Development of high throughput 96-blade solid phase microextraction-liquid chromatrography-mass spectrometry protocol for metabolomics

In metabolomics, the workflow for quantitative and comprehensive metabolic mapping of cellular metabolites can be a very challenging undertaking. Sampling and sample preparation play a significant role in untargeted analysis, as they may affect the composition of the analyzed metabolome. In the current work, different solid phase microextraction (SPME) coating chemistries were developed and applied to provide simultaneous extraction of a wide range of both hydrophobic and hydrophilic cellular metabolites produced by a model organism, Escherichia coli. Three different LC-MS methods were also evaluated for analysis of extracted metabolites. Finally, over 200 cellular metabolites were separated and detected with widely varying hydrophobicities ranging within −7 < log P < 15, including amino acids, peptides, nucleotides, carbohydrates, polycarboxylic acids, vitamins, phosphorylated compounds, and lipids such as hydrophobic phospholipids, prenol lipids, and fatty acids at the stationary phase of the E. coli life cycle using the developed 96-blade SPME-LC-MS method.     

Ultra-trace arsenic and mercury speciation and determination in blood samples by ionic liquid-based dispersive liquid-liquid microextraction combined with flow injection-hydride generation/cold vapor atomic absorption spectroscopy

A simple, fast, and sensitive method for speciation and determination of As (III, V) and Hg (II, R) in human blood samples based on ionic liquid-dispersive liquid-liquid microextraction (IL-DLLME) and flow injection hydride generation/cold vapor atomic absorption spectrometry (FI-HG/CV-AAS) has been developed. Tetraethylthiuram disulfide, mixed ionic liquids (hydrophobic and hydrophilic ILs) and acetone were used in the DLLME step as the chelating agent, extraction and dispersive solvents, respectively. Using a microwave assisted-UV system, organic mercury (R-Hg) was converted to Hg(II) and total mercury amount was measured in blood samples by the presented method. Total arsenic content was determined by reducing As(V) to As(III) with potassium iodide and ascorbic acid in a hydrochloric acid solution. Finally, As(V) and R-Hg were determined by mathematically subtracting the As(III) and Hg(II) content from the total arsenic and mercury, respectively. Under optimum conditions, linear range and detection limit (3σ) of 0.1–5.0 µg L^?1 and 0.02 µg L^?1 for As(III) and 0.15–8.50 µg L^?1 and 0.03 µg L^?1 for Hg(II) were achieved, respectively, at low RSD values of < 4% (N = 10). The developed method was successfully applied to determine the ultra-trace amounts of arsenic and mercury species in blood samples; the validation of the method was performed using standard reference materials.     

Analysis of plate in second strain gradient elasticity

The bending analysis of a thin rectangular plate is carried out in the framework of the second gradient elasticity. In contrast to the classical plate theory, the gradient elasticity can capture the size effects by introducing internal length. In second gradient elasticity model, two internal lengths are present, and the potential energy function is assumed to be quadratic function in terms of strain, first- and second-order gradient strain. Second gradient theory captures the size effects of a structure with high strain gradients more effectively rather than first strain gradient elasticity. Adopting the Kirchhoff’s theory of plate, the plane stress dimension reduction is applied to the stress field, and the governing equation and possible boundary conditions are derived in a variational approach. The governing partial differential equation can be simplified to the first gradient or classical elasticity by setting first or both internal lengths equal to zero, respectively. The clamped and simply supported boundary conditions are derived from the variational equations. As an example, static, stability and free vibration analyses of a simply supported rectangular plate are presented analytically.     

Experimental investigation of TiO2/water nanofluid laminar forced convective heat transfer through helical coiled tube

Coiled tubes and nanofludics are two significant techniques to enhance the heat transfer ability of thermal equipments. The forced convective heat transfer and the pressure drop of nanofluid inside straight tube and helical coiled one with a constant wall heat flux were studied experimentally. Distilled water was used as a host fluid and Nanofluids of aqueous TiO₂ nanoparticles (50 nm) suspensions were prepared in various volume concentrations of 0.25–2 %. The heat transfer coefficient of nanofluids is obtained for different nanoparticle concentrations as well as various Reynolds numbers. The experiments covered a range of Reynolds number of 500–4,500. The results show the considerable enhancement of heat transfer rate, which is due to the nanoparticles present in the fluid. Heat transfer coefficient increases by increasing the volume concentration of nanoparticles as well as Reynolds number. Moreover, due to the curvature of the tube when fluid flows inside helical coiled tube instead of straight one, both convective heat transfer coefficient and the pressure drop of fluid grow considerably. Also, the thermal performance factors for tested nanofluids are greater than unity and the maximum thermal performance factor of 3.72 is found with the use of 2.0 % volume concentration of nanofluid at Reynolds number of 1,750.     

