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This paper presents analytical expressions for the calculation of ratios of cation coordination polyhedra volumes ( VA/ VB) for perovskites ABX3 of the Stokes–Howard diagram directly from atomic coordinates. We show the advantages of quantifying perovskite structure distortion with polyhedral volume ratios rather than with tilting angles, and discuss why space groups with multiple crystallographically inequivalent A or B sites ( I4/ mmm, Immm, P42/ nmc etc.) are much less common than those with a single A and B site ( I4/ mcm, R c, Pnma etc.). Analysis of crystallographic data for approximately 1300 perovskite structures of oxides, halides and chalcogenides from the Inorganic Crystal Structure Database revealed that the most highly distorted perovskites belong to the space group Pnma and formally lower-symmetry perovskites ( I2/ m, I2/ a) are less distorted geometrically. Critical values of the VA/ VB ratios for the most common phase transitions Pnma↔ I4/ mcm and Pnma↔ R c are estimated to be ∼ 4.85 with the possible intermediate space group Imma stable in the very narrow range of VA/ VB≃ 4.8–4.9. Transitions to post-perovskite CaIrO3-type structures may be expected for VA/ VB < 3.8. [ABSTRACT FROM AUTHOR]

`Bridge-flipped' isomers may be defined as pairs of molecules related by a reversal of a bridge of atoms connecting two major parts of the individual molecules. This kind of isomerism is commonly found among benzylideneanilines and phenylhydrazones. Isostructural pairs might be suitable for co-crystallization and are thus useful in the preparation of new solid materials. Although most of the examples of bridge-flipped isomeric benzylideneanilines and phenylhydrazones in the crystallographic literature are not isostructural, a small number of isostructural pairs have been reported by previous workers. This paper describes the molecular and crystal structures of four pairs of bridge-flipped isomers: two isostructural phenylhydrazones, ( E)-2-bromobenzaldehyde 4-cyanophenylhydrazone (I) and ( E)-4-cyanobenzaldehyde 2-bromophenylhydrazone (II); two pairs of isostructural benzylideneanilines, N-(2-trifluoromethylbenzylidene)-2-methylaniline (III) and N-(2-methylbenzylidene)-2-trifluoromethylaniline (IV), and N-(2-bromobenzylidene)-2-methylaniline (V) and N-(2-methylbenzylidene)-2-bromoaniline (VI); and a pair of benzylideneanilines with closely similar unit-cell dimensions but different packing arrangements, N-(4-methylbenzylidene)-4-cyanoaniline (VII) and N-(4-cyanobenzylidene)-4-methylaniline (VIII). The structure of (V) is disordered. The packing arrangement of (VIII) resembles that of the chloro-/methyl-substituted benzylideneanilines MBZCLA/MBZCLB [ N-(4-methylbenzylidene)-4-chloroaniline and N-(4-chlorobenzylidene)-4-methylaniline]. Although intermolecular hydrogen bonding plays a part in the isostructuralism of the two phenylhydrazones, the other examples of isostructuralism occur in the absence of similar, relatively strong intermolecular interactions. [ABSTRACT FROM AUTHOR]

Aluminyl anions are low‐valent, anionic, and carbenoid aluminum species commonly found stabilized with potassium cations from the reaction of Al‐halogen precursors and alkali compounds. These systems are very reactive toward the activation of σ‐bonds and in reactions with electrophiles. Various research groups have detected that the potassium atoms play a stabilization role via electrostatic and cation⋯π interactions with nearby (aromatic)‐carbocyclic rings from both the ligand and from the reaction with unsaturated substrates. Since stabilizing K⋯H bonds are witnessed in the activation of this class of molecules, we aim to unveil the role of these metals in the activation of the smaller and less polarizable H2 molecule, together with a comprehensive characterization of the reaction mechanism. In this work, the activation of H2 utilizing a NON‐xanthene‐Al dimer, [K{Al(NON)}]2 (D) and monomeric, [Al(NON)]− (M) complexes are studied using density functional theory and high‐level coupled‐cluster theory to reveal the potential role of K+ atoms during the activation of this gas. Furthermore, we aim to reveal whether D is more reactive than M (or vice versa), or if complicity between the two monomer units exits within the D complex toward the activation of H2. The results suggest that activation energies using the dimeric and monomeric complexes were found to be very close (around 33 kcal mol−1). However, a partition of activation energies unveiled that the nature of the energy barriers for the monomeric and dimeric complexes are inherently different. The former is dominated by a more substantial distortion of the reactants (and increased interaction energies between them). Interestingly, during the oxidative addition, the distortion of the Al complex is minimal, while H2 distorts the most, usually over 0.77 ΔEdist≠. Overall, it is found here that electrostatic and induction energies between the complexes and H2 are the main stabilizing components up to the respective transition states. The results suggest that the K+ atoms act as stabilizers of the dimeric structure, and their cooperative role on the reaction mechanism may be negligible, acting as mere spectators in the activation of H2. Cooperation between the two monomers in D is lacking, and therefore the subsequent activation of H2 is wholly disengaged. [ABSTRACT FROM AUTHOR]

Only few efficient methods for the preparation of polyazoles containing three or four nitrogen atoms in each azole cycle exist. We have developed a novel synthetic strategy that allows the sequential assembly of 1,2,3‐triazole, 1,2,4‐triazole, and tetrazole fragments into a new stable polyazole. Along the novel strategy, some known procedures have been optimized to achieve better conversion, selectivity, and, in general, overall efficiency. [ABSTRACT FROM AUTHOR]

When calculating derivatives of structure factors, there is one particular term (the derivatives of the atomic form factors) that will always be zero in the case of tabulated spherical atomic form factors. What happens if the form factors are non‐spherical? The assumption that this particular term is very close to zero is generally made in non‐spherical refinements (for example, implementations of Hirshfeld atom refinement or transferable aspherical atom models), unless the form factors are refinable parameters (for example multipole modelling). To evaluate this general approximation for one specific method, a numerical differentiation was implemented within the NoSpherA2 framework to calculate the derivatives of the structure factors in a Hirshfeld atom refinement directly as accurately as possible, thus bypassing the approximation altogether. Comparing wR2 factors and atomic parameters, along with their uncertainties from the approximate and numerically differentiating refinements, it turns out that the impact of this approximation on the final crystallographic model is indeed negligible. [ABSTRACT FROM AUTHOR]

For the first time, ab initio direct methods have been used to solve the crystal structure of an RNA/DNA hybrid decamer. The RNA/DNA sequence corresponds to the leftmost two-thirds of the polypurine tract (PPT), the primer for second-strand DNA synthesis by HIV-1 reverse transcriptase (RT). Direct methods using Shake-and-Bake (SnB) yielded solutions for the RNA/DNA decamer molecule using 1.15 Å data, which is just on the resolution edge of what might work with direct methods. Atomic positions for 96% of the entire molecule, containing 514 non-H atoms including three Ca2+ ions, were easily interpreted from a Fourier map based on the `Shake-and-Bake' minimal function and CROQUE phasere finement program. Only six atoms, primarily in the sugar linkage, were missing in this Fourier map. At present, the R factor of the model is 0.143 (Rfree = 0.186) for the 562 non-H atom sites located. The conformation of the RNA/DNA helix is A-form, with a typical A-helix minor-groove width. This paper presents the methodology used in solving this structure. [ABSTRACT FROM AUTHOR]

