Effect of a Magnetic Field on a Micropolar Fluid Flow in the Vicinity of an Axisymmetric Stagnation Point on a Circular Cylinder

The effect of a magnetic field on a micropolar fluid flow in the vicinity of an axisymmetric stagnation point on a circular cylinder is studied numerically. The governing conservation equations of continuity, momentum and angular momentum are partial differential equations which are transformed into a system of ordinary differential equations by using the usual similarity transformations. The resulting system of coupled non‐linear ordinary differential equations is solved numerically by using the shooting method. The numerical results indicate the velocity, angular velocity and pressure distributions for different parameters of the problem including Reynolds number, magnetic parameter and dimensionless material properties, etc. In addition, the effect of the pertinent parameters on the local skin friction coefficient and the couple stress are discussed numerically and illustrated graphically.     

Kelvin-helmholtz instability in magnetic fluids with surface adsorption: Linear and nonlinear theory

The linear and nonlinear stability of the Kelvin-Helmholtz problem for magnetic fluids with surface adsorption is studied by employing the multiple scale method. The phenomenon of nonlinear focusing or collapse is considered. It is shown that the evolution of the amplitude is governed by a two-dimensional Schrödinger equation with cubic nonlinearity. This equation gives rise to a self-focusing singularity when the velocity difference is in the subcritical regime. Also from its equation, we obtain the condition for the existence of the modulational instability. The various regions of stability and instability are indicated.     

The gain and noise figure of Yb-Er-codoped fiber amplifiers based on the temperature-dependent model

A novel temperature-dependent model for Yb³⁺-Er³⁺-codoped fiber amplifier (EYDFA) based on the energy transfer from Yb³⁺ to Er³⁺ is established. Using appropriate fiber and energy transfer parameters, the coupled rate equations is numerically solved at 25 and 40 °C. The pumping powers are 100 and 200 mW at a pump wavelength of 1060 nm. The signal gain and noise characteristics of a 0.3 m erbium/ytterbium co-doped fiber (EYDF) in a single-pass configuration are investigated by using 1, 10 and 100 μW signals at 1535 nm. A maximum signal gain of 40.5 dB and a corresponding noise figure of 3.65 dB at the temperature of 25 °C are achieved.     

Electrospun Azithromycin-Laden Gelatin Methacryloyl Fibers for Endodontic Infection Control

This study was aimed at engineering photocrosslinkable azithromycin (AZ)-laden gelatin methacryloyl fibers via electrospinning to serve as a localized and biodegradable drug delivery system for endodontic infection control. AZ at three distinct amounts was mixed with solubilized gelatin methacryloyl and the photoinitiator to obtain the following fibers: GelMA+5%AZ, GelMA+10%AZ, and GelMA+15%AZ. Fiber morphology, diameter, AZ incorporation, mechanical properties, degradation profile, and antimicrobial action against Aggregatibacter actinomycetemcomitans and Actinomyces naeslundii were also studied. In vitro compatibility with human-derived dental pulp stem cells and inflammatory response in vivo using a subcutaneous rat model were also determined. A bead-free fibrous microstructure with interconnected pores was observed for all groups. GelMA and GelMA+10%AZ had the highest fiber diameter means. The tensile strength of the GelMA-based fibers was reduced upon AZ addition. A similar pattern was observed for the degradation profile in vitro. GelMA+15%AZ fibers led to the highest bacterial inhibition. The presence of AZ, regardless of the concentration, did not pose significant toxicity. In vivo findings indicated higher blood vessel formation, mild inflammation, and mature and thick well-oriented collagen fibers interweaving with the engineered fibers. Altogether, AZ-laden photocrosslinkable GelMA fibers had adequate mechanical and degradation properties, with 15%AZ displaying significant antimicrobial activity without compromising biocompatibility.     

Effect of electron irradiation on alternating current electrical properties of gelatin – cadmium sulfide nano-composite films

Gelatin was doped with 1 %, 3 %, 5 % and 10 % cadmium sulfide nanoparticles in weight concentrations forming the gelatin-cadmium sulfide nanocomposites and irradiated by various electron beam doses equals 50 kGy, 75 kGy, 100 kGy, and 150 kGy using 3 MeV – 3 mA electron accelerator. The applied alternating current electrical field frequency ranging from 70 Hz to 5 MHz is what caused the fluctuation in dielectric properties and alternating current electrical conductivity of these nanocomposites. The results showed that the films of 1 %, 3 %, 5 %, and 10 % for blank (nanocomposite film without electron beam irradiation) nanocomposites had the highest dielectric parameters (έ, ϵ′′, tan δ) at 0.5 kHz with values of (0.696, 0.0233, 0.034), (0.533, 0.0114, 0.0215), (0.402, 0.001196, 0.003), and (0.459, 0.00418, 0.0091), respectively. However, the lowest dielectric parameters were (0.645, 0.00618, 0.0066), (0.523, 0.00165, 0.0215), (0.417, 0.00035, 0.0008), and (0.455, 0.00066, 0.0015) at 5 MHz, respectively. The highest conductivity values for blank nanocomposites of 1 %, 3 %, 5 %, and 10 % were 1.79×10⁻⁴ S/m, 1.45×10⁻⁴ S/m, 1.16×10⁻⁴ S/m, 1.27×10⁻⁴ S/m at 5 MHz, and the lowest values were 1.92×10⁻⁸ S/m, 1.49×10⁻⁸ S/m, 1.13×10⁻⁸ S/m, 1.26×10⁻⁸ S/m at 0.5 kHz, respectively. For irradiated nanocomposites at 5 MHz, the dielectric constant order for 1 % was 100 kGy, 150 kGy, 50 kGy, and 75 kGy with values 0.63, 0.537, 0.532, and 0.523, respectively. For 10 % weight concentration, the order was 50 kGy, 100 kGy, 150 kGy, and 75 kGy with values 0.515, 0.477, 0.47, and 0.437, respectively. Otherwise the dielectric constant order for 3 % and 5 % was 100 kGy, 75 kGy, 150 kGy, and 50 kGy. The highest dielectric properties and conductivity values for blank and irradiated nanocomposites were observed at 100 kGy for 1 %, 3 %, and 5 %.     

