Métodos para la determinación de la carga última en vigas de acero en I sometidas a una carga concentrada excéntrica

Experimental tests show that most eccentrically patch loaded steel I-girders have a collapse mode quite different from that of centrically loaded girders. Concerning engineering practice, the most important difference between collapse modes is in ultimate load. The reduction in ultimate load with an increase in load eccentricity is obvious in some eccentrically loaded girders. Under certain circumstances, for a certain combination of influential parameters, eccentrically loaded girders behave as if loaded in the web plane, with no or no significant reduction in ultimate load due to load eccentricity. Dealing with such a big number of mutually dependant parameters that influence collapse mode and level of ultimate load reduction due to load eccentricity, still without theoretical formulation of collapse mechanism, two approaches for ultimate load determination are analysed: empirical mathematical expressions and artificial neural networks forecast models. Results of two procedures are compared. Recommendations for application in engineering practice are given.Las pruebas experimentales muestran que la mayoría de vigas en I de acero cargadas excéntricamente tienen un modo de colapso muy diferente del de las vigas cargadas centradas. En cuanto a la práctica de ingeniería, la diferencia más importante entre los modos de colapso es la carga final. La reducción de la carga última con un aumento de la excentricidad de carga es evidente en algunas vigas cargadas excéntricamente, mientras que bajo ciertas circunstancias, para una determinada combinación de parámetros influyentes, las vigas cargadas excéntricamente se comportan como si se carga en el plano del alma, con ninguna reducción significativa en la carga última debido a la carga excéntrica. Se analizan dos métodos para la determinación de la carga máxima: expresiones matemáticas empíricas y redes neuronales artificiales. Los resultados de ambos procedimientos se comparan. Se dan recomendaciones para su aplicación en la práctica

Penile morphology in six populations of Branchipus schaefferi Fischer, 1834 (Crustacea: Branchiopoda) from Serbia

Male genital morphology of six populations of Branchipus schaefferi from different locations in Serbia is described. Both qualitative and quantitative morphological traits were taken into consideration. The majority of males from lowland parts of the country (Pannonian Plane) had a long sickle-curved or arched spine situated on the basal part of the penis. Males sampled in the south-eastern part of the country (the region of Stara Planina Mountains) possessed short, straight or slightly bowed basal spine. A distal penile part appeared as a more stable character than the proximal one. Males from one of the examined populations possessed roundish and spineless penile tip, a feature heretofore not described in B. schaefferi.Acta Zoologica Bulgarica (2017), 69(1): 17-2

In Situ Manipulation of Vertically Migrating Gelatinous Zooplankton Using Nighttime Blue-Water Scuba in the South-Central Adriatic Sea

Technological advance in undersea exploration (e.g. tethered cameras, remotely operated vehicles [ROVs], Autonomous Underwater Vehicles [AUVsG, and manned submersibles)have opened new windows into diversityand distribution of fragile gelatinous organisms in the vast mesopelagic realm(300 m-1000 m deep). While exstraordinary in expanding our view of its richness, mesopelagic exploration remains largely a look but don\u27t touch environment and this limits of our ability to understand these animals through physical manipulation relevant to the finer scales of the individual organism. We have been conducting a series of in situ observations and manipulations using blue-water SCUBA during the night at a 1, 200 m station centraly located in the southern Adriatic Sea. We report here on a suite of vertically migrating gelatinous animals, including the narcomedusa Solmissus albescens and the physonect siphonophores Forskalia formosa and Agalma elegans, whose ranges extend to the mesopelagic realm during the day, but reach SCUBA diving depths during the night. Our in situ approach combined with proximity to shore exploits the natural vertical migratory behavior of some mesopelagic species, and we therefore add to the widening spectrum of methods needed to evaluate these ecologically important yet difficult to study organisms

Cuticular chemoprofile of the fruit fly Drosophila Subobscura (Diptera, drosophilidae)

In insects, cuticular hydrocarbon (CHC) profile is involved in many important biological functions and may vary in different conditions. Among fruit fly species, Drosophila subobscura is one of the most frequently used in genetic, ecological and evolutionary research, because of its rich chromosomal polymorphism, specific behavioral repertoires and habitat preferences. In this work, we identified and quantified cuticular chemoprofile of D. subobscura. Using gas chromatography (GC) and gas chromatography coupled with mass spectrometry (GC-MS), 25 chemical compounds were found in males and 23 compounds were found in females. Further, ANOVA confirmed significant sexual dimorphism in cuticular chemoprofile amounts. Knowledge of cuticular chemistry could contribute to further research in D. subobscura, starting from behavioral, up to ecological, since this species is recognized as an important model system for the study and monitoring of global climate changes. © 2018, Pakistan Agricultural Scientists Forum. All rights reserved

