Effect of 2D Image Resolution on 3D Stochastic Reconstruction and Developing Petrophysical Trend

Multi-resolution digital rock physics (DRP) makes it possible to up-scale petrophysical properties from micron size to core sample size using two-dimensional (2D) thin section images. Resolution of 3D images and sample size are challenging problems in DRP where high-resolution images are acquired from small samples using inefficient and expensive micro-CT facilities. Three-dimensional stochastic reconstruction is an alternative approach to overcome these challenges. In this paper, we use multi-resolution images and investigate effect of 2D image resolution on 3D stochastic reconstruction and development of petrophysical trends for our two sandstone and carbonate original representative volume elements (RVEs). The proposed method includes three steps. In the first step, the spatial resolution of our original RVEs is decreased synthetically. In the second step, stochastic RVEs are realized for each resolution using two perpendicular images, correlation functions, and phase recovery algorithm. In the reconstruction method, a full set of two-point correlation functions (TPCFs) is extracted from two perpendicular 2D images. Then TPCF vectors are decomposed and averaged to realize 3D stochastic RVEs. In the third step, petrophysical properties like relative and absolute permeability as well as porosity and formation factor are computed. The output is used to develop trends for petrophysical properties in different resolutions. Experimental results illustrate that the proposed method can be used to predict petrophysical properties and reconstruct 3D RVEs for resolutions unavailable in the acquired 2D or 3D data.     

Are the eigenvalues of preconditioned banded symmetric Toeplitz matrices known in almost closed form?

The problem of computing oscillatory integrals with general oscillators is considered. We employ a Filon-type method, where the interpolation basis functions are chosen in such a way that the moments are in terms of elementary functions and the oscillator only. This allows us to evaluate the moments rapidly and easily without needing to engage hypergeometric functions. The proposed basis functions form a Chebyshev set for any oscillator function even if it has some stationary points in the integration interval. This property enables us to employ the Filon-type method without needing any information about the stationary points if any. Interpolation by the proposed basis functions at the Fekete points (which are known as nearly optimal interpolation points), when combined with the idea of splines, leads to a reliable convergent method for computing the oscillatory integrals. Our numerical experiments show that the proposed method is more efficient than the earlier ones with the same advantages.     

Designing of new cationic surfactant based micellar systems as drug carriers: an investigation into the drug cell membrane interactions

This study highlights the utility of new pyridinium based cationic surfactants, N-(n-heptyl)-3-methylpyridinium bromide (Py7) and N-(n-nonyl)-3-methylpyridinium bromide (Py9), formed via a single step substitution reaction, for their application towards drugs delivery. Fourier-transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopic methods have been employed for the characterization of these amphiphiles. Aggregation behavior of the surfactants in solution i.e. the critical micelle concentration (CMC), has been investigated by conductometric and spectrophotometric analyses. The results reveal that the amphiphiles can act as excellent surface active agents due to their low critical micelle concentration (CMC). Furthermore, the interaction of these surfactants with two anionic drugs i.e., Ketoprofen (KP, 2-(3-Benzoylphenyl)propanoic acid) and Diclofenac sodium (DF, Sodium 2-(2,6-dichloranilino) phenylacetate), has been explored below and above the CMC value using UV-visible spectroscopy. The enhanced absorption intensities of both the drugs in the presence of synthesized surfactants indicated stronger interactions between surfactants and drugs molecules.     

