Stroke Frequency Research Articles

Dynamic characteristics analysis of long stroke reciprocating pump combined crank-linkage with rack-pinion mechanism

Drilling pump is the heart of drilling rig, its core structure is crank-linkage mechanism. However, the drilling pump is criticized for its short stroke and high stroke frequency. Aiming at these defects, a long stroke reciprocating (LSR) pump combined the crank-linkage with a rack-pinion mechanism is proposed, and its dynamic and flow characteristics are researched. The results reveal that the stroke of the LSR pump is extended twice when the crank radius stays the same. The stroke frequency and flow pulsation rate are lowered under the same rated power. A new multi-fulcrum crankshaft is designed to extend its fatigue life, and the reaction forces of each fulcrum are solved by simulation. The influence of the fulcrums position on the crankshaft modal frequency is further investigated. The flexible characteristics of the multi-fulcrum crankshaft are studied by rigid-flexible coupled analysis. The results show that more fulcrums can effectively reduce the stress of crankshaft, and the maximum stress of the multi-fulcrum crankshaft is only 178.6 MPa. The modal frequency of the multi-fulcrum crankshaft is increased due to more fulcrums, which proved its stiffness and stability are improved. The fatigue life of the multi-fulcrum crankshaft is predicted to reach 30,000 h by finite element analysis. This study would provide a theoretical basis for further development of the LSR pump.

Methane emission characteristics and model of CBM wells

CBM (CBM) development in coal mining area has good safety, economic and energy benefits, but methane emission is common in surface well sites. In view of this, taking the CBM wells in Qinshui County of Shanxi Province as an example, the methane emission location and emission volume of CBM wells are obtained, and the prediction model of methane emission volume is established through field investigation and multiple regression analysis. The results show that 81% of CBM wells have methane emission. Wellhead and drainage outlet are the two main positions of methane emission. The proportion of wells with emission volume between 0 and 10 m3/d is 59%. On the whole, the emission accounts for 1.53% of the gas well production. There is almost no methane emission in the single liquid phase flow stage. The methane emission in the gas-liquid two-phase flow stage is positively correlated with the bottom hole flow pressure, times of stroke and gas production, and negatively correlated with the pump embedment and water production. The bottom hole flow pressure and the pump embedment have the greatest impact on the methane emission. In the single-phase gas flow stage, methane emission is positively correlated with gas production and casing pressure, and negatively correlated with stroke frequency and water production.

Design and Analysis of a Novel 2-DOF Rotation–Translation Precision Positioning Stage

This paper presents the design, modeling, simulation, and experimental testing of a novel 2-DOF precision micro-positioning stage. A compact parallel structure is proposed and the rotation stroke of the stage is improved by reducing the rotation radius. Compared with other positioning stages, the developed stage has the advantage of large rotation stroke, compact structure, and high resonant frequency, and it can realize various positioning functions with fewer piezoelectric actuators. The simplified flexibility equation of the composite bridge mechanism was obtained through the equivalent replacement of the composite hinge, and then the transmission ratio and input stiffness analysis model of the stage are further established. Then, the simulation and experiment verify the accuracy of the model. The significant size parameters of the stage are determined according to the sensitivity analysis and verified by FEA. To decouple the rotation and translation, we establish the scale factor. The experimental results reveal that the workspace of the stage is 22.90 mrad × 95.03 μm. The step response time is 80 ms and the rotation resolution is 5 μrad under open-loop control.

Analysis and testing of internal combustion engine driven linear alternator

Introduction. Internal combustion engine technology has been considered for the alternator system in the last two decades. Especially when considering fuel diversity, reliability, portability, power density, research studies are increasing day by day. In this respect, interest has been focused on linear generator studies. Purpose. The goal of the research is to investigate the performance of a linear generator and its application to generate electrical energy from an internal combustion engine to solve the range problem of small electric powered vehicles. The generator, unlike a traditional generator, consists of a linear generator with a crank mechanism driven by an internal combustion engine. Originality. The configuration of the linear generator with internal combustion engine crank has not previously been reported. Methods. The numerical solution of the generator was carried out by the finite element method in the Ansys Maxwell software in a cylindrical coordinate system. The effect of stroke length and frequency on voltage and output power was investigated by monitoring an external electrical load. A prototype linear generator has been designed and produced considering the sizing dimensions. The configuration can be used in power-hungry applications and increase the range of small electric vehicles. Results. The results from simulation and practice are largely in agreement. Practical value. A practical mechanical system was built comprising a linear generator connected to a 2.2 kW internal combustion engine via a crank connecting rod for analysis.

