Evapotranspiration in the Nile Basin: Identifying Dynamics, Trends, and Drivers 2002-2011

Analysis of the relationship between evapotranspiration (ET) and its natural and anthropogenic drivers is critical in water-limited basins such as the Nile. The spatiotemporal relationships of ET with rainfall and vegetation dynamics in the Nile Basin during 2002–2011 were analyzed using satellite-derived data. Non-parametric statistics were used to quantify ET-rainfall interactions and trends across land cover types and subbasins. We found that 65% of the study area (2.5 million km2) showed significant (p \u3c 0.05) positive correlations between monthly ET and rainfall, whereas 7% showed significant negative correlations. As expected, positive ET-rainfall correlations were observed over natural vegetation, mixed croplands/natural vegetation, and croplands, with a few subbasin-specific exceptions. In particular, irrigated croplands, wetlands and some forests exhibited negative correlations. Trend tests revealed spatial clusters of statistically significant trends in ET (6% of study area was negative; 12% positive), vegetation greenness (24% negative; 12% positive) and rainfall (11% negative; 1% positive) during 2002–2011. The Nile Delta, Ethiopian highlands and central Uganda regions showed decline in ET while central parts of Sudan, South Sudan, southwestern Ethiopia and northeastern Uganda showed increases. Except for a decline in ET in central Uganda, the detected changes in ET (both positive and negative) were not associated with corresponding changes in rainfall. Detected declines in ET in the Nile delta and Ethiopian highlands were found to be attributable to anthropogenic land degradation, while the ET decline in central Uganda is likely caused by rainfall reduction

A model of mentorship for students from historically underrepresented groups in STEM

Mentorship is critical to student academic success and persistence, especially for students from historically underrepresented (HU) groups. In a program designed to support the academic success of HU undergraduates in STEM who wish to pursue a PhD in those fields, students experience comprehensive support including financial aid, highly-engaged mentoring, dual faculty mentorship, professional development workshops, and summer research experiences. Scholars in this program, the Cal-Bridge program, consistently report that faculty mentorship is the most impactful feature. While mentorship was rated highly, preliminary evaluation indicated an early deficit in a sense of community among scholars. In response, faculty professional development and support for peer networking were implemented to expand and enhance the relationships that support scholar success. Here we present a promising multifaceted model of mentorship that can support the academic success of HU undergraduates.Comment: Submitted to Understanding Interventions. 23 pages. 4 figures. Comments welcome

Functional insights from the structure of the 30S ribosomal subunit and its interactions with antibiotics

The 30S ribosomal subunit has two primary functions in protein synthesis. It discriminates against aminoacyl transfer RNAs that do not match the codon of messenger RNA, thereby ensuring accuracy in translation of the genetic message in a process called decoding. Also, it works with the 50S subunit to move the tRNAs and associated mRNA by precisely one codon, in a process called translocation. Here we describe the functional implications of the high-resolution 30S crystal structure presented in the accompanying paper, and infer details of the interactions between the 30S subunit and its tRNA and mRNA ligands. We also describe the crystal structure of the 30S subunit complexed with the antibiotics paromomycin, streptomycin and spectinomycin, which interfere with decoding and translocation. This work reveals the structural basis for the action of these antibiotics, and leads to a model for the role of the universally conserved 16S RNA residues A1492 and A1493 in the decoding process

HAS AN INTEGRATED PEST MANAGEMENT APPROACH REDUCED BLACKBIRD DAMAGE TO SUNFLOWER?

Since the mid- 1970s many new and modified damage abatement methods have been used to reduce blackbird damage to ripening sunflower in the northern Great Plains. To assess the overall impact of these techniques, we analyzed the dynamic relationship between breeding blackbird densities and sunflower damage. Breeding density estimates were made at both the regional and county levels, whereas, sunflower damage estimates were made at the county level only. Periodic regional estimates of breeding densities between 1967 and 1998 for red-winged blackbirds (Agelaius phoeniceus), common grackles (Quiscalus quiscula), and yellow-headed blackbirds (Xanthocephalus xanthocephalus) showed no differences among years. To increase our ability to detect changes in breeding density, we started intensive county-level surveys in 1996. These surveys, in four counties in North Dakota and South Dakota, showed that blackbird densities were greater in 1998 and 1999 than during the previous two years. We surveyed sunflower damage in two of these counties from 1994 to 1998 and found no difference in damage (F= 1.8%) among years. In 1997 and 1998, with the two other counties added to the survey, we found that damage was similar between years, averaging 2.2%. Dollar loss per hectare was trending lower in three of the study counties that had a historical database for comparison. This supports the idea that \u27local\u27 breeding densities are not correlated with damage levels. We will continue to use annual estimates of breeding densities and sunflower damage to assess the effects of an evolving Integrated Pest Management program

Atomic Structures of the 30S Subunit and Its Complexes with Ligands and Antibiotics

The two subunits that make up the ribosome have both distinct and cooperative functions. The 30S ribosomal subunit binds messenger RNA (mRNA) and is involved in the selection of cognate transfer RNA (tRNA) by monitoring codon–anticodon base-pairing during the decoding process. The 50S subunit catalyzes peptide-bond formation. Both subunits work in concert to move tRNAs and mRNAs relative to the ribosome in translocation, and both are the target of a large number of naturally occurring antibiotics. Thus, useful information about the mechanism of translation can be gleaned from structures of both individual subunits and the intact ribosome. In this paper, we describe our work on the determination of the atomic structure of the 30S ribosomal subunit and its complexes with RNA ligands, antibiotics, and initiation factor IF1. The results provide structural insights into how the ribosome recognizes cognate tRNA and discriminates against near-cognate tRNA. They also provide a structural basis for understanding the action of various antibiotics that target the 30S subunit

Phasing the 30S ribosomal subunit structure

The methods involved in determining the 850 kDa structure of the 30S ribosomal subunit from Thermus thermophilus were in many ways identical to those that are generally used in standard protein crystallography. This paper reviews and analyses the methods that can be used in phasing such large structures and shows that the anomalous signal collected from heavy-atom compounds bound to the RNA is both necessary and sufficient for ab initio structure determination at high resolution. In addition, measures to counter problems with non-isomorphism and radiation decay are described