635 research outputs found
Assessment of the environmental impacts of ASR schemes.
This report describes the results of modelling studies undertaken to assess the impacts of ASR on the local environment. Understanding and quantifying these impacts, in relation to other existing or proposed schemes, will be vital in the development, and subsequent licensing of any ASR scheme. As each individual scheme has its own hydrogeological and environmental setting, as well as operational requirements, an all-encompassing model cannot be prescribed. Rather, a set of models, of increasing complexity, have been run for âtypicalâ scenarios to illustrate their use and limitations. They are designed to act as screening tools to assist practitioners, at all stages of an investigation, to decide on the suitability of a site and to identify what additional data are required in order to proceed to the next stage. The models are appended to the report so practitioners can apply them to their specific site, as appropriate
Effect of 50 Hz Electromagnetic Fields on the Induction of Heat-Shock Protein Gene Expression in Human Leukocytes
Although evidence is controversial, exposure to environmental power-frequency magnetic fields is of public concern. Cells respond to some abnormal physiological conditions by producing cytoprotective heat-shock (or stress) proteins. In this study, we determined whether exposure to power-frequency magnetic fields in the range 0â100 ÎźT rms either alone or concomitant with mild heating induced heat-shock protein gene expression in human leukocytes, and we compared this response to that induced by heat alone. Samples of human peripheral blood were simultaneously exposed to a range of magnetic-field amplitudes using a regimen that was designed to allow field effects to be distinguished from possible artifacts due to the position of the samples in the exposure system. Power-frequency magnetic-field exposure for 4 h at 37°C had no detectable effect on expression of the genes encoding HSP27, HSP70A or HSP70B, as determined using reverse transcriptase-PCR, whereas 2 h at 42°C elicited 10-, 5- and 12-fold increases, respectively, in the expression of these genes. Gene expression in cells exposed to power-frequency magnetic fields at 40°C was not increased compared to cells incubated at 40°C without field exposure. These findings and the extant literature suggest that power-frequency electromagnetic fields are not a universal stressor, in contrast to physical agents such as heat
Transcranial Magnetic theta-burst stimulation of the human cerebellum distinguishes absolute, duration-based from relative, beat-based perception of subsecond time intervals
Cerebellar functions in two types of perceptual timing were assessed: the absolute (duration-based) timing of single intervals and the relative (beat-based) timing of rhythmic sequences. Continuous transcranial magnetic theta-burst stimulation (cTBS) was applied over the medial cerebellum and performance was measured adaptively before and after stimulation. A large and significant effect was found in the TBS (n = 12) compared to the SHAM (n = 12) group for single-interval timing but not for the detection of a regular beat or a deviation from it. The data support the existence of distinct perceptual timing mechanisms and an obligatory role of the cerebellum in absolute interval timing with a functional dissociation from relative timing of interval within rhythmic sequences based on a regular beat
Neural correlates of the behavioral-autonomic interaction response to potentially threatening stimuli
Subjective assessment of emotional valence is typically associated with both brain
activity and autonomic arousal. Accurately assessing emotional salience is particularly
important when perceiving threat. We sought to characterize the neural correlates of the
interaction between behavioral and autonomic responses to potentially threatening visual
and auditory stimuli. Twenty-five healthy male subjects underwent fMRI scanning whilst
skin conductance responses (SCR) were recorded. One hundred and eighty pictures,
sentences, and sounds were assessed as âharmlessâ or âthreatening.â Individualsâ
stimulus-locked, phasic SCRs and trial-by-trial behavioral assessments were entered as
regressors into a flexible factorial design to establish their separate autonomic and
behavioral neural correlates, and convolved to examine psycho-autonomic interaction
(PAI) effects. Across all stimuli, âthreatening,â compared with âharmlessâ behavioral
assessments were associated with mainly frontal and precuneus activation with specific
within-modality activations including bilateral parahippocampal gyri (pictures), bilateral
anterior cingulate cortex (ACC) and frontal pole (sentences), and right Heschlâs gyrus
and bilateral temporal gyri (sounds). Across stimulus modalities SCRs were associated
with activation of parieto-occipito-thalamic regions, an activation pattern which was largely
replicated within-modality. In contrast, PAI analyses revealed modality-specific activations
including right fusiform/parahippocampal gyrus (pictures), right insula (sentences), and
mid-cingulate gyrus (sounds). Phasic SCR activity was positively correlated with an
individualâs propensity to assess stimuli as âthreatening.â SCRs may modulate cognitive
assessments on a âharmlessâthreateningâ dimension, thereby modulating affective tone
and hence behavior
24-channel transcutaneous electrical sensory stimulation of the forearm: Effects on cognitive performance and autonomic arousal compared with single-electrode stimulation
We sought to establish the effects on cognitive performance and autonomic arousal of a multi-electrode transcutaneous electrical sensory stimulator compared with single-electrode stimulation. Progressing from a feasibility study (n = 10) to a repeated-measures, within-subject study (n = 67), healthy, right-handed participants (34 male, mean age 28 Âą 11.5 yrs.) received four separate predictable (âlinesâ or âringâ) or unpredictable (âflyâ or ârandomâ) complex electrical stimulation patterns to the non-dominant forearm via 24 individually programmable electrodes, or single-electrode stimulation. During stimulation, participants in the main study performed a series of cognitively demanding tests or a two-point discrimination task and had their autonomic arousal (skin conductance response) monitored. Single-electrode âfirst feltâ current intensity decreased from distal to proximal forearm, was positively correlated with forearm circumference and was lower in females. Single-electrode stimulation was associated with a significant decline in two-point discrimination performance. There were no significant autonomic arousal or cognitive performance differences between complex patterns, but all patterns were associated with greater autonomic arousal than single-electrode stimulation. In conclusion, gender and forearm location and circumference significantly influence perception-levels for electrical current. Future research should examine whether the induction of increased autonomic arousal, via multi-electrode complex patterns, has improved therapeutic application, compared with single-electrode stimulation
Magnetic phases of skyrmion-hosting GaV4S8âySey (y = 0, 2, 4, 8) probed with muon spectroscopy
We present the results of a muon-spin spectroscopy investigation of GaV4S8âySey with y = 0, 2, 4, and 8. Zero-field measurements suggest that GaV4Se8 and GaV4S8 have distinct magnetic ground states, with the latter material showing an anomalous temperature dependence of the local magnetic field. It is not possible to evolve the magnetic state continuously between these two systems, with the intermediate y = 2 and 4 materials showing glassy magnetic behavior at low temperature. The skyrmion lattice (SkL) phase is evident in the y = 0 and 8 materials through an enhanced response of the muon-spin relaxation to the emergent dynamics that accompany the SkL. For our polycrystalline samples of GaV4Se8, this enhanced dynamic response is confined to a smaller region of the magnetic field-temperature phase diagram than the previous reports of the SkL in single crystals
Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV
Results are presented from a search for a W' boson using a dataset
corresponding to 5.0 inverse femtobarns of integrated luminosity collected
during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV.
