Abstract Background The infection of humans with virus SARS-Cov-2 was first reported in December 2019, in Wuhan, China and in 11th March 2020, COVID-19 was declared a pandemic by the World Health Organization. Since transmission was mainly through inhalation of droplets, general anesthesia was considered a high-risk transmission procedure. In this context, to choose regional anesthesia whenever possible, was recommended. Our main aim was to analyze if COVID-19 lead to an increased use of regional anesthesia in orthopedic surgeries. Methods Based on the orthopedic anesthetic activity of Hospital de Cascais (Portugal), two six months periods were compared: one following the resume of surgical activity after the first pandemic wave (“after COVID period”) and the homologous period of the previous year (“before COVID period”). Both periods were assessed for homogeneity for: age, sex, ASA status, contraindications for regional anesthesia, type of surgery, duration, priority and outpatient/inpatient care. Chi-square or Fisher tests were applied, as well as a binary logistic regression. Results Periods were significantly different for care (p = 0,0028), with more outpatient surgery in the after COVID period (43% versus 37,2%). No bivariate association was identified between periods and anesthesia. However, the binary logistic regression showed higher odds of being submitted to regional anesthesia in the after COVID period (p = 0,002 OR = 1,507 CI95%[1,156-1,964]). Conclusions Possible explanations for absent bivariate association between period and anesthesia, are that all patients were tested for COVID-19, and the higher number of outpatient surgery (for which general anesthesia is preferred) in the after COVID period. When all predictors were controlled with the binary logistic regression, the guidelines seemed to have been followed. However, the lower limit of CI95% is near 1. This may indicate that in the future, further efforts to implement regional anesthesia guidelines, may be needed. Key messages • COVID-19 Guidelines for regional anesthesia were followed but additional efforts are needed, as new pandemics are expected. • As a preventive measure for future pandemics, training programs of regional anesthesia should be mandatory.

Combination of carbon-based nanomaterials (CNMs) with AuNPs has been demonstrated to enhance the LSPR response and facilitate the functionalization with specific and selective antibodies. Also, the introduction of CNMs in the plasmonic layer allows tuning of the LSPR central frequency. Joining the double dependence of the LSPR on the MNPs size and the presence of CNMs, it is possible to create a set of plasmonic layers whose LSPR wavelengths are distributed in a spectral range of few tenth of nanometers. This consideration paves the way to an LSPR sensor with an arrayed structure, where each element maximizes its specific LSPR at its own wavelength. Illumination with a broad light source produces a different response in each one of the elements. The working process underlying the sensing operation is that each element of the sensor array acts like a band-stop optical filter for a specific wavelength. The output can be extracted by the application of an image analysis approach to the spatially modulated light crossing the sensor area, based on a color recognition algorithm. A change in the refractive index over the sensor array will shift the rejection band of the sensing elements. An automatized method for color recognition can support the analysis of the refractive index variations yielding the final sensor output. A figure of merit, highlighting the LSPR central wavelength and spectral extension for different LSPR configurations, is also obtained for different sizes of the AuNPs and different flavors of CNMs.

The use of plasmonic nanoparticles for biomedical applications has been widely explored, resulting in significant advances in the construction of optical biosensors. The shape and size of AuNPs determines the spectral signature of their Localized Surface Plasmon Resonance (LSPR) and, therefore, the features of their plasmonic band can be used to monitor surface changes such as those related to protein binding or nanoparticle aggregation. In this work, gold nanoparticles (AuNPs) were produced based on a green and sustainable methodology using tea leaves. The phytochemicals present in tea act as reducing and stabilizing agents. To optimize the AuNPs deposition (nanomaterial proximity, homogenization and substrate coverage), ITO surfaces were modified with different materials, namely sol-gel matrices (e.g. (3-aminopropyl) triethoxysilane (APTES)), cross-linking agents (e.g., glutaraldehyde) and biopolymers (e.g., Bovine Serum Albumin (BSA)). The produced AuNPs were deposited directly onto ITO surfaces functionalized with APTES or in a mixture of BSA and glutaraldehyde; these matrices are transparent and thus suitable for optical applications. The functionalization procedure of ITO surfaces with the referred materials was performed by two methodologies: i) direct deposition of the matrix solution using a micropipette and ii) ultrasound irradiation. The resulting functionalized ITO surfaces were compared and characterized by light transmission spectroscopy. Accordingly, the tea-AuNPs deposited in the presence of BSA and glutaraldehyde provided the best plasmonic response, being the most promising ones for the development of an optical immunosensor.

