Search

Off-road autonomous vehicles such as tractors and agricultural machinery require an important power traction to cope with mobility issues on soft soils and rough terrains. This paper presents a simplified version of tyre modeling as an adapted Burckhardt tire model based on an analytical Bekker-Wong wheel-soil interaction model. The Bekker-Wong model is a fractional model in space and takes into account the plasticity theory and soil mechanics, however such a model is too complex to be usable in real-time. An adapted version of the Burckhardt model helps having a more compact model that can be usable in real-time. In this paper, an adapted Burckhardt tire model has been optimized for the E-Tract simulator and experiments have been carried out to validate the tractor simulator.

With the rapid expansion of mobile, blended, and seamless learning, researchers claim two factors, lack of self-discipline and poor time management, adversely impact learning performance. In online educational environments, reduced social interactions and low engagement levels generate high dropout rates. Self-regulated learning (SRL), the individual ability to check progress toward a goal and manage learning behavior, appears critical to adult online learning success. Clickstream data can observe, record, and evaluate patterns of users' real-time learning behavior in an online learning environment. Linking clickstream data with performance outcomes allows researchers to assess online learning behaviors and academic performance. The guiding research question was: Are students who apply SLR strategies more likely to demonstrate mastery of knowledge and skills in a self-directed e-learning context? Clickstream data and performance measures were analyzed to explore whether task and cognitive conditions influence how SLR strategies are applied in online training.

Ice speeds in Greenland are largely set by basal motion1, which is modulated by meltwater delivery to the ice base2–4. Evidence suggests that increasing melt rates enhance the subglacial drainage network’s capacity to evacuate basal water, increasing bed friction and causing the ice to slow5–10. This limits the potential of melt forcing to increase mass loss as temperatures increase11. Here we show that melt forcing has a pronounced influence on dynamics, but factors besides melt rates primarily control its impact. Using a method to examine friction variability across the entirety of western Greenland, we show that the main impact of melt forcing is an abrupt north-to-south change in bed strength that cannot be explained by changes in melt production. The southern ablation zone is weakened by 20–40 per cent compared with regions with no melt, whereas in northern Greenland the ablation zone is strengthened. We show that the weakening is consistent with persistent basal water storage and that the threshold is linked to differences in sliding and hydropotential gradients, which exert primary control on the pressures within drainage pathways that dewater the bed. These characteristics are mainly set by whether a margin is land or marine terminating, suggesting that dynamic changes that increase mass loss are likely to occur in northern Greenland as temperatures increase. Our results point to physical representations of these findings that will improve simulated ice-sheet evolution at centennial scales.

Basal shear stress on hard‐bedded glaciers results from normal stress against bed roughness, which depends on basal water pressure and cavity size. These quantities are related in a steady state but are expected to behave differently under rapid changes in water input, which may lead to a transient frictional response not captured by existing friction laws. Here, we investigate transient friction using Global Positioning System vertical displacement and horizontal velocity observations, basal water pressure measurements, and cavitation model predictions during rain‐induced speed‐up events at Glacier d'Argentière, French Alps. We observe up to a threefold increase in horizontal surface velocity, spatially migrating at rates consistent with subglacial flow drainage, and associated with surface uplift and increased water pressure. We show that frictional changes are mainly driven by changes in water pressure at nearly constant cavity size. We propose a generalized friction law capable of capturing observations in both the transient and steady‐state regimes. Changes in water input at the bed of glaciers greatly modify their sliding speed by changing subglacial water pressure. High water pressure, induced by extreme meltwater input, is thought to increase cavity size, a process known as cavitation, which reduces direct contact and increases basal sliding speed. Our Global Positioning System observations indicate that the existing cavitation law, which is based on multidecadal sliding velocities of an alpine glacier, fails at capturing short‐lived, rain‐induced speed‐ups. This is because cavities have insufficient time to adjust their size in response to water pressure changes. Here, we propose a generic friction law that satisfyingly captures observations by incorporating a direct dependency of basal friction on water pressure. With Global Positioning System we observe rain‐induced glacier speed‐up events associated with surface uplift and down‐glacier migrationObservations and modeling show that water pressure rather than cavity size mainly controls changes in basal friction during these eventsWe propose a generalized version of the "regularized” Coulomb friction law, adapted to transient friction under rapid water pressure variations With Global Positioning System we observe rain‐induced glacier speed‐up events associated with surface uplift and down‐glacier migration Observations and modeling show that water pressure rather than cavity size mainly controls changes in basal friction during these events We propose a generalized version of the "regularized” Coulomb friction law, adapted to transient friction under rapid water pressure variations

