Chiral spin-order in some purported Kitaev spin-liquid compounds

We examine recent magnetic torque measurements in two compounds, $\gamma$-Li$_2$IrO$_3$ and RuCl$_3$, which have been discussed as possible realizations of the Kitaev model. The analysis of the reported discontinuity in torque, as an external magnetic field is rotated across the $c-$axis in both crystals, suggests that they have a translationally-invariant chiral spin-order of the from $\ne 0$ in the ground state and persisting over a very wide range of magnetic field and temperature. An extra-ordinary $|B|B^2$ dependence of the torque for small fields, beside the usual $B^2$ part, is predicted due to the chiral spin-order, and found to be consistent with experiments upon further analysis of the data. Other experiments such as inelastic scattering and thermal Hall effect and several questions raised by the discovery of chiral spin-order, including its topological consequences are discussed.Comment: Clearer figures of the experimental data provided. Also clearer exposition and comment on related recent wor

Dynamical Evolution of Volume Fractions in Multipressure Multiphase Flow Models

Compared to single-pressure models, multipressure multiphase flow models require additional closure relations to determine the individual pressures of the different phases. These relations are often taken to be evolution equations for the volume fractions. We present a rigorous theoretical framework for constructing such equations for compressible multiphase mixtures in terms of submodels for the relative volumetric expansion rates ∆Ei of the phases. These quantities are essentially the rates at which the phases dynamically expand or contract in response to pressure differences, and represent the general tendency of the volume fractions to relax toward values that produce local pressure equilibrium. We present a simple provisional model of this type in which ∆Ei is proportional to pressure differences divided by the time required for sound waves to traverse an appropriate characteristic length. It is shown that the resulting approach to pressure equilibrium is monotonic rather than oscillatory, and occurs instantaneously in the incompressible limit

Study of mass transfer correlations for intensified absorbers in post-combustion CO2 capture based on chemical absorption

Process intensification (PI) technologies such as rotating packed beds (RPBs) could reduce the size of absorber used in post-combustion CO2 capture (PCC) based on chemical absorption processes by about 12 times compared to absorber with standard packed beds. However, mass transfer correlations for predicting effective interfacial area and liquid film mass transfer coefficient in RPBs are limited in literature and their prediction accuracy against experimental data is yet to be compared. This need is addressed in this study by evaluating the performances of different correlations through comparison with experimental data. Of all the correlations assessed, it is found that Lou et al. [1] and Tung and Mah [2] correlations give reliable estimate of the effective interfacial area and liquid film mass transfer coefficients respectively

Ground Waves Generated by Pile Driving, and Structural Interaction

Pre-formed steel or concrete pile elements are installed by high energy impact or vibro-driver, which causes outgoing ground waves. In severe cases, adjacent buildings are at risk of damage. Assessment of risk is conventionally by reference to threshold limits of vibration. The global approach considers neither the interactive effects between ground and structure, nor frequency and duration. Here, firstly, the dynamics of a pile head impact and of the transmission of a portion of the energy into the ground were modelled by a combination of finite elements (FE), springs and dashpots. The boundary disturbances were then applied to a second model of the soil as an elastic half space. This outer model was constructed of axisymmetric finite and infinite elements for calibration against on-site measurements. The infinite elements (IE) represented a wider zone, and avoided spurious wave reflections at boundaries. Next, the verified ground disturbances adjacent to the pile were used as input to a three-dimensional FE/IE wedge-shaped model of a ‘slice’ of the axisymmetric system. Various structural forms, of steel frame structures and of brick walls, were added, giving a dynamic soil-structure analysis. Results show the responses of flexible and stiff structures to outgoing waves caused by impact pile driving and vibro-driving

Home Away from Home: Diaspora Tourism and Transnational Attachment of Second-Generation Chinese-Americans

Globalization has allowed contemporary immigrants to live in two worlds and maintain virtual and physical contact with their homeland through leisure and diaspora tourism. This study examined the lived experience of second-generation Chinese-Americans as they traveled to their parents’ country of origin and explored the relationship between their transnational homeland attachment and diaspora tourism experience. Using a phenomenological approach, twenty-six second-generation Chinese-Americans who had the experience of traveling in China were interviewed. Four themes were identified from their travel experience: destination image, authenticity, family history, and homeland attachment. Findings revealed how being a secondgeneration immigrant influenced the way they saw and experienced China as both destination and homeland

Collagen-mimetic peptide-modifiable hydrogels for articular cartilage regeneration

Regenerative medicine strategies for restoring articular cartilage face significant challenges to recreate the complex and dynamic biochemical and biomechanical functions of native tissues. As an approach to recapitulate the complexity of the extracellular matrix, collagen-mimetic proteins offer a modular template to incorporate bioactive and biodegradable moieties into a single construct. We modified a Streptococcal collagen-like 2 protein with hyaluronic acid (HA) or chondroitin sulfate (CS)-binding peptides and then cross-linked with a matrix metalloproteinase 7 (MMP7)-sensitive peptide to form biodegradable hydrogels. Human mesenchymal stem cells (hMSCs) encapsulated in these hydrogels exhibited improved viability and significantly enhanced chondrogenic differentiation compared to controls that were not functionalized with glycosaminoglycan-binding peptides. Hydrogels functionalized with CS-binding peptides also led to significantly higher MMP7 gene expression and activity while the HA-binding peptides significantly increased chondrogenic differentiation of the hMSCs. Our results highlight the potential of this novel biomaterial to modulate cell-mediated processes and create functional tissue engineered constructs for regenerative medicine applications

Nonextensive Statistical Mechanics Application to Vibrational Dynamics of Protein Folding

The vibrational dynamics of protein folding is analyzed in the framework of Tsallis thermostatistics. The generalized partition functions, internal energies, free energies and temperature factor (or Debye-Waller factor) are calculated. It has also been observed that the temperature factor is dependent on the non-extensive parameter q which behaves like a scale parameter in the harmonic oscillator model. As $q\to 1$, we also show that these approximations agree with the result of Gaussian network model.Comment: 8 pages, 2 figure

Toward Generalized Entropy Composition with Different q Indices and H-Theorem

An attempt is made to construct composable composite entropy with different $q$ indices of subsystems and address the H-theorem problem of the composite system. Though the H-theorem does not hold in general situations, it is shown that some composite entropies do not decrease in time in near-equilibrium states and factorized states with negligibly weak interaction between the subsystems.Comment: 25 pages, corrected some typos, to be published in J. Phys. Soc. Ja