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We report the 10Be contents of 22 ureilites and the 26Al contents of 18 ureilites. When corrected for exposure age, where known, and for composition, the results give production rates, P, that are on average 20% lower than values typical of other meteorite classes. This depression of production rates, the weak correlation of both 26 and P10 with 22 Ne 21 Ne , and the generally high 3 He 21 Ne and 22 Ne 21 Ne ratios in ureilites all suggest that many of the samples occupied near-surface locations in their parent meteoroids. A reduced flux of cosmic rays does not by itself explain the elevated 22 Ne 21 Ne ratios and appears inconsistent with a proposed source for ureilites in the inner asteroid belt. Cosmogenic radionuclide data do not support the tentative pairing of ALHA 78019 with ALHA 78262 proposed on the basis of mineralogical similarities. The high 26Al content of LEW 85440 may be the result of irradiation by solar cosmic rays.

A sequential sample treatment system is described that permits use of an isotope‐ratio mass spectrometer for automated Rittenberg analyses of ammonium salts. This system is based on the design of McInteer and Montoya [Recent Developments in Mass Spectrometry in Biochemistry, Medicine and Environmental Research, edited by A. Frigerio (Elsevier, Amsterdam, 1981), Vol. 7, p. 343]. An x‐y table and a set of valves under computer control are used to automatically perform hypobromite oxidations, introduce the N2 thus liberated to the mass spectrometer for isotope‐ratio analysis, and effect spent sample pumpaway. Analyses can be performed on samples containing 20 μg of N. When operated with a Nuclide Model 3‐60‐RMS double‐collector mass spectrometer, the standard deviation for measurements at the natural abundance level (12 samples, 50 or 100 μg of N per sample) ranged from 0.0002 to 0.000 06 at. % 15N. Throughput capacity is 100–250 samples per day, and unattended operation can continue for at least three days.

We determined by ICP-MS the concentrations and isotopic ratios of Fe, Cu, and Zn in the Ti-rich lunar basalt 74275, in the lunar orange glass 74220, and in up to 10 lunar soils, namely, 14163, 15231, 64501, 66041, 68841, 69941, 70011, 72501, 75081, and 76501. Two analyses of zinc in lunar basalt 74275 give δ 66 Zn = 0.17‰ and 0.75‰, values within the range of those measured in terrestrial basalts; copper in lunar basalt 74275 has δ 65 Cu ∼ +1.4‰, which is isotopically heavier than values observed in terrestrial basalts. In the orange glass, we measured δ 56 Fe = −0.24‰, δ 65 Cu = −0.42‰, and δ 66 Zn ∼ −3.6‰. These values of δ are more negative than those obtained for 74275 and for typical lunar basalts, but for Cu, comparable to those observed in terrestrial sulfides and meteorites. In lunar soils we found 0.11‰ ⩽ δ 56 Fe ⩽ 0.51‰, 2.6‰ ⩽ δ 65 Cu ⩽ 4.5‰, and 2.2‰ ⩽ δ 66 Zn ⩽ 6.4‰. Insofar as we can generalize from a small sample set, S, Fe, Cu, Zn, and Cd show similar trends in isotopic fractionation on the Moon. Lunar basalts have nearly terrestrial isotopic ratios. Relative to the lunar basalt 74275, the pyroclastic glass 74220 is enriched in the lighter isotopes of Fe, Cu, and Zn, and the soils are enriched in the heavier isotopes of Fe, Cu, and Zn. The patterns in the basalts are likely inherited from the source material; the light-isotope enrichments seen in the orange glass originated during lava fountaining or, less probably, during partial condensation of vapor; and the heavy-isotope enrichments in the lunar soils were likely created by a combination of processes that included micrometeorite vaporization and sputtering. In the orange glass, the light-isotope enrichments (relative to lunar basalts) of Zn are larger than those of Cu. If these enrichments reflect accurately the isotopic composition of the gas, they suggest that Cu is more volatile than Zn in the liquid from which the gas derived. A simple model built on the known flux of micrometeorites to the lunar surface and a published estimate that micrometeorites generate 10 times their own mass of vapor, predicts heavy-isotope enrichments comparable to those observed in soils but only if the regolith gardening rate is set at about one twentieth of the generally accepted value of 1 cm/My. This discrepancy may reflect the difference in the time constants for micrometeorite milling and decimeter-scale gardening, or the importance of sputtering.

