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The objective of this work was to investigate the influence of hydrogen bonds between fibres on static and dynamic strength properties of paper. A commercial bleached pinewood kraft pulp was soaked in water, refined in a PFI, and used to form paper webs in different solvents, such as water, methanol, ethanol, n-propanol and n-butanol, to determine the effect of their dipole moment on static and dynamic strength properties of resulting paper sheets. Paper which was formed in water, being the solvent of the highest dipole moment among the tested ones, showed the highest breaking length and tear resistance. When paper webs were formed in n-butanol, which was the least polar among the solvents, these parameters were reduced by around 75%. These results provide evidence of the importance of water in paper web formation and strong impact of hydrogen bonds between fibres on strength properties of paper. [ABSTRACT FROM AUTHOR]

Microbial fuel cells (MFCs) can evolve in a viable technology if environmentally sound materials are developed and became available at low cost for these devices. This is especially important not only for the designing of large wastewater treatment systems, but also for the fabrication of low-cost, single-use devices. In this work we synthesized membranes by a simple procedure involving easily-biodegradable and economic materials such as poly (vinyl alcohol) (PVA), chitosan (CS) and the composite PVA:CS. Membranes were chemical and physically characterized and compared to Nafion®. Performance was studied using the membrane as separator in a typical H-Type MFCs showing that PVA:CS membrane outperform Nafion® 4 times (power production) while being 75 times more economic. We found that performance in MFC depends over interactions among several membrane characteristics such as oxygen permeability and ion conductivity. Moreover, we design a paper-based micro-scale MFC, which was used as a toxicity assay using 16 μL samples containing formaldehyde as a model toxicant. The PVA:CS membrane presented here can offer low environmental impact and become a very interesting option for point of need single-use analytical devices, especially in low-income countries where burning is used as disposal method, and toxic fluoride fumes (from Nafion®) can be released to the environment. [ABSTRACT FROM AUTHOR]

Analysis of cultural heritage samples by PIXE involves the risk of damaging precious samples due to MeV-proton irradiation. To investigate appropriate methods to detect invisible damage due to PIXE analysis, we analyzed the change in chemical bonding of the sample surface subjected to PIXE and RBS measurement by Fourier Transform InfraRed spectroscopy (FT-IR). We used Japanese hemp paper as a simulated cultural property sample. The proton irradiation for the PIXE/RBS measurement was performed in a vacuum with an incident beam energy of 2.5 MeV, a beam current of 1 nA, and an irradiation time up to 10 min. The corresponding beam flux and fluence were 0.06 nA/mm2 and 4 μ Coulomb/cm2, respectively. When the irradiation time was 10 min, the absorbed dose was 480 kGy on the sample surface. We identified neither change of elemental composition nor visible change such as discoloration due to irradiation. However, we found changes in peak heights in the measured FT-IR spectra, which suggest the destruction of chemical bonds such as O–H and C–O due to proton-induced radiation damage. [ABSTRACT FROM AUTHOR]

For a period of several years the philosopher of science Hasok Chang has promoted various inter-related views including pluralism, pragmatism, and an associated view of natural kinds. He has also argued for what he calls the persistence of everyday terms in the scientific view. Chang claims that terms like phlogiston were never truly abandoned but became transformed into different concepts that remain useful. On the other hand, Chang argues that some scientific terms such as acidity have suffered a form of "rupture", especially in the case of the modern Lewis definition of acids. Chang also complains that the degree of acidity of a Lewis acid cannot be measured using a pH meter and seems to regard this as a serious problem. The present paper examines some of these views, especially what Chang claims to be a rupture in the definition of acidity. It is suggested that there has been no such rupture but a genuine generalization, on moving from the Brønsted-Lowry theory to the Lewis theory of acidity. It will be shown how the quantification and measurement of Lewis acidity can easily be realized through the use of equilibrium theory and the use of stability constants. [ABSTRACT FROM AUTHOR]

In this paper, a range of sputtered ternary and quaternary (Si)(Ge)As x Te 3 layers (x: 2 or 5) and (Si)(Ge)As 2 Se 3 layers are examined using Raman spectroscopy. The results are linked to the Ovonic Threshold Switching properties of these materials when incorporated in selector devices, as observed in separate studies. In case of both the As-rich and As-poor tellurides, a large amount of homopolar bonds are present as the spectra are dominated by peaks associated with As–As and Te–Te bonds. Such homopolar bonds are commonly linked with drift in OTS properties. In the case of the selenides the spectra are dominated by modes associated with heteropolar As–Se bond vibrations. Adding Ge as an alloying element has a significant impact on the bond structure for both material systems. In contrast, Si has a much less pronounced impact and will mostly bond with itself. Time-resolved Raman measurements were also performed to determine the stability of the layers under micro-Raman laser excitation. At the regular exposure settings, no significant changes in the spectra were observed during the measurement. At elevated exposure settings, however, persistent changes in the bond structure can be induced for certain compositions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Broadband absorption of SiAlON films caused by chemical intermixing. • One-step magnetron co-sputtering method for fabricating SiAlON films. • Alterable IR optical properties based upon tunable compositions. • Flexible optical constants/absorbing bands that enables IR absorbers optimization. Broadband infrared absorbers have been intensively developed in recent decades due to their wide range of applications. Current infrared absorbers usually adapt complicated photonic designs to meet increasing demands, since natural infrared material (e.g., dielectrics, polymers, and metals) can hardly realize broadband and spectrally selective absorption simultaneously. In this paper, a novel infrared absorbing composite SiAlON is proposed and successfully fabricated by co-sputtering Si 3 N 4 and AlN. Its wide-band absorption characteristics across through 8 to 16 μm can be tuned simply via adjusting its deposition conditions. The corresponding optical and composition analyses confirm that the broadband features with spectral selectivity are attributed to chemical composition control and the chemical bonding state tunability. This work extends the bandwidth and improves the absorbing flexibility of single material, making a step forward to develop broadband infrared absorbers with simpler structure. [ABSTRACT FROM AUTHOR]

