Angular Sensitivity Research Articles

An ALMA view of SO and SO2 around oxygen-rich AGB stars

ABSTRACT We present and analyse SO and SO2, recently observed with high angular resolution and sensitivity in a spectral line survey with ALMA, for two oxygen-rich AGB stars: the low mass-loss rate R Dor and high mass-loss rate IK Tau. We analyse 8 lines of SO detected towards both stars, 78 lines of SO2 detected towards R Dor, and 52 lines of SO2 detected towards IK Tau. We detect several lines of 34SO, 33SO, and 34SO2 towards both stars, and tentatively S18O towards R Dor, and hence derive isotopic ratios for these species. The spatially resolved observations show us that the two sulphur oxides are co-located towards R Dor and trace out the same wind structures in the circumstellar envelope. Much of the emission is well reproduced with a Gaussian abundance distribution spatially centred on the star. Emission from the higher energy levels of SO and SO2 towards R Dor provides evidence in support of a rotating inner region of gas identified in earlier work. The new observations allow us to refine the abundance distribution of SO in IK Tau derived from prior observations with single antennas, and confirm that the distribution is shell like with the peak in the fractional abundance not centred on the star. The confirmation of different types of SO abundance distributions will help fine-tune chemical models and allows for an additional method to discriminate between low and high mass-loss rates for oxygen-rich AGB stars.

Tunable mid-infrared refractive index sensor with high angular sensitivity and ultra-high figure-of-merit based on Dirac semimetal

A tunable mid-infrared refractive index sensor consisting of bulk-Dirac-semimetal (BDS) and one-dimensional photonic crystals (1DPC) is proposed. This sensor has high angular sensitivity and ultra-high figure-of-merit (FOM), which is attributed to the optical Tamm states excited at the interfaces between BDS and 1DPC. Our numerical simulations show that the maximum value of the angular sensitivity and FOM of the sensor can reach up to 711.8°/RIU and 6001 RIU−1 respectively, which are much higher than those of the reported similar sensors. The simulations also demonstrate that the sensing performance can be adjusted by the Fermi energy and the structural parameters of the sensor. It is believed that, with the simple structure and the excellent performance, the proposed sensor has a broad application prospect in the field of biological detection.

Efficient and stable thin-film crystalline silicon solar cell by introducing rotation factor in surface square pillar array grating

To obtain efficient and stable light trapping, angle rotation is introduced to form rotated square pillar array grating (SPAG) solar cells. Compared with the unpatterned stack slab and the optimized uniform SPAG cells, the maximum short-circuit current ( J sc) of the optimized rotated SPAG is increased by 78.54% and 3.21%, respectively. Moreover, besides the fact that the low-incidence angular sensitivity of J sc could be maintained, J sc of the optimized rotated SPAG will always be larger than that of the optimized uniform SPAG at any incident angle. Furthermore, when the structural parameters of the subsquare pillar slightly deviate from the optimum, the absorption only deceases slightly as well, which indicates both a high structural tolerance and a stable absorption performance. In addition, our results show not only that the proposed rotated SPAG is promising to make light trapping efficient and stable but also that introducing rotation disorders is promising for other high-absorption pseudounordered surface structures.

Design and Analysis of a Next-Generation Wide Field-of-View Earth Radiation Budget Radiometer

Climate on Earth is determined by the Earth Radiation Budget (ERB), which quantifies the incoming and outgoing radiative energy fluxes. The ERB can be monitored by non-scanning wide field-of-view radiometers, or by scanning narrow field-of-view radiometers. We propose an enhanced design for the wide field-of-view radiometer, with as key features the use of a near-spherical cavity to obtain a uniform angular sensitivity and the integration of the shuttered electrical substitution principle, eliminating long term drifts of the radiometer and improving its time response. The target absolute accuracy is 1 W/m 2 and the target stability is 0.1 W/m 2 per decade for the measurement of the total outgoing Earth’s radiation. In order to increase the spatial resolution and to separate the total outgoing radiation into reflected Solar and emitted thermal radiation, we propose the joint use of the radiometer with wide field-of-view Shortwave (400–900 nm) and Longwave (8–14 μm) cameras. This paper presents the concept and design of the novel wide field-of-view radiometer, including simulations and analyses of its expected performance. We focus on mechanical design and the measurement characteristics based on optical and thermal analyses. In combination with the cameras, we obtain an estimated accuracy of 0.44 W/m 2 .

