1,056 research outputs found
Coherence freeze in an optical lattice investigated via pump-probe spectroscopy
Motivated by our observation of fast echo decay and a surprising coherence
freeze, we have developed a pump-probe spectroscopy technique for vibrational
states of ultracold Rb atoms in an optical lattice to gain information
about the memory dynamics of the system. We use pump-probe spectroscopy to
monitor the time-dependent changes of frequencies experienced by atoms and to
characterize the probability distribution of these frequency trajectories. We
show that the inferred distribution, unlike a naive microscopic model of the
lattice, correctly predicts the main features of the observed echo decay.Comment: 4 pages, 5 figure
Derivatives of spin dynamics simulations
We report analytical equations for the derivatives of spin dynamics
simulations with respect to pulse sequence and spin system parameters. The
methods described are significantly faster, more accurate and more reliable
than the finite difference approximations typically employed. The resulting
derivatives may be used in fitting, optimization, performance evaluation and
stability analysis of spin dynamics simulations and experiments.
Keywords: NMR, EPR, simulation, analytical derivatives, optimal control, spin
chemistry, radical pair.Comment: Accepted by The Journal of Chemical Physic
The thermal QCD transition with two flavours of twisted mass fermions
We investigate the thermal QCD transition with two flavors of maximally
twisted mass fermions for a set of pion masses, 300 MeV \textless
\textless 500 MeV, and lattice spacings \textless 0.09 fm. We determine the
pseudo-critical temperatures and discuss their extrapolation to the chiral
limit using scaling forms for different universality classes, as well as the
scaling form for the magnetic equation of state. For all pion masses considered
we find resonable consistency with O(4) scaling plus leading corrections.
However, a true distinction between the O(4) scenario and a first order
scenario in the chiral limit requires lighter pions than are currently in use
in simulations of Wilson fermions.Comment: 11 pages, 11 figure
Effects of Spawning Pacific Salmon on Terrestrial Invertebrates: Insects near Spawning Habitat Are Isotopically Enriched with Nitrogen-15 but Display No Differences in Body Size
When Pacific salmon (Oncorhynchus spp.) spawn and die, they deliver marine-derived nutrient subsidies to freshwater and riparian ecosystems. These subsidies can alter the behavior, productivity, and abundance of recipient species and their habitats. Isotopes, such as nitrogen-15 (15N), are often used to trace the destination of marine-derived nutrients in riparian habitats. However, few studies have tested for correlations between stable isotopes and physiological responses of riparian organisms. We examined whether increases in δ15N in terrestrial insect bodies adjacent to salmon spawning habitat translate to changes in percent nitrogen content and body size. This involved comparisons between distance from a salmon-bearing river, marine-derived nutrients in soils and insects, soil moisture content, and body size and nitrogen content in two common beetle families (Coleoptera: Curculionidae, Carabidae). As predicted, δ15N in riparian soils attenuated with distance from the river but was unaffected by soil moisture. This gradient was mirrored by δ15N in the herbivorous curculionid beetles, whereas carabid beetles, which feed at a higher trophic level and are more mobile, did not show discernable patterns in their δ15N content. Additionally, neither distance from the river nor body δ15N content was related to beetle body size. We also found that nitrogen-15 was not correlated with total percent nitrogen in insect bodies, meaning that the presence of spawning salmon did not increase the percent nitrogen content of these insects. We conclude that while salmon-derived nutrients had entered terrestrial food webs, the presence of δ15N alone did not indicate meaningful physiological changes in these insects in terms of percent nitrogen nor body size. While stable isotopes may be useful tracers of marine-derived nutrients, they cannot necessarily be used as a proxy for physiologically important response variables
Gene expression profiling in hepatic tissue of newly weaned pigs fed pharmacological zinc and phytase supplemented diets
