Synthesis and characterization of thermally stable second-order nonlinear optical side-chain polyimides containing thiazole and benzothiazole push-pull chromophores

Push-pull nonlinear optical (NLO) chromophores containing thiazole and benzothiazole acceptors were synthesized and characterized. Using these chromophores a series of second-order NLO polyimides were Successfully prepared from 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), pyromellitic dianhydride (PMDA) and 3,3'4,4'-benzophenone tetracarboxylic dianhydride (BTDA) by a standard condensation polymerization technique. These polyimides exhibit high glass transition temperatures ranging from 160 to 188 degrees C. UV-vis spectrum of polyimide exhibited a slight blue shift and decreases in absorption due to birefringence. From the order parameters, it was found that chromophores were aligned effectively. Using in situ poling and temperature ramping technique, the optical temperatures for corona poling were obtained. It was found that the optimal temperatures of polyimides approach their glass transition temperatures. These polyimides demonstrate relatively large d(33) values range between 35.15 and 45.20 pm/V at 532 nm. (C) 2008 Elsevier B.V. All rights reserved.

Provision of information about drug side-effects to patients

To make informed decisions about taking medicinal drugs, people need accurate information about side-effects. A European Union guideline now recommends use of qualitative descriptions for five bands of risk, ranging from very rare (affecting < 0·01% of the population), to very common (>10%). We did four studies of more than 750 people, whom we asked to estimate the probability of having a side-effect on the basis of qualitative and quantitative descriptions. Our results showed that qualitative descriptions led to gross overestimation of risk. Until further work is done on how patients taking the drugs interpret these terms, the terms should not be used in drug information leaflets.

Communicating information about medication side effects: effects on satisfaction, perceived risk to health, and intention to comply

Previous research has shown that people's evaluations of explanations about medication and their intention to comply with the prescription are detrimentally affected by the inclusion of information about adverse side effects of the medication. The present study (Experiment 1) examined which particular aspects of information about side effects (their number, likelihood of occurrence, or severity) are likely to have the greatest effect on people's satisfaction, perception of risk, and intention to comply, as well as how the information about side effects interacts with information about the severity of the illness for which the medication was prescribed. Across all measures, it was found that manipulations of side effect severity had the greatest impact on people's judgements, followed by manipulations of side effect likelihood and then number. Experiments 2 and 3 examined how the severity of the diagnosed illness and information about negative side effects interact with two other factors suggested by Social Cognition models of health behaviour to affect people's intention to comply: namely, perceived benefit of taking the prescribed drug, and the perceived level of control over preventing or alleviating the side effects. It was found that providing people with a statement about the positive benefit of taking the medication had relatively little effect on judgements, whereas informing them about how to reduce the chances of experiencing the side effects had an overall beneficial effect on ratings.

Is 15 per cent very common? Informing people about the risks of medication side effects

Objectives - To assess the general public's interpretation of the verbal descriptors for side effect frequency recommended for use in medicine information leaflets by a European Union (EU) guideline, and to examine the extent to which differences in interpretation affect people's perception of risk and their judgments of intention to comply with the prescribed treatment. Method - Two studies used a controlled empirical methodology in which people were presented with a hypothetical, but realistic, scenario about visiting their general practitioner and being prescribed medication. They were given an explanation that focused on the side effects of the medicine, together with information about the probability of occurrence using either numerical percentages or the corresponding EU verbal descriptors. Interpretation of the descriptors was assessed. In study 2, participants were also required to make various judgments, including risk to health and intention to comply. Key findings - In both studies, use of the EU recommended descriptors led to significant overestimations of the likelihood of particular side effects occurring. Study 2 further showed that the "overestimation" resulted in significantly increased ratings of perceived severity of side effects and risk to health, as well as significantly reduced ratings of intention to comply, compared with those for people who received the probability information in numerical form. Conclusion - While it is recognised that the current findings require replication in a clinical setting, the European and national authorities should suspend the use of the EU recommended terms until further research is available to allow the use of an evidence-based approach.

Evaluating explanations about drug prescriptions: effects of varying the nature of information about side effects and its relative position in explanations

This study evaluates computer-generated written explanations about drug prescriptions that are based on an analysis of both patient and doctor informational needs. Three experiments examine the effects of varying the type of information given about the possible side effects of the medication, and the order of information within the explanation. Experiment 1 investigated the effects of these two factors on people's ratings of how good they consider the explanations to be and of their perceived likelihood of taking the medication, as well as on their memory for the information in the explanation. Experiment 2 further examined the effects of varying information about side effects by separating out the contribution of number and severity of side effects. It was found that participants in this study did not “like” explanations that described severe side effects, and also judged that they would be less likely to take the medication if given such explanations. Experiment 3 therefore investigated whether information about severe side effects could be presented in such a way as to increase judgements of how good explanations are thought to be, as well as the perceived likelihood of adherence. The results showed some benefits of providing additional explanatory information.

