Minimally deformed anisotropic stars by gravitational decoupling in Einstein–Gauss–Bonnet gravity

The European Physical Journal C - Baryon inhomogeneities are generated early in the universe. These inhomogeneities affect the phase transition dynamics of subsequent phase transitions, they also...     

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     

Negative ions of transition metal-halogen clusters

A systematic density functional theory based study of the structure and spectroscopic properties of neutral and negatively charged MX(n) clusters formed by a transition metal atom M (M=Sc,Ti,V) and up to seven halogen atoms X (X=F,Cl,Br) has revealed a number of interesting features: (1) Halogen atoms are bound chemically to Sc, Ti, and V for n≤n(max), where the maximal valence n(max) equals to 3, 4, and 5 for Sc, Ti, and V, respectively. For n>n(max), two halogen atoms became dimerized in the neutral species, while dimerization begins at n=5, 6, and 7 for negatively charged clusters containing Sc, Ti, and V. (2) Magnetic moments of the transition metal atoms depend strongly on the number of halogen atoms in a cluster and the cluster charge. (3) The number of halogen atoms that can be attached to a metal atom exceeds the maximal formal valence of the metal atom. (4) The electron affinities of the neutral clusters abruptly rise at n=n(max), reaching values as high as 7 eV. The corresponding anions could be used in the synthesis of new salts, once appropriate counterions are identified.     

Monoclinic CuO nanoflowers on resin support: recyclable catalyst to obtain perylene compound

Monoclinic CuO crystallite in grams has been obtained from resin bound Cu(II)-1,10-phenanthroline complex, R(-)[Cu(1,10-phen)(2)](2+) that becomes a recyclable catalyst for oxidative phenol coupling (OPC) reaction. Thus an exclusively intuitive blue fluorescing perylene derivative is derived from colorless 2,7-dihydroxynaphthalene (2,7-DHN) in high yield.     

Fabrication of Large‐Scale Hierarchical ZnO Hollow Spheroids for Hydrophobicity and Photocatalysis

We report here the preparation of a crystalline, pure hexagonal phase of ZnO as hollow 500–800 nm spheroids in the presence of organic bases, such as pyridine, using zinc acetate as the precursor salt. The spheroids exhibit unique 3D hierarchical architectures, like cocoons, and demonstrate improved superhydrophobic (water contact angle, 150°) character due to the inherited air‐trapped capillarity within the cocoon structure. The simple synthetic strategy used in this process is modified hydrothermolysis (MHT), which represents a general approach and may contribute to the formation mechanism of the hollow nanostructures with highly improved porosity. Depending on the concentration of the precursor salt, it has been possible to cover glass plates or the inner wall of a reaction vessel with ZnO nanocrystals. A low salt concentration (<0.01 M ) allows the easy preparation of a superhydrophobic glass surface, whereas a high salt concentration (>0.01 M ) results in the precipitation of cocoons at the bottom of the reaction vessel as a solid mass together with a deposited thin film of ZnO nanocrystals covering the inner wall of the glass vessel. The thickness of the film successively grows through repetitive hydrothermolysis processes for which a low salt concentration (<0.01 M ) was employed. Because of the hollow cocoonlike morphology, the surface area of the film is greatly increased, which makes it accessible for functionalization by incoming substrates from both sides (internally and externally) and helps to drive a competent photocatalytic dye degradation pathway. The heterocyclic base pyridine exclusively develops cocoons. Thus, the mechanism of self‐aggregation of ZnO nanocrystals under MHT reaction conditions has been studied and the characterization of the compounds has been supported with physical measurements.     

Synthesis of nanocrystalline and mesoporous zinc sulphide from a single precursor Zn(SOCCH3)2Lut2 complex

We report the formation of mesoporous zinc sulphide, composed by the fine network of nanoparticles, which was formed via a single precursor Zn(SOCCH₃)₂Lut₂ complex. The complex was chemically synthesized using zinc carbonate basic, 3,5-lutidine and thioacetic acid, in air. The metal precursor complex was characterized using different conventional techniques. Thermogravimetric analysis (TGA) result indicates that the decomposition of the complex starts at 100 °C and continues up to 450 °C, finally yielding ZnS. ZnS nanocrystals were characterized by powder X-ray diffraction (XRD) technique, field emission scanning electron microscopy (FESEM), N₂-sorption isotherm, UV-vis spectroscopy and photoluminescence (PL) spectroscopy. The grain diameter of nanocrystals was found to be 4-5 nm. The material followed Type-IV N₂-sorption isotherm, which is the characteristic of mesoporous materials. The band gap energy, as obtained from optical measurements was around 3.8 eV.     

Anterior cingulate and cerebellar GABA and Glu correlations measured by ¹H J-difference spectroscopy

Gamma-aminobutyric acid (GABA) and glutamate (Glu) levels, normalized to total creatine (tCr), were measured in the anterior cingulate and cerebellar vermis in healthy adults (n=19, age=24.6±6.4 years) using ¹H MRS at 3 T, and metabolite correlations across regions and subjects were determined. Mean anterior cingulate and cerebellar GABA/tCr ratios were 0.31 (0.08) and 0.23 (0.06), respectively, while corresponding Glu levels were 1.16 (0.10) and 0.70 (0.07), respectively. Anterior cingulate and cerebellar glutamate levels were correlated (r=0.6103, P=.0140), although it is noted that when adjusted for multiple comparisons, all correlations reported here cluster to a P value of .0583. It is unlikely that this correlation is driven by correlations in tCr, since interregional correlations were not observed for other metabolites referenced to tCr. Correlations were also observed among metabolites in both the anterior cingulate and cerebellar vermis. In the former, N-acetylasparate was linearly dependent on glutamate (r=0.6577, P=.0063) and, at or below this significance threshold, four metabolites were correlated in the cerebellar vermis (Ins/tCh: r=0.6261, P=.0109. NAA/tCh: r=0.6426, P=.0082. NAA/Glu: r=0.6412, P=.0085. tCh/Glu: r=0.6193, P=0.0122).     

Optimum life testing plans in presence of hybrid censoring: A cost function approach

Hybrid censoring scheme is a combination of Type‐I and Type‐II censoring schemes. Determination of optimum hybrid censoring scheme is an important practical issue in designing life testing experiments to enhance the information on reliability of the product. In this work, we consider determination of optimum life testing plans under hybrid censoring scheme by minimizing the total cost associated with the experiment. It is shown that the proposed cost function is scale invariant for some selected distributions. Optimum solution cannot be obtained analytically. We propose a method for obtaining the optimum solution and consider Weibull distribution for illustration. We also studied the sensitivity of the optimal solution to the misspecification of parameter values and cost components through a well‐designed sensitivity analysis. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis of 3,8,13,18-tetrachloro-2,7,12,17-tetramethoxyporphyrin

Vilsmeier-Haack formylation of 3,4-dimethoxypyrrole led to the unprecedented formation of 3-chloro-4-methoxypyrrole-2-aldehyde instead of the desired dialdehyde. Subsequent reduction and acid catalyzed cyclization led to the formation of type I, 3,8,13,18-tetrachloro-2,7,12,17-tetramethoxyporphyrin in approximately 6% yield.