Applicability of Taylor's hypothesis in thermally driven turbulence

In this paper, we show that in the presence of large-scale circulation (LSC), Taylor's hypothesis can be invoked to deduce the energy spectrum in thermal convection using real space probes, a popular experimental tool. We perform numerical simulation of turbulent convection in a cube and observe that the velocity field follows Kolmogorov's spectrum ($k^{-5/3}$). We also record the velocity time series using real space probes near the lateral walls. The corresponding frequency spectrum exhibits Kolmogorov's spectrum ($f^{-5/3}$), thus validating Taylor's hypothesis with the steady LSC playing the role of a mean velocity field. The aforementioned findings based on real space probes provide valuable inputs for experimental measurements used for studying the spectrum of convective turbulence

Enhanced light output of GaN-based light-emitting diodes with ZnO nanorod arrays

We report enhanced light output of GaN-based light-emitting diodes (LEDs) with vertically aligned ZnO nanorod arrays. The ZnO nanorod arrays were prepared on the top layer of GaN LEDs using catalyst-free metalorganic vapor phase epitaxy. Compared to conventional GaN LEDs, light output of GaN LEDs with the ZnO nanorod arrays increased up to 50% and 100% at applied currents of 20 and 50 mA, respectively. The source of the enhanced light output is also discussed. (C) 2008 American Institute of Physics.open11132146sciescopu

On the exponential transform of lemniscates

It is known that the exponential transform of a quadrature domain is a rational function for which the denominator has a certain separable form. In the present paper we show that the exponential transform of lemniscate domains in general are not rational functions, of any form. Several examples are given to illustrate the general picture. The main tool used is that of polynomial and meromorphic resultants.Comment: 19 pages, to appear in the Julius Borcea Memorial Volume, (eds. Petter Branden, Mikael Passare and Mihai Putinar), Trends in Mathematics, Birkhauser Verla

Atomic-scale combination of germanium-zinc nanofibers for structural and electrochemical evolution

Alloys are recently receiving considerable attention in the community of rechargeable batteries as possible alternatives to carbonaceous negative electrodes; however, challenges remain for the practical utilization of these materials. Herein, we report the synthesis of germanium-zinc alloy nanofibers through electrospinning and a subsequent calcination step. Evidenced by in situ transmission electron microscopy and electrochemical impedance spectroscopy characterizations, this one-dimensional design possesses unique structures. Both germanium and zinc atoms are homogenously distributed allowing for outstanding electronic conductivity and high available capacity for lithium storage. The as-prepared materials present high rate capability (capacity of similar to 50% at 20 C compared to that at 0.2 C-rate) and cycle retention (73% at 3.0 C-rate) with a retaining capacity of 546 mAh g(-1) even after 1000 cycles. When assembled in a full cell, high energy density can be maintained during 400 cycles, which indicates that the current material has the potential to be used in a large-scale energy storage system

Reversible change in electrical and optical properties in epitaxially grown Al-doped ZnO thin films

Aluminum-doped ZnO (AZO) films were epitaxially grown on sapphire (0001) substrates using pulsed laser deposition. As-deposited AZO films had a low resistivity of 8.01× 10-4 Ω cm. However, after annealing at 450 °C in air, the electrical resistivity of the AZO films increased to 1.97× 10-1 Ω cm because of a decrease in the carrier concentration. Subsequent annealing of the air-annealed AZO films in H2 recovered the electrical conductivity of the AZO films. In addition, the conductivity change was reversible upon repeated air and H2 annealing. A photoluminescence study showed that oxygen interstitial (Oi′) is a critical material parameter allowing for the reversible control of the electrical conducting properties of AZO films. © 2008 American Institute of Physics

Fusidic acid resistance through changes in the dynamics of the drug target

Antibiotic resistance in clinically important bacteria can be mediated by target protection mechanisms, whereby a protein binds to the drug target and protects it from the inhibitory effects of the antibiotic. The most prevalent source of clinical resistance to the antibiotic fusidic acid (FA) is expression of the FusB family of proteins that bind to the drug target (Elongation factor G [EF-G]) and promote dissociation of EF-G from FA-stalled ribosome complexes. FusB binding causes changes in both the structure and conformational flexibility of EF-G, but which of these changes drives FA resistance was not understood. We present here detailed characterization of changes in the conformational flexibility of EF-G in response to FusB binding and showthat these changes are responsible for conferring FA resistance. Binding of FusB to EF-G causes a significant change in the dynamics of domain III of EF-GC3 that leads to an increase in a minor, more disordered state of EF-G domain III. This is sufficient to overcome the steric block of transmission of conformational changes within EF-G by which FA prevents release of EF-G from the ribosome. This study has identified an antibiotic resistance mechanism mediated by allosteric effects on the dynamics of the drug target

The filtering equations revisited

The problem of nonlinear filtering has engendered a surprising number of mathematical techniques for its treatment. A notable example is the change-of--probability-measure method originally introduced by Kallianpur and Striebel to derive the filtering equations and the Bayes-like formula that bears their names. More recent work, however, has generally preferred other methods. In this paper, we reconsider the change-of-measure approach to the derivation of the filtering equations and show that many of the technical conditions present in previous work can be relaxed. The filtering equations are established for general Markov signal processes that can be described by a martingale-problem formulation. Two specific applications are treated

Replenishment of microRNA-188-5p restores the synaptic and cognitive deficits in 5XFAD Mouse Model of Alzheimer’s Disease.

