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1.
J Oleo Sci ; 73(5): 787-799, 2024.
Artículo en Inglés | MEDLINE | ID: mdl-38692900

RESUMEN

Launaea sarmentosa, also known as Sa Sam Nam, is a widely used remedy in Vietnamese traditional medicine and cuisine. However, the chemical composition and bioactivity of its essential oil have not been elucidated yet. In this study, we identified 40 compounds (98.6% of total peak area) in the essential oil via GC-MS analysis at the first time. Among them, five main compounds including Thymohydroquinone dimethyl ether (52.4%), (E)-α-Atlantone (9.0%), Neryl isovalerate (6.6%), Davanol D2 (isomer 2) (3.9%), and trans-Sesquisabinene hydrate (3.9%) have accounted for 75.8% of total peak area. The anti-bacterial activity of the essential oil against 4 microorganisms including Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa has also investigated via agar well diffusion assay. The results showed that the essential oil exhibited a strong antibacterial activity against Bacillus subtilis with the inhibition zones ranging from 8.2 to 18.7 mm. To elucidate the anti-bacterial effect mechanism of the essential oil, docking study of five main compounds of the essential oil (Thymohydroquinone dimethyl ether, (E)-α-Atlantone, Neryl isovalerate, Davanol D2 (isomer 2), and trans-Sesquisabinene hydrate) against some key proteins for bacterial growth such as DNA gyrase B, penicillin binding protein 2A, tyrosyl-tRNA synthetase, and dihydrofolate reductase were performed. The results showed that the main constituents of essential oil were highly bound with penicillin binding protein 2A with the free energies ranging -27.7 to -44.8 kcal/mol, which suggests the relationship between the antibacterial effect of essential oil and the affinity of main compounds with penicillin binding protein. In addition, the free energies of main compounds of the essential oil with human cyclooxygenase 1, cyclooxygenase 2, and phospholipase A2, the crucial proteins related with inflammatory response were less than diclofenac, a non-steroidal antiinflammatory drug. These findings propose the essential oil as a novel and promising anti-bacterial and anti-inflammatory medicine or cosmetic products.


Asunto(s)
Antibacterianos , Bacillus subtilis , Hemiterpenos , Simulación del Acoplamiento Molecular , Aceites Volátiles , Ácidos Pentanoicos , Antibacterianos/farmacología , Antibacterianos/aislamiento & purificación , Antibacterianos/química , Aceites Volátiles/farmacología , Aceites Volátiles/química , Aceites Volátiles/aislamiento & purificación , Bacillus subtilis/efectos de los fármacos , Staphylococcus aureus/efectos de los fármacos , Pseudomonas aeruginosa/efectos de los fármacos , Escherichia coli/efectos de los fármacos , Tetrahidrofolato Deshidrogenasa/metabolismo , Girasa de ADN/metabolismo , Sesquiterpenos/aislamiento & purificación , Sesquiterpenos/farmacología , Pruebas de Sensibilidad Microbiana , Cromatografía de Gases y Espectrometría de Masas
2.
J Pers Med ; 14(4)2024 Mar 30.
Artículo en Inglés | MEDLINE | ID: mdl-38673000

RESUMEN

Scabies is a neglected tropical disease and represents a considerable global burden. Although consensus diagnostic criteria for scabies have been recently published, diagnosing scabies infestation remains challenging in clinical practice. We investigated the diagnostic utility of complete blood cell count (CBC) and CBC-derived ratios obtained at diagnosis in a set of 167 patients who are Vietnamese with confirmed scabies. These parameters were compared with those of patients with dermatophytosis (N = 800) and urticaria (N = 2023), two diseases frequent in Vietnam, which can present with similar skin manifestations to scabies and tend to pose a diagnostic challenge in vulnerable populations. Our analysis revealed that white blood cell, monocyte, and eosinophil counts were significantly higher among patients with scabies than the other two diseases. Similarly, the monocyte-to-lymphocyte ratio (MLR) and eosinophil-to-lymphocyte ratio (ELR) were significantly higher among patients with scabies. The optimal cut-off values to distinguish scabies from dermatophytosis and urticaria were 0.094 for ELR (sensitivity: 74.85%, specificity: 70.7%) and 0.295 for MLR (sensitivity: 52.69%, specificity: 73.54%). CBC, ELR, and MLR are low-cost and easily calculated parameters that may be helpful for the diagnosis of scabies.

