Calibration approach to electron probe microanalysis: A study with PWA-1480, a nickel base superalloy

The utility of an indirect calibration approach in electron probe microanalysis is explored. The methodology developed is based on establishing a functional relationship between the uncorrected k-ratios and the corresponding concentrations obtained using one of the ZAF correction schemes, for all the desired elements in the concentration range of interest. In cases where a very large number of analyses are desired, such a technique significantly reduces the total time required for the microprobe analysis without any significant loss of precision in the data. A typical application of the method in the concentration mapping of the transverse cross-section of a dendrite in directionally solidified PWA-1480, a nickel-based superalloy, is described

CVD of silicon carbide on structural fibers: Microstructure and composition

Structural fibers are currently being considered as reinforcements for intermetallic and ceramic materials. Some of these fibers, however, are easily degraded in a high temperature oxidative environment. Therefore, coatings are needed to protect the fibers from environmental attack. Silicon carbide (SiC) was chemically vapor deposited (CVD) on Textron's SCS6 fibers. Fiber temperatures ranging from 1350 to 1500 C were studied. Silane (SiH4) and propane (C2H8) were used for the source gases and different concentrations of these source gases were studied. Deposition rates were determined for each group of fibers at different temperatures. Less variation in deposition rates were observed for the dilute source gas experiments than the concentrated source gas experiments. A careful analysis was performed on the stoichiometry of the CVD SiC coating using electron microprobe. Microstructures for the different conditions were compared. At 1350 C, the microstructures were similar; however, at higher temperatures, the microstructure for the more concentrated source gas group were porous and columnar in comparison to the cross sections taken from the same area for the dilute source gas group

Adolescent Sleep Behavioral Interventions and Opportunities to Improve Cognitive Functioning: A Call for Action

Sleep is related to cognitive functioning, learning, and brain development in the adolescent population. Recent research indicates a rise in the presence of chronic sleep disorders such as insomnia in adolescents, particularly following the COVID-19 pandemic. Therefore, research on the effectiveness of sleep interventions for adolescents is necessary to guide treatment in adolescents. The authors conducted a systematic review of literature examining research on outcomes of treatment interventions for insomnia on sleep quality and cognitive functioning in adolescents. Results indicate a dearth of research examining effectiveness of treatment in adolescents, particularly in relation to the impact of such treatment on cognitive functioning in adolescents. The following paper provides a brief overview of existing research on treatment of insomnia or related problems including initiating, maintaining and awaking for adolescent populations with a focus on improvement of cognitive functioning within this population. The authors discuss existing barriers to research, emphasize the need to expand sleep research to include cognitive functioning outcomes, and inform best practices for treatment in adolescents following COVID-19. Lastly, the authors propose a call to action encouraging more widespread recognition of the need for research in this area

Brood parasite and host eggshells undergo similar levels of decalcification during embryonic development

Common cuckoos (Cuculus canorus) are obligate brood parasites that lay their eggs in the nests of other (host) species. To increase the likelihood of successful parasitism, common cuckoos lay eggs with thicker and structurally stronger eggshells than those of their hosts and non-parasitic relatives. Although hatching from thicker eggshells requires greater effort and may impose physiological costs on cuckoo embryos during hatching, it is unclear whether cuckoo eggshells are indeed thicker at the time of hatching. This is because avian embryos decalcify the innermost eggshell layer (mammillary layer) for organ development during embryogenesis, reducing eggshell thickness and making hatching easier. Therefore, common cuckoo eggshells may undergo a greater degree of decalcification during embryonic development to facilitate hatching from an initially thicker-shelled egg. We used scanning electron microscopy to test this hypothesis by comparing the thickness and degree of decalcification of eggshells collected either before incubation or after hatching. We found that cuckoo eggshells undergo similar degrees of decalcification during embryonic development as the thinner eggshells of a host that lays similarly sized eggs, the great reed warbler (Acrocephalus arundinaceus). Cuckoo eggshells hence remain thicker than eggshells of this host throughout embryogenesis, supporting the predicted trade-off between the benefits of laying puncture resistant eggs and the physiological costs associated with hatching

