bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermodynamically‐controlled processes on multicomponent alloy surfaces
Authors: Uebing Christian 
Published: July 2012

AbstractThe chemical composition of alloy surfaces is subject of segregation processes at elevated temperatures. In multicomponent alloy systems the joint surface enrichment of different solute atoms (cosegregation) is possible. Under thermodynamic control, i.e. when the temperature is sufficiently high to allow rapid bulk diffusion of the components, cosegregation may cause the formation of thermodynamically stable two‐dimensional chemical compounds (surface compounds), which are epitaxially arranged on alloy surfaces of suitable structure and orientation. The cosegregation‐induced surface confined formation of two‐dimensional chemical compounds must be distinguished from the precipitation of three‐dimensional compounds at surfaces (surface precipitates). According to the Gibbs phase rule, three‐dimensional precipitates can be formed upon oversaturation in coexistence with the saturated solid solution.In this contribution the cosegregation‐induced growth of two‐ and three‐dimensional surface compounds and surface precipitates on several multicomponent alloy single crystals will be described and discussed.
III. Highly reactive and multicomponent systems: On the constitution and thermodynamics of Ni‐Gd alloys
Authors: Dischinger J. , Schaller H.‐J. 
Published: July 2012

AbstractThe thermodynamic properties of Ni‐Gd alloys were determined by electromotive force measurements between 873 and 1073 K on galvanic cells using CaF2 single crystals as solid electrolytes. Results yield a complete set of thermodynamic functions for the intermetallic phases (Ni), Ni17Gd2, Ni5Gd, Ni4Gd, Ni7Gd2, Ni3Gd, Ni2Gd, NiGd, Ni2Gd3, and NiGd3, as well as information on the phase relations. The system is characterized by pronounced negative deviations from ideality. The relative partial excess Gibbs energy of gadolinium at infinite dilution, ΔG (xGd→0), was determined to be ‐(104±5) kJ/mol. A comparison with analogous systems indicates the influence of the electronic structure of the components on thermodynamic properties of mixing. In order to fix the liquidus curve, differential thermal analysis was carried out over the entire range of composition.
Thermodynamics of solid Co‐Cr alloys by Knudsen cell mass spectrometry and computation of the phase diagram
Authors: Havrankova J. , Vrestal J. , Tomiska J. 
Published: July 2012

AbstractThermodynamic excess properties of cobalt‐chromium alloys in both the bcc solid and fcc solid phases have been investigated by Knudsen cell mass spectrometry in the temperature range 1580‐1790 K. The molar excess Gibbs energy, excess entropy and heat of mixing as well as the thermodynamic activities were determined from the ion intensities as a function of composition and temperature by fitting to a sub‐regular solution model and optimised to the phase equilibrium data (2 parameter T.A.P.‐series; Fcc phase: C in J/mol: CH1=‐10600, CH2=‐26500; C in J/(mol·K): Cs1=4.15, Cs2=‐26.0; Bcc phase: C in J/mol: CH1=19500, CH2 =‐29500; C in J/(mol·K): Cs1=19.4, Cs2=‐32.0). Solid Co‐Cr alloys at 1673 K are characterized in the fcc phase by negative molar excess Gibbs energy GE, prevailing negative molar excess entropies SE and exothermic molar heats of mixing HE, and in the bcc phase by negative and positive (at high Cr content) molar excess Gibbs energy GE, positive and slight negative (at higher Cr content) molar excess entropies SE and endothermic and slight exothermic (at higher Cr content) molar heats of mixing HE.At 1673 K the following minimum and maximum excess properties result: a) Fcc phase, minimum values: HE=‐6400 J/mol (62 at.‐% Cr), SE=‐2.95 J/mol·K (70 at.‐% Cr), and GE=‐2650 J/mol (34 at.‐% Cr); b) Bcc phase, maximum values: HE=2300 J/mol (26 at.‐% Cr), SE=2.15 J/mol·K (26 at.‐% Cr), and GE=1090 J/mol (80 at.‐% Cr); bcc phase, minimum values: HE=‐140 J/mol (84 at.‐% Cr), SE=‐1.0 J/mol·K (82 at.‐%Cr), and GE=‐1300 J/mol (22 at.‐% Cr). The phase diagram has been recalculated by using these data, and the results of mass spectrometric investigations on the liquid phase.
Measurement of activity of gallium in liquid Ga‐Sb‐Ge alloys by EMF method with zirconia as solid electrolyte
Authors: Katayama Iwao , Fukuda Yutaka , Hattori Yoshiaki 
Published: July 2012

