A case study of the Hirsch index for 26 non‐prominent physicists

The h index was introduced by Hirsch to quantify an individual's scientific research output. It has been widely used in different fields to show the relevance of the research work of prominent scientists. I have worked out 26 practical cases of physicists which are not so prominent. Therefore this case study should be more relevant to discuss various features of the Hirsch index which are interesting or disturbing or both for the more average situation. In particular, I investigate quantitatively some pitfalls in the evaluation and the influence of self‐citations.     

Twenty Hirsch index variants and other indicators giving more or less preference to highly cited papers

The Hirsch index or h‐index is widely used to quantify the impact of an individual's scientific research output, determining the highest number h of a scientist's papers that received at least h citations. Several variants of the index have been proposed in order to give more or less preference to highly cited papers. I analyse the citation records of 26 physicists discussing various suggestions, in particular A, e, f, g, h(2), h_w, hT, ?, m, π, R, s, t, w, and maxprod. The total number of all and of all cited publications as well as the highest and the average number of citations are also compared. Advantages and disadvantages of these indices and indicators are discussed. Correlation coefficients are determined quantifying which indices and indicators yield similar and which yield more deviating rankings of the 26 datasets. For 6 datasets the determination of the indices and indicators is visualized.     

Self‐doping PPV oligomers – electrochemistry and structure of the self‐doped systems

A novel class of self‐doping conjugated oligomers, E,E‐2‐(sulfoalkoxy)‐5‐alkoxy‐1,4‐bis[2‐(2,4,6‐trimethoxyphenyl) ethenyl]benzenes, is presented. The synthesis and spectroscopic characterisation of five such oligomers are described, and an electrochemical analysis using cyclic voltammetry is performed to determine the anodic peak potentials. A structural study is performed on six self‐doping oligomers in which the structures and energies of the possible mono‐molecular forms of the electrically conducting doped material are described and evaluated using Hirshfeld charges and the Quantum Theory of Atoms In Molecules. Copyright © 2009 John Wiley & Sons, Ltd.     

Developing self‐mixing interferometry for instrumentation and measurements

In this review, self‐mixing interferometry (SMI), a new configuration of interferometry, is discussed. SMI has practical advantages compared to standard interferometry, for example SMI does not require any optical part external to the laser chip and can be employed in a variety of measurements. Applications range from the traditional measurements related to optical pathlength – like displacement, small‐amplitude vibrations, velocity – to sensing of weak optical echoes – for return loss and isolation factor measurements, CD readout and scroll sensing – and also, a special feature because of the interaction with the medium, measurements of physical parameters, like the laser linewidth, coherence length, and the alfa factor. Because it is also a coherent detection scheme, the SMI works close to the quantum limit of the received field, typically ‐90 dBm, so that minimum detectable amplitudes of 100 pm/ √Hz are currently achieved upon operation on diffusive targets, whereas a corner cube allows half‐wavelength counting mode – or 0.5 μm resolution – on a dynamic range up to 2 m and more. With its compact setup, the SMI is easy to deploy in the field and can interface a variety of experiments – from MEMS testing to rotating machines vibration testing to pickup of biological motility. The illustration shows a double‐channel, differential SMI incorporated in a thermomechanical test equipment to trace the mechanical hysteresis cycle of the beads of a motor‐engine brake.     

Evaluation of the scientific impact,productivity and biological age based upon the h‐index in three Latin American countries: the materials science case

We discuss the scientific impact of Latin American scientists in the field of materials science. The analysis is based on the h‐index as the scientometric index used to quantify the scientific productivity of an individual. In particular, we focus our analysis in México, Chile and Colombia. We compare the level of productivity between all these countries. We also analyzed the h‐index as function of the biological age, by using the first year of publication of a given scientists as a reference and discussed the general distribution of its quantification. We do not find a clear relationship between these two quantities. Based in our results we propose some political measures that these countries could implement to improve productivity as well as scientific development in this field.     

