Study of stability of high‐temperature polyimides using TG/MS technique

The oxidative stability of the carbon fiber‐reinforced composite of polyimide was examined, in real time, using the evolved gas analysis techniques. Off‐gas degradation products suggested the onset temperature for chain scissions to be fairly low at about 190–220°C. Based on the off‐gas products present and the trend of their release, the composite degradation mechanism appeared to be similar between 190 and 371°C, thereby marking 371°C to be the highest accelerated aging temperature for its long‐term lifetime prediction. Beyond 371°C, different degradation mechanisms would apply. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1219–1227, 2002     

Volatile Production by Buds and Corollas of Two Sympatric, Confamilial Plants, Ipomopsis aggregata and Polemonium foliosissimum

We used solid-phase microextraction of headspace samples followed by gas chromatography and mass spectrometry to identify and quantify the major volatile compounds produced by the buds and corollas of Ipomopsis aggregata (Polemoniaceae), and we compared them to a sympatric, confamilial plant species, Polemonium foliosissimum. The two species have distinct floral morphologies and pollinators, but share a common predispersal seed predator that oviposits under the calyces of buds. Ipomopsis aggregata buds emitted fewer compounds than the corollas. The buds of I. aggregata were dominated by -pinene and, to a lesser extent, -pinene. The corollas of I. aggregata emitted a mixture of 10 compounds. Like the buds, I. aggregata corollas produced relatively high concentrations of -pinene as well as caryophyllene. In addition, the emission of four terpenoids, three esters, and one ketone added to the volatile bouquet of the corollas. Polemonium foliosissimum buds also emitted fewer compounds than the corollas. The buds of P. foliosissimum were dominated by -pinene and, to a lesser extent, -pinene. The corollas of P. foliosissimum were also dominated by -pinene along with three terpenoids, three alcohols, one ester, and two aldehydes. Comparing I. aggregata and P. foliosissimum, bud samples from both species produced considerable amounts of - and -pinene. Ipomopsis aggregata emitted more -pinene than -pinene, while P. foliosissimum emitted more -pinene. The corollas of the two species, however, differed in their volatile bouquet. The partition of volatiles between I. aggregata and P. foliosissimum buds and corollas and differences in volatile production between I. aggregata and P. foliosissimum are consistent with selection pressures exerted by organisms interacting with these plants.     

SCRATCH RESISTANT POLYIMIDE COATINGS FOR ALUMINOSILICATE GLASS SURFACES

Several polyimide resins were tested as possible scratch resistant coatings for aluminosilicate glass centrifuge tubes. Tubes with siloxane pretreatments provided the best adhesion between the polyimide and glass surface. Resins synthesized with an alkoxysilane group incorporated into the polyimide chain also showed improved adhesion, but the results were not as significant as when the pretreatment was used. Elastic recovery and effective Young's modulus of the polyimide coatings were calculated from nano-scratching. The results indicate that polyimides with a lower modulus, and higher elastic recovery, protected the glass surface best, exhibiting compression of the coating layer. An example was poly-4-4'-oxydiphenylene pyromellitimide (PMDA-ODA), whereas the coatings with a high effective Young's modulus and low elastic recovery ruptured. An example of a failed coating was poly-4,4'-carbonyldiphenylene 3,3',4,4'-biphenylenetetracarboximide (BPDA-DABP) which had low amount of elastic recovery, high effective Young's modulus and a large amount of flaking during macroscratch testing.     

Impact of dietary n−3 FA deficiency on rat bone tissue FA composition

The effect of dietary n−3 FA deficiency on bone tissue FA composition was evaluated in growing rats. Two mixtures combining hydrogenated coconut oil with safflower oil served as the n−3-deficient dietary treatments and provided two levels of linoleic acid (LA). The n−3 treatments were formulated with added α-linolenic acid (LNA) from flaxseed oil (diet LNA) or LNA plus DHA, and both were balanced for LA. This study showed that bone is sensitive to changes in dietary n−3 FA and that DHA is more effective than LNA in maintaining DHA levels in these tissues.     

Effects of skim milk concentrate dry matter and spray drying air temperature on formation of capsules with varying particle size and the survival microbial cultures in a microcapsule matrix

The impact of total solid (TS) content in combination with the feed rate and air inlet temperature on the survival of Lactobacillus paracasei ssp. paracasei F19 after spray drying in a skim milk matrix has been investigated and correlated with the capsule size. Depending on the experimental conditions, the survival rates ranged from 64 to 0.2%. The higher the air inlet temperature, the lower was the survival rate and an inversely correlation between the TS content and particle size has been determined. These results clearly indicate that process stress analyses and product-related characteristics must not be regarded separately.     

