4,298 research outputs found
How to determine a quantum state by measurements: The Pauli problem for a particle with arbitrary potential
The problem of reconstructing a pure quantum state ĀæĀæ> from measurable quantities is considered for a particle moving in a one-dimensional potential V(x). Suppose that the position probability distribution ĀæĀæ(x,t)Āæ2 has been measured at time t, and let it have M nodes. It is shown that after measuring the time evolved distribution at a short-time interval Āæt later, ĀæĀæ(x,t+Āæt)Āæ2, the set of wave functions compatible with these distributions is given by a smooth manifold M in Hilbert space. The manifold M is isomorphic to an M-dimensional torus, TM. Finally, M additional expectation values of appropriately chosen nonlocal operators fix the quantum state uniquely. The method used here is the analog of an approach that has been applied successfully to the corresponding problem for a spin system
Susceptibility functions for slow relaxation processes in supercooled liquids and the search for universal relaxation patterns
In order to describe the slow response of a glass former we discuss some
distribution of correlation times, e.g., the generalized gamma distribution
(GG) and an extension thereof (GGE), the latter allowing to reproduce a simple
peak susceptibility such as of Cole-Davidson type as well as a susceptibility
exhibiting an additional high frequency power law contribution (excess wing).
Applying the GGE distribution to the dielectric spectra of glass formers
exhibiting no beta-process peak (glycerol, propylene carbonate and picoline) we
are able to reproduce the salient features of the slow response (1e-6 Hz - 1e9
Hz). A line shape analysis is carried out either in the time or frequency
domain and in both cases an excess wing can be identified. The latter evolves
in a universal way while cooling and shows up for correlation times tau_alpha >
1e-8 s. It appears that its first emergence marks the break down of the high
temperature scenario of mode coupling theory. - In order to describe a glass
former exhibiting a beta-process peak we have introduced a distribution
function which is compatible with assuming a thermally activated process in
contrast to some commonly used fit functions. Together with the GGE
distribution this function allows in the frame of the Williams-Watts approach
to completely interpolate the spectra, e.g. of fluoro aniline (1e-6 Hz - 1e9
Hz). The parameters obtained indicate an emergence of both the excess wing and
the beta-process again at tau_alpha > 1e-8s.Comment: 22 pages, 12 figure
Symmetric informationally complete positive operator valued measure and probability representation of quantum mechanics
Symmetric informationally complete positive operator valued measures
(SIC-POVMs) are studied within the framework of the probability representation
of quantum mechanics. A SIC-POVM is shown to be a special case of the
probability representation. The problem of SIC-POVM existence is formulated in
terms of symbols of operators associated with a star-product quantization
scheme. We show that SIC-POVMs (if they do exist) must obey general rules of
the star product, and, starting from this fact, we derive new relations on
SIC-projectors. The case of qubits is considered in detail, in particular, the
relation between the SIC probability representation and other probability
representations is established, the connection with mutually unbiased bases is
discussed, and comments to the Lie algebraic structure of SIC-POVMs are
presented.Comment: 22 pages, 1 figure, LaTeX, partially presented at the Workshop
"Nonlinearity and Coherence in Classical and Quantum Systems" held at the
University "Federico II" in Naples, Italy on December 4, 2009 in honor of
Prof. Margarita A. Man'ko in connection with her 70th birthday, minor
misprints are corrected in the second versio
Changes in macrophage phenotype and induction of epithelialātoāmesenchymal transition genes following acute Achilles tenotomy and repair
Tendon injuries occur frequently in physically active individuals, but the clinical outcomes for these injuries can be poor. In many injured tissues the repair process is orchestrated by two types of cells, macrophages and fibroblasts. Macrophages, which have both proāinflammatory (M1) and antiāinflammatory (M2) phenotypes, can directly participate in tissue remodeling and direct the response of other cells through the secretion of cytokines and growth factors. In many organ systems, epithelial cells can transādifferentiate into fibroblasts, which can then regenerate damaged ECM. This process is triggered via activation of epithelialātoāmesenchymal transition (EMT) signaling programs. Most tendons are surrounded by sheets of epithelial cells, and these tissue layers could provide a source of fibroblasts to repair injured tendons. To gain greater insight into the biology of tendon repair, we performed a tenotomy and repair in Achilles tendons of adult rats and determined changes in macrophage phenotype, and ECMā and EMTārelated genes over a 4āweek time course. The results from this study suggest that changes in macrophage phenotype and activation of EMTārelated programs likely contribute to the degradation and subsequent repair of injured tendon tissue. Ā© 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:944ā951, 2014.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106967/1/jor22624.pd
Trajectories of quality of life in early-stage dementia: individual variations and predictors of change
Background:
Little evidence is available about how quality of life (QoL) changes as dementia progresses.
