Search results for "Correlation"
showing 10 items of 2282 documents
Analysis of Inter-Station Daily Rainfall Correlation During the Southwest Monsoon in the Wet Zone of Sri Lanka
1993
Daily rainfall data have been analysed for 11 stations in the Wet Zone of Sri Lanka for the Southwest Monsoon season (May to September, 1971–1985) to yield the spatial organization of daily rainfal...
Sr/Ca and Mg/Ca ratios of ontogenetically old, long-lived bivalve shells (Arctica islandica) and their function as paleotemperature proxies
2011
International audience; The Sr/Ca and Mg/Ca ratios of many biogenic skeletons provide useful paleotemperature estimates. As yet however, it has remained largely impossible to obtain such information from bivalve shells. In the present study, metal-to-calcium values in the hinge plate (aragonite, outer shell layer) of four ontogenetically old (85 to 374 year-old) specimens of the long-lived bivalve, Arctica islandica, were measured on a LA-ICP-MS. The shells were collected alive in 1868, 1986 and 2003 from three different localities around Iceland. With increasing ontogenetic age and decreasing growth rate, a distinct trend toward increasing Sr/Ca (max. 5.17 mmol/mol) and Mg/Ca values (max. …
Warm season precipitation signal in δ 2 H values of wood lignin methoxyl groups from high elevation larch trees in Switzerland
2017
RATIONALE In this study, we tested stable hydrogen isotope ratios of wood lignin methoxyl groups (δ 2Hmethoxyl values) as a palaeoclimate proxy in dendrochronology. This is a quite new method in the field of dendrochronology and the sample preparation is much simpler than the methods used before to measure δ2H values from wood. METHODS We measured δ 2Hmethoxyl values in high elevation larch trees (Larix decidua Mill.) from Simplon Valley (southern Switzerland). Thirty-seven larch trees were sampled and five individuals analysed for their δ 2Hmethoxyl values at annual (1971-2009) and pentadal resolution (1746-2009). The δ 2Hmethoxyl values were measured as CH3I released upon treatment of the…
A Geometry-Based Underwater Acoustic Channel Model Allowing for Sloped Ocean Bottom Conditions
2017
This paper proposes a new geometry-based channel model for shallow-water ocean environments, in which the ocean bottom can slope gently down/up. The need for developing such an underwater acoustic (UWA) channel model is driven by the fact that the standard assumption of a flat ocean bottom does not hold in many realistic scenarios. Starting from a geometrical model, we develop a stochastic channel model for wideband single-input single-output vehicle-to-vehicle UWA channels using the ray theory assuming smooth ocean surface and bottom. We investigate the effect of the ocean-bottom slope angle on the distribution of the channel envelope, instantaneous channel capacity, temporal autocorrelati…
A Nonisovelocity Geometry-Based Underwater Acoustic Channel Model
2018
This paper proposes a new geometry-based shallow underwater acoustic (UWA) channel model allowing for nonisovelocity ocean conditions. The fact that the isovelocity assumption does not hold in many real-world scenarios motivates the need for developing channel models for nonisovelocity UWA propagation environments. Starting from a geometrical model, we develop a stochastic channel model for a single-input single-output (SISO) vehicle-to-vehicle UWA channel assuming that the ocean surface and bottom are rough and that the speed of sound varies with depth. The effect of the nonisovelocity condition has been assessed regarding its influence on the temporal autocorrelation function, the frequen…
Advances in Cretaceous palaeontology and stratigraphy – Christopher John Wood Memorial Volume; editors' preface
2018
Abstract In the last week of January 2016, the ‘Cretaceous community’ lost another of their prominent members, Chris Wood. During recent decades, Chris had been active in the United Kingdom as well as in mainland Europe, particularly in Germany and Poland. Several years ago he had been forced to leave the ranks of Associate Editors with Cretaceous Research , due to a severe illness that he was adamant to overcome. Later in 2016, two of us, fellow editors with that journal for a number of years, with the help of Rory Mortimore, approached former colleagues and friends of Chris's to contribute to a special issue. From the start, the idea has been to cover all aspects of Cretaceous stratigraph…
Ammonite dating of latest Cretaceous mosasaurid reptiles (Squamata, Mosasauroidea) from Jordan—preliminary observations
2017
Newly collected ammonoid material from the uppermost Cretaceous portion of the Muwaqqar Chalk Marl Formation exposed some 30 km southeast of the Qasr Al’Harrana area (east-central Jordan) includes medium-sized baculitids (Baculites ovatus auctorum, non Say), the sphenodiscid Libycoceras acutodorsatus (Noetling) and the pachydiscids Menuites fresvillensis (Seunes) and Pachydiscus (Pachydiscus) dossantosi (Maury). Of the two last named taxa, the former is a good marker species for the upper Maastrichtian, with records from Europe, central Chile, South India, Baluchistan (Pakistan), Australia, Madagascar and South Africa. The latter is known from the United Arab Emirates/Oman border area, from…
Carbon-isotope records of the Early Jurassic (Toarcian) Oceanix Anixic Event from the Valdorbia (Umbria-Marche Apennines) and Monte Mangart (Julian A…
2009
The Toarcian oceanic anoxic event (ca 183 Ma) coincides with a global perturbation marked by enhanced organic carbon burial and a general decrease in calcium carbonate production, probably triggered by changes in the composition of marine plankton and elevated carbon dioxide levels in the atmosphere. This study is based on high-resolution sampling of two stratigraphic successions, located in Valdorbia (Umbria-Marche Apennines) and Monte Mangart (Julian Alps), Italy, which represent expressions of the Toarcian oceanic anoxic event in deep-water pelagic sediments. These successions are characterized by the occurrence of black shales showing relatively low total organic carbon concentrations (…
Using latent variable models to identify large networks of species‐to‐species associations at different spatial scales
2015
Summary We present a hierarchical latent variable model that partitions variation in species occurrences and co-occurrences simultaneously at multiple spatial scales. We illustrate how the parameterized model can be used to predict the occurrences of a species by using as predictors not only the environmental covariates, but also the occurrences of all other species, at all spatial scales. We leverage recent progress in Bayesian latent variable models to implement a computationally effective algorithm that enables one to consider large communities and extensive sampling schemes. We exemplify the framework with a community of 98 fungal species sampled in c. 22 500 dead wood units in 230 plot…
Covariation and phenotypic integration in chemical communication displays: biosynthetic constraints and eco-evolutionary implications
2018
Chemical communication is ubiquitous. The identification of conserved structural elements in visual and acoustic communication is well established, but comparable information on chemical communication displays (CCDs) is lacking. We assessed the phenotypic integration of CCDs in a meta‐analysis to characterize patterns of covariation in CCDs and identified functional or biosynthetically constrained modules. Poorly integrated plant CCDs (i.e. low covariation between scent compounds) support the notion that plants often utilize one or few key compounds to repel antagonists or to attract pollinators and enemies of herbivores. Animal CCDs (mostly insect pheromones) were usually more integrated t…