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  • 1995-1999  (269)
  • 1980-1984
  • 1965-1969
  • 1950-1954
  • 1996  (269)
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  • 1995-1999  (269)
  • 1980-1984
  • 1965-1969
  • 1950-1954
Year
  • 1
    Electronic Resource
    Electronic Resource
    Propagating fronts, chaos and multistability in a cell replication model (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Chaos 6 (1996), S. 477-492 
    Details
    ISSN: 1089-7682
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Numerical solutions to a model equation that describes cell population dynamics are presented and analyzed. A distinctive feature of the model equation (a hyperbolic partial differential equation) is the presence of delayed arguments in the time (t) and maturation (x) variables due to the nonzero length of the cell cycle. This transport like equation balances a linear convection with a nonlinear, nonlocal, and delayed reaction term. The linear convection term acts to impress the value of u(t,x=0) on the entire population while the death term acts to drive the population to extinction. The rich phenomenology of solution behaviour presented here arises from the nonlinear, nonlocal birth term. The existence of this kinetic nonlinearity accounts for the existence and propagation of soliton-like or front solutions, while the increasing effect of nonlocality and temporal delays acts to produce a fine periodic structure on the trailing part of the front. This nonlinear, nonlocal, and delayed kinetic term is also shown to be responsible for the existence of a Hopf bifurcation and subsequent period doublings to apparent "chaos'' along the characteristics of this hyperbolic partial differential equation. In the time maturation plane, the combined effects of nonlinearity, nonlocality, and delays leads to solution behaviour exhibiting spatial chaos for certain parameter values. Although analytic results are not available for the system we have studied, consistency and validation of the numerical results was achieved by using different numerical methods. A general conclusion of this work, of interest for the understanding of any biological system modeled by a hyperbolic delayed partial differential equation, is that increasing the spatio-temporal delays will often lead to spatial complexity and irregular wave propagation. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.166195
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  • 2
    Electronic Resource
    Electronic Resource
    Subgenus Systematics of Acanthamoeba: Four Nuclear 18S rDNA Sequence Types (1996)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 43 (1996), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Classification of Acanthamoeba at the subgenus level has been problematic, but increasing reports of Acanthamoeba as an opportunistic human pathogen have generated an interest in finding a more consistent basis for classification. Thus, we are developing a classification scheme based on RNA gene sequences. This first report is based on analysis of complete sequences of nuclear small ribosomal subunit RNA genes (Rns) from 18 strains. Sequence variation was localized in 12 highly variable regions. Four distinct sequence types were identified based on parsimony and distance analyses. Three were obtained from single strains: Type T1 from Acanthamoeba castellanii V006, T2 from Acanthamoeba palestinensis Reich, and T3 from Acanthamoeba griffini S-7. T4, the fourth sequence type, included 15 isolates classified as A. castellanii, Acanthamoeba polyphaga, Acanthamoeba rhysodes, or Acanthamoeba sp., and included all 10 Acanthamoeba keratitis isolates. Interstrain sequence differences within T4 were 0%–4.3%, whereas differences among sequence types were 6%–12%. Branching orders obtained by parsimony and distance analyses were inconsistent with the current classification of T4 strains and provided further evidence of a need to reevaluate criteria for classification in this genus. Based on this report and others in preparation, we propose that Rns sequence types provide the consistent quantititive basis for classification that is needed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.1996.tb04510.x
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  • 3
    Electronic Resource
    Electronic Resource
    Protective Monoclonal Antibodies Define a Distinct, Conserved Epitope on an Apical Complex Exoantigen of Cryptosporidium parvum Sporozoites (1996)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 43 (1996), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.1996.tb05005.x
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  • 4
    Electronic Resource
    Electronic Resource
    Neutralizing Monoclonal Antibody Protects Against Cryptosporidium parvum Infection by Inhibiting Sporozoite Attachment and Invasion (1996)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 43 (1996), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.1996.tb05006.x
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  • 5
    Electronic Resource
    Electronic Resource
