Historical account: Francis William Aston: the man behind the mass spectrograph

Francis William Aston was among the most accomplished physicists of the 20th century. A Nobel laureate and Fellow of the Royal Society, his research career spanned four decades. During this time, he provided experimental proof for the existence of isotopes of many of the chemical elements and recorded their masses using several, hand-built mass spectrographs. A rather private man who lived alone in Trinity College for much of his adult life, Aston remains a somewhat elusive and mysterious figure. This biography attempts to shed some more light on the man, including his character and his personal life, and particularly how his life was shaped by his childhood, environment and education. It contains previously unpublished material and photographs and complements the biographies of Hevesy and Thomson, following Aston's death, and that by Squires detailing the construction and performance of his mass spectrographs at the Cavendish Laboratory. It is published at a timely juncture, some 100 years after Aston's first arrival at Cambridge.     

Phase titrations-V: Nitroalkanes: Improving the phase-titration end-point

End-points for direct phase titrations of binary solutions of nitropropanes in water-miscible solvents are fair and, because of the steepness of the calibration curve, results are adequate. Nitroethane, in binary combination, gives poor end-points but, over part of the optimum titration range, results are good. Nitromethane gives end-points which are almost useless. Addition of standard amounts of nitrobenzene, which gives excellent phase-titration end-points, improves the composite nitromethane-nitrobenzene-water-miscible component end-point markedly. Because the nitrobenzene concentration is constant, the water titre is a function only of the nitromethane concentration. Addition of constant amounts of nitrobenzene also increases the optimum titration range. Results given for all systems are comparable in accuracy with systems previously reported which are favourable to direct phase titration.     

Tilted peptides: the history

Nature has selected peptide motifs for protein functions. It is clear that specific sequence motifs can identify families of enzymes. These sequence motifs are one dimensional signatures and nature has also developed two dimension motifs which cannot be read in the one dimension of sequence language but can be detected in the three dimensional properties of a secondary structure. One of such motifs is tilted peptides. They do not correspond to any consensus of sequence but correspond to a consensus motif where hydrophobicity balance is used as a functional device. In the nineteen eighties, the first tilted peptide was deciphered from the sequence of a virus fusion protein by molecular modelling. It was described as a protein fragment hydrophobic enough to insert into a membrane but too short to span it. The fragment exhibited an asymmetric distribution of hydrophobicity along the helix long axis and hence, was unable to lie parallel or perpendicular to a membrane surface but adopted an orientation in between. Hydrophobicity motif was a very new and very challenging concept and tilted peptides were rapidly found to be involved in several mechanisms of virus fusion. They were also found to be involved in protein secretion and future studies could establish their involvement in the destabilization of 3D protein structures and in the alpha to beta transconformations, which drive the generation of amyloid deposits.     

Phosphino-carboxamides: the inconspicuous gems

Compounds combining phosphine and carboxamide moieties in their molecules have developed virtually unnoticed into a specific class of highly structurally versatile and tuneable donor molecules finding manifold use in various fields, particularly in coordination chemistry, biomedical sciences and in catalysis. In the latter field, some phosphinoamides became the real privileged ligands and an indispensable part of a standard toolbox for synthetic chemists. This critical review aims to give an overview of the multifaceted chemistry of such compounds, paying attention to both the fundamentals and recent developments in this continuously expanding field.     

Skin: the ultimate interface

The outer layer of the skin, the stratum corneum is a unique barrier membrane. On average it is only 20 μm thick (about a quarter the thickness of a normal sheet of paper) but it prevents us from losing excessive water and it protects us from our environment. It forms a special interface between our body, the air, water and various solids. In order to understand the barrier properties of the skin we need to determine its structure at various levels ranging from the macroscopic scale to the molecular level. This has been made easier by the advances that there have been over the recent decade. However, the amount of a material that is capable of penetrating this excellent barrier and reaching the underlying systemic circulation is still only of the order of 1 or 2 per cent of the total applied dose. The purpose of this publication is to explore the strategies currently employed to promote skin permeation and to consider the most exciting approaches currently under investigation. The limitations of current methodology to examine the problem are discussed. New opportunities to fill the gaps in our current knowledge are identified and the importance of interdisciplinary research in the field is emphasised.     

Micellar Copolymerization:the State of the Arts

Over the past two decades, hydrophobically modified water-soluble polymers (HMWSPs),particularly hydrophobically associating polyacrylamides (HAPAMs), have attracted increased interest owing to their practical and fundamental importance[1]. This system usually consists of a hydrophilic backbone with a small proportion (generally less than 2 mol %) of hydrophobic pendent groups. When dissolved in aqueous solutions, the apolar moieties tend to exclude water and are held together by intra- and intermolecular hydrophobic associations. This leads to a transitional network structure that induces a substantial increase in solution viscosity. Such viscosity-building ability is further elevated upon adding salt or increasing temperature due to the enhanced polarity.Additionally, the dynamic associating junctions can be ruptured upon high shear stress, but re-formed when the force ceases. All these unique properties enable HAPAMs attractiveness to various industrial uses in which the control of fluid theology is required.However, it is a great challenge to synthesize HAPAMs since acrylamide and hydrophobic comonomers are mutually incompatible. After attempts using heterogeneous, inverse emulsion,microemulsion, and precipitation copolymerization processes, the commonly accepted method is micellar free radical copolymerization in which an appropriate surfactant is used to solubilize the hydrophobic comonomer[2].In this paper, the sate of the arts for micellar copolymerization is comprehensively reviewed:1. the mechanism of micellar copolymerization;2. parameters affecting micellar copolymerization, including:(1) nature and level of hydrophobic comonomer;(2) nature and content of surfactant used;(3) initiator and temperature.3. structural characteristics of HAPAMs prepared via micellar copolymerization;4. properties of HAPAMs prepared via micellar copolymerization:(1) dilute solution properties;(2) semi-dilute solution properties.5. applications of micellar copolymerization.In short, the main goal of this review is trying to establish an interrelationship among .synthetic method, structure and properties, so as to give a guideline for "tailoring" the polymer structure to satisfy different specific end use.     

Communication: the rotational excitation of D2 by H: on the importance of the reactive channels

We report fully-quantum time-independent calculations of cross sections and rate coefficients for the collisional excitation and dissociation of D(2) by H, two astrophysically relevant processes. Our calculations are based on the recent H(3) global potential energy surface of Mielke et al. [J. Chem. Phys. 116, 4142 (2002)]. Results of exact three-dimensional calculations, i.e., including the reactive channels, are compared to pure inelastic two-dimensional calculations based on the rigid rotor approximation. A reasonable agreement is found between the two sets of inelastic cross sections over the whole energy range 10-9000 cm(-1). At the highest collisional energies, where the reactive channels are significant, the rigid rotor approach slightly overestimates the cross sections, as expected. At moderate collisional energies, however, the opposite behaviour is observed. The rigid rotor approach is found to be reliable at temperatures below ~500 K, with a significant but moderate contribution from reactive channels.     

Communication: Heavy Rydberg states: the H+H- system

Heavy Rydberg states are analogs of electronic Rydberg states, but with the electron replaced by a much heavier ion. We calculate ab initio the extremely long-range vibrational H(+)H(-) heavy Rydberg states in H(2), and compare these to recent experiments. The calculated resonance positions and widths agree well with experiment, but we predict additional sharp interloper resonances corresponding to vibrational states trapped inside the barrier on potential energy curve 7 (1)Σ(g)(+).