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81.
Marek Tulej Andreas Riedo Maike B. Neuland Stefan Meyer Peter Wurz Nicolas Thomas Valentine Grimaudo Pavel Moreno‐García Peter Broekmann Anna Neubeck Magnus Ivarsson 《Geostandards and Geoanalytical Research》2014,38(4):441-466
Performance studies of a microscope‐camera system (MCS) and a laser ablation/ionisation mass spectrometer (LIMS) instrument (referred to here as a laser mass spectrometer or LMS) are presented. These two instruments were designed independently for in situ analysis of solids on planetary surfaces and will be combined to a single miniature instrument suite for in situ chemical and morphological analysis of surface materials on planetary bodies. LMS can perform sensitive chemical (elemental, isotope and molecular) analyses with spatial resolution close to micrometre‐sized grains. It allows for studies with mass resolution (M/ΔM) up to 800 in ablation mode (elemental composition) and up to 1500 in desorption mode (molecular analysis). With an effective dynamic range of at least eight orders of magnitude, sensitive and quantitative measurements can be conducted of almost all elements and isotopes with a concentration larger than a few ppb atoms. Hence, in addition to the major element composition, which is important for the determination of mineralogical constituents of surface materials, trace elements can also be measured to provide information on mineral formation processes. Highly accurate isotope ratio measurements can be used to determine in situ geochronology of sample material and for investigations of various isotope fractionation processes. MCS can conduct optical imagery of mm‐sized objects at several wavelengths with micrometre spatial resolution for the characterisation of morphological surface details and to provide insight into surface mineralogy. Furthermore, MCS can help in the selection of sample surface areas for further mass spectrometric analysis of the chemical composition. Surface auto‐fluorescence measurements and images in polarised light are additional capabilities of the MCS, to identify either fluorescing minerals or organic materials, if present on the analysed surface, for further investigation by LMS. The results obtained by investigations of NIST reference materials, amino acid films and a natural graphite sample embedded in silicate rock are presented to illustrate the performance of the instruments and their potential to deliver chemical information for mineral and organic phases in their geological context. 相似文献
82.
Elías Moreno George Casella Antonio Garcia-Ferrer 《Stochastic Environmental Research and Risk Assessment (SERRA)》2005,19(3):191-204
The Bayesian literature on the change point problem deals with the inference of a change in the distribution of a set of time-ordered data based on a sample of fixed size. This is the so-called retrospective or off-line analysis of the change point problem. A related but different problem is that of the sequential change point detection, mainly analyzed from a frequentist viewpoint. While the former typically focuses on the estimation of the position in which the change point occurs, the latter is a testing problem which has a natural formulation as a Bayesian model selection problem. In this paper we provide such a Bayesian formulation, which generalizes previous formulations such as the well-known CUSUM stopping rule. We show that the conventional improper priors (also called non-informative, objective or default), cannot be used either for sequential detection of the change or for retrospective estimation. Then, we propose objective intrinsic prior distributions for the unknown model parameters. The normal and Poisson cases are studied in detail and examples with simulated and real data are provided. 相似文献
83.
Stratigraphical, sedimentological and paleoecological studies undertaken in lagoonal sediments of the Ria Formosa barrier lagoon indicate that a number of present-day aligned beaches outcropping within the marsh and detached from mainland (marsh detached beaches, MDB) represent the remnants of former ephemeral flood deltas, which established following barrier breaching induced by extreme storms from circa 1270 BC onwards. Dating of these beaches suggests that they resulted from multiple events of flooding separated both in time and space. Repeated emplacement of tidal deltas following overwash of the same location of the barrier is represented in the stratigraphical record by buried and partly overlapping marsh beaches. It is suggested that further refinement of the data presented in this paper and the extension of the stratigraphic survey to the entire lagoonal space will substantiate the usefulness of the stratigraphic record as a proxy to hindcast a time series of extreme storminess extending far beyond the instrumental and historical records. 相似文献
84.
Specialisation changes in European regions: the role played by externalities across regions 总被引:1,自引:1,他引:0
This paper seeks to determine the factors underpinning changes in regional specialisation patterns in the European Union between
1991 and 2002. First, we consider a set of determinants previously identified in the regional literature, including agglomeration
effects and other specific regional factors (business cycle, amount of investment, etc.). However, we then also take into
account the fact that the evolution in a region’s specialisation pattern may be affected by the specialisation behaviour of
other regions. Thus, not only do we consider the pattern of evolution in a region’s most proximate neighbours but we also
examine that of their regional peers, i.e., regions with a similar specialisation pattern independent of their location. Notwithstanding,
our empirical evidence indicates that physical distance still plays a very significant, and even more influential, role than
similarity in specialisation. 相似文献
85.
86.
