Rational Design Engineering Research Articles

Cs2CuBr4 perovskite quantum dots confined in mesoporous CuO framework as a p-n type S-scheme heterojunction for efficient CO2 photoconversion

Heterojunction engineering is recognized as a promising strategy to modulate the photocatalytic properties of semiconductors. Herein, lead-free Cs2CuBr4 perovskite quantum dots (PQDs) were confined in a mesoporous CuO framework and a p-n type S-scheme heterojunction of Cs2CuBr4/CuO (CCB/CuO) photocatalyst was fabricated. Experimental characterizations confirmed the effective confinement of the Cs2CuBr4 PQDs in the mesoporous CuO framework, which enabled intimate contact in the interface of CCB/CuO heterojunction, thus facilitating the interfacial charge migration and separation between p-type CuO and n-type Cs2CuBr4. Owing to the outstanding charge transport property and CO2 adsorption capacity, the developed CCB/CuO heterojunction exhibited remarkably enhanced photocatalytic CO2 conversion efficiency with an electron consumption rate (Relectron) of 281.1 µmol g−1 h−1, which was approximately 2.8 times higher than that of pristine Cs2CuBr4. These findings provide some insights into the rational engineering design of lead-free perovskite-based heterostructures for efficient photocatalytic CO2 conversion.

Two-photon excited-state dynamics of mEGFP-linker-mScarlet-I crowding biosensor in controlled environments.

Macromolecular crowding affects many cellular processes such as diffusion, biochemical reaction kinetics, protein-protein interactions, and protein folding. Mapping the heterogeneous, dynamic crowding in living cells or tissues requires genetically encoded, site-specific, crowding sensors that are compatible with quantitative, noninvasive fluorescence micro-spectroscopy. Here, we carried out time-resolved 2P-fluorescence measurements of a new mEGFP-linker-mScarlet-I macromolecular crowding construct (GE2.3) to characterize its environmental sensitivity in biomimetic crowded solutions (Ficoll-70, 0-300 g L-1) via Förster resonance energy transfer (FRET) analysis. The 2P-fluorescence lifetime of the donor (mEGFP) was measured under magic-angle polarization, in the presence (intact) and absence (enzymatically cleaved) of the acceptor (mScarlet-I), as a function of the Ficoll-70 concentration. The FRET efficiency was used to quantify the sensitivity of GE2.3 to macromolecular crowding and to determine the environmental dependence of the mEGFP-mScarlet-I distance. We also carried out time-resolved 2P-fluorescence depolarization anisotropy to examine both macromolecular crowding and linker flexibility effects on GE2.3 rotational dynamics within the context of the Stokes-Einstein model as compared with theoretical predictions based on its molecular weight. These time-resolved 2P-fluorescence depolarization measurements and conformational population analyses of GE2.3 were also used to estimate the free energy gain upon the structural collapse in crowded environment. Our results further the development of a rational engineering design for bioenvironmental sensors without the interference of cellular autofluorescence. Additionally, these results in well-defined environments will inform our future in vivo studies of genetically encoded GE2.3 towards the mapping of the crowded intracellular environment under different physiological conditions.

Time-resolved two-photon fluorescence dynamics of a novel mEGFP-linker-mScarlet-I crowding biosensor.

Laser-induced two-photon (2P) fluorescence microscopy is routinely used as a noninvasive, quantitative methodology for a wide range of cell and tissue studies due to its enhanced penetration depth, reduced laser scattering, and minimum extended photobleaching. Macromolecular crowding affects many cellular processes such as diffusion, biochemical reaction kinetics, protein-protein interactions, and protein folding. Here, we carried out time-resolved 2P fluorescence measurements of a novel mEGFP-linker-mScarlet-I macromolecular crowding construct (GE2.3) to characterize its environmental sensitivity in biomimetic crowded solutions (Ficoll-70, 0-300 g/L) using Förster resonance energy transfer (FRET) analysis. For these studies, the excited-state 2P-fluorescence dynamics of the donor (mEGFP) were investigated in the presence (intact) and absence (enzymatically cleaved) of the acceptor (mScarlet-I). In addition, time-resolved 2P-fluorescence measurements of intact GE2.3 were used to determine the corresponding equilibrium constant and the Gibbs free energy associated with the structural conformation equilibrium in response to environmental crowding. We further carried out time-resolved 2P-fluorescence depolarization anisotropy to examine both the macromolecular crowding and the linker flexibility effects on GE2.3 rotational dynamics within the context of Stokes-Einstein model as compared with theoretical predictions based on its molecular weight. Our results further the development of a rational engineering design of bioenvironmental sensors. Additionally, these results in well-defined environments will inform our future in vivo studies of genetically encoded GE2.3 towards the mapping of crowded intracellular environment under different physiological conditions. Importantly, this GE2.3 sensor allows for minimal interference of the intrinsic cellular autofluorescence with the FRET analysis and crowding studies.

