Engineering stem cell niches in bioreactors

Stem cells, including embryonic stem cells, induced pluripotent stem cells, mesenchymal stem cells and amniotic fluid stem cells have the potential to be expanded and differentiated into various cell types in the body.Efficient differentiation of stem cells with the desired tissue-specific function is critical for stem cell-based cell therapy, tissue engineering, drug discovery and disease modeling. Bioreactors provide a great platform to regulate the stem cell microenvironment, known as "niches",to impact stem cell fate decision. The niche factors include the regulatory factors such as oxygen, extracellular matrix(synthetic and decellularized), paracrine/autocrine signaling and physical forces(i.e., mechanical force, electrical force and flow shear). The use of novel bioreactors with precise control and recapitulation of niche factors through modulating reactor operation parameters can enable efficient stem cell expansion and differentiation. Recently, the development of microfluidic devices and microbioreactors also provides powerful tools to manipulate the stem cell microenvironment by adjusting flow rate and cytokine gradients. In general,bioreactor engineering can be used to better modulate stem cell niches critical for stem cell expansion, differentiation and applications as novel cell-based biomedicines. This paper reviews important factors that can be more precisely controlled in bioreactors and their effects on stem cell engineering.

Adaptive base-isolation of civil structures using variable amplification

Semi-active dampers are used in base-isolation to reduce the seismic response of civil engineering structures. In the present study, a new semi-active damping system using variable amplification will be investigated for adaptive baseisolation. It uses a novel variable amplification device （VAD） connected in series with a passive damper. The VAD is capable of producing multiple amplification factors, each corresponding to a different amplification state. Forces from the damper are amplified to the structure according to the current amplification state, which is selected via a semi-active control algorithm specifically tailored to the system＇s tmique damping characteristics. To demonstrate the effectiveness of the VAD-damper system for adaptive base-isolation, numerical simulations are conducted for three and seven-story base-isolated buildings subject to both far and near-field ground motions. The results indicate that the system can achieve significant reductions in response compared to the base-isolated buildings with no damper. The proposed system is also found to perform well compared to a typical semi-active damper.

A review of flexible halide perovskite solar cells towards scalable manufacturing and environmental sustainability

The perovskite material has many superb qualities which allow for its remarkable success as solar cells;flexibility is an emerging field for this technology.To encourage commercialization of flexible perovskite solar cells,two main areas are of focus:mitigation of stability issues and adaptation of production to flexible substrates.An in-depth report on stability concerns and solutions follows with a focus on Ruddlesden-Popper perovskites.Roll to roll processing of devices is desired to further reduce costs,so a review of flexible devices and their production methods follows as well.The final focus is on the sustainability of perovskite solar cell devices where recycling methods and holistic environmental impacts of devices are done.

Calibration and Evaluation of Link Congestion Functions: Applying Intrinsic Sensitivity of Link Speed as a Practical Consideration to Heterogeneous Facility Types within Urban Network

This paper explores the use of archived data to calibrate volume delay functions (VDFs) and updates their input parameters (capacity and free-flow speed) for planning applications. The sensitivity analysis of speed to change in congestion level is performed to capture functional characteristics of VDFs in modeling specific facility types. Different sensitivity characteristics shown by the VDFs indicate that each function is suitable to a particular facility type. The results of sensitivity analysis are confirmed by the root mean square percent error (RMSPE) values calculated using the Orlando Urban Area Transportation Study (OUATS) model results and observed data. The modified Davidson’s function exhibits remarkable performance in nearly all facility types. The strength of the modified Davidson’s function across a broad range of facilities can be attributed to the flexibility of its tuning parameter, μ. Fitted Bureau of Public Road (BPR) and conical delay functions show lower RMSPE for uninterrupted flow facilities (freeways/expressways, managed lanes) and higher values for toll roads (which might have partial interruptions due to toll booths) and signalized arterials. Akcelik function underperforms on freeways/expressways and managed lanes but shows some improvements for toll roads and superior results for the signalized arterials. This was a desired strength of Akcelik function when modeling link travel speed on facilities where stopped delays were encountered.

