Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • 1990-1994  (15)
Source
Material
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Entropy on charge density: making the quantum mechanical connection (1993)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 49 (1993), S. 86-89 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Entropy maximization has proven effective in treating certain aspects of the phase problem of X-ray diffraction. Much of its development has been expressed in probabilistic language, although image enhancement has been somewhat more physical or geometric in description. Here phasing and entropy maximization are embedded in the quantum mechanical problem of reconstructing an electronic one-matrix under experimental constraints. Entropy on an N-representable one-particle density matrix is well defined. The entropy is the expected form, and it is a simple function of the one-matrix eigenvalues which all must be non-negative. Certain other properties are pertinent to phasing which is implicit in one-matrix reconstruction governed by entropy maximization. Throughout this work reference is made to informational entropy, not the entropy of thermodynamics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444992009429
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Programs for phasing by entropy maximization as implemented in Xtal3.2: a crystallographic software system (1993)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 49 (1993), S. 100-106 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Xtal3.2, a crystallographic software package, is an international development project involving about 40 researchers over a full spectrum of crystallographic interests. This development has been supported by many national and international agencies and commercial institutions since the first version in 1983. The 1992 release, Xtal3.2, contains software for 95 different calculations. These range from the processing of raw diffraction data to interactive molecular graphics, atomic charge estimation, electronic publication preparation, and the structure solution and refinement of small and large molecules. Tests of the Xtal programs for phase determination and phase refinement by the application of `maximum entropy' are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444992008898
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Identification of Meat from Game and Domestic Species (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 57 (1992), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Isoelectric focusing combined with specific enzyme staining for creatine kinase was used to characterize banding patterns in meat from pronghorn, mule deer, white-tailed deer, sheep, moose, pork, bison, elk, caribou, red deer, beef and goat. Processed and cooked pork was differentiated from all species and beef and elk were separated from pronghorn. It was not possible to differentiate beef from elk, or prong-horn from sheep. The inability to separate some game from some domestic species and the lability of the staining proteins after heating above 67°C limits the application of this technique.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.1992.tb05529.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Genetic Diversity in Tall Fescue Ecotypes from Alabama I. Maturity, Morphological Traits, and Disease Reaction (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Plant breeding 107 (1991), S. 0 
    Details
    ISSN: 1439-0523
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: There is a large hectarage of tall fescue in Alabama. Recognition of the deleterious effects of the endophytic fungus Acremonium coenophialum has resulted in substantial acceptance of new endophyte-free cultivars. Destruction of old pastures and the concomitant loss of potentially valuable adapted germplasm could be a valid cause for concern. The objectives of this study were to evaluate genetic variation for maturity and plant morphological traits, both among and within tall fescue cv. ‘Kentucky 31’ populations from 18 to 38 year-old pastures in Alabama. Ten populations of approximately 50 plants each were collected from old Alabama tall fescue pastures. Two pastures were sampled in each of five counties, representing the five major land use areas of the state. In 1990, spaced plants of all populations were evaluated at heading time for maturity, morphological, and disease traits at two locations in central Alabama. Endophyte infection level of the populations ranged from 2 to 100 %. Maturity was highly correlated with tiller length and flag leaf width and was used as a covariate for these traits in the analysis of variance. Leaf rust and net blotch ratings were negatively correlated. Significant variation among populations was observed for maturity and flag leaf dimensions, most variation being due to differences among source counties. Significant variation was observed within all populations for maturity and morphological traits, but only in seven populations for leaf rust. No within-population variation was detected for net blotch. The average precipitation for the month of May explained 81 % of the variation among populations for maturity. Age of the pasture sampled had a significant effect on tiller diameter (r2= 0.55), and latitude of the pasture sampled was the best individual predictor of leaf width (r2= 0.42). This study reveals that considerable genetic diversity, largely influenced by climatic conditions, exists among ‘Kentucky 31’ tall fescue ecotypes from Alabama.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1439-0523.1991.tb01208.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Reflection high energy electron diffraction observation of anion exchange reactions on InAs surfaces (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 259-262 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have used time-resolved reflection high energy electron diffraction (RHEED) measurements to study anion exchange reactions in molecular beam epitaxy (MBE) grown III-V semiconductors. In the experiment, InAs surfaces are exposed to Sbx fluxes and subsequent changes in the crystals RHEED patterns are examined. We find that when an InAs surface is initially exposed to an Sb flux the specular spot intensity first decreases, then recovers back toward its initial value. The shape of the intensity versus time curves is extremely reproducible if the absolute Sb flux and the Sb species are kept constant. The length of time required for the RHEED pattern to stabilize is much shorter for cracked Sb than for uncracked Sb. The RHEED dynamics are also faster if the total Sb flux increases. The behavior of the RHEED dynamics as a function of Sb flux and Sb species is consistent with the changes in the RHEED pattern being due to an Sb/As exchange reaction on the crystal's surface. The RHEED data are compared to previously published x-ray photoelectron spectroscopy (XPS) data which studied exchange reactions on InAs surfaces exposed to Sb fluxes. The XPS study confirmed that the incident Sb did indeed exchange with As in the epilayer and estimated the exposure time needed to complete the Sb/As exchange reaction. The time scales for exchange associated with the RHEED and XPS data are in good agreement. This further indicates that RHEED could be used to indirectly probe anion exchange reactions, potentially opening up several avenues of research ranging from basic materials science to MBE process control in manufacturing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355893
