Conductance of Open Quantum Billiards and Classical Trajectories

We analyse the transport phenomena of 2D quantum billiards with convex boundary of different shape. The quantum mechanical analysis is performed by means of the poles of the S-matrix while the classical analysis is based on the motion of a free particle inside the cavity along trajectories with a different number of bounces at the boundary. The value of the conductance depends on the manner the leads are attached to the cavity. The Fourier transform of the transmission amplitudes is compared with the length of the classical paths. There is good agreement between classical and quantum mechanical results when the conductance is achieved mainly by special short-lived states such as whispering gallery modes (WGM) and bouncing ball modes (BBM). In these cases, also the localization of the wave functions agrees with the picture of the classical paths. The S-matrix is calculated classically and compared with the transmission coefficients of the quantum mechanical calculations for five modes in each lead. The number of modes coupled to the special states is effectively reduced.Comment: 19 pages, 6 figures (jpg), 2 table

Propagation of ultra-high energy protons in the nearby universe

We present a new calculation of the propagation of protons with energies above $10^{19}$ eV over distances of up to several hundred Mpc. The calculation is based on a Monte Carlo approach using the event generator SOPHIA for the simulation of hadronic nucleon-photon interactions and a realistic integration of the particle trajectories in a random extragalactic magnetic field. Accounting for the proton scattering in the magnetic field affects noticeably the nucleon energy as a function of the distance to their source and allows us to give realistic predictions on arrival energy, time delay, and arrival angle distributions and correlations as well as secondary particle production spectra.Comment: 12 pages, 9 figures, ReVTeX. Physical Review D, accepte

Time for a quick word? The striking benefits of training speed and accuracy of word retrieval in post-stroke aphasia

One-third of stroke survivors experience deficits in word retrieval as a core characteristic of their aphasia, which is frustrating, socially limiting and disabling for their professional and everyday lives. The, as yet, undiscovered ‘holy grail’ of clinical practice is to establish a treatment that not only improves item naming, but also generalizes to patients’ connected speech. Speech production in healthy participants is a remarkable feat of cognitive processing being both rapid (at least 120 words per minute) and accurate (∼one error per 1000 words). Accordingly, we tested the hypothesis that word-finding treatment will only be successful and generalize to connected speech if word retrieval is both accurate and quick. This study compared a novel combined speed- and accuracy-focused intervention—‘repeated, increasingly-speeded production’—to standard accuracy-focused treatment. Both treatments were evaluated for naming, connected speech outcomes, and related to participants’ neuropsychological and lesion profiles. Twenty participants with post-stroke chronic aphasia of varying severity and subtype took part in 12 computer-based treatment sessions over 6 weeks. Four carefully matched word sets were randomly allocated either to the speed- and accuracy-focused treatment, standard accuracy-only treatment, or untreated (two control sets). In the standard treatment, sound-based naming cues facilitated naming accuracy. The speed- and accuracy-focused treatment encouraged naming to become gradually quicker, aiming towards the naming time of age-matched controls. The novel treatment was significantly more effective in improving and maintaining picture naming accuracy and speed (reduced latencies). Generalization of treated vocabulary to connected speech was significantly increased for all items relative to the baseline. The speed- and accuracy-focused treatment generated substantial and significantly greater deployment of targeted items in connected speech. These gains were maintained at 1-month post-intervention. There was a significant negative correlation for the speed- and accuracy-focused treatment between the patients’ phonological scores and the magnitude of the therapy effect, which may have reflected the fact that the substantial beneficial effect of the novel treatment generated a ceiling effect in the milder patients. Maintenance of the speed- and accuracy-treatment effect correlated positively with executive skills. The neural correlate analyses revealed that participants with the greatest damage to the posterior superior temporal gyrus extending into the white matter of the inferior longitudinal fasciculus, showed the greatest speed- and accuracy treatment benefit. The novel treatment was well tolerated by participants across the range of severity and aphasia subtype, indicating that this type of intervention has considerable clinical utility and broad applicability

