The response of the pediatric head to impacts onto a rigid surface

The study of pediatric head injury relies heavily on the use of finite element models and child anthropomorphic test devices (ATDs). However, these tools, in the context of pediatric head injury, have yet to be validated due to a paucity of pediatric head response data. The goal of this study is to investigate the response and injury tolerance of the pediatric head to impact.Twelve pediatric heads were impacted in a series of drop tests. The heads were dropped onto five impact locations (forehead, occiput, vertex and right and left parietal) from drop heights of 15 and 30 cm. The head could freely fall without rotation onto a flat 19 mm thick platen. The impact force was measured using a 3-axis piezoelectric load cell attached to the platen.Age and drop height were found to be significant factors in the impact response of the pediatric head. The head acceleration (14%–15 cm; 103–30 cm), Head Injury Criterion (HIC) (253%–15 cm; 154%–30 cm) and impact stiffness (5800%–15 cm; 3755%–30 cm) when averaged across all impact locations increased with age from 33 weeks gestation to 16 years, while the pulse duration (66%–15 cm; 53%–30 cm) decreased with age. Increases in head acceleration, HIC and impact stiffness were also observed with increased drop height, while pulse duration decreased with increased drop height.One important observation was that three of the four cadaveric heads between the ages of 5-months and 22-months sustained fractures from the 15 cm and 30 cm drop heights. The 5-month-old sustained a right parietal linear fracture while the 11- and 22-month-old sustained diastatic linear fractures.     

后疫情时代全球可持续发展目标加速行动的推动

“SDGs加速行动”是国际组织、政府部门、私营机构和其他利益攸关方为加快落实2030年可持续发展议程采取的全球行动。2019年联合国可持续发展目标峰会后，政府、国际组织、私营部门等提出了214项SDGs加速行动。2019年爆发的新型冠状病毒肺炎（Corona Virus Disease 2019，COVID-19）对实现可持续发展目标带来了系列影响，后疫情时代如何推动全球SDGs加速行动的实施成为重要的问题。对可持续发展评估报告（2019）和可持续发展目标加速行动等政策文件进行信息提取，建立加速行动匹配性指数模型和各国应对新冠疫情的恢复力指数模型，根据匹配性-恢复力分类体系将各国按照17项可持续发展目标分为9类，为推动后疫情时代全球可持续发展目标加速行动提供支撑。研究发现：（1）现有可持续发展目标加速行动的实施与区域需求不匹配，且这种不匹配的情况在COVID-19爆发前已经出现；（2）加速行动的实施受限于现有可持续发展水平和国家经济基础，区域关注的可持续发展目标与其自然地理位置和社会发展水平有着密切的关系，多边组织机构和其他利益攸关方需要在发展中国家大力推动可持续发展加速行动；（3）下一步实施加速行动需要加强国际间的合作，根据分类框架和可持续发展目标的关联关系，分重点推进加速行动的实施，完善可持续发展指标监测体系，分类设立后疫情时代不同时期的阶段目标，分阶段循序渐进，定期反馈追踪，以在2030年促进17项可持续目标的实现。     

Internal consistency and test–retest reliability of an instrumented functional reaching task using wireless electromyographic sensors

The purpose of this study was to establish the internal consistency and test–retest reliability of the electromyographic and accelerometric data sampled from the prime movers of the dominant arm during an antigravity, within-arm’s length stand-reaching task without trunk restraint. Ten healthy young adults participated in two experimental sessions, approximately 7–10 days apart. During each session, subjects performed 15 trials of both a flexion- and an abduction-reaching task. Surface EMG and acceleration using wireless sensors were sampled from the anterior and middle deltoid. Reliability was established using Cronbach’s alpha, intraclass correlation coefficients (ICC 2, k) and standard error of measurements (SEM) for electromyographic reaction time, burst duration and normalized amplitude along with peak acceleration. Results indicated high degrees of inter-trial and test–retest reliability for flexion (Cronbach’s α range = 0.92–0.99; ICC range = 0.82–0.92) as well as abduction (Cronbach’s α range = 0.94–0.99; ICC range = 0.81–0.94) reaching. The SEM associated with response variables for flexion and abduction ranged from 1.55–3.26% and 3.33–3.95% of means, respectively. Findings from this study revealed that electromyographic and accelerometric data collected from prime movers of the arm during the relatively functional stand-reaching task were highly reproducible. Given its high reliability and portability, the proposed test could have applications in clinical and laboratory settings to quantify upper limb function.     

