New trepostomate bryozoans from the Upper Ordovician of Morocco and the temperature influence on zooid size

2015 ◽  
Vol 89 (3) ◽  
pp. 385-404 ◽  
Author(s):  
Andrea Jiménez-Sánchez ◽  
Enrique Villas ◽  
Enmanuelle Vennin
Keyword(s):  
Wave Activity ◽  
Limiting Factor ◽  
Primary Control ◽  
Congeneric Species ◽  
Ambient Water ◽  
Temperature Influence ◽  
Upper Ordovician ◽  
Low Latitudes ◽  
Intermediate Units ◽  
Size Increment

AbstractNew Upper Ordovician trepostomate bryozoans from the eastern Anti-Atlas of Morocco have been identified. They have been collected from the lower and intermediate units of the Khabt-el-Hajar Formation, late Katian in age, representing, respectively, bryozoan-pelmatozoan meadows with siliciclastic input, degraded by wave activity in a mid-ramp setting, and outer-ramp environments with marly substrates. Ten species of the generaCyphotrypa,Calloporella,Diplotrypa,Parvohallopora,Dekayia, andAostiporaare described. Of them, three species are new:Cyphotrypa regularisJiménez-Sánchez,Parvohallopora cystataJiménez-Sánchez, andAostipora elongataJiménez-Sánchez. Univariate statistical analyses of the sub-polar Moroccan species, in addition to other congeneric species of high, middle, and low latitudes, corroborate that for the trepostomate bryozoan the temperature of the ambient water was a primary control on zooecium size variations. Nevertheless, other environmental factors, besides temperature, must have also influenced significantly the zooid size, at least in low latitudes. Our data also give further support for considering the zooecium wall thickness as a limiting factor for the zooid size increment with latitude in the trepostomates.

scholarly journals Influence of the cloud-level neutral layer on the vertical propagation of topographically generated gravity waves on Venus

2019 ◽  
Vol 71 (1) ◽  
Author(s):  
Takeru Yamada ◽  
Takeshi Imamura ◽  
Tetsuya Fukuhara ◽  
Makoto Taguchi
Keyword(s):  
Layer Thickness ◽  
Gravity Wave ◽  
Local Time ◽  
Gravity Waves ◽  
Analytical Approach ◽  
Wave Activity ◽  
Neutral Layer ◽  
Low Latitudes ◽  
Vertical Propagation ◽  
The Waves

AbstractThe reason for stationary gravity waves at Venus’ cloud top to appear mostly at low latitudes in the afternoon is not understood. Since a neutral layer exists in the lower part of the cloud layer, the waves should be affected by the neutral layer before reaching the cloud top. To what extent gravity waves can propagate vertically through the neutral layer has been unclear. To examine the possibility that the variation of the neutral layer thickness is responsible for the dependence of the gravity wave activity on the latitude and the local time, we investigated the sensitivity of the vertical propagation of gravity waves on the neutral layer thickness using a numerical model. The results showed that stationary gravity waves with zonal wavelengths longer than 1000 km can propagate to the cloud-top level without notable attenuation in the neutral layer with realistic thicknesses of 5–15 km. This suggests that the observed latitudinal and local time variation of the gravity wave activity should be attributed to processes below the cloud. An analytical approach also showed that gravity waves with horizontal wavelengths shorter than tens of kilometers would be strongly attenuated in the neutral layer; such waves should originate in the altitude region above the neutral layer.

