Experimental study on dynamic bending rigidity of aluminium cable steel reinforced

The dynamic bending rigidity of aluminium cable steel reinforced (ACSR) is a key parameter for analyzing the breeze vibration, galloping and de-icing vibration response of overhead transmission lines. In this paper, the calculation formula of the dynamic bending rigidity under axial force is derived based on the theory of Bernoulli-Euler beam. The dynamic response of one typical ACSR with different spans and different axial forces are studied by white-noise excitation and hammer excitation. The variation rules of dynamic bending rigidity of ACSR are presented. The comparison between the experimental results of the static and dynamic bending rigidity shows that the dynamic bending rigidity of the ACSR is much larger than the static bending rigidity

An Adaptive Optics Survey of Stellar Variability at the Galactic Center

We present a $\approx 11.5$ year adaptive optics (AO) study of stellar variability and search for eclipsing binaries in the central $\sim 0.4$ pc ($\sim 10''$) of the Milky Way nuclear star cluster. We measure the photometry of 563 stars using the Keck II NIRC2 imager ($K'$-band, $\lambda_0 = 2.124 \text{ } \mu \text{m}$). We achieve a photometric uncertainty floor of $\Delta m_{K'} \sim 0.03$ ($\approx 3\%$), comparable to the highest precision achieved in other AO studies. Approximately half of our sample ($50 \pm 2 \%$) shows variability. $52 \pm 5\%$ of known early-type young stars and $43 \pm 4 \%$ of known late-type giants are variable. These variability fractions are higher than those of other young, massive star populations or late-type giants in globular clusters, and can be largely explained by two factors. First, our experiment time baseline is sensitive to long-term intrinsic stellar variability. Second, the proper motion of stars behind spatial inhomogeneities in the foreground extinction screen can lead to variability. We recover the two known Galactic center eclipsing binary systems: IRS 16SW and S4-258 (E60). We constrain the Galactic center eclipsing binary fraction of known early-type stars to be at least $2.4 \pm 1.7\%$. We find no evidence of an eclipsing binary among the young S-stars nor among the young stellar disk members. These results are consistent with the local OB eclipsing binary fraction. We identify a new periodic variable, S2-36, with a 39.43 day period. Further observations are necessary to determine the nature of this source.Comment: 69 pages, 28 figures, 12 tables. Accepted for publication in The Astrophysical Journa

Use of data imputation tools to reconstruct incomplete air quality datasets:a case-study in Temuco, Chile

© 2018 Elsevier LtdMissing data from air quality datasets is a common problem, but is much more severe in small cities or localities. This poses a great challenge for environmental epidemiology as high exposures to pollutants worldwide occur in these settings and gaps in datasets hinder health studies that could later inform local and international policies. Here, we propose the use of imputation methods as a tool to reconstruct air quality datasets and have applied this approach to an air quality dataset in Temuco, a mid-size city in Chile as a case-study. We attempted to reconstruct the database comparing five approaches: mean imputation, conditional mean imputation, K-Nearest Neighbor imputation, multiple imputation and Bayesian Principal Component Analysis imputation. As a base for the imputation methods, linear regression models were fitted for PM2.5 against other air quality and meteorological variables. Methods were challenged against validation sets where data was removed arti

Povezanost polimorfizma pojedinačnog nukleotida gena ARID4A i kvalitete sperme kineskog vodenog bivola

