Distribution by Scientific Domains
Distribution within Earth and Environmental Science

Kinds of Strata

  • age stratum
  • jurassic stratum
  • low-permeability stratum
  • mesozoic stratum
  • permian stratum
  • sedimentary stratum
  • social stratum
  • socioeconomic stratum
  • vegetation stratum

  • Terms modified by Strata

  • stratum corneum
  • stratum corneum hydration
  • stratum corneum lipid
  • stratum corneum turnover

  • Selected Abstracts


    S.N. Ehrenberg
    Eight samples of brachiopod shell material have been analyzed for their strontium isotope composition in order to more accurately date Lower to Upper Permian siliceous biogenic strata of Spitsbergen (Kapp Starostin Formation) and the southern Barents Sea (Røye Formation). The results are interpreted as showing a mid-Artinskian age for the basal Vøringen Member of the Kapp Starostin Formation and a range of late Artinskian to Roadian for the overlying part of this unit. The upper part of the Røye Formation yields ages in the range Roadian to Wuchiapingian. These results are consistent with available biostratigraphic data and confirm the potential of strontium isotope stratigraphy for developing a more accurate chronology of the widespread spiculite deposits that characterize the northern margin of Pangea in late-Early Permian to Late Permian time and which constitute a potential target for petroleum exploration. [source]

    SPE and large-volume sample stacking in MEKC for determination of doxycycline in biological fluids: Comparison of direct injection to SPE-MEKC

    ELECTROPHORESIS, Issue 21 2008
    Rade Injac
    Abstract A novel and simple method has been developed for the determination of doxycycline (DOX) in biological fluids. The method is based on SPE, large-volume sample stacking (LVSS) and MEKC with UV-DAD detection. Six SPE cartridges have been used in investigation for sample clean up and pre-concentration (Supelco® LC-8, LC-18, LC-SCX, and LC-WCX, as well as StrataÔ-X and X-C). DOX was determined on a 56,cm (effective length 50,cm)×50,,m id fused-silica capillary. The BGE was 20,mM borate buffer, pH 9.3, containing 80,mM SDS and 7.5%,v/v of methanol (30,s×50,mbar), and the temperature and voltage were 25°C and 30,kV, respectively. The analytical wavelength was set at 210,nm. Under optimized conditions it is possible to determine DOX in human serum, urine, semen, tears and saliva with recovery of 97.5% (RSD 2.5%). The method was shown to be sensitive (LOD is 1,,g/L) and precise (intra-day RSD 0.2 and 2.4%; inter-days 0.4 and 3.5% for migration time and peak area, respectively). Results for developed SPE-LVSS-MEKC were compared with LVSS-MEKC method with direct sample injection. The new LVSS-MEKC method is presented as a useful technique for rapid determination without extraction procedure of DOX in human urine and serum, using 80,mM of SDS, 10%,v/v of methanol and 40,mM borate buffer (pH 9.3; 30,s×50,mbar; 25°C; 30,kV; 350,nm), but not for the other biological fluids, according to lower sensitivity of the method and because of the sample composition. [source]

    Geoarchaeology and late glacial landscapes in the western lake superior region, Central North America

    Christopher L. Hill
    The transition from full glacial to interglacial conditions along the southern margin of the Laurentide ice sheet resulted in dramatic changes in landscapes and biotic habitats. Strata and landforms resulting from the Wisconsin Episode of glaciation in the area directly west of Lake Superior indicate a context for late Pleistocene biota (including human populations) connected to ice margins, proglacial lakes, and postglacial drainage systems. Late Glacial landscape features that have the potential for revealing the presence of Paleoindian artifacts include abandoned shorelines of proglacial lakes in the Superior and Agassiz basins and interior drainages on deglaciated terrains. The linkage between Late Pleistocene human populations and Rancholabrean fauna has yet to be demonstrated in the western Lake Superior region, although isolated remains of mammoth ( Mammuthus) have been documented, as well as fluted points assigned to Clovis, Folsom, and Holcombe-like artifact forms. Agate Basin and Hell Gap (Plano-type) artifacts also imply the presence of human groups in Late Glacial landscapes associated with the Agassiz and Superior basins. © 2007 Wiley Periodicals, Inc. [source]

    Diel Changes in Phytoplankton Composition and Abundance in the Surface and Sub-Surface Strata from a Shallow Eutrophic Pond

    bieta Wilk-Wo, niak
    Abstract Representative phytoplankton assemblages were identified in a eutrophic pond over a 24 hour period. One assemblage characterized species in the surface (neuston) layer and another consisted of algae from 2, 5, and 20 cm sub-surface depths. The surface layer (0 cm) included a similar, but less diverse assemblage of species, and a lower abundance of cells per unit volume, than those at the lower depths. At each of the sub-surface depths (2,20 cm), the major phytoplankton components initially followed similar patterns of abundance in reference to the time and depth of sample collections then later differed in their abundance levels. The dominant algae were chlorophytes, cryptophytes, diatoms, and cyanobacteria. Mean concentrations of total phytoplankton, over the 24 hours for the surface, were 3.3 × 103 cells ml,1, compared to 36.9 × 103 cells ml,1 for depths 2,20 cm. The autotrophic picoplankton abundance was recorded separately from the phytoplankton with mean concentrations of 472.9 × 103 cells ml,1 in the surface layer and 623.0 × 103 cells ml,1 for the three sub-surface depths. Photos of representative species from these surface layers are presented. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Effects of Near-Surface Absorption on Reflection Characteristics of Continental Interbedded Strata: the Dagang Oilfield as an Example

