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  • 11
    Electronic Resource
    Electronic Resource
    Density gradient columns: Dynamic modeling for linear profiles (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 3973-3980 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Rigorous mathematical modeling of the process dynamics associated with the construction and filling of density gradient columns is presented in this article. These models incorporate the hydrostatic driving forces for fluid flow, friction losses associated with this flow, and the unsteady-state behavior of the liquid levels in the filling vessels and in the column itself. Four different filling arrangements are considered, corresponding to the density order of the two fluids in the filling vessels and two methods for introducing the fluid of varying density into the column. Time requirements for filling of the column and the resulting calibration curve for liquid density versus height in the gradient column are both obtained as a result of this modeling procedure. Further, extremely important operating guidelines for the final achievement of a linear density gradient in the column, which is normally the desired objective in most laboratory applications, are derived and presented. Conversely, the causes leading to nonlinear gradients are elucidated and quantified. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147301
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  • 12
    Electronic Resource
    Electronic Resource
    Experimental examination of Eulerian frequency spectra in zero-mean-shear turbulence (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 7 (1995), S. 1168-1170 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Eulerian frequency spectra were measured in zero-mean-shear (oscillating-grid induced) turbulent flows and were compared with the spectral form proposed by Tennekes [J. Fluid Mech. 67, 561 (1975)]. A satisfactory agreement between the theoretical prediction and experimental results were obtained in a limited frequency range. The empirical constants pertinent to the spectral law, obtained experimentally, were in good agreement with the numerical simulation results. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.868560
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  • 13
    Electronic Resource
    Electronic Resource
    Electron cyclotron resonance etching characteristics of GaN in SiCl4/Ar (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 367-369 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electron cyclotron resonance (ECR) plasma etching characteristics of gallium nitride (GaN) are investigated using low pressure (4–10 mTorr) SiCl4/Ar ECR discharges. The purpose of this effort is to examine the dry etching processes of GaN that do not require hydrogen, which is known to cause carrier compensation in GaN. A maximum etching rate of 960 A(ring)/min and good surface morphologies are obtained. The etch rate is found to increase near-linearly with increasing dc bias, and a minimum dc bias of 100 V is required to initiate etching. Enhanced etching rates are obtained as the fraction of active chemical etchant species (SiCl4) in the discharge is increased. We have also found that the material quality significantly affects the etch rate. The latter decreases with x-ray rocking curve half-width and increases with defect density. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116718
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  • 14
    Electronic Resource
    Electronic Resource
    Nonalloyed Ti/Al Ohmic contacts to n-type GaN using high-temperature premetallization anneal (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 2737-2739 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: On Si-implanted n-type GaN, a nonalloyed Ti/Al metallization has been found to form an Ohmic contact that has a specific contact resistance as low as 1.0×10−5 Ω cm2. The Ohmic character is believed to be caused by the 1120 °C implant activation anneal which generates nitrogen vacancies that leave the surface heavily n type. This theory is indirectly confirmed on unimplanted n-type GaN by comparing the rc of nonalloyed Ti/Al on unannealed GaN with that of nonalloyed Ti/Al on 1120 °C annealed GaN. The former has rectifying electrical characteristics, while the latter forms an Ohmic contact with an rc=1.3×10−3 Ω cm2. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117695
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  • 15
    Electronic Resource
    Electronic Resource
    [3H]Homoquinolinate Binds to a Subpopulation of NMDA Receptors and to a Novel Binding Site (1998)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 71 (1998), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: NMDA receptors mediate several important functions in the CNS; however, little is known about the pharmacology, biochemistry, and function of distinct NMDA receptor subtypes in brain tissue. To facilitate the study of native NMDA receptor subpopulations, we have determined the radioligand binding properties of [3H]homoquinolinate, a potential subtype-selective ligand. Using quantitative receptor autoradiography, NMDA-specific [3H]homoquinolinate binding selectively labeled brain regions expressing NR2B mRNA (layers I–III of cerebral cortex, striatum, hippocampus, and septum). NMDA-specific [3H]homoquinolinate binding was low in brain regions that express NR2C and NR2D mRNA (cerebellar granular cell layer, NR2C; glomerular layer of olfactory bulb, NR2C/NR2D; and midline thalamic nuclei, NR2D). In forebrain, the pattern of NMDA-specific [3H]homoquinolinate binding paralleled NR2B and not NR2A distribution. In addition to NMDA-displaceable binding, there was a subpopulation of [3H]homoquinolinate binding sites in the forebrain, cerebellum, and choroid plexus that was not displaced by NMDA or l-glutamate. In contrast, we found that the derivative of homoquinolinate, 2-carboxy-3-carboxymethylquinoline, markedly inhibited the NMDA-insensitive binding of [3H]homoquinolinate without inhibiting the NMDA-sensitive population. [3H]Homoquinolinate may be useful for selectively characterizing NR2B-containing NMDA receptors in a preparation containing multiple receptor subtypes and for characterizing a novel binding site of unknown function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1998.71041464.x
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  • 16
    Electronic Resource
    Electronic Resource
    Spatial aggregation of pathotypes of barley powdery mildew (1997)
    Oxford, UK : Blackwell Science Ltd
