6,283 research outputs found
DC field induced enhancement and inhibition of spontaneous emission in a cavity
We demonstrate how spontaneous emission in a cavity can be controlled by the
application of a dc field. The method is specially suitable for Rydberg atoms.
We present a simple argument for the control of emission.Comment: 3-pages, 2figure. accepted in Phys. Rev.
A Simplest Swimmer at Low Reynolds Number: Three Linked Spheres
We propose a very simple one-dimensional swimmer consisting of three spheres
that are linked by rigid rods whose lengths can change between two values. With
a periodic motion in a non-reciprocal fashion, which breaks the time-reversal
symmetry as well as the translational symmetry, we show that the model device
can swim at low Reynolds number. This model system could be used in
constructing molecular-size machines
Recent Extreme Ultraviolet Solar Spectra and Spectroheliograms
Extreme ultraviolet solar spectra and spectroheliogram analyse
Current noise of a quantum dot p-i-n junction in a photonic crystal
The shot-noise spectrum of a quantum dot p-i-n junction embedded inside a
three-dimensional photonic crystal is investigated. Radiative decay properties
of quantum dot excitons can be obtained from the observation of the current
noise. The characteristic of the photonic band gap is revealed in the current
noise with discontinuous behavior. Applications of such a device in
entanglement generation and emission of single photons are pointed out, and may
be achieved with current technologies.Comment: 4 pages, 3 figures, to appear in Phys. Rev. B (2005
Graduate dress code: How undergraduates are planning to use hair, clothes and make-up to smooth their transition to the workplace
This article explores the relationship between students’ identities, their ideas about professional appearance and their anticipated transition to the world of work. It is based on a series of semi-structured interviews with 13 students from a vocationally-focused university in England. It was found that participants viewed clothing and appearance as an important aspect of their transition to the workplace. They believed that, if carefully handled, their appearance could help them to fit in and satisfy the expectations of employers, although some participants anticipated that this process of fitting in might compromise their identity and values. The article addresses students’ anticipated means of handling the tension between adapting to a new environment and ‘being themselves’. It is argued that the way this process is handled is intertwined with wider facets of identity – most notably those associated with gender.The article is based on research funded by the University of Derby. © 2015 IP Publishing Ltd. ((http://www.ippublishing.com). Reproduced by permission
Inertial Focusing of Particles in Curved Micro-channels
Inertial focusing is the migration of particles in flow laterally across a channel into well-defined equilibrium positions. In microfluidic channels, inertial focusing takes advantage of hydrodynamic interactions even at high flow speeds. Particle isolation through inertial focusing is a high throughput method of processing biological samples for point-of-care diagnostics. While photos provide qualitative analyses of inertial focusing, we desired quantitative characterization of these systems. In this study, we ran flow experiments, first with fluorescent polystyrene beads and later with cells in solution, through curved micro-channels at controlled rates using a syringe pump. Our results from polystyrene bead experiments confirmed previous studies on flow through curved micro-channels, in which particles are focused along both sides of the channel at low flow rates and transition towards the center of the channel as the flow rate increases. FWHM analysis also showed that the streamline width is minimized at an intermediate flow rate, indicating inertial focusing is optimized under that condition. As this method of analysis was confirmed with polystyrene beads, we further used this analysis method to characterize the focusing of cells in solution. To maximize both throughput and purity, microfluidic devices must be designed to operate at the highest flow rate at which effective separation from bulk fluid can occur. The device presented in this report indeed isolates the desired target cells to be studied in downstream characterization.http://deepblue.lib.umich.edu/bitstream/2027.42/169578/1/Honors_Capstone_Anna_Kaehr.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/169578/2/Kaehr_Anna_Capstone_Poster.pptxhttp://deepblue.lib.umich.edu/bitstream/2027.42/169578/3/Capstone_Presentation_Video_Anna_Kaehr.mp
Revisiting the Hanbury Brown-Twiss set-up for fractional statistics
The Hanbury Brown-Twiss experiment has proved to be an effective means of
probing statistics of particles. Here, in a set-up involving edge-state
quasiparticles in a fractional quantum Hall system, we show that a variant of
the experiment composed of two sources and two sinks can be used to unearth
fractional statistics. We find a clear cut signature of the statistics in the
equal-time current-current correlation function for quasiparticle currents
emerging from the two sources and collected at the sinks.Comment: 4 pages, 3 figure
Strongly Coupled Matter-Field and Non-Analytic Decay Rate of Dipole Molecules in a Waveguide
The decay rate \gam of an excited dipole molecule inside a waveguide is
evaluated for the strongly coupled matter-field case near a cutoff frequency
\ome_c without using perturbation analysis. Due to the singularity in the
density of photon states at the cutoff frequency, we find that \gam depends
non-analytically on the coupling constant as . In contrast
to the ordinary evaluation of \gam which relies on the Fermi golden rule
(itself based on perturbation analysis), \gam has an upper bound and does not
diverge at \ome_c even if we assume perfect conductance in the waveguide
walls. As a result, again in contrast to the statement found in the literature,
the speed of emitted light from the molecule does not vanish at \ome_c and is
proportional to which is on the order of m/s for
typical dipole molecules.Comment: 4 pages, 2 figure
Vertical beaming of wavelength-scale photonic crystal resonators
We report that of the photons generated inside a photonic crystal
slab resonator can be funneled within a small divergence angle of . The far-field radiation properties of a photonic crystal slab
resonant mode are modified by tuning the cavity geometry and by placing a
reflector below the cavity. The former method directly shapes the near-field
distribution so as to achieve directional and linearly-polarized far-field
patterns. The latter modification takes advantage of the interference effect
between the original waves and the reflected waves to enhance the
energy-directionality. We find that, regardless of the slab thickness, the
optimum distance between the slab and the reflector closely equals one
wavelength of the resonance under consideration. We have also discussed an
efficient far-field simulation algorithm based on the finite-difference
time-domain method and the near- to far-field transformation.Comment: 14 pages, 15 figures, submitted to Phys. Rev.
Magnetic field induced lattice anomaly inside the superconducting state of CeCoIn: evidence of the proposed Fulde-Ferrell-Larkin-Ovchinnikov state
We report high magnetic field linear magnetostriction experiments on
CeCoIn single crystals. Two features are remarkable: (i) a sharp
discontinuity in all the crystallographic axes associated with the upper
superconducting critical field that becomes less pronounced as the
temperature increases; (ii) a distinctive second order-like feature observed
only along the c-axis in the high field (10 T ) low
temperature ( 0.35 K) region. This second order transition is
observed only when the magnetic field lies within 20 of the ab-planes and
there is no signature of it above , which raises questions regarding
its interpretation as a field induced magnetically ordered phase. Good
agreement with previous results suggests that this anomaly is related to the
transition to the Fulde-Ferrel-Larkin-Ovchinnikov superconducting state.Comment: 3 figures, 5 page
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