Safety assessment of nanoparamagnetic contrast agents with different coatings for molecular MRI

Despite the wide application of gadolinium as a contrast agent for magnetic resonance imaging (MRI), there is a serious lack of information on its toxicity. Gadolinium and gadolinium oxide (Gd-oxide) are used as contrast agents for magnetic resonance imaging (MRI). There are methods for reducing toxicity of these materials, such as core nanoparticles coating or conjugating. Therefore, for toxicity evaluation, we compared the viability of commercial contrast agents in MRI (Gd-DTPA) and three nanoparticles with the same core Gd₂O₃ and small particulate gadolinium oxide or SPGO (< 40 nm) but different coatings of diethyleneglycol (DEG) as Gd₂O₃-DEG and methoxy polyethylene glycol-silane (mPEG-silane: 550 and 2000 Dalton) as SPGO-mPEG-silane550 and SPGO-mPEG-silane2000, respectively, in the SK-MEL3 cell line, by light microscopy, MTT assay using 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide, and the LDH assay detecting lactate dehydrogenase activity. The viability values were not statistically different between the three nanoparticles and Gd-DTPA. The MTT and LDH assay results showed that Gd₂O₃-DEG nanoparticles were more toxic than Gd-DTPA and other nanoparticles. Also, SPGO-mPEG-silane2000 was more biocompatible than other nanoparticles. The obtained results did not show any significant increase in cytotoxicity of the nanoparticles and Gd-DTPA, neither dose-dependent nor time-dependent. Therefore, DEG and PEG, due to their considerable properties and irregular sizes (different molecular weights), were selected as the useful surface covering materials of nanomagnetic particles that could reveal noticeable relaxivity and biocompatibility characteristics.     

Influence of pre-buckling displacements on the elastic critical loads of thin walled bars of open cross section

Nonlinear expressions for the strains occurring in thin walled bars of open cross section, when subjected to axial, flexural and torsional displacements, are incorporated in a general instability analysis based on the vanishing of the second variation of the total potential energy. It is shown that the influence of the pre-buckling displacements is automatically included in the analysis. A closed form solution for the lateral buckling of a simply supported beam subjected to uniform bending agrees exactly with a solution based on the governing differential equations. Solutions obtained using numerical methods are also presented. The significance of the second order axial strains induced by rotation about the shear centre, is investigated by considering the instability of an inverted T-beam subjected to uniform bending.     

Evaluating the Transferability of FT-NIR Calibration Models for Fatty Acid Determination of Edible Fats and Oils Among Five Same-make Spectrometers Using Transmission or Transflection Modes with Different Pathlengths

Fourier transform near-infrared (FT-NIR) spectroscopy in conjunction with partial least squares 1 (PLS1) calibration models was previously reported to be an alternative method to GC for the rapid determination of the fatty acid (FA) composition of fats and oils. These calibration models had been developed based on accurate GC data (primary reference method) and observed FT-NIR spectra. In the present three-laboratory limited collaborative study, the transferability of these pre-developed calibration models to four other FT-NIR spectrometers from the same manufacturer was evaluated. Six samples were selected that provided a wide range of FA contents. Our results indicate that these models were successfully transferable to spectrometers operating in the transflection mode with 2- or 4-mm pathlength fiber optic probes or in the transmission mode using 5-mm, but not 8-mm, outer diameter tubes. The predicted FA composition fell within the statistically accepted limits of agreement between FT-NIR and GC. The FT-NIR precision data were consistent with those reported in a published GC collaborative study. The application of FT-NIR to the determination of the total content of SFA, trans FA, MUFA, and PUFA is cost-effective and potentially suitable for the rapid screening of commercial products for compliance verification with labeling regulations.     

Nutrition Labeling: Rapid Determination of Total <Emphasis Type="Italic">trans</Emphasis> Fats by Using Internal Reflection Infrared Spectroscopy and a Second Derivative Procedure

In 2006, the US FDA mandated the declaration of the total trans fat content on the Nutrition Fact label of foods including dietary supplements when a product contained 0.5 or more grams of trans fatty acid per serving; the minimum corresponding trans fat content is estimated to be approximately 2% of total fat. The FDA definition is based on chemical structure and includes only fatty acids with one or more isolated double bonds in the trans configuration. Several issues negatively impacted the sensitivity of the current official infrared (IR) methods, thus limited the quantitation of trans fat to 5% of total fat. To improve sensitivity and accuracy and to meet the labeling requirement, a new internal reflection IR procedure called negative second derivative is described and evaluated for the quantitation of total trans fat in the present study. The enhanced spectral features of a second derivative resolved issues that traditionally limited the sensitivity of the IR methodology. Calibration standard mixtures starting at approximately 0.5% trielaidin in the total fat (tripalmitin or triarachidin) were successfully generated and used to determine the trans fat levels for unknown test samples with trans content as low as approximately 1% of total fat. Quantitative IR data were compared to those obtained by gas chromatography and were found to be in good agreement.     

