Simultaneous high-performance thin-layer chromatography analysis of phytoconstituents and antioxidant potential of Inula grandiflora Willd. from India

JPC – Journal of Planar Chromatography – Modern TLC - The Inula genus has been used for the cure of pulmonary, heart diseases and also acts as a rejuvenator, immunomodulator in...     

Influence of Size and Shape on the Photocatalytic Properties of SnO2 Nanocrystals

Tuning the functional properties of nanocrystals is an important issue in nanoscience. Here, we are able to tune the photocatalytic properties of SnO₂ nanocrystals by controlling their size and shape. A structural analysis was carried out by using X‐ray diffraction (XRD)/Rietveld and transmission electron microscopy (TEM). The results reveal that the number of oxygen‐related defects varies upon changing the size and shape of the nanocrystals, which eventually influences their photocatalytic properties. Time‐resolved spectroscopic studies of the carrier relaxation dynamics of the SnO₂ nanocrystals further confirm that the electron–hole recombination process is controlled by oxygen/defect states, which can be tuned by changing the shape and size of the materials. The degradation of dyes (90 %) in the presence of SnO₂ nanoparticles under UV light is comparable to that (88 %) in the presence of standard TiO₂ Degussa P‐25 (P25) powders. The photocatalytic activity of the nanoparticles is significantly higher than those of nanorods and nanospheres because the effective charge separation in the SnO₂ nanoparticles is controlled by defect states leading to enhanced photocatalytic properties. The size‐ and shape‐dependent photocatalytic properties of SnO₂ nanocrystals make these materials interesting candidates for photocatalytic applications.     

Preliminary Investigation of the Antioxidant,Anti-Diabetic,and Anti-Inflammatory Activity of Enteromorpha intestinalis Extracts

Marine algae are a promising source of potent bioactive agents against oxidative stress, diabetes, and inflammation. However, the possible therapeutic effects of many algal metabolites have not been exploited yet. In this regard, we explored the therapeutic potential of Enteromorpha intestinalis extracts obtained from methanol, ethanol, and hexane, in contrasting oxidative stress. The total phenolic (TPC) and flavonoids (TFC) content were quantified in all extracts, with ethanol yielding the best values (about 60 and 625 mg of gallic acid and rutin equivalents per gram of extract, respectively). Their antioxidant potential was also assessed through DPPH^•, hydroxyl radical, hydrogen peroxide, and superoxide anion scavenging assays, showing a concentration-dependent activity which was greater in the extracts from protic and more polar solvents. The α-amylase and α-glucosidase activities were estimated for checking the antidiabetic capacity, with IC₅₀ values of about 3.8 µg/mL for the methanolic extract, almost as low as those obtained with acarbose (about 2.8 and 3.3 µg/mL, respectively). The same extract also showed remarkable anti-inflammatory effect, as determined by hemolysis, protein denaturation, proteinase and lipoxygenase activity assays, with respectable IC₅₀ values (about 11, 4, 6, and 5 µg/mL, respectively), also in comparison to commercially used drugs, such as acetylsalicylic acid.     

Near‐forward/high‐pressure‐backward Raman study of Zn1 − xBexSe (x ~ 0.5) – evidence for percolation behavior of the long (Zn―Se) bond

The apparently universal 1‐bond → 2‐mode percolation behavior in the Raman spectra of zincblende semiconductor alloys is generally observed for the short bond only, and not for the long one. In this work we perform a combined high‐pressure‐backward/near‐forward Raman study of the leading percolation‐type (Zn,Be)Se alloy (~50 at.% Be), which exhibits a distinct percolation doublet in the spectral range of its short Be―Se bond, in search of a Zn―Se analogue. The high‐pressure‐backward insight is not conclusive per se, but clarifies the perspective behind the near‐forward Raman study. The latter reveals an unique Zn―Se phonon–polariton. Its fair contour modeling depending on the scattering angle is achieved within the linear dielectric approach, based on ellipsometry measurement of the ZnBeSe refractive index. Somewhat surprisingly this reveals that the phonon–polariton in question is a ‘fractional’ one in that it carries only half of the available Zn―Se oscillator strength, as ideally expected in case of a BeSe‐like bimodal Raman behavior of the long Zn―Se bond. Copyright © 2015 John Wiley & Sons, Ltd.     