Disability assessment due to stroke

Objectives: The main purpose of the study is to determine the frequency of stroke in patients who applied to the disability board. The secondary aim of the study is to determine the factors affecting disability rates in patients who applied to the disability board due to stroke. Methods: Patients over the age of 18 who applied to the physical nedicine and rehabilitation outpatient clinic for disability assessment were included in the study. Disability board files of all patients were scanned retrospectively and the information obtained was recorded. Results: It was found that 9.1% of patients who were evaluated for disability and were found to have any level of disability experienced disability due to stroke. A statistically significant relationship was found between stroke-related disability score and advanced age, female gender, and the presence of aphasia and dementia in the patients (p < 0.05). However, no statistically significant relationship was found between the type of stroke, the affected side and the stroke-related disability scores (p > 0.05). Conclusions: Stroke patients constitute a remarkable part of disability assessment. When evaluating stroke patients in terms of their disability, comorbid diseases and demographic characteristics of the patients should also be taken into consideration.

This Month in Anesthesiology

This Month in Anesthesiology

The Frequency of Ischemic Stroke Associated with Atrial Fibrillation at a Tertiary Care Hospital

Acute ischemic stroke is most commonly associated with atrial fibrillation. However, its prognostic impact on patients with acute cerebrovascular accidents is not fully clarified. Stroke associated with AF is associated with the worst outcome as compared to without atrial fibrillation. Atrial fibrillation is present in 20–30% of patients affected by stroke. Also, in Pakistan the prevalence of atrial fibrillation with ischemic stroke patients is still unknown. Objective: To determine the association of atrial fibrillation with acute ischemic stroke. Material & methods: This cross-sectional analytical study was conducted at Neurology ward of Aga Khan University Hospital, Karachi, over eight months from 19th May 2020 to 18th December 2020. A total of two hundred sixteen patients who were admitted with the diagnosis of ischemic stroke were included in the study. Results: The 216 patients with first-ever acute ischemic stroke for more than 24 hours, age range between 30 and 80 years, both male and female were included in the study. The mean systolic blood pressure SBP and diastolic blood pressure DBP was 132.64±17.68 & 84.45±15.01 & mean duration of diabetes mellitus in new onset ischemic stroke patients was 11.1±6.61years male outnumbered females, with 78(36%) women and 138(64%) men. Conclusion: In summary, it was found that incidence of atrial fibrillation with ischemic stroke is most common among Pakistani population. Bangladesh Journal of Medical Science Vol. 22 No. 01 January’23 Page : 91-96

Design and Development of a New Piezoelectric-Actuated Biaxial Compliant Microgripper With Long Strokes

In this paper, a new piezoelectric-actuated biaxial compliant microgripper with long strokes is proposed for automatically gripping and rolling tiny rigid objects. In order to improve the working stroke and maintain a compact footprint, a counter-side distributed two-stage lever amplifier with parallelogram mechanism is introduced. Based on the pseudo-rigid body model, analytical models of the displacement amplification ratio, input stiffness, and natural frequency of the left- and right-sided gripper mechanism are established. Structural optimization and performance simulation of the proposed microgripper mechanism are carried out with finite element analysis simulation. A prototype microgripper has been fabricated for open-loop and closed-loop tests to verify its working capabilities. The clamping and rubbing experiments show that the designed microgripper can grasp and rub an optical fiber with the diameter of 200 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> for rolling over 45°. The developed microgripper has a promising application in precision micromanipulation fields such as optical fiber alignment. Note to Practitioners—This work is motivated by the requirement of designing a biaxial microgripper with both a large working stroke and compact structure for complex operation in optical fiber alignment. Through a series of open-loop and closed-loop experiments on the developed prototype, it is demonstrated that the proposed dual-axis microgripper has superior working performance. The clamping stroke and rubbing stroke of the gripper are <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$251.2~\mu \text{m}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$225.0~\mu \text{m}$ </tex-math></inline-formula> , respectively. The first two natural frequencies of the gripper are 350.63 Hz and 603.37 Hz, which correspond to the working modes of the right-side and left-side gripper mechanisms, respectively. The closed-loop experimental results show that the resolution of output displacement of the gripper is close to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.2~\mu \text{m}$ </tex-math></inline-formula> and the resolution of the clamping force is 3 mN. As compared with the reported microgrippers in previous work, the designed mechanism exhibits both a large working stroke and high resonant frequency for ensuring the reliability and rapidity of micromanipulation task.

