1,072 research outputs found
Dimensionless ratios: characteristics of quantum liquids and their phase transitions
Dimensionless ratios of physical properties can characterize low-temperature
phases in a wide variety of materials. As such, the Wilson ratio (WR), the
Kadowaki-Woods ratio and the Wiedemann\--Franz law capture essential features
of Fermi liquids in metals, heavy fermions, etc. Here we prove that the phases
of many-body interacting multi-component quantum liquids in one dimension (1D)
can be described by WRs based on the compressibility, susceptibility and
specific heat associated with each component. These WRs arise due to additivity
rules within subsystems reminiscent of the rules for multi-resistor networks in
series and parallel --- a novel and useful characteristic of multi-component
Tomonaga-Luttinger liquids (TLL) independent of microscopic details of the
systems. Using experimentally realised multi-species cold atomic gases as
examples, we prove that the Wilson ratios uniquely identify phases of TLL,
while providing universal scaling relations at the boundaries between phases.
Their values within a phase are solely determined by the stiffnesses and sound
velocities of subsystems and identify the internal degrees of freedom of said
phase such as its spin-degeneracy. This finding can be directly applied to a
wide range of 1D many-body systems and reveals deep physical insights into
recent experimental measurements of the universal thermodynamics in ultracold
atoms and spins.Comment: 12 pages (main paper), (6 figures
Meso-scale Fracture Modelling of Concrete Cover Induced by Non-uniform Corrosion of Reinforcing Bar
Corrosion-induced concrete cracking is a significant durability problem for reinforced concrete structures. In practice, critical corrosion degree to surface cracking and crack width evolution are of significance in regards to the assessment of serviceability of reinforced concrete structures. Literature review suggests that, although considerable research has been undertaken on corrosion-induced concrete cracking, little has been focused on non-uniform corrosion of reinforcing bar, especially by considering concrete as a three-phase materials. In this paper, a meso-scale fracture model, consisting of aggregates, cement paste/mortar and ITZ, is established. To simulate arbitrary cracking in concrete, cohesive elements are inserted in the fine meshes and the process is achieved through a script written in Python. It has been found that some microcracks occur before they are connected to form a dominating discrete crack approaching to the surface. The surface crack width is obtained as a function of corrosion degree and verification against experimental results from literature is conducted
A New Model for Corrosion-induced Concrete Cracking
Corrosion of reinforced concrete is one of the major deterioration mechanisms which result in premature failure of the reinforced concrete structures. Due to the actual diffusion of chloride ingress, the corrosion products distribution is seldom uniform along the reinforcing bar. Recently, some non-uniform corrosion models have been proposed to investigate the corrosion-induced cracking mechanism of concrete. In this paper, a new corrosion model based on von Mises distribution is formulated and validated against experimental data. The developed model is then compared with the existing non-uniform models and the advantages are discussed. To demonstrate the application of the developed corrosion model, a concrete cover structure, containing aggregates, cement paste/mortar and ITZ, is simulated to predict the cracking phenomena of the concrete cover under different non-uniform coefficients in the developed corrosion model. It has been found that the non-uniform corrosion model can be used to simulate the realistic corrosion rust progression around the reinforcing bar, with the best accuracy. Moreover, parametric studies are conducted to investigate the effects of the basic factors formulated in the corrosion model on the surface cracking of the reinforced concrete structures
Search for stochastic gravitational-wave background from string cosmology with Advanced LIGO and Virgo's O1O3 data
String cosmology models predict a relic background of gravitational-wave (GW)
radiation in the early universe. The GW energy spectrum of radiated power
increases rapidly with the frequency, and therefore it becomes a potential and
meaningful observation object for high-frequency GW detector. We focus on the
stochastic background generated by superinflation in string theory and search
for such signal in the observing data of Advanced LIGO and Virgo O1O3
runs in a Bayesian framework. We do not find the existence of the signal, and
thus put constraints on the GW energy density. Our results indicate that at
, the fractional energy density of GW background is less than
