scholarly journals High frequency variations of the Earth's orbital parameters and climate change

2002 ◽  
Vol 29 (18) ◽  
pp. 40-1-40-4 ◽  
Author(s):  
C. Bertrand ◽  
M. F. Loutre ◽  
A. Berger
Keyword(s):  
Climate Change ◽  
High Frequency ◽  
Orbital Parameters ◽  
Frequency Variations

Dynamic Stability of a Water Brake Dynamometer

1998 ◽  
Vol 120 (1) ◽  
pp. 89-96 ◽  
Author(s):  
R. A. Van den Braembussche ◽  
H. Malys
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Lumped Parameter Model ◽  
Stable Operation ◽  
Pressure Oscillations ◽  
Lumped Parameter ◽  
Flow Oscillations ◽  
Brake Dynamometer ◽  
Low Torque ◽  
Frequency Variations

A lumped parameter model to predict the high frequency pressure oscillations observed in a water brake dynamometer is presented. It explains how the measured low frequency variations of the torque are a consequence of the variation in amplitude of the high frequency flow oscillations. Based on this model, geometrical modifications were defined, aiming to suppress the oscillations while maintaining mechanical integrity of the device. An experimental verification demonstrated the validity of the model and showed a very stable operation of the modified dynamometer even at very low torque.

scholarly journals Frequency variations of gravity waves interacting with a time-varying tide

2013 ◽  
Vol 31 (10) ◽  
pp. 1731-1743 ◽  
Author(s):  
C. M. Huang ◽  
S. D. Zhang ◽  
F. Yi ◽  
K. M. Huang ◽  
Y. H. Zhang ◽  
...  
Keyword(s):  
Gravity Waves ◽  
High Frequency ◽  
Lower Atmosphere ◽  
Horizontal Wind ◽  
Frequency Variation ◽  
Time Varying ◽  
Transient Nature ◽  
Critical Layers ◽  
Favorable Conditions ◽  
Frequency Variations

Abstract. Using a nonlinear, 2-D time-dependent numerical model, we simulate the propagation of gravity waves (GWs) in a time-varying tide. Our simulations show that when a GW packet propagates in a time-varying tidal-wind environment, not only its intrinsic frequency but also its ground-based frequency would change significantly. The tidal horizontal-wind acceleration dominates the GW frequency variation. Positive (negative) accelerations induce frequency increases (decreases) with time. More interestingly, tidal-wind acceleration near the critical layers always causes the GW frequency to increase, which may partially explain the observations that high-frequency GW components are more dominant in the middle and upper atmosphere than in the lower atmosphere. The combination of the increased ground-based frequency of propagating GWs in a time-varying tidal-wind field and the transient nature of the critical layer induced by a time-varying tidal zonal wind creates favorable conditions for GWs to penetrate their originally expected critical layers. Consequently, GWs have an impact on the background atmosphere at much higher altitudes than expected, which indicates that the dynamical effects of tidal–GW interactions are more complicated than usually taken into account by GW parameterizations in global models.

scholarly journals High Frequency Variations of Earth Rotation Parameters from GPS and GLONASS Observations

Sensors ◽  
2015 ◽  
Vol 15 (2) ◽  
pp. 2944-2963 ◽  
Author(s):  
Erhu Wei ◽  
Shuanggen Jin ◽  
Lihua Wan ◽  
Wenjie Liu ◽  
Yali Yang ◽  
...  
Keyword(s):  
Earth Rotation ◽  
High Frequency ◽  
Earth Rotation Parameters ◽  
Rotation Parameters ◽  
Frequency Variations

scholarly journals Callus induction and regeneration of Alkanna orientalis var. Orientalis and A. sieheana

2019 ◽  
Vol 48 (3) ◽  
pp. 633-640 ◽  
Author(s):  
Cenney Yaman ◽  
Serkan Uranbey ◽  
Hussein Abdullah Ahmed ◽  
Sabahattin Özcan ◽  
Osman Tugay ◽  
...  
Keyword(s):  
Shoot Regeneration ◽  
Callus Induction ◽  
High Frequency ◽  
Stem Segment ◽  
Leaf Base ◽  
Cotyledonary Leaf ◽  
Frequency Variations ◽  
Alkanna Orientalis ◽  
Stem Segments

