A canonical enriched Adams-Hilton model for simplicial sets

For any 1-reduced simplicial set $K$ we define a canonical, coassociative coproduct on \Om C(K), the cobar construction applied to the normalized, integral chains on $K$, such that any canonical quasi-isomorphism of chain algebras from \Om C(K) to the normalized, integral chains on $GK$, the loop group of $K$, is a coalgebra map up to strong homotopy. Our proof relies on the operadic description of the category of chain coalgebras and of strongly homotopy coalgebra maps given in math.AT/0505559.Comment: 28 pages. This revised version incorporates operadic techniques developed in math.AT/050555

Essays on dynamic capabilities: the role of intellectual human capital in firm innovation

Following the dynamic capabilities perspective, I suggest that antecedents to innovation can be found at the individual, firm, and network level. Thus, I challenge two assumptions common in prior research: (1) that significant variance exists at the focal level of analysis, while other levels of analysis are assumed to be homogeneous, and (2) that the focal level of analysis is independent from other levels of analysis. Accordingly, I advance a set of hypotheses to simultaneously assess the direct effects of antecedents at the individual, firm, and network level on innovation output. I then investigate whether a firm s antecedents to innovation lie across different levels. To accomplish this, I propose two competing interaction hypotheses. I juxtapose the hypothesis that the individual, firm, and network-level antecedents to innovation are substitutes versus the proposition that these innovation mechanisms are complements. I test my multi-level theoretical model using an unusually comprehensive and detailed panel dataset that documents the innovation attempts of global pharmaceutical companies within biotechnology over a 22-year time period (1980-2001). I find evidence that the antecedents to innovation lie across different levels of analysis and can have compensating or reinforcing effects on firm-level innovative output.Ph.D.Committee Chair: Frank T. Rothaermel; Committee Member: J. Jeongsik Lee; Committee Member: John Walsh; Committee Member: Luis Martins; Committee Member: Matt Higgin

States' Roles in Shaping High Performance Health Systems

Analyzes results from the State Health Policies Aimed at Promoting Excellent Systems survey and a review of current research on efforts to improve state healthcare systems, with a focus on coverage; quality, safety, and value; and infrastructure

The loop group and the cobar construction

We prove that for any 1-reduced simplicial set X, Adams' cobar construction, \Omega CX, on the normalised chain complex of X is naturally a strong deformation retract of the normalised chains CGX on the Kan loop group GX, opening up the possibility of applying the tools of homological algebra to transfering perturbations of algebraic structure from the latter to the former. In order to prove our theorem, we extend the definition of the cobar construction and actually obtain the existence of such a strong deformation retract for all 0-reduced simplicial sets.Comment: 14 page

Modelling departure time and mode choice

As a result of increasing road congestion and road pricing, modelling the temporal response of travellers to transport policy interventions has rapidly emerged as a major issue in many practical transport planning studies. A substantial body of research is therefore being carried out to understand the complexities involved in modelling time of day choice. These models are contributing substantially to our understanding of how travellers make time-of-day decisions (Hess et al, 2004; de Jong et al, 2003). These models, however, tend to be far too complex and far too data intensive to be of use for application in large-scale modelling forecasting systems, where socio-economic detail is limited and detailed scheduling information is rarely available. Moreover, model systems making use of the some of the latest analytical structures, such as Mixed Logit, are generally inapplicable in practical planning, since they rely on computer-intensive simulation in application just as well as in estimation. The aim of this paper, therefore, is to describe the development of time-period choice models which are suitable for application in large-scale modelling forecasting systems. Large-scale practical planning models often rely on systems of nested logit models, which can incorporate many of the most important interactions that are present in the complex models but which have low enough run-times to allow them to be used for practical planning. In these systems, temporal choice is represented as the choice between a finite set of discrete alternatives, represented by mutually exclusive time-periods that are obtained by aggregation of the actual observed continuous time values. The issues that face modellers are then: -how should the time periods be defined, and in particular how long should they be? -how should the choices of time periods be related to each other, e.g. is the elasticity for shorter shifts greater than for longer shifts? -how should time period choice be placed in the model system relative to other choices, such as that of the mode of travel? These questions cannot be answered on a purely theoretical basis but require the analysis of empirical data. However, there is not a great deal of data available on the relevant choices. The time period models described in the paper are developed from three related stated preference (SP) studies undertaken over the past decade in the United Kingdom and the Netherlands. Because of the complications involved with using advanced models in large-scale modelling forecasting systems, the model structures are limited to nested logit models. Two different tree structures are explored in the analysis, nesting mode above time period choice or time period choice above mode. The analysis examines how these structures differ by data set, purpose of travel and time period specification. Three time period specifications were tested, dividing the 24-hour day into: -twenty-four 1-hour periods; -five coarse time-periods; -sixteen 15-minute morning-peak periods, and two coarse pre-peak and post-peak periods. In each case, the time periods are used to define both the outbound and the return trip timings. The analysis shows that, with a few exceptions, the nested models outperform the basic Multinomial Logit structures, which operate under the assumption of equal substitution patterns across alternatives. With a single exception, the nested models in turn show higher substitution between alternative time periods than between alternative modes, showing that, for all the time period lengths studied, travellers are more sensitive to transport levels of service in their choice of departure time than in choice of mode. The advantages of the nesting structures are especially pronounced in the 1-hour and 15-minute models, while, in the coarse time-period models, the MNL model often remains the preferred structure; this is a clear effect of the broader time-periods, and the consequently lower substitution between time-periods.