Understanding glaciers structural heterogeneity is crucial for assessing their fate. Yet, places where structure changes are strong, such as crevasses fields, are often inaccessible for direct instrumentation. To overcome this limitation, we introduce an innovative technique that transforms seismic sources, here generated by crevasses, into virtual receivers using source‐to‐receiver spatial reciprocity. We demonstrate that phase interference patterns between well‐localized seismic sources can be leveraged to retrieve phase velocity maps using Seismic Michelson Interferometry. The obtained phase velocity exhibits sensitivity to changes in glacier structure, offering insights into the origins of mechanical property changes, with spatial resolution surpassing traditional methods by a factor of five. In particular, we observe sharp variations in phase velocity related to strongly damaged subsurface areas indicating a complex 3‐D medium. Applying this method more systematically and in other contexts will enhance our understanding of the structure of glaciers and other seismogenic environments. We transform seismic sources from crevasses into virtual receivers using source‐to‐receiver spatial reciprocityWe derive phase velocity maps in previously inaccessible areas with a resolution five times larger than traditional approachesWe retrieve the influence of glacier geometry and structural heterogeneity on the glacier mechanical properties We transform seismic sources from crevasses into virtual receivers using source‐to‐receiver spatial reciprocity We derive phase velocity maps in previously inaccessible areas with a resolution five times larger than traditional approaches We retrieve the influence of glacier geometry and structural heterogeneity on the glacier mechanical properties

The synthesis and characterization of the isomeric ruthenium complexes with the general formula cis-and trans-[Ru(trpy)(qc)X]n+(trpy is 2,2′:6′,2″-terpyridine, qc is 8-quinolinecarboxylate, cis-1and trans-1, X = Cl, n= 0; cis-2and trans-2, X=OH2, n= 1) with respect to the relative disposition of the carboxylate and X ligands are reported. For comparison purposes, another set of ruthenium complexes with general formula cis-and trans-[Ru(trpy)(pic)(OH2)]+(pic is 2-picolinate (cis-3, trans-3)) have been prepared. The complexes with a qc ligand show a more distorted geometry compared to the complexes with a pic ligand. In all of the cases, the trans isomers show lower potential values for all of the redox couples relative to the cis isomers. Complexes cis-2and trans-2with six-member chelate rings show higher catalytic activity than cis-3and trans-3. Overall, it was shown that the electronic perturbation to the metal center exerted by different orientation and geometry of the ligands significantly influences both redox properties and catalytic performance.

In the urgent quest for green energy vectors, the generation of hydrogen by water splitting with sunlight occupies a preeminent standpoint. The highest solar-to-hydrogen (STH) efficiencies have been achieved with photovoltaic-electrochemical (PV-EC) systems. However, most PV-EC water-splitting devices are required to work at extreme conditions, such as in concentrated solutions of HClO4or KOH or under highly concentrated solar illumination. In this work, a molecular catalyst-based anode is incorporated for the first time in a PV-EC configuration, achieving an impressive 21.2% STH efficiency at neutral pH. Moreover, as opposed to metal oxide-based anodes, the molecular catalyst-based anode allows us to work with extremely small catalyst loadings (<16 nmol/cm2) due to a well-defined metallic center, which is responsible for the fast catalysis of the reaction in the anodic compartment. This work paves the way for integrating molecular materials in efficient PV-EC water-splitting systems.

