Proper evaluation of the external convective heat transfer for the thermal analysis of cool roofs

Cool materials are characterized by high solar reflectance and high thermal emittance; when applied to the external surface of a roof, they make it possible to limit the amount of solar irradiance absorbed by the roof, and to increase the rate of heat flux emitted by irradiation to the environment, especially during nighttime. However, a roof also releases heat by convection on its external surface; this mechanism is not negligible, and an incorrect evaluation of its entity might introduce significant inaccuracy in the assessment of the thermal performance of a cool roof, in terms of surface temperature and rate of heat flux transferred to the indoors. This issue is particularly relevant in numerical simulations, which are essential in the design stage, therefore it deserves adequate attention. In the present paper, a review of the most common algorithms used for the calculation of the convective heat transfer coefficient due to wind on horizontal building surfaces is presented. Then, with reference to a case study in Italy, the simulated results are compared to the outcomes of a measurement campaign. Hence, the most appropriate algorithms for the convective coefficient are identified, and the errors deriving by an incorrect selection of this coefficient are discussed.

Thermal analysis of biodegradable microparticles containing ciprofloxacin hydrochloride obtained by spray drying technique

Thermal analysis has been extensively used to obtain information about drug-polymer interactions and to perform pre-formulation studies of pharmaceutical dosage forms. In this work, biodegradable microparticles of poly(D,L-lactide-co-glycolide) (PLGA) containing ciprofloxacin hydrochloride (CP) in various drug:polymer ratios were obtained by spray drying. The main purpose of this study was to investigate the effect of the spray drying process on the drug-polymer interactions and on the stability of microparticles using differential scanning calorimetry (DSC), thermogravimetry (TG) and derivative thermogravimetry (DTG) and infrared spectroscopy (IR). The results showed that the high levels of encapsulation efficiency were dependant on drug:polymer ratio. DSC and TG/DTG analyses showed that for physical mixtures of the microparticles components the thermal profiles were different from those signals obtained with the pure substances. Thermal analysis data disclosed that physical interaction between CP and PLGA in high temperatures had occurred. The DSC and TG profiles for drug-loaded microparticles were very similar to the physical mixtures of components and it was possible to characterize the thermal properties of microparticles according to drug content. These data indicated that the spray dryer technique does not affect the physicochemical properties of the microparticles. In addition, the results are in agreement with IR data analysis demonstrating that no significant chemical interaction occurs between CP and PLGA in both physical mixtures and microparticles. In conclusion, we have found that the spray drying procedure used in this work can be a secure methodology to produce CP-loaded microparticles. (C) 2007 Elsevier B.V. All rights reserved.

Purification, characterization, crystallization and theoretical molecular modeling of gyroxin fraction from Crotalus durissus terrificus venom (Laurenti, 1768)

The venom of Crotalus durissus terrificus snakes presents various substances, including a serine protease with thrombin-like activity, called gyroxin, that clots plasmatic fibrinogen and promote the fibrin formation. The aim of this study was to purify and structurally characterize the gyroxin enzyme from Crotalus durissus terrificus venom. For isolation and purification, the following methods were employed: gel filtration on Sephadex G75 column and affinity chromatography on benzamidine Sepharose 6B; 12% SDS-PAGE under reducing conditions; N-terminal sequence analysis; cDNA cloning and expression through RT-PCR and crystallization tests. Theoretical molecular modeling was performed using bioinformatics tools based on comparative analysis of other serine proteases deposited in the NCBI (National Center for Biotechnology Information) database. Protein N-terminal sequencing produced a single chain with a molecular mass of similar to 30 kDa while its full-length cDNA had 714 bp which encoded a mature protein containing 238 amino acids. Crystals were obtained from the solutions 2 and 5 of the Crystal Screen Kit (R), two and one respectively, that reveal the protein constitution of the sample. For multiple sequence alignments of gyroxin-like B2.1 with six other serine proteases obtained from snake venoms (SVSPs), the preservation of cysteine residues and their main structural elements (alpha-helices, beta-barrel and loops) was indicated. The localization of the catalytic triad in His57, Asp102 and Ser198 as well as S1 and S2 specific activity sites in Thr193 and Gli215 amino acids was pointed. The area of recognition and cleavage of fibrinogen in SVSPs for modeling gyroxin B2.1 sequence was located at Arg60, Arg72, Gln75, Arg81, Arg82, Lis85, Glu86 and Lis87 residues. Theoretical modeling of gyroxin fraction generated a classical structure consisting of two alpha-helices, two beta-barrel structures, five disulfide bridges and loops in positions 37, 60, 70, 99, 148, 174 and 218. These results provided information about the functional structure of gyroxin allowing its application in the design of new drugs.

Thermal analysis of chitosan based networks

In this work two kinds of material were studied: chitosan cross-linked with glutaraldehyde and in a blend with PEO. The resulting products as well as chitosan and PEO raw materials, were analyzed by TG/DTG, DSC and DMTA to determinate the in?uence of cross-linking and PEO addition on thermal properties of the resulting materials. It was observed by thermogravimetry that the water-polymer interaction will be different for the cross-linked material compared to the blend, according to the specific site availability. The in?uence of such modifications (cross-linking and PEO addition), on chitosan thermal stability was also studied. The DSC results showed a good agreement with the TG/DTG results, reinforcing the interpretation given for TG/DTG results. DMTA results indicate that glass transition temperature is around 50 degrees C for the polymer under study. (c) 2005 Elsevier Ltd. All rights reserved.

