193 research outputs found

    Analysis of Qos Aware Cloud Based Routing for Improved Security

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    The recent advances and the convergence of micro electro-mechanical systems technology, integrated circuit technologies, microprocessor hardware and Nano-technology, wireless communications, Ad-hoc networking routing protocols, distributed signal processing, and embedded systems have made the concept of Wireless Sensor Networks (WSNs). Sensor network nodes are limited with respect to energy supply, restricted computational capacity and communication bandwidth. Most of the attention, however, has been given to the routing protocols since they might differ depending on the application and network architecture. To prolong the lifetime of the sensor nodes, designing efficient routing protocols is critical. Even though sensor networks are primarily designed for monitoring and reporting events, since they are application dependent, a single routing protocol cannot be efficient for sensor networks across all applications. In this paper, we analyze the design issues of sensor networks and present a classification and comparison of routing protocols. This comparison reveals the important features that need to be taken into consideration while designing and evaluating new routing protocols for sensor networks. A reliable transmission of packet data information, with low latency and high energy-efficiency, is truly essential for wireless sensor networks, employed in delay sensitive industrial control applications. The proper selection of the routing protocol to achieve maximum efficiency is a challenging task, since latency, reliability and energy consumption are inter-related with each other. It is observed that, Quality of Service (QoS) of the network can improve by minimizing delay in packet delivery, and life time of the network, can be extend by using suitable energy efficient routing protocol

    Synthesis, characterization, biological and electrical conductivity studies of some Schiff base metal complexes

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    Metal complexes of VO(IV), Zr(IV), Th(IV) and UO2(VI) with Schiff base ligands derived from 4-nitrobenzoylhydrazide with 2-hydroxy-5-methylacetophenone (H2L1) or 2-hydroxy-5-chloroacetophenone (H2L2) have been prepared. All the complexes have been characterized on the basis of elemental analyses, magnetic susceptibility measurement, electronic and IR spectra and thermogravimetric analysis. The IR spectral data suggested that the ligands behave as dibasic tridentate moiety towards the central metal ion coordinating through phenolic oxygen, enolic oxygen and azomethine nitrogen atoms. The elemental analyses show a 1:1 metal:ligand stoichiometry for all the complexes except Th(IV) which has 1:2 stoichiometry. The thermal analysis evidenced that thermal transformations of complexes are processes according to TG curves including dehydration, thermolysis and oxidative degradation of Schiff base. The final product of decomposition is the most stable metallic oxide. The kinetic analysis of the thermogravimetric data was performed by using the Coats-Redfern method. Solid state electrical conductivity of the complexes has been measured in their compressed pellet form over a 310-413 K temperature range. All the complexes show semiconducting behavior as their conductivity increases with increasing temperature and a function of ionic size. All the complexes along with ligands were also screened for their antibacterial and antifungal activities. KEY WORDS: Aroylhydrazones, Metal complexes, Biological activity, TGA, Electrical conductivity Bull. Chem. Soc. Ethiop. 2014, 28(2), 255-264.DOI: http://dx.doi.org/10.4314/bcse.v28i2.

    Long-term performance analysis of copper indium gallium selenide thin-film photovoltaic modules

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    Current accelerated qualification tests of photovoltaic (PV) modules mostly assist in avoiding premature failures but can neither duplicate changes occurring in the field nor predict useful product lifetime. Therefore, outdoor monitoring of field-deployed thin-film PV modules was undertaken at FSEC with the goal of assessing their performance in hot and humid climate under high system-voltage operation. Significant and comparable degradation rate of -5.13 +/- 1.53% and -4.5 +/- 1.46% per year was found using PVUSA type regression analysis for the positive and negative strings, respectively of 40W glass-to-glass Cu-In-Ga-Se (CIGS) thin-film PV modules in the hot and humid climate of Florida. Using the current-voltage measurements, it was found that the performance degradation within the PV array was mainly due to a few (8% to 12%) modules that had substantially higher degradation. The remaining modules within the array continued to show reasonable performance ( \u3e 96% of the rated power after similar to four years)

    Technical Paper Session I-B - CIGSeS and CIGS2 Thin Film Solar Cells on Flexible Foils for Space Power