加强高校内部学术交流的方法及制度研究——以佛罗里达州立大学为例

随着社会的发展,科研生产力已经成为高校发展的核心竞争力,学术交流的地位也日益凸显。目前各高校的学术交流主要有高校内部学术交流和高校外部学术交流,两者相比之下,高校内部学术交流相对薄弱些。论文通过对佛罗里达州立大学(FSU)学术交流的深入研究,结合国内高校学术交流的现状,提出了加强我国高校内部学术交流的方法及相关制度,主要包括:举行实验室开放日活动,以培养学生的多学科视野和综合素质;进行多种形式的汇报展示,给予学生充足的锻炼机会;加强高校内部学科间研讨,以提高师生的科研素养和能力。

Evaluating Traffic Congestion Using the Traffic Occupancy and Speed Distribution Relationship: An Application of Bayesian Dirichlet Process Mixtures of Generalized Linear Model

Accurate classification and prediction of future traffic conditions are essential for developing effective strategies for congestion mitigation on the highway systems. Speed distribution is one of the traffic stream parameters, which has been used to quantify the traffic conditions. Previous studies have shown that multi-modal probability distribution of speeds gives excellent results when simultaneously evaluating congested and free-flow traffic conditions. However, most of these previous analytical studies do not incorporate the influencing factors in characterizing these conditions. This study evaluates the impact of traffic occupancy on the multi-state speed distribution using the Bayesian Dirichlet Process Mixtures of Generalized Linear Models (DPM-GLM). Further, the study estimates the speed cut-point values of traffic states, which separate them into homogeneous groups using Bayesian change-point detection (BCD) technique. The study used 2015 archived one-year traffic data collected on Florida’s Interstate 295 freeway corridor. Information criteria results revealed three traffic states, which were identified as free-flow, transitional flow condition (congestion onset/offset), and the congested condition. The findings of the DPM-GLM indicated that in all estimated states, the traffic speed decreases when traffic occupancy increases. Comparison of the influence of traffic occupancy between traffic states showed that traffic occupancy has more impact on the free-flow and the congested state than on the transitional flow condition. With respect to estimating the threshold speed value, the results of the BCD model revealed promising findings in characterizing levels of traffic congestion.

Preliminary Analyses of Controlled Release of Potassium Permanganate Encapsulated in Polycaprolactone

Potassium permanganate (KMnO4) has been used widely as an oxidant for remediation of contaminated soil and water systems. The present study evaluates the release of this oxidant from Polycaprolactone (PCL) polymer as part of a patented controlled release process (CRP) to be applied for targeted removal of contaminants from water. KMnO4 was encapsulated into PCL at a 1:5 oxidant to polymer ratio and placed in batch reactor systems with reagent water to be evaluated over a 96 hour period. SEM images showed that over time, the number of cavities and their sizes increased on the waxy surface of the PCL polymer. The experimental data from the release of KMnO4 from PCL was found to fit non-Fickian diffusion model after dissolution (R2 = 0.93) similar to other systems that describe the dispersal of other oxidants from wax matrices. In addition, the model parameters for data of this present study were also found to be comparable to previous release studies with the same oxidant encapsulated in different wax matrices at similar ratios. Overall, the similarity of release data between the diversity of polymers shows that the controlled release biodegradable polymer utilizing PCL provides effective release of the KMnO4 with the added benefit biodegradable nature of PCL.

Iron Reduction and Adsorption on Shewanella Putrefaciens nearby Landfills in Northwest Florida

In Northwest Florida, the soil is mainly covered by poorly drained sandy soil of Myakka, which is characterized by a subsurface accumulation of humus and AI and Fe oxides. When organic rich landfill leachate is leaked to the iron rich soils, ferrous iron is released with the oxidation of organic compounds in the leachate. In this research, we investigated the activities of S. putrefaciens in reducing iron oxide in the iron rich soil of Northwest Florida with landfill leachate serving as the carbon source. S. putrefaciens had similar maximum specific growth rate and half saturation coefficients for all the leachate and soil samples. The average maximum specific growth rate was 0.008 hr^-1 and the average half saturation coefficient was 243.8 mg/L. Averagely, 2.2 mg ferrous iron was generated per mg COD consumed. In addition, adsorption of reduced ferrous iron on S. putrefaciens was further characterized. Ferrous iron adsorption on S. putrefaciens was a kinetic process, which increased with the increase of the reaction time. Equilibrium ferrous iron adsorption on S. putrefaciens can be reached after three hours. Ferrous iron had linear adsorption isotherms on S. putrefaciens for the pH range of 5 to 9.

