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Various Properties (various + property)
Selected AbstractsSegmented Block Copolymers with Monodisperse Hard Segments: The Influence of H-Bonding on Various PropertiesMACROMOLECULAR MATERIALS & ENGINEERING, Issue 8 2009Gerard J. E. Biemond Abstract The properties of segmented-copolymer-based H-bonding and non-H-bonding crystallisable segments and poly(tetramethylene oxide) segments were studied. The crystallisable segments were monodisperse in length and the non-hydrogen-bonding segments were made of tetraamidepiperazineterephthalamide (TPTPT). The polymers were characterised by DSC, FT-IR, SAXS and DMTA. The mechanical properties were studied by tensile, compression set and tensile set measurements. The TPTPT segmented copolymers displayed low glass transition temperatures (Tg, ,70,°C), good low-temperature properties, moderate moduli (G,,,,10,33 MPa) and high melting temperatures (185,220,°C). However, as compared to H-bonded segments, both the modulus and the yield stress were relatively low. [source] Effect of Indium Intercalation on Various Properties of MoSe2 Single Crystals.CHEMINFORM, Issue 23 2007Aditya M. Vora Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Remote weather associated with South Pacific subtropical sea-level high propertiesINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 7 2004Richard Grotjahn Abstract The subtropical highs in sea-level pressure (SLP) are little studied and incompletely understood. In recent years, three groups of theories, i.e. tropical divergent circulations, subtropical Rossby wavetrains, and midlatitude frontal cyclone interactions, have been proposed for remote maintenance of these highs. The latter is presented here as a remote forcing of these highs for the first time in the reviewed literature. The focus of the study is upon illuminating associations between these mechanisms and the South Pacific subtropical high in SLP (SP high). Precipitation, outgoing longwave radiation, velocity potential, and divergent winds are used as proxy markers for the remote forcing mechanisms. The tools used include composites, one-point correlations, autocorrelations, cross-correlations, and cross-spectra. Observational evidence, in monthly and daily data, is examined that appears to support each mechanism. Associations seen in monthly data are better understood in daily data at various lags. Convection over Amazonia, coordinated with suppressed convection in the western tropical Pacific, leads to enhanced SLP on the tropical side of the high. Midlatitude weather systems are the strongest influence upon the maximum SLP and the SLP on the higher latitude side of the high. The western side is associated with both middle-and lower-latitude phenomena, such as the South Pacific convergence zone. Various properties of the high have a strong period around 45 days. Associations to the Madden,Julian oscillation and El Niño,southern oscillation are explored and are strong only for the tropical side of the SP high. Copyright © 2004 Royal Meteorological Society [source] Centrifugal Gel Casting: A Combined Process for the Consolidation of Homogenous and Reliable CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2010Saeed Maleksaeedi In this work, a combined process, called centrifugal gel casting (CGC), was proposed for the fabrication of homogenous and reliable monolithic and composite ceramics starting from submicrometer-sized powders. This method exploits the advantages of both conventional gel casting (GC) and centrifugal slip casting (CSC), while overcoming the limitations associated with the two methods. Via this process, a relatively low centrifugal force is applied to form a highly concentrated slurry in the mold cavity, which is then followed by in situ polymerization of slurry during gelation. In this work, concentrated alumina slurries with different solid contents from 45 to 65 vol% were consolidated by the three forming methods mentioned above. Various properties of green and fired products were measured and compared. Shorter processing time, lower centrifugal force, higher green strength, and minimal segregation are observed to be the characteristics of CGC in comparison with CSC. In situ elimination of bubbles with no need for degassing and the ability to remove heterogeneities, on top of high reliability and the potential to process higher viscosity slurries, are the main advantages of this method over the conventional GC. [source] Atomic Structures and Electrical Properties of ZnO Grain BoundariesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2007Yukio Sato Various properties of ceramics can be significantly influenced by the presence of grain boundaries. The influence on the properties is closely related to the grain-boundary atomic structures. As different grain boundaries have different atomic structure, different grain boundaries have different influence on the properties. It is difficult to examine the atomic structure and properties of individual grain boundaries in ceramics. In order to understand the atomic,structure,property relationships, well-defined single grain boundaries should be characterized. In the present paper, we review our recent results on the investigations of atomic structures and electrical properties of ZnO single grain boundaries. The relationships between the atomic structures and the electrical properties were investigated using ZnO bicrystals, whose grain-boundary orientation relationship and grain-boundary planes can be arbitrarily controlled. The discussion focuses on the microscopic origin of nonlinear current,voltage (I,V) characteristics