bluuebunny/crossref_metadata_2025 huggingface dataset:
Modelling the effects of reserve size and fishing mortality for Caribbean queen conch Strombus gigas
Authors: Hernandez‐Lamb Jennifer , Dibello Anthony , Lewis Shelley , Mackin Gail , Kirby Kevin , Acosta Charles
Published: July 2012

Overfishing has led to declines in many populations of Caribbean queen conch Strombus gigas, leading to its listing on CITES Appendix II. No‐take marine protected areas (MPA) are increasingly being used as a conservation tool for protecting stocks and sustaining fisheries.

A reaction–diffusion model was developed to study queen conch population responses to various sizes of MPAs, differing spatial and temporal fishing mortalities, and fluctuating recruitment rates. Movement behaviour and demographic data from a protected conch population at Glover's Reef, Belize, were used to parameterize the model and assess simulation results.

The model predicted increases in density ranging from 300% in an MPA encompassing one‐tenth of the total habitat area to 450% in an MPA encompassing half of the habitat, agreeing with field observations.

Queen conch stock in the fishing zone was predicted to decline 6‐40% with MPAs encompassing proportions of 0.1–0.5 of habitat area. Spillover estimated from conch movement was expected to reduce these losses and supplement the fishery by 2–4%.

Sensitivity analysis of fluctuating recruitment showed that larger reserves can sustain population buildup even with lower recruitment rates. Relatively small increases in recruitment rates can potentially reduce fishing losses to 0 from MPA closures.

Opening MPAs to fishing periodically or permanently is expected to rapidly deplete the conch population in a fraction of the time necessary for the initial buildup at the current fishing mortality rate.

These results support those of previous modelling studies but also showed complex dynamics for this case study. While MPAs reduce the stock available to the fishery, spillover can supplement the fishery, and increases in recruitment could increase fishery yield beyond pre‐MPA levels. With high fishing mortality, it would not be prudent to open MPAs to fishing for queen conch in any situation.

Copyright © 2012 John Wiley & Sons, Ltd.
Correlation Between Activity and Solubility of Water in Some Aliphatic Alcohols
Authors: Apelblat Alexander
Published: July 2012

The solubility of water in 2‐butanol, iso‐butanol, 2‐pentanol, n‐hexanol, n‐heptanol and n‐octanol as a function of water activity was determined at 25°C. Applying the Gibbs‐Duhem relationship, the activities of alcohols and the excess free energies of mixing were evaluated in the binary alcohol‐water systems.
Selective Adsorption of n‐Fatty Acids (C4–C12–C18) at the Alumina/n‐Heptane Interface: Adsorption Isotherms and Heats of Displacement
Authors: Stradella L. , Venturello G.
Published: July 2012

The isotherms and the heats of selective adsorption of n‐fatty acids (C4, C12, C18) at the alumina/n‐heptane interface have been determined at 313 K. All adsorption isotherms show stepwise trend of the L‐4 type isotherm according to Gile's classification. This behaviour has been interpreted assuming progressive rearrangement in the adsorbed layer with partial formation of dimers of n‐fatty acid molecules in correspondence of high surface coverage. – As the monocarboxylic acid orientation is concerned limiting adsorption from n‐heptane is consistent with the hypothesis of the surface structure made up of symmetric bidentate carboxylate ions, with the molecular symmetry axis rotating away from the perpendicular, orientation. – Studying the effects of the sample outgassing temperature upon the differential heats of adsorption, one may assume that:

At T ≤ 573 K the differential heats are typical of hydrogen bonding between fatty acids' carboxylic group and isolated surface hydroxyls groups.

At higher outgassing temperatures the heats of selective adsorption are representative of dissociative chemisorption on c.u.s. sites.

In correspondence of higher surface coverages aspecific Van der Waals interactions become prevalent. – The differential heats of adsorption for all η‐ and α‐alumina samples decrease as the chain length increases. – α‐Al2O3 differential heats are smaller than η‐Al2O3 adsorption heats.
The Viscosity and the Energies of Activation for Selected Cyclic Compounds at Pressures up to 2 kbar
Authors: Kuss E.
Published: July 2012

In order to investigate the relationship between the viscosity‐pressure behavior and the structure of the molecule the viscosities η of Diphenyl‐methane, Dicyclohexylmethane, Triphenylmethane, Tricyclohexylmethane as well as those of unhydrogenized and hydrogenized Bixylyltoluene and Terxylyltoluene were measured between 25 and 80°C up to 2 kbar. It is found, that in each case the viscosity‐pressure dependence is strongly enhanced by hydrogenation. – Furthermore the pVT‐data of unhydrogenized and hydrogenized Bixylyltoluene were measured and reproduced by the equation of Tait. The lg η‐isotherms as‐function of density ρ, the lg η‐isochors as function of 1/T, the heat of activation Ep and the energy of activation Ev are discussed. Ep is diminished to higher temperatures and is enhanced with increasing pressure. However the ration Ep/Ev is approximately equal to 2, independent of temperature and pressure.
The Dibutylphosphate + Benzene System
Authors: Atrops H. , Kohler Friedrich , Apelblat Alexander
Published: July 2012

Melting curves and densities have been determined for this system, from which activity coefficients, excess Gibbs energies and excess volumes were evaluated. The results are interpreted similar to the acetic acid + benzene system, with dibutylphosphate (HDBP) to undergo strong dimerization. But with HDBP + benzene, it seems necessary to consider the size differences of the species.
Magnetism and Hyperfine Interactions in Ti – Mn Intermetallic Hydrides
Authors: Hempelmann R. , Wicke E. , Hilscher G. , Wiesinger G.
Published: July 2012

