Search

The two-photon absorption (TPA) cross sections (δ) for tungsten(0) arylisocyanides (W(CNAr)6) were determined in the 800–1000 nm region using two-photon luminescence (TPL) spectroscopy. The complexes have high TPA cross sections, in the range 1000–2000 GM at 811.8 nm. In comparison, the cross section at 811.8 nm for tris-(2,2′-bipyridine)ruthenium(II), [Ru(bpy)_3]^(2+), is 7 GM. All measurements were performed using a nanosecond-pulsed laser system.

We report the rates of electron transfer (ET) reactions of electronically excited [Ir(COD)(μ-Me

The purpose of this study was to examine the prevalence of health-focused (healthy eating, physical activity) and weight-focused (weight, dieting) parent-child conversations, and to understand who is talking and who is listening, by exploring the associations these conversations have with parent and child characteristics. The study population included 546 parents (age 27–36 years) who participated in Project EAT (Eating and Activity in Teens and Young Adults)-IV (2015–2016) and had a child aged 2–17 years. Cross-sectional prevalence ratios were calculated to identify associations between parent and child characteristics and the parent-child conversations. Conversations about healthy eating (82%) and physical activity (75%) were more prevalent than those about the child's weight (30%), and dieting (25%). In adjusted models, parents meeting physical activity recommendations had a higher prevalence of health-focused conversations (healthy eating PR = 1.10, 95% CI = 1.01, 1.20; physical activity PR = 1.12, 95% CI = 1.02, 1.24); whereas, weight-focused conversations were more common among parents who had recently dieted and perceived their child to be overweight. Health-focused and weight-focused conversations were highly common among the oldest children aged 9–17 years (health-focused = 90–93% and weight-focused = 42–53%); though, a substantial prevalence of health- and weight-focused conversations (>50% and ≥10%, respectively) also occurred with the youngest children (2–4 years). Findings suggest that parent-child health- and weight-focused conversations are common and that characteristics, including child's age and parents' physical activity, dieting, and perceptions of child weight, may be useful to consider in public health messaging, interventions, and family education that address parent-child communication.

Nanoparticles are a promising cancer therapy for their use as drug carriers given their versatile functionalization with polyethylene glycol and proteins that can be recognized by overexpressed receptors in tumor cells. However, it has been suggested that in biological fluids, proteins cover nanoparticles, which gives the proteins a biological identity that could be responsible for unexpected biological responses: the so-called protein corona. A relevant biological event that is usually ignored in protein-corona formation is the interspecies differences in protein binding, which can be involved in the discrepancies observed in preclinical studies and the nanoparticle safety and efficiency. Hence, the aim of this study was to determine the differences between human and mouse plasma protein corona profiles in an active therapy model using silicon dioxide nanoparticles (SiO

US organic poultry producers are under pressure to find feed alternatives to corn and wheat. Hulless oats offer advantages such as wide geographic adaptation of the plant and high concentrations of protein and oil in the grain. They have shown considerable potential in experimental work as a feed grain for poultry, but more research is needed into their influence on the sensory and nutritional properties of eggs. In this study, hulless oats were substituted for corn or wheat at 200 g kg−1 in diets fed to Hy-Line Brown hens and eggs were sampled for sensory evaluation after 8 weeks. Discrimination tests of blended and baked egg samples found evidence of difference between eggs from oat-based diets and those from the oat-free control (p < 0.05 for eggs from an oat-corn diet, p < 0.01 for eggs from an oat-wheat diet). Acceptance tests of similar samples showed that eggs from the oat-wheat diet were significantly less liked than control eggs for their texture (p < 0.01) and response to cooking (p < 0.01), while eggs from the oat-corn diet were somewhat less liked. Yolk weight was greater (p < 0.05) in control eggs (34.1 g) than eggs from oat-corn (31.6 g) or oat-wheat (31.2 g) diets, leading to smaller yolk proportion in the oat-fed eggs. Fatty acid profile differences across treatments were not of nutritional significance, and no evidence was found that the feeding of hulless oats improved storage properties of eggs. In this study, modifying the carbohydrate source in layer diets was shown to change textural properties of cooked eggs in a way that was perceptible to untrained consumers, probably by reducing the yolk proportion. This finding was not commercially relevant owing to small effect size, and results overall add to existing evidence that hulless oats can be fed to poultry at a moderate proportion of the diet with no negative effect on consumer acceptability of eggs. Regardless of the small effect size, however, findings are interesting from the food chemistry perspective because they provide novel evidence of how the thermal properties of eggs can be altered by a change in hen dietary carbohydrate source.

