A derivation of thermodynamic quantities of liquid alloys from their structure factors

A method of deriving the thermodynamic properties of mixing in liquid alloys Delta G, Delta S and Delta H, from low-Q scattering data has been presented. As an example, the method has been demonstrated with liquid Na-Ga alloys for which both thermodynamic and diffraction data have recently been obtained by the authors.

Physical chemistry of mixed conducting zirconia ceramics

Suivant la pression partielle d'oxygène, la zircone peut être conducteur ionique ou électronique. Mise au point de méthodes de mesures de f.é.m. permettant de s'affranchir des sources d'erreur introduites par ces propriétés.

Physical chemistry of the reduction of calcium oxide with aluminium in vacuum

The physical chemistry of "aluminothermic" reduction of calcium oxide in vacuum is analyzed. Basic thermodynamic data required for the analysis have been generated by a variety of experiments. These include activity measurements in liquid AI-Ca alloys and determination of the Gibbs energies of formation of calcium aluminates. These data have been correlated with phase relations in the Ca-AI-0 system at 1373 K. The various stages of reduction, the end products and the corresponding equilibrium partial pressures of calcium have been established from thermodynamic considerations. In principle, the recovery of calcium can be improved by reducing the pressure in the reactor. However,, the cost of a high vacuum system and the enhanced time for reduction needed to achieve higher yields makes such a practice uneconomic. Aluminum contamination of calcium also increases at low pressures. The best compromise is to carry the reduction up to the stage where 3CaO-Al,O, is formed as the product. This corresponds to an equilibrium calcium partial pressure of 31.3 Pa at 1373 K and 91.6 Pa at 1460 K. Calcium can be extracted at this pressure using mechanical pumps in approximately 8 to 15 hr, depending on the size and the fill ratio of the retort and porosity of the charge briquettes.

15-deoxyspergualin hinders physical interaction between basic residues of transit peptide in PfENR and Hsp70-1

The apicoplast of Plasmodium harbors several metabolic pathways. The enzymes required to perform these reactions are all nuclearly encoded and apicoplast targeted (NEAT) proteins. Plasmodium falciparum Enoyl-ACP Reductase (PfENR) is one such NEAT protein. The NEAT proteins have a transit peptide which is required for crossing the membranes of apicoplast. We studied the importance of basic residues like Arginine and Lysine within the transit peptide. Previous studies have suggested that all basic residues are essential for apicoplast trafficking. In this study, we demonstrate that only some of these residues are essential (K44, R48, K51, and R52), whereas others are dispensable (R40, K42, and K49). On mutating these specific residues, PfENR is not imported into the apicoplast and is mislocalized to the cytoplasm. We also demonstrate that these residues are also crucial for interaction with Hsp70-1, implying that interactions of Lysine 44, Arginine 48, Lysine 51, and Arginine 52 of the transit peptide with PfHsp70-1 are required for apicoplast trafficking. 15-Deoxyspergualin, which has earlier been proposed to interact with EEVD motif of PfHsp70-1 hinders the physical interaction between these cationic residues of PfENR and Hsp70-1. Hence, we propose that in the transport competent state of NEAT proteins some specific positively charged amino acids in the transit peptide interact with PfHsp70-1, and this interaction is essential for apicoplast targeting.

Thermodynamics of ideal gas in doubly special relativity

We study thermodynamics of an ideal gas in doubly special relativity. A new type of special functions (which we call ``incomplete modified Bessel functions'') emerge. We obtain a series solution for the partition function and derive thermodynamic quantities. We observe that doubly special relativity thermodynamics is nonperturbative in the special relativity and massless limits. A stiffer equation of state is found.

Geotechnical properties of some Indian fly ashes

To reduce the cost of disposal of large quantities of fly ash generated and environmental problems associated with it, efforts are made to utilize fly ash for geotechnical applications. Geotechnical properties of fly ash play a key role in enhancing their application. Physical properties and chemical composition control the index properties arid engineering behaviour. The paper brings out the rob of surface area, surface characteristics, reactive silica and lime content of fly ashes on index, compaction, consolidation and strength properties of fly ashes.

