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Measurement of the inclusive J/psi polarization at forward rapidity in pp collisions at root s=8 TeV
No full textWe report on the measurement of the inclusive J/psi polarization parameters in pp collisions at a center of mass energy root s = 8 TeV with the ALICE detector at the LHC. The analysis is based on a data sample corresponding to an integrated luminosity of 1.23 pb(-1) J/psi resonances are reconstructed in their di-muon decay channel in the rapidity interval 2.5 < y < 4.0 and over the transverse-momentum interval 2 < pT < 15 GeV/c. The three polarization parameters (lambda(theta), lambda(phi), lambda(theta phi)) are measured as a function of pT both in the helicity and Collins-Soper reference frames. The measured J/psi polarization parameters are found to be compatible with zero within uncertainties, contrary to expectations from all available predictions. The results are compared with the measurement in pp collisions at root s = 7 TeV
Vector Galileon and inflationary magnetogenesis
No full textCosmological inflation provides the initial conditions for the structure formation. However, the origin of large-scale magnetic fields can not be addressed in this framework. The key issue for this long-standing problem is the conformal invariance of the electromagnetic (EM) field in 4-D. While many approaches have been proposed in the literature for breaking conformal invariance of the EM action, here, we provide a completely new way of looking at the modifications to the EM action and generation of primordial magnetic fields during inflation. We explicitly construct a higher derivative EM action that breaks conformal invariance by demanding three conditions - theory be described by vector potential A mu and its derivatives, Gauge invariance be satisfied, and equations of motion be linear in second derivatives of vector potential. The unique feature of our model is that appreciable magnetic fields are generated at small wavelengths while tiny magnetic fields are generated at large wavelengths that are consistent with current observations
A comprehensive mechanistic model for simulating algal-bacterial growth dynamics in photobioreactors
No full textA comprehensive mechanistic model with state of the art understanding and assumptions is presented to simulate major processes in a photobioreactor for describing the algal-bacterial growth dynamics. The model includes a total of 37 state variables that broadly cover all the essential physiological and physico-chemical processes in such a system. Model parameters are first calibrated with batch experimental data, and thereafter, extensive validation of the model is carried with long term independent experimental data in diverse conditions. The developed model is able to capture the complex system behavior with reasonable accuracy. Also, the comprehensive mathematical formulation with realistic assumptions make this model a valuable tool for gaining better insights into the complex system behavior
Modeling of nanosecond pulsed laser processing of polymers in air and water
No full textLaser ablation of polymers in water is known to generate distinct surface characteristics as compared to that in air. In order to understand the role of ambient media during laser ablation of polymers, this paper aims to develop a physics-based model of the process considering the effect of ambient media. Therefore, in the present work, models are developed for laser ablation of polymers in air and water considering all the relevant physical phenomena such as laser-polymer interaction, plasma generation, plasma expansion and plasma shielding. The current work focuses on near-infrared laser radiation (lambda-1064 nm) of nanosecond pulse duration. The laser-polymer interaction at such wavelengths is purely photo-thermal in nature and the laser-plasma interaction is assumed to occur mainly by inverse-bremsstrahlung photon absorption. The computational model is based on the finite volume method using the Crank-Nicholson scheme. The model predicts that underwater laser ablation results in subsurface heating effect in the polymer and confinement of the laser generated plasma, which makes it different from laser ablation in air. Plasma expansion velocities are much lower in water than in air. This results in an enhanced plasma shielding effect in the case of water. The predicted results of ablation depth versus fluence from the model are in qualitative agreement with those observed in experiments
Proactive safety evaluation of a multilane unsignalized intersection using surrogate measures
No full textRoad traffic safety is emerging as an area of increased attention and concern in many countries including India. Safety evaluation by conflict study using surrogate measures is a proactive method which does not require any accident data. Conflict study may be carried out using post encroachment time (PET) as a surrogate measure, where critical conflicts are determined based on certain threshold value of PET. Identifying critical conflicts using a threshold value of PET is good and correct for highways and major roads where traffic follows posted speed, but on highways with mixed traffic for varied speeds this is not correct. It can be seen that conflicts with PET less than the threshold value may not be critical if the speed of conflicting vehicle is less. Similarly, conflicts with PET more than threshold value may also be critical if the speed of conflicting vehicle is high. The speed of conflicting vehicle is also important in evaluating severity of conflict. Hence, the use of PET alone for conflict study is not correct for evaluating safety of intersections on highways where traffic follows varied speeds. Therefore, in the present study, safety evaluation of an unsignalized intersection is carried out using two surrogate measures, PET and the speed of corresponding conflicting through vehicle. A term critical speed is proposed to identify critical conflicts. Critical speed for a particular PET value is determined using stopping/braking distance concept. Results show that there are significant percent of conflicts which are critical at the intersection. This shows that drivers of right-turning vehicles do take risks in accepting small gaps in through traffic at the intersection, which is dangerous. As crossing maneuver depends on length and speed of turning vehicle, the effect of type of turning vehicle has also been studied. Results show that right-turning light motor vehicles are at higher risk compared to two wheelers and heavy vehicles at the intersection. Safety evaluation of such unsignalized intersections may be carried out using this concept
