Installation age of limestone masonry determined from its viscous remagnetization     

Graham John Borradaile  Bjarne Sven Almqvist 《Geoarchaeology》2006,21(1):29-60

Many rocks passively acquire some time‐dependent or “viscous” remanent magnetism (VRM) at ambient temperatures, without any extraordinary energetic intervention. This magnetization overprints existing remanent magnetization so that it is effectively a remagnetization subparallel to the contemporary geomagnetic field, averaging the geomagnetic field orientation. Certain limestone masonry remagnetizes viscously over an archaeologically useful interval (100 to 8000 Ka) so that the degree of remagnetization is monotonically (but not linearly) related to the construction age. The laboratory unblocking temperature (T_UB) that removes the viscous magnetization is a simple monotonic measure of relative age. The longer a piece of masonry remained stabilized in a certain orientation, the greater is its viscous remagnetization and the higher is its T_UB. Monuments of known age with a similar limestone source permit us to establish a calibration curve of T UB against historical ages. The resulting calibration curve may then be used to predict the ages of otherwise‐undated masonry. Viscous remanent magnetism dating provides precision of <50a in medieval monuments in England and <150a precision for classical to Neolithic monuments in Cyprus; precision depends on the remagnetization rate of the limestone in question. Our calibration curves, for the Jurassic Oolitic Limestone of England and for the Lefkara‐Pakhna Chalks of Cyprus, allowed us to investigate the authenticity of a medieval English synagogue in Lincoln, England, and of a medieval house in Cyprus. Multiple archaeologic VRMs show that masonry was recycled in historical times. © 2006 Wiley Periodicals, Inc.  相似文献   

Meio-epifaunal wood colonization in the vicinity of methane seeps     

Adriana Gracia C.  Lisa A. Levin  Sven Zea 《Marine Ecology》2020,41(1):e12573

In deep-sea environments, plant remains of several origins are found, including branches, twigs, leaves, and wood pieces, among others. As most of the deep-sea bottoms are oligotrophic and nutrient-limited, plant remains provide an oasis of localized organic enrichment and a substrate for colonization. Sunken wood was suggested to play an important evolutionary role in the diversification of chemosynthetic ecosystems, possibly representing stepping stones for the colonization between vent and seep ecosystems. In order to understand colonization processes of the Pacific Costa Rican meio-epifaunal assemblages associated with sunken wood, a field experiment was conducted on Mound 12 (8°55.778′N, 84°18.730′W) at ~1,000 m water depth. Woodblocks were placed in four different habitats (Mussel beds, tube worms, near mussel beds, rubble bottoms), and different local environmental conditions (seepage-active and seepage-inactive sites). Seven experimental Douglas fir woodblocks (each 1,047 cm² in surface area) were deployed from the R/V Atlantis using the manned submersible Alvin in February 2009 and recovered after 10.5 months in January 2010. Sample processing and analyses led to a data set of abundance (total 9,951 individuals) and spatial distribution of nine meio-epifaunal higher taxa/groups. Meio-epifaunal densities on individual woodblocks ranged from 3 to 26 ind.10 cm². Copepods accounted for the highest abundances (75.1%), followed by nauplii larvae (11.7%) and nematodes (9.8%). The maximum number of individuals (26.3 ind.10 cm⁻²) was found in blocks placed in seepage-inactive areas (near active mussel beds) in contrast to 2.9 ind.10 cm⁻² in active areas (within a mussel bed). A hierarchical cluster analysis grouped blocks according to seepage activity and not to habitat, but tests of similarity showed no significant differences in higher taxon composition and abundances, probably owing either to substrate homogeneity or low sample size. Copepods were the most abundant representatives, suggesting that this group is one of the most successful in colonizing in the early stage of succession, in this case while hardwood substrates are not yet decomposed or bored by bivalves.  相似文献   

Fixing problems in fisheries—integrating ITQs,CBM and MPAs in management     

Mark Brady  Staffan Waldo 《Marine Policy》2009

We aim to show how some of the important interdisciplinary fixes or solutions to diverse problems observed in fisheries can complement each other. This can be achieved through methodical allocation of the rights pertaining to fisheries and simultaneous implementation of policy instruments to correct for market failures and equity concerns. We emphasize via a roadmap that there are some general principles that should be invoked when choosing between alternative structures of rights. Our examples from Sweden provide evidence of the flexibility of fishing rights and how they can be adapted to integrate fixes from different disciplines into practical fisheries management.  相似文献   

