Low-cost and large-size nanoplasmonic sensor based on Fano resonances with fast response and high sensitivity.

We have developed a low-cost, fast and sensitive plasmonic sensor with a large-size for easy handling. The sensor is formed by a Au nanobelt grating fabricated by soft lithography with a period of 780 nm and a width of 355 nm in an even and uniform area of ~2 × 2 cm2. The sensor uses the Fano-shaped third order mode localized plasmon resonance of the Au nanobelts, which appears in the visible part of the transmission spectrum. We have found a detection resolution of 1.56 × 10-5 refractive index units with a temporal resolution of 1 s in a sensing area of 0.75 × 0.75 mm2. The high uniformity and size of the sensor permit the detection using a simple optical system, which provides the device with the potential to be used as an easy to handle, portable and disposable sensor.

Effectiveness of a three-dimensional anorectal ultrasound in perianal Crohn's disease: incompatibility with clinical and surgical examinations.

PURPOSE: We have correlated the 3D anorectal ultrasound (3D ARU) findings with clinical examination and the surgical findings and examined its capacity to provide ancillary information, which potentially alters patient management. PATIENTS AND METHODS: This is a prospective analysis conducted at a tertiary academic hospital. A total of 95 patients were included. We screened for sphincter defects and the presence of perianal Crohn's disease (PACD)-related lesions. RESULTS: We performed 150 3D ARUs. Exploratory ultrasound coincided with the rationale for diagnosis in 67.7% of cases, and fistulae were detected in 79% of cases where there was clinical suspicion. Fistulae were associated with abscesses in 29 cases, and isolated abscesses were identified in 19 cases (17.7%), only 12 of which (63.2%) were clinically suspected. Sphincter defects were observed in 15 cases with 7 cases (77.8%) presenting with clinical fecal incontinence. The operative findings coincided with ultrasonographic findings in 81.3% of the analyzed cases. The inter-observer variability of endosonographic classification resulted in a kappa score of 0.86. Ultrasonographic data altered the therapeutic plan of management in 73 cases (48.6%). CONCLUSIONS: Three-dimensional ARU is accurate in the diagnosis of fistula type in PACD and in the delineation of ancillary suspected and unsuspected abscess collections. Its use impacts therapeutic management in about half the cases examined. A new ultrasonographic-based PACD classification system is presented which has high inter-observer agreement but which requires future prospective validation in clinical PACD patients.

Percutaneous neuromodulation of the posterior tibial nerve for the treatment of faecal incontinence - mid-term results: is retreatment required?

AIM: Posterior tibial nerve stimulation (PTNS) has emerged in recent years as a therapy for faecal incontinence. Its long-term effectiveness is yet to be established, along with what the form of retreatment should be in the event of loss of effectiveness. The present study aimed to establish the mid-term results to identify the proportion of patients who may need further treatment, and if so when. METHOD: A prospective study including 30 patients was conducted at an academic hospital. The patients underwent 12 weekly outpatient treatment sessions, each lasting 30 min (first PTNS phase). Neuromodulation was discontinued in those patients who did not have a 40% decrease in their pretreatment Wexner score. Patients having a better than 40% response were offered another 12-week course of complete treatment (second PTNS phase), following which they received no further PTNS treatment (phase without PTNS) but were assessed at 6 months and 2 years. RESULTS: All patients finished the first phase and 22/30 patients continued to the second phase. During this phase 11 patients showed an improved Wexner score (baseline/first phase/second phase: 14.3 ± 4.2 vs 9.9 ± 5.4 vs 6.8 ± 5.4). After a 6-month period without any treatment, the score was still improved in 11/30 patients (9.1 ± 6.2). At 2 years there was improvement in 16/30 patients (8.8 ± 7.1). There was a significant improvement in three variables of the quality of life questionnaire: lifestyle, coping behaviour and embarrassment. CONCLUSION: The response to first and second phase PTNS was maintained for up to 2 years. Retreatment was not required in about half of patients, even when they had finished the treatment 6 months or 2 years previously.

