Behavior Of Spandrel Beams Strengthened With Steel Fibers Under Combined Loading

Anggota konkrit mengalami kilasan diiringi juga dengan lenturan dan ricihan. Sehingga kini, kod amalan reka bentuk anggota-anggota konkrit bertetulang menganggap bahawa kesan kilasan dapat dielakkan dengan selamat disebabkan faktor keselamatan yang tinggi digunakan dalam lenturan dan ricihan. Justeru itu, gabungan beban terhadap anggota-anggota tidak diberi perhatian yang serius. Namun demikian, andaian ini sudah tidak boleh diaplikasi lagi kerana isu kilasan kini merupakan perkara biasa dan memainkan peranan yang signifikan dalam struktur, contohnya rasuk spandrel. Rasuk spandrel atau dikenali juga sebagai rasuk-L, amat bergantung pada perimeter bangunan. Sebarang kegagalan pada rasuk spandrel boleh menjadi serius sehingga mencacatkan papak, sumbungan tiang-rasuk dan tebukan plat rata konkrit. Dengan mencampurkan gentian keluli sebagai bahan tambahan, ia boleh meningkatkan kekuatan kilasan rasuk spandrel di bawah beban gabungan dan prestasi struktur konkrit seperti beban maksimum, kemuluran dan rintangan retak. Gentian keluli boleh merintangi gabungan beban seperti rakap dan tetulang membujur, namun penyelidikan di dalam bidang ini masih samar dan terhad. Lebih-lebih lagi kepentingan menggunakan bertetulang gentian dalam struktur konkrit untuk diaplikasi dalam infrastruktur awam telah meningkat. Oleh yang demikian, pengetahuan sedia ada tentang konkrit gentian keluli sepaiknya digabungjalinkan dalam kod amalan reka bentuk. Eksperimen dijalankan untuk menilai perlakuan rasuk spandrel gentian yang diperkukuh dengan gentian keluli tertakluk pada gabungan kilasan, lenturan dan ricihan. Sejumlah 18 rasuk spandrel disediakan dan diuji dengan dua gabungan beban biasa i.e. kilasan tinggi terhadap nisbah lenturan dan kilasan rendah terhadap nisbah lenturan. Sampel rasuk dibahagikan kepada tiga kumpulan, iaitu rasuk konkrit biasa, spesimen dengan tetulang pengukuh memanjang, dan spesimen dengan tertulang dan rakap. Semua kes dikaji dengan pecahan isipadu gentian keluli 0%, 1%, dan 1.5%. Rasuk konkrit bertetulang gentian mempamerkan prestasi keseluruhan yang baik berbanding dengan rasuk kawalan tanpa gentian. Diperhatikan sumbangan utama daripada gentian keluli ke atas tingkah laku kilasan adalah terhadap keretakan konkrit. Penambahan gentian keluli adalah penting untuk rasuk tanpa tetulang keluli konvensional, penambahan ini terbukti mampu meningkatkan kapasiti semasa kilasan. Di samping itu, analisis berangka melalui kaedah elemen terhingga dilakukan terhadap data eksperimen untuk meramalkan tingkah laku struktur rasuk spandrel. Satu teknik baru diutara untuk mengambilkira kesan gentian keluli dalam elemen konkrit dan kesan titik lembut konkrit dalam mampatan dan tegangan. Kelakuan umum model unsur terhingga yang diwakili plot kilas-piuh dan plot bebanlenturan menunjukkan hubungan yang baik dengan data ujian daripada rasuk kawalan dan rasuk spandrel. Walau bagaimanapun, model unsur terhingga menunjukkan kekukuhan yang tinggi berbanding dengan data ujian dalam julat tidak linear untuk rasuk tanpa tetulang keluli. ________________________________________________________________________________________________________________________ Important concrete members are subjected to significant torsion accompanied by bending and shear. Until recent years, the design codes of reinforced concrete members assumed that the effects of torsion could be safely neglected due to high safety factors for shear and bending moment. Thus, members under combined loading were not treated with serious attention. However, this assumption cannot be applied anymore as torsion issues become common and play a significant role in structural members, such as spandrel beams. The spandrel beam, or the L-beam, lies on the perimeter of buildings. Any failure in spandrel beams can seriously damage slabs, beam-column connections, and punch concrete flat-plates. By incorporating steel fibers, it can enhance torsional behavior of spandrel beam under combined load in addition to the structural performance such as maximum load, ductility and cracking resistance. Steel fibers may provide resistance to combined loading as stirrups and longitudinal bars, this investigation is still scare and limited. Moreover, a worldwide interest in utilizing fiber reinforced concrete structures for civil infrastructure applications has increased. This study presents the advantage of using steel fiber concrete in strengthening spandrel beams under different reinforcement and loading cases. An experimental investigation was conducted to assess the behavior of steel fiber reinforced concrete spandrel beams subjected to combined torsion, bending, and shear. A total of 18 spandrel beams were prepared and tested with two common loading combinations i.e. high torque to bending ratio and low torque to bending ratio. All beams were divided into three groups, namely, plain concrete beams, specimens with longitudinal reinforcing bars and specimens with bars and stirrups. All cases were examined with 0%, 1%, and 1.5% steel fiber volume fractions. Fibrous concrete beams exhibited improved overall torsional performance with respect to the corresponding non-fibrous control beams. The main contribution of steel fibers on the torsional behavior is mainly observed after concrete cracking. The addition of steel fibers was essential to the beams without conventional steel reinforcement since fibers were the only reinforcement and proved capable to provide enhanced torsional moment capacities. Besides, a numerical analysis by finite element method was suggested against the experimental data to predict the structural behavior of spandrel beams. A new technique was presented to incorporate the effects of steel fibers within concrete element and the softening effect of concrete in compression and tension. The general behavior of the finite element model represented by the torque-twist plot and load-deflection plots show good agreement with the test data from the plain and fiber reinforced spandrel beam. However, the finite element models show higher stiffness than the test data in the nonlinear ranges for beams without steel reinforcement

