True Elevation Research Articles

Corneal curvature and thickness – Scheimpflug

AbstractAlthough the Scheimpflug principle was first described over a century ago, the clinical use of Scheimpflug camera in anterior segment imaging started only a decade ago. Scheimpflug imaging has since advanced significantly and modern instruments provide comprehensive imaging and topographic data of the anterior segment using a noncontact method. It provides anterior and posterior surface topography of the cornea that is derived from true elevation measurements. Approximately 25 000 data points are used to calculate topographic corneal thickness, corneal curvature, anterior chamber angle, volume, and height. Pachymetry and topography of the entire anterior and posterior surface of the cornea from limbus to limbus are calculated and displayed. Keratoconus detection maps may be generated to assist in the classification and diagnosis of keratoconus prior to contact lens fitting or refractive surgery. Zernike wavefront representation of the anterior and posterior surface of the cornea may be calculated based on the measured height data. In this presentation the clinical applications and limitations of Scheimpflug imaging will also be discussed.

Improved Single-Frequency Kinematic Orbit Determination Strategy of Small LEO Satellite with the Sun-Pointing Attitude Mode

Kinematic orbit determination (KOD) of low earth orbit (LEO) satellites only using single-frequency global navigation satellite system (GNSS) data is a suitable solution for space applications demanding meter-level orbit precision. For some small LEO satellites with the sun-pointing attitude mode, the rotation of the GNSS antenna radiation pattern changes the observation noise characteristics. Since the rotation angle information of the antenna plane may not be available for most low-cost missions, the true elevation cannot be computed and a general elevation-dependent weighting model remains invalid for the onboard GNSS observations. Furthermore, the low-stability GNSS receiver clock oscillator of the LEO satellite at high speeds makes single-frequency cycle slip detection ineffective and difficult since the clock steering events occur frequently. In this study, we investigated the improved KOD strategy to improve the performance of orbit solution using single-frequency GPS and BeiDou navigation satellite system (BDS) observations collected from the Luojia-1A satellite. The weighting model based on exponential function and signal strength is proposed according to the analysis of satellite attitude impact, and a joint single-frequency detection algorithm of receiver clock jump and cycle slip is investigated as well. Based on the GPS/BDS-combined KOD results, it is demonstrated that the clock jump and cycle slip can be properly detected and observations can be effectively utilized with the proposed weighting model considering satellite attitude, which significantly improves the availability and accuracy of orbit solution. The number of available epochs is increased by 12.9% benefitting from this strategy. The orbital root mean square (RMS) precision improvements in the radial, along-track, and cross-track directions are 22.1%, 16.4%, and 6.5%, respectively. Combining BDS observations also contributes to orbit precision improvement, which reaches up to 28.8%.

Improving Satellite Waveform Altimetry Measurements With a Probabilistic Relaxation Algorithm

The Geoscience Laser Altimeter System onboard the NASA Ice, Cloud, and land Elevation Satellite (ICESat/GLAS) provided elevation measurements of Earth’s surface between 2003 and 2009. The centroid and maximum-amplitude-peak (MAP) retracking methods have been designed and applied to process the returned laser waveforms for elevation measurements. Although these two methods work well in general, they may generate erroneous measurements when the returned waveform was complicated by adverse atmospheric conditions (clouds, ice fogs, blowing snow, and dust storms). The centroid retracking method is often more severely affected when compared with the MAP retracking method. In this study, we present a new retracking method that exploits the spatial contextual information from neighboring footprints along the satellite ground track, in addition to the single return waveform shape information. Our method uses a probabilistic relaxation (PR) algorithm to integrate the spatial contextual information and the waveform shape information to identify the waveform peak that most likely represents the true surface elevation, rather than simply detecting the peak with the maximum magnitude. For different types of land surfaces, such as inland lakes, polar tundra, ice sheet, and sand deserts, we demonstrate that our new PR retracking method is able to produce more reliable, consistent, and accurate elevation measurements than the standard NASA ICESat/GLAS data products. The root mean squares error (RMSE) is reduced from 0.85 to 0.17 m for inland lake, from 0.81 to 0.23 m for polar tundra, from 1.25 to 0.33 m for ice sheet, and from 2.48 to 2.34 m for sand desert.

