Physical-chemical Aspects Research Articles

Air and water stable ionic liquids in physical chemistry

Ionic liquids are defined today as liquids which solely consist of cations and anions and which by definition must have a melting point of 100 degrees C or below. Originating from electrochemistry in AlCl(3) based liquids an enormous progress was made during the recent 10 years to synthesize ionic liquids that can be handled under ambient conditions, and today about 300 ionic liquids are already commercially available. Whereas the main interest is still focussed on organic and technical chemistry, various aspects of physical chemistry in ionic liquids are discussed now in literature. In this review article we give a short overview on physicochemical aspects of ionic liquids, such as physical properties of ionic liquids, nanoparticles, nanotubes, batteries, spectroscopy, thermodynamics and catalysis of/in ionic liquids. The focus is set on air and water stable ionic liquids as they will presumably dominate various fields of chemistry in future.

Acidic demineralization of apatites studied by scanning X-ray microradiography and microtomography

AbstractThe mineral in bones and teeth is an impure form of hydroxylapatite (HAP), the principal impurity being 2—5 wt.% carbonate. This mineral dissolves during remodelling of bone and also in dental caries as a result of the action of acids produced by osteoclasts and by bacteria, respectively. In enamel, demineralization proceeds with preferential loss of carbonate relative to phosphate. Surprisingly, in the early stages, the demineralization is subsurface. In order to facilitate the understanding of physical chemical aspects of these processes, we have undertaken studies of demineralization in model systems. We give three examples here. The first two used scanning microradiography in which the specimen is stepped across a 10—30 μm diameter X-ray beam. Intensity measurements allow calculation of the mineral mass per unit area in the X-ray path through the specimen. In the first experiment, porous HAP sections were separated from a reservoir of acidic buffer by a column initially filled with water (the diffusion length) and scanned with the X-ray beam perpendicular to the axis of the diffusion length. The rate of total loss of mineral along each profile was calculated from the scans. The rate of demineralization fell as the diffusion length increased. We believe the explanation is that the rate-controlling step is the diffusion of dissolved HAP away from the solid to the buffer reservoir. In the second experiment, demineralizing solution and water were pumped alternately, for equal lengths of time, past blocks of porous HAP or enamel. The X-ray beam was perpendicular to the exposed surface. As the rate of switching between solutions decreased, the mean rate of demineralization also fell. We propose that this effect is due to retention of acid in the pores of the HAP during the time when water flows, allowing further demineralization to take place during this time. The third study used X-ray microtomography, a form of 3D microscopy, to study the loss of mineral in compacted carbonate apatite powders. The powders were packed in six 10 mm internal diameter acrylic cylinders to a depth of 4 mm (after pressing). One end was covered with a porous polyethylene disc and each tube placed in acidic buffer for 70 days. Periodic examination by microtomography showed the development of subsurface demineralization. Infrared spectroscopy of the dissected-out surface layers showed preferential loss of carbonate over phosphate by comparison with deeper layers. Rietveld analysis of X-ray powder diffraction data showed changes in the crystallographic structures of the apatites between the initial and dissected-out apatite.

Study on some physical chemistry aspects of extraction of uranium(VI) with bis(octylsulfinyl)methane

Summary The extraction equilibrium and kinetics of uranium(VI) from aqueous nitric acid with bis(octylsulfinyl)methane (BOSM) in 1,1,2,2-tetrachloroethane extraction has been studied. The extracted species was established to be UO2(NO3)2·2BOSM. The extraction process rate is controlled by the following reaction: The change in enthalpy associated with the extraction reaction was established to be −22 ± 3 kJ/mol.