In this paper a $T(1)$ theorem for Calder\'on--Zygmund operators (CZOs) valid for non-doubling measures with atoms is proved. In the classical Calder\'on--Zigmund theory an essential assumption is the doubling property of the underlying measure $\mu$ in ${\mathbb R}^n$. Some recent results have shown that a big part of the classical theory can be extended to the case of non-doubling measures, with only some mild `growth' condition on the measure $\mu$. In the particular case of the Cauchy transform $Cf(x) = \int f(y)/(y-x) \, d\mu(y)$, the main result of the paper can be stated easily: the Cauchy transform is bounded in $L^2(\mu)$ if and only if it is bounded in $L^2(\mu)$ over characteristic functions of squares. The proof of the main result is based on the use of the Haar basis with random dyadic lattices, following an idea of Nazarov, Treil and Volberg (`Cauchy integral and Calder\'on--Zygmund operators on nonhomogeneous spaces', {\em Internat. Math. Res. Notices} (1997) 15, 703--726), where a $T(1)$ theorem for non-doubling continuous measures was obtained. The case of a measure $\mu$ with atoms studied in the present paper is quite different from the case of continuous measures. For example, if $\mu$ has atoms, the $L^2(\mu)$ boundedness of a CZO does not imply its $L^p(\mu)$ boundedness for some $p\neq2$. The differences arise because a measure $\mu$ with atoms does not satisfy the essential `growth' condition that is involved in the arguments for proving the $L^2$ boundedness of CZOs for continuous measures. 2000 Mathematics Subject Classification: 42B20. [ABSTRACT FROM AUTHOR]

The behavior of atoms in the Jaynes–Cummings model has been discussed and analyzed extensively to date in terms of transition probability and entropy. In this paper, the Jaynes–Cummings model is described in terms of a quantum-mechanical channel expressing the state transition. For this channel, von Neumann entropy and quantum mutual entropy are derived. By means of these quantities, the variation of the atomic state and its nonreciprocity in this model are discussed. © 2000 Scripta Technica, Electron Comm Jpn Pt 3, 84(1): 95–103, 2001 [ABSTRACT FROM AUTHOR]

Invited for this month′s cover is the group of Steven Tait at Indiana University. The image shows single metal atoms stabilized by small molecules on a titanium dioxide powder support that are active in catalyzing ethylene hydrogenation. The Full Paper itself is available at10.1002/cssc.202100208. [ABSTRACT FROM AUTHOR]

ABSTRACT In this paper, a new effective medium ratio following miniaturized meta-atom structure designed, fabricated and measured for dual-band that has multiple circular concentric metal rings printed one inside the other. The each ring of meta-atom structure delivers a magnetic resonance at different frequencies. The number of concentric ring resonator has created same number of resonances. A different analysis has been performed to verify distinct resonance frequencies, effective medium ratio and electromagnetic transmission properties simply by altering the design parameters. Computer simulation technology (CST) electromagnetic simulator which is commercially available is utilized to investigate the design of the meta-atom. The dual-band response has been displayed of the meta-atom in conjunction with negative index material property over the certain span in the microwave regime. The proposed structure has become suitable for S- and C-band applications and has achieved efficient electrically small microwave structure. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:1233-1240, 2017 [ABSTRACT FROM AUTHOR]

Modern materials science increasingly advances via a knowledge-based development rather than a trial-and-error procedure. Gathering large amounts of data and getting deep understanding of non-trivial relationships between synthesis of materials, their structure and properties is experimentally a tedious work. Here, theoretical modeling plays a vital role. In this review paper we briefly introduce modeling approaches employed in materials science, their principles and fields of application. We then focus on atomistic modeling methods, mostly quantum mechanical ones but also Monte Carlo and classical molecular dynamics, to demonstrate their practical use on selected examples. [ABSTRACT FROM AUTHOR]

Platinum usually offers the most effective active center for hydrogen evolution reaction (HER), because of the optimal trade‐off between the adsorption and desorption of hydrogeN atoms (H*) on Pt atoms. Herein, we report an unusual result regarding the active center of a HER catalyst, which was synthesized by electrodepositing traces of Pt nanoparticles (NPs) into a porous nitrogen‐rich dodecahedron matrix derived from zeolitic imidazolate framework ZIF‐8. With an ultra‐low Pt loading of 2.76 μg cm−2, the N‐Pt‐bonded catalyst can produce a current density of 117 mA cm−2 for the HER in 1.0 m H2SO4 at an overpotential of 50 mV, whereas the commercial Pt/C (300 μg cm−2 Pt) can only reach 50 mA cm−2 under the same conditions. Cyclic voltammetry demonstrates that both the H* adsorption and the Pt oxidation are not allowed to occur on this catalyst, due to a full surface coverage of the trace Pt NPs by imidazole. The results from the specially designed experiments indicate that the imidazole N atoms may act as proton anchor‐sites for the HER due to their electron donor nature. Density functional theory calculations also support a catalytic HER mechanism centered at the Pt‐supported N active center, which needs a Gibbs free energy of H* absorption (ΔGH*) significantly smaller than the absolute value of ΔGH* on the Pt(111) surface. We hope that the results of this study will encourage the research on novel N‐centered catalysts for the HER. [ABSTRACT FROM AUTHOR]

Heteroleptic Sr complexes, [Sr(dmamp)(btsa)]2⋅DME (1), [Sr(dmamb)(btsa)]2⋅DME (2), [Sr(dmamp)(hfac)]3⋅DME (3), [Sr(dmamb)(hfac)]3⋅DME (4), [Sr(dmamp)(tmhd)]n (5), and Sr[(dmamb)(tmhd)]n (6) (dmampH=1‐(dimethylamino)‐2‐methylpropan‐2‐ol, dmambH=1‐(dimethylamino)‐2‐methylbutan‐2‐ol, DME=dimethoxyethane, hfacH=1,1,1,5,5,5‐hexafluoropentadione, tmhdH=2,2,6,6‐tetramethylheptane‐3,5‐dione, btsa=bis(trimethylsilyl)amide) were successfully prepared by two‐step substitution reactions using aminoalkoxy and β‐diketonate ligands. All complexes were characterized using various methods, including Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, elemental analysis, and thermogravimetric analysis. Single‐crystal X‐ray diffraction of crystals of 1 and 2 revealed dimeric structures with Sr metal centres connected by μ2‐O bonding of an alkoxy O atom, whereas 3 was a trimer consisting of two μ3‐O bridges and three μ2‐O bridges by the dmamp and hfac ligands, respectively. [ABSTRACT FROM AUTHOR]