Neural differentiation from pluripotent stem cells:The role of natural and synthetic extracellular matrix

Neural cells differentiated from pluripotent stem cells(PSCs), including both embryonic stem cells and induced pluripotent stem cells, provide a powerful tool for drug screening, disease modeling and regenerative medicine. High-purity oligodendrocyte progenitor cells(OPCs) and neural progenitor cells(NPCs) have been derived from PSCs recently due to the advancements in understanding the developmental signaling pathways. Extracellular matrices(ECM) have been shown to play important roles in regulating the survival, proliferation, and differentiation of neural cells. To improve the function and maturation of the derived neural cells from PSCs, understanding the effects of ECM over the course of neural differentiation of PSCs is critical. During neural differentiation of PSCs, the cells are sensitive to the properties of natural or synthetic ECMs, including biochemical composition, biomechanical properties, and structural/topographical features. This review summarizes recent advances in neural differentiation of humanPSCs into OPCs and NPCs, focusing on the role of ECM in modulating the composition and function of the differentiated cells. Especially, the importance of using three-dimensional ECM scaffolds to simulate the in vivo microenvironment for neural differentiation of PSCs is highlighted. Future perspectives including the immediate applications of PSC-derived neural cells in drug screening and disease modeling are also discussed.

A Review of the Current Status of Bamboo Usage with Special Emphasis on Orthopedic Rehabilitation

It was found that bamboo has been extensively used as infrastructure material in Asia and Africa due to its exceptional properties. Its usage has ranged from simple fence construction to bridges. Bamboo, as a biodegradable and renewable material, has been used for construction purposes. Both the natural and engineered form of the Bamboo has become a center of focus for most research scientists, materials experts and most important research and development aspects of Industries. The physical and mechanical properties of Bamboo culm in its dry and green state have shown promising prospects and this has further established the need to put together a regulatory body that will help to monitor and create standards for testing and utilizing Bamboo. This paper considered the various applications of Bamboo culm both in the past and present. An area the authors considered in this paper is the use of Bamboo in orthopedics. The number of people with gait dysfunction is fast growing due to population growth, war, ageing and accidents. The cost of orthopedic devices essential to restore function and improve quality of life is not affordable for many. Earlier research in this area suggests that bamboo is a suitable material for orthopedic appliances, especially exoskeleton. Bamboo use in applications such as orthopedic rehabilitation is common in developing countries where traditional bonesetters (TBS) use splints to treat fracture. In spite of the innovative discovery made by researchers in the use of Bamboo, standardization is a major challenge especially in orthopedic application. The focus of our work revealed varieties of Bamboo application.

Design and optimization of CSP power plants for Pakistan:a comparative study

Despite having very high solar irradiance,Pakistan still does not have any installed concentrated solar power(CSP)plant.Several studies have shown that multiple locations within the country are suitable for CSP plants,but there is limited availability of comprehensive comparative studies.Therefore,this article presents a comparative analysis of different CSP technologies in Pakistan,focusing on their potential to address the country’s energy crisis.The study evaluates the pros and cons of different CSP technologies at various locations through site assessment,modelling,optimization and economic analysis using the System Advisor Model.Quetta and Nawabshah were selected as the locations for modelling multiple scenarios of 100-MW plants,using central receiver systems,parabolic trough collectors and linear Fresnel reflectors.The plants were integrated with thermal energy storage and the storage capacity was optimized using parametric analysis.The results showed that a central receiver system for the location of Quetta was the most favourable option,with an annual energy yield of 622 GWh at 7.44 cents/kWh,followed by a central receiver system for Nawabshah(608 GWh,9.03 cents/kWh).This study is the first to show that switching between line-concentrated and point-concentrated CSP technologies can open new opportunities for sites in Pakistan with relatively high solar resources,resulting in a 21.3%reduction in the levelized cost.