Integument in Apfelbeckia insculpta (L. Koch, 1867) (Diplopoda, Callipodida) – morphoanatomical and ultrastructural study

The morphoanatomical and ultrastructural features of the integument (cuticle + epidermis) of an endemic Balkan millipede, Apfelbeckia insculpta (L. Koch, 1867), are investigated utilizing light (LM) and transmission electron microscopy (TEM). Cuticle consists of epicuticle (outermost layer), exocuticle, endocuticle and membranous layer that is in contact with the underlying epidermis. Epicuticle is layer of varying thickness, while exocuticle is composed of helicoidally arranged sheets of microfibriles that appear as close-spaced light and dark bands. Endocuticle is the widest part of cuticle with the broad light bands that are oriented in the same direction. TEM micrographs show that these bands are composed of lamellae arranged in arcuate pattern and curved microfibriles. Membranous layer is intersected in some regions by canals that connect epidermis and different levels of the cuticle and/or surface. The epidermis is monostratified layer of cells that are characterized by distinct polarity. Basal part of epidermal cells is rich in rough endoplasmic reticulum and mitochondria, while apical part contains numerous osmiophilic granules. Nuclei of epidermal cells are ovoid and positioned in different regions of cells. Interdigitations are formed among cells in some epidermal regions. Our study corroborates previous findings on integument organization in Diplopoda and shows that species-specific patterns of cuticular ultrastructure can be present in these arthropods

A Grazing-Incidence Small-Angle X-Ray Scattering View of Vertically Aligned ZnO Nanowires

We report a grazing-incidence small-angle X-ray scattering study of ZnO films with vertically aligned and randomly distributed nanowires, grown through a hydrothermal growth process on nanostructured ZnO seeding coatings and deposited by electron beam evaporation on silicon and glass, respectively. The comparison of the scattering patterns of seeding coatings and nanowires showed that the scattering of vertically aligned nanowires exhibited a specific feature: the dominant characteristic of their scattering patterns is the appearance of fine structure effects around the specular peak. These effects were clarified by the combined reflection and scattering phenomena, suggested for the aligned nanowires-substrate system. Furthermore, they enabled the calculation of the average gyration radius of nanowires in horizontal direction. The calculated value was in good agreement with the radii of nanowires estimated by surface electron microscopy. Therefore, the observed feature in the scattering pattern can serve as evidence of the aligned growth of nanowires

GEOSPATIAL MAPPING OF ECOLOGICAL RISK FROM POTENTIALLY TOXIC ELEMENTS IN SOIL IN THE PANNONIAN-CARPATHIAN BORDER AREA SOUTH OF THE DANUBE

This study collected agricultural surface soil samples from 200 sites in the district of Braničevo, located in the Carpathian Mountains – Pannonian Basin south of the Danube River (Serbia). The main objective was to determine the soil contamination by ten potentially toxic elements (As, B, Cd, Cr, Cu, Mn, Mo, Ni, Pb, Zn) and evaluate the associated ecological risk via different indices. The physicochemical parameters, pH, organic carbon, water content, and soil texture were also analyzed. The mean values of most metal concentrations remained below their corresponding national target values, except for Mo and Ni. The main soil texture types were silt loam (40.5 %) and silty clay loam (34.5 %). According to the mean values, pollution load index (PLI) and potential ecological risk (RI) demonstrated that the soil in the study area was exposed to moderate pollution and moderate ecological risk, while enrichment factor (EF), geoaccumulation index (Igeo), and contamination factor (CF) revealed very high enrichment and contamination with Mo, implying the impact of anthropogenic activities. There was a lack of strong correlations among elements and soil properties, except for Cd and Corg, while moderate to strong positive inter-metal relationships suggested their common sources. The chemometric analysis illustrated the classification of sampling sites into two distinct clusters of spatial similarities according to higher and lower metal concentrations. Geospatial mapping identified a few areas of considerable ecological risk. © 2022,Carpathian Journal of Earth and Environmental Sciences. All Rights Reserved