Barotropic, wind-driven circulation in a small basin

We study the asymptotic behavior (large time) of a simple, wind-driven, barotropic ocean model, described by a nonlinear partial differential equation with two spatial dimensions. Considered as a dynamical system, this model has an infinite-dimensional phase space. After discretization, the equivalent numerical model has a phase space of finite but large dimension. We find that for a considerable range of friction, the asymptotic states are low-dimensional attractors. We describe the changes in the structure of these asymptotic attractors as a function of the eddy viscosity of the model. A variety of different types of attractor are seen, with chaotic attractors predominating at higher Reynolds numbers. As the Reynolds number is increased, we observe a slow increase in the dimension of the chaotic attractors. Using an energy analysis, we examine the nature of the instability responsible for the Hopf bifurcation that initiates the transition from asymptotically steady states to time-dependent states

On the stability of the wind-driven circulation

This work examines the instabilities of steady circulations driven by stationary single-gyre wind forcing in closed rectangular basins with different aspect ratios. The stratified ocean is modeled with quasi-geostrophic 1.5-layer (equivalent-barotropic) and two-layer models. As friction is reduced, a stability threshold is encountered. In the vicinity of this threshold, unstable steady states and their unstable eigenmodes are determined. The structures of the eigenmodes and their associated energy conversion terms allow us to characterize the instabilities. In each case, the loss of stability is associated with an oscillatory instability. Several different instability mechanisms are observed. Which of these is responsible for the onset of instability depends upon the basin aspect ratio and the choice of stratification (1.5- or two-layer). The various mechanisms include instability of the western boundary current, baroclinic instability of the main recirculation gyre, instability of a standing meander located downstream of the main recirculation gyre and a complex instability involving several recirculations and the standing meander. The periods of the eigenmodes range from several months to several years depending upon the kind of instability and type of model. Additional insight into the western boundary current and baroclinic gyre instabilities is provided by an exploration of the stability of (a) the Munk boundary layer flow in 1.5- and two-layer models in an unbounded north-south channel, and (b) an isolated baroclinic vortex on an f-plane

Instabilities of a steady, barotropic, wind-driven circulation

We explore the stability characteristics of a single, barotropic, wind-driven gyre as a function of the strength of the wind forcing and the size and shape of the basin. We find steady solutions for the barotropic flow in a basin driven by a steady wind stress over a range of values of the Reynolds number and the strength of the wind stress. For those solutions that are close to the stability boundary, we examine the form of the most unstable normal mode. We find that for sufficiently weak forcing, the form of the first instability seen is an instability of the western boundary current. However, for larger values of the forcing, the first instability to set in, as the Reynolds number is reduced, is centered on a standing meander that forms on the continuation of the boundary current after it has left the boundary. Both types of instability are oscillatory. There are several different modes of standing meander instability each associated with Rossby wave-like disturbances in the eastern half of the basin. Each of these modes is most unstable when its frequency is close to a resonance with a basin mode with similar spatial scales

The dynamics of an equivalent-barotropic model of the wind-driven circulation

Various steady and time-dependent regimes of a quasi-geostrophic 1.5 layer model of an oceanic circulation driven by a steady wind stress are studied. After being discretized as a numerical model, the quasi-geostrophic equations of motion become a dynamical system with a large dimensional phase space. We find that, for a wide range of parameters, the large-time asymptotic regimes of the model correspond to low-dimensional attractors in this phase space. Motion on these attractors is significant in determining the intrinsic time scales of the system. In two sets of experiments, we explore the dependence of solutions on the viscosity coefficient and the deformation radius. Both experiments yielded a succession of solutions with different forms of time dependence including chaotic solutions. The transition to chaos in this model occurs through a modified classical Ruelle-Takens scenario. We computed some unstable steady regimes of the circulation and the associated fastest growing linear eigenmodes. The structure of the eigenmodes and the details of the energy conversion terms allow us to characterize the primary instability of the steady circulation. It is a complex instability of the western boundary intensification, the western gyre and the meander between the western and central gyres. The model exhibits ranges of parameters in which multiple, stable, time-dependent solutions exist. Further, we note that some bifurcations involve the appearance of variability at climatological time scales, purely as a result of the intrinsic dynamics of the wind-driven circulation

