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This paper describes new structures for stability-enhancing excitation controllers designed using a nonlinear multi-machine system model and Lyapunov's direct method. Two control structures are presented: a hierarchical structure in which the AVR is the master controller and the PSS the slave controller and a traditional structure in which the PSS constitutes a supplementary loop to the main AVR. Both controllers are shown to be robust, as the damping they introduce into the system is insensitive to changes in both the system topology/parameters and the pattern of network flows. Each individual controller contributes positively to the overall system damping with no undesirable interaction between controllers. These features should allow a decentralized approach to the design of the AVR + PSS. Such a design approach is compatible with the new competitive market structures and should result in savings on commissioning costs. Simulation results for a multi-machine power system are presented that confirm the above and show that the two control structures are very effective in damping both local and inter-area power swings. Index Terms--Power system control, power system stability, synchronous generator excitation.

In the earliest days of the COVID-19 pandemic, the collection of dried blood spots (DBS) enabled public health laboratories to undertake population-scale seroprevalence studies used to estimate rates of SARS-CoV-2 exposure. With SARS-CoV-2 seropositivity levels now estimated to exceed 94% in the United States, attention has turned to using DBS to assess neutralizing antibodies within cohorts of interest. With this goal in mind, we generated contrived DBS (cDBS) and whole blood-derived DBS from convalescent and vaccinated individuals and subjected DBS eluates to a battery of assays, including a SARS-CoV-2 multiplexed microsphere immunoassay (MIA), a receptor binding domain (RBD)-human ACE2 inhibition assay (iACE2), a cell-based pseudovirus neutralization assay, and real-time PCR-based surrogate neutralization assay (NAB-Sure). The DBS results were benchmarked against paired serum samples tested in a clinically validated SARS-CoV-2 plaque reduction neutralization titer (PRNT) assay. The results of an 8-plex MIA and NAB-Sure assays demonstrated highly significant correlations with PRNT values when evaluated with a panel of 86 paired serum-DBS samples. Both the MIA and NAB-Sure are adaptable to automated liquid handlers for high-throughput capacity. While neutralizing assays were limited to the ancestral SARS-CoV-2 WA1, this study nonetheless represents an important proof of concept demonstrating the potential utility of DBS as a biospecimen type for use in assessing immunity to SARS-CoV-2 at the community and population levels.IMPORTANCESARS-CoV-2 variants of concern continue to circulate globally and remain a serious health threat to large segments of the population. From a public health standpoint, identifying vulnerable communities based on immune status is critical in terms of vaccine booster recommendations. In this report, we investigated the utility of dried blood spots (DBS) as a biospecimen type from which to estimate SARS-CoV-2 neutralizing antibody titers. Using contrived and whole blood-derived DBS, we demonstrate that SARS-CoV-2 neutralizing antibodies are readily measurable in DBS eluates and correlate with plaque reduction neutralization titer (PRNT) values from paired serum samples. Moreover, several of the methods used to estimate SARS-CoV-2 neutralizing antibodies in DBS eluates are adaptable to high-throughput platforms.

The emergence of recombinant viruses is a threat to public health, as recombination may integrate variant-specific features that together result in escape from treatment or immunity. The selective advantages of recombinant SARS-CoV-2 isolates over their parental lineages remain unknown. We identified a Delta-Omicron (AY.45-BA.1) recombinant in an immunosuppressed transplant recipient treated with monoclonal antibody Sotrovimab. The single recombination breakpoint is located in the spike N-terminal domain adjacent to the Sotrovimab binding site. While Delta and BA.1 are sensitive to Sotrovimab neutralization, the Delta-Omicron recombinant is highly resistant. To our knowledge, this is the first described instance of recombination between circulating SARS-CoV-2 variants as a functional mechanism of resistance to treatment and immune escape., Competing Interests: The authors declare no competing interests., (© 2023 The Author(s).)