Contributions of adsorption, bioreduction and desorption to uranium immobilization by extracellular polymeric substances

Hexavalent uranium(U(VI))can be immobilized by various microbes.The role of extracellular polymeric substances(EPS)in U(VI)immobilization has not been quantified.This work provides a model framework to quantify the contributions of three processes involved in EPS-mediated U(VI)immobilization:adsorption,bioreduction and desorption.Loosely associated EPS was extracted from a pure bacterial strain,Klebsiella sp.J1,and then exposed to H_(2) and O_(2)(no bioreduction control)to immobilize U(VI)in batch experiments.U(VI)immobilization was faster when exposed to H_(2) than O_(2) and stabilized at 94%for H_(2) and 85%for O_(2),respectively.The non-equilibrium data from the H_(2) experiments were best simulated by a kinetic model consisting of pseudo-second-order adsorption(ka=2.87×10^(−3) g EPS·(mg U)^(−1)·min^(−1)),first-order bioreduction(kb=0.112 min−1)and first-order desorption(kd=7.00×10^(−3) min^(−1))and fitted the experimental data with R^(2) of 0.999.While adsorption was dominant in the first minute of the experiments with H_(2),bioreduction was dominant from the second minute to the 50th min.After 50 min,adsorption was negligible,and bioreduction was balanced by desorption.This work also provides the first set of equilibrium data for U(VI)adsorption by EPS alone.The equilibrium experiments with O_(2) were well simulated by both the Langmuir isotherm and the Freundlich isotherm,suggesting multiple mechanisms involved in the interactions between U(VI)and EPS.The thermodynamic study indicated that the adsorption of U(VI)onto EPS was endothermic,spontaneous and favorable at higher temperatures.

Upscaling human mesenchymal stromal cell production in a novel vertical-wheel bioreactor enhances extracellular vesicle secretion and cargo profile

Human mesenchymal stromal cells(hMSCs)are mechanically sensitive undergoing phenotypic alterations when subjected to shear stress,cell aggregation,and substrate changes encountered in 3D dynamic bioreactor cultures.However,little is known about how bioreactor microenvironment affects the secretion and cargo profiles of hMSC-derived extracellular vesicles(EVs)including the subset,“exosomes”,which contain therapeutic proteins,nucleic acids,and lipids from the parent cells.In this study,bone marrow-derived hMSCs were expanded on 3D Synthemax II microcarriers in the PBS mini 0.1L Vertical-Wheel bioreactor system under variable shear stress levels at 25,40,and 64 RPM(0.1-0.3 dyn/cm^(2)).The bioreactor system promotes EV secretion from hMSCs by 2.5-fold and upregulates the expression of EV biogenesis markers and glycolysis genes compared to the static 2D culture.The microRNA cargo was also altered in the EVs from bioreactor culture including the upregulation of miR-10,19a,19b,21,132,and 377.EV protein cargo was characterized by proteomics analysis,showing upregulation of metabolic,autophagy and ROS-related proteins comparing with 2D cultured EVs.In addition,the scalability of the Vertical-Wheel bioreactor system was demonstrated in a 0.5L bioreactor,showing similar or better hMSC-EV secretion and cargo content compared to the 0.1L bioreactor.This study advances our understanding of bio-manufacturing of stem cell-derived EVs for applications in cell-free therapy towards treating neurological disorders such as ischemic stroke,Alzheimer’s disease,and multiple sclerosis.

Suppression of discontinuous precipitation and strength improvement by Sc doping in Cu-6 wt%Ag alloys

In low-Ag Cu matrix alloys,the presence of coarse discontinuous precipitates may limit strength.We demonstrated that discontinuous precipitation was suppressed,and continuous precipitation was en-hanced by the doping of Cu-6 wt%Ag with Sc.A high-volume fraction of continuous precipitates,which nucleated on{111}planes,led to a 55 MPa increase in strength,with only a slight decrease in electri-cal conductivity.The addition of Sc inhibited the nucleation of discontinuous precipitates by causing the Sc and the Ag to co-segregate onto grain boundaries,thus forming a thin intermetallic compound layer between grains.After deformation,both discontinuous and continuous precipitates were drawn into Ag fibers.The combination of deformation strain and doping caused an increase in density and a decrease in the diameter of Ag fibers,resulting in about 205 MPa increase in doped samples when the deformation strain reached 4.9.The thinner,denser Ag fibers in the doped samples also caused higher electron scatter-ing at interfaces,leading to electrical conductivity that was 11%IACS lower than in non-doped samples.For reference,100%IACS(International Annealed Copper Standard)is equivalent to 1.7241μΩcm.

