Spatial Occurrences Research Articles

The biogeography of Early Triassic ammonoid faunas: Clusters, gradients, and networks

The aim of this paper is to quantitatively investigate the spatial and temporal biogeographical relationships of the recovery of ammonoid faunas after the Permian-Triassic mass extinction using three complementary numerical approaches among which is a new, non-hierarchical clustering strategy. The faunal data set consists of a taxonomically homogenised compilation of the spatial and temporal occurrences of ammonoid genera within 20 Early Triassic Tethyan and Panthalassic sites ranging from 40°S to 70°N in palaeolatitudes. In addition to hierarchical cluster analysis (hCA) and nonmetric multidimensional scaling (NMDS), we introduce a third, new non-hierarchical clustering technique allowing the visualisation of a nonmetric interassemblages similarity structure as a connected network constructed without inferring additional internal nodes. The resulting network, which we call a “ Bootstrapped Spanning Network” (BSN), allows the simultaneous identification of partially or totally nested as well as gradational linear or reticulated biogeographical structures. The identified interlocalities relationships indicate that the very beginning of the Early Triassic (Griesbachian) corresponds to a very simple biogeographical context, representing a time of great cosmopolitanism for ammonoids. This context shifts rapidly to a more complex configuration indicative of a more endemic and latitudinally-restricted distribution of the ammonoids during the middle and late Early Triassic (Smithian and Spathian). From an evolutionary dynamic point of view, our results illustrate a very rapid (less than ca. 1.4 myr) Early Triassic recovery of the ammonoid faunas, in contrast to many other marine organisms. This recovery is linked with a marked increase in the overall biogeographical heterogeneity, and parallels the formation of a latitudinal gradient of taxonomic richness, which may be essentially controlled by the progressive intensification of the gradient of sea surface temperature. From a methodological point of view, we show that a BSN is a simple, intuitively legible picture of the nested as well as gradational taxonomic similarity relationships, hence providing a good synthesis (and additional insights) between hierarchical clustering and ordination in reduced space results.

Problems with Heavy Snow Data at First-Order Stations in the United States

Abstract Various interests desire information and data on heavy snowfalls to define their spatial and temporal occurrences. Historical data at the nation’s 208 first-order stations for events with 15.2 cm or more snowfall in 2 days or less was assessed, and revealed various serious data problems at 118 stations with climatological quality data available for 90 stations. The data problems are described as guidelines for those seeking to utilize heavy snowfall data, and stations with quality data are listed.

Frizzled-7 dictates three-dimensional organization of colorectal cancer cell carcinoids

Progression of colorectal cancer (CRC) involves spatial and temporal occurrences of epithelial-mesenchymal transition (EMT), whereby tumour cells acquire a more invasive and metastatic phenotype. Subsequently, the disseminated mesenchymal tumour cells must undergo a reverse transition (mesenchymal-epithelial transition, MET) at the site of metastases, as most metastases recapitulate the pathology of their corresponding primary tumours. Importantly, initiation of tumour growth at the secondary site is the rate-limiting step in metastasis. However, investigation of this dynamic reversible EMT and MET that underpins CRC morphogenesis has been hindered by a lack of suitable in vitro models. To this end, we have established a unique in vitro model of CRC morphogenesis, which we term LIM1863-Mph (morphogenetic). LIM1863-Mph cells spontaneously undergo cyclic transitions between two-dimensional monolayer (migratory, mesenchymal) and three-dimensional sphere (carcinoid, epithelial) states. Using RNAi, we demonstrate that FZD7 is necessary for MET of the monolayer cells as loss of FZD7 results in the persistence of a mesenchymal state (increased SNAI2/decreased E-cadherin). Moreover, FZD7 is also required for migration of the LIM1863-Mph monolayer cells. During development, FZD7 orchestrates either migratory or epithelialization events depending on the context. Our findings strongly implicate similar functional diversity for FZD7 during CRC morphogenesis.

