22,963 research outputs found
Non-Abelian hydrodynamics and the flow of spin in spin-orbit coupled substances
Motivated by heavy ion collision experiments, we study the hydrodynamic
properties of non-Abelian systems. These issues arise in condensed matter
physics in the context of transport of spins in the presence of spin orbit
coupling: the Pauli Hamiltonian governing the leading relativistic corrections
in condensed matter systems can be rewritten in a language of SU(2) covariant
derivatives, where the role of the non-Abelian gauge fields is taken by the
physical electromagnetic fields. Taking a similar perspective as Jackiw and
coworkers, we show that non-abelian hydrodynamical currents can be factored in
a non-coherent 'classical' part, and a coherent part requiring macroscopic
non-abelian quantum entanglement. Non-abelian flow being thus a much richer
affair than familiar hydrodynamics, permits us to classify the various spin
transport phenomena in in condensed matter physics in a unifying framework.In
semiconductor spintronics, the absence of hydrodynamics is well known, but in
our formulation it is directly associated with the fact that non-abelian
currents are only covariantly conserved.We analyze the quantum mechanical
single particle currents of relevance to mesoscopic transport with as highlight
the Aharonov-Casher effect, where we demonstrate that the non-abelian transport
structure renders it much more fragile than its abelian counterpart, the
Aharonov-Bohm effect. We subsequently focus on spin flows protected by order
parameters, of which the spin-spiral magnets and the spin superfluids are
important examples. The surprising bonus is that the presence of an order
parameter, being single-valued, restores hydrodynamics. We demonstrate a new
effect: the trapping of electrical line charge, being the 'fixed frame'
non-Abelian analogue of the familiar magnetic flux trapping by superconductors.Comment: 23 pages, 7 figure
Astringent Food Compounds and Their Interactions with Taste Properties
Astringency is traditionally thought to be induced by plant tannins in foods. Because of this current research concerning the mechanism of astringency is focused on tanninâprotein interactions and thus on precipitation, which may be perceived by mechanoreceptors. However, astringency is elicited by a wide range of different phenolic compounds, as well as, some nonâphenolic compounds in various foods. Many ellagitannins or smaller compounds that contribute to astringent properties do not interact with salivary proteins and may be directly perceived through some receptors. Generally, the higher degree of polymerization of proanthocyanidins can be associated with more intense astringency. However, the astringent properties of smaller phenolic compounds may not be directly predicted from the structure of a compound, although glycosylation has a significant role. The astringency of organic acids may be directly linked to the perception of sourness, and this increases along with decreasing pH.
Astringency can be divided into different subâqualities, including even other qualities than traditional mouthâdrying, puckering or roughing sensations. Astringency is often accompanied by bitter or sour or both taste properties. The different subâqualities can be influenced by different astringent compounds. In general, the glycolysation of the phenolic compound results in more velvety and smooth mouthdrying astringency. Flavonol glycosides and other flavonoid compounds and ellagitannins contribute to this velvety mouthdrying astringency. Additionally, they often lack the bitter properties. Proanthocyanidins and phenolic acids elicit more puckering and roughing astringency with some additional bitter properties. Quercetin 3âOârutinoside, along with other quercetin glycosides, is among the key astringent compounds in black tea and red currants.
In foods, there are always various other additional attributes that are perceived at the same with astringency. Astringent compounds themselves may have other sensory characteristics, such as bitter or sour properties, or they may enhance or suppress other sensory properties. Components contributing to these other properties, such as sugars, may also have similar effects on astringent sensations. Food components eliciting sweetness or fattiness or some polymeric polysaccharides can be used to mask astringent subqualities.
Astringency can generally be referred to as a negative contributor to the liking of various foods. On the other hand, perceptions of astringent properties can vary among individuals. Many genetic factors that influence perceptions of taste properties, such as variations in perceiving a bitter taste or variations in saliva, may also effect the perception of astringency. Individuals who are more sensitive to different sensations may notice the differences between astringent properties more clearly. This may not have effects on the overall perception of astringency. However, in many cases, the liking of astringent foods may need to be learned by repetitive exposure. Astringency is often among the key sensory properties forming the unique overall flavour of certain foods, and therefore it also influences whether or not a food is liked. In many cases, astringency may be an important subâproperty suppressed by other more abundant sensory properties, but it may still have a significant contribution to the overall flavour and thus consumer preferences.