Broadband telecom transparency of semiconductor-coated metal nanowires: more transparent than glass.

Metallic nanowires (NW) coated with a high permittivity dielectric are proposed as means to strongly reduce the light scattering of the conducting NW, rendering them transparent at infrared wavelengths of interest in telecommunications. Based on a simple, universal law derived from electrostatics arguments, we find appropriate parameters to reduce the scattering efficiency of hybrid metal-dielectric NW by up to three orders of magnitude as compared with the scattering efficiency of the homogeneous metallic NW. We show that metal@dielectric structures are much more robust against fabrication imperfections than analogous dielectric@metal ones. The bandwidth of the transparent region entirely covers the near IR telecommunications range. Although this effect is optimum at normal incidence and for a given polarization, rigorous theoretical and numerical calculations reveal that transparency is robust against changes in polarization and angle of incidence, and also holds for relatively dense periodic or random arrangements. A wealth of applications based on metal-NWs may benefit from such invisibility.

Enhanced and directional emission of semiconductor nanowires tailored through leaky/guided modes.

Photoluminescence from finite semiconductor nanowires is theoretically investigated, exploring and predicting their antenna-like properties for light emission in a variety of configurations of interest in Nanophotonics. The theoretical analysis is based on the leaky/guided mode dispersion relation for infinite nanowires, which govern the local density of available electromagnetic states. Light emission from finite nanowires is then numerically investigated in various scenarios with regard to its enhancement and directionality. A simple analytical model is derived that, upon tuning leaky/guided mode coupling through dipole position/orientation and nanowire length, allows us to predict their antenna-like behavior and thus to tailor photoluminescence (including magnetic dipole transitions) at will, with regard to both enhancement/inhibition and associated radiation patterns.

Ultra low-loss, isotropic optical negative-index metamaterial based on hybrid metal-semiconductor nanowires.

Recently, many fascinating properties predicted for metamaterials (negative refraction, superlensing, electromagnetic cloaking,…) were experimentally demonstrated. Unfortunately, the best achievements have no direct translation to the optical domain, without being burdened by technological and conceptual difficulties. Of particular importance within the realm of optical negative-index metamaterials (NIM), is the issue of simultaneously achieving strong electric and magnetic responses and low associated losses. Here, hybrid metal-semiconductor nanowires are proposed as building blocks of optical NIMs. The metamaterial thus obtained, highly isotropic in the plane normal to the nanowires, presents a negative index of refraction in the near-infrared, with values of the real part well below -1, and extremely low losses (an order of magnitude better than present optical NIMs). Tunability of the system allows to select the operating range in the whole telecom spectrum. The design is proven in configurations such as prisms and slabs, directly observing negative refraction.

Heuristic optimization for the design of plasmonic nanowires with specific resonant and scattering properties.

In this contribution, we propose a computational tool for the synthesis of metallic nanowires with optimized optical properties, e.g. maximal scattering cross-section at a given wavelength. For this, we employ a rigorous numerical method, based on the solution of surface integral equations, along with a heuristic optimization technique that belongs to the population-based set known as Evolutionary Algorithms. Also, we make use of a general representation scheme to model, in a more realistic manner, the arbitrary geometry of the nanowires. The performance of this approach is evaluated through some examples involving various wavelengths, materials, and optimization strategies. The results of our numerical experiments show that this hybrid technique is a suitable and versatile tool straightforwardly extensible for the design of different configurations of interest in Plasmonics.

[Reasons residents choose to specialize in anesthesiology and postoperative critical care in the autonomous community of Madrid]. / Motivación de los residentes de Anestesia-Reanimación de la Comunidad de Madrid en la elección de su especialidad.

