978 research outputs found
Novel Phases in the Field Induced Spin Density Wave State in (TMTSF)_2PF_6
Magnetoresistance measurements on the quasi one-dimensional organic conductor
(TMTSF)_2PF_6 performed in magnetic fields B up to 16T, temperatures T down to
0.12K and under pressures P up to 14kbar have revealed new phases on its P-B-T
phase diagram. We found a new boundary which subdivides the field induced spin
density wave (FISDW) phase diagram into two regions. We showed that a
low-temperature region of the FISDW diagram is characterized by a hysteresis
behavior typical for the first order transitions, as observed in a number of
studies. In contrast to the common believe, in high temperature region of the
FISDW phase diagram, the hysteresis and, hence, the first order transitions
were found to disappear. Nevertheless, sharp changes in the resistivity slope
are observed both in the low and high temperature domains indicating that the
cascade of transitions between different subphases exists over all range of the
FISDW state. We also found that the temperature dependence of the resistance
(at a constant B) changes sign at about the same boundary. We compare these
results with recent theoretical models.Comment: LaTex, 4 pages, 4 figure
Measuring primordial gravitational waves from CMB B-modes in cosmologies with generalized expansion histories
We evaluate our capability to constrain the abundance of primordial tensor
perturbations in cosmologies with generalized expansion histories in the epoch
of cosmic acceleration. Forthcoming satellite and sub-orbital experiments
probing polarization in the CMB are expected to measure the B-mode power in CMB
polarization, coming from PGWs on the degree scale, as well as gravitational
lensing on arcmin scales; the latter is the main competitor for the measurement
of PGWs, and is directly affected by the underlying expansion history,
determined by the presence of a DE component. In particular, we consider early
DE possible scenarios, in which the expansion history is substantially modified
at the epoch in which the CMB lensing is most relevant. We show that the
introduction of a parametrized DE may induce a variation as large as 30% in the
ratio of the power of lensing and PGWs on the degree scale. We find that
adopting the nominal specifications of upcoming satellite measurements the
constraining power on PGWs is weakened by the inclusion of the extra degrees of
freedom, resulting in a reduction of about 10% of the upper limits on r in
fiducial models with no GWs, as well as a comparable increase in the error bars
in models with non-zero r. Moreover, we find that the inclusion of sub-orbital
CMB experiments, capable of mapping the B-mode power up to the angular scales
affected by lensing, can restore the forecasted performances with a
cosmological constant. Finally, we show how the combination of CMB data with
Type Ia SNe, BAO and Hubble constant allows to constrain simultaneously r and
the DE quantities in the parametrization we consider, consisting of present
abundance and first redshift derivative of the energy density. We compare this
study with results obtained using the forecasted lensing potential measurement
precision from CMB satellite observations, finding consistent results.Comment: 17 pages, 9 figures, accepted for publication by JCAP. Modified
version after the referee's comment
Lepton flavor violating signals of a little Higgs model at the high energy linear colliders
Littlest Higgs model predicts the existence of the doubly charged
scalars , which generally have large flavor changing couplings
to leptons. We calculate the contributions of to the lepton
flavor violating processes and , and compare our numerical results with the current
experimental upper limits on these processes. We find that some of these
processes can give severe constraints on the coupling constant and the
mass parameter . Taking into account the constraints on these free
parameters, we further discuss the possible lepton flavor violating signals of
at the high energy linear collider
experiments. Our numerical results show that the possible signals of
might be detected via the subprocesses in the future experiments.Comment: 16 pages, 7 figures. Discussions and references added, typos
correcte
Evidence Of Protein Collective Motions On The Picosecond Time Scale
We investigate the presence of structural collective motions on a picosecond
time scale for the heme protein, cytochrome c, as a function of oxidation and
hydration, using terahertz (THz) time-domain spectroscopy and molecular
dynamics simulations. The THz response dramatically increases with oxidation,
with the largest increase for lowest hydrations and highest frequencies. For
both oxidation states the THz response rapidly increases with hydration
saturating above ~25% (g H2O/g protein). Quasi-harmonic vibrational modes and
dipole-dipole correlation functions are calculated from molecular dynamics
trajectories. The collective mode density of states alone reproduces the
measured hydration dependence providing strong evidence of the existence of
these motions. The large oxidation dependence is reproduced only by the
dipole-dipole correlation function, indicating the contrast arises from
diffusive motions consistent with structural changes occurring in the vicinity
of a buried internal water molecule
Cerebral blood flow and cognitive performance in postural tachycardia syndrome: insights from sustained cognitive stress test
BACKGROUND: The physiology underlying "brain fog" in the absence of orthostatic stress in postural tachycardia syndrome(POTS) remains poorly understood. METHODS AND RESULTS: We evaluated cognitive and hemodynamic responses (cardiovascular and cerebral: heart rate, blood pressure, end-tidal carbon dioxide, and cerebral blood flow velocity (CBFv) in the middle cerebral artery at baseline, after initial cognitive testing, and after (30-minutes duration) prolonged cognitive stress test (PCST) whilst seated; as well as after 5-minute standing in consecutively enrolled participants with POTS (n=22) and healthy controls (n=18). Symptom severity was quantified with orthostatic hypotensive questionnaire at baseline and end of study. Subjects in POTS and control groups were frequency age- and sex-matched (29±11 versus 28±13 years; 86 versus 72% women, respectively; both P≥0.4). The CBFv decreased in both groups (condition, P=0.04) following PCST, but a greater reduction in CBFv was observed in the POTS versus control group (−7.8% versus −1.8%; interaction, P=0.038). Notably, the reduced CBFv following PCST in the POTS group was similar to that seen during orthostatic stress (60.0±14.9 versus 60.4±14.8 cm/s). Further, PCST resulted in greater slowing in psychomotor speed (6.1% versus 1.4%, interaction, P=0.027) and a greater increase in symptom scores at study completion (interaction, P0.05). CONCLUSIONS: Reduced CBFv and cognitive dysfunction were evident in patients with POTS following prolonged cognitive stress even in the absence of orthostatic stress.Rachel Wells, Varun Malik, Anthony G. Brooks, Dominik Linz, Adrian D. Elliott, Prashanthan Sanders ... et al
Lepton flavor violation decays in the topcolor-assisted technicolor model and the littlest Higgs model with parity
The new particles predicted by the topcolor-assisted technicolor ()
model and the littlest Higgs model with T-parity (called model) can
induce the lepton flavor violation () couplings at tree level or one loop
level, which might generate large contributions to some processes. Taking
into account the constraints of the experimental data on the relevant free
parameters, we calculate the branching ratios of the decay processes
with = , and
in the context of these two kinds of new physics models. We find
that the model and the model can indeed produce significant
contributions to some of these decay processes.Comment: 24 pages, 7 figure
Device-detected atrial fibrillation in a large remote-monitored cohort: implications for anticoagulation and need for new pathways of service delivery.
