Compounds with π(loc) → π*(deloc) electronic transitions and their solvatochromism

Molecular structures possessing atomic sites that contribute a non‐bonding electron pair to their π system (e.g. nitrogen atoms with sp² hybridization in pyrroles and anilines) usually exhibit a first absorption band whose solvatochromism is, surprisingly, sensitive only to the polarizability of the medium even though they are dipolar. As shown here, this solvatochromic behavior is a result of the first electronic transition in these compounds occurring from a substantially localized π orbital to a substantially delocalized π* orbital in the molecular structure. The high electronic delocalization present leads to a marked bathochromic band shift as the polarizability of the medium increases. It is especially relevant that this solvatochromism, which is because of the polarizability of the medium, explains the spectral shift that is only because of the redistribution of the electrons of the solvent molecules. It is important to take into account that this electronic redistribution happens instantaneously in this process. Copyright © 2015 John Wiley & Sons, Ltd.     

pH‐controlled reaction divergence of decarboxylation versus fragmentation in reactions of dihydroxyfumarate with glyoxylate and formaldehyde: parallels to biological pathways

The reactions of dihydroxyfumarate with glyoxylate and formaldehyde exhibit a unique pH‐controlled mechanistic divergence leading to different product suites by two distinct pathways. The divergent reactions proceed via a central intermediate (2,3‐dihydroxy‐oxalosuccinate, 3 , in the reaction with glyoxylate and 2‐hydroxy‐2‐hydroxymethyl‐3‐oxosuccinate, 14 , in the reaction with formaldehyde). At pH 7–8, products ( 7 , 8 , and 15 ) exclusively from a decarboxylation of the intermediate are observed, while at pH 13–14, products ( 9 , 10 , and 16 ) solely derived from a hydroxide‐promoted fragmentation of the intermediate are formed. The decarboxylative and fragmentation pathways are mutually exclusive and do not appear to coexist under the range of pH (7–14) conditions investigated. Herein, we employ a combination of quantitative ¹³C NMR measurements and density functional theory calculations to provide a rationale for this pH‐driven reaction divergence. These rationalizations also hold true for the reactions of dihydroxyfumarate produced in situ by the catalytic cyanide‐mediated dimerization of glyoxylate. In addition, the non‐enzymatic decarboxylation and fragmentation transformations of these central intermediates ( 3 and 14 ) appear to have intriguing parallels to the enzymatic reactions of oxalosuccinate and formation of glyceric acid derivatives in extant metabolism – the high and low pH mimicking the precise control exerted by the enzymes over reaction pathways. Copyright © 2016 John Wiley & Sons, Ltd.     

Substituent effects in the Diels–Alder reactions of butadienes,cyclopentadienes, furans and pyroles with maleic anhydride

In this study, activation energies in the Diels–Alder reactions of a series of substituted butadienes, cyclopentadienes, furans and pyroles with maleic anhydride were calculated by the M06‐2X/6‐31G(d) method. The substituent effects on the reactivity and the endo–exo selectivity have been examined. The strength of reactivity effect has an order of pyroles > furans > cyclopentadienes > butadienes, which is highly correlated with the lowest unoccupied molecular orbital energy, the electronic chemical potential and the electrophilicity of parent diene but relatively less correlated with the highest occupied molecular orbital energy and chemical hardness. The trend that an increase of necleophilicity caused by an electron‐donating group on the diene favors the endo TS is effective with C2 substitution. With C1 substitution, the trend is ambiguous or even opposite. Copyright © 2015 John Wiley & Sons, Ltd.     

Superexchange interaction in orbitally fluctuating RVO3

Changes in pressure and magnetic field in the orbital and magnetic ordering temperatures of RVO3 perovskites are reported; they reveal a competition between two magnetic orbitally ordered phases that have opposite preferences for the e-orbital component in the localized {3}T{1g} ground state of the V(3+) ion. This competition is shown to be biased by the VO{6/2} site distortion intrinsic to the orthorhombic structure. A remarkable enhancement of T{N} with pressure is found where the competition leads to enhanced orbital critical fluctuations.     

