Search Results (6)

Prestressed concrete (PC) continuous beam bridges are widely used in transportation infrastructure. However, their construction involves substantial material consumption, raising sustainability concerns amid increasing environmental pressures. This study aims to address the urgent need for resource-efficient bridge design by developing a comprehensive optimization framework that minimizes material usage while ensuring structural safety, durability, and compliance with engineering standards. The proposed methodology integrates a Genetic Algorithm (GA) with a Backpropagation (BP) neural network to optimize both the cross-sectional geometry and the overall alignment of PC continuous beam bridges. The GA is utilized to identify optimal cross-sectional parameters within regulatory constraints, while the BP neural network, trained on extensive design data, refines the bridge bottom height profile to enhance structural performance. The integrated GA-BP framework is validated through a case study of a continuous beam bridge, demonstrating a 94% improvement in design efficiency, a 14% reduction in concrete consumption, and a 34% reduction in prestressed steel usage during the preliminary design stage. These results highlight the framework’s significant potential in advancing sustainable and intelligent bridge design, offering a novel approach to combining artificial intelligence with structural optimization for practical engineering applications. Full article

Background: Acute ischemic stroke (AIS) is a leading cause of mortality and long-term disability worldwide, with upper-middle-income countries (UMICs) facing a disproportionate burden due to systemic inefficiencies in healthcare delivery. Kazakhstan reports the highest global age-standardized mortality rate from ischemic stroke, underscoring the need to evaluate current stroke care practices and identify areas for improvement. Objective: This study aimed to assess the current state of acute ischemic stroke care in Kazakhstan by examining key time metrics, protocol adherence, and the utilization of advanced technologies such as artificial intelligence (AI) and telemedicine. Additionally, this study sought to identify regional disparities in care and propose actionable recommendations to improve patient outcomes. Methods: A multi-center cross-sectional survey was conducted across 79 stroke centers in Kazakhstan. Data were collected from 145 healthcare professionals, including neurologists, neurosurgeons, and interventional radiologists, through a validated 23-question online questionnaire. Statistical analysis was performed to identify significant associations between variables. Results: Significant regional disparities were observed in stroke care timelines and technology adoption. Remote and rural areas experienced prolonged prehospital delays, with transport times ranging from 120 to 180 min, contributing to door-to-needle times exceeding the recommended benchmark. Urban centers with higher adoption of AI and telemedicine demonstrated faster treatment initiation and better protocol compliance. Staff training was significantly associated with improved treatment outcomes, with trained centers more likely to implement direct-to-angiography suite protocols, reducing in-hospital delays. Conclusions: Addressing acute ischemic stroke care disparities in Kazakhstan requires a multifaceted approach, including expanding AI and telemedicine, implementing targeted staff training programs, and establishing standardized national stroke protocols. These strategies can help reduce treatment delays, bridge the urban–rural healthcare divide, and improve patient outcomes. The findings have implications for other UMICs facing similar challenges in delivering equitable stroke care. Full article

Patients’ effective hand hygiene helps to reduce healthcare-associated infections and prevents the spread of nosocomial infections and communicable diseases, such as COVID-19. Accordingly, this study aimed to describe effective hand hygiene decisions based on the Health Action Process Approach (HAPA) and whether this pattern is invariant for mental health. Data were collected cross-sectionally from patients who had previously been admitted to a hospital (N_{study 1} = 279; study 1) and longitudinally from psychosomatic rehabilitation patients (N_{study 1} = 1073; study 2). The fit of the HAPA framework and changes in hand hygiene decisions regarding compliance, social-cognitive variables of the HAPA, and mental health status were examined. The results revealed that the trimmed HAPA framework fitted the data well (χ² = 27.1, df = 12, p < 0.01, CMIN/df = 2.26, CFI = 0.97, RMSEA = 0.08). According to multi-group structural equation modeling, the HAPA model with hand hygiene behavior was found to be invariant regarding mental health. To conclude, the trimmed HAPA framework was revealed to be a generic framework for explaining social-cognitive processes relating to hand hygiene decisions. Therefore, helping individuals to perform hand hygiene recommendations requires intention formation and bridging the intention–behavior gap. This can be undertaken by promoting planning and self-efficacy. All processes appear generic to participants with and without mental health challenges. Full article