3.
Urologia ; 91(1): 42-48, 2024 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-37916769

RESUMEN

OBJECTIVES: The aim of this study is to analyze the compositions of urinary stones and investigate their distributions in different ages, genders, seasons, and clinical features of Northern Vietnamese patients. METHODS: A total of 231 patients with urinary stones from Northern Vietnam were collected and analyzed composition from 1/2021-12/2022. For all patients, age, sex, stone location, stone side, urine pH, and hospitalized date (month) were collected. RESULTS: Kidney stones are more frequently found in men than women with the male: female urinary stones ratio in this study being 1.96:1. The highest stone prevalence appeared between 60 and 69 years old. The most common stone composition was calcium oxalate, followed by calcium phosphate, uric acid, struvite, and cysteine. Mix stones of CaOx and CaP were more prevalent than pure stones. Males submitted more CaOx, CaP, and UA stones, whereas females were susceptible to infectious stones. Stones were more frequently found on the left side of the upper urinary tract (51.9%) than on the right side (27.3%) and lower urinary tract (7.8%). Cultural tendency leads to a smaller number of stones during the Lunar new year (February), and Ghost month (August).


Asunto(s)
Cálculos Renales , Cálculos Urinarios , Sistema Urinario , Urolitiasis , Humanos , Femenino , Masculino , Persona de Mediana Edad , Anciano , Vietnam , Oxalato de Calcio , Estaciones del Año , Cálculos Renales/química
4.
Radiol Case Rep ; 18(12): 4414-4418, 2023 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-37840895

RESUMEN

Acute methanol intoxication is uncommon. Methanol is mildly toxic, but its metabolites are formic acid and formaldehyde, causing total metabolism, visual disturbances, and central nervous system disturbances, leading to coma and death. Magnetic resonance imaging (MRI) is very important for the diagnosis and prognosis of methanol intoxication. Putaminal necrosis with or without hemorrhage is the most frequently reported finding. Other affected areas that are reported in the literature are subcortical white matter, hippocampus, optic nerve, and cerebellum. We report 3 cases of methanol intoxication and discuss their brain lesions on MRI.

5.
Chem Biodivers ; 20(12): e202301192, 2023 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-37819841

RESUMEN

Epaltes australis Less. has been traditionally used to treat fever and snake bites, whereas Lindera myrrha (Lour.) Merr. is well-known for addressing colds, chest pain, indigestion, and worm infestations. This study marks the first report on the chemical compositions and biological potentials of essential oils extracted from the leaves of Epaltes australis and Lindera myrrha. Essential oils obtained by hydro-distillation were analysed using the GC/MS (gas chromatography-mass spectrometry). E. australis exhibited a predominant presence of non-terpenic compounds (46.3 %), with thymohydroquinone dimethyl ether as the major compound, constituting 44.2 % of the oil. L. myrrha leaf oil contained a good proportion of sesquiterpene hydrocarbons (56.8 %), with principal compounds including (E)-caryophyllene (22.2 %), ledene (9.7 %), selina-1,3,7(11)-trien-8-one (9.6 %), and α-pinene (7.0 %). Both essential oils exhibited antimicrobial activity against the bacteria Bacillus subtilis and Clostridium sporogenes, and Escherichia coli, and the fungus Aspergillus brasiliensis. L. myrrha leaf essential oil exhibited potent control over the yeast Saccharomyces cerevisiae with a MIC of 32 µg/mL. Additionally, L. myrrha leaf oil showed strong anti-inflammatory activity with an IC50 value of 15.20 µg/mL by inhibiting NO (nitric oxide) production in LPS (lipopolysaccharide)-stimulated RAW2647 murine macrophage cells. Regarding anti-tyrosinase activity, E. australis leaf oil showed the best monophenolase inhibition with the IC50 of 245.59 µg/mL, while L. myrrha leaf oil successfully inhibited diphenolase with the IC50 of 152.88 µg/mL. From molecular docking study, selina-1,3,7(11)-trien-8-one showed the highest affinity for both COX-2 (cyclooxygenase-2) and TNF-α (tumor necrosis factor-α) receptors. Hydrophobic interactions play a great role in the bindings of ligand-receptor complexes.


