328 research outputs found
Well-posedness of the Kolmogorov two-equation model of turbulence in optimal Sobolev spaces
In this paper, we study the well-posedness of the Kolmogorov two-equation
model of turbulence in a periodic domain , for space dimensions
. We admit the average turbulent kinetic energy to vanish in part of
the domain, \textsl{i.e.} we consider the case ; in this situation,
the parabolic structure of the equations becomes degenerate.
For this system, we prove a local well-posedness result in Sobolev spaces
, for any . We expect this regularity to be optimal, due to the
degeneracy of the system when . We also prove a continuation
criterion and provide a lower bound for the lifespan of the solutions. The
proof of the results is based on Littlewood-Paley analysis and paradifferential
calculus on the torus, together with a precise commutator decomposition of the
non-linear terms involved in the computations.Comment: Submitte
Liquid Chromatography-Tandem Mass Spectrometry Analysis of Perfluorooctane Sulfonate and Perfluorooctanoic Acid in Fish Fillet Samples
Perfluorooctane sulfonate (PFOS) and perfluorooctanoic (PFOA) acid are persistent contaminants which can be found in environmental and biological samples. A new and fast analytical method is described here for the analysis of these compounds in the edible part of fish samples. The method uses a simple liquid extraction by sonication, followed by a direct determination using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The linearity of the instrumental response was good, with average regression coefficients of 0.9971 and 0.9979 for PFOS and PFOA, respectively, and the coefficients of variation (CV) of the method ranged from 8% to 20%. Limits of detection (LOD) were 0.04 ng/g for both the analytes and recoveries were 90% for PFOS and 76% for PFOA. The method was applied to samples of homogenized fillets of wild and farmed fish from the Mediterranean Sea. Most of the samples showed little or no contamination by perfluorooctane sulfonate and perfluorooctanoic acid, and the highest concentrations detected among the fish species analyzed were, respectively, 5.96 ng/g and 1.89 ng/g. The developed analytical methodology can be used as a tool to monitor and to assess human exposure to perfluorinated compounds through sea food consumption
PHYLOGENETIC RELATIONSHIPS OF ENTOMOPATHOGENIC NEMATODES AND THEIR BACTERIAL SYMBIONTS FROM COASTAL AREAS IN LEBANON
Entomopathogenic nematodes (EPNs) are parasites of soil-dwelling insects that occur in natural and agricultural soils around the world. The current study focuses on the unexplored coastal zone of Lebanon where soil samples were taken in different sites chosen randomly along the coast like beaches, agricultural and herbaceous fields. In total, 350 soil samples were collected, mainly from the southern part of the country. An integrated approach, combining both traditional (morphological) and molecular methods, was used to characterize entomopathogenic nematode species encountered. Two named-species are added to the EPNs catalog in Lebanon from 4 samples out of the total 350 samples isolated: Heterorhabditis indica, reported for the first time in the country (samples AYAB6 and BRA20) and Steinernema feltiae (samples ANFA5 and EDA1). Furthermore, one undescribed potential entomopathogenic nematode belonging to Oscheius genus was recovered. The symbiotic bacteria from S. feltiae and H. indica were also molecularly identified through the use of five gene fragments recA, gyrB, dnaN, gltX and infB. Phylogenetic relationships of entomopathogenic nematodes and their symbiotic bacteria were inferred by using maximum-likelihood analysis. Soil studies were subsequently carried out in order to assess a possible relationship between soil parameters and their effects on EPNs. Results indicate that sandy texture and moisture are key factors for the presence and survival of EPNs in the soil in Lebanon
Natural zeolites chabazite/phillipsite/analcime increase blood levels of antioxidant enzymes
Imbalance between reactive oxygen species generation and antioxidant capacity induces a condition known as oxidative stress which is implicated in numerous pathological processes. In this study we evaluated whether natural zeolites chabazite/phillipsite/analcime may affect the levels of different antioxidant enzymes (gluthatione peroxidase, superoxide dismutase, gluthatione reductase), total antioxidant status and oxidative stress in 25 clinically healthy men, both non-smokers and smokers. Measurements were performed on whole blood or on plasma samples before (T0) and after 4-weeks zeolites intake (T1). At T1, gluthatione peroxidase, superoxide dismutase and gluthatione reductase increased compared to T0 levels, both considering all subjects as joint and after subdivision in non-smokers and smokers. Differently, a reduction in total antioxidant status was observed at T1. Anyway, total antioxidant status resulted higher than the reference values in both groups at each time point. A decrease in lipid peroxidation, a major indicator of oxidative stress assessed by monitoring thiobarbituric acid reactive substances, was also observed in all subjects at T1. Our results suggested that chabazite/phillipsite/analcime may help to counteract oxidative stress in apparently healthy subjects exposed to different oxidative stress risk factors, such as smoking, thus representing a particular kind of food with potential antioxidant properties