Photoelectrochemical cells that utilize water as a source of electrons are one of the most attractive solutions for the replacement of fossil fuels by clean and sustainable solar fuels. To achieve this, heterogeneous water oxidation catalysis needs to be mastered and properly understood. The search continues for a catalyst that is stable at the surface of electro(photo)anodes and can efficiently perform this reaction at the desired neutral pH. Here, we show how oligomeric Ru complexes can be anchored on the surfaces of graphitic materials through CH–πinteractions between the auxiliary ligands bonded to Ru and the hexagonal rings of the graphitic surfaces, providing control of their molecular coverage. These hybrid molecular materials behave as molecular electroanodes that catalyse water oxidation to dioxygen at pH 7 with high current densities. This strategy for the anchoring of molecular catalysts on graphitic surfaces can potentially be extended to other transition metals and other catalytic reactions.

In organometallic chemistry, especially in the catalysis area, accessing the finest tuning of a catalytic reaction pathway requires a detailed knowledge of the steric and electronic influences of the ligands bound to the metal center. Usually, the M–L bond between a ligand and metal is depicted by the Dewar–Chatt–Duncanson model involving two opposite interactions, σ-donor and π-acceptor effects of the ligand. The experimental evaluation of these effects is essential and complementary to in-depth theoretical approaches that are able to provide a detailed description of the M–L bond. In this work, we present a study of LMo(CO)5complexes with L being various tertiary phosphine ligands by means of mass-selected high-resolution photoelectron spectroscopy (PES) performed with synchrotron radiation, DFT, and energy decomposition analyses (EDA) combined with the natural orbitals for chemical valence (NOCV) analysis. These methods enable a separated access of the σ-donor and π-acceptor effects of ligands by probing either the electronic configuration of the complex (PES) or the interaction of the ligand with the metal (EDA). Three series of PR3ligands with various electronic influences are investigated: the strong donating alkyl substituents (PMe3, PEt3, and PiPr3), the intermediate PPhxMe(3–x)(x= 0–3) set, and the PPhxPyrl(3–x)set (x= 0–3 with Pyrl being the strong electron withdrawing pyrrolyl group C4H4N). For each complex, their adiabatic and vertical ionization energies (IEs) could be determined with a 0.03 eV precision. Experiment and theory show an excellent agreement, either for the IE determination or electronic effect analysis. The ability to interpret the spectra is shown to depend on the character of the ligand. “Innocent” ligands provide the spectra that are the most straightforward to analyze, whereas the “non-innocent” ligands (which are ionized prior to the metal center) render the analysis more difficult due to an increased number of molecular orbitals in the energy range considered. A very good linear correlation is finally found between the measured adiabatic ionization energies and the interaction energy term obtained by EDA for each of these two types of ligands, which opens interesting perspective for the prediction of ligand characters.

Water oxidation catalysis stands out as one of the most important reactions to design practical devices for artificial photosynthesis. Use of late first-row transition metal (TM) complexes provides an excellent platform for the development of inexpensive catalysts with exquisite control on their electronic and structural features via ligand design. However, the difficult access to their high oxidation states and the general labile character of their metal–ligand bonds pose important challenges. Herein, we explore a copper complex (12–) featuring an extended, π-delocalized, tetra-amidate macrocyclic ligand (TAML) as water oxidation catalyst and compare its activity to analogous systems with lower π-delocalization (22–and 32–). Their characterization evidences a special metal–ligand cooperativity in accommodating the required oxidative equivalents using 12–that is absent in 22–and 32–. This consists of charge delocalization promoted by easy access to different electronic states at a narrow energy range, corresponding to either metal-centered or ligand-centered oxidations, which we identify as an essential factor to stabilize the accumulated oxidative charges. This translates into a significant improvement in the catalytic performance of 12–compared to 22–and 32–and leads to one of the most active and robust molecular complexes for water oxidation at neutral pH with a kobsof 140 s–1at an overpotential of only 200 mV. In contrast, 22–degrades under oxidative conditions, which we associate to the impossibility of efficiently stabilizing several oxidative equivalents via charge delocalization, resulting in a highly reactive oxidized ligand. Finally, the acyclic structure of 32–prevents its use at neutral pH due to acidic demetalation, highlighting the importance of the macrocyclic stabilization.

