Application of Metallic Strip Gratings for Enhancement of Electromagnetic Performance of A-sandwich Radome

Enhancement of the electromagnetic (EM) performance characteristics of A-sandwich radome wall over X-band using metallic strip gratings is presented in this work. Equivalent transmission line method in conjunction with equivalent circuit model (ECM) is used for modeling the A-sandwich radome panel with metallic strip gratings and the computation of radome performance parameters. Metallic strip grating embedded in the mid-plane of the core and those in the skin-core interface are the configurations considered in the present work. For a given thickness of metallic strip grating, its width and pitch are optimized at different angles of incidence such that the new radome wall configuration offers superior EM performance over the entire X-band as compared to the conventional A-sandwich wall. The EM analysis shows that the superior EM performance of A-sandwich with metallic strip gratings makes it suitable for the design of normal incidence and streamlined airborne radomes.Defence Science Journal, 2013, 63(5), pp.508-514, DOI:http://dx.doi.org/10.14429/dsj.63.245

Land use change suppresses precipitation

Aerosols of natural and anthropogenic origin have important climate effects through interaction with clouds, which are among the main uncertainties in climate models due to the large variability of aerosol sizes, types and 3D-distributions [1]. Experimental investigations are typically restricted to high concentrations in industrial and urban aerosol plumes although in more remote areas already slight changes in the aerosol concentrations can have a large impact. This study reports on investigations of aerosols over a remote natural laboratory, along the ~1500 km long Vermin Proof Fence, also called “State Barrier Fence”, in Western Australia. This Fence, built in the first decade of the 20th century, separates an area of >100.000 square km of homogeneous terrain, converted to arable land (west), from the natural vegetation of inner Australia, conserved as a nature preserve (east). The Fence protects the agriculture from an invasion of animals but also protects the nature preserve from farming pressure and serves as a clear cut between the two types of landscape. Recent satellite images indicate that the Fence also works as a separation line between different meteorological regions. Clouds, for example, develop more often over regions with natural vegetation [2]. Early surveys of aerosols over Australia [3] found generally clean conditions with less than 1000 ultrafine (~ 20 nm) particles / cm3 throughout most of Australia. Local enhancements were occasionally observed in coastal areas, but, for the analysis of particle distributions they were considered to be unimportant. However, higher numbers of ultrafine particles were now also found downwind of tropical eucalyptus forests on the Australian east coast

Engineering the microbiota to treat metabolic disorders

Inborn errors of metabolism (IEM) are a family of more than 500 potentially lethal congenital genetic disorders that cumulatively affect 1 in 1000 newborns. In many IEMs, pathologies manifest as a result of improper metabolism of nutrients in food. In Phenylketonuria (PKU) for example, elevated levels of phenylalanine and the accumulation of aberrant metabolic intermediates in the system lead to acute and chronic toxicities. Resultantly, many disorders within this group are generally treated through lifelong nutritional management due to the lack of alternative and pharmacological options. Longitudinal studies have indicated that even with strict adherence to a diet of synthetic supplements, patients experience chronic issues like frailty, delayed growth, and intellectual disabilities. Recently, enzyme-replacement therapies (ERT) have demonstrated promise in pre-clinical and clinical settings by providing a metabolic sink for phenylalanine in PKU. As an enhancement to traditional ERT, we are developing a novel therapeutic for IEMs associated with amino acids by expressing metabolic enzymes in lactic acid bacteria (LAB) that natively colonize the human gastrointestinal (GI) tract. Starting with an enzyme under clinical development for PKU, phenylalanine ammonia-lyase (PAL), and by promoting the intestinal adhesion and colonization characteristics, the engineered LAB will intervene before amino acid absorption occurs in the small intestines during digestion. To engineer new enzymes with activities required for treating IEMs, we have developed a novel facile selection and screening methodology. This can potentially be utilized to enhance enzymatic properties or identify mutants with altered substrate specificity, creating a spectrum of PALs that can be used to treat IEMs associated with other amino acids. Here we describe the methodology, development, and optimization of this method. To characterize and engineer microbial adhesion to intestinal mucus, we developed a novel assay that is able to capture the quantitative and mechanistic binding thermodynamics of cells to mucus. We will discuss the development of this assay and its implementation for engineering improved mucus binding. The platform technologies discussed here will be instrumental in realizing microbiota-based therapeutics as an emerging and urgently-needed treatment for IEMs that currently have inadequate or no options

Storage Life of an Aluminised HE Composition .

