Abstract Adolescence refers to the period of physical and psychological development between childhood and adulthood. The beginning of adolescence is loosely anchored to the onset of puberty, which brings dramatic alterations in hormone levels and a number of consequent physical changes. Puberty onset is also associated with profound changes in drives, motivations, psychology, and social life; these changes continue throughout adolescence. There is an increasing number of neuroimaging studies looking at the development of the brain, both structurally and functionally, during adolescence. Almost all of these studies have defined development by chronological age, which shows a strong—but not unitary—correlation with pubertal stage. Very few neuroimaging studies have associated brain development with pubertal stage, and yet there is tentative evidence to suggest that puberty might play an important role in some aspects of brain and cognitive development. In this paper we describe this research, and we suggest that, in the future, developmental neuroimaging studies of adolescence should consider the role of puberty. Hum Brain Mapp, 2010. © 2010 Wiley‐Liss, Inc.
We present a bioinspired strategy for enhancing electrochemical carbon dioxide reduction catalysis by cooperative use of base-metal molecular catalysts with intermolecular second-sphere redox mediators that facilitate both electron and proton transfer. Functional synthetic mimics of the biological redox cofactor NADH, which are electrochemically stable and are capable of mediating both electron and proton transfer, can enhance the activity of an iron porphyrin catalyst for electrochemical reduction of CO<sub>2</sub> to CO, achieving a 13-fold rate improvement without altering the intrinsic high selectivity of this catalyst platform for CO<sub>2</sub> versus proton reduction. Evaluation of a systematic series of NADH analogs and redox-inactive control additives with varying proton and electron reservoir properties reveals that both electron and proton transfer contribute to the observed catalytic enhancements. This work establishes that second-sphere dual control of electron and proton inventories is a viable design strategy for developing more effective electrocatalysts for CO<sub>2</sub> reduction, providing a starting point for broader applications of this approach to other multi-electron, multi-proton transformations.
The productivity slowdown and the competitive difficulties experienced by many American firms in domestic and international markets have triggered considerable research into the reasons for the observed changes. Although rarely featured in systematic analysis of productivity trends, various writers have suggested that management miseducation may be part of the problem. In an award-winning article, Robert Hayes and William Abernathy assert
Two series of random copolymers, poly(styrene-d8-co-4-vinylbenzamide) and poly(styrene-d8-co-4-vinyl-N-ethylbenzamide), were prepared with varying compositions. The functionalized random copolymers were tested for their abilities to reinforce the weak interface between immiscible polymers: polystyrene and poly(2-vinylpyridine). The effect of the hydrogen-bonding groups with different interaction strengths (primary or secondary benzamide) was studied through the evaluation of interfacial fracture toughness and fracture surface characteristics. For the compositions investigated, the copolymers with the primary benzamide functionality were shown to attain higher fracture toughness values than the substituted benzamide copolymers. Additionally, the composition at which maximum interfacial strengthening was attained was much lower in the primary benzamide case (fmax = 0.06) than in the substituted benzamide case (fmax = 0.25). However, in both cases the observed strengthening was lower than our previous results using copolymers bearing phenolic groups. The effect of the copolymer functionality, including such variables as steric constraints and degree of self-association, and composition drift on the measured interfacial properties are discussed.
Two new mutants of Rhodobacter sphaeroides deficient in sulfolipid accumulation were isolated by directly screening mutagenized cell lines for polar lipid composition by thin-layer chromatography of lipid extracts. A genomic clone which complemented the mutations in these two lines, but not the previously described sulfolipid-deficient sqdA mutant, was identified. Sequence analysis of the relevant region of the clone revealed three, in tandem open reading frames, designated sqdB, ORF2, and sqdC. One of the mutants was complemented by the sqdB gene, and the other was complemented by the sqdC gene. Insertional inactivation of sqdB also inactivated sqdC, indicating that sqdB and sqdC are cotranscribed. The N-terminal region of the 46-kDa putative protein encoded by the sqdB gene showed slight homology to UDP-glucose epimerase from various organisms. The 30-kDa putative protein encoded by ORF2 showed very striking homology to rabbit muscle glycogenin, a UDP-glucose utilizing, autoglycosylating glycosyltransferase. The 26-kDa putative protein encoded by the sqdC gene was not homologous to any protein of known function.
We report Ir-catalyzed intramolecular silylation of secondary alkyl C-H bonds. (Hydrido)silyl ethers, generated in situ by dehydrogenative coupling of a tertiary or conformationally restricted secondary alcohol with diethylsilane, undergo regioselective silylation at a secondary C-H bond γ to the hydroxyl group. Oxidation of the resulting oxasilolanes in the same vessel generates 1,3-diols. This method provides a strategy to synthesize 1,3-diols through a hydroxyl-directed, functionalization of secondary alkyl C-H bonds. Mechanistic studies suggest that the C-H bond cleavage is the turnover-limiting step of the catalytic cycle. This silylation of secondary C-H bonds is only 40-50 times slower than the analogous silylation of primary C-H bonds.
This paper extends the theoretical model of the linkage between ethnoracial division and the penal state in the United States I have elaborated elsewhere (Wacquant 2001) to cover the stupendous surge in the incarceration of postcolonial migrants in the European Union over the past two decades, that is, in the era of triumphant neoliberalism.
The mechanism and structural requirements for ethanol oxidation to acetaldehyde were examined on VOx domains supported on γ-Al2O3 at surface densities of 1.7−11.8 VOx/nm2. Raman and UV−visible spectra showed that VOx species evolve from monovanadate to polyvanadate structures with increasing surface density with only traces of crystalline V2O5. Oxidative dehydrogenation (ODH) of ethanol to acetaldehyde occurs at low temperatures (473−523 K) with high primary selectivities of CH3CHO (∼80%) on a catalyst with one theoretical polyvanadate monolayer. ODH turnover rates (per V-atom) increased with increasing VOx surface density for surface densities up to 7.2 V/nm2, indicating that polyvanadate domain surfaces are more reactive than monovanadate structures. Similar trends were evident for alkane ODH reactions that also involve kinetically relevant H-abstraction steps within reduction−oxidation catalytic sequences. Turnover rates ultimately decreased at higher surface densities because of the incipient formation of three-dimensional structures. VOx domains of intermediate size therefore provide a compromise between site reactivity and accessibility during ethanol ODH. The effects of O2 and C2H5OH pressures on ethanol ODH rates and the kinetic isotope effects for C2H5OD and C2D5OD confirmed the kinetic relevance of H-abstraction from ethoxide species formed in quasiequilibrated ethanol dissociation steps; taken together with in situ infrared spectra, these data also show that ethoxide species are present at near saturation coverages on fully oxidized VOx domains that undergo reduction−oxidation cycles during each ethanol oxidation turnover.
