scholarly journals Receive Beam-Steering and Clutter Reduction for Imaging the Speed-of-Sound Inside the Carotid Artery

2018 ◽  
Vol 4 (12) ◽  
pp. 145 ◽  
Author(s):  
Maju Kuriakose ◽  
Jan-Willem Muller ◽  
Patrick Stähli ◽  
Martin Frenz ◽  
Michael Jaeger
Keyword(s):  
Carotid Artery ◽  
Speed Of Sound ◽  
Beam Steering ◽  
Phase Tracking ◽  
Spatially Resolved ◽  
Acquisition Speed ◽  
Phase Variations ◽  
Diagnostic Ultrasonography ◽  
The One ◽  
Clutter Reduction

Handheld imaging of the tissue’s speed-of-sound (SoS) is a promising multimodal addition to diagnostic ultrasonography for the examination of tissue composition. Computed ultrasound tomography in echo mode (CUTE) probes the spatial distribution of SoS, conventionally via scanning the tissue under a varying angle of ultrasound transmission, and quantifying—in a spatially resolved way—phase variations of the beamformed echoes. So far, this technique is not applicable to imaging the lumen of vessels, where blood flow and tissue clutter inhibit phase tracking of the blood echoes. With the goal to enable the assessment of atherosclerotic plaque composition inside the carotid artery, we propose two modifications to CUTE: (a) use receive (Rx) beam-steering as opposed to transmit (Tx) beam-steering to increase acquisition speed and to reduce flow-related phase decorrelation, and (b) conduct pairwise subtraction of data obtained from repetitions of the scan sequence, to highlight blood echoes relative to static echo clutter and thus enable the phase tracking of blood echoes. These modifications were tested in a phantom study, where the echogenicity of the vessel lumen was chosen to be similar to the one of the background medium, which allows a direct comparison of SoS images obtained with the different techniques. Our results demonstrate that the combination of Rx-steering with the subtraction technique results in an SoS image of the same quality as obtained with conventional Tx-steering. Together with the improved acquisition speed, this makes the proposed technique a key step towards successful imaging of the SoS inside the carotid artery.

scholarly journals A Review on the Development of Rotman Lens Antenna

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Shruti Vashist ◽  
M. K. Soni ◽  
P. K. Singhal
Keyword(s):  
High Performance ◽  
Beam Steering ◽  
Phase Error ◽  
Antenna System ◽  
Surveillance Systems ◽  
Electronic Warfare ◽  
Design Concepts ◽  
Low Profile ◽  
True Time ◽  
The One

Rotman lenses are the beguiling devices used by the beamforming networks (BFNs). These lenses are generally used in the radar surveillance systems to see targets in multiple directions due to its multibeam capability without physically moving the antenna system. Now a days these lenses are being integrated into many radars and electronic warfare systems around the world. The antenna should be capable of producing multiple beams which can be steered without changing the orientation of the antenna. Microwave lenses are the one who support low-phase error, wideband, and wide-angle scanning. They are the true time delay (TTD) devices producing frequency independent beam steering. The emerging printed lenses in recent years have facilitated the advancement of designing high performance but low-profile, light-weight, and small-size and networks (BFNs). This paper will review and analyze various design concepts used over the years to improve the scanning capability of the lens developed by various researchers.

scholarly journals Widely distributed exogenic materials of varying compositions and morphologies on asteroid (101955) Bennu

2021 ◽  
Author(s):  
Eri Tatsumi ◽  
Marcel Popescu ◽  
Humberto Campins ◽  
Julia de León ◽  
Juan Luis Rizos García ◽  
...  
Keyword(s):  
Near Infrared ◽  
Principal Component ◽  
Parent Body ◽  
Ordinary Chondrites ◽  
Near Infrared Reflectance ◽  
Spatially Resolved ◽  
Average Spectrum ◽  
Band Absorption ◽  
Rich Material ◽  
The One