The paper collects the answers of the authors to the following questions:Is the lack of precision in the definition of many chemical concepts one of the reasons for the coexistence of many partition schemes?Does the adoption of a given partition scheme imply a set of more precise definitions of the underlying chemical concepts?How can one use the results of a partition scheme to improve the clarity of definitions of concepts?Are partition schemes subject to scientific Darwinism? If so, what is the influence of a community's sociological pressure in the "natural selection" process?To what extent does/can/should investigated systems influence the choice of a particular partition scheme?Do we need more focused chemical validation of Energy Decomposition Analysis (EDA) methodology and descriptors/terms in general?Is there any interest in developing common benchmarks and test sets for cross‐validation of methods?Is it possible to contemplate a unified partition scheme (let us call it the "standard model" of partitioning), that is proper for all applications in chemistry, in the foreseeable future or even in principle?In the end, science is about experiments and the real world. Can one, therefore, use any experiment or experimental data be used to favor one partition scheme over another? © 2019 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Sigma factors are key proteins that mediate the recruitment of RNA polymerase to the promoter regions of genes, for the initiation of bacterial transcription. Multiple sigma factors in a bacterium selectively recognize their cognate promoter sequences, thereby inducing the expression of their own regulons. In this paper, we report the crystal structure of the σ4 domain of Bacillus subtilis SigW bound to the -35 promoter element. Purine-specific hydrogen bonds of the -35 promoter element with the recognition helix α9 of the σ4 domain occurs at three nucleotides of the consensus sequence (G-35, A-34, and G’-31 in G-35A-34A-33A-32C-31C-30T-29). The hydrogen bonds of the backbone with the α7 and α8 of the σ4 domain occurs at G’-30. These results elucidate the structural basis of the selective recognition of the promoter by SigW. In addition, comparison of SigW structures complexed with the -35 promoter element or with anti-sigma RsiW reveals that DNA recognition and anti-sigma factor binding of SigW are mutually exclusive. [ABSTRACT FROM AUTHOR]

Our understanding of how chromosomes structurally organize and dynamically interact has been revolutionized through the lens of long-chain polymer physics. Major protein contributors to chromosome structure and dynamics are condensin and cohesin that stochastically generate loops within and between chains, and entrap proximal strands of sister chromatids. In this paper, we explore the ability of transient, protein-mediated, gene-gene crosslinks to induce clusters of genes, thereby dynamic architecture, within the highly repeated ribosomal DNA that comprises the nucleolus of budding yeast. We implement three approaches: live cell microscopy; computational modeling of the full genome during G1 in budding yeast, exploring four decades of timescales for transient crosslinks between 5kbp domains (genes) in the nucleolus on Chromosome XII; and, temporal network models with automated community (cluster) detection algorithms applied to the full range of 4D modeling datasets. The data analysis tools detect and track gene clusters, their size, number, persistence time, and their plasticity (deformation). Of biological significance, our analysis reveals an optimal mean crosslink lifetime that promotes pairwise and cluster gene interactions through “flexible” clustering. In this state, large gene clusters self-assemble yet frequently interact (merge and separate), marked by gene exchanges between clusters, which in turn maximizes global gene interactions in the nucleolus. This regime stands between two limiting cases each with far less global gene interactions: with shorter crosslink lifetimes, “rigid” clustering emerges with clusters that interact infrequently; with longer crosslink lifetimes, there is a dissolution of clusters. These observations are compared with imaging experiments on a normal yeast strain and two condensin-modified mutant cell strains. We apply the same image analysis pipeline to the experimental and simulated datasets, providing support for the modeling predictions. [ABSTRACT FROM AUTHOR]

Growing demands of material science and, in particular, in the field of nonlinear optics (NLO) encourage us to look for stable highly polarizable molecules with excess diffuse electrons. An unusual class of compounds called electrides comply with these requirements. Many attempts have been made, yet only few electrides have been synthesized as solids and none of them as molecular species. In this paper, a new theoretically designed molecular species with electride characteristics is reported. The idea of this molecular electride comes from the formation of electride‐like features in the MgO crystal with defect F‐centers. The geometry of the investigated molecule can be described as a Mg4O4 cube with one oxygen atom removed. In Mg4O3, two 3s electrons are pushed out from the inner area of the molecule forming a diffuse electride multicentered bond. Our calculations show that this electride‐like cluster possesses a noticeably large first hyperpolarizability β=5733 au. At the same time, a complete cube Mg4O4 and Mg4O32+ without electride electron pair have much smaller β: 0 au and 741 au, respectively. This fact indicates the decisive role of the electride electron pair in NLO properties. Additionally, vertical detachment energies of isomers (VDE), excitation energies ΔE, polarizabilities α, and IR spectra were calculated. These properties, including β, are supposed to be observable experimentally and can serve as indirect evidence of the stable molecular electride formation. Elusive electride: Many attempts have been made, yet only few electrides have been synthesized as solids and none of them as molecular species. A theoretically designed molecular species with electride characteristics is reported based on the idea of formation of electride‐like features in MgO crystals with defect F‐centers. [ABSTRACT FROM AUTHOR]

Bacteria contain several nucleoid-associated proteins that organize their genomic DNA into the nucleoid by bending, wrapping or bridging DNA. The Histone-like Nucleoid Structuring protein H-NS found in many Gram-negative bacteria is a DNA bridging protein and can structure DNA by binding to two separate DNA duplexes or to adjacent sites on the same duplex, depending on external conditions. Several nucleotide sequences have been identified to which H-NS binds with high affinity, indicating H-NS prefers AT-rich DNA. To date, highly detailed structural information of the H-NS DNA complex remains elusive. Molecular simulation can complement experiments by modelling structures and their time evolution in atomistic detail. In this paper we report an exploration of the different binding modes of H-NS to a high affinity nucleotide sequence and an estimate of the associated rate constant. By means of molecular dynamics simulations, we identified three types of binding for H-NS to AT-rich DNA. To further sample the transitions between these binding modes, we performed Replica Exchange Transition Interface Sampling, providing predictions of the mechanism and rate constant of H-NS binding to DNA. H-NS interacts with the DNA through a conserved QGR motif, aided by a conserved arginine at position 93. The QGR motif interacts first with phosphate groups, followed by the formation of hydrogen bonds between acceptors in the DNA minor groove and the sidechains of either Q112 or R114. After R114 inserts into the minor groove, the rest of the QGR motif follows. Full insertion of the QGR motif in the minor groove is stable over several tens of nanoseconds, and involves hydrogen bonds between the bases and both backbone and sidechains of the QGR motif. The rate constant for the process of H-NS binding to AT-rich DNA resulting in full insertion of the QGR motif is in the order of 106 M−1s−1, which is rate limiting compared to the non-specific association of H-NS to the DNA backbone at a rate of 108 M−1s−1. [ABSTRACT FROM AUTHOR]