Performance Analysis of Interferometer Direction of Arrival Estimation under Frequency Mismatch of Array Manifold: DOA of Frequency Hopping Signal

We consider the direction of arrival (DOA) estimation of the frequency hopping (FH) signal. The frequency hopping (FH) signal has been widely used for communication to control UAVs. Since the frequency of the FH signal is continuously changing, a mismatch may occur between the actual frequency of the received signal and the nominal frequency of the array manifold. In this paper, the azimuth and elevation estimation error in DOA estimation due to frequency mismatch are analytically derived. It is shown that the azimuth error is equal to zero and that elevation error depends on true elevation angle of the incident signal, rather than the true azimuth angle of the incident signal. The elevation error is also dependent on the actual frequency and the nominal frequency.

Seismological constraints on the density, thickness and temperature of the lithospheric mantle in southwestern Tibet

We constrain the lithospheric mantle in southwest Tibet to be cold, thick, and dense by considering seismological observations, isostasy, and gravity anomalies. First, virtual deep seismic sounding (VDSS) indicates that the thickness of the crust increases from 50 ± 4 km beneath the Himalaya to 70 ± 4 km in the Lhasa terrane. This implies a ‘residual topography’ (difference between isostatic elevation of crust and true elevation) of −2.4 ± 1.5 km. Taking into account deviations from isostasy, the lithospheric mantle must be dense enough to depress the surface by 0.9 to 4.5 km. Our joint inversion of fundamental-mode Rayleigh wave dispersion and receiver functions suggests that the vertically-polarised shear-wave speed (Vsv) is 4.6 ± 0.1 kms−1 at depths of 120 to 300 km. From the shear-wave speed profile, we estimate the geotherm, which is on average 200°C below the 1350°C adiabat, and suggest that the base of the lithosphere is at a depth of 290 ± 30 km. To match the negative buoyancy, the lithospheric must be denser, on average, than ‘normal’ fertile adiabatic mantle, which rules out a depleted (harzburgite) composition. The density excess can be explained solely by thermal contraction, but we cannot rule out additional density increases due to composition. Our observations are not consistent with a depleted Indian slab underthrusting Tibet in this region, which would result in a lower average density and lower temperatures.

Data Mining for Adverse Drug Events With a Propensity Score-matched Tree-based Scan Statistic.

The tree-based scan statistic is a statistical data mining tool that has been used for signal detection with a self-controlled design in vaccine safety studies. This disproportionality statistic adjusts for multiple testing in evaluation of thousands of potential adverse events. However, many drug safety questions are not well suited for self-controlled analysis. We propose a method that combines tree-based scan statistics with propensity score-matched analysis of new initiator cohorts, a robust design for investigations of drug safety. We conducted plasmode simulations to evaluate performance. In multiple realistic scenarios, tree-based scan statistics in cohorts that were propensity score matched to adjust for confounding outperformed tree-based scan statistics in unmatched cohorts. In scenarios where confounding moved point estimates away from the null, adjusted analyses recovered the prespecified type 1 error while unadjusted analyses inflated type 1 error. In scenarios where confounding moved point estimates toward the null, adjusted analyses preserved power, whereas unadjusted analyses greatly reduced power. Although complete adjustment of true confounders had the best performance, matching on a moderately mis-specified propensity score substantially improved type 1 error and power compared with no adjustment. When there was true elevation in risk of an adverse event, there were often co-occurring signals for clinically related concepts. TreeScan with propensity score matching shows promise as a method for screening and prioritization of potential adverse events. It should be followed by clinical review and safety studies specifically designed to quantify the magnitude of effect, with confounding control targeted to the outcome of interest.

