Showing papers by "University of Rajasthan published in 2013"

Centrality dependence of pi, K, and p production in Pb-Pb collisions at root s(NN)=2.76 TeV

Abstract: In this paper measurements are presented of pi(+/-), K-+/-, p, and (p) over bar production at midrapidity (vertical bar y vertical bar < 0.5), in Pb-Pb collisions at root s(NN) = 2.76 TeV as a function of centrality. The measurement covers the transverse-momentum (p(T)) range from 100, 200, and 300 MeV/c up to 3, 3, and 4.6 GeV/c for pi, K, and p, respectively. The measured p(T) distributions and yields are compared to expectations based on hydrodynamic, thermal and recombination models. The spectral shapes of central collisions show a stronger radial flow than measured at lower energies, which can be described in hydrodynamic models. In peripheral collisions, the p(T) distributions are not well reproduced by hydrodynamic models. Ratios of integrated particle yields are found to be nearly independent of centrality. The yield of protons normalized to pions is a factor similar to 1.5 lower than the expectation from thermal models.

Centrality determination of Pb-Pb collisions at root s(NN)=2.76 TeV with ALICE

Abstract: This publication describes the methods used to measure the centrality of inelastic Pb-Pb collisions at a center-of-mass energy of 2.76 TeV per colliding nucleon pair with ALICE. The centrality is a key parameter in the study of the properties of QCD matter at extreme temperature and energy density, because it is directly related to the initial overlap region of the colliding nuclei. Geometrical properties of the collision, such as the number of participating nucleons and the number of binary nucleon-nucleon collisions, are deduced from a Glauber model with a sharp impact parameter selection and shown to be consistent with those extracted from the data. The centrality determination provides a tool to compare ALICE measurements with those of other experiments and with theoretical calculations.

Vitamin C in Disease Prevention and Cure: An Overview

Abstract: The recognition of vitamin C is associated with a history of an unrelenting search for the cause of the ancient haemorrhagic disease scurvy. Isolated in 1928, vitamin C is essential for the development and maintenance of connective tissues. It plays an important role in bone formation, wound healing and the maintenance of healthy gums. Vitamin C plays an important role in a number of metabolic functions including the activation of the B vitamin, folic acid, the conversion of cholesterol to bile acids and the conversion of the amino acid, tryptophan, to the neurotransmitter, serotonin. It is an antioxidant that protects body from free radical damage. It is used as therapeutic agent in many diseases and disorders. Vitamin C protects the immune system, reduces the severity of allergic reactions and helps to fight off infections. However the significance and beneficial effect of vitamin C in respect to human disease such as cancer, atherosclerosis, diabetes, neurodegenerative disease and metal toxicity however remains equivocal. Thus further continuous uninterrupted efforts may open new vistas to understand its significance in disease management.

K-S(0) and Lambda Production in Pb-Pb Collisions at root s(NN)=2: 76 TeV

Abstract: The ALICE measurement of K^0_S and {\Lambda} production at mid-rapidity in Pb-Pb collisions at sqrt(sNN) = 2.76 TeV is presented. The transverse momentum (pT) spectra are shown for several collision centrality intervals and in the pT range from 0.4 GeV/c (0.6 GeV/c for {\Lambda}) to 12 GeV/c. The pT dependence of the {\Lambda}/K^0_S ratios exhibits maxima in the vicinity of 3 GeV/c, and the positions of the maxima shift towards higher pT with increasing collision centrality. The magnitude of these maxima increases by almost a factor of three between most peripheral and most central Pb-Pb collisions. This baryon excess at intermediate pT is not observed in pp interactions at sqrt(s) = 0.9 TeV and at sqrt(s) = 7 TeV. Qualitatively, the baryon enhancement in heavy-ion collisions is expected from radial flow. However, the measured pT spectra above 2 GeV/c progressively decouple from hydrodynamical-model calculations. For higher values of pT, models that incorporate the influence of the medium on the fragmentation and hadronization processes describe qualitatively the pT dependence of the {\Lambda}/K^0_S ratio.

Long-range angular correlations of pi, K and p in p-Pb collisions at root s(NN)=5.02 TeV

