10,069 research outputs found
Metastable Solid Solutions in the Gallium Antimonide-Germanium Pseudobinary System
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Amorphous Phase in Palladium—Silicon Alloys
By rapid cooling from the melt, an amorphous phase has been obtained in palladium—silicon alloys containing 15 to 23 at.% Si. This phase is stable at room temperature and crystallization cannot be detected after one month at 250°C. With rates of heating greater than 20°C/min, rapid crystallization takes place at 400°C, with a heat release of approximately 1000 cal/mole. The electrical resistivity of an alloy containing 17 at.% Si at room temperature is 2.6 times that of the equilibrium alloy. The resistivity decreases linearly with decreasing temperature and is about 95% of the room-temperature value at 2°K. Various factors involved in the retention of amorphous phases in rapidly quenched liquid alloys are discussed
Metallopanstimulin as a marker for head and neck cancer
BACKGROUND: Metallopanstimulin (MPS-1) is a ribosomal protein that is found in elevated amounts in the sera of patients with head and neck squamous cell carcinoma (HNSCC). We used a test, denoted MPS-H, which detects MPS-1 and MPS-1-like proteins, to determine the relationship between MPS-H serum levels and clinical status of patients with, or at risk for, HNSCC. PATIENTS AND METHODS: A total of 125 patients were prospectively enrolled from a university head and neck oncology clinic. Participants included only newly diagnosed HNSCC patients. Two control groups, including 25 non-smokers and 64 smokers, were studied for comparison. A total of 821 serum samples collected over a twenty-four month period were analyzed by the MPS-H radioimmunoassay. RESULTS: HNSCC, non-smokers, and smokers had average MPS-H values of 41.5 ng/mL, 10.2 ng/mL, and 12.8 ng/mL, respectively (p = 0.0001). CONCLUSION: We conclude that MPS-1 and MPS-1-like proteins are elevated in patients with HNSCC, and that MPS-H appears to be a promising marker of presence of disease and response to treatment in HNSCC patients
Metastable amorphous phases in tellurium-base alloys
An amorphous structure has been reported in a gold-silicon alloy (2) obtained by rapid cooling through the solidification range.(3) This amorphous alloy, however, was not stable at room temperature. Crystallization into one or several metastable phases took place within twenty-four hours, and a detailed study of the structure could not easily be carried out
Softness dependence of the Anomalies for the Continuous Shouldered Well potential
By molecular dynamic simulations we study a system of particles interacting
through a continuous isotropic pairwise core-softened potential consisting of a
repulsive shoulder and an attractive well. The model displays a phase diagram
with three fluid phases, a gas-liquid critical point, a liquid-liquid critical
point, and anomalies in density, diffusion and structure. The hierarchy of the
anomalies is the same as for water. We study the effect on the anomalies of
varying the softness of the potential. We find that, making the soft-core
steeper, the regions of density and diffusion anomalies contract in the T -
{\rho} plane, while the region of structural anomaly is weakly affected.
Therefore, a liquid can have anomalous structural behavior without density or
diffusion anomalies. We show that, by considering as effective distances those
corresponding to the maxima of the first two peaks of the radial distribution
function g(r) in the high-density liquid, we can generalize to continuous
two-scales potentials a criterion for the occurrence of the anomalies of
density and diffusion, originally proposed for discontinuous potentials. We
observe that the knowledge of the structural behavior within the first two
coordination shells of the liquid is not enough to establish the occurrence of
the anomalies. By introducing the density derivative of the the cumulative
order integral of the excess entropy we show that the anomalous behavior is
regulated by the structural order at distances as large as the fourth
coordination shell. By comparing the results for different softness of the
potential, we conclude that the disappearing of the density and diffusion
anomalies for the steeper potentials is due to a more structured short-range
order. All these results increase our understanding on how, knowing the
interaction potential, we can evaluate the possible presence of anomalies for a
liquid
Fermi and intramode relaxation phenomena in CO2lasers
Using a 1 ns pulse from a short-pulse CO2laser system, the evolution of the gain in a TEA system was studied during and after amplification. This resulted in a very direct observation of a few relaxation processes. We estimated the effective intramode relaxation rate constant to be larger than6 times 10^{6}torr-1/s. The Fermi relaxation time constant was found to be 30 ± 7 ns at 760 torr. We conclude that for nanosecond pulse amplification, intramode relaxation cannot be neglected
Light transmission assisted by Brewster-Zennek modes in chromium films carrying a subwavelength hole array
This work confirms that not only surface plasmons but many other kinds of
electromagnetic eigenmodes should be considered in explaining the values of the
transmittivity through a slab bearing a two-dimensional periodic corrugation.
Specifically, the role of Brewster-Zennek modes appearing in metallic films
exhibiting regions of weak positive dielectric constant. It is proposed that
these modes play a significant role in the light transmission in a thin
chromium film perforated with normal cylindrical holes, for appropriate lattice
parameters.Comment: 5 pages, 4 figures. Published versio
Phase behaviour of binary mixtures of diamagnetic colloidal platelets in an external magnetic field
Using fundamental measure density functional theory we investigate
paranematic-nematic and nematic-nematic phase coexistence in binary mixtures of
circular platelets with vanishing thicknesses. An external magnetic field
induces uniaxial alignment and acts on the platelets with a strength that is
taken to scale with the platelet area. At particle diameter ratio lambda=1.5
the system displays paranematic-nematic coexistence. For lambda=2, demixing
into two nematic states with different compositions also occurs, between an
upper critical point and a paranematic-nematic-nematic triple point. Increasing
the field strength leads to shrinking of the coexistence regions. At high
enough field strength a closed loop of immiscibility is induced and phase
coexistence vanishes at a double critical point above which the system is
homogeneously nematic. For lambda=2.5, besides paranematic-nematic coexistence,
there is nematic-nematic coexistence which persists and hence does not end in a
critical point. The partial orientational order parameters along the binodals
vary strongly with composition and connect smoothly for each species when
closed loops of immiscibility are present in the corresponding phase diagram.Comment: 9 pages, to appear in J.Phys:Condensed Matte
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