Density, Refractive Index, Apparent Specific Volume, and Electrical Conductivity of Aqueous Solutions of Poly(ethylene glycol) 1500 at Different Temperatures

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Apparent specific volumes and tastes of cyclamates, other sulfamates, saccharins and acesulfame sweeteners

Measurements of apparent specific volume (ASV) for a series of alternative sweeteners (cyclamates, sulfamates, saccharins, acesulfames and anilinomethanesulfonates) have been made. Taste data have been obtained for many of the new compounds unless the toxicity of the associated metals precluded this. Apparent molar volume (AMV), isentropic specific (IASC) and isentropic molar (IAMC) compressibilities were also measured. Sixteen metallic cyclamates cyc-C6H11NHSO3M and two phenylsulfamates ArNHSO3Na, namely 3.5-dimethyl- and 3,4-dimethoxyphenylsulfamates have been examined. When the ASVs for these are combined with those for 15 aliphatic, aromatic and alicyclic sulfamates from a previous study, many of the values are seen to fall into the region that was previously identified as being the "sweet area", i.e. the ASVs lay between similar to0.5 and similar to0.7 (a few sweet compounds fall below this range and it is suggested that it could be extended slightly to accommodate these). Interestingly, the anilinomethanesulfonates, ArNHCH2SO3Na (Ar = C6H5-, 3-MeC6H4- and 3-ClC6H4-) lie clearly in the sweet region but only one of them shows slight sweetness showing that the molecular structural change made (compared with the 'parent' sulfamate-NHSO3-) cannot be accommodated at the receptor site. (C) 2003 Elsevier Ltd. All rights reserved.

Metodologia para determinação de volume de detenção em pequenas bacias urbanas: o caso do córrego Wenzel, Rio Claro/SP

With the accelerated urbanization process of Brazil from the 50s, there was a disorderly occupation of spaces and consequent soil sealing. Unlike this growth, the support capacity of urban environments has not evolved in the same way, generating negative environmental impacts to the citizens. Among these impacts are the effects of flooding. In order to minimize the negative effects of extreme precipitation over cities, the government invests in corrective measures, like compensatory techniques on urban drainage, which have as a basic principle the retention and infiltration of the rainfall, dampening the peak flow and runoff. An example of applying these techniques in urban areas are the detention basins, commonly called large pools. The hydraulic design of these structures is dependent of complex data and variables, and projects involving small areas generally use simplified methods for defining the reservoirs volume of the storage (Tassi, 2005). One of these methods is presented in this study, which relates to the percentage of soil sealing to the specific storage volume (m³/ha) in combination by applying the hydrological model of the Rational Method and analyzing regional rainfall and soil occupation over the basin. Within this context, the basin of the Wenzel stream, which is located amidst the urban area of Rio Claro/SP, also presents the problems related to human occupation in its valley. Thus, by the method presented has been adjusted a curve correlating the percentage of impermeable area and the specific volume of a detention basin. For the current situation of Wenzel Basin with 82% of impermeable area, and return period of 10 years, the specific volume is 262.1 m³/ha. The presented method is consistent with the results of other studies in the area, and the expression obtained allows estimating the volume of storage required to match hydrograph pre and post-occupancy. It presents itself as a useful tool in the planning stage of...

Structural transitions in (La,Ln)2CuO4 and La2(Cu,Ni)O4 systems

Solid solutions of the formula La2−xLnxCuO4 (Ln = Pr, Nd) possess the orthorhombic structure of La2CuO4 for small values of x and transform to the tetragonal Nd2CuO4 structure at a critical value of x. At the critical composition, there is an abrupt change in specific volume as well as the Image ratio. The material exhibits temperature-independent electrical resistivity below the critical value x and semiconducting behaviour above it. The specific volume and Image ratio smoothly decrease with increase in x in the La2Cu1−xNixO4 system, although the solid solution possess the tetragonal K2NiF4 structure when x>0.1. Compositions with x>0.1 exhibit a gradual semiconductor metal transition similar to that of La2NiO4, the transition temperature decreasing with increasing

Generalized Equation for Compression Ratio

For highly compressible normally consolidated saturated soil the compression index, Cc, is not constant over the entire pressure range. However, the ratio of the compression index and the initial specific volume, generally known as the compression ratio, appears to be constant. Thus settlement seems to depend on Cc/(1 + e) rather than Cc alone. Using the theoretical zero air voids line and the generalized compressibility equation for normally consolidated saturated soils, a generalized and simple equation for compression has been derived in the form: C'c = 0.003wL.

