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  • 1
    Publication Date: 2019-07-17
    Description: We present initial estimates of the physical properties of meteoric and marine ice in Larsen C ice shelf, Antarctic Peninsula, as derived from quality factor (Q) and amplitude-versus-angle (AVA) analysis of reflection-seismic datasets. The data were acquired during the 2008-09 austral summer in the south-eastern sector of the ice shelf, using explosive sources deployed in shallow shot holes, and 48 vertical-component 100 Hz geophones. 24 of these phones were installed horizontally and transverse to the acquisition line, such that compressional (P), verticallypolarised shear (SV) and horizontally-polarised shear (SH) could be recorded. The recorded data are rich in reflection events, with different phases identifiable as primary and multiple P-waves, SV- and SH-waves, and also P to SV mode conversions. The AVA character of these reflections is applied in a joint inversion, with a Bayesian statistical analysis used to obtain best-fit densities and wavelet velocities for the meteoric and marine ice, which allows estimates of the ices’ Young’s moduli and Poisson’s ratios. We further use prestack Q inversion (PSQI) to determine P- and S-wave quality factors for the two ice types, and consider these in terms of ice temperature and permeability. Our estimates of the physical properties of the meteoric and marine ices will ultimately be used to inform predictive models of the flow and fracture mechanics of Larsen C Ice Shelf.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 156 (1945), S. 51-52 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] IN a paper, to appear in full elsewhere, I have investigated the accuracy of the atomic co-ordinates obtained from the three-dimensional Fourier syntheses of X-ray crystal structure analysis. Representing the synthesis in the form: ? +HEL D{x,y,z)- = T/ SSS | F(hth9l) \ v -HKL cos ...
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0533
    Keywords: NCTR-Balb/C mouse ; Dysmyelination ; Neurovisceral storage disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A morphological survey of the central nervous system of a NCTR-Balb/C mouse afflicted by neurovisceral storage disease was performed. It has been demonstrated that this mutant is characterized by primary dysmyelination, which is evident as early as 12 days of age. The failure of myelin formation in the CNS was shown by histochemical and ultrastructural methods. Inasmuch as neither lipid-containing macrophages nor infiltrating mononuclear cells were apparent, secondary demyelination could be excluded. The multiform ultrastructural appearance of the storage material in the various CNS cell types suggested heterogeneity of the accumulated substances. The storage materials which reacted positively with periodate-Schiff reagent, but not with other histochemical stains, are most likely the accumulated gangliosides and neutral glycosphingolipids indentified previously in this mutant's brain. Considering the probable role of cholesterol ester in the early phases of myelinogenesis, in conjunction with the fact that the NCTR-Balb/C mouse carries a defect in the esterification of exogenously derived cholesterol, it is possible that the later metabolite is relevant to the impaired myelin formation.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 158 (1946), S. 380-380 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] THE extensive programme of work on the extra reflexions caused by thermal motion of the crystal lattice, which has been carried out by Lonsdale and her colleagues at the Davy Faraday Laboratory, has shown that these occur, not rarely as was at first thought, but in all crystalline substances. ...
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 157 (1946), S. 517-518 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] PREVIOUS work1,2 on this topic led to methods and formulae applicable to three-dimensional summation, and it was obviously desirable to extend this to the more limited (and usual) two- and one-dimensional cases. This has now been done, and in a paper, to appear in full elsewhere, ...
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 160 (1947), S. 196-196 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] ALTHOUGH the Fourier method of synthesis has enjoyed a long and justified supremacy in the armoury of techniques for X-ray structure analysis, the time is rapidly approaching when its use will be limited by the complexity of the structures investigated. In the absence of any universally ...
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 256 (1989), S. 105-112 
    ISSN: 1432-0878
    Keywords: Autonomic ganglia ; Retrograde labelling ; Colon ; Urinary bladder ; Genitalia, male ; Rat (Wistar)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In male rats a large number of the postganglionic neurons which innervate the pelvic organs are located in the major pelvic ganglion. In the present study we have identified the location within this ganglion of neurons which project to either of three pelvic organs, the penis, colon or urinary bladder. Two fluorescent retrogradely-transported dyes, Fast Blue and Fluoro-Gold, were used. For most animals one dye was injected into the cavernous space of the penis, the wall of the distal colon or the wall of the urinary bladder. In a small number of animals two organs were injected, each with a different dye. One to six weeks after injection the major pelvic ganglia were fixed in buffered formaldehyde. The distribution of fluorescent dye-labelled cells was observed in whole mounts of complete ganglia and, in most cases, also in small accessory ganglia located between the ureter and the prostate. The studies showed a unique pattern of distribution for each organ-specific group of neurons. Most of the colon neurons are located in the major pelvic ganglion near the entrance of the pelvic nerve, whereas almost all of the penis neurons are near or within the penile nerve. Bladder neurons are relatively evenly distributed throughout the ganglion. These results demonstrate a distinct topographical organization of organ-specific neurons of the major pelvic ganglion of the male rat, a phenomenon which has also been observed in other peripheral ganglia.