Abstract: Angular correlations between unidentified charged trigger particles and various species of charged associated particles (unidentified particles, pions, kaons, protons and antiprotons) are measured by the ALICE detector in p-Pb collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV in the transverse-momentum range 0.3 < p(T) < 4 GeV/c. The correlations expressed as associated yield per trigger particle are obtained in the pseudorapidity range vertical bar n(lab)vertical bar < 0.8. Fourier coefficients are extracted from the long-range correlations projected onto the azimuthal angle difference and studied as a function of p(T) and in intervals of event multiplicity. In high-multiplicity events, the second-order coefficient for protons, 4, is observed to be smaller than that for pions, v(2)(pi), up to about p(T) = 2 GeV/c. To reduce correlations due to jets, the per-trigger yield measured in low-multiplicity events is subtracted from that in high-multiplicity events. A two-ridge structure is obtained for all particle species. The Fourier decomposition of this structure shows that the second-order coefficients for pions and kaons are similar. The v(2)(p) is found to be smaller at low P-T and larger at higher p(T) than v(2)(pi), with a crossing occurring at about 2 GeV/c. This is qualitatively similar to the elliptic-flow pattern observed in heavy-ion collisions. A mass ordering effect at low transverse momenta is consistent with expectations from hydrodynamic model calculations assuming a collectively expanding system. (C) 2013 CERN. Published by Elsevier B.V. All rights reserved.

Performance of the ALICE VZERO system

Abstract: ALICE is an LHC experiment devoted to the study of strongly interacting matter in proton-proton, proton-nucleus and nucleus-nucleus collisions at ultra-relativistic energies. The ALICE VZERO system, made of two scintillator arrays at asymmetric positions, one on each side of the interaction point, plays a central role in ALICE. In addition to its core function as a trigger source, the VZERO system is used to monitor LHC beam conditions, to reject beam-induced backgrounds and to measure basic physics quantities such as luminosity, particle multiplicity, centrality and event plane direction in nucleus-nucleus collisions. After describing the VZERO system, this publication presents its performance over more than four years of operation at the LHC.

Charge separation relative to the reaction plane in Pb-Pb collisions at sNN−−−−√=2.76 TeV

Abstract: Measurements of charge-dependent azimuthal correlations with the ALICE detector at the LHC are reported for Pb-Pb collisions at root s(NN) = 2.76 TeV. Two- and three-particle charge-dependent azimuthal correlations in the pseudorapidity range vertical bar eta vertical bar < 0.8 are presented as a function of the collision centrality, particle separation in pseudorapidity, and transverse momentum. A clear signal compatible with a charge-dependent separation relative to the reaction plane is observed, which shows little or no collision energy dependence when compared to measurements at RHIC energies. This provides a new insight for understanding the nature of the charge-dependent azimuthal correlations observed at RHIC and LHC energies. DOI: 10.1103/PhysRevLett.110.012301

Coherent J/psi photoproduction in ultra-peripheral Pb-Pb collisions at root s(NN)=2.76 TeV

Abstract: The ALICE Collaboration has made the first measurement at the LHC of J/psi photoproduction in ultra-peripheral Pb-Pb collisions at root s(NN) = 2.76 TeV. The J/psi is identified via its dimuon decay in the forward rapidity region with the muon spectrometer for events where the hadronic activity is required to be minimal. The analysis is based on an event sample corresponding to an integrated luminosity of about 55 mu b(-1). The cross section for coherent J/psi production in the rapidity interval -3.6 < y < -2.6 is measured to be d sigma(coh)(J/psi)/dy = 1.00 +/- 0.18(stat)(-0.26)(+0.24)(syst) mb. The result is compared to theoretical models for coherent J/psi production and found to be in good agreement with those models which include nuclear gluon shadowing. (C) 2012 CERN. Published by Elsevier B.V. All rights reserved.

Transverse Momentum Distribution and Nuclear Modification Factor of Charged Particles in p plus Pb Collisions at root(NN)-N-s=5.02 TeV

Abstract: The transverse momentum (pT) distribution of primary charged particles is measured in minimum bias (non-single-diffractive) p + Pb collisions at root(NN)-N-s = 5.02 TeV with the ALICE detector at the LHC. The pT spectra measured near central rapidity in the range 0.5< p(T) < 20 GeV/c exhibit a weak pseudorapidity dependence. The nuclear modification factor R-pPb is consistent with unity for p(T) above 2 GeV/c. This measurement indicates that the strong suppression of hadron production at high p(T) observed in Pb + Pb collisions at the LHC is not due to an initial-state effect. The measurement is compared to theoretical calculations. DOI: 10.1103/PhysRevLett.110.082302

Pseudorapidity density of charged particles in p+Pb collisions at √sNN=5.02 TeV

Abstract: The charged-particle pseudorapidity density measured over four units of pseudorapidity in nonsingle-diffractive p + Pb collisions at a center-of-mass energy per nucleon pair root s(NN) = 5.02 TeV is presented. The average value at midrapidity is measured to be 16.81 +/- 0.71 (syst), which corresponds to 2.14 +/- 0.17 (syst) per participating nucleon, calculated with the Glauber model. This is 16% lower than in nonsingle-diffractive pp collisions interpolated to the same collision energy and 84% higher than in d + Au collisions at root s(NN) = 0.2 TeV. The measured pseudorapidity density in p + Pb collisions is compared to model predictions and provides new constraints on the description of particle production in high-energy nuclear collisions. DOI: 10.1103/PhysRevLett.110.032301

