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G Bauer

Publications and source records attributed to G Bauer.

At least 55 records · Page 3Linked to original sources
PubMed2001

Measurement of the top quark p(T) distribution.

We have measured the p(T) distribution of top quarks that are pair produced in pp collisions at sqrt[s] = 1.8 TeV using a sample of tt decays in which we observe a single high- p(T) charged lepton, a neutrino, and four or more jets. We use a likelihood technique that corrects for the experimental bias introduced due to event reconstruction and detector resolution effects. The observed distribution is consistent with the standard model prediction. We use these data to place limits on the production of high- p(T) top quarks suggested in some models of anomalous top quark pair production.

Journal Article↗
PubMed2001

Exclusion of quantum coherence as the origin of the 2D metallic state in high-mobility silicon inversion layers.

The temperature and density dependence of the phase coherence time tau(phi) in high-mobility silicon inversion layers was determined from the magnetoresistivity due to weak localization. The upper temperature limit for single-electron quantum interference effects was delineated by comparing tau(phi) with the momentum relaxation time tau. A comparison between the density dependence of the borders for quantum interference effects and the strong resistivity drop reveals that these effects are not related to each other. As the strong resistivity drop occurs in the Drude regime, the apparent metallic behavior cannot be caused by quantum coherent effects.

Journal Article↗
PubMed2001

Optimization of the time-dependent traveling salesman problem with Monte Carlo methods.

A problem often considered in operations research and computational physics is the traveling salesman problem, in which a traveling salesperson has to find the shortest closed tour between a certain set of cities. This problem has been extended to more realistic scenarios, e.g., the "real" traveling salesperson has to take rush hours into consideration. We will show how this extended problem is treated with physical optimization algorithms. We will present results for a specific instance of Reinelt's library TSPLIB95, in which we define a zone with traffic jams in the afternoon.

Journal Article↗
PubMed2001

Search for neutral supersymmetric Higgs bosons in pp collisions at sqrt[s] = 1.8TeV.

We present the results of a search for neutral Higgs bosons produced in association with b quarks in pp-->bb(phi)-->bbb final states with 91+/-7 pb(-1) of pp collisions at sqrt[s] = 1.8 TeV recorded by the Collider Detector at Fermilab. We find no evidence of such a signal and the data are interpreted in the context of the neutral Higgs sector of the minimal supersymmetric extension of the standard model. With basic parameter choices for the supersymmetric scale and the stop-quark mixing, we derive 95% C.L. lower mass limits for neutral Higgs bosons for tan(beta) values in excess of 35.

Journal Article↗
PubMed2001

Production of chi(c1) and chi(c2) in pp collisions at sqrt[S] = 1.8 TeV.

We have measured the ratio of prompt production rates of the charmonium states chi(c1) and chi(c2) in 110 pb(-1) of pp collisions at sqrt[s] = 1.8 TeV. The photon from their decay into J/psi(gamma) is reconstructed through conversion into e+e- pairs. The energy resolution this technique provides makes the resolution of the two states possible. We find the ratio of production cross sections sigma(chi(c2))/sigma(chi(c1)) = 0.96+/-0.27(stat)+/-0.11(syst) for events with pT(J/psi) > 4.0 GeV/c, /eta(J/psi)/ < 0.6, and pT(gamma) > 1.0 GeV/c.

Journal Article↗
PubMed2001

First measurement of the ratio B(t --> Wb)/B(t --> Wq) and associated limit on the Cabibbo-Kobayashi-Maskawa element /V(tb)/.

We present the first measurement of the ratio of branching fractions R identical withB(t-->Wb)/B(t-->Wq) from p_p collisions at sqrt[s] = 1.8 TeV. The data set corresponds to 109 pb(-1) of data recorded by the Collider Detector at Fermilab during the 1992-95 Tevatron run. We measure R = 0.94(+0.31)(-0.24)(stat+syst) or R>0.61 (0.56) at 90% (95)% C.L., in agreement with the standard model predictions. This measurement yields a limit on the Cabibbo-Kobayashi-Maskawa quark mixing matrix element /V(tb)/ under the assumption of three generations and unitarity.

