Lattice effect on the magnetic and magneto-transport properties of (La1/3Sm2/3)0.67Ba0.33−xSrxMnO3 (x = 0.0, 0.1, 0.2 and 0.33) compounds

The effect of substituting Sr for Ba on the magneto-transport and magnetic properties of (La_1/3Sm_2/3)_0.67Ba_0.33MnO₃ system, has been investigated. The samples, (La_1/3Sm_2/3)_0.67Ba_0.33−xSr_xMnO₃ (x = 0.0, 0.1, 0.2 and 0.33), synthesized by citrate gel route, crystallize in an orthorhombic structure (space group Pnma, no. 62). The unit cell volume decreases while the metal-insulator transition temperature (T_MI) increases with increasing Sr content. The localization of charge carriers occurs at low temperatures and becomes more pronounced with decreasing Sr content which leads to an enhancement of resistivity. This could be understood by the variation of MnOMn bond-distance and angle. Reappearance of semiconducting behavior (dρ/dT < 0) is observed only in samples with x = 0 and x = 0.1 below certain temperature (T < T_MI). These samples exhibit thermal irreversibility behavior for a field-cooled (FC) and zero-field-cooled (ZFC) magnetization data in a magnetic field of 100 Oe. This is ascribed to the competition between the superexchange and double exchange interactions. The change in physical properties has been correlated to chemical parameters such as ionic radii, tolerance factor, electronegativity and variation in MnOMn angle.     

Influence of SiC particle size on the structure and tribological properties of Ni-Co composites

Ni-Co composites incorporated with SiC particles of nano and micron size were produced by electrodeposition. The effect of cobalt content on the particle incorporation, microhardness, surface morphology and tribological behaviour has been studied. The Ni rich Ni-Co composite exhibited enhanced microhardness values. However, no appreciable increase in the microhardness was observed for Co rich Ni-Co-SiC composites. Scanning electron microscope, energy dispersive X-ray analysis and X-ray diffraction studies were used to characterize the coatings. A change in surface morphology, phase structure and SiC incorporation was observed with increase in cobalt content. Pin-on-disc tribo tester was employed to study the wear and friction behaviour of the Ni-Co-SiC coatings. The tribo studies indicated that the wear volume loss was less for micron SiC reinforced Ni-Co composites compared to nano SiC reinforced composites. However, no appreciable variation in the coefficient of friction was observed for both Ni rich and Co rich Ni-Co-SiC composites.     

Application of Azido Esters as Energetic Plasticizers for LOVA Propellant Formulations

The study of a cyclotrimethylene trinitramine‐based low vulnerable ammunition (LOVA) propellant having cellulose acetate (CA) and nitrocellulose (NC) combinations as binders is described herein. Two propellant compositions ( 1 and 2 ) were prepared by replacing the non energetic plasticizer triacetin (TA) with the novel tetraazido ester plasticizers tetraazido malonate and tetraazido glutarate, respectively, and their ballistic, mechanical, and thermal properties were studied. Both compositions 1 and 2 showed thermal stability up to 200 °C with a heat release of 1752.81 and 1774.34 J g⁻¹, respectively. Both compositions have high impact insensitivity (h₅₀: 39 cm), friction insensitivity up to 36 kg, and an ignition temperature greater than 250 °C. The flame temperatures of 1 and 2 are 3164 and 3243 K with linear burn rate coefficients of 0.117 and 0.122 cm s⁻¹ MPa⁻¹, respectively. Similar percentage elongations at three different temperatures (−20 °C, +27 °C, and +55 °C) conditions were recorded for both compositions.     

Thermal decomposition of GAP and GAP-based double-base propellants

This paper reports the thermal decomposition pattern of GAP and GAP-containing double-base (DB) compositions. Dynamic and isothermal TGA reveal a two-stage decomposition process for GAP. At temperatures below 200°C reactant-product interface diffusion, while at higher temperatures nucleation-based diffusion processes appear to be operative. Inclusion of GAP resulted in a drop in temperature for the onset of freeradical reaction.Explosives Research and Development Laboratory, Pune 411 008, India. Department of Chemistry, University of Poona, India. Published in Fizika Goreniya i Vzryva, Vol. 29, No. 3, pp. 27–31, May–June, 1993.     

Influence of SiC, Si3N4 and Al2O3 particles on the structure and properties of electrodeposited Ni

The structure and properties of electrodeposited nickel composites reinforced with inert particles like SiC, Si₃N₄ and Al₂O₃ were compared. A comparison was made with respect to structure, morphology, microhardness and tribological behaviour. The coatings were characterized with optical microscopy, Scanning electron microscopy (SEM), Energy dispersive X-ray analysis (EDX) and X-ray diffraction (XRD) technique. The cross-sectional microscopy studies revealed that the particles were uniformly distributed in all the composites. However, a difference in the surface morphology was revealed from SEM studies. The microhardness studies revealed that Si₃N₄ reinforced composite showed higher hardness compared to SiC and Al₂O₃ composite. This was attributed to the reduced crystallite size of Ni — 12 nm compared to 16 nm (SiC) and 23 nm (Al₂O₃) in the composite coating. The tribological performance of these coatings studied using a Pin-on-disk wear tester, revealed that Si₃N₄ reinforced composite exhibited better wear resistance compared to SiC and Al₂O₃ composites. However, no significant variation in the coefficient of friction was observed for all the three composites.     

Metallic nanoparticles for cancer immunotherapy

Cancer immunotherapy, or the utilization of the body’s immune system to attack tumor cells, has gained prominence over the past few decades as a viable cancer treatment strategy. Recently approved immunotherapeutics have conferred remission upon patients with previously bleak outcomes and have expanded the number of tools available to treat cancer. Nanoparticles – including polymeric, liposomal, and metallic formulations – naturally traffic to the spleen and lymph organs and the relevant immune cells therein, making them good candidates for delivery of immunotherapeutic agents. Metallic nanoparticle formulations, in particular, are advantageous because of their potential for dense surface functionalization and their capability for optical or heat-based therapeutic methods. Many research groups have investigated the potential of nanoparticle-mediated delivery platforms to improve the efficacy of immunotherapies. Despite the significant preclinical successes demonstrated by many of these platforms over the last twenty years, only a few metallic nanoparticles have successfully entered clinical trials with none achieving FDA approval for cancer therapy. In this review, we will discuss preclinical research and clinical trials involving metallic nanoparticles (MNPs) for cancer immunotherapy applications and discuss the potential for clinical translation of MNPs.     

Amelioration of F-OFDM Performance by Deterioration in BER

Wireless Personal Communications - Mobile and data communication systems are providing various services such as voice, video, text messaging, etc. They required enhanced data rates with a high...