Asunto(s)
Antiinfecciosos , Lindera , Aceites Volátiles , Animales , Ratones , Aceites Volátiles/química , Monofenol Monooxigenasa , Simulación del Acoplamiento Molecular , Antiinfecciosos/farmacología , Hojas de la Planta/química , Antiinflamatorios/química , Pruebas de Sensibilidad Microbiana
6.
BMJ Open ; 13(8): e069239, 2023 08 03.
Artículo en Inglés | MEDLINE | ID: mdl-37536968

RESUMEN

OBJECTIVE: We assessed the psychological impact posed by COVID-19 and its associated factors on the healthcare workforce nationwide during the peak of Vietnam's fourth outbreak. DESIGN: A cross-sectional study. SETTING: Our study was conducted in 61 provinces of Vietnam. METHODS: A total of 2814 healthcare professionals in 61/63 provinces of Vietnam. An online questionnaire using Patient Health Questionnaire-9 (PHQ-9), Perceived Stress Scale-4 (PSS-4) and Generalised Anxiety Disorder-7 (GAD-7) scales was distributed randomly to a subgroup of 503 respondents. PRIMARY AND SECONDARY OUTCOME MEASURES: To determine the impact of COVID-19 on the psychological of health workers, we conducted analyses to test a primary hypothesis related to participants based on three main scales including PHQ-9, PSS-4 and GAD-7 scales. RESULTS: Nearly half (49.7%) of healthcare workers experienced mild depression symptoms, 34.0% underwent moderate anxiety symptoms and 49.3% reported high-stress levels. Respondents who had a monthly income below 5 million VND (~US$212) and had more than 3 days of duty per week had a higher score on the anxiety scales. Compared with medical doctors, nurses/midwives had lower PHQ-9 (Coef=-2.53; 95% CI=-3.71 to -1.36) and GAD-7 scores (Coef=-2.36; 95% CI=-3.56 L to -1.16). Increased workload and work time was the harmful factor that increase the PHQ-9, GAD-7 or PSS-4 scores. More than half (53.9%) of respondents stated no demand for mental healthcare services. CONCLUSIONS: Health workers who gained less financial rewards are reported to have higher levels of mental distress than others, implying the need for a raise in basic salary as well as compensation and encouragement schemes. To tackle hesitancy in seeking mental help, integrating online mental health therapy with e-health consultations via social media can be strategically implemented to augment service delivery, and simultaneously enhance the standard of mental health services.


Asunto(s)
COVID-19 , Humanos , COVID-19/epidemiología , Estudios Transversales , Pueblos del Sudeste Asiático , Vietnam/epidemiología , Depresión/epidemiología , Depresión/psicología , Personal de Salud/psicología , Ansiedad/epidemiología , Ansiedad/psicología
7.
Curr Opin Chem Biol ; 76: 102338, 2023 10.
Artículo en Inglés | MEDLINE | ID: mdl-37295349

RESUMEN

Inorganic complexes of iron and sulfur, that is, iron-sulfur [FeS] clusters, have played a fundamental role in life on Earth since the prebiotic period. These clusters were involved in elementary reactions leading to the emergence of life and, since then, gained function in processes, such as respiration, replication, transcription, and the immune response. We discuss how three [FeS] proteins involved in the innate immune response play a role in oncogene expression/function and oncometabolism. Our analysis highlights the importance of future research into understanding the [FeS] clusters' roles in cancer progression and proliferation. The outcomes of these studies will help identify new targets and develop new anticancer therapeutics.


