151398 research outputs found
Sort by
Sequential phase optimization for coherent combination of distributed transmissions at a non-communicative receiver
No full textThis article provides a summary of the development of a technique for creating coherence of transmissions from multiple, independent, distributed transmitters at the location of a non-communicative receiver for the purposes of long-range wireless power transfer (WPT). This technique has been named sequential phase optimization. This article presents a brief review of long-range distributed WPT techniques, the development of the sequential phase optimization process including results of mathematical modeling performed in MATLAB, and the results of laboratory experiments to demonstrate the technique. This article presents new simulations and experimental results that are additional to what has been presented before. The testing demonstrated that each additional power beacon (PB) added approximately 3 dB of power at the receiver once the synchronization process had been completed. Synchronization time was demonstrated using phase cycling times as short as 24.6 μs
Energy efficiency of superoscillation
No full textThrough superoscillation arbitrarily small optical spots can be generated in the far field without evanescent fields. This can potentially revolutionize many photonic technologies, such as superresolution imaging, lithography, data storage, and optical trapping. However, it is generally believed that superoscillation comes with a price of extremely low energy efficiency, making it impractical for applications. Here we provide a detailed investigation of the energy efficiency of superoscillatory functions. We model a wide array of superoscillatory functions with prolate spheroidal wave functions (PSWF). The results show that extremely low energy efficiency is caused by strict modelling constraints and the intrinsic properties of PSWFs, rather than the fundamental limitation imposed by superoscillation. Energy efficiency can be significantly improved by relaxing the constraints. Using an optimization algorithm based on three PSWFs and setting the constraint conditions to two prescribed points, we show that the energy efficiency (the portion of energy contained within a superoscillatory spot) for a spot of size of 0.1λ can reach 10−3, which is ∼140 orders-of-magnitude improvement from the strict modelling results and is practically viable in many applications. We also establish a general relationship between energy efficiency and the field-of-view/size of a superoscillatory spot. It is revealed that generally energy efficiency decreases exponentially with field-of-view for a given spot size, and for a given field-of-view the logarithmic scale of energy efficiency decreases with reduced spot size following a double exponential law
Short peptides from Asian scorpions: bioactive molecules with promising therapeutic potential
No full textScorpion venom peptides, particularly those derived from Asian species, have garnered significant attention, offering therapeutic potential in pain management, cancer, anticoagulation, and infectious diseases. This review provides a comprehensive analysis of scorpion venom peptides, focusing on their roles as voltage-gated sodium (Nav), potassium (Kv), and calcium (Cav) channel modulators. It analyzed Nav1.7 inhibition for analgesia, Kv1.3 blockade for anticancer activity, and membrane disruption for antimicrobial effects. While the low targeting specificity and high toxicity of some scorpion venom peptides pose challenges to their clinical application, recent research has made strides in overcoming these limitations. This review summarizes the latest progress in scorpion venom peptide research, discussing their mechanisms of action, therapeutic potential, and challenges in clinical translation. This work aims to provide new insights and directions for the development of novel therapeutic drugs.<br/
Robust and secure multi-user STAR-RIS-aided communications: optimization vs machine learning
No full textThis paper investigates simultaneous transmitting and reflecting reconfigurable intelligent surface (STAR-RIS)-assisted multi-user downlink (dl) communications with a primary focus on maximizing information secrecy by considering the channel state information (CSI) error. Acquiring perfect CSI is particularly challenging due to the unavailability of radio frequency chains at the STAR-RIS, the inherent impact of noise and interference on the CSI estimation, as well as non-collaborative nature of the eavesdroppers. In particular, we tackle the worst-case robust beamforming design problem to maximize the sum secrecy rate of the system while considering transmit power limitations, quality of service requirements, and practical constraints on the STAR-RIS phase shifter array. To tackle the resulting non-convex problem, we employ the S-procedure as an initial step to