Oblique Measurements Research Articles

On the Use of SuperDARN Ground Backscatter Measurements for Ionospheric Propagation Model Validation

AbstractPrior to use in operational systems, it is essential to validate ionospheric models in a manner relevant to their intended application to ensure satisfactory performance. For Over‐the‐Horizon radars (OTHR) operating in the high‐frequency (HF) band (3–30 MHz), the problem of model validation is severe when used in Coordinate Registration (CR) and Frequency Management Systems (FMS). It is imperative that the full error characteristics of models is well understood in these applications due to the critical relationship they impose on system performance. To better understand model performance in the context of OTHR, we introduce an ionospheric model validation technique using the oblique ground backscatter measurements in soundings from the Super Dual Auroral Radar Network (SuperDARN). Analysis is performed in terms of the F‐region leading edge (LE) errors and assessment of range‐elevation distributions using calibrated interferometer data. This technique is demonstrated by validating the International Reference Ionosphere (IRI) 2016 for January and June in both 2014 and 2018. LE RMS errors of 100–400 km and 400–800 km are observed for winter and summer months, respectively. Evening errors regularly exceeding 1,000 km across all months are identified. Ionosonde driven corrections to the IRI‐2016 peak parameters provide improvements of 200–800 km to the LE, with the greatest improvements observed during the nighttime. Diagnostics of echo distributions indicate consistent underestimates in model NmF2 during the daytime hours of June 2014 due to offsets of −8° being observed in modeled elevation angles at 18:00 and 21:00 UT.

Factors influencing the reliability of measurements in eyes with full-thickness macular holes: are we measuring incorrectly?

PurposeThe calliper function is used for manual measurements of full thickness macular holes (FTMHs). We aimed to investigate whether a reproducible difference could be detected beyond interobserver variability between two...

Research on the RZB-Type Three-Dimensional Drilling Strain Measurement System.

Borehole strain gauges play a crucial role in geophysical, seismological, and crustal dynamics studies. While existing borehole strain gauges are proficient in measuring horizontal strains within vertical boreholes, their effectiveness in capturing vertical and oblique strains is limited due to technical constraints arising from the cylindrical probe's characteristics. However, the accurate measurement of three-dimensional strain is essential for a comprehensive understanding of crustal tectonics, dynamics, and geophysics, particularly considering the diverse geological structures and force sources within the crustal medium. In this study, we present a novel approach to address this challenge by enhancing an existing horizontal-component borehole strain gauge with a bellows structure and line strain measurement technology to enable vertical and borehole oblique strain measurements. Integrating these enhancements with horizontal strain measurement capabilities enables comprehensive three-dimensional borehole strain measurements within the same hole section. The system was deployed and tested at the Gongxian seismic station in Sichuan Province. Clear observations of solid tides were recorded across horizontal, oblique, and vertical measurement units, with the tidal morphology and amplitude being consistent with the theoretical calculations. The achieved measurement sensitivity of 10-10 meets the requirements for borehole strain measurement, enabling the characterization of three-dimensional strain states within boreholes through association methods.

Oblique radiographic measurement of knot position and orientation in logs

A novel X-ray scanner system to identify the positions of knots in logs is described. The scanner has a simple, low-cost design that is suitable for use in medium and smaller sawmills. It makes X-ray measurements in an oblique direction as the log moves longitudinally past the X-ray source and line-detector. This unconventional oblique measurement direction creates a more side-on view that better reveals the spatial arrangement of the knots within the log. This view, when combined with the knowledge that all knots start from along the pith and radiate outwards gives sufficient information to identify knot orientations in space. Experimental oblique X-ray measurements on a sample log are described, followed by the processing and analysis of the measured radiographs, and a comparison of the results with independent measurements of knot locations. With the knot identification algorithms developed, knot axial position could be identified within 11 mm, and knot circumferential orientation with a root mean square (rms) error of 7.9°–11.6° when using a single view X-ray scanner, or 5.6°–7.7° when using a dual view scanner.

