A photometric and spectroscopic study of the brightest northern Cepheids — II. Fundamental physical parameters

We present a new Cepheid reddening and effective temperature scale based on the uvby photometry published in the first paper of this series. Using all available information about the companion stars in Cepheids with bright blue secondaries, we remove their light from the observed light and colour curves. The resulting corrections are as large as 0.05–0.15 mag in several cases for different colour indices. A new photometric approach based on the ( b  −  y ) versus ( B  − V ) two-colour diagram is tested with three other previous calibrations taken from the literature. Two uvby relations in earlier studies turn out to be the most reliable and consistent, and so they are used in deriving colour excesses. We determine systematically higher reddenings for Cepheids with a significant secondary light correction. The dereddened Stro¨mgren colours are calibrated in terms of T _eff and log  g using the most recent synthetic colour grids. Our temperature scale is very close to that of Kraft, which is supported by other recent temperature determinations using the infrared flux method or Geneva photometry. The photometric gravities fit some of the earlier theoretical and observational (mainly spectroscopic) results very well.     

Automated classification of stellar spectra — II. Two-dimensional classification with neural networks and principal components analysis

We investigate the application of neural networks to the automation of MK spectral classification. The data set for this project consists of a set of over 5000 optical (3800–5200 Å) spectra obtained from objective prism plates from the Michigan Spectral Survey. These spectra, along with their two-dimensional MK classifications listed in the Michigan Henry Draper Catalogue, were used to develop supervised neural network classifiers. We show that neural networks can give accurate spectral type classifications (σ₆₈= 0.82 subtypes, σ_rms= 1.09 subtypes) across the full range of spectral types present in the data set (B2–M7). We show also that the networks yield correct luminosity classes for over 95 per cent of both dwarfs and giants with a high degree of confidence.   Stellar spectra generally contain a large amount of redundant information. We investigate the application of principal components analysis (PCA) to the optimal compression of spectra. We show that PCA can compress the spectra by a factor of over 30 while retaining essentially all of the useful information in the data set. Furthermore, it is shown that this compression optimally removes noise and can be used to identify unusual spectra.   This paper is a continuation of the work carried out by von Hippel et al. (Paper I).     

非对称双塔连体结构柔性连接体系参数研究

基于非对称双塔连体结构柔性连接体系的3自由度（3-DOF）力学模型,利用虚拟激励法分析了连接构件的频率比、阻尼比和质量比等参数对该复杂结构体系地震反应的影响。根据不同的控制目标,得到了非对称双塔连体结构柔性连接体系支座优化设计参数变化规律和连接参数的优化组合,可用来指导此类结构的减震初步设计。最后以某实际工程为算例进行数值分析,验证了优化理论的正确性。     

Comparison in copper accumulation and physiological responses of Gracilaria lemaneiformis and G. lichenoides (Rhodophyceae)

Heavy metal pollution has become a worldwide problem in aquaculture. We studied copper (Cu2+ ) accumulation and physiological responses of two red algae Gracilaria lemaneiformis and Gracilaria lichenoides from China under Cu2+ exposure of 0-500 μg/L in concentration. Compared with G. lemaneiformis, G. lichenoides was more capable in accumulating Cu2+ , specifically, more Cu2+ on extracellular side (cell wall) than on intracellular side (cytoplasm) and in cell organelles (especially chloroplast, cell nucleus, mitochondria, and ribosome). In addition, G. lichenoides contained more insoluble polysaccharide in cell wall, which might promote the extracellular Cu2+ -binding as an efficient barrier against metal toxicity. Conversely, G. lemaneiformis was more vulnerable than G. lichenoides to Cu 2+ toxin for decreases in growth, pigment (chlorophyll a, chlorophyll b, phycobiliprotein, and β-carotene) content, and photosynthetic activity. Moreover, more serious oxidative damages in G. lemaneiformis than in G. lichenoides, in accumulation of reactive oxidative species and malondialdehyde, and in electrolyte leakage, because of lower antioxidant enzyme (superoxide dismutase and glutathione reductase) activities. Therefore, G. lichenoides was less susceptible to Cu2+ stress than G. lemaneiformis.     

苏北地区大地电磁测深采集方法技术研究

根据苏北地区大地电磁勘探环境特点进行了电极距长度、磁场位置和采集时长的试验工作，确定了大地电磁测深勘探技术参数设置下限，电极距长度不能小于50m，采集时间要大于8h，磁距应控制在2km范围内。     

Reconstruction of protoliths of metamorphic rocks and tectonic setting of Wolegen Group

Parametamorphic rocks from Arong County in southeastern Inner Mongolia-Daxinganling district are regarded as Proterozoic in age,belonging to the Wolegen Group and composed of volcanoclastic and sandstone in origin,and have been disputed in tectonic setting.Because of the stability in metamorphism,the rare earth dements indicate the features of their protoliths.The authors integrated the petrologic methods with the geochemical parameters which include ∑REE,∑LREE/∑HREE,δCe,δEu,La/Yb,Sm/Nd,Th/Sc and the standard values of chondrite.The results show that the protoliths of Wolengen Group may be a group of voleanoclastic and continental margin elastic rocks,and their tectonic setting is the continent island arc.     

