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Patients with acute stroke often require venous access to facilitate diagnostic investigations or intravenous therapy. The primary aim of this study was to describe the rate and type of complications associated with the placement of a short peripheral catheter (SPC) in patients with acute ischemic or hemorrhagic stroke. A prospective, observational, single-cohort study was conducted at Niguarda Hospital, Italy, with enrolment in the Emergency Department. Adult patients with an ischemic or hemorrhagic stroke requiring an SPC were enrolled. Complications, such as infiltration, occlusion, phlebitis and dislodgment, were recorded daily. Descriptive statistics were used, and the incidence rate ratio (IRR) was estimated to assess the difference in complications, considering catheter calibre, dominant side, exit site, limb, and limb mobility, ictus type (ischemic/haemorrhagic), impairment deficit (language, motor, visual) and EA-DIVA score. A total of 269 participants and 755 SPC were analysed. Removal of SPC due to at least one local complication occurred in 451 (60%). Dislodgment was the major cause of SPC removal (31%), followed by infiltration (18%), occlusion (6%), and phlebitis (5%). The SPC calibre (22G), exit-site other than antecubital and forearm, visual deficit and EA-DIVA ≥ 8 were associated with a higher rate of SPC complications: IRR, 1.71 [1.31; 2.31]; 1.27 [1.01; 1.60], 1.38 [1.06; 1.80], 1.30 [1.04; 1.64], respectively. No other differences in complication rates were observed according to the insertion site, i.e. dominant side, left side, plegic/hyposthenic limb, or exit site. This study provides novel insights into the frequency and types of complications associated with SPC in patients with acute stroke. Compared to the literature, a higher dislodgment rate was observed, being the first cause of SPC removal, whereas no differences in the number of infiltrations, occlusions, and phlebitis were recorded.

Background: Continuous positive airway pressure (CPAP) is frequently used to treat patients with acute respiratory failure in out-of-hospital settings. Compared to a facemask, the helmet has many advantages for the patient but requires a minimum gas flow of 60 L/min to avoid CO2 rebreathing. The aim of the present bench study was to evaluate the performance of four Venturi devices, connected to a single oxygen cylinder, in delivering helmet-CPAP with clinically relevant gas flow, fraction of inspired oxygen (FiO2), and positive end-expiratory pressure (PEEP) values. Methods: Three double-inlet Venturi systems (EasyVent, Ventuplus, Compact-HAR) were connected to full 5-L oxygen cylinders using a double flowmeter, and their oxygen requirements to reach different setups (flow 60-80 L/min; FiO2 0.4-0.5-0.6, PEEP 7.5-10-12.5 cmH2O) were tested. The fourth Venturi system (O2-MAX) was directly attached to the tank, and the flow and FiO2 delivered at preset FiO2 0.3 and 0.6 were recorded. The runtime of the cylinder was assessed. Results: EasyVent, Ventuplus, and O2-MAX were able to deliver helmet-CPAP with clinically useful setups when connected to a single oxygen cylinder, while Compact-HAR did not. The runtime of the cylinders ranged between 28 and 60 minutes according to the preset flow and FiO2. The delivered gas flow decreased slowly and linearly with the drop in cylinder pressure until its exhaustion. Conclusions: Helmet-CPAP might be provided using portable Venturi systems connected to an oxygen cylinder, but not all of them are able to deliver it. The use of a double flowmeter allows delivery of both high flow and high FiO2 when double-inlet Venturi systems are used. Due to the flow drop observed during the cylinder consumption, a flow >60 L/min should be set when helmet-CPAP is started. Considering the flow drop phenomenon, the estimated duration of the tank runtime can be used with a margin of safety when planning patient transport.

We investigate samples of compositionally disordered potassium-based perovskite single crystals with different composition and stoichiometry. The dielectric and Raman response is inspected over the nominal cubic-to-tetragonal long-range phase transition. The comparison between results shows that the occurrence of the phase transition is controlled by the temperature evolution of polar nanoregions (PNRs). We are able to correlate PNR order, formation, percolation, and freezing to the characteristic temperatures of each macroscopic crystal. The onset of the phase transition is found to occur when PNRs undergo a percolative ordering process, in correlation to the sudden arising of a specific high-frequency Raman mode.

