Agricultural adaptation to climate policies under technical change

This study uses a partial equilibrium model of the US agricultural sector to examine how technical progress and carbon price levels affect land management adaptation. We find that the climate policy range, over which a more extensive agriculture is preferred, decreases as crop yields increase. Second, technical progress with traditional crops offers less mitigation benefits than progress with mitigation options themselves. Third, while agricultural producers benefit from technical progress on energy crops, they fare worse if technical progress improves traditional crops and low carbon prices.Technical Change, Producer Adaptation, Agricultural Sector Model, Carbon Sequestration, Mathematical Programming, Climate Policy Simulation

Remarks on a generalization of the Davenport constant

A generalization of the Davenport constant is investigated. For a finite abelian group $G$ and a positive integer $k$, let $D_k(G)$ denote the smallest $\ell$ such that each sequence over $G$ of length at least $\ell$ has $k$ disjoint non-empty zero-sum subsequences. For general $G$, expanding on known results, upper and lower bounds on these invariants are investigated and it is proved that the sequence $(D_k(G))_{k\in\mathbb{N}}$ is eventually an arithmetic progression with difference $\exp(G)$, and several questions arising from this fact are investigated. For elementary 2-groups, $D_k(G)$ is investigated in detail; in particular, the exact values are determined for groups of rank four and five (for rank at most three they were already known).Comment: Various expository changes, updated and slightly expanded bibliograph

Dendritic cells in dengue virus infection: Targets of virus replication and mediators of immunity

Dendritic cells (DCs) are sentinels of the immune system and detect pathogens at sites of entry, such as the skin. In addition to the ability of DCs to control infections directly via their innate immune functions, DCs help to prime adaptive B and T cell responses via antigen presentation in lymphoid tissues. Infected Aedes aegypti or Ae. albopictus mosquitoes transmit the four dengue virus (DENV) serotypes to humans while probing for small blood vessels in the skin. DENV causes the most prevalent arthropod-borne viral disease in humans, yet no vaccine or specific therapeutic is currently approved. Although primary DENV infection confers life-long protective immunity against re-infection with the same DENV serotype, secondary infection with a different DENV serotype can lead to increased disease severity via cross-reactive T cells or enhancing antibodies. This review summarizes recent findings in humans and animal models about DENV infection of DCs, monocytes and macrophages. We discuss the dual role of DCs as both targets of DENV replication and mediators of innate and adaptive immunity, and summarize immune evasion strategies whereby DENV impairs the function of infected DCs. We suggest that DCs play a key role in priming DENV-specific neutralizing or potentially harmful memory B and T cell responses, and that future DC-directed therapies may help induce protective memory responses and reduce dengue pathogenesis

Myeloid cells in tumor inflammation

Bone marrow derived myeloid cells progressively accumulate in tumors, where they establish an inflammatory microenvironment that is favorable for tumor growth and spread. These cells are comprised primarily of monocytic and granulocytic myeloid derived suppressor cells (MDSCs) or tumor-associated macrophages (TAMs), which are generally associated with a poor clinical outcome. MDSCs and TAMs promote tumor progression by stimulating immunosuppression, neovascularization, metastasis and resistance to anti-cancer therapy. Strategies to target the tumor-promoting functions of myeloid cells could provide substantial therapeutic benefit to cancer patients

Analytical Rebridging Monte Carlo: Application to cis/trans Isomerization in Proline-Containing, Cyclic Peptides

We present a new method, the analytical rebridging scheme, for Monte Carlo simulation of proline-containing, cyclic peptides. The cis/trans isomerization is accommodated by allowing for two states of the amide bond. We apply our method to five peptides that have been previously characterized by NMR methods. Our simulations achieve effective equilibration and agree well with experimental data in all cases. We discuss the importance of effective equilibration and the role of bond flexibility and solvent effects on the predicted equilibrium properties.Comment: 29 pages, 8 PostScript figures, LaTeX source. to appear in J. Chem. Phys., 199

The interdependencies between food and biofuel production in European agriculture - an application of EUFASOM

In the continuous quest to reduce anthropogenic emissions of carbon dioxide, the production and use of organically grown fuels in Europe has increased in importance in the recent past. However, the production of so-called biofuels is a direct competitor of agricultural food production for land, labor, water resources etc. with both land use options influencing each other depending on the respective boundary conditions defined by political regulations and economic considerations. In this study we will explore the economic and technical potentials of biofuels in Europe as well as the interdependencies between these two land use options for different economic incentives for biofuels using the European Forest and Agriculture Sector Optimization Model (EUFASOM). Key data on biodiesel and ethanol production have been gathered and are used for calibration of the model. The simulations extend until the year 2030, for which results are presented. Results indicate that moderate production targets of biofuels lead to an expansion of mainly the biodiesel production while more ambitious targets call for a focus on bioethanol. This has to do with the different levels of production efficiency depending on the production output. Growth of bioethanol feedstock is spread over entire Europe while the production of biodiesel feedstock occurs mainly in Central Europe.biodiesel, bioethanol, Europe, EUFASOM, modeling

The Internal Extinction Curve of NGC 6302 and its Extraordinary Spectrum

In this paper we present a new method for obtaining the optical wavelength-dependent reddening function of planetary nebulae, using the nebular and stellar continuum. The data used was a spectrum of NGC 6302 obtained with a mean signal to noise of >10^2 A^-1 in the nebular continuum. With such a high S/N the continuum can be accurately compared with a theoretical model nebular plus stellar continuum. The nebular electron temperature and density used in the model are determined using ratios of prominent emission lines. The reddening function can then be obtained from the ratio of the theoretical and the observed continuum. We find that for NGC 6302, the visible to IR extinction law is indistinguishable from `standard' interstellar reddening, but that the UV extinction curve is much steeper than normal, suggesting that more small dust grains had been ejected into the nebula by the PN central star. Finally, using the extinction law that we have determined, we present a complete de--reddened line list of nearly 600 emission lines, and report on the detection of the He(2-10) and He(2-8) Raman Features at 4331 A and 4852 A, and the detection of Raman-Scattered OVI features at 6830 and 7087 AA.Comment: 32 pages, 7 figures, to appear in PASA 2002, 1