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Biomedical subjects

H Fischer

Publications and source records attributed to H Fischer.

At least 37 records · Page 2Linked to original sources
PubMed2003

High statistics measurement of the K+-->pi0e+nu (K+e3) branching ratio.

E865 at the Brookhaven National Laboratory AGS collected about 70 000 K(+)(e3) events to measure the K(+)(e3) branching ratio relative to the observed K+-->pi(+)pi(0), K+-->pi(0)micro(+)nu, and K+-->pi(+)pi(0)pi(0) decays. The pi(0) in all the decays was detected using the e(+)e(-) pair from pi(0)-->e(+)e(-)gamma decay and no photons were required. Using the 2002 Particle Data Group branching ratios for the normalization decays, we obtain BR(K(+)(e3(gamma)))=(5.13+/-0.02(stat)+/-0.09(syst)+/-0.04(norm))%, where K(+)(e3(gamma)) includes the effect of virtual and real photons. This result is approximately 2.3sigma higher than the current Particle Data Group value. Implications for the V(us) element of the CKM matrix, and the matrix's unitarity are discussed.

Journal Article↗
PubMed2003

Evidence for quark-hadron duality in the proton spin asymmetry A1.

Spin-dependent lepton-nucleon scattering data have been used to investigate the validity of the concept of quark-hadron duality for the spin asymmetry A1. Longitudinally polarized positrons were scattered off a longitudinally polarized hydrogen target for values of Q2 between 1.2 and 12 GeV2 and values of W2 between 1 and 4 GeV2. The average double-spin asymmetry in the nucleon resonance region is found to agree with that measured in deep-inelastic scattering at the same values of the Bjorken scaling variable x. This finding implies that the description of A1 in terms of quark degrees of freedom is valid also in the nucleon resonance region for values of Q2 above 1.6 GeV2.

Journal Article↗
PubMed2003

The host response to urinary tract infection.

The authors use the UTI model to identify basic mechanisms of disease pathogenesis, host response induction, and defense. Their studies hold the promise to provide a molecular and genetic explanation for susceptibility to UTI, and to offer more precise tools for diagnosis and therapy of these infections. There are few infections where the host response is understood in such detail and where pathologic host responses can be linked to distinct disease states. The susceptibility to UTI varies greatly in the population. The studies suggest that distinct molecular defects can cause the clinical entity of acute pyelonephritis with renal scarring, and suggest that the susceptibility to UTI in certain patient groups may have a genetic basis. In addition, the distinct signal transduction pathways explain the development of symptoms, and propose that defects in those signaling mechanisms may occur in patients with ABU. In the future, it may be useful to include these host response parameters in the diagnostic arsenal, to help in early detection of patients susceptible to recurrent UTI and renal scarring. These patients may then be offered therapies that strengthen their defense, and be offered close surveillance for recurrences and other complications.

Animals↗
PubMed2003

Lifetime prediction of all-ceramic bridges by computational methods.

There has been limited use of ceramic materials for all-ceramic posterior bridges. Major reasons are the low strength, the strength scatter, and the time-dependent strength decrease of ceramics due to slow crack growth. The objective of this study was to predict the long-term failure probability and loading capability of all-ceramic bridges (Empress 1, Empress 2, In-Ceram Alumina, and ZrO(2)) by computational techniques. The lifetimes of different bridge model designs were predicted by means of the NASA post-processor CARES. Bridges made of zirconia showed a very high mechanical long-term reliability. Empress I and InCeram Alumina seem to be insufficient as posterior bridge materials based on this prediction. The lifetime of the all-ceramic bridges can be significantly increased by improving the design in the connector area. We conclude that computational techniques can help to judge a ceramic material and a specific ceramic bridge design with respect to mechanical reliability before clinical use.

Aluminum Oxide↗
PubMed2003

Effect of surface roughness on flexural strength of veneer ceramics.

