983 research outputs found
The Impact of Biofuels Policy on Agribusiness Stock Prices
Corn markets are important for many industries. These include the seed, fertilizer, meat production/processing and agricultural machinery sectors, all of which are highly concentrated. Oligopoly theory suggests that corn input and field equipment suppliers likely benefit from policies that support corn markets, such as U.S. biofuels policy, while meat companies likely lose. This study investigates the impact of biofuels policy on U.S. agribusiness stock prices. Corn futures prices are found to have a structural change in November 2006, consistent with the expansion of U.S. biofuels policy support. A linear two-factor (S&P500 and corn prices) equilibrium asset pricing model is estimated on two subsamples, one before and one after the estimated change point. Conditional heteroskedasticity in stock returns is accounted for using a GARCH(1,1) model. In the more recent period, corn price increases are found to have positive effects on excess stock returns for seed, fertilizer and machinery companies, while the impact on meat companies is negative. The results may be interpreted as evidence that crop input suppliers gain from U.S. biofuels policies while meat processors lose.Biofuels policy, excess stock returns, GARCH effect, linear factor model., Agribusiness, Agricultural and Food Policy, Agricultural Finance, D43, L13, Q14,
Endo-pectinase Production by Bacillus pumilus NRRL B-212 and Optimization by RSM using Sugar Beet Pulp
The present study aimed at optimization of culture conditions for endo-pectinase production by Bacillus pumilus NRRL B-212. In the first stage of the study,
submerged fermentation experiments were performed to investigate effects of initial pH, carbon and nitrogen sources, salts and phosphate on endo-pectinase activity and maximum enzyme production was at pH: 8. The effect of initial pectin concentration on enzyme production was examined, and 1 % (w/v) pectin concentration was selected as the optimum pectin concentration. Yeast extract, (NH4)2SO4, and peptone were used as nitrogen sources, and the medium containing 0.05 % (w/v) ammonium sulphate was the medium where maximum activity was achieved. In the experiments investigating the effect of salts, the maximum activity value was determined in the medium containing 0.02 % NaCl. In addition, the effect of phosphate concentration on enzyme production was investigated, and the highest endo-pectinase activity was determined in medium containing 0.3 % K2HPO4 + 0.15 % KH2PO4. In the second stage of the study, solid-state fermentation studies were performed, and sugar beet pulp was used as agricultural waste. In order to obtain maximum endo-pectinase production and reveal the parameters influencing enzyme activity using sugar beet pulp, a Central Composite Design (CCD) was applied. The highest endo-pectinase activity was obtained as 147.75 U mL–1 in medium containing 6.78 % sugar beet pulp, 0.48 % (NH4)2SO4 and 0.12 % yeast extract.
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Characterizing the Cauline Domatia of Two Newly Discovered Ecuadorian Ant Plants in Piper: An Example of Convergent Evolution
The stems of some myrmecophytes in Piper are used as domatia by resident ant colonies. Hollow, ant-occupied stems were previously known only in four species of southern Central American Piper, all members of Section Macrostachys. Here we present two additional, unrelated, hollow-stemmed myrmecophytes from Ecuador: P. immutatum and P. pterocladum (members of sections Radula and Peltobryon, respectively). Although similar superficially, stem cavities of the Ecuadorian Piper species differ morphologically and developmentally from those of Central American taxa. The stem cavities of P. immutatum, and possibly P. pterocladum, are formed during stem development, and begin forming only a few millimeters behind the apical meristem. This mode of cavity formation differs markedly from myrmecophytes in section Macrostachys, where the stems remain solid unless excavated by the specialized ant partner Pheidole bicornis. The stems of P. immutatum and P. pterocladum do not produce wound-response tissue around the cavity, unlike the stems in section Macrostachys. The entrance holes in stems of P. immutatum are formed through apoptotic processes and are located at each node below the petiole, whereas those in section Macrostachys are excavated by the ants in the leaf axil. This study documents convergent evolution of ant-plant associations in Piper, and emphasizes the need for careful comparison of apparently homologous, ant-associated structures in specialized myrmecophytes
Orientational phase transitions in the hexagonal phase of a diblock copolymer melt under shear flow
We generalize the earlier theory by Fredrickson [J. Rheol. v.38, 1045 (1994)]
to study the orientational behaviour of the hexagonal phase of diblock
copolymer melt subjected to steady shear flow. We use symmetry arguments to
show that the orientational ordering in the hexagonal phase is a much weaker
effect than in the lamellae. We predict the parallel orientation to be stable
