Coherent transport of atomic wave packets in amplitude-modulated vertical optical lattices

We report on the realization of dynamical control of transport for ultra-cold Sr88 atoms loaded in an accelerated and amplitude-modulated 1D optical lattice. We tailor the energy dispersion of traveling wave packets and reversibly switch between Wannier-Stark localization and driven transport based on coherent tunneling. Within a Loschmidt-echo scheme where the atomic group velocities are reversed at once, we demonstrate a novel mirror for matter waves working independently of the momentum state and discuss possible applications to force measurements at micrometric scales

Multiscale fractal dimension analysis of a reduced order model of coupled ocean–atmosphere dynamics

Atmosphere and ocean dynamics display many complex features and are characterized by a wide variety of processes and couplings across different timescales. Here we demonstrate the application of multivariate empirical mode decomposition (MEMD) to investigate the multivariate and multiscale properties of a reduced order model of the ocean–atmosphere coupled dynamics. MEMD provides a decomposition of the original multivariate time series into a series of oscillating patterns with time-dependent amplitude and phase by exploiting the local features of the data and without any a priori assumptions on the decomposition basis. Moreover, each oscillating pattern, usually named multivariate intrinsic mode function (MIMF), represents a local source of information that can be used to explore the behavior of fractal features at different scales by defining a sort of multiscale and multivariate generalized fractal dimensions. With these two complementary approaches, we show that the ocean–atmosphere dynamics presents a rich variety of features, with different multifractal properties for the ocean and the atmosphere at different timescales. For weak ocean–atmosphere coupling, the resulting dimensions of the two model components are very different, while for strong coupling for which coupled modes develop, the scaling properties are more similar especially at longer timescales. The latter result reflects the presence of a coherent coupled dynamics. Finally, we also compare our model results with those obtained from reanalysis data demonstrating that the latter exhibit a similar qualitative behavior in terms of multiscale dimensions and the existence of a scale dependency of the statistics of the phase-space density of points for different regions, which is related to the different drivers and processes occurring at different timescales in the coupled atmosphere–ocean system. Our approach can therefore be used to diagnose the strength of coupling in real applications

Rilievo in tempo reale di difetti superficiali su corpi in movimento a velocità elevata con ultrasuoni senza contatto

Il rilievo di difetti superficiali durante le ispezioni periodiche è importante poiché in genere le sollecitazioni sono maggiori in superficie e possono accelerare la crescita delle discontinuità. I difetti superficiali possono essere rilevati utilizzando alcuni metodi tradizionali di controllo non distruttivo, quali correnti indotte, liquidi penetranti, polveri magnetiche ed ultrasuoni. Alcuni tra questi metodi possono essere usati solo in condizioni statiche; gli altri presentano delle limitazioni per l’ispezione dinamica. I progressi recenti nel campo dei sensori ultrasonori senza contatto ci hanno permesso di sviluppare un sistema semplice per l’ispezione in tempo reale di corpi in movimento a velocità elevata. Nel lavoro viene presentata la possibilità di usare, col sistema sviluppato, due metodologie, basate sugli ultrasuoni generati e ricevuti senza contatto con la struttura, per rilevare difetti superficiali su corpi in movimento a 100 km/h, così da poter effettuare l’ispezione anche in servizio. Una metodologia, basata sull’uso di laser e trasduttori senza contatto, utilizza i vantaggi delle onde superficiali generate con il laser; l’analisi viene fatta sull’onda riflessa, creata dall’interazione dell’onda superficiale con il difetto. Lo spessore superficiale ispezionato è selezionabile dalla lunghezza d’onda dell’onda superficiale generata. L’altra metodologia, basata sull’uso di trasduttori senza contatto, sfrutta gli svantaggi della trasmissione degli ultrasuoni all’interfaccia aria/metallo; l’analisi viene fatta sulla diffrazione dell’onda riflessa dalla superficie. L’esecuzione delle ispezioni risulta semplice con entrambe le tecniche. I risultati sperimentali indicano una buona efficienza delle due metodologie proposte per il rilievo, in tempo reale, di difetti superficiali su corpi in movimento ad alta velocità

