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

Global food demand is increasing rapidly, as are the environmental impacts of agricultural expansion. Here, we project global demand for crop production in 2050 and evaluate the environmental impacts of alternative ways that this demand might be met. We find that per capita demand for crops, when measured as caloric or protein content of all crops combined, has been a similarly increasing function of per capita real income since 1960. This relationship forecasts a 100–110% increase in global crop demand from 2005 to 2050. Quantitative assessments show that the environmental impacts of meeting this demand depend on how global agriculture expands. If current trends of greater agricultural intensification in richer nations and greater land clearing (extensification) in poorer nations were to continue, ∼1 billion ha of land would be cleared globally by 2050, with CO2-C equivalent greenhouse gas emissions reaching ∼3 Gt y−1 and N use ∼250 Mt y−1 by then. In contrast, if 2050 crop demand was met by moderate intensification focused on existing croplands of underyielding nations, adaptation and transfer of high-yielding technologies to these croplands, and global technological improvements, our analyses forecast land clearing of only ∼0.2 billion ha, greenhouse gas emissions of ∼1 Gt y−1, and global N use of ∼225 Mt y−1. Efficient management practices could substantially lower nitrogen use. Attainment of high yields on existing croplands of underyielding nations is of great importance if global crop demand is to be met with minimal environmental impacts.

https://www.pnas.org/content/pnas/108/50/20260.full.pdf

Global food demand and the sustainable intensification of agriculture

Humans continue to transform the global nitrogen cycle at a record pace, reflecting an increased combustion of fossil fuels, growing demand for nitrogen in agriculture and industry, and pervasive inefficiencies in its use. Much anthropogenic nitrogen is lost to air, water, and land to cause a cascade of environmental and human health problems. Simultaneously, food production in some parts of the world is nitrogen-deficient, highlighting inequities in the distribution of nitrogen-containing fertilizers. Optimizing the need for a key human resource while minimizing its negative consequences requires an integrated interdisciplinary approach and the development of strategies to decrease nitrogen-containing waste.

/pdf/transformation-of-the-nitrogen-cycle-recent-trends-questions-3hakfwkgng.pdf

Transformation of the Nitrogen Cycle: Recent Trends, Questions, and Potential Solutions

This paper contrasts the natural and anthropogenic controls on the conversion of unreactive N2 to more reactive forms of nitrogen (Nr). A variety of data sets are used to construct global N budgets for 1860 and the early 1990s and to make projections for the global N budget in 2050. Regional N budgets for Asia, North America, and other major regions for the early 1990s, as well as the marine N budget, are presented to highlight the dominant fluxes of nitrogen in each region. Important findings are that human activities increasingly dominate the N budget at the global and at most regional scales, the terrestrial and open ocean N budgets are essentially dis- connected, and the fixed forms of N are accumulating in most environmental reservoirs. The largest uncertainties in our understanding of the N budget at most scales are the rates of natural biological nitrogen fixation, the amount of Nr storage in most environmental reservoirs, and the production rates of N2 by denitrification.

/pdf/nitrogen-cycles-past-present-and-future-1zdbw0976r.pdf

Nitrogen cycles: past, present, and future

When a person looks at an object while exploring it with their hand, vision and touch both provide information for estimating the properties of the object. Vision frequently dominates the integrated visual-haptic percept, for example when judging size, shape or position, but in some circumstances the percept is clearly affected by haptics. Here we propose that a general principle, which minimizes variance in the final estimate, determines the degree to which vision or haptics dominates. This principle is realized by using maximum-likelihood estimation to combine the inputs. To investigate cue combination quantitatively, we first measured the variances associated with visual and haptic estimation of height. We then used these measurements to construct a maximum-likelihood integrator. This model behaved very similarly to humans in a visual-haptic task. Thus, the nervous system seems to combine visual and haptic information in a fashion that is similar to a maximum-likelihood integrator. Visual dominance occurs when the variance associated with visual estimation is lower than that associated with haptic estimation.

