Semi-analytical modelling of linear mode coupling in few-mode fibers

This paper reviews and extends a method for the semi-analytical solution of the coupled linear differential equations that describe the linear mode coupling arising in few-mode fibers due to waveguide imperfections. The semi-analytical solutions obtained proved to be accurate when compared to numerical solution methods. These solutions were integrated into a multi-section model with split-steps for mode dispersion and mode coupling. Simulations using this model matched the analytical predictions for the statistics of group-delays in few-mode fiber links, considering different coupling regimes with and without mode delay management

On the group delay statistics of few-mode fibres with intermediate linear mode coupling

We report an investigation on the statistics of group delay for few-mode fibres operating in the weak and strong linear coupling regimes as well as in the intermediate coupling regime. A single expression linking the standard deviation of the group delay spread to the fibre linear mode coupling is validated for any coupling regime, considering up to six linearly polarized guided modes. Furthermore, the study of the probability density function of the group delays allowed deriving and validating an analytical estimation for the maximum group delay spread as a function of linear mode coupling

Receiver memory requirement in mode delay compensated few-mode fibre spans with intermediate coupling

The required receiver time window after propagation through few-mode fibre is studied for a broad range of coupling and mode delay span configurations. Under intermediate coupling, effective mode delay compensation is observed for a compensation period of 25km

Spectroscopy of globular clusters in the low-luminosity spiral galaxy NGC 45

CONTEXT: Extragalactic globular clusters have been studied in elliptical galaxies and in a few luminous spiral galaxies, but little is known about globular clusters in low-luminosity spirals. AIMS: Past observations with the ACS have shown that NGC 45 hosts a large population of globular clusters (19), as well as several young star clusters. In this work we aim to confirm the bona fide globular cluster status for 8 of 19 globular cluster candidates and to derive metallicities, ages, and velocities. METHODS: VLT/FORS2 multislit spectroscopy in combination with the Lick/IDS system was used to derive velocities and to constrain metallicities and [alpha/Fe] element ratio of the globular clusters. RESULTS: We confirm the 8 globular clusters as bona fide globular clusters. Their velocities indicate halo or bulge-like kinematics, with little or no overall rotation. From absorption indices such as H_beta, H_gamma, and H_delta and the combined [MgFe]' index, we found that the globular clusters are metal-poor [Z/H]<=-0.33 dex and [alpha/Fe]<=0.0 element ratio. These results argue in favor of a population of globular clusters formed during the assembling of the galaxy.Comment: Accepted for publication in Astronomy and Astrophysics. 10 pages, 6 figures. Table 6 and Fig. 6 will only be published in the electronic edition of the A&A journa

SkyMapper Southern Survey: First Data Release (DR1)

We present the first data release (DR1) of the SkyMapper Southern Survey, a hemispheric survey carried out with the SkyMapper Telescope at Siding Spring Observatory in Australia. Here, we present the survey strategy, data processing, catalogue construction and database schema. The DR1 dataset includes over 66,000 images from the Shallow Survey component, covering an area of 17,200 deg$^2$ in all six SkyMapper passbands $uvgriz$, while the full area covered by any passband exceeds 20,000 deg$^2$. The catalogues contain over 285 million unique astrophysical objects, complete to roughly 18 mag in all bands. We compare our $griz$ point-source photometry with PanSTARRS1 DR1 and note an RMS scatter of 2%. The internal reproducibility of SkyMapper photometry is on the order of 1%. Astrometric precision is better than 0.2 arcsec based on comparison with Gaia DR1. We describe the end-user database, through which data are presented to the world community, and provide some illustrative science queries.Comment: 31 pages, 19 figures, 10 tables, PASA, accepte

CHCHD4 regulates tumour proliferation and EMT-related phenotypes, through respiratory chain-mediated metabolism

Abstract: Background: Mitochondrial oxidative phosphorylation (OXPHOS) via the respiratory chain is required for the maintenance of tumour cell proliferation and regulation of epithelial to mesenchymal transition (EMT)-related phenotypes through mechanisms that are not fully understood. The essential mitochondrial import protein coiled-coil helix coiled-coil helix domain-containing protein 4 (CHCHD4) controls respiratory chain complex activity and oxygen consumption, and regulates the growth of tumours in vivo. In this study, we interrogate the importance of CHCHD4-regulated mitochondrial metabolism for tumour cell proliferation and EMT-related phenotypes, and elucidate key pathways involved. Results: Using in silico analyses of 967 tumour cell lines, and tumours from different cancer patient cohorts, we show that CHCHD4 expression positively correlates with OXPHOS and proliferative pathways including the mTORC1 signalling pathway. We show that CHCHD4 expression significantly correlates with the doubling time of a range of tumour cell lines, and that CHCHD4-mediated tumour cell growth and mTORC1 signalling is coupled to respiratory chain complex I (CI) activity. Using global metabolomics analysis, we show that CHCHD4 regulates amino acid metabolism, and that CHCHD4-mediated tumour cell growth is dependent on glutamine. We show that CHCHD4-mediated tumour cell growth is linked to CI-regulated mTORC1 signalling and amino acid metabolism. Finally, we show that CHCHD4 expression in tumours is inversely correlated with EMT-related gene expression, and that increased CHCHD4 expression in tumour cells modulates EMT-related phenotypes. Conclusions: CHCHD4 drives tumour cell growth and activates mTORC1 signalling through its control of respiratory chain mediated metabolism and complex I biology, and also regulates EMT-related phenotypes of tumour cells

