4,942 research outputs found
Pengaruh Ion Kromium(iii) pada Ekstraksi Ion Tembaga(ii) Menggunakan Emulsi Kerosen dengan 1-fenil-3-metil-4-benzoil-5-pirazolon sebagai Pembawa Kation
The influence of chromium(III) ion on copper(II) ion extraction using kerosene emulsion with 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (HPMBP) as a cation carrier was investigated. The optimum condition for copper(II) extraction were as follows: concentration of mixed surfactant (span 80+span 20) was 5%, volume ratio of kerosene and internal phase was 1, concentration of HPMBP was 0.025 M, concentration of HCl was 1 M, volume ratio of emulsion and external phase was 0.143. The results showed that the extraction of copper(II) ion was selective to chromium(III) ion, relatively. The result also showed that the presence of 500 ppm chromium(III) ion decrease the percentage of copper(II) ion extraction from 98.6 to 91.0
Ab-initio study of the bandgap engineering of Al(1-x)Ga(x)N for optoelectronic applications
A theoretical study of Al(1-x)Ga(x)N, based on full-potential linearized
augmented plane wave method, is used to investigate the variations in the
bandgap, optical properties and non-linear behavior of the compound with the
variation of Ga concentration. It is found that the bandgap decreases with the
increase of Ga in Al(1-x)Ga(x)N. A maximum value of 5.5 eV is determined for
the bandgap of pure AlN which reaches to minimum value of 3.0 eV when Al is
completely replaced by Ga. The static index of refraction and dielectric
constant decreases with the increase in bandgap of the material, assigning a
high index of refraction to pure GaN when compared to pure AlN. The refractive
index drops below 1 for photon energies larger than 14 eV results group
velocity of the incident radiation higher than the vacuum velocity of light.
This astonishing result shows that at higher energies the optical properties of
the material shifts from linear to non-linear. Furthermore, frequency dependent
reflectivity and absorption coefficients show that peak value of the absorption
coefficient and reflectivity shifts towards lower energy in the UV spectrum
with the increase in Ga concentration. This comprehensive theoretical study of
the optoelectronic properties of the alloys is presented for the first time
which predicts that the material can be effectively used in the optical devices
working in the visible and UV spectrum.Comment: 18 pages, 7 figure
Magnetism dependent phonon anomaly in LaFeAsO observed via inelastic x-ray scattering
The phonon dispersion was measured at room temperature along (0,0,L) in the
tetragonal phase of LaFeAsO using inelastic x-ray scattering. Spin-polarized
first-principles calculations imposing various types of antiferromagnetic order
are in better agreement with the experimental results than nonmagnetic
calculations, although the measurements were made well above the magnetic
ordering temperature, T_N. Splitting observed between two A_{1g} phonon modes
at 22 and 26 meV is only observed in spin-polarized calculations.
Magneto-structural effects similar to those observed in the AFe_2As_2 materials
are confirmed present in LaFeAsO. The presence of Fe-spin is necessary to find
reasonable agreement of the calculations with the measured spectrum well above
T_N. On-site Fe and As force constants show significant softening compared to
nonmagnetic calculations, however an investigation of the real-space force
constants associates the magnetoelastic coupling with a complex renormalization
instead of softening of a specific pairwise force.Comment: 7 pages, 4 figure
Ultrasonic Activation of Suzuki and Hiyama Cross-Coupling Reactions Catalyzed by Palladium
Abstract The coupling reaction of aryl bromide and aryl boronic acid in water/DMF as solvent was studied using a palladium-complex as a catalyst in the presence of ultrasound at room temperature. The effect on the reaction of a base and a solvent was also studied with and without ultrasound and was found to increase the speed of the reaction. In this regard, we propose reaction mechanisms that could explain the results obtained
âThey Called Them Communists ThenââŠâWhat D'You Call âEm Now?ââŠâInsurgents?â. Narratives of British Military Expatriates in the Context of the New Imperialism
This paper addresses the question of the extent to which the colonial past provides material for contemporary actors' understanding of difference. The research from which the paper is drawn involved interview and ethnographic work in three largely white working-class estates in an English provincial city. For this paper we focus on ten life-history interviews with older participants who had spent some time abroad in the British military. Our analysis adopts a postcolonial framework because research participants' current constructions of an amorphous 'Other' (labelled variously as black people, immigrants, foreigners, asylum-seekers or Muslims) reveal strong continuities with discourses deployed by the same individuals to narrate their past experiences of living and working as either military expatriates or spouses during British colonial rule. Theoretically, the paper engages with the work of Frantz Fanon and Edward Said. In keeping with a postcolonial approach, we work against essentialised notions of identity based on 'race' or class. Although we establish continuity between white working-class military emigration in the past and contemporary racialised discourses, we argue that the latter are not class-specific, being as much the creations of the middle-class media and political elite
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