A study of policies governing the employment of part-time professional nurses in hospitals

Thesis (M.S.)--Boston Universit

Synthetic Studies Towards the Total Synthesis of (–)-Lomaiviticin A

(–)-Lomaiviticin A (1) is a complex C2-symmetric bacterial metabolite which was isolated from a fermentation broth of Salinispora DPJ-19 by He and co-workers in 2001. The structure of 1 was proposed through detailed analysis of NMR spectral data (Figure 1). Due to the presence of a diazotetrahydrobenzo[b]fluorene substructure, 1 belongs to a family of natural products often referred to as “diazofluorenes” among which the kinamycins (A, C, and F seen in Figure 1) are the earliest known members. (–)-Lomaiviticin A (1) is the most cytotoxic member of the diazofluorene family known with half maximal inhibitory potencies (IC50S) in the nanomolar to picomolar range. In addition to the interesting biological activity of 1, 1 possesses a variety of synthetically challenging structural features including two diazotetrahydrobenzo[b]fluorene (diazofluorene) residues, four dideoxyglycosides, and a highly functionalized D-ring with the dimeric bond on the more hindered face of the monomeric unit. Thus, this intriguing structure has garnered significant attention from the synthetic community. However, as a result of the difficult synthetic challenges no synthetic intermediate has yet been linked to a semisynthetic compound or related natural product. More recently, the proposed structure of 1 has been called into question by emerging data obtained from microcrystal electron diffraction (MicroED) which has resulted in an alternative proposed structure for (–)-Lomaiviticin C (2) (linked to 1 via semisynthesis). This thesis descibes a continuation of synthetic studies towards 1, the structural revision of (–)-lomaiviticin A, and the development of a new synthetic strategy towards the revised structure

Modelling Agent Interdependency in Group Decision Making: Methodological Approaches to Interactive Agent Choice Experiments

The past thirty years has seen a growing interest in the development of statistical methods to model choices made by individual agents. The dominant method to emerge, discrete choice modelling, has been applied to a wide number of applications in the areas such as transportation, marketing, environmental science, health economics and public utility regulation. Yet despite the wide level of acceptance, those who employ discrete choice models have often failed to acknowledge that such models assume independency between decision makers. The assumption of independence has significant implications in terms of which contexts discrete choice models should appropriately be applied to. This paper begins by establishing the rationale behind interactive agency choice experiments (IACE), an extension to the traditional discrete choice method that is designed to model agent interdependence. The paper then proceeds to discuss how to model both independent and interdependent decision making processes using the IACE methodology in order to capture information on preferences for all agents within a decision making group. The empirical case study used to illustrate the IACE method focuses on distributive work practice choices

Demand for taxi services: New elasticity evidence for a neglected mode

This paper investigates the factors that influence the choice of, and hence demand for taxis services, a relatively neglected mode in the urban travel task. Given the importance of positioning preferences for taxi services within the broader set of modal options, we develop a modal choice model for all available modes of transport for trips undertaken by individuals or groups of individuals in a number of market segments. A sample of recent trips in Melbourne in 2012 was used to develop segmentspecific mode choice models to obtain direct (and cross) elasticities of interest for cost and service level attributes. Given the nonlinear functional form of the way attributes of interest are included in the modal choice models, a simple set of mean elasticity estimates are not behaviourally meaningful; hence a decision support system is developed to enable the calculation of mean elasticity estimates under specific future service and pricing levels. Some specific direct elasticity estimates are provided as the basis of illustrating the magnitudes of elasticity estimates under likely policy settings

The Population Dynamics of Two Rodents in Two Coastal Marshes in Virginia

The communities of small mammals were evaluated for 13 months with capture-mark-recapture methods in two Spartina-Juncus marshes of the Atlantic coast in Northampton County, Virginia. Small mammals were trapped for three days each month using live traps placed on floats on two study grids. Two rodents were numerically dominant (~90% of small mammals) there: marsh rice rat, Oryzomys palustris, and meadow vole, Microtus pennsylvanicus. Monthly estimates of population density were greater for rice rats (peak: 45/ha) than for those of meadow voles (peak: 30/ha). Survival rates were generally low, especially for rice rats, indicating highly vagile populations. Both species had greatest breeding activity in spring and autumn, with lower rates in summer and winter. Sex ratios favored males in rice rats but were unity in meadow voles. Although marsh rice rats, being semi-aquatic and capable swimmers, are more highly adapted to living in flooded marsh environments, meadow voles can thrive there too

