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1

Digitale Medien

Synthesis and ocular antihypertensive activity of new imidazolidine derivatives containing a .beta.-blocking side chain (1991)

Huber, D. ; Ehrhardt, J. D. ; Decker, N. ; [weitere]

s.l. : American Chemical Society

Journal of medicinal chemistry 34 (1991), S. 3197-3204

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ISSN: 1520-4804

Quelle: ACS Legacy Archives

Thema: Chemie und Pharmazie

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1021/jm00115a008

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2

Digitale Medien

Exchange stiffness of Ca-doped YIG : 38th Annual Conference on Magnetism an Magnetic Materials (1994)

Avgin, I. ; Huber, D. L.

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

Journal of Applied Physics 75 (1994), S. 5517-5519

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: An effective medium theory for the zero-temperature exchange stiffness of uncompensated Ca-doped YIG is presented. The theory is based on the assumption that the effect of the Ca impurities is to produce strong, random ferromagnetic interactions between spins on the a and d sublattices. In the simplest version of the theory, a fraction, x, of the ad exchange integrals are large and positive, x being related to the Ca concentration. The stiffness is calculated as function of x for arbitrary perturbed ad exchange integral, Jxad. For Jxad(approximately-greater-than)(1/5)||8Jaa+3Jdd||, with Jaa and Jdd denoting the aa and dd exchange integrals, respectively, there is a critical concentration, Xc, such that when x(approximately-greater-than)Xc, the stiffness is complex. It is suggested that Xc delineates the region where there are significant departures from colinearity in the ground state of the Fe spins. Extension of the theory to a model where the Ca doping is assumed to generate Fe4+ ions on the tetrahedral sites is discussed. Possible experimental tests of the theory are mentioned.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.355674

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3

Digitale Medien

Antiferromagnetic magnons in diluted triangular and Kagomé lattices (abstract) : 37th Annual conference on magnetism and magnetic materials (1993)

Huber, D. L. ; Ching, W. Y.

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

Journal of Applied Physics 73 (1993), S. 5657-5657

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Numerical results are presented for the local field distribution and the distribution of linearized magnon modes in diluted triangular and Kagomé lattices. A nearest-neighbor antiferromagnetic Heisenberg spin Hamiltonian is assumed, and the linearization is carried out with respect to classical ground states obtained by means of an energy minimization algorithm.1 In the case of the triangular lattice, the density of states associated with a 20% vacancy concentration is used to calculate the magnon contribution to the specific heat. With an exchange integral inferred from the Curie–Weiss constant, quantitative agreement is obtained with the experimental results for La0.2Gd0.8CuO2 reported by Ramirez et al.2 over the interval 0.1 K≤T≤0.2 K. The behavior of the diluted Kagomé lattice is compared with that of the triangular array. In contrast to the latter, the local fields in the diluted Kagomé lattice take on the discrete values 2JS, JS, and 0. In the case of a 14% vacancy concentration, the distribution of magnon modes resembles that of the fully occupied array with a noncoplanar ground state. The relevance of these results to the behavior of SrCr8Ga4O19 is discussed.3

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.353630

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4

Digitale Medien

Zone-center magnons in dilute magnetic semiconductors : 35th annual conference on magnetism and magnetic materials (1991)

Huber, D. L.

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

Journal of Applied Physics 69 (1991), S. 6112-6113

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: A calculation of the frequency of a zone-center magnon in a dilute magnetic semiconductor is outlined. It is based on the moments of the imaginary part of the dynamic spin susceptibility. Results are obtained at low temperatures for Cd1−xMnxTe in the zero- and high-magnetic-field limits. Good agreement with experiment is found assuming that (1) the dominant anisotropy mechanism is the Dzyaloshinski–Moriya interaction and (2) nearest-neighbor Mn spins are not colinear in the zero-field ground state.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.347783

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5

Digitale Medien

Zero-temperature statics of a random exchange model for the magnetic properties of La2−xSrxCuO4 (1990)

Huber, D. L. ; Ching, W. Y.

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

Journal of Applied Physics 67 (1990), S. 5743-5745

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Results are reported for the static properties of a random exchange model proposed for the magnetic propeties of La2−xSrxCuO4. Numerical calculations of the zero-temperature staggeredmagnetization and static structure factor are presented for 0.05≤c≤0.25, where c is the fraction of ferromagnetic exchange integrals in an otherwise perfect antiferromagnetic lattice with nearest-neighbor Heisenberg interactions between classical spins. The relevance of the findings to the magnetic properties of La-Sr-Cu-O in the insulating phase is assessed.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.345949

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6

Digitale Medien

Spectroscopy and photodissociation dynamics of a two-chromophore system: Raman scattering as a probe of nonadiabatic electronic coupling (1991)

Zhang, J. Z. ; Heller, E. J. ; Huber, D. ; [weitere]

s.l. : American Chemical Society

The @journal of physical chemistry 〈Washington, DC〉 95 (1991), S. 6129-6141

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Quelle: ACS Legacy Archives

Thema: Chemie und Pharmazie , Physik

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1021/j100169a017

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7

Digitale Medien

Modification of matrix polysaccharides during avocado (Persea americana) fruit ripening: an assessment of the role of Cx-cellulase (1992)

O'Donoghue, E. M. ; Huber, D. J.

