3,511 research outputs found
The role of secondary Reggeons in central meson production
We estimate the contribution of f_2 trajectory exchange to the central \eta
and \eta^\prime production. It is shown that secondary Reggeons may give a
large contribution to processes of double diffractive meson production at high
energy.Comment: 7 pages, Latex, 5 figure
The First Direct Distance and Luminosity Determination for a Self-Luminous Giant Exoplanet: The Trigonometric Parallax to 2MASS1207334-393254Ab
We present the first trigonometric parallax and distance for a young
planetary mass object. A likely TW Hya cluster member, 2MASSW J1207334-393254Ab
(hereafter 2M1207Ab) is an M8 brown dwarf with a mid to late L type planetary
mass companion. Recent observations of spectral variability have uncovered
clear signs of disk accretion and outflow, constraining the age of the system
to <10 Myr. Because of its late spectral type and the clearly youthful nature
of the system, 2M1207b is very likely a planetary mass object. We have measured
the first accurate distance and luminosity for a self-luminous planetary mass
object. Our parallax measurements are accurate to <2 mas (1sigma) for 2M1207Ab.
With 11 total epochs of data taken from January 2006 through April 2 007 (475
images for 2M1207Ab), we determine a distance of 58.8+-7.0 pc (17.0{+2.3}{-1.8}
mas, 1.28sigma) to 2M1207Ab and a calculated luminosity of 0.68-2.2x10^-5 Lsun
for 2M1207b. Hence 2M1207Ab is a clear member of the TW Hya cluster in terms of
its distance, proper motions, and youthful nature. However, as previously noted
by Mohanty and co-workers, 2M1207b's luminosity appears low compared to its
temperature according to evolutionary models.Comment: 12 pages, 3 figures, accepted to ApJ Letter
Developing digital interventions: a methodological guide.
Digital interventions are becoming an increasingly popular method of delivering healthcare as they enable and promote patient self-management. This paper provides a methodological guide to the processes involved in developing effective digital interventions, detailing how to plan and develop such interventions to avoid common pitfalls. It demonstrates the need for mixed qualitative and quantitative methods in order to develop digital interventions which are effective, feasible, and acceptable to users and stakeholders
The effects of eccentric exercise on delayed onset muscle soreness, muscle function and free radical production
Delayed onset muscle soreness (DOMS) is a muscle strain injury that presents as tender or aching muscles, often felt during palpation or movement. DOMS is associated with unaccustomed, high-force muscular work and is most pronounced if the work involves a significant eccentric component. Despite substantial research into DOMS its aetiology is still unresolved. There have been recent suggestions that reactive oxygen species (ROS) may be involved in the aetiology of DOMS, however the evidence for this association is equivocal. Therefore, the aims of this thesis were to investigate the effects of unaccustomed exercise (downhill running) on DOMS, specifically investigating the role of ROS in its aetiology. Once this had been established, the effects of dietary intervention and antioxidant supplementation on DOMS and ROS were also investigated.
Study 1 demonstrated that downhill running, which resulted in DOMS, also induced the production of ROS, detected by ESR spectroscopy as well as an increases in serum malondialdehyde (MDA) concentration. It was noted that this increase in ROS occurred -72 h post exercise and was therefore likely to be a result of increased phagocyte activity. Furthermore, the increase in ROS occurred after peak DOMS and when muscle function (as determined by losses of muscle torque assessed by isokinetic dynamometry) was returning to pre-exercise levels, suggesting a temporal dissociation between ROS production and DOMS following downhill running. Circulating levels of ROS were still increasing 72 h post exercise so this study was unable to map the full time-course of ROS production following downhill running.
Study 2 investigated the effects of dietary CHO intake on DOMS, ROS and muscle function. It was found that pre-exercise CHO status had no effect on ROS production, DOMS or losses of muscle function following downhill running. The study demonstrated a bi-phasic increase in creatine kinase (CK), with the second increase corresponding with the post-exercise ROS production. The study extended the postexercise sampling period to 96 h, however, ROS were still increasing at this time and therefore this study was also unable to conclude a definitive tune course of ROS production following downhill running.
Study 3 demonstrated that prolonged ascorbic acid supplementation attenuated the post-exercise increase in ROS production compared to placebo. This attenuation in ROS prevented the secondary peak in CK activity, however it had no effect on DOMS. Interestingly, supplementation with ascorbic acid resulted in more prolonged losses of muscle function. ROS peaked at 96 h post exercise and therefore the time course ofROS production following downhill running was established.
