479 research outputs found
Fermion family recurrences in the Dyson-Schwinger formalism
We study the multiple solutions of the truncated propagator Dyson-Schwinger
equation for a simple fermion theory with Yukawa coupling to a scalar field.
Upon increasing the coupling constant , other parameters being fixed, more
than one non-perturbative solution breaking chiral symmetry becomes possible
and we find these numerically. These ``recurrences'' appear as a mechanism to
generate different fermion generations as quanta of the same fundamental field
in an interacting field theory, without assuming any composite structure. The
number of recurrences or flavors is reduced to a question about the value of
the Yukawa coupling, and has no special profound significance in the Standard
Model. The resulting mass function can have one or more nodes and the
measurement that potentially detects them can be thought of as a collider-based
test of the virtual dispersion relation for the charged
lepton member of each family. This requires three independent measurements of
the charged lepton's energy, three-momentum and off-shellness. We illustrate
how this can be achieved for the (more difficult) case of the tau lepton
The BES f_0(1810): a new glueball candidate
We analyze the f_0(1810) state recently observed by the BES collaboration via
radiative J/\psi decay to a resonant \phi\omega spectrum and confront it with
DM2 data and glueball theory. The DM2 group only measured \omega\omega decays
and reported a pseudoscalar but no scalar resonance in this mass region. A
rescattering mechanism from the open flavored KKbar decay channel is considered
to explain why the resonance is only seen in the flavor asymmetric \omega\phi
branch along with a discussion of positive C parity charmonia decays to
strengthen the case for preferred open flavor glueball decays. We also
calculate the total glueball decay width to be roughly 100 MeV, in agreement
with the narrow, newly found f_0, and smaller than the expected estimate of
200-400 MeV. We conclude that this discovered scalar hadron is a solid glueball
candidate and deserves further experimental investigation, especially in the
K-Kbar channel. Finally we comment on other, but less likely, possible
assignments for this state.Comment: 11 pages, 4 figures. Major substantive additions, including an
ab-initio, QCD-based computation of the glueball inclusive decay width,
evaluation of final state effects, and enhanced discussion of several
alternative possibilities. Our conclusions are unchanged: the BES f_0(1810)
is a promising glueball candidat
The ratio of viscosity to entropy density in a pion gas satisfies the KSS holographic bound
We evaluate the ratio of shear viscosity to entropy density in a pion gas
employing the Uehling-Uehlenbeck equation and experimental phase-shifts
parameterized by means of the SU(2) Inverse Amplitude Method. We find that the
ratio for this monocomponent gas stays well above the KSS 1/(4 pi) bound. We
find similar results with other sets of phase shifts and conclude the bound is
nowhere violated.Comment: 2 page text, three figures. V2: short comment and graph added to
assert that a minimum of eta/s is not discarded from the hadron, low T side
in a heavy-ion collisio
Chirally symmetric quark description of low energy \pi-\pi scattering
Weinberg's theorem for \pi-\pi scattering, including the Adler zero at
threshold in the chiral limit, is analytically proved for microscopic quark
models that preserve chiral symmetry. Implementing Ward-Takahashi identities,
the isospin 0 and 2 scattering lengths are derived in exact agreement with
Weinberg's low energy results. Our proof applies to alternative quark
formulations including the Hamiltonian and Euclidean space Dyson-Schwinger
approaches. Finally, the threshold \pi-\pi scattering amplitudes are calculated
using the Dyson-Schwinger equations in the rainbow-ladder truncation,
confirming the formal derivation.Comment: 10 pages, 7 figures, Revtex
Perspectives about and approaches to weight gain in pregnancy: a qualitative study of physicians and nurse midwives
Abstract
Background
Over one third of reproductive age women in the US are obese. Pregnancy is a strong risk factor for obesity, with excess weight gain as the greatest predictor of long term obesity. The majority of pregnant women gain more weight than recommended by the Institute of Medicine guidelines. The objective of this study was to understand prenatal care providersâ perspectives on weight gain during pregnancy.