Micro‐Raman and stratigraphic studies of the paintings on the ‘Cembalo’ model musical instrument (A.D. 1650) and laser‐induced degradation of the detected pigments

Micro‐fragments of the painted part of the ‘Cembalo’ model by Michele Todini (1625–1689) are investigated. The technique used for painting the terracotta base was studied via the stratigraphic analyses. No background layer of inorganic materials, e.g. gypsum, was found. To prevent absorption effects due to the terracotta porosity, a very thin layer of proteinaceous material was probably used. The micro‐Raman analyses have revealed the use of pigments currently used in the post‐Renaissance period (lead white, indigo, yellow of iron hydroxide, gypsum, hematite and carbon black) mixed with a pigment, the Prussian blue, discovered in A.D . 1704. This raises the authenticity problem of the work of art, a problem analysed and discussed in presenting the history of the work of art, and after the pigment study. The presence of degraded lead white is recognized via the laser‐induced degradation of the irradiated material. The possibility of a restoring action of the painted parts, as opposite to the non‐originality of the work, is considered and discussed. Since most part of the investigated pigments shows laser‐induced effects, a careful study of this phenomenon is performed by using the modern counterparts of the ancient pigments. For different laser powers, the temperatures of the investigated zones have been obtained via the detailed balance principle and connected to the laser‐induced degradation effects. Copyright © 2007 John Wiley & Sons, Ltd.     

Effects of non‐extensive electrons on the sheath of dusty plasmas with variable dust charge

In this study, a detailed investigation of the problem of sheath is presented using the fluid model in a magnetized three‐component dusty plasma system comprising positive ions, dust grains with variable charge and q‐non‐extensive electrons (i.e., the electrons evolve far away from their Maxwellian thermodynamic equilibrium [q = 1]). The effects of q‐non‐extensivity parameter on the plasma sheath parameters are studied numerically. A significant change is observed in the quantities characterizing the sheath with the presence of the super‐extensive electrons (q < 1) and sub‐extensive electrons (q > 1). In addition, based on the orbital motion limited theory, by taking various forces acting on the dust particle into consideration, the dynamics of the dust located within the sheath, that is, the dust grain charging inside the sheath, is examined under different values of q. It is found that the q‐non‐extensivity has affected significantly the dynamics and the charging process of the dust grains in the sheath.     

Dynamics and Recovery of Genuine Multipartite Einstein–Podolsky–Rosen Steering and Genuine Multipartite Nonlocality for a Dissipative Dirac System via the Unruh Effect

The dynamics behaviors of genuine multipartite Einstein–Podolsky–Rosen steering (GMS) and genuine multipartite nonlocality (GMN) are investigated herein, and how the lost GMS and GMN under a mixed decoherence system can be recovered is explored. Explicitly, the decoherence system can be modeled by that a tripartite Werner‐type state suffers from the non‐Markovian regimes and one subsystem of the tripartite is under a non‐inertial frame. The conditions for steerable and nonlocal states can be obtained with respect to the tripartite Werner‐type state established initially. GMS and GMN are very fragile and vulnerable under the influence of the collective decoherence. GMS and GMN will vanish with growing intensity of the Unruh effect and the non‐Markovian reservoir. Besides, all achievable GMN's states are steerable, while not every steerable state (GMS's state) can achieve nonlocality. This means that the steering–nonlocality hierarchy is still tenable and GMN's states are a strict subset of the GMS's states in such a scenario. Subsequently, an available methodology to recover the damaged GMS and GMN is proposed. It turns out that the lost GMS and GMN can be effectively restored, and the ability of GMS and GMN to suppress the collective decoherence can be enhanced.     

In Vitro Evaluation of Non‐Protein Adsorbing Breast Cancer Theranostics Based on 19F‐Polymer Containing Nanoparticles

Eight fluorinated nanoparticles (NPs) are synthesized, loaded with doxorubicin (DOX), and evaluated as theranostic delivery platforms to breast cancer cells. The multifunctional NPs are formed by self‐assembly of either linear or star‐shaped amphiphilic block copolymers, with fluorinated segments incorporated in the hydrophilic corona of the carrier. The sizes of the NPs confirm that small circular NPs are formed. The release kinetics data of the particles reveals clear hydrophobic core dependence, with longer sustained release from particles with larger hydrophobic cores, suggesting that the DOX release from these carriers can be tailored. Viability assays and flow cytometry evaluation of the ratios of apoptosis/necrosis indicate that the materials are non‐toxic to breast cancer cells before DOX loading; however, they are very efficient, similar to free DOX, at killing cancer cells after drug encapsulation. Both flow cytometry and confocal microscopy confirm the cellular uptake of NPs and DOX‐NPs into breast cancer cells, and in vitro ¹⁹F‐MRI measurement shows that the fluorinated NPs have strong imaging signals, qualifying them as a potential in vivo contrast agent for ¹⁹F‐MRI.     

