1. Shiga toxin-producing Escherichia coli (STEC) strains are associated with disease outbreaks which cause a public health problem. The aim of this study was to determine the frequency of STEC ...strains, their virulence factors, phylogenetic groups and antimicrobial resistance profiles in broiler chickens.2. A total of 222 E.coli isolates were collected from the caecum of chickens intended to be slaughtered. Antibiotic susceptibility was tested against 21 antimicrobial agents and ESBL phenotype was assessed by double-disk synergy test. The presence of STEC virulence genes stx1, stx2,eaeA and ehxA was detected by PCR. The identification of STEC serogroups was realised by PCR amplification. Additive virulence genes, phylogenetic groups and integrons were examined among the STEC isolates.3. Out of 222 E.coli isolates, 72 (32%) were identified as STEC strains and the most predominant serogroups were O103, O145 and O157. Shiga toxin gene 1 (stx1) was found in 84.7% (61/72) of the STEC strains, and eae and stx2 were detected in 38.8% and 13.8%, respectively. The ESBL phenotype was documented in 48.6% (35/72) of isolates. Most of the isolates (90.3%) carried class 1 integron with the gene cassette encoding resistance to trimethoprim (dfrA) and streptomycin (aadA) in 31.9% of the isolates. Class 2 integron was identified in 36.1% of isolates.4. Broilers can be considered as a reservoir of STEC strains which have high virulence factors and integrons that might be transmitted to other chickens, environments and humans. It is important to undertake surveillance and efficient control measures in slaughterhouses and farms to control measures of STEC bacteria.1. Shiga toxin-producing Escherichia coli (STEC) strains are associated with disease outbreaks which cause a public health problem. The aim of this study was to determine the frequency of STEC strains, their virulence factors, phylogenetic groups and antimicrobial resistance profiles in broiler chickens.2. A total of 222 E.coli isolates were collected from the caecum of chickens intended to be slaughtered. Antibiotic susceptibility was tested against 21 antimicrobial agents and ESBL phenotype was assessed by double-disk synergy test. The presence of STEC virulence genes stx1, stx2,eaeA and ehxA was detected by PCR. The identification of STEC serogroups was realised by PCR amplification. Additive virulence genes, phylogenetic groups and integrons were examined among the STEC isolates.3. Out of 222 E.coli isolates, 72 (32%) were identified as STEC strains and the most predominant serogroups were O103, O145 and O157. Shiga toxin gene 1 (stx1) was found in 84.7% (61/72) of the STEC strains, and eae and stx2 were detected in 38.8% and 13.8%, respectively. The ESBL phenotype was documented in 48.6% (35/72) of isolates. Most of the isolates (90.3%) carried class 1 integron with the gene cassette encoding resistance to trimethoprim (dfrA) and streptomycin (aadA) in 31.9% of the isolates. Class 2 integron was identified in 36.1% of isolates.4. Broilers can be considered as a reservoir of STEC strains which have high virulence factors and integrons that might be transmitted to other chickens, environments and humans. It is important to undertake surveillance and efficient control measures in slaughterhouses and farms to control measures of STEC bacteria.
The possible fabrication of spintronic devices based on the Mn–Ge binary system supports extensive investigations on the magnetic properties of Mn–Ge structures. However, the global magnetic signal ...of a given sample is sometime complex due to the coexistence of several objects of unknown magnetic properties. We report the existence of ferromagnetic Mn–Ge nanoclusters (2–4nm) containing only 4–6% Mn with a Curie temperature of ∼43.5K, usually attributed to an 1.2% Mn-rich diluted magnetic semiconductuor.
