Since the onset of the coronavirus disease 2019 (COVID-19) pandemic, doctors and public authorities have demonstrated concern about the reduction in quality of care for other health conditions due to ...social restrictions and lack of resources. Using a population-based stroke registry, we investigated the impact of the onset of the COVID-19 pandemic in stroke admissions in Joinville, Brazil.
Patients admitted after the onset of COVID-19 restrictions in the city (defined as March 17, 2020) were compared with those admitted in 2019. We analyzed differences between stroke incidence, types, severity, reperfusion therapies, and time from stroke onset to admission. Statistical tests were also performed to compare the 30 days before and after COVID-19 to the same period in 2019.
We observed a decrease in total stroke admissions from an average of 12.9/100 000 per month in 2019 to 8.3 after COVID-19 (
=0.0029). When compared with the same period in 2019, there was a 36.4% reduction in stroke admissions. There was no difference in admissions for severe stroke (National Institutes of Health Stroke Scale score >8), intraparenchymal hemorrhage, and subarachnoid hemorrhage.
The onset of COVID-19 was correlated with a reduction in admissions for transient, mild, and moderate strokes. Given the need to prevent the worsening of symptoms and the occurrence of medical complications in these groups, a reorganization of the stroke-care networks is necessary to reduce collateral damage caused by COVID-19.
We extend in several directions the study of our fast sparse alternative to the standard (FFT-based) evaluation of dynamic phasors. We present analysis for an arbitrary shift between the waveform ...samples used to construct sub-cycle dynamic phasors. Next, we show that the transient response of sub-cycle dynamic power metrics can be improved by using a small number of waveform samples and adjusting the uniform inter-sample shift. Our real-life examples demonstrate that reduction of the inter-sample shift can be quite effective in the presence of fast transients (wide-band in frequency). We use a synthetic example to demonstrate that a metric obtained from a sub-cycle scheme provides surprisingly accurate information about the duration and onset-time of a transient. We also identify a range of shift values for which the steady-state error remains near-optimal, and we derive conditions for a superior performance for slow transients. Finally, our results suggest that in practical real-time implementations it may be advantageous to calculate at least two sets of phasors to cover both slow and fast transients: the computational cost of such a scheme is still significantly lower than that of a standard full-cycle calculation.
Wind turbines (WTs) are prone to transient instability during weak grid faults, which is caused by their complex interactions. However, it is a challenge to analyze the transient stability, due to ...high-order and strong nonlinearity. Moreover, the existing works mainly focus on a phase-locked loop (PLL) system while ignoring current control, which cannot fully reflect the transient instability mechanism. To fill this gap, this article studies the transient stability of type-3 WT considering both PLL and current control. First, to simplify the full model of type-3 WT, a slow-fast subsystem is established using the singular perturbation. Then, the sixth-order full model is simplified as a second-order slow subsystem and its small disturbance (i.e., fast subsystem). Based on it, Lyapunov's direct and indirect methods are adopted to analyze the stability of slow and fast subsystems, respectively. Meanwhile, the influence of various factors (e.g., the fault degree, grid inductance, current references, current controller, and PLL controller) on transient stability of type-3 WT is revealed. In addition, the proposed analytical method combining singular perturbation and Lyapunov methods is a new approach to studying transient stability, which can also be applied to other renewable energy resources. Finally, the analysis is validated by experiments.
With the wide application of inverter-fed motors (IFMs), it is necessary to monitor the groundwall (GW) insulation status to guarantee the reliable operation of motor drive system. This article first ...proposes a mathematical model of leakage current in IFM to analyze its time domain characteristics, and then an online GW insulation monitoring method is proposed based on the transient characteristics of leakage current. By using the initial oscillation amplitude, oscillation period, and attenuation time of leakage current, the phase, position, and severity of GW insulation degradation can be identified. The proposed method is validated using an IFM, and the experimental results agree well with theoretical analysis.
The power electronics' penetration in modern grids is rapidly increasing due to the growing proportion of renewable energy generation. As the important energy conversion interface, the stable ...operation of grid-tied converters is vital to the overall safe of the double-high power system. The prior arts have mainly focused on the varying negative damping in the phase-locked loop (PLL). Negative damping imposes energy into the system and is detrimental to system's transient stability and should not be neglected as the constant positive damping in synchronous generators. The deficiencies of the previous studies lie in the large conservatism of the criteria once considering the influence of negative damping. In this article, an elliptic-equal area criterion (EAC) is proposed to assess the damping impacts on the stable domain of the converter systems, which improves conservatism compared to previous transient stability criteria. In addition, a transient stability improved PLL is proposed by eliminating the negative damping term.
