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Träfflista för sökning "WFRF:(Schneider S) srt2:(1995-1999)"

Sökning: WFRF:(Schneider S) > (1995-1999)

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  • Andrés, E. C., et al. (författare)
  • The AMANDA neutrino telescope
  • 1999
  • Ingår i: Nuclear physics B, Proceedings supplements. - 0920-5632 .- 1873-3832. ; 77:1-3, s. 474-485
  • Tidskriftsartikel (refereegranskat)abstract
    • With an effective telescope area of order 104 m2 for TeV neutrinos, a threshold near ∼50 GeV and a pointing accuracy of 2.5 degrees per muon track, the AMANDA detector represents the first of a new generation of high energy neutrino telescopes, reaching a scale envisaged over 25 years ago. We describe early results on the calibration of natural deep ice as a particle detector as well as on AMANDA's performance as a neutrino telescope.
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4.
  • Andres, E., et al. (författare)
  • AMANDA : Status, results and future
  • 1999
  • Ingår i: Proceedings, 8th International Workshop, Venice, Italy, February 23-26, 1999. Vol. 1, 2. ; , s. 63-79
  • Konferensbidrag (refereegranskat)abstract
    • We review the status of the AMANDA neutrino telescope. We present resultsobtained from the four-string prototype array AMANDA-B4 and describe themethods of track reconstruction and neutrino event separation. We give also firstresults of the analysis of the 10-string detector AMANDA-B10, in particular onatmospheric neutrinos and the search for magnetic monopoles. We sketch thefuture schedule on the way to a cube kilometer telescope at the South Pole,ICECUBE.
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5.
  • Bay, R. C., et al. (författare)
  • The AMANDA neutrino telescope and the indirect search for dark matter : AMANDA Colaboration
  • 1998
  • Ingår i: Physics reports. - : Elsevier. - 0370-1573 .- 1873-6270. ; 307:1-4, s. 243-252
  • Tidskriftsartikel (refereegranskat)abstract
    • With an effective telescope area of order 104m2, a threshold of ~50GeV and a pointing accuracy of 2.5°, the AMANDA detector represents the first of a new generation of high energy neutrino telescopes, reaching a scale envisaged over 25 years ago. We describe its performance, focussing on the capability to detect halo dark matter particles via their annihilation into neutrinos.
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  • Miller, T. C., et al. (författare)
  • Particle astrophysics in antarctica
  • 1996
  • Ingår i: International School of Cosmic Ray Astrophysics: 10th Course: Toward the Millennium in Astrophysics: Problems and Prospects 16-26 Jun 1996. Erice, Italy. ; , s. 157-166
  • Konferensbidrag (refereegranskat)
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  • Wischnewski, R., et al. (författare)
  • The AMANDA neutrino detector
  • 1999
  • Ingår i: Nuclear physics B, Proceedings supplements. - : Elsevier. - 0920-5632 .- 1873-3832. ; 75:1-2, s. 412-414
  • Tidskriftsartikel (refereegranskat)abstract
    • The first stage of the AMANDA High Energy Neutrino Detector at the South Pole, the 302 PMT array AMANDA-B with an expected effective area for TeV neutrinos of ∼ 104 m2, has been taking data since 1997. Progress with calibration, investigation of ice properties, as well as muon and neutrino data analysis are described. The next stage 20-string detector AMANDA-II with ∼800 PMTs will be completed in spring 2000.
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10.
  • Andrés, E., et al. (författare)
  • Status of the AMANDA experiment
  • 1999
  • Ingår i: Nuclear physics B, Proceedings supplements. - : Elsevier. - 0920-5632 .- 1873-3832. ; 70:1-3, s. 448-452
  • Tidskriftsartikel (refereegranskat)abstract
    • The AMANDA high energy neutrino telescope has successfully been increased in size from four detector strings to ten detector strings during the 1996/1997 season. The first upward going muon-neutrino candidates have been reconstructed from the 1996 year's four-string data. Three new detector strings will be deployed during 1997/1998 to 2350 metres depth.
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11.
