1,376 research outputs found
Tuneable molecular doping of corrugated graphene
Density functional theory (DFT) modeling of the physisorption of four
different types of molecules (toluene, bromine dimmer, water and nitrogen
dioxide) over and above graphene ripples has been performed. For all types of
molecules changes of charge transfer and binding energies in respect to flat
graphene is found. The changes in electronic structure of corrugated graphene
and turn of {\pi}-orbitals of carbon atoms in combination with chemical
structure of adsorbed molecules are proposed as the causes of difference with
the perfect graphene case and variety of adsorption properties of different
types of the molecules. Results of calculation suggest that the tops of the
ripples are more attractive for large molecules and valley between ripples for
small molecules. Stability of molecules on the ripples and energy barriers for
migration over flat and corrugated graphene is also discussed.Comment: 15 pages, 5 figures, accepted in Surface Scienc
SU(3) lattice gauge theory with a mixed fundamental and adjoint plaquette action: Lattice artefacts
We study the four-dimensional SU(3) gauge model with a fundamental and an
adjoint plaquette term in the action. We investigate whether corrections to
scaling can be reduced by using a negative value of the adjoint coupling. To
this end, we have studied the finite temperature phase transition, the static
potential and the mass of the 0^{++} glueball. In order to compute these
quantities we have implemented variance reduced estimators that have been
proposed recently. Corrections to scaling are analysed in dimensionless
combinations such as T_c/\sqrt{\sigma} and m_{0^{++}}/T_c. We find that indeed
the lattice artefacts in e.g. m_{0^{++}}/T_c can be reduced considerably
compared with the pure Wilson (fundamental) gauge action at the same lattice
spacing.Comment: 36 pages, 12 figure
Supporting learning with 3D interactive applications in early years
Early years education is an key element for the introduction of children in the education system. In order to improve this process, the aim of this study was to explore how guided interaction with 3D apps can fit into a preschool setting, how it can help children learn through playing and how it can improve their learning outcomes. A study was conducted with six classes of 87 students aged between 3 years to 6 years, over a 12-week period. Children used 10 inch Android tablets with a series of apps developed by our research team, about houses of the world, the skeleton & five senses and, animals. A quasi-experimental design based on a nonequivalent groups pretest and posttest de-sign revealed that an active behavior and better learning outcomes are obtained by children participating in the experimental groupCascales Martínez, A.; Martínez Segura, MJ.; Laguna- Segobia, M.; Pérez Lopez, DC.; Contero, M. (2014). Supporting learning with 3D interactive applications in early years. Lecture Notes in Computer Science. 8524:11-22. doi:10.1007/978-3-319-07485-6_2S11228524Plowman, L., Stephen, C.: Children, Play and Computers in Preschool Education. British Journal of Educational Technology 36(2), 145–157 (2005)Tootell, H., Plumb, M., Hadfield, C., Dawson, L.: Gestural Interface Technology in early childhood education: A framework for fully-engaged communication. In: Proceedings of the Annual Hawaii International Conference on System Sciences, art. no. 6479836, pp. 13–20 (2013)Marco, J., Cerezo, E.: Bringing Tabletop Technologies to Kindergarten Children. In: HCI 2009 International Conference on Human-Computer Interaction–Celebrating People and Technology, pp. 103–111. Springer, Heidelberg (2009)Heft, T.M., Swaminathan, S.: Using Computers in Early Childhood Classrooms: Teachers’ Attitudes, Skills and Practices. Journal of Early Childhood Research 6(4), 169–188 (2006)Wang, X.C., Ching, C.C.: Social Construction of Computer Experience in a First-Grade Classroom: Social Processes and Mediating Artifacts. Early Education and Development 14(3), 335–361 (2003)Couse, L.J., Chen, D.W.: A Tablet Computer for Young Children? Exploring Its Viability for Early Childhood Education. Journal of Research on Technology in Education 43(1), 75–98 (2012)Kearney, J.: Educating Young Children - Learning and Teaching in the Early Childhood Years. Early Childhood Teachers’ Association (ECTA Inc.) 3(18) (2012)Rankothge, W.H., Sendanayake, S.V., Sudarshana, R.G.P., Balasooriya, B.G.G.H., Alahapperuma, D.R., Mallawarachchi, Y.: Technology Assisted Tool for Learning Skills Development in Early Childhood. In: Proc. of 2012 International Conference on Advances in ICT for Emerging Regions (ICTer), pp. 165–168 (2012)Sandvik, M., Smørdal, O., Østerud, S.: Exploring iPads in Practitioners’ Repertoires for Language Learning and Literacy Practices In Kindergarten. Nordic Journal of Digital Literacy 3(7), 204–221 (2012)Priyankara, K.W.T.G.T., Mahawaththa, D.C., Nawinna, D.P., Jayasundara, J.M.A., Tharuka, K.D.N., Rajapaksha, S.K.: Android Based e-Learning Solution for Early Childhood Education in Sri Lanka. In: Proceedings of the 8th International Conference on Computer Science & Education (ICCSE), pp. 715–718 (2013)Zanchi, C., Presser, A.L., Vahey, P.: Next Generation Preschool Math Demo: Tablet Games for Preschool Classrooms. In: Proceedings of the 12th International Conference on Interaction Design and Children, IDC 2013, pp. 527–530 (2013)Meyer, B.: Game-based Language Learning for Pre-School Children: A Design Perspective. Electronic Journal of e-Learning 11(1), 39–48 (2013)Straub, D.W.: Validating Instruments in MIS Research. MIS Quarterly 13(2), 147–169 (1989)Cook, T.D., Campbell, D.T., Day, A.: Quasi-experimentation: Design and Analysis Issues for Field Settings, pp. 19–21. Houghton Mifflin, Boston (1979)Buendía, L., Y Berrocal, E.: La Ética de la Investigación Educativa. Ágora Digital 1 (2011)Tojar, J., Serrano, J.: Ética e Investigación Educativa. RELIEVE 6(2) (2000)Cascales, A., Laguna, I., Pérez-López, D., Perona, P., Contero, M.: 3D Interactive Applications on Tablets for Preschoolers: Exploring the Human Skeleton and the Senses. In: Hernández-Leo, D., Ley, T., Klamma, R., Harrer, A. (eds.) EC-TEL 2013. LNCS, vol. 8095, pp. 71–83. Springer, Heidelberg (2013
On the relationship between continuous- and discrete-time quantum walk
Quantum walk is one of the main tools for quantum algorithms. Defined by
analogy to classical random walk, a quantum walk is a time-homogeneous quantum
process on a graph. Both random and quantum walks can be defined either in
continuous or discrete time. But whereas a continuous-time random walk can be
obtained as the limit of a sequence of discrete-time random walks, the two
types of quantum walk appear fundamentally different, owing to the need for
extra degrees of freedom in the discrete-time case.
In this article, I describe a precise correspondence between continuous- and
discrete-time quantum walks on arbitrary graphs. Using this correspondence, I
show that continuous-time quantum walk can be obtained as an appropriate limit
of discrete-time quantum walks. The correspondence also leads to a new
technique for simulating Hamiltonian dynamics, giving efficient simulations
even in cases where the Hamiltonian is not sparse. The complexity of the
simulation is linear in the total evolution time, an improvement over
simulations based on high-order approximations of the Lie product formula. As
applications, I describe a continuous-time quantum walk algorithm for element
distinctness and show how to optimally simulate continuous-time query
algorithms of a certain form in the conventional quantum query model. Finally,
I discuss limitations of the method for simulating Hamiltonians with negative
matrix elements, and present two problems that motivate attempting to
circumvent these limitations.Comment: 22 pages. v2: improved presentation, new section on Hamiltonian
oracles; v3: published version, with improved analysis of phase estimatio
Random fields on model sets with localized dependency and their diffraction
For a random field on a general discrete set, we introduce a condition that
the range of the correlation from each site is within a predefined compact set
D. For such a random field omega defined on the model set Lambda that satisfies
a natural geometric condition, we develop a method to calculate the diffraction
measure of the random field. The method partitions the random field into a
finite number of random fields, each being independent and admitting the law of
large numbers. The diffraction measure of omega consists almost surely of a
pure-point component and an absolutely continuous component. The former is the
diffraction measure of the expectation E[omega], while the inverse Fourier
transform of the absolutely continuous component of omega turns out to be a
weighted Dirac comb which satisfies a simple formula. Moreover, the pure-point
component will be understood quantitatively in a simple exact formula if the