A comparative study of NOAA–AVHRR derived drought indices using change vector analysis

The objective of this study was to compare the spatial occurrences of droughts, detected by remotely sensed drought-indices over the desert-steppe and desert geo-botanical zones of Mongolia. All indices were derived from reflectance and thermal data sets, obtained from the NOAA–AVHRR data between 1982 and 1999. One group of the drought-indices is based on vegetation state derived from the reflective channels. This group includes the Normalized Difference Vegetation Index (NDVI), Anomaly of Normalized Difference Vegetation Index (NDVIA), Standardized Vegetation Index (SVI), and Vegetation Condition Index (VCI). Another group, based on surface brightness temperature derived from the thermal channel of NOAA–AVHRR, includes the Temperature Condition Index (TCI). The third group is based on combination between the reflective and thermal channels includes the ratio between Land Surface Temperature (LST) and NDVI (LST/NDVI), the Vegetation Health Index (VH), and the Drought Severity Index (DSI). Change detection procedure was performed by using the Change Vector Analysis in the temporal domain. Comparison analysis among the drought-indices reveals that there is no spatial coincidence between them, even when the vegetation growing period was divided into 2-month sub-periods — beginning, middle, and end. Based on the statistical analysis, higher correlations were found among the reflective indices while lesser or no relationships were found between the thermal and combination of the thermal and reflective indices. Furthermore, no agreement was found between the spatial extent of the satellite-derived drought-indices and the meteorological-based Palmer Drought Severity Index (PDSI) and also between the traditional ground-observed drought-affected-areas (DAA) maps. It was found that the combination of satellite-derived drought-indices can identify wider drought-occurred areas rather than the PDSI and the DAA maps. In summary, this study concludes that it is difficult to point out the most reliable drought index, and that the ground observations cannot provide sufficient information for validation of satellite derived drought indices.

Forecasting Potential Distributions of Nonindigenous Species with a Genetic Algorithm

Forecasting species' potential distributions is a leading problem for research in invasion ecology and global change biology. Given the number of freshwater organisms, especially fishes, that have been introduced intentionally and unintentionally, an urgent need exists for the development of tools for forecasting their spread. New computational techniques partially overcome the defects of earlier environment-matching methods, including sensitivity to sparse and unbalanced data, inflated statistical significance, and asymmetrical (omission versus commission) errors. Here we apply one such method, the genetic algorithm for rule-set production (GARP), to predict spatial occurrences of suitable environments for two nonindigenous fishes that so far have limited distribution in North America, Eurasian ruffe (Gymnocephalus cernuus) and rainbow smelt (Osmerus mordax). For these two species, we conclude that although spread is not inevitable, their eventual range in North America will be considerable if management actions fail to prevent additional introductions.

Hatching of an Accountable Science

The Dinosauria 2nd ed. David B. Weishampel, Peter Dodson, and Halszka Osmólska, Eds. . University of California Press, Berkeley, 2004. 879 pp. $95, £62. ISBN 0-520-24209-2. The contributors offer dinosaur enthusiasts and researchers a definitive summary of our current knowledge of the group, which covers its systematics, spatial and temporal occurrences, and biology.

SPATIAL NESTED SCALES FOR ROAD ACCIDENTS IN THE PERIPHERY OF BRUSSELS

This paper tests the usefulness of a multilevel model (MLM) for explaining the spatial occurrence of road accidents; it also shows and confirms how far the characteristics of the geographical environment influence the location and concentration of road accidents at two levels of spatial aggregation. The results are compared to those obtained from a more classical logistic regression. The analysis is performed on the southern periphery of Brussels (Belgium). The main conclusions are: (1) that MLM is a potentially useful technique for modelling road accidents, but that hierarchical levels are not easy to define for spatial data and so MLM are less useful than other regression techniques for modelling spatial occurrences of road accidents; (2) that the characteristics of the environment and the road itself significantly influence the occurrence of road accidents, and changes in these characteristics are quite important elements in the explanation, leading to the suggestion that road users do not adapt their behaviour sufficiently to changes in road conditions. Hence, concentrations of road accidents often correspond to places where improvements could be made in terms of road design, signalling and land-use planning.

Larger miliolids of the Late Cretaceous and Paleogene seen through space and time

Spatial and temporal occurrences of the larger (complex) miliolids are discussed to give more light on biostratigraphy and paleobiogeographic provinces distribution. Seven genera and 47 species from the Late Cretaceous to Oligocene inhabited shallow marine settings in the Indo-Pacific, Tethyan and Caribbean regions. Of all genera only four (Idalina, Periloculina, Pseudolacazina, Lacazina) widespread throughout Tethys in the Late Cretaceous and Paleogene. Single occurrence of Lacazina was recorded further to east (Moluccas). By now the Late Cretaceous genus Adrahentina is known only from the Spain. The newcomer’s Eocene genera were Fabularia and Lacazinella. Fabularia reached high diversity in species term in the Central and Western Tethys and occured as unique genus in Caribbean realm, too. Conversely, during the same period, Lacazinella spread over the southern border of Neo-Tethys reaching New Guinea. On the Adriatic ‐ Dinaric Carbonate Platform, larger miliolids occurred from the Late Cretaceous to Cuisian, having the same biostratigraphically trends and distribution as contemporaneous larger miliolids from the Tethys.