Tandem, one‐pot, multicomponent reaction for direct α‐C(sp3)−H alkylation of phosphoramides and thiophosphoramides scaffolds are illustrated. The basic nature of phosphoramide leads to a diverse set of in situ generated Michael acceptors making the reactions highly atom and step economical. The reaction conditions are mild, entirely metal‐ and external additives free. Alkylated phosphoramides were obtained with good yields and selectivity using visible‐light organo‐photocatalysis. [ABSTRACT FROM AUTHOR]

Three metallosupramolecular assemblies composed of two bis‐NHCs and two silver atoms, [4](PF6)2, two tetra‐NHCs and four silver atoms, [7](PF6)4, and two tri‐NHCs and three silver atoms [8](BF4)3, have been prepared. Assemblies [4](PF6)2 and [7](PF6)4 feature NHC ligands decorated with terminal olefin groups. Irradiation of [4](PF6)2 yielded complex [5](PF6)2 with two terminal cyclobutane rings linking the two bis‐NHC ligands. Liberation of the macrocyclic tetrakisimidazolium salt H4‐6(PF6)4 was achieved by reaction of [5](PF6)2 with NH4Cl/NH4PF6. No [2+2] cycloaddition was observed upon irradiation of [7](PF6)4, apparently due to an unfavorable orientation of the olefin groups. Irradiation of complex [8](BF4)3 with three internal pairs of olefin groups leads to [9](BF4)3 as a mixture of two isomers that differ on the relative orientation of the internal cyclobutane rings. Reaction of [9](BF4)3 with NH4Cl/NH4BF4 yields an isomer mixture of the novel cage‐line hexakisimidazolium salt H6‐10(BF4)6. [ABSTRACT FROM AUTHOR]

Single transition metal (TM) atoms such as Fe, Co and Ni occupying a carbon divacancy in tetragonal graphene (TG) and bonded with four nitrogen atoms (TM@N4TG) as electrocatalysts are investigated by means of first-principles calculations. To consider the effect of solvent species on the local configuration of the active single metal, a thermodynamical full-landscape searching (TFLS) scheme is employed. The calculated thermodynamic overpotentials (ηtd) from our TFLS indicate that Co@N4TG displays high catalytic activity toward both oxygen evolution reaction (OER) and reduction reaction (ORR), with ηtd OER and ηtd ORR as 0.397 and 0.357 V, respectively. Its OER potential cannot be captured if only one four electron reaction loop (FERL) is considered. The actual active pathways do not always turn out to be the reactions starting from the bare site. Our findings demonstrate that TG is a promising support and TM confined TD can be used to design effective and cheap multifunctional electrocatalysts. [ABSTRACT FROM AUTHOR]

Invited for this month's cover picture is the group of Paul L. A. Popelier from Manchester Institute of Biotechnology (UK). The cover picture shows the quantum topological atoms in a configuration of the complex HF⋅⋅⋅OH2, where F is green and O is red. Read the full text of their Full Paper at 10.1002/open.201800275. [ABSTRACT FROM AUTHOR]

The Front Cover shows a general molecular structure for the first transition metal complexes bearing π‐coordinated λ3‐halophosphacyclohexadienyl ligands. A thorough comparison of their spectroscopic properties and computational data indicates the presence of polarized P–halogen bonds. The heavier halogen atoms have an increasing tendency to dissociate, leading to the formation of ionic structures. This situation is illustrated by a paddle ball game: depending on the size of the ball, the elastic string may snap, resulting in the separation of paddle and ball. More information can be found in the Full Paper by R. Wolf et al. For more on the story behind the cover research, see the Cover Profile. [ABSTRACT FROM AUTHOR]

The size of metal species plays a pivotal role in governing catalytic performance of supported metal catalysts. In this work, a series of Rh encapsulated within silicalite‐1 catalysts with different sizes were prepared by one‐pot hydrothermal method and employed to catalyze the decomposition of N2O. Detailed structure determinations by HAADF‐STEM, XPS and CO‐DRIFTS demonstrate that subtle modulation of the encapsulated Rh species were achieved easily from single‐atom to nanoclusters and nanoparticles by controlling the loading and reduction conditions of Rh. The turnover frequency (TOF) of N2O decomposition showed a typical volcano‐type dependence on Rh size. Kinetic studies revealed that this structure‐sensitive catalysis was related to the difference in N2O and O2 adsorption/desorption for various Rh species. Furthermore, a Rh@S‐1 catalyst with a proper Rh size (ca. 1.6 nm) was identified as the best‐performing catalyst with a maximum TOF (ca. 95 h−1), showing much superior activity than other reported Rh‐based catalysts. [ABSTRACT FROM AUTHOR]

The propensity of organic fluorine acting as a weak hydrogen bond acceptor (HBA) in intermolecular and intramolecular interactions has been the subject of many experimental and theoretical studies often reaching different conclusions. Over the last few years, new and stronger evidences have emerged for the direct involvement of fluorine in weak hydrogen bond (HB) formation. However, not all the fluorine atom types can act as weak HBA. In this work, the differential HBA propensity of various types of fluorine atoms was analyzed with a particular emphasis for the different types of alkyl fluorides. This was carried out by evaluating ab initio computed parameters, experimental 19F NMR chemical shifts and small molecule crystallographic structures (extracted from the CSD database). According to this analysis, shielded (with reference to the 19F NMR chemical shift) alkyl mono‐fluorinated motifs display the highest HBA propensity in agreement with solution studies. Although much weaker than other well‐characterized HB complexes, the fragile HBs formed by these fluorinated motifs have important implications for the chemical‐physical and structural properties of the molecules, chemical reactions, and protein–ligand recognition. [ABSTRACT FROM AUTHOR]

While developing methods for obtaining high-spin graphene nanostructures, we carried out a model cross-coupling reaction between 1,8-diiodonaphthalene and an organogold derivative of a nitronyl nitroxide. It was found that only one iodine atom reacted, leading to the corresponding 8-iodonaphthalen-1-yl-substituted nitronyl nitroxide. The latter was successfully isolated as two polymorphic modifications, whose X-ray structural analysis revealed a strong distortion of the paramagnet's geometry in comparison with a noniodinated analog. Moreover, the spatial proximity of the heavy iodine atom and the paramagnetic moiety resulted in unprecedented temperature dynamics of the EPR spectrum. To clarify these dynamics, quantum chemical calculations were performed using the exact two-component relativistic X2C method with the self-consistent account of spin-orbit coupling in conjunction with the B3LYP functional and relativistic STO-type basis set. These computations predicted a reasonable aiso(127l) value that can affect the EPR spectrum. Substitution of the second iodine atom would lead to the formation of a diradical with a 1,8-naphthalenediyl bridge, whose structure and magnetic properties were analyzed at the DFT level. Two stable conformations of the diradical with strongly distorted geometry were identified. In both conformations, calculations predict a ferromagnetic exchange between the paramagnetic centers with J=8 and 14 cm-1 (H= -2 J·S1S2). [ABSTRACT FROM AUTHOR]