Methods
Semi-structured qualitative interviews of 10 prenatal care providers (three family physicians, three obstetricians, and four nurse midwives) at a University Hospital in the Midwest, that included the ranking of important prenatal issues, and open-ended questions addressing: 1) general perceptions; 2) approach with patients; and 3) clinical care challenges.
Results
Providers felt that appropriate weight gain during pregnancy was not a high priority. Many providers waited until patients had gained excess weight before addressing the issue, were not familiar with established guidelines, and lacked resources for patients. Providers also believed that their counseling had low impact on patients, avoided counseling due to sensitivity of the topic, and believed that patients were more influenced by other factors, such as their family, habits, and culture.
Conclusions
Both providers and patients may benefit from increased awareness of the morbidity of excess weight gain during pregnancy. Practice-level policies that support the monitoring and management of weight gain during pregnancy could also improve care. Research that further investigates the barriers to appropriate weight gain is warranted.http://deepblue.lib.umich.edu/bitstream/2027.42/112570/1/12884_2012_Article_736.pd
Interface layer to improve polystyrene attachment on a quartz crystal resonator
Se describe el empleo de tĂ©cnicas de formaciĂłn de pelĂculas tendientes a mejorar el funcionamiento de un resonador
de cristal de cuarzo (QCR); dichas tecnologĂas fueron, por ejemplo, preparaciones de recubrimiento mediante
los mĂ©todos de spin y Langmuir-Blodgett (LB). La uniformidad y homogeneidad de la pelĂcula sobre el cristal de cuarzo
es fundamental para las aplicaciones que tiene un resonador como sensor quĂmico y biolĂłgico.
Se formaron pelĂculas de poliestireno (PS) y de cloruro de polivinilo (PVC) en solventes como ciclohexanona,
tetrahidrofurano (THF), dimetilformamida y cloroformo a diferentes concentraciones, usando el procedimiento de cubrimiento
por spin en soportes corrugados tipo wafer. La calidad de las pelĂculas fue determinada usando microscopĂa
Ăłptica, elipsometrĂa y perfilometrĂa. AdemĂĄs, se prepararon pelĂculas en soportes corrugados y en QRC con superficie de oro por irrigaciĂłn de la mencionada
sustancia en una subfase acuosa y transfiriéndola por impregnación de la superficie de subfase en el soporte.
Para la preparaciĂłn de la pelĂcula LB se empleĂł ĂĄcido araquĂdico y partĂculas de PS. Las preparaciones de pelĂculas
de monocapa y multicapa de estas sustancias en soportes corrugados o en superficies de cuarzo doradas se controlaron
adicionalmente por espectrometrĂa IR.
El comportamiento resonante del QCR antes y después del recubrimiento de su superficie se midió con un analizador
de red. En combinaciĂłn con una interfaz grĂĄfica los datos se pudieron fĂĄcilmente grabar y observar.Technologies for thin film deposition have been used to improve the functionalization of quartz crystal resonators
(QCR); such technologies, for example, are spin coating and Langmuir-Blodgett (LB) film preparation. These experiments
are required because the film uniformity and homogeneity over the quartz crystal resonator are fundamental for
its applications as chemical and biological sensors.
Film deposition of polystyrene (PS) particles, as well as polyvinyl chloride (PVC), was performed in solvents
such as cyclohexanone, tetrahydrofuran (THF), dimethylformamide and chloroform at different concentrations using
the spin coating procedure on wafer targets. The film quality was determined by optical microscopy, ellipsometry, and
profilometry.
Additionally, films on wafers or QCR with gold surface have been prepared by spreading the mentioned substances
on an aqueous subphase and transferring it by dipping from the subphase surface onto the target.
For LB film preparation arachidic acid and PS particles have been used. Prepared mono- or multilayered films of
these substances on wafer or gold quartzes have been controlled additionally by IR-spectrometry.
The resonant behavior of QCR before and after surface coating has been measured with a network analyzer. In
combination with a graphical user interface the data could be easily recorded and visualized
Health implications of an immigration raid: findings from a Latino community in the midwestern United States.
