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Minimizing platinum (Pt) loading while reserving high reaction efficiency in the catalyst layer (CL) has been confirmed as one of the key issues in improving the performance and application of proton exchange membrane fuel cells (PEMFCs). To enhance the reaction efficiency of Pt catalyst in CL, the interfacial interactions in the three-phase interface, i.e., carbon, Pt, and ionomer should be first clarified. In this study, a molecular model containing carbon, Pt, and ionomer compositions is built and the radial distribution functions (RDFs), diffusion coefficient, water cluster morphology, and thermal conductivity are investigated after the equilibrium molecular dynamics (MD) and nonequilibrium MD simulations. The results indicate that increasing water content improves water aggregation and cluster interconnection, both of which benefit the transport of oxygen and proton in the CL. The growing amount of ionomer promotes proton transport but generates additional resistance to oxygen. Both the increase of water and ionomer improve the thermal conductivity of the C. The above-mentioned findings are expected to help design catalyst layers with optimized Pt content and enhanced reaction efficiency, and further improve the performance of PEMFCs.

The traditional sound absorption problem has not been completely resolved over the last 200 years. At every stage, its research has changed depending on practical requirements and current technologies. Phononic crystals (PCs) and acoustic metamaterials (AMs) have gained attention because of their extensive investigation and development over the past 30 years. Especially, the use of these materials brings new vitality into the traditional sound absorption problem to figure out broad working band and low-frequency absorption. This review highlights recent progress in sound absorption-from airborne to waterborne absorption-and gradient-index AMs. Progress in gradient-index AMs is singled out because of their favorable impedance matching, good viscous and thermal dissipation, and lengthened propagation paths compared with those of other materials. The progress in sound absorption of PCs and AMs is promising to serve as the next-generation sound absorbing materials, trap and reuse acoustic energy, and attenuate earthquake/tsunami wave in the future., (Copyright © 2020 The Author(s). Published by Elsevier Inc. All rights reserved.)

Water slip at solid surfaces is important for a wide range of micro-/nanofluidic applications. While it is known that water slip behavior depends on surface functionalization, how it impacts the molecular level dynamics and mass transport at the interface is still not thoroughly understood. In this paper, we use nonequilibrium molecular dynamics simulations to investigate the slip behavior of water confined between gold surfaces functionalized by self-assembled monolayer (SAM) molecules with different polar functional groups. We observe a positive-to-negative slip transition from hydrophobic to hydrophilic SAM functionalizations, which is found to be related to the stronger interfacial interaction between water molecules and more hydrophilic SAM molecules. The stronger interaction increases the surface friction and local viscosity, making water slip more difficult. More hydrophilic functionalization also slows down the interfacial water relaxation and leads to more pronounced water trapping inside the SAM layer, both of which impede water slip. The results from this work will provide useful insights into the understanding of the water slip at functionalized surfaces and design guidelines for various applications.

Nucleic acid lateral flow assays (NALFAs) have attracted much attention due to their rapid, robust, simple, and cost-effective features. However, the current NALFAs are still limited by low sensitivity because of the poor understanding and control of the underlying complex flow and reaction processes. Although enormous efforts have been devoted to enhancing detection sensitivity of NALFAs, developing simple NALFAs with high sensitivity remains difficult. Thus, we proposed a novel physical-chemical coupling method using dissoluble saline barriers and developed the corresponding mathematical model to better understand the underlying processes to enhance the NALFA sensitivity. Through optimizing the design parameters (e.g., saline barriers patterns, volume, and concentrations) experimentally and numerically, we achieved the highest 10-fold sensitivity enhancement for detection of nucleic acids (including HBV, Staphylococcus aureus, and salmonella as model targets) using this method. The physical-chemical coupling method offers a facile strategy for developing highly sensitive NALFAs.