    Spin-resolved electron spectroscopies of epitaxial magnetite (001) (abstract) : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5841-5841 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We will present the first spin-resolving electron spectroscopic studies of a magnetite (Fe3O4)(001) surface. Magnetite is a semimetal with a high density of states in the minority band, but a large band gap in the majority states at the Fermi energy. The polarization of the secondary emission cascade is measured using spin-resolved secondary electron emission spectroscopy (SRSEES), and reflects the semimetallic spin structure of Fe3O4. The polarization plateau of spin-resolved secondary emission (29.8%) matches the average 3D band polarization of stoichiometric Fe3O4 as determined from spin-resolved band structure calculations (34.2%). An enhancement of the polarization of the secondary electrons at lowest energies will also be discussed. Spin-resolved Auger emission spectroscopy (SRAES) of the Fe3O4 films have been measured and show correlation effects in the valence-valence Auger transitions. Suppressed intensity and polarization of M23M45M45 Auger emission relative to M1M45M45 Auger emission is observed, as well as strong resonant emission with shake-up. Conversely, no spin polarization is detected in the spin-resolved oxygen LMM Auger features, although oxygen Auger emission (in which we can distinguish between adsorbed and bonded oxygen) is used to verify surface cleanliness of the samples.The synthesis of Fe3O4 films grown on magnesium oxide (001) substrates using oxygen plasma-assisted molecular beam epitaxy will be discussed, as will thin-film characterization using SQUID magnetometry and x-ray and electron diffraction. A unique angle-, energy-, and spin-resolved electron spectrometer has been designed and built for the study of magnetic surfaces, and these studies represent its' first use. That spectrometer is based on a tandem configuration of an energy-dispersive energy analyzer and Mott spin polarimeter. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362205
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  • 6
    Electronic Resource
    Electronic Resource
    Stable Isotopic Evaluation of the Relative Assimilation of Natural and Artificial Foods by Golden Shiners Notemigonus crysoleucas in Ponds (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the World Aquaculture Society 27 (1996), S. 0 
    Details
    ISSN: 1749-7345
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Stable carbon isotope ratios (δ13C) were used to estimate the relative contributions of natural and prepared feeds to the nutrition of golden shiners Notemigonus crysoleucas in ponds. Concurrent feeding trials were conducted in tanks (110 L) and ponds (0.04 ha) to determine the response of golden shiners to three isotopically distinct prepared diets both in the presence (pond) and absence (tank) of natural food. Seston was the primary indicator of the δ13C of natural foods available in the ponds, but δ13C's of free-swimming, unfed golden shiners provided an additional index. Fish receiving experimental diets were maintained in floating nets within the same ponds. After 6 wk, fish in tanks fed all three diets had acquired the diet label to some degree, while fish in ponds also tracked their respective feeds except for those fed diet 3. This diet contained a large amount of corn meal, which appeared to be poorly assimilated by golden shiners. The use of natural foods by golden shiners fed all three prepared feeds ranged from 40–83% and was inversely correlated with the relative assimilation of the prepared feeds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-7345.1996.tb00266.x
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  • 7
    Electronic Resource
    Electronic Resource
    Electronic spectroscopy and quenching dynamics of OH–H2/D2 pre-reactive complexes (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 6984-6996 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Binary complexes of OH X 2Π and H2/D2 have been stabilized in the entrance valley to the hydrogen abstraction reaction and identified in the OH A 2Σ+–X 2Π 0–0 spectra region. Nearly all of the intermolecular vibrational levels supported by the OH A 2Σ+ (v′=0)+H2/D2 potential energy surface have been observed in fluorescence depletion experiments. Rapid electronic quenching precludes the observation of OH–H2/D2 prepared in these levels by laser-induced fluorescence. A sharp onset of laser-induced fluorescence occurs at the OH A 2Σ+ (v′=0)+H2/D2 dissociation limit. The binding energies for OH–H2/D2 in the ground state correlating with OH X 2Π (v″=0)+H2/D2 have been determined to be 54 cm−1 and more than 66 cm−1, respectively. The OH A 2Σ+ (v′=0)+H2/D2 excited state is found to be at least 577 cm−1 (H2) and 639 cm−1 (D2) more strongly bound than the ground state. The positions of observed features are compared with the corresponding intermolecular levels observed by laser-induced fluorescence in the OH A–X 1–0 region as well as theoretical predictions of the transition energies based on ab initio potentials for the ground and excited electronic states. The OH–H2/D2 intermolecular levels correlating with OH A 2Σ+ (v′=0)+H2/D2 have lifetimes of 3.2–4.5 ps, deduced from homogeneous linewidths, due to quenching and/or chemical reaction. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.471408
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  • 8
    Electronic Resource
    Electronic Resource
