Biomedical subjects

Dieter Schneider

Publications and source records attributed to Dieter Schneider.

5 recordsLinked to original sources

PubMed2006

Beamline X29: a novel undulator source for X-ray crystallography.

A high-flux insertion device and beamline for macromolecular crystallography has been built at the National Synchrotron Light Source (NSLS) that employs a mini-gap undulator source developed by the NSLS. The mini-gap undulator at beamline X29 is a hybrid-magnet device of period 12.5 mm operating at proven gaps of 3.3-10 mm. The beamline provides hard X-rays for macromolecular crystallography experiments from the second and third harmonics over an energy range of 5-15 keV. The X-ray optics is designed to deliver intense and highly collimated X-rays. Horizontal focusing is achieved by a cryogenically cooled sagittally focusing double-crystal monochromator with approximately 4.1:1 demagnification. A vertical focusing mirror downstream of the monochromator is used for harmonic rejection and vertical focusing. The experimental station hosts an Area Detector Systems Quantum 315 CCD detector with 2.2 s readout time between exposures and Crystal Logic goniostat for crystal rotation and detector positioning. An auto-mounter crystal changer has been installed to facilitate the high-throughput data collection required by the major users, which includes structural genomics projects and the Macromolecular Crystallography Research Resource mail-in program. X29 is 10(3) times brighter than any existing bending-magnet beamline at NSLS with an actual flux of 2.5 x 10(11) photons s(-1) through a 0.12 mm square aperture at 11.271 keV.

Crystallography, X-Ray↗

PubMed2005

Comparison of pre-hospital combination-fibrinolysis plus conventional care with pre-hospital combination-fibrinolysis plus facilitated percutaneous coronary intervention in acute myocardial infarction.

AIMS: Early and complete reperfusion is the main treatment goal in ST-elevation myocardial infarction (STEMI). The timely optimal reperfusion strategy might be a pre-hospital initiated pharmacological reperfusion with subsequent facilitated percutaneous coronary intervention (PCI). This approach has been compared with pre-hospital combination-fibrinolysis only to determine whether either one of these methods offer advantages with respect to final infarct size. METHODS AND RESULTS: Patients with STEMI were randomized to either pre-hospital combination-fibrinolysis (half-dose reteplase+abciximab) with standard care (n=82) or pre-hospital combination-fibrinolysis with facilitated PCI (n=82). Primary endpoint was the infarct size assessed by delayed enhancement magnetic resonance. Secondary endpoints were ST-segment resolution at 90 min and a composite of death, re-myocardial infarction, major bleeding, and stroke at 6 months. The infarct size was lower after facilitated PCI with 5.2% [interquartile range (IQR) 1.3-11.2] as opposed to 10.4% (IQR 3.4-16.3) after pre-hospital combination-fibrinolysis (P=0.001). Complete ST-segment resolution was 80.0% after facilitated PCI vs. 51.9% after pre-hospital combination-fibrinolysis (P<0.001). After facilitated PCI, there was a trend towards a lower event rate in the combined clinical endpoint (15 vs. 25%, P=0.10, relative risk 0.57, 95% CI 0.28-1.13). CONCLUSION: In patients with STEMI, additional facilitated PCI after pre-hospital combination-fibrinolysis results in an improved tissue perfusion with subsequent smaller infarct size as opposed to pre-hospital combination-fibrinolysis alone. This translates into a trend towards a better clinical outcome.

Adult↗

PubMed2004

Combining Brillouin spectroscopy and laser-SAW technique for elastic property characterization of thick DLC films.

Surface Brillouin spectroscopy (SBS) has been widely used for elastic property characterization of thin films. For films thicker than 500 nm, however, the wavelength of surface acoustic wave in the frequency range available for SBS is smaller than film thickness, and the SBS measures only the Rayleigh wave of the film. The laser-SAW technique, on the other hand, measures only the low-frequency portion of the surface acoustic wave dispersion and can estimate only one elastic modulus of the film (typically Young's modulus). In this work, we have combined the two methods to determine both Young's modulus and Poisson's ratio of a diamond-like carbon (DLC) film. It was found that reasonable estimates can be obtained for the longitudinal wave velocity, shear wave velocity, and Young's modulus of the film. The Poisson's ratio, however, still has a relatively large measurement error.

Journal Article↗

PubMed2003

Three-beam interference is a sensitive measure of the efficacy of macromolecular refinement techniques.

Triplet phases recorded from insulin crystals were used to measure the improvement of phases during model refinement and to quantify the contribution made by each step in the refinement. Conventional amplitude data were recorded to 1.5 A resolution from rhombohedral pig insulin crystals using 1.54 A Cu Kalpha radiation. An initial atomic model and starting phases were obtained from a published structure and the atomic model was refined against the amplitude data using CNS. The refined phases were compared with 800 triplet phases that were measured from similar crystals using a three-beam interference technique and 1.1 A wavelength synchrotron radiation. The solvent region was improved further using a novel density-modification procedure. Calculated triplet phases were obtained from the model after each step in the refinement and were compared with the recorded triplet phases. The average difference between the recorded triplet phases and the calculated triplet phases was used as an unbiased measure of the correctness of the model at each stage in the refinement. The average individual phase error was estimated from discrepancies from triplet phases after each refinement step. Conventional atomic refinement of an approximate starting model reduced the average individual phase error from 21.6 to 14.7 degrees. Improvement of the solvent region, including the difference-map flattening procedure, reduced the individual phase error by a further 2.6 degrees. Modeling the discrete disorder of four amino acids accounted for an additional 0.5 degrees improvement and the final individual phase error was 11.6 degrees.

Crystallography, X-Ray↗

PubMed2002

Neurofeedback and quantitative electroencephalography.

This study was conducted in an attempt to determine the efficacy of neurofeedback (NFB) in the treatment of patients suffering from vertigo or tinnitus. Results indicated that after NFB, power for delta and theta bands was reduced; however, an increase of power was noted for the alpha bands. Furthermore, normalization was observed for the vestibular evoked potentials (VestEP). After NFB, a normalization of the VestEP was also demonstrated in a patient suffering from a bilateral tinnitus. A follow-up study (12 months after NFB) demonstrated that the VestEP were normal.

Adult↗