2,635 research outputs found
Synthetizing hydrodynamic turbulence from noise: formalism and applications to plankton dynamics
We present an analytical scheme, easily implemented numerically, to generate synthetic Gaussian 2D turbulent flows by using linear stochastic partial differential equations, where the noise term acts as a random force of well-prescribed statistics. This methodology leads to a divergence-free, isotropic, stationary and homogeneous velocity field, whose characteristic parameters are well reproduced, in particular the kinematic viscosity and energy spectrum. This practical approach to tailor a turbulent flow is justified by its versatility when analizing different physical processes occurring in advectely mixed systems. Here, we focuss on an application to study the dynamics of Planktonic populations in the ocean
Evaluating the performance of survey-based operational management procedures
The design and evaluation of survey-based management strategies is addressed in this article, using three case-study fisheries: North Sea herring, Bay of Biscay anchovy and North Sea cod, with a brief history and the main management issues with each fishery outlined. A range of operational management procedures for the case study stocks were designed and evaluated using trends that may be derived from survey indices (spawner biomass, year-class strength and total mortality) with an array of simple and more structured observation error regimes simulated. Model-free and model-based indicators of stock status were employed in the management procedures. On the basis of stochastic stock-specific simulations, we identified the following key determinants of successful management procedures: (i) adequate specification of the stock-recruit relationship (model structure, parameter estimates and variability), (ii) knowledge of the magnitude and structure of the variation in the survey indices, and (iii) explication of the particular management objectives, when assessing management performance. More conservative harvesting strategies are required to meet specified targets in the presence of increasing stochasticity, due to both process and observation error. It was seen that survey-based operational management procedures can perform well in the absence of commercial data, and can also inform aspects of survey design with respect to acceptable levels of error or bias in the surveys
Qubits in phase space: Wigner function approach to quantum error correction and the mean king problem
We analyze and further develop a new method to represent the quantum state of
a system of qubits in a phase space grid of points (where
). The method, which was recently proposed by Wootters and co--workers
(Gibbons {\it et al.}, quant-ph/0401155), is based on the use of the elements
of the finite field to label the phase space axes. We present a
self--contained overview of the method, we give new insights on some of its
features and we apply it to investigate problems which are of interest for
quantum information theory: We analyze the phase space representation of
stabilizer states and quantum error correction codes and present a phase space
solution to the so--called ``mean king problem''.Comment: 18 pages, 16 figures; typos fixed, some minor corrections, figures of
the circuits were change
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BRAF inhibitor and hairy cell leukemia-related transient acantholytic dermatosis
Grover disease (GD) is an acquired, nonfamilial, nonimmune mediated, transient or persistent acantholytic dermatosis. Herein, we present a 72-year-old man who had clinical and histopathologic findings of GD following two weeks of treatment with vemurafenib without MEK inhibitor. The patient was successfully treated with topical emollients and a high-potency corticosteroid. Meanwhile, vemurafenib was temporarily discontinued. Drug-induced GD has increasingly been reported in patients on BRAF inhibitor monotherapy as an immune-related adverse event. The cutaneous side effects seem to arise secondary to a paradoxical activation of the mitogen-activated protein kinase signaling of BRAF inhibitor treatment, leading to keratinocyte proliferation. Although the pathogenesis of GD has not been delineated, there is suggestion of activation of T lymphocytes, particularly helper cells under the action of pro-inflammatory cytokines, resulting in proliferation of keratinocytes. Combination therapy with a MEK inhibitor appears to prevent BRAF-induced GD. Given that there is a higher prevalence of GD in patients with hematologic malignancy, a direct causal relationship between the initiation of vemurafenib therapy and development of GD in this case may be difficult to establish
Effectiveness of zinc supplementation on diarrhea and average daily gain in pre-weaned dairy calves: A double-blind, block-randomized, placebo-controlled clinical trial.