Cemented Paste Backfill Hydraulic Conductivity Evolution from 30 Minutes to 1 Week

AbstractThe first one to four days constitutes a critical period in filling mining voids with cemented paste backfill (CPB, a mixture of mine tailings, binder, and water) and determining the saturated hydraulic conductivity (ksat) during this period is important to rational engineering design. However, most published studies started testing 24 h after specimen preparation, and those that started earlier did so by preconsolidating the specimens, which results in void ratios lower than those occurring in the field. This study uses a new test method that retains the backfill’s representative bulk properties and starts testing about one-half hour after specimen preparation. During backfilling, CPB undergoes three distinct ksat stages: a relatively constant high-value ksat stage associated with the portland cement’s (PC’s) dissolution phase; a rapidly declining ksat stage associated with PC’s acceleration phase; and then a slowly declining ksat stage associated with PC’s steady-stage and subsequent deceleration phase. The last two stages can be represented by modified Kozeny-Carman equations, in which the hydration effects are constant but different in each stage, and the ksat changes can be related to void ratio changes in each stage. In contrast, the distinct stages are not adequately represented by traditional PC “maturity” models, and, more importantly, the ksat values determined here are at least an order of magnitude higher than previously published results on similar materials.

Metabolic flux simulation of microbial systems based on optimal planning algorithms

The genomic scale metabolic networks of the microorganisms can be constructed based on their genome sequences, functional annotations, and biochemical reactions, reflecting almost all of the metabolic functions. Mathematical simulations of metabolic fluxes could make these functions be visualized, thereby providing guidance for rational engineering design and experimental operations. This review summarized recently developed flux simulation algorithms of microbial systems. For the single microbial systems, the optimal planning algorithm has low complexity because there is no interaction between microorganisms, and it can quickly simulate the stable metabolic states through the pseudo-steady hypothesis. Besides, the experimental conditions of single microbial systems are easier to reach or close to the optimal states of simulation, compared with polymicrobial systems. The polymicrobial culture systems could outcompete the single microbial systems as they could relieve metabolic pressure through metabolic division, resource exchange, and complex substrate co-utilization. Besides, they provide varieties of intracellular production environments, which render them the potential to achieve efficient bioproduct synthesis. However, due to the quasi-steady hypothesis that restricts the simulation of the dynamic processes of microbial interactions and the algorithm complexity, there are few researches on simulation algorithms of polymicrobial metabolic fluxes. Therefore, this review also analyzed and combed the microbial interactions based on the commonly used hypothesis of maximizing growth rates, and studied the strategies of coupling interactions with optimal planning simulations for metabolism. Finally, this review provided new insights into the genomic scale metabolic flux simulations of polymicrobial systems.

Monodisperse perovskite CoSn(OH)6 in-situ grown on NiCo hydroxide nanoflowers with strong interfacial bonds to boost broadband visible-light-driven photocatalytic CO2 reduction

Heterojunction engineering is a very prospective approach to modulate the photocatalytic behaviors of semiconductors. Herein, Venus flytrap-like NiCo hydroxide nanoflowers (HNF) with surface modification by different contents of CoSn(OH)6 were fabricated in situ for the first time. Interestingly, CoSn(OH)6 nanocubes (NC) are monodispersed on the nanosheet surface of NiCo HNF. Experimental characterizations and theoretical calculations comprehensively demonstrate the surface Sn atoms of CoSn(OH)6 are effectively embedded into the NiCo HNF interlayers, and co-sharing of the hydroxyl enables intimate contact in the heterointerface of NiCo HNF/CoSn(OH)6 hybrids and thereby largely shortens the charge migrating distance, contributing to an efficient interfacial charge migration and promoting charge separation. The optimized NiCo HNF/CoSn(OH)6 exhibits the remarkably enhanced photocatalytic efficiency for CO2 reduction with a TON of 601.2 and the CO and CH4 yield is about 3 folds that over CoSn(OH)6 NC. DRIFTS reveals the reaction intermediates in the CO2 photocatalytic process and proposes a possible mechanism for photocatalytic CO2 reaction. These findings may pave the way for rational engineering design of non-precious highly-dispersed broadband visible-light-driven CO2 reduction heterostructure catalysts.

