Finite‐volume stress analysis in multi‐material linear elastic body

Correct calculation of stresses at the interface of bonded or otherwise joined materials plays a significant role in many applications. It is therefore important that traction at the material interface is calculated as accurately as possible. This paper describes procedures that can be employed to achieve this goal by using centre‐based finite‐volume method. Total traction at the interface is calculated by decomposing it into normal and tangential components, both being calculated at each side of the interface, and applying the continuity assumption. The way in which the traction approximation is achieved depends on calculation of tangential gradient of displacement at the interface. To this end, three different methods are proposed and validated against problems with known solutions. It was shown that all methods can be successfully used to simulate problems with multi‐material domains, with the procedure based on finite area method being most accurate. Copyright © 2012 John Wiley & Sons, Ltd.     

A multivariate Poisson-lognormal regression model for prediction of crash counts by severity, using Bayesian methods

Numerous efforts have been devoted to investigating crash occurrence as related to roadway design features, environmental factors and traffic conditions. However, most of the research has relied on univariate count models; that is, traffic crash counts at different levels of severity are estimated separately, which may neglect shared information in unobserved error terms, reduce efficiency in parameter estimates, and lead to potential biases in sample databases. This paper offers a multivariate Poisson-lognormal (MVPLN) specification that simultaneously models crash counts by injury severity. The MVPLN specification allows for a more general correlation structure as well as overdispersion. This approach addresses several questions that are difficult to answer when estimating crash counts separately. Thanks to recent advances in crash modeling and Bayesian statistics, parameter estimation is done within the Bayesian paradigm, using a Gibbs Sampler and the Metropolis–Hastings (M–H) algorithms for crashes on Washington State rural two-lane highways. Estimation results from the MVPLN approach show statistically significant correlations between crash counts at different levels of injury severity. The non-zero diagonal elements suggest overdispersion in crash counts at all levels of severity. The results lend themselves to several recommendations for highway safety treatments and design policies. For example, wide lanes and shoulders are key for reducing crash frequencies, as are longer vertical curves.     

Impact of frying on key fatty acid ratios of canola oil

The study was carried out to investigate the changes in saturated (SFA), monoene (MUFA), trans (TFA), and polyunsaturated (PUFA) fatty acids and the key fatty acid ratios (SFA/UFA, cis PUFA/SFA, C18:2/C16:0 and C18:3/C16:0) during potato chips frying in canola oil using single bounce attenuated total reflectance FTIR (SB‐ATR‐FTIR) spectroscopy. The data obtained from GC‐FID were used as reference. The calibration of main fat groups and their key fatty acid ratios were developed by partial least square (PLS) regression coefficients using 4000 to 650 cm^?1 spectral range. FTIR PLS regression for the predicted SFA, MUFA, TFA, and PUFA were found 0.999, 0.998, 0.998, and 0.999, respectively, whereas for SFA/UFA, cis PUFA/SFA, C18:2/C16:0 and C18:3/C16:0 the regression coefficients were 0.991, 0.997, 0.996, and 0.994, respectively. We conclude that FTIR‐PLS could be used for rapid and accurate assessment of changes in the main fat groups and their key fatty acid ratios ratio during the frying process. Practical applications: FTIR‐ATR method is very simple, rapid, and environmentally friendly. No sample preparation is required and one drop of oil is enough for FTIR analysis. The proposed method could be applied for quick determination of key fatty acid ratios in the food processing industry.     

Chemometric approach to evaluate trace metal concentrations in some spices and herbs

Herbs (mint, thyme and rosemary) and spices (black pepper, chili pepper, cinnamon, cumin, sweet red pepper and turmeric) were analysed using atomic spectrometry and then subjected to chemometric evaluation in an attempt to classify them using their trace metallic analyte concentrations (As, Ba, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Sr and Zn). Trace metals in acid digests of these materials were determined using both inductively coupled plasma-atomic emission spectrometry and inductively coupled plasma-mass spectrometry. The chemometric techniques of principal component analysis (PCA), linear discriminant analysis (LDA) and cluster analysis (CA) were used for the classification studies. These herbs and spices were classified into five groups by PCA and CA. When the results of these techniques were compared with those from LDA, it was found that all group members determined by PCA and CA are in the predicted group that 100.0% of original grouped cases correctly classified by LDA.     

