In vitro bioactivity,physical and mechanical properties of carbonated-fluoroapatite during mechanochemical synthesis

Mechanochemical synthesis method has been used to prepare nanocrystalline B-type carbonated fluoroapatite (B-CFA). Fourier transform infrared (FTIR) spectroscopy along with X-ray diffraction (XRD) technique was carried out to investigate the effect of milling time on the preparation of B-CFA. In vitro bioactivity of FA during synthesis was examined also by FTIR spectroscopy after soaking in simulated body fluid (SBF). Furthermore, the mechanical properties including hardness, fracture toughness, compressive strength, longitudinal modulus, Young's modulus, shear modulus and bulk modulus of the sintered samples, at 1000 and 1200?°C, for different milling times were measured by ultrasonic non-destructive technique. Furthermore, theoretical model is presented for FA according to the formula Ca₁₀(PO₄)₆F₂·18H₂O. The QSAR properties including log P, total energy, heat of formation, energy gap, dipole moment, ionization potential, polarizability, molar refractivity and molecular weight were calculated. FTIR and XRD results revealed that single phase B-CFA was successfully formed after 9?h of milling. Moreover, the results also pointed out that the total energy of FA is much more than hydroxyapatite (HA) indicating that the structure of FA is more stable than HA. These results are in agreement with XRD ones for the sintered samples where they did not undergo decomposition reflecting its thermal stability.     

Mechanical properties,in vitro and in vivo bioactivity assessment of Na2O-CaO-P2O5-B2O3-SiO2 glass-ceramics

Glasses having chemical composition based on Na₂O-CaO-P₂O₅-SiO₂ system were crystallized. Then, the resultant crystallized phases were examined by X-ray diffraction technique. Furthermore, density, microhardness and fracture toughness were measured. In order to investigate the biological responses of these glass-ceramic samples, in vitro and in vivo experiments were performed. In vitro test was performed by soaking the prepared samples in simulated body fluid (SBF) for different time intervals and then, specimens were examined by Fourier transform infrared spectroscopy. Moreover, the conversion kinetics of these samples to hydroxyapatite (HA) were determined by measuring the weight loss of glass-ceramic grains, pH values of SBF solution and recording the ionic concentrations of Si, B, P and Ca using inductive coupled plasma-atomic emission spectroscopy. The results pointed out that the prepared samples possessed fair in vitro bioactivity. However, after six weeks of implantation, the prepared glass-ceramics, on the contrary to the parent glasses, did not exhibit any bioactivity suggesting that they may need longer time. On the other hand, the crystallization process caused significant increases of microhardness and density values. From these results, we can conclude that the prepared glasses and glass-ceramics had suitable properties for bone grafts and dental applications, respectively.     

Actin filaments facilitate insulin activation of the src and collagen homologous/mitogen-activated protein kinase pathway leading to DNA synthesis and c-fos expression

The exact mechanism of the spatial organization of the insulin signaling pathway leading to nuclear events remains unknown. Here, we investigated the involvement of the actin cytoskeleton in propagation of insulin signaling events leading to DNA synthesis and expression of the immediate early genes c-fos and c-jun in L6 muscle cells. Insulin reorganized the cellular actin network and increased the rate of DNA synthesis and the levels of c-fos mRNA, but not those of c-jun mRNA, in undifferentiated L6 myoblasts. Similarly, insulin markedly elevated the levels of c-fos mRNA but not of c-jun mRNA in differentiated L6 myotubes. Disassembly of the actin filaments by cytochalasin D, latrunculin B, or botulinum C2 toxin significantly inhibited insulin-mediated DNA synthesis in myoblasts and abolished stimulation of c-fos expression by the hormone in myoblasts and myotubes. Actin disassembly abolished insulin-induced phosphorylation and activation of extracellulor signal-regulated kinases, activation of a 65-kda member of the p21-activated kinases, and phosphorylation of p38 mitogen-activated protein kinases but did not prevent activation of phosphatidylinositol 3-kinase and p70(S6k). Under these conditions, insulin-induced Ras activation was also abolished, and Grb2 association with the Src and collogen homologous (Shc) molecule was inhibited without inhibition of the tyrosine phosphorylation of Shc. We conclude that the actin filament network plays an essential role in insulin regulation of Shc-dependent signaling events governing gene expression by facilitating the interaction of Shc with Grb2.     

