1,546 research outputs found
On the hull and interval numbers of oriented graphs
In this work, for a given oriented graph , we study its interval and hull
numbers, denoted by and , respectively, in the geodetic,
and convexities. This last one, we believe to be formally
defined and first studied in this paper, although its undirected version is
well-known in the literature. Concerning bounds, for a strongly oriented graph
, we prove that and that there is a strongly
oriented graph such that . We also determine exact
values for the hull numbers in these three convexities for tournaments, which
imply polynomial-time algorithms to compute them. These results allows us to
deduce polynomial-time algorithms to compute when the
underlying graph of is split or cobipartite. Moreover, we provide a
meta-theorem by proving that if deciding whether or
is NP-hard or W[i]-hard parameterized by , for some
, then the same holds even if the underlying graph of
is bipartite. Next, we prove that deciding whether or
is W[2]-hard parameterized by , even if the
underlying graph of is bipartite; that deciding whether or is NP-complete, even if has no directed
cycles and the underlying graph of is a chordal bipartite graph; and that
deciding whether or is W[2]-hard
parameterized by , even if the underlying graph of is split. We also
argue that the interval and hull numbers in the oriented and
convexities can be computed in polynomial time for graphs of bounded tree-width
by using Courcelle's theorem
Development of peach flower buds under low winter chilling conditions
Here, we reviewed both endogenous and exogenous factors involved in the processes of flower bud formation and flower development in peach, analyzing how they can be affected by climatic change in temperate zones, explored the expansion of peach to tropical or subtropical zones. The process of flower bud formation in peach differs between low winter chilling and temperate conditions. Although the main steps of flower development are maintained, the timing in which each one occurs is different, and some processes can be altered under low winter chilling conditions, with a great impact on fruit production and crop management. Further studies on flower bud induction and differentiation under warmer conditions are fundamental for addressing the alterations in flower bud development that negatively impact on next seasonâs harvest. In the future, horticulturalists and scientists will face several challenges, mainly how high temperatures affect the expression of the main genes regulating flower formation and how to improve crop management in these conditions
eStroop: Implementation, Standardization, and Systematic Comparison of a New Voice-Key Version of the Traditional Stroop Task
The Stroop effect is a well-documented phenomenon, demonstrating both interference and facilitation effects. Many versions of the Stroop task were created, according to the purposes of its applications, varying in numerous aspects. While many versions are developed to investigate the mechanisms of the effect itself, the Stroop effect is also considered a general measure of attention, inhibitory control, and executive functions. In this paper, we implement âeStroopâ: a new digital version based on verbal responses, measuring the main processes involved in the traditional effect. eStroop features four categories of stimuli in four different colors: (1) geometrical shapes, (2) neutral words, (3) congruent words, and (4) incongruent words. The results of the administration to 307 University students confirm the Stroop effect and offer baseline data for future research and clinical testing. Direct comparisons with other recent versions of the task are discussed, offering insights into differences and similarities between different task variables
Wave profile and tide monitoring system for scalable implementation
A versatile, miniaturized, cost-effective, low-power wave profile and tide monitoring system, capable of long-term and scalable deployment, was developed to integrate pressure and temperature sensors in an RS485 network, for standalone operation with organized memory or real-time shared data monitoring. The pressure and temperature sensors are controlled by low-power microcontrollers, that communicate the data periodically to a datalogger, that depending on the application, store it in a removable SD card or send it to a server via Wi-Fi. The data is then analyzed to compensate for the loss in amplitude sensitivity according to the sensorâs depth. The wave profile can be sampled at a maximum rate of 100 Hz, with a 1 cm resolution. The system was tested successfully in real-life conditions, in rivers Douro and CĂĄvado, and off the coast of Viana do Castelo.JoĂŁo Rocha was supported by the doctoral Grant PRT/BD/154322/2023 financed by the Portuguese Foundation for Science and Technology (FCT), and with funds from Portuguese State Budget, European Social Fund (ESF) and Por_Norte, under MIT Portugal
