Performance of an ablator for Space Shuttle inorbit repair in an arc-plasma airstream

An ablator patch material performed well in an arc plasma environment simulating nominal Earth entry conditions for the Space Shuttle. Ablation tests using vacuum molded cones provided data to optimize the formulation of a two part polymer system for application under space conditions. The blunt cones were made using a Teflon mold and a state of the art caulking gun. Char stability of formulations with various amounts of catalyst and diluent were investigated. The char was found to be unstable in formulations with low amounts of catalyst and high amounts of diluent. The best polymer system determined by these tests was evaluated using a half tile patch in a multiple High Temperature Reusable surface Insulation tile model. It was demonstrated that this ablator could be applied in a space environment using a state of the art caulking gun, would maintain the outer mold line of the thermal protection system during entry, and would keep the bond line temperature at the aluminum tile interface below the design limit

Task Structure and the Propensity to Collaborate vs. Cooperate

Researchers have long studied the group dynamics of teams with the goal of making teams more effective. This study looks at the task structure to determine if groups are more likely to collaborate or cooperate to successfully complete a project. Initial findings indicate that the higher the structure of a project the more likely teams will gravitate to cooperation while the less structured the project the more likely teams are to work collaboratively. Initial findings indicate that the determination of the “structuredness” of a project is a subjective rather than objective assessment

The total synthesis of alternaric acid and progress toward the synthesis of subglutinol

The Oshima-Utimoto reaction coupling an allylic alcohol and butyl vinyl ether is utilized to construct the furan ring of the natural product subglutinol B. Methodology for the diastereoselective substitution of furans is also reported. Methodology utilizing silylglyoxylates as latent acyl anions for use in stereoselective multicomponent reactions is developed in the form of addition of carbon nucleophiles followed by an intermolecular aldol reaction. This methodology was then applied towards the total synthesis of alternaric acid

Pair-induced spectral changes and variability in compact X-ray sources

Inverse Compton scattering of ultraviolet photons by GeV electrons produces γ-rays which in turn create electron–positron pairs if the source is sufficiently compact. The pairs modify the emergent radiation spectrum through their own inverse Compton scattering and through thermal Comptonization after they have cooled to sub-relativistic temperatures. Recent calculations of spectral reprocessing under these conditions are extended to situations in which the Thomson optical depth of the pair plasma exceeds unity, and to demonstrate time-dependent behaviour explicitly. The relevance of our results to X-ray observations of active galactic nuclei, binary X-ray sources and γ-ray bursters is discussed briefly

BSM-6G: Blockchain-based Dynamic Spectrum Management for 6G Networks: Addressing Interoperability and Scalability

The radio frequency spectrum serves as a fundamental resource for wireless communication, encompassing various frequency bands allocated for diverse services and applications. Dynamic spectrum management (DSM) is essential to optimise the utilisation of this limited and valuable natural resource, with the aim of improving performance and adapting to changing wireless communication demands. Traditional static spectrum allocation methods have shown inefficiencies, leading to spectrum scarcity and under-utilisation. To address these challenges, the integration of blockchain and Cognitive Radio (CR) technologies has emerged as a promising approach. Blockchain, with its decentralised and secure attributes, can improve transparency and trust in spectrum allocation processes, while CR enables intelligent spectrum sensing and allocation to maximise utilisation. However, this promising approach comes with its own critical challenges, especially when dealing with the 6th Generation (6G) mobile communication. These challenges are related to the fact that the blockchain ecosystem needs to be interoperable and scalable enough to be compatible with the 6G high-demand and substantial resources. Specifically, integrating blockchain with CR requires efficient interoperability techniques where blockchain can easily and effectively interact with the CR platforms as well as radio spectrum environments. Furthermore, the spectrum management system over 6G networks needs to be designed in a way where massive 6G resources can be accommodated and managed without having any service performance degradation. This paper introduces a novel radio spectrum management model in 6G networks, named as BSM-6G, which integrates blockchain technology with CR where interoperability is preserved and scalability is maximised. Specifically, the proposed BSM-6G model merges blockchain’s transparent record keeping with CR’s intelligent spectrum management capabilities. To overcome the interoperability issue, BSM-6G provides an interoperable blockchain Oracle approach which facilitates the real-time interaction among the blockchain platform, the CR, and any data sources off-chain. This paper details all the technical and procedural challenges when implementing the proposed interoperability Oracle approach. To address the scalability challenge, BSM-6G utilizes the Proof-of-History (PoH) consensus protocol to align with the requirements of DSM in advanced networks like Beyond 5th Generation (B5G) and 6G. Evaluation results indicate that BSM-6G offers viable and less complex blockchain Oracle integration architecture measured by the technical implementation of BSM-6G, as well as low interoperability cost measured by transaction response time and transaction fee cost. Compared to state-of-the-art spectrum-based blockchain systems, BSM-6G shows a high scalable DSM-based blockchain in 6G networks measured by transactions per second (TPS)

