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Showing papers by "University of Warsaw published in 2003"


Journal ArticleDOI
TL;DR: The algorithm for feature selection is based on an application of a rough set method to the result of principal components analysis (PCA) used for feature projection and reduction.

801 citations


Journal ArticleDOI
TL;DR: In this article, the precise mathematical structure underlying loop quantum cosmology and the sense in which it implements the full quantization program in a symmetry reduced model has been made explicit, thereby providing a firmer mathematical and conceptual foundation to the subject.
Abstract: Applications of Riemannian quantum geometry to cosmology have had notable successes. In particular, the fundamental discreteness underlying quantum geometry has led to a natural resolution of the big bang singularity. However, the precise mathematical structure underlying loop quantum cosmology and the sense in which it implements the full quantization program in a symmetry reduced model has not been made explicit. The purpose of this paper is to address these issues, thereby providing a firmer mathematical and conceptual foundation to the subject.

794 citations


Journal ArticleDOI
09 Jan 2003-Nature
TL;DR: In this article, the authors used infrared-laser atomic-force microscopy to reveal the native arrangement of rhodopsin, which forms paracrystalline arrays of dimers in mouse disc membranes.
Abstract: Neat rows of paired photon receptors are caught on camera in their natural state. In vertebrate retinal photoreceptors, the rod outer-segment disc membranes contain densely packed rhodopsin molecules for optimal light absorption and subsequent amplification by the visual signalling cascade1, but how these photon receptors are organized with respect to each other is not known. Here we use infrared-laser atomic-force microscopy to reveal the native arrangement of rhodopsin, which forms paracrystalline arrays of dimers in mouse disc membranes. The visualization of these closely packed rhodopsin dimers in native membranes gives experimental support to earlier inferences about their supramolecular structure2,3 and provides insight into how light signalling is controlled.

748 citations


Journal ArticleDOI
TL;DR: In this article, a nomenclature for restriction endonucleases, DNA methyltransferases, homing endon nucleases and related genes and gene products is described.
Abstract: A nomenclature is described for restriction endonucleases, DNA methyltransferases, homing endonucleases and related genes and gene products. It provides explicit categories for the many different Type II enzymes now identified and provides a system for naming the putative genes found by sequence analysis of microbial genomes.

710 citations


Journal ArticleDOI
S. Fukuda1, Y. Fukuda1, T. Hayakawa1, E. Ichihara1  +183 moreInstitutions (28)
TL;DR: Super-Kamiokande is the world's largest water Cherenkov detector, with net mass 50,000 tons as discussed by the authors, which collected 1678 live-days of data, observing neutrinos from the Sun, Earth's atmosphere, and the K2K long-baseline neutrino beam with high efficiency.
Abstract: Super-Kamiokande is the world's largest water Cherenkov detector, with net mass 50,000 tons. During the period April, 1996 to July, 2001, Super-Kamiokande I collected 1678 live-days of data, observing neutrinos from the Sun, Earth's atmosphere, and the K2K long-baseline neutrino beam with high efficiency. These data provided crucial information for our current understanding of neutrino oscillations, as well as setting stringent limits on nucleon decay. In this paper, we describe the detector in detail, including its site, configuration, data acquisition equipment, online and offline software, and calibration systems which were used during Super-Kamiokande I.

708 citations


Journal ArticleDOI
TL;DR: The K2K experiment observed indications of neutrino oscillation after 250 km flight of υμ. as mentioned in this paper The observed number of events in the data corresponding to 4.8 x 1019 protons on target is 56, while 80.1 5.4 + 6.2 is expected.
Abstract: The K2K experiment observed indications of neutrino oscillation after 250 km flight of υμ. The observed number of events in the data corresponding to 4.8 x 1019 protons on target is 56, while 80.1 5.4 +6.2 is expected. Both the decrease of the events and observed spectrum shape distortion are consistent with neutrino oscillation. The probability that the observations are statistical fluctuation of non oscillation is less than 1%. The allowed region of oscillation parameters is consistent with the one obtained from the atmospheric neutrino observation. After the accident of Super-Kamiokande (SK) detector, the reconstruction of SK has finished in 2002 and the K2K experiment resumed in December 2002.