The ambiguous behavior of metal–graphene interface has been addressed in this paper using density functional theory and nonequilibrium Green’s function formalism. For the first time, the fundamental chemistry of metal–graphene interface, in particular role of sp-hybridized and sp2-hybridized carbon atoms, has been emphasized and discussed in detail in this paper. It was discovered that the sp-hybridized sites at the edge of a graphene monolayer contribute to 40% of current conduction when compared with sp2-hybridized atom sites in the graphene–metal overlap region. Moreover, we highlighted the insignificance of an additional metal layer, i.e., sandwiched contact, due to lacking sp-hybridized carbon sites. A fundamental way of defining the contact resistance, while keeping chemical bonding in mind, has been proposed. The bonding insight has been further used to propose the novel ways of interfacing metal with graphene, which results in a 40% reduction in contact resistance. [ABSTRACT FROM PUBLISHER]

[Display omitted] First-principles molecular dynamics simulations were used to investigate pressure- and temperature-induced phase transitions in different TaN polymorphs. The driving forces and intermediate structures were established for the CoSn-like TaN (ε phase) to WC-type TaN (θ phase) and ε to NaCl type-TaN (δ phase) structural transformations that were observed in experiments and for the θ to hP4-194, θ to cP2-221, δ to cP2-221 and δ to tP4-129 phase transitions that were predicted in this investigation. Other possible TaN polytypes were systematically investigated and five new prospective phases were found: oP8-25, oP12-25, hP8-194, tP8-105 and tI8-109. All new structures are thermodynamically, dynamically and mechanically stable, and their formation energy is only slightly higher than that of the θ phase (by 0.014–0.032 eV/atom). The relative stability, electronic structure, chemical bonding, vibrational spectra, elastic moduli and their spatial anisotropy, Vickers hardness, fracture toughness, Debye temperature and optical properties (real and imaginary parts of the dielectric function, reflectivity spectrum) of the tantalum mononitrides mentioned above were systematically calculated and discussed. The oP12-25, tP8-105 and tI8-109 novel phases exhibit the Vickers hardness (33.1–34.2 GPa), fracture toughness (5.52–5.59 MPa m1/2) and Debye temperatures (609.7–616.1 K) that are higher compared to those of the known TaN structures. The TaN polytypes with the strong Ta-N bonds with minimal fraction of ionicity were found to possess the best mechanical properties. Further experimental investigations are highly desirable to confirm the results presented in this paper. [ABSTRACT FROM AUTHOR]

The aerospace industry uses aluminum alloys which have a good strength-to-weight ratio, but they have poor corrosion resistance. Additionally, in some cases the aluminum surface may need to be exposed to the adhesive and attached to other equipment. Therefore, it is necessary to have a coating with both adhesive bonding and corrosion resistance. Most effectively, anodized coatings are used to achieve these goals. Oxides made by anodizing are porous and can improve the adhesive bonding of surfaces due to their porous structure. Anodizing is done by using various electrolytes and processes that affect adhesive bonding and adhesion strength dramatically. In this paper, we describe methods to assess the adhesive bonding of anodized surfaces. The evaluation methods are divided into two categories. Chemical analysis is performed on anodized surfaces in the first category, and in the second category, mechanical interlocking is evaluated. [ABSTRACT FROM AUTHOR]

The increasing availability of computational data from quantum-chemical calculations on the reactivity and electronic structure of catalytically active oxidic systems make a revisitation of the classical questions on chemical bonding aspects of catalytically reactive systems useful. This Perspective paper starts with a short review of the different available systems. The elementary reactions that are part of the selective oxidation catalysis, such as substrate bond activation or oxygen insertion, are introduced. This is followed by a discussion of basic electronic features of the valence electron structure of oxide materials. We will initially compare the chemical bonding and reactivity of compounds with dominantly ionic versus covalent bonding. Surface reactivity descriptors for the two types of chemical bonds are indicated. It will appear that, except for longer range ionic interactions, binding to the metal cations is dominated by local covalent interactions and that ligand field theory type atomic orbital splitting as well as rehybridisation are important. Trends in bonding as a function of position of reducible metal in the periodic system are emphasized throughout the paper. At the surface, in addition to the changes in electronic structure, atom position relaxation and surface reconstruction effects may also have a large influence on the differences in reactivity. The reactivity of the oxygen atoms varies. They can be proton acceptors and generate Brønsted acidity, can assist heterolytic or radical type C H bond activation or when electrophilic will insert into hydrocarbon double bonds. At the end of the paper trends in catalytic reactivity are analyzed. The double volcano type curve found for the dependence of catalytic reactivity on the position of cation in the third row of the periodic system is shown to relate to the distribution of electrons with high spin over the ligand field split atomic orbitals of the respective cations. This will be discussed in the context of classical catalytic results that are based on Balandin type volcano plots of reactivity versus the catalyst material reactivity parameters. [ABSTRACT FROM AUTHOR]

The chemical bonding is usually not avoidable at a welding or fusion interface and sometimes is desirable to enhance the mechanical strength, while it might strongly affect the thermal contact resistance which plays a critical role in hindering heat dissipation of electronic devices. In this paper, we employ a non-equilibrium molecular dynamics method to study the effect of chemical bonding on the thermal contact resistance. Results show that the chemical bonding can greatly affect the thermal contact resistance. With the increase of the chemical bonding ratios, the thermal contact resistance firstly drops dramatically until arrives at a bonding ratio of about 20% where the thermal contact resistance is only about 15% that with a bonding ratio of 0%, and then gradually decreases to 0. Analyzing the spectral energy density of phonons at the interface, we conclude that the increase of the phonon velocity should be responsible for the decrease of the thermal contact resistance. By simulating the thermal contact resistance of silica with different morphologies (crystalline or amorphous silica), we found that different morphologies could lead to different thermal contact resistances, although this difference is less than 6%. This study is expected to provide references for managing thermal transport at a welding or fusion interface. [ABSTRACT FROM AUTHOR]

During clathrin-mediated endocytosis in yeast cells, short actin filaments (< 200nm) and crosslinking protein fimbrin assemble to drive the internalization of the plasma membrane. However, the organization of the actin meshwork during endocytosis remains largely unknown. In addition, only a small fraction of the force necessary to elongate and pinch off vesicles can be accounted for by actin polymerization alone. In this paper, we used mathematical modeling to study the self-organization of rigid actin filaments in the presence of elastic crosslinkers in conditions relevant to endocytosis. We found that actin filaments condense into either a disordered meshwork or an ordered bundle depending on filament length and the mechanical and kinetic properties of the crosslinkers. Our simulations also demonstrated that these nanometer-scale actin structures can store a large amount of elastic energy within the crosslinkers (up to 10kBT per crosslinker). This conversion of binding energy into elastic energy is the consequence of geometric constraints created by the helical pitch of the actin filaments, which results in frustrated configurations of crosslinkers attached to filaments. We propose that this stored elastic energy can be used at a later time in the endocytic process. As a proof of principle, we presented a simple mechanism for sustained torque production by ordered detachment of crosslinkers from a pair of parallel filaments. [ABSTRACT FROM AUTHOR]