Objectives:
We explored QoL trajectories over a 20-month period and examined what predicted change in QoL.
Method:
Fifty-one individuals with a diagnosis of Alzheimerās, vascular or mixed dementia (PwD) participating in the MIDAS study rated their QoL using the QoL-AD scale at baseline and at 20-month follow-up. PwD also rated their mood and quality of relationship with the carer. In each case the carer rated his/her level of stress and perceived quality of relationship with the PwD.
Results:
There was no change in mean QoL score. Nearly one-third of PwD rated QoL more positively at 20-month follow-up and nearly one-third rated QoL more negatively. These changes could be regarded as reliable in one-quarter of the sample. Participants taking AChEI medication at baseline were more likely to show a decline in QoL score. There were no other significant differences between those whose scores increased, decreased or stayed the same on any demographic or disease-related variables, or in mood or perceived quality of relationship with the carer. While baseline QoL score was the strongest predictor of QoL at 20 months, the quality of relationship with the carer as perceived by the PwD was also independently a significant predictor.
Conclusions:
There is a degree of individual variation in QoL trajectories. Use of AChEI medication appears linked to decline in QoL score, while positive relationships with carers play an important role in maintaining QoL in early-stage dementia
Single electron emission in two-phase xenon with application to the detection of coherent neutrino-nucleus scattering
We present an experimental study of single electron emission in ZEPLIN-III, a
two-phase xenon experiment built to search for dark matter WIMPs, and discuss
applications enabled by the excellent signal-to-noise ratio achieved in
detecting this signature. Firstly, we demonstrate a practical method for
precise measurement of the free electron lifetime in liquid xenon during normal
operation of these detectors. Then, using a realistic detector response model
and backgrounds, we assess the feasibility of deploying such an instrument for
measuring coherent neutrino-nucleus elastic scattering using the ionisation
channel in the few-electron regime. We conclude that it should be possible to
measure this elusive neutrino signature above an ionisation threshold of
3 electrons both at a stopped pion source and at a nuclear reactor.
Detectable signal rates are larger in the reactor case, but the triggered
measurement and harder recoil energy spectrum afforded by the accelerator
source enable lower overall background and fiducialisation of the active
volume
Examination and measurement of coping among adolescents with spinal cord injury
Objectives:
To describe coping strategy use in adolescents with spinal cord injury (SCI), to explore the underlying factor structure of a measure of coping among adolescents with SCI and to assess relationships between coping and psychosocial outcomes. Setting: Multiple pediatric SCI centers in the United States.
Methods:
One hundred and eighty-two participants aged 13ā17 years who experienced an SCI completed measures including the Kidcope, Childrenās Depression Inventory, Revised Childrenās Manifest Anxiety Scale and the Pediatric Quality of Life Inventory.
Results:
Participants reported that cognitive restructuring and resignation are the most used coping strategies, whereas social support, emotional regulation (calming) and cognitive restructuring are the most effective coping strategies. An exploratory factor analysis revealed that a three-factor solution provided the most parsimonious model for the relationships between the different coping strategies. However, only one of the three factors had acceptable internal consistency. This factor comprised escape-oriented coping strategies or an avoidant approach to coping with the sequelae of SCI. After controlling for demographic/injury-related factors, higher scores on the escape-oriented factor were associated with the lower quality of life and higher levels of depression and anxiety symptomatology.
