798 research outputs found
Quantum rotor theory of spinor condensates in tight traps
In this work, we theoretically construct exact mappings of many-particle
bosonic systems onto quantum rotor models. In particular, we analyze the rotor
representation of spinor Bose-Einstein condensates. In a previous work it was
shown that there is an exact mapping of a spin-one condensate of fixed particle
number with quadratic Zeeman interaction onto a quantum rotor model. Since the
rotor model has an unbounded spectrum from above, it has many more eigenstates
than the original bosonic model. Here we show that for each subset of states
with fixed spin F_z, the physical rotor eigenstates are always those with
lowest energy. We classify three distinct physical limits of the rotor model:
the Rabi, Josephson, and Fock regimes. The last regime corresponds to a
fragmented condensate and is thus not captured by the Bogoliubov theory. We
next consider the semiclassical limit of the rotor problem and make connections
with the quantum wave functions through use of the Husimi distribution
function. Finally, we describe how to extend the analysis to higher-spin
systems and derive a rotor model for the spin-two condensate. Theoretical
details of the rotor mapping are also provided here.Comment: 10 pages, 2 figure
Recommended from our members
LSD1-mediated enhancer silencing attenuates retinoic acid signalling during pancreatic endocrine cell development.
Developmental progression depends on temporally defined changes in gene expression mediated by transient exposure of lineage intermediates to signals in the progenitor niche. To determine whether cell-intrinsic epigenetic mechanisms contribute to signal-induced transcriptional responses, here we manipulate the signalling environment and activity of the histone demethylase LSD1 during differentiation of hESC-gut tube intermediates into pancreatic endocrine cells. We identify a transient requirement for LSD1 in endocrine cell differentiation spanning a short time-window early in pancreas development, a phenotype we reproduced in mice. Examination of enhancer and transcriptome landscapes revealed that LSD1 silences transiently active retinoic acid (RA)-induced enhancers and their target genes. Furthermore, prolonged RA exposure phenocopies LSD1 inhibition, suggesting that LSD1 regulates endocrine cell differentiation by limiting the duration of RA signalling. Our findings identify LSD1-mediated enhancer silencing as a cell-intrinsic epigenetic feedback mechanism by which the duration of the transcriptional response to a developmental signal is limited
E-cigarette Addiction and Harm perception: Does initiation flavor choice matter?
Introduction
The 21st century was marked by a dramatic increase in adolescent e-cigarette use in the United States (US). The popularity of non-traditional flavor types, including fruit and pastry, is thought to contribute toward growing product use nationally, leading to a variety of federal and state regulations limiting the use of non-traditional flavors in the US. The relationship between flavor type and increased adolescent use suggests a possible link between flavor use and addiction and harm perception. This study assessed if the flavor type used when initiating e-cigarette use predicted addiction and harm perceptions. Methods
The study utilized data from the multi-wave youth Population Assessment of Tobacco Health Study. It explored the impact initiating e-cigarette use with traditional versus non-traditional flavor types among cigarette users on the outcome variables: e-cigarette addiction and harm perception. Both e-cigarette addiction and harm perception were measured using self-report, Likert scale questionnaires. Descriptive statistics characterized the study variables and linear regression analyses performed to test whether flavor initiation type is associated with addiction and harm perception. Results
The study sample consisted of 1,043 youth (weighted N = 1,873,617) aged 12 to 17 years who reported at least one instance of e-cigarette use. After adjusting for age, age of onset, sex, race and annual household income there was no statistically significant difference in addiction levels between those initiating with traditional versus non-traditional flavors (p = 0.294). Similarly, traditional versus non-traditional flavor initiation did not show a statistically significant difference in adolescent e-cigarette harm perceptions (p = 0.601). Conclusions
