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Electric Chaos: A Challenging Case of Atrial Fibrillation in Wolff-Parkinson-White Sy...
Ahmad Murtaza  Anwar

Ahmad Murtaza Anwar

October 08, 2024
Electric Chaos: A Challenging Case of Atrial Fibrillation in Wolff-Parkinson-White Syndrome.
TITLE: Unexpected Complication: Granulomatous Inflammation at the Tattoo Site in a 22...
Muhammad Usama bin  Shabbir
Faryal Afridi

Muhammad Usama bin Shabbir

and 4 more

October 08, 2024
•Title:Unexpected Complication: Granulomatous Inflammation at the Tattoo Site in a 22-Year-Old Male
Navigating Emerging Contaminants: An In-Depth Review of Sources, Risks, and Remediati...
Vidiksha Singla
Shanvi Rana

Vidiksha Singla

and 4 more

October 08, 2024
not-yet-known not-yet-known not-yet-known unknown Water contamination through ECs is increasingly troublesome because of enhanced urbanization, industrialization, and agricultural practices. ECs are uncontrolled anthropogenic chemicals found primarily in airborne contaminants, soil, water, food, and human/animal tissues. This category includes a wide range of pollutants, consisting of pesticides, pharmaceuticals, pills, cosmetics, personal care products, surfactants, industrial chemical compounds, cleaning agents, food packaging substances, metalloids, food additives, nanomaterials, microplastics, rare earth elements and pathogens. The number one resources of ECs include household discharges, industrial wastewater, agricultural runoff, cattle and aquaculture operations, hospital effluents and landfill leachates. These contaminants can persist in the environment for prolonged intervals, inflicting adverse consequences to human health, flora and fauna and ecosystems. To cope with the challenges posed via ECs, numerous degradation and removal strategies have been investigated, such as physical, chemical, and organic methods. This review paper gives a comprehensive assessment of ECs, detailing their sources, regulatory status, and identity technologies. It also evaluates latest improvements in treatment technologies for EC elimination, highlighting the effectiveness and barriers of different physical, chemical, and biological strategies. By means of consolidating cutting-edge research, this paper objectives to enhance knowledge of EC management and offer insights into future studies to improve treatment tactics and mitigate the dangerous effects of these contaminants.
BJOG mini commentary on Systematic review of clinical prediction models for the risk...
Hala Eldamanhoury

Hala Eldamanhoury

October 08, 2024
A document by Hala Eldamanhoury. Click on the document to view its contents.
Multiple introductions of the Asian Longhorned Tick (Haemaphysalis longicornis) to th...
Zoe Narvaez
Andrea Egizi

Zoe Narvaez

and 28 more

October 08, 2024
not-yet-known not-yet-known not-yet-known unknown The Asian longhorned tick (ALT), Haemaphysalis longicornis, is a three-host hard tick native to East Asia. Its opportunistic feeding habits make it an acute agricultural and medical threat, capable of spreading various zoonotic pathogens. An affinity for livestock and companion animals has allowed parthenogenetic populations of ALT to travel to and establish in overseas locations including the United States. To better understand the population dynamics of this rapidly expanding species, we sequenced the complete mitogenome of specimens collected from native and invasive ranges and performed phylogeographic analyses. As well as illustrating the diversity of Australasian and US ALT haplotypes, these methods have allowed us to estimate the source and frequency of successful introductions to the US. We highlight four potential introductions of parthenogenetic ALT, with likely origin populations identified in the Republic of Korea and Japan. These findings provide insight into potential routes of entry for ALT and other invasive tick species.
Linked expression of genes associated with the circadian clock and behavioral plastic...
Biplabendu Das
Deborah Gordon

Biplabendu Das

and 1 more

October 08, 2024
not-yet-known not-yet-known not-yet-known unknown The expression of circadian clock genes shifts with changes in behavior. We examined the association of clock genes and those associated with behavioral plasticity in the diurnal, desert harvester ant, Pogonomyrmex barbatus and in a distantly related, tropical nocturnal species, Camponotus floridanus. A comparison of daily transcriptome in light-dark (LD) and total dark (DD) of ants in a laboratory colony of P. barbatus showed that most genes were expressed in both LD and DD at about the same level, while 460 genes were expressed only in LD, including many associated with olfaction and juvenile hormone signaling. Network analysis identified eleven modules of co-expressed genes under LD conditions; one module (C2) contained most of the clock-controlled genes that show circadian expression in both LD and DD, including Period and Clock. The clock-controlled genes in module C2, and in another neighboring module (C1) with circadian rhythms in DD only, showed significant overlap with those found in previous work to be associated in P. barbatus with plasticity in the regulation of foraging activity to manage water loss. The set of genes expressed in the ant brains with 24h rhythms were similar in P. barbatus and C. floridanus. The P. barbatus modules C2 and C1 showed a strong overlap with C. floridanus genes previously shown to differ in their periodicity of daily rhythms in nurses and foragers. The results suggest that genes associated with both circadian clock and behavioral plasticity may be broadly conserved in ants.
A Coupling Coordination Framework for Identifying the Balanced Development State betw...
Yixin Fang
Fanao Meng