Katian (Late Ordovician) conodonts on the northwestern margin of the North China Craton

2021 ◽  
pp. 1-22
Author(s):  
Zhihua Yang ◽  
Xiuchun Jing ◽  
Hongrui Zhou ◽  
Xunlian Wang ◽  
Hui Ren ◽  
...  
Keyword(s):  
North China Craton ◽  
North China ◽  
Late Ordovician ◽  
Carbonate Platforms ◽  
Upper Ordovician ◽  
The North ◽  
Low Latitudes ◽  
Northwestern Margin ◽  
Conodont Fauna ◽  
Stratigraphic Range

Abstract Upper Ordovician strata exposed from the Baiyanhuashan section is the most representative Late Ordovician unit in the northwestern margin of the North China Craton (NCC). In total, 1,215 conodont specimens were obtained from 24 samples through the Wulanhudong and Baiyanhuashan formations at the Baiyanhuashan section. Thirty-six species belonging to 17 genera, including Tasmanognathus coronatus new species, are present. Based on this material, three conodont biozones—the Belodina confluens Biozone, the Yaoxianognathus neimengguensis Biozone, and the Yaoxianognathus yaoxianensis Biozone—have been documented, suggesting that the Baiyanhuashan conodont fauna has a stratigraphic range spanning the early to middle Katian. The Baiyanhuashan conodont fauna includes species both endemic to North China and widespread in tropical zones, allowing a reassessment of the previous correlations of the Katian conodont zonal successions proposed for North China with those established for shallow-water carbonate platforms at low latitudes. UUID: http://zoobank.org/7cedbd4a-4f7a-4be6-912f-a27fd041b586

Trepostomate bryozoans from the upper Katian (Upper Ordovician) of Morocco: gigantism in high latitude Gondwana platforms

2015 ◽  
Vol 89 (2) ◽  
pp. 195-221 ◽  
Author(s):  
Andrea Jiménez-Sánchez ◽  
Enmanuelle Vennin ◽  
Enrique Villas
Keyword(s):  
Depositional Environments ◽  
Congeneric Species ◽  
Upper Ordovician ◽  
Supporting Surface ◽  
Great Stability ◽  
Fine Grained ◽  
Intermediate Unit ◽  
Alternative Proposal ◽  
The One ◽  
Giant Size

AbstractA study of the Upper Ordovician trepostomate bryozoans belonging to the families Amplexoporidae and Monticuliporidae, from the eastern Anti-Atlas of Morocco, is presented here. They occur in the marly to fine-grained limestone, intermediate unit of the Khabt-el-Hajar Formation, late Katian in age, representing outer-ramp depositional environments. They inhabited the highest paleolatitude known for a bryozoan fauna during the Ordovician, estimated at more than 65–70ºS. A total of 11 species of the generaAnaphragma,Atactoporella,Homotrypa,Monotrypa,Monticulipora, andPrasoporaare described. Three species are already known from the equatorial-tropical paleocontinents of Baltica, Laurentia, and Siberia:Anaphragma mirabile,Monotrypa jewensis, andPrasopora falesi. Four new taxa are described:Anaphragma undulata,Atactoporella moroccoensis,Monticulipora globulata, andMonticulipora irregularis.The two species ofAnaphragmaand the one ofAtactoporelladisplay significantly larger zoarial sizes than congeneric species, representing gigantism among bryozoans. Polar gigantism is rejected for the two species ofAnaphragmaas is gigantism related to photosynthetic endosymbionts. An alternative proposal for their giant size is their long zoarial life span due to their well-balanced, robust branching form, with a relatively wide basal supporting surface, adapted to unconsolidated substrates in environments below wave base. Their great stability in outer-ramp environments, with infrequent storms, would allow the zoaria to grow for an extended time and reach large sizes before being overturned and buried.Atactoporella moroccoensis, has both zoaria and zooecia gigantic, suggesting a hypothesis of polar gigantism.

scholarly journals Improving Seasonal Forecasting in the Low Latitudes

2006 ◽  
Vol 134 (7) ◽  
pp. 1859-1879 ◽  
Author(s):  
Heiko Paeth ◽  
Robin Girmes ◽  
Gunter Menz ◽  
Andreas Hense
Keyword(s):  
Statistical Model ◽  
Climate Models ◽  
Climate Model ◽  
Southern Oscillation ◽  
Limiting Factor ◽  
Model Output ◽  
Climate Anomalies ◽  
Skill Scores ◽  
Simulated Precipitation ◽  
Low Latitudes