Under oxygen‐rich conditions, achieving a selective and efficient reduction of NO by CO is always challenging. Here, we report the synthesis of the catalyst consisting of single Ir atoms anchored on mesoporous WO3 (denoted as Ir1/m‐WO3) using a facile template method followed by wet impregnation. X‐ray diffraction and transmission electron microscope studies indicated that the Ir atoms were distributed uniformly on the internal surface of m‐WO3. When tested for the reduction of NO by CO, the Ir1/m‐WO3 catalyst with a low Ir loading of 0.28 wt % exhibited excellent catalytic performance in the presence of 2 vol % O2 (volume ratio of CO to O2 being 1 : 10), achieving a NO conversion of 73 % and N2 selectivity of 100 % at 350 °C. In particular, its turnover frequency (TOF) value reached 0.30 s−1 at 200 °C, which is six times higher than that of the catalyst with Ir nanoparticles supported on mesoporous WO3 (0.05 s−1). The superior catalytic performance of Ir1/m‐WO3 is attributed to the formation of the isolated Ir atoms and the more newly generated Ir‐WO3 interfaces that can promote the adsorption and activation of NO, and the presence of accessible mesopores in m‐WO3 that facilitates the mass transfer of NO and CO. This study brings a new fundamental understanding of active sites in Ir‐based catalysts for the CO+NO reaction and provides a new way to the design and synthesis of single‐atom catalysts, especially precious metal catalysts for emissions control. [ABSTRACT FROM AUTHOR]

The drive to develop maximal atom‐efficient catalysts coupled to the continuous striving for more sustainable reactions has led to an ever‐increasing interest in single‐atom catalysis. Based on a periodic conceptual density functional theory (cDFT) approach, fundamental insights into the reactivity and adsorption of single late transition metal atoms supported on a fully hydroxylated amorphous silica surface have been acquired. In particular, this investigation revealed that the influence of van der Waals dispersion forces is especially significant for a silver (98 %) or gold (78 %) atom, whereas the oxophilicity of the Group 8–10 transition metals plays a major role in the interaction strength of these atoms on the irreducible SiO2 support. The adsorption energies for the less‐electronegative row 4 elements (Fe, Co, Ni) ranged from −1.40 to −1.92 eV, whereas for the heavier row 5 and 6 metals, with the exception of Pd, these values are between −2.20 and −2.92 eV. The deviating behavior of Pd can be attributed to a fully filled d‐shell and, hence, the absence of the hybridization effects. Through a systematic analysis of cDFT descriptors determined by using three different theoretical schemes, the Fermi weighted density of states approach was identified as the most suitable for describing the reactivity of the studied systems. The main advantage of this scheme is the fact that it is not influenced by fictitious Coulomb interactions between successive, charged reciprocal cells. Moreover, the contribution of the energy levels to the reactivity is simultaneously scaled based on their position relative to the Fermi level. Finally, the obtained Fermi weighted density of states reactivity trends show a good agreement with the chemical characteristics of the investigated metal atoms as well as the experimental data. [ABSTRACT FROM AUTHOR]

The wavelength stabilization of a semi-conductor laser under high-speed modulation is reported. The applied stabilization method uses the difference between an atomic absorption line and oscillation wavelength as a feedback signal. In this paper, this method was applied under high-speed modulation. The broadening of the oscillation wavelength width by generated sidebands under high-speed modulation distorts the feedback signal and degrades the stability. However, the wavelength stability (Allan variance) 10-10–10-8 was obtained by using the Rb - D2 absorption line under the modulation frequence 50 to 200 MHz and the modulation current smaller than 1.6 mAp-p. [ABSTRACT FROM AUTHOR]

Tuning the coordination structures of metal sites is intensively studied to improve the performances of single‐atom site catalysts (SASC). However, the pore structure of SASC, which is highly related to the accessibility of active sites, has received little attention. In this work, single‐atom ZnN4 sites embedded in P‐functionalized carbon with hollow‐wall and 3D ordered macroporous structure (denoted as H‐3DOM‐ZnN4/P‐C) are constructed. The creation of hollow walls in ordered macroporous structures can largely increase the external surface area to expose more active sites. The introduction of adjacent P atoms can optimize the electronic structure of ZnN4 sites through long‐rang regulation to enhance the intrinsic activity and selectivity. In the electrochemical CO2 reduction reaction, H‐3DOM‐ZnN4/P‐C exhibits high CO Faradaic efficiency over 90% in a wide potential window (500 mV) and a large turnover frequency up to 7.8 × 104 h−1 at −1.0 V versus reversible hydrogen electrode, much higher than its counterparts without the hierarchically ordered structure or P‐functionalization. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide (H2O2) production by the electrochemical 2‐electron oxygen reduction reaction (2e− ORR) is a promising alternative to the energy‐intensive anthraquinone process, and single‐atom electrocatalysts show the unique capability of high selectivity toward 2e− ORR against the 4e− one. The extremely low surface density of the single‐atom sites and the inflexibility in manipulating their geometric/electronic configurations, however, compromise the H2O2 yield and impede further performance enhancement. Herein, we construct a family of multiatom catalysts (MACs), on which two or three single atoms are closely coordinated to form high‐density active sites that are versatile in their atomic configurations for optimal adsorption of essential *OOH species. Among them, the Cox–Ni MAC presents excellent electrocatalytic performance for 2e− ORR, in terms of its exceptionally high H2O2 yield in acidic electrolytes (28.96 mol L−1 gcat.−1 h−1) and high selectivity under acidic to neutral conditions in a wide potential region (>80%, 0–0.7 V). Operando X‐ray absorption and density functional theory analyses jointly unveil its unique trimetallic Co2NiN8 configuration, which efficiently induces an appropriate Ni–d orbital filling and modulates the *OOH adsorption, together boosting the electrocatalytic 2e− ORR capability. This work thus provides a new MAC strategy for tuning the geometric/electronic structure of active sites for 2e− ORR and other potential electrochemical processes. [ABSTRACT FROM AUTHOR]