    LI Guofa
    Abstract: Due to the effects of seismic wave field interference, the reflection events generated from interbedded and superposed sand and shale strata no longer have an explicit corresponding relationship with the geological interface. The absorption of the near-surface layer decreases the resolution of the seismic wavelet, intensifies the interference of seismic reflections from different sand bodies, and makes seismic data interpretation of thin interbedded strata more complex and difficult. In order to concretely investigate and analyze the effects of the near-surface absorption on seismic reflection characteristics of interbedded strata, and to make clear the ability of current technologies to compensate the near-surface absorption, a geological model of continental interbedded strata with near-surface absorption was designed, and the prestack seismic wave field was numerically simulated with wave equations. Then, the simulated wave field was processed by the prestack time migration, the effects of near-surface absorption on prestack and poststack reflection characteristics were analyzed, and the near-surface absorption was compensated for by inverse Q -filtering. The model test shows that: (1) the reliability of prediction and delineation of a continental reservoir with AVO inversion is degraded due to the lateral variation of the near-surface structure; (2) the corresponding relationships between seismic reflection events and geological interfaces are further weakened as a result of near-surface absorption; and (3) the current technology of absorption compensation probably results in false geological structure and anomaly. Based on the model experiment, the real seismic data of the Dagang Oil Field were analyzed and processed. The seismic reflection characteristics of continental interbedded strata were improved, and the reliability of geological interpretation from seismic data was enhanced. [source]

    Origin and Accumulation of Natural Gases in the Upper Paleozoic Strata of the Ordos Basin in Central China

    Yangming ZHU
    Abstract: The natural gases in the Upper Paleozoic strata of the Ordos basin are characterized by relatively heavy C isotope of gaseous alkanes with ,13C1 and ,13C2 values ranging mainly from ,35, to ,30, and ,27, to ,22,, respectively, high ,13C excursions (round 10) between ethane and methane and predominant methane in hydrocarbon gases with most C1/(C1 -C5) ratios in excess of 0.95, suggesting an origin of coal-derived gas. The gases exhibit different carbon isotopic profiles for C1 -C4 alkanes with those of the natural gases found in the Lower Paleozoic of this basin, and believed to be originated from Carboniferous-Permian coal measures. The occurrence of regionally pervasive gas accumulation is distinct in the gently southward-dipping Shanbei slope of the central basin. It is noted that molecular and isotopic composition changes of the gases in various gas reservoirs are associated with the thermal maturities of gas source rocks. The abundances and ,13C values of methane generally decline northwards and from the basin center to its margins, and the effects of hydrocarbon migration on compositional modification seem insignificant. However, C isotopes of autogenetic calcites in the vertical and lateral section of reservoirs show a regular variation, and are as a whole depleted upwards and towards basin margins. Combination with gas maturity gradient, the analysis could be considered to be a useful tool for gas migration. [source]

    Discovery of Paleogene Sporopollen from the Matrix Strata of the Naij Tal Group-Complex in the Eastern Kunlun Orogenic Belt

    GUO Xianpu
    Abstract, The Naij Tal Group-complex is a suite of tectonic-sedimentary mélange aggregation of the Eastern Kunlun orogenic belt, which is composed of two parts, i.e. the exotic blocks of various ages and the matrix strata. On the basis of coral, brachiopod and gastropod fossils found in the exotic blocks, the age of this group-complex was once defined to the Late Ordovician or the Paleozoic. This paper reports for the first time 44 genera and 31 species of Mid-Late Oligocene sporopollen in samples from the matrix strata in this group-complex and the Paleogene Quercoidites-Persicarioipollis assemblage is named. The paper aims to provide some detailed evidence for determining the age of the matrix strata in this group-complex based upon a study at the Caiyuanzigou section, which would be of great geological significance for further understanding this group-complex as a suite of tectonic-sedimentary mélange aggregation. The new finding will certainly benefit from now on the investigation of formation and evolution mechanism for the Eastern Kunlun orogenic belt. [source]

    A General Algorithm for Univariate Stratification

    Sophie Baillargeon
    Summary This paper presents a general algorithm for constructing strata in a population using,X, a univariate stratification variable known for all the units in the population. Stratum,h,consists of all the units with an,X,value in the interval[bh,1,,bh). The stratum boundaries{bh}are obtained by minimizing the anticipated sample size for estimating the population total of a survey variable,Y,with a given level of precision. The stratification criterion allows the presence of a take-none and of a take-all stratum. The sample is allocated to the strata using a general rule that features proportional allocation, Neyman allocation, and power allocation as special cases. The optimization can take into account a stratum-specific anticipated non-response and a model for the relationship between the stratification variable,X,and the survey variable,Y. A loglinear model with stratum-specific mortality for,Y,given,X,is presented in detail. Two numerical algorithms for determining the optimal stratum boundaries, attributable to Sethi and Kozak, are compared in a numerical study. Several examples illustrate the stratified designs that can be constructed with the proposed methodology. All the calculations presented in this paper were carried out with stratification, an R package that will be available on CRAN (Comprehensive R Archive Network). Résumé Cet article présente un algorithme général pour construire des strates dans une population à l'aide de,X, une variable de stratification unidimensionnelle connue pour toutes les unités de la population. La strate,h,contient toutes les unités ayant une valeur de,X,dans l'intervalle [bh,1,,bh). Les frontières des strates {bh} sont obtenues en minimisant la taille d'échantillon anticipée pour l'estimation du total de la variable d'intérêt,Y,avec un niveau de précision prédéterminé. Le critère de stratification permet la présence d'une strate à tirage nul et de strates recensement. L'échantillon est réparti dans les strates à l'aide d'une règle générale qui inclut l'allocation proportionnelle, l'allocation de Neyman et l'allocation de puissance comme des cas particuliers. L'optimisation peut tenir compte d'un taux de non réponse spécifique à la strate et d'un modèle reliant la variable de stratification,X,à la variable d'intérêt,Y. Un modèle loglinéaire avec un taux de mortalité propre à la strate est présenté en détail. Deux algorithmes numériques pour déterminer les frontières de strates optimales, dus à Sethi et Kozak, sont comparés dans une étude numérique. Plusieurs exemples illustrent les plans stratifiés qui peuvent être construits avec la méthodologie proposée. Tous les calculs présentés dans l'article ont été effectués avec stratification, un package R disponible auprès des auteurs. [source]

