463 research outputs found
Supporting the development of shared understanding in distributed design teams
Distributed teams are an increasingly common feature of engineering design work. One key factor in the success of these teams is the development of short- and longer-term shared understanding. A lack of shared understanding has been recognized as a significant challenge, particularly in the context of globally distributed engineering activities. A major antecedent for shared understanding is question asking and feedback. Building on question-asking theory this work uses a quasi-experimental study to test the impact of questioning support on homogeneous and heterogeneous teams. The results show significant improvement in shared understanding for both team types (27% improvement for heterogeneous and 16% for homogeneous), as well as substantial differences in how this improvement is perceived. This extends theoretical insight on the development of shared understanding and contributes one of few empirical studies directly comparing homogeneous and heterogeneous teams in the engineering design context. This has implications for how distributed teams can be more effectively supported in practice, as well as how shared understanding can be facilitated in engineering design
Scaling anomalies in the coarsening dynamics of fractal viscous fingering patterns
We analyze a recent experiment of Sharon \textit{et al.} (2003) on the
coarsening, due to surface tension, of fractal viscous fingering patterns
(FVFPs) grown in a radial Hele-Shaw cell. We argue that an unforced Hele-Shaw
model, a natural model for that experiment, belongs to the same universality
class as model B of phase ordering. Two series of numerical simulations with
model B are performed, with the FVFPs grown in the experiment, and with
Diffusion Limited Aggregates, as the initial conditions. We observed
Lifshitz-Slyozov scaling at intermediate distances and very slow
convergence to this scaling at small distances. Dynamic scale invariance breaks
down at large distances.Comment: 4 pages, 4 eps figures; to appear in Phys. Rev.
Ising model with memory: coarsening and persistence properties
We consider the coarsening properties of a kinetic Ising model with a memory
field. The probability of a spin-flip depends on the persistence time of the
spin in a state. The more a spin has been in a given state, the less the
spin-flip probability is. We numerically studied the growth and persistence
properties of such a system on a two dimensional square lattice. The memory
introduces energy barriers which freeze the system at zero temperature. At
finite temperature we can observe an apparent arrest of coarsening for low
temperature and long memory length. However, since the energy barriers
introduced by memory are due to local effects, there exists a timescale on
which coarsening takes place as for the Ising model. Moreover the two point
correlation functions of the Ising model with and without memory are the same,
indicating that they belong to the same universality class.Comment: 10 pages, 7 figures; some figures and some comments adde
Dynamic SU(2) Lattice Gauge Theory at Finite Temperature
The dynamic relaxation process for the (2+1)--dimensional SU(2) lattice gauge
theory at critical temperature is investigated with Monte Carlo methods. The
critical initial increase of the Polyakov loop is observed. The dynamic
exponents and as well as the static critical exponent
are determined from the power law behaviour of the Polyakov loop, the
auto-correlation and the second moment at the early stage of the time
evolution. The results are well consistent and universal short-time scaling
behaviour of the dynamic system is confirmed. The values of the exponents show
that the dynamic SU(2) lattice gauge theory is in the same dynamic universality
class as the dynamic Ising model.Comment: 10 pages with 2 figure
Generalized Dynamic Scaling for Critical Relaxations
The dynamic relaxation process for the two dimensional Potts model at
criticality starting from an initial state with very high temperature and
arbitrary magnetization is investigated with Monte Carlo methods. The results
show that there exists universal scaling behaviour even in the short-time
regime of the dynamic evolution. In order to describe the dependence of the
scaling behaviour on the initial magnetization, a critical characteristic
function is introduced.Comment: Latex, 8 pages, 3 figures, to appear in Phys. Rev. Let
Normal scaling in globally conserved interface-controlled coarsening of fractal clusters
Globally conserved interface-controlled coarsening of fractal clusters
exhibits dynamic scale invariance and normal scaling. This is demonstrated by a
numerical solution of the Ginzburg-Landau equation with a global conservation
law. The sharp-interface limit of this equation is volume preserving motion by
mean curvature. The scaled form of the correlation function has a power-law
tail accommodating the fractal initial condition. The coarsening length
exhibits normal scaling with time. Finally, shrinking of the fractal clusters
with time is observed. The difference between global and local conservation is
discussed.Comment: 4 pages, 3 eps figure
Effects of Parvovirus B19 Infection in Renal Transplant Recipients: A Retrospective Review of Three Cases
Parvovirus B19 (PVB19) is a DNA virus which causes clinically relevant infection in renal transplant recipients (RTR) leading to significant morbidity. Manifestations include erythropoietin resistant anemia, proteinuria, and glomerulosclerosis in the allograft. Severe infection may require administration of intravenous immunoglobulin, reduction in immunosuppression and transfusions. The major challenge in managing and preventing the infection in RTR involves the act of balancing the decreased level of immunosuppression and the risk of rejection. The objective of this article is to understand the importance of PVB19 infection and its outcome in RTR. We reviewed the medical records of three RTR with confirmed PVB19 infection and recorded patient information including demographics, clinical and laboratory data, management, and outcome. The average time of occurrence of PVB19 infection as transplant was 8.6 weeks and they presented with symptomatic anemia. Elevated creatinine values were noted in two of them. Following treatment, anemia improved and creatinine values returned to baseline. One of them developed an early relapse and had to be treated once again similarly. We emphasize the importance of maintaining a high index of suspicion for PVB19 infection in patients with anemia in the posttransplant phase, especially in patients on higher doses of immunosuppressants. Early and proper treatment can prevent worsening clinical condition and possible effects on the allograft
Dynamic Approach to the Fully Frustrated XY Model
Using Monte Carlo simulations, we systematically investigate the
non-equilibrium dynamics of the chiral degree of freedom in the two-dimensional
fully frustrated XY model. The critical initial increase of the staggered
chiral magnetization is observed. By means of the short-time dynamics approach,
we estimate the second order phase transition temperature and all the
dynamic and static critical exponents , z, and .Comment: 5 pages with 6 figures include
Microscopic Non-Universality versus Macroscopic Universality in Algorithms for Critical Dynamics
We study relaxation processes in spin systems near criticality after a quench
from a high-temperature initial state. Special attention is paid to the stage
where universal behavior, with increasing order parameter emerges from an early
non-universal period. We compare various algorithms, lattice types, and
updating schemes and find in each case the same universal behavior at
macroscopic times, despite of surprising differences during the early
non-universal stages.Comment: 9 pages, 3 figures, RevTeX, submitted to Phys. Rev. Let
Passage of Heme-Iron Across the Envelope of Staphylococcus aureus
The cell wall envelope of Gram-positive pathogens functions as a scaffold for the attachment of virulence factors and as a sieve that prevents diffusion of molecules. Here the isdgenes (iron-regulated surface determinant) of Staphylococcus aureus were found to encode factors responsible for hemoglobin binding and passage of heme-iron to the cytoplasm, where it acts as an essential nutrient. Heme-iron passage required two sortases that tether Isd proteins to unique locations within the cell wall. Thus, Isd appears to act as an import apparatus that uses cell wall–anchored proteins to relay heme-iron across the bacterial envelope
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