抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

世界経済・社会統計 = World development indicators

Increasing population and consumption are placing unprecedented demands on agriculture and natural resources. Today, approximately a billion people are chronically malnourished while our agricultural systems are concurrently degrading land, water, biodiversity and climate on a global scale. To meet the world's future food security and sustainability needs, food production must grow substantially while, at the same time, agriculture's environmental footprint must shrink dramatically. Here we analyse solutions to this dilemma, showing that tremendous progress could be made by halting agricultural expansion, closing 'yield gaps' on underperforming lands, increasing cropping efficiency, shifting diets and reducing waste. Together, these strategies could double food production while greatly reducing the environmental impacts of agriculture.

https://escholarship.org/content/qt6xw5g085/qt6xw5g085.pdf?t=ovfwpc

Solutions for a cultivated planet

Most prior studies have found that substituting biofuels for gasoline will reduce greenhouse gases because biofuels sequester carbon through the growth of the feedstock. These analyses have failed to count the carbon emissions that occur as farmers worldwide respond to higher prices and convert forest and grassland to new cropland to replace the grain (or cropland) diverted to biofuels. By using a worldwide agricultural model to estimate emissions from land-use change, we found that corn-based ethanol, instead of producing a 20% savings, nearly doubles greenhouse emissions over 30 years and increases greenhouse gases for 167 years. Biofuels from switchgrass, if grown on U.S. corn lands, increase emissions by 50%. This result raises concerns about large biofuel mandates and highlights the value of using waste products.

/pdf/use-of-u-s-croplands-for-biofuels-increases-greenhouse-gases-48xnl16nx3.pdf

Use of U.S. Croplands for Biofuels Increases Greenhouse Gases Through Emissions from Land-Use Change

Sustainability is a key principle in natural resource management, and it involves operational efficiency, minimisation of environmental impact and socio-economic considerations; all of which are interdependent. It has become increasingly obvious that continued reliance on fossil fuel energy resources is unsustainable, owing to both depleting world reserves and the green house gas emissions associated with their use. Therefore, there are vigorous research initiatives aimed at developing alternative renewable and potentially carbon neutral solid, liquid and gaseous biofuels as alternative energy resources. However, alternate energy resources akin to first generation biofuels derived from terrestrial crops such as sugarcane, sugar beet, maize and rapeseed place an enormous strain on world food markets, contribute to water shortages and precipitate the destruction of the world's forests. Second generation biofuels derived from lignocellulosic agriculture and forest residues and from non-food crop feedstocks address some of the above problems; however there is concern over competing land use or required land use changes. Therefore, based on current knowledge and technology projections, third generation biofuels specifically derived from microalgae are considered to be a technically viable alternative energy resource that is devoid of the major drawbacks associated with first and second generation biofuels. Microalgae are photosynthetic microorganisms with simple growing requirements (light, sugars, CO 2 , N, P, and K) that can produce lipids, proteins and carbohydrates in large amounts over short periods of time. These products can be processed into both biofuels and valuable co-products. This study reviewed the technologies underpinning microalgae-to-biofuels systems, focusing on the biomass production, harvesting, conversion technologies, and the extraction of useful co-products. It also reviewed the synergistic coupling of microalgae propagation with carbon sequestration and wastewater treatment potential for mitigation of environmental impacts associated with energy conversion and utilisation. It was found that, whereas there are outstanding issues related to photosynthetic efficiencies and biomass output, microalgae-derived biofuels could progressively substitute a significant proportion of the fossil fuels required to meet the growing energy demand.

/pdf/biofuels-from-microalgae-a-review-of-technologies-for-1t1wwr5e69.pdf

Biofuels from microalgae—A review of technologies for production, processing, and extractions of biofuels and co-products

This report uses the CARD FAPRI model to evaluate the economy wide impacts of a disease outbreak that eliminates US pork and beef exports simultaneously and pork exports alone. In either case industry losses are enormous and spread well beyond the pork and beef sectors. Revenues fall significantly for poultry, corn and soybean producers and employment in rural areas is negatively impacted as the US pork and beef sectors are forced to downsize. Revenue losses in the combined US pork and beef industries fall by an average of $12.9 billion per year. The removal of this level of value added activity is equivalent to the loss of as many as 58,000 full time jobs. The report uses option prices to calculate the likelihood of a price impact of the magnitude reported here. This suggests a less than one percent possibility of an outbreak of this severity. Multiplying the probability of an outbreak times the reduction in pork industry net revenues over variable costs in the event of an outbreak, suggests that the annual benefit of eliminating the possibility of this outcome would be worth $137 million.