Most high explosive compositions are organic in nature and they tend to undergo slow decomposition during storage under different environmental conditions. The decomposition degrade the molecular stability of the explosive, thereby resulting in reduced performance and service life. The knowledge of decomposition behaviour of the explosive mass determines the storage life of the composition. Hence, change in the chemical stability, sensitivity, mechanical strength and performance are of utmost importance in the prediction of storage life of explosive/ammunitions systems. This paper presents the results on the rate of gas evolution, change in sensitivity, and thermal stability and weight loss of high explosive compositions, viz., Dentex and TNT when exposed to elevated temperature. Based on the collected data, a tentative storage life for the aluminised (Dentex) composition has been computed to be 15 years. The data has been compared with TNT, a standard explosive for assessing the storage life

Decadal analysis of the flatfish fishery of India

Decadal analysis of the flatfish fishery of Indi

Introduction to the classification of elasmobranchs

The term Elasmobranchs or chondrichthyans refers to the group of marine organisms with a skeleton made of cartilage. They include sharks, skates, rays and chimaeras. These organisms are characterised by and differ from their sister group of bony fishes in the characteristics like cartilaginous skeleton, absence of swim bladders and presence of five to seven pairs of naked gill slits that are not covered by an operculum. The chondrichthyans which are placed in Class Elasmobranchii are grouped into two main subdivisions Holocephalii (Chimaeras or ratfishes and elephant fishes) with three families and approximately 37 species inhabiting deep cool waters; and the Elasmobranchii, which is a large, diverse group (sharks, skates and rays) with representatives in all types of environments, from fresh waters to the bottom of marine trenches and from polar regions to warm tropical waters with over 950 different species

Tagging of Explosives for Detection

This paper gives the results of a study on estimation of shelf life of2,3-dimethyI2,3-dinitrobutane (DMNB)-tagged RDX and PETN expiosives by monitoring DMNB depletion by high performanceliquid chromatography and simultaneously recording the detectability of the tagged explosive composition using explosive vapoUf detector Model-97 HS. DMNB was incorporated in the explosive using methanol as solvent for DMNB and the explosive compositions were stored at 35,55 and 75 °C over a long period. Methods developed for preparing the homogeneously tagged composition with DMNB at 0.5 per cent level and for the analysis ofDMNB for ensuring homogeneity of DMNB in the composition are described. The results show no change in compatibility and sensitivity on the incorporation of DMNB in the explosive. Estimation of shelf life of DMNB in the explosive was done for a period of storage of 202-304 days at different temperatures

Cloud-resolving simulations of mercury scavenging and deposition in thunderstorms

This study examines dynamical and microphysical features of convective clouds that affect mercury (Hg) wet scavenging and concentrations in rainfall. Using idealized numerical model simulations in the Regional Atmospheric Modeling System (RAMS), we diagnose vertical transport and scavenging of soluble Hg species – gaseous oxidized mercury (GOM) and particle-bound mercury (HgP), collectively Hg(II) – in thunderstorms under typical environmental conditions found in the Northeast and Southeast United States (US). Mercury scavenging efficiencies from various initial altitudes are diagnosed for a case study of a typical strong convective storm in the Southeast US. Assuming that soluble mercury concentrations are initially vertically uniform, the model results suggest that 60% of mercury deposited to the surface in rainwater originates from above the boundary layer (> 2 km). The free troposphere could supply a larger fraction of mercury wet deposition if GOM and HgP concentrations increase with altitude. We use radiosonde observations in the Northeast and Southeast to characterize three important environmental characteristics that influence thunderstorm morphology: convective available potential energy (CAPE), vertical shear (0–6 km) of horizontal wind (SHEAR) and precipitable water (PW). The Southeast US generally has lower SHEAR and higher CAPE and PW. We then use RAMS to test how PW and SHEAR impact mercury scavenging and deposition, while keeping the initial Hg(II) concentrations fixed in all experiments. We found that the mercury concentration in rainfall is sensitive to SHEAR with the nature of sensitivity differing depending upon the PW. Since CAPE and PW cannot be perturbed independently, we test their combined influence using an ensemble of thunderstorm simulations initialized with environmental conditions for the Northeast and Southeast US. These simulations, which begin with identical Hg(II) concentrations, predict higher mercury concentrations in rainfall from thunderstorms forming in the environmental conditions over the Southeast US compared to the Northeast US. A final simulation of a stratiform rain event produces lower mercury concentrations than in thunderstorms forming in environments typical of the Southeast US. The stratiform cloud scavenges mercury from the lowest ~ 4 km of the atmosphere, while thunderstorms scavenge up to ~ 10 km