Yixin Fang

and 5 more

October 08, 2024
not-yet-known not-yet-known not-yet-known unknown The spatiotemporal differences between ecosystem services (ES) and human activities pose significant challenges to the coordinated development of human-earth systems, particularly in China’s Beijing-Tianjin-Hebei-Inner Mongolia (JJJM) region. However, a clear understanding of the changing relationship between the coupling and coordination of ES and human activities remains lacking. This study uses an adjusted ecosystem services matrix to calculate ES supply, demand, and balance, and develops a human activity intensity index (HAII) based on factors like nighttime light and grazing intensity. Then, methods such as Moran’s I and the Coupling Coordination Degree framework are employed to analyze the spatiotemporal evolution, coupling coordination relationship of ES supply, demand, balance, and HAII at regional, provincial, and grid scales between 2000 and 2020. The result reveals that over the past 20 years, ES supply in the region has increased, while ES balance first increased and then decreased. Concurrently, HAII has shown a continuous upward trend, indicating that the intensification of human activities may have contributed to the decline in ES balance. A bivariate local Moran’s I test result show that there is indeed a significant trade-off (-0.23) between ES balance and human activity intensity. Coupling coordination analysis shows over 86% of the region has a coordination degree below 0.7, indicating Barely Balanced Development. The coordination degree in the JJJM region is declining, with Tianjin seeing the most significant drop. Further study indicates that forests and grasslands contribute positively to ecosystem balance, accounting for over 88% of the cumulative contribution. Therefore, in the future development of regional space, timely replenishment of forest and grassland is the only way to maintain the harmony of human-earth systems. This study deepens the understanding of the relationship between ecosystem service balance and human socioeconomic activities and provides valuable insights for ecological compensation policies in the context of urban-rural integration.
Ghosal Type Hematodiaphyseal Dysplasia- A rare and unusual cause of cytopenias
Sirisha Siddaiahgari
A.K. Veena

Sirisha Siddaiahgari

and 1 more

October 08, 2024
Ghosal Type Hematodiaphyseal Dysplasia (GHDD) is an autosomal recessive disorder characterized by metadiaphyseal dysplasia, defective hematopoiesis and steroid sensitive anemia. The diagnosis of this rare syndrome is important as early diagnosis helps in initiation of treatment leading to improvement in anemia and bony changes. Herein, we report two cases where the diagnosis was confirmed by mutation analysis. Treatment typically involves steroid therapy. Both our cases were started on steroids after which haemoglobin & other counts have normalized.They need very low dose steroids to maintain normal hemoglobin and counts.
Neuroinflammation in Alzheimer’s Disease: Mechanistic Insights, Pathological Implicat...
Majd A.AbuAlrob

Majd AbuAlrob

October 08, 2024
Neuroinflammation is increasingly recognized as a pivotal factor in the pathogenesis of Alzheimer’s disease (AD), a neurodegenerative disorder characterized by amyloid-beta plaques and tau neurofibrillary tangles. Traditionally viewed as a secondary response to neuronal damage, recent research suggests that neuroinflammation actively contributes to both the initiation and progression of AD. Key mediators of neuroinflammation are glial cells, particularly microglia and astrocytes. When persistently activated, these cells release pro-inflammatory cytokines such as interleukin-1β (IL-1β) and tumor necrosis factor-alpha (TNF-α), exacerbating neuronal injury and promoting cognitive decline. Additionally, dysfunction of the blood-brain barrier permits peripheral immune cells to infiltrate the central nervous system, amplifying the inflammatory response and accelerating disease progression. The intricate interplay between neuroinflammation and AD pathology underscores the potential of targeting inflammatory processes as a therapeutic strategy. Current approaches involve anti-inflammatory agents, modulation of microglial activation states, and lifestyle interventions aimed at reducing systemic inflammation. Emerging therapies focus on targeted interventions, including monoclonal antibodies against pro-inflammatory mediators and inhibitors of inflammasome activation. Nonetheless, significant challenges remain, such as delineating the precise mechanisms by which neuroinflammation influences AD pathology and identifying optimal timing for therapeutic intervention. Addressing these challenges is critical for advancing treatment options by mitigating the detrimental effects of chronic neuroinflammation on neurodegeneration. Future research should concentrate on elucidating the mechanistic pathways of neuroinflammation in AD, developing targeted anti-inflammatory therapies, and enhancing early diagnostic capabilities through reliable biomarkers, ultimately aiming to alleviate the profound impact of this debilitating disease.
Empirical relation for a solar air heater with an equilateral triangular duct roughen...
Hadeel A. Hamed
Ammar Farhan

