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排序方式: 共有445条查询结果,搜索用时 31 毫秒
161.
Eduardo Leite Krüger 《Applied Acoustics》2007,68(10):1213-1223
The present paper presents acoustic and thermal performance evaluations carried out in low-cost houses located at the Vila Tecnológica de Curitiba (Technological Village of Curitiba), in Curitiba, Brazil. Two dwellings were evaluated, which were built according to different building systems: (1) the building system Batistella, built with pre-fabricated modules and elements, composed of reforestation wood and (2) the building system Constroyer, composed of expanded polystyrene (EPS) plates, framed in a welded iron mesh, with structural plastering. For the thermal performance evaluation, it was verified that the materials used in the envelope were quite significant for controlling heat gains and losses through the building elements as well as for regulating heat storage. In this case, the system with highest thermal inertia presented better results. Results showed that both building systems had poor acoustic performance, characterized by a low weighted apparent sound reduction index of the façade dB. The German DIN 4109 Norm recommends a minimum of dB. The weighted apparent sound reduction index measured for internal walls was dB and dB, for the building systems Battistela and Constroyer, respectively. The minimum required by German regulation VDI 4100 is dB, for internal walls. 相似文献
162.
The Influence of the Amide Linkage in the FeIII‐Binding Properties of Catechol‐Modified Rosamine Derivatives
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Carla Queirós Dr. Andreia Leite Maria G. M. Couto Dr. Luís Cunha‐Silva Prof. Giampaolo Barone Prof. Baltazar de Castro Prof. Maria Rangel Dr. André M. N. Silva Dr. Ana M. G. Silva 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(44):15692-15704
The two new fluorescent ligands RosCat1 and RosCat2 contain catechol receptors connected to rosamine platforms through an amide linkage and were synthesized by using microwave‐assisted coupling reactions of carboxyl‐ or amine‐substituted rosamines with the corresponding catechol units and subsequent deprotection. RosCat1 possesses a reverse amide, whereas RosCat2 has the usual oriented amide bond (HNCO vs. CONH, respectively). The ligands were characterized by means of NMR spectroscopy, mass‐spectrometry, and DFT calculations and X‐ray crystallography studies for RosCat1 . The influence of the amide linkage on the photophysical properties of the fluorescent ligands was assessed in different solvents and showed a higher fluorescence quantum yield for RosCat1 . The coordination chemistry of these ligands with a FeIII center has been rationalized by mass‐spectrometric analysis and semiempirical calculations. Octahedral FeIII complexes were obtained by the chelation of three RosCat1 or RosCat2 ligands. Interestingly, the unconventional amide connectivity in RosCat1 imposes the formation of an eight‐membered ring on the chelate complex through a “salicylate‐type” mode of coordination. 相似文献
163.
Determination of polycyclic aromatic hydrocarbons in fractions in asphalt mixtures using liquid chromatography coupled to mass spectrometry with atmospheric pressure chemical ionization
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Paulo Cicero Nascimento Luciana Assis Gobo Denise Bohrer Leandro Machado Carvalho Margareth Coutinho Cravo Leni Figueiredo Mathias Leite 《Journal of separation science》2015,38(13):2238-2244
An analytical method using liquid chromatography coupled to mass spectrometry with atmospheric pressure chemical ionization for the determination of polycyclic aromatic hydrocarbons in asphalt fractions has been developed. The 14 compounds determined, characterized by having two or more condensed aromatic rings, are expected to be present in asphalt and are considered carcinogenic and mutagenic. The parameters of the atmospheric pressure chemical ionization interface were optimized to obtain the highest possible sensitivity for all of the compounds. The limits of detection ranged from 0.5 to 346.5 μg/L and the limits of quantification ranged from 1.7 to 1550 μg/L. The method was validated against a diesel particulate extract standard reference material (NIST SRM 1975), and the obtained concentrations agreed with the certified values. The method was applied to asphalt samples after its fractionation according to ASTM D4124 and the method of Green. The concentrations of the seven polycyclic aromatic hydrocarbons quantified in the sample ranged from 0.86 mg/kg for benzo[ghi]perylene to 98.32 mg/kg for fluorene. 相似文献
164.
Determination of oxygen and nitrogen derivatives of polycyclic aromatic hydrocarbons in fractions of asphalt mixtures using liquid chromatography coupled to mass spectrometry with atmospheric pressure chemical ionization
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Paulo Cicero Nascimento Luciana Assis Gobo Denise Bohrer Leandro Machado Carvalho Margareth Coutinho Cravo Leni Figueiredo Mathias Leite 《Journal of separation science》2015,38(23):4055-4062
Liquid chromatography coupled to mass spectrometry with atmospheric pressure chemical ionization was used for the determination of polycyclic aromatic hydrocarbon derivatives, the oxygenated polycyclic aromatic hydrocarbons and nitrated polycyclic aromatic hydrocarbons, formed in asphalt fractions. Two different methods have been developed for the determination of five oxygenated and seven nitrated polycyclic aromatic hydrocarbons that are characterized by having two or more condensed aromatic rings and present mutagenic and carcinogenic properties. The parameters of the atmospheric pressure chemical ionization interface were optimized to obtain the highest possible sensitivity for all compounds. The detection limits of the methods ranged from 0.1 to 57.3 μg/L for nitrated and from 0.1 to 6.6 μg/L for oxygenated derivatives. The limits of quantification were in the range of 4.6–191 μg/L for nitrated and 0.3–8.9 μg/L for oxygenated derivatives. The methods were validated against a diesel particulate extract standard reference material (National Institute of Standards and Technology SRM 1975), and the obtained concentrations (two nitrated derivatives) agreed with the certified values. The methods were applied in the analysis of asphalt samples after their fractionation into asphaltenes and maltenes, according to American Society for Testing and Material D4124, where the maltenic fraction was further separated into its basic, acidic, and neutral parts following the method of Green. Only two nitrated derivatives were found in the asphalt sample, quinoline and 2‐nitrofluorene, with concentrations of 9.26 and 2146 mg/kg, respectively, whereas no oxygenated derivatives were detected. 相似文献
165.