The effect of citrate on calcium phosphate deposition from simulated milk ultrafiltrate (SMUF) solution

As has been widely reported, different calcium phosphate phases can be formed in solution depending on several physical-chemical aspects like the concentration of free calcium and phosphate ions, pH of the solution, temperature and the presence of interfering ions. The present work aims at studying the effect of pH and of citrates on the precipitation of calcium phosphate in a solution that simulates the mineral composition of milk (SMUF), as well as the subsequent effect on the deposition on stainless steel surfaces. The different calcium phosphate species formed during heating at different pH values and in the presence or absence of citrate were characterized by scanning electron microscopy, X-ray microanalysis and X-ray diffraction. Their fouling behaviour was characterized according to the amount of deposit formed on stainless steel surfaces and to the deposit’s resistance to removal by hydrodynamic shear forces. The absence of citrate was responsible for the decrease in the solution pH and for the formation of a crystalline dicalcium phosphate dihydrate structure with a deposited mass which was almost twice the one obtained in the presence of citrate.

Risk and management in hospital water systems for Legionella pneumophila: a case study in Rio de Janeiro - Brazil

This article analyses the water used at hospitals in Rio de Janeiro, Brazil. The research, based on microbiological and physical-chemical aspects, suggests subsidies for normalization of hospital potable water systems and makes recommendations for standardization of operational procedures for inspection for Legionella pneumophila. A total of 16 hospitals were inspected and positive results for the presence of L. pneumophila were found at five hospitals. These hospitals were integrated in a research project aiming at the detection and quantification of this pathogen. During 10 consecutive weeks, four collections representing a total of 200 analyses were done at the five researched hospitals. In this way seven physical-chemical parameters and three microbiological parameters were observed to evaluate the quality of water in each hospital. The results showed that routine surveillance for a hospital water distribution system is fundamental for public health and must include, as a priority, monitoring of L. pneumophila. The water quality varies in accordance with the hospital water system involved. It is important and necessary to implement environmental culturing in order to minimize hospital infection, in particular, pneumonia data and also to provide the basis for disinfection of the water system.

A química dos ésteres de fosfato

This work summarizes important aspects of the chemistry of phosphate esters, with special emphasis on: i) advances in the design of enzymatic models for phosphatases; and ii) nerve agents and currently used strategies for detoxification. The physical organic chemical aspects that are responsible by the reactivity of phosphate esters are also discussed.

Physical chemical aspects of human milk milked crude and freezing

Physical chemical aspects of human milk milked crude and freezing

Engineering of Ternary Ferromagnetic Semiconductors in Heterojunctions

Compatibility of room temperature ferromagnetic chalcopyrite compounds with Si, Ge, and GaAs wafers was considered. Physical–chemical aspects of heterophase epitaxial growth were analyzed. Ternary ferromagnetic compounds II–IV–V2〈Mn〉 already successfully grown on CdGeP2 and ZnGeP2 semiconductor single crystals are suggested to serve as good heteropartners as well for spin injecting contacts on Si- and GaAs-based devices.

The role of glycosphingolipids in HIV signaling, entry and pathogenesis.

Although HIV uses CD4 and coreceptors (CCR5 and CXCR4) for productive infection of T cells, glycosphingolipids (GSL) may play ancillary roles in lymphoid and non-lymphoid cells. Interactions of the HIV Envelope Glycoprotein (Env) with GSL may help HIV in various steps of its pathogenesis. Physical-chemical aspects of the interactions between HIV Env and GSL leading to CD4-dependent entry into lymphocytes, the role of GSL in HIV transcytosis, and CD4-independent entry into non-lymphoid cells are reviewed. An overview of signaling properties of HIV receptors is provided with some speculation on how GSL may play a role in these events by virtue of being in membrane rafts. Finally, we summarize how interactions between HIV and coreceptors leading to signaling and/or fusion can be analyzed by the use of various tyrosine kinase and cytoskeletal inhibitors.

Lake Superior: an invasion coldspot?

