Prevention of tooth hypersensitivity caused by the hydrodynamic action of zinc phosphate and composite resin luting cements (SEM) study

This study was done to determine the role of cement liner as a reducing factor to the fluid movement in order to prevent tooth hypersensitivity according to the hydrodynamic theory during cementation of crowns. A total of fourty freshly extracted intact lower molar were selected for this study. After conventional tooth preparation the teeth were sub-divided into four equal groups to identify the role of cement liner in preventing the penetration of used cement into the dentinal tubules. Scanning electron microscopic study proved the efficiency of glass ionomer liner on preventing cement penetration into the dentinal tubules.     

Degradation of benzene,toluene ethylbenzene and p‐xylene (BTEX) in aqueous solutions using UV/H2O2 system

The homogeneous degradation of benzene (B), toluene (T), ethylbenzene (E) and p‐xylene (X) (BTEX) was studied in aqueous solutions, at pH 3.0, of hydrogen peroxide (5.8 mM ) under UV irradiation in a photoreactor equipped with a 300 nm lamp of light intensity 3.5 × 10^?5 Ein L^?1 min^?1. BTEX was substantially degraded by the H₂O₂/UV system, with >90% disappearing in 10 min of irradiation. The decomposition of BTEX was studied either as single or as multi‐component systems. The effects of irradiation time, amounts of H₂O₂ in molar ratios, rate of degradation and competition between components were thoroughly examined. It can be stated that the rate of BTEX degradation in mixture was higher than those for the individual components due to external effects of the absorption of UV light by the mixture, and their effects on enhancing the formation of OH^? radicals. The appropriate figure of merit, the electrical energy per mass (EE/M), was estimated at various molar ratios and it was confirmed that the best value was the one depicted for p‐xylene (0.065 kWh kg^?1). A theoretical model for the degradation pathway was proposed. Copyright © 2004 Society of Chemical Industry     

Structure refinement, infrared and Raman spectra of KDyP4O12

Crystals of KDyP₄O₁₂ have been grown by the flux technique and characterized by single-crystal X-ray diffraction. KDyP₄O₁₂ crystallizes in the monoclinic C2/c space group with lattice parameters: a=7.8158(3), b=12.3401(5), c=10.4382(3) Å, β=111.053°(2), V=939.6(4) Å³, Z=4. The crystal structure has been refined yielding a final R(F²)=0.034 and R_w(F²)=0.082 for 902 independent reflections (F_o²≥2σ(F_o²)). The structure of KDyP₄O₁₂ consists of DyO₈ polyhedra and cyclotetraphosphate P₄O₁₂ groups sharing oxygen atoms to form a three-dimensional framework, delimiting intersecting tunnels in which the potassium ion is located. Each K⁺ ion is bonded to 10 oxygen atoms. The energies of the vibrational modes of the crystal were obtained from measurements of the infrared and Raman spectra.     

Reconfigurable multilevel phase-shift keying encoder-decoder for all-optical networks

We demonstrate the application of a uniform Bragg grating as a dynamically reconfigurable phase encoder-decoder for optical systems. Precise discrete phase modulation between chips is obtained simply by heating segments along the grating with fine resistive wires. Its reliability to generate and recognize various phase code sequences is demonstrated in a 16-chip 20-Gchip/s quaternary phase-shift keying coherent optical code-division multiple access experiment. The bit-error-rate response is also included to highlight its performance.     

Crystal structure and infrared spectrum of thallium holmium polyphosphate,TIHo（PO3）4

Crystals of thallium-holmium polyphosphate T1Ho（PO3）4 were grown by flux method technique and characterized by single crystal X-ray diffraction. Structure of T1Ho（PO3）4 was solved for the first time, and it crystallized in the monoclinic P21/n space group with the following unit-cell dimensions： a=1.02225（3） nm, b=0.88536（2） nm, c=1.09541（4） nm, β=105.888（1）°, V=0.95354（5） nm^3 and Z=4. The crystal structure was solved from 2174 independent reflections with final R1（F^2）=0.0442 and Rw（F^2）=0.0861 refined with 164 parameters. The atomic arrangement could be described as a long chain polyphosphate organization. Holmium atoms had eightfold coordination. The structure of T1Ho（PO3）4 consisted of HoO8 polyhedra sharing oxygen atoms with phosphoric group PO4. Infrared spectrum was investigated at room temperature in the frequencies range, 350--4000 cm^-1, showing some characteristic vibration bands of infinite chain structure of PO4 tetrahedra linked by bridging oxygen.     

Major reduction of malaria morbidity with combined vitamin A and zinc supplementation in young children in Burkina Faso: a randomized double blind trial

Background  

Vitamin A and zinc are crucial for normal immune function, and may play a synergistic role for reducing the risk of infection including malaria caused by Plasmodium falciparum.     