across ZnO grain boundaries. High-resolution transmission electron microscopy (HRTEM) observations and lattice-statics calculations revealed the atomic structures of the undoped ZnO [0001] ,7 and ,49 grain boundaries, enabling a comparison between coincidence site lattice (CSL) boundaries with small and large periodicity. These grain boundaries contained the common structural units (SUs) featuring atoms with coordination numbers that are unusual in ZnO. The ,49 boundary was found to have characteristic arrangement of the SUs, where two kinds of the SUs are alternatively formed. It is considered that the characteristic arrangement was formed to effectively relax the local strain in the vicinity of the boundary. Such a relaxation of local strain is considered to be one of dominant factors to determine the SU arrangements along grain boundaries. I,V measurements of the undoped ZnO bicrystals showed linear I,V characteristics. Although the coordination and bond lengths of atoms in the grain boundaries differ from those in the bulk crystal, this does apparently not generate deep unoccupied states in the band gap. This indicates that atomic structures of undoped ZnO grain boundaries are not responsible for the nonlinear I,V characteristics of ZnO ceramics. On the other hand, the nonlinear I,V characteristic appeared when doping the boundaries with Pr. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) image of Pr-doped boundaries revealed that Pr segregates to specific atomic columns, substituting Zn at the boundary. However, the Pr itself was not the direct origin of the nonlinear I,V characteristics, as the Pr existed in the three-plus state and would not produce acceptor states in the boundary. First-principles calculations revealed that Pr doping instead promotes the formations of acceptor-like native defects, such as Zn vacancies. We believe that such acceptor-like native defects are microscopic origin of the nonlinear I,V characteristics. Investigations of various types of grain boundaries in the Pr and Co-codoped ZnO bicrystals indicated that the amounts of Pr segregation and the nonlinear I,V characteristics significantly depend on the grain-boundary orientation relationship. Larger amount of Pr segregation and, as a result, higher nonlinearity in I,V characteristics was obtained for incoherent boundaries. This indicates that Pr doping to incoherent boundaries is one of the guidelines to design the single grain boundaries with highly nonlinear I,V characteristics. Finally, a Pr and Co-codoped bicrystal with an incoherent boundary was fabricated to demonstrate a highly nonlinear I,V characteristic. This result indicates that ZnO single-grain-boundary varistors can be designed by controlling grain-boundary atomic structures and fabrication processes. Summarizing, our work firstly enabled us to gain a deeper understanding for the atomic structure of ZnO grain boundaries. Secondly, we obtained important insight into the origin of nonlinear I,V characteristics across the ZnO grain boundaries. And, finally, based on these results, we demonstrated the potential of this knowledge for designing and fabricating ZnO single-grain-boundary varistors. [source] Association between plasticized starch and polyesters: Processing and performances of injected biodegradable systemsPOLYMER ENGINEERING & SCIENCE, Issue 5 2001Luc Avérous Different formulations of wheat thermoplastic starch (TPS) have been processed with various plasticizer/starch ratios and moisture contents. The biodegradable polyesters tested are polycaprolactone (PCL), polyester amide (PEA), polybutylene succinate adipate (PBSA) and polybutylene adipate co terephtalate (PBAT). TPS and polyesters are melt blended in different proportions by extrusion and then injected to obtain dumbbell specimens. Various properties are evaluated such as the mechanical properties (tensile and impact tests), and the hydrophilic character with contact angle measurements. Additionally, uniaxial shrinkage is evaluated. Results show that the addition of polyester to TPS increases the dimensional post-injection stability. Blend modulus values are close to the results of the classical rule of mixture. Elongation at break, resilience values and SEM observations seem to give some indications about the compatibility between both polymeric systems. PBAT and PEA present better results than PCL and PBSA. Contact angle measurement show that we have a drastic increase of the hydrophobic character from 10% of polyester in the blend. The different combinations of TPS and polyesters give a wide range of mechanical behavior for compostable materials, to be developed in specific applications. [source] A framework for fusion methods and rendering techniques of multimodal volume dataCOMPUTER ANIMATION AND VIRTUAL WORLDS (PREV: JNL OF VISUALISATION & COMPUTER ANIMATION), Issue 2 2004Maria Ferre Abstract Many different direct volume rendering methods have been developed to visualize 3D scalar fields on uniform rectilinear grids. However, little work has been done on rendering simultaneously various properties of the same 3D region measured with different registration devices or at different instants of time. The demand for this type of visualization is rapidly increasing in scientific applications such as medicine in which the visual integration of multiple modalities allows a better comprehension of the anatomy and a perception of its relationships with activity. This paper presents different strategies of direct multimodal volume rendering (DMVR). It is restricted to voxel models with a known 3D rigid alignment transformation. The paper evaluates at which steps