<p>Abstract</p> <p>Background</p> <p>Zinc (Zn) is an essential trace element. However, Zn bioavailability from commonly consumed plants may be reduced due to phytic acid. Zn supplementation has been used to treat diarrheal disease in children, and in the U.S. swine industry at pharmacological levels to promote growth and fecal consistency, but underlying mechanisms explaining these beneficial effects remain unknown. Moreover, adding supplemental phytase improves Zn bioavailability. Thus, we hypothesized that benefits of pharmacological Zn supplementation result from changes in gene expression that could be further affected by supplemental phytase. The goal of this study was to investigate the effects of feeding newly weaned pigs dietary Zn (150, 1,000, or 2,000 mg Zn/kg) as Zn oxide with or without phytase [500 phytase units (FTU)/kg] for 14 d on hepatic gene expression. Liver RNA from pigs fed 150, 1,000, or 2,000 mg Zn/kg, or 1,000 mg Zn/kg with phytase (n = 4 per treatment) was reverse transcribed and examined using the differential display reverse transcription polymerase chain reaction technique. Liver RNA from pigs fed 150 or 2,000 mg Zn/kg (n = 4 per treatment) was also evaluated using a 70-mer oligonucleotide microarray.</p> <p>Results</p> <p>Expressed sequence tags for 61 putatively differentially expressed transcripts were cloned and sequenced. In addition, interrogation of a 13,297 element oligonucleotide microarray revealed 650 annotated transcripts (FDR ≤ 0.05) affected by pharmacological Zn supplementation. Seven transcripts exhibiting differential expression in pigs fed pharmacological Zn with sequence similarities to genes encoding <it>GLO1</it>, <it>PRDX4</it>, <it>ACY1</it>, <it>ORM1</it>, <it>CPB2</it>, <it>GSTM4</it>, and <it>HSP70.2 </it>were selected for confirmation. Relative hepatic <it>GLO1 </it>(<it>P </it>< 0.0007), <it>PRDX4 </it>(<it>P </it>< 0.009) and <it>ACY1 </it>(<it>P </it>< 0.01) mRNA abundances were confirmed to be greater in pigs fed 1,000 (n = 8) and 2,000 (n = 8) mg Zn/kg than in pigs fed 150 (n = 7) mg Zn/kg. Relative hepatic <it>HSP70.2 </it>(P < 0.002) mRNA abundance was confirmed to be lower in pigs fed 2,000 mg Zn/kg than in pigs fed 150 or 1,000 mg Zn/kg.</p> <p>Conclusion</p> <p>Results suggest that feeding pharmacological Zn (1,000 or 2,000 mg Zn/kg) affects genes involved in reducing oxidative stress and in amino acid metabolism, which are essential for cell detoxification and proper cell function.</p
Ultrafast Proton Conduction in an Aqueous Electrolyte Confined in Adamantane-like Micropores of a Sulfonated, Aromatic Framework
Abnormal Attention Modulation of Fear Circuit Function in Pediatric Generalized Anxiety Disorder
1. Context. Considerable work implicates abnormal neural activation and disrupted attention to facial-threat cues in adult anxiety disorders. However, in pediatric anxiety, no research has examined attention modulation of neural response to threat cues. 2. Objective. To determine whether attention modulates amygdala and cortical responses to facial threat cues differentially in adolescents with generalized anxiety disorder (GAD) and healthy adolescents. 3. Design. Case-control study. 4. Setting. Government clinical research institute. 5. Participants. Adolescent volunteers, 15 with GAD and 20 diagnosis-free. 6. Main Outcome Measure(s). Blood oxygenation level-dependent (BOLD) signal, as measured via functional magnetic resonance imaging (fMRI). During fMRI scans, participants completed a face-emotion rating task that systematically manipulated attention. 7. Results. While attending to their own subjective fear, patients, but not controls, showed greater activation to fearful than to happy faces (small volume corrected p’s \u3c .05) in a distributed network including the amygdala, ventral PFC (vPFC), and anterior cingulate cortex (ACC). Right amygdala findings appeared particularly strong. Functional connectivity analyses demonstrated positive correlations among the amygdala, vPFC, and cingulate. 8. Conclusions. Findings provide the first evidence in juveniles that GAD-associated patterns of pathological fear-circuit activation are particularly evident during certain attention states. Specifically, fear-circuit hyperactivation occurred in an attention state involving focus on subjectively-experienced fear. These findings underscore the importance of attention and its interaction with emotion in shaping function of the adolescent human fear circuit
Pion-nucleus elastic scattering on 12C, 40Ca, 90Zr, and 208Pb at 400 and 500 MeV
Pion-nucleus elastic scattering at energies above the Delta(1232) resonance
is studied using both pi+ and pi- beams on 12C, 40Ca, 90Zr, and 208Pb. The
present data provide an opportunity to study the interaction of pions with
nuclei at energies where second-order corrections to impulse approximation
calculations should be small. The results are compared with other data sets at
similar energies, and with four different first-order impulse approximation
calculations. Significant disagreement exists between the calculations and the
data from this experiment
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