Two-peaked and flat-top perfect bright solitons in epsilon-near-zero nonlinear metamaterials: novel Kerr self-trapping mechanisms

We analytically investigate transverse magnetic (TM) spatial bright solitons, as exact solutions of Maxwell's equations, propagating through nonlinear metamaterials whose linear dielectric permittivity is very close to zero and whose effective nonlinear Kerr parameters can be tailored to achieve values not available in standard materials. Exploiting the fact that, in the considered medium, linear and nonlinear polarization can be comparable at feasible and realistic optical intensities, we identify two novel self-trapping mechanisms able to support two-peaked and flat-top solitons, respectively. Specifically, these two novel mechanisms are based on the occurrence of critical points at which the effective nonlinear permittivity vanishes, the two mechanisms differing in the way the compensation between linear and nonlinear polarization is achieved through the non-standard values of the nonlinear parameters.Comment: 7 pages, 4 figure

Pancreatic cystosis in cystic fibrosis. Sometimes a bike ride can help you decide

Pancreatic cystosis (PC) is an uncommon manifestation of pancreas involvement in cystic fibrosis (CF), characterized by the presence of multiple macrocysts partially or completely replacing pancreas. Only few reports are available from literature and management (surgery vs follow up) is commonly based on the presence of symptoms or complications due to local mass effect, although evidence-based recommendations are still not available. We here report the case of a young adult CF patient with PC, in which cardiopulmonary exercise testing (CPET) provided important information to be integrated to the radiological finding of inferior vena cava compression by the multicystic pancreas complex. Through the analysis of oxygen kinetic cardiodynamic phase pattern, CPET may be helpful to safely exclude significant mass effects on blood venous return and to improve the decision-making process on whether to consider surgery or not in patients with PC

A new modulation technique for high data rate low power UWB wireless optical communication in implantable biotelemetry systems

We report on the development of a novel modulation technique for UWB wireless optical communication systems for application in a transcutaneous biotelemetry. The solution, based on the generation of short laser pulses, allows for a high data rate link whilst achieving a significant power reduction (energy per bit) compared to the state-of-the-art. These features make this particularly suitable for emerging biomedical applications such as implantable neural/biosensor systems. The relatively simple architecture consists of a transmitter and receiver that can be integrated in a standard CMOS technology in a compact Silicon footprint. These parts include circuits for bias and drive current generation, conditioning and processing, optimised for low-volt age/low-power operation. Preliminary experimental findings validate the new paradigm and show good agreement with expected results. The complete system achieves a BER less than 10-7, with maximum data rate of 125Mbps and estimated total power consumption of less than 3mW

Extreme nonlinear electrodynamics in metamaterials with very small linear dielectric permittivity

We consider a sub-wavelength periodic layered medium whose slabs are filled by arbitrary linear metamaterials and standard nonlinear Kerr media and we show that the homogenized medium behaves as a Kerr medium whose parameters can assume values not available in standard materials. Exploiting such a parameter availability, we focus on the situation where the linear relative dielectric permittivity is very small thus allowing the observation of the extreme nonlinear regime where the nonlinear polarization is comparable with or even greater than the linear part of the overall dielectric response. The behavior of the electromagnetic field in the extreme nonlinear regime is very peculiar and characterized by novel features as, for example, the transverse power flow reversing. In order to probe the novel regime, we consider a class of fields (transverse magnetic nonlinear guided waves) admitting full analytical description and we show that these waves are allowed to propagate even in media with $\epsilon0$ since the nonlinear polarization produces a positive overall effective permittivity. The considered nonlinear waves exhibit, in addition to the mentioned features, a number of interesting properties like hyper-focusing induced by the phase difference between the field components.Comment: 12 pages, 7 figure

Bandwidth Optimisation and Frequency Tuning of Plasmonic Functionalised Metasurfaces for Optical Sensing of Chemical and Biological Substances

