Retirements of professional tennis players in second- and third-tier tournaments on the ATP and WTA tours.

The demands of professional tennis, including physical and psychological aspects, contribute to the frequency of retirements at elite levels of the sport. The aim of this study was to analyze epidemiological patterns and risk factors associated with retirements in previous ATP and WTA Tour tournaments. A retrospective cohort study was conducted. This study focused on previous ATP and WTA Tour tournaments. The ATP database encompassed 584,806 matches, while the WTA database included 267,380 matches. To assess retirements, potential risk factors such as playing surface, tournament category, match round, and player age were analyzed. Incidence rates were calculated for the period between 1978-2019 for men and 1994-2018 for women. The overall incidence rate was 1.56 (95%CI: 1.54, 1.59) and 1.36 (95%CI: 1.33, 1.39) retirements per 1000 games played in male and female competitions, respectively. Retirements increased over the years. Higher incidence rates were observed on hard (1.59 [95%CI: 1.56, 1.63] and 1.39 [95%CI: 1.34, 1.44]) and clay (1.60 [95%CI: 1.57, 1.63] and 1.36 [95%CI: 1.32, 1.41]) compared to grass courts (0.79 [95%CI: 0.65, 0.94] and 1.06 [95%CI: 0.88, 1.27]). Risk factors differed by gender, with tournament category significant in males (IRR: 1.23 [95%CI: 1.19, 1.28] in ITF vs ATP) and match round in females (IRR: 0.92 [95%CI: 0.88, 0.98] in preliminary vs final). This study provides valuable insights for coaches, players, support teams, and epidemiologists regarding retirements and associated risk factors in previous ATP and WTA Tour tournaments, contributing to injury prevention strategies.

MnO/ZnO:Zn Thin-Film Frequency Adaptive Heterostructure for Future Sustainable Memristive Systems.

In recent years, advances in materials engineering based on adaptive electronics have found a new paradigm to optimize drawbacks in signal processing. A two-layer MnO/ZnO:Zn heterostructure envisioned for frequency adaptive electronic signal processing is synthesized by sputtering, where the use of internal states allows reconfigurability to obtain new operating modes at different frequency input signals. X-ray diffraction (XRD) analysis is performed on each layer, revealing a cubic structure for MnO and a hexagonal structure for ZnO:Zn with preferential growth in [111] and [002] directions, respectively. Scanning electron microscope (SEM) micrographs show that the surface of both materials is homogeneous and smooth. The thickness for each layer is determined to be approximately 106.3 nm for MnO, 119.3 nm for ZnO:Zn and 224.1 nm for the MnO/ZnO:Zn structure. An electrical characterisation with an oscilloscope and signal generator was carried out to obtain the time-response signals and current-voltage (I-V) curves, where no degradation is detected when changing frequencies within the range of 100 Hz to 1 MHz. An equivalent circuit is proposed to explain the effects in the interface. Measurements of switching speeds from high resistance state (HRS) to low resistance state (LRS) at approximately 17 ns, highlight the device's rapid adaptability, and an estimated switching ratio of approximately 2 × 104 indicates its efficiency as a memristive component. Finally, the MnO/ZnO:Zn heterojunction delivers states that are stable, repeatable, and reproducible, demonstrating how the interaction of the materials can be utilised in adaptive device applications by applying frequencies and internal states to create new and innovative design schematics, thus reducing the number of components/connections in a system for future sustainable electronics.

Quantifying Hitting Load in Racket Sports: A Scoping Review of Key Technologies.

