Alumina Agglomerate Effects on Toughness-Curve Behavior of Alumina–Mullite Composites

Toughness-curve ( T -curve) behavior of composites of spherical, polycrystalline, coarse-grained, alumina agglomerates dispersed throughout a constant-toughness, fine-grained, 50–50 vol% alumina–mullite matrix has been evaluated as a function of agglomerate content for the range 15 to 45 vol%. T -curve behavior was evaluated using the indentation-strength method. Increasing alumina agglomerate content resulted in a progressive increase of large indentation load strengths with negligible change of plateau strength levels at small indentation loads. This behavior is consistent with underlying T -curves that rise to greater values and are shifted toward longer crack lengths with increasing agglomerate content, suggesting that both bridge spacing and bridge potency increase with increasing agglomerate content over the range tested. The proposed relationships between bridge spacing and agglomerate content, and bridge potency and agglomerate content, are rationalized in terms of residual stress considerations. The indentation-strength data also demonstrated that the composite containing the greatest alumina agglomerate content, 45 vol%, exhibited the greatest flaw tolerance.     

A comparative study of integral parameters for TRX and BAPL benchmark lattices of thermal reactors using the cross-section library generated from JENDL and JEF evaluated data files

The objective of this paper is to present the results of comparative study of integral parameters for TRX and BAPL benchmark lattices of thermal reactors. The nuclear data processing code NJOY'99 was deployed for the generation of the 69-group cross-section library from the basic evaluated nuclear data files JENDL-3.2 and JEF-2.2. TRX and BAPL benchmark lattices were modeled with optimized inputs, which were suggested in the final report of the WIMS Library Update Project Stage-I. The inputs were the results of a detailed parametric study of the WIMS input options and also optimized for accuracy. The integral parameters (such as k_eff, ρ²⁸, δ²⁵, δ²⁸, C¹) of five uranium-fuel thermal assemblies: TRX-1 and TRX-2 and BAPL-1, BAPL-2, and BAPL-3 were calculated with the help of WIMSD-5B code based on the generated 69-group cross-section library. The calculated results are compared with those of experiments and it is found that the obtained results between the two libraries are in good agreement with each other. Besides, the calculated integral parameters are also well consistent with the measured values, which reflect the validation of the generated 69-group cross-section library and this library thus obtained is necessary to meet up the nuclear data for neutronics calculation of TRIGA Mark-II research reactor at AERE, Savar, Dhaka, Bangladesh.     

Copper activated LiF nanorods as TLD material for high exposures of gamma-rays

Lithium fluoride (LiF) doped with proper activators is a highly sensitive phosphor commonly used for radiation dosimetry using thermoluminescence (TL) technique. Nanorods of this material activated with Cu, Mg and P as single dopants are synthesized in our laboratory and exposed to gamma-rays for their thermoluminescence (TL) properties. The induced TL glow curves of the Cu, Mg and P doped samples are similar with a single peak at 410 K. Copper doped sample is found to be the most sensitive sample with TL intensity around 65, 7 and 8 times of those of LiF:Mg, LiF:P and LiF:Mg,Cu,P, respectively, indicating that Cu is the luminescence center in the host of LiF nanorods, while Mg and P act as TL quencher particularly when used as codopants. These observations on the nanostructured form of LiF doped with these activators are entirely different from those of the widely studied LiF:Mg,Cu,P and LiF:Mg,Ti single crystals. The nanorods of LiF:Cu might be used for heavy doses measurement as they are sensitive to gamma-rays and have a linear TL response curve in a long span of exposures.     