Nucleosome core histone complex isolated gently and rapidly in 2 M NaCl is octameric

A relatively stable specific complex of the chromatin core histones H2A, H2B, H3, and H4 has been obtained in 2 M NaCl/25 mM sodium phosphate buffer, pH 7.0. The histone core complex has an apparent specific volume of 0.73 ml/g. Its sedimentation coefficient was dependent on rotor speed (angular velocity, omega) and attained different stable values at low and high rotor speeds. The drop in sedimentation coefficient occurred sharply between omega 2 values of about 9 x 10(6) and 1.1 x 10(7) (radians/sec)2. The s020,w corresponding to zero angular velocity (1 atmosphere pressure) was 6.6 S +/- (SEM) 0.1 S. At high rotor speeds the value decreased to 3.8 S +/- 0.1 S. The core complex has a diffusion coefficient, D20,w, of 5.4 x 10(-7) cm2/sec and a molecular weight of 108,000 +/- (SD) 2500.

Comparison of CO2 and steam in transcritical Rankine cycles for concentrated solar power

High temperature, high pressure transcritical condensing CO2 cycle (TC-CO2) is compared with transcritical steam (TC-steam) cycle. Performance indicators such as thermal efficiency, volumetric flow rates and entropy generation are used to analyze the power cycle wherein, irreversibilities in turbo-machinery and heat exchangers are taken into account. Although, both cycles yield comparable thermal efficiencies under identical operating conditions, TC-CO2 plant is significantly compact compared to a TC-steam plant. Large specific volume of steam is responsible for a bulky system. It is also found that the performance of a TC-CO2 cycle is less sensitive to source temperature variations, which is an important requirement of a solar thermal system. In addition, issues like wet expansion in turbine and vacuum in condenser are absent in case of a TC-CO2 cycle. External heat addition to working fluid is assumed to take place through a heat transfer fluid (HTF) which receives heat from a solar receiver. A TC-CO2 system receives heat though a single HTF loop, whereas, for TC-steam cycle two HTF loops in series are proposed to avoid high temperature differential between the steam and HTF. (C) 2013 P. Garg. Published by Elsevier Ltd.

Part I: Latent heat of vaporization of n-decane. Part II: Heat and mass transfer from a cylinder placed in a turbulent air stream - Sherwood and Frössling numbers as a function of free stream turbulence level and Reynolds number

Part I

The latent heat of vaporization of n-decane is measured calorimetrically at temperatures between 160° and 340°F. The internal energy change upon vaporization, and the specific volume of the vapor at its dew point are calculated from these data and are included in this work. The measurements are in excellent agreement with available data at 77° and also at 345°F, and are presented in graphical and tabular form.

Part II

Simultaneous material and energy transport from a one-inch adiabatic porous cylinder is studied as a function of free stream Reynolds Number and turbulence level. Experimental data is presented for Reynolds Numbers between 1600 and 15,000 based on the cylinder diameter, and for apparent turbulence levels between 1.3 and 25.0 per cent. n-heptane and n-octane are the evaporating fluids used in this investigation.

Gross Sherwood Numbers are calculated from the data and are in substantial agreement with existing correlations of the results of other workers. The Sherwood Numbers, characterizing mass transfer rates, increase approximately as the 0.55 power of the Reynolds Number. At a free stream Reynolds Number of 3700 the Sherwood Number showed a 40% increase as the apparent turbulence level of the free stream was raised from 1.3 to 25 per cent.

Within the uncertainties involved in the diffusion coefficients used for n-heptane and n-octane, the Sherwood Numbers are comparable for both materials. A dimensionless Frössling Number is computed which characterizes either heat or mass transfer rates for cylinders on a comparable basis. The calculated Frössling Numbers based on mass transfer measurements are in substantial agreement with Frössling Numbers calculated from the data of other workers in heat transfer.

