Limb Distances Research Articles

Correlation between pose estimation features regarding movements towards the midline in early infancy.

In infants, spontaneous movement towards the midline (MTM) indicates the initiation of anti-gravity ability development. Markerless 2D pose estimation is a cost-effective, time-efficient, and quantifiable alternative to movement assessment. We aimed to establish correlations between pose estimation features and MTM in early-age infants. Ninety-four infant videos were analysed to calculate the percentage and rate of MTM occurrence. 2D Pose estimation processed the videos and determined the distances and areas using wrist and ankle landmark coordinates. We collected data using video recordings from 20 infants aged 8-16 weeks post-term age. Correlations between MTM observations and distance values were evaluated. Differences in areas between groups of videos showing MTM and no MTM in the total, lower-limb, and upper-limb categories were examined. MTM observations revealed common occurrences of hand-to-trunk and foot-to-foot movements. Weak correlations were noted between limb distances to the midbody imaginary line and MTM occurrence values. Lower MTM showed significant differences in the lower part (p = 0.003) and whole area (p = 0.001). Video recording by parents or guardians could extract features using 2D pose estimation, assisting in the early identification of MTM in infants. Further research is required to assess a larger sample size with the diversity of MTM motor behaviour, and later developmental skills, and collect data from at-risk infants.

Hanle rotation signatures in Sr I 4607 Å

Context. Measuring small-scale magnetic fields and constraining their role in energy transport and dynamics in the solar atmosphere are crucial, albeit challenging, tasks in solar physics. To this aim, observations of scattering polarization and the Hanle effect in various spectral lines are increasingly used to complement traditional magnetic field determination techniques. Aims. One of the strongest scattering polarization signals in the photosphere is measured in the Sr I line at 4607.3 Å when observed close to the solar limb. Here, we present the first observational evidence of Hanle rotation in the linearly polarized spectrum of this line at several limb distances. Methods. We used the Zurich IMaging POLarimeter, ZIMPOL at the IRSOL observatory, with exceptionally good seeing conditions and long integration times. We combined the fast-modulating polarimeter with a slow modulator installed in front of the telescope. This combination allows for a high level of precision and unprecedented accuracy in the measurement of spectropolarimetric data. Results. Fixing the reference direction for positive Stokes Q parallel to the limb, we detected singly peaked U/I signals well above the noise level. We can exclude any instrumental origins for such U/I signals. These signatures are exclusively found in the Sr I line, but not in the adjoining Fe I line, therefore eliminating the Zeeman effect as the mechanism responsible for their appearance. However, we find a clear spatial correlation between the circular polarization produced by the Zeeman effect and the U/I amplitudes. This suggests that the detected U/I signals are the signatures of Hanle rotation caused by a spatially resolved magnetic field. Conclusions. A novel measurement technique allows for determining the absolute level of polarization with unprecedented precision. Using this technique, high-precision spectropolarimetric observations reveal, for the first time, unambiguous U/I signals attributed to Hanle rotation in the Sr I line.

The Lunar Geophysical Network Landing Sites Science Rationale

Abstract The Lunar Geophysical Network (LGN) mission is proposed to land on the Moon in 2030 and deploy packages at four locations to enable geophysical measurements for 6–10 yr. Returning to the lunar surface with a long-lived geophysical network is a key next step to advance lunar and planetary science. LGN will greatly expand our primarily Apollo-based knowledge of the deep lunar interior by identifying and characterizing mantle melt layers, as well as core size and state. To meet the mission objectives, the instrument suite provides complementary seismic, geodetic, heat flow, and electromagnetic observations. We discuss the network landing site requirements and provide example sites that meet these requirements. Landing site selection will continue to be optimized throughout the formulation of this mission. Possible sites include the P-5 region within the Procellarum KREEP Terrane (PKT; (lat: 15°; long: −35°), Schickard Basin (lat: −44.°3; long: −55.°1), Crisium Basin (lat: 18.°5; long: 61.°8), and the farside Korolev Basin (lat: −2.°4; long: −159.°3). Network optimization considers the best locations to observe seismic core phases, e.g., ScS and PKP. Ray path density and proximity to young fault scarps are also analyzed to provide increased opportunities for seismic observations. Geodetic constraints require the network to have at least three nearside stations at maximum limb distances. Heat flow and electromagnetic measurements should be obtained away from terrane boundaries and from magnetic anomalies at locations representative of global trends. An in-depth case study is provided for Crisium. In addition, we discuss the consequences for scientific return of less than optimal locations or number of stations.

