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Your search keyword '"R. E. Simpson"' showing total 3 results
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3 results on '"R. E. Simpson"'

1. Phase-Change Materials, 1/f Noise, and Phase Synchrony

Author

J. C. Martinez and R. E. Simpson

Subjects
Materials of engineering and construction. Mechanics of materials, TA401-492
Abstract

In this article, we study 1/fγ,γ≈1 electrical noise in amorphous phase-change materials. Given the relevance of noise in recent applications, it is necessary to gain a deeper perspective on its nature in phase-change semiconductors, a promising class of materials. Electron conduction is envisaged in terms of an envelope function and a field-dependent Bloch wave function; the electron transport across the structure is modeled as driven phase oscillators under a weak field and obeys a Kuramoto-type equation. Its solutions naturally divide into a phase-synchronized group and phase-desynchronized oscillators. The former is comprised by long-lived pairs or aggregates and are responsible for 1/f,γ=1 noise. We identify the dividing frequency between γ=1 noise and γ≠1 noise. The phase-desynchronized carriers generate γ≠1 noise and are single carriers, not aggregates, and are short-lived. We apply our analysis to recent experiments.

Published
2022
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2. Routine Gastric Decompression after Pancreatoduodenectomy: Treating the Surgeon?

Author

K F, Flick, M, Soufi, M T, Yip-Schneider, R E, Simpson, C L, Colgate, T K, Nguyen, E P, Ceppa, M G, House, N J, Zyromski, A, Nakeeb, and C M, Schmidt

Subjects
Decompression, Surgeons, Postoperative Complications, Gastric Emptying, Humans, Prospective Studies, Intubation, Gastrointestinal, Pancreaticoduodenectomy, Retrospective Studies
Abstract

The decision to routinely leave a nasogastric tube after pancreatoduodenectomy remains controversial. We sought to determine the impact of immediate nasogastric tube removal versus early nasogastric tube removal (24 h) on postoperative outcomes.A retrospective review of our institution's prospective ACS-NSQIP database identified patients that underwent pancreatoduodenectomy from 2015 to 2018. Outcomes were compared among patients with immediate nasogastric tube removal versus early nasogastric tube removal.A total of 365 patients were included in primary analysis (no nasogastric tube, n = 99; nasogastric tube removed24 h, n = 266). Thirty-day mortality and infectious, renal, cardiovascular, and pulmonary morbidity were similar in comparing those with no nasogastric tube versus early nasogastric tube removal on univariable and multivariable analyses (P0.05). Incidence of delayed gastric emptying (11.1 versus 13.2%) was similar between groups. Patients with no nasogastric tube less frequently required nasogastric tube reinsertion (n = 4, 4%) compared to patients with NGT24 h (n = 39, 15%) (OR = 3.83, 95% CI [1.39-10.58]; P = 0.009).Routine gastric decompression can be safely avoided after uneventful pancreaticoduodenectomy.

Published
2020

3. Enhanced Aflatoxin Production by Aspergillus flavus and Aspergillus parasiticus after Gamma Irradiation of the Spore Inoculum

Author

R. E. Simpson, A. N. Abadie, and A. F. Schindler

Subjects
Aflatoxin, biology, Chemistry, Inoculation, technology, industry, and agriculture, food and beverages, Aspergillus flavus, biology.organism_classification, Microbiology, Aspergillus parasiticus, Spore, chemistry.chemical_compound, Spore germination, heterocyclic compounds, Food science, Mycotoxin, Incubation, Food Science
Abstract

Distilled water plus 0.1% surfactant suspensions of spores of Aspergillus flavus and Aspergillus parasiticus were exposed to several radiation levels of cobalt-60 gamma rays. Spores of A. flavus isolate M-141 were exposed to radiation levels of approximately 16, 90 and 475 Krads and inoculated onto a sterile rice substrate which was then monitored for aflatoxin production. In this initial trial with A. flavus M-141, aflatoxins B1 and M production on rice increased as radiation dose increased. At the highest dose, this increase was more than 50 times higher than the non-irradiated controls. Spores of an aflatoxin G1-producing A. parasiticus isolate, M-1094, were exposed to 90, 215 and 430 Krads and resulted in increased production of aflatoxins G1, B1, and M. Aflatoxin production by M-1094 was highest at the low and medium dose levels. Irradiation of spores of this isolate with 430 Krads produced no observable spore germination or growth on rice and no detectable aflatoxin after 1 week of incubation at 27 ...

Published
2019

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