Search

Revealing the local structure of solid electrolytes (SEs) with electron microscopy is critical for the fundamental understanding of the performance of solid-state batteries (SSBs). However, the intrinsic structural information in the SSB can be misleading if the sample’s interactions with the electron beams are not fully understood. In this work, we systematically investigate the effect of electron beams on Al-doped lithium lanthanum zirconium oxide (LLZO) under different imaging conditions. Li metal is observed to grow directly on the clean surface of LLZO. The Li metal growth kinetics and the morphology obtained are found to be heavily influenced by the temperature, accelerating voltage, and electron beam intensity. We prove that the lithium growth is due to the LLZO delithiation activated by a positive charging effect under electron beam emission. Our results deepen the understanding of the electron beam impact on SEs and provide guidance for battery material characterization using electron microscopy.

Summary Metal penetration into a solid electrolyte (SE) is one of the critical problems impeding the practical application of solid-state batteries. In this study, we investigate the conditions under which electronic conductivity of the SE can lead to metal deposition and fracture within the SE. Three different stages for void filling (metal plating initiation, metal growth, and metal compression) in the SE are identified. We show that a micron-size isolated void in the SE near the anode can be quickly filled in by metal and fractured when the developed pressure in the void grows larger than the maximum pressure the SE material can sustain. We find that the anode voltage and applied current density play a significant role in determining the vulnerability to metal deposition. We discuss several strategies to prevent electronic conductivity-driven metal propagation in electrolytes that are not fully dense, including the densified layers between the anode and SE.

A pneumatic controlled nano-sieve device is demonstrated for the efficient capture and release of 15 nm quantum dots. This device consists of a 200 nm deep glass channel and a PDMS-based pneumatic pressure layer to enhance target capture. The fluid motion inside the nano-sieve is studied by computational fluidic dynamics (CFD) and microfluidic experiments, enabling efficient target capture with a flow rate as high as 100 μL/min. In addition, micro-grooves are fabricated inside the nano-sieve to create low flow rate regions, which further improves the target capture efficiency. A velocity contour plot is constructed with CFD, revealing the flow rate is lowest at the top and bottom of the micro-grooves. This phenomenon is supported by the observed nanoparticle clusters surrounding the micro-grooves. By changing the morphology and pneumatic pressure, this device will also facilitate rapid capture and release of various biomolecules.

Lithium-metal (Li0) anode is considered the holy grail of all-solid-state batteries owing to their exceedingly high energy density; in practice, their stability remains unsatisfactory because of the incompatibility between Li0 and solid-state electrolytes (SEs). One strategy is introducing an interlayer, which often consists of the mixed ionic-electronic conductor (MIEC), to stabilize the Li0. However, how Li ions (Li+) transport within MIEC remains unknown. Herein, we investigate the Li, including Li0 and Li+, dynamics in a graphite interlayer, a typical MIEC, using operando neutron imaging and Raman spectroscopy. Our study reveals the Li evolution during mechano-chemistry and mechano-electrochemistry reactions. During cell assembly, intercalation–extrusion-dominated mechano-chemical reactions transform the graphite into a Li-graphite interlayer consisting of SE, Li0, and diluted graphite-intercalation compounds. During battery operation, dictated by the lowest nucleation energy, Li0 plating preferentially occurred at the Li-graphite|SE interface and then transferred into the Li-graphite interlayer without intercalation. Upon further plating, Li0-dendrites formed, inducing short circuits and reverse immigration of Li0 from the anode to the cathode during charging. Continuum modeling was conducted to explain the Li dynamics. We concluded that with the MIEC interlayer, a lowest nucleation barrier at the Li0 side is necessary to drive the Li+ to transport across MIEC and preferentially deposit onto the Li0.

This work presents a direct observation and quantification of the fundamental mechanism of lithium penetration in Li6PS5Cl (LPS) solid electrolyte. Lithium plating in a nano-sized defect on the LPS surface led to the nucleation and propagation of a crack without external force. It also revealed a reduction in the mechanical strength of LPS when altering the electrochemical charge/discharge bias condition. A first principles atomistic simulation was performed to confirm that the disorder in the crystal structure of the LPS, both in lithium deficient and excess states, contributes to the reduced mechanical strength, and a decrease in the modulus is observed when lithium concentration is decreased from the stoichiometric amount. The results of this study suggest the importance of minimizing defects at the surface and grain boundaries to improve the stability of the solid-state electrolyte (SSE). Interfaces and boundaries can be bottlenecks for lithium diffusion, creating the concentration gradient. This can reduce the mechanical stabilities of the SSE, accelerating lithium penetration and degradation in all-solid-state lithium batteries. The insights obtained in this study provide useful information towards understanding the mechanism and designing the materials/structures to solve this issue.

