Specific Volume Changes Research Articles

Analysis of Polyurethane Foaming Flow

Polyurethane foam has many excellent features such as thermal insulation and shock and sound absorption, and is used for refrigerator parts, car parts and many other products. Simulating the precise behavior of polyurethane foaming is very effective for reducing the development period and production costs. Through experiments and foaming flow simulations, in this study it was found that for a given foaming condition, the maximum flow length of polyurethane foaming increases in proportion to the foaming weight, while the specific volume change with time is constant for all foaming weights. A foaming flow simulation was then developed by applying density and viscosity formulated as functions of elapsed polyurethane foaming time to a 3D flow simulation program. This foaming flow simulation allows precise determination of the foaming flow length, and the tendency and maximum pressure of foaming flow.

Volume, expansivity and isothermal compressibility changes associated with temperature and pressure unfolding of staphylococcal nuclease

We have characterized the temperature- and pressure-induced unfolding of staphylococcal nuclease (Snase) using high precision densitometric measurements. The changes in the apparent specific volume, expansion coefficient and isothermal compressibility were determined by these measurements. To our knowledge, these are the first measurements of the volume and isothermal compressibility changes of a protein undergoing pressure-induced unfolding. In order to aid in interpreting the temperature and pressure dependence of the apparent specific volume of Snase, we have also carried out differential scanning calorimetry under the solution conditions which are used for the volumetric studies. We have seen that large compensating volume and compressibility effects accompany the temperature and pressure-induced protein unfolding. Measurements of the apparent specific volume and thermal expansion coefficient of Snase at ambient pressure indicate the formation of a pre-transitional, molten globule type of intermediate structure about 10°C below the actual unfolding temperature of the protein. Compared to the folded state, the apparent specific volume of the unfolded protein is about 0.3-0.5 % smaller. In addition, we investigated the pressure dependence of the apparent specific volume of Snase at a number of different temperatures. At 45°C we calculate a decrease in apparent specific volume due to pressure-induced unfolding of −3.3 10−3 cm3 g−1 or −55 cm3 mol−1. The threefold increase in compressibility between 40 and 70 MPa reflects a transition to a partially unfolded state, which is consistent with our results obtained for the radius of gyration of the pressure-denatured state of Snase. At the lower temperature of 35°C, a significant increase in compressibility around 30 MPa is indicative of the formation of a pressure-induced molten globule-like intermediate. Changes in the apparent volume, expansion coefficient and isothermal compressibility are discussed in terms of instrinsic, hydrational and thermal contributions accompanying the unfolding transition.

Interaction of the antimicrobial peptide gramicidin S with dimyristoyl–phosphatidylcholine bilayer membranes: a densitometry and sound velocimetry study

We determined changes in the volume and adiabatic compressibility of large multi- and unilamellar vesicles composed of dimyristoylphosphatidylcholine containing various concentrations of the antimicrobial peptide gramicidin S (GS) by applying densitometry and sound velocimetry. Gramicidin S incorporation was found to progressively decrease the phase transition temperature of DMPC vesicles as well as to decrease the degree of cooperativity of the main phase transition and to increase the volume compressibility of the vesicles. GS probably enhanced thermal fluctuations at the region of main phase transition and provide more freedom of rotational movement for the phospholipid hydrocarbon chains. The ability of GS to increase the membrane compressibility and to decrease the phase transition temperature is evidence for regions of distorted membrane structure around incorporated gramicidin S molecules. At relatively high GS concentration (10 mol%), more significant changes of specific volume and compressibility appear. This might suggest changes in the integrity of the lipid bilayer upon interaction with high concentrations of GS.

Differential Scanning Calorimetry and Hydrodynamic Study of Bacterial Viruses. About possible heat effects in hermetically closed calorimetric vessels with free volume above the liquid

The phase transitions occurring in aqueous solutions of macromolecules and their complex structures (like order-disorder transitions in proteins or nucleic acids solutions) are usually accompanied by small changes in their specific partial volumes. If the quantity of these substances in the closed calorimetric vessels is relatively large (few mg) and if the phase transition is accompanied by a high change of specific partial volume (like in solution of bacteriophages),it is possible to detect some imaginary heat effects in the DSC calorimeters which have closed (sealed) vessels with free volume above the liquid.

