Comment on "Late-time tails of a self-gravitating massless scalar field revisited" by Bizon et al: The leading order asymptotics

In Class. Quantum Grav. 26 (2009) 175006 (arXiv:0812.4333v3) Bizon et al discuss the power-law tail in the long-time evolution of a spherically symmetric self-gravitating massless scalar field in odd spatial dimensions. They derive explicit expressions for the leading order asymptotics for solutions with small initial data by using formal series expansions. Unfortunately, this approach misses an interesting observation that the actual decay rate is a product of asymptotic cancellations occurring due to a special structure of the nonlinear terms. Here, we show that one can calculate the leading asymptotics more directly by recognizing the special structure and cancellations already on the level of the wave equation.Comment: 7 pages; minor simplifications in the notation; some comments withdrawn or rewritten after improvements in the new version (v3) of the commented paper; 1 reference adde

Optical lattice quantum simulator for QED in strong external fields: spontaneous pair creation and the Sauter-Schwinger effect

Spontaneous creation of electron-positron pairs out of the vacuum due to a strong electric field is a spectacular manifestation of the relativistic energy-momentum relation for the Dirac fermions. This fundamental prediction of Quantum Electrodynamics (QED) has not yet been confirmed experimentally as the generation of a sufficiently strong electric field extending over a large enough space-time volume still presents a challenge. Surprisingly, distant areas of physics may help us to circumvent this difficulty. In condensed matter and solid state physics (areas commonly considered as low energy physics), one usually deals with quasi-particles instead of real electrons and positrons. Since their mass gap can often be freely tuned, it is much easier to create these light quasi-particles by an analogue of the Sauter-Schwinger effect. This motivates our proposal of a quantum simulator in which excitations of ultra-cold atoms moving in a bichromatic optical lattice represent particles and antiparticles (holes) satisfying a discretized version of the Dirac equation together with fermionic anti-commutation relations. Using the language of second quantization, we are able to construct an analogue of the spontaneous pair creation which can be realized in an (almost) table-top experiment.Comment: 21 pages, 10 figure

Some thoughts about the conceptual / procedural distinction in translation: a key-logging and eye-tracking study of processing effort

This article builds on the conceptual / procedural distinction postulated by Relevance Theory to investigate processing effort in translation task execution. Drawing on relevance-theoretic assumptions, it assumes that instances related to procedural encodings will require more effortful processing not only in relation to the time spent on the task but also in terms of product indicators such as seconds per word and number of micro translation units per word. Drawing on key-logging and eye-tracking data, the article shows that there are statistically significant differences when conceptual and procedural encodings are analysed in selected areas of interest, with instances related to procedural encoding requiring more processing effort to be translated. The results are relevant for translation process research as they signal to where processing effort is predominantly located. Additionally, the discussion also contributes to validating experimentally some claims postulated by Relevance Theory.Este artículo se basa en la distinción entre codificaciones conceptuales y procedimentales postulada por la Teoría de la Relevancia para investigar el esfuerzo de procesamiento en tareas de traducción. Con base en esta teoría, se asume que los casos relacionados con codificaciones procedimentales requieren más esfuerzo de procesamiento no sólo en relación al tiempo empleado en la tarea, sino también en términos de indicadores de producto, tales como segundos por palabra y número de micro unidades de traducción por palabra. Utilizando datos de registro de teclado y ratón, así como datos de seguimiento ocular, el artículo muestra que existen diferencias estadísticamente significativas entre las codificaciones conceptuales y las procedimentales cuando se analizan áreas de interés seleccionadas. Los casos relacionados con la codificación procedimental requieren más esfuerzo de procesamiento para traducirlos. Los resultados son relevantes para la investigación del proceso de traducción, ya que indican dónde se concentra predominantemente el esfuerzo de procesamiento al traducir. Además, el debate contribuye a validar experimentalmente algunos principios postulados por la Teoría de la Relevancia.Research funded by CNPq, the Brazilian Research Council (grant 307964/2011-6); and FAPEMIG, the Research Agency of the State of Minas Gerais (grants SHA/PPM-00495-12 and SHA/PPM-00087-12)

