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  • 1
    Keywords: OPTIMIZATION ; DISTRIBUTIONS ; RADIATION-THERAPY ; PENALTY
    Abstract: Common problems in inverse radiotherapy planning are localized dose insufficiencies like hot spots in organs at risk or cold spots inside targets. These are hard to correct since the optimization is based on global evaluations like maximum/minimum doses, equivalent uniform doses or dose-volume constraints for whole structures. In this work, we present a new approach to locally correct the dose of any given treatment plan. Once a treatment plan has been found that is acceptable in general but requires local corrections, these areas are marked by the planner. Then the system generates new plans that fulfil the local dose goals. Consequently, it is possible to interactively explore all plans between the locally corrected plans and the original treatment plan, allowing one to exactly adjust the degree of local correction and how the plan changes overall. Both the amount (in Gy) and the size of the local dose change can be navigated. The method is introduced formally as a new mathematical optimization setting, and is evaluated using a clinical example of a meningioma at the base of the skull. It was possible to eliminate a hot spot outside the target volume while controlling the dose changes to all other parts of the treatment plan. The proposed method has the potential to become the final standard step of inverse treatment planning.
    Type of Publication: Journal article published
    PubMed ID: 23442519
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  • 2
  • 3
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a technique for fabricating laterally patterned 〈111〉 and 〈100〉-oriented regions of CdTe on GaAs by metalorganic chemical vapor deposition. Patterning of the crystal orientation is important for quasi-phase-matched nonlinear optical frequency conversion in semiconductor waveguides. Scanning electron micrographs and x-ray diffraction analysis are used to confirm the presence of 〈111〉/〈100〉 grating structures. The CdTe layer is shown to be a suitable template to pattern the orientation of subsequently grown wide-band-gap films of ZnSe and ZnTe.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 2012-2014 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report depth profiling of the d33 nonlinear coefficient in annealed proton exchanged LiNbO3 waveguides using reflected second-harmonic generation from angle-lapped samples. At depths greater than the initial proton exchange depth the d33 coefficient retains nearly its bulk LiNbO3 value, but within the initial proton exchange region the value of d33 varies with annealing time. These results reconcile previous conflicting measurements of the d33 coefficient and explain the variation in the efficiency of guided wave frequency conversion devices with annealing.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report quasi-phase-matched difference-frequency generation of 2.1 μm radiation at room temperature using the d33 nonlinear coefficient in a periodically poled lithium niobate channel waveguide. A tunable Ti:Al2O3 laser (λ≈0.8 μm) and a Nd:YAG laser (λ=1.32 μm) were the pump and signal sources, respectively. With 160 mW of 0.81 μm and 1 mW of 1.32 μm radiation coupled into the waveguide, 1.8 μW of 2.1 μm radiation was generated, tunable over a 6 nm bandwidth. We also show that the annealed proton exchange process can change the shape of ferroelectric domains in lithium niobate.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 1955-1957 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Light produced by a laser plasma light source (LPLS) is used to perform optical reflectivity measurements on single crystals from 5 to 40 eV in a single experiment. The intense continuum generated by the rare-earth plasma allows a significantly higher resolution above 15 eV and extends the measurements to higher energies than those attainable with other laboratory based light sources. This is the first application of a LPLS to vacuum ultraviolet spectroscopy of solids and we demonstrate this capability on two insulating materials, α-Al2O3 and MgAl2O4.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Fluency Disorders 19 (1994), S. 182 
    ISSN: 0094-730X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Linguistics and Literary Studies , Medicine
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Ag2PbO2, Optimization of Crystal Growth and Crystal Structure RefinementLarge single crystals of Ag2PbO2 (1×1×7 mm) suitable for measurements of anisotropic physical properties have been grown. The refinement of the crystal structure (I2/c; crystal size 0.08 × 0.08 × 0.31 mm; a = 6.0775(9), b = 8.704(1), c = 6.553(1) Å, β = 93.545(8)°; Z = 4; 1235 diffractometer data; R = 0.038) confirms the positions of the heavy atoms, and allows for an unambiguous determination of the oxygen coordinates.
    Notes: Von Ag2PbO2 wurden größere Einkristalle (1×1×7 mm) für richtungsabhängige physikalische Messungen und kleinere (0,08 × 0,08 × 0,31 mm) für die Röntgenstrukturanalyse gezüchtet. Die Verfeinerung der Kristallstruktur (I2/c; a = 6,0775(9), b = 8,704(1), c = 6,553(1) Å, β = 93,545(8)°; Z = 4.; 1235 Diffraktometerdaten; R = 0,038) bestätigt früher ermittelte Schweratomlagen und sichert die früher nur aufgrund kristallchemischer Überlegungen abgeleiteten Sauerstofflagen.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 612 (1992), S. 113-117 
    ISSN: 0044-2313
    Keywords: Silver bismuthate ; mixed valent bismuth ; preparation ; crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Ag25Bi3O18, a Mixed Valent BismuthateApplying oxygen pressures of 10 MPa black crystals of Ag25Bi3O18 are prepared for the first time by solid state reaction of Ag2O and ‘Bi2O5’. The crystal structure determination (P3, a = 11.5887(2), c = 6,2386(1) å, Z = 1, 1369 diffractometer data, Rw = 0.034) proves the presence of trivalent (d(Bi-O) = 2.21, and 2.51 å (3×)) and pentavalent bismuth (d(Bi-O) = 2.13 å (6×)). The structure allows a change in the oxidation states (Bi3+ → Bi5+) by pressure induced shift of the oxygen atoms leading to a delocalisation of the 6s2 valence electrons. First evidence for this phenomenon is given by the pressure dependence of the NIR reflectivity. The thermal decomposition was recorded by DTA/TG and measurements of the resistivity were performed.
