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  • 1
    Electronic Resource
    Electronic Resource
    GaNAs avalanche photodiode operating at 0.94 μm (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 2824-2825 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A p-i-n avalanche photodiode (APD) using GaNAs grown on GaAs has been demonstrated. Characterization of the excess noise in the material was used to determine that the ratio of ionization coefficients (k=β/α) is k=0.4. The quantum efficiency was above 25% at 0.94 μm for 0.75% nitrogen incorporation. The APDs exhibited low dark currents (〈60 nA/mm2 at 90% of breakdown) and a gain-bandwidth product of 42 GHz. GaNAs therefore shows promise for extending the operation of GaAs-based APDs to longer wavelengths. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126485
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  • 2
    Electronic Resource
    Electronic Resource
    GaNAs resonant-cavity avalanche photodiode operating at 1.064 μm (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 1543-1544 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A resonant-cavity avalanche photodiode using a GaNAs absorption region grown on GaAs has been demonstrated. The peak quantum efficiency was 59% at 1.064 μm with a full width at half maximum of 11 nm. The absorption coefficient was determined to be α=9×103/cm at this wavelength. The devices exhibited gain up to 100 at a low breakdown voltage of 13 V. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1308272
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  • 3
    Electronic Resource
    Electronic Resource
    Back illuminated AlGaN solar-blind photodetectors (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 1900-1902 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the growth, fabrication, and characterization of AlxGa1−xN (0≤x≤0.60) heteroepitaxial back-illuminated solar-blind p-i-n photodiodes on (0001) sapphire substrates. The group III-nitride heteroepitaxial layers are grown by low-pressure metalorganic chemical vapor deposition on double polished sapphire substrates using various growth conditions. The back-illuminated devices exhibit very low dark current densities. Furthermore, they exhibit external quantum efficiencies up to 35% at the peak of the photoresponse (λ∼280 nm). Improvements were made to the growth technique in order to achieve crack-free Al0.4Ga0.6N active regions on a thick Al0.6Ga0.4N window layer and to obtain activated p-type Al0.4Ga0.6N layers. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1311821
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  • 4
    Electronic Resource
    Electronic Resource
    Selective regrowth of Al0.30Ga0.70N p–i–n photodiodes (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 2810-2812 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the device performance of selective-area regrown Al0.30Ga0.70N p–i–n photodiodes. Tensile strain, induced by the lattice mismatch between AlxGa1−xN and GaN, leads to cracking above the critical thickness in layers with high aluminum concentration. Selective-area regrown devices with ≤70 μm diameters were fabricated without signs of cracking. These devices show low dark current densities with flat photoresponse and a forward turn-on current of ∼25 A/cm2 at 7 V. A quantum efficiency greater than 20% was achieved at zero bias with a peak wavelength of λ=315 nm. A differential resistance of R0=3.46×1014 Ω and a detectivity of D*=4.85×1013 cm Hz1/2 W−1 was demonstrated. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1322374
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  • 5
    Electronic Resource
    Electronic Resource
    Jansen type of spondylometaphyseal dysplasia (2000)
    Springer
    Skeletal radiology 29 (2000), S. 239-242 
    Details
    ISSN: 1432-2161
    Keywords: Key words Osteochondrodysplasia ; Metaphyseal dysplasia ; Metaphysis ; Spine ; Short stature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Metaphyseal dysplasia, type Jansen (JMD), is a rare skeletal dysplasia with characteristic radiographic abnormalities. Of the various types of metaphyseal dysplasia, JMD shows the most severe alteration in metaphyseal architecture. All of the long tubular bones, including those of the hands and feet, show metaphyseal irregularity with a fragmented appearance and slight widening. The adjacent physes are abnormally widened, while the epiphyses tend to be slightly enlarged, rounded but otherwise normal. The spine in infancy and childhood usually appears normal. This report describes a young girl with metaphyseal changes typical of JMD except for the hands and feet, which appeared normal. She also showed very unusual abnormalities of the spine. This appears, therefore, to represent a unique osteochondrodysplasia for which we propose the term spondylometaphyseal dysplasia, type Jansen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002560050601
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  • 6
    Electronic Resource
    Electronic Resource
    Developmental Toxicity of Lead-Contaminated Sediment to Mallard Ducklings (2000)
    Springer
    Archives of environmental contamination and toxicology 39 (2000), S. 221-232 
    Details
