Duality Theory And the Consistent Estimation Of Technological Parameters: Why Cost Function Estimation Can Be Wrong

In this article we show that technological parameter estimates obtained by estimating a cost function that is derivable as the dual of a production function can be biased and inconsistent if the stochastic structure of the model arises from certain types of behavioural assumptions made about rational agents. We consider a specific example in which firms are uncertain about prices. We show that when actual prices differ from expected prices and firms have to make decisions on the basis of their expectations, the inherited stochastic specification of the dual system is highly non-linear in the disturbance terms making consistent parameter estimation impossible by conventional methods. This is demonstrated by a Monte Carlo simulation study of two text-book examples using synthetic data. It is also shown that this type of result can arise when the researcher derives the error structure from the assumption that agents make optimization errors.cost functions; duality; estimation

The influence of off-diagonal disorder on resonant transmission and emergent phenomena in nanostructured carbon thin films

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of PhD. August 9, 2017Nano-structured carbon lms, long studied due to the promise of exceptional quantum transport properties, present a signi cant problem in condensed matter due to the disorder which inherently forms in these materials. This work addresses the role of structural disorder in low dimensional carbon systems. The in uence of structural disorder on resonant transmission is studied in diamond-like carbon superlattices. Having established a model for disorder, this model for the structural changes is then applied to interpret experimental measurements of diamond-like carbon superlattices. The role of phonons on resonant transmission under a high frequency gate potential was also studied. This model for structural disorder in heterogeneous carbon lms was then applied to disordered superconductors close to the Anderson-Mott transition using the inhomogeneous Bogoliubov-de Gennes theory. This analysis is then used in support of experimental work to understand the superconductor-insulator transition in boron doped nano-crystalline diamond lms. Coherent quantum transport e ects were demonstrated in structurally-disordered diamondlike carbon (DLC) superlattices through distinct current modulation (step-like features) with negative differential resistance in the current-voltage (I-V) measurements. A model for these structurally disordered superlattices was developed using tight-binding calculations within the Landauer-B uttiker formalism assuming a random variation of the hopping integral following a Gaussian distribution. Calculations of the I-V characteristics for different con gurations of superlattices compliment the interpretation of the measured I-V characteristics and illustrate that while these DLC superlattice structures do not behave like conventional superlattices, the present model can be used to tailor the properties of future devices. Furthermore this tandem theoretical and experimental analysis establishes the validity of the model for structural disorder. The same model for the variation of disorder was then applied to interpret the electronic transport properties of disordered graphene-like carbon thin films. The influence of disorder on the activation energy in few layer graphitic lms was modelled and compared with experimental observations through collaboration. The lms, grown by laser ablation, allowed the speci c e ects of structural disorder in the sp2 - C phase to be probed. Defects acted as effective barriers resulting in localization of charge carriers. Electron transmission spectra, calculated with a tight-binding model, accounted for the change of localization length as a result of disorder in the sp2 - C phase. This theoretical study showed that the localization length of the thin graphitic lms can be tuned with the level of disorder and was shown to be consistent with experimental studies. The in uence of nitrogen incorporation on resonant transmission in DLC superlattices was then studied theoretically. This study illuminated the speci c role of the nitrogen potential in relation to the Fermi level (EF ) in nitrogen incorporated amorphous carbon (a- CN) superlattice structures. In a-CN systems, the variation of conductivity with nitrogen percentage has been found to be strongly non-linear due to the change of disorder level. The e ect of correlated carbon and nitrogen disorder was investigated in conjunction with the nitrogen potential through analysis of transmission spectra, calculated using a tight binding model, which showed two broad peaks related to these species. It was shown that the characteristic transmission time through nitrogen centres can be controlled through a combination of the nitrogen potential and correlated disorder. In particular, by controlling the arrangement of the nitrogen sites within the sp2 - C clusters as well as their energetic position relative to EF , a crossover of the pronounced transmission peaks of nitrogen and carbon sites can be achieved. Furthermore, it was shown that nitrogen incorporated as a potential barrier can also enhance the transmission in the a-CN superlattice structures. The strong non-linear variation of resistance and the characteristic time of the structures can explain the transport features observed experimentally in a-CN fi lms. This analysis was then partnered with measurements performed on nitrogen-incorporated carbon superlattices (N-DLC QSL) by Neeraj Dwivedi (National University of Singapore). The electrical characteristics of these nitrogen incorporated superlattice devices revealed prominent negative di erential resistance (NDR) behavior. The interpretation of these measurements was supported by 1D tight