We have studied the magnetic properties of the C14 Laves phase Ti0.40Mn0.60 (homogeneity range from Ti0.33Mn0.67 to Ti0.45Mn0.55), of the p phase Ti0.46Mn0.54, and of the ϕ phase Ti0.48Mn0.52, as well as the magnetic properties of their hydrides. The investigation includes susceptibility measurements in the temperature range 5 to 360 K, magnetization measurements between 4.2 K and 250 K with fields up to 7.2 T, and Mössbauer effect measurements on 57Fe doped samples at 4.2 K and 295 K. Additionally, low temperature heat capacity measurements have been performed. While the Ti – Mn intermetallic C14, ρ and ϕ phases themselves are paramagnetic with susceptibilities independent of temperature, their hydrides are ferromagnetic with Curie temperatures of about 213 K, 87 and 155 K, respectively. The ρ and ϕ phase hydrides possess a weak itinerant ferromagnetism, whereas the ferromagnetism of the C14 Laves phase hydride is of a more localized type. The susceptibilities above Tc consist of Curie Weiss terms and large temperature independent contributions. The non‐symmetric quadrupole split Mössbauer spectrum at room temperature indicates a distortion of a fraction of the tetrahedrons in the uncharged Ti0.40Mn0.60 Laves phase which is removed by hydrogenation. The onset of ferromagnetism in the Ti – Mn ternary hydrides is due to the volume expansion which causes a narrowing of the d bands and thus increases the density of states at the Fermi level upon hydrogenation.
Electrical and Magnetic Properties of the Molten Tl – CuTlSe2 System
Authors: Uemura Osamu , Takahashi Kazuhiko , Satow Tsuneo
Published: July 2012

The electrical conductivity, the thermoelectric power and the magnetic susceptibility of molten Tl + CuTlSe2 mixtures have been measured up to 950°C. These mixtures exhibit a sharp decrease in electrical conductivity and a change in sign of thermoelectric power around the stoichiometric composition CuTl3Se2. Measurements of magnetic susceptibility also indicate a marked anomaly at this composition. These electronic properties for molten Tl + CuTlSe2 mixtures are discussed in the light of current transport theories employed in the amorphous and liquid semiconductors.
Untersuchungen zum Mechanismus und zur Katalyse der elektrochemischen Salpetersäurereduktion
Authors: Kreysa G. , Breidenbach G. , Müller K. J.
Published: July 2012

Electrochemical nitric acid reduction has been investigated on graphite and titanium electrodes obtaining current‐potential‐curves, current‐time‐curves and applying electrochemical mass spectrometry for product analysis. Integral current efficiencies and selectivities for the various products has been determined. On graphite at low reduction potentials only NO is formed. At potentials where thermodynamically hydrogen evolution is possible the main products are H2, NO, N2O, and NH. Under these conditions the reduction is catalysed by Cu2+, Ag+, and Pb2+‐ions which were deposited at the base electrode. These metals strongly influence the product distribution. A general reaction scheme is proposed, and the various electrocatalytic effects are discussed.
A NMR Study of Benzene Adsorbed on Graphitized Carbon Black
Authors: Boddenberg B. , Moreno J. A.
Published: July 2012

By means of pulsed NMR spectroscopy the spin‐lattice (T1) and spin‐spin (T2,T2R) proton relaxation times of benzene adsorbed on the graphitized carbon black Graphon were measured as functions of temperature (80 to 300 K), resonance frequency (4 to 60 MHz), and surface coverage (θ = 0.5 to 2). Using the deuterium dilution technique the intermolecular contributions to the relaxation rates were obtained separately. From the intra‐ and intermolecular relaxation times at low temperatures (<140 K) the following structural and dynamical model was developed. The benzene layer is a two‐dimensional quasi‐solid like layer in registry with the graphite (0001) planes (hexagonal unit cell length 0.56 nm) with the benzene molecular planes being oriented perpendicularly to the support. Reorientational motions occur about a two‐fold molecular symmetry axis in a sixfold potential well structure which is determined by the symmetry of the graphite basal planes. The residence time in a potential well is τ = 4.3 · 10−14exp(1070/T) [s]. – At high temperatures (>140 K) great translational mobility in the adsorbed layer is manifested by the irreversible damping of the Carr‐Purcell spin echoes and by the dispersion region ofT1,inter. The diffusion coefficient on the graphite planes isDtr= 3.2 · 10−8exp(−1365/T) [m2s−1]. The non‐inter spin‐lattice and the spin‐spin relaxation times are determined by the magnetic interactions of the adsorbate protons with delocalized and localized paramagnetic centers of Graphon, theT2data in addition by translational diffusion of the molecules among the faces of the polyhedral shaped particles. Only a fraction of 5 · 10−3of the localized centers is found on the surface of the particles, presumably being located on their edges.
Calorimetric Study of the Dipalmitoylphosphatidylcholine/Water Phase Diagram
Authors: Jürgens E. , Höhne G. , Sackmann E.
Published: July 2012

The dipalmitoylphosphatidylcholine (DPPC)/water‐system was studied by differential scanning calorimetry between 0.1 and 17 weight percent of water and from 22°C to 142°C. Main emphasis was directed towards the exact determination of the water content. This was achieved by a moisture meter based on the Karl‐Fischer method. – The scanning curves exhibit up to 6 transition lines altogether. In order to study the variation of transition temperatures with the water concentration, heating and cooling curves of one sample were run repeatedly up to 57 times. A small leakage of the sample capsule allowed for a very small water loss at each scanning cycle leading to a continuous decrease in water concent at each scanning run. The water content was thus changed from 5.5 to about 0.5 weight percent. A phase diagram of the DPPC/water‐system is established.
A Kinetic and Thermodynamic Study of the Reaction of Hydrogen and Deuterium with FeTi at Low Pressures
Authors: Pedersen Allan S. , Møller Preben J. , Sørensen O. Toft
Published: July 2012

