Simultaneous Element-Selective Detection of C,F, Cl,Br, and I by Capillary Gas Chromatography Coupled with Microplasma Mass Spectrometry

Simultaneous element-selective detection of the halogens and carbon was accomplished with capillary gas chromatography coupled with microplasma mass spectrometry. The microplasma ion source was a radio frequency plasma contained inside the last 4–5 cm of the 0.32 mm i.d. fused silica capillary column. The ion source was located inside the high vacuum housing of the MS, and only the GC carrier gas (2.3 mL min⁻¹ of helium) was used for plasma generation. Atomic ions were detected in the positive mode. Detection limits were in the low picogram area, and the selectivity to carbon ranged from 8×10² for fluorine to higher than 10⁴ for the other halogens. By introduction of both hydrogen and oxygen as reagent gases, peak tailing was avoided by suppression of analyte reactions with the silica walls of the ion source. Special attention was given to the fluorine-selective detection due to an interfering background species at m/z 19, assumed to be H₃O⁺ originating from the reagent gases. The background signal was minimized by careful control of the power level.     

Solid-phase analytical derivatization of alkylphenols in fish bile for gas chromatography-mass spectrometry analysis

Solid-phase analytical derivatization (SPAD) with bis(trimethylsilyl)trifluoroacetamide (BSTFA) has successfully been used as a sample preparation method for determination of (APs) in fish bile treated with beta-glucuronidase and sulfatase. Derivatized APs were analysed by gas chromatography-mass spectrometry in the electron ionization mode (GC-EI-MS). Overall limits of detection (LODs) ranged from 5 to 18ng/g bile for 19 out of 21 investigated compounds. LODs were not determined for 4-methylphenol and 4-tert-octylphenol due to high background levels in control bile. Recoveries ranged from 83 to 109%. The analysed APs vary in degree of alkylation from methyl (C(1)) to nonyl (C(9)), and represent various pollution sources, including produced water (PW) discharge from the offshore oil industry. The applicability and sensitivity of the method has been demonstrated by analysis of bile taken from Atlantic cod (Gadus morhua L.) exposed to two dilutions of PW (1:500 and 1:1500) in a continuous flow system.     

Biomedical applications of biodegradable polymers

Utilization of polymers as biomaterials has greatly impacted the advancement of modern medicine. Specifically, polymeric biomaterials that are biodegradable provide the significant advantage of being able to be broken down and removed after they have served their function. Applications are wide ranging with degradable polymers being used clinically as surgical sutures and implants. To fit functional demand, materials with desired physical, chemical, biological, biomechanical, and degradation properties must be selected. Fortunately, a wide range of natural and synthetic degradable polymers has been investigated for biomedical applications with novel materials constantly being developed to meet new challenges. This review summarizes the most recent advances in the field over the past 4 years, specifically highlighting new and interesting discoveries in tissue engineering and drug delivery applications. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Fracture of thick laminated composites

The fracture of thick laminated graphite/epoxy composites has been the subject of an extensive research program. The program was divided into three major areas of investigation which included laminate thickness, laminate stacking sequence, and part-through surface flaws. The results from this program are reviewed with emphasis placed on their applicability to the design of thick laminated composite structures. Paper was presented at 1985 SEM Spring Conference on Experimental Mechanics held in Las Vegas on June 9–14, 1985.     

An approximate analysis of drying operation of wet fabric

This study describes an approximate theoretical analysis of drying a moving wet fabric exposed to constant radiant heat and hot air blown normal to its surface. By considering the problem as a combination of heat and mass transfer processes, the governing dimensionless groups are identified and their influence on the residence time is established. These groups are then utilized in the prediction of either the residence time or the total length of travel needed to achieve a specific drying level of the fabric.     

Thiophene-based polyphosphazenes with tunable optoelectronic properties

The polyphosphazene backbone provides a versatile platform to explore numerous synthesis and structure–property relationships for many technological applications. In this study, a new class of polyphosphazene semiconducting materials was synthesized via macromolecular substitution, which integrates a  PN backbone with thiophene-based side groups. The synthesized thiophene-based polymers were subjected to chemical oxidation (oxidative coupling) to optimize their optoelectronic properties through side-chain chemistry. Both the spectroscopic and electronic analyses revealed that optical and electronic properties, as well as glass transition temperatures could be modulated by chemical oxidation of the polymers. The suitability of the polymers as potential semiconductors was further evaluated using their steady-state fluorescence quenching behavior in the presence of four different dopants (PC70BM, PC60BM, F4TCNQ, and TCNQ). It was found that the addition of dopant as a quencher to the polymer solutions does not form a complex in the ground state, and its excited state shows an efficient decrease in fluorescence intensity without altering the shape and peak position of the fluorescence band. The overall results demonstrate that the utilization of chemical oxidation via side-chain chemistry of polyphosphazenes offers an adaptable toolbox that can be used to make new and potentially useful polymeric semiconductors for applications in organic electronics.     