Agri-environment schemes are an increasingly important tool for the maintenance and restoration of farmland biodiversity in Europe but their ecological effects are poorly known. Scheme design is partly based on non-ecological considerations and poses important restrictions on evaluation studies. We describe a robust approach to evaluate agri-environment schemes and use it to evaluate the biodiversity effects of agri-environment schemes in five European countries. We compared species density of vascular plants, birds, bees, grasshoppers and crickets, and spiders on 202 paired fields, one with an agri-environment scheme, the other conventionally managed. In all countries, agri-environment schemes had marginal to moderately positive effects on biodiversity. However, uncommon species benefited in only two of five countries and species listed in Red Data Books rarely benefited from agri-environment schemes. Scheme objectives may need to differentiate between biodiversity of common species that can be enhanced with relatively simple modifications in farming practices and diversity or abundance of endangered species which require more elaborate conservation measures.

We present a coherent optical commu nication system for inter-satellite links with a new type of Optical Phase Lock Loop (OPLL). The OPLL requires no residual carrier transmission, although it employs a conventional 180° 3 dB hybrid and an AC-coupled balanced front end.

A new type of optical phase-locked loop (OPLL), called the dither loop, is mathematically analyzed. The dither loop extracts a phase-error signal by applying a small phase disturbance to the local oscillator laser, and synchronously demodulating the resulting power fluctuation in the output signal of the receiver. The dither loop is superior to other OPLL designs, because it does not need the transmission of a residual carrier, it employs a 180deg/3-dB hybrid, an ac-coupled front end, and it accepts a large variety of input signals. Furthermore, in a dither loop, the amount of power which is fed to the phase-locking branch can be adaptively controlled within the receiver. The analysis first focuses on an expression for the phase detector gain in a dither loop. Using a linearized model, the phase-error variance due to phase dithering, white frequency noise induced phase noise and shot noise is evaluated. A simplified expression for the power penalty generated by the phase dither signal is presented. In a more complex calculation, the overall power penalty due to phase dithering and the residual phase error is found. This allows us to synthesize a design rule for dither loops with optimum performance measures. The design rule determines all relevant system parameters, based on specified values of the system bit rate, the laser linewidth, the photodiode responsivity and the required bit-error rate

We measured the elemental compositions of material from 23 particles in aerogel and from residue in seven craters in aluminum foil that was collected during passage of the Stardust spacecraft through the coma of comet 81P/Wild 2. These particles are chemically heterogeneous at the largest size scale analyzed (∼180 ng). The mean elemental composition of this Wild 2 material is consistent with the CI meteorite composition, which is thought to represent the bulk composition of the solar system, for the elements Mg, Si, Mn, Fe, and Ni to 35%, and for Ca and Ti to 60%. The elements Cu, Zn, and Ga appear enriched in this Wild 2 material, which suggests that the CI meteorites may not represent the solar system composition for these moderately volatile minor elements.

