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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 2779-2785 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The pseudodielectric function spectra 〈ε〉 of wurtzite GaN, AlGaN, and GaN/AlGaN heterostructures were determined for photon energies ranging from 2 to 5 eV, using variable angle spectroscopic ellipsometry (SE). Samples were grown by low-pressure metalorganic chemical vapor deposition on c-plane sapphire substrates. The experimental 〈ε〉 spectra were analyzed using a multilayer approach, describing the dielectric functions of the individual layers by a parametric oscillator model. In this way, parametric dielectric function spectra of GaN and AlxGa1−xN (x≤0.16) were derived, as well as the composition dependence of the AlxGa1−xN band gap energy. The SE band gap data were found to be consistent with a bowing parameter close to 1 eV. Finally, the GaN and AlxGa1−xN parametric dielectric functions were used to quantitatively analyze the pseudodielectric function spectrum of GaN/AlGaN modulation doped field effect transistor structures, demonstrating the potential of SE in combination with a multilayer parametric dielectric function model for nondestructive ex situ control of GaN/AlGaN device structures. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 2853-2856 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Resonant Raman scattering from AlxGa1−xN (x≤0.17) layers in (Al, Ga, In)N heterostructures has been studied using optical excitation at a photon energy of hνL=3.72 eV (333.61 nm). Tuning of the AlGaN band-gap energy, and thus of the resonance condition, was achieved by variation of the sample temperature. A pronounced outgoing resonance behavior was observed for first- and second-order Raman scattering by the AlGaN A1(LO) phonon, which allows a separation of the AlGaN LO phonon signal from the corresponding GaN phonon line even in the presence of much thicker surrounding GaN layers. The composition dependence of the AlxGa1−xN A1(LO) phonon mode was determined to ωLO(x)=734+356.8x−814.7x2 (cm−1) for the present excitation conditions (hνL=3.72 eV) and composition range (x≤0.17). The use of resonantly enhanced Raman scattering by the AlGaN A1(LO) phonon allowed us to assess nondestructively the composition of the AlGaN cladding layers in an (Al, Ga, In)N laser structure, even though the Raman spectrum recorded for nonresonant subband-gap excitation was completely dominated by scattering from the much thicker GaN layers in the structure. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 2448-2450 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Quaternary pseudomorphically strained GaInAsN films and double-quantum wells were grown by plasma assisted molecular-beam epitaxy on an InP substrate. The In content ranged from 53% to 70% while the N content was varied between 0% and 2.4%. A reduction of compressive strain and a low-energy shift of photoluminescence (PL) peak position was observed with increasing N concentration, accompanied by a reduction in PL peak intensity and increase in linewidth. The net effect of N incorporation on the GaInAsN band gap energy was calculated from the measured PL peak energies. The thus obtained composition dependent GaInAsN band gap energy was fitted using the band anticrossing model, yielding values for the interaction parameter CMN for high In-containing GaInAsN being only slightly smaller than that reported for low In-content GaInAsN on GaAs. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 2081-2083 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The bonding of nitrogen in low N-content AlxGa1−xAs1−yNy with x≤0.05 and y≤0.04 has been studied by Raman spectroscopy. Upon the addition of Al to GaAsN, additional vibrational modes are observed at around 450 cm−1, which is below the GaN-like longitudinal optical (LO) phonon mode centered at 470 cm−1. These modes are attributed to the formation of Al and N containing complexes with Al-to-N bonding. With increasing Al content the Al–N related modes gain intensity at the expense of the GaN-like mode, and they become the dominant N-related feature for an Al-content