Key challenges in agent-based modelling for geo-spatial simulation

Agent-based modelling (ABM) is fast becoming the dominant paradigm in social simulation due primarily to a worldview that suggests that complex systems emerge from the bottom-up, are highly decentralised, and are composed of a multitude of heterogeneous objects called agents. These agents act with some purpose and their interaction, usually through time and space, generates emergent order, often at higher levels than those at which such agents operate. ABM however raises as many challenges as it seeks to resolve. It is the purpose of this paper to catalogue these challenges and to illustrate them using three somewhat different agent-based models applied to city systems. The seven challenges we pose involve: the purpose for which the model is built, the extent to which the model is rooted in independent theory, the extent to which the model can be replicated, the ways the model might be verified, calibrated and validated, the way model dynamics are represented in terms of agent interactions, the extent to which the model is operational, and the way the model can be communicated and shared with others. Once catalogued, we then illustrate these challenges with a pedestrian model for emergency evacuation in central London, a hypothetical model of residential segregation tuned to London data which elaborates the standard Schelling (1971) model, and an agent-based residential location built according to spatial interactions principles, calibrated to trip data for Greater London. The ambiguities posed by this new style of modelling are drawn out as conclusions

Impact of infection preventionists on Centers for Medicare and Medicaid quality measures in Maryland nursing homes.

BackgroundHealth care-associated infections are the leading cause of morbidity and mortality in US nursing homes (NHs). The objective of the research is to assess the impact of Maryland NH infection preventionists (IPs) on NH quality measures.MethodsTwo hundred thirty-four NHs were queried through mailed survey. These survey data were then linked with 2008 quality data from Nursing Home Compare and the On-line Survey Certification of Automated Records.ResultsThree of the 8 quality measures examined-influenza vaccination for both short- and long-stay residents and pressure ulcer prevention in high-risk residents-were significantly associated with the number of IPs. None of the quality measures were shown to be significant with IPs who received specialized training on infection prevention and management compared with those who did not receive specialized training.ConclusionIPs play a critical role in preventing and managing health care-associated infections in nursing homes, especially in the areas of influenza vaccination and pressure ulcer prevention among high-risk nursing home residents. Quality measures that reflect the effects of IP training may not have been elucidated yet. Further research is needed to support the IP role in order for policy to advocate for increased IP funding

Making the Cut: Lattice Kirigami Rules

In this paper we explore and develop a simple set of rules that apply to cutting, pasting, and folding honeycomb lattices. We consider origami-like structures that are extinsically flat away from zero-dimensional sources of Gaussian curvature and one-dimensional sources of mean curvature, and our cutting and pasting rules maintain the intrinsic bond lengths on both the lattice and its dual lattice. We find that a small set of rules is allowed providing a framework for exploring and building kirigami -- folding, cutting, and pasting the edges of paper.Comment: 5 pages, 5 figure

In-flight absolute radiometric calibration of the thematic mapper

In order to determine temporal changes of the absolute radiometric calibration of the entire TM system in flight spectroradiometric measurements of the ground and the atmosphere were made simultaneously with TM image collections over the White Sands, New Mexico area. By entering the measured values in an atmospheric radiative transfer program, the radiance levels in four of the spectral bands of the TM were determined, band 1:0.45 to 0.52 micrometers, band 2:0.53 to 0.61 micrometers band 3:0.62 to 0.70 micrometers and 4:0.78 to 0.91 micrometers. These levels were compared to the output digital counts from the detectors that sampled the radiometrically measured ground area, thus providing an absolute radiometric calibration of the entire TM system utilizing those detectors