Program. This work is co-funded by the projects K2D: Knowledge and Data from the Deep to Space (POCI-01-0247-FEDER-045941), SONDA (PTDC/EME-SIS/1960/2020), ATLĂNTIDA (NORTE-01-0145-FEDER-000040) and CMEMS - UIDB/04436/2020 and UIDP/04436/2020
Off-shell effects in dilepton production from hot interacting mesons
The production of dielectrons in reactions involving a_1 mesons and pions is
studied. We compare results obtained with different phenomenological
Lagrangians that have been used in connection with hadronic matter and finite
nuclei. We insist on the necessity for those interactions to satisfy known
empirical properties of the strong interaction. Large off-shell effects in
dielectron production are found and some consequences for the interpretation of
heavy ion data are outlined. We also compare with results obtained using
experimentally-extracted spectral functions.Comment: 14 pages, LaTeX2e, 2 figure
Intermediate-mass dilepton spectra and the role of secondary hadronic processes in heavy-ion collisions
We carry out a study of intermediate-mass (between 1 and 2.5 GeV) dilepton
spectra from hadronic interactions in heavy-ion collisions. The processes
considered are , , , , , and . The elementary cross sections for those are obtained
from chiral Lagrangians involving pseudoscalar, vector, and axial-vector
mesons. The respective electromagnetic form factors are determined by fitting
to experimental data for the reverse processes of . Based on
this input we calculate cross sections and thermal dilepton emission rates and
compare our results with those from other approaches. Finally we use these
elementary cross sections with a relativistic transport model and calculate
dilepton spectra in S+W collisions at SPS energies. The comparison of our
results with experimental data from the HELIOS-3 collaboration indicates the
importance of the secondary hadronic contributions to the intermediate-mass
dilepton spectra.Comment: 25 pages, including 20 postscript figure
Search for CP violation in decays
A model-independent search for direct CP violation in the Cabibbo suppressed
decay in a sample of approximately 370,000 decays is
carried out. The data were collected by the LHCb experiment in 2010 and
correspond to an integrated luminosity of 35 pb. The normalized Dalitz
plot distributions for and are compared using four different
binning schemes that are sensitive to different manifestations of CP violation.
No evidence for CP asymmetry is found.Comment: 13 pages, 8 figures, submitted to Phys. Rev.
Opposite-side flavour tagging of B mesons at the LHCb experiment
The calibration and performance of the oppositeside
flavour tagging algorithms used for the measurements
of time-dependent asymmetries at the LHCb experiment
are described. The algorithms have been developed using
simulated events and optimized and calibrated with
B
+ âJ/ÏK
+, B0 âJ/ÏK
â0 and B0 âD
ââ
Ό
+
ΜΌ decay
modes with 0.37 fbâ1 of data collected in pp collisions
at
â
s = 7 TeV during the 2011 physics run. The oppositeside
tagging power is determined in the B
+ â J/ÏK
+
channel to be (2.10 ± 0.08 ± 0.24) %, where the first uncertainty
is statistical and the second is systematic
Measurement of the ratio of branching fractions BR(B0 -> K*0 gamma)/BR(Bs0 -> phi gamma)
The ratio of branching fractions of the radiative B decays B0 -> K*0 gamma
and Bs0 -> phi gamma has been measured using 0.37 fb-1 of pp collisions at a
centre of mass energy of sqrt(s) = 7 TeV, collected by the LHCb experiment. The
value obtained is BR(B0 -> K*0 gamma)/BR(Bs0 -> phi gamma) = 1.12 +/- 0.08
^{+0.06}_{-0.04} ^{+0.09}_{-0.08}, where the first uncertainty is statistical,
the second systematic and the third is associated to the ratio of fragmentation
fractions fs/fd. Using the world average for BR(B0 -> K*0 gamma) = (4.33 +/-
0.15) x 10^{-5}, the branching fraction BR(Bs0 -> phi gamma) is measured to be
(3.9 +/- 0.5) x 10^{-5}, which is the most precise measurement to date.Comment: 15 pages, 1 figure, 2 table
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