178 research outputs found
Design of a Sustainable House for Residents of a Colonia in South Texas
This paper reviews the process of designing a
site-specific sustainable home for a family in a
colonia near Laredo, Texas. The home's design
derives from discussions with the family, the
constraints of the narrow site, and the incorporation
of sustainable materials and building practices.
Sustainable features include utilizing straw bale infill,
exploiting natural lighting and ventilation,
positioning the HVAC ductwork inside the
conditioned space, and employing appropriately sized
overhangs. In addition, the selection of
materials and construction methods encourages
family and community participation. Three cisterns
were integrated into the design to harvest scarce
rainwater. Results from heliodon modeling were
used to assure the appropriate amount of overhang
shading on the south facade during hot summer
months
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Improved methodologies for continuous-flow analysis of stable water isotopes in ice cores
Water isotopes in ice cores are used as a climate proxy
for local temperature and regional atmospheric circulation as well as
evaporative conditions in moisture source regions. Traditional measurements
of water isotopes have been achieved using magnetic sector isotope ratio
mass spectrometry (IRMS). However, a number of recent studies have shown
that laser absorption spectrometry (LAS) performs as well or better than
IRMS. The new LAS technology has been combined with continuous-flow analysis
(CFA) to improve data density and sample throughput in numerous prior ice
coring projects. Here, we present a comparable semi-automated LAS-CFA system
for measuring high-resolution water isotopes of ice cores. We outline new
methods for partitioning both system precision and mixing length into liquid
and vapor components – useful measures for defining and improving the
overall performance of the system. Critically, these methods take into
account the uncertainty of depth registration that is not present in IRMS
nor fully accounted for in other CFA studies. These analyses are achieved
using samples from a South Pole firn core, a Greenland ice core, and the
West Antarctic Ice Sheet (WAIS) Divide ice core. The measurement system
utilizes a 16-position carousel contained in a freezer to consecutively
deliver ∼ 1 m × 1.3 cm<sup>2</sup> ice sticks to a
temperature-controlled melt head, where the ice is converted to a continuous liquid
stream and eventually vaporized using a concentric nebulizer for isotopic
analysis. An integrated delivery system for water isotope standards is used
for calibration to the Vienna Standard Mean Ocean Water (VSMOW) scale, and depth registration is achieved using
a precise overhead laser distance device with an uncertainty of ±0.2
mm. As an added check on the system, we perform inter-lab LAS comparisons
using WAIS Divide ice samples, a corroboratory step not taken in prior CFA
studies. The overall results are important for substantiating data obtained
from LAS-CFA systems, including optimizing liquid and vapor mixing lengths,
determining melt rates for ice cores with different accumulation and
thinning histories, and removing system-wide mixing effects that are
convolved with the natural diffusional signal that results primarily from
water molecule diffusion in the firn column
Angiotensin II type 1-receptor activating antibodies in renal-allograft rejection (authors reply inN Engl J Med. 2005 May 12;352(19):2027-8)
BACKGROUND: Antibodies against HLA antigens cause refractory allograft rejection with vasculopathy in some, but not all, patients. METHODS: We studied 33 kidney-transplant recipients who had refractory vascular rejection. Thirteen had donor-specific anti-HLA antibodies, whereas 20 did not Malignant hypertension was present in 16 of the patients without anti-HLA antibodies, 4 of whom had seizures. The remaining 17 patients had no malignant hypertension. We hypothesized that activating antibodies targeting the angiotensin II type 1 (AT1) receptor might be involved. RESULTS: Activating IgG antibodies targeting the AT1 receptor were detected in serum from all 16 patients with malignant hypertension and without anti-HLA antibodies, but in no other patients. These receptor-activating antibodies are subclass IgG1 and IgG3 antibodies that bind to two different epitopes on the second extracellular loop of the AT1 receptor. Tissue factor expression was increased in renal-biopsy specimens from patients with these antibodies. In vitro stimulation of vascular cells with an AT1-receptor-activating antibody induced phosphorylation of ERK 1/2 kinase and increased the DNA binding activity of the transcription factors activator protein 1 (AP-1) and nuclear factor-κB. The AT1 antagonist losartan blocked agonistic AT1-receptor antibody-mediated effects, and passive antibody transfer induced vasculopathy and hypertension in a rat kidney-transplantation model. CONCLUSIONS: A non-HLA, AT1-receptor-mediated pathway may contribute to refractory vascular rejection, and affected patients might benefit from removal of AT 1-receptor antibodies or from pharmacologic blockade of AT 1 receptors
Sexual Selection and the Evolution of Brain Size in Primates
Reproductive competition among males has long been considered a powerful force in the evolution of primates. The evolution of brain size and complexity in the Order Primates has been widely regarded as the hallmark of primate evolutionary history. Despite their importance to our understanding of primate evolution, the relationship between sexual selection and the evolutionary development of brain size is not well studied. The present research examines the evolutionary relationship between brain size and two components of primate sexual selection, sperm competition and male competition for mates. Results indicate that there is not a significant relationship between relative brain size and sperm competition as measured by relative testis size in primates, suggesting sperm competition has not played an important role in the evolution of brain size in the primate order. There is, however, a significant negative evolutionary relationship between relative brain size and the level of male competition for mates. The present study shows that the largest relative brain sizes among primate species are associated with monogamous mating systems, suggesting primate monogamy may require greater social acuity and abilities of deception
