Review the Regulation of Plasma Membrane Calcium Channel in Cancer and Patch Clamp Technique

As one of the most versatile and universal second messengers, calcium plays an essential role in cell life. Here we briefly reviewed the research progress of how different calcium channels are located at the cell plasma membrane, including voltage-gated calcium channels (VGCCs), receptor-operated channels (ROC), and store-operated channels (ROC). These channels can regulate different cancer progression. Afterward, the patch clamp technique's development and operating principle, an important quantitative method used for ion channel investigation, are introduced in this paper

Understanding of Ion-Solid Interaction and Defect Evolution in Zinc-Blende Structured Materials

Zinc-blende structured materials have received considerable attentions due to their excellent performance in many fields. The major benefit has attributed to high power space energy systems and nuclear reactors. Their applications can expose to high energy radiation, including neutrons, ions and cosmic rays. Under these conditions, defects are generated in materials in amounts significantly exceeding their equilibrium concentrations. The accumulation of defects can lead to undesired consequences, which may alter the performance of the materials. Therefore, the fundamental understanding of ion-solid interaction and defect evolution is a key factor to the success of both nuclear and electronic materials. This thesis focuses on the study of zinc-blende materials, including GaAs, GaN, InAs, and SiC for their possible applications in both nuclear and space fields. SiC has unique capability in the applications of nuclear fuel. In tri-structural isotropic (TRISO) fuel particles, SiC coating is considered as a major barrier for the release of fission products (FPs). However, some metallic FPs (i.e. Ag, Pd, Ru, and I) release from fully intact fuel particles raises serious concern on the safety of high temperature gas-cooled reactors. This thesis first addresses atomistic process of FP diffusion in SiC. Ab initio calculations are used to determine the defects configurations, migration energy barriers and pathways of FPs in SiC. Based on the ab initio results, the interatomic potentials of FP-SiC are developed and evaluated to link between the density functional theory and next coarser level. Classical molecular dynamics (MD) simulations have been employed to investigate FP accommodation in SiC, interactions with point defects and grain boundaries (GBs), and their diffusion kinetics. These findings lead to a conclusion that the GB diffusion of FPs is faster than bulk diffusion with a strong segregation at the GBs. Analysis of the radiation enhanced diffusion obtained by experiments and diffusion by modeling work for Ru and I has suggested the interstitial migration is likely to be a major mechanism under irradiation condition. Moreover, the diffusivities can vary by GB types, whereas high energetic GBs can provide the fastest paths for FPs to diffuse. Particularly, an elevation of 1.5 J/m2 in GB energy can result in 2-3 orders of magnitude difference in Ag diffusion coefficient. We have further explored the defect production, clustering, and its evolution in GaAs, GaN, and InAs, and determined non-ionizing energy loss (NIEL) that indicates the rate of degradation in electronic devices in space applications. Nonlinear defect production is observed with an increasing of primary knock-on (PKA) energy in GaAs and InAs. This effect, which corresponds to the direct-impact amorphization, is observed for PKA energy over 2 keV. GaN is however different and presents a pseudometallic behavior resulting in a majority of surviving defects to be single interstitials or vacancies. With the damage density evaluated from MD simulations, a model to determine NIEL has been developed to qualify the radiation degradation. The NIELs for proton, alpha, and Xe particles are predicted, and provide a pathway to evaluate the capabilities of materials for the space applications. The comparisons of defect creation, density, and effective NIEL suggest GaN may be the best candidate as a radiation hard material for space applications at high-energy regime. For low incident particle energies at which the NIEL ratio of InAs-to-GaN is less than 1, the performance of InAs may be superior to that of GaN.PHDNuclear Engineering & Radiological SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/153333/1/njchen_1.pd

Atomic mixing mechanisms in nanocrystalline Cu/Ni composites under continuous shear deformation and thermal annealing

Molecular dynamics (MD) simulations are used to reveal the mechanisms of defect substructure evolution and atomic mixing in nanocrystalline Cu/Ni composites under severe shear deformation and subsequent thermal annealing. A continuous shear scheme of MD simulation utilizing an on-the-fly periodic boundary adjustment approach enables it to reach any large shear strain. The comprehensive evaluation on the evolution of dislocation structures at various strain states indicates partial dislocation-mediated plastic deformation and triple junction slide via partial dislocation nucleation and emission from triple junctions and grain boundaries. The analysis of atomic structures in unique mixing regions suggests that triple junction sliding can result in a long-range region of atomic mixing facilitated by net dislocation flux, which is the key mechanism of atomic mixing in nanocrystalline Cu/Ni composite under severe shear, while dislocation emissions at interfaces result in short-range mixing. It is also found that thermal annealing causes the evolution of non-equilibrium defect substructures which assists atomic mixing