Convergent Validity of the Y Balance Test and Hopping for Distance Tests

The Y Balance TestTM (YBT) and single (SH), triple (TH), and crossover hop (COH) for distance, functional tests that reportedly require dynamic balance, are commonly used to assess lower extremity injury risk. Convergent validity is the degree to which two different instruments measure the same underlying construct. If different tests are measuring the same construct, practitioners can select one test for use instead of a battery of assessments. PURPOSE: To determine the degree of convergent validity of the YBT and 3 hopping tests to measure dynamic balance. METHODS: Cross-sectional study of 41 recreationally active adults (27 female, 14 male, age: 23.4 ± 1.8 years old, height: 172.5 ± 9.5 cm, weight: 68.5 ± 10.7 kg) who performed the YBT, SH, TH, and COH on each leg. The YBT includes 3 reach directions: anterior, posteromedial, and posterolateral. YBT composite score (CS) was calculated by summing the 3 reach distances and dividing it by 3 times the participant’s leg length. Performance asymmetry was calculated by dividing the dominant limb by the non-dominant limb distances. Pearson (continuous) and Spearman (ordinal) correlation coefficients were used to assess correlation between performance, as well as limb asymmetry on the YBT and 3 hopping tests. RESULTS: The hopping tests were strongly and significantly correlated with each other (r = 0.82-0.84; p < 0.001 for all). YBT CS was strongly and significantly correlated with individual reach distances (r = 0.72-0.90; p < 0.001 for all). No statistically significant correlation was found between YBT and any of the hopping tests nor between YBT asymmetry measures. The only statistically significant correlation between performance asymmetry was between the COH and TH (r = 0.56; p < 0.001). CONCLUSION: Performance and asymmetry of YBT and 3 hopping tests are not measuring the same underlying construct of dynamic balance. Clinicians should not substitute the YBT for hop tests, and may consider including both to measure dynamic balance.

Observations on spatial variations of the Sr I 4607 Å scattering polarization signals at different limb distances with ZIMPOL

Context. The Sr I 4607 Å spectral line shows one of the strongest scattering polarization signals in the visible solar spectrum. The amplitude of this polarization signal is expected to vary at granular spatial scales, due to the combined action of the Hanle effect and the local anisotropy of the radiation field. Observing these variations would be of great interest because it would provide precious information on the small-scale activity of the solar photosphere. At present, few detections of such spatial variations have been reported. This is due to the difficulty of these measurements, which require combining high spatial (∼0.1″), spectral (≤20 mÅ), and temporal resolution (&lt; 1 min) with increased polarimetric sensitivity (∼10−4). Aims. We aim to detect spatial variations at granular scales of the scattering polarization peak of the Sr I 4607 Å line at different limb distances, and to study the correlation with the continuum intensity. Methods. Using the Zurich IMaging POLarimeter (ZIMPOL) system mounted at the GREGOR telescope and spectrograph in Tenerife, Spain, we carried out spectro-polarimetric measurements to obtain the four Stokes parameters in the Sr I line at different limb distances, from μ = 0.2 to μ = 0.8, on the solar disk. Results. Spatial variations of the scattering polarization signal in the Sr I 4607 Å line, with a spatial resolution of about 0.66″, are clearly observed at every μ. The spatial scale of these variations is comparable to the granular size. A statistical analysis reveals that the linear scattering polarization amplitude in this Sr I spectral line is positively correlated with the intensity in the continuum, corresponding to the granules, at every μ.

Verification of the Minor Snake-eyed Skink, Ablepharus grayanus (Stoliczka, 1872) (Sauria: Scincidae), from Iran

The rediscovery of the Minor Snake-eyed Skink, Ablepharus grayanus, from two different localities in Sistan and Baluchestan and Kerman Provinces, southeastern Iran is reported. A total of 24 specimens was examined based on morphometrics, colour pattern and pholidotic characters. One-way analyses of variance (ANOVA) based on morphometric measurements revealed significant differences in terms of the snoutvent length (SVL) and fore- and hind limb distances (GA) between eastern and western populations of Ablepharus pannonicus. The most distinguishing characters of Ablepharus grayanus are morphological features, especially ear opening status and scales around the midbody (18-20 versus 20-22). Based on morphological grounds, Ablepharus grayanus is clearly distinguished from A. pannonicus occurring in the eastern and western regions of the Iranian Plateau.