The strength of ceramic restorations depends on the occlusal surface roughness of the veneering porcelain, which is influenced by the final preparation. The hypothesis of the study was that roughnesses below a critical microscopic defect size--based only on fracture mechanics considerations--also affect flexural strength. The bending failure stress was evaluated on standard specimens of 4 veneer ceramics with 4 different surfaces of defined roughnesses, respectively. A linear correlation was found between roughness and failure stress. A "roughness-free" failure stress value was predicted for each tested material. This theoretical value can represent the "true" strength of the respective ceramic material. We conclude from our results that the final preparation of a ceramic restoration is critical to the strength of the material, and that ceramic veneering materials can be compared more objectively with respect to their strength by means of roughness-free strength values.

Air Abrasion, Dental↗
PubMed2003

[A new coating method for cemented femur shaft implants--biocompatibility, stability during sterlization and adhesive strength].

The main cause of aseptic loosening of cemented stems in total hip arthroplasty is the hydrolytic degradation of the metal-cement interface. In order to prevent this debonding a new multilayer method of coating the implant surface involving the use of a silica-/silane technique to create a durable adhesive bond between metal stem and bone cement has been developed. The biocompatibility of all the elements of the multilayer system was confirmed using a human osteoblast cell culture test. For sterilization purposes, gamma irradiation with a 25 kGy effective dose proved to be the method of choice. The proven biocompatibility and successful sterilization of the coated implants are the main prerequisites for in-vivo usage. On the technical side, the bonding effectiveness of the multilayer coating system was demonstrated by the tensile test, which revealed a significant improvement in the adhesive strength of the cement-metal bond under prolonged moist conditions similar to those met with in the human body.

Bone Cements↗
PubMed2002

Measurement of spin-transfer observables in p p-->Lambda Lambda at 1.637 GeV/c.

Spin-transfer observables for p p-->Lambda Lambda have been measured using a transversely polarized frozen-spin target and a beam momentum of 1.637 GeV/c. Current models of the reaction near threshold are in good agreement with existing measurements performed with unpolarized particles in the initial state but produce conflicting predictions for the spin-transfer observables Dnn and Knn (the normal-to-normal depolarization and polarization transfer), which are measurable only with polarized target or beam. Measurements of Dnn and Knn presented here are found to be in disagreement with predictions from these models.

Journal Article↗
PubMed2002

Global air pollution crossroads over the Mediterranean.

The Mediterranean Intensive Oxidant Study, performed in the summer of 2001, uncovered air pollution layers from the surface to an altitude of 15 kilometers. In the boundary layer, air pollution standards are exceeded throughout the region, caused by West and East European pollution from the north. Aerosol particles also reduce solar radiation penetration to the surface, which can suppress precipitation. In the middle troposphere, Asian and to a lesser extent North American pollution is transported from the west. Additional Asian pollution from the east, transported from the monsoon in the upper troposphere, crosses the Mediterranean tropopause, which pollutes the lower stratosphere at middle latitudes.

Aerosols↗
PubMed2002

Cold-receptor cells supply both cold- and warm-responsive projection neurons in the antennal lobe of the cockroach.

The temperature receptor cells on the cockroach antennae are all excited by rapid cooling. In the antennal lobe, however, cold- as well as warm-responsive neurons occur. They are excited either by rapid step-like cooling or rapid step-like warming. Responses to such temperature transients do not show, however, whether antennal lobe neurons convey information on slowly changing temperatures typical of temperature gradients used for orientation. In contrast slow temperature changes permit an analysis of the effects of both instantaneous temperature and its rate of change. We compared the effect of slow temperature oscillations on the responses of antennal cold-receptors cells and cold- and warm-responsive projection neurons. In all cases the discharge rates were modulated by the temperature oscillations. They displayed a double dependence on instantaneous temperature and its rate of change. Information about cooling and warming, first contained in the output of a single cold-receptor cell diverges to form the parallel pathways of cold- and warm-responsive projection neurons, thereby in particular improving the detection of fluctuations in temperature.

Animals↗
PubMed2002

Treatment of HIV-associated wasting with recombinant human growth hormone: monitoring of body composition changes by bioelectrical impedance analysis (BIA).

