Thermal Diffusivity Anisotropy In Calamitic-nematic Lyotropic Liquid Crystal

The temperature dependence of the thermal diffusivity of a lyotropic liquid crystal was studied using thermal lens technique. The sample under study was aligned in a magnetic field before measurements thus allowing the determination of the thermal diffusivity in both directions. The results show that the thermal diffusivity sharply decreases in the phase transition temperatures, and presents an anisotropy in the nematic phase.741 II822824Shen, J., Snook, R.D., (1993) J. Appl. Phys., 73, p. 5286Baesso, M.L., Shen, J., Snook, R.D., (1994) J. Appl. Phys., 75, p. 3732Bento, A.C., Palangana, A.J., Evangelista, L.R., Baesso, M.L., Pereira, J.R.D., Da Silva, E.C., Mansanares, A.M., (1996) Appl. Phys. Lett., 68, p. 3371Pereira, J.R.D., Mansanares, A.M., Palangana, A.J., Baesso, M.L., (1999) Mol. Cryst. Liq. Cryst., 332, p. 569Glorieux, C., Bozoki, Z., Fivez, J., Thoen, J., (1995) J. Appl. Phys., 78, p. 3096Mercuri, F., Zammit, U., Marinelli, M., (1998) Phys. Rev. E, 57, p. 596Touloukian, Y.S., Powel, R.W., Ho, C.Y., Nicolau, M.C., (1983) Thermal Properties of Matter, 10. , Plenum, New YorkGarlene, Y., Moarcerou, J.P., (1983) Phys. Rev. Lett., 51, p. 210

Baseline characteristics and risk factors for ulcer, amputation and severe neuropathy in diabetic foot at risk: the brazupa study

CNPQ – CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOStudies on diabetic foot and its complications involving a significant and representative sample of patients in South American countries are scarce. The main objective of this study was to acquire clinical and epidemiological data on a large cohort of diabetic patients from 19 centers from Brazil and focus on factors that could be associated with the risk of ulcer and amputation. Methods: This study presents cross sectional, Baseline results of the BRAZUPA Study. A total of 1455 patients were included. Parameters recorded included age, gender, ethnicity, diabetes and comorbidity-related records, previous ulcer or amputation, clinical symptomatic score, foot classification and microvascular complications. Results: Patients with ulcer had longer disease duration (17.2 +/- 9.9 vs. 13.2 +/- 9.4 years; p < 0.001), and poorer glycemic control (HbA1c 9.23 +/- 2.03 vs. 8.35 +/- 1.99; p < 0.001). Independent risk factors for ulcer were male gender (OR 1.71; 95 % CI 1.2-3.7), smoking (OR 1.78; 95 % CI 1.09-2.89), neuroischemic foot (OR 20.34; 95 % CI 9.31-44.38), region of origin (higher risk for those from developed regions, OR 2.39; 95 % CI 1.47-3.87), presence of retinopathy (OR 1.68; 95 % CI 1.08-2.62) and absence of vibratory sensation (OR 7.95; 95 % CI 4.65-13.59). Risk factors for amputation were male gender (OR 2.12; 95 % CI 1.2-3.73), type 2 diabetes (OR 3.33; 95 % CI 1.01-11.1), foot at risk classification (higher risk for ischemic foot, OR 19.63; 95 % CI 3.43-112.5), hypertension (lower risk, OR 0.3; 95 % CI 0.14-0.63), region of origin (South/Southeast, OR 2.2; 95 % CI 1.1-4.42), previous history of ulcer (OR 9.66; 95 % CI 4.67-19.98) and altered vibratory sensation (OR 3.46; 95 % CI 1.64-7.33). There was no association between either outcome and ethnicity. Conclusions: Ulcer and amputation rates were high. Age at presentation was low and patients with ulcer presented a higher prevalence of neuropathy compared to ischemic foot at risk. Ischemic disease was more associated with amputations. Ethnical differences were not of great importance in a miscegenated population825CNPQ – CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOCNPQ – CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOsem informaçã