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    The objective of the research is to develop flexible, lightweight, radiationresistant, high-specific-power, highly efficient CuIn1-xGaxSe2-ySy (CIGSeS) and CuIn1- xGaxS2 (CIGS2) thin-film solar cells for space electric power. The near optimum bandgap, potential for higher specific power, and superior radiation resistance make this technology an ideal candidate for space electric power. The superior radiation resistance of CIGSeS thin-film solar cells relative to the conventional silicon and gallium arsenide single-crystal cells in the space radiation environment would extend mission lifetimes substantially. The conventional rigid Si and GaAs cells must be folded in an accordion style for deployment space. This can cause problems of opening up and folding of the solar array as has happened recently with the International Space Station. On the other hand, the flexible solar cells and modules can be packaged and rolled out more easily. The stainless steel and titanium foil substrate materials are capable of withstanding high temperatures required for preparing good quality CIGSeS absorber layer. They also do not sag easily and hence do not require rigidizing as is the case with plastic sheet substrates. The CIGSeS absorber film is prepared by selenization/sulfurization of DC magnetron sputter-deposited CuGa, In metallic precursors on 10 cm x 10 cm metallic foil substrate coated with molybdenum back contact layer. CdS heterojunction partner is deposited by chemical bath deposition. Transparent and conducting bilayer of intrinsic ZnO and aluminum doped ZnO:Al is deposited by RF magnetron sputtering. Cells are completed by depositing Ni/Al front contact fingers by thermal evaporation. The sputtering technique utilized in the preparation of solar cells provides an added advantage of facilitating easy scale-up of the laboratory size cells for economic large-area manufacture by the roll-to-roll process. Chemical composition, crystallographic structure and morphology of CIGSeS thin films are analyzed by energy dispersive spectroscopy, Auger electron spectroscopy, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The photovoltaic properties of completed cells are studied by measurement of current-voltage characteristics and quantum efficiency. Best efficiencies of 10.4% under AM 1.5 conditions and 8.84% under AM 0 conditions were achieved on small-area CIGS2 thin-film solar cells

    Edaxadiene: A New Bioactive Diterpene from Mycobacterium tuberculosis

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    Mycobacterium tuberculosis remains a widespread and devastating human pathogen. Presented here is the characterization of an atypical class I diterpene cyclase from M. tuberculosis that catalyzes an unusual cyclization reaction in converting the known M. tuberculosis metabolite halimadienyl diphosphate to a further cyclized novel diterpene, which we have termed edaxadiene, as it directly inhibits maturation of the phagosomal compartment in which the bacterium is taken up during infection

    Mycobacterium tuberculosis antigen 85B and ESAT-6 expressed as a recombinant fusion protein in Mycobacterium smegmatis elicits cell-mediated immune response in a murine vaccination model

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    This is the post-print version of the final paper published in Molecular Immunology. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2012 Elsevier B.V.In this study, we investigated the potential molecular and immunological differences of a recombinant fusion protein (Hybrid-1), comprising of the immunodominant antigens Ag85B and ESAT-6 from Mycobacterium tuberculosis, derived from two different expression systems, namely Mycobacterium smegmatis and Escherichia coli. The fusion protein was successfully expressed and purified from both bacterial hosts and analyzed for any host-dependent post-translational modifications that might affect the immunogenicity of the protein. We investigated the immunogenicity of Hybrid-1 expressed in the two host species in a murine vaccination model, together with a reference standard Hybrid-1 (expressed in E. coli) from the Statens Serum Institut. No evidence of any post-translation modification was found in the M. smegmatis-derived Hybrid-1 fusion protein, nor were there any significant differences in the T-cell responses obtained to the three antigens analyzed. In conclusion, the Hybrid-1 fusion protein was successfully expressed in a homologous expression system using M. smegmatis and this system is worth considering as a primary source for vaccination trials, as it provided protein of excellent yield, stability and free from lipopolysaccharide.European TB-VAC consortium and Brunel University

    Standardization of stem thickness and length for harvesting cinnamon (Cinnamomum verum J. Pres.) bark

