Femtosecond Pulsed Laser Deposition of Indium on Si (100)

Deposition of indium on Si(100) substrates is performed under ultrahigh vacuum with an amplified Ti:sapphire laser (130 fs) at wavelength of 800 nm and laser fluence of 0.5 J/cm2. Indium films are grown at room temperature and at higher substrate temperatures with a deposition rate of similar to 0.05 ML/pulse. Reflection high-energy electron diffraction (RHEED) is used during the deposition to study the growth dynamics and the surface structure of the grown films. The morphology of the grown films is examined by ex situ atomic force microscopy (AFM). At room temperature indium is found to form epitaxial two-dimensional layers on the Si(100)-(2x1) surface followed by three-dimensional islands. AFM images show different indium island morphologies such as hexagonal and elongated shapes. At substrate temperatures of 400-420 °C, RHEED intensity oscillations are observed during film growth indicating that the indium film grows in the layer-by-layer mode

Activation Energy of Surface Diffusion and Terrace Width Dynamics During the Growth of in (4×3) on Si (100) - (2×1) by Femtosecond Pulsed Laser Deposition

The nucleation and growth of indium on a vicinal Si (100) - (2×1) surface at high temperature by femtosecond pulsed laser deposition was investigated by in situ reflection high energy electron diffraction (RHEED). RHEED intensity relaxation was observed for the first ∼2 ML during the growth of In (4×3) by step flow. From the temperature dependence of the rate of relaxation, an activation energy of 1.4±0.2 eV of surface diffusion was determined. The results indicate that indium small clusters diffused to terrace step edges with a diffusion frequency constant of (1.0±0.1) × 1011 s-1. The RHEED specular beam split peak spacing, which is characteristic of a vicinal surface, was analyzed with the growth temperature to obtain the average terrace width. Gradual reduction in the terrace width during growth of In (4×3) was observed with In coverage and is attributed to the detachment of In atoms from terrace edges. At a substrate temperature of 405 °C, the average terrace width decreased from 61±10 Å, which corresponds to the vicinal Si(100) surface, to an equilibrium value of 45±7 Å after deposition of ∼23 ML. Further In coverage showed a transition of the RHEED pattern from (4×3) to (1×1) and the growth of rounded In islands (average height of ∼1 nm and width of ∼25 nm), as examined by ex situ atomic force microscopy. © 2008 American Institute of Physics. [DOI: 10.1063/1.2909923

Atomic Hydrogen Cleaning of InP(100): Electron Yield and Surface Morphology of Negative Electron Affinity Activated Surfaces

Atomic hydrogen cleaning of the InP(100) surface has been investigated using quantitative reflection high-energy electron diffraction. The quantum efficiency of the surface when activated to negative electron affinity was correlated with surface morphology. The electron diffraction patterns showed that hydrogen cleaning is effective in removing surface contaminants, leaving a clean, ordered, and (2×4)-reconstructed surface. After activation to negative electron affinity, a quantum efficiency of ∼6% was produced in response to photoactivation at 632 nm. Secondary electron emission from the hydrogen-cleaned InP(100)-(2×4) surface was measured and correlated to the quantum efficiency. The morphology of the vicinal InP(100) surface was investigated using electron diffraction. The average terrace width and adatom-vacancy density were measured from the (00) specular beam at the out-of-phase condition. With hydrogen cleaning time, there was some reduction in the average terrace width. The surface quality was improved with hydrogen cleaning, as indicated by the increased (00) spot intensity-to-background ratio at the out-of-phase condition, and improved quantum efficiency after activation to negative electron affinity. © 2002 American Institute of Physics. [DOI: 10.1063/1.1429796

Identification, phylogenetic analysis and expression profile of an anionic insect defensin gene, with antibacterial activity, from bacterial-challenged cotton leafworm, Spodoptera littoralis

