Showing papers by "Ocean University of China published in 2014"

Increasing frequency of extreme El Niño events due to greenhouse warming

Abstract: Extreme El Nino events cause global disruption of weather patterns and affect ecosystems and agriculture through changes in rainfall. Model projections show that a doubling in the occurrence of such extreme episodes is caused by increased surface warming of the eastern equatorial Pacific Ocean, which results in the atmospheric conditions required for these event to occur.

Graphene in the Aquatic Environment: Adsorption, Dispersion, Toxicity and Transformation

Abstract: Graphene-family nanomaterials (GFNs) including pristine graphene, reduced graphene oxide (rGO) and graphene oxide (GO) offer great application potential, leading to the possibility of their release into aquatic environments. Upon exposure, graphene/rGO and GO exhibit different adsorption properties toward environmental adsorbates, thus the molecular interactions at the GFN–water interface are discussed. After solute adsorption, the dispersion/aggregation behaviors of GFNs can be altered by solution chemistry, as well as by the presence of colloidal particles and biocolloids. GO has different dispersion performance from pristine graphene and rGO, which is further demonstrated from surface properties. Upon exposure in aquatic environments, GFNs have adverse impacts on aquatic organisms (e.g., bacteria, algae, plants, invertebrates, and fish). The mechanisms of GFNs toxicity at the cellular level are reviewed and the remaining unclear points on toxic mechanisms such as membrane damage are presented. Moreover...

A global perspective on CMIP5 climate model biases

Abstract: The use of models for the prediction of future climate conditions is commonplace. This study investigates regional sea surface temperature biases across 22 climate models and finds that they are linked to the large circulation system in the Atlantic Ocean. Improvements to climate models will need to consider the impact of remote biases on regional processes.

Post-stroke cognitive impairment: epidemiology, mechanisms and management

Abstract: Post-stroke cognitive impairment occurs frequently in the patients with stroke. The prevalence of post-stroke cognitive impairment ranges from 20% to 80%, which varies for the difference between the countries, the races, and the diagnostic criteria. The risk of post-stroke cognitive impairment is related to both the demographic factors like age, education and occupation and vascular factors. The underlying mechanisms of post-stroke cognitive impairment are not known in detail. However, the neuroanatomical lesions caused by the stroke on strategic areas such as the hippocampus and the white matter lesions (WMLs), the cerebral microbleeds (CMBs) due to the small cerebrovascular diseases and the mixed AD with stroke, alone or in combination, contribute to the pathogenesis of post-stroke cognitive impairment. The treatment of post-stroke cognitive impairment may benefit not only from the anti-dementia drugs, but also the manage measures on cerebrovascular diseases. In this review, we will describe the epidemiological features and the mechanisms of post-stroke cognitive impairment, and discuss the promising management strategies for these patients.

Climate effects of dust aerosols over East Asian arid and semiarid regions

Abstract: East Asia is a major dust source in the world. Mineral dusts in the atmosphere and their interactions with clouds and precipitation have great impacts on regional climate in Asia, where there are large arid and semiarid regions. In this review paper, we summarize the typical transport paths of East Asian dust, which affect regional and global climates, and discuss numerous effects of dust aerosols on clouds and precipitation primarily over East Asian arid and semiarid regions. We hope to provide a benchmark of our present understanding of these issues. Compared with the aerosols of Saharan dust, those of East Asian dust are more absorptive of solar radiation, and its direct radiative forcing at the top of atmosphere is nearly positive or nil. It means that aerosols of East Asian dust can influence the cloud properties not only by acting as cloud condensation nuclei and ice nuclei (via first indirect effect, second indirect effect, and invigoration effect) but also through changing the relative humidity and stability of the atmosphere (via semidirect effect). Converting visible light to thermal energy, dust aerosols can burn clouds to produce a warming effect on climate, which is opposite to the first and second indirect effects of aerosols. The net dust aerosol radiative effects are still highly unclear. In addition, dust can inhibit or enhance precipitation under certain conditions, thus impacting the hydrological cycle. Over Asian arid and semiarid regions, the positive feedback loop in the aerosol-cloud-precipitation interaction may aggravate drought in its inner land.

