Simultaneous determination of methylcarbamate and ethylcarbamate in fermented foods and beverages by derivatization and GC-MS analysis

BACKGROUND: Methylcarbamate (MC) and ethylcarbamate (EC) are toxic compounds that commonly exist in fermented food and beverages. In order to estimate the risk for their exposure, a sensitive simultaneous analytical method is required RESULTS: A simultaneous determination of MC and EC was described based on derivatization with 9-xanthydrol and consecutive detection using gas chromatography–mass spectrometry. The derivatization of MC and EC was performed directly in food or beverages and the reaction conditions were established through changing various parameters. The detection and the quantification limits were 0.01-0.03 μg/kg and 0.03-0.1 μg/kg, respectively, and the interday relative standard deviation was less than 12% at concentrations of 2.0 and 50 μg/kg. MC and EC were measured from 0.4 μg/kg to 85.8 μg/kg in sixteen Korean fermented foods and eleven beverages. CONCLUSION: A simple, sensitive method to detect MC and EC in several solid foods and liquid foods was developed based on derivatization with 9-xanthydrol for 10 min at an ambient temperature. The method may useful for routine analysis of MC and EC in numerous food samples

In-Situ Polymerizatioon and Characterization of Polyethylene-Clay Nanocomposites

Abstract Chapter 1 provides an overview of this study and a literature review. Emphasis is put on the materials used, the different processes available to synthesize polymer-clay nanocomposites, analytical methods to characterize nanophase materials and on the impact of the nanophase on the final physical properties of polymer-clay nanocomposites. Chapter 2 discusses PE-clay nanocomposites which were synthesized using metallocene and Ni-diimine catalysts through in-situ polymerization. Morphological studies were carried out by XRD, SEM, EDX, and TEM to investigate the intercalation and exfoliation mechanism. Prior to its injection into the polymerization reactor, montmorillonite (MMT) was treated with triisobutyl aluminum and undecylenyl alcohol (UOH). Triisobutyl aluminum (TIBA) can react with hydroxyl groups on the surface of MMT and UOH is able to react with TIBA on the MMT surface. An alkoxy bond is generated by the reaction of the hydroxyl groups of UOH with the TIBA on the surface of MMT. A single site catalyst was then supported on the MMT/TIBA/UOH support, generating a MMT/TIBA/UOH/CAT system. The free vinyl groups of the surface UOH molecules can be copolymerized with ethylene, leading to the formation of chemical bonds between the MMT surface and polyethylene (PE). Ethylene polymerizations with the MMT/TIBA/UOH/CAT system were compared with ethylene polymerization with unsupported catalysts. The resulting PE-clay nanocomposites were analyzed with electronic and optical microscopes to confirm the nanophase distribution of MMT platelets in the polymer matrix. TEM images showed that the exfoliated MMT layers appeared as single layers or aggregated layers in the polyethylene matrix. After Soxhlet extraction with boiling 1,2,4-trichlorobenzene, the morphology of the residue particles remaining the thimble showed polymer fibrils stemming from the MMT surface, providing direct evidence of the chemical bonds between MMT surfaces and polymer matrix. Some residue particles also show PE-clay hybrid fibers between the particles. Through SEM/EDX analysis, it was confirmed that the fiber’s composition possessed silicone atoms together with carbon atoms. Chapter 3 discusses the results of in-situ polymerizations in gas-phase. The same catalyst systems and polymerization conditions discussed in Chapter 2 for slurry polymerization were applied to the gas-phase polymerization in order to investigate the particle fragmentation mechanism. After gas-phase polymerization at atmospheric pressure, the surface morphologies were investigated by SEM and TEM. In the case of the MMT/TIBA/UOH/Cp2ZrCl2 system, small particles ( 100 m) in the early stages of polymerization. After 24-hours of continuous polymerization, polymer fibrils growing from the inside of the MMT particles were observed by SEM. After further investigation with TEM, the cross-section profile of the particles showed curved bundles of MMT platelets, which illustrates exfoliation starting from the edges of the MMT particles. The MMT/TIBA/UOH/Ni-diimine system shows a different surface morphology after polymerization. In the early stages of the polymerization, polymer films were generated from the inside of the particles. After further polymerization, the MMT particles shattered and formed aggregates of PE-clay nanocomposites, similar to the ones proposed in the multigrain model. Chapter 4 discusses the copolymerization of ethylene and acrylonitrile. Ethylene/acrylonitrile copolymers were produced in the presence of a Ni-diimine/EASC catalyst system without the use of supports. Polymerizations of ethylene and acrylonitrile showed comparable activities in low concentrations of acrylonitrile. However, in higher concentrations, acrylonitrile induced a reductive elimination of the alkyl groups in the activated nickel-diimine catalyst. Conclusively, GPC analyses showed that acrylonitrile behaves as a chain transfer agent, showing reductive elimination of alkyl groups in the catalytic active center. The polymerization product morphology was analyzed by SEM and TEM. Polyacrylonitrile domains were observed in the polyethylene matrix and confirmed its nanosize distribution in the polyethylene matrix. DSC analysis of ethylene/acrylonitrile copolymers shows that an exothermic reaction takes place from 300 C to 370 C. This exotherm band detected by DSC can be related to the cyclization and aromatization of the nitrile groups of polyacrylonitrile. Through IR analysis of the ethylene and acrylonitrile polymer under high temperatures, this cyclization and aromatization was confirmed to be the cause of the decrease of the nitrile band (at 2244 cm-1) and increase of the vinyl bands (at 1640 cm-1). In addition, thermal treatment in DSC and successive XRD analysis showed the formation of the lamellar structures in the polyethylene matrix, reported as lamellar formation of polyacrylonitrile due to cyclization and aromatization of nitrile groups. The decomposition temperatures measured by TGA increased up to 50 C due to the presence of the nitrile groups in the polymer matrix. Tensile testing showed that the modulus increased, together with the yield strength and elongation. This phenomenon supports that strong interfacial interactions exist between the polyethylene matrix and polyacrylonitrile domains, as confirmed by TEM and IR analysis. Chapter 5 introduces the idea of acrylonitrile as a clay surface modifier. MMT was treated with acrylonitrile, using the same modification method of MMT that was applied in the MMT/TIBA/UOH/CAT system in Chapter 2. The nitrile groups in PE-MMT/TIBA/AN/CAT composites were confirmed at 2244 cm-1 by IR analysis. DSC analysis of PE-MMT/TIBA/AN/CAT showed that an exothermic reaction takes place from 300 C to 375 C. Successive DSC analysis with the same sample showed a new glass transition temperature band, induced by the reduction of polymer chain mobility. The basal diffraction band disappeared due to the exfoliation of MMT. Tensile tests showed an increase in modulus, without sacrificing the yield strength and elongation of PE-clay hybrid composites. Through these analyses, it was confirmed that strong interfacial forces exist between the polyethylene matrix and MMT layers in these PE-clay nanocomposites