Estimates of field activity and metabolic rates of bonefish (Albula vulpes) in coastal marine habitats using acoustic tri-axial accelerometer transmitters and intermittent-flow respirometry

We tested the utility of acoustic tri-axial acceleration transmitters in combination with ethogram and respirometry studies to quantify the activity patterns and field metabolic rates of free-swimming bonefish (Albula vulpes) in the coastal waters of Eleuthera, The Bahamas. Bonefish were found to exhibit relatively low activity levels in the field with no evidence of diel patterns or inter-sexual variation. Low activity levels reported by the accelerometers reflected low swimming speeds and intermittent swimming behaviours (i.e., swim-then-drift) that maximized energy efficiency. Such behaviours were also observed when conducting ethograms on bonefish held in a large field mesocosm. Laboratory derived standard metabolic rates and maximum metabolic rates during recovery from exercise were combined with acceleration transmitter calibrations to determine that individual bonefish typically operate at between 40 and 60% of their estimated metabolic scope in the field. However, occasionally acceleration values in the field were indicative of high intensity bursting activity that exhausted the majority of their estimated metabolic scope (0.7% of all field observations exceed 90% of estimated metabolic scope). Data gathered in this study provide a critical starting point for the development of a bioenergetics model for bonefish which will ultimately lend clues into how fish make a living in tropical tidal flats environments. Given that this paper is one of the first to use transmitters rather than archival loggers to collect data on tri-axial acceleration on fish, we also discuss the opportunities and limitations of using this new technology for marine fisheries research.     

Upper body accelerations during planned gait termination in young and older women

Transitory tasks, such as gait termination, involve interactions between neural and biomechanical factors that challenge postural stability and head stabilization patterns in older adults. The aim of the study was to compare upper body patterns of acceleration during planned gait termination at different speeds between young and older women. Ten young and 10 older women were asked to carry out three gait termination trials at slow, comfortable and fast speed. A stereophotogrammetric system and a 15-body segments model were used to calculate antero-posterior whole-body Center of Mass (AP CoM) speed and to reconstruct the centroids of head, trunk and pelvis segments. RMS of three-dimensional linear accelerations were calculated for each segment and the transmission of acceleration between two segments was expressed as a percentage difference. Older women reported lower AP CoM speed and acceleration RMS of the three upper body segments than young women across the three speed conditions. A lower pelvis-to-trunk attenuation of accelerations in the transverse plane was observed in older compared to young women, and mainly in the medio-lateral direction. As possible explanations, older women may not need to reduce acceleration as young women because of their lower progression speed and the subsequent acceleration at upper body levels. On the other hand, older women may prioritize a decrease in the whole body progression speed at expense of the involvement of upper body segments. This limits the attenuation of the accelerations, particularly in the transverse plane, implying an increased dynamic unbalance in performing this transitory task.     

Muscle mechanism: The acceleration of the load

The load (force/cross-section) determines the response of muscle power output, force and speed of contraction). The force is the product of the mass by the acceleration, thus the same force is generated by an infinite number of mass and acceleration couples and each one of these couples displays different physical and biological effects. Therefore, the load must be defined both by the mass and by the acceleration. Early muscle investigators were well aware of this situation as it is indicated by the work of Hill on the flexion of the arm against the “heavy fly-wheel”. By making use of a model of sarcomere contraction we show here that the acceleration of the load is the first determinant of the time course of the process of generation of the isometric tension. We also propose that, in order to reproduce the rapid release, it is not necessary to invoke the presence of a distinct elastic element in the contractile machinery. It is sufficient to assume that the stiffness of the same machinery increases with the contractile force.     