Callosal Atrophy Correlates with Temporal Lobe Volume and Mental Status in Alzheimer's Disease

Recent studies have reported significant atrophy of the corpus callosum (CC) in Alzheimer's Disease (AD). However, it is currently unknown whether CC atrophy is associated with specific cortical volume changes in AD. Moreover, possible atrophy in extra-callosal commissures has not been examined to date. The purpose of the present study was to quantify atrophy in two cerebral commissures [the CC and the anterior commissure (AC)], to correlate this measure with cognitive status, and to relate commissural size to independent measures of temporal lobe volume in AD patients. A sample of AD patients and of age- and education-matched normal control subjects (NCs) underwent MRI and a cognitive test battery including the Dementia Rating Scale and Mini Mental State examination. Mid-sagittal regional areas within CC and AC were measured along with superior, middle and inferior temporal lobes volumes. Alzheimer's Disease patients had significantly smaller callosa than did NCs. The callosal regions most affected in AD included the midbody, isthmus and genu. The isthmus and midbody areas of the CC were positively correlated with cognitive performance and with superior temporal lobe volume in AD patients. The mid-sagittal area of the AC and the superior temporal volumes did not differ between AD patients and NCs. The study demonstrated that the regional morphology of the CC correlates with current cognitive status and temporal lobe atrophy in AD. As well, the lack of difference for the AC suggests that commissural atrophy in AD is regionally specific.

Macroscopic pressure–volume–temperature properties versus free-volume characteristics of isotropic pressure-densified amorphous polymer glasses

We made a series of isotropic pressure-densified (0–200 MPa) amorphous homopolymer [atactic polystyrene (a-PS)] and copolymer [poly(styrene-co-acrylonitrile) (SAN) and poly(styreneco-maleic anhydride) (SMA)] glasses and studied their macroscopic pressure–volume–temperature (PVT) properties vs their free-volume characteristics from the Simha–Somcynsky equation-of-state (EOS) theory and from positron annihilation lifetime spectroscopy (PALS). The glass densities lie in the range of 1.0403–1.0535 g/cm3 (PS), 1.0573–1.0759 g/cm3 (SAN), and 1.0989–1.1196 g/cm3 (SMA). With increasing formation pressure, all pressure-densified glasses exhibit decreasing volume and free-volume characteristics such that the changes in specific volume (1.26%–1.85%) are <ortho-positronium (o-Ps) lifetime τ3 (5.5%–9.1%) <free-volume hole size V(τ3) (10.3%–17.1%) <free-volume fraction h (25.1%–30.5%). We find, furthermore, that the o-Ps formation probability I3 is independent of formation pressure. Likewise, the glasses’ thermal expansivity α0 remains constant. There is a one-to-one correlation of τ3 and of I3 when calculated from POSITRONFIT and the maximum entropy lifetime (MELT) program. The full width at half maximum of free-volume distributions determined from PALS data and MELT does not change with formation pressure within established limits of uncertainty. Neither h vs V(τ3) nor h vs bulk modulus K, calculated from the Tait EOS of the glasses, show unique relations that are common to all the studied glasses. On the other hand, K vs V(τ3) gives a universal curve for all pressure-densified glasses from this study and from our previous study on PMMA: K=8.190–4.479×10−2V(τ3) (r2=0.92). Moreover, three more polymers from the literature are well described by this curve. The bulk moduli increase by up to 11.5% (PMMA), 7.6% (PS), 11.2% (SAN), and 10.2% (SMA) and they follow the order PS<SMA<SAN<PMMA.

Thermal residual stresses in freely quenched slabs of semicrystalline polymers: Simulation and experiment

Thermal residual stresses in freely quenched semicrystalline polymer slabs were calculated based upon the modifications of the Indenbom theory for inorganic glasses and linear viscoelasticity. These modifications were introduced to include the influences of crystallization on mechanical and physical properties of the polymer during free quenching. The nonisothermal crystallization kinetic model due to Nakamura et al. was employed to calculate the variations of crystallinity. In the case of the Indenbom theory, a polymer during crystallization was assumed to undergo an abrupt transition from an ideal plastic state to an elastic state upon the completion of crystallization. In the case of linear viscoelasticity, the Morland–Lee constitutive equation was utilized with the effect of crystallization on the time–temperature dependent shear relaxation modulus taken into account. The Spencer–Gilmore P − V − T equation of state was employed to model the specific volume changes during crystallization and used to determine the local thermal loading that results from inhomogeneous densifications and gives rise to the thermal residual stresses in the slabs. Based on the above theoretical work, the thermoelastic and thermoviscoelastic models were developed, and the corresponding numerical simulation schemes were formulated to calculate the residual thermal stresses in freely quenched slabs of semicrystalline polymers. Free quenching experiments were carried out under various cooling conditions using isotactic polypropylene. The layer removal method due to Treuting and Read was utilized to measure the residual thermal stresses. The simulated and measured results were then compared. The effects of quenching conditions and crystallization on the development of residual thermal stresses were evaluated. It has been found that both coolant types and coolant temperature have significant effects on residual thermal stresses. In contrast, initial temperature of the polymer melt shows a slight influence only. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1404–1415, 2000

