Bayesian analysis of dynamic item response models in educational testing

Item response theory (IRT) models have been widely used in educational measurement testing. When there are repeated observations available for individuals through time, a dynamic structure for the latent trait of ability needs to be incorporated into the model, to accommodate changes in ability. Other complications that often arise in such settings include a violation of the common assumption that test results are conditionally independent, given ability and item difficulty, and that test item difficulties may be partially specified, but subject to uncertainty. Focusing on time series dichotomous response data, a new class of state space models, called Dynamic Item Response (DIR) models, is proposed. The models can be applied either retrospectively to the full data or on-line, in cases where real-time prediction is needed. The models are studied through simulated examples and applied to a large collection of reading test data obtained from MetaMetrics, Inc.Comment: Published in at http://dx.doi.org/10.1214/12-AOAS608 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

Whole mantle shear structure beneath the East Pacific Rise

We model broadband seismograms containing triplicated S, S2, and S3 along with ScS to produce a pure path one‐dimensional model extending from the crust to the core‐mantle boundary beneath the East Pacific Rise. We simultaneously model all body wave shapes and amplitudes, thereby eliminating depth‐velocity ambiguities. The data consist of western North American broadband recordings of East Pacific Rise (EPR) affiliate transform events that form a continuous record section out to 82° and sample nearly the entire East Pacific Rise. The best fitting synthetics contain attenuation and small changes in lithospheric thickness needed to correct for variation in bounce point ages. The 660‐km discontinuity is particularly well resolved and requires a steep gradient (4%), extending down to 745 km. We find no discernible variation in apparent depths of the 405‐ and 660‐km discontinuities over ridge‐orthogonal distances on the order of 1000 km (or 20 Ma lithosphere). Body waveform comparisons indicate that we can resolve discontinuity depths to less than ±10 km, providing an upper limit to transition zone topography. These depth estimates, in conjunction with the fan shot nature of the ray paths, lower the detection limit from S2 precursor analysis of the lateral length scale over which short‐wavelength topographic variation could occur and indicate the sub‐EPR Transition Zone and upper mantle are remarkably homogeneous. The lower mantle beneath the East Pacific Rise is well modeled by PREM, with the greatest variation occurring in ScS, reflecting strong heterogeneity along the core‐mantle boundary. Together, these observations require that the East Pacific Rise spreading ridge cannot be actively supplied from the local lower mantle and that tomographically imaged lateral variation beneath the ridge likely reflects lateral smearing of outlying velocity gradients. Dynamically, the transition zone therefore appears vertically decoupled from the overlying East Pacific Rise spreading system

Endoscopic spray cryotherapy for esophageal cancer: safety and efficacy

Few options exist for patients with localized esophageal cancer ineligible for conventional therapies. Endoscopic spray cryotherapy with low-pressure liquid nitrogen has demonstrated efficacy in this setting in early studies

A Taxonomic and Biological Study of the Genus Xyela Dalman in North America

THE GENUS Xyela is widely distributed in the Holarctic region, and may extend across the equator into Sumatra, together with its host, the genus Pinus. The genus belongs to the small and ancient family Xyelidae, which is known from a lower Jurassic fossil, Liadoxyelct praecox Martynov (Marty nov, 1937). This is the oldest hymenopteran fossil that can be placed in a modern family. With our present inadequate knowledge, neither the time nor the place of origin of Xyela can be hypothesized

Studies on the Early Stages of Two California Moths which Feed in the Staminate Cones of Digger Pine (Lepidoptera: Gelechiidae)

During life history investigations on Xyela minor Norton (Hymenoptera, X yelidae), larvae of two species of gelechiid moths were found feeding in the staminate cones of digger pine, Pinus sabiniana, along with the Xyela larvae. These moths are Exoteleia burkei Keifer ( 1931) and Chionodes sabinianae Powell (1959), the latter having been described from material collected during the course of our investigations. Exoteleia and Chionodes are not closely related genera within the family Gelechiidae, and the two species are related in the present study only by larval habitat

Biology of Methocha californica Westwood (Hymenoptera: Tiphiidae)

Only two genera in the family Tiphiidae, Methocha Latreille (Methochinae) and Pterornbrus Smith (Myzininae), are now known to include species parasitic on the larvae of tiger beetles. The genus Pteronibrus is primarily a tropical group with one species occurring in the United St ates. Williams (1919) in his study of two Philippine specie, P. cicindelicidus Williams and P. iheringi Ducke, has provided the basis of our knowledge on the biology of that genus. M ethochci is a relatively homogeneous group found in each major zoogc-ographical area of the world with exception of the Australian (Pate, 1941). The biology of several species of Methocha has been reported