    Plant pathology 46 (1997), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Aggregation in the distribution of pathotypes of Erysiphe graminis f.sp. hordei, the barley powdery mildew pathogen, was investigated in field plots of ‘Golden Promise’, ‘Proctor’ and ‘Tyra’. ‘Golden Promise’ and ‘Proctor’ have no effective mildew resistance alleles, whereas ‘Tyra’ has Mla1, which was only effective against a proportion of the mildew population. Isolates of mildew were sampled according to a grid sampling scheme and their virulence spectra ascertained in order to group them according to pathotype. The populations were very diverse, and evidence for aggregation (quantified using join counts) was found only in the ‘Tyra’ plots, at distances of up to 1m. This aggregation was reduced in a subsequent sample. The results are consistent with a model in which mildew epidemics are started by a large number of initial infections, which then form diffuse, overlapping aggregations of clones. These aggregations then become more diffuse, so that the amount of aggregation reduces with time. The greater amount of aggregation seen in the ‘Tyra’ plots might have been caused by there being less initial inoculum with virulence towards that cultivar.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3059.1997.d01-84.x
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  • 17
    Electronic Resource
    Electronic Resource
    The early development of Erysiphe pisi on Pisum sativum L. (1996)
    Oxford, U.K. and Cambridge, USA : Blackwell Science Ltd
    Plant pathology 45 (1996), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Erysiphe pisi, the powdery mildew pathogen of Pisum sativum, followed a developmental sequence that allowed the identification of 10 distinct growth stages (GS) over 30 h following inoculation. The growth stages were ungerminated conidia (GS1), germinated conidia, having produced a germ tube (GS2), germlings where the germ tube had forked (GS3), germlings with a multi-lobed germ tube (GS4), germlings with a single hypha (GS5), germlings with two (GS6 and 7) or three (GS8 and 9) hyphae, one of which may have formed from the appressorium (GS7 and 9), and germlings with abnormally long germ tubes (GS10), which did not develop hyphae. Conidia germinated rapidly, with a quarter of conidia producing germ tubes by 2 h after inoculation (hai). Most germlings produced multi-lobed appressoria, which showed considerable variation in structure. Haustoria, although often difficult to visualize, were first seen 4 hai, and the first hyphae 14 hai, growing from the body of the conidium. Subsequent hyphae developed from both the body of the conidium and from the appressorium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3059.1996.d01-111.x
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  • 18
    Electronic Resource
    Electronic Resource
    Colonic spread of three rectally administered mesalazine (Pentasa) dosage forms in healthy volunteers as assessed by gamma scintigraphy (1997)
    Oxford, UK : Blackwell Science Ltd
    Alimentary pharmacology & therapeutics 11 (1997), S. 0 
    Details
    ISSN: 1365-2036
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background: Rectal administration of enemas, foams and suppositories is the most efficient method of delivering locally-acting drugs to the distal colon, sigmoid colon and rectum. Healthy volunteers provide an effective population to compare different formulations for rectal drug delivery. However, there is still only limited comparative information available on the dispersion of such dosage forms in human subjects. Therefore, the objective of this scintigraphic study was to compare colonic spread of an enema, a rectal foam and a suppository formulation in healthy volunteers. Methods: This was a randomized, crossover study in eight healthy male volunteers. Each received Pentasa rectal formulations as either a 100 mL suspension enema (1 g mesalazine), one actuation of a non-CFC propellant rectal foam (1 g mesalazine in 5 mL concentrate, expanding to 40 mL on actuation), or one suppository (1 g mesalazine) on three separate occasions. The spread of the radiolabelled formulations was assessed over a 4-h period by gamma scintigraphy. Results: The formulations were retained by all subjects for the whole of the 4-h imaging period. The enema spread to the splenic flexure in 7 out of 8 subjects, but was retained in the rectum and sigmoid colon in one individual. The foam spread as far as the descending colon in four subjects. In the remaining individuals the foam was retained in the rectum and sigmoid colon. The spread of the suppository was limited and confined to the rectum. Conclusions: The findings of this study are consistent with previous research and support the intended clinical uses of the enema, foam and suppository formulations to treat distal ulcerative colitis, proctosigmoiditis and proctitis, respectively. The results highlight the potential of gamma scintigraphy in providing in vivo `proof of concept' data to help verify the targeting of pharmaceutical products to their intended site of delivery.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2036.1997.00193.x
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  • 19
    Electronic Resource
    Electronic Resource
    Movement of barley powdery mildew within field plots (1998)
    Oxford, U.K. and Cambridge, USA : Blackwell Science Ltd
    Plant pathology 47 (1998), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Movement of barley powdery mildew (caused by Erysiphe graminis f.sp. hordei) within fields was investigated by sowing the barley cultivars Tyra and Jupiter side by side in two field plots, and trapping spores along transects within the plots. The trapped spores were tested for virulence on the two cultivars. The epidemic on Tyra developed quickly, and a gradient in the proportion of spores with virulence on Tyra was detected in the Jupiter half-plots. In the Jupiter half-plots, the epidemic was much less severe; and no mildew could be found in one plot. Movement of spores from one half of the plot to the other usually declined steeply in the first 4 m from the boundary, and was not detectable beyond 12 m. There were exceptions where the gradient was much shallower, and these were consistent with differences in wind direction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3059.1998.00270.x
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  • 20
    Electronic Resource
    Electronic Resource
    Immigration of the barley mildew pathogen into field plots of barley (1996)
    Oxford, U.K. and Cambridge, USA : Blackwell Science Ltd
    Plant pathology 45 (1996), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Immigration of the barley powdery mildew pathogen (Erysiphe graminis f.sp. hordei) into field plots of the spring barley variety Tyra (carrying the resistance allele Mla1) was investigated. Spores were trapped from the top of the plot canopies, as well as from control plots of wheat with no barley nearby. Comparison of the frequencies of virulent and avirulent single-colony isolates showed that the amount of immigration, relative to the amount of inoculum being produced within the plot, reduced very rapidly, until it could not be detected in the middle of the growing season (mid-June).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3059.1996.d01-192.x
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