Inverse Scattering at Fixed Energy in de Sitter�CReissner�CNordstr?m Black Holes

In this paper, we consider massless Dirac fields propagating in the outer region of de Sitter–Reissner–Nordstr?m black holes. We show that the metric of such black holes is uniquely determined by the partial knowledge of the corresponding scattering matrix S(λ) at a fixed energy λ ≠ 0. More precisely, we consider the partial wave scattering matrices S(λ, n) (here λ ≠ 0 is the fixed energy and n ? \mathbbN^*{n \in \mathbb{N}^{*}} denotes the angular momentum) defined as the restrictions of the full scattering matrix on a well chosen basis of spin-weighted spherical harmonics. We prove that the mass M, the square of the charge Q ² and the cosmological constant Λ of a dS-RN black hole (and thus its metric) can be uniquely determined from the knowledge of either the transmission coefficients T(λ, n), or the reflexion coefficients R(λ, n) (resp. L(λ, n)), for all n ? L{n \in {\mathcal{L}}} where L{\mathcal{L}} is a subset of \mathbbN^*{\mathbb{N}^{*}} that satisfies the Müntz condition ?_{n ? L}\frac1n = +￥{\sum_{n \in{\mathcal{L}}}\frac{1}{n} = +\infty} . Our main tool consists in complexifying the angular momentum n and in studying the analytic properties of the “unphysical” scattering matrix S(λ, z) in the complex variable z. We show, in particular, that the quantities \frac1T(l,z){\frac{1}{T(\lambda,z)}}, \fracR(l,z)T(l,z){\frac{R(\lambda,z)}{T(\lambda,z)}} and \fracL(l,z)T(l,z){\frac{L(\lambda,z)}{T(\lambda,z)}} belong to the Nevanlinna class in the region ${\{z \in \mathbb{C}, Re(z) > 0 \}}${\{z \in \mathbb{C}, Re(z) > 0 \}} for which we have analytic uniqueness theorems at our disposal. Eventually, as a by-product of our method, we obtain reconstruction formulae for the surface gravities of the event and cosmological horizons of the black hole which have an important physical meaning in the Hawking effect.     

Plasma splashing from Al and Cu materials induced by an Nd:YAG pulsed laser

Plasma splashing from Al and Cu target materials and the growth of thin films on Cu and Al, respectively, has been studied using a Q-switched Nd:YAG laser with a 1064-nm, 80-mJ, 8-ns pulse width as the source of ablation. The target kept rotating and the substrate, Cu for Al and vice versa, was placed at an angle of 15° with respect to the beam axis. During the laser-matter interaction, the targets absorbed thermal energy within the thermal region depth of 4.7 (1.1) nm, yielding an ablated skin depth of 6.7 (4.2) nm. The surface morphology of the exposed targets was studied by analyzing SEM micrographs obtained using a ZEISS SUPRA 35 VP. The obtained results are explained on the basis of different sputtering/ablation mechanisms. Comparatively severe damage forming a bigger crater is seen on the Al target surface in contrast to the crater on the Cu surface. This observation is correlated with the blustering effect and/or debris formation. Energy dispersive spectroscopy (EDX) of the substrates yielded the deposition of micrometric grain-size particles.     

Electron acoustic solitary waves in unmagnetized nonthermal plasmas

Electron acoustic(EA) solitary waves(SWs) are studied in an unmagnetized plasma consisting of hot electrons(following Cairns-Tsalli distribution), inertial cold electrons, and stationary ions.By employing a reductive perturbation technique(RPT), the nonlinear Korteweg–de Vries(KdV) equation is derived and its SW solution is analyzed. Here, the effects of plasma parameters such as the nonextensivity parameter(q), the nonthermality of electrons(α), and the cold-to-hot electron density ratio(β) are investigated.     