The photochemistry of the self‐healing chromophore Disperse Orange 11

Recent interest in the self‐healing ability of the laser dye 1‐amino‐2‐methylanthraquinone, Disperse Orange 11, has lead us to investigate the possible alternative mechanisms of action, either intramolecular proton transfer (PT) or twisted intramolecular charge transfer (TICT) formation. AMPAC semiempirical PM3 CI (all single excited configurations) potential energy surfaces searches have been conducted with either reaction mechanism. Based purely on the potential energy surface results, no state, S0, T1, or S1, seems especially likely to be kinetically favorable for PT. The T1 state is favorable thermodynamically for PT. However, the S1 state TICT reaction is both thermodynamically favorable and kinetically preferred over all PT reactions. There is also a favorable T1 TICT reaction, but much slower kinetically on the triplet surface than S1 TICT. The Wentzel–Kramers–Brillouin (WKB) method has been used to ascertain proton tunneling contributions to PT. Even with proton tunneling, S1 TICT is still more highly favored, though proton tunneling could make the T1 PT reaction competitive depending on the rate of intersystem crossing. We also examine spectroscopic properties of PT transfer and TICT reaction path entities in comparison with published experimental evidence. However, this comparison leads to ambiguous findings that suggest that electronic spectral properties alone will not fully clarify the mechanism. Overall, results suggest that the TICT mechanism is the most likely for optical damage and self‐repair for Disperse Orange 11, and might be considered for the damage and repair mechanisms for other organic solid state laser materials. Copyright © 2012 John Wiley & Sons, Ltd.     

The effect of self‐consistent potentials on EXAFS analysis

A theory program intended for use with extended X‐ray‐absorption fine structure (EXAFS) spectroscopy and based on the popular FEFF8 is presented. It provides an application programming interface designed to make it easy to integrate high‐quality theory into EXAFS analysis software. This new code is then used to examine the impact of self‐consistent scattering potentials on EXAFS data analysis by methodical testing of theoretical fitting standards against a curated suite of measured EXAFS data. For each data set, the results of a fit are compared using a well characterized structural model and theoretical fitting standards computed both with and without self‐consistent potentials. It is demonstrated that the use of self‐consistent potentials has scant impact on the results of the EXAFS analysis.     

The self‐energy of the uniform electron gas in the second order of exchange

The on‐shell self‐energy of the homogeneous electron gas in second order of exchange, Σ_2x = Re Σ_2x (k_F, k² _F/2), is given by a certain integral. This integral is treated here in a similar way as Onsager, Mittag, and Stephen [Ann. Physik (Leipzig) 18 , 71 (1966)] have obtained their famous analytical expression e_2x = (in atomic units) for the correlation energy in second order of exchange. Here it is shown that the result for the corresponding on‐shell self‐energy is Σ_2x = e_2x. The off‐shell self‐energy Σ_2x (k, o) correctly yields 2e_2x (the potential component of e_2x) through the Galitskii‐Migdal formula. The quantities e_2x and Σ_2x appear in the high‐density limit of the Hugenholtz‐van Hove (Luttinger‐Ward) theorem.     

Analysis of self‐repair mechanisms of Phaseolus vulgaris var. saxa using near‐infrared surface‐enhanced Raman spectroscopy

We used surface‐enhanced Raman spectroscopy (SERS) to investigate ultrastructural changes in cell‐wall composition during the self‐repair of lacerated hypocotyls of Phaseolus vulgaris var. saxa. A detailed study of self‐repair mechanisms requires localized information about cell‐wall structure and morphology in addition to the chemical cell‐wall composition. Characteristic Raman and SER spectra yielded two‐dimensional maps of cross sections of P. vulgaris var. saxa visualizing chemical compositions in the walls of different cell types and during various repair phases. SERS substrate particles were produced by the reduction of gold chloride on the plant tissue surface and characterized with absorption spectroscopy, scanning electron microscopy and energy‐dispersive X‐ray spectroscopy. The SERS results were compared with stained cross sections of the same plant using dark‐field microscopy with focus on lignin and suberin contents in repairing cells. In addition, SERS measurements revealed Au cyanide compounds on the cell surface, indicating the formation of hydrogen cyanide during the self‐repair phase. Copyright © 2009 John Wiley & Sons, Ltd.     