Correlation between epidural space depth measured with ultrasound and MRI compared to clinical loss of resistance when performing lumbar epidural steroid injection

BackgroundThis prospective study assessed the accuracy of MRI and ultrasound (US) measurements as a preprocedural assessment tool for predicting clinical loss of resistance depth (CLORD) during fluoroscopy-guided lumbar epidural steroid...

Highly anisotropic spin transport in ultrathin black phosphorus.

In anisotropic crystals, the direction-dependent effective mass of carriers can have a profound impact on spin transport dynamics. The puckered crystal structure of black phosphorus leads to direction-dependent charge transport and optical response, suggesting that it is an ideal system for studying anisotropic spin transport. To this end, we fabricate and characterize high-mobility encapsulated ultrathin black-phosphorus-based spin valves in a four-terminal geometry. Our measurements show that in-plane spin lifetimes are strongly gate tunable and exceed one nanosecond. Through high out-of-plane magnetic fields, we observe a fivefold enhancement in the out-of-plane spin signal case compared to in-plane and estimate a colossal spin-lifetime anisotropy of ∼6. This finding is further confirmed by oblique Hanle measurements. Additionally, we estimate an in-plane spin-lifetime anisotropy ratio of up to 1.8. Our observation of strongly anisotropic spin transport along three orthogonal axes in this pristine material could be exploited to realize directionally tunable spin transport.

Controlling Surface of Rods With Entrained Particle as Asperities

Abstract Changing the surface properties (i.e., roughness or friction) can be instrumental for many applications but can be a complex and resource-intensive process. In this paper, we demonstrate a novel process of controlling the friction of a continuous rod by delivering inorganic microparticles. A standardized continuous particle transfer protocol has been developed in our laboratory for depositing particles from a liquid carrier system (LCS) to the cylindrical rod substrate. The particle transfer process can produce controllable and tunable surface properties. Polymeric binder is used to deliver the particles as asperities over the rod substrate and by controlling their size, shape, and distribution, the coefficient of friction of the rod is determined. Tabletop experiments are designed and performed to measure the friction coefficient following the Capstan equation. The entrained particles on the substrate will create size- and shape-based asperities, which will alter the surface morphology toward the desired direction. Both oblique and direct quantitative measurements are performed at different particles and binder concentrations. A systematic variation in the friction coefficient is observed and reported in the result section. It is observed from the capstan experiment that adding only 1% irregular shaped particles in the suspension changes the friction coefficient of the rods by almost 115%. The proposed friction control technique is a simple scale-up, low-cost, low-waste, and low-energy manufacturing method for controlling the surface morphology.

Development of a Miniature Embedded Imaging System For Internal Flow Measurements

Through this work, the foundation has been laid for the development of a system for small-scale, integrated, image- based flow diagnostics for ground and flight tests. This system addresses many of the challenges associated with alternative methods of performing these measurements. For this work a 120 fps imager was embedded in the ceiling of a Mach 2.0 wind tunnel to perform oblique shock impingement measurements. Illumination was provided via a ring-light system of micro-LEDs embedded around the camera lens aperture. The entire system was controlled using a Raspberry Pi 4 Model B to capture and process image data. The integrated system possesses a total aperture diameter of 20 mm. Pressure sensitive paint and UV oil flow visualization experiments capturing an oblique shock/boundary layer interaction were performed using this system.

Infrared multiple‐angle incidence resolution spectrometry for vapor‐deposited amorphous water