Elevated estradiol with prolonged mifepristone to treat progesterone-receptor positive meningioma

Objective: To report a finding of persistently elevated estradiol (E2) after prolonged mifepristone use for treatment of progesterone-receptor positive meningioma, an association which has not previously been reported. Design: This is a case report. Setting: Outpatient Reproductive Endocrine clinic at a tertiary referral center. Case Report: A 48-year-old gravida 1 para 0-0-1-0 with progesterone-receptor positive meningioma, recurrent after multiple debulking surgeries. Patient was treated with mifepristone for 11 years with symptomatic improvement and tumor shrinkage. Levels of follicle-stimulating hormone, luteinizing hormone, and estradiol (E2) were followed throughout the patient’s course of mifepristone therapy. E2 levels were found to be persistently elevated to 500–700 pg/mL. Materials and Methods: Enhanced E2 assay, a liquid-chromatography tandem mass spectrometry (LC-MS/MS) based assay, was measured simultaneously with the routinely used immunoassay for 5 years in attempt to obtain a more accurate assessment. Results: E2 levels using the standard immunoassay were found to be persistently elevated while the patient was taking mifepristone. Using the enhanced LC-MS/MS assay, E2 was initially elevated, however was subsequently low. After the patient discontinued the medication, E2 levels as measured by the immunoassay normalized. Conclusions: Prolonged mifepristone use was found to be associated with markedly elevated E2 levels in our patient. If this is a true elevation, it may help explain the incidence of endometrial hyperplasia and endometrial polyps with prolonged mifepristone use. However, this was likely a false elevation, potentially due to cross-reactivity of mifepristone with the immunoassay, given the normal values obtained with the enhanced LC-MS/MS E2 assay. Whether prolonged mifepristone use may cause true or falsely elevated E2 in a wider population, and the mechanism through which it does so, should be further investigated.

Weather Observation by an Electronically Scanned Dual-Polarization Phase-Tilt Radar

A dual-polarized X-band solid-state 1-D electronic scanning “phase-tilt” weather radar (PTWR) and its scanning geometry are presented. In this architecture, the true elevation angle decreases from the nominal array tilt angle and the true azimuth angle increases from the requested azimuth as one scans off boresight. Additionally, this scanning geometry induces a canting angle effect, which can be significant especially at higher elevation tilts. The predictions of potential biases in selected polarimetric variables due to this effect are derived. For elevation angles below 10°, where polarimetric measurements are of most value, predicted biases are negligible. The PTWR was deployed in Arlington, TX, USA, for an eight-week period during Spring 2014 collecting data on a number of weather events. The direct proximity (250 m away) of a mechanically scanning magnetron-based radar, employing a dual-polarized parabolic antenna allowed for a qualitative and quantitative data comparison. We find the differences in the observations made by the two radar systems are not attributable to the aforementioned biases, but appear primarily due to differences in sampling volumes of the two radars. We also find that at high-elevation tilts, the coupling of the true elevation angle with the array-relative azimuth scan angle complicates the interpretation of features at a constant altitude such as the melting layer.

A case of acute necrotizing pancreatitis complicated with non ST elevation myocardial infarction

BackgroundAcute pancreatitis is an inflammatory condition with varying severity and a range of local and systemic complications. Here we report a patient with acute necrotizing pancreatitis complicated with a true non ST elevation myocardial infarction.Case presentationA 58 year old lady was admitted to our unit with acute onset epigastric pain and vomiting for 4 h duration. Following admission she complained of retrosternal tightening type of a chest pain. She had elevated serum amylase and cardiac troponin. Electrocardiogram (ECG) revealed lateral ischaemia. Contrast computerized tomography abdomen revealed acute severe necrotizing pancreatitis.ConclusionsNonspecific ECG changes can occur in patients with acute pancreatitis. But the diagnosis of true myocardial infarction in a context of acute pancreatitis using ECGs, 2D echocardiography, cardiac biomarkers and coronary angiograms can be challenging with the choice of revascularization therapy and safety of antiplatelet agents and anticoagulant therapy. Decision making regarding the management of such a patient is also critical.

