On Bakhvalov-type meshes for a linear convection-diffusion problem in 2D

For singularly perturbed two-dimensional linear convection-diffusion problems, although optimal error estimates of an upwind finite difference scheme on Bakhvalov-type meshes are widely known, the analysis remains unanswered (Roos and Stynes in Comput. Meth. Appl. Math. 15 (2015), 531--550). In this short communication, by means of a new truncation error and barrier function based analysis, we address this open question for a generalization of Bakhvalov-type meshes in the sense of Boglaev and Kopteva. We prove that the upwind scheme on these mesh modifications is optimal first-order convergence, uniformly with respect to the perturbation parameter, in the discrete maximum norm. Furthermore, we derive a sufficient condition on the transition point choices to guarantee that our modified meshes can preserve the favorable properties of the original Bakhvalov mesh

On Bakhvalov-type meshes for a linear convection-diffusion problem in 2D

For singularly perturbed two-dimensional linear convection-diffusion problems, although optimal error estimates of an upwind finite difference scheme on Bakhvalov-type meshes are widely known, the analysis remains unanswered (Roos and Stynes in Comput. Meth. Appl. Math. 15 (2015), 531--550). In this short communication, by means of a new truncation error and barrier function based analysis, we address this open question for a generalization of Bakhvalov-type meshes in the sense of Boglaev and Kopteva. We prove that the upwind scheme on these mesh modifications is optimal first-order convergence, uniformly with respect to the perturbation parameter, in the discrete maximum norm. Furthermore, we derive a sufficient condition on the transition point choices to guarantee that our modified meshes can preserve the favorable properties of the original Bakhvalov mesh

Spatiotemporal evolution of SARS-CoV-2 Alpha and Delta variants during large nationwide outbreak of COVID-19, Vietnam, 2021

We analyzed 1,303 SARS-CoV-2 whole-genome sequences from Vietnam, and found the Alpha and Delta variants were responsible for a large nationwide outbreak of COVID-19 in 2021. The Delta variant was confined to the AY.57 lineage and caused >1.7 million infections and >32,000 deaths. Viral transmission was strongly affected by nonpharmaceutical interventions

Preconditioning techniques for singularly perturbed differential equations

This thesis considers computer methods for solving singularly perturbed differential equations. Standard algorithms are very inefficient when applied to these problems, although the exact reasons for this have not been well-understood. This thesis provides a new understanding for this phenomenon, and applies that understanding to designing new, highly efficient algorithms

The Association between POU1F1 Gene Polymorphisms and Growth as well as Carcass Traits of Noi Native Chickens

The study was conducted to detect and analyze the association between single nucleotide polymorphisms (SNP) in the POU1F1 (POU class 1 homeobox 1) gene and growth as well as carcass traits in Noi native chickens. Blood samples were taken at the wings, DNAs were extracted based on the phenol: chloroform technique and genotypes were analyzed by PCR-RFLP method. The frequencies of CC genotypes for three polymorphic sites (POU1F1_HhaI SNP, POU1F1_EcoRI SNP, POU1F1_BspHI SNP) were the highest. The corresponding C allele frequencies were higher than those of T alleles. Of three polymorphisms, POU1F1_BspHI SNP was found to be significantly linked with growth and carcass traits. Chickens bearing TT genotype showed higher body weight at 91 days, carcass weight, breast weight, and thigh weight than those of chickens with CC genotype. This SNP can be a useful marker for the selection of Noi chicken for improvement of growth and carcass traits

Effects of Lysine Supplemented on Growth, Apparent Nutrient Digestibility, and Slaughter Yield of Noi Broilers from 56–84 Days of Age

A total of 192 Noi broilers at 56 days of age were allotted in a completely randomized design consisting of four treatments and four replicates to evaluate the effect of dietary lysine added on body weight gain (BWG), feed conversion ratio (FCR), apparent nutrient digestibility (AND), and carcass characteristics. Treatments included a control with 0.8% lysine in the diet and three experimental treatments (Lys+0.1; Lys+0.2; Lys+0.3) with lysine added at 0.1, 0.2, and 0.3%, respectively. Crude protein (CP) was 15%, and metabolizable energy was 3,000 kcal/kg of feed. At 77 days of age, for each replicate, one male and one female chicken were selected for the estimation of AND by using Fe2O3 marker. The chickens were fed ad libitum and vaccinated against common diseases. The results showed that lysine's addition to the diet at 0.2–0.3% significantly improved the BWG and FCR (P <0.05). Furthermore, the addition of 0.1–0.3% lysine to the diet resulted in a significant increase in apparent CP digestibility and overall amino acid digestibility (P <0.05) but did not affect the apparent digestibility of Ca and P of Noi broilers. Finally, concerning the breast weight and yield of both male and female chickens, whereas the male broilers' dressing improved with the addition of 0.3% lysine to the diet, the breast yield of their female counterparts bettered when supplemented with 0.2% lysine

Occurrence of antibiotic residues and antibiotic-resistant bacteria in effluents of pharmaceutical manufacturers and other sources around Hanoi, Vietnam

