Modeling of strain-induced Pockels effect in Silicon

We propose a theoretical model to describe the strain-induced linear electro-optic (Pockels) effect in centro-symmetric crystals. The general formulation is presented and the specific case of the strained silicon is investigated in detail because of its attractive properties for integrated optics. The outcome of this analysis is a linear relation between the second order susceptibility tensor and the strain gradient tensor, depending generically on fifteen coefficients. The proposed model greatly simplifies the description of the electro-optic effect in strained silicon waveguides, providing a powerful and effective tool for design and optimization of optical devices.Comment: typos corrected in eq. 29 with respect to the published versio

Shape enhancement for rapid prototyping

Many applications, for instance in the reverse engineering and cultural heritage field, require to build a physical replica of 3D digital models. Recent 3D printers can easily perform this task in a relatively short time and using color to reproduce object textures. However, the finite resolution of printers and, most of all, some peculiar optical and physical properties of the used materials reduce their perceptual quality. The contribution of this paper is a shape enhancing technique, which allows users to increase readability of the tiniest details in physical replicas, without requiring manual post-reproduction interventions.831-840Pubblicat

Antimicrobial, antioxidant and anti-tyrosinase properties of extracts of the Mediterranean parasitic plant Cytinus hypocistis

Background: Cytinus is an endophytic parasitic plant occurring in South Africa, Madagascar, and in the Mediterranean region. We have extracted the inflorescences (the only visible part of the plant, emerging from the host roots at the time of blossom) of Cytinus hypocistis collected in Sardinia, Italy, and explored the antimicrobial, antioxidant, anti-tyrosinase, and cytotoxic activities of the extracts. Methods: Extracts from C. hypocistis were prepared using increasing polarity solvents: cyclohexane, ethanol, and water. Phenolic composition were determined through spectrophotometric assays, and antioxidant activity with both electron-transfer and hydrogen-atom assays. Nine different bacterial strains, including clinical isolate methicillin-resistant Staphylococcus aureus, were used in agar diffusion method. Cytotoxicity was tested using against the B16F10 melanoma cell line. Results: While cyclohexane extracts where biologically inactive, ethanolic and aqueous extracts displayed an intriguing activity against several Gram-positive bacterial strains, including methicillin-resistant S. aureus, and against the Gram-negative Acinetobacter baumanii. Compared to the conventional antibiotics like cloxacillin, ampicillin, and oxytetracycline, C. hypocistis extracts were less active in absolute terms, but displayed a wider spectrum (notably, cloxacillin and ampicillin were inactive against methicillin-resistant S. aureus). The ethanolic extract of C. hypocistis was found to be particularly rich in polyphenols, in most part hydrolysable tannins. The antioxidant activity of extracts, tested with several methodologies, resulted to be particularly high in the case of ethanolic extracts, in accordance with the composition in phenolics. In detail, ethanol extracts presented about a twofold higher activity than the water sample when tested through the oxygen radical absorbance capacity-pyrogallol red (ORAC-PYR) assay. Cytotoxicity analysis against the B16F10 melanoma cell line showed that both extracts have not significant cytotoxic effect, even at the highest dose (1000 μg/mL). Tests showed that ethanolic extracts also had the greatest tyrosinase inhibition activity, indicating that C. hypocistis-derived substances could find application in food formulations as anti-browning agents. Conclusions: Overall, these results point to the need of further studies on C. hypocistis extracts, aimed at isolating and fully characterizing its biologically active compounds. © 2015 Zucca et al

Monolithic integration of broadband optical isolators for polarization-diverse silicon photonics

Integrated optical isolators have been a longstanding challenge for photonic integrated circuits (PIC). An ideal integrated optical isolator for PIC should be made by a monolithic process, have a small footprint, exhibit broadband and polarization-diverse operation, and be compatible with multiple materials platforms. Despite significant progress, the optical isolators reported so far do not meet all these requirements. In this article we present monolithically integrated broadband magneto-optical isolators on silicon and silicon nitride (SiN) platforms operating for both TE and TM modes with record high performances, fulfilling all the essential characteristics for PIC applications. In particular, we demonstrate fully-TE broadband isolators by depositing high quality magneto-optical garnet thin films on the sidewalls of Si and SiN waveguides, a critical result for applications in TE-polarized on-chip lasers and amplifiers. This work demonstrates monolithic integration of high performance optical isolators on chip for polarization-diverse silicon photonic systems, enabling new pathways to impart nonreciprocal photonic functionality to a variety of integrated photonic devices

Participants with Normal Weight or with Obesity Show Different Relationships of 6-n-Propylthiouracil (PROP) Taster Status with BMI and Plasma Endocannabinoids

