Acoustic metamaterials for sound focusing and confinement

International audienceWe give a theoretical design for a locally resonant two-dimensional cylindrical structure involving a pair of C-shaped voids in an elastic medium which we term as double `C' resonators (DCRs) and imbedded thin stiff bars, that displays the negative refraction effect in the low frequency regime. DCRs are responsible for a low frequency band gap which hybridizes with a tiny gap associated with the presence of the thin bars. Using an asymptotic analysis, typical working frequencies are given in closed form: DCRs behave as Helmholtz resonators modeled by masses connected to clamped walls by springs on either side, while thin bars behave as a periodic bi-atomic chain of masses connected by springs. The discrete models give an accurate description of the location and width of the stop band in the case of the DCR and the first two dispersion bands for the periodic thin bars. We then combine our asymptotic formulae for arrays of DCR and thin-bars to design a composite structure that displays a negative refraction effect and has a negative phase velocity in a frequency band, and thus behaves in many ways as a negative refractive acoustic medium (NRAM). Finite element computations show that at this frequency, a slab of such NRAM works as a phononic flat superlens whereas two corners of such NRAM sharing a vertex act as an open resonator and can be used to confine sound to a certain extent

Arginase from kiwifruit: properties and seasonal variation

The in vitro activity of arginase (EC 3.5.3.1) was investigated in youngest-mature leaves and roots (1-3 mm diameter) of kiwifruit vines (Actinidia deliciosa var. deliciosa) during an annual growth cycle, and enzyme from root material partially purified. No seasonal trend in the specific activity of arginase was observed in roots. Measurements in leaves, however, rose gradually during early growth and plateaued c. 17 weeks after budbreak. Changes in arginase activity were not correlated with changes in the concentration of arginine (substrate) or glutamine (likely end-product of arginine catabolism) in either tissue during the growth cycle. Purification was by (NH4)2SO4 precipitation and DEAE-cellulose chromatography. The kinetic properties of the enzyme, purified 60-fold over that in crude extracts, indicated a pH optimum of 8.8, and a Km (L-arginine) of 7.85 mM. Partially-purified enzyme was deactivated by dialysis against EDTA, and reactivated in the presence of Mn²⁺, Co²⁺, and Ni²⁺

Reducing unnecessary prescriptions of antibiotics for acute cough: Adaptation of a leaflet aimed at Turkish immigrants in Germany

<p>Abstract</p> <p>Background</p> <p>The reduction in the number of unnecessary prescriptions of antibiotics has become one of the most important objectives for primary health care. German GPs report that they are under "pressure to prescribe" antibiotics particularly in consultations with Turkish immigrants. And so a qualitative approach was used to learn more about the socio-medical context of Turkish patients in regard to acute coughs. A German leaflet designed to improve the doctor-patient communication has been positively tested and then adapted for Turkish patients.</p> <p>Methods</p> <p>The original leaflet was first translated into Turkish. Then 57 patients belonging to 8 different GPs were interviewed about the leaflet using a semi-standardised script. The material was audio recorded, fully transcribed, and analysed by three independent researchers. As a first step a comprehensive content analysis was performed. Secondly, elements crucial to any Turkish version of the leaflet were identified.</p> <p>Results</p> <p>The interviews showed that the leaflets' messages were clearly understood by all patients irrespective of age, gender, and educational background. We identified no major problems in the perception of the translated leaflet but identified several minor points which could be improved. We found that patients were starting to reconsider their attitudes after reading the leaflet.</p> <p>Conclusion</p> <p>The leaflet successfully imparted relevant and new information to the target patients. A qualitative approach is a feasible way to prove general acceptance and provides additional information for its adaptation to medico-cultural factors.</p

General practitioners and tutors' experiences with peer group academic detailing: a qualitative study

<p>Abstract</p> <p>Background</p> <p>The Prescription Peer Academic Detailing (Rx-PAD) project is an educational intervention study aiming at improving GPs' competence in pharmacotherapy. GPs in CME peer groups were randomised to receive a tailored intervention, either to support a safer prescription practice for elderly patients or to improve prescribing of antibiotics to patients with respiratory tract infections. The project was based on the principles of peer group academic detailing, incorporating individual feedback on GPs' prescription patterns. We did a study to explore GPs and tutors' experiences with peer group academic detailing, and to explore GPs' reasons for deviating from recommended prescribing practice.</p> <p>Methods</p> <p>Data was collected through nine focus group interviews with a total of 39 GPs and 20 tutors. Transcripts from the interviews were analyzed by two researchers according to a procedure for thematic content analysis.</p> <p>Results</p> <p>A shared understanding of the complex decision-making involved in prescribing in general practice was reported by both GPs and tutors as essential for an open discussion in the CME groups. Tutors experienced that CME groups differed regarding structure and atmosphere, and in some groups it was a challenge to run the scheme as planned. Individual feedback motivated GPs to reflect on and to improve their prescribing practice, though feedback reports could cause distress if the prescribing practice was unfavourable. Explanations for inappropriate prescriptions were lack of knowledge, factors associated with patients, the GP's background, the practice, and other health professionals or health care facilities.</p> <p>Conclusions</p> <p>GPs and tutors experienced peer group academic detailing as a suitable method to discuss and learn more about pharmacotherapy. An important outcome for GPs was being more reflective about their prescriptions. Disclosure of inappropriate prescribing can cause distress in some doctors, and tutors must be prepared to recognise and manage such reactions.</p

