Hong Kong is an intermediate tuberculosis (TB) endemicity city dominated by reactivation diseases. A cross-sectional study on the clinical and epidemiologic data of newly diagnosed TB cases was conducted in such a setting, to examine the association between ambient PM2.5 and TB reactivation. After the exclusion of cases most likely resulting from recent infection, four distinct TB population phenotypes were delineated by latent class analysis based on their reactivation risk and clinical profiles (N = 2,153): ‘Elderly male’ (26%), ‘Otherwise healthy younger adult’ (34%), ‘Older female’ (19%) and ‘Male smoker’ (21%). Overall, exposure to high concentrations of ambient PM2.5 6 and 12 months before the notification was significantly associated with ‘Otherwise healthy younger adults’ membership (OR = 1.07 and 1.11, respectively) compared with ‘Elderly male’. Such association was less evident for other phenotypes. The differential pattern of association between ambient PM2.5 exposure and TB population phenotypes suggested the role of ambient PM2.5 in TB reactivation.

Seed coat colour in adzuki bean is an important quality trait and closely associated with anthocyanin metabolism pathways. To further understand the inheritance of seed coat colour pattern, the inheritance between multiple seed coat colours and ivory seed were analysed using F1:2, F2:3 and F3:4 populations derived from five bi-parental crosses. The differences between ivory and red mottle on ivory are controlled by a single recessive R locus and RI locus, respectively. Green, light brown and golden are all dominant to red and governed by two loci. The B (brown) locus shows dominant epistasis over T locus. The R (red) locus was recessive epistasis to B (black), T (light brown), G (golden), GR (green) and RI (red mottle on ivory) loci. The new insight into the strong recessive epistasis of the R locus will be important for gene mapping and cloning, candidate gene functional validation and quality improvement in adzuki bean.

Seed coat colour is an important quality trait, domestication trait and morphological marker, and is closely associated with flavonoid and anthocyanin metabolism pathways. The seed coat colour of adzuki bean, an important legume crop, influences the processing quality of its paste, the commodity and its nutritional quality. In this study, the genetic relationships of seed coat colour were analysed using 12 hybridized combinations of F2 individuals and four F3 families derived from hybridized combinations between the accessions of eight seed coat colours. The loci of the colour traits were analysed based on phenotypes and using the chi-square test. Ivory colour is recessive to red and is controlled by a single R locus. Black, black mottle on grey, black mottle on red, light brown, golden and brown are all dominant to red. The phenotypes of black mottle on red, light brown, golden and brown are all controlled by a single genetic locus. Black mottle on grey is controlled by two loci. Black is controlled with two loci, and the black locus shows dominant epistasis to another locus. A genetic model of these seed coat colours was predicted. Our results will be important for gene mapping and cloning of seed coat colour characters and for providing further insight into the regulatory network of seed coat colour.

We perform a numerical study of the heat transfer and flow structure of Rayleigh–Bénard (RB) convection in (in most cases regular) porous media, which are comprised of circular, solid obstacles located on a square lattice. This study is focused on the role of porosity $\unicode[STIX]{x1D719}$ in the flow properties during the transition process from the traditional RB convection with $\unicode[STIX]{x1D719}=1$ (so no obstacles included) to Darcy-type porous-media convection with $\unicode[STIX]{x1D719}$ approaching 0. Simulations are carried out in a cell with unity aspect ratio, for Rayleigh number $Ra$ from $10^{5}$ to $10^{10}$ and varying porosities $\unicode[STIX]{x1D719}$, at a fixed Prandtl number $Pr=4.3$, and we restrict ourselves to the two-dimensional case. For fixed $Ra$, the Nusselt number $Nu$ is found to vary non-monotonically as a function of $\unicode[STIX]{x1D719}$; namely, with decreasing $\unicode[STIX]{x1D719}$, it first increases, before it decreases for $\unicode[STIX]{x1D719}$ approaching 0. The non-monotonic behaviour of $Nu(\unicode[STIX]{x1D719})$ originates from two competing effects of the porous structure on the heat transfer. On the one hand, the flow coherence is enhanced in the porous media, which is beneficial for the heat transfer. On the other hand, the convection is slowed down by the enhanced resistance due to the porous structure, leading to heat transfer reduction. For fixed $\unicode[STIX]{x1D719}$, depending on $Ra$, two different heat transfer regimes are identified, with different effective power-law behaviours of $Nu$ versus $Ra$, namely a steep one for low $Ra$ when viscosity dominates, and the standard classical one for large $Ra$. The scaling crossover occurs when the thermal boundary layer thickness and the pore scale are comparable. The influences of the porous structure on the temperature and velocity fluctuations, convective heat flux and energy dissipation rates are analysed, further demonstrating the competing effects of the porous structure to enhance or reduce the heat transfer.

New-type Ni-based superalloys with and without Nb were designed in this study. Their hot corrosion behaviors were investigated at 800 °C with the deposition of a mixture of Na2SO4 and NaCl. The corrosion kinetics was studied by thermogravimetry. Microstructure of the corrosion scales was studied by SEM and the phase constituent was analyzed by XRD. Results showed that the corrosion kinetics followed approximately parabolic law. The corrosion scales on the two Ni-based alloys were comprised of Cr2O3, Al2O3, TiO2, and NiCr2O4. NiO was only detected in the scale on alloy without Nb. Nb2O5 appeared with the addition of 2.0 wt% Nb. No sulfide emerged in the scales. The corrosion scales both exhibited a layered structure. With Nb addition, the hot corrosion resistance of the alloy was notably improved. The action mechanism of Nb was investigated extensively in this study.