Asunto(s)
Proteínas Hierro-Azufre , Hierro , Hierro/metabolismo , Oncogenes , Azufre/metabolismo , Proteínas Hierro-Azufre/genética , Proteínas Hierro-Azufre/metabolismo
8.
J Glob Health ; 13: 06022, 2023 May 26.
Artículo en Inglés | MEDLINE | ID: mdl-37232446

RESUMEN

Background: The workload burden of the COVID-19 pandemic on health systems requires not only financial support but also long-term and contextualized policies. We assessed the work motivation and its determinants among health workers at Vietnamese hospitals and facilities during the prolonged COVID-19 outbreaks in 2021. Methods: A cross-sectional study was conducted among 2814 health care professionals across all three regions of Vietnam from October to November 2021. An online questionnaire, including the Work Motivation Scale, distributed by the snowball method to a subgroup of 939 respondents, investigated changes in working characteristics due to COVID-19, work motivation, and occupational intention. Results: Only 37.2% of respondents committed to their current job and about 40% reported a decrease in their job satisfaction. The Work Motivation Scale scored the lowest in "financial motivation" and the highest in "perception of work value". Participants who were in the north region, of younger age, unmarried, and who had a low level of adaptability to external work pressure, shorter experience, and less job satisfaction tended to be less motivated and committed to their current job. Conclusions: Intrinsic motivation has increased in importance during the pandemic. Therefore, policymakers should develop interventions that raise intrinsic, psychological motivation instead of only focusing on salary raises. Issues about intrinsic motivations of health care workers such as low adaptability to stress and professionalism in routine work should be prioritized during the pandemic preparedness and control.


Asunto(s)
COVID-19 , Motivación , Humanos , Estudios Transversales , Vietnam/epidemiología , Pandemias , Pueblos del Sudeste Asiático , Personal de Salud/psicología , Encuestas y Cuestionarios
9.
J Glob Health ; 13: 04033, 2023 May 05.
Artículo en Inglés | MEDLINE | ID: mdl-37144922

RESUMEN

Background: The latent monkeypox outbreak has become the most emergent public health challenge globally. This study was conducted to assess the acceptability, and willingness to take and pay for a hypothetical Monkeypox vaccine among the Vietnamese general public as well as investigate preference for individual vaccine attributes. Methods: An online cross-sectional study was conducted using snowball sampling among 842 respondents in Vietnam in 2022. A Discrete choice experiment (DCE) on preference for six major attributes of vaccine: effectiveness, immunity duration, side effects, mortality rate, restriction, and the cost was applied. Results: Fear of the impact of monkeypox on public health and the economy, vaccine service satisfaction and responsibility to the community were the most weighted factors in the decision to take a hypothetical monkeypox vaccine. Two-thirds of participants were willing to take the vaccine, while insufficient information on monkeypox and the vaccine were the main reasons for vaccine hesitancy. For vaccine attributes, the mortality rate after seven days of vaccination was the most weighted while cost was the least influential attribute. Factors associated with willingness to take and to pay for the monkeypox vaccine included knowledge of transmission, geographical location, service satisfaction, and risk of infection, while financial burden and fear of vaccine were major drivers of hesitancy. Conclusion: Our findings underline an urgent need for effective information dissemination through social media and counseling. The implementation of nationwide monkeypox vaccination requires prioritization and support for high-risk groups as well as consideration for the country's financial resources.