of 5% at a fixed N content of 1%. On the other hand, increasing the N content from 0% up to 4% at a constant Al concentration of 5% results first in the appearance and eventual saturation in intensity of the AlN-like modes, accompanied by a steep increase in intensity and eventual dominance of the GaN-like vibrational mode. Simultaneously the AlAs-like LO2 phonon mode shows a drastic decrease in intensity for N contents exceeding 2%. All these observations strongly indicate that there is a preferential formation of Al(Single Bond)N bonds in low N- and Al-content AlGaAsN, which is in direct contrast to GaInAsN, where even after thermal annealing the GaN-like mode remains dominant in the Raman spectrum compared to the InN-like modes. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Mechanics of composite materials 36 (2000), S. 429-438 
    ISSN: 1573-8922
    Keywords: liquid crystal polymers ; tribology ; crash ; thermoforming ; resin transfer molding ; aluminum foam ; melt impregnation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This article describes several European cooperative research examples in the field of polymer composite materials. The projects, which were carried out in collaboration between industrial and academic partners, were all supported by the European Union. They deal, e.g., with (a) the manufacturing and crash testing of thermoplastic composite structures, (b) the production of thermoplastic composite preforms, and (c) the energy absorption behavior of aluminum foams, and other interesting subjects.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1435-1420
    Keywords: Key words Intensive care medicine – personnel satisfaction –¶patient and family satisfaction – opinion formation ; Schlüsselwörter Intensivmedizin – Personalzufriedenheit – Patienten- und Angehörigenzufriedenheit – Meinungsbildung
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Intensivmedizinische Maßnahmen werden von den Patienten, den Angehörigen und dem Personal unterschiedlich bewertet. Ein mangelndes Verständnis für die Intensivtherapie kann zu einer negativen Einstellung zur Intensivmedizin führen, deren Bild in der Öffentlichkeit prägen und die Identifikation der Mitarbeiter mit der Intensivmedizin stören.¶   Zur Objektivierung führten wir auf unserer Intensivstation eine Befragung zur medizinischen Technik, zur räumlichen Umgebung, zu allgemeinen medizinischen Fragen und zum Ausmaß der intensivmedizinischen Therapie bei 40 Mitarbeitern (11 Ärzte, 23 Pflegekräfte, 6 Beschäftigte des Hilfspersonals) durch. Die Dauer der Beschäftigung auf der Intensivstation reichte von 1–240 Monaten (Median 18 M.), das Alter lag zwischen 21 und 53 Jahren (Median 30 J). 73% der Befragten hielten die Intensivmedizin in der jetzigen Form für sinnvoll, bei den Ärzten waren dies 100%, beim Pflegepersonal jedoch nur 57%. Nur 9% der Ärzte erachteten die Geräte als beängstigend für den Patienten gegenüber 61% beim Pflegepersonal. Die Geräuschkulisse wurde von 65% des Pflegepersonals als stark belästigend empfunden, 45% der Ärzte sahen dies genauso. Nur 22% des Pflegepersonals glaubten, dass sich die Patienten auf der Intensivstation wohl und beschützt fühlten, 48% gingen von unglücklich bis sehr unglücklich aus. 46% der Ärzte waren der Ansicht, dass sich die Patienten wohl fühlten. 100% des Pflegepersonals waren der Meinung, dass bei den verstorbenen Patienten die organersetzende Therapie zu lange fortgeführt würde, wohingegen nur 45% der Assistenzärzte dieser Meinung waren.¶   Vom ärztlichen Personal wurden die intensivmedizinischen Maßnahmen als sinnvoll, für den Patienten weniger belastend und effektiver eingestuft als durch das Pflegepersonal. Die Gruppe des Pflegepersonals vertrat in vielen Fällen eine konträre und negativistische Meinung, die ihre Ursache möglicherweise in Unsicherheit, mangelnder Information und in fehlenden Erfolgserlebnissen hat. Die kompetente Aufklärung und Information über Krankheit und Prognose, die wiederholte Besprechung diagnostischer und therapeutischer Maßnahmen innerhalb des Intensiv-Teams sind daher neben dem Patientenoutcome die entscheidenden Faktoren der Meinungsbildung zur Intensivmedizin.
