22,524 research outputs found
End-effects of strongly charged polyelectrolytes - a molecular dynamics study
We investigate end-effects in the ion distribution around strongly charged,
flexible polyelectrolytes with a quenched charge distribution by molecular
dynamics simulations of dilute polyelectrolyte solutions. We take the
counterions explicitly into account and calculate the full Coulomb interaction
via an Ewald summation method. We find that the free counterions of the
solution are distributed in such a way that a fraction of the chain charges is
effectively neutralized. This in turn leads to an effective charge distribution
which is similar to those found for weakly charged titrating polyelectrolytes
that have an annealed charge distribution. The delicate interplay between the
electrostatic interactions, the chain conformation and the counterion
distribution is studied in detail as a function of different system parameters
such as the chain length Nm, the charge fraction f, the charged particle
density rho, the ionic strength and the solvent quality. Comparisons are made
with predictions from a scaling theory.Comment: 20 pages, 10 figures. J. Chem. Phys, to appear June 200
Tunneling dynamics of few bosons in a double well
We study few-boson tunneling in a one-dimensional double well. As we pass
from weak interactions to the fermionization limit, the Rabi oscillations first
give way to highly delayed pair tunneling (for medium coupling), whereas for
very strong correlations multi-band Rabi oscillations emerge. All this is
explained on the basis of the exact few-body spectrum and without recourse to
the conventional two-mode approximation. Two-body correlations are found
essential to the understanding of the different tunnel mechanisms. The
investigation is complemented by discussing the effect of skewing the double
well, which offers the possibility to access specific tunnel resonancesComment: 10 pages, 8 figure
Clout, Activists and Budget: The Road to Presidency
Political campaigns involve, in the simplest case, two competing campaign
groups which try to obtain a majority of votes. We propose a novel mathematical
framework to study political campaign dynamics on social networks whose
constituents are either political activists or persuadable individuals.
Activists are convinced and do not change their opinion and they are able to
move around in the social network to motivate persuadable individuals to vote
according to their opinion. We describe the influence of the complex interplay
between the number of activists, political clout, budgets, and campaign costs
on the campaign result. We also identify situations where the choice of one
campaign group to send a certain number of activists already pre-determines
their victory. Moreover, we show that a candidate's advantage in terms of
political clout can overcome a substantial budget disadvantage or a lower
number of activists, as illustrated by the US presidential election 2016.Comment: 23 pages, 10 figure
Designing for Economies of Scale vs. Economies of Focus in Hospital Departments
Subject/Research problem: Hospitals traditionally segregate resources into centralized functional departments such as diagnostic departments, ambulatory care centres, and nursing wards. In recent years this organizational model has been challenged by the idea that higher quality of care and efficiency in service delivery can be achieved when services are organized around patient groups. Examples are specialized clinics for breast cancer patients and clinical pathways for diabetes patients. Hospitals are struggling with the question whether to become more centralized to achieve economies of scale or more decentralized to achieve economies of focus. In this paper service and patient group characteristics are examined to determine conditions where a centralized model is more efficient and conversely where a decentralized model is more efficient. - Research Question: When organizing hospital capacity what service and patient group characteristics indicate efficiency can be gained through economies of scale vs. economies of focus? - Approach: Using quantitative Queueing Theory and Simulation models the performance of centralized and decentralized hospital clinics is compared. This is done for a variety of services and patient groups. - Result: The study results in a model measuring the tradeoffs between economies of scale and economies of focus. From this model management guidelines are derived. - Application: The general results support strategic planning for a new facility at the Netherlands Cancer Institute - Antoni van Leeuwenhoek Hospital. A model developed during this research is also applied in the Chemotherapy Department of the same hospital
Efficiency evaluation for pooling resources in health care
Hospitals traditionally segregate resources into centralized functional departments such as diagnostic departments, ambulatory care centers, and nursing wards. In recent years this organizational model has been challenged by the idea that higher quality of care and efficiency in service delivery can be achieved when services are organized around patient groups. Examples include specialized clinics for breast cancer patients and clinical pathways for diabetes patients. Hospitals are struggling with the question of whether to become more centralized to achieve economies of scale or more decentralized to achieve economies of focus. In this paper we examine service and patient group characteristics to study the conditions where a centralized model is more efficient, and conversely, where a decentralized model is more efficient. This relationship is examined analytically with a queuing model to determine themost influential factors and then with simulation to fine-tune the results. The tradeoffs between economies of scale and economies of focus measured by these models are used to derive general management guidelines
Efficiency evaluation for pooling resources in health care: An interpretation for managers
Subject/Research problem\ud
Hospitals traditionally segregated resources into centralized functional departments such as diagnostic departments, ambulatory care centres, and nursing wards. In recent years this organizational model has been challenged by the idea that higher quality of care and efficiency in service delivery can be achieved when services are organized around patient groups. Examples are specialized clinics for breast cancer patients and clinical pathways for diabetes patients. Hospitals are grappling more and more with the question, should we become more centralized to achieve economies of scale or more decentralized to achieve economies of focus. In this paper service and patient group characteristics are examined to determine conditions where a centralized model is more efficient and conversely where a decentralized model is more efficient.\ud
Research Question\ud
When organizing hospital capacity what service and patient group characteristics indicate that efficiency can be gained through economies of scale vs. economies of focus?\ud
Approach\ud
Using quantitative models from the Queueing Theory and Simulation disciplines the performance of centralized and decentralized hospital clinics are compared. This is done for a variety of services and patient groups. \ud
Result\ud
The study results in a model measuring the tradeoffs between economies of scale and economies of focus. From this model ârules of thumbâ for managers are derived.\ud
Application\ud
The general results support strategic planning for a new facility at the Netherlands Cancer Institute - Antoni van Leeuwenhoek Hospital. A model developed during this study is also applied in the Chemotherapy Department of the same hospital.\u
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