Ecofriendly Route for the Synthesis of Highly Conductive Graphene Using Extremophiles for Green Electronics and Bioscience

Highly conductive biocompatible graphene is synthesized using ecofriendly reduction of graphene oxide (GO). Two strains of non‐pathogenic extremophilic bacteria are used for reducing GO under both aerobic and anaerobic conditions. Degree of reduction and quality of bacterially reduced graphene oxide (BRGO) are monitored using UV–vis spectroscopy, X‐ray photoelectron spectroscopy, and Raman spectroscopy. Structural morphology and variation in thickness are characterized using electron microscopy and atomic force microscopy, respectively. Electrical measurements by three‐probe method reveal that the conductivity has increased by 10⁴–10⁵ fold from GO to BRGO. Biocompatibility assay using mouse fibroblast cell line shows that BRGO is non‐cytotoxic and has a tendency to support as well as enhance the cell growth under laboratory conditions. Hereby, a cost effective, non‐toxic bulk reduction of GO to biocompatible graphene for green electronics and bioscience application is achieved using halophilic extremophiles for the first time.     

Mechanism for the reactions of sulfides and sulfoxides with hypochlorites: racemization and oxygen exchange of oxysulfonium salts and sulfoxides

Density functional theory computations have been performed on the oxidations of sulfides and sulfoxides with hypochlorite ion (OCl^?), hypochlorous acid, and alkyl hypochlorites to study the mechanism of the reactions. The OCl^? anion transforms sulfides to sulfoxides and sulfoxides to sulfones in oxygen transfers. The oxygen atom of QOCl hypochlorites (Q = H, Me, t‐Bu) attacks at the sulfur atom of the substrates, and oxysulfonium cation intermediates are formed; the departure of the leaving Cl^? is catalyzed by soft Lewis acids. The structures of the early transition states are determined by highest occupied molecular orbital–lowest unoccupied molecular orbital interactions. The sulfur compounds are the electron acceptors in the reaction with OCl^?, but they are the electron donors in the reactions with QOCl. The attack of Cl^? at the oxygen atom of oxysulfonium cation intermediates leads to the sulfide and QOCl precursors and can result in racemization, oxygen exchange, and reduction of oxysulfonium salts in reversible reactions. The attack of Cl^? at the sulfur atom of oxysulfonium salts produces λ⁴‐sulfane intermediates. Oxysulfonium cations can be transformed into sulfoxide products with the attack of Cl^? or water at the α‐carbon atom of the O‐alkyl group. The attack of water at the sulfur atom of oxysulfonium cation leads to hydrolysis or oxygen exchange reactions. Racemization and oxygen exchange of sulfoxides proceeds in similar reactions, through the formation of hydroxysulfonium cation intermediates in acidic media in the presence of Cl^?. Chlorosulfonium cations are of very high energy; their intermediacy can be ruled out in the reactions of sulfides with hypochlorites. Copyright © 2012 John Wiley & Sons, Ltd.     

Nucleophilic reactivity of aniline derivatives towards the nitroso group

This study investigates the reactivity of the electrophilic nitroso group towards nucleophilic aniline derivatives from various nitrosating agents. A relationship between the rate of nitrosation and Edwards' nucleophilic parameter (E_n) is disclosed, indicative of a transition state that is mostly product‐like in nature with respect to cleavage of the nitroso bond in the nitrosating agent. A similar relationship based on the work of Marcus provides a considerably better explanation of the data. Through application of the Marcus equation, the free energy change of reaction is calculated for the nitrosation reactions studied, which in turn is applied to develop an equation linking the free energy of formation of a nitrosamine and its corresponding protonated amine. This equation accounts for the often‐observed Brønsted relationships in nitrosation reactions. The intrinsic barrier to reaction is estimated to be 10 kJ mol^?1, indicating that the main impedance to nitrosation arises from the unfavourable reaction thermodynamics. However, for the nitrosation of aniline derivatives substituted with π‐electron withdrawing groups, an unbalancing of the transition state results in an increased intrinsic barrier, of the order of 19 kJ mol^?1. For electronic‐effect aniline derivatives, a More O'Ferrall–Jencks diagram shows the nitrosation transition state to be synchronously well balanced between reactants and products. This diagram also confirms that the reaction follows a concerted mechanism. The nitrosation of resonance‐stabilised aniline derivatives is somewhat less synchronous, however, due to delocalisation of the lone electron pair on the amino group, induced by π electron withdrawing substituents. Transition states were located according to the theory of harmonic parabolic wells. The results of these calculations agreed with transition state locations predicted using linear free energy relationship techniques. A method is developed which approximates free energy profiles by treating the product and reactant free energy wells as harmonic parabola, while the free energy profile around the transition state is taken as the parabolic barrier to the product and reactant energy wells. Applying this technique, free energy profiles for electronic‐effect and resonance‐stabilised aniline nitrosation are predicted, utilising measured kinetic values and predicted thermodynamic properties. We couple the simulated free energy profiles with their corresponding More O'Ferrall–Jencks diagrams in order to elucidate the three‐dimensional reaction path traversed between reactants and products, in terms of both structure and energy. We also demonstrate that the nitrosonium ion behaves as a soft acid, and should therefore undergo covalent frontier‐orbital controlled bonding. Copyright © 2007 John Wiley & Sons, Ltd.     