Including the fermion vacuum fluctuations in the (2+1) flavor Polyakov quark-meson model

We consider the (2 + 1) flavor Polyakov quark-meson model and study the effect of including fermion vacuum fluctuations on the thermodynamics and phase diagram. The resulting model predictions are compared to the recent QCD lattice simulations by the HotQCD and Wuppertal-Budapest collaborations. The variation of the thermodynamic quantities across the phase transition region becomes smoother. This results in better agreement with the lattice data. Depending on the value of the mass of the sigma meson, including the vacuum term results in either pushing the critical end point into higher values of the chemical potential or excluding the possibility of a critical end point altogether.

Tribology of soot suspension in hexadecane as distinguished by the physical structure and chemistry of soot particles

Ethylene gas is burnt to generate soot which is collected thermophoretically from different locations of the flame. Tribological performance of the collected soot in hexadecane suspension is compared with that of carbon black and diesel soot. The soots are analysed to yield a range of mechanical properties, physical structures and chemistry. The paper correlates these property variations with the corresponding variations in friction and wear when the soot suspended in hexadecane is used to lubricate a steel on steel sliding interaction. The particles are dispersed in hexadecane by a non-ionic surfactant, poly-isobutylene succinimide (PIBS), which is mono-functional with no free amine group. The grafting of the surfactant on the soot particles is found to have a profound effect on the dispersion of the soot, in general, while, between the different soot types, the tribology is differentiated by the physical structure and chemistry.

Thermo-physical and structural studies of sodium zinc borovanadate glasses in the region of high concentration of modifier oxides

This paper reports investigation of Na2O and ZnO modified borovanadate glasses in the highly modified regime of compositions. These glasses have been prepared by microwave route. Ultraviolet (UV) and visible, infrared (IR), Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) and Electron Paramagnetic Resonance (EPR) spectroscopies have been used to characterize the speciation in the glasses. Together with the variation of properties such as molar volume and glass transition temperatures, spectroscopic data indicate that at high levels of modification, ZnO tends to behave like network former. It is proposed that the observed variation of all the properties can be reasonably well understood with a structural model. The model considers that the modification and speciation in glasses are strongly determined by the hierarchy of group electronegativities. Further, it is proposed that the width of the transitions of glasses obtained under same condition reflects the fragility of the glasses. An empirical expression has been suggested to quantify fragility on the basis of width of the transition regions. (C) 2012 Elsevier Ltd. All rights reserved.

Glassy dynamics in a confined monatomic fluid

Molecular dynamic simulations of a strongly inhomogeneous system reveals that a single-component soft-sphere fluid can behave as a fragile glass former due to confinement. The self-intermediate scattering function, F-s(k,t), of a Lennard-Jones fluid confined in slit-shaped pores, which can accomodate two to four fluid layers, exhibits a two-step relaxation at moderate temperatures. The mean-squared displacement data are found to follow time-temperature superposition and both the self-diffusivity and late a relaxation times exhibit power-law divergences as the fluid is cooled. The system possesses a crossover temperature and follows the scalings of mode coupling theory for the glass transition. The temperature dependence of the self-diffusivity can be expressed using the Vogel-Fulcher-Tammann equation, and estimates of the fragility index of the system indicates a fragile glass former. At lower temperatures, signatures of additional relaxation processes are observed in the various dynamical quantities with a three-step relaxation observed in the F-s(k,t).

