47,300 research outputs found
Saccharomyces cerevisiae in the production of fermented beverages
Alcoholic beverages are produced following the fermentation of sugars by yeasts, mainly (but not exclusively) strains of the species, Saccharomyces cerevisiae. The sugary starting materials may emanate from cereal starches (which require enzymatic pre‐hydrolysis) in the case of beers and whiskies, sucrose‐rich plants (molasses or sugar juice from sugarcane) in the case of rums, or from fruits (which do not require pre‐hydrolysis) in the case of wines and brandies. In the presence of sugars, together with other essential nutrients such as amino acids, minerals and vitamins, S. cerevisiae will conduct fermentative metabolism to ethanol and carbon dioxide (as the primary fermentation metabolites) as the cells strive to make energy and regenerate the coenzyme NAD+ under anaerobic conditions. Yeasts will also produce numerous secondary metabolites which act as important beverage flavour congeners, including higher alcohols, esters, carbonyls and sulphur compounds. These are very important in dictating the final flavour and aroma characteristics of beverages such as beer and wine, but also in distilled beverages such as whisky, rum and brandy. Therefore, yeasts are of vital importance in providing the alcohol content and the sensory profiles of beverages. This Introductory Chapter reviews, in general, the growth, physiology and metabolism of S. cerevisiae in alcoholic beverage fermentations
Cosmic Strings Stabilized by Fermion Fluctuations
We provide a thorough exposition of recent results on the quantum
stabilization of cosmic strings. Stabilization occurs through the coupling to a
heavy fermion doublet in a reduced version of the standard model. The study
combines the vacuum polarization energy of fermion zero-point fluctuations and
the binding energy of occupied energy levels, which are of the same order in a
semi-classical expansion. Populating these bound states assigns a charge to the
string. Strings carrying fermion charge become stable if the Higgs and gauge
fields are coupled to a fermion that is less than twice as heavy as the top
quark. The vacuum remains stable in the model, because neutral strings are not
energetically favored. These findings suggest that extraordinarily large
fermion masses or unrealistic couplings are not required to bind a cosmic
string in the standard model.Comment: Based on talk by HW at QFEXT 11 (Benasque, Spain), 15p, uses
ws-ijmpcs.cls (incl
One Table to Count Them All: Parallel Frequency Estimation on Single-Board Computers
Sketches are probabilistic data structures that can provide approximate
results within mathematically proven error bounds while using orders of
magnitude less memory than traditional approaches. They are tailored for
streaming data analysis on architectures even with limited memory such as
single-board computers that are widely exploited for IoT and edge computing.
Since these devices offer multiple cores, with efficient parallel sketching
schemes, they are able to manage high volumes of data streams. However, since
their caches are relatively small, a careful parallelization is required. In
this work, we focus on the frequency estimation problem and evaluate the
performance of a high-end server, a 4-core Raspberry Pi and an 8-core Odroid.
As a sketch, we employed the widely used Count-Min Sketch. To hash the stream
in parallel and in a cache-friendly way, we applied a novel tabulation approach
and rearranged the auxiliary tables into a single one. To parallelize the
process with performance, we modified the workflow and applied a form of
buffering between hash computations and sketch updates. Today, many
single-board computers have heterogeneous processors in which slow and fast
cores are equipped together. To utilize all these cores to their full
potential, we proposed a dynamic load-balancing mechanism which significantly
increased the performance of frequency estimation.Comment: 12 pages, 4 figures, 3 algorithms, 1 table, submitted to EuroPar'1
Casimir Effects in Renormalizable Quantum Field Theories
We review the framework we and our collaborators have developed for the study
of one-loop quantum corrections to extended field configurations in
renormalizable quantum field theories. We work in the continuum, transforming
the standard Casimir sum over modes into a sum over bound states and an
integral over scattering states weighted by the density of states. We express
the density of states in terms of phase shifts, allowing us to extract
divergences by identifying Born approximations to the phase shifts with low
order Feynman diagrams. Once isolated in Feynman diagrams, the divergences are
canceled against standard counterterms. Thus regulated, the Casimir sum is
highly convergent and amenable to numerical computation. Our methods have
numerous applications to the theory of solitons, membranes, and quantum field
theories in strong external fields or subject to boundary conditions.Comment: 27 pp., 11 EPS figures, LaTeX using ijmpa1.sty; email correspondence
to R.L. Jaffe ; based on talks presented by the authors at
the 5th workshop `QFTEX', Leipzig, September 200
Bose-Einstein condensate of kicked rotators with time-dependent interaction
A modification of the quantum kicked rotator is suggested with a
time-dependent delta-kicked interaction parameter which can be realized by a
pulsed turn-on of a Feshbach resonance. The mean kinetic energy increases
exponentially with time in contrast to a merely diffusive or linear growth for
the first few kicks for the quantum kicked rotator with a constant interaction
parameter. A recursive relation is derived in a self-consistent random phase
approximation which describes this superdiffusive growth of the kinetic energy
and is compared with numerical simulations. Unlike in the case of the quantum
rotator with constant interaction, a Lax pair is not found. In general the
delta-kicked interaction is found to lead to strong chaotic behaviour.Comment: 4 pages, 3 figure
Aging, Emotion, Attention, and Binding in the Taboo Stroop Task: Data and Theories.
