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  • 1
    Electronic Resource
    Electronic Resource
    Singularities in the spectra of random matrices (1996)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 37 (1996), S. 5019-5032 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: We consider singularities of the set of energy levels En(X) of a quantum Hamiltonian, obtained by varying a set of d parameters X=(X1,..,Xd). Singularities such as minima, degeneracies, branch points, and avoided crossings can play an important role in physical applications. We discuss a general method for counting these singularities, and apply it to a random matrix model for the parameter dependence of energy levels. We also show how the density of avoided crossing singularities is related to a non-analyticity of a correlation function describing the energy levels. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.531686
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  • 2
    Electronic Resource
    Electronic Resource
    The Gaussian-2 method with proper dissociation, improved accuracy, and less cost (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 11679-11681 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The Gaussian-2 method (G2) is modified by deleting the empirical high-level correction and instead using empirical coefficients to extrapolate to full configuration interaction and an infinite basis set. The resulting method, called multicoefficient Gaussian-2 (MCG2) is less expensive than G2 but a factor of 1.7 more accurate for molecules composed of H and first-row atoms. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479112
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  • 3
    Electronic Resource
    Electronic Resource
    Infinite basis limits in electronic structure theory (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 2921-2926 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have developed a database of 29 molecules for which we have estimated the complete-one-electron-basis-set limit of the zero-point-exclusive atomization energy for five levels of electronic structure theory: Hartree–Fock (HF) theory, Møller–Plesset second- and fourth-order perturbation theory, coupled cluster theory based on single and double excitations (CCSD), and CCSD plus a quasiperturbative treatment of triple excitations [CCSD(T)], all at a single set of standard geometries. Convergence checks indicate that the estimates are within a few tenths of a kcal/mol of the n=infinity limit of the cc-pVnZ basis set sequence. This data is then used to obtain optimized power-law exponents for extrapolating to the basis-set-limit from correlation-consistent polarized valence double and triple zeta (cc-pVDZ and cc-pVTZ) basis sets. This allows one to get thermochemical accuracy comparable to polarized quadruple or quintuple zeta (cc-pVQZ or cc-pV5Z) basis sets with a cost very comparable to polarized triple zeta, which is one order of magnitude less expensive than polarized quadruple zeta and two orders of magnitude less expensive than polarized quintuple zeta. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479659
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  • 4
    Electronic Resource
    Electronic Resource
    Changes in ascorbic acid levels in apoplastic fluid during growth of pine hypocotyls. Effect on peroxidase activities associated with cell walls (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 101 (1997), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The apoplastic fluid of pine (Pinus pinaster Aiton) hypocotyls contains ascorbic acid (AA) and dehydroascorbic acid (DHA). The amounts of ascorbic and dehydroascorbic acids were in the nmol (g fresh weight)−1 range and decreased with the hypocotyl age as well as along the hypocotyl axis. The ratio AA/(AA+DHA) also decreased with the hypocotyl age and along the hypocotyl. Both ascorbic oxidase and peroxidase activity against ascorbic acid showed very low activity not only in the apoplastic fluid but also in the fractions ionically and covalently bound to the cell walls. However, the peroxidase activity in the three abovementioned fractions was strongly increased in the presence of ferulic acid. That stimulation effect increased with the hypocotyl age and from the apical towards the basal region of the hypocotyls of 10-day-old seedlings. Furthermore, the oxidation of ferulic acid by apoplastic and ionically- and covalently-bound peroxidases was inhibited by ascorbic acid as long as ascorbate was available. A regulatory role of apoplastic ascorbic acid levels in the formation of dehydrodiferulic bridges between wall polysaccharides catalysed by cell wall peroxidases and thus in the cell wall stiffening during plant growth is proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1997.tb01068.x
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  • 5
    Electronic Resource
    Electronic Resource