An Expression for Nonlinear Noise in Optical Phase Conjugation Systems with Lumped Amplifiers

We develop an analytical formula for evaluating the impact of fiber nonlinearity in systems employing optical phase conjugation with multi-span lumped amplification, highlighting the detailed balance of effects leading to compensation when the phase conjugator is added to the middle of the link. We apply the approach to the effect of adding a pre-dispersion element to improve the symmetry, deriving the required optimum predispersion. The closed-form is validated through simulation and shows good matching with the results within a margin of error less than 0.2 dB

Congenital Neosporosis in Goats from the State of Minas Gerais, Brazil

Congenital Neospora caninum infection was diagnosed in two Saanen goat kids from two distinct herds with a history of abortion and weak newborn goat kids in the Southern region of the State of Minas Gerais, Brazil. The first kid was weak at birth, had difficulty to rise and was unable to nurse. Gross lesions of porencephaly and hydrocephalus ex vacuo were seen. Multifocal necrosis, gliosis and non-supurative encephalitis were observed in the brain. Several parasitic cysts with a thick wall that reacted strongly only with polyclonal antiserum to Neospora caninum were seen in the cerebral cortex, brain stem and cerebellum. The second kid was born from a Neospora caninum seropositive mother that aborted in the last pregnancy. It was born without clinical signs. The diagnosis of neosporosis was based on antibody titer of 1:800 to N. caninum by indirect fluorescence antibody test obtained from blood collected before the goat kid ingested the colostrum and Neospora caninum DNA was detected by polymerase chain reaction and sequenced from placenta. This is the first report of neosporosis in goats in the southeast region of Brazil

SkyMapper Southern Survey: Second Data Release (DR2)

We present the second data release (DR2) of the SkyMapper Southern Survey, a hemispheric survey carried out with the SkyMapper Telescope at Siding Spring Observatory in Australia, using six optical filters: $u,v,g,r,i,z$. DR2 is the first release to go beyond the $\sim$18mag (10${\sigma}$) limit of the Shallow Survey released in DR1, and includes portions of the sky at full survey depth that reach >21mag in $g$ and $r$ filters. The DR2 photometry has a precision as measured by internal reproducibility of 1% in $u$ and $v$, and 0.7% in $griz$. More than 21 000 deg$^2$ have data in some filters (at either Shallow or Main Survey depth) and over 7 000 deg$^2$ have deep Main Survey coverage in all six filters. Finally, about 18 000 deg$^2$ have Main Survey data in $i$ and $z$ filters, albeit not yet at full depth. The release contains over 120 000 images, as well as catalogues with over 500 million unique astrophysical objects and nearly 5 billion individual detections. It also contains cross-matches with a range of external catalogues such as Gaia DR2, Pan-STARRS1 DR1, GALEX GUVcat, 2MASS, and AllWISE, as well as spectroscopic surveys such as 2MRS, GALAH, 6dFGS, and 2dFLenS.Comment: 21 pages, 17 figures. As of 25 Aug 2020, DR2 is available to the world at http://skymapper.anu.edu.a

Effects of N-functional groups on the electron transfer kinetics of VO²⁺/VO₂⁺ at carbon:Decoupling morphology from chemical effects using model systems

Carbons and nanocarbons are important electrode materials for vanadium redox flow battery applications, however, the kinetics of vanadium species are often sluggish at these surfaces, thus prompting interest in functionalization strategies to improve performance. Herein, we investigate the effect of N-functionalities on the VO2+/VO2+ redox process at carbon electrodes. We fabricate thin film carbon disk electrodes that are metal-free, possess well-defined geometry and display smooth topography, while featuring different N-site distribution, thus enabling a mechanistic investigation of the intrinsic surface activity towards VO2+/VO2+. Voltammetry and electrochemical impedance spectroscopy show that N-functionalities improve performance, with pyridinic/pyrrolic-N imparting the most significant improvements in charge transfer rates and reversibility, compared to graphitic-N. This was further supported by voltammetry studies on nitrogen-free electrodes modified via aryldiazonium chemistry with molecular pyridyl adlayers. Computational modeling using an electrochemical-chemical mechanism indicates that introduction of surface pyridinic/pyrrolic-N can increase the heterogeneous rate constants by approximately two orders of magnitude relative to those observed at nitrogen-free carbon (k0 = 1.29 × 10−4 vs 9.34 × 10−7 cm/s). Simulations also suggest that these N-functionalities play a role in affecting reaction rates in the chemical step. Our results indicate that nitrogen incorporation via basic functional groups offers an interesting route to the design of advanced carbon electrodes for VRFB devices.</p