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1

Electronic Resource

Moderate-convergence inertial confinement fusion implosions in tetrahedral hohlraums at Omega (2000)

Bennett, G. R. ; Wallace, J. M. ; Murphy, T. J. ; [et al.]

[S.l.] : American Institute of Physics (AIP)

Physics of Plasmas 7 (2000), S. 2594-2603

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ISSN: 1089-7674

Source: AIP Digital Archive

Topics: Physics

Notes: A highly uniform thermal x-radiation field for indirect-drive inertial confinement fusion implosions may be obtained by irradiating a four-hole, tetrahedral geometry, spherical hohlraum with all 60 Omega laser beams. Implosion studies and calculations [J. M. Wallace et al., Phys. Rev. Lett. 82, 3807 (1999)] indicate a drive uniformity comparable to that expected for the National Ignition Facility [J. A. Painser et al., Laser Focus World 30, 75 (1994)]. With 60 beams distributed over the cavity wall, tetrahedral hohlraums have a natural insensitivity to power balance and pointing errors. Standard, smooth Nova capsules imploded with this drive indicate that moderate convergence-ratio implosions, Cr∼18, have measured-neutron yield to calculated-clean-one-dimensional-neutronyield ratios similar to those previously investigated using the comparatively poor drive uniformity of Nova cylindrical hohlraums. This may indicate that a nonsymmetry-related neutron yield degradation mechanism, e.g., hydrodynamic mixing of cold, dense ablator material with the hot-spot region or some combination of nonsymmetry effects, is dominating in this Cr regime. © 2000 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.874101

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2

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Wisconsin x-ray lithography program (invited) : International conference on synchrotron radiation instrumentation (1989)

Wells, G. M. ; Chen, G. ; White, V. ; [et al.]

[S.l.] : American Institute of Physics (AIP)

Review of Scientific Instruments 60 (1989), S. 1636-1637

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ISSN: 1089-7623

Source: AIP Digital Archive

Topics: Physics , Electrical Engineering, Measurement and Control Technology

Notes: The facilities and research activities of the University of Wisconsin's Center for X-ray Lithography (CXrL) are outlined. We discuss recent modifications to the two x-ray lithography beamlines operated by CXrL at the Aladdin storage ring. Ongoing research in various aspects of x-ray lithography, including photoresist characterization, mask stability and distortion studies, and modeling of the x-ray lithography process are summarized. We present plans for the expansion of the CXrL research facilities.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.1141048

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3

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Bounds and heuristics for assembly-like queues (1989)

Hopp, Wallace J. ; Simon, John T.

Springer

Queueing systems 4 (1989), S. 137-155

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ISSN: 1572-9443

Keywords: Assembly-like queues ; bounds ; approximations

Source: Springer Online Journal Archives 1860-2000

Topics: Computer Science

Notes: Abstract We consider an assembly system with exponential service times, and derive bounds for its average throughput and inventories. We also present an easily computed approximation for the throughput, and compare it to an existing approximation.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01158549

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4

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Classification of vegetation in the Western Australian wheatbelt using Landsat MSS data (1989)

Hobbs, R. J. ; Wallace, J. F. ; Campbell, N. A.

Springer

Plant ecology 80 (1989), S. 91-105

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ISSN: 1573-5052

Keywords: Canonical variate analysis ; Landsat imagery ; Vegetation mapping ; Western Australia

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract We examined the use of Landsat multispectral scanner (MSS) data to provide preliminary information on broad vegetation types present within nature reserves in the wheatbelt region of Western Australia. We analysed Landsat data for an area of natural vegetation for which ground survey and aerial photographic data are available. We used canonical variate analysis to examine the degree of spectral separation between training sites selected in the main structural vegetation types. The training classes were then grouped into spectral classes and an allocation procedure used to map the pixels in the reserve into these classes. The analysis provided a good correspondence between spectral classes and broad vegetation types recognised from aerial photography, but did not discriminate between differences in dominant species (e.g. between different types of Eucalypt woodland). The classification derived from the study reserve was then applied successfully to two nearby reserves, indicating that the data can be used to provide initial information on the broad vegetation types present in wheatbelt reserves, although it is not suitable for finer resolution studies.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00048035

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5

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Quoting manufacturing due dates subject to a service level constraint (2000)

Hopp, Wallace J. ; Sturgis, Melanie L. Roof

Springer

IIE transactions 32 (2000), S. 771-784

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ISSN: 1573-9724

Source: Springer Online Journal Archives 1860-2000

Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: Abstract We develop a method for quoting manufacturing due dates to achieve a target service level (percent of orders filled on-time). We posit a very general function for determining leadtimes as a function of work in process and use a control chart method for adjusting the parameters in this function over time. We make almost no assumptions about the nature of the underlying production system (i.e., we do not require any particular distribution of process times, nor do we require that the system be in steady state). Using simulation we show that our method is very accurate for a simple case where an exact analytic solution is possible and that it outperforms other due date quoting methods from the literature in more complex situations.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1007625323807

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6

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The impact of repeated insecticidal treatments on drift and benthos of a headwater stream (1989)

Wallace, J. Bruce ; Lugthart, G. John ; Cuffney, Thomas F. ; [et al.]

