Supporting New Teachers of Color and Cultural Diversity

Educators and policy makers are calling for increasing the racial and cultural diversity of the teacher workforce, given the widening cultural gap between students and teachers (see Figure 1), and the widening achievement gap between students of color and White students. Some research suggests teachers of color can address the needs of students of color through culturally relevant practices (Quiocho & Rios, 2000). However, recent studies reveal teachers of color suffer greater job dissatisfaction and higher turnover than White teachers (Ingersoll & Connor, 2008; Marvel et al., 2007).Furthermore, cultural practices of teachers of color, if valued in our schools, need to be developed rather than assumed (Sheets, 2000). Given these circumstances, educators are faced with the following questions:- What factors impact retention and attrition of new teachers of color?- What factors support new teachers of color to develop and implement practices that address the needs of students from culturally and linguistically diverse backgrounds?These questions are addressed by a team of researchers at the New Teacher Center, UCSC in a study that followed 21 teachers of color over five years, from preparation through four years of teaching in high-need California schools serving low-income and high-minority student populations

Prebisch-Singer Redux

In light of ongoing concern about commodity specialization in Latin America, this paper revisits the argument of Prebisch (1950) that, over the long term, declining terms of trade would frustrate the development goals of the region. This paper has two main objectives. The first is to clarify the issues raised by Prebisch and Singer (1950), as they relate the commodity specialization of developing countries (and Latin America in particular). The second is to reconsider empirically the issue of trends in commodity prices, using recent data and techniques. We show that rather than a downward trend, real primary prices over the last century have experienced one or more abrupt shifts, or “structural breaks,” downwards. The preponderance evidence points to a single break in 1921, with no trend, positive or negative, before or since.

The Effects of Adrenal Steroids on Electrolyte and Water Balance in Force-Fed Adrenalectomized Rats

The literature dealing with various aspects of adrenal cortical function is so voluminous that any review is necessarily incomplete, both with respect to topics treated and references cited. In this paper discussion is restricted to certain features of cortex function, namely the effects on water and electrolyte balance and weight maintenance

Soil organic matter and aggregate dynamics in an Arctic ecosystem

2010 Fall.Includes bibliographical references.Warming has been linked to changes in Arctic soil carbon cycling. Cold temperatures and anoxic conditions in the Arctic diminish microbial activity. As a result mineralization rates are low and the system is nitrogen-limited, further reducing biological activity. Reducing this constraint on nutrient availability has resulted in a vegetation shift and loss of soil carbon; however, the mechanisms behind soil carbon loss are not well understood. The focus of this study was on the active mineral layer directly below the organic horizon. Soils were collected during the 2007 growing season from a long-term nutrient addition experiment in which soils had been fertilized with additional N and P since 1996 and 1989 at the Arctic LTER site at Toolik Lake, on the Alaskan North Slope. Roots were separated from the soil to estimate biomass. Soils were separated into four size classes of water-stable aggregates (Large and small macroaggregates, microaggregates, and silt+clay). Small macroaggregates were separated into three sub-fractions (coarse particulate organic matter (POM), occluded microaggregates, and silt+clay). Density floatation was used to separate light fraction (LF) organic matter from heavy fraction in small macroaggregates and microaggregates. Intra-aggregate POM (iPOM) content was determined in small macroaggregates and microaggregates. Differences in aggregate size distribution, C and N allocation, and C:N in each fraction were analyzed. Small Macroaggregates were the dominant aggregate fraction in all treatments. Mid-season declines in large macroaggregate abundance from soils with nutrient addition differed statistically from the control, though both comprised <10% of the whole soil. The ratio of free:occluded microaggregates rose over the growing season, which indicated that microaggregates occluded within small macroaggregates were released upon macroaggregate disruption. Occluded microaggregates tended to possess higher carbon and nitrogen contents than free microaggregates due to increased physical protection within the macroaggregate. As a result, the ratio of free:occluded microaggregate C:N declined over the growing season, possibly due to N-rich, formerly occluded microaggregates entering the free microaggregate pool. Nutrient addition resulted in changes in C allocation in the small aggregate LF and microaggregate iPOM to an increasingly large amount over the growing season. Nitrogen allocation responded in a similar manner, resulting in a lower C:N in the LF of soils under nutrient addition since 1989. Nutrient addition resulted in an increase in root biomass by the middle of the growing season; however by the final sampling date, root biomass declined. Nutrient addition affected aggregate size class distribution only in mid-June, which indicated that this is a dynamic period of aggregate formation and may be dependent on the microbial community and N availability. Macroaggregate turnover, as evidenced by free:occluded microaggregate abundance, occurred earlier in the growing season in soils with nutrient addition than the control. As a result, SOM formerly occluded within macroaggregates may be increasingly susceptible to decomposition by the microbial community over the growing season. The re-allocation of SOM from physically protected aggregates to light fraction with nutrient addition may result in shifts in SOM stability in these soils. The observed increases in the proportion of soil carbon as light fraction and iPOM with nutrient addition indicate a shift towards an increase in POM fractions that tend to be labile, potentially mineralizable sources of organic matter. The balance between the rates of organic matter input and decomposition may favor decomposition, resulting in a short-term loss of carbon in Arctic soil. Carbon content may stabilize in the future as its remaining stocks become increasingly processed by the microbial community. These results highlight the importance of multiple sample collection dates, which are necessary if we are to improve our understanding of factors driving SOM stabilization in Arctic soils

