A Holocaust-Based Investigative Project: Historical Research for Secondary School Students

Personalizing the Holocaust, that is, moving a study of the event beyond the staggering numbers that often play a central role in units about the Shoah to a focus that is meaningful for students, is a necessary factor in planning effective curricula about the topic. This article outlines an internet-based research project in which a personal bond develops between students and individuals whose lives were changed forever by the Holocaust. In addition, the project allows students to practice research skills that can be transferred to the study of other historical topics

Textbook Coverage of the Destruction of the Armenians

Abstract            Despite its importance as the event that established that the 20th century would be known as “the age of genocide,” the destruction of the Armenians that occurred between the mid-1890s and 1923 is given marginal coverage in contemporary high school history textbooks. This article critiques that coverage, identifying the overall flow of the information that is presented while noting several instances in which information is presented in an underdeveloped, confusing, or contradictory manner. It then makes several suggestions about topics that should be included in expanded coverage of the Armenian situation, thus ensuring that students develop accurate perspectives about this critical event.Key Words            History, study and teachingGenocide            Ethnic conflictTextbooks and teaching history            Teaching controversial issue

Distribution and Relative Abundance of Butterflyfishes and Angelfishes Across a Lagoon and Barrier Reef, Andros Island, Bahamas

Juveniles of Chaetodon capistratus, C. striatus, C. ocellatus, C. sedentarius, Pomacanthus arcuatus, P. paru, Holacanthus ciliaris, and H. tricolor occurred in the shallow lagoon habitats. Adults and subadults of these species were associated with the deeper barrier reef and seaward platform habitats. C. aculeatus occurred only on the outer seaward platform. In strip transects at a seaward platform site, C. capistratus and H. tricolor were found with significantly greater abundance than P. paru and C. striatus

Development and Construction of Low-Cracking High-Performance Concrete (LC-HPC) Bridge Decks: Free Shrinkage, Mixture Optimization, and Concrete Production

The development and evaluation of low-cracking high-performance concrete (LC-HPC) for use in bridge decks is described based on laboratory test results and experience gained during the construction of 14 bridges. The study is divided into three parts covering (1) the development of an aggregate optimization and concrete mixture design program entitled KU Mix, (2) free-shrinkage tests to evaluate potential LC-HPC mixtures developed for use in bridge decks, and (3) the construction and preliminary evaluation of LC-HPC bridge decks constructed in Kansas. This report emphasizes the material aspects of the construction process; a companion report will provide a detailed discussion of the construction, design, and environmental factors affecting the performance of LC-HPC bridge decks. The KU Mix design methodology for determining an optimized combined gradation uses the percent retained chart and the Modified Coarseness Factor Chart. The process begins by developing an ideal gradation followed by the determination of an optimum blend of user-selected aggregates. A Microsoft® Excel workbook enhanced with Visual Basic for Applications is available to perform the optimization process at www.iri.ku.edu. Experiences with the KU Mix design methodology during the construction of several LC-HPC bridge decks indicate that the process is easily implemented and transferred to concrete suppliers and governing officials. The second portion of the study involves evaluating the effect of paste content, water-cement (w/c) ratio, coarse aggregate type, mineral admixture type (silica fume, slag cement, and Class F fly ash each at two levels of replacement), cement type and fineness, a shrinkage reducing admixture, and the duration of curing on the free-shrinkage characteristics of concrete mixtures in the laboratory tested in accordance with ASTM C 157. The evaluation of shrinkage properties includes a total of 56 individual concrete batches. Both a high-absorption (2.5 to 3.0%) coarse iii aggregate and a low-absorption (less than 0.7%) coarse aggregate are evaluated in many of the comparisons. The results indicate that a reduction in w/c ratio (achieved by reducing the water content), longer curing periods, and the addition of a shrinkage reducing admixture reduce concrete shrinkage. When cast with a high-absorption coarse aggregate, the addition of either silica fume or slag cement results in a reduction in shrinkage at all ages, while the addition of fly ash increases early-age shrinkage but has little or no effect on long-term shrinkage. For mixtures containing a low-absorption coarse aggregate, the addition of silica fume or slag cement results in increased early-age shrinkage if the specimens are cured for seven days. These mixtures exhibit reduced shrinkage at all ages when the curing period is increased to 14 days. The addition of fly ash increases shrinkage at all ages for either curing period. The high-absorption limestone used in the study provides internal curing water, which results in the shrinkage of mixtures containing slag cement or silica fume. The final portion of the study presents the specifications, construction experiences, and the preliminary evaluation of 14 LC-HPC bridge decks that have been built or are planned in Kansas. The techniques used to reduce cracking in these bridge decks are presented, and the field experiences for the 18 individual LC-HPC placements completed to date are presented. The results indicate that LC-HPC decks with an optimized aggregate gradation and design w/c ratios of 0.44 and 0.45 with cement contents of 317 and 320 kg/m3 (535 and 540 lb/yd3) have more than adequate workability, finishability, and pumpability, in addition to reduced cracking. A preliminary evaluation of these decks indicates that, on average, the LC-HPC decks are performing at a level approximately equal to or exceeding the best performing monolithic decks in Kansas surveyed over the past 15 years

Cracking and Chloride Contents in Reinforced Concrete Bridge Decks

The effects of material properties, design specifications, construction practices, and environmental site conditions on the performance of reinforced concrete bridge decks are evaluated. Field surveys were performed on 59 bridges to measure deck cracking, chloride ingress, and delaminated area. The surveys were limited to steel girder bridges – bridges that are generally agreed to exhibit the greatest amount of cracking in the concrete decks. The study includes two bridge deck types with silica fume overlays, one in which 5% of the cement is replaced by silica fume (19 bridges) and the other in which 7% of the cement is replaced by silica fume (11 bridges), plus decks with conventional overlays (16 bridges) and monolithic bridge decks (13 bridges). Information from the current study is combined with data from two earlier studies. In total, 27 variables are evaluated, covering bridge age, construction practices, material properties, site conditions, bridge design, and traffic volume. The performance of silica fume overlay decks relative to conventional overlay and monolithic decks is of particular interest due to the widespread use of silica fume overlays in the state of Kansas. The results of the study indicate that chloride contents increase with the age of the bridge deck, regardless of deck type. In addition, concrete for all bridge deck types sampled in the same age range exhibit similar chloride contents for samples taken both at and away from cracks, regardless of deck type. For bridges within the same age range, the average chloride concentration taken away from cracks at the level of the top transverse reinforcement rarely exceeds even the most conservative estimates of the corrosion threshold for conventional reinforcement. Chloride concentrations taken at crack locations, however, can exceed the corrosion threshold in as little as nine months. Based on these observations, it appears clear that attention iii should be focused on minimizing bridge deck cracking rather than concrete permeability. The study demonstrates that crack density increases with increases in the volume of cement paste and that neither higher compressive strengths nor higher concrete slumps are beneficial to bridge deck performance. In addition, crack density is higher in the end regions of decks that are integral with the abutments than decks with pin-ended girders. The results of the crack surveys indicate that cracking increases with age, although a large percentage of the cracking is established early in the life of the deck. Even with the increase in crack density over time, however, both monolithic and conventional overlay bridges cast in the 1980s exhibit less cracking than those cast in the 1990s. The differences are attributed to changes in material properties and construction procedures over the past 20 years. The trend in cracking for decks with silica fume overlays cast in the 1990s (containing 5% silica fume), however, is quite the opposite. A decrease in crack density is observed for 5% silica fume overlay decks, which appears to be the result of increased efforts to limit evaporation prior to the initiation of wet curing. Recently constructed 7% silica fume overlay decks, however, have not shown continued improvement. In light of the chloride and cracking observations, conventional high-density overlays are recommended in lieu of silica fume overlays, and full-depth monolithic decks are recommended for new deck construction

Control of Cracking in Bridge Decks: Observations from the Field

Crack surveys of bridge decks, performed over a 10-year period in northeast Kansas as part of three studies, provide strong guidance in identifying the parameters that control cracking in these structures. The surveys involve steel girder bridges—bridges that are generally agreed to exhibit the greatest amount of cracking in the concrete decks. The surveys include monolithic decks and decks with silica fume and conventional concrete overlays. The study demonstrates that crack density increases as a function of cement and water content, and concrete strength. In addition, crack density is higher in the end spans of decks that are integral with the abutments than decks with pin-ended supports. Most cracking occurs early in the life of a bridge deck, but continues to increase over time. This is true for bridges cast in both the 1980s and the 1990s. A key observation, however, is that bridge decks cast in the 1980s exhibit less cracking than those in the 1990s, even with the increase in crack density over time. Changes in materials, primarily cement fineness, and construction procedures over the past 20 years, are discussed in light of these observations. A major bright spot has been the positive effect of efforts to limit early evaporation, suggesting that the early initiation of curing procedures will help reduce cracking in bridge decks

A Review of Mixed Methods Community-Based Participatory Research Applications in Mental Health

The aim of the paper was to methodologically review the intersection of mixed methods research (MMR) and community-based participatory research (CBPR) in the field of mental health research. We classify this intersecting approach as MMCBPR. The methodological review of empirical literature was conducted between October 2017 and March 2020 of full-text articles in Scopus, Pubmed, ProQuest Central, Web of Science, and EBSCOhost search engine databases in the English language. Twenty-nine studies meeting the inclusion criteria were included in the final analysis. We found some evidence of MMCBPR but it was limited by factors such as a lack of explicit rationales for the use of MMR and CBPR, limited evidence of long-term commitment to a community, and an ad hoc approach to the application of MMR and CBPR. These findings informed the development of practical recommendations for psychologists, mental health professionals, and researchers in the application of MMCBPR. In particular, our MMCBPR recommendations aim to advance the social justice agenda in counseling psychology, increase the rigor of MMCBPR approaches in mental health studies, and inform how advanced mixed methods applications can be used to address the complexities associated with mental health and well-being

Effect of Slag Cement on Drying Shrinkage of Concrete

The effect of a partial replacement of cement with slag cement on free shrinkage is evaluated for curing periods between 3 and 28 days. Mixtures include concrete containing different replacement levels of slag cement (30, 60, and 80% by volume) cast with limestone, granite, or quartzite coarse aggregate. Comparisons are only made with mixtures having the same paste content (by volume) and water-cementitious material ratio. The study shows that a partial replacement of cement with slag cement decreases free shrinkage compared to mixtures containing 100% portland cement; the reduction is greatest at early ages and is improved as the replacement level is increased. Increasing the curing period decreases free shrinkage for mixtures with and without slag cement. When slag cement is used in conjunction with a porous limestone coarse aggregate, where internal curing is provided by the water stored in the pores of limestone, an even greater reduction in free shrinkage is observed compared to mixtures cast with low-absorption coarse aggregate