Search

The new materialism holds that every substance can act agency. From the perspective of the new materialism, this paper re-discusses the expression of nature in Dickinson’s poetry to understand her environmental ethics. In Dickinson’s poetry, many “stories” arise from the internal “dynamics” of plants, and she always sees nature as an independent and active subject. The meanings generated by nature do not exist independently, but together form a complex network of meanings that are not affected by human beings. This perspective also reflects Dickinson’s De-anthropocentrism consciousness. Due to her careful observation of nature, Dickinson was able to insight into the “desire” of plants. In her nature poems, her way of looking at nature also influenced our perspective on nature and realized the transformation from human-centered to nature-centered. Nature is not an accessory that can only be changed with the changing environment, but a subject that can actively produce meaning. Finally, the boundary between human and object in her poems is eroded, which also reflects her De-anthropocentrism view of nature.

Digital polymerase chain reaction (PCR) plays important roles in the detection and quantification of nucleic acid targets, while there still remain challenges including high cost, complex operation, and low integration of the instrumental system. Here, in this work, a novel microfluidic chip based on co-flow step emulsification is proposed for droplet digital PCR (ddPCR), which can achieve droplet generation, droplet array self-assembly, PCR amplification, and fluorescence detection on a single device. With the combination of single-layer lithography and punching operation, a step microstructure was constructed and it served as the key element to develop a Laplace pressure gradient at the Rayleigh-Plateau instability interface so as to achieve droplet generation. It is demonstrated that the fabrication of step microstructure is low cost, easy-to-operate, and reliable. In addition, the single droplet volume can be adjusted flexibly due to the co-flow design; thus, the ddPCR chip can get an ultrahigh upper limit of quantification to deal with DNA templates with high concentrations. Furthermore, the volume fraction of the resulting droplets in this ddPCR chip can be up to 72% and it results in closely spaced droplet arrays, makes the best of CCD camera for fluorescence detections, and is beneficial for the minimization of a ddPCR system. The quantitative capability of the ddPCR chip was evaluated by measuring template DNA at concentrations from 20 to 50 000 copies/μL. Owing to the characteristics of low cost, easy operation, excellent quantitative capability, and minimization, the proposed ddPCR chip meets the requirements of DNA molecule quantification and is expected to be applied in the point-of-care testing field.

Image matching is an essential process in the mosaicking of unmanned aerial vehicle (UAV) image sets. At present, the most popular methods establish putative correspondences mainly based on local features; however, some mismatch will occur due to the repetitive pattern if only the feature similarity is employed. In this case, we propose a geometric information-assisted image matching method for UAV images. As the feature matching is restricted in pairwise geometric grid cells, some unnecessary feature similarity calculations are avoided, which is of great help to shorten the matching time. Compared to other methods, the proposed method greatly improves the matching speed without the sacrifice of accuracy, which has a practical significance for real-time remote sensing applications.

Microalgae concentrations have been studied as an important factor to reflect water qualities. High concentration of microalgae should cause water eutrophication then cause environment pollution. However, conventional methods to monitor algal concentration in source water whose use is hampered by high-cost, complicated operation and the need of a centralized laboratory for practical samples’ analysis. In order to overcome these constraints, here in this work, we developed a portable and real-time monitoring platform which consists of a microfluidic chip for algae enrichment, a portable microscopic imaging system integrated with a commercial smartphone. The chip is designed and fabricated with a multi-layer electrode structure to trap algaes via alternating current electrokinetics (ACEK) effect. A temperature dependent fully coupled numerical model is presented to calculate the ACEK flow, showing satisfied trapping performance by adjusting the applied voltage and frequency. Moreover, preliminary experiments are performed in our chip using freshwater samples, in which algae trapping behavior is visually observed and recorded by a self-designed portable microscope. Then the trapping performance of this system can be semi-quantitatively figured out by image processing. This lab-on-a-chip system shows high potential in concentrating bio-particles and developing a portable, integrated and automated system for monitoring the quality of water resources in nature. [2020-0381]