Point-of-use (POU) devices with satisfactory lead (Pb2+) removal performance are urgently needed in response to recent outbreaks of lead contamination in drinking water. This study experimentally demonstrated the excellent lead removal capability of two-dimensional (2D) MoS2 nanosheets in aqueous form and as part of a layer-stacked membrane. Among all materials ever reported in the literature, MoS2 nanosheets exhibit the highest adsorption capacity (740 mg/g), and the strongest selectivity/affinity toward Pb2+ with a distribution coefficient Kd that is orders of magnitude higher than that of other lead adsorption materials (5.2 × 107 mL/g). Density functional theory (DFT) simulation was performed to complement experimental measurements and to help understand the adsorption mechanisms. The results confirmed that the cation selectivity of MoS2 follows the order Pb2+ > Cu2+ ≫ Cd2+ > Zn2+, Ni2+ > Mg2+, K+, Ca2+. The membrane formed with layer-stacked MoS2 nanosheets exhibited a high water flux (145 L/m2/h/bar), while effectively decreasing Pb2+ concentration in drinking water from a few mg/L to less than 10 μg/L. The removal capacity of the MoS2 membrane is a few orders of magnitude higher than that of other literature-reported membrane filters. Therefore, the layer-stacked MoS2 membrane has great potential for POU removal of lead from drinking water.

Membranes synthesized by stacking two-dimensional graphene oxide (GO) hold great promise for applications in organic solvent nanofiltration. However, the performance of a layer-stacked GO membrane in organic solvent nanofiltration can be significantly affected by its swelling and interlayer spacing, which have not been systematically characterized. In this study, the interlayer spacing of the layer-stacked GO membrane in different organic solvents was experimentally characterized by liquid-phase ellipsometry. To understand the swelling mechanism, the solubility parameters of GO were experimentally determined and used to mathematically predict the Hansen solubility distance between GO and solvents, which is found to be a good predictor for GO swelling and interlayer spacing. Solvents with a small solubility distance (e.g., dimethylformamide, N-methyl-2-pyrrolidone) tend to cause significant GO swelling, resulting in an interlayer spacing of up to 2.7 nm. Solvents with a solubility distance larger than 9.5 (e.g., ethanol, acetone, hexane, and toluene) only cause minor swelling and are thus able to maintain an interlayer spacing of around 1 nm. Correspondingly, GO membranes in solvents with a large solubility distance exhibit good separation performance, for example, rejection of more than 90% of the small organic dye molecules (e.g., rhodamine B and methylene blue) in ethanol and acetone. Additionally, solvents with a large solubility distance result in a high slip velocity in GO channels and thus high solvent flux through the GO membrane. In summary, the GO membrane performs better in solvents that are unlike GO, i.e., solvents with large solubility distance.

Solid-state batteries (SSBs) are considered promising next-generation energy storage devices but tend to suffer from rapid capacity fade. Here, we demonstrate that mechanical contact loss between the solid conductor and cathode, induced by its volume changes during cycling, plays a significant role in the observed capacity fade. Focused ion beam-scanning electron microscope (FIB-SEM) tomography with nanoscale resolution was used for 3D characterization of the composite electrode morphology before and after cycling. The tomography data demonstrates the development of voids and cracks near the cathode particles and significant contact loss between the cathode particles and solid electrolyte after cycling. The observed mechanical degradation in the electrode composite highlights the difficulty and importance of engineering mechanically stable SSBs. The application of large external pressure after long-term cycling led to recovery of lost capacity and reduced the cell resistance, confirming the effect of mechanical degradation.

In this presentation, we will provide insight into the most prevalent failure mechanisms of solid-state batteries and correlates it with the relative density of the solid electrolyte pellet. We show that Li dendrites can be suppressed only when the relative density of the solid electrolyte pellet is beyond a threshold value of ~95%. Before this threshold value, the battery shorts easer if the pellet is denser due to faster Li dendrites growth within the percolating pores in the pellet. Detailed characterizations with FIB-SEM tomography and permeability test are employed to quantify the microstructural properties (such as pore size, connectivity, porosity and tortuosity) of the LPS pellet made at different relative densities. Our modeling results reveal the growth details of the Li filament inside pores with size ranging from 0.2 μm to 2 μm. The findings in this paper will greatly help understand the failure modes of solid-state batteries and advise the design strategies for the dendrite-free solid-state battery system.

