Biomedical subjects

J Berger

Publications and source records attributed to J Berger.

At least 37 records · Page 2Linked to original sources

PubMed2004

Multistrange baryon production in Au-Au collisions at sqrt[s(NN)]=130 GeV.

The transverse mass spectra and midrapidity yields for Xis and Omegas are presented. For the 10% most central collisions, the (-)Xi(+)/h(-) ratio increases from the Super Proton Synchrotron to the Relativistic Heavy Ion Collider energies while the Xi(-)/h(-) stays approximately constant. A hydrodynamically inspired model fit to the Xi spectra, which assumes a thermalized source, seems to indicate that these multistrange particles experience a significant transverse flow effect, but are emitted when the system is hotter and the flow is smaller than values obtained from a combined fit to pi, K, p, and Lambdas.

Journal Article↗

PubMed2004

Cross sections and transverse single-spin asymmetries in forward neutral-pion production from proton collisions at sqrt[s]=200 GeV.

Measurements of the production of forward high-energy pi(0) mesons from transversely polarized proton collisions at sqrt[s]=200 GeV are reported. The cross section is generally consistent with next-to-leading order perturbative QCD calculations. The analyzing power is small at x(F) below about 0.3, and becomes positive and large at higher x(F), similar to the trend in data at sqrt[s]< or =20 GeV. The analyzing power is in qualitative agreement with perturbative QCD model expectations. This is the first significant spin result seen for particles produced with p(T)>1 GeV/c at a polarized proton collider.

Journal Article↗

PubMed2004

Identified particle distributions in pp and Au+Au collisions at square root of (sNN)=200 GeV.

Transverse mass and rapidity distributions for charged pions, charged kaons, protons, and antiprotons are reported for square root of [sNN]=200 GeV pp and Au+Au collisions at Relativistic Heary Ion Collider (RHIC). Chemical and kinetic equilibrium model fits to our data reveal strong radial flow and long duration from chemical to kinetic freeze-out in central Au+Au collisions. The chemical freeze-out temperature appears to be independent of initial conditions at RHIC energies.

Journal Article↗

PubMed2004

Rho0 production and possible modification in Au+Au and p+p collisions at square root [sNN] = 200 GeV.

We report results on rho(770)(0)-->pi(+)pi(-) production at midrapidity in p+p and peripheral Au+Au collisions at sqrt[s(NN)]=200 GeV. This is the first direct measurement of rho(770)(0)-->pi(+)pi(-) in heavy-ion collisions. The measured rho(0) peak in the invariant mass distribution is shifted by approximately 40 MeV/c(2) in minimum bias p+p interactions and approximately 70 MeV/c(2) in peripheral Au+Au collisions. The rho(0) mass shift is dependent on transverse momentum and multiplicity. The modification of the rho(0) meson mass, width, and shape due to phase space and dynamical effects are discussed.

Journal Article↗

PubMed2004

Azimuthal anisotropy at the relativistic heavy ion collider: the first and fourth harmonics.

We report the first observations of the first harmonic (directed flow, v(1)) and the fourth harmonic (v(4)), in the azimuthal distribution of particles with respect to the reaction plane in Au+Au collisions at the BNL Relativistic Heavy Ion Collider (RHIC). Both measurements were done taking advantage of the large elliptic flow (v(2)) generated at RHIC. From the correlation of v(2) with v(1) it is determined that v(2) is positive, or in-plane. The integrated v(4) is about a factor of 10 smaller than v(2). For the sixth (v(6)) and eighth (v(8)) harmonics upper limits on the magnitudes are reported.

Journal Article↗

PubMed2004

Particle-type dependence of azimuthal anisotropy and nuclear modification of particle production in Au+Au collisions at square root of sNN=200 GeV.

We present STAR measurements of the azimuthal anisotropy parameter v(2) and the binary-collision scaled centrality ratio R(CP) for kaons and lambdas (Lambda+Lambda) at midrapidity in Au+Au collisions at square root of s(NN)=200 GeV. In combination, the v(2) and R(CP) particle-type dependencies contradict expectations from partonic energy loss followed by standard fragmentation in vacuum. We establish p(T) approximately 5 GeV/c as the value where the centrality dependent baryon enhancement ends. The K(0)(S) and Lambda+Lambda v(2) values are consistent with expectations of constituent-quark-number scaling from models of hadron formation by parton coalescence or recombination.

Journal Article↗

PubMed2004

Structure and interactions in chitosan hydrogels formed by complexation or aggregation for biomedical applications.