Compact and affordable microfluidic pumping is critical for point-of-care applications. Here we proposed a data driven dynamical system to build up a pressure-driven microfluidic pump with a small budget. Firstly, a precision flow sensor is required to obtain the dynamic flow rates as the responses to the driven pressures. Then the flow rate dataset under varying operation pressures is used for data training and model-based system identification. With a first-order or second-order transfer function model, the specifications of pressure-driven microfluidic pumping system are analyzed by the model-based system identification algorithm. Also, all the specifications including the gain, time constant, natural frequency, and damping ratio are updated online as new test data are introduced from more experimental trials. To perform a non-bulky design purpose, the data training system identification is taken on a commercial smartphone. Once the training performance is satisfied, the pressure-driven system could be operated without any flow sensors. The system is used for two-phase flow controls as a demonstration, showing a rapid response of pumping. Dynamic characteristics and the effects of flow resistance on the pumping performance are analyzed to verify its suitability for a wide range of microfluidic applications.

Droplet-based micromixers have shown great prospects in chemical synthesis, pharmacology, biologics, and diagnostics. When compared with the active method, passive micromixer is widely used because it relies on the droplet movement in the microchannel without extra energy, which is more concise and easier to operate. Here we present a droplet rotation-based microfluidic mixer that allows rapid mixing within individual droplets efficiently. PDMS deformation is used to construct subsidence on the roof of the microchannel, which can deviate the trajectory of droplets. Thus, the droplet shows a rotation behavior due to the non-uniform distribution of the flow field, which can introduce turbulence and induce cross-flow enhancing 3D mixing inside the droplet, achieving rapid and homogenous fluid mixing. In order to evaluate the performance of the droplet rotation-based microfluidic mixer, droplets with highly viscous fluid (60% w/w PEGDA solution) were generated, half of which was seeded with fluorescent dye for imaging. Mixing efficiency was quantified using the mixing index (MI), which shows as high as 92% mixing index was achieved within 12 mm traveling. Here in this work, it has been demonstrated that the microfluidic mixing method based on the droplet rotation has shown the advantages of low-cost, easy to operate, and high mixing efficiency. It is expected to find wide applications in the field of pharmaceutics, chemical synthesis, and biologics.

Droplet digital polymerase chain reaction (ddPCR) suffers from the need for specific equipment and skilled personnel, thus, we here present a chamber-based digital PCR microfluidic device that is compatible with fluorescence image read-out systems and removes bubbles by a pre-degassed microfluidic device that consists of a pilot channel and micro chamber arrays. Digitalized PCR reagents are introduced into micro chambers, and thermocycles are taken to perform a DNA amplification process. Then, fluorescence images of a micro chamber array are read out and analyzed to obtain the total number of positive chambers. Thereby, the copy numbers of target DNA are calculated for quantitative detections. As a validation, this device is evaluated by the application of meat authentication. We performed dPCR tests using DNA templates extracted from a pure mutton DNA template with different dilutions. Then, the dPCR chip was used to identify the meat authentication using mutton–chicken mixtures with different mass ratios, showing its performance in real biotechnical applications.

Positioning information has become one of the most important information for processing and displaying on smart mobile devices. In this paper, we propose a visual positioning method using RGB-D image on smart mobile devices. Firstly, the pose of each image in the training set is calculated through feature extraction and description, image registration, and pose map optimization. Then, in the image retrieval stage, the training set and the query set are clustered to generate the vector of local aggregated descriptors (VLAD) description vector. In order to overcome the problem that the description vector loses the image color information and improve the retrieval accuracy under different lighting conditions, the opponent color information and depth information are added to the description vector for retrieval. Finally, using the point cloud corresponding to the retrieval result image and its pose, the pose of the retrieved image is calculated by perspective-n-point (PnP) method. The results of indoor scene positioning under different illumination conditions show that the proposed method not only improves the positioning accuracy compared with the original VLAD and ORB-SLAM2, but also has high computational efficiency.