Concurrent Detection of Linear and Angular Motion using a Single-Mass 6-axis Piezoelectric IMU

This paper exhibits operating system and performances of a novel single-mass 6-axis Inertial Measurement Unit (IMU) using piezoelectric detection. The electronic processing circuitry for the concurrent detection of linear and angular motion is proposed. The IMU structure is based on the use of 2 rings, connected with eight electrodes, implemented on the top of a piezoelectric membrane used for both sense and drive modes. The four inner electrodes are used for components detection due to the direct piezoelectric effect, while the outer electrodes are used to generate the drive mode due to the reverse piezoelectric effect. Through finite element analysis, we show that linear accelerations generate an offset voltage on the sensing electrodes, while angular rates lead to a change in the amplitude of the initial AC signal caused by the drive mode. The present work represents an innovative design able to separate 6 motion data from signals using only 4 electrodes. The specific electronic circuitry for acceleration and angular rate data dissociation shows a very efficient method for signal separation since no leakage readout occurs in all six axes. Besides, other particular interest is that under no circumstances, angular outputs disturb or affect acceleration ones and vice versa. The evaluated sensitivities are 364 mV/g and 65.5 mV/g for in-plane and out-of-plane linear accelerations, respectively. Similarly, angular rates sensitivities are 2.59 mV/rad/s and 522 mV/rad/s.

Extraocular Vision in a Brittle Star Is Mediated by Chromatophore Movement in Response to Ambient Light.

Almost all animals can sense light, but only those with spatial vision can "see." Conventionally, this was restricted to animals possessing discrete visual organs (eyes), but extraocular vision could facilitate vision without eyes. Echinoderms form the focus of extraocular vision research [1-7], and the brittle star Ophiocoma wendtii, which exhibits light-responsive color change and shelter seeking, became a key species of interest [4, 8, 9]. Both O.wendtii and an apparently light-indifferent congeneric, O.pumila, possess an extensive network of r-opsin-reactive cells, but its function remains unclear [4]. We show that, although both species are strongly light averse, O.wendtii orients to stimuli necessitating spatial vision for detection, but O.pumila does not. However, O.wendtii's response disappears when chromatophores are contracted within the skeleton. Combining immunohistochemistry, histology, and synchrotron microtomography, we reconstructed models of photoreceptors in situ and extracted estimated angular apertures for O.wendtii and O.pumila. Angular sensitivity estimates, derived from these models, support the hypothesis that chromatophores constitute a screening mechanism in O.wendtii, providing sufficient resolving power to detect the stimuli. RNA sequencing (RNA-seq) identified opsin candidates in both species, including multiple r-opsins and transduction pathway constituents, congruent with immunohistochemistry and studies of other echinoderms [10, 11]. Finally, we note that differing body postures between the two species during experiments may reflect aspect of signal integration. This represents one of the most detailed mechanisms for extraocular vision yet proposed and draws interesting parallels with the only other confirmed extraocular visual system, that of some sea urchins, which also possess chromatophores [1].

A Ag–Au bimetallic nanograting surface plasmon resonance sensor based on a prism structure

A surface plasmon resonance (SPR) sensing structure based on gold–silver composite nanogratings and a prism is presented in this paper. Tuning the cycle, height and other relevant parameters of the silver–gold bimetallic nanometre grating sensor structure enabled the optimization of the plasma sensor. High sensitivity can be obtained using the transmission of the metal grating to excite a surface plasma. When a silver–gold bimetallic nanometre grating with the structural parameters of a silver film thickness of 20 nm, a gold nanometre grating height of 35 nm, and an incidence angle of 36°were used, ethanol solutions of different concentrations were detected. The numerical simulation shows that the angular sensitivity of the sensor reaches 342°/RIU (degrees per refractive index unit) with a FWHM (full width at half maximum) of 2.73°; in addition, good linearity is observed between the refractive index and resonance angle.