Many bacteria live in spatially structured assemblies where the microenvironment of a cell is shaped by the activities of its neighbors. Bacteria regulate their gene expression based on the inferred state of the environment. This raises the question whether the phenotypes of neighboring cells can become correlated through interactions via the shared microenvironment. Here, we addressed this question by following gene expression dynamics in Escherichia coli microcolonies. We observed strong spatial correlations in the expression dynamics for pathways involved in toxin production, SOS-stress response, and metabolism. These correlations can partly be explained by a combination of shared lineage history and spatial gradients in the colony. Interestingly, we also found evidence for cell-cell interactions in SOS-stress response, methionine biosynthesis and overall metabolic activity. Together our data suggests that intercellular feedbacks can couple the phenotypes of neighboring cells, raising the question whether gene-regulatory networks have evolved to spatially organize biological functions.

Transient absorption decay rate constants (k_(obs)) for reactions of electronically excited zinc tetraphenylporphyrin (^3ZnTPP*) with triruthenium oxo-centered acetate-bridged clusters [Ru_3(μ_3-O)(μ-CH_3CO_2)_6(CO)(L)]_2(μ-pz), where pz = pyrazine and L = 4-cyanopyridine (cpy) (1), pyridine (py) (2), or 4-dimethylaminopyridine (dmap) (3), were obtained from nanosecond flash-quench spectroscopic data (quenching constants, k_q, for ^3ZnTPP*/1–3 are 3.0 × 10^9, 1.5 × 10^9, and 1.1 × 10^9 M^(–1) s^(–1), respectively). Values of k_q for reactions of ^3ZnTPP* with 1–3 and Ru_3(μ_3-O)(μ-CH_3CO_2)_6(CO)(L)_2 [L = cpy (4), py (5), dmap (6)] monomeric analogues suggest that photoinduced electron transfer is the main pathway of excited-state decay; this mechanistic proposal is consistent with results from a photolysis control experiment, where growth of characteristic near-IR absorption bands attributable to reduced (mixed-valence) Ru_3O-cluster products were observed.

The role of a pharmacist as a member of the inpatient health care team has continued to evolve as the profession advances. Recent changes in recommended inpatient pharmacy practice models require increasing clinical involvement and interaction with patients and other health care practitioners.[1][1

To determine radiation doses incurred by inhaled thoron progeny, the Monte Carlo radon progeny lung dosimetry code IDEAL-DOSE was adapted to the inhalation of thoron progenies, comprising the alpha-emitting nuclides 216Po, 212Bi and 212Po. Dose calculations for defined exposure conditions yielded a dose conversion coefficient (DCC) of 4.6 mSv WLM(-1) or 94.2 nSv (Bq h m(-3))(-1) when compared with a DCC of 3.8 mSv WLM(-1) if based on the International Commission on Radiological Protection Human Respiratory Tract Model. Bronchial doses were computed for different thoron progenies exposure conditions measured in a Bavarian half-timbered house and in a thoron experimental house at the Helmholtz Zentrum München. DCCs ranged from 4.9 to 12.9 mSv WLM(-1), depending on particle size, unattached fraction and fractional activity concentrations. For exposure-specific indoor aerosol parameters, the thoron progeny DCC is smaller than the radon progeny DCC by about a factor of 2.

The stochastic dosimetry model presented here considers the distinctly asymmetric, stochastic branching pattern reported in morphometric measurements. This monopodial structure suggests that an airway diameter is a more appropriate morphometric parameter to classify bronchial dose distributions for inhaled radon progeny than the commonly assigned airway generation numbers. Bronchial doses were calculated for the typical exposure conditions reported for the Pacific Northwest National Laboratory rat inhalation studies, yielding an average bronchial dose of 7.75 mGy WLM(-1). If plotted as functions of airway generations, the resulting dose distributions are highest in the central bronchial airways, while significantly decreasing towards peripheral generations. However, if plotted as functions of airway diameters, doses are much more uniformly distributed among bronchial airways. The comparison between rat and human lungs indicates that dose conversion coefficients for the rat lung are higher than the corresponding values for the human lung by a factor of 1.34 for the experimental PNNL exposure conditions, and of 1.25 for typical human indoor conditions.

Splitting water to hydrogen and oxygen is a promising approach for storing energy from intermittent renewables, such as solar power. Efficient, scalable solar-driven electrolysis devices require active electrocatalysts made from earth-abundant elements. In this mini-review, we discuss recent investigations of homogeneous and heterogeneous hydrogen evolution electrocatalysts, with emphasis on our own work on cobalt and iron complexes and nickel-molybdenum alloys.

