Spatial Pixel Research Articles

Overview on Spectral Line Source Finding and Visualisation

AbstractHere I will outline successes and challenges for finding spectral line sources in large data cubes that are dominated by noise. This is a 3D challenge as the sources we wish to catalog are spread over several spatial pixels and spectral channels. While 2D searches can be applied, e.g. channel by channel, optimal searches take into account the 3-dimensional nature of the sources. In this overview I will focus on Hi 21-cm spectral line source detection in extragalactic surveys, in particular HIPASS, the Hi Parkes All-Sky Survey and WALLABY, the ASKAP Hi All-Sky Survey. I use the original HIPASS data to highlight the diversity of spectral signatures of galaxies and gaseous clouds, both in emission and absorption. Among others, I report the discovery of a 680 km s−1 wide Hi absorption trough in the megamaser galaxy NGC 5793. Issues such as source confusion and baseline ripples, typically encountered in single-dish Hi surveys, are much reduced in interferometric Hi surveys. Several large Hi emission and absorption surveys are planned for the Australian Square Kilometre Array Pathfinder (ASKAP): here we focus on WALLABY, the 21-cm survey of the sky (δ < + 30°; z < 0.26) which will take about one year of observing time with ASKAP. Novel phased array feeds (‘radio cameras’) will provide 30 deg2 instantaneous field-of-view. WALLABY is expected to detect more than 500 000 galaxies, unveil their large-scale structures and cosmological parameters, detect their extended, low-surface-brightness disks as well as gas streams and filaments between galaxies. It is a precursor for future Hi surveys with SKA Phase I and II, exploring galaxy formation and evolution. The compilation of highly reliable and complete source catalogs will require sophisticated source-finding algorithms as well as accurate source parametrisation.

High-Density Single Particle Tracking on the Plasma Membrane using High-Speed Hyperspectral Imaging

We have developed a high-speed, line-scanning hyperspectral microscope (HSM) capable of acquiring 30 frames per second with 128 spectral channels per spatial pixel. The HSM allows simultaneous single particle tracking (SPT) of up to eight spectrally distinct quantum dots (QDs), improving the useable labeling density in SPT by nearly an order of magnitude as compared to single-color SPT. In addition, HSM imaging allows the spectral uniqueness of QDs within the same spectral family to be used for resolving ambiguities in trajectory reconstruction.We describe our physical instrument as well as the required analysis for hyperspectral SPT of multi-color QDs. Our analysis extends multi-emitter fitting previously developed in our lab for accurate localization of single fluorophores at higher density [Huang, F. et al., Biomed Opt Express 2011;2(5):1377] to three dimensions (x, y, lambda). Using a finite pixel 3D Gaussian estimate for their combined point spread function and spectral features, simultaneous spatial localization and spectral identification of QDs is achieved. The algorithm is implemented in CUDA to take advantage of parallel processing of GPUs. Trajectories are constructed with spatial and spectral localization information using a cost matrix approach for global optimization. Finally, squared displacements from single particle trajectories are used to build viscosity maps of the plasma membrane.We demonstrate high-density SPT by performing viscosity mapping of the plasma membrane, which provides important spatial and temporal information about local membrane effects on receptor mobility. We have applied HSM viscosity mapping to investigate the influence of the membrane environment on QD-IgE bound to FceRI. Changes in mobility and confinement of FceRI due to receptor crosslinking (receptor aggregation and signal initiation), latrunculin-beta treatment (induces actin depolymerization), and PMA treatment (induces actin polymerization) are examined.

An Edge Detection Method in DCT Domain

This paper proposes a new edge detection method in DCT domain for compressed images. Instead of detection with spatial pixels, we generate the gradient patterns of DCT basis images with detection operators. The quantized coefficients are used to calculate the edge maps, which avoids the procedure of inverse quantization. It is shown that the proposed scheme leads to not only good edges but also computation speedup.

Q-type非球面技术在超短焦全景镜头设计中的应用

The Q-type novel aspherical polynomials and its advantages are introduced in the aspect of algorithm,fabrication and manufacturing relative to the traditional aspherical polynomial-based aspheres.The Q-type formulation is applied to design a panoramic lens based on the relationship of super short-focus panoramic lens′ focus and resolution.The designed panoramic lens′ focus is 0.657 mm and ratio of focus and image height is less than 0.184,which includes 4 aspheric surface.This result shows that the spatial pixel of scenic circle area with half vertical field 45°～90° is up to 1.163 7 mm/(°),and the modulation transformation function is greater than 0.3 at the spatial frequency of 227 lp/mm.The result demonstrates the Q-type formulations is certain advantages in super short-focus panoramic lens.