Evaluation of controlled low strength materials containing industrial by-products

A controlled low strength material (CLSM) is a self-compacted, cementitious material used primarily as a backfill. It is also known as a flowable fill which is usually a mixture of fine aggregates, small amount of cement, fly ash, and water. To be classified as a CLSM, the mixture must have a compressive strength between 345 and 8400 kPa. This paper evaluates the potential use of cement by-pass dust, incinerator ash and copper slag as a CLSM. Mixtures were designed to produce a CLSM, with a low compressive strength (less than 1034 kPa), that can be excavated without using any mechanical equipment. Slump, unit weight and unconfined compressive strength tests were conducted on various mixtures. Cubical and cylindrical specimens were prepared and cured at room temperature and in sealed plastic bags. Results indicate that with a good mix design it is possible to produce a CLSM with good mechanical properties to meet design requirements. Mixing these materials with cement and sand produced better results than using them alone due to their low pozzolanic activity. Curing method and period can have considerable effects on the strength of a CLSM.     

Perinatal intervention trial in Africa: effect of a birth canal cleansing intervention to prevent HIV transmission

BACKGROUND: Perinatal transmission of human immunodeficiency virus (HIV) type 1 contributes significantly to infant mortality. Exposure in the birth canal may account for some transmission. We examined the efficacy of a birth canal washing procedure in reducing perinatal transmission in Malawi. METHODS: The infection status of infants of 3327 control women (conventional delivery procedures) was compared with that of 3637 infants of intervention-delivered women. The infants' HIV status was determined by polymerase chain reaction on dried blood spots collected at 6 and 12 weeks of age. The intervention consisted of manual cleansing of the birth canal with a cotton pad soaked in 0.25% chlorhexidine, which was done on admission in labour and every 4 h until delivery. FINDINGS: No adverse reactions to the intervention procedure were seen. 2094 (30%) of the enrolled women were HIV-infected, and 59% of their infants were seen in follow-up. Among 982 vaginal vertex singleton deliveries to HIV-infected women, 269 (27%) infants were infected. The intervention had no significant impact on HIV transmission rates (27% in 505 intervention women compared with 28% in 477 control women), except when membranes were ruptured more than 4 h before delivery (transmission 25% in the intervention group vs 39% in the control group). INTERPRETATION: If birth canal exposure is an important risk factor, different or additional methods to reduce the risk of perinatal HIV transmission should be tested. Alternatively, perhaps birth canal exposure is not a major contributor to perinatal infection risk.     

Sorptivity: a reliable measurement for surface absorption of masonry brick units

An inherent weakness of masonry structures is low bond and bond strength. Although masonry bond is a result of many interrelated factors (e.g. surface texture, surface absorption and mortar composition, etc.), surface absorption of masonry units has a significant effect on masonry bond. Following a critical review of the current measurements of the surface absorption of masonry units, the theoretical bases of sorptivity as a measurement of surface absorption are presented. The limitations of sorptivity measurement are discussed through a review of the application of the concept of sorptivity to different porous building materials. An experimental programme to examine the surface absorption of masonry units is described. Analysis of the results showed sorptivity to be a simple and reliable measurement of surface absorption for masonry units that could be used in building standards.     

W-CDMA Uplink Capacity and Interference Statistics of Rural Highways Cross-Shaped Microcells

The capacity and the interference statistics of the sectors of the cross-shaped W-CDMA cell are studied using an analytical approach. A model of 49 cells is used to analyse the uplink, which limits the capacity. The cells are assumed to exist in rural zones. The capacity and the interference statistics of the microcell are studied for different sector ranges and different antenna sidelobe levels.     

A new rigorous two-phase kinetic model for accurate prediction of the asphaltene deposition rate during the oil flow in porous media of petroleum reservoirs

Asphaltene formation and deposition in oil reservoirs are the most important problems in petroleum industry. A new rigorous two-phase kinetic model for simulation of flow behavior considering the asphaltene deposition process is presented in this work. All governing equations considering the proposed new adsorption kinetic model are solved by finite difference method. The presented model is validated using the most accurate available data and different oil samples. The proposed approach can be used for accurate evaluation of the effect of asphaltene deposition on the oil flowing condition in porous media of petroleum reservoirs.     

Model‐predictive safety system for proactive detection of operation hazards

A method of designing model‐predictive safety systems that can detect operation hazards proactively is presented. Such a proactive safety system has two major components: a set of operability constraints and a robust state estimator. The safety system triggers alarm(s) in real time when the process is unable to satisfy an operability constraint over a receding time‐horizon into the future. In other words, the system uses a process model to project the process operability status and to generate alarm signals indicating the presence of a present or future operation hazard. Unlike typical existing safety systems, it systematically accounts for nonlinearities and interactions among process variables to generate alarm signals; it provides alarm signals tied to unmeasurable, but detectable, state variables; and it generates alarm signals before an actual operation hazard occurs. The application and performance of the method are shown using a polymerization reactor example. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2024–2042, 2016