3,204 research outputs found
Estrogen influences cocaine-induced blood oxygen level-dependent signal changes in female rats
We investigated the effect of estrogen on cocaine-induced brain activity using blood oxygen level-dependent (BOLD) magnetic resonance imaging. Ovariectomized (Ovx) rats without estrogen and Ovx rats with estrogen (Ovx+E) were given a single saline or cocaine injection (15 mg/kg, i.p.) for 5 d. After 7 d of withdrawal from injections, rats were challenged with cocaine during functional imaging. Acute cocaine administration produced positive BOLD activation in the prefrontal cortex, nucleus accumbens, striatum, ventral tegmental area, and hippocampus, among other brain regions. Positive BOLD signal changes were lower in Ovx+E than in Ovx rats. With repeated cocaine administration, Ovx+E rats showed enhanced BOLD signal changes in the nucleus accumbens, ventral tegmental area, and hippocampus compared with acutely treated animals. Our results indicate that estrogen influences the effects of acute and repeated cocaine administration on BOLD signal changes. The data suggest that in females with estrogen, cocaine-induced neuronal activity is enhanced after repeated cocaine administration. It is possible that the actions of estrogen within the aforementioned brain regions potentiate the behavioral response to cocaine observed in female rats
Dynamical instabilities of Bose-Einstein condensates at the band-edge in one-dimensional optical lattices
We report on experiments that demonstrate dynamical instability in a
Bose-Einstein condensate at the band-edge of a one-dimensional optical lattice.
The instability manifests as rapid depletion of the condensate and conversion
to a thermal cloud. We consider the collisional processes that can occur in
such a system, and perform numerical modeling of the experiments using both a
mean-field and beyond mean-field approach. We compare our numerical results to
the experimental data, and find that the Gross-Pitaevskii equation is not able
to describe this experiment. Our beyond mean-field approach, known as the
truncated Wigner method, allows us to make quantitative predictions for the
processes of parametric growth and thermalization that are observed in the
laboratory, and we find good agreement with the experimental results.Comment: v2: Added several reference
âIt was a whole other worldâ: the impact of residential outdoor trips on nature connectedness and wellbeing in young people
In England, after the 2021 COVID-19 lockdowns, funded residential outdoor experiences were offered to young people from a range of socioeconomic backgrounds, with the aim of supporting their wellbeing, connection to nature, and confidence in working with peers. This study evaluated the impact of outdoor residentials (2â5âdays) via a mixed methods design, with 132 young people aged 6â18. Results indicated that the residential experiences led to short-term increases in nature connectedness, confidence in making friends, feeling more aligned with nature, and recognising the importance of looking after nature. No significant differences were found for wellbeing, happiness, confidence in working as a group or confidence in trying new things. An inductive thematic analysis revealed that participants valued their experiences; they gained a greater sense of self, developed an enhanced understanding of the outdoors, and appreciated the contrast the natural environment gave them to explore new opportunities. Implications suggest that the pathways to nature connectedness are useful for curriculum design for young peopleâs outdoor residential experiences, however, post-residential activities are needed to sustain positive changes over time
A biophysical model of prokaryotic diversity in geothermal hot springs
Recent field investigations of photosynthetic bacteria living in geothermal
hot spring environments have revealed surprisingly complex ecosystems, with an
unexpected level of genetic diversity. One case of particular interest involves
the distribution along hot spring thermal gradients of genetically distinct
bacterial strains that differ in their preferred temperatures for reproduction
and photosynthesis. In such systems, a single variable, temperature, defines
the relevant environmental variation. In spite of this, each region along the
thermal gradient exhibits multiple strains of photosynthetic bacteria adapted
to several distinct thermal optima, rather than the expected single thermal
strain adapted to the local environmental temperature. Here we analyze
microbiology data from several ecological studies to show that the thermal
distribution field data exhibit several universal features independent of
location and specific bacterial strain. These include the distribution of
optimal temperatures of different thermal strains and the functional dependence
of the net population density on temperature. Further, we present a simple
population dynamics model of these systems that is highly constrained by
biophysical data and by physical features of the environment. This model can
explain in detail the observed diversity of different strains of the
photosynthetic bacteria. It also reproduces the observed thermal population
distributions, as well as certain features of population dynamics observed in
laboratory studies of the same organisms
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Dominant Control of Reservoir-Flow Behavior in Carbonate Reservoirs as Determined from Outcrop Studies
The investigation of carbonate-ramp deposits of the upper San Andres Formation that crop out along the Algerita Escarpment, New Mexico, is a research element of ongoing geologic and petrophysical studies conducted at the Bureau of Economic Geology's Reservoir Characterization Research Laboratory (RCRL). The primary goal of the investigation is to develop an integrated strategy involving geological, petrophysical, geostatistical, and reservoir-simulation studies that can be used to better predict flow characteristics in analogous subsurface reservoirs. Geologic investigations and detailed measurements of petrophysical parameters on continuous outcrop were used to determine not only the vertical distribution of the data but also their lateral distribution, which is typically lacking in subsurface studies.