The initial reaction of hydrogen and deuterium with clean surfaces of FeTi powder, following a five‐cycles activation procedure using hydrogen, were studied by volumetric and microgravimetric techniques. – It was concluded that within the 78 K to 88 K temperature range a non‐activated dissociative Temkin chemisorption process occurred upon a Ti surface layer, while at temperatures within the 300 K to 500 K range a dissolution process took place limited by diffusion in the α‐phase.
On the Orientational Structure and Dielectric Properties of Water. A Comparison of ST2 and MCY Potential
Authors: Steinhauser Othmar
Published: July 2012

Molecular dynamics simulations involving 500 and 1000 molecules are reported for the ST2 [7] and MCY [8] potential. The thermodynamic state corresponds to a density of ρ = 1 gcm−3 and a temperature around T = 400 K. Although traditionally used, atom‐atom correlation functions are found to be inappropriate for a detailed discussion of the orientational structure. Therefore the complete analysis is based on the full angle‐dependent pair correlation function g(R, Ω1, Ω2, Ω12). In the case of MCY considerable distortion of the ideal tetrahedral picture is observed. Although a collective property, the Kirkwood g‐factor turns out to be a sensitive probe of the input potentials and differs by a factor of 3 as a consequence of the angle‐dependent short‐range forces of the MCY potential. The mutual consistence of local and asymptotic dielectric properties is carefully examined. Thus a unique dielectric constant of ϵMCY = 30 ± 5 is derived. Possible refinements of the MCY potential are discussed in order to bring the computed ϵMCY closer to the experimental value ϵexp = 51.
Rotational Diffusion in Liquid 1,4‐Cyclohexadiene
Authors: Pajak Z. , Latanowicz L. , Jurga K.
Published: July 2012

The small‐step Brownian diffusion model, applied to the analysis of selectively measured proton spin‐lattice relaxation times T1 for 1,4‐cyclohexadiene solutions in carbon tetrachloride at various temperatures, yields the rotational diffusion coefficients of the molecule treated as a symmetrical top. The evidenced anisotropy of motion is pronounced – for the neat liquid at room temperature D∥ = 15.1 · 1010s−1 and D⟂ = 8.1 · 1010s−1. The last value characterizing reorientation of the major symmetry axis is well corroborated by contour analysis of two totally symmetrical Raman scattering bands. The usefulness of various hydrodynamic models in the description of motional behaviour is discussed.
Quenching of the 2Eg State of Hexacyanochromate(III) in Dimethylformamide Solution
Authors: Buckels H.‐W. , Wasgestian F.
Published: July 2012

The quenching efficiency of mild organic oxidants and of iodine cyanide was found to correlate with the polarographic half wave potentials, indicating oxidative quenching. The quenching by ICN was compared with that by naphthacene, which quenches by energy transfer. Both compounds differ in quenching rate (3 · 104 and 3.5 · 107 M−1 s−1 (22°C)), activation energy (38 and 2.6 kJ mol−1), activation entropy (−48 and −102 J mol−1 K−1), and salt effect. – From the data it is concluded that for the oxidative quenching close contact between quencher and the excited [Cr(CN)6]3− is necessary, the rate determining step being the formation of an encounter complex. Energy transfer is supposed to proceed via a solvent or counter ion separated donor acceptor pair with the intrinsic transfer step as rate determining.
Kinetics of the Hydrogen Abstraction from Hydrogen Cyanide by Trifluoromethyl Radicals
Authors: Lane Silvia , Oexler Elena V. , Staricco Eduardo H.
Published: July 2012

The reaction of CF3 radicals with HCN in the gas phase has been studied in the temperature range 573–673 K using CF3 radicals generated by thermal decomposition of CF3I. Arrhenius parameters for the reaction:

relative to CF3 recombination:

are given by:

Rate parameters are compared with those for other reactions of CF3 with polar and non‐polar substrates.
Early Stages of the Decomposition of Alloys
Authors: Haasen P.
Published: July 2012

Field ion microscopy combined with mass spectroscopy, the atom probe, is applied to the analysis of nuclei in the decomposition of alloys. The interface of the particles shows the sharp concentration profile expected from Becker's theory. The time evolution of particle size, density and matrix supersaturation is measured for the first time during the nucleation stage of alloy decomposition. It is shown that Ostwald ripening must be taken into account already during this stage in agreement with a recent theory of Langer and Schwartz. The alternative spinodal decomposition mode can also be clearly recognized in the atom probe but a satisfactory non‐linear theory for this mode is still missing.
Kinetics of a Unidirectionally Inhomogeneous Ising Alloy
Authors: van Baal C. M.
Published: July 2012

A new way of treating kinetic problems in crystalline systems, applied earlier to homogeneous systems, here is applied to the Hillert model of an alloy i.e. to a model in which it is assumed that inhomogeneities in composition only exist in one crystal direction. For this model the diffusion equations are derived and shown to lead to equilibrium. The equations are solved in linear approximation. The solutions are unstable inside the spinodal and have characteristics that are in very good agreement with the Cahn‐Hilliard theory of spinodal decomposition.
Phase Transitions and Incommensurability in Crystalline Model Bilayers
Authors: Kind R.
Published: July 2012