From these studies it was concluded that downhill running did result in post-exercise ROS production. This post-exercise ROS production was associated with secondary muscle damage as measured by plasma CK activity although it had no effect on DOMS. Since supplementation with ascorbic acid attenuated ROS production and prolonged the losses of muscle function, it was suggested that ROS produced by phagocytes m the days following muscle-damaging exercise have a positive role in assisting in the recovery from the traum
Glueball enhancements in p(gamma,VV)p through vector meson dominance
Double vector meson photoproduction, p(gamma, G -> VV)p, mediated by a scalar
glueball G is investigated. Using vector meson dominance (VMD) and
Regge/pomeron phenomenology, a measureable glueball enhancement is predicted in
the invariant VV = rho rho and omega omega mass spectra. The scalar glueball is
assumed to be the lightest physical state on the daughter pomeron trajectory
governing diffractive vector meson photoproduction. In addition to cross
sections, calculations for hadronic and electromagnetic glueball decays, G -> V
V' (V,V'= rho, omega, phi, gamma), and gamma_v V -> G transition form factors
are presented based upon flavor universality, VMD and phenomenological
couplings from phi photoproduction analyses. The predicted glueball decay
widths are similar to an independent theoretical study. A novel signature for
glueball detection is also discussed
Exercise redox biochemistry:conceptual, methodological and technical recommendations
Exercise redox biochemistry is of considerable interest owing to its translational value in health and disease. However, unaddressed conceptual, methodological and technical issues complicate attempts to unravel how exercise alters redox homeostasis in health and disease. Conceptual issues relate to misunderstandings that arise when the chemical heterogeneity of redox biology is disregarded which often complicate attempts to use redox-active compounds and assess redox signalling. Further, that oxidised macromolecule adduct levels reflect formation and repair is seldom considered. Methodological and technical issues relate to the use of out-dated assays and/or inappropriate sample preparation techniques that confound biochemical redox analysis. After considering each of the aforementioned issues, we outline how each issue can be resolved and provide a unifying set of recommendations. We specifically recommend that investigators: consider chemical heterogeneity, use redox-active compounds judiciously, abandon flawed assays, carefully prepare samples and assay buffers, consider repair/metabolism, use multiple biomarkers to assess oxidative damage and redox signalling
The strange-sea quark spin distribution in the nucleon from inclusive and semi-inclusive deep-inelastic scattering
We propose new method which allows determination of the strange-sea quark
spin distribution in the nucleon through measurement of various inclusive and
semi-inclusive polarized deep inelastic electron- or muon-proton reactions. It
is shown, that using combinations of inclusive data and semi-inclusive data
containing neutral pions in the final state, it is possible to extract the
strange-sea quark spin distribution. Similar result can be obtained for charged
pions and some other hadrons also
Structure of Light Scalar Mesons from D_s and D^0 Non-Leptonic Decays
Non-leptonic D meson decays may provide a reliable testbed for the multiquark
interpretation of light scalar mesons. In this letter we consider D_s decay and
show that a 4-quark f_0(980) meson could induce a decay pattern, which is
forbidden for a q-qbar constituent structure. Experimental tests to probe such
possibilities are within reach in the near future.Comment: 11 pages, 3 figures, minor changes. To appear in Phys. Lett.
Epsilon Indi Ba/Bb: the nearest binary brown dwarf
We have carried out high angular resolution near-infrared imaging and
low-resolution (R~1000) spectroscopy of the nearest known brown dwarf, Eps Indi
B, using the ESO VLT NAOS/CONICA adaptive optics system. We find it to be a
close binary (as also noted by Volk et al. 2003) with an angular separation of
0.732 arcsec, corresponding to 2.65AU at the 3.626pc distance of the Eps Indi
system. In our discovery paper (Scholz et al. 2003), we concluded that Eps Indi
B was a ~50Mjup T2.5 dwarf: our revised finding is that the two system
components (Eps Indi Ba and Eps Indi Bb) have spectral types of T1 and T6,
respectively, and estimated masses of 47 and 28Mjup, respectively, assuming an
age of 1.3Gyr. Errors in the masses are +/-10 and +/-7Mjup, respectively,
dominated by the uncertainty in the age determination (0.8-2Gyr range). This
uniquely well-characterised T dwarf binary system should prove important in the
study of low-mass, cool brown dwarfs. The two components are bright and
relatively well-resolved: Eps Indi B is the only T dwarf binary in which
spectra have been obtained for both components. They have a well-established
distance and age. Finally, their orbital motion can be measured on a fairly
short timescale (nominal orbital period 15 yrs), permitting an accurate
determination of the true total system mass, helping to calibrate brown dwarf
evolutionary models.Comment: Accepted for publication by Astronomy & Astrophysics main journal.
This replacement version includes minor changes made following comments by
the referee, along with a reworking of the photometric data and derived
quantities using 2MASS catalogue photometry as the basis, with only a minor
impact on the final result
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