Traditionally flavored e-cigarette initiation produces similar risk for addiction and harm perceptions as non-traditionally flavored initiation. These findings suggest that banning non-traditional flavors alone may be ineffective in curbing e-cigarette addiction and harm perception. Additional research is needed to better understand which e-cigarette product characteristics and behaviors may be associated with greater addiction and reduced harm perceptions
Multi-Domain Cognitive Assessment of Male Mice Shows Space Radiation Is Not Harmful to High-Level Cognition and Actually Improves Pattern Separation
Astronauts on interplanetary missions - such as to Mars - will be exposed to space radiation, a spectrum of highly-charged, fast-moving particles that includes 56Fe and 28Si. Earth-based preclinical studies show space radiation decreases rodent performance in low- and some high-level cognitive tasks. Given astronaut use of touchscreen platforms during training and space flight and given the ability of rodent touchscreen tasks to assess functional integrity of brain circuits and multiple cognitive domains in a non-aversive way, here we exposed 6-month-old C57BL/6J male mice to whole-body space radiation and subsequently assessed them on a touchscreen battery. Relative to Sham treatment, 56Fe irradiation did not overtly change performance on tasks of visual discrimination, reversal learning, rule-based, or object-spatial paired associates learning, suggesting preserved functional integrity of supporting brain circuits. Surprisingly, 56Fe irradiation improved performance on a dentate gyrus-reliant pattern separation task; irradiated mice learned faster and were more accurate than controls. Improved pattern separation performance did not appear to be touchscreen-, radiation particle-, or neurogenesis-dependent, as 56Fe and 28Si irradiation led to faster context discrimination in a non-touchscreen task and 56Fe decreased new dentate gyrus neurons relative to Sham. These data urge revisitation of the broadly-held view that space radiation is detrimental to cognition
Double-Peaked Balmer Emission Indicating Prompt Accretion Disk Formation in an X-Ray Faint Tidal Disruption Event
We present the multi-wavelength analysis of the tidal disruption event (TDE)
AT~2018hyz (ASASSN-18zj). From follow-up optical spectroscopy, we detect the
first unambiguous case of resolved double-peaked Balmer emission in a TDE. The
distinct line profile can be well-modelled by a low eccentricity
() accretion disk extending out to 100 and a
Gaussian component originating from non-disk clouds, though a bipolar outflow
origin cannot be completely ruled out. Our analysis indicates that in
AT~2018hyz, disk formation took place promptly after the most-bound debris
returned to pericenter, which we estimate to be roughly tens of days before the
first detection. Redistribution of angular momentum and mass transport,
possibly through shocks, must occur on the observed timescale of about a month
to create the large \Ha-emitting disk that comprises 5\% of the
initial stellar mass. With these new insights from AT~2018hyz, we infer that
circularization is efficient in at least some, if not all optically-bright,
X-ray faint TDEs. In these efficiently circularized TDEs, the detection of
double-peaked emission depends on the disk inclination angle and the relative
strength of the disk contribution to the non-disk component, possibly
explaining the diversity seen in the current sample.Comment: 24 pages, 8 figures, 6 tables. Accepted for publication in Ap
Discovery of a Fast Iron Low-ionization Outflow in the Early Evolution of the Nearby Tidal Disruption Event AT2019qiz
We report the results of UV and optical photometric and spectroscopic
analysis on the tidal disruption event (TDE) AT2019qiz. Our follow-up
observations started shortly after (10 days) its optical light begin
to rise and lasted for a period of six months. Our late-time host-dominated
spectrum indicates that the host galaxy likely harbours a weak AGN. The initial
HST spectrum of AT2019qiz exhibits a iron and low-ionization broad absorption
line (FeLoBAL) system that is seen for the first time in a TDE. This spectrum
also bears a striking resemblance to that of Gaia16apd, a superluminous
supernova. Our observations provide insights into the outflow properties in
TDEs and show evidence for a connection between TDEs and engine-powered
supernovae at early phase, as originally suggested in Metzger & Stone (2016).
