Optimizing Circular Side-Resonators to Reduce Computer Fan Noise

One of the main noise sources in computers are the cooling fans. Tonal noise at the rotational frequency of the fan, the blade passing frequency (BPF) and its higher harmonics are important in fan noise. So called 'side-resonators' integrated in the duct of an in-duct axial fan cause an impedance change in the duct and, having proper dimensions and correct position, act as an acoustic mirror reflecting the noise back to the fan. As a result, noise emitted from the computer can be reduced. In this paper, a model describing viscothermal wave propagation in the duct and side-resonator is outlined. The model can be used to determine the resonator dimension and position to optimally reflect noise near the BPF. The developed model is compared with the models for prismatic tube and cylindrical resonators and the physical differences between these three resonators are explained. Preliminary results of a parameter study are presented. The results point out that the range and magnitude of the effective frequency band of a resonator setup can be successfully manipulated by changing the different dimensions of the setup

Determinants for the adoption of angiotensin II receptor blockers by general practitioners

Results of studies conducted 10-20 years ago show the prominence of commercial information sources in the adoption process of new drugs. Over the past decade, there has been a growing emphasis on practicing evidence-based medicine in drug prescribing. This raises the question whether professional information sources currently counterbalance the influence of commercial information sources in the adoption process. The aim of this study was to identify determinants influencing the adoption of a new drug class, the angiotensin II receptor blockers (ARBs), by general practitioners (GPs) in The Netherlands. A retrospective study was conducted to assess prevalent ARB prescribing for hypertensive patients using the Integrated Primary Care Information (IPCI) database. We conducted a survey among all GPs who participated in the IPCI project in 2003 to assess their exposure to commercial and professional information sources, perceived benefits and risks of ARBs, perceived influences of the professional network, and general characteristics. Multilevel logistic regression was applied to identify determinants of ARB adoption while adjusting for patient characteristics. Data were obtained from 70 GPs and 9470 treated hypertensive patients. A total of 1093 patients received ARBs (12%). GPs who reported frequent use of commercial information sources were more likely to prescribe ARBs routinely in preference to other antihypertensives, whereas GPs who used a prescribing decision support system and those who were involved in pharmacotherapy education were less likely to prescribe ARBs. Other factors that were associated with higher levels of ARB adoption included a more positive perception of ARBs regarding their effectiveness in lowering blood pressure, and working in single-handed practices or in rural areas. Aside from determinants related to the patient population, adoption of a new drug class among Dutch GPs is still determined more by their reliance on promotional information than by their use of professional information sources.The Netherlands Angiotensin II receptor blockers Antihypertensive treatment Decision making Drug utilization Primary care

PHARMACOEPIDEMIOLOGY AND PRESCRIPTION Uptake of angiotensin II receptor blockers in the treatment of hypertension

Citation for published version (APA): Greving, JP., Denig, P., van der Veen, WJ., Beltman, FW., Sturkenboom, MCJM., de Zeeuw, D., & HaaijerRuskamp, FM. (2005). Uptake of angiotensin II receptor blockers in the treatment of hypertension. European Journal of Clinical Pharmacology, 61(5-6), 461-466. https://doi.org/10.1007/s00228-005-0924-7 Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons). Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. Abstract Objective: To examine trends in prescribing of angiotensin II receptor blockers (ARBs) as initial and second-line treatment of hypertension. Methods: We performed a cohort study in the Integrated Primary Care Information database, a general practice research database in The Netherlands. We included hypertensive patients who were newly treated with antihypertensive drugs between 1996 and 1999. Initial treatment was defined as the first prescribed antihypertensive drug after diagnosis of hypertension. As secondline treatment, we considered prescriptions of a second antihypertensive drug class, either as switch or addition. We used logistic regression and Cox proportional hazard analysis to estimate time trends in use of ARBs as initial or second-line treatment. Results: In total, 8% of the 3,102 newly treated hypertensive patients received ARBs as initial treatment. Initial ARB use increased significantly from 4% to 10% during the period 1996-1999, whereas calcium channel blocker and angiotensin-converting enzyme inhibitor (ACE-I) use decreased. ARBs were used as second-line treatment in less than 4% of 2,544 patients who were initially treated with an antihypertensive drug other than an ARB: 2% switched to an ARB (mostly from ACE-Is) and 1% received ARBs as add-on treatment. Diuretics and beta-blockers were used five to ten times more often as add-on treatment than ARBs. Conclusion: ARBs achieved a position in the treatment of hypertension as initial rather than second-line therapy