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  • 1
    Electronic Resource
    Electronic Resource
    Effect of surfactant Sb on carrier lifetime in GaInP epilayers (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 199-203 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Samples of Ga0.52In0.48P grown on (001) GaAs with small amounts of surfactant Sb were investigated using time-resolved photoluminescence. All samples show a luminescence that may be fit to a two-stage exponential decay with a fast and a slow lifetime. For growth without Sb (Sb/III(v)=0), the sample shows a strong CuPtB ordering and a fast component lifetime of 7 ns. As the Sb concentration is increased, the degree of order is reduced, with a consequent increase in band gap energy. In the highest band gap material, produced at Sb/III(v)=0.016, the fast lifetime is 2.9 ns, an order of magnitude larger than published values for GaInP disordered by misorienting the substrate. Increasing the Sb further causes the band gap energy to decrease due to the onset of composition modulation. At Sb/III(v)=0.064, the fast component lifetime decreases to 0.79 ns. Samples grown with Sb/III(v)〉0.016 show a lifetime that depends on energy and is fit well by a model of localized excitons. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1423396
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  • 2
    Electronic Resource
    Electronic Resource
    Surfactant controlled growth of GaInP by organometallic vapor phase epitaxy (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 3730-3735 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of the surfactant Sb has been studied for GaInP semiconductor alloys grown by organometallic vapor phase epitaxy. Dramatic changes in the optical and electrical properties of GaInP with CuPt ordering have been observed. A small concentration of triethylantimony (TESb) in the vapor is found to cause Sb to accumulate at the surface. In situ surface photoabsorption analysis indicates that Sb changes the surface bonding by replacing the [1¯10] P dimers that are responsible for the formation of the CuPt structure during growth with [1¯10] Sb dimers. As a result, the degree of order for the GaInP layers is decreased, as shown by transmission electron diffraction studies. The 20 K photoluminescence spectra show a 131 meV peak energy increase for GaInP layers grown on vicinal substrates when a small amount of Sb [Sb/P(v)=4×10−4] is added to the system during growth. The use of surfactants to control specific properties of materials is expected to be a powerful tool for producing complex structures. In this article, the growth of heterostructures by modulating the Sb concentration in the vapor is demonstrated. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372408
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  • 3
    Electronic Resource
    Electronic Resource
    Spectroscopic study of surfactant enhanced organometallic vapor phase epitaxy growth of GaInP (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 1040-1046 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Samples of GaxIn1−xP grown by organometallic vapor phase epitaxy on (001) GaAs substrates by addition of TESb demonstrating a lateral superlattice compositional modulation (CM) have been studied by low temperature polarized photoluminescence (PL), power dependent PL, and photoluminescence excitation (PLE) spectroscopy. Strong polarization is observed in the low temperature PL and PLE spectra at Sb concentrations below that where CuPtB ordering is removed and triple period ordering is produced. Low temperature polarized PL is shown to be the most sensitive optical technique for detecting the presence of CM. The radiative recombination mechanism at low temperature is excitonic, originating from the exponential tail of band gap states observed in the PLE spectra. From the measured band gaps, a continuum model of the band structure allows an estimate of an upper limit of the percent modulation present in the samples. Above Sb/III(v)=0.01, compositional modulation is the dominant factor determining the low temperature optical properties. The percent fluctuation of composition increases monotonically with increasing Sb during growth. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1378060
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  • 4
    Electronic Resource
    Electronic Resource
    Bi surfactant control of ordering and surface structure in GaInP grown by organometallic vapor phase epitaxy (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 4429-4433 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The surfactant Bi has been added during organometallic vapor phase epitaxial growth (OMVPE) of GaInP using the precursor trimethylbismuth. The addition of a small amount of Bi during growth results in disordered material using conditions that would otherwise produce highly ordered GaInP. Significant changes in the surface structure are observed to accompany the disordering. Atomic force microscopy measurements show that Bi causes an order of magnitude increase in step velocity, leading to the complete elimination of three-dimensional islands for growth on singular (001) GaAs substrates, and a significant reduction in surface roughness. Surface photoabsorption measurements indicate that Bi reduces the number of [1¯10] P dimers on the surface. Secondary ion mass spectroscopy measurements reveal that the Bi is rejected from the bulk, even though it changes the surface reconstruction. Clearly, Bi acts as a surfactant during OMVPE growth of GaInP. The difference in band gap energy caused by the reduction in order parameter during growth is measured using photoluminescence to be about 110 meV for layers grown on singular substrates. Disorder/order/disorder heterostructures were successfully produced in GaInP with a constant solid composition by modulating the TMBi flow rate during growth. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1289478
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  • 5
    Electronic Resource
    Electronic Resource
    Letter to the Editor (2001)
    Boston, MA, USA : Blackwell Science Inc
    The @breast journal 7 (2001), S. 0 
    Details
    ISSN: 1524-4741
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1524-4741.2001.20032.x
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  • 6
    Electronic Resource
    Electronic Resource
    The Perception of Risk (2003)
    350 Main Street , Malden , MA 02148 , USA , and 9600 Garsington Road , Oxford OX4 2DQ , UK . : Blackwell Publishing, Inc.