Effect of bark beetle infestation on secondary organic aerosol precursor emissions

Bark beetles are a potentially destructive force in forest ecosystems; however, it is not known how insect attacks affect the atmosphere. The emissions of volatile organic compounds (VOCs) were sampled i.) from bark beetle infested and healthy lodgepole pine (Pinus contorta var. latifolia) trees and ii.) from sites with and without active mountain pine beetle infestation. The emissions from the trunk and the canopy were collected via sorbent traps. After collection, the sorbent traps were extracted with hexane, and the extracts were separated and detected using gas chromatography/mass spectroscopy. Canister samples were also collected and analyzed by a multicolumn gas chromatographic system. The samples from bark beetle infested lodgepole pine trees suggest a 5- to 20-fold enhancement in total VOCs emissions. Furthermore, increases in the β-phellandrene emissions correlated with bark beetle infestation. A shift in the type and the quantity of VOC emissions can be used to identify bark beetle infestation but, more importantly, can lead to increases in secondary organic aerosol from these forests as potent SOA precursors are produced.     

The fatty acid and tocopherol constituents of the seed oil extracted from 21 grape varieties (Vitis spp.)

BACKGROUND: Fatty acids and tocopherols in appropriate quantities are invaluable attributes that are desirable in seeds of agricultural products. Studies have generally focused on the evaluation of the oil and tocopherol components of oil crops. Recently, investigations revealed that the grape seed has robust potential in the production of healthy fatty acids as well as tocopherols. This study was thus conducted to determine the oil and tocopherol components of grape seeds, obtained from various grape cultivars of different species, including two rootstock varieties. RESULTS: The grape seed oil concentration of the studied varieties ranged from 7.3 to 22.4%. The determined fatty acid profiles of the genotypes conformed to the pattern described in the literature for grapes. Linoleic acid is the major component comprising 53.6–69.6% of the total, followed by oleic (16.2–31.2%), palmitic (6.9–12.9%) and stearic (1.44–4.69%). The oils of all the seeds analysed showed a preponderance of α‐tocopherol (ranging from 260.5 to 153.1 mg kg^?1 oil extract). β‐Tocopherol, γ‐tocopherol and δ‐tocopherol were also detected with the general means of 0.98, 22.2 and 0.92 mg kg^?1, respectively. Linoleic acid showed a significantly negative correlation with all the fatty acids analysed. The strongest negative correlation existed between linoleic and oleic acids (r = ? 0.834, P < 0.01). CONCLUSION: Present investigations indicated that oil content, fatty acid composition and tocopherol constituents of grape seed show great variation among the genotypes. Markedly higher proportions of linoleic acid with considerable amounts of tocopherols found in the oil samples suggest that grape seed is a good source for culinary, pharmaceutical and cosmetic uses. Copyright © 2012 Society of Chemical Industry     

The synthesis of covalent bonded single‐walled carbon nanotube/polyvinylimidazole composites by in situ polymerization and their physical characterization

Single‐walled carbon nanotube (SWCNT) polyvinylimidazole (PVI) composites have been prepared by in situ emulsion polymerization. Dispersion of raw SWCNTs in the PVI matrix was improved by surface modification of the SWCNTs using nitric acid treatment and air oxidation. The carbonyl‐terminated SWCNTs were covalently bonded to PVI by in situ polymerization and the SWCNT/PVI composite was thus obtained. The morphological and structural characterizations of the surface‐functionalized SWCNTs and SWCNT/PVI composites were carried out by Fourier transform infrared spectroscopy, X‐ray diffraction, conductivity measurements, scanning, and transmission electron microscopy. Thermograms of the materials were determined by the differential scanning calorimetry technique. The characterization results indicate that PVI was covalently bonded to SWCNTs and a new material was then obtained. The functionalized SWCNTs showed homogenous dispersion in the composites, whereas purified SWCNT resulted in poor dispersion and nanotube agglomeration. SWCNT/PVI composites exhibited chemical stability enhancement in many common solvents. I–V curves of the samples exhibit an ohmic character. Conductivity values for pure SWCNTs, pure PVI and SWCNT/PVI composite were measured to be 3.47, 2.11 × 10⁻⁹, and 2.3 × 10⁻³ S/m, respectively. Because of resonance, a large dielectric constant is obtained for SWCNT/PVI composite, which is not observed for ordinary materials. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Topographic and biomechanical evaluation of cornea in patients with ichthyosis vulgaris