    Notes: Summary The measures taken in intensive care medicine are rated differently by the patients, their family, and personnel. A lack of understanding for intensive care therapy can lead to a negative attitude towards intensive care medicine, which in turn makes an impression on public opinion, and disturbs the reputation of the co-workers in intensive care medicine.¶   To form an objective view, we carried out a survey of 40 co-workers (11 physicians, 23 from the nursing staff, and 6 ancillary personnel) regarding the medical technology, the environment in the unit, general medical questions, and the extent of intensive care therapy. The length of employment in the intensive care unit ranged from 1–240 months (median 18 months), the ages ranged from 21 to 53 years (median 30 years). Of those questioned 73% found intensive care medicine in its current form to be purposeful: 100% of the physicians and only 57% of the nursing staff were of this opinion. Only 9% of the physicians believed the equipment to be fear-inducing for the patients; in contrast, 61% of the nursing staff believed this to be true. The noise level was rated as very disturbing by 65% of the nursing staff and 45% of the physicians. Only 22% of the nursing staff believed that the patients felt comfortable and protected on the intensive care unit; 48% felt that they were unhappy or even miserable. Of the physicians 46% believed that the patients were comfortable. Of the nursing staff 100% were of the opinion that for the deceased patients, organ substitution therapy had continued too long. On the other hand, only 45% of the residents shared this opinion.¶   The medical staff rated the intensive care measures as purposeful, less disturbing for the patients and more effective than did the nursing staff. In many cases, the nursing staff as a group exhibited a contrary and negative opinion. This could possibly be caused by insecurity, lack of information and lack of successful experiences. Next to patient outcome, the competent explanation and information regarding the disease and prognosis and the recurrent communication within the intensive care team, with respect to diagnostic and therapeutic measures are the deciding factors in the opinion formation regarding intensive care medicine.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1434-3916
    Keywords: Key words Shoulder ; Calcifying tendinitis ; Shock wave ; MRI ; Prediction parameters ; Clinical outcome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This prospective study examined 62 patients (65 shoulders) with chronic courses of calcifying tendinitis of the shoulder before and after low-energy extracorporeal shockwave application (ESWA) in order to identify variables associated with the outcome of this treatment. Before ESWA, radiographs and contrast-enhanced magnetic resonance imaging (MRI) of the affected shoulders were obtained in order to document the size and morphology of the calcifications and the contrast media reactions in areas of interest (deposit, synovia, bursae), respectively. In addition, a clinical evaluation was performed. After ESWA (mean follow-up 18.2 months), clinical evaluations of all 65 shoulders revealed an increase in the Constant score from 44% to 78% (p 〈 0.0001). While size (p = 0.61) and morphology (p = 0.7) of the deposits before ESWA were not associated with the clinical outcome, negative contrast reactions around the deposits (p = 0.0001), synovia (p = 0.0049) and bursae (p 〈 0.01) were associated with improved clinical outcomes. After the total study group was divided into two groups, one with Constant scores ≥ 75% (n = 43) and the other with scores 〈 75% (n = 22), the positive predictive value (ppv), specificity (sp) and sensitivity (se) were determined for the negative reaction around the deposit (ppv: 0.94; sp: 0.95; se: 0.38), synovia (ppv: 0.84; sp: 0.82; se: 0.49) and bursae (ppv: 0.86; sp: 0.86; se: 0.44). In 5 cases (7.7%), surgery of the affected shoulder during the follow-up period was performed. No major side-effects were seen in the study group. In conclusion, our results suggest that in patients with chronic calcifying tendinitis, the absence of contrast enhancement, especially around the deposit, is a strong predictive parameter of a positive clinical outcome of ESWA.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Der Ophthalmologe 97 (2000), S. 870-873 
    ISSN: 1433-0423
    Keywords: Schlüsselwörter Tränenwegsstenose ; Dakryoendoskopie ; Dakryozystorhinostomie ; Laserdakryoplastik ; Mikrodrill-Dacryoplastik ; Keywords Lacrimal stenosis ; Dacryoendoscopy ; Dacryocystorhinostomy ; Laser dacryoplasty ; Microdrill- dacryoplasty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract Purpose. Operative procedures to manage lacrimal outflow obstruction were made traditionally without endoscopic assistance. For dacryoendoscopy we previously used a 0.5-mm endoscope with a special wash cannula. We now use the microendoscope Vitroptic T for dacryoendoscopy and for endoscopically controlled surgery with a microdrill. Methods. In an attempt to perform microinvasive lacrimal surgery we use a 1.1-mm endoscope (Vitroptik T) with a wash cannula, a channel for the microoptic and a channel for a microdrill. We report on our initial experiences and on the results of eight patients with stenosis of the lacrimal outflow system who were treated with an endoscopic microdrill and silicone tubing. One patient had lacrimal stenosis after external dacryocystorhinostomy (DCR), and seven patients showed punctual stenosis in the nasolacrimal duct. Results. Using the dacryoendoscope (Vitroptic T) we were able to visualize pathologic changes of the lacrimal outflow system. Intraoperative situations during dacryoendoscopy are demonstrated. The Vitroptic T allows dacryoendoscopy and endoscopically controlled surgery of the lacrimal drainage system. Three months after surgery in six patients (75%) the lacrimal outflow system was patent with the silicone tube in place, and these patients had no epiphora. The patient with re-stenosis after external DCR showed patency. Conclusions. Dacryoendoscopy and endoscopic controlled surgery of the lacrimal drainage system enables atraumatic and minimally invasive surgery. The Vitroptik T with the microdrill allows endoscopically controlled microsurgery. Possible indications for the microdrill are punctual stenosis and re-stenosis after external DCR.
