Background:Information on the leading causes of mortality will continue to rely on verbal autopsy (VA) in developing countries. The accuracy of VA methods in correctly ascertaining the cause for each individual death is crucial in order to have confidence in the data collected through the procedure. Accuracy of the VA procedure is generally established by carrying out validation studies involving a comparison of the underlying cause of death derived from the VA with a reference underlying cause from medical records. Such validation is only possible in cases for which clinical records are available, and this is clearly not the case for most deaths in developing countries. We attempt to verify the accuracy of VA evidence by reviewing the responses to specific symptom questions and other information recorded in verbal autopsy questionnaires that were assigned cerebrovascular conditions (stroke) as causes of death upon physician review in Vietnam.Materials and Methods:A national sample mortality surveillance activity identified deaths and causes of death that had occurred during 2008 in selected communes in 16 provinces distributed across Vietnam. All cases from the northern provinces of Hanoi, Hai Duong, Quang Ninh and Thanh Hoa with ICD codes pertaining to cerebrovascular diseases were identified. A total of 326 VA questionnaires for deaths from cerebrovascular diseases were reviewed and analysed in detail for the presence of symptoms pertaining to stroke. The respondents’ narration of the chronological disease history and the hospital diagnosis was also examined with an aim to explore supporting signs for diagnosis and to verify the quality of VA interview. Differences between responses among cases with and without hospital admission were examined using Chi-squared test of statistical significance.Results:Ninty percent of the cases diagnosed as stroke were found to have positive response to the key symptoms; viz., paralysis (in structured question or free text) and history of stroke. For the remaining 10% of cases, stroke was assigned as a cause-of-death based on other suggestive cardiac signs and symptoms such as hypertension, unconsciousness, or headache, etc. Community had different perspectives of “paralysis” and “stroke” which might have affected the diagnosis of stroke in some aspects. Respondents of cases with hospital admission or visit were found to have a better recall of disease symptoms than those without hospital admission.Conclusion:The results of this study suggest the possible utility of VA content analysis method to back up the low coverage of conventional validation studies in developing countries owing to nonavailability of medical records. The understanding of the VA content would also form the basis for improvement in the quality of interviews and collection of data to achieve better quality information in future.
In this paper, we consider harvest-to-jam based secure multi-hop cluster multi-input multi-output networks, where a multi-antenna source sends its data to a multi-antenna destination via multi-antenna intermediate cluster heads. The data transmission at each hop is realized by using transmit antenna selection and selection combining techniques, and is overheard by a multi-antenna eavesdropper using selection combining. In addition, joint antenna and jammer selection methods are performed at each hop to reduce quality of the eavesdropping channels. The cluster members can harvest wireless energy from the previous cluster head, and use the harvested energy for emitting jamming noises on the eavesdropper. We propose three cooperative jamming algorithms, named best antenna and best jammer selection (BA-BJ), random antenna and all jammer selection (RA-AJ) and all antenna and all jammer selection (AA-AJ). Then, end-to-end outage probability and intercept probability of the proposed algorithms are evaluated via both simulation and analysis, under impact of hardware impairments, over Rayleigh fading channel.
Currently, with the fast modernization of wireless networking technologies as well as the very complex needs of the network users, multimedia data takes for a large proportion in the types of network services, this type of data requires Quality of Service (QoS) differs from traditional data, by ensuring the listening and viewing elements of the user. In this paper, we analyse the effect of video and voice data on QoS of wireless network services based on the establishment of an experimental evaluation (emulation) system or testbed, thereby providing empirical analysis on the effect of multimedia data on mobile wireless QoS.
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