of the rendering pipeline the data fusion must be realized in order to accomplish the desired visual integration and to provide fast re-renders when some fusion parameters are modified. In addition, it analyses how existing monomodal visualization algorithms can be extended to multiple datasets and it compares their efficiency and their computational cost. Copyright © 2004 John Wiley & Sons, Ltd. [source] Assessing macroinvertebrate metrics for classifying acidified rivers across northern EuropeFRESHWATER BIOLOGY, Issue 7 2010S. JANNICKE MOE Summary 1. The effects of acidification on ecological status of rivers in Northern Europe must be assessed according to the EU Water Framework Directive (WFD). Several acidification metrics based on macroinvertebrates already exist in different countries, and the WFD requires that they be comparable across northern Europe. Thus, we compiled macroinvertebrate monitoring data from the U.K. (n = 191 samples), Norway (n = 740) and Sweden (n = 531) for analysis against pH. 2. We tested new and existing acidification metrics developed nationally and used within the Northern Geographical Intercalibration Group. The new metrics were based on the acidification sensitivity of selected species and are proposed as a first step towards a new common indicator for acidification for Northern Europe. 3. Metrics were assessed according to responsiveness to mean pH, degree of nonlinearity in response and consistency in responses across countries. We used flexible, nonparametric regression models to explore various properties of the pressure,response relationships. Metrics were also analysed with humic content (total organic carbon above/below 5 mg L,1) as a covariate. 4. Most metrics responded clearly to pH, with the following metrics explaining most of the variance: Acid Water Indicator Community, Number of ephemeropteran families, Medin's index, Multimetric Indicator of Stream Acidification and the new metric ,Proportion of sensitive Ephemeroptera'. 5. Most metrics were significantly higher in humic than in clear-water rivers, suggesting smaller acidification effects in humic rivers. This result supports the proposed use of humic level as a typological factor in the assessment of acidification. 6. Some potentially important effects could not be considered in this study, such as the additional effects of metals, episodic acidification and the contrasting effects of natural versus anthropogenic acidity. We advocate further data collection and testing of metrics to incorporate these factors. [source] The Hill equation: a review of its capabilities in pharmacological modellingFUNDAMENTAL & CLINICAL PHARMACOLOGY, Issue 6 2008Sylvain Goutelle Abstract The Hill equation was first introduced by A.V. Hill to describe the equilibrium relationship between oxygen tension and the saturation of haemoglobin. In pharmacology, the Hill equation has been extensively used to analyse quantitative drug,receptor relationships. Many pharmacokinetic,pharmacodynamic models have used the Hill equation to describe nonlinear drug dose,response relationships. Although the Hill equation is widely used, its many properties are not all well known. This article aims at reviewing the various properties of the Hill equation. The descriptive aspects of the Hill equation, in particular mathematical and graphical properties, are examined, and related to Hill's original work. The mechanistic aspect of the Hill equation, involving a strong connection with the Guldberg and Waage law of mass action, is also described. Finally, a probabilistic view of the Hill equation is examined. Here, we provide some new calculation results, such as Fisher information and Shannon entropy, and we introduce multivariate probabilistic Hill equations. The main features and potential applications of this probabilistic approach are also discussed. Thus, within the same formalism, the Hill equation has many different properties which can be of great interest for those interested in mathematical modelling in pharmacology and biosciences. [source] Influence of environmental stress on skin tone, color and melanogenesis in Japanese skinINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 1 2005K. Kikuchi Introduction It is needless to say that one of the most potent environmental stress for melanogenesis of the human skin is the effect of ultraviolet (UV) light from the sunlight. Characteristic skin aging as a result of this UV light is recognized as photoaging. Clinical features in photoaging are wrinkles, skin laxity, coarseness, leathery, yellowing, lentigenes, mottled pigmentation, telangiectasia, sebaceous hypertrophy and purpura. There is an apparent difference in clinical features in photoaging among different races, i.e. between Caucasians, African American and Asians that include Japanese. Not only photo skin type but also environmental factors, such as climate, latitude, altitude and their habit of sunbathing, smoking and skin care influence the characteristic development of their photoaging. Racial difference in photoaging Caucasians tend to develop skin laxity and fine wrinkles more than Asians [1]. Asians tend to produce coarser wrinkles than the Caucasians although their development is rather late in life. There is also a difference in the skin color. Pigmentation is an earliest and prominent skin changes in Asians [1] and it increases with age [2]. In contrast, pigmentation is not apparent in the Caucasians although redness probably because of an increase in cutaneous vascularization becomes prominent in middle aged Caucasians [2]. Chung reported that seborrheic keratosis is a major pigmentary lesion in