Inter-laboratory calibration of low-field magnetic and anhysteretic susceptibility measurements     

Leonardo Sagnotti  Pierre RochetteMike Jackson  Fabienne VadeboinJaume Dinarès-Turell  Aldo Winkler 《Physics of the Earth and Planetary Interiors》2003,138(1):25-38

Inter-laboratory and absolute calibrations of rock magnetic parameters are fundamental for grounding a rock magnetic database and for semi-quantitative estimates about the magnetic mineral assemblage of a natural sample. Even a dimensionless ratio, such as anhysteretic susceptibility normalized by magnetic susceptibility (K_a/K) may be biased by improper calibration of one or both of the two instruments used to measure K_a and K. In addition, the intensity of the anhysteretic remanent magnetization (ARM) of a given sample depends on the experimental process by which the remanence is imparted. We report an inter-laboratory calibration of these two key parameters, using two sets of artificial reference samples: a paramagnetic rare earth salt, Gd₂O₃ and a commercial “pozzolanico” cement containing oxidized magnetite with grain size of less than 0.1 μm according to hysteresis properties. Using Gd₂O₃ the 10 Kappabridges magnetic susceptibility meters (AGICO KLY-2 or KLY-3 models) tested prove to be cross-calibrated to within 1%. On the other hand, Kappabridges provide a low-field susceptibility value that is ca. 6% lower than the tabulated value for Gd₂O₃, while average high-field susceptibility values measured on a range of instruments are indistinguishable from the tabulated value. Therefore, we suggest that Kappabridge values should be multiplied by 1.06 to achieve absolute calibration. Bartington Instruments magnetic susceptibility meters with MS2B sensors produce values that are 2-13% lower than Kappabridge values, with a strong dependence on sample centering within the sensor. The K_a/K ratio of ca. 11, originally obtained on discrete cement samples with a 2G Enterprises superconducting rock magnetometer and a KLY-2, is consistent with reference parameters for magnetites of grain size <0.1 μm. On the other hand, K_a values from a 2G Enterprises magnetometer and K values from a Bartington Instruments MS2C loop sensor for u-channel and discrete cement samples, will produce average K_a/K values that are unrealistically high if not properly corrected for the nominal volume detected by the sensors for these instruments. Inter-laboratory measurements of K and K_a for standard paleomagnetic plastic cubes filled with cement indicate remarkable differences in the intensity of the newly produced ARMs (with a standard deviation of ca. 21%), that are significantly larger than the differences observed from the calibration of the different magnetometers employed in each laboratory. Differences in the alternating field decay rate are likely the major source of these variations, but cannot account for all the observed variability. With such large variations in experimental conditions, classical interpretation of a “King plot” of K_a versus K would imply significant differences in the determination of grain size of magnetite particles on the same material.  相似文献   

Behind the scenes at the Nationaal Natuurhistorisch Museum, Leiden, and the Teyler Museum, Haarlem, The Netherlands: report of a visit by the Geologists' Association, 30 November and 1 December, 2002     

Stephen K. Donovan  Willem Renema  Isabel M. van Waveren  Cor F. Winkler Prins 《Proceedings of the Geologists' Association. Geologists' Association》2003,114(3):279-288

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Ground-Based and Airborne Measurements of Nonmethane Hydrocarbons in BERLIOZ: Analysis and Selected Results     

J. Winkler  P. Blank  K. Glaser  J. A. G. Gomes  M. Habram  C. Jambert  W. Jaeschke  S. Konrad  R. Kurtenbach  P. Lenschow  J. C. Lörzer  P. E. Perros  M. Pesch  H. J. Prümke  B. Rappenglück  Th. Schmitz  F. Slemr  A. Volz-Thomas  B. Wickert 《Journal of Atmospheric Chemistry》2002,42(1):465-492