    Risk analysis 23 (2003), S. 0 
    Details
    ISSN: 1539-6924
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1539-6924.00303
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  • 7
    Electronic Resource
    Electronic Resource
    Comparative Risk and Policy Analysis in Environmental Health (2003)
    350 Main Street , Malden , MA 02148 , USA , and 9600 Garsington Road , Oxford OX4 2DQ , UK . : Blackwell Publishing, Inc.
    Risk analysis 23 (2003), S. 0 
    Details
    ISSN: 1539-6924
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: There is increasing interest in the integration of quantitative risk analysis with benefit-cost and cost-effectiveness methods to evaluate environmental health policy making and perform comparative analyses. However, the combined use of these methods has revealed deficiencies in the available methods, and the lack of useful analytical frameworks currently constrains the utility of comparative risk and policy analyses. A principal issue in integrating risk and economic analysis is the lack of common performance metrics, particularly when conducting comparative analyses of regulations with disparate health endpoints (e.g., cancer and noncancer effects or risk-benefit analysis) and quantitative estimation of cumulative risk, whether from exposure to single agents with multiple health impacts or from exposure to mixtures. We propose a general quantitative framework and examine assumptions required for performing analyses of health risks and policies. We review existing and proposed risk and health-impact metrics for evaluating policies designed to protect public health from environmental exposures, and identify their strengths and weaknesses with respect to their use in a general comparative risk and policy analysis framework. Case studies are presented to demonstrate applications of this framework with risk-benefit and air pollution risk analyses. Through this analysis, we hope to generate discussions regarding the data requirements, analytical approaches, and assumptions required for general models to be used in comparative risk and policy analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.0272-4332.2003.00405.x
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  • 8
    Electronic Resource
    Electronic Resource
    Internal Mammary Lymph Node Inclusion in Standard Tangent Breast Fields: Effects of Body Habitus (2001)
    Boston, MA, USA : Blackwell Science Inc
    The @breast journal 7 (2001), S. 0 
    Details
    ISSN: 1524-4741
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The purpose of this study was to determine the variability of internal mammary node (IMN) coverage with standard breast tangent fields using surface anatomy as determined by computed tomography (CT) planning for patients treated with either breast-conserving treatment or postmastectomy, and to evaluate the influence of body habitus and shape on IMN coverage with standard tangent fields. This prospective study included consecutive women with breast cancer who underwent either local excision or mastectomy and had standard tangent fields intended to cover the breast plus a margin simulated using surface anatomy. CT planning determined the location of the IMN with respect to the tangent fields designed from surface anatomy. The internal mammary vessels were used as surrogates for the IMNs. CT measurements of the presternal fat thickness and anteroposterior (AP) and transverse skeletal diameters were made to determine their relationship to the inclusion of IMNs within the tangent fields. Only seven patients (14%) had their IMNs completely within the tangent fields. Twenty patients (40%) had partial coverage of their IMNs, and 23 (46%) had their IMNs completely outside the fields. IMN inclusion was inversely correlated with presternal fat thickness. Thoracic skeletal shape was not associated with IMN inclusion. Standard tangent fields generally do not cover the IMNs completely but may cover them at least partially in a majority of patients. The presternal fat thickness is inversely correlated with IMN inclusion in the tangent fields.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1524-4741.2001.007002111.x
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  • 9
    Electronic Resource
    Electronic Resource
    Use of Citicoline, a Source of Blood Choline and Cytidine/Uridine, for Neuroprotection (2000)
    Oxford, UK : Blackwell Publishing Ltd
    CNS drug reviews 6 (2000), S. 0 
    Details
    ISSN: 1527-3458
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1527-3458.2000.tb00166.x
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  • 10
    Electronic Resource
    Electronic Resource
    Atherosclerotic Occlusive Extracranial Vertebral Artery Disease: (2004)
    350 Main Street , Malden , MA 02148 , USA . : Blackwell Science Inc
    Journal of interventional cardiology 17 (2004), S. 0 
    Details
    ISSN: 1540-8183
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background: Atherosclerotic occlusive disease of the vertebral artery (VA) affects a significant proportion of patients with cerebrovascular disease and can cause significant morbidity and mortality despite maximal medical therapy. Careful selection of both symptomatic and asymptomatic patients for intervention based on neurological symptoms, as well as anatomical and hemodynamic considerations, is essential. Methods: To achieve proper results with angioplasty and stenting, standard endovascular techniques are modified for the unique anatomical considerations of the VA. Several technical nuances are described here to aid in the endoluminal revascularization of the VA. Results: Technical success (〈50% residual diameter stenosis) rates ranging from 94 to 98% and low rates of periprocedural complications have been achieved with VA angioplasty and stenting in select series with angiographic follow-up. The long-term success in those series is limited by the high (10–43%) rate of recurrent stenosis. Proper placement of the stent can reduce the risk of periprocedural complications and restenosis. In-stent stenosis appears most commonly during the first 6–12 months after stent placement, but does not appear to correlate with return of neurological symptoms. We believe the high rate of recurrent stenosis makes follow-up angiography essential, especially in the first 12 months after the procedure. Conclusion: Endovascular VA angioplasty with stent placement provides an innovative approach to treat a difficult clinical entity. Evolving therapies, including drug-eluting stents or bioresorbable stents, may prove to provide better long-term results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8183.2004.04055.x
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