The deprotonation of differently substituted propargyl xylosides with s-BuLi/TMEDA followed by protonation with t-butanol at −115 °C provided a range of new axially chiral 1,3-disubstituted alkoxyallenes in a diastereoselective way. Numerous reaction parameters such as solvent, temperature, or protonating agent were examined as well as protecting groups on the xyloside moiety and the influence of the substituents on the alkyne part. The configuration of the main diastereoisomer of 3-methyl-1-xyloside-allene was determined for the first time by single-crystal X-ray diffraction analysis and nOe NMR experiments. Furthermore, DFT calculations on the propargyl/allenyl lithium intermediates formed in the course of the deprotonation reaction provided new structural insights of these complexes. The subsequent protonation process with alcohols was investigated by theoretical surface exploration, revealing the importance of the approach of the alcohol toward the lithium compounds on the reaction outcome.

The tridentate meridional ligand pyridyl-2,6-dicarboxylato (pdc2–) has been used to prepare complexes [RuII(pdc-κ3-N1O2)(DMSO)2Cl]-(1II), [RuII(pdc-κ3-N1O2)(bpy)(DMSO)] (2II), and {[RuIII(pdc-κ3-N1O2)(bpy)]2(μ-O)} (5III,III), where bpy = 2,2′-bipyridine. All complexes have been fully characterized through spectroscopic, electrochemical, and single-crystal X-ray diffraction techniques. Compounds 1IIand 2IIshow S → O linkage isomerization of the DMSO ligand upon oxidation from RuIIto RuIII, and thermodynamic and kinetic data have been obtained from cyclic voltammetry experiments. Dimeric complex 5III,IIIis a precursor of the monomeric complex [RuII(pdc-κ3-N1O2)(bpy)(H2O)] (4II) which is a water oxidation catalyst. The electrochemistry and catalytic activity of 4IIhas been ascertained for the first time and compared with related Ru-aquo complexes that are also active for the water oxidation reaction. It shows a TOFmax= 0.2 s–1and overpotential of 240 mV in pH = 1. The overpotential shown by 4IIis one of the lowest reported in the literature and is associated with the role of the two carboxylato groups of the pdc ligand, providing high electron density to the ruthenium complex.

Ruthenium complexes containing the tetradentate 2,2′-bipyridine-6,6′-dicarboxylato (bda2–) equatorial ligand and ortho-subsituted pyridines in the axial position have been prepared and characterized using spectroscopic, crystallographic and electrochemical techniques. Complexes [Ru(Hbda)(DMSO)(pyC)] (1) and [Ru(bda)(DMSO)(pyA)] (2) (where pyC is 2-pyridinecarboxylate, pyA is pyridine-2-ylmethanol and DMSO is dimethyl sulfoxide) have been isolated in moderate to high yields. The solid state structures of (1-H)−and 2reveal the strong chelate effect of the axial pyridine ligand that coordinates in a bidentate fashion leaving the bda2–equatorial ligand coordinating in a tridentate mode. In solution, compound 2shows a dynamic equilibrium between different coordination modes of the bda2–and pyA ligands. This phenomenon does not occur for 1because the carboxylate binds stronger than the labile alcohol in 2. Cyclic voltammetry analysis of 1reveals a complex behavior with a pH-independent wave at E1/2= 1.12 V that is tentatively associated with the two-electron RuIV/IIcouple. In sharp contrast, complex 2shows a pH-dependent one-electron wave at E1/2= 0.83 V (pH 1), assigned to the proton-coupled electron transfer process of the RuIII/IIcouple and a pH-independent wave at E1/2= 1.06 V assigned to the RuIV/IIIcouple. Compound 2is used to prepare complex [Ru(bda)(pic)(pyA)] (4). This complex is air sensitive and converts to complex [Ru(bda)(pic)(pyE)] (5) (where pyE is methyl 2-pyridine carboxylate) in the presence of methanol. This oxidation also occurs by applying a positive potential to an aqueous solution of 4, producing the derivative [Ru(bda)(pic)(pyC)] (3). Cyclic voltammetry of 3shows two pH-independent one-electron oxidation waves at E1/2= 0.64 V and E1/2= 1.0 V, corresponding to the RuIII/IIand RuIV/IIIcouples, respectively. In addition, a water oxidation catalytic wave appears at Eonset≈ 1.4 V. Foot-of-the-wave analysis of this catalytic wave based on a water nucleophilic attack accounts for a TOFmax= 0.63–0.74 s–1.