During the Berlin Ozone Experiment BERLIOZ in July–August 1998 quasi-continuous measurements ofC₂–C₁₂ nonmethane hydrocarbons (NMHCs) were carried out at 10 sites in and around the city of Berlin using on-line gas-chromatographic systems (GCs) with a temporal resolution of 20–120 minutes. Additional airborne NMHCmeasurements were made using canister sampling on three aircraft and an on-line GC system on a fourth aircraft. The ground based data are analyzed to characterize the different sites and to identify the influence of emissions from Berlin on its surroundings. Benzene mixing ratios at the 4 rural sites were rather low (<0.5 ppbv). Berlin (and the surrounding highway ring) was identified as the main source of anthropogenic NMHCs at Eichstädt and Blossin, whilst other sources were important at the furthermost site Menz. The median toluene/benzene concentration ratio in Berlin was 2.3 ppbv/ppbv, agreeing well with measurements in other German cities. As expected, the ratios at the background sites decreased with increasing distance to Berlin and were usually around one or below. On 20 and 21 July, the three northwesterly sites were situated downwind of Berlin and thus were influenced by its emissions. Considering the distance between the sites and the windspeed, the city plume was observed at reasonable time scales, showing decreasing toluene/benzene ratios of 2.3, 1.6 and 1.3 with increasing distance from Berlin. Isoprene was the only biogenic NMHC measured at BERLIOZ. It was themost abundant compound at the background sites on the hotter days, dominating the local NMHC reactivity with averaged contributions to the total OH loss rate of 51% and 70% at Pabstthum and Blossin, respectively. Emissionratios (relative to CO and to the sum of analysed NMHCs) were derived from airborne measurements. The comparison with an emission inventory suggests traffic-related emissions to be the predominating source of the considered hydrocarbon species. Problems were identified with the emission inventory for propane, ethene and pentanes.  相似文献   

Palynological and sequence stratigraphic analysis of the Napo Group in the Pungarayacu 30 well, Sub-Andean Zone, Ecuador     

C. Vallejo  P. A. Hochuli  W. Winkler  K. von Salis   《Cretaceous Research》2002,23(6):845

The study of palynomorphs and calcareous nannofossils from the Albian–Campanian Napo Group in the Pungarayacu 30 well in the Subandean Zone of Ecuador has led to a new biostratigraphic framework revealing the existence of several hiatuses for this area. The palynological and palynofacies data are used together with other fossils and lithological evidence to define a sequence stratigraphic framework. The distribution of palynomorphs and palynofacies indicates a strong terrestrial input for the lower part of the Napo Group (Napo Basal and Lower Napo formations). In the upper part (Middle and Upper Napo formations), terrestrial input is reduced and a restricted marine environment with several dysoxic–anoxic intervals can be inferred. The hydrocarbons present in the well studied have traditionally been regarded as locally sourced. However, several lines of evidence (TAS, Tmax and VR) prove the immature stage of the source rock in this borehole as well as in a larger area.  相似文献   

Crystal field transitions in Co2[Al4Si5]O18 cordierite and CoAl2O4 spinel determined by neutron spectroscopy     

Björn Winkler  Mark J. Harris  Roger S. Eccleston  Karsten Knorr  Bernard Hennion 《Physics and Chemistry of Minerals》1997,25(1):79-82

Inelastic magnetic neutron scattering has been used to determine the energy of the ⁴ A ₂→⁴ T ₂ transition in CoAl₂O₄ spinel and the δ₁ transition in Co₂[Al₄Si₅]O₁₈ cordierite. The observed crystal field splitting in Co-spinel is 485 meV (3900 cm⁻¹), which corresponds to a crystal field stabilization energy of 56.2 kJmol⁻¹. The transition energy of the δ₁ transition in Co-cordierite has been determined to be 21 meV (170 cm⁻¹). The present data demonstrate that magnetic neutron scattering can be used to measure crystal field transitions at energies of interest in the study of 3d-containing silicates. It may be used to measure transition energies when the use of optical spectroscopy is inappropriate. Received: 30 January 1997 / Accepted: 5 July 1997  相似文献   