Visual and surface plasmon resonance sensor for zirconium based on zirconium-induced aggregation of adenosine triphosphate-stabilized gold nanoparticles

Owing to its high affinity with phosphate, Zr(IV) can induce the aggregation of adenosine 5′-triphosphate (ATP)-stabilized AuNPs, leading to the change of surface plasmon resonance (SPR) absorption spectra and color of ATP-stabilized AuNP solutions. Based on these phenomena, visual and SPR sensors for Zr(IV) have been developed for the first time. The A_660 nm/A_518 nm values of ATP-stabilized AuNPs in SPR absorption spectra increase linearly with the concentrations of Zr(IV) from 0.5 μM to 100 μM (r = 0.9971) with a detection limit of 95 nM. A visual Zr(IV) detection is achieved with a detection limit of 30 μM. The sensor shows excellent selectivity against other metal ions, such as Cu²⁺, Fe³⁺, Cd²⁺, and Pb²⁺. The recoveries for the detection of 5 μM, 10 μM, 25 μM and 75 μM Zr(IV) in lake water samples are 96.0%, 97.0%, 95.6% and 102.4%, respectively. The recoveries of the proposed SPR method are comparable with those of ICP-OES method.     

Is hairpin formation in single-stranded polynucleotide diffusion-controlled?

An intriguing puzzle in biopolymer science is the observation that single-stranded DNA and RNA oligomers form hairpin structures on time scales of tens of microseconds, considerably slower than the estimated time for loop formation for a semiflexible polymer of similar length. To address the origin of the slow kinetics and to determine whether hairpin dynamics are diffusion-controlled, the effect of solvent viscosity (eta) on hairpin kinetics was investigated using laser temperature-jump techniques. The viscosity was varied by addition of glycerol, which significantly destabilizes hairpins. A previous study on the viscosity dependence of hairpin dynamics, in which all the changes in the measured rates were attributed to a change in solvent viscosity, reported an apparent scaling of relaxation times (tau(r)) on eta as tau(r) approximately eta(0.8). In this study, we demonstrate that if the effect of viscosity on the measured rates is not deconvoluted from the inevitable effect of change in stability, then separation of tau(r) into opening (tau(o)) and closing (tau(c)) times yields erroneous behavior, with different values (and opposite signs) of the apparent scaling exponents, tau(o) approximately eta(-0.4) and tau(c) approximately eta(1.5). Under isostability conditions, obtained by varying the temperature to compensate for the destabilizing effect of glycerol, both tau(o) and tau(c) scale as approximately eta(1.1+/-0.1). Thus, hairpin dynamics are strongly coupled to solvent viscosity, indicating that diffusion of the polynucleotide chain through the solvent is involved in the rate-determining step.     

Ion Beam Modification of Polymethyl methacrylate (PMMA) Polymer Matrix Filled with Organometallic Complex

A Nickel Dimethylglyoxime (Ni‐DMG) compound was dispersed in polymethyl methacrylate (PMMA) films at different concentrations. PMMA was synthesized by a solution polymerization technique. These films were irradiated with 120 MeV Ni¹⁰⁺ ions at the fluences of 1×10¹¹ and 1×10¹² ions/cm². The radiation induced changes in dielectric properties and average surface roughness were investigated by using an LCR meter in the frequency range 50 Hz to 10 MHz and atomic force microscopy (AFM), respectively. The electrical properties of irradiated films are found to increase with the fluence and also with the concentration of Ni‐DMG. From the analysis of frequency, f, dependence of dielectric constant, ?, it has been found that the dielectric response in both pristine and irradiated samples obey the Universal law given by ? α f ^n?1. The dielectric constant/loss is observed to change significantly due to the irradiation. This suggests that ion beam irradiation promotes (i) the metal to polymer bonding (ii) convert the polymeric structure in to hydrogen depleted carbon network due to the emission of hydrogen gas and/or other volatile gases. Atomic force microscopy (AFM) shows that the average surface roughness and surface morphology of irradiated films are observed to change.     

Heat Transfer and Entropy in a Vertical Porous Plate Subjected to Suction Velocity and MHD

This article presents an investigation of heat transfer in a porous medium adjacent to a vertical plate. The porous medium is subjected to a magnetohydrodynamic effect and suction velocity. The governing equations are nondepersonalized and converted into ordinary differential equations. The resulting equations are solved with the help of the finite difference method. The impact of various parameters, such as the Prandtl number, Grashof number, permeability parameter, radiation parameter, Eckert number, viscous dissipation parameter, and magnetic parameter, on fluid flow characteristics inside the porous medium is discussed. Entropy generation in the medium is analyzed with respect to various parameters, including the Brinkman number and Reynolds number. It is noted that the velocity profile decreases in magnitude with respect to the Prandtl number, but increases with the radiation parameter. The Eckert number has a marginal effect on the velocity profile. An increased radiation effect leads to a reduced thermal gradient at the hot surface.     