Callus induction and proliferation of Alkanna orientalis var. orientalis and Alkanna sieheana containing valuable alkannin/shikonin (A/S) derivates were investigated using leaf base and stem segment explants. Stem segments and cotyledonary leaf base of both species were cultured on Murashige and Skoog medium fortified with different concentrations of BAP, Kn, NAA, IAA and IBA for callus induction and shoot regeneration. High frequency reproducible, prolific and compact calli formation was obtained from the stem segments of both species in all media tested. The frequency variations of callus induction and shoot regeneration were discussed in terms of different species, plant growth regulators and explant resources. A. orientalis and A. sieheana may be considered to be alternative plants for the A/S production in vitro.

Latitudinal insolation gradients throughout the Holocene II – High frequency variations

2020 ◽  
Vol 66 (8) ◽  
pp. 1992-2000
Author(s):  
Rodolfo G. Cionco ◽  
Willie W.-H. Soon ◽  
Ana G. Elias ◽  
Nancy E. Quaranta
Keyword(s):  
High Frequency ◽  
The Holocene ◽  
Frequency Variations

scholarly journals 53 Piscium, an SPB Star with Activity

2002 ◽  
Vol 185 ◽  
pp. 236-237
Author(s):  
J.-M. Le Contel ◽  
P. Mathias ◽  
E. Chapellier ◽  
J.-C. Valtier
Keyword(s):  
High Resolution ◽  
False Alarm ◽  
High Frequency ◽  
Signal To Noise Ratio ◽  
High Signal ◽  
Correlation Technique ◽  
Signal To Noise ◽  
Spectroscopic Observations ◽  
Auto Correlation ◽  
Frequency Variations

The star 53 Psc (HD 3379, B2.5IV) has been observed as variable by several authors (Sareyan et al., 1979) with frequencies around 10 c d–1 and has been classified as a β Cephei star. Conversely, other authors (e.g. Percy, 1971) found it to be constant.New high resolution, high signal-to-noise ratio, Spectroscopic observations have been performed at the Observatoire de Haute-Provence in 1996 over 11 nights. The spectral domain covers around 200 Å and is centered on Hδ. Radial velocities were deduced from an auto-correlation technique with a scatter around 0.4kms−1.No high frequency variations are observed. Three frequencies have been detected with a false alarm detection above the 1 % level. A fourth one may be present but its amplitude is below this 1 % level. Results are displayed in Table 1.

scholarly journals Inter-seasonal investigation of coupled C & N greenhouse gas fluxes in pristine northern ecosystems

2021 ◽  
Author(s):  
Lona van Delden ◽  
Julia Boike ◽  
Eeva-Stiina Tuittila ◽  
Timo Vesala ◽  
Claire Treat
Keyword(s):  
Climate Change ◽  
Greenhouse Gas ◽  
High Frequency ◽  
Global Climate ◽  
Climatic Variability ◽  
Direct Interaction ◽  
Growing Season ◽  
Global Scale ◽  
Soil Matrix ◽  
Wetland Ecosystems