Lake Superior receives a disproportionate number of ballast water discharges from transoceanic ships operating on the Laurentian Great Lakes. Although this provides dispersal opportunities for nonindigenous species (NIS), relatively few NIS were initially discovered in this lake prior to being recorded elsewhere in the basin. A lack of NIS records from this lake may be an artefact of sampling bias. We tested this hypothesis by sampling benthos and plankton from littoral and deepwater habitats around the perimeter of Lake Superior during June and August 2001. Using morphological analysis techniques, we identified a total of 230 invertebrate taxa representing planktonic, benthic and nektonic lifestyles. Five species with invasion histories in the lower Great Lakes, the bivalves Sphaerium corneum, Pisidium amnicum and P. moitessierianum, gastropod Potamopyrgus antipodarum and amphipod Echinogammarus ischnus, were identified for the first time in Lake Superior. In addition, records of expanded distributions within this lake are presented for the amphipod Gammarus fasciatus and oligochaetes Ripistes parasita and Vejdovskyella intermedia. Recently introduced NIS in Lake Superior were found near international ports, implicating shipping as the vector of their introduction. Intrinsic physical-chemical aspects of Lake Superior may account for the scarcity of NIS in this lake as compared to the lower Great Lakes.

Whither Bio-Science?

Click to increase image sizeClick to decrease image size Additional informationNotes on contributorsSushil MukhopadhyaySushil Mukhopadhyay as a post-graduate student in the University of Calcutta, came under the influence of Acharya P C Roy, The 'Father of Indian Chemistry. He specialized in Physical Chemistry although his first love was for Physics. He obtained a First Class and stood 1st in Physical Chemistry and also completed the Associateship course of IARI, New Delhi, in soil Science and Agricultural Chemistry, in 1938. In 1945, he was awarded the DSc degree of the University of Calcutta for his work on the electrochemical properties of hydrogen clays. During the period 1943–1947, Prof Mukherjee worked on a project for making an inventory of agricultural resources which involved extensive survey work in eastern India, including the inaccessible coastal regions of east Bengal, the hills of Assam, and the jungles of the Orissa and Central India. It laid the foundations of soil survey work in India.In 1947, Prof. Mukherjee joined the Chemistry Department of the University of Calcutta as a Lecturer, later as a Reader, till 1957. Prof. Mukherjee research carrier spans from late thirties till today.Prof Mukherjee's list of publications (around 200 numbers) gives only the barest picture of the true extent of his work, for he refused to take any credit even in publications by his own doctoral student. His major areas of research are clay minerals, membrane electrodes, humic substance, clay-organic complexes, soil nutrients and also various aspects of physical chemistry, agricultural, environmental and social science research. During the heydays of his research, Prof Mukherjee came under the influence of Acharya S N Bose, FRS, from whom he imbibed the idea of science education through mother tongue. This he put into action during his stay in Indonesia.In Indonesia, Prof Mukherjee worked as an UNESCO Professor and Consultant from 1957 to I960. A Linguist by nature, he had an excellent command over German, French, Russian, Dutch and Indonesian. Later he wrote monographs in Indonesian on Chemistry, Physics and Mathematics.On his return to, India, he joined as Professor of Macromolecules at the Indian Association for Cultivation of science, Calcutta and within a year moved to the newly formed Kalyani University as the professor of Chemistry and Dean, Faculty of Science. In 1968, he became the Vice-Chancellor of the University of Kalyani. In the same year, he became a member of the committee on Science and Technology, Government of India and came in close contact with Mrs Indira Gandhi. In 1976, Prof Mukherjee returned to Calcutta as Director, Bose Institute and within a year became the Vice-Chancellor of the University of Calcutta. He retired from the University of December 31, 1978. Prof. Mukherjee is a Fellow of the Indian National Science Academy, Foundation Fellow of the National Academy of Agricultural Science, the first President of the West Bengal Academy of Science and Technology and former President of Indian Society of Soil Science, Platinum Jubilee Distinguished Service Award of Indian Science Congress Association, Dr B C Roy Birth Centenary Oration and the DSc Degrees (Honoris Causa) of the Universities of Kalyani and Burdwan. Prof. Mukherjee served as Secretary and Editor of the Indian Chemical Society and Indian Society of Soil Science and as Editor, Indian Journal of History of Science; he is currently Editor of Everyman's Science. He is currently President, IASC, Seniormost Member of the Council, Bose Institute, Vice-President, Asiatic Society and Vice-Chairman, Commission of Compilation of History of science in India. Prof, Mukherjee has co-authored a book of Soil Science and another of Genetics. He is also involved in literary activities.

