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K Woźniak

Publications and source records attributed to K Woźniak.

At least 19 recordsLinked to original sources
PubMed2006

Energy dependence of directed flow over a wide range of pseudorapidity in Au + Au collisions at the BNL Relativistic Heavy Ion Collider.

We report on measurements of directed flow as a function of pseudorapidity in Au + Au collisions at energies of square root of SNN = 19.6, 62.4, 130 and 200 GeV as measured by the PHOBOS detector at the BNL Relativistic Heavy Ion Collider. These results are particularly valuable because of the extensive, continuous pseudorapidity coverage of the PHOBOS detector. There is no significant indication of structure near midrapidity and the data surprisingly exhibit extended longitudinal scaling similar to that seen for elliptic flow and charged particle pseudorapidity density.

Journal Article↗
PubMed2006

System size and centrality dependence of charged hadron transverse momentum spectra in Au + Au and Cu + Cu collisions at square root of SNN = 62.4 and 200 GeV.

We present transverse momentum distributions of charged hadrons produced in Cu + Cu collisions at square root of SNN = 62.4 and 200 GeV. The spectra are measured for transverse momenta of 0.25 < pT < 5.0 GeV/c at square root of SNN = 62.4 GeV and 0.25 < pT < 7.0 GeV/c at square root of SNN = 200 GeV, in a pseudorapidity range of 0.2 < eta < 1.4. The nuclear modification factor R(AA) is calculated relative to p + p data at both collision energies as a function of collision centrality. At a given collision energy and fractional cross section, R(AA) is observed to be systematically larger in Cu + Cu collisions compared to Au + Au. However, for the same number of participating nucleons, R(AA) is essentially the same in both systems over the measured range of pT, in spite of the significantly different geometries of the Cu + Cu and Au + Au systems.

Journal Article↗
PubMed2005

Alterations of basement membrane zone in autoimmune subepidermal bullous diseases.

BACKGROUND: Pemphigoid (BP), mucous membrane pemphigoid (MMP) and epidermolysis bullosa acquisita (EBA) are characterized by the presence of in vivo bound and circulating anti-basement membrane zone (BMZ) antibodies directed against different antigens localized in the upper part of the lamina lucida, lamina lucida-lamina densa border and in sublamina densa region, respectively. The alterations of BMZ lead to blister formation. OBJECTIVES: The aim of the present study was to compare the alterations of various regions of the BMZ in BP, MMP and EBA using laser scanning confocal microscopy (LSCM). METHODS: Biopsy specimens taken from perilesional patients' skin were cut into 40mum thick slides, followed by double immunofluorescence labeling with antibodies against different BMZ structures and anti-human IgG antibody. Three-dimensional reconstruction (3DR) of various regions of BMZ and of in vivo bound IgG was performed by computer program integrated with LSCM. RESULTS: In BP and MMP, LSCM studies revealed numerous invaginations of BMZ, most pronounced at the level of lamina lucida. Integrity of BMZ was preserved at the level of lamina lucida, lamina densa and sublamina densa. In EBA, continuity of lamina lucida was preserved and numerous invaginations were present. More pronounced invaginations of BMZ were observed at the level of lamina densa, whereas at the level of the sublamina densa region the staining along BMZ was discontinuous. Moreover, large clumps composed of collagen VII vertically oriented to the dermal-epidermal junction extending into the mid dermis were observed. CONCLUSIONS: The study showed that alterations of BMZ in BP and MMP occur mainly in the lamina lucida, and in EBA in the sublamina densa region. These alterations in various regions of BMZ in BP, MMP and EBA could be responsible for the differences in the level of blister formation and in the clinical course of the diseases.

Basement Membrane↗
PubMed2005

Energy dependence of elliptic flow over a large pseudorapidity range in Au+Au collisions at the BNL relativistic heavy ion collider.

This Letter describes the measurement of the energy dependence of elliptic flow for charged particles in Au+Au collisions using the PHOBOS detector at the Relativistic Heavy Ion Collider. Data taken at collision energies of square root of s(NN)=19.6, 62.4, 130, and 200 GeV are shown over a wide range in pseudorapidity. These results, when plotted as a function of eta(')=|eta|-y(beam), scale with approximate linearity throughout eta('), implying no sharp changes in the dynamics of particle production as a function of pseudorapidity or increasing beam energy.

Journal Article↗
PubMed2005

Centrality dependence of charged hadron transverse momentum spectra in Au+Au collisions from sqrt[s(NN)]=62.4 to 200 GeV.

We have measured transverse momentum distributions of charged hadrons produced in Au+Au collisions at sqrt[s(NN)]=62.4 GeV. The spectra are presented for transverse momenta 0.25<p(T)<4.5 GeV/c, in a pseudorapidity range of 0.2<eta<1.4. The nuclear modification factor R(AA) is calculated relative to p+p data at the same collision energy as a function of collision centrality. For 2<p(T)<4.5 GeV/c, R(AA) is found to be significantly larger than in Au+Au collisions at sqrt[s(NN)]= 130 and 200 GeV. In contrast to the large change in R(AA), we observe a very similar centrality evolution of the p(T) spectra at sqrt[s(NN)]=62.4 and 200 GeV. The dynamical origin of this surprising factorization of energy and centrality dependence of particle production in heavy-ion collisions remains to be understood.

