The economic transition and migration of Vietnam and the Mekong Delta region

Relationship between economic transition and migration has long attracted increasing attention of both policy-makers and researchers. Migration is seen as a response of changes during the economic transition in a country, because labour is an important production factor in the market, in which labourers have a desire to move to a place of better working conditions rather than going to a disadvantaged conditions (De Haas, 2010; Todaro, 1980).In this paper I extend this discussion by examining how effects of economic transition on internal migration since the late 1980s. This idea aims at gaining a broader insight into the relationship between economic transition and migration during the renovation processEconomic transition, migration

Technical efficiency of rice producing households in the Mekong Delta of Vietnam

Technical Efficiency (TE) is defined as an estimation of the ability of a household to produce the maximum output with the given inputs. It is usually estimated by using the data envelopment analysis (DEA) and stochastic frontier analysis (SFA). Data collected from 261 rice farming households in the Mekong Delta were used in the empirical analysis. Results show that the average TE among the surveyed households is above 76% in both the Constant (CRS) and the Variable Returns to Scale (VRS). The average scale efficiency score for these rice producing households is nearly one. The determinants of the quantity of rice or yields and of the TE for the households are significantly related with some variables such as the plot size, seed, and hired labor cost. However, technical inefficiency significantly depends on the farmers’ farming experience and adoption of advanced farming practices.Technical efficiency, rice-producing household

Electronic structure calculations for point defects, interfaces, and nanostructures of TiO2

Transparent conducting oxides (TCOs) play an important role not only in optoelectronic and photovoltaic devices but also in future transparent electronics. A transparent conductor arises upon degenerately doping a semiconductor (insulator) so that the conduction becomes metallic (resistivity ~ temperature). The extra electrons occupy the conduction band (CB) states of the host and the conductivity is determined by the electron optical effective mass. Recently, anatase TiO2 films doped with Nb, i.e., Ti1-xNbxO2 (TNO), have attracted a great deal of interest as a promising candidate for TCO applications because of their low resistivity (~ 10^-4 Omega.cm) and high optical transmittance (90 % in the visible light region). A few experimental studies have been reported for the optical effective mass of electrons as a function of the carrier concentration in Nb-doped anatase, on the directions which are either orthogonal or parallel to the tetragonal axis of the crystal. In this thesis, I have determined the optical effective mass of electrons in Nb-doped anatase based on band structure calculations. The anisotropy of the crystal and the nonparabolicity of the bands have both been taken into account. I have found that in the range concentration which is relevant to transparent conductive oxide applications, the optical effective mass is determined by several branches of the conduction band, leading to a complicated dependence on the carrier concentration. The function for the optical effective mass obtained by our calculations agrees well with that obtained experimentally. In particular, the strong anisotropy of the optical effective mass has already been confirmed. Although Ta-doping of anatase TiO2 appears to be effective as well, this possibility has been not well explored. I have compared the two dopants, i.e., Nb and Ta, for doping anatase TiO2. The Ta dopant has a considerably higher solubility and a lower optical effective mass, thus acquiring more advantages than Nb. Moreover, my calculations have also explained why a reducing atmosphere is necessary for the efficient dopant incorporation, without invoking oxygen vacancies as proposed in the literature. There is no study on the effects from the quantum confinement of dopants in anatase nanowires (ANWs). Therefore, I report here the first demonstration on the role of Nb- and Ta-dopants in ANWs. The pure ANWs cut by keeping the screw axis of the original bulk structures are consistently lower in energy than the similarly oriented nanowires in which the screw symmetry is destroyed. Both Nb and Ta dopants prefer the sub-corner sites of the most stable ANWs. At the highest symmetry, the band structure of the doped ANW is similar to that of the perfect one. The increase of the photocatalytic activity upon mixing rutile and anatase powders is usually explained by assuming change separation between the two phases. There are many contradicting theories regarding the particular charge transfer between these phases. Therefore, another goal of this thesis is to study the electronic properties of the interface between anatase and rutile phases of TiO2. By calculating the band line-up of a rutile-anatase interface, I have found that both the conduction band minimum (CBM) and the valence band maximum (VBM) of the rutile phase are higher than those of the anatase phase. As a result, electrons are expected to transfer from the rutile phase to the anatase phase while holes move in the opposite direction. In my work, the optical electron effective mass is determined from the band structure of the material, which is in turn calculated by the version of density functional theory (DFT) in the generalized gradient approximation (GGA) implemented in the Vienna Ab Initio Simulation Package (VASP) package. For bulk materials, both the Perdew-Berke-Enzerhof (PBE) and the screened hybrid functional (HSE06) are used for the exchange energy. Although the HSE06 functional gives better results compared with the existing experimental measurements for Nb- and Ta-doped anatase TiO2 bulk materials, similar calculations with HSE06 for nanowires are far more expensive. Therefore, my calculations for nanowires are carried out only with the pure GGA-PBE functional. To determine the rutile-anatase interface, I have used the density functional based tight binding (DFTB) method for the molecular dynamic simulations, and then relaxed by ab initio calculations with PBE functional at 0K