Prognostics and Health Management (PHM) for astronauts: a collaboration project on the International Space Station

Long-duration missions bring numerous risks that must be understood and mitigated in order to keep astronauts healthy, rather than treat a diagnosed health disorder. Having a limited medical support from mission control center on space exploration missions, crew members need a personal health-tracking tool to predict and assess his/her health risks if no preventive measures are taken. This paper refines a concept employing technologies from Prognostics and Health Management (PHM) for systems, namely real-time health monitoring and condition-based health maintenance with predictive diagnostics capabilities. Mapping particular PHM-based solutions to some Human Health and Performance (HH&P) technology candidates, namely by NASA designation, the Autonomous Medical Decision technology and the Integrated Biomedical Informatics technology, this conceptual paper emphasize key points that make the concept different from that of both current conventional medicine and telemedicine including space medicine. The primary benefit of the technologies development for the HH&P domain is the ability to successfully achieve affordable human space missions to Low Earth Orbit (LEO) and beyond. Space missions on the International Space Station (ISS) program directly contribute to the knowledge base and advancements in the HH&P domain, thanks to continued operations on the ISS, a unique human-tended test platform and the only test bed within the space environment. The concept is to be validated on the ISS, the only “test bed” on which to prepare for future manned exploration missions. The paper authors believe that early self-diagnostic coupled with autonomous identification of proper preventive responses on negative trends are critical in order to keep astronauts healthy

Rhetoric or Reality Exporting Democracy to the Middle East

Focuses on the promotion of democracy to the Middle East. Capacity of the U.S. to promote democracy in the Middle East; Discussion on the claim that spreading democracy in Iraq and Afghanistan is influenced by rhetorical flourish designed to impress American audiences; Assumption that the American brand of democracy is at a high price. From the EPIIC Symposium at Tufts University, February 2004

PReS-FINAL-2286: Mastitis in an adolescent patient with juvenile systemic lupus erythematous

Additional file 6: Figure S3. Accuracy of BayesB models with varying π values

Using variograms to detect and attribute hydrological change

There have been many published studies aiming to identify temporal changes in river flow time series, most of which use monotonic trend tests such as the Mann–Kendall test. Although robust to both the distribution of the data and incomplete records, these tests have important limitations and provide no information as to whether a change in variability mirrors a change in magnitude. This study develops a new method for detecting periods of change in a river flow time series, using temporally shifting variograms (TSVs) based on applying variograms to moving windows in a time series and comparing these to the long-term average variogram, which characterises the temporal dependence structure in the river flow time series. Variogram properties in each moving window can also be related to potential meteorological drivers. The method is applied to 91 UK catchments which were chosen to have minimal anthropogenic influences and good quality data between 1980 and 2012 inclusive. Each of the four variogram parameters (range, sill and two measures of semi-variance) characterise different aspects of the river flow regime, and have a different relationship with the precipitation characteristics. Three variogram parameters (the sill and the two measures of semi-variance) are related to variability (either day-to-day or over the time series) and have the largest correlations with indicators describing the magnitude and variability of precipitation. The fourth (the range) is dependent on the relationship between the river flow on successive days and is most correlated with the length of wet and dry periods. Two prominent periods of change were identified: 1995–2001 and 2004–2012. The first period of change is attributed to an increase in the magnitude of rainfall whilst the second period is attributed to an increase in variability of the rainfall. The study demonstrates that variograms have considerable potential for application in the detection and attribution of temporal variability and change in hydrological systems

Interactive stated choice surveys: A study of air travel behaviour

Stated preference (SP) experiments are becoming an increasingly popular survey methodology for investigating air travel choice behaviour. Nevertheless, some evidence suggests that SP experiments do not mirror decisions in real markets. In this paper we introduce a novel survey methodology that aims to make air travel surveys more consistent with real world settings, with the aim of obtaining more realistic results. The survey is modelled on the interface and functionality of an online travel agent (OTA). As with a real OTA, many ticket options are presented. Sort tools allow the options to be reordered, search tools allow options to be removed from consideration, and a further tool allows attributes to be hidden and shown. Extensive use of these tools is made by the 462 respondents, with the captured data revealing some attribute preferences at the individual level, and significant heterogeneity of preference across individuals. A traditional SP component was also completed by the respondents. Our exploratory analysis as well as random utility model estimation results confirm not only that respondents seem to engage more actively with the interactive survey, but also that the resulting data allows for better performance in model estimation. These results have implications for the study of other complex travel choices where interactive surveys may similarly be preferable to standard approaches