RESUMO
Low-dimensional quantum spin ½ system Cu2V2O7has been investigated in the framework of Mn-substitution at the Cu site, which is really un-investigated. The studied compounds Cu2 -xMnxV2O7(x= 0, 0.05, 0.1 and 0.15) have been synthesized and characterized structurally, spectroscopically, local structurally and magnetically via x-ray diffraction, Raman, x-ray absorption and temperature, field dependent magnetization measurements respectively. Although Cu2V2O7can be found inα, ßandγ-phase, however all of the studied compounds are found in single orthorhombicα-phase which has crucial magneto-electric application potential. Temperature dependent Raman spectra indicated anharmonic phonon-phonon scattering but there is no spin-phonon coupling for VO4vibrational modes. The local structure probed via x-ray absorption near edge structure and extended x-ray absorption fine structure spectroscopy at 15 K, 300 K indicates Cu2+, V5+and mixed valent Mn2+and Mn3+ionic states and justified local structure for the probed ions. Magnetic measurements indicate long-range antiferromagnetic ordering with doping independent Neel temperature (32.5 K). Further observations are strong magnetic hysteresis at 5 K (due to canted spin structure), zero field exchange-bias and their noteworthy enhancement upon Mn-substitution. Interesting correlation between structural parameters and magnetic exchanges has been developed.
RESUMO
The present work aims to study the effect of ion irradiation on structural and electrical properties and their correlation with the defects in the Zn(1 - x)Mn(x)O-type system. Zn(1 - x)Mn(x)O (x = 0.02, 0.04) samples have been synthesized by the solid-state reaction method and have been irradiated with 50 MeV Li(3+) ions. The concomitant changes have been probed by x-ray diffraction (XRD), temperature-dependent electrical resistivity and positron annihilation lifetime (PAL) spectroscopy. The XRD result shows a single-phase wurtzite structure for Zn(0.98)Mn(0.02)O, whereas for the Zn(0.96)Mn(0.04)O sample an impurity phase has been found, apart from the usual peaks of ZnO. Ion irradiation removes this impurity peak. The grain size of the samples is found to be uniform. For Zn(0.98)Mn(0.02)O, the observed sharp decrease in room temperature resistivity (ρ(RT)) with irradiation is consistent with the lowering of the full width at half maximum of the XRD peaks. However, for Zn(0.96)Mn(0.04)O, ρ(RT) decreases for the initial fluence but increases for a further increase in fluence. All the irradiated Zn(0.98)Mn(0.02)O samples show a metal-semiconductor transition in temperature-dependent resistivity measurements at low temperature. But all the irradiated Zn(0.96)Mn(0.04)O samples show a semiconducting nature in the whole range of temperatures. Results of room temperature resistivity, XRD and PAL measurements are consistent with each other.
RESUMO
Initial dietary advice for Asian diabetics attending a general practice diabetic clinic was given in Asian languages. Between 2 and 3 years later a questionnaire interview was conducted to assess the effectiveness of the advice given. Forty of the 59 Asian diabetic patients in the practice attended for interview. The majority continued to use sugar or 'gur' (jaggery), Asian sweets, and Asian snacks (which have a high fat content). Fat and oil consumption per person per month was also high. Failure to achieve dietary objectives seemed to result from lack of sufficient emphasis on the types of foods usually consumed and an inadequate understanding of eating and cooking habits of Asians. We conclude that for dietary advice to be successful, emphasis must be placed on specific types of food eaten together with an understanding of the sociocultural implications of eating practices in ethnic groups.