approximate semi-infinite inequality constraints. Subsequently, we leverage the alternating optimization with a line search framework to update the precoder and phase shift matrix iteratively. Furthermore, we extend our solution to address the non-convexity by leveraging a deep reinforcement learning (DRL) multi-agent (MA) framework based on Markov decision process. We also analyze practical phase shifts and the effect of direct links to showcase the practicality of our approach. Simulation results confirm STAR-RIS’s significant performance edge, exhibiting approximately 27.1% higher secrecy in conventional optimization and around 35.4% in the MA-DRL context compared over the conventional RIS. Moreover, our proposed MA-DRL approach surpasses single-agent schemes by about 8.6% in the case of proximal policy optimization and 19.9% in the case of deep deterministic policy gradient, emphasizing the benefits of the MA framework with STAR-RIS
Numerical modelling of elasto-plastic friction in bow-string interaction with guaranteed passivity
No full textIn order to simulate the function of bowed-string instruments, one needs to model the frictional interaction between the bow hair and the vibrating string. This is possible using an elasto-plastic friction model, which has previously succeeded in reproducing experimental data captured on a monochord setup. In this work, this elasto-plastic model is refined to guarantee passivity, and a stable numerical scheme is derived that inherits the energy balance of the underlying continuous model. The presented approach considers a finite-width bow, thus spreading the bow-string interaction over an area. The compliance of the bow hair and the torsional motion of the string are also taken into account. A sound example and animations of the string motion are provided to demonstrate the behaviour of the model
UML crisis! An educational perspective
No full textContext: Unified Modelling Language (UML) is not only a standard modelling language in the software industry but also the “lingua franca” of software engineering education. However, teaching and learning UML have been both identified as difficult tasks. Aim: This study aims to have a practical and deep understanding of what causes the difficulties in UML education (in addition to the known complexity of UML), and cor- respondingly to propose actionable mitigation strategies. Method: we conducted critical reflection on our educational activities, teaching materials, and students’ learning effects in a software engineering conversion programme, followed by consulting ex- ternal UML experts. Results: We observed and demonstrated a vicious cycle of the UML crisis in education, which in turn drove us to preliminarily propose a set of potential tactics for breaking the vicious cycle and addressing the UML crisis. Conclusions: Practitioners’ lack of good UML knowledge and skills could have been out of educators’ control. Breaking the vicious cycle of the UML crisis in education requires collaborative efforts across the whole community
Atovaquone-induced activation of the PERK/eIF2α signaling axis mitigates metabolic radiosensitisation
No full textBackgroundHypoxia, a key feature of most solid tumours, including head and neck cancer, reduces radiotherapy efficacy by promoting radiation resistance through micro-environmental and genomic alterations. Addressing these resistance mechanisms is crucial, as radiotherapy remains central to managing locally advanced disease. Atovaquone, a mitochondrial electron transport chain complex III inhibitor, is reported to reduce tumour hypoxia in preclinical models, however, this response does not consistently enhance radiation sensitivity. This work examines the potential of atovaquone to modify the hypoxic response in models of head and neck squamous cell carcinoma (HNSCC), uncovering an adaptive resistance mechanism driven by integrated stress response (ISR) signaling that limits the radiosensitising potential of this approach.MethodsThe bioenergetic response of HNSCC cells to atovaquone was assessed using the Seahorse XFe96 Analyzer with the XF Cell Mito Stress Test. Radiation dose modifying effects of atovaquone were tested by clonogenic survival assays, while ROS yields were analysed by flow cytometry. Western blotting and quantitative reverse transcription-PCR were employed to study activation of ISR signaling and the overall influence of atovaquone on the hypoxic response. Finally, the role of the ISR activation in modulating radiosensitivity was investigated using both siRNA and pharmacological inhibition of eIF2α, a central regulator of the ISR.ResultsHerein we report that atovaquone significantly disrupts mitochondrial respiration, triggering phosphorylation of eIF2α, a pivotal regulator of the ISR, and a master regulator of protein synthesis. Notably, atovaquone also increased the autophagic load under hypoxia, while autophagy