It is generally recognized that insect odorant binding proteins (OBPs) mediate the solubilisation and transport of hydrophobic odorant molecules and contribute to the sensitivity of the insect olfactory system. However, the exact mechanism by which OBPs deliver odorants to olfactory receptors and their role, if any, as selectivity filters for specific odorants, are still a matter of debate. In the case of Anopheles gambiae, recent studies indicate that ligand discrimination is effected through the formation of heterodimers such as AgamOBP1 and AgamOBP4 (odorant binding proteins 1 and 4 from Anopheles gambiae). Furthermore, AgamOBPs have been reported to be promiscuous in binding more than one ligand simultaneously and repellents such as DEET (N,N-diethyl-3-toluamide) and 6-MH (6-methyl-5-hepten-2-one) interact directly with mosquito OBPs and/or compete for the binding of attractive odorants thus disrupting OBP heterodimerisation. In this paper, we propose mechanisms of action of DEET and 6-MH. We also predict that ligand binding can occur in several locations of AgamOBP1 with partial occupancies and propose structural features appropriate for repellent pharmacophores. [ABSTRACT FROM AUTHOR]

The crucial role of water in the engine of life have encouraged many researchers in studying, both theoretically and experimentally, the possible “structure” of water. Many properties of water have been related to the interplay between two distinct and interconverting structural species, namely the low-density water (LDW) and the high-density water (HDW). Supported by the results obtained with other aqueous solutions, this paper deals with the possibility of using the ultra-weak delayed luminescence (DL) to investigate water structuring in a mixture with glycerol, characterized only by hydrogen bonds between the various molecules. Spectral and temporal characteristics of DL decays give information on the two components of the mixture, by evidencing the contribution of water at glycerol concentrations close to the values used in cryopreservation. DL results have shown a correlation with LDW clusters size as determined by other researchers on the basis of neutron diffraction experiments and computational modelling, as reported in Literature. [ABSTRACT FROM AUTHOR]

This paper reports on the results of comparative investigations of Si-C-N films prepared by using both plasma enhanced chemical vapor deposition (PECVD) and DC magnetron sputtering (MS) at different nitrogen flow rates (F N2 ). The films were characterized by an atomic force microscope, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, nanoindentation and photoluminescence spectroscopy. All the deposited films were X-ray amorphous. For the PECVD films, nanohardness (H) and elastic module (E) increase with F N2 , which can be assigned to decreasing the hydrogen content. On the contrary, for the films, deposited by magnetron sputtering, the values of H and E decrease, when F N2 increases. The latter is supposed to be due to decreasing a number of strong Si-C bonds and to increasing a number of weak Si N and C N bonds. The surface roughness of two types of the films is smaller compared to that of silicon substrates. An increase in nitrogen flow rate causes the smoothing of the film surfaces. The PECVD films deposited at high F N2 exhibit bright photoemission with the main peak at ∼440 nm. The intensity of this peak increases with increasing nitrogen content. [ABSTRACT FROM AUTHOR]

In a reaction, determination of an optimal path with a high reaction rate (or a low free energy barrier) is important for the study of the reaction mechanism. This is a complicated problem that involves lots of degrees of freedom. For simple models, one can build an initial path in the collective variable space by the interpolation method first and then update the whole path constantly in the optimization. However, such interpolation method could be risky in the high dimensional space for large molecules. On the path, steric clashes between neighboring atoms could cause extremely high energy barriers and thus fail the optimization. Moreover, performing simulations for all the snapshots on the path is also time-consuming. In this paper, we build and optimize the path by a growing method on the free energy surface. The method grows a path from the reactant and extends its length in the collective variable space step by step. The growing direction is determined by both the free energy gradient at the end of the path and the direction vector pointing at the product. With fewer snapshots on the path, this strategy can let the path avoid the high energy states in the growing process and save the precious simulation time at each iteration step. Applications show that the presented method is efficient enough to produce optimal paths on either the two-dimensional or the twelve-dimensional free energy surfaces of different small molecules. [ABSTRACT FROM AUTHOR]

[Display omitted] • The bicapped pentagonal prism and icosahedral geometry were found. • The species exhibit high stabilities, especially for closed-shell anionic clusters. • The enhanced stability of clusters can be explained by spherical aromaticity. • The delocalized bondings (4c-2e) are important in the clusters revealed by AdNDP. • The Au@Sn 12 cluster possesses the largest AEA value (3.00 eV). Group-14 (Ge, Sn, Pb) clusters have attracted a lot of attention not only because of their unique structural models but also the outstanding building blocks as cluster-assembled materials. In this paper, we have systematically investigated the structure, chemical stability, electronic property, spherical aromaticity, and bonding of neutral Au@X 12 (X = Ge, Sn, Pb) clusters and their anions using density-functional theory (DFT) calculations. It is found that the Au@Ge 12 cluster displays bicapped pentagonal prism geometry, whereas Au@X 12 (X = Sn, Pb) possess the perfect icosahedral geometry. Analysis of binding energy reveals that the species exhibit high chemical stabilities, especially for closed-shell anionic clusters, which contain 60 valence electrons. The hybridization between cage and Au enhances the chemical stability of clusters, while the enhanced stability can be explained by spherical aromaticity, confirmed by largely negative NICS values, of which eight π electrons satisfy 2(N + 1)2 counting rule, forming 2S22P6 set. The AdNDP analysis reveals that the delocalized chemical bonding is responsible for structural stabilization of clusters, e.g., eight delocalized 4c-2e σ-bonds on inner shell and five delocalized 4c-2e σ-bonds on outer shell. To summarize, the calculated results will provide further understanding for the design of novel building blocks as cluster-assembled nanomaterials. [ABSTRACT FROM AUTHOR]

