Effect of humic acids on numbers and activities of micro-organisms within physiological groups     

S.A. Visser 《Organic Geochemistry》1985,8(1):81-85

The incorporation of humic acid fractions in media designed for the enumeration of soil micro-organisms belonging to specific physiological groups was found to result for some groups in appreciably higher counts. It is suggested that by influencing the enzyme systems of certain micro-organisms, humic compounds may affect the range of substrates which they can utilize. The effect could have implications on the activity of organisms in environments in which humic substances are normally present, such as soils and natural waters.  相似文献   

The rotation of garnet porphyroblasts around a single fold, Lukmanier Pass, Central Alps     

Peter Visser  Neil S Mancktelow 《Journal of Structural Geology》1992,14(10)

The orientation of the straight internal foliation S_i within large ( 5 mm) garnet porphyroblasts has been measured relative to the orientation of the external foliation S_e around a single antiform of 0.5 m wavelength, which folds the dominant regional foliation. The internal foliation is not constant in orientation, but varies consistently both with position around the fold and with the porphyroblast ellipticity. The dip of S_i (hinge dip taken as zero) is consistently less than the dip of S_e; it increases with increasing dip of S_e and with increasing ellipticity of the porphyroblasts. S_i effectively defines a fold with an opening angle greater than that in the external foliation. The opening angle of this fold in S_i decreases with increasing porphyroblast ellipticity. The observed variation in the orientation of S_i can be explained qualitatively by a flattened flexural flow model for fold development, as could be expected for folding of a pre-existing, strongly anisotropic foliation. The measurements clearly demonstrate that rotation of porphyroblasts relative to geographical co-ordinates did occur during the development of this fold and that a model based on the classical theories of rotation of stiff inclusions in a weaker viscous matrix is most appropriate.  相似文献   

Magnetic susceptibility study of KNiAsO4, HMnAsO4·H2O and their organic-intercalated derivatives     

S. T. Bramwell  A. M. Buckley  D. Visser  P. Day 《Physics and Chemistry of Minerals》1988,15(5):465-469

The layer compounds KNiAsO₄ and krautite, HMnAsO₄·H₂O are found to be antiferromagnetic, ordering at 19.2 K and 3.2 K respectively. The behaviour of their derivatives C₁₀H₂₁NH₃NiAsO₄ and CH₃NH₃MnAsO₄·H₂O indicates similar exchange coupling J to that of the parent compound, confirming the two-dimensional nature of both series. The results are discussed in the context of low-dimensional model systems.  相似文献   

The Origins and Consequences of democratic citizens' Policy Agendas: A Study of Popular Concern about Global Warming     

Jon A. Krosnick  Allyson L. Holbrook  Laura Lowe  Penny S. Visser 《Climatic change》2006,77(1-2):7-43

This article proposes and tests a model of the causes and consequences of Americans’ judgments of the national seriousness of global warming. The model proposes that seriousness judgments about global warming are a function of beliefs about the existence of global warming, attitudes toward it, the certainty with which these beliefs and attitudes are held, and beliefs about human responsibility for causing global warming and people’s ability to remedy it. The model also proposes that beliefs about whether global warming is a problem are a function of relevant personal experiences (with the weather) and messages from informants (in this case, scientists), that attitudes toward global warming are a function of particular perceived consequences of global warming, and that certainty about these attitudes and beliefs is a function of knowledge and prior thought. Data from two representative sample surveys offer support for all of these propositions, document effects of national seriousness judgments on support for ameliorative efforts generally and specific ameliorative policies, and thereby point to psychological mechanisms that may be responsible for institutional and elite impact on the public’s assessments of national problem importance and on public policy preferences.  相似文献   

A New Method for Estimating Lengths for Partially Exposed Features     

Clemens A. Visser  Antonio G. Chessa 《Mathematical Geology》2000,32(1):109-126

Length distributions from sedimentary bodies can be measured in outcrop. A common feature in many outcrops is the occurrence of partially exposed bodies, i.e., sedimentary bodies that are cut by either one or both edges of the outcrop. Ignoring these partials while establishing a length distribution leads to a bias toward the smaller length classes. This is because larger bodies have a larger probability to occur as partials than smaller bodies. We present a new method for estimating the expected complete length for a partially exposed feature, based on the theory of conditional probability. The method is demonstrated and tested on a sandstone outcrop exhibiting over 200 interbedded thin silt/shale streaks. It is shown that the method can significantly enlarge both the size and the representativeness of length distributions.  相似文献   