Thermal Diffusivity Measurements In Lyotropic Ferronematics: Mode Mismatched Thermal Lens

The mode mismatched thermal lens technique was used in the determination of thermal diffusivity of oriented lyotropic liquid crystal doped with ferrofluid. It was found that the behavior of the parallel thermal diffusivity as a function of ferrofluid content could not be explained in terms of the order parameter alone. Additional contribution coming from the ferrofluid itself seems to be necessary for the interpretation of the experimental data.332569575Shen, J., Snook, R.D., (1993) J. Appl. Phys., 73, p. 5286Baesso, M.L., Shen, J., Snook, R.D., (1994) J. Appl. Phys., 75, p. 3732Bento, A.C., Palangana, A.J., Evangelista, L.R., Baesso, M.L., Pereira, J.R.D., Da Silva, E.C., Mansanares, A.M., (1996) Appl. Phys. Lett., 68, p. 3371Shibli, S.M., Dantas, A.L.L., Walton, D., (1998) Appl. Phys. Lett., 72, p. 674Mercuri, F., Zammit, U., Marinelli, M., (1998) Phys. Rev. E, 57, p. 59

Thermal properties of thin acrylic paints using thermal wave interferometry

In this paper, the thermal wave interferometry technique is explored in the investigation of thermal properties of thin layers from commercial paint sprays. The films were produced by manual spray techniques and analyzed for a set of different colors and mixtures, black, blue, graphite, metallic platinum and green. Thermal diffusivity and substrate/film effusivity ratios were fitted in order to obtain the thermal conductivity and volume heat capacity. Experimental results give evidence of a very good agreement between literature values for polymers and experimental values, $\alpha$ in the range from 1.0 to $3.0 \times 10^{-3}$ (cm$^2$/s) for all films, confirming the capability of this technique to inspect thin layers

Influence of probe beam multi-reflection on thermal lens measurements: Application to Nd:YAG rods

In this work time resolved thermal lens measurements were carried out in Nd-doped yttrium aluminum garnet laser crystal. We observed that due to the probe beam multi-reflection the thermal lens signal was influenced by the moving fringes that occurred in front of the detector. By using a heat sink device, this effect was minimized permitting the determination of the temperature coefficient of optical path length, the thermal diffusivity and the thermal conductivity of the sample. As a complementary technique, the thermal relaxation method was used to measure the sample specific heat

Temperature dependence of the thermo-optical properties of KDP single crystal measured by thermal relaxation and thermal lens methods

In this work, thermal lens spectrometry and the thermal relaxation method were applied to determine the thermo-optical properties of KDP single crystal as a function of temperature. The results showed the expected phase transitions of the crystal at different temperatures and also provided the behavior of the thermal lens amplitude when the crystal temperature was increased. This information is relevant since this material is widely used in many optical systems, especially in high power laser cavity

