9,387 research outputs found
Constraint on the Low Energy Constants of Wilson Chiral Perturbation Theory
Wilson chiral perturbation theory (WChPT) is the effective field theory
describing the long- distance properties of lattice QCD with Wilson or
twisted-mass fermions. We consider here WChPT for the theory with two light
flavors of Wilson fermions or a single light twisted-mass fermion.
Discretization errors introduce three low energy constants (LECs) into
partially quenched WChPT at O(a^2), conventionally called W'_6, W'_7 and W'_8 .
The phase structure of the theory at non-zero a depends on the sign of the
combination 2W'_6 + W'_8, while the spectrum of the lattice Hermitian
Wilson-Dirac operator depends on all three constants. It has been argued, based
on the positivity of partition functions of fixed topological charge, and on
the convergence of graded group integrals that arise in the epsilon-regime of
ChPT, that there is a constraint on the LECs arising from the underlying
lattice theory. In particular, for W'_6 = W'_7 = 0, the constraint found is
W'_8 \le 0. Here we provide an alternative line of argument, based on mass
inequalities for the underlying partially quenched theory. We find that W'_8
\le 0, irrespective of the values of W'_6 and W'_7. Our constraint implies that
2W'_6 > |W'_8| if the phase diagram is to be described by the first-order
scenario, as recent simulations suggest is the case for some choices of action.Comment: 10 pages, no figure
Is the quantum world composed of propensitons?
In this paper I outline my propensiton version of quantum theory (PQT). PQT is a fully micro-realistic version of quantum theory that provides us with a very natural possible solution to the fundamental wave/particle problem, and is free of the severe defects of orthodox quantum theory (OQT) as a result. PQT makes sense of the quantum world. PQT recovers all the empirical success of OQT and is, furthermore, empirically testable (although not as yet tested). I argue that Einstein almost put forward this version of quantum theory in 1916/17 in his papers on spontaneous and induced radiative transitions, but retreated from doing so because he disliked the probabilistic character of the idea. Subsequently, the idea was overlooked because debates about quantum theory polarised into the Bohr/Heisenberg camp, which argued for the abandonment of realism and determinism, and the Einstein/Schrƶdinger camp, which argued for the retention of realism and determinism, no one, as a result, pursuing the most obvious option of retaining realism but abandoning determinism. It is this third, overlooked option that leads to PQT. PQT has implications for quantum field theory, the standard model, string theory, and cosmology. The really important point, however, is that it is experimentally testable. I indicate two experiments in principle capable of deciding between PQT and OQT
Development of three dimensional constitutive theories based on lower dimensional experimental data
Most three dimensional constitutive relations that have been developed to
describe the behavior of bodies are correlated against one dimensional and two
dimensional experiments. What is usually lost sight of is the fact that
infinity of such three dimensional models may be able to explain these
experiments that are lower dimensional. Recently, the notion of maximization of
the rate of entropy production has been used to obtain constitutive relations
based on the choice of the stored energy and rate of entropy production, etc.
In this paper we show different choices for the manner in which the body stores
energy and dissipates energy and satisfies the requirement of maximization of
the rate of entropy production that leads to many three dimensional models. All
of these models, in one dimension, reduce to the model proposed by Burgers to
describe the viscoelastic behavior of bodies.Comment: 23 pages, 6 figure
Using Landsat satellite data to support pesticide exposure assessment in California
<p>Abstract</p> <p>Background</p> <p>The recent U.S. Geological Survey policy offering Landsat satellite data at no cost provides researchers new opportunities to explore relationships between environment and health. The purpose of this study was to examine the potential for using Landsat satellite data to support pesticide exposure assessment in California.</p> <p>Methods and Results</p> <p>We collected a dense time series of 24 Landsat 5 and 7 images spanning the year 2000 for an agricultural region in Fresno County. We intersected the Landsat time series with the California Department of Water Resources (CDWR) land use map and selected field samples to define the phenological characteristics of 17 major crop types or crop groups. We found the frequent overpass of Landsat enabled detection of crop field conditions (e.g., bare soil, vegetated) over most of the year. However, images were limited during the winter months due to cloud cover. Many samples designated as single-cropped in the CDWR map had phenological patterns that represented multi-cropped or non-cropped fields, indicating they may have been misclassified.</p> <p>Conclusions</p> <p>We found the combination of Landsat 5 and 7 image data would clearly benefit pesticide exposure assessment in this region by 1) providing information on crop field conditions at or near the time when pesticides are applied, and 2) providing information for validating the CDWR map. The Landsat image time-series was useful for identifying idle, single-, and multi-cropped fields. Landsat data will be limited during the winter months due to cloud cover, and for years prior to the Landsat 7 launch (1999) when only one satellite was operational at any given time. We suggest additional research to determine the feasibility of integrating CDWR land use maps and Landsat data to derive crop maps in locations and time periods where maps are not available, which will allow for substantial improvements to chemical exposure estimation.</p
Perfect imaging with positive refraction in three dimensions
Maxwell's fish eye has been known to be a perfect lens within the validity
range of ray optics since 1854. Solving Maxwell's equations we show that the
fish-eye lens in three dimensions has unlimited resolution for electromagnetic
waves
Relaxation dynamics and colossal magnetocapacitive effect in CdCr2S4
A thorough investigation of the relaxational dynamics in the recently
discovered multiferroic CdCr2S4 showing a colossal magnetocapacitive effect has
been performed. Broadband dielectric measurements without and with external
magnetic fields up to 10 T provide clear evidence that the observed
magnetocapacitive effect stems from enormous changes of the relaxation dynamics
induced by the development of magnetic order.Comment: 4 pages, 4 figure
Bowel dysfunction after transposition of intestinal segments into the urinary tract : 8-year prospective cohort study