The predictability of large-scale wind-driven flows

International audienceThe singular values associated with optimally growing perturbations to stationary and time-dependent solutions for the general circulation in an ocean basin provide a measure of the rate at which solutions with nearby initial conditions begin to diverge, and hence, a measure of the predictability of the flow. In this paper, the singular vectors and singular values of stationary and evolving examples of wind-driven, double-gyre circulations in different flow regimes are explored. By changing the Reynolds number in simple quasi-geostrophic models of the wind-driven circulation, steady, weakly aperiodic and chaotic states may be examined. The singular vectors of the steady state reveal some of the physical mechanisms responsible for optimally growing perturbations. In time-dependent cases, the dominant singular values show significant variability in time, indicating strong variations in the predictability of the flow. When the underlying flow is weakly aperiodic, the dominant singular values co-vary with integral measures of the large-scale flow, such as the basin-integrated upper ocean kinetic energy and the transport in the western boundary current extension. Furthermore, in a reduced gravity quasi-geostrophic model of a weakly aperiodic, double-gyre flow, the behaviour of the dominant singular values may be used to predict a change in the large-scale flow, a feature not shared by an analogous two-layer model. When the circulation is in a strongly aperiodic state, the dominant singular values no longer vary coherently with integral measures of the flow. Instead, they fluctuate in a very aperiodic fashion on mesoscale time scales. The dominant singular vectors then depend strongly on the arrangement of mesoscale features in the flow and the evolved forms of the associated singular vectors have relatively short spatial scales. These results have several implications. In weakly aperiodic, periodic, and stationary regimes, the mesoscale energy content is usually relatively low and the predictability of the wind-driven circulation is determined by the large-scale structure of the flow. In the more realistic, strongly chaotic regime, in which energetic mesoscale eddies are produced by the meandering of the separated western boundary current extension, the predictability of the flow locally tends to be a stronger function of the local mesoscale eddy structure than of the larger scale structure of the circulation. This has a broader implication for the effectiveness of different approaches to forecasting the ocean with models which sequentially assimilate new observations

One-stop Shop E-government Solution for South-Korean Government Multi-ministry Virtual Employment-Welfare Plus Center System

In this paper, a one-stop e-Government solution will be proposed for the existing Korean government multi-ministry Employment-Welfare plus system that utilizes latest IT technologies. Since 2001, the Korean government had established 11 initiatives and 31 roadmaps to build e-Government infrastructure. Although this infrastructure has been very successful and well-esteemed in the international society, several improvements are required towards a one-stop shop solution. Currently, the system used by the Korean government is not a one-stop solution with a single point for the citizen to access government services. A Virtual Employment – Welfare Plus Centre (VEWPC) is then introduced to unify the services offered to the citizen. Comparing this VEWS with UK’s e-Government solution and review of corresponding literature, several requirements for change towards a one-stop shop solution implementation have been identified. A refined architecture to implement a South Korean e-Government one-stop shop is identified and proposed in this paper. Future plans for the applicability and cost of its adoption are also identified

The alimentary impact of the hemp seed

Hemp seed and hemp seed oil can supply us with many important substances. Their essential fatty acid compositions are favourable, but they may contain non-psychotropic cannabinoids. Emerging data show that these components can influence the health status of the population beneficially. Some data also showed trace amounts of tetrahydrocannabinol in seed oils, the main psychotropic cannabinoid that is contraindicated.Our aim was to examine cannabinoids and fatty acid composition as well as metal and non-metal element compositions in products, like hemp seed oil and chopped hemp seed capsule.The cannabinoids were separated by thin layer chromatography. Fatty acid composition was determined with gas chromatography, and elements (Al, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, S, Si, Sn, Sr, V, and Zn) were measured by inductively coupled plasma optical emission spectrometric method. Selenium was determined with polarographic analyser.Cannabinoids were not detectable by thin layer chromatography, so hemp seed oil, as well as the capsule, have no psychotropic adverse effect. Our data showed that hemp seed contains essential fatty acids close to the recommended ratio. The B and Se concentrations of the oils and the P concentration of the capsule are also relevant

Examining the immunological effects of COVID-19 vaccination in patients with conditions potentially leading to diminished immune response capacity – the OCTAVE trial

