Dispersion of acoustic-like and optic-like vibrational excitations in Ni2B metallic glass

The dynamic structure factor S(Q, E) of Ni₂B metallic glass was studied by inelastic neutron scattering in the ranges of momentum transfers 0.7 < ?Q/Å^?1 < 7, and energy, 2 < E/meV < 70, transfers. The measurements were performed with the IN4 spectrometer (Institut Laue-Langevin (ILL), Grenoble, France) on three samples of the same chemical composition but with different contents of Ni and B isotopes, as a result of which partial contributions were determined. The cuts through S(Q, E) for different values of E and Q demonstrated a characteristic behavior indicating that vibrational excitations, similar to acoustic and optical phonon excitations in crystals, propagate in an amorphous medium in a certain energy and momentum range.     

Groups Quasi-Isometric to H2xR

The most powerful geometric tools are those of differentialgeometry, but to apply such techniques to finitely generatedgroups seems hopeless at first glance since the natural metricon a finitely generated group is discrete. However Gromov recognizedthat a group can metrically resemble a manifold in such a waythat geometric results about that manifold carry over to thegroup [18, 20]. This resemblance is formalized in the conceptof a ‘quasi-isometry’. This paper contributes toan ongoing program to understand which groups are quasi-isometricto which simply connected, homogeneous, Riemannian manifolds[15, 18, 20] by proving that any group quasi-isometric to H²xRis a finite extension of a cocompact lattice in Isom(H²xR) orIsom((2, R)).     

The feasibility of assessing branched-chain amino acid metabolism in cellular models of prostate cancer with hyperpolarized [1-C]-ketoisocaproate

Recent advancements in the field of hyperpolarized ¹³C magnetic resonance spectroscopy (MRS) have yielded powerful techniques capable of real-time analysis of metabolic pathways. These non-invasive methods have increasingly shown application in impacting disease diagnosis and have further been employed in mechanistic studies of disease onset and progression. Our goals were to investigate branched-chain aminotransferase (BCAT) activity in prostate cancer with a novel molecular probe, hyperpolarized [1-¹³C]-2-ketoisocaproate ([1-¹³C]-KIC), and explore the potential of branched-chain amino acid (BCAA) metabolism to serve as a biomarker. Using traditional spectrophotometric assays, BCAT enzymatic activities were determined in vitro for various sources of prostate cancer (human, transgenic adenocarcinoma of the mouse prostate (TRAMP) mouse and human cell lines). These preliminary studies indicated that low levels of BCAT activity were present in all models of prostate cancer but enzymatic levels are altered significantly in prostate cancer relative to healthy tissue. The MR spectroscopic studies were conducted with two cellular models (PC-3 and DU-145) that exhibited levels of BCAA metabolism comparable to the human disease state. Hyperpolarized [1-¹³C]-KIC was administered to prostate cancer cell lines, and the conversion of [1-¹³C]-KIC to the metabolic product, [1-¹³C]-leucine ([1-¹³C]-Leu), could be monitored via hyperpolarized ¹³C MRS.     

Development and validation of an improved algorithm for overlaying flexible molecules

A program for overlaying multiple flexible molecules has been developed. Candidate overlays are generated by a novel fingerprint algorithm, scored on three objective functions (union volume, hydrogen-bond match, and hydrophobic match), and ranked by constrained Pareto ranking. A diverse subset of the best ranked solutions is chosen using an overlay-dissimilarity metric. If necessary, the solutions can be optimised. A multi-objective genetic algorithm can be used to find additional overlays with a given mapping of chemical features but different ligand conformations. The fingerprint algorithm may also be used to produce constrained overlays, in which user-specified chemical groups are forced to be superimposed. The program has been tested on several sets of ligands, for each of which the true overlay is known from protein–ligand crystal structures. Both objective and subjective success criteria indicate that good results are obtained on the majority of these sets.     

Central‐Atom Size Effects on the Methyl Torsions of Group XIV Tetratolyls

The Group XIV tetratolyl series X(C₆H₄‐CH₃)₄ (X=C, Si, Ge, Sn, Pb) were studied by using inelastic neutron scattering to measure the low‐energy phonon spectra to directly access the methyl‐group torsional modes. The effect of increased molecular radius as a function of the size of the central atom was shown to have direct influence on the methyl dynamics, reinforced with the findings of molecular dynamics and contact surface calculations, based upon the solid‐state structures. The torsional modes in the lightest analogue were found to be predominantly intramolecular: the Si and Ge analogues have a high degree of intermolecular methyl–methyl group interactions, whilst the heaviest analogues (Sn and Pb) showed pronounced intermolecular methyl interactions with the whole phonon bath of the lattice modes.     

Diaryliodonium Salts: A Journey from Obscurity to Fame

The recent groundbreaking developments in the application of diaryliodonium salts in cross‐coupling reactions has brought this class of previously underdeveloped reagents to the forefront of organic chemistry. With the advent of novel, facile, and efficient synthetic routes to these compounds, many more applications can be foreseen. Herein we provide an overview of the historical and recent advances in the synthesis and applications of diaryliodonium salts.     

Facile synthesis of Koser's reagent and derivatives from iodine or aryl iodides

The first one-pot synthesis of neutral and electron-rich [hydroxy(tosyloxy)iodo]arenes (HTIBs) from iodine and arenes is presented, thereby avoiding the need for expensive iodine(III) precursors. A large set of HTIBs, including a polyfluorinated analogue, can be obtained from the corresponding aryl iodide under the same conditions. The reaction proceeds under mild conditions, without excess reagents, and is fast and high-yielding. Together, the two presented routes give access to a wide range of HTIBs, which are useful reagents in a variety of synthetic transformations.     

Enhanced reversible lithium storage in a nanosize silicon/graphene composite

Si/graphene composite was prepared by simply mixing of commercially available nanosize Si and graphene. Electrochemical tests show that the Si/graphene composite maintains a capacity of 1168 mAh g^?1 and an average coulombic efficiency of 93% up to 30 cycles. EIS indicates that the Si/graphene composite electrode has less than 50% of the charge-transfer resistance compared with nanosize Si electrode, evidencing the enhanced ionic conductivity of Si/graphene composite. The enhanced cycling stability is attributed to the fact that the Si/graphene composite can accommodate large volume charge of Si and maintain good electronic contact.     

Molecular Logic Gates for DNA Analysis: Detection of Rifampin Resistance in M. tuberculosis DNA

Elementary, Dr. Watson! A combination of YES and OR logic gates was applied to differentiate between DNA sequences of wild-type and rifampin-resistant (Rif(r) ) Mycobacterium tuberculosis (Mtb) in a multiplex real-time fluorescent assay.