8,208 research outputs found

### Transforming a 4th year Modern Optics Course Using a Deliberate Practice Framework

We present a study of active learning pedagogies in an upper division physics
course. This work was guided by the principle of deliberate practice for the
development of expertise, and this principle was used in the design of the
materials and the orchestration of the classroom activities of the students. We
present our process for efficiently converting a traditional lecture course
based on instructor notes into activities for such a course with active
learning methods. Ninety percent of the same material was covered and scores on
common exam problems showed a 15 % improvement with an effect size greater than
1 after the transformation. We observe that the improvement and the associated
effect size is sustained after handing off the materials to a second
instructor. Because the improvement on exam questions was independent of
specific problem topics and because the material tested was so mathematically
advanced and broad (including linear algebra, Fourier Transforms, partial
differential equations, vector calculus), we expect the transformation process
could be applied to most upper division physics courses having a similar
mathematical base.Comment: 31 page

### On the preservation of Lipschitz classes under the Faber transformation

Let [omega] be a nonempty open, simply connected subset of the complex plane and let [delta] = \z Ç Ç z Ç \u3c 1. Then there is a bijective analytic mapping g: \doubc - [macron][omega] â \doubc - [macron][delta]. We note that g has a continuous extension to the boundary [gamma] of [omega]. Let A([delta]) be the Banach algebra of functions continuous on [macron][delta] and analytic on [delta];We consider the tranformation T mapping f in A([delta]) to (Tf)(w) = 1 [over] 2[pi] i Ï”t[limits][subscript][gamma] f(g(t)) [over] t-w dtin the Banach algebra of functions continuous on [macron][omega] and analytic on [omega]. The mapping T is called the Faber transformation and is an injective continuous linear transformation;It is of interest to determine the properties of f which are preserved under the Faber transformation T. In particular, we assume that f satisifies a Lipschitz condition on [macron] [delta] and consider the Lipschitz class of Tf on [macron][omega]. We show that the Lipschitz class of Tf is affected by the Lipschitz class of f and the smoothness of [gamma], and, under suitable conditions on [gamma], we obtain qualitative results when g satisfies a Lipschitz condition

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### The acute respiratory distress syndrome in 2013.

Acute lung injury and the acute respiratory distress syndrome are major causes of morbidity and mortality in critically ill patients. This review focuses on new developments in definitions, epidemiology, clinical and basic research, and promising new directions in treatment. There is new information about the potential contribution of environmental factors, especially exposure to cigarette smoke. Pathologic findings in ARDS have been limited to case reports of open lung biopsies and post-mortem studies but there is some new information from a recent pathology study relative to the frequency of diffuse alveolar damage and the severity of arterial hypoxemia. Further, therapy with lung-protective ventilation and fluid conservative protocol has improved outcomes, but several new trials are in progress to test several promising strategies

### Everything is at stake; yet nothing is at stake : exploring meaning-making in game-centred approaches

While not wishing to cover old ground in articulating the promise or continued promise of phenomenology within the physical education and sports domains, this paper aims to explore the âhumanâ nature of the game-centred approach (GCA) from an existential-phenomenological perspective. In a recent review of literature on the current state of research on GCAs, Harvey and Jarrett made the call for phenomenological-oriented empirical studies. Urging the academic fraternity to embrace such âparticipatory epistemologiesâ is an extremely positive and important step by the authors. This is because, although they do not explicitly make the point, to call for the embrace of phenomenological-oriented research into GCAs, the authors are accepting the fundamental importance of individual experience and meaning in games teaching. If we focus on the individual it then becomes a distinct possibility of structuring increasingly meaningful game-centred practice. In this respect we analyze Martin Heidegger's notion of âbeing-in-the-worldâ and illustrate how Arnold's three categories of meaningful movementâprimordial, contextual and existentialâcan help facilitate ideas for pedagogical practice and provide an appropriate interpretive lens for future research into GCAs

### Nonlinear Particle Acceleration in Relativistic Shocks

Monte Carlo techniques are used to model nonlinear particle acceleration in
parallel collisionless shocks of various speeds, including mildly relativistic
ones. When the acceleration is efficient, the backreaction of accelerated
particles modifies the shock structure and causes the compression ratio, r, to
increase above test-particle values. Modified shocks with Lorentz factors less
than about 3 can have compression ratios considerably greater than 3 and the
momentum distribution of energetic particles no longer follows a power law
relation. These results may be important for the interpretation of gamma-ray
bursts if mildly relativistic internal and/or afterglow shocks play an
important role accelerating particles that produce the observed radiation. For
shock Lorentz factors greater than about 10, r approaches 3 and the so-called
`universal' test-particle result of N(E) proportional to E^{-2.3} is obtained
for sufficiently energetic particles. In all cases, the absolute normalization
of the particle distribution follows directly from our model assumptions and is
explicitly determined.Comment: Updated version, Astroparticle Physics, in press, 29 pages, 13
figure