In a time frame of 50 days, the UV spectra of AT2019qiz started to resemble
previous TDEs with only high-ionization BALs. The change in UV spectral
signatures is accompanied by a decrease in the outflow velocity, which began at
km s and decelerated to km s. A similar
evolution in the H emission line width further supports the speculation
that the broad Balmer emission lines are formed in TDE outflows. In addition,
we detect narrow absorption features on top of the FeLoBAL signatures in the
early HST UV spectrum of AT2019qiz. The measured HI column density corresponds
to a Lyman-limit system whereas the metal absorption lines, such as NV, CIV,
FeII, and MgII, are likely probing the circumnuclear gas and interstellar
medium in the host galaxy.Comment: 24 pages, 13 figures, 3 tables. Submitted to ApJ on Nov 03 202
Amplification and PI3KCA Mutation in a Case of Sclerosing Rhabdomyosarcoma
A rare sclerosing variant of rhabdomyosarcoma characterized by prominent hyalinization and pseudovascular pattern has recently been described as a subtype biologically distinct from embryonal, alveolar, and pleomorphic forms. We present cytogenetic and molecular findings as well as experimental studies of an unusual case of sclerosing rhabdomyosarcoma. The primary lesion arose within the plantar subcutaneous tissue of the left foot of an otherwise healthy 23-year-old male who eventually developed pulmonary nodules despite systemic chemotherapy. Two genetic abnormalities identified in surgical and/or autopsy samples of the tumor were introduced into 10T1/2 murine fibroblasts to determine whether these genetic changes cooperatively facilitated transformation and growth. Cytogenetic analysis revealed a complex abnormal hyperdiploid clone, and MDM2 gene amplification was confirmed by fluorescence in situ hybridization. Cancer gene mutation screening using a combination of multiplexed PCR and mass spectroscopy revealed a PIK3CA exon 20 H1047R mutation in the primary tumor, lung metastasis, and liver metastasis. However, this mutation was not cooperative with MDM2 overexpression in experimental assays for transformation or growth. Nevertheless, MDM2 and PIK3CA are genes worthy of further investigation in patients with sclerosing rhabdomyosarcoma and might be considered in the enrollment of these patients into clinical trials of targeted therapeutics
Measurement of Jet Shapes in Photoproduction at HERA
The shape of jets produced in quasi-real photon-proton collisions at
centre-of-mass energies in the range GeV has been measured using the
hadronic energy flow. The measurement was done with the ZEUS detector at HERA.
Jets are identified using a cone algorithm in the plane with a
cone radius of one unit. Measured jet shapes both in inclusive jet and dijet
production with transverse energies GeV are presented. The jet
shape broadens as the jet pseudorapidity () increases and narrows
as increases. In dijet photoproduction, the jet shapes have been
measured separately for samples dominated by resolved and by direct processes.
Leading-logarithm parton-shower Monte Carlo calculations of resolved and direct
processes describe well the measured jet shapes except for the inclusive
production of jets with high and low . The observed
broadening of the jet shape as increases is consistent with the
predicted increase in the fraction of final state gluon jets.Comment: 29 pages including 9 figure
D* Production in Deep Inelastic Scattering at HERA
This paper presents measurements of D^{*\pm} production in deep inelastic
scattering from collisions between 27.5 GeV positrons and 820 GeV protons. The
data have been taken with the ZEUS detector at HERA. The decay channel
(+ c.c.) has been used in the study. The
cross section for inclusive D^{*\pm} production with
and is 5.3 \pms 1.0 \pms 0.8 nb in the kinematic region
{ GeV and }. Differential cross
sections as functions of p_T(D^{*\pm}), and are
compared with next-to-leading order QCD calculations based on the photon-gluon
fusion production mechanism. After an extrapolation of the cross section to the
full kinematic region in p_T(D^{*\pm}) and (D^{*\pm}), the charm
contribution to the proton structure function is
determined for Bjorken between 2 10 and 5 10.Comment: 17 pages including 4 figure
Plastisol Foaming Process. Decomposition of the Foaming Agent, Polymer Behavior in the Corresponding Temperature Range and Resulting Foam Properties
The decomposition of azodicarbonamide, used as foaming agent in PVC - plasticizer (1/1) plastisols was studied by DSC. Nineteen different plasticizers, all belonging to the ester family, two being polymeric (polyadipates), were compared. The temperature of maximum decomposition rate (in anisothermal regime at 5 K min-1 scanning rate), ranges between 434 and 452 K. The heat of decomposition ranges between 8.7 and 12.5 J g -1. Some trends of variation of these parameters appear significant and are discussed in terms of solvent (matrix) and viscosity effects on the decomposition reactions. The shear modulus at 1 Hz frequency was determined at the temperature of maximum rate of foaming agent decomposition, and differs significantly from a sample to another. The foam density was determined at ambient temperature and the volume fraction of bubbles was used as criterion to judge the efficiency of the foaming process. The results reveal the existence of an optimal shear modulus of the order of 2 kPa that corresponds roughly to plasticizer molar masses of the order of 450 ± 50 g mol-1. Heavier plasticizers, especially polymeric ones are too difficult to deform. Lighter plasticizers such as diethyl phthalate (DEP) deform too easily and presumably facilitate bubble collapse
- …