Diet shifts of juvenile red snapper (Lutjanus campechanus) with changes in habitat and fish size

We examined the diets and habitat shift of juvenile red snapper (Lutjanus campechanus) in the northeast Gulf of Mexico. Fish were collected from open sand-mud habitat (little to no relief), and artificial reef habitat (1-m3 concrete or PVC blocks), from June 1993 through December 1994. In 1994, fish settled over open habitat from June to September, as shown by trawl collections, then began shifting to reef habitat — a shift that was almost completed by December as observed by SCUBA visual surveys. Stomachs were examined from 1639 red snapper that ranged in size from 18.0 to 280.0 mm SL. Of these, 850 fish had empty stomachs, and 346 fish from open habitat and 443 fish from reef habitat contained prey. Prey were identified to the lowest possible taxon and quantified by volumetric measurement. Specific volume of particular prey taxa were calculated by dividing prey volume by individual fish weight. Red snapper shifted diets with increasing size. Small red snapper (<60 mm SL) fed mostly on chaetognaths, copepods, shrimp, and squid. Large red snapper (60–280 mm SL) shifted feeding to fish prey, greater amounts of squid and crabs, and continued feeding on shrimp. We compared red snapper diets for overlapping size classes (70–160 mm SL) of fish that were collected from both habitats (Bray-Curtis dissimilarity index and multidimensional scaling analysis). Red snapper diets separated by habitat type rather than fish size for the size ranges that overlapped habitats. These diet shifts were attributed to feeding more on reef prey than on open-water prey. Thus, the shift in habitat shown by juvenile red snapper was reflected in their diet and suggested differential habitat values based not just on predation refuge but food resources as well.

LDPE/carbon black conductive composites: Influence of radiation crosslinking on PTC and NTC properties

The electrical resistivity of low-density polyethylene/carbon black composites irradiated by Co-60 gamma-rays was investigated as a function of temperature. The experimental results obtained by scanning electron microscopy, solvent extraction techniques, and pressure-specific volume-temperature analysis techniques showed that the positive temperature coefficient (PTC) and negative temperature coefficient (NTC) effects of the composites were influenced by the irradiation dose, network forming (gel), and soluble fractions (Sol). The NTC effect was effectively eliminated when the radiation dose reached 400 kGy. The results showed that the elimination of the NTC effect was related to the difference in the thermal expansion of the gel and Sol regions. The thermal expansion of the sol played an important role in both increasing the PTC intensity and decreasing the NTC intensity at 400 kGy.

Studies on the fusion heat of poly(ether ether ketone ketone)-poly(ether biphenyl ether ketone ketone) copolymers

On the basis of DSC measurements, the Delta H-f(0) values of the fusion heat for PEEKK-PEBEKK copolymers with various biphenyl contents were obtained by using thermodynamics statistical theory proposed by Flory and graphical method of the specific volume-fusion heat. The results reveal that Delta H-f(0) values determined by these two methods for PEEKK-PEBEKK copolymers with various biphenyl content are nearly the same, and that Delta H-f(0) values are closely dependent on biphenyl content. Delta H-f(0) value is minimum at n(B)=0.35.

CRYSTAL-STRUCTURE AND THERMODYNAMIC PARAMETERS OF NYLON-1010

WAXD, SAXS, FTIR, DSC and density techniques have been used to investigate the crystal structure, crystal density rho(c), amorphous density rho(a), equilibrium heat of fusion DELTAH(m)degrees and equilibrium melting temperature T(m)degrees. By extrapolating the straight lines in the FTIR absorbance against density plot to zero intensity, rho(c) and rho(a) were estimated to be 1.098 and 1.003 g/cm3 respectively. The rho(c) obtained was too low in value. From X-ray diffraction patterns of uniaxially oriented fibres, the crystal structure of Nylon-1010 was determined. The Nylon-1010 crystallized in the triclinic system, with lattice dimensions: a = 4.9 angstrom, b = 5.4 angstrom, c = 27.8 angstrom, alpha = 49-degrees, beta = 77-degrees, gamma = 63.5-degrees. The unit cell contained one monomeric unit, the space group was P1BAR, and the correct value of rho(c) was 1.135 g/cm3. The degree of crystallinity of the polymer was determined as about 60% (at RT) using Ruland's method. SAXS has been used to investigate the crystalline lamellar thickness, long period, transition zone, the specific inner surface and the electron density difference between the crystalline and amorphous regions for Nylon-1010. The analysis of data was based upon a one-dimensional electron-density correlation function. DELTAH(m)degrees was estimated to be 244.0 J/g by extrapolation of DELTAH(m)degrees in the plot of heat of fusion against specific volume of semicrystalline specimens to the completely crystalline condition (V(sp)c = 1/rho(c)). Owing to the ease of recrystallization of melt-crystallized Nylon-1010 specimens, the well-known Hoffman's T(m)-T(c) method failed in determining T(m)degrees and a Kamide double extrapolation method was adopted. The T(m)degrees value so obtained was 487 K.

