Deacetylation of Thioacetate using Acetyl Chloride in Methanol

A highly efficient method for the deacetylation of thioacetate is reported under mild acidic conditions employing acetyl chloride in methanol. Some of the major advantages are mild conditions, high efficiency, high yields, and easy operations.     

A highly sensitive sensor of paracetamol based on zinc-layered hydroxide-<Emphasis Type="Italic">L</Emphasis>-phenylalanate-modified multiwalled carbon nanotube paste electrode

A new zinc-layered hydroxide-L-phenylalanate (ZLH-LP)-modified multiwalled carbon nanotube (MWCNT) was prepared as a new material of paste electrode for the detection of paracetamol (PCM) in 1.0?×?10^?1 M phosphate buffer solution and at pH 7.5. The electrochemical characterization of the MWCNTs/ZLH-LP paste electrode was characterized by square wave voltammetry, electrochemical impedance spectroscopy, and cyclic voltammetry while the morphology properties of the MWCNTs, ZLH-LP, and MWCNTs/ZLH-LP were investigated using transmission electron microscopy and scanning electron microscopy. Under optimized conditions, the MWCNTs/ZLH-LP paste electrode demonstrated an excellent electrocatalytic activity towards oxidation of PCM in the linear responses’ ranges from 7.0?×?10^?7 M to 1.0?×?10^?4 M (correlation coefficient, 0.996) with the limit of detection obtained at 8.3?×?10^?8 M. As a conclusion, the MWCNTs/ZLH-LP paste electrode revealed good repeatability, reproducibility, and stability, and was found to be applicable for use in pharmaceutical tablet samples.

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Graphical abstract ?

     

The Effect of TiO2 and MgO on the Thermoluminescence Properties of a Lithium Potassium Borate Glass System

The influence of dopant TiO₂ and co-dopant MgO on the thermoluminescence (TL) properties of lithium potassium borate glass (LKB) is reported in this paper. The glow curve exhibits a prominent peak (T_m) at 230 °C. The TL intensity was enhanced by a factor of ~3 due to the incorporation of MgO, and this was attributed to the creation of extra electron traps mediated by radiative recombination energy transfer. We achieved good linearity of the TL yield with dose, low fading, excellent reproducibility and a promising effective atomic number (Z_eff=8.89), all of which are highly suitable for dosimetry. The effect of heating rate, sunlight and dose rate on the TL are also examined. These attractive features demonstrate that our dosimeter is useful in medical radiation therapy.     

Thermodynamic analysis of lithium ion cells

The thermodynamics of ideal and non-ideal solutions has been applied to the electrochemically active lithium-based positive electrode to provide insight into the electrostatic potential as a function of the state-of-discharge. The Nernst and the Margules expressions are incorporated in the derivation for the electrostatic potential expression using the total Gibbs free energy equation. The resulting expression is applied to a lithium cell in order to study its discharge profile. These predicted results are compared with established results from the literature and a comparison is performed to validate the agreement between the predicted and the published results. Paper presented at the International Conference on Functional Materials and Devices 2005, Kuala Lumpur, Malaysia, June 6 – 8, 2005.     

Accelerated life ac conductivity measurements of CRT oxide cathodes

The ac conductivity measurements have been carried out for the activated Ba/SrO cathode with additional 5% Ni powder for every 100 h acceleration life time at the temperature around 1125 K. The ac conductivity was studied as a function of temperature in the range 300-1200 K after conversion and activation of the cathode at 1200 K for 1 h in two cathodes face to face closed configuration. The experimental results prove that the hopping conductivity dominate in the temperature range 625-770 K through the traps of the WO₃ associate with activation energy E_a = 0.87 eV, whereas from 500-625 K it is most likely to be through the traps of the Al₂O₃ with activation energy of E_a = 1.05 eV. The hopping conductivity at the low temperature range 300-500 K is based on Ni powder link with some Ba contaminants in the oxide layer stricture which indicates very low activation energy E_a = 0.06 eV.     

Plasma wave interactions in the microwave to THz range between carriers in a semiconductor 2DEG and interdigital slow waves

Traveling wave interactions between the plasma wave in a two-dimensional electron gas (2DEG) in the AlGaAs/GaAs high electron mobility transistor (HEMT) structure and the electromagnetic space harmonic slow waves produced by interdigital metal electrodes were investigated both theoretically and experimentally. By means of a TM mode analysis, a general expression for the ω- and k-dependent effective permittivity of the 2DEG plasma was derived. The two-terminal admittance was calculated by a Green’s function method from the microwave to the THz wave region. Occurrences of negative admittance were predicted, and its peak values increased with frequency to a very large value in the THz region due to the reduction in the number of collisions per cycle. Preliminary admittance measurements at microwave frequencies showed good agreement with calculations, confirming the existence of plasma wave interactions.     