Different interactions of egg-yolk phosphatidylcholine and sphingomyelin with detergent bile salts

To examine physical–chemical aspects of bile salt–phospholipid interactions that could contribute to preferential phosphatidylcholine (PC) secretion into bile, we have compared transitions between vesicles and micelles in model systems containing taurocholate (TC) and either egg-yolk PC (EYPC), egg-yolk sphingomyelin (EYSM), buttermilk SM (BMSM) or dipalmitoyl PC (DPPC). Phase transitions from micelles to vesicles were observed at 4-fold dilution of serially diluted EYPC/TC systems, but not earlier than at 16-fold dilution of SM/TC or DPPC/TC systems, indicating lower concentrations of the detergent required for micellization in the case of SM or DPPC. Cryo-transmission electron microscopy of phase transitions initiated by addition of TC to phospholipid vesicles revealed extremely long SM-containing intermediate structures, but shorter EYPC-containing intermediate structures. Again, larger amounts of bile salt were required to induce phase transitions in the case of EYPC compared to SM. Sizes of TC–phospholipid micelles increased progressively upon increasing phospholipid contents in the rank order: DPPC–TC<EYSM–TC<BMSM–TC<EYPC–TC, consistent with higher micellization concentrations in the case of EYPC. Micelles were also separated from vesicular phases in two-phase model systems composed with TC, both EYPC and EYSM and 0, 10, 20 or 30 mol% cholesterol, by ultracentrifugation and ultrafiltration of the supernatant. At increasing cholesterol contents, EYPC preferentially distributed into the micellar phase. In contrast, no preferential micellar EYPC distribution occurred in the absence of the sterol. These results indicate different structural arrangements of EYPC–TC micelles compared to SM–TC micelles and lower detergent concentrations required for micellization in the case of SM-containing vesicles.

O estado vítreo dentro da perspectiva do curso de graduação em química (físico-química)

We consider the relevance of the study of the glassy state properties and the glass transition as important topics of the physical chemistry for undergraduate courses of Chemistry. Two of the most important theoretical approaches for the description of the glassy state, the thermodynamic and the kinetic models, are summarized with emphasis on the physical chemistry aspects. Examples illustrating the glass transition of some materials are also presented.

Modelling Oyster Population Response to Variation in Freshwater Input

This paper describes the linkage of a three-dimensional hydrodynamic circulation model with descriptive and experimental biological data concerning oyster (Crassostrea virginica) population dynamics in the Apalachicola Estuary (Florida, U.S.A.). Our intent was to determine the direct and indirect role of Apalachicola River flow in the maintenance of oyster production. Results of a monthly field sampling programme conducted on the oyster reefs in the Apalachicola system during 1985–1986 were used to develop statistical models relating several life-history characteristics of oysters to physical-chemical aspects of water quality. The same life-history characteristics were related statistically to output from a circulation model of Apalachicola Bay. Highest oyster densities and overall bar growth were found in the vicinity of the confluence of high salinity water moving westwards from St George Sound and river-dominated (low salinity) water moving south and eastwards from East Bay. With the exception of models for oyster mortality, the predictive capability of results from the parallel modelling efforts was low. A time-averaged model was developed for oyster mortality during the summer of 1985 by running a regression analysis with averaged predictors derived from the hydrodynamic model and observed (experimental) mortality rates throughout the estuary. A geographic information system was then used to depict the results spatially and to compare the extent of expected mortality in 1985 and 1986. High salinity, relatively low-velocity current patterns, and the proximity of a given oyster bar to entry points of saline Gulf water into the bay were important factors that contribute to increased oyster mortality. Mortality was a major determinant of oyster production in the Apalachicola Estuary with predation as a significant aspect of such mortality. By influencing salinity levels and current patterns throughout the bay, the Apalachicola River was important in controlling such mortality. Oyster production rates in the Apalachicola system depend on a combination of variables that are directly and indirectly associated with freshwater input as modified by wind, tidal factors, and the physiography of the bay. River flow reduction, whether through naturally occurring droughts, through increased upstream anthropogenous (consumptive) water use, or a combination of the two, could have serious adverse consequences for oyster populations. By coupling hydrodynamic modelling with descriptive and experimental biological data, we were able to determine the effects of potential freshwater diversions on oyster production in Apalachicola Bay.

