Assessing water quality in Marine Protected Areas from Southern California, USA     

Schiff K  Luk B  Gregorio D  Gruber S 《Marine pollution bulletin》2011,62(12):2780-2786

Despite the regulatory mandate to maintain “natural water quality”, there are ?271 storm drain discharges that potentially threaten the 14 designated marine water quality protected areas in Southern California called Areas of Special Biological Significance (ASBS). After sampling 35 site-events, the geomean concentrations of total suspended solids, nutrients, total and dissolved trace metals, and polycyclic aromatic hydrocarbons in the ocean following storm events were similar between reference drainages and ASBS discharge sites. Concentrations of chlorinated hydrocarbons were nondetectable and no post-storm sample exhibited significant toxicity to the endemic purple sea urchin (Strongylocentrotus purpuratus) near ASBS discharge sites. A reference-based threshold was developed and, despite the similarities in average concentrations, there were some individual ASBS discharge sites that were greater than reference background. Cumulatively across all ASBS, the constituents that were most frequently greater than the reference-based threshold were nutrients and general constituents, followed by dissolved and total trace metals.  相似文献   

Evaluation of the physical parameters of gas in the neutral atmospheres of comets: Method of isophots     

F. I. Kravtsov  I. V. Luk’yanyk 《Kinematics and Physics of Celestial Bodies》2015,31(6):276-280

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Spectral,Photometric, and Dynamic Analysis of Eight Draconid Meteors     

Jiří Borovička  Pavel Koten  Lukáš Shrbený  Rostislav Štork  Kamil Hornoch 《Earth, Moon, and Planets》2014,112(1-4):15-31

A Draconid meteor shower outburst was observed from on board two scientific aircraft deployed above Northern Europe on 8th October 2011. The activity profile was measured using a set of photographic and video cameras. The main peak of the activity occurred around 20:15 ± 0:0.5 UT which is consistent with the model prediction as well as with the IMO network visual observations. The corrected hourly rates reached a value of almost 350. The brighter meteors peaked about 15–20 min earlier than the dimmer ones. This difference can be explained by different directions of the ejection of the meteoroids from the parent comet. One of the instruments was even able to detect meteors connected with the material ejected from the parent comet before 1900 and thus confirmed the prediction of the model, although it was based on uncertain pre-1900 cometary data. Another small peak of the activity, which was caused by material ejected during the 1926 perihelion passage of the parent comet, was detected around 21:10 UT. The mass distribution index determined using the narrow field-of-view video camera was 2.0 ± 0.1. This work shows that the observation of meteor outbursts can constrain the orbital elements, outgassing activity and existence of jets at the surface of a comet.  相似文献   

Humidity of the tropical lower stratosphere: Observations and analysis     

S. M. Khaykin  V. A. Yushkov  L. I. Korshunov  A. N. Luk’yanov  J. -P. Pommereau  J. Nielsen  H. Vömel 《Izvestiya Atmospheric and Oceanic Physics》2010,46(1):76-84

The results of measurements of water-vapor vertical profiles in the upper troposphere and stratosphere on board a meteorological balloon with a FLASH-B optical fluorescent hygrometer (Russia) are presented. These data were obtained during two international field campaigns in West Africa (August 2006) and Central America (August 2007). Eleven high-resolution water-vapor vertical profiles measured in the course of these works make it possible to characterize the processes controlling humidity in the tropical tropopause region. Layers with increased humidity are detected in the lower stratosphere over West Africa to the level of the potential temperature 450 K. An analysis of satellite maps of the brightness temperature, balloon ozone measurements, and aerosol scattering, as well as trajectory modeling, display the relation between the observed layers with increased humidity and the phenomena of convective overshooting of the tropopause, as a result of which cold and ozone-depleted air penetrates into the lower stratosphere together with ice particles, which, rapidly sublimating, locally increase the water-vapor concentration. A comparison of the humidity data obtained in West Africa in 2006 and in Central America in 2007 reveals substantial distinctions in values and vertical structures of water vapor, both in the tropopause region and in the middle stratosphere.  相似文献   

Stress analysis of a deep rigid axially-loaded cylindrical anchor in an elastic medium     

V. K. Luk  L. M. Keer 《国际地质力学数值与分析法杂志》1980,4(3):215-232

The elastostatic problem of an infinite elastic medium containing an axially-loaded rigid cylindrical inclusion is investigated. This problem is of interest in connection with the geotechnical study of the time-independent, load-deflection characteristics of deep rigid anchors embedded in cohesive soil or rock media. The problem is formulated by means of Hankel integral transforms and reduced to a system of four coupled sing ular integral equations, where the unknown quantities are the normal and the shear stresses acting on the entire surface of the anchor. Numerical solutions are investigated for various Poisson's ratios and several values of the aspect ratio of radius to length of the cylindrical anchor.  相似文献   

Conditionally periodic solutions near the libration points of the restricted circular three-body problem     

L. G. Luk’yanov 《Astronomy Letters》2012,38(3):201-211

Families of conditionally periodic solutions have been found by a slightly modified Lyapunov method of determining periodic solutions near the libration points of the restricted three-body problem. When the frequencies of free oscillations are commensurable, the solutions found are transformed into planar or spatial periodic solutions. The results are confirmed by numerically integrating the starting nonlinear differential equations of motion.  相似文献   

Infra-low-frequency gravitational wave signals in the electric and magnetic fields of the earth     

L. V. Grunskaya  V. V. Isakevich  D. V. Isakevich  V. E. Luk’yanov  I. A. Leshchev 《Astronomy Reports》2017,61(4):368-375

Signals with infra-low frequencies corresponding to the frequencies of gravitational-wave radiation from known binary star systems have been detected in the electric and magnetic fields of the Earth. The use of a eigenvector and signal-component analyzer has proved effective in detecting energetically not dominant components in time series of the electric and geomagnetic fields. The amplitude and probability characteristics of these signals are estimated.  相似文献   

Galaxy formation from tepid inflation     

B. Lukács  G. Paál 《Astrophysics and Space Science》1988,146(2):347-354

It is argued that the primordial density fluctuations needed for galaxy formation may have been of thermal origin in a quasi-exponential state of inflation.  相似文献   

Relation between the structure of particles of the dispersion layer and its spectral optical thickness in an optically thin environment     

Miroslav Kocifaj  Ján Lukáč 《Studia Geophysica et Geodaetica》1994,38(4):399-415

Summary The paper focuses on the applicability of simple optimizing methods to determining the aerosol structure based on the measured values of the spectral optical thickness of aerosol δ(λ). The necessary conditions leading to a stable solution are assessed. By applying the particle distribution function in the form of summations of modified gamma functions we obtain the simple form of δ(λ). It is not suitable for proving Gaussian functions. The application of approximate methods to determine the aerosol structure from spectral optical thickness of atmospheric aerosol is based on measurements of the direct spectral solar radiation flux density which formed a part of the radiation experiment conducted in Zingst (Germany) on the coast of the Baltic Sea in 1987. on leave from the Astronomical Institute, Slovak Academy of Sciences  相似文献   

Absorption of direct solar radiation by water vapour     

Ján Lukáč  Reviewer V. Vítek 《Studia Geophysica et Geodaetica》1985,29(3):315-317

Summary Radiation absorption by water vapour plays an important role in the physics of the atmosphere. The calculation of the absorbed radiation energy by water vapour requires the amount of precipitable water in the atmosphere to be known. Actinometric and aerological measurements were used to establish the relation between vapour pressure and absorbed solar radiation.

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