The Origin and Initial Rise of Pelagic Cephalopods in the Ordovician
BACKGROUND: During the Ordovician the global diversity increased dramatically at family, genus and species levels. Partially the diversification is explained by an increased nutrient, and phytoplankton availability in the open water. Cephalopods are among the top predators of today's open oceans. Their Ordovician occurrences, diversity evolution and abundance pattern potentially provides information on the evolution of the pelagic food chain. METHODOLOGY/PRINCIPAL FINDINGS: We reconstructed the cephalopod departure from originally exclusively neritic habitats into the pelagic zone by the compilation of occurrence data in offshore paleoenvironments from the Paleobiology Database, and from own data, by evidence of the functional morphology, and the taphonomy of selected cephalopod faunas. The occurrence data show, that cephalopod associations in offshore depositional settings and black shales are characterized by a specific composition, often dominated by orthocerids and lituitids. The siphuncle and conch form of these cephalopods indicate a dominant lifestyle as pelagic, vertical migrants. The frequency distribution of conch sizes and the pattern of epibionts indicate an autochthonous origin of the majority of orthocerid and lituitid shells. The consistent concentration of these cephalopods in deep subtidal sediments, starting from the middle Tremadocian indicates the occupation of the pelagic zone early in the Early Ordovician and a subsequent diversification which peaked during the Darriwilian. CONCLUSIONS/SIGNIFICANCE: The exploitation of the pelagic realm started synchronously in several independent invertebrate clades during the latest Cambrian to Middle Ordovician. The initial rise and diversification of pelagic cephalopods during the Early and Middle Ordovician indicates the establishment of a pelagic food chain sustainable enough for the development of a diverse fauna of large predators. The earliest pelagic cephalopods were slowly swimming vertical migrants. The appearance and early diversification of pelagic cephalopods is interpreted as a consequence of the increased food availability in the open water since the latest Cambrian
Corpus Callosum Morphology in Capuchin Monkeys Is Influenced by Sex and Handedness
Sex differences have been reported in both overall corpus callosum area and its regional subdivisions in humans. Some have suggested this reflects a unique adaptation in humans, as similar sex differences in corpus callosum morphology have not been reported in any other species of primate examined to date. Furthermore, an association between various measurements of corpus callosum morphology and handedness has been found in humans and chimpanzees. In the current study, we report measurements of corpus callosum cross-sectional area from midsagittal MR images collected in vivo from 14 adult capuchin monkeys, 9 of which were also characterized for hand preference on a coordinated bimanual task. Adult females were found to have a significantly larger corpus callosum: brain volume ratio, rostral body, posterior midbody, isthmus, and splenium than adult males. Left-handed individuals had a larger relative overall corpus callosum area than did right-handed individuals. Additionally, a significant sex and handedness interaction was found for anterior midbody, with right-handed males having a significantly smaller area than right-handed females. These results suggest that sex and handedness influences on corpus callosum morphology are not restricted to Homo sapiens
Topography of the Chimpanzee Corpus Callosum
The corpus callosum (CC) is the largest commissural white matter tract in mammalian brains, connecting homotopic and heterotopic regions of the cerebral cortex. Knowledge of the distribution of callosal fibers projecting into specific cortical regions has important implications for understanding the evolution of lateralized structures and functions of the cerebral cortex. No comparisons of CC topography in humans and great apes have yet been conducted. We investigated the topography of the CC in 21 chimpanzees using high-resolution magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI). Tractography was conducted based on fiber assignment by continuous tracking (FACT) algorithm. We expected chimpanzees to display topographical organization similar to humans, especially concerning projections into the frontal cortical regions. Similar to recent studies in humans, tractography identified five clusters of CC fibers projecting into defined cortical regions: prefrontal; premotor and supplementary motor; motor; sensory; parietal, temporal and occipital. Significant differences in fractional anisotropy (FA) were found in callosal regions, with highest FA values in regions projecting to higher-association areas of posterior cortical (including parietal, temporal and occipital cortices) and prefrontal cortical regions (p<0.001). The lowest FA values were seen in regions projecting into motor and sensory cortical areas. Our results indicate chimpanzees display similar topography of the CC as humans, in terms of distribution of callosal projections and microstructure of fibers as determined by anisotropy measures
Розрахунок та проектування окремого фундаменту будівлі на природній ґрунтовій основі. Методичні рекомендації до виконання практичних завдань та курсового проекту з дисципліни «Механіка ґрунтів, основи і фундаменти» сту- дентами напрямів підготовки 6.060101 Будівництво та 6.050301 Гірництво
Подано методичні рекомендації до виконання практичних завдань та кур-
сового проекту з дисципліни «Механіка ґрунтів, основи і фундаменти» для сту-
дентів напрямів підготовки 6.060101 Будівництво та 6.050301 Гірництво.
Розглянуто порядок проектування фундаменту будівлі мілкого закладан-
ня на природній ґрунтовій основі.
Методичні рекомендації передбачають виконання курсового проекту
«Розрахунок та проектування окремого фундаменту будівлі на природній ґрун-
товій основі» як із викладачем, так і під час самостійної роботи.
Можна використовувати також у підготовці курсового та дипломного про-
ектування
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