Synthesis of ZSM-5 zeolite of improved bulk and surface properties via mixed templates

Hydrothermally synthesized ZSM-5 zeolites using tetrapropyl-ammonium bromide (TPA-Br), Xylitol (Xy) and tetrapropyl-ammonium bromide + Xylitol templates; those compared with that of the parent having the same Si/Al molar ratio (64) and purchased from Mobil, were characterized with several physicochemical techniques including N₂ adsorption, XRD, TG/DSC, FTIR and pyridine-FTIR. The effect of various templates on the crystallinity, crystallites size, surface properties and thermal stabilities of the produced ZSM-5 were investigated. ZSM-5 synthesized using TPA-Br + Xy; of S _BET = 393 m² g^?1, exhibited a crystallinity percentage comprises of 142% when compared with that of the parent (taken at 100% crystallinity) and measured as well a crystallites size of 61 nm exceeding that derived from Xy (41 nm) that measured the lowest crystallinity percentages (71%), lowest S _BET (303 m² g^?1) and highest yield (65%) between all samples. The former sample showed high thermal stability (till 1,000 °C) when compared with that derived from TPA-Br, as illustrated from TG/DSC thermograms that provided a criteria on decreasing the pore radius as a result of enclosing appreciable amounts of TPA⁺ and Xy inside narrow pores of ZSM-5. This sample also indicated a hydrophobic tendency when compared with that devoted from TPA-Br. Pyridine adsorption measurements showed that addition of Xy to TPA-Br stimulate the existence of basic sites in addition to acidic ones (mainly Brönsted ones) that was in the middle between that derived from Xy and TPA-Br templates. More infomations on the textural properties, morphologies, vibrational tetrahedral co-ordination T(Si or Al)–O modes and acidity were evaluated and discussed.     

Numerical Investigation of Forced Convection Flow of Nanofluids in Rotating U-Shaped Smooth and Ribbed Channels

The impact of the nanoparticles and ribs on the thermal performance of the rotating U-type cooling channel are investigated for turbulent forced convection flow of nanofluids. The nanofluids are provided by the inclusion of the nanoparticles of TiO₂ and Al₂O₃ in water as the base fluid, namely, water/Al₂O₃ and water/TiO₂ nanofluids mixtures. The simulations are performed for three-dimensional turbulent flow and heat transfer using an RNG k-? turbulence model for Reynolds number range of 5000 to 20,000. To show the effectiveness of the ribs and nanofluids, three criteria are employed: heat transfer enhancement, pressure drop or power consumed, and the thermal performance factor. It is found that the contribution of turbulence promotion in heat transfer enhancement of the ribbed channel is more effective than that of enlarging the heat surface area. The results show that using ribs at the lowest Reynolds number and utilizing nanofluids at the highest one provide high heat transfer rate and thermal performance. At the middle Reynolds numbers, the effects of these two methods on heat transfer enhancement are relatively close to each other. In this case, if the pumping power is the main concern, using nanofluids is recommended due to providing a smaller pressure drop penalty.     

Double spacing multi-wavelength L-band Brillouin erbium fiber laser with Raman pump

A new multi-wavelength Brillouin erbium fiber laser (BEFL), which operates in the L-band region with double frequency Brillouin spacing, is demonstrated. This design uses a Raman pump (RP) and a piece of 2?km highly nonlinear fiber as a gain medium. The double frequency spacing is achieved by employing a dual ring configuration, which is formed by utilizing a four-port circulator that removes the odd-order Stoke signals. Twenty Stokes and seventeen anti-Stokes lines, which have optical signal to noise ratio (OSNR) greater than 15?dB, are generated simultaneously with a spacing of 0.16?nm when Brillouin pump and RP powers were fixed at the optimum values of 8 dBm and 40?mW, respectively. The BEFL can be tuned in the range between 1591?nm to 1618?nm. The proposed configuration increases the number of lines generated and the OSNR, and thus allows a compact multi-wavelength laser source to be realized.     

Adaptive Sliding Mode Observer for Nonlinear Interconnected Systems with Time Varying Parameters

In this paper, a class of nonlinear interconnected systems with uncertain time varying parameters (TVPs) is considered. Both the interconnections and the isolated subsystems are nonlinear. Sliding mode control method and adaptive techniques are employed together to design an observer to estimate the state variables of the systems in presence of unknown TVPs. The Lyapunov direct method is used to analysis the stability of the sliding motion and it is not required to solve the so‐called constrained Lyapunov problem (CLP). A set of conditions is developed under which the augmented systems formed by the error dynamical systems and the designed adaptive laws, are globally uniformly ultimately bounded. A simulation example is presented and the results show that the method proposed in this paper is effective.