binding calculations of disordered superlattice structures (chains), which included signi cant bond alternation in sp3-hybridized regions. This analysis showed improved resonant transmission, which can be ascribed to nitrogendriven structural modi cation of the N-DLC QSL structures, especially the increased sp2-C clustering that provides additional conduction paths throughout the network. In order to determine the in uence of additional factors on coherent quantum states in molecular systems as an extension to the analysis on superlattices, a theoretical study of the electron-phonon interaction in double barrier structures under the in uence of a timedependent gate potential was undertaken. The Floquet theory was employed along with expansion in a polaron eigenbasis to render a multi-dimensional single body problem. An essentially exact solution was found using the Riccati matrix technique. It was demonstrated that optimal transmission can be achieved by varying the frequency of the gate potential. In addition, it was shown that the gate potential can be used to control the energy of the resonant states very precisely while maintaining optimal transmission. Having gained a deep understanding of the structural changes induced in carbon systems through the incorporation of nitrogen, a similar structural model was then applied to study the changes induced in diamond and nanocrystalline fi lms by boron incorpora- tion. Boron doped diamond provides an interesting superconductor with ongoing debate surrounding the nature of the impurity band and the effect on the superconducting phase transition of structural changes induced by boron incorporation. The in uence of disorder, both structural (non-diagonal) and on-site (diagonal), was studied through the inhomogeneous Bogoliubov-de Gennes (BdG) theory in narrow-band disordered superconductors with a view towards understanding superconductivity in boron doped diamond (BDD) and boron-doped nanocrystalline diamond (B-NCD) lms. We employed the attractive Hubbard model within the mean eld approximation, including a short range Coulomb interaction between holes in the narrow acceptor band. We studied substitutional boron incorporation in a triangular lattice, with disorder in the form of random potential uctuations at the boron sites. The role of structural disorder was investigated through non-uniform variation of the tight-binding coupling parameter where, following experimental ndings in BDD and B-NCD lms, we incorporated the concurrent increase in structural disorder with increasing boron concentration. Stark differences between the ffects of structural and on-site disorder were demonstrated and showed that structural disorder has a much greater e ect on the density of states, mean pairing amplitude and super uid density than on-site potential disorder. We showed that structural disorder can increase the mean pairing amplitude while the spectral gap in the density of states decreases, with states eventually appearing within the spectral gap for high levels of disorder. This study illustrated how the effects of structural disorder can explain some of the features found in superconducting BDD and B-NCD lms, such as a tendency towards saturation of the critical temperature (Tc) with boron doping and deviations from the expected Bardeen-Cooper-Shrie er (BCS) theory in the temperature dependence of the pairing amplitude and spectral gap. The variation of the super uid density considering only structural disorder was markedly different from the variation with on-site disorder only and revealed that structural disorder is far more detrimental to superconductivity and accounts for the relatively low Tc of BDD and B-NCD in comparison to the Tc predicted using the conventional BCS theory. This theoretical work was then used to interpret features in the measured transport properties of B-NCD lms with di erent doping concentrations and microstructures. The temperature dependence of a distinct local maximum in eld dependent magnetoresistance measurements showed suppression of the density of states as the system breaks up into superconducting regions separated by grain boundaries. Differential resistance measurements at different temperatures and magnetic fi elds showed a transition from a local minimum at zero applied current, indicative of persisting superconducting regions, to a local maximum. A power law dependence over a certain current range in the measured I-V characteristics at di erent magnetic elds suggests a Berezinski-Kosterlitz-Thouless (BKT) transition. In addition, features in the magnetoresistance clearly indicate additional phases. Together with features in current-voltage measurements, these signatures show the coexistence of superconductivity and additional competing phases close to the Anderson-Mott transition.LG201

Quantum effects in the diffusion of hydrogen on Ru(0001)

An understanding of hydrogen diffusion on metal surfaces is important, not just for its role in heterogeneous catalysis and hydrogen fuel cell technology, but also because it provides model systems where tunneling can be studied under well-defined conditions. Here we report helium spin-echo measurements of the atomic-scale motion of hydrogen on the Ru(0001) surface between 75 and 250 K. Quantum effects are evident at temperatures as high as 200 K, while below 120 K we observe a tunneling-dominated temperature independent jump rate of 1.9$\times$10$^9$ s$^{-1}$, many orders of magnitude faster than previously seen. Quantum transition state theory calculations based on ab initio path-integral simulations reproduce the temperature dependence of the rate at higher temperatures and predict a crossover to tunneling-dominated diffusion at low temperatures, although the tunneling rate is under-estimated, highlighting the need for future experimental and theoretical studies of hydrogen diffusion on well-defined surfaces.Comment: 15 pages, 3 figure

