Transfer of radioactivity from soil to vegetation in Rechna Doab,Pakistan

In Rechna Doab, samples of the most common vegetation, perennial grass Desmostachya bipinnata (dab), were collected along with soil samples from 29 sites. Natural radioactivity of ²²⁶Ra, ²³²Th/²²⁸Ac and ⁴⁰K was measured by using high purity germanium-based gamma ray spectrometer. Activity concentration levels of ²²⁶Ra, ²³²Th/²²⁸Ac and ⁴⁰K in soil were found to be 46.8±6.2 (36.0–57.6), 61.4±5.9 (48.2–73.2) and 644.8±73.9 (537.7–868.4) Bq kg^?1 (dry mass), respectively, and those in vegetation were 2.74±1.70 (1.00–6.39), 2.24±0.59 (1.56–2.61) and 172.72±113.37 (53.14–469.24) Bq kg^?1 (dry mass), respectively. The measured values of the activity concentration in vegetation are comparable with some other international data. Calculated soil to vegetation transfer factors of ²²⁶Ra, ²²⁸Ac and ⁴⁰K were 0.06±0.03 (0.02–0.14), 0.04±0.01 (0.03–0.04) and 0.26±0.16 (0.09–0.69). The mean outdoor absorbed dose rate in air for the area under study was determined as 8.22 nGy h^?1 and the mean indoor absorbed dose rate in air was 11.52 nGy h^?1. The total annual effective dose to the general public from the vegetation was found to be (0.02–0.16) mSv, which is below the recommended limit value of 1 mSv y^?1 for the general public. The dab vegetation under study was found to be radiologically safe for the population and environment.     

Synthesis and mechanical properties of Zr-based bulk amorphous alloys

Design and characterization of bulk amorphous alloys has been an active area of research due to their promising thermal and mechanical properties. An alloy composition Z₆₅Cu₁₇Ni₁₀Al₈ was designed and synthesized by Cu mold casting. In the base alloy 2 at.% Gd was added to study its effect on thermal and mechanical properties. Characterization of the alloys was done by techniques of X-ray diffraction (XRD), differential scanning calorimetry (DSC) and field emission scanning electron microscopy (FESEM). Many thermal parameters were evaluated to investigate the thermal stability and glass-forming ability of the alloys. In addition, the mechanical properties like nanohardness, elastic modulus and elastic recovery were measured. Thermal properties and activation energy reduced while mechanical properties like nanohardness, elastic modulus and percentage elastic recovery (% R) increased with Gd addition.     

Synthesis and characterization of a multicomponent Fe-based bulk amorphous alloy

A new bulk metallic glass (BMG) Fe₆₀B₁₅Zr₁₀Co₇Mo_5.5Y₂Si_0.5 was synthesized by Cu mold casting. The alloy was characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) techniques. The thermal stability and glass-forming ability (GFA) of the alloy have been discussed by evaluating a number of thermal parameters. The maximum values of the key thermal parameters like T_rg (T_g/T_m, T_g/T_l), γ, δ and β parameters were found to be ～(0.66, 0.64), 0.407, 1.84 and 3.83, respectively. The alloy showed double stage crystallization process. The activation energies for crystallization were found to be 606.6 and 623.1 kJ/mol by Kissinger and Ozawa equations, which indicate the high thermal stability. Crystallization behavior of the alloy was explored by XRD. Mechanical properties like Vicker’s hardness, nanohardness and elastic modulus are found to be very promising.     

Post modification of zinc based coordination polymer to prepare Zn‐Mo‐ICP nanoparticles as efficient self‐supported catalyst for olefin epoxidation

Preparation, characterization, and catalytic properties of bimetallic coordination polymer constructed from 2‐aminoterephthalic acid as linker, zinc cations as node, and cis‐dioxo molybdenum units as catalytic active sites are reported via two pathways. Molybdenum centers were placed in N,O positions created by condensation reaction of 2‐aminoterephthalic acid with salicylaldehyde while zinc cations coordinated via carboxylic acid groups of linker to achieve infinite chains of metalo‐ligand. The obtained coordination polymer was fully characterized and its catalytic properties in the epoxidation of olefins with tert‐butyl hydroperoxide (TBHP) described. In comparison with previously reported heterogenized molybdenum catalysts, this new coordination polymer exhibited good conversion as well as high selectivity in the epoxidation of olefins. The catalyst is stable under ambient conditions and could be reused as active catalyst for at least five times.     

Magnetic Field-Assisted Direct Immersion SPME of Endogenous Aldehydes in Human Urine

Direct immersion solid-phase microextraction (DI-SPME) is an effective microsampling strategy for polar and ionic species in aqueous media. Nevertheless, the fiber coating is in direct contact with sample solution and affected by its conditions. To compensate this limitation and to improve the extraction efficiency, a magnetic fiber coating was prepared and employed for DI-SPME sampling under the enhancing effect of a magnetic field. Magnetic iron oxide core–shell silica nanoparticles were synthesized and embedded in polypyrrole using an in situ electropolymerization method along with simultaneous coating on the surface of a platinized stainless-steel fiber. It was then applied for magnetic-assisted DI-SPME (MA-DI-SPME) sampling of endogenous aldehydes in human urine. Sample solution pH, the magnetic field intensity, ionic strength and extraction time were evaluated as the important affecting variables. Limits of detection were obtained 0.01–0.1 ng mL^?1; the calibration graphs were linear over the range of 0.1–10000 ng mL^?1. The inter-fiber (fiber-to-fiber) reproducibility was found to be 10.7–12.5%. Matrix effect from urine samples was not observed at concentration levels of 0.2, 2, and 8 µg mL^?1. The results showed that magnetic field increased the efficiency of DI-SPME method about two to four times. The developed strategy was successfully applied for the extraction and quantification of hexanal and heptanal (as the most important aldehyde biomarkers) in urine samples.

