Anomalous electrical conduction and negative temperature coefficient of resistance in nanostructured gold resistive switching films.

We report the observation of non-metallic electrical conduction, resistive switching, and a negative temperature coefficient of resistance in nanostructured gold films above the electrical percolation and in strong-coupling regime, from room down to cryogenic temperatures (24 K). Nanostructured continuous gold films are assembled by supersonic cluster beam deposition of Au aggregates formed in the gas phase. The structure of the cluster-assembled films is characterized by an extremely high density of randomly oriented crystalline nanodomains, separated by grain boundaries and with a large number of lattice defects. Our data indicates that space charge limited conduction and Coulomb blockade are at the origin of the anomalous electrical behavior. The high density of extended defects and grain boundaries causes the localization of conduction electrons over the entire investigated temperature range.

Development and installation of a radio frequency quadrupole cooler test.

A Radio Frequency Quadrupole Cooler (RFQC) prototype was adapted for insertion into a high uniformity magnetic field, with Bz up to 0.2 T, to improve radial confinement. While the RFQC purpose is to reduce (by gas collisions) the energy spread and emittance of a beam of radioactive nuclei, to finely select ion mass in nuclear physics, the prototype is tested in a setup including a stable ion source, a pepper pot emittance meter, and two Faraday cups; this makes a precise characterization of the RFQC feasible. The ion extraction was studied in detail by simulations, both to match it to the emittance meter granularity and to verify the effect of the typical nonuniformity of the longitudinal electric field Ez inside the RFQC; an average motion description (including friction force from gas collisions) was used, introducing the ballistic and diffusive regimes. With a preliminary optimization of the electrode shape, buffer gas pressure pg, and radio frequency voltage, the ion beam can be extracted with a significant cooling margin.

Demonstration of a 120° hybrid based simplified coherent receiver on SOI for high speed PON applications.

We demonstrate the first simplified coherent receiver using a 120° hybrid on silicon-on-insulator (SOI) for high speed PON applications. This coherent receiver integrates an inverse taper edge coupler for the received signal, a vertical grating coupler for the local oscillator input, a polarization splitter and rotator (PSR), a 120° hybrid based on a 3×3 multimode interference (MMI) coupler, and three germanium photodetectors. We achieved 25 Gbit/s two-level pulse amplitude modulation (PAM-2) transmission over 30 km standard single mode fiber (SMF) in the C-band without any digital signal processing (DSP) (e.g., pre-emphasis, pulse shaping, equalization, nonlinearity compensation) and dispersion compensation (e.g., optical or digital) either at the transmitter or at the receiver. The requirements for frequency and phase locking of the local oscillator (LO) were avoided due to the use of intensity modulated signals. Receiver sensitivities of -23.70 dBm, -20.30 dBm, and -15.10 dBm are achieved at a bit error rate (BER) below the hard-decision forward error correction (HD-FEC) threshold (i.e., 3.8 × 10-3) in back-to-back (B2B), after 21 km and 30 km, respectively. We also demonstrate 25 Gbit/s PAM-4 transmission achieving receiver sensitivities of -15.30 dBm, -13.90 dBm, and -9.50 dBm below the HD-FEC threshold in B2B, after 10.5 km and 21 km, respectively.

Integration of RFQ beam coolers and solenoidal magnetic fields.

Electromagnetic traps are a flexible and powerful method of controlling particle beams, possibly of exotic nuclei, with cooling (of energy spread and transverse oscillations) provided by collisions with light gases as in the Radio Frequency Quadrupole Cooler (RFQC). A RFQC prototype can be placed inside the existing Eltrap solenoid, capable of providing a magnetic flux density component B(z) up to 0.2 T, where z is the solenoid axis. Confinement in the transverse plane is provided both by B(z) and the rf voltage V(rf) (up to 1 kV at few MHz). Transport is provided by a static electric field E(z) (order of 100 V/m), while gas collisions (say He at 1 Pa, to be maintained by differential pumping) provide cooling or heating depending on V(rf). The beamline design and the major parameters V(rf), B(z) (which affect the beam transmission optimization) are here reported, with a brief description of the experimental setup.

