642 research outputs found
The construction of generalized Dirac operators on the lattice
We discuss the steps to construct Dirac operators which have arbitrary
fermion offsets, gauge paths, a general structure in Dirac space and satisfy
the basic symmetries (gauge symmetry, hermiticity condition, charge
conjugation, hypercubic rotations and reflections) on the lattice. We give an
extensive set of examples and offer help to add further structures.Comment: 19 pages, latex, maple code attache
Progress using generalized lattice Dirac operators to parametrize the Fixed-Point QCD action
We report on an ongoing project to parametrize the Fixed-Point Dirac operator
for massless quarks, using a very general construction which has arbitrarily
many fermion offsets and gauge paths, the complete Clifford algebra and
satisfies all required symmetries. Optimizing a specific construction with
hypercubic fermion offsets, we present some preliminary results.Comment: Lattice 2000 (Improvement), 9 pages, based on a talk by K.H. and a
poster by T.J. References adde
Airborne Measurements of Gravity Wave Breaking at the Tropopause
2000 FLORIDA AVE NW, WASHINGTON, DC,
2000
Methylmercury varies more than one order of magnitude in commercial European rice
P.M. thanks the Royal Thai Government for funding and C.C.B. thanks the School of Natural and Computing Science and PS Analytical for funding.Peer reviewedPostprin
a follow-up on bone graft stability and implant success
Background Until now, sinus floor elevation represents the gold standard
procedure in the atrophic maxilla in order to facilitate dental implant
insertion. Although the procedure remains highly predictive, the perforation
of the Schneiderian membrane might compromise the stability of the augmented
bone and implant success due to chronic sinus infection. The aim of this
retrospective cohort study was to show that a membrane tear, if detected and
surgically properly addressed, has no influence on the survival of dental
implants and bone resorption in the augmented area. Methods Thirty-one
patients with 39 perforations could be included in this evaluation, and a
control group of 32 patients with 40 sinus lift procedures without
complications were compared regarding the radiographically determined
development of bone level, peri-implant infection, and implant loss. Results
Implant survival was 98.9% in the perforation group over an observation period
of 2.7 (屉2.03) years compared to 100% in the control group after 1.8 (屉1.57)
years. The residual bone level was significantly lower in the perforation
group (pâ=â0.05) but showed no difference direct postoperatively (pâ=â0.7851)
or in the follow-up assessment (pâ=â0.2338). Bone resorption remained not
different between both groups (pâ=â0.945). A two-stage procedure was more
frequent in the perforation group (pâ=â0.0003) as well as peri-implantitis (p
=â0.0004). Conclusions Within the limits of our study, the perforation of the
Schneiderian membrane did not have a negative impact on long-term graft
stability or the overall implant survival
Gluing torus families across a singularity: The lens space for the hydrogen atom in crossed fields
We demonstrate that topological information that can be extracted from periodic orbits
in a near-integrable system can lead to a complete topological characterization of families
of invariant 2-tori in terms of lens spaces. This approach ties in with the techniques we
developed for classifying the tori in systems with more than two degrees of freedom. It
therefore offers a general way to investigate families of invariant 2-tori in higher-dimensional
Hamiltonian systems
A Thermal Window for Yawning in Humans: Yawning as a Brain Cooling Mechanism
The thermoregulatory theory of yawning posits that yawns function to cool the brain in part due to counter-current heat exchange with the deep inhalation of ambient air. Consequently, yawning should be constrained to an optimal thermal zone or range of temperature, i.e., a thermal window, in which we should expect a lower frequency at extreme temperatures. Previous research shows that yawn frequency diminishes as ambient temperatures rise and approach body temperature, but a lower bound to the thermal window has not been demonstrated. To test this, a total of 120 pedestrians were sampled for susceptibly to self-reported yawn contagion during distinct temperature ranges and seasons (winter: 1.4 °C, n = 60; summer: 19.4 °C, n = 60). As predicted, the proportion of pedestrians reporting yawning was significantly lower during winter than in summer (18.3% vs. 41.7%), with temperature being the only significant predictor of these differences across seasons. The underlying mechanism for yawning in humans, both spontaneous and contagious, appears to be involved in brain thermoregulation
Anatomy of Cirrus Clouds: Results from the Emerald Airborne Campaigns
2000 FLORIDA AVE NW, WASHINGTON, USA, DC,
2000
ApoE polymorphisms in narcolepsy
BACKGROUND: Narcolepsy is a common neuropsychiatric disorder characterized by increased daytime sleepiness, cataplexy and hypnagogic hallucinations. Deficiency of the hypocretin neurotransmitter system was shown to be involved in the pathogenesis of narcolepsy in animals and men. There are several hints that neurodegeneration of hypocretin producing neurons in the hypothalamus is the pathological correlate of narcolepsy. The ApoE4 allele is a major contributing factor to early-onset neuronal degeneration in Alzheimer disease and other neurodegenerative diseases as well. METHODS: To clarify whether the ApoE4 phenotype predisposes to narcolepsy or associates with an earlier disease onset, we have genotyped the ApoE gene in 103 patients with narcolepsy and 101 healthy controls. RESULTS: The frequency of the E4 allele of the ApoE gene was 11% in the patient and 15% in the control groups. Furthermore, the mean age of onset did not differ between the ApoE4(+) and ApoE4(-) patient groups. CONCLUSION: Our results exclude the ApoE4 allele as a major risk factor for narcolepsy
People that score high on psychopathic traits are less likely to yawn contagiously
Considerable variation exists in the contagiousness of yawning, and numerous studies have been conducted to investigate the proximate mechanisms involved in this response. Yet, findings within the psychological literature are mixed, with many studies conducted on relatively small and homogeneous samples. Here, we aimed to replicate and extend upon research suggesting a negative relationship between psychopathic traits and yawn contagion in community samples. In the largest study of contagious yawning to date (Nâ=â458), which included both university students and community members from across 50 nationalities, participants completed an online study in which they self-reported on their yawn contagion to a video stimulus and completed four measures of psychopathy: the primary and secondary psychopathy scales from the Levenson Self-Report Psychopathy Scale (LSRPS), the psychopathy construct from the Dirty Dozen, and the Psychopathic Personality Traits Scale (PPTS). Results support previous findings in that participants that yawned contagiously tended to score lower on the combined and primary measures of psychopathy. That said, tiredness was the strongest predictor across all models. These findings align with functional accounts of spontaneous and contagious yawning and a generalized impairment in overall patterns of behavioral contagion and biobehavioral synchrony among people high in psychopathic traits
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