MOLECULAR-WEIGHT DEPENDENCE OF THE GLASS-TRANSITION OF CYCLIC POLYSTYRENE

The glass transition temperature (T(g)) of cyclic polystyrene was measured by differential scanning calorimetry. There was a marked difference in the glass transition behaviour between cyclic and linear polystyrene. In the low molecular weight region (M(n) < 5 x 10(3)), the T(g) of the cyclic polystyrene increased with decreasing M(n), contrary to that of linear polystyrene. With M(n) higher than 5 x 10(3), the T(g) of cyclic polystyrene increased with increasing M(n). The T(g) of cyclic and linear polystyrene approached the same constant value when the M(n) was high enough (M(n) > 10(5)). Combining the results of specific volume, it is believed that the variation of T(g) with molecular weight does not depend only on free volume effects but that configurational entropy is also an important factor.

Characterisation and application of fruit by-products as novel ingredients in gluten-free products

The physicochemical and nutritional properties of two fruit by-products were initially studied. Apple pomace (AP) contained a high level of fibre and pectin. The isolated AP pectin had a high level of methylation which developed viscous pastes. Orange pomace also had high levels of fibre and pectin, and it was an abundant source of minerals such as potassium and magnesium. Due to the fibrous properties of orange pomace flour, proofing and water addition were studied in a bread formulation. When added at levels greater than 6%, the loaf volume decreased. An optimised formulation and proofing time was derived using the optimisation tool; these consisted of 5.5% orange pomace, 94.6% water inclusion and with 49 minutes proofing. These optimised parameters doubled the total dietary fibre content of the bread compared to the original control. Pasting results showed how orange pomace inclusions reduced the final viscosity of the batter, reducing the occurrence of starch gelatinisation. Rheological properties i.e. the storage modulus (G') and complex modulus (G*) increased in the orange pomace batter compared to the control batter. This demonstrates how the orange pomace as an ingredient improved the robustness of the formulation. Sensory panellists scored the orange pomace bread comparably to the control bread. Milled apple pomace was studied as a potential novel ingredient in an extruded snack. Parameters studied included apple pomace addition, die head temperature and screw speed. As screw speed increased the favourable extrudate characteristics such as radical expansion ratio, porosity and specific volume decreased. The inclusion of apple pomace had a negative effect on extrudate characteristics at levels greater than 8% addition. Including apple pomace reduced the hardness and increased the crispiness of the snack. The optimised and validated formulation and extrusion process contained the following parameters: 7.7% apple pomace, 150°C die head temperature and a screw speed of 69 rpm.

An elasto-plastic critical state framework for unsaturated soil.

Data from a series of controlled suction triaxial tests on samples of compacted speswhite kaolin were used in the development of an elasto–plastic critical state framework for unsaturated soil. The framework is defined in terms of four state variables: mean net stress, deviator stress, suction and specific volume. Included within the proposed framework are an isotropic normal compression hyperline, a critical state hyperline and a state boundary hypersurface. For states that lie inside the state boundary hypersurface the soil behaviour is assumed to be elastic, with movement over the state boundary hypersurface corresponding to expansion of a yield surface in stress space. The pattern of swelling and collapse observed during wetting, the elastic–plastic compression behaviour during isotropic loading and the increase of shear strength with suction were all related to the shape of the yield surface and the hardening law defined by the form of the state boundary. By assuming that constant–suction cross–sections of the yield surface were elliptical it was possible to predict test paths for different types of triaxial shear test that showed good agreement with observed behaviour. The development of shear strain was also predicted with reasonable success, by assuming an associated flow rule.