Generalizability of Predictive Performance Optimizer Predictions across Learning Task Type

The purpose of my study is to understand the relationship of learning and forgetting rates estimated by a cognitive model at the level of the individual and overall task performance across similar learning tasks. Cognitive computational models are formal representations of theories that enable better understanding and prediction of dynamic human behavior in complex environments (Adner, Polos, Ryall, & Sorenson, 2009). The Predictive Performance Optimizer (PPO) is a cognitive model and training aid based in learning theory that tracks quantitative performance data and also makes predictions for future performance. It does so by estimating learning and decay rates for specific tasks and trainees. In this study, I used three learning tasks to assess individual performance and the model\u27s potential to generalize parameters and retention interval predictions at the level of the individual and across similar-type tasks. The similar-type tasks were memory recall tasks and the different-type task was a spatial learning task. I hypothesized that the raw performance scores, PPO optimized parameter estimates, and PPO predictions for each individual would be similar for two learning tasks within the same type and different for the different type learning task. Fifty-eight participants completed four training sessions, each consisting of the three tasks. I used the PPO to assess performance on task, knowledge acquisition, learning, forgetting, and retention over time. Additionally, I tested PPO generalizability by assessing fit when PPO optimized parameters for one task were applied to another. Results showed similarities in performance, PPO optimization trends, and predicted performance trends across similar task types, and differences for the different type task. As hypothesized, the results for PPO parameter generalizability and overall performance predictions were less distinct. Outcomes of this study suggest potential differences in learning and retention based on task-type designation and potential generalizability of PPO by accounting for these differences. This decreases the requirements for individual performance data on a specific task to determine training optimization scheduling

The discontinuous nature of chromospheric activity evolution

Chromospheric activity has been thought to decay smoothly with time and, hence, to be a viable age indicator. Measurements in solar type stars in open clusters seem to point to a different conclusion: chromospheric activity undergoes a fast transition from Hyades level to that of the Sun after about 1 Gyr of main--sequence lifetime and any decaying trend before or after this transition must be much less significant than the short term variations.Comment: 6 pages, 1 figure, to be published in Astrophysics and Space Scienc

Reconsidering low-dose aspirin therapy for cardiovascular disease: a study protocol for physician and patient behavioral change

<p>Abstract</p> <p>Background</p> <p>There are often disparities between current evidence and current practice. Decreasing the gap between desired practice outcomes and observed practice outcomes in the healthcare system is not always easy. Stopping previously recommended or variably recommended interventions may be even harder to achieve than increasing the use of a desired but under-performed activity. For over a decade, aspirin has been prescribed for primary prevention of cardiovascular disease and for patients with the coronary artery disease risk equivalents; yet, there is no substantial evidence of an appropriate risk-benefit ratio to support this practice. This paper describes the protocol of a randomized trial being conducted in six primary care practices in the Denver metropolitan area to examine the effectiveness of three interventional strategies to change physician behavior regarding prescription of low-dose aspirin.</p> <p>Methods</p> <p>All practices received academic detailing, one arm received clinician reminders to reconsider aspirin, a second arm received both clinician and patient messages to reconsider aspirin. The intervention will run for 15 to 18 months. Data collected at baseline and for outcomes from an electronic health record will be used to assess pre- and post-interventional prescribing, as well as to explore any inappropriate decrease in aspirin use by patients with known cardiovascular disease.</p> <p>Discussion</p> <p>This study was designed to investigate effective methods of changing physician behavior to decrease the use of aspirin for primary cardiovascular disease prevention. The results of this study will contribute to the small pool of knowledge currently available on the topic of ceasing previously supported practices.</p> <p>Trial Registration</p> <p>ClinicalTrials.gov: <a href="http://www.clinicaltrials.gov/ct2/show/NCT01247454">NCT01247454</a></p

An investigation of chromospheric activity spanning the Vaughan--Preston gap: impact on stellar ages

Chromospheric activity is widely used as an age indicator for solar-type stars based on the early evidence that there is a smooth evolution from young and active to old and inactive stars. We analysed chromospheric activity in five solar-type stars in two open clusters, in order to study how chromospheric activity evolves with time. We took UVES high-resolution, high S/N ratio spectra of 3 stars in IC 4756 and 2 in NGC 5822, which were combined with a previously studied data-set and reanalysed here. The emission core of the deep, photospheric Ca II K line was used as a probe of the chromospheric activity. All of the 5 stars in the new sample, including those in the 1.2 Gyr-old NGC 5822, have activity levels comparable to those of Hyades and Praesepe. A likely interpretation of our data is that solar-type-star chromospheric activity, from the age of the Hyades until that of the Sun, does not evolve smoothly. Stars change from active to inactive on a short timescale. Evolution before and after such a transition is much less significant than cyclical and long-term variations. We show that data presented in the literature to support a correlation between age and activity could be also interpreted differently in the light of our results.Comment: 5 pages, 2 Figures, 1 Table, published in A&A

Deep inelastic scattering and final state interaction in an exactly solvable relativistic model

