355 research outputs found
Involvement of β3-Adrenoceptor in Altered β-Adrenergic Response in Senescent Heart: Role of Nitric Oxide Synthase 1–derived Nitric Oxide
Background: In senescent heart, β-adrenergic response is altered in parallel with β1- and β2-adrenoceptor down-regulation. A negative inotropic effect of β3-adrenoceptor could be involved. In this study, the authors tested the hypothesis that β3-adrenoceptor plays a role in β-adrenergic dysfunction in senescent heart.Methods: β-Adrenergic responses were investigated in vivo (echocardiography–dobutamine, electron paramagnetic resonance) and in vitro (isolated left ventricular papillary muscle, electron paramagnetic resonance) in young adult (3-month-old) and senescent (24-month-old) rats. Nitric oxide synthase (NOS) immunolabeling (confocal microscopy), nitric oxide production (electron paramagnetic resonance) and β-adrenoceptor Western blots were performed in vitro. Data are mean percentages of baseline ± SD. Results: An impaired positive inotropic effect (isoproterenol) was confirmed in senescent hearts in vivo (117 ± 23 vs. 162 ± 16%; P < 0.05) and in vitro (127 ± 10 vs. 179 ± 15%; P < 0.05). In the young adult group, the positive inotropic effect was not significantly modified by the nonselective NOS inhibitor NG-nitro-l-arginine methylester (l-NAME; 183 ± 19%), the selective NOS1 inhibitor vinyl-l-N-5(1-imino-3-butenyl)-l-ornithine (l-VNIO; 172 ± 13%), or the selective NOS2 inhibitor 1400W (183 ± 19%). In the senescent group, in parallel with β3-adrenoceptor up-regulation and increased nitric oxide production, the positive inotropic effect was partially restored by l-NAME (151 ± 8%; P < 0.05) and l-VNIO (149 ± 7%; P < 0.05) but not by 1400W (132 ± 11%; not significant). The positive inotropic effect induced by dibutyryl-cyclic adenosine monophosphate was decreased in the senescent group with the specific β3-adrenoceptor agonist BRL 37344 (167 ± 10 vs. 142 ± 10%; P < 0.05). NOS1 and NOS2 were significantly up-regulated in the senescent rat. Conclusions: In senescent cardiomyopathy, β3-adrenoceptor overexpression plays an important role in the altered β-adrenergic response via induction of NOS1-nitric oxide
Pure dephasing in flux qubits due to flux noise with spectral density scaling as
For many types of superconducting qubits, magnetic flux noise is a source of
pure dephasing. Measurements on a representative dc superconducting quantum
interference device (SQUID) over a range of temperatures show that , where is the flux noise spectral density,
is of the order of 1 and ; is the flux quantum. For a qubit with an energy level
splitting linearly coupled to the applied flux, calculations of the dependence
of the pure dephasing time of Ramsey and echo pulse sequences on
for fixed show that decreases rapidly as is
reduced. We find that is relatively insensitive to the noise
bandwidth, , for all provided the ultraviolet
cutoff frequency . We calculate the ratio of the echo () and Ramsey () sequences, and the dependence
of the decay function on and . We investigate the case in which
is fixed at the "pivot frequency" Hz while
is varied, and find that the choice of can greatly influence the
sensitivity of and to the value of .
Finally, we present calculated values of in a qubit corresponding
to the values of and measured in our SQUID.Comment: 7 pages, 8 figures, 1 tabl
Exploring parents' experiences of promoting physical activity for their child with intellectual disabilities
Introduction:
Children and adolescents with intellectual disabilities participate in low levels of physical activity and have a greater reliance on their parents to provide activity opportunities. This study explored parents’ experiences of promoting physical activity for their child with intellectual disabilities.
Methods:
Semi‐structured interviews were conducted with eight parents of children and adolescents with intellectual disabilities. Interviews were independently coded and analysed by two researchers using thematic analysis.
Results:
Four themes and nine subthemes were identified. Overall, parents had positive views of physical activity. However, parents face numerous barriers that limit their ability to promote physical activity for their child with intellectual disabilities.
