4,857 research outputs found
Atmospheric Heat Redistribution on Hot Jupiters
Infrared lightcurves of transiting hot Jupiters present a trend in which the
atmospheres of the hottest planets are less efficient at redistributing the
stellar energy absorbed on their daysides---and thus have a larger day-night
temperature contrast---than colder planets. No predictive atmospheric model has
been published that identifies which dynamical mechanisms determine the
atmospheric heat redistribution efficiency on tidally locked exoplanets. Here
we present a two-layer shallow water model of the atmospheric dynamics on
synchronously rotating planets that explains the observed trend. Our model
shows that planets with weak friction and weak irradiation exhibit a banded
zonal flow with minimal day-night temperature differences, while models with
strong irradiation and/or strong friction exhibit a day-night flow pattern with
order-unity fractional day-night temperature differences. To interpret the
model, we develop a scaling theory that shows that the timescale for gravity
waves to propagate horizontally over planetary scales, t_wave, plays a dominant
role in controlling the transition from small to large temperature contrasts.
This implies that heat redistribution is governed by a wave-like process,
similar to the one responsible for the weak temperature gradients in the
Earth's tropics. When atmospheric drag can be neglected, the transition from
small to large day-night temperature contrasts occurs when t_wave ~
sqrt(t_rad/Omega), where t_rad is the radiative relaxation time and Omega is
the planetary rotation frequency. Alternatively, this transition criterion can
be expressed as t_rad ~ t_vert, where t_vert is the timescale for a fluid
parcel to move vertically over the difference in day-night thickness. These
results subsume the commonly used timescale comparison for estimating heat
redistribution efficiency between t_rad and the global horizontal advection
timescale, t_adv.Comment: Accepted to ApJ with minor edits compared to version 1; 17 pages, 11
figure
Criticality without frustration for quantum spin-1 chains
Frustration-free (FF) spin chains have a property that their ground state
minimizes all individual terms in the chain Hamiltonian. We ask how entangled
the ground state of a FF quantum spin-s chain with nearest-neighbor
interactions can be for small values of s. While FF spin-1/2 chains are known
to have unentangled ground states, the case s=1 remains less explored. We
propose the first example of a FF translation-invariant spin-1 chain that has a
unique highly entangled ground state and exhibits some signatures of a critical
behavior. The ground state can be viewed as the uniform superposition of
balanced strings of left and right parentheses separated by empty spaces.
Entanglement entropy of one half of the chain scales as log(n)/2 + O(1), where
n is the number of spins. We prove that the energy gap above the ground state
is polynomial in 1/n. The proof relies on a new result concerning statistics of
Dyck paths which might be of independent interest.Comment: 11 pages, 2 figures. Version 2: minor changes in the proof of Lemma
Simulation of Classical Thermal States on a Quantum Computer: A Transfer Matrix Approach
We present a hybrid quantum-classical algorithm to simulate thermal states of
a classical Hamiltonians on a quantum computer. Our scheme employs a sequence
of locally controlled rotations, building up the desired state by adding qubits
one at a time. We identify a class of classical models for which our method is
efficient and avoids potential exponential overheads encountered by Grover-like
or quantum Metropolis schemes. Our algorithm also gives an exponential
advantage for 2D Ising models with magnetic field on a square lattice, compared
with the previously known Zalka's algorithm.Comment: 5 pages, 3 figures; (new in version 2: added new figure, title
changed, rearranged paragraphs
Nonmotor Symptoms Groups in Parkinson's Disease Patients: Results of a Pilot, Exploratory Study
Nonmotor symptoms (NMS) like neuropsychiatric symptoms, sleep disturbances or autonomic symptoms are a common feature of Parkinson's disease (PD). To explore the existence of groups of NMS and to relate them to PD characteristics, 71 idiopathic non-demented PD out-patients were recruited. Sleep was evaluated by the PD Sleep Scale (PDSS). Several neuropsychiatric, gastrointestinal and urogenital symptoms were obtained from the NMSQuest. Sialorrhea or dysphagia severity was obtained from the Unified PD Rating Scale activities of daily living section. MADRS depression scale was also administered. Exploratory factor analysis revealed the presence of 5 factors, explaining 70% of variance. The first factor included PDSS measurement of sleep quality, nocturnal restlessness, off-related problems and daytime somnolence; the second factor included nocturia (PDSS) and nocturnal activity; the third one included gastrointestinal and genitourinary symptoms; the forth one included nocturnal psychosis (PDSS), sialorrhea and dysphagia (UPDRS); and the last one included the MADRS score as well as neuropsychiatric symptoms. Sleep disorders correlated with presence of wearing-off, nocturia with age >69 years, and nocturnal psychosis with levodopa equivalent dose or UPDRS II score. Neuropsychiatric symptoms correlated with UPDRS II+III score and non-tricyclic antidepressants. These results support the occurrence of significant NMS grouping in PD patients
Large family cohorts of lymphoblastoid cells provide a new cellular model for investigating facioscapulohumeral muscular dystrophy
