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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 114 (1992), S. 1876-1877 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Marine biology 119 (1994), S. 211-219 
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Adult Gnathophausia ingens, a bioluminescent deep-sea mysid, were collected off the California coast and brought, protected from the light, to the Marine Laboratory of the University of California, Santa Barbara (UCSB) for single-unit recordings of afferent visual interneurons. These units, which traverse the optic stalk, were classified according to their response to light stimuli varying in intensity, duration and area. The most common were sustaining fibers responding throughout a continuous stimulus. The only other type, “on” fibers, showed a transient response without reference to stimulus movement. Sustaining fibers responded to irradiances as low as, 2.7×103 photons cm-2s-1sr-1, and were characterized by long temporal summations and large receptive fields. These are characteristics of a visual system adapted for maximizing sensitivity. However, the transient response of the “on” fibers also suggests a capability to react to rapidly changing light sources such as bioluminescence, a matter of importance since this mysid requires dietary coelenterazine to sustain its luminescent system.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Marine biology 123 (1995), S. 47-54 
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The temporal characteristics of the visual systems of deep-sea crustaceans were examined at varying light levels. Experimental organisms were collected off Hawaii and southern California in 1991 and 1992, and continually maintained in the dark. At the University of California Santa Barbara Marine Laboratory, the temporal components of both visual interneuron activity and electroretinograms (ERGs) of adult Gnathophausia ingens were tested at threshold and with background light levels up to 6 log units above threshold. To compare these responses with those of mid-water organisms inhabiting shallower depths, the temporal characteristics of the ERGs of Oplophorus spinosus and juvenile G. ingens were assessed. Adults of both species showed little or no change in the time components of their responses when light-adapted, except for the response latency. There was also no evidence of a circadian rhythm in visual sensitivity. O. spinosus, a vertical migrator, and juvenile G. ingens, which inhabit a shallower depth than the adults, exhibited more rapid responses than adult G. ingens. These varying responses are considered adaptations to the differences in light levels at the characteristic depths of the organisms.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Naturwissenschaften 1 (1913), S. 1238-1238 
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-1432
    Keywords: Chromosome evolution ; Restriction enzymes ; Nick translation ; DNA blot transfer ; Deer species ; Repetitive DNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The Cervidae show one of the largest variations in chromosome number found within a mammalian family. The five species of the deer family which are the subject of this study vary in chromosome number from 2n=70 to 2n=6. Digestion with the restriction enzymes EcoRI, HpaII, HaeIII and MspI reveals that there is a series of highly repetitive sequences forming similar band patterns in the different species. To obtain information on the degree of homology among these conserved sequences we isolated a HpaII restriction fragment of approximately 990 base pairs from reindeer DNA. This DNA sequence was32P-labelled and hybridized by the Southern blot technique to DNAs cleaved with HpaII and HaeIII from the reindeer and four other Cervidae species. Hybridization to specific restriction fragments was recorded in all species. The patterns of hybridization showed a higher degree of similarity between reindeer, elk and roe deer than between reindeer and the Asiatic species (fallow deer and muntjac). Homologies are still present between the highly repetitive sequences of the five species despite the drastic reorganization that led to a change in chromosome number from 6 to 70.
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  • 6
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 97 (1993), S. 2158-2166 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 9016-9030 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In a crossed molecular beam experiment, we have measured the angular and time-of-flight (TOF) distributions of the products KCl and KI formed in the reaction K+ICl→KI+Cl, KCl+I at an elevated collision energy of Etr=1.64 eV. Employing the brute force method, we have prepared an oriented ICl beam and studied in addition also the orientation dependence of these distributions. The results are (i) KCl is the dominant product, but also KI is substantially formed with a branching ratio of 4:1; (ii) the double differential reaction cross section in the center-of-mass frame (contour maps) indicates that all products are preferentially forward scattered and constrained to the forward hemisphere; (iii) the KCl flux consists of two distinct components which differ markedly in kinetic energy and dependence on the ICl orientation; there are also indications of the existence of two components of KI; (iv) 65%, 84%, and 64% of the available energy is vested into the internal degrees of freedom for the fast, slow component of KCl and KI, respectively; (v) the existence of two components can be rationalized on the basis of the harpooning mechanism where the jumping electron accesses the ground state or one of the low excited states of the ICl− ion and triggers the subsequent explosion of the ion with more or less kinetic energy of the fragments depending on the initially populated state; (vi) the energies released during dissociation of ICl− in the 2Σ ground state and the first 2Π state are ≤0.19 and ≤1.2 eV, respectively; (vii) the fast KCl component features a negative steric effect suggesting favorable product formation for attacks of K to the I end of ICl, the steric effect of the slow KI component is positive, i.e., attacks to the Cl end form products favorably; the other components exhibit no significant steric effect; (viii) the steric effects can be quantitatively rationalized using the same model as mentioned above; (ix) the magnitude of the steric effect suggests a rotational temperature of the low-lying states of the ICl beam of 14±1 K.