Thermal residual stresses in freely quenched slabs of semicrystalline polymers: Simulation and experiment

Thermal residual stresses in freely quenched semicrystalline polymer slabs were calculated based upon the modifications of the Indenbom theory for inorganic glasses and linear viscoelasticity. These modifications were introduced to include the influences of crystallization on mechanical and physical properties of the polymer during free quenching. The nonisothermal crystallization kinetic model due to Nakamura et al. was employed to calculate the variations of crystallinity. In the case of the Indenbom theory, a polymer during crystallization was assumed to undergo an abrupt transition from an ideal plastic state to an elastic state upon the completion of crystallization. In the case of linear viscoelasticity, the Morland–Lee constitutive equation was utilized with the effect of crystallization on the time–temperature dependent shear relaxation modulus taken into account. The Spencer–Gilmore P − V − T equation of state was employed to model the specific volume changes during crystallization and used to determine the local thermal loading that results from inhomogeneous densifications and gives rise to the thermal residual stresses in the slabs. Based on the above theoretical work, the thermoelastic and thermoviscoelastic models were developed, and the corresponding numerical simulation schemes were formulated to calculate the residual thermal stresses in freely quenched slabs of semicrystalline polymers. Free quenching experiments were carried out under various cooling conditions using isotactic polypropylene. The layer removal method due to Treuting and Read was utilized to measure the residual thermal stresses. The simulated and measured results were then compared. The effects of quenching conditions and crystallization on the development of residual thermal stresses were evaluated. It has been found that both coolant types and coolant temperature have significant effects on residual thermal stresses. In contrast, initial temperature of the polymer melt shows a slight influence only. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1404–1415, 2000

Decrepitation model for capacity loss during cycling of alloys in rechargeable electrochemical systems

Mechanisms that are involved in the loss of capacity upon the cycling of electrochemical cells are discussed. The inherent instability of the electrochemical interface and the resultant geometrical changes are characteristic of electrodes in which the reactant is a pure element. On the other hand, decrepitation can play an important role in the case of polyphase electrodes in which significant changes in specific volume occur. A simple one-dimensional model is presented that shows the mechanism and the important parameters that are involved in particle fracture. It predicts that decrepitation will lead to a terminal particle size, as is found experimentally.

Modified Tin(IV) Oxide (M/SnO2M=Cr, La, Pr, Nd, Sm, Gd) Catalysts for the Oxidation of Carbon Monoxide and Propane

Materials formed by the incorporation of rare earth cations (M=La, Pr, Nd, Sm, Gd) into tin(IV) oxide using coprecipitation methods show no significant enhancement of catalytic activity toward the oxidation of carbon monoxide or propane over that of tin(IV) oxide itself. For chromium-promoted tin(IV) oxide catalysts, the temperature by which complete conversion of carbon monoxide and propane occurs is dependent on both the Cr:Sn atom ratio in the catalyst and the preparative route by which the chromium is incorporated into the catalyst. As prepared all the materials are hydrous gels comprising very small (<10 nm) particles of tin(IV) oxide over which the modifying metal component appears to be dispersed uniformly. Chromium(VI) oxyanions of the types CrO42−, Cr2O72−, and Cr3O102− are sorbed on to the surface of the tin(IV) oxide particles in the freshly prepared material derived from aqueous CrO3 and tin(IV) oxide gel. Prior to calcination the materials are microporous, but significant changes in specific surface area, pore volume, and pore size occur at temperature >673 K. Powder X-ray diffraction and electron microscopy confirm the formation of Cr2O3 on calcination at 1273 K.

