Helium isotopic ratios in carbonaceous chondrites: Significant for the early solar nebula and circumstellar diamonds?

Stepwise etching of acid-resistant residues from carbonaceous chondrites yields a new, extraordinarily low He isotopic ratio for phase Q that might represent early solar nebula composition. A much lower ratio possibly characterizes He-P3 from circumstellar diamonds

Phase Q - A carrier for subsolar noble gases

We discuss noble gases in the E-chondrite St. Mark's indicating that the subsolar component does not exclusively reside in enstatite. Element and isotope abundances including He are presented. Fractionation probably took place prior to incorporation

Subsolar noble gases in an acid-resistant residue of the EH5 chondrite St Mark's

Extract from the introduction: Enstatite chondrites have remarkable properties: they were formed in a reducing environment, they are putatively similar to precursor material of Earth, Venus, or Mercury, have a terrestrial oxygen isotopic composition and an uncommon noble gas signature [1-5]. Trapped noble gases in Echondrites are intermediate between solar and chondritic composition and consist of two components: Subsolar, enriched in Ar and Kr relative to Xe and Q-gas, possibly residing in enstatite, micro-vesicles or graphite within enstatite [6,7] and Q-gases [5,8]

Solar noble bases in enstatite chondrites and implications for the formation of the terrestrial planets

We report evidence for tiny amounts of - most likely primordial - noble gases with solar-like elemental and isotopic composition admixed to Q-type primordial noble gases in an E chondrite. We will discuss possible implications of this finding for terrestrial planet formation

On line etching of bulk EH5 St. Mark's – Radiogenic and subsolar noble gases

Introduction: On line etching is very useful to analyse noble gas components such as 'Q' or the solar wind [1, 2]. A bulk meteorite sample, however, has never been analysed by on line etching in order to characterise its complete noble gas inventory

The ingredients of the “Subsolar” noble gas component

On the basis of several experiments on separates of the EH5 chondrite St. Mark–s, we will argue that the 'subsolar' noble gas component is a mixture of solar-like, Q- and terrestrial noble gases

SCR and GCR exposure ages of plagioclase grains from lunar soil

The concentrations of solar wind implanted Ar-36 in mineral grains extracted from lunar soils show that they were exposed to the solar wind on the lunar surface for an integrated time of 10E4 to 10E5 years. From the bulk soil 61501 plagioclase separates of 8 grain size ranges was prepared. The depletion of the implanted gases was achieved by etching aliquot samples of 4 grain sizes to various degrees. The experimental results pertinent to the present discussion are: The spallogenic Ne is, as in most plagioclases from lunar soils, affected by diffusive losses and of no use. The Ar-36 of solar wind origin amounts to (2030 + or - 100) x 10E-8 ccSTP/g in the 150 to 200 mm size fraction and shows that these grains were exposed to the solar wind for at least 10,000 years. The Ne-21/Ne-22 ratio of the spallogenic Ne is 0.75 + or - 0.01 and in very good agreement with the value of this ratio in a plagioclase separate from rock 76535. This rock has had a simple exposure history and its plagioclases have a chemical composition quite similar to those studied. In addition to the noble gases, the heavy particle tracks in an aliquot of the 150 to 200 mm plagioclase separate were investigated and found 92% of the grains to contain more than 10E8 tracks/sq cm. This corresponds to a mean track density of (5 + or - 1) x 10E8 tracks/sq cm. The exploration of the exposure history of the plagioclase separates from the soil 61501 do not contradict the model for the regolith dynamics but also fail to prove it

Nitrogen and noble gases in the 71501 bulk soil and ilmenite as records of the solar wind exposure: Which is correct?

The N determination in mg sized mineral separates from lunar soils by static mass spectrometry is an experimental break-through likely to contribute to the deciphering of the records left in the mineral grains by the exposure to the solar wind. In this discussion some comparisons of the results of N and noble gas analyses of the 71501 bulk soil and an ilmenite separate thereof are focussed on. Conclusions from noble gas data obtained on mineral separates from some 20 soils are summarized in a companion paper and are also discussed herein

Cosmic ray records in Antarctic meteorites

The cosmogenic radionuclides Be(10), Al(26), and Mn(53) and noble gases were determined in more than 28 meteorites from Antarctica by nuclear analytical techniques and static mass spectrometry, respectively. The summarized results are listed. The concentrations of Al(26) and Mn(53) are normalized to the repective main target elements and given in dpm/kg Si sub eq and dpm/kg Fe. The errors stated include statistical as well as systematical errors. For noble gas concentrations estimated errors are 5% and for isotopic ratios 1.5%. Cosmic ray exposure ages T sub 21 were calculated by the noble gas concentrations and the terrestrial residence time (T) on the basis of the spallogenic nuclide Al(26). The suggested pairing of the LL6 chondrite RKPA 80238 and RKPA 80248 and the eucrites ALHA 76005 and ALHA 79017 is confirmed not only by the noble gas data but also by the concentrations of the spallation produced radionuclides. Futhermore, ALHA 80122, clasified as an H6 chondrite, has a noble gas pattern which suggest that this meteorite belongs to the ALHA 80111 shower

Skill-Biased Demand Shifts and the Wage Collapse in the United States: A Critical Perspective

The earnings of low-skill workers in the United States have fallen sharply since the late 1970's in both real and relative terms, an experience not shared by other advanced nations. It is widely held that the problem lies in skill-biased technological change: strong shifts in labor demand away from the least skilled caused by workplace computerization. With measures developed from both household and establishment data, we show that the skill mix of employment remained virtually unchanged after 1982 in computer-intensive manufacturing and service sectors, precisely the period in which computerization should have had its greatest employment impacts. We also find no association between wage growth and changes in skill mix across large occupation-industry groups. We conclude by suggesting that more weight should be placed on shifts in labor market institutions, public policies and managerial strategies in explaining the wage collapse.Earnings; Labor Demand; Skill Biased; Skills; Technological Change; Wage