1,801 research outputs found
mGPT: A Probabilistic Planner Based on Heuristic Search
We describe the version of the GPT planner used in the probabilistic track of
the 4th International Planning Competition (IPC-4). This version, called mGPT,
solves Markov Decision Processes specified in the PPDDL language by extracting
and using different classes of lower bounds along with various heuristic-search
algorithms. The lower bounds are extracted from deterministic relaxations where
the alternative probabilistic effects of an action are mapped into different,
independent, deterministic actions. The heuristic-search algorithms use these
lower bounds for focusing the updates and delivering a consistent value
function over all states reachable from the initial state and the greedy
policy
Tobacco Spending and its Crowd-Out of Other Goods
Smoking is an expensive habit. Smoking households spend, on average, more than $1000 annually on cigarettes. For households in which some members smoke, smoking expenditures crowd-out other purchases, which may affect other household members, as well as the smoker. We empirically analyze how expenditures on tobacco crowd out consumption of other goods, estimating the patterns of substitution between tobacco products and other expenditures. We use the Consumer Expenditure Survey (1995 to 2001), which we complement with regional price data, and state cigarette prices. We estimate a consumer demand system of expenditures on cigarettes, food, alcohol, housing, apparel, transportation, medical care and controls for socio-economic variables and other sources of observable heterogeneity. Descriptive data indicate that, compared to non-smokers, smokers spend less on housing. Results from the demand system indicate that as the price of cigarettes rises, households increase the quantity of food purchased, and, in some samples, reduce the quantity of apparel and housing purchased.
Temporary withdrawal of immunosuppression for life-threatening infections after liver transplantation
Vortices in simulations of solar surface convection
We report on the occurrence of small-scale vortices in simulations of the
convective solar surface. Using an eigenanalysis of the velocity gradient
tensor, we find the subset of high vorticity regions in which the plasma is
swirling. The swirling regions form an unsteady, tangled network of filaments
in the turbulent downflow lanes. Near-surface vertical vortices are underdense
and cause a local depression of the optical surface. They are potentially
observable as bright points in the dark intergranular lanes. Vortex features
typically exist for a few minutes, during which they are moved and twisted by
the motion of the ambient plasma. The bigger vortices found in the simulations
are possibly, but not necessarily, related to observations of granular-scale
spiraling pathlines in "cork animations" or feature tracking.Comment: 11 pages, 13 figures, accepted for publication in A&A, complementary
movies at http://www.mps.mpg.de/homes/moll/strudel/papermovies
Kinetics of Particles Adsorption Processes Driven by Diffusion
The kinetics of the deposition of colloidal particles onto a solid surface is
analytically studied. We take into account both the diffusion of particles from
the bulk as well as the geometrical aspects of the layer of adsorbed particles.
We derive the first kinetic equation for the coverage of the surface (a
generalized Langmuir equation) whose predictions are in agreement with recent
simulation results where diffusion of particles from the bulk is explicitly
considered.Comment: 4 page
Evidence of photospheric vortex flows at supergranular junctions observed by FG/SOT (Hinode)
Twisting motions of different nature are observed in several layers of the
solar atmosphere. Chromospheric sunspot whorls and rotation of sunspots or even
higher up in the lower corona sigmoids are examples of the large scale twisted
topology of many solar features. Nevertheless, their occurrence at large scale
in the quiet photosphere has not been investigated. The present study reveals
the existence of vortex flows located at the supergranular junctions of the
quiet Sun. We use a 1-hour and a 5-hour time series of the granulation in Blue
continuum and G-band images from FG/SOT to derive the photospheric flows. A
feature tracking technique called Balltracking is performed to track the
granules and reveal the underlying flow fields. In both time series we identify
long-lasting vortex flow located at supergranular junctions. The first vortex
flow lasts at least 1 hour and is ~20-arcsec-wide (~15.5 Mm). The second vortex
flow lasts more than 2 hours and is ~27-arcsec-wide (~21 Mm).Comment: 4 pages, 10 figure
A Note on the Spectrum of Composition Operators on Spaces of Real Analytic Functions