Crystalline layer structure compounds containing aligned aliphatic chains show essentially the same phase transition behaviour as lipid bilayers in liquid systems. This is demonstrated on two representatives of the (CnH2n + 1NH3)2MCl4 family (n = 10, M = Cd and n = 3, M = Mn) and on one compound of the CnH2n + NH3Cl family (n = 10). Transitions from completely ordered closely packed structures to disordered states with “melted” chains, transitions from intercalated to nonintercalated structures, as well as modulated (“ripple”) phases can be observed in these model bilayers. A phenomenological description of these transitions is given in the framework of the Landau theory.
C. D. W. Phase Transition in NbSe3 and Related Compounds
Authors: Rouxel Jean , Meerschaut Alain , Gressier Pascal
Published: July 2012

Charge Density Wave instabilities represent a particular type of phase transitions which can be well illustrated by the properties of niobium and tantalum trichalcogenides. Some basic features of CDW's instabilities are reminded. Then, NbSe3 and some related compounds such as monoclinic TaS3 and the (Fe ‐ Nb)Nb2Se10 series, are the basis of an experimental illustration of the concepts. NbSe3 exhibits two CDW's phase transitions at T1 (145 K) and T2 (59 K). The feature which makes NbSe3 unique is the non ohmicity observed at very low electric field (few tenths of mV‐cm−1) just below T1 and T2. It is now well established that this non linear effect results from the depinning of CDW, which carries a current. Conclusion is indicative of the role of the anion pairing in the triangular base of the trigonal prism, of the cation pairing along the chain and of the interchain coupling.
Ten Years of X‐Ray Diffuse Scattering Studies of One Dimensional Conductors and Superconductors
Authors: Comes R.
Published: July 2012

Competing effects in real one dimensional conductors have considerably enriched the original structural picture of the instability of a single metallic chain. Such effects include transverse as well as longitudinal polarizations of the Peierls distorsion, instabilities on different molecular chains, 2 and 4kF instabilities, and commensurability effects. In the more recent class of organic superconductors (TMTSF)2X, superconductivity is not only in competition with the Peierls instability but also with order‐disorder phase transitions involving the non centrosymmetric counter ions.
Phase Equilibria in the H2/C2H4System at Temperatures from 114.1 to 247.1 K and Pressures to 600 MPa
Authors: Heintz Andreas , Streett William B.
Published: July 2012

Experimental data for liquid‐vapor phase compositions of Hydrogen + Ethylene are reported for 14 temperatures in the range 114.1 to 247.1 K and pressures up to 600 MPa. The data have been obtained using a vapor‐recirculating apparatus suitable for measurement up to 1000 MPa. The entire region of liquid‐vapor coexistence has been explored for the first time. The mixture critical line and the pressure temperature trace of the 3‐phase line solid‐liquid‐vapor have been located. These lines intersect at 153 K and 675 MPa to form an upper critical end point. Results obtained up to 52 MPa have been compared to published data. Calculations have been made to compare the experimental results with predictions of the Peng‐Robinson and Redlich‐Kwong equations of state.
Ostwald Ripening of Precipitates I. Numerical Solution for the Particle Size Distribution Function in Closed Systems
Authors: Venzl Gerd
Published: July 2012

A numerical solution shows the existence of an asymptotic regime for the Ostwald ripening of precipitates in closed but infinite systems. The asymptotic time evolution is independent of the preparation (initial conditions) and in accord with the predictions of the Lifshitz‐Slyozov‐Wagner‐theory. Diffusion‐limited growth is considered as a representative example. The relation to Kahlweit's approach and the applicability to large but finite systems and more complicated growth laws are discussed.
A Broadband Submillimeter Wave Spectrometer System with On‐Line Microcomputer Data Analysis
Authors: Schäfer Eckhard , Winnewisser Manfred
Published: July 2012

A submillimeter wave spectrometer operating in the frequency range 100 to 800 GHz has been constructed for the study of transient molecules in the gas phase. The instrument employs harmonic generation of millimeter wave frequencies and a He‐cooled InSb photoconducting detector. A high degree of flexibility is achieved using an exchangeable free‐space Pyrex absorption cell and a microcomputer for on‐line data analysis. The spectrometer can be operated in a free‐running video mode together with a fast signal averager or phase‐locked to a microwave reference with source modulation. It is shown that the reproducibility of line center frequency measurements up to 600 GHz is ± 10 kHz. Transitions with absorption coefficients of at least 3 · 10−8 cm−1 can be detected in the range from 150 to 250 GHz. Ground state rotational transitions of OCS between 200 and 690 GHz are reported and analysed together with previous data.
The Electrical Conductivity of Solid and Molten Cesium Hydroxide – A Contribution to Solid Proton Conductors
Authors: Haas K.‐H. , Schindewolf U.
Published: July 2012

The electrical conductivity of solid cesium hydroxide is by several powers of ten larger, its activation energy by a factor of two to three lower than those of normal solid salts. A steep tenfold increase of the conductivity is observed at the α‐β‐phase transition temperature of solid cesium hydroxide (220°C) above which the OH −‐ions can rotate freely (rotator phase). A further increase by three powers of ten occurs between 280°C and the melting point (335°C), above which the conductivity is that of a normal molten salt. The conductivity behaviour thus resembles that of potassium hydroxide (Stephen and Howe [10]), which also exhibits the pronounced breaks at the α‐β‐transition temperature (248°C) and at around 366°C. Since the second break in solid cesium hydroxide and potassium hydroxide coincides with the eutectic temperatures of the respective hydroxide‐carbonate systems (alkali hydroxides hardly can be obtained free of carbonate) it has to be assumed that it is caused by the increase of ionic charge carriers due to partial melting of the eutectic within the solid framework of the hydroxide. The relatively high conductivity of cesium hydroxide and potassium hydroxide below the eutectic temperatures is due to a “Grotthus”‐type proton conductivity mechanism (aided by CO‐ and H2O impurity defects) with OH−‐ion rotation.
Low‐Temperature Luminescence in Eu3+‐Doped Tungstates of the Perovskite Stacking‐Variant Type
Authors: Blasse G. , Kemmler‐Sack S.
Published: July 2012