Abstract Using the multiband imager MapCam onboard the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer) spacecraft, we identified 77 instances of proposed exogenic materials distributed globally on the surface of the B-type asteroid (101955) Bennu. We identified materials as exogenic on the basis of an absorption near 1 µm that is indicative of anhydrous silicates. The exogenic materials are spatially resolved by the telescopic camera PolyCam. All such materials are brighter than their surroundings, and they are expressed in a variety of morphologies: homogeneous, breccia-like, inclusion-like, and others. Inclusion-like features are the most common. Visible spectrophotometry was obtained for 46 of the 77 locations from MapCam images. Principal component analysis indicates at least two trends: (i) mixing of Bennu's average spectrum with a strong 1-µm band absorption, possibly from pyroxene-rich material, and (ii) mixing with a weak 1-µm band absorption. The endmember with a strong 1-µm feature is consistent with Howardite-Eucrite-Diogenite (HED) meteorites, whereas the one showing a weak 1-µm feature may be consistent with HEDs, ordinary chondrites, or carbonaceous chondrites. The variation in the few available near-infrared reflectance spectra strongly suggests varying compositions among the exogenic materials. Thus, Bennu might record the remnants of multiple impacts with different compositions to its parent body, which could have happened in the very early history of the Solar System. Moreover, at least one of the exogenic objects is compositionally different from the exogenic materials found on the similar asteroid (162173) Ryugu, and they suggest different impact tracks.

Standard B-Mode Ultrasound Measures Local Carotid Artery Characteristics as Reliably as Radiofrequency Phase Tracking in Symptomatic Carotid Artery Patients

2016 ◽  
Vol 42 (2) ◽  
pp. 586-595 ◽  
Author(s):  
Jeire Steinbuch ◽  
Arnold P.G. Hoeks ◽  
Evelien Hermeling ◽  
Martine T.B. Truijman ◽  
Floris H.B.M. Schreuder ◽  
...  
Keyword(s):  
Carotid Artery ◽  
Phase Tracking ◽  
Symptomatic Carotid

Evaluation of Surgical Freedom for One-and-a-Half Nostril, Mononostril, and Binostril Endoscopic Endonasal Transsphenoidal Approaches

2020 ◽  
Author(s):  
Jin Yang ◽  
Guodao Wen ◽  
Chao Tang ◽  
Chunyu Zhong ◽  
Junhao Zhu ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Carotid Artery ◽  
Internal Carotid ◽  
Attack Angle ◽  
Endoscopic Endonasal ◽  
Exposed Area ◽  
Neuronavigation System ◽  
Using Data ◽  
The One ◽  
The Right

Abstract Objective This article determines which of the one-and-a-half nostril, mononostril, and binostril endoscopic endonasal transsphenoidal approaches provide a superior manipulation during surgery. Methods The three approaches were orderly performed on 10 silicon-injected cadaveric heads to quantitatively assess surgical freedom and attack angle for sella. Measurements were determined with a standardized method under neuronavigation system using data of computed tomography. Results The one-and-a-half nostril endoscopic transsphenoidal approach (OETA) offered superior exposed area than that of the mononostril approach (META), and similar to that of the binostril approach (BETA). For surgical freedom at anatomic targets, the OETA showed greater surgical flexibility at pituitary center, the right medial optic carotid recess (R-mOCR), the left mOCR, the medial intersection of the right cavernous internal carotid artery, and extension line of upper margin of the clivus (R-mICC) than those of the META, and similar to those of the BETA.For sagittal angle of attack to the R-mOCR, R-mICC, and L-mOCR, the OETA can provide better angular freedom for surgeon than that of the META, and similar to that of the BETA. The OETA had the same axial attack to the pituitary center with the BETA. The OETA and the META had limited surgical freedom at L-mICC, and both inferior to the BETA. Conclusion The OETA has similar exposed area, surgical freedom, and attack angle for most anatomic targets to the BETA without resecting contralateral nasal septal mucosa, and obviously superior to the META.

scholarly journals Extended star-forming regions within galaxies in a dense proto-cluster core at z = 2.53†

