875 research outputs found
Optimization of conjugated linoleic acid production from safflower oil and purification by low temperature crystallization
The first objective of this study was to reveal the effect of temperature and time on the production of CLA isomers from safflower oil. For this purpose, CLA production was conducted at different temperatures (80–240 °C) and over different time durations (1–10 h). Alkali isomerisation gave a total conversion of 87.8% under the optimal conditions of 240 °C and 8 h (for maximum beneficial isomers), and produced 41.0% trans-10, cis-12, 40.4% cis-9, trans-11, and 6.4% undesirable CLA isomers. The second aim of this study was to determine the effect of temperature and solvents on the purification of CLA isomers. To achieve this, CLA solutions containing different solvents (acetone, methanol, and petroleum ether) were crystallized at several temperatures (0 to –85 °C). It was determined that although the highest CLA purities (94%) were obtained at –55 °C using acetone as the solvent with a yield of 38.1%, the highest yield (89.6%) was determined using petroleum ether at –85 °C with a purity of 88.1%. This paper presents methods to utilize safflower oil and low temperature crystallization process to inexpensively obtain beneficial CLA
Para-iliac actinomycetoma presenting as sarcoma, a late complication of appendicitis: A case report
AbstractINTRODUCTIONActinomycosis is known to mimic several types of neoplasms, leading to morbid surgical interventions.PRESENTATION OF CASEWe report the particular case of an extensive right para-iliac actinomycetoma presenting as a sarcoma, which to our knowledge has not yet been described in the literature, in a patient with previous ruptured appendicitis. Thanks to the collaborative work between the orthopedic and general surgeons, pathologist and microbiologist, the diagnosis of actinomycosis was made pre-operatively, saving this 15-year-old patient from a tumor resection protocol.DISCUSSIONActinomycetomas have often been reported to present in the same way as several abdominal and gynecological neoplasms, and on rare occasions been described as mimicking other soft-tissue sarcomas, leading to unnecessary morbid tumor resection protocols. The most common cause of abdominal actinomycosis is perforated appendicitis, and may present several years later.CONCLUSIONWhile faced with a soft tissue mass transgressing tissue planes and possibly extending to the region of the right lower quadrant, especially with a history of previous perforated appendicitis, one should consider the possibility of an abscess caused by pathogens of intestinal origin, including the gram positive anaerobe Actinomycosis israelii. Failure to actively search for this pathogen, which is not detectable with routine staining techniques and may take up to 1–2 weeks to isolate, may lead to unnecessary morbid surgical procedures
Search and Pursuit-Evasion in Mobile Robotics, A survey
This paper surveys recent results in pursuitevasion
and autonomous search relevant to applications
in mobile robotics. We provide a taxonomy of search
problems that highlights the differences resulting from
varying assumptions on the searchers, targets, and the
environment. We then list a number of fundamental
results in the areas of pursuit-evasion and probabilistic
search, and we discuss field implementations on mobile
robotic systems. In addition, we highlight current open
problems in the area and explore avenues for future
work
Gauge Invariant Formulations of Lineal Gravity
It is shown that the currently studied ``string-inspired'' model for gravity
on a line can be formulated as a gauge invariant theory based on the Poincar\'e
group with central extension -- a formulation that complements and simplifies
H.~Verlinde's construction based on the unextended Poincar\'e group.Comment: 11 p
Exact solution of the Zeeman effect in single-electron systems
Contrary to popular belief, the Zeeman effect can be treated exactly in
single-electron systems, for arbitrary magnetic field strengths, as long as the
term quadratic in the magnetic field can be ignored. These formulas were
actually derived already around 1927 by Darwin, using the classical picture of
angular momentum, and presented in their proper quantum-mechanical form in 1933
by Bethe, although without any proof. The expressions have since been more or
less lost from the literature; instead, the conventional treatment nowadays is
to present only the approximations for weak and strong fields, respectively.
However, in fusion research and other plasma physics applications, the magnetic
fields applied to control the shape and position of the plasma span the entire
region from weak to strong fields, and there is a need for a unified treatment.
In this paper we present the detailed quantum-mechanical derivation of the
exact eigenenergies and eigenstates of hydrogen-like atoms and ions in a static
magnetic field. Notably, these formulas are not much more complicated than the
better-known approximations. Moreover, the derivation allows the value of the
electron spin gyromagnetic ratio to be different from 2. For
completeness, we then review the details of dipole transitions between two
hydrogenic levels, and calculate the corresponding Zeeman spectrum. The various
approximations made in the derivation are also discussed in details.Comment: 18 pages, 4 figures. Submitted to Physica Script
Charge Exchange Processes between Excited Helium and Fully Stripped Ions
We made a classical trajectory Monte Carlo (CTMC) calculation of state
selective cross sections for processes between some light ions and excited
helium. The results, useful for analysis of spectroscopic data of fusion
devices, are in good agreement with theoretical predictions of scaling laws.Comment: LaTex, 8 pages, 4 figures (available on request to the authors),
DFPD/94/TH/57, to be published in Phys. Rev.
Assessment of intensity, prevalence and duration of everyday activities in Swiss school children: a cross-sectional analysis of accelerometer and diary data
BACKGROUND: Appropriately measuring habitual physical activity (PA) in children is a major challenge. Questionnaires and accelerometers are the most widely used instruments but both have well-known limitations. The aims of this study were to determine activity type/mode and to quantify intensity and duration of children's everyday PA by combining information of a time activity diary with accelerometer measurements and to assess differences by gender and age. METHODS: School children (n = 189) aged 6/7 years, 9/10 years and 13/14 years wore accelerometers during one week in winter 2004 and one in summer 2005. Simultaneously, they completed a newly developed time-activity diary during 4 days per week recording different activities performed during each 15 min interval. For each specific activity, the mean intensity (accelerometer counts/min), mean duration per day (min/d) and proportion of involved children were calculated using linear regression models. RESULTS: For the full range of activities, boys accumulated more mean counts/min than girls. Adolescents spent more time in high intensity sports activities than younger children (p < 0.001) but this increase was compensated by a reduction in time spent playing vigorously (p = 0.04). In addition, adolescents spent significantly more time in sedentary activities (p < 0.001) and accumulated less counts/min during these activities than younger children (p = 0.007). Among moderate to vigorous activities, children spent most time with vigorous play (43 min/day) and active transportation (56 min/day). CONCLUSION: The combination of accelerometers and time activity diaries provides insight into age and gender related differences in PA. This information is warranted to efficiently guide and evaluate PA promotion
Low Energy Skyrmion-Skyrmion Scattering
We study the scattering of Skyrmions at low energy and large separation using
the method proposed by Manton of truncation to a finite number of degrees
freedom. We calculate the induced metric on the manifold of the union of
gradient flow curves, which for large separation, to first non-trivial order is
parametrized by the variables of the product ansatz. (presented at the Lake
Louise Winter Institute, 1994)Comment: 6 page
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