PURPOSE: This scoping review aims to identify the primary racket and arm-mounted technologies based on inertial measurement units that enable the quantification of hitting load in racket sports. METHODS: A comprehensive search of several databases (PubMed, SPORTDiscus, Web of Science, and IEEE Xplore) and Google search engines was conducted following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) extension for scoping reviews guidelines. Included records primarily focused on monitoring hitting load in racket sports using commercialized racket or arm-mounted inertial sensors through noncompetitive and competitive racket-sports players. RESULTS: A total of 484 records were identified, and 19 finally met the inclusion criteria. The largest number of systems found were compatible with tennis (n = 11), followed by badminton (n = 4), table tennis (n = 2), padel (n = 1), and squash (n = 1). Four sensor locations were identified: grip-attached (n = 8), grip-embedded (n = 6), wrist (n = 3), and dampener sensors (n = 2). Among the tennis sensors, only 4 out of the 11 (36.4%) demonstrated excellent reliability (>.85) in monitoring the number of shots hit either during analytic drills or during simulated matches. None of the other racket-sports sensors have undergone successful, reliable validation for hitting-volume quantification. CONCLUSIONS: Despite recent advancements in this field, the quantification of hitting volume in racket sports remains a challenge, with only a limited number of tennis devices demonstrating reliable results. Thus, further progress in technology and research is essential to develop comprehensive solutions that adequately address these specific requirements.

Mechanistic Investigation of the Rhodium-Catalyzed Transfer Hydroarylation Reaction Involving Reversible C-C Bond Activation.

Carbon-carbon (C-C) bonds are ubiquitous but are among the least reactive bonds in organic chemistry. Recently, catalytic approaches to activate C-C bonds by transition metals have demonstrated the synthetic potential of directly reorganizing the skeleton of small molecules. However, these approaches are usually restricted to strained molecules or rely on directing groups, limiting their broader impact. We report a detailed mechanistic study of a rare example of catalytic C-C bond cleavage of unstrained alcohols that enables reversible ketone transfer hydroarylation under Rh-catalysis. Combined insight from kinetic analysis, in situ nuclear magnetic resonance (NMR) monitoring, and density functional theory (DFT) calculations supports a symmetric catalytic cycle, including a key reversible ß-carbon elimination event. In addition, we provide evidence regarding the turnover-limiting step, the catalyst resting state, and the role of the sterically encumbered NHC ligand. The study further led to an improved catalytic system with the discovery of two air-stable precatalysts that showed higher activity for the transformation in comparison to the original conditions.

Metal contents in house geckos (Squamata: Gekkonidae) from industrial and urban areas of southern Tamaulipas, Mexico and western Andalucía, Spain, may reflect airborne metal pollution.

House geckos share living quarters with humans in the tropical and subtropical regions inhabited by these reptiles. Gecko behavior, biological traits, continuous exposure to suspended particulate matter 0 µm in diameter (PM10) and dust, as well as status as exotic species, motivated the choice of these species to examine environmental exposure to ambient air pollutants, in particular metals, and subsequent accumulation in these organisms. One part of the study was conducted in Tamaulipas (Mexico) where Hemydactylus frenatus is abundant in urban and industrial environments, the other part was conducted in Andalucia (Spain) where Tarentola mauritanica is found in similar environments. Adult geckos were collected on buildings in locations affected by various air pollution sources. For both species, higher metal contents were observed in whole-body (including digestive tracts) analysis and were markedly different between collection sites. Contents in tails, digestive tracts, and carcasses without digestive tracts were not correlated. Based on contamination factor values, bioaccumulation in H. frenatus tissues occurred for 12 of the 15 metals analyzed. Data suggest that H. frenatus might serve as a biomonitor for Cu, Ni, Pb, Cr, Li, and V, whereas T. mauritanica might be a biomonitor for Cu, Ni, Pb, and Cr. To our knowledge, metal contents for H. frenatus are reported here for the first time. House gecko data could be integrated into a highly representative monitoring system and health risk assessments related to air quality in residential areas.

How do International Olympic Sport Federations innovate? The use of crowdfunding and the impact of COVID-19.

The purpose of this study was to contribute to the understanding of innovation and crowdfunding of International Olympic Sport Federations (IFs), which are the world governing bodies of their respective sports. Three research questions were addressed: the perceptions of the IFs on the implementation of their innovation programmes during the last four years (2016-2020), the impact of COVID-19 on the IFs capability to innovate, and the crowdfunding strategies of the IFs. A mixed method combining qualitative and quantitative approaches was used. An online semi-structured questionnaire which included an open answer section was completed by IFs executives (n = 22) and an analysis of the information provided by IFs through various content sources was conducted. Results showed that IFs with less funding had a significantly more innovative approach that their counterparts, that the perception of the impact of COVID-19 on the innovative capability was not unanimous, that they identified sport-specific programmes as the most innovative of all initiatives delivered during the pandemic, and that crowdfunding projects were implemented in their sport but mostly at individual and local levels. From a research perspective, since this is the first study that investigates the innovation and crowdfunding strategies of IFs, future directions include the need for further research with national and regional federations on these topics. Practical implications are suggested for IFs to deliver innovative programmes to satisfy their stakeholder needs and to consider new funding methods such as crowdfunding as part of their strategies.

