Low enriched uranium foil plate target for the production of fission Molybdenum-99 in Pakistan Research Reactor-1

Low enriched uranium foil (19.99% ²³⁵U) will be used as target material for the production of fission Molybdenum-99 in Pakistan Research Reactor-1 (PARR-1). LEU foil plate target proposed by University of Missouri Research Reactor (MURR) will be irradiated in PARR-1 for the production of 100Ci of Molybdenum-99 at the end of irradiation, which will be sufficient to prepare required ⁹⁹Mo/^99mTc generators at Pakistan Institute of Nuclear Science and Technology, Islamabad (PINSTECH) and its supply in the country. Neutronic and thermal hydraulic analysis for the fission Molybdenum-99 production at PARR-1 has been performed. Power levels in target foil plates and their corresponding irradiation time durations were initially determined by neutronic analysis to have the required neutron fluence. Finally, the thermal hydraulic analysis has been carried out for the proposed design of the target holder using LEU foil plates for fission Molybdenum-99 production at PARR-1. Data shows that LEU foil plate targets can be safely irradiated in PARR-1 for production of desired amount of fission Molybdenum-99.     

Diffuse and global solar spectral irradiance under cloudless skies

A simple empirical model to calculate solar spectral diffuse and global irradiance under cloudless skies is presented here. This formulation takes into account absorption of radiation by molecules such as O₃, H₂O and the uniformly-mixed gases. Attenuation by Rayleigh scattering and aerosol extinction are included. Aerosol attenuation is calculated through Ångström's turbidity parameters α and β. The diffuse radiation is assumed to be composed of three parts: (1) Rayleigh-scattered diffuse irradiance; (2) aerosol-scattered diffuse irradiance; and (3) irradiance arising out of multiple reflections between the atmosphere and the ground. The global irradiance is the sum of these three components of diffuse irradiance plus the direct irradiance. The input parameters include an extraterrestrial spectrum, zenith angle, turbidity coefficient β, wavelength exponent α, ground albedo _g, water vapor content and ozone content. The model is shown to yield very good results up to air mass two when compared to accurate theoretical calculations. No comparisons with measured spectra are presented because of a lack of accurate specifications of input parameters. Results are presented to show the effect of variation of certain of the input parameters.     

A spatially adaptive grid-refinement approach for the finite element solution of the even-parity Boltzmann transport equation

A spatially adaptive grid-refinement approach has been investigated to solve the even-parity Boltzmann transport equation. A residual based a posteriori error estimation scheme has been utilized for checking the approximate solutions for various finite element grids. The local particle balance has been considered as an error assessment criterion. To implement the adaptive approach, a computer program ADAFENT (adaptive finite elements for neutron transport) has been developed to solve the second order even-parity Boltzmann transport equation using K⁺ variational principle for slab geometry. The program has a core K⁺ module which employs Lagrange polynomials as spatial basis functions for the finite element formulation and Legendre polynomials for the directional dependence of the solution. The core module is called in by the adaptive grid generator to determine local gradients and residuals to explore the possibility of grid refinements in appropriate regions of the problem. The a posteriori error estimation scheme has been implemented in the outer grid refining iteration module. Numerical experiments indicate that local errors are large in regions where the flux gradients are large. A comparison of the spatially adaptive grid-refinement approach with that of uniform meshing approach for various benchmark cases confirms its superiority in greatly enhancing the accuracy of the solution without increasing the number of unknown coefficients. A reduction in the local errors of the order of 10² has been achieved using the new approach in some cases.     

Ferric nitrilotriacetate promotes N-diethylnitrosamine-induced renal tumorigenesis in the rat: implications for the involvement of oxidative stress