men, whereas hyperpigmented macules are prominent features in women in Koreans [3]. Melanogenesis pigmentation disorders in Japanese Ephelides (freckles) are commonly found in those with photo skin type I who have fair skin and red eyes and blond hair. They are also found in the Japanese. Clinical feature reveals that multiple small pigmentary macules on sun-exposed areas mainly on the mid-portion of the face. These lesions seem to be familial, becoming apparent even in early childhood after sun exposure. Melasma is an acquired pigmentary disorder commonly found in middle aged Japanese women characterized by irregular brown macules and patches on the sun-exposed areas on the face typically as bilaterally present macules on the cheeks. An increase in sex hormones as a result of pregnancy and intake of contraceptive pills is one of the etiological factors to develop melasma. Sun exposure also worsens it. Nevus of Ota is also a common pigmentary disorder found in the Japanese. It is usually unilateral, blue-brown to slate-gray pigmentary macules on the eyelid and cheek that appear in early childhood or in puberty. Acquired dermal melanocytosis is also a pigmentary disorder, in which dermal melanocytes are found as shown in nevus of Ota, characterized by bilateral brown to blue-gray macules on the forehead, temple, eyelid and malar areas in middle aged Japanese women. This tends to be misdiagnosed as melasma. Solar lentigo is an acquired pigmented macule induced by sun exposure. Solar lentigines are usually multiple, circumscribed brown macules. There are two types of solar lentigo. One is a small macular type, characterized by multiple, small brown macules whose diameter is less than 5 mm, being similar to ephelides (freckles). The other type is a large macular type, characterized by a few round to oval, brown macules whose diameter is beyond 1 cm. Some of their surface are hyperkeratotic and become elevated to produce seborrheic keratosis. Again, the early sign of photoaging in Japanese is pigmentated spots and these pigmentation disorders increase with age. Among the pigmentary changes, nevus of Ota, acquired dermal melanocytosis, melasma and large macular type of solar lentigo are characteristic skin changes found in the Japanese in addition to ephelides and small macular type of solar lentigo. Seasonal changes of the various functional properties of the skin including skin color assessed by non-invasive bioengineering techniques [4]. When we consider skin tone, color and melanogenesis, UV light from the sunlight is the most potent environmental stress, although we cannot forget also the important influence of environmental relative humidity affects our skin functions as well as its appearance. We investigated seasonal influences on the various properties of the skin in 39 healthy Japanese females consisting of different age groups. Their skin is thought to be affected by the UV light in summer, and by the exposure to the dry and cold air in winter. Materials and methods Biophysical, non-invasive measurements, including transepidermal water loss (TEWL) as a parameter for the barrier function of the stratum corneum (SC), high frequency conductance as a parameter for the hydration state of the SC, skin color and casual surface lipid levels, were conducted during late summer and winter months. Skin color was determined with a chromameter according to the L*a*b* CIE 1976 system, where L* is an attribute on the luminance scale, a* that on the red versus green scale and b* that on the yellow versus blue scale. All the measurements were conducted in an environment controlled-chamber (21 ± 1 °C room temperature, and 50 ± 3% relative humidity). Results The barrier function of the SC was found to be significantly impaired in winter on the cheek as compared with that measured in summer, whereas no such seasonal change was apparent both in the hydration state of the SC and sebum levels on the cheek. In the assessment of the skin color on the cheek, a significant increase in a* (redness) and a decrease in b* (yellowness) were observed in winter. In contrast, on the flexor forearm, the values of L* (luminescence) increased in winter, but no seasonal change was noted in the values of a* and b*. In this study, skin changes with aging were also found by the non-invasive bioengineering methods. The value of TEWL on the cheek tended to increase with age, whereas no significant change was observed in the value of TEWL on the forearm. In the assessment of skin color, b* value on the cheek significantly increased with age whereas a* and L* values on the cheek did not show any significant change with age. Summary of this study We think that such an increase in yellowness with aging of the cheek skin is a phenomenon unique to the Japanese (Asians) since an increase in b* value was not observed in Caucasians [2]. The facial skin that is always exposed shows barrier impairment in a dry and cold winter environment and demonstrates increased yellowness in skin color because of a prolonged exposure to the UV light from the sun in the summer season. The non-invasive bioengineering methods are useful to demonstrate even invisible seasonal changes occurring in the same individuals and changes with age occurring in the skin. References 1.,Goh, S.H. The treatment of visible signs of senescence: the Asian experience. Br. J. Dermatol.122, 105,109 (1990). 2.,LeFur, I., Numagami, K., Guinot, C. et al. Age-related reference values of skin color in Caucasian and Japanese healthy women according to skin site. Pigment Cell Res. 7, 67 (1999). 