Atmospheric heating alters the compositions and textures of micrometeorites. To understand the changes and to test a proposed relationship between a micrometeorite’s petrographic texture and its degree of heating, we made elemental and multiple isotope analyses of stony cosmic spherules (sCS) collected from the South Pole Water well. Specifically, we analyzed the elemental compositions of 94 sCS and the isotopic ratios of Fe, K and O, on 43, 12 and 8 of these sCS, respectively. Our results show that sCS classified as strongly heated generally have lower concentrations of volatile and moderately volatile elements. Of the 43 spherules analyzed for Fe isotopes, only 5 have δ57Fe >5‰. In contrast, enrichment of 41K is pervasive (δ41K >0 in all 12 spherules analyzed) and large (up to 183‰). The determination of K isotope abundances in sCS may therefore be useful in deciphering thermal histories. Three of the eight sCS analyzed for O isotopes are mass fractionated with δ18O >30‰. We attribute two of these three δ18O enrichments to evaporative losses of oxygen in the atmosphere and the third to the presence in the parent material of an exotic phase, perhaps a sulfate or a carbonate. The K isotope and O isotope data are broadly consistent with the proposed textural classification. Because most spherules were not heated enough to fractionate Al, Mg, or Si, we compared the measured Mg/Al and Si/Al ratios directly to those of conventional meteorites and their matrices. ∼30% of the sCS have compositions outside the range defined by the bulk and the matrix compositions of known meteorite groups but consistent with those of pyroxene- and olivine-rich materials and may be samples of chondrules. The other 70% have Mg/Al and Si/Al ratios similar to those of CI, CM, CO, and CV chondrites. Natural variability of the Mg/Al and Si/Al ratios precludes the assignment of an individual sCS to a particular class of C-chondrite.

We report systematic growth optimization of high Al-content AlGaAs, AlAs, and associated modulation-doped quantum well (QW) heterostructures on on-axis and misoriented GaAs (111)B by molecular beam epitaxy. Growth temperatures TG > 690 °C and low As4 fluxes close to group III-rich growth significantly suppress twin defects in high-Al content AlGaAs on on-axis GaAs (111)B, as quantified by atomic force and transmission electron microscopy as well as x-ray diffraction. Mirror-smooth and defect-free AlAs with pronounced step-flow morphology was further achieved by growth on 2° misoriented GaAs (111)B toward [01¯1] and [21¯1¯] orientations. Successful fabrication of modulation-doped AlAs QW structures on these misoriented substrates yielded record electron mobilities (at 1.15 K) in excess of 13 000 cm2/Vs at sheet carrier densities of 5 × 1011 cm−2.

Fragestellungen Das femoroacetabulare Impingement (FAI) wurde in jungerer Zeit als wichtige Ursache von anstrengungsabhangigem Leistenschmerz, verbunden mit Bewegungseinschrankung bei jungen, sportliche aktiven Patienten, erkannt. Zudem scheint es eine Verbindung zwischen FAI und der Entwicklung einer Coxarthrose in jungem Alter zu geben. Die chirurgische Therapie uber eine offene Huftluxation mit Trochanterosteotomie nach Ganz war bislang der Goldstandard. Seit einigen Jahren erfolgt die Behandlung des FAI zunehmend arthroskopisch. Angaben uber die sportliche Leistungsfahigkeit von Breitensportlern nach arthroskopischer Offset-Korrektur fehlen in der Literatur. Die vorliegende Arbeit analysiert deshalb detailiert die sportlichen Aktivitaten durchschnittlich 2,4 Jahre postoperativ. Methodik Es konnten konsekutiv 53 Patienten (41 Manner, 12 Frauen) mit CAM und Mixed Impingement pra- und postoperativ mit einer Follow-up-Dauer von durchschnittlich 2,4 Jahre (2–3,2 Jahre) evaluiert werden. Dies schloss Art und Ausmas der sportlichen Aktivitaten (Sports fequency score, SFS) sowie klinische Daten wie Schmerz (VAS, 0–10) und Funktion (Nonarthritic hip score, NAHS) ein. Ergebnisse 45 der 53 Patienten waren vor Symptombeginn regelmasig sportlichen Aktivitaten nachgegangen. Praoperativ waren nur vier dieser 45 Patienten in der Lage, ihr ursprungliches sportliches Niveau zu halten, die Mehrheit musste jegliche sportliche Aktivitat aufgeben. Postoperativ waren 31 der 45 sportlich aktiven Patienten wieder in der Lage, dieselbe sportliche Leistungsfahigkeit zu erreichen, wie vor Symptombeginn. Der SFS nahm von 0,78 auf 1,84 (p Praoperativ fand sich keine Korrelation zwischen SFS und NAHS (r=0,051, p=0,35), beziehungsweise zwischen SFS und Schmerzscore (r=0,159, p=0,140). Postoperativ war dies jedoch der Fall (SFS/NAHS: r=0,392, p=0,003; SFS/VAS: r=0,242, p=0,049). Die drei am haufigsten ausgeubten Sportarten waren postoperativ Wandern, Velofahren und Fitness. Schlussfolgerungen Die arthroskopische Offset-Korrektur bei femoroacetabularem Impingement kann sowohl die Rate sportlich aktiver Patienten als auch das Leistungsniveau Betroffener im Breitensport signifikant steigern. Das sportliche Leistungsniveau korrelierte nach dem Eingriff mit dem klinischen Resultat bezuglich Schmerz und Funktionsscore. Das Ausmas der wunschenswerten sportlichen Aktivitaten bei diesen Patienten, die oft bereits chondrale/labrale Schaden aufweisen, ist aber noch genauer zu definieren.

