1,476 research outputs found
Endogenous leadership in teams
In this paper we study the mechanics of “leading by example” in
teams. Leadership is beneficial for the entire team when agents are
conformists, i.e., dislike effort differentials. We also show how leadership
can arise endogenously and discuss what type of leader benefits
a team most
Transport Length Scales in Disordered Graphene-based Materials: Strong Localization Regimes and Dimensionality Effects
We report on a numerical study of quantum transport in disordered two
dimensional graphene and graphene nanoribbons. By using the Kubo and the
Landauer approaches, transport length scales in the diffusive (mean free path,
charge mobilities) and localized regimes (localization lengths) are computed,
assuming a short range disorder (Anderson-type). In agreement with localization
scaling theory, the electronic systems are found to undergo a conventional
Anderson localization in the zero temperature limit. Localization lengths in
weakly disordered ribbons are found to differ by two orders of magnitude
depending on their edge symmetry, but always remain several orders of magnitude
smaller than those computed for 2D graphene for the same disorder strength.
This pinpoints the role of transport dimensionality and edge effects.Comment: 4 pages, Phys. rev. Lett. (in press
Sc2CX (X=N2, ON, O2) MXenes as a promising anode material: A first-principles study
MXenes' tunable properties make them excellent candidates for many
applications in future nanoelectronics. In this work, we explore the
suitability of ScCX (X=N, ON, O) MXenes to act as the active anode
materials in Na-ion based batteries (NIBs) by means of \textsl{ab initio}
simulations. After analyzing the structural and elastic properties of all the
possible models to evaluate the energetically favorable N and O
functionalization sites, our calculations show that both ScCON and
ScCN present a clear metallic character, making them potential
candidates as anode materials. The investigation of the most relevant features
for anode performance, such as the adsorption and diffusion of Na atoms, the
intrinsic capacity, the open circuit voltage, and the storage capacity show
that both systems are serious alternatives to the most common 2D materials
currently employed in alkali metal batteries. In particular, ScCN
presents a better diffusion behavior thanks to the absence of Na clustering on
its surface, with optimal diffusion barriers comparable to other 2D materials
such as MoN, while the values of diffusion barriers for ScCON are at
least three times smaller than those found for other anode candidates.
Similarly, while the capacity of ScCON is close to the one reported for 2D
ScC, ScCN possesses a power density more than twice higher than the
ones of 2D materials such as ScC, graphite, and MoS. Our results thus
confirm the urge for further experimental exploration of the MXene ScCX
(X=N, ON, O) family as anode material in NIBs
Exploring a novel class of Janus MXenes by first principles calculations: structural, electronic and magnetic properties of Sc2CXT, X = O, F, OH; T = C, S, N
The already intriguing electronic and optical properties of the MXene Sc2C family can be further
tuned through a wide range of possible functionalizations. Here, by means of Density Functional
Theory, we show that the 36 possible elements of the Janus MXT (M:Sc2C, X:O, F, OH, T:C, N, S)
family, built by considering the four possible structural models (i) FCC, (ii) HCP , (iii) FCC + HCP,
and (iv) HCP + FCC, are all potentially stable. The analysis of their mechanical properties shows
the excellent mechanical flexibility of functionalized MXenes (f-MXenes) under large strain, making
them more suitable for applications where stress could be an issue. Interestingly, while Sc2C presents
a metallic character, Sc2COS, Sc2CFN and Sc2COHN are found to be semiconductors with bandgaps
of 2.5 eV (indirect), 1.67 eV (indirect) and 1.1 eV (direct), respectively, which presents promising
applications for nano- and optoelectronics. Moreover, Sc2CFC presents a ferromagnetic ground state
with the 2x2x1 supercell magnetic moment of 3.99 mB, while the ground state of Sc2COHC might be
antiferromagnetic with a magnetic moment of 3.98 mB, depending on the environment. Remarkably,
the band structures of Sc2CFC and Sc2COHC present a half-metallic character with an HSE06
fundamental band gap of 0.60 eV and 0.48 eV, respectively. Our results confirm the extraordinary
potential of the Janus MXT (M:Sc2C, X:O, F, OH, T:C, N, S) family for novel applications in 2D
nano-,opto- and spintronics.Junta de Andalucia P18-FR-4834AEI PID2021-125604NB-I0
Anderson localization in carbon nanotubes: defect density and temperature effects
The role of irradiation induced defects and temperature in the conducting
properties of single-walled (10,10) carbon nanotubes has been analyzed by means
of a first-principles approach. We find that di-vacancies modify strongly the
energy dependence of the differential conductance, reducing also the number of
contributing channels from two (ideal) to one. A small number of di-vacancies
(5-9) brings up strong Anderson localization effects and a seemly universal
curve for the resistance as a function of the number of defects. It is also
shown that low temperatures, around 15-65 K, are enough to smooth out the
fluctuations of the conductance without destroying the exponential dependence
of the resistivity as a function of the tube length.Comment: 4 pages, 4 figure
The cDNA and deduced amino acid sequence of the γ subunit of the L-type calcium channel from rabbit skeletal muscle
Complementary DNAs for the γ subunit of the calcium channel of rabbit skeletal muscle were isolated on the basis of peptide sequences derived from the purified protein. The deduced primary structure is without homology to other known protein sequences and is consistent with the γ subunit being an integral membrane protein
Cone Genesis Tracing by the Chrnb4-EGFP Mouse Line: Evidences of Cellular Material Fusion after Cone Precursor Transplantation.
