2,007 research outputs found
Recent results from systematic parameterizations of Ginsparg-Wilson fermions
The Fixed Point Dirac Operator and Chirally Improved Fermions both use large
numbers of gauge paths and the full Dirac structure to approximate a solution
of the Ginsparg-Wilson equation. After a brief review of the two approaches we
present recent results for quenched QCD with pion masses down to 210 MeV. We
discuss the limits and advantages of approximate parameterizations and outline
future perspectives.Comment: Lattice2002(plenary). References and Fig. 5 updated. Final version
submitted to the proceeding
Chiral Effective Lagrangian and Quark Masses
The status of lattice determinations of quark masses is reviewed (with the
exception of m_b). Attempts to extract the low-energy constants in the
effective chiral Lagrangian are discussed, with special emphasis on those
couplings which are required to test the hypothesis of a massless up-quark.
Furthermore, the issue of quenched chiral logarithms is addressed.Comment: Invited talk presented at Lattice2002(plenary), 12 pages, 3 figure
Does socioeconomic status affect mortality subsequent to hospital admission for community acquired pneumonia among older persons?
BACKGROUND: Low socioeconomic status has been associated with increased morbidity and mortality for various health conditions. The purpose of this study was twofold: to examine the mortality experience of older persons admitted to hospital with community acquired pneumonia and to test the hypothesis of whether an association exists between socioeconomic status and mortality subsequent to hospital admission for community-acquired pneumonia. METHODS: A population based retrospective cohort study was conducted including all older persons patients admitted to Ontario hospitals with community acquired pneumonia between April 1995 and March 2001. The main outcome measures were 30 day and 1 year mortality subsequent to hospital admission for community-acquired pneumonia. RESULTS: Socioeconomic status for each patient was imputed from median neighbourhood income. Multivariate analyses were undertaken to adjust for age, sex, co-morbid illness, hospital and physician characteristics. The study sample consisted of 60,457 people. Increasing age, male gender and high co-morbidity increased the risk for mortality at 30 days and one year. Female gender and having a family physician as attending physician reduced mortality risk. The adjusted odds of death after 30-days for the quintiles compared to the lowest income quintile (quintile 1) were 1.02 (95% CI: 0.95–1.09) for quintile 2, 1.04 (95% CI: 0.97–1.12) for quintile 3, 1.01 (95% CI: 0.94–1.08) for quintile 4 and 1.03 (95% CI: 0.96–1.12) for the highest income quintile (quintile 5). For 1 year mortality, compared to the lowest income quintile the adjusted odds ratios were 1.01 (95% CI: 0.96–1.06) for quintile 2, 0.99 (95% CI: 0.94–1.04) for quintile 3, 0.99 (95% CI: 0.93–1.05) for quintile 4 and 1.03 (95% CI: 0.97–1.10) for the highest income quintile. CONCLUSION: Socioeconomic status is not associated with mortality in the older persons from community-acquired pneumonia in Ontario, Canada
Electrical detection of 31P spin quantum states
In recent years, a variety of solid-state qubits has been realized, including
quantum dots, superconducting tunnel junctions and point defects. Due to its
potential compatibility with existing microelectronics, the proposal by Kane
based on phosphorus donors in Si has also been pursued intensively. A key issue
of this concept is the readout of the P quantum state. While electrical
measurements of magnetic resonance have been performed on single spins, the
statistical nature of these experiments based on random telegraph noise
measurements has impeded the readout of single spin states. In this letter, we
demonstrate the measurement of the spin state of P donor electrons in silicon
and the observation of Rabi flops by purely electric means, accomplished by
coherent manipulation of spin-dependent charge carrier recombination between
the P donor and paramagnetic localized states at the Si/SiO2 interface via
pulsed electrically detected magnetic resonance. The electron spin information
is shown to be coupled through the hyperfine interaction with the P nucleus,
which demonstrates the feasibility of a recombination-based readout of nuclear
spins
Index Theorem and Overlap Formalism with Naive and Minimally Doubled Fermions
We present a theoretical foundation for the Index theorem in naive and
minimally doubled lattice fermions by studying the spectral flow of a Hermitean
version of Dirac operators. We utilize the point splitting method to implement
flavored mass terms, which play an important role in constructing proper
Hermitean operators. We show the spectral flow correctly detects the index of
the would-be zero modes which is determined by gauge field topology. Using the
flavored mass terms, we present new types of overlap fermions from the naive
fermion kernels, with a number of flavors that depends on the choice of the
mass terms. We succeed to obtain a single-flavor naive overlap fermion which
maintains hypercubic symmetry.Comment: 27 pages, 17 figures; references added, version accepted in JHE
Firms' investment under financial constraints: a Euro area investigation
In this paper we describe a model of optimal investment of various types of financially constrained firms. We show that the resulting relationship between internal funds and investment is non-monotonic. In particular, the magnitude of the cash flow sensitivity of the investment is lower for firms with credit rationing compared to firms that are able to obtained short-term external financing. The inverse relationship is driven by the leverage multiplier effect. A positive cash flow shock increases the short-term borrowing capacity of the firm, which in turn has a positive effect on investment and firm's growth. Moreover, the leverage multiplier effect is the highest for firms relying on short-term credits and it is lower for firms that are able to obtain long-term financing. Analysing a large euro area data set we find strong empirical support for our theoretical predictions. The results also help to explain some contrasting findings in the financial constraints literature
