Characterization of dissolved organic matter fluorescence in the South Atlantic Bight with use of PARAFAC model: Relationships between fluorescence and its components,absorption coefficients and organic carbon concentrations     

Piotr Kowalczuk  William J. Cooper  Michael J. Durako  Amanda E. Kahn  Michael Gonsior  Heather Young 《Marine Chemistry》2010,118(1-2):22-36

In this study, the CDOM absorption coefficient at 350 nm [a_CDOM(350)] and CDOM excitation emission matrix (EEM) fluorescence were used to estimate annual fluxes of dissolved organic carbon (DOC) from the Cape Fear River to Long Bay in the South Atlantic Bight. Water samples were collected during a 3.5 year period, from October 2001 through March 2005, in the vicinity of the Cape Fear River (CFR) outlet and adjacent Onslow Bay (OB). Parallel factor analysis (PARAFAC) of CDOM EEM spectra identified six components: three terrestrial humic-like, one marine humic-like and two protein-like. Empirical relationships were derived from the PARAFAC model between DOC concentration and a_CDOM(350), total fluorescence intensity and the intensities of respective EEM components. DOC concentration and CDOM optical parameters were very well correlated and R² values ranged from 0.77 to 0.90. Regression analyses revealed that the non-absorbing DOC fraction, in DOC concentration estimated from CDOM optical parameters, varied with the qualitative composition of the CDOM. DOC concentration and intensity of the humic-like CDOM components characterized by excitation maxima at longer wavelengths have significantly higher estimated non-absorbing DOC compared to the analogous relationships between DOC and intensity of the humic-like CDOM components characterized by excitation maxima at shorter wavelengths. The relationships between DOC concentration and intensity of one of the protein-like components resulted in significantly reduced non-absorbing DOC fraction in DOC concentration estimation. Results of regression analyses between fluorescence intensities of specific EEM components and CDOM-specific absorption coefficients suggest that the relative proportion of humic-like CDOM components (characterized by excitation maximum at longer wavelengths) and the main protein-like component have the most impact on the values of a?_CDOM(350). Based on the relationships between a_CDOM(350), Cape Fear River flow, and DOC concentrations, DOC fluxes were estimated for 2002, 2003 and 2004. DOC fluxes varied from 1.5 to 6.2 × 10¹⁰ g C yr^? 1, depending on river flow.  相似文献   

Harmonizing the RR Lyrae and clump distance scales – stretching the short distance scale to intermediate ranges?     

Piotr Popowski 《Monthly notices of the Royal Astronomical Society》2001,321(3):502-506

I explore the consequences of making the RR Lyrae and clump giant distance scales consistent in the solar neighbourhood, Galactic bulge and Large Magellanic Cloud (LMC). I employ two major assumptions: (i) that the absolute magnitude–metallicity, M _V (RR)–[Fe/H], relation for RR Lyrae stars is universal, and (ii) that absolute I magnitudes of clump giants, M _I (RC), in Baade's Window are known (e.g. can be inferred from the local Hipparcos -based calibration or theoretical modelling). A comparison between the solar neighbourhood and Baade's Window sets M _V (RR) at [Fe/H]=−1.6 in the range (0.59±0.05, 0.70±0.05), somewhat brighter than the statistical parallax solution. More luminous RR Lyrae stars imply younger globular clusters, which would be in better agreement with the conclusions from the currently favoured stellar evolution and cosmological models. A comparison between Baade's Window and the LMC sets M ^LMC(RC) _I in the range (−0.33±0.09,−0.53±0.09). The distance modulus to the LMC is μ ^LMC∈(18.24±0.08,18.44±0.07). Unlike M ^LMC(RC) _I , this range in μ ^LMC does not depend on the adopted value of the dereddened LMC clump magnitude, I ^LMC(RC)₀. I argue that the currently available information is insufficient to select the correct distance scale with high confidence.  相似文献   

The Destruction of Heterogeneous Cometary Grains as the Possible Cause of Variations and Outbursts of Comets' Brightness     

Piotr Gronkowski 《Astrophysics and Space Science》2001,278(4):459-464

It is examined whether the destruction of heterogeneous cometary grains can explain the variation of cometary brightness and comet outburst.Calculations were carried out for water ice grains with carbonoxideinclusions. It was shown that for realistic chosen values of parametersthe comet luminosity can increase by even a few stellar magnitudes.  相似文献   