OBJECTIVES: Our main objective was to determine the reasons why residents chose to specialize in anesthesiology and postoperative critical care in the autonomous community of Madrid. We also wished to know if prior contact with this specialty influenced their choice, if those who chose it as a second specialization differed from those who were doing a first residency, what expectations the residents had and if they had been met, and if they were satisfied with their training. MATERIAL AND METHODS: Survey of all residents in anesthesiology and postoperative critical care medicine in the community of Madrid between November 2008 and February 2010. The questionnaire items covered demographic data, prior specialty training, undergraduate contact with the specialty, reasons for choosing this specialty (technical, social, or employment-related interests), satisfaction, and expectations met. RESULTS: We received 89 valid questionnaires, a sample that represented 35% of the residents. The reasons expressed most often were learning and performing techniques (97.8%); that the specialty was dynamic, with broad theoretical and practical content (98.9%), and an interest in providing critical care (93.3%). These 3 reasons were considered important or very important by most of the respondents; 55.8% considered that learning and carrying out techniques was the most important reason. All the respondents who had previously done specialty training said they were dissatisfied. Prior contact with the specialty was associated with having different reasons and interests, such as an interest in pain (F = .037) or emulating a role model (P = .014). CONCLUSIONS: The specialty's mix of theoretical and practical content and the chance to perform techniques and provide critical care are the features the residents find most attractive. Residents who already have another specialty are less satisfied and their expectations are not as well met.

Motivación de los residentes de Anestesia-Reanimación de la Comunidad de Madrid en la elección de su especialidad / Reasons residents choose to specialize in anesthesiology and postoperative critical care in the autonomous community of Madrid

Objetivos: El objetivo principal fue conocer las motivaciones que han determinado la elección de la especialidad en Anestesiología y Reanimación en la Comunidad de Madrid y determinar si el conocimiento o contacto previo con la especialidad contribuía a la elección de la misma, ver si existían diferencias en las motivaciones principales del grupo que elige la especialidad por primera vez, con respecto a los que lo hacen como segunda especialidad y saber cuáles eran sus expectativas y si éstas se habían cumplido, además de conocer el grado de satisfacción global. Material y métodos: Encuesta dirigida a todos los residentes de Anestesiología y Reanimación de la Comunidad de Madrid entre noviembre de 2008 y febrero de 2010. La encuesta incluía datos demográficos, especialidad previa, contacto pregraduado, motivos de elección (técnicos, sociales, laborales, satisfacción obtenida y expectativas cumplidas). Resultados: Se obtuvieron 89 encuestas válidas (35% de repuestas). Los aspectos más frecuentemente valorados fueron: el desarrollo y realización de técnicas (97,8%), el concepto de especialidad dinámica y con amplio contenido teórico práctico (98,9%), la valoración y el tratamiento del paciente crítico (93,3%). Asimismo estas tres razones las consideraron entre importantes y muy importantes en la valoración cuantitativa por la mayoría de los encuestados, siendo lo más importante para el 55,8% la realización y desarrollo de técnicas. El 100% de los que tenían especialidad previa, se definieron insatisfechos. El conocimiento previo de la especialidad establece diferencias en las motivaciones e intereses, como el interés por el dolor (p = 0,037) o el modelo profesional a emular (p = 0,014). Conclusiones. Lo que más atrae a los residentes es el contenido teórico práctico, la posibilidad de realizar técnicas y la valoración y tratamiento del paciente crítico. Los residentes con otra especialidad están menos satisfechos y sus expectativas menos cumplidas que el resto(AU)

Objectives: Our main objective was to determine the reasons why residents chose to specialize in anesthesiology and postoperative critical care in the autonomous community of Madrid. We also wished to know if prior contact with this specialty influenced their choice, if those who chose it as a second specialization differed from those who were doing a first residency, what expectations the residents had and if they had been met, and if they were satisfied with their training. Material and methods: Survey of all residents in anesthesiology and postoperative critical care medicine in the community of Madrid between November 2008 and February 2010. The questionnaire items covered demographic data, prior specialty training, undergraduate contact with the specialty, reasons for choosing this specialty (technical, social, or employment-related interests), satisfaction, and expectations met. Results: We received 89 valid questionnaires, a sample that represented 35% of the residents. The reasons expressed most often were learning and performing techniques (97.8%); that the specialty was dynamic, with broad theoretical and practical content (98.9%), and an interest in providing critical care (93.3%). These 3 reasons were considered important or very important by most of the respondents; 55.8% considered that learning and carrying out techniques was the most important reason. All the respondents who had previously done specialty training said they were dissatisfied. Prior contact with the specialty was associated with having different reasons and interests, such as an interest in pain (P=.037) or emulating a role model (P=.014). Conclusions: The specialty's mix of theoretical and practical content and the chance to perform techniques and provide critical care are the features the residents find most attractive. Residents who already have another specialty are less satisfied and their expectations are not as well met(AU)