The aim of this review was to provide a detailed overview of physical chitosan hydrogels and related networks formed by aggregation or complexation, which are intended for biomedical applications. The structural basis of these systems is discussed with particular emphasis on the network-forming interactions, the principles governing their formation and their physicochemical properties. An earlier review discussing crosslinked chitosan hydrogels highlighted the potential negative influence on biocompatibility of covalent crosslinkers and emphasised the need for alternative hydrogel systems. A possible means to avoid the use of covalent crosslinkers is to prepare physical chitosan hydrogels by direct interactions between polymeric chains, i.e. by complexation, e.g. polyelectrolyte complexes (PEC) and chitosan/poly (vinyl alcohol) (PVA) complexes, or by aggregation, e.g. grafted chitosan hydrogels. PEC exhibit a higher swelling sensitivity towards pH changes compared to covalently crosslinked chitosan hydrogels, which extends their potential application. Certain complexed polymers, such as glycosaminoglycans, can exhibit interesting intrinsic properties. Since PEC are formed by non-permanent networks, dissolution can occur. Chitosan/PVA complexes represent an interesting alternative for preparing biocompatible drug delivery systems if pH-controlled release is n/ot required. Grafted chitosan hydrogels are more complex to prepare and do not always improve biocompatibility compared to covalently crosslinked hydrogels, but can enhance certain intrinsic properties of chitosan such as bacteriostatic and wound-healing activity.

Biocompatible Materials↗

PubMed2004

Structure and interactions in covalently and ionically crosslinked chitosan hydrogels for biomedical applications.

This review presents a critical analysis of covalently and ionically crosslinked chitosan hydrogels and related networks for medical or pharmaceutical applications. The structural basis of these hydrogels is discussed with reference to the specific chemical interactions, which dictate gel formation. The synthesis and chemistry of these hydrogels is discussed using specific pharmaceutical examples. Covalent crosslinking leads to formation of hydrogels with a permanent network structure, since irreversible chemical links are formed. This type of linkage allows absorption of water and/or bioactive compounds without dissolution and permits drug release by diffusion. pH-controlled drug delivery is made possible by the addition of another polymer. Ionically crosslinked hydrogels are generally considered as biocompatible and well-tolerated. Their non-permanent network is formed by reversible links. Ionically crosslinked chitosan hydrogels exhibit a higher swelling sensitivity to pH changes compared to covalently crosslinked chitosan hydrogels. This extends their potential application, since dissolution can occur in extreme acidic or basic pH conditions.

Biomedical Technology↗

PubMed2004

[Is there a consensus in the division of the vocal folds in thirds?].

INTRODUCTION: In clinical routine we have noticed a disagreement of ENT-specialists and phoniatricians in the division of the vocal folds in thirds. To show if there is consensus in this field by the german phoniatricians this study was done. MATERIAL AND METHODS: In two parts of a study, a pilot study and a follow up study, we sent twelve different images of the larynx to all german phoniatricians. In six of these images the physicians should set the marks of the ventral and dorsal limitation of the second third of the vocal folds. In six different images a mark should be related to the particular third of the vocal folds. The phoniatricians were asked to assess how certain they were in their valuation. They were asked either, how long they have been working as a physician and how long they have been specialized as a phoniatrician and as an ENT-surgeon. In the follow up study the phoniatricians were requested to first divide up the thirds in a way that the dorsal third corresponds to the cartilaginous part of the vocal folds (scheme 1) and second divide up the thirds in a way that all three thirds correspond to the ligamental part of the vocal folds. DISCUSSION AND FINDINGS: In the pilot study, when no instructions for the division of the thirds were given, the data differed much more than in the follow up study, when the physicians were told to use scheme 1 and scheme 2. That was because some phoniatricians divided up just the ligamental part and others the ligamental plus the cartilaginous part of the vocal folds in thirds. The more the physicians could overlook the membraneous part of the vocal folds the more certain they were in their assessment. CONCLUSION: The assessment of the division of the vocal folds in thirds is more homogeneous when the phoniatricians were requested to divide up the thirds in a way that the dorsal third corresponds to the cartilaginous part of the vocal folds (scheme 1). Therefore we suggest that this way of division should be used further on.

Adult↗

PubMed2004

[Tumorectomy in conscious patient with suspected pregnancy associated breast cancer under cervical epidural anesthesia].

In this report we present a 35 year old pregnant woman (no significant disease in patient history, non smoker, primipara, gestational week 15) who had to undergo elective tumorectomy due to suspected pregnancy associated breast cancer. General anesthesia during pregnancy can potentially be harmful for the fetus (hypoxia, acidosis, premature delivery, teratogenicity). We decided to anesthetize the patient with a cervical segmental epidural block.

Adult↗

PubMed2004

Laser pediatric Class II composites utilizing no anesthesia.

Interproximal lesions can now be restored without local anesthesia and removing unnecessary healthy tooth structure. This paper will focus on a new ultra-conservative technique in Class II composites utilizing the laser, a new technique in cavity preparation.

Anesthesia, Dental↗

PubMed2003

Pion-Kaon correlations in central Au+Au collisions at square root [sNN] = 130 GeV.