    Phase I study of decitabine with doxorubicin and cyclophosphamide in children with neuroblastoma and other solid tumors: A children's oncology group study,,

    PEDIATRIC BLOOD & CANCER, Issue 4 2010
    MRCP, Rani E. George MD
    Abstract Background Demethylating agents may alter the expression of genes involved in chemotherapy resistance. We conducted a phase I trial to determine the toxicity and molecular effects of the demethylating agent, decitabine, followed by doxorubicin and cyclophosphamide in children with refractory solid tumors. Procedure Stratum A included children with any solid tumor; Stratum B included neuroblastoma patients only. Patients received a 1-hr decitabine infusion for 7 days, followed by doxorubicin (45,mg/m2) and cyclophosphamide (1,g/m2) on day 7. Pharmacokinetic studies were performed after the first dose of decitabine. Biological studies included methylation and gene expression analyses of caspase-8, MAGE-1 and fetal hemoglobin (HbF), and expression profiling of pre- and post-treatment peripheral blood and bone marrow cells. Results The maximum-tolerated dose of decitabine was 5,mg/m2/day for 7 days. Dose-limiting toxicities at 10,mg/m2/day were neutropenia and thrombocytopenia. Decitabine exhibited rapid clearance from plasma. Three of 9 patients in Stratum A and 4/12 patients in Stratum B had stable disease for ,4 months. Sustained MAGE-1 demethylation and increased HbF expression were observed in the majority of patients post-treatment (12/20 and 14/16, respectively). Caspase-8 promoter demethylation and gene expression were seen in 2/7 bone marrow samples. Differentially expressed genes were identified by microarray analysis. Conclusion Low-dose decitabine when combined with doxorubicin/cyclophosphamide has tolerable toxicity in children. However, doses of decitabine capable of producing clinically relevant biologic effects were not well tolerated with this combination. Alternative strategies of combining demethylating agents with non-cytotoxic, biologically targeted agents such as histone deactelyase inhibitors should be explored. Pediatr Blood Cancer. 2010;55:629,638. © 2010 Wiley-Liss, Inc. [source]

    Phase 1 trial of temozolomide plus irinotecan plus O6 -benzylguanine in adults with recurrent malignant glioma

    CANCER, Issue 13 2009
    Jennifer A. Quinn MD
    Abstract BACKGROUND: The current study was a phase 1 clinical trial conducted with patients who had recurrent or progressive malignant glioma (MG). The trial was designed to determine the maximum tolerated dose (MTD) and toxicity of irinotecan (CPT-11) when administered with temozolomide (TMZ) and O6 -benzylguanine (O6 -BG). METHODS: All 3 drugs, CPT-11, TMZ, and O6 -BG, were administered on Day 1 of a 21-day treatment. First, patients were treated with a 1-hour bolus infusion of O6 -BG at a dose of 120 mg/m2 followed immediately by a 48-hour continuous infusion of O6 -BG at a dose of 30 mg/m2/d. Second, within 60 minutes of the end of the 1-hour bolus infusion of O6 -BG, TMZ was administered orally at a dose of 355 mg/m2. Third, 1 hour after administration of TMZ, CPT-11 was infused over 90 minutes. Patients were accrued to 1 of 2 strata based on CYP3A1- and CYP3A4-inducing antiepileptic drug (EIAED) use; dose escalation was conducted independently within these strata. RESULTS: Fifty-five patients were enrolled. In both strata, the dose-limiting toxicities were hematologic and included grade 4 neutropenia, febrile neutropenia, leukopenia, and/or thrombocytopenia. For Stratum 1 (EIAEDs), when TMZ was administered at a dose of 355 mg/m2, the MTD of CPT-11 was determined to be 120 mg/m2. In contrast, for Stratum 2 (no EIAEDs), when TMZ was administered at a dose of 200 mg/m2, the MTD of CPT-11 was determined to be 80 mg/m2. CONCLUSIONS: The authors believe that the results of the current study provide the foundation for a phase 2 trial of O6 -BG in combination with CPT-11 and TMZ in patients with MG. Cancer 2009. © 2009 American Cancer Society. [source]

    Grammatical Inference Techniques and Their Application in Ground Investigation

    Ian Morrey
    The data obtained from trial pits can be coded into a form that can be used as sample observations for input to a grammatical inference machine. A grammatical inference machine is a black box, which when presented with a sample of observations of some unknown source language, produces a grammar which is compatible with the sample. This article presents a heuristic model for a grammatical inference machine, which takes as data sentences and non-sentences identified as such, and is capable of inferring grammars in the class of context-free grammars expressed in Chomsky Normal Form. An algorithm and its corresponding software implementation have been developed based on this model. The software takes, as input, coded representations of ground investigation data, and produces as output a grammar which describes and classifies the geotechnical data observed in the area, and also promises the possibility of being able to predict the likely configuration of strata across the site. [source]