### Particle acceleration at ultrarelativistic shocks: an eigenfunction method

We extend the eigenfunction method of computing the power-law spectrum of
particles accelerated at a relativistic shock fronts to apply to shocks of
arbitrarily high Lorentz factor. In agreement with the findings of Monte-Carlo
simulations, we find the index of the power-law distribution of accelerated
particles which undergo isotropic diffusion in angle at an ultrarelativistic,
unmagnetized shock is s=4.23 (where s=-d(ln f)/dp with f the Lorentz invariant
phase-space density and p the momentum). This corresponds to a synchrotron
index for uncooled electrons of a=0.62 (taking cooling into account a=1.12),
where a=-d(ln F)/dn, F is the radiation flux and n the frequency. We also
present an approximate analytic expression for the angular distribution of
accelerated particles, which displays the effect of particle trapping by the
shock: compared with the non-relativistic case the angular distribution is
weighted more towards the plane of the shock and away from its normal. We
investigate the sensitivity of our results to the transport properties of the
particles and the presence of a magnetic field. Shocks in which the ratio of
Poynting to kinetic energy flux upstream is not small are less compressive and
lead to larger values of $s$.Comment: Minor additions on publicatio

### Amino-terminal cysteine residues of RGS16 are required for palmitoylation and modulation of G(i)- and G(q)-mediated signaling

RGS proteins (Regulators of G protein Signaling) are a recently discovered family of proteins that accelerate the GTPase activity of heterotrimeric G protein Î± subunits of the i, q, and 12 classes. The proteins share a homologous core domain but have divergent amino-terminal sequences that are the site of palmitoylation for RGS-GAIP and RGS4. We investigated the function of palmitoylation for RGS16, which shares conserved amino-terminal cysteines with RGS4 and RGS5. Mutation of cysteine residues at residues 2 and 12 blocked the incorporation of [3H]palmitate into RGS16 in metabolic labeling studies of transfected cells or into purified RGS proteins in a cell-free palmitoylation assay. The purified RGS16 proteins with the cysteine mutations were still able to act as GTPase-activating protein for GiÎ±. Inhibition or a decrease in palmitoylation did not significantly change the amount of protein that was membrane-associated. However, palmitoylation-defective RGS16 mutants demonstrated impaired ability to inhibit both Gi- and Gq-linked signaling pathways when expressed in HEK293T cells. These findings suggest that the amino-terminal region of RGS16 may affect the affinity of these proteins for GÎ± subunits in vivo or that palmitoylation localizes the RGS protein in close proximity to GÎ± subunits on cellular membranes

### Diffusive Shock Acceleration of High Energy Cosmic Rays

The process of diffusive acceleration of charged particles in shocked plasmas
is widely invoked in astrophysics to account for the ubiquitous presence of
signatures of non-thermal relativistic electrons and ions in the universe. A
key characteristic of this statistical energization mechanism is the absence of
a momentum scale; astrophysical systems generally only impose scales at the
injection (low energy) and loss (high energy) ends of the particle spectrum.
The existence of structure in the cosmic ray spectrum (the "knee") at around
3000 TeV has promoted contentions that there are at least two origins for
cosmic rays, a galactic one supplying those up to the knee, and even beyond,
and perhaps an extragalactic one that can explain even the ultra-high energy
cosmic rays (UHECRs) seen at 1-300 EeV. Accounting for the UHECRs with familiar
astrophysical sites of acceleration has historically proven difficult due to
the need to assume high magnetic fields in order to reduce the shortest
diffusive acceleration timescale, the ion gyroperiod, to meaningful values. Yet
active galaxies and gamma-ray bursts remain strong and interesting candidate
sources for UHECRs, turning the theoretical focus to relativistic shocks. This
review summarizes properties of diffusive shock acceleration that are salient
to the issue of UHECR generation. These include spectral indices, acceleration
efficencies and timescales, as functions of the shock speed and mean field
orientation, and also the nature of the field turbulence. The interpretation of
these characteristics in the context of gamma-ray burst models for the
production of UHECRs is also examined.Comment: 10 pages, 2 embedded figures, To appear in Nuclear Physics B,
Proceedings Supplements, as part of the volume for the CRIS 2004, Cosmic Ray
International Seminar: "GZK and Surroundings.

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