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Evaluation of polypyrrole/silver/polyethylene glycol nanocomposite sorbent for electroenhanced direct-immersion solid-phase microextraction of carvacrol and thymol from medicinal plants

The unique features of nanostructured polypyrrole, conductivity enhancement effect of silver nanoparticles and high polar adsorptivity of polyethylene glycol were merged into polypyrrole/silver/polyethylene glycol (PPy/Ag/PEG) nanocomposite. It was synthesized and simultaneously coated on the surface of a stainless-steel fiber using an amended electropolymerization procedure. Before coating, the fiber substrate was made porous and sticky by allocating platinum dots on the surface of the stainless-steel fiber using the electrophoretic method. The prepared fiber was applied for the extraction of carvacrol and thymol (the most important antioxidants in medicinal plants) through an electroenhanced direct-immersion solid-phase microextraction (EE-DI-SPME) sampling strategy, followed by GC-FID quantification. To achieve the best efficiency, the effectual experimental variables including pH of sample solution, applied voltage, extraction temperature and time, stirring rate, and ionic strength were investigated. Under the optimal experimental conditions, the calibration curves were linear over the range of 0.5–30 µg mL^?1 for thymol and 0.01–30 µg mL^?1 for carvacrol. The detection limits (3S_b) and relative standard deviation (RSD%, n?=?6) were obtained to be 0.15, 0.003 µg mL^?1 and 10.2, 8.7% for thymol and carvacrol, respectively. The results demonstrated the priority of the proposed fiber compared with polypyrrole and polyacrylate fibers, in terms of extraction efficiency, durability and stability. The developed method was successfully employed for the analysis of thymol and carvacrol in medicinal plants.     

Size dependence of transition temperature in polymer nanowires

We studied the effect of changing temperature on the mechanical properties of nanosized poly(methyl methacrylate) wires fabricated by two-photon fabrication. At around room temperature, the nanowires showed a transition temperature where the shear modulus suddenly changed. This transition temperature was observed to decrease more than 40 K by decreasing the radius of the nanowires from 450 to 150 nm. This size is several times larger in nanowires than reported values of polymer thin film thickness showing a depression of the glass transition temperature.     

Synthesis and characterization of some Schiff-base-containing polyimides

The diamine, 4-aminophenyloxy-N-4-[(4-amiophenyloxy)benzylidene]aniline, was prepared via the nucleophilic substitution reaction and was polymerized with different dianhydrides either by one-step solution polymerization reaction or two-step procedure. The latter includes ring-opening polyaddition to give poly(amic acid), followed by cyclodehydration to polyimides. The inherent viscosity ranges from 0.61–0.79 dl/g. Some of the polymers were soluble in most of the organic solvents such as DMSO, DMF, DMAc, NMP, and m-cresol even at room temperature. The degradation temperature of the resultant polymers falls in the ranges from 240–500 °C in nitrogen with only 10% weight loss. Specific heat capacity at 200 °C ranges from 1.0929–2.6275 J g⁻¹ k⁻¹. The temperature at which the maximum degradation of the polymer occurs ranges from 600–630 °C. The glass transition temperature (Tg) values of the polyimides ranged from 185 to 272 °C. The activation energy and enthalpy of the polyimides ranged from 47.5–55.0 kJ/mole and 45.7–53.0 kJ/mole and the moisture absorption in the range of 0.23–0.72%.     

Inhibitory Effects of Tunisian Marine Algal Extracts on Digestive Lipases

The lipase inhibitory activity of ethanol extracts obtained from some marine algae collected on the Tunisian coast was evaluated. Caulerpa prolifera extract markedly reduced both dog gastric (DGL) and human pancreatic lipase (HPL) activities. Generally, the inhibition reached 100% after 40 to 60 min of incubation depending on lipase types and on substrates used. Moreover, the inhibitory effect of C. prolifera extract on lipases appeared to be accelerated by adding bile salts, which likely modified the interface and allowed the inhibitory compound to inactivate the lipase. The separation of C. prolifera extract by thin-layer chromatography (TLC) resulted in eight fractions showing efficient inhibition rate against DGL, compared to the crude extract. In the case of HPL, TLC fractionation reduced the inhibitory rates, suggesting that the effect of algal extract on lipases may be caused by a synergetic action of several compounds within the extract. High-performance liquid chromatograph separation resulted in isolation of a major compound displaying high inhibition capacity of HPL activity. Caulerpa prolifera extract may therefore be useful in developing antiobesity drugs.