702 citations


Posted Content
TL;DR: In this paper, the precise mathematical structure underlying loop quantum cosmology and the sense in which it implements the full quantization program in a symmetry reduced model has been made explicit, thereby providing a firmer mathematical and conceptual foundation to the subject.
Abstract: Applications of Riemannian quantum geometry to cosmology have had notable successes. In particular, the fundamental discreteness underlying quantum geometry has led to a natural resolution of the big bang singularity. However, the precise mathematical structure underlying loop quantum cosmology and the sense in which it implements the full quantization program in a symmetry reduced model has not been made explicit. The purpose of this paper is to address these issues, thereby providing a firmer mathematical and conceptual foundation to the subject.

533 citations


Journal ArticleDOI
TL;DR: In this article, surface-enhanced Raman scattering (SERS) spectra were recorded for p-mercaptobenzoic acid (PMBA) monolayers on Ag and Au surfaces.
Abstract: Surface-enhanced Raman scattering (SERS) spectra were recorded for p-mercaptobenzoic acid (PMBA) monolayers on Ag and Au surfaces. As evidenced by the relative intensities of the bands corresponding to the symmetric stretching COO− vibration and to the out-of-plane vibration of the phenyl ring, the molecules are at least tilted with respect to the surface and simultaneously bonded through the sulfur atom and COO− groups. This situation takes place when modification is carried out from aqueous solutions at natural or alkaline pH and at low concentrations of monomer. At higher concentration of the monomer (>10−3) and/or at acidic pH, carboxylic groups are protonated and PMBA molecules adopt a more vertical configuration. It was also found that rough Ag and Au surfaces that are applied in SERS experiments promote partial decarboxylation of PMBA. Copyright © 2002 John Wiley & Sons, Ltd.

524 citations


Journal ArticleDOI
TL;DR: Melatonin's functions as an antioxidant include: a), direct free radical scavenging, b), stimulation of antioxidative enzymes, c), increasing the efficiency of mitochondrial oxidative phosphorylation and reducing electron leakage (thereby lowering free radical generation), and 3), augmenting the efficiencyof other antioxidants.
Abstract: This brief resume enumerates the multiple actions of melatonin as an antioxidant. This indoleamine is produced in the vertebrate pineal gland, the retina and possibly some other organs. Additionally, however, it is found in invertebrates, bacteria, unicellular organisms as well as in plants, all of which do not have a pineal gland. Melatonin's functions as an antioxidant include: a), direct free radical scavenging, b), stimulation of antioxidative enzymes, c), increasing the efficiency of mitochondrial oxidative phosphorylation and reducing electron leakage (thereby lowering free radical generation), and 3), augmenting the efficiency of other antioxidants. There may be other functions of melatonin, yet undiscovered, which enhance its ability to protect against molecular damage by oxygen and nitrogen-based toxic reactants. Numerous in vitro and in vivo studies have documented the ability of both physiological and pharmacological concentrations to melatonin to protect against free radical destruction. Furthermore, clinical tests utilizing melatonin have proven highly successful; because of the positive outcomes of these studies, melatonin's use in disease states and processes where free radical damage is involved should be increased.

522 citations


Journal Article
TL;DR: The aim of this review is to present the current state of knowledge on plant chitinases and their regulation and function.
Abstract: The aim of this review is to present the current state of knowledge on plant chitinases and their regulation and function. Chitinases are up-regulated by a variety of stress conditions, both biotic and abiotic, and by such phytohormones as ethylene, jasmonic acid, and salicylic acid. Like other PR proteins, chitinases play a role in plant resistance against distinct pathogens. Moreover, by reducing the defence reaction of the plant, chitinases allow symbiotic interaction with nitrogen-fixing bacteria or mycorrhizal fungi. However, recent investigations have shown that these enzymes are also involved in numerous physiological events. The involvement of chitinases in development and growth processes is also described.