    Risk factors related to traumatic dental injuries in Brazilian schoolchildren

    Evelyne Pessoa Soriano
    Abstract,,, The aim of this pilot study was to analyse whether overjet, lip coverage and obesity represented risk factors associated with the occurrence of dental trauma in the permanent anterior teeth of schoolchildren in Recife, Brazil. It included a random sample of 116 boys and girls aged 12 years, attending both public and private schools. Data was collected through clinical examinations and interviews. Dental trauma was classified according to Andreasen's criteria (1994). Overjet was considered as risk factor when it presented values higher than 5 mm. Lip coverage was classified as adequate or inadequate, while obesity was considered according to National Center for Health Statistics (NCHS) procedures for the assessment of nutritional status. The prevalence of dental injuries was 23.3%. Boys experienced more injuries than girls, 30 and 16.1%, respectively (P > 0.05). There was a statistically significant difference between traumatic dental injuries and overjet (P < 0.05) and between traumatic dental injuries and lip coverage (P = 0.000). No statistical significant differences were found when obesity and dental trauma were analysed (P < 0.05). It was concluded that boys from lower social strata attending public schools, presenting an overjet size greater than 5 mm and an inadequate lip coverage, were more likely to have traumatic dental injuries in Recife, Brazil. Obesity was not a risk factor for dental trauma in this sample. [source]

    Do No Harm: Aid, Weak Institutions and the Missing Middle in Africa

    Nancy Birdsall
    The implicit assumption of the donor community is that Africa is trapped by its poverty, and that aid is necessary if it is to escape. This article suggests an alternative view: that Africa is caught in an institutional trap, signalled and reinforced by the small share of income of its independent middle strata. Theory and historical experience elsewhere suggest that a robust middle-income group contributes critically to the creation and sustenance of healthy institutions, particularly of the state. The article argues that if external aid is to be helpful for institution-building in Africa's weak and fragile states, donors need to emphasise not providing more aid but minimising the risks more aid poses for this group. [source]

    Efficacy and safety of sitagliptin when added to insulin therapy in patients with type 2 diabetes

    T. Vilsbøll
    Objective: To evaluate the efficacy and tolerability of sitagliptin when added to insulin therapy alone or in combination with metformin in patients with type 2 diabetes. Methods: After a 2 week placebo run-in period, eligible patients inadequately controlled on long-acting, intermediate-acting or premixed insulin (HbA1c , 7.5% and , 11%), were randomised 1:1 to the addition of once-daily sitagliptin 100 mg or matching placebo over a 24-week study period. The study capped the proportion of randomised patients on insulin plus metformin at 75%. Further, the study capped the proportion of randomised patients on premixed insulin at 25%. The metformin dose and the insulin dose were to remain stable throughout the study. The primary endpoint was HbA1c change from baseline at week 24. Results: Mean baseline characteristics were similar between the sitagliptin (n = 322) and placebo (n = 319) groups, including HbA1c (8.7 vs. 8.6%), diabetes duration (13 vs. 12 years), body mass index (31.4 vs. 31.4 kg/m2), and total daily insulin dose (51 vs. 52 IU), respectively. At 24 weeks, the addition of sitagliptin significantly (p < 0.001) reduced HbA1c by 0.6% compared with placebo (0.0%). A greater proportion of patients achieved an HbA1c level < 7% while randomised to sitagliptin as compared with placebo (13 vs. 5% respectively; p < 0.001). Similar HbA1c reductions were observed in the patient strata defined by insulin type (long-acting and intermediate-acting insulins or premixed insulins) and by baseline metformin treatment. The addition of sitagliptin significantly (p < 0.001) reduced fasting plasma glucose by 15.0 mg/dl (0.8 mmol/l) and 2-h postmeal glucose by 36.1 mg/dl (2.0 mmol/l) relative to placebo. A higher incidence of adverse experiences was reported with sitagliptin (52%) compared with placebo (43%), due mainly to the increased incidence of hypoglycaemia (sitagliptin, 16% vs. placebo, 8%). The number of hypoglycaemic events meeting the protocol-specified criteria for severity was low with sitagliptin (n = 2) and placebo (n = 1). No significant change from baseline in body weight was observed in either group. Conclusion: In this 24-week study, the addition of sitagliptin to ongoing, stable-dose insulin therapy with or without concomitant metformin improved glycaemic control and was generally well tolerated in patients with type 2 diabetes. [source]

    Brachial-ankle pulse wave velocity and cardiovascular risk factors in the non-diabetic and newly diagnosed diabetic Chinese: Guangzhou Biobank Cohort Study-CVD