A new risk factor for predicting stroke in patients with atrial fibrillation: morning blood pressure surge.

Stroke, the most feared complication in patients with atrial fibrillation (AF), is still an important cause of mortality and morbidity. In our study, we aimed to investigate the frequency of stroke and related parameters in patients with atrial fibrillation, for whom 24-h ambulatory blood pressure monitoring (ABPM) was performed. A total of 282 patients with permanent AF were included in this study. 24-h ABPM was performed in all patients. Morning blood pressure surge (MBPS) was defined as the difference between the mean SBP in the first 2 h after awakening and the lowest blood pressure (BP) at night. We evaluated parameters associated with stroke in patients with atrial fibrillation using univariate and multivariate Cox regression analysis. Patients were followed for 19 ± 9.3 months and 22 ischemic strokes were detected during the follow-up period. Also, strokes were significantly lower in atrial fibrillation patients with a dipper BP pattern, whereas strokes were significantly higher in atrial fibrillation patients with a reverse-dipper BP pattern. In multivariate analysis, a history of hypertension ( P = 0.020), BP pattern ( P < 0.001) and MBPS ( P < 0.001) were found to be significantly related to stroke. MBPS levels >32.5 mmHg predicted stroke with a sensitivity of 77% and a specificity of 60% (AUC, 0.741; 95% CI, 0.647-0.834; P < 0.001). MBPS, BP pattern and presence of hypertension as an independent risk factor in predicting stroke in patients with atrial fibrillation. The reduction of the MBPS may be a new therapeutic target for preventing stroke.

Honey bee flights near hover under ethanol-exposure show changes in body and wing kinematics.

Flying social insects can provide model systems for in-flight interactions in computationally-constrained aerial robot swarms. The social interactions in flying insects may be chemically modulated and quantified via recent measurement advancements able to simultaneously make precise measurements of insect wing and body motions. This paper presents the first in-flight quantitative measurements of ethanol-exposed honey bee body and wing kinematics in archival literature. Four high-speed cameras (9000 frames/sec) were used to record the wing and body motions of flying insects (Apis mellifera) and automated analysis was used to extract 9000 frame/sec measurements of honey bees' wing and body motions through data association, hull reconstruction, and segmentation. The kinematic changes induced by exposure to incremental ethanol concentrations from 0% to 5% were studied using statistical analysis tools. Analysis considered trial-wise mean and maximum values and gross wingstroke parameters, and tested deviations for statistical significance using Welch's t-test and Cohen's d test. The results indicate a decrease in maximal heading and pitch rates of the body, and that roll rate is affected at high concentrations (5%). The wingstroke effects include a stroke frequency decrease and stroke amplitude increase for 2.5% or greater concentrations, gradual stroke inclination angle increase up to 2.5% concentration, and a more planar wingstroke with increasing concentration according to bulk wingstroke analysis. These ethanol-exposure effects provide a basis to separate ethanol exposure and neighbor effects in chemically mediated interaction studies.

Abstract #1325490: The Frequency of Stroke in Patients with Diabetes Mellitus During Fasting Ramadan Compared to the Remaining Months of the Year in Khartoum State, 2017-2018

To study the frequency of stroke in patients with diabetes admitted during the month of Ramadan compared to the other months of the year. We sought to determine the frequency of stroke in patients with DM in relation to the demographics of the population studied and to determine risk factors of stroke during the month of Ramadan as compared with the remaining months of the year.