Background: High compliance to infection prevention and control (IPC) is vital to prevent health care-associated infections. In the worst 2014–2015 Ebola-affected district in Sierra Leone (Kenema), we assessed (a) average yearly IPC compliance (2016–2018) using a National IPC assessment tool in the district hospital and peripheral health units (PHUs), and (b) gaps in IPC activities, infrastructure and consumables in 2018. Methods: This was a cross-sectional study using secondary program data. Results: At the district hospital, compliance increased from 69% in 2016 to 73% in 2018 (expected minimal threshold = 70%; desired threshold ≥ 85%). Compliance for screening/isolation facilities and decontamination of medical equipment reached 100% in 2018. The two thematic areas with the lowest compliance were sanitation (44%) and sharps safety (56%). In PHUs (2018), the minimal 70% compliance threshold was not achieved in two (of 10 thematic areas) for Community Health Centers, four for Community Health Posts, and five for Maternal and Child Health Units. The lowest compliance was for screening and isolation facilities (range: 33–53%). Conclusion: This baseline assessment is an eye opener of what is working and what is not, and can be used to galvanize political, financial, and material resources to bridge the existing gaps. Full article

Muscular contraction is a fundamental phenomenon in all animals; without it life as we know it would be impossible. The basic mechanism in muscle, including heart muscle, involves the interaction of the protein filaments myosin and actin. Motility in all cells is also partly based on similar interactions of actin filaments with non-muscle myosins. Early studies of muscle contraction have informed later studies of these cellular actin-myosin systems. In muscles, projections on the myosin filaments, the so-called myosin heads or cross-bridges, interact with the nearby actin filaments and, in a mechanism powered by ATP-hydrolysis, they move the actin filaments past them in a kind of cyclic rowing action to produce the macroscopic muscular movements of which we are all aware. In this special issue the papers and reviews address different aspects of the actin-myosin interaction in muscle as studied by a plethora of complementary techniques. The present overview provides a brief and elementary introduction to muscle structure and function and the techniques used to study it. It goes on to give more detailed descriptions of what is known about muscle components and the cross-bridge cycle using structural biology techniques, particularly protein crystallography, electron microscopy and X-ray diffraction. It then has a quick look at muscle mechanics and it summarises what can be learnt about how muscle works based on the other studies covered in the different papers in the special issue. A picture emerges of the main molecular steps involved in the force-producing process; steps that are also likely to be seen in non-muscle myosin interactions with cellular actin filaments. Finally, the remarkable advances made in studying the effects of mutations in the contractile assembly in causing specific muscle diseases, particularly those in heart muscle, are outlined and discussed. Full article

The stiffness of the myosin cross-bridges is a key factor in analysing possible scenarios to explain myosin head changes during force generation in active muscles. The seminal study of Huxley and Simmons (1971: Nature 233: 533) suggested that most of the observed half-sarcomere instantaneous compliance (=1/stiffness) resides in the myosin heads. They showed with a so-called T₁ plot that, after a very fast release, the half-sarcomere tension reduced to zero after a step size of about 60Å (later with improved experiments reduced to 40Å). However, later X-ray diffraction studies showed that myosin and actin filaments themselves stretch slightly under tension, which means that most (at least two-thirds) of the half sarcomere compliance comes from the filaments and not from cross-bridges. Here we have used a different approach, namely to model the compliances in a virtual half sarcomere structure in silico. We confirm that the T₁ curve comes almost entirely from length changes in the myosin and actin filaments, because the calculated cross-bridge stiffness (probably greater than 0.4 pN/Å) is higher than previous studies have suggested. Our model demonstrates that the formulations produced by previous authors give very similar results to our model if the same starting parameters are used. However, we find that it is necessary to model the X-ray diffraction data as well as mechanics data to get a reliable estimate of the cross-bridge stiffness. In the light of the high cross-bridge stiffness found in the present study, we present a plausible modified scenario to describe aspects of the myosin cross-bridge cycle in active muscle. In particular, we suggest that, apart from the filament compliances, most of the cross-bridge contribution to the instantaneous T₁ response may come from weakly-bound myosin heads, not myosin heads in strongly attached states. The strongly attached heads would still contribute to the T₁ curve, but only in a very minor way, with a stiffness that we postulate could be around 0.1 pN/Å, a value which would generate a working stroke close to 100 Å from the hydrolysis of one ATP molecule. The new model can serve as a tool to calculate sarcomere elastic properties for any vertebrate striated muscle once various parameters have been determined (e.g., tension, T₁ intercept, temperature, X-ray diffraction spacing results). Full article