    Lin Xu
    Abstract Background Increased arterial stiffness is an important cause of cardiovascular disease (CVD). We examined determinants of arterial stiffness in subjects across strata of glycaemic status. Methods A total of 1249 subjects from a sub-study of the Guangzhou Biobank Cohort Study (GBCS-CVD) had brachial-ankle pulse wave velocity (baPWV) measured by automatic oscillometric method. Major cardiovascular risk factors including glycosylated haemoglobin A1c (HbA1c), high sensitivity C-reactive protein (hsCRP), fasting triglyceride, low- and high-density lipoprotein cholesterol and both fasting and post 2-h oral glucose-load glucose, systolic and diastolic blood pressure were assessed. Results In all, 649, 479 and 121 subjects were classified into normoglycaemia, impaired glucose metabolism (IGM) and newly diagnosed diabetes groups, respectively. Both age and systolic blood pressure were significantly associated with increased baPWV in all three groups (all p < 0.001). In both normoglycaemic and IGM groups, hsCRP and HbA1c were positively associated with baPWV (p from 0.04 to < 0.001), whereas current smoking and triglyceride were associated with baPWV in the normoglycaemic and IGM group, respectively (p = 0.04 and 0.001). No gender difference in baPWV was observed in the normoglycaemic or IGM groups. However, in the newly diagnosed diabetes group, men had higher baPWV than women (p = 0.01). Conclusions In the normoglycaemic and IGM subjects, after adjusting for age, blood pressure and other confounders, increasing HbA1c was associated with increased baPWV, suggesting a pathophysiological role of chronic glycaemia that can contribute to vascular disease risk in persons without diabetes. Copyright © 2010 John Wiley & Sons, Ltd. [source]

    Answers and echoes: the Libellus responsionum and the hagiography of north-western European mission

    Bill Friesen
    This article examines three aspects of Augustine of Canterbury's Libellus responsionum. Through recent scholarship it provides a summary of the Libellus's textual context. It also clarifies the very contentious issue of just how familiar the Libellus was to missionaries, not only those preaching in England but also on the Continent, and specifically Augustine of Canterbury and Boniface. Finally, in light of the pastoral and textual circumstances, it explores the largely neglected question of just how the Libellus may (or may not) have illuminated the various literary features and strata of Augustinian and Bonifatian biography. [source]

    Meltwater discharge through the subglacial bed and its land-forming consequences from numerical experiments in the Polish lowland during the last glaciation

    Jan A. Piotrowski
    Abstract Numerical experiments suggest that the last glaciation severely affected the upper lithosphere groundwater system in NW Poland: primarily its flow pattern, velocities and fluxes. We have simulated subglacial groundwater flow in two and three spatial dimensions using finite difference codes for steady-state and transient conditions. The results show how profoundly the ice sheet modifies groundwater pressure heads beneath and some distance beyond the ice margin. All model runs show water discharge at the ice forefield driven by ice-sheet-thickness-modulated, down-ice-decreasing hydraulic heads. In relation to non-glacial times, the transient 3D model shows significant changes in the groundwater flow directions in a regionally extensive aquifer ca. 90 m below the ice,bed interface and up to 40 km in front of the glacier. Comparison with empirical data suggests that, depending on the model run, only between 5 and 24% of the meltwater formed at the ice sole drained through the bed as groundwater. This is consistent with field observations documenting abundant occurrence of tunnel valleys, indicating that the remaining portion of basal meltwater was evacuated through a channelized subglacial drainage system. Groundwater flow simulation suggests that in areas of very low hydraulic conductivity and adverse subglacial slopes water ponding at the ice sole was likely. In these areas the relief shows distinct palaeo-ice lobes, indicating fast ice flow, possibly triggered by the undrained water at the ice,bed interface. Owing to the abundance of low-permeability strata in the bed, the simulated groundwater flow depth is less than ca. 200 m. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Geomorphology of the onset area of a paleo-ice stream, Marguerite Bay, Antarctic Peninsula

    John B. Anderson
    Abstract Geomorphic features indicate that both glacial and melt-water erosion characterize the onset area of the ancestral Marguerite Ice Stream. The large size of these features indicates that they formed over repeated glacial cycles, most recently during the Last Glacial Maximum. Ice drainage within the bay and on the inner continental shelf was strongly influenced by tectonic fabric. Deep, isolated basins surrounded by rugged bedrock bathymetry characterize the innermost part of the bay. Drumlins and other streamlined features occur in the floors of these basins at depths of up to 900 m. The outer bay has three large interconnected basins. Drumlins and megaflutings within these basins indicate ice was grounded at water depths up to 1000 m. The orientations of these features show convergence of drainage from the northeast, east and south into the Marguerite paleo-ice stream. On the inner continental shelf, the ice converged into a single, wide trough dominated by mega-scale glacial lineations. This transition in geomorphic features from drumlins and megaflutings to mega-scale glacial lineations occurs at the location on the continental shelf where sedimentary strata blanket bedrock, and marks a zone of acceleration of the ice stream. The glacially sculptured geomorphic features within Marguerite Bay co-exist with anastomosing, radial and relatively straight channels, which become increasingly focused in a seaward direction. This implies that a well organized subglacial drainage system existed within the bay at some point in the past. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Herbivory patterns in mature sugar maple: variation with vertical canopy strata and tree ontogeny

    1. Although leaf morphology and chemistry show profound changes as trees age, the consequences of such changes to herbivory have received little attention, particularly late in the ontogeny of canopy trees. 2. Using a mobile aerial lift for canopy access, patterns of leaf damage were evaluated in canopy-dominant mature sugar maple (Acer saccharum Marsh) trees ranging from ,20 to 70 cm in diameter, corresponding to an age range of ,40,180 years. 3. Herbivore damage patterns varied in relation to both vertical canopy position (among upper-, mid-, and lower-canopy positions) and with tree size. Damage types attributable to herbivores active on leaf surfaces, including leaf skeletonizers and leaf cutters (both principally Lepidoptera), and leaf stippling inducers (Hemiptera) showed decreases with tree size, and with increasing height in the canopy. In contrast, leaf damage from the most abundant gall-forming arthropod in the system, the eriophyid mite Vasates aceriscrumena, increased markedly with tree size. 4. The results indicate that herbivory patterns vary with both canopy stratum and with tree size in sugar maple, and that the relative strength of vertical stratification and tree ontogeny effects are similar in magnitude. The predominant patterns are of a decrease in herbivory with increasing height in the canopy and with tree size, but certain galling arthropods exhibit the reverse trends. [source]

