1,095 research outputs found
On the generalized semigroup relation in the strong operator topology
AbstractLet be a Banach space, and let â() denote the Banach algebra of endomorphisms of . A one-parameter family of operator-valued functions {S(t), tâR+}, where S(t):R+ââ(), is said to be a generalized semigroup of operators on if (1) S(s+t)ââS(s)S(t)=F(s, t), s, tâR+, (2) S(s)S(t)=S(t)S(s), (3) S(O)=I, where F(s,t): R+Ă ĂR+ â â(). Solutions of Eq. (1) in the vmiform operator topology were considered in an earlier paper of the authors (Proc. Nat. Acad. Sci. U.S.A. 60 (1968), 1170â1174). In this paper the authors investigate the analytical properties of Eq. (1) in the strong operator topology, when it is assumed that the perturbation family F(s, t) is bounded relative to the family S(t). A representation of S(t) is given; and, as an example, a generalized semigroup of translations on C[0, â] is considered
Condensation of the roots of real random polynomials on the real axis
We introduce a family of real random polynomials of degree n whose
coefficients a_k are symmetric independent Gaussian variables with variance
= e^{-k^\alpha}, indexed by a real \alpha \geq 0. We compute exactly
the mean number of real roots for large n. As \alpha is varied, one finds
three different phases. First, for 0 \leq \alpha \sim
(\frac{2}{\pi}) \log{n}. For 1 < \alpha < 2, there is an intermediate phase
where grows algebraically with a continuously varying exponent,
\sim \frac{2}{\pi} \sqrt{\frac{\alpha-1}{\alpha}} n^{\alpha/2}. And finally for
\alpha > 2, one finds a third phase where \sim n. This family of real
random polynomials thus exhibits a condensation of their roots on the real line
in the sense that, for large n, a finite fraction of their roots /n are
real. This condensation occurs via a localization of the real roots around the
values \pm \exp{[\frac{\alpha}{2}(k+{1/2})^{\alpha-1} ]}, 1 \ll k \leq n.Comment: 13 pages, 2 figure
Mitochondrial dysfunction contributes to the senescent phenotype of IPF lung fibroblasts
Increasing evidence highlights that senescence plays an important role in idiopathic pulmonary fibrosis (IPF). This study delineates the specific contribution of mitochondria and the superoxide they form to the senescent phenotype of lung fibroblasts from IPF patients (IPF-LFs). Primary cultures of IPF-LFs exhibited an intensified DNA damage response (DDR) and were more senescent than age-matched fibroblasts from control donors (Ctrl-LFs). Furthermore, IPF-LFs exhibited mitochondrial dysfunction, exemplified by increases in mitochondrial superoxide, DNA, stress and activation of mTORC1. The DNA damaging agent etoposide elicited a DDR and augmented senescence in Ctrl-LFs, which were accompanied by disturbances in mitochondrial homoeostasis including heightened superoxide production. However, etoposide had no effect on IPF-LFs. Mitochondrial perturbation by rotenone involving sharp increases in superoxide production also evoked a DDR and senescence in Ctrl-LFs, but not IPF-LFs. Inhibition of mTORC1, antioxidant treatment and a mitochondrial targeting antioxidant decelerated IPF-LF senescence and/or attenuated pharmacologically induced Ctrl-LF senescence. In conclusion, increased superoxide production by dysfunctional mitochondria reinforces lung fibroblast senescence via prolongation of the DDR. As part of an auto-amplifying loop, mTORC1 is activated, altering mitochondrial homoeostasis and increasing superoxide production. Deeper understanding the mechanisms by which mitochondria contribute to fibroblast senescence in IPF has potentially important therapeutic implications
Science policies: How should science funding be allocated? An evolutionary biologistsâ perspective
In an ideal world, funding agencies could identify the best scientists and projects and provide them with the resources to undertake these projects. Most scientists would agree that in practice, how funding for scientific research is allocated is far from ideal and likely compromises research quality. We, nine evolutionary biologists from different countries and career stages, provide a comparative summary of our impressions on funding strategies for evolutionary biology across eleven different funding agencies. We also assess whether and how funding effectiveness might be improved. We focused this assessment on 14 elements within four broad categories: (a) topical shaping of science, (b) distribution of funds, (c) application and review procedures, and (d) incentives for mobility and diversity. These comparisons revealed striking amongâcountry variation in those elements, including wide variation in funding rates, the effort and burden required for grant applications, and the extent of emphasis on societal relevance and individual mobility. We use these observations to provide constructive suggestions for the future and urge the need to further gather informed considerations from scientists on the effects of funding policies on science across countries and research fields
Determinants of the maternal 25-hydroxyvitamin D response to vitamin D supplementation during pregnancy