  • Askebjer, P., et al. (författare)
  • AMANDA : status report from the 1993-94 campaign and optical properties of the South Pole ice
  • 1995
  • Ingår i: Nuclear physics B, Proceedings supplements. - : Elsevier. - 0920-5632 .- 1873-3832. ; 38:1-3, s. 287-292
  • Tidskriftsartikel (refereegranskat)abstract
    • We report the first results of the AMANDA detector. During the antarctic summer 1993-94 four strings were deployed between 0.8 an 1 km depth, each equipped with 20 photomultiplier tubes (PMTs). A laser source was used to investigate the optical properties of the ice in situ. We find that the ice is intrinsically extremely transparent. The measured absorption length is 59 ± 3 m, i.e. comparable with the quality of the ultra-pure water used in the IMB and Kamiokande proton-decay and neutrino experiments [1,2] and more than two times longer than the best value reported for laboratory ice [3]. Due to a residual density of air bubbles at these depths, the motion of photons in the medium is randomized. For spherical, smooth bubbles we find that, at 1 km depth, the average distance between collisions is about 25 cm. The measured inverse scattering length on bubbles decreases linearly with increasing depth in the volume of ice investigated. © 1995 Elsevier Science B.V. All rights reserved.
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12.
  • Askebjer, P., et al. (författare)
  • Optical properties of deep ice at the South Pole : Absorption
  • 1997
  • Ingår i: Applied Optics. - : Optical Society of America. - 0003-6935 .- 1539-4522. ; 36:18, s. 4168-4180
  • Tidskriftsartikel (refereegranskat)abstract
    • We discuss recent measurements of the wavelength-dependent absorption coefficients in deep South Pole ice. The method uses transit-time distributions of pulses from a variable-frequency laser sent between emitters and receivers embedded in the ice. At depths of 800-1000 m scattering is dominated by residual air bubbles, whereas absorption occurs both in ice itself and in insoluble impurities. The absorption coefficient increases approximately exponentially with wavelength in the measured interval 410-610 nm. At the shortest wavelength our value is approximately a factor 20 below previous values obtained for laboratory ice and lake ice; with increasing wavelength the discrepancy with previous measurements decreases. At ∼415 to ∼500 nm the experimental uncertainties are small enough for us to resolve an extrinsic contribution to absorption in ice: submicrometer dust particles contribute by an amount that increases with depth and corresponds well with the expected increase seen near the Last Glacial Maximum in Vostok and Dome C ice cores. The laser pulse method allows remote mapping of gross structure in dust concentration as a function of depth in glacial ice.
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  • Askebjer, P., et al. (författare)
  • Optical properties of the South Pole ice at depths between 0.8 and 1 kilometer
  • 1995
  • Ingår i: Science. - 0036-8075 .- 1095-9203. ; 267:5201, s. 1147-1150
  • Tidskriftsartikel (refereegranskat)abstract
    • The optical properties of the ice at the geographical South Pole have been investigated at depths between 0.8 and 1 kilometer. The absorption and scattering lengths of visible light (∼515 nanometers) have been measured in situ with the use of the laser calibration setup of the Antarctic Muon and Neutrino Detector Array (AMANDA) neutrino detector. The ice is intrinsically extremely transparent. The measured absorption length is 59 ± 3 meters, comparable with the quality of the ultrapure water used in the Irvine-Michigan-Brookhaven and Kamiokande proton-decay and neutrino experiments and more than twice as long as the best value reported for laboratory ice. Because of a residual density of air bubbles at these depths, the trajectories of photons in the medium are randomized. If the bubbles are assumed to be smooth and spherical, the average distance between collisions at a depth of 1 kilometer is about 25 centimeters. The measured inverse scattering length on bubbles decreases linearly with increasing depth in the volume of ice investigated.
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14.
  • Askebjer, P., et al. (författare)
  • UV and optical light transmission properties in deep ice at the South Pole
  • 1997
  • Ingår i: Geophysical Research Letters. - : American Geophysical Union (AGU). - 0094-8276 .- 1944-8007. ; 24:11, s. 1355-1358
  • Tidskriftsartikel (refereegranskat)abstract
    • Both absorption and scattering of light at wavelengths 410 to 610 nanometers were measured in the South Pole ice at depths 0.8 to 1 kilometer with the laser calibration system of the Antarctic Muon And Neutrino Detector Array (AMANDA). At the shortest wavelengths the absorption lengths exceeded 200 meters - an order of magnitude longer than has been reported for laboratory ice. The absorption shows a strong wavelength dependence while the scattering length is found to be independent of the wavelength, consistent with the hypothesis of a residual density of air bubbles in the ice. The observed linear decrease of the inverse scattering length with depth is compatible with an earlier measurement by the AMANDA collaboration (at ∼515 nanometers).
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15.
