Heat capacities of iron disulfides Thermodynamics of marcasite from 5 to 700 K, pyrite from 300 to 780 K, and the transformation of marcasite to pyrite

The heat capacity of purified natural marcasite has been determined by adiabatic-shield calorimetry in the region 5 to 700 K where it transforms to pyrite exothermically. Values of thermodynamic functions at 298.15 K are Cp, {So(T) - So(0)}, and {Ho(T) - Ho(0)} are 14.92 calth K-1 mol-1, 12.88 calth K-1 mol-1, and 2328 calth mol-1, respectively, for marcasite (FeS2). Our earlier measurements on pyrite have been extended to 770 K, and show that the heat capacity of marcasite is slightly higher than that of pyrite over the entire range of mutual existence. The transformation to pyrite is significantly exothermic at 700 K, [Delta]Ht = - (1.05 +/- 0.05) kcalth mol-1, and correspondingly, Ho(T = 0, marcasite) - Ho(T = 0, pyrite) = (0.99 +/- 0.05) kcalth mol-1. Marcasite is thus metastable with regard to pyrite over the whole temperature region and owes its formation and persistence to kinetic factors. At 298.15 K the standard enthalpies, entropies, and Gibbs energies of formation for FeS2 phases are:Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/21922/1/0000329.pd

Heat capacity and thermodynamic properties of CrSb2 from 5 to 1050 K. Magnetic transition and enthalpy of decomposition

The heat capacity of CrSb2 has been measured by adiabatic calorimetry from 5 to 991.3 K. At the latter temperature the CrSb2-phase decomposes into the CrSb-phase and an antimonyrich melt. The heat capacity of the two-phase mixture was measured from 991.3 to 1050 K. The heat capacity of CrSb2 shows a small sharp [lambda]-type transition with a maximum at 274.1 K where the change from the antiferromagnetic to the paramagnetic state occurs. The low entropy of the clearly cooperative part of the transition, [Delta]St = 0.12 calth K-1 mol-1, shows that this contribution is only a small part of the total. From an estimate of the lattice heat capacity of CrSb2 outside the [lambda]-transition region we find an excess heat capacity amounting to about 1.7 calth K-1 mol-1 at 300 K, 1.6 calth K-1 mol-1 at 500 K, and 1.1 calth K-1 mol-1 at 800 K, which we attribute to the population of excited electronic states in CrSb2. The total transitional entropy amounts to about 2.6 calth K-1 mol-1 at 900 K only slightly more than the R 1n 3 (= 2.17 calth K-1 mol-1) expected from randomization of two unpaired spins per chromium atom. The enthalpy of the peritectic decomposition of CrSb2 at 991.3 K is (8325 +/- 20) calth mol-1.The high heat capacity above 991 K is presumably related to the solution of CrSb(s) in the melt. Thermodynamic functions have been evaluated and the values of Cp, {So(T)-So(0)}, and -{Go-Ho(0)}/T at 298.15 K are (19.66+/-0.02), (27.46+/-0.03), (14.009+/-0.014) calth K-1 mol-1. CrSb2 loses antimony on approaching the peritectic temperature and the composition of the decomposing phase is in the range CrSb1.90 to CrSb1.95. To explore further the homogeneity range of the CrSb2-phase some heat-capacity measurements on CrSb1.85 have also been carried out. Combination of the present results with standard Gibbs energies of formation at 850 K from the literature gives for CrSb2.00:Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22711/1/0000266.pd

Current state of quality of life and patient-reported outcomes research

The 5th EORTC Quality of Life in Cancer Clinical Trials Conference presented the current state of quality of life and other patient-reported outcomes (PROs) research from the perspectives of researchers, regulators, industry representatives, patients and patient advocates and health care professionals. A major theme was the assessment of the burden of cancer treatments, and this was discussed in terms of regulatory challenges in using PRO assessments in clinical trials, patients' experiences in cancer clinical trials, innovative methods and standardisation in cancer research, innovative methods across the disease sites or populations and cancer survivorship. Conferees demonstrated that PROs are becoming more accepted and major efforts are ongoing internationally to standardise PROs measurement, analysis and reporting in trials. Regulators are keen to collaborate with all stakeholders to ensure that the right questions are asked and the right answers are communicated. Improved technology and increased flexibility of measurement instruments are making PROs data more robust. Patients are being encouraged to be patient partners. International collaborations are essential, because this work cannot be accomplished on a national level

Size Dependence of a Temperature-Induced Solid–Solid Phase Transition in Copper(I) Sulfide

Determination of the phase diagrams for the nanocrystalline forms of materials is crucial for our understanding of nanostructures and the design of functional materials using nanoscale building blocks. The ability to study such transformations in nanomaterials with controlled shape offers further insight into transition mechanisms and the influence of particular facets. Here we present an investigation of the size-dependent, temperature-induced solid-solid phase transition in copper sulfide nanorods from low- to high-chalcocite. We find the transition temperature to be substantially reduced, with the high chalcocite phase appearing in the smallest nanocrystals at temperatures so low that they are typical of photovoltaic operation. Size dependence in phase trans- formations suggests the possibility of accessing morphologies that are not found in bulk solids at ambient conditions. These other- wise-inaccessible crystal phases could enable higher-performing materials in a range of applications, including sensing, switching, lighting, and photovoltaics

Alpha Ferric Oxide: Low Temperature Heat Capacity and Thermodynamic Functions

ABS>The heat capacity of synthetic alpha ferric oxide was determined at 5 to 350 K. The experimental technique is described, and the heat capacity and molal thermodyamic functions are tabulated. The heat capacity vs. temperature is shown graphically. (J.R.D.

Heat capacities of the wustites Fe0.9379O and Fe0.9254O at temperatures T from 5 K to 350 K. Thermodynamics of the reactions: xFe(s) + (1/4)Fe3O4(s) = Fe0.7500+xO(s) = Fe1-yO(s) at T [approximate] 850 K, and properties of Fe1-yO(s) to T = 1000 K. Thermodynamics of formation of wustite

Thermodynamic properties of wustites prepared from iron and iron(III) oxide, have been studied by adiabatic calorimetry. Heat-capacity measurements of metastable Fe0.9379O and Fe0.9254O from T = 5 K to 350 K yielded the following integrated values at T = 298.15 K: [[formula]] The wustites were decomposed to iron and iron(II, III) oxide at T [approximate] 800 K and then recombined in the calorimeter. The enthalpy absorption started at T [approximate] 850 K. It needed increased temperature and several days for completion: up to T = 932 K and 7.1 d total for Fe0.9254O, up to T = 898.4 K and 2.1 d for Fe0.9379O, and up to T = 948 K and 3.0 d for Fe0.9254O. By averaging the results for the two last determinations, the molar enthalpy of the eutectoid formation reaction:0.1817Fe+(1/4)Fe3O4 = Fe0.9317O, is [Delta]rHom = (9.04+/-0.25) kJ[middle dot]mol-1. The observed eutectoid formation temperature on heating was 854 K on the iron side and 844 K on the magnetite side. In order to delineate the composition range of wustite at T 0.90O were estimated and combined with available standard Gibbs free energies of formation for wustite and the neighboring magnetite phase at T = 1270 K. The resulting eutectoid composition is Fe0.932+/-0.004O and the calculated eutectoid temperature is (847+/-7) K.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30621/1/0000262.pd