1,316 research outputs found
The First Law for Boosted Kaluza-Klein Black Holes
We study the thermodynamics of Kaluza-Klein black holes with momentum along
the compact dimension, but vanishing angular momentum. These black holes are
stationary, but non-rotating. We derive the first law for these spacetimes and
find that the parameter conjugate to variations in the length of the compact
direction is an effective tension, which generally differs from the ADM
tension. For the boosted black string, this effective tension is always
positive, while the ADM tension is negative for large boost parameter. We also
derive two Smarr formulas, one that follows from time translation invariance,
and a second one that holds only in the case of exact translation symmetry in
the compact dimension. Finally, we show that the `tension first law' derived by
Traschen and Fox in the static case has the form of a thermodynamic Gibbs-Duhem
relation and give its extension in the stationary, non-rotating case.Comment: 20 pages, 0 figures; v2 - reference adde
Homology of Distributive Lattices
We outline the theory of sets with distributive operations: multishelves and
multispindles, with examples provided by semi-lattices, lattices and skew
lattices. For every such a structure we define multi-term distributive homology
and show some of its properties. The main result is a complete formula for the
homology of a finite distributive lattice. We also indicate the answer for
unital spindles and conjecture the general formula for semi-lattices and some
skew lattices. Then we propose a generalization of a lattice as a set with a
number of idempotent operations satisfying the absorption law.Comment: 30 pages, 3 tables, 3 figure
Differences in Chemical Composition of Plant Sample Fractions Resulting from Grinding and Screening
Alfalfa, barley straw, corn leaves, peas, red clover, and
wheat straw samples were ground in a Wiley mill and
screened to separate particle sizes. Particle size samples
were analyzed for N, P, K, Ca, Mg, Zn, Se, and SiO?
The percentage comeosition of N, P, Ca, Mg, and SiO?
generally increased with decreasing particle sizes of three
wheat straw varieties, one baled and one hand-cut sample
each of barley straw and alfalfa, corn leaves, red
clover, and peas. The K concentrations were unpredictable.
Selenium tended to be more concentrated in the
smaller than in larger particles. The variability in
chemical composition because of particle sizes points out
the necessity for adequate sample grinding and mixing
for obtaining representative subsamples for chemical analyses
and biological experiments
Changes in physical activity behaviour and physical function after bariatric surgery: A systematic review and meta-analysis
© 2016 World Obesity. Although physical activity performed after bariatric surgery is associated with enhanced weight loss outcomes, there is limited information on patients' physical activity behaviour in this context. This systematic review and meta-analysis assessed pre-operative to post-operative changes in physical activity and physical function outcomes among obese adults undergoing bariatric surgery. A total of 50 studies met inclusion criteria with 26 papers reporting data for meta-analysis. Increases in both objectively recorded and self-reported physical activity at 12months were demonstrated. Studies indicated that there was a shift towards a greater amount of active time, but of a lower intensity within the first 6months of bariatric surgery, suggested by a reduction in moderate to vigorous physical activity but an increase in step count. A standardized mean difference (SMD) of 1.53 (95% CI: 1.02-2.04) based on nine studies indicated improved walking performance at 12months. Similarly, analysis of five studies demonstrated increased musculoskeletal function at 3-6months (SMD: 1.51; 95% CI: 0.60-2.42). No relationship was identified between changes in weight and walking performance post-surgery. More studies assessing physical activity, physical function and weight loss would help understand the role of physical activity in optimizing post-operative weight and functional outcomes
Strong-field terahertz-optical mixing in excitons
Driving a double-quantum-well excitonic intersubband resonance with a
terahertz (THz) electric field of frequency \omega_{THz} generated terahertz
optical sidebands \omega=\omega_{THz}+\omega_{NIR} on a weak NIR probe. At high
THz intensities, the intersubband dipole energy which coupled two excitons was
comparable to the THz photon energy. In this strong-field regime the sideband
intensity displayed a non-monotonic dependence on the THz field strength. The
oscillating refractive index which gives rise to the sidebands may be
understood by the formation of Floquet states, which oscillate with the same
periodicity as the driving THz field.Comment: 4 pages, 6 figure
The effects of supervised exercise training 12–24 months after bariatric surgery on physical function and body composition: a randomised controlled trial
