A Kiloparsec-scale Molecular Wave in the Inner Galaxy: Feather of the Milky Way?

We report the discovery of a velocity coherent, kiloparsec-scale molecular structure toward the Galactic center region with an angular extent of 30° and an aspect ratio of 60:1. The kinematic distance of the CO structure ranges between 4.4 and 6.5 kpc. Analysis of the velocity data and comparison with the existing spiral arm models support that a major portion of this structure is either a subbranch of the Norma arm or an interarm giant molecular filament, likely to be a kiloparsec-scale feather (or spur) of the Milky Way, similar to those observed in nearby spiral galaxies. The filamentary cloud is at least 2.0 kpc in extent, considering the uncertainties in the kinematic distances, and it could be as long as 4 kpc. The vertical distribution of this highly elongated structure reveals a pattern similar to that of a sinusoidal wave. The exact mechanisms responsible for the origin of such a kiloparsec-scale filament and its wavy morphology remains unclear. The distinct wave-like shape and its peculiar orientation makes this cloud, named as the Gangotri wave, one of the largest and most intriguing structures identified in the Milky Way.

Choroidal microvasculature dropout is spatially associated with optic nerve head microvasculature loss in open-angle glaucoma

The presence of parapapillary choroidal microvasculature dropout (CMvD) may affect optic nerve head (ONH) perfusion in glaucoma patients, since parapapillary choroidal vessels provide vascular supply to the neighboring ONH. However, it remains to be determined whether the presence of parapapillary CMvD is associated with diminished perfusion in the nearby ONH. The present study investigated the spatial relationship between CMvD and ONH vessel density (ONH-VD) loss in open-angle glaucoma (OAG) eyes using optical coherence tomography angiography (OCT-A). This study included 48 OAG eyes with a single localized CMvD confined to the inferotemporal parapapillary sector and 48 OAG eyes without CMvD, matched for demographic and ocular characteristics. Global and regional ONH-VD values were compared between eyes with and without CMvD. The relationships between ONH-VD outcomes and clinical variables were assessed. ONH-VDs at the inferotemporal ONH sectors corresponding to the CMvD location were significantly lower in eyes with compared to those without CMvD. Multivariable linear regression analyses indicated that a lower inferotemporal ONH-VD was independently associated with CMvD presence and a greater CMvD angular extent (both P < 0.05). The localized presence of parapapillary CMvD in OAG eyes is significantly associated with ONH-VD loss in the neighboring ONH location, with a spatial correlation.

Ten-year-and-beyond longitudinal change of ß-zone parapapillary atrophy in glaucoma: association with retinal nerve fibre layer defect

BackgroundTo investigate the longitudinal change of localised retinal nerve fibre layer (RNFL) defects associated with change of ß-zone parapapillary atrophy (PPA) in primary open-angle glaucoma (POAG) eyes.MethodsPOAG patients with a localised RNFL defect and ß-zone PPA who had undergone disc/RNFL photography at 1-year intervals for 10 years or longer were enrolled. The topographic parameters of ß-zone PPA (area, maximal radial extent and angular extent around disc) were measured. Progression of RNFL defect was defined as widening of defect and/or appearance of new defect. The factors associated with progression of RNFL defect were assessed by OR using multivariable logistic regression.ResultsA total of 209 patients (209 eyes) with POAG were included (mean: 54 years old). Over the course of 11.5±2.3-year follow-up period, progression of RNFL defect was detected in 114 eyes (54.5%). Enlargement of PPA parameters (area and angular extent) was significantly more common in patients with RNFL defect progression than in eyes without progression (all p<0.001, respectively). Widening of radial extent did not show a significant difference in both groups (p=0.61). Increment of angular extent was in the direction of RNFL defect progression in 82.1% of eyes. Progression of RNFL defect was significantly associated with disc haemorrhage (OR: 6.653, p<0.001), enlargement of PPA area (OR: 4.114, p=0.004) and angular extent (OR: 6.572, p<0.001).ConclusionsProgression of RNFL defect is associated with increment of angular extent of PPA in POAG eyes.

