Aeration measurement

Soil oxygen enables aerobic respiration of plant roots and soil micro- and meso-flora and fauna. Its availability can be limited by soil wetness, compaction, discontinuous pores, or high respiration in moist soil due to elevated soil temperature or incorporation of fresh organic substrate. With oxygen depletion, soil redox potential shifts from oxidative to reducing conditions, hampering plant growth because of less efficient metabolic pathways and release into soil of toxic by-products of reduction chemistry or anaerobic respiration. Several texts are excellent sources for fundamental soil aeration concepts (1-3). Measurements of soil aeration fall into three categories: "capacity," volume of gas-filled void space; "Intensity," partial pressure or concentration of oxygen (or other gases) in the voids; and "transport rate," the rapidity at which oxygen can be supplied to a point in the soil. Measurement difficulty increases in the order capacity < intensity < rate, as do the value and insight of the measurements

Bragg soybeans grown on a Southern Coastal Plain soil. IV. Seasonal changes in nodal N and P concentrations

Determinate soybean [Glycine max (L.) Merr.] has been characterized by few detailed nitrogen and phosphorous partitioning studies. Knowledge of the variation in N and P concentrations with plant part, nodal position, and plant age is needed for a better understanding of plant functions. In this field study, 'Bragg' soybean was grown on an Aquic Paleudult soil (series Goldsboro loamy sand). Plants were sampled at 10 to 14 day intervals beginning 44 days after planting (July 7) until harvest. Maximum observed N concentrations were 3.1, 2.8, 5.8, and 5.4% for stem internodes, petioles (+branches), leaf blades, and pods, respectively. Maximum observed P concentrations were 0.34, 0.48, 0.78, and 0.52 for the same respective plant parts. Nodal and temporal mean N and P concentrations varied considerably with plant age and nodal position in all plant parts. These data show that mean N and concentrations in all four plant parts can vary several fold, depending upon plant age and nodal position for the sample. This suggests caution should be exercised in tissue sampling and interpretation of plant analysis. Concentrations of N and P generally decreased with time for stem internode, petioles (+branches), and leaf blades, but increased with time for pods. Except for N concentration in stem internodes, which increases with internode number, the N and P concentrations remain nearly constant throughout the growing season. The relationships provide insight for developing accurate plant models depicting N and P concentrations and translocations over time and among plant parts in determinate soybean

Root oxygen deprivation and the reduction of leaf stomatal aperture and gas exchange

The most ubiquitous plant abiotic stress in the global environment is generally thought to be water deficit. The opposite of water-deficit stress. flooding, initially involves relief of the abiotic factor of water deficit and only becomes stressful after flooding persists long enough to directly or indirectly interfere with a variety of plant functions via several mechanisms. The relief of stress with short term flooding (typically a day or less) is the principle upon which irrigation hinges. By contrast, the negative impacts of prolonged flooding on ecosystems, and particularly agricultural production systems, are substantial [I] and may be as significant as drought, depending on one's accounting strategy. Much of this impact is the result of the combination of soil and plant chemical, physical, and biological changes that cause stomata to close after prolonged flooding. This contributes significantly to a drastic reduction in photosynthesis and damages many other plant functions by disrupting transpiration and the complex system of hormonal control of plant systems and processes

Cluster expansion in the canonical ensemble

We consider a system of particles confined in a box \La\subset\R^d interacting via a tempered and stable pair potential. We prove the validity of the cluster expansion for the canonical partition function in the high temperature - low density regime. The convergence is uniform in the volume and in the thermodynamic limit it reproduces Mayer's virial expansion providing an alternative and more direct derivation which avoids the deep combinatorial issues present in the original proof

Morphological, temporal, and nodal accumulation of nutrients by determinate soybean

