluxes also decreased according to both official and independent data. A comparison of the official and the independent data sets for 1988 revealed significant differences, reflecting the need for more rigorous sampling and analytical protocols for both data sets. According to the OGSNK/GSN data, the flux rates of the five largest rivers were ranked (from largest to smallest) as follows: Don > Dnestr > Danube > Kuban > Dnepro (alpha-HCH); Danube > Don > Dnestr > Dnepro > Kuban (gamma-HCH); Dnestr > Danube > Don > Dnepro-Kuban (DDT+DDE). For rivers with lower annual riverine discharges, the DDT fluxes were surprisingly high (0.43 to 1.49 tonnes a(-1)). According to independent data for 1988 the rankings of the rivers was: Danube > Don > Dnepro > Dnestr > Kuban (alpha-HCH); Danube > Don > Dnestr > Dnepro > Kuban (gamma-HCH); Danube > Dnepro > Dnestr > Don > Kuban (DDT); Danube > Dnepro > Don > Kuban > Dnestr (DDE). The DDT flux estimates for small rivers derived from independent data were 19 to 46 times lower than those calculated using OGSNK/GSN data. According to the independent data, the total riverine OCP transport from the Russian Federation into the Azov Sea from 1988 to 1996 was 1.288 tonnes of gamma-HCH+alpha-HCH and 1.693 tonnes of DDT+DDE while for the Black Sea they were 3.830 tonnes and 5.116 tonnes for gamma-HCH+alpha-HCH and DDT+DDE, respectively.

[Thrombocytopathies and their role in the development of hemorrhagic syndrome in vascular diseases of the fundus oculi]. / Trombotsitopatii i ikh rol' v razvitii gemorragicheskogo sindroma pri sosudistykh zabolevaniiakh glaznogo dna.

Examinations of 407 patients with angiological disorders of the fundus oculi (diabetic retinopathy, retinal vein thrombosis, central chorioretinal dystrophy, retinal angiitis) revealed relapsing hemorrhagic syndrome in 40% (170) patients. No thrombocytopenia was revealed in any of the patients, which suggests qualitative impairment of platelets in such patients. Evaluation of the platelet aggregation coefficient (PAC) using thrombin aggregation inducers and adenosine diphosphate disodium revealed a statistically significant decrease of PAC for one or both aggregants in all 170 patients with the hemorrhagic syndrome, which indicated platelet dysfunction. A course of intramuscular injections of 1% adenosine triphosphate sodium normalized platelet function and stimulated resorption of hemorrhages.

[L-arginine in the lacrimal fluid of patients with diabetic retinopathy and the possible role of nitric oxide in the pathogenesis of retinal ischemia]. / L-arginin v sleznoi zhidkosti bol'nykh s diabeticheskoi retinopatiei i vozmozhnaia rol' oksida azota v patogeneze ishemii setchatki.

The concentrations of 23 free amino acids and some other components (ammonium, urea, ethanolamine) were measured by liquid chromatography in the lacrimal fluid of 40 patients with diabetic retinopathy (DR) (15 with the preproliferative stage and 25 with proliferative stage) and 15 normal subjects. The mean level of L-arginine in DR patients was 3.5-5 times decreased in comparison with the control (1.2 +/- 0.4 vs. 6.1 +/- 1.5%, p < 0.005). The level of ornithine inversely correlated with the level of L-arginine. The mean level of ornithine in DR patients was increased twofold (12.3 +/- 1.0 vs 6.8 +/- 1.0% in the control, p < 0.005). The mean concentrations of other amino acids virtually did not change. Decreased level of L-arginine in the lacrimal fluid of DR patients may be indicative of increased utilization of this amino acid in retinal ischemia, which, according to the modern concept of DR pathogenesis, can be caused by activation of nitric oxide production. Measurement of L-arginine in the lacrimal fluid can serve as a simple noninvasive and reliable method for early diagnosis of ischemic changes in the retina.

[Effect of therapy with blood component (activated autoplasma) on blood glutathione level in patients with vascular abnormalities on the fundus oculi]. / Vliianie gemokomponentnoi terapii (aktivirovannoi autoplazmy) na uroven' glutationa v krovi u bol'nykh s sosudistoi patologiei glaznogo dna.