Molekularna genetika i SSR markeri kao nova praksa u genomskoj analizi farmskih životinja u reprodukciji i kontroli bolesti

Molecular genetics investigates the genetic makeup of individuals at the DNA level. That includes the identification and mapping of molecular genetic markers and genetic polymorphisms. Molecular genetic markers (DNA markers) are one of the most powerful means for the genomic analysis and allow the connection of hereditary traits with genomic variation. Molecular marker technology has developed rapidly over the last decade and two shapes of specific DNA based marker, Simple Sequence Repeats (SSRs), also known as microsatellites, and Single Nucleotide Polymorphisms (SNPs) prevail applications in modern genetic analysis. Genomic simple sequence repeats (SSRs, microsatellites) have been used for a variety of purposes, including gene tagging, physical mapping, genome mapping, estimation of genetic diversity, phylogenetic and conservation genetic purposes in farm animal breeding. SSR analyses are applied successfully in parentage verification and pedigree analysis, as disease markers and to locate the mutation in genetic disorders in livestock animals. The ultimate use of SSRs markers is for mapping quantitative trait loci (QTL), marker assisted selection (MAS) in order to practice genomic selection and improve the farm animal health. Developments in 'omics' technologies, such as genomic selection, may help overcome several of the limitations of traditional breeding programmes and will be especially beneficial in breeding for lowly heritable disease traits that only manifest themselves following exposure to pathogens or environmental stressors in adulthood. The current paper provides a brief overview of the present - day application of microsatellites markers in animal breeding and make significant contribution to the overall farm animal health and resistance to disease.Molekularna genetika istražuje genetski sastav pojedinaca na nivou DNK. To uključuje identifikaciju i mapiranje molekularnih genetskih markera i genetskih polimorfizama. Molekularni genetski markeri (DNK markeri) su jedan od najmoćnijih sredstava genomske analize i pružaju mogućnost povezivanja naslednih osobina sa genomskim varijacijama. Tehnologija molekularnih markera se brzo razvila u poslednjoj deceniji, a dva oblika markera na bazi DNK, Simple Sequence Repeats (SSR), takođe poznati kao mikrosateliti, i polimorfizam pojedinačnih nukleotida - Single Nucleotide Polymorphisms (SNP) preovlađuju u primeni u modernoj genetskoj analizi. Genomske sekvence - ponavljanja (Simple Sequence Repeats - SSR, mikrosateliti) se koriste za razne svrhe, uključujući označavanje gena, fizičko mapiranje, mapiranje genoma, procena genetičke raznovrsnosti, filogenetske i u svrhu genetičke konzervacije u uzgoju farmskih životinja. SSR analiza se uspešno primenjuju u verifikaciji roditeljstva, i analizi pedigrea, kao markeri bolesti i u pronalaženju mutacije i genetskih poremećaja kod farmskih životinja. Krajnja upotreba SSR markera je za mapiranje lokusa kvantitativnih osobina (QTL), selekciji pomoću markera (MAS), kako bi se u praksi primenjivala genomska selekciju i unapređenje zdravlja farmskih životinja. Razvoj u tehnologijama 'omics'', kao što je genomska selekcija, može pomoći u prevazilaženju nekoliko ograničenja tradicionalnih odgajivačkih programa a posebno će biti korisna za oplemenjivanje i odgoj na nižu naslednost naslednih osobina bolesti koje se ispoljavaju tek nakon izloženosti patogenima ili ekološkim stresorima u odraslom dobu. Ovaj rad daje kratak pregled današnje primene mikrosatelit markera u stočarstvu i daje značajan doprinos ukupnom zdravlju životinja uzgajanih na farmi i otpornosti na bolesti