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    An experiment was conducted during 2008–09, 2009–10 & 2010–11 at Dapoli (Maharashtra) to study the effect of stem thickness and stem length for harvesting cinnamon bark. Twelve treatment combinations viz., two genotypes; Konkan Tej (G1), ACC-11 (G2), two lengths of stem; 50 cm (L1), 100 cm (L2) and three thicknesses of stem; 1–2 cm (T1), 2–3 cm (T2), 5–6 cm (T3) were used for experimentation. There were no significant differences in bark thickness before and after drying, fresh and dry weights of quill in the genotypes studied and length of cinnamon stem selected for bark extraction. Significantly highest bark thicknesses before (1.14 mm) and after (0.82 mm) drying and fresh (111.21 g) and dry (56.64 g) weights of quill were recorded in T3 (5–6 cm thick stem) treatment. Interaction effect of genotype, length and thickness of stem selected for coppicing indicate significant differences in bark thickness before and after drying and fresh and dry weights of quill. Significantly maximum bark thickness before drying (1.74 mm) was recorded in treatment combination G2L1T3, which was at par with G1L2T3 (1.72 mm), G2L2T3 (1.71 mm) and G1L1T3 (1.67 mm). The treatment combination G1L2T3 produced significantly highest bark thickness after drying (1.33 mm) fresh (223.31 g) and dry (117.28 g) weights of quill respectively. Significantly low bark thickness before drying (1.00 mm) fresh (49.13 g) and dry (22.92 g) weights of quill were recorded in treatment combination G1L1T1, which were at par with treatment combination G2L1T1. Higher oil percentage was observed in 5–6 cm thick stem i.e. Konkan Tej (3%) and ACC-11 (2.50%) respectively. Thus for coppicing of cinnamon for extraction of bark, harvesting of 5-6 cm thick stem is recommended. &nbsp

    Standardization of stem thickness and length for harvesting cinnamon (Cinnamomum verum J. Pres.) bark

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    An experiment was conducted during 2008–09, 2009–10 & 2010–11 at Dapoli (Maharashtra) to study the effect of stem thickness and stem length for harvesting cinnamon bark. Twelve treatment combinations viz., two genotypes; Konkan Tej (G1), ACC-11 (G2), two lengths of stem; 50 cm (L1), 100 cm (L2) and three thicknesses of stem; 1–2 cm (T1), 2–3 cm (T2), 5–6 cm (T3) were used for experimentation. There were no significant differences in bark thickness before and after drying, fresh and dry weights of quill in the genotypes studied and length of cinnamon stem selected for bark extraction. Significantly highest bark thicknesses before (1.14 mm) and after (0.82 mm) drying and fresh (111.21 g) and dry (56.64 g) weights of quill were recorded in T3 (5–6 cm thick stem) treatment. Interaction effect of genotype, length and thickness of stem selected for coppicing indicate significant differences in bark thickness before and after drying and fresh and dry weights of quill. Significantly maximum bark thickness before drying (1.74 mm) was recorded in treatment combination G2L1T3, which was at par with G1L2T3 (1.72 mm), G2L2T3 (1.71 mm) and G1L1T3 (1.67 mm). The treatment combination G1L2T3 produced significantly highest bark thickness after drying (1.33 mm) fresh (223.31 g) and dry (117.28 g) weights of quill respectively. Significantly low bark thickness before drying (1.00 mm) fresh (49.13 g) and dry (22.92 g) weights of quill were recorded in treatment combination G1L1T1, which were at par with treatment combination G2L1T1. Higher oil percentage was observed in 5–6 cm thick stem i.e. Konkan Tej (3%) and ACC-11 (2.50%) respectively. Thus for coppicing of cinnamon for extraction of bark, harvesting of 5-6 cm thick stem is recommended. &nbsp

    Genetic diversity studies in kodo millet (Paspalum scrobiculatum L.)

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    The present investigation was undertaken to assess genetic diversity in seventy genotypes of kodo millet. The analysis of variance revealed the presence of significant variation among the genotypes for all 13 characters. Higher genotypic coefficient of variation (GCV), phenotypic coefficient of variation (PCV), heritability and genetic advance as per cent mean were recorded for thumb raceme length, number of productive tillers per plant, length of panicle, raceme length and grain yield per plant, indicating that simple selection could be practised for improving these traits. Seventy genotypes were grouped into seven different clusters on the basis of magnitude of D2 values by Mahalanobis D2 analysis. Cluster I had 51 genotypes followed by cluster II with 14 genotypes, while clusters III, IV, V, VI and VII were mono genotypic. The inter–cluster distance was high between clusters II and III and therefore it is suggested to use these genotypes as parents for hybridization to evolve potential segregants

