14 research outputs found
High-Q optomechanical GaAs nanomembranes
We present a simple fabrication method for the realization of suspended GaAs
nanomembranes for cavity quantum optomechanics experiments. GaAs nanomembranes
with an area of 1.36 mm by 1.91 mm and a thickness of 160 nm are obtained by
using a two-step selective wet-etching technique. The frequency noise spectrum
reveals several mechanical modes in the kilohertz regime with mechanical
Q-factors up to 2,300,000 at room temperature. The measured mechanical mode
profiles agree well with a taut rectangular drumhead model. Our results show
that GaAs nanomembranes provide a promising path towards quantum optical
control of massive nanomechanical systems.Comment: 3 pages, 3 figure
COVID-19 Detection from Respiratory Sounds with Hierarchical Spectrogram Transformers
Monitoring of prevalent airborne diseases such as COVID-19 characteristically
involves respiratory assessments. While auscultation is a mainstream method for
preliminary screening of disease symptoms, its utility is hampered by the need
for dedicated hospital visits. Remote monitoring based on recordings of
respiratory sounds on portable devices is a promising alternative, which can
assist in early assessment of COVID-19 that primarily affects the lower
respiratory tract. In this study, we introduce a novel deep learning approach
to distinguish patients with COVID-19 from healthy controls given audio
recordings of cough or breathing sounds. The proposed approach leverages a
novel hierarchical spectrogram transformer (HST) on spectrogram representations
of respiratory sounds. HST embodies self-attention mechanisms over local
windows in spectrograms, and window size is progressively grown over model
stages to capture local to global context. HST is compared against
state-of-the-art conventional and deep-learning baselines. Demonstrations on
crowd-sourced multi-national datasets indicate that HST outperforms competing
methods, achieving over 83% area under the receiver operating characteristic
curve (AUC) in detecting COVID-19 cases
Single-layer graphene on silicon nitride micromembrane resonators
Due to their exceptional mechanical and optical properties, dielectric
silicon nitride (SiN) micromembrane resonators have become the centerpiece of
many optomechanical experiments. Efficient capacitive coupling of the membrane
to an electrical system would facilitate exciting hybrid optoelectromechanical
devices. However, capacitive coupling of such dielectric membranes is rather
weak. Here we add a single layer of graphene on SiN micromembranes and compare
electromechanical coupling and mechanical properties to bare dielectric
membranes and to membranes metallized with an aluminium layer. The
electrostatic coupling of graphene coated membranes is found to be equal to a
perfectly conductive membrane. Our results show that a single layer of graphene
substantially enhances the electromechanical capacitive coupling without
significantly adding mass, decreasing the superior mechanical quality factor or
affecting the optical properties of SiN micromembrane resonators
PDTB-16. ASSESSING THE FUNCTION OF CHROMATIN MODIFYING ENZYMES IN MEDULLOBLASTOMA
Medulloblastoma is the most common pediatric brain tumor that arises during infancy and childhood and is a major cause of cancer related-morbidity and mortality in children. Recently, medulloblastomas are described as four distinct molecular subgroups (Wnt, sonic hedgehog, Group 3 and Group 4), which have distinct transcriptional, cytogenetic, and mutational spectra
Optical Sensing Device through Monitoring Cut-off Wavelength of Asymmetric Transmission
20th International Conference on Transparent Optical Networks, ICTON (2018 ; Bucharest, Romani)In this study, we propose and design a subwavelength optical sensing device to detect material refractive index through metallic structure providing asymmetric transmission behavior. The proposed metallic structure consists of trapezoidal aluminum arrays embedded in Polydimethylsiloxane (PDMS) substrate. We show that a spectral band, where asymmetric transmission takes place shifts depending on the refractive index of the materials which are placed on top of the structure. In this way, optical sensing device can be designed to operate at visible and near infrared regions using the asymmetric transmission effect. The physical concept is based on Wood Rayleigh anomaly. Different sensing applications can be considered to integrate the proposed idea with the optical technologies