Home ranges and diving behavior of endangered New Zealand sea lions along the Catlins coast of South Island, New Zealand

AbstractNew Zealand sea lions (NZSL, Phocarctos hookeri) were extirpated from mainland New Zealand during pre‐European subsistence hunting. They began reoccupying South Island in 1994, and the newest breeding colony arose in 2006 along the Catlins Coast on southeastern South Island and currently consists of &lt;10 individuals. The goal of this study was to use animal‐borne satellite telemeters and miniature data recorders (MDRs) to determine home ranges, three‐dimensional movements, and foraging strategy of female NZSL along the Catlins Coast during the austral winter of 2019. Total home ranges were small (97 km2) and primarily restricted to nearshore areas. Dives were shallow (8.9 m), short in duration (1.4 min), and had a mean swimming speed of 1.5 m s−1. We identified three dive types based primarily on total dive duration, mean maximum depth, total distance swam, and path linearity. The estimated at‐sea metabolic rate varied among dive types because of differences in flipper stroke frequency and swim speed. Female NZSL along the Catlins Coast have smaller home ranges and make shorter foraging trips compared with females in the Auckland Islands, and suitable habitat for breeding and prey availability along the southeast coast are encouraging for future population growth.

Abstract 14424: Comparative Evaluation of Various Risk Scores in Non-ST-Segment Elevation Myocardial Infarction

Introduction: Risk stratification is an integral component of the management strategy in patients with non-ST-elevation myocardial infarction (NSTEMI). Multiple risk scores have been proposed however, these have not been validated in developing countries such as India. Hypothesis: This study aims to determine the various prognostic factors in patients with NSTEMI as well as to compare and validate the performance of different risk stratification scores in these subjects. Methods: This was a single center prospective observational study wherein diagnosed with NSTEMI were enrolled. A detailed clinical history including symptomatology, presence of risk factors and family history were recorded. In all enrolled patients based on the prospectively collected data, five risk scores i.e. TIMI, GRACE version 2.0, PURSUIT, HEART and CAMI-NSTEMI were computed. Outcome data in terms of both in-patient as well as at 14 days, six months and one year major adverse cardiovascular events (MACE) were obtained. Results: A total of 1102 patients were enrolled with a mean age of 59.6 ± 11.2 years. MACE occurred in 140/1102 subjects (12.7%) with mortality in 89 (8.1%) patients. Patients with MACE were elderly, had higher frequency of smoking, hypertension, diabetes and stroke. Multivariate logistic regression analysis revealed that angina in last 48 hours, diabetes, smoking, cardiac arrest on presentation and fragmented QRS on ECG were independent predictors of MACE. All risk scores were able to predict MACE events equally well however, for in-hospital MACE, TIMI risk score had the highest predictive ability. However, for 14-day, 6 month and one year MACE, GRACE scores had highest predictive ability. Conclusions: Our study showed that all risk scores had a good predictive ability for both short term as well as intermediate-term MACE events.

Exposure to whale watching vessels affects dive ascents and resting behavior in sperm whales

Disturbance from whale watching can induce a wide range of behavioral responses in cetaceans, some of which can affect their energetic balance and, ultimately, their long-term fitness. However, assessing disturbance effects on deep-diving cetaceans remains challenging, as the majority of their activities occurs underwater and are difficult to monitor from surface observations. To surpass this limitation, we attached high-resolution multi-sensor tags (DTAGs) on 24 sperm whales (Physeter macrocephalus) off the Azores, an area of intense whale watching, to evaluate changes in movement and acoustic parameters related to foraging effort and dives, locomotion effort, and non-foraging behavior. These parameters were compared between periods of exposure and non-exposure to whale watching vessels, using linear mixed-effect models to assess the presence of short-term effects, accounting for individual differences in behavior. We found no significant changes in foraging effort (number of buzzes, bottom phase depth, proportion of search and foraging phases) and overall dive behavior (dive duration, proportion of dive phases, and descending or ascending pitch) between non-exposure and exposure periods. In contrast, variation in body pitch during non-foraging periods increased during exposure but not variation in body roll. Taken together, these results suggest increased movements during resting activity, which may carry energetic costs to whales and impact their health. Vertical velocity during ascents was also significantly higher in response to vessel exposure, suggesting that sperm whales increased the frequency of fluke strokes, which was consistent with a higher Overall Dynamic Body Acceleration (ODBA) during ascents, incurring in higher energy expenditure. If the detected changes are repeated across multiple exposures, they might affect the individual’s energetic budget, and consequently their fitness. Our study contributes to a better understanding of the short-term behavioral responses of sperm whales to whale watching vessels and highlights the need for further studies examining the potential consequences from repeated disturbance to individuals.