(Un)twisted: talking back to media representations of eating disorders

In 2014-15, there were several news reports about a rise in the diagnoses and treatment of eating disorders (EDs), as attributed to the use of image-driven social media. Such coverage can be situated within a long history of concern in which those diagnosed with an ED are constructed as ‘especially vulnerable’ to the power of media images – a subjectivity which is pathologised and devalued precisely through its association with femininity. The most incisive objections to EDs being presented as a response to the ‘weight’ of media representation have come from Abigail Bray (2005) in her work on how anorexia is constructed as a reading as well as an eating disorder. Indeed, there is a whole history of empirical work in Feminist Media Studies and Girlhood Studies which has challenged the pernicious construction of female subjectivity as ‘excessively’ invested in, and ‘damaged’ by, the consumption of mass mediated forms. Yet the media consumption practices of those with experience of an ED have not been subject to similar feminist re-evaluation – an omission which this research seeks to address. In exploring the results of 17 semi-structured interviews with people who have experience of an ED discussing their encounters with media representations of EDs (material that is often co-opted into debates about the ‘toxic’ nature of media culture in this regard), this article seeks to intervene in how such imagined media consumption practices are often defined. In seeking to speak back to historically pathologising constructions, the article seeks to explore the qualitative responses in the context of more ‘every day’ understandings of media engagement, thus working against the gendered othering which has persistently occurred

Overview of the coordinated ground-based observations of Titan during the Huygens mission

Coordinated ground-based observations of Titan were performed around or during the Huygens atmospheric probe mission at Titan on 14 January 2005, connecting the momentary in situ observations by the probe with the synoptic coverage provided by continuing ground-based programs. These observations consisted of three different categories: (1) radio telescope tracking of the Huygens signal at 2040 MHz, (2) observations of the atmosphere and surface of Titan, and (3) attempts to observe radiation emitted during the Huygens Probe entry into Titan's atmosphere. The Probe radio signal was successfully acquired by a network of terrestrial telescopes, recovering a vertical profile of wind speed in Titan's atmosphere from 140 km altitude down to the surface. Ground-based observations brought new information on atmosphere and surface properties of the largest Satumian moon. No positive detection of phenomena associated with the Probe entry was reported. This paper reviews all these measurements and highlights the achieved results. The ground-based observations, both radio and optical, are of fundamental imnortance for the interpretatinn of results from the Huygens mission

Neutrinos from propagation of ultra-high energy protons

We present a calculation of the production of neutrinos during propagation of ultra-high energy cosmic rays from their astrophysical sources to us. Photoproduction interactions are modeled with the event generator SOPHIA that represents very well the experimentally measured particle production cross sections at accelerator energies. We give the fluxes expected from different assumptions on cosmic ray source distributions, cosmic ray injection spectra, cosmological evolution of the sources and different cosmologies, and compare them to the Waxman-Bahcall limit on source neutrinos. We estimate rates for detection of neutrino induced showers in a km3 water detector. The ratio of the local high energy neutrino flux to the ultra-high energy cosmic ray flux is a crucial parameter in distinguishing between astrophysical and cosmological (top-down) scenarios of the ultra-high energy cosmic ray origin.Comment: 11 pages, revtex, 10 ps figures, extensively revised version, error in numerical calculation corrected, author adde

The 13th Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-IV Survey Mapping Nearby Galaxies at Apache Point Observatory

The fourth generation of the Sloan Digital Sky Survey (SDSS-IV) began observations in July 2014. It pursues three core programs: APOGEE-2,MaNGA, and eBOSS. In addition, eBOSS contains two major subprograms: TDSS and SPIDERS. This paper describes the first data release from SDSS-IV, Data Release 13 (DR13), which contains new data, reanalysis of existing data sets and, like all SDSS data releases, is inclusive of previously released data. DR13 makes publicly available 1390 spatially resolved integral field unit observations of nearby galaxies from MaNGA,the first data released from this survey. It includes new observations from eBOSS, completing SEQUELS. In addition to targeting galaxies and quasars, SEQUELS also targeted variability-selected objects from TDSS and X-ray selected objects from SPIDERS. DR13 includes new reductions ofthe SDSS-III BOSS data, improving the spectrophotometric calibration and redshift classification. DR13 releases new reductions of the APOGEE-1data from SDSS-III, with abundances of elements not previously included and improved stellar parameters for dwarf stars and cooler stars. For the SDSS imaging data, DR13 provides new, more robust and precise photometric calibrations. Several value-added catalogs are being released in tandem with DR13, in particular target catalogs relevant for eBOSS, TDSS, and SPIDERS, and an updated red-clump catalog for APOGEE.This paper describes the location and format of the data now publicly available, as well as providing references to the important technical papers that describe the targeting, observing, and data reduction. The SDSS website, http://www.sdss.org, provides links to the data, tutorials and examples of data access, and extensive documentation of the reduction and analysis procedures. DR13 is the first of a scheduled set that will contain new data and analyses from the planned ~6-year operations of SDSS-IV.PostprintPeer reviewe