Current noise as a probe for Wigner molecules.

The effects of a Wigner molecule on the current noise and conductance of a one-dimensional quantum dot with two electrons are investigated. Focusing on a lateral transport setup, the sequential regime is considered. Tunnelling rates through the dot are evaluated within an exact diagonalisation scheme. They strongly depend on electron interactions, showing a markedly different behaviour in the presence of a Wigner molecule with respect to the weak interactions case, and thus modify the transport and current noise and the dot. For weak interactions negative differential conductance and super-Poissonian noise are found. As interactions increase, a Wigner molecule develops: it suppresses the negative differential conductance and turns the shot noise to sub-Poissonian values. In particular, the noise is found to be a sensitive probe of the Wigner molecule.

Sub-Nyquist field trial using time frequency packed DP-QPSK super-channel within fixed ITU-T grid.

Sub-Nyquist time frequency packing technique was demonstrated for the first time in a super-channel field trial transmission over long-haul distances. The technique allows a limited spectral occupancy even with low order modulation formats. The transmission was successfully performed on a deployed Australian link between Sydney and Melbourne which included 995 km of uncompensated SMF with coexistent traffic. 40 and 100 Gb/s co-propagating channels were transmitted together with the super-channel in a 50 GHz ITU-T grid without additional penalty. The super-channel consisted of eight sub-channels with low-level modulation format, i.e. DP-QPSK, guaranteeing better OSNR robustness and reduced complexity with respect to higher order formats. At the receiver side, coherent detection was used together with iterative maximum-a-posteriori (MAP) detection and decoding. A 975 Gb/s DP-QPSK super-channel was successfully transmitted between Sydney and Melbourne within four 50GHz WSS channels (200 GHz). A maximum potential SE of 5.58 bit/s/Hz was achieved with an OSNR = 15.8 dB, comparable to the OSNR of the installed 100 Gb/s channels. The system reliability was proven through long term measurements. In addition, by closing the link in a loop back configuration, a potential SE∙d product of 9254 bit/s/Hz·km was achieved.

Thermally enhanced Wigner oscillations in two-electron 1D quantum dots.

Motivated by a recent experiment (Pecker et al 2013 Nat. Phys. 9 576), we study the stability, with respect to thermal effects, of Friedel and Wigner density fluctuations for two electrons trapped in a one-dimensional quantum dot. Diagonalizing the system exactly, the finite-temperature average electron density is computed. While the weak and strong interaction regimes display a Friedel oscillation or a Wigner molecule state at zero temperature, which as expected smear and melt as the temperature increases, a peculiar thermal enhancement of Wigner correlations in the intermediate interaction regime is found. We demonstrate that this effect is due to the presence of two different characteristic temperature scales: T(F), dictating the smearing of Friedel oscillations, and T(W), smoothing Wigner oscillations. In the early Wigner molecule regime, for intermediate interactions, T(F) < T(W) leading to the enhancement of the visibility of Wigner oscillations. These results complement those obtained within the Luttinger liquid picture, valid for larger numbers of particles.

Plasma-beam traps and radiofrequency quadrupole beam coolers.

Two linear trap devices for particle beam manipulation (including emittance reduction, cooling, control of instabilities, dust dynamics, and non-neutral plasmas) are here presented, namely, a radiofrequency quadrupole (RFQ) beam cooler and a compact Penning trap with a dust injector. Both beam dynamics studies by means of dedicated codes including the interaction of the ions with a buffer gas (up to 3 Pa pressure), and the electromagnetic design of the RFQ beam cooler are reported. The compact multipurpose Penning trap is aimed to the study of multispecies charged particle samples, primarily electron beams interacting with a background gas and/or a micrometric dust contaminant. Using a 0.9 T solenoid and an electrode stack where both static and RF electric fields can be applied, both beam transport and confinement operations will be available. The design of the apparatus is presented.

A year in review in Minerva Anestesiologica 2013.

BACKGROUND: We organized a training program for oral fiber optic intubation (FOI) under conscious sedation. The efficacy of the program was evaluated by comparing the performances of experts and novices. METHODS: The training procedure was divided into two sessions: a theoretical session on difficult airways, the fiber optic bronchoscope (FOB), remifentanil, topical anesthesia and patient interactions; and a session involving simulations of the FOI technique on dummies. For in vivo FOI, we enrolled patients requiring orotracheal intubation for elective surgery. Electrocardiograms, mean arterial pressure was railroaded over the fiberscope, and tracheal intubati6 and 7) FOIs, respectively, joined the study. To reach ±23 bpm, P=0.02), and RR was decreased (from 16±3 to 12±4 bpm, P<0.05). No differences were recorded between the experts and less-experienced anesthesiologists. The average duration of FOI was 3.3±2.0 min for experts and 4.2±2.4 min for novices (P=0.03). Procedures were successful in both groups, with patients in each group being equally satisfied with the procedures. CONCLUSION: This study highlights the importance of a structured FOI training program, demonstrating that it is possible to learn to perform FOI proficiently by practicing on dummies.

Blood from the right atrium may provide closer estimates of mixed venous saturation than blood from the superior vena cava. A pilot study.

BACKGROUND: As a rule, central venous catheters (CVC) should not be positioned in the right atrium (RA) to avoid the risk of perforation and cardiac tamponade. However, in ICUs where ECG monitoring can detect any initial damage of the atrial wall, CVCs may probably be safely positioned in the RA. We investigated whether mixed venous saturation (SvO2) was better estimated by measuring central venous saturation (ScvO2) in the RA or in the superior vena cava (SVC) in patients undergoing cardiac surgery. METHODS: A CVC and a pulmonary artery catheter (PAC) were positioned before surgical coronary revascularization in sixty patients. Under transesophageal echocardiographic guidance, CVC tips were randomly positioned inside the RA (group A) or the SVC (group C). In each patient, eight pairs of blood samples were collected from CVC and PAC distal ports and saturation measured. Cardiac arrhythmias that occurred in the first 48 postoperative hours and CVC tip position on chest X-rays were also registered. RESULTS: ScvO2 and SvO2 correlated better in group A (r=0.95) than in group C (r=0.84). The 95% interval of confidence of the gap between ScvO2 and SvO2 was narrower in group A (-6.9/+ 3.2 vs. -11.6/+5.5; p<.01). The incidence of arrhythmias was equal in the two groups (16.7%). On chest X-rays, CVC tips were 5.4 (SD=3.6) cm below the tracheal carina in group A and 5.3 (SD=3.9) cm in group C. CONCLUSION: In monitored patients, positioning CVC tips in the RA rather than in the SVC may allow closer estimates of SvO2 and may be safe. Yet, safety should be confirmed by further studies with larger samples of patients.

Probing Wigner correlations in a suspended carbon nanotube.

The influence of electron­vibron coupling on the transport properties of a strongly interacting quantum dot built in a suspended carbon nanotube (CNT) is analyzed. The latter is probed by a charged atomic force microscope tip scanned along the axis of the CNT which induces oscillations of the chemical potential and of the linear conductance. These oscillations are due to the competition between finite-size effects and the formation of a Wigner molecule for strong interactions. Such oscillations are shown to be suppressed by the electron­vibron coupling. The suppression is more pronounced in the regime of weak Coulomb interactions, which ensures that probing Wigner correlations in such a system is in principle possible.

Quantification of IgM and IgA anti-pneumococcal capsular polysaccharides by a new ELISA assay: a valuable diagnostic and prognostic tool for common variable immunodeficiency.

PURPOSE: Existing ways of assessing CVID patients at risk of pulmonary infections are not universally accepted. The need to identify additional prognostic factors allowed us to evaluate the anti-polysaccharide IgA and IgM responses in 125 CVID patients immunized with the 23-valent pneumococcal polysaccharide (PS) vaccine (Pneumovax(®)). METHODS: We used a new anti-PS23 IgM and IgA ELISA assay, which evaluates a global response to all 23 polysaccharides contained in Pneumovax(®). RESULTS: Anti-PS23 IgM and/or IgA antibodies were detectable in a minority of CVID patients. Antibody responses were correlated to B cell subpopulations and serum immunoglobulin concentrations. The non responders had a higher incidence of pneumonia and bronchiectasis and responders had the lowest incidence of respiratory complications. CONCLUSIONS: This new ELISA assay allows for studying vaccine response in patients on Ig replacement therapy. This test also is an additional method of evaluation of specific antibody responses representing a valuable contribution to identify prognostic marker in CVID patients.

1-42 ß-amyloid peptide requires PDK1/nPKC/Rac 1 pathway to induce neuronal death.

1-42 ß-Amyloid (Aß(1-42)) peptide is a key molecule involved in the development of Alzheimer's disease. Some of its effects are manifested at the neuronal morphological level. These morphological changes involve loss of neurites due to cytoskeleton alterations. However, the mechanism of Aß(1-42) peptide activation of the neurodegenerative program is still poorly understood. Here, Aß(1-42) peptide-induced transduction of cellular death signals through the phosphatidylinositol 3-kinase (PI3K)/phosphoinositol-dependent kinase (PDK)/novel protein kinase C (nPKC)/Rac 1 axis is described. Furthermore, pharmacological inhibition of PDK1 and nPKC activities blocks Rac 1 activation and neuronal cell death. Our results provide insights into an unsuspected connection between PDK1, nPKCs and Rac 1 in the same signal-transduction pathway and points out nPKCs and Rac 1 as potential therapeutic targets to block the toxic effects of Aß(1-42) peptide in neurons.

The best timing for defibrillation in shockable cardiac arrest.

High quality cardiopulmonary resuscitation (CPR, i.e. chest compressions and ventilations) and prompt defibrillation when appropriate (i.e. in ventricular fibrillation and pulseless ventricular tachycardia, VF/VT) are currently the best early treatment for cardiac arrest (CA). In cases of prolonged CA due to shockable rhythms, it is reasonable to presume that a period of CPR before defibrillation could partially revert the metabolic and hemodynamic deteriorations imposed to the heart by the no flow state, thus increasing the chances of successful defibrillation. Despite supporting early evidences in CA cases in which Emergency Medical System response time was longer than 5 minutes, recent studies have failed to confirm a survival benefit of routine CPR before defibrillation. These data have imposed a change in guidelines from 2005 to 2010. To take in account all the variables encountered when treating CA (heart condition before CA, time elapsed, metabolic and hemodynamic changes, efficacy of CPR, responsiveness to defibrillation attempt), it would be very helpful to have a real-time and non invasive tool able to predict the chances of defibrillation success. Recent evidences have suggested that ECG waveform analysis of VF, such as the derived Amplitude Spectrum Area, can fit the purpose of monitoring the CPR effectiveness and predicting the responsiveness to defibrillation. While awaiting clinical studies confirming this promising approach, CPR performed according to high quality standard and with minimal interruptions together with early defibrillation are the best immediate way to achieve resuscitation in CA due to shochable rhythms..

Non-linear Coulomb blockade microscopy of a correlated one-dimensional quantum dot.

We evaluate the chemical potential of a one-dimensional quantum dot coupled to an atomic force microscope tip. The dot is described within the Luttinger liquid framework, and the conductance peak positions as a function of the tip location are calculated in the linear and non-linear transport regimes for an arbitrary number of particles. The differences between the chemical potential oscillations induced by the Friedel and Wigner terms are carefully analysed in the whole range of interaction strengths. It is shown that Friedel oscillations, unlike the Wigner ones, are sensitive probes for detecting excited spin states and collective spin density waves involved in the transport.