2,930 research outputs found

    Spin precession and inverted Hanle effect in a semiconductor near a finite-roughness ferromagnetic interface

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    Although the creation of spin polarization in various non-magnetic media via electrical spin injection from a ferromagnetic tunnel contact has been demonstrated, much of the basic behavior is heavily debated. It is reported here for semiconductor/Al2O3/ferromagnet tunnel structures based on Si or GaAs that local magnetostatic fields arising from interface roughness dramatically alter and even dominate the accumulation and dynamics of spins in the semiconductor. Spin precession in the inhomogeneous magnetic fields is shown to reduce the spin accumulation up to tenfold, and causes it to be inhomogeneous and non-collinear with the injector magnetization. The inverted Hanle effect serves as experimental signature. This interaction needs to be taken into account in the analysis of experimental data, particularly in extracting the spin lifetime and its variation with different parameters (temperature, doping concentration). It produces a broadening of the standard Hanle curve and thereby an apparent reduction of the spin lifetime. For heavily doped n-type Si at room temperature it is shown that the spin lifetime is larger than previously determined, and a new lower bound of 0.29 ns is obtained. The results are expected to be general and occur for spins near a magnetic interface not only in semiconductors but also in metals, organic and carbon-based materials including graphene, and in various spintronic device structures.Comment: Final version, with text restructured and appendices added (25 pages, 9 figures). To appear in Phys. Rev.

    Shoot regeneration in the genotypes of cauliflower

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    Larvicidal activity of neem oil (Azadirachta indica) formulation against mosquitoes

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    <p>Abstract</p> <p>Background</p> <p>Mosquitoes transmit serious human diseases, causing millions of deaths every year. Use of synthetic insecticides to control vector mosquitoes has caused physiological resistance and adverse environmental effects in addition to high operational cost. Insecticides of botanical origin have been reported as useful for control of mosquitoes. <it>Azadirachta indica </it>(Meliaceae) and its derived products have shown a variety of insecticidal properties. The present paper discusses the larvicidal activity of neem-based biopesticide for the control of mosquitoes.</p> <p>Methods</p> <p>Larvicidal efficacy of an emulsified concentrate of neem oil formulation (neem oil with polyoxyethylene ether, sorbitan dioleate and epichlorohydrin) developed by BMR & Company, Pune, India, was evaluated against late 3<sup>rd </sup>and early 4<sup>th </sup>instar larvae of different genera of mosquitoes. The larvae were exposed to different concentrations (0.5–5.0 ppm) of the formulation along with untreated control. Larvicidal activity of the formulation was also evaluated in field against <it>Anopheles</it>, <it>Culex</it>, and <it>Aedes </it>mosquitoes. The formulation was diluted with equal volumes of water and applied @ 140 mg <it>a.i</it>./m<sup>2 </sup>to different mosquito breeding sites with the help of pre calibrated knapsack sprayer. Larval density was determined at pre and post application of the formulation using a standard dipper.</p> <p>Results</p> <p>Median lethal concentration (LC<sub>50</sub>) of the formulation against <it>Anopheles stephensi</it>, <it>Culex quinquefasciatus </it>and <it>Aedes aegypti </it>was found to be 1.6, 1.8 and 1.7 ppm respectively. LC<sub>50 </sub>values of the formulation stored at 26°C, 40°C and 45°C for 48 hours against <it>Ae. aegypti </it>were 1.7, 1.7, 1.8 ppm while LC<sub>90 </sub>values were 3.7, 3.7 and 3.8 ppm respectively. Further no significant difference in LC<sub>50 </sub>and LC<sub>90 </sub>values of the formulation was observed against <it>Ae. aegypti </it>during 18 months storage period at room temperature. An application of the formulation at the rate of 140 mg <it>a.i</it>./m<sup>2 </sup>in different breeding sites under natural field conditions provided 98.1% reduction of <it>Anopheles </it>larvae on day 1; thereafter 100% reduction was recorded up to week 1 and more than 80% reduction up to week 3, while percent reduction against <it>Culex </it>larvae was 95.5% on day 1, and thereafter 80% reduction was achieved up to week 3. The formulation also showed 95.1% and, 99.7% reduction of <it>Aedes </it>larvae on day 1 and day 2 respectively; thereafter 100% larval control was observed up to day 7.</p> <p>Conclusion</p> <p>The neem oil formulation was found effective in controlling mosquito larvae in different breeding sites under natural field conditions. As neem trees are widely distributed in India, their formulations may prove to be an effective and eco-friendly larvicide, which could be used as an alternative for malaria control.</p

