N, P and K budgets for crop rotations on nine organic farms in the UK

On organic farms, where the importation of materials to build/maintain soil fertility is restricted, it is important that a balance between inputs and outputs of nutrients is achieved to ensure both short-term productivity and long-term sustainability. This paper considers different approaches to nutrient budgeting on organic farms and evaluates the sources of bias in the measurements and/or estimates of the nutrient inputs and outputs. The paper collates 88 nutrient budgets compiled at the farm scale in 9 temperate countries. All the nitrogen (N) budgets showed an N surplus (average 83.2 kg N ha-1 year-1). The efficiency of N use, defined as outputs/inputs, was highest (0.9) and lowest (0.2) in arable and beef systems respectively. The phosphorus (P) and potassium (K) budgets showed both surpluses and deficits (average 3.6 kg P ha-1 year-1, 14.2 kg K ha-1 year-1) with horticultural systems showing large surpluses resulting from purchased manure. The estimation of N fixation and quantities of nutrients in purchased manures may introduce significant errors in nutrient budgets. Overall, the data illustrate the diversity of management systems in place on organic farms, and suggest that used together with soil analysis, nutrient budgets are a useful tool for improving the long-term sustainability of organic systems

Continuous-spin Ising ferromagnets.

Thesis. 1976. Ph.D.--Massachusetts Institute of Technology. Dept. of Mathematics.Microfiche copy available in Archives and Science.Bibliography: leaves 171-175.Ph.D

Earthquake swarm in the Santa Barbara Channel, California, 1968

Sixty-three minor earthquakes (maximum magnitude = 5.2) occurred in the Santa Barbara Channel during the period June 26 to August 3 1968. The epicenters form a shot-scatter pattern upon a broad, high-standing fault block in the channel midway between Santa Cruz Island and the City of Santa Barbara. Focal mechanism studies indicate that oblique-slip movement occurred along a northwest-striking fault even though the major folds and faults strike nearly east-west. Preliminary studies of the areal hydrocarbon production data show no compelling evidence for a causal relationship with the swarm

Drawing a line:Grasses and boundaries

Delineation between distinct populations of cells is essential for organ development. Boundary formation is necessary for the maintenance of pluripotent meristematic cells in the shoot apical meristem (SAM) and differentiation of developing organs. Boundaries form between the meristem and organs, as well as between organs and within organs. Much of the research into the boundary gene regulatory network (GRN) has been carried out in the eudicot model Arabidopsis thaliana. This work has identified a dynamic network of hormone and gene interactions. Comparisons with other eudicot models, like tomato and pea, have shown key conserved nodes in the GRN and species-specific alterations, including the recruitment of the boundary GRN in leaf margin development. How boundaries are defined in monocots, and in particular the grass family which contains many of the world’s staple food crops, is not clear. In this study, we review knowledge of the grass boundary GRN during vegetative development. We particularly focus on the development of a grass-specific within-organ boundary, the ligule, which directly impacts leaf architecture. We also consider how genome engineering and the use of natural diversity could be leveraged to influence key agronomic traits relative to leaf and plant architecture in the future, which is guided by knowledge of boundary GRNs

Changes in Adolescent Birth Rates within Appalachian Subregions and Non-Appalachian Counties in the United States, 2012–2018

Background: Adolescent births are associated with numerous challenges. While adolescent birth rates have declined across the U.S., disparities persist and little is known about the extent to which broader declines are seen within Appalachia. Purpose: The purpose of this study was to examine the extent to which adolescent birth rates have declined across the subregions of Appalachia relative to non-Appalachia. Methods: We conducted a retrospective study of adolescent birth rates between 2012 and 2018 using county-level vital records data. Differences were examined across the subregions of Appalachia and among non-Appalachian counties. Multiple regression models were used to examine changes in the rate of decline over time, adjusting for additional covariates of relevance. Results: About 13.4% of all counties in the U.S. are within the Appalachian region. The rate of adolescent births decreased by 12.6 adolescent births per 1,000 females between 2012 and 2018 across the U.S. While all regions experienced declines in the rate of adolescent births, Central Appalachia had the largest reduction in adolescent births (18.5 per 1,000 females), which was also noted in the adjusted models when compared to the counties of non-Appalachia (b= –5.78, CI: –9.58, –1.97). Rates of adolescent birth were markedly higher in counties considered among the most socially and economically vulnerable. Implications: This study demonstrates that the rates of adolescent births vary across the subregions of Appalachia but have declined proportional to rates in non-Appalachia. While adolescent birth rates remain higher in select subregions of Appalachia compared to non-Appalachia, the gap has narrowed considerably

