37 research outputs found
Numerical study of the one-dimensional quantum compass model
The ground state magnetic phase diagram of the one-dimensional quantum
compass model (QCM) is studied using the numerical Lanczos method. A detailed
numerical analysis of the low energy excitation spectrum is presented. The
energy gap and the spin-spin correlation functions are calculated for finite
chains. Two kind of the magnetic long-range orders, the Neel and a type of the
stripe-antiferromagnet, in the ground state phase diagram are identified. Based
on the numerical analysis, the first and second order quantum phase transitions
in the ground state phase diagram are identified.Comment: 6 pages, 8 figures. arXiv admin note: text overlap with
arXiv:1105.211
Thermodynamic Properties of the One-Dimensional Extended Quantum Compass Model in the Presence of a Transverse Field
The presence of a quantum critical point can significantly affect the
thermodynamic properties of a material at finite temperatures. This is
reflected, e.g., in the entropy landscape S(T; c) in the vicinity of a quantum
critical point, yielding particularly strong variations for varying the tuning
parameter c such as magnetic field. In this work we have studied the
thermodynamic properties of the quantum compass model in the presence of a
transverse field. The specific heat, entropy and cooling rate under an
adiabatic demagnetization process have been calculated. During an adiabatic
(de)magnetization process temperature drops in the vicinity of a field-induced
zero-temperature quantum phase transitions. However close to field-induced
quantum phase transitions we observe a large magnetocaloric effect
Quantum phase transitions in the exactly solved spin-1/2 Heisenberg-Ising ladder
Ground-state behaviour of the frustrated quantum spin-1/2 two-leg ladder with
the Heisenberg intra-rung and Ising inter-rung interactions is examined in
detail. The investigated model is transformed to the quantum Ising chain with
composite spins in an effective transverse and longitudinal field by employing
either the bond-state representation or the unitary transformation. It is shown
that the ground state of the Heisenberg-Ising ladder can be descended from
three exactly solvable models: the quantum Ising chain in a transverse field,
the 'classical' Ising chain in a longitudinal field or the spin-chain model in
a staggered longitudinal-transverse field. The last model serves in evidence of
the staggered bond phase with alternating singlet and triplet bonds on the
rungs of two-leg ladder, which appears at moderate values of the external
magnetic field and consequently leads to a fractional plateau at a half of the
saturation magnetization. The ground-state phase diagram totally consists of
five ordered and one quantum disordered phase, which are separated from each
other either by the lines of discontinuous or continuous quantum phase
transitions. The order parameters are exactly calculated for all five ordered
phases and the quantum disordered phase is characterized through different
short-range spin-spin correlations.Comment: corrected version, figure A1 has been changed, accepted in J. Phys.
A, 19 pages, 7 figure
Topology of chalcogen chains
We investigate the topological properties of the helical atomic chains
occurring in elemental selenium and tellurium. We postulate a realistic model
that includes spin-orbit interaction and show this to be topologically
non-trivial, with a topological invariant protected by a crystalline symmetry.
We describe the end-states, which are orbitally polarized, with an orbital
density modulation strongly peaked at the edge. Furthermore, we propose a
simplified model that decomposes into three orbital chains, allowing us to
define a topological invariant protected by a crystalline symmetry. We contrast
this result with recent observations made for the orbital Su-Schrieffer-Heeger
model containing a -orbital zigzag chain.Comment: 10 figure
Quantum Correlation in One-dimensional Extend Quantum Compass Model
We study the correlations in the one-dimensional extended quantum compass
model in a transverse magnetic field. By exactly solving the Hamiltonian, we
find that the quantum correlation of the ground state of one-dimensional
quantum compass model is vanishing. We show that quantum discord can not only
locate the quantum critical points, but also discern the orders of phase
transitions. Furthermore, entanglement quantified by concurrence is also
compared.Comment: 8 pages, 14 figures, to appear in Eur. Phys. J.
