30,280 research outputs found
The Density of Titanium(IV) Oxide Liquid
The density of TiO2 liquid in equilibrium with air has been measured at 1875° to 1925°C using an Ir double bob Archimedean method. The melt density data have been combined with data extrapolated from the CaSiO3─TiO2 join at 1600°C. A combined fit to these density data yields the following description of the density of liquid TiO2: ρ= 3.7611 - 0.00028T(°C), in the temperature range of 1600° to 1925°C. This expansivity value is consistent with those obtained on TiO2-rich melts using a Pt-based system at lower temperature and with multicomponent oxide data. The similarity between the volume of liquid TiO2 and that of crystalline rutile implies a dominantly octahedral coordination of Ti in the liquid state
Shock-induced CO2 loss from CaCO3: Implications for early planetary atmospheres
Recovered samples from shock recovery experiments on single crystal calcite were subjected to thermogravimetric analysis to determine the amount of post-shock CO2, the decarbonization interval and the activation energy, for the removal of remaining CO2 in shock-loaded calcite. Comparison of post-shock CO2 with that initially present determines shock-induced CO2 loss as a function of shock pressure. Incipient to complete CO2 loss occurs over a pressure range of approximately 10 to approximately 70 GPa. Optical and scanning electron microscopy reveal structural changes, which are related to the shock-loading. The occurrence of dark, diffuse areas, which can be resolved as highly vesicular areas as observed with a scanning electron microscope are interpreted as representing quenched partial melts, into which shock-released CO2 was injected. The experimental results are used to constrain models of shock-produced, primary CO2 atmospheres on the accreting terrestrial planets
Magnetooptical sum rules close to the Mott transition
We derive new sum rules for the real and imaginary parts of the
frequency-dependent Hall constant and Hall conductivity. As an example, we
discuss their relevance to the doped Mott insulator that we describe within the
dynamical mean-field theory of strongly correlated electron systems.Comment: 4 pages, 4 ps figures; accepted for publication in PR
Setting high expectations is not enough: linkages between expectation climate strength, trust, and employee performance
Drawing on Climate Theory and Social Exchange Theory, we examine whether and how the strength of the expectation climate, defined as the degree of agreement amongst job incumbents on what is expected from them, affects their job performance. To explain this relationship, we utilize mediating trust-in-the-organization effects as an explanatory avenue. In a time-lagged data sample of 568 public service employees, whose job performance is rated by their 242 line managers, we apply multilevel modelling. We employed stratified random sampling techniques across 75 job functions in a large, public sector organization in Belgium. Our analysis provides support for the argument that expectation climate strength via mediating trust-in-the-organization effects impacts positively on the relationship between employee expectations and performance. Specifically, the significant association of the expectation climate strength with trust suggests that the perceived consensus about the expectations among different job incumbents demonstrates an organization’s trustworthiness and reliability to pursue intentions that are deemed favorable for employees. We conjecture that expectation climate strength breeds trust which strengthens employees’ job performance. HRM professionals in general, and line managers in particular, should heed our advice and carefully manage their tools and practices in an effort to signal compatible expectancies to different job incumbents in the same or similar roles. Our results shed new light on the mechanisms through which the strength of collective expectations impacts employee outcomes
Infrared Astronomical Satellite (IRAS) analysis of the transmittance of off-axis energy due to scattering and diffraction
Stray light transmittance is analyzed. Mathematical models are evaluated. The results of scatter and diffraction are considered separately, and the combined transmittance values evaluated
B-Meson Distribution Amplitudes of Geometric Twist vs. Dynamical Twist
Two- and three-particle distribution amplitudes of heavy pseudoscalar mesons
of well-defined geometric twist are introduced. They are obtained from
appropriately parametrized vacuum-to-meson matrix elements by applying those
twist projectors which determine the enclosed light-cone operators of definite
geometric twist and, in addition, observing the heavy quark constraint.
Comparing these distribution amplitudes with the conventional ones of dynamical
twist we derive relations between them, partially being of Wandzura-Wilczek
type; also sum rules of Burkhardt-Cottingham type are derived.The derivation is
performed for the (double) Mellin moments and then re-summed to the non-local
distribution amplitudes. Furthermore, a parametrization of vacuum-to-meson
matrix elements for non-local operators off the light-cone in terms of
distribution amplitudes accompanying independent kinematical structures is
derived.Comment: 18 pages, Latex 2e, no figure
Hall effect in quasi one-dimensional organic conductors
We study the Hall effect in a system of weakly coupled Luttinger Liquid
chains, using a Memory function approach to compute the Hall constant in the
presence of umklapp scattering along the chains. In this approximation, the
Hall constant decomposes into two terms: a high-frequency term and a Memory
function term. For the case of zero umklapp scattering, where the Memory
function vanishes, the Hall constant is simply the band value, in agreement
with former results in a similar model with no dissipation along the chains.
With umklapp scattering along the chains, we find a power-law temperature
dependance of the Hall constant. We discuss the applications to quasi 1D
organic conductors at high temperatures.Comment: Proceedings of the ISCOM conference "Sixth International Symposium on
Crystalline Organic Metals, Superconductors, and Ferromagnets", Key West,
Florida, USA (Sept. 2005), to be plublished in the Journal of Low Temperature
Physic
Cognitive performance in multiple system atrophy
The cognitive performance of a group of patients with multiple system atrophy (MSA) of striato-nigral predominance was compared with that of age and IQ matched control subjects, using three tests sensitive to frontal lobe dysfunction and a battery sensitive to memory and learning deficits in Parkinson's disease and dementia of the Alzheimer type. The MSA group showed significant deficits in all three of the tests previously shown to be sensitive to frontal lobe dysfunction. Thus, a significant proportion of patients from the MSA group failed an attentional set-shifting test, specifically at the stage when an extra-dimensional shift was required. They were also impaired in a subject-ordered test of spatial working memory. The MSA group showed deficits mostly confined to measures of speed of thinking, rather than accuracy, on the Tower of London task. These deficits were seen in the absence of consistent impairments in language or visual perception. Moreover, the MSA group showed no significant deficits in tests of spatial and pattern recognition previously shown to be sensitive to patients early in the course of probable Alzheimer's disease and only a few patients exhibited impairment on the Warrington Recognition Memory Test. There were impairments on other tests of visual memory and learning relative to matched controls, but these could not easily be related to fundamental deficits of memory or learning. Thus, on a matching-to-sample task the patients were impaired at simultaneous but not delayed matching to sample, whereas difficulties in a pattern-location learning task were more evident at its initial, easier stages. The MSA group showed no consistent evidence of intellectual deterioration as assessed from their performance on subtests of the Wechsler Adult Intelligence Scale (WAIS) and the National Adult Reading Test (NART). Consideration of individual cases showed that there was some heterogeneity in the pattern of deficits in the MSA group, with one patient showing no impairment, even in the face of considerable physical disability. The results show a distinctive pattern of cognitive deficits, unlike those previously seen using the same tests in patients with Parkinson's and Alzheimer's diseases, and suggesting a prominent frontal-lobe-like component. The implications for concepts of 'subcortical' dementia and 'fronto-striatal' cognitive dysfunction are considered
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