Chemical correlates of α-tocopherol (Vitamin E) alteredMalacosoma disstria herbivory inFraxinus pennsylvanica var.Subintegerrinia,green ash

The antioxidant -tocopherol (vitamin E), applied in a basal trunk band to the green ash tree,Fraxinus pennsylvanica var.subintergerrinia, elicited an alteration of foliar feeding byMalacosoma disstria larvae (Lepidoptera: Lasiocampidae). The bioassayed effects were dependent on the dosage of elicitor, the time after elicitation, and the position in the tree. Leaves for chemical analysis were collected from trees receiving two dosages and at two intervals after elicitation. Compounds in the ethyl acetate extractables from the ash tree leaves were separated by TLC and HPLC. TLC separations showed differences in the nonhydrolyzed extractables attributable to elicitor dosage and time after elicitation. TLC-resolved differences were also evident among acid-hydrolyzed samples. HPLC-resolved profiles revealed eight peaks in the nonhydrolyzed extractables that were quantitatively negatively correlated with larval feeding preference between elicited versus control foliage on at least one of the two sampling dates. Results from this study and other investigations reported in the literature indicate that the antioxidant-tocopherol (vitamin E) can function as an environmental-stress elicitor of alterable defensive chemistry in green ash and other plants.     

On the comparison of conceptual clustering and numerical taxonomy

Conceptual clustering requires that clusters formed in the process shall be definable in terms of simple formulas in the predicate calculus. Michalski and Stepp [1] have argued that the results obtained with this method are clearly superior to traditional methods of numerical classification, so that an order of magnitude degradation in performance is acceptable. In this paper the results and comparisons presented by Michalski and Stepp are reviewed and shown to be less than adequate to support such a conclusion. There are considerable problems with data coding and standardization, as well as choice of similarity measure, that make the results difficult to evaluate. Even accepting the clusters, two different valorizing schemes are used to evaluate the results obtained. In addition, the traditional agglomerative algorithm employed in numerical classification procedures can be adapted to perform conceptual clustering without an enormous degradation in performance. However, the value of the method can only be regarded as unproven.     

Irrigation infrastructure development in the Limarí Basin in Central Chile: implications for adaptation to climate variability and climate change

One option to deal with climate variability in agriculture is to build irrigation infrastructure, although this may lead to the overdevelopment of water resources, leading to ‘basin closure’. The Limarí Basin, in central north Chile, has relied on irrigation infrastructure over the last 30 years to increase water supply reliability and extend irrigated acreage, especially for permanent crops. This situation has reduced adaptation opportunities in the basin, which is currently experiencing a severe drought that, according to climate change projections, is expected to persist in the future, with important consequences for the sustainability of agriculture production.     

A Digitally Controlled Stimulator for Neurophysiological Applications

A stimulator circuit is presented which is capable of generating pulse train waveforms suitable for neurophysiological experiments are available, as well as special test conditions such as dishabituation. Digital and linear integrated circuits are used to provide precise control over the stimulus parameters.     

Online Engineering Education: Learning Anywhere,Anytime

The emergence of worldwide communications networks and powerful computer technologies has redefined the concept of distance learning and the delivery of engineering education content. This article discusses the Sloan Consortium's quest for quality, scale, and breadth in online learning, the impact on both continuing education of graduate engineers as well as degree‐seeking engineering students, and the future of engineering colleges and schools as worldwide providers of engineering education.     

Computer optimization of trailer suspensionsOptimisation par ordinateur des suspensions de remorque

This paper presents an optimization procedure which has been developed to select appropriate suspension design parameters for a simple two wheel trailer. A modern approach to the optimization problem has been used applying non-linear programming to the constrained search for the minimum of an objective function. The acceleration response to roadway input of selected points on the load of the trailer has been designated for minimization. This acceleration has an important significance to the trailer design because of its effect on the stable and smooth ride of the trailer. Two computational procedures have been used and the results compared. The first approach involves the linear superposition of responses to a series of discrete sinusoidal inputs while the second applies more contemporary random vibration theory using power spectral density curves to simulate the actual road surfaces. The results of the optimization procedure are then compared with the response characteristics of the original trailer design and demonstrate that a substantial improvement has been made.     