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract Sediment ingestion has been identified as an important exposure route for toxicants in waterfowl. The toxicity of lead-contaminated sediment from the Coeur d'Alene River Basin (CDARB) in Idaho was examined on posthatching development of mallard (Anas platyrhynchos) ducklings for 6 weeks. Day-old ducklings received either untreated control diet, clean sediment (24%) supplemented control diet, CDARB sediment (3,449 μg/g lead) supplemented diets at 12% or 24%, or a positive control diet containing lead acetate equivalent to that found in 24% CDARB. The 12% CDARB diet resulted in a geometric mean blood lead concentration of 1.41 ppm (WW) with over 90% depression of red blood cell ALAD activity and over threefold elevation of free erythrocyte protoporphyrin concentration. The 24% CDARB diet resulted in blood lead of 2.56 ppm with over sixfold elevation of protoporphyrin and lower brain weight. In this group the liver lead concentration was 7.92 ppm (WW), and there was a 40% increase in hepatic reduced glutathione concentration. The kidney lead concentration in this group was 7.97 ppm, and acid-fast inclusion bodies were present in the kidneys of four of nine ducklings. The lead acetate positive control group was more adversely affected in most respects than the 24% CDARB group. With a less optimal diet (mixture of two thirds corn and one third standard diet), CDARB sediment was more toxic; blood lead levels were higher, body growth and liver biochemistry (TBARS) were more affected, and prevalence of acid-fast inclusion bodies increased. Lead from CDARB sediment accumulated more readily in duckling blood and liver than reported in goslings, but at given concentrations was generally less toxic to ducklings. Many of these effects are similar to ones reported in wild mallards and geese within the CDARB.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002440010099
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  • 7
    Electronic Resource
    Electronic Resource
    A comparative study of the constitutive equations to predict the work hardening characteristics of cast Al-7wt.%Si-0.20wt.%Mg alloys (2000)
    Springer
    Journal of materials science 19 (2000), S. 2179-2181 
    Details
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006706912301
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  • 8
    Electronic Resource
    Electronic Resource
    Comparison of Scintillation Detection Efficiencies of Depleted Uranium (DU) in Wounds (2000)
    Springer
    Journal of radioanalytical and nuclear chemistry 243 (2000), S. 451-457 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Three tissue-equivalent cylindrical wound phantoms with varying activities of DU metal imbedded at varying depths were used to compare the efficiencies of a bismuth germinate (BGO) detector, a sodium iodide (NaI), and two identical wound probes with smaller sodium iodide crystals. Our results show that the BGO detector had the highest efficiency (1.0·10-3) and the lowest minimum detectable activity (MDA = 5.8 kBq) for the shallow depth DU phantom, relative to the other detectors. The BGO detector also had the highest peak efficiencies (1.7·10-3 and 5.8·10-4) and the lowest MDAs (3.5 and 10.0 kBq) for the medium and deep phantoms, respectively. Other detectors' performance data are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016034300588
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  • 9
    Electronic Resource
    Electronic Resource
    Changing the Learning Environment to Enhance Explaining and Understanding in a Year 12 Chemistry Classroom (2000)
    Springer
    Learning environments research 3 (2000), S. 209-227 
    Details
    ISSN: 1573-1855
    Keywords: explaining ; learning environments ; science laboratories ; science reasoning ; teacher change
    Source: Springer Online Journal Archives 1860-2000
    Topics: Education
    Notes: Abstract Internationally there is concern in relation to the traditional learning environments evident in many science classrooms and the levels of understanding of science developed by students in such environments. Further, students have generally been found to be poor in relation to thinking in terms of models or theories and in terms of evidence to support their theories. The majority of research on classroom environments has focused on characterising the learning environment in classrooms rather than monitoring changes to a class's or an individual's perceptions to their learning environments as a consequence of interventions. This study reports an attempt to change the learning environment in a classroom and documents changes in participants' perceptions of their learning environments and the corresponding changes in a teacher's and her students' perceptions of their reasoning and understanding that such changes facilitated. A community of learners in which students and teachers began to understand the processes and the value of reasoning in terms of theories and evidence was developed as a result of the involvement of the researchers with the teacher and her class of students.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011473716075
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  • 10
    Electronic Resource
    Electronic Resource
    Atomic force microscopy using plastic replicas (2000)
    Springer
    Journal of materials science 35 (2000), S. 757-765 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Scanning probe microscopy is now an accepted tool in both industrial and research efforts. Its development parallels the advances in technology and imaging applications found in the history of progress of both transmission electron microscopy and scanning electron microscopy. All three forms of microscopy ultimately suffer a fundamental application problem—situations arise where it is either unreasonable or impossible to observe a particular sample within the sample stage of the microscope. For the transmission and electron and scanning electron microscopies, this problem has been resolved by resorting to making a replica of the area of interest on the actual sample and preparing the replica so that it may be imaged directly by the desired microscopy technique. This work attempts to ascertain the suitability of observing replicas using a scanned probe microscope; specifically, employing the techniques of atomic force microscopy to image plastic surface replicas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004769620450
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