Influence of Specific Surface Area of Aluminium Powder on the reactivity of aluminium/ammonium perchlorate composition

Aluminium/ammonium perchlorate (40/60 wt.%) is a pyrotechnic composition widely used as an igniter charge for small calibre rocket motors. Five different types of aluminium powders with specific surface area varying from 0.52 m²/g to 6.00 m²/g have been studied to evaluate the influence of specific surface area on the ignition characteristics of the charge. While the peak pressure varies from 35.5 ksc to 54.5 ksc (0.30 g in 48.0 cm³ vol.), the corresponding time to P_max varies from 11.2 ms to 1.6 ms showing higher reactivity of the mix with increase in aluminium surface area. This order of reactivity agrees with the order of reactivity determined from the DTG curves of the metal oxidation by comparing the peak height to half width ratio. However, the total gas generated by all the charges is approximately the same and the difference in peak pressure is caused by the difference in the rate of reaction and after about 30 ms all the compositions exhibit the same order of temperature and pressure. The charge has got an ignition temperature of about 640 K and the ignition is preceded by the exothermic decomposition of ammonium perchlorate. The activation energy varies from 92.2 kJ/mol to 127.6 kJ/mol and the corresponding pre-exponential factor from 9.7 × 10⁶ min⁻¹ to 7.1 × 10⁹ min⁻¹ and they exhibit the kinetic compensation effect with an isokinetic temperature of 647 K.     

Embolization with temporary balloon occlusion of the internal carotid artery and in vivo proton spectroscopy improves radical removal of petrous-tentorial meningioma

A highly vascular petroclival meningioma supplied by tentorial branches of the internal carotid artery was embolized by temporary balloon occlusion of the parent vessel distal to the tumor, followed by obliteration of the tumor vascularity with polyvinyl alcohol particles. Subsequently, in vivo proton spectroscopy showed necrosis of a large portion of the tumor and helped determine the timing of surgery. Both innovative techniques considerably facilitated the subsequent radical excision of the tumor with no neurological morbidity.     

Novel Li-ion conduction on poly(vinyl acetate)-based hybrid polymer electrolytes with double plasticizers

Polymer blend electrolytes comprising of poly(vinyl acetate), poly(vinylidene fluoride-co-hexafluoropropylene), LiClO₄, and EC-based plasticizer combinations (EC + PC, EC + GBL, EC + DMP, EC + DBP, EC + DEC) are prepared by solvent casting technique. Ionic conductivities of the electrolytes are determined by ac impedance studies in the temperature range 303–363 K. Among the various combinations of plasticizers, EC + PC added complex exhibits maximum ionic conductivity of the order of 10⁻⁴ S cm⁻¹ and the temperature-dependent ionic conductivity plots seem to obey the VTF relation. The structural and complex formations of the prepared samples have been confirmed by X-ray diffraction analysis. DSC technique is used to study the thermal behaviour. The surface images of the sample having maximum ionic conductivity are analyzed with the help of SEM and AFM techniques.