Surface ozone over the Atlantic ocean     

Peter Winkler 《Journal of Atmospheric Chemistry》1988,7(1):73-91

During the past decade (1977–1986) ozone has been measured on board various research vessels between 83° N and 76° S. The latitudinal distribution shows nearly twice as high an ozone concentration in the Northern Hemisphere (30 ppb) as compared to the Southern Hemisphere (15 ppb). North of 70° N the concentration rapidly drops to low values (17 ppb). In the ITCZ we frequently observed a pronounced secondary maximum which indicates that tropospheric-stratospheric exchange may be induced by deep convection. During other occasions, ozone concentrations below 10 ppb were observed in the ITCZ. Secondary maxima are also found in each hemisphere, indicating the latitudes in which stratospheric-tropospheric exchange occurs. One such pronounced maximum is found between 60 and 65° N. A comparable counterpart does not, however, occur in the respective southern latitudes.The observations, although incomplete, allow for conclusions with respect to seasonal cycles, at least in some of the latitudes or for some part of the year. In the tropics differences between continental and maritime yearly cycles are found. In mid to high northern latitudes, a sharp maximum is found which extends to the summer months over continental European sites. In the respective southern latitudes, such a spring maximum is only indicated.Comparison with occasionally concurrent Kr 85 measurements by other groups allows for the conclusion that in some cases photochemically produced ozone in polluted air masses is seen over the Atlantic ocean.  相似文献   

Microphysics of clouds at Kleiner Feldberg     

B. G. Arends  G. P. A. Kos  R. Maser  D. Schell  W. Wobrock  P. Winkler  J. A. Ogren  K. J. Noone  A. Hallberg  I. B. Svenningsson  A. Wiedensohler  H. -C. Hansson  A. Berner  I. Solly  C. Kruisz 《Journal of Atmospheric Chemistry》1994,19(1-2):59-85

During a field measuring campaign at Kleiner Feldberg (Taunus) in 1990, microphysical characteristics of clouds have been measured by Forward Scattering Spectrometer Probes (FSSP). The aim was to study the influence of aerosol and meteorological factors on droplet size and number. The results are: More mass in the accumulation size range of the aerosol leads to more droplets in stratocumulus clouds and to higher soluble masses in droplets of stratus clouds. However, the aerosol distribution was coarser in the stratus clouds compared to the stratocumulus clouds. Within the first 200 m from cloud base, the droplets grow while their number decreases. The growth results in a stable size of about 14 µm diameter over a large distance from cloud base in many stratocumulus clouds. Two types of mixing processes were observed: processes with reductions in the number of droplets (inhomogeneous mixing) and with reductions in the size of the droplets (homogeneous mixing).  相似文献   

The Kleiner Feldberg Cloud Experiment 1990. An overview     

W. Wobrock  D. Schell  R. Maser  W. Jaeschke  H. -W. Georgii  W. Wieprecht  B. G. Arends  J. J. Mols  G. P. A. Kos  S. Fuzzi  M. C. Facchini  G. Orsi  A. Berner  I. Solly  C. Kruisz  I. B. Svenningsson  A. Wiedensohler  H. -C. Hansson  J. A. Ogren  K. J. Noone  A. Hallberg  S. Pahl  T. Schneider  P. Winkler  W. Winiwarter  R. N. Colvile  T. W. Choularton  A. I. Flossmann  S. Borrmann 《Journal of Atmospheric Chemistry》1994,19(1-2):3-35

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Ab initio total energy study of brucite,diaspore and hypothetical hydrous wadsleyite     

B. Winkler  V. Milman  B. Hennion  M. C. Payne  M. -H. Lee  J. S. Lin 《Physics and Chemistry of Minerals》1995,22(7):461-467

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The influence of pressure on the OH valence vibration of zoisite     

B. Winkler  K. Langer  P. G. Johannsen 《Physics and Chemistry of Minerals》1989,16(7):668-671

The influence of pressure on the OH-stretching vibration of zoiste has been studied by single crystal high pressure infrared spectroscopy. A band related to the OH-stretching vibration displayed a linear shift from 3170 cm^?1 at 1 bar to 2795 cm^?1 at 116 kbar. The half-band width increased linearly with respect to pressure from 60 cm^?1 at 1 bar to 500 cm^?1 at 116 kbar. The strength of the absorption of this band is strongly frequency dependent. The high-energy shift of a band at around 2200 cm^?1 on pressure increase indicates that this band is not due to a second OH-stretching vibration as previously suggested by Langer and Lattard (1980).  相似文献