Context: Current approaches to antenatal vitamin D supplementation do not account for interindividual differences in 25-hydroxyvitamin D (25(OH)D) response.Objective: We assessed which maternal and environmental characteristics were associated with 25(OH)D after supplementation with cholecalciferol.Design: Within-randomization-group analysis of participants in the Maternal Vitamin D Osteoporosis Study trial of vitamin D supplementation in pregnancy.Setting: Hospital antenatal clinics.Participants: A total of 829 pregnant women (422 placebo, 407 cholecalciferol). At 14 and 34 weeks of gestation, maternal anthropometry, health, and lifestyle were assessed and 25(OH)D measured. Compliance was determined using pill counts at 19 and 34 weeks.Interventions: 1000 IU/d of cholecalciferol or matched placebo from 14 weeks of gestation until delivery.Main Outcome Measure: 25(OH)D at 34 weeks, measured in a single batch (Diasorin Liaison).Results: 25(OH)D at 34 weeks of gestation was higher in the women randomized to vitamin D (mean [SD], 67.7 [21.3] nmol/L) compared with placebo (43.1 [22.5] nmol/L; P < .001). In women randomized to cholecalciferol, higher pregnancy weight gain from 14 to 34 weeks of gestation (kg) (? = ?0.81 [95% confidence interval ?1.39, ?0.22]), lower compliance with study medication (%) (? = ?0.28 [?0.072, ?0.48]), lower early pregnancy 25(OH)D (nmol/L) (? = 0.28 [0.16, 0.40]), and delivery in the winter vs the summer (? = ?10.5 [?6.4, ?14.6]) were independently associated with lower 25(OH)D at 34 weeks of gestation.Conclusions: Women who gained more weight during pregnancy had lower 25(OH)D in early pregnancy and delivered in winter achieved a lower 25(OH)D in late pregnancy when supplemented with 1000 IU/d cholecalciferol. Future studies should aim to determine appropriate doses to enable consistent repletion of 25(OH)D during pregnancy.<br/
The T2K Side Muon Range Detector
The T2K experiment is a long baseline neutrino oscillation experiment aiming
to observe the appearance of {\nu} e in a {\nu}{\mu} beam. The {\nu}{\mu} beam
is produced at the Japan Proton Accelerator Research Complex (J-PARC), observed
with the 295 km distant Super- Kamiokande Detector and monitored by a suite of
near detectors at 280m from the proton target. The near detectors include a
magnetized off-axis detector (ND280) which measures the un-oscillated neutrino
flux and neutrino cross sections. The present paper describes the outermost
component of ND280 which is a side muon range detector (SMRD) composed of
scintillation counters with embedded wavelength shifting fibers and Multi-Pixel
Photon Counter read-out. The components, performance and response of the SMRD
are presented.Comment: 13 pages, 19 figures v2: fixed several typos; fixed reference
Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV
Results are presented from a search for a W' boson using a dataset
corresponding to 5.0 inverse femtobarns of integrated luminosity collected
during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV.
The W' boson is modeled as a heavy W boson, but different scenarios for the
couplings to fermions are considered, involving both left-handed and
right-handed chiral projections of the fermions, as well as an arbitrary
mixture of the two. The search is performed in the decay channel W' to t b,
leading to a final state signature with a single lepton (e, mu), missing
transverse energy, and jets, at least one of which is tagged as a b-jet. A W'
boson that couples to fermions with the same coupling constant as the W, but to
the right-handed rather than left-handed chiral projections, is excluded for
masses below 1.85 TeV at the 95% confidence level. For the first time using LHC
data, constraints on the W' gauge coupling for a set of left- and right-handed
coupling combinations have been placed. These results represent a significant
improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe
Search for the standard model Higgs boson decaying into two photons in pp collisions at sqrt(s)=7 TeV
A search for a Higgs boson decaying into two photons is described. The
analysis is performed using a dataset recorded by the CMS experiment at the LHC
from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an
integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross
section of the standard model Higgs boson decaying to two photons. The expected
exclusion limit at 95% confidence level is between 1.4 and 2.4 times the
standard model cross section in the mass range between 110 and 150 GeV. The
analysis of the data excludes, at 95% confidence level, the standard model
Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The
largest excess of events above the expected standard model background is
observed for a Higgs boson mass hypothesis of 124 GeV with a local significance
of 3.1 sigma. The global significance of observing an excess with a local
significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is
estimated to be 1.8 sigma. More data are required to ascertain the origin of
this excess.Comment: Submitted to Physics Letters
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