SARS-COV-2 vaccines have been shown to be efficacious primarily in healthy volunteer populations and population level studies. Immune responses following SARS-CoV-2 vaccination are less well characterised in potentially immune vulnerable patient groups, including those with immune-mediated inflammatory and chronic diseases (inflammatory arthritis [IA] incorporating rheumatoid arthritis [RA] and psoriatic arthritis [PsA]; ANCA-Associated Vasculitis [AAV]; inflammatory bowel disease [IBD]); hepatic disease (HepD), end stage kidney disease requiring haemodialysis (HD) without or with immunosuppression (HDIS); solid cancers (SC) and haematological malignancies (HM), and those that have undergone haemopoietic stem cell transplant (HSCT). The OCTAVE trial is a multi-centre, multi-disease, prospective cohort that will comprehensively assess SARS-CoV-2 vaccine responses within and between the abovementioned disease cohorts using common analytical platforms in patients recruited across the United Kingdom (UK). The majority of subjects received either COVID-19 mRNA Vaccine BNT162b2 (Pfizer/BioNTech) or ChAdOx1 Vaccine (AstraZeneca formerly AZD1222) as part of the UK National COVID19 vaccination programme. As of 13 th August 2021; 2,583 patients have been recruited. We report herein the humoral and T cell immune response results from the first 600 participants recruited where serology data are available at baseline, pre-second vaccine dose (boost) and/or 4 weeks post second dose. We also include in the analysis, data obtained from 231 healthy individuals from the PITCH (Protective Immunity from T cells in Healthcare workers) study. Overall, in comparison to PITCH where 100% of tested individuals (n=93) generated anti-Spike antibodies after vaccine doses, 89% of patients within OCTAVE seroconverted 4 weeks after second vaccine dose. By corollary, approximately 11% of patients across all disease cohorts fail to generate antibodies that react to SARS-CoV-2 spike 4 weeks after two vaccines. Failure to generate spike reactive antibodies was found at a higher proportion in some specific patient subgroups, particularly AAV (72.4%), HD-IS (16.7%) and HepD (16.7%). Importantly, all recruited AAV patients had received Rituximab; a targeted B cell depletion therapy. Furthermore, even in those who seroconverted, 40% of patients across disease cohorts generate lower levels of SARS-CoV-2 antibody reactivity compared to healthy subjects after two SARS-CoV-2 vaccines; the functional significance of these findings in providing protection from subsequent SARS-CoV-2 exposure is not currently known. In contrast to the observed serological response, evaluation of the Spike-specific T cell response revealed that across all patient sub-groups (including AAV) a response similar to healthy individuals was generated. Our data argue strongly for further vaccination strategies to optimise humoral immune responses against SARS-CoV-2 in patients with chronic diseases and/or patients on immune suppressive therapies. Trial Registration: The trial is registered on ISRCTN 12821688.Funding: This work was supported by the Medical Research Council COVID-19 Immunity – National Core Study (IMM-NCS) [grant number MC-PC-20031]. Staff at the Cancer Research UK Clinical Trials Unit (CRCTU) are supported by a core funding grant from Cancer Research UK (C22436/A25354). PK and EB are supported by the NIHR Birmingham Biomedical Research Centres at the University Hospitals Birmingham NHS Foundation Trust and the University of Birmingham Biomedical Research Centres. EB and PK are supported by an NIHR Senior Investigator award. PK is funded by WT109965MA. SJD is funded by an NIHR Global Research Professorship (NIHR300791). TdS is funded by a Wellcome Trust Intermediate Clinical Fellowship (110058/Z/15/Z). DS is supported by the NIHR Academic Clinical Lecturer programme in Oxford. LT is supported by the Wellcome Trust (grant number 205228/Z/16/Z), the U.S. Food and Drug Administration Medical Countermeasures Initiative contract 75F40120C00085. and the National Institute for Health Research Health Protection Research Unit (NIHR HPRU) in Emerging and Zoonotic Infections (NIHR200907) at University of Liverpool in partnership with Public Health England (PHE), in collaboration with Liverpool School of Tropical Medicine and the University of Oxford. The PITCH (Protective Immunity from T cells to Covid-19 in Health workers) Consortium, is funded by the UK Department of Health and Social Care with contributions from UKRI/NIHR through the UK Coronavirus Immunology Consortium (UKCIC), the Huo Family Foundation and The National Institute for Health Research (UKRIDHSC COVID-19 Rapid Response Rolling Call, Grant Reference Number COV19-RECPLAS).Declaration of Interest: None to declare. Ethical Approval: This study was approved by the UK Medicines and Healthcare Products Regulatory Agency on the 5th February 2021 and the London and Chelsea Research Ethics Committee (REC Ref:21/HRA/0489) on 12th February 2021, with subsequent amendments approved on 3rd March 2021, 19th April 2021 and 26th April 2021)