    Intermolecular vibrations and relaxation dynamics in complexes of OH A 2Σ+ (v′=0,1) with N2 (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 10224-10236 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The intermolecular vibrational energy levels supported by the OH A 2Σ+ (v′=0,1)+N2 potentials have been characterized spectroscopically through excitation of OH–N2 complexes in the OH A 2Σ+–X 2Π 0–0 and 1–0 spectral regions. At least 95 levels correlating with OH A 2Σ+ (v′=0)+N2 are observed in fluorescence depletion experiments. OH–N2 complexes prepared in these levels have lifetimes with lower limits ranging from 1.4 to 8 ps due to rapid electronic quenching which precludes their detection by laser-induced fluorescence. An onset of OH–N2 laser-induced fluorescence occurs at the OH A 2Σ+ (v′=0)+N2 dissociation limit, enabling determination of the ground and excited state binding energies at ∼250 and ≥1372 cm−1, respectively. In the OH A–X 1–0 region, OH–N2 transitions originating from a common ground state level to single or groups of intermolecular vibrational levels correlating with OH A 2Σ+ (v′=1)+N2 are observed via laser-induced fluorescence and fluorescence depletion measurements. Comparison of the OH–N2 spectra obtained in the OH A–X 0–0 and 1–0 regions reveals that vibrational excitation of OH A 2Σ+ increases the OH–N2 binding energy by 139 cm−1. OH–N2 complexes excited in the OH A–X 1–0 region undergo ultrafast dynamics (〈200 fs) which give rise to extensive spectral line broadening. A kinetic model indicates that vibrational predissociation is the dominant decay channel for OH–N2 prepared in the intermolecular levels derived from OH A 2Σ+ (v′=1)+N2. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472732
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  • 9
    Electronic Resource
    Electronic Resource
    THE beta-KETOADIPATE PATHWAY AND THE BIOLOGY OF SELF-IDENTITY (1996)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Microbiology 50 (1996), S. 553-590 
    Details
    ISSN: 0066-4227
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract The beta-ketoadipate pathway is a chromosomally encoded convergent pathway for aromatic compound degradation that is widely distributed in soil bacteria and fungi. One branch converts protocatechuate, derived from phenolic compounds including p-cresol, 4-hydroxybenzoate and numerous lignin monomers, to beta-ketoadipate. The other branch converts catechol, generated from various aromatic hydrocarbons, amino aromatics, and lignin monomers, also to beta-ketoadipate. Two additional steps accomplish the conversion of beta-ketoadipate to tricarboxylic acid cycle intermediates. Enzyme studies and amino acid sequence data indicate that the pathway is highly conserved in diverse bacteria, including Pseudomonas putida, Acinetobacter calcoaceticus, Agrobacterium tumefaciens, Rhodococcus erythropolis, and many others. The catechol branch of the beta-ketoadipate pathway appears to be the evolutionary precursor for portions of the plasmid-borne ortho-pathways for chlorocatechol degradation. However, accumulating evidence points to an independent and convergent evolutionary origin for the eukaryotic beta-ketoadipate pathway. In the face of enzyme conservation, the beta-ketoadipate pathway exhibits many permutations in different bacterial groups with respect to enzyme distribution (isozymes, points of branch convergence), regulation (inducing metabolites, regulatory proteins), and gene organization. Diversity is also evident in the behavioral responses of different bacteria to beta-ketoadipate pathway-associated aromatic compounds. The presence and versatility of transport systems encoded by beta-ketoadipate pathway regulons is just beginning to be explored in various microbial groups. It appears that in the course of evolution, natural selection has caused the beta-ketoadipate pathway to assume a characteristic set of features or identity in different bacteria. Presumably such identities have been shaped to optimally serve the diverse lifestyles of bacteria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.micro.50.1.553
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  • 10
    Electronic Resource
    Electronic Resource
    QUANTITATIVE OPTICAL SPECTROSCOPY FOR TISSUE DIAGNOSIS (1996)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Physical Chemistry 47 (1996), S. 555-606 
    Details
    ISSN: 0066-426X
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The interaction of light within tissue has been used to recognize disease since the mid-1800s. The recent developments of small light sources, detectors, and fiber optic probes provide opportunities to quantitatively measure these interactions, which yield information for diagnosis at the biochemical, structural, or (patho)physiological level within intact tissues. However, because of the strong scattering properties of tissues, the reemitted optical signal is often influenced by changes in biochemistry (as detected by these spectroscopic approaches) and by physiological and pathophysiological changes in tissue scattering. One challenge of biomedical optics is to uncouple the signals influenced by biochemistry, which themselves provide specificity for identifying diseased states, from those influenced by tissue scattering, which are typically unspecific to a pathology. In this review, we describe optical interactions pursued for biomedical applications (fluorescence, fluorescence lifetime, phosphorescence, and Raman from cells, cultures, and tissues) and then provide a descriptive framework for light interaction based upon tissue absorption and scattering properties. Finally, we review important endogenous and exogenous biological chromophores and describe current work to employ these signals for detection and diagnosis of disease.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.physchem.47.1.555
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