Impact of 18F-FDG PET/CT on the staging of patients with non-small cell lung cancer

Background: Non-small cell lung cancer (NSCLC) accounts for approximately 80% of new diagnoses of pulmonary carcinoma. This study investigated the correlation between 18 F-fluorodeoxyglucose uptake in computerized tomography integrated positron emission tomography and tumor size, lymph node metastasis, and distant metastasis in patients with NSCLC.Methods: The records of 318 NSCLC patients (220 male, 98 females; mean age 60.94 years) were evaluated retrospectively.Results: 278 cases were adenocarcinomas; 28 squamous cell carcinomas; and 12 large cell carcinoma. When the cases were categorized according to tumor size (group 1, ≤3 cm; group 2, >3 and ≤5 cm; group 3, >5 cm), the maximum standardized uptake value (SUVmax) was significantly lower in groups 1 and 2 compared with group 3 (p<0,001 for each). Considering all cases, tumor SUVmax was not correlated with age, gender or histopathological type. Lymph node metastases were seen in 250 cases: 80.2% of these were adenocarcinomas, 71.4% squamous cell carcinomas, and 58.3% large cell carcinomas. Neither lymph node involvement nor distant metastases were correlated with tumor SUVmax, although lymph node size was positively correlated with lymph node SUVmax (r=0.758; p<0.001).Conclusions: SUVmax was significantly associated with tumor size, but not with distant metastases or lymph node involvement. Therefore, SUVmax on positron emission tomography is not predictive of the presence of metastases.

Determinants Affecting Intention to Use E-Wallets in Vietnam: An Empirical Case of Momo

This research endeavors to identify and assess the determinants influencing the intention to use Momo e-wallet in Ho Chi Minh City, establishing connections between these factors. The research methodology involved the design of a questionnaire based on the UTAUT model, tailored to evaluate the determinants affecting the intention to use e-wallets in Vietnam, with a specific focus on Momo. A total of 388 respondents, all Momo users, participated in the study. The results of the regression analysis revealed that all four determinants significantly impact the intention to use the Momo e-wallet, with varying levels of significance: Effort Expectancy (β=0.45), Promotional Benefits (β=0.379), Performance Expectancy (β=0.13), and Facilitating Conditions (β=0.072). Understanding these factors that influence usage intention and gaining insights into user preferences can facilitate the development of e-wallet systems that support e-wallet providers in penetrating the market and retaining their existing user base. Keywords: intention to use, e-wallets, Momo, Vietna

Can positron emission tomography - computed tomography imaging predict of metastases in patients with small cell lung cancer

