Evidence for strain glass in the ferroelastic-martensitic system Ti(50-x)Ni(50+x)

We report here "strain glass," a new glassy phenomenon in ferroelastic-martensitic system of Ni-rich intermetallic Ti(50-x)Ni(50+x) (x > 1), where local strain is frozen in disordered configuration below a critical temperature Tg. The ac elastic modulus shows a minimum at Tg, which exhibits logarithmic frequency dependence following Vogel-Fulcher relationship, and the corresponding internal friction shows a frequency-dependent peak located at a lower temperature. In situ high-resolution transmission electron microscopy observations reveal uncorrelated nanoclusters of martensiticlike phase, randomly frozen in the otherwise untransformed parentlike matrix. Being parallel to spin glass and relaxor, strain glass may shed new light on the fundamental physics of glass and lead to the discovery of novel properties.     

Gold nanoparticles functionalized with deep-cavity cavitands: synthesis, characterization, and photophysical studies

In this report, we present methods of functionalization of AuNP's with deep-cavity cavitands that can include organic molecules. Two types of deep-cavity cavitand-functionalized AuNP's have been synthesized and characterized, one soluble in organic solvents and the other in water. Functionalized AuNP soluble in organic solvents forms a 1:1 host-guest complex where the guest is exposed to the exterior solvents. The one soluble in water forms a 2:1 host-guest complex where the guest is protected from solvent water. Phosphorescence from thiones and benzil included within heterocapsules attached to AuNP was quenched by gold atoms present closer to the guests included within deep-cavity cavitands. During this investigation, we have synthesized four new deep-cavity cavitands. Of these, two thiol-functionalized hosts allowed us to make stable AuNP's. However, AuNP's protected with two amine-functionalized cavitands tended to aggregate within a day.     

Ethanolic or Aqueous Formic Acid (1:1) - A New Efficient Reagent for the Regeneration of Ketones from Phenylhydrazones

50% Ethanolic or aqueous formic acid has been found to be extremely efficacious for the regeneration of aliphatic and aromatic ketones from phenylhydrazones.     

Photodimerization of hydrophobic guests within a water-soluble nanocapsule

Conducting reactions in environmentally benign conditions is one of the major objectives of “green chemistry.” In this context, developing ways to conduct reactions in water seems obvious. In this report, we present our results on photodimerization of select guest molecules placed within the rigid reaction cavity of a water-soluble cavitand, octa acid. The results presented herein highlight the value of a supramolecular approach in achieving selectivity in photoreactions and opening reaction pathways that are latent in solution chemistry.     

Limits of the creation of electronic wave packets using time-dependent density functional theory

Explicitly time-dependent density functional theory (TDDFT) has often been suggested as the method of choice for controlling the correlated dynamics of many electron systems. However, it is not yet clear which control tasks can be achieved reliably and how this depends on the functionals used. In this article, we show that the control task of creating a simple wave packet, having a population of 50% in the excited state, can indeed be achieved if a certain condition is fulfilled. This result is in contrast to the observation that a full population inversion is extremely difficult to achieve. In addition, we identify a rule to predict when TDDFT produces the correct wave packet. To illustrate our findings, we study the molecules Li(2)C(2), Li(7)OH, and B(2)N(2)CO using two different functionals as well as time-dependent Hartree-Fock (TDHF). To assess the performance of TDDFT and TDHF, we compare with time-dependent configuration interaction calculations.     