A new Ru complex containing the deprotonated 2,2′:6′,2′′-terpyridine-6,6′′-diphosphonic acid (H4tPa) and pyridine (py) of general formula [RuII(H3tPa-κ-N3O)(py)2]+, 2+, has been prepared and thoroughly characterized by means of spectroscopic and electrochemical techniques, X-ray diffraction analysis, and density functional theory (DFT) calculations. Complex 2+presents a dynamic behavior in the solution that involves the synchronous coordination and the decoordination of the dangling phosphonic groups of the tPa4–ligand. However, at oxidation state IV, complex 2+becomes seven coordinated with the two phosphonic groups now bonded to the metal center. Further, at this oxidation state at neutral and basic pH, the Ru complex undergoes the coordination of an exogenous OH–group from the solvent that leads to an intramolecular aromatic O atom insertion into the CH bond of one of the pyridyl groups, forming the corresponding phenoxo-phosphonate Ru complex [RuIII(tPaO-κ-N2OPOC)(py)2]2–, 42–, where tPaO5–is the 3-(hydroxo-[2,2′:6′,2′′-terpyridine]-6,6′′-diyl)bis(phosphonate) ligand. This new in situ generated Ru complex, 42–, has been isolated and spectroscopically and electrochemically characterized. In addition, a crystal structure has been also obtained using single-crystal X-ray diffraction techniques. Complex 42–turns out to be an exceptional water oxidation catalyst achieving record maximum turnover frequencies (TOFmax) on the order of 16 000 s–1. A mechanistic analysis complemented with DFT calculations has also been carried out, showing the critical role of intramolecular second coordination sphere effects exerted by the phosphonate groups in lowering the activation energy at the rate-determining step.

Cataract surgery is one of the most common operations in health care. Femtosecond laser-assisted cataract surgery (FLACS) enables more precise ocular incisions and lens fragmentation than does phacoemulsification cataract surgery (PCS). We hypothesised that FLACS might improve outcomes in cataract surgery compared with PCS despite having higher costs.

Under photocatalytic reductive conditions, trifluoromethyl radical addition onto an ynamide followed by cyclization on a benzoyl moiety produces diverse isoindolinone platforms with good yields. The selectivity of the radical cyclization, N-benzoyl vs. N-benzyl as radical acceptor and the E/Zratio of isomers have been rationalized by modeling.

