The effect of processing and other factors on the colour characteristics of some red wines

Red wines were made from the same batch of Cascade grapes (Seibel 13.053) at Long Ashton by three different processing methods (a) extraction on the skins, (b) thermovinification and (c) carbonic maceration and were analysed at intervals. The wine made by thermovinification was much more coloured than that fermented on its skins, but it contained less anthocyanin and more polymeric pigment. The wine made by carbonic maceration was the least coloured, despite containing anthocyanins similar in amount to those in the thermovinified wine, and it appeared more brown. The red colour differences were attributed to variations in the physicochemical state of the anthocyanins and were expressed numerically in terms of their degrees of ionisation. There was a remarkably exact linear relationship between wine colour density and the degree of ionisation of the anthocyanins in the three wines.Factors affecting anthocyanin ionisation were studied in the Long Ashton wines and in some commercial young Beaujolais wines. Exposure to air augmented colour, increased anthocyanin polymerisation and, in some of the commercial wines, actually increased the amount of anthocyanins, presumably by oxidation of unknown colourless forms. The effects of adding acetaldehyde were even more striking. Large increases in the degree of ionisation of the anthocyanins occurred concurrently with losses of anthocyanins by further transformations into polymeric pigments. Of the Long Ashton wines, that made by thermovinification contained an excess of acetaldehyde over bisulphite, which was probably a factor augmenting its colour.lt was concluded that these fermentation and storage factors were superimposed upon the main effects which were attributed to the different mechanisms of anthocyanin-phenolic interactions operative under the various extraction procedures.Der Einfluß der Weinbereitung und anderer Faktoren auf die Farbmerkmale von RotweinenIn Long Ashton wurden aus demselben Lesegut von Cascade-Trauben (Seibel 13.053) Rotweine nach drei verschiedenen Verfahren - (a) Vergärung auf der Maische, (b) Maischeerhitzung, (c) Kohlensäuremazeration - hergestellt und in bestimmten zeitlichen Abständen analysiert. Der Wein nach (b) war viel intensiver gefärbt als derjenige nach (a); er enthielt jedoch weniger Anthocyan- und mehr polymere Farbstoffe. Der Wein nach (c) war am schwächsten gefärbt, obgleich er einen ähnlichen Anthocyangehalt aufwies wie nach (b) hergestellter Wein; außerdem war er stärker braun getönt. Die Unterschiede in der Rotfärbung wurden auf Schwankungen im physiko-chemischen Zustand der Anthocyane zurückgeführt und zahlenmäßig durch den Ionisationsgrad ausgedrückt. Zwischen der optischen Dichte der Rotweine und dem Ionisationsgrad ihrer Anthocyane bestand eine auffällig genaue lineare Beziehung. Bei den Weinen aus Long Ashton und einigen jungen Beaujolais-Weinen aus dem Handel wurden die Faktoren untersucht, welche die Ionisierung der Anthocyane beeinflussen. Einwirkung von Luft verstärkte die Färbung, steigerte die Polymerisation der Anthocyane und erhöhte bei einigen kommerziellen Weinen, wohl durch Oxidation unbekannter farbloser Vorstufen, den tatsächlichen Anthocyangehalt. Ein Zusatz von Acetaldehyd war noch wirkungsvoller: Ein beträchtlicher Zuwachs ionisierter Anthocyane war begleitet von Anthocyanverlusten durch verstärkte Umwandlung in polymere Farbstoffe. Bei den Weinen aus Long Ashton überwog in den nach (b) hergestellten das Acetaldehyd gegenüber dem Bisulfit, wodurch wahrscheinlich die Färbung vertieft wurde.Die unterschiedliche Ausprägung der Rotweinfärbung ist in erster Linie durch das angewandte Extraktionsverfahren bedingt, wobei Anthocyane und Phenole in verschiedener Weise miteinander reagieren. Im Verlauf der Gärung und Lagerung wird der Farbcharakter durch weitere Faktoren abgewandelt