    Structure and vertical stratification of plant galler,parasitoid food webs in two tropical forests

    Abstract 1.,Networks of feeding interactions among insect herbivores and natural enemies such as parasitoids, describe the structure of these assemblages and may be critically linked to their dynamics and stability. The present paper describes the first quantitative study of parasitoids associated with gall-inducing insect assemblages in the tropics, and the first investigation of vertical stratification in quantitative food web structure. 2.,Galls and associated parasitoids were sampled in the understorey and canopy of Parque Natural Metropolitano in the Pacific forest, and in the understorey of San Lorenzo Protected Area in the Caribbean forest of Panama. Quantitative host,parasitoid food webs were constructed for each assemblage, including 34 gall maker species, 28 host plants, and 57 parasitoid species. 3.,Species richness was higher in the understorey for parasitoids, but higher in the canopy for gall makers. There was an almost complete turnover in gall maker and parasitoid assemblage composition between strata, and the few parasitoid species shared between strata were associated with the same host species. 4.,Most parasitoid species were host specific, and the few polyphagous parasitoid species were restricted to the understorey. 5.,These results suggest that, in contrast to better-studied leaf miner,parasitoid assemblages, the influence of apparent competition mediated by shared parasitoids as a structuring factor is likely to be minimal in the understorey and practically absent in the canopy, increasing the potential for coexistence of parasitoid species. 6.,High parasitoid beta diversity and high host specificity, particularly in the poorly studied canopy, indicate that tropical forests may be even more species rich in hymenopteran parasitoids than previously suspected. [source]

    Assessing the habitat quality of oil mallees and other planted farmland vegetation with reference to natural woodland

    F. Patrick Smith
    Summary, Much of the tree and shrub planting that has been conducted on farms in Western Australia over the past three decades has not been done with the specific intention of creating habitat or conserving biodiversity, particularly commercially oriented monocultures like oil mallee plantings. However, such plantings may nonetheless provide some habitat resources for native plants and animals. This study assessed the habitat quality of farm plantings (most of which were not planted with the primary intention of biodiversity conservation) at 72 sites across a study region in the central wheatbelt of Western Australia. Widely accepted habitat metrics were used to compare the habitat resources provided by planted farmland vegetation with those provided by remnant woodland on the same farms. The impact of adjacency of plantings to woodland and, in the case of oil mallees, the planting configuration on predicted habitat quality is assessed. Condition Benchmarks for five local native vegetation communities are proposed. Farmland plantings achieved an average Vegetation Condition Score (VCS) of 46 out of a possible 100, while remnant woodland on the same farms scored an average 72. The average scores for farm plantings ranged from 38,59 depending on which of five natural vegetation communities was used as its benchmark, but farm plantings always scored significantly less than remnant woodland (P < 0.001). Mixed species plantings on average were rated more highly than oil mallees (e.g. scores of 42 and 36 respectively using the Wandoo benchmark) and adjacency to remnant woodland improved the score for mixed plantings, but not for oil mallees. Configuration of oil mallees as blocks or belts (i.e. as an alley farming system) had no impact on the VCS. Planted farmland vegetation fell short of remnant woodland in both floristic richness (51 planted native species in total compared with a total of more than 166 naturally occurring plant species in woodland) and structural diversity (with height, multiple vegetation strata, tree hollows and woody debris all absent in the relatively young 7,15-year-old farm plantings). Nonetheless farmland plantings do have measurable habitat values and recruitment and apparent recolonization of plantings with native plant species was observed. Habitat values might be expected to increase as the plantings age. The VCS approach, including the application of locally relevant Benchmarks is considered to be valuable for assessing potential habitat quality in farmland vegetation, particularly as a tool for engaging landholders and natural resource management practitioners. [source]


    ECONOMIC AFFAIRS, Issue 2 2009
    Saad Azmat
    This paper uses Douglass North's theories of institutional economics to explain progress in Muslim Spain. It argues that it was efficient economic institutions in the guise of a free-market economy where the property rights of different strata of society were well protected, which ensured lasting prosperity. This paper postulates that while a population explosion could have been responsible for the initial growth in Spain, it was an efficient formal,informal institutional matrix that ensured a high level of long-term growth. [source]

    Effects of Predation Threat on the Structure and Benefits from Vacancy Chains in the Hermit Crab Pagurus bernhardus

    ETHOLOGY, Issue 11 2009
    Mark Briffa
    Vacancy chains occur when individuals occupy discrete re-useable resource units, which once abandoned by the current owner can then be occupied by a new owner. In order to enter the newly vacated resource the new owner must first vacate its current resource unit, such that a vacancy chain consists of a series of linked moves between resource units of different value, equivalent to different ,strata' in the chain. Vacancy chains may represent an important route by which resources are distributed through populations. Indeed, the arrival of a new resource has the potential to initiate a series of moves propagating beyond the individual that encounters the new resource unit. Thus, the chain participants as a whole may experience ,aggregate benefits' from the arrival of the new resource unit. The extent of these benefits, however, may not necessarily be evenly distributed between all chain participants; some individuals could receive greater than average benefits by moving through more than one stratum (,skipping') and some individuals could experience a reduction in resource value by moving to a resource unit of lower quality than that occupied initially (a ,backward move'). Such moves represent deviations from the ,ideal' vacancy chains assumed by theory. Here we analyse the aggregate benefits and benefits to individuals participating in vacancy chains of empty gastropod shells in the hermit crab Pagurus bernhardus. We also investigate the effect of predation risk on these two levels of benefits and on chain structure. Adding a new shell at the top of the chain causes an overall increase in shell quality after 24 h but the distribution of benefits between strata in the chain varies with the presence and absence of the predator cue. Although there was significant concordance between chain structure in the presence and absence of the predator cue, the structure was significantly different from an ideal vacancy chain in the absence but not the presence of the predator cue. [source]