Inhibition of HIV replication by amino-sugar derivatives

AbstractThe plant alkaloids castanospermine, dihydroxymethyldihydroxypyrrolidine and deoxynojirimycin have recently been shown to have potential anti-HIV activity [(1987) Proc. Natl. Acad. Sci. USA 84, 8120–8124; (1987) Nature 330, 74–77; (1987) Lancet i, 1025–1026]. They are thought to act by inhibiting α-glucosidase I, an enzyme involved in the processing of N-linked oligosaccharides on glycoproteins. We report here the relative efficacy of a spectrum of amino-sugar derivatives as inhibition of HIV cytopathicity. Several α-glucosidase inhibitors and α-fucosidase inhibitors were found to be active at concentrations which were non-cytotoxic

Use and feasibility of delayed prescribing for respiratory tract infections: A questionnaire survey

<p>Abstract</p> <p>Background</p> <p>Delayed prescribing of antibiotics for respiratory tract infections (RTIs) lowers the amount of antibiotics consumed. Several national treatment guidelines on RTIs recommend the strategy. When advocating treatment innovations, the feasibility and credibility of the innovation must be taken into account. The objective of this study was to explore GPs use and patients uptake of wait-and-see prescriptions for RTIs, and to investigate the feasibility of the strategy from GPs' and patients' perspectives.</p> <p>Methods</p> <p>Questionnaire survey among Norwegian GPs issuing and patients receiving a wait-and-see-prescription for RTIs. Patients reported symptoms, confidence and antibiotics consumption, GPs reported diagnoses, reason for issuing a wait-and-see-prescription and their opinion about the method.</p> <p>Results</p> <p>304 response pairs from consultations with 49 GPs were received. The patient response rate was 80%. The most common diagnosis for the GPs to issue a wait-and-see prescription was sinusitis (33%) and otitis (21%). 46% of the patients reported to consume the antibiotics. When adjusted for other factors, the diagnosis did not predict antibiotic consumption, but both being 16 years or more (p = 0,006) and reporting to have a fever (p = 0,012) doubled the odds of antibiotic consumption, while feeling very ill more than quadrupled the odds (p = 0,002). In 210 cases (69%), the GP found delayed prescribing a very reasonable strategy, and 270 patients (89%) would prefer to receive a wait-and-see prescription in a similar situation in the future. The GPs found delayed prescribing very reasonable most frequently in cases of sinusitis (79%, p = 0,007) and least frequently in cases of lower RTIs (49%, p = 0,002).</p> <p>Conclusion</p> <p>Most patients and GPs are satisfied with the delayed prescribing strategy. The patients' age, symptoms and malaise are more important than the diagnosis in predicting antibiotic consumption. The GP's view of the method as a reasonable approach depends on the patient's diagnosis. In our setting, delayed prescribing seems to be a feasible strategy, especially in cases of sinusitis and otitis. Educational efforts to promote delayed prescribing in similar settings should focus on these diagnoses.</p

Infectious disease management in primary care: perceptions of GPs

<p>Abstract</p> <p>Background</p> <p>It is important to keep the level of antibiotic prescribing low to contain the development of resistant bacteria. This study was conducted to reveal new knowledge about how GPs think in relation to the prescribing of antibiotics - knowledge that could be used in efforts toward rational treatment of infectious diseases in primary care. The aim was to explore and describe the variations in GPs' perceptions of infectious disease management, with special reference to antibiotic prescribing.</p> <p>Methods</p> <p>Twenty GPs working at primary care centres in a county in south-west Sweden were purposively selected based on the strategy of including GPs with different kinds of experience. The GPs were interviewed and perceptions among GPs were analysed by a phenomenographic approach.</p> <p>Results</p> <p>Five qualitatively different perceptions of infectious disease management were identified. They were: (A) the GP must help the patient to achieve health and well-being; (B) the management must meet the GP's perceived personal, professional and organisational demands; (C) restrictive antibiotic prescribing is time-consuming; (D) restrictive antibiotic prescribing can protect the effectiveness of antibiotics; and (E) patients benefit personally from restrictive antibiotic prescribing.</p> <p>Conclusions</p> <p>Restrictive antibiotic prescribing was considered important in two perceptions, was not an issue as such in two others, and was considered in one perception although the actual prescribing was greatly influenced by the interaction between patient and GP. Accordingly, to encourage restrictive antibiotic prescribing several aspects must be addressed. Furthermore, different GPs need various kinds of support. Infectious disease management in primary care is complex and time-consuming, which must be acknowledged in healthcare organisation and planning.</p