Enhancement of magnetoresistance in manganite multilayers

Magnanite multilayers have been fabricated using La0.67Ca0.33MnO3 as the ferromagnetic layer and Pr0.7Ca0.3MnO3 and Nd0.5Ca0.5MnO3 as the spacer layers. All the multilayers were grown on LaAlO3 (100) by pulse laser deposition. An enhanced magnetoresistnace (defined (RH- R0)/R0) of more than 98% is observed in these multilayers. Also a low field magnetoresistance of 41% at 5000 Oe is observed in these multilayer films. The enhanced MR is attributed to the induced double exchange in the spacer layer, which is giving rise to more number of conducting carriers. This is compared by replacing the spacer layer with LaMnO3 where Mn exists only in 3+ state and no enhancement is observed in the La0.67Ca0.33MnO3 / LaMnO3 multilayers as double exchange mechanism can not be induced by external magnetic fields.Comment: 13 pages, 5 Figure

New Convertible Authenticated Encryption Scheme with Message Linkages

The digital signature provides the signing message with functions like authentication, integration and non-repudiation. However, in some of the applications, the signature has to be verified only by specific recipients of the message and it should be hidden from the public. For achieving this, authenticated encryption systems are used. Authenticated Encryption schemes are highly helpful to send a confidential message over an insecure network path. In order to protect the recipients benefit and for ensuring non-repudiation, we help the receiver to change the signature from encrypted one to an ordinary one. With this we avoid any sort of later disputes. Few years back, Araki et al. has proposed a convertible authenticated scheme for giving a solution to the problem. His scheme enables the recipient to convert the senders signature into an ordinary one. However, the conversion requires the cooperation of the signer. In this thesis, we present a convertible authenticated encryption scheme that can produce the ordinary signature without the cooperation of the signer with a greater ease. Here, we display a validated encryption plan using message linkages used to convey a message. For the collector's advantage, the beneficiary can surely change the encrypted signature into an ordinary signature that which anyone can check. A few attainable assaults shall be examined, and the security investigation will demonstrate that none of the them can effectively break the proposed plan

C-band superconductor/semiconductor hybrid field-effect transistor amplifier on a LaAlO3 substrate

A single-stage C-band superconductor/semiconductor hybrid field-effect transistor amplifier was designed, fabricated, and tested at 77 K. The large area (1 inch x 0.5 inches) high temperature superconducting Tl-Ba-Ca-Cu-O (TBCCO) thin film was rf magnetron sputtered onto a LaAlO3 substrate. The film had a transition temperature of about 92 K after it was patterned and etched. The amplifier showed a gain of 6 dB and a 3 dB bandwidth of 100 MHz centered at 7.9 GHz. An identical gold amplifier circuit was tested at 77 K, and these results are compared with those from the hybrid amplifier

Dietary vitamin E and physical exercise: II. Antioxidant status and lipofuscin-like substances in aging rat heart

The heart faces a high risk of free radical injury owing to a slow generation of antioxidant (AO) enzymes by its cells. A general decline in this system may be another reason for the development of age-related diseases. Although the correlation between aging and exercise has been studied extensively, these studies have produced conflicting data on the effects of vitamin E on the aging heart, when it is introduced as an intervening factor. To investigate these effects, we determined the activities of antioxidant enzymes (AOEs) such as superoxide dismutase (SOD) and catalase (CAT), lipid peroxidation (LP), lipofuscin (LF)-like autofluorescent substances and vitamin E content in the left and right ventricles (LV and RV) of the heart in male Wistar albino rats of 4-(young adults), 8-(old adults), 12-(middle-age) and 22-mos(old) of age. Animals were orally supplemented with vitamin E and allowed to swim for 30min/day, 5 days/week and for a total period of 60 days. Exercise training in all the age groups except the old was effective in upregulating the SOD activity. Old trainees showed an increase in SOD activity when supplemented with vitamin E. In the 22-mo-olds, a remarkable decrease in CAT activity was seen. Exercise by itself upregulated the CAT as well as SOD activity in all age groups except the old wherein vitamin E was effective in increasing the activities of AOEs. Supplementation significantly reduced LP as evidenced by lowered malondialdehyde (MDA) and LF-like autofluorescent substances in the trained as well as sedentary rats. Tissue vitamin E content was low in the swim trainees that were not supplemented. This change, well emphasized in the trainee groups of 22-mo-old suggests the probable utilization of vitamin E in keeping free radicals at bay. Our results suggest that vitamin E can stand out as a significant tool in ameliorating the declining AO defense in the old rats. © 2002 Elsevier Science Inc. All rights reserved