and for dilaton-string and dilaton only
cases respectively, and further rule out the parameter space restricted by the
model itself due to the non-decreasing dilaton and stable cosmology background
( bound).Comment: Accepted by Journal of Cosmology and Astroparticle Physic
Numerical modelling of non-uniform corrosion induced concrete crack width
Corrosion of reinforced concrete is one of the major deterioration mechanisms which result in premature failure of the reinforced concrete structures. Crack width is often used as an effective criterion to assess the serviceability of concrete structures. However, research on prediction of corrosion-induced concrete crack width, especially by considering the corrosion as a non-uniform process, has still been scarce. This paper attempts to develop a finite element model to predict the crack width for corrosion-affected concrete structures under realistic non-uniform corrosion of the reinforcement. A non-uniform corrosion model was first formulated as a function of time. To simulate arbitrary cracking in concrete, cohesive elements are inserted in the sufficiently fine mesh which is achieved through a script written in Python. The surface crack width is obtained as a function of service time and verification against experimental results from literature is conducted. Accurate prediction of crack width can allow timely maintenance which prolongs the service life of the reinforced concrete structures
Noise suppression of on-chip mechanical resonators by chaotic coherent feedback
We propose a method to decouple the nanomechanical resonator in
optomechanical systems from the environmental noise by introducing a chaotic
coherent feedback loop. We find that the chaotic controller in the feedback
loop can modulate the dynamics of the controlled optomechanical system and
induce a broadband response of the mechanical mode. This broadband response of
the mechanical mode will cut off the coupling between the mechanical mode and
the environment and thus suppress the environmental noise of the mechanical
modes. As an application, we use the protected optomechanical system to act as
a quantum memory. It's shown that the noise-decoupled optomechanical quantum
memory is efficient for storing information transferred from coherent or
squeezed light
Exact Spectral Function of One-Dimensional Bose Gases
Strong correlation in one-dimensional (1D) quantum systems drastically
changes their dynamic and transport properties in the presence of the
interaction. In this letter, combining quantum integrable theory with numerics,
we exactly compute the spectral function of 1D Lieb-Liniger gas at a many-body
level of large scales. It turns out that a full capture of the power-law
singularities in the vicinities of thresholds requires system size as large as
thousands of particles. Our research essentially confirms the validity of the
nonlinear Tomonaga-Luttinger liquid and provides a reliable technique for
studying critical behaviour emerged only in thermodynamic limit.Comment: 6 pages, 3 figures, Supplementary Materia
Neuroprotective effect of thiamine triethylorthoformate conjugate against Parkinson disease in a mouse model
Purpose: To investigate the effect of thiamine triethylorthoformate conjugate (TTO) on Parkinson disease (PD) in vitro and in vivo in a mice model.
Methods: The effect of TTO on behavioural changes in PD mouse model was studied using pole, traction and swimming tests. Astrocyte proliferation after TTO treatment was assessed using 3 (4, 5 dimethyl 2 thi¬azolyl) 2, 5 diphenyl 2 H tetrazolium bromide (MTT) assay. Apoptosis was determined with flow cytometry using Annexin V Fluorescein isothiocyanate kit.
Results: Treatment of PD mice with TTO led to a decrease in climbing time, increase in suspension score and enhancement of swimming score, when compared to the untreated group (p < 0.05). Treatment of astrocytes with TTO prior to MPP incubation significantly increased proliferation (p < 0.05). Apoptosis induction in astrocytes by MPP was attenuated by pre-treatment with TTO. Pre-treatment of astrocytes with 10 µM TTO markedly reduced JNK activation, when compared to astrocytes incubated with MPP alone (p < 0.05). Up-regulation of Bax and down-regulation of Bcl 2 by MPP in astrocytes were attenuated by pre-treatment with TTO. MPP-induced up-regulation of cleaved caspase 3 was suppressed in astrocytes by TTO pre-treatment (p < 0.05).
Conclusion: Treatment with TTO prevents MPP+ -induced neuronal damage in vitro in astrocytes and in vivo in mice. The neuro-protective effect of TTO involves down-regulation of JNK activation, inhibition of caspase-3 level, decrease in Bax and increase in Bcl-2 expression. Thus, TTO has a potential for use in the treatment of Parkinson’s disease
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