485 citations


Journal ArticleDOI
TL;DR: It is considered that neuronal networks involved in epilepsy possess multistable dynamics (i.e., they may display several dynamic states), and at least two states are possible: an interictal one characterized by a normal, apparently random, steady ‐state of ongoing activity, and another one that is characterized by the paroxysmal occurrence of a synchronous oscillations (seizure).
Abstract: Summary: Purpose: The occurrence of abnormal dynamics in a physiological system can become manifest as a sudden qualitative change in the behavior of characteristic physiologic variables. We assume that this is what happens in the brain with regard to epilepsy. We consider that neuronal networks involved in epilepsy possess multistable dynamics (i.e., they may display several dynamic states). To illustrate this concept, we may assume, for simplicity, that at least two states are possible: an interictal one characterized by a normal, apparently random, steady -state of ongoing activity, and another one that is characterized by the paroxysmal occurrence of a synchronous oscillations (seizure). Methods: By using the terminology of the mathematics of nonlinear systems, we can say that such a bistable system has two attractors, to which the trajectories describing the system's output converge, depending on initial conditions and on the system's parameters. In phase-space, the basins of attraction corresponding to the two states are separated by what is called a “separatrix.” We propose, schematically, that the transition between the normal ongoing and the seizure activity can take place according to three basic models: Model I: In certain epileptic brains (e.g., in absence seizures of idiopathic primary generalized epilepsies), the distance between “normal steady -state” and “paroxysmal” attractors is very small in contrast to that of a normal brain (possibly due to genetic and/or developmental factors). In the former, discrete random fluctuations of some variables can be sufficient for the occurrence of a transition to the paroxysmal state. In this case, such seizures are not predictable. Model II and model III: In other kinds of epileptic brains (e.g., limbic cortex epilepsies), the distance between “normal steady-state” and “paroxysmal” attractors is, in general, rather large, such that random fluctuations, of themselves, are commonly not capable of triggering a seizure. However, in these brains, neuronal networks have abnormal features characterized by unstable parameters that are very vulnerable to the influence of endogenous (model II) and/or exogenous (model III) factors. In these cases, these critical parameters may gradually change with time, in such a way that the attractor can deform either gradually or suddenly, with the consequence that the distance between the basin of attraction of the normal state and the separatrix tends to zero. This can lead, eventually, to a transition to a seizure. Results: The changes of the system's dynamics preceding a seizure in these models either may be detectable in the EEG and thus the route to the seizure may be predictable, or may be unobservable by using only measurements of the dynamical state. It is thinkable, however, that in some cases, changes in the excitability state of the underlying networks may be uncovered by using appropriate stimuli configurations before changes in the dynamics of the ongoing EEG activity are evident. A typical example of model III that we discuss here is photosensitive epilepsy. Conclusions: We present an overview of these basic models, based on neurophysiologic recordings combined with signal analysis and on simulations performed by using computational models of neuronal networks. We pay especial attention to recent model studies and to novel experimental results obtained while analyzing EEG features preceding limbic seizures and during intermittent photic stimulation that precedes the transition to paroxysmal epileptic activity.

Journal ArticleDOI
TL;DR: Schwarzer et al. as mentioned in this paper found that women may be reluctant to perform breast self-examination (B.S.E.) regularly due to motivational or self-regulatory deficits.
Abstract: Many women may be reluctant to perform breast self-examination (B.S.E.) regularly due to motivational or self-regulatory deficits. The Health Action Process Approach (Schwarzer, R. (1992). Self-efficacy in the adoption and maintenance of health behaviors: theoretical approaches and a new model. In: Schwarzer, R. (Ed.), Self-efficacy: Thought Control of Action , pp. 217-243. Hemisphere, Washington DC; Schwarzer, R. (2001). Social-cognitive factors in changing health-related behavior. Current Directions in Psychological Science , 10 , 47-51.), a health behavior change model that advocates the separation of motivation and action phases, such as goal setting and goal pursuit, was applied to data from 418 young women whose risk perceptions, outcome expectancies, self-efficacy, intention to perform B.S.E., planning, and reported examination behaviors were examined at two points in time. Risk perception was found to have a negligible influence in a path analysis, whereas self-efficacy emerged as the best predict...

