Thermal emission in the early X-ray afterglows of GRBs: following the prompt phase to the late times

Thermal radiation, peaking in soft X-rays, has now been detected in a handful of GRB afterglows and has to date been interpreted as shock break-out of the GRB's progenitor star. We present a search for thermal emission in the early X-ray afterglows of a sample of Swift bursts selected by their brightness in X-rays at early times. We identify a clear thermal component in eight GRBs and track the evolution. We show that at least some of the emission must come from highly relativistic material since two show an apparent super-luminal expansion of the thermal component. Furthermore we determine very large luminosities and high temperatures for many of the components-too high to originate in a SN shock break-out. Instead we suggest that the component may be modelled as late photospheric emission from the jet, linking it to the apparently thermal component observed in the prompt emission of some GRBs at gamma-ray and hard X-ray energies. By comparing the parameters from the prompt emission and the early afterglow emission we find that the results are compatible with the interpretation that we are observing the prompt quasi-thermal emission component in soft X-rays at a later point in its evolution.Comment: 9 pages, 4 figures, ApJ accepte

Entanglement generation in relativistic quantum fields

We present a general, analytic recipe to compute the entanglement that is generated between arbitrary, discrete modes of bosonic quantum fields by Bogoliubov transformations. Our setup allows the complete characterization of the quantum correlations in all Gaussian field states. Additionally, it holds for all Bogoliubov transformations. These are commonly applied in quantum optics for the description of squeezing operations, relate the mode decompositions of observers in different regions of curved spacetimes, and describe observers moving along non-stationary trajectories. We focus on a quantum optical example in a cavity quantum electrodynamics setting: an uncharged scalar field within a cavity provides a model for an optical resonator, in which entanglement is created by non-uniform acceleration. We show that the amount of generated entanglement can be magnified by initial single-mode squeezing, for which we provide an explicit formula. Applications to quantum fields in curved spacetimes, such as an expanding universe, are discussed.Comment: 8 pages, 2 figures, Ivette Fuentes previously published as Ivette Fuentes-Guridi and Ivette Fuentes-Schuller; v2: published version (online), to appear in the J. Mod. Opt. Special Issue on the Physics of Quantum Electronic

Modelling extrudate expansion in a twin-screw food extrusion cooking process through dimensional analysis methodology

A new phenomenological modelling framework is proposed to correlate the extrudate expansion and extrusion process parameters through dimensional analysis methodology. As dimensional analysis is independent of system or equipment structure, the proposed equation may provide a general expression for the extrudate expansion behaviours and process operation conditions. This work includes extrusion cooking trials, model development and data analysis

Expansion of the whole wheat flour extrusion

A new model framework is proposed to describe the expansion of extrudates with extruder operating conditions based on dimensional analysis principle. The Buckingham pi dimensional analysis method is applied to form the basic structure of the model from extrusion process operational parameters. Using the Central Composite Design (CCD) method, whole wheat flour was processed in a twin-screw extruder with 16 trials. The proposed model can well correlate the expansion of the 16 trials using 3 regression parameters. The average deviation of the correlation is 5.9%

Precision and Work Fluctuations in Gaussian Battery Charging

One of the most fundamental tasks in quantum thermodynamics is extracting energy from one system and subsequently storing this energy in an appropriate battery. Both of these steps, work extraction and charging, can be viewed as cyclic Hamiltonian processes acting on individual quantum systems. Interestingly, so-called passive states exist, whose energy cannot be lowered by unitary operations, but it is safe to assume that the energy of any not fully charged battery may be increased unitarily. However, unitaries raising the average energy by the same amount may differ in qualities such as their precision, fluctuations, and charging power. Moreover, some unitaries may be extremely difficult to realize in practice. It is hence of crucial importance to understand the qualities that can be expected from practically implementable transformations. Here, we consider the limitations on charging batteries when restricting to the feasibly realizable family of Gaussian unitaries. We derive optimal protocols for general unitary operations as well as for the restriction to easier implementable Gaussian unitaries. We find that practical Gaussian battery charging, while performing significantly less well than is possible in principle, still offers asymptotically vanishing relative charge variances and fluctuations.Comment: 14+8 pages, 8 figures, accepted for publication in Quantu

A new engineering method for understanding extrusion cooking process

A new engineering method is proposed to understand extrudate expansion and extrusion operation parameters for starch based food extrusion cooking process through dimensional analysis principle, i.e. Buckingham pi theorem. Three dimensionless groups, i.e. pump efficiency, water content and temperature, are suggested to describe the extrudate expansion. Using the three dimensionless groups, an equation is derived to express the extrudate expansion. The model has been used to correlate the experimental data for whole wheat flour and fish feed extrusion cooking. The average deviations of the correlation are respectively 5.9% and 9% for the whole wheat flour and the fish feed extrusion. An alternative 4-coefficient equation is also suggested from the 3 dimensionless groups. The average deviations of the alternative equation are respectively 5.8% and 2.5% in correlation with the same set of experimental data

Capacity Building for Pro-Poor Trade: Learning from the Limitations in Current Models

human development, aid, trade, security

Audit fees and IFRS accounting - Is information costly?

Since 2005 companies with equity instruments traded on regulated markets in the European Economic Area have prepared their financial reports in accordance with accounting standards issued by the IASB. A survey conducted in 2007 indicated that most of the EU companies that changed from local to IFRS rules incurred additional costs in connection with the transition. Also, companies expected additional future costs from using IFRS. Although the main part of these stemmed from the companies’ internal work on IFRS statements, additional costs for external auditing and other external services were identified as substantial but independent of company size. We analyze whether the application of IFRS standards has increased Danish companies’ cost of auditing. Our study is based on a sample of financial reports from large Danish companies from 2002 to 2008. Controlling for a number of general audit fee driving aspects, we find that overall, audit fees have not increased significantly for companies using IFRS rules. However, when combining IFRS with company size and complexity, we find that large and complex companies using IFRS pay a heavy audit fee premium compared to small and less complex companies that also use IFRS. Our results for nonaudit fees are less conclusive.Audit fees; non audit fees; IFRS; transition of accounting regime; empirical study