Synthesis of the ester side chains of some potently antileukemic harringtonia alkaloids from chiral citrates

The selective reduction of one of the three carboxyl groups of two chiral citric acid derivatives to the corresponding aldehydes, under Rosenmund conditions, are reported together with the application of these aldehydes to the syntheses of the ester side chains of some potently antileukemic Cephalotaxus alkaloids e.g. anhydroharringtonine.

A rheological and SAXS study of the lamellar order in a side-on liquid crystalline block copolymer

We study the structure and shear flow behavior of a side-on liquid crystalline triblock copolymer, named PBA-b-PA444-b-PBA (PBA is poly(butyl acrylate) and PA444 is a poly(acrylate) with a nematic liquid crystal side-on mesogen), in the self-assembled lamellar phase and in the disordered phase. Simultaneous oscillatory shear and small-angle X-ray scattering experiments show that shearing PBA-b-PA444-b-PBA at high frequency and strain amplitudes leads to the alignment of the lamellae with normals perpendicular to the shear direction and to the velocity gradient direction, i.e., in the perpendicular orientation. The order-to-disorder transition temperature (T-ODT) is independent of the applied strain, in contrast to results reported in the literature for coil-coil diblock copolymers, which show an increase in T-ODT with shear rate. It is possible that in our system, T-ODT does not depend on the applied strain because the fluctuations are weaker than those present in coil-coil diblock copolymer systems.

Ordering on multiple lengthscales in a series of side group liquid crystal block copolymers containing a cholesteryl-based mesogen

Hierarchical ordering in a side group liquid crystal block copolymer is investigated by differential scanning calorimetry, polarized optical microscopy, small-angle X-ray and neutron scattering (SAXS and SANS) and transmission electron microscopy (TEM). A series of block copolymers with a range of compositions was prepared by atom transfer radical polymerization, comprising a polystyrene block and a poly(methyl methacrylate) block bearing chiral cholesteryl mesogens. Smectic ordering is observed as well as microphase separation of the block copolymer. Lamellar structures were observed for far larger volume fractions than for coil-coil copolymers (up to a volume fraction of liquid crystal block, f(LC) = 0.8). A sample with f(LC) = 0.86 exhibited a hexagonal-packed cylinder morphology, as confirmed by SAXS and TEM. The matrix comprised the liquid crystal block, with the mesogens forming smectic layers. For the liquid crystal homopolymer and samples with high f(LC), a smectic-smectic phase transition was observed below the clearing point. At low temperature, the smectic phase comprises coexisting domains with monolayer S-A,S-1 coexisting with interdigitated S-A,S-d domains. At high temperature a SA,1 phase is observed. This is the only structure observed for samples with lower f(LC). These unprecedented results point to the influence of block copolymer microphase separation on the smectic ordering.

Comparison of two methods of presenting risk information to patients about the side effects of medicines

Objective: To determine whether the use of verbal descriptors suggested by the European Union (EU) such as "common" (1-10% frequency) and "rare" (0.01-0.1%) effectively conveys the level of risk of side effects to people taking a medicine. Design: Randomised controlled study with unconcealed allocation. Participants: 120 adults taking simvastatin or atorvastatin after cardiac surgery or myocardial infarction. Setting: Cardiac rehabilitation clinics at two hospitals in Leeds, UK. Intervention: A written statement about one of the side effects of the medicine (either constipation or pancreatitis). Within each side effect condition half the patients were given the information in verbal form and half in numerical form (for constipation, "common" or 2.5%; for pancreatitis, "rare" or 0.04%). Main outcome measure: The estimated likelihood of the side effect occurring. Other outcome measures related to the perceived severity of the side effect, its risk to health, and its effect on decisions about whether to take the medicine. Results: The mean likelihood estimate given for the constipation side effect was 34.2% in the verbal group and 8.1% in the numerical group; for pancreatitis it was 18% in the verbal group and 2.1% in the numerical group. The verbal descriptors were associated with more negative perceptions of the medicine than their equivalent numerical descriptors. Conclusions: Patients want and need understandable information about medicines and their risks and benefits. This is essential if they are to become partners in medicine taking. The use of verbal descriptors to improve the level of information about side effect risk leads to overestimation of the level of harm and may lead patients to make inappropriate decisions about whether or not they take the medicine.