A Maternal High Fat Diet Has Long‐Lasting Effects on Skeletal Muscle Lipid and PLIN Protein Content in Rat Offspring at Young Adulthood

A maternal high fat diet (HFD) can have adverse effects on skeletal muscle development. Skeletal muscle PLIN proteins (PLIN2, 3 and 5) are thought to play critical roles in lipid metabolism, however effects of HFD on PLIN and lipases (HSL, ATGL, CGI‐58) in mothers as well as their offspring have yet to be investigated. The primary objective of this study was to determine whether maternal HFD would influence skeletal muscle lipase and PLIN protein content in offspring at weaning (19d) and young adulthood (3mo). Female rats (28d old, n = 9/group) were fed control (CON, AIN93G, 7 % soybean oil) or HFD (AIN93G, 20 % lard) for 10 weeks prior to mating and throughout pregnancy and lactation. All offspring were weaned to CON [n = 18/group, 1 female and 1 male pup per litter were studied at weaning (19d) and 3mo of age]. There was no effect of sex for the main outcomes measured in plantaris, therefore male and female data was combined. Maternal HFD resulted in higher triacylglycerol content in pups at 3mo (p < 0.05), as well as in the dams (p = 0.015). Maternal HFD resulted in higher PLIN5 content in pups at weaning and 3mo (p = 0.05). PLIN2 and PLIN5 content decreased at 3mo versus weaning (p < 0.001). HFD dams had a higher PLIN3 content (p = 0.016). Diet had no effect on ATGL, CGI‐58, or HSL content. In conclusion, exposure to a maternal HFD resulted in higher skeletal muscle lipid and PLIN5 content in plantaris of offspring through to young adulthood.     

Computer-controlled Raman microspectroscopy (CC-Raman): A method for the rapid characterization of individual atmospheric aerosol particles

The ability of an atmospheric aerosol particle to impact climate by acting as a cloud condensation nucleus (CCN) or an ice nucleus (IN), as well as scatter and absorb solar radiation is determined by its physicochemical properties at the single particle level, specifically size, morphology, and chemical composition. The identification of the secondary species present in individual aerosol particles is important as aging, which leads to the formation of these species, can modify the climate relevant behavior of particles. Raman microspectroscopy has a great deal of promise for identifying secondary species and their mixing with primary components, as it can provide detailed information on functional groups present, morphology, and internal structure. However, as with many other detailed spectroscopic techniques, manual analysis by Raman microspectroscopy can be slow, limiting single particle statistics and the number of samples that can be analyzed. Herein, the application of computer-controlled Raman (CC-Raman) for detailed physicochemical analysis that increases throughput and minimizes user bias is described. CC-Raman applies automated mapping to increase analysis speed allowing for up to 100 particles to be analyzed in an hour. CC-Raman is applied to both laboratory and ambient samples to demonstrate its utility for the analysis of both primary and, most importantly, secondary components (sulfate, nitrate, ammonium, and organic material). Reproducibility and precision are compared to computer controlled-scanning electron microscopy (CCSEM). The greater sample throughput shows the potential for CC-Raman to improve particle statistics and advance our understanding of aerosol particle composition and mixing state, and, thus, climate-relevant properties.

© 2017 American Association for Aerosol Research     

Field evaluation of a Portable Fine Particle Concentrator (PFPC) for ice nucleating particle measurements

The custom-built Portable Fine Particle Concentrator (PFPC) is evaluated for the measurement of ice nucleating particles (INPs) in the atmosphere. The concentrations of INPs in remote regions of the atmosphere are very low, often close to instrumental detection limits. The PFPC is a dual slit-nozzle virtual impactor where particles are concentrated from an input flow of 250 LPM (litres per minute) into an output flow of 10 LPM. The enrichment factors (EFs) for ambient particles with diameters between 0.4 and 2.5?µm were found to be 21?±?5 at sea level and 18?±?2 at a field station 3580 meters above sea level for the PFPC operated in horizontal configuration. Similar enhancement factors (16?±?5) in the concentrations of INPs measured by the Horizontal Ice Nucleation Chamber at the high-altitude station were observed when the air mass was characterized by high numbers of particles larger than 0.5?µm. When the number size distribution was dominated by particles smaller than 0.5?µm, the INP EF was considerably lower. Corroborating short-term measurements were provided by additional INP-measuring instruments, the Fast Ice Nucleus CHamber and the Frankfurt Ice Deposition Freezing Experiment. Results from two aerosol mass spectrometers also indicate significant particle enhancement using the PFPC. These results indicate that the PFPC can be usefully deployed to improve the detection efficiency of ambient INP measurements.

Copyright © 2019 American Association for Aerosol Research     

Preparation and characterization of acrylic acid/itaconic acid hydrogel coatings containing silver nanoparticles

Hydrogel silver nanocomposites have been used in applications with excellent antibacterial performance. Acrylic acid (AA)/itaconic acid (IA) hydrogels silver nanocomposites were prepared and applied as a coating on a textile substrate. Hydrogel matrices were synthesized first by the polymerization of an AA/IA aqueous (80/20 v/v) solution and mixed with 2‐2‐azobis(2‐methylpropionamide) diclorohydrate and N,N′‐methylene bisacrylamide until the hydrogel was formed. Silver nanoparticles were generated throughout the hydrogel networks with an in situ method via the incorporation of the silver ions and subsequent reduction with sodium borohydride. Cotton (C) and cotton/polyester (CP) textile fibers were then coated with these hydrogel silver nanocomposites. The influence of these nanocomposite hydrogels on the properties of the textile fiber were investigated by infrared spectroscopy (attenuated total reflectance), scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, and antibacterial tests against Pseudomona aeruginosa and Staphylococcus aureus. The better conditions, in which no serious aggregation of the silver nanoparticles occurred, were determined. It was proven that the textiles coated with hydrogels containing nanosilver had an excellent antibacterial abilities. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2713–2721, 2013