A minimum sample size required from Schmidt hammer measurements     

Tomasz Niedzielski  Piotr Migoń  Agnieszka Placek 《地球表面变化过程与地形》2009,34(13):1713-1725

The Schmidt hammer is a useful tool applied by geomorphologists to measure rock strength in field conditions. The essence of field application is to obtain a sufficiently large dataset of individual rebound values, which yields a meaningful numerical value of mean strength. Although there is general agreement that a certain minimum sample size is required to proceed with the statistics, the choice of size (i.e. number of individual impacts) was usually intuitive and arbitrary. In this paper we show a simple statistical method, based on the two‐sample Student's t‐test, to objectively estimate the minimum number of rebound measurements. We present the results as (1) the ‘mean’ and ‘median’ solutions, each providing a single estimate value, and (2) the empirical probability distribution of such estimates based on many field samples. Schmidt hammer data for 14 lithologies, 13–81 samples for each, with each sample consisting of 40 individual readings, have been evaluated, assuming different significance levels. The principal recommendations are: (1) the recommended minimum sample size for weak and moderately strong rock is 25; (2) a sample size of 15 is sufficient for sandstones and shales; (3) strong and coarse rocks require 30 readings at a site; (4) the minimum sample size may be reduced by one‐third if the context of research allows for higher significance level for test statistics. Interpretations based on less than 10 readings from a site should definitely be avoided. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Seasonal and spatial changes in the zooplankton community of Kongsfjorden, Svalbard   总被引：1，自引：0，他引：1  

Wojciech Walkusz  Slawek Kwasniewski  Stig Falk-Petersen  Haakon Hop  Vigdis Tverberg  Piotr Wieczorek  & Jan Marcin Weslawski 《Polar research》2009,28(2):254-281

Seasonal changes in the zooplankton composition of the glacially influenced Kongsfjorden, Svalbard (79°N, 12°E), and its adjacent shelf were studied in 2002. Samples were collected in the spring, summer and autumn in stratified hauls (according to hydrographic characteristics), by means of a 0.180-mm Multi Plankton Sampler. A strong front between the open sea and the fjord waters was observed during the spring, preventing water mass exchange, but was not observed later in the season. The considerable seasonal changes in zooplankton abundance were related to the seasonal variation in hydrographical regime. The total zooplankton abundance during the spring (40–2010 individuals m⁻³) was much lower than in the summer and autumn (410–10 560 individuals m⁻³). The main factors shaping the zooplankton community in the fjord include: the presence of a local front, advection, the flow pattern and the decreasing depth of the basin in the inner fjord. Presumably these factors regulate the gross pattern of zooplankton density and distribution, and override the importance of biological processes. This study increased our understanding of seasonal processes in fjords, particularly with regard to the strong seasonal variability in the Arctic.  相似文献   

2-Gyr Simulation of the Oort-cloud Formation II. A Close View of the Inner Oort cloud after the First Two Giga-years     

Giuseppe Leto  Marián Jakubík  Tomáš Paulech  Luboš Neslušan  Piotr A. Dybczyński 《Earth, Moon, and Planets》2009,105(2-4):263-266

We simulate the formation of the Oort cloud (OC) till the age of 2 Gyr starting from an initial disc of planetesimals made by 10 038 test particles. The results on the outer part of the distant comet reservoir are reported by Neslu?an et al. (this issue). Here we deal with the evolution of the population and structure at 2 Gyr of the complementary inner part of the Oort cloud. The dynamical evolution of the massless test particles was followed via the numerical integration of their orbits. We considered the perturbations produced by four giant planets assuming they have their current orbits and masses, as well as the perturbations caused by the Galactic tide and passing stars. The efficiency of the formation of inner OC is found to be very low: only about 1.1% of all considered particles ended in this part of the OC. At 2 Gyr, the dynamics of the inner cloud is mainly governed by the dominant z-term of the Galactic tide. The number density of the bodies is proportional to the heliocentric distance, r, as r ^?3.53. The directional distribution of orbits is still strongly inhomogeneous. There are large empty regions in the space angles around the Galactic Equator points with the galactic longitude 90 and 270° (non-rotating frame), or there are only few bodies having the ecliptical latitude higher than +60° or lower than 60°. A strong concentration of objects at the Ecliptic is apparent up to ≈1,000 AU, with a possible—but still not proved—extension to ≈1,500 AU. Beyond r ≈ 6,000 AU, bodies directly above and below the Sun, with respect to the Ecliptic, are absent.  相似文献   