We have combined numerous characterization techniques to investigate the growth of tensile-strained and n-doped Ge films on Si(001) substrates by means of solid-source molecular-beam epitaxy. The Ge ...growth was carried out using a two-step growth method: a low-temperature growth to produce strain relaxed and smooth buffer layers, followed by a high-temperature growth to get high crystalline quality Ge layers. It is shown that the Ge/Si Stranski–Krastanov growth mode can be completely suppressed when the growth is performed at substrate temperatures ranging between 260°C and 300°C. X-ray diffraction measurements indicate that the Ge films grown at temperatures of 700–770°C are tensile-strained with typical values lying in the range of 0.22–0.24%. Cyclic annealing allows further increase in the tensile strain up to 0.30%, which represents the highest value ever reported in the Ge/Si system. n-Doping of Ge was carried out using a GaP decomposition source. It is shown that heavy n-doping levels are obtained at low substrate temperatures (210–250°C). For a GaP source temperature of 725°C and a substrate temperature of 210°C, a phosphorus concentration of about 1019cm−3 can be obtained. Photoluminescence measurements reveal an intensity enhancement of about 16 times of the direct band gap emission and display a redshift of 25meV that can be attributed to band gap narrowing due to a high n-doping level. Finally, we discuss about growth strategies allowing optimizing the Ge growth/doping process for optoelectronic applications.
•We investigate the effect of tensile strain and n-doping on Ge optical properties.•We show that cyclic annealing allows getting a tensile strain up to 0.30% in Ge.•n-Doping of Ge/Si films is performed using a GaP decomposition source.•We show that n-doping is more important to enhance the photoluminescence intensity.•We present new growth strategies to develop Ge-based optoelectronic devices.
The diffusion of a half monolayer of Mn deposited by molecular beam epitaxy on a Ge(001) substrate was studied via secondary ion mass spectrometry. Mn diffused in Ge under extrinsic conditions, ...exhibiting a solubility of 0.7–0.9%. All the Mn atoms were activated, occupying Ge substitutional sites and exhibiting a negative charge, in agreement with semiconductor doping theory. The diffusion mechanism being vacancy (V)-mediated, the formation of Mn–V pairs is suggested. Mn surface desorption occurred for temperatures >600°C.
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•Physical properties of SiNWs are studied under different preparation conditions.•A degradation of the resistivity and the minority carrier lifetime in SiNWs is observed.•SiNWs ...enhance optical absorption in a solar cell, but they decrease its PV performances.•Degradation of electrical parameters is attributed to the length and the oxidation of SiNWs.
Morphological, optical and electrical properties of SiNWs are studied under different preparation conditions. Despite an ultra-low reflectivity revealing a high light-trapping effect, we obtained a degradation of the resistivity and the minority carrier lifetime in SiNWs which are ascribed to a high electron-trapping. For solar cells application, we determine a trade-off between optical and electrical properties of SiNWs. However, even with this optimization, we obtained a degradation of the electrical parameters of the solar cell when SiNWs are used as compared to the cell without SiNWs. From the obtained results in this work, we put in evidence for the first time that despite the very low reflectivity that a SiNWs film has, its use in PV is faced to four major challenges; (1): an unbalancing between the length of SiNWs and the electron diffusion length, (2): a thick SiO2 layer covering silicon wires formed during the solar cell processing (observed using dark field transmission electron microscopy), (3) a high density of dangling bonds of porous-SiNWs when the SiO2 film is etched, and, (4) a poor metal/SiNWs front contact.
•Humic and organic acids increased antibodies against viral bronchitis and Newcastle disease at d 16.•Humic acid increased antibody titers against infectious bronchitis virus at d 26.•Humic acid and ...organic acids did not affect blood biochemical constituents.•Humic acid and organic acids had no effect on feed conversion ratio and mortality.
