7,310 research outputs found
Effects of Joint-Fixing on the Velocity of the Racket Head in the Tennis Serve
The velocity of the racket head in a tennis serve is one of the significant factors in a match. The fastest velocity of the racket head before impact may be performed by the appropriate sequence of segmental rotations. Anderson (1979) and Miyashita et al. (1980) reported that there was a close relationship between the muscular activities patterning in the overarm throw and the tennis serve. Elliott (1983) observed the movement pattern for the power serve in tennis using kinematic data. However, there were no reports concerning effects of joint fixing on the velocity of the racket head in a tennis serve.
The purpose of this study was first to investigate the serving motion in tennis by means of a kinematic method. Second, it was to more clearly define the appropriate sequence of segmental rotations employed
Arc-like distribution of high CO(J=3-2)/CO(J=1-0) ratio gas surrounding the central star cluster of the supergiant HII region NGC 604
We report the discovery of a high CO(J=3-2)/CO(J=1-0) ratio gas with an
arc-like distribution (``high-ratio gas arc'') surrounding the central star
cluster of the supergiant HII region NGC 604 in the nearby spiral galaxy M 33,
based on multi-J CO observations of a 5' 5' region of NGC 604
conducted using the ASTE 10-m and NRO 45-m telescopes. The discovered
``high-ratio gas arc'' extends to the south-east to north-west direction with a
size of 200 pc. The western part of the high-ratio gas arc closely
coincides well with the shells of the HII regions traced by H and radio
continuum peaks. The CO(J=3-2)/CO(J=1-0) ratio, R_{3-2/1-0}, ranges between 0.3
and 1.2 in the observed region, and the R_{3-2/1-0} values of the high-ratio
gas arc are around or higher than unity, indicating very warm (T_kin > 60 K)
and dense (n(H_2) > 10^{3-4} cm^{-3}) conditions of the high-ratio gas arc. We
suggest that the dense gas formation and second-generation star formation occur
in the surrounding gas compressed by the stellar wind and/or supernova of the
first-generation stars of NGC 604, i.e., the central star cluster of NGC 604.Comment: 4 pages, 4 figures. The Astrophysical Journal Letters, in pres
Ultralow mode-volume photonic crystal nanobeam cavities for high efficiency coupling to individual carbon nanotube emitters
We report on high efficency coupling of individual air-suspended carbon
nanotubes to silicon photonic crystal nanobeam cavities. Photoluminescence
images of dielectric- and air-mode cavities reflect their distinctly different
mode profiles and show that fields in the air are important for coupling. We
find that the air-mode cavities couple more efficiently, and estimated
spontaneous emission coupling factors reach a value as high as 0.85. Our
results demonstrate advantages of ultralow mode-volumes in air-mode cavities
for coupling to low-dimensional nanoscale emitters.Comment: 4 pages, 4 figure
Direct evidence for ferromagnetic spin polarization in gold nanoparticles
We report the first direct observation of ferromagnetic spin polarization of
Au nanoparticles with a mean diameter of 1.9 nm using X-ray magnetic circular
dichroism (XMCD). Owing to the element selectivity of XMCD, only the gold
magnetization is explored. Magnetization of gold atoms estimated by XMCD shows
a good agreement with the results obtained by conventional magnetometry. This
result is evidence of intrinsic spin polarization in nano-sized gold.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Let
Superoxide dismutase analog (Tempol: 4-hydroxy-2, 2, 6, 6-tetramethylpiperidine 1-oxyl) treatment restores erectile function in diabetes-induced impotence.
We hypothesized that the administration of the superoxide dismutase (SOD) mimetic Tempol (4-hydroxy-2, 2, 6, 6-tetramethylpiperidine 1-oxyl) may reverse diabetes-induced erectile dysfunction. To test this hypothesis, reactive oxygen species-related genes (SOD1, SOD2, GP x 1, CAT, NOS2, NOS3) were tested, erectile functional studies and immunohistochemical analysis were carried out in diabetic rats treated with or without Tempol. Thirty Sprague-Dawley (3-4 months old) rats were divided into three groups (n=10 each), 20 with diabetes (diabetic control and Tempol treatment) and 10 healthy controls. At 12 weeks after the induction of diabetes by streptozotocin and Tempol treatment, all groups underwent in vivo cavernous nerve stimulation. Rat crura were harvested and the expression of antioxidative defense enzymes were examined by semi-quantitative reverse transcriptase PCR (RT-PCR). To confirm the RT-PCR results, we carried out immunohistochemistry (IHC) for catalase (CAT) and iNOS (NOS2). Nitration of tyrosine groups in proteins was also examined by IHC. Mean intracavernous pressure in the diabetic group was significantly lower than in the healthy controls (P <0.001) and was reversed by Tempol treatment (P <0.0108). NOS2 protein expression was significantly increased in diabetic animals compared with healthy controls and Tempol restored NOS2 protein level. Nitrotyrosine was also higher in diabetic animals and although Tempol treatment decreased its formation, it remained higher than that found in healthy controls. This study suggests that Tempol treatment increased erectile function through modulating oxidative stress-related genes in diabetic rats. This is the first report about the relationship between diabetes-induced erectile dysfunction and oxidative stress, and antioxidative therapy using the superoxide dismutase mimetic, Tempol, to restore erectile function
Measurement of Resonant Frequency and Quality Factor of Microwave Resonators: Comparison of Methods
Precise microwave measurements of sample conductivity, dielectric, and
magnetic properties are routinely performed with cavity perturbation
measurements. These methods require the accurate determination of quality
factor and resonant frequency of microwave resonators. Seven different methods
to determine the resonant frequency and quality factor from complex
transmission coefficient data are discussed and compared to find which is most
accurate and precise when tested using identical data. We find that the
nonlinear least-squares fit to the phase vs. frequency is the most accurate and
precise when the signal-to-noise ratio is greater than 65. For noisier data,
the nonlinear least squares fit to a Lorentzian curve is more accurate and
precise. The results are general and can be applied to the analysis of many
kinds of resonant phenomena.Comment: 29 pages, 11 figure
Optical control of individual carbon nanotube light emitters by spectral double resonance in silicon microdisk resonators
Single-walled carbon nanotubes have advantages as a nanoscale light source
compatible with silicon photonics because they show room-temperature
luminescence at telecom-wavelengths and can be directly synthesized on silicon
substrates. Here we demonstrate integration of individual light-emitting carbon
nanotubes with silicon microdisk resonators. Photons emitted from nanotubes are
efficiently coupled to whispering gallery modes, circulating within the disks
and lighting up their perimeters. Furthermore, we control such emission by
tuning the excitation wavelength in and out of resonance with higher order
modes in the same disk. Our results open up the possibilities of using nanotube
emitters embedded in photonic circuits that are individually addressable
through spectral double resonance.Comment: 5 pages, 4 figure
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