© 2002 The American Physical Society. We thank L. C. Andreani and B. Méndez for the careful reading of the manuscript and G. Guizzetti for enlightening discussions. V.B. was partially supported by MURST (Project ‘Giovani Ricercato’). Work at Madrid was supported by DGI-MCyT (Project No. MAT2000-0734) and CAM (Project No. 07N/0075/20019., We studied the optical properties of ordered and intentionally disordered GaAs-AlxGa1-xAs superlattices, with and without dimer-type correlations in the disorder, by means of spectroscopic ellipsometry. The electronic structure of the superlattices has been calculated and compared with the experiments. The optical transitions in ordered, correlated, and uncorrelated disordered superlattices show specific features that we relate to their different electronic structures., MURST, DGI-MCyT, CAM, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2001 The American Physical Society. We are grateful to J. C. Flores, K. Fujiwara, G. Guizzetti, M. Hilke, C. Kanyinda-Malu, A. Stella, and D. Tsui for their enlightening discussions. Work in Italy has been supported by the INFM Network ‘‘Fisica e Tecnologia dei Semiconduttori III-V’’ and in Madrid by DGES under Project MAT2000-0734., We report a systematic study of several GaAs-AlxGa1-xAs semiconductor superlattices grown by molecular-beam epitaxy specifically designed to explore the existence of extended states in random dimer superlattices. We have confirmed our previous results [V. Bellani et al., Phys. Rev. Lett. 82, 2159 (1999)] with much additional evidence that allows us to lay claim to a clear-cut experimental verification of the presence of extended states in random dimer superlattices due to the short-range correlations (dimers) that inhibit the localization effects of the disorder., DGES, INFM Network ‘‘Fisica e Tecnologia dei Semiconduttori III-V’’, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

Nonlinear response in a material increases with its index of refraction as n4. Commonly, n ~ 1 so that diffraction, dispersion, and chromatic walk-off limit nonlinear scattering. Ferroelectric crystals with a periodic 3D polarization structure overcome some of these constraints through versatile Cherenkov and quasi-phase-matching mechanisms. Threedimensional self-structuring can also lead to a giant optical refraction. Here, we perform second-harmonic-generation experiments in KTN:Li in conditions of giant broadband refraction. Enhanced response causes wavelength conversion to occur in the form of bulk Cherenkov radiation without diffraction and chromatic walk-off, even in the presence of strong wave-vector mismatch and highly focused beams. The process occurs with a wide spectral acceptance of more than 100 nm in the near infrared spectrum, an ultra-wide angular acceptance of up to ±40∘, with no polarization selectivity, and can be tuned to allow bulk supercontinuum generation. Results pave the way to highly efficient and adaptable nonlinear optical devices with the promise of single-photon-to-single-photon nonlinear optics.

We perform redundant X-ray diraction versus temperature experiments in bulk transparent KTN. We nd a violation of the standard perovskite cubic-to-tetragonal symmetry-breaking at the Curie point in the form of an orthorhombic cell distortion. The lattice distortion spans coherently macroscopic volumes of the sample and is characterized by a negative-to-zero thermal volumeexpansion. Dielectric measurements and calorimetry indicate that the anomalous behavior is not associated to a distinct thermodynamic phase. The comparison of linear and nonlinear optical scattering experiments with structural data suggests that the lattice distortion is a consequence of strain relaxation to a 3D superlattice of polarization vortices.

Double-loop electric-field vs polarization hysteresis is investigated in a depoled compositionally disordered lithium-enriched potassium tantalate niobate crystal. Comparing electro-optic response and dielectric spectroscopy indicates that the anomalous response occurs for those temperatures in which the sample also manifests a temperature hysteresis in the low-frequency dielectric function. An electric-field hysteresis at concurrent temperatures suggests an underlying role of reorienting mesoscopic polar regions that accompany the nonergodic phase.

Using temperature-resolved dielectric spectroscopy in the range 25-320 K we investigate the macroscopic response, phase symmetry, and order/disorder states in bulk ferroelectric K1-yLiyTa1-xNbx (KLTN). Four long-range symmetry phases are identified with their relative transitions. Directional analysis of the order/disorder states using Fröhlich entropy indicates global symmetry breaking along the growth axis and an anisotropic dipolar effective thermodynamic behavior, which ranges from disordered to ordered at the same temperature for different directions in the sample. Results indicate that the macroscopic polarization, driven by nanosized polar regions, follows a microscopic perovskite eight-sites lattice model.

We study the formation of 2D self-trapped beams in nanodisordered potassium-sodium-tantalate-niobate (KNTN) cooled below the dynamic glass transition. Supercooling is shown to accelerate the photorefractive response and enhance steady-state anisotropy. Effects in the excited state are attributed to the anomalous slim-loop polarization curve typical of relaxors dominated by non-interacting polar-nano-regions. © 2014 Optical Society of America.

We study two-dimensional soliton beams in disordered ferroelectrics. Super- cooling accelerates photorefractive response and changes steady-state anisotropy. Effects are attributed to the anomalous polarization response of polar-nano-regions.

We report an electro-optic response that is linear but independent of the sign of the electric field. Temperature dependence allows us to attribute the phenomenon to a reduced thermal agitation in the response of polar-nanoregions. © 2014 OSA.