Multicolor Super-Resolution Imaging using a Laser Line Scanning Hyperspectral Microscope

Single-molecule super-resolution imaging techniques have proven to be successful in observing cellular structures with a resolution below the diffraction limit. However, these experiments often restrict observations to a region of shallow z-depth near the cover slip due to TIRF imaging or else suffer from high backgrounds due to wide field excitation. Confocal microscopy, which offers good background rejection, is prohibitively slow and cannot be used effectively for single-molecule localization based super-resolution. Here we introduce a new method that uses a fast, laser line scanning system that can be used to image a z-section anywhere within a cell and is not restricted to regions near the cover slip. The line scanning system allows a trade-off between acquisition speed and background rejection. Emission light is passed through a prism spectrometer, and a complete spectrum is collected for each spatial pixel. We exploit this hyperspectral emission path to make simultaneous measurements of multiple fluorophore species in the same sample.

Three-dimensional Binocular Holographic Display Using Liquid Crystal Shutter

We present a novel approach to the holographic three-dimensional display using a liquid crystal shutter for binocular display applications. One of the difficult problems in implementing a binocular holographic three-dimensional display is the extremely narrow viewing angle. This problem is attributed to the spatial light modulator pixel number which restricts the maximum spatial bandwidth of the spatial light modulator. In our proposed method, a beam splitter and liquid crystal shutter are used to present two holograms of a three-dimensional scene to the corresponding eyes. The combination of holographic display and liquid crystal shutter can overcome the problem of the extremely narrow viewing angle, presenting threedimensional images to both eyes with correct accommodation depth cues.

Time series hyperspectral chemical imaging data: Challenges, solutions and applications

Hyperspectral chemical imaging (HCI) integrates imaging and spectroscopy resulting in three-dimensional data structures, hypercubes, with two spatial and one wavelength dimension. Each spatial image pixel in a hypercube contains a spectrum with >100 datapoints. While HCI facilitates enhanced monitoring of multi-component systems; time series HCI offers the possibility of a more comprehensive understanding of the dynamics of such systems and processes. This implies a need for modeling strategies that can cope with the large multivariate data structures generated in time series HCI experiments. The challenges posed by such data include dimensionality reduction, temporal morphological variation of samples and instrumental drift. This article presents potential solutions to these challenges, including multiway analysis, object tracking, multivariate curve resolution and non-linear regression. Several real world examples of time series HCI data are presented to illustrate the proposed solutions.

A stringent upper limit to SO2in the Martian atmosphere

Surfur-bearing molecules have been found at the surface of Mars by the Viking lander, the Spirit and Opportunity rovers, and the OMEGA infrared spectrometer aboard Mars Express. However, no gaseous sulfur-bearing species have ever been detected in the Martian atmosphere. We search for SO2 signatures in the thermal spectrum of Mars at 7.4 μm using the Texas Echelon Cross Echelle Spectrograph (TEXES) at the NASA Infrared Telescope Facility (IRTF). Data were obtained on Oct. 12, 2009 (Ls = 353 ◦ ), in the 1350–1360 cm −1 range, with a spatial resolution of 1 arcsec (after convolution over three pixels along the N-S axis and two steps along the E-W axis) and a resolving power of 80 000. To improve the signal-to-noise ratio (S/N), we co-added the Martian spectrum around the positions of nine selected SO2 transitions with a high S/N and no telluric contamination. From a mean spectrum, averaged over 35 pixels in the region of maximum continuum, we infer a 2σ upper limit of 0.3 ppb to the SO2 mixing ratio, assuming that our instrumental errors are combined according to Gaussian statistics. Our upper limit is three times lower than the upper limit derived by Krasnopolsky (2005, Icarus, 178, 487), who used the same technique on previous TEXES data. In addition, we derive an upper limit of 2 ppb at each spatial pixel of the region observed by TEXES, which covers the longitude ranges 50 E–170 E for latitudes above 30 N, 100 E–170 E for latitudes between 0 and 30 N, and 110 E–170 E for latitudes between 15 S and 0. The non-detection of localized SO2 sources in the observed area is consistent with a homogeneous distribution being expected around equinox for noncondensible species with a lifetime longer than the global mixing time. In view of the typically large SO2/CH4 ratio observed in terrestrial volcanoes, and assuming a comparable volcanic composition for Mars and the Earth, our result reaffirms that a volcanic origin is unlikely for any methane in the Martian atmosphere.