Hadeel A. Hamed

and 1 more

October 08, 2024
A practical and environmentally friendly way to harness solar energy is through solar air heaters (SAHs). Various techniques to enhance heat transfer have been explored to boost the thermal efficiency of SAHs. The present experimental work examined the impact of dimpled rib coarseness on the performance of a SAH with an equilateral triangular duct. Experiments were conducted under various operating conditions, including relative roughness height (e/D) ranging from 0.023 to 0.058, relative roughness pitch (L/e) from 3 to 9, relative roughness width (S/e) from 6 to 18, and Reynolds numbers from 6000 to 18000. The improvement in Nusselt number (Nu) and friction factor ( f) over a flat surface under similar operating and flow conditions has been performed. Experimental findings showed that the SAH equipped with dimple ribs achieved higher heat transfer rates compared to traditional SAH. The maximum improvement in Nu, f is 5.78, and 2.26, respectively, greater than that of a smooth SAH. The best value of performance enhancement criteria (PEC) is 4.64 which is found at e/D of 0.058, L/e of 3, and S/e of 6. The experimental findings have been used to derive empirical correlations for Nu and f .
Significant abundance of viable flagellated bacteria and expression of flagellin-sign...
Nontlantla J. Haindongo
L. Mapaseka Seheri

Nontlantla J. Haindongo

and 2 more

October 08, 2024
Bacterial flagellin, a potent intestinal innate immune activator, prevents murine rotavirus (RV) infection independent of adaptive immunity. The flagellin-induced immunity is mediated by Toll-like receptor (TLR5) and Nod-like receptor C4 (NLRC4), which elicit the production of interleukins 22 (IL-22) and IL-18, respectively. Here, we assessed whether a high abundance of flagellin at the time of vaccination would negatively affect the RV vaccine take. Fecal samples were collected from infants at 7 days post first dose of Rotarix vaccination to establish (a) vaccine shedders (n = 50) and (non-shedders (n = 44). QPCR was used to assay the abundance of flagellin and expression of flagellin-encoding fliC, TLR5, NLRC4, IL-22 and IL-18 genes. There was no difference in abundance of flagellin between vaccine shedders and non-shedders ( p = 0.15). However, the expression of FliC was increased 7.5-fold in non-shedders versus shedders ( p = 0.001). Similarly, TLR5 ( p = 0.045), and not NLRC4 ( p = 0.507,) was significantly expressed in non-shedders versus shedders. The expression of IL-22 ( p = 0.054), and not IL-18 dependent NLRC4 ( p = 0.650), was increased 3.4-fold in non-shedders versus shedders. Collectively, our observations suggest that the abundance of viable flagellated bacteria at the time vaccination can negatively impact the performance of RV vaccines.
Ransomware Detection Using LSTM Networks and File Entropy Analysis: A Sequence-Based...
Samuel Kiyol

Samuel Kiyol

and 5 more

October 08, 2024
Ransomware attacks have rapidly escalated, posing a significant threat to both individuals and organisations by encrypting critical data and demanding substantial ransoms. A novel approach to detecting ransomware is proposed, which combines the sequential learning capabilities of Long Short-Term Memory (LSTM) networks with entropy-based analysis to capture the distinct behavioral patterns that emerge during ransomware encryption. The integration of these two techniques allows for a more adaptive detection system that can identify previously unseen ransomware strains based on their dynamic alterations of file entropy. The model's performance was rigorously evaluated across multiple ransomware families, demonstrating high levels of accuracy, precision, and recall. While some challenges were observed, particularly in cases involving stealthy encryption strategies or minimal entropy fluctuations, the overall system proved highly effective in detecting ransomware attacks before significant damage occurred. The results indicate that LSTM networks, when paired with entropy analysis, offer a promising avenue for enhancing ransomware detection and providing an advanced solution to mitigate evolving cybersecurity threats.
Feature Selection using Teaching-Learning-Based Optimization Algorithm for Classifica...
Ali (GHOUL)