INTRODUCTION: Recombinant human growth hormone (r-hGH) has demonstrated efficacy in treating HIV-associated wasting (HAW), however, HAW has become less prominent since the introduction of highly active antiretroviral therapy (HAART). Recent studies suggest that patients receiving HAART may still experience HAW. We investigated the nature of HAW and the efficacy of r-hGH in these patients. METHODS: We treated 27 HIV-positive patients receiving HAART who had either recent loss of >5% body weight or weight <90% lower limit of normal with 12 weeks of r-hGH (6 mg given either daily or every other day). Body composition changes were monitored using bioelectrical impedance analysis (BIA). RESULTS were assessed for all patients and for a subgroup meeting more stringent definitions of wasting (BIA phase angle a<5.6 degrees, n = 14). - RESULTS: Significant increases from baseline in weight and body cell mass (BCM) occurred in the full population (medians: 2.0 kg weight, 1.5 kg BCM). Patients with phase angle alpha<5.6 degrees also showed increases in weight and BCM (medians: 2.5 kg weight, 1.95 kg BCM), and 10 of 14 showed improvements in the ratio of extracellular mass (ECM) to BCM. At follow-up there was a trend towards loss of the weight and BCM gained on treatment. Treatment was well tolerated. CONCLUSION: Patients receiving HAART continue to experience wasting, and respond well to r-hGH therapy as monitored by BIA.

Adult↗
PubMed2002

European quadricentric evaluation of a breast MR biopsy and localization device: technical improvements based on phase-I evaluation.

Our purpose was to report about technical success, problems and solutions, as experienced in a first multicentre study on MR-guided localisation or vacuum biopsy of breast lesions. The study was carried out at four European sites using a dedicated prototype breast biopsy device. Experiences with 49 scheduled localisation procedures and 188 vacuum biopsies are reported. Apart from 35 dropped indications, one localisation procedure and 9 vacuum biopsies were not possible (3 times space problems due to obesity, 2 times too strong compression, 3 times impaired access from medially, 2 times impaired access due to a metal bar). Problems due to too strong compression were recognised by repeat MR without compression. During the procedure problems leading to an uncertain result occurred in eight vacuum biopsies, two related to the procedure: one limited access, and one strong post-biopsy enhancement. Improvements after phase-I study concerned removal of the metal bar, development of an improved medial access, of a profile imitating the biopsy gun, optimisation of compression plates and improved software support. The partners agreed that the improvements answered all important technical problems.

Biopsy, Needle↗
PubMed2002

[Change in process management by implementing RIS, PACS and flat-panel detectors].

Implementation of radiological information systems (RIS) and picture archiving and communicating systems (PACS) results in significant changes of workflow in a radiological department. Additional connection with flat-panel detectors leads to a shortening of the work process. RIS and PACS implementation alone reduces the complete workflow by 21-80%. With flatpanel technology the image production process is further shortened by 25-30%. The workflow-steps are changed from original 17-12 with the implementation of RIS and PACS and to 5 with the integrated use of flatpanels. This clearly recognizable advantages in the workflow need an according financial investment. Several studies could show that the capitalisation-factor calculated over eight years is positive, with a gain range between 5-25%. Whether the additional implementation of flatpanel detectors results also in a positive capitalisation over the years, cannot be estimated exactly, at the moment, because the experiences are too short. Particularly critical are the interfaces, which needs a constant quality control. Our flatpanel detector-system is fixed, special images--as we have them in about 3-5% of all cases--need still conventional filmscreen or phosphorplate-systems. Full-spine and long-leg examinations cannot be performed with sufficient exactness. Without any questions implementation of integrated RIS, PACS and flatpanel detector-system needs excellent training of the employees, because of the changes in workflow etc. The main profits of such an integrated implementation are an increase in quality in image and report datas, easier handling--there are almost no more cassettes necessary--and excessive shortening of workflow.

Austria↗
PubMed2002

Application of a multi-laser tunable diode laser absorption spectrometer for atmospheric trace gas measurements at sub-ppbv levels.

