A Study of Block Scheduling and Instructional Strategies and their Influence on Algebra Achievement in Classrooms Throughout North Central Texas

The purpose of this study was to evaluate the influence of block scheduling and instructional strategies on student achievement in Algebra I. The study was conducted during the 1997-98 school year. This study was comprised of two components, a quantitative study and a qualitative study. The quantitative study focused on block and traditional scheduling and the influence identified through scores on the Texas End-of-Course exam for Algebra I. The sample for this study consisted of 59 school districts from five counties in the north Texas area. The qualitative portion of this study focused on 10 classrooms, 5 block and 5 traditional, taken from the sample of 59 districts. Data for the qualitative study included questionnaires, interviews, and observations. The End-of-Course scores were analyzed using an ANOVA at the .05 level of significance, no significant difference was identified in the achievement levels of the two groups. The qualitative data was organized by categories derived from the NCTM teaching standards. Data from this portion of the study indicated that teachers in both block and traditionally scheduled classes spend their class time in a similar manner, using similar materials, and using more traditional strategies. Additional analyses of data based upon usage of the graphing calculator and manipulatives also resulted in no significant difference. Although all comparisons between block and traditional scheduling and usage or non-usage of technology and/or manipulatives resulted in no significant difference, the block groups and those using technology and/or manipulatives had higher mean scores. This indicates that allowing teachers more time to use alternative instructional strategies would benefit the student, but this will not take place without the teacher receiving training and support

Costing Reference: Issues, Approaches, and Directions for Research

The Assessing Quality in Digital Reference project is a first step toward understanding the cost of digital reference services in libraries. This article presents three measures isolated by project participants as being most useful for their immediate needs: total cost of providing digital reference service, the cost of digital reference service as a percent of the total reference budget, and the cost of reference as a percent of the total library or organizational budget. In addition, it reviews selected outstanding issues in the ongoing question of how to determine the cost of reference services in libraries and offers direction for further study toward a general cost model for information servicesInformatio

Influence of Dust Grain Evolution on the Structure of Protoplanetary Disks.

he formation and composition of planets is a direct consequence of the processing of solid dust particles in protoplanetary disks: e.g. grain growth, dust settling, crystallization, and segregation of different dust species. Understanding the connections between these effects and how they vary as a function of time is the first step to producing a map of how planet-forming materials are distributed in disks, providing initial conditions for planet formation and evolution models. These will be necessary to analyze the composition and migration history of increasingly large numbers of confirmed exoplanets. Here I present near-, mid-, and far-infrared observations of young protoplanetary disks and their surroundings to identify when grain processing starts and how far it proceeds in the first 1-2Myr, by which time planet formation is observed. Using Spitzer IRS 5-40um spectra, I construct an extinction curve for molecular clouds, which I use to measure dust processing in IRS spectra of the youngest disks (<1Myr) in the Ophiuchus star-forming region. I then develop a method, using 1-5um (NASA IRTF SpeX), to extract the inner disk excess from these systems and determine the dust properties of that region, finding strong evidence for increased grain growth and settling in the inner disk relative the the outer disk. Fitting this excess using radiative transfer disk structure models suggests a grain-size limit of ~10um in the midplane due to accretion heating in the inner 0.5AU. Iron-rich dust was required to fit the inner disk excess. In Herschel PACS spectra, I detect water ice originating in the disk upper layers, below the photodesorption layer. At half-solar abundance, these detections indicate settling of icy grains. There is evidence of radial structure in the snowline in some of these disks, which combined with the implications of the vertical iron gradient in the inner disk suggests strong spatially variable gas compositions. This has implications for the type of molecules expected to be detectable in the atmospheres of planets forming there. Further work, including interferometry and scattered light observations, are necessary to fully map the distribution of planetary building blocks in these disks at all ages.PHDAstronomy and AstrophysicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/108774/1/melisma_1.pd

Path-specific causal decomposition analysis with multiple correlated mediator variables

