Inhibiting Effect of Additives on Pressure Solution of Calcite

The task of protection of cultural heritage requires a better understanding of combined effects of mechanical and chemical factors involved in environmental deterioration of monuments. The present paper deals with extending some known physicochemical methods proposed for inhibiting the decay of unstressed materials to their study during water-assisted deformation. The tests have been carried out on natural limestone samples and calcite powders in CaCO₃ saturated aqueous solutions under static loads causing measurable pressure solution creep. In the solutions containing 1-hydroxyethylidene-1,1-diphosphonic acid, nitrilotriacetic acid, or ethylenediaminetetraacetic acid, the creep rate decreases considerably with increasing concentration of additives. The extent of creep deceleration has been found to be proportional to the independently estimated calcite surface area occupied by adsorbed species. This fact enables us to discriminate the adsorption-induced effect from other variables controlling the pressure solution rate and may be used in screening of compounds able to minimize the environmental impact on marble and limestone objects undergoing mechanical stresses.     

Treatment of vertigo with betaserk in patients with vascular and traumatic cerebral injuries

Managed care's focus on patient-centered care has made the need for point-of-care (POC) clinical systems more critical than ever. This article examines some of the more common POC options available, explains what nurses need to know to choose among them, and suggests ways to ensure that nursing's needs are addressed in the selection process.     

Effect of Heat Treatment on the Structure and Properties of Sheet Semifinished Products Made of a Heat-Resistant Alloy Based on Titanium and Alloyed with Rare-Earth Metal

This study is a continuation of investigations into the influence of microalloying with rare-earth metal gadolinium on the structure formation and properties of the titanium alloy under the thermal effect. It has been established previously that the introduction of gadolinium into an experimental heat-resistant alloy promotes the structural transformation in the cast state, leads to a decrease in size of structural components, and affects the growth and nucleation rates of the particles. It is revealed that additional alloying with gadolinium exerts no significant effect on the formation of the microstructure of hot-rolled sheets made of heat-resistant experimental alloy after annealing at 950°C. The structure is presented by equiaxial particles of the primary α-phase, secondary α-phase with lamellar morphology, and a small amount of the β-phase. It is determined that ordering proceeds in primary α-phase particles and precipitation α₂-phase particles is observed during isothermal holding (t = 700°C, τ = 100 h), while silicide chemical compounds form at the α/β-boundary. It is shown that the α₂-phase is formed in the body of the particles of the primary α-phase, while its near-boundary regions are free of inclusions, which is caused by their depletion with aluminum due to the β → α transformation. It is established that the sizes of precipitating silicide particles decrease with an increase in the gadolinium content in the alloy. The average particle size is 0.2–0.3 μm in the alloy with 0% Gd; on the contrary, it decreases to 0.05–0.1 μm in the alloy with 0.2% Gd. It is shown that the introduction of 0.2% Gd into the heat-resistant titanium alloy leads to a decrease in the depth of the “alpha-case” layer and an increase in cyclic durability and short-term strength at 700°C by 30%.     

Notes on wormhole existence in scalar-tensor and <Emphasis Type="Italic">F</Emphasis>(<Emphasis Type="Italic">R</Emphasis>) gravity

Some recent papers have claimed the existence of static, spherically symmetric wormhole solutions to gravitational field equations in the absence of ghost (or phantom) degrees of freedom. We show that in some such cases the solutions in question are actually not of wormhole nature while in cases where a wormhole is obtained, the effective gravitational constant G _eff is negative in some region of space, i.e., the graviton becomes a ghost. In particular, it is confirmed that there are no vacuum wormhole solutions of the Brans-Dicke theory with zero potential and the coupling constant ω > −3/2, except for the case ω = 0; in the latter case, G _eff < 0 in the region beyond the throat. The same is true for wormhole solutions of F(R) gravity: special wormhole solutions are only possible if F(R) contains an extremum at which G _eff changes its sign.