Bases of quasi-hereditary covers of diagram algebras

We extend the the combinatorics of tableaux to the study of diagram algebras and give a uniform construction of their quasi-hereditary covers.Comment: Examples now include the classical Brauer, walled Brauer, and partition algebra

Opposites Attract: Synthesis and Electrochemical Studies of Electron-Rich and Electron-Poor Rhodium Complexes for Hydrogen Evolution Catalysis

Electrocatalysis represents an attractive route to coupling renewable energy sources such as wind or solar power with sustainable generation of chemicals. An attractive target chemical would be hydrogen gas because it can be used as a fuel that does not emit pollution (CO2). Progress toward this goal is hampered by a poor mechanistic understanding of how the electrocatalysts couple electrons with substrates to generate products. This problem is especially serious in the case of highly active catalysts that involve redox-active or proton-responsive ligands. Rhodium compounds featuring pentamethylcyclopentadienyl (Cp*) and diimine-type ligands are especially complex because they involve both of these modes of non-innocence. Changes in ligand substitution patterns are often used to improve the activity and stability of catalysts, but the consequences of such modifications are unknown in this class of catalysts. This limits the usefulness of these compounds and their incorporation into more elaborate energy-conversion systems. Here, we will discuss two specific cases that involve use of electron-donating and electron-withdrawing bipyridine variants. Specifically, this thesis describes the synthesis and electrochemical properties of two novel rhodium compounds featuring pentamethylcyclopentadienyl (Cp*) and 4,4′-disubstituted 2,2′-bipyridine (bpy) ligands. The compounds were prepared with two disubstituted bipyridine derivatives, 4,4′-bis(tert-butyl)-2,2′-bipyridine (tBu-bpy) and 4,4′-bis(trifluoromethyl)-2,2′-bipyridine (CF3-bpy); these ligands are more electron-donating and electron-withdrawing, respectively, than the parent underivatized bpy system. Once synthesized these compounds were characterized using 1H, 13C{1H}, and 31P{1H} nuclear magnetic resonance, mass spectrometry, UV-visible spectroscopy and single-crystal X-ray diffraction. Electrochemical studies with these complexes revealed that they are catalysts for hydrogen production. The catalytic activity is modulated by the choice of ligand. Compared to the parent bpy complex, the overpotential for hydrogen evolution is shifted to a smaller value for the [Cp*Rh(CF3-bpy)Cl]+(PF6)– complex, but shifted to a larger value for [Cp*Rh(tBu-bpy)Cl]+(PF6)–. Bulk electrolyses carried out with these complexes confirmed catalytic turnover and a high faradaic efficiency for hydrogen evolution in all cases. Notably, [(Cp*H)Rh(CF3-bpy)NCMe]+, a putative intermediate in the process of hydrogen evolution, was detected by 1H NMR following electrocatalytic H2 generation with [Cp*Rh(CF3-bpy)Cl]+(PF6)–. Few such [(Cp*H)Rh] complexes have been observed or reported in past work, and the observation of a species of this type therefore suggests a general role for such intermediates in hydrogen evolution with this class of catalysts

Relevance of basic laboratory and clinical research activities as part of the vascular surgery fellowship: An assessment by program directors and postfellowship surgeons