Survey on Entomopathogens from the Arasbaran Biosphere Reserve (Iran) with a Modified Bait Insect Technique
A survey on entomopathogens was carried out in Arasbaran Biosphere Reserve soils during June 2018 using Galleria mellonella L. (Lepidoptera, Pyralidae)
larvae as bait insect with a modified bait insect technique. Three entomopathogen’s categories were recorded in 34 out of 36 soil samples (94.4%)
collected from different natural habitat; the entomopathogens were identified as nematodes (23.5%), fungi (61%) and bacteria (15.5%) using molecular
and morphological techniques
Whole-brain functional imaging to highlight differences between the diurnal and nocturnal neuronal activity in zebrafish larvae
Most living organisms show highly conserved physiological changes following a
24-hour cycle which goes by the name of circadian rhythm. Among experimental
models, the effects of light-dark cycle have been recently investigated in the
larval zebrafish. Owing to its small size and transparency, this vertebrate
enables optical access to the entire brain. Indeed, the combination of this
organism with light-sheet imaging grants high spatio-temporal resolution
volumetric recording of neuronal activity. This imaging technique, in its
multiphoton variant, allows functional investigations without unwanted visual
stimulation. Here, we employed a custom two-photon light-sheet microscope to
study whole-brain differences in neuronal activity between diurnal and
nocturnal periods in larval zebrafish. We describe for the first time an
activity increase in the low frequency domain of the pretectum and a
frequency-localised activity decrease of the anterior rhombencephalic turning
region during the nocturnal period. Moreover, our data confirm a nocturnal
reduction in habenular activity. Furthermore, whole-brain detrended fluctuation
analysis revealed a nocturnal decrease in the self-affinity of the neuronal
signals in parts of the dorsal thalamus and the medulla oblongata. Our data
show that whole-brain nonlinear light-sheet imaging represents a useful tool to
investigate circadian rhythm effects on neuronal activity.Comment: 18 pages, 6 figure
Determination of the binding epitope of RGD-peptidomimetics to \u3b1v\u3b23 and \u3b1IIb\u3b23 integrin-rich intact cells by NMR and computational studies
NMR experiments (transferred NOE and Saturation Transfer Difference) were used to shed light on the binding epitope of RGD peptidomimetics 1-3 with integrins \u3b1v\u3b23 and \u3b1IIb\u3b23, expressed on the membrane of ECV304 bladder cancer cells and human platelets, respectively. The NMR results were supported by docking calculations in the active sites of \u3b1v\u3b23 and \u3b1IIb\u3b23 integrin receptors and were compared to the results of competitive \u3b1v\u3b23 receptor binding assays and competitive ECV304 cell adhesion experiments. While cis RGD ligand 1 interacts mainly with the \u3b1 integrin subunit through its basic guanidine group, trans RGD ligands 2 and 3 are able to interact with both the \u3b1 and \u3b2 integrin subunits via an electrostatic clam
Morphological and molecular characterization of a Steinernema carpocapsae (Nematoda Steinernematidae) strain isolated in Veneto Region (Italy)
Benefits of glucocorticoids in non-ambulant boys/men with Duchenne muscular dystrophy: A multicentric longitudinal study using the Performance of Upper Limb test
The aim of this study was to establish the possible effect of glucocorticoid treatment on upper limb function in a cohort of 91 non-ambulant DMD boys and adults of age between 11 and 26 years.
All 91 were assessed using the Performance of Upper Limb test. Forty-eight were still on glucocorticoid after loss of ambulation, 25 stopped steroids at the time they lost ambulation and 18 were GC naive or had steroids while ambulant for less than a year.
At baseline the total scores ranged between 0 and 74 (mean 41.20). The mean total scores were 47.92 in the glucocorticoid group, 36 in those who stopped at loss of ambulation and 30.5 in the naive group (p <0.001).
The 12-month changes ranged between -20 and 4 (mean -4.4). The mean changes were -3.79 in the glucocorticoid group, -5.52 in those who stopped at loss of ambulation and -4.44 in the naive group. This was more obvious in the patients between 12 and 18 years and at shoulder and elbow levels.
Our findings suggest that continuing glucocorticoids throughout teenage years and adulthood after loss of ambulation appears to have a beneficial effect on upper limb function. (C) 2015 The Authors. Published by Elsevier B.V
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