304 research outputs found
Resonances and adiabatic invariance in classical and quantum scattering theory
We discover that the energy-integral of time-delay is an adiabatic invariant
in quantum scattering theory and corresponds classically to the phase space
volume. The integral thus found provides a quantization condition for
resonances, explaining a series of results recently found in non-relativistic
and relativistic regimes. Further, a connection between statistical quantities
like quantal resonance-width and classical friction has been established with a
classically deterministic quantity, the stability exponent of an adiabatically
perturbed periodic orbit. This relation can be employed to estimate the rate of
energy dissipation in finite quantum systems.Comment: 8 page
Larmor precession and tunneling time of a relativistic neutral spinning particle through an arbitrary potential barrier
The Larmor precession of a relativistic neutral spin-1/2 particle in a
uniform constant magnetic field confined to the region of a one-dimensional
arbitrary potential barrier is investigated. The spin precession serves as a
clock to measure the time spent by a quantum particle traversing a potential
barrier. With the help of general spin coherent state it is explicitly shown
that the precession time is equal to the dwell time.Comment: 10 pages, 1 figure. To be published in Phys. Rev. A (01 February
2002
Tunneling Time Distribution by means of Nelson's Quantum Mechanics and Wave-Particle Duality
We calculate a tunneling time distribution by means of Nelson's quantum
mechanics and investigate its statistical properties. The relationship between
the average and deviation of tunneling time suggests the exsistence of
``wave-particle duality'' in the tunneling phenomena.Comment: 14 pages including 11 figures, the text has been revise
Environmentalism, performance and applications: uncertainties and emancipations
This introductory article for a themed edition on environmentalism provides a particular context for those articles that follow, each of which engages with different aspects of environmentalism and performance in community-related settings. Responding to the proposition that there is a lacuna in the field of applied drama and environmentalism (Bottoms, 2010), we suggest that the more significant lack is that of ecocriticism. As the articles in this journal testify, there are many examples of applied theatre practice; what is required is sustained and rigorous critical engagement. It is to the gap of ecocriticism that we address this issue, signalling what we hope is the emergence of a critical field. One response to the multiple challenges of climate change is to more transparently locate the human animal within the environment, as one agent amongst many. Here, we seek to transparently locate the critic, intertwining the personal â ourselves, human actants â with global environmental concerns. This tactic mirrors much contemporary writing on climate change and its education, privileging personal engagement â a shift we interrogate as much as we perform. The key trope we anchor is that of uncertainty: the uncertainties that accompany stepping into a new research environment; the uncertainties arising from multiple relations (human and non-human); the uncertainties of scientific fact; the uncertainties of forecasting the future; and the uncertainties of outcomes â including those of performance practices. Having analysed a particular turn in environmental education (towards social learning) and the failure to successfully combine âart and realityâ in recent UK mainstream theatre events, such uncertainties lead to our suggestion for an âemancipatedâ environmentalism. In support of this proposal, we offer up a reflection on a key weekend of performance practice that brought us to attend to the small â but not insignificant â and to consider first hand the complex relationships between environmental âgrand narrativesâ and personal experiential encounters. Locating ourselves within the field and mapping out some of the many conceptual challenges attached to it serves to introduce the territories which the following journal articles expand upon
Partial Densities of States, Scattering Matrices, and Green's Functions
The response of an arbitrary scattering problem to quasi-static perturbations
in the scattering potential is naturally expressed in terms of a set of local
partial densities of states and a set of sensitivities each associated with one
element of the scattering matrix. We define the local partial densities of
states and the sensitivities in terms of functional derivatives of the
scattering matrix and discuss their relation to the Green's function. Certain
combinations of the local partial densities of states represent the injectivity
of a scattering channel into the system and the emissivity into a scattering
channel. It is shown that the injectivities and emissivities are simply related
to the absolute square of the scattering wave-function. We discuss also the
connection of the partial densities of states and the sensitivities to
characteristic times. We apply these concepts to a delta-barrier and to the
local Larmor clock.Comment: 13 pages (revtex), 4 figure
Unified time analysis of photon and (nonrelativistic) particle Tunnelling, and the Superluminal group-velocity problem
A unified approach to the time analysis of tunnelling of nonrelativistic
particles is presented, in which Time is regarded as a quantum-mechanical
observable, canonically conjugated to Energy. The validity of the Hartman
effect (independence of the Tunnelling Time of the opaque barrier width, with
Superluminal group velocities as a consequence) is verified for ALL the known
expressions of the mean tunnelling time. Moreover, the analogy between particle
and photon tunnelling is suitably exploited. On the basis of such an analogy,
an explanation of some recent microwave and optics experimental results on
tunnelling times is proposed. Attention is devoted to some aspects of the
causality problem for particle and photon tunnelling.Comment: plain (old) LaTeX; 42 pages; plus figures 1, 2, 3, 4a, 4b, and
Recommended from our members
Reprogramming human T cell function and specificity with non-viral genome targeting.
Decades of work have aimed to genetically reprogram T cells for therapeutic purposes1,2 using recombinant viral vectors, which do not target transgenes to specific genomic sites3,4. The need for viral vectors has slowed down research and clinical use as their manufacturing and testing is lengthy and expensive. Genome editing brought the promise of specific and efficient insertion of large transgenes into target cells using homology-directed repair5,6. Here we developed a CRISPR-Cas9 genome-targeting system that does not require viral vectors, allowing rapid and efficient insertion of large DNA sequences (greater than one kilobase) at specific sites in the genomes of primary human T cells, while preserving cell viability and function. This permits individual or multiplexed modification of endogenous genes. First, we applied this strategy to correct a pathogenic IL2RA mutation in cells from patients with monogenic autoimmune disease, and demonstrate improved signalling function. Second, we replaced the endogenous T cell receptor (TCR) locus with a new TCR that redirected T cells to a cancer antigen. The resulting TCR-engineered T cells specifically recognized tumour antigens and mounted productive anti-tumour cell responses in vitro and in vivo. Together, these studies provide preclinical evidence that non-viral genome targeting can enable rapid and flexible experimental manipulation and therapeutic engineering of primary human immune cells
Twiceâweekly ixazomib in combination with lenalidomideâdexamethasone in patients with newly diagnosed multiple myeloma
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/144661/1/bjh15394.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/144661/2/bjh15394_am.pd
- âŠ