166.
A new method to stabilize silver nanoparticles by the addition of ammonia is proposed. Colloidal dispersions of silver nanoparticles were synthesized by the Turkevich method using sodium citrate to reduce silver nitrate at high pH and at 90 °C. After approximately 12 min, a diluted ammonia solution was added to the reaction flask to form soluble diamine silver (I) complexes that played an important growth moderating role, making it possible to stabilize metallic silver nanoparticles with sizes as small as 1.6 nm after 17 min of reaction. Colloidal dispersions were characterized by UV-visible absorption spectroscopy, X-ray diffraction, and transmission electronic microscopy. 相似文献
167.
Tácito Dantas F. Leite Rainério Escalfoni Jr. Teresa Cristina O. da FonsecaNorbert Miekeley 《Spectrochimica Acta Part B: Atomic Spectroscopy》2011,66(5):314-320
The present work is a continuation of a research study performed at our laboratory aiming at the multielement analysis of rock samples (basalts and shale) by inductively coupled plasma mass spectrometry in combination with laser ablation using borate glasses as analytical targets. Argon, nitrogen-argon mixtures and helium were evaluated as cell gases, the latter confirming its better performance. Different operational parameters of the laser, such as gas flow, energy, focus, scanning speed and sampling frequency were optimized. External calibration was made with standards prepared by fusion of geological reference materials (basalts 688 and BCR-2, obsidian SRM 278, and shale SGR-1) of different mass fractions in the meta-tetra borate matrix. Coefficients of determination (R2) were > 0.99 for 30 elements from o total of 40 determined. Method validation was then performed using additional certified reference materials (BHVO-2, BIR-1, SCo-1) produced as borate targets in a similar way. Accuracies were better than 10% for most of the elements studied and analytical precisions, calculated from the residual standard deviations of calibration curves were, typically, between 6% and 10%. Additionally, the semiquantitative TotalQuant® technique was applied, which gave, within the expected uncertainty for this calibration technique, concordant results when compared to the quantitative external calibration procedure. Both methods were then used for the analysis of marine shale samples, which are of great geological interest in petroleum prospecting. 相似文献
168.
Daniel Leite da Silva Eder do Couto Tavares Leila de Souza Conegero ?ngelo de F??tima Ronaldo Aloise Pilli Sergio Antonio Fernandes 《Journal of inclusion phenomena and macrocyclic chemistry》2011,69(1-2):149-155
Accidental or intentional drug toxicity in humans and animals is a major concern and the search for detoxificant agents is a challenge. Pyrrolizidine-producing forages are a threat not only to livestock, but also to humans as a consequence of food contamination. Supramolecular systems are promising as detoxificant agents by decreasing the bioavailability of toxic compounds in biological environment. Cyclodextrin and calix[n]arenes are well known hosts for a variety of molecules and/or ions. Surprisingly, only few studies describe the potential of calix[n]arenes as host for toxic molecules. This study focused on the use of NMR techniques as tools for the investigation of the interactions between p-sulfonic acid calix[6]arene and retronecine, a toxic pyrrolizidine alkaloid. 相似文献
169.
Eric Oliveira Faria Antônio Carlos Viera Lopes Junior Dênio Emanuel Pires Souto Fernando Roberto Figueiredo Leite Flávio Santos Damos Rita de Cássia Silva Luz Alexandre Soares dos Santos Diego Leoni Franco Wallans Torres Pio dos Santos 《Electroanalysis》2012,24(5):1141-1146
This work presents a simple, fast and low‐cost method for simultaneous determination of acetylsalicylic acid (ASA), without alkaline hydrolysis and caffeine (CF) in pharmaceutical formulations using a boron‐doped diamond as the working electrode through differential pulse voltammetry. A good repeatability was reached for 20 measurements, with a low relative standard deviation of less than 1.0 %. The calibration curves presented a great linear correlation coefficient for both drugs (R=0.999) with a limit of detection of 1.6×10?7 mol L?1 for CF and 2.3×10?7 mol L?1 for ASA. The system was validated in comparison with the official method. 相似文献
170.
G.V. Salmoria J.L. Leite L.F. Vieira A.T.N. Pires C.R.M. Roesler 《Polymer Testing》2012,31(3):411-416
The use of polymeric blends can increase the range of structures and properties of selective laser sintering (SLS) parts. This study investigates the processing of a binary polar system using polyamide 6 (PA6) and polyamide 12 (PA12) by SLS. The mixture composition and processing conditions, and their influence on the dynamic mechanical properties of the specimens manufactured were evaluated. The maximum tan δ values suggest that PA6 and PA12 have similar visco-dissipative behavior. The PA6/PA12 blends behavior varied according to the relaxation phenomena of the pure components, proportionally to the blend composition. The creep test showed that blends with a higher amount of PA6 had greater plastic deformation and less elastic recovery. In the fatigue test the 20/80 and 50/50 blends presented good fatigue resistance under the test conditions. 相似文献