Soil resources, microbial activity, and primary production across an agricultural ecosystem

Includes bibliographical references (pages 169-170).The degree to which soil resource availability is linked to patterns of microbial activity and plant productivity within ecosystems has important consequences for our understanding of how ecosystems are structured and for the management of systems for agricultural production. We studied this linkage in a 48-ha site in southwest Michigan, USA, that had been cultivated and planted to row crops for decades. Prior to seeding the site to genetically identical soybean plants (Glycine max) in early spring, we removed soil samples from ≈600 locations; plant biomass was harvested from these same locations later in the season. Soil samples were analyzed for physical properties (texture, bulk density), chemical properties (moisture, pH, total C, total N, inorganic N), and biological attributes (microbial biomass, microbial population size, respiration potential, and nitrification and N-mineralization potentials). Plant analyses included biomass and C and N contents. Soil resource variability across this long-cultivated site was remarkably high, as was variability in microbial activity and primary productivity. In almost all cases variability exhibited a strong spatially explicit structure: for most properties and processes > 50% of sample variance was spatially dependent at a scale of 5–60 m. Exceptions included microtopography, soil pH, and inorganic P, which were spatially dependent across the entire 1–1200 m range of separation distances examined in this study, and the culturable-bacteria population, which was not spatially autocorrelated at any scale examined. Both topographic relief and soil pH exhibited strongly nested structures, with autocorrelation occurring within two (topography) or more (pH) distinct ranges. Multiple regression analysis showed surprisingly little correlation between biological processes (soybean productivity, soil N turnover, soil respiration), and static soil properties. The best predictor of soybean biomass at late reproductive stages (r2 = 0.42) was a combination of nitrate N, bulk density, inorganic P, N-mineralization rates, and pH. Overall, results suggest a remarkable degree of spatial variability for a pedogenically homogeneous site that has been plowed and cropped mostly as a single field for > 100 yr. Such variability is likely to be generic to most ecosystems and should be carefully evaluated when making inferences about ecological relationships in these systems and when considering alternative sampling and management strategies

Pediatric diabetes consortium T1D New Onset ( NeOn ) study: clinical outcomes during the first year following diagnosis

Objective There have been few prospective, multicenter studies investigating the natural history of type 1 diabetes ( T1D ) from the time of diagnosis. The objective of this report from the Pediatric Diabetes Consortium ( PDC ) T1D New Onset ( NeOn ) study was to assess the natural history and clinical outcomes in children during the first year after diagnosis of T1D . Research design and methods: Clinical measures from the first year following diagnosis were analyzed for 857 participants (mean age 9.1 yr, 51% female, 66% non‐Hispanic White) not participating in an intervention study who had a HbA1c result at 12 months. Results Mean HbA1c ± SD was 102 ± 25 mmol/mol (11.4 ± 2.3%) at diagnosis, 55 ± 12 mmol/mol (7.2 ± 1.1%) at 3 months, 56 ± 15 mmol/mol (7.3 ± 1.3%) at 6 months and 62 ± 16 mmol/mol (7.8 ± 1.5%) at 12 months from diagnosis. A severe hypoglycemic ( SH ) event occurred in 31 (4%) participants (44 events, 5.2 events per 100 person‐years). Diabetic ketoacidosis ( DKA ) not including diagnosis occurred in 10 (1%) participants (13 events, 1.5 events per 100 person‐years). Conclusions After onset of T1D , mean HbA1c reaches its nadir at 3–6 months with a gradual increase through 12 months. SH and DKA are uncommon but still occur during the first year with T1D . Data from large cohorts, such as the PDC T1D NeOn study, provide important insights into the course of T1D during the first year following diagnosis, which will help to inform the development of models to target future interventions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/107374/1/pedi12068.pd

Vitamin D status in youth with type 1 and type 2 diabetes enrolled in the Pediatric Diabetes Consortium (PDC) is not worse than in youth without diabetes

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134500/1/pedi12340.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134500/2/pedi12340_am.pd

Texture Analysis and Radial Basis Function Approximation for IVUS Image Segmentation

>Intravascular ultrasound (IVUS) has become in the last years an important tool in both clinical and research applications. The detection of lumen and media-adventitia borders in IVUS images represents a first necessary step in the utilization of the IVUS data for the 3D reconstruction of human coronary arteries and the reliable quantitative assessment of the atherosclerotic lesions. To serve this goal, a fully automated technique for the detection of lumen and media-adventitia boundaries has been developed. This comprises two different steps for contour initialization, one for each corresponding contour of interest, based on the results of texture analysis, and a procedure for approximating the initialization results with smooth continuous curves. A multilevel Discrete Wavelet Frames decomposition is used for texture analysis, whereas Radial Basis Function approximation is employed for producing smooth contours. The proposed method shows promising results compared to a previous approach for texture-based IVUS image analysis

Trends in High-Risk HLA Susceptibility Genes Among Colorado Youth With Type 1 Diabetes

OBJECTIVE—Type 1 diabetes is associated with a wide spectrum of susceptibility and protective genotypes within the HLA class II system. It has been reported that adults diagnosed with youth-onset type 1 diabetes more recently have been found to have fewer classical high-risk HLA class II genotypes than those diagnosed several decades ago. We hypothesized that such temporal trends in the distribution of HLA-DR, DQ genotypes would be evident, and perhaps even stronger, among 5- to 17-year-old Hispanic and non-Hispanic white (NHW) youth diagnosed with type 1 diabetes in Colorado between 1978 and 2004

Insulin Regimens and Clinical Outcomes in a Type 1 Diabetes Cohort: The SEARCH for Diabetes in Youth study

OBJECTIVE To examine the patterns and associations of insulin regimens and change in regimens with clinical outcomes in a diverse population of children with recently diagnosed type 1 diabetes