Micromechanical loading events such as pop-in and indentation size effect (ISE) are well understood at room temperature and have been widely accepted as fundamental factors in the study of material mechanics at the microscale. Experimentally it has been observed that such phenomena can be greatly affected by temperature, but quantitative studies of temperature effects are rarely conducted. This paper presents the effects of high-temperature on the pop-in load and ISE of calcium fluoride (CaF2) single crystal material through in-situ high-temperature nanoindentation experiments and explains the localized dislocation events at the atomic level with molecular dynamic (MD) calculations. Our experimental results show that an increase in temperature leads to a reduction of the pop-in load, the hardness of the material, and the material dependent length scale during plasticity (defined in the Nix-Gao relation). Our computed results show that the differences in dislocation nucleation characteristics of CaF2 at various temperatures are the main reasons for the changes in its material properties. Such an experimental-computational study provides a comprehensive analysis of the relationships between temperature and dislocation mechanisms during nanoindentation.

A concept of the porous graphene membrane centrifuge is proposed aiming at fabrication of large scale, fouling-free desalination machine with nanomaterial-based reverse osmosis modules. The concept as well as strategy of such porous rotating graphene membrane device is approved through molecular dynamics (MD) modeling and simulation of a nano-fluidic device that in order to make a quantitative evaluation. First, an analytical formulation is derived for the critical angular velocity above which the centrifugal force is able to counter-balance osmosis pressure, so that the reverse osmosis (RO) desalination process can proceed. The critical angular velocity derived from this formulation is compared with MD simulated critical angular velocity. Based on MD simulation results, it is shown that the rotating porous membrane device may significantly improve desalination efficiency by combining the centrifugal separation and and the selectivity of porous graphene membrane to achieve reverse-osmosis desalination. Furthermore, we have shown that the proposed desalination device has an intrinsic anti-fouling mechanism, and then we have studied the effect of pore size on the flux rate by conducting simulations with the applied rotating speed. Moreover, we have conducted energy and efficiency analysis for the proposed desalination device model, and we obtained the relationship between fresh water flux rate and the angular velocity, at the same time, with the pore size. By choosing the most efficient angular velocity and the pore size that ensures salt rejection, an optimal nano-fluidic device design is achieved.

Li-metal all-solid-state batteries (SSBs) has emerged in recent years as a potentially safer and higher energy density energy storage device. Metal penetration into a solid electrolyte (SE) is one of the critical problems impeding the practical application of solid-state batteries. In this study, we investigate the conditions under which electronic conductivity of the solid electrolyte can lead to metal deposition and fracture within the electrolyte, by building an electro-chemo-mechanical model which incorporates mixed ionic-electronic conduction and SE mechanics. Three different stages for void filling (metal plating initiation, metal growth, and metal compression) in the solid electrolyte are identified. We show that a micron-size isolated void in the SE near the anode can be quickly filled in by metal and fractured when the developed hydrostatic pressure in the void grows larger than the maximum pressure the SE material can sustain. We find that the anode voltage, applied current density, overall cell potential, and the SE surface quality play a very significant role in determining the vulnerability to metal deposition in the SE, and relate these features to a critical current density. We discuss several strategies to reduce/prevent electronic conductivity-driven metal propagation in electrolytes that are not fully dense, including the positive effect of thin densified layers between the anode and solid electrolyte.

Point-of-use (POU) devices with satisfactory lead (Pb

In this work, we systematically study a rotational nanofluidic device for reverse osmosis (RO) desalination by using large scale molecular dynamics modeling and simulation. Moreover, we have compared Molecular Dynamics simulation with fluid mechanics modeling. We have found that the pressure generated by the centrifugal motion of nanofluids can counterbalance the osmosis pressure developed from the concentration gradient, and hence provide a driving force to filtrate fresh water from salt water. Molecular Dynamics modeling of two different types of designs are performed and compared. Results indicate that this novel nanofluidic device is not only able to alleviate the fouling problem significantly, but it is also capable of maintaining high membrane permeability and energy efficiency. The angular velocity of the nanofluids within the device is investigated, and the critical angular velocity needed for the fluids to overcome the osmotic pressure is derived. Meanwhile, a maximal angular velocity value is also identified to avoid Taylor-Couette instability. The MD simulation results agree well with continuum modeling results obtained from fluid hydrodynamics theory, which provides a theoretical foundation for scaling up the proposed rotational osmosis device. Successful fabrication of such rotational RO membrane centrifuge may potentially revolutionize the membrane desalination technology by providing a fundamental solution to the water resource problem.

Two-dimensional materials such as graphene and carbon nanotube have promising applications in the preparation of permeable membranes and the field of environmental protection due to their unique structures and components. This paper conducts a study on graphene and nanotubes in salt solution using molecular dynamics computational method, and ascertains the quantitative relations between the ionic concentration, water flux and reverse osmosis pressure by setting up theoretical porous models of the two materials. This fundamental research provides much guidance in the determination of critical parameters like pressure and water flux in the actual application of membranes.