Microfluidic fluorescence-activated cell sorters (μFACS) have attracted considerable interest because of their ability to identify and separate cells in inexpensive and biosafe ways. Here a high-performance μFACS is presented by integrating a standing surface acoustic wave (SSAW)-based, 3D cell-focusing unit, an in-plane fluorescent detection unit, and an SSAW-based cell-deflection unit on a single chip. Without using sheath flow or precise flow rate control, the SSAW-based cell-focusing technique can focus cells into a single file at a designated position. The tight focusing of cells enables an in-plane-integrated optical detection system to accurately distinguish individual cells of interest. In the acoustic-based cell-deflection unit, a focused interdigital transducer design is utilized to deflect cells from the focused stream within a minimized area, resulting in a high-throughput sorting ability. Each unit is experimentally characterized, respectively, and the integrated SSAW-based FACS is used to sort mammalian cells (HeLa) at different throughputs. A sorting purity of greater than 90% is achieved at a throughput of 2500 events s -1 . The SSAW-based FACS is efficient, fast, biosafe, biocompatible and has a small footprint, making it a competitive alternative to more expensive, bulkier traditional FACS., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Lateral flow assays (LFAs) have attracted considerable attention in biomedical diagnostics. However, it's still challenging to achieve a high detection sensitivity and extensive working range, mainly because the underlying mechanism of complex reaction processes in LFAs remains unclear. Many mathematical models have been developed to analyze the complex reaction processes, which are only qualitative with limited guidance for LFA design. Now, a semi-quantitative convection-diffusion-reaction model is developed by considering the kinetics of renaturation of nucleic acids and the model is validated by our experiments. We established a method to convert the LFA design parameters between the simulation and experiment (i.e., inlet reporter particle concentration, initial capture probe concentration, and association rate constant), with which we achieved a semi-quantitative comparison of the detection limit and working range between simulations and experiments. Based on our model, we have improved the detection sensitivity and working range by using high concentrations of the inlet reporter particles and initial capture probe. Besides, we also found that target nucleic acid sequences with a high association rate constant are beneficial to improve the LFA performance. The developed model can predict the detection limit and working range and would be helpful to optimize the design of LFAs.

Network coding is an effective means to enhance the communication efficiency. The characterization of network solvability is one of the most important topic in this field. However, for general network, the solvability conditions are still a challenge. In this paper, we consider the solvability of general quantum k-pair network in measurement-based framework. For the first time, a detailed account of measurement-based quantum network coding(MB-QNC) is specified systematically. Differing from existing coding schemes, single qubit measurements on a pre-shared graph state are the only allowed coding operations. Since no control operations are concluded, it makes MB-QNC schemes more feasible. Further, the sufficient conditions formulating by eigenvalue equations and stabilizer matrix are presented, which build an unambiguous relation among the solvability and the general network. And this result can also analyze the feasibility of sharing k EPR pairs task in large-scale networks. Finally, in the presence of noise, we analyze the advantage of MB-QNC in contrast to gate-based way. By an instance network [Formula: see text], we show that MB-QNC allows higher error thresholds. Specially, for X error, the error threshold is about 30% higher than 10% in gate-based way. In addition, the specific expressions of fidelity subject to some constraint conditions are given.

Hepatitis B virus (HBV) infection is a serious public health problem, which can be transmitted through various routes (e.g., blood donation) and cause hepatitis, liver cirrhosis and liver cancer. Hence, it is necessary to do diagnostic screening for high-risk HBV patients in these transmission routes. Nowadays, protein-based technologies have been used for HBV testing, which however involve the issues of large sample volume, antibody instability and poor specificity. Nucleic acid hybridization-based lateral flow assay (LFA) holds great potential to address these limitations due to its low-cost, rapid, and simple features, but the poor analytical sensitivity of LFA restricts its application. In this study, we developed a low-cost, simple and easy-to-use method to improve analytical sensitivity by integrating sponge shunt into LFA to decrease the fluid flow rate. The thickness, length and hydrophobicity of the sponge shunt were sequentially optimized, and achieved 10-fold signal enhancement in nucleic acid testing of HBV as compared to the unmodified LFA. The enhancement was further confirmed by using HBV clinical samples, where we achieved the detection limit of 10 3 copies/ml as compared to 10 4 copies/ml in unmodified LFA. The improved LFA holds great potential for diseases diagnostics, food safety control and environment monitoring at point-of-care.