Experimental implementation of maximally synchronizable networks

Maximally synchronizable networks (MSNs) are acyclic directed networks that maximize synchronizability. In this paper, we investigate the feasibility of transforming networks of coupled oscillators into their corresponding MSNs. By tuning the weights of any given network so as to reach the lowest possible eigenratio lambdaN/lambda2, the synchronized state is guaranteed to be maintained across the longest possible range of coupling strengths. We check the robustness of the resulting MSNs with an experimental implementation of a network of nonlinear electronic oscillators and study the propagation of the synchronization errors through the network. Importantly, a method to study the effects of topological uncertainties on the synchronizability is proposed and explored both theoretically and experimentally.The authors acknowledge J.L. Echenausía-Monroy, V.P. Vera-Ávila, J. Moreno de León, C. Hapo and P.L. del Barrio for assistance in the laboratory, and the support of MINECO (FIS2012-38949-C03-01 and FIS2013-41057-P). One anonymous referee is acknowledged for having provided valuable advice that has influenced our understanding of the origin of the propagation of the synchronization error, and helped us improve the manuscript in several ways. The authors also acknowledge the computational resources, facilities and assistance provided by the Centro computazionale di RicErca sui Sistemi COmplessi (CRESCO) of the Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA). R.S.E. acknowledges Universidad de Guadalajara, CULagos (Mexico) for financial support (PRO-SNI-2015/228069, PROINPEP/005/2014, UDG-CONACyT/I010/163/2014) and CONACyT (Becas Mixtas MZO2015/290842). D.-U. Hwang acknowledges National Institute for Mathematical Sciences (NIMS) funded by the Ministry of Science, ICT & Future Planning (A21501-3)

Plasma miRNAs as biomarkers for endometriosis

STUDY QUESTION: Can plasma miRNAs be used for the non-invasive diagnosis of endometriosis in infertile women? SUMMARY ANSWER: miRNA-based diagnostic models for endometriosis failed the test of independent validation. WHAT IS KNOWN ALREADY: Circulating miRNAs have been described to be differentially expressed in patients with endometriosis compared with women without endometriosis, suggesting that they could be used for the non-invasive diagnosis of endometriosis. However, these studies have shown limited consistency or conflicting results, and no miRNA-based diagnostic test has been validated in an independent patient cohort. STUDY DESIGN, SIZE, DURATION: We performed genome-wide miRNA expression profiling by small RNA sequencing to identify a set of plasma miRNAs with discriminative potential between patients with and without endometriosis. Expression of this set of miRNAs was confirmed by RT-qPCR. Diagnostic models were built using multivariate logistic regression with stepwise feature selection. In a final step, the models were tested for validation in an independent patient cohort. PARTICIPANTS/MATERIALS, SETTINGS, METHODS: Plasma of all patients was available in the biobank of the Leuven Endometriosis Centre of Excellence. Biomarker discovery and model development were performed in a discovery cohort of 120 patients (controls= 38, endometriosis= 82), and models were tested for validation in an independent cohort of 90 patients (controls= 30, endometriosis= 60). RNA was extracted with the miRNeasy Plasma Kit. Genome-wide miRNA expression analysis was done by small RNA sequencing using the NEBNext small RNA library prep kit and the NextSeq 500 System. cDNA synthesis and qPCR were performed using the Qiagen miScript technology. MAIN RESULTS AND THE ROLE OF CHANCE: We identified a set of 42 miRNAs with discriminative power between patients with and without endometriosis based on genome-wide miRNA expression profiling. Expression of 41 miRNAs was confirmed by RT-qPCR, and 3 diagnostic models were built. Only the model for minimal-mild endometriosis (Model 2: hsa-miR-125b-5p, hsa-miR-28-5p and hsa-miR-29a-3p) had diagnostic power above chance performance in the independent validation (AUC= 60%) with an acceptable sensitivity (78%) but poor specificity (37%). LIMITATIONS, REASONS FOR CAUTION: The diagnostic models were built and tested for validation in two patient cohorts from a single tertiary endometriosis centre. Further validation tests in large cohorts with patients from multiple endometriosis centres are needed. WIDER IMPLICATION OF THE FINDINGS: Our study supports a possible biological link between certain miRNAs and endometriosis, but the potential of these miRNAs as clinically useful biomarkers is questionable in women with infertility. Large studies in well-described patient cohorts, with rigorous methodology for miRNA expression analysis, sufficient statistical power and an independent validation step, are necessary to answer the question of whether miRNAs can be used as diagnostics markers for endometriosis