This paper reports a fully automated plasma-enhanced plasma chemical vapor deposition (PECVD) system for thin-film deposition. This system can be used for the deposition of hydrogenated amorphous silicon (a-Si:H) and nanocrystalline silicon for devices like solar cells or optical sensors with good film homogeneity and material properties reproducibility. The control software enables two modes of system operation: semi-manual and full-auto. In the semi-manual mode the user sets all process parameters and controls all depositions steps. In the full-auto mode, the program performs the process steps according to script commands in a recipe file. This way, complex multilayered devices can be fabricated, with a high degree of reproducibility of the device characteristics.

Tin doped indium oxide (ITO) films were deposited on glass substrates by rf reactive magnetron sputtering using a metallic alloy target (In-Sn, 90-10). The post-deposition annealing has been done for ITO films in air and the effect of annealing temperature on the electrical, optical and structural properties of ITO films was studied. It has been found that the increase of the annealing temperature will improve the film electrical properties. The resistivity of as deposited film is about 1.3 × 10−1 gW∗cm and decreases down to 6.9 × 10−3 Ω∗cm as the annealing temperature is increased up to 500 °C. In addition, the annealing will also increase the film surface roughness which can improve the efficiency of amorphous silicon solar cells by increasing the amount of light trapping.

Wide band gap microcrystalline silicon films have aroused considerable interest since they combine some electro-optical advantages of amorphous and crystalline materials highly important to produce electro-optical devices such as TFTs and solar cells. In this paper we present results concerning the electro-optical characteristics of highly transparent and conductive n-type μc-Si based films. Here, emphasis is given to the production of n-type μc-films with optical gaps of 2.3 eV and dark conductivity’s of 6.5 Scm−1.

Thick large-area particle or X-ray detectors suffer degradation during operation due to creation of defects that act as deep traps. Measuring the photocurrent under homogeneously absorbed weak light can monitor variation in detector performance. We describe how photocapacitance can be used as an alternative method to measure the creation of defects and their energy level after intense irradiation with protons or He ions at 1.5 MeV and after exposure to intense laser pulses. The possibility to detect small areas of high defect density in a large-area detector structure is discussed. (C) 2008 Elsevier B.V. All rights reserved.

We report radiation effects on intrinsic a-Si:H thin films subjected to a 1.5MeV He4 beam for particle fluences up to 1016cm−2. Photothermal deflection spectroscopy is used to obtain information on the sub-gap density of states. Photoconductivity detects changes in the μτ-product of the electrons. Steady-state photocarrier grating technique is used for measuring the ambipolar diffusion length and estimating the hole μτ-product. The 1.5MeV He4 beam radiation results in pronounced changes in the a-Si:H absorption spectrum. Optical absorption due to deep defects increases with particle fluence by more than one order of magnitude. Electronic transport properties consistently degrade with increasing particle fluence and correlate with the density of radiation-induced defects.

Single and stacked p-i-n sensing elements for image recognition and color extraction applications are presented. The aim of this work is to optimize the performance of the a-SiC:H thin films layers in order to enhance its performance when making part of the structure of large area image and color sensors. The efforts are focused mainly on doped n- and p-type layers at high and low doping levels with and without carbon. The structural and optoelectronic properties of the single layers were determined through infrared and visible spectroscopy, temperature-dependent conductivity, and were complemented by CPM measurements. Junction properties, carrier transport, photogeneration and collection efficiency are investigated from dark and illuminated current-voltage characteristics and spectral response measurements, with and without additional background illumination and under different light bias conditions. The spectral response dependence on the applied voltage and on optical bias was also studied. Results show that the spectral sensitivity is strongly dependent on the applied voltage, namely the maximum spectral sensitivity shifts with the voltage, and at certain wavelengths the spectral response goes down to zero, which allows a different selectivity, and enables color recognition.

The aim of this work is to optimize a-SixC1-x:H alloy material characteristics in order to improve the performance of large area single and stacked p-i-n sensors.The efforts are focused mainly on n- and p-type doped layers at low doping levels with and without carbon. The hydrogen content and optoelectronic properties of the single layers were determined through infrared and visible spectroscopy, temperature-dependent conductivity, and were complemented by CPM measurements. Junction properties, carrier transport, photogeneration and collection efficiency are investigated using dark and illuminated current-voltage characteristics and spectral response measurements, with and without additional background illumination and under different light bias conditions.

Photoconductivity as a measure of the majority carrier mobility–lifetime product is monitored in intrinsic amorphous silicon film (a-Si:H) when subjected to a 1.5 MeV He4 beam. In a second step we looked at the changes of device performance in a 5 μm thick a-Si:H based detector structure which was subjected to a 1 MeV proton beam that assures a homogeneous damage profile. We find that the Rose coefficient increases to near unity after strong irradiation indicating the transition from bi- to monomolecular recombination. The p–i–n device shows changes that can be related to the properties of the thick intrinsic layer. As a by-product we can reconstruct the particle beam profile using the analytical fit to the fluence dependence of photosensitivity.

