Enrichment of the Hot Intracluster Medium: Observations

Four decades ago, the firm detection of an Fe-K emission feature in the X-ray spectrum of the Perseus cluster revealed the presence of iron in its hot intracluster medium (ICM). With more advanced missions successfully launched over the last 20 years, this discovery has been extended to many other metals and to the hot atmospheres of many other galaxy clusters, groups, and giant elliptical galaxies, as evidence that the elemental bricks of life—synthesized by stars and supernovae—are also found at the largest scales of the Universe. Because the ICM, emitting in X-rays, is in collisional ionisation equilibrium, its elemental abundances can in principle be accurately measured. These abundance measurements, in turn, are valuable to constrain the physics and environmental conditions of the Type Ia and core-collapse supernovae that exploded and enriched the ICM over the entire cluster volume. On the other hand, the spatial distribution of metals across the ICM constitutes a remarkable signature of the chemical history and evolution of clusters, groups, and ellipticals. Here, we summarise the most significant achievements in measuring elemental abundances in the ICM, from the very first attempts up to the era of XMM-Newton, Chandra, and Suzaku and the unprecedented results obtained by Hitomi. We also discuss the current systematic limitations of these measurements and how the future missions XRISM and Athena will further improve our current knowledge of the ICM enrichment.     

Spirulina acceptability trials in rats. A study for the "MELISSA" life-support system.

Groups of five rats were fed for sixteen weeks a slightly deficient diet, supplemented with 0-40% of a dried preparation of the blue-green alga Spirulina as a protein source. Control groups were fed a normal rat diet. No significant differences between groups were found in food intake, growth rate or carbon dioxide production. All animals remained apparently healthy, and had similar organ weights. The study suggests that Spirulina may be used as a protein source in rat diets.     

The soft X-ray spectrum of NGC 4151

EXOSAT observations of the Seyfert galaxy NGC 4151 over the period July 1983 to April 1984 have revealed a decreasing flux in the 2 –10 keV band. In accord with previous measurements a power law spectrum attenuated with a simple column of cold gas does not provide a satisfactory spectral fit below 3 keV, where a lower relative opacity is required. Inclusion of additional low energy data from the EXOSAT telescopes allows the modelling of the absorbing column to be improved and reveals a second, separate, soft X-ray spectral component.     

Possible influence of solar radiation variability on the stratospheric temperature

Using daily temperature data available from radio-sonde measurements over Barajas (Madrid), La Coruña and Palma de Mallorca stations, for the time span 1971–1982 and an altitude range 100-30 mb, a study is made comparing temperatures at differents levels with the 10.7 cm flux in order to check whether radiation variability must be included in lower stratospheric models. At the latitude studied, stratospheric temperatures are uninfluenced by sudden warming phenomena avoiding difficulties of masking found in previous studies.     

VTOL Aircraft Control Output Tracking Sensitivity Design

A method is presented for reducing trajectory sensitivity and achieving robust asymptotic tracking for linear feedback systems when there are parameter perturbations and disturbance inputs. The controller consists of a servocompensator containing the modes of the reference signals and disturbance inputs, a stabilizing feedback loop, and a feedforward compensator. Application of the method to the design of a vertical takeoff and landing (VTOL) aircraft flight control system is discussed. The use of a precompensator allows performance maneuvers such that the aircraft tracks desired trajectories and the feedforward and feedback signals aid in reducing the trajectory sensitivity to variations of parameters due to change in airspeed and to wind gust. Simulation results are presented to show the robust tracking, disturbance rejection, and sensitivity reduction capabilities of the flight control system.     

A new window on the cosmos: The Stratospheric Observatory for Infrared Astronomy (SOFIA)

The Stratospheric Observatory for Infrared Astronomy (SOFIA) is a joint US/German Project to develop and operate a gyrostabilized 2.5-m telescope in a Boeing 747-SP. This observatory will allow astronomical observations from 0.3 μm to sub-millimeter wavelengths at stratospheric altitudes as high as 45,000 ft where the atmosphere is not only cloud-free, but largely transparent at infrared wavelengths. The dynamics and chemistry of interstellar matter, and the details of embedded star formation will be key science goals. In addition, SOFIA’s unique portability will enable large-telescope observations at sites required to observe transient phenomena and location specific events. SOFIA will offer the convenient accessibility of a ground-based telescope for servicing, maintenance, and regular technology upgrades, yet will also have many of the performance advantages of a space-based telescope. Initially, SOFIA will fly with nine first-generation focal plane instruments that include broad-band imagers, moderate resolution spectrographs that will resolve broad features from dust and large molecules, and high resolution spectrometers capable of studying the chemistry and detailed kinematics of molecular and atomic gas. First science flights will begin in 2010, leading to a full operations schedule of about 120 8–10 h flights per year by 2014. The next call for instrument development that can respond to scientifically exciting new technologies will be issued in 2010. We describe the SOFIA facility and outline the opportunities for observations by the general scientific community with cutting edge focal plane technology. We summarize the operational characteristics of the first-generation instruments and give specific examples of the types of fundamental scientific studies these instruments are expected to make.     

布撒器气动特性分析

为了确定布撒器的气动特性 ,在中国空气动力研究与发展中心高速所 0 .6m× 0 .6m风洞中进行了 1 :7缩比模型常规测力试验。实验结果表明 :在实验攻角下 ,布撒器横向稳定 ;在小攻角下布撒器呈方向静安定 ;如果俯仰舵偏为可用偏转角度的一半 ,布撒器纵向最大配平攻角约为 4°～ 6°之间 ;如果采用全部舵偏 ,布撒器在所有实验攻角下均可配平。