Effect of a harmonic surface pressure on wave propagation over a beach.

The objective is to study the harmonic forced wave motion over a beach by a finite Fourier transform technique. The constructed approximate solution has a logarithmic singularity at the shoreline. It accounts for reflexion and local perturbations. Trapping of waves may take place for particular choices of the applied surface pressure excess. The case of a wave incident against a cliff with horizontal bottom is solved exactly. The method deals invariably with a variety of bottom shapes, including the case where there is an additional corrugation of the bottom on a finite interval. Other bottom boundary conditions than impermeability can be treated as well. The results may be of interest in several practical applications, in particular the evaluation of the reflected wave. Numerical applications for a plane sloping beach, a parabolic-type beach and a shelf-type beach are presented and the systems of streamlines have been drawn over and in the proximity of the beach.

Multiple wave scattering by submerged obstacles in an infinite channel of finite depth with surface pressure excess.

The objective is to study the combined effect of an incident wave, a surface pressure excess and a finite number of submerged obstacles, in the phenomenon of power transfer to an infinite fluid layer of finite depth. The incident wave and the surface pressure excess have the same harmonic time dependence, a fact that allows to eliminate time altogether and consider only steady-state solutions. The surface pressure excess simulates the effect of winds blowing above the water surface in oceans. The technique used in a first part of the paper relying upon the use of finite Fourier transform and separation of variables is extended here to this end. The method allows to separate local perturbations from progressive or standing wave. Our formulae yield the exact solution in closed form in the absence of obstacles, and provide a clearer insight into the flow properties, as compared to previous investigations. Applications are given for discontinuous surface pressure functions. We put in evidence solutions with no outgoing waves, for which the energy transmitted by the surface pressure is exhausted in generating a standing wave, together with local perturbations. Two numerical applications without/with obstacles, for a parabolic surface pressure profile, allow to assess the energy transfer from the pressure-obstacles system to the fluid. The results may be of interest in the field of oscillating water columns and, generally, water power converting technology.

Nonlinear Rayleigh wave propagation in a layered half-space in dual-phase-lag.

We investigate nonlinear Rayleigh wave propagation in a layered thermoelastic medium composed of a slab rigidly bonded to the surface of a half-space under prescribed external thermal boundary conditions within the dual-phase-lag theory. The heat conduction coefficient for both the slab and the matrix have a linear dependence on temperature. Our aim is to assess the effect of temperature dependence of the heat conductivity, as well as the thermal relaxation times, on the process of wave propagation in the layered medium. Poincaré expansion of the solution in a small parameter and the generation of higher harmonics allow to evaluate the coefficient of this nonlinear coupling in the slab through heat wave propagation measurement. For the used numerical values, the results show that some characteristics of the problem, e.g. the temperature, heat flux and one stress component suffer jumps at the interface, while the other stress components are continuous there. The jump in the heat flux is noticeable only in the first order of nonlinearity. The existence of jumps at the interface may be of interest for measurements. Comparison with the case of the half-space showed that the presence of the slab contributes to faster damping of the solution with depth in the half-space.

Nonlinear Rayleigh wave propagation in thermoelastic media in dual-phase-lag.

A model of generalized thermoelasticity within dual-phase-lag is used to investigate nonlinear Rayleigh wave propagation in a half-space of a transversely isotropic elastic material. It is assumed that the coefficient of heat conduction is temperature-dependent, a fact that plays an important role in the coupling behaviour analysis of thermoelastic and piezo-thermoelastic solids. Taking such a dependence into account becomes a necessity at higher temperatures and in nano-structures, when the material properties can no longer be considered as constants. Normal mode analysis is applied to find a particular solution to the problem under consideration. A concrete case is solved under prescribed boundary conditions and tentative values of the different material coefficients. The results are discussed to reveal the effect of temperature dependence of the heat conduction coefficient, as well as the thermal relaxation times, on nonlinear Rayleigh wave propagation. All quantities of practical interest are illustrated in two-and three-dimensional plots. The presented results may be useful in the detection of the second harmonic amplitudes through measurements related to the propagating heat wave.

On a two-dimensional model of generalized thermoelasticity with application.

A 2D first order linear system of partial differential equations of plane strain thermoelasticity within the frame of extended thermodynamics is presented and analyzed. The system is composed of the equations of classical thermoelasticity in which displacements are replaced with velocities, complemented with Cattaneo evolution equation for heat flux. For a particular choice of the characteristic quantities and for positive thermal conductivity, it is shown that this system may be cast in a form that is symmetric t-hyperbolic without further recurrence to entropy principle. While hyperbolicity means a finite speed of propagation of heat waves, it is known that symmetric hyperbolic systems have the desirable property of well-posedness of Cauchy problems. A study of the characteristics of this system is carried out, and an energy integral is derived, that can be used to prove uniqueness of solution under some boundary conditions. A numerical application for a finite slab is considered and the numerical results are plotted and discussed. In particular, the wave propagation nature of the solution is put in evidence.

Chromatographic Methods for the Determination of Aminexil, Pyridoxine, and Niacinamide in a Novel Cosmetic Hair Preparation.