Microfluidic chips&mdash, in which chemical or biological fluid samples are mixed into linear or nonlinear concentration distribution profiles&mdash, have generated enormous enthusiasm of their ability to develop patterns for drug release and their potential toxicology applications. These microfluidic devices have untapped potential for varying concentration patterns by the use of one single device or by easy-to-operate procedures. To address this challenge, we developed a soft-lithography-fabricated microfluidic platform that enabled one single device to be used as a concentration maker, which could generate linear, bell-type, or even S-type concentration profiles by tuning the feed flow rate ratios of each independent inlet. Here, we present an FFRR (feed flow rate ratio) adjustment approach to generate tens of types of concentration gradient profiles with one single device. To demonstrate the advantages of this approach, we used a Christmas-tree-like microfluidic chip as the demo. Its performance was analyzed using numerical simulation models and experimental investigations, and it showed an excellent time response (~10 s). With on-demand flow rate ratios, the FFRR microfluidic device could be used for many lab-on-a-chip applications where flexible concentration profiles are required for analysis.

Summary Recombinant bacterial colonization plays an indispensable role in disease prevention, alleviation, and treatment. Successful application mainly depends on whether bacteria can efficiently spatiotemporally colonize the host gut. However, a primary limitation of existing methods is the lack of precise spatiotemporal regulation, resulting in uncontrolled methods that are less effective. Herein, we design upconversion microgels (UCMs) to convert near-infrared light (NIR) into blue light to activate recombinant light-responsive bacteria (Lresb) in vivo, where autocrine “functional cellular glues” made of adhesive proteins assist Lresb inefficiently colonizing the gut. The programmable engineering platform is further developed for the controlled and effective colonization of Escherichia coli Nissle 1917 (EcN) in the gut. The colonizing bacteria effectively alleviate DSS-induced colitis in mice. We anticipate that this approach could facilitate the clinical application of engineered microbial therapeutics to accurately and effectively regulate host health.

Ethylene treaters are widely used in the petrochemical industry to remove impurities from ethylene feedstock imported from pipeline networks or storage caverns. The safety concerns of dense phase ethylene treaters due to the reactive and highly flammable nature of ethylene are well known and studied. Under certain conditions, ethylene may self-polymerize and decompose violently with heat release. Under other conditions, ethylene will auto-refrigerate, generating cold liquids that may cause potential brittle fracture hazards. Therefore, dense phase ethylene treaters present design challenges with the unique combination of high temperature decomposition and cold temperature brittle fracture hazards. Due to these safety concerns, it is important to select the appropriate engineering design options for dense phase ethylene treaters and the associated regeneration facilities. Totally automated treater regeneration systems add complexity and instrument maintenance requirements while manually operated systems rely heavily on operator training and procedures. Unfortunately, little or no information or design guidance is available from published research findings in the literature on the evaluation and risk assessment of current industrial design options and practices for dense phase ethylene treaters. This paper presents a systematic risk assessment method to evaluate the engineering design and safe operation options for dense phase ethylene treaters. The proposed risk assessment method integrates human factors task analysis into the traditional HAZOP, LOPA and fault tree analysis to allow evaluation of automated, manual and hybrid approaches with a goal of selecting and optimizing design options to ensure plant safety. This approach provides a realistic assessment of the operational risk and allows identification of fit-for-purpose risk reduction. Applying this systematic risk assessment approach, a simpler and more cost effective design solution can be justified, thereby avoiding the need for a high integrity protective system.

The accurate calculation of the pipe network module contributes to the effective simulation of chemical processes and can improve the production of chemical processes. At present, the pipe network calculation of chemical processes is generally solved by the secant method. Although this method is convenient, it cannot meet the accuracy of the pipe network calculation, and even cannot converge. Therefore, this paper proposes an improved Newton Jacobian iterative method to improve the accuracy of the pipe network calculation, which realizes the efficient, stable and accurate solution of the flow and pressure of the pipe network system. By improving the selection of the initial value, the convergence of the pipe network calculation and the operation efficiency of the Jacobian iterative method are improved. The effectiveness of the proposed method is illustrated by comparison with the secant method. Finally, the minimum branch and the merge-branch pipeline are actually calculated for the simulation test. The results show that the flow rate calculated by the pipe network and the pressure accuracy are significantly improved.

