Zone Of Vietnam Research Articles

Otolith morphology, age, and growth of freckled goatfish Upeneus tragula (Mullidae) in the coastal zone of Vietnam

Otolith morphology and microstructure of the sagitta are described in freckled goatfish Upeneus tragula. The first increments (from the second to sixth or eighth) are the most well defined, and subsequent zones of less contrasting increments are bounded by increments with more contrasting borders. These borders are less expressed close to the edge of the sagitta. The width of the majority of increments ranges from 1.5 to 2.5 μm. Based on the results of the experiments on in vivo marking of the sagittae, daily periodicity of increment deposition is supported. Age composition of the populations from the coastal zone of Vietnam (Nha Trang and Ha Long bays) is assessed based on the calculation of daily increments. The growth rate of the fishes is characterized by a substantial variation. In Nha Trang Bay, the females grow more rapidly than the males, and the growth rate of the fishes in Nha Trang Bay is lower than that in Ha Long Bay. Maximum age of the fish in both bays is 3 years 99 days and 2 years 129 days, respectively.

Subduction initiation of Indochina and South China blocks: insight from the forearc ophiolitic peridotites of the Song Ma Suture Zone in Vietnam

The Song Ma region, which is located in the northwestern Vietnam represents the zone of amalgamation between Indochina and South China blocks. Numerous scattered ultramafic rocks occur in this region in association with Early to Middle Palaeozoic greenschists and paragneisses, and all these rocks were subjected to hydrous metamorphism and deformation. Here, we present new field data, mineral chemistry and geochemistry from a suite of hydrated peridotites within the Song Ma region and discuss the tectonic significances of the region. We also combine the available data within the Song Ma region and Indochina–South China blocks to discuss the tectonic evolution of the subduction zone. Based on the results, we suggest that the peridotites from the Song Ma are mantle residues that suffered a high degree of partial melting in a forearc tectonic setting. The present data together with the available data within the Song Ma region and the Indochina and South China blocks clearly represent a southward directed Middle Palaeozoic subduction system. The Middle Palaeozoic subduction and accretion events mark the evolutionary history along an active convergent margin between the Indochina and South China blocks, possibly related to the amalgamation of the Pangaea supercontinent. Copyright © 2015 John Wiley & Sons, Ltd.

Gonadal condition, sperm motility, and initial stages of embryonic development in freckled goatfish Upeneus tragula (Mullidae)

Development of sex cells, sperm motility, and initial stages of embryonic development are described in a tropical representative of the family Mullidae, freckled goatfish Upeneus tragula, from the coastal zone of Vietnam. In Nha Trang Bay, the gonads in the majority of sexually mature females are at IV, IV–V, and VI–IV maturity stages over the entire year, and the type of oogenesis is continuous. Anomalous structure of oocytes is registered in 15% of investigated females. In Ha Long Bay, the gonads of almost all sexually mature females are at maturity stage II in December. In adult males, spermatozoa are the most numerous in elongated spermiducts. Based on computer-assisted analysis of motility of spermatozoa removed from a spermiduct and activated in marine water, sperm velocity reaches 53 μm/s in 1 min after activation, and the duration of progressive movements of spermatozoa does not exceed 5 min.

Reproduction of freckled goatfish Upeneus tragula (Mullidae) in the coastal zone of Vietnam

Features of reproduction are described in the tropical representative of the family Mullidae freckled goatfish Upeneus tragula from southern Central Vietnam (Nha Trang Bay) and North Vietnam (Ha Long Bay). Sex ratios of the fishes (females: males) in Nha Trang and Ha Long bays are 0.93: 1 and 1.2: 1, respectively. In both bays, the body length-body weight relationship is not substantially different between the females and males. In Nha Trang Bay, the females reach sexual maturity by 10.2 cm fork length (50% of individuals), and the fishes spawn over the entire year. In a part of the population (on average, 23.5% of fishes), the interruptions in spawning not associated with a certain season of the year are registered. In Ha Long Bay, a distinct spawning interruption is observed in all fishes during winter.

Transformation of iso-pentylbenzene by a biofilm-forming strain of Candida viswanathii TH1 isolated from oil-polluted sediments collected in coastal zones in Vietnam

This work is aimed to assess the aerobic biotransformation of a branched side chain alkylbenzene, iso-pentylbenzene, by Candida viswanathii TH1. The yeast Candida viswanathii TH1 isolated from oil-polluted sediments collected in coastal zones in Vietnam exhibited as a strain that could better transform branched aromatic hydrocarbons in biofilm (pellicle) than in planktonic form. During incubation of TH1 as biofilm with iso-pentylbenzene, the seven intermediates produced were benzoic acid, phenylacetic acid, 2-methyl-4-phenyl-butan-1-ol, 2-hydroxy-phenylacetic acid, 2-methyl-4-phenylbutyric acid, succinic acid and iso-valerophenone as revealed by gas chromatography/mass spectra and high-performance liquid chromatography analyses. The occurrence of these intermediates showed that iso-pentylbenzene could be oxidized not only via mono- but also by a sub-terminal oxidation pathway. This is the first study on iso-pentylbenzene transformation by a biofilm-forming Candida viswanathii strain. The catabolic versatility of the biofilm-forming strain TH1 and its use for mono and sub-terminal oxidation during the transformation of iso-pentylbenzene enhance our understanding of the degradation of branched side chain phenylalkanes and give new insight into the potential role of such species in the transformation of other recalcitrant aromatic compounds.