Required Plug Strength for Continuously Poured Cemented Paste Backfill in Longhole Stopes

Continuously poured paste backfill dramatically improves underground mining efficiency through reduced stope cycle time and simplified logistics. For longhole stopes, a backfill “plug” is poured to a few meters above the undercut brow and must gain sufficient strength to prevent failure through the plug when the “main” pour begins. A novel, rational engineering design approach that determines the required plug strength is developed. The potential failure mechanism during continuous pouring is identified and the theoretical solution and its numerical validation/calibration are discussed. Four field case histories are then used, three of them involving continuous pours, to demonstrate the theoretical solution’s validity in back-analysis. These case studies are unique in the extent and quality of total stress and water pressure measurements made throughout backfilling. Additionally, comprehensive laboratory data are available to characterize strength development during binder hydration in the first few days, which are critical to the back-analyses. Results indicate that continuous backfilling is feasible with reasonably attainable backfill strengths at most mines. However, mines must undertake comprehensive early strength laboratory testing, and must carry out field measurements during the pour to ensure the placed backfill behaviour is consistent with the analysis assumptions.

An industrially applied biocatalyst: 2-Deoxy-d-ribose-5- phosphate aldolase

Abstract 2-Deoxy- d -ribose-5-phosphate aldolase (DERA) belongs to the family of lyases and can form C–C bonds to generate multiple chiral centers, thus providing an interesting route to produce key chiral compounds. However, several problems, such as low activity and poor stability (poor tolerance to high aldehyde concentrations), limit the practical application of DERA in large-scale production. Many approaches have been introduced to address these issues. Specifically, in the last decade, many new DERAs, with high catalytic activity or excellent aldehyde tolerance, have been cloned from various extremophilic microorganisms. In addition, on the basis of the analysis of the catalytic mechanism of DERA, rational design engineering and computational design have been used to reconstruct DERA enzymes to alter their stability and catalytic activity.

Production of Oil in Plant Vegetative Tissues

Synthetic biology is an emerging area of science focused on the development of well‐defined molecular components that can be assembled and utilized for rational engineering design. In many cases, the process is geared towards production of high‐value compounds, and in biofuels research, a major goal is to maximize the amount of oil that can be recovered from plants. While seeds are the traditional source of plant oil, we and others are considering the engineering of oil in plant vegetative tissues. The rationale is that the biomass of plants is dominated by leaves and stems, and as such, production of even modest amounts of oil in these tissues may significantly increase the amount of oil recovered from plants. In this seminar I will describe a variety of approaches that we are using to increase the steady‐state amount of oil in plant leaves, including enhancement of the mechanisms for oil synthesis and disruption of processes for oil breakdown. Furthermore, we have recently identified proteins involved in lipid droplet biogenesis and compartmentation, which provide additional tools for modulating the packaging and storage of lipids in plant cells. Collectively, these studies define a growing set of molecular components that can be used for lipid modification. The results of these studies are informing not only the engineering of oil content in plant leaves, but also providing new insights to oil production in plant seeds. Implications for both food and fuel will be discussed.

Analytic Models of a Thin Glass–Polymer Laminate and Development of a Rational Engineering Design Methodology

Analytic models that describe the mechanical behavior of thin glass–polymer laminate structures have been investigated experimentally and via finite-element analysis (FEA). Standard laminate effective thickness models were shown to be applicable to a wide range of glass/interlayer thickness ratios and to a wide range of interlayer shear moduli, covering most currently existing glass laminates. In addition, an analytic comparison of the effective thickness model with the traditional composite beam model clarified the applicable limits of the former model in the range of the interlayer/glass thickness ratio and interlayer shear modulus. These modeling approaches enable a rational engineering design approach for structurally efficient, lightweight, and safe glazing laminates.

‘Unknown’ proteins and ‘orphan’ enzymes: the missing half of the engineering parts list – and how to find it