Taking the Metabolic Pulse of the World\u27s Coral Reefs

Worldwide, coral reef ecosystems are experiencing increasing pressure from a variety of anthropogenic perturbations including ocean warming and acidification, increased sedimentation, eutrophication, and overfishing, which could shift reefs to a condition of net calcium carbonate (CaCO3) dissolution and erosion. Herein, we determine the net calcification potential and the relative balance of net organic carbon metabolism (net community production; NCP) and net inorganic carbon metabolism (net community calcification; NCC) within 23 coral reef locations across the globe. In light of these results, we consider the suitability of using these two metrics developed from total alkalinity (TA) and dissolved inorganic carbon (DIC) measurements collected on different spatiotemporal scales to monitor coral reef biogeochemistry under anthropogenic change. All reefs in this study were net calcifying for the majority of observations as inferred from alkalinity depletion relative to offshore, although occasional observations of net dissolution occurred at most locations. However, reefs with lower net calcification potential (i.e., lower TA depletion) could shift towards net dissolution sooner than reefs with a higher potential. The percent influence of organic carbon fluxes on total changes in dissolved inorganic carbon (DIC) (i.e., NCP compared to the sum of NCP and NCC) ranged from 32% to 88% and reflected inherent biogeochemical differences between reefs. Reefs with the largest relative percentage of NCP experienced the largest variability in seawater pH for a given change in DIC, which is directly related to the reefs ability to elevate or suppress local pH relative to the open ocean. This work highlights the value of measuring coral reef carbonate chemistry when evaluating their susceptibility to ongoing global environmental change and offers a baseline from which to guide future conservation efforts aimed at preserving these valuable ecosystems

Cyanobacteria of the thermal spring at Pancharevo, Sofia, Bulgaria

Eight taxa of cyanobacteria were identified in the thermal spring at Pancharevo (in the Sofia basin, Bulgaria). As well as the widespread Lyngbya thermalis, Phormidesmis molle (syn. Phormidium molle), Phormidium papyraceum, Phormidium corium and Mastigocladus laminosus, four species were identified for the first time in Bulgaria: Calothrix thermalis, Gloeocapsa gelatinosa, Leibleinia epiphytica and Symploca thermalis

Oxidschichtbildung und Materialprobleme metallischer Werkstoffe bei Verbrennungsprozessen mit Heizöl EL