Edward A. Terepka oral history interview

Oral history interview with Holocaust concentration camp liberator Edward A. Terepka. Terepka was a member of the 45th Infantry Division, which liberated Dachau on April 29, 1945. When his unit got to the camp, they let the prisoners out and then had to bring them back into the compound as the medical personnel were concerned for their health. Terepka saw the gas chamber and the crematorium, outside of which there was a pile of ashes four feet high. He and his comrades were so angry at the Germans that they shot at anyone wearing a German uniform. Terepka does not remember how long they spent at Dachau but recalls that they then went to Munich and thence back to Le Havre; when the war ended, they were ready to get on their ship and were one of the first to return to the United States. In this interview, he also tells several other stories from his wartime experience

Edward A. Terepka oral history interview

Oral history interview with Holocaust concentration camp liberator Edward A. Terepka. Terepka was a member of the 45th Infantry Division, which liberated Dachau on April 29, 1945. When his unit got to the camp, they let the prisoners out and then had to bring them back into the compound as the medical personnel were concerned for their health. Terepka saw the gas chamber and the crematorium, outside of which there was a pile of ashes four feet high. He and his comrades were so angry at the Germans that they shot at anyone wearing a German uniform. Terepka does not remember how long they spent at Dachau but recalls that they then went to Munich and thence back to Le Havre; when the war ended, they were ready to get on their ship and were one of the first to return to the United States. In this interview, he also tells several other stories from his wartime experience

A comparative study of the exchange in vivo of major constituents of bone mineral.

Groups of young and old rats were injected with a variety of labelled substanzes (urea, Cl-, K+, Na+, HCO3-, PO43-, Ca++). Data for Mg++ were taken from the literature. One and a half hours later, compact shafts of long bones were removed and cleaned scrupulously, and analyses were performed for both "cold" and isotopic concentrations of substances. This time point was chosen to insure equilibration of the aqueous phase of bone while minimizing contributions from surface exchange, recrystallization, solid diffusion, growth or resorption. With fixed variables of time, species, bone specimen, and methodology, uambiguous comparisons of the exchange in bone could be made between the many substances studied. The exchange data could be divided into three categories: a) complete exchange (urea Cl-, and K+); b) partial exchange, decreasing variably with age (Na+, CO2, and Mg++); and c) minimal exchange (Ca++ and PO43-). Clearly the traditional classification of "available" and "unavailable" skeleton is ambiguous and determined by the conditions and the ion or substance chosen for study. Clearly also, a new overall concept of bone exchange in vivo is badly needed. Calculations of the apparent concentration of the various electrolytes in bone water reveal that the aqueous phase of bone has a composition markedly different from plasma water. In particular, the concentration of potassium in bone water was found to be remarkably high. © 1968 Springer-Verlag

A comparative study of the exchange in vivo of major constituents of bone mineral

Groups of young and old rats were injected with a variety of labelled substanzes (urea, Cl-, K+, Na+, HCO3-, PO43-, Ca++). Data for Mg++ were taken from the literature. One and a half hours later, compact shafts of long bones were removed and cleaned scrupulously, and analyses were performed for both "cold" and isotopic concentrations of substances. This time point was chosen to insure equilibration of the aqueous phase of bone while minimizing contributions from surface exchange, recrystallization, solid diffusion, growth or resorption. With fixed variables of time, species, bone specimen, and methodology, uambiguous comparisons of the exchange in bone could be made between the many substances studied. The exchange data could be divided into three categories: a) complete exchange (urea Cl-, and K+); b) partial exchange, decreasing variably with age (Na+, CO2, and Mg++); and c) minimal exchange (Ca++ and PO43-). Clearly the traditional classification of "available" and "unavailable" skeleton is ambiguous and determined by the conditions and the ion or substance chosen for study. Clearly also, a new overall concept of bone exchange in vivo is badly needed. Calculations of the apparent concentration of the various electrolytes in bone water reveal that the aqueous phase of bone has a composition markedly different from plasma water. In particular, the concentration of potassium in bone water was found to be remarkably high. © 1968 Springer-Verlag