    Notes: Zusammenfassung Hintergrund. Die operative Versorgung der Tränenwege erfolgte traditionell ohne endoskopische Hilfsmittel. Für die Dakryoendoskopie benutzten wir früher eine Zwei-Wege-Sonde mit einem Kanal für das Miniendoskop und einem Spülkanal. Beschrieben wird der Einsatz einer Drei-Wege-Sonde (Vitroptik T®) mit einem Kanal für die Mikrooptik, einem Spülkanal und einem Arbeitskanal für den Mikrobohrer. Methoden. Für die minimal invasive Tränenwegchirurgie setzen wir ein 1,1 mm Drei-Wege-Endoskop (Vitroptik T®) mit einem zusätzlichen Kanal für einen Mikrobohrer ein. Wir berichten über unsere ersten Erfahrungen und die Ergebnisse von 8 Patienten mit Tränenwegstenose, die wir mit dem endoskopischen Mikrobohrer und anschließender Intubation mit einem Silikonschläuchlein behandelten. Ein Patient zeigte eine Restenose nach externer Dakryozystorhinostomie (DCR), 7 Patienten hatten kurzstreckige Stenosen im Ductus nasolacrimalis. Ergebnisse. Die Dakryoendoskopie erlaubt neben der direkten Beurteilung der Schleimhautverhältnisse die Lokalisation von Stenosen und den Nachweis von Konkrementen. Mit dem 3-Kanal-Endoskop (Vitroptik T®) ist eine endoskopisch kontrollierte Chirurgie der ableitenden Tränenwege möglich. 3 Monate nach dem Eingriff zeigten 6 Patienten (75%) eine Durchgängigkeit der ableitenden Tränenwege bei liegendem Silikonschläuchlein. Diese Patienten hatten keine Epiphora mehr. Auch der Patient mit einer Restenose war symptomfrei. Schlussfolgerungen. Die Dakryoendoskopie und die endoskopisch kontrollierte Mikrochirurgie der ableitenden Tränenwege gewährleisten ein atraumatisches Vorgehen und eine minimal invasive Chirurgie. Das Endoskop Vitroptik T® mit dem Mikrobohrer erlaubt die Mikrochirurgie unter endoskopischer Sicht. Mögliche Indikationen für den Mikrobohrer stellen kurzstreckige Stenosen und Restenosen nach externer DCR dar.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 21 (2001), S. 363-367 
    ISSN: 1434-6036
    Keywords: PACS. 71.15.Ap Basis sets (plane-wave, APS, LCAO, etc.) and related methodology (scattering methods, ASA, linearized methods) – 71.20.-b Electron density of states and band structure of crystalline solids – 71.20.Be Transition metals and alloys – 78.70.Dm X-ray absorption spectra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The fine structure of the copper L3 edge in fcc Cu was simulated using a full potential linearised augmented plane wave method (WIEN97). The computations were based on a single cell-model by introducing a partial core hole and on a 2×2×1 super-cell-model with one full core hole. No difference between the single cell with a full core hole and the 16 atoms supercell with one core hole could be observed. Comparison with experimental spectra of two Cu specimens prepared by different methods showed that after removing the Cu2O contribution to the spectrum the best fit was obtained for half a core hole. This shows that the core hole in Cu metal is only partially screened by the valence electrons.
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  • 10
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract SHIPTRAP is an ion trap facility which is being set up to deliver very clean and cool beams of singly-charged recoil ions produced at the SHIP velocity filter at GSI Darmstadt. SHIPTRAP consists of a gas cell for stopping and thermalizing high-energy recoil ions from SHIP, a rf ion guide for extraction of the ions from the gas cell, a linear rf trap for accumulation and bunching of the ions, and a Penning trap for isobaric purification. The physics programme of the SHIPTRAP facility comprises mass spectrometry, nuclear spectroscopy, laser spectroscopy and chemistry of transeinsteinium elements.
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