196,259 research outputs found
Tailoring the electrooptic response and improving the performance of integrated LiNbO3 modulators by domain engineering
No full textOptimizing gold nanoparticle size and shape for the fabrication of SERS substrates by means of the Langmuir-Blodgett technique
No full textThe Langmuir-Blodgett technique, in which a layer of nanoparticles is spread at the water/air interface and further transferred onto a solid support, is a versatile approach for the preparation of SERS substrates with a controllable arrangement of hotspots. In a previous work, we demonstrated that fine-tuning the lateral packing and subsequent seed growth of 10 nm gold nanoparticles led to a quasi-resonant enhanced in the SERS signal of a test analyte. Here, we explore further enhancements by modifying the size and shape of the spread gold nanoparticles in order to take advantage of the inherent interparticle repulsion mechanisms present at the interface. We show that the size of the used nanoparticles is also a determinant factor, which cannot be compensated by the subsequent electroless growth. We also show that, although the seeded growth leads to rough hotspots, the sensitivity can be optimized by self-assembling urchin-shaped nanoparticles, with a roughness that is fine-tuned a priori. Our results suggest an intriguing correlation between surface homogeneity and SERS signal enhancement, indicating that regular substrates will have the optimal performance
Electrode-free optical sensor for high voltage using a domain-inverted LiNbO3 waveguide near cut-off
No full textWe present a novel all-optical electric field sensor based on a proton-exchange waveguide near cut-off, centered on a few microns wide domain-inverted region in a z-cut LiNbO3 substrate. The output intensity from the waveguide is modulated by an external electric field via the electro-optic effect. We also demonstrate the sensor's performance by detecting DC fields up to 2.6 MV/m and high-frequency (1.1 GHz) fields ranging from 19 V/m to 23 kV/m. These features and the proposed design allow operating the sensor without the use of any metal antenna, thus making it suited for use in high electric field and harsh conditions-e.g. power stations and transmission lines-without any danger for the operator or risk of damage to the sensor head
Orlando Furioso dalla specola del costrutto causativo
No full textAnalisi e riflessioni sulle ricorrenze del costrutto causativo nell'Orlando Furioso che si rivela tratto saliente della lingua e dell'espressione dell'opera.
Il poema di Ariosto pullula naturalmente di attori che, osservati dalla specola del costrutto causativo, si qualificano appunto come né sovrumani né subumani. Attori siffatti ne sono i protagonisti. Le loro vicissitudini costituiscono il tema dell’opera e ne sostanziano la trama. Che il costrutto causativo sia tanto frequente nel Furioso non è dunque un accidente e il dato è a questo punto comprensibile, perché integrato in un sistema. Il costrutto causativo è nel cuore del processo narrativo, ne è un motore
Tailoring plasmonic response by Langmuir–Blodgett gold nanoparticle templating for the fabrication of SERS substrates
No full textNanoparticle self-assembly is a robust and versatile strategy for the development of functional nanostructured materials, offering low-cost and scalable methods that can be fine-tuned for many different specific application. In this work, we demonstrate a pathway for the fabrication of tailorable quasi-two-dimensional lattices of gold nanoparticles to be used in Surface Enhanced Raman Scattering (SERS) detection of biomolecules. As a first step, nanoparticles are spread as a monolayer at the water/air interface, compressed to a target lateral density in a Langmuir–Blodgett technique, and transferred to a properly functionalized substrate surface. Once firmly adhered to the substrate, the lattice of nanoparticles can be directly used or be further processed using electroless gold deposition to let the nanoparticle grow thus tuning the plasmonic response and SERS enhancement. Compared to direct deposition or self-assembly methods, our protocol enables to obtain consistent results and much higher coverage of Au nanoparticles thanks to the active control of the surface pressure of the spread monolayer
Arbitrary-order all-fiber temporal differentiator based on a fiber Bragg grating: design and experimental demonstration
No full textMiniaturized polymer-coated FBGs for high-sensitivity biomedical pressure sensing
No full textContinuous and real-time physiological pressure monitoring is essential for diagnosing and managing conditions such as intracranial hypertension, cardiovascular diseases, and gastrointestinal motility disorders. While fiber Bragg gratings (FBGs) offer several advantages over conventional electrical sensors, including immunity to electromagnetic interference and multiplexing capability for simultaneous multi-point sensing, their inherent low-pressure sensitivity limits their applicability in biomedical environments. This study investigates the enhancement of FBG pressure sensitivity through a polymer coating, such as polydimethylsiloxane (PDMS), is used to improve strain transfer and amplify the Bragg wavelength shift, with coating dimensions (∼500 µ m) compatible with pressure guidewires or catheters. A combined approach of finite element modeling and experimental validation demonstrated that, compared to uncoated sensors, PDMS-coated FBGs achieved up to 43-fold and 154-fold sensitivity enhancements for 500 µ m and 800 µ m coatings on 125 µ m cladding fibers, and up to 212-fold and 339-fold improvements for corresponding coatings on 80 µ m cladding FBGs. Under dynamic pressure, the sensors exhibited minimum detectable pressure amplitudes of 0.5 mmHg. These enhancements bring standard FBG sensors closer to real-time, minimally invasive continuous monitoring in pressure-guided catheters. Additionally, the mechanical robustness and multiplexing potential of coated FBGs enable non-invasive applications, such as smart walkers or wearable devices, broadening their utility across clinical and rehabilitative settings
[Growth: what is normal?]
No full textGrowth is an inherent property of life, which has to be checked and controlled by any general physician following children. Therefore, the common knowledge about the normal pattern/course of growth is essential in order to act proactively whenever the child's growth does not progress adequately
Costrutti causativi e con verbi di percezione nell'epica cavalleresca
No full textanalizza la sintassi dei costrutti causativi (fare/lasciare + verbo) e dei verbi di percezione (vedere/sentire + verbo) nell'epica cavalleresca, concentrandosi in particolare sull'Orlando Furioso. La ricerca indaga come queste costruzioni, che uniscono più predicazioni in un nesso integrato, si manifestano nel test
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