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Thermal Characterization of Alkali Treated Kenaf Fibers and Kenaf-Epoxy Composites
Levi Gardner,Troy Munro,Ezekiel Villarreal,Kurt Harris,Thomas Fronk,Heng Ban 한국섬유공학회 2018 Fibers and polymers Vol.19 No.2
Chemical treatment of natural fibers is a well-defined means of mechanical property improvement in natural fiberreinforced composites. An understanding of mechanical and thermal properties in these media is essential for evaluating heat transfer, thermal degradation, and overall performance of these composites over their product lifetime. However, very little information is available illustrating the effect of such treatment on the thermal properties of kenaf composites. Also, no study to date has reported the thermal conductivity of individual kenaf fibers. This study reports the effects of fiber treatment (in 6 % NaOH) on thermal transport in unidirectionally oriented kenaf-epoxy composites and individual kenaf fibers. The effective thermal conductivities and thermal diffusivities of chemically treated fiber composites show a general increase over untreated fiber composites (0.210 to 0.232 W/m/K at 28 ℃, 0.206 to 0.234 W/m/K at 200 ℃). This improvement may be attributed to improved interfacial contact between the fibers and epoxy matrix shown in microstructural images after chemical treatment. The thermal conductivity of individual fibers was evaluated at room temperature using two techniques. Results from both techniques showed slight increases after chemical treatment (0.58±0.53 to 1.0±0.13 W/m/K and 1.2±0.54 to 1.6±0.28 W/m/K) but lacked statistical significance. Any improvement in surface crystallinity after chemical treatmentdoes not appear to affect overall fiber thermal conductivity. A better understanding of thermal transport in kenaf fibers and composites enables better estimation of the performance of these composites in different applications. Moreover, the thermal conductivities of individual fibers are useful in understanding the fiber’s contribution to conduction in different fiber reinforcement configurations.
Levi, F.,Shirley, J.H.,Heavner, T.P.,Yu, Dai-Hyuk,Jefferts, S.R. IEEE 2006 and Frequency Control Vol.53 No.9
The presence of spurious spectral components in the microwave excitation may induce frequency shifts in an atomic fountain frequency standard. We discuss how such shifts behave as a function of power variations of the excitation carrier and in the spur-to-carrier ratio. The discussion here is limited to the case of single-sideband spurs, which are generally much more troublesome due to their ability to cause frequency shifts. We find an extremely rich and unintuitive behavior of these frequency shifts. We also discuss how pulsed operation, typical of today's fountain frequency standards, relates to frequency shifts caused by spurs in the microwave spectrum. The conclusion of these investigations is that it is, at best, difficult to use elevated power microwaves in fountain frequency standards to test for the presence of spurs in the microwave spectrum.
Beneficial Effects of Flavonoids on Skeletal Muscle Health: A Systematic Review and Meta-Analysis
Levy Munguı´a,Cristian Gonza´lez,Andre´s Portilla,Eduardo Meaney,Francisco Villarreal,Nayelli Na´jera,Guillermo Ceballos 한국식품영양과학회 2022 Journal of medicinal food Vol.25 No.5
Skeletal muscle (SkM) is a highly dynamic tissue that responds to physiological adaptations or pathological conditions, and SkM mitochondria play a major role in bioenergetics, regulation of intracellular calcium homeostasis, pro-oxidant/antioxidant balance, and apoptosis. Flavonoids are polyphenolic compounds with the ability to modulate molecular pathways implicated in the development of mitochondrial myopathy. Therefore, it is pertinent to explore its potential application in conditions such as aging, disuse, denervation, diabetes, obesity, and cancer. To evaluate preclinical and clinical effects of flavonoids on SkM structure and function. We performed a systematic review of published studies, with no date restrictions applied, using PubMed and Scopus. The following search terms were used: “flavonoids” OR “flavanols” OR “flavones” OR “anthocyanidins” OR “flavanones” OR “flavan-3-ols” OR “catechins” OR “epicatechin” OR “(−)-epicatechin” AND “skeletal muscle.” The studies included in this review were preclinical studies, clinical trials, controlled clinical trials, and randomized-controlled trials that investigated the influence of flavonoids on SkM health. Three authors, independently, assessed trials for the review. Any disagreement was resolved by consensus. The use of flavonoids could be a potential tool for the prevention of muscle loss. Their effects on metabolism and on mitochondria function suggest their use as muscle regulators.
Mixed Adenoneuroendocrine Gastric Carcinoma: A Case Report and Review of the Literature
Levi Sandri, Giovanni Battista,Carboni, Fabio,Valle, Mario,Visca, Paolo,Garofalo, Alfredo The Korean Gastric Cancer Association 2014 Journal of gastric cancer Vol.14 No.1
We present a rare case of a gastric mixed adenoneuroendocrine tumor and review the related English literature. A 77-year-old Caucasian woman was admitted to our department with nausea, anorexia, weight loss, and anemia. Esophagogastroduodenoscopy showed a large (>7 cm) ulcerative mass in the greater curvature of the stomach. Biopsy showed the presence of an adenocarcinoma with moderate differentiation. The patient underwent D2 subtotal gastrectomy. Histopathological analysis revealed a diagnosis of mixed gastric adenoneuroendocrine carcinoma. The post-operative course was uneventful, and at the 6-month follow-up, the patient was alive without evidence of recurrence. Our review of the English literature suggested that such cases are most often reported from eastern countries. Multimodal treatment should be the aim for these patients because of the neuroendocrine component of the tumor.