The Effect of Mn-rich Precipitates on the Strength of AZ31 Extrudates

The commercial magnesium alloy AZ31 has been subjected to a range of solution treatment regimes. These have then been extruded and their microstructure, texture, and precipitate populations characterized along with their mechanical properties. During the solution treatment, Mn-enriched particles develop and these remain largely unchanged throughout subsequent processing steps. A direct link between grain size and texture has been found, with coarser-grained specimens showing sharper textures. VPSC modeling has been used to quantify the effect of texture on the tensile yield strength, and it has been found that sharper textures have larger tensile yield strengths. Since coarser grain sizes have reduced Hall–Petch hardening, but have an additional texture-strengthening component, a region on the Hall–Petch plot for tension has been identified in which there is an insensitivity of strength to grain size. This has been quantitatively modeled and a texture-modified Hall–Petch plot for tension has been developed. The Mn-rich particles have also been shown to provide precipitate strengthening to the alloy of up to 40 MPa. The compressive behavior was clearer, with the compressive yield strength being directly correlated to grain size and unaffected by texture or precipitation hardening.     

Fine limestone additions to regulate setting in high volume fly ash mixtures

High volume fly ash (HVFA) concrete mixtures are being considered more frequently due to their cost and sustainability advantages. While the long term performance of these HVFA concretes typically meets or exceeds that of conventional concretes, their early age performance is often characterized by excessive retardation of the hydration reactions, delayed setting times, and low strengths. Extending an HVFA mixture to a ternary blend that incorporates a fine limestone powder may provide a viable solution to these deficiencies, particularly the hydration retardation and setting issues. In this paper, a nano-limestone powder and two other limestone fillers of increasing median particle size (4.4 μm and 16.4 μm) are investigated for their propensity to accelerate early age reactions and reduce setting times in a Class C fly ash/cement blend. The fineness of the limestone has measurable effects on its efficacy in accelerating hydration and decreasing setting times. Companion specimens prepared with a fine silica powder suggest that the fine limestone may act favorably through both a physical and a chemical mechanism. Isothermal calorimetry and Vicat needle penetration measurements on pastes are accompanied by strength measurements on mortars, to verify that the limestone powder substitutions are not negatively impacting strength development. A linear relationship with a reasonable correlation is found to exist between 1 d and 7 d compressive strengths of mortars and their accompanying cumulative heat release values as determined using isothermal calorimetry.     

Effect of Fiber Length on Carbon Nanotube-Induced Fibrogenesis

Given their extremely small size and light weight, carbon nanotubes (CNTs) can be readily inhaled by human lungs resulting in increased rates of pulmonary disorders, particularly fibrosis. Although the fibrogenic potential of CNTs is well established, there is a lack of consensus regarding the contribution of physicochemical attributes of CNTs on the underlying fibrotic outcome. We designed an experimentally validated in vitro fibroblast culture model aimed at investigating the effect of fiber length on single-walled CNT (SWCNT)-induced pulmonary fibrosis. The fibrogenic response to short and long SWCNTs was assessed via oxidative stress generation, collagen expression and transforming growth factor-beta (TGF-β) production as potential fibrosis biomarkers. Long SWCNTs were significantly more potent than short SWCNTs in terms of reactive oxygen species (ROS) response, collagen production and TGF-β release. Furthermore, our finding on the length-dependent in vitro fibrogenic response was validated by the in vivo lung fibrosis outcome, thus supporting the predictive value of the in vitro model. Our results also demonstrated the key role of ROS in SWCNT-induced collagen expression and TGF-β activation, indicating the potential mechanisms of length-dependent SWCNT-induced fibrosis. Together, our study provides new evidence for the role of fiber length in SWCNT-induced lung fibrosis and offers a rapid cell-based assay for fibrogenicity testing of nanomaterials with the ability to predict pulmonary fibrogenic response in vivo.