4,212 research outputs found
Shape Transition of Nanostructures created on Si(100) surfaces after MeV Implantation
We have studied the modification in the Surface morphology of the Si(100)
surfaces after 1.5 MeV Sb implantation. Scanning Probe Microscopy has been
utilized to investigate the ion implanted surfaces. We observe the formation of
nano-sized defect features on the Si surfaces for various fluences. These
nanostructures are elliptical in shape and inflate in sizefor higher fluences.
Furthermore, these nanostructures undergo a shape transition from an elliptical
shape to a circular-like at a high fluence. We will also discuss the
modification in surface roughness as a function of Sb fluence.Comment: 9 pages, 4 figure
Characterisation of production, marketing and consumption patterns of farmed tilapia in the Nile Delta of Egypt
AbstractEgypt has one of the world’s largest aquaculture sectors which makes a significant contribution to income, employment creation and food security. However, there are very limited data available on the farmed tilapia value chain. The aim of this study therefore was to characterise production, marketing and consumption patterns of farmed tilapia in the Nile Delta of Egypt. A cross sectional study was conducted to collect data from tilapia producers (100), transporters (32), retailers (100), fish fry shops (20) and households (300) in three case study communities (fish producing, peri-urban and rural community). We conducted structured questionnaire interviews and participatory assessments for producers and consumers. Focus group discussions with mothers were also held to collect data for the availability, sources and consumption patterns of tilapia.Results showed that, more than half of producers were small scale, having a farm size of 10feddan or less (1feddan=4200m2). The main water supply for almost all farms was agricultural drain water, a potential source of contamination with chemical and biological hazards. The main production constraints were reported to be feed prices, water quality and availability, land rent, fuel and energy sources and environmental conditions. The farmed tilapia value chain was short with some value added in the form of marketing fresh and live fish as well as selling tilapia in fried or grilled form. The majority of produced tilapia was transported to retail sale and sold to consumers as fresh, while only a small proportion was processed by cleaning, grilling or frying. A lack of hygiene during transportation and marketing of farmed tilapia was found that could be potential sources for post-harvesting contamination. The availability and frequency of tilapia consumption were higher in the community in the production areas than in other communities. In non-producing areas, tilapia may be available in the market once a week during the village market day. Potential areas for further research in order to improve safety, quality and production of farmed tilapia were identified
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Discrete wavelet transform based freezing of gait detection in Parkinson's disease
Wearable on body sensors have been employed in many applications including ambulatory monitoring and pervasive computing systems. In this work, a wearable assistant has been created for people suffering from Parkinson’s disease (PD), specifically with the Freezing of Gait (FoG) symptom. Wearable accelerometers were placed on the person’s body and used for movement measure. When FoG is detected, a rhythmic audio signal was given from the wearable assistant to motivate the wearer to continue walking. Long term monitoring results in collecting huge amounts of complex raw data; therefore, data analysis becomes impractical or infeasible resulting in the need for data reduction. In the present study, Discrete Wavelet Transform (DWT) has been used to extract the main features inherent in the key movement indicators for FoG detection. The discrimination capacities of these features were assessed using, i) Support Vector Machine (SVM) using a linear kernel function, and ii) Artificial Neural Network (ANN) with a two-layer feed-forward with hidden layer of 20 neurons that trained with conjugate gradient back- propagation. Using these two different machine learning techniques, we were capable of detecting FoG with an accuracy of 87.50% and 93.8%, respectively. Additionally, the comparison between the extracted features from DWT coefficients with those using Fast Fourier Transform (FFT) established accuracies of 93.8% and 81.3%, respectively. Finally, the discriminative features extracted from DWT yield to a robust multidimensional classification model compared to models in the literature based on a single feature. The work presented paves the way for reliable, real-time wearable sensors to aid people with PD
The structure of the infinite models in integer programming
The infinite models in integer programming can be described as the convex
hull of some points or as the intersection of halfspaces derived from valid
functions. In this paper we study the relationships between these two
descriptions. Our results have implications for corner polyhedra. One
consequence is that nonnegative, continuous valid functions suffice to describe
corner polyhedra (with or without rational data)
Urban–rural differences of gynaecological malignancies in Egypt (1999–2002)
Please cite this paper as: Dey S, Hablas A, Seifeldin I, Ismail K, Ramadan M, El-Hamzawy H, Wilson M, Banerjee M, Boffetta P, Harford J, Merajver S, Soliman A. Urban–rural differences of gynaecological malignancies in Egypt (1999–2002). BJOG 2010;117:348–355.In previous studies, we have shown a three to four times higher urban incidence of breast cancer and estrogen receptor-positive breast cancers in the Gharbiah Province of Egypt. We investigated the urban–rural incidence differences of gynaecologic malignancies (uterine, ovarian and cervical cancers) to explore if they show the same trend that we found for breast cancer.Cancer registry-based incidence comparison.Gharbiah population-based cancer registry (GPCR), Tanta, Egypt.All patients with uterine, ovarian and cervical cancer in GPCR from 1999 to 2002.We calculated uterine, ovarian and cervical cancer incidence from 1999 to 2002. For each of the three cancers, we calculated the overall and age-specific rates for the province as a whole, and by urban–rural status, as well as for the eight districts of the province.Incidence of all three cancer sites was higher in urban than in rural areas. Uterine cancer showed the highest urban–rural incidence rate ratio (IRR = 6.07, 95% CI = 4.17, 8.85). Uterine cancer also showed the highest urban incidence in the oldest age group (70+ age category, IRR = 14.39, 95% CI = 4.24, 48.87) and in developed districts (Tanta, IRR = 4.14, 95% CI = 0.41, 42.04). Incidence rates by groups of cancer sites showed an increasing gradient of urban incidence for cancers related to hormonal aetiology, mainly of the breast and uterus (IRR = 4.96, 95% CI = 2.86, 8.61).The higher urban incidence of uterine cancer, coupled with our previous findings of higher incidence of breast cancer and estrogen receptor positive breast cancer in urban areas in this region, may be suggestive of possible higher exposure to environmental estrogenic compounds, such as xenoestrogens, in urban areas.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/78726/1/j.1471-0528.2009.02447.x.pd