Optimal Contract Design for Co-development of Companion Diagnostics

As the number of new drugs requiring companion diagnostics rises, more and more partnerships are formed between drug and diagnostics manufacturers to develop the necessary companion diagnostic. An increasingly significant issue is that of the optimal revenue/profit sharing or compensation schemes for such partnerships. We investigate the structure of an optimal compensation scheme under a scenario where a large pharmaceutical firm that is developing a drug intends to partner with a smaller diagnostics firm to develop a companion diagnostic test for the drug. We describe an optimal contract as one that maximizes the pharmaceutical firm\u27s expected profits while offering enough incentives for the diagnostics firm to accept the contract and then work at an effort level that is preferred by the pharmaceutical firm. We formulate the problem of determining the optimal contract as an instance of the Principal-Agent problem. We then present a numerical approach for solving the problem

Shear Bond Strength Comparison between Two Orthodontic Adhesives and Self-Ligating and Conventional Brackets

Objective: To evaluate and compare the shear bond strengths of two adhesives using two types of brackets: a conventional and a self-ligating bracket system. Materials and Methods: Sixty extracted human premolars were collected. The premolars were randomly divided into three groups of 20 teeth. All three groups were direct bonded. Groups 1 and 2 used light-cured adhesive and primer (Transbond XT) with a conventional (Orthos) and a self-ligating bracket (Damon 2), respectively. Group 3 used a light-cured primer (Orthosolo) and a light-cured adhesive (Blūgloo) with a self-ligating bracket (Damon 2). The specimens were stored in distilled water at 37°C for 40 ± 2 hours, after which they were debonded and inspected for Adhesive Remnant Index (ARI) scoring. Results: The mean shear bond strength was 15.2 MPa for group 1, 23.2 MPa for group 2, and 24.8 MPa for group 3. A one-way analysis of variance and post hoc Tukey test showed significant differences in bond strength (P \u3c .001) between group 1 and groups 2 and 3 but no significant difference (P \u3e .05) between groups 2 and 3. A Weibull analysis demonstrated that all three groups provided sufficient bond strength with over 90% survival rate at normal masticatory and orthodontic force levels. A Kruskal-Wallis test showed no significant difference (P \u3e .05) in ARI scores among all three groups. Conclusions: All three groups demonstrated clinically acceptable bond strength. The Damon 2 self-ligating bracket exhibited satisfactory in vitro bond strength with both adhesive systems used

Joint Resource Optimization for Multicell Networks with Wireless Energy Harvesting Relays

This paper first considers a multicell network deployment where the base station (BS) of each cell communicates with its cell-edge user with the assistance of an amplify-and-forward (AF) relay node. Equipped with a power splitter and a wireless energy harvester, the self-sustaining relay scavenges radio frequency (RF) energy from the received signals to process and forward the information. Our aim is to develop a resource allocation scheme that jointly optimizes (i) BS transmit powers, (ii) received power splitting factors for energy harvesting and information processing at the relays, and (iii) relay transmit powers. In the face of strong intercell interference and limited radio resources, we formulate three highly-nonconvex problems with the objectives of sum-rate maximization, max-min throughput fairness and sum-power minimization. To solve such challenging problems, we propose to apply the successive convex approximation (SCA) approach and devise iterative algorithms based on geometric programming and difference-of-convex-functions programming. The proposed algorithms transform the nonconvex problems into a sequence of convex problems, each of which is solved very efficiently by the interior-point method. We prove that our algorithms converge to the locally optimal solutions that satisfy the Karush-Kuhn-Tucker conditions of the original nonconvex problems. We then extend our results to the case of decode-and-forward (DF) relaying with variable timeslot durations. We show that our resource allocation solutions in this case offer better throughput than that of the AF counterpart with equal timeslot durations, albeit at a higher computational complexity. Numerical results confirm that the proposed joint optimization solutions substantially improve the network performance, compared with cases where the radio resource parameters are individually optimized