University of North Texas

About: University of North Texas is a education organization based out in Denton, Texas, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 11866 authors who have published 26984 publications receiving 705376 citations. The organization is also known as: Fight, North Texas & UNT.

Convergence of multi-valley bands as the electronic origin of high thermoelectric performance in CoSb3 skutterudites.

Abstract: Filled skutterudites R_xCo_4Sb_(12) are excellent n-type thermoelectric materials owing to their high electronic mobility and high effective mass, combined with low thermal conductivity associated with the addition of filler atoms into the void site. The favourable electronic band structure in n-type CoSb3 is typically attributed to threefold degeneracy at the conduction band minimum accompanied by linear band behaviour at higher carrier concentrations, which is thought to be related to the increase in effective mass as the doping level increases. Using combined experimental and computational studies, we show instead that a secondary conduction band with 12 conducting carrier pockets (which converges with the primary band at high temperatures) is responsible for the extraordinary thermoelectric performance of n-type CoSb_3 skutterudites. A theoretical explanation is also provided as to why the linear (or Kane-type) band feature is not beneficial for thermoelectrics.

Economic Interdependence: A Path to Peace or a Source of Interstate Conflict?

Abstract: This article investigates the long-standing liberal hypothesis that trade ties facilitate interstate peace. Rather than assuming that trade will always promote peace, the author highlights the need to consider both the nature and context of economic linkages in assessing whether such ties are more likely to dampen or amplify interstate conflict. The study encompasses a diverse group of dyadic relationships for the period 1870-1938, 14,341 dyad years, and includes 270 militarized interstate disputes and 14 wars. After controlling for the potentially confounding influences of contiguity, regime type (joint democracy), relative capabilities, and alliance commitments, the author finds evidence that economic linkages have a dramatic influence on whether or not dyads engage in militarized disputes, but no influence on the occurrence of wars. Rather than inhibiting conflict, extensive economic interdependence increases the likelihood that dyads will engage in militarized interstate disputes. Peace through trade is most likely to arise among dyads composed of mutually dependent trading partners. Even then, the relationship between interdependence and conflict appears to be curvilinear, where low to moderate degrees of interdependence reduce the likelihood of dyadic disputes, and extensive economic linkages increase the probability of militarized disputes. Extreme interdependence, whether symmetrical or asymmetrical, has the greatest potential for increasing the likelihood of conflict.

Production of Calcite (Calcium Carbonate) Crystals by Soil Bacteria is a General Phenomenon

Abstract: CERTAIN bacteria form crystals from the solutes in their aqueous environment, and some authors have associated this activity with the extensive deposits of CaCO3 in such places as the Grand Bahama, in spite of the belief that physicochemical effects, such as rapid changes in pH, salinity and temperature, are responsible1–4. Drew5 isolated a denitrifying bacterium able to form CaCO3 crystals in liquid media and named it “Bacterium calcis” (later named Pseudomonas calcis6). Greenfield7 obtained aragonite (another form of CaCO3) crystals in cultures of Pseudomonas in an artificial seawater medium containing Na2CO3 or (NH4)2CO3. Buck and Greenfield reported the same result with marine yeast, and claimed that calcium crystals resulted from the accumulation of calcium deposits on the surface of the cells8. McCallum and Guhathakurta9 observed calcium carbonate deposition by marine bacteria isolated from Bahama Island sediments, and when these were cultured in different media aragonite crystals formed. Shinano10 described many marine bacteria able to form crystals in liquid media. Ramos-Cormenzana11 has also reported crystal formation by soil bacteria in solid media. This, together with the knowledge that previous research concerned only marine bacteria in liquid media, stimulated us to investigate crystal formation by soil bacteria cultured on solid media.

Multiple Regression Approach to Analyzing Contingency Tables: Post Hoc and Planned Comparison Procedures.

Abstract: Post hoc and planned comparison procedures for interpreting chi-square contingency-table test results, not currently discussed in most standard textbooks, are presented. A planned comparison procedure that simplifies the tedious process of partitioning a contingency table by creating single-degree-of-freedom contrasts through a regression-based approach is proposed. Importantly, these post hoc methods supplement the analysis of standardized residuals by reporting the percentage contribution for each cell to the overall chi-square statistic (relative contribution) and to the percentage of variance shared by the two factors (absolute contribution). Both methods can be readily incorporated into existing statistical packages such as SAS or SPSS. The equivalence of the percentage contribution method to the more common standardized residual method is also presented along with an example of a typical application.