    Identification and quantification of biological active constituents of Amritarishta, a herbal formulation

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    Herbal formulations have been used by Indian and Chinese traditional systems of medication for a long time. Amritarishtais one of the herbal formulations that possess various biological activity viz., antioxidant, anticancer, analgesic, antipyretic,antidiabetic, etc. The active constituents include gallic acid, tannic acid, piperine, and quercetin, etc. Ethanolic extract of theformulation was analysed and quantified. Rf (Retardation factor), functional groups and amount of some of the major chemicalconstituents were analysed by TLC, FTIR, LC/MS, HPTLC and HPLC, respectively. LC/MS results reveal the presence ofquercetin, piperine, tannic acid and gallic acid in the formulation. With the help of HPTLC and HPLC, the quantity of 4chemical constituents in the formulation was estimated. This type of study is completely new to herbal research

    One pot synthesis of luminescent Mn doped ZnSe nanoparticles and its silica based water dispersible formulation for targeted delivery of doxorubicin 

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    The manganese doped zinc selenide nanoparticles (ZnSe:Mn NPs) were synthesized by thermolysis method using oleic acid and oleylamine as a capping agent, 1-octadecene as solvent. Coating of mesoporous silica was done on ZnSe:Mn (ZnSe:Mn@mSilica) which was further functionalized with amine functional groups by treating with (3-aminopropyl)trimethoxysilane. Further pegylation was done to achieve water dispersibility by conjugating carboxyl groups of poly(ethylene glycol) diacid with the amine groups. These pegylated NPs were subsequently treated with ethylenediamine followed by acrylic acid. Conjugation of tris-(hydroxymethyl-aminomethan) was performed by Michael-type addition reaction to afford ZnSe:Mn@mSilica-PEG-Tris-OH. These TRIS functionalized NPs exhibited broad emission ranging from 590-620 nm that is an indicative for their suitability in diagnosis and monitoring progress of cancer treatment. To explore the usefulness of increased surface area because of mesoporosity, doxorubicin was loaded on ZnSe:Mn@mSilica-PEG-Tris-OH NPs through silyl ether linkage and evaluated for cytotoxicity against WEHI-164 mouse fibrosarcoma and RAJI human hematopoietic origin cancer cell lines. A decrease in 12 % of cell viability of WEHI-164 cells while 30% decrease in RAJI cell lines (IC50 ≈ 45 nM) were observed.  This shows that our formulation has more cytotoxic in RAJI cancer cell lines than that of WEHI-164 cancer cells. These results revealed that the formulation has potential for the application in drug delivery and diagnosis in chemotherapeutics

    One pot synthesis of luminescent Mn doped ZnSe nanoparticles and their silica based water dispersible formulation for targeted delivery of doxorubicin

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    348-355The manganese doped zinc selenide nanoparticles (ZnSe:Mn NPs) have been synthesized by thermolysis method using oleic acid and oleylamine as capping agents, and 1-octadecene as solvent. Coating of mesoporous silica is done on ZnSe:Mn (ZnSe:Mn@mSilica) which is further functionalized with amine functional groups by treating with (3-aminopropyl)trimethoxysilane. Further pegylation is done to achieve water dispersibility by conjugating carboxyl groups of poly(ethylene glycol) diacid with the amine groups. These pegylated NPs are subsequently treated with ethylenediamine followed by acrylic acid. Conjugation of tris-(hydroxymethyl-aminomethane) is performed by Michael-type addition reaction to afford ZnSe:Mn@mSilica-PEG-Tris-OH. These tris functionalized NPs have exhibited broad emission ranging from 590-620 nm that is an indicative for their suitability in diagnosis and monitoring progress of cancer treatment. To explore the usefulness of increased surface area because of mesoporosity, doxorubicin is loaded on ZnSe:Mn@mSilica-PEG-Tris-OH NPs through silyl ether linkage and evaluated for cytotoxicity against WEHI-164 mouse fibrosarcoma and RAJI human hematopoietic origin cancer cell lines. A decrease in 12% of cell viability of WEHI-164 cells while 30% decrease in RAJI cell lines (IC50 ≈ 45 nM) are observed. This shows that our formulation has more cytotoxic in RAJI cancer cell lines than that of WEHI-164 cancer cells. These results reveal that the formulation has potential for the application in drug delivery and diagnosis in chemotherapeutics