To characterize the complex heterogeneity associated with depositional and diagenetic processes at the interwell scale, detailed permeability data were collected within the overall geologic framework from the outcrop at Lawyer Canyon, Algerita Escarpment, New Mexico (fig. 1). Geologic mapping showed a series of upward-shallowing parasequences (10 to 40 ft thick and several thousand feet long). Parasequence boundaries are typically marked by tight mudstone/wackestone beds that display variable degrees of lateral continuity ranging from several hundred feet to more than 2,500 ft and are potentially important as flow barriers (fig. 2). Within these parasequences, distinct variability of facies and petrophysical characteristics is present at scales well below those of interwell spacing typical for their subsurface counterparts (660 to 1,330 ft). Pore types and permeability-porosity relationships can also be specific to individual parasequences.Bureau of Economic Geolog
Loss of redundant gene expression after polyploidization in plants
Based on chromosomal location data of genes encoding 28 biochemical systems in allohexaploid wheat,Triticum aestivum L. (genomes AABBDD), it is concluded that the proportions of systems controlled by triplicate, duplicate, and single loci are 57%, 25%, and 18% respectively
Hybrid Newton-type method for a class of semismooth equations
In this paper, we present a hybrid method for the solution of a class of composite semismooth equations encountered frequently in applications. The method is obtained by combining a generalized finite-difference Newton method to an inexpensive direct search method. We prove that, under standard assumptions, the method is globally convergent with a local rate of convergence which is superlinear or quadratic. We report also several numerical results obtained applying the method to suitable reformulations of well-known nonlinear complementarity problem
Reduced tillage, but not organic matter input, increased nematode diversity and food web stability in European longâterm field experiments
Soil nematode communities and food web indices can inform about the complexity, nutrient flows and decomposition pathways of soil food webs, reflecting soil quality. Relative abundance of nematode feeding and lifeâhistory groups are used for calculating food web indices, i.e., maturity index (MI), enrichment index (EI), structure index (SI) and channel index (CI). Molecular methods to study nematode communities potentially offer advantages compared to traditional methods in terms of resolution, throughput, cost and time. In spite of such advantages, molecular data have not often been adopted so far to assess the effects of soil management on nematode communities and to calculate these food web indices. Here, we used highâthroughput amplicon sequencing to investigate the effects of tillage (conventional vs. reduced) and organic matter addition (low vs. high) on nematode communities and food web indices in 10 European longâterm field experiments and we assessed the relationship between nematode communities and soil parameters. We found that nematode communities were more strongly affected by tillage than by organic matter addition. Compared to conventional tillage, reduced tillage increased nematode diversity (23% higher Shannon diversity index), nematode community stability (12% higher MI), structure (24% higher SI), and the fungal decomposition channel (59% higher CI), and also the number of herbivorous nematodes (70% higher). Total and labile organic carbon, available K and microbial parameters explained nematode community structure. Our findings show that nematode communities are sensitive indicators of soil quality and that molecular profiling of nematode communities has the potential to reveal the effects of soil management on soil quality
Use of MMG signals for the control of powered orthotic devices: Development of a rectus femoris measurement protocol
Copyright © 2009 Rehabilitation Engineering and Assistive Technology Society (RESNA). This is an Author's Accepted Manuscript of an article published in Assistive Technology, 21(1), 1 - 12, 2009, copyright Taylor & Francis, available online at: http://www.tandfonline.com/10.1080/10400430902945678.A test protocol is defined for the purpose of measuring rectus femoris mechanomyographic (MMG) signals. The protocol is specified in terms of the following: measurement equipment, signal processing requirements, human postural requirements, test rig, sensor placement, sensor dermal fixation, and test procedure. Preliminary tests of the statistical nature of rectus femoris MMG signals were performed, and Gaussianity was evaluated by means of a two-sided Kolmogorov-Smirnov test. For all 100 MMG data sets obtained from the testing of two volunteers, the null hypothesis of Gaussianity was rejected at the 1%, 5%, and 10%âsignificance levels. Most skewness values were found to be greater than 0.0, while all kurtosis values were found to be greater than 3.0. A statistical convergence analysis also performed on the same 100 MMG data sets suggested that 25 MMG acquisitions should prove sufficient to statistically characterize rectus femoris MMG. This conclusion is supported by the qualitative characteristics of the mean rectus femoris MMG power spectral densities obtained using 25 averages
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