The deformation of a circular fault in a thin floating ice plate imposed by a slow rotational displacement is investigated. Temporal changes in shear strength, as a proxy for the resistance of the fault as a whole, are monitored by the torque required to impose a constant displacement rate. Micro‐seismic monitoring is used to study the relationship between fault average resistance (torque) and micro‐ruptures. The size distribution of ruptures follows a power‐law scaling characterized by an unusually high exponent (b≃3), characteristic of a deformation driven by small ruptures. In strong contrast to the typical brittle dynamics of crustal faults, an 'apparently aseismic' deformation regime is observed in which small undetected seismic ruptures, below the detection level of the monitoring system, control the slip budget. Most (≃71%) of the detected ruptures are organized in bursts with highly similar waveforms, suggesting that these ruptures are only a passive by‐product of apparently aseismic slip events. The seismic signature of this deformation regime has strong similarities with crustal faulting in settings characterized by high temperature and with non‐volcanic tremors. A micro‐seismic monitoring of a fault is setup to monitor its deformationSmall undetected fractures control the slip and energy budgets of the faultFractures are mostly a by‐product of the imposed slip, similarly to swarm‐seismicity

The well-established oxidative addition–reductive elimination pathway is the most followed one in transition metal-catalysed cross-coupling reactions. While readily occurring with a series of transition metals, gold(i) complexes have shown some reluctance to undergo oxidative addition unless special sets of ligands on gold(i), reagents or reaction conditions are used. Here we show that under visible-light irradiation, an iridium photocatalyst triggers—via triplet sensitization—the oxidative addition of an alkynyl iodide onto a vinylgold(i) intermediate to deliver C(sp)2–C(sp) coupling products after reductive elimination. Mechanistic and modelling studies support that an energy-transfer event takes place, rather than a redox pathway. This particular mode of activation in gold homogenous catalysis was applied in several dual catalytic processes. Alkynylbenzofuran derivatives were obtained from o-alkynylphenols and iodoalkynes in the presence of catalytic gold(i) and iridium(iii) complexes under blue light-emitting diode irradiation. Studies into gold-catalysed cross-coupling reactions have expanded over recent decades; however, oxidative addition to gold(i) complexes remains challenging. Now it has been shown that a dual catalytic transformation involving iridium photosensitization to trigger oxidative addition to organogold intermediates enables C(sp2)–C(sp) cross-coupling reactions that are useful for the alkynylation of benzofurans.

The self-rigidification of ionized π-conjugated systems based on two combinations of thiophene (T) and 3,4-Ethylenedioxythiophene (E) is investigated using mass-analyzed ion kinetic energy spectrometry (MIKES) of ions produced from electron impact ionization at 70 eV. The m/z446 radical cations of the two isomers ETTE and TEET lead to detect m/z418 and 390 daughter ions. The MIKE spectra differ only by the intensities of these fragment ions. As the m/z418 daughter ion is produced through a same retro-Diels Alder reaction whatever the fragmenting isomer, the difference in daughter ion intensities is interpreted in term of unimolecular dissociation rate constants (k(Eint)) ratios. Considering that the transition state (TS) of such reaction is attributed to a quinoid form, equivalent vibration modes are assumed for the TS of both dissociating ETTE and TEET radical cations. As a result, by using the Rice–Ramsperger–Kassel–Marcus (RRKM) theory, the difference in daughter ion intensities is interpreted by considering that the fragmenting ion is more or less ordered in its ground state than at the transition state, resulting from the influence of the number of the S…O interactions in the planarization of the TEET ion toward the ETTE charged species. The comparison of this behavior in MIKES experiments is supported by the modeling of ion behavior in mass spectrometer and the calibration in internal energy of the radical cations produced in an EI source.

Proline proton affinity PA(Pro) was previously measured by extended kinetic methods with several amines as reference bases using a triple quadrupole mass spectrometer (J Mass Spectrom2005; 40: 1300). The measured value of 947.5 ± 5 kJ.mol−1differs by more than 10 kJ.mol−1from previous reported experimental or calculated values. This difference may be explained in part by the existence of relatively large entropy difference between the two dissociation channels (ΔΔS‡avg= 31 ± 10 J.mol−1.K−1) and by the inaccuracy of the amines proton affinity used as reference bases. In the present work, these experimental measurements were reinvestigated by RRKM modeling using MassKineticssoftware. From this modeling, a new PA value of 944.5 ± 5 kJ.mol−1and a ΔΔS‡avg(600K)value of 33 ± 10 J.mol−1.K−1are determined. However, the difference between experiment and recent theoretical calculations remains large (10 kJ.mol−1). These RRKM simulations allow also accessing to the effective temperature parameter (Teff) and to discuss the meaning of this term. As previously reported, Teffmainly depends on the internal energy and on the decomposition time as well. It also depends on the critical energies and on the transition state. Considering the entrance of the collision cell as a new ion source, Teffis finally shown to be close to a characteristic temperature (Tchar).

