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  • 1
    Electronic Resource
    Electronic Resource
    Ferromagnetic critical correlations and dynamics in AuFe reentrant ferromagnets : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 6158-6160 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We determined the paramagnetic critical scattering of the reentrant ferromagnets Au1−xFex, with x=0.2, 0.18, and 0.16, i.e., close to the threshold (xc∼0.155), below which ferromagnetism disappears and a spin-glass state sets in. Following the Ornstein–Zernicke formalism, we derived the inverse critical ferromagnetic correlation length (κ=ξ−1) and the related magnetic susceptibility. The macroscopic susceptibility χq=0 of the samples was also determined in a separate experiment with a Faraday balance. The neutron results show the same behavior of critical type with χq=0 for x=0.18 but not for x=0.16. We interpret this discrepancy as an indication for a non-well-defined ferromagnetic transition for x=0.16. A further comparison of our results with those for Fe shows that the amplitude of the correlation length increase with increasing disorder so that, at the same reduced temperature τ, the correlations are much larger in the disordered samples than in Fe. As a consequence of this, the ferromagnetic correlations in the disordered samples persist well above Tc and lead to a much wider critical region than is the case in Fe and in usual ferromagnets. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362058
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  • 2
    Electronic Resource
    Electronic Resource
    Amino Acid Reiterations in Yeast Are Overrepresented in Particular Classes of Proteins and Show Evidence of a Slippage-Like Mutational Process (1999)
    Springer
    Journal of molecular evolution 49 (1999), S. 789-797 
    Details
    ISSN: 1432-1432
    Keywords: Key words: Yeast — Slippage — Amino acid tandem repeats — Homopeptides — Protein function — Genome analysis — Codon composition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Long amino acid repeats are often observed in eukaryotic proteins. In humans, several neurological disorders are caused by proteins containing abnormally long polyglutamines. However, no systematic analysis has attempted to investigate the relationship between reiterations of particular amino acids and protein function, the possible mechanisms involved in the generation of these regions, or the contribution of selection in restricting their genomic distribution, in a large collection of wild-type proteins. We have used baker's yeast open reading frames to study these questions. The most abundant amino acid repeats found in yeast proteins are repeats of glutamine, asparagine, aspartic acid, glutamic acid, and serine. Different amino acid repeats are concentrated in different classes of proteins. Acidic and polar amino acid repeats are significantly associated with transcription factors and protein kinases, while serine repeats are significantly associated with membrane transporter proteins. In most cases the codon structures encoding the repeats at the gene level show a significant bias toward long tracts of one of the possible codons, suggesting that trinucleotide slippage has played an important role in generating these reiterations. However, many, particularly those encoding serine repeats, do not show evidence of slippage. The distributions of codon repeats within proteins and between coding and noncoding regions of the genome, and of amino acids between proteins with different functions, suggest that repeats of these kinds are subject to strong selection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00006601
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  • 3
    Electronic Resource
    Electronic Resource
    Microscopic measurement of the linear compressibilities of two-dimensional fatty acid mesophases (1998)
    Springer
    The European physical journal 1 (1998), S. 57-69 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 61.10-i X-ray diffraction and scattering - 68.10.Et Interface elasticity, viscosity and viscoelasticity - 68.60.Bs Mechanical and acoustical properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The linear compressibility of two-dimensional fatty acid mesophases has been determined by grazing incidence X-ray diffraction. The unit cell parameters of the , , , S and phases of behenic acid and of the phase of myristic acid were determined as a function of surface pressure and temperature. Surface pressure versus molecular area isotherms were reconstructed from these measurements, and the linear compressibility (relative distortion along a given direction for a two-dimensional isotropic applied stress) was determined both in the sample plane and in a plane normal to the aliphatic chain director (transverse plane). The linear compressibilities range over two orders of magnitude from 0.1 to 10 m/N and are distributed depending on their magnitude in 4 different sets which we are able to associate with different molecular mechanisms. The largest compressibilities (10 m/N) are observed in the tilted phases. They are apparently independent on the chain length and could be related to the reorganization of the headgroup hydrogen-bounded network, whose role should be revalued. Intermediate compressibilities are observed in phases with quasi long-range order (directions normal to the molecular tilt in the or phases, S phase, and could be related to the ordering of these phases. The lowest compressibilities are observed in the solid untilted phase and for one direction of the S and phases. They are similar to the compressibility of crystalline polymers and correspond to the interactions between methyl groups in the crystal. Finally, negative compressibilities are observed in the transverse plane for the and phases and can be traced to subtle reorganizations upon untilting.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100510050152