3.,Chung, J.H., Lee, S.H., Youn, C.S. et al. Cutaneous photodamage in Koreans: influence of sex, sun exposure, smoking, and skin color. Arch. Dermatol. 137, 1043,1051 (2001). 4.,Kikuchi, K., Kobayashi, H., Le Fur, I. et al. Winter season affects more severely the facial skin than the forearm skin: comparative biophysical studies conducted in the same Japanese females in later summer and winter. Exog. Dermatol. 1, 32,38 (2002). [source] Thermodynamic analysis of subcooling and superheating effects of alternative refrigerants for vapour compression refrigeration cyclesINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 5 2006encan Abstract This paper presents a computer-based first law and exergy analysis applied to vapour compression refrigeration systems for determining subcooling and superheating effects of environmentally safe new refrigerants. Three refrigerants are considered: R134a, R407c and R410a. It is found that subcooling and superheating temperatures directly influence the system performance as both condenser and evaporator temperatures are affected. The thermodynamic properties of the refrigerants are formulated using artificial neural network (ANN) methodology. Six ANNs were trained to predict various properties of the three refrigerants. The training and validation of the ANNs were performed with good accuracy. The correlation coefficient obtained when unknown data were used to the networks were found to be equal or very near to 1 which is very satisfactory. Additionally, the present methodology proved to be much better than the linear multiple regression analysis. From the analysis of the results it is found that condenser and evaporator temperatures have strong effects on coefficient of performance (COP) and system irreversibility. Also both subcooling and superheating affect the system performance. This effect is similar for R134a and R407c, and different for R410a. Copyright © 2005 John Wiley & Sons, Ltd. [source] The (Ir)Relevance of Militarized Interstate Disputes for International TradeINTERNATIONAL STUDIES QUARTERLY, Issue 1 2002Quan Li Do military disputes between two states suppress trade between their firms? Both liberals and realists suggest that conflict occurrence reduces bilateral trade. However, using a rational expectation argument, Morrow (1999) proposes that conflict occurrence and trade should be uncorrelated statistically. Empirical evidence to date both supports expectations and appears contradictory and inconclusive. We offer a theory that reconciles, encompasses, and extends the competing arguments, explaining the empirical inconsistency. By incorporating rational expectations and uncertainty into the profit calculus of trading firms, the theory identifies the conditions under which various properties of a conflict (onset, duration, and severity) should and should not reduce bilateral trade ex ante and ex post. We test the ex post effects in two datasets that cover either a wider range of countries or a longer time period than previous quantitative studies. Both an unexpected MID onset and the unexpectedness of a MID onset reduce bilateral trade substantially ex post. Preliminary tests suggest that MID duration and severity also affect bilateral trade ex post. We conclude by discussing the implications of our research. [source] Supercapacitor studies of electrochemically deposited PEDOT on stainless steel substrateJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2007S. Patra Abstract There has been increasing interest on various properties and applications of electronically conducting polymers. Polyethylenedioxythiophene (PEDOT) is an interesting polymer of this type as it exhibits very high ionic conductivity. In the present study, PEDOT has been electrochemically deposited on stainless steel (SS) substrate for supercapacitor studies. PEDOT/SS electrodes prepared in 0.1M H2SO4 in presence of a surfactant, sodium dodecylsulphate (SDS), have been found to yield higher specific capacitance (SC) than the electrodes prepared from neutral aqueous electrolyte. The effects of concentration of H2SO4, concentration of SDS, potential of deposition, and nature of supporting electrolytes used for capacitor studies on SC of the PEDOT/SS electrodes have been studied. SC values as high as 250 F/g in 1M oxalic acid have been obtained during the initial stages of cycling. However, there is a rapid decrease in SC on repeated charge-discharge cycling. Spectroscopic data reflect structural changes in PEDOT on extended cycling. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Influence of powder particle size distribution on complex viscosity and other properties of acrylic bone cement for vertebroplasty and kyphoplasty,JOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2006Lidia Hernández Abstract For use in vertebroplasty and kyphoplasty, an acrylic bone cement should possess many characteristics, such as high radiopacity, low and constant viscosity during its application, low value of the maximum temperature reached during the polymerization process (Tmax), a setting time (tset) that is neither too low nor too high, and high compressive strength. The objective of this study was to investigate the influence of the powder particle distribution on various properties of one acrylic bone cement; namely, residual monomer content, Tmax, tset, complex viscosity, storage and loss moduli, injectability, and quasi-static compressive strength and modulus. It was found that the formulations that possessed the most suitable complex viscosity-versus-mixing time characteristics are those in which the ratio of the large poly(methyl methacrylate) beads (of mean diameter 118.4 ,m) to the small ones (of mean diameter 69.7 ,m) was at least 90% w/w. For these formulations, the values of the other properties determined were acceptable. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006 [source] Preparation of high-temperature polyurethane by alloying with reactive polyamideJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2002Tsutomu Takeichi Abstract A series of novel poly(urethane amide) films were prepared by the reaction of a polyurethane (PU) prepolymer and a soluble polyamide (PA) containing aliphatic hydroxyl groups in the backbone. The PU prepolymer was prepared by the reaction of polyester polyol and 2,4-tolylenediisocyanate and then was end-capped with phenol. Soluble PA was prepared by the reaction of 1-(m -aminophenyl)-2-(p -aminophenyl)ethanol and terephthaloyl chloride. The PU prepolymer and PA were blended, and the clear, transparent solutions were cast on glass substrates; this was followed by thermal treatments at various temperatures to produce reactions between the isocyanate group of the PU prepolymer and the hydroxyl group of PA. The opaque poly(urethane amide) films showed various properties, from those of plastics to those of elastomers, depending on the ratio of the PU and PA components. Dynamic mechanical analysis showed two glass-transition temperatures (Tg's), a lower Tg due to the PU component and a higher Tg due to the PA component, suggesting that the two polymer components were phase-separated. The rubbery plateau region of the storage modulus for the elastic films was maintained up to about 250 °C, which is considerably higher than for conventional PUs. Tensile measurements of the elastic films of 90/10 PU/PA showed that the elongation was as high as 347%. This indicated that the alloying of PU with PA containing aliphatic hydroxyl groups in the backbone improved the high-temperature properties of PU and, therefore, enhanced the use temperature of PU. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3497,3503, 2002 [source] Effect of pressure and temperature on Raman spectra of solids: anharmonicity,JOURNAL OF RAMAN SPECTROSCOPY, Issue 7-8 2003Guy Lucazeau Abstract This paper gives a brief review of the effect of temperature and pressure on Raman spectra. Anharmonicity, defined by the cubic, quartic and higher terms in the potential expansion, is shown to be responsible for various properties such as dilatation or for variations of wavenumber and half-width of Raman bands with temperature and pressure, or may be strongly involved in phase transitions. This contribution does not pretend to be an exhaustive review on the subject but aims to introduce some basic concepts in a tutorial way before showing how intricated are these manifestations of anharmonicity. Copyright © 2003 John Wiley & Sons, Ltd. [source] Effect of coverage density and structure of chemically bonded silica stationary phases on the separation of compounds with various propertiesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 6 2006Bogus, aw Buszewski Abstract The chemical character, geometry, and architecture of chemically formed surface layers determine interactions between stationary phase, analyte, and mobile phase, and therefore the retention mechanisms (partitioning, adsorption, ion exchange, steric exclusion) of separated analytes. These interactions also depend on the structure and chemical character of the solutes and the composition of the mobile phase. High-molecular-weight fullerenes (C60 and C70) and water-soluble selenium-containing peptides (833 and 2607 Da) were used for the evaluation of laboratory-prepared octadecyl stationary phases with high and low coverage density before and after end-capping. The aim of this work was to study differences in surface coverage density and homogeneity and conformational changes of chemically bonded moieties and the influence of these parameters on the separation of mixtures of selenopeptides and fullerenes with significantly different molecular masses. A topographical model of the chemically modified stationary surface is presented. [source] Biodegradable Nanogels Prepared by Self-Assembly of Poly(L- lactide)-Grafted Dextran: Entrapment and Release of ProteinsMACROMOLECULAR BIOSCIENCE, Issue 11 2008Koji Nagahama Abstract We showed previously that poly(L- lactide)-grafted dextran could form biodegradable nanogels in water. In this paper, various properties of Dex -g- PLLA nanogels were compared with Dex-Chol (dextran-cholesterol conjugate) nanogels to investigate the effects of hydrophobic units. Dex -g- PLLA nanogels exhibited significantly lower CAC and higher colloidal stability, indicating a strong tendency to form nanogels. We prepared lysozyme-loaded Dex -g- PLLA nanogels, and they exhibited a sustained release of lysozyme for 1 week without denaturation in PBS at 37,°C. The Dex -g- PLLA nanogels therefore have great potential as a delivery vehicle for therapeutic protein. [source] Ordering in Stretched Bernoullian CopolymersMACROMOLECULAR THEORY AND SIMULATIONS, Issue 1 2003Arkady D. Litmanovich Abstract A new approach is suggested to estimate the theoretical maximum capability to order for stretched Bernoullian copolymers AB, provided interchain AB contacts are unfavorable. A simple Monte Carlo procedure simulating the ordering of such copolymers via rotation of ring-shaped chains reveals the capability to order even for quite long copolymer chains. The analytical probabilistic consideration is elaborated, which enables one to interpret the ordering via rotation in terms of a sliding of periodic Bernoullian chains. Using both the probabilistic analysis and Monte Carlo simulations it is shown that estimations of a capability to order