Asunto(s)
Mpox , Vacuna contra Viruela , Vacunas , Humanos , Estudios Transversales , Salud Global
10.
iScience ; 26(2): 105956, 2023 Feb 17.
Artículo en Inglés | MEDLINE | ID: mdl-36711242

RESUMEN

Introducing extra mitochondrial DNA (mtDNA) into oocytes at fertilization can rescue poor quality oocytes. However, supplementation alters DNA methylation and gene expression profiles of preimplantation embryos. To determine if these alterations impacted offspring, we introduced mtDNA from failed-to-mature sister (autologous) or third party (heterologous) oocytes into mature oocytes and transferred zygotes into surrogates. Founders exhibited significantly greater daily weight gain (heterologous) and growth rates (heterologous and autologous) to controls. In weaners, cholesterol, bilirubin (heterologous and autologous), anion gap, and lymphocyte count (autologous) were elevated. In mature pigs, potassium (heterologous) and bicarbonate (autologous) were altered. mtDNA and imprinted gene analyses did not reveal aberrant profiles. Neither group exhibited gross anatomical, morphological, or histopathological differences that would lead to clinically significant lesions. Female founders were fertile and their offspring exhibited modified weight and height gain, biochemical, and hematological profiles. mtDNA supplementation induced minor differences that did not affect health and well-being.

11.
Cancer Prev Res (Phila) ; 15(11): 777-784, 2022 11 01.
Artículo en Inglés | MEDLINE | ID: mdl-35969832

RESUMEN

The human papillomavirus (HPV) vaccine was indicated for the prevention of vulvovaginal cancers in 2008, but its impact on the incidence of vulvar cancers within the US is unknown. To determine this, we conducted a secondary analysis of 88,942 vulvar cancer cases among women 20+ years old using the US Cancer Statistics 2001-2018 databases. Data were stratified by tumor behavior (in situ or invasive), age (20-44, 45-64, 65+ years old), race/ethnicity (non-Hispanic White, non-Hispanic Black, Hispanic), and US census region (Northeast, South, Midwest, West), and incidence rates and average annual percentage changes (AAPC) were calculated by group. Reversing previous trends, the incidence of vulvar carcinoma in situ significantly decreased between 2001 and 2018 among women from all age groups, races/ethnicities, and regions (combined AAPC,  -4.3; 95% confidence interval (CI), -4.7 to -3.8). The incidence of invasive vulvar squamous cell carcinoma decreased significantly among 20- to 44-year-old women (AAPC, -0.8; 95% CI, -1.3 to -0.3), but significantly increased among those 45 to 64 (AAPC, 2.3; 95% CI, 1.8-2.8) and 65+ years old (AAPC, 1.2; 95% CI, 1.1-1.4). Regardless of tumor behavior, incidence was highest among non-Hispanic Whites and the Midwest region. Overall, the significant declines in vulvar carcinoma in situ among all ages, as well as invasive vulvar cancer among younger women, are encouraging and complement other recent data suggesting HPV vaccinations are already reducing anal and cervical cancer incidence. Over time, further declines in vulvar carcinoma incidence are likely as uptake and completion rates of the HPV vaccine increase in the US. PREVENTION RELEVANCE: We found evidence that HPV vaccinations likely contributed to a decrease in the incidences of vulvar carcinoma in situ and invasive vulvar carcinoma among 20- to 44-year-old women between 2001 and 2018. Our data add to the growing evidence that HPV vaccinations are reducing the incidence of HPV-related anogenital cancers.


Asunto(s)
Alphapapillomavirus , Carcinoma in Situ , Infecciones por Papillomavirus , Vacunas contra Papillomavirus , Neoplasias del Cuello Uterino , Neoplasias de la Vulva , Estados Unidos/epidemiología , Femenino , Humanos , Adulto Joven , Adulto , Neoplasias de la Vulva/epidemiología , Neoplasias de la Vulva/prevención & control , Neoplasias de la Vulva/complicaciones , Vacunas contra Papillomavirus/uso terapéutico , Incidencia , Infecciones por Papillomavirus/complicaciones , Infecciones por Papillomavirus/epidemiología , Infecciones por Papillomavirus/prevención & control , Neoplasias del Cuello Uterino/epidemiología , Neoplasias del Cuello Uterino/prevención & control , Neoplasias del Cuello Uterino/patología , Carcinoma in Situ/epidemiología , Carcinoma in Situ/prevención & control , Vacunación
12.
PhytoKeys ; 193: 43-53, 2022.
Artículo en Inglés | MEDLINE | ID: mdl-35586123

