758 research outputs found
On the Spin content of the Nucleon
A QCD sum rule calculation of Balistky and Ji on the spin content of the
nucleon is done with a different approach to the evaluation of the bilocal
contributions and to the extraction of the nucleon pole residues. The result
obtained is much more numerically stable which puts their conclusion that about
half of the nucleon spin is carried by gluons on firmer ground.Comment: 7 pages, two (eps) figure, minor corrections and one figure adde
Diversidade genética de isolados monouredinias de Phakopsora pachyrhizi coletados em diferentes regiões do Brasil.
O objetivo deste trabalho foi avaliar a diversidade genética de isolados monourediniais do fungo Phakopsora pachyrhizi coletados em diferentes regiões produtoras de soja no Brasil, por meio da análise das sequências da região do espaçador interno transcrito 1 (ITS1)
Acceleration effect of coupled oscillator systems
We have developed a curved isochron clock (CIC) by modifying the radial
isochron clock to provide a clean example of the acceleration (deceleration)
effect. By analyzing a two-body system of coupled CICs, we determined that an
unbalanced mutual interaction caused by curved isochron sets is the minimum
mechanism needed for generating the acceleration (deceleration) effect in
coupled oscillator systems. From this we can see that the Sakaguchi and
Kuramoto (SK) model which is a class of non-frustrated mean feild model has an
acceleration (deceleration) effect mechanism. To study frustrated coupled
oscillator systems, we extended the SK model to two oscillator associative
memory models, one with symmetric and one with asymmetric dilution of coupling,
which also have the minimum mechanism of the acceleration (deceleration)
effect. We theoretically found that the {\it Onsager reaction term} (ORT),
which is unique to frustrated systems, plays an important role in the
acceleration (de! celeration) effect. These two models are ideal for evaluating
the effect of the ORT because, with the exception of the ORT, they have the
same order parameter equations. We found that the two models have identical
macroscopic properties, except for the acceleration effect caused by the ORT.
By comparing the results of the two models, we can extract the effect of the
ORT from only the rotation speeds of the oscillators.Comment: 35 pages, 10 figure
A Study of the \eta \pi^{0} Spectrum and Search for a J^{PC} = 1^{-+} Exotic Meson
A partial wave analysis (PWA) of the of the system (where ) produced in the charge exchange reaction at an incident momentum of 18 GeV is presented as a function of
invariant mass, , and momentum transfer squared,
, from the incident to the outgoing system. , and waves were included in the PWA. The
and states are clearly observed in the overall
effective mass distribution as well as in the amplitudes associated with
wave and waves respectively after partial wave decomposition. The observed
distributions in moments (averages of spherical harmonics) were compared to the
results from the PWA and the two are consistent. The distribution in
for individual waves associated with natural and
unnatural parity exchange in the -channel are consistent with Regge
phenomenology. Of particular interest in this study is the wave since this
leads to an exotic for the system. A wave is
present in the data, however attempts to describe the mass dependence of the
amplitude and phase motion with respect to the wave as a Breit-Wigner
resonance are problematic. This has implications regarding the existence of a
reported exotic meson decaying into with a mass
near 1.4 GeV.Comment: 19 pages, 29 figures, to appear in Phys. Rev.
An associative memory of Hodgkin-Huxley neuron networks with Willshaw-type synaptic couplings
An associative memory has been discussed of neural networks consisting of
spiking N (=100) Hodgkin-Huxley (HH) neurons with time-delayed couplings, which
memorize P patterns in their synaptic weights. In addition to excitatory
synapses whose strengths are modified after the Willshaw-type learning rule
with the 0/1 code for quiescent/active states, the network includes uniform
inhibitory synapses which are introduced to reduce cross-talk noises. Our
simulations of the HH neuron network for the noise-free state have shown to
yield a fairly good performance with the storage capacity of for the low neuron activity of . This
storage capacity of our temporal-code network is comparable to that of the
rate-code model with the Willshaw-type synapses. Our HH neuron network is
realized not to be vulnerable to the distribution of time delays in couplings.
