123 research outputs found

    Towards conserving regional mammalian species diversity: a case study and data critique

    Get PDF
    Species richness maps were derived for the Transvaal region from two different databases, namely a primary point database based on actual survey records and a generalized distribution map database. It is shown that sixteenth degree grid square (= QDS in Lombard 1995) species richness maps based on these two data sets for the region are highly disparate, which may be attributed to overestimation of species distributions by distribution maps and uneven sampling reflected in the primary point database. The limitations and problems associated with the two databases are discussed. Of the 10% most species-rich grid squares based on distribution maps and primary point data, 33,3% and 12% respectively are fully encompassed by existing conservation areas and are well represented in the sixteenth degree grid square networks selected by two iterative reserve selection algorithms

    Artificial neural network surrogate modeling for uncertainty quantification and structural optimization of reinforced concrete structures

    Get PDF
    Optimization approaches are important to design sustainable structures. In structural mechanics, different design objectives can be defined, for example, to minimize the required construction material or to maximize the structural durability. In this paper, the durability of a reinforced concrete (RC) structure is assessed by advanced finite element (FE) models to simulate the cracking behavior and the chloride transport process. The corrosion initiation time is used as durability measure to be maximized within an optimization approach, where the concrete cover is defined as design variable. The variability of structural loads and material parameters and unavoidable construction imprecision leads to a probabilistic reliability and durability assessment, where aleatory as well as epistemic uncertainties are quantified by random variables, intervals and probability-boxes. The FE simulation models cannot directly be applied to structural analyses and optimizations with polymorphic uncertain parameters and design variables because of the high computational demand of the multi-loop algorithm (Monte Carlo simulation, interval analysis, global optimization). In this paper, a new surrogate modeling strategy is presented, where artificial neural networks are trained sequentially to speed-up the coupled mechanical and transport simulation FE models. The new approach is applied to the uncertainty quantification and the structural durability optimization of a RC structure

    Amplitude changes in the electrophysiological response of retinal cells during simultaneous current stimulation

    Get PDF
    Purpose : Ocular electrical stimulation exhibit potential for the treatment of neurodegenerative ocular diseases. However, the underlying mechanism in the retinal cells remains subject of research. Studies applying transcranial electrical stimulation show that direct current stimulation (DCS) over the visual cortex manipulates the amplitudes of visual evoked potentials. An anodal DCS leads to increased amplitudes while a cathodal DCS decreased these amplitudes. We hypothesize that the retinal cells show similar reactions. Methods : We stimulated 15 volunteers (8m, 7f, 23.5 ± 1.6 years, one eye) with a cathodal DCS of 500 µA (DC-stimulator MC, neuroConn GmbH, Ilmenau) for 10 minutes. For DCS we used six cup electrodes (diameter: 0.95 cm) placed around one eye . Before, during and after DCS we measured the electrophysiological answer of the retinal ganglion cells using a pattern-reversal stimulus (stimulus field: 1° individual checks, 16° total; reversals per second: 4; Michelson contrast: 99%; mean luminance: 186 cd/m^2). For recording, we used Ag/AgCl ring electrodes located at the lower eyelid and the earlobe. For statistical analysis the Friedman test for paired samples and a confidence interval analysis was performed. Results : The characteristic amplitudes of the the electrophysiological answer (P50 and N95 component) as well as its peak-to-peak difference (PPD) were decreased during the stimulation. The visible trend was statistically not significant (Friedman test P50/N95/PPD: p = 0.527/0.574/0.297). Under consideration of specific volunteers (showed expected reduction of the N95 component, n = 9) we found a significant change of the N95 component for the difference between before and during DCS (confidence interval analysis, lower limit: -2.45 µV; upper limit: -0.38 µV; after Bonferroni correction α = 0.0143). Conclusions : The performed study indicates a trend that a cathodal DCS decreasing electrophysiological activity in the retina

    Efeitos dos óleos essenciais de Rosmarinus officinalis Linn. e Origanum vulgare Linn. de diferentes origens em Sporothrix brasiliensis e complexo Sporothrix schenckii

