352 research outputs found
Dynamics of the Changjiang River Plume
The extension of the Changjiang River plume is one of the fundamental processes in the Yellow and East China Seas, which is responsible not only for the physical properties of seawater but also for the numerous physical, biogeochemical, and sedimentary processes in this region. The studies of the Changjiang River plume dated back to 1960s, followed by generations, and are still attracting numerous focuses nowadays. Here in this chapter, we will review the past studies on the Changjiang River plume and present some latest studies on this massive river plume. The latest research progresses on the Changjiang River plume are mainly related to the tidal modulation mechanisms. It is found that the tide shifts the Changjiang Rive plume to the northeast outside the river mouth, bifurcates the plume at the head of submarine canyon, and arrests the unreal up-shelf plume intrusion that occurred frequently in previous model studies. It is also found that the tidal residual current transports part of the Changjiang River plume to the Subei Coastal Water. These tidal modulation effects can answer the questions on the dynamics of Changjiang River plume that puzzled the research community for decades
Saltwater Intrusion in the Changjiang Estuary
Saltwater intrusion in the Changjiang Estuary and the impacts of river discharge, tide, wind, sea level rise, river basin, and major estuary projects on saltwater intrusion are studied in this chapter. There is a net landward flow in the NB (North Branch) when river discharge is low during spring tide, resulting in a type of saltwater intrusion known as the SSO (saltwater-spilling-over from the NB into the SB (South Branch)), which is the most striking characteristic of saltwater intrusion in the estuary. A three-dimension numerical model with HSIMT-TVD advection scheme was developed to study the hydrodynamic processes and saltwater intrusion in the Changjiang Estuary. Saltwater intrusion in the estuary is controlled mainly by river discharge and tide, but is also influenced by wind, sea level rise, river basin, and estuary projects. Saltwater intrusion is enhanced when river discharge decreases. There is more time for the reservoir to take freshwater from the river when river discharge is larger. The fortnightly spring tide generates greater saltwater intrusion than the neap tide. The saltwater intrusion in the SP (South Passage) is stronger than that in the NP (North Passage), and the intrusion in the NP is stronger than that in the NC (North Channel). The northerly wind produces southward currents along the Subei coast as well as the landward Ekman transport, which enhances the saltwater intrusion in the NC and NB and weakens the saltwater intrusion in the NP and SP. Saltwater intrusion becomes stronger as the sea level rises and is much stronger when river discharge is much small. The DWP (Deep Waterway Project) alleviates the saltwater intrusion in the NC and the lower reaches of the NP and enhances the saltwater intrusion in the SP and in the upper reaches of the NP. The Three Gorges Dam (TGD) increases river discharge in winter, which weakens saltwater intrusion, and is favorable for reducing the burden of freshwater supplement in the highly populated estuarine region. The Water Diversion South to the North Project (WDP) decreases river discharge, enhances saltwater intrusion, and is unfavorable for freshwater supply in the estuary
The transformation of salinity variance : a new approach to quantifying the influence of straining and mixing on estuarine stratification
Author Posting. © American Meteorological Society, 2018. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 48 (2018): 607-623, doi:10.1175/JPO-D-17-0189.1.The roles of straining and dissipation in controlling stratification are derived analytically using a vertical salinity variance method. Stratification is produced by converting horizontal variance to vertical variance via straining, that is, differential advection of horizontal salinity gradients, and stratification is destroyed by the dissipation of vertical variance through turbulent mixing. A numerical model is applied to the Changjiang estuary in order to demonstrate the salinity variance balance and how it reveals the factors controlling stratification. The variance analysis reveals that dissipation reaches its maximum during spring tide in the Changjiang estuary, leading to the lowest stratification. Stratification increases from spring tide to neap tide because of the increasing excess of straining over dissipation. Throughout the spring–neap tidal cycle, straining is almost always larger than dissipation, indicating a net excess of production of vertical variance relative to dissipation. This excess is balanced on average by advection, which exports vertical variance out of the estuarine region into the plume. During neap tide, tidal straining shows a general tendency of destratification during the flood tide and restratification during ebb, consistent with the one-dimensional theory of tidal straining. During spring tide, however, positive straining occurs during flood because of the strong baroclinicity induced by the intensified horizontal salinity gradient. These results indicate that the salinity variance method provides a valuable approach for examining the spatial and temporal variability of stratification in estuaries and coastal environments.X. Li was supported by the China
Scholarship Council. W. R. Geyer was supported by
NSF Grants OCE 1736539 and OCE 1634480. J. Zhu
was supported by the National Natural Science Foundation
of China (41476077 and 41676083). H. Wu was
supported by the National Natural Science Foundation
of China (41576088 and 41776101).2018-09-0
Tidal modulation on the Changjiang River plume in summer