2019 ◽  
Vol 71 (4) ◽  
Author(s):  
Tomoko L Suzuki ◽  
Yosuke Minowa ◽  
Yusei Koyama ◽  
Tadayuki Kodama ◽  
Masao Hayashi ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Structural Evolution ◽  
Cluster Core ◽  
Star Forming ◽  
Spatially Resolved ◽  
Star Forming Regions ◽  
Star Formation Activity ◽  
Radial Profiles ◽  
Structural Growth ◽  
The One

Abstract At z ∼ 2, star formation activity is thought to be high even in high-density environments such as galaxy clusters and proto-clusters. One of the critical but outstanding issues is if the structural growth of star-forming galaxies can differ depending on their surrounding environments. In order to investigate how galaxies grow their structures and what physical processes are involved in the evolution of galaxies, one requires spatially resolved images of not only stellar components but also star-forming regions within galaxies. We conducted (Adaptive Optics) AO-assisted imaging observations for star-forming galaxies in a dense proto-cluster core at z = 2.53 with IRCS and AO188 mounted on the Subaru Telescope. A combination of AO and narrow-band filters allows us to obtain resolved maps of Hα-emitting regions with an angular resolution of ${0{^{\prime\prime}_{.}}1}$–${0{^{\prime\prime}_{.}}2}$, which corresponds to ∼1 kpc at z ∼ 2.5. Based on stacking analyses, we compare radial profiles of star-forming regions and stellar components and find that the star-forming region of a sub-sample with log (M*/$M_\odot$) ∼ 10–11 is more extended than the stellar component, indicating the inside-out growth of the structure. This trend is similar to the one for star-forming galaxies in general fields at z = 2–2.5 obtained with the same observational technique. Our results suggest that the structural evolution of star-forming galaxies at z = 2–2.5 is mainly driven by internal secular processes irrespective of surrounding environments.

Spatially Resolved Defect Analysis in Cz-Silicon after Copper-Nickel Co-Precipitation by Virtue of Light-Beam-Induced Current Measurements

2009 ◽  
Vol 156-158 ◽  
pp. 431-436
Author(s):  
P. Saring ◽  
C. Rudolf ◽  
L. Stolze ◽  
A. Falkenberg ◽  
Michael Seibt
Keyword(s):  
Light Beam ◽  
Induced Current ◽  
Copper Precipitation ◽  
Copper Nickel ◽  
Spatially Resolved ◽  
Transmission Electron ◽  
Nucleation Sites ◽  
The One ◽  
Co Precipitation ◽  
Wafer Direct Bonding

We report on a light-beam-induced current (LBIC)-analysis of metal silicide defects arising from co-precipitation of copper and nickel in Cz-silicon-bicrystals produced by wafer direct bonding. Large colonies of silicide precipitates in the one wafer emerging from undisturbed growth from few nucleation sites were observed in different orientations with respect to the surface which correspond to Si {110} planes. From this, the colonies formed during copper-nickel co-precipitation reveal the same attributes as those colonies typical for copper precipitation in the absence of nickel. Oxygen related defects associated with a higher defect distribution in the other wafer were characterized by means of high resolution Transmission Electron Microscopy (TEM) and their temperature dependent LBIC signal.

scholarly journals High-precision measurement of velocity profiles in laser-created chlorine plasma

1995 ◽  
Vol 13 (4) ◽  
pp. 503-510 ◽  
Author(s):  
O. Renner ◽  
E. Krouský ◽  
T. Mißalla ◽  
E. Förster ◽  
G. Hölzer
Keyword(s):  
Spectral Lines ◽  
Plasma Parameters ◽  
High Precision Measurement ◽  
One Dimensional ◽  
Electron Temperature Gradient ◽  
Spatially Resolved ◽  
Doppler Shifts ◽  
Velocity Gradients ◽  
Marquardt Algorithm ◽  
The One