Tristimulus measurements (CIELAB 76) of port wine colour

Tristimulus colour values were measured using the CIELAB 76 convention and compared with conventional measurements on 87 freshly-made and ageing single cultivar port wines from 5 sites for up to 6 years. There were high correlations between a* (redness) and A520nm, and saturation and colour density, and a high negative correlation between L* (Lightness) and colour density. There was little correlation between b* (yellowness) and A420nm; consequently hue angle did not correspond to tint. Amongst the tristimulus parameters, there were high correlations between L* or saturation and a*. In individual ports L* varied linearly but negatively with hue angle, but in the group of ports examined there was no significant relationship between L* and hue angle because of adc;litional variable phenolic browning depending upon cultivar. In model anthocyanin solutions increasing L* (by decreasing pigment concentration or increasing pH) caused a linear reduction in hue angle but an increase in tint; the latter was attributed to dissociation of associated anthocyanin molecules. Measurement of hue angle in ageing ports gives an indication of the relative occurrence of two competing ageing mechanisms, involving or not involving acetaldehyde. Hue angle is a more discriminating parameter for expressing the colour nuance of red wines than tint

Bacterial genes and genome dynamics in the environment

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Biological Engineering, 2013Cataloged from PDF version of thesis.Includes bibliographical references (p. 143-158).One of the most marvelous features of microbial life is its ability to thrive in such diverse and dynamic environments. My scientific interest lies in the variety of modes by which microbial life accomplishes this feat. In the first half of this thesis I present tools to leverage high throughput sequencing for the study of environmental genomes. In the second half of this thesis, I describe modes of environmental adaptation by bacteria via gene content or gene expression evolution. Associating genes' usage and evolution to adaptation in various environments is a cornerstone of microbiology. New technologies and approaches have revolutionized this pursuit, and I begin by describing the computational challenges I resolved in order to bring these technologies to bear on microbial genomics. In Chapter 1, I describe SHE-RA, an algorithm that increases the useable read length of ultra-high throughput sequencing technologies, thus extending their range of applications to include environmental sequencing. In Chapter 2, I design a new hybrid assembly approach for short reads and assemble 82 Vibrio genomes. Using the ecologically defined groups of this bacterial family, I investigate the genomic and metabolic correlates of habitat and differentiation, and evaluate a neutral model of gene content. In Chapter 3, I report the extent to which orthologous genes in bacteria exhibit the same transcriptional response to the same change in environment, and describe the features and functions of bacterial transcriptional networks that are conserved. I conclude this thesis with a summary of my tools and results, their use in other studies, and their relevance to future work. In particular, I discuss the future experiments and analytical strategies that I am eager to see applied to compelling open questions in microbial ecology and evolution.by Sonia C. Timberlake.Ph.D

Probing modified gravity with magnetically levitated resonators

We present an experimental procedure, based on Meissner effect levitation of neodymium ferromagnets, as a method of measuring the gravitational interactions between milligram masses. The scheme consists of two superconducting lead traps, with a magnet levitating in each trap. The levitating magnets behave as harmonic oscillators and, by carefully driving the motion of one magnet on resonance with the other, we find that it should easily be possible to measure the gravitational field produced by a 4 mg sphere, with the gravitational attraction from masses as small as 30 μg predicted to be measurable within a realistic measurement time frame. We apply this acceleration sensitivity to one concrete example and show the abilities of testing models of modified Newtonian dynamics

Comparing periodic-orbit theory to perturbation theory in the asymmetric infinite square well

An infinite square well with a discontinuous step is one of the simplest systems to exhibit non-Newtonian ray-splitting periodic orbits in the semiclassical limit. This system is analyzed using both time-independent perturbation theory (PT) and periodic-orbit theory and the approximate formulas for the energy eigenvalues derived from these two approaches are compared. The periodic orbits of the system can be divided into classes according to how many times they reflect from the potential step. Different classes of orbits contribute to different orders of PT. The dominant term in the second-order PT correction is due to non-Newtonian orbits that reflect from the step exactly once. In the limit in which PT converges the periodic-orbit theory results agree with those of PT, but outside of this limit the periodic-orbit theory gives much more accurate results for energies above the potential step.Comment: 22 pages, 2 figures, 2 tables, submitted to Physical Review

The colours, pigment and phenol contents of young port wines: Effects of cultivar, season and site