Ali (GHOUL)

October 08, 2024
This paper investigates feature selection for data dimensionality reduction in the binary classification of high-resolution remote sensing images. For this aim, a Teaching-Learning-Based Optimization (TLBO) algorithm is used within a wrapper feature selection (WFS) framework to pick the optimal features for the classification. In this work, the TLBO is used in conjunction with the support vector machine (SVM) classifier to constitute a machine learning paradigm. Compared to other evolutionary optimization algorithms, the proposed TLBO framework is characterized by less computational effort and no algorithm-specific parameter requirements. In the end, experimental tests are conducted to show the effectiveness of the proposed TLBO-based WFS approach by using multi-spectral data from Earth Observing-One Advanced Land Imager. The comparative results demonstrate the advantages of the proposed TLBO algorithm in achieving high classification accuracy in comparison to the genetic algorithm (GA) and particle swarm optimization (PSO).
Enhancing Stability: Novel Control Techniques for Two-Wheeled Self-Balancing Robots
Vinod Kumar P
Kamala Narayanan

Vinod Kumar P

and 3 more

September 26, 2024
The article focuses on developing a TWSBR (Two-Wheeled Self-Balancing Robots) controller aimed at enhancing the performance of underperforming robotic systems, particularly in maintaining stability and precision during movements. It underscores the importance of a novel control approach to address specific performance metrics such as balance, agility, and responsiveness. The paper outlines the establishment of a non-linear system model to capture the intricate dynamics of robotic movements. It briefly discusses the incorporation of non-linearity within the model, potentially involving factors like frictional forces or dynamic load variations. This non-linear framework helps in addressing inherent complexities, thereby improving the performance of two-wheeled robotic systems, especially in scenarios requiring precise balance and regulation. The paper evaluates the performance of various controllers, such as LQR (Linear Quadratic Regulator), ANN (Artificial Neural Network), and PID (Proportional-Integral-Derivative), within the context of the TWSBR system. This analysis provides insights into the effectiveness of different control approaches in improving system stability and precision.
not-yet-known not-yet-known not-yet-known...
Rohit Agrahari
G  Chakraborthy

Rohit Agrahari

and 2 more

October 08, 2024
The pathophysiology of vitiligo is very complex. It is an autoimmunity disease that causes white patches on the skin. Basically, when we decrease the melanin production in our body, they cause the skin depigmentation. Highly sensitive C-reactive protein is a susceptible marker for the systemic inflammation in the body. Interlukins-6 and TNF-alpha are the inflammation mediators they cause systemic inflammation. Homocysteine is increased they play a vital role in the pathophysiology of vitiligo. When the nutrient deficiency then increases the level of homocysteine because they inhibit the tyrosine enzyme by binding with copper it is reversible hypopigmentation. The S100B protein is increased in the patient with vitiligo. This protein is reacted with less than 6 months in all vitiligo patients. When the rapidity increases the concentration of S100B protein in the patients they cause neuronal dysfunction and cell death. It produces pro-inflammatory cytokines that are harmful for the tissue. The neutrophil growth factor is also the factor causing the depigmentation of skin because when the person is suffering from schizophrenia, depression and other mental disorders they are also causing the depigmentation. When we decrease the vitamin D level in our body then they cause different diseases such as diabetes mellitus, rheumatoid arthritis, depigmentation, multiple sclerosis, and other diseases. It is affecting the variable immune response through receptor T or B lymphocytes and dendritic cells. The treatment of depigmentation to form a combination of vitamin D with UV light or corticosteroids is to increase the repigmentation.
Tricuspid Valve Infective Endocarditis Following Septic Abortion: A Case Report
Rebicca Pradhan
Bibek Shrestha

Rebicca Pradhan

and 2 more

October 08, 2024
Title PageManuscript type Case Report
A Case of Ischemia with Non-Obstructive Coronary Arteries (INOCA) in a non-smoker 50-...
Antonio Georgiev
Alsada Abazi

