Modeling of Covalent Bonding in Solids by Inversion of Cohesive Energy Curves

We provide a systematic test of empirical theories of covalent bonding in solids using an exact procedure to invert ab initio cohesive energy curves. By considering multiple structures of the same material, it is possible for the first time to test competing angular functions, expose inconsistencies in the basic assumption of a cluster expansion, and extract general features of covalent bonding. We test our methods on silicon, and provide the direct evidence that the Tersoff-type bond order formalism correctly describes coordination dependence. For bond-bending forces, we obtain skewed angular functions that favor small angles, unlike existing models. As a proof-of-principle demonstration, we derive a Si interatomic potential which exhibits comparable accuracy to existing models.Comment: 4 pages revtex (twocolumn, psfig), 3 figures. Title and some wording (but no content) changed since original submission on 24 April 199

Over the counter (OTC) oral remedies for arthritis and rheumatism: How effective are they?

Increasingly patients resort to alternative remedies for arthritis and rheumatism, perhaps partly impelled by reports of toxicities from prescribed non-steroid anti-inflammatory drugs (NSAID). There is uncertainty about whether the most common alternative treatments provide relief or may cause adverse reactions.To ascertain the validity of manufacturers' claims permitted by the Therapeutic Goods Administration (TGA) in Australia for a range of self-medication products to treat the pain and inflammation of arthritis, available in local pharmacies, supermarkets or by mail order and in other countries.OTC products were administered orally to rats in standard assays for suppressing experimental arthritis and fever and for determining potential gastrotoxicity.The three NSAIDs available OTC were efficacious but gastrotoxic. Of the 37 herbal formulations examined, seven were as effective as ibuprofen in the anti-arthritic assay without causing gastric bleeding. Five of the 10 animal-sourced products tested were also effective without evident toxicity. Within a certain class of product, e.g. celery seed extracts or dried mussel preparations, efficacies ranged from almost zero to highly effective.Consumers currently have no guide to the likely efficacy of TGA-approved remedies. Quality control is urgently needed to justify the veracity of TGA-permitted and other claims on product labels