The geometrical model introduced previously by the authors has been extended quantitatively to document changes in angular correlations between and among residues as azurin unfolds. In the early stages of denaturation, these changes are found to be more pronounced than changes in the spatial displacement of residues, a result that is also found for residues acting in concert, viz., α-helices, β-sheet residues and residues in ‘turning regions.’ Our analysis leads to a picture of the large-scale motion of the polypeptide chain as azurin denatures. Flanking a central ‘ribbon’ of residues whose orientation remains essentially invariant, we find that in the early stages of unfolding, left- and right-hand ‘wings’ adjacent to this stationary scaffolding pivot counterclockwise, while smaller regions on opposing ends of the β-barrel pivot clockwise. As spatial constraints characterising the native state are further relaxed, our calculations show that some regions reverse their orientational motion, reflecting the enhanced flexibility of the polypeptide chain in the denatured state.

Surfactant-free, size- and composition-controlled, unsupported

We report a new metallolabeled blue copper protein, Re126W122Cu(I) Pseudomonas aeruginosa azurin, which has three redox sites at well-defined distances in the protein fold: Re(I)(CO)3(4,7-dimethyl-1,10-phenanthroline) covalently bound at H126, a Cu center, and an indole side chain W122 situated between the Re and Cu sites (Re-W122(indole) = 13.1 Å, dmp-W122(indole) = 10.0 Å, Re-Cu = 25.6 Å). Near-UV excitation of the Re chromophore leads to prompt Cu(I) oxidation (50 ns), followed by slow back ET to regenerate Cu(I) and ground-state Re(I) with biexponential kinetics, 220 ns and 6 μs. From spectroscopic measurements of kinetics and relative ET yields at different concentrations, it is likely that the photoinduced ET reactions occur in protein dimers, (Re126W122Cu(I))2 and that the forward ET is accelerated by intermolecular electron hopping through the interfacial tryptophan: *Re//←W122←Cu(I), where // denotes a protein-protein interface. Solution mass spectrometry confirms a broad oligomer distribution with prevalent monomers and dimers, and the crystal structure of the Cu(II) form shows two Re126W122Cu(II) molecules oriented such that redox cofactors Re(dmp) and W122-indole on different protein molecules are located at the interface at much shorter intermolecular distances (Re-W122(indole) = 6.9 Å, dmp-W122(indole) = 3.5 Å, and Re-Cu = 14.0 Å) than within single protein folds. Whereas forward ET is accelerated by hopping through W122, BET is retarded by a space jump at the interface that lacks specific interactions or water molecules. These findings on interfacial electron hopping in (Re126W122Cu(I))2 shed new light on optimal redox-unit placements required for functional long-range charge separation in protein complexes.

The homoleptic arylisocyanide tungsten complexes, W(CNXy)_6 and W(CNIph)_6 (Xy = 2,6-dimethylphenyl, Iph = 2,6-diisopropylphenyl), display intense metal to ligand charge transfer (MLCT) absorptions in the visible region (400–550 nm). MLCT emission (λ_max ≈ 580 nm) in tetrahydrofuran (THF) solution at rt is observed for W(CNXy)6 and W(CNIph)_6 with lifetimes of 17 and 73 ns, respectively. Diffusion-controlled energy transfer from electronically excited W(CNIph)_6 (*W) to the lowest energy triplet excited state of anthracene (anth) is the dominant quenching pathway in THF solution. Introduction of tetrabutylammonium hexafluorophosphate, [Bun4N][PF_6], to the THF solution promotes formation of electron transfer (ET) quenching products, [W(CNIph)6]+ and [anth]^•–. ET from *W to benzophenone and cobalticenium also is observed in [Bun4N][PF6]/THF solutions. The estimated reduction potential for the [W(CNIph)6]^(+)/*W couple is −2.8 V vs Cp_(2)Fe^(+/0), establishing W(CNIph)_6 as one of the most powerful photoreductants that has been generated with visible light.

We report the kinetics of CO rebinding to the heme in His134Ser, Ile223Val and His134Ser/Ile223Ser mutants of Geobacillus stearothermophilus nitric oxide synthase (gsNOS). The amplitudes of the two observed kinetics phases, which are insensitive to CO concentration, depend on enzyme concentration. We suggest that two forms of gsNOS are in equilibrium under the conditions employed (6.1–27 μM gsNOS with 20 or 100% CO atmosphere). The kinetics of CO rebinding to the heme do not depend on the identity of the NO-gate residues at positions 134 and 223.