Chromatic information processing in the first optic ganglion of the butterfly Papilio xuthus

The butterfly Papilio xuthus has acute tetrachromatic color vision. Its eyes are furnished with eight spectral classes of photoreceptors, situated in three types of ommatidia, randomly distributed in the retinal mosaic. Here, we investigated early chromatic information processing by recording spectral, angular, and polarization sensitivities of photoreceptors and lamina monopolar cells (LMCs). We identified three spectral classes of LMCs whose spectral sensitivities corresponded to weighted linear sums of the spectral sensitivities of the photoreceptors present in the three ommatidial types. In ~ 25% of the photoreceptor axons, the spectral sensitivities differed from those recorded at the photoreceptor cell bodies. These axons showed spectral opponency, most likely mediated by chloride ion currents through histaminergic interphotoreceptor synapses. The opponency was most prominent in the processes of the long visual fibers in the medulla. We recalculated the wavelength discrimination function using the noise-limited opponency model to reflect the new spectral sensitivity data and found that it matched well with the behaviorally determined function. Our results reveal opponency at the first stage of Papilio’s visual system, indicating that spectral information is preprocessed with signals from photoreceptors within each ommatidium in the lamina, before being conveyed downstream by the long visual fibers and the LMCs.

Simple wedge plate based lateral shearing interferometry technique for coherent alignment of tiled grating assembly

A simple, sensitive and robust technique is proposed for coherent alignment of tiled grating assembly using wedge plate lateral shearing interferometry. In this technique, two thick glass wedge plates are used to generate interferograms from reflected and diffracted laser beams, from the tiled grating assembly under alignment. This single optical element based interferometric technique is easy to set up, insensitive to the vibrations and provides simultaneous information of both reference as well as error interference patterns, which are used to estimate the alignment errors. Performance of this technique was tested through alignment of two reflective gratings (size 140 mm X 120 mm), with an angular and translation sensitivities of less than 1 μrad and 50 nm respectively.

Beam angle optimization using angular dependency of range variation assessed via water equivalent path length (WEPL) calculation for head and neck proton therapy

PurposeTo investigate angular sensitivity of proton range variation due to anatomic change in patients and patient setup error via water equivalent path length (WEPL) calculations. MethodsProton range was estimated by calculating WEPL to the distal edge of target volume using planning CT (pCT) and weekly scatter-corrected cone-beam CT (CBCT) images of 11 head and neck patients. Range variation was estimated as the difference between the distal WEPLs calculated on pCT and scatter-corrected CBCT (cCBCT). This WEPL analysis was performed every five degrees ipsilaterally to the target. Statistics of the distal WEPL difference were calculated over the distal area to compare between different beam angles. Physician-defined contours were used for the WEPL calculation on both pCT and cCBCT, not considering local deformation of target volume. It was also tested if a couch kick (10°) can mitigate the range variation due to anatomic change and patient setup error. ResultsFor most of the patients considered, median, 75% quantile, and 95% quantile of the distal WEPL difference were largest for posterior oblique angles, indicating a higher chance of overdosing normal tissues at distal edge with these angles. Using a couch kick resulted in decrease in the WEPL difference for some posterior oblique angles. ConclusionsIt was demonstrated that the WEPL change has angular dependency for the cohort of head and neck cancer patients. Selecting beam configuration robust to anatomic change in patient and patient setup error may improve the treatment outcome of head and neck proton therapy.

Sensitivity Enhancement of Ag-ITO-TMDCs-Graphene Nanostructure Based on Surface Plasmon Resonance Biosensors

The novel configuration of surface plasmon resonance (SPR) based on Ag-indium tin oxide (ITO)-transition metal dichalcogenides (TMDCs)-graphene hybrid structures is proposed for highly sensitivity biosensor. When the WS2 and graphene are 3 layers and monolayer, respectively, the highest angular sensitivity up to 213.2°/RIU is obtained. Moreover, sensing media with different refractive indices can be detected by SPR biosensor. The phase sensitivity of 3.6 × 106 deg/RIU is obtained when the MoS2 and graphene are 3 layers and 4 layers, respectively. The highest phase sensitivity of the proposed SPR biosensor is about 2.79 times the Ag-ITO-MoS2-graphene structure and 4.16 times the Ag-ITO hybrid structure. The SPR biosensor has the advantages of high phase sensitivity, reusability, and reproducibility which make the sensor have the potential application prospects in medical diagnosis, environmental, and biochemical detection.

Absolute metrology method of the x-ray mirror with speckle scanning technique.