AbstractThe emf of galvanic cells with zirconia solid electrolytes was measured from 975 to 1242 K on binary Ga‐Ge alloys and from 1058 to 1236 K on ternary Ga‐Sb‐Ge alloys by use of Ga‐Ga2O3 as a reference electrode. From the emf values the activity of gallium in the liquid alloys is determined. At 1073 K the activity of gallium in the Ga‐Ge alloys and in the three pseudobinary alloys Ga‐(SbyGe1‐y) where y=0.25, 0.50 and 0.75 shows small negative deviations from ideality. Isoactivity curves in the ternary Ga‐Sb‐Ge alloys were derived by combining the activity data of Ga‐Sb, Ga‐Ge and the ternary alloys. The shape of the curves at 1073 K is simple in the Ga‐poor region, but shows a very small wavy form with increasing Ga concentration. Isovalues curves in the excess Gibbs energies of mixing in the ternary alloys are derived from Darken's method, and the results are compared with the model calculation proposed by Chou based on the experimental data in three binary systems. The shape of isovalue curves in ΔGxs is similar to those obtained from Chou's method, but the agreement between them in the values is not good.
Polyanionic clustering and electronic properties of the expanded equiatomic liquid alloy cesium‐lead
Authors: Hochgesand K. , Kurzhöfer R. , Leichtweiß O. , Winter R. 
Published: July 2012

AbstractWe present measurements of the electrical dc‐conductivity σ of the solid and liquid equiatomic Zintl‐alloy CsPb as a function of temperature in the range from 553 K to 2023 K. Due to significant charge transfer the alloy shows semiconducting behaviour. In the solid state the conductivity increases continuously from 0.2 Ω−1 cm−1 at 553 K up to 5 Ω−1 cm−1 at 800 K, where a drastic increase of σ is observed which is due to a rotor phase transition as discovered by Price, Saboungi et al. [1, 2]. In the liquid state (melting temperature Tm ≈︁ 870 K), σ reaches a maximum value of 1000 Ω−1 cm−1 around 1400 K. In addition, neutron diffraction measurements were carried out on the liquid from temperatures near the melting point up to 1900 K. The total Faber‐Ziman structure factors S(Q) exhibit a distinct prepeak remaining even up to the highest temperatures measured. This prepeak at 0.88–0.73 Å−1 is indicative of intermediate range ordering. We conclude that polyanions survive not only the melting process, but also persist through the whole temperature range up to about 1000 K above the melting point. RMC simulations were used to generate three‐dimensional models of the liquid and to determine the partial structure factors and pair correlation functions. With increasing temperature, the size of the polyanion clusters undergoes significant changes.
Thermodynamic study of intermediate phases in the Ru‐Ge, Ru‐Sn and Ru‐Si systems by Knudsen cell‐mass spectrometry
Authors: Ciccioli A. , Balducci G. , Gigli G. , Perring L. , Kuntz J.J. , Gachon J.C. 
Published: July 2012

AbstractThe enthalpies of formation of the intermediate phases in the systems Ru‐Ge and Ru‐Sn were measured by Knudsen cell‐mass spectrometry. The interest for these systems lies in their large implications in semiconducting materials and catalysts industry. The germanium and tin equilibrium vapour pressures were measured at various temperatures over two‐phase domains. The enthalpy changes of the decomposition reactions were determined by the second‐law method and the third‐law methods. Less extensive measurements have been carried out also for the Ru‐Si systems. The obtained values are compared with literature data and with those furnished by the semi‐empirical Miedema's model.
Properties of thermoreversible gels
Authors: Borchard W. 
Published: July 2012

AbstractIn a short survey chemical and physical aspects characterising thermoreversibly gelling systems are gathered. Rheological properties of the system gelatin/water for different polymer concentrations at various temperatures and varying angular frequencies are presented. The results are interpreted following the percolation theory. The relevant exponents of the storage and loss modulus are close to the percolation model of Arbabi and Sahimi. The pre‐gel properties favour the Zimm‐limit whereas the post‐gel properties are close to the Rouse‐limit. This controversial behaviour is discussed. The gel‐point has been determined by the divergence criterion of the dynamic viscosity at zero frequency when the storage modulus vanishes. The critical times in the percolation results agree fairly well with the time of gelation but not with the cross over time of the storage and loss modulus curves versus time at zero frequency.An equilibrium aggregation model for the post gelation processes is presented which is based on the percolation approach. The time dependence of the storage modulus can be described in the total time range between gel point and the final equilibrium value after very long times.
Phase transitions of Poly(acrylic acid) Gels Grafted with Poly(N‐Isopropylacrylamide) Side Chains
Authors: Mikosch W. , Geissler E. 
Published: July 2012

