1,022 research outputs found
Coupled charge and spin dynamics in high-density ensembles of nitrogen-vacancy centers in diamond
We studied the spin depolarization of ensembles of nitrogen-vacancy (NV)
centers in nitrogen-rich single crystal diamonds. We found a strong dependence
of the evolution of the polarized state in the dark on the concentration of NV
centers. At low excitation power, we observed a simple exponential decay
profile in the low-density regime and a paradoxical inverted exponential
profile in the high-density regime. At higher excitation power, we observed
complex behavior, with an initial sharp rise in luminescence signal after the
preparation pulse followed by a slower exponential decay. Magnetic field and
excitation laser power-dependent measurements suggest that the rapid initial
increase of the luminescence signal is related to recharging of the
nitrogen-vacancy centers (from neutral to negatively charged) in the dark. The
slow relaxing component corresponds to the longitudinal spin relaxation of the
NV ensemble. The shape of the decay profile reflects the interplay between two
mechanisms: the NV charge state conversion in the dark and the longitudinal
spin relaxation. These mechanisms, in turn, are influenced by ionization,
recharging and polarization dynamics during excitation. Interestingly, we found
that charge dynamics are dominant in NV-dense samples even at very feeble
excitation power. These observations may be important for the use of ensembles
of NV centers in precession magnetometry and sensing applications.Comment: 7 pages, 6 figure
Particle-Based Mesoscale Hydrodynamic Techniques
Dissipative particle dynamics (DPD) and multi-particle collision (MPC)
dynamics are powerful tools to study mesoscale hydrodynamic phenomena
accompanied by thermal fluctuations. To understand the advantages of these
types of mesoscale simulation techniques in more detail, we propose new two
methods, which are intermediate between DPD and MPC -- DPD with a multibody
thermostat (DPD-MT), and MPC-Langevin dynamics (MPC-LD). The key features are
applying a Langevin thermostat to the relative velocities of pairs of particles
or multi-particle collisions, and whether or not to employ collision cells. The
viscosity of MPC-LD is derived analytically, in very good agreement with the
results of numerical simulations.Comment: 7 pages, 2 figures, 1 tabl
Global Attractors for an Extensible Thermoelastic Beam System
This work is focused on the dissipative system describing the dynamics of an
extensible thermoelastic beam, where the dissipation is entirely contributed by
the second equation ruling the evolution of the temperature. Under natural
boundary conditions, we prove the existence of bounded absorbing sets. When
both the external body force and the heat source are time-independent, the
related semigroup of solutions is shown to possess the global attractor of
optimal regularity for all values of the external axial load. The same result
holds true when the rotational inertia is taken into consideration. In both
cases, the solutions on the attractor are strong solutions.Comment: 21 pages, no figur
Milk production of lacaune sheep with different degrees of crossing with manchega sheep in a commercial flock in Spain
The objective of the present study was to evaluate the effect of the grade of crossbreeding (Lacaune x Manchega) and environmental factors on milk production in a commercial flock in Spain. A total of 5769 milk production records of sheep with different degrees of purity of the Lacaune breed crossed with Manchega were used as follows: 100% Lacaune (n = 2960), 7/8 Lacaune (n = 502), 13/16 Lacaune (n = 306), 3/4 (n = 1288), 5/8 Lacaune (n = 441) and 1/2 Lacaune: Manchega (n = 272). Additional available information included the number of parity (1 to 8), litter size (single or multiple), and the season of the year of lambing (spring, summer, autumn and winter). A mixed model was used to evaluate the level of crossbreeding and environmental factors on milk production. The 100% Lacaune sheep presented the highest milk production with respect to the F1 Lacaune x Manchega sheep (p < 0.01), showing that as the degree of gene absorption increases with the Manchega breed, it presents lower milk yield. The 100%, 13/16, and 3/4 Lacaune genotypes had the highest milk yields with respect to the 1/2 Lacaune/Manchega breed (p < 0.001). The Lacaune registered on average 181.1 L in a period adjusted to 160 days of lactation (1.13 L/ day). Likewise, the parity number, litter size, and season of lambing effects showed significant differences (p < 0.01). It was concluded that 13/16 and 3/4 Lacaune/Manchega ewes presented the highest milk yields with respect to the other crosses
