Concentration of Uranium Particulates from Soils Using a Novel Density-Separation Technique

1997 ◽  
Vol 61 (2) ◽  
pp. 626 ◽  
Author(s):  
M. P. Elless ◽  
M. E. Timpson ◽  
S. Y. Lee
Radiocarbon ◽  
2010 ◽  
Vol 52 (3) ◽  
pp. 1301-1311 ◽  
Author(s):  
Christopher M Russo ◽  
Jennifer A Tripp ◽  
Katerina Douka ◽  
Thomas F G Higham

Coastal archaeological sites that lack organic remains for radiocarbon dating are often abundant sources of molluscan shells. As a substitute for materials such as bone and charcoal, shells can be analyzed with 14C dating to determine a site's age. Despite their being convenient, non-mobile archaeological artifacts, molluscan shells are plagued by several issues, including carbonate remodeling, in which aragonite in shells is converted to calcite as predicted by thermodynamics. We present here a carbonate density separation technique that addresses the issue of carbonate remodeling. Using a density fractionation with bromoform, aragonite concentrations are enriched in shells that have undergone significant remodeling. The technique has been applied to archaeological shells and has returned dates that are younger than those previously determined for the same shells.


1981 ◽  
Vol 78 (2) ◽  
pp. 141-150 ◽  
Author(s):  
J C Parker

A phthalate density-separation technique has been used to study the heterogeneity of dog red blood cells that becomes manifest when they are suspended in KCl media. It is demonstrated that the proportions of cells that separate into light and dense fractions can be varied by altering the tonicity of the KCl medium. This results from the fact that the Na and K permeabilities of each cell are continuous functions of cell volume. It was found that quinidine inhibits selectively the volume dependence of Na permeability. In the presence of this drug, the heterogeneity demonstrated by KCl incubation disappears. The notion that dog red blood cells are heterogeneous in their permeabilities to Na and K is thus upheld, but the heterogeneity is not an abruptly discontinuous one, as has been claimed. A sample of dog blood does not contain two discrete populations of red cells.


Author(s):  
Abentin Estim ◽  
Rafidah Sudirman

The amount of marine debris is increasing worldwide and has become a matter of serious concern. It is important to identify the nature of debris to understand the sources and to devise practically feasible methods for managing this problem. This study was carried out at Sebatik Island on the east coast of Sabah with the aim of examining the types and abundance of macro – and micro-debris. The observations covered a period of December 2015 – May 2016. Debris collected from different stations was compared. Transect line method was used to assess the stranded macro-marine debris (SMD). Evaluation of floating macro- debris (FMD) was done by surveys of the selected areas. Density separation technique was applied in order to extract the micro marine debris (MMD). Results showed 14 types of SMD and 9 types of FMD in the study areas. Three major types of SMD and FMD were discarded plastic, organic debris and plastic bottles. Four types of MMD recorded at the beach and mudflat areas were fragments, fiber, films and polystyrene. Based on the comparison between stations (S), S2 showed the highest abundance of SMD with 80 items m-2. Meanwhile, FMD at one location was as high as 94 items m-2. Station S3 has the highest of MMD with 22 items ml-1. Plastic formed (40%) of the SMD category whereas FMD constituted 42 % at the Sebatik Island. Small fragments and film were the most abundant of MMD (32 %). This study highlights the scale of the marine debris problem in Sebatik Island and calls for a comprehensive plan of action to protect the Island’s marine ecosystem services.


PAMM ◽  
2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Ramona Mehling ◽  
Denise Gruner ◽  
Adrian Ehrenhofer ◽  
Andreas Richter ◽  
Thomas Wallmersperger

1977 ◽  
Vol 9 (1-2) ◽  
pp. 26-32 ◽  
Author(s):  
R. E. Beard

In reference [1] Dr. G. C. Taylor has described a useful advance in the techniques available for verification of outstanding claims estimates when the data provided is the cohort development of numbers and amounts of claims. In this note it is assumed that the numbers relate to settled claims and that the amounts relate to claim payments, so there is an implicit assumption that the pattern of partial payments is constant. If the amounts of settled claims were to be used, there would be a one/one relationship between the numbers and amounts, but the effect of the exogeneous factor would be blurred because the settlements in a year other than the first include partial payments made some time previously, and, by hypothesis, based on different factors. If information relating to partial payments is available the data can be examined for any major fluctuation in the pattern and allowance made accordingly.In paragraph (2) of reference [1] a brief description is given of a standard routine calculation in which the average distribution function of claim payments in time is estimated from the triangle of payments by a chain ladder technique. This distribution function is then used to estimate the expected development of the incomplete cohorts, the implicit assumption being made that the function was stable in time. With a constant rate of inflation the results obtained by this technique were found to be satisfactory but with a rapid increase in the rate of inflation the distribution function changed so that projection led to underestimates of the future claims payments. Various methods of adjusting the projections to allow for the change in the rate of inflation have been investigated, but they all involve an important element of subjective judgment and so far no generally suitable basis for “automatic” verification by this particular technique has been discovered. See however reference [2].


2021 ◽  
pp. 1-1
Author(s):  
J.J. Kosse ◽  
M. Dhalle ◽  
G. Tomas ◽  
P.C. Rem ◽  
H.J.M. Ter Brake ◽  
...  

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