Transport model for the propagation of partially coherent, partially polarized, polarization-gradient vector beams.

Recently we predicted and experimentally validated a new physical mechanism for altering the propagation path of a monochromatic beam [Opt. Express30, 38907 (2022)OPEXFF1094-408710.1364/OE.467678]. Specifically, we showed that by properly tailoring the spatial distribution of the linear state of polarization transverse to the direction of propagation, the beam followed a curved trajectory in free space. Here we extend the model to the partially coherent and partially polarized polychromatic case by redefining the beam amplitude, phase, and polarization angle as appropriate statistical quantities. In particular, the definition of polarization angle represents a fundamentally new quantity in modeling beam propagation and is shown to be consistent with recent works on energy and momentum flow. In the new model, the beam curvature matches that of our previous work in the fully coherent case but is predicted to vanish for an unpolarized, spatially incoherent beam. Simulated beam trajectories are shown for varying levels of initial partial coherence and for different polarization profiles. A new class of non-diffracting beams is also suggested by way of example.

Vector beam bending via a polarization gradient.

We propose, analyze and demonstrate experimentally an entirely new optical effect in which the centroid of a coherent optical beam can be designed to propagate along a curved trajectory in free space by tailoring the spatial distribution of linear polarization across the transverse beam profile. Specifically, a non-zero spatial gradient of second order or higher in the linear state of polarization is shown to cause the beam centroid to "accelerate" in the direction transverse to the direction of propagation. The effect is confirmed experimentally using spatial light modulation to create the distribution in linear polarization and then measuring the transverse location of the beam profile at varying propagation distances. The observed displacement of the beam centroid is shown to closely match the theory out to 34m propagation distance.

Trabecular bone score and its association with Cobb angle kyphosis in older men: a cross-sectional study for the Osteoporotic Fractures in Men (MrOS) Study.

Hyperkyphosis (HK), or accentuated forward spinal curvature, commonly affects older people, although its causes are not completely understood. We tested whether a measure of bone quality, trabecular bone score (TBS), is associated with HK in 1997 older men, and determined that men with degraded TBS were more likely to have HK. INTRODUCTION: While vertebral fractures and low bone mineral density (BMD) contribute to kyphosis progression, it is unknown whether the trabecular bone score (TBS) may provide additional information on bone quality that could influence the degree of kyphosis. We hypothesized that degraded TBS would be associated with hyperkyphosis (HK) defined as a Cobb angle > 50°. METHODS: Using data from 1997 participants of the Osteoporotic Fractures in Men (MrOS) Study who had baseline TBS and Cobb angle kyphosis measured, we investigated whether men with degraded TBS were more likely to be hyperkyphotic, even after adjustment for BMD and prevalent vertebral fractures. RESULTS: Men were an average age of 74 ± 6 (mean ± SD) years with a mean kyphosis angle of 38.6 ± 11.5°, 295 (15%) were classified as hyperkyphotic, and 416 (21%) had degraded TBS. Compared with men with TBS > 1.2, men with degraded TBS were more likely to have HK (OR: 1.47, 95% CI: 1.06-2.06, p = 0.02) after adjusting for age, clinic, race, BMI, hip BMD, and prevalent vertebral fracture. If spine instead of hip BMD was included in the model, the odds ratio decreased to 1.35 (95% CI: 0.97-1.89, p = 0.08). CONCLUSIONS: Older men with degraded TBS are more likely to have HK not explained by underlying vertebral fractures.

Jupiter's X-Ray and UV Dark Polar Region.

We present 14 simultaneous Chandra X-ray Observatory (CXO)-Hubble Space Telescope (HST) observations of Jupiter's Northern X-ray and ultraviolet (UV) aurorae from 2016 to 2019. Despite the variety of dynamic UV and X-ray auroral structures, one region is conspicuous by its persistent absence of emission: the dark polar region (DPR). Previous HST observations have shown that very little UV emission is produced by the DPR. We find that the DPR also produces very few X-ray photons. For all 14 observations, the low level of X-ray emission from the DPR is consistent (within 2-standard deviations) with scattered solar emission and/or photons spread by Chandra's Point Spread Function from known X-ray-bright regions. We therefore conclude that for these 14 observations the DPR produced no statistically significant detectable X-ray signature.

Soil erosion response to land use change in a mountainous rural area of Son La Province of Vietnam.

This study investigated the changes in soil erosion associated with land use change from 2000 to 2020 in a mountainous rural area. Land use change was detected using Landsat images and soil erosion was estimated using the revised universal soil loss equation (RUSLE). The results show that deforestation and fallow cultivation caused substantial soil loss, whereas conversion from uncultivated land to cropland reduced soil erosion. A conversion from 711 ha cropland and 234 ha forestland to uncultivated land increased the average soil loss from 17 ton·ha-1·year-1 to 42 ton·ha-1·year-1 and the area of eroded soil at the very high level from 276 to 1058 ha between 2000 and 2010. In contrast, a wide expansion of cropland from 637 ha uncultivated land decreased the average soil loss from 42 ton·ha-1·year-1 to 32 ton·ha-1·year-1 and the area of eroded soil at the very high level from 1058 to 690 ha between 2010 and 2020. We suggest management measures such as forest protection, afforestation, reforestation, fruit tree development, and soil erosion control practices in coffee and maize cultivation to reduce soil erosion.