    MUCOADHESIVE MICROSPHERES: AN EMINENT ROLE IN CONTROLLED DRUG DELIVERY

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    ABSTRACT Mucoadhesion is simply known as interfacial force interactions between polymeric materials and mucosal tissues. In the last two decades mucoadhesive microspheres have received considerable attention for design of novel drug delivery systems due to their ability to prolong the residence time of dosage forms and to enhance drug bioavailability. Mucoadhesive microspheres have advantages like efficient absorption and enhanced bioavailability of the drugs due to a high surface to volume ratio, a much more intimate contact with the mucus layer, controlled and sustained release of drug from dosage form and specific targeting of drugs to the absorption site. Microspheres are the carrier linked drug delivery system in which particle size is ranges from 1-1000 μm range in diameter having a core of drug and entirely outer layers of polymer as coating material. Keywords: mucoadhesion, microspheres, controlled release, residence time. INTRODUCTION Since many years several kinds of diseases that may be acute or chronic diseases can be treated by using pharmaceutical dosage form like solutions, tablets, capsules, syrups, suspension, emulsion, ointments, creams, gels which can be used as orally, topically, or intravascular route. To get the proper therapeutic effect of these pharmaceutical dosage forms they should be administered several times a day, this results consequently undesirable toxicity, fluctuation in drug level and poor efficiency or therapeutic effect. Controlled release dosage form plays eminent role to overcome the problems which are discussed above. The most important example of controlled drug delivery system is mucoadhesive microspheres which can improve the therapeutic effect of administered drug. Also bioavailability of drug is also better than other conventional system because mucoadhesive microspheres remain close to the mucous membrane and absorption tissue. Drug delivery systems (DDS) that can precisely control the release rates or target drugs to a specific body site have had an enormous impact on the healthcare system. The last two and developing novel delivery systems referred to as "mucoadhesive microspheres". [1] Physiology of mucin Mucus is produced in the eye, ear, nose and mouth. It also lines the respiratory, gastrointestinal and reproductive tracts. Its primary functions are the protection and lubrication of the underlying epithelium. Human cervical mucus, for instance, plays an integral role in both conception and contraception. It is essential to understand the structure and physical chemistry of mucus if the latter is to be exploited as a site for bioadhesive controlled drug release. Since the gastrointestinal tract is the primary site for drug absorption, the physiology of this site will be the focus of this discussion. The gelling properties which are essential to the function of mucus are the direct result of the glycoprotein present in the mucosal secretion. This glycoprotein is generally the same for various secretion sites within the body; however, specific and subtle biochemical differences have been identified. Mucus may be either constantly or intermittently secreted. The amount of mucus secreted also varies. The glycoproteinic component of mucus is a high molecular weight, highly glycosylated macromolecular system. This polydisperse natural polymer makes up between 0.5 and 5% of the fully hydrated mucus secretion. [10] The size of the intact molecule is approximately 1.8 x 10 6 , but the molecular weight of undegraded gastric mucin is as high as 4.5 x 10 7 . These macromolecules are highly expanded random coils made up of monomeric glycoproteins which for humans range from 5.5 x 1o 5 in the stomach to 2.4 x lo 5 in the small intestine. Oligosaccharide branches are attached to 63% of the protein core while the remainder of There are 34 disulphide bridges per molecule of rat goblet cell mucin, which has a molecular weight of 2 x 10 6 , while porcine intestinal mucin has 28 bridges per molecule. Human mucin has a similar density of disulphide bonds. The protein spine of the macromolecule has about 800 amino acid residues. Sugar chains are attached at about every three residues along the glycosylated regions; this results in approximately 200 side chains per molecule. This molecule is resistant to proteolytic attack in the glycosylated regions only. Thus, charge interactions may have a significant effect on the behaviour of mucus glycoproteins. The mucous gel covering the epithelium varies in thickness. In the human stomach, the mean thickness is 192 pm, while in the duodenum the thickness ranges from 10 to 400 pm In the gastrointestinal tract, mucus facilitates the passage of food and boluses through the alimentary canal. It also helps shield the epithelium from shear forces induced by peristaltic waves, and resists auto digestion. These functions are promoted by the constant secretion of mucus to replenish losses from turbulence and degradation. In response to an irritant, the amount of acidic side chains in the glycoprotein increases from 50 to 80%, making the macromolecule more negatively charged. The submucosal gland layer increases in depth and the number of goblet cells increases. The total content of non dialysable solids and pH also increase. In the GI tract, DNA and albumin thicken mucus in the diseased state. Mucosal irritation, such as exposure to alcohol or bile salts, elicits accelerated mucin release. Disease can significantly alter the nature and thickness of the mucus. This may lead to a change in the behaviour of the delivery system. Any drug delivery system which is intended to adhere to the mucus epithelium will need to adapt to a substrate which varies in depth and consistency, and may