Edgard C. Moreno, PhD: a tribute to his major contributions to oral biology research.

The seminal contributions of Dr. Edgard C. Moreno to physical chemical aspects of oral biology research are reviewed, with personal insights provided by the author. Dr. Moreno has made major contributions to our understanding of fundamental processes which occur within the oral cavity and which control the formation of mineralized tissues. These contributions include extensive research in the areas of: the chemistry of synthetic calcium phosphates and biominerals, the interaction of salivary proteins and other molecules of biological interest with calcium phosphate surfaces, the mechanism of dental caries formation and the effects of fluoride on this process, the mechanism of dental calculus formation and prevention, and the mechanism of dental enamel formation.

Physical-chemical aspects of the frying process

Frying is a very elaborate cooking procedure where the heat is distributed to the food by a medium, the oil or fat that intervenes in the process, interacting with the food itself. The interactions are depending on the quality of the oil or fat, the technology utilized and the nature of the substrate. In effect that last is a mixture of various chemical entities that behave differently toward the heat, between them and with the cooking fat. One of the most important component of the food is water and the hydration conditions are of great importance in determining the various step of the cooking operation and the type of interactions between the food itself and the oily phase. Chemical nature of the substrate is important in determining the type of secondary processes that develop during frying and in effect transformations of the lipidic medium are notably influenced. Main chemical reactions that occur during the frying process are of oxydative nature but their importance must not be overestimated and still frying conditions as well as chemical and physical nature of the food is important in determining the extent at which it occurs. Hydrolysis is another of the reactions that develop during frying. Interchange of fats occurs between the substrate and the lipidic phase, sometime bringing to healthier foods, provided a proper choice in the quality of the frying media has been done. Exchanges of many components, usually minor components occur and are of interest in the repeated frying because they have influence on the behaviour of the cooking operation. In general terms frying must be evaluated as a beneficial operation directed to enhance the nutritional value of a food, provided that the fundamental rules governing the process are observed.

Physical chemistry of flavour

The sensation of flavour occurs when certain flavour‐active molecules are released from food and are transported to stimulate sensors in the mouth and nose. The human brain integrates all the signals from the sensors and produces an overall flavour perception. The way in which flavour molecules are released from food during eating, and the manner in which they are retained during processing and storage, are all governed by various aspects of physical chemistry. This review describes some of the basic principles of partition, a key parameter in the physical chemistry of flavour. An overview of the theory and measurement of partition is given, along with some applications to model and real food systems.

Electrochemistry in association colloids

The electrochemistry of oxidizable and reducible substances solubilized in association colloids is reviewed. The systems considered are aqueous micelles and both oil and water continuous microemulsions. The emphasis is on the basic physical-chemical aspects of the electrochemical processes, and includes discussion of the effect of surfactant adsorption on the electrode as well as the effect of these colloidal media on the diffusion, discharge potential, and electron transfer mechanisms of the electroactive species.

Interactions mécaniques et physico-chimiques aux interfaces de liaisons céramo-métalliques en fonction de la technique d'assemblage

The joining between ceramics and metallic alloys can be analyzed by three fundamentals aspects. -The thermodynamic aspects of physical chemistry and mechanic. -The kinetic aspects of the physical chemistry reaction. -The electric aspects. On the outside specifics reactions physical chemistry and mechanical of junctions developped between ceramics and metallic alloys, the reactions is still in existence a function of the joining technical appliqued. It is distingued: -The method of junction by wettability of liquide metallic interlayer and junction by technical a solid state bonding. -The reactives and non reactives junctions. The work set out underline the different macromechanic, reactionnal aspects that can explain the adhesion between certain ceramics and metallic alloys. We study the influence of residual stresses, of the nature of components in the area of ceramic/metal interlayer on the life duration of junction

ChemInform Abstract: Physical Chemical Aspects of Redox Reactions of Free Radicals

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.