Journal Article↗
PubMed2001

Drug-related emergencies and drug-related deaths in Vienna, 1995-1997.

The demographics of drug-related emergencies and drug-related deaths that occurred in Vienna between January 1st, 1995 and December 31st, 1997 were compared to investigate whether they represent two different subgroups of the drug-taking community. Analysis indicated that drug-related emergencies were significantly younger and that the proportion of females was higher than amongst the fatalities. In addition, emergencies were more likely than fatalities to occur in private residences than public places. No significant association between the number of contacts with the Vienna Ambulance Service and the fatal outcome of drug use could be substantiated. The results of this study indicate that drug-related emergencies and drug-related deaths represent two different subpopulations of the drug-taking community. Therefore, different strategies of prevention are considered.

Accidents, Home↗
PubMed2001

Slide-format proteomic biochips based on surface-enhanced nanocluster-resonance.

The most fundamental properties of metal nanoclusters, namely the high local-field enhancement and nanoscale resonance behavior of the cluster electron plasma when exited by electromagnetic radiation, have been used to set up a variety of sensors transducing biorecognitive interactions into optical signals. This paper focuses on applications of resonant-cluster technology, which enabled us to monitor biorecognitive binding of a variety of proteins on a chip, thus constructing high-throughput interaction-screening devices. Decisive for this type of sensor is the nanometric distance from the local field surrounding a cluster to other parts of the sensor interacting with this field. In particular, the cluster-mirror or cluster-fluorophore distance gives rise to a variety of enhancement phenomena. Depending on the desired application this "resonance"- distance is approximately 5-400 nm. All types of sensor can be set up on photolithographically constructed microchips, but microscopic glass slides can also be employed; this also enables the use of standard devices for dotting and read out. Using slide based chips a standard format of 3,200 microdots (125 microm in diameter) was the basis of either microassays applying direct optical transduction via surfaceenhanced absorption or striking for more sensitivity via surface-enhanced fluorescence.

Animals↗
PubMed2001

High-throughput assays on the chip based on metal nano-cluster resonance transducers.

High throughput transducers using metal cluster resonance technology are based on surface-enhancement of metal cluster light absorption. These devices can be used for detection of biorecognitive binding, as well as structural changes of nucleic acids, proteins or any other polymer. The optical property for the analytical application of metal cluster films is the so-called anomalous absorption. An absorbing film of clusters positioned 10--400 nm to a mirror surface reacts in a similar way to a reflection filter. At a certain distance of the absorbing layer to the mirror the reflected electromagnetic field has the same phase at the position of the absorbing cluster as the incident fields. This feedback mechanism strongly enhances the effective cluster absorption coefficient. The system is characterised by a narrow reflection minimum whose spectral position shifts sensitively with the interlayer thickness, because a given cluster-mirror distance and wavelength defines the optimum phase. Based on this principle a set of novel tools including biochips and micro arrays is presented, which enabled us to transduce binding, as well as changes of protein-, DNA- and polymer-conformation, quantitatively into an optical signal which can be observed directly as a colour change of a sensor-chip surface.

Electromagnetic Fields↗
PubMed2001

Idiopathic generalized epilepsies with pure grand mal: clinical data and genetics.

OBJECTIVE: To analyze the clinical features and family history of patients with idiopathic generalized epilepsy (IGE), with pure grand mal (GM), divided into epilepsies with GM occurring exclusively on awakening (GMA) and random GM (RGM). METHODS: We studied retrospectively 98 patients from a large epilepsy outpatient clinic. All patients had a full clinical examination and computed cerebral tomography scans (CCT) or magnetic resonance imaging (MRI) when feasible. We analyzed seizure type, seizure frequency, provocative factors, prognosis, electroencephalography (EEG) findings and family history. RESULTS: Sixty-eight patients had GMA and 30 had RGM. The mean age at seizure onset was 16.6 years (+/-6.3 S.D., range: 5-41) and 16.7 years in those with RGM (+/-7.5 S.D., range: 4-42, NSD). Patients with GMA had a longer course of active epilepsy (median 8.5 years) compared to RGM (median 2 years). Seizure-provoking factors, especially sleep deprivation, were significantly (P=0.001) more common in patients with GMA (52/68, 77%) than in the group with RGM (13/30, 43%). Of all patients, 23% (23/98) reported first degree relatives with seizures or epilepsy. Pure GM was found in 41% (12/29) of affected first degree relatives, other idiopathic generalized epilepsy syndromes were less frequently observed (4/29, 14%). The concordance rate was high within the syndrome - none of the patients with RGM had an affected relative with GMA and vice versa only two of affected relatives of GMA patients had RGM. CONCLUSION: GMA seems to be associated with a longer duration of active epilepsy, a higher relapse rate and a stronger tendency to be precipitated by seizure provoking factors. The different concordance rates between the syndromes suggest a genetically different background.

