Convergence analysis of a Crank-Nicolson Galerkin method for an inverse source problem for parabolic equations with boundary observations

This work is devoted to an inverse problem of identifying a source term depending on both spatial and time variables in a parabolic equation from single Cauchy data on a part of the boundary. A Crank-Nicolson Galerkin method is applied to the least squares functional with an quadratic stabilizing penalty term. The convergence of finite dimensional regularized approximations to the sought source as measurement noise levels and mesh sizes approach to zero with an appropriate regularization parameter is proved. Moreover, under a suitable source condition, an error bound and corresponding convergence rates are proved. Finally, several numerical experiments are presented to illustrate the theoretical findings.Comment: Inverse source problem, Tikhonov regularization, Crank-Nicolson Galerkin method, Source condition, Convergence rates, Ill-posedness, Parabolic proble

Adversarial Light Projection Attacks on Face Recognition Systems: A Feasibility Study

Deep learning-based systems have been shown to be vulnerable to adversarial attacks in both digital and physical domains. While feasible, digital attacks have limited applicability in attacking deployed systems, including face recognition systems, where an adversary typically has access to the input and not the transmission channel. In such setting, physical attacks that directly provide a malicious input through the input channel pose a bigger threat. We investigate the feasibility of conducting real-time physical attacks on face recognition systems using adversarial light projections. A setup comprising a commercially available web camera and a projector is used to conduct the attack. The adversary uses a transformation-invariant adversarial pattern generation method to generate a digital adversarial pattern using one or more images of the target available to the adversary. The digital adversarial pattern is then projected onto the adversary's face in the physical domain to either impersonate a target (impersonation) or evade recognition (obfuscation). We conduct preliminary experiments using two open-source and one commercial face recognition system on a pool of 50 subjects. Our experimental results demonstrate the vulnerability of face recognition systems to light projection attacks in both white-box and black-box attack settings.Comment: To appear in the proceedings of the IEEE Computer Vision and Pattern Recognition (CVPR) Biometrics Workshop 2020 - 9 pages, 8 figure

Farming systems in the sandy area of the Thua Thien Hue Province, Central Vietnam, survey of socio-economic situation and constraints identified by farmers

peer reviewe

The Efficacy and Safety of Hyaluronic Acid Microinjection for Skin Rejuvenation in Vietnam

BACKGROUND: Aging is an increasing concern of modern society, particularly facial ageing. In recent years, the microinjection technique has increasingly been emphasised as a skin rejuvenation strategy. Hyaluronic acid (HA) plays an important role in the hydration of the extracellular space and can thus improve skin hydration, firmness and viscoelastic properties. AIM: To evaluate the efficacy and safety of HA microinjection in skin rejuvenation. METHODS: We enrolled thirty participants underwent three sessions of HA microinjection involving multiple injections in the face or back of the hands at 2-week intervals. The aesthetic outcomes were assessed at baseline and after 2, 4 and 8 weeks. Clinical evaluation was based on the Global Aesthetic Improvement Scale (GAIS) and the Wrinkle Severity Rating Scale (WSRS). RESULTS: Evaluation of photographs from 2, 4 and 8 weeks revealed significant clinical improvement in the brightness, texture and wrinkling of the skin. Analysis of the GAIS and WSRS scores revealed statistically significant results after 2 months. CONCLUSION: Most of the participants felt satisfied with the treatment (93.3%)

A modified Sequential Organ Failure Assessment score for dengue: development, evaluation and proposal for use in clinical trials

Background Dengue is a neglected tropical disease, for which no therapeutic agents have shown clinical efficacy to date. Clinical trials have used strikingly variable clinical endpoints, which hampers reproducibility and comparability of findings. We investigated a delta modified Sequential Organ Failure Assessment (delta mSOFA) score as a uniform composite clinical endpoint for use in clinical trials investigating therapeutics for moderate and severe dengue. Methods We developed a modified SOFA score for dengue, measured and evaluated its performance at baseline and 48 h after enrolment in a prospective observational cohort of 124 adults admitted to a tertiary referral hospital in Vietnam with dengue shock. The modified SOFA score included pulse pressure in the cardiovascular component. Binary logistic regression, cox proportional hazard and linear regression models were used to estimate association between mSOFA, delta mSOFA and clinical outcomes. Results The analysis included 124 adults with dengue shock. 29 (23.4%) patients required ICU admission for organ support or due to persistent haemodynamic instability: 9/124 (7.3%) required mechanical ventilation, 8/124 (6.5%) required vasopressors, 6/124 (4.8%) required haemofiltration and 5/124 (4.0%) patients died. In univariate analyses, higher baseline and delta (48 h) mSOFA score for dengue were associated with admission to ICU, requirement for organ support and mortality, duration of ICU and hospital admission and IV fluid use. Conclusions The baseline and delta mSOFA scores for dengue performed well to discriminate patients with dengue shock by clinical outcomes, including duration of ICU and hospital admission, requirement for organ support and death. We plan to use delta mSOFA as the primary endpoint in an upcoming host-directed therapeutic trial and investigate the performance of this score in other phenotypes of severe dengue in adults and children

