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  • Electronic Resource  (13)
  • 1990-1994  (13)
  • 1930-1934
  • 1905-1909
  • 1994  (13)
  • 1
    Electronic Resource
    Electronic Resource
    Frankfurt EBIS development: Fundamental research and new applications : Proceedings of 5th international conference on ion sources (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1069-1071 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Fundamental questions of electron beam ion sources (EBIS) are studied using three different setups. Cryogenic classical EBIS: The limit of ion–ion cooling in EBIS devices operating near the space-charge neutralization limit has been studied experimentally. To investigate different degrees of compensation of the electron beam by highly charged ions, a hemispherical analyzer has been constructed including a novel deceleration optic for high resolution. Using its energy definition we tested different modes of ion transportation in our multipassage magnetic spectrometer, which can be operated chromatically as well as extremely dispersively: up to 200 passages could be obtained. EBIS without magnetic field: First results on ion production in the short trap at the very dense crossover of an electron beam (XEBIS) confined only inertially without the use of magnetic fields are presented. Normal conducting short EBIS: Using a normal conducting field of 0.8 T of 25-cm length an EBIS is under construction to study extremely short ion extraction of approximately 4 μs for single turn injection into a medical synchrotron for cancer therapy (MEDEBIS).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145065
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  • 2
    Electronic Resource
    Electronic Resource
    Liquid scintillation detectors for gamma and neutron diagnostic at TEXTOR and results of runaway and sawtooth oscillations (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2594-2598 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Time and energy resolved neutron and gamma measurements are performed at the TEXTOR tokamak with a fast liquid NE-213 scintillator. To distinguish between neutron and gamma (γ)-ray induced events, pulse shape discrimination is used. To suppress scattered radiation, the detector is installed in well-shielded collimators aligned radially or tangentially to the plasma current. Count rates up to 2–3×105 s−1 can be processed without considerable reduction of n/γ discrimination and without gain instability. To demonstrate the capability of this system, typical results are presented as obtained from plasmas in TEXTOR during sawtooth oscillations, runaway discharges, pellet injection, and neutral beam injection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144657
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  • 3
    Electronic Resource
    Electronic Resource
    Quantization error of slit-grid emittance measurement devices : Proceedings of 5th international conference on ion sources (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1462-1464 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Slit-grid emittance measurement devices usually do not scan the beam continously but in fixed linear (x) and angular (x') steps. Thus in an emittance measurement performed with a slit-grid system, the beam is represented by a number of phase space boxes with a constant area or volume determined by the linear and angular resolution. Considering the emittance as the area in the two-dimensional subspace (x,x') covered by the beam, the quantization error and its dependence on the resolution (linear and angular) as well as the influence of the beam parameters is discussed. Measuring the very low emittance of the high efficiency source (HIEFS) proved that the quantization error can be unacceptably high ((very-much-greater-than)100%). With an optimized measuring device, the normalized emittance came down from 10−1 to 3.6×10−3 π mm mrad. Finally, a typical misleading result of an emittance measurement, caused by the quantization error, is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144946
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  • 4
    Electronic Resource
    Electronic Resource
    Laser-cooling effects in few-ion clouds of Yb+ (1994)
    Springer
    Applied physics 59 (1994), S. 179-185 
    Details
    ISSN: 1432-0649
    Keywords: 32.80.Pj
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We report some laser-cooling effects in a few172Yb+ ions held in a Paul trap. Pronounced cloud-to-crystal phase transitions have been observed as discontinuities in the Yb+ fluorescence spectrum of the 369 nm cooling transition. The first reported two-dimensional images of Yb+ clouds with evidence of crystal structure have been recorded using a photon-counting position-sensitive detector. An ion temperature of 100 mK has been estimated from the size of a single ion image. Step-wise cooling of a re-heated, few-ion Yb+ cloud was also observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01081168
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  • 5
    Electronic Resource
    Electronic Resource
    Pleomorphic pineocytoma with extensive neuronal differentiation: report of two cases (1994)
    Springer
    Acta neuropathologica 88 (1994), S. 448-453 
    Details
    ISSN: 1432-0533
    Keywords: Key words Pineal parenchymal tumors ; Pineocytoma ; Pineoblastoma ; Central neurocytoma ; Neuronal differentiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Two pineal parenchymal tumors are presented, arising in a 54-year-old man and a 72-year-old woman; respectively. They showed isomorphic, cellular areas of small cells, often with characteristic pineocytomatous rosettes, and of medium-sized cells, as well as less cellular regions with highly pleomorphic, often ganglioid large cells. Immunohistochemistry disclosed extensive neuronal differentiation. There was intense positivity for neurofilament protein and microtubule-associated protein 2 in the pleomorphic areas and more variable expression in the isomorphic regions. Diffuse synaptophysin positivity was seen, accentuated along the borders of pleomorphic cells and in the rosettes, as well as diffuse interstitial and/or cytoplasmic expression of neuron-specific enolase, PGP 9.5 and tau. β-Tubulin III was detected in most cells and slight positivity was found in the rosettes. Expression of glial fibrillary acidic protein, however, was restricted to resident astrocytes and an interstitial network of processes. These neuronally differentiated pleomorphic pineocytomas underline the broad histomorphological spectrum of pineal parenchymal tumors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00389497
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  • 6
    Electronic Resource
    Electronic Resource
    Pleomorphic pineocytoma with extensive neuronal differentiation: report of two cases (1994)
    Springer
    Acta neuropathologica 88 (1994), S. 448-453 
    Details
    ISSN: 1432-0533
