Unbound Star-forming Molecular Clouds

We explore whether observed molecular clouds could include a substantial population of unbound clouds. Using simulations which include only turbulence and gravity, we are able to match observed relations and naturally reproduce the observed scatter in the cloud size-linewidth coefficient, at fixed surface density. We identify the source of this scatter as a spread in the intrinsic virial parameter. Thus these observational trends do not require that clouds exist in a state of dynamical equilibrium. We demonstrate that cloud virial parameters can be accurately determined observationally with an appropriate size estimator. All our simulated clouds eventually form collapsing cores, regardless of whether the cloud is bound overall. This supports the idea that molecular clouds do not have to be bound to form stars or to have observed properties like those of nearby low-mass clouds.Comment: 9 pages, 6 figures, Accepted for publication by MNRA

Evolving Molecular Cloud Structure and the Column Density Probability Distribution Function

The structure of molecular clouds can be characterized with the probability distribution function (PDF) of the mass surface density. In particular, the properties of the distribution can reveal the nature of the turbulence and star formation present inside the molecular cloud. In this paper, we explore how these structural characteristics evolve with time and also how they relate to various cloud properties as measured from a sample of synthetic column density maps of molecular clouds. We find that, as a cloud evolves, the peak of its column density PDF will shift to surface densities below the observational threshold for detection, resulting in an underlying lognormal distribution which has been effectively lost at late times. Our results explain why certain observations of actively star-forming, dynamically older clouds, such as the Orion molecular cloud, do not appear to have any evidence of a lognormal distribution in their column density PDFs. We also study the evolution of the slope and deviation point of the power-law tails for our sample of simulated clouds and show that both properties trend towards constant values, thus linking the column density structure of the molecular cloud to the surface density threshold for star formation.Comment: 10 pages, 9 figures, Accepted for publication by MNRA

A temporal study of the phytoplankton spring bloom in Prince William Sound, Alaska

Thesis (M.S.) University of Alaska Fairbanks, 1997The phytoplankton bloom in southwest Prince William Sound, Alaska began in early April, declined by May and had a small recovery in June 1995 and 1996. Phytoplankton bloom was nutrient-limited in April and phytoplankton biomass was controlled by zooplankton grazing in May. The bloom consisted of 80 % microplankton; the post bloom was predominandy flagellates, followed by a small diatom recovery. A seasonal succession in the diatom community occurred from Skeletonema costatum, Thalassiosira spp. and Chaetoceros spp. in April to Rhizosolenia fragilissima in June. There was little vertical variation in species composition. More than twice as much organic carbon due to phytoplankton was present in 1996 as in 1995. In 1995, Thalassiosira spp. was 73-80 % of diatom carbon and in 1996 Skeletonema costatum made up 58-78 %. The timing of the bloom, cell abundance and patterns of succession resembled other marine environments of similar latitude

Genetic and dietary interactions of fishy-egg taint in brown-shelled laying hens

Fishy-egg tainting has long been a problem associated with feeding canola meal (CM) to brown-shelled laying hens. It is a classical example of nutrigenetics, as both dietary and genetic factors must be present for a hen to lay fishy-tainted eggs. Trimethylamine (TMA), the compound responsible for the fishy smell, is produced by bacterial fermentation of choline in the lower gut. CM contains large amounts of choline in the form of sinapine. Choline must first be hydrolyzed from sinapine before it can be absorbed or converted to TMA. Normally, the malodourous TMA is metabolized to the odourless trimethylamine N-oxide (TMAO) by flavin-containing monooxygenase 3 (FMO3). A mutation in FMO3 (c.984A>T) prevents TMA from being oxidized to TMAO, and subsequently TMA accumulates in the developing egg yolks. Our objective was to determine the inheritance pattern of fishy-egg tainting when hens are fed canola meal, reflecting typical industry conditions. In the first of two trials, hens of a commercial brown-shelled strain were genotyped at FMO3 c.984A>T and fed graded levels of CM (0, 6, 12, or 18%). These hens were bred to produce a second generation of hens, which were also genotyped and fed graded levels of CM (0, 6, 12, 18, or 24%) or choline chloride (0, 0.055, 0.110, 0.165, or 0.220%). Choline chloride, at levels up to 0.220%, does not lead to the production of fishy tainted-eggs. When fed CM, TT hens laid fishy-tainted eggs. Mean yolk TMA concentration was not significantly different between hens of the AA and AT genotypes, with means from both genotypes remaining below the human detection threshold for all of the dietary treatments. Large day-to-day variations in yolk TMA concentration were seen in hens of all three genotypes. We concluded that fishy-egg tainting is recessive when hens are fed CM at levels reflecting typical commercial practices