Spatial and Temporal Occurrences of Intermittent Turbulence During CASES-99

Occurrences of intermittent turbulence in very stable conditions during theCASES-99 field study near Leon, Kansas were detected at several sites separatedby horizontal distances from 1 km to 25 km using sonic anemometers, minisodarsand a laser scintillometer. Periods with significant turbulent heat fluxes wereseparated by extended quiescent periods with little or no flux, and most of theflux during a night was realized in relatively small fractions (<20%) of thetotal time. There appeared to be no relationship between this intermittencyfraction and the median z/L (z being height and L the Obukhov length)value for the night, although overall sensible heat flux values on very stablenights were significantly less than those on less stable nights. The intermittencyfraction at 7 m was found to increase with mean wind speed at 20 m and, to alesser extent, with wind shear between 20 m and 30 m. While correspondenceof turbulent episodes at two sites separated by 1 km was common, it was less common at separations on the order of 20 km. There were time periods, however, during which enhanced turbulence levels were seen nearly simultaneously at large separation distances. Turbulence episodes were found to propagate upward or downward at different times with no readily defined large-scale controlling mechanism.

The charged‐particle fluxes at auroral and polar latitudes and related low‐frequency auroral kilometric radiation‐type and high‐frequency wideband emission

The results of simultaneous observations of charged particle fluxes within the energy range 50 eV to 20 keV (plasma energy‐angle spectrometer, PEAS experiment) and plasma waves within the frequency range 0.1 to 10 MHz (plasma radio spectrometer, PRS 3 experiment) on board the APEX spacecraft are presented. The data were obtained at polar and auroral latitudes in the dawn‐dusk and noon‐midnight time sectors. The low‐frequency (LF) sporadic emission mainly on frequencies lower than the local gyrofrequency was commonly observed within a comparatively narrow latitude interval (∼5°– 6°) of the auroral oval. The maximum of spectral wave intensity was revealed at a frequency of ∼ 200 kHz. The sporadic character of the observed emissions, the spectra, are very similar to those reported for auroral kilometric radiation (AKR), and the temporal and spatial occurrences imply its relation to the source of AKR emissions measured at the higher altitudes, with regards to our wave measurements as LF AKR‐type emissions. Comparative analysis of spatial distributions of charged particle energy spectra and variations of wave spectra at auroral oval latitudes showed that several conditions should be fulfilled for LF AKR generation. These conditions are related both to the intensity and energy of precipitating ion and electron fluxes, and to albedo electrons and the ionospheric plasma parameters. The wideband HF emission was observed together with the LF AKR‐type emission during the morning auroral oval crossing. At spacecraft apogee altitudes, in the polar cap zone intense electron precipitations and an increase of plasma noise intensity at frequencies equal or below ƒHe were observed at the period when the IMF was northward These precipitations and emissions were accompanied by the horizontal currents crossing the polar cap, the so‐called theta structure.

Prehistoric Charcoal in Peat Profiles at North Gill, North Yorkshire Moors, England

In the multiprofile sequence at North Gill, North Yorkshire, charcoal has been recognized in the profiles and its stratigraphic and spatial occurrences during the mid-Holocene are discussed here. Two size classes are recognized and their relationships and possible origins discussed; the relation of the whole to questions of fire management by hunter –gatherer cultures in north-west Europe is also addressed.

