An Octagonal Shaped Monopole Antenna for UWB Applications with Band Notch Characteristics

Wireless Personal Communications - This article presents a microstrip-fed octagonal shaped monopole antenna with dual band notched characteristics for UWB applications. Partial ground plane has...     

Pressure induced transformations in condensed and molecular phases of C60

Solid C₆₀ is known to undergo dimerization under suitable conditions of temperature and pressure. We use a potential model (6-exponential potential) to study the changes leading to the formation of various dimers by hydrostatic pressure on C₆₀ solid at elevated temperatures. We have earlier shown, using Tersoff and Brenner potentials, that a system of two bucky-balls can form a dimer by bonding in different ways, when they start with different orientations at close distances. Based on this, we suggest the required preconditions (P-T curve) for the formation of different dimers from the pristine solid. Stability of the bucky-ball under internal or external pressure has also been studied using Tersoff and Brenner potentials. These two potentials have been compared for their applicability under high pressure conditions as well as for dimerization. We have also estimated the bulk modulus of the bucky-ball at several pressures (under which the molecule remains stable). The values of bulk modulus agree closely with those reported in earlier calculations around zero pressure. When the pressure inside the bucky-ball exceeds 116 GPa, it is seen to break open. This is in close agreement with the findings of molecular dynamics calculations.     

Production,thermal stability and immobilisation of inulinase from Fmarium oxysporum

Fusarium oxysporum produced maximum extracellular inulinase after 9 days of its growth at 25°C on a medium (pH 5.5) containing 3% fructan and 0.2% sodium nitrate. The level of this enzyme decreased on the addition of either glucose, fructose, galactose or sucrose to F. oxysporum already growing on a fructan-containing medium. A significant increase in invertase production which resulted in an increase of the invertase/inulinase (S/I) ratio, was observed on addition of inulin to this fungus growing on other carbon sources. Glycerol (10%) gave better protection to inulinase against thermal denaturation at 50°C compared to ethylene glycol and sorbitol. Inulinase immobilised in polyacrylamide gel retained 45% of its original activity. The immobilised enzyme showed a higher optimum temperature (45°C) compared to free enzyme (37°C). The immobilised enzyme after storage at 25°C for 96 h showed 58% activity. Thermal stability of entrapped inulinase increased in the presence of inulin.     

Microstructural,optical and electrical investigations of large scale selenium nanowires prepared by template electrodeposition

Large scale selenium nanowires have been prepared into the pores of polycarbonate track-etched membrane by template electrodeposition. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and UV–Visible spectroscopy have been used to characterize as-prepared crop of selenium nanowires. XRD and FESEM studies confirmed the formation of dense crop of selenium nanowires with trigonal phase. The spectra exhibited a highly crystalline peak corresponding to (100) plane suggesting a preferential growth along [001] direction. Williamson–Hall analysis has been used to determine the crystallite size and micro strain induced due to lattice deformation. The band gap of as-prepared selenium nanowires has been found to be 1.76 eV and of the direct type of transition. The blue shift observed in the optical band gap of selenium nanowires has been attributed to quantum size effect in semiconductor nanowires. Electrical properties of selenium nanowires have been examined using two probe method and showed double diode like current–voltage characteristics. The possible reaction mechanism of the formation of selenium nanowires has also been discussed.     

Performance evaluation of CBN,coated carbide,cryogenically treated uncoated/coated carbide inserts in finish-turning of hardened steel

In the present work, the performance of cubic boron nitride (CBN) inserts was compared with coated carbide and cryogenically treated coated/uncoated carbide inserts in terms of flank wear, surface roughness, white layer formation, and microhardness variation under dry cutting conditions for finish turning of hardened AISI H11 steel (48–49 HRC). The flank wear of CBN tools was observed to be lower than that of other inserts, but the accumulated machining time for all the four edges of carbide inserts were nearer to or better than the PCBN inserts. Results showed that tool life of carbide inserts decreased at higher cutting speeds. The surface roughness achieved under all cutting conditions for coated-carbide-treated/untreated inserts was comparable with that achieved with CBN inserts and was below 1.6 μm. The white layer formation and microhardness variation is less while turning with cryogenically treated carbide inserts than the CBN and untreated carbide. At low to medium cutting speed and feed, the performance of carbide inserts was comparable with CBN both in terms of tool life and surface integrity.     

Effect of pharmacological suppression of secondary hyperparathyroidism on cardiovascular hemodynamics in predialysis CKD patients: A preliminary observation

Cardiovascular events are the principal cause of mortality in patients with chronic kidney disease (CKD). Secondary hyperparathyroidism (SHPT), a common complication of CKD, contributes to cardiac dysfunction. This study is an attempt to demonstrate the effects of parathyroid hormone suppression with oral calcitriol on cardiovascular hemodynamics. Twenty predialysis CKD patients with SHPT were given calcitriol therapy for 12 weeks. Ten similar patients received placebo. Echocardiographic assessment of cardiac function was performed at baseline and after 12 weeks of treatment. Calcitriol therapy effectively suppressed SHPT. Baseline left ventricular (LV) end diastolic diameter and LV end systolic diameter were 4.86+/-0.48 and 2.86+/-0.33 cm, and the mean FS was 41.02+/-4.79%. Left ventricular end systolic and end diastolic volumes were normal (42.30+/-9.07 and 91.40+/-19.68 mL). The ejection fraction was slightly reduced (53.54+/-3.57%). Pretreatment Doppler indices including E velocity (0.816+/-0.087 m/s), A velocity (0.696+/-0.089 m/s), and E/A ratio (1.193+/-0.210) were significantly impaired. After 12 weeks of calcitriol therapy, there was no significant change in the LV dimensions or ejection fraction, but there was a significant improvement in the diastolic parameters, namely the A velocity (0.680+/-0.084) and E/A ratio (1.238+/-0.180). Secondary hyperparathyroidism is an important factor in the pathogenesis of cardiovascular complications in CKD. There is evidence to support that correction of hyperparathyroidism can improve the systolic dysfunction seen in advanced kidney disease. This study shows that diastolic dysfunction seen in predialysis CKD patients may also be possibly improved with calcitriol therapy.     

On Development of Functionally Graded Material Through Fused Deposition Modelling Assisted Investment Casting from Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/SiC Reinforced Waste Low Density Polyethylene

The recycling of packaging materials such as low density polyethylene (LDPE) into useful product is one of the challenging tasks. Since waste LDPE has some issues like low mechanical strength and thermal degradation; some studies have been reported in recent past to improve these properties with ceramic/metallic reinforcements. In this work reusability of LDPE has been ascertained as functionally graded material (FGM) through aluminum (Al) matrix based investment casting (IC). This study highlights the use of SiC and Al₂O₃ as reinforcement in LDPE for IC applications as a novel method for development of FGM. The master patterns for IC were prepared from reinforced LDPE based feed stock filament (prepared on conventional screw extruder) on open source fused deposition modelling setup. The in-house prepared filament wire was subjected to mechanical and thermal testing to ensure recyclability and stability of the material. The photo micrographs and SEM images were collected to ensure the dispersion of SiC and Al₂O₃ reinforcements in Al based FGM.     

Effect of irrigation on the lipid composition of taramira seed

The effect of irrigation on the lipid composition in maturing taramira (Eruca sativa, Mill) seed was studied. Decreasing the number of irrigations had an adverse effect on oil setting. Restricted irrigations affected adversely the biosynthesis of erucic acid in the oil at initial stages, though at later stages of seed development, irrigation had no such effect.