A critical assessment of unbalanced surface stresses: Some complementary considerations

The wide-ranging survey of twisted growth in polymers by Lotz and Cheng cites extensive evidence consistent with the relief of surface stress being the underlying cause. This complementary note contributes to the discussion by making three main points. First, it is necessary to go further and explain the key issue of how a consistent twist is maintained when, as commonly, this habit has a lower symmetry than the crystallographic lattice. Detailed study has shown that, in polyethylene, this occurs by reorganization of the initial fold surfaces. Second, the suggested explanation by Keith and Padden that. in polyethylene, the asymmetric habit derives from molecules adding to lamellae with inclined fold surfaces is invalid being doubly inconsistent with observation. Third, twisting has now been linked to faster growth by study of row structures in polyethylene. This produces inherently rough fold surfaces in Regime II whose internal stresses drive reorganization and twisting. For slower (Regime I) growth, fold surfaces form with and maintain ordered packing so providing no basis for twisting. These new insights radically alter the context of twisted growth and provide a firm factual basis for further work. (c) 2005 Elsevier Ltd. All rights reserved.

Crystal structure of the complementary quadruplex formed by d(GCATGCT) at atomic resolution

Here we report the crystal structure of the DNA heptanucleotide sequence d(GCATGCT) determined to a resolution of 1.1 Angstrom. The sequence folds into a complementary loop structure generating several unusual base pairings and is stabilised through cobalt hexammine and highly defined water sites. The single stranded loop is bound together through the G(N2)-C(O2) intra-strand H-bonds for the available G/C residues, which form further Watson-Crick pairings to a complementary sequence, through 2-fold symmetry, generating a pair of non-planar quadruplexes at the heart of the structure. Further, four adenine residues stack in pairs at one end, H-bonding through their N7-N6 positions, and are additionally stabilised through two highly conserved water positions at the structural terminus. This conformation is achieved through the rotation of the central thymine base at the pinnacle of the loop structure, where it stacks with an adjacent thymine residue within the lattice. The crystal packing yields two halved biological units, each related across a 2-fold symmetry axis spanning a cobalt hexammine residue between them, which stabilises the quadruplex structure through H-bonds to the phosphate oxygens and localised hydration.

Complementary therapies, the placebo effect and the pharmacist

Pharmacists need to know about complementary therapies so they can advise patients on their suitability, and also their compatibility with conventional drugs. This article discusses, from a pharmaceutical perspective, the types of therapies available, their applications and indications, and issues surrounding the placebo effect.

Multiple diversity measures to identify complementary conservation areas for the Baja California peninsular cacti

The Baja California Peninsula is home to 85 species of cacti, of which 54 are endemic, highlighting its importance as a cactus diverse region within Mexico. Many species are under threat due to collection pressure and habitat loss, but ensuring maximal protection of cacti species requires a better understanding of diversity patterns. We assessed species richness, endemism, and phylogenetic and morphological diversity using herbarium records and a molecular phylogeny for 82 species of cacti found in the peninsula. The four diversity measures were estimated for the existing nature reserve network and for 314 hexagrids of 726 km2. Using the hexagrid data, we surveyed our results for areas that best complement the current protected cacti diversity in the Baja California Peninsula. Currently, the natural reserve network in Baja shelters an important amount of the cacti diversity (74% of the species, 85.9% of the phylogenetic diversity, 76% of endemics and all the growth forms). While species richness produced several solutions to complement the diversity protected, by identifying priority species (endemic species with high contribution to overall PD) one best solution is reported. Three areas (San Matías, Magdalena and Margarita Islands and El Triunfo), selected using species richness, PD and endemism, best complement the diversity currently protected, increasing species richness to 89%, PD to 94% and endemism to 89%, and should be considered in future conservation plans. Two of these areas could be included within nature reserves already established.

An examination of the complementary volume–volatility information theories

The volume–volatility relationship during the dissemination stages of information flow is examined by analyzing various theories relating volume and volatility as complementary rather than competing models. The mixture of distributions hypothesis, sequential arrival of information hypothesis, the dispersion of beliefs hypothesis, and the noise trader hypothesis all add to the understanding of how volume and volatility interact for different types of futures traders. An integrated picture of the volume–volatility relationship is provided by investigating the dynamic linear and nonlinear associations between volatility and the volume of informed (institutional) and uninformed (the general public) traders. In particular, the trading behavior explanation for the persistence of futures volatility, the effect of the timing of private information arrival, and the response of institutional traders to excess noise trading risk is examined

Duality, observability, and controllability for linear time-varying descriptor systems

A characterization of observability for linear time-varying descriptor systemsE(t)x(t)+F(t)x(t)=B(t)u(t), y(t)=C(t)x(t) was recently developed. NeitherE norC were required to have constant rank. This paper defines a dual system, and a type of controllability so that observability of the original system is equivalent to controllability of the dual system. Criteria for observability and controllability are given in terms of arrays of derivatives of the original coefficients. In addition, the duality results of this paper lead to an improvement on a previous fundamental structure result for solvable systems of the formE(t)x(t)+F(t)x(t)=f(tt).

Managing the duality of IHRM: unravelling the strategy and perceptions of key actors in South Korean MNCs

This research aims to extend our understanding of the duality between global integration and local responsiveness in multinational corporations (MNCs) by exploring the perceptions of corporate HR actors regarding the intra-organisational factors that alter the balance between these pressures. It examines the perceptions and actions of key actors in the context of two Korean MNCs. The study shows the importance attributed to a range of socio-procedural factors by corporate actors and which, therefore, inform the practical management of the dual forces, notably: HR expertise, social ties, trustworthy relationships and co-involvement in decision processes.