Die Evaluation interdisziplinarer Ambulatorien in der Primarversorgung von Kindern und Jugendlichen mit entwicklungs- und/oder psychischen Storungen ist mit der Schwierigkeit verbunden, dass keine allgemeinen Standards zur Beurteilung des Behandlungserfolgs vorliegen und Erfolgskriterien nur eingeschrankt erfassbar sind. Pro mente: kinder jugend familie GmbH (pmkijufa) stellt sich dieser Herausforderung, indem Effektivitat und Effizienz diagnostischer Masnahmen und therapeutischer Interventionen kontinuierlich uberpruft werden und damit Qualitat messbar gemacht wird. Als Kriterien fur die Qualitat sind eine Verbesserung der in der Eingangsdiagnostik festgestellten Symptome sowie eine Veranderung der Lebensqualitat definiert. In diesem Beitrag werden die Ergebnisse einer 3-Jahres-Evaluation vorgestellt. Diese belegen substanzielle Behandlungserfolge hinsichtlich beider Qualitatskriterien. Zudem lassen sich aus den Ergebnissen und Erfahrungen mit der Evaluation Schwierigkeiten in der Primarversorgung von Kindern und Jugendlichen aufzeigen und Verbesserungspotenziale des Behandlungsangebots sowie die Notwendigkeit der Entwicklung geeigneter Messinstrumente fur verschiedene Alters- und Zielgruppen ableiten.

The computation of the degree d of an approximate greatest common divisor of two Bernstein basis polynomials f(y) and g(y) that are noisy forms of, respectively, the exact polynomials f@?(y) and g@?(y) that have a non-constant common divisor is considered using the singular value decomposition of their Sylvester S(f,g) and Bezout B(f,g) resultant matrices. It is shown that the best estimate of d is obtained when S(f,g) is postmultiplied by a diagonal matrix Q that is derived from the vectors that lie in the null space of S(f,g), where the correct value of d is defined as the degree of the greatest common divisor of the exact polynomials f@?(y) and g@?(y). The computed value of d is improved further by preprocessing f(y) and g(y), and examples of the computation of d using S(f,g), S(f,g)Q and B(f,g) are presented.

The Gamma-Ray Energy Tracking In-beam Nuclear Array (GRETINA) is a new generation high-resolution γ - ray spectrometer consisting of electrically segmented high-purity germanium crystals. GRETINA is capable of reconstructing the energy and position of each γ - ray interaction point inside the crystal with high resolution. This enables γ - ray energy tracking which in turn provides an array with large photopeak efficiency, high resolution and good peak-to-total ratio. GRETINA is used for nuclear structure studies with demanding γ - ray detection requirements and it is suitable for experiments with radioactive-ion beams with high recoil velocities. The GRETINA array has a 1 π solid angle coverage and constitutes the first stage towards the full 4 π array GRETA. We present in this paper the main parts and the performance of the GRETINA system.

We investigate the stability to structural perturbation of Pseudomonas aeruginosa azurin using a previously developed geometric model. Our analysis considers Ru(2,2′,6′,2″-terpyridine)(1,10-phenanthroline)(His83)-labeled wild-type azurin and five variants with mutations to Cu-ligating residues. We find that in the early stages of unfolding, the β-strands exhibit the most structural stability. The conserved residues comprising the hydrophobic core are dislocated only after nearly complete unfolding of the β-barrel. Attachment of the Ru-complex at His83 does not destabilize the protein fold, despite causing some degree of structural rearrangement. Notably, replacing the Cys112 and/or Met121 Cu ligands does not affect the conformational integrity of the protein. Notably, these results are in accord with experimental evidence, as well as molecular dynamics simulations of the denaturation of azurin.

Parents demonstrate an important influence on adolescent obesity and dietary behavior; yet, family-based obesity interventions continue to exhibit limited success among adolescents. To further inform family-based approaches for adolescent obesity treatment, we examined the perceptions of adolescent females with obesity and their mothers of the influences experienced within the parent-adolescent relationship that affect everyday dietary practices. We conducted six focus group interviews (three adolescent female and three mother) among 15 adolescent (12–17 years old) females with obesity and 12 of their mothers. Content analysis techniques were used to analyze the transcribed interviews. Adolescent females with obesity discussed a diverse set of parental influences (controlling, supporting and cultivating, overlooking and tempting, acquiescing, providing, attending, and not providing and avoiding) on their daily dietary practices. Among mother focus groups, mothers discussed specific intentional and unintentional types of influences from children that affected the food and drink they consumed, prepared, and acquired. Findings provide a fuller view of the varied social influences on everyday dietary practices within the parent-adolescent relationship. They indicate the importance of examining both parent-to-child and child-to-parent influences and begin to illuminate the value of attending to the social circumstances surrounding dietary behaviors to strengthen family-based obesity treatment approaches.