Journal ArticleDOI
TL;DR: G-protein-coupled receptors 1 constitute a large superfamily of receptor proteins responsible for signal transduction, with family A being by far the largest and more closely related to each other within a few functional domains than those of the other families.
Abstract: G-protein-coupled receptors (GPCRs) 1 constitute a large superfamily of receptor proteins responsible for signal transduction (see http://www.gpcr.org/7tm). Throughout all higher organisms, these receptors mediate recognition of environmental stimuli like light, odor, and taste, but also hormonal and other types of communications across plasma membranes (1). They are also important targets for pharmacological intervention via activating or blocking their action (2). Three families of GPCRs were identified, with family A being by far the largest (reviewed in refs 3-5). Its members are more closely related to each other within a few functional domains than those of the other families. In addition, numerous diseases have been linked to specific mutations within the genes encoding GPCRs, also making these receptors targets for specific therapeutic interventions including gene transfer (6-9).

Journal ArticleDOI
TL;DR: The OGLE-2003-BLG-262 microlensing event as mentioned in this paper was generated by a point-mass lens transiting the face of a K giant source in the Galactic bulge, and the resulting finite-source effects were used to measure the angular Einstein radius, theta_E=195+-17muas, and so constrain the lens mass to the fullwidth half-maximum interval 0.08 < M/M_sun < 0.54.
Abstract: We analyze OGLE-2003-BLG-262, a relatively short, t_E=12.5+-0.1day, microlensing event generated by a point-mass lens transiting the face of a K giant source in the Galactic bulge. We use the resulting finite-source effects to measure the angular Einstein radius, theta_E=195+-17muas, and so constrain the lens mass to the full-width half-maximum interval 0.08 < M/M_sun < 0.54. The lens-source relative proper motion is mu_rel = 27+-2 km/s/kpc. Both values are typical of what is expected for lenses detected toward the bulge. Despite the short duration of the event, we detect marginal evidence for a "parallax asymmetry", but argue that this is more likely to be induced by acceleration of the source, a binary lens, or possibly by statistical fluctuations. Although OGLE-2003-BLG-262 is only the second published event to date in which the lens transits the source, such events will become more common with the new OGLE-III survey in place. We therefore give a detailed account of the analysis of this event to facilitate the study of future events of this type.

Journal ArticleDOI
TL;DR: The present results demonstrate the effectiveness of the new dDTF method and indicate that the dD TF method can be used to obtain the reliable patterns of connections between various brain structures.

Journal ArticleDOI
TL;DR: A method is proposed for calculations of dispersion energy at finite intermonomer separations that uses a generalized Casimir-Polder formula evaluated with dynamic density susceptibilities provided by time-dependent density-functional theory.
Abstract: A method is proposed for calculations of dispersion energy at finite intermonomer separations. It uses a generalized Casimir-Polder formula evaluated with dynamic density susceptibilities provided by time-dependent density-functional theory. The method recovers the dispersion energies of He, Ne, and H2O dimers to within 3% or better. Since the computational effort of the new algorithm scales approximately as the third power of system size, the method is much more efficient than standard wave-function methods capable of predicting the dispersion energy at a similarly high level of accuracy.

