View makes a difference: Presenting human figures from the back or front affects mental spatial transformations of children and adults

Previous research suggested that performance in spatial judgments involving rotated human figures is poorer if these figures are presented from the front than from the back. We further investigated this effect, controlling for visible facial information in front and back view by presenting figures' faces as profile. Children's and adults' judgments were still faster and less error prone if figures were presented from the back. Moreover, reaction times indicated that participants did not mentally rotate figures in front view. Children performed overall more poorly than adults, but there were also qualitative differences suggesting that children are more susceptible to embodiment effects than adults. This study underlines that embodiment may have differential effects in spatial transformation tasks, enhancing or impairing performance.     

Plasma Motion and Kinematics in Cool and Hot Stars

The environments of both hot and cool stars are the sites of highly dynamic processes involving motion of gas and plasma in winds, flows across shocks, plasma motions in closed magnetic fields, or streams along magnetospheric accretion funnels. X-ray spectroscopy has opened new windows toward the study of these processes. Kinematics are evident in line shifts and line broadening, and also more indirectly through the analysis and interpretation of density-sensitive lines. In hot stellar winds, expanding-wind kinematics are directly seen in broadened lines although the broadening has turned out to often be smaller than anticipated, and some lines are so narrow that coronal models have been revived. Although X-ray spectra of cool stars have shown line shifts and broadening due to the kinematics of the entire corona, e.g., in binary systems, intrinsic mass motions are challenging to observe at the presently available resolution. Much indirect evidence for mass motion in magnetic coronae is nevertheless available. And finally, spectral diagnostics has also led to a new picture of X-ray production in accreting pre-main sequence stars where massive accretion flows collide with the photospheric gas, producing shocks in which gas is heated to high temperatures. We summarize evidence for the above mechanisms based on spectroscopic data from XMM-Newton and Chandra.     

应用级信息安全解决方案的研究与设计

计算机网络的发展向信息安全提出了新的挑战,在电子商务给人们带来巨大便利的同时,也产生了很多的安全隐患。信息安全是一个不容忽视的问题,而且也越来越得到人们的重视。本文结合开发远程教材管理信息系统的实例,对应用级信息安全需求进行研究分析,根据应用系统的实际业务流程,构建其信息安全解决方案并加以实现。信息安全方案的实施保障了系统的安全性、远程数据传输的完整性和保密性。     

A material experiment for small satellites to characterise the behaviour of carbon nanotubes in space – development and ground validation

Over the last years, Carbon Nanotubes (CNT) drew interdisciplinary attention. Regarding space technologies a variety of potential applications were proposed and investigated. However, no complex data on the behaviour and degradation process of carbon nanotubes under space environment exist. Therefore, it is necessary to investigate the performance of these new materials in space environment and to revaluate the application potential of CNTs in space technologies.Hence, CiREX (Carbon Nanotubes – Resistance Experiment) was developed as a part of a student project. It is a small and compact experiment, which is designed for CubeSat class space satellites. These are a class of nanosatellites with a standardized size and shape. The CiREX design, electrical measurements and the satellites interfaces will be discussed in detail. CiREX is the first in-situ space material experiment for CNTs.To evaluate the data obtained from CiREX, ground validation tests are mandatory. As part of an extensive test series the behaviour of CNTs under solar ultra violet light (UV) and vacuum ultraviolet light (VUV) was examined. Single-walled carbon nanotubes (SWNT), multi-walled carbon nanotubes (MWNT) and MWNT/resin composite (ME) were exposed to different light sources. After the exposure, the defect density was investigated with Raman spectroscopy. There is a clear indication that UV and VUV light can increase the defect density of untreated CNTs and influence the electrical behaviour.     

The Swift X-Ray Telescope

he Swift Gamma-Ray Explorer is designed to make prompt multiwavelength observations of gamma-ray bursts (GRBs) and GRB afterglows. The X-ray telescope (XRT) enables Swift to determine GRB positions with a few arcseconds accuracy within 100 s of the burst onset. The XRT utilizes a mirror set built for JET-X and an XMM-Newton/EPIC MOS CCD detector to provide a sensitive broad-band (0.2–10 keV) X-ray imager with effective area of > 120 cm² at 1.5 keV, field of view of 23.6 × 23.6 arcminutes, and angular resolution of 18 arcseconds (HPD). The detection sensitivity is 2×10⁻¹⁴ erg cm⁻² s⁻¹ in 10⁴ s. The instrument is designed to provide automated source detection and position reporting within 5 s of target acquisition. It can also measure the redshifts of GRBs with Fe line emission or other spectral features. The XRT operates in an auto-exposure mode, adjusting the CCD readout mode automatically to optimize the science return for each frame as the source intensity fades. The XRT will measure spectra and lightcurves of the GRB afterglow beginning about a minute after the burst and will follow each burst for days or weeks. Dedicated to David J. Watson, in memory of his valuable contributions to this instrument.     

