Teachers in a New Political Landscape

Teachers’ positionality within the political landscape has evolved rapidly over recent election cycles. In Texas, nationwide teacher advocacy and anti-teacher state legislation motivated teachers to become politically involved. Increased teacher voting greatly impacted the 2018 election results, which led statewide leaders and legislators of the 86th Texas legislative session (2019) to center teachers as a key component of school finance reform. Moving forward, it is important to understand other factors that are interrelated with the positionality of the education profession, such as gender, class, and the ability to run for office. Additionally, in order to maintain their centrality in the legislative decision-making process, teachers must develop action plans collectively.Educatio

Carbide factor predicts rolling-element bearing fatigue life

Analysis was made to determine correlation between number and size of carbide particles and rolling-element fatigue. Correlation was established, and carbide factor was derived that can be used to predict fatigue life more effectively than such variables as heat treatment, chemical composition, and hardening mechanism

Saffman-Taylor instability in a non-Brownian suspension: finger selection and destabilization

We study the Saffman-Taylor instability in a non-Brownian suspension by injection of air. We find that flow structuration in the Hele-Shaw cell can be described by an effective viscosity depending on the volume fraction. When this viscosity is used to define the control parameter of the instability, the classical finger selection for Newtonian fluids is recovered. However, this picture breaks down when the cell thickness is decreased below approximatively 10 grain sizes. The discrete nature of the grains plays also a determinant role in the the early destabilization of the fingers observed. The grains produce a perturbation at the interface proportional to the grain size and can thus be considered as a "controlled noise". The finite amplitude instability mechanism proposed earlier by Bensimon et al. allows to link this perturbation to the actual values of the destabilization threshold.Comment: 4 pages, 4 figures, submitted to PR

Study of hot hardness characteristics of tool steels

Hardness measurements of tool steel materials in electric furnace at elevated temperatures and low oxygen environment are discussed. Development of equation to predict short term hardness as function of intial room temperature hardness of steel is reported. Types of steel involved in the process are identified

Why Don't Prices Rise During Periods of Peak Demand? Evidence from Scanner Data

We examine the retail prices and wholesale prices of a large supermarket chain in Chicago over seven and one-half years. We show that prices tend to fall during the seasonal demand peak for a product and that changes in retail margins account for most of those price changes; thus we add to the growing body of evidence that markups are counter-cyclical. The pattern of margin changes that we observe is consistent with loss leader' models such as the Lal and Matutes (1994) model of retailer pricing and advertising competition. Other models of imperfect competition are less consistent with retailer behavior. Manufacturer behavior plays a more limited role in the counter-cyclicality of prices.

A Nano-Scale Chemical and Structural Characterization of Chinook Salmon (Oncorhynchus tshawytscha) Otoliths Using a FIB and HRTEM

We used a focused ion beam (FIB) to create thin sections from the post-hatch and core regions of Chinook salmon (Oncorhynchus tshawytscha) otoliths. The nano-scale chemistry and structure of these regions was characterized in thin section using scanning electron microscopy (SEM) in conjunction with cathodoluminescence (CL) and high resolution transmission electron microscopy (HRTEM). The results constrained the relative distribution of several elements; silicon-enriched nodules were found in the post-hatch otolith, and manganese, an element known to be enriched in the greater otolith core, was most concentrated at the center of primordia and at the primordia-core interfaces. Calcium was less abundant and carbon was observed in greater relative concentrations in the primordia relative to the surrounding core. HRTEM revealed a lack of crystallinity in the core relative to the post-hatch otolith. This is the first study to successfully thin-section an otolith using a FIB and characterize the thin section using HRTEM

Short-term hot hardness characteristics of rolling-element steels

Short-term hot hardness studies were performed with five vacuum-melted steels at temperatures from 294 to 887 K (70 to 1140 F). Based upon a minimum Rockwell C hardness of 58, the temperature limitation on all materials studied was dependent on the initial room temperature hardness and the tempering temperature of each material. For the same room temperature hardness, the short-term hot hardness characteristics were identical and independent of material composition. An equation was developed to predict the short-term hardness at temperature as a function of initial room temperature hardness for AISI 52100, as well as the high-speed tool steels

A microbe-bryozoan reef from the middle Visean of the Namur Syncline (Enginoul quarry)

A microbe-bryozoan patch-reef was temporarily exposed in the Lives Formation (middle Visean) at the Engihoul Quarry, southern limb of the Namur syncline. It developed within the Corphalie Member during the transition from bioclastic to stromatolitic facies. Reef formation is the result of a complex meshwork of calcified microbes, which formed complex layers which resemble “Osagia”-biocenose and individual columnar aggregates, fenestellid bryozoans, and early cements. Reef growth began on a hard-substrate provided by brachiopods and microbial crusts. Brachiopods (Composita sp.) are locally abundant in the reef facies, and contributed substantial firm ground for encrustation. Reef growth was controlled mainly by the abundance of fenestellid bryozoans. Their presence indicates reef formation during normal marine conditions. The reef developed in a high-energy area of the inner shelf. Reef growth probably stopped with the establishment of a peloidal mudstone facies, eventually indicating hypersaline conditions. The Engihoul reef is similar to Bomel reefs (also in the Lives Formation). All are the same age and developed in the transitional phase of the Corphalie Member, but minor differences in the individual reef fauna occur. The transitional phase of the Corphalie Member is an important horizon for reef formation with clear independence from other reef forming episodes within the Belgian Dinantian succession

Radio and X-ray Observations of the Type Ic SN 2007gr Reveal an Ordinary, Non-relativistic Explosion

We present extensive radio and X-ray observations of the nearby Type Ic SN 2007gr in NGC 1058 obtained with the Very Large Array and the Chandra X-ray Observatory and spanning 5 to 150 days after explosion. Through our detailed modeling of these data, we estimate the properties of the blastwave and the circumstellar environment. We find evidence for a freely-expanding and non-relativistic explosion with an average blastwave velocity, v~0.2c, and a total internal energy for the radio emitting material of E ~ 2 x 10^46 erg assuming equipartition of energy between electrons and magnetic fields (epsilon_e=epsilon_B=0.1). The temporal and spectral evolution of the radio emission points to a stellar wind-blown environment shaped by a steady progenitor mass loss rate of Mdot ~ 6 x 10^-7 solar masses per year (wind velocity, v_w=10^3 km/s). These parameters are fully consistent with those inferred for other SNe Ibc and are in line with the expectations for an ordinary, homologous SN explosion. Our results are at odds with those of Paragi et al. (2010) who recently reported evidence for a relativistic blastwave in SN 2007gr based on their claim that the radio emission was resolved away in a low signal-to-noise Very Long Baseline Interferometry (VLBI) observation. Here we show that the exotic physical scenarios required to explain the claimed relativistic velocity -- extreme departures from equipartition and/or a highly collimated outflow -- are excluded by our detailed Very Large Array radio observations. Moreover, we present an independent analysis of the VLBI data and propose that a modest loss of phase coherence provides a more natural explanation for the apparent flux density loss which is evident on both short and long baselines. We conclude that SN 2007gr is an ordinary Type Ibc supernova.Comment: 14 pages, 6 figures, submitted to Ap