<p>Accurate annual greenhouse gas (GHG) budgets are the crucial baseline for global climate change forecast scenarios. On the other hand, the parameterization of these forecast models requires more than high-quality GHG datasets, but also the constant improvement of the representation of GHG producing and consuming processes. Extensive research efforts are therefore focusing on increasing our knowledge of the main GHG producing carbon (C) and nitrogen (N) cycles, though surprisingly not so much into their direct interaction. Most annual GHG budgets from pristine northern ecosystems are based on interpolated datasets from sampling campaigns mainly taken during the growing season. Within the ERC funded FluxWIN project, we are investigating how soil and pore water C & N interact and their biogeochemical GHG drivers change over seasons. Freeze-thaw events have previously been identified as significant GHG drivers by rapidly changing moisture and oxygen conditions in the soil matrix, but it remains unclear if and how C & N coupling contributes to these non-growing season emissions. Therefore, a fully automated static chamber system is monitoring GHG fluxes in high frequency at a boreal peatland ecosystem in Siikaneva, Finland. Nutrient stocks and biogeochemical dynamics within the soil matrix are compared to GHG soil-atmosphere exchange in the form of carbon dioxide (CO<sub>2</sub>), methane (CH<sub>4</sub>) and nitrous oxide (N<sub>2</sub>O) all year-round. We control for climatic variability and isolate differences in non-growing season emissions by using a moisture gradient from well-drained upland soils to adjacent wetland ecosystems. The use of these automated high-frequency GHG measurements in combination with year-round biogeochemical monitoring maximizes the likelihood of capturing episodic emissions and their drivers, which are particularly important during fall freeze and spring thaw periods. The gained information on the coupled C & N biogeochemical cycles will improve feedback estimates of climate change by including non-growing season processes in global-scale process-based models.</p>

scholarly journals Novel Techniques to Study Ancient Micro Amber from Tropical Beach Sand Reveal a Treasurehouse of Exceptionally Well Preserved Fossilized Microfungi

2017 ◽  
Author(s):  
Dabolkar Sujata ◽  
Kamat Nandkumar
Keyword(s):  
Climate Change ◽  
Sea Level ◽  
Microscopic Examination ◽  
High Frequency ◽  
Sampling Method ◽  
Size Range ◽  
Beach Sand ◽  
Morphometric Study ◽  
The World ◽  
Rich Information

AbstractSimple, novel techniques developed for separation and simultaneous direct morphometric study of Amber micro fragments (AMF) from tropical beach sand are reported yielding rich information on unidentified fossilized microfungi. Sieves of different mesh sizes were used to separate AMF from tropical beach sand. Fractions below 150 μm which proved rich in AMF were used for manual retrieval using stereomicroscope. A handprinted slide microarray having 4 X 12 squares used for microscopic examination of multiple AMF mounts revealed AMF having either rough or smooth surfaces and with or without microinclusions. The microinclusions could be morphologically attributed to fungi. The potential for systematic and comprehensive studies to retrieve and examine AMF at high frequency from tropical beach sand in the world and especially those which are threatened due to sea level rise due to climate change was demonstrated. The potential of retrievable AMF from tropical beach sand in microbiological, metagenomic studies and as biological proxies to reconstruct bygone biospheres has been highlighted.SummaryNovel techniques for retrieval of AMF and visualization using slide microarray are described. Sand samples from various locations from Goa were collected by pool sampling method. Microscopic study helped to reveal that fraction between 150 and below 53 μm contained microscopic fragments of Amber ranging from size of within the size range of 70 μm or below and with or without bio inclusions. AMF Specimens with microinclusions such as fungi were identified and studied using standard keys.

scholarly journals Long and short-term trends of stream hydrochemistry and high frequency surveys as indicators of the influence of climate change, agricultural practices and internal processes (Aurade agricultural catchment, SW France)

2020 ◽  
Vol 110 ◽  
pp. 105894 ◽  
Author(s):  
Vivien Ponnou-Delaffon ◽  
Anne Probst ◽  
Virginie Payre-Suc ◽  
Franck Granouillac ◽  
Sylvain Ferrant ◽  
...  
Keyword(s):  
Climate Change ◽  
High Frequency ◽  
Agricultural Practices ◽  
Short Term ◽  
Sw France

scholarly journals Are landscapes buffered to high-frequency climate change? A comparison of sediment fluxes and depositional volumes in the Corinth Rift, central Greece, over the past 130 k.y.

2018 ◽  
Vol 131 (3-4) ◽  
pp. 372-388 ◽  
Author(s):  
Stephen E. Watkins ◽  
Alexander C. Whittaker ◽  
Rebecca E. Bell ◽  
Lisa C. McNeill ◽  
Robert L. Gawthorpe ◽  
...  
Keyword(s):  
Climate Change ◽  
High Frequency ◽  
Sediment Fluxes ◽  
Central Greece ◽  
The Past
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