Purpose: The purpose of this study was to determine the accuracy of arthroscopic restoration of femoral offset as well as the early clinical outcome of arthroscopic debridement and femoral offset restoration and whether there is a correlation between accuracy and outcome. Methods: Twenty-two patients with symptomatic femoroacetabular cam impingement underwent arthroscopic correction of the femoral offset and debridement. The α angle was measured with magnetic resonance imaging preoperatively and postoperatively for quantification of the offset, and the clinical status was determined by documenting the impingement sign, range of motion, intensity of pain on a visual analog scale, Nonarthritic Hip Score, and complications preoperatively and 6 months postoperatively. Results: The α angle improved from a mean of 75° to 54°. Internal rotation increased from a mean of 5° to 22°, flexion increased from a mean of 107° to 124°, and the pain score decreased from a mean of 5.8 to 1.4. The Nonarthritic Hip Score increased from a mean of 49 to 74 points. No major complications were encountered. Patients with early osteoarthritis did substantially worse than those without it. The α angle did not correlate with any clinical outcome measure. Conclusions: The femoral offset can be precisely restored via an arthroscopic technique in the treatment of femoroacetabular cam impingement. The early clinical outcome of arthroscopic offset restoration and debridement is good in patients with no or only mild osteoarthritis. The accuracy of correction is not correlated with the early clinical outcome. Level of Evidence: Level IV, therapeutic case series.

A novel type of optical phase locked loop (OPLL), optimized for homodyne inter-satellite communication, is presented. The loop employs a conventional 180? 3 dB optical hybrid and an AC-coupled balanced front end. No residual carrier transmission is required for phase locking. The loop accepts analog as well as digital data and various modulation formats. The only requirement to the transmitted user signal is a constant envelope. Phase error extraction occurs through applying a small sinusoidal local oscillator (LO) phase disturbance, while measuring its impact on the power of the baseband output signal. First experimental results indicate a receiver sensitivity of 36 photons/bit (-55.7 dBm) for a BER of 10 ;-9, when transmitting a PRBS-31 signal at a data rate of 400 Mbit/s. The system setup employs diode-pumped Nd:YAG lasers at a wavelength of 1.06 mum.

