A 20 cm2 CCD mosaic camera for a dark matter search part I : Mechanics,optics and cryogeny     

Arnaud  M.  Aubourg  E.  Bareyre  P.  Br';ehin  S.  Caridroit  R.  de Kat  J.  Dispau  G.  Djidi  K.  Gros  M.  Lachièze-Rey  M.  Laigneau  Y.  Laurent  B.  Lesquoy  E.  Lavocat  Ph.  Magneville  C.  Mazeau  B.  Milsztajn  A.  Moscoso  L.  Pasquaud  J.  Paul  B.  Perrin  P.  Petibon  J.  Piret  Y.  Queinnec  F.  Rich  J.  Spiro  M.  de Trogoff  J.  Vigroux  L.  Zylberajch  S.  Ansari  R.  Cavalier  F.  Moniez  M.  Beaulieu  J. P.  Ferlet  R.  Grison  Ph.  Vidal-Madjar  A.  Adrianzyk  G.  Berger  J. P.  Burnage  R.  Delclite  J. C.  Kohler  D.  Magnan  R.  Richaud  A.  Guibert  J.  Moreau  O.  Tajahmady  F.  Baranne  A.  Maurice  E.  Prévôt  L.  Gry  C. 《Experimental Astronomy》1994,4(3-4):265-278

A 20cm ² CCD mosaic camera has been especially built to search for dark galactic halo objects by the gravitational microlensing effect. The sensitive area is made of 16 edge-buttable CCDs developped by Thomson-CTS, with 23×23 µm ² pixels. The 35 kg camera housing and mechanical equipment is presented. The associated electronics and data acquisition system are described in a separate paper. The camera resides at the focal plane of a 40 cm, f/10, Ferson reflector. The instrument has been in operation since December 1991 at the La Silla Observatory (ESO).  相似文献   

Inner part observation of theβ pictoris disk     

R. Ferlet  A. Lecavelier Des Etangs  G. Perrin  A. Vidal-Madjar  F. Sèvre  F. Colas  J. E. Arlot  C. Buil  H. Beust  A. M. Lagrange-Henri  J. Lecacheux  M. Deleuil  C. Gry 《Astrophysics and Space Science》1994,212(1-2):173-180

The inner regions of the circumstellar disk around Pictoris might be dust-free due to a possible planet which may have cleared up dust particles. We present a new observational technique based on the use of an anti-blooming CCD in order to directly image this zone. The structure of the disk is revealed down to 2 arcsec from the star (30 AU). We show that the Pic disk brightness is neutral inV, R, andI _C , but drops down when going inward inB, possibly related to a change in the dust composition. Also, a slight disk asymmetry is present but inverted from the outer to the inner zones.Paper presented at the Conference onPlanetary Systems: Formation, Evolution, and Detection held 7–10 December, 1992 at CalTech, Pasadena, California, U.S.A.  相似文献   

A 20cm 2 CCD mosaic camera for a dark matter search part II : Electronics,data acquisition and performance     

Arnaud  M.  Aubourg  E.  Bareyre  P.  Br';ehin  S.  Caridroit  R.  de Kat  J.  Dispau  G.  Djidi  K.  Gros  M.  Lachièze-Rey  M.  Laigneau  Y.  Laurent  B.  Lesquoy  E.  Lavocat  Ph.  Magneville  C.  Mazeau  B.  Milsztajn  A.  Moscoso  L.  Pasquaud  J.  Paul  B.  Perrin  P.  Petibon  J.  Piret  Y.  Queinnec  F.  Rich  J.  Spiro  M.  de Trogoff  J.  Vigroux  L.  Zylberajch  S.  Ansari  R.  Cavalier  F.  Moniez  M.  Beaulieu  J. P.  Ferlet  R.  Grison  Ph.  Vidal-Madjar  A.  Adrianzyk  G.  Berger  J. P.  Burnage  R.  Delclite  J. C.  Kohler  D.  Magnan  R.  Richaud  A.  Guibert  J.  Moreau  O.  Tajahmady  F.  Baranne  A.  Maurice  E.  Prévôt  L.  Gry  C. 《Experimental Astronomy》1994,4(3-4):279-296

