Design of a high-performance optical tweezer for nanoparticle trapping

Integrated optical nanotweezers offer a novel paradigm for optical trapping, as their ability to confine light at the nanoscale leads to extremely high gradient forces. To date, nanotweezers have been realized either as photonic crystal or as plasmonic nanocavities. Here, we propose a nanotweezer device based on a hybrid photonic/plasmonic cavity with the goal of achieving a very high quality factor-to-mode volume (Q/V) ratio. The structure includes a 1D photonic crystal dielectric cavity vertically coupled to a bowtie nanoantenna. A very high Q/V ~ 107 (λ/n)−3 with a resonance transmission T = 29 % at λR = 1381.1 nm has been calculated by 3D finite element method, affording strong light–matter interaction and making the hybrid cavity suitable for optical trapping. A maximum optical force F = −4.4 pN, high values of stability S = 30 and optical stiffness k = 90 pN/nm W have been obtained with an input power Pin = 1 mW, for a polystyrene nanoparticle with a diameter of 40 nm. This performance confirms the high efficiency of the optical nanotweezer and its potential for trapping living matter at the nanoscale, such as viruses, proteins and small bacteria

Theoretical investigation on the scale factor of a triple ring cavity to be used in frequency sensitive resonant gyroscopes

In this paper we study a multi-ring resonant structure including three evanescently coupled ring resonators (named triple ring resonator,TRR), with different ring radii and coupling coefficients, and coupled to two bus waveguides. The potential application of a TRR as a rotationsensor is analyzed and its advantages over a single ring resonator (SRR) under rotation conditions are also highlighted. When the coupledrings have different size and their inter-ring coupling coefficients are lower than the ring-bus coupling coefficients, the resonance frequencydifference between two counter-propagating beams induced by rotation is enhanced with respect to that of a single ring resonator (SRR)with the same footprint. The scale factor of the rotating TRR, which depends on the structural parameters (i.e. inter-ring and ring-buscoupling coefficients, lengths of the rings, overall propagation loss within the rings), is up to 1.88 times the value of the scale factor of aSRR, which depends only on the ring radius, by assuming that the waveguide structure in both configurations is the same. This promisingnumerical achievement results in a reduction of the sensor footprint of about two times, with respect to a single ring with the same scalefactor. The results obtained may be useful to define new configurations of frequency sensitive optical gyros in low-loss technology, havinga small volume. In fact, by properly choosing the structural parameters, the spectral response of the TRR is forced to assume a shape moresensitive to the resonant frequency shift due to the rotation with respect to that one of a SRR

Surface plasmon resonance-enhanced light interaction in an integrated ormocomp nanowire

An integrated ormocomp nanowire coated with gold metal layer is proposed and its optical characteristics with the effect of surface plasmon resonance (SPR) are studied. The integrated rib-like nanowire has a trapezoidal shape with sidewall angles of 75°. It is coated with 50 nm gold layer to introduce the SPR and enhance the evanescent field in the sensing region located at the dielectric/metal interface. The possible field modes, the normalized power confinement, and the SPR peak position of the nanowire are studied over the wavelength and the metal thickness by using the full-vectorial H-field FEM in quasi-TM mode. The attenuation coefficient of the nanowire, the SPR peak wavelength, and the wavelength shift is experimentally extracted for three different cladding materials. The redshift of the supermode coupling between the dielectric mode and the anti-symmetric supermode is observed with the higher cladding-index and larger metal thickness. The improvement of the power confinement in the sensing region with the SPR effect is ten times (10×) better than a previous similar study

Design of a high-performance optical tweezer for nanoparticle trapping

Integrated optical nanotweezers offer a novel paradigm for optical trapping, as their ability to confine light at the nanoscale leads to extremely high gradient forces. To date, nanotweezers have been realized either as photonic crystal or as plasmonic nanocavities. Here, we propose a nanotweezer device based on a hybrid photonic/plasmonic cavity with the goal of achieving a very high quality factor-to-mode volume (Q/V) ratio. The structure includes a 1D photonic crystal dielectric cavity vertically coupled to a bowtie nanoantenna. A very high Q/V ~ 107 (λ/n)−3 with a resonance transmission T = 29 % at λR = 1381.1 nm has been calculated by 3D finite element method, affording strong light–matter interaction and making the hybrid cavity suitable for optical trapping. A maximum optical force F = −4.4 pN, high values of stability S = 30 and optical stiffness k = 90 pN/nm W have been obtained with an input power Pin = 1 mW, for a polystyrene nanoparticle with a diameter of 40 nm. This performance confirms the high efficiency of the optical nanotweezer and its potential for trapping living matter at the nanoscale, such as viruses, proteins and small bacteria