In the theory of deep inelastic scattering (DIS) the final state interaction (FSI) between the struck quark and the remnants of the target is usually assumed to be negligible in the Bjorken limit. This assumption, still awaiting a full validation within nonperturbative QCD, is investigated in a model composed by two relativistic particles, interacting via a relativistic harmonic oscillator potential, within light-cone hamiltonian dynamics. An electromagnetic current operator whose matrix elements behave properly under Poincar\'e transformations is adopted. It is shown that: i) the parton model is recovered, once the standard parton model assumptions are adopted; and ii) when relativistic, interacting eigenfunctions are exactly taken into account for both the initial and final states, the values of the structure functions, averaged over small, but finite intervals of the Bjorken variable $x$, coincide with the results of the parton model in the Bjorken limit.Comment: 26 pages, to appear in Phys. Rev. C (May 1998

The Wilson--Bappu Effect: a tool to determine stellar distances

Wilson and Bappu (1957) have shown the existence of a remarkable correlation between the width of the emission in the core of the K line of Ca II and the absolute visual magnitude of late--type stars. Here we present a new calibration of the Wilson--Bappu effect based on a sample of 119 nearby stars. We use, for the first time, width measurements based on high resolution and high signal to noise ratio CCD spectra and absolute visual magnitudes from the Hipparcos database. Our primary goal is to investigate the possibility of using the Wilson--Bappu effect to determine accurate distances to single stars and groups. The result of our calibration fitting of the Wilson--Bappu relationship is M_V=33.2-18.0*log W_0, and the determination seems free of systematic effects. The root mean square error of the fitting is 0.6 magnitudes. This error is mostly accounted for by measurement errors and intrinsic variability of W_0, but in addition a possible dependence on the metallicity is found, which becomes clearly noticeable for metallicities below [Fe/H]=-0.4. This detection is possible because in our sample [Fe/H] ranges from -1.5 to 0.4. The Wilson--Bappu effect can be used confidently for all metallicities not lower than -0.4, including the LMC. While it does not provide accurate distances to single stars, it is a useful tool to determine accurate distances to clusters and aggregates, where a sufficient number of stars can be observed. We apply the Wilson--Bappu effect to published data of the open cluster M67; the retrieved distance modulus is of 9.65 magnitude, in very good agreement with the best distance estimations for this cluster, based on main sequence fitting.Comment: 19 pages, 7 figure, accepted by A&

The p68 and p72 DEAD box RNA helicases interact with HDAC1 and repress transcription in a promoter-specific manner

BACKGROUND: p68 (Ddx5) and p72 (Ddx17) are highly related members of the DEAD box family and are established RNA helicases. They have been implicated in growth regulation and have been shown to be involved in both pre-mRNA and pre-rRNA processing. More recently, however, these proteins have been reported to act as transcriptional co-activators for estrogen-receptor alpha (ERα). Furthermore these proteins were shown to interact with co-activators p300/CBP and the RNA polymerase II holoenzyme. Taken together these reports suggest a role for p68 and p72 in transcriptional activation. RESULTS: In this report we show that p68 and p72 can, in some contexts, act as transcriptional repressors. Targeting of p68 or p72 to constitutive promoters leads to repression of transcription; this repression is promoter-specific. Moreover both p68 and p72 associate with histone deacetylase 1 (HDAC1), a well-established transcriptional repression protein. CONCLUSIONS: It is therefore clear that p68 and p72 are important transcriptional regulators, functioning as co-activators and/or co-repressors depending on the context of the promoter and the transcriptional complex in which they exist

Importance of the different posterolateral knee static stabilizers: biomechanical study

PURPOSE: The purpose of this study was to evaluate the relative importance of the different static stabilizers of the posterolateral corner of the knee in cadavers. METHODS: Tests were performed with the application of a varus and external rotation force to the knee in extension at 30 and 60 degrees of flexion using 10 cadaver knees. The forces were applied initially to an intact knee and then repeated after a selective sectioning of the ligaments into the following: section of the lateral collateral ligament; section of the lateral collateral ligament and the popliteofibular complex; and section of the lateral collateral ligament, the popliteofibular complex and the posterolateral capsule. The parameters studied were the angular deformity and stiffness when the knees were submitted to a 15 Newton-meter varus torque and a 6 Newton-meter external tibial torque. Statistical analysis was performed using the ANOVA (Analysis of Variance) and Tukey's tests. RESULTS AND CONCLUSION: Our findings showed that the lateral collateral ligament was important in varus stability at 0, 30 and 60 degrees. The popliteofibular complex was the most important structure for external rotation stability at all angles of flexion and was also important for varus stability at 30 and 60 degrees. The posterolateral capsule was important for varus stability at 0 and 30 degrees and for external rotation stability in extension. Level of evidence: Level IV (cadaver study)

A concept for a visual computer interface to make error taxonomies useful at the point of primary care

Evidence suggests that the quality of care delivered by the healthcare industry currently falls far short of its capabilities. Whilst most patient safety and quality improvement work to date has focused on inpatient settings, some estimates suggest that outpatient settings are equally important, with up to 200 000 avoidable deaths annually in the United States of America (USA) alone. There is currently a need for improved error reporting and taxonomy systems that are useful at the point of care. This provides an opportunity to harness the benefits of computer visualisation to help structure and illustrate the 'stories' behind errors. In this paper we present a concept for a visual taxonomy of errors, based on visual models of the healthcare system at both macrosystem and microsystem levels (previously published in this journal), and describe how this could be used to create a visual database of errors. In an alphatest in a US context, we were able to code a sample of 20 errors from an existing error database using the visual taxonomy. The approach is designed to capture and disseminate patient safety information in an unambiguous format that is useful to all members of the healthcare team (including the patient) at the point of care as well as at the policy-making level