    Get PDF
    Rosmarinus officinalis L. (rosemary) and Origanum vulgare L. (oregano) are known to have antimicrobial properties, but studies on sporotrichosis are scarce. This study aimed to evaluate the anti-Sporothrix spp. activity of essential oils from commercial products and oils extracted from aerial parts of these plants and analyze their chemical constituents. S. schenckii complex and S. brasiliensis (n: 25) isolated from humans, cats, dogs, and environmental soil were tested through M27-A3 guidelines of CLSI with modification for phytotherapics. The essential oils of R. officinalis L. were similar for MIC50 and MFC50 ≤2.25mg/mL for extracted oil; and 4.5mg/mL and 9mg/mL, respectively, for commercial oil. Both products showed MIC90 of 18mg/mL and MFC90 of 36mg/mL. In O. vulgare L., the extracted oil had better activity with MIC50 and MFC50 ≤2.25mg/mL, and MIC90 and MFC90 of 4.5mg/mL, whereas the commercial oil showed MIC50 and MFC50 of 9mg/mL and MIC90 18mg/mL, respectively, and MFC90 of 36mg/mL. Through gas chromatography (CG/FID), thymol and α-terpinene were majority for extracted oil of O. vulgare L., and carvacrol and γ-terpinene made up the majority of the commercial oil. Both essential oils of R. officinalis L. showed 1,8-cineole and α-pinene as major. The fungal isolates were susceptible to all tested essential oils, including in itraconazole-resistant S. brasiliensis isolates. The extracted and commercial oils of the plants presented in vitro anti-Sporothrix spp. activity, and they are promising for treatment of sporotrichosis, including in cases refractory to itraconazole. More studies should be performed about toxicity and in vivo efficacy for its safe use.Rosmarinus officinalis L. (alecrim) e Origanum vulgare L. (orégano) são conhecidos pelas propriedades antimicrobianas, entretanto seus estudos na esporotricose são escassos. Este trabalho objetivou avaliar a atividade anti-Sporothrix spp. de óleos extraídos e comerciais dessas plantas e analisar seus constituintes químicos. Isolados do complexo S. schenckii e S. brasiliensis (n: 25) de humanos, gatos, cães e solo, foram testados pela diretriz M27-A3 do CLSI com modificações para fitoterápicos. Os óleos de R. officinalis L. foram similares com CIM50 e CFM50 ≤2.25mg/mL para extraído; e 4.5mg/mL e 9mg/mL, respectivamente, para comercial. Ambos os produtos demonstraram CIM90 de 18mg/mL e CFM90 de 36mg/mL. Em O. vulgare L., o óleo extraído apresentou melhor atividade com CIM50 e CFM50≤2.25mg/mL e CIM90 e CFM90 de 4.5mg/mL, ao passo que o óleo comercial mostrou CIM50 e CFM50 de 9mg/mL; e CIM90 de 18mg/mL e CFM90 de 36mg/mL. Por meio da cromatografia gasosa (CG/FID), timol e α-terpineno foram majoritários para o óleo extraído de O. vulgare L., e carvacrol e γ-terpineno para o comercial. Ambos os óleos de R. officinalis L. apresentaram 1,8-cineol e α-pineno como prevalentes. Os isolados foram sensíveis a todos os óleos essenciais testados, inclusive S. brasiliensis, resistentes ao itraconazol. Os óleos extraídos e comerciais de R. officinalis L. e O. vulgare L. apresentaram atividade anti-Sporothrix spp. in vitro e são promissores para o tratamento da esporotricose, inclusive em casos refratários ao itraconazol. Mais estudos devem ser realizados sobre toxicidade e eficácia in vivo para seu uso seguro

    Pulsed electrical stimulation of the human eye enhances retinal vessel reaction to flickering light

    Get PDF
    Recent studies indicate therapeutic benefits of electrical stimulation in cases of specific ophthalmic diseases that are associated with dysfunctional ocular microcirculation. This suggests effects of electrical stimulation on vascular functions. In the present study, we investigated the effects of electrical stimulation on retinal vessel reactions using dynamic vessel analysis (DVA). Eighty healthy subjects were randomly assigned to one of three groups receiving electrical stimulation with different current intensities: 400 μA (n = 26); 800 μA (n = 27); 1200 μA (n = 27). The electrode montage for electrical stimulation consisted of a ring-shaped active electrode surrounding one eye and a square return electrode at the occiput. Rectangular, monophasic, positive current pulses were applied at 10 Hz for a duration of 60 s per stimulation period. DVA was used to observe the stimulation-induced reactions of retinal vessel diameters in response to different provocations. In three DVA measurements, three stimulus conditions were investigated: flicker light stimulation (FLS); electrical stimulation (ES); simultaneous electrical and flicker light stimulation (ES+FLS). Retinal vasodilation caused by these stimuli was compared using paired t-test. The subjects receiving electrical stimulation with 800 μA showed significantly increased retinal vasodilation for ES+FLS compared to FLS (p < 0.05). No significant differences in retinal vessel reactions were found between ES+FLS and FLS in the 400 and 1200 μA groups. No retinal vasodilation was observed for ES for all investigated current intensities. The results indicate that positive pulsed electrical stimulation of an adequate intensity enhances the flicker light-induced retinal vasodilation
    corecore