鲢快速逃逸游泳行为研究

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3D propagation of the shock-induced vibrations through the whole lower-limb during running

Shock-induced vibrations to the feet have been related to the feel of comfort, the biomechanical control of performance, and the risk of fatigue or injury. Up to recently, the complexity of measuring the human biodynamic response to vibration exposure implied to focus most of the research on the axial acceleration at the tibia. Using wireless three-dimensional accelerometers, this paper investigates the propagation of shock-induced vibrations through the whole lower-limb during running in the temporal and the spectral domains. Results indicated that the vibrations were not consistent across the lower-limb, showing various spatial and spectral distributions of energy. The amount of energy was not constantly decreasing from the distal to the proximal extremity of the runner’s lower-limb, especially regarding the lateral epicondyle of the femur. Vibrations in the transversal plane of the segments were substantial compared to the longitudinal axis regarding the distal extremity of the tibia, and the lateral epicondyle of the femur. Further, the spectral content was wider at the distal than at the proximal end of the lower-limb. Finally, to get a thorough understanding of the risks incurred by the runners, the need to account for shock-induced vibrations up to 50 Hz has been stressed when investigating three-dimensional vibrations. The overall study raises attention on the substantial importance of the transverse components of the acceleration, and their potential relation to shear fatigue and injury during running.     

Adaptive radiation in sauropod dinosaurs: bone histology indicates rapid evolution of giant body size through acceleration

The well-preserved histology of the geologically oldest sauropod dinosaur from the Late Triassic allows new insights into the timing and mechanism of the evolution of the gigantic body size of the sauropod dinosaurs. The oldest sauropods were already very large and show the same long-bone histology, laminar fibro-lamellar bone lacking growth marks, as the well-known Jurassic sauropods. This bone histology is unequivocal evidence for very fast growth. Our histologic study of growth series of the Norian Plateosaurus indicates that the sauropod sistergroup, the Late Triassic and early Jurassic Prosauropoda, reached a much more modest body size in a not much shorter ontogeny. Increase in growth rate compared to the ancestor (acceleration) is thus the underlying process in the phylogenetic size increase of sauropods. Compared to all other dinosaur lineages, sauropods were not only much larger but evolved very large body size much faster. The prerequisite for this increase in growth rate must have been a considerable increase in metabolic rate, and we speculate that a bird-like lung was important in this regard.     

Biochemical and kinetic analysis of the GH3 family beta-xylosidase from Aspergillus awamori X-100

The beta-xylosidase from Aspergillus awamori X-100 belonging to the family 3 glycoside hydrolase revealed a distinctive transglycosylating ability to produce xylooligosaccharides with degree of polymerization more than 7. In order to explain this fact, the enzyme has been subjected to the detailed biochemical study. The enzymatic hydrolysis of p-nitrophenyl beta-D-xylopyranoside was found to occur with overall retention of substrate anomeric configuration suggesting cleavage of xylosidic bonds through a double-displacement mechanism. Kinetic study with aryl beta-xylopyranosides substrates, in which leaving group pK(a)s were in the range of 3.96-10.32, revealed monotonic function of log(k(cat)) and no correlation of log(k(cat)/Km) versus pKa values indicating deglycosylation as a rate-limiting step for the enzymatic hydrolysis. The classical bell-shaped pH dependence of k(cat)/Km indicated two ionizable groups in the beta-xylosidase active site with apparent pKa values of 2.2 and 6.4. The kinetic parameters of hydrolysis, Km and k(cat), of p-nitrophenyl beta-D-1,4-xylooligosaccharides were very close to those for hydrolysis of p-nitrophenyl-beta-D-xylopyranoside. Increase of p-nitrophenyl-beta-D-xylopyranoside concentration up to 80 mM led to increasing of the reaction velocity resulting in k(cat)(app)=81 s(-1). Addition of alpha-methyl D-xylopyranoside to the reaction mixture at high concentration of p-nitrophenyl-beta-D-xylopyranoside (50 mM) caused an acceleration of the beta-xylosidase-catalyzed reactions and appearance of a new transglycosylation product, alpha-methyl D-xylopyranosyl-1,4-beta-D-xylopyranoside, that was identified by 1H NMR spectroscopy. The kinetic model suggested for the enzymatic reaction was consistent with the results obtained.