Biogenic Silica Record of the Lake Baikal Response to Climatic Forcing during the Brunhes

2001 ◽  
Vol 55 (2) ◽  
pp. 123-132 ◽  
Author(s):  
Alexander A. Prokopenko ◽  
Eugene B. Karabanov ◽  
Douglas F. Williams ◽  
Mikhail I. Kuzmin ◽  
Nicholas J. Shackleton ◽  
...  
Keyword(s):  
Lake Baikal ◽  
Biogenic Silica ◽  
Thermal Structure ◽  
High Amplitude ◽  
Oxygen Isotope Record ◽  
Isotope Record ◽  
Oxygen Isotopic ◽  
Brunhes Chron ◽  
Diatom Blooms ◽  
The Impact

AbstractThis work presents a detailed, orbitally tuned biogenic silica record of continental paleoclimate change during the Brunhes chron. The Brunhes/Matuyama boundary lies within the warm isotopic stage 19 in Baikal, and the boundaries between eight lithological cycles correspond to terminations in the marine oxygen isotope record. The high amplitude and resolution of climatically driven changes in BioSi content in Lake Baikal sediments permits tuning of almost every precessional cycle during the Brunhes and reveals the structure of interglacial stages. For example, the last three interglacial stages (MIS 5, 7, and 9) clearly consist of five substages (a, b, c, d, e) corresponding to precessional insolation peaks. Abrupt and intense regional glaciations in Siberia during substages 5d and 7d were driven by extreme insolation minima. During substage 9d cooling was more gradual in response to more moderate forcing. The impact of strong glaciation is also observed in the middle of stage 15, where full glacial conditions appear to have lasted for over 30,000 yr during substages 15d, 15c, and 15b. Marine oxygen isotopic stage 11 appears to be the warmest period during the Brunhes in the Lake Baikal record, with at least three substages.A new hypothesis is presented regarding the response of the Lake Baikal BioSi record to insolation forcing. Based on the mechanism controlling modern diatom blooms, biogenic silica production is hypothesized to be dependent on changes in the heat balance of the lake and consequently on changes in the thermal structure of the water column. This mechanism is also sensitive to short-term sub-Milankovich cooling events, such as the mid-Eemian cooling, the Montaigu event during substage 5c, and a cooling which appears to be analogous to the Montaigu event during substage 9c. The continuity of the Lake Baikal paleoclimate record, its sensitivity to orbital forcing, and its high resolution make it an excellent candidate for a new “paleoclimatic stratotype” section for continental Asia.

scholarly journals Hydrological instability during the Last Interglacial in central Asia: a new diatom oxygen isotope record from Lake Baikal

2013 ◽  
Vol 66 ◽  
pp. 45-54 ◽  
Author(s):  
Anson W. Mackay ◽  
George E.A. Swann ◽  
Nathalie Fagel ◽  
Susanne Fietz ◽  
Melanie J. Leng ◽  
...  
Keyword(s):  
Central Asia ◽  
Oxygen Isotope ◽  
Lake Baikal ◽  
Last Interglacial ◽  
Oxygen Isotope Record ◽  
Isotope Record

Stable carbon and oxygen isotope record in the Paleogene La Meseta Formation, Seymour Island, Antarctica

1992 ◽  
Vol 4 (4) ◽  
pp. 461-468 ◽  
Author(s):  
Andrzej Gaździcki ◽  
Michał Gruszczyński ◽  
Antoni Hoffman ◽  
Krzysztof Małkowski ◽  
Sergio A. Marenssi ◽  
...  
Keyword(s):  
Middle Part ◽  
Weddell Sea ◽  
Stable Carbon ◽  
Carbon Isotopic ◽  
Early Oligocene ◽  
Oxygen Isotope Record ◽  
Carbon And Oxygen Isotope ◽  
La Meseta Formation ◽  
Isotope Record ◽  
Oxygen Isotopic

Stable carbon and oxygen isotopic relations have been analysed in brachiopod, gastropod, and bivalve fossils from the La Meseta Formation (Eocene-?early Oligocene), Seymour (Marambio) Island, West Antarctica. The results indicate a shift in δ13C by 6 permil beginning in the middle part of the Unit II of the formation. This shift may imply a change from a largely stratified to a vigorously mixed ocean. Such an interpretation is corroborated by changes in the elemental proportions in the shell material. Alternatively, the carbon isotopic shift may be regarded as reflecting a change in the local depositional enviornment. Such an interpretation agrees with isotopic data from the Weddell Sea, which do not confirm the pattern observed in the La Meseta Formation. In any event, the oxygen isotopic curve does not decline parallel to the carbon curve and may thus imply a considerable climatic cooling event. This effect is so profound that it might be interpreted as evidence for glaciation, especially when taking into account the fact that this phenomenon coincides with the well-known cooling trend throughout the Eocene. If this interpretation is correct, the hypothesized Glaciation may possibly be correlated with the Polonez Glaciation, the largest Cenozoic glaciation known in the Antarctic Peninsula sector. Alternatively, it may be regarded as a local phenomenon, predating development of the icesheet.

scholarly journals A reassessment of late glacial - Holocene diatom oxygen isotope record from Lake Baikal using a geochemical mass-balance approach

