Far-UVC light as a new tool to reduce microbial burden during spacecraft assembly

This work aims to investigate far-UVC light at 222 nm as a new microbial reduction tool for planetary protection purposes which could potentially be integrated into the spacecraft assembly process. The major advantage of far-UVC (222 nm) compared to traditional germicidal UVC (254 nm) is the potential for application throughout the spacecraft assembly process in the presence of humans without adverse health effects due to the limited penetration of far-UVC light into biological materials. Testing the efficacy of 222-nm light at inactivating hardy bacterial cells and spores isolated from spacecraft and associated surfaces is a necessary step to evaluate this technology. We assessed survival of Bacillus pumilus SAFR-032 and Acinetobacter radioresistens 50v1 exposed to 222-nm light on proxy spacecraft surfaces simulated by drying the bacteria on aluminum coupons. The survival fraction of both bacteria followed a single stage decay function up to 60 mJ/cm², revealing similar susceptibility of both species to 222-nm light, which was independent of the exposure rate. Irradiation with far-UVC light at 222 nm is an effective method to decontaminate the proxy spacecraft materials tested in this study.     

Facile Fabrication of Hierarchical Porous N/O Functionalized Carbon Derived from Blighted Grains Towards Electrochemical Capacitors

The hierarchical porous N/O co-functionalized carbon(HPNOC)was scalably prepared by using the lowcost and renewable blighted grains as the raw material coupled with mild KHCO_3 activation for electrochemical capacitors(ECs).The elemental N was in situ doped in the obtained HPNOC without any N-containing additives.Remarkably,the obtained HPNOC was endowed with a large specific surface area(about 2 624m~2·g~(-1)),high pore volume(about 1.35cm~3·g~(-1)),as well as high-content N/O functionalization(about 1.9%(in atom)N and about 10.2%(in atom)O.Furthermore,the as-resulted HPNOC electrode with a high mass loading of 5mg·cm~(-2 )exhibited competitive gravimetric capacitances of about 373.6F·g~(-1 )at 0.5A·g~(-1),and even about 260.4F·g~(-1 )at a high rate of 10A·g~(-1);superior capacitance retention of about 98.8%at 1A·g~(-1 )over 10 000consecutive cycles;and high specific energy of about 9.6W·h·kg~(-1 )at a power of 500W·kg~(-1),when evaluated as a promising electrode in 6mol KOH for advanced electrochemical supercapacitors.More encouragingly,the green synthetic strategy we developed holds a huge promise in generalizing for other biomass-derived carbon materials for versatile energy-related applications.     

Water Partitioning in Planetary Embryos and Protoplanets with Magma Oceans

The water content of magma oceans is widely accepted as a key factor that determines whether a terrestrial planet is habitable. Water ocean mass is determined as a result not only of water delivery and loss, but also of water partitioning among several reservoirs. Here we review our current understanding of water partitioning among the atmosphere, magma ocean, and solid mantle of accreting planetary embryos and protoplanets just after giant collisions. Magma oceans are readily formed in planetary embryos and protoplanets in their accretion phase. Significant amounts of water are partitioned into magma oceans, provided the planetary building blocks are water-rich enough. Particularly important but still quite uncertain issues are how much water the planetary building blocks contain initially and how water goes out of the solidifying mantle and is finally degassed to the atmosphere. Constraints from both solar-system explorations and exoplanet observations and also from laboratory experiments are needed to resolve these issues.     

The Role and Contributions of Energetic Neutral Atom (ENA) Imaging in Magnetospheric Substorm Research

Energetic Neutral Atom (ENA) imaging has contributed substantially to substorm research. This technique has allowed significant advances in areas such as observation and quantification of injected particle drift as a function of energy, observation of dynamics in the tail that are directly related to the effects of imposed (growth phase) and induced (expansion phase) electric fields on the plasma, the prompt extraction of oxygen from the ionosphere during substorms, the relationship between storms and substorms, and the timing of substorm ENA signatures. We present discussion of the advantages and shortcomings of the ENA technique for studying space plasmas. Although the technique is in its infancy, it is yielding results that enrich our understanding of the substorm process and its effects.     