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 28 (1995), S. 553-560 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Small-angle X-ray scattering (SAXS) is a powerful tool to study the kinetics of phase separation in materials. A simple procedure is presented that allows one to prove if the particle-size distribution established in a system in the late stages of phase separation corresponds to the predictions of the classical Lifshitz–Slyozov–Wagner (LSW) theory for the asymptotic stage of Ostwald ripening. The method is based on the correlations between certain SAXS size parameters and the higher moments of the LSW size distribution functions for diffusion-limited or reaction-limited ripening. It is suggested that the use of these size parameters, which can be obtained with high accuracy from the scattering curve, is frequently more advantageous than a direct comparison of the experimentally obtained size distributions with the asymptotic size-distribution functions predicted by the LSW theory. The method is applicable if the suppositions made in the LSW theory that the precipitated particles should be homogeneous spheres with volume fraction tending to zero are fulfilled. The method is applied to a photochromic glass; although the silver-halide precipitates contained in the glass develop according to the power law of diffusion-limited Ostwald ripening, their size distribution is shown not to correspond to the features of the LSW size distribution. Consequently, in this case the LSW theory cannot describe quantitatively the kinetics of ripening.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 125 (1978), S. 217-225 
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The responses of 230 single neurons in the inferior colliculus of the horseshoebat to single tones have been studied, emphasizing systematic analysis of the effective frequency bands, dynamic properties and the time course of responses. Distribution of the units' best excitatory frequencies (BEF) is: low frequency neurons 23% (BEF 3–65 kHz); FM-frequency neurons 25% (BEF 65–81 kHz, i.e., frequencies occurring in the FM-part of the bat's echo signal); filter neurons 45% (BEF 81–88 kHz, i.e., frequencies occurring in the stabilized CF-part of the bat's echo=reference frequency (RF)); high frequency neurons about 7% (BEF 〉 88 kHz). Tuning curves show conventional shapes (Fig. 1), apart from those of filter neurons, which are extremely narrow. Accordingly, Q10dB-values (BEF divided by the bandwidth of the tuning curve at 10 dB above threshold) are 80–450 in filter neurons (Fig. 2). Response patterns (Fig. 3) are similar to those of Nucleus cochlearis units (transient, sustained, negative and complex responders) with an increased percentage of complex responders up to 38% and a decreased number of transient responders. All types of spike-count functions are found (Fig. 4); nonmonotonic ones dominating. Maximal spike counts are not at the BEF but a few kHz below. Distinct upper thresholds, especially at the BEF of filter neurons (Fig. 5) lead to abrupt changes in activity by slightly shifting stimulus frequency or intensity. The hallmark of inferior colliculus neurons is inhibition, disclosed by distinct inhibitory areas enfolding and overlapping excitatory ones (Figs. 3 and 5). Duration of inhibition varies with stimulus frequency, but is largely independent of stimulus duration (Fig. 6), whereas rebound of inhibition depends on stimulus duration building up periodic rebound activities, if stimulus duration is lengthened. In addition, there are neurons responding only periodically, regardless of stimulus frequency and intensity (Fig. 7). Inhibition is discussed in terms of improving the neuronal signal/spontaneous noise ratio and altering responsiveness of neurons after stimulation, so that these neurons may be suited to time processing in the acoustic pathway.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 106 (1976), S. 111-125 
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary For echolocation,Rhinolophus ferrumequinum emits orientation sounds, each of which consists of a long constant-frequency (CF) component and short frequency-modulated (FM) components. The CF component is about 83 kHz and is used for Doppler-shift compensation. In this bat, single auditory nerve fibers and cochlear nuclear neurons tuned at about 83 kHz show low threshold and very sharp filter characteristics. The slopes of their tuning curves ranged between 1,000 and 3,500 dB/octave and their Q-10 dB values were between 20 and 400, 140 on the average (Figs. 3–5). The peripheral auditory system is apparently specialized for the reception and fine frequency analysis of the CF component in orientation sounds and Doppler-shift compensated echoes. This specialization is not due to suppression or inhibition comparable to lateral inhibition, but due to the mechanical specialization of the cochlea. Peripheral auditory neurons with the best frequency between 77 and 87 kHz showed not only on-responses, but also off-responses to tonal stimuli (Figs. 1, 2, and 6). The off-responses with a latency comparable to that of N1-off were not due to a rebound from either suppression or inhibition, but probably due to a mechanical transient occurring in the cochlea at the cessation of a tone burst.
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