AbstractInfrared multiple‐angle incidence resolution spectrometry (IR‐MAIRS) is a recently developed spectroscopic technique that combines oblique incidence transmission measurements and chemometrics (multivariate analysis) to obtain both pure in‐plane (IP) and out‐of‐plane (OP) vibration spectra for a thin sample. IR‐MAIRS is established for analyzing the molecular orientation of organic thin films at atmospheric pressure, but it should also be powerful for the structural characterization of vapor‐deposited thin samples prepared in a vacuum. The application of IR‐MAIRS to vapor‐deposited amorphous water is particularly interesting in the fields of physical and interstellar chemistry, because it is a representative model material for interstellar icy dust grains. We recently developed an experimental setup for in situ IR‐MAIRS under low‐temperature, ultrahigh‐vacuum conditions, which thus facilitates measurements of interstellar ice analogs such as vapor‐deposited amorphous water. This review considers the theoretical framework of IR‐MAIRS and our recent experimental results for vapor‐deposited amorphous water. We present spectroscopic signatures for the perpendicular orientation of dangling‐OH bonds for three‐coordinated water molecules at the surface of amorphous water at 90 K. The absolute absorption cross section of the three‐coordinated dangling‐OH bonds is quantitatively measured as 1.0 ± 0.2 × 10−18 cm2 at 3696 cm−1. As IR‐MAIRS can essentially be conducted using only a Fourier‐transform IR spectrometer and an angle‐controllable linear polarizer, it is a useful, low‐cost, and simple spectroscopic technique for studying laboratory analogs of interstellar ices including vapor‐deposited amorphous water.

Evaluating Intervertebral Foramen Measurements for Patients with Anterior Cervical Disc Surgery in Oblique CT

Objective: It is particularly difficult to determine the level of radiculopathy pain. Because radicular pain usually doesn't fit the dermatomal map. unlike the foramen lumbar vertebrae, where the cervical nerve root is exerted, it has a slope of approximately 45 degrees to the vertebrae in the axical plane and 10-15 degrees in the horizontal plane. Due to this structure of cervical foremen, the evaluation of conventional ct results in incorrect or incomplete diagnosis. In our study, we compared the change in cervical foramen patients with anterior cervical discectomy and cage (fusion) to oblique ct reconstructive and preop and postop. Methods: CT images were acquired in a 64 slice CT system (60–80 mAs, 120 kVp, FC86 reconstruction core and 2.0 mm slice thickness at 2.0 mm intervals). Oblique sagittal images were created with OsiriX Lite v. 12.0.1 version and measurements were performed. For each level, the area has been measured in addition to the short and long axle length of the neural foramens from the pre-op and post-op oblique sagittal images.Results: In our study, 98 cervical intervertebral foramen oblique CT de preop-postop, long axle, short axle and field measurements were evaluated with 43 patients from 16/01/2019 to 03/02/2020, 3 patients with two levels of anterior ceral discectomy + interbody cage. Right side, long axle, short axle, and area respectively; 13,37%, 5,99%, 16,87% increase. Left side, long axle, short axle, and area respectively, increased by 14,27%, 7,11%, 23,20%Conclusion: The cage, which is placed on the intervertebral level, will increase the area of the foramen, increase the space of the foramen, and allow the nerve to decompression. This is why it is necessary to insert the material with the highest height of the intervertebral disk level that can be placed during surgery.

Analysis of non-idealities in rhomb compensators.

In-line rotatable rhombs that are only weakly chromatic are desired as compensators for a wide variety of applications in spectroscopic polarimetry and Mueller matrix spectroscopic ellipsometry. These devices employ multiple total internal reflections to generate differences in the phase shifts upon reflection for orthogonal fast and slow axis optical electric field components. A framework has been developed for characterization of non-idealities in the performance of rhombs due to dissipation and associated dichroism upon each reflection as well as stress-induced birefringence along each beam path. External oblique reflection measurements by spectroscopic ellipsometry for the internally reflecting interface structures has enabled characterization of the dichroic effects and retardance generated by the reflections. The framework for analysis of the effects of stress relies on simulations demonstrating that the contributions to polarization modification from each beam path depend only on the accumulated stress-induced retardance and average azimuthal angle of the fast principal stress axis along the given path. The overall approach has been applied to straight-through Mueller matrix measurements of a three-reflection rhomb in its operational configuration to establish the set of stress parameters for each of the four beam paths needed to fit the measurements. Thus, device geometry and optical structure, including layer thicknesses and component media optical properties, as well as stress-induced retardances and average stress azimuthal angles, which are all deduced in the analysis, enable a complete description of the polarization modifying properties of the rhomb when serving as a compensator.

Quantification of fluoroscopic fundoplication anatomy: inter- and intraobserver reliability.