Variation in patient dose due to differences in calibration and dosimetry protocols

For precise and accurate patient dose delivery,the dosimetry system must be calibrated properly according to the recommendations of standard dosimetry protocols such as TG-51 and TRS-398. However, the dosimetry protocol followed by a calibration laboratory is usually different from the protocols that are followed by different clinics, which may result in variations in the patient dose.Our prime objective in this study was to investigate the effect of the two protocols on dosimetry measurements.Dose measurements were performed for a Co-60 teletherapy unit and a high-energy Varian linear accelerator with 6 and 15 MV photon and 6, 9, 12, and 15 MeV electron beams, following the recommendations and procedures of the AAPM TG-51 and IAEA TRS-398 dosimetry protocols. The dosimetry systems used for this study were calibrated in a Co-60 radiation beam at the Secondary Standard Dosimetry Laboratory(SSDL) PINSTECH,Pakistan, following the IAEA TRS-398 protocol. The ratio of the measured absorbed doses to water in clinical setting,D_w(TG-51/TRS-398), was 0.999 and 0.997 for 6 and15 MV photon beams,whereas these ratios were 1.013,1.009, 1.003, and 1.000 for 6, 9, 12, and 15 MeV electron beams, respectively. This difference in the absorbed dosesto-water D_w ratio may be attributed mainly due to beam quality(K_Q) and ion recombination correction factor.     

Micro-RNA and Proteomic Profiles of Plasma-Derived Exosomes from Irradiated Mice Reveal Molecular Changes Preventing Apoptosis in Neonatal Cerebellum

Cell communication via exosomes is capable of influencing cell fate in stress situations such as exposure to ionizing radiation. In vitro and in vivo studies have shown that exosomes might play a role in out-of-target radiation effects by carrying molecular signaling mediators of radiation damage, as well as opposite protective functions resulting in resistance to radiotherapy. However, a global understanding of exosomes and their radiation-induced regulation, especially within the context of an intact mammalian organism, has been lacking. In this in vivo study, we demonstrate that, compared to sham-irradiated (SI) mice, a distinct pattern of proteins and miRNAs is found packaged into circulating plasma exosomes after whole-body and partial-body irradiation (WBI and PBI) with 2 Gy X-rays. A high number of deregulated proteins (59% of WBI and 67% of PBI) was found in the exosomes of irradiated mice. In total, 57 and 13 miRNAs were deregulated in WBI and PBI groups, respectively, suggesting that the miRNA cargo is influenced by the tissue volume exposed to radiation. In addition, five miRNAs (miR-99b-3p, miR-200a-3p, miR-200a, miR-182-5p, miR-182) were commonly overexpressed in the exosomes from the WBI and PBI groups. In this study, particular emphasis was also given to the determination of the in vivo effect of exosome transfer by intracranial injection in the highly radiosensitive neonatal cerebellum at postnatal day 3. In accordance with a major overall anti-apoptotic function of the commonly deregulated miRNAs, here, we report that exosomes from the plasma of irradiated mice, especially in the case of WBI, prevent radiation-induced apoptosis, thus holding promise for exosome-based future therapeutic applications against radiation injury.     

The Plastome Sequences of Triticum sphaerococcum (ABD) and Triticum turgidum subsp. durum (AB) Exhibit Evolutionary Changes,Structural Characterization,Comparative Analysis,Phylogenomics and Time Divergence

The mechanism and course of Triticum plastome evolution is currently unknown; thus, it remains unclear how Triticum plastomes evolved during recent polyploidization. Here, we report the complete plastomes of two polyploid wheat species, Triticum sphaerococcum (AABBDD) and Triticum turgidum subsp. durum (AABB), and compare them with 19 available and complete Triticum plastomes to create the first map of genomic structural variation. Both T. sphaerococcum and T. turgidum subsp. durum plastomes were found to have a quadripartite structure, with plastome lengths of 134,531 bp and 134,015 bp, respectively. Furthermore, diploid (AA), tetraploid (AB, AG) and hexaploid (ABD, AGA^m) Triticum species plastomes displayed a conserved gene content and commonly harbored an identical set of annotated unique genes. Overall, there was a positive correlation between the number of repeats and plastome size. In all plastomes, the number of tandem repeats was higher than the number of palindromic and forward repeats. We constructed a Triticum phylogeny based on the complete plastomes and 42 shared genes from 71 plastomes. We estimated the divergence of Hordeum vulgare from wheat around 11.04–11.9 million years ago (mya) using a well-resolved plastome tree. Similarly, Sitopsis species diverged 2.8–2.9 mya before Triticum urartu (AA) and Triticum monococcum (AA). Aegilops speltoides was shown to be the maternal donor of polyploid wheat genomes and diverged ~0.2–0.9 mya. The phylogeny and divergence time estimates presented here can act as a reference framework for future studies of Triticum evolution.     