Thirty-three patients with central chorioretinal dystrophy, 18 with proliferative diabetic retinopathy, and 15 controls without ocular diseases were examined. All patients were treated by blood components. The treatment started with activation of blood plasma platelets. Glutathione was measured in two portions of plasma: intact and containing platelet activation products. The content of glutathione was higher in activated autoplasma of 21 patients with central chorioretinal dystrophy and 6 patients with diabetic retinopathy than in intact plasma by 107 and 72%, respectively. A decrease in glutathione level in activated autoplasma was observed in 1 patient with central chorioretinal dystrophy and in 9 with diabetic retinopathy. Hence, antioxidant defense is decreased in diabetic retinopathy, since glutathione is involved in reduction of organic hydroperoxides.

[Effects of activated autoplasma on platelet aggregation in patients with vascular diseases of the fundus oculi]. / Vliianie aktivirovannoi autoplazmy na agregatsiiu trombotsitov u bol'nykh s sosudistymi zabolevaniiami glaznogo dna.

Activated autoplasma (AAP) was used in the treatment of patients with central chorioretinal dystrophy and diabetic retinopathy. The therapeutic effect of AAP injected intrabulbarly and its effect on platelet aggregation in the peripheral blood after intramuscular and intravenous injections were assessed. Intravenous AAP was found to exert a manifest disaggregating effect, whereas intramuscular injections did not affect platelet aggregation.

[Hemocomponent therapy of central involution chorioretinal dystrophy]. / Gemokomponentnaia terapiia tsentral'noi involiutsionnoi khorioretinal'noi distrofii.

Hemocomponent therapy was used in 181 patients (347 eyes) with central chorioretinal dystrophy. Activated autoplasma possessing a marked resorptive effect, consisting in resorption of hemorrhages and exudations on the fundus oculi, was used. Vision acuity improved in 75% of examined eyes by an average of 0.2 diopters.

[Results of phlebo-destruction surgery and blood rheology indicators in patients with central chorioretinal dystrophy]. / Rezul'taty operatsii flebodestruktsii i gemoreologicheskie pokazateli u bol'nykh s tsentral'noi khorioretinal'noi distrofiei.

Hemorheologic parameters were analyzed in 34 patients with central chorioretinal dystrophy and the effects of these parameters on the outcome of phlebodestruction studied. Blood viscosity and red cell aggregation coefficient were found increased in such patients. Phlebodestruction was found ineffective in the patients with significant disturbances of blood rheology. The authors come to a conclusion on the usefulness of using blood rheologic parameters for the prediction of phlebodestruction surgery outcome in patients with central chorioretinal dystrophy.

[Trans-scleral cryopexy in hemophthalmos of diabetic etiology]. / Transskleral'naia kriopeksiia pri gemoftal'makh diabeticheskogo geneza.

Trans-scleral cryopexy (TSC) was carried out in 81 eyes with recurrent hemophthalmos of diabetic genesis. 73 patients were followed up after surgery for a period of 3 months to 5 years. Hemophthalmos resolved in 80 percent of eyes (completely in 60, partially in 20 percent). The condition recurred in 10 percent of eyes, detachment of the retina developed in 13, neovascular glaucoma in 4 percent, and cataract progressed in 10 percent of eyes. Vision acuity improved in 36 percent of eyes; the best results were observed in type II diabetes mellitus. TSC proved to be an effective method for the management of hemophthalmos of diabetic nature.

[Surgical destruction of varicose veins in involutional central chorioretinal dystrophy]. / Operatsiia destruktsii vortikoznykh ven pri involiutsionnoi tsentral'noi khorioretinal'noi distrofii.

The authors analyze the results of this surgery. The treatment efficacy has been monitored by traditional ophthalmological methods: rheo-ophthalmography, fluorescent angiography, examination of the central visual field, rhythmic and macular electroretinography. The vision acuity has improved in 70% of the cases. Remote results evidence a high stability of the results in the majority of cases.