Synthetic silicate sulphate apatite: mechanical properties and biocompatibility testing

The solid solution series of Ca₁₀(PO₄)₆F₂–Ca₁₀(SiO₄)₃(SO₄)₃F₂ was synthesized by solidstate methods. Tensile strength testing by diametral compression indicated that the silicate sulphate apatites have strength comparable with that of phosphate apatite, with the centre member of the solid solution series [Ca₁₀(PO₄)₃(SiO₄)_1.5(SO₄)_1.5F₂] having the highest tensile strength of 20.7 MN m^–2. The in vivo behaviour of three compositions was evaluated. These materials have increased resorption rate compared with phosphate apatite, and good biocompatibility. The silicatian sulphatian apatites appear to be excellent materials for lowload-bearing bone graft applications.     

Experimental preparation and measurement of quantum states of motion of a trapped atom

Abstract

We report the creation and full determination of several quantum states of motion of a ⁹Be⁺ ion bound in a RF (Paul) trap. The states are coherently prepared from an ion which has been initially laser cooled to the zero-point of motion. We create states having both classical and non-classical character including thermal, number, coherent, squeezed, and ?Schrödinger cat‘ states. The motional quantum state is fully reconstructed using two novel schemes that determine the density matrix in the number state basis or the Wigner function. Our techniques allow well controlled experiments decoherence and related phenomena on the quantum-classical borderline.     

Comparison of cognitive models of depression: Relationships between cognitive constructs and cognitive diathesis–stress match.

The authors examined the relationship between the cognitive components of the Beckian and Hopelessness models of depression by administering measures of dysfunctional attitudes, attributional style, and life stress to a sample of 59 depressed adults. Confirmatory factor analyses indicated that dysfunctional attitudes and attributional style load on separate factors as opposed to a single factor. Additional analyses revealed that depressed persons conforming to diathesis-stress criteria according to each model were largely independent of one another. Results supported the conclusion that the Beckian and Hopelessness models of depression describe distinct cognitive constructs and refer to distinct subsets of depressed persons. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Thrombin activates factor XI on activated platelets in the absence of factor XII

Thrombin can activate factor XI in the presence of dextran sulfate or sulfatides. However, a physiological cofactor for thrombin activation of factor XI has not been identified. We examined this question in a cell-based, tissue factor-initiated model system. In the absence of factor XII, factor XI enhanced thrombin generation in this model. The effect on thrombin generation was reproduced by 2 to 5 pmol/L factor XIa. A specific inhibitor of factor XIIa did not diminish the effect of factor XI. Thus, factor XI can be activated in a model system that does not contain factor XIIa or nonphysiological cofactors. Preincubation of factor XI with activated platelets and thrombin or factor Xa enhanced subsequent thrombin generation in the model system. Preincubation of factor XI with thrombin or factor Xa, but without platelets, did not enhance thrombin generation, suggesting that these proteases might activate factor XI on platelet surfaces. Thrombin and factor Xa were then directly tested for their ability to activate factor XI. In the presence of dextran sulfate, thrombin or factor Xa activated factor XI. Thrombin, but not factor Xa, also cleaved detectable amounts of factor XI in the presence of activated platelets. Thus, thrombin activates enough factor XI to enhance subsequent thrombin generation in a model system. Platelet surfaces might provide the site for thrombin activation of functionally significant amounts of factor XI in vivo.     

Urethane foams from animal fats. IV. Rigid foams from epoxidized glycerides

Liquid polyols have been prepared from epoxidized glyceryl trioleate, glyceryl monooleate, lard oil, neatsfoot oil, and soybean oil by hydration with 24% fluoboric acid. Upon adjustment of the equivalent weight to 100 with triisopropanolamine, the polyols were foamed by reaction with a prepolymer made from oxypropylated sorbitol and tolylene diisocyanate. The resulting rigid foams had densities between 1.66 and 2.34 lbs/ft³ and compressive strengths ranging from 23 to 39 psi (10% compression). The same polyols were used in one-step systems with PAPI as the isocyanate. In general, foam properties were comparable with those obtained from the prepolymer systems. Presented at the AOCS Meeting, New Orleans, 1967. E. Utiliz. Res. Dev. Div., ARS, USDA.     

Childhood depression: A critique of the concept.

Examines the concept of early childhood depression as an independent constellation of symptoms. Opposed to this concept is the view that putative symptoms of depression observed clinically are merely transitory developmental phenomena that dissipate as a function of time. Examination of the published clinical literature indicates that childhood depression is diagnosed and treated as a distinct syndrome; some reports suggest that the condition may even be underdiagnosed. Data adduced from longitudinal and epidemiological studies, however, show marked variations of such symptoms with children's age: symptoms are less frequent in older children. Moreover, the prevalence of many of these symptoms in normal children is great enough to suggest that clinical manifestations are neither statistically atypical nor psychopathologic. Pertinent epidemiological reasearch has not, however, been undertaken. It is concluded that no reliable and valid method for assessing this presumed condition in children has been developed, and diagnosis is based largely on surmise. It is suggested that the question of iatrogenic effects of treatment needs to be studied. (56 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Liquid crystal order in colloidal suspensions of spheroidal particles by direct current electric field assembly

DC electric fields are used to produce colloidal assemblies with orientational and layered positional order from a dilute suspension of spheroidal particles. These 3D assemblies, which can be visualized in situ by confocal microscopy, are achieved in short time spans (t < 1 h) by the application of a constant voltage across the capacitor-like device. This method yields denser and more ordered assemblies than had been previously reported with other assembly methods. Structures with a high degree of orientational order as well as layered positional order normal to the electrode surface are observed. These colloidal structures are explained as a consequence of electrophoretic deposition and field-assisted assembly. The interplay between the deposition rate and the rotational Brownian motion is found to be critical for the optimal ordering, which occurs when these rates, as quantified by the Peclet number, are of order one. The results suggest that the mechanism leading to ordering is equilibrium self-assembly but with kinetics dramatically accelerated by the application of the DC electric field. Finally, the crystalline symmetry of the densest structure formed is determined and compared with previously studied spheroidal assemblies.