Vulnerability Assessment of Different Socio-Economic Groups to Floods in the Rural Mekong Delta of Vietnam

The objective of the study is to identify and understand the different factors that characterize vulnerability towards slow-onset floods in rural areas of the Vietnamese Mekong Delta. This thesis aims to explore losses and harm that people experience through floods; to achieve this, criteria and indicators to assess vulnerability have been developed. Emphasis is given to how varying socio-economic groups access and use their livelihood resources to build livelihood strategies in the context of floods. It also explores the influence shaped by the transforming processes and structures in their flood response. Factors such as wealth, land ownership, main sources of income and settlement durations are identified as being key drivers of vulnerability to floods in the Vietnamese Mekong Delta. Both qualitative and quantitative methods were used to explore and triangulate information in order to ensure reliability and consistency of data collected. A literature review and secondary data analysis provided the trends of floods, flood damage patterns, land use alternatives, major flows of resettlement and flood-related policies. In-depth interviews and focus group discussions as well as participatory methods such as key informant panels, transect walk, timeline analysis, wealth ranking and seasonal calendars were applied to understand flood vulnerability of local residents. Three hundred and seventy households located in riverbank and inland areas in the Plain of Reeds: An Hoa and Phu Hiep Communes, Tam Nong District in Dong Thap Province were interviewed using standardized questionnaires. According to these explorations, the relevant indicators and their weighting which were verified by involved stakeholders’ perceptions was constructed, and using this approach, vulnerability at the household level was estimated. The indicators were identified by using scientific literature and primary data. The indicators were then consolidated and validated through household interviews, flood damage reports, expert interviews and focus group discussions with people exposed to floods. In-depth interviews during the field research enabled the research to probe deeper research findings and explore main relations among determinants influencing flood vulnerability. Theoretically and conceptually, the study is based on a modified framework, which is essentially associated with the BBC Conceptual Framework and the Sustainable Livelihood Framework. In order to get a more in-depth understanding of the framework components, the study draws on theoretical ideas related to disasters, disaster risk management, coupled human-environmental systems, and institutional economics. Access to land that is key to reducing flood vulnerability is also heavily modified by the transforming structures and processes including physical attributes such as embankments, relocation, agricultural intensification and socio-economic reforms. There are various indicators influencing flood vulnerability however, with regard to the selected indicators for this study they are related to flood-related exposure, susceptibility, capacity of response and rural livelihoods. Seven indicators were found to be the most important drivers of flood vulnerability: (1) access to agricultural land, (2) access to residential land, (3) type of house, (4) household assets, (5) demographic composition of household, (6) remittance and (7) income dependency. A modified framework based on vulnerability and livelihood approaches has provided conceptual means to explore the subject matter from a holistic perspective comprising not only objective facts but also subjective meanings of flood implications. This is because vulnerability assessment can enable comparison of the flood vulnerability of different socio-economic groups. The various research tools to assess flood vulnerability, particularly participatory qualitative approaches, further helped to identify root causes of vulnerability to floods. The study enables policy makers and researchers to identify specific measures, such as flood-based physical assets and knowledge enhancement, livelihood improvement for the landless and the relocated, as well as flood risk reduction strategies to reduce the overall vulnerability of different socio-economic groups in the Vietnamese Mekong Delta

Dissipation bounds asymmetry of finite-time cross-correlations

Recent studies have revealed an intimate connection between the asymmetry of cross-correlations and thermodynamic quantities in the short-time limit. In the finite-time regime, however, this relationship remains poorly understood. In this Letter, we comprehensively examine this issue and provide an affirmative resolution. Focusing on Markovian dynamics, we show that the asymmetry observed in finite-time cross-correlations is always upper bounded by dissipation. Precisely, we prove that, for systems in a steady state with arbitrary operational durations, the asymmetry exhibits, at most, linear growth over time, with the growth speed determined by the rates of entropy production and dynamical activity. In the long-time regime, the asymmetry exhibits exponential decay, with the decay rate dictated by the spectral gap of the transition matrix. Furthermore, we generalize the short-time bounds on correlation asymmetry, as reported by Shiraishi [arXiv:2304.12775] and Ohga et al.~[arXiv:2303.13116], to encompass finite-time scenarios. These findings offer novel insights into the thermodynamic aspects of correlation asymmetry.Comment: 6+6 pages, 1 figur

Per os infectivity of white spot syndrome virus (WSSV) in white-legged shrimp (Litopenaeus vannamei) and role of peritrophic membrane

As earlier observations on peroral infectivity of WSSV in white-legged shrimp are conflicting, here, a standardized peroral intubation technique was used to examine (i) the role of the physical composition of the viral inoculum and (ii) the barrier function of the PM. In a first experiment, the infectivity of a WSSV stock was compared by determining the SID50 by intramuscular injection, peroral inoculation or via feeding. The following titers were obtained: 108.77 SID50/g by intramuscular injection, 10(1.23) SID50/g by peroral inoculation and 100.73 SID50/g by feeding. These results demonstrated that 10(7.54)-10(8.03) infectious virus is needed to infect shrimp by peroral inoculation and via feeding. Next, it was examined if damage of the PM may increase the susceptibility for WSSV by peroral route. The infectivity of a virus stock was tested upon peroral inoculation of shrimp with and without removal of the PM and compared with the infectivity upon intramuscular inoculation. The virus titers obtained upon intramuscular injection and peroral inoculation of shrimp with and without PM were 10(8.63), 10(1.13) and 10(1.53) SID50/mL, respectively. This experiment confirmed the need of 10(7.1)-10(7.5) infectious virus to infect shrimp via peroral route and showed that the removal of the PM slightly but not significantly (p > 0.05) facilitated the infection of shrimp. This study indicated that WSSV contaminated feed is poorly infectious via peroral route, whereas it is highly infectious when injected into shrimp. The PM plays a minor role as internal barrier of shrimp against WSSV infection