Measuring the Impact of Health Education Modules in Cameroon, West Africa

Each year, more than two million people die from diarrhea-associated diseases. Although there is a global need for safe drinking water, culturally appropriate health teaching is essential to behavior change. This study evaluated the impact of a health education program in a small rural community in Cameroon. Flash cards and a modified version of the CDC-KPC 2000 survey were used to collect data in 57 homes. Children who lived in households with working Manz BioSand filters were less likely to have had diarrhea in the 2 weeks prior to the evaluation. There remained a gap between health knowledge and healthy behaviors for hand hygiene and malaria prevention. This gap was significant in the diarrheal treatment (McNemar’s test, p \u3c .000). The interdisciplinary program and 7-year time frame were crucial to sustainability. Faculty and students learned the importance of pairing service learning and research that respect local cultures in fostering a healthier global community

High-Sensitivity Biosensing with Silicon Photonic Ring Resonators

Silicon ring resonators have emerged as a very promising technology in the field of medical diagnostics, with many applications for the highly sensitive detection of analytes associated with pathological conditions. In our work, we report on the design, fabrication, and preliminary characterization of miniaturized silicon-on-insulator integrated optical ring resonators, showcasing their capability to detect biomarkers with high sensitivity. The results contribute to the advancement of silicon-based optical biosensors and lay the basis for future developments in the field of medical diagnostics

Long-term outcome of patients with localized aggressive non-Hodgkin lymphoma treated with ProMECE-CytaBOM plus involved-field radiation therapy: a study of the Gruppo Italiano Studio Linfomi.

We conducted a retrospective analysis on 168 adult patients with newly diagnosed, limited-stage (I and II) diffuse large B-cell lymphoma (DLBCL) treated from 1988 to 2004 with PROMECE-CYTABOM (P-C) plus involved-field radiation therapy (IF-RT). At the end of P-C, the overall response rate was 92%. Radiotherapy (RT) was delivered to 84% of cases. With a median follow-up of 95 months, overall survival (OS), relapse free survival (RFS), and failure free survival at 5 and 10 years was 84% and 77%, 81% and 75%, 71% and 67%, respectively. Age (>60 years, p = 0.002), serum albumin (<3.5 g/dL; p = 0.015), and RT (p < 0.001) were independent predictors of OS. For patients in complete remission the administration of RT didn't improve both RFS and OS. This study confirms that patients with localized aggressive lymphoma have a high chance of cure with anthracycline containing regimens. Though the regimen used to treat these patients does not contain rituximab, results are considered excellent both in terms of efficacy and safety

Bus service quality prediction and attribute ranking: a neural network approach

Evaluation of service quality (SQ) based on user preferences has become a primary concern for the transportation authorities. The most significant attributes of public transportation systems are revealed through service quality analysis. This information serves as valuable input in constantly updating the quality of public transportation services. An appropriate tool is therefore mandatory in this regard. This paper represents a comparative study on the bus SQ prediction capabilities of three effective Artificial Neural Network (ANN) approaches, namely: Generalized Regression Neural Network (GRNN), Probabilistic Neural Network (PNN) and Pattern Recognition Neural Network (PRNN). To calibrate the parameters of the developed ANN models, data on users’ perception toward bus services of Dhaka city, Bangladesh, have been used. Taking the public opinion as baseline, GRNN and PNN have proven to be better prediction models since both have achieved higher accuracy compared to PRNN. Among 22 selected SQ attributes, the most significant attributes have been ranked according to their influence on the users’ decision making process. According to the GRNN and PNN models, punctuality and reliability, service frequency, seat availability and commuting experience are found to be the most significant attributes, which support the user-stated preferences