This study was conducted to investigate the efficacy of humic acid (HA) and organic acids (OA) alone or in combination (HA-OA) on feed conversion ratio, mortality, antibody responses to infectious bronchitis virus (IBV) and Newcastle disease virus (NDV), and plasma biochemical constituents in broiler chickens. For this purpose, a total of 2,100 one-day-old mix-sexed broiler chickens were randomly allotted to 4 treatments with 5 replicate pens. Each pen holding 105 broiler chickens was used as an experimental unit. Broiler chickens of the control treatment were fed with basal diet. The 3 other treatments were: 0.1% HA, or 0.02% OA, or both 0.1% HA-0.02% OA. On d 16, 26, and 33, a sample of 30 broiler chickens from each treatment were randomly selected and blood samples were collected to determine plasma biochemical constituents and antibody responses to IBV and NDV. Antibody responses were measured by enzyme-linked immune-sorbent assays. There was no difference in the feed conversion ratio and mortality among experimental treatments. Antibody titers against NDV and IBV were increased in broiler chickens fed with HA-OA supplemented diet compared to OA treatment at d 16 (P < 0.05). Dietary supplementation of HA increased antibody titers against IBV at d 26 (P < 0.05). Dietary supplementation of HA-OA maintained anti-NDV maternal antibody titers at d 16 compared to d 1. Amount of anti- NDV antibody was increased at d 33 compared to d 16 in broiler chickens fed the diet supplemented with 0.02% OA (P < 0.05). The HA, OA, or HA-OA diets did not affect the plasma biochemical concentrations (creatinine, total protein, glucose, cholesterol, triglyceride, aspartate aminotransferase, Ca, P, Na, K, and Fe). It was concluded that the inclusion of HA in combination with OA in broiler chickens’ diets improved antibody response against NDV and IBV at d 16 without remarkable change in blood biochemical constituents. Therefore, HA-OA combination could be used as a functional feed additive in broiler chickens.
•3−4 nm sized Si-NCs are formed by annealing a-Si:H film.•SEM, TEM, FTIR and 300 K PL are used to confirm the presence of Si-NCs.•The PV conversion efficiency is enhanced by 36.3 %.•The short circuit ...current density is enhanced by 30.3 %.•The thermalisation effect in silicon solar cells is reduced.
Despite their interesting efficiencies and stabilities, first and second generations solar cells suffer from thermalisation that reduces the photovoltaic performances under operating conditions. In third generation solar cells scenarios, the use of Nano-Crystals (NCs) with suitable dimensions can be a realistic alternative to overcome the thermalisation phenomena. Due to the quantum confinement, silicon NCs with sizes less than 5 nm could be an efficient tool for down conversion and/or carriers multiplication by converting high energy photons (UV) to visible ones via photoluminescence (PL).
This paper gives interesting results by stacking silicon NCs in Silicon NanoWires (SiNWs) which are elaborated at the top of a silicon pn homo-junction. NCs are obtained by annealing an amorphous silicon layer deposited on the SiNWs layer. Room temperature photoluminescence measurement at an incident wavelength of 250 nm shows three PL peaks at 378 nm, 480 nm and 587 nm. The latter is attributed to silicon NCs. Furthermore, the photovoltaic efficiency is considerably enhanced by an amount of 36.3 % from 6.9 % to 9.4 % which is due to an important enhancement of 30.3 % in the absolute value of the short-circuit current density values in presence of Si-NCs. We discuss these results with regard to the physical characterizations performed on fabricated samples.
Deposition of 0.5 monolayer of Mn by molecular beam epitaxy on the surface of a Ge(001) substrate, and annealing, allowed the fabrication of a cluster-free Ge(Mn) diluted solution. Electronic spin ...resonance (ESR) was used to study the magnetic properties of this solution. These measurements, combined with secondary ion mass spectrometry, atomic force microscopy, and Auger electron spectroscopy, show that the detected ferromagnetic signal is due to surface islands, while Mn atoms on Ge substitutional sites gives no detectable ESR signal.
•A diluted Ge(Mn) solid solution was prepared without Mn–Si clusters.•The magnetic property of this solution was studied by electronic spin resonance.•A ferromagnetic signal was measured due to Mn–Ge islands on the sample surface.•Mn atoms located on the Ge crystal substitutional sites are not ferromagnetic.
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