Adolescent↗
PubMed2001

Recent advances in the diagnosis and treatment of epilepsy.

Recent advances in the diagnosis and treatment of epilepsies are discussed with special consideration of epidemiology and classification, progress in neuroimaging, electrophysiological studies using EEG and MEG, initiation of medical and surgical treatment, the role of new antiepileptic drugs and selected aspects of genetics of idiopathic epilepsies. In addition from conclusions obtained by the review of recent developments suggestions for future work in Europe are discussed. A constructive approach from multicenter studies requires homologous definitions, documentations and standardization of procedures of trials for European multicenter studies.

Anticonvulsants↗
PubMed2001

Deep wound infection after vagus nerve stimulator implantation: treatment without removal of the device.

Effective treatment of deep wound infection without removal of a previously implanted foreign body is difficult. The Neurocybernetic Prosthesis (NCP) System (Cyberonics Inc., Webster, TX, U.S.A.), implanted for vagus nerve stimulation in patients with medically refractory epilepsy, uses coil-like electrodes placed around the left vagus nerve after exposure of the nerve in the carotid sheath. Infection within this compartment endangers the contained structures and makes removal of the system hazardous. We report the case of one patient implanted with the NCP who underwent successful open wound treatment without removal of the system. A 35-year-old man had local signs of wound infection 5 weeks after implantation of a vagus nerve stimulator. Systemic signs of infection were absent. C-reactive protein was slightly elevated, but all other laboratory values were normal. After open wound debridement and thorough rinsing with bacitracin-containing solution, the wound was packed with 3% iodoformized gauze. The NCP was left in place. Systemic antibiotic therapy with fosfomycin and cefmenoxim was started. Cultures confirmed an infection with Staphylococcus aureus. The wound was rinsed daily with 3% hydrogen peroxide solution and 5% saline until cultures were sterile and granulation tissue started to fill the wound. Delayed primary closure was performed 2 weeks later. Wound healing was accomplished without removal of the device. No signs of recurrent infection were observed during a follow-up of 1 year. Open wound treatment without removal of the implanted vagus nerve stimulator is feasible in cases of deep cervical wound infection and can be an alternative if removal of the device appears hazardous.

Adult↗
PubMed2001

Lactobacilli-mediated control of vaginal cancer through specific reactive oxygen species interaction.

Klebanoff et al. proposed that hydrogen peroxide-producing lactobacilli and peroxidase in the vagina of healthy women might be responsible for the prevention of vaginosis and also might exert an antitumor effect (1). Based on recent evidence on superoxide anion generation by transformed cells (2,3) and on the potential of myeloperoxidase for selective apoptosis induction in transformed cells (4), a model for specific reactive oxygen species interaction during lactobacilli-mediated tumor control in the vagina is presented here. We propose that peroxidase, which converts hydrogen peroxide into hypochlorous acid, is responsible for creating a microbicidal vaginal milieu by maintaining a balanced, non-toxic, steady state level of the microbicides H(2)O(2)and HOCI. In case individual superoxide anion-producing transformed cells eventually appear in the mucosa they will be driven into apoptosis by interaction of HOCI with superoxide anions which leads to the generation of hydroxyl radicals. Hence selective apoptosis induction in transformed cells represents the key element of lactobacilli-mediated antitumor defense. Since papilloma virus infected cells are resistant to this pathway of apoptosis induction, they are plausible candidates for circumvention of lactobacilli-mediated control of oncogenesis.