The gravitomagnetic clock effect and its possible observation

The general relativistic gravitomagnetic clock effect involves a coupling between the orbital motion of a test particle and the rotation of the central mass and results in a difference in the proper periods of two counter–revolving satellites. It is shown that at ??(c^‐2) this effect has a simple analogue in the electromagnetic case. Moreover, in view of a possible measurement of the clock effect in the gravitational field of the Earth, we investigate the influence of some classical perturbing forces of the terrestrial space environment on the orbital motion of test bodies along opposite trajectories.     

A combined quantum mechanical and experimental approach towards chiral diketopiperazine hydroperoxides

In order to improve hydroperoxide formation from heterocyclic compounds relating to the formation rate and to allow a suitable choice of starting materials for autoxidation, theoretical studies on a set of different amino acid‐derived diketopiperazines and pyrazinoquinazolines were carried out. To estimate their reactivity towards hydroperoxide formation, bond dissociation enthalpies (BDEs) of tertiary α‐C? H bonds as well as reaction enthalpies to the corresponding hydroperoxides were calculated at the B3LYP/TZVP and RMP2/aug‐cc‐pVTZ level of theory. The Evans–Polanyi relation was then used to correlate substrate reactivity with calculated BDEs. Thermal and zero point vibrational energy (ZPE) corrections were determined in the classical harmonic oscillator‐rigid rotor‐particle in a box model. While for the investigated set of diketopiperazines BDEs of 318.8–327.0 kJ mol^?1 were found, BDEs for pyrazinoquinazolines spread between 248.4 and 368.4 kJ mol^?1 at the B3LYP/TZVP level of theory. A selected subset of heterocycles was converted to the corresponding hydroperoxides and the diketopiperazines were obtained in up to 39% yield after 5–7 days, whereas the pyrazinoquinazoline hydroperoxides were isolated in up to 67% yield after 24 h. Thus, replacing an amido moiety in an N‐aryl‐imino moiety when using pyrazinoquinazolines instead of diketopiperazines leads indeed to an improved captodative stabilization of the radical intermediate. Furthermore the theoretical calculations allowed a distinctive forecast of the preferred regioisomeric hydroperoxide. Copyright © 2010 John Wiley & Sons, Ltd.     

Fluctuation effects in disordered Peierls systems

We review the density of states (DOS) and related quantities of quasi one‐dimensional disordered Peierls systems in which fluctuation effects of a backscattering potential play a crucial role. The low‐energy behavior of non‐interacting fermions which are subject to a static random backscattering potential will be described by the strictly one‐dimensional fluctuating gap model (FGM). Recently, the FGM has also been used to explain the pseudogap phenomenon in high‐T_c superconductors. We develop a non‐perturbative method which allows for a simultaneous calculation of the DOS and inverse localization length for an arbitrary given disorder potential by solving a simple initial value problem. In the white noise limit, we recover all known results by solving a Fokker‐Planck equation. For the physically interesting case of finite correlation lengths, we use analytical and numerical methods to show that a complex order parameter leads to a suppression of the DOS, i.e. a pseudogap, and that for a real order parameter this pseudogap is overshadowed by a singularity in the DOS. We will also consider the case of classical phase fluctuations which applies to low temperatures where amplitude fluctuations are frozen out. For this regime we present analytic results for the DOS, the inverse localization length, the specific heat, and the Pauli susceptibility.     

Joined ellipsometry and voltametry investigation on the second discharge plateau in Ni(OH)2

The electrochemical properties of nickel hydroxide, produced via an electrodialysis process are studied by means of cyclic voltametry and in-situ ellipsometry methods. The Ni(OH)₂ electrodes are thin layers of nickel hydroxide powder deposited on a polished platinum substrate. Electrochemical and optical properties are investigated in a voltage domain including the so-called “second discharge process”. The reduction of nickel hydroxide proceeds at two successive potentials with a recovering of the initial optical data only after the second discharge step. The first discharge step leads to a nickel hydroxide not fully discharged while the second discharge step is coupled both to a sudden change in the nickel hydroxide properties and an agglomeration of particles phenomenon. Project financed by the E.U., program Brite Euram BRPR-CT97-0515 (NEARBY) Paper presented at the 7th Euroconference on Ionics, Calcatoggio, Corsica, France, Oct. 1–7, 2000.     