Amorphous particle deposition and product quality under different conditions in a spray dryer

Deposition of amorphous particles, as a prevalent problem particularly in the spray drying of fruit and vegetable juices, is due to low-molecular weight sugars and is strongly dependent on the condition of the particles upon collision with the dryer wall. This paper investigates the condition of the amorphous particles impacting the wall at different drying conditions with the aim of elucidating the deposition mechanism and physical phenomena in the drying chamber. A model sucrose-maltodextrin solution was used to represent the low-molecular-weight sugar. Particle deposits were collected on sampling plates placed inside the dryer for analyses of moisture content, particle rigidity (using SEM) and size distribution. Moisture content was adopted as a general indicator of stickiness. Product particles collected at the bottom of the experimental dryer were found to have higher moisture than particle deposits on samplers inside the dryer. Moisture content profile in the dryer shows that apart from the atomizer region, where particles are relatively wet, particle deposits at other regions exhibit similar lower moisture content. At the highest temperature adopted in the experiments, particles became rubbery suggesting liquid-bridge formation as the dominant deposition mechanism. Further analysis on particles size distribution reveals a particle segregation mechanism whereby smaller particles follow preferentially to the central air stream while larger particles tend to re-circulate in the chamber, as predicted in past CFD simulation. The findings from this work will form the basis and provide validating data for further modeling of wall deposition of amorphous particles in spray drying using CFD.     

Electrospray Mass Spectrometry of Aqueous Solutions of Isopolyoxotungstates

Electrospray mass spectrometry (ESMS) has been conducted on aqueous solutions of isopolyoxotungstate systems. There is direct evidence that the desorption process in the ESMS technique has resulted in significant chemical effects, resulting in the detection of many new anions and cations. For the ammonium polyoxotungstate system, negative-ion ESMS yields ions of the form [HW _m O_3m+1]^–, [W _m O_3m+1]^2–, and [HW _m O_3m+2]^3– (with the latter being better formulated as [H₂W_2m O_6m+4]^6–). For the alkali metal polyoxotungstate systems ions of the form [W _m O_3m+1A]^– and [W _m O_4m A_2m–2]^2– (where A=Li⁺, Na⁺, K⁺) were observed. For positive-ion ESMS two series were observed, namely, the [W _m O_4m A_2m+1]⁺ and [W _m O_4m A_2m+2]²⁺ ions. In the ammonium polyoxotungstate system, aggregates of both the [HW _m O_3m+1]^– and the [W _m O_3m+1]^2– series can be classified as open-chained structures of tetrahedra that are corner shared, whereas the more highly charged anions [H₂W_2m O_6m+4]^6– are consistent with closed-packed structures which are based on the structure of paratungstate-B [H₂W₁₂O₄₂]^10–. For the alkali metal tungstate systems, the ESMS spectra are consistent with open-chained structures of octahedral units that are edge shared, with a terminating tetrahedral unit. Linear correlations suggest that the assembly of these aggregates occurs via an additive polymerization mechanism for which the additive moieties (WO₃, WO²⁺ ₂, and W₂O₈A₄) in aqueous solution can be identified.     

Textural characteristics, surface chemistry and oxidation of activated carbon

Numerous researches were reviewed and interpreted to depict a comprehensive illustration of activated carbon and its behavior towards oxidation. Activated carbon as one of the most important adsorbents is tried to be described in this review paper by terms of its "Textural Characteristics" and "Surface Chemistry". These two terms, coupled with each other, are responsible for behavior of activated carbon in adsorption processes and in catalytic applications. Although as-prepared activated carbons are usually non-selective and their surfaces suffer from lack of enough reactive groups, their different aspects may be improved and developed by diverse types of modifications. Oxidation is one of the most conventional modifications used for activated carbons. It may be used as a final modification or as a pre-modification followed by further treatment. In this paper, methods of oxidation of activated carbon and other graphene-layer carbon materials are introduced and wet oxidation as an extensively-used category of oxidation is discussed in more detail.