Interaction of a relativistic dense electron beam with a laser wiggler in a vacuum: self‐field effects on the electron orbits and free‐electron laser gain

Employing laser wigglers and accelerators provides the potential to dramatically cut the size and cost of X‐ray light sources. Owing to recent technological developments in the production of high‐brilliance electron beams and high‐power laser pulses, it is now conceivable to make steps toward the practical realisation of laser‐pumped X‐ray free‐electron lasers (FELs). In this regard, here the head‐on collision of a relativistic dense electron beam with a linearly polarized laser pulse as a wiggler is studied, in which the laser wiggler can be realised using a conventional quantum laser. In addition, an external guide magnetic field is employed to confine the electron beam against self‐fields, therefore improving the FEL operation. Conditions allowing such an operating regime are presented and its relevant validity checked using a set of general scaling formulae. Rigorous analytical solutions of the dynamic equations are provided. These solutions are verified by performing calculations using the derived solutions and well known Runge–Kutta procedure to simulate the electron trajectories. The effects of self‐fields on the FEL gain in this configuration are estimated. Numerical calculations indicate that in the presence of self‐fields the sensitivity of the gain increases in the vicinity of resonance regions. Besides, diamagnetic and paramagnetic effects of the wiggler‐induced self‐magnetic field cause gain decrement and enhancement for different electron orbits, while these diamagnetic and paramagnetic effects increase with increasing beam density. The results are compared with findings of planar magnetostatic wiggler FELs.     

Immobilization of galactose oxidase on self‐assembled monolayers of thiols on Au and Ag surfaces

Galactose oxidase (GalOD) was immobilized on self‐assembled monolayers of thiols on silver and gold surfaces using trans‐stilbene (4,4′‐diisothiocyanate)‐2,2′disulphonic acid (DIDS) as the bridging compound. DIDS is the symmetrical bifunctional reagent that reacted with the amine moiety of the thiol and with primary amino groups of enzyme. The Raman measurement revealed that onto cysteamine‐modified silver and gold electrodes, bands corresponding to the galactose oxidase (about 694, 1076, 1274 cm^—1 on Au and 762, 1058, 1274 cm^–1 on Ag ) appeared and clearly demonstrated its immobilization onto Au and Ag surfaces. Simultaneously, we have also observed changes in the ratio of trans–gauche conformers of adsorbed cysteamine molecules. Layers revealing high content of trans conformer are transformed into layers composed mainly of cysteamine molecule in gauche conformation after galactose oxidase adsorption. These observations deliver a strong support for enzyme immobilization on cysteamine‐modified gold and silver surfaces. The surface plasmon resonance experiment gave a surface coverage of ~8.4 × 10⁷ g/cm² for gold electrode modified cysteamine using DIDS chemistry and 1.1 × 10⁷ g/cm² for the cysteamine only modified gold substrate and demonstrated that galactose oxidase layers immobilized with DIDS coupling reagent are quite stable and cannot be easily removed from the surface by treatment with a buffer solution. The surface plasmon resonance results indicated that in this method, a multilayer of galactose oxidase have been immobilized. Our new method of covalent attachment of enzymes seems to be quite promising as a new way of manufacturing biosensors. Copyright © 2012 John Wiley & Sons, Ltd.     

Effect of solvent evaporation on the self‐assembly of poly(3‐hexylthiophene‐2,5‐diyl) and on the film morphology during electrospray deposition

A high‐voltage rectangular pulse was applied to the electro‐spray deposition (ESD) to control the evaporation‐induced self‐assembly of poly(3‐hexylthiophene‐2,5‐diyl) (P3HT). Two groups of P3HT thin films were deposited by a series of high‐voltage rectangular pulses. Compared with the ESD driven by a constant voltage, the pulse‐driven ESD enables to probe the effect of solvent evaporation on the self‐assembly of P3HT molecules. The droplet size and the evaporation of residual solvent in the droplet determine the film morphology. Ultraviolet–visible absorption spectroscopy was used to identify the ordering of P3HT molecules in the films. The self‐assembly of P3HT molecules took place during the solvent evaporation which can be controlled by a combination of the pulse amplitude and the pulse interval. With an appropriate combination of the amplitude and the interval, the ESD produced a P3HT thin film with high chain ordering.