Pharmaceutical manufacturers in Vietnam are producing a wide variety of antibiotics for human and veterinary use. Consequently, the water discharged from those facilities can contain residues of antibiotics, which could have adverse impact on the environment. However, studies on the occurrence of antibiotics in the wastewater from pharmaceutical manufacturers in Vietnam are almost non-existent. In this study, water samples were collected at around the outlets of four pharmaceutical manufacturing plants as well as from a hospital and an aquaculture farm around Hanoi in 2016 and 2017. Fifteen antibiotics from four major classes (β-lactam, quinolones, macrolides, sulfonamides) were monitored, using a validated LC-MS/MS method, based on their number of registrations at the Ministry of Health. Ten antibiotics, ampicillin, cefuroxime, cefotaxime, clarithromycin, azithromycin, sulfamethoxazole, trimethoprim, ofloxacin, norfloxacin, and ciprofloxacin were detected in the samples at different concentrations. Notably, sulfonamides and quinolones were occasionally detected at very high concentration, such as sulfamethoxazole (252 μg/L), trimethoprim (107 μg/L), ofloxacin (85 μg/L), and ciprofloxacin (41 μg/L). In this study, concentrations of antibiotic residues in effluent of pharmaceutical plants were higher than those from other sources. The antibiotic-resistance tests indicated the widespread resistance to common antibiotics like quinolone and sulfonamides in the collected samples. This finding suggests that wastewater from pharmaceutical manufacturers could be an important source of antibiotics and antibiotic-resistant bacteria in the aquatic environment of Vietnam

A randomized comparison of Chloroquine versus Dihydroartemisinin-Piperaquine for the treatment of Plasmodium vivax infection in Vietnam

A total of 128 Vietnamese patients with symptomatic Plasmodium vivax mono-infections were enrolled in a prospective, open-label, randomized trial to receive either chloroquine or dihydroartemisinin–piperaquine (DHA-PPQ). The proportions of patients with adequate clinical and parasitological responses were 47% in the chloroquine arm (31 of 65 patients) and 66% in the DHA-PPQ arm (42 of 63 patients) in the Kaplan–Meier intention-to-treat analysis (absolute difference 19%, 95% confidence interval = 0–37%), thus establishing non-inferiority of DHA-PPQ. Fever clearance time (median 24 versus 12 hours, P = 0.02), parasite clearance time (median 36 versus 18 hours, P < 0.001), and parasite clearance half-life (mean 3.98 versus 1.80 hours, P < 0.001) were all significantly shorter in the DHA-PPQ arm. All cases of recurrent parasitemia in the chloroquine arm occurred from day 33 onward, with corresponding whole blood chloroquine concentration lower than 100 ng/mL in all patients. Chloroquine thus remains efficacious for the treatment of P. vivax malaria in southern Vietnam, but DHA-PPQ provides more rapid symptomatic and parasitological recovery

A randomized comparison of chloroquine versus dihydroartemisinin-piperaquine for the treatment of Plasmodium vivax infection in Vietnam

A total of 128 Vietnamese patients with symptomatic Plasmodium vivax mono-infections were enrolled in a prospective, open-label, randomized trial to receive either chloroquine or dihydroartemisinin-piperaquine (DHA-PPQ). The proportions of patients with adequate clinical and parasitological responses were 47% in the chloroquine arm (31 of 65 patients) and 66% in the DHA-PPQ arm (42 of 63 patients) in the Kaplan-Meier intention-to-treat analysis (absolute difference 19%, 95% confidence interval = 0-37%), thus establishing non-inferiority of DHA-PPQ. Fever clearance time (median 24 versus 12 hours, P = 0.02), parasite clearance time (median 36 versus 18 hours, P < 0.001), and parasite clearance half-life (mean 3.98 versus 1.80 hours, P < 0.001) were all significantly shorter in the DHA-PPQ arm. All cases of recurrent parasitemia in the chloroquine arm occurred from day 33 onward, with corresponding whole blood chloroquine concentration lower than 100 ng/mL in all patients. Chloroquine thus remains efficacious for the treatment of P. vivax malaria in southern Vietnam, but DHA-PPQ provides more rapid symptomatic and parasitological recovery

A randomized comparison of Chloroquine versus Dihydroartemisinin-Piperaquine for the treatment of Plasmodium vivax infection in Vietnam

A total of 128 Vietnamese patients with symptomatic Plasmodium vivax mono-infections were enrolled in a prospective, open-label, randomized trial to receive either chloroquine or dihydroartemisinin–piperaquine (DHA-PPQ). The proportions of patients with adequate clinical and parasitological responses were 47% in the chloroquine arm (31 of 65 patients) and 66% in the DHA-PPQ arm (42 of 63 patients) in the Kaplan–Meier intention-to-treat analysis (absolute difference 19%, 95% confidence interval = 0–37%), thus establishing non-inferiority of DHA-PPQ. Fever clearance time (median 24 versus 12 hours, P = 0.02), parasite clearance time (median 36 versus 18 hours, P < 0.001), and parasite clearance half-life (mean 3.98 versus 1.80 hours, P < 0.001) were all significantly shorter in the DHA-PPQ arm. All cases of recurrent parasitemia in the chloroquine arm occurred from day 33 onward, with corresponding whole blood chloroquine concentration lower than 100 ng/mL in all patients. Chloroquine thus remains efficacious for the treatment of P. vivax malaria in southern Vietnam, but DHA-PPQ provides more rapid symptomatic and parasitological recovery