The impact of image and class structure upon sub-pixel mapping accuracy using the pixel-swapping algorithm

A series of tests assess the impact of image and class structure within input imagery upon the accuracy of outputs from the pixel-swapping algorithm (PSA) to better assess the viability of this sub-pixel mapping algorithm to spatially locate class proportions and improve soft classification accuracies. Simulated maps with known spatial autocorrelation, class proportion and mixed pixel percentages are sub-pixel mapped at varying zoom factors using the PSA and accuracies measured. Block majority filtering (BMF) of input images is an experimental accuracy control. Results quantify PSA accuracies compared to the BMF based on the interrelationship between spatial autocorrelation, class proportions, zoom factor and mixed pixel quantities. Findings, while validating the known positive correlation between spatial autocorrelation and PSA accuracy, demonstrate class proportion difference and mixed pixel quantities to be positively and negatively related to PSA accuracy, respectively. Class proportion affects PSA accuracy to a greater degree on maps exhibiting low spatial autocorrelation levels versus maps with high spatial autocorrelation levels. Traditional accuracy measures, such as overall accuracy, are shown to overestimate the true performance of the PSA. The difference in overall accuracy of the PSA between all map pixels and within mixed map pixels alone can be over 20%. Overall, in general, the PSA accurately sub-pixel mapped input images with an approximate minimum level of spatial autocorrelation at a Moran's I of 0.63, a maximum of 30% of mixed pixels relative to entire image pixels, a difference in class proportions greater than 40% and at zoom factors below 10.

Adaptive Fuzzy Filtering for Artifact Reduction in Compressed images and videos

In this paper, spatial neighboring pixels are used to deal with blocking and ringing artifacts while temporal neighboring pixels are utilized to remove mosquito and flickering artifacts. To avoid the blurring effect of linear filters, a fuzzy filter is implemented. Fuzzy filter is a specific case of bilateral filters [15], [16]. Fuzzy filters help denoising the artifacts while retaining the sharpness of real edges. In image and video compression, the artifacts such as blocking or ringing artifacts are spatially directional and flickering artifacts are temporally directional. For compressed video sequences, the motion compensated spatiotemporal filter (MCSTF) is applied to intraframe and interframe pixels to deal with both spatial and temporal artifacts. In this work, a novel fuzzy filter is proposed to adapt to the pixel’s activity and directions between the pixel of interest and its surrounding pixels.

Construction of computer-aided simulation system for carpal anatomy

Objective To design and construct a 3-dimensional carpal anatomy computer-aided simulation system (3DCACAS) which can realize three-dimensional segmentation and anatomical dissection of the carpal, diagnose and analysis, surgical design, outcome evaluation and 3D measurement. Methods The software ran on Windows XP operating system, was developed with Microsoft Visual C + + platform and was in virtue of OpenGL. In the system, optimized Marching Cube(MC)was used in 3D reconstruction. 3D display and control was designed by OpenGL. 3D arbitrary region segmentation was realized by spatial segmentation and pixels superimposition was used in 3D measurement. Results A computer-aided surgical simulation system for carpal anatomy was developed. Its functions included 3D reality display of images, 3D segmentation, 3D measurement and computer-aided surgical design of internal fixation of the carpus. Conclusion The construction of 3DCACAS provides a reference for studying carpal kinematics, diagnosing pathological changes of carpal ailment and planning surgeries around the carpus. Key words: Carpal bones; Imaging,three-dimensional; Kinematics

Phishing web image segmentation based on improving spectral clustering

This paper proposes a novel phishing web image segmentation algorithm which based on improving spectral clustering. Firstly, we construct a set of points which are composed of spatial location pixels and gray levels from a given image. Secondly, the data is clustered in spectral space of the similar matrix of the set points, in order to avoid the drawbacks of K-means algorithm in the conventional spectral clustering method that is sensitive to initial clustering centroids and convergence to local optimal solution, we introduce the clone operator, Cauthy mutation to enlarge the scale of clustering centers, quantum-inspired evolutionary algorithm to find the global optimal clustering centroids. Compared with phishing web image segmentation based on K-means, experimental results show that the segmentation performance of our method gains much improvement. Moreover, our method can convergence to global optimal solution and is better in accuracy of phishing web segmentation.