Antonio Georgiev

and 2 more

October 08, 2024
A Case of Ischemia with Non-Obstructive Coronary Arteries (INOCA) in a non-smoker 50-Year-Old Female: Diagnostic Challenges and Management StrategiesAntonio Georgiev1, Alsada Abazi1,3, Vegim Zhaku1,2,1 University Clinic of Cardiology, Ss. Cyril and Methodius University, Skopje, North Macedonia2 Faculty of Medical Sciences, Department of Physiology, University of Tetova, North Macedonia3 General Hospital “Ferid Murad”, Department of Internal Department, Gostivar, North Macedonia
Induction of labor at 39 weeks versus expectant management: a...
Charishma Bondada
Pruthwiraj Sethi

Charishma Bondada

and 4 more

October 08, 2024
Objective: To evaluate caesarean delivery rates in low-risk women who were electively induced from 39 weeks 0 day to 39 weeks 6 days in comparison to expectant management. Design: Prospective randomized control trial Setting: The study setting of Obstetrics and Gynaecology and Neonatology , All India Institute of Medical Sciences, Bhubaneswar from 2021-2022 Population: All low-risk antenatal women beyond 37 weeks of gestation visiting the outpatient department of Obstetrics and Gynecology were recruited according to inclusion and exclusion criteria. Methods: A prospective randomized controlled trial at tertiary care centre from 2021 to 2022 included 156 low-risk antenatal women, divided into two groups of 78. One group underwent elective induction at 39 weeks, while the other had expectant management after 40 weeks. Main outcome measures: We compared caesarean delivery rates and adverse perinatal outcomes. Results: We randomly assigned 87 participants to each group and analysed data from 78 in each at the conclusion of the study. Caesarean delivery rates were 41% in the elective induction group and 51.3% in the expectant management group, showing no statistically significant difference (p = 0.199). A higher occurrence of meconium-stained amniotic fluid was noted in the expectant management group (p = 0.032), while other adverse perinatal outcomes showed no significant differences. Author’s conclusions: It showed that elective induction of labor reduces caesarean delivery rates and positively impacts the overall pregnancy experience for mothers. It can be considered advantageous for mother to opt for induction of labour rather than waiting for it to commence naturally for better anticipation and preparation of perinatal outcomes.
Naked Ambitions: Undressed To Impress Nudism & Identity In Nigeria
Dr. Nahna James

Dr. Nahna James

October 08, 2024
This study explores the relationship between identity and nudism in Nigeria, a phenomenon often associated with Western civilizations. It examines the complexities of nudism and its impact on identity in Nigeria, focusing on social media, cultural views, community dynamics, and legal frameworks. The research uses qualitative methods like thematic analysis and interviews to reveal the complexity of nudist activities and the challenges faced by Nigerian nudist groups. The findings reveal that freedom of expression, cultural, religious, and personal convictions influence nudism in Nigeria. Lobbying for legal recognition and preservation of nudist rights, breaking social taboos, and fostering inclusivity is crucial. The study also highlights the intersection of gender, sexual orientation, and spirituality with nudism. The findings contribute to a more comprehensive understanding of nudism and its role in defining identity within Nigerian society.
BARE TRUTHS: THE ART OF BEING A NUDIST IN SAINT LUCIA
Dr. Nahna James

Dr. Nahna James

and 4 more

October 08, 2024
Historically, nudism has been rooted in the very active struggles across Western societies for personal freedom and going back to one's natural state but there is something unique in this practice in the Caribbean region, particularly in Saint Lucia. This study examines the different dimensions of nudism as a practice in Saint Lucia and relates it to the historical context and culture of the island nation. Given the context of Saint Lucia having the effects of colonialism, African people and Christian beliefs, nudism in this context is more than just a lifestyle-it is a weaving of one's identity amidst social expectations of decency and traditional views on women's positions in the society. However, in a Western context, nudism is often characterized as a movement of free and public self-expression characterized with group living, whereas in Saint Lucia it is rather subtle, restrained. Aside from a few exceptions as pointed out in the publication 'The Nude Caribbean: Exploring Nudist Culture in the Tropics', people are not free to nude in the streets in St. Lucia due to the law as well as the beliefs of the culture. The island nudists, on the other hand, need to contend with the new order in the form of
Storage Capacity Enhancement of SSD-based Image Deduplication
Berhe, Yowhannes kifle