We describe the application of a three-laser tunable diode laser absorption spectrometer (TDLAS), called 'tracer in-situ TDLAS for atmospheric research' (TRISTAR), to measure nitrogen dioxide (NO2), formaldehyde (HCHO) and hydrogen peroxide (H2O2), during an intensive measurement campaign on Mt. Cimone (44 degrees 11'N, 10 degrees 42'E, 2165 m asl), Northern Appenines, Italy in June 2000 as part of the EU-project 'mineral dust and tropospheric chemistry' (MINATROC). The TRISTAR instrument was a major component of an instrument package, provided by the Max-Planck-Insitut für Chemie, to investigate free tropospheric gas-phase chemistry over the Appenines. Here we discuss the optical, electronic, gas flow, and calibration setup of the TDLAS used during the campaign. We characterized extensively the instrument's performance during a preparatory phase in the laboratory and compared the laboratory results to the in-field results. Consistency checks with additional trace gas measurements obtained during the campaign create high confidence in the measured concentrations. Correlations between different trace gas species, along with other evaluation tools, allow a full chemical characterization of air masses to meet the goals of the campaign.

Formaldehyde↗
PubMed2002

The perspective effect of wide-angle lenses in laparoscopes.

PURPOSE: To evaluate the effect of perspective distortion of wide-angle lenses in laparoscopes on hand-eye coordination during endoscopic manipulation. METHODS: Sixteen subjects repeatedly performed a standardized positioning task in a pelvi-trainer under two conditions. The subjects had no prior experience with endoscopic manipulation. In one condition, a wide-angle lens with considerable perspective distortion was used; in the other, a telephoto lens without perspective distortion was used. Task time and number of errors were measured. RESULTS: Task time and the number of errors did not significantly increase in the condition with a wide-angle lens. CONCLUSIONS: The perspective effect did not influence task performance in endoscopic manipulation in this experiment. Subjects indicated that they even preferred the wide-angle lens because its extreme perspective improved their perception of depth.

Adult↗
PubMed2002

R-curve behavior of dental ceramic materials.

Some technical ceramics exhibit the R-curve effect, i.e., an increasing fracture resistance with crack extension which is a desirable material property because more energy is necessary to propagate a microscopic crack. The objective of this study was to prove whether dental ceramic materials exhibit R-curve behavior. Nine dental ceramics were examined by the indentation-strength method. It was found that all of the tested ceramic materials exhibit a rising R-curve with crack extension. The R-curve behavior was more pronounced for the high-strength materials In-Ceram Alumina, monolithic alumina, and especially Empress 2. We conclude from our results that the mechanical behavior of a dental ceramic material can be judged more comprehensively, if the R-curve of the respective material is known.

Algorithms↗
PubMed2002

[Development of an optical 3-D position measuring system for simultaneous detection of 6 degrees of freedom].

A few years ago it became possible to carry out complicated surgical procedures in humans with the required precision by combining medical imaging (MRI, CT) with minimally invasive surgery. The confined space within these imaging systems and the resulting inaccuracies associated with the manual use of instruments increasingly make necessary the help of aids ranging from positioning systems to robotic devices, which themselves must be position controlled. A position sensor has been developed for a medical robotic system allowing the image-controlled insertion of injection needles and the simultaneous administration of different drugs. The 3D position coordinates are determined by a noncontact optical principle, which also enables simultaneous determination of all 6 basic degrees of freedom of the robotic system (3 translational, 3 rotational). On the basis of an area image sensor and the measurement of a geometrically defined structure in the path of the rays between sensor and light source, the position coordinates are calculated almost real time. Special emphasis was placed on designing the sensor system to cover a sufficiently large workspace to enable it to cover the entire intervention area. The sensor described herein determines the position coordinates in a volume of 10 x 10 x 10 cm at a resolution of up to 1 mm for translations and 1 degree for rotations.

Equipment Design↗
PubMed2002

ROBITOM-robot for biopsy and therapy of the mamma.

MR-Mammography reaches a high sensitivity in detecting breast carcinomas of 3 mm in size at least. In cooperation with the Institute of Diagnostic and Interventional Radiology of the Friedrich-Schiller-University of Jena, a manipulator has been developed by the IMB, which combines the advantages of MRM imaging with a minimal invasive biopsy and a possible subsequent therapy. Referring to this ROBITOM I was introduced in November 1999 as worldwide first, precise operating manipulator system in the ISO center of a closed MR, at RSNA in Chicago. Clinical trials started at 22. November 2000. The experiences and results of these tests were brought into the following prototype ROBITOM II, that is currently developed at the IMB. The completion of this Prototype is planned at the end of 2002.

Biopsy↗