CV10_28 Irish Sea cruise report

Cruise CV10_28 mobilized and demobilized from Howth, Co. Dublin, on the 2nd and 7th June 2010 respectively, and totalled over 112 operational hours. The objectives of this cruise were primarily to investigate and sample previously identified methane-related seepage structures in the Irish Designated Seabed Zone (IDSZ) of the Irish Sea, to carry out sampling grids of Dublin Bay and of the region of the IDSZ from Dublin Bay to Dundalk Bay for multidisciplinary geochemical and microbiological studies, and also to sample the water column for dissolved organic matter studies. A total of 113 sampling stations were successfully sampled: 46 grabs; 55 boxcores (0.25m2); 5 gravity cores (1m); and 7 vibrocores (3m). Gas-related seepage features successfully investigated were methane-derived authigenic carbonates (MDAC) in the Codling Fault Zone (CFZ), the Lambay Deep mud diapir, and also a shallow pockmark in the northen mudbelt region. Four videolines with over six hours of video footage were acquired in the MDAC target sites. Video footage and image stills of clusters of MDAC slabs, nodules and outcroppings, as well as indications enhanced anaerobic oxidation of methane (AOM) were successfully obtained. These features were subsequently successfully ground-truthed, sampled and preliminary geochemical analysis was carried out, thereby proving MDAC mounds in the CFZ are distinct features caused by active sub-surface seepage of methane. The Lambay Deep mud diapir was investigated by videoline deployment, whereby no distinct differences in seabed structure or biodiversity were observed. Fine sandy muds with relatively high macrofaunal biodiversity characterized seabed both inside and outside of Lambay Deep. The feature and surrounding seabed was ground-truthed by vibrocore and boxcore, and results supported the videoline findings. Sub-surface sediment (0-3m) was characterized by homogenous well-sorted fine sandy mud, with low infauna and shell presence, and little or no evidence of sub-surface anoxia. The mudbelt pockmark was investigated by videoline deployment and also subsequently ground-truthed by gravity core and boxcore. Videoline and sampling evidence suggests that the pockmark and reference samples from the surrounding seabed is uniform, and characterized by very fine mud with little sub-surface zonation. Previous sub-bottom profiling of the feature suggests no evidence of gas seepage or accumulations in the vicinity of the pockmark. The weather and sampling conditions were overall favourable throughout the cruise but the lack of dynamic positioning aboard the Celtic Voyager and also the restriction on the vibrocore to slack water and day-time use resulted in some sampling limitations and incomplete secondary objectives. Overall CV10_28 achieved the vast majority of its objectives, and a comprehensive foundation for numerous studies and peer-reviewed publications has been established

Quantum simulator for the Schwinger effect with atoms in bi-chromatic optical lattices

Ultra-cold atoms in specifically designed optical lattices can be used to mimic the many-particle Hamiltonian describing electrons and positrons in an external electric field. This facilitates the experimental simulation of (so far unobserved) fundamental quantum phenomena such as the Schwinger effect, i.e., spontaneous electron-positron pair creation out of the vacuum by a strong electric field.Comment: 4 pages, 2 figures; minor corrections and improvements in text and in figures; references adde

Hydrographic controls on marine organic matter fate and microbial diversity in the western Irish Sea

Cycling of organic matter (OM) is the key biological process in the marine environment and knowledge of the sources and the reactivity of OM, in addition to factors controlling its distribution in estuarine, coastal and shelf sediments are of key importance for understanding global biogeochemical cycles. With recent advances in cultivation-independent molecular approaches to microbial ecology, the key role of prokaryotes in global biogeochemical cycling in marine ecosystems has been emphasised. However, spatial studies combining the distribution and fate of OM with microbial community abundance and diversity remain rare. Here, a combined spatial lipid biomarker and 16S rRNA tagged pyrosequencing study was conducted in surface sediments and particulate matter across hydrographically distinct zones associated with the seasonal western Irish Sea gyre. The aim was to assess the spatial variation of, and factors controlling, marine organic cycling and sedimentary microbial communities across these distinct zones. The distribution of phospholipid fatty acids, source-specific sterols, wax esters and C25 highly branched isoprenoids indicate that diatoms, dinoflagellates and green algae were the major contributors of marine organic matter, while the distribution of cholesterol, wax esters and C20 and C22 polyunsaturated fatty acids have highlighted the importance of copepod grazing for mineralizing organic matter in the water column5. This marine OM production and mineralisation was greatest in well-mixed waters compared to offshore stratified waters. Lipid analysis and 16S rRNA PCR-DGGE profiling also suggests that sedimentary bacterial abundance increases while community diversity decreases in offshore stratified waters. The major bacterial classes are the Deltaproteobacteria, Clostridia, Flavobacteriia, Gammaproteobactera and Bacteroiidia. At the family/genus level most groups appear to be associated with organoheterotrophic processing of sedimentary OM, ranging from degradation of complex organic matter (e.g. Tepidibacter sp.) to sulfur-dependent utilisation of simple organic molecules (e.g. Desulfobulbaceae and Desulfuromonadaceae)