Conclusions:
Parents experience high levels of exclusion and stigma that negatively affect their promotion of physical activity for their child with intellectual disabilities. Overcoming the barriers faced by parents could therefore be an indirect method to increase physical activity in children and adolescents with intellectual disabilities
The significance of motivation in student-centred learning : a reflective case study
The theoretical underpinnings of student-centred learning suggest motivation to be an integral component. However, lack of clarification of what is involved in motivation in education often results in unchallenged assumptions that fail to recognise that what motivates some students may alienate others. This case study, using socio-cognitive motivational theory to analyse previously collected data, derives three fuzzy propositions which, collectively, suggest that motivation interacts with the whole cycle of episodes in the teachinglearning process. It argues that the development of the higherlevel cognitive competencies that are implied by the term, student-centred learning, must integrate motivational constructs such as goal orientation, volition, interest and attributions into pedagogical practices
Deuteron Photodissociation in Ultraperipheral Relativistic Heavy-Ion on Deuteron Collisions
In ultraperipheral relativistic deuteron on heavy-ion collisions, a photon
emitted from the heavy nucleus may dissociate the deuterium ion. We find
deuterium breakup cross sections of 1.38 barns for deuterium-gold collisions at
a center of mass energy of 200 GeV per nucleon, as studied at the Relativistic
Heavy Ion Collider, and 2.49 barns for deuterium-lead collisions at a center of
mass energy of 6.2 TeV, as proposed for the Large Hadron Collider. This cross
section includes an energy-independent 140 mb contribution from hadronic
diffractive dissociation. At the LHC, the cross section is as large as that of
hadronic interactions. The estimated error is 5%. Deuteron dissociation could
be used as a luminosity monitor and a `tag' for moderate impact parameter
collisions.Comment: Final version, to appear in Phys. Rev. C. Diffractive dissociation
included 10 pages with 3 figure
Wage losses in the year after breast cancer: Extent and determinants among Canadian women
This article is available open access through the publisher’s website at the link below. © The Author 2008.Background - Wage losses after breast cancer may result in considerable financial burden. Their assessment is made more urgent because more women now participate in the workforce and because breast cancer is managed using multiple treatment modalities that could lead to long work absences. We evaluated wage losses, their determinants, and the associations between wage losses and changes for the worse in the family's financial situation among Canadian women over the first 12 months after diagnosis of early breast cancer.
Methods - We conducted a prospective cohort study among women with breast cancer from eight hospitals throughout the province of Quebec. Information that permitted the calculation of wage losses and information on potential determinants of wage losses were collected by three pretested telephone interviews conducted over the year following the start of treatment. Information on medical characteristics was obtained from medical records. The main outcome was the proportion of annual wages lost because of breast cancer. Multivariable analysis of variance using the general linear model was used to identify personal, medical, and employment characteristics associated with the proportion of wages lost. All statistical tests were two-sided.
Results - Among 962 eligible breast cancer patients, 800 completed all three interviews. Of these, 459 had a paying job during the month before diagnosis. On average, these working women lost 27% of their projected usual annual wages (median = 19%) after compensation received had been taken into account. Multivariable analysis showed that a higher percentage of lost wages was statistically significantly associated with a lower level of education (Ptrend = .0018), living 50 km or more from the hospital where surgery was performed (P = .070), lower social support (P = .012), having invasive disease (P = .086), receipt of chemotherapy (P < .001), self-employment (P < .001), shorter tenure in the job (Ptrend < .001), and part-time work (P < .001).
Conclusion - Wage losses and their effects on financial situation constitute an important adverse consequence of breast cancer in Canada.The Canadian Breast Cancer Research Alliance, Canadian
Institutes of Health Research, and Fondation de l’Université Laval
Photon data shed new light upon the GDR spreading width in heavy nuclei
A global study of the electric dipole strength in and below the isovector
giant dipole resonance (GDR) is presented for mass numbers A>80. It relies on
the recently established remarkably good match between data for the nuclear
photo effect to novel photon scattering data covering the region below the
neutron emission threshold as well as by average resonance neutron capture
(ARC). From the wide energy coverage of these data the correlation of the GDR
spreading width with energy can be studied with remarkable accuracy. A clear
sensitivity to details of the nuclear shape, i.e. the beta- and
gamma-deformations, is demonstrated. Based hereon a new parameterization of the
energy dependence of the nuclear electric-dipole strength is proposed which -
with only two new parameters - allows to describe the dipole strength in all
heavy nuclei with A>80. Although it differs significantly from previous
parameterizations it holds for spherical, transitional, triaxial and well
deformed nuclei. The GDR spreading width depends in a regular way on the
respective resonance energy, but it is independent of the photon energy.Comment: accepted by Phys. Lett. B after minor modification
Influence of Gamma-Ray Emission on the Isotopic Composition of Clouds in the Interstellar Medium
We investigate one mechanism of the change in the isotopic composition of
cosmologically distant clouds of interstellar gas whose matter was subjected
only slightly to star formation processes. According to the standard
cosmological model, the isotopic composition of the gas in such clouds was
formed at the epoch of Big Bang nucleosynthesis and is determined only by the
baryon density in the Universe. The dispersion in the available cloud
composition observations exceeds the errors of individual measurements. This
may indicate that there are mechanisms of the change in the composition of
matter in the Universe after the completion of Big Bang nucleosynthesis. We
have calculated the destruction and production rates of light isotopes (D, 3He,
4He) under the influence of photonuclear reactions triggered by the gamma-ray
emission from active galactic nuclei (AGNs). We investigate the destruction and
production of light elements depending on the spectral characteristics of the
gamma-ray emission. We show that in comparison with previous works, taking into
account the influence of spectral hardness on the photonuclear reaction rates
can increase the characteristic radii of influence of the gamma-ray emission
from AGNs by a factor of 2-8. The high gamma-ray luminosities of AGNs observed
in recent years increase the previous estimates of the characteristic radii by
two orders of magnitude. This may suggest that the influence of the emission
from AGNs on the change in the composition of the medium in the immediate
neighborhood (the host galaxy) has been underestimated.Comment: 13 pages, 13 figures, 3 table
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