Conocimientos sobre la perspectiva Ciencia, Tecnología y Sociedad del personal administrativo docente para la gestión de procesos universitarios

Introducción: El personal administrativo con una visión de Ciencia, Tecnología y Sociedad puede influir en las funciones universitarias con un enfoque social de la formación, investigación y extensión. Objetivo: Diagnosticar el nivel de conocimientos sobre la perspectiva Ciencia, Tecnología y Sociedad del personal administrativo docente de la Universidad de Ciencias Médicas de Ciego de Ávila, Cuba. Método: Se realizó un estudio observacional descriptivo durante el año 2022 en dicha universidad donde la población estuvo conformada por 52 administrativos en funciones docentes (N=52). Se seleccionó una muestra de 34 por muestreo simple aleatorio (n=34). Se aplicó un cuestionario validado como método empírico para la recolección de la información. Se establecieron escalas de medición para variables cuantitativas. Resultados: El diagnóstico reveló un bajo nivel de conocimientos sobre las definiciones de Ciencia, Tecnología e Innovación (85 %, 69 % y 44 %, respectivamente). La mayoría del personal administrativo docente no reconoció los modelos que designan las relaciones Ciencia, Tecnología y Sociedad y consideró que no se posiciona la universidad médica como actor relevante para el desarrollo local (53 %). El 41 % refirió que casi siempre aparece la perspectiva Ciencia, Tecnología y Sociedad en los documentos normativos de los ministerios de Educación Superior y Salud Pública. Conclusiones: Se aportan evidencias sobre insuficiencias en los conocimientos por el personal administrativo docente sobre Ciencia, Tecnología y Sociedad y su uso en la gestión de los procesos universitarios. Se recomienda diseñar acciones de superación sobre la temática.

Introduction: Administrative personnel with a vision on Science, Technology and Society can influence universities functions through a social approach, the training, research and, extension process. Objective: To diagnose the level of knowledge on the Science, Technology and Society perspective of the administrative teaching personnel of the Universidad de Ciencias Médicas de Ciego de Avila, Cuba. Method: A descriptive observational study was carried out in 2022 at the aforementioned university, where the population study consisted of 52 administrative personnel in teaching functions (N=52). A sample of 34 was selected by simple random sampling (n=34). A validated questionnaire was applied as an empirical method for data collection. Measurement scales were established for quantitative variables. Results: The diagnosis revealed a low level of knowledge on Science, Technology and Innovation definitions (85%, 69% and 44%, respectively). Most of the teaching and administrative personnel (53%) did not recognize the models that revealed the relationships between Science, Technology and Society and have in consideration that the University of Medicine is not positioned as a relevant actor in the local development. Forty-one percent reported that the Science, Technology and Society perspective almost always appears in the normative documents of the Ministerios de Educación Superior y de Salud Pública. Conclusions: There is evidence of insufficient knowledge on Science, Technology and Society and its use in the process management at universities. It is recommended to design related improvement actions on the subject.