Journal ArticleDOI
01 Sep 2003-RNA
TL;DR: Seven new cap analogs modified in the C2' and C3' positions of m(7)Guo and in the number of phosphate residues are synthesized, indicating that modifications at C2', like those at C3', prevent reverse incorporation, and that tetra- and pentaphosphate cap analogues bind eIF4E and inhibit translation more strongly than their triphosphate counterparts.
Abstract: Synthetic analogs of the 5'-terminal caps of eukaryotic mRNAs and snRNAs are used in elucidating such physiological processes as mRNA translation, pre-mRNA splicing, intracellular transport of mRNA and snRNAs, and mRNA turnover. Particularly useful are RNAs capped with synthetic analogs, which are produced by in vitro transcription of a DNA template using a bacteriophage RNA polymerase in the presence of ribonucleoside triphosphates and a cap dinucleotide such as m(7)Gp(3)G. Unfortunately, because of the presence of a 3'-OH on both the m(7)Guo and Guo moieties, up to half of the mRNAs contain caps incorporated in the reverse orientation. Previously we designed and synthesized two "anti-reverse" cap analogs (ARCAs), m(7)3'dGp(3)G and m(2)(7,3'-)(O)Gp(3)G, that cannot be incorporated in the reverse orientation because of modifications at the C3' position of m(7)Guo. In the present study, we have synthesized seven new cap analogs modified in the C2' and C3' positions of m(7)Guo and in the number of phosphate residues, m(2)(7,2'-)(O)Gp(3)G, m(7)2'dGp(3)G, m(7)2'dGp(4)G, m(2)(7,2'-)(O)Gp(4)G, m(2)(7,3'-)(O)Gp(4)G, m(7)Gp(5)G, and m(2)(7,3'-)(O)Gp(5)G. These were analyzed for conformation in solution, binding affinity to eIF4E, inhibition of in vitro translation, degree of reverse capping during in vitro transcription, capping efficiency, and the ability to stimulate cap-dependent translation in vitro when incorporated into mRNA. The results indicate that modifications at C2', like those at C3', prevent reverse incorporation, that tetra- and pentaphosphate cap analogs bind eIF4E and inhibit translation more strongly than their triphosphate counterparts, and that tetraphosphate ARCAs promote cap-dependent translation more effectively than previous cap analogs.

Journal ArticleDOI
TL;DR: In this article, simulations and experimental characterizations of a stationary plasma thruster are compared for four different wall materials to investigate near-wall conductivity (dielectric materials) and in-wallconductivity (conducting materials) in such a discharge.
Abstract: Simulations and experimental characterizations of a stationary plasma thruster are compared for four different wall materials to investigate near-wall conductivity (dielectric materials) and in-wall conductivity (conducting materials) in such a discharge. Using a one-dimensional transient fluid model that takes into account a possible electron temperature anisotropy, it is shown that electron-wall backscattering plays a crucial role by maintaining a relatively high electron temperature along the magnetic field lines which in turn drives large electron currents toward the walls. The large differences in discharge current observed experimentally for the dielectric materials are qualitatively recovered, confirming that near-wall conductivity results from the combined effects of secondary electron emission and electron backscattering. A clear correlation is found between the appearance of space charge saturation at the walls and a jump of the discharge current observed in experiments when varying the discharge voltage or the magnetic field. The anomalously high values of discharge current observed experimentally with graphite are also correctly recovered in simulations, which highlight a plasma short-circuiting effect resulting from in-wall currents.

Journal ArticleDOI
TL;DR: In this paper, a new combined approach for ab initio protein structure prediction is proposed, which combines short-range and long-range knowledge-based potentials derived from a statistical analysis of the regularities of protein structures.