Evolution of UV-B regulation and protection in plants.

Plants have evolved under the influence of UV-B radiation and have acquired systems for monitoring it and investing appropriate resources for protection against it, i.e., filters, quenchers of radicals and reactive oxygen species, and repair systems. An hypothesis for how plants monitor radiation has been presented.     

Observations of the Acceleration of Polar Solar Wind Near Solar Maximum

In a previous paper (Tappin et al., 1999) we used cross-correlation analysis of high-cadence observations with the LASCO coronagraphs to trace the acceleration of the solar wind at low latitudes. In this paper we present a similar analysis carried out over the North pole of the Sun. The observations which were made in March 2000 with the C3 coronagraph show low bulk flow speeds (comparable to or lower than those seen at the equator in early 1998). We observe the acceleration continuing to the edge of the C3 field of view at about 30 R _⊙. We also observe, as at low latitude, a high-speed tail but now reaching out well beyond 2000 km s⁻¹. We do not see a clear signature of a fast polar bulk flow. We therefore conclude that at this phase of the solar cycle, any fast bulk flow occupies only a small part of the line of sight and is therefore overwhelmed by the denser slow solar wind in these observations. We also show that the fast component is consistent with observed solar wind speeds at 1 AU. This revised version was published online in August 2006 with corrections to the Cover Date.     

晶体管h参数微变等效电路的研究

晶体管h参数微变等效电路是电子技术中求解低频、小信号放大电路常用的分析方法.本文通过具体分析,将模拟放大电路进行了新的分类,并且明确而系统地给出运用微变等效电路求解各类模拟放大电路动态指标Av、ri和γ0公式、解题难点及规律.     

Magnetic turbulence at the magnetopause, a key problem for understanding the solar wind/ magnetosphere exchanges

According to ideal MHD, the magnetopause boundary should split the terrestrial environment in two disconnected domains: outside, the solar wind (including its shocked part, the magnetosheath), and inside, the magnetosphere. This view is at variance with the experimental data, which show that the magnetopause is not tight and that a net transfer of matter exists from the solar wind to the magnetosphere; it implies that the frozen-in condition must break down on the magnetopause, either over the whole boundary or at some points. In the absence of ordinary collisions, only short scale phenomena (temporal and/or spatial) can be invoked to explain this breakdown, and the best candidates in this respect appear to be the ULF magnetic fluctuations which show very strong amplitudes in the vicinity of the magnetopause boundary. It has been shown that these fluctuations are likely to originate in the magnetosheath, probably downstream of the quasi-parallel shock region, and that they can get amplified by a propagation effect when crossing the magnetopause. When studying the propagation across the magnetopause boundary, several effects are to be taken into account simultaneously to get reliable results: the magnetopause density gradient, the temperature effects, and the magnetic field rotation can be introduced while remaining in the framework of ideal MHD. In these conditions, the magnetopause amplification has been interpreted in term of Alfvén and slow resonances occurring in the layer. When, in addition, one takes the ion inertia effects into account, by the way of the Hall-MHD equations, the result appears drastically different: no resonance occurs, but a strong Alfvén wave can be trapped in the boundary between the point where it is converted from the incident wave and the point where it stops propagating back, i.e., the point where k _\|=0, which can exist thanks to the magnetic field rotation. This effect can bring about a new interpretation to the magnetopause transfers, since the Hall effect can allow reconnection near this particular point. The plasma transfer through the magnetopause could then be interpreted in terms of a reconnection mechanism directly driven by the magnetosheath turbulence, which is permanent, rather than due to any local instability of the boundary, for instance of the tearing type, which should be subject to an instability threshold and thus, as far as it exists, more sporadic.