274 research outputs found
The impact of in-season national team soccer play on injury and player availability in a professional club
This study investigated the impact of in-season national team duty on injury rates and player availability in a professional soccer club. Time-loss injuries and exposure time during club and national team duties were recorded prospectively over 5 seasons (2009â2014). A time-loss injury was sustained by 37.7% of squad members participating in national duty, all injuries occurring in match-play. The incidence (per 1000 h exposure) for national team player match-play injuries did not differ (P = 0.608) to that for all players in club competitions: 48.0 (95% CI 20.9â75.5) vs. 41.9 (95% CI 36.5â47.4), incidence rate ratio = 1.2 (CI: 0.8â2.4). The majority (58%) of national team injuries resulted in a layoff â€1 week. Of all working days lost to injury generally, 5.2% were lost through injury on national duty. Injury incidence in the week following national duty was comparable (P = 0.818) in players participating or not: 7.8 (95% CI 3.6â12.0) vs. 7.1 (95% CI: 4.6â9.6), incidence rate ratio = 1.1 (CI: 0.7â2.7). While approximately 40% of participating players incurred a time-loss injury on national duty, no training injuries were sustained and injuries made up a negligible part of overall club working days lost to injury. Following duty, players had a similar injury risk to peers without national obligations
An image analysis based damage classification methodology
Measurement of the extent of damage in a real structure is extremely important in terms of
any maintenance strategy. However, this measurement often turns out to be difficult, time consuming and
error â prone. The necessity of a simple, fast and relatively inexpensive damage monitoring system with
reliable measurements is growing for quite sometime. The paper proposes a camera based image analysis
technique to quantify and classify damage in structures at various levels of scale. The general method has
been applied to corroded plate specimens in the laboratory with the aim to identify the affected areas on a
steel pile due to pitting corrosion. The method depends on the contrast of the corroded region with respect to
its surroundings, performs intelligent edge detection through image processing techniques and computes each
affected and closed region to predict the total area of the affected part along with its spatial distribution on a
two dimensional plane. Moreover the performance of the camera allows defining a detection threshold and the
so-called probability of detection (PoD) and probability of false alarms (PFA). PoD are suggested as functions
of the area of the pitting for the construction of Receiver-Operating-Characteristic (ROC) curves. The
methodology can be used as a tool for the owners/managers of the structure for objectively quantifying and
localising the extent of pitting corrosion, rather than providing information through a subjective visual
assessment. Moreover, it allows introducing the probability of detection and probability of false alarms in the
decision chain and in risk analysis. The method is shown to be robust, reliable, simple and inexpensive
Reliability based assessment of structures in marine environment
The Atlantic Zone in Europe, like any coastal region, has many harbours, communication infrastructures and tourist buildings. These infrastructural elements are necessary for the economic life and sustainability of the region. The managers/owners of such structures in the region are therefore confronted with questions concerning the damage, maintenance, rehabilitation and the extent to which this maintenance or rehabilitation should be carried out. Since there are many parameters affecting the damage of a structure, it is of prime importance to know which of those parameters are guiding and what their relative importance are. Also, the effects of various critical limit states, possible conflicts between the engineerâs and the owners criteria of failure and the mutual interrelationships among possible health assessment, monitoring techniques and repair options need to be assimilated within a single probabilistic framework accounting for the various epistemic and aleatory uncertainties accompanied with such decision making process. A central factor in this decision making process is the choice of damage model of a material and its evolution in time. In this paper, a general probabilistic format is proposed for structural assessment and maintenance. A questionnaire based survey has been carried out to procure information compatible with the proposed framework with special emphasis on damage of materials in the marine environment. Parameter importance based studies on steel and concrete have been subsequently performed in order to illustrate the impacts of the interrelationships of some critical components in the proposed framework. The study provides the owners/managers with a method of establishing a choice protocol for receiver operating characteristics (ROC) of non-destructive assessment techniques of structures based on its specific needs. This methodology, in association with reliable information regarding the choice of rehabilitation of a structure at an optimised cost can be helpful for any kind of decision making process in relation to a structure