The objective of this clinical trial was to evaluate the effectiveness of zinc supplementation on diarrhea and average daily weight gain (ADG) in pre-weaned dairy calves. A total of 1,482 healthy Holstein heifer and bull calves from a large California dairy were enrolled at 24 to 48 hours of age until hutch exit at approximately 90 days of age. Calves were block-randomized by time to one of three treatments: 1) placebo, 2) zinc methionine (ZM), or 3) zinc sulfate (ZS) administered in milk once daily for 14 days. Serum total protein at enrollment and body weight at birth, treatment end, and hutch exit were measured. Fecal consistency was assessed daily for 28 days post-enrollment. For a random sample of 127 calves, serum zinc concentrations before and after treatment and a fecal antigen ELISA at diarrhea start and resolution for Escherichia coli K99, rotavirus, coronavirus, and Cryptosporidium parvum were performed. Linear regression showed that ZM-treated bull calves had 22 g increased ADG compared to placebo-treated bulls (P = 0.042). ZM-treated heifers had 9 g decreased ADG compared to placebo-treated heifers (P = 0.037), after adjusting for average birth weight. Sex-stratified models showed that high birth weight heifers treated with ZM gained more than placebo-treated heifers of the same birth weight, which suggests a dose-response effect rather than a true sex-specific effect of ZM on ADG. Cox regression showed that ZM and ZS-treated calves had a 14.7% (P = 0.015) and 13.9% (P = 0.022) reduced hazard of diarrhea, respectively, compared to placebo-treated calves. Calves supplemented for at least the first five days of diarrhea with ZM and ZS had a 21.4% (P = 0.027) and 13.0% (P = 0.040) increased hazard of cure from diarrhea, respectively, compared to placebo-treated calves. Logistic regression showed that the odds of microbiological cure at diarrhea resolution for rotavirus, C. parvum, or any single fecal pathogen was not different between treatment groups. Zinc supplementation delayed diarrhea and expedited diarrhea recovery in pre-weaned calves. Additionally, zinc improved weight gain differentially in bulls compared to heifers, indicating a research need for sex-specific dosing
The underactive bladder: detection and diagnosis.
The inability to generate a voiding contraction sufficient to allow efficient bladder emptying within a reasonable time frame is a common problem seen in urological practice. Typically, the symptoms that arise are voiding symptoms, such as weak and slow urinary flow. These symptoms can cause considerable bother to patients and impact upon quality of life. The urodynamic finding of inadequate detrusor contraction has been termed detrusor underactivity (DUA). Although a definition is available for this entity, there are no widely accepted diagnostic criteria. Drawing parallels to detrusor overactivity and the overactive bladder, the symptoms arising from DUA have been referred to as the "underactive bladder" (UAB), while attempts to crystallize the definition of UAB are now ongoing. In this article, we review the contemporary literature pertaining to the epidemiology and etiopathogenesis of DUA as well as discuss the definitional aspects that are currently under consideration
Gravitational Radiation from First-Order Phase Transitions
It is believed that first-order phase transitions at or around the GUT scale
will produce high-frequency gravitational radiation. This radiation is a
consequence of the collisions and coalescence of multiple bubbles during the
transition. We employ high-resolution lattice simulations to numerically evolve
a system of bubbles using only scalar fields, track the anisotropic stress
during the process and evolve the metric perturbations associated with
gravitational radiation. Although the radiation produced during the bubble
collisions has previously been estimated, we find that the coalescence phase
enhances this radiation even in the absence of a coupled fluid or turbulence.
We comment on how these simulations scale and propose that the same enhancement
should be found at the Electroweak scale; this modification should make direct
detection of a first-order electroweak phase transition easier.Comment: 7 pages, 7 figure
Optimal minimal measurements of mixed states
The optimal and minimal measuring strategy is obtained for a two-state system
prepared in a mixed state with a probability given by any isotropic a priori
distribution. We explicitly construct the specific optimal and minimal
generalized measurements, which turn out to be independent of the a priori
probability distribution, obtaining the best guesses for the unknown state as
well as a closed expression for the maximal mean averaged fidelity. We do this
for up to three copies of the unknown state in a way which leads to the
generalization to any number of copies, which we then present and prove.Comment: 20 pages, no figure
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