346 research outputs found
Satellites and large doping- and temperature-dependence of electronic properties in hole-doped BaFe2As2
Over the last years, superconductivity has been discovered in several
families of iron-based compounds. Despite intense research, even basic
electronic properties of these materials, such as Fermi surfaces, effective
electron masses, or orbital characters are still subject to debate. Here, we
address an issue that has not been considered before, namely the consequences
of dynamical screening of the Coulomb interactions among Fe-d electrons. We
demonstrate its importance not only for correlation satellites seen in
photoemission spectroscopy, but also for the low-energy electronic structure.
From our analysis of the normal phase of BaFe2As2 emerges the picture of a
strongly correlated compound with strongly doping- and temperature-dependent
properties. In the hole overdoped regime, an incoherent metal is found, while
Fermi-liquid behavior is recovered in the undoped compound. At optimal doping,
the self-energy exhibits an unusual square-root energy dependence which leads
to strong band renormalizations near the Fermi level
Oxide Heterostructures from a Realistic Many-Body Perspective
Oxide heterostructures are a new class of materials by design, that open the
possibility for engineering challenging electronic properties, in particular
correlation effects beyond an effective single-particle description. This short
review tries to highlight some of the demanding aspects and questions,
motivated by the goal to describe the encountered physics from first
principles. The state-of-the-art methodology to approach realistic many-body
effects in strongly correlated oxides, the combination of density functional
theory with dynamical mean-field theory, will be briefly introduced. Discussed
examples deal with prominent Mott-band- and band-band-insulating type of oxide
heterostructures, where different electronic characteristics may be stabilized
within a single architectured oxide material.Comment: 19 pages, 9 figure
Anisakis simplex Larvae: Infection Status in Marine Fish and Cephalopods Purchased from the Cooperative Fish Market in Busan, Korea
The infection status of marine fish and cephalopods with Anisakis simplex third stage larva (L3) was studied over a period of 1 year. A total of 2,537 specimens, which consisted of 40 species of fish and 3 species of cephalopods, were purchased from the Cooperative Fish Market in Busan, Korea, from August 2006 to July 2007. They were examined for A. simplex L3 from the whole body cavity, viscera, and muscles. A. simplex L3 were confirmed by light microscopy. The overall infection rate reached 34.3%, and average 17.1 larvae were parasitized per infected fish. Fish that recorded the highest infection rate was Lophiomus setigerus (100%), followed by Liparis tessellates (90%), Pleurogrammus azonus (90%), and Scomber japonicus (88.7%). The intensity of infection was the highest in Gadus macrocephalus (117.7 larvae per fish), followed by S. japonicus (103.9 larvae) and L. setigerus (54.2 larvae). Although abundance of A. simplex L3 was not seasonal in most of the fish species, 10 of the 16 selected species showed the highest abundance in February and April. A positive correlation between the intensity of L3 infection and the fish length was obvious in S. japonicus and G. macrocephalus. It was likely that A. simplex L3 are more frequently infected during the spring season in some species of fish. Our study revealed that eating raw or undercooked fish or cephalopods could still be a source of human infection with A. simplex L3 in Korea
Assessment of intradialysis calcium mass balance by single pool variable-volume calcium kinetic model
Introduction: A reliable method of intradialysis calcium mass balance quantification is far from been established. We herein investigated the use of a single-pool variable-volume Calcium kinetic model to assess calcium mass balance in chronic and stable dialysis patients. Methods: Thirty-four patients on thrice-weekly HD were studied during 240 dialysis sessions. All patients were dialyzed with a nominal total calcium concentration of 1.50 mmol/L. The main assumption of the model is that the calcium distribution volume is equal to the extracellular volume during dialysis. This hypothesis is assumed valid if measured and predicted end dialysis plasma water ionized calcium concentrations are equal. A difference between predicted and measured end-dialysis ionized plasma water calcium concentration is a deviation on our main hypothesis, meaning that a substantial amount of calcium is exchanged between the extracellular volume and a nonmodeled compartment. Findings: The difference between predicted and measured values was 0.02 mmol/L (range -0.08:0.16 mmol/L). With a mean ionized dialysate calcium concentration of 1.25 mmol/L, calcium mass balance was on average negative (mean±SD -0.84±1.33 mmol, range -5.42:2.75). Predialysis ionized plasma water concentration and total ultrafiltrate were the most important predictors of calcium mass balance. A significant mobilization of calcium from the extracellular pool to a nonmodeled pool was calculated in a group of patients. Discussion: The proposed single pool variable-volume Calcium kinetic model is adequate for prediction and quantification of intradialysis calcium mass balance, it can evaluate the eventual calcium transfer outside the extracellular pool in clinical practice
A Common Origin for Neutrino Anarchy and Charged Hierarchies
The generation of exponential flavor hierarchies from extra-dimensional
wavefunction overlaps is re-examined. We find, surprisingly, that coexistence
of anarchic fermion mass matrices with such hierarchies is intrinsic and
natural to this setting. The salient features of charged fermion and neutrino
masses and mixings can thereby be captured within a single framework. Both
Dirac and Majorana neutrinos can be realized. The minimal phenomenological
consequences are discussed, including the need for a fundamental scale far
above the weak scale to adequately suppress flavor-changing neutral currents.