Immigration raids exemplify the reach of immigration law enforcement into the lives of Latino community members, yet little research characterizes the health effects of these raids. We examined the health implications of an immigration raid that resulted in multiple arrests and deportations and occurred midway through a community survey of a Latino population. We used linear regression following principal axis factoring to examine the influence of raid timing on immigration enforcement stress and self-rated health. We controlled for age, sex, relationship status, years in the county in which the raid occurred, children in the home, and nativity. 325 participants completed the survey before the raid and 151 after. Completing the survey after the raid was associated with higher levels of immigration enforcement stress and lower self-rated health scores. Findings indicate the negative impact of immigration raids on Latino communities. Immigration discussions should include holistic assessments of health.UL1 TR000433 - NCATS NIH HH
A Lower Bound on List Size for List Decoding
A q-ary error-correcting code C â {1,2,...,q}n is said to be list decodable to radius Ï with list size L if every Hamming ball of radius Ï contains at most L codewords of C. We prove that in order for a q -ary code to be list-decodable up to radius (1-1/q)(1- Δ)n, we must have L = Ω(1/ Δ2) . Specifically, we prove that there exists a constant cq > 0 and a function fq such that for small enough Δ > 0, if C is list-decodable to radius (1-1/q)(1- Δ)n with list size cq/ Δ2, then C has at most fq( Δ) codewords, independent of n . This result is asymptotically tight (treating q as a constant), since such codes with an exponential (in n ) number of codewords are known for list size L = O(1/ Δ2). A result similar to ours is implicit in Blinovsky ( Problems of Information Transmission, 1986) for the binary (q=2) case. Our proof is simpler and works for all alphabet sizes, and provides more intuition for why the lower bound arises.Engineering and Applied Science
Surface topography quantification of super hard abrasive tools by laser scanning microscopy
Non-conventional super hard abrasive tools are made of composite materials containing super hard grains, e.g., diamond or cubic boron nitride (CBN) grains, bound by a metallic constitutive phase. These tools are usually produced by means of sintering, and are widely applied in the abrasive machining processes of modern manufacturing, especially in precision machining. The abrasive grains, which induce the material removal processes, are embedded in the metallic binder. They emerge as a consequence of self-dressing, resulting in a self-sharping effect. Therefore, the cutting surface of the tool displays an irregular topography. Quantification of surface topography scenario may supply valuable information to evaluate and understand its correlation to wear mechanisms. In this study, an experimental protocol consisting of five steps: specimen preparation, surface scanning, image assembly, image digital processing and surface quantification, was proposed and validated by characterizing two CBN honing tools used for precision machining: B151/L2/2010/50 (B151) and B91/128/x44/35 (B91) CBN honing stones. It involved the use of laser scanning microscopy and digital imaging processing for assessing significant dimensional, geometrical, and positional properties of CBN grains at the surface of super hard abrasive tools. It was shown that surface topography quantification is an effective method to evaluate and obtain the defined parameters. However, smaller grains may require images with higher resolution; thus, scanning must be refined. Finally, a critical comparative analysis of the experimental results attained for the studied tools pointed out honing stone B91 as more appropriated than B151 one for achieving a higher machining quality of the workpiece.Peer ReviewedPostprint (author's final draft
To what extent is Gluon Confinement an empirical fact?
Experimental verifications of Confinement in hadron physics have established
the absence of charges with a fraction of the electron's charge by studying the
energy deposited in ionization tracks at high energies, and performing Millikan
experiments with charged droplets at rest. These experiments test only the
absence of particles with fractional charge in the asymptotic spectrum, and
thus "Quark" Confinement. However what theory suggests is that Color is
confined, that is, all asymptotic particles are color singlets. Since QCD is a
non-Abelian theory, the gluon force carriers (indirectly revealed in hadron
jets) are colored. We empirically examine what can be said about Gluon
Confinement based on the lack of detection of appropriate events, aiming at an
upper bound for high-energy free-gluon production.Comment: 14 pages, 12 figures, version accepted at Few Body Physic
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