Features of etiopathogenetic factors and course of stroke after coronavirus infection

Disorder of coronary circulation is one of the most severe complications of COVID‑19. Strokes that develop against the background of coronavirus infection are more often associated with occlusion of large vessels and have a more severe course. The frequency of strokes associated with COVID‑19, according to different authors, ranges from 1 to 6 %.Objective. To analyze the etiopathogenetic factors, the course of stroke after a coronavirus infection, and to analyze the possible relationship between the severity of COVID‑19 and the severity of stroke.Materials and methods. Observation of 110 patients of the neurological department of the First Republican Clinical Hospital of Udmurtia for the period from 2020 to 2021 with confirmed ischemic or hemorrhagic stroke associated with COVID‑19. Statistical data processing was carried out in Microsoft Excel 2013, MedCalc.Results. Hypertension, atherosclerosis, and cardiac arrhythmia predominated in the structure of comorbidities in the examined patients. In 88.0 % of cases, ischemic stroke was observed in patients after infection, mainly the lesion concerned the carotid basin (55.5 %). Patients more often had focal neurological symptoms, among which hemiparesis and hemiplegia prevailed. Features of the results of laboratory diagnostics is the presence of coagulopathy, renal and hepatic insufficiency: increased levels of fibrinogen, D-dimers, creatinine, urea, proteinuria. According to neuroimaging data, in 54.5 % of cases, the stroke focus was more than 15 mm; duplex scanning of vessels in 95.0 % of cases revealed signs of atherosclerosis of the brachiocephalic arteries, carotid arteries in 54.5 % of cases. Correlation analysis revealed the relationship between the severity of COVID‑19 and the clinical manifestations of stroke. Most of the strokes occurred in the subjects within 1–6 months (40.9 %) after suffering COVID‑19.Conclusion. In the development of stroke after suffering COVID‑19, coagulopathy, renal liver failure, cardiovascular comorbidities, especially hypertension, and atherosclerosis play a significant role. Stroke severity is correlated with the severity of COVID‑19.

Cerebrovascular disease and mortality in hospitalized patients with COVID-19 in a Latin American country, Peru.

Objective: This study aimed at: 1) Assessment of the frequency of stroke and related mortality rate in patients hospitalized for COVID-19 in two major hospital referral centers in Peru; 2) Exploration of factors associated to mortality and dependency in these patients; 3) Comparisons of frequency of admissions of stroke patients and reperfusion treatments in similar periods of time prior to (2019) and during the pandemia occurrence. Material and Methods: A retrospective cohort study was conducted in two of the largest referral hospital centers for COVID-19 in Peru. The study included patient victims of stroke and COVID-19, hospitalized between April and August 2020. Demographic, clinical and laboratory data, radiological findings, and severity levels measured by the NIHSS scale were collected. Poisson regression models to evaluate associated factors to mortality and dependency were applied. Results: A 31% reduction of admissions for stroke, and of 81% of intravenous reperfusion treatment, respectively, were found in 2020 when compared with 2019. 1.37% of the patients with COVID-19 experienced a stroke, with an overall mortality rate of 40.6%, and a dependency rate of 68.3% at discharge time (Rankin &gt; 2). An age increase of 10 years was found in mortality, associated with a 29% increase in mortality risk. As well, having hypertension, chronic kidney disease, inflammatory markers (D dimer and ferritin) and the severity of the stroke were associated with mortality. Finally, the severity of stroke, lymphopenia, and inflammatory markers (D dimer and fibrinogen) were associated with greater risk of dependency. Conclusions: The care system of stroke patients was affected by the COVID-19 pandemic in two of Perú’s major public hospitals. There was a decrease in admissions and reperfusion treatments of stroke cases, and 1.37% of patients with COVID-19 presented a stroke. Age, hypertension, chronic kidney disease, inflammatory markers and severity of stroke were associated with mortality in these patients.

