Shape Approximation and Size Difference of the Upper Part of the Talus: Implication for Implant Design of the Talar Component for Total Ankle Replacement

The implant design of the talar component for total ankle replacement (TAR) should match the surface morphology of the talus so that the replaced ankle can restore the natural motion of the tibiotalar joint and may reduce postoperative complications. The purpose of this study was to introduce a new 3D fitting method (the two-sphere fitting method of the talar trochlea with three fitting resection planes) to approximate the shape of the upper part of the talus for the Chinese population. 90 models of the tali from CT images of healthy volunteers were used in this study. Geometrical fitting and morphological measurements were performed for the surface morphology of the upper part of the talus. The accuracy of the two-sphere fitting method of the talar trochlea was assessed by a comparison of previously reported data. Parameters of the fitting geometries with different sizes were recorded and compared. Results showed that compared with previously reported one-sphere, cylinder, and bitruncated cone fitting methods, the two-sphere fitting method presented the smallest maximum distance difference, indicating that talar trochlea can be approximated well as two spheres. The radius of the medial fitting sphere R M was 20.69 ± 2.19 mm which was significantly smaller than the radius of the lateral fitting sphere R L of 21.32 ± 1.88 mm. After grouping all data by the average radius of fitting spheres, the result showed that different sizes of the upper part of the talus presented significantly different parameters except the orientation of the lateral cutting plane, indicating that the orientation of the lateral cutting plane may keep consistent for all upper part of the talus and have no relationship with the size. The linear regression analyses demonstrated a weak correlation ( R 2 < 0.5 ) between the majority of parameters and the average radius of the fitting spheres. Therefore, different sizes of the upper part of the talus presented unique morphological features, and the design of different sizes of talar components for TAR should consider the size-specific characteristics of the talus. The parameters measured in this study provided a further understanding of the talus and can guide the design of different sizes of the talar components of the TAR implant.

Superflares and Starspots: when size does not matter

Within the last decade, space missions have provided a wealth of information about stellar flares. Nevertheless, what triggers these superflares, and whether they are similar to the solar counterparts, remains a great mystery. How are flares connected to active regions and what are the main causes of their occurrence? Here we investigate the activity of two K-type stars, similar in every way from mass to rotation periods and planetary systems. Even if both stars exhibited hundreds of spots, Kepler-411 produced 65 superflares, while Kepler-210 presented none. The spots of both stars were characterised using the planetary transit mapping technique which yields the intensity, temperature, and radius of starspots. The only discrepant parameter was the size of the spots. While the average radius of spots on Kepler-411 was (17 ± 7) × 103 km, for Kepler-210 the mean radius was (39 ± 18) × 103 km. That is, the star with no superflare exhibited spots twice as large as the one with 65 superflares. Thus starspot area appears not to be the main culprit of superflare triggering, but rather the magnetic complexity seems more important, as in the case of the Sun. These are important clues to the magnetic dynamo acting on these solar-type stars.

A Lattice Model on the Rate of DNA Hybridization

We develop a lattice model on the rate of hybridization of the complementary single-stranded DNAs (c-ssDNAs). Upon translational diffusion mediated collisions, c-ssDNAs interpenetrate each other to form correct (cc), incorrect (icc) and trap-correct contacts (tcc) inside the reaction volume. Correct contacts are those with exact registry matches which leads to nucleation and zipping. Incorrect contacts are the mismatch contacts which are less stable compared to tcc which can occur in the repetitive c-ssDNAs. Although tcc possess registry match within the repeating sequences, they are incorrect contacts in the view of the whole c-ssDNAs. The nucleation rate (kN) is directly proportional to the collision rate and the average number of correct-contacts (<ncc>) formed when both the c-ssDNAs interpenetrate each other. Detailed lattice model simulations suggest that 〈n_cc 〉∝L⁄V where L is the length of c-ssDNAs and V is the reaction volume. Further numerical analysis revealed the scaling for the average radius of gyration of c-ssDNAs (Rg) with their length as R_g∝√L. Since the reaction space will be approximately a sphere with radius equals to 2Rg and V∝L^(3⁄2), one obtains k_N∝1/√L. When c-ssDNAs are nonrepetitive, then the overall renaturation rate becomes as k_R∝k_N L and one finally obtains k_R∝√L in line with the experimental observations. When c-ssDNAs are repetitive with a complexity of c, then earlier models suggested the scaling k_R∝√L/c which breaks down at c = L. This clearly suggested the existence of at least two different pathways of renaturation in case of repetitive c-ssDNAs viz. via incorrect contacts and trap correct contacts. The trap correct contacts can lead to the formation of partial duplexes which can keep the complementary strands in the close vicinity for a prolonged timescale. This is essential for the extended 1D slithering, inchworm movements and internal displacement mechanisms which can accelerate the searching for the correct contacts. Clearly, the extent of slithering dynamics will be inversely proportional to the complexity. When the complexity is close to the length of c-ssDNAs, then the pathway via incorrect contacts will dominate. When the complexity is much lesser than the length of c-ssDNA, then pathway via trap correct contacts would be the dominating one.