Accounting for Heterogeneity in the Variance of Unobserved Effects in Mixed Logit Models

The growing popularity of mixed logit to obtain estimates of willingness to pay (WTP) has focussed on the distribution of the random parameters and the possibility of estimating deep parameters to account for heterogeneity around the mean of the distribution. However the possibility exists to add further behavioural information associated with the variance of the random parameter distribution, through parameterisation of its heterogeneity (or heteroskedasticity). In this paper we extend the mixed logit model to account for this heterogeneity and illustrate the implications this has on the moments of the willingness to pay for travel time savings in the context of commuter choice of mode. The empirical study highlights the statistical and behavioural gains but warns of the potential downside of exposing the distribution of the parameterised numerator and/or denominator of the more complex WTP function to a sign change and extreme values over the range of the distribution

Property rights, right to efficiency?

The assignment of property rights to incentivise risk-sharing in a principal-agent relationship is a recurrent theme of contract theory. This paper examines the incentive effects of property rights in a principal-agent relationship involving government as the principal, that is, the ownership concession model of publicprivate- partnership (PPP) procurement contracts for tollroads. Specifically, the paper investigates the effects of property rights on the agent’s preference for contract structure to manage risks and to exert performance effort; and the effects on both parties’ risk preferences when ownership transfer is being perceived as transferring accountability. Analysis of data collected through an online experiment surveying stakeholders who have been engaging in road contracts procured under the PPP model in 32 countries concludes that: (1) property rights offer the agent a protective shield against poor planning by the principal in the meantime gives rise to ex ante opportunism; (2) the agent’s reservation on ex post decision rights distorts allocative efficiency; and (3) revenue-sharing is a powerful incentive for non-revenueenhancing performance effort. Further investigation attests that incentive effects of property rights can be enhanced through equitable allocation of risks; nevertheless, ex post efficiency is debilitated by considerations of political sensitivity concerning toll pricing

Willingness to pay for travel time reliability in passenger transport: A review and some new empirical evidence

This paper reviews and critiques the modelling frameworks and empirical measurement paradigms used to obtain willingness to pay (WTP) for improved travel time reliability, suggesting new directions for ongoing research. We also estimate models to derive values of reliability, scheduling costs and reliability ratios in the context of Australian toll roads and use the new evidence to highlight the important influence of the way that trip time variability is included in stated preference studies in deriving WTP estimates of reliability in absolute terms, and relative to the value of travel time savings

TLR ligand-induced podosome disassembly in dendritic cells is ADAM17 dependent

Toll-like receptor (TLR) signaling induces a rapid reorganization of the actin cytoskeleton in cultured mouse dendritic cells (DC), leading to enhanced antigen endocytosis and a concomitant loss of filamentous actin–rich podosomes. We show that as podosomes are lost, TLR signaling induces prominent focal contacts and a transient reduction in DC migratory capacity in vitro. We further show that podosomes in mouse DC are foci of pronounced gelatinase activity, dependent on the enzyme membrane type I matrix metalloprotease (MT1-MMP), and that DC transiently lose the ability to degrade the extracellular matrix after TLR signaling. Surprisingly, MMP inhibitors block TLR signaling–induced podosome disassembly, although stimulated endocytosis is unaffected, which demonstrates that the two phenomena are not obligatorily coupled. Podosome disassembly caused by TLR signaling occurs normally in DC lacking MT1-MMP, and instead requires the tumor necrosis factor α–converting enzyme ADAM17 (a disintegrin and metalloprotease 17), which demonstrates a novel role for this “sheddase” in regulating an actin-based structure