Introdução: O pessoal administrativo com visão de Ciência, Tecnologia e Sociedade pode influenciar as funções universitárias com enfoque social na formação, pesquisa e extensão. Objetivo: Diagnosticar o nível de conhecimento sobre a perspectiva de Ciência, Tecnologia e Sociedade do pessoal docente administrativo da Universidade de Ciências Médicas de Ciego de Ávila, Cuba. Método: Estudo observacional descritivo realizado durante o ano de 2022 na referida universidade onde a população foi constituída por 52 funcionários administrativos em funções docentes (N=52). Uma amostra de 34 foi selecionada por amostragem aleatória simples (n=34). Um questionário validado foi aplicado como método empírico para a coleta de informações. Escalas de medida foram estabelecidas para variáveis quantitativas. Resultados: O diagnóstico revelou baixo nível de conhecimento sobre as definições de Ciência, Tecnologia e Inovação (85%, 69% e 44%, respectivamente). A maioria dos docentes administrativos não reconheceu os modelos que designam as relações Ciência, Tecnologia e Sociedade e considerou que a universidade médica não se posiciona como ator relevante para o desenvolvimento local (53%). 41% relataram que a perspectiva de Ciência, Tecnologia e Sociedade quase sempre aparece nos documentos normativos dos Ministérios da Educação Superior e da Saúde Pública. Conclusões: Evidenciam-se as insuficiências de conhecimento do pessoal administrativo docente sobre Ciência, Tecnologia e Sociedade e a sua utilização na gestão dos processos universitários. Recomenda-se projetar ações de melhoria sobre o assunto.

Non-line-of-sight imaging in the presence of scattering media using phasor fields.

Non-line-of-sight (NLOS) imaging aims to reconstruct partially or completely occluded scenes. Recent approaches have demonstrated high-quality reconstructions of complex scenes with arbitrary reflectance, occlusions, and significant multi-path effects. However, previous works focused on surface scattering only, which reduces the generality in more challenging scenarios such as scenes submerged in scattering media. In this work, we investigate current state-of-the-art NLOS imaging methods based on phasor fields to reconstruct scenes submerged in scattering media. We empirically analyze the capability of phasor fields in reconstructing complex synthetic scenes submerged in thick scattering media. We also apply the method to real scenes, showing that it performs similarly to recent diffuse optical tomography methods.

Mechanistic Investigation of the Nickel-Catalyzed Metathesis between Aryl Thioethers and Aryl Nitriles.

Functional group metathesis is an emerging field in organic chemistry with promising synthetic applications. However, no complete mechanistic studies of these reactions have been reported to date, particularly regarding the nature of the key functional group transfer mechanism. Unraveling the mechanism of these transformations would not only allow for their further improvement but would also lead to the design of novel reactions. Herein, we describe our detailed mechanistic studies of the nickel-catalyzed functional group metathesis reaction between aryl methyl sulfides and aryl nitriles, combining experimental and computational results. These studies did not support a mechanism proceeding through reversible migratory insertion of the nitrile into a Ni-Ar bond and provided strong support for an alternative mechanism involving a key transmetalation step between two independently generated oxidative addition complexes. Extensive kinetic analysis, including rate law determination and Eyring analysis, indicated the oxidative addition complex of aryl nitrile as the resting state of the catalytic reaction. Depending on the concentration of aryl methyl sulfide, either the reductive elimination of aryl nitrile or the oxidative addition into the C(sp2)-S bond of aryl methyl sulfide is the turnover-limiting step of the reaction. NMR studies, including an unusual 31P-2H HMBC experiment using deuterium-labeled complexes, unambiguously demonstrated that the sulfide and cyanide groups exchange during the transmetalation step, rather than the two aryl moieties. In addition, Eyring and Hammett analyses of the transmetalation between two Ni(II) complexes revealed that this central step proceeds via an associative mechanism. Organometallic studies involving the synthesis, isolation, and characterization of all putative intermediates and possible deactivation complexes have further shed light on the reaction mechanism, including the identification of a key deactivation pathway, which has led to an improved catalytic protocol.

Impact of match-induced pressure on HRV of junior tennis players.

The present study aimed to assess the impact of a tennis competition on the HRV of nationally ranked junior girls and boys tennis players. A total of 22 nationally ranked tennis players (8 girls and 14 boys), with a mean age of 14.18 (2.15) and experience in national tournaments of 4.23 (2.27) years, participated in this cross-sectional study. Boys had a mean age of 14.36 (1.86) years-old and girls had a mean age of 13.87 (2.69) years old. Participants were assessed the day before and 20 min before the competition match. Significantly reduction in time-domain variables such as the time between intervals R-R (RR-interval) (p-value = 0.001), the percentage of intervals >50 ms different from the previous interval (pNN50) (p-value = 0.020) and the square root of the mean of the squares of the successive differences of the interval RR (RMSSD) (p-value = 0.028) were found between baseline and pre-match assessments. Furthermore, the non-linear measure based on the dispersion, standard deviation, of points perpendicular to the axis of line-of-identity in the Poincaré plot (SD1) (p-value = 0.028) was also significantly reduced before the match when compared to the baseline. However, differences between girls and boys junior tennis players were not found in the pre-competitive heart rate variability (HRV) variables (p-value >0.05). HRV is a convenient, non-invasive measurement that can be easily performed with a watch at home and on the field in order to control and manage match-induced pressure.

