711 research outputs found
Quantum mechanics on non commutative spaces and squeezed states: a functional approach
We review here the quantum mechanics of some noncommutative theories in which
no state saturates simultaneously all the non trivial Heisenberg uncertainty
relations. We show how the difference of structure between the Poisson brackets
and the commutators in these theories generically leads to a harmonic
oscillator whose positions and momenta mean values are not strictly equal to
the ones predicted by classical mechanics.
This raises the question of the nature of quasi classical states in these
models. We propose an extension based on a variational principle. The action
considered is the sum of the absolute values of the expressions associated to
the non trivial Heisenberg uncertainty relations. We first verify that our
proposal works in the usual theory i.e we recover the known Gaussian functions.
Besides them, we find other states which can be expressed as products of
Gaussians with specific hyper geometrics.
We illustrate our construction in two models defined on a four dimensional
phase space: a model endowed with a minimal length uncertainty and the non
commutative plane. Our proposal leads to second order partial differential
equations. We find analytical solutions in specific cases. We briefly discuss
how our proposal may be applied to the fuzzy sphere and analyze its
shortcomings.Comment: 15 pages revtex. The title has been modified,the paper shortened and
misprints have been corrected. Version to appear in JHE
The Brightness of Density Structures at Large Solar Elongation Angles: What is Being Observed by STEREO/SECCHI?
We discuss features of coronal mass ejections (CMEs) that are specific to
heliospheric observations at large elongation angles. Our analysis is focused
on a series of two eruptions that occurred on 2007 January 24-25, which were
tracked by the Heliospheric Imagers (HIs) onboard STEREO. Using a
three-dimensional (3-D) magneto-hydrodynamic simulation of these ejections with
the Space Weather Modeling Framework (SWMF), we illustrate how the combination
of the 3-D nature of CMEs, solar rotation, and geometry associated with the
Thomson sphere results in complex effects in the brightness observed by the
HIs. Our results demonstrate that these effects make any in-depth analysis of
CME observations without 3-D simulations challenging. In particular, the
association of bright features seen by the HIs with fronts of CME-driven shocks
is far from trivial. In this Letter, we argue that, on 2007 January 26, the HIs
observed not only two CMEs, but also a dense corotating stream compressed by
the CME-driven shocks.Comment: 5 pages, 2 figures, accepted for ApJ Lette
Tuning the Exo-Space Weather Radio for Stellar Coronal Mass Ejections
Coronal mass ejections (CMEs) on stars other than the Sun have proven very
difficult to detect. One promising pathway lies in the detection of type II
radio bursts. Their appearance and distinctive properties are associated with
the development of an outward propagating CME-driven shock. However, dedicated
radio searches have not been able to identify these transient features in other
stars. Large Alfv\'en speeds and the magnetic suppression of CMEs in active
stars have been proposed to render stellar eruptions "radio-quiet". Employing
3D magnetohydrodynamic simulations, we study here the distribution of the
coronal Alfv\'en speed, focusing on two cases representative of a young
Sun-like star and a mid-activity M-dwarf (Proxima Centauri). These results are
compared with a standard solar simulation and used to characterize the
shock-prone regions in the stellar corona and wind. Furthermore, using a
flux-rope eruption model, we drive realistic CME events within our M-dwarf
simulation. We consider eruptions with different energies to probe the regimes
of weak and partial CME magnetic confinement. While these CMEs are able to
generate shocks in the corona, those are pushed much farther out compared to
their solar counterparts. This drastically reduces the resulting type II radio
burst frequencies down to the ionospheric cutoff, which impedes their detection
with ground-based instrumentation.Comment: 13 Pages, 6 Figures, 2 Tables. Accepted for publication in The
Astrophysical Journa
Association between 8 P-glycoprotein (MDR1/ABCB1) gene polymorphisms and antipsychotic drug-induced hyperprolactinaemia
INTRODUCTION: Hyperprolactinaemia, a common adverse effect of antipsychotic drugs, is primarily linked to blockade of dopamine D2 receptors in the pituitary gland. Certain antipsychotic drugs, such as, for example risperidone and paliperidone, are more likely to induce hyperprolactinaemia compared to others. This effect is probably caused by a relatively high blood/brain concentration ratio, a consequence of being a substrate of P-glycoprotein. Genetic variants of P-glycoprotein with changed functional activity might influence the potential of risperidone and paliperidone to cause hyperprolactinaemia as the altered blood/brain concentration ratio would lead to a reduced therapeutic drug level within essential brain areas making dose adaptations necessary. This increases exposure of dopamine D2 receptors within the pituitary gland. AIMS: To investigate possible associations between MDR1/ABCB1 gene polymorphisms and antipsychotic drug-induced hyperprolactinaemia in Russian patients with schizophrenia and to determine possible differences between risperidone/paliperidone and other antipsychotics. METHODS: In total, 446 patients with schizophrenia were included from 3 psychiatric hospitals in Siberia. Blood samples were obtained in a cross-sectional study design for DNA extraction and prolactin measurement. Associations between hyperprolactinaemia and 8 MDR1/ABCB1 gene-polymorphisms were assessed using logistic regression analysis accounting for covariates. The analysis was repeated in a patient subgroup using risperidone or paliperidone. RESULTS: We did not observe an association between any of the 8 single nucleotide polymorphisms and the prevalence of antipsychotic-induced hyperprolactinaemia in the total patient population. However, in the risperidone/paliperidone subgroup, the single nucleotide polymorphism rs2032582 (G2677T) was found to be negatively associated with risperidone/paliperidone-induced hyperprolactinaemia. CONCLUSION: This study revealed a significant association between the ABCB1 gene polymorphism rs2032582 (G2677T) and risperidone/paliperidone-induced hyperprolactinaemia
