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  • 1
    ISSN: 1520-5002
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Macromolecules 27 (1994), S. 5476-5486 
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-041X
    Keywords: Key words Limb development ; Heterochrony ; Evolutionary innovation ; Hoxa-11 ; Xenopus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The wrist (carpus) and ankle (tarsus) of most tetrapods, as well as the wrist of anurans, contains relatively small nodular skeletal elements. The anuran tarsus, however, comprises a pair of long bones, the proximal tarsals tibiale and fibulare, which resemble the lower leg bones, tibia and fibula (zeugopodium). In this paper we investigate whether the proximal tarsals of Xenopus are of zeugopodial character identity, i.e. whether they develop under the influence of the same genes that pattern the lower limb. We compare Hoxa-11 expression in the forelimb bud with that in the hind limb bud by whole-mount in situ hybridization. Hoxa-11 has been implicated in the development of the lower limb. In Xenopus we note three differences between Hoxa-11 expression in fore- and hind limb buds: (1) Hoxa-11 expression is maintained until the hind limb bud reaches a larger size (2 mm) than that of the forelimb bud (1.5 mm); (2) Hoxa-11 expression is maintained over larger spatial domains than in the forelimb; and (3) Hoxa-11 expression has a pronounced posterior polarity in the hind limb, but not in the forelimb. Hind limb expression of Hoxa-11 can be understood as a heterochronic prolonging of the expression dynamic in the forelimb. Finally we found that the proximal tarsals start to develop within the expression domain of Hoxa-11, while in the forelimb the lower arm elements reach the distal expression limit of Hoxa-11. The gene expression data presented here support the notion of a zeugopodial identity of the proximal tarsal elements in Xenopus.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 186 (1992), S. 153-165 
    ISSN: 1432-0568
    Keywords: Blenniidae ; Pectoral fin regeneration ; Fin histogenesis ; Developmental character adjustment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The pectoral fin of blennies is differentiated into a dorsal field and a ventral hook field. A histogenetic analysis of the regenerating pectoral fin was related to two questions. First, are histological specializations of the hook field responsible for the impairment of the regenerative capacity of pectoral fins of blennies? Second, can analysis of the temporal sequence of histogenetic events be used to make testable predictions about the tissue interactions required to re-establish the adult pattern? Regeneration of pectoral fins was examined in Salaria pavo (Blenniidae, Teleostei). Approximately 80% of the length of the fin rays was amputated. Fin ray stumps were evaluated 7,14, 24, 48 and 72 h after amputation, regenerates 4, 5, and 6 days after amputation and at length of about 30%, 50% and 60% regeneration of the original fin length. The regeneration process is subdivided into four stages: wound healing, blastema formation, fin ray formation and distal outgrowth and differentiation of hook characters. Analysis of the early events of regeneration, wound healing, blastema formation and distal outgrowth, yielded no profound differences from those of conventional fins in general. Impairment of regenerative capacity becomes manifested before histological differentiation of hook characters, and it is thus unlikely that their presence is the proximate cause of heteromorphic regeneration. The sequence in which the anatomical specializations characteristic of fin hooks (lepidotrichal cord, cuticle, fin web regression) appear was variable. Detailed analysis of older regenerates revealed a more regular pattern. In the first phase the characters appear to be largely independently organized, while they become locally correlated later. It is concluded that the anatomical differentiation passes through two stages, initiation of anatomical differentiation, and then mutual adjustment of character expression leading to spatially correlated expression of the lepidotrichal cord, the cuticle and the fin web regression.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 23 (1980), S. 199-207 
    ISSN: 1432-0630