Kyphosis and 3-year fall risk in community-dwelling older men.

Hyperkyhosis is thought to be a fall risk factor in older adults. This large study of older men found that fall risk increased with greater kyphosis measured with the blocks method, but did not find an association between kyphosis and falls when measured by the commonly used the Cobb angle method. INTRODUCTION: Research suggests an association between hyperkyphosis and falls in community-dwelling older adults, though this has not been investigated within large, population-based studies. This study sought to determine whether two measures of kyphosis prospectively predict fall risk over 3 years among older men. METHODS: Within the Osteoporotic Fractures in Men Study (MrOS), we conducted two 3-year prospective studies of 2346 and 2928 men. The first group had kyphosis measured by the Cobb angle at visit 1, while the second group had kyphosis assessed with the blocks method at visit 3; both groups then self-reported falls tri-annually for 3 years. Poisson regression with GEE was used to obtain relative risks (RR) of falls. RESULTS: The fall rates over 3 years were 651/1000 person-years among the visit 1 sample (mean age 74 ± 6 years) and 839/1000 person-years among the visit 3 sample (mean age 79 ± 5 years). In adjusted models of the visit 3 sample, the risk of falls was increased by 12% for each standard deviation increase (1.4 blocks) in the number of blocks required to achieve a neutral head and neck position (RR = 1.12, 95% CI = 1.06, 1.18). The Cobb angle was not associated with falls in the visit 1 sample. CONCLUSIONS: Although the Cobb angle did not predict falls in community-dwelling older men over 3 years, the blocks method of measuring kyphosis was predictive of falls in this population. This difference could be due to the Cobb angle's focus on thoracic kyphosis, whereas the blocks method may additionally capture abnormal cervical spine curvature.

Learned linear models for detecting watercraft in a maritime environment.

This work provides a new, to the best of our knowledge, approach to constructing linear models for object detection in a scene. Specifically, we use representative training data in order to estimate the parameters describing a generalized wavelet model for the express purpose of detecting the presence of maritime targets in a scene. The parameter estimates are taken as those that maximize the probability of detecting the targets for a fixed probability of false alarm. The approach is then demonstrated on a database of short-wave infrared imagery containing various watercraft. Results are then compared to some of the more standard wavelet bases used in detection applications.

Kyphosis and incident falls among community-dwelling older adults.

Hyperkyphosis commonly affects older persons and is associated with morbidity and mortality. Many have hypothesized that hyperkyphosis increases fall risk. Within this prospective study of older adults, kyphosis was significantly associated with incident falls over 1 year. Measures of hyperkyphosis could enhance falls risk assessments during primary care office visits. INTRODUCTION: To determine the association between four measures of kyphosis and incident and injurious falls in older persons. METHODS: Community-dwelling adults aged 65 and older (n = 72) residing in southern California were invited to participate in a prospective cohort study. Participants had kyphosis assessed four ways. Two standing measures included a flexicurve ruler placed against the back to derive a kyphotic index and the Debrunner kyphometer, a protractor used to measure the kyphotic angle in degrees. Two lying measures included the blocks method (number of 1.7 cm blocks needed to achieve a neutral head position while lying supine) and traditional Cobb angle calculation derived from DXA based lateral vertebral assessment. Baseline demographic, clinical, and other health information (including a timed up and go (TUG) test) were assessed at a clinic visit. Participants were followed monthly through email or postcard for 1 year, with falls outcomes confirmed through telephone interview. RESULTS: Mean age was 77.8 (± 7.1) among the 52 women and 20 men. Over 12 months, 64% of participants experienced at least one incident fall and 35% experienced an injurious fall. Each standard deviation increase in kyphosis resulted in more than doubling the adjusted odds of an incident fall, even after adjusting for TUG. Odds of injurious falls were less consistent across measures; after adjusting for TUG, only the blocks method was associated with injurious falls. CONCLUSIONS: Each kyphosis measure was independently associated with incident falls. Findings were inconsistent for injurious falls; the blocks measure suggested the strongest association. If these findings are replicated, the blocks measure could be incorporated into office visits as a quick and efficient tool to identify patients at increased fall risk.

Distribution of splice loss in single mode optical fiber.

This work investigates a probabilistic model for splice loss in single mode optical fibers. We derive the probability density function for loss values as a function of lateral and angular misalignment. We then use observed data to estimate these model parameters; both Bayesian and maximum likelihood estimation procedures are described. These estimates can then be used to provide an indication of the relative importance of various loss mechanisms. Alternatively, if one is given values for maximum lateral and angular misalignment, our results allow for predictions of expected distribution of loss values. An overall goal of this paper is to demonstrate that, beyond the mean and variance of splice loss, there is significant information in the shape of the distribution of values. A second goal is to understand the trade-off between the number of splice loss measurements and the confidence in estimates of parameters in the splice loss model.