This paper reports on a method to optimise the sensitivity of plasmonics sensors based on functionalised metasurfaces of 2D-array of Al NanoAntennas (NA) deposited on a SiO2 substrate operating in the visible region of the electromagnetic spectrum. Moreover, we analysed the characteristics of a double layer metasurface configuration where two different NA 2D-arrays are separated by a dielectric spacer. The optical properties of both the metasurface configurations have been studied analysing how their maximum transmittance and Full-Width-at-Half-Maximum (FWHM) of the transmission curve are related to the variations of the NA geometrical parameters and dielectric spacer thickness. The tailoring of the FWHM is particular important for improving the plasmonic sensors sensitivity in probing the presence of chemical/biological substances absorbed on the NA surface when their absorption curve is superimposed with the metasurface transmission curve. In particular, better is this superposition better will be the plasmonic sensor sensitivity in probing variations of small concentrations of the adsorbed substances. The simulation results of the optical response of the designed plasmonic sensors suggest a methodology in choosing the NA parameters able to modify the bandwidth of the metasurface transmittance so fitting the absorption curve of chemical/biological substances absorbed on them. As a case-example, we simulated the response of a plasmonic sensor on which has been deposited a 3nm-thick layer of Rhodamine-6G (R6G) proving that is possible to increase the sensor detection sensitivity of about two orders of magnitude in the measurement of the R6G absorbance. Furthermore we proved the capability of the double layer plasmonic sensors to tune the transmission curve peak wavelength without changing the main optical characteristics

Multistability at arbitrary low optical intensities in a metallo-dielectric layered structure

We show that a nonlinear metallo-dielectric layered slab of subwavelength thickness and very small average dielectric permittivity displays optical multistable behavior at arbitrary low optical intensities. This is due to the fact that, in the presence of the small linear permittivity, one of the multiple electromagnetic slab states exists no matter how small is the transmitted optical intensity. We prove that multiple states at ultra-low optical intensities can be reached only by simultaneously operating on the incident optical intensity and incidence angle. By performing full wave simulations, we prove that the predicted phenomenology is feasible and very robust.Comment: 4 pages, 4 figure

Implementing Mindfulness in General Life and Organizations. Validation of the Time Flow Mindfulness Questionnaire for Effective Health Management

The primary purpose of the current research was to examine the psychometric properties of the Time Flow Mindfulness Questionnaire (TFMQ), a new self-report scale designed to measure cognitive, emotional, bodily, context-related, and action-related distracting inputs experienced by the mind during three different time windows of mindfulness practice (preliminary moments, during-the-practice, after-the-practice). The 42-item scale assesses the following second-order and first-order factors: Practice (preliminary, during), Benefits (short-term, long-term) and Benefits at work. Three studies were conducted. The first study assessed the factor structure and internal consistency on a sample of 141 mindfulness practitioners. Using a two-wave lagged design on a different sample of 46 trainees attending MBSR courses, the second study examined concurrent validity by performing correlations between the TFMQ and Five Facets Mindfulness Questionnaire (FFMQ). The third study (same sample as study 1) examined criterion validity by testing a structural equation model wherein mindfulness practice predicts job burnout, both directly and indirectly through mindfulness benefits at work. All studies relied on anonymous surveys. Our findings suggest that the TFMQ: a) has a factor structure consistent with the hypothesized conceptual dimensions; b) has good concurrent validity as demonstrated by significant correlations with the FFMQ dimensions; and c) consists of mindfulness dimensions that predict job burnout in organizations (i.e., criterion validity). The TFMQ is a valid and reliable mindfulness measure that may help a) practitioners gain awareness of different types of inputs that potentially distract the mind and mindfulness beneficial consequences, and b) organizations implement mindfulness in work-settings

Transverse power flow reversing of confined waves in extreme nonlinear metamaterials

We theoretically prove that electromagnetic beams propagating through a nonlinear cubic metamaterial can exhibit a power flow whose direction reverses its sign along the transverse profile. This effect is peculiar of the hitherto unexplored extreme nonlinear regime where the nonlinear response is comparable or even greater than the linear contribution, a condition achievable even at relatively small intensities. We propose a possible metamaterial structure able to support the extreme conditions where the polarization cubic nonlinear contribution does not act as a mere perturbation of the linear part