Hydrolysis of tetracalcium phosphate in H3PO4 and KH2PO4

The activity product of tetracalcium phosphate (TTCP, Ca₄(PO₄)₂O), was determined at 37°C, and the hydrolysis of TTCP was investigated in 0.01–0.1 mol l^–1 H₃PO₄ and KH₂PO₄ solutions by means of calcium and phosphorus analyses, X-ray diffraction and infrared analysis. The activity product, defined as K _sp=(Ca²⁺)⁴ (PO ₄ ^3– )² (OH^–)², was 37.36 as pK _sp, which was smaller than that previously reported (42.4). TTCP easily hydrolysed to form calcium-deficient apatite (Ca-def OHAp, Ca_5–x (HPO₄) _x (PO₄)_3–x (OH)_1–x ), or dicalcium phosphate dihydrate (DCPD, CaHPO₄2H₂O), depending on the initial phosphate concentration. With 0.1 mol l^–1 H₃PO₄, TTCP hydrolysed to form DCPD within several minutes. In 0.025 mol l^–1 H₃PO₄ and 0.1 mol l^–1 KH₂PO₄, TTCP hydrolysed to form Ca-def OHAp through DCPD. In the latter solution, a small amount of octacalcium phosphate (OCP, Ca₈(H₂PO₄)₂(PO₄)₄5H₂O), was detected as an intermediate product. In 0.025 mol l^–1 KH₂PO₄, TTCP hydrolysed directly to form Ca-def OHAp. In 0.01 mol l^–1 H₃PO₄, hydrolysis of TTCP was not completed, although Ca-def OHAp was only a product. Thus the final product and the degree of hydrolysis depended on the pH and the overall Ca/P ratio in the reaction system. The rate of Ca-def OHAp formation seemed to be controlled by the dissolution rate of TTCP rather than the crystallization rate of the OHAp.     

Silicon carbide-toughened zirconia ceramics

Tetragonal zirconia polycrystalline (TZP) ceramics containing SiC reinforcement in the form of fine particles (nano-scale), particles (micro-scale), whiskers and platelets were synthesized by hot-pressing. The effects of morphology and grain size of SiC reinforcement on the strength and fracture toughness at room temperature were investigated. The addition of SiC (in whatever form) caused decreases in strength and toughness at room temperature with the exception of whisker-reinforced materials. Toughness fell off with increasing temperature, but nevertheless retained about one-half of the room-temperature value for that particular SiC reinforcement. However, the whisker- and particle-reinforced materials had higher K _lc values at high temperature than fine particle- or platelet-reinforced materials, with values in excess of 7 MPa m^1/2 at 1000 °C. The microstructure was examined for SiC whisker-reinforced/TZP materials by TEM and HREM, to examine the nature of the whisker/zirconia interface.     

Finite twist and extension of a cylindrical elastic membrane

Summary We consider a circular cylindrical membrane subjected to longitudinal extension and twist. The associated equilibrium deformation is considered to be axisymmetric and the analysis is based on a direct two-dimensional formulation. Wrinkling of the membrane is taken into account in an approximate way by introducing arelaxed strain energy function derived from the neo-Hookean strain energy for isotropic elastic solids. Analytical formulae for wrinkled parts of the membrane are used to corroborate the results of a numerical treatment of the full boundary value problem.Dedicated to the memory of A. C. Pipkin     

Direct algorithms for data analysis in the location of sources of radiation from measured differences in distance: Model experiment

Results are presented from a model (numerical) experiment performed to check the efficiency of three groups of direct data-analysis algorithms to be used in satellite location of ground or ocean sources of radiation. The methodology behind the experiment is also explained. Translated from Izmeritel'naya Tekhnika, No. 12, pp. 40–44, December, 1996.     

Ascitic fluid analysis in hepatocellular carcinoma

BACKGROUND: Ascites in patients with hepatocellular carcinoma (HCC) is a poorly characterized subgroup of malignancy-related ascites. Not only the underlying liver disease, but also the tumor growth and spread contributes to the ascites formation. The authors differentiated ascites in HCC from other types of ascites. METHODS: The authors analyzed the ascitic fluid of 185 consecutive patients (89 liver cirrhosis, 33 HCC, 31 peritoneal carcinomatosis, 22 liver metastases, 10 spontaneous bacterial peritonitis). RESULTS: Each subgroup showed a typical pattern. Compared with the cirrhotic patients, those with HCC showed a higher frequency of positive cytologic findings (4 of 33 versus 0/89, P < 0.004), elevated fibronectin concentration (10/33 versus 8/89, P < 0.004), and elevated polymorphonuclear cell count (10/33 versus 5/89 P < 0.004). CONCLUSIONS: A significant number of patients with ascites and HCC patients showed signs of peritoneal infiltration with positive cytologic findings and increased concentration of fibronectin. Moreover, neutrocytic ascites without signs of superinfection is relatively common (30%).     

Comparison of two Varieties of Microcrystalline Cellulose as Filler-Binders II. Hydrochlorothiazide Tablets

In tests of direct-compression hydrochlorothiazide tablets prepared with either of two varieties of microcrystalline cellulose (Avicel PH 101 and Avicel PH 102), PH 102 tablets had better mechanical properties (owing to lower compressibility of mixtures and greater Interparticle bonding), while PH 101 tablets released the active principle faster. These differences are related to observed differences In tablet micropore structure.     

GRAIN SORGHUM WAX AS AN EDIBLE COATING FOR GELATIN-BASED CANDIES1

Gelatin-based candies were coated with medium chain triglyceride (MCT) oil or MCT oil combined with grain sorghum or carnauba wax (8.7% w/w of oil). Compared with uncoated samples, oil/sorghum wax and oil/carnauba wax coatings were equally effective in reducing protein solubility of candies in water (25C) and differences between initial and final diameters of candies subjected to melting. At 0, 5, and 10 days of storage (over calcium sulfate), the candies were evaluated by sensory panelists for surface reflection, pink color, clarity, chalkiness, firmness, adhesiveness, chewiness, cohesiveness, sweetness, sourness, fruit flavor, off-flavor, and aftertaste. Firmness, adhesiveness, chewiness, cohesiveness, and sourness scores increased (P<0.05) linearly with storage time. Samples treated with sorghum or carnauba wax were less shiny, more opaque, chalkier, and had more intense off-flavor and aftertaste than uncoated samples. Samples treated with the laboratory-extracted sorghum wax rated lower than carnauba wax-treated samples for surface reflection, clarity, chalkiness, off-flavor, and aftertaste.     

Ocular toxocariasis

Toxocara canis is a preventable cause of intraocular inflammation and visual loss ... caused by the larvae of toxocara canis usually occurring in children and young adults following accidental ingestion of the larvae from infected dogs. Treatment of ocular toxocariasis can include a combination of cryopexy and photocoagulation, with vitrectomy surgery utilized in the more serious cases.