Varying planetary heat sink led to global-warming slowdown and acceleration

Abstract: A vacillating global heat sink at intermediate ocean depths is associated with different climate regimes of surface warming under anthropogenic forcing: The latter part of the 20th century saw rapid global warming as more heat stayed near the surface. In the 21st century, surface warming slowed as more heat moved into deeper oceans. In situ and reanalyzed data are used to trace the pathways of ocean heat uptake. In addition to the shallow La Nina–like patterns in the Pacific that were the previous focus, we found that the slowdown is mainly caused by heat transported to deeper layers in the Atlantic and the Southern oceans, initiated by a recurrent salinity anomaly in the subpolar North Atlantic. Cooling periods associated with the latter deeper heat-sequestration mechanism historically lasted 20 to 35 years.

The origin of high electrolyte-electrode interfacial resistances in lithium cells containing garnet type solid electrolytes

Abstract: Dense LLZO (Al-substituted Li7La3Zr2O12) pellets were processed in controlled atmospheres to investigate the relationships between the surface chemistry and interfacial behavior in lithium cells. Laser induced breakdown spectroscopy (LIBS), scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, synchrotron X-ray photoelectron spectroscopy (XPS) and soft X-ray absorption spectroscopy (XAS) studies revealed that Li2CO3 was formed on the surface when LLZO pellets were exposed to air. The distribution and thickness of the Li2CO3 layer were estimated by a combination of bulk and surface sensitive techniques with various probing depths. First-principles thermodynamic calculations confirmed that LLZO has an energetic preference to form Li2CO3 in air. Exposure to air and the subsequent formation of Li2CO3 at the LLZO surface is the source of the high interfacial impedances observed in cells with lithium electrodes. Surface polishing can effectively remove Li2CO3 and dramatically improve the interfacial properties. Polished samples in lithium cells had an area specific resistance (ASR) of only 109 Ω cm(2) for the LLZO/Li interface, the lowest reported value for Al-substituted LLZO. Galvanostatic cycling results obtained from lithium symmetrical cells also suggest that the quality of the LLZO/lithium interface has a significant impact on the device lifetime.

Oceanic mass transport by mesoscale eddies

Abstract: Oceanic transports of heat, salt, fresh water, dissolved CO2, and other tracers regulate global climate change and the distribution of natural marine resources. The time-mean ocean circulation transports fluid as a conveyor belt, but fluid parcels can also be trapped and transported discretely by migrating mesoscale eddies. By combining available satellite altimetry and Argo profiling float data, we showed that the eddy-induced zonal mass transport can reach a total meridionally integrated value of up to 30 to 40 sverdrups (Sv) (1 Sv = 10(6) cubic meters per second), and it occurs mainly in subtropical regions, where the background flows are weak. This transport is comparable in magnitude to that of the large-scale wind- and thermohaline-driven circulation.

Efficacy and safety of donepezil, galantamine, rivastigmine, and memantine for the treatment of Alzheimer's disease: a systematic review and meta-analysis.

Abstract: Background The role of currently available drugs for Alzheimer's disease (AD) has been controversial, with some national formularies restricting their use, and health economists questioning whether the small clinical effects are economically worthwhile. Objective To estimate the efficacy and safety of donepezil, galantamine, rivastigmine, and memantine for the treatment of AD. Methods Double-blind, placebo-controlled, with random assignment to a cholinesterase inhibitor or memantine trials were included into the pooled studies. Results Cognitive effects were significant for all drugs, ranging from a -1.29 points mean difference (95% CI -2.30 to -0.28) in the 20 mg daily memantine trials to -3.20 points (95% CI -3.28 to -3.12) in the 32 mg daily galantamine group. Only memantine had no effect on the Clinicians' Global Impression of Change scale. No behavioral benefits were observed, except for -2.72 (95% CI -4.92 to -0.52) in the 10 mg daily donepezil group and -1.72 (95% CI -3.12 to -0.33) for 24 mg daily galantamine trial. Only 5 mg daily donepezil had no effect on the function outcome. Compared with placebo, more dropouts and adverse events occurred with the cholinesterase inhibitors, but not with memantine. Conclusions Cholinesterase inhibitors and memantine are able to stabilize or slow decline in cognition, function, behavior, and global change.