Ferric nitrilotriacetate (Fe-NTA) is a known complete renal carcinogen. In this study we show that Fe-NTA is a potent inducer of renal ornithine decarboxylase (ODC) activity and DNA synthesis and promoter of N-diethylnitrosamine (DEN)-induced renal tumorigenesis in rat. Fe-NTA induced renal ODC activity several fold as compared with saline-treated rats. Renal DNA synthesis, measured as [3H]thymidine incorporation into DNA, was increased after Fe-NTA treatment. Similar to other known tumor promoters, Fe-NTA also depleted the antioxidant armory of the tissue. It depleted glutathione (GSH) levels to approximately 55% of saline-treated controls. It also led to a dose-dependent decrease in the activities of glutathione reductase and glutathione S-transferase. Similarly, activities of catalase, glutathione peroxidase and glucose 6-phosphate dehydrogenase decreased significantly (45-65%). In contrast, gamma-glutamyl transpeptidase activity showed an increase. The maximum changes in activities of these enzymes could be observed at 12 h following Fe-NTA treatment. In addition, Fe-NTA augmented renal microsomal lipid peroxidation >150% over saline-treated controls, which was concomitant with the alterations in GSH metabolizing enzymes and depletion of the antioxidant armory. These effects were alleviated in rats which received a pretreatment with an antioxidant, BHA or BHT. Fe-NTA promoted DEN-induced renal tumorigenesis. In saline alone- and DEN alone-treated animals no tumors could be recorded, whereas in Fe-NTA alone-treated animals 17% tumor incidence was observed. However, in DEN-initiated and Fe-NTA-promoted animals tumor incidence increased to 71%. Our results show that Fe-NTA induces oxidative stress in the kidney and decreases antioxidant defenses, as indicated by the fall in GSH level and in the activities of glutathione peroxidase and catalase. Concomitantly, Fe-NTA increases ODC activity and DNA synthesis, which may be compensatory changes following oxidative injury to renal cells in addition to providing a strong stimulus for renal tumor promotion. Thus oxidative stress and impaired antioxidant defenses induced by Fe-NTA in the kidney may contribute to the observed nephrotoxicity and carcinogenicity.     

Integrated four-wavelength DFB laser array with 10 Gb/s speed and 5nm continuous tuning range

A 1.5 μm, four-wavelength DFB (distributed feedback) laser array operating at a speed of 10 Gb/s and with a continuous tuning range of 5 nm for each laser has been demonstrated. An adjacent channel electrical crosstalk penalty of 0.6 dB was measured, and the thermal tuning limitation was identified. Each laser could be modulated at a speed of 10 Gb/s with moderate electrical crosstalk penalty (~0.6 dB) from the adjacent laser. The high-speed performance was not degraded by thermal tuning up to 3.2 nm     

Critical link identification and prioritization using Bayesian theorem for dynamic channel assignment in wireless mesh networks

Wireless Networks - Wireless Mesh Networks (WMN) is a key backhaul technology used in 802.11 networks to provide ubiquitous coverage to isolated areas that require high-speed connectivity. The...     

IoT-Enabled Smart Socket

Wireless Personal Communications - Conserving energy efficiently is becoming a challenging problem around the globe, specifically in developing countries. One main reason is the lack of awareness...     

Synthesis of lanthanum titanate (La2Ti2O7) for high temperature sensor applications

Lanthanum titanate (La₂Ti₂O₇) with perovskite-like layered structure is a candidate material for high temperature sensor application due to its high curie temperature (T_c?=?1461 °C) and linearity of temperature vs. electrical resistance. La₂Ti₂O₇ (LTO) was synthesized by solid state reaction using constituent powders at 1250 °C for 2 h. The LTO samples prepared in the form of circular pellets were sintered in temperature ranges (1350 to 1400 °C for 2 h). The sintered density was found highest at 1400 °C for LTO samples (>?97.24% Th.). Moreover, the sintered LTO samples were characterized for their ferroelectric properties as well as DC electrical resistivity (ρ) measured in the temperature range of 100 to 900 °C. The electrical resistivity was decreased from 10¹³ to 10⁶ Ω cm linearly with the increase in temperature from 100 to 900 °C. Hence, LTO is a promising sensor material for high temperature applications.

     

Green and eco-friendly synthesis of cobalt-oxide nanoparticle: Characterization and photo-catalytic activity

Cobalt-oxide nanoparticles (NPs) were fabricated using Punica granatum peel extract from cobalt nitrate hexahydrate at low temperature. The synthesized cobalt-oxide NPs were characterized using X-ray powder diffraction, scanning electron microscopy, energy-dispersive X-ray, atomic force microscopy, fourier transform infrared spectroscopy and UV-visible techniques. The cobalt-oxide NPs were in highly uniform shape and size was in the size of 40–80 nm. Photo-catalytic activity (PCA) of the synthesized NPs was evaluated by degrading Remazol Brilliant Orange 3R (RBO 3R) dye and a degradation of 78.45% was achieved (dye conc. 150 mg/L) using 0.5 g cobalt-oxide NPs for 50 min irradiation time. In view of eco-benign and cost-effective nature, the present investigation revealed that P. granatum could be used for the synthesis of cobalt-oxide NPs for photo-catalytic applications.