Comparison of 1 MeV electron,Co-60 gamma and 1 MeV proton irradiation effects on silicon NPN transistors

The total dose effects of 1?MeV electrons on the dc electrical characteristics of silicon NPN transistors are investigated in the dose range from 100?krad to 100?Mrad. The different electrical characteristics such as Gummel characteristics, excess base current (ΔI_B), dc current gain (h_FE), transconductance (g_m), displacement damage factor (K) and output characteristics were studied in situ as a function of total dose. A considerable increase in base current (I_B) and a decrease in h_FE, g_m and I_CSat was observed after 1?MeV electron irradiation. The collector–base (C–B) junction capacitance of transistors was measured to estimate the change in the effective carrier concentration. After 1?MeV electron irradiation, a considerable degradation in capacitance was observed. The plot of (1/C²) versus voltage shows that the effective carrier concentration and built-in voltage (V_bi) increase marginally upon 1?MeV electron irradiation. The results of 1?MeV electron irradiation were compared with 1?MeV proton and Co-60 gamma irradiation results in the same dose range. The degradation for 1?MeV electron and Co-60 gamma-irradiated transistors was significantly less when compared to 1?MeV proton-irradiated transistor. The 1?MeV proton, 1?MeV electron and Co-60 gamma-irradiated transistors were subjected to isochronal annealing to analyze the recovery of the electrical parameters.     

Theoretical investigations of half-metallic ferromagnetism in new Half-Heusler YCrSb and YMnSb alloys using first-principle calculations

Structural,electronic,and magnetic properties of new predicted half-Heusler YCrSb and YMnSb compounds within the ordered MgAgAs Clb-type structure are investigated by employing first-principal calculations based on density functional theory.Through the calculated total energies of three possible atomic placements,we find the most stable structures regarding YCrSb and YMnSb materials,where Y,Cr(Mn),and Sb atoms occupy the(0.5,0.5,0.5),(0.25,0.25,0.25),and(0,0,0) positions,respectively.Furthermore,structural properties are explored for the non-magnetic and ferromagnetic and anti-ferromagnetic states and it is found that both materials prefer ferromagnetic states.The electronic band structure shows that YCrSb has a direct band gap of 0.78 eV while YMnSb has an indirect band gap of 0.40 eV in the majority spin channel.Our findings show that YCrSb and YMnSb materials exhibit half-metallic characteristics at their optimized lattice constants of 6.67  and 6.56 ,respectively.The half-metallicities associated with YCrSb and YMnSb are found to be robust under large in-plane strains which make them potential contenders for spintronic applications.     

Influence of sputtering power and Ar–N2 flow on the structure and optical properties of indium nitride films prepared by magnetron sputtering

ABSTRACT

This paper discusses the deposition of indium nitride (InN) thin films on Si (100) substrates by using pulsed DC magnetron sputtering. Effects of varying sputtering power and Ar–N₂ flow ratio on the structural, morphological, and optical properties of indium nitride (InN) films were investigated. The structural characterization indicated nanocrystalline InN film with preferred orientation towards (101) plane that exhibited the optimum crystalline quality at 130?W and for 40:60 Ar–N₂ ratio. The surface morphology of InN, as observed through FESEM, contained irregularly shaped nanocrystals with size that increases with higher sputtering power and Ar:N₂ flow ratio. The optical properties of InN films were studied using ellipsometer at room temperature. The band gap of InN was decreased with the increase of sputtering power to 130?W, whereas an increase in the band gap was noticed with the increase of the Ar:N₂ flow ratio.