OpenGeoSys: An open-source initiative for numerical simulation of thermo-hydro-mechanical/chemical (THM/C) processes in porous media

Abstract: In this paper we describe the OpenGeoSys (OGS) project, which is a scientific open-source initiative for numerical simulation of thermo-hydro-mechanical-chemical processes in porous media. The basic concept is to provide a flexible numerical framework (using primarily the Finite Element Method (FEM)) for solving multifield problems in porous and fractured media for applications in geoscience and hydrology. To this purpose OGS is based on an object-oriented FEM concept including a broad spectrum of interfaces for pre- and postprocessing. The OGS idea has been in development since the mid-eighties. We provide a short historical note about the continuous process of concept and software development having evolved through Fortran, C, and C++ implementations. The idea behind OGS is to provide an open platform to the community, outfitted with professional software-engineering tools such as platform-independent compiling and automated benchmarking. A comprehensive benchmarking book has been prepared for publication. Benchmarking has been proven to be a valuable tool for cooperation between different developer teams, for example, for code comparison and validation purposes (DEVOVALEX and CO2 BENCH projects). On one hand, object-orientation (OO) provides a suitable framework for distributed code development; however, the parallelization of OO codes still lacks efficiency. High-performance-computing efficiency of OO codes is subject to future research.

Microglia in Alzheimer’s Disease

Abstract: Alzheimer's disease (AD) is a familiar neurodegenerative disease in the elderly. In this paper, we will review current viewpoints of microglial activation, inflammatory regulatory systems, and their relationship with AD pathology and etiology. Microglia cells are macrophage and representative of the innate immune system in brain. AD brain is marked by obvious inflammatory features, in which microglial activation is the driving force. β-amyloid protein sedimentation activates microglia cells, which causes the inflammation in AD. Microglia cells have dual roles: they provoke the release of inflammatory factors and cytotoxins leading to neuronal injuries and death; on the other hand, they have the neuroprotective effects. Through this, we hope to illustrate that the anti-inflammatory defenses of neurons can be practiced in the future strategy for recuperating the balance between the levels of inflammatory mediators and immune regulators in AD.

Increased frequency of extreme Indian Ocean Dipole events due to greenhouse warming

Abstract: Extreme positive-Indian-Ocean-dipole events cause devastating floods in eastern tropical Africa and severe droughts in Asia; increasing greenhouse gas emissions will make these dipole events about three times more frequent in the twenty-first century. Countries in the southern tropical Indian Ocean region are prone to extensive flooding and droughts in years when the Indian Ocean dipole (IOD) climate cycle is in an extreme positive phase. In these bad years, such as 1961, 1994 and 1997, warm waters appear in the western part of the basin and precipitation increases, whereas in the east cooler waters predominate and precipitation decreases. Here Wenju Cai et al. assess climate model projections in a scenario of high greenhouse gas emissions and find that the frequency of extreme positive IODs is likely to increase from one event approximately every 17.3 years through the twentieth century to one event every 6.3 years during the twenty-first century. The Indian Ocean dipole is a prominent mode of coupled ocean–atmosphere variability1,2,3,4, affecting the lives of millions of people in Indian Ocean rim countries5,6,7,8,9,10,11,12,13,14,15. In its positive phase, sea surface temperatures are lower than normal off the Sumatra–Java coast, but higher in the western tropical Indian Ocean. During the extreme positive-IOD (pIOD) events of 1961, 1994 and 1997, the eastern cooling strengthened and extended westward along the equatorial Indian Ocean through strong reversal of both the mean westerly winds and the associated eastward-flowing upper ocean currents1,2. This created anomalously dry conditions from the eastern to the central Indian Ocean along the Equator and atmospheric convergence farther west, leading to catastrophic floods in eastern tropical African countries13,14 but devastating droughts in eastern Indian Ocean rim countries8,9,10,16,17. Despite these serious consequences, the response of pIOD events to greenhouse warming is unknown. Here, using an ensemble of climate models forced by a scenario of high greenhouse gas emissions (Representative Concentration Pathway 8.5), we project that the frequency of extreme pIOD events will increase by almost a factor of three, from one event every 17.3 years over the twentieth century to one event every 6.3 years over the twenty-first century. We find that a mean state change—with weakening of both equatorial westerly winds and eastward oceanic currents in association with a faster warming in the western than the eastern equatorial Indian Ocean—facilitates more frequent occurrences of wind and oceanic current reversal. This leads to more frequent extreme pIOD events, suggesting an increasing frequency of extreme climate and weather events in regions affected by the pIOD.