Background:Bariatric surgery is effective for the treatment of stage II and III obesity and its related diseases, although increasing evidence is showing weight regain ~12–24 months postsurgery. Weight regain increases the risk of physical function decline, which negatively affects an individual's ability to undertake activities of daily living. The study assessed the effects of a 12-week supervised exercise intervention on physical function and body composition in patients between 12 and 24 months post bariatric surgery.Methods:Twenty-four inactive adult bariatric surgery patients whose body mass index remained ⩾30 kg m2 12 to 24 months post surgery were randomised to an exercise intervention (n=12) or control group (n=12). Supervised exercise consisted of three 60-min gym sessions per week of moderate intensity aerobic and resistance training for 12 weeks. Control participants received usual care. The incremental shuttle walk test (ISWT) was used to assess functional walking performance after the 12-week exercise intervention, and at 24 weeks follow-up. Measures of anthropometric, physical activity, cardiovascular and psychological outcomes were also examined. Using an intention-to-treat protocol, independent t-tests were used to compare outcome measures between groups.Results:Significant improvements in the exercise group were observed for the ISWT, body composition, physical function, cardiovascular and self-efficacy measures from baseline to 12 weeks. A large baseline to 12-week change was observed for the ISWT (exercise: 325.00±117.28 m; control: 355.00±80.62 m, P<0.001). The exercise group at 24 weeks recorded an overall mean improvement of 143.3±86.6 m and the control group recorded a reduction of −32.50±75.93 m. Findings show a 5.6 kg difference between groups in body mass change from baseline to 24 weeks favouring the exercise group.Conclusions:A 12-week supervised exercise intervention led to significant improvements in body mass and functional walking ability post intervention, with further improvements at the 24-week follow-up
Tensor-scalar gravity and binary-pulsar experiments
Some recently discovered nonperturbative strong-field effects in
tensor-scalar theories of gravitation are interpreted as a scalar analog of
ferromagnetism: "spontaneous scalarization". This phenomenon leads to very
significant deviations from general relativity in conditions involving strong
gravitational fields, notably binary-pulsar experiments. Contrary to
solar-system experiments, these deviations do not necessarily vanish when the
weak-field scalar coupling tends to zero. We compute the scalar "form factors"
measuring these deviations, and notably a parameter entering the pulsar timing
observable gamma through scalar-field-induced variations of the inertia moment
of the pulsar. An exploratory investigation of the confrontation between
tensor-scalar theories and binary-pulsar experiments shows that nonperturbative
scalar field effects are already very tightly constrained by published data on
three binary-pulsar systems. We contrast the probing power of pulsar
experiments with that of solar-system ones by plotting the regions they exclude
in a generic two-dimensional plane of tensor-scalar theories.Comment: 35 pages, REVTeX 3.0, uses epsf.tex to include 9 Postscript figure
Correlated variability of Mkn 421 at X-ray and TeV wavelengths on timescales of hours
Mkn 421 was observed for about two days with BeppoSAX, prior to and partly
overlapping the start of a 1 week continuous exposure with ASCA in April 1998,
as part of a world-wide multiwavelength campaign. A pronounced, well defined,
flare observed in X-rays was also observed simultaneously at TeV energies by
the Whipple Observatory's 10 m gamma-ray telescope. These data provide the
first evidence that the X-ray and TeV intensities are well correlated on
time-scales of hours.Comment: 4 pages, 1 figure, presented at the VERITAS Workshop on the TeV
Astrophysics of Extragalactic Object
Orbital resonances in discs around braneworld Kerr black holes
Rotating black holes in the brany universe of the Randall-Sundrum type are
described by the Kerr geometry with a tidal charge b representing the
interaction of the brany black hole and the bulk spacetime. For b<0 rotating
black holes with dimensionless spin a>1 are allowed. We investigate the role of
the tidal charge b in the orbital resonance model of QPOs in black hole
systems. The orbital Keplerian, the radial and vertical epicyclic frequencies
of the equatorial, quasicircular geodetical motion are given and their radial
profiles are discussed. The resonant conditions are given in three
astrophysically relevant situations: for direct (parametric) resonances, for
the relativistic precession model, and for some trapped oscillations of the
warped discs, with resonant combinational frequencies. It is shown, how b could
influence matching of the observational data indicating the 3:2 frequency ratio
observed in GRS 1915+105 microquasar with prediction of the orbital resonance
model; limits on allowed range of the black hole parameters a and b are
established. The "magic" dimensionless black hole spin enabling presence of
strong resonant phenomena at the radius where \nu_K:\nu_{\theta}:\nu_r=3:2:1 is
determined in dependence on b. Such strong resonances could be relevant even in
sources with highly scattered resonant frequencies, as those expected in Sgr
A*. The specific values of a and b are given also for existence of specific
radius where \nu_K:\nu_{\theta}:\nu_r=s:t:u with 5>=s>t>u being small natural
numbers. It is shown that for some ratios such situation is impossible in the
field of black holes. We can conclude that analysing the microquasars
high-frequency QPOs in the framework of orbital resonance models, we can put
relevant limits on the tidal charge of brany Kerr black holes.Comment: 31 pages, 19 figures, to appear in General Relativity and Gravitatio
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The structure of blocks with a Klein four defect group
We prove Erdmann’s conjecture [16] stating that every block with a Klein four defect group has a simple module with trivial source, and deduce from this that Puig’s finiteness conjecture holds for source algebras of blocks with a Klein four defect group. The proof uses the classification of finite simple groups
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