Comparison of Bifurcated Halogen with Hydrogen Bonds

Bifurcated halogen bonds are constructed with FBr and FI as Lewis acids, paired with NH3 and NCH bases. The first type considered places two bases together with a single acid, while the reverse case of two acids sharing a single base constitutes the second type. These bifurcated systems are compared with the analogous H-bonds wherein FH serves as the acid. In most cases, a bifurcated system is energetically inferior to a single linear bond. There is a larger energetic cost to forcing the single σ-hole of an acid to interact with a pair of bases, than the other way around where two acids engage with the lone pair of a single base. In comparison to FBr and FI, the H-bonding FH acid is better able to participate in a bifurcated sharing with two bases. This behavior is traced to the properties of the monomers, in particular the specific shape of the molecular electrostatic potential, the anisotropy of the orbitals of the acid and base that interact directly with one another, and the angular extent of the total electron density of the two molecules.

Trutinor: A Conceptual Study for a Next-Generation Earth Radiant Energy Instrument

Uninterrupted and overlapping satellite instrument measurements of Earth’s radiation budget from space are required to sufficiently monitor the planet’s changing climate, detect trends in key climate variables, constrain climate models, and quantify climate feedbacks. The Clouds and Earth’s Radiant Energy System (CERES) instruments are currently making these vital measurements for the scientific community and society, but with modern technologies, there are more efficient and cost-effective alternatives to the CERES implementation. We present a compact radiometer concept, Trutinor (meaning “balance” in Latin), with two broadband channels, shortwave (0.2–3 μm) and longwave (5–50 μm), capable of continuing the CERES record by flying in formation with an existing imager on another satellite platform. The instrument uses a three-mirror off-axis anastigmat telescope as the front optics to image these broadband radiances onto a microbolometer array coated with gold black, providing the required performance across the full spectral range. Each pixel of the sensor has a field of view of 0.6°, which was chosen so the shortwave band can be efficiently calibrated using the Moon as an on-orbit light source with the same angular extent, thereby reducing mass and improving measurement accuracy, towards the goal of a gap-tolerant observing system. The longwave band will utilize compact blackbodies with phase-change cells for an absolute calibration reference, establishing a clear path for SI-traceability. Trutinor’s instrument breadboard has been designed and is currently being built and tested.

Solid circular plate unilaterally supported along two antipodal edge arcs and deflected by a central transverse concentrated force

A solid circular plate unilaterally supported along two antipodal edge arcs and deflected by a static central transverse concentrated force is considered. It is clarified that two distinct mechanical responses are possible, depending on the angular extent of the supports; in the first kind of response, valid for small support angular widths, the plate rotates about the support lateral sides, lifting from the supports along their central zone. The second response is valid for high support angular extents, and according to this response the plate additionally beds over the central portion of the support upper faces. Only the first kind of response is examined in this paper. This plate contact problem is classifiable as receding, and the plate deflection is described in terms of a plate Kirchhoff model. The plate deflection is analytically expressed together with the transitional value of the support angular width that describes the passage from the first to the second mechanical response.

Ab initiophasing of the diffraction of crystals with translational disorder

To date X-ray protein crystallography is the most successful technique available for the determination of high-resolution 3D structures of biological molecules and their complexes. In X-ray protein crystallography the structure of a protein is refined against the set of observed Bragg reflections from a protein crystal. The resolution of the refined protein structure is limited by the highest angle at which Bragg reflections can be observed. In addition, the Bragg reflections alone are typically insufficient (by a factor of two) to determine the structureab initio, and so prior information is required. Crystals formed from an imperfect packing of the protein molecules may also exhibit continuous diffraction between and beyond these Bragg reflections. When this is due to random displacements of the molecules from each crystal lattice site, the continuous diffraction provides the necessary information to determine the protein structure without prior knowledge, to a resolution that is not limited by the angular extent of the observed Bragg reflections but instead by that of the diffraction as a whole. This article presents an iterative projection algorithm that simultaneously uses the continuous diffraction as well as the Bragg reflections for the determination of protein structures. The viability of this method is demonstrated on simulated crystal diffraction.