Crop growth models that account for nutrient accumulation offer insight into soil fertility and plant nutrition interactions. This understanding provides opportunities to develop improved management practices. During the 1980s, several process-level growth models were developed for soybean [Glycine max (I..) Merr.). Model validation and application to different locations and weather require detailed, independent data sets. An extensive data set describing the nutrient status of a determinate soybean ('Bragg') was collected in 1979 on a Goldsboro (Aquic Paleudult) loamy sand near Florence, SC, USA. Because of its importance to subsequent model development, we concluded that providing this entire data set in a readily accessible form was a logical step in the course of this experiment. We report here, in tabular form, mean and standard deviation data for aerial accumulation of dry matter and eight nutrients (N, P, K, Ca, Mg, Mn, Fe, and Zn) for 10 dates, for four plant components (stems, leaves, petioles, pods, and total), and for each node (and whole plant). We will provide, upon arrangement, these same data on diskette for use in simulation models or other applications

Gene Dosage–limiting Role of Aire in Thymic Expression, Clonal Deletion, and Organ-specific Autoimmunity

Inactivation of the autoimmune regulator (Aire) gene causes a rare recessive disorder, autoimmune polyendocrine syndrome 1 (APS1), but it is not known if Aire-dependent tolerance mechanisms are susceptible to the quantitative genetic changes thought to underlie more common autoimmune diseases. In mice with a targeted mutation, complete loss of Aire abolished expression of an insulin promoter transgene in thymic epithelium, but had no effect in pancreatic islets or the testes. Loss of one copy of Aire diminished thymic expression of the endogenous insulin gene and the transgene, resulting in a 300% increase in islet-reactive CD4 T cells escaping thymic deletion in T cell receptor transgenic mice, and dramatically increased progression to diabetes. Thymic deletion induced by antigen under control of the thyroglobulin promoter was abolished in Aire homozygotes and less efficient in heterozygotes, providing an explanation for thyroid autoimmunity in APS1. In contrast, Aire deficiency had no effect on thymic deletion to antigen controlled by a systemic H-2K promoter. The sensitivity of Aire-dependent thymic deletion to small reductions in function makes this pathway a prime candidate for more subtle autoimmune quantitative trait loci, and suggests that methods to increase Aire activity would be a potent strategy to lower the incidence of organ-specific autoimmunity

Sagittal Growth of the Nasomaxillary Complex during the Second Trimester of Human Prenatal Development

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66545/2/10.1177_00220345650440010401.pd

Deficiencies in the soil quality concept and its application

Soil quality is a concept that has deeply divided the soil science community. It has been institutionalized and advocated without full consideration of concept weaknesses and contradictions. Our paper highlights its disfunctional definition, flawed approach to quantification, and failure to integrate simultaneous functions, which often require contradictory soil properties and/or management. While the concept arose from a call to protect the environment and sustain the soil resource, soil quality indexing as implemented may actually impair some soil functions, environmental quality, or other societal priorities. We offer the alternative view that emphasis on known principles of soil management is a better expenditure of limited resources for soil stewardship than developing and deploying subjective indices which fail to integrate across the necessary spectrum of management outcomes. If the soil quality concept is retained, we suggest precisely specifying soil use, not function or capacity, as the criteria for attribute evaluation. Emphasis should be directed toward using available technical information to motivate and educate farmers on management practices that optimize the combined goals of high crop production, low environmental degradation, and a sustained resource

'Making Friends or Making Things?': Interfirm Transactions in the Sheffield Metal-working Cluster

The paper comprises an examination of the material inputs of a sample of 70 small firms in the Sheffield metal-working cluster and an assessment of the extent to which purchases are accompanied by face-to-face (embodied) transactions. It is shown that there are no significant differences between the level of embodied transactions accompanying local (intra-cluster) material links and those associated with non-local flows. It seems that, on this measure at least and within this cluster, the Sheffield metal-working cluster lacks the dense network of embodied transactions with local suppliers suggested in the wider literature. The lower-than-expected measures of embodied transactions suggest that one of the mechanisms for the transfer of knowledge between buyers and suppliers within an industrial cluster is poorly developed in this particular case.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline