Evidence for a Quantum Hall Insulator in an InGaAs/InP Heterostructure

We study the quantum critical behavior of the plateau-insulator (PI) transition in a low mobility InGaAs/InP heterostructure. By reversing the direction of the magnetic field (B) we find an averaged Hall resistance \rho_xy which remains quantized at the plateau value h/e^2 throughout the PI transition. We extract a critical exponent \kappa'= 0.57 +/- 0.02 for the PI transition which is slightly different from (and possibly more accurate than) the established value 0.42 +/- 0.04 as previously obtained from the plateau-plateau (PP) transitions.Comment: 3pages, 2 figures; submitted to EP2DS-14 conference proceeding

Mechanical and electrical characterization of wearable textile pressure and strain sensors based on PEDOT:PSS

Il termine tecnologia indossabile si riferisce a quei dispositivi elettronici incorporati negli indumenti od accessori che possono essere comodamente indossati. Essi sono ampiamente utilizzati in campo medico, sportivo, educativo o per monitorare disabilità. In questa tesi sono stati sviluppati sensori di pressione e di deformazione tessili, proponendo il modello teorico che ne descrive il comportamento. L'elemento attivo di tali sensori tessili è basato sul polimero intrinsecamente conduttivo (PEDOT:PSS). La soluzione conduttiva è stata depositata sui tessuti tramite il metodo drop-casting e la tecnica screen printing. La teoria sviluppata per il tessuto di cotone ha dimostrato che è possibile cambiare il range di pressione in cui i sensori rispondono cambiando la concentrazione di glicole etilenico presente nella soluzione di PEDOT:PSS pur mantenendo la geometria dei sensori inalterata. Per realizzare un'applicazione reale, il sensore di pressione tessile è stato fabbricato su un tessuto tecnico sportivo elastico. Comportamenti simili sono stati ottenuti dimostrando la validità del modello proposto. Successivamente, sono presentati i processi di fabbricazione e la caratterizzazione elettro-meccanica di sensori di deformazione tessili. Range tests e stability tests eseguiti su questi sensori di deformazione forniscono notizie circa le loro prestazioni:affidabilità e gauge factor. Il meccanismo di rilevamento è stato analizzato con un modello teorico basato sulle proprietà del tessuto e sulla deformazione della struttura wale-course tipica dei tessuti a maglia. I risultati ottenuti durante questo lavoro permettono lo sviluppo di una nuova generazione di sensori di pressione e di deformazione tessili che potranno essere comodamente indossati nella vita di tutti i giorni

Critical behavior of thermopower and conductivity at the metal-insulator transition in high-mobility Si-MOSFET's

This letter reports thermopower and conductivity measurements through the metal-insulator transition for 2-dimensional electron gases in high mobility Si-MOSFET's. At low temperatures both thermopower and conductivity show critical behavior as a function of electron density which is very similar to that expected for an Anderson transition. In particular, when approaching the critical density from the metallic side the diffusion thermopower appears to diverge and the conductivity vanishes. On the insulating side the thermopower shows an upturn with decreasing temperature.Comment: 4 pages with 3 figure

Postoperative MR Defecography following Failed STARR Procedure for Obstructive Defecation Syndrome: A Three-Centre Experience

Aim. To describe the abnormalities at MR imaging and related complaints in patients with poor outcome after STARR procedure. Materials and Methods. The medical records of 21 symptomatic patients from centre 1, 31 patients from centre 2, and 63 patients from centre 3 were reviewed with regard to findings at MR defecography and related symptoms. Results. Regardless of the centre, most relevant imaging features and related complaints were (a) impaired emptying (82.11%), related complaint ODS; (b) persistent rectocele >2 cm and intussusception (39.3%), split evacuation and digitation; (c) pelvic organ descent on straining (39.8%), prolapse sensation; (d) small neorectum and loss of contrast (32.5%), urgency and incontinence; (e) anastomotic stricture and granuloma (28.4%), pain; and (f) nonrelaxing puborectalis muscle (19.5%), tenesmus. Less frequent findings included rectal pocket formation (5.6%) and rectovaginal sinus tract (1.6%). Patients were referred to MR imaging with an average time interval of 5 ± 2, 4 ± 1, and 2 ± 1 years in the three centres, respectively, and only rarely by the same surgeon who performed the operation: 1/21 (4.8%) in centre 1, 3/39 (7.7%) in centre 2, and 9/63 (14.3%) in centre 3. Conclusion. Most surgeons involved in STARR operation with subsequent poor outcome do not rely on MR imaging

Analysis of polycyclic aromatic hydrocarbons in atmospheric particulate samples by microwaveassisted extraction and liquid chromatography

