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Selected AbstractsFast and accurate calculation of transmission coefficients for an EBG microstrip structureMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2010Shao Ying Huang Abstract In this article, an approach is proposed to provide an accurate and fast calculation on the transmission coefficients of an electromagnetic band-gap (EBG) structures where patches are periodically inserted into the microstrip line (capacitive loaded EBG microstrip structure). The stopband performance, such as the center frequency, bandwidth, and attenuation, of these EBG structures can be predicted at a high degree of accuracy through the calculation of the transmission coefficient. The dispersion relation of electromagnetic waves in the structure is derived, plotted, and analyzed. The grating nature of the structure is demonstrated. This approach can be applied to periodic microstrip structures of a similar nature to simplify the analysis and design procedures. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:793,797, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25046 [source] Thermal and mechanical characterization of epoxy resins toughened using preformed particlesPOLYMER INTERNATIONAL, Issue 8 2001J Day Abstract Preformed, multilayer particles have been used to toughen an epoxy resin. The particles were formed by emulsion polymerization and consist of alternate glassy and rubbery layers, the outer layer having glycidyl groups to give the possibility of chemical bonding of the particles in the cured resin. Two variants of this type of particle were used, termed GM(47/15) and GM(47/37); both types have an overall diameter of 0.5,µm, but the former have a thicker rubbery layer. For comparison, acrylic toughening particles (ATP) with no surface functionality and a liquid carboxyl-terminated butadiene,acrylonitrile (CTBN) rubber were used as toughening agents. The epoxy resin system consisted of a commercial diglycidyl ether of bisphenol A (Shell Epon 828) with diamino-3,5-diethyl toluene as hardener, two commercial sources of which were used, namely Ethacure-100 (Albemarle SA) and DX6509 (Shell Chemicals). These hardeners contain a mixture of two isomers, namely 2,6-diamino-3,5-diethyltoluene and 2,4-diamino-3,5-diethyltoluene Thermogravimetry in nitrogen shows that the preformed toughening particles begin to degrade at 230,°C, whereas the cured resin begins to degrade rapidly at 350,°C. Thus, even though the particles are less thermally stable than the cured resin, their degradation temperature is well above the glass transition temperature of the resin, and their use does not affect the thermal stability of the toughened materials at normal use temperatures. The performance of the toughening agents was compared using Ethacure-100 as the hardener. The GM(47/15) and GM(47/37) toughening particles gave rise to a greater toughening effect than the ATP and the CTBN. For example, the fracture energies were: 0.26,kJ,m,2 for the unmodified resin; 0.60,kJ,m,2 for the resin toughened with CTBN; and 0.69,kJ,m,2 for the resin toughened with the GM(47/15) particles. The ultimate tensile stress of the unmodified epoxy resin was 43,MPa, which increased to 55,MPa when 20,wt% of GM(47/15) toughening particles were added. The toughness of resins cured with the DX6509 hardener were superior to those obtained with the Ethacure-100 hardener, most probably due to DX6509 producing a less-highly-crosslinked network. This highlights the sensitivity of the toughening process to the hardener used, even for hardeners of a similar nature. © 2001 Society of Chemical Industry [source] COMPARISON OF INFECTION RATE USING DIFFERENT METHODS OF ASSESSMENT FOR SURVEILLANCE OF TOTAL HIP REPLACEMENT SURGICAL SITE INFECTIONSANZ JOURNAL OF SURGERY, Issue 7 2007Yoke-Fong Chiew Background: The surveillance of surgical site infections (SSI) has been undertaken in many centres worldwide to ascertain the extent of the problem and where possible, to improve the incidence rates, thereby decreasing the undesirable outcomes. The study investigates the processes and outcomes of total hip replacement SSI surveillance carried out in Dunedin Public Hospital in 2004. Methods: Two hundred and six patients were enlisted in the study and 189 primary replacements and 22 revision replacements were carried out. Four methods of diagnosis of SSI were applied: (i) clinician diagnosis; (ii) ASEPSIS score; (iii) presence of pus cells; and (iv) assessment by a clinical microbiologist. Infection rates were calculated according to the risk indexes. Results: The incidence of infections varies considerably among these four methods. The infection rates for risk index 0 were 4.35% (method 1), 2.61% (method 2), 0.87% (methods 3 and 4); and for risk indexes 1 and 2 were 4.17% (method 1), 2.08% (method 2), 1.04% (methods 3 and 4). Conclusion: There is a need for accurate infection data so that the appropriate follow-up responses, including infection control measures for total hip replacement SSI can be carried out. The preponderance of elderly patients in the study who are frequently on ,polypharmacy' regimens adds pressure to the need to obtain true infection rates. This is because when antimicrobials are prescribed to them, drug interactions, adverse effects of the antimicrobials and the selective pressure of antimicrobials causing resistances may occur. More resources and a multidisciplinary approach are required for future studies of similar nature. [source] Day case stapled haemorrhoidopexy for prolapsing haemorrhoidsCOLORECTAL DISEASE, Issue 1 2006G. C. Beattie Abstract Objective, Conventional surgical management of prolapsing haemorrhoids is by excisional haemorrhoidectomy. Postoperative pain has restricted the application of such procedures in the day case setting. These operations remain associated with a period of restricted activity. The use of circular stapling devices as an alternative to the excisional approach in the management of haemorrhoids has been described. This study reports our experience of stapled haemorrhoidopexy as a day case procedure. Methods, Patients with third or fourth degree haemorrhoids were eligible for the procedure. Patients were considered suitable candidates for day case surgery based on conventional parameters. Symptoms were assessed using a previously validated symptom severity rating score. Stapled haemorrhoidopexy was carried out using a circular stapling device. Pain scores were obtained prior to discharge. Patients were admitted if pain was uncontrolled despite oral analgesia. Symptoms were re-scored at six-week follow-up. Results, Over a 70-month period 168 consecutive stapled haemorrhoidopexies were performed or directly supervised by one consultant colorectal surgeon. One hundred and ten (65%) patients were considered appropriate candidates for day case surgery by conventional criteria. Ninety-six (87.3%) patients successfully underwent stapled haemorrhoidopexy on a day case basis. Fourteen (12.7%) patients required admission on the day of surgery (5 for early postoperative bleeding, 4 for pain necessitating continuing opiate analgesia, two for urinary retention and three for surgery performed late in the day). Six (5%) patients were re-admitted postoperatively; four for pain relief and two because of urinary retention. Of the day case patients, 91 (82.7%) and 56 (50.9%) had been seen for 6 week and 6 month review, respectively, at the time of analysis. Symptom scores were 6 (pre-operatively) vs 0 (postoperatively) (P < 0.01). 76/91 (83.5%) patients reviewed at 6/52 were asymptomatic. Conclusion, Stapled haemorrhoidopexy is a safe and effective procedure that can be carried out on selected patients on a day case basis. Complications are of a similar nature to excisional haemorrhoidectomy. [source] | ||||||||||