34,805 research outputs found
Flavor asymmetry of polarized antiquark distributions and semi-inclusive DIS
The -expansion of QCD suggests large flavor asymmetries of the
polarized antiquark distributions in the nucleon. This is confirmed by model
calculations in the large- limit (chiral quark-soliton model), which give
sizable results for and . We compute the contributions of
these flavor asymmetries to the spin asymmetries in hadron production in
semi-inclusive deep-inelastic scattering. We show that the large flavor
asymmetries predicted by the chiral quark-soliton model are consistent with the
recent HERMES data for spin asymmetries in charged hadron production.Comment: 21 pages, LaTeX2e, 9 eps figures include
A numerical approach to robust in-line control of roll forming processes
The quality of roll formed products is known to be highly sensitive and dependent on the process parameters and thus the unavoidable variations of these parameters during mass production. To maintain a constant high product quality, a new roll former with an adjustable final roll forming stand is developed at Deakin University enabling the continuous compensation for possible shape defects. In this work, a numerical approach to robust in-line control of the roll forming of a V-section profile is presented, combining the aspects of robust process design and in-line compensation methods. A numerical study is performed to determine the relationship between controllable process settings and uncontrollable variation of incoming material properties with respect to the common product defects longitudinal bow and springback. The computationally expensive non-linear FE simulations used in this study are subsequently replaced by metamod-els based on efficient Single Response Surfaces. Using these metamodels, the optimal setting for the adjustable stand is determined with robust optimization techniques and the effect on product quality analyzed. It is shown that the subsequent adjustment of the final roll stand position leads to a significantly improved product quality by preventing product defects and minimizing the deteriorating effects of scattering variables
On the detection of Lorentzian profiles in a power spectrum: A Bayesian approach using ignorance priors
Aims. Deriving accurate frequencies, amplitudes, and mode lifetimes from
stochastically driven pulsation is challenging, more so, if one demands that
realistic error estimates be given for all model fitting parameters. As has
been shown by other authors, the traditional method of fitting Lorentzian
profiles to the power spectrum of time-resolved photometric or spectroscopic
data via the Maximum Likelihood Estimation (MLE) procedure delivers good
approximations for these quantities. We, however, show that a conservative
Bayesian approach allows one to treat the detection of modes with minimal
assumptions (i.e., about the existence and identity of the modes).
Methods. We derive a conservative Bayesian treatment for the probability of
Lorentzian profiles being present in a power spectrum and describe an efficient
implementation that evaluates the probability density distribution of
parameters by using a Markov-Chain Monte Carlo (MCMC) technique.
Results. Potentially superior to "best-fit" procedure like MLE, which only
provides formal uncertainties, our method samples and approximates the actual
probability distributions for all parameters involved. Moreover, it avoids
shortcomings that make the MLE treatment susceptible to the built-in
assumptions of a model that is fitted to the data. This is especially relevant
when analyzing solar-type pulsation in stars other than the Sun where the
observations are of lower quality and can be over-interpreted. As an example,
we apply our technique to CoRoT observations of the solar-type pulsator HD
49933.Comment: 12 pages, 11 figures, accepted for publication in Astronomy and
Astrophysic
Ideabook: Libraries for Families
The IDEABOOK is a research-based framework to guide and broaden family engagement in libraries.The framework helps libraries move beyond thinking of family engagement as random, individual activities or programs, but rather as a system where library leadership, activities, and resources that are linked to goals. The framework represents a theory of change that begins with a set of elements—leadership, engagement, and support services—that build a pathway for meaningful family engagement beginning in the early childhood years and extending through young adulthood.This IDEABOOK was developed for anyone who works in a library setting—from library directors and children's and youth librarians, to volunteers and support staff—and shares many innovative ways that libraries support and guide families in children's learning and development
Single- and double-drift bunchers as possible injection schemes for the CPS linac
