Enhanced adsorptive removal of fluoride using mesoporous alumina

Two different kinds of mesoporous alumina samples were prepared using aluminum tri-sec-butoxide in the presence of either cetyltrimethylammonium bromide (MA-1) or stearic acid (MA-2) as a structure-directing agent, and tested for adsorptive removal of fluoride in water. Both materials contain a wormhole-like mesopore structure, but exhibited different textural properties: surface area (421 or 650 m²/g) and pore volume (0.96 or 0.59 cm³/g). These mesoporous aluminas demonstrated significantly improved adsorption capacity and faster kinetics to those of the commercial activated aluminas in fluoride removal by adsorption process. MA-2 prepared using stearic acid, in particular, demonstrated an adsorption capacity (14.26 mg/g) and initial adsorption rate (14.6 mg/g min) that were respectively 2.2 and 45 times higher than those of a commercial gamma alumina. The textural features of larger surface area and relatively smaller pore size in MA-2 compared to the activated aluminas are believed to be responsible for this enhancement in adsorption process.     

Study of Band Structure Properties of Pnictide LaO1−xF x FeAs (x = 0, 0.2) Superconducting Compound

This paper reports on the band structure properties and changes in band structure of fluorine-doped LaO_1?x F _x FeAs (x = 0, 0.2) compound, measured using X-ray photoemission spectroscopy (XPS). The band structure of the superconducting compound is compared with nonsuperconducting parent compound LaOFeAs. With fluorine doping, a shift of the shallow core level is observed in XPS spectra, which may be a response of the band structure due to fluorine doping in the system. The balance of the chemical potential shift with the screening effect of conduction electrons near the Fe and As ions is discussed using nearly unchanged Fe 2p and As 3d core-level spectra. The La 3d core-level spectra shift towards the high energy, ～0.36 eV, may be due to the chemical potential shift caused by fluorine doping. In our valence band spectra, a small peak at around 0.2 eV is observed, which disappeared with the fluorine doping in the system, indicating a change of Fe 3d state from low spin to high spin states and also confirming the nature of Fe 3d electrons as itinerant, which is responsible for superconductivity in these compounds.     

Quality improvement and backorder price discount under controllable lead time in an inventory model

The proposed study investigates a continuous review inventory model with order quantity, reorder point, backorder price discount, process quality, and lead time as decision variables. An investment function is used to improve the process quality. Two models are developed based on the probability distribution of lead time demand. The lead time demand follows a normal distribution in the first model and in the second model it does not follow any specific distribution but mean and standard deviation are known. We prove two lemmas to obtain optimal solutions for the normal distribution model and distribution free model. Finally, some numerical examples are given to illustrate the model.     

First-Principles Investigation of Electronic Properties of GaAsxSb1 –x Ternary Alloys

Semiconductors - Compositional variations in GaAs based ternary alloys have exhibited wide range alterations in electronic properties. In the present paper, first-principles study of...     

Political YouTube Channel Reputation (PYCR): Development and validation of a multidimensional scale

Although YouTube is driving change in the news and information environment and earning a reputation as an alternative media, there is a lack of research examining what determines people’s reputational judgments on YouTube’s political channels. Based on in-depth interviews with 32 experts and empirical findings from 380 adults, this research identified factors that impact YouTube users’ reputation perception of political channels and developed a scale. The results showed that the Political YouTube Channel Reputation (PYCR) scale comprises four distinctive dimensions: news credibility, political ideology, user-oriented communication, and quality management. The reliability and validity of the scale were assessed, using exploratory and confirmatory analyses and construct validity. The PYCR scale has a variety of potential applications for users, political influencers, and YouTube, and it can serve as a theoretical framework for future empirical research in this novel and emerging area.     

Implementation and solution of the diffusion–reaction equation using high-order methods

The orthogonal collocation, Galerkin, tau and least-squares methods are applied to solve a diffusion–reaction problem. In general, the least-squares method suffers from lower accuracy than the other weighted residual methods. The least-squares method holds the most complex linear algebra theory and is thus associated with the most complex implementation. On the other hand, an advantage of the least-squares method is that it always produces a symmetric and positive definite system matrix which can be solved with an efficient iterative technique such as the conjugate gradient method or its preconditioned version. For the present problem, neither the Galerkin, tau and orthogonal collocation techniques produce symmetric and positive definite system matrices, hence the conjugate gradient method is not applicable for these numerical techniques.     

A modified intuitionistic fuzzy c-means clustering approach to segment human brain MRI image

Multimedia Tools and Applications - Fuzzy c-means (FCM) is one of the prominent method utilized for medical image segmentation. In literature intuitionistic fuzzy c-means (IFCM) is suggested which...     

C60 Concentration Influence on MEH-PPV:C60 Bulk Heterojunction-Based Schottky Devices

We have investigated the effect of C60 concentration on the performance of poly[2-methoxy-5-(2′-ethylhexoxy-p-phenylene vinylene] (MEH-PPV):C60 blend-based Schottky barrier-based devices. Incorporation of C60 in MEH-PPV leads to a red shift and the reduction of intensity in MEH-PPV absorption spectra. The appearance of a C60 characteristic band in the Raman spectra of the composites indicates the presence of C60 in the blends. A FESEM study reveals that the addition of C60 significantly modifies the surface morphology of the blend films. However, higher concentrations (>?5 wt.%) results in agglomeration of C60 particles. Dark I–V measurements allow us to extract various diode parameters including barrier height, ideality factor, and saturation current. Profound variations have been observed in the dominant charge carrier transport mechanism for different C60 concentrations. A photoresponse study demonstrates the enhancement in the photocurrent with the increase in the C60 concentration up to 5 wt.%. Beyond this concentration, agglomeration impedes exciton dissociation and charge transport, which results in a decrease in the photocurrent. Finally, an impedance spectroscopy analysis has been extensively carried out to estimate the internal device parameters, such as junction resistance, capacitance and carrier lifetime. The correlation between these parameters and I–V curves has been established.     

X-ray diffraction investigation of cation distribution in CdχCu1-χFe2O4 ferrite system

Assuming the distribution of copper ions on tetrahedral (A) and octahedral (B) sites in the polycrystalline Cd_χCu_1-χFe₂O₄ (χ=0.2, 0.4, 0.6, 0.8 and 1.0) ferrite system, the theoretical intensities are calculated. Structural refinement of the diffraction pattern converges the R factor to between 0.0103 and 0.0315. Theoretical intensity ratios of (220) to (222) planes are considered, as these reflections are sensitive to cations on the A and B sites. Close agreement of the theoretical intensity ratio with the intensity ratio observed from X-ray diffraction pattern supports the occupancy of cadmium on the tetrahedral site. The cation distribution is predicted employing a new method wherein a graph of theoretical intensity is plotted against the inversion parameter for the (220) plane. The experimentally observed intensity of the same plane is then used to get an exact inversion parameter with the help of this plot. The cation distribution estimated by this method supports the cation distribution predicted by the magnetization method.