at low and the perpendicular orientation at high shear rates. Our analysis
reproduces the experimental results by Tepe et al. [Macromolecules v.28, 3008
(1995)] and explains the difficulties in experimental observation of the
different orientations in the hexagonal phase.Comment: 21 pages, 6 eps figures, submitted to Physical Review
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Selection of the best proper DC-SQUIDs in a multi-SQUID configuration
We have carried out experimental investigation of multi-DC-SQUID magnetometer configuration fabricated on YBa2Cu30 7-δ thin films onto 24 degree SrTiO3 bicrystal substrates by directly coupling the pick-up loop to DC-SQUIDs. The layout of the magnetometer pick-up loop was chosen as a square washer configuration by maximizing loop effective area and minimizing loop inductance. We have used De-Magnetron Sputtering technique for deposition of the films and chemical etching process for patterning the Josephson junctions having 4 μm widths. The use of multi-SQUID configuration is related to the selection of the best proper junctions for SQUID to improve the chip sensitivity with selectivity option of choosing the squid junctions rather than multichannel operation. Selection of the best junctions compared to each other depending on the junction critical currents and noise levels caused by the fabrication process and placements of the junctions on the grain boundary enable having an increased output signal of the DC-SQUID. © 2007 IEEE
Induction of tolerogenic lung CD4+ T cells by local treatment with a pSTAT-3 and pSTAT-5 inhibitor ameliorated experimental allergic asthma
Signal transducer and activator of transcription (STAT)-3 inhibitors play an important role in regulating immune responses. Galiellalactone (GL) is a fungal secondary metabolite known to interfere with the binding of phosphorylated signal transducer and activator of transcription (pSTAT)-3 as well of pSTAT-6 dimers to their target DNA in vitro. Intra nasal delivery of 50 μg GL into the lung of naive Balb/c mice induced FoxP3 expression locally and IL-10 production and IL-12p40 in RNA expression in the airways in vivo. In a murine model of allergic asthma, GL significantly suppressed the cardinal features of asthma, such as airway hyperresponsiveness, eosinophilia and mucus production, after sensitization and subsequent challenge with ovalbumin (OVA). These changes resulted in induction of IL-12p70 and IL-10 production by lung CD11c+ dendritic cells (DCs) accompanied by an increase of IL-3 receptor α chain and indoleamine-2,3-dioxygenase expression in these cells. Furthermore, GL inhibited IL-4 production in T-bet-deficient CD4+ T cells and down-regulated the suppressor of cytokine signaling-3 (SOCS-3), also in the absence of STAT-3 in T cells, in the lung in a murine model of asthma. In addition, we found reduced amounts of pSTAT-5 in the lung of GL-treated mice that correlated with decreased release of IL-2 by lung OVA-specific CD4+ T cells after treatment with GL in vitro also in the absence of T-bet. Thus, GL treatment in vivo and in vitro emerges as a novel therapeutic approach for allergic asthma by modulating lung DC phenotype and function resulting in a protective response via CD4+FoxP3+ regulatory T cells locall
Influence of confinement on the orientational phase transitions in the lamellar phase of a block copolymer melt under shear flow
In this work we incorporate some real-system effects into the theory of
orientational phase transitions under shear flow (M. E. Cates and S. T. Milner,
Phys. Rev. Lett. v.62, p.1856 (1989) and G. H. Fredrickson, J. Rheol. v.38,
p.1045 (1994)). In particular, we study the influence of the shear-cell
boundaries on the orientation of the lamellar phase. We predict that at low
shear rates the parallel orientation appears to be stable. We show that there
is a critical value of the shear rate at which the parallel orientation loses
its stability and the perpendicular one appears immediately below the spinodal.
We associate this transition with a crossover from the fluctuation to the
mean-field behaviour. At lower temperatures the stability of the parallel
orientation is restored. We find that the region of stability of the
perpendicular orientation rapidly decreases as shear rate increases. This
behaviour might be misinterpreted as an additional perpendicular to parallel
transition recently discussed in literature.Comment: 25 pages, 4 figures, submitted to Phys. Rev.
Dependence of Josephson junction critical current on the deposition rate of YBa2Cu3O7-δ thin films
We have reported the effect of YBa2Cu3O 7-δ (YBCO) thin film deposition rate on the 24 and 30 degree STO bicrystal Josephson junctions critical currents by fabricating series of junctions with different deposition rates. Dependence of YBCO thin film structures on the deposition rate was investigated. We have observed that the critical currents of junctions are strongly affected by the thin film deposition rate. © 2007 American Institute of Physics
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