    Keywords: 42.30 ; 42.40 ; 72.40 ; 78.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Reduced KNbO3 is a photoconductive ferroelectric in which holograms can be recorded by the photorefractive effect. Read-write volume hologram storage and erase sensitivities ofS −1=100 J/cm2 andS −1=84 J/cm2 (S=d(Δn)/d(I0t)‖t=0) have been measured at zero applied electric field, where the charge transport is shown to be due to diffusion of photoexcited electrons. By applying an electric field along thec-axis, the migration length of the photoexcited electrons becomes comparable to the holographic grating spacing. This leads to storage sensitivities comparable to high-resolution photographic plates. Experimental data on storage and erase sensitivity as a function of the grating spacing, applied electric field, writing light intensity and temperature are reported and interpreted on the basis of the theoretical results of Young et al. and Amodei. Changes of the intensity ratio of the writing beams by self diffraction (beam coupling), reflections from surfaces and the residual dark conductivity are assumed to cause experimental results which deviate from the theoretical models. It is shown, that in reduced KNbO3 and other ferroelectric photoconductors having photocarrier transport lengths much larger than the unit cell dimension, photovoltaic currents do not contribute significantly to the build-up of space-charges leading to the photorefractive effect.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 2062-2064 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A method of growing high quality 4-(N,N-dimethylamino)-3-acetamidonitrobenzene (DAN) single crystals is presented. Crystal plates with dimensions of up to 10×5×2 mm3 were produced and optically characterized. The transparency region extends from 485 to 2270 nm. Large birefringence and strong dispersion of the refractive indices were measured allowing two branches of type I and two of type II phase-matched second-harmonic generation. From effective second-order nonlinear optical susceptibilities measured along the branches all nonlinear susceptibilities were evaluated, the highest being d23 =(50±15) pm/V.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 1671-1675 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Permanent optical channel waveguides in single crystals of KNbO3 are formed with low-dose MeV He ion irradiation. A single energy implantation forms a confinement barrier at the projected range of the ions whereas multiple energy implantations combined with a positive shielding mask form the side walls. Guiding modes are produced and propagation losses as low as 1.0 dB/cm are measured without the need for any annealing. The irradiation induced refractive index changes that define the boundaries of the waveguiding channels are made visible with cross-polarized light microscopy.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 487-489 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 4-(N,N-dimethylamino)-3-acetamidonitrobenzene (DAN) single-crystal cored fibers with high optical nonlinearity were grown in glass capillaries with diameters between 7 and 40 μm. X-ray diffraction experiments showed that DAN crystals grown in the glass capillaries have an orientation with the a axis [100] along the fiber axis. This favorable orientation with the twofold axis perpendicular to the fiber axis allows the full use of the nonvanishing second-order nonlinear susceptibilities d22, d23, and d34. First experiments in a 20-mm-long fiber with a diameter d=7 μm showed a peak conversion efficiency of about 10−4 for frequency doubling of the 1.064 μm line of a pulsed Nd:YAG laser with a fundamental peak power P(ω) =57.1 W.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 1204-1206 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The linear and nonlinear optical properties of well-ordered Y-type Langmuir–Blodgett (LB) multilayers of 2-docosylamino-5-nitropyridine (DCANP) have been investigated. The nonlinear optical susceptibilities have been determined for the wavelengths λ=1064 nm [d33=(7.8±1) pm/V, d31=(2.0±0.5) pm/V] and λ=1318 nm [d33=(5.6±1) pm/V]. In first waveguiding experiments carried out TE0 and TM0 modes propagating over more than 20 mm could be excited. Coupling experiments allowed the determination of the dispersion of the refractive index n3 (n632.8 nm3 =1.598). Guided wave attenuation coefficients as low as 12 dB/cm (at the wavelength λ=632.8 nm) are reported.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1287-1297 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The elastic, piezoelectric, dielectric, elasto-optic, and electro-optic tensors have been determined by numerically evaluating the measurements published until now and using the additional measurements presented in this work. The dependence of the speed of two elastic waves on the applied electric field is measured yielding one electroelastic constant g13133=(95±10)NV−1 m−1. The complete set of parameters consisting of the low-frequency clamped dielectric constants εSij, refractive indices, elastic stiffness constants at constant electric field CEijkl, piezoelectric coefficients eijk, elasto-optic tensor at constant electric field pEijkl, and clamped electro-optic coefficients rSijk is used to calculate effective electro-optic coefficients and effective dielectric constants that have to be used in photorefractive experiments where the elastic deformations associated with a periodic space-charge field have to be considered.
    Type of Medium: Electronic Resource
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