Thermal cure monitoring of phenolic resole resins based on in situ fluorescence technique

The thermal curing reaction of two phenolic resole resins is monitored using the fluorescence technique. The intrinsic fluorescence can be used as an indicator for cure monitoring for the first resole. As the thermal curing proceeds, the intrinsic fluorescence intensity of the resole resin decreases and exhibits a few nanometers of redshift. The fluorescence intensity of the emission maxima is correlated with the conversion measured by differential scanning spectroscopy. A linear correlation is found at three different temperatures. The intrinsic fluorescence cannot always be used for monitoring the curing process of phenolic resole resins. Thus, three intramolecular charge transfer compounds and two organic donor–π‐acceptor salts are selected and applied for the cure monitoring of the second phenolic resole resin. As the curing reaction proceeds, the fluorescence emission spectra of the probes exhibit a blue spectral shift and the intensity changes because of environmental changes. An intensity ratio method is applied in which the ratios of the low‐ to high‐intensity changes in the emission bands are used to determine the degree of the curing process. There is a smooth correlation between the intensity ratio method and the degree of cure. The method enables one to follow the changes in the polymer structure at low and intermediate degrees of the curing process (below 70%) and obtain comparable results from different types of probes during the same curing process. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1773–1780, 2002     

On the system of word equations x i 1 x i 2…x i m=y i 1 y i 2…y i n (i=1, 2, …) in a free monoid

 It is proved that the system of word equations x ⁱ ₁=y ⁱ ₁ y ⁱ ₂…y ⁱ _n , i=1, 2,…, ⌈n/2⌉ +1, has only cyclic solutions. Some sharpenings concerning the cases n=5, 7 and n≥9 are derived as well as results concerning the general system of equations x ⁱ ₁ x ⁱ ₂…x ⁱ _m =y ⁱ ₁ y ⁱ ₂…y ⁱ _n , i=1, 2,… . Applications to test sets of certain bounded languages are considered. Received: 18 May 1995/2 January 1996     

Development of LC/MS/MS methods for cocktail dosed Caco-2 samples using atmospheric pressure photoionization and electrospray ionization

Good reliability of Caco-2 permeability studies requires competent sampling and analytical methods to ensure the comparability of day-to-day experiments. In this work, two n-in-one LC/MS/MS methods based on two different ionization techniques were developed and validated for a group of reference compounds; eight of them are recommended by the Food and Drug Administration (FDA) for the evaluation of oral drug permeability. The performance of a new ionization technique, atmospheric pressure photoionization (APPI), as an interface for quantitative LC/MS analysis was evaluated in comparison to the electrospray ionization (ESI). Generally, the validation parameters, including sensitivity, accuracy, and repeatability, were comparable for the APPI and ESI methods. The main difference was that the linear quantitative range of APPI was 3-4 orders of magnitude (r(2) >/= 0.998) whereas in ESI it was typically 2-3 orders of magnitude (r(2) >/= 0.990). By the APPI and ESI methods, the simultaneous analysis of nine highly heterogeneous compounds was achieved within 5.5-7 min, which leads to significant savings in time and cost of the analyses. The successful validation data indicate the usefulness of both the methods for the rapid and sensitive (LOD values typically 相似文献   

Metallocene‐based functionalized polyolefins as compatibilizers in polyolefin nanocomposites

This article reports a study of some functionalized polyolefins evaluated as compatibilizers in polyethylene nanocomposites. The functionalized polymers were prepared by direct metallocene‐mediated copolymerizations of ethylene and a functional comonomer. The prepared nanocomposites were evaluated for mechanical and barrier property enhancement. A good combination of mechanical and barrier properties was obtained with the metallocene‐based functionalized polyethylene. The toughness–stiffness balance was better than or comparable to that achieved with conventional functionalized polymers such as maleic anhydride grafted polyethylene. The results also indicated that these metallocene‐based functionalized polyolefins, when used as compatibilizers, could have relatively higher molar masses and lower functionality than those of conventional post‐reactor‐modified compatibilizers, and so the drawbacks associated with the latter could be avoided. Their inherent properties could also further improve the final nanocomposite properties. This was attributed to the more homogeneous nature of metallocene‐catalyzed polymers in comparison with post‐reactor‐modified products. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1094–1100, 2004     

High prevalence of rheumatoid factor in community-based series of patients with rheumatoid arthritis meeting the new (1987) ARA criteria: RF-negative non-erosive rheumatoid arthritis is very rare

The possible relation of acquired cystic kidney disease to renal cell carcinoma resulted in an interdisciplinary concern about this disease. Kidneys from 125 autopsies of dialysis patients were studied. Twenty-four of the patients had tumors. Beside four renal adenocarcinomas and two urothelial carcinomas, incidental small tumor nodules were described in 15.1%. Men had more nodules than women. Patients with nodules had a higher average cyst count, often with multi-layered epithelium. There was no difference in age or time of dialysis. This suggests a factor which mediates cyst and tumor proliferation, independent from the time of dialysis. With the improvement in imaging techniques, an increasing number of small renal tumors will be found. Further studies are necessary to evaluate the risk of small kidney cell tumors and their association with acquired cystic kidney disease.     