A causal decomposition analysis allows researchers to determine whether the difference in a health outcome between two groups can be attributed to a difference in each group's distribution of one or more modifiable mediator variables. With this knowledge, researchers and policymakers can focus on designing interventions that target these mediator variables. Existing methods for causal decomposition analysis either focus on one mediator variable or assume that each mediator variable is conditionally independent given the group label and the mediator-outcome confounders. In this paper, we propose a flexible causal decomposition analysis method that can accommodate multiple correlated and interacting mediator variables, which are frequently seen in studies of health behaviors and studies of environmental pollutants. We extend a Monte Carlo-based causal decomposition analysis method to this setting by using a multivariate mediator model that can accommodate any combination of binary and continuous mediator variables. Furthermore, we state the causal assumptions needed to identify both joint and path-specific decomposition effects through each mediator variable. To illustrate the reduction in bias and confidence interval width of the decomposition effects under our proposed method, we perform a simulation study. We also apply our approach to examine whether differences in smoking status and dietary inflammation score explain any of the Black-White differences in incident diabetes using data from a national cohort study

The Evolution of Protoplanetary Disks: Probing the Inner Disk of Very Low Accretors

We report FUV, optical, and NIR observations of three T Tauri stars in the Orion OB1b subassociation with H$\alpha$ equivalent widths consistent with low or absent accretion and various degrees of excess flux in the mid-infrared. We aim to search for evidence of gas in the inner disk in HST ACS/SBC spectra, and to probe the accretion flows onto the star using H$\alpha$ and He I $\lambda$10830 in spectra obtained at the Magellan and SOAR telescopes. At the critical age of 5 Myr, the targets are at different stages of disk evolution. One of our targets is clearly accreting, as shown by redshifted absorption at free-fall velocities in the He I line and wide wings in H$\alpha$; however, a marginal detection of FUV H$_2$ suggests that little gas is present in the inner disk, although the spectral energy distribution indicates that small dust still remains close to the star. Another target is surrounded by a transitional disk, with an inner cavity in which little sub-micron dust remains. Still, the inner disk shows substantial amounts of gas, accreting onto the star at a probably low, but uncertain rate. The third target lacks both a He I line or FUV emission, consistent with no accretion or inner gas disk; its very weak IR excess is consistent with a debris disk. Different processes occurring in targets with ages close to the disk dispersal time suggest that the end of accretion phase is reached in diverse ways.Comment: 13 pages, 3 figures. Accepted for publication in The Astrophysical Journa

Relationship between cardiovascular risk and lipid testing in one health care system: a retrospective cohort study.

BackgroundThe US Preventive Services Taskforce (USPSTF) recommends routine lipid screening beginning age 35 for men [1]. For women age 20 and older, as well as men age 20-34, screening is recommended if cardiovascular risk factors are present. Prior research has focused on underutilization but not overuse of lipid testing. The objective is to document over- and under-use of lipid testing in an insured population of persons at low, moderate and high cardiovascular disease (CVD) risk for persons not already on statins.MethodsThe study is a retrospective cohort study that included all adults without prior CVD who were continuously enrolled in a large integrated healthcare system from 2005 to 2010. Measures included lipid test frequency extracted from administrative data and Framingham cardiovascular risk equations applied using electronic medical record data. Five year lipid testing patterns were examined by age, sex and CVD risk. Generalized linear models were used to estimate the relative risk for over testing associated with patient characteristics.ResultsAmong males and females for whom testing is not recommended, 35.8 % and 61.5 % received at least one lipid test in the prior 5 years and 8.4 % and 24.4 % had two or more. Over-testing was associated with age, race, comorbidity, primary care use and neighborhood income. Among individuals at moderate and high-risk (not already treated with statins) and for whom screening is recommended, between 21.4 % and 25.1 % of individuals received no screening in the prior 5 years.ConclusionsBased on USPSTF lipid screening recommendations, this study documents substantial over-testing among individuals with low CVD risk and under-testing among individuals with moderate to high-risk not already on statins. Opportunity exists to better focus lipid screening efforts appropriate to CVD risk