Apoptosis↗
PubMed2001

An alternative signaling pathway based on nitryl chloride during intercellular induction of apoptosis.

Transforming growth factor (TGF)-beta pretreated nontransformed fibroblasts induce apoptosis selectively in transformed fibroblasts. This potential control step during oncogenesis has been termed intercellular induction of apoptosis. Selectivity and efficiency of intercellular induction of apoptosis depend on transformed target cell-derived superoxide anions that drive two intercellular signaling pathways--the HOCl/hydroxyl radical and the nitric oxide (NO)/peroxynitrite pathway. Other natural antitumor systems like macrophages or cells of the granulocyte lineage seem to utilize the same signaling chemistry. Our data demonstrate the existence of an alternative signaling pathway in these systems. This pathway depends on the presence of nitrite and is still effective when the two conventional signaling pathways are blocked by superoxide dismutase (SOD). Nitrite-dependent apoptosis induction is neither blocked by SOD nor by the hydroxyl radical scavenger terephthalate, but it is inhibited by the peroxidase inhibitor aminobenzoyl hydrazide and by the hypochlorous acid (HOCl) scavenger taurine. Therefore, nitrite, that is nontoxic for our cells, seems to interact with HOCl to form the apoptosis inducer nitryl chloride. Nitryl chloride-mediated apoptosis induction might be relevant for apoptosis induction in tumor cells that release SOD and thus escape the two classical signaling pathways.

Animals↗
PubMed2001

ras oncogene expression determines sensitivity for intercellular induction of apoptosis.

Fibroblasts carrying an inducible ras oncogene acquire the transformed phenotype after oncogene induction. As a consequence, the transformed cells become sensitive to intercellular induction of apoptosis, a novel regulatory process directed by non-transformed fibroblasts against their transformed descendants. The causal relationship between oncogene expression and sensitivity to intercellular induction of apoptosis is based on extracellular superoxide anion production by oncogene-expressing cells. Superoxide anions (after dismutation to hydrogen peroxide) thereby foster HOCl synthesis and at the same time direct the selectivity of apoptosis induction through hydroxyl generation from HOCl. In parallel, ras expression enhances the sensitivity of fibroblasts for apoptosis-inducing stimuli like cycloheximide, ceramide and mitomycin C. This sensitization seems to be based on a decreased concentration of short lived endogenous apoptosis inhibitors. TGF-beta, like ras induction, decreases the concentration of endogenous apoptosis inhibitors, but does not induce the transformed phenotype. Therefore, TGF-beta treatment alone is not sufficient to render fibroblasts sensitive for intercellular induction of apoptosis, but TGF-beta treatment in parallel with ras activation enhances intercellular induction of apoptosis. Our findings demonstrate that Ras-mediated superoxide anion production determines sensitivity to intercellular induction of apoptosis, whereas the parallel decrease in endogenous apoptosis inhibitors modulates the kinetics of apoptosis induction.

Animals↗
PubMed2001

Nanofilms and nanoclusters: energy sources driving fluorophores of biochip bound labels.

Nanoclusters and nanofilms have the potential to amplify fluorescence and thus to enhance the signal of labeled biomolecules on biochip surfaces. Fluorescent molecules are bound at a certain distance to a resonant layer of a metal or a semiconductor or both, resulting in enhanced absorption and emission of the fluorophore within the electromagnetic near-field. This property makes the system highly useful for interaction studies, including those of DNA and proteins. Due to the amount of data, derived from various sequencing projects and from Proteomic interaction studies within the next years, microarrays (or biochips) will represent a central technology in every lab facilitating high-throughput screening and being easily interfaced with computer databases. However, most chips suffer from the disadvantage of insufficient signal-to-noise (background) ratio and are thus limited to molecules of medium-to-high abundance. Novel approaches are needed for identification of, e.g., low copy RNAs or regulatory proteins. Here we present a study, using novel surface enhanced chips in the standard glass-slide-formats. Applying surface-enhanced fluorescence (SEF), the chips turned out to be useful for interaction studies, such as DNA hybridization, thereby strongly enhancing the on-chip-signals. Compared to standard glass-slide-DNA chips, both the fluorescent signals as well as signal-to-noise ratio were considerably higher.

Animals↗