Numerical study of a slip-link model for polymer melts and nanocomposites

We present a numerical study of the slip link model introduced by Likhtman for describing the dy- namics of dense polymer melts. After reviewing the technical aspects associated with the implemen- tation of the model, we extend previous work in several directions. The dependence of the relaxation modulus with the slip link density and the slip link stiffness is reported. Then the nonlinear rheolog- ical properties of the model, for a particular set of parameters, are explored. Finally, we introduce excluded volume interactions in a mean field such as manner in order to describe inhomogeneous systems, and we apply this description to a simple nanocomposite model. With this extension, the slip link model appears as a simple and generic model of a polymer melt, that can be used as an alternative to molecular dynamics for coarse grained simulations of complex polymeric systems

Carbon fluxes in coral reefs. II. Eulerian study of inorganic carbon dynamics and measurement of air-sea CO₂ exchanges

Air-sea CO2 exchanges and the partial pressure of CO2 were measured in surface water overlying 2 coral reefs: Moorea (French Polynesia, austral winter, August 1992), where coral diversity and surface cover are low, and Yonge Reef (Great Barrier Reef, austral summer, December 1993), where coral diversity and cover are comparatively higher. A procedure is proposed to estimate the potential CO2 exchange with the atmosphere by taking into account both the saturation level of oceanic seawater and the equilibration process occurring after water leaves the reef. It is shown that both sites were net sources of CO2 to the atmosphere as a result of the effect of calcification on the dynamics of the inorganic carbon system. The potential global CO2 evasion from the ocean to the atmosphere is about 4 times higher at Yonge Reef than at Moorea. It is also demonstrated that, at both sites, the major exchange of CO2 from sea to air occurs as seawater returns to chemical equilibrium after it has crossed and left the reef. The dynamics of inorganic carbon were studied using the so-called homogeneous buffer factor [beta = dln(pCO(2))/dln(DIC)] (where pCO(2) is the CO2 partial pressure in surface water and DIC is dissolved inorganic carbon), which gave estimates that approximately 80% of the change in inorganic carbon was related to photosynthesis and respiration. This approach showed that the calcification rate was proportional to the net organic production during the day and to the respiration rate at night

Investigation of Advanced Processed Single-Crystal Turbine Blade Alloys

This investigation studied the influence of thermal processing and microstructure on the mechanical properties of the single-crystal, nickel-based superalloys PWA 1482 and PWA 1484. The objective of the program was to develop an improved single-crystal turbine blade alloy that is specifically tailored for use in hydrogen fueled rocket engine turbopumps. High-gradient casting, hot isostatic pressing (HIP), and alternate heat treatment (HT) processing parameters were developed to produce pore-free, eutectic-free microstructures with different (gamma)' precipitate morphologies. Test materials were cast in high thermal gradient solidification (greater than 30 C/cm (137 F/in.)) casting furnaces for reduced dendrite arm spacing, improved chemical homogeneity, and reduced interdendritic pore size. The HIP processing was conducted in 40 cm (15.7 in.) diameter production furnaces using a set of parameters selected from a trial matrix study. Metallography was conducted on test samples taken from each respective trial run to characterize the as-HIP microstructure. Post-HIP alternate HT processes were developed for each of the two alloys. The goal of the alternate HT processing was to fully solution the eutectic gamma/(gamma)' phase islands and to develop a series of modified (gamma)' morphologies for subsequent characterization testing. This was accomplished by slow cooling through the (gamma)' solvus at controlled rates to precipitate volume fractions of large (gamma)'. Post-solution alternate HT parameters were established for each alloy providing additional volume fractions of finer precipitates. Screening tests included tensile, high-cycle fatigue (HCF), smooth and notched low-cycle fatigue (LCF), creep, and fatigue crack growth evaluations performed in air and high pressure (34.5 MPa (5 ksi)) hydrogen at room and elevated temperature. Under the most severe embrittling conditions (HCF and smooth and notched LCF in 34.5 MPa (5 ksi) hydrogen at 20 C (68 F), screening test results showed increases in fatigue life typically on the order of 1OX, when compared to the current Space Shuttle Main Engine (SSME) Alternate Turbopump (AT) blade alloy (PWA 1480)