As an important characterization method for beamline optics, at-wavelength metrology technology based on wavefront measurements has been developed for many years. However, the previous studies on at-wavelength metrology of reflective mirrors is limited to the indirect method. So, the accurate surface information of the mirror under test would normally be inaccessible because of lack of experimental deconvolution between the mirror and any backgrounds from upstream optics. In this study, an absolute metrology method is developed based on the speckle scanning technique. Using this method, the surface profile of the mirror can be extracted exactly from the mixed information of the entire upstream beamline. At the same time, data acquisition time can also be significantly reduced by the processing algorithm introduced in this study without sacrificing the angular sensitivity.

Performance Enhancement of Surface Plasmon Resonance Biosensors Based on Noble Metals-Graphene-WS2 at Visible and Near-Infrared Wavelengths

In this paper, some biological sensors based on surface plasmon resonance are proposed at visible and near-infrared wavelengths and their performance is improved. The structure of these sensors includes metals, graphene, and 2D transition metal dichalcogenides (TMDCs). Metals such as gold, silver, and copper and a different number of graphene and WS2 layers are investigated for improving the performance of this sensor. The sensitivity of this sensor is studied at the three wavelengths of 633 nm, 660 nm, and 785 nm. In addition, by using the particle swarm optimization (PSO) method, reflectivity is optimized in terms of structural parameters. The best absorption belongs to gold with a reflectivity of 1.3383 × 10−5 (a.u). The results show that this structure which includes metals, graphene, and WS2 has a better performance in near-infrared wavelengths than in visible wavelengths. In this paper, the angular sensitivity and the figure of merit can reach as high as 336 (Deg/RIU) and 48.27 (1/RIU), respectively, as obtained by the optimized structure.

Quantum remote sensing of the angular rotation of structured objects

Based on two-photon entanglement, quantum remote sensing enables the measurement and detection to be done non-locally and remotely. However, little attention has been paid to implement a noncontact way to sense a real objects angular rotation, which is a key step towards the practical applications of precise measurements with entangled twisted photons. Here, we use photon pairs entangled in orbital angular momentum (OAM) to show that a real object's angular rotation can be measured non-locally. Our experiment reveals that the angular sensitivity of the object encoded with idler photons is proportional to the measured OAM values of signal photons. It suggests potential applications in developing a noncontact way for angle remote sensing of an object with customized measurement resolution. Moreover, this feature may provide potential application in sensing of some light-sensitive specimens when the entangled photon pairs, which have significantly different wavelengths, are used, such as one photon is infrared but the other one is visible.

A millipede compound eye mediating low-resolution vision

Millipedes are a species-rich and ancient arthropod clade which typically bear a pair of lateral compound eyes with a small number of large facets. To understand the visual tasks that underlie the evolution of millipede eyes, their spatial resolving performance is of key importance. We here investigate the spatial resolution of the millipede Cylindroiulus punctatus using behavioural assays. Individual animals were placed in the centre of a cylindrical arena under bright downwelling light, with dark stimuli of varying angular dimensions placed on the arena wall. We used continuous isoluminant stimuli based on a difference of Gaussians signal to test for orientation to the dark target via object taxis. Headings of individual animals were tracked in relation to the stimuli to determine whether the animals oriented towards the stimulus. We implemented a multilevel logistic regression model to identify the arc width of the stimulus that animals could resolve. We then modelled the angular sensitivity needed to identify this. We also related the visual performance to the 3D anatomy of the eye. We found that C. punctatus can resolve a stimulus of 56° period (sufficient to detect a 20° dark target). Assuming a contrast threshold of 10%, this requires a receptor acceptance angle of 72° or narrower. Spatial resolving power this low would only suffice for the simplest visual tasks, such as shelter-seeking.

Preliminary evaluation of dual-head Compton camera with Si/CZT material for breast cancer detection: Monte Carlo simulation study

Recently, the Compton camera imaging system has attracted attention in the field of nuclear medicine for breast cancer detection. Among the detector materials available for use with the Compton camera, Si and CZT can dramatically improve angular resolution and sensitivity. The purpose of this study was to design a Si/CZT Compton camera imaging system with Monte Carlo simulation using Geant4 Application for Tomographic Emission (GATE) and to evaluate its performance in breast cancer detection. The Compton camera was designed with a dual-head detection system using Si/CZT detector materials. Two breast cancer phantoms with masses in the medial region of the breast were used to evaluate the image reconstruction algorithm. The results confirmed the feasibility of an image reconstruction algorithm with our Compton camera imaging system using various evaluation factors, including the no-reference evaluation parameter. In conclusion, our results confirm the feasibility of a Compton camera imaging system for detection of breast cancer.