Based on 10Be denudation rates previously found (3.6 m/Ma, [2]; 3.44 m/Ma, [1]), the landscape across the CoH is considered old and eroding slowly. High erosion rates similar to our results (5.13 - 15.02 m/Ma) for chert bedrock are ascribed to fast river incision or a recent partial collapse event [1,2]. In contrast, we think our high outcrop erosion rates reflect true denudation and low apparent values from soil samples indicate long retention of quartz on surface, while dolomite is largely removed in solution. The quartz then experiences periods of burial and reworking in caves and river terraces, resulting in low 26Al/10Be ratios.

This chapter is devoted to spin-orbit torques and their interplay with the magnetization of magnetically ordered materials. We will introduce basic concepts of spin dynamics and mechanisms to manipulate magnetization by spin torques. Besides that, we will review recent theoretical and experimental progress in this field. The scope of this chapter is to provide an elementary discussion of important aspects of the physics of spin torques as it relates to switching or dynamically exciting magnetization in ferromagnets.

The complex structure of the valence band in many semiconductors leads to multifaceted and unusual properties for spin-3/2 hole systems compared to common spin-1/2 electron systems. In particular, two-dimensional hole systems show a highly anisotropic Zeeman interaction. We have investigated this anisotropy in GaAs/AlAs quantum well structures both experimentally and theoretically. By performing time-resolved Kerr rotation measurements, we found a nondiagonal tensor g that manifests itself in unusual precessional motion, as well as distinct dependencies of hole-spin dynamics on the direction of the magnetic field B. We quantify the individual components of the tensor g for [113]-, [111]-, and [110]-grown samples. We complement the experiments by a comprehensive theoretical study of Zeeman coupling in in-plane and out-of-plane fields B. To this end, we develop a detailed multiband theory for the tensor g. Using perturbation theory, we derive transparent analytical expressions for the components of the tensor g that we complement with accurate numerical calculations based on our theoretical framework. We obtain very good agreement between experiment and theory. Our study demonstrates that the tensor g is neither symmetric nor antisymmetric. Opposite off-diagonal components can differ in size by up to an order of magnitude. The tensor g encodes not only the Zeeman energy splitting but also the direction of the axis about which the spins precess in the external field B. In general, this axis is not aligned with B. Hence our study extends the general concept of optical orientation to the regime of nontrivial Zeeman coupling.

VERA, the Vienna Environmental Research Accelerator, is especially equipped for the measurement of actinides, and performs a growing number of measurements on environmental samples. While AMS is not the optimum method for each particular plutonium isotope, the possibility to measure 239Pu, 240Pu, 241Pu, 242Pu and 244Pu on the same AMS sputter target is a great simplification. We have obtained a first result on the global fallout value of 244Pu/239Pu=(5.7±1.0)×10−5 based on soil samples from Salzburg prefecture, Austria. Furthermore, we suggest using the 242Pu/240Pu ratio as an estimate of the initial 241Pu/239Pu ratio, which allows dating of the time of irradiation based solely on Pu isotopes. We have checked the validity of this estimate using literature data, simulations, and environmental samples from soil from the Salzburg prefecture (Austria), from the shut down Garigliano Nuclear Power Plant (Sessa Aurunca, Italy) and from the Irish Sea near the Sellafield nuclear facility. The maximum deviation of the estimated dates from the expected ages is 6years, while relative dating of material from the same source seems to be possible with a precision of less than 2years. Additional information carried by the minor plutonium isotopes may allow further improvements of the precision of the method.

This paper presents the overall design for large ( $$\sim $$ 400 mm aperture) reference blackbody cavities currently under development at the Science and Technology Facilities Council Rutherford Appleton Laboratory Space Department (STFC RAL Space), in collaboration with the National Physical Laboratory (NPL). These blackbodies are designed to operate in vacuum over a temperature range from 160 K to 370 K, with an additional capability to operate at $$\sim $$ 100 K as a point of near-zero radiance. This is a challenging problem for a single blackbody. The novel thermal design presented in this paper enables one target that can physically achieve and operate successfully at both thermal extremes, whilst also meeting stringent temperature gradient requirements. The overall blackbody design is based upon a helium gas-gap heat switch and modified to allow for variable thermal conductance. The blackbody design consists of three main concentric cylinder components—an inner cavity (aluminium alloy), a radiation shield (aluminium) and an outer liquid nitrogen ( $$\hbox {LN}_{2}$$ ) jacket (stainless steel). The internal surface of the cavity is the effective radiating surface. There is a helium gas interspace surrounding the radiation shield and enclosed by the $$\hbox {LN}_{2}$$ jacket and the inner cavity. The blackbodies are now at a mature stage of development. In this paper, the overall design, focusing upon the thermal design solution, is detailed. This paper will also concern the full-scale prototype breadboard model, for which results on thermal stability, spatial gradients and other sensitivities will be presented.

