Teacher Of Color Retention: Stories Of Staying From Teachers Of Color In A Suburban School District

A teaching force which is representative of the student population is critical to creating equitable learning opportunities in the increasingly diverse United States. Both students of color and White students must see themselves represented in their teachers. Additionally, it is important for all students to see people of color as educators as well as in positions of power. Unfortunately, the proportion of teachers of color currently in the field of education does not come close to the proportion of students of color in public schools in the United States. While there are many aspects which add to the problem of teacher of color representation, this research addresses teacher of color retention. Current research suggests that while teachers of color enter the field of teaching at a similar rate to White teachers, retention for teachers of color is far worse than for their White peers. Many previous research studies have discussed the challenges faced in the field by teachers of color and why many teachers of color leave due to these challenges. This dissertation, instead, focuses on the positive “stories of staying” from teachers of color who have remained teaching. This research draws from the narratives of eight teachers of color to bring forward patterns that have supported their retention in the field. All participants were drawn from a teacher of color affinity program in one suburban school district. Participants in this study spoke specifically about the importance of racial matching with their students as an important internal factor for their retention in the field. They also discussed the interpersonal connections with a racial affinity group and/or mentor as critical. Finally, they discussed the external support of their site-level administrators as well as a district focus on providing opportunities for conversations about race as important to their retention in the field. Based on these participant narratives, recommendations are provided for professional practice which might support conditions favorable to teacher of color retention. Additionally, recommendations for White educators are listed as the overwhelming majority of educators are still White. Finally, a discussion of colorism within the participant narratives provides recommendations for future research to understand how teachers of different races are impacted by challenging racial conditions

Alternate Materials for High-speed Projectile Casing

A high-speed projectile impact is a highly complex dynamic problem that can be simplified with the use of finite element analysis solvers. Abaqus/Explicit was used to evaluate the impact of various projectiles using a plane strain setup. Using a baseline stainless steel projectile, the proposed sandwich construction design was analyzed and compared to the baseline projectile. The overall goal was to see if a new composite casing could perform similarly to the simple baseline projectile. The sandwich construction used stainless steel, tungsten, and silicon-carbide reinforce aluminum as outer and inner shell materials. The core material was created using additive manufacturing of inconel 718. The inconel 718 core is a triply periodic minimal surface structure manufactured to provide the projectile casing with high stiffness and strength while reducing material used to manufacture it. A monolithic concrete target using a brittle cracking model for a projectile hitting a concrete wall in order to simulate a projectile impacting a bunker, road, or other concrete structure. Each projectile was evaluated using either the Johnson-Cook damage model or the Hashin damage model depending on if the shell materials were ductile metals or a metal matrix composite. By implementing the sandwich design, the negatives and benefits can be considered for mission feasibility

Early Permian Seawater from the delta18O Record Of Fossil Bivalves: Seasonality And A Latitudinal Gradient

The transition from a glaciated world to one that was ice-free makes the early Permian a time interval that in many ways mirrors the present, and hence there is great interest in constraining paleoclimate conditions over that transition. A common method for estimating ancient temperatures uses the oxygen isotope composition of marine carbonate, but this approach becomes significantly more complicated prior to the Cretaceous due to uncertainties about diagenesis and the isotopic composition of seawater, which has been hypothesized to be more depleted than during the Cenozoic. I use stable isotope compositions of sequentially microsampled accretionary calcite from fossil bivalves in SE Australia to evaluate Permian seawater isotope composition and water temperature seasonality. Co-occurring dropstones, diamicts, and glendonites constrain winter temperatures to near-freezing and hence allow calculations of water composition. Records from microsampled specimens of the bivalve Eurydesma, spanning roughly 11° of paleolatitude (North Sydney Basin, New South Wales to Hobart, Tasmania) reveal cyclic seasonal fluctuations in δ18Ocarb that vary with latitude. The δ13Ccarb values exhibit ~1 / of seasonal variation, and are in agreement with characteristically positive values published for the early Permian of ~5.5 /. The δ18Ocarb values vary seasonally by up to 3.3 /around a mean that decreases from -1.2 / to -1.75 / moving towards the pole; more enriched isotope values correspond to dark growth bands within the shells, suggesting slower growth in the winter months. Mean δ18O and seasonal amplitude both decrease with increasing paleolatitude, similar to an observed gradient in the modern high latitudes off the coast of Greenland. Decreasing seasonality is a reflection of decreasing summer temperatures with increasing latitude, while winter temperature minima are presumed to be constant because of freezing conditions. The decrease in mean δ18Ocarb with latitude reflects decreasing δ18Owater, similar to that observed over a similar latitudinal range off Greenland today. As with Greenland, the slope of the δ18O-latitude relationship is steeper than that seen in the global ocean today, indicating some contribution of isotopically negative fresh water. Whether this reflects progressive mixing with isotopically negative water from higher latitudes (e.g., the Arctic Ocean today) or similar amounts of runoff/precipitation at each location that itself is progressively more negative with latitude is as yet unclear, though significant departure from marine salinities is not observed

Data From: Root Distributions Predict Shrub-Steppe Responses to Precipitation Intensity

