368 research outputs found
Subsidence across the Antler foreland of Montana and Idaho: Tectonic versus eustatic effects
Devonian and Mississippian sedimentary rocks of western Montana and east-central Idaho were deposited on a cratonic platform that faced a deep basin to the west. The deep basin in Idaho was a northern extension of the Antler foredeep and formed as a flexural response to loading of the ancient North American continental margin by an inferred arc and thrust belt complex. Subsidence analyses of the Devonian-Mississippian strata indicate episodic subsidence events in the proximal foredeep and adjacent cratonic platform, an area approximately 800 km (500 mi) wide (palinspastic). Isopach maps for this sequence illustrate that many depocenters and paleohighs were geographically coincident across the foreland through time. The Devonian-Mississippian foreland structures had cross-sectional wavelengths of 50-200 km (30-120 mi) and amplitudes of about 50-350 m (160-1,150 ft). Some of these structures were tectonically inverted (i.e., paleohighs became depocenters and vice versa) several times during the 50-60 m.y. represented by this stratigraphic sequence. Many of these generally east-west-trending paleostructures were oriented at high angles to the north-south-trending axis of the Antler foredeep and the inferred strike of the Antler orogenic belt. These foreland structures coincide geographically with structural trends produced during Proterozoic extension, suggesting that the Proterozoic faults were reactivated during Antler convergence. The isopach maps also show progressive southeastward migration of Antler foredeep depocenters from Late Devonian to Early Pennsylvanian time. The southeastward migration of the foredeep depocenter suggests that the maximum thrust load moved progressively southeastward from Late Devonian to Early Pennsylvanian time. The complex patterns of subsidence across the Montana-Idaho foreland do not fit into simple flexural models for vertical loading of unbroken elastic plates. Instead, differential subsidence of the foreland may be related to several mechanisms: (1) flexure of mechanically independent, fault-bounded segments of the foreland produced by areally limited thrust loads (subregional vertical loading); (2) transmission of compressive in-plane stresses through the foreland lithosphere (regional horizontal loading) that may have reactivated Proterozoic fault systems; and (3) waxing and waning of in-plane compressive stresses resulting from the episodic nature of Antler convergence. Results from this study suggest that, in settings where the foreland lithosphere is broken by ancient fault systems, the foreland may exhibit complex patterns of differential subsidence that probably reflect a composite response to both vertical and horizontal loads. Also, the simultaneous pulses of subsidence documented across large parts of the Antler foreland suggest that it may be possible to date episodes of convergence along ancient continental margins, even when the ancient thrust belt complex is poorly preserved
Subsidence across the Antler foreland of Montana and Idaho: Tectonic versus eustatic effects
Devonian and Mississippian sedimentary rocks of western Montana and east-central Idaho were deposited on a cratonic platform that faced a deep basin to the west. The deep basin in Idaho was a northern extension of the Antler foredeep and formed as a flexural response to loading of the ancient North American continental margin by an inferred arc and thrust belt complex. Subsidence analyses of the Devonian-Mississippian strata indicate episodic subsidence events in the proximal foredeep and adjacent cratonic platform, an area approximately 800 km (500 mi) wide (palinspastic). Isopach maps for this sequence illustrate that many depocenters and paleohighs were geographically coincident across the foreland through time. The Devonian-Mississippian foreland structures had cross-sectional wavelengths of 50-200 km (30-120 mi) and amplitudes of about 50-350 m (160-1,150 ft). Some of these structures were tectonically inverted (i.e., paleohighs became depocenters and vice versa) several times during the 50-60 m.y. represented by this stratigraphic sequence. Many of these generally east-west-trending paleostructures were oriented at high angles to the north-south-trending axis of the Antler foredeep and the inferred strike of the Antler orogenic belt. These foreland structures coincide geographically with structural trends produced during Proterozoic extension, suggesting that the Proterozoic faults were reactivated during Antler convergence. The isopach maps also show progressive southeastward migration of Antler foredeep depocenters from Late Devonian to Early Pennsylvanian time. The southeastward migration of the foredeep depocenter suggests that the maximum thrust load moved progressively southeastward from Late Devonian to Early Pennsylvanian time. The complex patterns of subsidence across the Montana-Idaho foreland do not fit into simple flexural models for vertical loading of unbroken elastic plates. Instead, differential subsidence of the foreland may be related to several mechanisms: (1) flexure of mechanically independent, fault-bounded segments of the foreland produced by areally limited thrust loads (subregional vertical loading); (2) transmission of compressive in-plane stresses through the foreland lithosphere (regional horizontal loading) that may have reactivated Proterozoic fault systems; and (3) waxing and waning of in-plane compressive stresses resulting from the episodic nature of Antler convergence. Results from this study suggest that, in settings where the foreland lithosphere is broken by ancient fault systems, the foreland may exhibit complex patterns of differential subsidence that probably reflect a composite response to both vertical and horizontal loads. Also, the simultaneous pulses of subsidence documented across large parts of the Antler foreland suggest that it may be possible to date episodes of convergence along ancient continental margins, even when the ancient thrust belt complex is poorly preserved
BCR-ABL activity and its response to drugs can be determined in CD34+ CML stem cells by CrkL phosphorylation status using flow cytometry.
