34,594 research outputs found
Formulating a State Approach to Professional Development
When viewed from the perspective of an entire state\u27s needs, the challenges of designing professional development to meet the requirements of the federal No Child Left Behind legislation of 2001 are daunting. In Oklahoma, the concerns about delivering to rural and urban populations which contain a variety of underserved populations are further complicated by the differences in the way science and mathematics are structured as disciplines. We describe two model programs, one in science and one in mathematics, which take much different approaches. However, the programs have three common elements that make them highly successful. Each program engages teachers strongly, seeks to change learning by altering both teachers\u27 behavior and content knowledge, and is continuously reflective
Generalizations of the St\"ormer Problem for Dust Grain Orbits
We consider the generalized St\"ormer Problem that includes the
electromagnetic and gravitational forces on a charged dust grain near a planet.
For dust grains a typical charge to mass ratio is such that neither force can
be neglected. Including the gravitational force gives rise to stable circular
orbits that encircle that plane entirely above/below the equatorial plane. The
effects of the different forces are discussed in detail. A modified 3rd
Kepler's law is found and analyzed for dust grains.Comment: 21 pages LaTeX, 12 figure
Simplification of the tug-of-war model for cellular transport in cells
The transport of organelles and vesicles in living cells can be well
described by a kinetic tug-of-war model advanced by M\"uller, Klumpp and
Lipowsky. In which, the cargo is attached by two motor species, kinesin and
dynein, and the direction of motion is determined by the number of motors which
bind to the track. In recent work [Phys. Rev. E 79, 061918 (2009)], this model
was studied by mean field theory, and it was found that, usually the tug-of-war
model has one, two, or three distinct stable stationary points. However, the
results there are mostly obtained by numerical calculations, since it is hard
to do detailed theoretical studies to a two-dimensional nonlinear system. In
this paper, we will carry out further detailed analysis about this model, and
try to find more properties theoretically. Firstly, the tug-of-war model is
simplified to a one-dimensional equation. Then we claim that the stationary
points of the tug-of-war model correspond to the roots of the simplified
equation, and the stable stationary points correspond to the roots with
positive derivative. Bifurcation occurs at the corresponding parameters, under
which the simplified one-dimensional equation exists root with zero derivative.
Using the simplified equation, not only more properties of the tug-of-war model
can be obtained analytically, the related numerical calculations will become
more accurate and more efficient. This simplification will be helpful to future
studies of the tug-of-war model
A model for hand-over-hand motion of molecular motors
A simple flashing ratchet model in two dimensions is proposed to simulate the
hand-over-hand motion of two head molecular motors like kinesin. Extensive
Langevin simulations of the model are performed. Good qualitative agreement
with the expected behavior is observed. We discuss different regimes of motion
and efficiency depending of model parameters.Comment: 8 pages, Phys. Rev. E (in press
A subsystem-independent generalization of entanglement
We introduce a generalization of entanglement based on the idea that
entanglement is relative to a distinguished subspace of observables rather than
a distinguished subsystem decomposition. A pure quantum state is entangled
relative to such a subspace if its expectations are a proper mixture of those
of other states. Many information-theoretic aspects of entanglement can be
extended to the general setting, suggesting new ways of measuring and
classifying entanglement in multipartite systems. By going beyond the
distinguishable-subsystem framework, generalized entanglement also provides
novel tools for probing quantum correlations in interacting many-body systems.Comment: 5 pages, 1 encapsulated color figure, REVTeX4 styl
Compositional modulation in AlxGa1−xAs epilayers grown by molecular beam epitaxy on the (111) facets of grooves in a nonplanar substrate
We report the first observation of a lateral junction formed in an alloy due to an abrupt transition from segregated to random AlGaAs alloy compositions. Al0.25Ga0.75As epilayers were grown by molecular beam epitaxy on [011-bar] oriented grooves in a nonplanar (100) GaAs substrate. A quasi-periodic modulation of the aluminum concentration occurs spontaneously in material grown on the (111) facets of the groove, with a period of 50–70 Å along the [111] direction. The compositional modulation is associated with a reduction of the band gap by 130 meV, with respect to the random alloy. While segregation of the AlGaAs alloy has been seen previously, this is the first observation of segregation of AlGaAs grown on a (111) surface. The compositional modulation terminates abruptly at the boundaries of the (111) facet, forming abrupt lateral junctions in the AlGaAs layers grown on a groove
Changing Consumer Food Prices: A User's Guide to ERS Analyses
USDA's Economic Research Service (ERS) uses different economic models to estimate the impact of higher input prices on consumer food prices. The present study compares three ERS models. In the first two models, neither consumers nor food producers respond to market prices. We refer to these two models as short-run models. In the third model, both consumers and food producers respond to changing prices, and we refer to this model as a long-run model. Given published parameter estimates, we simulate the impact of a higher energy price on consumer food prices, and our empirical findings are consistent with our understanding of market responses. In the short run, we find that the full effect of an increase in the price of energy is fully (or nearly fully) passed on to consumers, because neither food producers nor consumers can immediately respond to changing prices. In the long run, however, the price response of food producers and consumers serves to mitigate the increase in consumer food prices.price-spread model, input-output model, variable-proportions model, food prices, energy prices, input prices, Demand and Price Analysis,
Markov Process of Muscle Motors
We study a Markov random process describing a muscle molecular motor
behavior. Every motor is either bound up with a thin filament or unbound. In
the bound state the motor creates a force proportional to its displacement from
the neutral position. In both states the motor spend an exponential time
depending on the state. The thin filament moves at its velocity proportional to
average of all displacements of all motors. We assume that the time which a
motor stays at the bound state does not depend on its displacement. Then one
can find an exact solution of a non-linear equation appearing in the limit of
infinite number of the motors.Comment: 10 page
Writing in your own voice: An intervention that reduces plagiarism and common writing problems in students' scientific writing.
In many of our courses, particularly laboratory courses, students are expected to engage in scientific writing. Despite various efforts by other courses and library resources, as instructors we are often faced with the frustration of student plagiarism and related writing problems. Here, we describe a simple Writing in Your Own Voice intervention designed to help students become more aware of different types of plagiarism and writing problems, avoid those problems, and practice writing in their own voice. In this article, we will introduce the types of plagiarism and writing problems commonly encountered in our molecular biology laboratory course, the intervention, and the results of our study. From the evaluation of 365 student reports, we found the intervention resulted in nearly 50% fewer instances of plagiarism and common writing problems. We also observed significantly fewer instances of severe plagiarism (e.g. several sentences copied from an external source). In addition, we find that the effects last for several weeks after the students complete the intervention assignment. This assignment is particularly easy to implement and can be a very useful tool for teaching students how to write in their own voices. © 2019 International Union of Biochemistry and Molecular Biology, 47(5):589-598, 2019
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