1,373 research outputs found
Progression of Performance Over Four Decades in Mastersā Athletics
Athletic performance at the highest level of competition has improved in a variety of sports over the last 40 years, most notably in swimming and track. Although improvements in performance have also been observed among mastersā athletes (ages 35 and older), data concerning mastersā athletic performance have only been certain since the 1970ās. Whether the magnitude of improvement in athletic performance from 1970 onward is different between elite and mastersā athletes, as well as between different age groups of mastersā athletes, has yet to be determined. PURPOSE: The purpose of this study was to investigate differences in progression of athletic performance between different age groups of mastersā athletes and elite athletes. METHODS: Track (100m and 400m running) and swimming (100m freestyle) times were collected from the World Masters Track and Field and the USA Swimming database. The time span ranged from 1975 to 2013. Age groups were separated into eight 5-year segments spanning from age 40 to 79 years. The top three times of each age group for each year were selected. Moreover, the top 3 track and field and swimming times of any age were collected for the same years to represent a reference standard from which to compare age-group records. A multiple linear regression analysis was used to evaluate the effect of the age Ć year Ć sex interaction with SPSS software. When a significant interaction was present, a comparison of slope between age groups and sexes was performed. RESULTS: There were significant age Ć year Ć sex interactions in all athletic events examined. Improvements in race times were significant (p\u3c0.05) in both sexes and for age groups 45 and older. Relative improvements in the 45+ age groups were significantly different from the fastest running times. The general trends were similar for 400m middle-distance running. The progressions of 100m swimming times were significant (p\u3c0.05) for all age groups and for both sexes. Analysis of differences in the slope showed that older athletes and women had a greater slope of improvement in performance during that time. CONCLUSION: We demonstrated that there have been significant improvements in athletic performance in mastersā athletes aged 45 and older in the track and field events, and those aged 40 and older in the swimming events in the past thirty nine years
Magnetic Reconnection in Black-Hole Magnetospheres: Lepton Loading into Jets, Superluminal Radio Blobs, and Multi-wavelength Flares
Supermassive black holes in active galactic nuclei launch relativistic jets,
as indicated by observed superluminal radio blobs. The energy source of these
jets is widely discussed in the theoretical framework of Blandford-Znajek
process, the electromagnetic energy extraction from rotating black holes (BHs),
while formation mechanism of the radio blobs in the
electromagnetically-dominated jets has been a long-standing problem. Recent
high-resolution magnetohydrodynamic simulations of magnetically arrested disks
exhibited magnetic reconnection in a transient magnetically-dominated part of
the equatorial disk near the BH horizon, which led to a promising scenario of
efficient MeV gamma-ray production and subsequent electron-positron pair
loading into BH magnetosphere. We develop this scenario to build a theoretical
framework on energetics, timescales and particle number density of the
superluminal radio blobs and discuss observable signatures in other wavebands.
We analytically show that the non-thermal electrons emit broadband photons from
optical to multi-MeV bands. The electron-positron pairs produced in the
magnetosphere are optically thick for synchrotron-self absorption, so that the
injected energy is stored in the plasma. The stored energy is enough to power
the superluminal radio blobs observed in M87. This scenario predicts rather dim
radio blobs around Sgr A*, which are consistent with no clear detection by
current facilities. In addition, this scenario inevitably produces strong X-ray
flares in a short timescale, which will be detectable by future X-ray
satellites.Comment: 14 pages, 5 figures, 1 table, accepted for publication in ApJ
Diabetic Cardiovascular Disease Induced by Oxidative Stress.
Cardiovascular disease (CVD) is the leading cause of morbidity and mortality among patients with diabetes mellitus (DM). DM can lead to multiple cardiovascular complications, including coronary artery disease (CAD), cardiac hypertrophy, and heart failure (HF). HF represents one of the most common causes of death in patients with DM and results from DM-induced CAD and diabetic cardiomyopathy. Oxidative stress is closely associated with the pathogenesis of DM and results from overproduction of reactive oxygen species (ROS). ROS overproduction is associated with hyperglycemia and metabolic disorders, such as impaired antioxidant function in conjunction with impaired antioxidant activity. Long-term exposure to oxidative stress in DM induces chronic inflammation and fibrosis in a range of tissues, leading to formation and progression of disease states in these tissues. Indeed, markers for oxidative stress are overexpressed in patients with DM, suggesting that increased ROS may be primarily responsible for the development of diabetic complications. Therefore, an understanding of the pathophysiological mechanisms mediated by oxidative stress is crucial to the prevention and treatment of diabetes-induced CVD. The current review focuses on the relationship between diabetes-induced CVD and oxidative stress, while highlighting the latest insights into this relationship from findings on diabetic heart and vascular disease
The integrin-binding defective FGF2 mutants potently suppress FGF2 signalling and angiogenesis.