Abstract Seasonal forecast of climate anomalies holds the prospect of improving agricultural planning and food security, particularly in the low latitudes where rainfall represents a limiting factor in agrarian production. Present-day methods are usually based on simulated precipitation as a predictor for the forthcoming rainy season. However, climate models often have low skill in predicting rainfall due to the uncertainties in physical parameterization. Here, the authors present an extended statistical model approach using three-dimensional dynamical variables from climate model experiments like temperature, geopotential height, wind components, and atmospheric moisture. A cross-validated multiple regression analysis is applied in order to fit the model output to observed seasonal precipitation during the twentieth century. This model output statistics (MOS) system is evaluated in various regions of the globe with potential predictability and compared with the conventional superensemble approach, which refers to the same variable for predictand and predictors. It is found that predictability is highest in the low latitudes. Given the remarkable spatial teleconnections in the Tropics, a large number of dynamical predictors can be determined for each region of interest. To avoid overfitting in the regression model an EOF analysis is carried out, combining predictors that are largely in-phase with each other. In addition, a bootstrap approach is used to evaluate the predictability of the statistical model. As measured by different skill scores, the MOS system reaches much higher explained variance than the superensemble approach in all considered regions. In some cases, predictability only occurs if dynamical predictor variables are taken into account, whereas the superensemble forecast fails. The best results are found for the tropical Pacific sector, the Nordeste region, Central America, and tropical Africa, amounting to 50% to 80% of total interannual variability. In general, the statistical relationships between the leading predictors and the predictand are physically interpretable and basically highlight the interplay between regional climate anomalies and the omnipresent role of El Niño–Southern Oscillation in the tropical climate system.

Role of procollagen mRNA levels in controlling the rate of procollagen synthesis

1983 ◽  
Vol 3 (2) ◽  
pp. 241-249
Author(s):  
L B Rowe ◽  
R I Schwarz
Keyword(s):  
Cell Density ◽  
High Cell Density ◽  
Control Point ◽  
Relative Increase ◽  
Limiting Factor ◽  
Mrna Levels ◽  
Primary Control ◽  
High Cell ◽  
Mrna Induction ◽  
Tendon Cells

Two factors must be present for primary avian tendon cells to commit 50% of their total protein production to procollagen: ascorbate and high cell density. Scorbutic primary avian tendon cells at high cell density (greater than 4 X 10(4) cells per cm2) responded to the addition of ascorbate by a sixfold increase in the rate of procollagen synthesis. The kinetics were biphasic, showing a slow increase during the first 12 h followed by a more rapid rise to a maximum after 36 to 48 h. In contrast, after ascorbate addition, the level of accumulated cytoplasmic procollagen mRNA (alpha 2) showed a 12-h lag followed by a slow linear increase requiring 60 to 72 h to reach full induction. At all stages of the induction process, the relative increase in the rate of procollagen synthesis over the uninduced state exceeded the relative increase in the accumulation of procollagen mRNA. A similar delay in mRNA induction was observed when the cells were grown in an ascorbate-containing medium but the cell density was allowed to increase. In all cases, the rate of procollagen synthesis peaked approximately 24 h before the maximum accumulation of procollagen mRNA. The kinetics for the increase in procollagen synthesis are not, therefore, in agreement with the simple model that mRNA levels are the rate-limiting factor in the collagen pathway. We propose that the primary control point is at a later step. Further support for this idea comes from inhibitor studies, using alpha, alpha'-dipyridyl to block ascorbate action. In the presence of 0.3 mM alpha, alpha'-dipyridyl there was a specific two- to threefold decrease in procollagen production after 4 h, but this was unaccompanied by a drop in procollagen mRNA levels. Therefore, inhibitor studies give further support to the idea that primary action of ascorbate is to release a post-translational block.