The etiology of postfundoplication dysphagia remains incompletely understood. Subtle changes of gastroesophageal junction (GEJ) anatomy may be contributory. Barium swallows have potential for standardization to evaluate postsurgical anatomical features. Using structured barium swallows, we aim to identify reproducible, objectively measured postfundoplication anatomical features that will permit future comparison between patients with/without dysphagia. At 6-12months of postfundoplication, 31 patients underwent structured barium swallow with video-fluoroscopy recording: standing anteroposterior; standing oblique (×2); prone oblique (×2); and prone oblique with continuous free drinking. A primary observer recorded 11 variables of GEJ anatomy for each view, repeated 3months later, forming two datasets to assess intraobserver consistency. Interobserver reliability was determined using a dataset each from the primary observer and two medical students (after training). Intraclass correlation coefficients (ICC) were based on two-way mixed-effects model (ICC agreement: 0.40-0.59 'fair'; 0.60-0.74 'good'; 0.75-1.00 'excellent'). Interobserver reliability was good-excellent for 47 of 66 measurements. Measures of maximal esophageal diameter cf. wrap opening diameter and posterior esophageal angle showed high interobserver reproducibility on all views (ICC range 0.84-0.91; 0.68-0.80, respectively). Interobserver agreement was good-excellent for 5/6 views when measuring anterior GEJ displacement and axis deviation (ICC range 0.56-0.79; 0.41-0.77, respectively). Measures of wrap length showed lower reproducibility. Prone oblique measurements showed highest reproducibility (good-excellent agreement in 19/22 measurements). Intraobserver consistency was excellent for 98% of measurements (ICC range 0.74-0.99). Objective measurements of postfundoplication GEJ anatomy using structured barium swallow are reproducible and may allow further interrogation of anatomical features contributing to postfundoplication dysphagia.

A New Concept of Narrowing Genioplasty: Home Plate-Shaped Sliding Osteotomy.

Narrowing genioplasty is commonly performed among East Asian populations, as a broad and/or square chin can be aesthetically unappealing. This study was aimed to introduce the home plate-shaped sliding osteotomy technique for narrowing genioplasty and to evaluate the results of this technique. A retrospective chart review of 117 patients who underwent home plate-shaped sliding osteotomy alone between 2011 and 2019 was performed. The angles of oblique osteotomy lines and measurements of caudal repositioning, which significantly affect the postoperative chin shape, were evaluated. The home plate-shaped sliding osteotomy technique was successfully accomplished for narrowing genioplasty as an isolated procedure. The mean distance of caudal repositioning was 3.9 ± 0.8 mm, and the mean angles of oblique osteotomy lines were 23.3 ± 4.8 degrees on the right and 21.8 ± 3.5 degrees on the left. This produced an aesthetically pleasing rounded and proportionately narrow chin. The incidence of minor complications was 6.0 percent. There were no major complications. In particular, the risk of inferior alveolar nerve injury was obviated, as an additional mandibular border osteotomy was not typically used with this technique. This new surgical procedure for narrowing genioplasty provides improved aesthetic results by altering the chin shape, rather than reducing the transverse width of the chin. The versatility of this procedure allows the chin shape to be adjusted with respect to narrowing, vertical lengthening, anterior advancement, and asymmetric or cleft chin correction. The present study suggests that home plate-shaped sliding genioplasty may be an excellent alternative for correcting broad and/or square chins and more complex chin deformities. Therapeutic, IV.

Accuracy of virtual 3-dimensional cephalometric images constructed with 2-dimensional cephalograms using the biplanar radiography principle.

PurposeThe purpose of this study was to evaluate the accuracy of virtual 3-dimensional (3D) cephalograms constructed using the principle of biplanar radiography by comparing them with cone-beam computed tomography(CBCT) images.Materials and MethodsThirty orthodontic patients were enrolled in this study. Frontal and lateral cephalograms were obtained with the use of a head posture aligner and reconstructed into 3D cephalograms using biplanar radiography software. Thirty-four measurements representing the height, width, depth, and oblique distance were computed in 3 dimensions, and compared with the measurements from the 3D images obtained by CBCT, using the paired t-test and Bland-Altman analysis.ResultsComparison of height, width, depth, and oblique measurements showed no statistically significant differences between the measurements obtained from 3D cephalograms and those from CBCT images (P>0.05). Bland-Altman plots also showed high agreement between the 3D cephalograms and CBCT images.ConclusionAccurate 3D cephalograms can be constructed using the principle of biplanar radiography if frontal and lateral cephalograms can be obtained with a head posture aligner. Three-dimensional cephalograms generated using biplanar radiography can replace CBCT images taken for diagnostic purposes.

