Solutions to the 1d Klein-Gordon equation with cutoff Coulomb potentials

In a recent paper by Barton (J. Phys. A40, 1011 (2007)), the 1-dimensional Klein-Gordon equation was solved analytically for the non-singular Coulomb-like potential V_1(|x|) = -\alpha/(|x|+a). In the present paper, these results are completely confirmed by a numerical formulation that also allows a solution for an alternative cutoff Coulomb potential V_2(|x|) = -\alpha/|x|, ~|x| > a, and otherwise V_2(|x|) = -\alpha/a.Comment: 8 pages, 4 figure

Modulational instability of partially coherent signals in electrical transmission lines

We present an investigation of the modulational instability of partially coherent signals in electrical transmission lines. Starting from the modified Ginzburg-Landau equations and the Wigner-Moyal representation, we derive a nonlinear dispersion relation for the modulational instability. It is found that the effect of signal broadbandness reduces the growth rate of the modulational instability.Comment: 5 pages, 1 figure, to appear in Physical Review

Interference of an Array of Independent Bose-Einstein Condensates

Interference of an array of independent Bose-Einstein condensates, whose experiment has been performed recently, is theoretically studied in detail. Even if the number of the atoms in each gas is kept finite and the phases of the gases are not well defined, interference fringes are observed on each snapshot. The statistics of the snapshot interference patterns, i.e., the average fringe amplitudes and their fluctuations (covariance), are computed analytically, and concise formulas for their asymptotic values for long time of flight are derived. Processes contributing to these quantities are clarified and the relationship with the description on the basis of the symmetry-breaking scenario is revealed.Comment: 13 pages, 3 figure

Transform-Limited-Pulse Representation of Excitation with Natural Incoherent Light

We study the natural excitation of molecular systems, applicable to, for example, photosynthetic light-harvesting complexes, by natural incoherent light. In contrast with the conventional classical models, we show that the light need not have random character to properly represent the resultant linear excitation. Rather, thermal excitation can be interpreted as a collection of individual events resulting from the system's interaction with individual, deterministic pulsed realizations that constitute the field. The derived expressions for the individual field realizations and excitation events allow for a wave function formalism, and therefore constitute a useful calculational tool to study dynamics following thermal-light excitation. Further, they provide a route to the experimental determination of natural incoherent excitation using pulsed laser techniques.Comment: 5 pages, 3 figures, 1 page supplementary information. Comments welcom

Antiferromagnetism in NiO Observed by Transmission Electron Diffraction

Neutron diffraction has been used to investigate antiferromagnetism since 1949. Here we show that antiferromagnetic reflections can also be seen in transmission electron diffraction patterns from NiO. The diffraction patterns taken here came from regions as small as 10.5 nm and such patterns could be used to form an image of the antiferromagnetic structure with a nanometre resolution.Comment: 10 pages, 7 figures. Typos corrected. To appear in Physical Review Letter

Spatial quantum correlations in multiple scattered light

We predict a new spatial quantum correlation in light propagating through a multiple scattering random medium. The correlation depends on the quantum state of the light illuminating the medium, is infinite range, and dominates over classical mesoscopic intensity correlations. The spatial quantum correlation is revealed in the quantum fluctuations of the total transmission or reflection through the sample and should be readily observable experimentally.Comment: Reference adde

Healthcare professional’s guide to cardiopulmonary exercise testing

Cardiopulmonary exercise testing (CPEX) is a valuable clinical tool that has proven indications within the fields of cardiovascular, respiratory and pre-operative medical care. Validated uses include investigation of the underlying mechanism in patients with breathlessness, monitoring functional status in patients with known cardiovascular disease and pre-operative functional state assessment. An understanding of the underlying physiology of exercise, and the perturbations associated with pathological states, is essential for healthcare professionals to provide optimal patient care. Healthcare professionals may find performing CPEX to be daunting, yet this is often due to a lack of local expertise and guidance with testing. We outline the indications for CPEX within the clinical setting, present a typical protocol that is easy to implement, explain the key underlying physiological changes assessed by CPEX, and review the evidence behind its use in routine clinical practice. There is mounting evidence for the use of CPEX clinically, and an ever-growing utilisation of the test within research fields; a sound knowledge of CPEX is essential for healthcare professionals involved in routine patient care

Economic evaluation of the treatment of grade II haemorrhoids : a comparison of stapled haemorrhoidopexy and rubber band ligation.

The definitive version is available at www3.interscience.wiley.comPeer reviewedPostprin

Intensity fluctuations in steady state superradiance

Alkaline-earth like atoms with ultra-narrow optical transitions enable superradiance in steady state. The emitted light promises to have an unprecedented stability with a linewidth as narrow as a few millihertz. In order to evaluate the potential usefulness of this light source as an ultrastable oscillator in clock and precision metrology applications it is crucial to understand the noise properties of this device. In this paper we present a detailed analysis of the intensity fluctuations by means of Monte-Carlo simulations and semi-classical approximations. We find that the light exhibits bunching below threshold, is to a good approximation coherent in the superradiant regime, and is chaotic above the second threshold.Comment: 8 pages, 5 figure

Extension of the Huttner-Barnett model to a magnetodielectric medium

The Huttner$-$Barnett model is extended to a magnetodielectric medium by adding a new matter field to this model. The eigenoperators for the coupled system are calculated and electromagnetic field is written in terms of these operators. The electric and magnetic susceptibility of the medium are explicitly derived and shown to satisfy the Kramers$-$Kronig relations. It is shown that the results obtained in this model are equivalent to the results obtained from the phenomenological methods.Comment: 25 page