also change biochemically. Hypersecretion, which is more common than hyposecretion during disease, increases the transit rate through the GI tract, and thus reduces the residence time of a mucoadhesive device. Thus, it is essential to consider the physiology of the system when optimizing the formulation of an adhesive controlled release device. CLASSIFICATION OF MUCOADHESIVE POLYMERS Mucoadhesion is defined as interfacial force interactions between polymeric materials and mucosal tissues. In the last two decades mucoadhesive polymers have received considerable attention for design of novel drug delivery systems due to their ability to prolong the residence time of dosage forms and to enhance drug bioavailability. Various administration routes, such as ocular, nasal, gastrointestinal, vaginal and rectal, make mucoadhesive drug delivery systems attractive and flexible in dosage forms development. Mucoadhesive polymers can be classified as,- I. Traditional non-specific first-generation mucoadhesive polymers First-generation mucoadhesive polymers may be divided into three main subsets, namely: (1) Anionic polymers:-Anionic polymers are widely employed for its greatest mucoadhesive strength and low toxicity. These polymers are characterised by the presence of sulphate and carboxyl group that gives rise to net negative charge at PH values exceeding the pka of polymer. Example:-polyacrylic acid (PAA) & its weakly cross linked derivatives, Sodium carboxymethyl cellulose (NACMC) [30] (2) Cationic polymers: -The most conveniently and widely used cationic polymer is chitosan which is produced by deacetylation of chitin. Chitin is a natural polysaccharide found predominantly in the shells of crustaceans such as crabs and shrimp, the cuticles of insects, and the cell walls of fungi. It is one of the most abundant biopolymers next to cellulose Most of the naturally occurring polysaccharides, e.g. cellulose, dextran, pectin, alginic acid, agar, agarose and carrageenans, are neutral or acidic in nature, whereas chitin and chitosan are examples of highly basic polysaccharides. The unique properties include II.Novel second-generation mucoadhesive polymers: The major disadvantage in using traditional nonspecific mucoadhesive systems (first generation) is that adhesion may occur at sites other than those intended. Unlike first-generation non-specific platforms, certain second-generation polymer platforms are less susceptible to mucus turnover rates, with some species binding directly to mucosal surfaces; more accurately termed ''cytoadhesives". Furthermore as surface carbohydrate and protein composition at potential target sites vary regionally, more accurate drug delivery may be achievable. MUCOADHESION Due its relative complexity, it is likely that the process of mucoadhesion cannot be described by just one of these theories. In considering the mechanism of mucoadhesion, a whole range 'scenarios' for in-vivo mucoadhesive bond formation are possible. These include: A). Dry or partially hydrated dosage forms contacting surfaces with substantial mucus layers (typically particulates administered into the nasal cavity). B). fully hydrated dosage forms contacting surfaces with substantial mucus layers (typically particulates of many 'First Generation'mucoadhesives that have hydrated in the luminal contents on delivery to the lower gastrointestinal tract). C). Dry or partially hydrated dosage forms contacting surfaces with thin/discontinuous mucus layers (typically tablets or patches in the oral cavity or vagina). D). fully hydrated dosage forms contacting surfaces with thin/discontinuous mucus layers (typically aqueous semisolids or liquids administered into the oesophagus or eye). It is unlikely that the mucoadhesive process will be the same in each case. In the study of adhesion generally, two steps in the adhesive process have been identified Step 2 -Consolidation stage: Various physicochemical interactions occur to consolidate and strengthen the adhesive joint, leading to prolonged adhesion. THEORIES ON MUCOADHESION [4, 5] Various kinds of theories are there which can explain the mechanism of mucoadhesion they are discussed below, TYPES OF MICROSPHERES Mucoadhesive microspheres:-Adhesion can be defined as sticking of drug to the membrane by using the sticking property of the water soluble polymers. Adhesion of drug delivery device to the mucosal membrane such as buccal, ocular, rectal, nasal etc can be termed as bio -adhesion. These kinds of microspheres exhibit a prolonged residence time at the site of application and causes intimate contact with the absorption site and produces better therapeutic action. [26] Magnetic microspheres:-This kind of delivery system is very much important which localises the drug to the disease site. In this larger amount of freely circulating drug can be replaced by smaller amount of magnetically targeted drug. Magnetic carriers receive magnetic responses to a magnetic field from incorporated materials that are used for magnetic microspheres are chitosan, dextran etc. The different type are, Therapeutic magnetic microspheres: Are used to deliver chemotherapeutic agent to liver tumour. Drugs like proteins and peptides can also be targeted through this system.6 Diagnostic microspheres: Can be used for imaging liver metastases and also can be used to distinguish bowel loops from other abdominal structures by forming nano size particles supramagnetic iron oxides. Floating microspheres:-In this type of microspheres the bulk density is less than the gastric fluid and so remains buoyant in stomach without affecting gastric emptying rate. The release rate of drug is slow at the desired rate, if the system is floating on gasteric content and increases gastric residence and increases fluctuation in plasma concentration
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