Variability of Disk Emission in Pre-Main Sequence and Related Stars. I. HD 31648 and HD 163296 - Isolated Herbig Ae Stars Driving Herbig-Haro Flows

Infrared photometry and spectroscopy covering a time span of a quarter century are presented for HD 31648 (MWC 480) and HD 163296 (MWC 275). Both are isolated Herbig Ae stars that exhibit signs of active accretion, including driving bipolar flows with embedded Herbig-Haro (HH) objects. HD 163296 was found to be relatively quiescent photometrically in its inner disk region, with the exception of a major increase in emitted flux in a broad wavelength region centered near 3 microns in 2002. In contrast, HD 31648 has exhibited sporadic changes in the entire 3-13 micron region throughout this span of time. In both stars the changes in the 1-5 micron flux indicate structural changes in the region of the disk near the dust sublimation zone, possibly causing its distance from the star to vary with time. Repeated thermal cycling through this region will result in the preferential survival of large grains, and an increase in the degree of crystallinity. The variability observed in these objects has important consequences for the interpretation of other types of observations. For example, source variability will compromise models based on interferometry measurements unless the interferometry observations are accompanied by nearly-simultaneous photometric data.Comment: 55 pages, 18 figures, 2 tables, Accepted by Ap

Three (Potential) Pillars of Transnational Economic Justice: The Bretton Woods Institutions as Guarantors of Global Equal Treatment and Market Completion

This essay aims to bring two important lines of inquiry and criticism together. It first lays out an institutionally enriched account of what a just world economic order will look like. That account prescribes, via the requisites to that mechanism which most directly instantiate the account, three realms of equal treatment and market completion - the global products, services, and labor markets; the global investment/financial markets; and the global preparticipation opportunity allocation. The essay then suggests how, with minimal if any departure from familiar canons of traditional international legal mandate interpretation, each of the Bretton Woods institutions - particularly the GATT/WTO and the IMF - can be viewed at least in part as charged with the task of fostering equal treatment and ultimate market completion within one of those three realms. The piece then argues that one of the institutions in particular - the World Bank - has, for reasons of at best negligent and at worst willful injustice on the part of influential state actors in the world community, fallen farthest short in pursuit of what should be viewed as its proper mandate. The article accordingly concludes that a fuller empowerment of the Bank to effect its ideal mission will press the Bretton Woods system more nearly into ethical balance, and with it the world into justice; and that full empowerment of the GATT/WTO and IMF should be partly conditioned upon the fuller empowerment of the Bank

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Nutritive value and herbage mass of Pueraria phaseoloides (tropical kudzu) in un-utilized open grasslands in north-eastern and central Trinidad and Tobago

Pueraria phaseoloides is an important forage for ruminants in the tropics. However, its nutritive value and availability in areas easily accessed by ruminants and ruminant farmers in Trinidad and Tobago is unknown. This study, therefore, evaluated the effects of harvest date and location on the nutritive value, herbage mass and crude protein yield of P. phaseoloides in un-utilized open grasslands in three locations with high livestock density in Trinidad. Pueraria phaseoloides herbage (whole fraction and leaf) trailing on the upper canopy of open un-utilized grasslands were harvested in the late wet season of 2019 (October - November), early dry (January - February) and early wet (July - August) seasons of 2020 following a stratified random sampling scheme. The crude protein (CP) concentrations of P. phaseoloides leaves (235 g/kg DM) and whole fraction (217 g/kg DM) were highest in Wallerfield during the early wet season. Neutral detergent fibre (NDF), acid detergent fibre (ADF) and lignin were lowest in the early dry season (P < 0.01). Crude protein yield (376–478 kg CP ha−1) and herbage mass (1,742–2,654 kg DM ha−1) were highest during the late wet and early dry season, respectively. In vitro organic matter digestibility (IVOMD) of P. phaseoloides leaf (548–598 g/kg) and whole fraction (549 –580 g/kg) were highest in the late wet season. It was, therefore concluded that open un-utilized grasslands in Trinidad and Tobago produced significant amount of P. phaseoloides herbage year-round to support ruminant livestock production. However, the nutritive value, herbage mass and CP yield of P. phaseoloides herbage were highest during the late wet and early dry seasons