Exploring the possibilities of cryogenic cooling in liquid chromatography for biological applications: a proof of principle

The possibilities to use cryogenic cooling to trap components in liquid chromatography was investigated. In a first step, van 't Hoff plots were measured with a reversed-phase column using the temperature control unit of a conventional high performance liquid chromatography (HPLC) system to gain insight in the retention behavior of proteins at low temperatures. It was estimated that retention factors in the range of k = 10(4) could be achieved at T = -20 °C for lysozyme, indicating that temperature is a usable parameter to trap components in LC. In a next step, trapping experiments were carried out on a nano-LC system, equipped with a UV-detector, using a commercial reversed-phase column. An in-house built setup, allowing cooling of a segment of the column down to temperatures below T = -20 °C, was used to trap components. Experiments were conducted under isocratic and gradient conditions with methanol as organic solvent. It is demonstrated that, by thermally trapping and elution of components, an enhanced S/N ratio and decreased peak widths can be obtained. At the same time, a significant increase in pressure drop occurs during the cooling process. Limitations and benefits of the technique are further discussed.     

Silicon Decorated Cone Shaped Carbon Nanotube Clusters for Lithium Ion Battery Anodes

In this work, we report the synthesis of an three‐dimensional (3D) cone‐shape CNT clusters (CCC) via chemical vapor deposition (CVD) with subsequent inductively coupled plasma (ICP) treatment. An innovative silicon decorated cone‐shape CNT clusters (SCCC) is prepared by simply depositing amorphous silicon onto CCC via magnetron sputtering. The seamless connection between silicon decorated CNT cones and graphene facilitates the charge transfer in the system and suggests a binder‐free technique of preparing lithium ion battery (LIB) anodes. Lithium ion batteries based on this novel 3D SCCC architecture demonstrates high reversible capacity of 1954 mAh g^?1 and excellent cycling stability (>1200 mAh g^?1 capacity with ≈100% coulombic efficiency after 230 cycles).     

Thermo-acoustic random response of temperature-dependent functionally graded material panels

A nonlinear finite element model is provided for the nonlinear random response of functionally graded material panels subject to combined thermal and random acoustic loads. Material properties are assumed to be temperature-dependent, and graded in the thickness direction according to a simple power law distribution in terms of the volume fractions of the constituents. The governing equations are derived using the first-order shear-deformable plate theory with von Karman geometric nonlinearity and the principle of virtual work. The thermal load is assumed to be steady state constant temperature distribution, and the acoustic excitation is considered to be a stationary white-Gaussian random pressure with zero mean and uniform magnitude over the plate surface. The governing equations are transformed to modal coordinates to reduce the computational efforts. Newton–Raphson iteration method is employed to obtain the dynamic response at each time step of the Newmark implicit scheme for numerical integration. Finally, numerical results are provided to study the effects of volume fraction exponent, temperature rise, and the sound pressure level on the panel response.     

Evolution of microstructure and hardness in NiTi shape memory alloys processed by high-pressure torsion

Experiments were conducted on Ni-50.2 at.% Ti and Ni-50 at.% Ti alloys in order to examine the evolution of hardness and microstructure after processing by high-pressure torsion at room temperature. Disks were pressed through different numbers of revolutions up to a maximum of 40 using an applied pressure of 2.0 GPa. It is shown that there is a gradual evolution in both the hardness and the microstructure with increasing numbers of turns but even after 40 turns there is not full homogeneity. There is evidence that after 10 turns the edges of the disks achieve a well-defined saturation hardness and by further processing to 40 turns the hardness in the centers of the disks increases. The results show that a martensite-to-austenite transformation occurs during processing. The austenitic transformation around the edge of the disks achieves saturation after 5 and 10 turns in the Ni-50 at.% Ti and Ni-50.2 at.% Ti alloys, respectively.     

Numerical study on heat transfer and entropy generation of developing laminar nanofluid flow in helical tube using two-phase mixture model

Nanofluids and helical tubes are among the best methods for heat transfer enhancement. In the present study, laminar, developing nanofluid flow in helical tube at constant wall temperature is investigated. The numerical simulation of Al₂O₃-water nanofluid with temperature dependent properties is performed using the two-phase mixture model by control volume method in order to study convective heat transfer and entropy generation. The numerical results is compared with three test cases including nanofluid forced convection in straight tube, velocity profile in curved tube and Nusselt number in helical tubes that good agreement for all cases is observed. Heat transfer coefficient in developing region inside a straight tube using mixture model shows a better prediction compared to the homogenous model. The effect of Reynolds number and nanoparticle volume fraction on flow and temperature fields, local and overall heat transfer coefficient, local entropy generation due to viscous dissipation and heat transfer, and the Bejan number is discussed in detail and compared with the base fluid. The results show that the nanofluid and the base fluid have almost the same axial velocity profile, but their temperature profile has significant difference in developing and fully developed region. Entropy generation ratio by nanofluid to the base fluid in each axial location along the coil length showed that the entropy generation is reduced by using nanofluid in at most length of the helical tube. Also, better heat transfer enhancement and entropy generation reduction can be achieved at low Reynolds number.     

