Projection-free methods for solving smooth convex bilevel optimisation problems

When faced with multiple minima of an "inner-level" convex optimisation problem, the convex bilevel optimisation problem selects an optimal solution which also minimises an auxiliary "outer-level" convex objective of interest. Bilevel optimisation requires a different approach compared to single-level optimisation problems since the set of minimisers for the inner-level objective is not given explicitly. In this thesis, we propose new projection-free methods for convex bilevel optimisation which require only a linear optimisation oracle over the base domain. We provide convergence guarantees for both inner- and outer-level objectives that hold under our proposed projection-free methods. In particular, we highlight how our guarantees are affected by the presence or absence of an optimal dual solution. Lastly, we conduct numerical experiments that demonstrate the performance of the proposed methods

Projection-Free Methods for Solving Convex Bilevel Optimization Problems

When faced with multiple minima of an "inner-level" convex optimization problem, the convex bilevel optimization problem selects an optimal solution which also minimizes an auxiliary "outer-level" convex objective of interest. Bilevel optimization requires a different approach compared to single-level optimization problems since the set of minimizers for the inner-level objective is not given explicitly. In this paper, we propose new projection-free methods for convex bilevel optimization which require only a linear optimization oracle over the base domain. We provide convergence guarantees for both inner- and outer-level objectives that hold under our proposed projection-free methods. In particular, we highlight how our guarantees are affected by the presence or absence of an optimal dual solution. Lastly, we conduct numerical experiments that demonstrate the performance of the proposed methods

Assessing the efficacy and safety of magnesium sulfate for management of autonomic nervous system dysregulation in Vietnamese children with severe hand foot and mouth disease.

BACKGROUND: Brainstem encephalitis is a serious complication of hand foot and mouth disease (HFMD) in children. Autonomic nervous system (ANS) dysregulation and hypertension may occur, sometimes progressing to cardiopulmonary failure and death. Vietnamese national guidelines recommend use of milrinone if ANS dysregulation with Stage 2 hypertension develops. We wished to investigate whether magnesium sulfate (MgSO4) improved outcomes in children with HFMD if used earlier in the evolution of the ANS dysregulation (Stage 1 hypertension). METHODS: During a regional epidemic we conducted a randomized, double-blind, placebo-controlled trial of MgSO4 in children with HFMD, ANS dysregulation and Stage 1 hypertension, at the Hospital for Tropical Diseases in Ho Chi Minh city. Study participants received an infusion of MgSO4 or matched placebo for 72 h. We also reviewed data from non-trial HFMD patients in whom milrinone failed to control hypertension, some of whom received MgSO4 as second line therapy. The primary outcome for both analyses was a composite of disease progression within 72 h - addition of milrinone (trial participants only), need for ventilation, shock, or death. RESULTS: Between June 2014 and September 2016, 14 and 12 participants received MgSO4 or placebo respectively, before the trial was stopped due to futility. Among 45 non-trial cases with poorly controlled hypertension despite high-dose milrinone, 33 received MgSO4 while 12 did not. There were no statistically significant differences in the composite outcome between the MgSO4 and the placebo/control groups in either study (adjusted relative risk (95%CI) of [6/14 (43%) vs. 6/12 (50%)], 0.84 (0.37, 1.92), p = 0.682 in the trial and [1/33 (3%) vs. 2/12 (17%)], 0.16 (0.01, 1.79), p = 0.132 in the observational cohort). The incidence of adverse events was similar between the groups. Potentially toxic magnesium levels occurred very rarely with the infusion regime used. CONCLUSION: Although we could not demonstrate efficacy in these studies, there were no safety signals associated with use of 30-50 mg/kg/hr. MgSO4 in severe HFMD. Intermittent outbreaks of HFMD are likely to continue across the region, and an adequately powered trial is still needed to evaluate use of MgSO4 in controlling hypertension in severe HFMD, potentially involving a higher dose regimen. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT01940250 (Registered 22 AUG 2013). Trial sponsor: University of Oxford

Evaluation of Factors Affecting Antimicrobial Activity of Bacteriocin from Lactobacillus plantarum Microencapsulated in Alginate-Gelatin Capsules and Its Application on Pork Meat as a Bio-Preservative

