Transport Properties of Bulk Thermoelectrics—An International Round-Robin Study, Part I: Seebeck Coefficient and Electrical Resistivity

Recent research and development of high-temperature thermoelectric materials has demonstrated great potential for converting automobile exhaust heat directly into electricity. Thermoelectrics based on classic bismuth telluride have also started to impact the automotive industry by enhancing air-conditioning efficiency and integrated cabin climate control. In addition to engineering challenges of making reliable and efficient devices to withstand thermal and mechanical cycling, the remaining issues in thermoelectric power generation and refrigeration are mostly materials related. The dimensionless figure of merit, ZT, still needs to be improved from the current value of 1.0 to 1.5 to above 2.0 to be competitive with other alternative technologies. In the meantime, the thermoelectric community could greatly benefit from the development of international test standards, improved test methods, and better characterization tools. Internationally, thermoelectrics have been recognized by many countries as a key component for improving energy efficiency. The International Energy Agency (IEA) group under the Implementing Agreement for Advanced Materials for Transportation (AMT) identified thermoelectric materials as an important area in 2009. This paper is part I of the international round-robin testing of transport properties of bulk thermoelectrics. The main foci in part I are the measurement of two electronic transport properties: Seebeck coefficient and electrical resistivity.     

Analysis of user-driven peer selection in peer-to-peer backup and?storage systems

In this paper we present a model of peer-to-peer backup and storage systems in which users have the ability to selfishly select remote peers they want to exchange data with. In our work, peer characteristics (e.g., on-line availability, dedicated bandwidth) play an important role and are reflected in the model through a single parameter, termed profile. We show that selecting remote peers selfishly, based on their profiles, creates incentives for users to improve their contribution to the system. Our work is based on an extension to well known results in Matching Theory, which allows us to formulate the Stable Exchange Game, in which we shift the algorithmic nature of matching problems to a game theoretic framework. We propose a polynomial-time algorithm to compute welfare-maximizing stable exchanges between peers and show, using an evolutionary game theoretic framework, that even semi-random peer selection strategies, that are easily implementable in practice, can be effective in providing incentives to users in order to improve their profiles.     

Order statistics and random matrix theory of multicarrier continuous‐variable quantum key distribution

In a multicarrier continuous‐variable quantum key distribution (CVQKD) protocol, the information is granulated into Gaussian subcarrier CVs and the physical Gaussian link is divided into Gaussian sub‐channels. Here, we propose a combined mathematical framework of order statistics and random matrix theory for multicarrier continuous‐variable quantum key distribution. The analysis covers the study of the distribution of the sub‐channel transmittance coefficients in the presence of a Gaussian noise and the utilization of the moment generation function (MGF) in the error analysis. We reveal the mathematical formalism of sub‐channel selection and formulation of the transmittance coefficients and show a reduced complexity progressive sub‐channel scanning method. We define a framework to evaluate the statistical properties of the information flowing processes in multicarrier CVQKD protocols. Using random matrix theory, we express the achievable secret key rates and study the efficiency of the adaptive multicarrier quadrature division‐multiuser quadrature allocation (AMQD‐MQA) multiple‐access multicarrier CVQKD. The proposed combined framework is particularly convenient for the characterization of the physical processes of experimental multicarrier CVQKD.     

The evolution of inertia

This article examines some evolutionary consequences of architecturalinertia in organizations. The main theorem holds that selectionfavors architectural inertia in the sense that the median levelof inertia in a closed population of organizations increasesover time. The other key theorems hold that the selection intensityfavoring architectural inertia increases with the levels ofintricacy and structural opacity and decreases with culturalasperity.     

Cinnamoyl esters of lesquerella and castor oil: Novel sunscreen active ingredients

Lesquerella and castor oils were esterified with cinnamic acid (CA) and 4-methoxycinnamic acid (MCA). Esterification of the hydroxy oils reached 85% completion with CA and 50% conversion with MCA. The hydroxy oils were esterified at 200°C under a nitrogen atmosphere within a sealed system. Unreacted CA and MCA were removed from the reaction mixtures by sublimation at 100°C under vacuum. The resultant methoxycinnamic oils possessed a broader, more blue-shifted UV absorbance, 250 to 345 nm with a λ_max of 305 nm, compared with the cinnamic oils, which absorbed from 260 to 315 nm, λ_max of 270 nm. The methoxycinnamic oils provide better UV-B absorption and thus are better candidates to be used as sunscreen active ingredients. Esterifications of the hydroxy oils with MCA at 200°C resulted in conversion of 40% of the MCA to undesirable by-products. Esterifications with MCA performed at 175°C in the presence of a tin catalyst resulted in similar percent conversions to product without degradation of MCA. Esterifications of lesquerella oil with MCA at 175°C resulted in higher conversions, 43%, than analogous esterifications with castor oil, 29%. The hydroxyl groups of the lesquerella and castor oils provide their excellent emolliency, lubricity, and noncomedogenicity in skin and personal-care products. Therefore, reactions that convert only 50% of the available hydroxyl groups of the lesquerella oil to cinnamoyl-esters are preferred.     

Rapid broth macrodilution method for determination of MICs for Mycobacterium avium isolates

A multicenter study was done to investigate the accuracy and reproducibility of a method for determining the MICs of antimicrobial agents against the Mycobacterium avium complex in 7H12 broth with the BACTEC system. In phase I, with eight drugs and 10 strains, intralaboratory reproducibility was 95.7 to 100%, allowing a 1-dilution difference upon repeat testing. The results of phase II testing with 41 additional strains were consistent with those obtained in phase I, with good interlaboratory reproducibility. The radiometric method was validated by sampling and plating of the same broth cultures and determining, by the number of CFU per milliliter, the lowest drug concentration that inhibited more than 99% of the initial bacterial population. Three test concentrations of each drug and the tentative interpretation of results are proposed. Radiometric MIC determination has the potential to become the method of choice for clinical microbiology laboratories and evaluation of new agents for the treatment of M. avium infections, both pulmonary and disseminated.     

Effect of sodium iodide additive on the electrochemical performance of sodium/nickel chloride cells

The effect of sodium iodide and sulfur additives on the performance of Na/-alumina/NaAlCl₄/NiCl₂/Ni cells was investigated in quasi-sealed laboratory research cells (0.5–1.0 Ah capacity) and in sealed full-size cells (4 Ah capacity). It was found that sodium iodide additive especially in combination with sulfur in Na/NiCl₂ cells significantly increases the usable capacity and reduces the impedance of the Na/NiCl₂ cells. It is proposed that the use of sodium iodide enhances the energy and power performance of the NiCl₂ electrode by two different mechanisms. The first mechanism, iodide ion doping of the anodically formed solid NiCl₂, is dominant at potentials lower than that of iodine evolution. The doping effect of the iodide ions produces a higher-capacity, lower-impedance NiCl₂ layer on the positive electrode. The second mechanism, anodic formation of very reactive iodine species, is effective when the cell is cycled through the iodine evolution potential range (2.8–3.1 V vs Na). During this process, the dissolved iodine species improve electrode kinetics through liquid-phase mass transport. Use of the sodium iodide additive is safe in sealed cells, causing no over-pressurizing problems. A maximum pressure increase of only 10 kPa was detected by a pressure sensor during severe overcharge tests.