ROC dependent event isolation method for image processing based assessment of corroded harbour structures
The localisation and calibration of damage in a structure are often difficult, time consuming, subjective and error prone. The importance of a simple, fast and relatively inexpensive non-destructive technique (NDT) with reliable measurements is thus greatly felt. The usefulness and the efficiency of any such technique are often affected by environmental conditions. The definition of damage and the subsequent interpretation of the possible consequences due to the damage introduce subjectivity into an NDT technique and affect its performance. It is of great importance in terms of practical application to find out the efficiency of an NDT technique in a probabilistic way for various damage definitions and environmental conditions through the use of receiver operating characteristic (ROC) curves. Such variations of performance of an NDT tool can be predicted through simulation processes, and the test conditions conducive to good detections can be isolated and ranked according to their relative efficiency. This paper considers a camera based image analysis technique to identify,quantify and classify damage in structures at various levels of scale. The general method has been applied to identify the affected areas on aluminium due to pitting corrosion. The method depends on the optical contrast of the corroded region with respect to its surroundings, performs intelligent edge detection through image processing techniques and computes each affected and closed region to predict the total area of the affected part, together with its spatial distribution on a two-dimensional plane. The effects of various environmental factors on the quality of such images are simulated from an original photograph. The objectivity and the amount of available information, quantification and localisation and the extent of pitting corrosion are observed, together with the various constructed ROC curves. The method provides the engineer, the owner of the structure and the end-user of the NDT technique with a tool to assess the performance of the structure in an as-built condition and decide on the appropriateness of a certain NDT, under a given environmental condition and a certain definition of damage. Moreover, it allows the findings of the NDT results to be introduced in the decision chain and risk analysis
Improved image analysis based corrosion assessment using preprocessing techniques
The importance of non-destructive techniques (NDT) in structural health monitoring programmes is being critically felt in the recent times. The quality of the measured data, often affected by various environmental conditions can be a guiding factor in terms usefulness and prediction efficiencies of the various detection and monitoring methods used in this regard. Often, a preprocessing of the acquired data in relation to the affecting environmental parameters can improve the information quality and lead towards a significantly more efficient and correct prediction process. The improvement can be directly related to the final decision making policy about a structure or a network of structures and is compatible with general probabilistic frameworks of such assessment and decision making programmes. This paper considers a preprocessing technique employed for an image analysis based structural health monitoring methodology to identify sub-marine pitting corrosion in the presence of variable luminosity, contrast and noise affecting the quality of images. A preprocessing of the gray-level threshold of the various images is observed to bring about a significant improvement in terms of damage detection as compared to an automatically computed gray-level threshold. The case dependent adjustments of the threshold enable to obtain the best possible information from an existing image. The corresponding improvements are observed in a qualitative manner in the present study
Structural characterization of water-bearing silicate and aluminosilicate glasses by high-resolution solid-state NMR
Various one- and two-dimensional high-resolution solid-state NMR techniques have been applied to hydrous silicate and aluminosilicate glasses: simple acquisition, cross-polarization (CP-MAS), heteronuclear correlation (HETCOR), dipolar dephasing, spin counting, double-quantum correlation, and rotational echo double resonance (REDOR). The comparison of the results obtained for sodium tetrasilicate and phonolite glasses suggests that the water incorporation mechanisms are qualitatively similar for these two compositions. From proton NMR experiments, we observe no evidence of proton clustering and a wide range of chemical shifts ranging from 0 to 16 ppm, even for the aluminosilicate phonolite glass, identifying at least three types of hydroxyl (OH) protons in addition to molecular H2O. This variety of OH groups can be discussed in terms of hydrogen bonding strength. For both compositions, the results indicate some depolymerization of the tetrahedral network, but the picture cannot be so simple as to completely exclude any of the different previously proposed models for water incorporation in silicate glasses
