Templating of arrays of Ru nanoclusters by monolayer graphene/Ru Moirés with different periodicities

We have studied the formation of Ru nanocluster arrays on several monolayer graphene/Ru Moiré structures with different relative orientations of the graphene and Ru lattices. Experiments and ab initio calculations clearly show that the presence of a graphene/Ru Moiré does not guarantee the ordered adsorption of Ru nanoclusters. The simultaneous deposition of Ru onto coexisting Moirés demonstrates that a structure with aligned graphene and Ru lattices templates the formation of arrays of small Ru clusters with narrow size spread and adsorption exclusively in a single site (the 'low fcc' site). The other Moirés considered here gave rise to substantially larger clusters with broader size distribution and without detectable site selectivity. Calculations explain these findings via the density of states (DOS) at different sites of the graphene/Ru Moiré. The ordered nucleation of many small clusters instead of incorporation of metal atoms into larger ones requires one Moiré site with a large DOS at the Fermi level, so that the binding of metal adatoms to this site is stronger than to competing sites in the Moiré and to existing metal clusters.     

The effect of fractional parameter on a perfect conducting elastic half-space in generalized magneto-thermoelasticity

Recently, Sherief et al. (Int. J. Solids Struct. 47:269–275, 2010) proposed a model in generalized thermoelasticity based on the fractional order time derivatives. The propagation of electro-magneto-thermoelastic disturbances in a perfectly conducting elastic half-space is investigated in the context of the above fractional order theory of generalized thermoelasticity. There acts an initial magnetic field parallel to the plane boundary of the half-space. Normal mode analysis together with the eigenvalue approach technique is used to solve the resulting non-dimensional coupled governing equations of the problem. The obtained solution is then applied to two specific problems for the half-space, whose boundary is subjected to (i) thermally isolated surfaces subjected to time-dependent compression and (ii) a time-dependent thermal shock and zero stress. The effects of fractional parameter and magnetic field on the variations of different field quantities inside the half-space are analyzed graphically.     

Immobilisation of no-carrier-added <Superscript>93m</Superscript>Mo on a biopolymer calcium alginate: a candidate radiopharmaceutical

No-carrier-added ^93mMo radionuclide with high specific activity is a potential candidate radionuclide in the field of nuclear medicine due to its suitable half-life and gamma energy with significant intensity. In the present paper, we report the immobilization of radioisotopically and radiochemically pure no-carrier-added (nca) ^93mMo onto calcium alginate biopolymer. The experiment has been performed to examine the possibility of polymeric delivery of ^93mMo radionuclide by measuring the adsorption of ^93mMo on calcium alginate beads. Maximum adsorption was found at pH 2.     

Heterohexanuclear (Cu3Fe3) Complexes of Substituted Hexaazatrinaphthylene (HATN) Ligands: Twofold BF4− Association in the Solid and Stepwise Oxidation (3e) or Reduction (2e) to Spectroelectrochemically Characterized Species

New tris(ferrocenylcopper) compounds [(μ₃‐dqp){Cu(dppf)}₃][X]₃ (dppf=1,1′‐bis(diphenylphosphinoferrocene), dqp=hexamethyl‐, hexachloro‐ or un‐substituted diquinoxalino[2,3‐a:2′,3′‐c]phenazine=hexaazatrinaphthylene (HATN), X^?=BF₄^? or PF₆^?) undergo at least two different, reversible one‐electron reductions and three very closely spaced one‐electron oxidations. While the latter are attributed to the stepwise ferrocene→ferrocenium conversions, the first electron addition occurs in the ligand bridge to yield EPR detectable radical complexes. X‐band EPR measurements at 9.5 GHz showed a partially resolved hyperfine structure, while high‐frequency EPR measurements at 95 or 115 GHz revealed a small but variable axial g tensor anisotropy. All reversible steps were investigated by optically transparent thin‐layer electrode (OTTLE) spectroelectrochemistry (UV/Vis/NIR regions), revealing very low energy transitions for the reduced forms in agreement with the frontier MO arrangement. A crystal structure of the compound with unsubstituted dqp shows notable deviation from the trigonal symmetry and the close association of two tetrafluoroborate anions with the complex trication along the quasi‐trigonal axis to yield [(μ₃‐dqp){Cu(dppf)}₃(BF₄)₂]BF₄.     