    Keywords: Pineal parenchymal tumors ; Pineocytoma ; Pineoblastoma ; Central neurocytoma ; Neuronal differentiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Two pineal parenchymal tumors are presented, arising in a 54-year-old man and a 72-year-old woman; respectively. They showed isomorphic, cellular areas of small cells, often with characteristic pineocytomatous rosettes, and of medium-sized cells, as well as less cellular regions with highly pleomorphic, often ganglioid large cells. Immunohistochemistry disclosed extensive neuronal differentiation. There was intense positivity for neurofilament protein and microtubule-associated protein 2 in the pleomorphic areas and more variable expression in the isomorphic regions. Diffuse synaptophysin positivity was seen, accentuated along the borders of pleomorphic cells and in the rosettes, as well as diffuse interstitial and/or cytoplasmic expression of neuron-specific enolase, PGP 9.5 and tau. β-Tubulin III was detected in most cells and slight positivity was found in the rosettes. Expression of glial fibrillary acidic protein, however, was restricted to resident astrocytes and an interstitial network of processes. These neuronally differentiated pleomorphic pineocytomas under-line the broad histomorphological spectrum of pineal parenchymal tumors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00389497
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  • 7
    Electronic Resource
    Electronic Resource
    Ultrasound-guided craniotomy for minimally invasive exposure of cerebral convexity lesions (1994)
    Springer
    Acta neurochirurgica 131 (1994), S. 270-273 
    Details
    ISSN: 0942-0940
    Keywords: Intraoperative ultrasound ; craniotomy ; cerebral convexity ; brain neoplasms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The authors describe a method of real-time ultrasound-guided craniotomy for an approach to cerebral convexity lesions. During surgery, a specially designed high frequency (7.5 MHz) sector probe with a thin (11 mm), extended tip is used to image the cerebral lesion through a single burr-hole. The distance between burr-hole and lesion and the direction of the target are then determined from the ultrasound images, and craniotomy is completed with the aid of these parameters. Errors in the preoperative planning of the approach, which might result in incorrect placement of the craniotomy, can easily be recognized and corrected at an early stage of the operation, before the craniotomy has been completed. This technique greatly improves the accuracy in placing craniotomy flaps. Since the risk of misplacing the craniotomy is virtually eliminated in lesions which are identifiable on ultrasound images, the technique allows the surgeon to keep the skull opening as limited as possible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01808626
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  • 8
    Electronic Resource
    Electronic Resource
    Three-dimensional spiral CT for neurosurgical planning (1994)
    Springer
    Neuroradiology 36 (1994), S. 435-439 
    Details
    ISSN: 1432-1920
    Keywords: Spiral CT ; Craniofacial surgery ; Contrast media ; 3D image processing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We carried out 22 examinations to determine the value of three-dimensional (3D) volumetric CT (spiral CT) for planning neurosurgical procedures. All examinations were carried out on a of the first generation spiral CT. A tube model was used to investigate the influence of different parameter settings. Bolus injection of nonionic contrast medium was used when vessels or strongly enhancing tumours were to be delineated. 3D reconstructions were carried out using the integrated 3D software of the scanner. We found a table feed of 3 mm/s with a slice thickness of 2 mm and an increment of 1 mm to be suitable for most purposes. For larger regions of interest a table feed of 5 mm was the maximum which could be used without blurring of the 3D images. Particular advantages of 3D reconstructed spiral scanning were seen in the planning of approaches to the lower clivus, acquired or congenital bony abnormalities and when the relationship between vessels, tumour and bone was important.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00593678
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  • 9
    Electronic Resource
    Electronic Resource
    Absorption heat of GHz sound in polycrystalline metal films detected by multiple-beam interferometry and second-sound emission (1994)
    Springer
    Journal of low temperature physics 94 (1994), S. 567-583 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In the GHz range, sound attenuation in polycrystalline films is dominated by elastic scattering at the grain boundaries. The attenuation by the much smaller absorption is hidden in the whole attenuation. We present a first attempt to detect the absorption. Sound-pulse experiments were done at low temperatures at frequencies of 8.8 GHz and 24 GHz in wedge-shaped Cu and Ag films using the method of multiple-beam interferometry with a lateral movable, highly collimated sound beam. The absorption heat is detected by recording the power of the second sound pulses emitted into the surrounding superfluid helium. The absorption coefficients can be obtained by fitting the measured interferograms to a proposed scattering model. They are many orders of magnitude lower than the measured attenuation coefficients, but are comparable with the predictions of Pippard.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00753828
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  • 10
    Electronic Resource
    Electronic Resource
    Social control and social contract in networking (1994)
    Springer
    Computer supported cooperative work 2 (1994), S. 89-108 
    Details
    ISSN: 1573-7551
    Keywords: TQM ; Communication ; Social Contract ; Empowerment ; Control ; Teams
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Networks can be understood as organizational control strategies. As an example, we present two case studies of team-based networking strategies associated with the Total Quality Management movement in the United States. TQM's implied social contract requires some form of power sharing. In practice TQM team organization can also become another form of labor intensification. Similarly, TQM appeals to democratic values by emphasizing participation, communication, cooperation and team work. Such claims can also serve to legitimize major organizational changes, some of which follow familiar Taylorist patterns. Two cases illustrate how the technical components of communications systems help redefine control systems in TQM-based work rerganization experiments. In the manufacturing setting, communications took the form of web-and-hub networks, centralizing off-site engineering control of production workers. In the design and engineering workplace, peer-to-peer communications implemented by self-managed teams reduced intellectual ‘slack time’. In both cases the communications systems provided means to intensify labor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00749285
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