    Boredom, "Trouble," and the Realities of Postcolonial Reservation Life

    ETHOS, Issue 1 2003
    Assistant professor Lori L. Jervis
    Perhaps because of its reputation as an inconsequential emotion, the significance of boredom in human social life has often been minimized if not ignored. Boredom has been theoretically linked to modernity, affluence, and the growing problem of filling "leisure time. "It has also been attributed to the expansion of individualism with its heightened expectations of personal gratification. Whether a reaction to the sensation ofunderstimulation or "overload," boredom appears to be, ultimately, a problem of meaning. In this article, we consider the applicability of these notions to the contemporary American Indian reservation context, examining discourse about boredom as expressed in interviews with members of a northern plains tribe. Of special interest is how boredom figures into the phenomenon of "trouble" (e.g., alcohol and drug abuse, violence, and illegal activities). Although boredom is certainly familiar to various strata of contemporary U.S. society,and arguably part of what it means to be human,we propose that the realities of postcolonial reservation life provide an especially fertile and undertheorized breeding ground for this condition, and our examination of the relationship between boredom and trouble suggests that boredom's implications for both individual subjectivity and group sociality are far from trivial. [source]

    Experimental and numerical studies on dynamic crack growth in layered slate rock under wedge impact loads: part II , non-plane strain problem

    M. R. ALAM
    ABSTRACT Dynamic crack propagation in non-plane strain (or 3D) slate blocks under wedge impact loads was investigated numerically in this part of the paper. A parabolic-shaped crack trajectory was taken into consideration to model the crack propagation in slate blocks for analyzing the impact splitting of layered slate rock. Major and minor axes of the parabola were determined from the condition of equal mode I stress intensity factors (SIFs) along the crack front. Mode I SIFs were determined for experimental breaking loads for each increment of crack growth in a manner similar to that mentioned in part I of this paper. These values were compared with the plane strain material fracture toughness value obtained from experimental studies and very good agreement was obtained between them, for the case of actual load applied on the specimen. Numerical analysis of a field problem, i.e., separation of a large-sized slate slab from the rock strata in a slate quarry using wedge impacting, was also carried out in this paper. It can be observed that a large magnitude of load is required to break large-sized slate blocks; but this load is applied through a number of smaller load-capacity actuators-in-parallel, requiring large power capacity for the hydraulic pumps. However, this required power could be reduced considerably if the load applied on the line of hydraulic actuators is cascaded across the (line of) actuators (starting from centrally placed actuators) with a small time delay (equal to the initial crushing time in slate rock). [source]

    Fossil fruits of Salsola L. s.l. and Halanthium K.Koch (Chenopodiaceae) from Lower Pleistocene lacustrine sediments in Armenia,

    FEDDES REPERTORIUM, Issue 3-4 2008
    Janna Akopian Dr.
    For the first time imprints of fossil fruits of Salsola L. s.l. and Halanthium K.Koch (Chenopodiaceae, Salsoloideae,) are reported from the territory of Armenia, the latter being the first fossil record of the Southwest Asian genus worldwide. They were collected from fluvio-lacustrine diatomite layers of the Lower Pleistocene (Sisian series) in the upper-middle Vorotan river valley recently dated at 1.4,0.935 my (Early Pleistocene). The fossils are described, figured and compared with recent relatives. Due to poor preservation, the identity of the Salsola fruit cannot be specified but the similar genus Kochia can be excluded. The Halanthium fruit seems to differ from those of extant species. Both are also discussed in the context of the very poor fossil Salsoloideae record and of the actual and lower Pleistocene vegetation and environment. The findings of truly semidesert species underline the presence of open landscapes and extremely semiarid to arid conditions. However, stratigraphically more refined analyses are needed to draw conclusions about the former vegetation and the duration of arid periods because most macrofossils reported from the same strata indicate semiarid and even humid environments. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) Fossile Früchte von Salsola L. und Halanthium K.Koch (Chenopodiaceae) aus unterpleistozänen lakustrischen Sedimenten in Armenien Erstmals wird über Funde fossiler Früchte der Gattungen Salsola L. s.l. und Halanthium K.Koch (Chenopodiaceae, Salsoloideae) aus Armenien berichtet. Für die letztere Gattung handelt es sich weltweit um einen Erstfund. Die nur mäßig guten Abdrucke stammen aus fluvio-lakustrischen Diatomiten der Sisian Serie vom oberen Vorotan-Tal, die nach neuesten Datierungen 1,4,0,935 Millionen Jahre alt sind und damit in das Unterpleistozän gehören. Die Fossilien werden beschrieben, abgebildet und mit den nächsten rezenten Verwandten verglichen. Während bei der Salsola -Frucht wegen Beschädigungen vor der Einbettung keine Artbestimmung möglich ist, die Zugehörigkeit zu Kochia aber ausgeschlossen werden kann, stimmt die besser erhaltene Halanthium- Frucht mit keiner rezenten Art überein. Beide Arten werden im Zusammenhang mit dem bisher äußerst spärlichen Fossilbefund und im Hinblick auf ihren möglichen ökologischen und vegetationskundlichen Indikatorwert diskutiert. Die Nachweise dieser Halbwüstenpflanzen sprechen für eine waldfreie Umgebung und ein extremsemiarides oder arides Klima zur Zeit der Einbettung. Die gleichen Schichten enthalten aber vor allem Makrofossilien mesophytischer Gehölze, die an ein semiarides bis humides Klima gebunden sind. Weitergehende Rückschlüsse sind erst dann möglich, wenn eine feinstratigraphische Analyse vorliegt, durch die größere klimatische Fluktuationen nachgewiesen werden könnten. [source]

