Estimation of Models in a Rasch Family for Polytomous Items and Multiple Latent Variables

The Rasch family of models considered in this paper includes models for polytomous items and multiple correlated latent traits, as well as for dichotomous items and a single latent variable. An R package is described that computes estimates of parameters and robust standard errors of a class of log-linear-by-linear association (LLLA) models, which are derived from a Rasch family of models. The LLLA models are special cases of log-linear models with bivariate interactions. Maximum likelihood estimation of LLLA models in this form is limited to relatively small problems; however, pseudo-likelihood estimation overcomes this limitation. Maximizing the pseudo-likelihood function is achieved by maximizing the likelihood of a single conditional multinomial logistic regression model. The parameter estimates are asymptotically normal and consistent. Based on our simulation studies, the pseudo-likelihood and maximum likelihood estimates of the parameters of LLLA models are nearly identical and the loss of efficiency is negligible. Recovery of parameters of Rasch models fit to simulated data is excellent.

Estimation of Models in a Rasch Family for Polytomous Items and Multiple Latent Variables

The Rasch family of models considered in this paper includes models for polytomous items and multiple correlated latent traits, as well as for dichotomous items and a single latent variable. An R package is described that computes estimates of parameters and robust standard errors of a class of log-linear-by-linear association (LLLA) models, which are derived from a Rasch family of models. The LLLA models are special cases of log-linear models with bivariate interactions. Maximum likelihood estimation of LLLA models in this form is limited to relatively small problems; however, pseudo-likelihood estimation overcomes this limitation. Maximizing the pseudo-likelihood function is achieved by maximizing the likelihood of a single conditional multinomial logistic regression model. The parameter estimates are asymptotically normal and consistent. Based on our simulation studies, the pseudo-likelihood and maximum likelihood estimates of the parameters of LLLA models are nearly identical and the loss of efficiency is negligible. Recovery of parameters of Rasch models fit to simulated data is excellent

Constructing the military landscape: the Board of Ordnance maps and plans of Scotland, 1689–1815

This thesis examines the mapping of eighteenth-century Scotland in relation to the British state’s imperatives to know the spaces of the nation. It examines the idea of the ‘military landscape’—that conjunction of forts, roads, and barracks—represented and constructed by the military engineers, surveyors, and draughtsmen of the Board of Ordnance between 1689 and 1815. In total, 940 maps constitute the Board of Ordnance ‘archive’ housed mainly in the National Library of Scotland, the British Library, the National Archives (Kew), and the Royal Library at Windsor. The study of the Board of Ordnance military maps of Scotland is considered in relation to the epistemological foundations of map making in the Enlightenment, particular focus being paid to the relations between government institutions and military cartography. The thesis considers how political and military power was embodied in the engineers’ maps and plans. It explores the extent to which the Scottish landscape—especially the Highlands—was an unknown territory demanding intellectual and material civilisation in cartographic form. In its main chapters on forts, movement, and battles, the thesis is organised to reflect the purpose behind the creation of military maps. It includes representations of military activities that consistently had recourse to mapping—fortifying, intelligence, reconnaissance, marching, encamping, and battle—and explains why military maps were conceived thus and how they were used. Fortification cartography dominates the representation of Scottish military landscapes: 73% of the archive constitutes maps, plans, sections, and views of forts, barracks, and coastal batteries; 22% maps associated with military movement; and 5% battle maps. By examining the different genres of military mapping, the thesis offers an evaluation of the Board’s endeavours to rationalise and to codify military cartography in order to bring it in line with wider European practices. This review of the nature and extent of military mapping of eighteenth-century Scotland reveals the practice to be a result of institutional imperatives to assert territorial control rather than simply a cartographic enterprise. In (re)constructing the military landscape, the thesis extends current knowledge of military mapping in eighteenth-century Scotland and provides for the first time a substantive examination of the Board of Ordnance as an agency of state and cartographic authority

Development and evaluation of a geographic information system based method to estimate flooding susceptibility in an area of Broward County, Florida

The objective of this study was to develop a GIS-based multi-class index overlay model to determine areas susceptible to inland flooding during extreme precipitation events in Broward County, Florida. Data layers used in the method include Airborne Laser Terrain Mapper (ALTM) elevation data, excess precipitation depth determined through performing a Soil Conservation Service (SCS) Curve Number (CN) analysis, and the slope of the terrain. The method includes a calibration procedure that uses weights and scores criteria obtained from Hurricane Irene (1999) records, a reported 100-year precipitation event, Doppler radar data and documented flooding locations. Results are displayed in maps of Eastern Broward County depicting types of flooding scenarios for a 100-year, 24-hour storm based on the soil saturation conditions. As expected the results of the multi-class index overlay analysis showed that an increase for the potential of inland flooding could be expected when a higher antecedent moisture condition is experienced. The proposed method proves to have some potential as a predictive tool for flooding susceptibility based on a relatively simple approach