    Photosynthetic response of P-deficient Gracilaria tenuistipitata under two different phosphate treatments (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 96 (1996), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Phosphorus-deficient Gracilaria tenuistipitata Zhang et Xia was cultured for 15 days at two different inorganic phosphate (Pi) concentrations: 3 μM (low Pi treatmenl) or 30 μM phosphate (high Pi treatment). The amount of ribulose-l,5-bisphosphate carboxy-lase/oxygenase (Rubisco), phycobiliproteins, Chl a and total soluble proteins were higher in the high Pi than in the low Pi treatment. The total N content of the low Pi plants was lower than in plants grown at high Pi concentrations whereas the amount of total C was highest in low Pi plants. The increase of Rubisco content in the high Pi treatment (3-fold) was parallel to the enhancement of the maximum photosynthetic rate which increased 5-fold. This correspondence was also found in the low Pi treatment in which Rubisco content and maximum photosynthesis did not change significantly from the initial values. The photosynthetic efficiency was also higher at high than at low Pi. The high Pi plants also showed higher dark respiration and growth rates. The data presented here suggest that marine macroalgae submitted to Pi deficiency exhibit a decrease in growth caused not only by Pi implication on energy transfer in photosynthesis and respiration, but also by the diminution of the amount of photosynthetic pigments and Rubisco.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1996.tb00232.x
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  • 6
    Electronic Resource
    Electronic Resource
    Molecular genetic analysis of patients carrying steroid 21-hydroxylase deficiency in the Mexican population: identification of possible new mutations and high prevalence of apparent germ-line mutations (1998)
    Springer
    Human genetics 〈Berlin〉 102 (1998), S. 170-177 
    Details
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Steroid 21-hydroxylase deficiency is the underlying cause in over 90% of patients with congenital adrenal hyperplasia, an inherited metabolic disorder of adrenal steroidogenesis. We have characterized 94 mutant alleles from 47 unrelated Mexican patients and the corresponding mutant alleles in their parents by amplification of the functional CYP21 gene by PCR, followed by direct sequence analysis. The study included patients diagnosed with the three clinical forms of the disease. Our results revealed: (1) the presence of relatively few mutations or combinations of mutations associated with particular phenotypes; (2) the presence of putative new mutations; (3) the finding of identical genotypes in patients displaying discordant phenotypes; (4) the identification of patients lacking all previous reported mutations; and (5) an apparent high frequency of germ-line mutations. The absence of previously reported mutations in about 22% of the disease alleles, the finding of putative new mutations in some of the patients lacking previously known mutations, and the apparent high prevalence of germ-line mutations make evident the differences in the genetic background leading to this disorder between the Caucasian and the Mexican populations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004390050672
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  • 7
    Electronic Resource
    Electronic Resource
    Characterization and DNA sequence of the b6w2 allotype of the rabbit immunoglobulin kappa 1 light chain (b locus) (1995)
    Springer
    Immunogenetics 42 (1995), S. 333-341 
    Details
    ISSN: 1432-1211
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The b6w2 allotype of the constant region of the rabbit immunoglobulin kappa 1 (k1) light chain (b locus) was discovered in wild populations from northern Spain. At the serological level, the b6w2 allotype is characterized by the presentation of all b6-specific epitopes, while an allotypic determinant which is shared between the nominal b5 and b6 allotypes is lacking. The DNA fragment encoding the b6w2 allotype was amplified by means of the polymerase chain reaction, and sequenced directly by dideoxy-DNA-sequencing. When compared with the sequence of the nominal b6 allele, the b6w2 sequence differs at eleven nucleotide positions (96.5% similarity). This variation corresponds to amino acid replacements at 1) the three positions C-terminal to the peptidyl junction with the variable region (amino acid positions 109–111);2) the four positions N-terminal to the interdomain disulfide bond (167–170); and 3) two positions in the vicinity of the interchain disulfide bond (190 and 210). The nature and distribution of the observed nucleotide substitutions strongly suggest a possible role of the extra interdomain disulfide bond in the unusual evolutionary dynamics of the rabbit K1 light chain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00179394
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  • 8
    Electronic Resource
    Electronic Resource
    The allotypic patchwork pattern of the rabbit IGKC1 allele b5wf: genic exchange or common ancestry? (1999)
