Evaluating the effects of polices on nursing care as promoted by the Veneto region: the research protocol and its implications for public health.

Study design: Multi-centre mixed-method study design organised into several phases. Background: The Veneto region has recently defined a set of policies on nursing care by determining the needed amount of daily care in minutes and by initiating a systematic measurement of nursing outcomes; also, with a more recent policy, missed nursing care (MNC) has been established as a process measure of interest. To measure the effect of these policies, a research protocol - aimed at evaluating several end points - has been designed, involving a large target population and hospital units. The aim of this manuscript is to briefly present the research protocol and to discuss the public health implications of its expected end-points. Methods: The endpoints of the protocol are: (a) to describe the frequency of MNC as perceived by nurses; (b) to identify contributing factors; (c) to identify practices adopted in low-occurrence MNC units and to assess the effectiveness of implementing them in units with higher levels of MNC; (d) to explore the relationship between the amount of nursing care provided, MNC, and patient outcomes; and (e) to validate a tool that measures MNC as perceived by patients/caregivers. A total of 3,460 nurses, 5,000 patient/day and 160 nursing coordinators of the medical and surgical units of public hospitals in the Veneto Region will be included. Conclusions: Measuring the association between the amount of nursing care and patient outcomes, as well as evaluating the role of MNC as perceived by nurses and patients in hindering or increasing the risk of some patient outcomes can provide a body of evidence capable of further informing policies in the field, both at the national and at the international level. Moreover, emerging good practices capable of preventing or minimising MNC, sharing and implementing them in other units where high levels of missed care are reported and evaluating their effectiveness, can also inform public health policies.

Perfect secrecy cryptography via mixing of chaotic waves in irreversible time-varying silicon chips.

Protecting confidential data is a major worldwide challenge. Classical cryptography is fast and scalable, but is broken by quantum algorithms. Quantum cryptography is unclonable, but requires quantum installations that are more expensive, slower, and less scalable than classical optical networks. Here we show a perfect secrecy cryptography in classical optical channels. The system exploits correlated chaotic wavepackets, which are mixed in inexpensive and CMOS compatible silicon chips. The chips can generate 0.1 Tbit of different keys for every mm of length of the input channel, and require the transmission of an amount of data that can be as small as 1/1000 of the message's length. We discuss the security of this protocol for an attacker with unlimited technological power, and who can access the system copying any of its part, including the chips. The second law of thermodynamics and the exponential sensitivity of chaos unconditionally protect this scheme against any possible attack.

Nonlinear optical memory effect.

Light propagating through random media produces characteristic speckle patterns, directly related to the large multitude of scattering events. These complex dynamics remarkably display robustness to perturbation of the incoming light parameters, maintaining correlation in the scattered wavefront. This behavior is known as the optical memory effect. Here we unveil the properties of the nonlinear optical memory effect, which occurs when an optothermal nonlinearity perturbs the random material. The effect is characterized through a series of pump and probe experiments in silica aerogel, in the visible range. This additional degree of freedom further generalizes the memory effect, opening the road to applications based on the nonlinear response of random media.

Persistence and Lifelong Fidelity of Phase Singularities in Optical Random Waves.

Phase singularities are locations where light is twisted like a corkscrew, with positive or negative topological charge depending on the twisting direction. Among the multitude of singularities arising in random wave fields, some can be found at the same location, but only when they exhibit opposite topological charge, which results in their mutual annihilation. New pairs can be created as well. With near-field experiments supported by theory and numerical simulations, we study the persistence and pairing statistics of phase singularities in random optical fields as a function of the excitation wavelength. We demonstrate how such entities can encrypt fundamental properties of the random fields in which they arise.

Spatial Distribution of Phase Singularities in Optical Random Vector Waves.

Phase singularities are dislocations widely studied in optical fields as well as in other areas of physics. With experiment and theory we show that the vectorial nature of light affects the spatial distribution of phase singularities in random light fields. While in scalar random waves phase singularities exhibit spatial distributions reminiscent of particles in isotropic liquids, in vector fields their distribution for the different vector components becomes anisotropic due to the direct relation between propagation and field direction. By incorporating this relation in the theory for scalar fields by Berry and Dennis [Proc. R. Soc. A 456, 2059 (2000)], we quantitatively describe our experiments.

Optically induced metal-to-dielectric transition in Epsilon-Near-Zero metamaterials.