The variability of interspace interval (ISI) of output spike trains in the
process of retrieving stored patterns is also discussed.Comment: 15 pages, 3 figures, changed Titl
Evidence for Exotic J^{PC}=1^{-+} Meson Production in the Reaction pi- p --> eta pi- p at 18 GeV/c
Details of the analysis of the eta pi- system studied in the reaction pi^{-}
p --> eta pi^{-} p at 18 GeV/c are given. Separate analyses for the 2 gamma and
pi+ pi- pi0 decay modes of the eta are presented. An amplitude analysis of the
data indicates the presence of interference between the a(2)(1320)- and a
J^{PC}=1^{-+} wave between 1.2 and 1.6 GeV/c^2. The phase difference between
these waves shows phase motion not attributable solely to the a(2)(1320)-. The
data can be fitted by interference between the a(2)(1320)- and an exotic 1^{-+}
resonance with M = 1370 +-16 +50 -30} MeV/c^2 and Gamma = 385 +- 40 +65 -105
MeV/c^2. Our results are compared with those of other experiments.Comment: 50 pages of text and 34 figure
How many steps/day are enough? For older adults and special populations
Older adults and special populations (living with disability and/or chronic illness that may limit mobility and/or physical endurance) can benefit from practicing a more physically active lifestyle, typically by increasing ambulatory activity. Step counting devices (accelerometers and pedometers) offer an opportunity to monitor daily ambulatory activity; however, an appropriate translation of public health guidelines in terms of steps/day is unknown. Therefore this review was conducted to translate public health recommendations in terms of steps/day. Normative data indicates that 1) healthy older adults average 2,000-9,000 steps/day, and 2) special populations average 1,200-8,800 steps/day. Pedometer-based interventions in older adults and special populations elicit a weighted increase of approximately 775 steps/day (or an effect size of 0.26) and 2,215 steps/day (or an effect size of 0.67), respectively. There is no evidence to inform a moderate intensity cadence (i.e., steps/minute) in older adults at this time. However, using the adult cadence of 100 steps/minute to demark the lower end of an absolutely-defined moderate intensity (i.e., 3 METs), and multiplying this by 30 minutes produces a reasonable heuristic (i.e., guiding) value of 3,000 steps. However, this cadence may be unattainable in some frail/diseased populations. Regardless, to truly translate public health guidelines, these steps should be taken over and above activities performed in the course of daily living, be of at least moderate intensity accumulated in minimally 10 minute bouts, and add up to at least 150 minutes over the week. Considering a daily background of 5,000 steps/day (which may actually be too high for some older adults and/or special populations), a computed translation approximates 8,000 steps on days that include a target of achieving 30 minutes of moderate-to-vigorous physical activity (MVPA), and approximately 7,100 steps/day if averaged over a week. Measured directly and including these background activities, the evidence suggests that 30 minutes of daily MVPA accumulated in addition to habitual daily activities in healthy older adults is equivalent to taking approximately 7,000-10,000 steps/day. Those living with disability and/or chronic illness (that limits mobility and or/physical endurance) display lower levels of background daily activity, and this will affect whole-day estimates of recommended physical activity
Hand Grip Strength: age and gender stratified normative data in a population-based study
Extent: 5p.Background: The North West Adelaide Health Study is a representative longitudinal cohort study of people originally aged 18 years and over. The aim of this study was to describe normative data for hand grip strength in a community-based Australian population. Secondary aims were to investigate the relationship between body mass index (BMI) and hand grip strength, and to compare Australian data with international hand grip strength norms. Methods: The sample was randomly selected and recruited by telephone interview. Overall, 3 206 (81% of those recruited) participants returned to the clinic during the second stage (2004-2006) which specifically focused on the collection of information relating to musculoskeletal conditions. Results: Following the exclusion of 435 participants who had hand pain and/or arthritis, 1366 men and 1312 women participants provided hand grip strength measurement. The study population was relatively young, with 41.5% under 40 years; and their mean BMI was 28.1 kg/m2 (SD 5.5). Higher hand grip strength was weakly related to higher BMI in adults under the age of 30 and over the age of 70, but inversely related to higher BMI between these ages. Australian norms from this sample had amongst the lowest of the hand grip strength of the internationally published norms, except those from underweight populations. Conclusions: This population demonstrated higher BMI and lower grip strength in younger participants than much of the international published, population data. A complete exploration of the relationship between BMI and hand grip strength was not fully explored as there were very few participants with BMI in the underweight range. The age and gender grip strength values are lower in younger adults than those reported in international literature.Nicola M Massy-Westropp, Tiffany K Gill, Anne W Taylor, Richard W Bohannon and Catherine L Hil
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