In chronic myeloid leukaemia, CD34(+) stem/progenitor cells appear resistant to imatinib mesylate (IM) in vitro and in vivo. To investigate the underlying mechanism(s) of IM resistance, it is essential to quantify Bcr-Abl kinase status at the stem cell level. We developed a flow cytometry method to measure CrkL phosphorylation (P-CrkL) in samples with <10(4) cells. The method was first validated in wild-type (K562) and mutant (BAF3) BCR-ABL(+) as well as BCR-ABL(-) (HL60) cell lines. In response to increasing IM concentration, there was a linear reduction in P-CrkL, which was Bcr-Abl specific and correlated with known resistance. The results were comparable to those from Western blotting. The method also proved to be reproducible with small samples of normal and Ph(+) CD34(+) cells and was able to discriminate between Ph(-), sensitive and resistant Ph(+) cells. This assay should now enable investigators to unravel the mechanism(s) of IM resistance in stem cells
Nonequilibrium fluctuation dissipation relations of interacting Brownian particles driven by shear
We present a detailed analysis of the fluctuation dissipation theorem (FDT)
close to the glass transition in colloidal suspensions under steady shear using
mode coupling approximations. Starting point is the many-particle Smoluchowski
equation. Under shear, detailed balance is broken and the response functions in
the stationary state are smaller at long times than estimated from the
equilibrium FDT. An asymptotically constant relation connects response and
fluctuations during the shear driven decay, restoring the form of the FDT with,
however, a ratio different from the equilibrium one. At short times, the
equilibrium FDT holds. We follow two independent approaches whose results are
in qualitative agreement. To discuss the derived fluctuation dissipation
ratios, we show an exact reformulation of the susceptibility which contains not
the full Smoluchowski operator as in equilibrium, but only its well defined
Hermitian part. This Hermitian part can be interpreted as governing the
dynamics in the frame comoving with the probability current. We present a
simple toy model which illustrates the FDT violation in the sheared colloidal
system.Comment: 21 pages, 13 figures, submitted to Phys. Rev.
Single-hole properties in the - and strong-coupling models
We report numerical results for the single-hole properties in the -
model and the strong-coupling approximation to the Hubbard model in two
dimensions. Using the hopping basis with over states we discuss (for an
infinite system) the bandwidth, the leading Fourier coefficients in the
dispersion, the band masses, and the spin-spin correlations near the hole. We
compare our results with those obtained by other methods. The band minimum is
found to be at () for the - model for , and for the strong-coupling model for . The bandwidth
in both models is approximately at large , in rough agreement with
loop-expansion results but in disagreement with other results. The
strong-coupling bandwidth for t/J\agt6 can be obtained from the - model
by treating the three-site terms in first-order perturbation theory. The
dispersion along the magnetic zone face is flat, giving a large
parallel/perpendicular band mass ratio.Comment: 1 RevTeX file with epsf directives to include 8 .eps figures 8 figure
files encoded using uufile
HEJ 2.2: W boson pairs and Higgs boson plus jet production at high energies
We present version 2.2 of the High Energy Jets (HEJ) Monte Carlo event
generator for hadronic scattering processes at high energies. The new version
adds support for two further processes of central phenomenological interest,
namely the production of a W boson pair with equal charge together with two or
more jets and the production of a Higgs boson with at least one jet.