PurposeTo compare the topographic and biomechanical properties of corneas in eyes of patients with ichthyosis vulgaris (IV) and eyes of healthy individuals.MethodsThirty healthy individuals (control group) and 30 patients with IV (study group) were enrolled in this prospective study. Topographic measurements, including keratometry values, irregularity, and surface asymmetry index in the right eye of each participant were obtained using Scheimpflug camera with a Placido disc topographer (Sirius). Corneal hysteresis (CH), corneal resistance factor (CRF), corneal-compensated intraocular pressure (IOPcc) and Goldman-related intraocular pressure (IOPg) were measured using the Reichert Ocular Response Analyzer (ORA). Central corneal thickness (CCT) was also measured with ultrasonic pachymetry and the Sirius corneal topography system.ResultsTopographic parameters were not significantly different between both groups (p > 0.05). Although mean CH was not significantly different between the groups, the CRF was significantly lower in patients with IV (p = 0.249 and p = 0.005, respectively). The CCT was significantly lower in patients with IV compared to healthy controls (p < 0.001). The IOPg and IOPcc were significantly lower in the patients with ichthyosis than in healthy controls (p = 0.001 and p = 0.004, respectively).ConclusionsThe study demonstrated that while the eyes of patients with IV had corneal topographic findings and corneal hysteresis similar to those of healthy controls, some of corneal biomechanical properties such CRF and CCT and IOP values such as IOPg and IOPcc were significantly lower in patients with IV. These results should be taken into account when planning a corneal refractive surgery and glaucoma screening for patients with IV.     

Relationships among health perceptions vary depending on stage of readiness for colorectal cancer screening.

Objective: We explored whether relationships among health perceptions differ depending on individuals' stage of readiness for colorectal cancer screening (CRCS). Methods: Data from the National Cancer Institute's Health Information National Trends Survey (HINTS) were used to stage adults over 50 years of age (N = 2324) using a modified version of the Precaution Adoption Process Model (PAPM) staging algorithm. Health perceptions examined included perceived risk of cancer, worry about cancer, fatalism, and beliefs about ambiguity of cancer prevention recommendations. Results: Meaningful differences in patterns of relationships among health perceptions by stage were found. Conclusions: The nonlinear patterns that emerged indicate support for the role of these health perceptions in screening, the idea that behavioral readiness may moderate the relationship between important health perceptions, and the use of the stage construct in this context. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Vinyl triazole carrying metal‐chelated beads for the reversible immobilization of glucoamylase

Poly(ethylene glycol dimethacrylate–1‐vinyl‐1,2,4‐triazole) [poly(EGDMA–VTAZ)] beads with an average diameter of 100–200 μm were obtained by the copolymerization of ethylene glycol dimethacrylate (EGDMA) with 1‐vinyl‐1,2,4‐triazole (VTAZ). The copolymer hydrogel bead composition was determined by elemental analysis and was found to contain 5 EGDMA monomer units for each VTAZ monomer unit. The poly(EGDMA–VTAZ) beads were characterized by swelling studies and scanning electron microscopy (SEM). The specific surface area of the poly(EGDMA–VTAZ) beads was found 65.8 m²/g. Cu²⁺ ions were chelated on the poly(EGDMA–VTAZ) beads. The Cu²⁺ loading was 82.6 μmol/g of support. Cu²⁺‐chelated poly(EGDMA–VTAZ) beads with a swelling ratio of 84% were used in the immobilization of Aspergillus niger glucoamylase in a batch system. The maximum glucoamylase adsorption capacity of the poly(EGDMA–VTAZ)–Cu²⁺ beads was 104 mg/g at pH 6.5. The adsorption isotherm of the poly(EGDMA–VTAZ)–Cu²⁺ beads fitted well with the Langmuir model. Adsorption kinetics data were tested with pseudo‐first‐ and second‐order models. The kinetic studies showed that the adsorption followed a pseudo‐second‐order reaction model. The Michaelis constant value for the immobilized glucoamylase (1.15 mg/mL) was higher than that for free glucoamylase (1.00 mg/mL). The maximum initial rate of the reaction values were 42.9 U/mg for the free enzyme and 33.3 U/mg for the immobilized enzyme. The optimum temperature for the immobilized preparation of poly(EGDMA–VTAZ)–Cu²⁺–glucoamylase was 65°C; this was 5°C higher than that of the free enzyme at 60°C. The glucoamylase adsorption capacity and adsorbed enzyme activity slightly decreased after 10 batch successive reactions; this demonstrated the usefulness of the enzyme‐loaded beads in biocatalytic applications. The storage stability was found to increase with immobilization. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011