Aim of the Study: The 4C Mortality Score was created to predict mortality in hospitalised patients with COVID-19 and has to date been evaluated only in respiratory system disorders. The aim of this study was to investigate its application in patients with COVID-19-associated acute ischaemic stroke (AIS)., Clinical Rationale for Study: COVID-19 is a risk factor for AIS. COVID-19-associated AIS results in higher mortality and worse functional outcome. Predictors of functional outcome in COVID-19-associated AIS are required., Materials and Methods: This was a retrospective observational study of patients with AIS hospitalised in seven neurological wards in Małopolska Voivodship (Poland) between August and December 2020. We gathered data concerning the patients' age, sex, presence of cardiovascular risk factors, type of treatment received, and the presence of stroke-associated infections (including pneumonia, urinary tract infection and infection of unknown source). We calculated 4C Mortality Score at stroke onset, and investigated whether there was a correlation with neurological deficit measured using the National Health Institute Stroke Scale (NIHSS) and functional outcome assessed using the modified Rankin Scale (mRS) at discharge., Results: The study included 52 patients with COVID-19-associated AIS. The 4C Mortality Score at stroke onset correlated with mRS (rs = 0.565, p < 0.01) at discharge. There was also a statistically significant difference in the mean 4C Mortality Score between patients who died and patients who survived the stroke (13.08 ± 2.71 vs. 9.85 ± 3.47, p = 0.04)., Conclusions and Clinical Implications: 4C Mortality Score predicts functional outcome at discharge in COVID-19-associated AIS patients.

Introduction: Observational studies have shown that migraine has been associated with patent foramen ovale (PFO). Whilst studies investigating PFO closure for the treatment of migraine have been neutral, there is some evidence that symptoms of migraine may improve if the PFO was closed after ischemic stroke., Aim: To establish whether closure of PFO in patients with stroke or transient ischemic attack (TIA) is associated with reduction in the severity of co-existent migraine headaches., Material and Methods: Patients with ischemic stroke or TIA, PFO suitable for percutaneous closure and migraine, were given migraine severity questionnaires prior to PFO closure. These were followed up at 6 and 12 months after closure with the same questionnaire. The primary endpoint was change in migraine severity using the Migraine Severity Scale (MIGSEV). Migraine episode frequency, disability (using the MIDAS scale), and pain intensity were also assessed., Results: Sixty-two patients were included in the analysis. MIGSEV scores reduced from 7 (7-8) at baseline to 4 (3.25-6) at 6-month follow-up, and 3 (0-4) at 12-month follow-up ( p < 0.001). Other measures of migraine headache were also improved at both 6- and 12-month follow-up. Twenty-four (38%) patients were rendered migraine free at 12 months., Conclusions: PFO closure for stroke or TIA prevention in patients with migraine was associated with a reduction in markers of migraine headache severity., Competing Interests: Dr Calvert undertakes proctoring for Abbott Vascular and Occlutech. Other authors declare no conflict of interest., (Copyright © 2020 Termedia Sp. z o. o.)

Background: Patent foramen ovale (PFO) is a potential risk factor for ischaemic stroke in young individuals. An interventional method of secondary stroke prevention in PFO patients is its percutaneous closure., Aim: To assess safety and effectiveness (i.e. lack of residual shunt) of percutaneous PFO closure in patients with history of cryptogenic cerebrovascular event., Methods: 149 patients (56 men/93 women), aged 39 ± 12 years, underwent percutaneous PFO closure. The implantation was performed under local anaesthesia, guided by trans-oesophageal echocardiography (TEE) and fluoroscopy. Follow-up trans-thoracic echocardiography (TTE) was performed at 1 month and follow-up TEE at 6-months. In cases of residual shunt, additional TEE was performed after ensuing 6 months., Results: Effective PFO closure (no residual shunt) was achieved in 91.3% patients at 6 months and 95.3% patients at 12 months. In 2 patients transient atrial fibrillation was observed during the procedure. In 2 patients, a puncture site haematoma developed and in 1 patient superficial thrombophlebitis was noted. In 1 patient a small pericardial effusion was observed, which resolved at day 3 post-procedurally, after administration of non-steroidal anti-inflammatory drugs., Conclusions: Percutaneous PFO closure seems to be a safe procedure when performed in a centre with adequate expertise with regard to these procedures.

A case of a 55-year-old woman with anterior communicating artery aneurysm has been described. The aneurysm led to subarachnoid haemorrhage 8 years after ligation of the right internal carotid artery in order to turn off an aneurysm of this artery. Angiography showed the existence of collateral circulation through the arterial circle of the brain with haemodynamic disturbances, confirmed by Doppler ultrasonography. According to the views found in the literature these disturbances are considered the probable factor of initiation of the described aneurysm.