Exact Mode Shapes of T-shaped and Overhang-shaped Microcantilevers

Resonance frequencies and mode shapes of microcantilevers are of important interest in micro-mechanical systems for enhancing the functionality and applicable range of the cantilevers in vibration transducing, energy harvesting, and highly sensitive measurement. In this study, using the Euler-Bernoulli theory for beam, we figured out the exact mode shapes of cantilevers of varying widths such as the overhang- or T-shaped cantilevers. The obtained mode shapes have been shown to significantly deviate from the approximate forms of a rectangular cantilever that are commonly used in mechanics and physics. They were then used to figure out the resonance frequencies of the cantilever. The analytical solutions have been confirmed by using the finite element method simulations with very low deviation. This study suggested a method for correctly obtaining the resonance frequency of microcantilevers with complicated dimensions, such as the doubly clamped cantilever with the undercut, with the overhangs at the clamped positions, or with an attached mass in the middle

A Theoretical Study of Deflection of AFM Bimaterial Cantilevers Versus Irradiated Position

The bimaterial cantilevers of atomic force microscopes have been widely used in chemical and bio-sensing. Due to the difference in the thermal expansion coefficients of the two layers, the cantilever is deflected and its deflections is dependent on the heat absorption from the ambient environment or the objects adsorbed on the cantilever surface. In this study, we theoretically examine the deflection of this cantilever considering different irradiated configurations of a laser beam and thicknesses of the coating layer. We show that the temperature difference between the end and the clamped position is maximized for an irradiation at the cantilever end and this difference reduces with increasing coating thickness. Especially, the maximal deflection is seen for an irradiation in the middle of the cantilever, around 0.6 of the cantilever length from the clamped position. The obtained results could help determining an irradiated configuration of laser and the coating thickness to optimize the sensitivity of the cantilevers in thermally sensing devices

Triterpene saponins with <i>α</i>-glucosidase inhibition and cytotoxic activity from the leaves of <i>Schefflera sessiliflora</i>

<p>From the leaves of <i>Schefflera sessiliflora</i> De P. V., two new triterpene saponins including one oleanane-type saponin, named scheffleraside C (<b>1</b>) and one lupane-type saponin scheffleraside D (<b>2</b>), together with six known triterpene saponins (<b>3–8</b>), were isolated by various chromatography methods. Among them, <b>3</b> was found for the first time from natural sources, while <b>6–8</b> were isolated for the first time from the genus <i>Schefflera</i>. Their structures were elucidated by IR, UV, HR-ESI-MS, NMR 1D and 2D experiments, and comparison of their NMR data with previously reported data. Their <i>α</i>-glucosidase inhibition and cytotoxic activity against MCF-7 human breast cancer cell lines were evaluated. The isolates (<b>1</b>, <b>3–5, 8</b>) showed stronger <i>α</i>-glucosidase inhibitory activity (IC₅₀ = 5.99–76.58 μM) than the standard drug acarbose (IC₅₀ = 214.50 μM). At the concentration of 100 μg/ml, the isolates (<b>1</b>, <b>2</b>) showed appreciable cytotoxic activity (67.92, 63.83%, respectively).</p

Pattern and perceived changes in quality of life of Vietnamese medical and nursing students during the COVID-19 pandemic.

BackgroundThe COVID-19 pandemic and governments' response lead to dramatical change in quality of life worldwide. However, the extent of this change in Vietnamese medical and nursing students has not been documented.ObjectivesThe study aims to describe the quality of life and changes in quality of life of medical and nursing students during the COVID-19 pandemic and examine the association of quality of life and changes in quality of life with fear of COVID-19 and other socio-economic and demographic factors.MethodsThe study was a cross-sectional study on all students of Hanoi Medical University from 3 majors: General Medicine, Preventive Medicine, Nursing (3672 invited students); from 7th to 29th of April 2020; using an online questionnaire that included demographic and academic information, the Vietnamese version of the SF-36 Quality of Life questionnaire and the Fear of COVID-19 Scale (FCV-19S). Linear and modified Poisson regression was used to examine the association between quality of life, changes in quality of life and other factors.ResultsThe number of participants was 1583 (response rate 43%). Among 8 dimensions of the SF-36 (ranged 0-100), Vitality had the lowest score with a median score of 46. The median physical composite score (PCS) of the sample was 40.6 (IQR:20.8-53.2), 33.5% of the sample had an above-population average PCS score. The median mental composite score (MCS) of the sample was 20.3 (IQR:3.8-31.7), and 98.2% had an MCS score below average. 9.9% (95%CI:8.5%-11.4%) of the population reported a significant negative change in the quality of life. Fear of COVID-19 was not associated with significant changes in quality of life, nor MCS while having some association with PCS (Coef:-5.39;95%CI:-3to-7.8). Perceived reduction in quality of life was also associated with: being on clinical rotation COVID-19 (PR:1.5;95%CI:1.05-2.2), difficulties affording health services (PR:1.4;95%CI:1.02-1.95), obesity (PR:2.38;95%CI:1.08-5.25) and chronic disease (PR:1.92;95%CI:1.23-3), typical symptoms (PR:1.85; 95%CI:1.23-2.78) and atypical symptoms of COVID-19 (PR:2.32;95%CI:1.41-3.81).ConclusionThe majority of medical and nursing students had below average quality of life, with lower vitality and mental composite health score in the settings of COVID-19. Perceived decrease in quality of life was associated with clinical rotation, difficulties affording healthcare services and was not associated with Fear of COVID-19

Synthesis and Selective Cytotoxic Activities on Rhabdomyosarcoma and Noncancerous Cells of Some Heterocyclic Chalcones

Chemically diverse heterocyclic chalcones were prepared and evaluated for cytotoxicity, aiming to push forward potency and selectivity. They were tested against rhabdomyosarcoma (RMS) and noncancerous cell line (LLC-PK1). The influence of heteroaryl patterns on rings A and B was studied. Heterocycle functionalities on both rings, such as phenothiazine, thiophene, furan and pyridine were evaluated. Notably, the introduction of three methoxy groups at positions 3, 4, 5 on ring B appears to be critical for cytotoxicity. The best compound, with potent and selective cytotoxicity (IC50 = 12.51 μM in comparison with the value 10.84 μM of paclitaxel), contains a phenothiazine moiety on ring A and a thiophene heterocycle on ring B. Most of the potential compounds only show weak cytoxicity on the noncancerous cell line LLC-PK1

New C₂₀-gibberellin diterpene from the leaves of <i>Schefflera sessiliflora</i> De P. V.

<div><p>From the leaves of <i>Schefflera sessiliflora</i> De P. V., one new C₂₀-gibberellin diterpene 2β,12β-dihydroxygibberellin (12β-hydroxy-GA₁₁₀ or 2β-hydroxy-GA₁₁₂) (<b>1</b>), together with three known compounds, <i>trans</i>-tiliroside (<b>2</b>), kaempferol 3-<i>O</i>-β-d-glucuronopyranoside (<b>3</b>), 5-<i>p</i>-<i>trans</i>-coumaroylquinic acid (<b>4</b>), was isolated for the first time from the genus <i>Schefflera</i> by various chromatography methods. Their structures were elucidated by IR, UV, HR-ESI-MS, NMR 1D and 2D experiments and comparison with previous reported data. The α-glucosidase inhibitory activity of all compounds was measured. The isolates (<b>2</b>, <b>3</b>) showed better α-glucosidase inhibitory activity (IC₅₀ = 134.60, 147.10 μM, respectively) than the standard drug acarbose (IC₅₀ = 214.50 μM).</p></div