Analysis of plant nutrient management strategies: Conventional and alternative approaches

During times of economic uncertainty, such as the current period, all costs of agricultural production become important and worthy of close scrutiny if the threat of farm foreclosures is to be minimized. This concern particularly applies to the cost of plant nutrients, which, under conventional approaches, typically represents 24%–30% (or more) of the total variable costs of production [Lu et al. (2000) Food Reviews International 16(2): 121–157; Bullen and Brown (2001) Economic Evaluation of UNR Cotton, NC State University, Raleigh, North Carolina]. The purpose of this paper is to examine, via a review of the literature, the economics and profitability of various plant nutrient management strategies–both conventional and alternative ones–in an attempt to identify those strategies that can lead to financial resource optimization and, ultimately, maximum profits for farm enterprises. The results of this analysis are as follows: In a meta-analysis of 120 studies, conventional nutrient management systems, using commercial fertilizers, showed higher profit for most grain crops (with the exception of corn and sorghum), than organic nutrient management systems. Both cover crop and animal manure-based systems show considerable promise as alternative nutrient management strategies for increasing farm profitability. A cover crop system produced the highest average corn yield and gross margin per hectare with the smallest coefficient of variation compared to no-tillage conventional, manure-based, or crownvetch systems. Manure-based systems that do not require purchase or transport of the manure (as in combined animal and crop production systems) can be considerably more profitable than conventional systems. Both manure-based and cover crop systems that do not include the use of commercial fertilizers (i.e., organic systems), hold particular promise due to the output price premiums typically garnered by the organic crops grown under such conditions.     

Astrophysical observations: lensing and eclipsing Einstein's theories

Albert Einstein postulated the equivalence of energy and mass, developed the theory of special relativity, explained the photoelectric effect, and described Brownian motion in five papers, all published in 1905, 100 years ago. With these papers, Einstein provided the framework for understanding modern astrophysical phenomena. Conversely, astrophysical observations provide one of the most effective means for testing Einstein's theories. Here, I review astrophysical advances precipitated by Einstein's insights, including gravitational redshifts, gravitational lensing, gravitational waves, the Lense-Thirring effect, and modern cosmology. A complete understanding of cosmology, from the earliest moments to the ultimate fate of the universe, will require developments in physics beyond Einstein, to a unified theory of gravity and quantum physics.     

Periodically triggered seismicity at Mount Wrangell, Alaska, after the Sumatra earthquake

As surface waves from the 26 December 2004 earthquake in Sumatra swept across Alaska, they triggered an 11-minute swarm of 14 local earthquakes near Mount Wrangell, almost 11,000 kilometers away. Earthquakes occurred at intervals of 20 to 30 seconds, in phase with the largest positive vertical ground displacements during the Rayleigh surface waves. We were able to observe this correlation because of the combination of unusually long surface waves and seismic stations near the local earthquakes. This phase of Rayleigh wave motion was dominated by horizontal extensional stresses reaching 25 kilopascals. These observations imply that local events were triggered by simple shear failure on normal faults.     

Local macrophage proliferation, rather than recruitment from the blood, is a signature of TH2 inflammation

A defining feature of inflammation is the accumulation of innate immune cells in the tissue that are thought to be recruited from the blood. We reveal that a distinct process exists in which tissue macrophages undergo rapid in situ proliferation in order to increase population density. This inflammatory mechanism occurred during T helper 2 (T(H)2)-related pathologies under the control of the archetypal T(H)2 cytokine interleukin-4 (IL-4) and was a fundamental component of T(H)2 inflammation because exogenous IL-4 was sufficient to drive accumulation of tissue macrophages through self-renewal. Thus, expansion of innate cells necessary for pathogen control or wound repair can occur without recruitment of potentially tissue-destructive inflammatory cells.     

Rapid pneumococcal evolution in response to clinical interventions

Epidemiological studies of the naturally transformable bacterial pathogen Streptococcus pneumoniae have previously been confounded by high rates of recombination. Sequencing 240 isolates of the PMEN1 (Spain(23F)-1) multidrug-resistant lineage enabled base substitutions to be distinguished from polymorphisms arising through horizontal sequence transfer. More than 700 recombinations were detected, with genes encoding major antigens frequently affected. Among these were 10 capsule-switching events, one of which accompanied a population shift as vaccine-escape serotype 19A isolates emerged in the USA after the introduction of the conjugate polysaccharide vaccine. The evolution of resistance to fluoroquinolones, rifampicin, and macrolides was observed to occur on multiple occasions. This study details how genomic plasticity within lineages of recombinogenic bacteria can permit adaptation to clinical interventions over remarkably short time scales.     

Computational design of peptides that target transmembrane helices

A variety of methods exist for the design or selection of antibodies and other proteins that recognize the water-soluble regions of proteins; however, companion methods for targeting transmembrane (TM) regions are not available. Here, we describe a method for the computational design of peptides that target TM helices in a sequence-specific manner. To illustrate the method, peptides were designed that specifically recognize the TM helices of two closely related integrins (alphaIIbbeta3 and alphavbeta3) in micelles, bacterial membranes, and mammalian cells. These data show that sequence-specific recognition of helices in TM proteins can be achieved through optimization of the geometric complementarity of the target-host complex.