The value of the superstring tension and dark matter

We start from our extended scenario for the formation of astronomical objects from fragmenting macroscopic superstrings, and we combine it with our view of an “orderly” fragmentation applied to the formation of black holes (Brosche, Lentes & Tassie 2003), now to the whole objects: the radial order of the matter should be preserved. Then we have to adapt the value of the superstring tension derived from the observed ratios of κ = (angular momentum)/(mass squared). If we calculate potential energies on the basis of a fragmentation until baryonic elementary particles, it turns out that the changed string tension explains as well the mechanical state of observed astronomical objects (without large energy loss on the way from the parent string parts) as also the fraction of bound to unbound matter (about 1:10). The implied superstring tension is about μ = (1/3000) c ²/G . This corresponds to a string tension of 4 × 10⁴⁰ Newton. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Study of Star/Galaxy Classification Based on the XGBoost Algorithm

Machine learning has achieved great success in many areas today. The lifting algorithm has a strong ability to adapt to various scenarios with a high accuracy, and has played a great role in many fields. But in astronomy, the application of lifting algorithms is still rare. In response to the low classification accuracy of the dark star/galaxy source set in the Sloan Digital Sky Survey (SDSS), a new research result of machine learning, eXtreme Gradient Boosting (XGBoost), has been introduced. The complete photometric data set is obtained from the SDSS-DR7, and divided into a bright source set and a dark source set according to the star magnitude. Firstly, the ten-fold cross-validation method is used for the bright source set and the dark source set respectively, and the XGBoost algorithm is used to establish the star/galaxy classification model. Then, the grid search and other methods are used to adjust the XGBoost parameters. Finally, based on the galaxy classification accuracy and other indicators, the classification results are analyzed, by comparing with the models of function tree (FT), Adaptive boosting (Adaboost), Random Forest (RF), Gradient Boosting Decision Tree (GBDT), Stacked Denoising AutoEncoders (SDAE), and Deep Belief Nets (DBN). The experimental results show that, the XGBoost improves the classification accuracy of galaxies in the dark source classification by nearly 10% as compared to the function tree algorithm, and improves the classification accuracy of sources with the darkest magnitudes in the dark source set by nearly 5% as compared to the function tree algorithm. Compared with other traditional machine learning algorithms and deep neural networks, the XGBoost also has different degrees of improvement.     

More than two hundred and fifty thousand spectroscopic binary or variable star candidates discovered by LAMOST

About 786.4 thousand stars were observed by LAMOST twice or more during the first stage of its spectroscopic survey. The radial velocity differences for about 256 thousand targets are larger than10 km s^-1 and they are possible spectroscopic binary or variable candidates(SBVCs). It is shown that most SBVCs are slightly metal poorer than the Sun. There are two peaks in the temperature distribution of SBVCs around 5760 K and 4870 K, while there are three peaks in the distribution of the gravitational acceleration at 2.461, 4.171 and 4.621 cm s^-2. The locations of SBVCs on the [Fe/H]-T, [Fe/H]-log g, log g-T and H-R diagrams are investigated. It is found that the detected SBVCs could be classified into four groups. The first group has higher log g～4.621 and lower T ～ 4870 K which are mainly cool red dwarf binaries. The second group of SBVCs has logg around 4.171 cm s^-2 that includes binaries and pulsating stars such as δSet and γ Dor variables. The gravitational accelerations of the third group of SBVCs are higher and some of them are below the zero-age main sequence. They may be contact binaries in which the primary components are losing energy to the secondaries in the common envelopes and are at a special stellar evolutionary stage.The last group is composed of giants or supergiants with log g around 2.461 cm s^-2 that may be evolved pulsating stars. One target(C134624.29+333921.2) is confirmed as an eclipsing binary with a period of 0.65 days. A preliminary analysis suggests that it is a detached binary with a mass ratio of 0.46. The primary fills its critical Roche lobe by about 89%, indicating that mass transfer will occur between the two components.     

Galaxy groups at 0.3 ≤z≤ 0.55 – I. Group properties

The evolution of galaxies in groups may have important implications for the evolution of the star formation history of the Universe, since many processes which operate in groups may suppress star formation and the fraction of galaxies in bound groups grows rapidly between   z = 1  and the present day. In this paper, we present an investigation of the properties of galaxies in galaxy groups at intermediate redshift  ( z ∼ 0.4)  . The groups were selected from the Canadian Network for Observational Cosmology Redshift Survey (CNOC2) redshift survey as described by Carlberg et al., with further spectroscopic follow-up undertaken at the Magellan telescope in order to improve the completeness and depth of the sample. We present the data for the individual groups, and find no clear trend in the fraction of passive galaxies with group velocity dispersion and group concentration. We stack the galaxy groups in order to compare the properties of group galaxies with those of field galaxies at the same redshift. The groups contain a larger fraction of passive galaxies than the field, this trend being particularly clear for galaxies brighter than   M _{B J} < −20  in the higher velocity dispersion groups. In addition, we see evidence for an excess of bright passive galaxies in the groups relative to the field. In contrast, the luminosity functions of the star-forming galaxies in the groups and the field are consistent. These trends are qualitatively consistent with the differences between group and field galaxies seen in the local Universe.