Corrosion and Wear Resistance Characterization of Environmentally Friendly Sol-gel Hybrid Nanocomposite Coating on AA5083

Environmentally friendly organic-inorganic hybrid nanocomposite films have been developed by sol-gel method for corrosion protection of AA5083 alloy.The hybrid nanocomposite coatings have been synthesized from tetraethylorthosilicate(TEOS) and 3-glycidoxypropyltrimethoxysilane(GPTMS) precursors.The multilayer coatings were prepared by dip-coating technique.Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy was carried out to show the formation of the Si-O-Si structural backbone of the hybrid coatings.Structure and surface morphology of the coatings were studied by optical microscopy(OM), scanning electron microscopy(SEM) and atomic force microscopy(AFM).Characterization of the coatings with respect to pencil scratch hardness,adhesive and abrasion resistance was performed.The corrosion protection performance of these coatings was examined by using cyclic potentiodynamic polarization technique in Persian Gulf water.The results revealed that crack-free films with smooth surface were obtained. With increasing the number of sol—gel coated layers,corrosion resistance increased from 81 to 419 kΩcm~2, while the abrasion wear resistance did not change significantly.However,the triple sol-gel coated layer offered excellent protection against corrosion.     

Non-linear vibrations of variable stiffness composite laminated plates

It is the objective of this work to analyze vibrations of variable stiffness composite laminated plates (VSCL), and investigate the differences between the oscillations of these plates and traditional laminates. The analysis is based on numerical experiments and a new p-version finite element with hierarchic basis functions, which follows first order shear deformation theory and considers geometrical non-linearity, is derived. Considering first linear oscillations, the natural frequencies and mode shapes of different VSCL are computed and compared with the ones of constant stiffness laminates. The linear natural frequencies of the present model are also compared with the ones computed using a recently developed higher-order model for VSCL. After, numerical tests are carried out in the time domain and, for the first time in VSCL, taking geometric non-linearity into account, to investigate the response to external forces. The non-linear ordinary differential equations of motion are solved by Newmark’s method. It is verified that the variation of the fibre orientation can lead to significant differences in the amplitudes of the non-linear response.     

On the Magnetic and Structural Properties of Neodymium Iron Boron Nanoparticles

Neodymium iron boron nanoparticles were synthesized by means of sol–gel method. Correlation between magnetic properties and structural features were evaluated. The Nd–Fe–B gel was formed in hydrogen atmosphere. The gel was subsequently annealed under vacuum condition to obtain Nd–Fe–B oxide phases. The oxides powders were reduced at different temperatures of 750, 775, 800, 825, 850, and 875 ^°C for 3 h in a mixture of Ar and H₂ atmosphere to prepare Nd₂Fe₁₄B nanoparticles. The role of reduction temperature on phase, morphologies, microstructure, and magnetic properties of the final powders was investigated by employing X-ray diffraction (XRD), field emission-scanning electron microscope (FE-SEM), and vibrating sample magnetometer (VSM), respectively. The results show that Nd₂Fe₁₄B phase was formed successfully at temperatures of 750–875 ^°C. Maximum coercivity of 1757 Oe was obtained at 875 ^°C. The variation of coercivity was described by considering the particle size and magnetocrystalline anisotropy constant.     

Airflow‐Assisted 3D Bioprinting of Human Heterogeneous Microspheroidal Organoids with Microfluidic Nozzle

Hydrogel microspheroids are widely used in tissue engineering, such as injection therapy and 3D cell culture, and among which, heterogeneous microspheroids are drawing much attention as a promising tool to carry multiple cell types in separated phases. However, it is still a big challenge to fabricate heterogeneous microspheroids that can reconstruct built‐up tissues' microarchitecture with excellent resolution and spatial organization in limited sizes. Here, a novel airflow‐assisted 3D bioprinting method is reported, which can print versatile spiral microarchitectures inside the microspheroids, permitting one‐step bioprinting of fascinating hydrogel structures, such as the spherical helix, rose, and saddle. A microfluidic nozzle is developed to improve the capability of intricate cell encapsulation with heterotypic contact. Complex structures, such as a rose, Tai chi pattern, and single cell line can be easily printed in spheroids. The theoretical model during printing is established and process parameters are systematically investigated. As a demonstration, a human multicellular organoid of spirally vascularized ossification is reconstructed with this method, which shows that it is a powerful tool to build mini tissues on microspheroids.