Pion-kaon correlation functions are constructed from central Au+Au STAR data taken at sqrt[s(NN)]=130 GeV by the STAR detector at the Relativistic Heavy Ion Collider (RHIC). The results suggest that pions and kaons are not emitted at the same average space-time point. Space-momentum correlations, i.e., transverse flow, lead to a space-time emission asymmetry of pions and kaons that is consistent with the data. This result provides new independent evidence that the system created at RHIC undergoes a collective transverse expansion.

Journal Article↗

PubMed2003

Three-pion Hanbury Brown-Twiss correlations in relativistic heavy-ion collisions from the STAR experiment.

Data from the first physics run at the Relativistic Heavy-Ion Collider at Brookhaven National Laboratory, Au+Au collisions at sqrt[s(NN)]=130 GeV, have been analyzed by the STAR Collaboration using three-pion correlations with charged pions to study whether pions are emitted independently at freeze-out. We have made a high-statistics measurement of the three-pion correlation function and calculated the normalized three-particle correlator to obtain a quantitative measurement of the degree of chaoticity of the pion source. It is found that the degree of chaoticity seems to increase with increasing particle multiplicity.

Journal Article↗

PubMed2003

Transverse-momentum and collision-energy dependence of high-pT hadron suppression in Au+Au collisions at ultrarelativistic energies.

We report high statistics measurements of inclusive charged hadron production in Au+Au and p+p collisions at sqrt[s(NN)]=200 GeV. A large, approximately constant hadron suppression is observed in central Au+Au collisions for 5<p(T)<12 GeV/c. The collision energy dependence of the yields and the centrality and p(T) dependence of the suppression provide stringent constraints on theoretical models of suppression. Models incorporating initial-state gluon saturation or partonic energy loss in dense matter are largely consistent with observations. We observe no evidence of p(T)-dependent suppression, which may be expected from models incorporating jet attenuation in cold nuclear matter or scattering of fragmentation hadrons.

Journal Article↗

PubMed2003

Evidence from d+Au measurements for final-state suppression of high-p(T) hadrons in Au+Au collisions at RHIC.

We report measurements of single-particle inclusive spectra and two-particle azimuthal distributions of charged hadrons at high transverse momentum (high p(T)) in minimum bias and central d+Au collisions at sqrt[s(NN)]=200 GeV. The inclusive yield is enhanced in d+Au collisions relative to binary-scaled p+p collisions, while the two-particle azimuthal distributions are very similar to those observed in p+p collisions. These results demonstrate that the strong suppression of the inclusive yield and back-to-back correlations at high p(T) previously observed in central Au+Au collisions are due to final-state interactions with the dense medium generated in such collisions.

Journal Article↗

PubMed2003

Narrowing of the balance function with centrality in Au+Au collisions at the square root of SNN = 130 GeV.

The balance function is a new observable based on the principle that charge is locally conserved when particles are pair produced. Balance functions have been measured for charged particle pairs and identified charged pion pairs in Au+Au collisions at the square root of SNN = 130 GeV at the Relativistic Heavy Ion Collider using STAR. Balance functions for peripheral collisions have widths consistent with model predictions based on a superposition of nucleon-nucleon scattering. Widths in central collisions are smaller, consistent with trends predicted by models incorporating late hadronization.

Journal Article↗

PubMed2003

Disappearance of back-to-back high-pT hadron correlations in central Au+Au collisions at sqrt[s NN ] =200 GeV.

Azimuthal correlations for large transverse momentum charged hadrons have been measured over a wide pseudorapidity range and full azimuth in Au+Au and p+p collisions at sqrt[s(NN)]=200 GeV. The small-angle correlations observed in p+p collisions and at all centralities of Au+Au collisions are characteristic of hard-scattering processes previously observed in high-energy collisions. A strong back-to-back correlation exists for p+p and peripheral Au+Au. In contrast, the back-to-back correlations are reduced considerably in the most central Au+Au collisions, indicating substantial interaction as the hard-scattered partons or their fragmentation products traverse the medium.

Journal Article↗

PubMed2003

Host defense against Pseudomonas aeruginosa requires ceramide-rich membrane rafts.

Pseudomonas aeruginosa infection is a serious complication in patients with cystic fibrosis and in immunocompromised individuals. Here we show that P. aeruginosa infection triggers activation of the acid sphingomyelinase and the release of ceramide in sphingolipid-rich rafts. Ceramide reorganizes these rafts into larger signaling platforms that are required to internalize P. aeruginosa, induce apoptosis and regulate the cytokine response in infected cells. Failure to generate ceramide-enriched membrane platforms in infected cells results in an unabated inflammatory response, massive release of interleukin (IL)-1 and septic death of mice. Our findings show that ceramide-enriched membrane platforms are central to the host defense against this potentially lethal pathogen.

Animals↗