<p>Abstract</p> <p>Background</p> <p>Defensins are a well known family of cationic antibacterial peptides (AMPs) isolated from fungi, plants, insects, mussels, birds, and various mammals. They are predominantly active against gram (+) bacteria, and a few of them are also active against gram (-) bacteria and fungi. All insect defensins belonging to the invertebrate class have a consensus motif, C-X_5-16-C-X₃-C-X_9-10-C-X_4-7-CX₁-C. Only seven AMPs have already been found in different lepidopteran species. No report was published on the isolation of defensin from the Egyptian cotton leafworm, <it>Spodoptera littoralis</it>.</p> <p>Results</p> <p>An anionic defensin, termed <it>Spli</it>Def, was isolated from the haemolymph of the cotton leafworm, <it>S. littoralis</it>, after bacterial challenge using differential display technique. Based on sequence analyses of the data, specific primers for full length and mature peptide of defensin were designed and successfully amplified 471 and 150 bp amplicons. The integration of the results revealed that the 471 bp-PCR product has one open reading frame (<it>orf</it>) of 303 bp long, including both start codon (AUG) and stop codon (UGA). The deduced peptide consists of a 23-residues signal peptide, a 27-residues propeptide and a 50-residues mature peptide with the conserved six-cysteine motif of insect defensins. Both haemolymph and expressed protein exhibited antibacterial activities comparable to positive control. The RT-qPCR indicated that it was more than 41-folds up-regulated at 48 h p.i.</p> <p>Conclusion</p> <p>Our results highlight an important immune role of the defensin gene in <it>Spodoptera littoralis </it>by cooperating with other AMPs to control bacterial infection.</p

Atomic Hydrogen Cleaning of InP(100) for Preparation of a Negative Electron Affinity Photocathode

Atomic hydrogen cleaning is used to clean InP(100) negative electron affinity photocathodes. Reflection high-energy electron diffraction patterns of reconstructed, phosphorus-stabilized, InP(100) surfaces are obtained after cleaning at ∼400 °C. These surfaces produce high quantum efficiency photocathodes (∼8.5%), in response to 632.8 nm light. Without atomic hydrogen cleaning, activation of InP to negative electron affinity requires heating to ∼530 °C. At this high temperature, phosphorus evaporates preferentially and a rough surface is obtained. These surfaces produce low quantum efficiency photocathodes (∼0.1%). The use of reflection high-energy electron diffraction to measure the thickness of the deposited cesium layer during activation by correlating diffraction intensity with photoemission is demonstrated. © 1998 American Institute of Physics

Preventive effect of the flavonoid, quercetin, on hepatic cancer in rats via oxidant/antioxidant activity: molecular and histological evidences

<p>Abstract</p> <p>Background</p> <p>The incidence of hepatocellular carcinoma is increasing in many countries. The estimated number of new cases annually is over 500,000, and the yearly incidence comprises between 2.5 and 7% of patients with liver cirrhosis. The incidence varies between different geographic areas, being higher in developing areas; males are predominantly affected, with a 2:3 male/female ratio</p> <p>Methods</p> <p>Experiments were designed to examine the effect of <it>N</it>-Nitrosodiethylamine (NDEA) as cancer-inducer compound and to confirm the preventive effect of the flavonoid quercetin on hepatocellular carcinoma in rats. Briefly, thirty six male albino rats of Wistar strain were divided into 3 groups: the 1^stgroup was administered NDEA alone (NDEA-treated), the 2^ndgroup was treated simultaneously with NDEA and quercetin (NDEA+Q) and the 3^rdgroup was used as control (CON). Randomly amplified polymorphic DNA polymerase chain reaction (RAPD-PCR) as well as <it>p53</it>-specifi PCR assays were employed to determine genomic difference between treated, and control animals. Histological confirmation as well as oxidant/antioxidant status of the liver tissue was done.</p> <p>Results</p> <p>RAPD analysis of liver samples generated 8 monomorphic bands and 22 polymorphic bands in a total of 30-banded RAPD patterns. Cluster analysis and statistical analyses of RAPD data resulted in grouping control and NDEA+Q samples in the same group with 80% similarity cut-off value. NDEA-treated samples were clustered in a separate group. Specific PCR assay for polymorphism of <it>P</it>⁵³gene revealed a uniform pattern of allele separation in both control and NDEA+Q samples. Quercetin anticancer effect was exhibited in significant decrease of oxidative stress and significant decrease of antioxidant activity. Histopathological studies showed normal liver histology of the NDEA+Q samples. Meanwhile, several cancer-induced features were clearly observable in NDEA-treated samples.</p> <p>Conclusion</p> <p>This paper demonstrated that preventive effect of quercetin on hepatocarcinoma in rats by RAPD-PCR, tracing the effect on <it>p53 </it>gene and by histopathological evidence. Hereby, it was proved that quercetin exerted its preventive effect via decreased oxidative stress and decreased antioxidant activity.</p