Study of strut interference in high-speed flows

Strut-support interference effects were investigated at a nominal Mach number of 6. Cylinder and rhombus models are used; moreover, models called half shock-bump (SB) and SB applied to the front and both sides of the shock-bump shape are used. This is beneficial for free-stream flow recovery around the model surface by bumping the compression and expansion waves at a unit Reynolds number of approximately $$17.8 \times 10^{3}/\hbox {m}$$ and a total enthalpy of approximately 1.9 MJ/kg. A quantitative density field analysis is conducted using the background-oriented schlieren technique, which is validated by measuring the shock stand-off distance and density increase rate on a hemisphere model. In this study, flow interference is divided into the measurements of the recompression shock zone thickness as a wake interference and the free-stream flow density recovery beyond the oblique shock as a strut interference. In the SB model, the thickness of the recompression shock zone is approximately 4.4 ± 0.2 mm, which is a reduction of approximately 53% compared with the cylinder model. In the oblique shock wave height measurements, defined by measuring the intersection of the increasing and decreasing points of density, the SB model shows a height of 16.4 mm, which is approximately 33.6% less than the 24.7 mm height of the cylinder model. In addition, the free-stream flow density beyond the oblique shock wave in the SB model is found to have an approximately 10% deviation from the free-stream density of 0.016 $$\hbox {kg/m}^{3}$$, which is more effective than the 106% higher value in the cylinder model. Through such studies of flow interference, the effect of the SB shape on the strut-support is verified.

Relationships between the anisotropy parameters for transversely isotropic mudrocks

Studying the empirical relations between seismic anisotropy parameters is important for the simplification and practical applications of seismic anisotropy. The elastic properties of mudrocks are often described by transverse isotropy. Knowing the elastic properties in the vertical and horizontal directions, a sole oblique anisotropy parameter determines the pattern of variation of the elastic properties of a transversely isotropic (TI) medium in all of the other directions. The oblique seismic anisotropy parameter [Formula: see text], which determines seismic reflection moveout behavior, is important in anisotropic seismic data processing and interpretation. Compared to the other anisotropy parameters, the oblique anisotropy parameter is more sensitive to the measurement error. Although, theoretically, only one oblique velocity is needed to determine the oblique anisotropy parameter, the uncertainty can be greatly reduced if multiple oblique velocities in different directions are measured. If a mudrock is not a perfect TI medium but it is expediently treated as one, then multiple oblique velocity measurements in different directions should lead to a more representative approximation of [Formula: see text] or [Formula: see text] because the directional bias can be reduced. Based on a data quality analysis of the laboratory seismic anisotropy measurement data from the literature, we found that there are strong correlations between the oblique anisotropy parameter and the principal anisotropy parameters when data points of more uncertainty are excluded. Examples of potential applications of these empirical relations are discussed.

Detection of heavy hydrocarbon plumes (Ethane, propane and Butane) using airborne longwave (7.6–13.5 μm) infrared hyperspectral data