The aim of this work is the optoelectronic characterization of double p–i–n stacked devices based on a-Si alloy materials, in order to evaluate their suitability in large area optical sensors. Photogeneration, collection efficiency and carrier transport are investigated from dark and illuminated current–voltage characteristics and spectral response measurements, with and without additional background illumination and different electrical bias conditions. Results show that the collection efficiency depends on the device configuration and on the optical and electrical bias. The carrier collection is mainly dependent on the front and back intrinsic layers thickness and on the composition of the p-type doped layers. When wide band gap p-layers are used, the asymmetric distribution of the electrical field controls the transport mechanism. Under red optical bias the electrical field is enhanced at the front cell and decreased at the back one leading to an increased red light-to dark sensitivity. A numerical simulation supports the discussion of the experimental results. Considerations about induced electric field and inversion layers at the interfaces and generationrecombination process are used to explain the device output.

Amorphous glass/ZnO:Al/p(a-Si:H)/i(a-Si:H)/n(a-Si1-xCx:H)/Al imagers with different n-layer resistivities were produced by plasma enhanced chemical vapour deposition technique (PE-CVD). The image is projected onto the active surface of the sensor and defines itself spatially confined depletion regions that can be readout by scanning the photodiode with a low power modulated laser beam. The essence of the scheme is the analogue readout and the absence of semiconductor arrays or electrode potential manipulations to transfer the information coming from the transducer. The effect of the image intensity on the sensor output characteristics (sensitivity, linearity, blooming, resolution and signal-to-noise ratio) are analysed for different material composition (0.5 < x < 1). The results show that the response and the spatial resolution are limited by the conductivity of the doped layers. An enhancement of 75% in the image resolution is achieved with responsivity of 0.2 mW/cm(2) decreasing the n-layer conductivity by one order of magnitude. An analysis of the image acquisition and representation is performed. A physical model supported by an electrical simulation gave insight into the methodology used for image representation. (C) 2002 Elsevier Science Ltd. All rights reserved.

This paper presents a one-dimensional numerical simulation of the charge carrier transport and photogeneration within a p-i-n (a-Si:H) homojunction and a p (a-SiC:H)/ i (a-Si:H)/ n (a-SiC:H) heterojunction with weakly-doped n -layers. A good matching between the simulated J-V characteristics and the corresponding experimental curves has been achieved for both configurations. By analysing the simulated band diagrams, electric field distributions, the electron and hole current densities, and the free carrier population profiles we conclude that in short-circuit mode the carrier transport is different in the homojunction and heterojunction due to band offsets. Our results show that in the heterostructure, as the light intensity increases, the potential drop across the a-SiC:H n -layer increases leading to a significant change in the drift-diffusion balance across the i -layer. In the homojunction, at the same incident fluxes, the transport process remains drift dominated.

Amorphous glass/ZnO-Al/p(a-Si:H)/i(a-Si:H)/n(a-Si1-xCx:H)/Al imagers with different n-layer resistivities were produced by plasma enhanced chemical vapour deposition technique (PE-CVD). An image is projected onto the sensing element and leads to spatially confined depletion regions that can be readout by scanning the photodiode with a low-power modulated laser beam. The essence of the scheme is the analog readout, and the absence of semiconductor arrays or electrode potential manipulations to transfer the information coming from the transducer.The influence of the intensity of the optical image projected onto the sensor surface is correlated with the sensor output characteristics (sensitivity, linearity blooming, resolution and signal-to-noise ratio) are analysed for different material compositions (0.5 < x < 1). The results show that the responsivity and the spatial resolution are limited by the conductivity of the doped layers. An enhancement of one order of magnitude in the image intensity signal and on the spatial resolution are achieved at 0.2 mW cm(-2) light flux by decreasing the n-layer conductivity by the same amount.A physical model supported by electrical simulation gives insight into the image-sensing technique used. (C) 2001 Elsevier Science B.V. All rights reserved.

Amorphous ZnO:Al/ a-SixC1-x:H-p-i-n/Al optical imagers that use a small-signal scanning beam to read out the photogenerated carriers are presented. The effect of the image intensity on the sensor output characteristics (distortion, sensitivity and signal-to-noise ratio) are analysed for different sensor configurations (0.5 < x < 1). Results show that the sensitivity and the geometrical distortion are limited by the conductivity of the doped layers. A 75% image distortion reduction with a responsivity of 2 W/m (2) is obtained by decreasing the n-layer conductivity by one order of magnitude. An analysis of the image acquisition and representation is performed. A physical model supported by an electrical simulation gave insight into the methodology used for image representation. (C) 2001 Elsevier Science B.V. All rights reserved.