Gas phase acidities of CH bonds adjacent to oxygen and to sulphur

It has been shown, by double zeta quality ab initio MO calculations, that, in the gas phase, a CH bond adjacent to sulphur is more acidic than a CH bond adjacent to oxygen. This trend is in agreement with experimental observations in solution.     

Improving the stability of photosystem I–based bioelectrodes for solar energy conversion

Isolated photosystem I (PSI) has been integrated into numerous technologies for solar energy conversion. Interest in PSI is a consequence of its high internal quantum efficiency, thermal stability, ease of extraction, and adaptability. While there has been success in improving performance to elevate PSI biohybrid technologies toward a practical realm, the stability of PSI bioelectrodes is also of critical importance. Commercial solar energy conversion technologies are expected to achieve lifetimes of the order of ten years; however, many research-scale PSI bioelectrodes have only been tested for tens of days. Key areas affecting PSI bioelectrode stability include the effects of reactive oxygen species, immobilization strategies, and the environment within solid-state PSI biohybrid photovoltaics. At the current state, further investigation of long-term stability is necessary in enabling the development of PSI bioelectrodes for both photoelectrochemical cells and solid-state biohybrid photovoltaics.     

Synthesis of saturated 1,4-benzodiazepines via Pd-catalyzed carboamination reactions

A new synthesis of 1,4-benzodiazepines and 1,4-benzodiazepin-5-ones is reported. The Pd-catalyzed coupling of N-allyl-2-aminobenzylamine derivatives with aryl bromides affords the heterocyclic products in good yield, and substrates bearing allylic methyl groups are transformed to cis-2,3-disubstituted products with >20:1 dr.     

NUPACK: Analysis and design of nucleic acid systems

The Nucleic Acid Package (NUPACK) is a growing software suite for the analysis and design of nucleic acid systems. The NUPACK web server ( http://www.nupack.org ) currently enables:

• Analysis: thermodynamic analysis of dilute solutions of interacting nucleic acid strands.
• Design: sequence design for complexes of nucleic acid strands intended to adopt a target secondary structure at equilibrium.
• Utilities: evaluation, display, and annotation of equilibrium properties of a complex of nucleic acid strands.

NUPACK algorithms are formulated in terms of nucleic acid secondary structure. In most cases, pseudoknots are excluded from the structural ensemble. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010     

Vocal tract resonances and the sound of the Australian didjeridu (yidaki) II. Theory

The didjeridu (didgeridoo) or yidaki of the Australian Aboriginal people consists of the narrow trunk of a small Eucalypt tree that has been hollowed out by the action of termites, cut to a length of about 1.5 m, smoothed, and decorated. It is lip-blown like a trumpet and produces a simple drone in the frequency range 55 to 80 Hz. Interest arises from the fact that a skilled player can make a very wide variety of sounds with formants rather like those of human vowels, and can also produce additional complex sounds by adding vocalization. An outline is given of the way in which the whole system can be analyzed using the harmonic-balance technique, but a simpler approach with lip motion assumed shows easily that upper harmonics of the drone with frequencies lying close to impedance maxima of the vocal tract are suppressed, so that formant bands appear near impedance minima of the vocal tract. This agrees with experimental findings. Simultaneous vibration of the player's lips and vocal folds is shown to generate multiple sum and difference tones, and can be used to produce subharmonics of the drone. A brief discussion is given of player preference of particular bore profiles.     

Multipartite Composition of Contextuality Scenarios

Contextuality is a particular quantum phenomenon that has no analogue in classical probability theory. Given two independent systems, a natural question is how to represent such a situation as a single test space. In other words, how separate contextuality scenarios combine into a joint scenario. Under the premise that the the allowed probabilistic models satisfy the No Signalling principle, Foulis and Randall defined the unique possible way to compose two contextuality scenarios. When composing strictly-more than two test spaces, however, a variety of possible composition methods have been conceived. Nevertheless, all these formally-distinct composition methods appear to give rise to observationally equivalent scenarios, in the sense that the different compositions all allow precisely the same sets of classical and quantum probabilistic models. This raises the question of whether this property of invariance-under-composition-method is special to classical and quantum probabilistic models, or if it generalizes to other probabilistic models as well, our particular focus being \(\mathcal {Q}_1\) models. \(\mathcal {Q}_1\) models are physically important since, when applied to scenarios constructed by a particular composition rule, coincide with the well-defined “Almost Quantum Correlations”. In this work we see that some composition rules, however, give rise to scenarios with inequivalent allowed sets of \(\mathcal {Q}_1\) models. We find that the non-trivial dependence of \(\mathcal {Q}_1\) models on the choice of composition method is apparently an artifact of failure of those composition rules to capture the orthogonality relations given by the Local Orthogonality principle. We prove that \(\mathcal {Q}_1\) models satisfy invariance-under-composition-method for all the constructive compositions protocols which do capture this notion of Local Orthogonality.