95 port wines were made under standard small scale conditions from grapes of 16 individual cultivars grown at 5 different sites in the Douro valley in northern Portugal during 1977-1983. Grape specific grayity and pH values were measured. The ports were analysed immediately after fortification for colour, pigment and phenol contents and pH. Cultivar variations were up to 12-fold in total pigments, 14-fold in colour density, but only 3.6-fold in total phenols . Seasonal vari ations were up to 2-fold in total pigments and colour density and 1.6-fold in total phenols . Because of seasonal effects and variation in the numbers of each cultivar examined, cultivar characteristics were compared by their mean values with reference to an arbitrarily chosen standard cultivar (Touriga Nacional). Statistical analysis confirmed that the variation in total pigments was affected much more by cultivar than by season. Souzão, Tinta da Barca and Touriga Nacional ports (all from Tua) were the most coloured and contained most pigments. Mourisco (Tua) and Tinta Cão (Baixo Corgo) were the least coloured and contained least pigments. Port colour was dependent principally on pigments content and pH, but small effects attributed to anthocyanin selfassociation and co-pigmentation were also discerned. Differences between sites were generally not significant, apart from some characteristics of Touriga Nacional from Pinhão compared with Tua and Vilariça. which were attributed to the particular strain of fruit at Pinhäo. Nevertheless, there was some indication that the inferior status of Baixo Corgo compared with Cima Corgo fruit may be attributed not only to its generally lower pigments content, but also to smaller percentages of the pigments being expressed in coloured forms

Testing Dissipative Collapse Models with a Levitated Micromagnet

We present experimental tests of dissipative extensions of spontaneous wave function collapse models based on a levitated micromagnet with ultralow dissipation. The spherical micromagnet, with radius $R=27$ $\mu$m, is levitated by Meissner effect in a lead trap at $4.2$ K and its motion is detected by a SQUID. We perform accurate ringdown measurements on the vertical translational mode with frequency $57$ Hz, and infer the residual damping at vanishing pressure $\gamma/2\pi<9$ $\mu$Hz. From this upper limit we derive improved bounds on the dissipative versions of the CSL (continuous spontaneous localization) and the DP (Di\'{o}si-Penrose) models with proper choices of the reference mass. In particular, dissipative models give rise to an intrinsic damping of an isolated system with the effect parameterized by a temperature constant; the dissipative CSL model with temperatures below 1 nK is ruled out, while the dissipative DP model is excluded for temperatures below $10^{-13}$ K. Furthermore, we present the first bounds on dissipative effects in a more recent model, which relates the wave function collapse to fluctuations of a generalized complex-valued spacetime metric.Comment: 10 pages, 7 figure

Classical Scattering for a driven inverted Gaussian potential in terms of the chaotic invariant set

We study the classical electron scattering from a driven inverted Gaussian potential, an open system, in terms of its chaotic invariant set. This chaotic invariant set is described by a ternary horseshoe construction on an appropriate Poincare surface of section. We find the development parameters that describe the hyperbolic component of the chaotic invariant set. In addition, we show that the hierarchical structure of the fractal set of singularities of the scattering functions is the same as the structure of the chaotic invariant set. Finally, we construct a symbolic encoding of the hierarchical structure of the set of singularities of the scattering functions and use concepts from the thermodynamical formalism to obtain one of the measures of chaos of the fractal set of singularities, the topological entropy.Comment: accepted in Phy. Rev.

Drugs of Abuse Can Entrain Circadian Rhythms

Circadian rhythms prepare organisms for predictable events during the Earth's 24-h day. These rhythms are entrained by a variety of stimuli. Light is the most ubiquitous and best known zeitgeber, but a number of others have been identified, including food, social cues, locomotor activity, and, most recently drugs of abuse. Given the diversity of zeitgebers, it is probably not surprising that genes capable of clock functions are located throughout almost all organs and tissues. Recent evidence suggests that drugs of abuse can directly entrain some circadian rhythms. We have report here that entrainment by drugs of abuse is independent of the suprachiasmatic nucleus and the light/dark cycle, is not dependent on direct locomotor stimulation, and is shared by a variety of classes of drugs of abuse. We suggest that drug-entrained rhythms reflect variations in underlying neurophysiological states. This could be the basis for known daily variations in drug metabolism, tolerance, and sensitivity to drug reward. These rhythms could also take the form of daily periods of increased motivation to seek and take drugs, and thus contribute to abuse, addiction and relapse

Scattering properties of a cut-circle billiard waveguide with two conical leads

We examine a two-dimensional electron waveguide with a cut-circle cavity and conical leads. By considering Wigner delay times and the Landauer-B\"{u}ttiker conductance for this system, we probe the effects of the closed billiard energy spectrum on scattering properties in the limit of weakly coupled leads. We investigate how lead placement and cavity shape affect these conductance and time delay spectra of the waveguide.Comment: 18 pages, 11 figures, accepted for publication in Phys. Rev. E (Jan. 2001