Modeling the power flow in normal conductor-insulator-superconductor junctions

Normal conductor-insulator-superconductor (NIS) junctions promise to be interesting for x-ray and phonon sensing applications, in particular due to the expected self-cooling of the N electrode by the tunneling current. Such cooling would enable the operation of the active element of the sensor below the cryostat temperature and at a correspondingly higher sensitivity. It would also allow the use of MS junctions as microcoolers. At present, this cooling has not been realized in large area junctions (suitable for a number of detector applications). In this article, we discuss a detailed modeling of the heat flow in such junctions; we show how the heat flow into the normal electrode by quasiparticle back-tunneling and phonon absorption from quasiparticle pair recombination can overcompensate the cooling power. This provides a microscopic explanation of the self-heating effects we observe in our large area NIS junctions. The model suggests a number of possible solutions

In-flight absolute radiometric calibration of the thematic mapper

The TM multispectral scanner system was calibrated in an absolute manner before launch. To determine the temporal changes of the absolute radiometric calibration of the entire system, spectroradiometric measurements of the ground and the atmosphere were made simultaneously with TM collections over White Sands, New Mexico. By entering the measured values in an atmospheric radiative transfer program, the radiance levels of the in four of the spectral bands of the TM were determined. Tables show values for the reflectance of snow at White Sands measured by a modular 8 channel radiometer, and values for exoatmospheric irradiance within the TM passbands, calculated for the Earth-Sun distance using a solar radiometer

Expression of 24,426 human alternative splicing events and predicted cis regulation in 48 tissues and cell lines

partially because of the limited scale at which the expression of specific splicing events has been measured. We generated the first genome-scale expression compendium of human alternative splicing events using custom whole-transcript microarrays monitoring expression of 24,426 alternative splicing events in 48 diverse human samples. Over 11,700 genes and 9,500 splicing events were differentially expressed, providing a rich resource for studying splicing regulation. An unbiased, systematic screen of 21,760 4-mer to 7-mer words for cis-regulatory motifs identified 143 RNA 'words' enriched near regulated cassette exons, including six clusters of motifs represented by UCUCU, UGCAUG, UGCU, UGUGU, UUUU and AGGG, which map to trans-acting regulators PTB, Fox, Muscleblind, CELF/CUG-BP, TIA-1 and hnRNP F/H, respectively. Each cluster showed a distinct pattern of genomic location and tissue specificity. For example, UCUCU occurs 110 to 35 nucleotides preceding cassette exons upregulated in brain and striated muscle but depleted in other tissues. UCUCU and UGCAUG seem to have similar function but independent action, occurring 5' and 3', respectively, of 33% of the cassette exons upregulated in skeletal muscle but co-occurring for only 2%

In vitro fusion of single synaptic and dense core vesicles reproduces key physiological properties.

Regulated exocytosis of synaptic vesicles is substantially faster than of endocrine dense core vesicles despite similar molecular machineries. The reasons for this difference are unknown and could be due to different regulatory proteins, different spatial arrangements, different vesicle sizes, or other factors. To address these questions, we take a reconstitution approach and compare regulated SNARE-mediated fusion of purified synaptic and dense core chromaffin and insulin vesicles using a single vesicle-supported membrane fusion assay. In all cases, Munc18 and complexin are required to restrict fusion in the absence of calcium. Calcium triggers fusion of all docked vesicles. Munc13 (C1C2MUN domain) is required for synaptic and enhanced insulin vesicle fusion, but not for chromaffin vesicles, correlating inversely with the presence of CAPS protein on purified vesicles. Striking disparities in calcium-triggered fusion rates are observed, increasing with curvature with time constants 0.23 s (synaptic vesicles), 3.3 s (chromaffin vesicles), and 9.1 s (insulin vesicles) and correlating with rate differences in cells

Topics in Quantum Computers

I provide an introduction to quantum computers, describing how they might be realized using language accessible to a solid state physicist. A listing of the minimal requirements for creating a quantum computer is given. I also discuss several recent developments in the area of quantum error correction, a subject of importance not only to quantum computation, but also to some aspects of the foundations of quantum theory.Comment: 22 pages, Latex, 1 eps figure, Paper to be published in "Mesoscopic Electron Transport", edited by L. Kowenhoven, G. Schoen and L. Sohn, NATO ASI Series E, Kluwer Ac. Publ., Dordrecht. v2: typos in refrences fixe