  • Bergstrom, L., et al. (författare)
  • The AMANDA experiment : Status and prospects for indirect dark matter detection
  • 1996
  • Ingår i: The identification of dark matter. Proceedings, 1st International Workshop, Sheffield, UK, September 8-12, 1996. ; , s. 521-528
  • Konferensbidrag (refereegranskat)abstract
    • At the AMANDA South Pole site, four new holes were drilled to depths 2050m to 2180 m and instrumented with 86 photomultipliers (PMTs) at depths1520-2000 m. Of these PMTs 79 are working, with 4-ns timing resolutionand noise rates 300 to 600 Hz. Various diagnostic devices were deployedand are working. An observed factor 60 increase in scattering length anda sharpening of the distribution of arrival times of laser pulses relative tomeasurements at 800-1000 m showed that bubbles are absent below 1500 m.Absorption lengths are 100 to 150 m at wavelengths in the blue and UV to337 nm. Muon coincidences are seen between the SPASE air shower arrayand the AMANDA PMTs at 800-1000 m and 1500-1900 m. The muon trackrate is 30 Hz for 8-fold triggers and 10 Hz for 10-fold triggers. The presentarray is the nucleus for a future expanded array. The potential of AMANDAfor SUSY dark matter search through the detection of high-energy neutrinosfrom the centre of the Sun or Earth is discussed.
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  • Hulth, P. O., et al. (författare)
  • The AMANDA experiment
  • 1996
  • Ingår i: Neutrino '96. Proceedings, 17th International Conference on Neutrino Physics and Astrophysics, Helsinki, Finland, June 13-19, 1996. ; , s. 518-523
  • Konferensbidrag (refereegranskat)abstract
    • At the AMANDA South Pole site, four new holes were drilled to depths 2050 m to 2180 m and instrumented with 86 photomultipliers (PMTs) at depths 1520-2000 m. Of these PMTs 79 are working, with 4-ns timing resolution and noise rates 300 to 600 Hz. Various diagnostic devices were deployed and are working. An observed factor 60 increase in scattering length and a sharpening of the distribution of arrival times of laser pulses relative to measurements at 800-1000 m showed that bubbles are absent below 1500 m. Absorption lengths are 100 to 150 m at wavelengths in the blue and UV to 337 nm. Muon coincidences are seen between the SPASE air shower array and the AMANDA PMTs at 800-1000 m and 1500-1900 m. The muon track rate is 30 Hz for 8-fold triggers and 10 Hz for 10-fold triggers. The present array is the nucleus for a future expanded array.
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18.
  • Belletti, S., et al. (författare)
  • Quality assurance in radiotherapy: the importance of medical physics staffing levels. Recommendations from an ESTRO/EFOMP joint task group
  • 1996
  • Ingår i: Radiotherapy and Oncology. - 1879-0887. ; 41:9, s. 89-94
  • Tidskriftsartikel (refereegranskat)abstract
    • The safe application of ionising radiation for diagnosis and therapy requires a high level of knowledge of the underlying processes and of quality assurance. Sophisticated modern equipment can be used effectively for complicated diagnostic and therapeutic techniques only with adequate physics support. In the light of recent analyses and recommendations by national and international societies a joint working group of representatives from ESTRO (European Society for Therapeutic Radiology and Oncology) and from EFOMP (European Federation of Organisations for Medical Physics) was set up to assess the necessary staffing levels for physics support to radiotherapy. The method used to assess the staffing levels, the resulting recommendations and examples of their practical application are described.
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  • Koch, S, et al. (författare)
  • Controlled diagnosis-oriented enhancement of automatically segmented radiographs in dentistry
  • 1998
  • Ingår i: COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE. - : ELSEVIER SCI IRELAND LTD. - 0169-2607. ; 57:1-2, s. 125-131
  • Tidskriftsartikel (refereegranskat)abstract
    • A method for controlled diagnosis-oriented enhancement of selected regions of interest in intraoral radiographs is presented. Image enhancement is accomplished by adaptive non-linear grey scale transformation depending on the result of objective quality m
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  • Koch, S, et al. (författare)
  • IT-based evaluation and automatic improvement of the quality of intraoral radiographs
  • 1995
  • Ingår i: COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE. - : ELSEVIER SCI PUBL IRELAND LTD. - 0169-2607. ; 46:1, s. 41-50
  • Tidskriftsartikel (refereegranskat)abstract
    • The quality of intraoral radiographs made in dental practices is too often not adequate for diagnostic purposes. This necessitates standardized measures for the quality of intraoral radiographs and controlled techniques for automatic image improvement. Fo
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  • Seipel, S, et al. (författare)
  • Oral implant treatment planning in a virtual reality environment
  • 1998
  • Ingår i: COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE. - : ELSEVIER SCI IRELAND LTD. - 0169-2607. ; 57:1-2, s. 95-103
  • Tidskriftsartikel (refereegranskat)abstract