Noise Attenuation in a Secondary Controlled Electro-Hydraulic Actuator Using an Extended Kalman Filter

2021 ◽  
Author(s):  
Niklas Simonsen ◽  
Emil Munk Sørensen ◽  
Mikkel van Binsbergen-Galán ◽  
Stine Flindt Hornemann Kleine ◽  
Mikkel Hvid Nielsen ◽  
...  
Keyword(s):  
Kalman Filter ◽  
Extended Kalman Filter ◽  
Speed Control ◽  
Limiting Factor ◽  
Primary Control ◽  
Variable Speed ◽  
Hydraulic Actuator ◽  
Secondary Control ◽  
Control Approach ◽  
The Impact

Abstract Conventionally, variable-speed electro-hydraulic linear actuators utilize the speed control loops of electric machines and associated drives to control the pump flows, thereby realizing primary control functions. An alternative control approach is secondary control, which realizes a pressure coupling between the motor/pump and cylinder via the electromagnetic motor torque, with a flow reaction. Secondary controls in such drives has theoretically been shown to enable significantly higher control band-widths compared to primary control approaches. The theoretical bandwidth improvement is possible as the secondary control approach utilizes the faster dynamics of the electric machine, whereas the primary control approach revolves about the slower hydraulic dynamics present in the speed control loop. This paper considers the design and implementation of a secondary control function in a variable-speed electro-hydraulic actuator test bench, in order to validate the properties of such controls. Initial results show that the proposed secondary control approach is highly sensitive to measurement noise, which proves to be a limiting factor for the achievable control bandwidth, if smooth operation of the system is to be maintained. To attenuate the noise impact an extended Kalman filter is proposed in conjunction with the secondary control approach. Results demonstrate that the inclusion of the extended Kalman filter significantly reduces the impact of signal noise on the internal drive states, thereby enabling increased bandwidth and expanding the application range for this control method.

Sensitivity of the Stratospheric Circulation to the Latitude of Thermal Surface Forcing*

2011 ◽  
Vol 24 (20) ◽  
pp. 5397-5415 ◽  
Author(s):  
Barbara Winter ◽  
Michel S. Bourqui
Keyword(s):  
Surface Temperature ◽  
Northern Hemisphere ◽  
Ozone Concentration ◽  
Planetary Wave ◽  
Wave Generation ◽  
Wave Activity ◽  
High Latitudes ◽  
Thermal Forcing ◽  
Eddy Heat Flux ◽  
Low Latitudes

Abstract Using the chemistry climate model Intermediate General Circulation Model–Fast Stratospheric Ozone Chemistry (IGCM-FASTOC), the authors analyze the response in the Northern Hemisphere winter stratosphere to idealized thermal forcing imposed at the surface. The forcing is a 2-K temperature anomaly added to the control surface temperature at all grid points within a latitudinal window of 10° or 30°. The bandwise forcing is applied systematically throughout all latitudes of the Northern Hemisphere. Thermal forcing applied anywhere equatorward of 20°N, or continuously from the equator to 30°N, increases planetary-wave generation in the troposphere and enhances the flux of wave activity propagating vertically into the stratosphere. Consequently, a greater flux of wave activity breaks in the polar vortex, increasing the Brewer–Dobson circulation and leading to a warm anomaly in the polar stratosphere. Ozone concentration increases at high latitudes and decreases at low latitudes. Thermal surface forcing imposed between 30° and 60°N has the reverse effect—decreased planetary-wave generation in the lower troposphere and reduced vertically propagating wave flux entering the stratosphere—and leads to a stronger and colder vortex. Thermal forcing applied poleward of 60°N has little effect on the tropospheric mean state but nonetheless decreases the planetary-scale eddy heat flux from the surface to the tropopause, resulting in a sufficient decrease of the vertical flux of wave activity for the vortex to be anomalously strong and cold. When surface forcing is imposed only poleward of 30°N, ozone concentration decreases at high latitudes but is not affected at low latitudes. Combining the forcing in an equatorial and an extratropical band leads to a response similar to that of the equatorial forcing, demonstrating that the subtropical surface temperature changes determine the sign of the surface-driven response in the vortex.

scholarly journals Role of procollagen mRNA levels in controlling the rate of procollagen synthesis.