given by the rotation procedure are also good for a sliding of true Bernoullian copolymers. Therefore, the simple Monte Carlo procedure seems suitable for estimating ordering in other classes of copolymers for which an analytical approach is more complicated. Such estimations might be useful for a consideration of various properties of irregular copolymers connected with their tendency to order. Ordering by rotation of rings. As an example, an ordering for M,=,10,000 chains of length N,=,20 and composition p,=,0.50 (p is the mole fraction of A units) is shown. See text. [source] Cover Picture , Mol.MOLECULAR NUTRITION & FOOD RESEARCH (FORMERLY NAHRUNG/FOOD), Issue 5 2009Nutr. This special issue covers various properties of arsenic: how arsenic enters into the food chain, how it may exert its toxicity, and to what extent protein expression is influenced by arsenic exposure. In addition to these negative health effects, the issue reports about arsenics use as a medicine, also covering its anticancer activity. [source] Red star-forming and blue passive galaxies in clustersMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2009Smriti Mahajan ABSTRACT We explore the relation between colour (measured from photometry) and specific star formation rate (derived from optical spectra obtained by the Sloan Digital Sky Survey Data Release 4) of over 6000 galaxies (Mr,,20.5) in and around (<3 r200) low-redshift (z < 0.12) Abell clusters. Even though, as expected, most red sequence galaxies have little or no ongoing star formation, and most blue galaxies are currently forming stars, there are significant populations of red star-forming and blue passive galaxies. This paper examines various properties of galaxies belonging to the latter two categories, to understand why they deviate from the norm. These properties include morphological parameters, internal extinction, spectral features such as EW(H,) and the 4000 Å break, and metallicity. Our analysis shows that the blue passive galaxies have properties very similar to their star-forming counterparts, except that their large range in H, equivalent width indicates recent truncation of star formation. The red star-forming galaxies fall into two broad categories, one of them being massive galaxies in cluster cores dominated by an old stellar population, but with evidence of current star formation in the core (possibly linked with active galactic nuclei). For the remaining red star-forming galaxies, it is evident from spectral indices, stellar and gas-phase metallicities and mean stellar ages that their colours result from the predominance of a metal-rich stellar population. Only half of the red star-forming galaxies have extinction values consistent with a significant presence of dust. The implication of the properties of these star-forming galaxies on environmental studies, like that of the Butcher,Oemler effect, is discussed. [source] The 2dF Galaxy Redshift Survey: correlation functions, peculiar velocities and the matter density of the UniverseMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2003Ed Hawkins ABSTRACT We present a detailed analysis of the two-point correlation function, ,(,, ,), from the 2dF Galaxy Redshift Survey (2dFGRS). The large size of the catalogue, which contains ,220 000 redshifts, allows us to make high-precision measurements of various properties of the galaxy clustering pattern. The effective redshift at which our estimates are made is zs, 0.15, and similarly the effective luminosity, Ls, 1.4L*. We estimate the redshift-space correlation function, ,(s), from which we measure the redshift-space clustering length, s0= 6.82 ± 0.28 h,1 Mpc. We also estimate the projected correlation function, ,(,), and the real-space correlation function, ,(r), which can be fit by a power law (r/r0), with r0= 5.05 ± 0.26 h,1 Mpc, ,r= 1.67 ± 0.03. For r, 20 h,1 Mpc, , drops below a power law as, for instance, is expected in the popular , cold dark matter model. The ratio of amplitudes of the real- and redshift-space correlation functions on scales of 8,30 h,1 Mpc gives an estimate of the redshift-space distortion parameter ,. The quadrupole moment of ,(,, ,) on scales 30,40 h,1 Mpc provides another estimate of ,. We also estimate the distribution function of pairwise peculiar velocities, f(v), including rigorously the significant effect due to the infall velocities, and we find that the distribution is well fit by an exponential form. The accuracy of our ,(,, ,) measurement is sufficient to constrain a model, which simultaneously fits the shape and amplitude of ,(r) and the two redshift-space distortion effects parametrized by , and velocity dispersion, a. We find ,= 0.49 ± 0.09 and a= 506 ± 52 km s,1, although the best-fitting values are strongly correlated. We measure the variation of the peculiar velocity dispersion with projected separation, a(,), and find that the shape is consistent with models and simulations. This is the first time that , and f(v) have been estimated from a self-consistent model of galaxy velocities. Using the constraints on bias from recent estimates, and taking account of redshift evolution, we conclude that , (L=L*, z= 0) = 0.47 ± 0.08, and that the present-day matter density of the Universe, ,m, 0.3, consistent with other 2dFGRS estimates and independent analyses. [source] Characterization of Vernix Caseosa as a Natural Biofilm: Comparison to Standard Oil-Based OintmentsPEDIATRIC DERMATOLOGY, Issue 4 2000Maria Imelda B. Bautista M.D. Such infants have a structurally immature stratum corneum and lack a surface coating of vernix caseosa. In this study we examined the short-term effects of topical