Alkene difunctionalization is a very attractive tool in synthetic organic chemistry. Herein, we disclose an operationally and practically simple method to access 2-hydroxytrifluoroethylacetophenones from styrene derivatives via photoredox catalysis. This light-mediated transformation promotes the generation of the 1-hydroxy-2,2,2-trifluoroethyl carbon-centered radical as key synthon, which undergoes Giese addition with styrenes followed by a Kornblum oxidation process. The presented method is not only mild and cost-effective, but also utilizes an organic photocatalyst and DMSO as oxidant. Experimental investigations support the operative mechanism via net-neutral radical/polar crossover.

Herein, we report the preparation of bifunctional silica nanoparticles by covalent attachment of both an anti-inflammatory drug (ibuprofen) and an antibiotic (levofloxacin or norfloxacin) through amide groups. We also describe the coating of cotton fabrics with silica nanoparticles containing both ibuprofen and norfloxacin moieties linked by amide groups by using a one-step coating procedure under ultrasonic conditions. The functionalized nanoparticles and cotton fabrics have been characterized using spectroscopic and microscopic techniques. The functionalized nanoparticles and textiles have been treated with model proteases for the in situ release of the drugs by the amide bond enzymatic cleavage. Topical dermal applications in medical bandages are expected, which favor wound healing.

Research has affirmed the importance of principals and mentors in supporting novice teachers; however, little is known about how teacher leaders contribute to this work. We employed a mixed methods design to examine teacher leaders’ contributions to induction by surveying principals, teachers, and other staff (n= 246) and interviewing teacher leaders (n= 8). We analyzed data using rank-order and constant comparative analyses. Teacher induction tasks were distributed across teacher leaders, principals, mentor teachers, and other positions. Teacher leaders primarily contributed to professional development and promoting collaboration. They mediated support from colleagues by advancing principal-initiated structures for collaboration, referring novice teachers to experienced teachers, requesting principal support, and recommending induction program improvements. Findings have implications for how leader preparation programs and central office supervisors prepare and support principals and teacher leaders with communicating responsibilities, monitoring workloads, and coordinating distributed leadership for school improvement, particularly in the context of supporting novice teachers.

Cobalt nanoparticles (NPs) have been prepared by hydrogenation of the organometallic complex [Co(η3-C8H13)(η4-C8H12)] in 1-heptanol in the absence of any other stabilizer and then transformed into Co3O4NPs using mild oxidative reaction conditions. After deposition onto glassy carbon rotating disk electrodes, the electrocatalytic performance of the Co3O4NPs in water oxidation has been tested in 1M NaOH. The activity has been benchmarked with that of state-of-the-art Co3O4NPs through electrochemically-active surface area (ECSA) and specific current density measurements. Furthermore, the covalent grafting of photosensitive polypyridyl-based RuIIcomplexes onto the surface of Co3O4NPs afforded hybrid nanostructured materials able to photo-oxidize water into O2, while steady-state and time-resolved spectroscopic measurements gave some further insight into kinetics and pertinent reaction steps following excitation. These first-row transition metal oxide hybrid nanocatalysts display better catalytic performance than simple mixtures of non-grafted photosensitizers and Co3O4NPs, thus evidencing the advantage of the direct coupling between the two entities for the photo-induced water oxidation reaction.