weights are continuous over the internal space of Lambda Then we provide a
sufficient condition that the diffraction measure of a random field on a model
set is still pure-point.Comment: 21 page
The impact of perceived organizational commitment and leader commitment on organizational citizenship behaviour
Orbital order in the low-dimensional quantum spin system TiOCl probed by ESR
We present electron spin resonance data of Ti (3) ions in single
crystals of the novel layered quantum spin magnet TiOCl. The analysis of the g
tensor yields direct evidence that the d_{xy} orbital from the t_{2g} set is
predominantly occupied and owing to the occurrence of orbital order a linear
spin chain forms along the crystallographic b axis. This result corroborates
recent theoretical LDA+U calculations of the band structure. The temperature
dependence of the parameters of the resonance signal suggests a strong coupling
between spin and lattice degrees of freedom and gives evidence for a transition
to a nonmagnetic ground state at 67 K.Comment: revised version, accepted for publication in Phys. Rev. B, Rapid Com
Effects of rapid prey evolution on predator-prey cycles
We study the qualitative properties of population cycles in a predator-prey
system where genetic variability allows contemporary rapid evolution of the
prey. Previous numerical studies have found that prey evolution in response to
changing predation risk can have major quantitative and qualitative effects on
predator-prey cycles, including: (i) large increases in cycle period, (ii)
changes in phase relations (so that predator and prey are cycling exactly out
of phase, rather than the classical quarter-period phase lag), and (iii)
"cryptic" cycles in which total prey density remains nearly constant while
predator density and prey traits cycle. Here we focus on a chemostat model
motivated by our experimental system [Fussmann et al. 2000,Yoshida et al. 2003]
with algae (prey) and rotifers (predators), in which the prey exhibit rapid
evolution in their level of defense against predation. We show that the effects
of rapid prey evolution are robust and general, and furthermore that they occur
in a specific but biologically relevant region of parameter space: when traits
that greatly reduce predation risk are relatively cheap (in terms of reductions
in other fitness components), when there is coexistence between the two prey
types and the predator, and when the interaction between predators and
undefended prey alone would produce cycles. Because defense has been shown to
be inexpensive, even cost-free, in a number of systems [Andersson and Levin
1999, Gagneux et al. 2006,Yoshida et al. 2004], our discoveries may well be
reproduced in other model systems, and in nature. Finally, some of our key
results are extended to a general model in which functional forms for the
predation rate and prey birth rate are not specified.Comment: 35 pages, 8 figure
phosphorus and potassium fertilizer effects on alfalfa and soil in a non limited soil
Fertilization strategies for high-yielding alfalfa (Medicago sativa L.) should take in account the increase in soil nutritional status that occurred during the last decades in areas with intensive agricultural use. A field study was conducted at the University of Padova, northeastern Italy, to determine the response of alfalfa yield and nutritive value to various combinations of P and K rates in a soil lacking nutrient deficiency. Alfalfa cultivar Delta was seeded in March 2005 on a silt loam soil having 38 mg kg -1 available P and 178 mg kg -1 exchangeable K. Nine treatments deriving from the combination of three P fertilization rates (0, 100, and 200 kg ha -1 P 2 O 5 ) and three K rates (0, 300, and 600 kg ha -1 K 2 O) were compared in a randomized complete block design. Plots were harvested at bud stage during three growing seasons (2005-2007) and dry matter (DM) yield, forage nutritive value, P and K contents, canopy height, and stem density were measured at each harvest. Soil samples were collected at the end of the research period for determination of available P and exchangeable K. The results demonstrated that P application had no impact on yield and did not interact with K in determining productivity, while K had a positive effect on yield. However, the 300 kg ha -1 K 2 O rate appeared sufficient to maximize yield, without adverse effects on the forage nutritive value. Data from soil analyses showed that alfalfa has a high K uptake even when it is fertilized at high rates
- …