This article is the sixth and last of a series devoted to the primary structure of bovine β-casein [1–5]. In the preceding paper, we presented a partial sequence of this protein in which 156 out of the 209 amino-acid residues were exactly positioned [5]. Only a few data were given on the tryptic peptides T2 and T3 [1] which corresponded to the unknown part of the molecule. In the present communication, we establish the amino-acid sequence of these 2 peptides, and discuss the salient features of the β-casein molecule. Bovine β-casein A2 is a phosphoprotein constituted of a single polypeptide chain containing 209 amino-acid residues. Among them are five phosphoseryl residues. From sequence data, it can be written: Asp4, Asn5, Thr9, Ser11, SerP5, Glu17, Gln22, Pro35, Gly5, Ala5, Val19, Met6, Ile10, Leu22, Tyr4, Phe9, Trp, Lys11, His5, Arg4. Its exact molecular weight is 23982, a little higher than that of αs1-casein, which is 23616 [6]. The total number of 27 amide groups (Asn + Gln) agrees well with previous data obtained by Pion et al. [7] and Peterson et al. [8]. The average hydrophobicity, calculated according to Bigelow [9], is 1330 and it places β-casein among the most hydrophobic proteins. The sequence obtained emphasizes the uneven charge distribution along the peptide chain. A high negative net charge is located in the first 50 residues. The high proline residue content (16.7%) and the rather uniform repartition of this residue exclude the possibility of a high α-helix content. Furthermore, the complete absence of segments containing more than 2 adjacent prolyl residues seems to preclude the possibility of poly-L-proline structure that was expected from optical-rotatory-dispersion studies [10]. An interesting extension of the present work is the discovery by Gordon et al [11] that γ-, TS-, R- and S-caseins are fragments of β-casein likely originating from tryptic-like cleavages of the peptide chain next to the carbonyl groups of some lysyl residues. The γ-, TS. A2- and S-, TS. B- and R-caseins respectively represent residues 29 to 209, 106 to 209 and 108 to 209. These results explain the occurrence of only one phosphorus atom in the γ-caseins, the absence of phosphorus in the TS-, R- and S-caseins [12]. Localization of the substitutions which differentiate the known variants of bovine β-casein also explains the relationship between β-, γ-, R-, S- and TS-caseins [12,13]. The NH2-terminal tryptic phosphopeptide, previously analyzed by Peterson et al. [14], has been sequenced independently by Manson and Annan [15]. Their results are identical to those reported in a preceding paper [4]. [ABSTRACT FROM AUTHOR]

Previous reports [1-5], we have described some of the features of the primary structure of bovine αs1-casein. In the present work, the complete amino acid sequence has been established and the salient features of this phosphoprotein have been discussed. In the polyeptide chain, the region containing the phosphopeptides Tm1 (T1-T2), Tm1T2 and Tm1T1 [1,4,5], had only been slightly studied as yet. Because of the difficulties encountered in the breakdown of these phosphopeptides, hydrolysis with endopeptidases and exopeptidases were performed on both native and dephosphorylated peptides. It was confirmed that peptide Tm1T2 contains three hydroxy-amino acids (2 Ser, 1 Thr), but, instead of three [1], two phosphorus atoms were found with purified preparations. Partial acid hydrolysis and dephosphorylation using an orthophosphoric-monoester phosphohydrolase indicate that the two seryl residues m this peptide are O-phosphorylated. The remaining gap in the sequence of the central part of peptide Tm1T2 was bridged by studying two fragments obtained by papain digestion of the dephosphorylated preparation. Instead of four serines, postulated earlier from the results of the amino-acid composition of peptide Tm1T1 [1], five were shown to be present after detailed analysis of the fragments. Since the five phosphate groups could be ready removed by an orthophosphoric-monoester phosphohydrolase, the five seryl residues could be O-phosphorylated. The fragments obtained after hydrolysis with thermolysin of both native and dephosphorylated peptide Tra1T1 were further degraded using classical methods for the determination of the amino acid sequence. In the light of all the results obtained on this phosphoprotein (αs1-casein B), the total number of amino acid residues has been corrected to 199, instead of 198, as reported previously [1-5], and the molecular weight has been calculated to be 23616. The following amino-acid composition; Asp7, Asn8, Thr5, Ser8, SerP8, Glu25, Gln14, Pro17, Gly9, Ala9, Val11, Met5, Ile11, Leu17, Tyr10, Phe8, Lys14, His5, Trp2, Arg6, indicates that there is a higher number of acidic than basic residues in this protein. On the basis of the intrinsic dissociation constants of titratable groups in proteins [6], the negative net charge of the molecule was estimated to be 22 at pH 6.5 and 28 at pH 8.6. Since Bigelow's parameter for thc average hydrophobicity [7] of this protein is 1170, it could be considered to be a hydrophobic protein The high amount (8.5%) and uniform distribution of prolyl residues indicate that this protein has limited structuralcoiling possibilities. The polypeptide chain contains three hydrophobic regions, viz. 1-44, 90-113 and 132-199. The first two are characterized by the fact that basic residues predominate over acidic residues. The third region, where most of the aromatic residues are located, contains very few basic residues and is therefore of more acidic character. Two regions, 45-89 and 114-131, are hydrophilic. The former contains more than half of the total acidic residues, in particular seven of the total eight phosphoseryl residues. Another remarkable feature is the concentration of amino acids with carboxylic side chains, particularly glutamic acid, in the vicinity of two clusters of phosphoseryl residues. It may be noticed that the phosphoseryl residues m αs1-casein are arranged m a manner similar to those in β-casein [8]. In particular, in αs1-casein, the 62-70 region containing four phosphoseryl residues, is similar to the 13-21 region in β-casein [8]. It is interesting to point out that ail but one of the phosphoseryl residues always occur m position n with relation to a glutamyl or a phosphoseryl residue, which is in position n + 2. From this, it would appear that there is an enzymatic phosphorylation of the polypeptide chum (carried out by a phosphoryl kinase which may require a negative charge in the phosphorylation site) rather than a direct incorporation of phosphoserine into the polypeptide chain during protein synthesis. The location of the amino-acid substitutions that characterize the αs1-Casein D and the β-casein C variants has provided evidence for an enzymatic phosphorylation of casein [9]. The problem of the phosphorylated sites in αs1- and β-caseins will be discussed in a forthcoming paper. The repeating amino-acid sequences located in the two regions of αs1-casein, viz. 70-84 and 110-125, are also of interest. The primary structure of αs1-casein given here is that of the genetic variant B. The three other variants A, C and D have also been studied. The C and D variants differ from the B variant by the substitutions of Gly/Glu in position 192 [10] and ThrP/Ala in position 53 [9], respectively. The A variant is characterized by a deletion of thirteen amino-acid residues from position 14 to position 26 in the hydrophobic NH2-terminal part of the polypeptide chain [11]. Because of this deletion, there m an important change in the physico-chemical properties of αs1-casein [12, 13]. Some important features of the amino-acid-sequence determination should be noted. Firstly, the great value of maleic anhydride as a reversible-blocking reagent for amino groups of proteins [14], and the usefulness of thermolysin as a specific enzyme for degrading polypeptides [15]. Secondly, the difficulties encountered during the study of the phosphopeptides: these peptides were difficult to purify since they have similar anionic characters and only react slightly with ninhydrin during paper revelation; other difficulties have been the high destruction of phosphoserine during hydrolysis with HCl 5.7 N, the poor yield in the substractive Edman degradation when the NH2-terminal residue is a phosphoserine, and the failure of endopeptidases and exopeptidases to split off peptide bonds that are close to phosphate groups. Fortunately, alkaline phosphatase has proved to be a useful tool for removing phosphate groups, thus avoiding most of these difficulties. Since the amino-acid sequence of αs1-casein is now known, the degradation of this protein by coagulating and other proteolytic enzymes during cheese ripening may be studied. In particular, bitter peptides originating from αs1-casein may be located. As we have already briefly noted [4], it is obvious that one of the three bitter peptides isolated by Matoba et al. [16] from a tryptic hydrolysate of whole casein, was the segment 23-34 of the polypeptide chain of αs1-casein. In addition, the knowledge of the primary structure will be of help in understanding many aspects of the relations between structure and physical properties in this phosphoprotein. [ABSTRACT FROM AUTHOR]

The article presents information on a research paper regarding the basic facts and principles of radioactivity and properties of radioisotopes related to this. This paper is a back-ground work for the more specialized treatments and applications appearing in this regard. The present state of atomic science is the culmination of researches resulted in three monumental discoveries such as X-rays, radioactivity and the electron that provided novel and powerful methods for studying the nature and the structure of the atom. Later investigations revealed that radioactivity is a property of the atom and thus it is a nuclear phenomenon. The nature of these radiations was resolved into three types of rays, the alpha, the beta and the gamma rays. Further studies revealed that the elements that have radio activity die away according to an exponential law. Scientists adopted some convenient definition of the life of a radio active element that is usually called the half-life period. Based on this they defined the properties of radioisotopes as well.