Relative Geometric Refinement of Patch Images Without Use of Ground Control Points for the Geostationary Optical Satellite GaoFen4

Patch imaging is an important capability of GaoFen4, which is the first Chinese high-resolution planar array satellite in geosynchronous orbit. When the satellite collects images in the patch-imaging mode, overlapping images can be successively obtained. As these images are captured at different times and from a very high orbit, the initial geometric accuracy of the overlapping area between images is inconsistent, which directly affects image mosaicking. In this paper, a novel bundle block adjustment method based on the rational function model without ground control points (GCPs) is proposed to eliminate the relative geometric error among the images and to generate refined rational polynomial coefficients (RPCs). In this method, the average elevation is used instead of the true elevation of the ground points to solve the problem of weak convergence of corresponding bundles, which would result in unstable calculation in the height direction. Virtual control points (VCPs) generated from the original RPCs are used to restrain the freedom of the entire block in the horizontal direction, thereby ensuring stable calculation without the use of GCPs. A successive RPC regeneration method based on VCPs is also presented. To verify the effectiveness of the proposed method, four experiments were performed using real data to assess the geometric accuracy of the method, and the satisfactory experimental results indicate that the presented method is both practical and effective.

Nietzsche y el mejoramiento humano. Reflexiones en torno a la noción de vida

El presente trabajo expone el diálogo entre nietzsche y la escuela darwinista, destacando el contraste entre dos nociones de «vida» opuestas: vida como lucha por la supervivencia o vida como voluntad de poder. En oposición a la selección natural, que según nietzsche no favorece a los fuertes y poderosos sino a lo mediano y al «gran número», el filósofo alemán idea un proyecto de cría (Züchtung), una formación tanto fisiológica como moral que aspira a una auténtica elevación del ser humano, mediante la superación de las interpretaciones nihilistas y la transvaloración de los valores desde una perspectiva vitalista.

PREDICTORS OF TRUE ST-SEGMENT ELEVATION MYOCARDIAL INFARCTION IN COCAINE POSITIVE PATIENTS

Background: More than 500,000 emergency department visits in the United States each year are related to cocaine use. This patient population tends to have a low incidence of a true ST-segment elevation myocardial infarction (STEMI) (0.7% to 6.0%). Identification of the frequency and factors

Vertical Accuracy Assessment of SRTM Ver 4.1 and ASTER GDEM Ver 2 Using GPS Measurements in Central West of Tunisia

This paper focuses on the quality of the vertical accuracy of two Digital Elevation Models, corresponding to Kasserine region, central west Tunisia. The vertical accuracy assessment is based on 23 GPS ground control points belonging to the study area. We applied a statistic analysis approach and established 3 elevation profiles corresponding to GPS, ASTER and SRTM. The erected statistical analysis reveals that the Root Mean Squared Error (RMSE) was 8.88 and 10.13 respectively for SRTM and ASTER DTMs. 2D elevation profiles constructed for GPS measurements, ASTER and SRTM, highlight that both DTMs underestimate the true elevation and that SRTM DTM is quite closer to the GPS elevation profile. Relying on this investigation, we think that both DTMs are significant for the vertical accuracy assessment and we urge that SRTM DTM might scheme the Kasserine area features better than ASTER DTM.

TCT-258 Reasons for False ST Elevation Myocardial Infarction activations at a Primary Percutaneous Coronary Intervention Capable Center

Several conditions may mimic a true ST Elevation Myocardial Infarction (STEMI) and lead to false activation of the Cardiac Catheterization Laboratory (CCL). We investigated the reasons for false STEMI activations at our institution. We reviewed the medical records of all patients presenting to our

False-positive elevations of carcinoembryonic antigen in patients with a history of resected colorectal cancer.

