531 research outputs found
Bond between steel and concrete made with ceramic waste aggregate
The reduction of natural resources combined with a substantial increase in the generation of solid waste in large urban centers, justifies the search for methods of reusing the construction industry waste. The ceramic industry has a high disposal rate during the manufacturing, transportation and eventual replacement of its products. In this case, research on the reuse of ceramic materials is urgent. A possible solution is the employment of ceramic waste as a coarse aggregate in structural concrete. Therefore, the mechanical properties of this new mix of concrete have to be assessed. This study evaluates the bond strength between steel rebar and concrete with ceramic waste aggregates, by means of the pull-out test method, proposed by RILEM-FIP-CEB (1978). Three concrete mixtures were produced: a mixture without any replacement, and two other mixtures with gradual substitution of natural coarse aggregate by ceramic coarse aggregate (40% and 100% substitution, in volume). Nine cylindrical specimens, three for each of the concrete mixtures, were evaluated in laboratorial conditions. Results concerning bond stress between concrete and steel rebar indicated the feasibility of employing ceramic waste to replace part of the coarse aggregate in structural concrete721313
BIOMECHANICAL APPROACH TO BALLET MOVEMENTS: A PRELIMINARY STUDY
Movements in ballet dance often involve extreme joint positions and muscular efforts that may exceed normal ranges of motion and generate high stresses on bone and soft tissues. The primary aim of this study was to apply the principles and techniques of biomechanics to study ballet movements. Ground reaction forces and plantar pressure distribution were registered with a Kistler Platform and a Tekscan Systems respectively.
Knee joint action in the sagittal plane was simultaneously collected with an electrogoniometer. Peak vertical forces, peak pressures and knee flexion-extension were analyzed and discussed. A better understanding of these biomechanical aspects may lead to a decrease of the injury risks and also to more graceful and efficient dance movements
Characterization of alpha thalassemic genotypes by multiplex ligation-dependent probe amplification in the Brazilian population
Alpha-thalassemia is the most common inherited disorder of hemoglobin synthesis. Genomic deletions involving the alpha-globin gene cluster on chromosome 16p13.3 are the most frequent molecular causes of the disease. Although common deletions can be detected by a single multiplex gap-PCR, the rare and novel deletions depend on more laborious techniques for their identification. The multiplex ligation-dependent probe amplification (MLPA) technique has recently been used for this purpose and was successfully used in the present study to detect the molecular alterations responsible for the alpha-thalassemic phenotypes in 8 unrelated individuals (3 males and 5 females; age, 4 months to 30 years) in whom the molecular basis of the disease could not be determined by conventional methods. A total of 44 probe pairs were used for MLPA, covering approximately 800 kb from the telomere to the MSLN gene in the 16p13.3 region. Eight deletions were detected. Four of these varied in size from 240 to 720 kb and affected a large region including the entire alpha-globin gene cluster and its upstream regulatory element (alpha-MRE), while the other four varied in size from 0.4 to 100 kb and were limited to a region containing this element. This study is the first in Brazil to use the MLPA method to determine the molecular basis of alpha-thalassemia. The variety of rearrangements identified highlights the need to investigate all cases presenting microcytosis and hypochromia, but without iron deficiency or elevated hemoglobin A2 levels and suggests that these rearrangements may be more frequent in our population than previously estimated.162
The formation of voids in a universe with cold dark matter and a cosmological constant
A spherical Lagrangian hydrodynamical code has been written to study the
formation of cosmological structures in the early Universe. In this code we
take into account the presence of collisionless non-baryonic cold dark matter
(CDM), the cosmological constant and a series of physical processes present
during and after the recombination era, such as photon drag resulting from the
cosmic background radiation and hydrogen molecular production. We follow the
evolution of the structure since the recombination era until the present epoch.
As an application of this code we study the formation of voids starting from
negative density perturbations which evolved during and after the recombination
era. We analyse a set of COBE-normalized models, using different spectra to see
their influence on the formation of voids. Our results show that large voids
with diameters ranging from 10h^{-1} Mpc up to 50h^{-1} Mpc can be formed in a
universe model dominated by the cosmological constant (\Omega_\Lambda ~ 0.8).
This particular scenario is capable of forming large and deep empty regions
(with density contrasts \delta < -0.6). Our results also show that the physical
processes acting on the baryonic matter produce a transition region where the
radius of the dark matter component is greater than the baryonic void radius.