Developing low‐cost and highly efficient electrocatalysts for nitrogen reduction reaction (NRR) is one of the most attractive challenges. In this work, we systematically investigated the catalytic properties of the single atom catalysts (SAC) and the double atom catalysts (DAC) for NRR via First‐Principle calculations. The SAC and DAC were formed by single and double transition metal (TM) atoms anchored on N‐doped graphene monolayers (TMxN3x‐graphene, x=1, 2; TM=Mo, Fe, Co, Ni and Cu). It is shown that both the SAC and the DAC have exhibited high catalytic properties for NRR. Moreover, when N2 is absorbed by its side‐on sites, SAC even performs better than DAC. And in five kinds of TM atoms, Fe‐complexes exhibit significantly improved catalytic properties. Especially, Fe1N3‐graphene has the best catalytic activity for NRR with the lowest free energy change of 0.04 eV in the rate determining step (RDS). This work not only proposes the differences of SAC and DAC but also provides a new kind of single atom catalysts (SAC) for NNR. [ABSTRACT FROM AUTHOR]

Hematite nanoarrays are important photoanode materials. However, they suffer from serious problems of charge transfer and surface states; in particular, the surface states hinder the increase in photocurrent. A previous strategy to suppress the surface state is the deposition of an Fe‐free metal oxide overlayer. Herein, from the viewpoint of atomic bonding energy, it is found that the strength of bonding around Fe atoms in the hematite is the key to suppressing the surface states. By treating the surface of hematite with Se and NaBH4, the Fe2O3 transforms to a double‐layer nanostructure. In the outer layer, the Fe−O bonding is reinforced and the Fe−Se bonding is even stronger. Therefore, the surface states are inhibited and the increase in the photocurrent density becomes much faster. Besides, the treatment constructs a nanoscale p–n junction to promote the charge transfer. Improvements are achieved in onset potential (0.25 V shift) and in photocurrent density (5.8 times). This work pinpoints the key to suppressing the surface states and preparing a high‐efficiency hematite nanoarray, and deepens our understanding of hematite photoanodes. [ABSTRACT FROM AUTHOR]

Summary: In various research of atom and molecule physical movements, molecular dynamics (MD) simulation is a common tool to simulate and investigate the real molecular motion. However, it introduces a significant penalty in performance, power, electricity, and running time. Consequently, once the simulation size scales up and computing demands keep growing, it comes at substantial costs in performance and energy usage. In this paper, an optimized MD implementation on the Sunway TaihuLight supercomputer with heterogeneous many‐core processors is developed to address the abovementioned issues. The Sunway TaihuLight is a totally independently designed and developed Chinese supercomputer with a profusely customized integration approach and a brand new many‐core processor, the SW26010. The computing power mainly supported by the homegrown many‐core SW26010 processors differs from other existing heterogeneous supercomputers. The Sunway TaihuLight is a heterogeneous supercomputer that ranks first in the world with its peak performance over 100 PFLOPS. Firstly, we propose a new algorithm based on cluster particles to fit the special architecture of SW26010. Then, three optimization methods of the MD simulation are implemented step by step: parallelized extensions to SW26010, memory‐access optimizations, and vectorization. After these optimization processes, a 14x speedup is achieved on a single computing node and yields significant performance and energy improvements. Superiorly, almost 24,000 computing nodes (6,000,000 cores) are applied in our experiments, which gain an almost linear speedup. Besides, the proposed methods also can be adapted and fit to other molecular dynamics codes, even other similar scientific applications. [ABSTRACT FROM AUTHOR]

Cyclic silylated chalconium borates 13[B(C6F5)4] and 14[B(C6F5)4] with peri‐acenaphthyl and peri‐naphthyl skeletons were synthesized from unsymmetrically substituted silanes 3, 4, 6, 7, 9 and 10 using the standard Corey protocol (Chalcogen Ch=O, S, Se, Te). The configuration at the chalcogen atom is trigonal pyramidal for Ch=S, Se, Te, leading to the formation of cis‐ and trans‐isomers in the case of phenylmethylsilyl cations. With the bulkier tert‐butyl group at silicon, the configuration at the chalcogen atoms is predetermined to give almost exclusively the trans‐configurated cyclic silylchalconium ions. The barriers for the inversion of the configuration at the sulfur atoms of sulfonium ions 13 c and 14 a are substantial (72–74 kJ mol−1) as shown by variable temperature NMR spectroscopy. The neighboring group effect of the thiophenyl substituent is sufficiently strong to preserve chiral information at the silicon atom at low temperatures. [ABSTRACT FROM AUTHOR]

The unique electronic and mechanical properties, of graphene make it an ideal material for nanoelectromechanical system (NEMS) applications. Here, a miniature optical fiber current sensor based on a quasistatic graphene NEMS with a graphene membrane covering the hole on a pre-etched fiber tip and two gold electrodes on opposite sides of the tip has been demonstrated. The sensor overcomes the shortcomings of conventional optical fiber current sensors based on thermal effects, such as relatively low sensitivity, long response time, and huge device size; it has simultaneously a high sensitivity of 2.2 × 105 nm/A2, a short response time of ∼0.25 s and a compact device size of ∼15 μm, and has found practical application. Using a smaller graphene membrane with better quality can reduce the response time to submillisecond levels with a more precise measurement system. The sensor presented in this paper may pave the way for the practical usage of optical fiber current sensors based on thermal effects. [ABSTRACT FROM AUTHOR]

We designed and synthesized a new and novel octahedral hexamolybdenum(II) cluster bearing terminal pyridine‐3‐carboxylate (3L) or pyridine‐4‐carboxylate ligands (4L), [{Mo6Br8}(3L)6]2– (3) or [{Mo6Br8}(4L)6]2– (4), to demonstrate proton‐switched emission behaviour of the cluster. X‐ray crystal analysis of 4 demonstrated that the O‐atom in the carboxylate group of 4L coordinates to each Mo atom in the {Mo6Br8}4+‐core, indicating that the N‐atom of 4L in 4 is open for protonation. Reflecting such structural characteristics of the cluster, both 3 and 4 showed proton‐switched emission behaviour owing to the changes in the electron‐donating abilities of the relevant terminal ligands upon protonation to the pyridine N atoms: blue shifts of the emission spectra and increases in the emission lifetimes of the clusters. [ABSTRACT FROM AUTHOR]