    Effects of catch and release angling on Atlantic salmon, Salmo salar L., of the Conne River, Newfoundland

    The effects of catch and release angling on survival of Atlantic salmon, Salmo salar L., at Conne River, Newfoundland, were investigated by retaining angled (n=49; experimental group) and trap-caught (n=20; control group) fish in holding cages for up to 40 days. Samples were obtained from 8 June to 4 July, 2000, and partitioned among four water temperature strata. Apart from not being angled, control fish were handled, tagged, and transferred to holding cages in a manner similar to angled salmon. Water temperatures and discharge were monitored throughout the duration of the study. Overall, 8.2% of salmon caught and released died, but 12% died among salmon angled in water temperatures , 17.9 °C. No control fish died. There were no significant differences in time associated with angling, exposure to air, tagging, transfer to holding cages, nor total handling time between salmon that survived vs. those that died. Results of the study should encourage managers to continue to use catch and release as a viable tool in the management of Atlantic salmon stocks. [source]

    Hypoxia-based habitat compression of tropical pelagic fishes

    Abstract Large areas of cold hypoxic water occur as distinct strata in the eastern tropical Pacific (ETP) and Atlantic oceans as a result of high productivity initiated by intense nutrient upwelling. We show that this stratum restricts the depth distribution of tropical pelagic marlins, sailfish, and tunas by compressing the acceptable physical habitat into a narrow surface layer. This layer extends downward to a variable boundary defined by a shallow thermocline, often at 25 m, above a barrier of cold hypoxic water. The depth distributions of marlin and sailfish monitored with electronic tags and average dissolved oxygen (DO) and temperature profiles show that this cold hypoxic environment constitutes a lower habitat boundary in the ETP, but not in the western North Atlantic (WNA), where DO is not limiting. Eastern Pacific and eastern Atlantic sailfish are larger than those in WNA, where the hypoxic zone is much deeper or absent. Larger sizes may reflect enhanced foraging opportunities afforded by the closer proximity of predator and prey in compressed habitat, as well as by the higher productivity. The shallow band of acceptable habitat restricts these fishes to a very narrow surface layer and makes them more vulnerable to over-exploitation by surface gears. Predictably, the long-term landings of tropical pelagic tunas from areas of habitat compression have been far greater than in surrounding areas. Many tropical pelagic species in the Atlantic Ocean are currently either fully exploited or overfished and their future status could be quite sensitive to increased fishing pressures, particularly in areas of habitat compression. [source]

    In vivo morphological and antifungal study of the activity of a bergamot essential oil by-product

    Francesco Carmelo Pizzimenti
    Abstract The in vivo antifungal activity of a bergamot processing by-product, named ,Peratoner', was evaluated through applications to male Wistar rats' back skin, previously infected with Candida albicans. Following the treatment, samples were taken to evaluate the fungal load and punch biopsies were carried out for morphological studies. In infected rats without Peratoner treatment, skin detachment with infiltrating cells was observed. The presence of C. albicans cells was evident on the surface strata of the epidermis, which was detached from the basal cells. After 24 h, in the case of Peratoner treatment, the epidermic strata were still few in number, while the infiltrating elements in the dermis were fewer in quantity and a small cluster of C. albicans cells, above the stratum corneous, was also visible. After 48 h of treatment, the skin revealed proliferation of the strata, while in the dermis infiltrating cells were still evident. Following this period and up to a week after treatment, a full recovery of the cutaneous structure was observed. Copyright © 2006 John Wiley & Sons, Ltd. [source]

    How internal waves influence the vertical distribution of zooplankton

    FRESHWATER BIOLOGY, Issue 1 2007
    Summary 1. We present data with a high spatio-temporal resolution from a 72-h field survey in Bautzen Reservoir (Saxony, Germany). The aims of this survey were to observe hydrophysical processes during a period of unstable stratification in spring and investigate the effect of wind-induced internal waves on the vertical distribution of zooplankton. 2. Wind velocities up to 10 m s,1 caused a strong downwelling event of warm water at the sampling site and led to the generation of internal waves with an amplitude of 4 m. 3. The zooplankton community, which was dominated by Daphnia galeata, inhabited epilimnetic waters. Downwelling enlarged the thickness of the epilimnetic layer and, hence, led to high zooplankton abundances down to relatively deep water strata indicating lateral transport of zooplankton. As a consequence, area-specific zooplankton abundances increased considerably (max. fourfold) during downwelling. 4. We conclude that classical limnological field sampling, such as for monitoring purposes, can lead to severely biased estimates of zooplankton abundance due to the interfering effects of hydrophysical processes like internal waves. 5. Backscattering strengths measured by a simultaneously deployed Acoustic Doppler Current Profiler (600 kHz) were found to be correlated with estimated zooplankton abundances based on plankton samples. [source]