Like other forms of engineering, metabolic engineering requires knowledge of the components (the 'parts list') of the target system. Lack of such knowledge impairs both rational engineering design and diagnosis of the reasons for failures; it also poses problems for the related field of metabolic reconstruction, which uses a cell's parts list to recreate its metabolic activities in silico. Despite spectacular progress in genome sequencing, the parts lists for most organisms that we seek to manipulate remain highly incomplete, due to the dual problem of 'unknown' proteins and 'orphan' enzymes. The former are all the proteins deduced from genome sequence that have no known function, and the latter are all the enzymes described in the literature (and often catalogued in the EC database) for which no corresponding gene has been reported. Unknown proteins constitute up to about half of the proteins in prokaryotic genomes, and much more than this in higher plants and animals. Orphan enzymes make up more than a third of the EC database. Attacking the 'missing parts list' problem is accordingly one of the great challenges for post-genomic biology, and a tremendous opportunity to discover new facets of life's machinery. Success will require a co-ordinated community-wide attack, sustained over years. In this attack, comparative genomics is probably the single most effective strategy, for it can reliably predict functions for unknown proteins and genes for orphan enzymes. Furthermore, it is cost-efficient and increasingly straightforward to deploy owing to a proliferation of databases and associated tools.

Simulation of Digital Control Systems

A computer technique for simulating digital control systems is presented. It is conceived with recursion formulas to describe the interconnected elements of the system, those of the digital and the continuous elements, in a unified fashion. The technique permitted experimentation with different combinations of system parameters and system configurations. The efficiency of the techniques suggest its suitability for a rational engineering design of a control system before implementation.

Engineering dynamics of growth factors and other therapeutic ligands

Peptide growth factors and other receptor-binding cytokine ligands are of interest in contemporary molecular health care approaches in applications such as wound healing, tissue regeneration, and gene therapy. Development of effective technologies based on operation of these regulatory molecules requires an ability to deliver the ligands to target cells in a reliable and well-characterizable manner. Quantitative information concerning the fate of peptide ligands within tissues is necessary for adequate interpretation of experimental observations at the tissue level and for truly rational engineering design of ligand-based therapies. To address this need, we are undertaking efforts to elucidate effects of key molecular and cellular parameters on temporal and spatial distribution of cytokines in cell population and cell/matrix systems. In this article we summarize some of our recent findings on dynamics of growth factor depletion by cellular endocytic trafficking, growth factor transport through cellular matrices, and growth factor production and release by autocrine cell systems. (c) 1996 John Wiley & Sons, Inc.

Simulation of a feedback and adaptive systems

A computer approach for simulating a feedback system and its adaptive versions is presented. It is conceived with recursion formulas to describe the interconnected elements of the system. The potential of the approach is explored by applying it to an existing practical system. It is then enhanced by a performance analysis leading to a provision of a unified system evaluation technique. The approach permitted experimentation with different combination of system parameters, system inputs and system configuration. The efficiency of the approach suggets its suitability for a rational engineering design of systems.

Solvent‐Crazing criteria

AbstractCraze initiation in amorphous thermoplastics can be regarded as a transition from the safe to the unsafe state and, as such, can constitute a rational engineering design limit. A critical appraisal is made of three different criteria for initiation, which are of current interest. From this, it is concluded that the approach presented in this article, which is based upon the concept of inelastic strain, is to be preferred to the two other criteria, which are based upon an asymptotic total strain or constant inelastic strain energy criterion. The inelastic strain criterion is not only capable of modeling high stress/strain crazing in air but also satisfies the case of low stress/strain crazing in solvents. Furthermore, it offers an accurate method of extrapolating data to long times and, thus, satisfies a fundamental requirement for a parameter that can be used in engineering design.

BEACH FILL PLANNING - BRUNSWICK COUNTY, NORTH CAROLINA

Planning has recently been completed for a shore protection project along a 9-mile (14.5 km) reach of shoreline fronting the Towns of Yaupon Beach and Long Beach in Brunswick County, North Carolina. The investigative program related to this planning effort embodied numerous interrelated elements which, on integration, resulted in a rational engineering design having a continuous beach fill as the central feature. Specifically, the investigation included: (a) definition of the environment, viz, wind, waves, storm tide frequencies, beach profile characteristics, shore processes, and ecological habitats along the proposed project area as well as in potential beach fill sources; (b) Designs and cost estimates including establishment of various fill profile configurations, cost optimization of fill positions, evaluation of the frequency of shoreline retreat and the attendant displacement of fill materials, evaluation of the compatability of materials from various fill sources with the natural beach materials, environmental impact studies, and economic studies; and (c) Final plan formulation arriving at the optimum fill plan in terms of engineering functionality, economics, and minimal adverse environmental impacts.

A system of deformation data for rational engineering design with plastics

AbstractThe paper discusses the deformational behaviour of thermoplastics, particularly in relation to their utilization through rational engineering design procedures. It describes the comprehensive systems of data that are replacing the old single datum quantities published hitherto and comments briefly on the corrdination of materials testing through the activities of B.S.I. Committee PLC/36.