Spot-test identification and rapid quantitative sequential analysis of dipyrone

A qualitative spot-test and tandem quantitative analysis of dipyrone in the bulk drug and in pharmaceutical preparations is proposed. The formation of a reddish-violet color indicates a positive result. In sequence a quantitative procedure can be performed in the same flask. The quantitative results obtained were statistically compared with those obtained with the method indicated by the Brazilian Pharmacopoeia, using the Student's t and the F tests. Considering the concentration in a 100 µL aliquot, the qualitative visual limit of detection is about 5×10-6 g; instrumental LOD ≅ 1.4×10-4 mol L-1 ; LOQ ≅ 4.5×10-4 mol L-1.Um método spot-test qualitativo e seqüencialmente quantitativo é proposto para análise de dipirona em fármaco puro e em preparações farmacêuticas. A formação de coloração vermelho-violeta indica um resultado qualitativo positivo. Na seqüência, um procedimento quantitativo pode ser realizado no mesmo frasco. Os resultados quantitativos obtidos foram comparados estatisticamente com os resultados obtidos pelo método indicado pela Farmacopéia Brasileira, utilizando o teste t de Student e o teste F. Considerando a concentração em uma alíquota de 100 µL, o limite qualitativo visual de detecção foi de cerca 5×10-6 g; instrumentalmente o limite de detecção foi de LOD ≅ 1.4×10-4 mol L-1 e o limite de quantificação de LOQ ≅ 4.5×10-4 mol L-1.4146Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Proposta de plano de manejo orgânico na transição agroecológica para produção orgânica de hortaliças em uma pequena propriedade em Encantado - Vale do Taquari/RS.

Made available in DSpace on 2015-02-12T09:14:48Z (GMT). No. of bitstreams: 1 164.pdf: 487343 bytes, checksum: 88fb7d91a9f945fd0f295f187d732a44 (MD5) Previous issue date: 2014-11-19201

Uso Da Casca Do Abacate (persea Americana)na Formulação De Chá: Um Produto Funcional Contendo Compostos Fenólicos E Atividade Antioxidante

The peels of avocados, like other fruit peels, are commonly discarded, not knowing their potential use. In order to reuse avocado peel, the chemical and mineral compositions, total phenolic and flavonoid contents as well as antioxidant activities have been investigated by DPPH (1,1-diphenyl-2- picrylhydrazyl) and FRAP(ferric-reducing antioxidant power) methods in in natura and dehydrated avocado peel. Dehydrated avocado-peel tea was manufactured and the antioxidant activity was evaluated, as well as their flavonoid and phenolic compound contents, and compared with other teas marketed. Avocado peel, especially dried avocado peel, contains major phenolic compounds (10,848.27 ± 162.34 mg GAE kg-1) and flavonoids (1,360.34 ± 188.65 mg EQ kg-1). The avocado-peel tea showed antioxidant activity by DPPH (1,954.24 ± 87.92 e 2518.27 ± 192.59 mg TE L-1) and phenolic and flavonoids contents highest than apple tea. The avocado-peel tea showed good antioxidant activity and had good acceptability by sensory analysis as a promising product. © 2016, Eduem - Editora da Universidade Estadual de Maringa. All rights reserved.381232

Natural vs. Anthropic influence on the multidecadal shoreline changes of mediterranean urban beaches: Lessons from the Gulf of Cagliari (Sardinia)

Urban Mediterranean beaches are often characterized by a fragile and unstable equilibrium that can be easily altered by ongoing climate change and by the increase in human pressure. This may pose serious threats to the survival of beach systems that cannot accommodate these modifications. In this paper, the spatio-temporal shift of the shoreline was investigated along two urban beaches in the Gulf of Cagliari (Poetto and Giorgino; southern Sardinia, western Mediterranean Sea) across a time frame of 62 years (1954–2016). The Digital Shoreline Analysis System (DSAS) ArcGIS™ extension was used to extract different statistical parameters which allowed us to quantify the erosion and accretion rates. These data were further examined in relation to a number of anthropic and natural forcings in order to disentangle the factors controlling shoreline evolution. Eight sectors with interchanging net erosive and accretion trends were identified along the Poetto and Giorgino beaches. In six decades, some sectors of the two study sites appeared to have undergone great shoreline modification as a result of the intense anthropogenic activities impacting these coastal areas. The westernmost portions of both beaches were found to be the most vulnerable to erosion processes; such conditions were likely controlled by the interplaying of local hydrodynamics and by the intense coastal development which affected these sectors. The highest retreat rates (mean end point rate (EPR) = −0.51/year) were recorded in the western limit of Giorgino beach. Along the western limit of Poetto beach, EPR erosion rates (mean EPR = −2.92/year) considerably increased in the years after the artificial beach nourishment carried out in 2002, suggesting that the majority of the nourished material was lost offshore or partly redistributed along the beach. Coastal structures, urban development, river catchment modification, industrial and port activities, beach cleaning and touristic and recreational activities have been identified as the ongoing causes of coastal alteration. If these factors remain constant, under projected climate change scenarios, these beaches are at risk of further increased flooding and erosion. In this context, the application of DSAS appeared as an essential tool, supporting a monitoring system able to provide understanding and, potentially, predictions of the short-to long-term evolution of these beach systems