Construction of transferable spherically-averaged electron potentials

A new scheme for constructing approximate effective electron potentials within density-functional theory is proposed. The scheme consists of calculating the effective potential for a series of reference systems, and then using these potentials to construct the potential of a general system. To make contact to the reference system the neutral-sphere radius of each atom is used. The scheme can simplify calculations with partial wave methods in the atomic-sphere or muffin-tin approximation, since potential parameters can be precalculated and then for a general system obtained through simple interpolation formulas. We have applied the scheme to construct electron potentials of phonons, surfaces, and different crystal structures of silicon and aluminum atoms, and found excellent agreement with the self-consistent effective potential. By using an approximate total electron density obtained from a superposition of atom-based densities, the energy zero of the corresponding effective potential can be found and the energy shifts in the mean potential between inequivalent atoms can therefore be directly estimated. This approach is shown to work well for surfaces and phonons of silicon.Comment: 8 pages (3 uuencoded Postscript figures appended), LaTeX, CAMP-090594-

The Long-Term Impacts of Teachers: Teacher Value-Added and Student Outcomes in Adulthood

Are teachers’ impacts on students’ test scores (“value-added”) a good measure of their quality? This question has sparked debate largely because of disagreement about (1) whether value-added (VA) provides unbiased estimates of teachers’ impacts on student achievement and (2) whether high-VA teachers improve students’ long-term outcomes. We address these two issues by analyzing school district data from grades 3-8 for 2.5 million children linked to tax records on parent characteristics and adult outcomes. We find no evidence of bias in VA estimates using previously unobserved parent characteristics and a quasi-experimental research design based on changes in teaching staff. Students assigned to high-VA teachers are more likely to attend college, attend higher- ranked colleges, earn higher salaries, live in higher SES neighborhoods, and save more for retirement. They are also less likely to have children as teenagers. Teachers have large impacts in all grades from 4 to 8. On average, a one standard deviation improvement in teacher VA in a single grade raises earnings by about 1% at age 28. Replacing a teacher whose VA is in the bottom 5% with an average teacher would increase the present value of students’ lifetime income by more than $250,000 for the average class- room in our sample. We conclude that good teachers create substantial economic value and that test score impacts are helpful in identifying such teachers.

Adjustment Costs, Firm Responses, and Labor Supply Elasticities: Evidence from Danish Tax Records

We show that the effects of taxes on labor supply are shaped by interactions between adjustment costs for workers and hours constraints set by firms. We develop a model in which firms post job offers characterized by an hours requirement and workers pay search costs to find jobs. In this model, micro elasticities are smaller than macro elasticities because they do not account for adjustment costs and firm responses. We present evidence supporting three predictions of the model by analyzing bunching at kinks using the universe of tax records in Denmark. First, larger kinks generate larger taxable income elasticities because they are more likely to overcome search costs. Second, kinks that apply to a larger group of workers generate larger elasticities because they induce changes in hours constraints. Third, firms tailor job offers to match workers.aggregate tax preferences in equilibrium. Calibrating our model to match these empirical findings, we obtain a lower bound on the intensive-margin macro elasticity of 0:34, an order of magnitude larger than the estimates obtained using standard microeconometric methods for wage earners in our data.

Pyle metaphyseal dysplasia in an African child: Case report and review of the literature

Pyle disease (OMIM 265900), also known as metaphyseal dysplasia, is a rare autosomal recessive disorder with no known gene mutation. We report a case of Pyle disease in a 7-year-old African boy of mixed ancestry who presented with finger and wrist fractures following minor trauma. The radiological findings revealed abnormally broad metaphyses of the tubular bones, known as Erlenmeyer-flask bone deformity, and mild cranial sclerosis, both hallmarks of the condition. We report the first case in a patient with African ancestry, which could help in the gene discovery of this rare autosomal recessive skeletal dysplasia with unknown mutations.DHE