Oxford, UK : Blackwell Publishing Ltd

Physiologia plantarum 86 (1992), S. 0

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ISSN: 1399-3054

Quelle: Blackwell Publishing Journal Backfiles 1879-2005

Thema: Biologie

Notizen: The role of Cx-cellulase (EC 3.2.1.4) in fruit ripening and softening is unknown. In the present study, avocado (Persea americana) fruit, a rich source of Cx-cellulase, were examined to determine if the enzyme plays a role in ripening-related hemicellulose metabolism. Hemicelluloses (4 M alkali-soluble) from avocado fruit exhibited a very broad distribution of polymer sizes and an overall decrease in Mr during ripening. Polymers affected were primarily those of large Mr (relative molecular mass). The characteristic total hemicellulose Mr distribution and changes with ripening were also evident for xyloglucan (XG), a putative substrate for avocado Cx-cellulase. Hydrolytic activity toward hemicelluloses from preripe fruit was detected in crude buffer-soluble protein extracts derived from ripe avocado mesocarp tissue. XG was also degraded, and in a pattern similar to that observed during ripening. Purified Cx-cellulase also exhibited activity against specific components of isolated hemicelluloses; however, in contrast to the crude protein. Cx-cellulase alone was without influence on the Mr distribution of avocado XG. Protein depleted of Cx-cellulase was capable of moderate XG depolymerization. We conclude from the present studies that the enzyme Cx-cellulase is not involved in the ripening-related depolymerization of XG in avocado fruit.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1111/j.1399-3054.1992.tb01308.x

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8

Digitale Medien

Cell wall changes during the expansion and senescence of carnation (Dianthus caryophyllus) petals (1990)

Vetten, N. C. ; Huber, D. J.

Oxford, UK : Blackwell Publishing Ltd

Physiologia plantarum 78 (1990), S. 0

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ISSN: 1399-3054

Quelle: Blackwell Publishing Journal Backfiles 1879-2005

Thema: Biologie

Notizen: Senescence of carnation (Dianthus caryophyllus L. ev. White Sim) petals coincided with a decrease on a per flower basis in the yield of cell wall and ethanol-insoluble solids. The decrease in cell wall yield per flower was due largely to a loss of neutral sugars, primarily galactose (45%) and arabinose (23%). On a per flower basis, water-and chelator-soluble pectins increased throughout development, comprising in senescent petals 18 and 58%, respectively, of total pectin. Alkali-soluble pectins ranged from 35 to 45% of the total pectin and decreased during senescence. Gel chromatography of chelator- and alkali-soluble pectins revealed no change in molecular size and polygalacturonase activity was not detected. Large-molecular-size hemicelluloses decreased during development, an observation reminiscent of the changes affecting hemicelluloses during the ripening of a number of fruit types. Compositional analysis of the large hemicellulosic polymers revealed a decrease in xylose and galactose content.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1111/j.1399-3054.1990.tb09062.x

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9

Digitale Medien

Influence of avocado (Persea americana) Cx-cellulase on the structural features of avocado cellulose (1994)

O'Donoghue, E. M. ; Huber, D. J. ; Timpa, J. D. ; [weitere]

Springer

Planta 194 (1994), S. 573-584

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ISSN: 1432-2048

Schlagwort(e): Cellulose ; Cx cellulase ; Fruit (ripening, softening) ; Persea (fruit ripening)

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Abstract Avocado (Persea americana Mill.) fruit produce copious quantities of the enzyme Cx-cellulase (EC 3.2.1.4) during ripening. The possibility that Cx-cellulase is able to disrupt cellulose microfibril oranization was investigated using molecular weight (Mr), x-ray diffraction, and ultrastructural analyses of cell walls from unripe avocado fruit incubated with the purified enzyme. Results indicate that Cx-cellulase causes a downshift in the Mr of unbranched cell-wall polymers in the Mr range of 106–107 Da. There is an increase in the proportion of crystalline cellulose, and cellulose fibrils appear to lose cohesiveness in response to enzyme activity. We propose that Cx-cellulase attacks avocado cellulose at accessible sites in the peripheral and integral noncrystalline regions of the microfibril, resulting in a loss of cohesiveness within the fibril structure and an alteration in the binding of associated cell-wall matrix polysaccharides. The initial loss of avocado mesocarp firmness during fruit ripening may be linked to the onset of Cx-cellulase activity.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00714472

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10

Digitale Medien

Effect of disorder on the trapping of Frenkel excitons in three-dimensional systems (1991)

Huber, D. L. ; Ching, W. Y.

Springer

Journal of statistical physics 65 (1991), S. 1155-1159

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ISSN: 1572-9613

Schlagwort(e): Frenkel excitons ; three-dimensional systems

Quelle: Springer Online Journal Archives 1860-2000

Thema: Physik

Notizen: Abstract A numerical study is made of the effect of disorder on the trapping of Frenkel excitons in three-dimensional systems atT=0 K. A Gaussian distribution of optical transition frequencies is assumed. The disorder enhances the decay of ak = 0 exciton created by pulsed optical excitation, but reduces the overall exciton trapping rate. An interpretation of the results in terms of increased exciton scattering and reduced exciton mobility is outlined.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01049604

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