Journal ArticleDOI
C. Alt1, Tome Anticic, B. Baatar2, D. Barna3, J. Bartke4, M. Behler5, L. Betev1, Helena Bialkowska, A. Billmeier6, Christoph Blume1, Bożena Boimska, Nicolas Borghini7, M. Botje, J. Bracinik8, R. Bramm1, Rene Brun9, Predrag Buncic9, Predrag Buncic1, V. Cerny8, O. Chvala6, G.E. Cooper10, J. G. Cramer11, P. Csato3, Phuong Mai Dinh12, P. Dinkelaker1, V. Eckardt13, P. Filip13, Z. Fodor14, Panagiota Foka15, P. Freund13, V. Friese5, J. Gál3, Marek Gaździcki1, G. Georgopoulos16, E. Gladysz4, S. Hegyi3, C. Höhne5, Peter Martin Jacobs10, Kreso Kadija9, A. Karev13, S. Kniege1, V. I. Kolesnikov2, Thorsten Sven Kollegger1, R. Korus17, Marek Kowalski4, I. Kraus15, Michal Kreps8, M. van Leeuwen, Peter Levai3, Alexander Malakhov2, Christina Markert15, B. W. Mayes18, G. L. Melkumov2, C. Meurer1, Andre Mischke15, M. K. Mitrovski1, Jozsef Molnar3, St Mrówczyński17, G. Odyniec10, J. Y. Ollitrault19, Gergely Palla3, Apostolos Panagiotou16, K. Perl20, Andreas Petridis16, Miroslav Pikna8, Lawrence Pinsky18, A. M. Poskanzer10, F. Pühlhofer5, Jeffrey G. Reid11, Rainer Arno Ernst Renfordt1, W. Retyk20, H. G. Ritter10, Christof Roland21, Gunther Roland21, M. Rybczynśki17, A. Rybicki9, A. Rybicki4, A. Sandoval15, H. Sann15, N. Schmitz13, P. Seyboth13, Ferenc Sikler3, Branislav Sitar8, E. Skrzypczak20, R.J.M. Snellings10, G. Stefanek17, R. Stock1, H. Ströbele1, Tatjana Susa, I. Szentpetery3, J. Sziklai3, Thomas A. Trainor11, Dezso Varga3, M. Vassiliou16, Gabor Istvan Veres3, Gyorgy Vesztergombi3, Sergey Voloshin22, D. Vranic15, A. Wetzler1, Zbigniew Wlodarczyk17, I. K. Yoo23, I. K. Yoo15, J. Zaranek1, J. Zimányi3 
TL;DR: In this paper, both the standard method of correlating particles with an event plane and the cumulant method of studying multiparticle correlations were used to reconstruct the collective motion in A+A collisions at SPS energies.
Abstract: Directed and elliptic flow measurements for charged pions and protons are reported as a function of transverse momentum, rapidity, and centrality for 40A and 158A GeV Pb+Pb collisions, as recorded by the NA49 detector. Both the standard method of correlating particles with an event plane and the cumulant method of studying multiparticle correlations are used. In the standard method the directed flow is corrected for conservation of momentum. In the cumulant method elliptic flow is reconstructed from genuine four-, six-, and eight-particle correlations, showing the first unequivocal evidence for collective motion in A+A collisions at SPS energies.

Journal ArticleDOI
TL;DR: An improved prescription for choosing a transformed harmonic-oscillator (THO) basis for use in configuration-space Hartree-Fock-Bogoliubov (HFB) calculations is presented in this article.
Abstract: An improved prescription for choosing a transformed harmonic-oscillator (THO) basis for use in configuration-space Hartree-Fock-Bogoliubov (HFB) calculations is presented. The new $\text{HFB}+\text{THO}$ framework that follows accurately reproduces the results of coordinate-space HFB calculations for spherical nuclei, including those that are weakly bound. Furthermore, it is fully automated, facilitating its use in systematic investigations of large sets of nuclei throughout the periodic table. As a first application, we have carried out calculations using the Skyrme force SLy4 and volume pairing, with exact particle-number projection following application of the Lipkin-Nogami prescription. Calculations were performed for all even-even nuclei from the proton drip line to the neutron drip line having proton numbers $Z=2,4,\dots{},108$ and neutron numbers $N=2,4,\dots{},188$. We focus on nuclei near the neutron drip line and find that there exist numerous particle-bound even-even nuclei (i.e., nuclei with negative Fermi energies) that have at the same time negative two-neutron separation energies. This phenomenon, which was earlier noted for light nuclei, is attributed to bound shape isomers beyond the drip line.