Nanogapped impedimetric immunosensor for the detection of 16 kDa heat shock protein against <Emphasis Type="Italic">Mycobacterium tuberculosis</Emphasis>

The 16 kDa heat shock protein (16 kDa HSP) against Mycobacterium tuberculosis (MT), expressed during the growth phase of MT, is a potential target in diagnostic tests for tuberculosis (TB). We describe here a method for impedimetric determination of the antigen by using a nanogapped dielectric surface consisting of a silver support coated with a thin finger-shaped coating made from zinc oxide and gold and patterned through a lift-off process. The electrode was characterized by scanning electron microscopy, field emission scanning electron microscopy, atomic force microscopy, and energy-dispersive X-ray spectroscopy. Surface chemical functionalization and immobilization of antibody against the 16 kDa HSP was evidenced by FTIR. In order to improve the detection limit, the antigen was conjugated to 10 nm gold nanoparticles. The resulting biosensor is capable of detecting the 16 kDa HSP in concentrations as low as 100 fM. The method covers a wide analytical range that extends from 100 fM to 1 nM.

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Graphical abstract Schematic presentation of the nanogapped impedimetric immunosensor for the diagnosis of tuberculosis

     

Radioprotective Effects of Kelulut Honey in Zebrafish Model

Large doses of ionizing radiation can damage human tissues. Therefore, there is a need to investigate the radiation effects as well as identify effective and non-toxic radioprotectors. This study evaluated the radioprotective effects of Kelulut honey (KH) from stingless bee (Trigona sp.) on zebrafish (Danio rerio) embryos. Viable zebrafish embryos at 24 hpf were dechorionated and divided into four groups, namely untreated and non-irradiated, untreated and irradiated, KH pre-treatment and amifostine pre-treatment. The embryos were first treated with KH (8 mg/mL) or amifostine (4 mM) before irradiation at doses of 11 Gy to 20 Gy using gamma ray source, caesium-137 (¹³⁷Cs). Lethality and abnormality analysis were performed on all of the embryos in the study. Immunohistochemistry assay was also performed using selected proteins, namely γ-H2AX and caspase-3, to investigate DNA damages and incidences of apoptosis. KH was found to reduce coagulation effects at up to 20 Gy in the lethality analysis. The embryos developed combinations of abnormality, namely microphthalmia (M), body curvature and microphthalmia (BM), body curvature with microphthalmia and microcephaly (BMC), microphthalmia and pericardial oedema (MO), pericardial oedema (O), microphthalmia with microcephaly and pericardial oedema (MCO) and all of the abnormalities (AA). There were more abnormalities developed from 24 to 72 h (h) post-irradiation in all groups. At 96 h post-irradiation, KH was identified to reduce body curvature effect in the irradiated embryos (up to 16 Gy). γ-H2AX and caspase-3 intensities in the embryos pre-treated with KH were also found to be lower than the untreated group at gamma irradiation doses of 11 Gy to 20 Gy and 11 Gy to 19 Gy, respectively. KH was proven to increase the survival rate of zebrafish embryos and exhibited protection against organ-specific abnormality. KH was also found to possess cellular protective mechanism by reducing DNA damage and apoptosis proteins expression.     

Assessment of Aqueous Extraction Methods on Extractable Organic Matter and Hydrophobic/Hydrophilic Fractions of Virgin Forest Soils

The assessment of water-extractable organic matter using an autoclave can provide useful information on physical, chemical, and biological changes within the soil. The present study used virgin forest soils from Chini Forest Reserve, Langkawi Island, and Kenyir Forest Reserve (Malaysia), extracted using different extraction methods. The dissolved organic carbon (DOC), total dissolved nitrogen (TDN), total dissolved phosphorus (TDP), and ammonium-nitrate content were higher in the autoclave treatments, up to 3.0, 1.3, 1.2, and 1.4 times more than by natural extraction (extracted for 24 h at room temperature). Overall, the highest extractable DOC, TDN, TDP, ammonium and nitrate could be seen under autoclaved conditions 121 °C 2×, up to 146.74 mg C/L, 8.97 mg N/L, 0.23 mg P/L, 5.43 mg N mg/L and 3.47 N mg/L, respectively. The soil extracts became slightly acidic with a higher temperature and longer duration. Similar trends were observed in the humic and nonhumic substances, where different types of soil extract treatments influenced the concentrations of the fractions. Different soil extraction methods can provide further details, thus widening the application of soil extracts, especially in microbes.     

Cyclic Voltammetry of Metallic Acetylacetonate Salts in Quaternary Ammonium and Phosphonium Based Deep Eutectic Solvents

Seven commercially sourced acetylacetonate salts were investigated in deep eutectic solvents (DESs that were prepared from ethylene glycol and trifluoroacetamide hydrogen bond donors) by cyclic voltammetry, to identify electrolytes suitable for future applications in electrochemical energy storage devices. Although the solubilities are low and on the order of 0.02 mol·L^?1 for the most soluble salts, some were found to display encouraging quasi-reversible electrochemical kinetics. For instance, the diffusion coefficients of copper(II) acetylacetonate and iron(III) acetylacetonate in the trifluoroacetamide based DES are 1.14 × 10^?8 and 5.12 × 10^?9 cm²·s^?1, which yields rate constants of 3.16 × 10^?3 and 8.43 × 10^?6 cm·s^?1, respectively. These results are better than those obtained with the DESs prepared from ethylene glycol. The poor kinetics of the iron(III) acetylacetonate system was possibly due to the hygroscopic nature of the DESs that resulted in a continuous build-up of moisture in the system in spite of the maintenance of an inert atmosphere by means of a plastic glove bag. Further work is thus envisaged in an inert dry box that could lead to H-type glass cell charge/discharge experiments in the future.