Transient and stationary behavior of the Olami-Feder-Christensen earthquake model

Using long-term computer simulations and mean-field like arguments, we investigate the transient time and the properties of the stationary state of the Olami-Feder-Christensen earthquake model as function of the coupling parameter $\alpha$ and the system size $N$. The most important findings are that the transient time diverges nonanalytically when $\alpha$ approaches zero, and that the avalanche-size distribution will not approach a power law with increasing system size.Comment: 10 pages, 8 figure

Prioritising energy efficiency measures in Maltese restaurants

The 2018 Energy Performance of Buildings Directive (EU) 2018/844, focuses on building energy renovation. With the increase in tourists and working opportunities in Malta, the restaurants’ sector is experiencing a business boom. Despite this sector being a major energy consumer, the energy performance of restaurants in Malta has been given little attention. This paper investigates the energy performance of four representative restaurants in Malta. Refrigeration accounted for the highest share of 40% electricity consumption, followed by kitchen exhaust ventilation, domestic hot water and space cooling, which accounted for about 50%, while lighting consumed only 6%. Energy saving potential was primarily identified for refrigeration, water heating and air-conditioning. Although, the fuel sources used for cooking equipment accounted for more than 50% of the overall energy used in these restaurants, electricity is the fuel of primary concern as on average it contributes to 70% of total carbon emissions and results in the highest operational cost. The total potential of carbon emission savings was found to be 17%, when the recommended energy efficiency measures are applied. A benchmark of 14.51 kWh primary energy per person served was established for energy-efficient restaurants. This paper provides evidence-based results that are useful for policy makers to introduce fiscal incentives to support the transition of Maltese restaurants to nearly-zero energy status.peer-reviewe

Long-lived refractive index changes induced by femtosecond ionization in gas-filled single-ring photonic crystal fibers

We investigate refractive index changes caused by femtosecond photoionization in a gas-filled hollow-core photonic crystal fiber. Using spatially-resolved interferometric side-probing, we find that these changes live for tens of microseconds after the photoionization event - eight orders of magnitude longer than the pulse duration. Oscillations in the megahertz frequency range are simultaneously observed, caused by mechanical vibrations of the thin-walled capillaries surrounding the hollow core. These two non-local effects can affect the propagation of a second pulse that arrives within their lifetime, which works out to repetition rates of tens of kilohertz. Filling the fiber with an atomically lighter gas significantly reduces ionization, lessening the strength of the refractive index changes. The results will be important for understanding the dynamics of gas-based fiber systems operating at high intensities and high repetition rates, when temporally non-local interactions between successive laser pulses become relevant.Comment: 5 pages with four figures and one tabl

A deep learning framework for quality assessment and restoration in video endoscopy

Endoscopy is a routine imaging technique used for both diagnosis and minimally invasive surgical treatment. Artifacts such as motion blur, bubbles, specular reflections, floating objects and pixel saturation impede the visual interpretation and the automated analysis of endoscopy videos. Given the widespread use of endoscopy in different clinical applications, we contend that the robust and reliable identification of such artifacts and the automated restoration of corrupted video frames is a fundamental medical imaging problem. Existing state-of-the-art methods only deal with the detection and restoration of selected artifacts. However, typically endoscopy videos contain numerous artifacts which motivates to establish a comprehensive solution. We propose a fully automatic framework that can: 1) detect and classify six different primary artifacts, 2) provide a quality score for each frame and 3) restore mildly corrupted frames. To detect different artifacts our framework exploits fast multi-scale, single stage convolutional neural network detector. We introduce a quality metric to assess frame quality and predict image restoration success. Generative adversarial networks with carefully chosen regularization are finally used to restore corrupted frames. Our detector yields the highest mean average precision (mAP at 5% threshold) of 49.0 and the lowest computational time of 88 ms allowing for accurate real-time processing. Our restoration models for blind deblurring, saturation correction and inpainting demonstrate significant improvements over previous methods. On a set of 10 test videos we show that our approach preserves an average of 68.7% which is 25% more frames than that retained from the raw videos.Comment: 14 page

Reservation wages and the wage flexibility puzzle

Wages are only mildly cyclical, implying that shocks to labour demand have a larger short-run impact on unemployment rather than wages, at odds with the quantitative predictions of the canonical search model – even if wages are only occasionally renegotiated. We argue that one source of the wage flexibility puzzles is plausibly the model for the determination of reservation wages, and consider an alternative reservation wage model based on reference dependence in job search. This extension generates less cyclical reservation wages than the canonical model, as long as reference points are less cyclical than forward-looking components of reservation wages such as the arrival rate of job offers. We provide evidence that reservation wages significantly respond to backward looking reference points, as proxied by rents earned in previous jobs. In a model calibration we show that backward-looking reference dependence markedly reduces the predicted cyclicality of both wages and reservation wages and can reconcile theoretical predictions of the canonical model with the observed cyclicality of wages and reservation wages

Reservation wages and the wage flexibility puzzle

Wages are only mildly cyclical, implying that shocks to labour demand have a larger short-run impact on unemployment rather than wages, at odds with the quantitative predictions of the canonical search and matching model. This paper provides an alternative perspective on the wage flexibility puzzle, explaining why the canonical model can only match the observed cyclicality of wages if the replacement ratio is implausibly high. We show that this failure remains even if wages are only occasionally renegotiated, unless the persistence in unemployment is implausibly low. We then provide some evidence that part of the problem comes from the implicit model for the determination of reservation wages. Estimates for the UK and West Germany provide evidence that reservation wages are much less cyclical than predicted even conditional on the observed level of wage cyclicality. We present evidence that elements of perceived “fairness” or “reference points” in reservation wages may address this model failure

Long-term balancing selection drives evolution of immunity genes in Capsella.

Genetic drift is expected to remove polymorphism from populations over long periods of time, with the rate of polymorphism loss being accelerated when species experience strong reductions in population size. Adaptive forces that maintain genetic variation in populations, or balancing selection, might counteract this process. To understand the extent to which natural selection can drive the retention of genetic diversity, we document genomic variability after two parallel species-wide bottlenecks in the genus Capsella. We find that ancestral variation preferentially persists at immunity related loci, and that the same collection of alleles has been maintained in different lineages that have been separated for several million years. By reconstructing the evolution of the disease-related locus MLO2b, we find that divergence between ancient haplotypes can be obscured by referenced based re-sequencing methods, and that trans-specific alleles can encode substantially diverged protein sequences. Our data point to long-term balancing selection as an important factor shaping the genetics of immune systems in plants and as the predominant driver of genomic variability after a population bottleneck

Reconstruction of the skull inverting the deformed surface of the bone after exeresis of a frontal arachnoid cyst

Intracranial arachnoid cysts need to be operated on when they are causing symptoms and aesthetic problems. The aim of this case report was to describe a new method of reconstructing the skull by eliminating a left frontal bone deformity by turning the inside out and the outside inward, which provided good aesthetics and protected the region of surgical interest after the removal of an arachnoid cyst of the left frontal lob