9,633 research outputs found
Now the wars are over: The past, present and future of Scottish battlefields
Battlefield archaeology has provided a new way of appreciating historic battlefields. This paper provides a summary of the long history of warfare and conflict in Scotland which has given rise to a large number of battlefield sites. Recent moves to highlight the archaeological importance of these sites, in the form
of Historic Scotland’s Battlefields Inventory are discussed, along with some of the problems associated with the preservation and management of these important
cultural sites
Stochastic unraveling of Redfield master equations and its application to electron transfer problems
A method for stochastic unraveling of general time-local quantum master
equations (QMEs) is proposed. The present kind of jump algorithm allows a
numerically efficient treatment of QMEs which are not in Lindblad form, i.e.
are not positive semidefinite by definition. The unraveling can be achieved by
allowing for trajectories with negative weights. Such a property is necessary,
e.g. to unravel the Redfield QME and to treat various related problems with
high numerical efficiency. The method is successfully tested on the damped
harmonic oscillator and on electron transfer models including one and two
reaction coordinates. The obtained results are compared to those from a direct
propagation of the reduced density matrix (RDM) as well as from the standard
quantum jump method. Comparison of the numerical efficiency is performed
considering both the population dynamics and the RDM in the Wigner phase space
representation.Comment: accepted in J. Chem. Phys.; 26 pages, 6 figures; the order of
authors' names on the title page correcte
Off-fault tensile cracks: A link between geological fault observations, lab experiments, and dynamic rupture models
We examine the local nature of the dynamic stress field in the vicinity of the tip of a semi-infinite sub-Rayleigh (slower than the Rayleigh wave speed, c_R) mode II crack with a velocity-weakening cohesive zone. We constrain the model using results from dynamic photoelastic experiments, in which shear ruptures were nucleated spontaneously in Homalite-100 plates along a bonded, precut, and inclined interface subject to a far-field uniaxial prestress. During the experiments, tensile cracks grew periodically along one side of the shear rupture interface at a roughly constant angle relative to the shear rupture interface. The occurrence and inclination of the tensile cracks are explained by our analytical model. With slight modifications, the model can be scaled to natural faults, providing diagnostic criteria for interpreting velocity, directivity, and static prestress state associated with past earthquakes on exhumed faults. Indirectly, this method also allows one to constrain the velocity-weakening nature of natural ruptures, providing an important link between field geology, laboratory experiments, and seismology
The people's choice: community management of RWS
The people's choice: community management of RW
Optimising risk reduction: An expected utility approach for marginal risk reduction during regulatory decision making
In practice, risk and uncertainty are essentially unavoidable in many regulation
processes. Regulators frequently face a risk-benefit trade-off since zero risk
is neither practicable nor affordable. Although it is accepted that cost-benefit
analysis is important in many scenarios of risk management, what role it should
play in a decision process is still controversial. One criticism of cost-benefit
analysis is that decision makers should consider marginal benefits and costs,
not present ones, in their decision making. In this paper, we investigate the
problem of regulatory decision making under risk by applying expected utility
theory and present a new approach of cost-benefit analysis. Directly taking into
consideration the reduction of the risks, this approach achieves marginal cost-
benefit analysis. By applying this approach, the optimal regulatory decision
that maximizes the marginal benefit of risk reduction can be considered. This
provides a transparent and reasonable criterion for stakeholders involved in the
regulatory activity. An example of evaluating seismic retrofitting alternatives
is provided to demonstrate the potential of the proposed approach. (C) 2009
Elsevier Ltd. All rights reserved
Eastern Beringia and beyond: Late Wisconsinan and Holocene landscape dynamics along the Yukon Coastal Plain, Canada
Terrestrial permafrost archives along the Yukon Coastal Plain (northwest Canada) have recorded landscape
development and environmental change since the Late Wisconsinan at the interface of unglaciated Beringia
(i.e. Komakuk Beach) and the northwestern limit of the Laurentide Ice Sheet (i.e. Herschel Island). The objective of this paper is to compare the late glacial and Holocene landscape development on both sides of the former ice margin based on permafrost sequences and ground ice. Analyses at these sites involved a multi-proxy approach including: sedimentology, cryostratigraphy, palaeoecology of ostracods, stable water isotopes in ground ice, hydrochemistry, and AMS radiocarbon and infrared stimulated luminescence (IRSL) dating. AMS and IRSL age determinations yielded full glacial ages at Komakuk Beach that is the northeastern limit of ice-free Beringia. Herschel Island to the east marks the Late Wisconsinan limit of the northwest Laurentide Ice Sheet and is composed of ice-thrust sediments containing plant detritus as young as 16.2 cal ka BP that might provide a maximum age on ice arrival. Late Wisconsinan ice wedges with sediment-rich fillings on Herschel Island are depleted in heavy oxygen isotopes (mean δ18O of −29.1‰); this, together with low dexcess values, indicates colder-than-modern winter temperatures and probably reduced snow depths.
Grain-size distribution and fossil ostracod assemblages indicate that deglaciation of the Herschel Island icethrust moraine was accompanied by alluvial, proluvial, and eolian sedimentation on the adjacent unglaciated
Yukon Coastal Plain until ~11 cal ka BP during a period of low glacio-eustatic sea level. The late glacial–Holocene transition was marked by higher-than-modern summer temperatures leading to permafrost degradation
that began no later than 11.2 cal ka BP and caused a regional thaw unconformity. Cryostructures and ice wedges were truncated while organic matter was incorporated and soluble ions were leached in the thaw zone. Thermokarst activity led to the formation of ice-wedge casts and deposition of thermokarst lake sediments. These were subsequently covered by rapidly accumulating peat during the early Holocene Thermal Maximum. A rising permafrost table, reduced peat accumulation, and extensive ice-wedge growth resulted from climate cooling starting in the middle Holocene until the late 20th century. The reconstruction of palaeolandscape dynamics on the Yukon Coastal Plain and the eastern Beringian edge contributes to unraveling the linkages between ice sheet, ocean, and permafrost that have existed since the Late Wisconsinan
Colony Stimulating Factor-1 Is Required to Recruit Macrophages into the Mammary Gland to Facilitate Mammary Ductal Outgrowth
AbstractMammary gland development initiates postnatally with the development of terminal end buds (TEBs) at the end of the rudimentary ducts. These grow out through the fat pad and bifurcate to lay down the rudimentary ductal tree. At the initiation of their development, TEBs recruit to their surrounding stroma a substantial population of macrophages. Using mice homozygous for a null mutation in the gene for the macrophage growth factor, colony stimulating factor-1 (CSF-1), that are severely depleted in macrophages, we demonstrated that CSF-1-regulated macrophages are required for normal branching morphogenesis in the mammary gland. However, these mice have a pleiotropic phenotype as a result of the generalized macrophage deficiency. To test that the effect of the mutation observed in the mammary gland was organ-autonomous, we developed a tetracycline-binary system whereby CSF-1 was specifically expressed in the mammary epithelium under the regulation of the MMTV-promoter. This restored mammary macrophage populations but not those in other tissues and corrected the branching morphogenesis defect. Inhibition of CSF-1 expression by tetracycline treatment for varying periods suggested that CSF-1-regulated macrophages are required throughout early mammary gland development. These data show that macrophages acting locally are required for branching morphogenesis of the mammary gland
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