1983 ◽  
Vol 3 (2) ◽  
pp. 241-249 ◽  
Author(s):  
L B Rowe ◽  
R I Schwarz
Keyword(s):  
Cell Density ◽  
High Cell Density ◽  
Control Point ◽  
Relative Increase ◽  
Limiting Factor ◽  
Mrna Levels ◽  
Primary Control ◽  
High Cell ◽  
Mrna Induction ◽  
Tendon Cells

Two factors must be present for primary avian tendon cells to commit 50% of their total protein production to procollagen: ascorbate and high cell density. Scorbutic primary avian tendon cells at high cell density (greater than 4 X 10(4) cells per cm2) responded to the addition of ascorbate by a sixfold increase in the rate of procollagen synthesis. The kinetics were biphasic, showing a slow increase during the first 12 h followed by a more rapid rise to a maximum after 36 to 48 h. In contrast, after ascorbate addition, the level of accumulated cytoplasmic procollagen mRNA (alpha 2) showed a 12-h lag followed by a slow linear increase requiring 60 to 72 h to reach full induction. At all stages of the induction process, the relative increase in the rate of procollagen synthesis over the uninduced state exceeded the relative increase in the accumulation of procollagen mRNA. A similar delay in mRNA induction was observed when the cells were grown in an ascorbate-containing medium but the cell density was allowed to increase. In all cases, the rate of procollagen synthesis peaked approximately 24 h before the maximum accumulation of procollagen mRNA. The kinetics for the increase in procollagen synthesis are not, therefore, in agreement with the simple model that mRNA levels are the rate-limiting factor in the collagen pathway. We propose that the primary control point is at a later step. Further support for this idea comes from inhibitor studies, using alpha, alpha'-dipyridyl to block ascorbate action. In the presence of 0.3 mM alpha, alpha'-dipyridyl there was a specific two- to threefold decrease in procollagen production after 4 h, but this was unaccompanied by a drop in procollagen mRNA levels. Therefore, inhibitor studies give further support to the idea that primary action of ascorbate is to release a post-translational block.

scholarly journals Rayleigh lidar observation of a warm stratopause over a tropical site, Gadanki (13.5° N; 79.2° E)

2004 ◽  
Vol 4 (7) ◽  
pp. 1989-1996 ◽  
Author(s):  
V. Sivakumar ◽  
B. Morel ◽  
H. Bencherif ◽  
J. L. Baray ◽  
S. Baldy ◽  
...  
Keyword(s):  
Planetary Wave ◽  
Wave Activity ◽  
Weather Forecasts ◽  
Lidar Observation ◽  
Mean Temperature ◽  
Low Latitudes ◽  
Show Evidence ◽  
P Flux ◽  
Rayleigh Lidar ◽  
Environmental Prediction

Abstract. The first Rayleigh lidar observation of a stratopause warming over a tropical site, Gadanki (13.5° N; 79.2° E), is presented in this paper. The warming event was observed on 22-23 February 2001, and found to occur in the stratopause region (~45km). The magnitude of the warming was found to be ~18K with respect to the winter-mean temperature profile derived from the lidar data collected over March 1998 to July 2001. The event observed by the lidar has also been seen in data from the Halogen Occultation Experiment (HALOE) on board the UARS satellite. The zonal-mean temperature at 80° N and the zonal-mean zonal wind at 60° N from the National Centre for Environmental Prediction (NCEP) reanalysis and the European Centre for Medium-Range Weather Forecasts (ECMWF) analysis indicate that a major warming episode took place in the northern polar hemisphere a week before the day of the observation over Gadanki. Eliassen-Palm (E-P) flux calculations from ECMWF analysis show evidence of propagation of planetary-wave activity from high and mid- to low latitudes subsequent to the major warming episode over the pole. Our results support the view that the most likely source mechanism for the observed stratopause warming is the increase in planetary-wave activity.

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