Journal Article↗
PubMed2004

Pseudorapidity distribution of charged particles in d+Au collisions at sqrt[sNN]=200 GeV.

The measured pseudorapidity distribution of primary charged particles in minimum-bias d+Au collisions at sqrt[s(NN)]=200 GeV is presented for the first time. This distribution falls off less rapidly in the gold direction as compared to the deuteron direction. The average value of the charged particle pseudorapidity density at midrapidity is |eta|< or =0.6)=9.4+/-0.7(syst) and the integrated primary charged particle multiplicity in the measured region is 82+/-6(syst). Estimates of the total charged particle production, based on extrapolations outside the measured pseudorapidity region, are also presented. The pseudorapidity distribution, normalized to the number of participants in d+Au collisions, is compared to those of Au+Au and p+(-)p systems at the same energy. The d+Au distribution is also compared to the predictions of the parton saturation model, as well as microscopic models.

Journal Article↗
PubMed2003

Centrality dependence of charged-hadron transverse-momentum spectra in d+Au collisions at sqrt[s(NN)]=200 GeV.

We have measured transverse momentum distributions of charged hadrons produced in d+Au collisions at sqrt[s(NN)]=200 GeV. The spectra were obtained for transverse momenta 0.25<p(T)<6.0 GeV/c, in a pseudorapidity range of 0.2<eta<1.4 in the deuteron direction. The evolution of the spectra with collision centrality is presented in comparison to p+pmacr; collisions at the same collision energy. With increasing centrality, the yield at high transverse momenta increases more rapidly than the overall particle density, leading to a strong modification of the spectral shape. This change in spectral shape is qualitatively different from observations in Au+Au collisions at the same energy. The results provide important information for discriminating between different models for the suppression of high-p(T) hadrons observed in Au+Au collisions.

Journal Article↗
PubMed2003

Significance of the fragmentation region in ultrarelativistic heavy-ion collisions.

We present measurements of the pseudorapidity distribution of primary charged particles produced in Au+Au collisions at three energies, sqrt[s(NN)]=19.6, 130, and 200 GeV, for a range of collision centrali-ties. The distribution narrows for more central collisions and excess particles are produced at high pseudorapidity in peripheral collisions. For a given centrality, however, the distributions are found to scale with energy according to the "limiting fragmentation" hypothesis. The universal fragmentation region described by this scaling grows in pseudorapidity with increasing collision energy, extending well away from the beam rapidity and covering more than half of the pseudorapidity range over which particles are produced. This approach to a universal limiting curve appears to be a dominant feature of the pseudorapidity distribution and therefore of the total particle production in these collisions.

Journal Article↗
PubMed2002

Pseudorapidity and centrality dependence of the collective flow of charged particles in Au+Au collisions at sqrt[s(NN)]=130 GeV.

This paper describes the measurement of collective flow for charged particles in Au+Au collisions at sqrt[s(NN)]=130 GeV using the PHOBOS detector at the Relativistic Heavy Ion Collider (RHIC). The measured azimuthal hit anisotropy is presented over a wide range of pseudorapidity (-5.0<eta<5.3) for the first time at this energy. The result, averaged over momenta and particle species, is observed to reach 7% for peripheral collisions at midrapidity, falling off with centrality and increasing |eta|. These results call into question the common assumption of longitudinal boost invariance over a large region of rapidity in RHIC collisions.

Journal Article↗
PubMed2002

DNA damage in human colonic mucosa cells evoked by nickel and protective action of quercetin - involvement of free radicals?

Nickel is a toxic and carcinogenic environmental and occupational pollutant and quercetin is a dietary flavonoid that is reported to modulate effects of many mutagens and carcinogens. We investigated the ability of nickel chloride to induce DNA damage in human colonic mucosa cells in the presence of quercetin, using the alkaline comet assay. Nickel chloride (5-250 micromol/L) evoked dose-dependent DNA damage and quercetin at 50 micromol/L decreased the extent of this damage. The cells exposed to nickel chloride progressively removed their DNA damage and the presence of 50 micromol/L quercetin in the repair-incubation medium did not affect the repair kinetics. Cells exposed to nickel and treated with endonuclease III, an enzyme recognizing oxidized bases, displayed a greater extent of DNA damage than those not treated with the enzyme. Quercetin did not exert a significant effect on the production of oxidized bases by nickel. Pretreatment of the cells with a nitrone spin trap, N-tert-butyl-alpha-phenylnitrone, decreased the extent of DNA damage evoked by nickel. Quercetin caused a further decrease in the extent of the damage in the presence of the trap. The results obtained suggest that reactive oxygen species, including free radicals, might be involved in the formation of DNA lesions induced by nickel chloride in colonic mucosa cells and that quercetin may exert protective effects in these cells.