We have measured significant concentrations of 36Cl, 41Ca, 36Ar from decay of 36Cl, and 150Sm produced from the capture of thermalized neutrons in the large Chico L6 chondrite. Activities of 36Cl and 41Ca, corrected for a high-energy spallogenic component and a terrestrial age of ∼50 ka, give average neutron-capture production rates of 208 atoms/min/g-Cl and 1525 atoms/min/kg-Ca, which correspond to thermal neutron (n) fluxes of 6.2 n/cm2/s and 4.3 n/cm2/s, respectively. If sustained for the ∼65 Ma single-stage, cosmic ray exposure age of Chico, these values correspond to thermal neutron fluences of ∼1.3×1016 and 0.8 × 1016 n/cm2 for 36Cl and 41Ca, respectively. Stepwise temperature extraction of Ar in Chico impact melt shows 36Ar/38Ar ratios as large as ∼9. The correlation of high 36Ar/38Ar with high Cl/Ca phases in neutron-irradiated Chico indicates that the excess 36Ar above that expected from spallation is due to decay of neutron-produced 36Cl. Excess 36Ar in Chico requires a thermal neutron fluence of 0.9–1.7×1016 n/cm2. Decreases in 149Sm/152Sm due to neutron-capture by 149Sm correlate with increases in 150Sm/152Sm for three samples of Chico, and one of the Torino H-chondrite. The 0.08% decrease in 149Sm/152Sm shown by Chico corresponds to a neutron fluence of 1.23×1016 n/cm2. This fluence derived from Sm considers capture of epithermal neutrons and effects of chemical composition on the neutron energy distribution. Excess 36Ar identified in the Arapahoe, Bruderheim, and Torino chondrites and the Shallowater aubrite suggest exposure to neutron fluences of ∼0.2–0.6×1016 n/cm2. Depletion of 149Sm in Torino and the LEW86010 angrite suggest neutron fluences of 0.8×1016 n/cm2 and 0.25×1016 n/cm2, respectively. Neutron fluences of ∼1016 n/cm2 in Chico are almost as large as those previously observed for some lunar soils. Consideration of exposure ages suggests that the neutron flux in Chico may have been greater than that in many lunar soils. Neutron-capture effects, although seldom reported, may be common for large meteorites and could affect calculation of exposure ages based on cosmogenic Ar. Combining measurements of radioactive and stable species produced from neutron-capture has the potential for identifying large meteorites with complex exposure histories.

10 Be and 26 Al concentrations measured by accelerator mass spectrometry in 20 samples of quartz separated from rhyolitic volcanic ash-flow tuffs collected on the Pajarito plateau of the Valles caldera, New Mexico, were used to model time-integrated erosion rates and cosmic ray-exposure histories. The model erosion rates determined for different stratigraphic units within the Tshirege member, upper Bandelier Tuff, vary from 0.1 cm/ka for the resistant unit to 1.1 cm/ka for the softer unit. Intermediate erosion rates are thought to indicate earlier age cover by post-tuff lithologies of different hardness. The geographic distribution of these intermediate rates allows an approximate determination of the extent of material now gone (stratigraphic ghosts). Periods of burial can be determined from 26 Al/ 10 Be ratios. For the Pajarito plateau, burial most likely resulted from cover by soil and sediment held in place by vegetation. Our data allow us to model the duration and extent of thick forest cover, which today exists only at higher altitudes.

He, Ne and Ar have been measured in 8 samples of Dalgety Downs (DD) and 5 samples of Ness County, 1894 (NC). 26Al, K, Th and U have been measured in 4 samples of DD and the chondrites Etter, Bledsoe, Seminole #2 and Zerga. Weathering probably explains the correlation between 26Al and 21Ne in DD, the independence of 3He/21Ne and 22Ne/21Ne in DD and NC and the > 2σ reduction of all 26Al contents from calculated saturation values.

A method of measurement of specific 10Be contents of naturally occurring materials is described. The method is based on mass spectrometry of 10Be/9Be ratios, using the Rutgers-Bell tandem van de Graaff accelerator. The detection limit is currently approximately 107 atoms 10Be, and the precision, when not limited by counting statistics, is 13%. The linear proportionality of observed 10Be/9Be ratio to actual ratio in sample has been verified within uncertainty over more than two orders of magnitude in ratio. Results are presented for the application of the method to determination of 10Be contents of six samples from various locations in the Antarctic H-chondrite ALHA 78084. No significant variations among the samples due to differences in shielding from cosmic rays were observed.

Beryllium-10 contents in the 20-28 dpm/kg range, averaging 24.5 + or - 0.9 dpm/kg, have been obtained for 11 samples taken from along the 35-cm core AIII of the St. Severin LL chondrite. Be-10 content increases with depth in the outermost 8 cm, and there is little change in content at greater depths. Significant disagreement is noted between the measured values and the results of calculations based on the cross sections for proton-induced Be-generating reactions. Cosmogenic Be-10 in stony meteorites is better described as a medium-energy product than a high energy one.

The cross sections for 21Na production induced by 10-, 12-, 14-, and 16-MeV protons on natural Mg targets have been measured as 0.21 ± 0.08,17.0 ± 2.5, 45.2 ± 6.8, and 44.0 ± 6.6 mb, respectively. These values imply that just below the surface the 22Ne/21Ne ratios found in extraterrestrial samples would be lowered by an excess of low-energy protons. Unfortunately, the lowering will in most cases be masked by other effects.