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Experimental observation of negative differential resistance from an InAs/GaSb interface (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 683-685 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have observed negative differential resistance at room temperature from devices consisting of a single interface between n-type InAs and p-type GaSb. InAs and GaSb have a type II staggered band alignment; hence, the negative differential resistance arises from the same mechanism as in a p+-n+ tunnel diode. Room-temperature peak current densities of 8.2×104 A/cm2 and 4.2×104 A/cm2 were measured for structures with and without undoped spacer layers at the heterointerface, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103591
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    p-type doping of gallium antimonide grown by molecular beam epitaxy using silicon (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 2256-2258 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the first effective p-type doping of molecular beam epitaxy (MBE) grown GaSb using silicon. The samples were grown by molecular beam epitaxy and characterized by Hall-effect measurements and photoluminescence. Room-temperature hole concentrations ranging from 4.0×1015 to 4.3×1018 cm−3 were obtained. Photoluminescence (PL) spectra undergo considerable broadening with increasing doping concentration, consistent with an impurity banding picture. Furthermore, the MBE-grown samples display only one of the two PL features found in a melt-grown substrate and no other satellites, suggesting higher material purity. This may be a direct benefit from the use of an antimony cracker, ultrahigh vacuum conditions, and high-purity elemental sources. The short-period strained-layer superlattice buffering scheme employed may have also contributed to better structural quality.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103907
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Large peak current densities in novel resonant interband tunneling heterostructures (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 1257-1259 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have observed negative differential resistance (NDR) and large peak current densities in a novel resonant interband tunneling structure grown by molecular beam epitaxy in the InAs/GaSb/AlSb material system. The structure consists of a thin AlSb barrier layer displaced from an InAs(n)/GaSp(p) interface. NDR is readily observable at room temperature with peak current densities greater than 105 A/cm2. The enhancement in peak current density relative to a structure with no AlSb barrier is consistent with the existence of a quasi-bound state in the region between the barrier and the InAs/GaAs interface. Furthermore, we demonstrate that by growing the AlSb layer on either the InAs or GaSb side of the interface, the quasi-bound state can be localized in either material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103502
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Experimental observation of large room-temperature current gains in a Stark effect transistor (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 1673-1675 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report experimental observation of room-temperature current gains as large as 50 in a novel transistor grown in the InAs/GaSb/AlSb material system. Due to the unique degree of flexibility this material system offers in choosing band alignments, the base and collector terminals are separated by a quantum barrier while electrons traveling between the emitter and collector terminals do not tunnel across any classically forbidden regions, even though a quasi-bound state exists in the quantum well collector. This asymmetry in current conduction between the terminals of the device leads to transistor action: applying a bias to the base terminal electrostatically modulates the emitter-collector current through Stark shifts of the energy levels in the quantum well collector, while the quantum barrier between the base and collector terminals suppresses the base current. Because transport through the structure is dependent on resonant transmission, this novel transistor holds promise for the fabrication of high-speed circuits.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105107
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Demonstration of resonant transmission in InAs/GaSb/InAs interband tunneling devices (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 2675-2677 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have performed a theoretical and experimental analysis of current transport in InAs/GaSb/InAs interband tunneling devices as a function of GaSb layer width. Our results demonstrate that current transport in these devices occurs not through simple ohmic conduction, as had been previously proposed, but via light-hole-like resonances in the GaSb valence band formed due to the imperfect matching of InAs conduction-band and GaSb valence-band wave functions at the InAs/GaSb interfaces. These resonances produce a strong dependence of the current-voltage characteristics on GaSb layer width that is both predicted theoretically and observed experimentally. Our results also suggest that coupling between InAs conduction-band and GaSb heavy-hole valence-band states is relatively unimportant in these devices. In addition, we have been able to obtain peak current densities of ∼9×104 A/cm2, significantly higher than any previously reported current densities for this structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104109
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...