Topoclimatic Modeling of Thermopluviometric Variables for the Bío Bío and La Araucanía Regions, Chile

Climatic mapping in the Bio Bio and La Araucania Regions of Chile is primarily in analog form (paper) and delineation of contours, making it unsuitable for digital handling by geographic information systems (GIS). Therefore, in this study, topoclimatic models were created and spatially represented to explain the spatial and temporal variation of monthly mean temperature and precipitation, as a function of variability and singularity of the physiographic characteristics of the Bio Bio and La Araucania Regions. The physiographic factors considered were latitude, longitude, altitude, aspect and distance to coastline. To elaborate equations, data from thermopluviometric stations of the study area were compiled and systematized. These stations were standardized to a common reference system in order to locate them in space and obtain the value of physiographic factors for each station. With this information, the equations were calculated using a stepwise (backward) regression procedure, with a statistical significance of 95%. The regression equations obtained for mean monthly and annual temperature and precipitation were all significant (P ≤ 0.05) and had R 2 > 0.7. These equations were applied to the rest of the study area in raster format using a GIS, which yields a spatially continuous cartography. The spatial resolution or pixel size was 90 m, which allows carrying out research at a 1:100 000 scale, commonly used at the regional or provincial level.

Clutter suppression algorithm based on bidirectional local binary pattern for moving point target detection in infrared image sequences

A clutter suppression algorithm called the rectification filter with indications of bidirectional local binary patterns (BDLBP-RF) is proposed as a resolution to the problem of detecting dim targets in infrared (IR) image sequences. First of all, a local binary pattern (LBP) operator with properties of grayscale and rotation invariance is introduced in the application of clutter suppression. Each pixel in the image is estimated by its spatial neighbor pixels and the corresponding LBPs in prior and posterior frames. The approach proposed is based on a spatiotemporal process, in which interframe and intraframe properties of the IR image sequence are both taken into account. The method is evaluated by the comparative experiments, and the LBP operator's optimum values of radius and number of neighbors are discussed. The results of the experiment prove that BDLBP-RF has excellent performance and stability in clutter suppression under various situations. The target point in images processed by our approach received high signal-to-clutter ratio gain, and the detectability of the target is enhanced.

Research on the Splitting Measurement Method of Space Position in Three-Dimensional Field

A research on measurement method of space position in three-dimensional field was demonstrated in this paper. According to the basic methods and principles of three-dimensional spatial position measurement, optical path of splitting design was used to divide an object point, through the red and green filters, into two beams of red and green, and then, through flat mirror, rectangular prism, cube prism and other optical design, it imaged on the same CCD camera film. Standard mesh was used to determine the relationship between two different spatial coordinates and the spatial pixel coordinates in the measurement space, and then the calibration relationship between object point coordinates and pixel coordinates were determined. This calibration relationship clear the error caused by the method of measurement and the measurement system. Through the determination algorithm of spatial location in three-dimensional field, the two corresponding lines of space was obtained, and its point of intersection is the spatial coordinate.

Origin of the hot gas in low-mass protostars

'Water in Star-forming regions with Herschel' (WISH) is a Herschel Key Programme aimed at understanding the physical and chemical structure of young stellar objects (YSOs) with a focus on water and related species. The low-mass protostar HH 46 was observed with the Photodetector Array Camera and Spectrometer (PACS) on the Herschel Space Observatory to measure emission in H2O, CO, OH, [OI], and [CII] lines located between 63 and 186 um. The excitation and spatial distribution of emission can disentangle the different heating mechanisms of YSOs, with better spatial resolution and sensitivity than previously possible. Far-IR line emission is detected at the position of the protostar and along the outflow axis. The OH emission is concentrated at the central position, CO emission is bright at the central position and along the outflow, and H2O emission is concentrated in the outflow. In addition, [OI] emission is seen in low-velocity gas, assumed to be related to the envelope, and is also seen shifted up to 170 km/s in both the red- and blue-shifted jets. Envelope models are constructed based on previous observational constraints. They indicate that passive heating of a spherical envelope by the protostellar luminosity cannot explain the high-excitation molecular gas detected with PACS, including CO lines with upper levels at >2500 K above the ground state. Instead, warm CO and H2O emission is probably produced in the walls of an outflow-carved cavity in the envelope, which are heated by UV photons and non-dissociative C-type shocks. The bright OH and [OI] emission is attributed to J-type shocks in dense gas close to the protostar. In the scenario described here, the combined cooling by far-IR lines within the central spatial pixel is estimated to be 2 \times 10-2 L_sun, with 60-80% attributed to J- and C-type shocks produced by interactions between the jet and the envelope.