Amyloid-β induces NLRP1-dependent neuronal pyroptosis in models of Alzheimer's disease.

Abstract: Increasing evidence has shown the aberrant expression of inflammasome-related proteins in Alzheimer's disease (AD) brain; these proteins, including NLRP1 inflammasome, are implicated in the execution of inflammatory response and pyroptotic death Although current data are associated NLRP1 genetic variants with AD, the involvement of NLRP1 inflammasome in AD pathogenesis is still unknown Using APPswe/PS1dE9 transgenic mice, we found that cerebral NLRP1 levels were upregulated Our in vitro studies further showed that increased NLRP1-mediated caspase-1-dependent ‘pyroptosis' in cultured cortical neurons in response to amyloid-β Moreover, we employed direct in vivo infusion of non-viral small-interfering RNA to knockdown NLRP1 or caspase-1 in APPswe/PS1dE9 brain, and discovered that these NLRP1 or caspase-1 deficiency mice resulted in significantly reduced neuronal pyroptosis and reversed cognitive impairments Taken together, our findings indicate an important role for NLRP1/caspase-1 signaling in AD progression, and point to the modulation of NLRP1 inflammasome as a promising strategy for AD therapy

Effects of solution chemistry on adsorption of selected pharmaceuticals and personal care products (PPCPs) by graphenes and carbon nanotubes.

Abstract: Adsorption of three selected pharmaceuticals and personal care products (PPCPs) (ketoprofen (KEP), carbamazepine (CBZ), and bisphenol A (BPA)) by two reduced graphene oxides (rGO1 and rGO2) and one commercial graphene was examined under different solution conditions. Single-walled carbon nanotubes (SWCNTs), multiwalled carbon nanotubes (MWCNTs), and powdered graphite were also investigated for comparison. All adsorption isotherms followed the order of SWCNTs > rGO1 > rGO2 > MWCNTs > graphene > graphite, consistent with the orders of their surface areas and micropore volumes. After surface area normalization, adsorption affinities of the three PPCPs onto graphenes were lower than onto graphite, suggesting incomplete occupation for adsorption sites because of the aggregation of graphene sheets and the presence of oxygen-containing functional groups. The observed pH effects on adsorption correlated well with the pH-regulated distribution of the protonated neutral species of the three PPCPs. Increasing ionic ...

Transparent Metal Selenide Alloy Counter Electrodes for High-Efficiency Bifacial Dye-Sensitized Solar Cells†

Abstract: The exploration of cost-effective and transparent counter electrodes (CEs) is a persistent objective in the development of bifacial dye-sensitized solar cells (DSSCs). Transparent counter electrodes based on binary-alloy metal selenides (M-Se; M=Co, Ni, Cu, Fe, Ru) are now obtained by a mild, solution-based method and employed in efficient bifacial DSSCs. Owing to superior charge-transfer ability for the I−/I3− redox couple, electrocatalytic activity toward I3− reduction, and optical transparency, the bifacial DSSCs with CEs consisting of a metal selenide alloy yield front and rear efficiencies of 8.30 % and 4.63 % for Co0.85Se, 7.85 % and 4.37 % for Ni0.85Se, 6.43 % and 4.24 % for Cu0.50Se, 7.64 % and 5.05 % for FeSe, and 9.22 % and 5.90 % for Ru0.33Se in comparison with 6.18 % and 3.56 % for a cell with an electrode based on pristine platinum, respectively. Moreover, fast activity onset, high multiple start/stop capability, and relatively good stability demonstrate that these new electrodes should find applications in solar panels.