Incorporating travel time reliability in predicting the likelihood of severe crashes on arterial highways using non-parametric random-effect regression

Travel time reliability(TTR) modeling has gain attention among researchers’ due to its ability to represent road user satisfaction as well as providing a predictability of a trip travel time.Despite this significant effort,its impact on the severity of a crash is not well explored.This study analyzes the effect of TTR and other variables on the probability of the crash severity occurring on arterial roads.To address the unobserved heterogeneity problem,two random-effect regressions were applied;the Dirichlet random-effect(DRE)and the traditional random-effect(TRE) logistic regression.The difference between the two models is that the random-effect in the DRE is non-parametrically specified while in the TRE model is parametrically specified.The Markov Chain Monte Carlo simulations were adopted to infer the parameters’ posterior distributions of the two developed models.Using four-year police-reported crash data and travel speeds from Northeast Florida,the analysis of goodness-of-fit found the DRE model to best fit the data.Hence,it was used in studying the influence of TTR and other variables on crash severity.The DRE model findings suggest that TTR is statistically significant,at 95 percent credible intervals,influencing the severity level of a crash.A unit increases in TTR reduces the likelihood of a severe crash occurrence by 25 percent.Moreover,among the significant variables,alcohol/drug impairment was found to have the highest impact in influencing the occurrence of severe crashes.Other significant factors included traffic volume,weekends,speed,work-zone,land use,visibility,seatbelt usage,segment length,undivided/divided highway,and age.

Polymer-based thermoelectric materials:A review of power factor improving strategies

Thermoelectric(TE)materials are receiving increasing attention due to their ability to directly converting heat to electricity.They are used to harvest electrical energy from the wasted heat in order to increase the efficiency of global energy.Polymer-based TE materials are particularly fascinating to wearable and mobile devices due to their low density,good flexibility,and low toxicity.This review summarizes the recent breakthroughs and optimization strategies of polymer-based TE materials.Among a large number of different organic TE materials,those with remarkable TE performance are selected and divided into three categories,which are poly(3,4-ethylenedioxythiophene)derivatives,carbon nanotube/conductive polymer composites,and inorganic semiconductive nanomaterial/polymer composites.The effect of components and structures on the power factor are presented and discussed.Finally,some challenges are described and suggestions are provided for preparing the next-generation of polymer-based materials with high TE performance.

Assessment of traffic performance measures and safety based on driver age and experience:A microsimulation based analysis for an unsignalized T-intersection

Traffic safety and performance measures such as crash risk and queue lengths or travel times are influenced by several important factors including those related to environment,human,and roadway design,especially at intersections.Previous research has studied different aspects related to these factors,yet these characteristics are not fully investigated with a focus on age and experience of drivers.In this paper,we investigate this issue by using a two-phase approach via a case study application on a critical T-intersection in the City of Tallahassee,Florida.The first phase includes a scenario-based microsimulation analysis through the use of a microscopic simulation software,namely VISSIM,to illustrate the variations in traffic performance measures with respect to driver compositions of different age groups in the traffic stream.A variety of scenarios is created where the driving characteristics are provided as inputs to these scenarios in terms of decision making and risk taking.This is also supported by a sensitivity analysis conducted based on the driver composition in the traffic.The second phase includes the analysis of microsimulation outputs via a tool developed by Federal Highway Administration tool,namely the Surrogate Safety Assessment Model(SSAM),in order to determine the traffic conflicts that occur in each scenario.These conflicts are also compared with real-life crash data for validation purposes.Results show that(a) the differences in risk perception that affect driving behavior might be significant in influencing traffic safety and performance measures,and(b) the proposed approach is considerably successful in simulating the actual crash conflict points.

