Running Uphill: An Experimental Result and its Applications

An experimentally derived formula has implications for (i) the measurement of a runner's workrate; (ii) choice of gradient in running uphill; and (iii) the use of Naismith's rule in deriving schedules for fell runners.     

Guaranteed error bounds for the initial value problem using polytope arithmetic

In this paper we propose and compare modifications of the method of co-ordinate transformations for finding guaranteed bounds for the numerical solution of the initial value problem. These modifications are judged on their success in overcoming exponentially too large growth of the computed error bound.     

Linking solution chemistry to crystal nucleation: the case of tetrolic acid

The application of FTIR spectroscopy to concentrated solutions of tetrolic acid shows, for the first time, a direct relationship between molecular self association in solution and H-bonded motifs in the subsequently crystallised solid phases.     

Solid state dehydration processes: mechanism of water loss from crystalline inosine dihydrate

The solid state dehydration of inosine dihydrate has been investigated using powder X-ray diffraction, differential scanning calorimetry, thermal gravimetric analysis, dynamic vapor sorption, hot stage microscopy, 13C solid state NMR, and variable temperature Fourier transform infrared spectroscopy. The information obtained from these experiments has been combined with an analysis of the crystallographic packing of inosine dihydrate and its two anhydrous polymorphs to yield mechanistic insights into the modes of water loss. The results allow an understanding of why, surprisingly, the dehydration of the dihydrate is always found to give the anhydrous, metastable, alpha-form.     

Crystal and molecular structure of diglycollic acid

The crystal structure of diglycollic acid has been determined by X-ray diffraction techniques and refined by full-matrix least squares, with three-dimensional counter data. The crystals are monoclinic:C2/c,a = 9·708(4),b = 3·938(3),c = 15·685(6) Å, = 112·01(3) °, andZ = 4. The finalR-factor for 673 observed reflections is 0·050. The carboxyl groups are related by a two-fold axis, parallel tob, passing through the central oxygen atom of the molecule. Polymeric chains of molecules are formed by hydrogen bonding. The intermolecular O—O separation is 2·668 Å, and is consistent with the observed infrared spectrum of solid diglycollic acid.     

Crystallization of a salt of a weak organic acid and base: solubility relations, supersaturation control and polymorphic behavior

Control of crystallization processes for organic salts is of importance to the pharmaceutical industry as many active pharmaceutical materials are marketed as salts. In this study, a method for estimating the solubility product of a salt of a weak acid and weak base from measured pH-solubility data is described for the first time. This allows calculation of the supersaturation of solutions at known pH. Ethylenediammonium 3,5-dinitrobenzoate is a polymorphic organic salt. A detailed study of the effects of pH, supersaturation, and temperature of crystallization on the physical properties of this salt shows that the desired polymorph may be produced by appropriate selection of the pH and supersaturation of crystallization. Crystal morphology is also controlled by these crystallization conditions.     

Viability of plant cell suspensions exposed to homogeneous ultrasonic fields of different energy density and wave type

Exposure of Petunia hybrida cell suspensions to ultrasound at a frequency of 2.43 MHz in a standing wave field at an energy density of 70 Jm-3 (pressure amplitude of 0.78 MPa) decreased their mean viability to 35% after 20 min of sonication. A comparison of propagating wave and standing wave treatments at equal frequency (2.15 MHz) and energy density (8.5 Jm-3) showed, in the first case, a rapid decline in mean viability of cells (to 30% after 10 min of sonication) and, in the second case, a retaining of the initial viability (95%), respectively. Cells sonicated 4 days after subculture were more sensitive than cells sonicated 2 or 6 days after transfer to new culture medium. It was concluded that cellular viability depends primarily on the acoustic energy density, the exposure time, and the mechanical properties of the cells determined by age. As a consequence of the trapping of cells in the anti-node planes of the standing wave, propagating wave fields reduced cellular viability compared with standing wave fields at equal energy density.     

Platinum drug adduct formation in the nucleosome core alters nucleosome mobility but not positioning

Nucleosome positioning and reorganization regulate DNA site exposure in chromatin. Platinum anticancer agents form DNA adducts that disrupt nuclear activities, triggering apoptosis. Mechanistic insight would aid in the development of improved therapies to circumvent drug toxicity and resistance. We show that platinum adducts formed by reaction of cisplatin or oxaliplatin with the nucleosome core inhibit histone octamer-DNA sliding but do not cause significant alteration of positioning. Thus, adduct formation reinforces positional preferences intrinsic to the DNA sequence, which indicates that modulation of platinum drug site selectivity by histone octamer association may relate to nucleosome-specific properties of DNA. This sheds light on platinum drug-mediated inhibition of chromatin remodeling in vivo and suggests that adducts can shield their own repair and interfere with genomic activities by directly altering nucleosome dynamics.     

Organic pH Buffer for Dendrite-Free and Shuttle-Free Zn-I2 Batteries

Aqueous Zn-Iodine (I₂) batteries are attractive for large-scale energy storage. However, drawbacks include, Zn dendrites, hydrogen evolution reaction (HER), corrosion and, cathode “shuttle” of polyiodines. Here we report a class of N-containing heterocyclic compounds as organic pH buffers to obviate these. We evidence that addition of pyridine /imidazole regulates electrolyte pH, and inhibits HER and anode corrosion. In addition, pyridine and imidazole preferentially absorb on Zn metal, regulating non-dendritic Zn plating /stripping, and achieving a high Coulombic efficiency of 99.6 % and long-term cycling stability of 3200 h at 2 mA cm⁻², 2 mAh cm⁻². It is also confirmed that pyridine inhibits polyiodines shuttling and boosts conversion kinetics for I⁻/I₂. As a result, the Zn-I₂ full battery exhibits long cycle stability of >25 000 cycles and high specific capacity of 105.5 mAh g⁻¹ at 10 A g⁻¹. We conclude organic pH buffer engineering is practical for dendrite-free and shuttle-free Zn-I₂ batteries.     

Synthesis and Optical Properties of Group 14 Element–Thienyl Polymers

The syntheses of several types of polymers containing silicon, germanium and tin in the main chain are described. Optical studies show that they exhibit absorption in the far-ultraviolet region of the spectrum (200–400 nm). Electrical studies show that these polymers behave as insulators. Preliminary studies indicate, that depending on the chemical structure of the backbone, it is possible to dope some of the polymers via partial oxidation in solution. © 1997 John Wiley & Sons, Ltd.