BACKGROUND: Aminexil, a new compound patented by L'Oreal, has a stimulating effect on human keratin fibers. Pyridoxine HCl and niacinamide are added to boost the hair tonic effect of aminexil. OBJECTIVE: Two novel chromatographic methods were developed for the determination of aminexil (AX), niacinamide (NA) and pyridoxine HCl (PD) in the novel hair tonic preparation. METHODS: The developed methods were high-performance liquid chromatography (HPLC) and thin layer chromatography (TLC) with densitometric determination. Different experimental parameters were investigated and optimized to achieve complete baseline separation and well resolved peaks. The RP-HPLC separation was achieved using a Thermoscientific BDS hypersil C18 (250 × 4.6 mm, 5 µm) column using 0.005 M hexane sulfonic acid: methanol (80: 20, v/v) as a mobile phase. For the TLC method, the three analytes were partitioned between propanol: toluene: ammonia solution (40:60:2, v/v/v) and fluorescent silica plates. The two methods were validated in compliance with International Conference on Harmonization (ICH) guidelines. The obtained data were statistically analyzed to confirm the existing results. The developed methods were successfully applied for determination of the studied drugs in pure forms and in the cosmetic preparation. RESULTS: For the HPLC method, the RSDs of AX, NA and PD were 0.70, 0.88 and 1.17 respectively. For the TLC method, the RSDs of AX, NA and PD were 1.06, 1.37 and 0.73 respectively. CONCLUSIONS: The proposed chromatographic methods showed high sensitivity and selectivity for the three compounds under analysis in the laboratory prepared mixture and in the hair tonic preparation. HIGHLIGHTS: Aminexil, Pyridoxine, Niacinamide, HPLC. The present work offers two reproducible, accurate, validated, time and cost saving alternatives for the quantitative and qualitative determination of medicated hair preparation.

Fluorescein Angiographic Findings in Patients with Active Systemic Lupus Erythematosus.

PURPOSE: To evaluate the retina of patients with active systemic lupus erythematosus (SLE) using fundus fluorescein angiography (FFA), irrespective of their visual acuity or fundus examination. METHODS: A descriptive study was performed on 30 patients with active SLE; disease activity was calculated using The Systemic Lupus Erythematosus Disease Activity Index (SLEDAI). Fundus examination and FFA angiography were done to all patients. RESULTS: A total of 60 eyes of 30 patients were included. Their mean age was 32.6 ± 1.17 years. All patients showed disease activity at time of examination according to SLEDAI. Retinopathy was detected by FAF in 24 eyes (40%), 10 eyes of which had normal fundus examination. SLEDAI was positively correlated to the presence of retinopathy. CONCLUSIONS: All patients with ocular lupus should be carefully evaluated for systemic involvement and, vice versa, all patients diagnosed with SLE should have a thorough ocular examination and FFA, even if they had normal fundus.

Role of dehydroepiandrosterone in management of glucocorticoid-induced secondary osteoporosis in female rats.

The current study aimed to evaluate the potential role of dehydroepiandrosterone (DHEA) in the protection and intervention of glucocorticoid-induced secondary osteoporosis in female rats. For this purpose this study was conducted on five groups of female Sprague Dawley rats which were classified into: (1) negative control group received saline as vehicle, (2) osteoporotic group orally administered with prednisolone (5 mg/kg b.wt.) daily for six months, (3) positive control group orally administered with DHEA (250 mg/kg b.wt.) three times weekly for six months, (4) protective group orally administered with prednisolone daily with simultaneous oral administration of DHEA three times weekly for six months and (5) therapeutic group orally administered with prednisolone daily for six months then orally administered with DHEA three times weekly for other six months. The obtained data revealed that prednisolone administration resulted in significant decrease in serum osteocalcin (OC), 1,25-dihydroxyvitamin D(3) (1,25-(OH)(2) D(3)) and osteoprotegerin (OPG) levels accompanied with significant increase in serum parathyroid hormone (PTH) and receptor activator nuclear factor kappa B ligand (RANKL) levels. Histopathological investigation of left femur bone showed that prednisolone administration produced compression of the reduced articular surface and atrophy of the epiphyseal bone. On the other hand, DHEA supplementation to osteoporotic rats increased serum OC, 1,25-(OH)(2) D(3) and OPG levels while decreased serum PTH and RANKL levels. Moreover, DHEA administration resulted in restoration of intact epiphyseal bony structure and articular surface. In conclusion, DHEA via its control on glucocorticoid activity and androgenic action provided potent effect on bone.

Sorbitol dehydrogenase inhibitors (SDIs): a new potent, enantiomeric SDI, 4-[2-1R-hydroxy-ethyl)-pyrimidin-4-yl]piperazine-1-sulfonic acid dimethylamide.

We report here on our medicinal chemistry and pharmacology efforts to provide a potent sorbitol dehydrogenase inhibitor (SDI) as a tool to probe a recently disclosed hypothesis centered on the role of sorbitol dehydrogenase (SDH) in the second step of the polyol pathway, under conditions of high glucose flux. Starting from a weak literature lead, 2, and through newly developed structure-activity relationships, we have designed and executed an unambiguous synthesis of enantiomeric SDI, 6, which is at least 10x more potent than 2. Also, 6 potently inhibits SDH in streptozotocin-diabetic rat sciatic nerve. We have described an expedient synthesis of a key building template, 33, for future research in the SDI area that may facilitate the discovery of even more potent SDIs with longer duration of action in vivo.