Soil carbon and nitrogen erosion in forested catchments: Implications for erosion-induced terrestrial carbon sequestration

Lateral movement of organic matter (OM) due to erosion is now considered an important flux term in terrestrial carbon (C) and nitrogen (N) budgets, yet most published studies on the role of erosion focus on agricultural or grassland ecosystems. To date, little information is available on the rate and nature of OM eroded from forest ecosystems. We present annual sediment composition and yield, for water years 2005-2011, from eight catchments in the southern part of the Sierra Nevada, California. Sediment was compared to soil at three different landform positions from the source slopes to determine if there is selective transport of organic matter or different mineral particle size classes. Sediment export varied from 0.4 to 177 kg ha-1, while export of C in sediment was between 0.025 and 4.2 kg C ha-1 and export of N in sediment was between 0.001 and 0.04 kg N ha-1. Sediment yield and composition showed high interannual variation. In our study catchments, erosion laterally mobilized OM-rich litter material and topsoil, some of which enters streams owing to the catchment topography where steep slopes border stream channels. Annual lateral sediment export was positively and strongly correlated with stream discharge, while C and N concentrations were both negatively correlated with stream discharge; hence, C: N ratios were not strongly correlated to sediment yield. Our results suggest that stream discharge, more than sediment source, is a primary factor controlling the magnitude of C and N export from upland forest catchments. The OM-rich nature of eroded sediment raises important questions about the fate of the eroded OM. If a large fraction of the soil organic matter (SOM) eroded from forest ecosystems is lost during transport or after deposition, the contribution of forest ecosystems to the erosion-induced C sink is likely to be small (compared to croplands and grasslands)

Imaging African trypanosomes

Trypanosoma brucei are extracellular kinetoplastid parasites transmitted by the blood-sucking tsetse fly. They are responsible for the fatal disease human African trypanosomiasis (HAT), also known as sleeping sickness. In late-stage infection, trypanosomes cross the blood–brain barrier (BBB) and invade the central nervous system (CNS) invariably leading to coma and death if untreated. There is no available vaccine and current late-stage HAT chemotherapy consists of either melarsoprol, which is highly toxic causing up to 8% of deaths, or nifurtimox–eflornithine combination therapy (NECT), which is costly and difficult to administer. There is therefore an urgent need to identify new late-stage HAT drug candidates. Here, we review how current imaging tools, ranging from fluorescent confocal microscopy of live immobilized cells in culture to whole-animal imaging, are providing insight into T. brucei biology, parasite-host interplay, trypanosome CNS invasion and disease progression. We also consider how imaging tools can be used for candidate drug screening purposes that could lead to new chemotherapies

Tracing the source of soil organic matter eroded from temperate forest catchments using carbon and nitrogen isotopes

Soil erosion continuously redistributes soil and associated soil organic matter (SOM) on the Earth's surface, with important implications for biogeochemical cycling of essential elements and terrestrial carbon sequestration. Despite the importance of soil erosion, surprisingly few studies have evaluated the sources of eroded carbon (C). We used natural abundance levels of the stable and radioactive isotopes of C (13C and 14C) and stable isotope of nitrogen (15N) to elucidate the origins of SOM eroded from low-order catchments along the western slopes of the Sierra Nevada of California, USA. Our work was conducted in two relatively undisturbed catchments (low elevation = 1800 m, and high elevation = 2300 m) of the Kings River Experimental Watersheds (KREW) in the Sierra National Forest. Sediment captured in basins at the outlet of each gauged watershed were compared to possible source materials, which included: upland surficial organic horizons (i.e., forest floor) and mineral soils (0–0.6 m) from three landform positions (i.e., crest, backslope, and toeslope), stream bank soils (0–0.6 m), and stream-bed materials (0–0.05 m). We found that most of the organic matter (OM) in the captured sediments was composed of O-horizon material that had high C concentrations. Radiocarbon analyses also showed that the captured OM is composed of modern (post-1950) C, with fraction modern values at or above 1.0. Our results suggest that surface (sheet) erosion, as opposed to channeling through established streams and episodic mass wasting events, is likely the largest source of sediment exported out of these minimally disturbed, headwater catchments. The erosional export of sediment with a high concentration of C, especially in the form of relatively undecomposed litter from the O horizon, suggests that a large fraction of the exported C is likely to be decomposed during or after erosion; hence, it is unlikely that soil erosion acts as a significant net sink for atmospheric CO2 in these low-order, temperate forest catchments

Framework for Accessible and Inclusive Teaching Materials for Statistics and Data Science Courses

Despite rapid growth in the data science workforce, people of color, women, those with disabilities, and others remain underrepresented in, underserved by, and sometimes excluded from the field. This pattern prevents equal opportunities for individuals, while also creating products and policies that perpetuate inequality. Thus, it is critical that, as statistics and data science educators of the next generation, we center accessibility and inclusion throughout our curriculum, classroom environment, modes of assessment, course materials, and more. Though some common strategies apply across these areas, this article focuses on providing a framework for developing accessible and inclusive course materials (e.g., in-class activities, course manuals, lecture slides, etc.), with examples drawn from our experience co-writing a statistics textbook. In turn, this framework establishes a structure for holding ourselves accountable to these principles