Two broad scenarios for stabilizing this electroweak hierarchy are studied,
warped compactification and supersymmetry. In warped compactifications and
"Flavorful Supersymmetry," where non-trivial flavor structure appears in the
new TeV physics, Dirac neutrinos are strongly favored over Majorana by lepton
flavor violation tests. We argue that this is part of a more general result for
flavor-sensitive TeV-scale physics. Our scenario strongly suggests that the
supersymmetric flavor problem is not solved locally in the extra dimension, but
rather at or below the compactification scale. In the supersymmetric Dirac
case, we discuss how the appearance of light right-handed sneutrinos
considerably alters the physics of dark matter.Comment: Comparison with the Froggatt-Nielsen mechanism omitted. Some
clarifications added. This is the version accepted by PRL with a longer
abstract
3D-MRI rendering of the anatomical structures related to acupuncture points of the Dai mai, Yin qiao mai and Yang qiao mai meridians within the context of the WOMED concept of lateral tension: implications for musculoskeletal disease
BACKGROUND: A conceptual model of lateral muscular tension in patients presenting thyroid associated ophthalmopathy (TAO) has been recently described. Clinical improvement has been achieved by using acupuncture on points belonging to the so-called extraordinary meridians. The aim of this study was to characterize the anatomical structures related to these acupuncture points by means of 3D MRI image rendering relying on external markers. METHODS: The investigation was carried out the index case patient of the lateral tension model. A licensed medical acupuncture practitioner located the following acupuncture points: 1) Yin qiao mai meridian (medial ankle): Kidney 3, Kidney 6, the plantar Kidney 6 (Nan jing description); 2) Yang qiao mai meridian (lateral ankle): Bladder 62, Bladder 59, Bladder 61, and the plantar Bladder 62 (Nan jing description); 3) Dai mai meridian (wait): Liver 13, Gall bladder 26, Gall bladder 27, Gall bladder 28, and Gall bladder 29. The points were marked by taping a nitro-glycerin capsule on the skin. Imaging was done on a Siemens Magnetom Avanto MR scanner using an array head and body coil. Mainly T1-weighted imaging sequences, as routinely used for patient exams, were used to obtain multi-slice images. The image data were rendered in 3D modus using dedicated software (Leonardo, Siemens). RESULTS: Points of the Dai mai meridian – at the level of the waist – corresponded to the obliquus externus abdominis and the obliquus internus abdominis. Points of the Yin qiao mai meridian – at the medial side of the ankle – corresponded to tendinous structures of the flexor digitorum longus as well as to muscular structures of the abductor hallucis on the foot sole. Points of the Yang qiao mai meridian – at the lateral side of the ankle – corresponded to tendinous structures of the peroneus brevis, the peroneous longus, and the lateral surface of the calcaneus and close to the foot sole to the abductor digiti minimi. CONCLUSION: This non-invasive MRI investigation has revealed the anatomical relations of acupuncture points belonging to 3 of the so-called extraordinary meridians. We conclude that the clinically developed "WOMED concept of lateral tension" is related to tendino-muscular structures
Quantum oscillations and the Fermi surface in an underdoped high-Tc superconductor
Despite twenty years of research, the phase diagram of high transition-
temperature superconductors remains enigmatic. A central issue is the origin of
the differences in the physical properties of these copper oxides doped to
opposite sides of the superconducting region. In the overdoped regime, the
material behaves as a reasonably conventional metal, with a large Fermi
surface. The underdoped regime, however, is highly anomalous and appears to
have no coherent Fermi surface, but only disconnected "Fermi arcs". The
fundamental question, then, is whether underdoped copper oxides have a Fermi
surface, and if so, whether it is topologically different from that seen in the
overdoped regime. Here we report the observation of quantum oscillations in the
electrical resistance of the oxygen-ordered copper oxide YBa2Cu3O6.5,
establishing the existence of a well-defined Fermi surface in the ground state
of underdoped copper oxides, once superconductivity is suppressed by a magnetic
field. The low oscillation frequency reveals a Fermi surface made of small
pockets, in contrast to the large cylinder characteristic of the overdoped
regime. Two possible interpretations are discussed: either a small pocket is
part of the band structure specific to YBa2Cu3O6.5 or small pockets arise from
a topological change at a critical point in the phase diagram. Our
understanding of high-transition temperature (high-Tc) superconductors will
depend critically on which of these two interpretations proves to be correct
Asthma exacerbation and proximity of residence to major roads: a population-based matched case-control study among the pediatric Medicaid population in Detroit, Michigan
<p>Abstract</p> <p>Background</p> <p>The relationship between asthma and traffic-related pollutants has received considerable attention. The use of individual-level exposure measures, such as residence location or proximity to emission sources, may avoid ecological biases.</p> <p>Method</p> <p>This study focused on the pediatric Medicaid population in Detroit, MI, a high-risk population for asthma-related events. A population-based matched case-control analysis was used to investigate associations between acute asthma outcomes and proximity of residence to major roads, including freeways. Asthma cases were identified as all children who made at least one asthma claim, including inpatient and emergency department visits, during the three-year study period, 2004-06. Individually matched controls were randomly selected from the rest of the Medicaid population on the basis of non-respiratory related illness. We used conditional logistic regression with distance as both categorical and continuous variables, and examined non-linear relationships with distance using polynomial splines. The conditional logistic regression models were then extended by considering multiple asthma states (based on the frequency of acute asthma outcomes) using polychotomous conditional logistic regression.</p> <p>Results</p> <p>Asthma events were associated with proximity to primary roads with an odds ratio of 0.97 (95% CI: 0.94, 0.99) for a 1 km increase in distance using conditional logistic regression, implying that asthma events are less likely as the distance between the residence and a primary road increases. Similar relationships and effect sizes were found using polychotomous conditional logistic regression. Another plausible exposure metric, a reduced form response surface model that represents atmospheric dispersion of pollutants from roads, was not associated under that exposure model.</p> <p>Conclusions</p> <p>There is moderately strong evidence of elevated risk of asthma close to major roads based on the results obtained in this population-based matched case-control study.</p
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