COVAD survey 2 long-term outcomes: unmet need and protocol

Vaccine hesitancy is considered a major barrier to achieving herd immunity against COVID-19. While multiple alternative and synergistic approaches including heterologous vaccination, booster doses, and antiviral drugs have been developed, equitable vaccine uptake remains the foremost strategy to manage pandemic. Although none of the currently approved vaccines are live-attenuated, several reports of disease flares, waning protection, and acute-onset syndromes have emerged as short-term adverse events after vaccination. Hence, scientific literature falls short when discussing potential long-term effects in vulnerable cohorts. The COVAD-2 survey follows on from the baseline COVAD-1 survey with the aim to collect patient-reported data on the long-term safety and tolerability of COVID-19 vaccines in immune modulation. The e-survey has been extensively pilot-tested and validated with translations into multiple languages. Anticipated results will help improve vaccination efforts and reduce the imminent risks of COVID-19 infection, especially in understudied vulnerable groups

Electrochemical corrosion behaviour of Pb-free SAC 105 and SAC 305 solder alloys: a comparative study

Sn-Ag based solder alloy seems to be a promising lead-free solder for the application on electronic assembly. The corrosion behavior of different lead free solder alloys such as Sn-3.0Ag, Sn-1.0Ag-0.5Cu and Sn-3.0Ag-0.5Cu was investigated in 3.5% NaCl solution by potentiodynamic polarization and electrochemical impedance spectroscopy. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) were used to characterize the samples after the tests. The results showed that the addition of 0.5 wt. % copper with Sn-3.0 Ag solder alloy led to a better corrosion resistance while lowering of Ag content from 3.0 to 1.0 wt. % decreased the resistance. Sn-3.0Ag-0.5Cu exhibits a better corrosion resistance in terms of increased charge transfer resistance and impedance values as well as the lowest capacitance. These characteristics signify its suitability for the application in electronic packaging

MENINGKATKAN KEMAMPUAN BERPIKIR KREATIF DAN KEMAMPUAN PEMECAHAN MASALAH MATEMATIK PESERTA DIDIK MELALUI PENGGUNAAN MODEL PEMBELAJARAN PROBLEM BASED LEARNING (PBL)

Kemampuan berpikir kreatif dan kemampuan pemecahan masalah matematik merupakan hal yang penting bagi peserta didik dan perlu ditingkatkan melalui proses pembelajaran. Oleh karena itu diperlukan kompetensi guru dalam memilih model pembelajaran yang dapat mengantarkan peserta didik memahami konsep matematiknya. Salah satu model tersebut adalah model Problem Based Learning (PBL). Adapun tujuan dari penelitian adalah untuk mengetahui: Peningkatan kemampuan berpikir kreatif dan pemecahan masalah matematik peserta didik yang pembelajarannya dengan menggunakan model pembelajaran Problem Based Learning (PBL) lebih baik daripada peningkatan kemampuan berpikir kreatif matematik peserta didik yang menggunakan model pembelajaran konvensional berdasarkan Kemampuan Awal Matematik (KAM) (tinggi, sedang, rendah); korelasi antara kemampuan berpikir kreatif matematik dan pemecahan masalah matematik peserta didik; sikap peserta didik terhadap pembelajaran matematika dengan menggunakan model pembelajaran Problem Based Learning (PBL). Penelitian ini merupakan penelitian quasi eksperimen dengan pendekatan kuantitatif. Populasi dalam penelitian ini adalah seluruh peserta didik kelas VII SMP Negeri 4 Langkaplancar Tahun Pelajaran 2014/2015. Sampel yang digunakan adalah kelas VII A dengan menggunakan model pembelajaran Problem Based Learning (PBL) dan untuk kelas kontrol yaitu kelas VII D dengan menggunakan model pembelajaran konvensional. Instrumen yang digunakan dalam penelitian ini adalah soal tes kemampuan berpikir kreatif matematik, kemampuan pemecahan masalah matematik dan angket skala sikap peserta didik terhadap pembelajaran matematika dengan menggunakan model Problem Based Learning (PBL). Hasil penelitian menunjukan bahwa: 1) Peningkatan kemampuan berpikir kreatif dan pemecahan masalah matematik peserta didik yang pembelajarannya dengan menggunakan model pembelajaran Problem Based Learning (PBL) lebih baik daripada peningkatan kemampuan berpikir kreatif matematik peserta didik yang menggunakan model pembelajaran konvensional berdasarkan Kemampuan Awal Matematik (KAM) (tinggi, sedang, rendah); 2) Terdapat korelasi antara kemampuan berpikir kreatif matematik dan pemecahan masalah matematik peserta didik; 3) Sikap peserta didik positif terhadap pembelajaran matematika dengan menggunakan model pembelajaran Problem Based Learning (PBL). Kata kunci: Problem Based Learning, Kemampuan Berpikir Kreatif, Kemampuan Pemecahan Masalah, dan Sikap Peserta Didi