Objective The current study examined the relationship between sleep state development across the preterm and early post-term periods and subsequent growth trajectories from 1 to 27 months corrected age. Study Design Retrospective analysis of data collected prospectively from 111 preterm infants (≤ 34 weeks gestation) who participated in a multi-site longitudinal study. Separate longitudinal parallel process models were calculated for each sleep state (active and quiet sleep) and growth (weight, length, and BMI z scores) variable to estimate the associations between their developmental trajectories. Results Significant associations were identified between the trajectories of quiet sleep and weight, active sleep and weight, quiet sleep and BMI, and active sleep and BMI. No statistically meaningful associations were identified between the trajectories of early childhood length and the preterm sleep states. Conclusions Faster preterm period sleep development appears to predict more favorable early childhood growth trajectories, particularly for weight, indicating preterm sleep may be an important biomarker for subsequent growth outcomes.

Traces of 2-3 Myr old 60Fe were recently discovered in a manganese crust and in lunar samples. We have found that this signal is extended in time and is present in globally distributed deep-sea archives. A second 6.5-8.7 Myr old signature was revealed in a manganese crust. The existence of the Local Bubble hints to a recent nearby supernova-activity starting 13 Myr ago. With analytical and numerical models generating the Local Bubble, we explain the younger 60Fe-signature and thus link the evolution of the solar neighborhood to terrestrial anomalies., 4 pages, 3 figures, accepted for publication in JPS Conf. Proc

Prior to 1950, the consensus was that biological transformations occurred in two-electron steps, thereby avoiding the generation of free radicals. Dramatic advances in spectroscopy, biochemistry, and molecular biology have led to the realization that protein-based radicals participate in a vast array of vital biological mechanisms. Redox processes involving high-potential intermediates formed in reactions with O_2 are particularly susceptible to radical formation. Clusters of tyrosine (Tyr) and tryptophan (Trp) residues have been found in many O_2-reactive enzymes, raising the possibility that they play an antioxidant protective role. In blue copper proteins with plastocyanin-like domains, Tyr/Trp clusters are uncommon in the low-potential single-domain electron-transfer proteins and in the two-domain copper nitrite reductases. The two-domain muticopper oxidases, however, exhibit clusters of Tyr and Trp residues near the trinuclear copper active site where O_2 is reduced. These clusters may play a protective role to ensure that reactive oxygen species are not liberated during O_2 reduction.

Prior to 1950, the consensus was that biological transformations occurred in two-electron steps, thereby avoiding the generation of free radicals. Dramatic advances in spectroscopy, biochemistry, and molecular biology have led to the realization that protein-based radicals participate in a vast array of vital biological mechanisms. Redox processes involving high-potential intermediates formed in reactions with O_2 are particularly susceptible to radical formation. Clusters of tyrosine (Tyr) and tryptophan (Trp) residues have been found in many O_2-reactive enzymes, raising the possibility that they play an antioxidant protective role. In blue copper proteins with plastocyanin-like domains, Tyr/Trp clusters are uncommon in the low-potential single-domain electron-transfer proteins and in the two-domain copper nitrite reductases. The two-domain muticopper oxidases, however, exhibit clusters of Tyr and Trp residues near the trinuclear copper active site where O_2 is reduced. These clusters may play a protective role to ensure that reactive oxygen species are not liberated during O_2 reduction.

International audience; One-neutron knockout reactions have been performed on a beam of radioactive 53Co in a high-spinisomeric state. The analysis is shown to yield a highly selective population of high-spin states in an exoticnucleus with a significant cross section, and hence represents a technique that is applicable to the plannednew generation of fragmentation-based radioactive beam facilities. Additionally, the relative cross sectionsamong the excited states can be predicted to a high level of accuracy when reliable shell-model input isavailable. The work has resulted in a new level scheme, up to the 11þ band-termination state, of the protonrichnucleus 52Co (Z ¼ 27, N ¼ 25). This has in turn enabled a study of mirror energy differences inthe A ¼ 52 odd-odd mirror nuclei, interpreted in terms of isospin-nonconserving (INC) forces in nuclei.The analysis demonstrates the importance of using a full set of J-dependent INC terms to explain theexperimental observations.