A scale-up nanoporous membrane centrifuge is designed and modeled. It can be used for nanoscale scale separation including reverse osmosis desalination. There are micron-size pores on the wall of the centrifuge and nanoscale pores on local graphene membrane patches that cover the micron-size pores. In this work, we derived the critical angular velocity required to counter-balance osmosis force, so that the reverse-osmosis (RO) desalination process can proceed. To validate this result, we conducted a large scale (four million atoms) full atom molecular dynamics (MD) simulation to examine the critical angular velocity required for reverse osmosis at nanoscale. It is shown that the analytical results derived based on fluid mechanics and the simulation results observed in MD simulation are consistent and well matched. The main advantage of such nanomaterial based centrifuge is its intrinsic anti-fouling ability to clear [Formula: see text] and [Formula: see text] ions accumulated at the vicinity of the pores due to the Coriolis effect. Analyses have been conducted to study the relation between osmotic pressure, centrifugal pressure, and water permeability.

Layer-stacked graphene oxide (GO) membranes, in which unique two-dimensional (2D) water channels are formed between two neighboring GO nanosheets, have demonstrated great potential for aqueous phase separation. Subjects of crucial importance are to fundamentally understand the interlayer spacing (i.e. channel height) of GO membranes in an aqueous environment, elucidate the mechanisms for water transport within such 2D channels, and precisely control the interlayer spacing to tune the membrane separation capability for targeted applications. In this investigation, we used an integrated quartz crystal mass balance (QCM-D) and ellipsometry to experimentally monitor the interlayer spacing of GO, reduced GO and crosslinked GO in aqueous solution and found that crosslinking can effectively prevent GO from swelling and precisely control the interlayer spacing. We then used molecular dynamics simulations to study the mass transport inside the 2D channels and proved that the chemical functional groups on the GO plane dramatically slow down water transport in the channels. Our findings on GO structure and water transport provide a necessary basis for further tailoring and optimizing the design and fabrication of GO membranes in various separation applications.

Membranes made of layer-stacked two-dimensional molybdenum disulfide (MoS2) nanosheets have recently shown great promise for water filtration. At present, the reported water fluxes vary significantly, while the accountable structure and properties of MoS2 nanochannels are largely unknown. This paper aims to mechanistically relate the performance of MoS2 membranes to the size of their nanochannels in different hydration states. We discovered that fully hydrated MoS2 membranes retained a 1.2 nm interlayer spacing (or 0.9 nm free spacing), leading to high water permeability and moderate-to-high ionic and molecular rejection. In comparison, completely dry MoS2 membranes had a 0.62 nm interlayer spacing (or 0.3 nm free spacing) due to irreversible nanosheet restacking and were almost impermeable to water. Furthermore, we revealed that the interlayer spacing of MoS2 membranes in aqueous solution is maintained by comparable van der Waals and hydration forces, thereby ensuring the aqueous stability of MoS2 membra...

In this work, we have developed an updated Lagrangian particle hydrodynamics (ULPH) for Newtonian fluid. Unlike the smoothed particle hydrodynamics, the non-local particle hydrodynamics formulation proposed here is consistent and convergence. Unlike the state-based peridynamics, the discrete particle dynamics proposed here has no internal material bond between particles, and it is not formulated with respect to initial or a fixed referential configuration. In specific, we have shown that (1) the non-local update Lagrangian particle hydrodynamics formulation converges to the conventional local fluid mechanics formulation; (2) the non-local updated Lagrangian particle hydrodynamics can capture arbitrary flow discontinuities without any changes in the formulation, and (3) the proposed non-local particle hydrodynamics is computationally efficient and robust.

Author(s): Xiao, Y; Jun, KJ; Wang, Y; Miara, LJ; Tu, Q; Ceder, G | Abstract: The key component in lithium solid-state batteries (SSBs) is the solid electrolyte composed of lithium superionic conductors (SICs). Lithium oxide SICs offer improved electrochemical and chemical stability compared with sulfides, and their recent advancements have largely been achieved using materials in the garnet- and NASICON (sodium superionic conductor)- structured families. In this work, using the ion-conduction mechanisms in garnet and NASICON as inspiration, a common pattern of an “activated diffusion network” and three structural features that are beneficial for superionic conduction: a 3D percolation Li diffusion network, short distances between occupied Li sites, and the “homogeneity” of the transport path are identified. A high-throughput computational screening is performed to search for new lithium oxide SICs that share these features. From this search, seven candidates are proposed exhibiting high room-temperature ionic conductivity evaluated using ab initio molecular dynamics simulations. Their structural frameworks including spinel, oxy-argyrodite, sodalite, and LiM(SeO3)2 present new opportunities for enriching the structural families of lithium oxide SICs.