There is significant interest in the models for production of short gamma-ray bursts (GRBs). Until now, the number of known short GRBs with multi-wavelength afterglows has been small. While the Fermi ...GRB Monitor detects many GRBs relative to the Neil Gehrels Swift Observatory, the large localization regions makes the search for counterparts difficult. With the Zwicky Transient Facility (ZTF) recently achieving first light, it is now fruitful to use its combination of depth (m
AB ∼ 20.6), field of view (≈47 square degrees), and survey cadence (every ∼3 days) to perform Target of Opportunity observations. We demonstrate this capability on GRB 180523B, which was recently announced by the Fermi GRB Monitor as a short GRB. ZTF imaged ≈2900 square degrees of the localization region, resulting in the coverage of 61.6% of the enclosed probability over two nights to a depth of m
AB ∼ 20.5. We characterized 14 previously unidentified transients, and none were found to be consistent with a short GRB counterpart. This search with the ZTF shows it is an efficient camera for searching for coarsely localized short GRB and gravitational-wave counterparts, allowing for a sensitive search with minimal interruption to its nominal cadence.
Evidence for the clinical use of neuroprotective drugs for the treatment of cerebral ischemia (CI) is still greatly limited. Spatial/temporal disorientation and cognitive dysfunction are among the ...most prominent long-term sequelae of CI. Cannabidiol (CBD) is a non-psychotomimetic constituent of
Cannabis sativa
that exerts neuroprotective effects against experimental CI. The present study investigated possible neuroprotective mechanisms of action of CBD on spatial memory impairments that are caused by transient global cerebral ischemia (TGCI) in rats. Hippocampal synaptic plasticity is a fundamental mechanism of learning and memory. Thus, we also evaluated the impact of CBD on neuroplastic changes in the hippocampus after TGCI. Wistar rats were trained to learn an eight-arm aversive radial maze (AvRM) task and underwent either sham or TGCI surgery. The animals received vehicle or 10 mg/kg CBD (i.p.) 30 min before surgery, 3 h after surgery, and then once daily for 14 days. On days 7 and 14, we performed a retention memory test. Another group of rats that received the same pharmacological treatment was tested in the object location test (OLT). Brains were removed and processed to assess neuronal degeneration, synaptic protein levels, and dendritic remodeling in the hippocampus. Cannabidiol treatment attenuated ischemia-induced memory deficits. In rats that were subjected to TGCI, CBD attenuated hippocampal CA1 neurodegeneration and increased brain-derived neurotrophic factor levels. Additionally, CBD protected neurons against the deleterious effects of TGCI on dendritic spine number and the length of dendritic arborization. These results suggest that the neuroprotective effects of CBD against TGCI-induced memory impairments involve changes in synaptic plasticity in the hippocampus.
Graphical abstract
As one of promising power interfaces in Microgrids, dual active bridge (DAB) converters have been extensively studied and widely applied. However, dc-bias current during its transient process, as ...well as the electromagnetic interference and the reduced efficiency caused by the hard-switching operation, urgently need to be addressed. In addition, traditional transient optimization strategies mainly focus on unidirectional power transmission, which cannot ensure fast power reverse operation of DAB converters and eliminate dc-bias current and hard-switching defects at the same time. To address this issue, a novel transient power reversal control (TPRC) strategy based on the principle of straightforward phase-shift optimization is proposed in this article. Extensive and comparative experimental evaluations under various scenarios have been conducted to verify the effectiveness of the proposed TPRC strategy.
Fault detection and classification (FDAC) for islanded power networks is a challenge due to low short circuit current fed by inverter interfaced distributed generator (IIDGs), control dependent fault ...models and bi-directional current flow. This article proposes a FDAC scheme, which utilizes the local voltages, measured at relay terminals. The transient monitoring function (TMF) of the voltage signal (<inline-formula><tex-math notation="LaTeX">T_{v}</tex-math></inline-formula>) gives the information of the fault transients. The proposed scheme is validated on the modified CIGRE test microgrid and IEEE 33 bus distribution network. Several test cases are simulated in MATLAB/Simulink at various locations with different inception angles, loading conditions, and fault resistances. The obtained results proves the accuracy of proposed FDAC scheme, with local information available at relaying points. The relays can be programmed to adapt to the proposed scheme, and hence there is no need for additional communication. Experimental validation with Texas Instruments digital signal controller (DSC) TMS320F28377D and OPAL-RT real time digital simulator shows the efficacy of the proposed scheme for practical implementation. Further, performance during no-fault scenarios, and accuracy with different controllers and current limiting algorithms are also illustrated.
Chronic lung diseases such as asthma, chronic obstructive pulmonary disease and idiopathic pulmonary fibrosis are a major and increasing global health burden with a high unmet need. Drug discovery ...efforts in this area have been largely disappointing and so new therapeutic targets are needed. Transient receptor potential ion channels are emerging as possible therapeutic targets, given their widespread expression in the lung, their role in the modulation of inflammatory and structural changes and in the production of respiratory symptoms, such as bronchospasm and cough, seen in chronic lung disease.
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