Dietary vitamin E and physical exercise: I. Altered endurance capacity and plasma lipid profile in ageing rats

The effect of vitamin E on the exercise performance and plasma lipid profile was studied in male Wistar rats of 4-(young adults), 8-(old adults), 12-(middle-age) and 22-months (old) of age. Animals were orally supplemented with vitamin E and allowed to swim for 30min/day, 5 days/week and for a total period of 60 days. Swim velocity (Sv), external work done (Wext) and endurance (E) capacity were the parameters that were used to assess the exercise performance of the trained rats that were either supplemented or non-supplemented with the dietary antioxidant. Plasma lipid profile analyses were in terms of low-density lipoprotein (LDL-C), high-density lipoprotein, (HDL-C) cholesterol and total cholesterol (C). Age-related decline in Sv was noticeable in the 22-months old rats. However, the effect of vitamin E on the Sv between the trained groups was not evident in any of the age groups. Wext increased linearly with age with no significant variations between the trainees. Trainee rats, when allowed to swim to exhaustion, showed a higher endurance capacity when supplemented with vitamin E. However, this capacity declined with age. There was a significant age-associated elevation in plasma C with corresponding increase in LDL-C. Exercise training in conjunction with vitamin E supplementation was most effective in elevating HDL-C levels in all age groups. These changes were accompanied by significant reductions in cholesterol/HDL-C ratios in animals receiving vitamin E, sedentary or otherwise. Our data suggests that it may be important to consider vitamin E while attempting to derive the benefits of swim training, both in terms of favorably altering the plasma lipid profile as well as enhancing the endurance capacity of exercise trainees. Dietary supplementation by vitamin E could attenuate the early onset of fatigue in the old. © 2002 Elsevier Science Inc. All rights reserved

Swim exercise training and adaptations in the antioxidant defense system of myocardium of old rats: Relationship to swim intensity and duration

We examined a suitable swim program of different intensities and durations that could evoke changes in the myocardial antioxidant capacity in 22-month-old rats. Male rats (Rattus norvegicus) were assigned to either a sedentary control (SE-C) group or one of six trainee groups. Animals were swim-exercised for 4 weeks with either 20 min or 40 min/day, and three intensities, low, moderate and high. Low-intensity at 20 min/day elicited maximum swim velocity (S v) and endurance capacity (P<0.05). While serum total cholesterol, triglyceride and low-density lipoprotein (LDL-C) levels were significantly reduced, high-density lipoprotein (HDL-C) showed an increase (P<0.05) in low-intensity trained rats (20 min/day) over SE-C. Notable reduction in blood lactate was also evident. Exercise training significantly increased superoxide dismutase (Mn-SOD), decreased lipid peroxidation products, malondialdehyde and lipofuscin in the left and right ventricles. Increased Mn-SOD with concomitant decrease in lipofuscin in left ventricle was significantly greater than in right ventricle. Moderate- to high-intensity exercise was not effective in either reducing lipid peroxidation products or elevating Mn-SOD activity. These data suggest that swim training at low-intensity of 20 min/day is beneficial as a major protective adaptation against oxidative stress in old myocardium. © 2003 Elsevier Inc. All rights reserved

Enhancement of magnetoresistance in manganite multilayers

Magnanite multilayers have been fabricated using La0.67Ca0.33MnO3 as the ferromagnetic layer and Pr0.7Ca0.3MnO3 and Nd0.5Ca0.5MnO3 as the spacer layers. All the multilayers were grown on LaAlO3 (100) by pulse laser deposition. An enhanced magnetoresistnace (defined (RH- R0)/R0) of more than 98% is observed in these multilayers. Also a low field magnetoresistance of 41% at 5000 Oe is observed in these multilayer films. The enhanced MR is attributed to the induced double exchange in the spacer layer, which is giving rise to more number of conducting carriers. This is compared by replacing the spacer layer with LaMnO3 where Mn exists only in 3+ state and no enhancement is observed in the La0.67Ca0.33MnO3 / LaMnO3 multilayers as double exchange mechanism can not be induced by external magnetic fields.Comment: 13 pages, 5 Figure

