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Ca-,Al-rich refractory inclusions and Pt-metal nuggets in the Ningqiang carbonaceous chondrite

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Chinese Science Bulletin 1999年第8期44卷 725-731页

作者： A.El Goresy max-planck-institut fr Kernphysik 6 900 Heidelberg 1 Germany

Petrography and mineral chemistry of Ca, Al-rich inclusions of Ningqiang carbonaceous chondrite are studied and the highly Re-Os fractionated Pt-metal nuggets in it is discovered. The refractory inclusions are classified into melilite-spinel-rich, and spinel-pyroxene-rich types. The former probably crystallized from melts, while the latter could be aggregates of the nebular condensates. The strong f ractionation between Re and Os suggests a pre-solar origin of the Pt-metal nuggets, which probably experienced various processes of formation and evolution before being captured by the refractory inclusions as indicated by the depletions of W and Mo.

关键词： meteorite refractory inclusion Pt-metal nuggets solar nebula.

Refractive Focusing by Interstellar Clouds and the Rapid Polarization Angle Swing in QSO 1150+812

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Chinese Journal of Astronomy and Astrophysics 2006年第1期6卷 1-14页

作者： Shan-Jie Qian T. P. Krichbaum Xi-Zhen Zhang L. Fuhrmann G. Cimò A. Kraus T. Beckert S. Britzen A. Witzel J.A. Zensus National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 max-planck-institut für Radioastronomie Auf dem Hügel 69 53121 Bonn Germany max-planck-institut für astronomie KSnigstuhl 17 69117 Heidelberg Germany

A very rapid polarization position angle swing of -180° （with a time scale of ,-6 hours） observed at 2 cm in QSO 1150＋812 （z = 1.25） was reported by Kochenov ＆ Gabuzda. This very rare event is difficult to explain. We found a possible interpretation in the framework of a source model consisting of three polarized components, in which two compact polarized components are nearly simultaneously occulted by an interstellar cloud, with consequent focusing-defocusing effects. A specific plasma-lens model is proposed which can reasonably fit the polarized flux density curve with results derived for the two lensed components. Some physical parameters of the plasma-lens and the source components are estimated. The two compact polarized components are estimated to have brightness temperatures of -6 ×10^12 K. Thus a bulk relativistic motion with a Lorentz factor less than 10 is required to meet the inverse-Compton limit.

关键词： radio continuum: galaxies - galaxies: compact - polarization - scattering- quasars: individual: 1150+812

Tracking moving magnetic features in the photosphere

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Science China(Physics,Mechanics & Astronomy) 2009年第11期52卷 1737-1748页

作者： BCHNER Jrg max-planck-institut fr Sonnensystemforschung

This research aims for an objective identification, tracking, and a statistical analysis of the Moving Magnetic Features (MMFs) around sunspots using SOHO/MDI high-resolution magnetograms. To this end, we develop a computerized tracking program and study the motion and magnetism of the outflows of MMFs around 26 sunspots. Our method locates 4-27 MMFs per hour, with higher counts for large sunspots. We differentiate MMFs into type α that have a polarity opposite to the parent sunspots, and type β that share the sunspot's polarity. These sunspots' MMF subsets exhibit a wide range of central tendencies which have distinctive correlations with the sunspots. In general, α-MMFs emerge farther from the sunspot, carry less flux, and move faster than β-MMFs. The typical α/β-MMFs emerge at 2.2 - 8.1/0.1 - 3.2 Mm outside the penumbra limb, with lifetimes of 1.1 - 3.1/1.3 - 2.0 h. They are 1.1 - 6.6/1.4 - 3.6 Mm2 in area and carry 1.4 - 12.5/4.8 - 11.4 ×1018 Mx of flux. They travel a distance of 2.7 - 5.9/2.8 - 3.6 Mm with the speed of 0.5 - 0.9/0.4 - 0.7 km/s. Compared to the α-MMFs produced by large sunspots, those of small spots are smaller. They emerge closer to sunspot, move farther, live longer, and carry less flux. β-MMFs show much less correlation with the sunspots. The flux outflow carried by the MMFs ranges from 0.2 to 8.3 × 1019Mx· h-1 and does not show obvious correlation with the sunspots' evolution. The frequency distributions of the MMFs' distance traveled, area, and flux are exponential. This suggests the existence of numerous small, weak, and short-timescale magnetic objects which might contribute to the sunspot flux outflow.

关键词： sun activity magnetic fields photosphere sunspots moat moving magnetic features

Development of Powerful RF Plasma Sources for Present and Future NBI Systems

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Plasma Science and Technology 2004年第1期6卷 2135-2140页

作者： E.Speth NBI-Team max-planck-institut fiir Plasmaphysik 85748 Garching Germany EURATOM-AssociationMax-Planck-Institut fiir Plasmaphysik 85748 Garching Germany EURATOM-Association

This paper deals with the topic of RF plasma sources and their application inhigh-power neutral beam heating systems for nuclear fusion devices. RF sources represent aninteresting alternative to the conventional arc discharge sources. Due to the absence of hotfilaments they exhibit an inherent simplicity both in mechanical and electrical aspects andconsequently offer advantages in terms of cost savings, gain in availability and reliability andreduced maintenance. This renders the RF plasma source attractive for any long pulse (> 10 sec) NBIsystem and in particular for the ITER NBI system. The latter, however, requires that the RF plasmasource is also capable of delivering negative rather than positive hydrogen ions. In the first partof the paper the types, characteristics and operation experience of RF plasma sources for positiveions in operation are described. The second part is devoted to the development for ITER NBI: thebasic requirements, physics and technology issues and the present status are discussed.