Corrosion of magnesium and aluminum in palm biodiesel: A comparative evaluation

10.1016/j.energy.2013.04.067Energy57478-483ENEY

Biodiesel feasibility study: An evaluation of material compatibility; performance; emission and engine durability

Biodiesel, derived from the transesterification of vegetable oils or animal fats, is composed of saturated and unsaturated long-chain fatty acid alkyl esters. In spite of having some application problems, recently it is being considered as one of the most promising alternative fuels in internal combustion engine. From scientific literatures, this paper has collected and analyzed the data on both advantages and disadvantages of biodiesel over conventional diesel. Since the aim of this study is to evaluate the biodiesel feasibility in automobiles, the first section is dedicated to materials compatibility in biodiesel as compared to that in diesel. The highest consensus is related to enhanced corrosion of automotive parts due to its compositional differences. In the subsequent sections, data on performance, emission and engine durability have been analyzed and compared. In this case, the highest consensus is found in reducing emissions as well as in increasing moving parts sticking, injector coking and filter plugging. This paper has also summarized the factors of biodiesel in contributing these technical performances.Biodiesel Material compatibility Performance Emission Engine durability

Effect of aluminum addition on the electrochemical corrosion behavior of Sn–3Ag–0.5Cu solder alloy in 3.5 wt% NaCl solution

The ternary eutectic Sn–Ag–Cu (SAC) solder alloys has become the most promising Pb-containing solders for the application in electronic packaging. The effect of Aluminum on the electrochemical corrosion behavior of Sn–3.0Ag–0.5Cu (SAC 305) solder alloy was investigated in 3.5 wt% NaCl solution in terms of potentiodynamic polarization and electrochemical impedance spectroscopy. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and atomic force microscopy (AFM) were used to characterize the samples after the electrochemical tests. Polarization studies indicated that an addition of 0.1 and 0.5 wt% Al in the Sn–3.0Ag–0.5Cu solder alloy shifted the corrosion potential (Ecorr) towards more negative values. The Impedance results revealed that the addition of Al with Sn–3.0Ag–0.5Cu solder alloy led to a lower corrosion resistance in terms of impedance values and the capacitance. The SEM images revealed existence of openings and pores in the corrosion product of solders containing Al. EDX and XRD analysis confirmed that the oxides and hydroxides of Sn and Al were the major corrosion products. AFM images exhibited that the surface becomes more rough and non-uniform with Al addition to SAC 305 solder alloy

Investigation of friction and wear characteristics of palm biodiesel

Use of biodiesel in automobile engine is creating tribology related new challenges. The present study aims to assess the friction and wear characteristics of palm biodiesel at different concentration level by using four-ball wear machine. The investigated fuels were biodiesel (B100), diesel (B0) and three different biodiesel blends such as B10 (10% biodiesel in diesel), B20, B50. Tests were conducted at 75 °C under a normal load of 40 kg for 1 h at four different speeds viz, 600, 900, 1200 and 1500 rpm. Worn surfaces of the balls were examined by SEM. Results showed that wear and friction decreased with the increase of biodiesel concentration. The wear of steel ball in B100 was appeared to be 20% lower than that in diesel (B0)

Effect of temperature on the corrosion behavior of mild steel upon exposure to palm biodiesel

Recently biodiesel, as an alternative fuel is getting more significance to replace diesel fuel completely or partially. However, corrosion of automotive materials in biodiesel is a major concern as this can reduce engine life. This study aims to investigate the corrosion behavior of mild steel at three different temperatures such as room temperature, 50 and 80 degrees C. Static immersion tests in B0 (diesel), B50 (50 biodiesel in diesel), B100 (biodiesel) were carried out for 1200 h. At the end of the tests, corrosion characteristic was investigated by weight loss measurements and changes of the exposed metal surface. Fuels were analyzed by using TAN analyzer and Fourier transform infrared spectroscopy (FTIR) in order to investigate the change in acidity and oxidation of fuel respectively upon exposure. Surface morphology was examined by optical microscope and scanning electron microscope equipped with energy dispersive spectroscopy. Corrosion products were detected by X-ray diffraction (XRD). Results showed that the corrosion of mild steel increases with increase of temperature. Upon exposure of biodiesel to mild steel at high temperature, the water content and oxidation products are increased. (C) 2011 Elsevier Ltd. All rights reserved