We have previously grafted human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) with blood plasma to treat rat tibia nonunion. To further examine the biological characteristics of this process, we applied an established hUC-MSCs-treated rat nonunion model with the addition of an inhibitor of AKT. SD rats (80) were randomly divided into four groups: a fracture group (positive control); a nonunion group (negative control); a hUC-MSCs grafting with blood plasma group; and a hUC-MSCs grafting with blood plasma & AKT blocker group. The animals were sacrificed under deep anesthesia at 4 and 8 weeks post fracture for analysis. The fracture line became less defined at 4 weeks and disappeared at 8 weeks postoperatively in both the hUC-MSCs grafting with blood plasma and grafting with blood plasma & the AKT blocker, which is similar to the fracture group. Histological immunofluorescence studies showed that the numbers of hUC-MSCs in the calluses were significantly higher in the hUC-MSCs grafting with blood plasma than those in group with the AKT blocker. More bone morphogenetic protein 2 and bone sialoprotein expression and less osteoprotegerin and bone gla protein expression were observed in the AKT blocker group compared to the hUC-MSCs grafting with blood plasma. AKT gene expression in the AKT blocker group was decreased 50% compared to the hUC-MSCs with plasma group and decreased 70% compared to the fracture group, while the elastic modulus was decreased. In summary, our work demonstrates that AKT may play a role in modulating osteogenesis induced by hUC-MSCs.

We evaluated the biological characteristics/effect of human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) grafting with blood plasma on bone regeneration in rat tibia nonunion. SD rats (142) were randomly divided into four groups: fracture group (positive control); nonunion group (negative control); hUC-MSCs grafting with blood plasma group; and hUC-MSCs grafting with saline group. Rats were administered tetracycline (30 mg/kg) and calcein blue (5 mg/kg) 8 days before killing. The animals were killed under deep anesthesia at 4 and 8 weeks post fracture for radiological evaluation and histological/immunohistological studies. The hUC-MSCs grafting with blood plasma group was similar to fracture group: the fracture line blurred in 4 weeks and disappeared in 8 weeks postoperatively. Histological/immunohistological studies showed that hUC-MSCs were of low immunogenicity which merged in rat bone tissue, differentiated into osteogenic lineages, and completed the healing of nonunion. After stem cell transplantation, regardless of whether plasma or saline was used, new multi-center bone formation was observed; fracture site density was better in stem cell grafting with blood plasma group. We, therefore, concluded that the biological characteristics of hUC-MSCs-treated nonunion were different from the standard fracture healing process, and the proliferative and localization capacity of hUC-MSCs might benefit from the use of blood plasma.

Objective: To investigate the clinical effect of MSCs transplantation derived from human umbilical cord on bone nonunion., Methods: From December 2005 to December 2007, 72 patients with traumatic bone nonunion were treated. Auto-iliac bone transplantation was used in 36 patients (group A), including 27 males and 9 females, aging (34.0 +/- 2.1) years; including 18 cases of femoral fracture and 18 cases of tibia fracture; and the time of bone nonunion being (9.1 +/- 1.7) months. Percutaneous MSCs transplantation derived from human umbilical cord was used in 36 patients (group B), including 28 males and 8 females, aging (36.0 +/- 1.6) years; including 18 cases of femoral fracture and 18 cases of tibia fracture; and the time of bone nonunion being (6.4 +/- 1.9) months. There were no statistically significant differences in general data between two groups (P > 0.05). In group A, the site of bone nonunion was filled with relevant auto-iliac bone. In group B, the mixture of 6-8 mL platelet-rich plasma prepared by centrifugalizing venous blood and 1 x (10(6)-10(7)) P5 MSCs extracted from human umbilical cord denoted by volunteers was injected into the region of bone nonunion with 0.2 g demineralized bone powder., Results: Incision healed by first intention in group A. No puncture, deep infection, rejection and general fever reaction occurred in group B. All patients in two groups were followed up for (13.2 +/- 4.6) months. No loosening and breakage of internal fixation were observed in two groups. The motility and function of hip, knee and ankle were good. The time of bone union was (10.3 +/- 2.8) months in group A and (5.6 +/- 0.8) months in groups B, showing significant difference between two groups (P < 0.05)., Conclusion: The percutaneous MSCs transplantation derived from human umbilical cord is more effective on bone nonunion than the traditional treatment, it is easily-to-operate, safe, reliable, and rapid for union. It is one of effective methods in treating bone nonunion.