Abstract  Acetylene, C2H2, is a highly reactive, commercially important hydrocarbon. Its reactivity is related to its triple bond between carbon atoms and, as a consequence, its high positive free energy of formation. Because of its explosive nature, long distance shipping or pressurized storage is not recommended. Thus acetylene is generally used as it is produced without shipping or storage. Commercially, acetylene is used primarily as a raw material for the synthesis of a variety of organic chemicals. In the United States, this accounts for ∼90% of acetylene usage, with the balance being used for metal welding and cutting. Worldwide acetylene production peaked in the mid-1960s, after which it declined dramatically as processes were developed to substitute lower cost olefins and paraffins for the acetylene feedstock. 1,4-Butanediol production accounts for 90% of the demand for acetylene for chemical production. Although acetylene production in Japan, China, and Eastern Europe is still based on the calcium carbide process, the large producers in the United States, Western Europe, and Russia now rely principally on the partial oxidation of natural gas. However, much of the incremental growth in production is based on producing acetylene as a coproduct of ethylene in the steam cracking process. As a coproduct, acetylene is much less costly than as produced from partial oxidation or calcium carbide.

Abstract  OBJECTIVES: The exposure of seven workers and three on-site study examiners to N-methyl-2-pyrrolidone (NMP) was studied in an adhesive bonding compound and glue production facility.

METHODS: Airborne NMP was analysed by personal and stationary sampling on activated charcoal tubes. NMP and its main metabolites, 5-hydroxy-N-methyl-2-pyrrolidone (5-HNMP) and 2-hydroxy-N-methylsuccinimide (2-HMSI), were analysed in pre-shift and post-shift spot urine samples by gas chromatography-mass spectrometry. The workers were examined with respect to irritation of the eyes, the mucous membranes and the skin, and health complaints before and after the work-shift were recorded.

RESULTS: The time-weighted average concentration of NMP in most work areas varied between 0.2 and 3.0 mg/m3. During the manual cleaning of stirring vessels, valves and tools, 8-h TWA exposures of up to 15.5 mg/m3 and single peak exposures of up to 85 mg/m3) were observed. NMP and its metabolites were detected in two pre-shift urine specimens. NMP and 5-HNMP concentrations in post-shift urine samples of five workers and three on-site study examiners were below 125 microg/g creatinine and 15 mg/g creatinine, respectively, while two vessel-cleaning workers showed significantly higher urinary NMP concentrations of 472 and 711 microg/g creatinine and 5-HNMP concentrations of 33.5 and 124 mg/g creatinine. 2-HMSI was detectable in four post-shift samples (range: 1.6-14.7 mg/g creatinine). The vessel cleaner with the highest NMP exposure reported irritation of the eyes, the upper respiratory tract and headaches.

CONCLUSIONS: The results of this study indicate a relatively low overall exposure to NMP in the facility. An increased uptake of NMP occurred only during extensive manual vessel cleaning. Health complaints associated with NMP exposure were recorded in one case and might be related to an excessive dermal exposure due to infrequent and inadequate use of personal protective equipment.

Abstract  N-Methyl-2-pyrrolidone (NMP) is a versatile organic solvent frequently used for surface cleaning such as paint stripping or graffiti removal. Liquid NMP is rapidly absorbed through the skin but dermal vapour phase absorption might also play an important role for the uptake of the solvent. This particular aspect was investigated in an experimental study with 16 volunteers exposed to 80 mg/m(3) NMP for 8 h under either whole-body, i.e. inhalational plus dermal, or dermal-only conditions. Additionally, the influence of moderate physical workload on the uptake of NMP was studied. The urinary concentrations of NMP and its metabolites 5-hydroxy-N-methyl-2-pyrrolidone (5-HNMP) and 2-hydroxy-N-methylsuccinimide (2-HMSI) were followed for 48 h and analysed by gas chromatography-mass spectrometry (GC-MS). Percutaneous uptake delayed the elimination peak times and the apparent biological half-lives of NMP and 5-HNMP. Under resting conditions, dermal-only exposure resulted in the elimination of 71 +/- 8 mg NMP equivalents as compared to 169 +/- 15 mg for whole-body exposure. Moderate workload yielded 79 +/- 8 mg NMP (dermal-only) and 238 +/- 18 mg (whole-body). Thus, dermal absorption from the vapour phase may contribute significantly to the total uptake of NMP, e.g. from workplace atmospheres. As the concentration of airborne NMP does not reflect the body dose, biomonitoring should be carried out for surveillance purposes.