    Type of Medium: Electronic Resource
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  • 8
    Publication Date: 2011-03-04
    Description: Available studies do not allow comparison and quantification of the effects of biological geotextiles on runoff and water erosion rates under different agro-environmental conditions. Hence, this paper addresses this issue by comparing runoff and soil loss data obtained from field experiments (using different types of biological geotextiles) conducted in the United Kingdom, Hungary, South Africa, China, Thailand and Vietnam. Palm leaf mats (Borassus and Buriti mats) were used in the European countries. In the UK, Borassus mats were used as whole plot cover (area coverage ∼76 per cent; termed Borassus completely covered to differentiate from the Borassus buffer strip plots) and as buffer zones (area coverage ∼10 per cent), whereas Buriti mats were used only as buffer zones (area coverage ∼10 per cent). Only Lala mats were used in South Africa. Elsewhere (China, Thailand and Vietnam) biological geotextiles were constructed using other indigenous local materials, such as bamboo, rice straw and maize stalks. Biological geotextiles were used on bare plots in South Africa and the European countries. In the UK, plots were maintained bare by need based herbicide spraying. However, in South Asia, different crops were grown on the geotextile-covered plots. Results suggest that biological geotextiles were very effective for soil erosion control in all locations and the effectiveness for decreasing soil erosion rates by water was in the range of ∼67–99 per cent. The effectiveness of biological geotextiles in reducing runoff volume was in the range of ∼26–81 per cent. In the UK, total runoff and soil loss (during 8 January 2007–6 May 2008; total precipitation = 1145.8 mm) from the Borassus (one metre wide) buffer zone plots (cover percentage ∼7.6 per cent) were, respectively, ∼81 and ∼93 per cent less than bare plots. In Hungary and China, plots with ∼38 and 22 per cent geotextile-cover, respectively, had ∼88 and 96 per cent less soil loss, than bare plots. In most months with low precipitation (depth) in Hungary and the UK, runoff volume was greater from plots with geotextile-cover than from bare soils. However, complete data sets indicate that in the UK and Hungary, runoff reduction by different treatments over bare plots ranged between ∼26 and 81 per cent. Results from the UK showed that plots with buffer strips of Borassus and Buriti mats had similar effects in reducing soil losses as completely covered plots of the Borassus mats. Thus, foreseeing biological geotextile-cover on vulnerable segments of the landscape is highly effective for soil erosion control. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 1085-3278
    Electronic ISSN: 1099-145X
    Topics: Geography , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley-Blackwell
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  • 9
    Publication Date: 2011-03-04
    Description: Preliminary investigations suggest biological geotextiles could be an effective and inexpensive soil conservation method, with enormous global potential. However, limited quantitative data are available on the erosion-reducing effects of biological geotextiles. Therefore, the objective is to evaluate the effectiveness of biological geotextiles in reducing runoff and soil loss under controlled laboratory conditions and under field conditions reflecting continental, temperate and tropical environments. In laboratory experiments, interrill runoff, interrill erosion and concentrated flow erosion were simulated using various rainfall intensities, flow shear stresses and slope gradients. Field plot data on the effects of biological geotextiles on sheet and rill erosion were collected in several countries (UK, Hungary, Lithuania, South Africa, Brazil, China and Thailand) under natural rainfall. Overall, based on the field plot data, the tested biological geotextiles reduce runoff depth and soil loss rates on average by 46 per cent and 79 per cent, respectively, compared to the values for bare soil. For the field and laboratory data of all tested geotextiles combined, no significant difference in relative runoff depth between field measurements and interrill laboratory experiments is observed. However, relative soil loss rate for the concentrated flow laboratory experiments are significantly higher compared to the interrill laboratory experiments and the field plot measurements. Although this study points to some shortcomings of conducting laboratory experiments to represent true field conditions, it can be concluded that the range and the mean relative runoff depth and soil loss rate as observed with the field measurements is similar to those as observed with the interrill laboratory experiments. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 1085-3278
    Electronic ISSN: 1099-145X
    Topics: Geography , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley-Blackwell
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  • 10
    Publication Date: 2013-09-16
    Description: Ventricular fibrillation (VF) in the globally ischemic heart is characterized by a progressive electrical depression manifested as a decline in the VF excitation rate (VFR) and loss of excitability, which occur first in the subepicardium (Epi) and spread to the subendocardium (Endo). Early electrical failure is detrimental to successful defibrillation and resuscitation during cardiac arrest. Hyperkalemia and/or the activation of ATP-sensitive K + (K ATP ) channels have been implicated in electrical failure, but the role of these factors in ischemic VF is poorly understood. We determined the VFR-extracellular K + concentration ([K + ] o ) relationship in the Endo and Epi of the left ventricle during VF in globally ischemic hearts (Isch group) and normoxic hearts subjected to hyperkalemia (HighK group) or a combination of hyperkalemia and the K ATP channel opener cromakalim (HighK-Crom group). In the Isch group, Endo and Epi values of [K + ] o and VFR were compared in the early (0–6 min), middle (7–13 min), and late (14–20 min) phases of ischemic VF. A significant transmural gradient in VFR (Endo 〉 Epi) was observed in all three phases, whereas a significant transmural gradient in [K + ] o (Epi 〉 Endo) occurred only in the late phase of ischemic VF. In the Isch group, the VFR decrease and inexcitability started to occur at much lower [K + ] o than in the HighK group, especially in the Epi. Combining K ATP activation with hyperkalemia only shifted the VFR-[K + ] o curve upward (an effect opposite to real ischemia) without changing the [K + ] o threshold for asystole. We conclude that hyperkalemia and/or K ATP activation cannot adequately explain the heterogeneous electrical depression and electrical failure during ischemic VF.
    Print ISSN: 0363-6135
    Electronic ISSN: 1522-1539
    Topics: Medicine
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