Azetidinium Lead Halide Ruddlesden–Popper Phases

A family of Ruddlesden–Popper (n = 1) layered perovskite-related phases, Az2PbClxBr4−x with composition 0 ≤ x ≤ 4 were obtained using mechanosynthesis. These compounds are isostructural with K2NiF4 and therefore adopt the idealised n = 1 Ruddlesden–Popper structure. A linear variation in unit cell volume as a function of anion average radius is observed. A tunable bandgap is achieved, ranging from 2.81 to 3.43 eV, and the bandgap varies in a second-order polynomial relationship with the halide composition.

Azetidinium lead halide Ruddlesden-Popper phases

A family of Ruddlesden-Popper (n = 1) layered perovskite-related phases, Az2PbClxBr4-x with composition 0 ≤ x ≤ 4 were obtained using mechanosynthesis. A linear variation in unit cell volume as a function of anion average radius is observed. A tunable bandgap is achieved, ranging from 2.81 to 3.43 eV, and the bandgap varies in a second order polynomial relationship with the halide composition.

Revisiting neutron yield in table-top nuclear fusion driven by an intense femtosecond laser pulse interaction with the gas clusters

With the development of femtosecond (fs) laser technology, an fs laser pulse with 10s of Joule, even 100s of Joule energy is available and the focused laser intensity can be expected to induce the pure Coulomb explosion of the cluster with a much larger average radius than before. Meanwhile, the production of gas cluster with an average radius of upto 10s of nanometer has been possible. In this case, it is necessary to reinvestigate the feasibility of 109 n/shot neutron yield for the practical application in the intense fs laser-driven nuclear fusion. In this work, the neutron yield from the explosions of the D2 clusters of 6–20 nm average radius at the 0.5–100 J pulse energy and the CD4 clusters was investigated theoretically. It is found that the optimum neutron yield of 109 n/shot can be obtained at the laser energy and the cluster radius currently available. However, a clustered-gas jet with a large cross-section is demanded to match the proper plasma diameter.

Synthesis, Characterization and Size Evaluation of Biosynthesized Silver Nanoparticles by UV–Vis Spectroscopy

Mie-Gans (MG) fitting model theoretical model utilizing the phenomena of scattering light to determine the morphologies, shape, and size of metallic nanoparticles in solution. In the present work, the average radius of biosynthesized silver nanoparticles (AgNPs) was evaluated based on the fitting of their Ultraviolet-visible (UV-Vis) spectra by the MG fitting model for spherical and non-spherical particles. Biosynthesis of AgNPs using Lemon (Citrus Limon) leaves extract as a reducing agent and Gum Acacia as a capping and stabilizing agent was studied for various concentrations of Citrus Limon leaves extract. The investigation of structural and optical properties was carried out for the synthesized samples using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and UV-Vis spectroscopy. XRD confirmed the structure of AgNPs and revealed that the structure of these nanoparticles was face-centered cubic (fcc). FTIR measurements indicate the presence of citric acid in Citrus Limon leaf extract which is responsible for reducing bioreduced AgNPs. UV-Vis spectroscopy determined the surface plasmon resonance (SPR) for AgNPs; the peaks of resonances of samples appear at 436-461nm range. MG fitting evaluations show that most of AgNPs were spherical in shape with an average radius in the range of 39-47nm. Moreover, this model allows the estimation of the fraction of nonspherical and aggregated AgNPs. These unique characteristics of AgNPs have made them applicable in a large number of fields like water treatment, biomedical, energy science, catalysis, etc.

The Supervision of Dough Fermentation Using Image Analysis Complemented by a Continuous Discrete Extended Kalman Filter

Dough fermentation is an important step during the preparation of fermented baking goods. For the supervision of dough fermentation, a continuous-discrete extended Kalman filter was applied, which uses an image analysis system as the measurement. By estimation a fixed number of gas bubbles inside the dough, the radius of an average bubble was determined. A mathematical dough model was used by the extended Kalman filter to estimate the radius of the average bubble, the CO2 concentration of the non-gas dough phase and the number of CO2 molecules in the average bubble. During a fermentation of 50 min, the extended Kalman filter estimated that the average radius increased from 50 µm to 127 µm, the CO2 concentration in the non-gas dough increased to 23 mol/m³, and the CO2 amount in the bubble increased from 0.1 × 10−10 to 4 × 10−10 mol. Also, the specific CO2 production rate was estimated to be in the range from 1.5 × 10−3 to more than 4 × 10−3 mol·m³/kg/s. The advantages of an extended Kalman filter for the supervision of the dough fermentation process are discussed.

Evaluation of the parameters of the porous structure and permeability of monofraction ceramics

A method for assessing the structure parameters of porous ceramic materials by porosity and particle size is presented. Based on it, a physically more rigorous than the well-known Cozeny formula is obtained, a formula for determining the average (hydraulic) radius of the capillaries of permeable materials. The presented results of the calculation of the average radius of the capillaries of porous ceramics based on electrocorundum according to the obtained formula are in better agreement with experimental data than the calculations by the Cozeny formula.