AbstractIntroduction: Decreased federal monies for graduate medical education, increased clinical training demands, and a decreased pool of general surgery trainees applying to vascular surgery fellowships have brought into question the relevance of the fellowship research experience. This study sought to describe the recent laboratory experience of the fellows, the value of this experience to program directors (PDs) and the trainees, and what factors related to this experience contributed to the trainee entering an academic career versus a private practice career. Methods: A survey regarding the relevance of research experience during fellowship training was mailed in 2001 to all Accreditation Council for Graduate Medical Education-approved vascular surgery fellowship PDs and vascular surgery fellows (VSFs) from 1988 to 2000 applying for the American Board of Surgery Certificate of Added Qualification in General Vascular Surgery. Results: Survey responses were received from 89% of the PDs (74/83) and 69% of the VSFs (259/378). Among the PDs, 70% had completed an approved fellowship, and current bench research was performed by 46%. The PDs afforded protected research time to 69% of the VSFs (with a mean duration of 12 months). This research was in the basic science laboratory 34% of the time. Only 42% of the PDs considered basic laboratory research to be an important part of the fellowship, whereas 99% believed that clinical research was important. Among the PDs, 42% believed that more practice-oriented fellowships with no basic research were needed, whereas 35% believed that basic research should remain an integral component of the fellowship. VSF basic science productivity was significantly greater from those programs that offered protected research time as compared with those that did not (mean basic science paper published, 1.7 ± 0.1 versus 0.3 ± 0.6 per VSF; P < .001). At the time of the survey, 99 VSFs had entered academic careers and 136 were in private practice. Basic science research had been undertaken by 56% of the VSFs during medical school and by 53% during general surgery residency. Research during the fellowship was performed by 65% of the VSFs. This experience was considered helpful in choosing an academic or private practice career by 44% of the VSFs. A greater proportion of academic surgeons had research experience as VSFs when compared with VSFs who became private practitioners (71% versus 57%; P < .05). VSFs who entered academic careers had a more productive publication record in fellowship than did those who chose private practice (mean paper, 2.4 versus 1.5; P < .05). Overall, 78% of the VSFs believed that their research experience was maturing beyond the technical skills learned. Conclusion: This report provides a benchmark of the vascular surgery fellowship research experience. Most VSFs considered the research experience as it now exists to be worthwhile, and less than half of the PDs believed that it should remain as it is. Research experience in fellowship seemed more influential than that in medical school or general surgical residency in promoting an academic career. (J Vasc Surg 2002;36:1083-91.

Observations of Peak Strength Behavior in CSA Cement Mortars

The purpose of this study was to assess the mechanical property performance behavior of calcium sulfoaluminate (CSA) cement mortar when cured at ambient laboratory temperature of ~23°C (73°F) and constant 50% relative humidity for an extended period of time. Four CSA cement mortars were tested. Three CSA cement mortars contained equivalent mass amounts of calcium sulfate; whereas, the fourth mortar contained double the amount of calcium sulfate. The three CSA cement mortars containing constant mass amounts of calcium sulfate differed as the specific type of calcium sulfate varied across the three formulations—one mortar containing solely anhydrite, one mortar contained half anhydrite and half gypsum while the other mortar solely contained gypsum. The fourth mortar contained double the amount of calcium sulfate when compared with the others while having a 1/1 blend of anhydrite and gypsum. Specific mortars were either tested for direct tensile strength according to ASTM C307 or for compressive strength according to ASTM C109. All tested mortars displayed statistically significant strength loss trends versus time when cured at constant 50% relative humidity. Cement paste samples were analyzed with TGA/SDT and XRD in an effort to identify microstructure changes corresponding to observed strength loss. Cement paste analysis suggests strength loss within the tested CSA cement mortars occurred as a result of ettringite decomposition

Retaining memory after hibernation: performance varies independently of activity levels in wild grey mouse (advance online)

Abstract Hibernation, a hypometabolic state associated with low body temperature and reduced metabolic and activity rates, represents one adaptation to harsh seasonal environmental conditions. As a consequence of hypometabolism, energetically costly neuronal processes also ought to be reduced. Since active neuronal pathways are prerequisites for learning and memory, and because previous studies revealed variable patterns, it remains unclear whether and how hibernating animals retain memories, however. Here, we investigated the effect of seasonally reduced activity on memory retention in 36 wild grey mouse lemurs (Microcebus murinus). Data from activity loggers confirmed that female grey mouse lemurs entered hibernation during the cool dry season, whereas males exhibited episodic bursts of activity throughout the austral winter. Thus, compared to males, we predicted females to show lower memory retention of visual and spatial stimulus?reward associations learned before hibernation. In contrast to our prediction, all individuals performed worse in the post-hibernation testing session in both types of tests, compared to the pre-hibernation learning session, and males (N =?11) performed even worse than females (N =?14) in the post-hibernation testing session. Although females (N =?9) equipped with activity loggers tended to be less active than males (N =?4), sex-specific activity levels were unrelated to interindividual differences in memory retention. Hence, the post-hibernation decrease in performance of grey mouse lemurs may reflect a more general disability to retain stimulus?reward associations than a lack of memory retention due to seasonal hypometabolism, as suggested for some species of bats or squirrels

Chilabothrus subflavus

Number of pages = 30Geological SciencesIntegrative Biolog