Conformational analysis and the binding sites of nitrilotriacetamide: A computational study

The conformational analysis of nitrilotriacetamide has been carried out computationally, at both the semi‐empirical AM1 and density functional theory (DFT) (B3LYP/6‐31+G*) levels of theory. The lowest‐energy conformation predicted with the Monte Carlo search method, using the AM1 model, has two amide functionalities aligned on the same side; however, the DFT calculations at B3LYP/6‐31+G* predicted the global minimum with all three acetamide functionalities on the same side in the gas phase. In the aqueous phase, the DFT results predicted the orientations of amides similar to that of the reported crystal structure. The rotation barriers to transition to different low‐energy conformers of nitrilotriacetamide are lower in energy (5.0 kcal/mol) in water. The molecular electrostatic isopotentials (MESP) generated for the selected conformers at DFT level show that the nitrilotriacetamide could interact more effectively with the sodium chloride surface than that of its monomeric unit nitrilomonoacetamide. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Neat Formic Acid: an Excellent N-Formylating Agent for Carbazoles, 3-Alkylindoles,Diphenylamine and Moderately Weak Nucleophilic Anilines

Neat formic acid alone efficiently N-formylates carbazoles, 3-alkylindoles, diphenylamine and even moderately weak nucleophilic anilines to furnish the corresponding N-formyl derivatives in 72--87% yields.     

Characterization of a specific arabinosyltransferase activity involved in mycobacterial arabinan biosynthesis

Mycobacterium smegmatis strains that contain inactivated EmbA or EmbB proteins are unable to synthesize terminal Arabeta1-->2Araalpha1-->5(Arabeta1-->2Araalpha1-->3)Araalpha1-->5Araalpha1-->(Ara(6)) motif in the cell wall polysaccharide arabinogalactan. Instead, the mutants contain a linear Arabeta1-->2Araalpha1-->5Araalpha1-->5Araalpha1-->(Ara(4)) motif, suggesting that these proteins are involved in the synthesis or transfer of the disaccharide Arabeta1-->2Araalpha1--> to an internal 5-linked Ara. Therefore, we synthesized a linear Arabeta1-->2Araalpha1-->5Araalpha1-->5Araalpha1-->5Araalpha1--> with an octyl aglycon as an arabinosyl acceptor in cell-free assays. A facile assay was developed using the chemically synthesized glycan, membrane, and particulate cell wall as the enzyme source, and 5-phosphoribose diphosphate pR[(14)C]pp as the arabinose donor. The results unequivocally show that two arabinofuranosyl residues were added at the tertiary -->5Araalpha1--> of the synthetic glycan. This activity was undetectable in strains of M. smegmatis where embB or embA had been genetically disrupted. Normal activity could be restored only in the presence of both EmbA and EmbB proteins.     

Fluorometric study of solvation characteristics of ketocyanine dyes in mixed binary solvents

The fluorescence characteristics of two ketocyanine dyes have been studied in six mixed binary solvents. Several parameters such as the maximum energy E₁₂(F) of fluorescence, the quantum yield Φ₁₂ of fluorescence and the normalized intensity of the fluorescence have been investigated as functions of solvent composition. In protic+aprotic binary mixtures a dramatic change at the aprotic end has been observed. The results point to a preferential solvation of the solute by the protic component.     

Computational study of urea and its homologue glycinamide: conformations, rotational barriers, and relative interactions with sodium chloride

Conformational behaviors of urea and glycinamide have been investigated using the B3LYP functional with the 6-311+G* and 6-311+G** basis sets. Urea monomers have nonplanar minima at all the levels studied, even in the aqueous phase. In the case of glycinamide, the intramolecular hydrogen bond formed from the amide to the amine is important for stabilizing the global minimum. Bond rotations and nitrogen inversion barriers for glycinamide conformations have also been reported. The DFT calculated results suggest that urea conformers interact preferentially with the {111} surface of sodium chloride and such interactions can be responsible for the change in the habit of sodium chloride. Glycinamide conformers have a lower affinity toward the {111} surface of sodium chloride in water. The pyramidality of nitrogens in urea conformers does not influence the relative trends of interaction energies with sodium chloride surfaces. The mode of interactions predicted at the LDA/PWC/DND level for urea and glycinamide with sodium chloride for both slab and cluster models shows that the amide functionality (-CONH2) interacts with both Na(+) and Cl(-) ions on the {100} surface; however, the carbonyl oxygen of these additives predominantly interacts with the sodium ions on the {111} surface.