The results of the practical work of this thesis show that the astringent phenolic compounds are mostly located in the skin fractions of black currants, crowberries and bilberries (publications IâIII). The skin fractions themselves are rather tasteless. However, the astringent phenolic compounds can be efficiently removed from these skin fractions by consecutive ethanol extractions. Berries contain a wide range of different flavonol glycosides, hydroxycinnamic acid derivatives and anthocyanins and some of them strongly contribute to the different astringent and bitterness properties. Sweetness and sourness are located in the juice fractions along with the majority of sugars and fruit acids. The sweet and sour properties of the juice may be used to mask the astringent and bitterness properties of the extracts. Enzymatic treatments increase the astringent properties and fermented flavour of the black currant juice and decrease sweetness and freshness due to the effects on chemical compositions (IV). Sourness and sweetness are positive contributors to the liking of crowberry and bilberry fractions, whereas bitterness is more negative (V). Some astringent properties in berries are clearly negative factors, whereas some may be more positive. The liking of berries is strongly influenced by various consumer background factors, such as motives and health concerns. The liking of berries and berry fractions may also be affected by genetic factors, such as variations in the gene hTAS2R38, which codes bitter taste receptors (V).Siirretty Doriast
Quantification of condensed tannins in red wines by Fourier transform mid-infrared spectroscopy (FTIR)
Mestrado Vinifera EuroMaster - Instituto Superior de AgronomiaGrape-derived condensed tannins, also known as proanthocyanidins, are critical quality components for red wines. They have been subject of numerous studies in order to find a fast and reliable methodology for their quantification. In this work it has been tested the method using Fourier transform mid-infrared (FTIR) and chemometrics to quantify the amount of condensed tannins present in 88 different red wines, with the reference method of precipitation with methylcellulose. As well it has been provided a single laboratory validation of the method of fractionation of condensed tannins by reverse phase and quantification by reaction with vanillin. The models developed for the FTIR spectroscopy were not enough robust for the estimation of total condensed tannins, with low values of coefficient of determination and low RPD values (R2 cross-validation: 0,76 and RPD cross-validation: 1,86). Validation of the fractionation method showed good performance in precision, with values of coefficient of variance for the three fractions FIII, FII and FI respectively of 5,2%; 11,4% and 11,6% and values of reproducibility of 168,1; 32,9 and 3,4 mg/L of epicatechin equivalents, but it was not possible to perform effective recovery studie
Visually Characterizing Source Code Changes
International audienceRevision Control Systems (e.g., SVN, Git, Mercurial) include automatic and advanced merging algorithms that help developers to merge their modifications with development repositories. While these systems can help to textually detect conflicts, they do not help to identify the semantic consequences of a change. Unfortunately, there is little support to help release masters (integrators) to take decisions about the integration of changes into the system release. Most of the time, the release master needs to read all the modified code, check the diffs to build an idea of a change, and dig for details from related unchanged code to understand the context and potential impact of some changes. As a result, such a task can be overwhelming. In this article we present a visualization tool to support integrators of object-oriented programs in comprehending changes. Our approach named Torch characterizes changes based on structural informa- tion, authors and symbolic information. It mixes text-based diff information with visual representation and metrics characterizing the changes. The current implementation of our approach analyses Smalltalk programs, and thus we de- scribe our experiments applying it to Pharo, a large open-source system. We also report on the evaluations of our approach by release masters and developers of several open-source projects
Relativistic density functional theory for finite nuclei and neutron stars
The main goal of the present contribution is a pedagogical introduction to
the fascinating world of neutron stars by relying on relativistic density
functional theory. Density functional theory provides a powerful--and perhaps
unique--framework for the calculation of both the properties of finite nuclei
and neutron stars. Given the enormous densities that may be reached in the core
of neutron stars, it is essential that such theoretical framework incorporates
from the outset the basic principles of Lorentz covariance and special
relativity. After a brief historical perspective, we present the necessary
details required to compute the equation of state of dense, neutron-rich
matter. As the equation of state is all that is needed to compute the structure
of neutron stars, we discuss how nuclear physics--particularly certain kind of
laboratory experiments--can provide significant constrains on the behavior of
neutron-rich matter.Comment: Contributing chapter to the book "Relativistic Density Functional for
Nuclear Structure"; World Scientific Publishing Company (Singapore); Editor
Prof. Jie Meng (Peking University
Optical Mineralogy in a Modern Earth Sciences Curriculum
Provides pedagogical insight concerning the skill of studying minerals The resource being annotated is: http://www.dlese.org/dds/catalog_SERC-NAGT-000-000-000-651.htm
Interactions between wine phenolic compounds and human saliva in astringency perception
[EN] Astringency is a complex perceptual phenomenon involving several sensations that are perceived simultaneously. The mechanism leading to these sensations has been thoroughly and controversially discussed in the literature and it is still not well understood since there are many contributing factors. Although we are still far from elucidating the mechanisms whereby astringency develops, the interaction between phenolic compounds and proteins (from saliva, oral mucosa or cells) seems to be most important. This review summarizes the recent trends in the proteinâphenol interaction, focusing on the effect of the structure of the phenolic compound on the interaction with salivary proteins and on methodologies based on these interactions to determine astringency
Enhanced at puberty 1 (EAP1) is a new transcriptional regulator of the female neuroendocrine reproductive axis
The initiation of mammalian puberty and the maintenance of female reproductive cycles are events controlled by hypothalamic neurons that secrete the decapeptide gonadotropin-releasing hormone (GnRH). GnRH secretion is, in turn, controlled by changes in neuronal and glial inputs to GnRH-producing neurons. The hierarchical control of the process is unknown, but it requires coordinated regulation of these cell-cell interactions. Here we report the functional characterization of a gene (termed enhanced at puberty 1 [EAP1]) that appears to act as an upstream transcriptional regulator of neuronal networks controlling female reproductive function. EAP1 expression increased selectively at puberty in both the nonhuman primate and rodent hypothalamus. EAP1 encoded a nuclear protein expressed in neurons involved in the inhibitory and facilitatory control of reproduction. EAP1 transactivated genes required for reproductive function, such as GNRH1, and repressed inhibitory genes, such as preproenkephalin. It contained a RING finger domain of the C3HC4 subclass required for this dual transcriptional activity. Inhibition of EAP1 expression, targeted to the rodent hypothalamus via lentivirus-mediated delivery of EAP1 siRNAs, delayed puberty, disrupted estrous cyclicity, and resulted in ovarian abnormalities. These results suggest that EAP1 is a transcriptional regulator that, acting within the neuroendocrine brain, contributes to controlling female reproductive function.This work was supported by grants from the NIH, the National Institute of Child Health and Human Development/NIH (to S.R. Ojeda), the European Society for Paediatric Endocrinology (to H. Jung), the German Research Foundation (to S. Heger), and the European Commission (PIONEER to S. Heger)
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