Modeling demand for catastrophic flood risk insurance in coastal zones in Vietnam using choice experiments

AbstractIn a choice experiment, households in Vietnam are offered flood insurance to mitigate increasing catastrophic flood risks due to climate change. Participants are asked to choose their most preferred insurance policy given expected future flood and mortality risks, insurance cover and associated insurance premiums. Although not affordable to everyone, there exists substantial demand for flood insurance. Insurance demand is spatially differentiated, non-linear in flood probabilities and mortality risks, and subject to significant preference heterogeneity. Since respondents are unfamiliar with the concept of flood insurance and education levels are low, choice consistency tests were conducted. These show that choice consistency depends on a combination of respondent characteristics, such as gender and education level, and experimental design characteristics.

Late Cenozoic tectonics of the Red River Fault Zone, Vietnam, in the light of geomorphic studies

The main episode of Pliocene–Quaternary tectonic activity in the Red River Fault Zone in Vietnam was related to dextral strike-slip motions while uplift of the SW and NE sides of the fault zone was limited. In the Vietnamese segment of this zone, traces of pre-Pliocene mature relief were preserved to a much smaller extent compared to those in Yunnan Province, China. The main factors controlling headward erosion of tributary streams were lithologic contrasts within the solid bedrock. Tectonic-geomorphic studies indicate that the amount of Quaternary dextral offset of the Red River Fault Zone in Vietnam, calculated from offset and deflection of tributary valleys of the Red River, ranges between some 400m and 5.3km, averaging 1.1–2km. The corresponding rates of slip are 0.43–1.1mm/yr for individual displaced segments and 5.5–7.8mm/yr for the inferred cumulative displacement. Fluvial terraces in the medial segment were mainly shaped in the Late Pleistocene and Holocene, except the highest one (40–50m) which was probably formed in Mid-Pleistocene time. Taking into account the amount of dextral displacement of terrace steps and related alluvial fans, the most realistic estimation of Mid-Pleistocene through Holocene slip rate is 0.9–3.9mm/yr. The axis of maximum horizontal compression associated with dextral slip of the fault zone was aligned NNW–SSE to N–S, and the fault motion in the Quaternary resulted mainly from aseismic creep.

Segmenting Visitors to Battlefield Sites: International Visitors to The Former Demilitarized Zone in Vietnam

ABSTRACT Paradoxically, part of the appeal of Vietnam as an emerging destination lies in the commodification of images, artifacts, and battlefield sites of the Vietnam War. While studied from the supply-side, little research has been undertaken yet in terms of the patterns of demand for battlefield tourism. Based on a survey of 481 visitors to the former Demilitarized Zone (DMZ), this article uses factor analysis and cluster analysis to segment then profile battlefield visitors based on their motivations. Three groups of visitors to the DMZ were identified: the Battlefield Tourism Enthusiast, the Opportunist, and Passive Tourists. Significant differences were found between the three segments with regard to various sociodemographics and trip characteristics. However, results from the study also emphasize that analyses of demand based on site visits should be contextualized in terms of visits to the country as a whole and that care must be taken in distinguishing specialist visitors from generalists.

Comment on “An alternative plate tectonic model for the Palaeozoic–Early Mesozoic Palaeotethyan evolution of Southeast Asia (Northern Thailand–Burma)” by O.M. Ferrari, C. Hochard & G.M. Stampfli, Tectonophysics 451, 346-365 (doi:10.1016/j.tecto.2007.11.065)

Ferrari et al. [Ferrari, O.M., Hochard, C., Stampfli, G.M., 2008. An alternative plate tectonic model for the Palaeozoic–Early Mesozoic Palaeotethyan evolution of Southeast Asia (Northern Thailand–Burma). Tectonophysics 451, 346–365. doi:10.1016/j.tecto.2007.11.065.] redefine the “Shan-Thai” terrane in Thailand as a Cathaysian Indochina-derived terrane when this has traditionally been defined and used as a Gondwana-derived continental block, hence introducing unnecessary confusion. In their definition of “Shan-Thai”, they also inappropriately combine oceanic suture zone rocks (the Palaeo-Tethys Inthanon suture) and continental arc rocks (Sukhothai Island Arc system). The Mai Yuam Fault, identified by Ferrari et al. (2008) as the Palaeo-Tethys suture, is in fact a Cenozoic fault and the Palaeo-Tethys suture zone is represented by the Inthanon Suture zone in Thailand which is equivalent to the previously recognised Inthanon zone. The concept of derivation of “Orang Laut” terranes from South China-Indochina by back-arc spreading is innovative but the proposed Permo-Triassic back-arc along the Song Da/Song Ma zone in Vietnam is less convincing. There is little evidence to support the proposed southwards subduction of Palaeo-Tethys beneath eastern Gondwana in the Permian.