    Springer
    Immunogenetics 49 (1999), S. 7-14 
    Details
    ISSN: 1432-1211
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  The protein sequences of different alleles of the rabbit immunoglobulin IGKC1 gene can differ at more than 40% of the amino acid positions. This exceptional degree of allelic divergence raises questions concerning the causal underlying mechanisms. We report the DNA sequence of the coding region of an allotype which is associated with the mitochondrial lineage A (Southwestern Spain). At the serological level, this b5wf allotype presents a patchwork of antigenic determinants which in domestic breeds are characteristic of the b4, b5, and b6 allotypes. The inferred protein sequence of the b5wf allotype was found to differ from that of the b4, b5, and b6 allotypes at 25, 10, and 15% of the amino acid positions, respectively. Sequence comparisons show that the b4-specific epitopes of the b5wf allotype are probably due to a shared ThrThrGlnThr motif at Kabat positions 153–156. Similarly, the shared b5-specific determinants should relate to the motifs 161ThrSerLys163 and/or 182LysSerAspGlu185. A monoclonal antibody binding epitope shared among the b5wf, b5, and b6 sequences appeared to be correlated with the presence of Asp190. Although there is evidence of interallelic genic exchange, sequence comparisons suggest that the apparent mosaic structure of the b5wf allotype is better explained by common ancestry and point mutation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002510050458
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  • 9
    Electronic Resource
    Electronic Resource
    Modulation of Synapsin I Gene Expression in Rat Cortical Neurons by Extracellular Matrix (1998)
    Springer
    Cellular and molecular neurobiology 18 (1998), S. 369-378 
    Details
    ISSN: 1573-6830
    Keywords: neuronal differentiation ; synapsin I ; extracellular matrix ; laminin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 1. Neuronal differentiation depends on crosstalk between genetic program and environmental cues. In this study we tried to dissect this complex interplay by culturing neurons from fetal rat brain cortices in a chemically defined, neuron-specific, medium and on different substrata, either artificial (poly-D-lysine) or natural. 2. Among the extracellular matrix compounds used in this study, two (collagen I and fibronectin) allowed only a weak attachment of cortical neurons to the substratum, while the others (collagen IV, laminin, and basal lamina from Engelbreth-Holm-Swarm sarcoma) allowed both firm attachment and moderate to extensive neurite outgrowth from neuronal cell bodies. 3. By using synapsin I gene expression as a parameter of neuronal differentiation, we found that neurite outgrowth and neuronal differentiation are not linearly linked. Synapsin I gene expression, in fact, was maximal in neurons cultured on laminin, while the fastest neuritic outgrowth was recorded in cultures on poly-D-lysine. 4. The data presented in this paper are consistent with the hypothesis that the extracellular matrix plays an active role in modulating the differentiative program of neurons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022562813846
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  • 10
    Electronic Resource
    Electronic Resource
    Isabela Crater-Lake: a Mexican insular saline lake (1998)
    Springer
    Hydrobiologia 381 (1998), S. 1-7 
    Details
    ISSN: 1573-5117
    Keywords: Tropical limnology ; meromixis ; nutrients ; plankton ; Nayarit ; Mexico ; Isabela island
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Isabela Crater-Lake is a bright-green, hypersaline lake (68–112.5 mS cm-1) on Isabela Island off the Pacific coast of Nayarit, Mexico. Some salient features were documented in November 1993. It appears meromictic, with three well-defined strata separated by sharp pycnoclines. Surface water was warm (32 °C) reaching a subsurface (0.5–1 m) maximum temperature (33 °C), declining gradually to 26.7 °C at maximum depth (17.5 m). Dissolved oxygen was near saturation at the surface, attained 145 percent saturation at 0.5 m, but was completely absent by 2.5 m. Eh was maximum at the surface (123 mV), declining to a minimum at 3 m (–261 mV), and was about –240 mV from 3.5 m to the bottom. The pH varied from 9.3 in surface waters to slightly acid (6.4) in deep anoxic layers. Atypically, NO3 was more abundant than NH4 in both aerobic and anaerobic strata. PO4 and SiO2 concentrations were extremely high. The planktonic microbial community was formed by four groups: bacteria (photosynthetic sulfur bacteria and heterotrophic bacteria), phytoflagellates (mainly cryptomonads), heterotrophic nanoflagellates ( Spumella spp., Bodo spp.) and ciliates (Hypotricha and Oligotricha). Bacteria occurred throughout the water column, but other biota were restricted to surface waters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003239910574
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