Adaptations of the antioxidant system in erythrocytes of trained adult rats: Impact of intermittent hypobaric-hypoxia at two altitudes

We have investigated the effects of daily exposure to intermittent hypobaric-hypoxia to two simulated altitudes (5700 m and 6300 m) in adult male rats that had been regularly swim trained in normoxia at sea level prior to exposures. Superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) along with the oxidative stress (OS) indices, malondialdehyde (MDA) and protein carbonyl content were measured in erythrocytes and their membranes. Hemoglobin increased in the trained animals exposed to 5700 m and in untrained rats exposed to 6300 m. Osmotic fragility in terms of hemolysis increased in altitude exposed animals. SOD increased in those exposed to 6300 m, while CAT increased in trained rats exposed to 5700 m and to 6300 m unlike in untrained rats where CAT increased only at 6300 m. GSH-Px showed varying degrees of elevation in all animals exposed to both altitudes. Erythrocyte membranes showed significant elevations in malondialdehyde (MDA) at 6300 m, while elevated protein carbonyls were noticeable at both altitudes in whole cells and membranes. These results suggest a positively associated elevation in protein oxidation with altitude in trained rats. At 5700 m, animals were less stressed, unlike at 6300 m, as seen from the magnitude of elevations in the OS indices and from the responses of the antioxidant enzymes. © 2005 Elsevier Inc. All rights reserved

Tuberculin skin test results in HIV-infected patients in India: implications for latent tuberculosis treatment

OBJECTIVE: To evaluate the utility of the tuberculin skin test (TST) in detecting latent and active tuberculosis (TB) among human immunodeficiency virus (HIV) infected patients in South India. DESIGN: TSTs and CD4 counts were collected from 631 HIV-infected individuals without active TB and 209 antiretroviral and anti-tuberculosis treatment-naïve HIVinfected patients with TB. We calculated the proportion of TST-positive individuals, as well as the sensitivity, specificity, positive predictive value (PPV) and negative predictive value of TST in the diagnosis of TB. RESULTS: Among subjects without active TB, 28% with a CD4 count �100 cells/�l vs. 43% of the total cohort had a TST �5 mm (P � 0.14), while the proportions with induration �10 mm were 14% vs. 36%, respectively (P � 0.01). Among those with active TB, using a 5 mm cut-off, the sensitivity was 42% for those with CD4 counts �200 cells/�l compared to 70% for those with CD4 counts �200 cells/�l (P � 0.001). The PPV for detecting active TB was 29%. CONCLUSIONS: TST is a poor predictor of both latent and active TB in HIV-infected individuals in TB endemic countries. Programmes offering treatment for latent TB should consider including all HIV-positive patients regardless of TST status, or use other indicators, such as CD4 count

High sensitivity C-reactive protein levels across spectrum and severity of coronary artery disease

Background: C-reactive protein (CRP) is an acute-phase reactant protein synthesized by the liver in response to acute\ud stress in a wide range of acute and chronic inflammatory conditions. In healthy subjects and patients presenting with\ud coronary artery disease (CAD), elevated levels of CRP has repeatedly been demonstrated to predict future cardiovascular\ud events.\ud Methods: We measured high sensitivity C-reactive protein (hs-CRP) levels in 382 consecutive patients with CAD and 60 healthy controls by immunoturbidimetry method. Risk factors like hypertension, diabetes mellitus, dyslipidaemia,smoking, obesity and family history of premature CAD were assessed.\ud Results: The mean age of patients with CAD was 53.5±11.8 years (303 males) and that of control group was 50.83±8.07(28 males). The patient group had significant higher concentration of mean hs-CRP levels when compared\ud with the healthy control group (1.8±1.9 mg/L vs 0.35±1.1 mg/L, p<0.001). The mean hs-CRP levels of unstable angina\ud (USA) and myocardial infarction (MI) patients was higher than chronic stable angina (CSA) patients (p<0.05). Based\ud on the disease severity, we found a significantly higher hs-CRP levels in patients of triple vessel disease when compared\ud to patients with single vessel disease (p=0.01).\ud Conclusions: Elevated serum hs-CRP levels provide a useful marker for cardiovascular risk which, when combined\ud with traditional risk factors, may help improve global risk prediction. Our study showed a significant contribution of\ud hs-CRP to coronary risk prediction with better discrimination