Abstract  The use of polymethylmethacrylate (PMMA) to reinforce vertebral bodies (Vertebroplasty) leads to an increase in the Young's modulus of the augmented vertebral body. Fractures in the adjacent vertebrae may be the consequence thereof. Hence, PMMA with a reduced Young's modulus may be suitable for vertebroplasty. The goal of this study was to produce and characterize stiffness-adapted PMMA cements. Modified PMMA bone cements were produced by adding N-methyl-pyrrolidone (NMP). Young's modulus, yield strength, polymerization temperature, setting time, and hardening behavior of different cements were analyzed. Focus was on the mechanical properties of the material after different storage conditions (in air at room temperature and in PBS at 37 degrees C). The Young's modulus decreased from 2670 MPa (air)/2384 MPa (PBS) for the regular cement to 76 MPa (air)/320 MPa (PBS) for a material composition with 60% of the MMA substituted by NMP. Yield strength decreased from 85 MPa (air)/78 MPa (PBS) to 2 MPa (air)/24 MPa (PBS) between the regular cement and the 60% composition. Polymerization temperature decreased from 70 degrees C (regular cement) to 48 degrees C for the 30% composition. The hardening behavior exhibited an extension in handling time up to 200% by the modification presented. Modification of PMMA cement using NMP seems to be a promising method to make the PMMA cement more compliant for the use in cancellous bone augmentation in osteoporotic patients: adjustment of its mechanical properties close to those of cancellous bone, lower polymerization temperature, and extended handling time.

Abstract  Novel polylactide (PLA) microspheres endowed with hydrophilic and bioadhesive surfaces as injectable formulations for the controlled release of fenretinide were prepared, using a novel technique based on the co-precipitation of PLA with gelatin, at the interface of a liquid dispersion formed by the addition of N-methylpyrrolidone containing PLA and dextrin (DX), towards an aqueous solution of gelatin (G). The resulting PLA-G-DX microspheres were compared with others prepared by the same technique using polylactide-co-glycolide (PLGA), with or without DX, and with or without phosphatidylcholine. Of the different systems, the PLA-G-DX microspheres had the best morphological, dimensional and functional characteristics. They had the highest drug loading, and their drug release was the most efficient over time without any burst effect. Their in vitro anti-tumoural activity was strongly enhanced with respect to the pure fenretinide. This paralleled the increased drug concentration inside the cells due to their marked bioadhesion to the tumour cell membranes as indicated by scanning electron microscope images.

Abstract  Aramid macroscale fibers, also called Kevlar fibers, exhibit extremely high mechanical performance. Previous studies have demonstrated that bulk aramid macroscale fibers can be effectively split into aramid nanofibers (ANFs) by dissolution in dimethylsulfoxide (DMSO) in the presence of potassium hydroxide (KOH). In this paper, we first introduced the ANFs into the structure of graphene nanosheets through non-covalent functionalization through π-π stacking interactions. Aramid nanofiber-functionalized graphene sheets (ANFGS) were successfully obtained by adding the graphene oxide (GO)/DMSO dispersion into the ANFs/DMSO solution followed by reduction with hydrazine hydrate. The ANFGS, with ANFs absorbed on the surface of the graphene nanosheets, can be easily exfoliated and dispersed in N-methyl-2-pyrrolidone (NMP). Through a combination of these two ultra-strong materials, ANFs and graphene nanosheets (GS), the resultant ANFGS can act as novel nanofillers for polymer reinforcement. We used the ANFGS as an additive for reinforcing the mechanical properties of poly(methyl methacrylate) (PMMA). With a loading of 0.7 wt% of the ANFGS, the tensile strength and Young's modulus of the ANFGS/PMMA composite film approached 63.2 MPa and 3.42 GPa, which are increases of ∼84.5% and ∼70.6%, respectively. The thermal stabilities of ANFGS/PMMA composite films were improved by the addition of ANFGS. Additionally, the transparencies of the ANFGS/PMMA composite films have a degree of UV-shielding due to the ultraviolet light absorption of the ANFs in the ANFGS.

Abstract  There is an increasing commercial demand for naturally sourced indigo that meets the purity standards set by the synthetic product. This study concerns the indigo made from leaves of woad (Isatis tinctoria L.), and in particular its interaction with particulate impurities arising from soil and plant materials. Also, a more reliable method using N-methyl-2-pyrrolidone has been developed for the spectrophotometric determination of indigo. In a novel application of fluorescence spectroscopy, indoxyl intermediates in indigo formation are shown to be stable for minutes. The main indigo precursor from woad can be adsorbed onto Amberlite XAD16 in conformity with a Langmuir isotherm, but indigo precursors break down on this and other resin beads to yield indigo and red compounds. Indigo made from indoxyl acetate aggregates into particles, the size distribution of which can be modified by the inclusion of a fine dispersion of calcium hydroxide. Bright field microscopy of indigo products made under defined conditions and scanning electron microscopy combined with energy-dispersive X-ray analysis reveal the relationship of indigo with particulate materials. A model illustrating the interaction of indigo with particulate contaminants is developed on the basis of the results obtained, and recommendations are made for improving the purity of natural indigo.