The rich physics of A-site-ordered quadruple perovskite manganites AMn₇O₁₂

Perovskite-structure AMnO3 manganites played an important role in the development of numerous physical concepts such as double exchange, small polarons, electron–phonon coupling, and Jahn–Teller effects, and they host a variety of important properties such as colossal magnetoresistance and spin-induced ferroelectric polarization (multiferroicity). A-site-ordered quadruple perovskite manganites AMn7O12 were discovered shortly after, but at that time their exploration was quite limited. Significant progress in their understanding has been reached in recent years after the wider use of high-pressure synthesis techniques needed to prepare such materials. Here we review this progress, and show that the AMn7O12 compounds host rich physics beyond the canonical AMnO3 materials

Competing electronic instabilities in the quadruple perovskite manganite PbMn₇O₁₂

Structural behavior of PbMn_{7}O_{12} has been studied by high resolution synchrotron x-ray powder diffraction. This material belongs to a family of quadruple perovskite manganites that exhibit an incommensurate structural modulation associated with an orbital density wave. It has been found that the structural modulation in PbMn_{7}O_{12} onsets at 294 K with the incommensurate propagation vector ks=(0,0,∼2.08). At 110 K another structural transition takes place where the propagation vector suddenly drops down to a quasicommensurate value ks=(0,0,2.0060(6)). The quasicommensurate phase is stable in the temperature range of 40-110 K, and below 40 K the propagation vector jumps back to the incommensurate value ks=(0,0,∼2.06). Both low temperature structural transitions are strongly first order with large thermal hysteresis. The orbital density wave in the quasicommensurate phase has been found to be substantially suppressed in comparison with the incommensurate phases, which naturally explains unusual magnetic behavior recently reported for this perovskite. Analysis of the refined structural parameters revealed that that the presence of the quasicommensurate phase is likely to be associated with a competition between the Pb^{2+} lone electron pair and Mn^{3+} Jahn-Teller instabilities

BiMn7 O12: Polar antiferromagnetism by inverse exchange striction

Despite extensive research on magnetically induced ferroelectricity there exist relatively few studies on how a preexisting electric polarization affects magnetic order. Given that well-established magnetoelectric coupling schemes can in principle work in reverse, one might anticipate that primary, polar magnetic structures could be uniquely stabilized in ferroelectric crystals, however, this scenario is apparently rare. Here, we show that in ferroelectric BiMn7O12, a pure, polar E-type antiferromagnetic order emerges below T1=59 K, and we present a phenomenological model of trilinear magnetoelectric coupling consistent with Bi3+ lone-pair driven polar distortions uniquely stabilizing the polar antiferromagnetism via modulation of Heisenberg exchange pathways, i.e., inverse exchange striction. In addition, below T2=55 K there occurs large commensurate canting of the E-type structure due to the onset of ferrimagnetic order on a separate crystallographic sublattice that may be exploited for additional magnetoelectric functionality

Childhood pneumonia at the University of Ilorin Teaching Hospital, Ilorin Nigeria

Background/Objectives: Pneumonia is a leading cause of morbidity and mortality in children and thus this study was designed to document the sociodemographic, clinical features as well as the bacterial agents  responsible for pneumonia in children seen at University of Ilorin Teaching Hospital.Methodology: A descriptive cross -sectional study of children aged one month to 14 years with features of pneumonia admitted between July 1st 2010 and June 31st, 2011 was carried out. Sociodemograpic data, clinical features, complications and outcome were obtained. Chest radiographs and blood samples for culture of bacterial organism and full bloodcounts were obtained in all children.Results: Pneumonia accounted for 13.3% (167 out of 1254) of the all admissions during this period. The male: female ratio was 1.5:1, and 101(60.5%) of the children were infants. Bronchopneumonia was identified in 147(88%) children, lobar pneumonia in 15 (9%) while 5(3%) had a combination of both. Cough, fever, difficulty in breathing, tachypnoea andchest wall recessions were recognised as clinical features in the study population. Bacteraemia was present in 46(27%)children and Staphylococcus aureus was the most common organism cultured from the blood of children with pneumonia present in 11 (23.9%) out of the 46 (100.0%) isolates. Heart failure was associated complication present in 52 of the 60 children with one or more complications accounting for over 30% of all patients. Eleven out of the 15 children with lobar pneumonia hadpneumonia-related complications which was significantly higher compared to 46 of 157 children with bronchopneumonia, p=0.003. The case fatality was 6.6%. Eight (72.7%) of the children that died were infants while the remaining three (27.3%) were aged between 12 and 60 months. The mean duration of hospitalization among those who survived of 6.5 ±5.0 days was significantly lower than the corresponding value of 10.2 ±12.3 days in those that died, p= 0.042. Conclusion: Pneumonia-related mortality and morbidity is high in under-five children, with the infant age group most affected. Bronchopneumonia is the most prevalent ALRI diagnosis but lobar pneumonia is associated with a higher mortality