Modeling the center-to-limb variation of the Ca i 4227 Å line using FCHHT models

AbstractThe Ca i 4227 Å is a chromospheric line exhibiting the largest degree of linear polarization near the limb, in the visible spectrum of the Sun. Modeling the observations of the center-to-limb variations (CLV) of different lines in the Second Solar Spectrum helps to sample the height dependence of the magnetic field, as the observations made at different lines of sight sample different heights in the solar atmosphere. Supriya et al. (2014) attempted to simultaneously model the CLV of the (I, Q/I) spectra of the Ca i 4227 Å line using the standard 1-D FAL model atmospheres. They found that the standard FAL model atmospheres and also any appropriate combination of them, fail to simultaneously fit the observed Stokes (I, Q/I) profiles at all the limb distances (μ) satisfying at the same time all the observational constraints. This failure of 1-D modeling approach can probably be overcome by using multi-dimensional modeling which is computationally expensive. To eliminate an even wider choice of 1-D models, we attempt here to simultaneously model the CLV of the (I, Q/I) spectra using the FCHHT solar model atmospheres which are updated and recent versions of the FAL models. The details of our modeling efforts and the results are presented.

CENTER-TO-LIMB OBSERVATIONS AND MODELING OF THE Ca I 4227 Å LINE

The observed center-to-limb variation (CLV) of the scattering polarization in different lines of the Second Solar Spectrum can be used to constrain the height variation of various atmospheric parameters, in particular the magnetic fields via the Hanle effect. Here we attempt to model non-magnetic CLV observations of the $Q/I$ profiles of the Ca I 4227 A line recorded with the ZIMPOL-3 at IRSOL. For modeling, we use the polarized radiative transfer with partial frequency redistribution with a number of realistic 1-D model atmospheres. We find that all the standard FAL model atmospheres, used by us, fail to simultaneously fit the observed ($I$, $Q/I$) at all the limb distances ($\mu$). However, an attempt is made to find a single model which can provide a fit at least to the CLV of the observed $Q/I$ instead of a simultaneous fit to the ($I$, $Q/I$) at all $\mu$. To this end we construct a new 1-D model by combining two of the standard models after modifying their temperature structures in the appropriate height ranges. This new combined model closely reproduces the observed $Q/I$ at all the $\mu$, but fails to reproduce the observed rest intensity at different $\mu$. Hence we find that no single 1-D model atmosphere succeeds in providing a good representation of the real Sun. This failure of 1-D models does not however cause an impediment to the magnetic field diagnostic potential of the Ca I 4227 A line. To demonstrate this we deduce the field strength at various $\mu$ positions without invoking the use of radiative transfer.

VECTOR TOMOGRAPHY FOR THE CORONAL MAGNETIC FIELD. II. HANLE EFFECT MEASUREMENTS

In this paper, we investigate the feasibility of saturated coronal Hanle effect vector tomography or the application of vector tomographic inversion techniques to reconstruct the three-dimensional magnetic field configuration of the solar corona using linear polarization measurements of coronal emission lines. We applied Hanle effect vector tomographic inversion to artificial data produced from analytical coronal magnetic field models with equatorial and meridional currents and global coronal magnetic field models constructed by extrapolation of real photospheric magnetic field measurements. We tested tomographic inversion with only Stokes Q, U, electron density, and temperature inputs to simulate observations over large limb distances where the Stokes I parameters are difficult to obtain with ground-based coronagraphs. We synthesized the coronal linear polarization maps by inputting realistic noise appropriate for ground-based observations over a period of two weeks into the inversion algorithm. We found that our Hanle effect vector tomographic inversion can partially recover the coronal field with a poloidal field configuration, but that it is insensitive to a corona with a toroidal field. This result demonstrates that Hanle effect vector tomography is an effective tool for studying the solar corona and that it is complementary to Zeeman effect vector tomography for the reconstruction of the coronal magnetic field.

Solar turbulent magnetic fields: surprisingly homogeneous distribution during the solar minimum