The photoluminescence at low temperatures of Eu3+‐activated tungstates of the perovskite stacking‐variant type are reported. The main examples are Ba2La2‐xEuxMgW2□O12 (12 layer) and Ba2Y2‐xEuxW3□O18 (18 layer). The luminescence of 12 and 18 layer compounds are strikingly different. Not only are the emission and absorption spectra of the Eu3+ ions different, but also the energy transfer processes are not the same. These phenomena are discussed in terms of existing theories.
Photochemistry of the Di‐Deuterated Benzenes
Authors: Semeluk G. P. , Synnott J. A. , Unger I.
Published: July 2012

The photochemistry of the di‐deuterated benzenes has been examined in the vapour phase over the wavelength range of 245 to 270 nm. The sensitized emission of biacetyl technique was used to obtain the triplet yields. The sums of the singlet and triplet yields for all three molecules were found to be unity between 255 and 265 nm. – Phosphorescence lifetimes in EPA and methylcyclohexane glasses have been recorded and found to be non‐exponential. – Mechanisms consistent with the experimental observations are presented and various rate constants have been examined.
On the “Anomalous” Temperature Dependence of the FIR‐Absorption Band of Acetonitrile
Authors: Goslich R. , Chatzidimitriou‐Dreismann C. A. , Lippert E.
Published: July 2012

An anomalous red‐shift of the FIR‐absorption band of CH3CN in n‐heptane with increasing temperature had been reported in Ref. [1]. This result is experimentally confirmed. We also observed the same effect in some other solvents (CCl4, CS2, and cyclohexane). In the case of n‐heptane the temperature dependence of the overall absorption intensity attains a maximum within the temperature range under examination. The theoretical interpretation of the anomalous red‐shift as given in previous papers is mentioned.
Thermodynamische Untersuchungen an Menshutkin‐Komplexen V. Wärmekapazitäten fester Komplexe und flüssiger Mischungen
Authors: Sondern Ch R. , Perkampus H.‐H.
Published: July 2012

The influence of complex formation upon heat capacities was investigated for the systems SbCl3/benzene and SbCl3/mesitylene. While the cρ value of the solid complex 2SbCl3 · benzene was exactly the sum of the cρ‐values of the components, positive heat capacities were found in the liquid mixtures, which are due to the existence of dissolved charge transfer complexes. A simple model is able to describe these results on a semiquantitative level.
Thermodynamische Untersuchungen an Menshutkin‐Komplexen VI. Exzßenthalpien flüssiger SbCl3/Aromat‐Mischungen und Bildungsenthalpien fester Komplexe
Authors: Sondern Chr. , Perkampus H.‐H.
Published: July 2012

The mixing enthalpies of liquid mixtures of SbCl3/C3H6–nXn (X = CH3 for 1 ≤ n ≤ 6; X = Cl for 1 ≤ n ≤ 3) were measured at one composition and temperature (T > 350 K). The system SbCl3/mesitylene was investigated over the whole range of concentrations. With these and earlier measured data it was possible to calculate the formation enthalpies of the solid complexes. In one case it was also possible to evaluate the formation entropy by additional vapour pressure measurements. The dependency of the excess enthalpies upon the benzene substituents confirms our assumptions about the formation of dissolved change transfer complexes in the liquid mixtures of SbCl3 with aromatic compounds.
The Temperature Dependence of the Properties of Electrolyte Solutions. V. Determination of the Glass Transition Temperature and Comparison of the Temperature Coefficients of Electrolyte Conductance and Solvent Viscosity of Propylene Carbonate Solutions
Authors: Barthel J. , Gores H.‐J. , Carlier P. , Feuerlein F. , Utz M.
Published: July 2012

Viscosity measurements on pure propylene carbonate and conductance measurements on solutions of 13 salts in propylene carbonate from low to high concentrations were carried out in the temperature range −45°C ≤ θ ≤ +25°C. Data analysis based on the Vogel‐Fulcher‐Tammann equation yields equal values for the glass transition temperature of propylene carbonate, T0, from both conductance [T0 = (151.6 ± 0.9) K] and viscosity [T0 = (152.3 ± 1.6) K] measurements. The energies of activation of conductance at infinite dilution, E (m → 0, T) = (3350 ± 50) [T/(T‐T0)]2 J mol−1, of all the electrolyte solutions investigated are independent of the solute and equal to that of the viscosity of the solvent, E = (3420 ± 50) [T/(T‐T0)]2 J mol−1, at every temperature.
A Calorimetric Study on the Effect of Non‐Complementary Bases on the Stability of Helical Complexes with Poly U
Authors: Stulz J. , Ackermann Th.
Published: July 2012