The rabbit as an animal model for proctology research: anatomical and histological description.

PURPOSE: This study was designed to describe the surgical anatomy and histology of the rabbit anorectum comparing it to that of humans, in order to decide whether it can be a good experimental model for research in proctology. MATERIAL AND METHODS: This study of the anorectal region was performed on six female New Zealand white rabbits, weighting between 2.5-2.9 kg. An autopsy was performed immediately after sacrificing the animal and an anatomical and histological description was performed. RESULTS: The mean rectum and anal canal lengths were of 7.2 cm and 0.9 cm, respectively. The macroscopic study showed that the musculature of the anal canal is formed by the coccygeus muscle, which serves as puborectalis in humans. It also defined an external anal sphincter with a deep and superficial portion. The histological evaluation showed similarity to that of humans, with mucosa of simple columnar type, muscularis mucosae, a small submucosa, with a muscular wall divided into internal and external layers, separated by the myenteric plexus. CONCLUSION: The great similarity to both the anatomy and the histology of humans, appropriate size and easy-handling and care, make the rabbit an attractive animal for the use as experimental and research model in proctology.

Local and anisotropic excitation of surface plasmon polaritons by semiconductor nanowires.

We demonstrate a novel functionality of semiconductor nanowires as local sources for surface plasmon polaritons (SPPs). Photoexcited semiconductor nanowires decay non-radiatively exciting SPPs when they are on top of a metallic surface. We have investigated the anisotropic excitation of SPPs by nanowires by placing individual InP nanowires inside gold bullseye gratings. The gratings serve to couple SPPs to free space radiation that is detected with a scanning confocal microscope. The circular geometry of the grating allows to conclude that SPPs are preferentially generated in the direction along the nanowire axis.

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Excitation and emission enhancement of single molecule fluorescence through multiple surface-plasmon resonances on metal trimer nanoantennas.

We study theoretically the light scattering from trimers of metal nanowires, with emphasis on the occurrence of multiple surface-plasmon resonances, showing that such resonances can be exploited to achieve twofold-enhanced fluorescence from a single molecule placed in the nanotrimer gaps, even if excitation and emission frequencies are separated. Pump enhancement stems from the local field enhancement coinciding with one of the resonances, whereas a strong enhancement of the radiative decay rate (and quantum yield) is revealed at a different resonance, leading to a large overall signal emission.

Electromagnetic model and calculations of the surface-enhanced Raman-shifted emission from Langmuir-Blodgett films on metal nanostructures.

We present a theoretical study of the electromagnetic contribution to surface-enhanced Raman scattering (SERS) from a Langmuir-Blodgett film close to a metal surface. This macroscopic dipolar model fully accounts for the Raman-shifted emission so that meaningful SERS (electromagnetic) enhancement factors that do not depend only on the local electromagnetic field enhancement at the pump frequency are defined. For a plane metal surface, analytical SERS enhancement factors that are consistent for all pump beam polarization and molecular orientation are obtained. In order to investigate SERS on complex nanostructured metal surfaces, we introduce this model into the formally exact, Green's theorem surface integral equation formulation of the scattered electromagnetic field. This formulation is thus employed to calculate numerically the near-field and far-field emissions at the Raman-shifted frequency for very rough, random nanostructured surfaces, with emphasis on the impact of collective processes for varying pump frequency and Raman shift. Our results reveal that the widely used |E|4 approximation tends to overestimate average SERS enhancement factors.