AbstractPoly(acrylic acid) (PAAc) hydrogels with poly(N‐isopropylacrylamide) (PNTPA) side chains display a phase transition on being subjected either to a change of temperature or of pH in the surrounding medium. Changes of pH induce volume transitions of the PAAc network, while the temperature influences the conformation of the PNIPA side chains. We describe the synthesis of this novel hybrid hydrogel, its phase diagram and preliminary results of local polymer structure investigations using contrast variation with small‐angle neutron scattering.
The volume transition in thermosensitive micronetworks as observed by small‐angle x‐ray scattering
Authors: Dingenouts N. , Norhausen Ch. , Ballauff M. 
Published: July 2012

AbstractWe present a study of the volume transition in colloidal particles composed of a temperature independent core and a shell of thermosensitive crosslinked polymer chains by small‐angle X‐ray scattering (SAXS). The poly(styrene) (PS) cores of the particles have a diameter of 80 nm whereas the shell composed of cross‐linked poly(N‐isopropylacrylamide) has a thickness of 32 nm in the swollen state at 25°C which shrinks to 18 nm at 50°C during a continuous volume transition. The SAXS‐intensities measured at high scattering angles could be described by a Lorenz‐type function at both states. This indicates the presence of marked liquid‐like local concentration fluctuations of the gel with a correlation length ξ of the order of a few nanometers even in the collapsed state (25°C: ξ = 3.2 nm; 50°C: ξ = 2.1 nm). The analysis thus shows that the core‐shell microgels behave in a distinctly different manner than ordinary thermosensitive gels. This is discussed in terms of the spatial constraint exerted by the core‐shell morphology onto the network.
Spherical microgel colloids — Hard spheres from soft matter
Authors: Bartsch E. , Kirsch S. , Lindner P. , Scherer T. , Stölken S. 
Published: July 2012

AbstractWhile gels are usually considered to be soft materials, we demonstrate that it is possible to model hard sphere behaviour when the gel structure is confined to spherical objects of sizes in the colloidal range. We have measured the static structure factor of microgel spheres dispersed in good solvents, differing in size, crosslink density and swelling behaviour, by light scattering and small angle neutron scattering. Comparing with theoretical calculations for polydisperse hard spheres we show how the interactions in highly concentrated dispersions of spherical microgel colloids are determined by an interplay of the relative length of dangling polymer ends at the surface (determined by the average crosslink density and the particle size) and the swelling ratio (determined by the average crosslink density and the solvent quality). In addition the swelling ratio controls the volume fraction range in which colloidal behaviour is not superposed by the gel character. The latter leads to a loss of structural order due to the deformability of the microgel spheres, an effect that occurs at increasingly lower volume fractions if the swelling ratio increases. To achieve hard sphere behaviour up to very high volume fractions, thus, requires high crosslink densities and small swelling ratios.
Reversible gels of synthetic polymers: Phase relations, formation mechanisms and structure
Authors: Berghmans H. , Aerts L. , Buyse K. , Deberdt F. , Roels T. , De Rudder J. , Vereecke S. 
Published: July 2012

AbstractThe complex problem of thermoreversible gelation of solutions of synthetic polymers is discussed. Several possible mechanisms, based on supramolecular structure formation in solution, are discussed. The gelation of polyethylene solutions illustrates the structure formation through lamellar, folded chain crystallization. Gelation of solutions of stereoisomers of polystyrene and poly(methyl methacrylate) is more complex and two mechanisms can are proposed. The complex temperature‐concentration phase diagrams of syndiotactic polystyrene/solvent systems illustrate the competition between gelation by crystallization and the formation of elastic gels. The influence of chain conformation, participation of the solvent in the structure formation and the influence of solvent quality is discussed. Insight in the formation mechanism of elastic gels is obtained through the study of the gelation of solutions of syndiotactic poly(methyl methacrylate).
Gelierungstheorie: Versäumte Zusammenarbeit von Physik und Chemie
Authors: Stauffer D. 
Published: July 2012

AbstractWe describe how percolation theory, invented by Flory in 1941 to describe gelation, was in its later developments ignored by gelation theorists and only within the last decade confirmed experimentally. Also the mathematical theorems concerning uniqueness of the percolating network were long ignored and seem partially wrong or misleading. Finally, Flory's theory was applied to simulate stock market fluctuations.
Structure formation during precipitation reaction in gels: New liesegang patterns
Authors: Sydow U. , Plath P.J. 
Published: July 2012