Ruthenium-Catalyzed Aerobic Oxidation of Amines
No full textAmine oxidation is one of the fundamental reactions in organic synthesis as it leads to a variety of value-added products such as oximes, nitriles, imines, and amides among many others. These products comprise the key N-containing building blocks in the modern chemical industry, and such transformations, when achieved in the presence of molecular oxygen without using stoichiometric oxidants, are much preferred as they circumvent the production of unwanted wastes. In parallel, the versatility of ruthenium catalysts in various oxidative transformations is well-documented. Herein, this review focuses on aerobic oxidation of amines specifically by using ruthenium catalysts and highlights the major achievements in this direction and challenges that still need to be addressed
Lanthanide-Based Porous Coordination Polymers: Syntheses, Slow Relaxation of Magnetization, and Magnetocaloric Effect
No full textTwo lanthanide-containing structurally analogous porous coordination polymers (PCPs) have been isolated with the general molecular formula [Ln(2)(L-1)(2)(H2O)(4)(ox)(n).4nH(2)O (where L-1 = fumarate, ox = oxalate; Ln = Dy (1), Gd (2)). Thermogravimetric analysis (TGA) and TG-MS measurements performed on 1 and 2 suggest that not only the solvated water molecules in the crystal lattice but also the four coordinated water molecules on the respective lanthanides in 1 and 2 are removed upon activation. Due to the removal of the waters, 1 and 2 lost their crystallinity and became amorphous, as confirmed by powder X-ray diffraction (PXRD). We propose the molecular formula [Ln(2)(L-1)(2)(ox)](n) for the amorphous phase of 1 and 2 (where Ln = Dy (1'), Gd (2')) on the basis of XANES, EXAFS, and other experimental investigations. Magnetization relaxation dynamics probed on 1 and 1' reveal two different relaxation processes with effective energy barriers of 53.5 and 7.0 cm(-1) for 1 and 45.1 and 6.4 crn(-1) for 1', which have been rationalized by detailed ab initio calculations. For the isotropic lanthanide complexes 2 and 2', magnetocaloric effect (MCE) efficiency was estimated through detailed magnetization measurements. We have estimated -Delta S-m values of 52.48 and 41.62 J kg(1-)K(-1) for 2' and 2, respectively, which are one of the largest values reported for an extended structure. In addition, a 26% increase in -Delta S-m value in 2' in comparison to 2 is achieved by simply removing the passively contributing (for MCE) solvated water molecule in the lattice and coordinated water molecules
Ag decorated silica nanostructures for surface plasmon enhanced photocatalysis
No full textIn this article, we present a novel synthesis of mesoporous SiO2/Ag nanostructures for dye (methylene blue) adsorption and surface plasmon mediated photocatalysis. Mesoporous SiO2 nanoparticles with a pore size of 3.2nm were synthesized using cetyltrimethylammonium bromide as a structure directing agent and functionalized with (3-aminopropyl)trimethoxysilane to introduce amine groups. The adsorption behavior of non-porous SiO2 nanoparticles was compared with that of the mesoporous silica nanoparticles. The large surface area and higher porosity of mesoporous SiO2 facilitated better adsorption of the dye as compared to the non-porous silica. Ag decorated SiO2 nanoparticles were synthesized by attaching silver (Ag) nanoparticles of different morphologies, i.e. spherical and triangular, on amine functionalized silica. The photocatalytic activity of the mesoporous SiO2/Ag was compared with that of non-porous SiO2/Ag nanoparticles and pristine Ag nanoparticles. Mesoporous SiO2 nanoparticles (k(d) = 31.3 x 10(-3) g mg(-1) min(-1)) showed remarkable improvement in the rate of degradation of methylene blue as compared to non-porous SiO2 (k(d) = 25.1 x 10(-3) g mg(-1) min(-1)) and pristine Ag nanoparticles (k(d) = 19.3 x 10(-3) g mg(-1) min(-1)). Blue Ag nanoparticles, owing to their better charge carrier generation and enhanced surface plasmon resonance, exhibited superior photocatalysis performance as compared to yellow Ag nanoparticles in all nanostructures
Performance analysis of nanostructured Peltier coolers
No full textEmploying non-equilibrium quantum transport models, we investigate the details and operating conditions of nano-structured Peltier coolers embedded with an energy filtering barrier. Our investigations point out non-trivial aspects of Peltier cooling which include an inevitable trade-off between the cooling power and the coefficient of performance, the coefficient of performance being high at a low voltage bias and subsequently deteriorating with increasing voltage bias. We point out that there is an optimum energy barrier height for nanowire Peltier coolers at which the cooling performance is optimized. However, for bulk Peltier coolers, the cooling performance is enhanced with the height of the energy filtering barrier. Exploring further, we point out that a degradation in cooling performance with respect to bulk is inevitable as a single moded nanowire transitions to a multi-moded one. The results discussed here can provide theoretical insights into optimal design of nano Peltier coolers. Published by AIP Publishing
Effects of phosphorus implantation time on the optical, structural, and elemental properties of ZnO thin films and its correlation with the 3.31-eV peak
No full textTo study the effects of implantation on ZnO thin films grown on Si substrates, we have subjected it to phosphorous ion implantation for 10, 40, and 70 s through plasma immersion ion implantation and rapid thermal annealing. Low-temperature photoluminescence spectra of the as-implanted samples exhibited a reduction in the donor-bound exciton peak at 3.36 eV with implantation time. The photoluminescence spectrum of the 70 s implanted 1000 degrees C-annealed sample confirmed acceptor-type doping. X-ray diffraction measurements showed a reduction in the c-axis length along the direction with implantation time, evidencing phosphorous-ion incorporation in the implanted films, which was further confirmed by the blue shifting of the E2 high peak in the Raman spectra. XPS measurements affirmed the presence of the P 2p peak, a signature of P-O bond, and confirmed the substitution of Zn atoms by P atoms and the subsequent formation of the Pzn-2Vzn complex essential for acceptor-type conductivity. (C) 2018 Elsevier B.V. All rights reserved