关键词： neutral beam injection negative ions RF plasma source

Super-large-scale structures in the distribution of infrared galaxies

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Science China Mathematics 1999年第8期42卷 873-882页

作者：邓祖淦夏晓阳 G.Borner max-planck-institut for Astrophysik 85740 Garching

Typical scales in the distribution of IRAS galaxies with the unnormalized pair count method. Samples are those provided by QDOT redshift survey and sorted out from the IRAS faint sources catalog. Analysis is concentrated on the structures at super-large scales. The results show that statistically significant typical scales do exist in the distribution of all these samples from both 2-dimensiortal and 3-dimensional analyses. These scales are consistent with those found from the analyses of galaxies and clusters of galaxies by Mo et al. and also consistent with those found from analysis of quasars by Deng et al. The analysis provides additional evidence for the existence of typical scales in the large-scale structure of the universe. The existence of typical scales challenges all the existing models on the formation of galaxies and structures.

关键词： cosmology large-scale structures galaxies evolution formation.

High Brightness Temperatures in IDV Sources

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Chinese Journal of Astronomy and Astrophysics 2006年第5期6卷 530-542页

作者： Shan-Jie Qian T.P. Krichbaum A. Witzel J. A. Zensus Xi-Zhen Zhang National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 max-planck-institut for Radio astronomie Auf dem Htige169 53121 Bonn Germany

High brightness temperatures are a characteristic feature of IntraDay Variability （IDV） of extragalactic radio sources. Recent studies of the polarization properties of some IDV sources （e.g., 1150＋812, PKS 0405-385 and 0716＋714） have shown that these sources harbor several compact IDV components with angular sizes of -10-30μas and very high polarizations （of up to -50%-70%）. These results indicate the possibility of the existence of uniform magnetic fields in the IDV components. We investigate the incoherent synchrotron and self- Compton radiation of an anisotropic distribution of relativistic electrons which spin around the magnetic field lines at small pitch angles. The brightness temperature limit caused by second-order Compton losses is discussed and compared to the brightness temperatures derived from energy equipartition arguments. It is found that anisotropic distributions of electrons moving in ordered magnetic fields can raise the equipartition and Compton brightness temperatures by a factor of up to -3-5. This would remove some of the difficulties in the interpretation of extremely high intrinsic brightness temperatures of 〉 1012 K （or apparent brightness temperatures of - 10^14 K with a Doppler factor of -30）.

关键词： radio continuum galaxies - Quasars individual PKS 0405-385

Modeling the arc and ring structures in the HD 143006 disk

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Science China(Physics,Mechanics & Astronomy) 2022年第6期65卷 137-149页

作者： Yao Liu Mario Flock Min Fang Purple Mountain Observatory&Key Laboratory for Radio Astronomy Chinese Academy of SciencesNanjing 210023China max-planck-institut für astronomie Heidelberg D-69117Germany

Rings and asymmetries in protoplanetary disks are considered as signposts of ongoing planet *** this work,we con-duct three-dimensional radiative transfer simulations to model the intriguing disk around HD143006 that has three dust rings and a bright arc.A complex geometric configuration,with a misaligned inner disk,is assumed to account for the asymmetric *** two-dimensional surface density is constructed by iteratively fitting the ALMA *** find that the dust tem-perature displays a notable discontinuity at the boundary of the *** ring masses range from 0.6 to 16 M⊕that are systematically lower than those inferred in the younger HL Tau *** arc occupies nearly 20%of the total dust *** a high mass fraction of dust grains concentrated in a local region is consistent with the mechanism of dust trapping into *** a gas-to-dust mass ratio of 30 that is constant throughout the disk,the dense and cold arc is close to the threshold of being gravitationally unstable,with the Toomre parameter Q∼***,our estimate of Q relies on the assumption for the unknown gas-to-dust mass *** a lower gas-to-dust mass ratio would increase the inferred Q ***-up high resolution observations of dust and gas lines are needed to clarify the origin of the substructures.

关键词： protoplanetary disks radiative transfer planet formation

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Many faces of neuronal activity manipulation in Drosophila

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Neural Regeneration Research 2025年第9期20卷 2574-2576页

作者： Amber Krebs Steffen Kautzmann Christian Klämbt institut für Neuro-und Verhaltensbiologie MünsterGermany

Animals exhibit complex responses to external and internal *** information is computed by interconnected neurons that express numerous ion channels,which modulate the neuronal membrane *** can neuronal activity orchestrate complex motor patterns or allow learning from previous experience?To answer such questions,we need the ability not only to record,but also to modulate neuronal activity in both space(e.g.,neuronal subsets)and time.

关键词： manipulation potential. neuronal

CWA Formalizations in Multi-Valued Logics

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Journal of Computer Science & Technology 2001年第3期16卷 263-269页

作者：吴尽昭 max-planck-institut für Informatik Saarbrücken Germany

To enhance the expressive power and the declarative ability of a deductive database, various CWA (Closed World Assumption) formalizations including the naive CWA, the generalized CWA and the careful CWA are extended to multi-valued logics. The basic idea is to embed logic formulas into some polynomial ring. The extensions can be applied in a uniform manner to any finitely multi-valued logics. Therefore they are also of computational significance.

关键词： CWA formalization multi-valued logic polynomial form query evaluation