A comparative solid state C-13 NMR and thermal study of CO2 capture by amidines PMDBD and DBN

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

New palladium(II) complexes with pyrazole ligands Part II. Synthesis, spectral and thermal studies, and antitumor evaluation

This study describes the synthesis, IR, (1)H, and (13)C{(1)H} NMR spectroscopic as well the thermal characterization of the new palladium(II) pyrazolyl complexes [PdCl(2)(HmPz)(2)] 1, [PdBr(2)(HmPz)(2)] 2, [PdI(2)(HmPz)(2)] 3, [Pd(SCN)(2)(HmPz)(2)] 4 {HmPz = 4-methylpyrazole}. The residues of the thermal decomposition were identified as Pd(0) by X-ray powder diffraction. From the initial decomposition temperatures, the thermal stability of the complexes can be ordered in the sequence: 1 > 2 > 4 a parts per thousand 3. The cytotoxic activities of the complexes and the ligand were investigated against two murine cancer cell lines: mammary adenocarcinoma (LM3) and lung adenocarcinoma (LP07) and compared to cisplatin under the same experimental conditions.

New palladium(II) complexes with pyrazole ligands Part I. Synthesis, spectral and thermal studies, and antitumor evaluation

The pyrazole ligand 3,5-dimethyl-4-iodopyrazole (HdmIPz) has been used to obtain a series of palladium(II) complexes (1-4) of the type [PdX(2)(HdmIPz)(2)] {X = Cl(-) (1); Br(-) (2); I(-) (3); SCN(-) (4)}. All compounds have been isolated, purified, and characterized by means of elemental analysis, IR spectroscopy, (1)H and (13)C{(1)H}-NMR experiments, differential thermal analysis (DTA), and thermogravimetry (TG). The TG/DTA curves showed that the compounds released ligands in the temperature range 137-605 A degrees C, yielding metallic palladium as final residue. The complexes and the ligand together with cisplatin have been tested in vitro by MTT assay for their cytotoxicity against two murine cancer cell lines: mammary adenocarcinoma (LM3) and lung adenocarcinoma (LP07).

Thermal analysis of biodegradable microparticles containing ciprofloxacin hydrochloride obtained by spray drying technique

Thermal analysis has been extensively used to obtain information about drug-polymer interactions and to perform pre-formulation studies of pharmaceutical dosage forms. In this work, biodegradable microparticles of poly(D,L-lactide-co-glycolide) (PLGA) containing ciprofloxacin hydrochloride (CP) in various drug:polymer ratios were obtained by spray drying. The main purpose of this study was to investigate the effect of the spray drying process on the drug-polymer interactions and on the stability of microparticles using differential scanning calorimetry (DSC), thermogravimetry (TG) and derivative thermogravimetry (DTG) and infrared spectroscopy (IR). The results showed that the high levels of encapsulation efficiency were dependant on drug:polymer ratio. DSC and TG/DTG analyses showed that for physical mixtures of the microparticles components the thermal profiles were different from those signals obtained with the pure substances. Thermal analysis data disclosed that physical interaction between CP and PLGA in high temperatures had occurred. The DSC and TG profiles for drug-loaded microparticles were very similar to the physical mixtures of components and it was possible to characterize the thermal properties of microparticles according to drug content. These data indicated that the spray dryer technique does not affect the physicochemical properties of the microparticles. In addition, the results are in agreement with IR data analysis demonstrating that no significant chemical interaction occurs between CP and PLGA in both physical mixtures and microparticles. In conclusion, we have found that the spray drying procedure used in this work can be a secure methodology to produce CP-loaded microparticles. (C) 2007 Elsevier B.V. All rights reserved.

Effect of pH of colloidal suspension on crystallization and activation energy of deep levels in SnO2 thin films obtained via sol-gel

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Thermal stability and thermal decomposition of sucralose

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Synthesis, characterization and thermal studies on solid 3-methoxybenzoate of some bivalent transition metal ions

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Synthesis, characterization and thermal studies of solid state 4-methylbenzylidenepyruvate of some trivalent metal ions

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Synthesis, characterization and thermal behaviour on solid pyruvates of light trivalent lanthanides

Foram sintetizados compostos Ln-L no estado sólido, onde Ln significa os lantanídeos leves trivalentes e L é o piruvato. Estes compostos foram caracterizados e estudados utilizando-se a Termogravimetria e Termogravimetria derivada (TG/DTG), calorimetria exploratória diferencial (DSC) difratometria de raios X pelo método do pó, espectroscopia na região do infravermelho, análise elementar e complexometria. Os resultados permitiram obter informações com respeito a composição, desidratação, sitio de coordenação, comportamento térmico e a decomposição térmica destes compotos.

Synthesis, characterization and thermal behaviour of solid-state compounds of benzoates with some bivalent transition metal ions

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Synthesis, characterization and thermal behaviour of solid-state compounds of 4-methoxybenzoate with lanthanum (III) and trivalent lighter lanthanides

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)