Facioscapulohumeral muscular dystrophy (FSHD) is associated with aberrant epigenetic regulation of the chromosome 4q35 D4Z4 macrosatellite repeat. The resulting DNA hypomethylation and relaxation of epigenetic repression leads to increased expression of the deleterious DUX4-fl mRNA encoded within the distal D4Z4 repeat. With the typical late onset of muscle weakness, prevalence of asymptomatic individuals, and an autosomal dominant mode of inheritance, FSHD is often passed on from one generation to the next and affects multiple individuals within a family. Here we have characterized unique collections of 114 lymphoblastoid cell lines (LCLs) generated from 12 multigenerational FSHD families, including 56 LCLs from large, genetically homogeneous families in Utah. We found robust expression of DUX4-fl in most FSHD LCLs and a good correlation between DNA hypomethylation and repeat length. In addition, DUX4-fl levels can be manipulated using epigenetic drugs as in myocytes, suggesting that some epigenetic pathways regulating DUX4-fl in myocytes are maintained in LCLs. Overall, these FSHD LCLs provide an alternative cellular model in which to study many aspects of D4Z4, DUX4, and FSHD gene regulation in a background of low genetic variation. Significantly, these non-adherent immortal LCLs are amenable for high-throughput screening of potential therapeutics targeting DUX4-fl mRNA or protein expression
APOGEE Kinematics I: Overview of the Kinematics of the Galactic Bulge as Mapped by APOGEE
We present the stellar kinematics across the Galactic bulge and into the disk
at positive longitudes from the SDSS-III APOGEE spectroscopic survey of the
Milky Way. APOGEE includes extensive coverage of the stellar populations of the
bulge along the mid-plane and near-plane regions. From these data, we have
produced kinematic maps of 10,000 stars across longitudes 0 deg < l < 65 deg,
and primarily across latitudes of |b| < 5 deg in the bulge region. The APOGEE
data reveal that the bulge is cylindrically rotating across all latitudes and
is kinematically hottest at the very centre of the bulge, with the smallest
gradients in both kinematic and chemical space inside the inner-most region
(l,|b|) < (5,5) deg. The results from APOGEE show good agreement with data from
other surveys at higher latitudes and a remarkable similarity to the rotation
and dispersion maps of barred galaxies viewed edge on. The thin bar that is
reported to be present in the inner disk within a narrow latitude range of |b|
< 2 deg appears to have a corresponding signature in [Fe/H] and [alpha/Fe].
Stars with [Fe/H] > -0.5 have dispersion and rotation profiles that are similar
to that of N-body models of boxy/peanut bulges. There is a smooth kinematic
transition from the thin bar and boxy bulge (l,|b|) < (15,12) deg out into the
disk for stars with [Fe/H] > -1.0, and the chemodynamics across (l,b) suggests
the stars in the inner Galaxy with [Fe/H] > -1.0 have an origin in the disk.Comment: Accepted by ApJ 15 December 201
Understanding Nanoparticle Toxicity to Direct a Safe-by-Design Approach in Cancer Nanomedicine
Nanomedicine is a rapidly growing field that uses nanomaterials for the diagnosis, treatment and prevention of various diseases, including cancer. Various biocompatible nanoplatforms with diversified capabilities for tumor targeting, imaging, and therapy have materialized to yield individualized therapy. However, due to their unique properties brought about by their small size, safety concerns have emerged as their physicochemical properties can lead to altered pharmacokinetics, with the potential to cross biological barriers. In addition, the intrinsic toxicity of some of the inorganic materials (i.e., heavy metals) and their ability to accumulate and persist in the human body has been a challenge to their translation. Successful clinical translation of these nanoparticles is heavily dependent on their stability, circulation time, access and bioavailability to disease sites, and their safety profile. This review covers preclinical and clinical inorganic-nanoparticle based nanomaterial utilized for cancer imaging and therapeutics. A special emphasis is put on the rational design to develop non-toxic/safe inorganic nanoparticle constructs to increase their viability as translatable nanomedicine for cancer therapies
Parkinson’s disease sleep scale, sleep logs, and actigraphy in the evaluation of sleep in parkinsonian patients
The aim of this study was to compare the results of the day-to-day self-evaluation of sleep quality by sleep logs with Parkinson’s disease sleep scale (PDSS) in Parkinson’s disease (PD) patients. Actigraphy was used as an independent analysis of nighttime activity interfering with sleep. A total of 71 idiopathic PD patients and 21 age- and sex-matched normal individuals lacking any type of sleep disturbance were recruited. Sleep was evaluated by PDSS, 7-d sleep log and actigraphy. Sleep logs and PDSS showed reduced sleep quality and daytime somnolence scores in moderate/severe PD patients as compared to healthy controls. Significant correlations were found between sleep quality in sleep logs and all domains of PDSS sleep quality, except for the presence of nocturia, which correlated with nocturnal activity. PD severity and depression were the only predictors of reduced sleep quality. The retrospective and day-to-day sleep self-evaluations were coincident. Reduced sleep quality was related to increased PD severity and depression scores
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