Reduced taste sensitivity to 6-n-propylthiouracil (PROP), a genetic trait regarded as a general index for oral chemosensory perception, has been associated with a calorie-rich food preference and lower circulating endocannabinoid levels in participants with normal weight (NW), which suggests an adaptive mechanism to maintain a lean phenotype. In this study, we assessed whether participants with obesity (OB) show different patterns of plasma endocannabinoids and lipid metabolism biomarkers from those of NW, with further categorization based on their PROP sensitivity. NW and OB were classified by their PROP taster status as non-tasters (NT), medium-tasters (MT) and supertasters (ST). The blood samples were analysed for plasma endocannabinoids, nonesterified fatty acids (NEFA) and retinol, which have been associated to metabolic syndrome. In OB, we found a higher BMI and lower circulating endocannabinoids in ST vs. OB NT. However, OB ST showed lower circulating NEFA and retinol levels, which suggested a more favourable lipid metabolism and body fat distribution than those of OB NT. We confirmed lower plasma endocannabinoid levels in NW NT than in NW ST. These data suggest that PROP taste sensitivity determines metabolic changes and ultimately body mass composition differently in OB and NW

Biological activities and nutraceutical potentials of water extracts from different parts of Cynomorium coccineum L. (Maltese Mushroom)

Maltese Mushroom (Cynomorium coccineum L.) is a non-photosynthetic plant that has been used in traditional medicine for many centuries. In this paper, water extracts from the whole plant, external layer and peeled plant were studied to determine the main components responsible for its biological activities, i.e., its antimicrobial, antioxidant, and anti-tyrosinase activities; its cytotoxicity against mouse melanoma B16F10 cells; and its pro-erectile activity in adult male rats. The results of electron transfer and hydrogen transfer assays showed that the antioxidant activity was mainly due to anthocyanins in the external layer, whereas the external layer and peeled plant extracts both inhibited the microbial growth of several Gram-positive strains. In contrast, the whole plant extract had the highest anti-tyrosinase activity and exhibited pro-erectile activity when administered subcutane-ously. Overall, this study elucidated which parts of Maltese Mushroom are responsible for its antimicrobial, antioxidant, and anti-tyrosinase activities and thus which extracts have potential for use in nutraceutical formulation

Ultralow voltage, High-speed, and Energy-efficient Cryogenic Electro-Optic Modulator

Photonic integrated circuits (PICs) at cryogenic temperatures enable a wide range of applications in scalable classical and quantum systems for computing and sensing. A promising application of cryogenic PICs is to provide optical interconnects by upconverting signals from the electrical to the optical domain, allowing a massive data transfer from 4 K superconducting (SC) electronics to the room temperature environment. Such a solution can overcome a major bottleneck in the scalability of cryogenic systems that currently rely on bulky coaxial cables that suffer from limited bandwidth, a large heat load, and poor scalability. A key element to realize a cryogenic-to-room temperature optical interconnect is a high-speed, electro-optic (EO) modulator operating at 4 K with a modulation voltage at the mV scale, compatible with SC electronics. Although several cryogenic EO modulators have been demonstrated, their driving voltages are substantially large (several hundred mV to a few V) compared to the mV scale voltage provided by SC circuits. Here, we demonstrate a cryogenic modulator with similar to 10 mV peak-to-peak driving voltage and Gb/s data rate, with an ultralow electric energy consumption of similar to 10.4 aJ/bit and an optical energy consumption of similar to 213 fJ/bit. We achieve this record performance by designing and fabricating a compact optical ring resonator modulator in a heterogeneous InP-on-Si platform, where we optimize a multi-quantum-well layer of InAlGaAs to achieve a strong EO effect at 4 K. Unlike other semiconductors such as silicon, our platform benefits from the high-carrier mobility and minimal freecarrier freezing of III-V compounds at low temperatures, with a moderate doping level and a correspondingly low loss (intrinsic resonator Q similar to 272,000). These modulators can pave the path for complex cryogenic photonic functionalities and massive data transmission between cryogenic and room-temperature electronics. (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreemen

Active elderly and health-can moderate exercise improve health and wellbeing in older adults? Protocol for a randomized controlled trial

Abstract Background: Aging is marked by a progressive rise in chronic diseases with an impact on social and healthcare costs. Physical activity (PA) may soothe the inconveniences related to chronic diseases, has positive effects on the quality of life and biological rhythms, and can prevent the decline in motor functions and the consequent falls, which are associated with early death and disability in older adults. Methods: We randomized 120 over-65 males and females into groups of similar size and timing and will give each either moderate physical activity or cultural and recreational activities. Being younger than 65 years, inability to participate in physical activity for any medical reason, and involvement in a massive program of physical exercise are the exclusion criteria. The primary outcome measures are quality of life, walking speed, and postural sway. Participants are tested at baseline, post-treatment, and 6-month (24 weeks) and 12-month (48 weeks) follow-ups. Discussion: This study aims at improving the quality of life, wellness, and cognitive functioning in the elderly through a low-cost affordable program of moderate physical activity. Given the growing aging of the world population and the social and economic burden of disability in the elderly, our results might have a major impact on future practices