Conference of Microelectronic Research 1996
https://scholarworks.rit.edu/meec_archive/1005/thumbnail.jp
The Coupled Evolution of Electrons and Ions in Coronal Mass Ejection-driven shocks
We present simulations of coronal mass ejections (CMEs) performed with a new two-temperature coronal model developed at the University of Michigan, which is able to address the coupled thermodynamics of the electron and proton populations in the context of a single fluid. This model employs heat conduction for electrons, constant adiabatic index (γ = 5/3), and includes Alfvén wave pressure to accelerate the solar wind. The Wang-Sheeley-Arge empirical model is used to determine the Alfvén wave pressure necessary to produce the observed bimodal solar wind speed. The Alfvén waves are dissipated as they propagate from the Sun and heat protons on open magnetic field lines to temperatures above 2 MK. The model is driven by empirical boundary conditions that includes GONG magnetogram data to calculate the coronal field, and STEREO /EUVI observations to specify the density and temperature at the coronal boundary by the Differential Emission Measure Tomography method. With this model, we simulate the propagation of fast CMEs and study the thermodynamics of CME-driven shocks. Since the thermal speed of the electrons greatly exceeds the speed of the CME, only protons are directly heated by the shock. Coulomb collisions low in the corona couple the protons and electrons allowing heat exchange between the two species. However, the coupling is so brief that the electrons never achieve more than 10% of the maximum temperature of the protons. We find that heat is able to conduct on open magnetic field lines and rapidly propagates ahead of the CME to form a shock precursor of hot electrons.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98571/1/0004-637X_756_1_81.pd
The clubfoot assessment protocol (CAP); description and reliability of a structured multi-level instrument for follow-up
BACKGROUND: In most clubfoot studies, the outcome instruments used are designed to evaluate classification or long-term cross-sectional results. Variables deal mainly with factors on body function/structure level. Wide scorings intervals and total sum scores increase the risk that important changes and information are not detected. Studies of the reliability, validity and responsiveness of these instruments are sparse. The lack of an instrument for longitudinal follow-up led the investigators to develop the Clubfoot Assessment Protocol (CAP). The aim of this article is to introduce and describe the CAP and evaluate the items inter- and intra reliability in relation to patient age. METHODS: The CAP was created from 22 items divided between body function/structure (three subgroups) and activity (one subgroup) levels according to the International Classification of Function, Disability and Health (ICF). The focus is on item and subgroup development. Two experienced examiners assessed 69 clubfeet in 48 children who had a median age of 2.1 years (range, 0 to 6.7 years). Both treated and untreated feet with different grades of severity were included. Three age groups were constructed for studying the influence of age on reliability. The intra- rater study included 32 feet in 20 children who had a median age of 2.5 years (range, 4 months to 6.8 years). The Unweighted Kappa statistics, percentage observer agreement, and amount of categories defined how reliability was to be interpreted. RESULTS: The inter-rater reliability was assessed as moderate to good for all but one item. Eighteen items had kappa values > 0.40. Three items varied from 0.35 to 0.38. The mean percentage observed agreement was 82% (range, 62 to 95%). Different age groups showed sufficient agreement. Intra- rater; all items had kappa values > 0.40 [range, 0.54 to 1.00] and a mean percentage agreement of 89.5%. Categories varied from 3 to 5. CONCLUSION: The CAP contains more detailed information than previous protocols. It is a multi-dimensional observer administered standardized measurement instrument with the focus on item and subgroup level. It can be used with sufficient reliability, independent of age, during the first seven years of childhood by examiners with good clinical experience. A few items showed low reliability, partly dependent on the child's age and /or varying professional backgrounds between the examiners. These items should be interpreted with caution, until further studies have confirmed the validity and sensitivity of the instrument
Long range transport of soil dust and smoke pollution in the South Asian Region.
Transboundary transport of air pollution in the South Asian region has been an issue of increasing importance over the past several decades. Long–range transport of anthropogenic pollution is contrasted with that of pollution produced by natural processes such as dust storms or natural forest fires. Airborne particulate matter datasets covering the period from 2002 to 2007 from the neighboring countries like Bangladesh, India, Pakistan and Sri Lanka were used to find the source areas that are primarily responsible for long range transported pollutants. All four countries collected samples with the same type of sampler and follow the same technique for mass and BC measurements. It was found that high fine soil contributions were from dust storms. On the other hand, smoke in this region mainly comes from northern India where agricultural waste is often burned. © Elsevier B.V
Stellar Coronal and Wind Models: Impact on Exoplanets
Surface magnetism is believed to be the main driver of coronal heating and
stellar wind acceleration. Coronae are believed to be formed by plasma confined
in closed magnetic coronal loops of the stars, with winds mainly originating in
open magnetic field line regions. In this Chapter, we review some basic
properties of stellar coronae and winds and present some existing models. In
the last part of this Chapter, we discuss the effects of coronal winds on
exoplanets.Comment: Chapter published in the "Handbook of Exoplanets", Editors in Chief:
Juan Antonio Belmonte and Hans Deeg, Section Editor: Nuccio Lanza. Springer
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