Evaluating the influence of air pollution on solar radiation observations over the coastal region of Alicante (Southeastern Spain).

The present study evaluates ground-based downward surface shortwave radiation (Rs) over the coastal region of Alicante (Southeastern Spain). Hourly measurements collected over the eleven-year period 2010-2020 are used. Two weather stations located over the region capital, Alicante, have been selected as representative of urban and suburban typologies. Two additional weather stations far from the city have been selected representing rural typologies. Rs is significantly reduced over the urban station during the morning hours within the winter season compared to the observations recorded over the suburban and rural stations, with a global mean difference of -81 and -120 W/m2 at 10 LT, respectively. However, no significant differences are obtained during the midday sun, with a global mean difference of -20 W/m2 between the urban and rural stations. With the aim of explaining these differences, the current paper investigates the relationship between Rs and different air pollutants: NOx, SO2, and fine particulate matter (PM2.5 and PM10) as well as the wind field measured at the urban and suburban stations. The results found in this work point towards a close relationship between Rs and NOx concentrations annual cycles, which are also influenced by the prevailing wind circulations observed over the study area. A global mean NOx concentration of 107 µg/m3 is observed over the urban station at 10 LT during the winter season. In contrast, these high concentrations are significantly reduced over the suburban station, with global mean value of 40 µg/m3 at 10 LT, for this period of the year.

Analysis of Radon Measurements in Relation to Daily Seismic Activity Rates in the Vrancea Region, Romania.

Many previous research studies have shown how local and even regional earthquakes can significantly affect the release of radon in the soil. The aim of this work is to investigate the relationship between radon measurements and the daily seismic activity rate and develop a methodology that allows estimating the seismic activity rate using only radon measurements. To carry out this study, the earthquake catalogue of the Vrancea region (Romania) has been used to estimate the daily seismic activity rate during a given time period, in which radon measurements were also recorded, from January 2016 to September 2020. The Vrancea zone represents the most active seismic zone in Europe and is located on the eastern edge of the strongly bent Carpathian arc. In the case of the radon measurements, seasonal behaviours and linear trends due to non-seismic factors have been identified and subsequently removed. The discrete wavelet transform has been used to analyse the radon signal at two different scales: long and short periods. From the analysis carried out on a long-period scale, an approximate linear relationship has been obtained between the radon series and the daily seismic activity rate, which provides insights into the behaviour of the seismic activity in the study region with only the radon information. In addition, the study reveals certain characteristics that could be used as precursors of earthquakes at different scales: weeks in the case of the estimated daily seismic activity rate, and days in the case of the short-period signal obtained by the wavelet analysis. The results obtained for this region allow us to hope that the analysis of the radon time series can become an effective complement to the conventional seismic analysis used in operational earthquake forecasting.

Raspberry Shake-Based Rapid Structural Identification of Existing Buildings Subject to Earthquake Ground Motion: The Case Study of Bucharest.

The Internet of things concept empowered by low-cost sensor technologies and headless computers has upscaled the applicability of vibration monitoring systems in recent years. Raspberry Shake devices are among those systems, constituting a crowdsourcing framework and forming a worldwide seismic network of over a thousand nodes. While Raspberry Shake devices have been proven to densify seismograph arrays efficiently, their potential for structural health monitoring (SHM) is still unknown and is open to discovery. This paper presents recent findings from existing buildings located in Bucharest (Romania) equipped with Raspberry Shake 4D (RS4D) devices, whose signal recorded under multiple seismic events has been analyzed using different modal identification algorithms. The obtained results show that RS4D modules can capture the building vibration behavior despite the short-duration and low-amplitude excitation sources. Based on 15 RS4D device readings from five different multistorey buildings, the results do not indicate damage in terms of modal frequency decay. The findings of this research propose a baseline for future seismic events that can track the changes in vibration characteristics as a consequence of future strong earthquakes. In summary, this research presents multi-device, multi-testbed, and multi-algorithm evidence on the feasibility of RS4D modules as SHM instruments, which are yet to be explored in earthquake engineering.

Additive Manufacturing of Gold Nanostructures Using Nonlinear Photoreduction under Controlled Ionic Diffusion.

