Static aeroelasticity of a composite oblique wing in transonic flows

One aircraft configuration that shows great promise in achieving high performance is that of an asymmetrically swept wing. When compared to conventional swept wings, these advantages include higher lift to drag ratios and reduced takeoff and landing speeds, which translate into greater performance in terms of fuel comsumption, loiter time, and range. However, the oblique wing has a number of disadvantages because of its asymmetric configuration. The question is how to best achieve maximum stability and roll equilibrium without compromising performance. Using aeroelastic tailoring to enhance aeroelastic stability and control has been demonstrated in several analyses, especially for the forward swept wing. The advantages and disadvantages for the oblique wing configuration are discussed

Segmented switchers and retailer pricing strategies

Empirical studies reveal a surprisingly wide variety of price promotion strategies among retailers, even among Internet sellers of undifferentiated homogenous goods such as books and music CD’s. Several empirical findings remain puzzling, particularly that within the same market some small retailers decide to deeply discount, while other small retailers forgo the price-sensitive switchers and price high to play their niche. We present theoretical and empirical analyses that address these varied pricing strategies. Our model of three asymmetric firms shows that under multiple switcher segments, where different switchers compare prices at different retailers, firm-specific loyalty is not sufficient to explain the variety of retailer pricing strategies. We demonstrate that a retailer’s pricing strategy is driven by the ratio of the size of switcher segments for which the retailer competes to its loyal segment size. The relative switcher-to-loyal ratios among retailers explain when a firm is more or less inclined to discount deeply or frequently. We thereby identify when a small firm finds it optimal to play the niche and price high, despite having few loyals, or to discount and go for the switchers. Our analysis reveals several interesting findings, such as a small firm that benefits from strategically limiting its access to switchers. The results of two empirical studies confirm our model’s predictions for varied retailer pricing strategies in the context of Internet booksellers

Segmented Switchers and Retailer Pricing Strategies

Empirical studies reveal a surprisingly wide variety of pricing strategies among retailers, even among Internet sellers of undifferentiated homogeneous goods, such as books and music CDs. Several empirical findings remain puzzling; for example, within the same market, some small retailers decide to discount deeply, whereas others forgo the price-sensitive switchers and price high. The authors present theoretical and empirical analyses that address these varied pricing strategies. A model of three asymmetric firms shows that under multiple switcher segments, in which different switchers compare prices at different retailers, firm-specific loyalty is not sufficient to explain the variety of pricing strategies. The authors demonstrate that a retailer's strategy to discount deeply or frequently is driven by the ratio of the size of switcher segments for which the retailer competes to its loyal segment size. The relative switcher-to-loyal ratios among retailers explain situations in which a small retailer finds it optimal to price high, despite having few loyals, or to discount and go for the switchers. The results of two empirical studies confirm the model's predictions for varied pricing strategies in the context of Internet booksellers. The analyses also present several implications. A small retailer can sometimes benefit from strategically limiting its access to switchers to soften price competition. A midsized retailer can benefit from targeting its switcher acquisition activities toward its larger rival, given the shallower discounts involved. When most switchers widely compare prices, a large retailer should offer few shallow discounts because other firms will more aggressively discount. The importance of switcher segmentation suggests that managers should carefully measure switching behavior in devising pricing strategies

Pricing best sellers and traffic generators: the role of asymmetric cross-selling

Among the many items online retailers sell, some stand out as best sellers and are often sold at considerable discounts. Best seller discounting can encourage customer traffic and the purchase of a basket of other products in the same transaction. Although most studies treat retailers as symmetric, the cross-selling potential is generally asymmetric across retailers, since some online retailers have more products to sell. In addition, the cross-selling effect works both ways – customers intending to buy a best seller may buy other items in their shopping basket, while other customers intending to buy a basket may buy a best seller while visiting the retailer. The authors model the pricing implications of this rich variety of asymmetric cross-selling, with both best sellers and typical baskets acting as traffic generators and cross-sold products. The common wisdom that loss leader pricing leads to neither a significant increase in store traffic nor an increase in profits does not apply in an asymmetric case where one retailer has more products to cross-sell. The cross-selling potential of products even far down the best seller list is demonstrated. Empirical analyses provide support for key findings of the theoretical model using book pricing and sales rank data from multiple online retailers

Functional identification and differential expression of 1-deoxy-D-xylulose 5-phosphate synthase in induced terpenoid resin formation of Norway spruce (Picea abies)

