Effects of Surface Roughness on the Electrochemical Reduction of CO2 over Cu

We have investigated the role of surface roughening on the CO2 reduction reaction (CO2RR) over Cu. The activity and product selectivity of Cu surfaces roughened by plasma pretreatment in Ar, O2, or N2 were compared with that of electrochemically polished Cu samples. Differences in total and product current densities, the ratio of current densities for HER (the hydrogen evolution reaction) to CO2RR, and the ratio of current densities for C2+ to C1 products depend on the electrochemically active surface and are nearly independent of plasma composition. Theoretical analysis of an electropolished and roughened Cu surface reveals a higher fraction of undercoordinated Cu sites on the roughened surface, sites that bind CO preferentially. Roughened surfaces also contain square sites similar to those on a Cu(100) surface but with neighboring step sites, which adsorb OC-COH, a precursor to C2+ products. These findings explain the increases in the formation of oxygenates and hydrocarbons relative to CO and the ratio of oxygenates to hydrocarbons observed with increasing surface roughness

Atomic Analogy of Poverty

An analogy between the model of an atom and poverty of an individual in a poverty field is presented to construe that poverty levels are quantized in similar notions as in the models of an atom. This analogy provides a rational explanation of the observed phenomena in society in part as well as it can be used to predict future observations. Concepts proposed in this paper may lead to a framework to quantify poverty, absolute or relative, and suggest enhanced collaboration between moral science and natural science to study poverty dynamic

Coherence, subgroup separability, and metacyclic structures for a class of cyclically presented groups

We study a class M of cyclically presented groups that includes both finite and infinite groups and is defined by a certain combinatorial condition on the defining relations. This class includes many finite metacyclic generalized Fibonacci groups that have been previously identified in the literature. By analysing their shift extensions we show that the groups in the class M are are coherent, sub-group separable, satisfy the Tits alternative, possess finite index subgroups of geometric dimension at most two, and that their finite subgroups are all meta-cyclic. Many of the groups in M are virtually free, some are free products of metacyclic groups and free groups, and some have geometric dimension two. We classify the finite groups that occur in M, giving extensive details about the metacyclic structures that occur, and we use this to prove an earlier conjecture concerning cyclically presented groups in which the relators are positive words of length three. We show that any finite group in the class M that has fixed point free shift automorphism must be cyclic

Comparison of bungee-aided and free-bouncing accelerations on trampoline

Trampolines remain the single best apparatus for the training of aerial acrobatics skills. Trampoline use has led to catastrophic injuries from poor landings. Passive injury prevention countermeasures such as specialized matting have been largely ineffective. Active injury countermeasures such as hand spotting, “throw-in” mats, and overhead spotting rigs provide the most effective methods. The recent addition of several bungee cords between the ropes and the gymnast’s spotting harness has resulted in altered teaching and coaching of trampoline-related acrobatics. Bungee cords have eliminated the need for a coach/spotter to manage the ropes during skill learning. The purpose of this study was to assess the influence of the addition of bungee cords with a traditional rope-based overhead spotting rig. There is a paucity of any research involving trampoline injury countermeasures. Ten experienced trampoline acrobatic athletes (5 males, 5 females) from the U.S. Ski and Snowboard Association Aerials National Team performed 10 bounces as high as they could control. A triaxial accelerometer (200 Hz) characterized 10 bungee cord aided bounces and 10 freebounces on a trampoline from each athlete. Bed contact times, peak accelerations, and average accelerations were obtained. The results supported our hypotheses that the bungeeaided bounces achieved only 40% (average) to 70% (peak) of the free-bouncing accelerations (all ρ 0.092). The bed contact time was approximately 65% longer during the bungee-aided bounces (ρ < 0.001). Bungee cords may reduce the harshness of landings on trampoline

Solving the riddle of codon usage preferences: a test for translational selection

Translational selection is responsible for the unequal usage of synonymous codons in protein coding genes in a wide variety of organisms. It is one of the most subtle and pervasive forces of molecular evolution, yet, establishing the underlying causes for its idiosyncratic behaviour across living kingdoms has proven elusive to researchers over the past 20 years. In this study, a statistical model for measuring translational selection in any given genome is developed, and the test is applied to 126 fully sequenced genomes, ranging from archaea to eukaryotes. It is shown that tRNA gene redundancy and genome size are interacting forces that ultimately determine the action of translational selection, and that an optimal genome size exists for which this kind of selection is maximal. Accordingly, genome size also presents upper and lower boundaries beyond which selection on codon usage is not possible. We propose a model where the coevolution of genome size and tRNA genes explains the observed patterns in translational selection in all living organisms. This model finally unifies our understanding of codon usage across prokaryotes and eukaryotes. Helicobacter pylori, Saccharomyces cerevisiae and Homo sapiens are codon usage paradigms that can be better understood under the proposed model

Role of IPAA for Crohn's Disease

Proctocolectomy and creation of an ileal pouch-anal anastomosis (IPAA), first described by Parks and Nicholls, is the preferred and most commonly performed surgical procedure for patients requiring resection of the entire large intestine provided they demonstrate good sphincter function and lack risk factors for postoperative complications or dysfunction. The operation was initially developed for patients with ulcerative colitis or familial adenomatous polyposis to preserve the normal route of defecation and avoid the need for a permanent stoma while ensuring acceptable functional results and satisfactory patient-reported quality of life

Tuning of coupling modes in laterally parallel double open quantum dots

We consider electronic transport through laterally parallel double open quantum dots embedded in a quantum wire in a perpendicular magnetic field. The coupling modes of the dots are tunable by adjusting the strength of a central barrier and the applied magnetic field. Probability density and electron current density are calculated to demonstrate transport effects including magnetic blocking, magnetic turbulence, and a hole-like quasibound state feature. Fano to dip line-shape crossover in the conductance is found by varying the magnetic field.Comment: RevTeX, 13 pages with 18 included postscript figures, high resolution version is available at http://hartree.raunvis.hi.is/~vidar/Rann/CSTVG_DOQD_05.pd

Associative polynomial functions over bounded distributive lattices

The associativity property, usually defined for binary functions, can be generalized to functions of a given fixed arity n>=1 as well as to functions of multiple arities. In this paper, we investigate these two generalizations in the case of polynomial functions over bounded distributive lattices and present explicit descriptions of the corresponding associative functions. We also show that, in this case, both generalizations of associativity are essentially the same.Comment: Final versio

Characterizations of quasitrivial symmetric nondecreasing associative operations

We provide a description of the class of n-ary operations on an arbitrary chain that are quasitrivial, symmetric, nondecreasing, and associative. We also prove that associativity can be replaced with bisymmetry in the definition of this class. Finally we investigate the special situation where the chain is finite