A multiscale 3D finite element analysis of fluid/solute transport in mechanically loaded bone

The transport of fluid, nutrients, and signaling molecules in the bone lacunar-canalicular system （LCS） is critical for osteocyte survival and function. We have applied the fluorescence recovery after photobleaching （FRAP） approach to quantify load-induced fluid and solute transport in the LCS in situ, but the measurements were limited to cortical regions 30-50 μm underneath the periosteum due to the constrains of laser penetration. With this work, we aimed to expand our understanding of load-induced fluid and solute transport in both trabecular and cortical bone using a multiscaled image-based finite element analysis （FEA） approach. An intact murine tibia was first re-constructed from microCT images into a three-dimensional （3D） linear elastic FEA model, and the matrix deformations at various locations were calculated under axial loading. A segment of the above 3D model was then imported to the biphasic poroelasticity analysis platform （FEBio） to predict load-induced fluid pressure fields, and interstitial solute/fluid flows through LCS in both cortical and trabecular regions. Further, secondary flow effects such as the shear stress and/or drag force acting on osteocytes, the presumed mechano-sensors in bone, were derived using the previously developed ultrastructural model of Brinkman flow in the canaliculi. The material properties assumed in the FEA models were validated against previously obtained strain and FRAP transport data measured on the cortical cortex. Our results demonstrated the feasibility of this computational approach in estimating the fluid flux in the LCS and the cellular stimulation forces （shear and drag forces） for osteocytes in any cortical and trabecular bone locations, allowing further studies of how the activation of osteocytes correlates with in vivo functional bone formation. The study provides a promising platform to reveal potential cellular mechanisms underlying the anabolic power of exercises and physical activities in treating patients with skeletal deficiencies.

Tungsten oxide/nitrogen-doped carbon nanotubes composite catalysts for enhanced redox kinetics in lithium-sulfur batteries

The sluggish redox kinetics of polysulfides in lithium-sulfur(Li-S)batteries are a significant obstacle to their widespread adoption as energy storage devices.However,recent studies have shown that tungsten oxide(WO_(3))can facilitate the conversion kinetics of polysulfides in Li-S batteries.Herein,we fabricated host materials for sulfur using nitrogen-doped carbon nanotubes(N-CNTs)and WO_(3).We used low-cost components and simple procedures to overcome the poor electrical conductivity that is a disadvantage of metal oxides.The composites of WO_(3) and N-CNTs(WO_(3)/N-CNTs)create a stable framework structure,fast ion diffusion channels,and a 3D electron transport network during electrochemical reaction processes.As a result,the WO_(3)/N-CNT-Li2S6 cathode demonstrates high initial capacity(1162 mA·h·g^(-1) at 0.5℃),excellent rate performance(618 mA·h·g^(-1) at 5.5℃),and a low capacity decay rate(0.093%up to 600 cycles at 2℃).This work presents a novel approach for preparing tungsten oxide/carbon composite catalysts that facilitate the redox kinetics of polysulfide conversion.

Regulating the non-effective carriers transport for high-performance lithium metal batteries

The absence of control over carriers transport during electrochemical cycling,accompanied by the deterioration of the solid electrolyte interphase(SEI)and the growth of lithium dendrites,has hindered the development of lithium metal batteries.Herein,a separator complexion consisting of polyacrylonitrile(PAN)nanofiber and MIL-101(Cr)particles prepared by electrospinning is proposed to bind the anions from the electrolyte utilizing abundant effective open metal sites in the MIL-101(Cr)particles to modulate the transport of non-effective carriers.The binding effect of the PANM separator promotes uniform lithium metal deposition and enhances the stability of the SEI layer and long cycling stability of ultra-high nickel layered oxide cathodes.Taking PANM as the Li||NCM96 separator enables high-voltage cycling stability,maintaining 72%capacity retention after 800 cycles at a charging and discharging rate of 0.2 C at a cut-off voltage of 4.5 V and 0°C.Meanwhile,the excellent high-rate performance delivers a specific capacity of 156.3 mA h g^(-1) at 10 C.In addition,outstanding cycling performance is realized from−20 to 60°C.The separator engineering facilitates the electrochemical performance of lithium metal batteries and enlightens a facile and promising strategy to develop fast charge/discharge over a wide range of temperatures.

A Municipal Management Plan for Urban Groundwater Investigation and Remediation

The project MAGPIan, funded by the European Commission under the program LIFE＋2008, aims to develop and implement an optimal strategy for integral groundwater investigation and efficient remediation of key sources of pollution for the whole inner city area. The first investigations included descriptions of the complex hydro-geological system of the eight aquifers, drilling of monitoring wells and set up of the conceptual contaminant model. A conceptual contaminant model was developed to describe the status quo of the present contaminant distribution, as well as the basic processes controlling contaminant migration within the observed aquifers. This included the characterization of redox conditions and natural chlorinated hydrocarbons degradation processes, as well as age dating, forensic interpretations with respect to the contaminant origin, and determination of radioactive and stable isotopes. Further on, a numerical unsteady groundwater flow and contaminant transport model were developed, which enabled a quantitative description of the mass balance within the project area. The unsteady numerical model provided detection of migration paths in the valley of Stuttgart and identification of key sources of pollution.

Origins of three-dimensional charge and two-dimensional phonon transports in Pnma phase PbSnSe_(2)thermoelectric crystal

Recently,PbSnSe_(2)alloy was found to exhibit a large hysteresis effect on transport properties,demonstrating its significant potential for thermoelectric applications.Using ab initio approaches,we studied the carrier transport properties of PbSnSe_(2)crystal,which is a special case of the alloy with the shortest-range order.A peak power factor of 134.2μW cm^(-1)K^(-2)was found along the crossplane direction in the n-type PbSnSe_(2)at a doping concentration of 7×10^(20)cm^(-3)at 700 K.This high power factor originates from delocalized p electrons between intra-plane Pb-Se pairs and between cross-plane Sn-Se pairs that can build up transport channels for conducting electrons,leading to a high electrical conductivity of 5.9×10^(5)S m^(-1).Introducing Pb atoms into Pnma phase SnSe can decrease the phonon group velocities and enhance the phonon-phonon scatterings,leading to a low thermal conductivity of 0.53 W m^(-1)K^(-1)at 700 K along the cross-plane direction.The calculated peak ZT of~3 along the cross-plane direction at an n-type doping concentration of around 5×10^(19)cm^(-3),which represents a theoretical upper limit for an idealized PbSnSe_(2)crystal.This work interprets the origins of three-dimensional charge and two-dimensional phonon transport behavior in PbSnSe_(2)and demonstrates that such crystals are promising high-performance thermoelectric semiconductors.