Precipitation events are becoming more intense around the world, changing the way water moves through soils and plants. Plant rooting strategies that sustain water uptake under these conditions are likely to become more abundant (e.g., shrub encroachment). Yet, it remains difficult to predict species responses to climate change because we typically do not know where active roots are located or how much water they absorb. Here, we applied a water tracer experiment to describe forb, grass, and shrub root distributions. These measurements were made in 8 m by 8 m field shelters with low or high precipitation intensity. We used tracer uptake data in a soil water flow model to estimate how much water respective plant root tissues absorb over time. In low precipitation intensity plots, deep shrub roots were estimated to absorb the most water (93 mm yr-1) and shrubs had the greatest aboveground cover (27%). Grass root distributions were estimated to absorb an intermediate amount of water (80 mm yr-1) and grasses had intermediate aboveground cover (18%). Forb root distributions were estimated to absorb the least water (79 mm yr-1) and had the least aboveground cover (12%). In high precipitation intensity plots, shrub and forb root distributions changed in ways that increased their water uptake relative to grasses, predicting the increased aboveground growth of shrubs and forbs in these plots. In short, water uptake caused by different rooting distributions predicted plant aboveground cover. Our results suggest that detailed descriptions of active plant root distributions can predict plant growth responses to climate change in arid and semi-arid ecosystems

Root Niche Partitioning among Grasses, Saplings, and Trees Measured Using a Tracer Technique

Niche partitioning of resources by plants is believed to be a fundamental aspect of plant coexistence and biogeochemical cycles; however, measurements of the timing and location of resource use are often lacking because of the difficulties of belowground research. To measure niche partitioning of soil water by grasses, planted saplings, and trees in a mesic savanna (Kruger National Park, South Africa), we injected deuterium oxide into 102,000 points in 15, 154-m2 plots randomly assigned to one of five depths (0–120 cm) and one of three time periods during the 2008/2009 growing season. Grasses, saplings and trees all demonstrated an exponential decline in water uptake early in the season when resources were abundant. Later in the season, when resources were scarce, grasses continued to extract the most water from the shallowest soil depths (5 cm), but saplings and trees shifted water uptake to deeper depths (30–60 cm). Saplings, in particular, rapidly established roots to at least 1 m and used these deep roots to a greater extent than grasses or trees. Helping to resolve contradictory observations of the relative importance of deep and shallow roots, our results showed that grasses, saplings and trees all extract the most water from shallow soils when it is available but that woody plants can rapidly shift water uptake to deeper soils when resources are scarce. Results highlight the importance of temporal changes in water uptake and the problems with inferring spatial and temporal partitioning of soil water uptake from root biomass measurements alone

Chronosequence and Direct Observation Approaches Reveal Complementary Community Dynamics in a Novel Ecosystem

Non-native, early-successional plants have been observed to maintain dominance for decades, particularly in semi-arid systems. Here, two approaches were used to detect potentially slow successional patterns in an invaded semi-arid system: chronosequence and direct observation. Plant communities in 25 shrub-steppe sites that represented a 50-year chronosequence of agricultural abandonment were monitored for 13 years. Each site contained a field abandoned from agriculture (ex-arable) and an adjacent never-tilled field. Ex-arable fields were dominated by short-lived, non-native plants. These ‘weedy’ communities had lower species richness, diversity and ground cover, and greater annual and forb cover than communities in never-tilled fields. Never-tilled fields were dominated by long-lived native plants. Across the chronosequence, plant community composition remained unchanged in both ex-arable and never-tilled fields. In contrast, 13 years of direct observation detected directional changes in plant community composition within each field type. Despite within-community changes in both field types during direct observation, there was little evidence that native plants were invading ex-arable fields or that non-native plants were invading never-tilled fields. The more-controlled, direct observation approach was more sensitive to changes in community composition, but the chronosequence approach suggested that these changes are unlikely to manifest over longer time periods, at least in part because of disturbances in the system. Results highlight the long-term consequences of soil disturbance and the difficulty of restoring native perennials in disturbed semi-arid systems

Total or Partial Knee Arthroplasty Trial - TOPKAT : study protocol for a randomised controlled trial

Peer reviewedPublisher PD

Winter Wheat Resistant to Increases in Rain and Snow Intensity in a Semi-Arid System

As the atmosphere warms, precipitation events have been predicted and observed to become fewer and larger. Changes in precipitation patterns can have large effects on dryland agricultural production, but experimental tests on the effects of changing precipitation intensity are limited. Over 3 years, we tested the effects of increased precipitation intensity on winter wheat (Triticum aestivum L.; Promontory variety) in a temperate dryland agricultural system that was on a rotation of crop and fallow years. We used 11 (2.1 × 2.5 m) shelters to collect and redeposit rain and snow as larger, more intense events. Total precipitation was the same in all plots, but event sizes in each plot varied from 1 to 18 mm. Treatments increased soil water availability, but winter wheat biomass and grain yield did not differ among treatments. Similarly, other measured plant growth responses, including vegetation greenness, leaf area index, canopy temperature, photochemical efficiency, root area, and new root growth, did not differ among treatments. Results indicate that at least in the semiarid climate and silt loam soils studied here, anticipated increases in precipitation intensity are unlikely to affect winter wheat production negatively. Further, increased precipitation intensity may mitigate water stress caused by increasing temperatures and encourage the use of wheat varieties that utilize deeper, later season soil water