Disentangling hadronic from leptonic emission in the composite SNR G326.3−1.8

Context. G326.3−1.8 (also known as MSH 15−56) has been detected in radio as middle-aged composite supernova remnant (SNR) consisting of an SNR shell and a pulsar wind nebula (PWN) that has been crushed by the SNR reverse shock. Previous γ-ray studies of SNR G326.3−1.8 revealed bright and extended emission with uncertain origin. Understanding the nature of the γ-ray emission allows probing the population of high-energy particles (leptons or hadrons), but can be challenging for sources of small angular extent. Aims. With the recent Fermi Large Area Telescope data release Pass 8, which provides increased acceptance and angular resolution, we investigate the morphology of this SNR to disentangle the PWN from the SNR contribution. In particular, we take advantage of the new possibility to filter events based on their angular reconstruction quality. Methods. We performed a morphological and spectral analysis from 300 MeV to 300 GeV. We used the reconstructed events with the best angular resolution (PSF3 event type) to separately investigate the PWN and the SNR emissions, which is crucial to accurately determine the spectral properties of G326.3−1.8 and understand its nature. Results. The centroid of the γ-ray emission evolves with energy and is spatially coincident with the radio PWN at high energies (E > 3 GeV). The morphological analysis reveals that a model considering two contributions from the SNR and the PWN reproduces the γ-ray data better than a single-component model. The associated spectral analysis using power laws shows two distinct spectral features, a softer spectrum for the remnant (Γ = 2.17 ± 0.06) and a harder spectrum for the PWN (Γ = 1.79 ± 0.12), consistent with hadronic and leptonic origin for the SNR and the PWN, respectively. Focusing on the SNR spectrum, we use one-zone models to derive some physical properties, and we find in particular, that the emission is best explained with a hadronic scenario in which the high target density is provided by radiative shocks in H I clouds struck by the SNR.

Can AERONET data be used to accurately model the monochromatic beam and circumsolar irradiances under cloud-free conditions in desert environment?

Routine measurements of the beam irradiance at normal incidence include the irradiance originating from within the extent of the solar disc only (DNIS), whose angular extent is 0.266° ± 1.7 %, and from a larger circumsolar region, called the circumsolar normal irradiance (CSNI). This study investigates whether the spectral aerosol optical properties of the AERONET stations are sufficient for an accurate modelling of the monochromatic DNIS and CSNI under cloud-free conditions in a desert environment. The data from an AERONET station in Abu Dhabi, United Arab Emirates, and the collocated Sun and Aureole Measurement instrument which offers reference measurements of the monochromatic profile of solar radiance were exploited. Using the AERONET data both the radiative transfer models libRadtran and SMARTS offer an accurate estimate of the monochromatic DNIS, with a relative root mean square error (RMSE) of 6 % and a coefficient of determination greater than 0.96. The observed relative bias obtained with libRadtran is +2 %, while that obtained with SMARTS is −1 %. After testing two configurations in SMARTS and three in libRadtran for modelling the monochromatic CSNI, libRadtran exhibits the most accurate results when the AERONET aerosol phase function is presented as a two-term Henyey–Greenstein phase function. In this case libRadtran exhibited a relative RMSE and a bias of respectively 27 and −24 % and a coefficient of determination of 0.882. Therefore, AERONET data may very well be used to model the monochromatic DNIS and the monochromatic CSNI. The results are promising and pave the way towards reporting the contribution of the broadband circumsolar irradiance to standard measurements of the beam irradiance.

Can AERONET data be used to accurately model the monochromatic beam and circumsolar irradiances under cloud-free conditions in desert environment?

Routine measurements of the beam irradiance at normal incidence (DNI) include the irradiance originating from within the extent of the solar disc only (DNIS) whose angular extent is 0.266° ± 1.7 %, and that from a larger circumsolar region, called the circumsolar normal irradiance (CSNI). This study investigates if the spectral aerosol optical properties of the AERONET stations are sufficient for an accurate modelling of the monochromatic DNIS and CSNI under cloud-free conditions in a desert environment. The data from an AERONET station in Abu Dhabi, United Arab Emirates, and a collocated Sun and Aureole Measurement (SAM) instrument which offers reference measurements of the monochromatic profile of solar radiance, were exploited. Using the AERONET data both the radiative transfer models libRadtran and SMARTS offer an accurate estimate of the monochromatic DNIS, with a relative root mean square error (RMSE) of 5 %, a relative bias of +1 % and acoefficient of determination greater than 0.97. After testing two configurations in SMARTS and three in libRadtran for modelling the monochromatic CSNI, libRadtran exhibits the most accurate results when the AERONET aerosol phase function is presented as a Two Term Henyey–Greenstein phase function. In this case libRadtran exhibited a relative RMSE and a bias of respectively 22 and −19 % and a coefficient of determination of 0.89. The results are promising and pave the way towards reporting the contribution of the broadband circumsolar irradiance to standard DNI measurements.