Increased incidence of alcohol-related deaths from accidents and violence in subjects with ankylosing spondylitis

Subjects with ankylosing spondylitis (AS) have an increased incidence of deaths from accidents and violence, which is due in part, but perhaps not entirely, to the vulnerability of the affected spine to fractures. The present study covered all the 71 subjects (58 men and 13 women) who had died in Finland in 1989 and who were entitled under the nationwide sickness insurance scheme to receive specially reimbursed medication for AS. The death certificates of an earlier cohort study dealing with mortality in AS were also re-examined. Sixteen subjects (14 men and two women) in the 1989 mortality series had died of accidents and violence. Nine of the deaths (three accidents, two suicides and four alcohol poisonings) were alcohol related. The relative risk of such deaths in subjects with AS compared to the Finnish population as a whole was 2.64 (95% confidence interval 1.44-4.84). In the cohort study, 16 deaths had been due to accidents and violence, the expected number being 11.4. Eight of the 16 deaths had been alcohol related. Uncontrolled use of alcohol is an important determinant in the surplus of deaths from accidents and violence in Finnish patients with AS.     

Alteration in adrenocortical function in horses with recurrent airway obstruction after aerosol and parenteral administration of beclomethasone dipropionate and dexamethasone, respectively

OBJECTIVE: To determine alteration in adrenocortical function in horses with recurrent airway obstruction (heaves) after aerosol and parenteral administration of beclomethasone dipropionate and dexamethasone, respectively. ANIMALS: 6 horses with inducible and reversible heaves. PROCEDURE: Episodes of heaves were induced by exposure to moldy hay and straw for 7 days (natural challenge). Horses then underwent treatment (aerosolized beclomethasone, parenterally administered dexamethasone, and aerosolized propellant) for 7 days. Horses remained in the mold-contaminated environment for 7 days after discontinuation of drugs. Adrenocortical function was determine by serial evaluation of cortisol concentration in serum obtained on days 0, 7, 9, 12, 14, 16, 19, and 21. Adrenocorticotropic hormone stimulation testing was performed in 4 horses/treatment group on days 0, 7, 14, and 21. RESULTS: Endogenous cortisol production was suppressed in beclomethasone- and dexamethasone-treated horses within 2 days of treatment but recovered to values similar to those in propellant-treated horses approximately 2 and 4 days after discontinuation of drugs. Serum cortisol concentration in propellant-treated horses gradually decreased during the study and was significantly lower than baseline on days 14, 16, 19, and 21. Mean increase in serum cortisol concentration in response to ACTH stimulation testing after beclomethasone and dexamethasone administration did not differ significantly from the response observed in propellant-treated horses. CONCLUSIONS: Aerosol and parenteral administration of beclomethasone and dexamethasone, respectively, suppressed adrenocortical function; however, endogenous cortisol production resumed approximately 2 and 4 days after discontinuation of drugs. Responsiveness to ACTH stimulation testing was not affected by the 7-day treatment period.     

Influence of dissolved organic matter and Fe(II) on the abiotic reduction of pentachloronitrobenzene

Nitroaromatic pesticides (NAPs) are hydrophobic contaminants that can accumulate in sediments by the deposition of suspended solids from surface waters. Fe(II) and dissolved organic matter (DOM), present in suboxic and anoxic zones of freshwater sediments, can transform NAPs in natural systems. We studied the reduction of pentachloronitrobenzene (PCNB) to pentachloroaniline (PCA) in controlled studies using Fe(II) and surface water DOM isolates from Pony Lake, Antarctica, and Suwannee River, GA, in unfiltered and 0.45 microm filtered solutions. We observed rapid reduction of PCNB to PCA in the presence of Fe(II) and DOM (t(1/2) approximately = 30 min to 4 h) and very limited reduction in DOM-only systems. DOM in unfiltered systems inhibited iron colloid formation and potentially limited the formation of reactive Fe(ll)-iron colloid surface complexes, causing reductive transformation in Fe(II)-DOM media to be slower in some cases relative to Fe(ll)-only controls. Conversely, in 0.45 microm filtered solutions, PCNB reduction in Fe(III)-DOM media was faster than the Fe(II)-only controls, suggesting that DOM enhances the reductive capacity of Fe(ll) in the absence of iron colloids. This work shows that DOM may significantly affect the reactivity of Fe(ll) toward NAPs under suboxic and anoxic conditions in natural wetland sediments.     

Expected shifts in Fusarium species' composition on cereal grain in Northern Europe due to climatic change

In Northern Europe, changes in climate may result in better growing conditions for many crops. However, the expected warmer and more humid conditions are favourable for Fusarium head blight infections on cereals. The Fusarium species prevalent in Nordic areas to date are the same as in Central Europe: F. avenaceum, F. culmorum, F. graminearum and F. poae. The prevalence of F. graminearum in cereal grain has already increased in Central Europe and is likely to increase in the North due to the expected changes in weather conditions, reduced tillage and the predicted increase in maize cultivation in Nordic countries. The possible weather extremes predispose cereals to Fusarium infections by increasing the populations of insect pests injuring plants. Adverse conditions may even create conditions suitable for F. subglutinans or F. verticilloides to infect maize and possibly other cereals in rotation in southern parts of Scandinavia. The importance of the species that infect in relatively dry conditions, F. langsethiae and F. poae, may also increase on winter cereals which are predicted to be more prevalent in future farming. If the number of crop species cultivated will increase and non-cereal crops are included in rotations effects of reduced tillage on Fusarium infections in grain could be limited. The predicted changes in climate towards 2050 are expected to slightly change Fusarium species composition in Northern Europe. An increase in F. graminearum and possibly the invasion of northern parts of Central Europe and Denmark by fumonisin producers is expected.