[EN] In this paper the spectrum of composition operators on the space of real analytic functions is investigated. In some cases it is completely determined while in some other cases it is only estimated.The research of the authors was partially supported by MEC and FEDER Project MTM2013-43540-P and the work of of Bonet by the Grant GV Project Prometeo II/2013/013. The research of Domanski was supported by National Center of Science, Poland, Grant No. DEC-2013/10/A/ST1/00091.Bonet Solves, JA.; Domanski, P. (2017). A Note on the Spectrum of Composition Operators on Spaces of Real Analytic Functions. Complex Analysis and Operator Theory. 11(1):161-174. https://doi.org/10.1007/s11785-016-0589-5S161174111Belitskii, G., Lyubich, Y.: The Abel equation and total solvability of linear functional equations. Studia Math. 127, 81–97 (1998)Belitskii, G., Lyubich, Y.: The real analytic solutions of the Abel functional equation. Studia Math. 134, 135–141 (1999)Belitskii, G., Tkachenko, V.: One-Dimensional Functional Equations. Springer, Basel (2003)Belitskii, G., Tkachenko, V.: Functional equations in real analytic functions. Studia Math. 143, 153–174 (2000)Bonet, J., Domański, P.: Power bounded composition operators on spaces of analytic functions. Collect. Math. 62, 69–83 (2011)Bonet, J., Domański, P.: Hypercyclic composition operators on spaces of real analytic fucntions. Math. Proc. Cambridge Phil. Soc. 153, 489–503 (2012)Bonet, J., Domański, P.: Abel’s functional equation and eigenvalues of composition operators on spaces of real analytic functions. Integr. Equ. Oper. Theor. 81, 455–482 (2015). doi: 10.1007/s00020-014-2175-4Cartan, H.: Variétés analytiques réelles et variétés analytiques complexes. Bull. Soc. Math. France 85, 77–99 (1957)Domański, P.: Notes on real analytic functions and classical operators, Topics in Complex Analysis and Operator Theory (Winter School in Complex Analysis and Operator Theory, Valencia, February 2010), Contemporary Math. 561 (2012) 3–47. Amer. Math. Soc, Providence (2012)Domański, P., Goliński, M., Langenbruch, M.: A note on composition operators on spaces of real analytic functions. Ann. Polon. Mat. 103, 209–216 (2012)Domański, P., Langenbruch, M.: Composition operators on spaces of real analytic functions. Math. Nachr. 254–255, 68–86 (2003)Domański, P., Langenbruch, M.: Coherent analytic sets and composition of real analytic functions. J. reine angew. Math. 582, 41–59 (2005)Domański, P., Langenbruch, M.: Composition operators with closed image on spaces of real analytic functions. Bull. Lond. Math. Soc. 38, 636–646 (2006)Domański, P., Vogt, D.: The space of real analytic functions has no basis. Studia Math. 142, 187–200 (2000)Hörmander, L.: An Introduction to Complex Analysis in Several Variables. North Holland, Amsterdam (1986)Meise, R., Vogt, D.: Introduction to Functional Analysis. Clarendon, Oxford (1997)Smajdor, W.: On the existence and uniqueness of analytic solutions of the functional equation φ ( z ) = h ( z , φ [ f ( z ) ] ) . Ann. Polon. Math. 19, 37–45 (1967
Serum S-adenosylmethionine, but not methionine, increases in response to overfeeding in humans
Background: Plasma concentration of the methyl donor S-adenosylmethionine (SAM) is linearly associated with body mass index (BMI) and fat mass. As SAM is a high-energy compound and a sensor of cellular nutrient status, we hypothesized that SAM would increase with overfeeding. Methods: Forty normal to overweight men and women were overfed by 1250 kcal per day for 28 days. Results: Serum SAM increased from 106 to 130 nmol/l (P=0.006). In stratified analysis, only those with weight gain above the median (high-weight gainers; average weight gain 3.9±0.3 kg) had increased SAM (+42%, P=0.001), whereas low-weight gainers (weight gain 1.5±0.2 kg) did not (Pinteraction=0.018). Overfeeding did not alter serum concentrations of the SAM precursor, methionine or the products, S-adenosyl-homocysteine and homocysteine. The SAM/SAH (S-adenosylhomocysteine) ratio was unchanged in the total population, but increased in high-weight gainers (+52%, P=0.006, Pinteraction =0.005). Change in SAM correlated positively with change in weight (r=0.33, P=0.041) and fat mass (r=0.44, P=0.009), but not with change in protein intake or plasma methionine, glucose, insulin or low-density lipoprotein (LDL)-cholesterol. Conclusion: Overfeeding raised serum SAM in proportion to the fat mass gained. The increase in SAM may help stabilize methionine levels, and denotes a responsiveness of SAM to nutrient state in humans. The role of SAM in human energy metabolism deserves further attention.A K Elshorbagy, F Jernerén, D Samocha-Bonet, H Refsum and L K Heilbron
Histogram Reweighting Method for Dynamic Properties
The histogram reweighting technique, widely used to analyze Monte Carlo data,
is shown to be applicable to dynamic properties obtained from Molecular
Dynamics simulations. The theory presented here is based on the fact that the
correlation functions in systems in thermodynamic equilibrium are averages over
initial conditions of functions of the trajectory of the system in phase-space,
the latter depending on the volume, the total number of particles and the
classical Hamiltonian. Thus, the well-known histogram reweighting method can
almost straightforwardly be applied to reconstruct the probability distribution
of initial states at different thermodynamic conditions, without extra
computational effort. Correlation functions and transport coefficients are
obtained with this method from few simulation data sets.Comment: 4 pages, 3 figure
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