How does aging impact relations between emotion, memory, and attention? To address this question, young and older adults named the font colors of taboo and neutral words, some of which recurred in the same font color or screen location throughout two color-naming experiments. The results indicated longer color-naming response times (RTs) for taboo than neutral base-words (taboo Stroop interference); better incidental recognition of colors and locations consistently associated with taboo versus neutral words (taboo context-memory enhancement); and greater speed-up in color-naming RTs with repetition of color-consistent than color-inconsistent taboo words, but no analogous speed-up with repetition of location-consistent or location-inconsistent taboo words (the consistency type by repetition interaction for taboo words). All three phenomena remained constant with aging, consistent with the transmission deficit hypothesis and binding theory, where familiar emotional words trigger age-invariant reactions for prioritizing the binding of contextual features to the source of emotion. Binding theory also accurately predicted the interaction between consistency type and repetition for taboo words. However, one or more aspects of these phenomena failed to support the inhibition deficit hypothesis, resource capacity theory, or socio-emotional selectivity theory. We conclude that binding theory warrants further test in a range of paradigms, and that relations between aging and emotion, memory, and attention may depend on whether the task and stimuli trigger fast-reaction, involuntary binding processes, as in the taboo Stroop paradigm
Hyperentanglement-enabled Direct Characterization of Quantum Dynamics
We use hyperentangled photons to experimentally implement an
entanglement-assisted quantum process tomography technique known as Direct
Characterization of Quantum Dynamics. Specifically, hyperentanglement-assisted
Bell-state analysis enabled us to characterize a variety of single-qubit
quantum processes using far fewer experimental configurations than are required
by Standard Quantum Process Tomography (SQPT). Furthermore, we demonstrate how
known errors in Bell-state measurement may be compensated for in the data
analysis. Using these techniques, we have obtained single-qubit process
fidelities as high as 98.2% but with one-third the number experimental
configurations required for SQPT. Extensions of these techniques to multi-qubit
quantum processes are discussed.Comment: This is part of a joint submission with an implementation with Ions:
"Experimental characterization of quantum dynamics through many-body
interactions" by Daniel Nigg, Julio T. Barreiro, Philipp Schindler, Masoud
Mohseni, Thomas Monz, Michael Chwalla, Markus Hennrich and Rainer Blat
Coarse Brownian Dynamics for Nematic Liquid Crystals: Bifurcation Diagrams via Stochastic Simulation
We demonstrate how time-integration of stochastic differential equations
(i.e. Brownian dynamics simulations) can be combined with continuum numerical
bifurcation analysis techniques to analyze the dynamics of liquid crystalline
polymers (LCPs). Sidestepping the necessity of obtaining explicit closures, the
approach analyzes the (unavailable in closed form) coarse macroscopic
equations, estimating the necessary quantities through appropriately
initialized, short bursts of Brownian dynamics simulation. Through this
approach, both stable and unstable branches of the equilibrium bifurcation
diagram are obtained for the Doi model of LCPs and their coarse stability is
estimated. Additional macroscopic computational tasks enabled through this
approach, such as coarse projective integration and coarse stabilizing
controller design, are also demonstrated
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