Platinum‐Free Binary Co‐Ni Alloy Counter Electrodes for Efficient Dye‐Sensitized Solar Cells

Abstract: Dye-sensitized solar cells (DSSCs) have attracted growing interest because of their application in renewable energy technologies in developing modern low-carbon economies. However, the commercial application of DSSCs has been hindered by the high expenses of platinum (Pt) counter electrodes (CEs). Here we use Pt-free binary Co-Ni alloys synthesized by a mild hydrothermal strategy as CE materials in efficient DSSCs. As a result of the rapid charge transfer, good electrical conduction, and reasonable electrocatalysis, the power conversion efficiencies of Co-Ni-based DSSCs are higher than those of Pt-only CEs, and the fabrication expense is markedly reduced. The DSSCs based on a CoNi0.25 alloy CE displays an impressive power conversion efficiency of 8.39 %, fast start-up, multiple start/stop cycling, and good stability under extended irradiation.

Acute metformin preconditioning confers neuroprotection against focal cerebral ischaemia by pre-activation of AMPK-dependent autophagy.

Abstract: Background and Purpose Recent clinical trials report that metformin, an activator of AMP-activated protein kinase (AMPK) used to treat type 2 diabetes, significantly reduces the risk of stroke by actions that are independent of its glucose-lowering effects. However, the underlying molecular mechanisms are not known. Here, we tested the possibility that acute metformin preconditioning confers neuroprotection by pre-activation of AMPK-dependent autophagy in a rat model of permanent middle cerebral artery occlusion (pMCAO). Experimental Approach Male Sprague-Dawley rats were pretreated with either vehicle, an AMPK inhibitor, Compound C, or an autophagy inhibitor, 3-methyladenine, and were injected with a single dose of metformin (10 mg kg−1, i.p.). Then, AMPK activity and autophagy biomarkers in the brain were assessed. At 24 h after metformin treatment, rats were subjected to pMCAO; infarct volume, neurological deficits and cell apoptosis were evaluated 24 and 96 h later. Key Results A single dose of metformin significantly activated AMPK and induced autophagy in the brain. The enhanced autophagic activity was inhibited by Compound C pretreatment. Furthermore, acute metformin preconditioning significantly reduced infarct volume, neurological deficits and cell apoptosis during a subsequent focal cerebral ischaemia. The neuroprotection mediated by metformin preconditioning was fully abolished by Compound C and partially inhibited by 3-methyladenine. Conclusions and Implications These results provide the first evidence that acute metformin preconditioning induces autophagy by activation of brain AMPK, which confers neuroprotection against subsequent cerebral ischaemia. This suggests that metformin, a well-known hypoglycaemic drug, may have a practical clinical use for stroke prevention.

Stabilization of Singular Markovian Jump Systems With Generally Uncertain Transition Rates

Abstract: This note is devoted to investigating the stability and stabilization problems for continuous-time singular Markovian jump systems (SMJSs) with generally uncertain transition rates (GUTRs). In this GUTR singular model, each transition rate can be completely unknown or only its estimate value is known. In terms of a set of coupled linear matrix inequalities (LMIs), a sufficient condition is established to ensure the systems to be regular, impulse-free and stochastically stable. Moreover, the corresponding sufficient condition on the existence of a mode-dependent state-feedback controller is derived to guarantee the closed-loop systems stochastically admissible by applying the LMI technique. Finally, a numerical example is presented to illustrate the effectiveness and efficiency of the proposed method.