AbstractThe paper reports on an investigation carried out into one‐ to three‐dimensional Liesegang systems (test tube arrangement) composed of different concentrations of lead nitrate in Agar gel with either potassium iodide or potassium dichromate as the precipitation reagent. A rich variety of different structure formations, including screw formations of the weakly soluble reaction product is documented.Measurements of the progression of the precipitation front show a dependence of the diffusion path on time that which deviates from the Einstein‐Smoluchowski root mean square displacement. The measured exponent n of the displacement xn =f(t) is discussed in detail and interpreted as the dynamic dimension dw of the diffusion through the fractal medium of the gel, the backbone dimension of which could be estimated. A cellular automaton model is used to describe the DLA cluster formation of the precipitate as well as the geometrical shape of the Liesegang patterns.
Molecular dynamics study of electrolyte‐filled pores
Authors: Hartnig C. , Witschel W. , Spohr E. 
Published: July 2012

AbstractThe structure and dynamics of aqueous electrolyte solutions in cylindrical pores with pore radii of 11.1 Å have been investigated by molecular dynamics simulations. The pores serve as models for porous polymer membranes that have recently been produced. Polar functionalized pores were modeled by positive and negative surface charges on the cylinder surface. The observed correlation between ion mobility and the extent of contact ion pair formation with the surface charges provides a possible explanation for the experimentally observed ion selectivity in these pores.
Polymerization of styrene in microemulsion using gemini surfactants with hydrophilic and hydrophobic spacer groups
Authors: Dreja Michael , Tieke Bernd 
Published: July 2012

AbstractThe use of cationic gemini surfactants with various spacer groups in the polymerization of styrene in ternary microemulsion is reported. Gemini surfactants show a solubilization behaviour for styrene in water being superior over conventional single‐tail surfactants. Polymerization of the styrene‐in‐water microemulsions in the presence of a cross‐linker leads to spherical microgel particles of a size range being controlled by the surfactant/monomer ratio. For the two series of gemini surfactants with flexible hydrophobic alkylene spacer chains and flexible hydrophilic oligo(oxyethylene) spacers, the polymer particle size is significantly dependent on the length of the spacer chain. Both series also show the same dependence of the polymerization temperature on the particle size. If instead a hydrophobic aromatic unit is present as spacer group, the resulting particle size is no longer uniform. The results indicate that the process of particle formation and the resulting particle size are influenced by the microdroplet structure in the single phase microemulsion, which in turn is affected by the different interfacial properties of the surfactants.
Wetting phenomena near the bulk critical point of fluid mercury
Authors: Hensel F. , Yao M. 
Published: July 2012

AbstractWe have studied the adsorption of mercury on sapphire at temperatures and pressures close to the liquid‐vapour critical point (Tc= 1478°C, pc= 1673 bar, pc = 5.8 g/cm3) of mercury. The mercury film undergoes a first‐order phase transition known as prewetting. At low temperatures, the prewetting line meets the bulk coexistence curve tangentially at the wetting temperatures Tw = 1310°C. At high temperatures the prewetting line terminates at the prewetting critical point Tcpw = 1468°C and the prewetting pressure pcpw = 1586 bar lying close to the bulk critical point. In analogy with the line of compressibility maxima extending above the liquid‐vapor critical point, we can identify an extension of the prewetting phase line for T>Tcpw which marks the maximum in the two‐dimensional compressibility of the prewetting supercritical phase.
Synthesis, photoluminescence properties and theoretical insights on 1,3‐diphenyl‐5‐(9‐anthryl)‐2‐pyrazoline and ‐1H‐pyrazole
Authors: Dong Baoli , Wang Mingliang , Xu Chunxiang 
Published: July 2012