Inter type-2 fuzzy model has been confirmed to be more effective in Takagi–Sugeno (T–S) fuzzy model identification compared to type-1 fuzzy model. It is indisputable that some algorithms based on inter type-2 fuzzy model have already been developed and shown remarkable modeling performance. To further improve the modeling accuracy, the optimization methods and the neural network are taken into consideration. In this paper, an evolving modified inter type-2 fuzzy c-regression model (MIT2-FCRM) algorithm based on gravitational search algorithm (GSA) and a consequent parameter identification method based on extreme learning machine algorithm with forgetting factor for processing online sequences (namely WOS-ELM) were proposed. Then a novel approach for T–S fuzzy modeling was presented, in which, the coefficients of the upper and lower hyperplanes were obtained by evolving MIT2-FCRM algorithm based on GSA, a hyper-plane-shaped membership function (MF) was utilized to identify the antecedent parameters of the T–S fuzzy model, and WOS-ELM was employed to identify the consequent parameters. The modeling results of six examples indicate that the proposed approach is superior to other studies in terms of identification accuracy, compact fuzzy rules and noise resistance ability.

As a platform to mix the bioagents (i.e. serum, urine), we take advantage of the alternating current electrothermal (ACET) effect which is quite suitable for rapid pumping/mixing of high conductive biomicrofluids. Here we demonstrate the concept of a high-efficient mixing microfluidic chip as a basic unit to provide rapid mixing for lab-on-a-chip applications. As an active mixer, two streams are introduced into a ring-shape microchamber by a passive flow rate regulator, and then the microfluids in the chamber are actuated by a nonuniform electric field with a phase shift of 180°. It shows perfect mixing performance by arranging four arc-electrodes around the ring-shape microchamber subsequently. Taking the Joule heating and conductivity/permittivity changes into consideration, a temperature dependent fully coupled numerical model is presented. Then, the effects of applied voltages on mixing performance and temperature rise are provided to get an optimized design for ACET mixer. Moreover, the arrangement of the electrode array is analyzed to show the effects of electrode patterns on the swirls and mixing efficiencies. Since all the electrodes here are located along a ring-shape central microchamber, the ring-shape micromixer is quite suitable to function as a compact element modular for integrated microfluidic chips.

Hydroxylamine nitrate (HAN) is an important member of the hydroxylamine compound family with applications that include equipment decontamination in the nuclear industry and aqueous or solid propellants. Due to its instability and autocatalytic behavior, HAN has been involved in several incidents at the Hanford and Savannah River Site (SRS) [Technical Report on Hydroxylamine Nitrate, US Department of Energy, 1998]. Much research has been conducted on HAN in different areas, such as combustion mechanism, decomposition mechanism, and runaway behavior. However, the autocatalytic decomposition behavior of HAN at runaway stage has not been fully addressed due to its highly exothermic and rapid decomposition behavior. This work is focused on extracting HAN autocatalytic kinetics and analyzing HAN critical behavior from adiabatic calorimetry measurements. A lumped autocatalytic kinetic model for HAN and associated model parameters are determined. Also the storage and handling critical conditions of diluted HAN solution without metal presence are quantified.

Many industrial incidents are caused by thermal runaway reactions. Therefore, a good understanding of runaway reactions is necessary to predict and control reactive hazards. A detailed kinetic modeling approach is proposed to simulate runaway reactions under industrial conditions. This paper addresses the first step of this approach—mechanism generation. Computational chemistry was employed to estimate thermodynamic properties of reactants, intermediates, and products, and the Evans–Polanyi linear free energy relationship was used to estimate activation barriers of elementary reactions. To illustrate this mechanism generation approach, hydroxylamine is used as an example. The distribution of the predicted final products agrees with experimental results.