Recent developments in the detection of gaseous hydrocarbons (HCs) through remote sensing are focused on the characterization of methane (CH4). Basically, there is no research related to remote sensing of other heavier HC gases (ethane: C2H6, propane: C3H8, butane: C4H10), whether derived from natural seeps or from leaks at various stages of production, transportation and storage of petroleum resources. Just as methane; ethane, propane and butane have typical spectral signatures in the longwave infrared region (7.6–13.5 μm), which potentiates their detection by means of airborne hyperspectral sensors (nadir or oblique measurements) or by fixed, ground-based hyperspectral and ultraspectral sensors (horizontal/profile measurements). In this context, the aim of this work is to evaluate the detection limits of the Spatially-Enhanced Broadband Array Spectrograph System (SEBASS) for the identification of ethane, propane and butane in gaseous emissions under controlled leaks. Due to the low content of heavy HCs (C2-C4) in the tested mixtures, they were only identified in plumes derived from sources with emission rates equal to or greater than 1000 standard cubic feet per hour (scf/h). Despite the complex mixture comprised in the plume, the spectral absorption features of each HC allowed their individualization in the SEBASS imagery. The methodology introduced here demonstrates that airborne hyperspectral thermal sensors can identify the different types of HC gases composing the plume, strengthening the possibilities for the evaluation of gas leaks from petroleum installations and natural seeps, assisting in exploration campaigns and diminishing the risk for technological accidents in industrial plants.

Derivation of Fiber Orientations From Oblique Views Through Human Brain Sections in 3D-Polarized Light Imaging.

3D-Polarized Light Imaging (3D-PLI) enables high-resolution three-dimensional mapping of the nerve fiber architecture in unstained histological brain sections based on the intrinsic birefringence of myelinated nerve fibers. The interpretation of the measured birefringent signals comes with conjointly measured information about the local fiber birefringence strength and the fiber orientation. In this study, we present a novel approach to disentangle both parameters from each other based on a weighted least squares routine (ROFL) applied to oblique polarimetric 3D-PLI measurements. This approach was compared to a previously described analytical method on simulated and experimental data obtained from a post mortem human brain. Analysis of the simulations revealed in case of ROFL a distinctly increased level of confidence to determine steep and flat fiber orientations with respect to the brain sectioning plane. Based on analysis of histological sections of a human brain dataset, it was demonstrated that ROFL provides a coherent characterization of cortical, subcortical, and white matter regions in terms of fiber orientation and birefringence strength, within and across sections. Oblique measurements combined with ROFL analysis opens up new ways to determine physical brain tissue properties by means of 3D-PLI microscopy.

Strong and Tunable Spin-Lifetime Anisotropy in Dual-Gated Bilayer Graphene.

We report the discovery of a strong and tunable spin-lifetime anisotropy with excellent out-of-plane spin lifetimes up to 7.8ns at 100K in dual-gated bilayer graphene. Remarkably, this realizes the manipulation of spins in graphene by electrically controlled spin-orbit fields, which is unexpected due to graphene's weak intrinsic spin-orbit coupling (∼12 μeV). We utilize both the in-plane magnetic field Hanle precession and oblique Hanle precession measurements to directly compare the lifetimes of out-of-plane vs in-plane spins. We find that near the charge neutrality point, the application of a perpendicular electric field opens a band gap and generates an out-of-plane spin-orbit field that stabilizes out-of-plane spins against spin relaxation, leading to a large spin-lifetime anisotropy (defined as the ratio between out-of-plane and in-plane spin lifetime) up to ∼12 at 100K. This intriguing behavior occurs because of the unique spin-valley coupled band structure of bilayer graphene. Our results demonstrate the potential for highly tunable spintronic devices based on dual-gated 2D materials.

Evaluation of fontanel size variation and closure time in children followed up from birth to 24 months.

OBJECTIVE Anterior fontanel size and closure time can be useful clinical signs for the early diagnosis of diseases. Knowing age-related normal variations is important to decide on further investigations. The authors of this study aimed to describe fontanel size variation according to age, determine fontanel closure time, and identify the optimal method for assessing fontanel size. METHODS For this prospective cohort study, 321 healthy term babies who fulfilled the inclusion criteria were consecutively recruited. Percentile charts for the mean anterior fontanel size and oblique measurements from birth to 24 months of age were created. RESULTS The mean fontanel closure time was 9.7 ± 5.0 months (girls 10.3 ± 4.7 months, boys 9.2 ± 5.1 months). No differences were observed between the traditional method and oblique measurements. Early fontanel closure was not associated with microcephaly. CONCLUSIONS Oblique measurements can be used because they are as accurate as the traditional method. Children with fontanels measuring above the 95th percentile should be monitored closely and investigated further for potentially associated diseases.