15,336 research outputs found
The great outdoors: how a green exercise environment can benefit all
The studies of human and environment interactions usually consider the extremes of environment on individuals or how humans affect the environment. It is well known that physical activity improves both physiological and psychological well-being, but further evidence is required to ascertain how different environments influence and shape health. This review considers the declining levels of physical activity, particularly in the Western world, and how the environment may help motivate and facilitate physical activity. It also addresses the additional physiological and mental health benefits that appear to occur when exercise is performed in an outdoor environment. However, people's connectedness to nature appears to be changing and this has important implications as to how humans are now interacting with nature. Barriers exist, and it is important that these are considered when discussing how to make exercise in the outdoors accessible and beneficial for all. The synergistic combination of exercise and exposure to nature and thus the 'great outdoors' could be used as a powerful tool to help fight the growing incidence of both physical inactivity and non-communicable disease. © 2013 Gladwell et al.; licensee BioMed Central Ltd
Transfer of molybdenum disulfide to various metals
Sliding friction experiments were conducted with molybdenum disulfide single crystals in contact with sputter cleaned surfaces of copper, nickel, gold, and 304 stainless steel. Transfer of the molybdenum disulfide to the metals was monitored with Auger electron spectroscopy. Results of the investigation indicate molybdenum disulfide transfers to all clean metal surfaces after a single pass over the metal surface with film thickness observed to increase with repeated passes over the same surfaces. Large particle transfer occurs when the orientation of the crystallites is other than basal. This is frequently accompanied by abrasion of the metal. Adhesion of molybdenum disulfide films occurred readily to copper and nickel, less readily to 304 stainless steel, and even less effectively to the gold, which indicates a chemical effect
THE INDUSTRY HAS CHANGED, HAVE YOU? THE AGCO STORY
AGCO Corporation is a success story in the agricultural machinery sector. Utilizing marketing strategies of out-sourcing, cross-over selling, and a full line of products, AGCO markets its own way. In 7 years, AGCO has 18 brands sold through 7,000 dealerships in 140 countries. Acquisition and consolidation powered the growth of AGCO using nontraditional buyout financing. Herein lies its real success.Agribusiness, Industrial Organization,
Surface plasmon modes and the Casimir energy
We show the influence of surface plasmons on the Casimir effect between two
plane parallel metallic mirrors at arbitrary distances. Using the plasma model
to describe the optical response of the metal, we express the Casimir energy as
a sum of contributions associated with evanescent surface plasmon modes and
propagative cavity modes. In contrast to naive expectations, the plasmonic
modes contribution is essential at all distances in order to ensure the correct
result for the Casimir energy. One of the two plasmonic modes gives rise to a
repulsive contribution, balancing out the attractive contributions from
propagating cavity modes, while both contributions taken separately are much
larger than the actual value of the Casimir energy. This also suggests
possibilities to tailor the sign of the Casimir force via surface plasmons.Comment: 4 pages, 3 figures, revtex
Minimal Forbidden Factors of Circular Words
Minimal forbidden factors are a useful tool for investigating properties of
words and languages. Two factorial languages are distinct if and only if they
have different (antifactorial) sets of minimal forbidden factors. There exist
algorithms for computing the minimal forbidden factors of a word, as well as of
a regular factorial language. Conversely, Crochemore et al. [IPL, 1998] gave an
algorithm that, given the trie recognizing a finite antifactorial language ,
computes a DFA recognizing the language whose set of minimal forbidden factors
is . In the same paper, they showed that the obtained DFA is minimal if the
input trie recognizes the minimal forbidden factors of a single word. We
generalize this result to the case of a circular word. We discuss several
combinatorial properties of the minimal forbidden factors of a circular word.
As a byproduct, we obtain a formal definition of the factor automaton of a
circular word. Finally, we investigate the case of minimal forbidden factors of
the circular Fibonacci words.Comment: To appear in Theoretical Computer Scienc
Ultra-high-sensitivity two-dimensional bend sensor
A multicore fibre Fabry-Perot-based strain sensor interrogated with tandem interferometry for bend measurement is described. Curvature in two dimensions is obtained by measuring the difference in strain between three co-located low finesse Fabry-Perot interferometers formed in each core of the fibre by pairs of Bragg gratings. This sensor provides a responsivity enhancement of up to 30 times that of a previously reported fibre Bragg grating based sensor. Strain resolutions of 0.6 n epsilon/Hz(1/2) above 1 Hz are demonstrated, which corresponds to a curvature resolution of similar to 0.012 km(-1)/Hz(1/2)
Casimir-Polder forces, boundary conditions and fluctuations
We review different aspects of the atom-atom and atom-wall Casimir-Polder
forces. We first discuss the role of a boundary condition on the interatomic
Casimir-Polder potential between two ground-state atoms, and give a physically
transparent interpretation of the results in terms of vacuum fluctuations and
image atomic dipoles. We then discuss the known atom-wall Casimir-Polder force
for ground- and excited-state atoms, using a different method which is also
suited for extension to time-dependent situations. Finally, we consider the
fluctuation of the Casimir-Polder force between a ground-state atom and a
conducting wall, and discuss possible observation of this force fluctuation.Comment: 5 page
Stress Tensor Correlators in the Schwinger-Keldysh Formalism
We express stress tensor correlators using the Schwinger-Keldysh formalism.
The absence of off-diagonal counterterms in this formalism ensures that the +-
and -+ correlators are free of primitive divergences. We use dimensional
regularization in position space to explicitly check this at one loop order for
a massless scalar on a flat space background. We use the same procedure to show
that the ++ correlator contains the divergences first computed by `t Hooft and
Veltman for the scalar contribution to the graviton self-energy.Comment: 14 pages, LaTeX 2epsilon, no figures, revised for publicatio
Novel features of the energy momentum tensor of a Casimir apparatus in a weak gravitational field
The influence of the gravity acceleration on the regularized energy-momentum
tensor of the quantized electromagnetic field between two plane parallel
conducting plates is derived. A perturbative expansion, to first order in the
constant acceleration parameter, of the Green functions involved and of the
energy-momentum tensor is derived by means of the covariant geodesic point
splitting procedure. The energy-momentum tensor is covariantly conserved and
satisfies the expected relation between gauge-breaking and ghost parts.Comment: 8 pages, based on a talk given by Luigi Rosa at the QFEXT07
Conference, Leipzig. Equation (13) and the formulae for rho and energy E
stored in the Casimir device have been amended, jointly with related
discussio
Moving Mirrors and Thermodynamic Paradoxes
Quantum fields responding to "moving mirrors" have been predicted to give
rise to thermodynamic paradoxes. I show that the assumption in such work that
the mirror can be treated as an external field is invalid: the exotic
energy-transfer effects necessary to the paradoxes are well below the scales at
which the model is credible. For a first-quantized point-particle mirror, it
appears that exotic energy-transfers are lost in the quantum uncertainty in the
mirror's state. An accurate accounting of these energies will require a model
which recognizes the mirror's finite reflectivity, and almost certainly a model
which allows for the excitation of internal mirror modes, that is, a
second-quantized model.Comment: 7 pages, Revtex with Latex2
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