Relaying is one of the useful techniques to enhance wireless physical-layer security. Existing literature shows that employing full-duplex relay instead of conventional half-duplex relay improves secrecy capacity and secrecy outage probability, but this is at the price of sophisticated implementation. As an alternative, two-path successive relaying has been proposed to emulate operation of full-duplex relay by scheduling a pair of half-duplex relays to assist the source transmission alternately. However, the performance of two-path successive relaying in secrecy communication remains unexplored. This paper proposes a secrecy two-path successive relaying protocol for a scenario with one source, one destination and two half-duplex relays. The relays operate alternately in a time division mode to forward messages continuously from source to destination in the presence of an eavesdropper. Analytical results reveal that the use of two half-duplex relays in the proposed scheme contributes towards a quadratically lower probability of interception compared to full-duplex relaying. Numerical simulations show that the proposed protocol achieves the ergodic achievable secrecy rate of full-duplex relaying while delivering the lowest probability of interception and secrecy outage probability compared to the existing half duplex relaying, full duplex relaying and full duplex jamming schemes.
Rupture of the sinus of valsalva (RSOV) is an uncommon condition with a variety of manifestations ranging from an asymptomatic murmur to cardiogenic shock. This retrospective 10-year review (1985-1995) of 18 patients from a single institution revealed that 6 (33%) were female and 12 (67%) were male with a mean age of 37.6 +/- 13.4 years and that 72% were Chinese by ethnic descent with the remaining 28% being Malay. Eight patients (44.4%) presented with an asymptomatic murmur, 4 (22.2%) with acute chest pain, 4 (22.2%) with mild heart failure, 2 (11.1%) with severe heart failure, and 2 (11.1%) with cardiogenic shock. Rupture of the right aneurysmal coronary cusp (RCC) made up 15 (83.3%) while those of the non-coronary cusp (NCC) made up the remaining. Most of the RCC ruptures were directed into the right ventricle and all of the NCC ruptures were into the right atrium. Ventricular septal defects (VSDs) were found in 9 (50%) of the patients, (although detected by echocardiography in only one third of those patients), aortic regurgitation in 6 (33.3%) and aortic valve vegetations in 2 (11.1%). Echocardiography was found to be accurate in diagnosing RSOVs with 100% diagnostic accuracy after 1990 with four misdiagnoses before 1990. Of these four patients, two were misdiagnosed as having VSDs, one as having a coronary arteriovenous fistula and one as having a patent ductus arteriosus. The anatomical structure of the "windsock" was seen in 64% of the patients who were correctly diagnosed. The pattern of colour flow and spectral Doppler was seen in all patients and helped to localise the site of rupture and the direction of flow. In summary, echocardiography is a simple and accurate way of diagnosing and defining RSOVs and is the imaging modality of choice.
OBJECTIVE: To determine the ethnic variation of short and long term female vulnerability after an acute coronary event in a population of Chinese, Indians, and Malays.
DESIGN: Population based registry.
PATIENTS: Residents of Singapore between the ages of 20-64 years with coronary events. Case identification and classification procedures were modified from the MONICA (monitoring trends and determinants in cardiovascular disease) project.
MAIN OUTCOME MEASURES: Adjusted 28 day case fatality and long term mortality.
RESULTS: From 1991 to 1999, there were 16 320 acute coronary events, including 3497 women. Age adjusted 28 day case fatality was greater in women (51.5% v 38.6%, p < 0.001), with a larger sex difference evident among younger Malay patients. This inequality between the sexes was observed in both the pre-hospitalisation and post-admission periods. Among hospitalised patients, women were older, were less likely to have suffered from a previous Q wave or anterior wall myocardial infarction, and had lower peak creatine kinase concentrations. Case fatality was higher among women, with adjusted hazard ratios of 1.64 (95% confidence interval (CI) 1.43 to 1.88) and 1.50 (95% CI 1.37 to 1.64) for 28 day and mean four year follow up periods. There were significant interactions of sex and age with ethnic group (p = 0.017). The adjusted hazards for mortality among Chinese, Indian, and Malay women versus men were 1.30, 1.71, and 1.96, respectively. The excess mortality among women diminished with age.
CONCLUSION: In this multiethnic population, both pre-hospitalisation and post-admission case fatality rates were substantially higher among women. The sex discrepancy in long term mortality was greatest among Malays and in the younger age groups.