Step Two in Flood Recovery of Pastures Is Renovation

As flood waters recede, the renovation of flooded pastures is just beginning. Now is a good time to check pasture plants for survival. Forage production is a function of the plant species, and their density and growth. Evaluate live plants (plant vigor), plant density, and desirable species versus weeds

Enhancing the Value of Cover Crops through Utilization by Beef Stocker Cattle: Progress Report (Year 2)

The increase in cover crops across Iowa presents a substantial amount of potential forage available to the beef industry that would otherwise go unutilized. While the benefits of improved soil health and nutrient retention through cover crops are well known, limited data are available on utilization by beef cattle. Thus, a study was designed to measure cattle performance while spring grazing cereal rye and to evaluate the impact grazing had on the soil profile. Preliminary data suggests that with proper supplementation, cattle grazing cereal rye may achieve average daily gains of 1.5 to 3.0 lb/d. Initial analysis of soil bulk density indicates minimal negative changes in compaction due to grazing. Because many variables impact the successful integration of cover crops and livestock into row crops, this is a four-year study summarizing data from year two

Dark energy and the evolution of spherical overdensities

We use the non-linear spherical model in cold dark matter (CDM) cosmologies with dark energy to investigate the effects of dark energy on the growth of structure and the formation of virialised structures. We consider dark energy models with a constant equation of state parameter w. For -1<w<-1/3, clusters form earlier and are more concentrated in quintessence than in LambdaCDM models, but they form later and are less concentrated than in the corresponding open model with the same matter density and no dark energy. We point out some confusion in the literature around the expression of the collapse factor (ratio of the radius of the sphere at virialisation to that at turn-around) derived from the virial theorem. We use the Sheth & Tormen extension of the Press-Schechter framework to calculate the evolution of the cluster abundance in different models and show the sensitivity of the cluster abundance to both the amplitude of the mass fluctuations, sigma8, and the sigma8-w normalisation, selected to match either the cosmic microwave background observations or the abundance of X-ray clusters.Comment: 9 pages, 8 figures. Accepted for publication in MNRA

Scientific Goals and Objectives for the Human Exploration of Mars: 1. Biology and Atmosphere/Climate

To prepare for the exploration of Mars by humans, as outlined in the new national vision for Space Exploration (VSE), the Mars Exploration Program Analysis Group (MEPAG), chartered by NASA's Mars Exploration Program (MEP), formed a Human Exploration of Mars Science Analysis Group (HEM-SAG), in March 2007. HEM-SAG was chartered to develop the scientific goals and objectives for the human exploration of Mars based on the Mars Scientific Goals, Objectives, Investigations, and Priorities.1 The HEM-SAG is one of several humans to Mars scientific, engineering and mission architecture studies chartered in 2007 to support NASA s plans for the human exploration of Mars. The HEM-SAG is composed of about 30 Mars scientists representing the disciplines of Mars biology, climate/atmosphere, geology and geophysics from the U.S., Canada, England, France, Italy and Spain. MEPAG selected Drs. James B. Garvin (NASA Goddard Space Flight Center) and Joel S. Levine (NASA Langley Research Center) to serve as HEMSAG co-chairs. The HEM-SAG team conducted 20 telecons and convened three face-to-face meetings from March through October 2007. The management of MEP and MEPAG were briefed on the HEM-SAG interim findings in May. The HEM-SAG final report was presented on-line to the full MEPAG membership and was presented at the MEPAG meeting on February 20-21, 2008. This presentation will outline the HEM-SAG biology and climate/atmosphere goals and objectives. A companion paper will outline the HEM-SAG geology and geophysics goals and objectives

Sixteen diverse laboratory mouse reference genomes define strain-specific haplotypes and novel functional loci.

We report full-length draft de novo genome assemblies for 16 widely used inbred mouse strains and find extensive strain-specific haplotype variation. We identify and characterize 2,567 regions on the current mouse reference genome exhibiting the greatest sequence diversity. These regions are enriched for genes involved in pathogen defence and immunity and exhibit enrichment of transposable elements and signatures of recent retrotransposition events. Combinations of alleles and genes unique to an individual strain are commonly observed at these loci, reflecting distinct strain phenotypes. We used these genomes to improve the mouse reference genome, resulting in the completion of 10 new gene structures. Also, 62 new coding loci were added to the reference genome annotation. These genomes identified a large, previously unannotated, gene (Efcab3-like) encoding 5,874 amino acids. Mutant Efcab3-like mice display anomalies in multiple brain regions, suggesting a possible role for this gene in the regulation of brain development

Methane bursts as a trigger for intermittent lake-forming climates on post-Noachian Mars

Lakes existed on Mars later than 3.6 billion years ago, according to sedimentary evidence for deltaic deposition. The observed fluviolacustrine deposits suggest that individual lake-forming climates persisted for at least several thousand years (assuming dilute flow). But the lake watersheds’ little-weathered soils indicate a largely dry climate history, with intermittent runoff events. Here we show that these observational constraints, although inconsistent with many previously proposed triggers for lake-forming climates, are consistent with a methane burst scenario. In this scenario, chaotic transitions in mean obliquity drive latitudinal shifts in temperature and ice loading that destabilize methane clathrate. Using numerical simulations, we find that outgassed methane can build up to atmospheric levels sufficient for lake-forming climates, if methane clathrate initially occupies more than 4% of the total volume in which it is thermodynamically stable. Such occupancy fractions are consistent with methane production by water–rock reactions due to hydrothermal circulation on early Mars. We further estimate that photochemical destruction of atmospheric methane curtails the duration of individual lake-forming climates to less than a million years, consistent with observations. We conclude that methane bursts represent a potential pathway for intermittent excursions to a warm, wet climate state on early Mars

Step Two in Flood Recovery of Pastures Is Renovation

As flood waters recede, the renovation of flooded pastures is just beginning. Now is a good time to check pasture plants for survival. Forage production is a function of the plant species, and their density and growth. Evaluate live plants (plant vigor), plant density, and desirable species versus weeds.</p

Enhancing the Value of Cover Crops through Utilization by Beef Stocker Cattle: Progress Report (Year 2)

Cover crops are an important component of the Iowa Nutrient Reduction Strategy to improve Iowa’s water quality. To meet the goal of a 45 percent reduction in the total nitrogen and phosphorus loads, it is estimated the total number of acres planted to cover crops will need to be at a minimum of four million acres or equivalent to about 20 percent of Iowa’s row crop acres. This implies millions of acres may be seasonally available for grazing. Although the benefits of improved soil health and nutrient retention through cover crops are well known, limited data is available on utilization by beef cattle. Therefore, a study was designed to measure cattle performance while spring grazing cereal rye and to evaluate the impact grazing had on the soil profile. Most of the limited research conducted on cover crop grazing has focused on integrating cover crops into row crop systems that cow-calf producers already raise. However, many Iowa row crop producers do not have a cattle enterprise. Stocker cattle may be an opportunity to utilize a cover crop grazing system that allows cattle to be bought and sold based on forage availability. It is important for livestock producers to check for crop rotational restrictions on labels of pesticides used during the growing season as well as grazing restrictions if they intend to use the cover crop as a forage source. Because many variables impact the successful integration of cover crops and livestock into row crops, this is a four-year study summarizing data from year two.</p