403 Background: Routine monitoring of carcinoembryonic antigen (CEA) is standard practice in patients with a history of resected colorectal cancer. While it is known that false positive elevations of CEA can occur, the incidence of false positives and the upper limits of false positive elevations have not been previously well characterized. We evaluated these factors retrospectively in a large, single center, 10-year experience. Methods: Computerized medical records of Memorial Sloan-Kettering were searched electronically and then manually confirmed to identify patients who underwent an R0 resection of local-regional colorectal cancer between January, 2003 and December, 2012 and who had a rise in CEA above the normal range after a normal perioperative CEA. CEA elevations were regarded as false-positive if workup failed to identify the source of the CEA with at least 1 year follow up after the CEA first became abnormal. Results: 728 patients were identified who met all inclusion criteria. Of these, 358 patients (49%) were determined to have had a false-positive CEA elevation, 335 patients (46%) had a true-positive CEA elevation indicative of recurrent colorectal cancer, and 35 patients (5%) had a true positive CEA elevation indicative of development of a new, non-colorectal malignancy. Of those with false elevations, 111 had a single isolated CEA elevation (median highest CEA of 5.5ng/ml, range: 5.1-45.2ng/ml) with no further abnormal CEAs, while 247 had CEA elevations on two or more readings with median highest CEA of 6.7 (range: 5.2-34.9ng/ml). Of these 247 patients with confirmed false-positive CEA elevations, only 5 patients (2%) were above 15ng/ml and no confirmed CEA elevation over 35ng/ml was a false positive. Conclusions: False positive CEAs in the 5-15 range are relatively common. Confirmation of CEA elevation in this range prior to initiating imaging studies may be appropriate. False positive CEAs above 15 are rare. In our large data set, all CEAs above 35 were associated with actual cancer recurrence; hence CEA levels above 35 appear to be virtually diagnostic of the presence of cancer.

Improved Floodplain Delineation Method Using High‐Density LiDAR Data

Abstract: With the improvements in sensor technologies over the past decade, there has been a significant decrease in the cost of acquisition and increase in the density and accuracy of Light Detection and Ranging (LiDAR) data. Due to its advantages over traditional surveying techniques, LiDAR data are widely preferred for floodplain delineation. But, processing dense LiDAR data is time‐consuming and memory intense. Therefore, it is divided into manageable areas/tiles or simplified to raster DEM (Digital Elevation Model) format for feature extraction process such as floodplain delineation. This results in increase in processing time and decrease in accuracy due to loss of true elevation. Furthermore, as floodplain boundaries are unknown prior to delineation, processing time also increases as LiDAR data over larger extent is processed. Hence, there is a need of improved, automated method that will process only the LiDAR data that contribute to the floodplain. This article, describes a time‐efficient floodplain delineation method that divides the LiDAR data into regular tiles and processes only the tiles that contribute to floodplain. This method is experimented using LiDAR data saved in ArcGIS “Terrain” format at 0.0, 0.1, and 0.3 m pyramid levels. These data are then preprocessed to obtain elevation information which is used to filter and process only LiDAR data tiles that truly contribute to the floodplain boundary; thus, reducing processing time. Results from two pilot hydraulic models showed that this method saved 12–34% of processing time compared to the conventional method.

Incorporating vegetation into visual exposure modelling in urban environments

Visual exposure modelling establishes the extent to which a nominated feature may be seen from a specified location. The advent of high-resolution light detection and ranging (LiDAR)-sourced elevation models has enabled visual exposure modelling to be applied in urban regions, for example, to calculate the field of view occupied by a landmark building when observed from a nearby street. Currently, visual exposure models access a single surface elevation model to establish the lines of sight (LoSs) between the observer and the landmark feature. This is a cause for concern in vegetated areas where trees are represented as solid protrusions in the surface model totally blocking the LoSs. Additionally, the observer's elevation, as read from the surface model, would be incorrectly set to the tree top height in those regions. The research presented here overcomes these issues by introducing a new visual exposure model, which accesses a bare earth terrain model, to establish the observer's true elevation even when passing through vegetated regions, a surface model for the city profile and an additional vegetation map. Where there is a difference between terrain and surface elevations, the vegetation map is consulted. In vegetated areas the LoS is permitted to continue its journey, either passing under the canopy with clear views or partially through it depending on foliage density, otherwise the LoS is terminated. This approach enables landmark visual exposure to be modelled more realistically, with consideration given to urban trees. The model's improvements are demonstrated through a number of real-world trials and compared to current visual exposure methods.