Cell Line↗
PubMed2001

Energy dependence of particle multiplicities in central Au+Au collisions.

We present the first measurement of the pseudorapidity density of primary charged particles in Au+Au collisions at root square[s(NN)] = 200 GeV. For the 6% most central collisions, we obtain dN(ch)/d(eta)/(/eta/<1) = 650+/-35(syst). Compared to collisions at root square[s(NN)] = 130 GeV, the highest energy studied previously, an increase by a factor of 1.14+/-0.05 at 90% confidence level, is found. The energy dependence of the pseudorapidity density is discussed in comparison with data from proton-induced collisions and theoretical predictions.

Journal Article↗
PubMed2001

Novel [2]catenane structures introducing communication between transition metal centers via pi...pi interactions.

[2]Catenane systems containing copper(II) and nickel(II) as metal centers have been self-assembled using tetraazamacrocyclic complexes and benzo-24-crown-8 as building blocks. A variety of methods, including X-ray crystallography, ESI mass spectrometry, (13)C and (1)H NMR, and electrochemistry, were applied to characterize these new face-to-face bismacrocyclic systems. Weak pi...pi interactions introduced by interlocking transition metal complexes with benzocrown moieties were shown to increase the communication (cooperativity) of metal centers. Introduction of the benzocrown increases the stability of the mixed valence state of the macrocyclic complex, which is reflected in high values of conproportionation constants. Moreover, this effect was found to be stronger than that obtained by shortening the length of the spacer between the two tetraazamacrocyclic subunits in the parent bismacrocycles. The extent of communication is larger for the nickel catenane than for the copper one.

Journal Article↗
PubMed2001

Charged-particle pseudorapidity density distributions from Au+Au collisions at sqrt[s(NN)]=130 GeV.

The charged-particle pseudorapidity density dN(ch)/d eta has been measured for Au+Au collisions at sqrt[s(NN)] = 130 GeV at RHIC, using the PHOBOS apparatus. The total number of charged particles produced for the 3% most-central Au+Au collisions for /eta/<or=5.4 is found to be 4200+/-470. The evolution of dN(ch)/d eta with centrality is discussed, and compared to model calculations and to data from proton-induced collisions. The data show an enhancement in charged-particle production at midrapidity, while in the fragmentation regions, the results are consistent with expectations from pp and pA scattering.

Journal Article↗
PubMed2001

Ratios of charged antiparticles-to-particles near mid-rapidity in Au + Au collisions at sqrt[s(NN)]=130 GeV.

We have measured the ratios of antiparticles to particles for charged pions, kaons, and protons near mid-rapidity in central Au+Au collisions at sqrt[s(NN)] = 130 GeV. We observe / = 1.00+/-0.01(stat)+/-0.02(syst), / = 0.91+/-0.07(stat)+/-0.06(syst), and / = 0.60+/-0.04(stat)+/-0.06(syst). The / and / ratios give a consistent estimate of the baryo-chemical potential mu(B) of 45 MeV, a factor of 5-6 smaller than in central Pb+Pb collisions at sqrt[s(NN)] = 17.2 GeV.

Journal Article↗
PubMed2000

Charge densities from high-resolution synchrotron X-ray diffraction experiments.

The combination of intense X-ray sources, especially synchrotron radiation, with area-detector technology has accomplished an enormous advance in the experimental conditions available for charge-density analysis by single-crystal high-resolution X-ray diffraction. Such experiments can now be carried out in a time measured in hours rather than weeks. Some features of these experiments are examined and preliminary results are reported for charge-density studies of 2-hydroxy-5-nitrobenzaldehyde N-cyclohexylimine (1), octakis(m-tolylthio)naphthalene (2), and 7-fluoro-4-styrylcoumarin (3). Weak interactions in crystals of (1) and (3) are found to have similar charge-density characteristics. Cages in the crystal lattice of (2) have a complex charge distribution.

Journal Article↗
PubMed2000

Does potassium dichromate induce apoptosis in lymphocytes?

The aim of this work was to investigate the possibility of apoptosis in the human peripheral blood lymphocytes after treatment with potassium dichromate (K2Cr2O7), a potential occupational carcinogenic and mutagenic agent. Lymphocytes were stimulated by phytohemagglutinin, cultured for 72 h and incubated with either 0.2 mM or 0.4 mM K2Cr2O7 for the last 24 h or 48 h of culture. The condensation and margination of chromatin with emerging 'half-moon' structure, characteristic of apoptosis were observed. Phosphatidylserine displaced from the inner to outer side of the cellular membrane in 54% of cells after a 48-h incubation with 0.4 mM K2Cr2O7 (annexin-V+/PI-); 39% of these cells were of late apoptotic--secondary necrotic form (annexin-V+/PI+). Following the agarose gel electrophoresis of DNA, a 'ladder pattern' typical of apoptosis, was found. The results of the present study demonstrate that K2Cr2O7 can induce in the human peripheral blood lymphocytes changes similar to apoptotic ones.

Apoptosis↗