Searching for the Parent of the Tunguska Cosmic Body     

Tadeusz Jan Jopek  Christiane Froeschlé  Robert Gonczi  Piotr A. Dybczyński 《Earth, Moon, and Planets》2008,102(1-4):53-58

We present the results of an extensive study of the Tunguska Cosmic Body (TCB) origin on dynamical grounds. To identify the TCB parent, or a plausible candidate, we applied the well-known concept of dynamical similarity whereby we have compared the geocentric and heliocentric dynamical parameters of a selected set of the Near Earth Objects (NEOs) and TCB particles. First, we made use the idea of Kresak by comparing geocentric coordinates of the TCB radiant with those of the NEOs. Second, we studied the long-term dynamical evolution of all NEOs and TCB particles searching for similarities between their heliocentric orbits. As a general result, we observed many more similar cases and a different pattern of the high orbital similarity among the TCB particles and the asteroid orbits than we did for comets.  相似文献   

Permanence of economic potential of cities based on sector development     

Piotr Raźniak  Sławomir Dorocki  Anna Winiarczyk-Raźniak 《中国地理科学(英文版)》2017,27(1):123-136

The paper attempts to answer the following key question: how will a city′s world rank change in the face of crisis in its main economic sector? Crisis is defined here as a decline in financial performance in the given sector, which leads to the decline of its constituent firms and corporations on the world economic scene. The World Economic Center Index(WECI) has been created in order to rank cities based on the value of their resident corporations by sector and show their level of stability upon the removal of the most important sector. This provides information on the potential of each analyzed city as well as on its advanced features or area of specialization. Research has shown that nearly half the World Economic Centers are dominated by the financial and materials sectors of the economy. Different sectors dominate different regions of the world. For example, consumer staples and materials were dominant in North America, while information technology and financials were dominant in Europe. In Asia, several sectors tend to dominate the economy. Research has shown that the ability of a principal economic sector to resist economic crisis largely depends on the strength of the command and control function of a city. Finally, a high globalization level of a city is a key determinant of its susceptibility to economic crisis.  相似文献   

A New Subfamily of Aphids (Hemiptera,Aphidomorpha) from the Early Cretaceous Lebanese Amber with a Description of the Oldest Apterous Morphs   总被引：1，自引：1，他引：0  

Piotr Wegierek  and David A. Grimaldi 《《地质学报》英文版》2010,84(4):665-672

<正>Aphids are marked by their high polymorphism,but species reported from the Early Cretaceous are known only from alate morphs.The discovery of an apterous adult morph in Lebanese amber and a larva of the same species are very important for the understanding of both the morphological and biological evolution of this insect group at the very early stage of development.Gondvanoaphis estephani new subfamily,new genus and species of the recent aphids family Thelaxidae is described.The characters of the new genus in respect to other genera placed in Thelaxidae are reviewed.The palaeoecological and palaeogeographical data concerning Gondvanoaphis new genus are also discussed.  相似文献   

Study of litter influence on magnetic susceptibility measurements of urban forest topsoils using the MS2D sensor   总被引：1，自引：1，他引：0  

Jarosław Zawadzki  Piotr Fabijańczyk  Tadeusz Magiera  Zygmunt Strzyszcz 《Environmental Earth Sciences》2010,61(2):223-230

Field magnetometry is fast and convenient method used to detect areas contaminated by technogenic magnetic particles and potentially polluted with heavy metals. Frequently, measurements of soil magnetic susceptibility (κ) are carried out with MS2D Bartington sensor, which penetration range equals 10 cm, although 90% of the total signal is detected from a depth of up to 6 cm. Thick uppermost organic soil layers may significantly influence on the measured κ because the penetration range may be not large enough to cover the layers where the most of anthropogenic contaminants are cumulated. The aim of the study was to investigate on how the removal of the litter improves the MS2D measurements of soil pollution. Accordingly, the correlations between κ values measured on the successively removed overlying soil sub-horizons were investigated. Measurements were performed at 15 sites located in different forest in the Upper Silesian Industrial Area, Poland. The results showed that the litter removal enabled the MS2D to measure the κ more related to the anthropogenic pollution, and did not affect the measuring variance.  相似文献