Platelet-derived growth factor receptor (PDGFR)-β is an important tyrosine kinase and its downregulation has been reported to alter the radiosensitivity of glioma cells, although the underlying mechanism is unclear. In order to investigate the effect of PDGFR-β on the radiosensitivity of glioblastoma, the present study transfected C6 glioma cells with a PDGFR-β-specific small interfering (si)RNA expression plasmid, and downregulation of the expression of PDGFR-β in C6 glioma cells was confirmed by western blotting and immunohistochemical analysis. Clone formation assays and xenograft growth curves demonstrated that PDGFR-β-siRNA enhanced the radiosensitivity of C6 glioma cells in vitro and in vivo. Furthermore, MTT and xenograft growth curves demonstrated that PDGFR-β-siRNA inhibited the proliferation of C6 glioma cells in vitro and in vivo, and terminal deoxynucleotidyl transferase dUTP nick end-labeling and immunohistochemical analyses demonstrated that PDGFR-β-siRNA induced apoptosis and inhibited the expression of Ki-67, cyclin B1 and vascular endothelial growth factor in C6 glioma cell xenografts. Taken together, these results suggested that PDGFR-β may be used as a target for the radiosensitization of glioblastoma.

The effect of ionic and electronic conductivity in the solid electrolytes (SE) on metal (such as Li, Na) deposition and dendrite propagation in the SE are investigated. A new framework for metal formation inside defects (such as voids, grain boundaries) in the SE due to the electronic conductivity of the SE is established. We find that for typical SE material (with ionic conductivity ~0.1mS/cm and electronic conductivity ~10^-5 mS/cm) isolated voids in the SE that are close enough to the anode side (~0.1 um) may be filled in with metal within several minutes under typical galvanostatic charging condition (with current density 0.1~1mA/cm^2). Continuous deposited metal in the voids may lead to fracture of the SE, which triggers mode II dendrite growth (isolated dendrites growth in the SE). We will propose two strategies to prevent metal deposition in the SE.

Summary Interfacial deposition stability between lithium metal and a solid electrolyte (SE) is important in preventing interfacial contact loss, mechanical fracture, and dendrite growth in Li-metal solid-state batteries (SSBs). In this work, we investigate the deposition and mechanical stability at the Li-metal/SE interface and its consequences (such as SE fracture and contact loss). A wide range of contributing factors are investigated, such as charge and mass transfer kinetics, plasticity of Li-metal and fracture of the SE, and the applied stack pressure. We quantify the effect of the ionic conductivity of the SE, the exchange current density of the interfacial charge-transfer reaction, and SE surface roughness on the Li deposition stability at the Li-metal/SE interface. We also propose a “mechanical stability window” for the applied stack pressure that can prevent both contact loss and SE fracture, which can be extended to other metal-electrode (e.g., sodium) SSB systems.

Author(s): Barroso-Luque, L; Tu, Q; Ceder, G | Abstract: 1. Equation 4 in the text and in Table I has two wrong minus signs in the publication. It should read, αeEv/(1+v) (1+2v)tr(∈e)II + E/1+v ∈e[1] This term is eventually neglected as described in the publication and thus does not affect the subsequent analysis and results.2. Equation 9 in the text and in Table I, is missing a factor of 2 and should involve the strain rate tensor ˙∈p. It is correctly stated as follows, -λP + 2λ·η˙∈p = 0. [2] This mistype does not affect our results since the factor of 2 is correctly accounted for in our simplification of the above equation (Eq. 17). We reproduce Eq. 17 for reference, -λP + η λ2˙u = 0 [3].

Author(s): Barroso-Luque, L; Tu, Q; Ceder, G | Abstract: The use of inorganic solid-ionic conductors with a metal electrode, has been proposed as a way to increase energy density, decrease capacity loss and prevent failure from metal propagation. Current observations of Li-metal electrodes causing cell shorting in solid-state systems have been identified as main obstacles limiting the development of this technology. However, many aspects of the involved phenomenon have not been fully addressed theoretically. In this work, we derive a mathematical model of electrodeposition-induced plastic flow in metal/inorganic solid-conductor systems. We use a semi-analytical solution to derive pressure increase expressions at metal protrusions and assess the possibility of fracture. The results give flow solutions analogous to laminar channel flow. The solutions also show how taking into account a boundary traction potential from built up pressure, leads to ionic redistribution and effectively screens isolated flaws, making local current focusing an incomplete explanation for observed electrolyte fracture. We show that the boundary traction potential sets a maximum value for the pressure increase that can occur from deposition at an isolated flaw. We derive conditions under which fracture can occur, and quantify the role of ionic conductivity and electrolyte fracture toughness in extending safe operating regimes of solid-state electrolytes with metal electrodes.