This paper presents the Be-10 contents of 20 and the Al-26 contents of nine eucrites. Most have Be-10 production rates between 16 and 26 dpm/kg. The average value of 21.8 dpm/kg agrees to within 10 percent with the value expected and does not support the suggestion that the eucrites received an unusually low flux of cosmic rays during the last few million years. Measured Be-10 and Al-26 contents are consistent with semiempirical calculations of nuclear production rates. The Al-26 contents provide a basis for computing shielding-corrected Ar-38 exposure ages of eucrites which show little evidence for clustering. Relatively more eucrites than diogenites are younger than 20 Ma.

Heating the JET plasma well above temperatures reached in the ohmic phase is the aim of the two additional heating systems planned for JET: ion cyclotron resonance heating (ICRF) and neutral beam injection (NBI). Operations with the latter started in February 1986, initially with hydrogen injection, up to a power level of 7 MW. ICRF power has been delivered to the plasma by three antennae and has reached power levels of 6 MW for 2 s. In most experiments, the frequency of the waves is adjusted to position the minority ion resonance layer close to the centre of the discharge, resulting in a centrally peaked power deposition profile. Results have also shown that the increase of the volume averaged electron temperature was much less dependent on the radial position of the ion resonance layer than were the central temperatures of both ions and electrons which can both approach 5 keV. In cases of 'on axis' heating, large increases in the sawtooth activity is observed with sawtooth periods exceeding 0.3 s. Initial results with NBI have shown a decrease of the global energy confinement time with additional power similar to the one observed with ICRF heating.

Accelerator mass spectrometry gives the following Be-10 contents (dpm/kg) for the SNC meteorites: Shergotty, 13.0 + or - 1.5 and 17.3 + or - 2.7; Zagami, 18.6 + or - 2.5 and 20.0 + or - 3.2; ALHA 77005, 15 + or - 3; EETA 79001A, 7.8 + or - 1.1 and 6.3 + or - 0.5; EETA 79001B, 8.5 + or - 1.1; Nakhla, 19.7 + or - 3.3; Lafayette, 18.1 + or - 2.5; Governador Valadares, 25.6 + or - 3.6; Chassigny, 20.5 + or - 3.1. The Be-10 contents of the NC meteorites indicate that significant accumulation of cosmogenic nuclides occurred in decimeter rather than planetary-size bodies. The agreement of the He-3, Ne-21, and Be-10 exposure ages of the shergottites also supports small-body irradiation. A long terrestrial age for EETA 79001 appears unlikely.

A high-energy mass spectrometer based on the XTU Tandem accelerator of the Laboratori Nazionali di Legnaro is described. Preliminary measurements on standard samples with known10Be/9Be atom ratio show the capability of the system to measure natural concentrations of10Be for geological and cosmochronological studies. The modifications necessary to improve sensitivity and precision of the measurements are discussed.

Al-26 (dpm/kg) and/or He, Ne, and Ar have been measured in samples of the Norton County meteorite from three different depths. The gas contents yield a shielding-corrected age of 75.8 + or - 5.7 million years. The ratio of atomic production rates P(Al-26)/P(Ne-21) is 0.22 + or - 0.02. He-3, Ne-21, and Al-26 increase with decreasing Ne-22/Ne-21 at nearly the same rates as they do in the smaller Keyes chondrite. Al-26 contents were measured in Bustee, Khor Temiki, Pesyanoe, and Shallowater meteorites. The ratio of observed to predicted Al-26 content correlates with Ne-22/Ne-21, and comparison with the corresponding chondrite correlation indicates that such aubrites as Malakal may have experienced an unusually high flux of cosmic rays.

The hardware and software structure of the control and data acquisition system (CODAS) of the Joint European Torus is described. CODAS is a large distributed real-time process control system. The operation is centralized in two adjacent control rooms through a fully programmable man-machine interface. The plant interface is based on CAMAC instrumentation and Eurocard signal conditioning. The system is based on a network of minicomputers with a link to a host mainframe.

