Plasma calcining of pigment particles for thermal control coatings

Method utilizes an RF excited plasma to surface deactivate thermally stable powders at high temperatures. Utilization of this plasma heat treatment at high temperatures can be carried out without grain growth, calcination, or agglomeration

Induction plasma calcining of pigment particles for thermal control coatings

Induction plasma calcining of pigment particles for thermal control coatings on space vehicle

Induction plasma calcining of pigment particles for thermal control coatings Interim technical report, 1 Aug. 1969 - 31 Mar. 1970

Induction plasma heating for calcining pigment particles in thermal control coating

Passivation of pigment particles for thermal control coatings

The preparation of a matrix of 48 samples consisting of pigments and pigmented paints is described. The results obtained from testing these samples by electron spin resonance and by in situ spectral reflectance measurements in space simulation tests are presented. Conclusions and recommendations for further research are given

Black hole evaporation in a spherically symmetric non-commutative space-time

Recent work in the literature has studied the quantum-mechanical decay of a Schwarzschild-like black hole, formed by gravitational collapse, into almost-flat space-time and weak radiation at a very late time. The relevant quantum amplitudes have been evaluated for bosonic and fermionic fields, showing that no information is lost in collapse to a black hole. On the other hand, recent developments in noncommutative geometry have shown that, in general relativity, the effects of non-commutativity can be taken into account by keeping the standard form of the Einstein tensor on the left-hand side of the field equations and introducing a modified energy-momentum tensor as a source on the right-hand side. Relying on the recently obtained non-commutativity effect on a static, spherically symmetric metric, we have considered from a new perspective the quantum amplitudes in black hole evaporation. The general relativity analysis of spin-2 amplitudes has been shown to be modified by a multiplicative factor F depending on a constant non-commutativity parameter and on the upper limit R of the radial coordinate. Limiting forms of F have been derived which are compatible with the adiabatic approximation.Comment: 8 pages, Latex file with IOP macros, prepared for the QFEXT07 Conference, Leipzig, September 200

Constraints on mantle ^3He fluxes and deep-sea circulation from an oceanic general circulation model

We have simulated the steady-state distribution of helium in the deep sea to investigate the magnitude and spatial and temporal variability of mantle degassing and to characterize deep-sea circulation and ventilation. The simulation was produced by linking a simple source function for helium injected at mid-ocean ridges with an oceanic general circulation model (GCM). By assuming that the flux of mantle helium is linearly proportional to the seafloor spreading rate and by using previous estimates for the total flux of mantle helium into the oceans, the GCM yields an oceanic ^3He distribution which is in qualitative agreement with observations both in overall magnitude and in general distribution. This provides new evidence that the flux of mantle ^3He into the oceans is about 1000 mol/yr and that mid-ocean ridges are the dominant source of mantle helium. Although the match with observations is good in the Pacific and Indian Oceans, the simulated ^3He anomalies throughout the Atlantic Ocean are much higher than has been measured. Because the GCM is thought to reproduce Atlantic circulation reasonably well, this discrepancy suggests an error in the helium source function. Either helium injection is not a linear function of seafloor emplacement rate, or eruption and concomitant degassing are highly episodic at the slow spreading rates characteristic of the Mid-Atlantic Ridge (MAR). The latter explanation would imply minimal volcanic activity along the entire length of the MAR over the last few centuries. In addition to constraints on the degassing flux, our work provides information on the transport and ventilation of deep ocean waters and constrains the degree to which current GCMs can reproduce deep-water circulation patterns. While the results generally support the GCM's abyssal circulation, our simulation reveals regions of overly-intense lateral diffusion and upwelling in the model, particularly in the equatorial Pacific. Similarly, there appears to be insufficient production of He-ventilated bottom waters in the model Antarctic. These observations suggest that further refinement of the GCM abyssal circulation is required

Sclerostin does not play a major role in the pathogenesis of skeletal complications in type 2 diabetes mellitus

In contrast to previously reported elevations in serum sclerostin levels in diabetic patients, the present study shows that the impaired bone microarchitecture and cellular turnover associated with type 2 diabetes mellitus (T2DM)-like conditions in ZDF rats are not correlated with changes in serum and bone sclerostin expression. INTRODUCTION: T2DM is associated with impaired skeletal structure and a higher prevalence of bone fractures. Sclerostin, a negative regulator of bone formation, is elevated in serum of diabetic patients. We aimed to relate changes in bone architecture and cellular activities to sclerostin production in the Zucker diabetic fatty (ZDF) rat. METHODS: Bone density and architecture were measured by micro-CT and bone remodelling by histomorphometry in tibiae and femurs of 14-week-old male ZDF rats and lean Zucker controls (n = 6/group). RESULTS: ZDF rats showed lower trabecular bone mineral density and bone mass compared to controls, due to decreases in bone volume and thickness, along with impaired bone connectivity and cortical bone geometry. Bone remodelling was impaired in diabetic rats, demonstrated by decreased bone formation rate and increased percentage of tartrate-resistant acid phosphatase-positive osteoclastic surfaces. Serum sclerostin levels (ELISA) were higher in ZDF compared to lean rats at 9 weeks (+40 %, p < 0.01), but this difference disappeared as their glucose control deteriorated and by week 14, ZDF rats had lower sclerostin levels than control rats (-44 %, p < 0.0001). Bone sclerostin mRNA (qPCR) and protein (immunohistochemistry) were similar in ZDF, and lean rats at 14 weeks and genotype did not affect the number of empty osteocytic lacunae in cortical and trabecular bone. CONCLUSION: T2DM results in impaired skeletal architecture through altered remodelling pathways, but despite altered serum levels, it does not appear that sclerostin contributes to the deleterious effect of T2DM in rat bone

Strain dependence of the Mn anisotropy in ferromagnetic semiconductors observed by x-ray magnetic circular dichroism

We demonstrate sensitivity of the Mn 3d valence states to strain in the ferromagnetic semiconductors (Ga,Mn)As and (Al,Ga,Mn)As, using x-ray magnetic circular dichroism (XMCD). The spectral shape of the Mn $L_{2,3}$ XMCD is dependent on the orientation of the magnetization, and features with cubic and uniaxial dependence are distinguished. Reversing the strain reverses the sign of the uniaxial anisotropy of the Mn $L_3$ pre-peak which is ascribed to transitions from the Mn 2p core level to p-d hybridized valence band hole states. With increasing carrier localization, the $L_3$ pre-peak intensity increases, indicating an increasing 3d character of the hybridized holes.Comment: 4 pages plus 2 figures, accepted for publication in Physical Review

In-plane uniaxial anisotropy rotations in (Ga,Mn)As thin films

We show, by SQUID magnetometry, that in (Ga,Mn)As films the in-plane uniaxial magnetic easy axis is consistently associated with particular crystallographic directions and that it can be rotated from the [-110] direction to the [110] direction by low temperature annealing. We show that this behavior is hole-density-dependent and does not originate from surface anisotropy. The presence of uniaxial anisotropy as well its dependence on the hole-concentration and temperature can be explained in terms of the p-d Zener model of the ferromagnetism assuming a small trigonal distortion.Comment: 4 pages, 6 Postscript figures, uses revtex