Double and triple helical complexes of poly U with oligo‐ and polynucleotides containing complementary adenine residues and non‐complementary guanine residues are studied by calorimetry. The complexes are characterized by IR‐spectroscopy. The transition enthalpies of the polynucleotides are corrected using the stacking enthalpies of poly A and poly (A,G), which were determined independently. The enthalpy change for the formation of a GU‐base pair depends on the temperature. In spite of the relatively high value of 28 kJ/mol base pair for the enthalpy change, the change of free enthalpy is low and may reach slightly positive or negative values, depending on the temperature and the NaCl‐concentration. The formation of triple helical complexes with poly U leads to a comparatively constant value of enthalpy change for poly A, ApA and poly (A,G), whereas both stabilities and transition enthalpies are reduced in the analogous complexes of poly U with ApApG and ApGpA. A “phase diagram” of the system poly (A,G)/poly U shows reduced transition temperatures and an increased area of stability for the double helix in comparison with the analogous diagram of the system poly A/poly U.
Photochemistry of Colloidal Metal Sulfides. 4. Cathodic Dissolution of CdS and Excess Cd2+ Reduction
Authors: Gutiérrez M. , Henglein A.
Published: July 2012

A highly reactive cadmium deposit is formed, when colloidal cadmium sulfide is illuminated in the presence of sulfite or dithionite anions (10−4−10−3M). It is oxidized by oxygen, nitrous oxide, hydrogen ions and methylviologen. The quantum yield amounts to 0.005 in the absence of excess cadmium ions. In the presence of 5 · 10−4 Cd2+ ions, the quantum yield is 0.053. The rate of cadmium formation was investigated as a function of the excess Cd2+ concentration, sulfite concentration and the pH. The effects are explained in terms of the formation of electrons and positive holes upon illumination, scavenging of the holes by adsorbed sulfite anions and reaction of the excess electrons with Cd2+ ions. The sulfite anions react mainly in an one‐hole oxidation process yielding SO radicals that form SO and S2O via the respective disproportionations and combinations. The deposition of cadmium metal was also observed in the illumination of CdS powder suspended in a 1 M sulfite solution. In the beginning of the illumination Cd was formed, later on hydrogen was generated. These effects are explained in terms of a large overpotential for the reduction of water by excess electrons in CdS and the catalytic action of a cadmium layer. — Cadmium metal is formed with practically 100% efficiency when colloidal CdS solutions are γ‐irradiated in the presence of suitable organic additives. This effect is attributed to the transfer of electrons from reducing organic radicals to the colloidal particles.
Effects of Temperature and Pressure on the Thermal Conductivity of Solid n‐Undecane
Authors: Forsman H. , Andersson P.
Published: July 2012

We have measured the thermal conductivity, λ, of n‐undecane, using the transient hot‐wire technique. At low pressures, n‐undecane has a plastic crystal phase αH. The increase in λ, going from the liquid to phase αH, was 35%. For a liquid → plastic crystal transition, this is a high value. It reflects that orientational disorder is mainly limited to rotation of the rod‐shaped molecule around its chain axis. The low temperature phase βO, was shown to exhibit a weak temperature dependence of λ at isochoric conditions. This suggests the presence of structural disorder, probably caused by reorientation of the chain‐end methyl groups. The volume dependence of λ in phase βO,g= ‐(∂ln λ/∂lnV)T, was found to be about 9.5. This result is discussed in terms of the anharmonicity of the weak interchain van der Waal's bonds. Some heat capacity results were also obtained.
Chemical Bonding and Electronic Structure of Small Homonuclear Clusters of Elements of Groups IA, IIA, IIIA and IVA
Authors: Pacchioni Gianfranco , Plavšić Dejan , Koutecký Jaroslav
Published: July 2012

The clusters Lik(k = 3–8), Na4, K4, Bex(x = 3–13), Mgy, Cay, Aly(y = 3–5) and Gez(z = 3–6) are investigated employing the ab initio CI method. — The bond in alkali metal clusters is due to the interaction of the outer s orbitals but p polarization functions are essential for a correct prediction of the electronic structure and stability of possible geometries of these clusters. In alkaline earth metal clusters the role of sp hybridization is crucial for the appearance of attractive interactions. The most relevant factor determining the stability of Al and Ge clusters is the bonding between p atomic orbitals. The spin properties of small clusters, which are important for their stability, are determined by their geometry and symmetry. — The most stable clusters of elements which crystallize in compact structures (bcc, fcc and hcp) are always sections of the corresponding crystal lattices. On the contrary, the Ge clusters exhibiting large stability are not parts of the diamond lattice and can be considered as deformed parts of more compact lattices. — The binding energy per atom of Li and Be clusters qualitatively converges to the cohesive energy of the metals with the growth of the cluster size. — In the largest clusters the existence of very small singlet‐triplet energy splittings indicates the development of a metallic character.
Relating Cation Solvation in Solvent Mixtures with Solvent Exchange Rates — A 1H‐NMR Study on Co(II)‐Ions
Authors: Dickert F. L. , Hellmann S. W.
Published: July 2012

Specific and statistical solvation of Co(II)‐ions in mixtures of methanol with dimethylformamide respectively hexamethylphosphoric triamide was found by 1H‐NMR‐spectroscopy. Relations are given, which correlate these possible solvation models with the kinetics of solvent exchange. On this basis, specific outersphere solvation of the methanol rich Co(II)‐solvate‐complexes by dimethylformamide can be deduced. For mixtures of hexamethylphosphoric triamide with methanol, the statistical solvation behaviour is additionally favoured by a strong solvent‐solvent interaction.
Optical Spectra of Matrix‐Isolated Aluminium
Authors: Abe H. , Kolb D. M.
Published: July 2012