A vertical dispersion variant of the Johann spectrometer has been used to record the highresolution X-ray spectra of the chlorine He-like resonance line group emitted from lowradiance plasma. The emission profiles were measured at two observation angles and decomposed into single spectral lines by using a fit based on the Levenberg-Marquardt algorithm. The results of computerized analysis of the one-dimensional (1-D) spatially resolved spectra were used to evaluate the distribution of the main plasma parameters. The electron temperature gradient 7.5·104 eV cm-1 was computed by modeling the measured spectra with the collisional-radiative package RATION. The blowoff maximum velocities 4.2–6.1·107 cm s-1 and the velocity gradients 0.9–1.6·109 s-1 were determined from the Doppler shifts of individual spectral lines within their different spatial extent.

scholarly journals Analytical studies of suspension acoustics

2019 ◽  
Vol 14 (1) ◽  
pp. 27-35
Author(s):  
M.N. Galimzyanov ◽  
V.Sh. Shagapov
Keyword(s):  
Sound Velocity ◽  
Speed Of Sound ◽  
Carrier Phase ◽  
Original System ◽  
Solid Particles ◽  
Dispersed Phase ◽  
Low Frequencies ◽  
One Dimensional ◽  
Perturbation Frequency ◽  
The One

The one-dimensional unsteady flow of the suspension is considered taking into account the standard assumptions for this problems: the mixture is monodisperse, there is no crushing and sticking of particles, viscosity and thermal conductivity are essential only in the process of interfacial interaction. The mixture supposed perfect. The particles are taken absolutely solid and spherical, and the liquid is linearly compressible. The frictional force acting on a single spherical particle is taken into account. The solution to the original system is sought in the form of a traveling wave. On the basis of one-dimensional unsteady equations of fluid flow with solid particles dispersion relations are written out and formulas for phase velocities are derived. Formulas for the attenuation coefficient of the perturbation frequency are got. It has been established that at low frequencies, depending on the magnitude of <i>ρ&#771;<sup>0</sup><sub>p0</sub>=ρ<sup>0</sup><sub>p0</sub>/ρ<sup>0</sup><sub>&#8467;0</sub></i> the equilibrium speed can be higher or lower than the speed of sound in the carrier phase. If the dispersed phase is heavier than the carrier phase (<i>ρ&#771;<sup>0</sup><sub>p0</sub>>1</i>), then the equilibrium velocity exceeds the speed of sound. This is due to the fact that at low frequencies, when velocity equilibrium is realized, the compressibility of the mixture occurs only owing to the carrier phase, and the mixture becomes heavier (inertial) because of the content of the dispersed phase at (<i>ρ&#771;<sup>0</sup><sub>p0</sub>>1</i>). When (<i>ρ&#771;<sup>0</sup><sub>p0</sub><1</i>), the mixture in contrast is lighter than the carrier phase, and the equilibrium velocity becomes higher than the speed of sound. At high frequencies the sound velocity does not depend on <i>ρ&#771;<sup>0</sup><sub>p0</sub></i> and is equal to the sound velocity for the carrier phase.

scholarly journals Theoretical and practical considerations regarding the study of cranial circulation by measuring blood pressure at the two ends of the carotid artery

2020 ◽  
Vol VI (2) ◽  
pp. 95-119
Author(s):  
F. N. Telyatnik
Keyword(s):  
Blood Pressure ◽  
Carotid Artery ◽  
Peripheral Nerve ◽  
Lower Limb ◽  
Blood Circulation ◽  
The State ◽  
The Body ◽  
The Other ◽  
Small Arteries ◽  
The One

Of all the methods of studying cranial blood circulation, which I will not list here, the best is the one in which the state of cranial blood circulation is judged by the blood pressure in the two ends of the carotid artery. Hrthle was the first to observe this method, and therefore the method itself is often called the Hrthle method. However, as Hrthle himself says, the idea of ​​a method existed before. So, A. Dastre and J. Morat, for the purpose of proving the existence of vasomotor fibers for the lower limb in n. ischiadicus, determined the blood pressure in the central end of one a. cruralis and in the peripheral end the other; on the side last n. ischiadicus overcame. With irritation of a peripheral nerve cut, the pressure increased in the peripheral end of the а. cruralis, remaining unchanged in the central cut. This increase in pressure in the operated limb, which coincides with the unchanged pressure in the rest of the body, proves that (with the indicated irritation) there is a reduction in small arteries.

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