Optimal Filling of Shapes

We present filling as a type of spatial subdivision problem similar to covering and packing. Filling addresses the optimal placement of overlapping objects lying entirely inside an arbitrary shape so as to cover the most interior volume. In n-dimensional space, if the objects are polydisperse n-balls, we show that solutions correspond to sets of maximal n-balls. For polygons, we provide a heuristic for finding solutions of maximal discs. We consider the properties of ideal distributions of N discs as N approaches infinity. We note an analogy with energy landscapes.Comment: 5 page

Pb-Pb Dating of Terrestrial and Extraterrestrial Samples Using Resonance Ionization Mass Spectrometry

We are developing an in-situ, rock-dating spectrometer for spaceflight called the Chemistry, Organics, and Dating EXperiment (CODEX). CODEX will measure Rb-Sr ages on the Moon or Mars, and can be augmented to obtain Pb-Pb ages. Coupling Rb-Sr and Pb-Pb measurements broadens the suite of samples that can be dated, and could provide tests of concordance. Here we assess whether geochronologically meaningful Pb-Pb data could be measured in situ by tuning the prototype CODEX to acquire Pb-Pb data from a suite of well-characterized specimens from the Earth, Moon, and Mars. For Keuhl Lake zircon 91500 our 207Pb/206Pb age of 1090 ± 40 Ma is indistinguishable from the accepted age. In each of the Martian meteorites we studied, we could not resolve more than a single component of Pb, and could not uniquely determine ages. Nevertheless, our measurements were consistent with most previous studies of Pb in these meteorites. On the other hand, we determined 204.206,207 Pb isochron ages for all three lunar meteorites we studied. Our age for MIL 05035 is 3500 ± 200 Ma, within 2σ of published ages for this specimen, in spite of its having \u3c1 ppm Pb. LAP 02205 was contaminated by terrestrial Pb, but by filtering our data to exclude the most contaminated spots, we obtained an age of 3010 ± 70 Ma, coincident with published values. Finally, our age for NWA 032 is nearly 1000 Myr older than its age determined from other isotopic systems, and is supported by additional Pb measurements made after chemical leaching

Imaging of EGFR and EGFR Tyrosine Kinase Overexpression in Tumors by Nuclear Medicine Modalities

Protein tyrosine kinases (PTKs) play a pivotal role in signal transduction pathways and in the development and maintenance of various cancers. They are involved in multiple processes such as transcription, cell cycle progression, proliferation, angiogenesis and inhibition of apoptosis. Among the PTKs, the EGFR is one of the most widely studied and has emerged as a promising key target for the treatment of cancer. Indeed, several drugs directed at this receptor are FDA-approved and many others are at various stages of development. However, thus far, the therapeutic outcome of EGFR-targeted therapy is suboptimal and needs to be refined. Quantitative PET molecular imaging coupled with selective labelled biomarkers may facilitate in vivo EGFR-targeted drug efficacy by noninvasively assessing the expression of EGFR in tumor, guiding dose and regime by measuring target drug binding and receptor occupancy as well as potentially detecting the existence of a primary or secondary mutation leading to either drug interaction or failure of EGFR recognition by the drug. This review describes the attempts to develop labelled EGFR molecular imaging agents that are based either on low molecular weight tyrosine kinase inhibitors or monoclonal antibodies directed to the extracellular binding domain of the receptor to be used in nuclear medicine modalities

Positron emission tomographic imaging of Copper 64- and Gallium 68-labeled chelator conjugates of the somatostatin agonist Tyr3-octreotate

The bifunctional chelator and radiometal have been shown to have a direct effect on the pharmacokinetics of somatostatin receptor (SSTR)-targeted imaging agents. We evaluated three Y3-TATE analogues conjugated to NOTA-based chelators for radiolabeling with 64 Cu and 68 Ga for small-animal positron emission tomographic/computed tomograhic (PET/CT) imaging. Two commercially available NOTA analogues, p-SCN-Bn-NOTA and NODAGA, were evaluated. The p-SCN-Bn-NOTA analogues were conjugated to Y3- TATE through β-Ala and PEG 8 linkages. The NODAGA chelator was directly conjugated to Y3-TATE. The analogues labeled with 64 Cu or 68 Ga were analyzed in vitro for binding affinity and internalization and in vivo by PET/CT imaging, biodistribution, and Cerenkov imaging ( 68 Ga analogues). We evaluated the effects of the radiometals, chelators, and linkers on the performance of the SSTR subtype 2–targeted imaging agents and also compared them to a previously reported agent, 64 Cu-CB-TE2A-Y3-TATE. We found that the method of conjugation, particularly the length of the linkage between the chelator and the peptide, significantly impacted tumor and nontarget tissue uptake and clearance. Among the 64 Cu- and 68 Ga-labeled NOTA analogues, NODAGA-Y3-TATE had the most optimal in vivo behavior and was comparable to 64 Cu-CB-TE2A-Y3-TATE. An advantage of NODAGA-Y3-TATE is that it allows labeling with 64 Cu and 68 Ga, providing a versatile PET probe for imaging SSTr subtype 2-positive tumors