ABSTRACT1,3‐Diphenyl‐5‐(9‐anthryl)‐2‐pyrazoline and 1,3‐diphenyl‐5‐(9‐anthryl)‐1H‐pyrazole with an anthryl chromophore were synthesized and characterized using 1H NMR, 13C NMR, FT‐IR, mass spectrometry and elemental analysis. Their optical properties were characterized by UV–vis absorption and fluorescence spectroscopy. It was observed that the absorption and fluorescence spectra of the two compounds showed a red shift with respect to that of anthracene. Pyrazole exhibited high fluorescent quantum yields (Φf = 0.90 in toluene) while pyrazoline showed nearly no fluorescence in solution. The significant fluorescence divergence of the two similar compounds was investigated theoretically through density functional theory (DFT) calculations. The energetically lowest‐lying state S1 in the pyrazoline exhibited both characteristics of locally excited and electron‐transfer states that resulted in the fluorescence quenching of anthryl chromophore whereas the S1 state in the pyrazole corresponded to an optically allowed state that led to high fluorescence quantum yields in solutions. Copyright © 2012 John Wiley & Sons, Ltd.
Enzyme‐mediated methodologies for protein modification and bioconjugate synthesis
Authors: Matsumoto Takuya , Tanaka Tsutomu , Kondo Akihiko 
Published: July 2012

AbstractBioconjugates are valuable tools in many fields, including protein engineering and environmental and therapeutic research. Chemical methods are commonly used to synthesize protein‐protein and protein‐functional molecule bioconjugates because they permit easy tethering through covalent bonds. However, chemical methods often produce heterogeneous products and lead to degradation of protein activity due to random modifications. Recently, a number of techniques for modifying proteins or synthesizing bioconjugates have been reported, including more sophisticated chemical modification methods, utilization of noncovalent affinity, and protein splicing. Enzymatic methods in particular have attracted much attention due to the substrate specificity of enzymes, which enables site‐specific tethering of proteins to other proteins or functional molecules. Here, we discuss newly developed methods for protein modification and bioconjugate synthesis that exploit the properties of acyltransferases, ligases, and other enzymes.
The sweet tooth of biopharmaceuticals: Importance of recombinant protein glycosylation analysis
Authors: Lingg Nico , Zhang Peiqing , Song Zhiwei , Bardor Muriel 
Published: July 2012

AbstractBiopharmaceuticals currently represent the fastest growing sector of the pharmaceutical industry, mainly driven by a rapid expansion in the manufacture of recombinant protein‐based drugs. Glycosylation is the most prominent post‐translational modification occurring on these protein drugs. It constitutes one of the critical quality attributes that requires thorough analysis for optimal efficacy and safety. This review examines the functional importance of glycosylation of recombinant protein drugs, illustrated using three examples of protein biopharmaceuticals: IgG antibodies, erythropoietin and glucocerebrosidase. Current analytical methods are reviewed as solutions for qualitative and quantitative measurements of glycosylation to monitor quality target product profiles of recombinant glycoprotein drugs. Finally, we propose a framework for designing the quality target product profile of recombinant glycoproteins and planning workflow for glycosylation analysis with the selection of available analytical methods and tools.
Ab Initio Based conformational study of the crystalline α‐chitin
Authors: Petrov Michal , Lymperakis Liverios , Friák Martin , Neugebauer Jörg 
Published: July 2012

AbstractThe equilibrium structure including the network of hydrogen bonds of an α‐chitin crystal is determined combining density‐functional theory (DFT), self‐consistent DFT‐based tight‐binding (SCC‐DFTB), and empirical forcefield molecular dynamics (MD) simulations. Based on the equilibrium geometry several possible crystal conformations (local energy minima) have been identified and related to hydrogen bond patterns. Our results provide new insight and allow to resolve the contradicting α‐chitin structural models proposed by various experiments. © 2012 Wiley Periodicals, Inc.
On‐demand killing of adherent cells on photo‐acid‐generating culture substrates
Authors: Sumaru Kimio , Kikuchi Kyoko , Takagi Toshiyuki , Yamaguchi Manae , Satoh Taku , Morishita Kana , Kanamori Toshiyuki 
Published: July 2012

AbstractAs a powerful tool of cell screening and cell purification, we developed a novel method to kill adherent cells as cultured on a substrate by micro‐projection of incoherent visible light. To kill the cells by the mild light irradiated by electrically controllable micro‐projection systems currently available, we introduced the assist of the photo‐responsive culture substrates functionalized with a photo‐acid‐generating polymer. In clear contrast to the existing laser‐based methods requiring point scanning, areal micro‐prjection of blue light with the wavelength 436 nm killed many CHO‐K1 cells at a time in the irradiated area on the substrate. The effect of the photo‐generated acid was so confined that selective killing of targeted cells was achieved without critical damage to the neighboring cells. Further, we demonstrated the photo‐selective killing of the adherent cells after preliminarily patterning through the photo‐induced removal of cell adhesion‐inhibiting polymer. Biotechnol. Bioeng. 2013; 110: 348–352. © 2012 Wiley Periodicals, Inc.