Activity-Based Approach for Selective Molecular CO2 Sensing.

Carbon dioxide (CO2) impacts every aspect of life, and numerous sensing technologies have been established to detect and monitor this ubiquitous molecule. However, its selective sensing at the molecular level remains an unmet challenge, despite the tremendous potential of such an approach for understanding this molecule's role in complex environments. In this work, we introduce a unique class of selective fluorescent carbon dioxide molecular sensors (CarboSen) that addresses these existing challenges through an activity-based approach. Besides the design, synthesis, and evaluation of these small molecules as CO2 sensors, we demonstrate their utility by tailoring their reactivity and optical properties, allowing their use in a broad spectrum of multidisciplinary applications, including atmospheric sensing, chemical reaction monitoring, enzymology, and live-cell imaging. Collectively, these results showcase the potential of CarboSen sensors as broadly applicable tools to monitor and visualize carbon dioxide across multiple disciplines.

In Situ Growth of Silver Nanoparticles on Chitosan Matrix for the Synthesis of Hybrid Electrospun Fibers: Analysis of Microstructural and Mechanical Properties.

A viable alternative for the next generation of wound dressings is the preparation of electrospun fibers from biodegradable polymers in combination with inorganic nanoparticles. A poly(vinyl alcohol)-chitosan-silver nanoparticles (PVA-CTS-Ag NPs) system has been developed for antimicrobial and wound healing applications. Here, the preparation of PVA-CTS-Ag electrospun fibers using a two-step process is reported in order to analyze changes in the microstructural, mechanical, and antibacterial properties and confirm their potential application in the biomedical field. The Ag nanoparticles were well-dispersed into the chitosan matrix and their cubic structure after the electrospinning process was also retained. The Ag NPs displayed an average diameter of ~33 nm into the CTS matrix, while the size increased up to 213 nm in the PVA-CTS-Ag(NPs) fibers. It was observed that strong chemical interactions exist between organic (CTS) and inorganic phases through nitrogenous groups and the oxygen of the glycosidic bonds. A defect-free morphology was obtained in the PVA-CTS-Ag NPs final fibers with an important enhancement of the mechanical properties as well as of the antibacterial activity compared with pure PVA-CTS electrospun fibers. The results of antibacterial activity against E. coli and S. aureus confirmed that PVA-CTS-Ag(NPs) fibers can be potentially used as a material for biomedical applications.

Dispersal-induced resilience to stochastic environmental fluctuations in populations with Allee effect.

Many species are unsustainable at small population densities (Allee effect); i.e., below the so-called Allee threshold, the population decreases instead of growing. In a closed local population, environmental fluctuations always lead to extinction. Here, we show how, in spatially extended habitats, dispersal can lead to a sustainable population in a region, provided the amplitude of environmental fluctuations is below an extinction threshold. We have identified two types of sustainable populations: high-density and low-density populations (through a mean-field approximation, valid in the limit of large dispersal length). Our results show that patches where population is high, low, or extinct coexist when the population is close to global extinction (even for homogeneous habitats). The extinction threshold is maximum for characteristic dispersal distances much larger than the spatial scale of synchrony of environmental fluctuations. The extinction threshold increases proportionally to the square root of the dispersal rate and decreases with the Allee threshold. The low-population-density solution can allow understanding of difficulties in recovery after harvesting. This theoretical framework provides a unique approach to address other factors, such as habitat fragmentation or harvesting, impacting population resilience to environmental fluctuations.

Heart Rate Variability in Elite International ITF Junior Davis Cup Tennis Players.