Substrate temperature influenced physical properties of silicon MOS devices with TiO2 gate dielectric

DC reactive magnetron sputtering technique was employed for deposition of titanium dioxide (TiO2) films. The films were formed on Corning glass and p-Si (100) substrates by sputtering of titanium target in an oxygen partial pressure of 6x10-2 Pa and at different substrate temperatures in the range 303 673 K. The films formed at 303 K were X-ray amorphous whereas those deposited at substrate temperatures?=?473 K were transformed into polycrystalline nature with anatase phase of TiO2. Fourier transform infrared spectroscopic studies confirmed the presence of characteristic bonding configuration of TiO2. The surface morphology of the films was significantly influenced by the substrate temperature. MOS capacitor with Al/TiO2/p-Si sandwich structure was fabricated and performed currentvoltage and capacitancevoltage characteristics. At an applied gate voltage of 1.5 V, the leakage current density of the device decreased from 1.8?x?10-6 to 5.4?x?10-8 A/cm2 with the increase of substrate temperature from 303 to 673 K. The electrical conduction in the MOS structure was more predominant with Schottky emission and Fowler-Nordheim conduction. The dielectric constant (at 1 MHz) of the films increased from 6 to 20 with increase of substrate temperature. The optical band gap of the films increased from 3.50 to 3.56 eV and refractive index from 2.20 to 2.37 with the increase of substrate temperature from 303 to 673 K. Copyright (c) 2012 John Wiley & Sons, Ltd.

A Novel Fiber Bragg Grating Based Sensing Methodology for Direct Measurement of Surface Strain on Body Muscles during Physical Exercises

The present work proposes a new sensing methodology, which uses Fiber Bragg Gratings (FBGs) to measure in vivo the surface strain and strain rate on calf muscles while performing certain exercises. Two simple exercises, namely ankle dorsi-flexion and ankle plantar-flexion, have been considered and the strain induced on the medial head of the gastrocnemius muscle while performing these exercises has been monitored. The real time strain generated has been recorded and the results are compared with those obtained using a commercial Color Doppler Ultrasound (CDU) system. It is found that the proposed sensing methodology is promising for surface strain measurements in biomechanical applications.

Direct Observation of Valley Hybridization and Universal Symmetry of Graphene with Mesoscopic Conductance Fluctuations

In graphene, the valleys represent spinlike quantities and can act as a physical resource in valley-based electronics to produce novel quantum computation schemes. Here we demonstrate a direct route to tune and read the valley quantum states of disordered graphene by measuring the mesoscopic conductance fluctuations. We show that the conductance fluctuations in graphene at low temperatures are reduced by a factor of 4 when valley triplet states are gapped in the presence of short-range potential scatterers at high carrier densities. We also show that this implies a gate tunable universal symmetry class that outlines a fundamental feature arising from graphene's unique crystal structure.

Self-Adapting Peripherally Heterofunctionalized Hyperbranched Polymers: Formation of Janus and Tripodal Structures

A peripherally clickable hyperbranched polyester carrying numerous propargyl terminal groups was prepared by a simple melt transesterification polycondensation of a suitably designed AB(2) monomer; this clickable hyperscaffold was then transformed into a variety of different derivatives by using the Cu-catalyzed azide-yne click reaction. Functionalization of the periphery with equimolar quantities of mutually immiscible segments, such as hydrocarbon, fluorocarbon, and PEG, yielded frustrated molecular systems that readapt and form structures wherein the immiscible segments appear to self-segregate to generate either Janus structures (when two immiscible segments are present) or tripodal structures (when three immiscible segments are present). Evidence for such self-segregation was obtained from a variety of studies, such as differential scanning calorimetry, Langmuir isotherms, AFM imaging, and small-angle X-ray scattering measurements. Crystallization of one or more of the peripheral segments reinforced this self-segregation; the weight-fraction-normalized enthalpies of melting associated with the different domains revealed a competition between the segments to optimize their crystalline organization. When one or more of the segments are amorphous, the remaining segments crystallize more effectively and consequently exhibit a higher melting enthalpy. AFM images of monolayers, transferred from the Langmuir trough, revealed that the thickness matches the expected values; furthermore, contact angle measurements clearly demonstrated that the monolayer films are fairly hydrophobic, and in the case of the tripodal hybramers, the presence of domains of hydrocarbon and fluorocarbon appears to impart nanoscale chemical heterogeneity that is reflected in the strong hysteresis in the advancing and receding contact angles.