Recombinant expression of proteins has become an indispensable tool in modern day research. The large yields of recombinantly expressed proteins accelerate the structural and functional characterization of proteins. Nevertheless, there are literature reported that the recombinant proteins show some differences in structure and function as compared with the native ones. Now there have been more than 100,000 structures (from both recombinant and native sources) publicly available in the Protein Data Bank (PDB) archive, which makes it possible to investigate if there exist any proteins in the RCSB PDB archive that have identical sequence but have some difference in structures. In this paper, we present the results of a systematic comparative study of the 3D structures of identical naturally purified versus recombinantly expressed proteins. The structural data and sequence information of the proteins were mined from the RCSB PDB archive. The combinatorial extension (CE), FATCAT-flexible and TM-Align methods were employed to align the protein structures. The root-mean-square distance (RMSD), TM-score, P-value, Z-score, secondary structural elements and hydrogen bonds were used to assess the structure similarity. A thorough analysis of the PDB archive generated five-hundred-seventeen pairs of native and recombinant proteins that have identical sequence. There were no pairs of proteins that had the same sequence and significantly different structural fold, which support the hypothesis that expression in a heterologous host usually could fold correctly into their native forms. [ABSTRACT FROM AUTHOR]

Nowadays, it is common to observe unmotivated students with little interest in learning what is taught by the teacher. It is up to the educator to develop strategies that aim to contribute significantly to both teaching and student learning processes. We know that the game is inherent in childhood, but it remains alive in each stage of a person's life. This experience takes place from simple toys, such as dominoes to virtual video games, they are all common to children, young teens and adults. The act of playing brings to the human being feelings of pleasure and excitement, thus, becoming a useful tool for students and teachers when combining theoretical concepts learned in the classroom. In this context, this paper addresses the topic of Chemical Bonding from a dynamic and attractive approach by using games and playing as tools in the classroom. [ABSTRACT FROM AUTHOR]

The lowest lying states of LiH have been widely used to develop and calibrate many different methods in quantum mechanics. In this paper, we show that the electron-transfer processes occurring in these two states are a difficult test for chemical bonding descriptors and can be used to assess new bonding descriptors on its ability to recognise the harpoon mechanism. To this aim, we study the bond formation mechanism in a series of diatomic molecules. In all studied electron reorganisation mechanisms, the maximal electron-transfer variation point along the bond formation path occurs when about half electron has been transferred from one atom to another. If the process takes place through a harpoon mechanism, this point of the reaction path coincides with the avoided crossing. The electron sharing indices and one-dimensional plots of the electron localisation function and the Laplacian of the electron density along the molecular axis can be used to monitor the bond formation in diatomics and provide a distinction between the harpoon mechanism and a regular electron reorganisation process. [ABSTRACT FROM PUBLISHER]

The Source Function (SF), introduced in 1998 by Richard Bader and Carlo Gatti, is succinctly reviewed and a number of paradigmatic applications to in vacuo and crystal systems are illustrated to exemplify how the SF may be used to discuss chemical bonding in both conventional and highly challenging cases. The SF enables the electron density to be seen at a point determined by source contributions from the atoms or a group of atoms of a system, and it is therefore well linked to the chemist's awareness that any local property and chemical behaviour is to some degree influenced by all the remaining parts of a system. The key and captivating feature of the SF is that its evaluation requires only knowledge of the electron density (ED) of a system, thereby enabling a comparison of ab initio and X-ray diffraction derived electron density properties on a common and rigorous basis. The capability of the SF to detect electron-delocalization effects and to quantify their degree of transferability is systematically explored in this paper through the analysis and comparison of experimentally X-ray derived Source Function patterns in benzene, naphthalene and (±)-8′-benzhydrylideneamino-1,1′-binaphthyl-2-ol (BAB) molecular crystals. It is shown that the SF tool recovers the characteristic SF percentage patterns caused by π-electron conjugation in the first two paradigmatic aromatic molecules in almost perfect quantitative agreement with those obtained from ab initio periodic calculations. Moreover, the effect of chemical substitution on the degree of transferability of such patterns to the benzene- and naphthalene-like moieties of BAB is neatly shown and quantified by the observed systematic deviations, relative to benzene and naphthalene, of only those SF contributions from the substituted C atoms. Finally, the capability of the SF to reveal electron-delocalization effects is challenged by using a promolecule density, rather than the proper quantum mechanical density, to determine the changes in SF patterns along the cyclohexene, 1,3-cyclohexadiene and benzene molecule series. It is shown that, differently from the proper quantum density, the promolecular density is unable to reproduce the SF trends anticipated by the increase of electron delocalization along the series, therefore ruling out the geometrical effect as being the only cause for the observed SF patterns changes. [ABSTRACT FROM AUTHOR]

Non-coding RNAs play a pivotal role in a number of diseases promoting an aberrant sequestration of nuclear RNA-binding proteins. In the particular case of myotonic dystrophy type 1 (DM1), a multisystemic autosomal dominant disease, the formation of large non-coding CUG repeats set up long-tract hairpins able to bind muscleblind-like proteins (MBNL), which trigger the deregulation of several splicing events such as cardiac troponin T (cTNT) and insulin receptor’s, among others. Evidence suggests that conformational changes in RNA are determinant for the recognition and binding of splicing proteins, molecular modeling simulations can attempt to shed light on the structural diversity of CUG repeats and to understand their pathogenic mechanisms. Molecular dynamics (MD) are widely used to obtain accurate results at atomistic level, despite being very time consuming, and they contrast with fast but simplified coarse-grained methods such as Elastic Network Model (ENM). In this paper, we assess the application of ENM (traditionally applied on proteins) for studying the conformational space of CUG repeats and compare it to conventional and accelerated MD conformational sampling. Overall, the results provided here reveal that ANM can provide useful insights into dynamic rCUG structures at a global level, and that their dynamics depend on both backbone and nucleobase fluctuations. On the other hand, ANM fail to describe local U-U dynamics of the rCUG system, which require more computationally expensive methods such as MD. Given that several limitations are inherent to both methods, we discuss here the usefulness of the current theoretical approaches for studying highly dynamic RNA systems such as CUG trinucleotide repeat overexpansions. [ABSTRACT FROM AUTHOR]