Conclusion:
Escape-oriented coping is associated with maladaptive psychosocial outcomes in adolescents with SCI. These adolescents report that active coping strategies are most effective in reducing SCI-related distress. Coping strategy use may mediate psychosocial outcomes in adolescents with SCI and represent an intervention target in adolescents who overly rely on escape-oriented coping
Microtubule-Associated Protein EB3 Regulates IP3 Receptor Clustering and Ca(2+) Signaling in Endothelial Cells.
The mechanisms by which the microtubule cytoskeleton regulates the permeability of endothelial barrier are not well understood. Here, we demonstrate that microtubule-associated end-binding protein 3 (EB3), a core component of the microtubule plus-end protein complex, binds to inositol 1,4,5-trisphosphate receptors (IP3Rs) through an S/TxIP EB-binding motif. In endothelial cells, Ī±-thrombin, a pro-inflammatory mediator that stimulates phospholipase CĪ², increases the cytosolic Ca(2+) concentration and elicits clustering of IP3R3s. These responses, and the resulting Ca(2+)-dependent phosphorylation of myosin light chain, are prevented by depletion of either EB3 or mutation of the TxIP motif of IP3R3 responsible for mediating its binding to EB3. We also show that selective EB3 gene deletion in endothelial cells of mice abrogates Ī±-thrombin-induced increase in endothelial permeability. We conclude that the EB3-mediated interaction of IP3Rs with microtubules controls the assembly of IP3Rs into effective Ca(2+) signaling clusters, which thereby regulate microtubule-dependent endothelial permeability.Supported by NIH grants R01 HL103922 and Giles F. Filley Memorial Award to Y.A.K.;
PO1 HL60678 to A.B.M; T32 HL07829-17 and AHA AWARD 13PRE17090090 to M. G. and a Wellcome Trust Senior Investigator Award (101844) to C.W.T.This is the final version of the article. It first appeared from Elsevier via http://dx.doi.org/10.1016/j.celrep.2015.06.00
Characteristics of patients initiating raloxifene compared to those initiating bisphosphonates
<p>Abstract</p> <p>Background</p> <p>Both raloxifene and bisphosphonates are indicated for the prevention and treatment of postmenopausal osteoporosis, however these medications have different efficacy and safety profiles. It is plausible that physicians would prescribe these agents to optimize the benefit/risk profile for individual patients. The objective of this study was to compare demographic and clinical characteristics of patients initiating raloxifene with those of patients initiating bisphosphonates for the prevention and treatment of osteoporosis.</p> <p>Methods</p> <p>This study was conducted using a retrospective cohort design. Female beneficiaries (45 years and older) with at least one claim for raloxifene or a bisphosphonate in 2003 through 2005 and continuous enrollment in the previous 12 months and subsequent 6 months were identified using a collection of large national commercial, Medicare supplemental, and Medicaid administrative claims databases (MarketScan<sup>Ā®</sup>). Patients were divided into two cohorts, a combined commercial/Medicare cohort and a Medicaid cohort. Within each cohort, characteristics (demographic, clinical, and resource utilization) of patients initiating raloxifene were compared to those of patients initiating bisphosphonate therapy. Group comparisons were made using chi-square tests for proportions of categorical measures and Wilcoxon rank-sum tests for continuous variables. Logistic regression was used to simultaneously examine factors independently associated with initiation of raloxifene versus a bisphosphonate.</p> <p>Results</p> <p>Within both the commercial/Medicare and Medicaid cohorts, raloxifene patients were younger, had fewer comorbid conditions, and fewer pre-existing fractures than bisphosphonate patients. Raloxifene patients in both cohorts were less likely to have had a bone mineral density (BMD) screening in the previous year than were bisphosphonate patients, and were also more likely to have used estrogen or estrogen/progestin therapy in the previous 12 months. These differences remained statistically significant in the multivariate model.</p> <p>Conclusion</p> <p>In this sample of patients enrolled in commercial, Medicare, and Medicaid plans, patients who initiated raloxifene treatment differed from those initiating bisphosphonates. Raloxifene patients were younger, had better overall health status and appeared to be less likely to have risk factors for new osteoporotic fractures than bisphosphonate patients. Differences in the clinical profiles of these agents may impact prescribing decisions. Investigators using observational data to make comparisons of treatment outcomes associated with these medications should take these important differences in patient characteristics into consideration.</p
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