BACKGROUND: Remote monitoring (RM) can facilitate early detection of subclinical and symptomatic atrial fibrillation (AF), providing an opportunity to evaluate the need for stroke prevention therapies. We aimed to characterize the burden of RM AF alerts and its impact on anticoagulation of patients with device-detected AF. METHODS: Consecutive patients with a cardiac implantable electronic device, at least one AF episode, undergoing RM were included and assigned an estimated minimum CHA2DS2-VASc score based on age and device type. RM was provided via automated software system, providing rapid alert processing by device specialists and systematic, recurrent prompts for anticoagulation. RESULTS: From 7651 individual, 389,188 AF episodes were identified, 3120 (40.8%) permanent pacemakers, 2260 (29.5%) implantable loop recorders (ILRs), 987 (12.9%) implantable cardioverter defibrillators, 968 (12.7%) cardiac resynchronization therapy (CRT) defibrillators, and 316 (4.1%) CRT pacemakers. ILRs transmitted 48.8% of all AF episodes. At twelve-months, 3404 (44.5%) AF < 6 min, 1367 (17.9%) 6 min-6 h, 1206 (15.8%) 6-24 h, and 1674 (21.9%) ≥ 24 h. A minimum CHA2DS2-VASc score of 2 was assigned to 1704 (63.1%) of the patients with an AF episode of ≥ 6 h, 531 (31.2%) who were not anticoagulated at 12-months, and 1031 (61.6%) patients with an AF episode duration of ≥ 24 h, 290 (28.1%) were not anticoagulated. CONCLUSIONS: Despite being intensively managed via RM software system incorporating cues for anticoagulation, a substantial proportion of patients with increased stroke risk remained unanticoagulated after a device-detected AF episode of significant duration. These data highlight the need for improved clinical response pathways and an integrated care approach to RM. TRIAL REGISTRATION: Australian New Zealand Clinical Trial Registry: ACTRN12620001232921.Catherine J. O, Shea, Anthony G. Brooks, Melissa E. Middeldorp, Curtis Harper, Jeroen M. Hendriks, Andrea M. Russo, James V. Freeman, Rakesh Gopinathannair, Niraj Varma, Thomas F. Deering, Kevin Campbell, Prashanthan Sander
Exploring flavor structure of supersymmetry breaking from rare B decays and unitarity triangle
We study effects of supersymmetric particles in various rare B decay
processes as well as in the unitarity triangle analysis. We consider three
different supersymmetric models, the minimal supergravity, SU(5) SUSY GUT with
right-handed neutrinos, and the minimal supersymmetric standard model with U(2)
flavor symmetry. In the SU(5) SUSY GUT with right-handed neutrinos, we consider
two cases of the mass matrix of the right-handed neutrinos. We calculate direct
and mixing-induced CP asymmetries in the b to s gamma decay and CP asymmetry in
B_d to phi K_S as well as the B_s--anti-B_s mixing amplitude for the unitarity
triangle analysis in these models. We show that large deviations are possible
for the SU(5) SUSY GUT and the U(2) model. The pattern and correlations of
deviations from the standard model will be useful to discriminate the different
SUSY models in future B experiments.Comment: revtex4, 36 pages, 10 figure
Orbital effect of a magnetic field on the low temperature state in the organic metal -(BEDT-TTF)KHg(SCN)
The effect of pressure on the B--T phase diagram of
-(BEDT-TTF)KHg(SCN) is studied. The measured phase lines can be
well described by a recent model of a charge-density wave system with varying
nesting conditions. A remarkable increase of the transition temperature with
magnetic field is found in a certain pressure and field range. We associate
this result with a dramatic enhancement of the orbital effect of magnetic field
due to a deterioration of the nesting conditions by pressure. Furthermore, we
present data which can be interpreted as a first sign of field-induced
charge-density waves.Comment: 9 pages, 5 figure
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