This paper depicts the first report from an Indian population on the association between the variant Arg399Gln of XRCC1 locus in the DNA repair system and schizophrenia, the debilitating disease that affects 1% of the world population. Genotypic analysis of a total of 523 subjects (260 patients and 263 controls) revealed an overwhelming presence of Gln399Gln in the case subjects against the controls (P < 0.0068), indicating significant level of association of this nsSNP with schizophrenia; the Gln399 allele frequency was also perceptibly more in cases than in controls (p < 0.003; OR = 1.448). The results of the genotypic studies were further validated using pathogenicity and stability prediction analysis employing computational tools [I-Mutant Suite, iStable, PolyPhen2, SNAP, and PROVEAN], with a view toassess the magnitude of deleteriousness of the mutation. The pathogenicity analysis reveals that the nsSNP could be deleterious inasmuch as it could affect the functionality of the gene, and interfere with protein function. Molecular dynamics simulation of 60ns was performed using GROMACS to analyse structural change due to a mutation (Arg399Gln) that was never examined before. RMSD, RMSF, hydrogen bonds, radius of gyration and SASA analysis showedthe existence of asignificant difference between the native and the mutant protein. The present study gives astrong indication that the XRCC1 locus deserves serious attention, as it could be a potential candidatecontributing to the etio-pathogenesis of the disease. [ABSTRACT FROM AUTHOR]

[Display omitted] • A direct Z-scheme heterojunction of NU/CC was fabricated for CO 2 photoreduction. • The heterojunction of NH 2 -UiO-66/CeCO 3 OH was featured with O-Zr-CO 3 2- bond. • The rate of electron consumption of NU/CC is 152.8 μmol/g h, 5-fold of that of NU. NH 2 -UiO-66 is recently regarded as a potential photocatalyst for CO 2 reduction reaction due to the high CO 2 adsorption capacity, high UV–vis light absorption capacity and chemical stability. Aiming to further improve its activity, in this paper, a composite of NH 2 -UiO-66 and CeCO 3 OH (NU/CC) was fabricated via an in-situ growth method of NH 2 -UiO-66 on CeCO 3 OH. The X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR) characterizations indicated that a direct Z-scheme heterojunction between CeCO 3 OH and NH 2 -UiO-66 was formed via the formation of O-Zr-CO 3 2- bond. The CO 2 adsorption measurement, UV–vis DRS spectra and photo(electro)chemical measurements indicated that the optimal composite NU/CC-1.6–90 exhibited the higher CO 2 adsorption capacity, stronger respond and wider absorption range to UV–vis light, as well as the significantly delayed recombination of photogenerated electron-hole pairs, compared with other control samples. As a result, NU/CC-1.6–90 delivered the obviously enhanced photocatalytic activity of CO 2 to both CO and CH 4 , and the rate of electron consumption reached 152.8 μmol/g h, 5-fold of that of NH 2 -UiO-66. [ABSTRACT FROM AUTHOR]

• High-temperature non-Arrhenius dynamical crossover is probed in a Au-based metallic glass melt by nuclear magnetic resonance. • The dynamical crossover temperature is about 2.3 times of the glass-transition temperature. • The tendency to form covalent bonds become increasingly strong below the crossover temperature. • The emergence of strong covalent bonds may be responsible for such a non-Arrhenius behavior by promoting the spatial connectivity of energetically preferred short-range clusters. The structure and dynamics of melts have critical influence on the glass formation and solidification of crystals, which attracts broad interest to clarify the underlying mechanisms. In this paper, the quadrupolar spin-lattice relaxation rates of 63Cu and 65Cu nuclei in a Au 50 Cu 25.5 Ag 7.5 Si 17 metallic glass melt are studied by using a home-designed high-precision high-temperature NMR equipment. The relaxation rates follow the Arrhenius behavior at high temperatures above 870 K, but become non-Arrhenius at low temperatures, which indicates a non-Arrhenius dynamical crossover. The crossover temperature T A is about 2.3 times of the glass-transition temperature (T g =378 K). Based on the analysis of Knight shift and magnetic relaxation rates, Cu and Si atoms are found to tend to form stronger covalent-like bonds below T A. Such an increase in bonding strength may promote the connectivity of energetically preferred short-range clusters, which is responsible for the observed sluggish dynamics. [ABSTRACT FROM AUTHOR]

• The electrostatic interaction dominant bonding mechanism for uranyl-ligand, with some covalent bonding character. • The equatorial σ-type orbital interactions between U 5 f 6 d 7 s AOs and O, N, S- n p AOs result in substantial covalency. • The binding ability of [AmO 2 ]2+ to both ligands of PDA and PDTA is stronger than that of [UO 2 ]2+. • The large orbital interactions in [AmO 2 ]2+ complexes arise from significant participant of Am 5 f in chemical bonding. In this paper, we studied the electronic structure and chemical bonding in a series tridentate ligand-actinyl complexes, [AnO 2 (L) 2 ]2+ (An: U and Am; L: pyridine-2,6-dicarboxamide (PDA), pyridine-2,6-dicarboxthioamide (PDTA) and furan-2,6-dicarboxamide (FDA)) via using relativistic density functional theory. According to the calculation results, it is found that the actinyl is coordinated by two ligands via six donor atoms with the formation of a 1:2 complex. Among these thermodynamic achievable complexes, the [UO 2 (PDA) 2 ]2+ species generally show the largest thermal stability, and differences in stability mainly arise from differences in the valence shell levels of the donor atoms. The main U − Ligand bonding character in uranyl complexes favors electrostatic interaction over orbital interaction. We subsequently assessed the bonding difference of uranium and americium in [AnO 2 (L) 2 ]2+ (L: PDA and PDTA), finding out that binding ability of [AmO 2 ]2+ to both ligands of PDA and PDTA is stronger than that of [UO 2 ]2+, due to the larger orbital interactions in [AmO 2 (L) 2 ]2+ complexes, which arises from significant participant of Am 5 f in chemical bonding. This finding provides a fundamentally qualitative understanding of bonding nature in actinyl complexes and could provide some guidelines when selection of ligands for the best complexation behaviors toward actinyl. [ABSTRACT FROM AUTHOR]

Abstract: Developments in the application of quantum mechanics to the understanding of the chemical bond are traced with a view to examining the evolving conception of the covalent bond. Beginning with the first quantum mechanical resolution of the apparent paradox in Lewis’s conception of a shared electron pair bond by Heitler and London, the ensuing account takes up the challenge molecular orbital theory seemed to pose to the classical conception of the bond. We will see that the threat of delocalisation can be overstated, although it is questionable whether this should be seen as reinstating the issue of the existence of the chemical bond. More salient are some recent developments in a longstanding discussion of how to understand the causal aspects of the bonding interaction—the nature of the force involved in the covalent link—which are taken up in the latter part of the paper. [Copyright &y& Elsevier]

Highlights: [•] The stability and elastic constants of carbides are studied by first principles. [•] The rules of modulus of MC compounds are discussed by their group. [•] The hardness of carbides is estimated in this paper at the first time. [ABSTRACT FROM AUTHOR]