EVALUATION OF ROBOTIC CLEANING TECHNOLOGIES: PRESERVING A BRITISH ICONIC BUILDING

The engineering building of the University Leicester built-in 1963 has been a British icon for decades now. Applications of Robotic technologies are uprising nowadays, which provides a contingency to manipulate the benefits of robotics for executing challenging and precarious facade cleaning processes. This paper surveys the facade cleaning robotic technologies exist in the market. It exhibits the comparative analysis of four notorious robotic facade cleaning solutions namely Sky Pro, Gekko, BFMR (Building Façade Maintenance Robot) and Sirius_c. The comparison is executed using Multi Criteria Decision Analysis (MCDA) and Quality Function Deployment (QFD) techniques. This study analyses the performance of the robots based on the critical parameters such as water consumption, cleaning efficiency, cleaning dimensions and ease of implementation. Although none of these robotic solutions are implemented off the shelf, some adaptation on these solutions is necessary for the development of robotic techniques work successfully in real time. This paper proposes a hybrid robotic solution combining the vacuum pump adhesion and wheeled locomotion for the effective cleaning of the complex external building structure based on the MCDA and QFD analysis. It highlights the significant future research directions in this field

Adjustment Costs, Firm Responses, and Micro vs. Macro Labor Supply Elasticities: Evidence from Danish Tax Records

We show that the effects of taxes on labor supply are shaped by interactions between adjustment costs for workers and hours constraints set by firms. We develop a model in which firms post job offers characterized by an hours requirement and workers pay search costs to find jobs. In this model, micro elasticities are smaller than macro elasticities because they do not account for adjustment costs and firm responses. We present evidence supporting three predictions of the model by analyzing bunching at kinks using the universe of tax records in Denmark. First, larger kinks generate larger taxable income elasticities because they are more likely to overcome search costs. Second, kinks that apply to a larger group of workers generate larger elasticities because they induce changes in hours constraints. Third, firms tailor job offers to match workers’ aggregate tax preferences in equilibrium. Calibrating our model to match these empirical findings, we obtain a lower bound on the intensive-margin macro elasticity of 0.34, an order of magnitude larger than the estimates obtained using standard microeconometric methods for wage earners in our data.

'They are inconveniencing us' - exploring how gaps in patient education and patient centred approaches interfere with TB treatment adherence: perspectives from patients and clinicians in the Free State Province, South Africa

Background: Tuberculosis (TB) treatment loss to follow up (LTFU) plays an important contributory role to the staggering TB epidemic in South Africa. Reasons for treatment interruption are poorly understood. Treatment interruption appears to be the culmination of poor health literacy of patients and inadequate health education provided by clinicians. We explored clinician and patient perspectives of the gaps in TB messaging that influence TB treatment LTFU. Methods: We conducted semi-structured in-depth interviews between January and May 2018 with a sample of 15 clinicians managing TB and 7 patients identified as LTFU in public clinics in the Free State Province, South Africa. Thematic analysis using a mixed deductive/inductive thematic approach was used. Results: Limited occupational opportunities, fear of disclosure and stigmatization all contributed to treatment LTFU. Patients felt that the TB messaging received was inadequate. Many of the clinicians interviewed felt that improving patient's TB knowledge would reinforce adherence to treatment and thus focused on sharing information on treatment completion, side effects and infection control. However, the inability of clinicians to establish rapport with patients or to identify social support challenged TB treatment adherence by patients. Clinicians perceived this as patients not following their instructions despite what they considered lengthy TB education. Having said this, clinicians concurred that their medical management of TB lacked the psycho-social dimension to treat a social disease of this magnitude. Conclusions: Limited occupational opportunities, fear of disclosure and stigmatization all contributed to treatment LTFU. Clinicians concurred that poor patient understanding of TB and that biomedical management lacking a psycho-social dimension further exacerbated the poor treatment outcome. TB remains a social disease, the successful management of which hinges on patient-centred care

QUANTITATIVE FEEDBACK THEORY DESIGN OF LINE CURRENT COMMUTATED HVDC CONTROL SYSTEMS

Abstract: Line Current Commutated (LCC) HVDC systems consists of uncertain plants. These uncertainties are result of changes/disturbances in the ac networks or in the LCC HVDC system itself. Further uncertainties can be introduced due to simplified system modelling techniques. Quantitative Feedback Theory is a frequency-domain technique that utilises the Nichols chart to achieve a robust design over a specified region of uncertainty. The Quantitative Feedback Theory design philosophy was applied to design the LCC HVDC control system parameters. The stable start-up and step responses of the LCC HVDC system, for varying ac system conditions, conclusively validate the Quantitative Feedback Theory design method of the LCC HVDC control system parameters