Abstract  Epoxyols are generally accepted as crucial intermediates in lipid oxidation. The reactivity of tert-butyl (9R,10S,11E,13S)-9, 10-epoxy-13-hydroxy-11-octadecenoate (11a,b) toward lysine moieties is investigated, employing N(2)-acetyllysine 4-methylcoumar-7-ylamide (12) as a model for protein-bound lysine. The prefixes R and S denote the relative configuration at the respective stereogenic centers. Independent synthesis and unequivocal structural characterization are reported for 11a,b, its precursors, and tert-butyl (9R,10R,11E, 13S)-10-(¿5-(acetylamino)-6-[(4-methyl-2-oxo-2H-chromen-7-yl)amino ]-6 -oxohexyl¿amino)-9,13-dihydroxy-11-octadecenoate (13a-d). Reactions of 11a,b and 12 in 1-methyl-2-pyrrolidone (MP) and MP/water mixtures at pH 7.4 and 37 degrees C for 56 days show formation of the aminols 13a-d to be favored by an increased water content. The same trend is observed for hydrolytic cleavage of 11a,b to tert-butyl (E)-9,10, 13-trihydroxy-11-octadecenoate (14) and tert-butyl (E)-9,12, 13-trihydroxy-10-octadecenoate (15). Under the given conditions, aminolysis proceeds via an S(N)2 substitution, in contrast with the S(N)1 process for hydrolysis. In the MP/water (8:2) incubation, 15. 8% of 12 has been transformed to 13a-d and 10.5% of 11a,b hydrolyzed to the regioisomers 14 and 15 after 8 weeks, respectively. Aminolysis of alpha,beta-unsaturated epoxides by lysine moieties therefore is expected to be an important mode of interaction between proteins and lipid oxidation products.

Abstract  In this study, uniform nitrogen-doped carbon quantum dots (N-CDs) were synthesized through a one-step solvothermal process of cyclic and nitrogen-rich solvents, such as N-methyl-2-pyrrolidone (NMP) and dimethyl-imidazolidinone (DMEU), under mild conditions. The products exhibited strong light blue fluorescence, good cell permeability and low cytotoxicity. Moreover, after a facile post-thermal treatment, it developed a lotus seedpod surface-like structure of seed-like N-CDs decorating on the surface of carbon layers with a high proportion of quaternary nitrogen moieties that exhibited excellent electrocatalytic activity and long-term durability towards the oxygen reduction reaction (ORR). The peak potential was -160 mV, which was comparable to or even lower than commercial Pt/C catalysts. Therefore, this study provides an alternative facile approach to the synthesis of versatile carbon quantum dots (CDs) with widespread commercial application prospects, not only as bioimaging probes but also as promising electrocatalysts for the metal-free ORR.

Abstract  Graphene platelets (GnPs) are a class of novel 2D nanomaterials owing to their very small thickness (∼3 nm), high mechanical strength and electric conductivity (1460 S cm(-1)), and good compatibility with most polymers as well as cost-effectiveness. In this paper we present a low-cost processing technique for producing modified GnPs and an investigation of the electrical and mechanical properties of the resulting composites. After dispersing GnPs in solvent N-methyl-2-pyrrolidone, a long-chain surfactant (Jeffamine D 2000, denoted J2000) was added to covalently modify GnPs, yielding J2000-GnPs. By adjusting the ratio of GnPs to the solvent, the modified GnPs show different average thickness and thus electrical conductivity ranging from 694 to 1200 S cm(-1). To promote the exfoliation and dispersion of J2000-GnPs in a polymeric matrix, they were dispersed in the solvent again and further modified using diglycidyl ether of bisphenol A (DGEBA) producing m-GnPs, which were then compounded with an epoxy resin for the development of epoxy/m-GnP composites. A percolation threshold of electrical volume resistivity for the resulting composites was observed at 0.31 vol%. It was found that epoxy/m-GnP composites demonstrated far better mechanical properties than those of unmodified GnPs of the same volume fraction. For example, m-GnPs at 0.25 vol% increased the fracture energy release rate G1c from 0.204 ± 0.03 to 1.422 ± 0.24 kJ m(-2), while the same fraction of unmodified GnPs increased G1c to 1.01 ± 0.24 kJ m(-2). The interface modification also enhanced the glass transition temperature of neat epoxy from 58.9 to 73.8 °C.

Abstract  In situ forming implants (ISFI) have shown promise in delivering adjuvant chemotherapy following minimally invasive cancer therapies such as thermal ablation of tumors. Although ISFI systems have been thoroughly investigated for delivery of high molecular weight (Mw) therapeutics, little research has been conducted to optimize their design for delivery of low Mw drugs. This study examined the effect of varying the formulation components on the low Mw drug release profile from a ISFI consisting of poly(D,L-lactide-co-glycolide) (PLGA), fluorescein (model drug), and excipient dissolved in 1-methyl-2-pyrrolidinone (NMP). Effects of varying PLGA Mw, excipient concentration, and drug loading were studied. Additionally, solubility studies were conducted to determine the critical water concentration required for phase inversion. Results demonstrated that PLGA Mw was the most significant factor in modulating low Mw drug release from the ISFI systems. ISFI formulations comprised of a low Mw (16 kDa) PLGA showed a significantly (p < 0.05) lower burst release (after 24 h), 28.2 +/- 0.5%, compared with higher Mw PLGA (60 kDa), 55.1 +/- 3.1%. Critical water concentration studies also demonstrated that formulations with lower Mw PLGA had increased solubility in water and may thus require more time to phase invert and release the drug.