Extremozymes from metagenome: Potential applications in food processing

The long-established use of enzymes for food processing and product formulation has resulted in an increased enzyme market compounding to 7.0% annual growth rate. Advancements in molecular biology and recognition that enzymes with specific properties have application for industrial production of infant, baby and functional foods boosted research toward sourcing the genes of microorganisms for enzymes with distinctive properties. In this regard, functional metagenomics for extremozymes has gained attention on the premise that such enzymes can catalyze specific reactions. Hence, metagenomics that can isolate functional genes of unculturable extremophilic microorganisms has expanded attention as a promising tool. Developments in this field of research in relation to food sector are reviewed.     

Multilayer Partially Homomorphic Encryption Text Steganography (MLPHE-TS): A Zero Steganography Approach

Wireless Personal Communications - This paper presents a Multilayer Partially Homomorphic Encryption Text Steganography, an invisible approach for covert communication. Existing text-based schemes...     

Investigation of charge transport mechanism in semiconducting La<Subscript>0.5</Subscript>Ca<Subscript>0.5</Subscript>Mn<Subscript>0.5</Subscript>Fe<Subscript>0.5</Subscript>O<Subscript>3</Subscript> manganite prepared by sol–gel method

Here in, we report the charge transport mechanism in semiconducting La_0.5Ca_0.5Mn_0.5Fe_0.5O₃ (LCMFO) polycrystalline material synthesized via sol–gel auto combustion route. X-ray diffraction (XRD) analysis confirmed the orthorhombic phase of the prepared material. Temperature dependent resistivity and impedance spectroscopy measurements have been carried out to probe the dielectric and electrical conduction mechanism which revealed a change of Mott variable range to the small polaronic hopping conduction mechanism around 303 K. The complex impedance and modulus spectra undoubtedly showed the contribution of both grain and grain boundary effect on the conduction properties of LCMFO. An equivalent circuit [(R_gbQ_gb) (R_gQ_g)] model has been used to address the electrical parameters associated with the different phases (grains and grain boundaries) having different relaxation times. The values of resistances of two phases obtained after fitting the equivalent circuit in the nyquist plot have been analyzed which confirmed the change of conduction mechanism around 303 K. The resultant change in conduction mechanism is also supported by the conductivity plots.     

Thermophoresis and MHD mixed convection three-dimensional flow of viscoelastic fluid with Soret and Dufour effects

Heat and mass transfer effects in three-dimensional mixed convection flow of viscoelastic fluid over a stretching surface with convective boundary conditions are investigated. The fluid is electrically conducting in the presence of constant applied magnetic field. Conservation laws of energy and concentration are based upon the Soret and Dufour effects. First order chemical reaction effects are also taken into account. By using the similarity transformations, the governing boundary layer equations are reduced into the ordinary differential equations. The transformed boundary layer equations are computed for the series solutions. Dimensionless velocity, temperature, and concentration distributions are shown graphically for different values of involved parameters. Numerical values of local Nusselt and Sherwood numbers are computed and analyzed. It is found that the behaviors of viscoelastic, mixed convection, and concentration buoyancy parameters on the Nusselt and Sherwood numbers are similar. However, the Nusselt and Sherwood numbers have qualitative opposite effects for Biot number, thermophoretic parameter, and Soret-Dufour parameters.