Rock mass rating in Bükk Mts., N Hungary based on petrophysical parameters and parting conditions

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The Stability of Market Extracted Overall Capitalization Rates*

Willard McIntosh is an Assistant Professor of Finance and Real Estate and Director of the Center for Real Estate Studies, College of Business and Economics at the University of Kentucky and William M. Whitaker III is Professor of Finance and Head, Department of Finance and Economics at Georgia Southern University

The effects of heat versus cold disinfection on the Wesley-Jessen Durasoft 4 Litetint soft contact lens

An evaluation of the Wesley-Jessen 74% water Durasoft 4 LiteTint soft contact lens was made using 18 lenses on nine subjects and two pairs of control lenses. Five subjects cold disinfected the lenses and four subjects heat disinfected the lenses using Softmate PS regimens. One pair of control lenses was disinfected with each system . The results of the study show that heat disinfection can damage these lenses. Three of five pairs of lenses that were heat disinfected showed discoloration upon completion of the study. This includes one pair of control lenses which were heated once daily for 6 months, the duration of the study. All cold disinfected lenses remained normal. Other results show problems with Durasoft 4 lenses not attributable to the type of disinfection used. These problems include: difficulty in handling and determining whether inside-out or not, discomfort and severe drying symptoms, a rapid decrease in wearing time, and a tendency to accumulate deposits rapidly. Only one subject remained in the study for the 6 month duration. All others left early due to lens discomfort. Each subject was seen on a follow-up schedule and normal clinical methods were used to evaluate symptomology, fitting characteristics, and refractive changes. The results suggest that dehydration in these high water content lenses is the primary problem leading to discomfort

How Adolescent-Parent Relationships Effect Adolescent Religiosity

The relationship between adolescents and their parents has a significant impact on their positive development into adulthood. This study analyzes data from the National Study of Youth and Religion (NSYR) in order to determine if an adolescent’s relationship with his or her parents has an impact on the religiosity of adolescents between the ages of 17-24 years old. This study distinguished the difference between religiosity and spirituality. Religiosity involves a relationship with a particular institutionalized doctrine about a supernatural power; a relationship that occurs through affiliation with an organized faith and participation in its prescribed rituals (Reich, Oser, & Scarlett, 1999). This is opposed to spirituality, which is a more general way of thinking about a higher being or purpose without the affiliation of an organized doctrine or faith. The study is framed by James Fowler’s faith development theory (Fowler, 1984), which contends that religion can be an important aspect of positive youth development for older adolescents. The theory supposes that the more autonomous a person grows in their faith the less influence others have on their faith development. Utilizing the NSYR, adolescent-parent relationships were measured using 12 indicators from the NSYR, such as “how close do you feel to your mother?” or “how often do you talk to your father?” Adolescent religiosity was also measured using 12 indicators from the NSYR, such as “how important is religious faith in shaping how you live your daily life?” or “how often do you pray by yourself alone?” Exploratory factor analysis reveled two major factors describing adolescent religiosity: adolescent religious importance and adolescent respect for religion. The EFA also revealed three factors for adolescent-parent relationships: mother-adolescent relationships, father-adolescent relationships, and parental visitation. These factors were tested against the two factors of adolescent religiosity to determine the effect of adolescent-parent relationships on adolescent religiosity. While parental visitation did not have a significant effect on adolescent religiosity, the study determined that adolescent-parent relationships have a positive effect on adolescent religiosity of adolescents 17-24 years old. The closer an adolescent of this age is to their parents the more likely they are to have respect for religion and find it important. However, adolescent-parent relationships are not the only indicators of adolescent religiosity. Faith development theory states that as adolescents grow they begin to think abstractly. This growth allows them to make their own decisions on abstract subjects such as religious belief (King & Roeser, 2009). Further research can explore other impacts on adolescent religiosity from ages 17-24 and examine how abstract thought impacts religious development. The findings in this study provide researchers and practitioners a glimpse into the influences of religion on older adolescents. This presentation will shine a light on these influences and suggest ways that these findings can be implemented into practice