New 4-(N-cinnamoylbutyl)aminoacridines as potential multi-stage antiplasmodial leads
A novel family of 4-aminoacridine derivatives was obtained by linking this heteroaromatic core to different trans-cinnamic acids. The 4-(N-cinnamoylbutyl)aminoacridines obtained exhibited in vitro activity in the low- or sub-micromolar range against (i) hepatic stages of Plasmodium berghei, (ii) erythrocytic forms of Plasmodium falciparum, and (iii) early and mature gametocytes of Plasmodium falciparum. The most active compound, having a meta-fluorocinnamoyl group linked to the acridine core, was 20- and 120-fold more potent, respectively, against the hepatic and gametocyte stages of Plasmodium infection than the reference drug, primaquine. Moreover, no cytotoxicity towards mammalian and red blood cells at the concentrations tested was observed for any of the compounds under investigation. These novel conjugates represent promising leads for the development of new multi-target antiplasmodials.Copyright © 2023 The Authors. Published by Elsevier Masson SAS.. All rights reserved
A reduced model for shock and detonation waves. II. The reactive case
We present a mesoscopic model for reactive shock waves, which extends a
previous model proposed in [G. Stoltz, Europhys. Lett. 76 (2006), 849]. A
complex molecule (or a group of molecules) is replaced by a single
mesoparticle, evolving according to some Dissipative Particle Dynamics.
Chemical reactions can be handled in a mean way by considering an additional
variable per particle describing a rate of reaction. The evolution of this rate
is governed by the kinetics of a reversible exothermic reaction. Numerical
results give profiles in qualitative agreement with all-atom studies
Integrating reproductive phenology in ecological niche models changed the predicted future ranges of a marine invader
Aim Phenology of a wide diversity of organisms has a dependency on climate, usually with reproductive periods beginning earlier in the year and lasting longer at lower latitudes. Temperature and day length are known environmental drivers of the reproductive timing of many species. Hence, reproductive phenology is sensitive to warming and is important to be considered for reliable predictions of species distributions. This is particularly relevant for rapidly spreading non-indigenous species (NIS). In this study, we forecast the future ranges of a NIS, the seaweed Sargassum muticum, including its reproductive phenology. Location Coastal areas of the Northern Hemisphere (Pacific and Atlantic oceans). Methods We used ecological niche modelling to predict the distribution of S. muticum under two scenarios forecasting limited (RCP 2.6) and severe (RCP 8.5) future climate changes. We then refined our predictions with a hybrid model using sea surface temperature constraints on reproductive phenology. Results Under the most severe climate change scenario, we predicted northward expansions which may have significant ecological consequences for subarctic coastal ecosystems. However, in lower latitudes, habitats currently occupied by S. muticum will no longer be suitable, creating opportunities for substantial community changes. The temperature constraints imposed by the reproductive window were shown to restrict the modelled future species expansion strongly. Under the RCP 8.5 scenario, the total range area was expected to increase by 61.75% by 2100, but only by 1.63% when the reproductive temperature window was considered. Main conclusions Altogether these results exemplify the need to integrate phenology better to improve the prediction of future distributional shifts at local and regional scales.AgĂȘncia financiadora NĂșmero do subsĂdio
Fundacao para a Ciencia e a Tecnologia
CCMAR/Multi/04326/2019
FCT-BIODIVERSA/004/2015
FCT-SEAS-ERA/0001/2012
SFRH/BPD/107878/2015
SFRH/BPD/85040/2012
Erasmus Mundus Doctoral Programme MARES on Marine Ecosystem Health Conservation
MARES_13_08
Pew Marineinfo:eu-repo/semantics/publishedVersio
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