Structures of D2 layers on LiF(001).

Classical Monte Carlo (MC) simulations of D(2) molecules physisorbed on LiF(001) surfaces are reported and show a series of interesting commensurate structure forms, viz., p(2x2) -->p(8x2) -->p(4x2), with coverages Theta=0.5, 0.625, and 0.75, respectively, and are stable up to 8 K. These structures are consistent with recent helium atom scattering (HAS) results (the p(4x2) is not observed) in terms of coverage and stability, but disagree in terms of symmetry. The p(2x2) structure contains two D(2) molecules per unit cell, with each molecule lying parallel to the plane of the surface directly above every other cationic site. For the p(4x2) structure, there are two kinds of adsorption sites: a parallel site, as in the case of p(2x2), and a tilted site, where the D(2) molecules sit between cationic and anionic sites with the molecular axis directed toward the anionic site, with a tilt angle of theta approximately 63 degrees. Perturbation theory calculations show that the adsorbed D(2) molecules are azimuthally delocalized and hence the structures are indeed c-type. Our calculations also indicate that o-D(2) and helicoptering p-D(2) species prefer cationic sites, compared to cartwheeling p-D(2) species.

Monte Carlo simulations of the adsorption of CO2 on the MgO(100) surface.

The adsorption of CO2 gas on the MgO (100) crystal surface is investigated using grand canonical Monte Carlo simulations. This allows us to obtain adsorption isotherms that can be compared with experiment, as well as to explore the possible formation of monolayers of different densities. Our model calculations agree reasonably well with the available experimental results. We find a "low-density" adsorbed monolayer where each CO2 molecule is bound to two Mg2+ ions on the MgO substrate. We also observe the formation of monolayers of higher density, where some of the CO2 molecules have rotated and tilted to expose additional binding sites. Low-temperature simulations of both the low- and high-density monolayers reveal that these states are very close in energy, with binding energies of approximately 7 kcal/mol at T=5 K. The high-density monolayer given by our model has a density that is significantly less than the reported experimental value. We discuss this discrepancy and offer suggestions for resolving it.

Novel medicines from nature.

A meeting held at the Royal Society of Medicine brought together a wide variety of people to look at a number of scientific, legal and ethical issues associated with the discovery of new drugs from nature, including plant, marine and animal sources. The meeting began with a historic overview of plant medicine, followed by presentations and discussion on particular aspects of bioprospecting and biodiversity. This was followed by an overview of the methods that can be used to identify potentially important drugs from natural products. The session on biological sources was the most important of the meeting as far as the discovery of new drugs was concerned. The final session of the meeting was pharmaco-socioeconomic in nature.

Aiming for quality as well as quantity.

The 4(th) International Congress on Drug Therapy in HIV Infection was held November 8-12, 1998, in Glasgow, Scotland. Triple combination therapy, the so-called HAART (highly active antiretroviral therapy), has now become established as the cornerstone of treatment, but a number of new approaches are under investigation. Current treatments have a number of limitations, including problems achieving patient compliance with complicated drug regimens and the development of resistance. One of the most interesting drugs that may become more important in any future treatment is hydroxyurea. A patient genotyping approach may also become more popular in future in order to provide an objective means of selecting a new drug regimen. As well as attacking the HIV virus, some researchers believe that it is equally important to stimulate the patient's immune system, and a number of different methods are under study. Many still believe that an effective vaccine is the best way to combat the spread of HIV/AIDS; unfortunately, progress has been painfully slow in this area. Sadly, research in this area is concentrating on HIV subtypes found in North America and Europe, while most cases of HIV are in the Third World. Greater efforts should be made in this area since it offers the best way of helping the greatest number of HIV sufferers.

The search for new antifungal drugs and strategies continues.

Much of the research presented at the 4th Congress of the European Confederation of Medical Mycology involved new ways of combating the problem of resistance to antifungal agents. Among the possible ways forward in medical mycology are improvements in the bioavailability of existing agents, more clinical testing of new agents and further development of the lipid formulations of amphotericin B. A current major concern of clinicians is that they are now seeing the appearance of cross-resistance between a number of previously very effective antifungals drugs. New in vitro results of terbinafine were presented at this congress, along with the latest information on voriconazole. There is little doubt that the only way to combat emerging drug resistance is at a subcellular level. This will require a much more detailed understanding than we have at present of how fungi and yeasts work.

Drug-resistant bacteria: responding to the infectious disease crisis.

The 1990s have been a period of growing anxiety about the emergence of antibiotic-resistant bacteria. Public health, society and the research community must respond quickly to safeguard existing drugs and develop new ones to prevent resistance overwhelming healthcare systems worldwide.

Type II diabetes: tips for managing your older patients.

In older type II diabetics, complications progress more rapidly than in younger diabetics for any given degree of hyperglycemia. Therefore, it is important to closely monitor blood glucose levels. When their sugars are controlled, older diabetics will have less nocturia and polyuria; fewer infections; better wound healing; a decrease in the rate of progression of cataracts, diabetic retinopathy, and nerve and renal disease; and better control of dyslipidemia. To learn some useful tips for managing older patients with type II diabetes, GERIATRICS reader David B Jack, MD, interviewed Nancy J.V. Bohannon, MD, for this "Ask the Expert" article.

Psychometric profiling of the elderly using the Cambridge Cognitive Examination.

OBJECTIVES: To (1) build a psychometric profile of elderly subjects attending specialists day care centers and residential homes using the Cambridge Cognitive Examination (CAMCOG); (2) identify factors that are predictive of the score obtained; and (3) determine whether scores from CAMCOG and the less time-consuming Mini-Mental State Examination (MMSE) were correlated sufficiently for the latter to replace the former for general cognitive screening. DESIGN: Nonrandom convenience sampling of elderly subjects attending specialist day care centers, residential homes, and units for the elderly mentally ill. SETTING: Belfast, Northern Ireland. MAIN OUTCOME: CAMCOG and MMSE scores with age, sex, educational level, marital status, visual and hearing ability, various central nervous system diseases, and handedness as independent variables. RESULTS: Age, sex, the wearing of glasses, Parkinson's disease, stroke, and epilepsy were found to be significant predictors of the CAMCOG score. This pattern held true for the MMSE score, except for stroke. CAMCOG and MMSE scores were correlated closely, even after deletion of overlapping scores. However, the CAMCOG score showed an increasing bias when the mean score increased. The cognitive function of the subjects attending the 3 types of establishment differed significantly, with those in the residential homes being the most heterogenous. CONCLUSIONS: The subjects profiled showed significant cognitive impairment. The MMSE score appears to give much the same information as the CAMCOG score in this general screening of our patient group. The population considered is probably representative of subjects attending similar units in the United Kingdom.

Keep taking the tomatoes--the exciting world of nutraceuticals.

The market for functional of health foods is growing steadily, and new legislation in the USA is likely to give it an enormous boost. Although the public has been aware of health foods for a long time, the latest products really merit the label 'designer foods'. There are still a number of important issues to be resolved, but industry is preparing itself for major investment in a market that could dwarf that for drugs.