    Notes: Schwarze Einkristalle von Ag25Bi3O18 wurden neu dargestellt (Festkörperreaktion zwischen Ag2O und „Bi2O5“ bei 350°C unter einem Sauerstoffdruck von 10 MPa). Nach dem Ergebnis der Röntgenstrukturanalyse (P3, a = 11,5887(2), c = 6,2386(1) å, Z = 1,1369 Diffraktometerdaten, Rw = (0,034) liegt zweifelsfrei dreiwertiges Bismut (d(Bi-O) = 2,21 und 2,51 å, je 3×) neben fünfwertigem (d(Bi-O) = 2,13 å (6×)) je 3×) neben fünfwertigem (d(Bi-O) = 2,13 å (6×)) vor. Strukturchemisch ist ein displaziver, druckinduzierter Valenzwechsel unter Delokalisierung von Valenzelektronen möglich, für den durch charakteristische druckabhängige NIR Reflexionen ein erster experimenteller Beleg gegeben ist. Das Abbauverhalten wurde mittels DTA/TG untersucht, ferner wurden Leitfähigkeitsmessungen durchgeführt.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 619 (1993), S. 1446-1454 
    ISSN: 0044-2313
    Keywords: Silver bismuthate ; preparation ; crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Ag3BiO3 and Ag5BiO4,the first Silver Oxobismuthates(III)Applying high oxygen pressures (100 MPa) Ag3BiO3 and Ag5BiO4 were prepared for the first time by reacting the binary components Ag2O and Bi2O3 at temperatures between 770 and 800 K. Single crystals of both compounds were grown hydrothermally from Ag2O and Bi2O3 at 620 K and at oxygen pressures of 10 MPa. The crystal structure determination (Ag3BiO3: I41, a = 14.1924(1), c = 8.7997(1) Å, Z = 16, 1 729 diffractometer data, Rw = 0.057; Ag5BiO4: P21/n, a = 5.855(1), b = 8.984(1), c = 12.457(1) Å, β = 91.49(1)Å, Z = 4, 2716 diffractometer data, Rw = 0.036) shows that in Ag5BiO4 bismuth approximately has a square pyramidal coordination by five oxygen atoms. Two such pyramids share an edge thus forming ‘isolated’ Bi2O810- anions. In Ag3BiO3 the same groups are linked by the terminal oxygen atoms to form a three dimensional network. In both structures the cation arrangements form variants of the Laves-phases MgCu2 with silver occupying the copper positions. The Mg positions are ordered occupied by bismuth and silver.
    Notes: Ag3BiO3 und Ag5BiO4 wurden durch Festkörperreaktion aus den binären Komponenten Ag2O und Bi2O3 bei Temperaturen zwischen 770 und 800 K und Sauerstoffdrücken von 100 MPa erstmals dargestellt. Einkristalle von beiden Verbindungen konnten durch Hydrothermalreaktion zwischen Ag2O und Bi2O3 bei 620 K unter einem Sauerstoffdruck von 10 MPa dargestellt werden. Nach den Ergebnissen der Röntgenstrukturanalyse (Ag3BiO3: I41, a = 14,1924(1), c = 8,7997(1) Å, Z = 16, 1 729 Diffraktometerdaten, Rw = 0,057; Ag5BiO4: P21/n, a = 5,855(1), b = 8,984(1), c = 12,457(1) Å, β = 91,49(1)Å, Z = 4, 2716 Diffraktometerdaten, Rw = 0,036) liegt in Ag5BiO4 eine transständige Verknüpfung von quadratisch-pyramidal mit Sauerstoff koordinierten BiO5-Baueinheiten zu dimeren, ‘isolierten’, Bi2O810--Gruppen vor. In Ag3BiO3 findet man die gleichen Bi2O8-Baugruppen, die hier jedoch dreidimensional über die terminalen Sauerstoffatome verknüpft sind. In beiden Verbindungen sind die Kationen analog zur Laves-Phase MgCu2 angeordnet mit gemischter Besetzung der Mg-Position durch Silber und Bismut sowie Besetzung der Cu-Positionen ausschließlich durch Silber.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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