Berhe Yowhannes Kifle

and 1 more

October 11, 2024
As Cyber Physical Systems (CPSs), notably autonomous vehicles, generate increasing volumes of image-based data, efficient storage solutions become paramount. Leveraging high-density white-box SSDs and tailored data deduplication techniques presents a promising approach. However, conventional deduplication methods are ill-equipped to handle image file characteristics effectively, while existing image-specific solutions like imgDedup have limitations in format support and SSD integration. To address these challenges, we propose an SSDbased Approximate Image Deduplication (AID) system. SSD-AID comprises an image-customized deduplication, called AID, and an SSD-aware Image Consolidation. AID combines exact and approximate matching methods, along with optimized content compression, to enhance deduplication efficacy while integrating seamlessly with white-box SSDs. Furthermore, our SSD-aware Image Consolidation optimizes flash page utilization by grouping images based on access frequencies. Experimental results across multiple datasets demonstrate significant improvements in deduplication ratio and SSD page utilization. SSD-AID offers a comprehensive solution for efficient image data management in CPSs, addressing challenges in large-scale storage utilization and minimizing unused space.
Mismatch negativity response declines with age in human beings
Florian Schmidt
David Mißler

Florian Schmidt

and 5 more

October 08, 2024
In the early stage of presbyacusis, patients often experience reduced speech perception in noisy environments despite normal audiometry, a condition known as ‘hidden hearing loss’. Diagnostic indicators like reduced amplitude of the ABR wave I, elevated hearing thresholds in the extended high-frequency range and decreased middle ear muscle reflex amplitudes aims to identify biomarkers for peripheral auditory pathology but remain inconsistent. Mismatch negativity (MMN) is a cortical auditory evoked potential generated when the brain detects sound changes. This study aimed to assess MMN as a diagnostic tool for hidden hearing loss in adults. Seventy-three subjects with normal hearing underwent an extended pure-tone audiogram examination ranging from 0.125 to 16 kHz and a subsequent MMN assessment with 2 different stimuli: two verbal (ba/da) and two non-verbal stimuli (1/2 kHz). The MMN’s amplitude and latency were measured and analyzed. A significant age-related effect on the MMN amplitude in the speech condition was found (χ² = 13.0, p = 0.002). Additionally, no further effects of age were observed on the cortical potentials examined. Also, no significant influence of EHT on the amplitude or latency of either the MMN or the P300 was detected in both the tone and speech paradigms. Thus, EHFT was used as an indirect biomarker to detect pathology, specifically cochlear synaptopathy, in the peripheral auditory system, but it is not suitable for detecting changes in the central auditory system. The amplitude of MMN, however, can be used to detect early pathological changes in the central auditory system.
”Evaluation of Postpartum Hemorrhage Management in the Dominican Republic: A Cross-Se...
Yotin Ramón Pérez D.

Yotin Ramón Pérez D.

October 08, 2024
Objective: To evaluate postpartum hemorrhage (PPH) management in the Dominican Republic and analyze clinical training and available resources in maternal health contexts. Design: Cross-sectional study. Setting: Public and private hospitals in the Dominican Republic. Population: 500 obstetricians and gynecology residents. Methods: A survey assessing PPH management practices, resource availability, and training was administered to participants. Descriptive statistics were used to analyze the data. Main Outcome Measures: Clinical training in obstetric emergencies, availability of resources for managing PPH, and the role of multidisciplinary care. Results: 45% of respondents reported inadequate training for PPH management. Only 30% had access to Bakri balloons, and 60% used oxytocin as the first-line uterotonic. 80% emphasized the importance of a multidisciplinary approach. Conclusions: Significant gaps in clinical training and access to critical resources for PPH management were identified in the Dominican Republic. Addressing these gaps is essential to reducing maternal mortality rates.
Robust Instability Analysis of Discrete-Time LTI Systems via Phase Change Rate Maximi...
Kao Chung-Yao
Sei Zhen Khong

Kao Chung-Yao

and 3 more

October 08, 2024
The problem of phase change rate (PCR) maximization for discrete-time transfer functions is examined and shown to facilitate the search for a minimum-norm stable controller to stabilize an unstable system — an effort that is closely related to robust instability analysis. The latter arises in the study of sustained oscillatory phenomena in nonlinear systems and other practical applications. This paper formulates the PCR maximization problem for discrete-time systems subject to constraints at the unique peak gain frequency, and provides a step-by-step solution to the problem. A first-order all-pass function is shown to be the optimal solution to PCR maximization and can be viewed as the worst-case strongly stabilizing perturbation, thereby providing a sufficient condition for determining the robust instability radius — an effective measure of instability — of an unstable system. Two real-world applications are presented to illustrate the utility of our results. The first is the strong stabilization of a magnetic levitation system using a minimum-effort digital controller for improved energy efficiency. The second involves quantifying the robustness of the oscillatory behavior associated with neural spike generations in the FitzHugh–Nagumo model subject to perturbations.
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