We recently found that integrin Ī±vĪ²3 binds to fibroblast growth factor (FGF)-Ī±vĪ²31 (FGF1), and that the integrin-binding defective FGF1 mutant (Arg-50 to glutamic acid, R50E) is defective in signalling and antagonistic to FGF1 signalling. R50E suppressed angiogenesis and tumour growth, suggesting that R50E has potential as a therapeutic. However, FGF1 is unstable, and we had to express R50E in cancer cells for xenograft study, since injected R50E may rapidly disappear from circulation. We studied if we can develop antagonist of more stable FGF2. FGF2 is widely involved in important biological processes such as stem cell proliferation and angiogenesis. Previous studies found that FGF2 bound to Ī±vĪ²3 and antagonists to Ī±vĪ²3 suppressed FGF2-induced angiogenesis. However, it is unclear how FGF2 interacts with integrins. Here, we describe that substituting Lys-119/Arg-120 and Lys-125 residues in the predicted integrin-binding interface of FGF2 to glutamic acid (the K119E/R120E and K125E mutations) effectively reduced integrin binding to FGF2. These FGF2 mutants were defective in signalling functions (ERK1/2 activation and DNA synthesis) in NIH3T3 cells. Notably they suppressed, FGF2 signalling induced by WT FGF2 in endothelial cells, suggesting that the FGF2 mutants are antagonists. The FGF2 mutants effectively suppressed tube formation in vitro, sprouting in aorta ring assays ex vivo and angiogenesis in vivo The positions of amino acids critical for integrin binding are different between FGF1 and FGF2, suggesting that they do not interact with integrins in the same manner. The newly developed FGF2 mutants have potential as anti-angiogenic agents and useful tools for studying the role of integrins in FGF2 signalling
Position-Selected Molecular Ruler
The molecular ruler method allows the precise control of the gap between a parent gold structure and a deposited daughter structure using a conveniently grown self-assembled molecular multilayer as a lithographic mask. However, we cannot choose a position where the gap should be placed, since the ruler attaches to all exposed gold surfaces. In this work, a convenient method of selecting the position of nanogaps by further patterning the molecular multilayer using low-energy electron beam irradiation and piranha etchant is described
Multiorbital analysis of the effects of uniaxial and hydrostatic pressure on in the single-layered cuprate superconductors
The origin of uniaxial and hydrostatic pressure effects on in the
single-layered cuprate superconductors is theoretically explored. A two-orbital
model, derived from first principles and analyzed with the fluctuation exchange
approximation gives axial-dependent pressure coefficients, , , with a hydrostatic response
for both La214 and Hg1201 cuprates, in qualitative
agreement with experiments. Physically, this is shown to come from a unified
picture in which higher is achieved with an "orbital distillation",
namely, the less the main band is hybridized with the
and orbitals higher the . Some implications for obtaining higher
materials are discussed.Comment: 6pages, 4 figure
Nonlinear Elasticity of Single Collapsed Polyelectrolytes
Nonlinear elastic responses of short and stiff polyelectrolytes are
investigated by dynamic simulations on a single molecule level. When a
polyelectrolyte condensate undergoes a mechanical unfolding, two types of
force-extension curves, i.e., a force plateau and a stick-release pattern, are
observed depending on the strength of the electrostatic interaction. We provide
a physical interpretation of such force-extension behavior in terms of
intramolecular structures of the condensates. We also describe a charge
distribution of condensed counterions onto a highly stretched polyelectrolyte,
which clarifies a formation of one-dimensional strongly correlated liquid at
large Coulomb coupling regime where a stick-release pattern is observed. These
findings may provide significant insights into the relationship between a
molecular elasticity and a molecular mechanism of like-charge attractions
observed in a wide range of charged biopolymer systems.Comment: 5pages, 5figure
Prolactin alters blood pressure by modulating the activity of endothelial nitric oxide synthase
Prolactin is a hormone secreted by the pituitary gland that controls changes in the breast to enable milk production after the baby is born. In some mothers with pregnancy-related high blood pressure (BP), the concentration of prolactin in the blood is higher than normal, but whether this causes the high BP or is a consequence of it is uncertain. To answer this question, we have generated experimental mice that produce prolactin in the liver when we feed them a substance, indole-3-carbinol (IC3), that is found in broccoli. When fed normal chow, the mice are well, but, when fed IC3, they develop high BP and heart problems. This suggests that pregnant women with abnormally high prolactin levels may need special attention
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