Hydroxylamine nitrate (HAN) is an important member of the hydroxylamine family and it is a liquid propellant when combined with alkylammonium nitrate fuel in an aqueous solution. Low concentrations of HAN are used primarily in the nuclear industry as a reductant in nuclear material processing and for decontamination of equipment. Also, HAN has been involved in several incidents because of its instability and autocatalytic decomposition behavior. This paper presents calorimetric measurement for the thermal decomposition of 24 mass% HAN/water. Gas phase enthalpy of formation of HAN is calculated using both semi-empirical methods with MOPAC and high-level quantum chemical methods of Gaussian 03. CHETAH is used to estimate the energy release potential of HAN. A Reactive System Screening Tool (RSST) and an Automatic Pressure Tracking Adiabatic Calorimeter (APTAC) are used to characterize thermal decomposition of HAN and to provide guidance about safe conditions for handling and storing of HAN.

Characterization of autocatalytic decomposition reactions is important for the safe handling and storage of energetic materials. Isothermal differential scanning calorimetry (DSC) has been widely used to detect autocatalytic decomposition of energetic materials. However, isothermal DSC tests are time consuming and the choice of experimental temperature is crucial. This paper shows that an automatic pressure tracking calorimeter (APTAC) can be a reliable and efficient screening tool for the identification of autocatalytic decomposition behavior of energetic materials.

There has been considerable interest in predicting the stabilities of energetic materials to improve safety during manufacture, handling, storage, and transportation. Although a variety of experimental techniques are available to test the properties of energetic materials, computational screening techniques can harness the convenience of modern computers to reduce the cost of destructive tests. In this paper quantitative structure–property relationships (QSPRs) based on quantum mechanical calculations were employed to correlate the measured impact sensitivities from shock or impact tests with molecular properties. Molecular descriptors were evaluated using both the Hartree-Fock method with a STO-3G basis set and the semiempirical method PM3. Equations that correlate impact sensitivities to the energy of lowest unoccupied molecular orbital (ϵLUMO), energy of highest occupied molecular orbital (ϵHOMO), midpoint potential (MPP), ionization potential (IP), dipole moment (DM), and total energy (E) of ...

Hydroxylamine (HA) has been involved in two incidents since 1999 because of its thermal instability and incompatibility. In this study, thermal runaway reactions of hydroxylamine with various concentrations of KOH and HCl were studied using the reactive system screening tool (RSST) and automatic pressure tracking adiabatic calorimeter (APTAC). The thermokinetic data, such as onset temperature, heat of reaction, maximum self-heat rate, maximum pressure rate, and non-condensable gas pressure, were compared with those of hydroxylamine solution without added impurity. Our study shows that the thermal decomposition behavior of hydroxylamine is affected by the presence of acid/base, and mixing of hydroxylamine with acid/base may cause thermal decomposition at lower temperatures. Different decomposition pathways can be initiated by hydrogen ion and hydroxide ion. The decomposition mechanisms of hydroxylamine in alkaline and acidic solutions are proposed based on the products, information from the literature, and quantum mechanical calculations. The experimental results are discussed in terms of the proposed reaction mechanisms.

Reactive chemical incidents have led to numerous losses in the process industries and have affected the environment and the public. However, at present there is no real consensus on how to manage or regulate reactive chemicals. This paper analyzes 167 reactive incidents reported in a study conducted by the US Chemical Safety and Hazard Investigation Board (CSB). This analysis concludes that most of the information to identify and assess hazards in order to prevent incidents already existed in the literature. This paper discusses a few simple and easy approaches to access the needed hazard information. Using the described screening tools, reactive hazards can be easily identified. These tools will be especially helpful for small- or medium-sized companies who do not have extensive capabilities or resources for experimental testing.

The roles of moisture in resistive switching (RS) devices are closely related to the RS mechanism. In principle, the nonpolar RS promises symmetric behaviors independent of the polarities of operating voltages. However, the effect of humidity on the RS characteristics of Pt/TiO2− x /Pt nonpolar cells is confirmed to be polarity-dependent. The positive electroforming threshold voltage decreases when humidity increases, whereas the negative one is unaffected. This asymmetric phenomenon can be attributed to the polarity-associated rule of current varying with humidity before electroforming. The voltage distribution in the device and then the electroforming threshold voltage are modified.