Rheological and baking properties of cowpea and wheat flour blends

Effect of blending 50 to 250 g kg−1 cowpea flour in wheat flour on rheological, baking and sensory characteristics of bread, chapati, cookies and muffins was studied. Farinograph water absorption, dough development time, mixing tolerance index and dough stability increased significantly with increased amount of cowpea flour. Incorporation of cowpea flour lowered gelatinisation time and peak viscosity. Loaf volume and overall acceptability scores of bread were reduced significantly beyond 150 g kg−1 incorporation of cowpea flour. There were significant changes in specific volume and overall acceptability scores of muffins, registering an initial improvement up to 50 g kg−1 and a significant decline thereafter. © 1999 Society of Chemical Industry

Shifts in thermal expansivity with Fe content for solid solutions of MgSiO3-FeSiO3with the perovskite structure

This study presents evidence that for a solid solution of MgxFe x-1 SiO 3 perovskite, the shift in volume thermal expansivity, α, is small as the index χ is changed. According to data obtained theoretically by Hama and Suito (1998), α decreases by 0.3-0.4% as χ changes from 1 to 0.9 in a temperature range of 1900 K. Furthermore, the relative shift in α for Fe substitution is -0.4% under lower mantle conditions. Hama and Suito used the Vinet equation of state to calculate thermoelastic properties. Using a thermodynamic approach applied to the properties of a Debye solid, the data show that the relative shift in a is less than the relative change in specific volume, and, as χ changes from 1 to 0.9, V increases by 0.6% and a decreases by 0.4%.

Clathrate eustasy: Methane hydrate melting as a mechanism for geologically rapid sea-level fall

Research Article| October 01, 1999 Clathrate eustasy: Methane hydrate melting as a mechanism for geologically rapid sea-level fall John F. Bratton John F. Bratton 1U.S. Geological Survey, Woods Hole Field Center, 384 Woods Hole Road, Woods Hole, Massachusetts 02543-1598, USA, E-mail: jbratton@usgs.gov. Search for other works by this author on: GSW Google Scholar Geology (1999) 27 (10): 915–918. https://doi.org/10.1130/0091-7613(1999)027<0915:CEMHMA>2.3.CO;2 Article history first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation John F. Bratton; Clathrate eustasy: Methane hydrate melting as a mechanism for geologically rapid sea-level fall. Geology 1999;; 27 (10): 915–918. doi: https://doi.org/10.1130/0091-7613(1999)027<0915:CEMHMA>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Although submarine methane hydrates or clathrates have been highlighted as potential amplifiers of modern global climate change and associated glacio-eustatic sea-level rise, their potential role in sea-level fall has not been appreciated. Recent estimates of the total volume occupied by gas hydrates in marine sediments vary 20-fold, from 1.2 × 1014 to 2.4 × 1015 m3. Using a specific volume change on melting of −21%, dissociation of the current global inventory of hydrate would result in a decrease of submarine hydrate volume of 2.4 × 1013 to 5.0 × 1014 m3. Release of free gas bubbles present beneath hydrates would increase these volumes by 1.1–2.0 × 1013 m3. The combined effects of hydrate melting and subhydrate gas release would result conservatively in a global sea-level fall of 10–146 cm. Such a mechanism may offset some future sea-level rise associated with thermal expansion of the oceans. It could also explain anomalous sea-level drops during ice-free periods such as the early Eocene, the Cretaceous, and the Devonian. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Crumb Firming Kinetics of Wheat Breads with Anti-staling Additives

Single effects of and interactions among flour type, breadmaking process and anti-staling additives—monoglycerides, diacetyl tartaric ester of monoglycerides, sodium stearoyl lactylate, carboxymethylcellulose and hydroxypropylmethylcellulose andalpha-amylase—on crumb firmness during storage were estimated by fitting Avrami equations. Effects of additives were highly dependent on both the flour type and the breadmaking process used. Highly significant correlations between fresh bread crumb firmness and crumb firmness at any storage time were found. The Gluten Index of unfermented doughs was a good indicator for fresh bread crumb firmness and influenced firming kinetic parameters. Ionic surfactants, hydrocolloids andalpha-amylose increased the Gluten Index, and significantly interacted with both the flour type and the breadmaking process used. The Avrami exponent was correlated significantly with Amylogram parameters related to the formation of lipid–starch complex. Changes in specific volume by additive incorporation largely explained effects on crumb firming kinetics.

Progress toward a better understanding of signal generation in laser-excited photothermal spectrometry of homogeneous samples

This article examines some recent experiments and theories that have advanced our understanding of the physical effects following thermal relaxation of the excited state. Experiments which show that the temperature-dependent refractive index is composed of density and pure-thermal terms are discussed. The importance of the purely thermal term is that it allows ultra-fast pulsed excitation sources to be used in photothermal refraction spectroscopy. This opens up new areas of applications in ultra-fast measurement. The effect of and progress towards the elucidation of specific volume changes are reviewed. Finally, recent progress in understanding nonlinear optical absorption and its effect on the photothermal signal are summarized.

