Casimir force on a piston

We consider a massless scalar field obeying Dirichlet boundary conditions on the walls of a two-dimensional L x b rectangular box, divided by a movable partition (piston) into two compartments of dimensions a x b and (L-a) x b. We compute the Casimir force on the piston in the limit L -> infinity. Regardless of the value of a/b, the piston is attracted to the nearest end of the box. Asymptotic expressions for the Casimir force on the piston are derived for a << b and a >> b.Comment: 10 pages, 1 figure. Final version, accepted for publication in Phys. Rev.

Ultrafast Optical Control of the Electronic Properties of ZrTe5ZrTe_5

We report on the temperature dependence of the $ZrTe_5$ electronic properties, studied at equilibrium and out of equilibrium, by means of time and angle resolved photoelectron spectroscopy. Our results unveil the dependence of the electronic band structure across the Fermi energy on the sample temperature. This finding is regarded as the dominant mechanism responsible for the anomalous resistivity observed at T* $\sim$ 160 K along with the change of the charge carrier character from holelike to electronlike. Having addressed these long-lasting questions, we prove the possibility to control, at the ultrashort time scale, both the binding energy and the quasiparticle lifetime of the valence band. These experimental evidences pave the way for optically controlling the thermoelectric and magnetoelectric transport properties of $ZrTe_5$

A Self-Adaptive Approach to Exploit Topological Properties of Different GAs’ Crossover Operators

Evolutionary algorithms (EAs) are a family of optimization algorithms inspired by the Darwinian theory of evolution, and Genetic Algorithm (GA) is a popular technique among EAs. Similar to other EAs, common limitations of GAs have geometrical origins, like premature convergence, where the final population’s convex hull might not include the global optimum. Population diversity maintenance is a central idea to tackle this problem but is often performed through methods that constantly diminish the search space’s area. This work presents a self- adaptive approach, where the non-geometric crossover is strategically employed with geometric crossover to maintain diversity from a geometrical/topological perspective. To evaluate the performance of the proposed method, the experimental phase compares it against well-known diversity maintenance methods over well-known benchmarks. Experimental results clearly demonstrate the suitability of the proposed self-adaptive approach and the possibility of applying it to different types of crossover and EAs

Probabilistic reconstruction via machine-learning of the Po watershed aquifer system (Italy)

A machine-learning-based methodology is proposed to delineate the spatial distribution of geomaterials across a large-scale three-dimensional subsurface system. The study area spans the entire Po River Basin in northern Italy. As uncertainty quantification is critical for subsurface characterization, the methodology is specifically designed to provide a quantitative evaluation of prediction uncertainty at each location of the reconstructed domain. The analysis is grounded on a unique dataset that encompasses lithostratigraphic data obtained from diverse sources of information. A hyperparameter selection technique based on a stratified cross-validation procedure is employed to improve model prediction performance. The quality of the results is assessed through validation against pointwise information and available hydrogeological cross-sections. The large-scale patterns identified are in line with the main features highlighted by typical hydrogeological surveys. Reconstruction of prediction uncertainty is consistent with the spatial distribution of available data and model accuracy estimates. It enables one to identify regions where availability of new information could assist in the constraining of uncertainty. The comprehensive dataset provided in this study, complemented by the model-based reconstruction of the subsurface system and the assessment of the associated uncertainty, is relevant from a water resources management and protection perspective. As such, it can be readily employed in the context of groundwater availability and quality studies aimed at identifying the main dynamics and patterns associated with the action of climate drivers in large-scale aquifer systems of the kind here analyzed, while fully embedding model and parametric uncertainties that are tied to the scale of investigation

Wide-range optical spin orientation in Ge from near-infrared to visible light

Ge-based spin-photodiodes have been employed to investigate the spectral dependence of optical spin orientation in germanium, in the range 400-1550 nm. We found the expected maximum in the spin polarization of photocarriers for excitation at the direct gap in Γ (1550 nm) and a second sizable peak due to photogeneration in the L valleys (530 nm). Data suggest distinct spin depolarization mechanisms for excitation at Γ and L, with shorter spin relaxation times whether the X point is involved. These devices can be used as integrated photon-helicity detectors over a wide spectral range

Electron-Phonon Coupling in High-Temperature Cuprate Superconductors Determined from Electron Relaxation Rates

We determined electronic relaxation times via pump-probe optical spectroscopy using sub-15 fs pulses for the normal state of two different cuprate superconductors.We show that the primary relaxation process is the electron-phonon interaction and extract a measure of its strength, the second moment of the Eliashberg function\lambda=800\pm200 meV^{2} for La_{1.85}Sr_{0.15}CuO_{4} and \lambda=400\pm100 meV^{2} for YBa_{2}Cu_{3}O_{6.5}. These values suggest a possible fundamental role of the electron-phonon interaction in the superconducting pairing mechanism.Comment: As published in PR

A full non-parametric approach for SAR Coherent Change Detection

Synthetic Aperture Radar (SAR) is widely used in heterogeneous fields with aims strictly dependent on the objectives of the application. One of the most common is the exploitation of the Interferometric-SAR (InSAR) to measure millimeter movements on the Earth's surface, aiming to monitor failures or measure infrastructures' health state. In this context, developing algorithms to detect temporal and spatial changes in the radar targets becomes very important. This paper focuses on the temporal change detection framework, proposing a non-parametric Coherent Change Detection (CCD) algorithm called Permutational Change Detection (PCD). The PCD estimates the temporal Change Points (CPs) of a radar target recognizing blocks structure in the coherence matrix without making any assumptions. The performance analysis on simulated data is accomplished, considering a realistic scenario where the geometrical and temporal decorrelation are properly modeled. Finally, the PCD is compared with a parametric CCD algorithm based on the Generalized Likelihood Ratio Test (GLRT)

Robot-assisted laparoscopic pyeloplasty (RALP) in children with horseshoe kidneys: results of a multicentric study

This multicentric study aimed to report our experience with robot-assisted laparoscopic pyeloplasty (RALP) in children with horseshoe kidney (HSK). METHODS: The records of 14 patients (11 boys and 3 girls with an average age of 9 years), who underwent RALP for repair of pelvi-ureteric junction obstruction (PUJO) in HSK in five international pediatric urology units over a 5-year period, were retrospectively reviewed. A dismembered pyeloplasty with no division of isthmus was performed in all the cases. RESULTS: The average operative time including docking was 143.5 min (range 100-205). No conversions to laparoscopy or open surgery or intra-operative complications occurred. Patients were discharged on postoperative day 2 following catheter and drain removal. The JJ stent was removed at mean 33 days postoperatively. Overall success rate was 92.8%. As for postoperative complications, we recorded a urinary tract infection (UTI) and stent-related irritative symptoms, managed with medical therapy, in two patients (II Clavien) and an anastomotic stricture in one patient needing surgical revision with no further recurrence (IIIb Clavien). At follow-up, all the patients (one after redo-surgery) reported complete resolution of symptoms, improvement of hydronephrosis on ultrasound and no residual obstruction on diuretic renogram. CONCLUSIONS: Our experience suggested that RALP in HSK is safe, feasible and with good medium-term outcomes in expert hands. An accurate pre-operative planning associated with a standardized technique is key points to achieve good surgical and functional outcomes in these challenging cases. The da Vinci robot technology offers the advantages of MIS procedures and overcomes the technical challenges of laparoscopic approach