On an Analytical Framework for Voids: Their abundances, density profiles and local mass functions
We present a general analytical procedure for computing the number density of
voids with radius above a given value within the context of gravitational
formation of the large scale structure of the universe out of Gaussian initial
conditions. To this end we develop an accurate (under generally satisfied
conditions) extension of unconditional mass function to constrained
environments, which allowes us both to obtain the number density of collapsed
objects of certain mass at any distance from the center of the void, and to
derive the number density of voids defined by those collapsed objects. We have
made detailed calculations for the spherically averaged mass density and halo
number density profiles for individual voids. We also present a formal
expression for the number density of voids defined by galaxies of a given type
and luminosity. This expression contains the probability for a collapsed object
of certain mass to host a galaxy of that type and luminosity as a function of
the environmental density. We propose a procedure to infer this function, which
may provide useful clues as to the galaxy formation process, from the observed
void densities.Comment: 14 pages, 7 figures, MNRAS in pres
The formation of voids in a universe with cold dark matter and a cosmological constant
A spherical Lagrangian hydrodynamical code has been written to study the
formation of cosmological structures in the early Universe. In this code we
take into account the presence of collisionless non-baryonic cold dark matter
(CDM), the cosmological constant and a series of physical processes present
during and after the recombination era, such as photon drag resulting from the
cosmic background radiation and hydrogen molecular production. We follow the
evolution of the structure since the recombination era until the present epoch.
As an application of this code we study the formation of voids starting from
negative density perturbations which evolved during and after the recombination
era. We analyse a set of COBE-normalized models, using different spectra to see
their influence on the formation of voids. Our results show that large voids
with diameters ranging from 10h^{-1} Mpc up to 50h^{-1} Mpc can be formed in a
universe model dominated by the cosmological constant (\Omega_\Lambda ~ 0.8).
This particular scenario is capable of forming large and deep empty regions
(with density contrasts \delta < -0.6). Our results also show that the physical
processes acting on the baryonic matter produce a transition region where the
radius of the dark matter component is greater than the baryonic void radius.
The thickness of this transition region ranges from about tens of kiloparsecs
up to a few megaparsecs, depending on the spectrum considered. Putative objects
formed near voids and within the transition region would have a different
amount of baryonic/dark matter when compared with \Omega_b/\Omega_d. If one
were to use these galaxies to determine, by dynamical effects or other
techniques, the quantity of dark matter present in the Universe, the result
obtained would be only local and not representative of the Universe as a whole.Comment: MNRAS (in press); 9 pages, no figure
Formation of voids in the Universe within the Lemaitre-Tolman model
We develop models of void formation starting from a small initial fluctuation
at recombination and growing to a realistic present day density profile in
agreement with observations of voids. The model construction is an extension of
previously developed algorithms for finding a Lemaitre-Tolman metric that
evolves between two profiles of either density or velocity specified at two
times. Of the 4 profiles of concern -- those of density and velocity at
recombination and at the present day -- two can be specified and the other two
follow from the derived model. We find that, in order to reproduce the
present-day void density profiles, the initial velocity profile is more
important than the initial density profile. Extrapolation of current CMB
observations to the scales relevant to proto-voids is very uncertain. Even so,
we find that it is very difficult to make both the initial density and velocity
fluctuation amplitudes small enough, and still obtain a realistic void by
today.Comment: MN2e LaTeX style file, 17 pages, 16 figures, 22 figure files;
replecement has minor changes in reference
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Regulation of expression of the rat orthologue of mouse double minute 2 (MDM2) by H2O2-induced oxidative stress in neonatal rat cardiac myocytes.
The Mdm2 ubiquitin ligase is an important regulator of p53 abundance and p53-dependent apoptosis. Mdm2 expression is frequently regulated by a p53 Mdm2 autoregulatory loop whereby p53 stimulates Mdm2 expression and hence its own degradation. Although extensively studied in cell lines, relatively little is known about Mdm2 expression in heart where oxidative stress (exacerbated during ischemia-reperfusion) is an important pro-apoptotic stimulus. We demonstrate that Mdm2 transcript and protein expression are induced by oxidative stress (0.2 mm H(2)O(2)) in neonatal rat cardiac myocytes. In other cells, constitutive Mdm2 expression is regulated by the P1 promoter (5' to exon 1), with inducible expression regulated by the P2 promoter (in intron 1). In myocytes, H(2)O(2) increased Mdm2 expression from the P2 promoter, which contains two p53-response elements (REs), one AP-1 RE, and two Ets REs. H(2)O(2) did not detectably increase expression of p53 mRNA or protein but did increase expression of several AP-1 transcription factors. H(2)O(2) increased binding of AP-1 proteins (c-Jun, JunB, JunD, c-Fos, FosB, and Fra-1) to an Mdm2 AP-1 oligodeoxynucleotide probe, and chromatin immunoprecipitation assays showed it increased binding of c-Jun or JunB to the P2 AP-1 RE. Finally, antisense oligonucleotide-mediated reduction of H(2)O(2)-induced Mdm2 expression increased caspase 3 activation. Thus, increased Mdm2 expression is associated with transactivation at the P2 AP-1 RE (rather than the p53 or Ets REs), and Mdm2 induction potentially represents a cardioprotective response to oxidative stress
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