Spitzer/MIPS Observations of Stars in the Beta Pictoris Moving Group

We present Multiband Imaging Photometer for Spitzer (MIPS) observations at 24 and 70 microns for 30 stars, and at 160 microns for a subset of 12 stars, in the nearby (~30 pc), young (~12 Myr) Beta Pictoris Moving Group (BPMG). In several cases, the new MIPS measurements resolve source confusion and background contamination issues in the IRAS data for this sample. We find that 7 members have 24 micron excesses, implying a debris disk fraction of 23%, and that at least 11 have 70 micron excesses (disk fraction of >=37%). Five disks are detected at 160 microns (out of a biased sample of 12 stars observed), with a range of 160/70 flux ratios. The disk fraction at 24 and 70 microns, and the size of the excesses measured at each wavelength, are both consistent with an "inside-out" infrared excess decrease with time, wherein the shorter-wavelength excesses disappear before longer-wavelength excesses, and consistent with the overall decrease of infrared excess frequency with stellar age, as seen in Spitzer studies of other young stellar groups. Assuming that the infrared excesses are entirely due to circumstellar disks, we characterize the disk properties using simple models and fractional infrared luminosities. Optically thick disks, seen in the younger TW Hya and eta Cha associations, are entirely absent in the BPMG. Additional flux density measurements at 24 and 70 microns are reported for nine Tucanae-Horologium Association member stars. Since this is <20% of the association membership, limited analysis on the complete disk fraction of this association is possible.Comment: Accepted for Ap

The mass-loss rates of red supergiants and the de Jager prescription

Mass loss of red supergiants (RSG) is important for the evolution of massive stars, but is not fully explained. Several empirical prescriptions have been proposed, trying to express the mass-loss rate (Mdot) as a function of fundamental stellar parameters (mass, luminosity, effective temperature). Our goal is to test whether the de Jager et al. (1988) prescription, used in some stellar evolution models, is still valid in view of more recent mass-loss determinations. By considering 40 Galactic RSGs presenting an infrared excess and an IRAS 60-mu flux larger than 2 Jy, and assuming a gas-to-dust mass ratio of 200, it is found that the de Jager rate agrees within a factor 4 with most Mdot estimates based on the 60-mu signal. It is also in agreement with 6 of the only 8 Galactic RSGs for which Mdot can be measured more directly through observations of the circumstellar gas. The two objects that do not follow the de Jager prescription (by an order of magnitude) are mu Cep and NML Cyg. We have also considered the RSGs of the Magellanic Clouds. Thanks to the works of Groenewegen et al. (2009) and Bonanos et al. (2010), we find that the RSGs of the SMC have Mdots consistent with the de Jager rate scaled by (Z/Zsun)**(alpha), where Z is the metallicity and alpha is 0.7. The situation is less clear for the LMC RSGs. In particular, for luminosties larger than 1.6E+05 Lsun, one finds numerous RSGs (except WOH-G64) having Mdot significantly smaller than the de Jager rate, and indicating that Mdot would no longer increase with L. Before this odd situation is confirmed through further analysis of LMC RSGs, we suggest to keep the de Jager prescription unchanged at solar metallicity in the stellar evolutionary models and to apply a (Z/Zsun)**0.7 dependence.Comment: 13 pages, 9 figures. Accepted by Astronomy and Astrophysic