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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 4766-4774 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The 9–0 and 9–1 transitions of the A 1Πu–X 1Σ+g system of N2+2 have been observed by fast ion beam photofragment spectroscopy. Multireference configuration interaction ab initio calculations predict v'=8 to be the highest bound level which seemed to be supported by experimental evidence. The dominant predissociation mechanism for the v'=9 level appears to be through tunneling, unlike the v'=6, 7, and 8 levels, which show an e/f symmetry-dependent electronic predissociation. Calculated tunneling lifetimes from our own modified A 1Πu state potential gives good agreement with the experimental lifetimes. In addition to the 9–1 and 9–0 bands, we have also measured the previously unobserved 7–0 and 8–0 rovibronic transitions thus extending Cosby, Müller, and Helm's study to the blue [Phys. Rev. A 28, 766 (1983)]. Molecular constants have been determined for the v=0 of the X 1Σ+g state and v=7, 8, and 9 of the A 1Πu state.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 2121-2123 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The thin strained superlattice (TSSL) concept is introduced as a means for extending the practical range of application for pseudomorphic Inx Ga1−x As on GaAs. Growth and characterization results are presented for pseudomorphic high electron mobility transistor structures with GaAs-In0.3 Ga0.7 As TSSL active layers grown by molecular beam epitaxy. The TSSLs are composed of three periods of GaAs(15 A(ring))- In0.3 Ga0.7 As(h2 ), where h2 ranges from 30 to 52 A(ring). Modulation doping of the TSSLs is provided by atomic planar-doped Al0.3 Ga0.7 As overlayers with 45 A(ring) undoped spacers. 77 K Hall effect and transmission electron microscopy reveal that relatively thick TSSLs can be grown with high electronic and structural quality, comparable to much thinner In0.3 Ga0.7 As single quantum wells. Results are compared with a model for critical layer thickness and discussed in light of in situ reflection high-energy electron diffraction measurements.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1365-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Four silages were prepared from grass treated with additives designed to produce different extents of fermentation in the silo. The additive treatments were: formic acid at 5 l t−1; a bacterial inoculant (Ecosyl, ICI plc); the inoculant plus molasses at 20 kg t−1; and a noadditive control. All silages were well preserved. Formic acid severely restricted the extent of fermentation, the concentration of lactic acid being only 50% of that seen for the other treatments, all of which were similar in lactic acid concentrations.The silages were offered ad libitum, either as the sole component of the diet or together with three supplement treatments to 16 British Friesian cows, in four 4 treatment × 4 period Latin squares with periods of 28 d duration. The supplements were: a barley-based mixture at 5 kg d−1 (B); a high-fat, high-protein product at 2 kg d−1 (FPI) and at 3 kg d −1 (FP2); both FP treatments were given with 1 kg d−1 of molassed sugarbeet pulp. A preliminary experiment, using three lactating, rumen-cannulated cows in a 3×3 Latin square design with 28-d periods, provided information on rumen digestion when the supplements were given with a separate, non-experimental silage.In the preliminary experiment, neither of the FP treatments influenced the molar proportion of the major rumen volatile fatty acids compared with treatment B; nor were there any depressive effects of the FP treatments on silage intake compared with treatment B.In the main experiment, the intake of silage with the inoculant treatment was less than that with the other treatments, the effect being generally significant (at least P〈0·05) for all three supplements. When the silages were given unsupplemented, there were differences in the concentration (P〈0·001) and yield (P〈0·01) of milk fat, both of which were lowest for the no-additive control and highest for the formic acid silage. When supplement B was given, the concentration and yield of milk fat were lowest for the no-additive control and the concentration and yield of milk protein were highest for the formic acid silage. For all silages both FP treatments tended to depress silage intake and reduce the concentration of fat and protein in milk compared with treatment B.Although there were clear indications of differences in nutritional characteristics between the silages, there was little evidence that the differences between silages influenced the responses to changes in the composition of the supplements.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the temperature-dependent characteristics of photoluminescence emission in modulation δ-doped AlxGa1−xAs/InyGa1−yAs/GaAs structures. Transition energies are analyzed using a self-consistent solution of the coupled k⋅P Hamiltonian–Poisson equation. At low temperatures, dominant emissions are due to the transitions from the first electron subband to the first heavy-hole subband and from the second electron subband to the first heavy-hole subband irrespective of the location of modulation doping. The second hole subband related transitions associated with the first electron subband or the second electron subband emerges with increasing temperature depending on the location of doping. The relative intensities of the transitions from the first and second electron subbands to the first heavy-hole subband transitions are analyzed as a function of the Fermi energy position. An excellent agreement is found between the measurements and calculations. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 973-976 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electrical and optical properties of AlGaAs grown by metalorganic molecular-beam epitaxy using triethylaluminum, tri-isobutylaluminum, and trimethylamine-alane are compared. It is found that tri-isobutylaluminum yields the lowest residual carbon incorporation in the layers (Na − Nd = 4 × 1015 cm−3) and the highest electron and hole mobilities. Photoluminescence spectra for the higher-quality AlGaAs, grown using TiBAl, show excitonic luminescence. However, this luminescence appears to be defect related.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 2882-2885 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present preliminary results of a study of defects in GaAs-AlGaAs superlattices using deep-level transient spectroscopy (DLTS). A dramatic difference is observed between the DLTS spectra of two superlattices when the superlattice period is doubled. This is explained by the presence of miniband conduction in the case of the smaller period and its absence in the case of the larger, and by the consequent difference in the distribution of electrons in the superlattice. Observed activation energies must be reinterpreted for comparisons to bulk material.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the temperature dependent characteristics of photoluminescence linewidth in terms of two-dimensional electron gas sheet concentration for modulation δ-doped AlxGa1−xAs/InyGa1−yAs/GaAs structures. The electron concentration is obtained using a self-consistent solution of the coupled k⋅P Hamiltonian–Poisson equation. We find that only the full width at half maximum of the n=2 electron-subband-to-n=1 hole subband transition is useful for characterizing high electron density at T=2–300 K. The importance of hole localization for correlating the electron density with photoluminescence linewidth is discussed. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 98 (1991), S. 0 
    ISSN: 1471-0528
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Objective— To identify those congenital fetal anomalies, previously identified by ultrasound scanning, in which fast-scan magnetic resonance imaging (F-SMRI) would give additional information for the perinatal management of the infants.Design— Observational clinical study.Setting— Hospital Department of Obstetrics and Gynaecology/Resonance Research Centre.Subjects— Seven women carrying eight fetuses in whom congenital abnormal-ities had been identified using ultrasound scans. The duration of the pregnancies was 28 to 39 weeks gestation.Interventions— Fast-scan magnetic resonance imaging at between 28 and 39 weeks gestation.Main outcome measures— Identification of fetal abnormalities.Results and conclusions— F-SMRI was of limited value in the diagnosis of further assessment of fetuses with abnormalities of accumulation of tissue fluid. Renal anomalies were poorly identified unless associated with cystic formation of the kidney. Further study is required in the imaging of fetal central nervous system anomalies. Until echoplanar imaging is more widely available, MRI does not contribute to the diagnosis of cardiac anomalies. F-SMRI appears to be most useful in the diagnosis and management of soft tissue gastro intestinal abnormalities.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of nondestructive evaluation 11 (1992), S. 167-174 
    ISSN: 1573-4862
    Keywords: Elastic waves ; interface layers ; inclusions ; boundary integral equations ; uniqueness
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Elastic waves are scattered by an elastic inclusion. The interface between the inclusion and the surrounding material is imperfect: the displacement and traction vectors on one side of the interface are assumed to be linearly related to both the displacement vector and the traction vector on the other side of the interface. The literature on such inclusion problems is reviewed, with special emphasis on the development of interface conditions modeling different types of interface layer. Inclusion problems are formulated mathematically, and uniqueness theorems are proved. Finally, various systems of boundary integral equations over the interface are derived.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-1262
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The aim of this study was to assess (a) the incidence of perineal descent and (b) the relationship between radiological abnormalities of the pelvic floor and rectoanal manometric disturbances in patients consulting for constipation. Lateral radiographs in both the left lateral and supine positions studied pelvic floor descent. Results obtained in the 25 patients (mean age 47 years) studied were compared with those of 12 controls (mean age 58 years). Pelvic floor descent, never seen in controls, was demonstrated in 14 patients who were older (53±3 years, mean ±SD) than the 11 with a normal radiological examination (38±3 years,p〈0.05). Anal low pressures (3 cases) and a low amplitude of rectoanal inhibitory reflex (RAIR) (5 cases) were shown only in patients with perineal descent and anal high pressures only in those with normal radiology. Our results suggest that (a) perineal descent is a common finding in over 50% of constipated patients and (b) anorectal motility is related to pelvic floor function.
    Type of Medium: Electronic Resource
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