The quantum theory of atoms in molecules (QTAIM) uses physics to define an atom and its contribution to observable properties in a given system. It does so using the electron density and its flow in a magnetic field, the current density. These are the two fields that Schrödinger said should be used to explain and understand the properties of matter. It is the purpose of this paper to show how QTAIM bridges the conceptual gulf that separates the observations of chemistry from the realm of physics and do so in a manner that is both rigorous and conceptually simple. Since QTAIM employs real measurable fields, it enables one to present the findings of complex quantum mechanical calculations in a pictorial manner that isolates the essential physics. The time has arrived for a sea change in our attempts to predict and classify the observations of chemistry, time to replace the use of simplified and arbitrary models with the full predictive power of physics, as applied to an atom in a molecule. [ABSTRACT FROM AUTHOR]

The fine conformational subtleties of DNA structure modulate many fundamental cellular processes including gene activation/repression, cellular division, and DNA repair. Most of these cellular processes rely on the conformational heterogeneity of specific DNA sequences. Factors including those structural characteristics inherent in the particular base sequence as well as those induced through interaction with solvent components combine to produce fine DNA structural variation including helical flexibility and conformation. Cation-pi interactions between solvent cations or their first hydration shell waters and the faces of DNA bases form sequence selectively and contribute to DNA structural heterogeneity. In this paper, we detect and characterize the binding patterns found in cation-pi interactions between solvent cations and DNA bases in a set of high resolution x-ray crystal structures. Specifically, we found that monovalent cations (Tl+) and the polarized first hydration shell waters of divalent cations (Mg2+, Ca2+) form cation-pi interactions with DNA bases stabilizing unstacked conformations. When these cation-pi interactions are combined with electrostatic interactions a pattern of specific binding motifs is formed within the grooves. [ABSTRACT FROM AUTHOR]

Abstract: This work was motivated by the desire to improve the long-term durability of E-glass/Hysol 9394 epoxy/Al-6XN stainless steel joints whose fracture energy in a previous study was shown to fall from ∼950J/m2 (ambient) to a mere ∼88J/m2 after only two days of exposure to a 90%RH, 50°C environment. This paper reports a new polyurea chemistry to bond the E-glass and steel sections with very promising results. The fracture energy under ambient condition was measured to be 1232±15J/m2 using a double cantilever beam experiment. This value degraded by only 13% to 1070±35J/m2 in samples that were conditioned for 30days at 90%RH and 50°C. The failure in all samples was cohesive, within the first ply of the E-glass composite that neighbored the polyurea interface. The intrinsic fracture energy measurements, devoid of inelastic effects, were also carried out by submerging samples in a liquid nitrogen bath. Values of 590±25J/m2 were obtained, which can be used by the designers to set the local failure condition in design simulations of large-scale structures. [Copyright &y& Elsevier]

The recently discovered ditantalaboranes CpTaBH ( n = 4, 5) are isoelectronic with the previously discovered dimetallaboranes CpMBH of the group 6 metals Cr, Mo, and W where Cp = η-cyclopentadienyl or substituted cyclopentadienyl. Their oblatonido polyhedral structures can be derived from the oblate (flattened) deltahedra of the oblatocloso dirhenaboranes CpReBH by removal of an equatorial BH vertex with adjustment of the skeletal electron count by changing the metal atoms and adding hydrogen atoms. In these oblatocloso dirhenaborane deltahedra, the approximately antipodal rhenium atoms are close enough together to form a formal Re=Re double bond with lengths in the range 2.69-2.82 Å. Similarly, short M=M distances are maintained in the related oblatonido derivatives CpTaBH ( n = 4, 5) and CpMBH (M=Cr, Mo, W). However, the synthesis of CpTaBH ( n = 4, 5) from CpTaCl + LiBH/BH also gives a less-reduced product CpTaClBH with a longer Ta-Ta distance of ~3.2 Å. This may be regarded as a formal single bond bridged by one of the hydrogen atoms. Vertices of degree 5 (excluding terminal atoms/groups but not edge-bridging hydrogens) are sites of highest stability/lowest chemical reactivity not only in metal-free boranes but also in the dimetallaboranes discussed in this paper. For example, all four boron vertices in CpTaBH have the favorable degree or 5. Graphical Abstract: The recently discovered ditantalaboranes CpTaBH ( n = 4, 5) are isoelectronic with the previously discovered dimetallaboranes CpMBH (M=Cr, Mo, W). They have oblatonido structures derived by removal of one BH vertex from the flattened oblatocloso polyhedra of the dirhenaboranes CpReBH. All of these structures have internal M=M formal double bonds inside the deltahedron. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: The bonding of the beryllium diatomic molecule (Be2) in the ground state is exclusively made from the electron correlation effect. Unlike the ordinary van der Waals bond, where the electron correlation of the dispersion type makes weak bond energy (De) at large bond distance (Re), the Bes surprisingly strong with De =830cm−1 and Re =245pm. This paper presents in an analytical way the different electron correlation effects with the corresponding spectroscopic data. [Copyright &y& Elsevier]

Abstract: Finding an alternative way to fabricate higher performance and more cost effective diamond tools can revolutionize tooling industry. Laser cladding due to its unique features such as low interaction time and high cooling rate can be a better alternative. In this paper the deposition of metal matrix diamond composite on mild steel substrate is investigated. Pre-mixed powders of copper, tin, titanium, and diamond with the weight ratio of 54%, 13.5%, 7.5%, and 25%, respectively, were deposited on mild steel substrates by the use of pre-placed laser cladding using a continuous wave and a pulsed laser. The effect of scanning speed and laser power on the clad–substrate bonding, porosity and micro-cracks in the deposit, diamond graphitization, chemical bondings between diamond particles and the matrix, and distribution of diamond particles are discussed. Development of an interfacial layer between diamond particles and the matrix was detected. The layer was characterized as titanium carbide by the use of EDS analysis and nanoindentation. The effects of scanning speed and laser power on the thickness of the titanium carbide layer are discussed. Results of deposition by a continuous wave laser are compared with those of a pulsed laser and it is concluded that with the same laser power and scanning speed, the deposit by the pulsed laser had a slightly lower diamond graphitization and thinner TiC layers. [Copyright &y& Elsevier]