Tide effects on the structure of the near-field Changjiang River plume and on the extension of the far-field plume have often been neglected in analysis and numerical simulations, which is the focus of this study. Numerical experiments highlighted the crucial role of the tidal forcing in modulating the Changjiang River plume. Without the tidal forcing, the plume results in an unrealistic upstream extension along the Jiangsu coast. With the tidal forcing, the vertical mixing increases, resulting in a strong horizontal salinity gradient at the northern side of the Changjiang River mouth along the Jiangsu coast, which acts as a dynamic barrier and restricts the northward migration of the plume. Furthermore, the tidal forcing produces a bidirectional plume structure in the near field, and the plume separation is located at the head of the submarine canyon. A significant bulge occurs around the head of the submarine canyon and rotates anticyclonically, which carries a large portion of the diluted water toward the northeast and merges into the far-field plume. A portion of the diluted water moves toward the southeast, which is mainly caused by tidal rectification. This bidirectional plume structure is more evident under certain wind conditions. During the neap tide with the reduced tidal energy, the near-field plume extends farther offshore, and the bulge becomes less evident. These dynamic behaviors are maintained and are fundamentally important in the region around the river mouth even under the summer monsoon and the shelf currents, although in the far field the wind forcing and shelf currents eventually dominate the plume extension
l-Peptide functionalized dual-responsive nanoparticles for controlled paclitaxel release and enhanced apoptosis in breast cancer cells
Nanoparticles and macromolecular carriers have been widely used to increase the efficacy of chemotherapeutics, largely through passive accumulation provided by their enhanced permeability and retention effect. However, the therapeutic efficacy of nanoscale anticancer drug delivery systems is severely truncated by their low tumor-targetability and inefficient drug release at the target site. Here, the design and development of novel l-peptide functionalized dual-responsive nanoparticles (l-CS-g-PNIPAM-PTX) for active targeting and effective treatment of GRP78-overexpressing human breast cancer in vitro and in vivo are reported. l-CS-g-PNIPAM-PTX NPs have a relative high drug loading (13.5%) and excellent encapsulation efficiency (74.3%) and an average diameter of 275 nm. The release of PTX is slow at pH 7.4 and 25 °C but greatly accelerated at pH 5.0 and 37 °C. MTT assays and confocal experiments showed that the l-CS-g-PNIPAM-PTX NPs possessed high targetability and antitumor activity toward GRP78 overexpressing MDA-MB-231 human breast cancer cells. As expected, l-CS-g-PNIPAM-PTX NPs could effectively treat mice bearing MDA-MB-231 human breast tumor xenografts with little side effects, resulting in complete inhibition of tumor growth and a high survival rate over an experimental period of 60 days. These results indicate that l-peptide-functionalized acid - and thermally activated - PTX prodrug NPs have a great potential for targeted chemotherapy in breast cancer.</p
Li-rich and super Li-rich giants produced by element diffusion
Context. About 0.2-2% of giant stars are Li-rich, whose lithium abundance
(A(Li)) is higher than 1.5 dex. Among them, near 6% are super Li-rich with
A(Li) exceeding 3.2 dex. Meanwhile, the formation mechanism of these Li-rich
and super Li-rich giants is still under debate. Aims. Considering the compact
He core of red giants, attention is paid to the effect of element diffusion on
A(Li). In particular, when the He core flash occurs, the element diffusion
makes the thermohaline mixing zone extend inward and connect to the inner
convection region of stars. Then, a large amount of 7Be produced by the He
flash can be transferred to stellar surface, finally turning into 7Li. Thus,
the goal of this work is to propose the mechanism of A(Li) enrichment and
achieve the consistency between the theoretical and observation data. Methods.
Using the Modules for Experiments in Stellar Astrophysics (MESA), we simulate
the evolution of low-mass stars, with considering the effects of element
diffusion on the Li abundances. The timescale ratio of Li-rich giants to normal
giants is estimated by population synthesis method. Then we get the theoretical
value of A(Li) and make a comparison with observations. Results. Considering
the influence of element diffusion in the model results in the increase of
lithium abundance up to about 1.8dex, which can reveal Li-rich giants.
Simultaneously, introducing high constant diffusive mixing coefficients (Dmix)
with the values from 10e11 to 10e15in the model allows A(Li) to increase from
2.4 to 4.5dex, which can explain the most of Li-rich and super Li-rich giant
stars. The population synthesis method reveals that the amount of Li-rich
giants among giants is about 0.2-2%, which is consistent with observation
estimated levels
A multifunctional nanoplatform based on MoS2-nanosheets for targeted drug delivery and chemo-photothermal therapy
Synergistic tumor treatment has recently attracted more and more attention due to its remarkable therapeutic effect. Herein, a multifunctional drug delivery system based on hyaluronic acid (HA) targeted dual stimulation responsive MoS2 nanosheets (HA-PEI-LA-MoS2-PEG, HPMP) for active interaction with CD44 receptor positive MCF-7 cells is reported. Melanin (Mel), a new type of photothermal agent and doxorubicin (DOX) are both loaded onto the HPMP nanocomposite and can be released by mild acid or hyperthermia. The prepared HPMP nanocomposite has a uniform hydrodynamic diameter (104 nm), a high drug loading (944.3 mg.g-1 HPMP), a remarkable photothermal effect (photothermal conversion efficiency: 55.3%) and excellent biocompatibility. The DOX release from HPMP@(DOX/Mel) can be precisely controlled by the dual stimuli of utilizing the acidic environment in the tumor cells and external laser irradiation. Meanwhile, loading of Mel onto the surface can enhance the photothermal effect of the MoS2 nanosheets. In vitro experiments showed that the HPMP@(DOX/Mel) nanoplatform could efficiently deliver DOX into MCF-7 cells and demonstrated enhanced cytotoxicity compared to that of the non-targeted nanoplatform. In vivo experiments in a breast cancer model of nude mice further confirmed that the HPMP@(DOX/Mel) significantly inhibited tumor growth under near infrared (NIR) laser irradiation, which is superior to any single therapy. In summary, this flexible nanoplatform, based on multi-faceted loaded MoS2 nanosheets, exhibits considerable potential for efficient pH/NIR-responsive targeted drug delivery and chemo-photothermal synergistic tumor therapy
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