25,444 research outputs found
Determination of organic acids evolution during apple cider fermentation using an improved HPLC analysis method
An efficient method for analyzing ten organic acids in food, namely citric, pyruvic, malic, lactic, succinic, formic, acetic, adipic, propionic and butyric acids, using HPLC was developed. Boric acid was added into the mobile phase to separate lactic and succinic acids, and a post-column buffer solution [5 mmol/L p-toluensulfonic acid (p-TSA) + 20 mmol/L bis (2-hydroxyethyl) iminotris (hydroxymethyl) methane (bisÂżtris) + 100 Âżmol/L sodium ethylenediaminetetraacetic (EDTA-2Na)] was used to improve the sensitivity of detection. The average spiked recoveries for the ten organic acids ranged from 82.9 to 127.9% with relative standard deviations of 1.44Âż4.71%. The linear ranges of determination were from 15 to 1,000 mg/L with correlation coefficients of 0.9995Âż0.9999. The metabolism of organic acids in cider, and the effect of nutrients including diammonium phosphate (DAP), thiamine, biotin, niacinamide and pantothenic acid on their metabolism, were studied using this method of analysis. We found that before cider brewing, additions of 200 mg/L DAP and 0.3 mg/L thiamine to apple juice concentrate results in a high quality cider
Quantum Doubles from a Class of Noncocommutative Weak Hopf Algebras
The concept of biperfect (noncocommutative) weak Hopf algebras is introduced
and their properties are discussed. A new type of quasi-bicrossed products are
constructed by means of weak Hopf skew-pairs of the weak Hopf algebras which
are generalizations of the Hopf pairs introduced by Takeuchi. As a special
case, the quantum double of a finite dimensional biperfect (noncocommutative)
weak Hopf algebra is built. Examples of quantum doubles from a Clifford monoid
as well as a noncommutative and noncocommutative weak Hopf algebra are given,
generalizing quantum doubles from a group and a noncommutative and
noncocommutative Hopf algebra, respectively. Moreover, some characterisations
of quantum doubles of finite dimensional biperfect weak Hopf algebras are
obtained.Comment: LaTex 18 pages, to appear in J. Math. Phys. (To compile, need
pb-diagram.sty, pb-lams.sty, pb-xy.sty and lamsarrow.sty
The multi-band nonthermal emission from the supernova remnant RX J1713.7-3946
Nonthermal X-rays and very high-energy (VHE) -rays have been detected
from the supernova remnant (SNR) RX J1713.7-3946, and especially the recent
observations with the \textit{Suzaku} satellite clearly reveal a spectral
cutoff in the X-ray spectrum, which directly relates to the cutoff of the
energy spectrum of the parent electrons. However, whether the origin of the VHE
-rays from the SNR is hadronic or leptonic is still in debate. We
studied the multi-band nonthermal emission from RX J1713.7-3946 based on a
semi-analytical approach to the nonlinear shock acceleration process by
including the contribution of the accelerated electrons to the nonthermal
radiation. The results show that the multi-band observations on RX J1713.7-3946
can be well explained in the model with appropriate parameters and the TeV
-rays have hadronic origin, i.e., they are produced via proton-proton
(p-p) interactions as the relativistic protons accelerated at the shock collide
with the ambient matter.Comment: 6 pages, 5 figures, accepted by MNRA
LDA+Gutzwiller Method for Correlated Electron Systems
Combining the density functional theory (DFT) and the Gutzwiller variational
approach, a LDA+Gutzwiller method is developed to treat the correlated electron
systems from {\it ab-initio}. All variational parameters are self-consistently
determined from total energy minimization. The method is computationally
cheaper, yet the quasi-particle spectrum is well described through kinetic
energy renormalization. It can be applied equally to the systems from weakly
correlated metals to strongly correlated insulators. The calculated results for
SrVO, Fe, Ni and NiO, show dramatic improvement over LDA and LDA+U.Comment: 4 pages, 3 figures, 1 tabl
HeadScan: A Wearable System for Radio-Based Sensing of Head and Mouth-Related Activities
The popularity of wearables continues to rise. However, possible applications, and even their raw functionality are constrained by the types of sensors that are currently available. Accelerometers and gyroscopes struggle to capture complex user activities. Microphones and image sensors are more powerful but capture privacy sensitive information. Physiological sensors are obtrusive to users as they often require skin contact and must be placed at certain body positions to function. In contrast, radio-based sensing uses wireless radio signals to capture movements of different parts of the body, and therefore provides a contactless and privacy-preserving approach to detect and monitor human activities. In this paper, we contribute to the search for new sensing modalities for the next generation of wearable devices by exploring the feasibility of mobile radiobased human activity recognition. We believe radio-based sensing has the potential to fundamentally transform wearables as we currently know them. As the first step to achieve our vision, we have designed and developed HeadScan, a first-of-its-kind wearable for radio-based sensing of a number of human activities that involve head and mouth movements. HeadScan only requires a pair of small antennas placed on the shoulder and collar and one wearable unit worn on the arm or the belt of the user. Head- Scan uses the fine-grained CSI measurements extracted from radio signals and incorporates a novel signal processing pipeline that converts the raw CSI measurements into the targeted human activities. To examine the feasibility and performance of HeadScan, we have collected approximate 50.5 hours data from seven users. Our wide-ranging experiments include comparisons to a conventional skin-contact audio-based sensing approach to tracking the same set of head and mouth-related activities. Our experimental results highlight the enormous potential of our radio-based mobile sensing approach and provide guidance to future explorations
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