Abstract: Integrated microprojectors are being developed to project a large image on any surface chosen by users. For a laser-based microprojector, a piezo-electric based adaptive optics unit is adopted in the green laser architecture. Nanolubrication of adaptive optics sliding components is needed to reduce wear and for smooth operation. Mobile lubricant film thickness needs to be optimized for a given interface with a certain surface roughness to minimize stiction/friction and maximize durability. In this paper, the role of roughness and film thickness on adhesion, friction, and wear of the interface is studied. The results and associated mechanisms are presented. [ABSTRACT FROM AUTHOR]

Chemical bonding is one of the key and basic concepts in chemistry. The learning of many of the concepts taught in chemistry, in both secondary schools as well as in the colleges, is dependent upon understanding fundamental ideas related to chemical bonding. Nevertheless, the concept is perceived by teachers, as well as by learners, as difficult, with teaching commonly leading to students developing misconceptions. Many of these misconceptions result from over-simplified models used in text books, by the use of traditional pedagogy that presents a rather limited and sometimes incorrect picture of the issues related to chemical bonding and by assessments of students' achievement that influence the way the topic is taught. In addition, there are discrepancies between scientists regarding key definitions in the topic and the most appropriate models to teach it. In particular, teaching models that are intended to have transitional epistemological value in introducing abstract ideas are often instead understood by students as accounts of ontological reality. In this review paper we provide science educators, curricula developers and pre-service and in-service professional development providers an up-to-date picture regarding research and developments in teaching about chemical bonding. We review the external and internal variables that might lead to misconceptions and the problematic issue of using limited teaching/learning models. Finally, we review the approaches to teaching the concept that might overcome some of these misconceptions. [ABSTRACT FROM AUTHOR]

This paper aims to determine the effect of conceptual change texts accompanied with computer animations on 11th grade students’ understanding and alternative conceptions related to chemical bonding. One experimental group (EG; N =28) and one comparison group (CG; N =30) were used in the study. While the comparison group taught traditional instruction, the experimental group received conceptual change text accompanied with computer animations instruction. Chemical bonding achievement test was applied as pre-test, post-test and delayed test to collect data. The results of the study indicated that while there is no statistically significant difference between groups in pre-test, performance of EG students is greater than the CG ones in post-test and delayed test. And also, the EG students are better in remediating their alternative conceptions related to chemical bonding. Based on the study, it is concluded that conceptual change texts combined with computer animations can be effective instructional tools to improve students’ conceptual understanding of chemical concepts. [Copyright &y& Elsevier]

A unified theoretical or computational odd-electrons approach is suggested to nanomaterials, making possible their consideration on the same conceptual basis as well as on the same computational footing. The current paper presents the approach application to the chemistry of fullerenes, carbon single-walled nanotubes, surface science of silicon crystal, as well as to the molecular magnetism of both molecular crystals composed of transitional metal complexes and solid polymerized fullerenes. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [ABSTRACT FROM AUTHOR]

Abstract: We show in this paper by using quantum chemical methods how added hydrogen to cyclic triborane forms a 3c–2e bond to two boron atoms. Attached ammonia renders the storaged hydrogen more easily detached. The optimization of the structures were carried out at the MP2/6-311++G∗∗ level of theory and the bonding properties were then analyzed by topological methods applied to charge density as well as by the methods based upon natural bonding orbital theory. [Copyright &y& Elsevier]

This paper reports the microstructure of LiXPO4 (X=Ni, Co, Mn) materials prepared by solid state chemical reaction. The variation in microstructure of these phospho-olivines is mainly due to a difference in the XO6 cationic octahedral environment, which is discussed using a molecular vibration model to elucidate the bonding between various structural units. A direct relationship is established between the vibrational frequencies and the second ionisation potential of the metal (X) in LiXPO4. [Copyright &y& Elsevier]

Abstract: The paper is a review of some cathode materials used in lithium batteries. A correlation between chemical bonding, electronic structure, and electrochemical properties of the cathode materials LixMaXb (M=transition metal; X=O, S) has been demonstrated. [Copyright &y& Elsevier]

Students' misconceptions before or after formal instruction have become a major concern among researchers in science education because they influence how students learn new scientific knowledge, play an essential role in subsequent learning and become a hindrance in acquiring the correct body of knowledge. In this paper some students' misconceptions on chemical bonding reported in the literature were investigated and presented. With this aim, a detailed literature review of chemical bonding was carried out and the collected data was presented from past to day historically. On the basis of the results some suggestions for teaching were made. [ABSTRACT FROM AUTHOR]

Identifying the phase evolution and revealing the chemical bonds of hydrated cements accurately is crucial to regulate the performance of cementitious materials. In this paper, a coupled Raman/BSE-EDS analysis was proposed to determine the chemical bonds of tricalcium silicate hydrates and the interface transition zone (ITZ) between inner C-S-H and anhydrates. The results show that the Raman/BSE-EDS method can accurately identify the chemical bonds of inner C-S-H and inner ITZ regions, which confirms the mixed structure of inner C-S-H and nano calcium hydroxide (CH). The inner ITZ shows a lattice change region with a thickness of 700–1000 nm, which can be attributed to the pre-disassembly process of C3S crystal. The successful application of coupled Raman/BSE-EDS provides new insight into the hydration process and multi-structure features of traditional cementitious materials. [ABSTRACT FROM AUTHOR]

X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDX) are applied to investigate the properties of fine-grained concentrates on artisanal, small-scale gold mining samples from the Kubi Gold Project of the Asante Gold Corporation near Dunwka-on-Offin in the Central Region of Ghana. Both techniques show that the Au-containing residual sediments are dominated by the host elements Fe, Ag, Al, N, O, Si, Hg, and Ti that either form alloys with gold or with inherent elements in the sediments. For comparison, a bulk nugget sample mainly consisting of Au forms an electrum, i.e., a solid solution with Ag. Untreated (impure) sediments, fine-grained Au concentrate, coarse-grained Au concentrate, and processed ore (Au bulk/nugget) samples were found to contain clusters of O, C, N, and Ag, with Au concentrations significantly lower than that of the related elements. This finding can be attributed to primary geochemical dispersion, which evolved from the crystallization of magma and hydrothermal liquids as well as the migration of metasomatic elements and the rapid rate of chemical weathering of lateralization in secondary processes. The results indicate that Si and Ag are strongly concomitant with Au because of their eutectic characteristics, while N, C, and O follow alongside because of their affinity to Si. These non-noble elements thus act as pathfinders for Au ores in the exploration area. This paper further discusses relationships between gold and sediments of auriferous lodes as key to determining indicator minerals of gold in mining sites. [ABSTRACT FROM AUTHOR]