Scope of the present work was the investigation of the oxide scale formation on metallic high-temperature alloys resulting during reaction with the atmosphere of the combustion of industrial gas oil (IGO). The Ni-Cr-based alloys 601 (2.4851), 602 (2.4633), 603, 693 and 617 (2.4663) were tested at elevated temperatures between 900°C and 1050°C in a burner rig equipped with a low-NOx recirculation burner by application as material of the burner flame tube. Further on, the oxide scale on a woven wire cloth made of a Ni-Cr-based alloy was analysed. The wire cloth was used as the hot surface of a radiant burner at temperatures of approximately 685°C for an operation time of 844 h. All alloys investigated in the low-NOx burner rig showed following oxide scale structure: a chromium oxide scale at the alloy surface and aluminium or silicon oxide (on alloy 603) beneath. Particles with a composition similar to that of the bulk alloy were found enclosed in the chromium oxide scale. Frequently these particles were located near the oxide-gas boundary indicating an impending local degradation of the chromium oxide scale. Aluminium oxide grew predominantly along grain boundaries in the depth of the bulk. During the test period of up to 3000 h no aluminium oxide scale was found. For longer investigation times accelerated internal oxidation of aluminium was observed.In contrast to aluminium, silicon formed an albeit noncontinuous scale of silicon oxide directly below the chromium oxide layer. The diffusion of chromium towards the surface was inhibited by the silicon scale, which resulted in a slower kinetic of the chromium oxide growth and consequently a thinner chromium oxide scale. However, as the silicon oxide scale was not protective. Mo-oxides formed in the bulk – Mo being an alloying element of alloy 603 – followed by breakaway oxidation. In case of the aluminium alloyed material the formation of nitrides in the bulk indicated the breakdown of the oxide scale. Failure of the alloys was related to massive inward nitrogen diffusion and the formation of aluminium nitrides in the bulk. Therefore it is assumed that in nitrogen rich atmospheres a high aluminium content is unfavourable due to the strong affinity of aluminium to nitrogen. In general it was observed, that at lower temperatures, as a result of a slower growth kinetic, the nitride formation began later.Short term tests of 50 hours of alloy 602, alloy 603 and alloy 693 showed, that a thicker and more uniform oxide layer formed when the burner was operated with standard quality IGO (1700 mg/kg S), compared with the oxide scale formed in the case of operation with fuel with reduced sulphur content (20 mg/kg S). Ventilation with air after burner shut down had no significant effect on chromium oxide scale thickness.The time dependence of the observed growth of the chromium oxide scale was fitted with a power law. A deviation from the parabolic law has been found indicating an oxide loss due to spallation.Reasonable estimation of life time was achieved by logarithmic plots of the time dependence of the chromium depletion measured by line scans on cross sections of the samples.The metallographic investigation of the hot surface of the radiant burner showed a thin continuous chromium oxide layer. No indication of damage of the scale, a small depth of internal oxidation and the absence of a significant chromium depletion zone were found. Hence, a long life time of the woven wire cloth can be expected

Oxidschichtbildung und Materialprobleme metallischer Werkstoffe bei Verbrennungsprozessen mit Heizöl EL

Scope of the present work was the investigation of the oxide scale formation on metallic high-temperature alloys resulting during reaction with the atmosphere of the combustion of industrial gas oil (IGO). The Ni-Cr-based alloys 601 (2.4851), 602 (2.4633), 603, 693 and 617 (2.4663) were tested at elevated temperatures between 900°C and 1050°C in a burner rig equipped with a low-NOx recirculation burner by application as material of the burner flame tube. Further on, the oxide scale on a woven wire cloth made of a Ni-Cr-based alloy was analysed. The wire cloth was used as the hot surface of a radiant burner at temperatures of approximately 685°C for an operation time of 844 h. All alloys investigated in the low-NOx burner rig showed following oxide scale structure: a chromium oxide scale at the alloy surface and aluminium or silicon oxide (on alloy 603) beneath. Particles with a composition similar to that of the bulk alloy were found enclosed in the chromium oxide scale. Frequently these particles were located near the oxide-gas boundary indicating an impending local degradation of the chromium oxide scale. Aluminium oxide grew predominantly along grain boundaries in the depth of the bulk. During the test period of up to 3000 h no aluminium oxide scale was found. For longer investigation times accelerated internal oxidation of aluminium was observed.In contrast to aluminium, silicon formed an albeit noncontinuous scale of silicon oxide directly below the chromium oxide layer. The diffusion of chromium towards the surface was inhibited by the silicon scale, which resulted in a slower kinetic of the chromium oxide growth and consequently a thinner chromium oxide scale. However, as the silicon oxide scale was not protective. Mo-oxides formed in the bulk – Mo being an alloying element of alloy 603 – followed by breakaway oxidation. In case of the aluminium alloyed material the formation of nitrides in the bulk indicated the breakdown of the oxide scale. Failure of the alloys was related to massive inward nitrogen diffusion and the formation of aluminium nitrides in the bulk. Therefore it is assumed that in nitrogen rich atmospheres a high aluminium content is unfavourable due to the strong affinity of aluminium to nitrogen. In general it was observed, that at lower temperatures, as a result of a slower growth kinetic, the nitride formation began later.Short term tests of 50 hours of alloy 602, alloy 603 and alloy 693 showed, that a thicker and more uniform oxide layer formed when the burner was operated with standard quality IGO (1700 mg/kg S), compared with the oxide scale formed in the case of operation with fuel with reduced sulphur content (20 mg/kg S). Ventilation with air after burner shut down had no significant effect on chromium oxide scale thickness.The time dependence of the observed growth of the chromium oxide scale was fitted with a power law. A deviation from the parabolic law has been found indicating an oxide loss due to spallation.Reasonable estimation of life time was achieved by logarithmic plots of the time dependence of the chromium depletion measured by line scans on cross sections of the samples.The metallographic investigation of the hot surface of the radiant burner showed a thin continuous chromium oxide layer. No indication of damage of the scale, a small depth of internal oxidation and the absence of a significant chromium depletion zone were found. Hence, a long life time of the woven wire cloth can be expected