     

Correction method for the self‐absorption effects in fluorescence extended X‐ray absorption fine structure on multilayer samples

A novel correction method for self‐absorption effects is proposed for extended X‐ray absorption fine structure (EXAFS) detected in the fluorescence mode on multilayer samples. The effects of refraction and multiple reflection at the interfaces are fully considered in this correction method. The correction is performed in k‐space before any further data analysis, and it can be applied to single‐layer or multilayer samples with flat surfaces and without thickness limit when the model parameters for the samples are known. The validity of this method is verified by the fluorescence EXAFS data collected for a Cr/C multilayer sample measured at different experimental geometries.     

The generalized SIC‐OEP formalism and the generalized SIC‐Slater approximation (stationary and time‐dependent cases)

We present a generalized formulation of the Optimized Effective Potential (OEP) approach to the Self Interaction Correction (SIC) problem in Time Dependent (TD) Density Functional Theory (DFT). The formulation relies on the introduction of a double set of single electron orbitals. It allows the derivation of a generalized Slater approximation to the full OEP formulation, which extends the domain of validity of the standard Slater approximation. We discuss both formal aspects and practical applications of the new formalism and give illustrations in cluster and molecules. The new formalism provides a valuable ansatz to more elaborate (and computationally very demanding) full TD OEP and full TD SIC calculations especially in the linear domain.     

Substrate effects on photophysical properties of fluorescent self‐assembled monolayers (SAMs)

Substrate materials play an important role to modulate the photophysical properties of fluorescent self‐assembled monolayers (SAMs) constructed on them. The substrate–fluorophore interactions in fluorescent SAMs can affect their fluorescence intensity. Hence, it is important to take into account such alteration of fluorescence properties and study the underlying mechanisms. In this brief overview, substrate effects on fluorescence properties of chemisorbed or physisorbed fluorescent SAMs on two‐dimensional (chips) and three‐dimensional (nanoparticles) surfaces are highlighted. Examples of fluorescence quenching and enhancement on various substrate materials by different factors are discussed and analyzed. Additionally, some strategies to limit metallic substrate–fluorophore interactions are discussed briefly. Copyright © 2016 John Wiley & Sons, Ltd.     

Using magnetic levitation for 2D and 3D self‐assembly of cubic silicon macroparticles

Today's micro‐ and nano‐fabrication is essentially two‐dimensional, with very limited possibilities of accessing the third dimension. The most viable way to mass‐fabricate functional structures at the nano‐scale, such as electronics or MEMS, with equal feature sizes in all directions, is by three‐dimensional self‐assembly. Up to now, three‐dimensional self‐assembly has mainly been restricted to crystals of polymer spheres. We report on two‐ and three‐dimensional self‐assembly of silicon cubes, levitated in a paramagnetic fluid. We demonstrate the benefits of templating and study the effect of a change in hydrophilicity of the cubes. These experiments bring us one step closer to three‐dimensional self‐assembly of anisotropic, semiconducting units, which is a crucial milestone in overcoming the scaling limits imposed by contemporary 2D microfabrication.