RESUMEN

Oreocharisphuongii, a new species of Gesneriaceae from central Vietnam, is described and illustrated here. The new species is most similar to O.longifolia by sharing peduncles up to 22 cm long, bracts 2, zygomorphic, yellow flowers with tubular corolla, stamens 4 with two pairs of coherent anthers and capsules up to 6 cm long. It mainly differs from the latter by the combination of some morphological characters of leaves (shape, base, apex and margin), size of calyx lobes, indumentum of corolla tube and inner surface of three lower corolla lobes. Detailed morphological description together with colour illustration, information on phenology, distribution, ecology, preliminarily conservation status of the new species and comparison with its similar species are also presented.

14.
Int J Surg Case Rep ; 79: 299-301, 2021 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-33508612

RESUMEN

INTRODUCTION AND IMPORTANCE: Pneumopericardium is collection of gas in pericardial space. Retrospective reviews have described pneumopericardium as a complication of laparoscopic surgery, however, without any symptoms. By this report, we present a case who developed acute cardiopulmonary symptoms after retroperitoneal laparoscopic radical nephrectomy because of pneumopericardium. CASE PRESENTATION: A 40-year-old Vietnamese woman was admitted due to left flank pain. She was diagnosed with left dysfunctional hydronephrosis and right urolithiasis. Six hours post-operation of an elective retroperitoneal laparoscopic radical nephrectomy, she suddenly developed severe substernal chest pain and dyspnea. Evaluations for acute myocardial infarction and pulmonary embolism were immediately ordered with no abnormality. However, computed tomography scan of the chest showed pneumopericardium, pneumomediastinum, subcutaneous emphysema, gas collection in sub-peritoneal space and next to the aortic arch. She was then closely monitored and effectively managed by conservative treatments. CLINICAL DISCUSSION: Pneumopericardium is a rare complication of laparoscopy and mainly detected by radiographical measures incidentally. Several case studies reported symptomatic pneumopericardium, as in our presenting case. Some factors might contribute to the mechanism of our case that include retroperitoneal approach, thoroughly dissection the renal helium area and long-lasting operation. Post-operative collection of carbon dioxide is well self-limited; therefore, conservative treatments are efficient for stable cases. CONCLUSION: Pneumopericardium following laparoscopy is uncommon, and mostly subclinical. However, it can manifest as acute cardiopulmonary symptoms and signs that require carefully evaluation. The presence of gas in pericardial space is a negative prognosis factor itself; consequently, clinicians should be aware of when managing pneumopericardium subsequent to laparoscopic procedures.

15.
PLoS One ; 15(12): e0244170, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-33338067

RESUMEN

BACKGROUND: Vietnam applied strict quarantine measures to mitigate the rapid transmission of the SARS-COV-2 virus. Central questions were how the COVID-19 pandemic affected health-related quality of life (HRQOL) of the Vietnamese general population, and whether there is any difference in HRQOL among people under different quarantine conditions. METHODS: This cross-sectional study was conducted during 1 April- 30 May 2020 when the COVID-19 pandemic was at its peak in Vietnam. Data was collected via an online survey using Google survey tool. A convenient sampling approach was employed, with participants being sorted into three groups: people who were in government quarantine facilities; people who were under self-isolation at their own place; and the general population who did not need enforced quarantine. The Vietnamese EQ-5D-5L instrument was used to measure HRQOL. Differences in HRQOL among people of isolation groups and their socio-demographic characteristics were statistically tested. RESULTS: A final sample was made of 406 people, including 10 persons from government quarantine facilities, 57 persons under self-isolation at private places, and the rest were the general population. The mean EQ-VAS was reported the highest at 90.5 (SD: 7.98) among people in government quarantine facilities, followed by 88.54 (SD: 12.24) among general population and 86.54 (SD 13.69) among people in self-isolation group. The EQ-5D-5L value was reported the highest among general population at 0.95 (SD: 0.07), followed by 0.94 (SD: 0.12) among people in government quarantine facilities, and 0.93 (SD: 0.13) among people who did self-isolation. Overall, most people, at any level, reported having problems with anxiety and/or depression in all groups. CONCLUSION: While there have been some worries and debates on implementing strict quarantine measures can hinder people's quality of life, Vietnam showed an opposite tendency in people's HRQOL even under the highest level of enforcement in the prevention and control of COVID-19.