Characterization of network formation during crosslinking of nematic polyesters by PVT measurements

We have investigated the formation of nematic networks during thermally initiated crosslinking of liquid crystalline unsaturated copolyesters. Since it is not easy to follow the crosslinking over the whole range from zero to complete conversion of the double bonds by any other method, we studied the network formation by following the changes in specific volume of the polymer by PVT measurements. It is shown that in the range between 10 MPa and 30 MPa the rate of crosslinking is almost independent of pressure while an increase in temperature from 200°C to 240°C speeds up the reaction considerably. The increase in density of the polymer during crosslinking correlates with the decrease in double bonds detected by FTIR and the increase in gel content.

Effect of hydrogen bonding on the viscosity of alcohols at high pressures

Viscosities of several alcohols and vinyl acetate were measured with a rollingball viscometer. The viscosity measurements were performed at temperatures from 298 to 413 K and pressures up to 195 MPa with an accuracy of ±2%. The viscosities of the alcohols show a stronger dependence on temperature compared with that of substances that do not form hydrogen bonds. In addition, the secondary and tertiary alcohols show a viscosity-temperature dependence not in accordance with an Arrhenius law. An effect of pressure on the association of alcohol molecules resulting from hydrogen bonding was not resolved by means of viscosity data. Separation of the effect of association size upon increasing temperature from the viscosity caused by the change of specific volume was carried out using the Utracki free volume model.

Consideration of dilation in studying the dynamics of crushing zone development in an elastoplastic material with camouflet explosion of a concentrated charge

UDC 622.235 A solution was presented in [1] for the problem of shear crushing zone development in an elastoplastic material with camouftet explosion of a concentrated charge in a dynamic arrangement for the grinding zone and surrounding elastic material. Here it was assumed that the material was incompressible both in the grinding zone and in the elasticity zone. This is a first approximation based on the fact that elastic volumetric strains are small with deformation of rocks. In a more accurate consideration it is necessary to account for the effect of a change in specific volume caused by shear strains in the grinding zone (the dilation effect). The aim of the present work is a study of the effect of dilation on development of the grinding zone in an elastoplastic material with camouflet explosion of a concentrated charge. In addition comparison is carried out with an equilibrium static solution in order to explain the effect of dynamics in considering the effect of dilation on breaking process parameters. We consider the definition of the problem. Let an explosive charge be placed in a spherical cavity of radius a 0 in a boundless elastic material. In the initial instant of time as a result of the explosion the cavity is filled by gases with initial pressure P0. We shall consider that with expansion of the cavity radius a(t) gas pressure within it is determined by a Jones-Miller two-element adiabat [2] for a trotyl cylindrical charge p(a) = ~a ~ -3yl

Ab initio calculations of the pressure-induced structural phase transitionsfor four II-VI compounds

We report on pseudopotential calculations of the structural properties and pressure-induced solid-solid phase transitions for four II-VI compounds: ZnSe, ZnTe, CdSe, and CdTe. For each of these compounds, we fix the zinc-blende structure as the ambient pressure phase and consider the rocksalt, cinnabar, and Cmcm structures as candidates for the high-pressure phases. We calculate the transition pressures and the changes in specific volume for each compound. The pressure dependences of the structural parameters of the cinnabar and the Cmcm phases are determined. The Cmcm structure appears to be a common high-pressure phase for the II-VI and III-V semiconductors.

Molten globule of human alpha-lactalbumin: hydration, density, and compressibility of the interior.

Specific partial volume, partial compressibility, and sound absorption changes induced by the native-to-molten globule state (acid) transition of the human alpha-lactalbumin were measured by means of densitometric and ultrasonic techniques and interpreted in terms of the protein molecule phase transition and interphase water transfer. The molten globule is a highly hydrated state containing about 270 water molecules inside. Intrinsic mass density of the hydrated (swollen) interior of the protein molecule is 5% smaller and the intrinsic compressibility coefficient 2 times higher than those in the native molecule. The obtained intrinsic compressibility falls into the range of values characteristic of highly associated liquids. Water inside the molten globule interior occupies less volume and is less compressible than in solvent phase. The acoustic relaxation was found to increase indicating an appearance of pressure-dependent processes. The commonly used approach to the calculation of the volume fluctuations of protein molecules, based on the well-known relation between the volume fluctuations and compressibility, is of limited applicability to the highly hydrated molten globule state because a large, if not predominant, part of the fluctuations may be determined by the process of water exchange between the molten globule and bulk solvent.