Author(s): Shi, T; Tu, Q; Tian, Y; Xiao, Y; Miara, LJ; Kononova, O; Ceder, G | Abstract: Low active material loading in the composite electrode of all-solid-state batteries (SSBs) is one of the main reasons for the low energy density in current SSBs. In this work, it is demonstrated with both modeling and experiments that in the regime of high cathode loading, the utilization of cathode material in the solid-state composite is highly dependent on the particle size ratio of the cathode to the solid-state conductor. The modeling, confirmed by experimental data, shows that higher cathode loading and therefore an increased energy density can be achieved by increasing the ratio of the cathode to conductor particle size. These results are consistent with ionic percolation being the limiting factor in cold-pressed solid-state cathode materials and provide specific guidelines on how to improve the energy density of composite cathodes for solid-state batteries. By reducing solid electrolyte particle size and increasing the cathode active material particle size, over 50 vol% cathode active material loading with high cathode utilization is able to be experimentally achieved, demonstrating that a commercially-relevant, energy-dense cathode composite is achievable through simple mixing and pressing method.

In this work, molecular dynamics (MD) and molecular mechanics (MM) simulations are used to study well-equilibrated models of 4,4′-bis(3,4-dicyanophenoxy)biphenyl (BPh)–1,3-bis(3-aminophenoxy)benzene (m-APB) phthalonitrile (PN) system with a range of crosslink densities. A cross-linking technique is introduced to build a series of systems with different crosslink densities; several key properties of this material, including thermal expansion, mechanical properties and dielectric properties are studied and compared with experimental results. It is found that the coefficient of linear thermal expansion predicted by the model is in good agreement with experimental results and indicative of the good thermal stability of the PN polymeric system. The simulation also shows that this polymer has excellent mechanical property, whose strength increases with increasing crosslink density. Lastly and most importantly, the calculated dielectric constant—which shows that this polymer is an excellent insulating material—indicates that there is an inverse relation between cross-linking density and dielectric constant. The trend gave rise to an empirical quadratic function which can be used to predict the limits of attainable dielectric constant for highly crosslinked polymer systems. The current computational work provides strong evidence that this polymer is a promising material for aerospace applications and offers guidance for experimental studies of the effect of cross-linking density on the thermal, mechanical and dielectric properties of the material.

Membranes made of layer-stacked two-dimensional molybdenum disulfide (MoS

Graphene oxide (GO) has recently emerged as a promising 2D nanomaterial to make high-performance membranes for important applications. However, the aqueous-phase separation capability of a layer-stacked GO membrane can be significantly limited by its natural tendency to swell, that is, absorb water into the GO channel and form an enlarged interlayer spacing (d-spacing). In this study, the d-spacing of a GO membrane in an aqueous environment was experimentally characterized using an integrated quartz crystal microbalance with dissipation and ellipsometry. This method can accurately quantify a d-spacing in liquid and well beyond the typical measurement limit of ∼2 nm. Molecular simulations were conducted to fundamentally understand the structure and mobility of water in the GO channel, and a theoretical model was developed to predict the d-spacing. It was found that, as a dry GO membrane was soaked in water, it initially maintained a d-spacing of 0.76 nm, and water molecules in the GO channel formed a semiordered network with a density 30% higher than that of bulk water but 20% lower than that of the rhombus-shaped water network formed in a graphene channel. The corresponding mobility of water in the GO channel was much lower than in the graphene channel, where water exhibited almost the same mobility as in the bulk. As the GO membrane remained in water, its d-spacing increased and reached 6 to 7 nm at equilibrium. In comparison, the d-spacing of a GO membrane in NaCl and Na

This work presents the novel application of hydrocyclones for mixed liquor recirculation (MLR) treatment in the anoxic/aerobic (A/O) process to enhance the denitrification process. An exhaustive investigation on treated activated sludge and A/O effluents was conducted in batch and continuous operation tests. The median diameter of the sludge flocs was decreased from 78.82 μm to 15.77–23.31 μm, and the extracellular polymeric substances (EPS) desorption was observed, thus leading to the release of the soluble chemical oxygen demand (SCOD). A marked increase in the BOD5/TN ratio was consequently achieved, which supplied the carbon source and improved the biodegradability of the MLR. The hydrocyclone treatment also enabled a 7.17% ± 0.93% specific oxygen utilization rate (SOUR) increase at the optimal hydrocyclone intensity of 0.13 MPa, owing to the desorption of positioned microbial secretion from the microorganism cells. The nitrate reductase and nitrite reductase were also improved by 15.13% ± 1.16% and 17.61% ± 1.55%, respectively. The nitrate removal efficiency was enhanced by 13.6%, and the nitrogen oxide gases varied slightly; this behavior was consistent with the variations in the key enzymes involved in denitrification. The A/O process operated in the mode of hydrocyclone-treated MLR, compared with in the conventional mode, resulted in a 15.56% higher TN removal, and the other effluent parameters remained stable. Hydrocyclone disruption is thus a convenient and energy-efficient process with broad implications in denitrification development.

