Kinetic and Chemical Effects of Clays and Other Fillers in the Preparation of Epoxy-Vinyl Ether Composites Using Radical-Induced Cationic Frontal Polymerization.

Addition of fillers to formulations can generate composites with improved mechanical properties and lower the overall cost through a reduction of chemicals needed. In this study, fillers were added to resin systems consisting of epoxies and vinyl ethers that frontally polymerized through a radical-induced cationic frontal polymerization (RICFP) mechanism. Different clays, along with inert fumed silica, were added to increase the viscosity and reduce the convection, results of which did not follow many trends present in free-radical frontal polymerization. The clays were found to reduce the front velocity of RICFP systems overall compared to systems with only fumed silica. It is hypothesized that chemical effects and water content produce this reduction when clays are added to the cationic system. Mechanical and thermal properties of composites were studied, along with filler dispersion in the cured material. Drying the clays in an oven increased the front velocity. Comparing thermally insulating wood flour to thermally conducting carbon fibers, we observed that the carbon fibers resulted in an increase in front velocity, while the wood flour reduced the front velocity. Finally, it was shown that acid-treated montmorillonite K10 polymerizes RICFP systems containing vinyl ether even in the absence of an initiator, resulting in a short pot life.

Rapid frontal polymerization achieved with thermally conductive metal strips.

Frontal polymerization, which involves a self-propagating polymerizing reaction front, has been considered as a rapid, energy-efficient, and environmentally friendly methodology to manufacture lightweight, high-performance thermoset polymers, and composites. Previous work has reported that the introduction of thermally conductive elements can enhance the front velocity. As follow-up research, the present work investigates this problem more systemically using both numerical and experimental approaches by investigating the front shape, front width, and heat exchange when aluminum and cooper metal strips are embedded in the resin. The study reveals that the enhancement in the front velocity is mainly due to a preheating effect associated with the conductive element. Moreover, the numerical parametric study for the system size shows that the front speed increases as the system size decreases, ultimately approaching a prediction provided by a homogenized model for polymer-metal composites.

A Comparison of Insulin Doses for the Treatment of Hyperkalemia in Patients with Renal Insufficiency.

STUDY OBJECTIVE: To compare the safety and efficacy of 5 units versus 10 units of insulin for the treatment of hyperkalemia in patients with renal insufficiency. DESIGN: Retrospective cohort study. SETTING: Large academic medical center emergency department. PATIENTS: Between March 1, 2008, and February 29, 2016, 675 patients met the inclusion criteria of age 18 years and older, serum potassium greater than 5 mEq/L, renal insufficiency, 5 units or 10 units of intravenous regular insulin administered in the emergency department, and blood glucose documented within 5 hours after insulin administration. Of these patients, 133 (19.7%) received 5 units of insulin and 542 (80.3%) received 10 units of insulin. MEASUREMENTS AND RESULTS: The primary outcome was incidence of hypoglycemia (blood glucose < 70 mg/dl). Secondary outcomes were incidence of severe hypoglycemia (blood glucose < 40 mg/dl) and change in serum potassium after insulin therapy. Hypoglycemia occurred in 26 of 133 patients receiving 5 units of insulin (19.5%) and in 155 of 542 patients receiving 10 units (28.6%) (difference = -9.1%, 95% confidence interval [CI] -16.8% to -1.3%). Severe hypoglycemia occurred in 4 of 133 patients (3.0%) and 37 of 542 patients (6.8%) receiving insulin 5 units and 10 units, respectively (difference = -3.8%, 95% CI -7.4% to 0%). Change in serum potassium was similar between groups (-1.0 ± 0.8 vs -1.0 ± 0.7 mEq/L, difference = 0, 95% CI -0.1 to 0.1). CONCLUSION: In patients with renal insufficiency and hyperkalemia, 5 units of insulin reduced serum potassium to the same extent as 10 units of insulin but with a lower rate of hypoglycemia. Further controlled studies are needed to confirm these findings.

Methane-induced Activation Mechanism of Fused Ferric Oxide-Alumina Catalysts during Methane Decomposition.

Activation of Fe2 O3 -Al2 O3 with CH4 (instead of H2 ) is a meaningful method to achieve catalytic methane decomposition (CMD). This reaction of CMD is more economic and simple against commercial methane steam reforming (MSR) as it produces COx -free H2 . In this study, for the first time, structure changes of the catalyst were screened during CH4 reduction with time on stream. The aim was to optimize the pretreatment conditions through understanding the activation mechanism. Based on results from various characterization techniques, reduction of Fe2 O3 by CH4 proceeds in three steps: Fe2 O3 →Fe3 O4 →FeO→Fe0. Once Fe0 is formed, it decomposes CH4 with formation of Fe3 C, which is the crucial initiation step in the CMD process to initiate formation of multiwall carbon nanotubes.

Catalytic Methane Decomposition over Fe-Al2 O3.