Dynamic NMR and computational study of 5,5-dimethyl-3,4-di-p-tolyl-2-cylopenten-1-one

The restricted rotation of p-tolyl moiety in 5,5-dimethyl-3,4-di-p-tolyl-2-cyclopenten-1-one was studied by variable temperature NMR spectroscopy at a temperature range of 218-368 K. A free rotation, in NMR time scale, was observed at temperatures higher than 368 K; while, the rotation froze below 248 K. From dynamic NMR analysis, the Arrhenius energy of activation ΔG? was calculated as 56.37 kJ mol(-1). The experimental results were confirmed by theoretical calculation using the density functional theory method B3LYP with basis sets, 6-31G and 6-31+G.     

Effect of Nanoclay along with Other Effective Parameters on Gelation Time of Hydro Polymer Gels

In this work, a hydrogel was prepared by crosslinking of aqueous solutions of sulfonated polyacrylamide/chromium triacetate for the purpose of water shut-off treatment in oil fields. In order to screen the factors that affect the gelation time and investigate their interactions, a 32 run fractional factorial design was used in experimentation with eight factors (pH, CaCl₂ concentration, crosslinker/copolymer ratio, NaCl concentration, copolymer concentration and presence or absence of sodium lactate, nanoclay, and thiouria) and one response (gelation time). Furthermore, the analysis of variance (ANOVA) was implemented as a significant tool to evaluate the quality of the quadratic model. The ANOVA results of the developed model showed it was significant with a 99% confidence limit. Among the eight factors, presence of sodium lactate, copolymer concentration, presence of nanoclay, presence of thiouria, and crosslinker/copolymer ratio had, in order, the main effects, and the interactions between sodium lactate and crosslinker/copolymer ratio and between pH and crosslinker/copolymer ratio were highly significant.     

Electromagnetically induced polarization conversion

Electromagnetically induced transparency and polarization conversion due to interference between two polarization-selective plasmonic resonances coexisting in the same planar metamaterial are studied. The metasurface represents a periodic array of two topologically distinct metamolecules combined on the same substrate: i) monopole antennas connected to wires and supporting a high-Q resonance radiatively coupled to x-polarization, and ii) dipolar antennas supporting a low-Q resonance coupled to y-polarization. We demonstrate that due to the interaction between these modes through a capacitive coupling between the metamolecules, one can observe a circularly-polarized Electromagnetically Induced Transparency (EIT) and thereby achieve an efficient ultra-thin quarter-wave plate.     

Controlling the optical bistability via interacting dark-state resonances

We analyze the behavior of optical bistability in a four-level mercury atomic system driven by a cavity and two external coherent fields by means of a unidirectional ring cavity. We find that without interacting dark resonances and for large intensity of coupling field, the optical bistability disappears. So, the double dark resonances could significantly establish the optical bistability. Moreover, we demonstrate that the double dark resonances can dramatically reduce the threshold of optical bistability.     

On Superconductivity State in Pure Graphene

We study theoretically the possibility of superconductivity state in pure graphene within the extended attractive Hubbard model. In the absence of disorder, when we use the local attractive interaction potential, U ≌ 5t, where t is hopping term, pure graphene can be in superconductivity state.     

Supercapacitors in Motion: Autonomous Microswimmers for Natural‐Resource Recovery

An electroadsorption technique similar to the ultrafast charging mechanism in supercapacitors is utilized to remove metals with different sizes and hydrophilicities from contaminated water using self‐propelled microswimmers. The swimmers carry graphite fibre or bismuth with a layered crystal structure providing high electrostatic double‐layer capacitances. Unlike previous methods, this electrochemical technique does not only utilize the surface of the swimmers, but due to the interlayer spacing of the graphite and bismuth, it is able to store metals in ≈400 layers, allowing removal and recovery of >50 ppm lithium in only 5 min. A larger interlayer distance between bismuth sheets allows the removal of bigger cations (sodium and calcium), expanding the application of this method to a large variety of natural elements. Finally, magnetic navigation of charged swimmers to an oxygen‐saturated media causes oxidation and thus immediate release of the metal ions from the swimmers.