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  • 4
    Electronic Resource
    Electronic Resource
    Synaptic Membrane Freezing Affects Modulatory Sites in Avian Central Nervous System GABAA Receptor (1999)
    Springer
    Neurochemical research 24 (1999), S. 1347-1355 
    Details
    ISSN: 1573-6903
    Keywords: GABAA receptor ; barbiturates ; neurosteroids ; freeze-thawing ; chick optic lobe ; endogenous factors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Studies were carried out to determine whether barbiturates and neurosteroids share common recognition sites at the GABAA receptor complex in avian CNS. To achieve this, differentially prepared fresh and frozen synaptic membranes were used. Both the barbiturate, pentobarbital, and the neurosteroid, 3α-hydroxy-5α-pregnan-20-one, were able to stimulate GABA binding in both types of membranes. Stimulation differed markedly when both drugs were added jointly to different treated tissue. In frozen membranes drugs acted synergistically and were differentially displaced by picrotoxinin, while in fresh ones, where both compounds were inhibited by the convulsant, this additivity was absent. Post-freezing wash supernatants were collected and used as a source of putative endogenous factors involved in the above mentioned membrane differences. Addition of a high molecular weight fraction from supernatants to frozen synaptic membranes led to an inhibition of barbiturate and neurosteroid potentiation, as well as a loss of their additive effect. Our results indicate that GABAA receptor modulation by barbiturates and neurosteroids is affected by synaptic membrane treatment, with a common modulatory site in fresh membranes and separate recognition sites after a freeze-thawing procedure. There may also be endogenous factors involved in overlapping of modulatory sites, which would thus regulate GABAA receptor functionality by direct interaction with the complex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022520320556
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  • 5
    Electronic Resource
    Electronic Resource
    Drought signal transduction in plants (1996)
    Springer
    Plant growth regulation 20 (1996), S. 105-110 
    Details
    ISSN: 1573-5087
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Water deficit is one of the most common environmental limitations of crop productivity by affecting growth through alterations in metabolism and gene expression. The mechanisms involved in drought perception and signal transduction pathways are poorly understood. The participation of the plant hormone abscisic acid (ABA) has been well established. ABA levels increase when there are changes in the environment that result in cellular dehydration. Different approaches have been taken to understanding the molecular responses to desiccation and how ABA regulates gene expression. Recent efforts have identified particular topics of importance in the dissection of the signal transduction pathway which are summarized as follows: physiological approaches: identification of signalling molecules. Genetic approaches: the use of mutants, and Molecular approaches: promoter analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00024006
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  • 6
    Electronic Resource
    Electronic Resource
    Morphological differentiation of the conjunctival goblet cells in the chick (Gallus domesticus) (1997)
    Springer
    Graefe's archive for clinical and experimental ophthalmology 235 (1997), S. 717-722 
    Details
    ISSN: 1435-702X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract • Background: These is no consensus in the literature regarding the differentiation of conjunctival goblet cells in vertebrates. • Method: The conjunctival epithelium of the chick was studied before and after hatching in order to demonstrate the morphological evolution of the goblet cells. The entire conjunctiva was processed for light microscopy either on semithin sections stained with toluidine blue-pironine or on traditional sections stained with Alcian blue pH 2.5-PAS. • Results: It was possible to demonstrate that goblet cells underwent remarkable changes in their secretory activity. At 12 h after hatching, isolated Alcian blue-positive cells were present in the fornix. At 24 h after hatching, cells positive for both Alcian blue and PAS were scattered among epithelial cells. Two days after hatching, cells which reacted positively only to PAS were also present. • Conclusion: It is suggested that the differentiation of conjunctival goblet cells occurs first in the fornix, probably due to the particular vascular environment of this region, and then spreads all over the conjunctiva.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01880671
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