A model of a small meteorite, 10 cm in diameter, made of granodiorite was rotated in a beam of 600 MeV protons to simulate 4π-irradiation conditions in space. Analysis of Al foils placed at known locations within the model give depth profiles of high energy (7Be, 10Be) and low energy (24Na, 22Na) spallation products. These isotopes were measured by means of high-resolution gamma-ray or accelerator mass spectroscopy (AMS). While the production rate profiles of the high energy products are flat within the limits of uncertainty, the profiles of the low energy products increase from the surface to the center by a factor of approximately 1.2. This increase indicates the importance of secondary neutrons and protons for the production of low energy spallation products, even within small meteorites.

The Yale tandem Van de Graaff accelerator was used as a mass spectrometer to detect 26Al. The ion source was modified by the addition of a Pierce electrode and the source was operated with a reflected cesium beam geometry utilizing ∼ 1 mg samples of Al2O3. An electrostatic analyzer was installed after the analyzing magnet in order to separate the Al5+ beam from various background beams. We were able to detect 26Al in Al extracted from the iron meteorite Mundrabilla. The measured 26Al/27Al ratios ranged from 1 × 10−12 to 1 × 10−9 atoms/atom. Using the model of Hampel et al., we have determined the exposure age of Mundrabilla to be 220±60 million years. This age agrees fairly well with the exposure age as determined with 53Mn and 38Ar.

Noble gas contents and shock effects have been studied in 21 Odessa irons from known geographic locations. Cosmogenic He-3, Ne-21, Ar-38 contents and He-3/Ne-21 ratios vary by factors of 62, 91, 68, and 1.55, respectively, while Ne-22/Ne-21 ratios are virtually constant at 1.07. The samples fall into two groups differing by a factor of 4.1 in exposure age, 1000 in source mass, or some combination of these. Three samples show significant shock effects, two of them to above 130 kbar, probably arising during terrestrial impact from the crater-forming explosion. As in Canyon Diablo plains specimens, noble gas contents do not correlate with siting or shock.

Fifteen ordinary chondrites for which unusually high spallogenic Ne-22/Ne-21 or He-3/Ne-21 ratios had been reported and one meteorite with marked shock characteristics were selected in order to investigate the relations between Ne-22/Ne-21 ratios, Al-26 contents and depth. We report Al-26 and K contents of 13 samples from 11 of these and noble gas contents of 30 samples from all of these stones.

The evolution of the data acquisition process at JET since June 1983 is described. The evolution of software, hardware, and volume of data is reviewed. The analysis of the performance of a multicomputer data acquisition system has required modeling of the various components. The effects of data compression have recently been analyzed and included in the model. Guidelines for future projects are derived. >

We calculated hard gluon bremsstrahlung effects on the missing pT signatures of gluino pair production at the CERN p p collider. Large corrections are found for gluinos of mass m g 1 0 GeV the enhancement of the gluino pair production cross section is comparable with the suppression due to gluino fragmentation. For m g ≳ 40 GeV the bremsstrahlung effect is less important, giving corrections of about 30–50%.

The accelerator mass spectrometry system based on the 16 MV tandem accelerator at the Laboratori Nazionali di Legnaro is described. A high-resolution electrostatic deflector rejects isotopic background and other unwanted beams transmitted with the same magnetic rigidity as the rare isotope. Use of this system for 10 Be and 36 Cl measurements in enriched and natural samples is presented.

Summary We report the 10Be and Be contents of 22 sediment samples of lacustrine silt from the Wilson Creek section of Mono Lake, California. The section spans about 20–35 kyr bp and contains a record of a geomagnetic excursion for which the relative palaeointensity is estimated from the ratio of natural remanent magnetization to anhysteretic remanent magnetization. The 10Be contents of the excursion samples are somewhat higher than the average of non-excursion samples (0.24 ± 0.02 versus 0.15 ± 0.02 dpm kg−1). It is clear however that geomagnetic effects are not the sole cause of the observed variations.