The cone function is essential to mediate high visual acuity, color vision, and daylight vision. Inherited cone dystrophies and age-related macular degeneration affect a substantial percentage of the world population. To identify and isolate the most competent cells for transplantation and integration into the retina, cone tracing during development would be an important added value. To that aim, the Chrnb4-EGFP mouse line was characterized throughout retinogenesis. It revealed a sub-population of early retinal progenitors expressing the reporter gene that is progressively restricted to mature cones during retina development. The presence of the native CHRNB4 protein was confirmed in EGFP-positive cells, and it presents a similar pattern in the human retina. Sub-retinal transplantations of distinct subpopulations of Chrnb4-EGFP-expressing cells revealed the embryonic day 15.5 high-EGFP population the most efficient cells to interact with host retinas to provoke the appearance of EGFP-positive cones in the photoreceptor layer. Importantly, transplantations into the DsRed retinas revealed material exchanges between donor and host retinas, as >80% of transplanted EGFP-positive cones also were DsRed positive. Whether this cell material fusion is of significant therapeutic advantage requires further thorough investigations. The Chrnb4-EGFP mouse line definitely opens new research perspectives in cone genesis and retina repair
Transient Phenomena Generated in Emptying Operations in Large-Scale Hydraulic Pipelines
[EN] Air pockets generated during emptying operations in pressurized hydraulic systems cause
significant pressure drops inside pipes. To avoid these sudden pressure changes, one of the most
widely used methods involves the installation of air valves along the pipeline route. These elements
allow air exchange between the exterior and the interior of the pipe, which alleviates the pressure
drops produced and thus prevents possible breaks or failures in the structure of the installation.
This study uses a mathematical model previously validated by the authors in smaller installations
to simulate all hydraulic variables involved in emptying processes over time. The purpose of these
simulations is the validation of the mathematical model in real large-scale installations, and to do this,
the results obtained with the mathematical model are compared with actual measurements made
by the partner company. The hydraulic system selected for the study is a pipeline with a nominal
diameter of 400 mm and a total length of 1020 m. The results obtained from the mathematical model
show great similarity with the experimental measurements, thus validating the model for emptying
large pipes.Romero, G.; Fuertes-Miquel, VS.; Coronado-Hernández, ÓE.; Ponz-Carcelén, R.; Biel Sanchis, F. (2020). Transient Phenomena Generated in Emptying Operations in Large-Scale Hydraulic Pipelines. Water. 12(8):1-11. https://doi.org/10.3390/w12082313S111128Laanearu, J., Annus, I., Koppel, T., Bergant, A., Vučković, S., Hou, Q., … van’t Westende, J. M. C. (2012). Emptying of Large-Scale Pipeline by Pressurized Air. Journal of Hydraulic Engineering, 138(12), 1090-1100. doi:10.1061/(asce)hy.1943-7900.0000631Fuertes-Miquel, V. S., Coronado-Hernández, O. E., Mora-Meliá, D., & Iglesias-Rey, P. L. (2019). Hydraulic modeling during filling and emptying processes in pressurized pipelines: a literature review. Urban Water Journal, 16(4), 299-311. doi:10.1080/1573062x.2019.1669188Vasconcelos, J. G., & Wright, S. J. (2008). Rapid