Complexes containing odd‐electron Be−Be bonds are still rare until now. Hereby, a series of neutral di‐beryllium amidinate complexes containing a Be−Be bond were explored theoretically. The complexes with direct chelation with the Be2 dimer by the bidentate amidinate (AMD) ligands are always corresponding to their global minimum structures. The detailed bonding analyses reveal that the localized electrons of the Be−Be fragment can be adjusted by the amount of AMD ligands because each AMD ligand only takes one electron from the Be2 fragment. Meanwhile, the hybridization of the central Be atom also changes as the number of AMD ligands increases. In particular, the sp3‐hybridized single‐electron Be−Be bond is firstly identified in the tri‐AMD‐ligands‐chelated neutral D3h‐Be2(AMD)3 complex, which also possesses the higher stability compared to its monoanionic D3h‐Be2(AMD)3− and monocationic C3‐Be2(AMD)3+ analogues. Importantly, our study provides a new approach to obtain a neutral odd‐electron Be−Be bond, namely by the use of radical ligands through side‐on chelation. [ABSTRACT FROM AUTHOR]

Exploring novel cocatalysts with sufficient active sites and rapid photogenerated carrier separation remains challenge for boosting photocatalytic reactions. Recently, two‐dimensional (2D) black phosphorus (BP) has been developed and recognized to be an ideal platform for anchoring metal ions through lone pair electrons. Herein, we propose a new structure that cobalt atomically dispersed on BP nanosheets (BP−Co), and apply it as cocatalyst for photocatalytic H2 evolution and CO2 reduction under visible light (>420 nm) irradiation. Both scanning transmission electron microscope and X‐ray absorption near edge structure verified the existence of phosphorous‐coordinated Co sites. The interaction between Co and P brings greatly improvement on photocatalytic activities, and 18‐fold enhancement can be achieved on CdS when taking BP−Co as a noble‐metal‐free cocatalyst for H2 evolution, which is higher than that of Pt under the same conditions. Besides, BP−Co can also be used as an effective cocatalyst to promote photocatalytic CO2 reduction in the presence of photosensitizer [Ru(2, 2'‐bipyridy)3]Cl2 with a CO evolution rate of 88.6 μmol h−1, superior to those obtained from the state‐of‐the‐art cocatalysts. It is anticipated that the current work might provide basic understanding as well as new opportunities on 2D BP nanosheets for versatile photocatalytic reactions. [ABSTRACT FROM AUTHOR]

The production of ammonia under ambient conditions through electrocatalytic nitrogen reduction reaction is significant but challenging. The lack of an available active NRR electrocatalyst with a high selectivity impedes the development of the electrochemical ammonia synthesis. In this work, via first‐principles density functional theory calculations, we investigated various transition metal atoms (Fe, Cr, V, and Mo) substitution modified defective (with an oxygen vacancy) α‐MnO2 (001) as NRR electrocatalyst. It was found that the incorporation of a single Mo atom substituent at Mn site of α‐MnO2 (001) shows the best performance of nitrogen fixation through enzymatic mechanism with a favorable limiting potential of −0.14 V. The superior selectivity for NH3 over H2 is observed with high Faradaic efficiency of 99 %. The dz2 ‐like characteristics of occupied states around the Fermi level of Mo active center maximizes the p‐d orbital hybridization and thus promotes the stabilities of *N2 and *N2H, which leads to the superior NRR performance. These findings provide theoretical guidance to the development of highly efficient NRR electrocatalysts via defect engineering. [ABSTRACT FROM AUTHOR]

Premade and readily transportable mononuclear zero‐valent metal atoms in stock solvents offer the potential capability for bottom‐up designable metallic material fabrication. This work demonstrates a potentially universal and practical strategy to prepare weakly shielded mononuclear metal atoms in a volatile solvent, which also constitutes a strippable ligand to the metal atoms. Herein, M1(0) (M=Pt, Au) atoms are prepared by reducing H2PtCl6 and HAuCl4 with ethanol in ethylene glycol diethyl ether (EGDE) under mild temperatures. The diether oxygens of EGDE, H+, and Cl− coordinating to the M1(0) atoms, make the M1(0) atoms stable in the solvent under low pH. However, the M1(0) atoms can be released either by evaporation of HCl and EGDE or through neutralization of the HCl with a base. The premade M1(0) atoms can be used as primary building blocks to construct designable materials. To demonstrate a potential application, the M1(0) atoms are conveniently transported onto the surface of TiO2 through impregnation followed by mild heating. The atomic dispersion and reduced state of the metal atoms are well preserved, as verified by HAADF‐STEM images, XPS, and DRIFT spectroscopy. [ABSTRACT FROM AUTHOR]

The crystal structure of new Mg9Ni6Ga14 and Mg3Ni2Ga compounds were investigated by single‐crystal diffraction. Both structures can be described as three‐core‐shell cluster compounds. In the Mg6Ni9Ga14 structure, the [Ni6Ga6] icosahedron is encapsulated within the [Mg20] dodecahedron, which is again encapsulated within a [Ni18Ga42] fullerene‐like truncated icosahedron, thus the three core–shell cluster [Ni6Ga6@Mg20@Ni18Ga42] results. In the Mg3Ni2Ga structure, the [Mg6] octahedron is encapsulated within the [Ni12Ga6] flattened icosahedron in vertices of which there are 12 nickel atoms, and six lateral edges are centered by gallium atoms, which in turn is encapsulated within a [Mg36] pseudo‐rhombicuboctahedron with 12 additional atoms centering the lateral faces; thus for Mg3Ni2Ga the three‐shell cluster is [Mg6@Ni12Ga6@Mg36]. [ABSTRACT FROM AUTHOR]

The Debye scattering equation is now over 100 years old and has been widely used to interpret diffraction patterns from randomly oriented groups of atoms. The present work develops and applies a related equation that calculates diffraction intensity from groups of atoms randomly oriented about a fixed axis, a scenario that occurs when molecules are oriented at an interface by the presentation of a binding motif as in antibody binding. Using an example biomolecule, the high level of sensitivity of the diffraction pattern to the orientation of the molecule and to the direction of the incident beam is shown. The use of the method is proposed not only for determining the orientation of molecules in biosensors and at membrane interfaces, but also for determining molecular conformation without the need for crystallization. [ABSTRACT FROM AUTHOR]

