A comparison of scores of kindergarten children and nonkindergarten children in specific background abilities at first grade entrance

Thesis (Ed.M.)--Boston Universit

Organic matter decomposition pathways and oxygen consumption in coastal marine sediments

In this study, we investigate the possible use of ∑CO2 production, determined from anoxic incubation experiments, and natural solute (O2, NH4+, SO4–) distributions to infer the pathways of organic matter decomposition in nearshore marine sediments. Integrated ∑CO2 production from anoxic incubation experiments agreed well with direct measurements of ∑CO2 fluxes across oxic sediment-water interfaces in Long Island Sound and Flax Pond salt marsh. This implies that anoxic incubations give reliable estimates of organic carbon remineralization rates. Therefore, anoxic ∑CO2 production, as a function of depth, was used to derive the relative roles of different electron acceptors in the organic matter decomposition process. These calculations indicate that the maximum contribution of O2 to total organic matter decomposition in the environments investigated ranges from 3–14%, whereas the minimum contribution of SO4– to total decomposition ranges from 65–85%. One-dimensional models of O2 distributions in sediments indicate that O2 reduction can be a significant component of organic matter decomposition (\u3e20%) only in benthic environments characterized by: (1) low total organic matter decomposition rates, (2) extremely rapid attenuation of organic matter decomposition with depth, and/or (3) very intense bioturbation. These results bring into question the generality of previous assertions that O2 accounts for 50% or more of total organic matter decomposition in reactive nearshore marine sediments

Open-incubation, diffusion methods for measuring solute reaction rates in sediments

Sedimentary solute distributions and fluxes are determined in part by the kinetics of production/consumption reactions in a deposit. It is possible to estimate rates and investigate kinetic relations in undisturbed or manipulated sediments by documenting build-up or depletion patterns of solutes allowed to diffuse either between relatively thin sections of sediment and a well-stirred water reservoir (plug incubation); or through a large section of sediment without an overlying reservoir (whole-core incubation). The time-dependent concentrations in the sediment in both cases depend on reaction rates, kinetics, diffusion coefficients, and geometric scaling of the sediment and contacting reservoir. Major advantages of the plug incubation method are that interactions between classes of sedimentary reactions can be examined by manipulating the composition of the stirred water reservoir, and kinetic relations, such as reaction order, can be inferred from comparisons of reaction rate with steady-state concentrations of pore water solutes. The water reservoir size and sediment thickness can be altered to allow rapid estimates of reaction rates at near steady-state or to examine nonsteady-state behavior. Nonsteady-state models are always required for the whole-core incubation method. This latter method has the advantages that it is less labor-intensive than many other rate measurement methods and the incubations can be performed in situ. Experimental comparisons between open-incubation and more traditional closed-incubation estimates of reaction rates show good agreement for solutes such as NH4+, SO4–, HPO4– and I–. In some cases, such as Mn++, Fe++, and HPO4– production, where major back-reactions with sediment occur, open-incubations without substantial build-up of solutes may provide the most accurate method for estimating production rates. In principle, the open incubation methods described in this paper can be used for any diffusable species

Conceptualizing control in everyday music listening: defining dominance

Mehrabian and Russell’s Pleasure-Arousal-Dominance model states that people’s interactions and interpretation of their surroundings result from variations in three factors – pleasure, arousal, and dominance. Applied to music, pleasure has been operationalized as how much a person likes the music heard, arousal as how arousing the person considers the music to be, and dominance as the person’s control over the music heard. However, conceptualizing dominance broadly as control means that the construct is not well defined. This research aimed to define the elements related to a listener’s desire for control over music encountered in everyday life. Participants residing in Australia and USA (N ¼ 590) completed an online questionnaire. An exploratory factor analysis of the quantitative items identified five components defining control over music listening: “being personally in charge”, “selection by other people”, “contextual control”, “playback variety”, and “no need for control”. A thematic analysis of open-ended responses indicated additional facets of control including mood regulation, emotional investment, and identity. While the quantitative findings reaffirm previous research, the qualitative findings indicate previous conceptualizations of the control dimension have been limited. These results contribute to our understanding of the model’s dominance component with regard to explaining everyday music listening

EGO-1 is related to RNA-directed RNA polymerase and functions in germ-line development and RNA interference in C. elegans

AbstractBackground: Cell-fate determination requires that cells choose between alternative developmental pathways. For example, germ cells in the nematode worm Caenorhabditis elegans choose between mitotic and meiotic division, and between oogenesis and spermatogenesis. Germ-line mitosis depends on a somatic signal that is mediated by a Notch-type signaling pathway. The ego-1 gene was originally identified on the basis of genetic interactions with the receptor in this pathway and was also shown to be required for oogenesis. Here, we provide more insight into the role of ego-1 in germ-line development.Results: We have determined the ego-1 gene structure and the molecular basis of ego-1 alleles. Putative ego-1 null mutants had multiple, previously unreported defects in germ-line development. The ego-1 transcript was found predominantly in the germ line. The predicted EGO-1 protein was found to be related to the tomato RNA-directed RNA polymerase (RdRP) and to Neurospora crassa QDE-1, two proteins implicated in post-transcriptional gene silencing (PTGS). For a number of germ-line-expressed genes, ego-1 mutants were resistant to a form of PTGS called RNA interference.Conclusions: The ego-1 gene is the first example of a gene encoding an RdRP-related protein with an essential developmental function. The ego-1 gene is also required for a robust response to RNA interference by certain genes. Hence, a protein required for germ-line development in C. elegans may be a component of the RNA interference/PTGS machinery