Assessment and Management of Rice, Taro and Tropical Fruit Trees in Contrasting Agro-ecosystems in Vietnam

Understanding farmer household and community management of crop diversity is necessary in order to effectively strengthen the local plant genetic resources management system in Vietnam, Assessment and management for distribution of farmer`s cultivars of rice, taro and tropical tree species were conducted in four different agro-ecological zones in Vietnam using participatory approaches, focus surveys, diversity fairs, agro-morphological field trials, isozyme analysis to understand why Vietnamese farmers grow diverse types of these crop cultivars, when and where these crops cultivars are grown and how farmers maintain and use them. Results showed significant differences in the extent, distribution and use pattern crop cultivars diversity in contrasting environments and between community farmer households. Seed system is an important role in the access and use of diversity in eco-geographical regions.

40Ar/ 39Ar Single Grain Dating and Mineral Chemistry of Hornblendes South of the Red River Shear Zone (Vietnam): New Evidence for Early Proterozoic Tectonothermal Event

The pre-Mesozoic metamorphic belt runs parallel to the Day Nui Con Voi - Red River shear zone in Vietnam to the south. The belt is mainly composed of hornblende gneisses, amphibolite lenses and mica-schists. Five hornblendes from a gneiss and an amphibolite were analyzed chemically and chronologically by Electron Probe Micro Analysis (EPMA) and 40Ar/ 39Ar methods. EPMA analyses show that hornblendes in the gneiss and the amphibolite have significant amount of edenite component and similar average composition. However, the recalculated Fe 3+ content is significantly heterogeneous in a thin section while total Fe is nearly the same among the analyses. The rim of each crystal is higher in Fe 3+/(Fe 3+ + Fe 2+) than the core. These chemical and petrological features suggest that the hornblendes have suffered significant oxidation, in particular, largely in the gneiss. 40Ar/ 39Ar analyses showed that the gneiss has a significant variation of plateau ages (2089±14, 1977±19 and 1873±13 Ma) among three hornblende grains, whereas the amphibolite gives the same plateau ages (2056±14 and 2044±21 Ma) for two grains. All grains of both samples have excess ages in the first few fractions at low temperatures and partial-loss ages between the excess and plateau spectra. The Ca/K ratios indicate some disturbed phases for the lower temperature spectra but the partial-loss ages are also derived from hornblende phase. These facts suggest that hornblende in the gneiss has experienced partial argon loss by oxidation and/or thermally activated argon diffusion process. However, the gneiss and the associated amphibolite have preserved the early Proterozoic tectono-metamorphic event in the hornblende crystals except for their rims, giving new evidence for the early Proterozoic event within the pre-Mesozoic metamorphic belt (northern Vietnam) south of the Red River shear zone in Indochina.

P– T– t paths and post-metamorphic exhumation of the Day Nui Con Voi shear zone in Vietnam

The Day Nui Con Voi belt in Vietnam is the southeasternmost part of the Red River shear zone in Asia. It is a narrow high-grade metamorphic core complex consisting of garnet–sillimanite–biotite gneisses, mylonite bands, amphibolite layers and migmatites. Geothermobarometric study of the complex revealed that the peak metamorphism took place under amphibolite-facies conditions of 690 −60 +30°C and 0.65±0.15 GPa and the subsequent mylonitization occurred under greenschist-facies conditions of ∼480°C and under 0.3 GPa. Fifteen synkinematic hornblende and biotite separates from gneisses, amphibolites and mylonites were dated with the K/Ar method. Hornblende separates from the Day Nui Con Voi give K–Ar ages of 26.4–28.5 Ma, and the biotite separates do give 24.5–24.7 Ma. Combination of thermobarometric and geochronological data yields the cooling history of 500°C at 28 Ma and 300°C at 24 Ma with a cooling rate of 70–110°C Ma −1, and 23 km post-metamorphic exhumation of the core complex. The first 16 km exhumation from the peak of metamorphism (at probably 31 Ma) to 28 Ma was triggered by the left-lateral strike-slip displacement of the Red River shear zone.

The Israeli-Syrian Demilitarized Zone: An Examination of Unresolved Conflict

Abstract Political geography has long been a major field of interest for geography teachers and students. One of the most interesting areas of political geography is the study of boundaries and boundary zones. In this context, the demilitarized zone (DMZ) as a political separating agent has been one of the most controversial issues in the twentieth century. The demilitarized zone of Vietnam, Korea, and Israel all constitute major zones of tension and friction. The major reason for the instability attending these frictions is that the DMZ's were created by military armistice agreements rather than more conventional political processes. Thus the DMZ's are the product of an unresolved conflict. This geopolitical analysis of the Israel-Syrian DMZ describes how the zone was created and how it functioned between 1949 and 1967.