Molecular ratchets - verification of the principle of detailed balance

We argue that the recent experiments of Kelly et. al.(Angew. Chem. Int. Ed. Engl. 36, 1866 (1997)) on molecular ratchets, in addition to being in agreement with the second law of thermodynamics, is a test of the principle of detailed balance for the ratchet. We suggest new experiments, using an asymmetric ratchet, to further test the principle. We also point out methods involving a time variation of the temperature to to give it a directional motion

A six-coordinate aryl-germanium complex formed by the Kläui ligand

PhGeCl₃ reacts with Na{[OP(OEt)₂]₃CoCp} to give the six-coordinate complex PhCl₂Ge{[OP(OEt)₂]₃CoCp}, characterised spectroscopically and by an X-ray crystal structure determination which showed a firmly-attached tridentate ligand [Ge–O 1.973(2) Å]

Lateral transfer in Stochastic Dollo models

Lateral transfer, a process whereby species exchange evolutionary traits through non-ancestral relationships, is a frequent source of model misspecification in phylogenetic inference. Lateral transfer obscures the phylogenetic signal in the data as the histories of affected traits are mosaics of the overall phylogeny. We control for the effect of lateral transfer in a Stochastic Dollo model and a Bayesian setting. Our likelihood is highly intractable as the parameters are the solution of a sequence of large systems of differential equations representing the expected evolution of traits along a tree. We illustrate our method on a data set of lexical traits in Eastern Polynesian languages and obtain an improved fit over the corresponding model without lateral transfer.Comment: Improvements suggested by reviewer

Predicting blade vortex interaction, airloads and acoustics using the vorticity transport model

Interactions between the blades and vortical structures within the wake of a helicopter rotor are a significant source of impulsive loading and noise, particularly in descending flight. Advances in the prediction and understanding of such blade vortex interactions have been aided in recent years by the extensive experimental dataset made available through the HART test programme. Brown’s Vorticity Transport Model was used to predict the rotor blade loading, the resultant wake system and the acoustic noise radiation for the HART II rotor. The vorticity conserving properties of the Vorticity Transport Model allow the detailed wake features that are associated with blade vortex interactions to be resolved. The experimental airload data, in particular the higher harmonic loading associated with blade vortex interactions, is matched well by the computations. The computed vorticity distribution in the wake also shows good correlation with the experimentally measured vortex positions. Including a representation of the fuselage within the computation yields marked improvement in the prediction of the vortex positions compared to similar calculations with an isolated rotor. An accoustic analysis, based on a Ffowcs-Williams Hawkings approach, is able to predict accurately the locations of the sound pressure maxima and the upstream attenuation of the sound radiated by the rotor. The principal discrepancies in airload, vortex position and acoustic prediction are confined almost exclusively to the rear of the advancing side of the rotor and, if errors in measuring the blade deflection can be discounted, may be due to minor inaccuracies in modelling the roll-up of the wake

Unions against governments: explaining general strikes in Western Europe, 1980-2006

Across Western Europe, unions have increasingly engaged in staging general strikes against governments since 1980. This increase in general strikes is puzzling as it has occurred at the same time as economic strikes have been on the decline. We posit that theories developed to explain economic strikes hold little explanatory power in accounting for variation in general strikes across countries and over time. Instead, we develop a framework based on political variables; in particular, whether governments have included or excluded unions in framing policy reforms; the party position of the government; and the type of government. Our empirical analysis, based on a conditional fixed-effects logit estimation of 84 general strikes between 1980 and 2006, shows that union exclusion from the process of reforming policies, government strength, and the party position of the government can provide an initial explanation for the occurrence of general strikes

Cycloauration of pyridyl sulphonamides

The pyridyl-2-alkylsulfonamides C₅H₄N(CH₂)nNHSO₂R (n = 1,2; R = Me, Ph or p-C₆H₄Me) and 8-(p-tosylamino)quinoline undergo facile cycloauration reactions with H[AuCl₄] in water, giving metallacyclic complexes coordinated through the pyridyl (or quinolyl) nitrogen atom and the deprotonated nitrogen of the sulfonamide group. The complexes have been fully characterised by NMR spectroscopy, ESI mass spectrometry and elemental analysis. The X-ray crystal structures of two derivatives reveal the presence of non-planar sulfonamide nitrogen atoms. The complexes show low activity against P388 murine leukaemia cells, possibly as a result of their ease of reduction with mild reducing agents

English Literacy Development for English Language Learners: Does Spanish Instruction Promote or Hinder?

In this brief, the authors consider whether instruction in a child\u27s native language (particularly Spanish) hinders or promotes learning of literacy in English. The authors conduct a four-step process for identifying research on this topic, examining this literature, and then determining the answer to this clinical question. The results suggest that supporting a child\u27s home/native language promotes rather than hinders development of English literacy skills

The cycloauration of pyridine-2-thiocarboxamide ligands

Reactions of H[AuCl₄] with N-substituted 2-pyridine thiocarboxamide ligands 2-(C₅H₄N)C(S)NHR (R= p-C₆H₄Me, CH₂Ph, Me, p-C₆H₄OMe) gave cycloaurated derivatives {(C₅H₄N)C(S)NR}AuCl₂, with the ligand bonded as the thiol tautomer through the deprotonated SH group and the pyridine N atom to give a five-membered metallacyclic ring. The X-ray structure determination of the R = CH₂Ph derivative shows a square-planar gold(III) complex that dimerises in the solid state by weak Au...S intermolecular interactions. In contrast, in the reaction of H[AuCl₄] with 2-(C₅H₄N)C(S)NHR where R = 2-pyridyl, the ligand was oxidised to give a 1,2,4-thiadiazolo[2,3-a]pyridinium heterocyclic ring that was crystallographically characterised

Five-coordinate gold(III) complexes of the Kläui ligands [(η⁵-C₅H₅)Co{P(O)(OR)₂}₃]− (R°=°Me, Et)

The reactions of cycloaurated gold(III) dichloride complexes [LAuCl₂] (L°=°2-C₆H₄CH₂NMe₂ or 2-C₆H₄PPh₂ NPh) with monoanionic tripodal oxygen donor Kläui ligands [(η⁵-C₅H₅)Co{P(O)(OR) ₂}₃]− (R°=°Me or Et) results in the formation of cationic gold(III) salts [LAu{OP(OR) ₂}₃Co(η⁵-C₅H₅)]+. An X-ray structure determination on [(2-C₆H₄PPh₂ NPh)Au{OP(OR) ₂}₃Co(η⁵-C₅H₅)]BF₄shows that the Kläui ligand coordinates strongly to the gold through two oxygen atoms, and weakly through the third, giving the gold(III) a distorted square pyramidal geometry. This is the first structurally characterised example of this geometry for gold(III) with ligands other than those containing rigid bipyridine or phenanthroline backbones. In solution at room temperature there is rapid interchange (on the NMR timescale) between the oxygen atoms of the Kläui ligands, which is frozen out on cooling