Prothrombotic states associated with retinal venous occlusion in young adults

BACKGROUND: The etiology of retinal venous occlusion in young patients is not well understood although thrombosis does occur histologically. A search for the risk factors that may lead to thrombosis is highly desirable may contribute to our understanding of the pathogenesis of this complication and may improve our therapeutic strategies. METHODS: We studied 17 patients with retinal venous occlusion. All patients were under 45 years of age (mean 37.8 +/- 7.1). Antiphospholipid antibodies (APAs) and certain hemostatic factors were determined. The results obtained in these patients were compared to those of normal controls. RESULTS: We found APAs in 8 out of 17 patients compared to 5 out of 60 controls (p = 0.0002). In patients with major trunk occlusion, there was a trend for the presence of APAs in those with poor visual acuity at presentation. Deficiencies of the coagulation inhibitor proteins C and S and antithrombin III activities were detected in 6 patients, and reduced levels of Factor XII were found in 4 patients. Levels of hematocrit, erythrocyte sedimentation rate. Fibrinogen, alpha 1-globulin, and alpha 2-globulin were significantly higher in patients compared to the controls (p = 0.019; 0.014; 0.0001; 0.011; 0.047), indicating increased blood viscosity in patients with retinal venous occlusion. CONCLUSION: Prothrombotic changes in the form of APAs and/or deficiencies of coagulation inhibitors and Factor XII may contribute to the etiology of retinal venous occlusion in young adults. Young patients with retinal venous occlusion should be evaluated for these prothrombotic states.     

Potassium hexacyanocobalt ferrate and ammonium molybdophosphate sorption bags for the removal of 137Cs from aqueous solutions and a simulated waste

In the present study, the removal and immobilization of ¹³⁷Cs from aqueous waste solutions and a simulated waste was investigated. Two inorganic ion‐exchange complexes: di‐potassium hexacyanocobalt(II)‐ferrate(II), K₂CoFe(CN)_6·xH₂O (KCFC), and ammonium‐12‐molybdophosphate [(NH₄)₃PMo₁₂O_40·aq] (AMP), were charged separately into porous nylon bags (sorption bags) of 5 µm pore diameter. The first complex (KCFC) was prepared in our laboratory. The second (AMP) was used for comparison. Easy handling and increased potential for reuse characterize the sorption bag technique. The KCFC complex was investigated by thermal gravimetric analysis (TGA) and differential thermal analysis (DTA), porosity, infra‐red (IR) and X‐ray powder diffraction (XRD). The chemical and structural investigations revealed that the KCFC complex has adequate ion‐exchange capacity and high affinity for ¹³⁷Cs. The sorption bag technique showed promising results for the removal of ¹³⁷Cs from aqueous waste solutions. The KCFC bags showed the highest ¹³⁷Cs removal (～0.91 g g^?1), at pH 8.5; AMP bags gave the highest ¹³⁷Cs removal (～0.97 g g^?1) in 0.1 N HNO₃ and 1.5 N HNO₃, both with a waste: sorbent ratio of 80 cm³ g^?1. Sorption data for both KCFC and AMP revealed a good fit to the Freundlich sorption isotherm. To assess the potential of sorption bags, the used bags were regenerated in different leachants and reused in further sorption investigations. ¹³⁷Cs recovery from the used sorbents was ～0.46 g g^?1 using 6 N HCl as leachant for AMP, compared with ～0.253 g g^?1 for KCFC using 6 N NaCl. These results indicated stronger cesium immobilization in the KCFC complex. Copyright © 2003 Society of Chemical Industry     

Toxicity of Piper abyssinica seeds to Nubian goats

An investigation is described in which Nubian goats were given daily oral doses of Piper abyssinica seeds at 0.25; 1 and 5 g/kg body weight. The results of liver and kidney function tests were correlated with the clinical and pathological changes. In goats receiving the plant seed at 5 g/kg body weight/day, death occurred within 5-14 days and the main signs were bloated rumen, diarrhoea, dysponoea and ataxia. Enterohepatonephropathy was accompanied by increases in the activity of serum ALP and GGT, in the concentration of cholesterol, globulin, total lipids and urea and decreases in the level of albumin. Piper seed was toxic but not lethal to goats at doses of 0.25 and 1 g/kg body weight.     

Microprocessor-based real time system for eye motion analysis

A microprocessor-based real time video analysis system has been built and used in conjunction with an oculometer to perform some aspects of eye motion analysis. An outstanding feature of this system is its ability to process data in real time so that information concerning instantaneous eye point of regard is readily available for direct observation.     

Effect of drilling speed on the required torque and thrust force for non-ferrous materials

Constant-feed-rate drilling tests under conditions of dry cutting were performed on three non-ferrous materials, namely free machining brass, aluminium and lead. The tests covered a wide range of cutting speeds. Both thrust forces and torques were affected by the drill diameter and by speed variations. Empirical relationships between the thrust force, the torque and the cutting parameters were derived for the materials used.