2011 ◽  
Vol 26 (6) ◽  
pp. 627-634 ◽  
Author(s):  
Anson W. Mackay ◽  
George E. A. Swann ◽  
Tim S. Brewer ◽  
Melanie J. Leng ◽  
David W. Morley ◽  
...  
Keyword(s):  
Mass Balance ◽  
Oxygen Isotope ◽  
Lake Baikal ◽  
Late Glacial ◽  
Balance Approach ◽  
Oxygen Isotope Record ◽  
Isotope Record ◽  
Geochemical Mass Balance ◽  
Mass Balance Approach

Holocene climatic change in Swedish Lapland inferred from an oxygen-isotope record of lacustrine biogenic silica

The Holocene ◽  
2001 ◽  
Vol 11 (4) ◽  
pp. 447-454 ◽  
Author(s):  
Aldo Shemesh ◽  
Gunhild Rosqvist ◽  
Miri Rietti-Shati ◽  
Lena Rubensdotter ◽  
Christian Bigler ◽  
...  
Keyword(s):  
Oxygen Isotope ◽  
Climatic Change ◽  
Biogenic Silica ◽  
Oxygen Isotope Record ◽  
Isotope Record

INTEGRAL ASSESSMENT OF ANTHROPOGENIC PRESSURE ON WATER BODIES IN THE LAKE BAIKAL BASIN

2020 ◽  
Author(s):  
Irina Ulzetueva ◽  
Bair Gomboev ◽  
Daba Zhamyanov ◽  
Valentin Batomunkuev ◽  
Zorikto Banzaraktsaev
Keyword(s):  
Lake Baikal ◽  
River Basins ◽  
Anthropogenic Load ◽  
Anthropogenic Pressure ◽  
Linear Network ◽  
Baikal Basin ◽  
Discharge Water ◽  
Lake Baikal Basin ◽  
Integral Assessment ◽  
The Impact

The integrated assessment of the ecological state of the main rivers of the lake Baikal basin - Verkhnyaya Angara, Tyya, Barguzin, Selenga, Snezhnaya, Bolshaya Rechka, Khilok, Chikoy is based on the assessment of the variability of the basin system under the influence of two groups of indicators: 1) Direct (immediate) impact - the volume of water intake and wastewater discharge, water use and sequential water supply. Assessment of the impact on the state of the above-listed rivers basins from wastewater was performed using the algorithm proposed by A. Korolev et al. (2007). 2) Indirect (mediate) impact - indicators of areal and linear-network impacts on the catchment area. Based on the calculation of the integral anthropogenic pressure on the territory of the above-listed river basins, only the Selenga river experiences an “average” anthropogenic load. On the territory of most river basins, the anthropogenic load is “lowered” and “low”.

scholarly journals Modified Gold Nanoparticles for Efficient Delivery of Betulinic Acid to Cancer Cell Mitochondria

2021 ◽  
Vol 22 (10) ◽  
pp. 5072
Author(s):  
Olakunle Oladimeji ◽  
Jude Akinyelu ◽  
Aliscia Daniels ◽  
Moganavelli Singh
Keyword(s):  
Polyethylene Glycol ◽  
Cancer Cell ◽  
Betulinic Acid ◽  
Targeted Delivery ◽  
Epigallocatechin Gallate ◽  
High Amplitude ◽  
Significant Inhibition ◽  
Mitochondrial Targeting ◽  
The Impact

Advances in nanomedicine have seen the adaptation of nanoparticles (NPs) for subcellular delivery for enhanced therapeutic impact and reduced side effects. The pivotal role of the mitochondria in apoptosis and their potential as a target in cancers enables selective induction of cancer cell death. In this study, we examined the mitochondrial targeted delivery of betulinic acid (BA) by the mitochondriotropic TPP+-functionalized epigallocatechin gallate (EGCG)-capped gold NPs (AuNPs), comparing the impact of polyethylene glycol (PEG) and poly-L-lysine-graft-polyethylene glycol (PLL-g-PEG) copolymer on delivery efficacy. This included the assessment of their cellular uptake, mitochondrial localization and efficacy as therapeutic delivery platforms for BA in the human Caco-2, HeLa and MCF-7 cancer cell lines. These mitochondrial-targeted nanocomplexes demonstrated significant inhibition of cancer cell growth, with targeted nanocomplexes recording IC50 values in the range of 3.12–13.2 µM compared to that of the free BA (9.74–36.31 µM) in vitro, demonstrating the merit of mitochondrial targeting. Their mechanisms of action implicated high amplitude mitochondrial depolarization, caspases 3/7 activation, with an associated arrest at the G0/G1 phase of the cell cycle. This nano-delivery system is a potentially viable platform for mitochondrial-targeted delivery of BA and highlights mitochondrial targeting as an option in cancer therapy.

A revised seawater sulfate oxygen isotope record for the last 4 Myr

2016 ◽  
Vol 175 ◽  
pp. 239-251 ◽  
Author(s):  
Stefan Markovic ◽  
Adina Paytan ◽  
Hong Li ◽  
Ulrich G. Wortmann
Keyword(s):  
Oxygen Isotope ◽  
Seawater Sulfate ◽  
Oxygen Isotope Record ◽  
Isotope Record
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