Asunto(s)
COVID-19/epidemiología , COVID-19/psicología , Calidad de Vida , Adulto , Anciano , Ansiedad/complicaciones , Control de Enfermedades Transmisibles , Estudios Transversales , Depresión/complicaciones , Femenino , Estado de Salud , Humanos , Masculino , Persona de Mediana Edad , Pandemias , Distanciamiento Físico , Salud Pública , Cuarentena , Motor de Búsqueda , Clase Social , Aislamiento Social , Encuestas y Cuestionarios , Vietnam/epidemiología , Adulto Joven
16.
J Am Chem Soc ; 140(17): 5791-5797, 2018 05 02.
Artículo en Inglés | MEDLINE | ID: mdl-29620896

RESUMEN

Electrodeposition of CuAg alloy films from plating baths containing 3,5-diamino-1,2,4-triazole (DAT) as an inhibitor yields high surface area catalysts for the active and selective electroreduction of CO2 to multicarbon hydrocarbons and oxygenates. EXAFS shows the co-deposited alloy film to be homogeneously mixed. The alloy film containing 6% Ag exhibits the best CO2 electroreduction performance, with the Faradaic efficiency for C2H4 and C2H5OH production reaching nearly 60 and 25%, respectively, at a cathode potential of just -0.7 V vs RHE and a total current density of ∼ - 300 mA/cm2. Such high levels of selectivity at high activity and low applied potential are the highest reported to date. In situ Raman and electroanalysis studies suggest the origin of the high selectivity toward C2 products to be a combined effect of the enhanced stabilization of the Cu2O overlayer and the optimal availability of the CO intermediate due to the Ag incorporated in the alloy.

17.
ACS Biomater Sci Eng ; 3(10): 2267-2277, 2017 Oct 09.
Artículo en Inglés | MEDLINE | ID: mdl-33445286

RESUMEN

Acrylic bone cements, although successful in the field of orthopedics, suffer from a lack of bioactivity, not truly integrating with surrounding bone. Bioactive fixation is expected to enhance cement performance because of the natural interlocking and bonding with bone, which can improve the augmentative potential of the material in applications such as vertebroplasty (VP). In a recent study, two composite cements (PMMA-hydroxyapatite and PMMA-brushite) showed promising results demonstrating no deterioration in rheological and mechanical properties after CaP filler addition. In this study, the dynamic properties of the cements were investigated in vitro and in vivo. The hypothesis was that these composite cements will provide osseointegration around the implanted cement and increase new bone formation, thus decreasing the risk of bone structural failure. The effects of CaP elution were thus analyzed in vitro using these cements. Mass-loss, pore formation, and mechanical changes were tracked after cement immersion in Hank's salt solution. PMMA-brushite was the only cement with a significant mass loss; however it showed low bulk porosity. Surface porosity increases were observed in both composite cements. Mechanical properties were maintained after cement immersion. In vitro culture studies tested preosteoblast cell viability and differentiation on the cement surface. Cell viability was demonstrated with MTT assay and confirmed on the cement surface. ALP assays showed no inhibition of osteoblast differentiation on the cement surface. In vivo experiments were performed using a rat tibiae model to demonstrate bone ingrowth around the implanted cements. Critical size defects were created and then filled with the cements. The animal studies showed no loss in mechanical strength after implantation and increased bone ingrowth around the composite cements. In summary, the composite cements provided bioactivity without sacrificing mechanical strength.