Background: Small-cell lung cancer (SCLC) accounts for 15%-20% of all lung cancer cases. positron emission tomography - computed tomography (PET/CT) has become increasingly used as an initial staging tool in patients with SCLC. We aimed to explore the relationships between primary tumor 18F-FDG uptake measured as the maximum standardized uptake value (SUV max) and clinical stage at PET/CT for small cell lung cancer patients (SCLC).Methods: Patients with SCLC who underwent 18F-FDG PET/CT scans before the treatment were included in the study at Bach Mai hospital of Vietnam, from November 2014 to May 2018. The primary tumor and secondary lesion SUVmax was calculated; the tumor size was measured; the TNM status was determined mainly by FDG PET/CT imaging according to The 8th Edition of the TNM Classification for Lung Cancer were recorded. An evaluation was made of the linear relationship between tumor size, T stage, N stage, and M stages of the patients and their SUVmax using Spearman’s correlation.Results: Total 37 cases (34 men and 3 women; age range 38 - 81 years, median 64 years) were analyzed. The average of primary tumor size and SUVmax were 5.95±2.77 cm and 10.21±4.75, respectively. The SUVmax of primary tumor is significantly greater than that of nodal and distant organ metastasis (10.21±4.75 vs 8.20±4.35 and 6.44±3.17, p<0.01). There was a moderate correlation between SUVmax and tumor size (r =0.596, p<0.001), tumor stage (r = 0.502, p<0.01) but not significant with nodal stage (r =-0.218, p=0.194), metastasis stage (r = -0.055, p=0.747), and overall stage (r=-0.060, p=0.725).Conclusions: SUVmax was significantly correlated with tumor size, but not with distant metastases or lymph node involvement. Therefore, SUVmax on positron emission tomography is not predictive of the presence of metastases in patients with SCLC

Using positron emission tomography - computed tomography imaging to distinguish of metastatic disease from second primary lung tumours in patients with non-small cell lung cancer

Background: In NSCLC patients with multiple lesions, the differentiation between metastases and second primary tumours has significant therapeutic and prognostic implications. The aim of this retrospective study was to investigate the potential of 18F-FDG PET to discriminate metastatic disease from second primary lung tumours.Methods: Of 318 NSCLC patients between November 2015 and October 2018 at Bach Mai hospital, patients with a synchronous second primary lung cancer were selected. Patients with metastatic disease involving the lungs served as the control group. Maximum standardized uptake values (SUVs) measured with 18F-FDG PET were determined for two tumours in each patient. The SUVmax was determined and compared between the second primary group and metastatic disease group. Receiver-operating characteristic (ROC) curve analysis was performed to determine the sensitivity and specificity of the SUVmax for an optimal cut-off value.Results: A total of 81 NSCLC patients (44 metastatic disease, 37 second primary cancer) were included for analysis. The SUVmax was significantly higher in patients with second primary cancer than in those with metastatic disease (7.53±4.33 vs 4.35±2.58, respectively, p<0.001). The area under the ROC curve was 0.81 and the odds ratio for the optimal cut-off was 7.52.Conclusions: SUVmax from 18F-FDG PET images can be helpful in differentiating metastatic disease from second primary tumours in patients with synchronous pulmonary lesions. Further studies are warranted to confirm the consistency of these results.

The economic transition and migration of Vietnam and the Mekong Delta region

Relationship between economic transition and migration has long attracted increasing attention of both policy-makers and researchers. Migration is seen as a response of changes during the economic transition in a country, because labour is an important production factor in the market, in which labourers have a desire to move to a place of better working conditions rather than going to a disadvantaged conditions (De Haas, 2010; Todaro, 1980).In this paper I extend this discussion by examining how effects of economic transition on internal migration since the late 1980s. This idea aims at gaining a broader insight into the relationship between economic transition and migration during the renovation proces

Technical efficiency of rice producing households in the Mekong Delta of Vietnam

Technical Efficiency (TE) is defined as an estimation of the ability of a household to produce the maximum output with the given inputs. It is usually estimated by using the data envelopment analysis (DEA) and stochastic frontier analysis (SFA). Data collected from 261 rice farming households in the Mekong Delta were used in the empirical analysis. Results show that the average TE among the surveyed households is above 76% in both the Constant (CRS) and the Variable Returns to Scale (VRS). The average scale efficiency score for these rice producing households is nearly one. The determinants of the quantity of rice or yields and of the TE for the households are significantly related with some variables such as the plot size, seed, and hired labor cost. However, technical inefficiency significantly depends on the farmers’ farming experience and adoption of advanced farming practices