Quantitative analysis of summer air masses in the eastern United States and an application to human mortality

CR Climate Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials CR 07:43-53 (1996) - DOI: https://doi.org/10.3354/cr007043 Quantitative analysis of summer air masses in the eastern United States and an application to human mortality Greene JS, Kalkstein LS A recently developed continental-scale air mass-based classification is used to identify the spatial occurrences of 6 air masses (dry polar, dry temperate, dry tropical, moist polar, moist temperate, and moist tropical) in the eastern United States for summer from 1961 to 1990. This procedure, the spatial synoptic classification (SSC), is based on 'seed' day identification of synoptic events and discriminant analysis to group days together which are within the same air mass type. Thus, the evaluation of the frequency and modification of air masses across a large region is possible. Using the SSC, maps of air mass frequencies and afternoon temperatures and dew points are developed. Rates of modification are determined as each air mass traverses the region. As an example of the environmental applicability of the SSC, the impact of climate upon human mortality is analyzed at 3 climatically different locations (New Orleans, LA; Memphis, TN; and Chicago, IL). Results show how the day-to-day mortality fluctuations are sensitive to air mass type. A particular air mass which is associated with distinctly high mortality is identified for Memphis and Chicago; no such air mass is apparent for New Orleans, where the weather/mortality signal is very weak. Synoptic climatology · Weather/health relationships · Air masses Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in CR Vol. 07, No. 1. Publication date: August 22, 1996 Print ISSN: 0936-577X; Online ISSN: 1616-1572 Copyright © 1996 Inter-Research.

Measures of geographic range size: the effects of sample size

A number of methods have been used for quantifying the sizes of the geographic ranges of species. The consequences of different levels of sampling (the proportion of actual spatial occurrences) are explored for eight of these, using data on the occurrences of butterfly species on a 10 x 10 km grid across Britain. For all methods, the percentage error of estimation (PEE) decreases with the number of 10 x 10 km squares which a species occupies, most rapidly for extent measures, and more rapidly for area measures than for measures of numbers of units occupied. The rate of decline in PEE itself falls as sampling effort increases. At a given sampling level, rank correlations between range sizes measured by different methods are generally high. but there is no consistent change in the magnitude of these correlations as the level of sampling increases. The composition of the set of species with the smallest range sizes changes with the level of sampling.

Prototype development of GEOEXPLORER, a knowledge-based system for supergene deposits: Identification of favorable areas for bauxite

GEOEXPLORER is a knowledge-based system under development to support the prospecting and exploration of supergene deposits. As a new type of multi-stage expert systetn, GEOEXPLORER is not only able to deal with problems of searching for supergene deposits, but will also cover both the evaluation of the spatial occurrences and the economic values of the deposits considered. A first prototype of GEOEXPLORER has been developed for bauxite deposits. It is a rule-based system implemented in PROLOG and can be used to identify favorable areas for bauxite prospecting. This paper discusses this prototype of GEOEXPLORER.

Processing hierarchy for 2-D image structures

The processing hierarchy for 2-D image structures based on geometric considerations is presented. The proposed pattern-recognition system is based on a structural approach that couples symbolic and numerical methods to manipulate symbolic descriptions, namely spatial occurrences of lines, arcs, circular regions, etc., each with values, properties and constrained relationships to other symbolic entities. The processing hierarchy includes hierarchical modeling and symbolic manipulation of 2-D image structures—aspects of the image-formation process. In this paper, a hybrid strategy for designing a character-recognition system is proposed that contains embedded coupled numerical and symbolic processing units and identified raw data and stored model's knowledge sources. Among the issues discussed is the process for evaluating image structures via computing dissimilarity levels (or variations) between feature descriptions of the prestored and extracted image structures. The variational concept has been implemented and the results are very encouraging.

ECOLOGICAL EFFECTS OF COOLING WATER DISCHARGE ON HYDROLITTORAL EPILITHIC DIATOM COMMUNITIES IN THE NORTHERN BALTIC SEA

The discharge of brackish cooling water from a nuclear power plant on the Swedish Baltic coast has major effects on the species composition, biomass and seasonal variation of epilithic diatom communities in the hydrolittoral zone. Greatest effects occur in winter and early spring, when enormous diatom blooms are caused by the higher water temperatures (6–10°C above natural level) and by the absence of an ice cover, which implies high light availability early in the season. A low light regime in mid-winter inhibits growth for a short period only. Canonical correspondence analysis (CCA) was used to display the relationship of community composition to sampling site and date. CCA reproduced the seasonal cycle, and placed each site in its correct relative position in terms of annual-mean temperature anomaly and flow rate. Individual species were placed according to their ecological optima with respect to the seasonal cycles of light, temperature and water level, and the site-dependent anomalies in temperature and flow rate. Seasonal variation exceeded variation between sites, and within-site variation was smaller than variation between sites. Seasonal variation can be attributed to the seasonal cycles of light, temperature and water level; variation between sites to temperature and flow rate anomalies, and the presence or absence of winter ice. Parallel studies (in press) of macroalgae, including macroscopic colonies of microalgae (blue-greens and diatoms), and macrofauna show weaker seasonal cycles, but all groups show some seasonal pattern and the patterns of variation between sites are similar for all three groups. Shannon-Weaver diversity is generally lower in the cold season than in the warm season; the cooling water discharge has no effect on diversity. The seasonal and spatial occurrences of the species can be related to growth forms and life-form strategies. Melosira spp. and Nitzschia filiformis are especially favoured by the cooling water discharge in winter. They respond opportunistically by growing fast in large upright colonies and do not need macroalgae as substrata to reach into the water column. Different morphologies and life histories affect the competititive balance among eurythermic species in different environments.