Furthermore, a new prediction for charged lepton pair production with high jet
multiplicities is provided in the high-energy limit. The accuracy of HEJ 2.2
can be increased further through an enhanced interface to standard predictions
based on conventional perturbation theory. We describe all improvements and
provide extensive usage examples. HEJ 2.2 can be obtained from
https://hej.hepforge.org.Comment: 29 pages, 2 figures and many code listing
Recommended from our members
Multi-processing CTH: Porting legacy FORTRAN code to MP hardware
CTH is a family of codes developed at Sandia National Laboratories for use in modeling complex multi-dimensional, multi-material problems that are characterized by large deformations and/or strong shocks. A two-step, second-order accurate Eulerian solution algorithm is used to solve the mass, momentum, and energy conservation equations. CTH has historically been run on systems where the data are directly accessible to the cpu, such as workstations and vector supercomputers. Multiple cpus can be used if all data are accessible to all cpus. This is accomplished by placing compiler directives or subroutine calls within the source code. The CTH team has implemented this scheme for Cray shared memory machines under the Unicos operating system. This technique is effective, but difficult to port to other (similar) shared memory architectures because each vendor has a different format of directives or subroutine calls. A different model of high performance computing is one where many (> 1,000) cpus work on a portion of the entire problem and communicate by passing messages that contain boundary data. Most, if not all, codes that run effectively on parallel hardware were written with a parallel computing paradigm in mind. Modifying an existing code written for serial nodes poses a significantly different set of challenges that will be discussed. CTH, a legacy FORTRAN code, has been modified to allow for solutions on distributed memory parallel computers such as the IBM SP2, the Intel Paragon, Cray T3D, or a network of workstations. The message passing version of CTH will be discussed and example calculations will be presented along with performance data. Current timing studies indicate that CTH is 2--3 times faster than equivalent C++ code written specifically for parallel hardware. CTH on the Intel Paragon exhibits linear speed up with problems that are scaled (constant problem size per node) for the number of parallel nodes
Roadblocks to low temperature district heating
Energy usage in buildings is coming increasingly under the spotlight as carbon policy focus shifts towards the utilization of thermal energy. In the UK, heating and hot water accounts for around 40% of energy consumption and 20% of greenhouse gas emissions. Heating is typically produced onsite, making widescale carbon or energetic improvements challenging. District heating networks (DHNs) can offer significant carbon reduction for many users but can only be implemented if the end user buildings have good thermal energy efficiency. This greatly limits the ability to implement advancing 4th and 5th generation DHNs, which are the most advanced systems available. We elucidate the current state of thermal efficiency in buildings in the UK and provide recommendations for necessary building requirements and modifications in order to accommodate 4th and 5th generation district heating. We conclude that key sectors must be addressed including creating a skilled workforce, producing relevant metrics and benchmarks, and providing financial support for early stage design exploration
Self-diffusion in dense granular shear flows
Diffusivity is a key quantity in describing velocity fluctuations in granular
materials. These fluctuations are the basis of many thermodynamic and
hydrodynamic models which aim to provide a statistical description of granular
systems. We present experimental results on diffusivity in dense, granular
shear in a 2D Couette geometry. We find that self-diffusivities are
proportional to the local shear rate with diffusivities along the mean flow
approximately twice as large as those in the perpendicular direction. The
magnitude of the diffusivity is D \approx \dot\gamma a^2 where a is the
particle radius. However, the gradient in shear rate, coupling to the mean
flow, and drag at the moving boundary lead to particle displacements that can
appear sub- or super-diffusive. In particular, diffusion appears superdiffusive
along the mean flow direction due to Taylor dispersion effects and subdiffusive
along the perpendicular direction due to the gradient in shear rate. The
anisotropic force network leads to an additional anisotropy in the diffusivity
that is a property of dense systems with no obvious analog in rapid flows.
Specifically, the diffusivity is supressed along the direction of the strong
force network. A simple random walk simulation reproduces the key features of
the data, such as the apparent superdiffusive and subdiffusive behavior arising
from the mean flow, confirming the underlying diffusive motion. The additional
anisotropy is not observed in the simulation since the strong force network is
not included. Examples of correlated motion, such as transient vortices, and
Levy flights are also observed. Although correlated motion creates velocity
fields qualitatively different from Brownian motion and can introduce
non-diffusive effects, on average the system appears simply diffusive.Comment: 13 pages, 20 figures (accepted to Phys. Rev. E
- …