Conclusion To summarize, the readout and the control system of the CCD mosaic camera are running since December 1991 at the La Silla Observatory (ESO). The overall performance of the camera has been good. About 12000 pictures (data and flat-fields) have been successfully registered up to now. We will report in the near future preliminary scientific results of the EROS experiment.  相似文献   

Variability in inorganic and organic nitrogen uptake associated with riverine nutrient input in the Gulf of Riga, Baltic Sea     

Gry Mine Berg  Patricia M. Glibert  Niels O. G. Jørgensen  Maija Balode  Ingrida Purina 《Estuaries and Coasts》2001,24(2):204-214

Concentrations and rates of uptake of dissolved organic nitrogen (DON, free amino acids, and urea) and inorganic nitrogen (DIN, nitrate, and ammonium) were measured along two transects in the Gulf of Riga, a sub-basin of the Baltic Sea, during May and July 1996. Concentrations of total dissolved nitrogen (TDN) were 23±3 μg-at N 1⁻¹ in the northern region (mouth) and 41±5 μg-at N 1⁻¹ in the southern region (head) of the Gulf. Rates of nitrogen uptake, determined with¹⁵N-labeled substrates, reflected differences in TDN concentration between the regions. In May, uptake of DIN+DON measured 0.17 and 0.43 μg-at N 1⁻¹ h⁻¹ in the northern and southern parts of the Gulf, respectively. In July, DIN+DON uptake measured 0.38 and 0.68 μg-at N 1⁻¹ h⁻¹ in the north and south, respectively. Most of the variability in total nitrogen flux between the northern and southern regions was due to heterogeneity of DON utilization. Uptake of urea and dissolved free amino acid were up to 6 and 3 times greater in the south compared to the north. As evidenced by size-fractionation, plankton size structure appeared to play a role in the uptake of DON. The community in the southern part was largely composed of cells <5 μm, while up to 67% of the community in the northern part was composed of cells >5 μm. Our results indicate that DON was a major source of nitrogen to phytoplankton, particularly in the southern part of the Gulf.  相似文献   

Eine Methode zur Charakterisierung der Kornverteilung; klastischer Sedimente     

Helge Gry 《International Journal of Earth Sciences》1938,29(3-5):175-195

Zusammenfassung Weil die früher angewandten Methoden, die Kornverteilung der Sedimente mit Hilfe von wenigen Zahlen (Mittelkorngröße, Sortierung, Streuung, Schiefe usw.) zu charakterisieren, für schiefe und zweigipfelige Kurven keine Bedeutung haben, wird eine Methode vorgelegt, bei der die Kornverteilung folgendermaßen charakterisiert wird: 1. Durch Bestimmung der Korngröße, die dem Maximum der Verteilungskurve entspricht; 2. durch Bestimmung der Prozentmenge (M) in einem Intervall von einer bestimmten Größe, das symmetrisch um das Maximum herum gebildet wurde; 3. durch Bestimmung der Menge der Nebenbestandteile, die gröber (G) oder feiner (F) als die Maximumsfraktionen sind. Die Methode beruht auf einer Bestimmung der Lage des Maximums mit Hilfe einer Differenzkurve und auf Interpolation auf der Summenlinie. Zweigipfelige Kurven werden nach der Lage des Minimums geteilt und die beiden Teile werden auf dieselbe Art berechnet, worauf die Zahlen jedes Gipfelbezirkes auf 100% umgerechnet werden. Der Inhalt der Sedimente an G, M und F kann in Dreiecksdiagrammen dargestellt werden, wobei sich zeigt, daß verschiedene Sedimentgruppen verschiedene Felder bilden.Weiter wird eine Methode vorgelegt, mit der man die durchschnittliche Kornverteilung einer Reihe Analysen des gleichen Sedimenttyps angeben kann. Dies kann durch Interpolation auf der Summenlinie geschehen, indem man ständig von der Lage des Maximums als festem Punkt ausgeht und die Mittelzahl der Ordinaten der Punkte mit gleicher relativer Lage bildet.  相似文献   