ELECTROMYOGRAPHICAL ANALYSIS OF TRUNK MUSCLE ACTIVITIES DURING A GOLF SWING

The purposes of this study were to describe and compare the activation patterns of the trunk muscles during a golf swing using surface electromyographic (EMG) techniques. Five male collegiate golfers were the subjects. The golf swing was broken into five phases using the critical instants identified from video recordings. Wilcoxon signed ranks tests were used to test for significant differences (12 < .05) in average and peak normalized EMG values between the left and right muscles for each phase. The significant bilateral differences in muscle activation were only found in the average and peak rectus abdominus (acceleration phase), external oblique (acceleration and early follow-through phases), and erector spinae (late follow-through phase). The trunk muscles were highly active in the follow-through phases which may indicate the hyperextension of the trunk, which leads to lower back injury

Superficial cervical plexus block for management of herpes zoster neuralgia in the C3 dermatome: a case report

INTRODUCTION: Herpes zoster is a well-known reactivating viral disease that gives rise to painful skin lesions. Although this vesicular rash heals up within a few weeks, pain sometimes continues, becoming postherpetic neuralgia. In the case of those at high risk of developing postherpetic neuralgia, early interventional pain management is generally recommended as a preventive measure. Pain specialists usually do not see patients face-to-face for chronic refractory pain until the stage of postherpetic neuralgia. However, active and aggressive management, including antiviral treatment, of herpetic neuralgia during the acute stage of herpes zoster promises better results. In this respect, superficial cervical plexus block can help patients, such as the case reported here, by relieving the pain of herpes zoster involving the C3 dermatome. CASE PRESENTATION: A 65-year-old Korean man with severe pain in his left C3 dermatome due to herpes zoster was admitted to our hospital. His pain was so refractory to medication that he consulted our pain clinic for pain control. Due to the medication limitations imposed by his underlying diseases (hepatitis B, liver cirrhosis, atrial fibrillation, and asthma), early interventional therapy including stellate ganglion block was planned. In addition, because his painful C3 dermatome overlapped significantly with the superficial cervical plexus dermatome, ultrasound-guided superficial cervical plexus block was utilized for pain control of the intractable herpes zoster neuritis in his C3 dermatome. The result with respect to his sporadic neuralgia was satisfactory. CONCLUSIONS: We found superficial cervical plexus block to be an effective interventional procedure for pain management of herpes zoster, particularly at the C3-dermatomal level

Temperature change in pig rib bone during implant site preparation by low-speed drilling

OBJECTIVES: The purpose of this study was to evaluate the temperature change during low-speed drilling using infrared thermography. MATERIAL AND METHODS: Pig ribs were used to provide cortical bone of a similar quality to human mandible. Heat production by three implant drill systems (two conventional drilling systems and one low-speed drilling system) was evaluated by measuring the bone temperature using infrared thermography. Each system had two different bur sizes. The drill systems used were twist drill (2.0 mm/2.5 mm), which establishes the direction of the implant, and finally a 3.0 mm-pilot drill. Thermal images were recorded using the IRI1001 system (Infrared Integrated Systems Ltd.). Baseline temperature was 31±1ºC. Measurements were repeated 10 times, and a static load of 10 kg was applied while drilling. Data were analyzed using descriptive statistics. Statistical analysis was conducted with two-way ANOVA. RESULTS AND CONCLUSIONS: Mean values (n=10 drill sequences) for maximum recorded temperature (Max TºC), change in temperature (&#916;TºC) from baseline were as follows. The changes in temperature (&#916;TºC) were 1.57ºC and 2.46ºC for the lowest and the highest values, respectively. Drilling at 50 rpm without irrigation did not produce overheating. There was no significant difference in heat production between the 3 implant drill systems (p>;0.05). No implant drill system produced heat exceeding 47ºC, which is the critical temperature for bone necrosis during low-speed drilling. Low-speed drilling without irrigation could be used during implant site preparation