Atrial Cardiomyopathy and Cryptogenic Stroke

Background The frequency of cryptogenic stroke (CS) is about 30% of all cases of ischemic stroke (IS). Patients with CS represent a heterogeneous group of patients and require an individualized approach to antithrombotic therapy for secondary prevention. The frequency of development of repeated acute cerebrovascular events in patients with CS is 4.5% per year, which exceeds this indicator in patients with an established pathogenetic variant of IS. Until recently, the dominant point of view, suggesting that the main cause of CS is paroxysmal atrial fibrillation (AF) and for the secondary prevention of IS in this cohort of patients, oral anticoagulants may be more effective than antiplatelet agents, has not been confirmed. The causal relationship between IS and AF is currently not fully understood. Apparently, AF serves as a marker of atrial cardiomyopathy, which is the direct cause of IS. Aim of study Raising the awareness of neurologists about the causes, pathogenetic mechanisms of development and methods for diagnosing IS in patients with atrial cardiomyopathy. Material and methods To achieve this aim, the results of scientific studies on atrial cardiomyopathy as a risk factor for CS were analyzed. The literature search was carried out in electronic search systems Scopus, eLibrary, PubMed using the keywords: ischemic stroke, cryptogenic stroke, atrial cardiomyopathy, pathogenesis of ischemic stroke. Scientific articles published between 1957 and 2021 were selected to be analyzed. And 36% of the analyzed papers on the topic of CS were published no more than 5 years ago. Conclusion The cumulative evidence suggests that atrial fibrillation is not the only cause of embolic events in patients with evidence of atrial dysfunction. Atrial cardiomyopathy can be the cause of thromboembolic syndrome and cryptogenic stroke, even in the absence of atrial fibrillation, therefore, the latter should be considered as a common manifestation of the underlying atrial cardiomyopathy. Since the majority of cardiac thrombi in patients with atrial fibrillation originate in the left atrium, it is likely that patients with atrial cardiomyopathy and cryptogenic stroke represent a group of patients who may be indicated for anticoagulant therapy as a secondary prevention of ischemic stroke and systemic embolism. However, this hypothesis needs to be confirmed.

Preoperative β-Blocker Therapy and Stroke or Major Adverse Cardiac Events in Major Abdominal Surgery: A Retrospective Cohort Study.

Perioperative β-blocker therapy has been associated with increased risk of stroke. However, the association between β-blocker initiation before the day of surgery and the risk of stroke is unknown. The authors hypothesized there would be no association between preoperative β-blocker initiation within 60 days of surgery or chronic β-blockade (more than 60 days) and the risk of stroke in patients undergoing major abdominal surgery. Data on elective major abdominal surgery were obtained from the IBM (USA) Truven Health MarketScan 2005 to 2015 Commercial and Medicare Supplemental Databases. Patients were stratified by β-blocker dispensing exposure: (1) β-blocker-naïve, (2) preoperative β-blocker initiation within 60 days of surgery, and (3) chronic β-blocker dispensing (more than 60 days). The authors compared in-hospital stroke and major adverse cardiac events between the different β-blocker therapy exposures. There were 204,981 patients who underwent major abdominal surgery. β-Blocker exposure was as follows: perioperative initiation within 60 days of surgery for 4,026 (2.0%) patients, chronic β-blocker therapy for 45,424 (22.2%) patients, and β-blocker-naïve for 155,531 (75.9%) patients. The unadjusted frequency of stroke for patients with β-blocker initiation (0.4%, 17 of 4,026) and chronic β-blocker therapy (0.4%, 171 of 45,424) was greater than in β-blocker-naïve patients (0.2%, 235 of 155,531; P < 0.001). After propensity score weighting, patients initiated on a β-blocker within 60 days of surgery (odds ratio, 0.90; 95% CI, 0.31 to 2.04; P = 0.757) or on chronic β-blocker therapy (odds ratio, 0.86; 95% CI, 0.65 to 1.15; P = 0.901) demonstrated similar stroke risk compared to β-blocker-naïve patients. Patients on chronic β-blocker therapy demonstrated lower adjusted risk of major adverse cardiac events compared to β-blocker-naïve patients (odds ratio, 0.81; 95% CI, 0.72 to 0.91; P = 0.007), despite higher unadjusted absolute event rate (2.6% [1,173 of 45,424] vs. 0.6% [872 of 155,531]). Among patients undergoing elective major abdominal surgery, the authors observed no association between preoperative β-blocker initiation within 60 days of surgery or chronic β-blocker therapy and stroke.