Integrity of Clay Till Aquitards to DNAPL Migration: Assessment Using Current and Emerging Characterization Tools          下载免费PDF全文

Annika S. Fjordbøge  Gry S. Janniche  Torben H. Jørgensen  Bernt Grosen  Gary Wealthall  Anders G. Christensen  Henriette Kerrn‐Jespersen  Mette M. Broholm 《Ground Water Monitoring & Remediation》2017,37(3):45-61

Field investigations were carried out to determine the occurrence of tetrachloroethene (PCE) dense nonaqueous phase liquid (DNAPL), the source zone architecture and the aquitard integrity at a 30‐ to 50‐year old DNAPL release site. The DNAPL source zone is located in the clay till unit overlying a limestone aquifer. The DNAPL source zone architecture was investigated through a multiple‐lines‐of‐evidence approach using various characterization tools; the most favorable combination of tools for the DNAPL characterization was geophysical investigations, membrane interface probe, core subsampling with quantification of chlorinated solvents, hydrophobic dye test with Sudan IV, and Flexible Liner Underground Technologies (FLUTe) NAPL liners with activated carbon felt (FACT). While the occurrence of DNAPL was best determined by quantification of chlorinated solvents in soil samples supported by the hydrophobic dye tests (Sudan IV and NAPL FLUTe), the conceptual understanding of source zone architecture was greatly assisted by the indirect continuous characterization tools. Although mobile or high residual DNAPL (S _t > 1%) only occurred in 11% of the source zone samples (intact cores), they comprised 86% of the total PCE mass. The dataset, and associated data analysis, supported vertical migration of DNAPL through fractures in the upper part of the clay till, horizontal migration along high permeability features around the redox boundary in the clay till, and to some extent vertical migration through the fractures in the reduced part of the clay till aquitard to the underlying limestone aquifer. The aquitard integrity to DNAPL migration was found to be compromised at a thickness of reduced clay till of less than 2 m.  相似文献   

Lu-Hf and PbSL geochronology of apatites from Proterozoic terranes: A first look at Lu-Hf isotopic closure in metamorphic apatite   总被引：3，自引：0，他引：3  

Gry Hoffmann Barfod  Eirik Jens Krogstad  Francis Albarède 《Geochimica et cosmochimica acta》2005,69(7):1847-1859

The mineral apatite is characterized by elevated and highly variable Lu/Hf ratios that, in some cases, allow for single-crystal dating by the Lu-Hf isotopic system. Apatites from the Adirondack Lowlands and Otter Lake area in the Grenville Province, and from the Black Hills, South Dakota, yield Lu-Hf ages that are consistently older than their respective Pb step leaching ages. Isotopic closure for the Lu-Hf system, therefore, occurs before U-Pb system closure in this mineral. In the Adirondack Lowlands, where H₂O activity was low, Lu-Hf systematics of cm-sized apatite crystals remained undisturbed during upper amphibolite facies metamorphism (∼700 to 675 °C) at 1170-1130 Ma. The relatively old Lu-Hf ages of 1270 and 1230 Ma observed for these apatites correlate with decreasing crystal size. In contrast, apatite from the fluid-rich Otter Lake area and Black Hills yields unrealistically low apparent Lu-Hf closure temperatures, implying that in these apatites, fluids facilitated late exchange. The Lu-Hf ages for the metamorphic apatites were thus controlled either by the prevailing temperature and grain size, or by fluid activity.  相似文献   

UVMag: stellar formation,evolution, structure and environment with space UV and visible spectropolarimetry     

C. Neiner  D. Baade  A. Fullerton  C. Gry  G. Hussain  A. Lèbre  J. Morin  P. Petit  J. O. Sundqvist  A. ud-Doula  A. A. Vidotto  G. A. Wade  The UVMag consortium 《Astrophysics and Space Science》2014,354(1):215-227