Neutron Monitor Records in Broader Historical Context

Man-made neutron monitors have provided a continuous detailed record of the cosmic-ray flux over only about the last 5 decades. Fortunately, nature operates its own detectors and offers the opportunity to extend the cosmic-ray records over much longer time scales. Two different types of `natural detectors' can be distinguished. The first is based on long lived radionuclides that are produced by cosmic-ray interactions in the atmosphere and subsequently become stored in archives such as ice sheets or tree rings. The second type are rocks that are exposed to cosmic-rays at a certain time and from then on integrate the production of cosmogenic nuclides over the whole exposure time. The analysis of ¹⁰Be in polar ice cores and ¹⁴C in tree rings clearly reveals solar and geomagnetic modulation of the cosmic-ray flux on different time scales ranging from decades (11-year Schwabe cycle) to millennia. This revised version was published online in August 2006 with corrections to the Cover Date.     

Qualitative Spatial Reasoning for Topological Map Learning

Abstract

In this paper we investigate the application of qualitative spatial reasoning methods for learning the topological map of an unknown environment. We develop a topological mapping framework that achieves robustness against ambiguity in the available information by tracking all possible graph hypotheses simultaneously. We then exploit spatial reasoning to reduce the space of possible hypotheses. The considered constraints are qualitative direction information and the assumption that the map is planar. We investigate the effects of absolute and relative direction information using two different spatial calculi and combine the approach with a real mapping system based on Voronoi graphs.     

Heavy ion induced double strand breaks in bacteria and bacteriophages.

DNA damage induced by heavy ions in bacterial cells and bacteriophages such as Bacillus subtilis, E. coli and Bacteriophage T1 were investigated by analyzing the double strand breaks in the chromosomal DNA. This kind of lesion is considered as one of the main reasons for lethal events. To analyze double strand breaks in long molecules of DNA--up to some Mbp in length--the technique of pulse field agarose gel electrophoresis has been used. This allows the detection of one double strand break per genome. Cell lysis and DNA isolation were performed in small agarose blocks directly. This procedure secured minimum DNA destruction by shearing forces. After running a gel, the DNA was stained with ethidium bromide. The light intensity of ethidium bromide fluorescence for both the outcoming (running) DNA and the remaining intact DNA were measured by scanning. The mean number of double strand breaks was calculated by determining the quotient of these intensities. Strand break induction after heavy ion and X-ray irradiation was compared.     

Direct radiation action of heavy ions on DNA as studied by ESR-spectroscopy.

The effects of heavy ions on the mechanisms of free radical formation in DNA-constituents as compared to low-LET irradiation are investigated by means of Electron Spin Resonance (ESR) spectroscopy. Dose-yield curves were measured at low (T < 100 K) and ambient temperatures in order to obtain the G-value, that is number of radicals formed per 100 eV absorbed energy. These G-values show a characteristic LET-dependence and are one to two orders of magnitude lower than for low-LET irradiation. Measurements on 2'Deoxycytidine at 300 K using combined heavy ion and X-ray irradiation methods suggested that this effect can be partially explained by a destruction of radicals during the irradiation.     

Global Non-Potential Magnetic Models of the Solar Corona During the March 2015 Eclipse

Seven different models are applied to the same problem of simulating the Sun’s coronal magnetic field during the solar eclipse on 2015 March 20. All of the models are non-potential, allowing for free magnetic energy, but the associated electric currents are developed in significantly different ways. This is not a direct comparison of the coronal modelling techniques, in that the different models also use different photospheric boundary conditions, reflecting the range of approaches currently used in the community. Despite the significant differences, the results show broad agreement in the overall magnetic topology. Among those models with significant volume currents in much of the corona, there is general agreement that the ratio of total to potential magnetic energy should be approximately 1.4. However, there are significant differences in the electric current distributions; while static extrapolations are best able to reproduce active regions, they are unable to recover sheared magnetic fields in filament channels using currently available vector magnetogram data. By contrast, time-evolving simulations can recover the filament channel fields at the expense of not matching the observed vector magnetic fields within active regions. We suggest that, at present, the best approach may be a hybrid model using static extrapolations but with additional energization informed by simplified evolution models. This is demonstrated by one of the models.