Metamorphosis of Heteroxenia fuscescens planulae (Cnidaria: octocorallia) is inhibited by crude oil: a novel short term toxicity bioassay     

A. Kushmaro  G. Henning  D.K. Hofmann  Y. Benayahu 《Marine environmental research》1997,43(4):295-302

By using TPA (12-tetra-decanoyl-phorbol-13-acetate) an artificial inducer for metamorphosis, it was possible to determine the effect of crude oil on settlement and metamorphosis of planulae of the soft coral Heteroxenia fuscescens. In the absence of crude oil, TPA induced metamorphosis in 97% of these planulae. The effect of crude oil on metamorphosis and appearance of deformed primary polyps was concentration dependent. Only 50% of the planulae grown in experimental vessels with crude oil at a concentration of 0.1 ppm covering the bottom and walls of the vessels underwent metamorphosis when triggered by TPA. Of those planulae exposed to 100 ppm of the pollutant only 3% metamorphosed after being induced by TPA. Furthermore, oil film on the water surface was less toxic to the larvae than the crude oil covering the bottom and walls of the experimental vessels. Some of the oil treated planulae died, while others remained viable, looked normal, but did not metamorphose after being presented with TPA. These findings suggest that even at very low concentrations crude oil affects larvae of H. fuscescens preventing their settlement and metamorphosis. Therefore it is possible that oil spills affect coral recruitment by decreasing the viability and the settlement of coral planulae. This assay represents a new sensitive bioindicator to detect the impact of oil pollution on tropical and subtropical marine environments.  相似文献   

Estimating the catching efficiency of a 2-m beam trawl for sampling epifauna by removal experiments   总被引：1，自引：0，他引：1  

Reiss  Henning; Kroncke  Ingrid; Ehrich  Siegfried 《ICES Journal of Marine Science》2006,63(8):1453-1464

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Analysis of the IR and sub-MM emission of four post-AGB stars     

Carsten Kömpe  Joachim Gürtler  Thomas Henning 《Astrophysics and Space Science》1995,224(1-2):353-356

The goal of this work is to derive the physical properties of dust envelopes around post-AGB stars by means of radiative transfer calculations. The model spectral energy distributions (SEDs) have been compared with observational data of the post-AGB stars IRAS 10215-5916, 16342-3814, 17150-3224, and 19500-1709 in the wavelength range from 0.4 to 1300µm. The match between our model SEDs and the observational data is very satisfactory. As a result, we have obtained estimates of the inner and outer radii, the density, the temperature, and the mass of the envelopes of the four objects.  相似文献   

New candidates for objects with a 21 micron feature     

S. J. Chan  Th. Henning  B. Begemann 《Astrophysics and Space Science》1995,224(1-2):435-437

We report the preliminary result of studying the nature of objects with a 21µm feature. New candidates are presented and possible carriers of the 21µm feature are discussed.  相似文献   

Cold dust around chamaeleon stars     

Th. Henning  E. Thamm 《Astrophysics and Space Science》1994,212(1-2):215-220

Here we present the results of 1.3 millimetre continuum measurements for intermediatemass stars in the Chamaeleon system of dark clouds. The detected millimetre radiation is most probably thermal emission from cold circumstellar dust grains. The measured millimetre fluxes are combined with infrared observations to model the broad-band spectral energy distribution (SED). In this way the parameters of the emission regions are determined.Paper presented at the Conference onPlanetary Systems: Formation, Evolution, and Detection held 7–10 December, 1992 at CalTech, Pasadena, California, U.S.A.  相似文献   

Zur Interpretation eines Zirkulationskriteriums     

Dr. D. Henning 《Meteorology and Atmospheric Physics》1967,16(2-3):126-136

Zusammenfassung Ein vonPhillips formuliertes und vonSmagorinsky umgeschriebenes Kriterium, das vor allem Aussagen über die Bedingungen gestattet, unter denen sich Störungen vom Typ der Rossby-Wellen entwickeln können, wird näher untersucht. Die Parameter, die in verschiedener Weise voneinander abhängen, sind die Zahl dieser Wellen, meriodionaler und vertikaler Gradient der potentiellen Temperatur und geographische Breite. Die Lage der planetarischen Hochdruckgürtel ist, worauf zuerstFlohn hingewiesen aht, bestimmbar in Abhängigkeit von den genannten Gradienten (Abb. 1). Ein funktionaler Zusammenhang zwischen Wellenzahl und Baroklinität besteht dann, wenn bei labilster Kombination von Wellenzahl, thermischer Schichtung und Breite gerade Indifferenz erreicht wird: beide Größen ändern sich dann entgegengesetzt (Abb. 2). Für thermische Schichtung und Wellenzahl kann ein solcher Zusammenhang bei fester Breite für beliebige Zustände exisitieren — bei Labilisierung der Schichtung vergrößert sich die Wellenzahl.

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Summary A baroclinic instability criterion is analysed in some detail which has been derived byPhillips, and has been rewritten bySmagorinsky. This criterion essentially permkits to make statements about the conditions by which disturbances of the Rossby-typemay develop. The parameters depending on one another in different ways are the wave number, the meridional and vertical gradients of potential temperature, and the latitude. The position of the planetary high pressure belts can be determined as a function of these gradients (Fig. 1), as has been demonstrated byFlohn. The wave number represents a function of the meridional temperature gradient by the condition that the most unstable combination of wave number, static stability, and latitude just leads to indifiference (in the sense of the criterion): both quantities are then varying in opposite directions (Fig. 2). At constant latitude and arbitary conditions otherwise the wave number is a function of static stability, or vice versa — the wave number increases if static, stability decreases.