A reinvestigation of matrix‐isolated aluminium shows that the optical spectra of previously published work on Al contained prominent bands originating from Al2O. We report for the first time the absorption and emission yield spectra of Al atoms in noble gas matrices which are free of aluminium suboxide contamination. A study of the concentration dependence allowed a decision as to which bands in the spectral range from 450 nm to 200 nm belong to Al, Al2 and Al2O. From the vibronic fine structure of an absorption band at 3 eV for Al2, ωe = 238 ± 5 cm−1 is found for the dimer in Ar, Kr and Xe. For Al atoms in Kr two rather stable trapping sites are observed.
Measurements of Solubilities of Solid CO2 in C2H4, C3H6, i‐C4H8, n‐C5H12 and of n‐C5H12 in C3H6
Authors: Teller Matthias , Knapp Helmut
Published: July 2012

Liquidus curves for five binary mixtures were determined in a low temperature equilibrium apparatus. It can be assumed that the solid phase consists of the pure solute. The experimental results were correlated and binary coefficients for a simple gE model were calculated as a function of temperature.
Röntgenographische und dilatometrische Untersuchungen zur Fehlordnung im Strontiumchlorid
Authors: Daniel G. , Nölting J.
Published: July 2012

SrCl2 cristallizes in the fluorite structure and shows, like all materials with this structure, anomal properties with regard to thermodynamic as well as to transport phenomena. In a temperature region starting about 200 K below the melting point (1146 K) a pronounced maximum of Cp is found, which is to be identified with a Schottky anomaly. Most significant are the increasing values of ionic conductivity with rising temperature. They mostly exceed those of a typical ionic melt. The degree of the “molten” anion lattice and the distinct places of the defect ions are not clarified until now. The temperature of transition at the maximum of the expansion coefficient value at T = 1000 K has been determined by dilatometric measurements. The existence of predominant Frenkel‐disorder has been demonstrated by comparing X‐ray and dilatometric measurements. The ratio of ionic radii relative to the configuration in the fluorite structure has been determined from lattice parameter and the crystal structure.

The enthalpy of formation of Frenkel disorder has been calculated from dilatometric measurements to ΔHf = (248 ± 8) kJ mol.
The Effect of Added Salts on the Proton Exchange Rate of Water as Studied by17O NMR
Authors: Hertz H. G. , Versmold H. , Yoon C.
Published: July 2012

Line shapes of the17O n.m.r. of the solvent water have been measured in solutions containing small amounts of HCl or NaOH and various inorganic and organic salts. Proton life times τ in the water molecule have been derived from these spectra. The life time in the neutral electrolyte solutions, the maximum life time, the rate constants for the proton exchange catalized by H+and OH−ions, and the pH value at which the maximum r occurs are reported. Correlations with the well‐known structure forming and structure breaking properties of ions are discussed. The results are also compared with the electrical extraconductivity observed in these solutions.
Investigation of Hydrogen Atom Addition to Vinyl Monomers by Time Resolved ESR Spectroscopy
Authors: Beckert D. , Mehler K.
Published: July 2012

By means of time resolved ESR spectroscopy in the microsecond time scale the H atom addition to different vinyl monomers was investigated. The H atoms produced by pulse radiolysis of aqueous solutions show a strong recombination CIDEP effect which also allows the recombination rate constant of H atoms to be determined. By analysis of ESR time profiles with the modified Bloch equations the relaxation times T1, T2, the polarization factors and the chemical rate constants with scavengers were obtained. Besides the H atom addition rate constants to different vinyl monomers the structure of the monomer radical was determined for acrylic acid.
The Thermal Conductivity of Argon, Nitrogen and Carbon Monoxide in the Temperature Range 300 — 430 K at Pressures up to 10 MPa
Authors: Haran K. N. , Maitland G. C. , Mustafa M. , Wakeham W. A.
Published: July 2012

Measurements of the thermal conductivity of argon, nitrogen and carbon monoxide have been carried out over the temperature range 300 – 430 K and at pressures up to 10 MPa in a transient hot‐wire apparatus. The measurements on argon confirm that the accuracy of the experimental results is one of ± 0.3%. Substantial differences have been found between the thermal conductivity of nitrogen and carbon monoxide in the limit of zero density. This observation can only be satisfactorily explained by the existence of large differences between the diffusion coefficients for internal energy for the two gases. In turn these results indicate that this functional of the intermolecular pair potential may be particularly sensitive to its non‐spherical part. – At elevated densities the temperature independence of the excess thermal conductivity as a function of density is confirmed to a high degree of precision.
Morphologie und Phasenunterschiede bei V2O5 und TiO2 in Mischoxidkatalysatoren — Ursachen und gegenseitige Beeinflussung
Authors: Backhaus K. O. , Haase R. , Illgen U. , Jancke K. , Richter‐Mendau J. , Scheve J. , Schulz I. , Vetter J.
Published: July 2012

Coated catalysts, consisting of a compact ceramic core and a shelly coat prepared by mixing TiO2 with vanadium oxalate are investigated After thermal decomposition of the oxalate crystalline phases of vanadium oxide were observed on the anatase surface area. The thermal transformation of anatase into rutile is determined by these phases as proved by X‐ray analysis. A model describes the formation of V6O13 and the transformation of anatase into rutile by structural fits.
Anisotropy of Rotational Diffusion in Liquid α,ω‐Dichloroalkanes
Authors: Peplińska B. , Pąjak Z.
Published: July 2012

From the analysis of 1H and 13C spin‐lattice relaxation times and self‐diffusion coefficients measured for α,ω‐dichloropentane, ‐hexane and ‐octane, the rotational diffusion coefficients of the prolate ellipsoid type molecules treated as rigid symmetrical tops are derived. The effect of slow internal motions on the predominant dipolar relaxation is shown to be negligible as compared to the overall reorientation. The evidenced anisotropy is very pronounced — reorientation about the major symmetry axis is over ten times faster than about the perpendicular axes. Some hydrodynamic models, tested by the experimentally determined intramolecular contributions to the proton spin‐lattice relaxation rates, appear to be insufficient for the adequate description of the motional behaviour.
High Temperature Thermodynamics of Solutions of Hydrogen and Deuterium in Palladium and its Alloys
Authors: Kleppa O. J.
Published: July 2012