The aim of the present study was to investigate the evolution of the HRV during an international team tennis tournament in elite junior tennis players. A total of 11 tennis players, with a mean age of 15.36 (0.67) from six nationalities, participated in this cross-sectional study. Participants were measured one day before the event, before the first match, and before the second match of the ITF Junior Davis Cup event. Each of the registers lasted 5 min and the time domain, frequency domain and non-linear variables were extracted. The tournament took place in Valencia (Spain). Results showed that there was not a significant decrease in the heart rate variability (HRV) induced by precompetitive stress. However, significant differences (p-value < 0.05) were found between baseline and second match pre-competition HRV values in low frequency (LFNu) (p-value = 0.008) and high frequency (HFNu) power (p-value = 0.008), LF/HF ratio (p-value = 0.008) and Sample Entropy (SampEn) (p-value = 0.033) variables. Furthermore, cognitive anxiety (measured by CSAI-2r) (p-value = 0.017) and anxiety (measured by STAI-S) (p-value = 0.042) were higher before the first match than before the second match. Coaches and physical trainers could use HRV to control and manage the precompetitive anxiety of junior tennis players. The experience in international tournaments and the familiarization with the environment in the second match could explain these results.

COVID-19 Prevention Measures Implemented by Tennis Coaches: The Role of Continent, Experience, and Type of Facility.

The prevention strategies used by tennis coaches when delivering tennis lessons during the COVID-19 pandemic were analyzed in this study. An ad hoc questionnaire collected data from 655 Spanish and Portuguese speaking tennis coaches working in Latin America and Europe. Differences in the prevention measures were analyzed according to the continent, the coaches' experience, and the type of facility they worked in. Results showed that coaches used information provided from local and national organizations more than from international ones. Hand hygiene, communication of preventive strategies, and changes in the coaching methodology were the most used prevention measures. Latin American coaches and those working in public facilities implemented the measures more often than their European colleagues or those working in private venues. Finally, more experienced coaches showed a greater awareness of the adoption of the measures than their less experienced counterparts. The data provided by this research may assist in developing new specific guidelines, protocols, and interventions to help better understand the daily delivery of tennis coaching in this challenging context.

Preparation of Recyclable and Versatile Porous Poly(aryl thioether)s by Reversible Pd-Catalyzed C-S/C-S Metathesis.

Porous organic materials (polymers and COFs) have shown a number of promising properties; however, the lability of their linkages often limits their robustness and can hamper downstream industrial application. Inspired by the outstanding chemical, mechanical, and thermal resistance of the 1D polymer poly(phenylene sulfide) (PPS), we have designed a new family of porous poly(aryl thioether)s, synthesized via a mild Pd-catalyzed C-S/C-S metathesis-based method, that merges the attractive features common to porous polymers and PPS in a single material. In addition, the method is highly modular, allowing to easily introduce application-oriented functionalities in the materials for a series of environmentally relevant applications including metal capture, metal sensing, and heterogeneous catalysis. Moreover, despite their extreme chemical resistance, the polymers can be easily recycled to recover the original monomers, offering an attractive perspective for their sustainable use. In a broader context, these results clearly demonstrate the untapped potential of emerging single-bond metathesis reactions in the preparation of new, recyclable materials.

Acid Catalysis with Alkane/Water Microdroplets in Ionic Liquids.

Ionic liquids are composed of an organic cation and a highly delocalized perfluorinated anion, which remain tight to each other and neutral across the extended liquid framework. Here we show that n-alkanes in millimolar amounts enable a sufficient ion charge separation to release the innate acidity of the ionic liquid and catalyze the industrially relevant alkylation of phenol, after generating homogeneous, self-stabilized, and surfactant-free microdroplets (1-5 µm). This extremely mild and simple protocol circumvents any external additive or potential ionic liquid degradation and can be extended to water, which spontaneously generates microdroplets (ca. 3 µm) and catalyzes Brönsted rather than Lewis acid reactions. These results open new avenues not only in the use of ionic liquids as acid catalysts/solvents but also in the preparation of surfactant-free, well-defined ionic liquid microemulsions.