Advancing Raman Microspectroscopy for Cellular and Subcellular Analysis: Towards in Vitro High Content Spectralomic Analysis
In the confocal mode, Raman microspectroscopy can profile the biochemical content of biological cells at a subcellular level, and any changes to it by exogenous agents, such as therapeutic drugs or toxicants. As an exploration of the potential of the technique as a high content, label free analysis technique, this report reviews work to monitor the spectroscopic signatures associated with the uptake and response pathways of commercial chemotherapeutic agents and polymeric nanoparticles by human lung cells. It is demonstrated that the signatures are reproducible and characteristic of the cellular event, and can be used, for example, to identify the mode of action of the agent as well as the subsequent cell death pathway, and even mechanisms of cellular resistance. Data mining approaches are discussed and a spectralomics approach is proposed
Proposal to conserve the name Bosea yervamora (Amaranthaceae) with a conserved type
Linnaeus (Crit. Bot.: 77. 1737) coined the genus name âBoseaâ
to honor Caspar Bose (1645â1700), who owned a famous garden in
Leipzig (âBose Senator Lipsiensisâ). Later Linnaeus (Hort. Cliff.:
84. 1738) spelled the name as âBosiaâ, provided a description and
referenced earlier works, viz., Plukenet (Almagestum: 42. 1696),
Sloane (Cat. Pl. Jamaica: 135 [sub Tilia]. 1696, Voy. Jamaica 2:
19 [sub Tilia], t. 158, fig. 3. 1725), Ray (Hist. Pl. 3 (24: DendrologiĂŠ): 88 [sub Tilia]. 1704), Walther (Design. Pl.: 24 [sub Frutex],
t. 10. 1735), and Thran (Index Pl. Horti Carolsruh.: 44. 1733). Subsequently, Linnaeus (Gen. Pl., ed. 2: 102. 1742, Sp. Pl.: 225. 1753;
Gen. Pl., ed. 5: 105. 1754) reverted to the original spelling, and it
was validated as Bosea, monotypic when published in 1753 with
B. yervamora L. as generitype. The epithet is a noun in apposition.
The name B. yervamora L. is still in use to refer to the only species
of Amaranthaceae endemic in the Canary Islands, where it is common in thermophilous woodlan
Southern California Seismic Network Update
The authoritative region of the Southern California Seismic Network (SCSN) extends across southern California, from the U.S./Mexico international border to Coalinga and Owens Valley in central California (Figure 1). This area contains almost 20 million inhabitants, including two of the ten largest cities in the United States (Los Angeles and San Diego) and the two largest harbors (Los Angeles and Long Beach) in the nation. SCSN also reports on earthquakes in Baja California, which could potentially cause damage in the U.S. More than fifty earthquakes (not including aftershocks) are felt each year, and an average of 1.5 events per year are potentially damaging (magnitude greater than 5.0). Immediately after a moderate or large earthquake, SCSN provides information about the size, location, and distribution of ground shaking. Emergency managers use this information to coordinate rescue operations, guide inspectors in the search for damage, and satisfy the public's need for information. The historical record of earthquake occurrences in California is important to insurers, geotechnical engineers, and city planners
Injury risk factors, screening tests and preventative strategies: A systematic review of the evidence that underpins the perceptions and practices of 44 football (soccer) teams from various premier leagues
Purpose: To systematically review the scientific level of evidence for the âTop 3â risk factors, screening tests and preventative exercises identified by a previously published survey of 44 premier league football (soccer) teams. Also, to provide an overall scientific level of evidence and graded recommendation based on the current research literature.
Methods: A systematic literature search (Pubmed [MEDLINE], SportDiscus, PEDRO and Cochrane databases). The quality of the articles was assessed and a level of evidence (1++ to 4) was assigned. Level 1++ corresponded to the highest level of evidence available and 4, the lowest. A graded recommendation (A: strong, B: moderate, C: weak, D: insufficient evidence to assign a specific recommendation) for use in the practical setting was given.
Results: Fourteen studies were analysed. The overall level of evidence for the risk factors previous injury, fatigue and muscle imbalance were 2++, 4 and âinconclusiveâ, respectively. The graded recommendation for functional movement screen, psychological questionnaire and isokinetic muscle testing were all âDâ. Hamstring eccentric had a weak graded âCâ recommendation, and eccentric exercise for other body parts was âDâ. Balance/proprioception exercise to reduce ankle and knee sprain injury was assigned a graded recommendation âDâ.
Conclusions: The majority of perceptions and practices of premier league teams have a low level of evidence and low graded recommendation. This does not imply that these perceptions and practices are not important or not valid, as it may simply be that they are yet to be sufficiently validated or refuted by research
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