Multiphoton photoreduction of photosensitive metallic precursors via direct laser writing (DLW) is a promising technique for the synthesis of metallic structures onto solid substrates at the sub-micron scale. DLW triggered by a two photon absorption process is done using a femtosecond NIR laser (λ = 780 nm), tetrachloroauric acid (HAuCl4) as a gold precursor, and isinglass as a natural hydrogel matrix. The presence of a polymeric, transparent matrix avoids unwanted diffusive processes acting as a network for the metallic nanoparticles. After the writing process, a bath in deionized water removes the gold precursor ions and eliminates the polymer matrix. Different aspects underlying the growth of the gold nanostructures (AuNSs) are here investigated to achieve full control on the size and density of the AuNSs. Writing parameters (laser power, exposure time, and scanning speed) are optimized to control the patterns and the AuNSs size. The influence of a second bath containing Au3+ to further control the size and density of the AuNSs is also investigated, observing that these AuNSs are composed of individual gold nanoparticles (AuNPs) that grow individually. A fine-tuning of these parameters leads to an important improvement of the created structures' quality, with a fine control on size and density of AuNSs.

Heterometallic Titanium-Organic Frameworks by Metal-Induced Dynamic Topological Transformations.

Reticular chemistry has boosted the design of thousands of metal and covalent organic frameworks for unlimited chemical compositions, structures, and sizable porosities. The ability to generate porous materials at will on the basis of geometrical design concepts is responsible for the rapid growth of the field and the increasing number of applications derived. Despite their promising features, the synthesis of targeted homo- and heterometallic titanium-organic frameworks amenable to these principles is relentlessly limited by the high reactivity of this metal in solution that impedes the controlled assembly of titanium molecular clusters. We describe an unprecedented methodology for the synthesis of heterometallic titanium frameworks by metal-exchange reactions of MOF crystals at temperatures below those conventionally used in solvothermal synthesis. The combination of hard (titanium) and soft (calcium) metals in the heterometallic nodes of MUV-10(Ca) enables controlled metal exchange in soft positions for the generation of heterometallic secondary building units (SBUs) with variable nuclearity, controlled by the metal incorporated. The structural information encoded in the newly formed SBUs drives an MOF-to-MOF conversion into bipartite nets compatible with the connectivity of the organic linker originally present in the crystal. Our simulations show that this transformation has a thermodynamic origin and is controlled by the terminations of the (111) surfaces of the crystal. The reaction of MUV-10(Ca) with first-row transition metals permits the production of crystals of MUV-101(Fe,Co,Ni,Zn) and MUV-102(Cu), heterometallic titanium MOFs isostructural with archetypical solids such as MIL-100 and HKUST. In comparison to de novo synthesis, this metal-induced topological transformation provides control over the formation of hierarchical micro-/mesopore structures at different reaction times and enables the formation of heterometallic titanium MOFs not accessible under solvothermal conditions at high temperature, thus opening the door for the isolation of additional titanium heterometallic phases not linked exclusively to trimesate linkers.

High Spatial Resolution Mapping of Localized Surface Plasmon Resonances in Single Gallium Nanoparticles.

Plasmonics has emerged as an attractive field driving the development of optical systems in order to control and exploit light-matter interactions. The increasing interest around plasmonic systems is pushing the research of alternative plasmonic materials, spreading the operability range from IR to UV. Within this context, gallium appears as an ideal candidate, potentially active within a broad spectral range (UV-VIS-IR), whose optical properties are scarcely reported. Importantly, the smart design of active plasmonic materials requires their characterization at high spatial and spectral resolution to access the optical fingerprint of individual nanostructures, attainable by transmission electron microscopy techniques (i.e., by means of electron energy-loss spectroscopy, EELS). Therefore, the optical response of individual Ga nanoparticles (NPs) by means of EELS measurements is analyzed, in order to spread the understanding of the plasmonic response of Ga NPs. The results show that single Ga NPs may support several plasmon modes, whose nature is extensively discussed.

Comparison of the accuracy and proximal shunt failure rate of freehand placement versus intraoperative guidance in parietooccipital ventricular catheter placement.

OBJECTIVE The aim of this paper is to compare the accuracy of the freehand technique versus the use of intraoperative guidance (either ultrasound guidance or frameless stereotaxy) for placement of parietooccipital ventricular catheters and to determine factors associated with reduced proximal shunt failure. METHODS This retrospective cohort study included all patients from 2 institutions who underwent a ventricular cerebrospinal fluid (CSF) shunting procedure in which a new parietooccipital ventricular catheter was placed between January 2005 and December 2013. Data abstracted for each patient included age, sex, method of ventricular catheter placement, side of ventricular catheter placement, Evans ratio, and bifrontal ventricular span. Postoperative radiographic studies were reviewed for accuracy of ventricular catheter placement. Medical records were also reviewed for evidence of shunt failure requiring revision. Standard statistical methods were used for analysis. RESULTS A total of 257 patients were included in the study: 134 from the University of Michigan and 123 from Washington University in St. Louis. Accurate ventricular catheter placement was achieved in 81.2% of cases in which intraoperative guidance was used versus 67.3% when the freehand technique was used. Increasing age reduced the likelihood of accurate catheter placement (OR 0.983, 95% CI 0.971-0.995; p = 0.005), while the use of intraoperative guidance significantly increased the likelihood (OR 2.809, 95% CI 1.406-5.618; p = 0.016). During the study period, 108 patients (42.0%) experienced shunt failure, 79 patients (30.7%) had failure involving the proximal catheter, and 53 patients (20.6%) had distal failure (valve or distal catheter). Increasing age reduced the likelihood of being free from proximal shunt failure (OR 0.983, 95% CI 0.970-0.995; p = 0.008), while both the use of intraoperative guidance (OR 2.385, 95% CI 1.227-5.032; p = 0.011), and accurate ventricular catheter placement (OR 3.424, 95% CI 1.796-6.524; p = 0.009) increased the likelihood. CONCLUSIONS The use of intraoperative guidance during parietooccipital ventricular catheter placement as part of a CSF shunt system significantly increases the likelihood of accurate catheter placement and subsequently reduces the rate of proximal shunt failure.