Journal ArticleDOI
TL;DR: The high-resolution structure of bovine rhodopsin provides a template for understanding how GPCRs work and is described to describe the sensitivity and complexity of rhodopin that lead to its important role in vision.
Abstract: Rhodopsin is a retinal photoreceptor protein of bipartite structure consisting of the transmembrane protein opsin and a light-sensitive chromophore 11-cis-retinal, linked to opsin via a protonated Schiff base. Studies on rhodopsin have unveiled many structural and functional features that are common to a large and pharmacologically important group of proteins from the G protein-coupled receptor (GPCR) superfamily, of which rhodopsin is the best-studied member. In this work, we focus on structural features of rhodopsin as revealed by many biochemical and structural investigations. In particular, the high-resolution structure of bovine rhodopsin provides a template for understanding how GPCRs work. We describe the sensitivity and complexity of rhodopsin that lead to its important role in vision.

Journal ArticleDOI
TL;DR: In this paper, a pharmacological chaperone, 11-cis-7-ring retinal, was used to induce the in vivo folding of P23H-opsin and the rescued protein formed pigment, acquired mature glycosylation, and was transported to the cell surface.

Journal ArticleDOI
TL;DR: In this article, a conducting polymer matrix is integrated into a polyaniline matrix to form a hybrid material to harness the electrochemical activity of nanosized oxide clusters, which can be put to work in energy storage applications.

Journal ArticleDOI
TL;DR: It is shown that DDM1 is an ATPase stimulated by both naked and nucleosomal DNA and induces nucleosome repositioning on a short DNA fragment, which promotes chromatin remodeling in an ATP-dependent manner.

Journal ArticleDOI
01 Jan 2003-Carbon
TL;DR: In this paper, carbon nanostructures (onions, nanotubes and encapsulates) were generated by arc discharge in water between pure and catalyst-doped graphite electrodes.

Journal ArticleDOI
TL;DR: In this paper, an effective Lagrangian formalism for the calculation of flavour changing neutral and charged scalar currents in weak decays including SU(2)×U(1) symmetry breaking effects and the effects of the electroweak couplings g1 and g2 was presented.

Journal ArticleDOI
TL;DR: In this paper, the authors used surface-enhanced Raman scattering (SEMS) to measure the strength of thioglycolic acid (TGA) adsorption on silver and gold.


Journal ArticleDOI
TL;DR: The spectral energy distribution determined from the early broadband photometry is a power law with Fν ∝ ν-0.66±0.13 after correcting for a large reddening as mentioned in this paper.
Abstract: We present the discovery and follow-up observations of the afterglow of the gamma-ray burst GRB 011121 and its associated supernova SN 2001ke. Images were obtained with the Optical Gravitational Lensing Experiment 1.3 m telescope in BVRI passbands, starting 10.3 hr after the burst. The temporal analysis of our early data indicates a steep decay, independent of wavelength, with Fν ∝ t-1.72±0.05. There is no evidence for a break in the light curve earlier than 2.5 days after the burst. The spectral energy distribution determined from the early broadband photometry is a power law with Fν ∝ ν-0.66±0.13 after correcting for a large reddening. Spectra obtained with the Magellan 6.5 m Baade telescope reveal narrow emission lines from the host galaxy that provide a redshift of z = 0.362 ± 0.001 to the GRB. We also present late R- and J-band observations of the afterglow ~7-17 days after the burst. The late-time photometry shows a large deviation from the initial decline, and our data combined with Hubble Space Telescope photometry provide strong evidence for a supernova peaking about 12 rest-frame days after the GRB. The first spectrum ever obtained of a GRB supernova at cosmological distance revealed a blue continuum. SN 2001ke was more blue near maximum than SN 1998bw and faded more quickly, which demonstrates that a range of properties are possible in supernovae that generate GRBs. The blue color is consistent with a supernova interacting with circumstellar gas, and this progenitor wind is also evident in the optical afterglow. This is the best evidence to date that classical, long GRBs are generated by core-collapse supernovae.