The Heliospheric Imagers Onboard the STEREO Mission

Mounted on the sides of two widely separated spacecraft, the two Heliospheric Imager (HI) instruments onboard NASA’s STEREO mission view, for the first time, the space between the Sun and Earth. These instruments are wide-angle visible-light imagers that incorporate sufficient baffling to eliminate scattered light to the extent that the passage of solar coronal mass ejections (CMEs) through the heliosphere can be detected. Each HI instrument comprises two cameras, HI-1 and HI-2, which have 20° and 70° fields of view and are off-pointed from the Sun direction by 14.0° and 53.7°, respectively, with their optical axes aligned in the ecliptic plane. This arrangement provides coverage over solar elongation angles from 4.0° to 88.7° at the viewpoints of the two spacecraft, thereby allowing the observation of Earth-directed CMEs along the Sun?–?Earth line to the vicinity of the Earth and beyond. Given the two separated platforms, this also presents the first opportunity to view the structure and evolution of CMEs in three dimensions. The STEREO spacecraft were launched from Cape Canaveral Air Force Base in late October 2006, and the HI instruments have been performing scientific observations since early 2007. The design, development, manufacture, and calibration of these unique instruments are reviewed in this paper. Mission operations, including the initial commissioning phase and the science operations phase, are described. Data processing and analysis procedures are briefly discussed, and ground-test results and in-orbit observations are used to demonstrate that the performance of the instruments meets the original scientific requirements.     

Microscale pressure fluctuations in a mature deciduous forest

Static pressure fluctuations in the microscale range were measured in a mature deciduous forest. Pressure measurements were taken at the ground and above the canopy, and mean profile data of windspeed were collected from above the canopy to near the forest floor. Time series, spectra, and cross-correlations were calculated under different canopy conditions, and relationships between surface pressure fluctuations and mean windspeeds were determined. High-frequency pressure fluctuations that occur over aerodynamically smoother surfaces do not occur at the forest floor. These surface fluctuations are advected by the wind above the canopy, not that within the trunk space. The shapes of the pressure spectra are affected by changes in windspeed. Comparisons of spectra above and below the canopy also show some effect of the canopy itself on the shape of the pressure spectra.     

64层锥束CT扫描的优化系统

近年来X射线断层成像(CT)技术获得了突飞猛进的发展,自1998年推出4层螺旋CT后,CT扫描设备在容积覆盖,空间分辨率,扫描速度,切片数方面取得了长足进展.这不仅给医学应用带来了深远的影响,同时也给CT系统设计提出了巨大的挑战.容积CT(VCT)的设计过程引入了各种策略来战胜其复杂性.这些方法学包括:理论分析,系统性能预测的图像分析工具,各种基于专家背对背评价的参数优化.本文论述了64层CT系统设计中的一些考虑因素及优化过程.这些设计过程保证了锥束CT的优化性能.首批客户的应用反馈显示了我们设计实践的有效率性.     

Entanglement of Cape fur seals with man-made objects

The number of Cape fur seals Arctocephalus pusillus entangled with man-made objects was recorded during harvests of immature seals from 1972 to 1974 in one colony and from 1977 to 1979 in several colonies. Most of the objects were around the seals' necks. The percentage of harvested seals that were entangled was 0.12 in 1977 and 1979, and 0.11 in 1978. The highest incidence among harvested seals was recorded at the Cape Cross colony, viz., 0.56–0.66% from 1977 to 1979. These rates of entanglement at Cape Cross are possibly higher than those recorded at harvests of northern fur seals on the Pribilof Islands. Cape fur seals were entangled in string, monofilament line, fishing net, rope, plastic straps, rubber O-rings and wire.     

Long-term variation in mesohaline Chesapeake Bay macrobenthos: Spatial and temporal patterns

Macrobenthos, sediments, and environmental conditions were sampled in the mesohaline region of western Chesapeake Bay (1971–1984) and the Potomac River (1980–1984). The survey data were used to quantify variation in macrobenthos and the physicochemical environment due to seasonal dynamics, spatial pattern (regional and local), and annual as well as long-term trends. Field experiments were conducted to test hypotheses suggested by the analysis of the survey data. Long-term and regional changes in the physiochemical environment, particularly salinity and dissolved oxygen concentration, had major influences on regional and long-term abundance patterns of macrobenthos. Two major species groups were identified along the mesohaline salinity gradient: those characteristic of high and low mesohaline salinities. Salinity increased and dissolved oxygen concentration below the pycnocline declined over the 14 yr. Estuarine endemic and euryhaline marine species concomitantly decreased in abundance. Opportunist species responded to increasing salinity and declining oxygen levels with increases in abundance. Predation on macrobenthos by fish and crabs affected the amplitude of annual recruitment pulses. Food availability apparently determined the magnitude of summer macrobenthic mortality. Spring was a critical period for the establishment of distributional patterns. The macrobenthos of the upper Chesapeake Bay was relatively stable over the study period mainly due to the stability and predictability of physicochemical processes controlling recruitment patterns.     

The EUV Imaging Spectrometer for Hinode

The EUV Imaging Spectrometer (EIS) on Hinode will observe solar corona and upper transition region emission lines in the wavelength ranges 170?–?210 Å and 250?–?290 Å. The line centroid positions and profile widths will allow plasma velocities and turbulent or non-thermal line broadenings to be measured. We will derive local plasma temperatures and densities from the line intensities. The spectra will allow accurate determination of differential emission measure and element abundances within a variety of corona and transition region structures. These powerful spectroscopic diagnostics will allow identification and characterization of magnetic reconnection and wave propagation processes in the upper solar atmosphere. We will also directly study the detailed evolution and heating of coronal loops. The EIS instrument incorporates a unique two element, normal incidence design. The optics are coated with optimized multilayer coatings. We have selected highly efficient, backside-illuminated, thinned CCDs. These design features result in an instrument that has significantly greater effective area than previous orbiting EUV spectrographs with typical active region 2?–?5 s exposure times in the brightest lines. EIS can scan a field of 6×8.5 arc?min with spatial and velocity scales of 1 arc?sec and 25 km?s^?1 per pixel. The instrument design, its absolute calibration, and performance are described in detail in this paper. EIS will be used along with the Solar Optical Telescope (SOT) and the X-ray Telescope (XRT) for a wide range of studies of the solar atmosphere.     

Entanglement of Australian sea lions and New Zealand fur seals in lost fishing gear and other marine debris before and after Government and industry attempts to reduce the problem

In recent years, Australian governments and fishing industry associations have developed guiding principles aimed at reducing the impact of fishing on non-target species and the benthos and increasing community awareness of their efforts. To determine whether they reduced seal entanglement in lost fishing gear and other marine debris, we analysed Australian sea lion and New Zealand fur seal entanglement data collected from Kangaroo Island, South Australia. Contrary to our expectations, we found that entanglement rates did not decrease in recent years. The Australian sea lion entanglement rate (1.3% in 2002) and the New Zealand fur seal entanglement rate (0.9% in 2002) are the third and fourth highest reported for any seal species. Australian sea lions were most frequently entangled in monofilament gillnet that most likely originated from the shark fishery, which operates in the region where sea lions forage--south and east of Kangaroo Island. In contrast, New Zealand fur seals were most commonly entangled in loops of packing tape and trawl net fragments suspected to be from regional rock lobster and trawl fisheries. Based on recent entanglement studies, we estimate that 1478 seals die from entanglement each year in Australia. We discuss remedies such as education programs and government incentives that may reduce entanglements.