Unusual PLS application for Pd(ii) sensing in extremely acidic solutions

An economic and extremely selective device for Pd(ii) determination in very acidic solutions, TazoC-Mar@ is presented. The sensor was prepared via an ion exchange technique of an azoic ligand, (2-(tetrazolylazo)-1,8 dihydroxy naphthalene-3,6,-disulphonic acid), named TazoC, on a Macroporous Strong Anion Exchange Resin, namely Marathon® (Dow Chemical-USA). The TazoC-Mar@ rapidly forms complexes with palladium(ii) ions, which give an intense blue colour to the solid phase, even at low pH. The reaction is highly selective and no other metal ions react with the device at this pH. Moreover, the quantification of Pd(ii) is reliable when applying partial least squares regression (PLS) to relate the signal to the metal ion concentration. The regression model gives a good fit and correct predictions of Pd(ii) concentrations in unknown samples. The method presented here is highly sensitive with an LOD and LOQ equal to 0.2 nM and 0.5 nM, respectively

Current trends in polymer based sensors

This review illustrates various types of polymer and nanocomposite polymeric based sensors used in a wide variety of devices. Moreover, it provides an overview of the trends and challenges in sensor research. As fundamental components of new devices, polymers play an important role in sensing applications. Indeed, polymers offer many advantages for sensor technologies: their manufacturing methods are pretty simple, they are relatively low-cost materials, and they can be functionalized and placed on different substrates. Polymers can participate in sensing mechanisms or act as supports for the sensing units. Another good quality of polymer-based materials is that their chemical structure can be modified to enhance their reactivity, biocompatibility, resistance to degradation, and flexibility

Disentangling nonlinear geomagnetic variability during magnetic storms and quiescence by timescale dependent recurrence properties

Understanding the complex behavior of the near-Earth electromagnetic environment is one of the main challenges of Space Weather studies. This includes both the correct characterization of the different physical mechanisms responsible for its configuration and dynamics as well as the efforts which are needed for a correct forecasting of several phenomena. By using a nonlinear multi-scale dynamical systems approach, we provide here new insights into the scale-to-scale dynamical behavior of both quiet and disturbed periods of geomagnetic activity. The results show that a scale-dependent dynamical transition occurs when moving from short to long timescales, i.e., from fast to slow dynamical processes, the latter being characterized by a more regular behavior, while more dynamical anomalies are found in the behavior of the fast component. This suggests that different physical processes are typical for both dynamical regimes: the fast component, being characterized by a more chaotic and less predictable behavior, can be related to the internal dynamical state of the near-Earth electromagnetic environment, while the slow component seems to be less chaotic and associated with the directly driven processes related to the interplanetary medium variability. Moreover, a clear difference has been found between quiet and disturbed periods, the former being more complex than the latter. These findings support the view that, for a correct forecasting in the framework of Space Weather studies, more attention needs to be devoted to the identification of proxies describing the internal dynamical state of the near-Earth electromagnetic environment

Probability density functions of photochemicals over a coastal area of Northern Italy

The present paper surveys the findings of experimental studies and analyses of statistical probability density functions (PDFs) applied to air pollutant concentrations to provide an interpretation of the ground-level distributions of photochemical oxidants in the coastal area of Ravenna (Italy). The atmospheric pollution data set was collected from the local environmental monitoring network for the period 1978-1989. Results suggest that the statistical distribution of surface ozone, once normalised over the solar radiation PDF for the whole measurement period, follows a log-normal law as found for other pollutants. Although the Weibull distribution also offers a good fit of the experimental data, the area’s meteorological features seem to favour the former distribution once the statistical index estimates have been analysed. Local transport phenomena are discussed to explain the data tail trends