Sickle cell anemia pathophysiology: Back to the data

Sickle cell anemia pathophysiology: Back to the data

Radiographic Analysis of Metatarsus Primus Elevatus and Hallux Rigidus

Controversy exists about the role of metatarsus primus elevatus (MPE) in the presence of hallux rigidus. Previous studies could neither confirm nor reject a causative relationship. Measurement of the true elevation of the first metatarsal according to current techniques lack either precision or accuracy or both. The purpose of this study was to assess MPE by means of a new radiographic measurement method and to analyze how the MPE-values differed among hallux rigidus, hallux valgus and control groups. A retrospective study was performed of standing AP and lateral radiographs of 295 feet (221 patients; average age 54 years) randomly selected from our databank. According to general radiographic and clinical criteria, 99 were defined as hallux rigidus. Ninety-nine feet had a hallux valgus deformity without severe arthritis. Ninety-seven radiographs with normal MP-I joints and no other forefoot deformity served as a control group. The elevation of the first metatarsal bone in relation to the second metatarsal (MPE), the first metatarsopahlangeal dorsiflexion angle (DFA), the hallux valgus angle (HVA), the intermetatarsal angle (IMA), the interphalangeal angle (IPA) and the degeneration of the first metatarsophalangeal joint were measured. Three independent raters were involved to assess the inter-rater reliability of a new MPE measurement method. For statistic analyses, ANOVA testing was used. MPE was significantly greater in patients with hallux rigidus (+5.2 mm; 95% CI: 4.7 to 5.7) when compared with hallux valgus (+2.8 mm; 95% CI: 2.2 to 3.4) or the control group (+2.6; 95% CI: 2.0-3.2; p < 0.0001). The DFA was found to be significantly lower in the hallux rigidus group (9 degrees; 95% CI: 8 to 10) when compared with those measured in the hallux valgus (14 degrees; 95% CI: 13 to 16) and control groups (11 degrees; 95% CI: 10 to 12; p < 0.0001). There was a no correlation found between MPE and osteoarthritis at MP-I joint (r = 0.35; p < 0.0001). A moderate correlation was found between increasing MPE and decreasing DFA (r = 0.5; p < 0.0001). The inter-rater reliability of the MPE measurement method was found to be accurate and reproducible (r = 0.9; p < 0.0001). Based on the findings in this study, an MPE greater than 5 mm could be considered a predictive factor in the presence of hallux rigidus. However, the mechanism of MPE has yet to be determined.

Corneal wavefront aberration measured by a rotary scanning system

Abstract Purpose Corneal wavefront aberration measurements are important in many areas such as refractive surgery, diagnosis and management of corneal disease as well as to understand the eye’s optical system. In this work the authors present the corneal anterior and posterior surface wavefront aberrations measured by an optical corneal tomographer that uses two Scheimpflug cameras attached to an innovative illumination system that allows a rotary scanning of the entire cornea. Methods The corneal wavefront aberration was computed from the corneal topographic height data of both corneal surfaces obtained by an innovative rotary scanning system. The topographic height data was computed from corneal optical sections obtained by illumination with a collimated beam expanded in a fan by a small cylindrical lens; this lens is provided with motor driven rotation in order to perform automated rotary scan of the whole cornea. This system has two stationary Scheimpflug cameras whose images are combined as if there was one virtual rotary camera synchronized with the cylindrical lens. Results After appropriate processing of the cameras images it is possible to produce true elevation maps and consequently, to compute wavefront aberrations of both corneal surfaces. In this work we present corneal aberrations measured with this system and explained how this is achieved. Conclusion This new optical system allows the measurement of corneal wavefront aberration as well as corneal thickness and 3‐D mapping of both corneal surfaces.