State of the Art in Building FaƧades
This chapter presents a portfolio of building materials suitable for facades. It describes the relationship between material type, building element, facade, and the entire building structure. Traditional facades based on static components, as well as adaptive concepts able to interact with changing environmental conditions, are briefly described and illustrated with pictures. Climatic design principles, biomimicry, and bioinspiration in architecture are introduced with the purpose of inspiring future developments
Toksikokinetika prometrina u mozgu miŔeva
Prometryne is a methylthio-s-triazine herbicide. Signifi cant trace amounts are found in the environment,
mainly in water, soil, and food plants. The aim of this study was to establish brain and blood prometryne levels after single oral dose (1 g kg-1) in adult male and female mice. Prometryne was measured using the GC/MS assay at 1, 2, 4, 8, and 24 h after prometryne administration. Peak brain and blood prometryne values were observed 1 h after administration and they decreased in a time-dependent manner. Male mice had consistently higher brain and blood prometryne levels than female mice. The observed prometryne
kinetics was similar to that reported for the structurally related herbicide atrazine.Prometrin je metiltio-s-triazinski herbicid. ZnaÄajne koliÄine prometrina zaostaju u tragovima u okoliÅ”u, poglavito u vodi, tlu i biljkama koje rabimo za prehranu. Cilj je rada izmjeriti koliÄinu prometrina koja se apsorbira u mozgu i krvi nakon primijenjene akutne oralne doze (1 g kg-1 tjelesne mase) u odraslih miÅ”eva
obaju spolova. Razine prometrina u mozgu i krvi izmjerene su GC/MS-om tijekom 1., 2., 4., 8. i 24. sata nakon izlaganja. UtvrÄeno je da je udio prometrina koji se zadržava u živÄanom tkivu relativno nizak ali detektabilan u odnosu na koncentraciju u krvi i koncentraciju primijenjene doze. NajviÅ”e koncentracije u krvi i maseni udjeli u mozgu zabilježeni su tijekom 1. sata nakon izlaganja, a s vremenom izmjerene vrijednosti znaÄajno opadaju. UoÄena je znaÄajna razlika izmeÄu mužjaka i ženki pri Äemu mužjaci imaju
znaÄajno viÅ”e razine prometrina u mozgu i krvi nego ženke. Opisana toksikokinetika prometrina pokazuje sliÄnosti s otprije opisanom i poznatom toksikokinetikom strukturalno sliÄnog herbicida atrazina
Desired morphology in energy capture and storage advanced facades
Current strategies for facades envelopes are determined by a static response defined by a single prescriptive value. This code requirement diminishes the ability of a facade to interact with the environment by constant readjustment of functional performance. This is the knowledge gap between present code compliant facades, based on measures in the reduction of thermal conduction to what could be.
The research proposes methods to demonstrate principle functions to capture and storage energy in facades that is derived by natural systems. It demonstrates natureās characterization of materials by methods to control material assembly and functionality by hierarchical strategies that can be applied to envelope functionality. Nature generates materials with defined parameters to move neighbouring atoms within and between materials at a micrometer or nanometer levels. This interface reaction between different materials is driven by chemical composition and temperature with unprecedented levels of complexity and prevision. This is a thermal measurement system of precise modulation response as a dynamic reaction diffusion system. The question is, why is this characterization of function not emulated in envelope design?
The aim of the research is therefore to demonstrate how utilizing bio-inspired engineering aims would progress the knowledge gap in understanding, to advance energy capture and storage materials and to determine hierarchical rule based measures defined by steady state theory, in the control of solar heat load. The application to observe and quantify heat flow targeting theory will progress our understanding to derive proof of principle results. To embed natures approach
to advanced materials of energy capture and storage will ultimately lead to desired morphology in functional facades. This through a case studies approach.
Embarking on the biological solutions, the requirement of the maximizing the solar energy capture can be fulfilled by following the present and previously recognized natural strategies of heliotropism (following the sun, which could be observed e.g. in the sunflowers). The plans use a phytochrome, a photoreceptor pigment to detect light. Light-detection mechanism is utilized in long and shortrange behaviour regulation. It regulates the circadian rhythm as well as the seasonal rhythms like time of flowering and seeding. Leaf position is modified in the mechanism of stem elongation that is called phototropism: a chemical compound called auxin causes the plant cells to have an elongated shape on the further side form the light (this makes the stem bend towards the light)