Fourth Grade Writing Instruction: A Case Study of Three Teachers in Title I Schools

The purpose of this study was to explore writing instruction provided to students in fourth grade classrooms of two Title I schools. The researchers observed the writing instruction and classroom procedures of three fourth grade teachers at these two Title I campuses. The following three research questions guided this study: (1) How do fourth grade writing teachers in two Title I schools in Texas approach the teaching of writing? (2) How does the challenge of standardized testing impact writing instruction? (3) How do these fourth grade teachers perceive their effectiveness as teachers of writing? Analysis of data led to the following conclusions: for these three teachers, district mandates and a centralized curriculum established the agenda for classroom writing instruction for the most part. However, even within these constraints, researchers observed that efforts were made by each teacher to adapt some of the curriculum needs of their students and to incorporate their own teaching styles and strategies as much as possible

Interactive Regulation of Dissolved Copper Toxicity by an Estuarine Microbial Community

Cultured marine microorganisms under copper stress produce extracellular compounds having a high affinity for copper (copper-complexing ligands). These ligands are similar in binding strength to those found in natural waters, but few studies have examined the relationship between copper, copper-complexing ligand concentrations, and natural microbial populations. A series of in situ experiments in the Elizabeth River, Virginia, revealed that an intact estuarine microbial community responded to copper stress by production of extracellular, high-affinity copper-complexing ligands. The rate of ligand production was dependent on copper concentration and resulted in a reduction of the concentration of free cupric ions, Cu2+, by more than three orders of magnitude during a 2-week period in one experiment. We believe that this interactive response to copper stress represents a feedback system through which microbial communities can potentially buffer dissolved Cu2+ ion concentrations, thereby regulating copper bioavailability and toxicity

The Effect of Storm Events on Diet of Adult Mummichogs (Fundulus heteroclitus)

More frequent storms due to climate change may impact estuarine species such as the mummichog (Fundulus hetereoclitus), an ecologically important salt marsh fish. This study investigated the effect of storm events and month on consumption of terrestrial insects by mummichogs in Hoffler Creek, Portsmouth, VA, as well as the effect of storms on consumption of major categories of benthic prey. Samples were taken monthly in the summers of 2017 and 2019. Additional paired samples were taken in June and July 2019, with the first collection during dry weather and the second during a subsequent storm. Month had a significant effect on the proportion of terrestrial insect prey in the diet in both years; consumption was highest in August, particularly in 2017 when the sample coincided with a storm event. However, storms increased consumption of terrestrial insects in only one of four paired dry weather-storm samples in 2019, indicating that temporal variation in insect abundance has a larger effect than increased availability that might occur when storms knock insects into the water. Storms had a significant effect on the proportion of different benthic prey in the diet in paired samples from 2019, but these effects were not consistent across months, sites, or in whether storms increased or decreased consumption. These patterns may be driven by mummichogs taking advantage of small-scale temporal or spatial variation in benthic prey. The ability to utilize locally abundant resources, including terrestrial insects, may help minimize the negative impacts of climate change on mummichogs

Alleviation of restriction by DNA condensation and non-specific DNA binding ligands

During conditions of cell stress, the type I restriction and modification enzymes of bacteria show reduced, but not zero, levels of restriction of unmethylated foreign DNA. In such conditions, chemically identical unmethylated recognition sequences also occur on the chromosome of the host but restriction alleviation prevents the enzymes from destroying the host DNA. How is this distinction between chemically identical DNA molecules achieved? For some, but not all, type I restriction enzymes, alleviation is partially due to proteolytic degradation of a subunit of the enzyme. We identify that the additional alleviation factor is attributable to the structural difference between foreign DNA entering the cell as a random coil and host DNA, which exists in a condensed nucleoid structure coated with many non-specific ligands. The type I restriction enzyme is able to destroy the ‘naked’ DNA using a complex reaction linked to DNA translocation, but this essential translocation process is inhibited by DNA condensation and the presence of non-specific ligands bound along the DNA

Cyclostationary Processes on Shape Spaces for Gait-Based Recognition

Abstract. We present a geometric and statistical approach to gaitbased human recognition. The novelty here is to consider observations of gait, considered as planar silhouettes, to be cyclostationary processes on a shape space of simple closed curves. Consequently, gait analysis reduces to quantifying differences between underlying stochastic processes using their observations. Individual shapes can be compared using geodesic lengths, but the comparison of gait cycles requires tools for extraction, interpolation, registration, and averaging of individual gait cycles before comparisons. The main steps in our approach are: (i) off-line extraction of human silhouettes from IR video data, (ii) use of piecewise-geodesic paths, connecting the observed shapes, to smoothly interpolate between them, (iii) computation of an average gait cycle within class (i.e. associated with a person) using Karcher means, (iv) registration of average cycles using linear and nonlinear time scaling, (iv) comparisons of average cycles using geodesic lengths between the corresponding shapes. We illustrate this approach on gait sequence obtained from infrared video clips. Experimental results are presented for a data set of 26 subjects.

StpA protein from Escherichia coli condenses supercoiled DNA in preference to linear DNA and protects it from digestion by DNase I and EcoKI

The nucleoid-associated protein, StpA, of Escherichia coli binds non-specifically to double-stranded DNA (dsDNA) and apparently forms bridges between adjacent segments of the DNA. Such a coating of protein on the DNA would be expected to hinder the action of nucleases. We demonstrate that StpA binding hinders dsDNA cleavage by both the non-specific endonuclease, DNase I, and by the site-specific type I restriction endonuclease, EcoKI. It requires approximately one StpA molecule per 250–300 bp of supercoiled DNA and approximately one StpA molecule per 60–100 bp on linear DNA for strong inhibition of the nucleases. These results support the role of StpA as a nucleoid-structuring protein which binds DNA segments together. The inhibition of EcoKI, which cleaves DNA at a site remote from its initial target sequence after extensive DNA translocation driven by ATP hydrolysis, suggests that these enzymes would be unable to function on chromosomal DNA even during times of DNA damage when potentially lethal, unmodified target sites occur on the chromosome. This supports a role for nucleoid-associated proteins in restriction alleviation during times of cell stress

Impact of target site distribution for Type I restriction enzymes on the evolution of methicillin-resistant Staphylococcus aureus (MRSA) populations.

A limited number of Methicillin-resistant Staphylococcus aureus (MRSA) clones are responsible for MRSA infections worldwide, and those of different lineages carry unique Type I restriction-modification (RM) variants. We have identified the specific DNA sequence targets for the dominant MRSA lineages CC1, CC5, CC8 and ST239. We experimentally demonstrate that this RM system is sufficient to block horizontal gene transfer between clinically important MRSA, confirming the bioinformatic evidence that each lineage is evolving independently. Target sites are distributed randomly in S. aureus genomes, except in a set of large conjugative plasmids encoding resistance genes that show evidence of spreading between two successful MRSA lineages. This analysis of the identification and distribution of target sites explains evolutionary patterns in a pathogenic bacterium. We show that a lack of specific target sites enables plasmids to evade the Type I RM system thereby contributing to the evolution of increasingly resistant community and hospital MRSA