Site-directed mutants of human myoglobin have been prepared and characterized; each protein has a single surface-modifiable histidine (at position 48, 70, or 83). The proteins were modified by covalent attachment of pentaammineruthenium (a_5Ru) to the surface histidine and substitution of zinc mesoporphyrin IX diacid (ZnP) for the heme. Donor-acceptor separations (edge-edge distances d) in the modified proteins are 9.5 A, His70; 12.7 A, His48; and 15.5 A, His83. Rates of photoinduced electron transfer in these ruthenium-modified myoglobins were measured by transient absorption spectroscopy. The ^(3)ZnP* → Ru^3+ rate constants are 1.6 × 10^7 (His70), 7.2 × 10^4 (His48), and 4.0 × 10^2 s^-1 (His83) (-ΔG°= 0.82 eV); charge-recombination (Ru^2+ → ZnP^+) rates are 1.1 × 10^5 (His48) and 7.3 × 10^2 s^-1 (His83) (-ΔG° = 0.96 eV). Activationless (maximum) rates assuming h = 1.3 eV are 7.2 X lo7 (His70), 3.3 × 10^5 (His48) and 1.8 × 10^3 s^-1 (His83). Distant electronic couplings, which limit the maximum rates in the modified myoglobins, have been analyzed along with data from Ru-modified cytochromes c in terms of a tunneling pathway model. Single dominant pathways adequately describe the electronic couplings in cytochrome c but do not satisfactorily account for the myoglobin couplings. The correlation of electronic coupling with tunneling length for myoglobin is improved significantly by the inclusion of multiple pathways.

It was recently shown that a finite imbalance between electron densities in the $\mathbf{K}$ and $\mathbf{K}'$ valleys of bilayer graphene induces a magnetoelectric coupling. Here we explore ramifications of this electronically tunable magnetoelectric effect for the optical conductivity and dielectric permittivity of this material. Our results augment current understanding of longitudinal magnetoresistance and magnetocapacitance in unconventional materials., 4 pages, 1 figure, IOP style

Population structure and genetic architecture of phenotypic traits in oat (Avena sativa L.) remain relatively under-researched compared to other small grain species. This study explores the historic context of current elite germplasm, including phenotypic and genetic characterization, with a particular focus on identifying under-utilized areas. A diverse panel of cultivated oat accessions was assembled from the USDA National Small Grains Collection to represent a gene pool relatively unaffected by twentieth century breeding activity and unlikely to have been included in recent molecular studies. The panel was genotyped using an oat iSelect 6K beadchip SNP array. The final dataset included 759 unique individuals and 2,715 polymorphic markers. Some population structure was apparent; with the first three principal components accounting for 38.8% of variation and 73% of individuals belonging to one of three clusters. One cluster with high genetic distinctness appears to have been largely overlooked in twentieth century breeding. Classification and phenotype data provided by the Germplasm Resources Information Network were evaluated for their relationship to population structure. Of the structuring variables evaluated, improvement status (cultivar or landrace) was relatively unimportant, indicating that landraces and cultivars included in the panel were all sampled from a similar underlying population. Instead, lemma color and region of origin showed the strongest explanatory power. An exploratory association mapping study of the panel using a subset of 2,588 mapped markers generated novel indications of genomic regions associated with awn frequency, kernels per spikelet, lemma color and panicle type. Further results supported previous findings of loci associated with barley yellow dwarf virus tolerance, crown rust (caused by Puccinia coronata f. sp. avenae) resistance, days to anthesis and growth habit (winter/spring). In addition, two novel loci were identified for crown rust resistance.

We report a discovery that perfunctionalized icosahedral dodecaborate clusters of the type B_(12)(OCH_2Ar)_(12) (Ar = Ph or C_6F_5) can undergo photo-excitation with visible light, leading to a new class of metal-free photooxidants. Excitation in these species occurs as a result of the charge transfer between low-lying orbitals located on the benzyl substituents and an unoccupied orbital delocalized throughout the boron cluster core. Here we show how these species, photo-excited with a benchtop blue LED source, can exhibit excited-state reduction potentials as high as 3 V and can participate in electron-transfer processes with a broad range of styrene monomers, initiating their polymerization. Initiation is observed in cases of both electron-rich and electron-deficient styrene monomers at cluster loadings as low as 0.005 mol%. Furthermore, photo-excitation of B_(12)(OCH_2C_6F_5)_(12) in the presence of a less activated olefin such as isobutylene results in the production of highly branched poly(isobutylene). This work introduces a new class of air-stable, metal-free photo-redox reagents capable of mediating chemical transformations.

