3,686 research outputs found
On the Fixed-Point Structure of Scalar Fields
In a recent Letter (K.Halpern and K.Huang, Phys. Rev. Lett. 74 (1995) 3526),
certain properties of the Local Potential Approximation (LPA) to the Wilson
renormalization group were uncovered, which led the authors to conclude that
dimensional scalar field theories endowed with {\sl non-polynomial}
interactions allow for a continuum of renormalization group fixed points, and
that around the Gaussian fixed point, asymptotically free interactions exist.
If true, this could herald very important new physics, particularly for the
Higgs sector of the Standard Model. Continuing work in support of these ideas,
has motivated us to point out that we previously studied the same properties
and showed that they lead to very different conclusions. Indeed, in as much as
the statements in hep-th/9406199 are correct, they point to some deep and
beautiful facts about the LPA and its generalisations, but however no new
physics.Comment: Typos corrected. A Comment - to be published in Phys. Rev. Lett. 1
page, 1 eps figure, uses LaTeX, RevTex and eps
Effect of Contrast-Enhanced Echocardiograms on the Prognosis of Infective Endocarditis
Objective - Infective endocarditis (IE) is an infectious disease of the cardiac valves where bacteria colonize the valves; typically, via the formation of vegetations. Recent research has shown that the microbubbles in a contrast-enhanced ultrasound (CEUS) examination can move and dislodge bacterial vegetations in vitro. This study investigated whether CEUS resulted in faster resolution of IE in vivo by dislodging the vegetations.
Methods - This IRB approved retrospective study reviewed 36 patients who were diagnosed with IE via echocardiography. Data was sourced from patients within the Jefferson University Hospital’s Cardiology EMR system by searching for contrast and vegetation from January 1st, 2013 – January 1st, 2018. Fifteen patients were not given contrast, whereas 21 patients were given contrast via agitated saline (n=16) or an ultrasound contrast agent (n=5). All patients received an echocardiogram after blood cultures confirmed an infection, but before resolution of infection (defined by negative blood cultures). A student’s t-test was used for analyses.
Results - The study population was heterogeneous in terms of sex (67.5% male) and race (70% Caucasian, 25% African American, and 5% Asian), with an average age of 51±20 years, and an average BMI of 29.65±7.43 in the contrast group and 27.67±3.16 in the non-contrast group (p=0.37). Following ultrasound, no patients had documented stroke, pulmonary embolism, or systemic blood clot, which physicians could have attributed to a thrombus resulting from dislodging of bacterial vegetation. Overall, blood cultures did not clear faster in patients receiving CEUS compared to those undergoing standard echocardiography, (2.63±2.69 days vs. 1.34 ±1.11 days, p=0.09). CEUS also did not shorten the admission length in patients with IE, (16.9±7.7 days vs. 19.9±12.1 days; p=0.36).
Conclusion - Based on this limited sample size, patients who underwent CEUS did not have a different prognosis when compared to patients who received a non-contrast echocardiogram
Generation of maximally entangled states with sub-luminal Lorentz boost
Recent work has studied entanglement between the spin and momentum components
of a single spin-1/2 particle and showed that maximal entanglement is obtained
only when boosts approach the speed of light. Here we extend the boost scenario
to general geometries and show that, intriguingly, maximal entanglement can be
achieved with boosts less than the speed of light. Boosts approaching the speed
of light may even decrease entanglement. We also provide a geometric
explanation for this behavior
Systematic approach to cyclic orbifolds
We introduce an orbifold induction procedure which provides a systematic
construction of cyclic orbifolds, including their twisted sectors. The
procedure gives counterparts in the orbifold theory of all the
current-algebraic constructions of conformal field theory and enables us to
find the orbifold characters and their modular transformation properties.Comment: 39 pages, LaTeX. v2,3: references added. v4: typos correcte
Lorentz transformations that entangle spins and entangle momenta
Simple examples are presented of Lorentz transformations that entangle the
spins and momenta of two particles with positive mass and spin 1/2. They apply
to indistinguishable particles, produce maximal entanglement from finite
Lorentz transformations of states for finite momenta, and describe entanglement
of spins produced together with entanglement of momenta. From the entanglements
considered, no sum of entanglements is found to be unchanged.Comment: 5 Pages, 2 Figures, One new paragraph and reference adde
Discovery of the Putative Pulsar and Wind Nebula Associated with the TeV Gamma-ray Source HESS J1813-178
We present a Chandra X-ray observation of G12.82-0.02, a shell-like radio
supernova remnant coincident with the TeV gamma-ray source HESS J1813-178. We
resolve the X-ray emission from the co-located ASCA source into a point source
surrounded by structured diffuse emission that fills the interior of the radio
shell. The morphology of the diffuse emission strongly resembles that of a
pulsar wind nebula. The spectrum of the compact source is well-characterized by
a power-law with index Gamma approx 1.3, typical of young and energetic
rotation-powered pulsars. For a distance of 4.5 kpc, consistent with the X-ray
absorption and an association with the nearby star formation region W33, the
2-10 keV X-ray luminosities of the putative pulsar and nebula are L(PSR) =
3.2E33 ergs/s and L(PWN) = 1.4E34 ergs/s, respectively. Both the flux ratio of
L(PWN)/L(PSR) = 4.3 and the total luminosity of this system predict a pulsar
spin-down power of Edot > 1E37 ergs/s, placing it within the ten most energetic
young pulsars in the Galaxy. A deep search for radio pulsations using the
Parkes telescope sets an upper-limit of approx 0.07 mJy at 1.4 GHz for periods
>~ 50 ms. We discuss the energetics of this source, and consider briefly the
proximity of bright H2 regions to this and several other HESS sources, which
may produce their TeV emission via inverse Compton scattering.Comment: 7 pages, 6 figure, Latex, emulateapj style. To appear in the
Astrophysical Journa
Levels-of-Processing Effects on Remember Responses in Recognition For Familiar and Unfamiliar Tunes
We investigated the effect of level-of-processing manipulations on remember and know responses in episodic melody recognition (Experiments 1 and 2) and how this effect is modulated by item familiarity (Experiment 2). In Experiment 1, participants performed 2 conceptual and 2 perceptual orienting tasks while listening to familiar melodies: judging the mood, continuing the tune, tracing the pitch contour, and counting long notes. The conceptual mood task led to higher d\u27 rates for remember but not know responses. In Experiment 2, participants either judged the mood or counted long notes of tunes with high and low familiarity. A level-of-processing effect emerged again in participants\u27 remember d\u27 rates regardless of melody familiarity. Results are discussed within the distinctive processing framework
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