Combination of multi-mission altimetry data along the Mekong River with spatio-temporal kriging     

Eva Boergens  Sven Buhl  Denise Dettmering  Claudia Klüppelberg  Florian Seitz 《Journal of Geodesy》2017,91(5):519-534

River water-level time series at fixed geographical locations, so-called virtual stations, have been computed from single altimeter crossings for many years. Their temporal resolution is limited by the repeat cycle of the individual altimetry missions. The combination of all altimetry measurements along a river enables computing a water-level time series with improved temporal and spatial resolutions. This study uses the geostatistical method of spatio-temporal ordinary kriging to link multi-mission altimetry data along the Mekong River. The required covariance models reflecting the water flow are estimated based on empirical covariance values between altimetry observations at various locations. In this study, two covariance models are developed and tested in the case of the Mekong River: a stationary and a non-stationary covariance model. The proposed approach predicts water-level time series at different locations along the Mekong River with a temporal resolution of 5 days. Validation is performed against in situ data from four gauging stations, yielding RMS differences between 0.82 and 1.29 m and squared correlation coefficients between 0.89 and 0.94. Both models produce comparable results when used for combining data from Envisat, Jason-1, and SARAL for the time period between 2002 and 2015. The quality of the predicted time series turns out to be robust against a possibly decreasing availability of altimetry mission data. This demonstrates that our method is able to close the data gap between the end of the Envisat and the launch of the SARAL mission with interpolated time series.  相似文献   

Regional vulnerability assessment for debris flows in China—a CWS approach     

Mingtao Ding  Micha Heiser  Johannes Hübl  Sven Fuchs 《Landslides》2016,13(3):537-550

Based on former conceptual models of vulnerability, this paper aims to improve the quantitative model for regional vulnerability assessment by analyzing in-depth the relation between vulnerability, exposure, coping capacity, and resilience. Taking the mountain settlements in the upper reaches of Min River, China, as a case study, the method of Contributing Weight Superposition (CWS) is applied in establishing both a model and a system for the vulnerability assessment of elements at risk. The CWS approach consists of 13 index factors including population, economic and road densities, building and farmland coverage, hazard-affected areas, urbanization rate, and GDP per capita. Accordingly, a debris flow hazard vulnerability zoning map was obtained and the assessment results show that the distribution of high and comparatively high vulnerability zones, where economic activities are considerably high, has a close correlation to the topography of the catchment and population characteristics. The results thus may serve as a pertinent guidance for settlement relocation, population distribution readjustment, and management to prevent and reduce hazards in the upper reaches of Min River and beyond.  相似文献   

Nature,Temporality and Environmental Management: Scandinavian and Australian Perspectives on Peoples and Landscapes     

Sven Arntzen 《Norsk geografisk tidsskrift. Norwegian journal of geography》2017,71(5):315-316

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Hubble Space Telescope survey of the Perseus Cluster – I. The structure and dark matter content of cluster dwarf spheroidals     

Samantha J. Penny  Christopher J. Conselice  Sven De Rijcke  Enrico V. Held 《Monthly notices of the Royal Astronomical Society》2009,393(3):1054-1062

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Carbonaceous materials in size-segregated atmospheric aerosols from urban and coastal-rural areas at the Western European Coast   总被引：1，自引：1，他引：0  

Regina M.B.O. Duarte  Cludia L. Mieiro  Ana Penetra  Casimiro A. Pio  Armando C. Duarte 《Atmospheric Research》2008,90(2-4):253-ICNAA07