To investigate effects of MARCH6 gene knockdown on MCF-7 cell proliferation and cell cycle. Methods: 293T cells were transfected with MARCH6 shRNA lentivirus. Fluorescence microscope was used to observe and verify the transfection efficiency. The initial effect of the MARCH6 gene knockdown in MCF-7 cells was observed via fluorescence microscope. Real-time PCR and Western blot were used to detect the expression of MARCH6. MTT and BrdU assay were used to examine cell proliferation, and staining flow cytometry was used to analyze cycle distribution of MCF-7 cells. Results: MARCH6 shRNA lentivirus was successfully transfected and about 80% of the cells expressed green fluorescent in comparison of the control. About 90% of the cells showed green fluorescence. The mRNA and protein in MCF-7 cells were transcription and expression of protein was significantly decreased after the transfection of MARCH6 shRNA lentivirus accompanied by a decrease in MCF-7 cell proliferation (P0.01). Flow cytometry showed that the cell cycles were inhibited at the G1 phase and the proliferation index was significantly reduced. Conclusion: Knockdown of MARCH6 gene by RNA interference inhibits the proliferation of MCF-7 cells, suggesting that the expression of MARCH6 promotes proliferation of breast cancer cells through regulation of the cell cycle.目的：应用慢病毒介导的RNAi技术，在乳腺癌MCF-7细胞中敲减MARCH6基因的表达，研究其对MCF-7细胞增殖及细胞周期的影响。方法：靶向MARCH6基因的shRNA慢病毒转染293T细胞后，在荧光显微镜下观察转染效率；收集慢病毒液感染MCF-7细胞后，应用实时荧光PCR和Western印迹验证RNAi敲减MARCH6基因后，MARCH6基因mRNA和蛋白的表达影响；应用MTT，BrdU细胞增殖实验检测细胞增殖能力的变化；采用增殖指数染色流式细胞术检测细胞周期和增殖的改变。结果：通过在荧光显微镜下观察，MARCH6 shRNA慢病毒质粒成功转染293T细胞，与同明视野对比，可见80%左右的细胞带绿色荧光；感染MCF-7细胞，90%的细胞均带绿色荧光； 实时荧光PCR和Western印迹验证了MARCH6 shRNA慢病毒感染MCF-7细胞后，MARCH6在转录水平和蛋白水平表达均显著下降；MTT实验、BrdU法结果显示MARCH6基因敲减组的MCF-7细胞增殖显著下降(P0.01)，流式细胞术分析显示MARCH6敲减后MCF-7细胞出现细胞周期抑制，细胞分裂处于G1期细胞数明显增多，增殖指数显著降低。结论：敲减乳腺癌MCF-7细胞的MARCH6基因表达后，抑制了MCF-7细胞的增殖，并引起细胞周期G1期阻滞。提示MARCH6通过影响细胞周期的进展，促进乳腺癌细胞的增殖。.

We have designed a porous nanofluidic desalination device, a rotating carbon nanotube membrane filter (RCNT-MF), for the reverse osmosis desalination that can turn salt water into fresh water. The concept as well as design strategy of RCNT-MF is modeled, and demonstrated by using molecular dynamics simulation. It has been shown that the RCNT-MF device may significantly improve desalination efficiency by combining the centrifugal force propelled reverse osmosis process and the porous CNT-based fine scale selective separation technology.

Epigenetic alteration induced loss function of the transcription factor 21 (TCF21) has been associated with different types of human cancers. However, the epigenetic regulation and molecular functions of TCF21 in colorectal cancer (CRC) remain unknown. In this study, TCF21 expression levels and methylation status of its promoter region in CRC cell lines (n = 5) and CRC tissues (n = 151) as well as normal colorectal mucosa (n = 30) were assessed by RTq-PCR and methylation analysis (methylation specific PCR, MSP and bisulfite sequencing PCR, BSP), respectively. The cellular functions of TCF21 on CRC cell proliferation, apoptosis, invasion and migration were investigated in vitro. Our data revealed that TCF21 was frequently silenced by promoter hypermethylation in both tested CRC cell lines and primary CRC, and correlation analysis between methylation status and clinicopathologic parameters found that TCF21 methylation was significantly correlated with lymph node invasion (P = 0.013), while no significant correlation was found in other parameters. In addition, demethylation treatment resulted in re-expression of TCF21 in CRC cell lines, and cellular function experiments revealed that restoration of TCF21 inhibited CRC cell proliferation, promoted apoptosis and suppressed cell invasion and migration, suggesting that TCF21 may function as a tumor suppressor gene, which is downregulated through promoter hypermethylation in CRC development.