Second homes and local development: Issues arising from Cape Town's De Waterkant     

Gustav Visser 《GeoJournal》2004,60(3):259-271

The paper aims to make a contribution towards addressing the current paucity of academic reflection on second home development in South Africa. The paper focuses on the intersection between tourism, second homes and local development, as embodied in the empirical realities of a Cape Town neighbourhood — De Waterkant. It is argued that this particular case study presents an example of the types of local development impacts that second home expansion holds for host communities. These impacts include employment generation, urban conservation, a range of forward and backward economic linkages, as well as a flexible tourist accommodation supply. Moreover, the case study elucidates an interesting example of second homes as sites of simultaneous tourism space production and consumption at work. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Calibration of GOCE SGG data using high–low SST, terrestrial gravity data and global gravity field models     

J. Bouman  R. Koop  C. C. Tscherning  P. Visser 《Journal of Geodesy》2004,78(1-2):124-137

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The turbidity of the southern North Sea     

M. P. Visser 《Ocean Dynamics》1970,23(3):97-117

Summary A brief survey is given of environmental factors influencing turbidity: tides, vertical stratification, seasonal factors, state of sea. Observations of Secchi disc visibility, averaged per half-degree, square, are compared with surface readings of beam attenuation of the seawater. Considering also results of measurements of daylight penetration in the North Sea, a thumb rule is found for the depth of the level of 1% daylight intensity, viz. three times the Secchi dept. For the southern North Sea it is possible to indicate lines of equal mean depth of that level during the periods December/May and June/November.

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Die Trübung der südlichen Nordsee

Zusammenfassung Es wird ein kurzer Überblick der die Trübung beeinflussenden Umweltsbedingungen gegeben: Tiden, vertikale Schichtung, jahreszeitliche Faktoren, Zustand der Meeresoberfläche. Beobachtungen der Durchsichtigkeit mit Hilfe von Secchi-Scheiben, gemittelt über Halbgradfelder werden verglichen mit Oberflächenmessungen der Lichtabschwächung des Seewassers. Unter Berücksichtigung auch von Meßergebnissen von Tageslichtdurchdringung in der Nordsee ist eine Faustregel für die Tiefe auf der Basis von 1% Tageslichtintensität gefunden worden, nämlich das Dreifache der Secchi-Tiefe. Für die südliche Nordsee ist es möglich, Linien gleicher mittlerer Tiefen auf dieser Basis während der Perioden Dezember/Mai und Juni/November zu bestimmen.

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La turbidité dans la partie Sud de la mer du Nord

Résumé On passe en revue brièvement les facteurs ambiants qui influencent la turbidité: marées, stratification verticale, facteurs saisonniers, état de la mer. Des observations de transparence par disque de Secchi, calculées en moyenne par carré d'un demi-degré, sont comparées avec l'affaiblissement du rayonnement lumineux dans l'eau de mer constaté à la surface. En tenant compte aussi des mesures de la pénétration de la lumière du jour dans la mer du Nord, on établit une loi approximative donnant la profondeur au niveau de laquelle l'intensité de cette lumière est de 1% et qui est trois fois la profondeur de Secchi. Pour la partie Sud de la mer du Nord, il est possible de déterminer des lignes d'égale profondeur moyenne de ce niveau pour les périodes de Décembre à Mai et de Juin à Novembre.

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Nach einem Vortrag gehalten auf der ICES-Tagung 1969 in Dublin.  相似文献   

On the connections between the 11-year sunspot period and the periods of about 3 and 7 years in world weather     

Dr. S. W. Visser 《Pure and Applied Geophysics》1959,43(1):302-318

Summary Five ofBerlage's eight empirical rules concerning the Southern Oscillation (1957) may be united in one general rule with regard to the different influence of solar activity during 11-year sunspot cycles with annual maximum numberR above or below 85 (Tables 2, 3, 4, 5 and 6). The opposite character of strong and weak 11-year cycles of solar activity is also present in the 7-year period (Tables 7, 8, 9 and 10; Fig. 1). Finally it is shown that a similar contrast obviously exists in the appearance of polar lights (Table 11, Fig. 2 and 3).The results have not been statistically tested. Because of the rather small number of solar periods involved and the complicated character of the relations found, I could not find a satisfactory statistical method to operate with. I may emphasize, however, the converging evidence enlarging considerably the statistical significance of my results.  相似文献   

The Crustal Structure From Teleseismic P-Wave Coda-Ii. Application to Data of the Nars Array In Western Europe and Comparison With Deep Seismic Sounding Data     

Jeanette Visser  Hanneke Paulssen 《Geophysical Journal International》1993,112(1):26-38

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