Elliptic flow of identified hadrons in Au+Au collisions at s NN =7.7-62.4 GeV

Abstract: Measurements of the elliptic flow, upsilon(2), of identified hadrons (pi(+/-), K-+/-, K-s(0), p, (p) over bar, phi, Lambda, (Lambda) over bar, Xi(-), (Xi) over bar (+), Omega(-), (Omega) over bar (+)) in Au + Au collisions at root s(NN) = 7.7, 11.5, 19.6, 27, 39, and 62.4 GeV are presented. The measurements were done at midrapidity using the time-projection chamber and the time-of-flight detectors of the Solenoidal Tracker at RHIC experiment during the beam-energy scan program at Relativistic Heavy Ion Collider. A significant difference in the upsilon(2) values for particles and the corresponding antiparticles was observed at all transverse momenta for the first time. The difference increases with decreasing center-of-mass energy, root s(NN) (or increasing baryon chemical potential, mu(B)), and is larger for the baryons as compared to the mesons. This implies that particles and antiparticles are no longer consistent with the universal number-of-constituent quark (NCQ) scaling of upsilon(2) that was observed at root s(NN) = 200 GeV. However, for the selected group of particles (p(+), K+, K-s(0), p, Lambda, Xi(-), Omega(-)) NCQ scaling at (m(T) - m(0))/n(q) > 0.4 GeV/c(2) is not violated within +/- 10%. The upsilon(2) values for f mesons at 7.7 and 11.5 GeV are approximately two standard deviations from the trend defined by the other hadrons at the highest measured p(T) values.

Fluctuations of charge separation perpendicular to the event plane and local parity violation in s NN = 200 GeV Au + Au collisions at the BNL Relativistic Heavy Ion Collider

Abstract: Previous experimental results based on data (∼15×106 events) collected by the STAR detector at the BNL Relativistic Heavy Ion Collider suggest event-by-event charge-separation fluctuations perpendicular to the event plane in noncentral heavy-ion collisions. Here we present the correlator previously used split into its two component parts to reveal correlations parallel and perpendicular to the event plane. The results are from a high-statistics 200-GeV Au + Au collisions data set (57×106 events) collected by the STAR experiment. We explicitly count units of charge separation from which we find clear evidence for more charge-separation fluctuations perpendicular than parallel to the event plane. We also employ a modified correlator to study the possible P-even background in same- and opposite-charge correlations, and find that the P-even background may largely be explained by momentum conservation and collective motion. © 2013 American Physical Society.

J/psi Elliptic Flow in Pb-Pb Collisions at root s(NN)=2.76 TeV

Abstract: We report on the first measurement of inclusive J/psi elliptic flow v(2) in heavy-ion collisions at the LHC. The measurement is performed with the ALICE detector in Pb-Pb collisions at root s(NN) = 2.76 TeV in the rapidity range 2.5 < y < 4.0. The dependence of the J/psi v(2) on the collision centrality and on the J/psi transverse momentum is studied in the range 0 <= p(T) < 10 GeV/c. For semicentral Pb-Pb collisions at root s(NN) = 2.76 TeV, an indication of nonzero v(2) is observed with a largest measured value of v(2) = 0.116 +/-0.046(stat) +/- 0.029(syst) for J/psi in the transverse momentum range 2 <= p(T) < 4 GeV/c. The elliptic flow measurement complements the previously reported ALICE results on the inclusive J/psi nuclear modification factor and favors the scenario of a significant fraction of J/psi production from charm quarks in a deconfined partonic phase.

Ultrasound-Assisted Synthesis of Pyrazolo[3,4-b]pyridines as Potential Corrosion Inhibitors for Mild Steel in 1.0 M HCl

Abstract: Five synthesized pyrazolopyridine derivatives, such as 4-(2-chloro-6-flurpphenyl)-3-methyl-6-oxo-4,5,6,7-tetrahydro-2H-pyrazolo[3,4-b]pyridine-5-carbonitrile (AP-1), 3-methyl-6-oxo-4,5,6,7-tetrahydro-2H-pyrazolo[3,4-b]pyridine-5-carbonitrile (AP-2), 3-methyl-6-oxo-4-(p-tolyl)-4,5,6,7-tetrahydro-2H-pyrazolo[3,4-b]pyridine-5-carbonitrile (AP-3), 4-(4-methoxyphenyl)-3-methyl-6-oxo-4,5,6,7-tetrahydro-2H-pyrazolo[3,4-b]pyridine-5-carbonitrile (AP-4), and 3-methyl-6-oxo-4-(3,4,5-trimethoxyphenyl)-4,5,6,7-tetrahydro-2H-pyrazolo[3,4-b]pyridine-5-carbonitrile (AP-5) have been synthesized using ultrasonic irradiation in aqueous medium using p-TSA as a catalyst, and their effect on corrosion of mild steel (MS) in 1.0 M HCl has been investigated using different experimental techniques like weight loss, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization techniques. The potentiodynamic polarization data indicated that the pyrazolo[3,4-b]pyridine derivatives behaved as a mixed type. The catho...