Flow Startup in Filled Horizontal Pipelines. Journal of Hydraulic Engineering, 134(7), 984-992. doi:10.1061/(asce)0733-9429(2008)134:7(984)Bashiri-Atrabi, H., & Hosoda, T. (2015). The motion of entrapped air cavities in inclined ducts. Journal of Hydraulic Research, 53(6), 814-819. doi:10.1080/00221686.2015.1060272Zhou, L., Liu, D., Karney, B., & Wang, P. (2013). Phenomenon of White Mist in Pipelines Rapidly Filling with Water with Entrapped Air Pockets. Journal of Hydraulic Engineering, 139(10), 1041-1051. doi:10.1061/(asce)hy.1943-7900.0000765Ramezani, L., Karney, B., & Malekpour, A. (2015). The Challenge of Air Valves: A Selective Critical Literature Review. Journal of Water Resources Planning and Management, 141(10), 04015017. doi:10.1061/(asce)wr.1943-5452.0000530Ramezani, L., Karney, B., & Malekpour, A. (2016). Encouraging Effective Air Management in Water Pipelines: A Critical Review. Journal of Water Resources Planning and Management, 142(12), 04016055. doi:10.1061/(asce)wr.1943-5452.0000695Coronado-Hernández, O., Fuertes-Miquel, V., Besharat, M., & Ramos, H. (2017). Experimental and Numerical Analysis of a Water Emptying Pipeline Using Different Air Valves. Water, 9(2), 98. doi:10.3390/w9020098Liou, C. P., & Hunt, W. A. (1996). Filling of Pipelines with Undulating Elevation Profiles. Journal of Hydraulic Engineering, 122(10), 534-539. doi:10.1061/(asce)0733-9429(1996)122:10(534)Zhou, L., & Liu, D. (2013). Experimental investigation of entrapped air pocket in a partially full water pipe. Journal of Hydraulic Research, 51(4), 469-474. doi:10.1080/00221686.2013.785985Fuertes-Miquel, V. S., López-Jiménez, P. A., Martínez-Solano, F. J., & López-Patiño, G. (2016). Numerical modelling of pipelines with air pockets and air valves. Canadian Journal of Civil Engineering, 43(12), 1052-1061. doi:10.1139/cjce-2016-0209Martins, S. C., Ramos, H. M., & Almeida, A. B. (2015). Conceptual analogy for modelling entrapped air action in hydraulic systems. Journal of Hydraulic Research, 53(5), 678-686. doi:10.1080/00221686.2015.1077353Balacco, G., Apollonio, C., & Piccinni, A. F. (2015). Experimental analysis of air valve behaviour during hydraulic transients. Journal of Applied Water Engineering and Research, 3(1), 3-11. doi:10.1080/23249676.2015.1032374Abreu, J., Cabrera, E., Izquierdo, J., & García-Serra, J. (1999). Flow Modeling in Pressurized Systems Revisited. Journal of Hydraulic Engineering, 125(11), 1154-1169. doi:10.1061/(asce)0733-9429(1999)125:11(1154)De Marchis, M., Freni, G., & Milici, B. (2018). Experimental analysis of pressure-discharge relationship in a private water supply tank. Journal of Hydroinformatics, 20(3), 608-621. doi:10.2166/hydro.2018.135Alexander, J., Lee, P. J., Davidson, M., Duan, H.-F., Li, Z., Murch, R., … Brunone, B. (2019). Experimental Validation of Existing Numerical Models for the Interaction of Fluid Transients With In-Line Air Pockets. Journal of Fluids Engineering, 141(12). doi:10.1115/1.4043776Besharat, M., Tarinejad, R., Aalami, M. T., & Ramos, H. M. (2016). Study of a Compressed Air Vessel for Controlling the Pressure Surge in Water Networks: CFD and Experimental Analysis. Water Resources Management, 30(8), 2687-2702. doi:10.1007/s11269-016-1310-1Covas, D., Stoianov, I., Ramos, H., Graham, N., Maksimović, Č., & Butler, D. (2004). Water hammer in pressurized polyethylene pipes: conceptual model and experimental analysis. Urban Water Journal, 1(2), 177-197. doi:10.1080/1573062041233128997
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