Humans integrate visual and haptic information in a statistically optimal fashion.

Baojing Gu,1,2,* Hans J.M. van Grinsven,3 Shu Kee Lam,4 Oene Oenema,5 Mark A. Sutton,6 Arvin Mosier,4 and Deli Chen4,* 1College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, PR China 2Policy Simulation Laboratory, Zhejiang University, 310058 Hangzhou, China 3Netherlands Environmental Assessment Agency (PBL), Postbus 30314, The Netherlands 4School of Agriculture and Food, The University of Melbourne, Melbourne, VIC 3010 Australia 5Wageningen University & Research, P.O. Box 47, 6700 AA, Wageningen, The Netherlands 6NERC Centre for Ecology & Hydrology, Bush Estate, Penicuik, EH26 0QB, UK *Correspondence: bjgu@zju.edu.cn (B.G.); delichen@unimelb.edu.au (D.C.) Received: November 6, 2020; Accepted: January 5, 2021; Published Online: January 6, 2021; https://doi.org/10.1016/j.xinn.2021.100079 a 2021 The Author(s). This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Citation: Gu B., van Grinsven H.J.M., Lam S.K., et al. (2021). A Credit System to Solve Agricultural Nitrogen Pollution. The Innovation 2(1), 100079.

A Credit System to Solve Agricultural Nitrogen Pollution.

The effectiveness of two polyolefin coated products, ‘Meister 70’ and ‘Meister 270’, as slow-release sources of nitrogen (N) for irrigated cotton, and uncoated calcium carbide as a source of acetylene to inhibit nitrification of urea-N and reduce losses by denitrification were studied. The crop was grown on a grey clay in the Namoi Valley of north western New South Wales. The fertilisers were applied at 50 and 150 kg N/ha, combined factorialy with two application times, either pre- or post-sowing. Meister 270 did not release N fast enough to supply the plant’s requirements, and is not recommended as a source of N for cotton. Meister 70 was worthy of further study as a pre-sowing source of N because it maintained a higher concentration of ammonium in the soil for longer than urea, resulted in lower soil nitrate concentrations at all times, and increased the apparent recovery efficiency of fertilizer N. The uncoated calcium carbide was not as effective as the wax-coated material tested in previous studies.

Evaluation of a polyolefin coated urea (Meister) as a fertilizer for irrigated cotton

Field measurement of denitrification.

Diffusion of Soil Extracts for Nitrogen and Nitrogen‐15 Analyses by Automated Combustion/Mass Spectrometry

Publisher Summary
This chapter provides an overview of the DAYCENT ecosystem model and describes the nitrogen gas sub-model of DAYCENT. The model was used to explore how land use, precipitation, and soil texture impact total nitrogen losses and nitrogen gas emissions at the national scale using county level resolution simulations of cropped lands, grazed land, and native vegetation. Total nitrogen losses and the proportion of total losses due to NO3 leaching both tended to increase with nitrogen inputs. At the national scale, NO3 leaching was the major loss vector for both native and cropped/grazed systems because both nitrogen inputs and leaching are positively correlated with water inputs. However, leaching was responsible for less than half of total nitrogen losses for ∼50% of the counties under native vegetation and ∼15% of the counties for cropped/grazed systems.

/pdf/chapter-18-daycent-simulated-effects-of-land-use-and-climate-jairo5zqfs.pdf

Arvin R. Mosier

Papers

A Credit System to Solve Agricultural Nitrogen Pollution.

Evaluation of a polyolefin coated urea (Meister) as a fertilizer for irrigated cotton

Field measurement of denitrification.

Diffusion of Soil Extracts for Nitrogen and Nitrogen‐15 Analyses by Automated Combustion/Mass Spectrometry

Chapter 18. DAYCENT Simulated Effects of Land Use and Climate on County Level N Loss Vectors in the USA