5,013 research outputs found
An Updated Numerical Analysis of eV Seesaw with Four Generations
We consider the so-called "eV seesaw" scenario, with right-handed Majorana
mass at eV order, extended to four lepton generations. The fourth
generation gives a heavy pseudo-Dirac neutral lepton, which largely decouples
from other generations and is relatively stable. The framework naturally gives
3 active and 3 sterile neutrinos. We update a previous numerical analysis of a
3+3 study of the LSND anomaly, taking into account the more recent results from
the MiniBooNE experiment. In particular, we study the implications for the
third mixing angle , as well as CP violation. We
find that current data do not seriously constrain more than one sterile
neutrinos.Comment: References updated, and a Note Adde
Fourth Generation Leptons and Muon
We consider the contributions to from fourth generation heavy
neutral and charged leptons, and , at the one-loop level.
Diagrammatically, there are two types of contributions: boson-boson-, and
--boson in the loop diagram. In general, the effect from is
suppressed by off-diagonal lepton mixing matrix elements. For , we consider
flavor changing neutral couplings arising from various New Physics models,
which are stringently constrained by . We assess how the
existence of a fourth generation would affect these New Physics models.Comment: Minor changes, with references update
Existence theorems for a crystal surface model involving the p-Laplace operator
The manufacturing of crystal films lies at the heart of modern
nanotechnology. How to accurately predict the motion of a crystal surface is of
fundamental importance. Many continuum models have been developed for this
purpose, including a number of PDE models, which are often obtained as the
continuum limit of a family of kinetic Monte Carlo models of crystal surface
relaxation that includes both the solid-on-solid and discrete Gaussian models.
In this paper we offer an analytical perspective into some of these models. To
be specific, we study the existence of a weak solution to the boundary value
problem for the equation - \Delta e^{-\mbox{div}\left(|\nabla u|^{p-2}\nabla
u\right)}+au=f, where are given numbers and is a given
function. This problem is derived from a crystal surface model proposed by
J.L.~Marzuola and J.~Weare (2013 Physical Review, E 88, 032403). The
mathematical challenge is due to the fact that the principal term in our
equation is an exponential function of a p-Laplacian. Existence of a
suitably-defined weak solution is established under the assumptions that
, and . Our investigations reveal that the
key to our existence assertion is how to control the set where
-\mbox{div}\left(|\nabla u|^{p-2}\nabla u\right) is
Cosmological Constraints on the Modified Entropic Force Model
Very recently, Verlinde considered a theory in which space is emergent
through a holographic scenario, and proposed that gravity can be explained as
an entropic force caused by changes in the information associated with the
positions of material bodies. Then, motivated by the Debye model in
thermodynamics which is very successful in very low temperatures, Gao modified
the entropic force scenario. The modified entropic force (MEF) model is in fact
a modified gravity model, and the universe can be accelerated without dark
energy. In the present work, we consider the cosmological constraints on the
MEF model, and successfully constrain the model parameters to a narrow range.
We also discuss many other issues of the MEF model. In particular, we clearly
reveal the implicit root to accelerate the universe in the MEF model.Comment: 16 pages, 7 figures, revtex4; v2: discussions added, Phys. Lett. B in
press; v3: published versio
Prescription profile of potentially aristolochic acid containing Chinese herbal products: an analysis of National Health Insurance data in Taiwan between 1997 and 2003
A Programmably Compliant Origami Mechanism for Dynamically Dexterous Robots
We present an approach to overcoming challenges in dynamical dexterity for robots through programmably compliant origami mechanisms. Our work leverages a one-parameter family of flat sheet crease patterns that folds into origami bellows, whose axial compliance can be tuned to select desired stiffness. Concentrically arranged cylinder pairs reliably manifest additive stiffness, extending the programmable range by nearly an order of magnitude and achieving bulk axial stiffness spanning 200–1500 N/m using 8 mil thick polyester-coated paper. Accordingly, we design origami energy-storing springs with a stiffness of 1035 N/m each and incorporate them into a three degree-of-freedom (DOF) tendon-driven spatial pointing mechanism that exhibits trajectory tracking accuracy less than 15% rms error within a (2 cm)^3 volume. The origami springs can sustain high power throughput, enabling the robot to achieve asymptotically stable juggling for both highly elastic (1 kg resilient shotput ball) and highly damped (“medicine ball”) collisions in the vertical direction with apex heights approaching 10 cm. The results demonstrate that “soft” robotic mechanisms are able to perform a controlled, dynamically actuated task
The increase of NADH fluorescence lifetime is associated with the metabolic change during osteogenic differentiation of human mesenchymal stem cells (hMSCs)
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