The aim of this study was to evaluate the predictors of long-term survival following postoperative therapy for suprasellar germ cell tumors (GCTs). A total of 23 patients with pathologically confirmed suprasellar GCTs were reviewed between April, 1987 and October, 2008. The predictors were identified with a univariate Cox proportional hazards model and the results were used to group patients according to outcome. The overall survival (OS) and progression-free survival (PFS) rates for the good- and poor-prognosis two groups were estimated with Kaplan-Meier analysis, with log-rank tests used to assess differences between the groups. The OS rate for all patients was 82.6% at 5 and 72.9% at 10 years. Lesion size (2–4 vs. >4 cm) and pathological type (pure germinoma vs. mixed GCT) were the only significant predictors of OS (P

The electromagnetic performance of phased array antenna (PAA) is degraded because of the array plane structural errors caused by manufacturing processing and assembly. It seriously restrict the realization of high performance of the phased array antenna. Therefore, by introducing the plane structural errors into the antenna pattern function as an additional phase factor, a coupled structural-electromagnetic model is developed, which described the effect on the performance of planar hexagonal phased array antenna with the plane structural errors. Then the direct influence relationship of the electromagnetic performances of antenna with the plane installation accuracy and flatness tolerance are analyzed. The critical value of array plane structural errors is given when meet antenna performance requirement. The analysis results provide a theoretical guidance for engineer to set the reasonable tolerance in manufacturing antenna.

Radiotherapy is an important weapon in the treatment of breast cancer, but normal tissue injury after radiotherapy can be a threat for patients. Genetic markers conferring the ability to identify hyper-sensitive patients at risk of normal tissue injury in advance would considerably improve therapy. Association studies on genetic variation and occurrence of normal tissue injury can help us identify such markers, but previous studies on the association between XRCC1 R399Q polymorphism and risk of normal tissue injury after radiotherapy in breast cancer patients report conflicting findings. We performed a meta-analysis to comprehensively evaluate the association between XRCC1 R399Q polymorphism and risk of normal tissue injury after radiotherapy in breast cancer patients. The pooled odds ratios (ORs) with their 95 % confidence interval (95 % CIs) were calculated to assess the strength of the association. Fourteen case–control studies with a total of 2,448 breast cancer cases were finally included into the meta-analysis. Overall, XRCC1 R399Q polymorphism was significantly associated with increased risk of normal tissue injury after radiotherapy under all three models (for QQ versus RR: fixed-effects OR = 1.06, 95 % CI 1.00–1.13, P = 0.050; for RQ versus RR: fixed-effects OR = 1.05, 95 % CI 1.00–1.10, P = 0.047; for QQ/RQ versus RR: fixed-effects OR = 1.26, 95 % CI 1.01–1.58, P = 0.041). The meta-analysis suggests that XRCC1 R399Q polymorphism was significantly associated with increased risk of normal tissue injury after radiotherapy in breast cancer patients, and XRCC1 R399Q polymorphism is a genetic marker of normal tissue injury after radiotherapy in breast cancer patients.

To report the prospective efficacy of 45 patients intracranial germinoma treated by radiotherapy and discuss its treatment.From February 1998 to October 2007, a total of 45 intracranial germinoma patients were performed radiotherapy, including 15 combined chemotherapy in the Department of Oncology. Of them 23 were pathologically diagnosed while 22 cases were clinical diagnosed. Life table method showed the 5-year and 10-year survival rate.Forty patients were followed-up. Most symptoms of the patients were significantly reduced or disappeared completely. The 5-year and 10-year survival rate of all patients were 84% and 74%.Radiotherapy is the main treatment for intracranial germinoma. Craniospinal irradiation, whole brain irradiation and partial brain irradiation are the main treatments. Radiotherapy combined with chemotherapy, which can reduce the radiation range and dose will be the trend.

In this work, the Eshelby tensor of a finite spherical domain is employed to construct an interphase model to evaluate elastic properties of concrete composites. Explicit formulations of the interphase model via multi-inclusion method for a class of concrete composites are derived. The theoretical estimate based on an improved Hashin–Shtrikman bounds for the Young’s modulus of two-phase concrete composite material are used as a comparison result in the analysis, and the influence of the interfacial transition zone (ITZ) on elastic properties of three-phase concrete composite is studied. Moreover, the homogenization results predicted by the proposed interphase model are compared with the published experimental data. Results obtained in this work show that the proposed interphase model can provide a very accurate estimate of the effective elastic properties of complex concrete composite materials.