Mapping the plasmonic response of gold nanoparticles embedded in TiO2 thin films.

We present the mapping of the plasmonic properties of gold nanoparticles that are embedded in a TiO2 thin film deposited over two different substrates, glass and silicon. An improved electron energy-loss spectroscopy (EELS) imaging technique was used to extract plasmon maps with nanometre resolution. Several representative cases of randomly dispersed NPs have been examined to carefully evaluate surrounding effects on the optical response of such nanostructured material. Data were compared to analytical calculations and showed good agreement. These results validate previous structural and far-field optical results and provide a clear description of the optical phenomena that take place at a nanometre scale in these materials. They are of primary importance for enlightening the way to the fabrication of thin film materials including metallic nanostructures for photovoltaic applications.

Plasmonic Characterization of 3D Printable Metal-Polymer Nanocomposites.

Plasmonic polymer nanocomposites (i.e., polymer matrices containing plasmonic nanostructures) are appealing candidates for the development of manifold technological devices relying on light-matter interactions, provided that they have inherent properties and processing capabilities. The smart development of plasmonic nanocomposites requires in-depth optical analyses proving the material performance, along with correlative studies guiding the synthesis of tailored materials. Importantly, plasmon resonances emerging from metal nanoparticles affect the macroscopic optical response of the nanocomposite, leading to far- and near-field perturbations useful to address the optical activity of the material. We analyze the plasmonic behavior of two nanocomposites suitable for 3D printing, based on acrylic resin matrices loaded with Au or Ag nanoparticles. We compare experimental and computed UV-vis macroscopic spectra (far-field) with single-particle electron energy loss spectroscopy (EELS) analyses (near-field). We extended the calculations of Au and Ag plasmon-related resonances over different environments and nanoparticle sizes. Discrepancies between UV-vis and EELS are dependent on the interplay between the metal considered, the surrounding media, and the size of the nanoparticles. The study allows comparing in detail the plasmonic performance of Au- and Ag-polymer nanocomposites, whose plasmonic response is better addressed, accounting for their intended applications (i.e., whether they rely on far- or near-field interactions).

Chitin Nanocomposites for Fused Filament Fabrication: Flexible Materials with Enhanced Interlayer Adhesion.

In this work, we present a series of nanocomposites for Fused filament fabrication (FFF) based on polycaprolactone (PCL) and chitin nanocrystals (ChNCs). The ChNCs were synthesized by acid hydrolysis using HCl or lactic acid (LA). The approach using LA, an organic acid, makes the ChNCs synthesis more sustainable and modifies their surface with lactate groups, increasing their compatibility with the PCL matrix. The ChNCs characterization by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy revealed that both ChNCs presented similar morphologies and crystallinity, while differential scanning calorimetry and thermogravimetric analysis proved that they can bear temperatures up to 210 °C without degrading, which allows their processing in the manufacturing of PCL composites by twin-screw extrusion. Therefore, PCL composites in the form of filaments containing 0.5-1.0 wt % ChNCs were produced and used as feedstock in FFF, and standard tensile and flexural specimens were printed at different temperatures, up to 170 °C, to assess the influence of the ChNCs in the mechanical properties of the material. The tensile testing results showed that the presence of ChNCs enhances the strength and ductility of the PCL matrix, increasing the elongation at break around 20-50%. Moreover, the vertically printed flexural specimens showed a very different bending behavior, such that the pure PCL specimens presented a brittle fracture at 7% strain, while the ChNCs composites were able to bend over themselves. Hence, this work proves that the presence of ChNCs aims to improve the interlayer adhesion of the objects manufactured by FFF due to their good adhesive properties, which is currently a concern for the scientific community and the industrial sector.