inhibition significantly enhanced apoptosis, improving radiation sensitivity. Combined eIF2α inhibition and atovaquone promotes cell cycle redistribution and significantly enhances mitochondrial ROS production and compared to atovaquone alone, restoring atovaquone mediated radiosensitisation.ConclusionsOur data highlight dual counter opposing impacts of atovaquone, serving as a hypoxic radiosensitiser though oxidative phosphorylation (OXPHOS) inhibition, but also in promoting stress induced ISR signaling, conferring resistance to radiation treatment. Importantly, if ISR activation is impeded, the metabolic radiosensitising properties of atovaquone is restored. These data provide a new insight to a molecular response that could help counteract hypoxia-induced radioresistance.<br/
Correction: An integrated microbiome- and metabolome-genome-wide association study reveals the role of heritable ruminal microbial carbohydrate metabolism in lactation performance in Holstein dairy cows
No full textNon-LTE radiative transfer simulations: improved agreement of the double detonation with normal Type Ia supernovae
No full textThe double detonation is a widely discussed explosion mechanism for Type Ia supernovae, whereby a helium shell detonation ignites a secondary detonation in the carbon/oxygen core of a white dwarf. Even for modern models that invoke relatively small He shell masses, many previous studies have found that the products of the helium shell detonation lead to discrepancies with normal Type Ia supernovae, such as strong Ti ii absorption features, extremely red light curves, and too large a variation with viewing direction. It has been suggested that non-local thermodynamic equilibrium (non-LTE) effects may help reduce these discrepancies between observations. Here we carry out full non-LTE radiative transfer simulations for a recent double detonation model with a relatively small helium mass of 0.05 . We construct 1D models representative of directions in a 3D explosion model to give an indication of viewing angle dependence, and show that at early times up to around maximum light, this gives a reasonable approximation of the different directions in the 3D model. This approximation breaks down once the ejecta start to become optically thin. The full non-LTE treatment leads to improved agreement between the models and observations. The light curves become less red, due to reduced absorption by the helium shell detonation products, since these species are more highly ionized. Additionally, the expected variation with observer direction is reduced. The full non-LTE treatment shows promising improvements and reduces the discrepancies between the double detonation models and observations of normal Type Ia supernovae
SMALL: open surgery versus minimally invasive vacuum-assisted excision for small screen-detected breast cancer-protocol for a phase III randomised multicentre trial
No full textINTRODUCTION: Mammographic screening identifies many women with small breast cancers with favourable biological features, which have an excellent prognosis. Some of these may never have become clinically apparent without screening and are commonly described as 'overdiagnosed' cancers. Despite this, all patients with screen-detected cancers are currently treated with surgical excision and sentinel lymph node biopsy, although this may represent overtreatment. There is, therefore, a need for less invasive approaches to reduce treatment burden for patients while maintaining current excellent oncological outcomes. Vacuum-assisted excision (VAE) may represent such an alternative treatment approach, and the SMALL (Open Surgery versus Minimally invasive-vacuum Assisted excision for smaLL screen-detected breast cancer) trial aims to investigate the use of VAE for the safe de-escalation of surgical treatment for such excellent prognosis invasive breast cancers.METHODS: SMALL is a prospective, multicentre, randomised phase III trial of VAE versus surgery in patients with small, biologically favourable screen-detected invasive breast cancer. SMALL has an innovative hybrid design with coprimary endpoints. These include a randomised non-inferiority comparison of surgical re-excision rates following initial treatment, and a single-arm analysis of local recurrence at 5 years following VAE. Secondary outcomes include complication rates, overall survival, quality of life and a health economic analysis. The trial includes a QuinteT Recruitment Intervention to support recruitment.ETHICS AND DISSEMINATION: Ethical approval was obtained from the Office for Research Ethics (Northern Ireland) for all UK sites. Results will be submitted for publication in a peer-reviewed journal, presented, shared with patient partners and with relevant professional organisations to inform future guideline development for the management of screen-detected breast cancer.TRIAL REGISTRATION NUMBER: ISRCTN12240119.</p