Purpose Bowel function may be disturbed after intestinal segments are transposed into the urinary tract to reconstruct or replace the bladder. In 1997, our group were the first to report major bowel dysfunction in a cohort of such patients: up to 42% of those who were asymptomatic preoperatively describing new bowel symptoms postoperatively including explosive diarrhoea, nocturnal diarrhoea, faecal urgency, faecal incontinence and flatus leakage . We now describe bowel symptoms in this same cohort eight years later (2005). Materials and Methods 116 patients were evaluable. Of the remaining 37 from the original report: 30 had died, five no longer wished to be involved, and two could not be traced. Patients were asked to complete postal questionnaires identical to those used in the first follow-up, assessing the severity of bowel symptoms and quality of life using two validated instruments. Responses were compared with those from the original study. The Nottingham Health Profile quality of life scores were also compared to age and sex matched norms. Results 96 (83%) completed eight-year follow-up questionnaires: 43 after ileal conduit diversion (Group 1), 17 after clam enterocystoplasty for overactive bladder (Group 2), 18 after reconstructed bladder for neurogenic bladder dysfunction (Group 3), and 18 with bladder replacement for non-neurogenic causes (Group 4). High prevalence rates of bowel symptoms persisted with no statistically significant differences between the two time points. Of those with symptoms in 2005, around 50% had reported similar symptoms in 1997. Clam enterocystoplasty patients (Group 2) still reported the highest prevalence (59%) of troublesome diarrhoea with one in two on regular anti-diarrhoeal medication. They also had high rates of faecal incontinence (47%), faecal urgency (41%) and nocturnal bowel movement (18%); with high proportions reporting a moderate or severe adverse effect on work (36%), social life (50%) and sex life (43%). High rates were also reported by neurogenic bladder dysfunction patients, including 50% with troublesome diarrhoea. This symptom was reported by 19% after ileal conduit and by 17% after bladder replacement for non-neurogenic causes. The impact of bowel symptoms on every-day activities and quality of life persisted, remaining most severe after clam enterocystoplasty, with 24% regretting undergoing the procedure because of subsequent bowel symptoms. Conclusions: After more than eight years, operations involving transposition of intestinal segments continue to be associated with high rates of bowel symptoms, which impact on everyday activities. These are particularly troublesome following enterocystoplasty for overactive bladder and bladder reconstruction for neurogenic bladder dysfunction. These risks should influence patient selection and potential patients should be warned prior to surgery
Bowel dysfunction after transposition of intestinal segments into the urinary tract : 8-year prospective cohort study
Purpose Bowel function may be disturbed after intestinal segments are transposed into the urinary tract to reconstruct or replace the bladder. In 1997, our group were the first to report major bowel dysfunction in a cohort of such patients: up to 42% of those who were asymptomatic preoperatively describing new bowel symptoms postoperatively including explosive diarrhoea, nocturnal diarrhoea, faecal urgency, faecal incontinence and flatus leakage . We now describe bowel symptoms in this same cohort eight years later (2005). Materials and Methods 116 patients were evaluable. Of the remaining 37 from the original report: 30 had died, five no longer wished to be involved, and two could not be traced. Patients were asked to complete postal questionnaires identical to those used in the first follow-up, assessing the severity of bowel symptoms and quality of life using two validated instruments. Responses were compared with those from the original study. The Nottingham Health Profile quality of life scores were also compared to age and sex matched norms. Results 96 (83%) completed eight-year follow-up questionnaires: 43 after ileal conduit diversion (Group 1), 17 after clam enterocystoplasty for overactive bladder (Group 2), 18 after reconstructed bladder for neurogenic bladder dysfunction (Group 3), and 18 with bladder replacement for non-neurogenic causes (Group 4). High prevalence rates of bowel symptoms persisted with no statistically significant differences between the two time points. Of those with symptoms in 2005, around 50% had reported similar symptoms in 1997. Clam enterocystoplasty patients (Group 2) still reported the highest prevalence (59%) of troublesome diarrhoea with one in two on regular anti-diarrhoeal medication. They also had high rates of faecal incontinence (47%), faecal urgency (41%) and nocturnal bowel movement (18%); with high proportions reporting a moderate or severe adverse effect on work (36%), social life (50%) and sex life (43%). High rates were also reported by neurogenic bladder dysfunction patients, including 50% with troublesome diarrhoea. This symptom was reported by 19% after ileal conduit and by 17% after bladder replacement for non-neurogenic causes. The impact of bowel symptoms on every-day activities and quality of life persisted, remaining most severe after clam enterocystoplasty, with 24% regretting undergoing the procedure because of subsequent bowel symptoms. Conclusions: After more than eight years, operations involving transposition of intestinal segments continue to be associated with high rates of bowel symptoms, which impact on everyday activities. These are particularly troublesome following enterocystoplasty for overactive bladder and bladder reconstruction for neurogenic bladder dysfunction. These risks should influence patient selection and potential patients should be warned prior to surgery
Sequential Strong Measurements and Heat Vision
We study scenarios where a finite set of non-demolition von-Neumann
measurements are available. We note that, in some situations, repeated
application of such measurements allows estimating an infinite number of
parameters of the initial quantum state, and illustrate the point with a
physical example. We then move on to study how the system under observation is
perturbed after several rounds of projective measurements. While in the finite
dimensional case the effect of this perturbation always saturates, there are
some instances of infinite dimensional systems where such a perturbation is
accumulative, and the act of retrieving information about the system increases
its energy indefinitely (i.e., we have `Heat Vision'). We analyze this effect
and discuss a specific physical system with two dichotomic von-Neumann
measurements where Heat Vision is expected to show.Comment: See the Appendix for weird examples of heat visio
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