    Allelic dimorphism of Plasmodium vivax gam-1 in the Indian subcontinent

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    BACKGROUND: Genetic polymorphism is an inevitable component of a complex organism especially in multistage infectious organisms such as malaria parasites. Understanding the population genetic structure of the parasites would provide valuable information for effective malaria control strategies. Recently, the development of molecular tools like PCR has made analysis of field samples possible and easier and research on Plasmodium vivax has also been strengthened. Not many reports are available on the genetic polymorphism of P. vivax from the Indian sub-continent. This study evaluates the extent of diversity in field isolates of India with respect to Pvgam-1. METHODS: A study was designed to assess the diversity of Pvgam-1 among field isolates from India, using a nested PCR assay. Field isolates were collected from different regions of the country and the observed variability was confirmed by sequencing data. RESULTS: Both Belem and Chesson type alleles were present either exclusively or in mixed form among isolates of all 10 study sites. The Belem type allele was predominant, occurring in 67% of isolates. The proportion of isolates showing the mixed form (both Belem and Chesson type alleles occurring together in the same isolate) was about 13 overall (up to 38.5% in some isolates). Sequencing of the PCR-amplified Belem and Chesson type alleles confirmed the PCR results. Among the 10 study sequences, 11 polymorphic sites and four singleton variations were observed. All the nucleotide substitutions were non-synonymous. CONCLUSION: Study shows limited diversity of Pvgam-1 marker in Indian isolates with well representation of both Belem and Chesson type alleles

    Polymorphisms of TNF-enhancer and gene for FcγRIIa correlate with the severity of falciparum malaria in the ethnically diverse Indian population

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    <p>Abstract</p> <p>Background</p> <p>Susceptibility/resistance to <it>Plasmodium falciparum </it>malaria has been correlated with polymorphisms in more than 30 human genes with most association analyses having been carried out on patients from Africa and south-east Asia. The aim of this study was to examine the possible contribution of genetic variants in the <it>TNF </it>and <it>FCGR2A </it>genes in determining severity/resistance to <it>P. falciparum </it>malaria in Indian subjects.</p> <p>Methods</p> <p>Allelic frequency distribution in populations across India was first determined by typing genetic variants of the <it>TNF </it>enhancer and the <it>FCGR2A </it>G/A SNP in 1871 individuals from 55 populations. Genotyping was carried out by DNA sequencing, single base extension (SNaPshot), and DNA mass array (Sequenom). Plasma TNF was determined by ELISA. Comparison of datasets was carried out by Kruskal-Wallis and Mann-Whitney tests. Haplotypes and LD plots were generated by PHASE and Haploview, respectively. Odds ratio (OR) for risk assessment was calculated using EpiInfo™ version 3.4.</p> <p>Results</p> <p>A novel single nucleotide polymorphism (SNP) at position -76 was identified in the <it>TNF </it>enhancer along with other reported variants. Five <it>TNF </it>enhancer SNPs and the <it>FCGR2A </it>R131H (G/A) SNP were analyzed for association with severity of <it>P. falciparum </it>malaria in a malaria-endemic and a non-endemic region of India in a case-control study with ethnically-matched controls enrolled from both regions. <it>TNF </it>-1031C and -863A alleles as well as homozygotes for the TNF enhancer haplotype CACGG (-1031T>C, -863C>A, -857C>T, -308G>A, -238G>A) correlated with enhanced plasma TNF levels in both patients and controls. Significantly higher TNF levels were observed in patients with severe malaria. Minor alleles of -1031 and -863 SNPs were associated with increased susceptibility to severe malaria. The high-affinity IgG2 binding FcγRIIa AA (131H) genotype was significantly associated with protection from disease manifestation, with stronger association observed in the malaria non-endemic region. These results represent the first genetic analysis of the two immune regulatory molecules in the context of <it>P. falciparum </it>severity/resistance in the Indian population.</p> <p>Conclusion</p> <p>Association of specific <it>TNF </it>and <it>FCGR2A </it>SNPs with cytokine levels and disease severity/resistance was indicated in patients from areas with differential disease endemicity. The data emphasizes the need for addressing the contribution of human genetic factors in malaria in the context of disease epidemiology and population genetic substructure within India.</p
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