Observation of an energy-dependent difference in elliptic flow between particles and antiparticles in relativistic heavy ion collisions

Abstract: Elliptic flow (v(2)) values for identified particles at midrapidity in Au + Au collisions, measured by the STAR experiment in the beam energy scan at RHIC at root s(NN) = 7.7-62.4 GeV, are presented. A beamenergy-dependent difference of the values of v(2) between particles and corresponding antiparticles was observed. The difference increases with decreasing beam energy and is larger for baryons compared to mesons. This implies that, at lower energies, particles and antiparticles are not consistent with the universal number-of-constituent-quark scaling of v(2) that was observed at root s(NN) = 200 GeV. DOI: 10.1103/PhysRevLett.110.142301

Third harmonic flow of charged particles in Au + Au collisions at √sNN = 200 GeV

Abstract: In this proceedings, we report measurements of the third harmonic coefficient of the azimuthal anisotropy, v3, known as triangular flow. The analysis is for charged particles near midrapidity in Au+Au collisions at GeV, based on data from the STAR experiment at the Relativistic Heavy Ion Collider. Triangular flow as a function of centrality, pseudorapidity and transverse momentum are reported using various methods, including a study of the signal for particle pairs as a function of their pseudorapidity separation. Results are compared with other experiments and model predictions.

CuFe2O4 nanoparticles as a highly efficient and magnetically recoverable catalyst for the synthesis of medicinally privileged spiropyrimidine scaffolds

Abstract: A highly efficient and green protocol for the synthesis of medicinally important fluorinated spiropyrimidine derivatives involving creation of six new covalent bonds has been developed using a magnetically separable and reusable heterogeneous copper ferrite nanocatalyst under mild reaction conditions. The synthesis of inverse spinel copper ferrite magnetic nanoparticles with average size of 38 nm has been achieved using combined sonochemical and co-precipitation techniques in aqueous medium from readily available inexpensive starting materials without any surfactant or capping agent. The particle size was determined by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The magnetic nature of catalyst facilitates its easy removal from the reaction medium and can be reused five times without any significant loss of its catalytic activity. Negligible leaching of Cu and Fe in consecutive cycles makes the catalyst economical and environmentally benign. The structure of final products was established by single crystal X-ray analysis and spectroscopic techniques.

Silver nanoparticle induced cytotoxicity, oxidative stress, and DNA damage in CHO cells

Abstract: Silver nanoparticles (Ag NPs) are being used increasingly in wound dressings, catheters, and in various household products due to their antimicrobial activity. The present study reports the toxicity evaluation of synthesized and well characterized Ag NPs using Chinese hamster ovary (CHO) cells. The UV–Vis spectroscopy reveals the formation of silver nanoparticles by exhibiting the typical surface plasmon absorption maxima at 408–410 nm. Transmission electron microscopy (TEM) reveals that the average diameter of silver nanoparticles is about 5.0 ± 1.0 nm and that they have spherical shape. Cell visibility and cell viability percentage show dose-dependent cellular toxicity of Ag NPs. The half maximal inhibitory concentration (IC50) for CHO cells is 68.0 ± 2.65 μg/ml after 24 h Ag NPs exposure. Toxicity evaluations, including cellular morphology, mitochondrial function (MTT assay), reactive oxygen species (ROS), and DNA fragmentation assay (Ladder pattern) were assessed in unexposed CHO cells (control) and the cells exposed to Ag NPs concentrations of 15, 30, and 60 μg/ml for 24 h. The findings may assist in the designing of Ag NPs for various applications and provide insights into their toxicity.

Net-charge fluctuations in Pb-Pb collisions at √sNN=2.76 TeV

Abstract: We report the first measurement of the net-charge fluctuations in Pb-Pb collisions at \surd s_NN 2.76 TeV, measured with the ALICE detector at the CERN Large Hadron Collider. The dynamical fluctuations per unit entropy are observed to decrease when going from peripheral to central collisions. An additional reduction in the amount of fluctuations is seen in comparison to the results from lower energies. We examine the dependence of fluctuations on the pseudo-rapidity interval, which may account for the dilution of fluctuations during the evolution of the system. We find that the ALICE data points are between the theoretically predicted values for a hadron gas and a Quark-Gluon Plasma.