Important insights into the formation, structure, evolution and environment of all types of stars can be obtained through the measurement of their winds and possible magnetospheres. However, this has hardly been done up to now mainly because of the lack of UV instrumentation available for long periods of time. To reach this aim, we have designed UVMag, an M-size space mission equipped with a high-resolution spectropolarimeter working in the UV and visible spectral range. The UV domain is crucial in stellar physics as it is very rich in atomic and molecular lines and contains most of the flux of hot stars. Moreover, covering the UV and visible spectral domains at the same time will allow us to study the star and its environment simultaneously. Adding polarimetric power to the spectrograph will multiply tenfold the capabilities of extracting information on stellar magnetospheres, winds, disks, and magnetic fields. Examples of science objectives that can be reached with UVMag are presented for pre-main sequence, main sequence and evolved stars. They will cast new light onto stellar physics by addressing many exciting and important questions. UVMag is currently undergoing a Research & Technology study and will be proposed at the forthcoming ESA call for M-size missions. This spectropolarimeter could also be installed on a large UV and visible observatory (e.g. NASA’s LUVOIR project) within a suite of instruments.  相似文献   

New Lu-Hf and Pb-Pb age constraints on the earliest animal fossils   总被引：1，自引：0，他引：1  

Gry H Barfod  Francis AlbarèdeAndrew H Knoll  Shuhai XiaoPhilippe Télouk  Robert Frei  Joel Baker 《Earth and Planetary Science Letters》2002,201(1):203-212

The Neoproterozoic Doushantuo Formation, South China, preserves a unique assemblage of early multicellular fossils and overlies rocks, which are thought to have formed during an ice age of global extent. The age of this formation is thus critical for understanding the important biological and climatic events that occurred towards the end of the Proterozoic Eon. Until now, direct dating of sedimentary formations such as the Doushantuo has been difficult and associated with large uncertainties. Here, we show that dating of Doushantuo phosphorites by a novel Lu-Hf dating method and conventional Pb-Pb geochronometry independently yield ages of 584±26 Ma and 599.3±4.2 Ma, respectively. These ages are in agreement with bio- and chemostratigraphical observations and show that the Doushantuo animal remains predate diverse Ediacaran fossil assemblages, making them the oldest unambiguous remains of metazoans currently known. Furthermore, the Pb-Pb age for the post-glacial Doushantuo rocks suggests that the Neoproterozoic glaciation in China might predate glacial rocks in Eastern North America commonly associated with the younger (Marinoan) of two major Neoproterozoic glaciations. The combination of Lu-Hf and Pb-Pb dating shows considerable potential for dating other phosphorite successions and future application of these methods could therefore provide further constraints on Proterozoic biological and environmental history.  相似文献   

Phosphate Lu–Hf geochronology     

Gry H. Barfod  Olga Otero  Francis Albarde 《Chemical Geology》2003,200(3-4):241-253

Igneous, metamorphic and biogenic apatite contains Lu and Hf in proportions that make this mineral suitable for dating by the ¹⁷⁶Lu–¹⁷⁶Hf method. We present a new method for separation of Lu and Hf from apatite that involves a single extraction column step for Hf and a second exchange column step for Lu. This procedure allows rapid sample processing prior to analysis by MC-ICP-MS. Results from the igneous Gardiner, Skaergaard and Khibina Intrusions indicate that the closure temperature for the Lu–Hf isotopic system in apatite is relatively high. The Lu–Hf isochron age of 60 Ma for the Skaergaard Intrusion, East Greenland, is older than the generally accepted emplacement age, but does not appear to be a product of mixing. A centimeter-sized apatite from the Otter Lake area, Grenvillian Province, yields high and variable ¹⁷⁶Lu/¹⁷⁷Hf ratios showing that metamorphic apatite may, in some cases, allow for mono-mineral dating. The most important application of the method is undoubtedly its potential use for dating sedimentary formations. Although we find biogenic apatite in porous matrix highly susceptible to post-depositional resetting of the Lu–Hf isotopic system, the preservation of a near-depositional age for a shark tooth from the impermeable London Clay and recent work on crystalline authigenic phosphorites [Earth Planet. Sci. Lett. 201 (2002) 203] show the Lu–Hf system to be a promising tool for direct dating of sedimentary formations.  相似文献