Prediction of stagnation point heat transfer for a single round jet impinging on a concave hemispherical surface

This paper deals with a systematic procedure for assessment of fluid flow and heat transfer parameters for a single round jet impinging on a concave hemispherical surface. Based on Scholkemeier's modifications of the Karman-Pohlhausen integral method, expressions are derived for evaluation of the momentum thickness, boundary layer thickness and the displacement thickness at the stagnation point. This is followed by the estimation of thermal boundary layer thickness and local heat transfer coefficients. A correlation is presented for the Nusselt number at the stagnation point as a function of the Reynolds number for different non-dimensional distances from the exit plane of the jet to the impingement surface.

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Bestimmung des Staupunktes bei der Wärmeübertragung für einen einzelnen Strahl, der auf eine konkave halbkugelige Oberfläche trifft

Zusammenfassung Diese Arbeit beschäftigt sich mit dem systematischen Verfahren der Bewertung von Fluidströmungen und Wärmeübertragungsparametern für einen einzelnen runden Strahl, der auf eine konkave halbkugelförmige Oberfläche trifft. Das Verfahren beruht auf Scholkemeiers Modifikation des Karman-Pohlhausen Integrationsverfahrens. Ausdrücke sind für die Berechnung der Impuls-Dicke, der Grenzschichtdicke und der Verschiebungsdicke am Staupunkt hergeleitet worden. Dies ist aus der Berechnung der thermischen Grenzschichtdicke und des lokalen Wärmeübertragungskoeffizienten abgeleitet worden. Es wird eine Gleichung für die Nusselt-Zahl am Staupunkt als Funktion der Reynolds-Zahl für verschiedene dimensionslose Abstände vom Strahlaustrittspunkt bis zum Auftreffpunkt auf die Oberfläche vorgestellt.

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Nomenclature c _p specific heat at constant pressure - d diameter of single round nozzle - h ₀ heat transfer coefficient at the stagnation point - H distance from the exit plane of the jet to the impingement surface - k thermal conductivity - Nu _0.5 Nusselt number based on impinging jet quantities=h _0.50/k - Nu _{0.5, 0} stagnation point Nusselt number=h _{0 0,50}/k - p pressure - p _a ambient pressure - p ₀ maximum pressure or stagnation pressure - p(x) static pressure at a distancex from the stagnation point - R radius of curvature of the hemisphere - Re _J jet Reynolds number=U _Jd/ - Re _0.5 Reynolds number based on impinging jet quantities=u _{m0 0.50}/ - T temperature - T _a room temperature - T _J jet temperature - T _W wall temperature - u velocity component inx andx directions (Fig. 1) - u _m jet centerline (or maximum) free jet velocity: external (or maximum) boundary layer velocity aty= _m - u _m0 arrival velocity defined as the maximum velocity the free jet would have at the plane of impingement if the plane were not there - U _J jet exit velocity - x* non-dimensional coordinate starting at the stagnation point=x/2 _0.50 - x, y rectangular Cartesian coordinates - y coordinate normal to the wall starting at the wall - ratio of thermal to velocity boundary layer thickness= _T/_m - ₀ ratio of thermal to velocity boundary layer thickness at the stagnation point - * inner layer displacement thickness - _0.50 jet half width at the plane of impingement if the plate were not there - _m inner boundary layer thickness atu=u _m - Pohlhausen's form parameter - dynamic viscosity - kinematic viscosity=/ - fluid density - momentum thickness - ₀ momentum thickness at the stagnation point     

Two-Fluid Dark Energy Models in Bianchi Type-III Universe with Variable Deceleration Parameter

Some new exact solutions of Einstein’s field equations have come forth within the scope of a spatially homogeneous and anisotropic Bianchi type-III space-time filled with barotropic fluid and dark energy by considering a variable deceleration parameter. We consider the case when the dark energy is minimally coupled to the perfect fluid as well as direct interaction with it. Under the suitable condition, the anisotropic models approach to isotropic scenario. We also find that during the evolution of the universe, the equation of state (EoS) for dark energy ω ^(de), in both cases, tends to ?1 (cosmological constant, ω ^(de)=?1), by displaying various patterns as time increases, which is consistent with recent observations. The cosmic jerk parameter in our derived models are in good agreement with the recent data of astrophysical observations under appropriate condition. It is observed that the universe starts from an asymptotic Einstein static era and reaches to the ΛCDM model. So from recently developed Statefinder parameters, the behaviour of different stages of the universe has been studied. The physical and geometric properties of cosmological models are also discussed.