Springer

Hydrobiologia 179 (1989), S. 135-147

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ISSN: 1573-5117

Keywords: insecticide ; stream ; invertebrates ; drift ; benthos ; functional structure

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract A small first-order, Appalachian Mountain stream received successive seasonal treatments with the insecticide, methoxychlor. Despite an application rate of 10 mg/1 methoxychlor for 4 hours, based on stream discharge, only a small fraction (1.6%) of the insecticide was exported to downstream reaches for a 31 h period during and following treatment. Most of the insecticide was incorporated into sediments of the streambed, which had residues ranging from 0.038 to 11.7 µg methoxychlor/g dry wt of sediments in June 1986 following treatments in December 1985 and March 1986. Despite low concentrations of methoxychlor measured in stream water (maximum = 128 µg/l) during the initial treatment, massive drift (〉 950 000 organisms, and 70 g AFDM biomass) occurred from a stream area of about 144 m2. Numerically, collector-gatherer taxa (primarily Chironomidae) dominated drift (63 %) followed by shredders and predators; however, biomass of drift was dominated by shredders (48.9%), followed by predators and collector-gatherers. Compared with pre-treatment benthic abundances, insects were reduced by 75% following the initial treatment in December 1985, and 85% following an additional treatment in March 1986. Benthic abundances of non-insect taxa showed no significant changes. Benthic abundances of shredder, collector-filterer, and scraper functional groups exhibited significant decreases in the first month following treatment. Although benthic abundances of collector-gatherer and predator taxa were reduced by 48.6 and 40.5%, respectively, the reduction was not statistically significant because of high-sample variance. Comparisons of drift composition during the initial treatment with successive quarterly treatments (March 1986 to January 1988) reflected of ongoing pesticide disturbance of the biota as the community structure shifted from one consisting of a diverse insect and non-insect fauna toward one dominated by copepods, oligochaetes, Collembola, and chironomids.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00007601

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7

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Biocatalytic synthesis of polymers. II. Preparation of [AA-BB]x polyesters by porcine pancreatic lipase catalyzed transesterification in anhydrous, low polarity organic solvents (1989)

Wallace, J. Shield ; Morrow, Cary J.

Bognor Regis [u.a.] : Wiley-Blackwell

Journal of Polymer Science Part A: Polymer Chemistry 27 (1989), S. 3271-3284

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ISSN: 0887-624X

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Enzyme-catalyzed preparation of polymers offers several potentially valuable advantages over the usual polymerization procedures. (1) Such polymerizations may allow the polymer to retain functionality that would be destroyed under normal polymerization conditions. (2) The selectivity provided by enzyme catalysts may permit polymers, including optically active polymers, to be prepared that are either not accessible or accessible only with difficulty by other methods. (3) The characteristics of the enzyme and the mild polymerization conditions may permit formation of polymers having highly regular sizes and backbone structures. This report describes the first successful use of an enzyme-catalyzed polycondensation to prepare a chiral (AA-BB)x polyesters of more than a few repeat units. Polymerization of bis(2,2,2-trichloroethyl) alkanedioates (BB) with diols (AA) using the enzyme porcine pancreatic lipase (PPL) as a catalyst is detailed. The polycondensations were carried out at ambient temperature in anhydrous, low polarity organic solvents such as ether, THF, and methylene chloride. End group analysis by NMR provided Mn values of 1300-8200 daltons while GPC provided Mw values of 2800-14900 daltons for the polymers. Based on proton NMR spectra obtained during the polymerization, relatively rapid formation of an AA-BB “dimer” and an AA-BB-AA “trimer,” slower formation of a BB-AA-BB “trimer,” and subsequent condensation of these to give higher polymers are suggested to be components of the polymerization mechanism.

Additional Material: 2 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/pola.1989.080271008

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8

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Biocatalytic synthesis of polymers. Synthesis of an optically active, epoxy-substituted polyester by lipase-catalyzed polymerization (1989)

Wallace, J. Shield ; Morrow, Cary J.

Bognor Regis [u.a.] : Wiley-Blackwell

Journal of Polymer Science Part A: Polymer Chemistry 27 (1989), S. 2553-2567

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ISSN: 0887-624X

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The enantioselective polymerization of bis(2,2,2-trichloroethyl) trans-3,4-epoxyadipate with 1,4-butanediol using the enzyme porcine pancreatic lipase as a catalyst is described. The polymerization was carried out at ambient temperature in anhydrous ethyl ether. End group analysis provided MN = 5,300 daltons, whereas GPC provided Mw = 7,900 daltons for the polymer. The unchanged (+)-enantiomer of the diester was shown to have an enantiomeric purity of 〉 95% by proton NMR in the presence of the chiral shift reagent Eu(hfc)3. The stereochemical purity of the (-)-polymer was estimated at 〉 96% by consideration of the amount of the slower reacting enantiomer that could have been incorporated and still attain the observed degree of polymerization (25) when the starting ratio of racemic diester to diol was 2:1. Direct determination of the stereochemical purity of the polymer using Eu(hfc)3 was unsuccessful. Similar studies on polymer having random stereochemical orientations of the epoxide showed that such polymers do not behave as if they are racemic in the presence of the shift reagent. The polymer required for the latter studies was prepared by epoxidation of the product from enzyme catalyzed polymerization of bis(2,2,2-trichloroethyl) trans-3-hexenedioate with 1,4-butanediol.

Additional Material: 2 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/pola.1989.080270807

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