Antimicrobial compounds from traditional fermented foods have shown activity against a wide range of pathogen and spoilage microorganisms for several years. In this study, a Lactic acid bacteria (LAB), isolated from Vietnamese traditional fermented yogurt (Lactobacillus plantarum SC01), was encapsulated in alginate-gelatin (ALG-GEL) and the effect of incubation temperature, medium pH and surfactants were assessed. The aims of this research were to evaluate antimicrobial activity of bacteriocin produced by L. plantarum SC01. Another aim the research was to study the quality of pork meat treated with its Bacteriocin in 2 h as a bio-preservative at different storage times (0 h, 12 h, 24 h and 48 h) in room temperature, compared to control (treated with salt 40.0%). The antimicrobial activity of L. plantarum SC01 was identified through the inhibition rate of five indicator organisms, including Escherichia coli, Salmonella sp., Staphylococcus aureus, Listeria monocytogenes, and Bacillus subtilis by co-culture method. The results showed that L. plantarum SC01 microencapsulated in ALG-GEL (2.5% alginate and 6.0% gelatin, w/v) and 3.0% bacteria supplied into modified MRS medium (MRSOPTSC01) produced highly active compound inhibited the growth of indicator organisms at a density of 104–108 CFU/mL. Antibacterial compounds were highly active in a treatment at 80 °C; not to be affected by pH; affected by surfactant as Ethylenediaminetetraacetic acid (EDTA), Sodium dodecyl sulfate (SDS), and Tween. Moreover, LAB obtained from this study show the potent Bacteriocin in its usage as a preservative in food

Hyperhomocysteinemia in Patients with Newly Diagnosed Primary Hypertension in Can Tho City, Vietnam

Background: Elevated levels of blood total homocysteine is one of the cardiovascular risk factors in hypertensive patients. Objectives: Determine the prevalence of hyperhomocysteinemia and its associated factors in newly diagnosed primary hypertension patients. Materials and methods: A cross-sectional descriptive study on 105 patients with newly diagnosed primary hypertension at Can Tho University of Medicine and Pharmacy Hospital from May 2017 to May 2018. Total homocysteine levels and related factors were collected at the study time. Results: The mean plasma total homocysteine level was 16.24 ± 4.49 µmol/L. There were 78 patients with elevated plasma total homocysteine levels ≥15 µmol/L, accounting for 74.3% of all patients. Being elderly, gender, hypertension stage, and diabetes were factors associated with hyperhomocysteinemia (p < 0.05). Total homocysteine levels were positively correlated with SBP, DBP, and age with r(SBP) = 0.696, r(DBP) = 0.585, and r(age) = 0.286. Conclusion: Research on the subpopulation of Vietnamese people shows that hyperhomocysteinemia is common in patients with newly diagnosed primary hypertension, and high blood total homocysteine levels are often related to age, sex, hypertension stage, and diabetes

Effectiveness of Spironolactone in Terms of Galectin-3 Levels in Patients with Heart Failure with a Reduced Ejection Fraction in the Vietnamese Population

Background: Galectin-3 is a biomarker that has been demonstrated to play a significant role in myocardial fibrosis and remodeling in the pathogenesis of heart failure. Furthermore, spironolactone has the ability to control galectin-3 levels in heart failure patients. Objectives: The aim of our study was to determine the factors associated with the increase in galectin-3 and the alteration of galectin-3 concentration in patients with heart failure with a reduced ejection fraction after 12 weeks of treatment with spironolactone. Materials and methods: A cross-sectional descriptive study was conducted on 122 patients with heart failure with a reduced ejection fraction. Those patients were nonusers of spironolactone and presented for examination or had been hospitalized at the Can Tho Cardiovascular Hospital in Vietnam. The demographic and cardiovascular risk factor details were obtained at baseline, and galectin-3 levels were measured at baseline and also 12 weeks after taking spironolactone 25 mg once daily vs. 50 mg once daily. Results: The median baseline galectin-3 was 54.82 ± 26.06. Galectin-3 levels were positively correlated with age, NT-proBNP, and negatively correlated between EF and galectin-3 levels (p p p p < 0.05) (reduced 6.87%), respectively. Conclusion: Treatment with spironolactone played an essential role in reducing galectin-3 concentrations, especially spironolactone 50 mg once daily, which showed a significant effect on reducing galectin-3 compared with a 25 mg once-daily dose

Additional file 1 of A study of genetic variants associated with skin traits in the Vietnamese population

Supplementary Material