Conifers produce terpenoid-based oleoresins as constitutive and inducible defenses against herbivores and pathogens. Much information is available about the genes and enzymes of the late steps of oleoresin terpenoid biosynthesis in conifers, but almost nothing is known about the early steps which proceed via the methylerythritol phosphate (MEP) pathway. Here we report the cDNA cloning and functional identification of three Norway spruce (Picea abies) genes encoding 1-deoxy-D-xylulose 5-phosphate synthase (DXS), which catalyzes the first step of the MEP pathway, and their differential expression in the stems of young saplings. Among them are representatives of both types of plant DXS genes. A single type I DXS gene is constitutively expressed in bark tissue and not affected by wounding or fungal application. In contrast, two distinct type II DXS genes, PaDXS2A and PaDXS2B, showed increased transcript abundance after these treatments as did two other genes of the MEP pathway tested, 1-deoxy-D-xylulose 5-phosphate reductoisomerase (DXR) and 4-hydroxyl 3-methylbutenyl diphosphate reductase (HDR). We also measured gene expression in a Norway spruce cell suspension culture system that, like intact trees, accumulates monoterpenes after treatment with methyl jasmonate. These cell cultures were characterized by an up-regulation of monoterpene synthase gene transcripts and enzyme activity after elicitor treatment, as well as induced formation of octadecanoids, including jasmonic acid and 12-oxophytodienoic acid. Among the Type II DXS genes in cell cultures, PaDXS2A was induced by treatment with chitosan, methyl salicylate, and Ceratocystis polonica (a bark beetle-associated, blue-staining fungal pathogen of Norway spruce). However, PaDXS2B was induced by treatment with methyl jasmonate and chitosan, but was not affected by methyl salicylate or C. polonica. Our results suggest distinct functions of the three DXS genes in primary and defensive terpenoid metabolism in Norway spruce.The research reported in this paper was supported with funds from the Max Planck Society (to JG), Genome British Columbia and Genome Canada in support of the TREENOMIX:Conifer Forest Health Project (grant to JB), and the Natural Sciences and Engineering Council of Canada (NSERC, grant to JB). JB is an NSERC E.W.R. Steacie Memorial fellow.Peer reviewe

Does egg deposition by herbivorous pine sawflies affect transcription of sesquiterpene synthases in pine?

Scots pine (Pinus sylvestris; Pinaceae, Pinales) is known to defend against egg deposition by herbivorous sawflies by changing its terpenoid volatile blend. The oviposition-induced pine odor attracts egg parasitoids that kill the sawfly eggs. Here, we investigated whether sawfly egg deposition activates genes encoding pine terpene synthases by extracting mRNA from oviposition-induced P. sylvestris. Three new sesquiterpene synthases, PsTPS 1, PsTPS 2, and PsTPS 3, were isolated that were shown on heterologous expression in Escherichia coli to produce (E)-β-caryophyllene and α-humulene (PsTPS 1), 1(10),5-germacradiene-4-ol (PsTPS 2), and longifolene and α-longipinene (PsTPS 3) as their principal products. Quantitative RT-PCR analyses revealed that transcript levels of PsTPS 1 and PsTPS 2 were significantly higher in oviposition-induced twigs that were attractive to the parasitoids than in non-attractive, artificially damaged twigs. Thus, our results demonstrate a specific transcription response to egg deposition, distinct from that caused by artificial wounding. Transcripts of PsTPS 3 did not change in response to egg deposition. The transcript levels of PsTPS 1, PsTPS 2, and PsTPS 3 were also determined in relation to time after egg deposition, since pine odor is attractive to the parasitoid only 72 h after egg deposition. Transcription rates of PsTPS 1 and PsTPS 2 were significantly enhanced only 72 h after egg deposition, thus matching the timing of odor attractiveness, while for PsTPS 3, enhanced transcription was not detected at any time period studied after egg deposition. The ecological significance of the oviposition-induced increase of sesquiterpene synthase transcripts is discussed

Disconfirmed expectations and group decision behavior

Thesis (Ph. D.)--Massachusetts Institute of Technology, Sloan School of Management, 1996.Includes bibliographical references (p. 159-167).by Jonathan D. Bohlmann.Ph.D

Induction of Volatile Terpene Biosynthesis and Diurnal Emission by Methyl Jasmonate in Foliage of Norway Spruce

Terpenoids are characteristic constitutive and inducible defense chemicals of conifers. The biochemical regulation of terpene formation, accumulation, and release from conifer needles was studied in Norway spruce [Picea abies L. (Karst)] saplings using methyl jasmonate (MeJA) to induce defensive responses without inflicting physical damage to terpene storage structures. MeJA treatment caused a 2-fold increase in monoterpene and sesquiterpene accumulation in needles without changes in terpene composition, much less than the 10- and 40-fold increases in monoterpenes and diterpenes, respectively, observed in wood tissue after MeJA treatment (D. Martin, D. Tholl, J. Gershenzon, J. Bohlmann [2002] Plant Physiol 129: 1003–1018). At the same time, MeJA triggered a 5-fold increase in total terpene emission from foliage, with a shift in composition to a blend dominated by oxygenated monoterpenes (e.g. linalool) and sesquiterpenes [e.g. (E)-β-farnesene] that also included methyl salicylate. The rate of linalool emission increased more than 100-fold and that of sesquiterpenes increased more than 30-fold. Emission of these compounds followed a pronounced diurnal rhythm with the maximum amount released during the light period. The major MeJA-induced volatile terpenes appear to be synthesized de novo after treatment, rather than being released from stored terpene pools, because they are almost completely absent from needle oleoresin and are the major products of terpene synthase activity measured after MeJA treatment. Based on precedents in other species, the induced emission of terpenes from Norway spruce foliage may have ecological and physiological significance