Discovering exotic AGN behind the Magellanic Clouds

AbstractThe nearby Magellanic Clouds system covers more than 200 square degrees on the sky. Much of it has been mapped across the electromagnetic spectrum at high angular resolution and sensitivity –X-ray (XMM-Newton), UV (UVIT), optical (SMASH), IR (VISTA, WISE, Spitzer, Herschel), radio (ATCA, ASKAP, MeerKAT). This provides us with an excellent dataset to explore the galaxy populations behind the stellar-rich Magellanic Clouds. We seek to identify and characterise AGN via machine learning algorithms on this exquisite data set. Our project focuses not on establishing sequences and distributions of common types of galaxies and active galactic nuclei (AGN), but seeks to identify extreme examples, building on the recent accidental discoveries of unique AGN behind the Magellanic Clouds.

All-Optical Quantum Sensor of the Magnetic Field Deflection

A method is proposed for precise measurement of the deflection of the magnetic field vector. This method does not require the use of artificially created magnetic fields; a scheme of an all-optical quantum sensor based on this method has been experimentally tested. The proposed method does not involve the use of radiofrequency field, since it is based on measuring the polarization properties of an oriented paramagnetic medium and does not use the phenomenon of magnetic resonance. However, the inclusion of a resonant radiofrequency field into the proposed scheme allows the information about the angle of the magnetic field vector to be supplemented with information about its module. The proposed method maintains operability and provides the same angular sensitivity of the order of tens of angular milliseconds in a wide range of magnetic fields, from hundreds of nT to hundreds of µT and above.

Design and Testing of a Miniaturized Five-Hole Fast Response Pressure Probe With Large Frequency Bandwidth and High Angular Sensitivity

Abstract A miniaturized five-hole fast response pressure probe is presented, and the methods for the aerodynamic design and performance characterization are explained in detail. The probe design is aimed for three-dimensional (3D) time-resolved measurements in turbomachinery flows, therefore requiring high frequency response and directional sensitivity. It features five encapsulated piezoresistive pressure transducers, recessed inside the probe hemispherical head. Theoretical and numerical analyses are carried out to estimate the dynamic response of the pressure tap line-cavity systems and to investigate unsteady effects that can influence the pressure readings. A prototype is manufactured and submitted to experimental tests that demonstrate performance in line with the theoretical and numerical predictions of the dynamic response: the natural frequency of the central and lateral taps extends to 200 and 25 kHz, respectively. An aerodynamic calibration is also performed at different Reynolds and Mach numbers. The probe geometry offers a good angular sensitivity in a ± 30 deg incidence range, while a frequency analysis reveals the presence of pressure oscillations related to vortex shedding at large angles of attack.

Development of a balloon-style pressure vessel gondola for balloon-borne emulsion gamma-ray telescopes

A gamma-ray telescope using nuclear emulsions allows observations of stellar objects in the 0.01–100 GeV energy region with high angular resolution, polarization sensitivity, and large aperture area. The Gamma-Ray Astro-Imager with Nuclear Emulsion (GRAINE) project is designed to enable high-precision observation of cosmic gamma rays through the use of balloon-borne emulsion telescopes. We have developed a balloon-style pressure vessel gondola for the GRAINE 2018 balloon-borne experiment. It enables us to maintain robust and vacuum-packed emulsion chambers even at balloon altitudes. The greater part of the vessel is made of membrane materials consisting of ultra-thin polyurethane-coated polyester fabric. It is lightweight and portable, and can be used to expand the mounting area of the detector, unlike mostly metal vessels. Moreover, the absorption of signal gamma rays and background gamma-ray production due to interactions between cosmic rays and the vessel can be minimized. The pressure vessel gondola, equipped with a 0.38-m2 emulsion telescope and other equipment, was launched on April 26, 2018. During the whole observation (17 h 21 m), the internal pressure was kept above 230 hPa. The GRAINE project will start scientific observation using enlarged telescopes and the pressure vessel gondola is planned to include an expansion of the mounting area of the detector to ∼10 m2 while following the design on the GRAINE 2018 model.