Low Temperature Specific Heat Of Doped And Undoped Glasses

In this work we have measured the specific heat, cp, of several glasses between 2 and 160 K. The experiments were performed in low silica calcium aluminosilicate (prepared under vacuum and room atmosphere conditions), in silicate and in fluoride glasses. The influence of neodymium, iron and cobalt in cp values at low temperature was also investigated. The scaling proposed by Liu and Löhneysen was used to analyze the experimental data. The temperatures in which the maxima in cp/T3, the so called boson peak, occur are discussed in terms of the Hrubý coefficient, which provides information about the glass forming ability. © 2006 Elsevier B.V. All rights reserved.35232-3535723576Zeller, R.C., Pohl, R.O., (1971) Phys. Rev. B, 4, p. 2029Stephens, R.B., (1973) Phys. Rev. B, 8, p. 2896(1981) Amorphous Solids: Low Temperature Properties, , Phillips W.A. (Ed), Springer, BerlinGil, L., Ramos, M.A., Bringer, A., Buchenau, U., (1993) Phys. Rev. Lett., 70, p. 182Buchenau, U., Prager, M., Nücker, N., Dianoux, A.J., Ahmad, N., Phillips, W., (1986) Phys. Rev. B, 34, p. 5665Anderson, P.W., Halperin, B.I., Varma, C.M., (1972) Philos. Mag., 25, p. 1Phillips, W.A., (1972) J. Low Temp. Phys., 7, p. 351Astrath, N.G.C., Baesso, M.L., Bento, A.C., Colucci, C.C., Medina, A.N., Evangelista, L.R., (2006) Philos. Mag., 86, p. 227Masciovecchio, C., Ruocco, G., Sette, F., Krisch, M., Verbeni, R., Bergmann, U., Soltwisch, M., (1996) Phys. Rev. Lett., 76, p. 3356Sokolov, A.P., Rossler, E., Kisliuk, A., Quitmann, D., (1993) Phys. Rev. Lett., 71, p. 2062Liu, X., Löhneysen, H.v., (1996) Europhys. Lett., 33, p. 617Hrubý, A., (1972) Czech. J. Phys. B, 22, p. 1187Baesso, M.L., Bento, A.C., Andrade, A.A., Sampaio, J.A., Pecoraro, E., Nunes, L.A.O., Catunda, T., Gama, S., (1998) Phys. Rev. B, 57, p. 10545Lima, S.M., Sampaio, J.A., Catunda, T., Lebullenger, R., Hernandes, A.C., Baesso, M.L., Bento, A.C., Gandra, F.C.G., (1999) J. Non-Cryst. Solids, 256-257, p. 337Sokolov, A.P., Calemczuk, R., Salce, B., Kisliuk, A., Quitmann, D., Durval, E., (1997) Phys. Rev. Lett., 72, p. 2405Ramos, M.A., Tálon, C., Vieira, S., (2002) J. Non-Cryst. Solids, 307-310, p. 80Duval, E., Achibat, T., Boukenter, A., Varrel, B., Calemczuk, R., Salce, B., (1999) J. Non-Cryst. Solids, 190, p. 258Angell, C.A., (1995) Science, 267, p. 1924Fisher, R.A., Brodale, G.E., Hornung, E.W., Giauque, W.F., (1968) Rev. Sci. Inst., 39, p. 108Sampaio, J.A., Gama, S., (2004) Phys. Rev. B, 69, p. 104203Baesso, M.L., Bento, A.C., Duarte, A.R., Neto, A.M., Miranda, L.C.M., Sampaio, J.A., Catunda, T., Gandra, F.C.G., (1999) J. Appl. Phys., 85, p. 8112Zimmermann, J., Weber, G., (1981) Phys. Lett., 86, p. 32Pérez-Enciso, E., Ramos, M.A., Vieira, S., (1997) Phys. Rev. B, 56, p. 32Pinango, E.S., Ramos, M.A., Villar, R., Vieira, S., (1990) Basic Features of the Glassy State, p. 509. , Colmenero J., and Alegria A. (Eds), World Scientific, SingaporeTropf, W.J., Thomas, M.E., Harris, T.J., (1995) Handbook of Optics, II, p. 33. , Bass M. (Ed), McGraw-Hill, New YorkSampaio, J.A., Catunda, T., Gandra, F.C.G., Gama, S., Bento, A.C., Miranda, L.C.M., Baesso, M.L., (1999) J. Non-Cryst. Solids, 247, p. 19

Thermo-optical properties of iron-doped low silica calcium aluminosilicate glasses determined by photothermal methods

The aim of this work is to investigate Fe$^{3+}$ and Fe$^{2+}$ influence on the thermo-optical properties of low silica calcium aluminosilicate glass. Conventional optical absorption spectroscopy, thermal relaxation calorimetry and thermal lens spectrometry were applied to analyze the samples. The results provided the specific heat, the thermal diffusivity and the optical absorption coefficient as a function of the ions concentration. A significant variation in these parameters was observed, revealing the influence of the iron ions on the glass structure