Microstructural Evolution, Thermodynamics, and Kinetics of Mo-Tm2O3 Powder Mixtures during Ball Milling

The microstructural evolution, thermodynamics, and kinetics of Mo (21 wt %) Tm2O3 powder mixtures during ball milling were investigated using X-ray diffraction and transmission electron microscopy. Ball milling induced Tm2O3 to be decomposed and then dissolved into Mo crystal. After 96 h of ball milling, Tm2O3 was dissolved completely and the supersaturated nanocrystalline solid solution of Mo (Tm, O) was obtained. The Mo lattice parameter increased with increasing ball-milling time, opposite for the Mo grain size. The size and lattice parameter of Mo grains was about 8 nm and 0.31564 nm after 96 h of ball milling, respectively. Ball milling induced the elements of Mo, Tm, and O to be distributed uniformly in the ball-milled particles. Based on the semi-experimental theory of Miedema, a thermodynamic model was developed to calculate the driving force of phase evolution. There was no chemical driving force to form a crystal solid solution of Tm atoms in Mo crystal or an amorphous phase because the Gibbs free energy for both processes was higher than zero. For Mo (21 wt %) Tm2O3, it was mechanical work, not the negative heat of mixing, which provided the driving force to form a supersaturated nanocrystalline Mo (Tm, O) solid solution

Ultrathin Covalent Organic Framework Nanosheets/Ti₃C₂T_x-Based Photoelectrochemical Biosensor for Efficient Detection of Prostate-Specific Antigen

Designable and ultrathin covalent organic framework nanosheets (CONs) with good photoelectric activity are promising candidates for the construction of photoelectrochemical (PEC) biosensors for the detection of low-abundance biological substrates. However, achieving highly sensitive PEC properties by using emerging covalent organic framework nanosheets (CONs) remains a great challenge due to the polymeric nature and poor photoelectric activity of CONs. Herein, we report for the first time the preparation of novel composites and their PEC sensing properties by electrostatic self-assembly of ultrathin CONs (called TTPA-CONs) with Ti3C2Tx. The prepared TTPA-CONs/Ti3C2Tx composites can be used as photocathodes for PEC detection of prostate-specific antigen (PSA) with high sensitivity, low detection limit, and good stability. This work not only expands the application of CONs but also opens new avenues for the development of efficient PEC sensing platforms

Investigation of mechanical properties and proton irradiation behaviors of SA-738 Gr.B steel used as reactor containment

The proton irradiation behaviors of two kinds of SA-738Gr.B steels prepared by different heat treatment used as AP1000 reactor containment were investigated by transmission electron microscopy and positron annihilation lifetime spectrum (PAS). The mechanical properties of as-received steels were also measured. In the unirradiated conditions, the SA-738Gr.B steels had high tensile strength and excellent impact fracture toughness, which met the performance requirements of ASME codes. Both kinds of SA-738Gr.B steels were irradiated by 400keV proton from 1.07×1017H+/cm2 to 5.37×1017H+/cm2 fluence at 150 ºC. Some voids and dislocation loops with several nanometers were observed in the cross-section irradiated samples prepared by electroplating and then twin-jet electropolishing technology. The number of irradiation defects increased with increasing of displacement damage, as well as for the mean positron lifetimes. The stress-relief annealing treatment improved irradiation resistance based on open volume defect analysis from proton irradiation. SA-738Gr.B (SR) steel had higher proton irradiation resistance ability than that of SA-738Gr.B (QT) steel. The mechanism of irradiation behaviors were also analyzed and discussed

Migration characteristics and profile control capabilities of preformed particle gel in porous media