Economy Wide Impacts of a Foreign Animal Disease in the United States

Socioeconomic and Environmental Impacts of Biofuels: Implications of Global Ethanol Expansion on Brazilian Regional Land use

We analyse the consequences on agricultural markets of enlargement of the European Union (EU) to include the Czech Republic, Hungary, and Poland. We produce a market outlook up to 2010 for two enlargement scenarios assuming different policy restrictions on grain and dairy production in the acceding countries. Accession of the three Central and Eastern European countries (CEECs) leads to a permanent but moderate decrease in EU prices for most commodities. In the three acceding CEECs, domestic prices increase drastically, final consumption of agricultural products decreases in most instances, while production increases. Higher domestic prices in the CEECs reduce exports of most commodities to non-union countries. Consequently, excess supplies are placed in stocks or exported to the original 15 member countries. Supply management mechanisms in the dairy and grain sectors would reduce the build-up of surpluses in the new member states, but limit their ability to take advantage of the expanded market. Accession of the three CEECs would increase the CAP budget over its proposed maximum if area payments are extended to incoming crop producers.

Accession of the Czech Republic, Hungary and Poland to the European Union: Impacts on Agricultural Markets

The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, gender, religion, age, disability, political beliefs, sexual orientation, and marital or family status. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA’s TARGET Center at (202) 720-2600 (voice and TDD). To file a complaint of discrimination, write USDA, Director, Office of Civil Rights, Room 326-W, Whitten Building, 14th and Independence Avenue, SW, Washington, DC 20250-9410 or call (202) 720-5964 (voice and TDD). USDA is an equal opportunity provider and employer.

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1012&context=card_staffreports

An analysis of the proposed doha round modalities

This analysis uses the 2011 FAPRI-CARD (Food and Agricultural Policy Research Instituteâ€“Center for Agricultural and Rural Development) baseline to evaluate the impact of four alternative scenarios on U.S. and world agricultural markets, as well as on world fertilizer use and world agricultural greenhouse gas emissions. A key assumption in the 2011 baseline is that ethanol support policies disappear in 2012. The baseline also assumes that existing biofuel mandates remain in place and are binding. Two of the scenarios are adverse supply shocks, the first being a 10% increase in the price of nitrogen fertilizer in the United States, and the second, a reversion of cropland into forestland. The third scenario examines how lower energy prices would impact world agriculture. The fourth scenario reintroduces biofuel tax credits and duties. Given that the baseline excludes these policies, the fourth scenario is an attempt to understand the impact of these policies under the market conditions that prevail in early 2011. A key to understanding the results of this fourth scenario is that in the absence of tax credits and duties, the mandate drives biofuel use. Therefore, when the tax credits and duties are reintroduced, the impacts are relatively small. In general, the results show that the entire international commodity market system is remarkably robust with respect to policy changes in one country or in one sector. The policy implication is that domestic policy changes implemented by a large agricultural producer like the United States can have fairly significant impacts on the aggregate world commodity markets. A second point that emerges from the results is that the law of unintended consequences is at work in world agriculture. For example, a U.S. nitrogen tax that might presumably be motivated for environmental benefit results in an increase in world greenhouse gas emissions. A similar situation occurs in the afforestation scenario in which crop production shifts from high-yielding land in the United States to low-yielding land and probably native vegetation in the rest of the world, resulting in an unintended increase in global greenhouse gas emissions.

Jacinto F. Fabiosa

Papers

Economy Wide Impacts of a Foreign Animal Disease in the United States

Socioeconomic and Environmental Impacts of Biofuels: Implications of Global Ethanol Expansion on Brazilian Regional Land use

Accession of the Czech Republic, Hungary and Poland to the European Union: Impacts on Agricultural Markets

An analysis of the proposed doha round modalities

Greenhouse Gas and Nitrogen Fertilizer Scenarios for U.S. Agriculture and Global Biofuels