Estimation of radiological indices in Indian Sundarbans: a mangrove habitat

Stereoscopic porous microspheres based gellan gum (GG–Ca) were successfully prepared by sol–gel method using ethyl acetate as porogen and glutaraldehyde as crosslinker. The obtained GG–Ca microspheres were mainly of mesoporous with the average pore diameter was about 4 nm. It displayed a higher ability for uranium removal. In addition, the uranium adsorption process was endothermic and spontaneous following a pseudo-second-order and the adsorption isotherm was the best fit with the Freundlich model with maximum uranium capacity of 202.26 mg g⁻¹. The UO²⁺ adsorption mechanism is ion-exchange with Ca²⁺ based on SEM, EDX and XPS data analysis.

     

Quantitative estimation of total potassium and 40K in surface soil samples of Indian Sundarbans

The present study attempts to quantitatively estimate total potassium content in soil samples collected from different areas of Indian Sundarbans by gamma-spectrometry, exploiting the radiogenic properties of potassium and by wavelength dispersive X-ray fluorescence technique. The elemental K concentration varied in between 2.08 ± 0.05 and 3.46 ± 0.06% in the soil samples. Besides estimation of total potassium, the activity of ⁴⁰K was also estimated in the same soil samples and found to be in the range of 532 ± 8.9 to 1043 ± 13.2 Bq kg⁻¹.

     

Binding of a dimeric derivative of vancomycin to L-Lys-D-Ala-D-lactate in solution and at a surface.

BACKGROUND: The emergence of bacteria that are resistant to vancomycin (V), a glycopeptide antibiotic, results from the replacement of the carboxy-terminal D-Ala-D-Ala of bacterial cell wall precursors by D-Ala-D-lactate. Recently, it has been demonstrated that covalent dimeric variants of V are active against vancomycin-resistant enterococci (VRE). To study the contribution of divalency to the activities of these variants, we modeled the interactions of V and a dimeric V with L-Lys-D-Ala-D-lactate, an analog of the cell-wall precursors of the vancomycin-resistant bacteria. RESULTS: A dimeric derivative of V (V-Rd-V) was found to be much more effective than V in inhibiting the growth of VRE. The interactions of V and V-Rd-V with a monomeric lactate ligand - diacetyl-L-Lys-D-Ala-D-lactate (Ac2KDADLac) - and a dimeric derivative of L-Lys-D-Ala-D-lactate (Lac-R'd-Lac) in solution have been examined using isothermal titration calorimetry and UV spectroscopy titrations; the results reveal that V-Rd-V binds Lac-R'd-Lac approximately 40 times more tightly than V binds Ac2KDADLac. Binding of V and of V-Rd-V to Nalpha-Ac-L-Lys-D-Ala-D-lactate presented on the surface of mixed self-assembled monolayers (SAMs) of alkanethiolates on gold indicates that the apparent off-rate for dissociation of V-Rd-V from the surface is much slower than that of V from the same surface. CONCLUSIONS: The results are compatible with the hypothesis that divalency is responsible for tight binding, which correlates with small values of minimum inhibitory concentrations of V and V-Rd-V.     

Brück Conjecture for a linear differential polynomial

In the paper we study the Brück Conjecture for a linear differential polynomial.     

Study of naturally occurring radioactive material (NORM) in top soil of Punjab State from the North Western part of India

The concentration levels of ²³⁸U, ²³² Th, ⁴⁰K and ¹³⁷Cs in top soils of State of Punjab located in the North Western part of India were measured using conventional low background gamma ray spectrometric setup as well as Compton suppressed gamma ray spectrometric setup. The radioactivity level of ²³⁸U and ²³²Th was found to vary between 15 Bq/kg and 27 Bq/kg and between 16 Bq/kg and 57 Bq/kg respectively. The radioactivity level of ⁴⁰K was found to vary between 266 Bq/kg and 799 Bq/kg. The mean radioactivity level of the NORM in general was found to be similar to what is expected as a result of their normal abundance.