Intensification of decadal and multi-decadal sea level variability in the western tropical Pacific during recent decades

Abstract: Previous studies have linked the rapid sea level rise (SLR) in the western tropical Pacific (WTP) since the early 1990s to the Pacific decadal climate modes, notably the Pacific Decadal Oscillation in the north Pacific or Interdecadal Pacific Oscillation (IPO) considering its basin wide signature. Here, the authors investigate the changing patterns of decadal (10-20 years) and multidecadal (> 20 years) sea level variability (global mean SLR removed) in the Pacific associated with the IPO, by analyzing satellite and in situ observations, together with reconstructed and reanalysis products, and performing ocean and atmosphere model experiments. Robust intensification is detected for both decadal and multidecadal sea level variability in the WTP since the early 1990s. The IPO intensity, however, did not increase and thus cannot explain the faster SLR. The observed, accelerated WTP SLR results from the combined effects of Indian Ocean and WTP warming and central-eastern tropical Pacific cooling associated with the IPO cold transition. The warm Indian Ocean acts in concert with the warm WTP and cold central-eastern tropical Pacific to drive intensified easterlies and negative Ekman pumping velocity in western-central tropical Pacific, thereby enhancing the western tropical Pacific SLR. On decadal timescales, the intensified sea level variability since the late 1980s or early 1990s results from the "out of phase" relationship of sea surface temperature anomalies between the Indian and central-eastern tropical Pacific since 1985, which produces "in phase" effects on the WTP sea level variability.

Genome-wide serum microRNA expression profiling identifies serum biomarkers for Alzheimer's disease.

Abstract: Recent findings that human serum contains stably expressed microRNAs (miRNAs) have revealed a great potential of serum miRNA signature as disease fingerprints to diagnosis. Here we used genome-wide serum miRNA expression analysis to investigate the value of serum miRNAs as biomarkers for the diagnosis of Alzheimer's disease (AD). Illumina HiSeq 2000 sequencing followed by individual quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) assays was used to test the difference in levels of serum miRNAs between 50 AD patients and 50 controls in the screening stages. The detected serum miRNAs then were validated by qRT-PCR in 158 patients and 155 controls. MiR-98-5p, miR-885-5p, miR-483-3p, miR-342-3p, miR-191-5p, and miR-let-7d-5p displayed significantly different expression levels in AD patients compared with controls. Among the 6 miRNAs, miR-342-3p has the best sensitivity (81.5%) and specificity (70.1%) and was correlated to Mini-Mental State Examination score. This study identified six serum miRNAs that distinguish AD patients from healthy controls with high sensitivity and specificity. Serum miRNA panel (or miR-342-3p alone) may serve as a novel, noninvasive biomarker for AD.

Efficacy and adverse effects of ginkgo biloba for cognitive impairment and dementia: a systematic review and meta-analysis.

Abstract: Background Research into Ginkgo biloba has been ongoing for many years, while the benefit and adverse effects of Ginkgo biloba extract EGb761 for cognitive impairment and dementia has been discussed controversially Objective To discuss new evidence on the clinical and adverse effects of standardized Ginkgo biloba extract EGb761 for cognitive impairment and dementia Methods MEDLINE, EMBASE, Cochrane, and other relevant databases were searched in March 2014 for eligible randomized controlled trials of Ginkgo biloba EGb761 therapy in patients with cognitive impairment and dementia Results Nine trials met our inclusion criteria Trials were of 22-26 weeks duration and included 2,561 patients in total In the meta-analysis, the weighted mean differences in change scores for cognition were in favor of EGb761 compared to placebo (-286, 95%CI -318; -254); the standardized mean differences in change scores for activities in daily living (ADLs) were also in favor of EGb761 compared to placebo (-036, 95%CI -044; -028); Peto OR showed a statistically significant difference from placebo for Clinicians' Global Impression of Change (CGIC) scale (188, 95%CI 154; 229) All these benefits are mainly associated with EGb761 at a dose of 240 mg/day For subgroup analysis in patients with neuropsychiatric symptoms, 240 mg/day EGb761 improved cognitive function, ADLs, CGIC, and also neuropsychiatric symptoms with statistical superiority than for the whole group For the Alzheimer's disease subgroup, the main outcomes were almost the same as the whole group of patients with no statistical superiority Finally, safety data revealed no important safety concerns with EGb761 Conclusions EGb761 at 240 mg/day is able to stabilize or slow decline in cognition, function, behavior, and global change at 22-26 weeks in cognitive impairment and dementia, especially for patients with neuropsychiatric symptoms