Industrial energy use and the human life history
The demographic rates of most organisms are supported by the consumption of food energy, which is used to produce new biomass and fuel physiological processes. Unlike other species, modern humans use ‘extra-metabolic' energy sources acquired independent of physiology, which also influence demographics. We ask whether the amount of extra-metabolic energy added to the energy budget affects demographic and life history traits in a predictable way. Currently it is not known how human demographics respond to energy use, and we characterize this response using an allometric approach. All of the human life history traits we examine are significant functions of per capita energy use across industrialized populations. We find a continuum of traits from those that respond strongly to the amount of extra-metabolic energy used, to those that respond with shallow slopes. We also show that the differences in plasticity across traits can drive the net reproductive rate to below-replacement levels
Socioeconomic considerations in the health of urban areas
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45780/1/11524_2006_Article_BF02345090.pd
Pathogenesis of adolescent idiopathic scoliosis in girls - a double neuro-osseous theory involving disharmony between two nervous systems, somatic and autonomic expressed in the spine and trunk: possible dependency on sympathetic nervous system and hormones with implications for medical therapy
Anthropometric data from three groups of adolescent girls - preoperative adolescent idiopathic scoliosis (AIS), screened for scoliosis and normals were analysed by comparing skeletal data between higher and lower body mass index subsets. Unexpected findings for each of skeletal maturation, asymmetries and overgrowth are not explained by prevailing theories of AIS pathogenesis. A speculative pathogenetic theory for girls is formulated after surveying evidence including: (1) the thoracospinal concept for right thoracic AIS in girls; (2) the new neuroskeletal biology relating the sympathetic nervous system to bone formation/resorption and bone growth; (3) white adipose tissue storing triglycerides and the adiposity hormone leptin which functions as satiety hormone and sentinel of energy balance to the hypothalamus for long-term adiposity; and (4) central leptin resistance in obesity and possibly in healthy females. The new theory states that AIS in girls results from developmental disharmony expressed in spine and trunk between autonomic and somatic nervous systems. The autonomic component of this double neuro-osseous theory for AIS pathogenesis in girls involves selectively increased sensitivity of the hypothalamus to circulating leptin (genetically-determined up-regulation possibly involving inhibitory or sensitizing intracellular molecules, such as SOC3, PTP-1B and SH2B1 respectively), with asymmetry as an adverse response (hormesis); this asymmetry is routed bilaterally via the sympathetic nervous system to the growing axial skeleton where it may initiate the scoliosis deformity (leptin-hypothalamic-sympathetic nervous system concept = LHS concept). In some younger preoperative AIS girls, the hypothalamic up-regulation to circulating leptin also involves the somatotropic (growth hormone/IGF) axis which exaggerates the sympathetically-induced asymmetric skeletal effects and contributes to curve progression, a concept with therapeutic implications. In the somatic nervous system, dysfunction of a postural mechanism involving the CNS body schema fails to control, or may induce, the spinal deformity of AIS in girls (escalator concept). Biomechanical factors affecting ribs and/or vertebrae and spinal cord during growth may localize AIS to the thoracic spine and contribute to sagittal spinal shape alterations. The developmental disharmony in spine and trunk is compounded by any osteopenia, biomechanical spinal growth modulation, disc degeneration and platelet calmodulin dysfunction. Methods for testing the theory are outlined. Implications are discussed for neuroendocrine dysfunctions, osteopontin, sympathoactivation, medical therapy, Rett and Prader-Willi syndromes, infantile idiopathic scoliosis, and human evolution. AIS pathogenesis in girls is predicated on two putative normal mechanisms involved in trunk growth, each acquired in evolution and unique to humans
Density functional theory study of the multimode Jahn-Teller effect – ground state distortion of benzene cation
The multideterminental-DFT approach performed to analyze Jahn-Teller (JT) active molecules is described. Extension of this method for the analysis of the adiabatic potential energy surfaces and the multimode JT effect is presented. Conceptually a simple model, based on the analogy between the JT distortion and reaction coordinates gives further information about microscopic origin of the JT effect. Within the harmonic approximation the JT distortion can be expressed as a linear combination of all totally symmetric normal modes in the low symmetry minimum energy conformation, which allows calculating the Intrinsic Distortion Path, IDP, exactly from the high symmetry nuclear configuration to the low symmetry energy minimum. It is possible to quantify the contribution of different normal modes to the distortion, their energy contribution to the total stabilization energy and how their contribution changes along the IDP. It is noteworthy that the results obtained by both multideterminental-DFT and IDP methods for different classes of JT active molecules are consistent and in agreement with available theoretical and experimental values. As an example, detailed description of the ground state distortion of benzene cation is given
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