Significance The discovery of efficient hydrogen evolution catalysts for solar fuels production continues to be an active research field. Catalyst optimization depends on detailed knowledge of the elementary chemical reaction steps involved in catalysis. Isolation of intermediates in catalytic processes is uncommon owing to their necessarily low stability. By using weak acids, we have isolated and characterized an intermediate in the 2 e − + 2H + → H 2 reaction catalyzed by η 5 -pentamethylcyclopentadienyl (Cp*) Rh(κ 2 -2,2′-bipyridyl) [Rh(bpy)]. We find that the preferred site of Cp*Rh(bpy) protonation is not the metal center but is the Cp* ligand. Despite the reputation of Cp* as a stable ligand in organometallic chemistry, these results suggest an important role for close metal–ligand cooperation in promoting hydrogen–evolution catalysis.

Background: The study of excited states in mirror nuclei allows us to extract information on charge-dependent (i.e., isospin-nonconserving) interactions in nuclei. Purpose: To extend previous studies of mirror nuclei in the f7/2 region, investigating charge symmetry breaking of the strong nuclear force. Methods: γ-ray spectroscopy has been performed for the mirror (Tz= ±3/2) pair 53Ni and 53Mn, produced via mirrored one-nucleon knockout reactions. Results: Several new transitions have been identified in 53Ni from which a new level scheme has been constructed. Cross sections for knockout have been analyzed and compared with reaction model calculations where evidence is found for knockout from high-spin isomeric states. Mirror energy differences between isobaric analog states have been computed, compared to large scale shell-model calculations, and interpreted in terms of isospin-nonconserving effects. In addition, lifetimes for the long-lived J π = 5 /2 − 1 analog states in both 53Mn and 53Ni have been extracted through lineshape analysis, giving half-lives of t1/2 = 120 (14) ps and t1/2 = 198 (12) ps,respectively. Conclusions: The inclusion of a set of isovector isospin-nonconserving matrix elements to the shell-model calculations gave the best agreement with the experimental data.

We succeeded in obtaining the depth profile of

The neutron-deficient nucleus Sn 107 has been studied by using the one-neutron knockout reaction. By measuring the decay γ rays and momentum distributions of reaction residues, the spins of the ground, 5/2 + , and first-excited, 7/2 + , states of Sn 107 have been assigned by comparisons to eikonal-model reaction calculations. Limits on the inclusive and exclusive cross sections have been measured and transitions due to neutron removals from below the N=50 closed shell have been observed. New excited states up to 5.5 MeV in Sn 107 have been identified.

Several cobalt complexes catalyze the evolution of hydrogen from acidic solutions, both homogeneously and at electrodes. The detailed molecular mechanisms of these transformations remain unresolved, largely owing to the fact that key reactive intermediates have eluded detection. One method of stabilizing reactive intermediates involves minimizing the overall reaction free-energy change. Here, we report a new cobalt(I) complex that reacts with tosylic acid to evolve hydrogen with a driving force of just 30 meV/Co. Protonation of Co I produces a transient Co III -H complex that was characterized by nuclear magnetic resonance spectroscopy. The Co III -H intermediate decays by second-order kinetics with an inverse dependence on acid concentration. Analysis of the kinetics suggests that Co III -H produces hydrogen by two competing pathways: a slower homolytic route involving two Co III -H species and a dominant heterolytic channel in which a highly reactive Co II -H transient is generated by Co I reduction of Co III -H.

A comparative study of the early stages of unfolding of five proteins: cyt c, c-b_(562), cyt c′, azurin, and lysozyme is reported. From crystallographic data, helical regions and intervening non-helical (or ‘turning’) regions are identified in each. Exploiting a previously introduced geometrical model, the paper describes quantitatively the stepwise extension of a polypeptide chain subject to the geometrical constraint that the spatial relationship among the residues of each triplet is fixed by native-state crystallographic data. Despite differences among the above-cited proteins, remarkable universality of behavior is found in the early stages of unfolding. At the very earliest stages, internal residues in each helical region have a common unfolding history; the terminal residues, however, are extraordinarily sensitive to structural perturbations. Residues in non-helical sections of the polypeptide unfold after residues in the internal helical regions, but with increasing steric perturbation playing a dominant role in advancing denaturation.