Effectiveness of dicyandiamide as a nitrification inhibitor in biochar-amended soil

Overuse of nitrogen(N) fertilizers may lead to many environmental issues via N leaching into groundwater and agricultural runoff into surface water.Biochar, a sustainable soil amendment agent, has been widely studied because of its potential to retain moisture and nutrients. However, recent studies have shown that biochar has a very limited ability to improve the retention of negatively charged nitrite(NO2-) or nitrate(NO3-). Although positively charged ammonium(NH4+) can be better held by biochar, it is usually susceptible to nitrification and can be easily transformed into highly mobile NO2- and/or NO3-.In practice, dicyandiamide(DCD) has been used to inhibit nitrification, preserving N in its relatively immobile form as NH4+. Therefore, it is likely that the effects of DCD and biochar in soils would be synergistic. In this study, the influences of biochar on the effectiveness of DCD as a nitrification inhibitor in a biochar-amended soil were investigated by combining the experimental results of incubation, adsorption isotherm, and column transport with the simulated results of different mathematical models. Biochar was found to stimulate the degradation of DCD, as the maximum degradation rate slightly increased from 1.237 to 1.276 mg kg-1 d-1 but the half-saturation coefficient significantly increased from 5.766 to 9.834 mg kg-1. Considering the fact that the availability of DCD for nitrification inhibition was continuously decreasing because of its degradation, a novel model assuming non-competitive inhibition was developed to simulate nitrification in the presence of a decreasing amount of DCD. Depending on the environmental conditions, if the degradation of DCD and NH4+ in biochar-amended soil is not significant, improved contact due to the mitigated spatial separation between NH4+and DCD could possibly enhance the effectiveness of DCD.

Tailored morphology and highly enhanced phonon transport in polymer fibers:a multiscale computational framework

Although tremendous efforts have been devoted to enhance thermal conductivity in polymer fibers,correlation between the thermal-drawing conditions and the resulting chain alignment,crystallinity,and phonon transport properties have remained obscure.Using a carefully trained coarse-grained force field,we systematically interrogate the thermal-drawing conditions of bulk polyethylene samples using large-scale molecular dynamics simulations.An optimal combination of moderate drawing temperature and strain rate is found to achieve highest degrees of chain alignment,crystallinity,and the resulting thermal conductivity.Such combination is rationalized by competing effects in viscoelastic relaxation and condensed to the Deborah number,a predictive metric for the thermal-drawing protocols,showing a delicate balance between stress localizations and chain diffusions.Upon tensile deformation,the thermal conductivity of amorphous polyethylene is enhanced to 80% of the theoretical limit,that is,its pure crystalline counterpart.An effective-medium-theory model,based on the serial-parallel heat conducting nature of semicrystalline polymers,is developed here to predict the impacts from both chain alignment and crystallinity on thermal conductivity.The enhancement in thermal conductivity is mainly attributed to the increases in the intrinsic phonon mean free path and the longitudinal group velocity.This work provides fundamental insights into the polymer thermal-drawing process and establishes a complete process–structure–property relationship for enhanced phonon transport in all-organic electronic devices and efficiency of polymeric heat dissipaters.

Determination of growth kinetics of microorganisms linked with 1,4-dioxane degradation in a consortium based on two improved methods

The conventional method for determining growth kinetics of microbial consortia relies on the total biomass concentration.This may be inaccurate for substrates that are uncommon in nature and can only be degraded by a small portion of the microbial community.1,4-dioxane,an emerging contaminant,is an example of such substrates.In this work,we evaluated an improved method for determining the growth kinetics of a 1,4-dioxane-degrading microbial consortium.In the improved method,we considered only bacterial taxa whose concentration increase correlated to 1,4-dioxane concentration decrease in duplicate microcosm tests.Using PEST(Parameter Estimation),a modelindependent parameter estimator,the kinetic constants were estimated by fitting the Monod kineticsbased simulation results to the experimental data that consisted of the concentrations of 1,4-dioxane and the considered bacterial taxa.The estimated kinetic constants were evaluated by comparing the simulation results with experimental results from another set of microcosm tests.The evaluation was quantified by the sum of squared relative residual,which was four orders of magnitude lower for the improved method than the conventional method.By further dividing the considered bacterial taxa into oligotrophs and copiotrophs,the sum of squared relative residual further decreased.