Hydrogen Generation Catalyzed by Fluorinated Diglyoxime−Iron Complexes at Low Overpotentials

Fe^(II) complexes containing the fluorinated ligand 1,2-bis(perfluorophenyl)ethane-1,2-dionedioxime (dAr^FgH_2; H = dissociable proton) exhibit relatively positive Fe^(II/I) reduction potentials. The air-stable difluoroborated species [(dAr^FgBF_2)_2Fe(py)_2] (2) electrocatalyzes H_2 generation at −0.9 V vs SCE with i_(cat)/i_p ≈ 4, corresponding to a turnover frequency (TOF) of ~ 20 s^(–1) [Faradaic yield (FY) = 82 ± 13%]. The corresponding monofluoroborated, proton-bridged complex [(dArFg2H-BF2)Fe(py)2] (3) exhibits an improved TOF of ~ 200 s^(–1) (i_(cat)/i_p ≈ 8; FY = 68 ± 14%) at −0.8 V with an overpotential of 300 mV. Simulations of the electrocatalytic cyclic voltammograms of 2 suggest rate-limiting protonation of an Fe“0” intermediate (k_(RLS) ≈ 200 M^(–1) s^(–1)) that undergoes hydride protonation to form H_2. Complex 3 likely reacts via protonation of an Fe^I intermediate that subsequently forms H_2 via a bimetallic mechanism (k_(RLS) ≈ 2000 M^(–1) s^(–1)). 3 catalyzes production at relatively positive potentials compared with other iron complexes

The Effects of Ability Homophily on Individual Performance

Homophily is the sociological term for a principle that is easily observed and understood: similar people tend to associate with one another (or the well-known saying Birds of a feather flock together ). Homophily creates divides among people with numerous demographic characteristics and causes people to surround themselves with others who are similar to themselves (McPherson et al., 2001). Race and ethnicity have the greatest influence on relationship choices followed by age, religion, education, occupation, and gender (McPherson et al., 2001). While studies of homophily of race and gender are quite common, few studies have examined homophily based on instrumental attributes such as a person\u27s ability or intelligence. Most of the previous research on homophily related to ability comes from educational researchers. Homophily of ability could lead to grouping of people who have similar performance levels. Grouping by ability is of interest because it has been linked to increased performance in experiments involving undergraduate (Goethals, 2001) and primary (Lou et al., 1996; Tieso, 2003) school students. However, previous studies have not examined the consequences of ability grouping when it results from homophily occurring naturally rather than being imposed by a researcher or teacher. To determine if performance benefits are associated with ability homophily, a longitudinal study was conducted to measure the advice and friendship relationships of 404 adults in a military management training course. Performance was measured by an end-of-course formative test, instructor evaluations, and peer evaluations. The results confirm that ability homophily in advice relationships is related to increased performance. Ability homophily among friendship relationships was not related to increased performance

U3 snoRNA genes are multi-copy and frequently linked to U5 snRNA genes in Euglena gracilis§

<p>Abstract</p> <p>Background</p> <p>U3 snoRNA is a box C/D small nucleolar RNA (snoRNA) involved in the processing events that liberate 18S rRNA from the ribosomal RNA precursor (pre-rRNA). Although U3 snoRNA is present in all eukaryotic organisms, most investigations of it have focused on fungi (particularly yeasts), animals and plants. Relatively little is known about U3 snoRNA and its gene(s) in the phylogenetically broad assemblage of protists (mostly unicellular eukaryotes). In the euglenozoon <it>Euglena gracilis</it>, a distant relative of the kinetoplastid protozoa, Southern analysis had previously revealed at least 13 bands hybridizing with U3 snoRNA, suggesting the existence of multiple copies of U3 snoRNA genes.</p> <p>Results</p> <p>Through screening of a λ genomic library and PCR amplification, we recovered 14 U3 snoRNA gene variants, defined by sequence heterogeneities that are mostly located in the U3 3'-stem-loop domain. We identified three different genomic arrangements of <it>Euglena </it>U3 snoRNA genes: <it>i</it>) stand-alone, <it>ii</it>) linked to tRNA^Arggenes, and <it>iii</it>) linked to a U5 snRNA gene. In arrangement <it>ii</it>), the U3 snoRNA gene is positioned upstream of two identical tRNA^Arggenes that are convergently transcribed relative to the U3 gene. This scenario is reminiscent of a U3 snoRNA-tRNA gene linkage previously described in trypanosomatids. We document here twelve different U3 snoRNA-U5 snRNA gene arrangements in <it>Euglena</it>; in each case, the U3 gene is linked to a downstream and convergently oriented U5 gene, with the intergenic region differing in length and sequence among the variants.</p> <p>Conclusion</p> <p>The multiple U3 snoRNA-U5 snRNA gene linkages, which cluster into distinct families based on sequence similarities within the intergenic spacer, presumably arose by genome, chromosome, and/or locus duplications. We discuss possible reasons for the existence of the unusually large number of U3 snoRNA genes in the <it>Euglena </it>genome. Variability in the signal intensities of the multiple Southern hybridization bands raises the possibility that <it>Euglena </it>contains a naturally aneuploid chromosome complement.</p

Rotational dynamics of a superhelix towed in a Stokes fluid

Motivated by the intriguing motility of spirochetes (helically-shaped bacteria that screw through viscous fluids due to the action of internal periplasmic flagella), we examine the fundamental fluid dynamics of superhelices translating and rotating in a Stokes fluid. A superhelical structure may be thought of as a helix whose axial centerline is not straight, but also a helix. We examine the particular case where these two superimposed helices have different handedness, and employ a combination of experimental, analytic, and computational methods to determine the rotational velocity of superhelical bodies being towed through a very viscous fluid. We find that the direction and rate of the rotation of the body is a result of competition between the two superimposed helices; for small axial helix amplitude, the body dynamics is controlled by the short-pitched helix, while there is a cross-over at larger amplitude to control by the axial helix. We find far better, and excellent, agreement of our experimental results with numerical computations based upon the method of Regularized Stokeslets than upon the predictions of classical resistive force theory

