Ensuring of environmental safety in the reclamation of anthropogenic placer gold deposits in the North of Khabarovsk Krai

The results of studying mercury pollution of ecosystem in the zone affected by anthropogenic placer gold deposits are given. A major hazard to the environment and human health results from minerals processing wastes polluted with mercury and dumped in the placer gold-concentrating sites (PGCS) near mining villages, which have transformed into unequipped authorized landfills. The recent tendency to their reclamation should favor extensive mercury pollution. Actions have been proposed to ensure environmental safety of mineral processing wastes and reclamation of anthropogenic placer gold deposits.     

Emerging Bottom-Up Strategies for the Synthesis of Graphene Nanoribbons and Related Structures

The solution-phase synthesis is one of the most promising strategies for the preparation of well-defined graphene nanoribbons (GNRs) in large scale. To prepare high quality, defect-free GNRs, cycloaromatization reactions need to be very efficient, proceed without side reaction and mild enough to accommodate the presence of various functional groups. In this Minireview, we present the latest synthetic approaches for the synthesis of GNRs and related structures, including alkyne benzannulation, photochemical cyclodehydrohalogenation, Mallory and Pd- and Ni-catalyzed reactions.     

Approaching the Integer-Charge Transfer Regime in Molecularly Doped Oligothiophenes by Efficient Decarboxylative Cross-Coupling

A library of symmetrical linear oligothiophene was prepared employing decarboxylative cross-coupling reaction as the key transformation. Thiophene potassium carboxylate salts were used as cross-coupling partners without the need of co-catalyst, base, or additives. This method demonstrates complete chemoselectivity and is a comprehensive greener approach compared to the existing methods. The modularity of this approach is demonstrated with the preparation of discreet oligothiophenes with up to 10 thiophene repeat units. Symmetrical oligothiophenes are prototypical organic semiconductors where their molecular electrical doping as a function of the chain length can be assessed spectroscopically. An oligothiophene critical length for integer charge transfer was observed to be 10 thiophene units, highlighting the potential use of discrete oligothiophenes as doped conduction or injection layers in organic electronics applications.     

Emerging Bottom‐Up Strategies for the Synthesis of Graphene Nanoribbons and Related Structures

The solution‐phase synthesis is one of the most promising strategies for the preparation of well‐defined graphene nanoribbons (GNRs) in large scale. To prepare high quality, defect‐free GNRs, cycloaromatization reactions need to be very efficient, proceed without side reaction and mild enough to accommodate the presence of various functional groups. In this Minireview, we present the latest synthetic approaches for the synthesis of GNRs and related structures, including alkyne benzannulation, photochemical cyclodehydrohalogenation, Mallory and Pd‐ and Ni‐catalyzed reactions.     

Studies on the Reactivity of 4-Acetoxy-3-acylamino-2-azetidinones: Stereospecific trans Carbon-Carbon Bond Formation

The recent publication of Reuschling and co-workers2 on the synthesis of a carbapenem utilizing, as the key step in the sequence, the stereospecific C-C coupling of 3-substituted-acetoxy-2-azetidinones with cuprates, prompts us to report our related work in this area.     

Radiation damage in soft X-ray microscopy

The rates of chemical transformation by radiation damage of polystyrene (PS), poly(methyl methacrylate) (PMMA), and fibrinogen (Fg) in a X-ray photoemission electron microscope (X-PEEM) and in a scanning transmission X-ray microscope (STXM) have been measured quantitatively using synchrotron radiation. As part of the method of dose evaluation in X-PEEM, the characteristic (1/e) sampling depth of X-PEEM for polystyrene in the C 1s region was measured to be 4 ± 1 nm. Critical doses for chemical change as monitored by changes in the X-ray absorption spectra are 80 (12), 280 (40) and 1230 (180) MGy (1 MGy = 6.242*ρ eV/nm³, where ρ is the polymer density in g/cm³) at 300 eV photon energy for PMMA, Fg and PS, respectively. The critical dose for each material is comparable in X-PEEM and STXM and the values cited are thus the mean of the values determined by X-PEEM and STXM. C 1s, N 1s and O 1s spectroscopy of the damaged materials is used to gain insight into the chemical changes that soft X-rays induce in these materials.     

Nondipolar electron angular distributions from fixed-in-space molecules

The first indication of nondipole effects in the azimuthal dependence of photoelectron angular distributions emitted from fixed-in-space molecules is demonstrated in N (2). Comparison of the results with angular distributions observed for randomly oriented molecules and theoretical derivations for the nondipole correction first order in photon momentum suggests that higher orders will be needed to describe distributions measured in the molecular frame.     

A new type of scanning electron microscope using the coaxial backscattered electrons

A new coaxial detection system for backscattered electrons in SEM is described. This coaxial detection system allows us to collect only the backscattered electrons that have lost a small percentage of the primary energy, emerging from the sample surface with a take-off angle defined by the objective lens. This new configuration reinforces the atomic-number contrast and suppresses effectively the topographic contrast. The simulation and experimental results confirm these expectations: this new type of SEM is very suitable for observing differences in atomic number. Moreover, by associating the obtained image with a conventional secondary electron image, we build a third (color) image that allows us to give finally at the same time, in a single image, both of the chemical and topographic information.     

Focus on H/D exchange of proteins in solution

Editorial

Focus on H/D exchange of proteins in solution     

Calorimetric evidence for two magnetic phases in CePb3 under pressure

Low-temperature specific heat measurements on the heavy-fermion antiferromagnet CePb₃ have been performed under pressures up to 1.3 GPa. From the shift of the anomaly atT _N the magnetic phase diagram is constructed. The change of the shape of the anomaly, when the pressure exceeds 0.7 GPa, clearly indicates the crossover from one magnetic structure to another as had already been concluded from formern-scattering results. The Kondo temperature does not show a peculiar variation with pressure.