Cytotoxicity and apoptotic effects of microcystin-LR and anatoxin-a in mouse lymphocytes

There is an increasing amount of knowledge on the cytotoxic properties of cyanotoxins, but relatively little is known regarding their fine specificity and mechanisms of action. In this study, we investigated the influence of microcystin-LR and AnTx-a on mouse B- and T-lymphocyte subpopulations in vitro. Cyanotoxins significantly decreased the cell viability after 4 and 24 h, compared to the untreated control. After 24 h exposure to microcystin-LR and anatoxin-a, the viability of splenocytes dropped to 23% and 57%, respectively. Our data demonstrate that microcystin-LR induced apoptosis specifically in mouse B cells, probably via the B-cell antigen receptor and mitochondrial pathway, while the T cells were not affected. AnTx-a showed cytotoxic effects on both lymphocyte subpopulations, but the effects were driven by mechanisms different from apoptosis. These findings demonstrate that the cyanotoxins could cause cytotoxic alterations in a variety of cell types different from the major targets, operating via distinct mechanisms

Publisher: Institute for Animal Husbandry, Belgrade-Zemun UDC 639.112 RABBIT PRODUCTION IN BULGARIA**

Bulgarian board of bird and rabbit meat processin

Morphological, genetic and functional variability of a T-cell hybridoma line.

The variability in the morphology, modal number of chromosomes, TCR expression and functional reactivity of a CII-specific T-cell hybridoma at continuous subcultivation have been investigated. As the number of passages increased, besides the oval semiadherent cells (normal phenotype), fibroblast-like cells (transformed phenotype) were also observed. The two cell subpopulations differed in their karyotype characteristic, as well as in their functional reactivity. The cell population with a normal phenotype was characterized by a tetramodal number of chromosomes (30, 40, 48 and 70) and trisomies of chromosomes 6 and 14, while the cell population with a transformed phenotype was characterized by a trimodal number of chromosomes (11, 68 and 74) and trisomy of chromosome 12. A nullisomy of sex chromosomes was established in both types of cells. In the initial passages of subcultivation, 73.04% of the cells with a normal morphological phenotype expressed TCR-CD3 complexes on their surface and possessed high functional reactivity. After a two-week subcultivation, the values of these indices went down considerably: 46.11% of the cells expressed functional TCR-CD3 complexes, as a result of which their functional reactivity decreased. Only 2.71% of the cells with a transformed morphological phenotype expressed functional TCR-CD3 complexes on their surface. In these cells, a total loss of reactivity towards the specific antigens was established. The achieved results show that at continuous subcultivation the T-cell hybridomas are unstable, and with the increase in the number of passages there appear chromosome rearrangements, leading to loss of their functional reactivity