The rhizosphere differs from the bulk soil in a range of biochemical, chemical and physical processes that occur as a consequence of root growth, water and nutrient uptake, respiration and ...rhizodeposition. These processes also affect microbial ecology and plant physiology to a considerable extent. This review concentrates on two features of this unique environment: rhizosphere geometry and heterogeneity in both space and time. Although it is often depicted as a soil cylinder of a given radius around the root, drawing a boundary between the rhizosphere and bulk soil is an impossible task because rhizosphere processes result in gradients of different sizes. For instance, because of diffusional constraints, root uptake can result in a depletion zone extending <1 mm for phosphate to several centimetres for nitrate, while respiration may affect the bulk of the soil. Rhizosphere processes are responsible for spatial and temporal heterogeneities in the soil, although these are sometimes difficult to distinguish from intrinsic soil heterogeneity. A further complexity is that these processes are regulated by plants, microbial communities and soil constituents, and their many interactions. Novel in situ techniques and modelling will help in providing a holistic view of rhizosphere functioning, which is a prerequisite for its management and manipulation.
The structure of a water-soluble levan produced by Streptococcus salivarius SS2 has been determined by means of various chemical and instrumental methods. Methylation and periodate oxidation studies ...demonstrate that the levan is comprised of D-fructofuranosyl backbone residues linked beta-(2---6) (about 70%) with beta-(2---1) branches (about 30%). 13C-N.m.r. spectral analysis of the polymer is consistent with the structure determined by chemical means.
Spatial theory-the study of the relationship between material and discursive spatial practices-has great potential for recasting our understanding of urban life in Europe during the late medieval and ...early modern period, a formative moment in the history of Western urbanity. Urban space-and spaces-acquired powerful, effective valences in this age, producing new social possibilities and new historical actors while simultaneously eliminating others. Examining spatial practices through the lens of legal space, ritual space, and textual space not only exposes the assumptions about early modern urbanity that underlay existing historiography on city space in the period but also points toward the spatial histories that have not yet been written on markets, gender, and the public.
Historically, proton-induced single-event effects (SEES) ground test data are collected independent of the orientation of the microelectronic device to the proton beam direction. In this study, we ...present experimental and simulation evidence that shows an effect of over an order of magnitude on the proton-induced single-event upset (SEU) cross section when the angle of incidence of the proton beam is varied. The magnitude of this effect is shown to depend on the incidence proton energy and the device critical charge. The angular effect is demonstrated for Silicon-On-Sapphire and Silicon-On-Insulator technologies, but would not necessarily be limited to these technologies.
Background: Ras is a GDP/GTP binding G protein that acts as a molecular switch converting signals from the cell membrane to the nucleus to regulate cell proliferation, differentiation, and protein ...synthesis. Activation of ras oncogenes has been identified in a variety of cancers, including 30% of patients with acute myelogenous leukemia (AML). Large granular lymphocyte (LGL) leukemia is a clonal T-cell lymphoproliferative disorder associated with chronic neutropenia, anemia, or autoimmune diseases, particularly rheumatoid arthritis. The purpose of this study was to evaluate serum ras levels in patients with LGL leukemia.
Methods: A novel ras p21 ELISA (Oncogene Science/Bayer HealthCare) employing two monoclonal antibodies was utilized to quantify ras levels in baseline serum obtained from 32 patients with LGL leukemia. A control group of 48 healthy subjects was also used to establish a cutoff for the upper limit of normal for serum ras levels. A 95% non-parametric cut-off was used to determine significant differences in the frequency of elevated serum ras levels in control vs. LGL leukemia patients.
Results: The median serum ras level in the 48 healthy control subjects was 125 pg/mL, with a 5% to 95% range of 50–422 pg/mL. The upper limit of normal for serum ras was defined as 422 pg/mL, as determined using the 95 % non-parametric cut-off. In the LGL leukemia patient group, 19 of 32 patients (59 %) had elevated baseline serum ras levels (median 484 pg/mL) (p=0.0001) when utilizing the healthy control upper limit of normal cut-off value.
Conclusions: The results of this study indicate that the majority of LGL leukemia patients have significantly elevated serum ras levels when compared to healthy controls. Serum ras should be evaluated as a potential biomarker in larger leukemia trials, especially for response to treatment with inhibitors of the ras signaling pathway.
PDF