The phenylbenzothiazole compounds show antitumor properties and are highly selective. In this paper, the 99Tc chemical shifts based on the (99mTc)(CO)3(NNO) complex conjugated to the antitumor agent 2-(4′-aminophenyl)benzothiazole are reported. Thermal and solvent effects were studied computationally by quantum-chemical methods, using the density functional theory (DFT) (DFT level BPW91/aug-cc-pVTZ for the Tc and BPW91/IGLO-II for the other atoms) to compute the NMR parameters for the complex. We have calculated the 99Tc NMR chemical shifts of the complex in gas phase and solution using different solvation models (polarizable continuum model and explicit solvation). To evaluate the thermal effect, molecular dynamics simulations were carried, using the atom-centered density matrix propagation method at the DFT level (BP86/LanL2dz). The results highlight that the 99Tc NMR spectroscopy can be a promising technique for structural investigation of biomolecules, at the molecular level, in different environments. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The traditional method for opening the electron shells of noble gas atoms involves a strong electronegative atom or group. However, this approach is limited to only heavy noble-gas atoms, such as Kr and Xe. In this paper, we performed accurate calculations of He@C8H8 and He@C10H16 and showed the possibility of opening the electron shell of a light noble-gas atom. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

This paper presents a tutorial discussion of the principles underlying the depth-dependent Kikuchi pattern formation of backscattered electrons in the scanning electron microscope. To illustrate the connections between various electron diffraction methods, the formation of Kikuchi bands in electron backscatter diffraction in the scanning electron microscope and in transmission electron microscopy are compared with the help of simulations employing the dynamical theory of electron diffraction. The close relationship between backscattered electron diffraction and convergent beam electron diffraction is illuminated by showing how both effects can be calculated within the same theoretical framework. The influence of the depth-dependence of diffuse electron scattering on the formation of the experimentally observed electron backscatter diffraction contrast and intensity is visualized by calculations of depth-resolved Kikuchi patterns. Comparison of an experimental electron backscatter diffraction pattern with simulations assuming several different depth distributions shows that the depth-distribution of backscattered electrons needs to be taken into account in quantitative descriptions. This should make it possible to obtain more quantitative depth-dependent information from experimental electron backscatter diffraction patterns via correlation with dynamical diffraction simulations and Monte Carlo models of electron scattering. [ABSTRACT FROM AUTHOR]

In the present paper, kinetic isotope effects of the title reaction are studied with canonical variational transition state theory on the modified Wang Bowman (MWB) potential energy surface (PES) (Chem Phys Lett 2005, 409, 249) and the ab initio calculations at the quadratic configuration interaction (QCISD (T, full))/aug-cc-pVTZ//QCISD (full)/cc-pVTZ level. The calculated rate constants for the isotopic variants of this title reaction on the MWB PES have good agreement with those of the present ab initio calculations over the temperature range of 20–5000 K for the forward reactions and 800–5000 K for the reverse reactions, respectively. In particular, the forward rate constants for the title reaction and its isotopically substituted reactions have negative temperature dependences at about 40 K. Rate expressions are presented for all the studied reactions. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 289–298, 2010 [ABSTRACT FROM AUTHOR]

Sedimentologists recognize that development of a fine-resolution, truly three-dimensional analytical tool is essential if the internal structure of an opaque material is to be examined. This paper therefore seeks to: (i) test the viability of magnetic resonance imaging for sedimentological research; and (ii) investigate fine-sediment infiltration into gravel beds. The results of six experiments are analysed quantitatively using ImageJ post-processing software. Data indicate that magnetic resonance imaging-based measurements of particle axes and volumes are comparable with standard laboratory techniques. Furthermore, the technique permits visualization and analysis of differences in the pattern of fine-sediment infiltration (median particle diameter, d) into a framework of gravel (median particle diameter, D). Data clearly illustrate a siltation process for samples of D/ d = 34 and a sealing process for samples of D/ d = 7 where the seal is restricted to a depth equal to 2 D. This pore-scale visualization is valuable to the understanding of hydraulic–sediment–habitat interactions. [ABSTRACT FROM AUTHOR]

Organic photochromic molecules are well established as colorants in the manufacture of niche products, providing striking colour change effects when irradiated with light. This paper describes the industrially important classes of photochromic dye in terms of their development and chemistries, the applications in which their photochromism is employed commercially, and the technical features behind their success. Photochromic systems form the subject of much industrially funded research into nascent high-tech applications that have the potential to become the most commercially significant outlets for photochromic dyes. Those types being scrutinised are therefore also discussed along with the directions in which the industrial use of photochromic colorants may take. [ABSTRACT FROM AUTHOR]

This paper deals with the specific interaction of the dispersant 3,6,9-trioxadecanoic acid (TODA) with nano-ZrO2 surfaces. Special interest was directed towards degradation behavior of the adsorbates and its influence on dispersant capabilities of TODA regarding stabilization of ethanolic nano-ZrO2 suspensions. ZrO2 adsorption sites and the adsorbates formed are examined by diffuse reflectance infrared Fourier transform spectroscopy, thermal analysis, 1H-, and 13C-cross polarization magic angle spinning solid-state nuclear magnetic resonance spectroscopy. 1H as well as 13C-chemical shifts and the configurations of the corresponding adsorbed TODA species on zirconia sites are predicted by means of density functional theory quantum chemical calculations for supporting the interpretation of the experimental spectral data obtained. This work shows that combination of analytical and theoretical methods is an effective approach characterizing surface chemical properties of ceramic materials, determining sorption properties of organic process additives, investigating correspondent elementary and degradation reactions as well as clarifying cause-effect relationships in ceramic processes. [ABSTRACT FROM AUTHOR]

Two new polymorphs of N,N′-bis(2-acetylphenyl)ethanediamide, C18H16N2O4, are reported, one crystallizing in the space group P21/n, in the present paper, and one in P1¯ [Brewer, Jasinski, Butcher & Scheidt, (2007). Acta Cryst. E63, o4889]. In both structures, the 2- acetyl group is twisted slightly away from the plane of the benzene ring. In the present paper, this polymorph crystallizes with one-half of the molecule in the asymmetric unit, as the molecule lies on an inversion centre located at the centroid of the ethanamide system. The molecule adopts a trans ethanediamide (oxanilide) configuration, whereby the amide H atoms are bifurcated intramolecular hydrogen-bonding donors to oxamide and acetyl O atoms. The crystal packing is stabilized by intermolecular C—H⋯Cg packing interactions. [ABSTRACT FROM AUTHOR]

Two new polymorphs of N,N′-bis(2-acetylphenyl)ethanediamide, C18H16N2O4, are reported, one crystallizing in the space group P1¯, in the present paper, and one in P21/n [Brewer, Jasinski, Butcher & Scheidt (2007). Acta Cryst. E63, o4887-o4888]. In both structures, the 2-acetyl group is twisted slightly away from the plane of the benzene ring. In the present paper, this polymorph crystallizes with two half-molecules (A and B) in the asymmetric unit, each of which lies on an inversion center located at the centroid of an ethanediamide unit. The molecules adopt trans ethanediamide (oxanalide) configurations, whereby the amide H atoms are bifurcated intramolecular hydrogen-bonding donors to oxamine and acetyl O atoms. The crystal packing is stabilized by intermolecular C—H⋯O hydrogen-bond interactions. [ABSTRACT FROM AUTHOR]