1,964 research outputs found
Entangled Quantum States of Magnetic Dipoles
Free magnetic moments usually manifest themselves in Curie Laws, where weak
external magnetic fields produce magnetizations diverging as the reciprocal 1/T
of the temperature. for a variety of materials that do not disply static
magnetism, including doped semiconductors and certain rare earth
intermetallics, the 1/T law is changed to a power law T^-a with a<1. We report
here that a considerably simpler material, namely an insulating magneticsalt
can also display such a power law, and show via comparison to specific heat
data and numerical simulations that quantum mechanics is crucial for its
formation. Two quantum mechanical phenomena are needed, namely level splitting
- which affects the spectrum of excited states - and entanglement - where the
wavefunction of a system with several degrees of freedom cannot be written as a
product of wavefunctions for each degree of freedom. Entanglement effects
become visible for remarkably small tunnelling terms, and are turned on well
before tunnelling has visible effects on the spectrum. Our work is significant
because it illustrates that entanglement is at the very heart of a very simple
experimental observation for an insulating quantum spin system.Comment: 17 pages, 4 figure
Resveratrol inhibits benzo[a]pyrene–DNA adduct formation in human bronchial epithelial cells
Resveratrol ( trans-3,4’,5-trihydroxystilbene), a phytoalexin present in various plants and foods, has in several in vitro and in vivo studies demonstrated cancer chemopreventive and chemotherapeutic potential. We investigated the in vitro effect of resveratrol on benzo[ a] pyrene ( B[ a] P)-induced DNA adducts in human bronchial epithelial cells. This was compared to the effect of resveratrol on the expression of the cytochrome P450 (CYP) genes CYP1A1 and CYP1B1 and the formation of B[ a] P metabolites. Exposure of BEAS-2B and BEP2D cells to B[ a] P and increasing concentrations of resveratrol resulted in a dose- and time-dependent inhibition of DNA adduct formation quantified by P-32-postlabelling. Supporting this result, resveratrol was shown to inhibit CYP1A1 and CYP1B1 gene expression, as measured by real-time reverse transcriptase - polymerase chain reaction. Also, a significant correlation was found between the number of DNA adducts and the mRNA levels of these genes. Using HPLC analysis, a concomitant decrease in the formation of B[ a]P-derived metabolic products was detected. In conclusion, these data lend support to a chemopreventive role of resveratrol in polycyclic aromatic hydrocarbon-induced carcinogenesis
The effect of hospital volume on length of stay, re-admissions, and complications of total hip arthroplasty: A population-based register analysis of 72 hospitals and 30,266 replacements
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Identifying factors likely to influence compliance with diagnostic imaging guideline recommendations for spine disorders among chiropractors in North America: a focus group study using the Theoretical Domains Framework
Background: The Theoretical Domains Framework (TDF) was developed to investigate determinants of specific clinical behaviors and inform the design of interventions to change professional behavior. This framework was used to explore the beliefs of chiropractors in an American Provider Network and two Canadian provinces about their adherence to evidence-based recommendations for spine radiography for uncomplicated back pain. The primary objective of the study was to identify chiropractors’ beliefs about managing uncomplicated back pain without xrays and to explore barriers and facilitators to implementing evidence-based recommendations on lumbar spine xrays. A secondary objective was to compare chiropractors in the United States and Canada on their beliefs regarding the use of spine x-rays.
Methods: Six focus groups exploring beliefs about managing back pain without x-rays were conducted with a purposive sample. The interview guide was based upon the TDF. Focus groups were digitally recorded, transcribed verbatim, and analyzed by two independent assessors using thematic content analysis based on the TDF.
Results: Five domains were identified as likely relevant. Key beliefs within these domains included the following: conflicting comments about the potential consequences of not ordering x-rays (risk of missing a pathology, avoiding adverse treatment effects, risks of litigation, determining the treatment plan, and using x-ray-driven techniques contrasted with perceived benefits of minimizing patient radiation exposure and reducing costs; beliefs about consequences); beliefs regarding professional autonomy, professional credibility, lack of standardization, and agreement with guidelines widely varied (social/professional role & identity); the influence of formal training, colleagues, and patients also appeared to be important factors (social influences); conflicting comments regarding levels of confidence and comfort in managing patients without x-rays (belief about capabilities); and guideline awareness and agreements (knowledge).
Conclusions: Chiropractors’ use of diagnostic imaging appears to be influenced by a number of factors. Five key domains may be important considering the presence of conflicting beliefs, evidence of strong beliefs likely to impact the behavior of interest, and high frequency of beliefs. The results will inform the development of a theorybased survey to help identify potential targets for behavioral-change strategies
Observation of the Baryonic Flavor-Changing Neutral Current Decay Lambda_b -> Lambda mu+ mu-
We report the first observation of the baryonic flavor-changing neutral
current decay Lambda_b -> Lambda mu+ mu- with 24 signal events and a
statistical significance of 5.8 Gaussian standard deviations. This measurement
uses ppbar collisions data sample corresponding to 6.8fb-1 at sqrt{s}=1.96TeV
collected by the CDF II detector at the Tevatron collider. The total and
differential branching ratios for Lambda_b -> Lambda mu+ mu- are measured. We
find B(Lambda_b -> Lambda mu+ mu-) = [1.73+-0.42(stat)+-0.55(syst)] x 10^{-6}.