Drynaria fortunei (Kunze) J. Sm. (DF), a Chinese herb commonly used for the treatment of bone fracture, was previously shown to exert anabolic effects on bone. However, its active ingredients as well as the mechanisms of action are far from clear. The present study aimed to characterise the bone anabolic effects of DF flavonoid fraction (DFTF) in ovariectomised (OVX) mice and to determine if DFTF and its isolated compounds exert oestrogen-like effects in rat osteoblast-like UMR-106 cells. Young OVX C57/BL6J mice were treated orally with DFTF (0·087, 0·173 or 0·346 mg/g per d), 17β-oestradiol (2 μg/g per d) or its vehicle for 6 weeks. Serum and urine samples were collected for biochemical marker analysis. Bones were collected for computed tomography analysis. UMR-106 cells were treated with DFTF and isolated compounds naringin, (2S)-5,7,3′,5′-tetrahydroxy-flavonone 7-O-neohesperidoside (compound 1) and 5,7-dihydroxychromone 7-O-neohesperidoside (compound 2). DFTF exerted dose-dependent effects in improving bone mineral densities as well as bone strength at the femur, tibia and lumbar spine L1 in OVX mice. DFTF and the three isolated compounds stimulated osteoblastic cell proliferation and alkaline phosphatase activities in a dose-dependent manner. In addition, they stimulated the ratio of osteoprotegrin and receptor-activator NF-κB ligand mRNA expression, suggesting their involvement in inhibiting osteoclastogenesis. These stimulatory effects on osteoblastic functions were abolished in the presence of oestrogen receptor (ER) antagonist, ICI 182780. The present results suggested that DFTF is effective in protecting against OVX-induced bone loss in mice, and its actions in regulating osteoblastic activities appear to be mediated by ER.

Hierarchical and hollow SnS2 nanostructures as precursors were fabricated via a surfactant-assisted assembly process using sodium dodecyl sulfate as soft templates. The as-prepared SnS2 nanostructures were further oxidized to form porous SnO2 conversion for investigating their gas-sensing properties in drug-precursor detection. On the basis of a series of time- and ratio-dependent reactions, a formation mechanism of the special nanostructures and factors influencing morphology and structure were determined. Gas-sensing measurements revealed that the porous and hierarchical SnO2 hollow nanostructures were sensitive to drug precursors, indicating promising applications in environmental monitoring and public safety investigation. In addition, we found that the assembled SnO2 nanomaterials possessed significantly enhanced gas-sensing properties compared with unassembled SnO2 with a solid interior.

Due to the difficulty in handling nanofibers, little is reported and understood on the dry adhesion between electrospun nanofibers. In this study, we develop a technique to measure the dry adhesive forces between electrospun nanofibers. Of critical importance is the ability to mimic naturally occurring dry adhesion such as that between gecko's and spider's foot hairs and untreated surfaces. The adhesion test was performed on two poly(e-caprolactone) electrospun ultrafine fibers using a nanoforce tensile tester. It was found that the adhesive force per unit area increased with decreasing fiber diameter. The degree of crystallinity, order parameters of macromolecules in the amorphous region and crystallite orientation of the spun fibers were determined by the differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD). The high measured adhesion between single PCL fibers in comparison to other reported values was attributed to crystal orientation due to electrospinning and the increase of adhesive force per unit area with decreasing fiber diameter.

A new theoretical model is constructed for the viscoelastic response of a clamped circular membrane deformed by a spherical indenter, using the classical Maxwell and Standard Linear Solid (SLS) constitutive equations. Preliminary stress-relaxation experiments are performed for a hydrogel membrane and the corresponding data fitted to the SLS-based viscoelastic model.

It has been experimentally and theoretically found that the critical applied stress intensity factor for indentation cracking also depends linearly on the reciprocal of the square root of crack length when the indentation fracture technique is used to measure residual stresses in thin films.

Experiments on thin mica sheets are used to demonstrate that coplanar cracks in double-cantilever beam specimens do not universally attract each other, as conventionally portrayed, but, at long range, actually repel. An elasticity analysis explains the repulsion in terms of a compression zone, ≍0.35 times the beam half-thickness ahead of the crack tip, generated by bending moments from the cantilever arms on the remaining specimen section.

Results of crack growth observations on mica in water-containing environments are described. The study focuses on equilibrium crack states for reversed loading cycles, i.e., for initial propagation through virgin solid and subsequent retraction-repropagation through healed or misoriented-healed interfaces. Departures from these equilibrium states are manifest as steady-state forward or backward crack velocities at specific applied loads. The equilibria are thereby interpreted as quiescent, threshold configurations G = WE, with G the Griffith mechanical-energy-release rate and WE the Dupré work of adhesion, on crack velocity (v-G) diagrams. Generally, WE is found to decrease with concentration of water, in accordance with a Gibbs formalism. Hysteresis is observed in the forward-backward-forward crack propagation cycle, signifying a reduction in the adhesion energy on exposure of the open interface to environmental species prior to healing. This hysteresis is especially marked for those interfaces that are misoriented before healing, indicating that the structure of the underlying solid substrate as well as of the intervening fluid is an important consideration in the interface energetics. The equilibrium states for different environments can be represented on a simple energy-level diagram, as differences between thermodynamic end-point states: initial, closed-interface states refer to crystallographic bonding configurations ahead of the crack-tip adhesion zone; final, open interface states refer to configurations behind the crack-tip zone. The significance of this diagram in relation to the fundamental atomic structure of interfaces in fracture and other adhesion geometries, including implications concerning kinetics, is discussed.