Magnetospheric electrostatic emissions and cold plasma densities

A synoptic study of electric wave, magnetometer, and plasma data from Imp 6 has been carried out for times when banded electrostatic waves are observed between harmonics of the electron gyrofrequency in the earth's outer magnetosphere. Four separate classes of such waves have previously been identified by us. The spatial and temporal occurrences of waves in each class are summarized here, as are correlations of occurrence with geomagnetic activity. Most importantly, associations between the observations of waves of different classes and the relative portions of cold and hot electrons present at the position of the spacecraft are established. The cold to hot ratio varies in accordance with the predictions of our previous theoretical work, which models the emission as arising unstably from a hot loss cone distribution existing simultaneously with a cold isotropic electron component. Finally, evidence for the signature of the loss cone is sought in the plasma data.

Mineral Parageneses in Franciscan Metamorphic Rocks, Panoche Pass, California

Approximately 33 square miles of Franciscan terrane near Panoche Pass in the Diablo Range of the central California Coast Ranges were mapped at an initial scale of 1:12,000. Serpentinite intrusions present in the area are not mantled by metasomatic glaucophane schist aureoles, but do appear to contain tectonic inclusions of chloritized eclogite, “glaucophane eclogite,” amphibolite, glaucophane schist, and greenstone. Petrographic and X-ray investigations of country rocks reveal systematic mineral parageneses in metabasalts, metacherts, and metagraywackes. Conversion of greenstones to blueschists involved reaction of albite + actinolite + chlorite to form crossite + lawsonite; greenstones contain calcite, mafic glaucophane schists calcite or aragonite. Least metamorphosed metacherts contain very minor albite + calcite; with progressive recrystallization these phases are replaced by acgirme, riebeckite, and aragonite. Metagraywacke paragenesis is from albite metagraywackes containing accessory lawsonite + calcite or aragonite, to jadeitic pyroxene + law-sonite metagraywackes carrying accessory glaucophane + aragonite. The “jadeitic pyroxene + lawsonite isograd” is recognized on the basis of metagraywacke assemblages. The aragonite isograd cannot be located precisely because of rapid postmetamorphic inversion to calcite. More extreme conditions of recrystallization appear to have been required to produce aragonite and the jadeitic pyroxene + lawsonite (+ quartz) compatibility than to convert greenstones to blueschists. Mineral parageneses and inferred phase relationships in the system CaCO 3 and in the pseudoternary system Ab-An-H 2 O suggest that metamorphism at Panoche Pass involved temperatures of about 200–300°C, lithostatic pressures approaching 7–8 kb, and high chemical potential of H 2 O. Presence of a separate aqueous phase during the metamorphism is indicated. Based on observed mineral assemblages, experimental phase equilibrium data, tectonic and spatial occurrences of blueschists, available geophysical evidence, fossil occurrences, and radiometric dates, the following tentative geologic model is proposed. Franciscan rocks principally of the Diablo Range are hypothesized to have been deposited in an oceanic trench bordering the continental margin in later Jurassic and possibly earliest Cretaceous time. Rapid deposition and subsidence could have accounted for thermal disequilibrium and consequent relatively high pressure, low temperature recrystallization in axial portions of the trench. Thickness of the Franciscan rocks in the Diablo Range is thought to have approached 30 km near the trough axis. Diastrophism nearly contemporaneous with deposition locally deformed the structural trough, resulted in periodic intrusion of serpentinized mantle material and in rapid uplift, and allowed preservation of the blueschist facies mineral assemblages. Elsewhere, portions of the trench apparently were not destroyed and continued to receive sediments well into Cretaceous time.