Self-trapping vs. non-trapping of electrons and holes in organic insulators: polyethylene

We show, by electronic structure based molecular dynamics simulations, that an extra electron injected in crystalline polyethylene should fall spontaneously into a self-trapped state, a shallow donor with a large novel distortion pattern involving a pair of trans-gauche defects. Parallel calculations show instead that a hole will remain free and delocalized. We trace the difference of behavior to the intrachain nature of the hole, as opposed to the interchain one of the electron, and argue that applicability of this concept could be more general. Thus electrons (but not holes) should tend to self-trap in saturated organic insulators, but not for example in aromatic insulators, where both carriers are intrachain.     

Fuzzball solutions for black holes and D1-brane-D5-brane microstates

We revisit the relation between fuzzball solutions and D1-brane-D5-brane microstates. A consequence of the fact that the R ground states (in the usual basis) are eigenstates of the R charge is that only neutral operators can have nonvanishing expectation values on these states. We compute the holographic 1-point functions of the fuzzball solutions and find that charged chiral primaries have nonzero expectation values, except when the curve characterizing the solution is circular. The nonzero vacuum expectation values reflect the fact that a generic curve breaks R symmetry completely. This implies that fuzzball solutions (excepting circular ones) can only correspond to superpositions of R states and we give a proposal for the superposition corresponding to a given curve. We also address the question of what would be the geometric dual of a given R ground state.     

Disposable roll-to-roll hot embossed electrophoresis chip for detection of antibiotic resistance gene mecA in bacteria

We present a high-throughput roll-to-roll (R2R) manufacturing process for foil-based polymethyl methacrylate (PMMA) chips of excellent optical quality. These disposable, R2R hot embossed microfluidic chips are used for the identification of the antibiotic resistance gene mecA in Staphylococcus epidermidis. R2R hot embossing is an emerging manufacturing technology for polymer microfluidic devices. It is based on continuous feeding of a thermoplastic foil through a pressurized area between a heated embossing cylinder and a blank counter cylinder. Although mass fabrication of foil-based microfluidic chips and their use for biological applications were foreseen already some years ago, no such studies have been published previously.     

Nitrenium ions. Reactions of N,N-dimethyl-p-benzoyloxyanilineiminium chloride with indoles and indolizines. X-ray structure of unexpected [2-chloro-4-(4-dimethylaminophenyl-ONN-azoxy)phenylldimethylamine (azoxy derivative)

N,N-Dimethyl-p-nitrosoaniline reacts with benzoyl chloride affording a complex salt containing a cation, a hybrid between a nitrenium ion and an iminium ion. The salt reacts with nucleophiles (indoles, indolizines) yielding compounds characterized by a new carbon-nitrogen bond, derived from the nitrenium ion form. According to the type of nucleophile, the reaction, to differing extents, is in competition with an electron transfer process which leads to the formation of the dimer of the nucleophile and of the azoxy corresponding to the N,N-dimethyl-p-nitrosoaniline. In one of the reactions studied, a chlorinated azoxy derivative was also isolated, and its structure was elucidated by X-ray analysis.     

The first water‐soluble copper(I) complexes bearing sulfonated imidazole‐ and benzimidazole‐derived N‐heterocyclic carbenes: Synthesis and anticancer studies

The first water‐soluble bis(NHC^SO3)CuCl complexes (NHC^SO3 = NaIm^Bn,PrSO3, Na₂(4‐Me)Im^PrSO3 and Na₂BzIm^PrSO3) derived from the sulfonated N‐heterocyclic carbene precursors HIm^Bn,PrSO3 (3‐(1‐benzyl‐1H‐imidazol‐3‐ium‐3‐yl)propane‐1‐sulfonate), Na(4‐Me)HIm^PrSO3 (sodium 3,3′‐(4‐methyl‐1H‐imidazole‐3‐ium‐1,3‐diyl)dipropane‐1‐sulfonate) and NaHBzIm^PrSO3 (sodium 3,3′‐(1H‐benzoimidazole‐3‐ium‐1,3‐diyl)dipropane‐1‐sulfonate) have been synthesized. These compounds have been characterized using infrared and NMR spectroscopy and electrospray ionization mass spectrometry. The in vitro anti‐tumour effects of the bis(NHC^SO3)CuCl complexes and the corresponding free ligands were evaluated for a panel of various human tumour cell lines, including examples of lung, colon, ovarian and cervical carcinoma as well as of melanoma. Their cytotoxic properties were also evaluated against non‐transformed human cells and on a cellular model of cisplatin resistance. NHC–copper complexes induced cell killing effects preferentially against tumour cells, with IC₅₀ values in the micromolar range. Additionally, they were found able to overcome acquired cisplatin resistance.     

Direct, one-pot reductive alkylation of anilines with functionalized acetals mediated by triethylsilane and TFA. Straightforward route for unsymmetrically substituted ethylenediamine

A new, robust, and reliable method has been developed for the selective reductive N-alkylation of primary and secondary aromatic amines with some functionalized acetals using TFA/Et(3)SiH as a reagent combination. A variety of unsymmetrically substituted ethylenediamines can be synthesized in a one-pot procedure in excellent yields at room temperature. This new procedure offers significant advantages over previous synthetic approaches, including brevity, mild reaction conditions, excellent yields, and high functional group tolerance.     

Regioselective synthesis of 1,3,5- and 1,3,4,5-substituted pyrazoles via acylation of N-Boc-N-substituted hydrazones

Acylation of N-Boc-N-methylhydrazones followed by TFA treatment affords regioselective access to substituted pyrazoles. Both regioisomers of 1-methyl-3,5-disubstituted-1H-pyrazoles can be selectively obtained. This procedure can also be employed for the regioselective preparation of fully substituted 1H-pyrazoles.     

The fluorescence properties and NMR analysis of protopine and allocryptopine

The fluorescence properties of protopine and allocryptopine in aqueous and organic environments are described for the first time. The fluorescence of alkaloids and their pH-dependent interconversion to cationic forms (transannular interaction) were studied using steady-state and time-resolved fluorescence techniques. For the analysis of tricyclic base and cis/trans tetracyclic cations of the alkaloids, NMR and X-ray crystallography were used.     

The Steiner connectivity problem

The Steiner connectivity problem has the same significance for line planning in public transport as the Steiner tree problem for telecommunication network design. It consists in finding a minimum cost set of elementary paths to connect a subset of nodes in an undirected graph and is, therefore, a generalization of the Steiner tree problem. We propose an extended directed cut formulation for the problem which is, in comparison to the canonical undirected cut formulation, provably strong, implying, e.g., a class of facet defining Steiner partition inequalities. Since a direct application of this formulation is computationally intractable for large instances, we develop a partial projection method to produce a strong relaxation in the space of canonical variables that approximates the extended formulation. We also investigate the separation of Steiner partition inequalities and give computational evidence that these inequalities essentially close the gap between undirected and extended directed cut formulation. Using these techniques, large Steiner connectivity problems with up to 900 nodes can be solved within reasonable optimality gaps of typically less than five percent.