A high-volume cascade impactor, equipped with a PM10 inlet, was used to collect size-segregated aerosol samples during the summer of 2004 at two Portuguese locations: a coastal-rural area (Moitinhos) and an urban area (Oporto). Concentrations of airborne particulate matter (PM), total carbon (TC), organic carbon (OC), elemental carbon (EC), and water-soluble organic carbon (WSOC) were determined for the following particle size ranges: < 0.49, 0.49–0.95, 0.95–3.0, and 3.0–10 µm. The total PM mass concentrations at the urban and coastal-rural sites ranged from 22.8 to 79.6 μg m^− 3 and 19.9 to 28.2 μg m^− 3, respectively, and more than 56% of the total aerosol mass was found in the fractions below 3.0 μm. At both locations the highest concentrations of OC and EC were found in the submicrometer size range. The regional variability for the OC and EC concentrations, with the highest concentrations being found in the urban area, was related to the contribution of local primary sources (mostly traffic emissions). It was also verified an enrichment of the small size particles in WSOC, representing on average 37.3(± 12.4)% and 59.7(± 18.0)% of OC in the very fine aerosol at the coastal-rural and urban areas, respectively. The amount of secondary OC calculated by the minimum OC/EC ratio method indicates that secondary organic aerosol formation was important throughout the study at both sites. The obtained results suggest that long-range transport and favourable summer conditions for photochemical oxidation are key factors determining secondary OC formation in the coastal-rural and urban areas. The ultraviolet absorption properties of the chromophoric constituents of the WSOC fractions were also different among the different particle size ranges and also between the two sampling locations, thus suggesting the strong impact of the diverse emission sources into the composition of the size-segregated organic aerosol.  相似文献   

Thermal expansion and decomposition of jarosite: a high-temperature neutron diffraction study     

Hongwu Xu  Yusheng Zhao  Sven C. Vogel  Donald D. Hickmott  Luke L. Daemen  Monika A. Hartl 《Physics and Chemistry of Minerals》2010,37(2):73-82

The structure of deuterated jarosite, KFe₃(SO₄)₂(OD)₆, was investigated using time-of-flight neutron diffraction up to its dehydroxylation temperature. Rietveld analysis reveals that with increasing temperature, its c dimension expands at a rate ~10 times greater than that for a. This anisotropy of thermal expansion is due to rapid increase in the thickness of the (001) sheet of [Fe(O,OH)₆] octahedra and [SO₄] tetrahedra with increasing temperature. Fitting of the measured cell volumes yields a coefficient of thermal expansion, α = α₀ + α₁ T, where α₀ = 1.01 × 10⁻⁴ K⁻¹ and α₁ = −1.15 × 10⁻⁷ K⁻². On heating, the hydrogen bonds, O1···D–O3, through which the (001) octahedral–tetrahedral sheets are held together, become weakened, as reflected by an increase in the D···O1 distance and a concomitant decrease in the O3–D distance with increasing temperature. On further heating to 575 K, jarosite starts to decompose into nanocrystalline yavapaiite and hematite (as well as water vapor), a direct result of the breaking of the hydrogen bonds that hold the jarosite structure together.  相似文献   

Dynamics of Saturn's magnetodisk near Titan's orbit: Comparison of Cassini magnetometer observations from real and virtual Titan flybys     

Sven Simon  Alexandre Wennmacher  Cesar L. Bertucci  Hendrik Kriegel  Michele K. Dougherty 《Planetary and Space Science》2010,58(12):1625-1635

We analyze the variability of the ambient magnetospheric field along Titan's orbit at 20.3 Saturn radii. However, while our preceding study (Simon et al., 2010) focused on Cassini magnetometer observations from the 62 Titan flybys (TA-T62) between October 2004 and October 2009, the present work discusses magnetic field data that were collected near Titan's orbit when the moon was far away. In analogy to the observations during TA-T62, the magnetospheric fields detected during these 79 “virtual” Titan flybys are strongly affected by the presence of Saturn's bowl-shaped and highly dynamic magnetodisk current sheet. We therefore provide a systematic classification of the magnetic field observations as magnetodisk current sheet or lobe-type scenarios. Among the 141 (62 real+79 virtual) crossings of Titan's orbit between July 2004 and December 2009, only 17 encounters (9 real+8 virtual) took place within quiet, magnetodisk lobe-type fields. During another 50 encounters (21 real+29 virtual), rapid transitions between current sheet and lobe fields were observed around the moon's orbital plane. Most of the encounters (54=22 real+32 virtual) occurred when Titan's orbit was embedded in highly distorted current sheet fields, thereby invalidating the frequently applied idealized picture of Titan interacting with a homogeneous and stationary magnetospheric background field. The locations of real and virtual Titan flybys are correlated to each other. Each of the 62 real Titan flybys possesses at least one virtual counterpart that occurred shortly before or after the real encounter and at nearly the same orbital position. A systematic comparison between Cassini magnetometer observations from the real Titan flybys and their virtual companions suggests that there is no clear evidence of Titan exerting a significant level of control on the vertical oscillatory motion of the magnetodisk near its orbit.  相似文献