The thickness of this transition region ranges from about tens of kiloparsecs
up to a few megaparsecs, depending on the spectrum considered. Putative objects
formed near voids and within the transition region would have a different
amount of baryonic/dark matter when compared with \Omega_b/\Omega_d. If one
were to use these galaxies to determine, by dynamical effects or other
techniques, the quantity of dark matter present in the Universe, the result
obtained would be only local and not representative of the Universe as a whole.Comment: MNRAS (in press); 9 pages, no figure
Significant Biochemical, Biophysical and Metabolic Diversity in Circulating Human Cord Blood Reticulocytes
10.1371/journal.pone.0076062PLoS ONE810-POLN
Dietary docosahexaenoic acid supplementation modulates hippocampal development in the pemt-/- mouse
The development of fetal brain is influenced by nutrients such as docosahexaenoic acid (DHA, 22:6) and choline. Phosphatidylethanolamine-N-methyltransferase (PEMT) catalyzes the biosynthesis of phosphatidylcholine from phosphatidylethanolamine enriched in DHA and many humans have functional genetic polymorphisms in the PEMT gene. Previously, it was reported that Pemt-/- mice have altered hippocampal development. The present study explores whether abnormal phosphatidylcholine biosynthesis causes altered incorporation of DHA into membranes, thereby influencing brain development, and determines whether supplemental dietary DHA can reverse some of these changes. Pregnant C57BL/6 wild type (WT) and Pemt-/- mice were fed a control diet, or a diet supplemented with 3 g/kg of DHA, from gestational day 11 to 17. Brains from embryonic day 17 fetuses derived from Pemt-/- dams fed the control diet had 25-50% less phospholipid-DHA as compared with WT (p < 0.05). Also, they had 60% more neural progenitor cell proliferation (p < 0.05), 60% more neuronal apoptosis (p < 0.01), and 30% less calretinin expression (p < 0.05; a marker of neuronal differentiation) in the hippocampus compared with WT. The DHA-supplemented diet increased fetal brain Pemt-/- phospholipid-DHA to WT levels, and abrogated the neural progenitor cell proliferation and apoptosis differences. Although this diet did not change proliferation in the WT group, it halved the rate of apoptosis (p < 0.05). In both genotypes, the DHA-supplemented diet increased calretinin expression 2-fold (p < 0.05). These results suggest that the changes in hippocampal development in the Pemt-/- mouse could be mediated by altered DHA incorporation into membrane phospholipids, and that maternal dietary DHA can influence fetal brain development
Quotients of AdS_{p+1} x S^q: causally well-behaved spaces and black holes
Starting from the recent classification of quotients of Freund--Rubin
backgrounds in string theory of the type AdS_{p+1} x S^q by one-parameter
subgroups of isometries, we investigate the physical interpretation of the
associated quotients by discrete cyclic subgroups. We establish which quotients
have well-behaved causal structures, and of those containing closed timelike
curves, which have interpretations as black holes. We explain the relation to
previous investigations of quotients of asymptotically flat spacetimes and
plane waves, of black holes in AdS and of Godel-type universes.Comment: 48 pages; v2: minor typos correcte
ANÁLISE DE AGROTÓXICOS ORGANOCLORADOS EM CAMARÃO E PESCADO POR CROMATOGRAFIA A GÁS COM DETECTOR DE MICRO CAPTURA DE ELETRONS (GC-µECD)
Otimizou-se um método analítico para a determinação de multirresíduos de organoclorados em camarão marinho para a espécie Litopenaeus vannamei e em músculo de peixes da espécie Oreochromis sp., chamada popularmente de tilápia-vermelha. Utilizou-se a técnica de extração denominada QuEChERS, empregando cromatografia a gás com detector de micro captura de elétrons (CG-µECD) para análise dos seguintes organoclorados em amostras de camarão e em músculo de peixes: hexaclorobenzeno, lindano, DDE, DDT, clorpirifós, endossulfan sulfato, endossulfan beta, endossulfan alfa, heptacloro, aldrin, endrin e dieldrin. O limite de detecção para todos os compostos foi de 0,0005 µg∙g-1 e o limite de quantificação do método foi estabelecido em 0,005 µg∙g-1. Os valores de recuperação variaram entre 80 % e 120 % com desvio padrão (RSD) abaixo de 20 % para todos os compostos
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