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Résumé On examkine ici de plus près un critère formulé parPhillips et midifié parSmagorinsky, cirtère qui permet de déterminer les conditions initiales en partant desquelles des perturbations du type des ondes de Rossby peuvent se former. Les paramètres — dont l'interdépendance est complexe —sont: le nombre de ces ondes, les gradients méditional et vertical de la température potentielle et la latitude. La position des ceintures planétaires de haute pression, dont l'importance a àté signalée parFlohn — peutêtre déterminée à l'aide de ces gradients (Fig. 1). Un rapport fonctionnel entre le nombre d'ondullations et la baroclinité s'établit lorsque — par suite de la combinaison la moins stable du nombre d'ondulations, de l'étagement thermique et de la latitude —on obtient juste un état indifférent: ces deux grandeurs se modifient alors en sens inverse (Fig. 2). A une latitude donnée, un tel rapport entre l'étagement thermique et le nombre d'ondulations peut exister dans n'importe quelles conditions: si l'étagement devient moins stable, le nombre des ondulatiosn augmente.

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Mit 2 Textabbildungen  相似文献   

Assessment and Control of Ore Dilution in Long Hole Mining: Case Studies     

John G. Henning  Hani S. Mitri 《Geotechnical and Geological Engineering》2008,26(4):349-366

Unplanned ore dilution has a direct and large influence on the cost of a stope, and ultimately on the profitability of a mining operation. This paper presents the results of an examination of factors influencing ore dilution in a blasthole stoping environment. For the study, a comprehensive database was established, incorporating information related to the design, construction, excavation and cavity surveys of 172 sequentially mined long hole stope case histories from two orezones. Through a review of the case studies, it was demonstrated that, in addition to stope dimension, the amount of unplanned dilution differed according to stope type. Five stope types were identified, based on their position within a tabular blasthole mining sequence. Measured overbreak varies with stope type, with secondary stopes generating a greater volume of hanging-wall dilution than do primary stopes. Furthermore, a case study is presented to demonstrate the role cablebolts installed in the stope hanging-wall play to control ore dilution. The study illustrates relationships between measured hanging-wall overbreak, cablebolt orientation and stope type.  相似文献   

Molecular structure of brown-dwarf disks     

D. S. Wiebe  D. A. Semenov  T. Henning 《Astronomy Reports》2008,52(11):941-949

We describe typical features of the chemical composition of proto-planetary disks around brown dwarfs. We model the chemical evolution in the disks around a low-mass T Tauri star and a cooler brown dwarf over a time span of 1 Myr using a model for the physical structure of an accretion disk with a vertical temperature gradient and an extensive set of gas-phase chemical reactions. We find that the disks of T Tauri stars are, in general, hotter and denser than the disks of lower-luminosity substellar objects. In addition, they have more pronounced vertical temperature gradients. The atmospheres of the disks around low-mass stars are more strongly ionized by UV and X-ray radiation, while less dense brown-dwarf disks have higher fractional ionizations in their midplanes. Nevertheless, in both cases, most molecules are concentrated in the so-called warm molecular layer between the ionized atmosphere and cold midplane, where grains with ice mantles are abundant.  相似文献   

The physical properties of an analytic model for a relativistic star     

Henning Knutsen 《Astrophysics and Space Science》1989,162(2):315-336

An exact solution of Einstein's equations for a static isentropic perfect fluid sphere is examined in detail. The analysis yields a strong indication that the model isstable with respect to infinitesimal radial pulsations. This means that the temperature is decreasing outwards. We prove that the adiabatic speed of sound is everywhere less than the speed of light if and only if the radius of the sphere is larger than 1.61 times its Schwarzschild radius. We further show that the strong energy condition is fulfilled everywhere if and only if the radius is larger than 1.76 times the Schwarzschild radius. The necessary and sufficient condition for the speed of sound to be decreasing outwards is given, and we find that this criterion is fulfilled if the fluid is causal. Taking the values of the pressure and the density to be somewhere given by the maximum values from Baymet al.'s equation of state, i.e., ₀=5.1×10¹⁴ g cm^–3 andp ₀=7.4×10³³ dyne cm^–2, we find the maximum mass of the fluid sphere to be 2.5 solar masses.Dedicated to the memory of the late George Cunliffe McVittie (1904–1988).  相似文献   

Correction of precipitation based on off-site weather information     

Peter Allerup  Henning Madsen  Flemming Vejen 《Atmospheric Research》2000,53(4)

Owing to aerodynamic errors, correction of precipitation measurements, liquid, mixed or solid, is often carried out by means of an explicit mathematical statistical model. The magnitude of correction, e.g., calculated as a correction factor to the observed amount of precipitation, is the dependent variable, and wind speed, temperature and a measure of precipitation intensity are independent variables entering the correction model. Usually these independent variables are accessible on site where the precipitation measurements are recorded. However, in many standard precipitation networks the gauge measurements are not accompanied by on site information of these variables, and information from remote stations must be used. The aim of the paper is to describe how the statistical models can be used in evaluating if the set of remote information of the independent variables can be used for the estimation of a reliable correction factor on site. The technique is then applied to an example of precipitation network in Denmark where the typical situation for the standard gauges is that only the amount of precipitation is available. It is expected that not only can the methods be adapted to other countries, but for landscapes similar to Denmark even the conclusions can be applied directly: extrapolation of all independent variables from remote sites should be conducted with caution, wind speed information can be extrapolated from remote sites not farther away than approximately 50 km, while information on rain intensity and temperature can be safely extrapolated across longer distances.  相似文献