Inspired by the viscoelastic displacement theory, a product called preformed particle gel (PPG) is developed as conformance control agent to enhance oil recovery and control excess water production. The migration law of PPG suspension in porous media is related to its deep profile control and displacement capability. Laboratory experiments indicate that PPG suspension has good viscosity increasing, and the apparent viscosity decreases with the increase of shear rate. PPG suspension is mainly elastic, and its network structure makes it have certain shear stability. PPG particles realize migration in porous media in the way of “accumulation and blockage→pressure increase→deformation and migration”. When the ratio of the PPG particle size to the pore throat diameter δ ranges from 35.52 to 53.38, the particles can match through the porous medium. When the permeability difference of the parallel model is 5, PPG suspension has the highest profile improvement rate, 69.10%. PPG suspension can adjust the planar heterogeneity, and increase the oil recovery rate by 20.75%. The PPG suspension can effectively start “cluster''、 “film” and “blind end residual oil”, and has a high oil washing efficiency. The core NMR T2 spectrum shows that PPG suspension mainly reduces oil saturation in mesopores and macropores. After PPG flooding, the EOR capacity of small pores is the highest, 39.11%

Synthesis and Solution Properties of a Novel Hyperbranched Polymer Based on Chitosan for Enhanced Oil Recovery

A new type of chitosan-modified hyperbranched polymer (named HPDACS) was synthesized through the free-radical polymerization of surface-modified chitosan with acrylic acid (AA) and acrylamide (AM) to achieve an enhanced oil recovery. The optimal polymerization conditions of HPDACS were explored and its structure was characterized by Fourier-transform infrared spectroscopy, hydrogen nuclear magnetic resonance, and environmental scanning electron microscopy. The solution properties of HPDACS in ultrapure water and simulated brine were deeply studied and then compared with those of partially hydrolyzed polyacrylamide (HPAM) and a dendritic polymer named HPDA. The experimental results showed that HPDACS has a good thickening ability, temperature resistance, and salt resistance. Its viscosity retention rate exceeded 79.49% after 90 days of aging, thus meeting the performance requirements of polymer flooding. After mechanical shearing, the viscosity retention rates of HPDACS in ultrapure water and simulated brine were higher than those of HPAM and HPDA, indicating its excellent shear resistance and good viscoelasticity. Following a 95% water cut after preliminary water flooding, 0.3 pore volume (PV) and 1500 mg/L HPDACS solution flooding and extended water flooding could further increase the oil recovery by 19.20%, which was higher than that by HPAM at 10.65% and HPDA at 13.72%. This finding indicates that HPDACS has great potential for oil displacement

Defect substructure energy landscape in polycrystalline Al under large deformation: insights from molecular dynamics

Tens-nanometer sized defect substructures such as dislocation network, nanotwin and new grain or phase may form during solid phase processing (SPP), which affect the energy landscape, hence, the stability and evolution of phase and structure. Developing non-equilibrium thermodynamic models needs the correlation among the energy, defect substructure and deformation. In the current work, we use molecular dynamics (MD) method to simulate defect substructure evolutions in polycrystalline Al under compress and shear stresses. The effect of local stresses on the formation and transformation of typical defect substructures were analyzed. It was found that transitions from FCC, nanotwin, HCP, BCC, HCP to FCC lead to the formation of subgrains facilitated with large grain rotation. Our results demonstrate that point defect concentrations (e.g., HCP, dislocation core atoms) can be used as internal variables to describe defect substructures, such as dislocations, nanotwins and sub-grain boundaries. An energy landscape of defect substructures in polycrystalline Al under compress and shear stresses was established which shows unstable and metastable defect substructures. Approaches to developing more accurate energy landscapes for understanding and predicting microstructure evolution under SPP was discussed

Effect of Crystal Orientation on Self-Assembly Nanocones Formed on Tungsten Surface Induced by Helium Ion Irradiation and Annealing

The self-assembly nanocone structures on the surface of polycrystalline tungsten were created by He+ ion irradiation and then annealing, and the resulting topography and morphology were characterized using atomic force microscopy and scanning electron microscopy. The cross-sectional samples of the self-assembly nanocones were prepared using an in situ–focused ion beam and then observed using transmission electron microscopy. The self-assembly nanocones were induced by the combined effect of He+ ion irradiation, the annealing process and the chromium impurity. The distribution characteristics, density and morphology of the nanocones exhibited a distinct difference relating to the crystal orientations. The highest density of the nanocones was observed on the grain surface with a (1 1 1) orientation, with the opposite for that with a (0 0 1) orientation and a medium value on the (1 0 1)-oriented grain. The size of the self-assembly nanocones increased with increasing the annealing time which met a power-law relationship. Irradiation-induced defects acted as the nucleation locations of the protrusions which attracted the migration of the tiny amount of chromium atoms. Under the action of temperature, the protrusions finally evolved into the nanocones