Photonic band gaps analysis of Thue-Morse multilayers made of porous silicon

Dielectric aperiodic Thue-Morse structures up to 128 layers have been fabricated by using porous silicon technology. The photonic band gap properties of Thue-Morse multilayers have been theoretically investigated by means of the transfer matrix method and the integrated density of states. The theoretical approach has been compared and discussed with the reflectivity measurements at variable angles for both the transverse electric and transverse magnetic polarizations of light. The photonic band gap regions, wide 70 nm and 90 nm, included between 0 and 30°, have been observed for the sixth and seventh orders, respectively

Asymmetric MSM sub-bandgap all-silicon photodetector with low dark current

Design, fabrication, and characterization of an asymmetric metal-semiconductor-metal photodetector, based on internal photoemission effect and integrated into a silicon-on-insulator waveguide, are reported. For this photodetector, a responsivity of 4.5 mA/W has been measured at 1550 nm, making it suitable for power monitoring applications. Because the absorbing metal is deposited strictly around the vertical output facet of the waveguide, a very small contact area of about 3 µm2 is obtained and a transit-time-limited bandwidth of about 1 GHz is demonstrated. Taking advantage of this small area and electrode asymmetry, a significant reduction in the dark current (2.2 nA at -21 V) is achieved. Interestingly, applying reverse voltage, the photodetector is able to tune its cut-off wavelength, extending its range of application into the MID infrared regime

Playing with light in diatoms: microalgae with a natural photonic crystal structure

Complex micro- and nano-structured materials for photonic applications are designed and fabricated using top technologies. A completely different approach to engineering systems at the sub-micron-scale consists in recognizing the nanostructures and morphologies that nature has optimized during life’s history on earth. In fact, biological organisms could exhibit ordered geometries and complex photonic structures which often overcome the products of the best available fabrication technologies [1]. An example is given by diatoms, microalgae with a peculiar cell wall consisting of amorphous hydrated silica valves reciprocally interconnected in a structure called the frustule. Valve surfaces exhibit specie-specific patterns of regular arrays of chambers, called areolae, developed into the frustule depth. Areolae range in diameter from few hundreds of nanometers up to few microns, and can be circular, polygonal or elongate [2]. The formation of these patterns can be modeled by self-organised, genetically controlled processes. Despite of the high level of knowledge on the genesis and morphology of diatom frustules, their functions are not completely understood [2]. In this work, we show that the silica valves of marine diatoms, characterized by a photonic crystal-like structure, have surprising optical properties, being capable of filtering and focalizing light, as well as exhibiting optical sensing capabilities

Report of a Case of Video-Assisted Thoracoscopic Resection of Bronchogenic Cyst Developed in the Aorto-Pulmonary Window

We report the case of a 28-years-old male with a bronchogenic cyst developed in the aorto-pulmonary window. Left video-assisted thoracoscopy was performed and the cyst was removed intact and completely. Operative time was 48 minutes. The postoperative course was uneventful and the patient was discharged on the third postoperative day. We believe that an uncomplicated mediastinal bronchogenic cyst can be successfully approached by video-assisted thoracoscopy. In the case of an intraparenchymal or complicated cyst, thoracoscopic resection can be technically difficult and hazardous, and open approach is preferable

Estrogen receptors in colorectal cancer: Facts, novelties and perspectives

Colorectal cancer (CRC) is the second cause of cancer-related death in both sexes worldwide. As pre-menopausal women are less likely to develop CRC compared to age-matched men, a protective role for estrogens has been hypothesized. Indeed, two isoforms of nuclear estrogen receptors (ER) have been described: ERα and ERβ. While the binding of 17beta-estradiol to ERα activates anti-apoptotic pathways, the interaction with ERβ activates caspase-3, inducing apoptosis. In this regard, several pieces of evidence show that ERβ tends to be under-regulated in advanced adenomas and CRC, with an opposite trend for ERα. Furthermore, ERβ stimulation slows adenomatous polyp growth and modulates relevant CRC pathways. Based on such considerations, dietary modulation of ER is promising, particularly in subjects with genetic predisposition for CRC. Nevertheless, the main limitation is the lack of clinical trials on a large population scale

Daily Minority Stress and Affect among Gay and Bisexual Men: A 30-day Diary Study

Background. This study examined the time-variant association between daily minority stress and daily affect among gay and bisexual men. Tests of time-lagged associations allow for a stronger causal examination of minority stress-affect associations compared with static assessments. Multilevel modeling allows for comparison of associations between minority stress and daily affect when minority stress is modeled as a between-person factor and a within-person time-fluctuating state. Methods. 371 gay and bisexual men in New York City completed a 30-day daily diary, recording daily experiences of minority stress and positive affect (PA), negative affect (NA), and anxious affect (AA). Multilevel analyses examined associations between minority stress and affect in both same-day and time-lagged analyses, with minority stress assessed as both a between-person factor and a within-person state. Results. Daily minority stress, modeled as both a between-person and within-person construct, significantly predicted lower PA and higher NA and AA. Daily minority stress also predicted lower subsequent-day PA and higher subsequent-day NA and AA. Limitations. Self-report assessments and the unique sample may limit generalizability of this study. Conclusions. The time-variant association between sexual minority stress and affect found here substantiates the basic tenet of minority stress theory with a fine-grained analysis of gay and bisexual men’s daily experience. Time-lagged effects suggest a potentially causal pathway between minority stress as a social determinant of mood and anxiety disorder symptoms among gay and bisexual men. When modeled as both a between-person factor and within-person state, minority stress demonstrated expected patterns with affect

The ligand-receptor interactions based on silicon technology

We explored the use of porous silicon (pSi) technology for the construction of a biotechnological device, in which the ligand-receptor interactions are revealed by means of laser optical measurements. Here we report the settling of chemical procedures for the functionalization of the silicon wafers and for the subsequent anchoring of biological molecules such as a purified murine monoclonal antibody (UN1 mAb), an antibody anti-P8 protein of M13 phage and an antibody anti-A20 murine lymphoma cell line. The optical analysis of the interaction on the biochips between the bound biomolecules and their corresponding ligands indicated that the pSi is suitable for thi

Frontiers of light manipulation in natural, metallic, and dielectric nanostructures

AbstractThe ability to control light at the nanoscale is at the basis of contemporary photonics and plasmonics. In particular, properly engineered periodic nanostructures not only allow the inhibition of propagation of light at specific spectral ranges or its confinement in nanocavities or waveguides, but make also possible field enhancement effects in vibrational, Raman, infrared and fluorescence spectroscopies, paving the way to the development of novel high-performance optical sensors. All these devices find an impressive analogy in nearly-periodic photonic nanostructures present in several plants, animals and algae, which can represent a source of inspiration in the development and optimization of new artificial nano-optical systems. Here we present the main properties and applications of cutting-edge nanostructures starting from several examples of natural photonic architectures, up to the most recent technologies based on metallic and dielectric metasurfaces