Determinants of countermovement jump performance: a kinetic and kinematic analysis

This study aimed to investigate the contributions of kinetic and kinematic parameters to inter-individual variation in countermovement jump (CMJ) performance. Two-dimensional kinematic data and ground reaction forces during a CMJ were recorded for 18 males of varying jumping experience. Ten kinetic and eight kinematic parameters were determined for each performance, describing peak lower-limb joint torques and powers, concentric knee extension rate of torque development and CMJ technique. Participants also completed a series of isometric knee extensions to measure the rate of torque development and peak torque. CMJ height ranged from 0.38 to 0.73 m (mean 0.55 ± 0.09 m). CMJ peak knee power, peak ankle power and take-off shoulder angle explained 74% of this observed variation. CMJ kinematic (58%) and CMJ kinetic (57%) parameters explained a much larger proportion of the jump height variation than the isometric parameters (18%), suggesting that coachable technique factors and the joint kinetics during the jump are important determinants of CMJ performance. Technique, specifically greater ankle plantar-flexion and shoulder flexion at take-off (together explaining 58% of the CMJ height variation), likely influences the extent to which maximal muscle capabilities can be utilised during the jump

Rapid Circumstellar Disk Evolution and an Accelerating Star Formation Rate in the Infrared Dark Cloud M17 SWex

We present a catalog of 840 X-ray sources and first results from a 100 ks Chandra X-ray Observatory imaging study of the filamentary infrared dark cloud G014.225$-$00.506, which forms the central regions of a larger cloud complex known as the M17 southwest extension (M17 SWex). In addition to the rich population of protostars and young stellar objects with dusty circumstellar disks revealed by Spitzer Space Telescope archival data, we discover a population of X-ray-emitting, intermediate-mass pre--main-sequence stars (IMPS) that lack infrared excess emission from circumstellar disks. We model the infrared spectral energy distributions of this source population to measure its mass function and place new constraints on the inner dust disk destruction timescales for 2-8 $M_{\odot}$ stars. We also place a lower limit on the star formation rate (SFR) and find that it is quite high ($\dot{M}\ge 0.007~M_{\odot}$ yr$^{-1}$), equivalent to several Orion Nebula Clusters in G14.225$-$0.506 alone, and likely accelerating. The cloud complex has not produced a population of massive, O-type stars commensurate with its SFR. This absence of very massive (${\ge}20~M_{\odot}$) stars suggests that either (1) M17 SWex is an example of a distributed mode of star formation that will produce a large OB association dominated by intermediate-mass stars but relatively few massive clusters, or (2) the massive cores are still in the process of accreting sufficient mass to form massive clusters hosting O stars.Comment: 29 pages, 9 figures, accepted to Ap

SURFACE MEASURED ACCELERATIONS DURING CRICKET FAST-BOWLING

The aim of this research was to quantify the magnitude and timing of surface measured accelerations during the fast-bowling action. Eleven males performed 6 maximum velocity deliveries with accelerometers positioned over: both ankles; knees; hips; L5; L1; and the C7 vertebrae. Accelerometer signals exhibited decreased peak and increased time to peak acceleration from the ankle to the C7 sensor. Even when distal accelerations were largest at front foot contact, the body was still able to dissipate more than 90% of the acceleration. Active and passive mechanisms such as joint compliance and spinal compression within the body therefore likely contribute to the progressive attenuation of accelerations. The effects of such compliance on investigations of the intersegmental forces and moments during cricket fast-bowling via inverse dynamics warrants further investigation. KEYWORDS: accelerometer, attenuation, inertial measurement unit, ground reaction force

Transcript Profiling of Elf5+/− Mammary Glands during Pregnancy Identifies Novel Targets of Elf5

Background: Elf5, an epithelial specific Ets transcription factor, plays a crucial role in the pregnancy-associated development of the mouse mammary gland. Elf5 2/2 embryos do not survive, however the Elf5 +/2 mammary gland displays a severe pregnancy-associated developmental defect. While it is known that Elf5 is crucial for correct mammary development and lactation, the molecular mechanisms employed by Elf5 to exert its effects on the mammary gland are largely unknown. Principal Findings: Transcript profiling was used to investigate the transcriptional changes that occur as a result of Elf5 haploinsufficiency in the Elf5 +/2 mouse model. We show that the development of the mouse Elf5 +/2 mammary gland is delayed at a transcriptional and morphological level, due to the delayed increase in Elf5 protein in these glands. We also identify a number of potential Elf5 target genes, including Mucin 4, whose expression, is directly regulated by the binding of Elf5 to an Ets binding site within its promoter. Conclusion: We identify novel transcriptional targets of Elf5 and show that Muc4 is a direct target of Elf5, further elucidatin

Termination detection for fine-grained message-passing architectures

Barrier primitives provided by standard parallel programming APIs are the primary means by which applications implement global synchronisation. Typically these primitives are fully-committed to synchronisation in the sense that, once a barrier is entered, synchronisation is the only way out. For message-passing applications, this raises the question of what happens when a message arrives at a thread that already resides in a barrier. Without a satisfactory answer, barriers do not interact with message-passing in any useful way. In this paper, we propose a new refutable barrier primitive that combines with message-passing to form a simple, expressive, efficient, well-defined API. It has a clear semantics based on termination detection, and supports the development of both globally-synchronous and asynchronous parallel applications. To evaluate the new primitive, we implement it in a prototype large-scale message-passing machine with 49,152 RISC-V threads distributed over 48 FPGAs. We show that hardware support for the primitive leads to a highly-efficient implementation, capable of synchronisation rates that are an order-of-magnitude higher than what is achievable in software. Using the primitive, we implement synchronous and asynchronous versions of a range of applications, observing that each version can have significant advantages over the other, depending on the application. Therefore, a barrier primitive supporting both styles can greatly assist the development of parallel programs.Funded by EPSRC grant EP/N031768/1 (POETS project

Converting GLX2-1 into an Active Glyoxalase II

Arabidopsis thaliana glyoxalase 2-1 (GLX2-1) exhibits extensive sequence similarity with GLX2 enzymes but is catalytically inactive with SLG, the GLX2 substrate. In an effort to identify residues essential for GLX2 activity, amino acid residues were altered at positions 219, 246, 248, 325, and 328 in GLX2-1 to be the same as those in catalytically active human GLX2. The resulting enzymes were overexpressed, purified, and characterized using metal analyses, fluorescence spectroscopy, and steady-state kinetics to evaluate how these residues affect metal binding, structure, and catalysis. The R246H/N248Y double mutant exhibited low level S-lactoylglutathione hydrolase activity, while the R246H/N248Y/Q325R/R328K mutant exhibited a 1.5−2-fold increase in kcat and a decrease in Km as compared to the values exhibited by the double mutant. In contrast, the R246H mutant of GLX2-1 did not exhibit glyoxalase 2 activity. Zn(II)-loaded R246H GLX2-1 enzyme bound 2 equiv of Zn(II), and 1H NMR spectra of the Co(II)-substituted analogue of this enzyme strongly suggest that the introduced histidine binds to Co(II). EPR studies indicate the presence of significant amounts a dinuclear metal ion-containing center. Therefore, an active GLX2 enzyme requires both the presence of a properly positioned metal center and significant nonmetal, enzyme−substrate contacts, with tyrosine 255 being particularly important