Context. Small-scale, weak magnetic fields are ubiquitous in the quiet solar atmosphere. Yet their properties and temporal and spatial variations are not well known. Aims. We have initiated a synoptic program, carried out at the Istituto Ricerche Solari Locarno (IRSOL), to investigate both turbulent, mixed-polarity magnetic fields and nearly horizontal, directed fields and their variation with the solar cycle. Methods. Through spectropolarimetric observations we monitor linear and circular polarization at the solar limb (5 �� on the disk) at five positional angles (N, NW, S, SW, W) with the sensitivity of ∼10 −5 . In addition, we analyzed measurements taken at different limb distances. We measure signatures in the 5141 A region including two C2 triplets and three Fe i lines. Linear polarization in these lines arises from scattering and can be modified via the Hanle effect in the presence of turbulent magnetic fields. Through the application of the differential Hanle effect to the C2 R-triplet line ratios and the use of a simplified line formation model, we are able to infer a strength of turbulent magnetic fields while using the P-triplet to further restrict it. A Zeeman analysis of Fe i Stokes V/I is used to evaluate flux densities of horizontally directed fields. Results. We conclude that weak fields were evenly distributed over the Sun during this solar minimum. The turbulent field strength was at least 4.7 ± 0.2 G, and it did not vary during the last two years. This result was complemented with earlier, mainly unpublished measurements in the same region, which extend our set to nearly one decade. A statistical analysis of these all data suggests that there could be a very small variation of the turbulent field strength (3σ-limit) since the solar maximum in 2000. The Zeeman analysis of Fe i Stokes V/I reveals weak horizontal flux densities of 3–8 G. Conclusions. Our results demonstrate the potential of long-term observations of small-scale magnetic fields, which may vary with the solar cycle in both mean strength and spatial distribution. This provides important constraints on the energy budget of the solar cycle. Extending this synoptic program to many spectral lines would provide a sample of heights in the solar atmosphere.

Second solar spectrum of the Sr I 4607 Å line: depth probing of the turbulent magnetic field strength in a quiet region

Aims. This paper is devoted to an interpretation of Quiet-Sun, spatially-resolved spectropolarimetric observations of the Hanle effect in terms of turbulent weak magnetic field determination. Methods. Observations: the slit was positioned perpendicular to the limb, and the spatial resolution along the slit was 1 arcsec, leading to a depth probing along 132 different limb distances. The new polarimeter of the Pic-du-Midi Turret Dome was used on May 14, 2004 to observe a quiet region at the East limb equator in the resonance line of neutral Strontium at 4607 A. Results. For each limb distance, we properly adjusted the theoretical intensity profile obtained by applying a zero-field model to the observed one. Micro- and macroturbulent velocities were thus derived (average values vmicro = 1.77 km s −1 and vmacro = 1.95 km s −1 ). The magnetic field was determined in a second step by interpreting the Hanle effect on the line center linear polarization degree. The depolarizing collisions with neutral hydrogen were taken fully into account through a semi-classical calculation of their rates. An average value of B = 38 Gauss was thus derived. Finally, error bars on the magnetic field values were evaluated from a) the polarimetric inaccuracy, b) the limb distance determination inaccuracy, and c) the uncertainty on our theoretical collisional depolarizing rates that we evaluated. This combination leads to ∼10−20% as total relative error on the magnetic field determination by the Hanle effect method. Since the inaccuracy due to the model itself was hard to properly evaluate, it was ignored. An uncertainty of ±60 km on the line formation depth was, however, derived from the contribution functions. The magnetic field is found to increase slowly with height in the height range 220−300 km above τ5000 = 1 and then decrease in the height range 300−370 km.

Interpretation of second solar spectrum observations of the Sr I 4607 Å line in a quiet region: Turbulent magnetic field strength determination

This paper presents and interprets some observations of the limb polarization of 4607 Å obtained with the spectropolarimeter of the French-Italian telescope THEMIS in quiet regions close to the solar North Pole on 2002 December 7–9. The linear polarization was measured for a series of limb distances ranging from 4 to 160 arcsec, corresponding to heights of optical depth unity in the line core ranging from about 330 to 220 km, respectively, above the level. To increase the polarimetric sensitivity, the data were averaged along the spectrograph slit (one arcmin long) set parallel to the solar limb. Since the data show no rotation of the linear polarization direction with respect to the limb direction, the observed depolarization is ascribed to the Hanle effect of a turbulent weak magnetic field, the zero-field polarization being derived from a model. The interpretation is performed by means of an algorithm which describes the process of line formation in terms of the atomic density matrix formalism, the solar atmosphere being described by an empirical, plane-parallel model. The collisional rates entering the model (inelastic collisions with electrons, elastic depolarizing collisions with neutral hydrogen), have been computed by applying fast semi-classical methods having a typical accuracy of the order of 20% or better (see Derouich [CITE]), leading to 6% inaccuracy on the magnetic field strength determination. We assume a unimodal distribution for the intensity of the turbulent field. The computed intensity profile has been adjusted to the observed one in both depth and width, by varying both microturbulent and macroturbulent velocities. The best adjustment is obtained for respectively 1.87 km s-1 (micro) and 1.78 km s-1 (macro). The evaluation of the magnetic depolarization leads then to the average value of 46 Gauss for the turbulent magnetic field strength, with a gradient of -0.12 Gauss/km. Our results are in very good agreement with the value of 60 Gauss determined at large μ, in the volume-filling field case, by Trujillo Bueno et al. ([CITE], Nature, 430, 326), using a 3D magneto-convective simulation. This validates our method.