The impact of mitral regurgitation on the incidence of stroke in patients with atrial fibrillation

Abstract Background Stroke is a significant cause of mortality and a leading cause of disability in elderly patients. Atrial fibrillation (Af) is the most common cardiac disease with assumed embolic stroke. Therefore, patients with Af need anti-coagulant therapy with a Warfarin (vitamin K antagonist) or a DOAC (Direct Oral Anti-Coagulant), also considering the risk and benefit net balance. It has been suggested that significant mitral regurgitation (MR) and its vortex jet in the left atrium might reduce embolic stroke source in patients with Af. However, the effect of MR on the risk of stroke in patients with Af is still controversial. Therefore, we hypothesized whether MR might be associated with a lower risk of thromboembolic events in patients with Af. Purpose This study aims to investigate whether MR was associated with a decreased risk of stroke in patients with Af, especially in the elderly population. Methods We studied 1,714,955 patients in the LIFE Study database, comprising Japanese claims data for public insurance policyholders between 2014 and 2020. We identified 51,939 patients with new-onset Af. Among them, patients with pre-existing stroke patients (N=28,519) were excluded, and new-onset Af patients without stroke (N=23,420) were obtained. Based on the baseline information, the Af patients were stratified into the MR group (N=3,439) and Without-MR group (N=19,981). Propensity score matching (the nearest neighbor method with a caliper of 0.2) was performed to balance baseline features and stroke risk factors between the MR group (N=3439) and the Without-MR group (N=3439). Propensity scores were estimated using logistic regression with age, sex, and all factors in Elixhauser's comorbidity system. The incidence rate of the stroke (events per person-year) was calculated by the event numbers divided by the overall period for the observations months × 12. Kaplan-Meier curves of stroke-free survival were generated, and the two groups' comparisons were performed using the log-rank test. Results As expected, patients' characteristics were comparable between the two groups. The observation period was 3 years for both groups. In the MR group, 136 patients with stroke were detected. On the other hand, 122 patients with stroke were detected in the Without-MR group. The incidence rate of the stroke per person-year was 0.027 and 0.025 events per person-year in patients with the MR and Without-MR groups. In addition, the Kaplan-Meier analysis showed that the incidence rate of stroke was comparable between the two groups (P=0.43). Conclusions The frequency of stroke in patients with atrial fibrillation was similar, despite mitral regurgitation. Therefore, patients with atrial fibrillation should have anti-coagulation therapy, regardless of the presence or absence of mitral regurgitation. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): This work was supported by grants provided by the Japan Science and Technology Agency (JST) Fusion Oriented Research for disruptive Science and Technology (FOREST) Program (Grant Number: JPMJFR205J) and the Japan Society for the Promotion of Science (JSPS) Grants-in-Aid for Scientific Research (KAKENHI) Program (Grant Numbers: JP20H00563 and JP19K21590).

A Novel Compliant Nanopositioning Stage Driven by a Normal-Stressed Electromagnetic Actuator

This article reports on the design, modeling, control, and testing of a novel compliant nanopositioning stage driven by a self-developed normal-stressed electromagnetic actuator. To facilitate the parameter selection for the stage to achieve the desired stroke and natural frequency, an analytical model of both the electromagnetic circuit and flexure mechanism is established, which is then systematically verified through finite element analysis. By combining a proportional—integral—differential (PID)-based main controller with a system dynamics inversion-based feedforward compensator, a closed-loop control system for the stage is constructed with the main controller being tuned through Bode’s ideal transfer function-based loop-shaping method. The experimental result shows that a stroke of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\pm } 95 ~\mu \text{m}$ </tex-math></inline-formula> and a first natural frequency of 743 Hz are achieved for the designed stage. Finally, taking advantage of the constructed control system, the nanopositioning capability is demonstrated by finely tracking the harmonic and nanostair commands. Note to Practitioners—Piezoelectric actuators (PEAs) and voice coil motors (VCMs) are commonly adopted for the actuation of nanopositioning stages. In general, constrained by the inherent small strain, PEA is more suitable for the generation of dynamic motions in dozens of micrometers. Meanwhile, VCM has a theoretically infinite motion range but a slow response due to its low force density nature. Taking advantage of a newly developed normal-stressed electromagnetic actuator (NSEA), we demonstrate the design, modeling, control, and testing of an NSEA-based nanopositioning stage with a relatively long motion range, high bandwidth, and compact size. Considering the high force density and relatively large motion range only constrained by the effective air gap, the NSEA-based stage is demonstrated herein to be very promising to achieve highly dynamic motions within hundreds of micrometers.