Chicory abrogates oxidative stress, inflammation and caspase-dependent apoptosis in acute hepatic injury model induced by acetaminophen in rats

In this study the protective effect of chicory leaves hydroalcoholic extract (CIE) against acute liver injury induced by a single dose of acetaminophen (700 mg/kg, i.p.) was investigated in rats. The CIE and silymarin treatment (standard reference) were given in a dose of (100 mg/kg, p.o.) for 3 days before and at 1 and 12 h following acetaminophen administration. Treatment with CIE significantly reduced the levels of serum ALT, AST, alkaline phosphatase, bilirubin, total cholesterol, triglycerides, urea, creatinine, TNF-α and hepatic contents of malondialdehyde (MDA), nitric oxide, caspase-3 and hydroxyproline, with significant increases in serum total protein, albumin, HDL- cholesterol and hepatic activities of reduced glutathione (GSH), superoxide dismutase (SOD) and catalase (CAT) as compared with the acetaminophen group. The histopathological alterations mediated by acetaminophen were ameliorated by CIE. It was concluded that CIE protects rat liver against acetaminophen hepatotoxicity, most probably through abrogation of oxidative stress, inflammation and caspase-3 dependent apoptosis

Root extracts of Saussurea costus as prospective detoxifying food additive against sodium nitrite toxicity in male rats

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGThe goal of this study was to investigate the effects of three different extracts of Saussurea costus roots (ethanol, methanol, and water) as a food additive in alleviating the harmful effect of sodium nitrite in rat meals. Thirty-five adult male rats were divided into five groups as follows: control, sodium nitrite (NaNO2; 75 mg/kg BW, single oral dose), S. costus 70% ethanol, 70% methanol, and aqueous extracts (300 mg/kg BW), respectively for four weeks followed by a single dose of NaNO2 24h before decapitation. Results showed that the 70% ethanol extract of S. costus has a higher concentration of total phenolic content, total flavonoids, and antioxidant effect than the 70% methanol and water extracts. Rats pretreated with S. costus extracts reduced the harmful effects induced by NaNO2 and improved the hematological parameters, liver, and kidney function biomarkers as well as lipid profile as compared to the NaNO2 group. Furthermore, S. costus improved the histopathological alterations in the liver and kidney induced by NaNO2 and improved meat sensory evaluation. Conclusively, the 70% ethanol extract of S. costus roots is the most effective extract as an antioxidant against the toxicity of sodium nitrite in male rats and might be used safely as a natural additive in the food industry

Interference Effects of Salinity on Growth and Some Metabolic Activities of Two Chlorella Species

The unicellular green algae Chlorella minutissima and Chlorella oocystoides were isolated from different regions in Upper Egypt. The effect of different concentrations of salinity (100, 250 and 500 mM NaCl) on growth parameters (optical density, dry weight, and total photosynthetic pigments) and primary products (total carbohydrates, total proteins, and lipids contents) were measured after 7 days. The growth parameters, and the primary products of Chlorella minutissima and Chlorella oocystoides were significantly increased at lower and moderate concentrations (100 and 250 mM NaCl). Under higher concentration 500 mM of NaCl, the growth parameters, and the primary products (total carbohydrates, and total proteins) were significantly decreased. However, the lipid contents were markedly increased