Identification of aerosol particle sources in semi‐rural area of Kwabenya,near Accra,Ghana, by EDXRF techniques

Small aerosol particles have for a long time been known to be harmful to humans, and are today regarded to cause a larger number of deaths than traffic accidents globally. Energy dispersive x‐ray fluorescence (EDXRF) is a well known method that has been used for identification of toxic as well as non‐toxic elements in the particles. The combination of elements will together with other information help to identify the sources and predict the effects of particles on environment and human health. The present work was conducted in Kwabenya, a suburb of the capital Accra of Ghana, which is frequently exposed to Harmattan dust from the Sahara–Sahel region. In total 171 filters each of PM2.5 and PM(2.5–10) were collected during 1 year. Levels of elements, black carbon (BC) and mass, were determined for both particle sizes. Principal component analysis (PCA) was performed on the datasets from Harmattan and non‐Harmattan periods. The daily average of PM10 was very high, 179 µg m^?3 and the BC contents were 4 µg m^?3. The presence of crustal elements was large in PM(2.5–10) as well as in PM2.5, and had a more than tenfold increase in PM(2.5–10) during the Harmattan period. Major characteristic elements for different sources were identified from correlation coefficients and regression analysis of the data. Sahara sand aerosol was the major source in both study periods, but influence from biomass burning, sea‐spray and metal industries was also observed. Copyright © 2009 John Wiley & Sons, Ltd.     

Sonochemical synthesis of hierarchical ZnO nanostructures

This work is about fabrication of ZnO nanostructures (ZnO-NS) via a simple sonochemical method. The chemicals used for the synthesis of various shaped ZnO are Zn salt, sodium hydroxide and ammonia solution without other structure directing agent or surfactant needed. This method is feasible and green, as it does not require high temperature and/or highly toxic chemicals. The shape of the ZnO-NS can be tuned by adjusting the ultrasound energy dissipated via varying the ultrasonication time from 5 to 60 min. It was found that uniform ZnO nanorods with diameter around 50 nm were formed after 15 min of ultrasonication while flowerlike ZnO-NS was formed after 30 min. This method produces high quality ZnO-NS with controllable shapes, uniformity, and purity.     

Instabilities of a Fermi Gas with Nested Fermi Surfaces

The nesting of the Fermi surfaces of an electron and a hole pocket separated by a vector Q commensurate with the lattice in conjunction with the interaction between the quasiparticles can give rise to a rich phase diagram. Of particular importance is itinerant antiferromagnetic order in the context of pnictides and heavy fermion compounds. By mismatching the nesting the order can gradually be suppressed and as the Néel temperature tends to zero a quantum critical point is obtained. A superconducting dome above the quantum critical point can be induced by the transfer of pairs of electrons between the pockets. The conditions under which such a dome arises are studied. In addition numerous other phases may arise, e.g. charge density waves, non‐Fermi liquid behavior, non‐s‐wave superconductivity, Pomeranchuk instabilities of the Fermi surface, nematic order, and phases with persistent orbital currents.     

On the Eigen‐Mode Excitation of Linear Oscillators and the Earth's Polar Motion

By transforming a 1D second‐order linear oscillator into a 2D first‐order polar motion differential equation, it can be shown that the finite smoothness (i.e., the presence of jump in finite order derivatives) of the applied Newtonian forcing constitutes the sufficient and necessary condition for instantaneous excitation of free eigen‐mode. This condition can be met by forcing functions originated from turbulent and multiphase fluid motions. Sub‐macroscopic transition time associated with astatic elastic deformation limits the physical smoothness of the applied forcing for the Earth's polar motion. Eigen‐modes can also be excited by an infinitely smooth forcing that has a finite domain of non‐zero values. The eigen‐period serves as a macroscopic timescale to characterize the inertia of a linear oscillator. If a zero mean irregular forcing of finite smoothness exhibits a high degree of randomness and the timescale is much shorter than the eigen‐period, then for negligible damping the eigen‐waveform will increase in proportion to the squareroot of time, while the waveform distortion is statistically a constant. As a result, the pattern of distinctive eigen‐oscillation will dominate the forced solution for longer enough duration.