18.
J Phys Chem Lett ; 7(18): 3542-7, 2016 Sep 15.
Artículo en Inglés | MEDLINE | ID: mdl-27550191

RESUMEN

The development of non-precious-metal (NPM) catalysts to replace the Pt alloys currently used in fuel cells to facilitate the oxygen reduction reaction (ORR) is a vital step in the widespread utilization of fuel cells. Currently, the ORR mechanism for NPM catalysts is not well understood, prohibiting the design and preparation of improved NPM catalysts. We conducted a kinetic isotope effect (KIE) study to identify the rate-determining step (RDS) of this intricate electrocatalytic reaction involving multiple proton-coupled electron transfer (PCET) processes. We observed a KIE of about 2 for the ORR catalyzed by a NPM catalyst, which demonstrates that for these electrocatalysts protons are involved in the RDS during ORR. These results contribute to a more complete understanding of the ORR mechanism and suggest that the design of future NPM catalysts must include careful consideration of the role of protons during ORR.

19.
Anal Chem ; 86(22): 11290-7, 2014 Nov 18.
Artículo en Inglés | MEDLINE | ID: mdl-25343569

RESUMEN

In situ electrochemical stress measurements are used to interrogate changes in oxide structure before and during the oxygen evolution reaction (OER) from Ir, Ni, Co, Au, and Pt electrodes in alkaline electrolyte. Stress evolution during potential cycling reports on changes in oxidation state and oxide forms. Hysteresis observed in the potential-dependent stress from Ir, Au, and Pt electrodes is associated with chemical irreversibility in electrode composition and roughness. Alternatively, Ni and Co exhibit reversible conversion between hydroxide and oxyhydroxide forms during cycling. From the experimentally determined stress, charge passed during electrode oxidation, and Young's modulus, the change in strain exhibited by Ni and Co electrodes during hydroxide-oxyhydroxide conversion is calculated to be 7.0% and 8.4%, respectively. We also show that the magnitude of change in stress is proportional to the amount of material that is further oxidized.

20.
Anal Chem ; 86(16): 8368-75, 2014 Aug 19.
Artículo en Inglés | MEDLINE | ID: mdl-25066179

RESUMEN

Microcantilever stress measurements are examined to contrast and compare their attributes with those from in situ X-ray absorption spectroscopy to elucidate bonding dynamics during the oxygen reduction reaction (ORR) on a Pt catalyst. The present work explores multiple atomistic catalyst properties that notably include features of the Pt-Pt bonding and changes in bond strains that occur upon exposure to O2 in the electrochemical environment. The alteration of the Pt electronic and physical structures due to O2 exposure occurs over a wide potential range (1.2 to 0.4 V vs normal hydrogen electrode), a range spanning potentials where Pt catalyzes the ORR to those where Pt-oxide forms and all ORR activity ceases. We show that Pt-Pt surface bond strains due to oxygen interactions with Pt-Pt bonds are discernible at macroscopic scales in cantilever-based bending measurements of Pt thin films under O2 and Ar. Complementary extended X-ray absorption fine structure (EXAFS) measurements of nanoscale Pt clusters supported on carbon provide an estimate of the magnitude and direction of the in-operando bond strains. The data show that under O2 the M-M bonds elongate as compared to an N2 atmosphere across a broad range of potentials and ORR rates, an interfacial bond expansion that falls within a range of 0.23 (±0.15)% to 0.40 (±0.20)%. The EXAFS-measured Pt-Pt bond strains correspond to a stress thickness and magnitude that is well matched to the predictions of a mechanics mode applied to experimentally determined data obtained via the cantilever bending method. The data provide new quantitative understandings of bonding dynamics that will need to be considered in theoretical treatments of ORR catalysis and substantiate the subpicometer resolution of electrochemically mediated bond strains detected on the macroscale.

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