     

Electron‐counting rules,three‐dimensional aromaticity,and the boundaries of the Periodic Table

To describe aromaticity of planar and three‐dimensional molecules, different electron counting rules are employed. Here, the relationship between the Hückel 4n + 2 rule and the Hirsch 2(n + 1)² rule is established based on formal approach considering the electrons as objects in an arbitrary n‐dimensional space of states. Two types of three‐dimensional aromaticity, referred to as ‘spherical’ (following the 4n + 2 electron counting rule) and ‘spatial’ (following the 2(n + 1)² electron counting rule) are distinguished. A conclusion concerning the boundaries of the Periodic Table of Elements is made based on the same formal approach that no g‐ (or higher) elements can exist and that possible extension of the Periodic Table beyond the seventh period must be followed by filling of the 8p or inner 6f or 7d levels. Copyright © 2011 John Wiley & Sons, Ltd.     

Theoretical model for the effect of dust grains on self‐filamentation of a gaussian electromagnetic beam in a fully ionized plasma

A theoretical model for the effect of dust grains on the self‐filamentation of a Gaussian electromagnetic beam propagating in a fully ionized plasma has been developed by employing the energy balance of the plasma constituents, perturbed electron and ion concentrations, and temperature. In this model, neutral atom ionization, re‐integration and accumulation of electrons and ions, photoelectric emission of electrons from the surface of dust grains, as well as elastic and charging collisions have also been considered. The effective dielectric constant in the presence of dust grains has been constructed. The effect of temporal growth of dust grains on various plasma parameters for different values of the dust density has been explored. The variation of the beam width with the normalized channel of propagation has been observed for distinct dust densities and dust charge states. It is observed that the non‐linearity induced by the effective dielectric constant in the presence of dust grains increases the self‐filamentation of the beam, thus enhancing the effective critical power with the dust density. Some of the outcomes of our approach are in line with experimental observations. These outcomes may be useful for explaining space and laboratory plasma experiments as well as for future studies in complex plasmas.     

Downward self‐polarization of lead‐free (K0.5Na0.5)(Mn0.005Nb0.995)O3 ferroelectric thin films on Nb:SrTiO3 substrate

Spontaneously appearing macroscopic polarization (self‐polarization) in ferroelectrics without an electrode or an external electric field would enable the freedom to design many ferroelectric heterostructures and devices. The (K_0.5Na_0.5)(Mn_0.005Nb_0.995)O₃ (KNMN) thin film was grown on Nb:SrTiO₃ single‐crystal substrate and the resultant self‐polarization behavior due to strain relaxation was investigated. The lattice mismatch and difference in TEC between the KNMN thin film and the Nb:SrTiO₃ substrate creates a compressive strain. The compressive strain gradient may be the main cause for the observed downward self‐polarization. The downward self‐polarization of the KNMN thin film can be explained by the strong inhomogeneous compressive strain caused by strain relaxation. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

4‐Phenyl‐1,2,4‐triazoline‐3,5‐dione in the ene reactions with cyclohexene, 1‐hexene and 2,3‐dimethyl‐2‐butene. The heat of reaction and the influence of temperature and pressure on the reaction rate

The values of the enthalpy (53.3; 51.3; 20.0 kJ mol^?1), entropy (?106; ?122; ?144 J mol^?1K^?1), and volume of activation (?29.1; ?31.0; ?cm³ mol^?1), the reaction volume (?25.0; ?26.6; ?cm³ mol^?1) and reaction enthalpy (?155.9; ?158.2; ?150.2 kJ mol^?1) have been obtained for the first time for the ene reactions of 4‐phenyl‐1,2,4‐triazoline‐3,5‐dione 1 , with cyclohexene 4 , 1‐hexene 6 , and with 2,3‐dimethyl‐2‐butene 8 , respectively. The ratio of the values of the activation volume to the reaction volume (?V^≠_corr/ΔV_{r ? n}) in the ene reactions under study, 1 + 4 → 5 and 1 + 6 → 7 , appeared to be the same, namely 1.16. The large negative values of the entropy and the volume of activation of studied reactions 1 + 4 → 5 and 1 + 6 → 7 better correspond to the cyclic structure of the activated complex at the stage determining the reaction rate. The equilibrium constants of these ene reactions can be estimated as exceeding 10¹⁸ L mol^?1, and these reactions can be considered irreversible. Copyright © 2014 John Wiley & Sons, Ltd.