MicroRNAs have emerged as key factors in development, neurogenesis and synaptic functions in the central nervous system. In the present study, we investigated a pathophysiological significance of microRNA-188-5p (miR-188-5p) in Alzheimer's disease (AD). We found that oligomeric A beta(1-42) treatment diminished miR-188-5p expression in primary hippocampal neuron cultures and that miR-188-5p rescued the A beta(1-42)-mediated synapse elimination and synaptic dysfunctions. Moreover, the impairments in cognitive function and synaptic transmission observed in 7-month-old five familial AD (5XFAD) transgenic mice, were ameliorated via viral-mediated expression of miR-188-5p. miR-188-5p expression was down-regulated in the brain tissues from AD patients and 5XFAD mice. The addition of miR-188-5p rescued the reduction in dendritic spine density in the primary hippocampal neurons treated with oligomeric A beta(1-42) and cultured from 5XFAD mice. The reduction in the frequency of mEPSCs was also restored by addition of miR-188-5p. The impairments in basal fEPSPs and cognition observed in 7-month-old 5XFAD mice were ameliorated via the viral-mediated expression of miR-188-5p in the hippocampus. Furthermore, we found that miR-188 expression is CREB-dependent. Taken together, our results suggest that dysregulation of miR-188-5p expression contributes to the pathogenesis of AD by inducing synaptic dysfunction and cognitive deficits associated with A beta-mediated pathophysiology in the disease.1186Ysciescopu

The UK register of HIV seroconverters: Methods and analytical issues

A Register of HIV-infected persons who have had a negative antibody test within 3 years of their first antibody positive test (seroconverters) is being set up in the UK to monitor the distribution of times from HIV seroconversion to AIDS (the incubation period) and to death. It will also provide a national resource for use by those designing studies in this group of individuals. Clinicians caring for HIV-positive persons in Genito-Urinary Medicine, Infectious Disease and other departments throughout the UK were asked to participate by providing information on eligible subjects. Most laboratories undertaking HIV antibody testing were also contacted and asked to provide the name of the attending clinician for all seroconverters identified through the HIV laboratory reporting systems of the PHLS Communicable Disease Surveillance Centre (CDSC) and the Scottish Centre for Infection and Environmental Health (SCIEH) and for any other seroconverters known to them but not identified by CDSC or SCIEH. Data items sought for the Register include: sex, ethnic group, probable route of HIV transmission, annual CD4 counts, details of therapy and prophylaxis prescribed, AIDS-defining events and vital status. Follow up information is collected annually. Wherever possible, all seroconverters known to a clinic have been identified, whether currently alive or dead, either from clinic records or laboratory reporting or both. The objective is to establish and update a complete register of seroconverters on a long-term basis to provide reliable estimates of the incubation period on which future projections of AIDS cases in the UK can be made

Phytosanitary practices and evaluation of 17 pesticides residues in tomatoes fruits produced in Foumbot District Western Highland-Cameroon

The involvement of pesticides in agriculture requires the implementation of best phytosanitary practices in order to guarantee the health of populations and preserve the environment. This study focused on the assessment of phytosanitary practices of tomato producers in Foumbot, Western Highlands-Cameroon, and evaluated the residues of 17 pesticides in tomatoes. The methodological approach consisted of field investigations by survey, collection of samples, pesticide residue extraction using QuEChERS method, and their analysis by gas chromatography tandem mass spectrometry (GC-MS). Survey of 100 farmers showed that, they did not comply with the instructions for the use of plant protection products: 56% of farmers interviewed increased the dose of products when they noticed its ineffectiveness; 93% did not the respect pre-harvest intervals; while 77% increased the application frequency at the time of fruiting. All the producers work without personal protective equipment (PPE) and 68% of them use empty packaging for packaging consumable including water, red oil and palm wine. The reuse of empty packaging could expose populations (producers and consumers) to numerous health risks. Regarding pesticides residues, 03 actives ingredients were detected and quantified in the samples, all the samples were contaminated by lambda-cyhalothrin, 86.66% by cypermethrin and 66.66% by acetamiprid. Moreover, residue concentrations above the maximum residue limit (MRL) were found in all the positive samples of lambda-cyhalothrin, and 92.30% of cypermethrin positive samples. This study shows that utilization of plant protection products in Foumbot requires extensive monitoring with producers, in order to reduce risk of consumers exposure