Santiago Giralt Ana Moreno Roberto Bao Alberto Sáez Ricardo Prego Blas L. Valero-Garcés Juan José Pueyo Penélope González-Sampériz Conxita Taberner 《Journal of Paleolimnology》2008,40(1):195-215
A high resolution multiproxy study (magnetic susceptibility, X-ray diffraction, XRF scanner, gray-colour values, Total Organic
Carbon, Total Inorganic Carbon, Total Carbon and Total Biogenic Silica) of the sedimentary infill of Lago Chungará (northern
Chilean Altiplano) was undertaken to unravel the environmental forcings controlling its evolution using a number of different
multivariate statistical techniques. Redundancy analyses enabled us to identify the main provenance of the studied proxies
whereas stratigraphically unconstrained cluster analyses allowed us to distinguish the “outsiders” as result of anomalous
XRF scanner acquisitions. Principal Component Analysis (PCA) was employed to identify and isolate the main underlying environmental
gradients that characterize the sedimentary infill of Lago Chungará. The first eigenvector of the PCA could be interpreted
as an indicator of changes in the input of volcaniclastic material, whereas the second one would indicate changes in water
availability. The chronological model of this sedimentary sequence was constructed using 17 AMS 14C and 1 238U/230Th dates in order to characterize the volcaniclastic input and the changes in water availability in the last 12,300 cal years
BP.
Comparison of the reconstructed volcaniclastic input of Lago Chungará with the dust particle record from the Nevado Sajama
ice core suggested that the Parinacota volcano eruptions were the main source of dust during the mid and Late Holocene rather
than the dry out lakes as has previously been pointed out. The comparison of the water availability reconstruction of Lago
Chungará with three of the most detailed paleoenvironmental records of the region (Paco Cocha, Lake Titicaca and Salar Uyuni)
showed an heterogeneous (and sometimes contradictory) temporal and spatial pattern distribution of moisture. Although the
four reconstructions showed a good correlation, each lacustrine ecosystem responded differently to the moisture oscillations
that affected this region. The variations in the paleoenvironmental records could be attributed to the dating uncertainities,
lake size, lake morphology, catchment size and lacustrine ecosystem responses to the abrupt arid events. 相似文献
87.
Anne Browning-Aiken Barbara Morehouse Allison Davis Margaret Wilder Robert Varady David Goodrich Rebecca Carter Denise Moreno Emily Dellinger McGovern 《Climatic change》2007,85(3-4):323-341
This paper reviews regional climate knowledge and vulnerability in the northern Mexico San Pedro River Basin, with a focus
on water quality, quantity, and management issues on the Mexican side of the border. A discussion based on the available literature
is supplemented by a survey assessing concerns about water and the quality and usability of climate and hydrologic information
available to water managers and communities. The surveys indicate that the central concern for urban residents is the lack
of reliable potable water due to frequent service breakdowns–with climate change and variability, specifically drought and
high temperatures, as contributing factors. Water managers desire appropriate meteorological and hydrologic information to
improve planning strategies, but access to this information remains limited. Considerable disagreement exists about who should
pay for previously free or low-cost water and wastewater treatment. Urban users have little incentive to conserve because
of the present flat, low rate and frustration with service. In rural areas, while a majority of ranchers recognize that variable
climate and water loss could increasingly jeopardize their lifestyle, they seldom use meteorological information in planning
or modify their water consumption. Climate vulnerability also includes potential for serious environmental health issues due
to the presence of heavy metals and organic contaminants in the San Pedro. 相似文献
88.
89.
90.
P.I. Moreno J.P. François R.P. Villa-Martínez C.M. Moy 《Quaternary Science Reviews》2009,28(1-2):25-38
Here we report results from a high-resolution palynological record and stratigraphic/geochronologic data related to a Neoglacial event in Torres del Paine National Park, southern Chile (51°S, 71°W), to investigate climatic variations in Southwest Patagonia during the last 5000 years. The record reveals a stepwise expansion of Nothofagus-dominated woodlands and forests with discrete pulses at 4400, 2900, 1300, and 570 cal yr BP. Superimposed upon this trend we identify a relative opening of the woodlands between 4100–2900 and 2300–1300 cal yr BP. Closed-canopy forests dominated the landscape between 570–60 cal yr BP, followed by a rapid decline at the end of the 19th century that coincided with intense fire activity and the appearance of Rumex cf. acetocella, an exotic species introduced by European settlers. We interpret these changes as variations in the intensity and/or position of the southern margin of the westerly winds, which culminated with a net eastward shift of the forest–steppe ecotone during the Little Ice Age. We propose that millennial-scale changes in either the latitudinal position and/or the overall strength of the southern westerlies may be responsible for vegetation changes, fire occurrence, and the dynamic behavior of Patagonian glaciers during the last 5000 years. Because the modern maximum in near-surface wind velocities and precipitation is located between 48° and 50°S, we suggest that the core of the southern westerlies may have achieved this modern position ~570 years ago. 相似文献