ARID4A (AT-rich interaction domain 4A) is closely related to animal sperm quality traits. In the present study, the association between ARID4A gene polymorphisms of Chinese water buffalo (Bubalus bubalis) with sperm quality traits was examined, including ejaculate volume, sperm concentration, post-thaw sperm motility, and sperm abnormality of buffalo semen. Seven single-nucleotide polymorphisms (SNPs) of ARID4A gene were detected in 156 Chinese water buffaloes by Sanger sequencing and identifying overlap peaks. Among the SNPs, six were associated with at least one sperm quality trait. In brief, g.21192G>C, g.21285C>G, and g.21364A>G could be used as potential markers for selecting semen with low sperm abnormality, high ejaculate volume, sperm concentration, and sperm motility. Furthermore, 10 haplotypes (H1: -CTCGG, H2: GTGGCA, H3: GCGGCA, H4: GCTGCA, H5: GCTCGA, H6: GTGGGG, H7: GCTCCG, H8: -CGGGA, H9: GCGGCG, and H10: GTTGCA) were formed by the six SNPs through linkage disequilibrium analysis, and then 14 different combined haplotypes were collected. Correlation analysis showed that the combined H1H2 haplotype had the highest genotype frequency. Notably, the combined H1H2 haplotype had low sperm concentration, low sperm motility, and high sperm abnormality. The combined H2H3 haplotype could be used as a potential molecular marker for selecting semen with high sperm motility. In general, we illustrated a significant correlation between SNPs in ARID4A and sperm quality traits of Chinese water buffalo, which may be useful in the marker-assisted selection of buffalo breeding. This study was the first to analyze the genetic polymorphisms of ARID4A and association with sperm qualities of Chinese buffalo.Gen ARID4A (engl AT-rich interaction domain 4A) usko je povezan s kvalitetom sperme. U ovom je radu istraživana povezanost polimorfizma gena ARID4A u kineskih vodenih bivola (Bubalus bubalis) s kvalitetom sperme, uključujući volumen ejakulata, koncentraciju sperme, pokretljivost spermija nakon odmrzavanja i abnormalnost spermija u sjemenu bivola. U 156 kineskih vodenih bivola otkriveno je sedam polimorfizama pojedinačnog nukleotida (SNPs) gena ARID4A Sangerovim sekvenciranjem i identifikacijom preklopljenih vrhova. Među SNP-ovima njih je šest bilo povezano s barem jednim svojstvom kvalitete spermija. Ukratko, g. 21192G>C, g. 21285C>G i g. 21364A>G mogu se upotrijebiti kao potencijalni markeri za selekciju sjemena s niskom abnormalnošću spermija, većim volumenom ejakulata, većom koncentracijom i pokretljivošću spermija. Nadalje, šest SNP-ova formiralo je 10 haplotipova (H1: -CTCGG, H2: GTGGCA, H3: GCGGCA, H4: GCTGCA, H5: GCTCGA, H6: GTGGGG, H7: GCTCCG, H8: -CGGGA, H9: GCGGCG i H10: GTTGCA) analizom povezanosti nepodudarnosti te je ustanovljeno 14 različitih kombiniranih haplotipova. Analiza korelacije pokazala je da kombinirani haplotip H1H2 ima najveću učestalost. Kombinirani haplotip H1H2 imao je najmanju koncentraciju sperme, slabu pokretljivost seprmija i znatnu abnormalnost spermija. Kombinirani haplotip H2H3 može se upotrijebiti kao potencijalni molekularni marker za odabir sjemena s većom pokretljivošću. Općenito je pokazana znakovita korelacija između SNP-ova u ARID4A i kvalitete sperme kineskog vodenog bivola, što može biti korisno u selekciji bivola potpomognutoj markerima. Ovo je prvo istraživanje koje je analiziralo genske polimorfizme ARID4A i njihovu povezanost s kvalitetom sjemena kineskih vodenih bivola

Galactic Center: Improved Relative Astrometry for Velocities, Accelerations, and Orbits near the Supermassive Black Hole

We present improved relative astrometry for stars within the central half parsec of our Galactic Center (GC) based on data obtained with the 10 m W. M. Keck Observatory from 1995 to 2017. The new methods used to improve the astrometric precision and accuracy include correcting for local astrometric distortions, applying a magnitude-dependent additive error, and more carefully removing instances of stellar confusion. Additionally, we adopt jackknife methods to calculate velocity and acceleration uncertainties. The resulting median proper motion uncertainty is 0.05 mas yr^(−1) for our complete sample of 1184 stars in the central 10'' (0.4 pc). We have detected 24 accelerating sources, 2.6 times more than the number of previously published accelerating sources, which extend out to 4'' (0.16 pc) from the black hole. Based on S0-2's orbit, our new astrometric analysis has reduced the systematic error of the supermassive black hole (SMBH) by a factor of 2. The linear drift in our astrometric reference frame is also reduced in the north–south direction by a factor of 4. We also find the first potential astrometric binary candidate S0-27 in the GC. These astrometric improvements provide a foundation for future studies of the origin and dynamics of the young stars around the SMBH, the structure and dynamics of the old nuclear star cluster, the SMBH's properties derived from orbits, and tests of general relativity in a strong gravitational field

Analyzing long-term performance of the Keck-II adaptive optics system

We present an analysis of the long-term performance of the W. M. Keck Observatory Laser Guide Star Adaptive Optics (LGS-AO) system and explore factors that influence the overall AO performance most strongly. Astronomical surveys can take years or decades to finish, so it is worthwhile to characterize the AO performance on such timescales in order to better understand future results. Keck Observatory has two of the longest-running LGS-AO systems in use today and represents an excellent test-bed for investigating large amounts of AO data. Here, we use LGS-AO observations of the Galactic Center (GC) from 2005 to 2019, all taken with the NIRC2 instrument on the Keck-II telescope, for our analysis. We combine image metrics with AO telemetry files, MASS/DIMM turbulence profiles, seeing information, and weather data in one cohesive dataset to highlight areas of potential performance improvement and train a simple machine learning algorithm to predict the delivered image quality given current atmospheric conditions. The complete dataset will be released to the public as a resource for testing new predictive control and PSF-reconstruction algorithms