Baryogenesis by Brane-Collision

We present a new scenario for baryogenesis in the context of heterotic brane-world models. The baryon asymmetry of the universe is generated at a small-instanton phase transition which is initiated by a moving brane colliding with the observable boundary. We demonstrate, in the context of a simple model, that reasonable values for the baryon asymmetry can be obtained. As a byproduct we find a new class of moving-brane cosmological solutions in the presence of a perfect fluid.Comment: 20 pages, Latex, 2 eps-figure

Blatant Discrimination within Federal Law: A 14th Amendment Analysis of Medicaid’s IMD Exclusion

A discriminatory piece of Medicaid law, the institution for mental diseases (IMD) exclusion, is denying people with serious mental illness equal levels of treatment as those with only primary healthcare needs. The IMD exclusion denies the use of federal funding in psychiatric hospitals for inpatient care. This article discusses the history and collateral implications of the IMD exclusion, then examines it through the lens of the Equal Protection Clause of the Fourteenth Amendment, argues that people with severe mental illness constitute a quasi-suspect class, and that application of intermediate scrutiny would render the IMD exclusion unenforceable

Allosteric Communication Occurs via Networks of Tertiary and Quaternary Motions in Proteins

Allosteric proteins bind an effector molecule at one site resulting in a functional change at a second site. We hypothesize that allosteric communication in proteins relies upon networks of quaternary (collective, rigid-body) and tertiary (residue–residue contact) motions. We argue that cyclic topology of these networks is necessary for allosteric communication. An automated algorithm identifies rigid bodies from the displacement between the inactive and the active structures and constructs “quaternary networks” from these rigid bodies and the substrate and effector ligands. We then integrate quaternary networks with a coarse-grained representation of contact rearrangements to form “global communication networks” (GCNs). The GCN reveals allosteric communication among all substrate and effector sites in 15 of 18 multidomain and multimeric proteins, while tertiary and quaternary networks exhibit such communication in only 4 and 3 of these proteins, respectively. Furthermore, in 7 of the 15 proteins connected by the GCN, 50% or more of the substrate-effector paths via the GCN are “interdependent” paths that do not exist via either the tertiary or the quaternary network. Substrate-effector “pathways” typically are not linear but rather consist of polycyclic networks of rigid bodies and clusters of rearranging residue contacts. These results argue for broad applicability of allosteric communication based on structural changes and demonstrate the utility of the GCN. Global communication networks may inform a variety of experiments on allosteric proteins as well as the design of allostery into non-allosteric proteins

Youth vaping and smoking and parental vaping: a panel survey

Background: Concerns remain about potential negative impacts of e-cigarettes including possibilities that: youth e-cigarette use (vaping) increases risk of youth smoking; and vaping by parents may have impacts on their children’s vaping and smoking behaviour. Methods: With panel data from 3291 youth aged 10–15 years from the 7th wave of the UK Understanding Society Survey (2015–2017), we estimated effects of youth vaping on youth smoking (ever, current and past year initiation), and of parental vaping on youth smoking and vaping, and examined whether the latter differed by parental smoking status. Propensity weighting was used to adjust for measured confounders and estimate average effects of vaping for all youth, and among youth who vaped. E-values were calculated to assess the strength of unmeasured confounding influences needed to negate our estimates. Results: Associations between youth vaping and youth smoking were attenuated considerably by adjustment for measured confounders. Estimated average effects of youth vaping on youth smoking were stronger for all youth (e.g. OR for smoking initiation: 32.5; 95% CI: 9.8–107.1) than among youth who vaped (OR: 4.4; 0.6–30.9). Relatively strong unmeasured confounding would be needed to explain these effects. Associations between parental vaping and youth vaping were explained by measured confounders. Estimates indicated effects of parental vaping on youth smoking, especially for youth with ex-smoking parents (e.g. OR for smoking initiation: 11.3; 2.7–46.4) rather than youth with currently smoking parents (OR: 1.0; 0.2–6.4), but these could be explained by relatively weak unmeasured confounding. Conclusions While measured confounding accounted for much of the associations between youth vaping and youth smoking, indicating support for underlying propensities, our estimates suggested residual effects that could only be explained away by considerable unmeasured confounding or by smoking leading to vaping. Estimated effects of youth vaping on youth smoking were stronger among the general youth population than among the small group of youth who actually vaped. Associations of parental vaping with youth smoking and vaping were either explained by measured confounding or could be relatively easily explained by unmeasured confounding

Spectroscopic and redox properties of amine-unctionalized K_2[Os-^(II)(bpy)(CN)_4] complexes

We report the first examples of amine-functionalized K_2[Os^(II)(bpy)(CN)_4] (bpy = 2,2'-bipyridine) complexes. The tetracyanoosmate complexes were prepared by UV irradiation (λ = 254 nm) of K_4[Os^(II)(CN)_6] and primary amine-functionalized bpy ligands in acidic aqueous media. The aqueous solution pH dependences of the spectroscopic and redox properties of 4,4'- and 5,5'-substituted complexes have been investigated. The pendant amine functional groups and coordinated cyanide ligands are basic sites that can be sequentially protonated, thereby allowing systematic tuning of electrochemical and optical spectroscopic properties