7,868 research outputs found
A taxonomic study of the genus Atheas Champion (Heteroptera: Tingidae)
The genus Atheas Champion is revised. A key to all 14 species cataloged in the genus is included. Species occurring in Mexico are redefined and illustrated. Descriptions of species not occurring in Mexico are also provided. Host plant information has been included, when available
Archives Conservation Discussion Group 2011: Digitization and Its Effect on Conservation Treatment Decisions: How Has Wide-Spread Digitizing of Collections Changed Our Approach to Treatment?
In line with this year’s AIC theme: ETHOS, LOGOS, PATHOS: ethical principles and critical thinking in conservation, The Archives Conservation Discussion Group 2011 examined the impact of providing digital collections in museums and libraries, and their conservation implications. Presentations and a subsequent discussion covered topics such as: How conservators are balancing ethical concerns, especially as dictated by the AIC Code of Ethics, with increased demand from digital projects. How conservators are keeping pace with large-scale or fast-paced digitizing projects, while maintaining standards. And the impact of limiting access to original materials by providing digital surrogates and its effect on treatment decisions
Reynolds number limits for jet propulsion: A numerical study of simplified jellyfish
The Scallop Theorem states that reciprocal methods of locomotion, such as jet
propulsion or paddling, will not work in Stokes flow (Reynolds number = 0). In
nature the effective limit of jet propulsion is still in the range where
inertial forces are significant. It appears that almost all animals that use
jet propulsion swim at Reynolds numbers (Re) of about 5 or more. Juvenile squid
and octopods hatch from the egg already swimming in this inertial regime. The
limitations of jet propulsion at intermediate Re is explored here using the
immersed boundary method to solve the two-dimensional Navier Stokes equations
coupled to the motion of a simplified jellyfish. The contraction and expansion
kinematics are prescribed, but the forward and backward swimming motions of the
idealized jellyfish are emergent properties determined by the resulting fluid
dynamics. Simulations are performed for both an oblate bell shape using a
paddling mode of swimming and a prolate bell shape using jet propulsion.
Average forward velocities and work put into the system are calculated for
Reynolds numbers between 1 and 320. The results show that forward velocities
rapidly decay with decreasing Re for all bell shapes when Re < 10. Similarly,
the work required to generate the pulsing motion increases significantly for Re
< 10. When compared actual organisms, the swimming velocities and vortex
separation patterns for the model prolate agree with those observed in Nemopsis
bachei. The forward swimming velocities of the model oblate jellyfish after two
pulse cycles are comparable to those reported for Aurelia aurita, but
discrepancies are observed in the vortex dynamics between when the 2D model
oblate jellyfish and the organism
Leaf roll-up and aquaplaning in strong winds and floods
Flexible plants, fungi, and sessile animals are thought to reconfigure in the
wind and water to reduce the drag forces that act upon them. In strong winds,
for example, leaves roll up into cone shapes that reduce flutter and drag when
compared to paper cut-outs with similar shapes and flexibility. During flash
floods, herbaceous broad leaves aquaplane on the surface of the water which
reduces drag. Simple mathematical models of a flexible beam immersed in a
two-dimensional flow will also reconfigure in flow. What is less understood is
how the mechanical properties of a two-dimensional leaf in a three-dimensional
flow will passively allow roll up and aquaplaning. In this study, we film leaf
roll-up and aquaplaning in tree and vine leaves in both strong winds and water
flows
Bifurcations in valveless pumping techniques from a coupled fluid-structure-electrophysiology model in heart development
We explore an embryonic heart model that couples electrophysiology and
muscle-force generation to flow induced using a fluid-structure
interaction framework based on the immersed boundary method. The propagation of
action potentials are coupled to muscular contraction and hence the overall
pumping dynamics. In comparison to previous models, the electro-dynamical model
does not use prescribed motion to initiate the pumping motion, but rather the
pumping dynamics are fully coupled to an underlying electrophysiology model,
governed by the FitzHugh-Nagumo equations. Perturbing the diffusion parameter
in the FitzHugh-Nagumo model leads to a bifurcation in dynamics of action
potential propagation. This bifurcation is able to capture a spectrum of
different pumping regimes, with dynamic suction pumping and peristaltic-like
pumping at the extremes. We find that more bulk flow is produced within the
realm of peristaltic-like pumping.Comment: 11 pages, 13 figures. arXiv admin note: text overlap with
arXiv:1610.0342
Working Together Toward Better Health Outcomes
Healthcare organizations and community-based organizations (CBOs) that provide human services are partnering in shared pursuit of better health outcomes. The Partnership for Healthy Outcomes – Nonprofit Finance Fund (NFF), the Center for Health Care Strategies (CHCS), and the Alliance for Strong Families and Communities (Alliance), with support from the Robert Wood Johnson Foundation (RWJF) – set out to capture and analyze the lessons emerging in this dynamic space. Information from more than 200 partnerships serving all 50 US states provide important lessons from, and for, partnerships that hope to improve access to care, address health inequities, and make progress on social issues like food, education, and housing
Binomial D-modules
We study quotients of the Weyl algebra by left ideals whose generators
consist of an arbitrary Z^d-graded binomial ideal I along with Euler operators
defined by the grading and a parameter in C^d. We determine the parameters for
which these D-modules (i) are holonomic (equivalently, regular holonomic, when
I is standard-graded); (ii) decompose as direct sums indexed by the primary
components of I; and (iii) have holonomic rank greater than the generic rank.
In each of these three cases, the parameters in question are precisely those
outside of a certain explicitly described affine subspace arrangement in C^d.
In the special case of Horn hypergeometric D-modules, when I is a lattice basis
ideal, we furthermore compute the generic holonomic rank combinatorially and
write down a basis of solutions in terms of associated A-hypergeometric
functions. This study relies fundamentally on the explicit lattice point
description of the primary components of an arbitrary binomial ideal in
characteristic zero, which we derive in our companion article arxiv:0803.3846.Comment: This version is shorter than v2. The material on binomial primary
decomposition has been split off and now appears in its own paper
arxiv:0803.384
"Financial Development and Economic Growth in Transition Economies: Empirical Evidence from the CEE and CIS Countries"
We examine the role of financial development in economic growth in the former Communist countries of Central and Eastern Europe and the Commonwealth of Independent States during the first two decades since the beginning of transition. These countries, which had undeveloped financial systems under Communism, provide an interesting test of the relationship between financial development and growth. We show that credit to the private sector had a positive effect on growth in these countries; however, high levels of inflation can render the positive effect of private credit insignificant. High interest rate spreads and reduced banking competition hampered economic growth.transition economies, CEE, CIS, financial sector development, economic growth, panel data
CRRES: Combined Release and Radiation Effects Satellite Program Summary
The experiments that comprise the Combined Release and Radiation Effects Satellite Program (CRRES) (Apr. 1990 - Jul. 1992) are presented. The experiments are as follows: PEGSAT; El Coqui; the Kwajalein Campaign; and experiments G1 - G14
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