Understanding Outcomes in a Randomized Controlled Trial of a Ward-based Intervention on Psychiatric Inpatient Wards: A Qualitative Analysis of Staff and Patient Experiences.

OBJECTIVE: Team formulation is advocated to improve quality of care in mental health care and evidence from a recent U.K.-based trial supports its use in inpatient settings. This study aimed to identify the effects of formulation on practice from the perspectives of staff and patient participating in the trial, including barriers and enhancers to implementing the intervention. METHOD: We carried out semistructured interviews with 57 staff and 20 patients. Data were analyzed using thematic analysis. RESULTS: Main outcomes were: improved staff understanding of patients, better team collaboration and increased staff awareness of their own feelings. Key contextual factors were as follows: overcoming both staff and patient anxiety, unwelcome expert versus collaborative stance, competing demands, and management support. CONCLUSION: Team formulation should be implemented to improve quality of care in inpatient settings and larger definitive trials should be carried out to assess the effect of this intervention on patient outcomes

Intermediate behavior of Kerr tails

The numerical investigation of wave propagation in the asymptotic domain of Kerr spacetime has only recently been possible thanks to the construction of suitable hyperboloidal coordinates. The asymptotics revealed an apparent puzzle in the decay rates of scalar fields: the late-time rates seemed to depend on whether finite distance observers are in the strong field domain or far away from the rotating black hole, an apparent phenomenon dubbed "splitting". We discuss far-field "splitting" in the full field and near-horizon "splitting" in certain projected modes using horizon-penetrating, hyperboloidal coordinates. For either case we propose an explanation to the cause of the "splitting" behavior, and we determine uniquely decay rates that previous studies found to be ambiguous or immeasurable. The far-field "splitting" is explained by competition between projected modes. The near-horizon "splitting" is due to excitation of lower multipole modes that back excite the multipole mode for which "splitting" is observed. In both cases "splitting" is an intermediate effect, such that asymptotically in time strong field rates are valid at all finite distances. At any finite time, however, there are three domains with different decay rates whose boundaries move outwards during evolution. We then propose a formula for the decay rate of tails that takes into account the inter--mode excitation effect that we study.Comment: 16 page

Biomarkers reveal the effects of hydrography on the sources and fate of marine and terrestrial organic matter in the western Irish Sea

A suite of lipid biomarkers were investigated from surface sediments and particulatematter across hydrographically distinct zones associated with the western Irish Sea gyre and the seasonal bloom. The aim was to assess the variation of organic matter (OM) composition, production, distribution and fate associated with coastal and southern mixed regions and also the summer stratified region. Based on the distribution of a suite of diagnostic biomarkers, including phospholipid fatty acids, source-specific sterols, wax esters and C25 highly branched isoprenoids, diatoms, dinoflagellates and green algae were identified as major contributors of marine organic matter (MOM) in this setting. The distribution of cholesterol, wax esters and C20 and C22 polyunsaturated fatty acids indicate that copepod grazing represents an important process for mineralising this primary production. Net tow data from 2010 revealed much greater phytoplankton and zooplankton biomass in well-mixed waters compared to stratified waters. This appears to be largely reflected in MOM input to surface sediments. Terrestrial organic matter (TOM), derived from higher plants, was identified as a major source of OM regionally, but was concentrated in proximity to major riverine input at the Boyne Estuary and Dundalk Bay. Near-bottom residual circulation and the seasonal gyre also likely play a role in the fate of TOM in the western Irish Sea