    • A system for three-dimensional oral implant treatment planning is presented. Virtual reality technologies are used in order to improve the human image interpretation and planning performance. The methods described are based on computer tomography (CT) dat
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  • Seipel, S., Wagner, I-V., Koch, S., Schneider, W. (författare)
  • A Virtual Reality Environment for Enhanced Oral Implantology
  • 1995
  • Ingår i: Proc. 8th World Congress on Medical Informatics. - : North-Holland, Amsterdam London New York. ; , s. 1710-
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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  • Dobritzsch, Doreen, 1972-, et al. (författare)
  • High resolution crystal structure of pyruvate decarboxylase from Zymomonas mobilis : Implications for substrate activation in pyruvate decarboxylases
  • 1998
  • Ingår i: Journal of Biological Chemistry. - : Elsevier BV. - 0021-9258 .- 1083-351X. ; 273:32, s. 20196-20204
  • Tidskriftsartikel (refereegranskat)abstract
    • The crystal structure of tetrameric pyruvate decarboxylase from Zymomonas mobilis has been determined at 1.9 A resolution and refined to a crystallographic R-factor of 16.2% and Rfree of 19.7%. The subunit consists of three domains, all of the alpha/beta type. Two of the subunits form a tight dimer with an extensive interface area. The thiamin diphosphate binding site is located at the subunit-subunit interface, and the cofactor, bound in the V conformation, interacts with residues from the N-terminal domain of one subunit and the C-terminal domain of the second subunit. The 2-fold symmetry generates the second thiamin diphosphate binding site in the dimer. Two of the dimers form a tightly packed tetramer with pseudo 222 symmetry. The interface area between the dimers is much larger in pyruvate decarboxylase from Z. mobilis than in the yeast enzyme, and structural differences in these parts result in a completely different packing of the subunits in the two enzymes. In contrast to other pyruvate decarboxylases, the enzyme from Z. mobilis is not subject to allosteric activation by the substrate. The tight packing of the dimers in the tetramer prevents large rearrangements in the quaternary structure as seen in the yeast enzyme and locks the enzyme in an activated conformation. The architecture of the cofactor binding site and the active site is similar in the two enzymes. However, the x-ray analysis reveals subtle but significant structural differences in the active site that might be responsible for variations in the biochemical properties in these enzymes.
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  • Lu, G, et al. (författare)
  • Novel tetramer assembly of pyruvate decarboxylase from brewer's yeast observed in a new crystal form
  • 1997
  • Ingår i: FEBS Letters. - 0014-5793 .- 1873-3468. ; 403:3, s. 249-253
  • Tidskriftsartikel (refereegranskat)abstract
    • A new crystal form of thiamine diphosphate dependent pyruvate decarboxylase from Saccharomyces cerevisiae has been obtained in the presence of the activator pyruvamide. The crystallographic structure analysis reveals differences in the domain packing in the enzyme subunit and a novel assembly of the subunits in the tetramer, when compared to the structure of native PDC. The orientation of the beta domains in the subunit differs by a 6.3 degrees and 8.3 degrees rotation, respectively, whereas the subunit-subunit interface in the dimer, formed by the alpha and gamma domains, is essentially maintained. In the tetramer, one of the dimers rotates relative to the second dimer by approximately 30 degrees creating a new dimer-dimer interface.
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  • Seipel, Stefan, et al. (författare)
  • Oral Implant Treatment Planning in a Virtual Reality Environment
  • 1998
  • Ingår i: Computer Methods and Programs in Biomedicine. - 0169-2607 .- 1872-7565. ; 57:1-2, s. 95-103
  • Tidskriftsartikel (refereegranskat)abstract
    • A system for three-dimensional oral implant treatment planning is presented. Virtual reality technologies are used in order to improve the human image interpretation and planning performance. The methods described are based on computer tomography (CT) data of the mandible and of the maxilla. A novel approach to volume rendering and voxel based modelling of implants is introduced which allows interactive three-dimensional manipulation of the anatomic model and real-time manipulation of virtual implants. A spline-based reconstruction method is described to assess the implant site in a clinically oriented view with regard to bone structures and angulation. Two parameters are deduced which represent the bone properties at the surface of implants. While an implant is navigated with six degrees of freedom, these parameters are acoustically rendered which is a novel approach to exploration of spatial bone properties in a CT data set.
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50.
  • Wagner I-V., Schneider W., Balconi D., Han F., Koch S (författare)
  • ALL in ONE - das europäische Projekt ORQUEST
  • 1998
  • Ingår i: Computer in der Zahnarztpraxis und Dentallabor” Das EDV-Jahrbuch ‘98. - : Hüthig-Verlag, Heidelberg. ; , s. 80-83
  • Bokkapitel (refereegranskat)
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