DD-optimal saturated designs: a simulation study

In this work we focus on saturated $D$-optimal designs. Using recent results, we identify $D$-optimal designs with the solutions of an optimization problem with linear constraints. We introduce new objective functions based on the geometric structure of the design and we compare them with the classical $D$-efficiency criterion. We perform a simulation study. In all the test cases we observe that designs with high values of $D$-efficiency have also high values of the new objective functions.Comment: 8 pages. Preliminary version submitted to the 7th IWS Proceeding

Large thermomagnetic effects in weakly disordered Heisenberg chains

The interplay of different scattering mechanisms can lead to novel effects in transport. We show theoretically that the interplay of weak impurity and Umklapp scattering in spin-1/2 chains leads to a pronounced dip in the magnetic field dependence of the thermal conductivity $\kappa$ at a magnetic field $B \sim T$. In sufficiently clean samples, the reduction of the magnetic contribution to heat transport can easily become larger than 50% and the effect is predicted to exist even in samples with a large exchange coupling, J >> B, where the field-induced magnetization is small. Qualitatively, our theory might explain dips at $B \sim T$ observed in recent heat transport measurements on copper pyrazine dinitrate, but a fully quantitative description is not possible within our model.Comment: 5 pages, 2 figure

TRU Management in the Site Treatment Plan at the INEEL

The storage of any form of hazardous waste is prohibited unless the waste has available treatment to meet land disposal restriction (LDR) requirements in accordance with 40 CFR 268 of the Resource Conservation and Recovery Act (RCRA). In 1992, Congress passed the Federal Facility Compliance Act (FFCA), which allows for the storage of radioactive and hazardous mixed waste (mixed waste) until available treatment can be developed that meets the LDR requirements. Transuranic-contaminated mixed (TRU) waste is covered under the FFCA through the Site Treatment Plan (STP) since the implementation of the plan in November, 1995. The Idaho National Engineering and Environmental Laboratory (INEEL) STP required schedules and milestones for the treatment and shipment of TRU waste to the Waste Isolation Pilot Plant (WIPP). Potential enforcement actions for missing compliance milestones exist in the INEEL STP

Magnetoelastic coupling in triangular lattice antiferromagnet CuCrS2

CuCrS2 is a triangular lattice Heisenberg antiferromagnet with a rhombohedral crystal structure. We report on neutron and synchrotron powder diffraction results which reveal a monoclinic lattice distortion at the magnetic transition and verify a magnetoelastic coupling. CuCrS2 is therefore an interesting material to study the influence of magnetism on the relief of geometrical frustration.Comment: 6 pages, 6 figures, 1 tabl

Using item response theory to explore the psychometric properties of extended matching questions examination in undergraduate medical education

BACKGROUND: As assessment has been shown to direct learning, it is critical that the examinations developed to test clinical competence in medical undergraduates are valid and reliable. The use of extended matching questions (EMQ) has been advocated to overcome some of the criticisms of using multiple-choice questions to test factual and applied knowledge. METHODS: We analysed the results from the Extended Matching Questions Examination taken by 4th year undergraduate medical students in the academic year 2001 to 2002. Rasch analysis was used to examine whether the set of questions used in the examination mapped on to a unidimensional scale, the degree of difficulty of questions within and between the various medical and surgical specialties and the pattern of responses within individual questions to assess the impact of the distractor options. RESULTS: Analysis of a subset of items and of the full examination demonstrated internal construct validity and the absence of bias on the majority of questions. Three main patterns of response selection were identified. CONCLUSION: Modern psychometric methods based upon the work of Rasch provide a useful approach to the calibration and analysis of EMQ undergraduate medical assessments. The approach allows for a formal test of the unidimensionality of the questions and thus the validity of the summed score. Given the metric calibration which follows fit to the model, it also allows for the establishment of items banks to facilitate continuity and equity in exam standards

Aligning physical elements with persons' attitude: an approach using Rasch measurement theory

Affective engineering uses mathematical models to convert the information obtained from persons' attitude to physical elements into an ergonomic design. However, applications in the domain have not in many cases met measurement assumptions. This paper proposes a novel approach based on Rasch measurement theory to overcome the problem. The research demonstrates that if data fit the model, further variables can be added to a scale. An empirical study was designed to determine the range of compliance where consumers could obtain an impression of a moisturizer cream when touching some product containers. Persons, variables and stimulus objects were parameterised independently on a linear continuum. The results showed that a calibrated scale preserves comparability although incorporating further variables

The Effect of AICAR-Induced AMPK Activation on Gene Expression in Sarcopenic Muscle

The loss of muscle mass and function (sarcopenia) afflicts 11-74% of all aging adults, with prevalence increasing with age. Exercise training is clearly effective in preventing or attenuating sarcopenia. The cellular mechanisms of exercise’s protective effects are not entirely clear, but AMP-activated protein kinase (AMPK) is thought to play an important role, in part by regulating gene expression. PURPOSE: To determine the effect of chronic pharmacological AMPK activation on skeletal muscle gene expression in sarcopenic muscle. METHODS: 24-month-old C57Bl/6J mice received either one acute injection or chronic daily saline injections of the AMPK-activating drug AICAR for 31 days. 5-month-old saline-injected mice served as young controls for reference. Treadmill running capacity was measured before and after treatment. Expression of genes relating to mitochondria, muscle size regulation, and inflammation was measured by real-time polymerase chain reaction (RT-PCR). RESULTS: One hour after a single injection of AICAR, raptor phosphorylation was increased in both young and old mice, indicating AMPK activation. Phosphorylation of the mTORC1 targets 4EBP1, and S6k were both elevated in old muscle, consistent with previous reports of hyperactivated mTORC1 in aged muscle. Acute AICAR injection returned 4EBP1 and S6k phosphorylation to young levels. RNA sequencing demonstrated that chronic AICAR injections restored the expression of many genes in old muscle to the levels observed in young muscle. Among these, mitochondrial splicing suppressor 51 (Mss51) expression, which is associated with impaired mitochondrial function and muscle loss, was elevated in sarcopenic muscle but attenuated by AICAR treatment, and this was confirmed by RT-PCR analysis. CONCLUSION: AICAR treatment reverses several critical age-related changes in gene expression and mTORC1 activity. Our findings support further investigation of AMPK activation and Mss51 repression as targets for therapeutic interventions in sarcopenia