1,667 research outputs found
Optical properties of the iron-pnictide analog BaMn2As2
We have investigated the infrared and Raman optical properties of BaMn2As2 in
the ab-plane and along the c-axis. The most prominent features in the infrared
spectra are the Eu and A2u phonon modes which show clear TO-LO splitting from
the energy loss function analysis. All the phonon features we observed in
infrared and Raman spectra are consistent with the calculated values. Compared
to the iron-pnictide analog AFe2As2, this compound is much more two-dimensional
in its electronic properties. For E || c-axis, the overall infrared
reflectivity is insulating like. Within the ab-plane the material exhibits a
semiconducting behavior. An energy gap 2{\Delta}=48 meV can be clearly
identified below room temperature.Comment: 5 pages, 7 figure
Probability distribution of magnetization in the one-dimensional Ising model: Effects of boundary conditions
Finite-size scaling functions are investigated both for the mean-square
magnetization fluctuations and for the probability distribution of the
magnetization in the one-dimensional Ising model. The scaling functions are
evaluated in the limit of the temperature going to zero (T -> 0), the size of
the system going to infinity (N -> oo) while N[1-tanh(J/k_BT)] is kept finite
(J being the nearest neighbor coupling). Exact calculations using various
boundary conditions (periodic, antiperiodic, free, block) demonstrate
explicitly how the scaling functions depend on the boundary conditions. We also
show that the block (small part of a large system) magnetization distribution
results are identical to those obtained for free boundary conditions.Comment: 8 pages, 5 figure
Mutation accumulation in exponentially growing populations
Stochastic models of mutation accumulation in exponentially growing cellular
populations are widely used to quantify cancer and bacterial evolution. Across
manifold scenarios, recurrent research questions are: how many cells exist with
a given set of alterations, and how long will it take for these cells to
appear. These questions have been tackled in special cases, often within a
branching processes framework. However, the general situation of cells
sequentially acquiring an arbitrary number of mutations which may be
selectively advantageous, neutral, or disadvantageous remains unaddressed.
Here, we consider this setting in the biologically relevant limiting regimes of
large times and small mutation rates. We provide analytic expressions for the
number, and arrival time, of cells with mutations. Universal probability
distributions for both quantities are presented, and the consequences of our
results on cancer driver mutation accumulation and bacterial fluctuation assays
are highlighted
Expanders with superquadratic growth
We prove several expanders with exponent strictly greater than 2. For any finite set A ⊂ ℝ, we prove the following six-variable expander results: (Formula Presented)
N_f=2+1 flavour equation of state
We conclude our investigation on the QCD equation of state (EoS) with 2+1
staggered flavors and one-link stout improvement. We extend our previous study
[JHEP 0601:089 (2006)] by choosing even finer lattices. These new results [for
details see arXiv:1007.2580] support our earlier findings. Lattices with
N_t=6,8 and 10 are used, and the continuum limit is approached by checking the
results at N_t=12. A Symanzik improved gauge and a stout-link improved
staggered fermion action is taken; the light and strange quark masses are set
to their physical values. Various observables are calculated in the temperature
(T) interval of 100 to 1000~MeV. We compare our data to the equation of state
obtained by the "hotQCD" collaboration.Comment: presented at the XXVIII. International Symposium on Lattice Field
Theory, June 14-19,2010, Villasimius, Sardinia Ital
Grasp force sensor for robotic hands
A grasp force sensor for robotic hands is disclosed. A flexible block is located in the base of each claw through which the grasp force is exerted. The block yields minute parallelogram deflection when the claws are subjected to grasping forces. A parallelogram deflection closely resembles pure translational deflection, whereby the claws remain in substantial alignment with each other during grasping. Strain gauge transducers supply signals which provide precise knowledge of and control over grasp forces
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