Combustion of ethylamine,dimethylamine and diethylamine: Theoretical and kinetic modeling study

Aliphatic amines are an important class of nitrogen-containing compounds present in renewable fuels such as bio-oils. Conversion of this fuel-bound nitrogen can lead to the formation of HCN and NH₃, as well as NO_x emissions. In this work, the combustion chemistry of small aliphatic amines is investigated via a combination of quantum chemical calculations, chemical kinetic modeling and experimental validation. The influence of the degree of substitution on the nitrogen atom and the alkyl chain length on the reactivity and product distribution is studied via three model compounds, i.e. ethylamine (EA, CH₃CH₂NH₂), dimethylamine (DMA, (CH₃)₂NH) and diethylamine (DEA, (CH₃CH₂)₂NH). A detailed kinetic model containing 258 species and 2274 reactions is developed to describe their combustion over a wide range of conditions. The proposed model captures the trends in ignition delay times and species concentrations over a temperature range from 500 to 2000 K and pressures from 4 to 170 kPa. The ignition delay data are predicted with an average deviation of 10%. The difference between experimental and simulated species concentrations from laminar premixed flames is for the major species on average 50%, while the agreement for the JSR is even better, with an average deviation of 10%. The dominant decomposition pathway under all the studied conditions is a set of hydrogen abstractions from the C_α and N positions followed by β-scission of the fuel radicals. Among the unimolecular decomposition pathways, the homolytic CC and CN scissions and four-centered elimination play a minor role. HCN is the main intermediate and at temperatures above 1100 K the amines are completely converted to N₂ and NO.     

Insulin immobilized PCL‐cellulose acetate micro‐nanostructured fibrous scaffolds for tendon tissue engineering

Use of growth factors as biochemical molecules to elicit cellular differentiation is a common strategy in tissue engineering. However, limitations associated with growth factors, such as short half‐life, high effective physiological doses, and high costs, have prompted the search for growth factor alternatives, such as growth factor mimics and other proteins. This work explores the use of insulin protein as a biochemical factor to aid in tendon healing and differentiation of cells on a biomimetic electrospun micro‐nanostructured scaffold. Dose response studies were conducted using human mesenchymal stem cells (MSCs) in basal media supplemented with varied insulin concentrations. A dose of 100‐ng/mL insulin showed increased expression of tendon markers. Synthetic‐natural blends of various ratios of polycaprolactone (PCL) and cellulose acetate (CA) were used to fabricate micro‐nanofibers to balance physicochemical properties of the scaffolds in terms of mechanical strength, hydrophilicity, and insulin delivery. A 75:25 ratio of PCL:CA was found to be optimal in promoting cellular attachment and insulin immobilization. Insulin immobilized fiber matrices also showed increased expression of tendon phenotypic markers by MSCs similar to findings with insulin supplemented media, indicating preservation of insulin bioactivity. Insulin functionalized scaffolds may have potential applications in tendon healing and regeneration.     

Monitoring Farmed Fish Welfare by Measurement of Cortisol as a Stress Marker in Fish Feces by Liquid Chromatography Coupled with Tandem Mass Spectrometry

The aquaculture industry has become a sustainable source of food for humans. Remaining challenges include disease issues and ethical concerns for the discomfort and stress of farmed fish. There is a need for reliable biomarkers to monitor welfare in fish, and the stress hormone cortisol has been suggested as a good candidate. This study presents a novel method for measurement of cortisol in fish feces based on enzymatic hydrolysis, liquid–liquid extraction, derivatization, and finally instrumental analysis by liquid chromatography coupled with tandem mass spectrometry. Hydrolysis and extraction conditions were optimized. Cortisol appeared to be mostly conjugated to sulfate and less conjugated to glucuronic acid in the studied samples of feces from farmed Atlantic salmon. The method was suitable for quantification of cortisol after enzymatic deconjugation by either combined glucuronidase and sulfatase activity, or by glucuronidase activity alone. The limit of detection was 0.15 ng/g, the limit of quantification was 0.34 ng/g, and the method was linear (R² > 0.997) up to 380 ng/g, for measurement of cortisol in wet feces. Method repeatability and intermediate precision were acceptable, both with a coefficient of variation (CV) of 11%. Stress level was high in fish released into seawater, and significantly reduced after eight days.