Role of projection effects on solar coronal mass ejection properties: 1. A study of CMEs associated with limb activity

Many properties of Coronal Mass Ejections (CMEs), such as size, location and brightness, have been determined from measurements of white light coronal observations. We expect the average properties derived from these measurements contain systematic inaccuracies due to projection effects and suggest that CME properties are most accurately determined for those events occurring near the plane‐of‐the‐sky (i.e., over the solar limb as observed from Earth), where projection effects are minimized. A set of 111 such “limb” events have been identified in Solar Maximum Mission (SMM) white light observations through associations with Erupting Prominences at the Limb (EPLs), and X‐ray and limb optical flares. These “limb” CMEs have greater average speeds (519 ± 46 km/sec) and masses (4.5 ± .5 × 1015 grams) than the average values obtained from all SMM CMEs, consistent with the expected behavior of projection effects. Only a very small percentage of “limb” CMEs are centered at high latitudes, suggesting there are many fewer “true” high latitude CMEs than has previously been reported. No “limb” CMEs have widths greater than 110°, consistent with the interpretation that very wide CMEs (i.e., halos) are actually events of more typical widths originating away from the solar limb and viewed in projection. Only a small percentage of “limb” CMEs have measured speeds below 200 km/sec, indicating there may be fewer “true” subsonic SMM CMEs than previously reported. The correlation detected between the kinetic energy of the “limb” CMEs and the peak intensity of the associated GOES X‐ray flares, is stronger than was previously found using a set of CMEs of undetermined limb distances. All these results provide strong evidence that projection effects systematically influence the deduced properties of CME events.

High spatial resolution solar polarimetry with interference filters

A new type of two-dimensional polarimeter is used to measure the center-to-limb variation of the scattering induced polarization in a narrow continuum window up to the extreme limb. The polarimeter is set on the Tenerife Gregory Coude telescope's hour axis, where the two folding flat mirrors cancel their polarizing eects for zero solar declination at the equinox. The short CCD exposure of only 5 ms allows high spatial resolution images in polarized light. A beam switching technique together with an integration parallel to the solar limb over 20 00 , yields a high polarimetric accuracy with an rms noise of 2 10 4 . Our results for a continuum window at 4506-4508 A agree with model calculations down to limb distances of 0: 00 32 (i.e. cos#<0:025).

Modification of strategies induced by climbers' level of expertise during postures characterized by high lateral inter limb distances

Modification of strategies induced by climbers' level of expertise during postures characterized by high lateral inter limb distances

Effect of Los Lobos Thrust Fault on Tertiary Recovery in West San Ardo Oil Field, Salinas Basin, California: ABSTRACT

Field observations and correlation of wireline logs from wells in the west San Ardo oil field reveal the geometry and character of the Los Lobos thrust fault. The Los Lobos thrust is a northwest-trending, southwest-dipping fault of Pliocene to Pleistocene age, located in the southwest Salinas basin. The surface trace separates the Salinas River on the east from the Aurignac Hills on the west. The Aurignac Hills form the hanging wall and are comprised of fine-grained rocks of the Monterey Formation, which have been thrust northeast over oil-productive Aurignac sand, a shallow marine shelf sand of Miocene age. Analyses of electric and dip logs indicate that the fault plane is steepest near the surface, and flattens with depth. Deformation on the hanging wall involves tight folding with limb distances ranging from 50 to 100 ft, slickensides, and abundant imbricate thrusts that change in orientation from horizontal to vertical over distances of several hundred feet. Deformation on the footwall is much less intense, consisting of drag folding and additional thrust faulting, decreasing in intensity eastward away from the Los Lobos fault plane. These associated thrust-faults displace the oil-productive Aurignac sand and affect tertiary recovery of low-gravity oil.

On the centre-to-limb variation and latitude dependence of the asymmetry and wavelength shift of the solar line ? 5576

Low noise photoelectric measurements of the line profile of the g = 0 Fe line gl 5576.097 combined with determinations of the wavelength shift of its centre calibrated by use of an I2 absorption tube are reported. Measurements taken at various limb distances (1.0 ≤ cos ϑ ≤ 0.2) and along 4 different diameters of the Sun are used to investigate the behaviour of the line asymmetry (C-shape) and wavelength shift of the line centre as functions of cos ϑ and of latitude and to search for possible pole-equator differences.