Synthetic H i observations of a simulated spiral galaxy

Using the Torus radiative transfer code we produce synthetic observations of the 21 cm neutral hydrogen line from an SPH simulation of a spiral galaxy. The SPH representation of the galaxy is mapped onto an AMR grid, and a ray tracing method is used to calculate 21 cm line emission for lines of sight through the AMR grid in different velocity channels and spatial pixels. The result is a synthetic spectral cube which can be directly compared to real observations. We compare our synthetic spectral cubes to observations of M31 and M33 and find good agreement, whereby increasing velocity channels trace the main disc of the galaxy. The synthetic data also show kinks in the velocity across the spiral arms, evidence of non-circular velocities. These are still present even when we blur our data to a similar resolution as the observations, but largely absent in M31 and M33, indicating those galaxies do not contain significant spiral shocks. Thus the detailed velocity structure of our maps better represent previous observations of the grand design spiral M81.

FTIR spectroscopy with a focal plane array detector: A novel tool to monitor the spatial OH-defect distribution in single crystals applied to synthetic enstatite

Single crystals of pure enstatite (Mg2Si2O6) were synthesized under water-saturated conditions at 6 GPa and 1250 °C and variable silica activity. Run products were investigated using a novel technology: a FTIR spectrometer equipped with a focal plane array detector enabling IR-imaging with a spatial pixel resolution of 2.7 μm. IR spectra within the OH-absorption region show strong pleochroic behavior: absorption bands at 3687 and 3592 cm−1 show strongest absorptions for E||nβ, whereas absorption bands at 3362 and 3067 cm−1 show strongest absorptions for E||nγ. Furthermore, absorption bands are sensitive to the silica activity—the ratio of the integral absorbance of the absorption bands at 3687 and 3592 cm−1 to the absorption bands at 3362 and 3067 cm−1 increases with increasing Mg/Si-ratio of the bulk charge. The most probable interpretation is an assignment of the high-energy absorption bands to tetrahedral (T-site) defects caused by a lower availability of Si and the low-energy absorption bands to octahedral (M-site) defects caused by a lower availability of Mg. All crystals show an internal zonation pattern with an increasing T-site to M-site defect ratio from core to rim, which is interpreted to be caused by changing silica-activity and T during the experiments. The defect ratio and the zonation pattern are applied as a monitor of crystal growth conditions.

The nano-morphological relationships between apatite crystals and collagen fibrils in ivory dentine

In this work, analytical transmission electron microscopy (TEM) was used to study the nanostructure of mineralised ivory dentine, in order to gain a clearer understanding of the relationship between the organic (collagen fibrils) and inorganic (calcium phosphate apatite crystals) components. Thin sections prepared by both focused ion beam (FIB) milling and ultramicrotomy, in the longitudinal and transverse planes, were investigated using electron energy-loss spectroscopy (EELS) in a monochromated field-emission gun scanning TEM (FEI Titan 80-300 FEGSTEM). Both low- and core-loss spectroscopy were used in the investigation, and the signals from phosphorous, carbon, calcium, nitrogen and oxygen were studied in detail. A combination of HAADF (high-angle annular dark-field)-STEM imaging and EELS analysis was used for simultaneous acquisition of both spatial and spectral information pixel by pixel (spectrum imaging). Across the collagen D banding in longitudinal sections, the relative thickness of the bright bands was significantly higher than that of the dark bands. Core-loss spectroscopy showed that the bright bands were richer in apatite than the dark bands. However, no ELNES variation was observed across the D banding. In transverse sections, significant changes in the carbon edge fine structure were observed at the interface between the extra- and intra-fibrillar regions.

Super-resolved Imaging based upon spatial depolarization of light

In this paper we present a new approach allowing the surpassing of the diffraction based limitation for the achievable resolution provided by imaging systems. It is based on an encoding-decoding process of various spatial pixels or regions in the field of view of the imaged object by orthogonal and differently time varying polarization states. The reconstruction of the original spatial information is obtained by applying a decoding process in a way similar to the encoding one. Although all the spatial information is summed and mixed together by the system, the decoding provides super resolved imaging since in every spatial position the undesired spatial information having time varying polarization dependence, that is uncorrelated to the decoding sequence applied on that specific spatial position, is averaged to zero and, on the other hand, the information which corresponds to that specific spatial region is being reinforced. The proposed approach can be used not only for super resolved imaging but also for imaging module that maintains the same spatial resolution while providing enlarged field of view