application of vernix caseosa to human skin and contrasted these effects with commonly used ointments and water-in-oil emulsions. Specifically, vernix, Eucerin®, Aquaphor®, and petrolatum were applied to the volar skin surface of adult volunteers. Surface electrical capacitance (SEC) and transepidermal water loss (TEWL) were measured as indices of surface hydration. Sorption-desorption profiles were performed to determine skin surface hydrophobicity. Particular attention was given to monitoring the acute (0,120 minutes) changes following vernix treatment in order to compare these effects with earlier reports on the rate of skin surface drying in newborn infants following birth. Immediately after vernix application there was an increase in the rate of water loss from the skin surface. Relative to control skin and skin treated with the ointments and water-in-oil emulsions, the application of vernix to freshly bathed human skin resulted in a unique profile of temporal change in baseline surface hydration, moisture accumulation, and water-holding capacity. These results demonstrate major differences between human vernix and standard oil-based topical ointments. The results provide a framework for discussing the various properties of topical barriers applied to the very low birthweight infant. [source] Meridional energy transport in the coupled atmosphere,ocean system: scaling and numerical experimentsTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 644 2009Geoffrey K. Vallis Abstract We explore meridional energy transfer in the coupled atmosphere,ocean system, with a focus on the extratropics. We present various elementary scaling arguments for the partitioning of the energy transfer between atmosphere and ocean, and illustrate those arguments by numerical experimentation. The numerical experiments are designed to explore the effects of changing various properties of the ocean (its size, geometry and diapycnal diffusivity), the atmosphere (its water vapour content) and the forcing of the system (the distribution of incoming solar radiation and the rotation rate of the planet). We find that the energy transport associated with wind-driven ocean gyres is closely coupled to the energy transport of the midlatitude atmosphere so that, for example, the heat transport of both systems scales in approximately the same way with the meridional temperature gradient in midlatitudes. On the other hand, the deep circulation of the ocean is not tightly coupled with the atmosphere and its energy transport varies in a different fashion. Although for present-day conditions the atmosphere transports more energy polewards than does the ocean, we find that a wider or more diffusive ocean is able to transport more energy than the atmosphere. The polewards energy transport of the ocean is smaller in the Southern Hemisphere than in the Northern Hemisphere; this arises because of the effects of a circumpolar channel on the deep overturning circulation. The atmosphere is able to compensate for changes in oceanic heat transport due to changes in diapycnal diffusivity or geometry, but we find that the compensation is not perfect. We also find that the transports of both atmosphere and ocean decrease if the planetary rotation rate increases substantially, indicating that there is no a priori constraint on the total meridional heat transport in the coupled system. Copyright © 2009 Royal Meteorological Society [source] Expanded Pyridiniums: Bis-cyclization of Branched Pyridiniums into Their Fused Polycyclic and Positively Charged Derivatives,Assessing the Impact of Pericondensation on Structural, Electrochemical, Electronic, and Photophysical FeaturesCHEMISTRY - A EUROPEAN JOURNAL, Issue 36 2010Dr. Jérôme Fortage Abstract This study evaluates the impact of the extension of the ,-conjugated system of pyridiniums on their various properties. The molecular scaffold of aryl-substituted expanded pyridiniums (referred to as branched species) can be photochemically bis-cyclized into the corresponding fused polycyclic derivatives (referred to as pericondensed species). The representative 1,2,4,6-tetraphenylpyridinium (1H) and 1,2,3,5,6-pentaphenyl-4-(p -tolyl)pyridinium (2Me) tetra- and hexa-branched pyridiniums are herein compared with their corresponding pericondensed derivatives, the fully fused 9-phenylbenzo[1,2]quinolizino[3,4,5,6- def]phenanthridinium (1Hf) and the hitherto unknown hemifused 9-methyl-1,2,3-triphenylbenzo[h]phenanthro[9,10,1- def]isoquinolinium (2Mef). Combined solid-state X-ray crystallography and solution NMR experiments showed that stacking interactions are barely efficient when the pericondensed pyridiniums are not appropriately substituted. The electrochemical study revealed that the first reduction process of all the expanded pyridiniums occurs at around ,1,V vs. SCE, which indicates that the lowest unoccupied molecular orbital (LUMO) remains essentially localized on the pyridinium core regardless of pericondensation. In contrast, the electronic and photophysical properties are significantly affected on going from branched to pericondensed pyridiniums. Typically, the number of absorption bands increases with extended activity towards the visible region (down to ca. 450,nm in MeCN), whereas emission quantum yields are increased by three orders of magnitude (at ca. 0.25 on average). A relationship is established between the observed differential impact of the pericondensation and the importance of the localized LUMO on the properties considered: predominant for the first reduction process compared with secondary for the optical and photophysical properties. [source] | |||||||||||||||||||||||||