A methodology based on microwave-assisted extraction (MAE) and LC with fluorescence detection (FLD) was investigated for the efficient determination of 15 polycyclic aromatic hydrocarbons (PAHs) regarded as priority pollutants by the US Environmental Protection Agency and dibenzo(a,l)pyrene in atmospheric particulate samples. PAHs were successfully extracted from real outdoor particulate matter (PM) samples with recoveries ranging from 81.4±8.8 to 112.0±1.1%, for all the compounds except for naphthalene (62.3±18.0%) and anthracene (67.3±5.7%), under the optimum MAE conditions (30.0 mL of ACN for 20 min at 110ºC). No clean-up steps were necessary prior to LC analysis. LOQs ranging from 0.0054 ng/m3 for benzo( a)anthracene to 0.089 ng/m3 for naphthalene were reached. The validated MAE methodology was applied to the determination of PAHs from a set of real world PM samples collected in Oporto (north of Portugal). The sum of particulate-bound PAHs in outdoor PM ranged from 2.5 and 28 ng/m3.http://recipp.ipp.pt/handle/10400.22/289

Fully Textile X-Ray Detectors Based on Fabric-Embedded Perovskite Crystals

The interest and thrust for wearable ionizing radiation dosimeters are rapidly growing, stimulated by a large number of different applications impacting on humankind, spanning from medicine to civil security and space missions. Lead halide perovskites are considered one of the most promising classes of novel materials for X-ray detectors due to their superior electronic and detection performance coupled with compatibility with solution-based printing processes, allowing fabrication onto flexible substrates. It is reported on fully textile perovskite-based direct X-ray detectors, where the photoactive layer is constituted by a silk-satin fabric functionalized with methylammonium lead bromide perovskite crystals embedded in the textile. The reliability of the proposed fabrication process, based on simple and low-tech deposition techniques adaptable to industrial printing technologies for textiles, is assessed by realizing different detector's architectures that exhibit comparable detection performances. Sensitivity values up to (12.2 +/- 0.6) mu C Gy(-1) cm(-2) and a limit of detection down to 3 mu Gy s(-1) are achieved, and low bias operation (down to 1 V) is demonstrated, validating wearable applications. Further, fully textile pixelated matrix X-ray sensors are implemented and tested, providing the proof of principle for large-area scalability

Textile chemical sensors based on conductive polymers for the analysis of sweat

Wearable textile chemical sensors are promising devices due to the potential applications in medicine, sports activities and occupational safety and health. Reaching the maturity required for commercialization is a technology challenge that mainly involves material science because these sensors should be adapted to flexible and light-weight substrates to preserve the comfort of the wearer. Conductive polymers (CPs) are a fascinating solution to meet this demand, as they exhibit the mechanical properties of polymers, with an electrical conductivity typical of semiconductors. Moreover, their biocompatibility makes them promising candidates for effectively interfacing the human body. In particular, sweat analysis is very attractive to wearable technologies as perspiration is a naturally occurring process and sweat can be sampled non-invasively and continuously over time. This review discusses the role of CPs in the development of textile electrochemical sensors specifically designed for real-time sweat monitoring and the main challenges related to this topic

Design of an electrochemically gated organic semiconductor for pH sensing

Since the development of potentiometric ion-selective electrodes, remarkable steps have been taken towards progressive simplification and improved robustness of pH sensing probes. In particular, the design of compact sensing architectures using solid-state components holds great potential for portable and wearable applications. Here we report the development of an electrochemically gated device for pH detection, combining the robustness of potentiometric-like transduction with an extremely simple and integrated geometry requiring no reference. The sensor is a two-point probe device comprising two thin polymeric films, i.e. a charge transport layer and a pH-sensitive layer, and exhibits a sensitivity of (8.3 ± 0.2) × 10−3 pH unit−1 in the pH range from 2 to 7. Thanks to the versatility and robustness of the optimised design, a textile pH sensor was fabricated whose performance is comparable with that of glass sensors

A wearable electrochemical gas sensor for ammonia detection

The next future strategies for improved occupational safety and health management could largely benefit from wearable and Internet of Things technologies, enabling the real-time monitoring of health-related and environmental information to the wearer, to emergency responders, and to inspectors. The aim of this study is the development of a wearable gas sensor for the detection of NH3 at room temperature based on the organic semiconductor poly(3,4-ethylenedioxythiophene) (PEDOT), electrochemically deposited iridium oxide particles, and a hydrogel film. The hydrogel composition was finely optimised to obtain self-healing properties, as well as the desired porosity, adhesion to the substrate, and stability in humidity variations. Its chemical structure and morphology were characterised by infrared spectroscopy and scanning electron microscopy, respectively, and were found to play a key role in the transduction process and in the achievement of a reversible and selective response. The sensing properties rely on a potentiometric-like mechanism that significantly differs from most of the state-of-the-art NH3 gas sensors and provides superior robustness to the final device. Thanks to the reliability of the analytical response, the simple two-terminal configuration and the low power consumption, the PEDOT:PSS/IrOx Ps/hydrogel sensor was realised on a flexible plastic foil and successfully tested in a wearable configuration with wireless connectivity to a smartphone. The wearable sensor showed stability to mechanical deformations and good analytical performances, with a sensitivity of 60 ± 8 µA decade−1 in a wide concentration range (17–7899 ppm), which includes the safety limits set by law for NH3 exposure