We demonstrate an optically employable negative permittivity regime in a photorefractive dipolar glass. Signature anti-diffraction is detected when the transparent glass is cast far from equilibrium through a rapid small-amplitude temperature swing. © 2012 OSA.

Using temperature-resolved dielectric spectroscopy in the range of 75-320 K we have inspected the solid-like and liquid-like arrangements of nanometric dipoles (polar nanoregions) embedded in sodium-enriched potassium-tantalate-niobate (KNTN), a chemically-substituted complex perovskite crystal hosting inherent substitutional disorder. The study of order versus direction is carried out using Fröhlich entropy measurements and indicates the presence of four long-range symmetry phases, two of which are found to display profoundly anisotropic features. Exotic phases are found for which the dipoles at one fixed temperature manifest a liquid reorientational response along one crystal axis and a solid-like behavior along another axis. The macroscopic anisotropy observed in the sequence of different phases is found to match a microscopic order-disorder sequence typical of nominally pure perovskites. Moreover, experimental demonstration of the onset of a frozen state above transitions is provided.

Propagating light beams with widths down to and below the optical wavelength require bulky large-aperture lenses and remain focused only for micrometric distances. Here, we report the observation of light beams that violate this localization/depth-of-focus law by shrinking as they propagate, allowing resolution to be maintained and increased over macroscopic propagation lengths. In nanodisordered ferroelectrics we observe a non-paraxial propagation of a sub-micrometre-sized beam for over 1,000 diffraction lengths, the narrowest visible beam reported to date. This unprecedented effect is caused by the nonlinear response of a dipolar glass, which transforms the leading optical wave equation into a Klein-Gordon-type equation that describes a massive particle field. Our findings open the way to high-resolution optics over large depths of focus, and a route to merging bulk optics into nanodevices.

The origin and magnitude of a paramagnetic contribution to the CuO susceptibility at T<150 K are studied by analysing electron paramagnetic resonance and static magnetic susceptibility measurements carried out on a set of CuO single crystals. This has allowed the authors to confirm a previous supposition about the behaviour of the susceptibility for T<150 K. The asymptotic finite value of the susceptibility in the antiferromagnetic phase is also discussed by means of a crystal-field calculation which seems to rule out contributions to the local magnetic moments from incompletely quenched orbital angular moments of the Cu2+ ions. Preliminary magnetization measurements suggest the presence of weak ferromagnetism, which may explain the unusual behaviour of the CuO susceptibility.

We demonstrate an electro-optic response that is linear in the amplitude but independent of the sign of the applied electric field. The symmetry-preserving linear electro-optic effect emerges at low applied electric fields in freezing nanodisordered KNTN above the dielectric peak temperature, deep into the nominal paraelectric phase. Strong temperature dependence allows us to attribute the phenomenon to an anomalously reduced thermal agitation in the reorientational response of the underlying polar-nanoregions.

An investigation of the permittivity and ac conductivity was performed for the first time on the isostructural tetrasubstituted alkylammonium (CH 3)4NBF4 and (CH3) 4NClO4 single crystals, in the wide temperature range 12-300 K. For both the explored compounds, an orientational order/disorder phase transition was brought out as a result of the overlapping of two distinct transitions occurring with different dynamics. The first one is the settlement of a stable array, at low temperature, of the anionic groups (orientationally disordered at RT) with a first order character; the second one is the correspondent cationic sublattice rearrangement with the characteristics of second order. The critical temperatures and limits of the transitions were defined. Different conductivity processes above and below the transition were detected and analyzed. At lower temperatures the intra- and inter-molecular motions of the cationic group were brought out through their contribution to the dielectric constant. The temperature values of the freezing out of the vibrational motions were experimentally established for both the observed ionic crystals. Furthermore, the IR spectroscopy has provided spectra of the vibrational modes in the different phases below and above the phase transition, in excellent agreement with the dielectric data. In a general perspective, the obtained results clearly suggest that the thermal evolution displayed by the two investigated compounds is characteristic of the isostructural tetramethylammonium salts; the expected variations for different anionic groups are discussed. © 2014 Elsevier B.V. All rights reserved

Dielectric spectroscopy is applied to the study of phase transitions in the range from room temperature down to 12 K in single crystals of tetracene (TEN), a well known material which, as most organic semiconductors, shows polymorphism. The present analysis, through proper experimental procedures, permits to identify the wide range (T > 150 K) of instabilities and of strong hysteresis effects as clear evidence of a non-ergodic state, then also clarifying some open questions, first of all the role of the sample thermal history, including the temperature variation rate and some apparent sample-dependence of the results. Furthermore evidence is obtained of two transitions at 144 K and 45 K