Theoretical Investigation of Capture,Collection, and Targeted Transfer of Underwater Gas Bubbles Using Janus-Faced Carbon Cloth

Recently, a straightforward method for the preparation of a Janus carbon cloth (Janus-CC) is reported. The method relies on polydimethylsiloxane (PDMS) coating, followed by flame exposure of one face of the PDMS-coated CC. The nonexposed to the flame face of the Janus-CC is superhydrophobic, while the exposed to the flame face is superhydrophilic. Underwater, the superhydrophobic face shows superaerophilicity, while the supherhydophilic face shows superaerophobicity. A tethered gas bubble onto the superhydrophobic face has a paraboloid of revolution shape due to the cohesion force between the bubble and the gaseous film. Herein, the geometrical parameters of underwater tethered gas bubbles onto the Janus-CC are obtained, and the tendency of Janus-CC for capturing of bubbles is interpreted based on the derived Gibbs free-energy change equation. It is experimentally observed that a small sited bubble moves toward the bigger one through the formed gaseous film, but this observation cannot be interpreted based on the classical Young–Laplace equation because here the smaller bubble has bigger curvature radius. Herein, a modified Young–Laplace equation is derived and applied for interpretation of the movement of a small bubble toward the bigger one. Also, the buoyancy force for a sited bubble on the gaseous film is discussed.     

Removal of thiophenic compounds from liquid fuel by different modified activated carbon cloths

The adsorption behavior of benzothiophene (BT), dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (DMDBT) from n-heptane was investigated onto activated carbon cloth (ACC) and its modified forms at 30 °C in batch condition. ACC was modified by HNO₃, (NH₄)₂S₂O₈, H₂SO₄, HCl and NaOH at ambient temperature. The adsorbents were characterized using nitrogen adsorption/desorption. It was found that the adsorbents are mainly microporous but differ in their surface chemistry, which is related to the effect of oxidizing agent. The adsorption process was studied from both equilibrium and kinetics point of view. The equilibrium experimental data were fitted to the Langmuir, Freundlich and Langmuir-Freundlich by non-linear method. Among the tested adsorbents, the modified ACC with HNO₃ (ACC-HNO₃) had the highest capacity for adsorption of DBT. Kinetic characterization of the adsorption process indicated that the mixed-order and modified pseudo-n-order models can describe the kinetics of adsorption of thiophenic compounds onto ACCs. The ACC and ACC-HNO₃ were used to test the removal efficiency of total sulfur contents (BT, DBT and DMDBT, 150 ppmw for each of them), too. The effect of shaking and ultrasound methods and also temperature and time on the regeneration of saturated ACC-HNO₃ with DBT was studied.     

Rapid quantitation of fish oil fatty acids and their ethyl esters by FT‐NIR models

Consumption of fish oil and dietary supplements containing eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) has steadily increased because of their reported health benefits. A rapid procedure based on Fourier Transform Near Infrared Spectroscopy (FT‐NIR) models was developed for analysis of fish oil and their ethyl ester derivatives to replace the time consuming GC method. Inclusion of fish oil or ethyl esters containing varied concentrations of OA, EPA, and DHA into the FT‐NIR classification models made possible their classification and quantification. Accurate GC analysis is essential in developing reliable quantitative models since FT‐NIR is matrix dependent. Development of FT‐NIR models based on 30 m PEG capillary GC column results, as recommended by the official GC method for analysis of marine oils, proved problematic, since these columns did not resolve many geometric isomers compared to 100 m highly polar cyanopropyl polysiloxane columns. Depending on the content of geometric isomers in fish oils and ethyl esters, the levels of long‐chain n‐3 PUFA would be overestimated if the model used were based on the results from a 30 m column. The FT‐NIR method was found to be applicable to all fish oil and ethyl ester samples, except when fatty acids were outside the range examined, or contaminants were present. The FT‐NIR method was applicable to analysis of in‐plant intermediates provided contaminants were absent, or identified so they could be incorporated into the model. The FT‐NIR method was suitable to evaluate the shelf life of n‐3 PUFA concentrates.