The W' boson is modeled as a heavy W boson, but different scenarios for the
couplings to fermions are considered, involving both left-handed and
right-handed chiral projections of the fermions, as well as an arbitrary
mixture of the two. The search is performed in the decay channel W' to t b,
leading to a final state signature with a single lepton (e, mu), missing
transverse energy, and jets, at least one of which is tagged as a b-jet. A W'
boson that couples to fermions with the same coupling constant as the W, but to
the right-handed rather than left-handed chiral projections, is excluded for
masses below 1.85 TeV at the 95% confidence level. For the first time using LHC
data, constraints on the W' gauge coupling for a set of left- and right-handed
coupling combinations have been placed. These results represent a significant
improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe
Search for the standard model Higgs boson decaying into two photons in pp collisions at sqrt(s)=7 TeV
A search for a Higgs boson decaying into two photons is described. The
analysis is performed using a dataset recorded by the CMS experiment at the LHC
from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an
integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross
section of the standard model Higgs boson decaying to two photons. The expected
exclusion limit at 95% confidence level is between 1.4 and 2.4 times the
standard model cross section in the mass range between 110 and 150 GeV. The
analysis of the data excludes, at 95% confidence level, the standard model
Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The
largest excess of events above the expected standard model background is
observed for a Higgs boson mass hypothesis of 124 GeV with a local significance
of 3.1 sigma. The global significance of observing an excess with a local
significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is
estimated to be 1.8 sigma. More data are required to ascertain the origin of
this excess.Comment: Submitted to Physics Letters
Measurement of the Lambda(b) cross section and the anti-Lambda(b) to Lambda(b) ratio with Lambda(b) to J/Psi Lambda decays in pp collisions at sqrt(s) = 7 TeV
The Lambda(b) differential production cross section and the cross section
ratio anti-Lambda(b)/Lambda(b) are measured as functions of transverse momentum
pt(Lambda(b)) and rapidity abs(y(Lambda(b))) in pp collisions at sqrt(s) = 7
TeV using data collected by the CMS experiment at the LHC. The measurements are
based on Lambda(b) decays reconstructed in the exclusive final state J/Psi
Lambda, with the subsequent decays J/Psi to an opposite-sign muon pair and
Lambda to proton pion, using a data sample corresponding to an integrated
luminosity of 1.9 inverse femtobarns. The product of the cross section times
the branching ratio for Lambda(b) to J/Psi Lambda versus pt(Lambda(b)) falls
faster than that of b mesons. The measured value of the cross section times the
branching ratio for pt(Lambda(b)) > 10 GeV and abs(y(Lambda(b))) < 2.0 is 1.06
+/- 0.06 +/- 0.12 nb, and the integrated cross section ratio for
anti-Lambda(b)/Lambda(b) is 1.02 +/- 0.07 +/- 0.09, where the uncertainties are
statistical and systematic, respectively.Comment: Submitted to Physics Letters
Search for new physics in events with opposite-sign leptons, jets, and missing transverse energy in pp collisions at sqrt(s) = 7 TeV
A search is presented for physics beyond the standard model (BSM) in final
states with a pair of opposite-sign isolated leptons accompanied by jets and
missing transverse energy. The search uses LHC data recorded at a
center-of-mass energy sqrt(s) = 7 TeV with the CMS detector, corresponding to
an integrated luminosity of approximately 5 inverse femtobarns. Two
complementary search strategies are employed. The first probes models with a
specific dilepton production mechanism that leads to a characteristic kinematic
edge in the dilepton mass distribution. The second strategy probes models of
dilepton production with heavy, colored objects that decay to final states
including invisible particles, leading to very large hadronic activity and
missing transverse energy. No evidence for an event yield in excess of the
standard model expectations is found. Upper limits on the BSM contributions to
the signal regions are deduced from the results, which are used to exclude a
region of the parameter space of the constrained minimal supersymmetric
extension of the standard model. Additional information related to detector
efficiencies and response is provided to allow testing specific models of BSM
physics not considered in this paper.Comment: Replaced with published version. Added journal reference and DO
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