Two bunching schemes are considered in the frame of the CPS Linac, one with a single buncher, the other with a double-drift harmonic buncher. The matching of the beam to the Linac acceptance in six phase-space dimensions is achieved by computer programs in an iterative way: zero current solutions are found first, and then the intensity is progressively raised until 200 mA are trapped into the Linac. (9 refs)
QCD NLO with Powheg matching and top threshold matching in WHIZARD
We present the status of the automation of NLO processes within the event
generator WHIZARD. The program provides an automated FKS subtraction and phase
space integration over the FKS regions, while the (QCD) NLO matrix element is
accessed via the Binoth Les Houches Interface from an externally linked
one-loop program. Massless and massive test cases and validation are shown for
several e+e- processes. Furthermore, we discuss work in progress and future
plans. The second part covers the matching of the NRQCD prediction with NLL
threshold resummation to the NLO continuum top pair production at lepton
colliders. Both the S-wave and P-wave production of the top pair are taken into
account in the resummation. The inclusion in WHIZARD allows to study more
exclusive observables than just the total cross section and automatically
accounts for important electroweak and relativistic corrections in the
threshold region.Comment: 9 pages, 3 figures, Talk given at 12th International Symposium on
Radiative Corrections (Radcor 2015) and LoopFest XIV (Radiative Corrections
for the LHC and Future Colliders); v2: reference adde
Bacteriome-localized intracellular symbionts in pollen-feeding beetles of the genus dasytes (Coleoptera, Dasytidae)
Several insect taxa are associated with intracellular symbionts that provision limiting nutrients to their hosts. Such tightly integrated symbioses are especially common in insects feeding on nutritionally challenging diets like phloem sap or vertebrate blood, but also occur in seed-eating and omnivorous taxa. Here, we characterize an intracellular symbiosis in pollen-feeding beetles of the genus Dasytes (Coleoptera, Dasytidae). High-throughput tag-encoded 16S amplicon pyrosequencing of adult D. plumbeus and D. virens revealed a single gamma-proteobacterial symbiont ('Candidatus Dasytiphilus stammeri') that amounts to 52.4-98.7% of the adult beetles' entire microbial community. Almost complete 16S rRNA sequences phylogenetically placed the symbiont into a clade comprising Buchnera and other insect endosymbionts, but sequence similarities to these closest relatives were surprisingly low (83.4-87.4%). Using histological examination, three-dimensional reconstructions, and fluorescence in situ hybridization, we localized the symbionts in three mulberry-shaped bacteriomes that are associated with the mid- to hind-gut transition in adult male and female beetles. Given the specialized pollen-feeding habits of the adults that contrasts with the larvae's carnivorous lifestyle, the symbionts may provision limiting essential amino acids or vitamins as in other intracellular symbioses, or they might produce digestive enzymes that break up the fastidious pollen walls and thereby contribute to the host's nutrition. In either case, the presence of gamma-proteobacterial symbionts in pollen-feeding beetles indicates that intracellular mutualists are more widely distributed across insects with diverse feeding habits than previously recognized
Entanglement Energetics in the Ground State
We show how many-body ground state entanglement information may be extracted
from sub-system energy measurements at zero temperature. A precise relation
between entanglement and energy fluctuations is demonstrated in the weak
coupling limit. Examples are given with the two-state system and the harmonic
oscillator, and energy probability distributions are calculated. Comparisons
made with recent qubit experiments show this type of measurement provides
another method to quantify entanglement with the environment.Comment: 7 pages, 3 figures, Conference proceeding for the Physics of Quantum
Electronics; Utah, USA, January 200
The extensive nature of group quality
We consider groups of interacting nodes engaged in an activity as many-body,
complex systems and analyse their cooperative behaviour from a mean-field point
of view. We show that inter-nodal interactions rather than accumulated
individual node strengths dominate the quality of group activity, and give rise
to phenomena akin to phase transitions, where the extensive relationship
between group quality and quantity reduces. The theory is tested using
empirical data on quantity and quality of scientific research groups, for which
critical masses are determined.Comment: 6 pages, 6 figures containing 13 plots. Very minor changes to
coincide with published versio
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