Vitamin A and intramuscular fat deposition: a nutrigenetic investigation in beef cattle

Vitamin A restriction has been associated with increased marbling in beef cattle. The purpose of this study was to investigate a possible nutrigenetic mechanism leading to this increase in intramuscular fat. Four genes involved in the vitamin A pathway were examined for genetic polymorphisms that could alter mRNA expression or protein structure. A total of fourteen SNPs were found in bovine alcohol dehydrogenase 1C (ADH1C), aldehyde dehydrogenase 1A1 (ALDH1A1), peroxisome proliferator-activated receptor (PPAR), and retinol binding protein 4 (RBP4). Five of these SNPs were examined for associations with production and carcass traits in a previously reported population of 400 crossbred steers. ALDH1A1 c.*27C>T was significantly associated with backgrounding average daily gain (PC, ADH1C c.967C>T, ALDH1A1 c.*109A>G, or PPAR c.1344G>T with any of the parameters measured. A nutritional study was performed to examine the interaction between ADH1C c.-64T>C and vitamin A restriction on production and carcass traits in cattle. It was hypothesized that a phenotypic effect would be observed only when vitamin A was restricted. An initial population of 450 black Angus cross steers were genotyped at ADH1C c.-64T>C and from that population 130 steers (50 TT, 50 CT, and 30 CC) were randomly selected for use in the vitamin A restriction study. They were backgrounded for three months on a low -carotene diet and finished for five months on a diet that did not contain supplemental vitamin A. During the finishing period the steers were treated with monthly boluses of either 0 IU (unsupplemented) or 750,000 IU (supplemented) supplemental vitamin A. Liver and fat biopsies were obtained at the start and end of finishing from a subgroup of five steers per genotype per treatment to assess vitamin A status and measure gene expression. Marbling score was significantly greater (PC in combination with reduced vitamin A supplementation could potentially be implemented in marker-assisted management to maximize intramuscular fat deposition in finishing cattle

Marginalized Youth, Mental Health, and Connection with Others: A Review of the Literature

For marginalized youth, the transition to adulthood is a stage of life in which inequalities can be either magnified or reduced. While most descriptions of these young people highlight their difficulties achieving self-sufficiency, the ability to form connections with others is an equally significant marker of adult maturity. Given that social isolation poses serious risks to health and well-being, the relational experiences of marginalized youth are a critical component of the transition to adulthood. Experiences of trauma, marginalization, and involvement in public systems of care can place these youth at heightened risk for mental health difficulties, all of which can pose particular challenges for interpersonal relationships. This critical review of the literature explores the research on the relational experiences of marginalized young people living with emotional and behavioral challenges. It discusses the unique developmental context of marginalized youth, including experiences with trauma, mental illness, marginalization, and involvement in public systems of care. It then reviews the benefits young people derive from mutually empathic connections with others. The review explores facilitators of connection for marginalized youth, as well as barriers to connection for these young people. Following this review, the article identifies several gaps in the literature, and ends with a call for both practitioners and researcher

From unskilled to employable: using a qualitative examination of the ‘Placement Timeline Research Method’ to explore student professional and personal development whilst on multiple WIL experiences.

This paper explores the method and findings of a qualitative examination into multiple work integrated learning (MWIL) placements. The research consisted of 14 reflective interviews with students from across discipline areas who had undertaken a series of work placements. The range of MWIL experiences included professional placements in nursing and youth work, yearlong placements in accountancy and engineering, self-directed WIL experiences in arts, informal and part-time placements. The aim of this study was to explore the transitions that took place throughout multiple placements that helped the student to become a work ready and an effective professional. A research method, 'Placement Timeline' was developed. This allows a reflective structure for the researcher to tease out skill development and work readiness. All interviews were transcribed and coded using NVivo qualitative software. The paper will discuss selected findings from the research. These provide insights into how multiple WIL experiences may benefit students in their preparation for work. In effect it was as if the work readiness and skills relating to an uncertain and ever changing job market skills were fast tracked over MWIL.This research highlights the key transitional features of MWIL