The presence of a Fe-FeAl2 O4 structure over an Fe-Al2 O3 catalysts is demonstrated to be vital for the catalytic methane decomposition (CMD) activity. After H2 reduction at 750 °C, Fe-Al2 O3 prepared by means of a fusion method, containing 86.5 wt % FeAl2 O4 and 13.5 wt % Fe(0) , showed a stable CMD activity at 750 °C for as long as 10 h.

Sleep patterns during an antarctic field expedition.

UNLABELLED: Extreme conditions in Antarctica pose a significant challenge to members of field parties, stationed military personnel, and civilian support personnel. One of the key issues noted in anecdotal evidence during expeditions is the presence of sleep disturbances, that can lead to a marked loss in the ability to cognitively respond to unusual or dangerous situations. METHOD: A study was conducted using 14 volunteers who traveled to Antarctica and spent several days in a field camp in Windless Bight (Ross Sea Region). Each participant recorded subjective sleep measures daily and wore an accelerometer on their dominant wrist while in bed for the night before, and while on deployment. Stroop and digit recall tests were given four times, at approximately 3-day intervals. RESULTS: Overall subjective sleep quality was fair to good in both environments, and neither sleep disturbance nor total hours of sleep showed reliable differences. There were no reliable associations between 3-day sleep disturbance and test performance for either cognitive measure. CONCLUSION: The results show no sign of effects of 24-hour daylight on sleep and cognitive performance. The impact of these findings on the theoretical connection of light to sleep and performance are discussed, as well as the practical implications for management of sleep while in the field.

Laboratory methods in the study of endometrial Claudin-4.

Immunohistochemistry is a suitable method for the detection of proteins from the Claudin family and several antibodies are commercially available for the detection of Claudin congeners. Immunodetection of Caludin-4 in the paraffin-embedded specimens might be a useful tool for studying the role of these proteins in the cyclic transformation of the endometrium and its role in the endometrial receptivity; furthermore, other components of the junctional zone involved in the transformational process of the endometrium can be detected by means of immunohistochemistry/immunofluorescence with several polyclonal or monoclonal antibodies. The aim of this chapter is to comprehensively overview the materials and methods to perform the endometrial biopsy and to detect Claudin-4 in paraffin-embedded samples of endometrium. Additionally, the interpretation of the results is addressed.

Microfluidic culture of single human embryonic stem cell colonies.

We have developed a miniaturized microfluidic culture system that allows experimentation on individual human embryonic stem cell (hESC) colonies in dynamic (flow applied) or static (without flow) conditions. The system consists of three inlet channels that converge into a cell-culture channel and provides the capability to spatially and temporally deliver specific treatments by using patterned laminar fluid flow to different parts of a single hESC colony. We show that microfluidic culture for 96 h with or without flow results in similar maintenance of hESC self-renewal, the capability to differentiate into three germ cell lineages, and to maintain a normal karyotype, as in standard culture dishes. Localized delivery of a fluorescent nucleic acid dye was achieved with laminar flow, producing staining only in nuclei of exposed cells. Likewise, cells in desired regions of colonies could be removed with enzymatic treatment and collected for analysis. Re-coating the enzyme treated area of the channel with extracellular matrix led to re-growth of hESC colonies into this region. Our study demonstrates the culture of hESCs in a microfluidic device that can deliver specific treatments to desired regions of a single colony. This miniaturized culture system allows in situ treatment and analysis with the ability to obtain cell samples from part of a colony without micromanipulation and to perform sensitive molecular analysis while permitting further growth of the hESC colony.

Protein profile of the luteal phase endometrium by tissue microarray assessment.

To investigate the luteal phase endometrial expression of leukemia inhibitor factor (LIF), insulin-like growth factor 1 (IGF-1), progesterone receptor (PR), claudin 4 (CLDN4), vascular-endothelial growth factor receptor 3 (VEGFR-3), bone morphogenetic protein 4 (BMP-4) and citokeratin 7 (CK-7), we obtained luteal phase endometrial samples from 52 women. Samples were dated and integrated using a tissue microarray (TMA). Samples were immunostained for LIF, IGF-1, PR, CLDN4, VEGFR-3, BMP-4 and CK-7. Frequencies of positive expressions at the early, mid and late luteal phases were compared by two proportions test. Concomitant expression of these proteins was assessed with Chi-square or Fischer's test. The frequency of LIF was positively correlated to the frequency of IGF-1 (r = 0.99; p < 0.05) and PR (r = 0.99; p < 0.05), and the correlation between IGF-1 and PR tended to be significant (r = 0.98; p < 0.1). The expression of PR was associated with the absence of CLDN4 (p < 0.001). Thus, expression of LIF, IGF-1 and PR are correlated during the luteal phase, and immunohistochemistry for these proteins might be used to assist in the assessment of endometrial maturation. In addition, the expression of CLDN4 and PR was not concomitant, warranting further investigation on the relationship of their endometrial expression.

Highly conductive Ni steam reforming catalysts prepared by electrodeposition.

New highly conductive, active and stable Ni steam reforming catalysts were prepared through a method consisting of the calcination of a hydrotalcite-like compound electrodeposited in a single step on FeCrAlloy foams.