The solutions of hydrogen in palladium and its alloys are classical examples of interstitial metallic solutions. Although these alloys have been studied for a very long time, a good deal of new information has become available in recent years, partly as a result of the application of the combined calorimetric‐equilibrium approach. This experimental method, which was developed in our laboratory about 10 years ago, allows essentially simultaneous determinations of the Gibbs energies, the enthalpies and the entropies of solution. This approach has been particularly useful in throwing new light on the temperature dependence of the thermodynamic properties, and also on their dependence on the alloying constituents. Special interest is attached to the new information on the partial entropies of hydrogen, which points strongly toward a temperature dependent, non‐random distribution of the hydrogen atoms among the available interstitial sites.
Application of Thermodynamic Models in Phase Diagram Assessment
Authors: Hillert Mats
Published: July 2012

By the use of examples which mainly concern the configurational entropy of alloy systems an attempt is made to illustrate the application of physical and mathematical models to the assessment of alloy systems. It is emphasized that methods, which are often regarded as independent of models, depend very strongly on some hidden choice of a model. It is shown that different physical models can give the same mathematical model. For further developments it may be essential to test what physical model gives the most realistic description of the situation in the real system. It is also shown that different mathematical models can represent the data very well even when the properties of the system are very specific.
Calculation and Representation of Phase Equilibria in Multicomponent Systems
Authors: Henig E.‐Th. , Kattner U. , Petzow G.
Published: July 2012

The general features of thermodynamic calculation of phase equilibria are reviewed. This includes analytical description of the thermodynamic functions by approximations or models, determination of the resulting adjustable coefficients from experimental data, calculation of phase equilibria based on the Gibbs free energy functions of individual phases and graphical representation of the results. Special emphasis is given to different types of two‐dimensional representations only containing partial information about the multidimensional higher order systems.
Enthalpy Measurements on Refractory Metals and Alloys by Levitation Calorimetry
Authors: Frohberg Martin G. , Betz Cerhard
Published: July 2012

Measurements of enthalpy by levitation drop‐calorimetry. Principle of measurement. Experimental data of Nb, Mo, Ta in solid and liquid state. Determination of enthalpies of mixing by levitation technique. Temperature measurement. Investigation of Fe–Cu and Nb–Si‐alloys.
Enthalpies of Formation of Ag — Si, Au — Si and Ag — Au — Si Liquid Alloys at 1423 K
Authors: Hassam S. , Gaune‐Escard M. , Bros J. P.
Published: July 2012

The enthalpies of formation of silver‐silicon, gold‐silicon and silver‐gold‐silicon were determined at 1423 K over a large concentration range; a very high temperature calorimeter was used for these investigations. Our ternary experimental results were represented correctly with a modified Kohler's relation.
Calorimetric Investigations of Liquid Alkaline Earth Metal Alloys
Authors: Sommer F. , Lee J. J. , Predel B.
Published: July 2012

The concentration dependences of the enthalpy of mixing of liquid copper‐magnesium and calcium‐copper alloys have been determined, applying direct mixing calorimetry, in the temperature range between 1120 and 1225 K. The enthalpies of mixing are discussed in connection with known thermodynamic quantities and the asymmetrical concentration course obtained can be described by an association model. Systematic comparison is carried out between the experimentally obtained enthalpies of mixing – together with other recent experimental data – and those obtained according to the Miedema model. The concentration dependence used in the model is not able to describe the results of alloy melts with strong compound formation tendency. The enthalpy of mixing can be calculated in nearly 40% of the systems investigated with less than 30% error and in 64% with an error less than 2.5 kJ mol−1.
Prediction of Formation Enthalpies of the Compounds MgHg(s) and CaHg(s)
Authors: Hilpert K.
Published: July 2012

The formation enthalpies per mole of an atom of the compounds MgHg(s) and CaHg(s) are determined as − 28.2 ± 0.8 and − 56.8 ± 4.6 kJ mol−1 respectively, by studying the vaporization of compounds of the Mg – Hg and Ca – Hg systems with a new Knudsen cell‐mass spectrometer system. Values of − 30 [MgHg(s)] and − 59 kJ mol−1 [CaHg(s)] are predicted with the volume contraction model, as well as − 34.6 [MgHg(s)] and − 1.6 kJ mol−1 [CaHg(s)] with the Pauling model of ionic bond using the electronegativities of Gordy and Thomas. The enthalpies of formation are discussed and compared with those of intermetallic compounds with predominantly ionic bond. The enthalpies of formation per mole of an atom of the compounds BaHg(s) and SrHg(s) are predicted as − 61.6 and − 77.9 kJ mol−1, by applying the Pauling model of ionic bond with the electronegativities of Gordy and Thomas.
The Palladium‐Silver‐Hydrogen System: A Quasi‐Chemical Approach
Authors: De Avillez R. R.
Published: July 2012

The quasi‐chemical model extended to include both first and second neighbor interactions between interstitial and substitutional matrix atoms [7] was applied to the Pd – Ag – H system and found to provide a satisfactory fitting for the available experimental data over the temperature range from 350 to 850 K. The calculated interaction coefficients suggest that hydrogen solution in Pd – Ag alloys will tend to be short‐range ordered, the hydrogen atoms occupying preferentially the interstitial sites surrounded by first neighbor palladium atoms and second neighbor silver atoms.