We also report the first measurement of the differential branching ratio of B_s
-> phi mu+ mu- using 49 signal events. In addition, we report branching ratios
for B+ -> K+ mu+ mu-, B0 -> K0 mu+ mu-, and B -> K*(892) mu+ mu- decays.Comment: 8 pages, 2 figures, 4 tables. Submitted to Phys. Rev. Let
Search for New Physics in Lepton + Photon + X Events with L=305 pb-1 of ppbar Collisions at roots=1.96 TeV
We present results of a search for anomalous production of events containing
a charged lepton (either electron or muon) and a photon, both with high
transverse momentum, accompanied by additional signatures, X, including missing
transverse energy (MET) and additional leptons and photons. We use the same
kinematic selection criteria as in a previous CDF search, but with a
substantially larger data set, 305 pb-1, a ppbar collision energy of 1.96 TeV,
and the upgraded CDF II detector. We find 42 Lepton+Photon+MET events versus a
standard model expectation of 37.3 +- 5.4 events. The level of excess observed
in Run I, 16 events with an expectation of 7.6 +- 0.7 events (corresponding to
a 2.7 sigma effect), is not supported by the new data. In the signature of
Multi-Lepton+Photon+X we observe 31 events versus an expectation of 23.0 +- 2.7
events. In this sample we find no events with an extra photon or MET and so
find no events like the one ee+gg+MET event observed in Run I.Comment: 7 pages, 3 figures, 1 table. Accepted to PR
Top Quark Mass Measurement from Dilepton Events at CDF II with the Matrix-Element Method
We describe a measurement of the top quark mass using events with two charged
leptons collected by the CDF II detector from collisions with TeV at the Fermilab Tevatron. The likelihood in top mass is
calculated for each event by convoluting the leading order matrix element
describing
with detector resolution functions. The presence of background events in the
data sample is modeled using similar calculations involving the matrix elements
for major background processes. In a data sample with integrated luminosity of
340 pb, we observe 33 candidate events and measure This
measurement represents the first application of this method to events with two
charged leptons and is the most precise single measurement of the top quark
mass in this channel.Comment: 21 pages, 14 figure
Observation of WZ Production
We report the first observation of the associated production of a W boson and
a Z boson. This result is based on 1.1 fb-1 of integrated luminosity from ppbar
collisions at sqrt{s} = 1.96 TeV collected with the CDF II detector at the
Fermilab Tevatron. We observe 16 WZ candidates passing our event selection with
an expected background of 2.7 +/- 0.4 events. A fit to the missing transverse
energy distribution indicates an excess of events compared to the background
expectation corresponding to a significance equivalent to six standard
deviations. The measured cross section is sigma(ppbar -> WZ) =
5.0^{+1.8}_{-1.6} pb, consistent with the standard model expectation.Comment: 7 pages, 3 figures. Submitted to Phys. Rev. Let
Analysis of the Quantum Numbers of the X(3872) Particle
We present an analysis of angular distributions and correlations of the
X(3872) particle in the exclusive decay mode X(3872)->J/psi pi+ pi- with
J/psi->mu+ mu-. We use 780 pb -1 of data from ppbar collisions at sqrt{s} =
1.96 TeV collected with the CDF II detector at the Fermilab Tevatron. We derive
constraints on spin, parity, and charge conjugation parity of the X(3872)
particle by comparing measured angular distributions of the decay products with
predictions for different JPC hypotheses. The assignments JPC = 1++ and 2-+ are
the only ones consistent with the data.Comment: update to journal versio
Measurement of the Lambda_b Lifetime in Lambda_b --> J/psi Lambda0 in p-pbar Collisions at sqrt(s)=1.96 TeV
We report a measurement of the Lambda_b lifetime in the exclusive decay
Lambda_b --> J/psi Lambda0 in p-pbar collisions at sqrt(s) = 1.96 TeV using an
integrated luminosity of 1.0 fb^{-1} of data collected by the CDF II detector
at the Fermilab Tevatron. Using fully reconstructed decays, we measure
tau(Lambda_b) = 1.593 ^{+0.083}_{-0.078} (stat.) +- 0.033 (syst.) ps. This is
the single most precise measurement of tau(Lambda_b) and is 3.2 sigma higher
than the current world average.Comment: 7 Pages, 2 Figures, 1 Table. Submitted to Phys. Rev. Let
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