The Decline of PUVA Therapy in Vietnam: Effective Treatment of Narrow Band UVB in Vietnamese Vitiligo Patients

AIM: To examine the efficacy and safety of Narrowband ultraviolet B (NB-UVB) in Vietnamese vitiligo patients. METHODS: We recruited thirty-one patients (14 males, 17 females), aged from 7 to 67 years, with both segmental vitiligo (SV) and non-segmental vitiligo (NSV), treated three times weekly with NB-UVB. The starting dose for adults from 15 years old and children less than 15 years old was 200 mJ/cm2 and 150 mJ/cm2, respectively, with 50 mJ/cm2 and 20 mJ/cm2 dose increments at each subsequent visit, respectively, until mild erythema lasting less than 24 hrs reported by patient, given for a period of 6 months. Response to therapy was assessed based on VASI score changes. RESULTS: Based upon our results, 38.7% (12/31) of patients achieved a very good response of more than 50% VASI changes, 41.9% (13/31) obtained a good response (VASI changed from 25 to 50%). Total good and very good response to therapy significantly increased with prolonged treatment, increasing from 19.4% to 64.5% and 80.6% after 2, 4 and 6 months, respectively. Localised NSV patients obtained good and very good response significantly more frequently than generalised NSV (55.6% versus 18.2%). Adverse effects were minimal, of which one case developed herpes simplex, and 4 cases reported mild photo burn reaction which completely disappeared after adjusting the dose. CONCLUSION: NB-UVB therapy is an effective and safe tool in the management of Vietnamese vitiligo patients

Ventilator-associated respiratory infection in a resource-restricted setting: impact and etiology.

BACKGROUND: Ventilator-associated respiratory infection (VARI) is a significant problem in resource-restricted intensive care units (ICUs), but differences in casemix and etiology means VARI in resource-restricted ICUs may be different from that found in resource-rich units. Data from these settings are vital to plan preventative interventions and assess their cost-effectiveness, but few are available. METHODS: We conducted a prospective observational study in four Vietnamese ICUs to assess the incidence and impact of VARI. Patients ≥ 16 years old and expected to be mechanically ventilated > 48 h were enrolled in the study and followed daily for 28 days following ICU admission. RESULTS: Four hundred fifty eligible patients were enrolled over 24 months, and after exclusions, 374 patients' data were analyzed. A total of 92/374 cases of VARI (21.7/1000 ventilator days) were diagnosed; 37 (9.9%) of these met ventilator-associated pneumonia (VAP) criteria (8.7/1000 ventilator days). Patients with any VARI, VAP, or VARI without VAP experienced increased hospital and ICU stay, ICU cost, and antibiotic use (p < 0.01 for all). This was also true for all VARI (p < 0.01 for all) with/without tetanus. There was no increased risk of in-hospital death in patients with VARI compared to those without (VAP HR 1.58, 95% CI 0.75-3.33, p = 0.23; VARI without VAP HR 0.40, 95% CI 0.14-1.17, p = 0.09). In patients with positive endotracheal aspirate cultures, most VARI was caused by Gram-negative organisms; the most frequent were Acinetobacter baumannii (32/73, 43.8%) Klebsiella pneumoniae (26/73, 35.6%), and Pseudomonas aeruginosa (24/73, 32.9%). 40/68 (58.8%) patients with positive cultures for these had carbapenem-resistant isolates. Patients with carbapenem-resistant VARI had significantly greater ICU costs than patients with carbapenem-susceptible isolates (6053 USD (IQR 3806-7824) vs 3131 USD (IQR 2108-7551), p = 0.04) and after correction for adequacy of initial antibiotics and APACHE II score, showed a trend towards increased risk of in-hospital death (HR 2.82, 95% CI 0.75-6.75, p = 0.15). CONCLUSIONS: VARI in a resource-restricted setting has limited impact on mortality, but shows significant association with increased patient costs, length of stay, and antibiotic use, particularly when caused by carbapenem-resistant bacteria. Evidence-based interventions to reduce VARI in these settings are urgently needed