Epsilon-Near-Zero materials exhibit a transition in the real part of the dielectric permittivity from positive to negative value as a function of wavelength. Here we study metal-dielectric layered metamaterials in the homogenised regime (each layer has strongly subwavelength thickness) with zero real part of the permittivity in the near-infrared region. By optically pumping the metamaterial we experimentally show that close to the Epsilon-Near-Zero (ENZ) wavelength the permittivity exhibits a marked transition from metallic (negative permittivity) to dielectric (positive permittivity) as a function of the optical power. Remarkably, this transition is linear as a function of pump power and occurs on time scales of the order of the 100 fs pump pulse that need not be tuned to a specific wavelength. The linearity of the permittivity increase allows us to express the response of the metamaterial in terms of a standard third order optical nonlinearity: this shows a clear inversion of the roles of the real and imaginary parts in crossing the ENZ wavelength, further supporting an optically induced change in the physical behaviour of the metamaterial.

Enhanced Nonlinear Refractive Index in ε-Near-Zero Materials.

New propagation regimes for light arise from the ability to tune the dielectric permittivity to extremely low values. Here, we demonstrate a universal approach based on the low linear permittivity values attained in the ε-near-zero (ENZ) regime for enhancing the nonlinear refractive index, which enables remarkable light-induced changes of the material properties. Experiments performed on Al-doped ZnO (AZO) thin films show a sixfold increase of the Kerr nonlinear refractive index (n_{2}) at the ENZ wavelength, located in the 1300 nm region. This in turn leads to ultrafast light-induced refractive index changes of the order of unity, thus representing a new paradigm for nonlinear optics.

Optical shock waves in silica aerogel.

Silica aerogels are materials well suited for high power nonlinear optical applications. In such regime, the non-trivial thermal properties may give rise to the generation of optical shock waves, which are also affected by the structural disorder due to the porous solid-state gel. Here we report on an experimental investigation in terms of beam waist and input power, and identify various regimes of the generation of wave-breaking phenomena in silica aerogels.

Bidirectional optical sorting of gold nanoparticles.

We present a generic technique allowing size-based all-optical sorting of gold nanoparticles. Optical forces acting on metallic nanoparticles are substantially enhanced when they are illuminated at a wavelength near the plasmon resonance, as determined by the particle's geometry. Exploiting these resonances, we realize sorting in a system of two counter-propagating evanescent waves, each at different wavelengths that selectively guide nanoparticles of different sizes in opposite directions. We validate this concept by demonstrating bidirectional sorting of gold nanoparticles of either 150 or 130 nm in diameter from those of 100 nm in diameter within a mixture.

Slotted photonic crystal cavities with integrated microfluidics for biosensing applications.

We demonstrate the detection of dissolved avidin concentrations as low as 15 nM or 1 µg/ml using functionalized slotted photonic crystal cavities with integrated microfluidics. With a cavity sensing surface area of approximately 2.2 µm(2), we are able to detect surface mass densities of order 60 pg/mm(2) corresponding to a bound mass of approximately 100 ag. The ultra-compact size of the sensors makes them attractive for lab-on-a-chip applications where high densities of independent sensing elements are desired within a small area. The high sensitivity over an extremely small area is due to the strong modal overlap with the analyte enabled by the slotted waveguide cavity geometry that we employ. This strong overlap results in larger shifts in the cavity peak wavelength when compared to competing approaches.

Terahertz pulse generation via optical rectification in photonic crystal microcavities.

Using a three-dimensional fully vectorial nonlinear time-domain analysis, we numerically investigate generation of terahertz radiation by pumping a photonic crystal microcavity out of resonance. High quality factors and a quadratic susceptibility lead to few-cycle terahertz pulses via optical rectification. Material dispersion as well as linear and nonlinear anisotropy is fully accounted for.

[Catch-up growth and final height in celiac disease].

BACKGROUND: Growth retardation resulting from celiac disease diagnosed in infancy or in early childhood is remediable after introduction of a gluten-free diet. The aim of this study was to evaluate long-term growth, catch-up growth and final height in a group of treated patients with celiac disease. METHODS: The study population consisted of 35 patients (13 M, 22 F) with typical celiac disease. Age at diagnosis was 1.17 (+/- 0.69) years. For each patient, the standard deviation score (SDS) and centile of height at diagnosis, target height and final height were elaborated, and linear regression and correlations between SDS of final height and age at diagnosis, SDS of height at diagnosis and SDS of target height, respectively, were calculated. RESULTS: At diagnosis patients had a general tendency to short stature: mean height was 81.8 cm +/- 22.9 cm (SDS -0.75 +/- 1.61), while target height was 164.3 cm +/- 13.5 cm (SDS -0.14 +/- 1.04) and final height 169.2 cm +/- 7.7 cm (SDS 0.41 +/- 1.04). Linear regression and correlations between SDS of final height and age at diagnosis, SDS of height at diagnosis and SDS of target height, respectively, proved nonsignificant. CONCLUSIONS: Irrespective of age and height at diagnosis, catch-up growth was complete in this group of patients, with satisfactory achievement of final height. Only one patient (age at diagnosis 13 years) failed to reach the target height.