541 research outputs found

    Deterioration of Retro-Reflective Sheet Under Outdoor Weathering and Weather-O-Meter

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    ABSTRACTMore than one million road signs are installed over thousands of kilometers of highways in India. It is a matter of great concern that there is no strategy to assess their deterioration in terms of quality of retro reflective sheets under natural outdoor weathering and artificial accelerated weathering. The work reported in this paper is focused on how fast the deterioration of reflective sheets of different colors is occurring under natural weathering conditions in India. The deterioration is simulated with artificial weathering under Xenon-Arc chamber with known parameters of weather prevailing in India. This study will help in evaluating the performance of retro-reflective sheets in hours in weather-o-meter to same level of deterioration in the field in terms of days. Data for co-efficient of retro-reflectivity was collected for White, Yellow, Red, Orange, Green, and Blue Type III reflective sheets over a period of seven years in natural weather conditions of Delhi.The best-fit curves technique was adopted to predict the life of retro reflective sheets of different colors in terms of days/months to reach its minimum allowable level. The higher values of R2 for all colors indicate that there is a strong relationship between deterioration and age of reflective sheets in terms exposure in months/days, similarly the R2 values were also found high when the exposure was made in weather-o-meter for few hours. It means that weather conditions in weather-o-meter are exactly being stimulated with prevailing weather conditions in Delhi. The study concludes that over a period of seven years the deterioration of blue color sheet is maximum and deterioration of green color sheet is minimum. This conclusion is also evident from physical parameters such as appearance of signs installed in India. The signs with blue base normally need early replacement in comparison to the signs made out of green sheet for National Highways. The parameters, which were set in weather-o-meter, need the exposure of different hours for different colors of sheets for achieving minimum allowable level of reflectivity as per ASTM standard. The tentative results indicate that reduction of retro reflectivity after 124 months outdoors could be achieved in 90 hours exposure in weather-o-meter. The deterioration varies from color to color and the exposure hours are different for different colours of sheets. This is due to difference in the properties of the pigments used in reflective sheets

    Calculations of electronic band structure and optical properties of HgTe under pressure

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    The electronic band structure and optical properties of HgTe have been reported using the full potential linearized augmented plane wave (FP-LAPW) method based on density functional theory. In this approach, generalized gradient approximation (GGA) and Engel-Vosko generalized gradient approximation (EV-GGA) have been used for the exchange correlation potential in the calculations. The electronic band structures have been calculated to discuss the electronic properties and optical properties of the compound. Moreover, optical properties including dielectric functions, absorption, optical conductivity, refractive index, reflectivity and energy loss spectrum have been obtained and analyzed in details within the energy range up to 14 eV. The obtained results have been compared with the previous calculations and available experimental data. Overall good agreement is found

    Electronic, mechanical, thermodynamic and optical properties of CdS under pressure

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    We report high pressure study of CdS using the full-potential linear augmented plane wave (FP-LAPW) method based on density functional theory approach. In this approach, generalized gradient approximation (GGA) and Engel- Vosko generalized gradient approximation (EV-GGA) have been used for the exchange correlation potential in the calculations. The equilibrium lattice constant, electronic band structure, elastic constants, Debye temperature and melting temperature of binary solid CdS have been calculated under ambient and high pressure. Furthermore, the linear optical properties such as dielectric function, absorption, optical conductivity reflectivity, refractive index and energy loss are computed and analyzed in detail within the energy range up to 14 eV. The obtained results are in good agreement with earlier reported experimental and other theoretical results

    Thyroid dysfunction in patients of depression and anxiety and response to therapy

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    Background: Depression and anxiety are the most common psychiatric presentation in thyroid dysfunction. Aim of the study was to determine the thyroid profile in patients with depressive and anxiety symptoms and to determine the change in symptoms with correction of thyroid profile.Methods: This longitudinal observational study was conducted in patients presented with depressive or anxiety symptoms who visited the psychiatry out patient department (OPD) first time. Two groups were made based on the serum thyroid profile. First group, (n=27) was patients with depression and anxiety with hypothyroidism (experimental group) and second was (n=123) without hypothyroidism (control group). Experimental group, (n=27) was then exposed to thyroxine, 15 patients came for first follow up and 11 patients came for second follow up.Results: The 63% of patients in the experimental group and 62.6% of patients in the control group were of female gender, 66.7% and 33.3% of patients in the experimental group had depressive disorder and anxiety disorder respectively. TSH level of 11 patients of experimental group had significantly less value in first follow up compared to entry point (p=0.002). Generalized anxiety disorder (GAD) 7 scores were significantly lower in first and second follow up than that of the entry point in 11 patients of experimental group (p=0.008, 0.016 respectively).Conclusions: Many patients of the clinical diagnosis of depression (17.6%) and clinical diagnosis of anxiety (18.75%) had hypothyroidism during the first visit to the psychiatry OPD. There was significant reduction in the hypothyroid patients of the serum thyroid stimulating hormone (TSH) value and anxiety scores during the follow up after treatment with levothyroxine

    Status of exploitation of tuna, mackerel and seerfish in Andaman and Nicobar Islands

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    Annual fish landing of Andaman and Nicobar Islands during 1989-'99 and the contribution of scombroids viz., tuna, mackerel and seerfishes are described. During the period the exploitation of tuna ranged between 321 to 3,8231, the average contribution being about 5% of the total fish landings. Among the tuna species, yellowfin tuna Thunnus albacares is the major contributor followed by skipjack tuna Katsuwonus pelamis and bigeye tuna Thunns obesus all of which are best caught during March to August. The mackerfel fishery is supported by Rastrelliger brachysoma followed by R.kanagurta. The total mackerel landings ranged between 806 to 1,9551, the major fishing season being from March to June and September to October and is best caught in the gill nets and boat seines. Seerfishes are dominantly represented by two genera and three species vjz. Scomberomorus commerson, S. guttatus and Acanthocybium solandri. Their major fishing season is from March to August and November to Febmary, being generally caught by gill nets, troll lines and hand lines. During the period of 1989 -'99, the total exploitation of seerfishes ranged between 293 to 1,172 t and showed a gradual increase in their production
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