Series Of Macro Research Articles

Saturated permeability and water retention capacity in biochar-methanotrophs-clay for new landfill cover system

A new landfill cover system, biochar-methanotrophs-clay (BMC) cover is recommended for reducing methane emissions at landfills. It also contributes to decreasing soil permeability and improving soil water retention in a long time, due to highly porous structure of biochar and the growth metabolism of methanotrophs. To determine the effects of biochar content, oxidation aging times and methane-filled days on hydraulic properties, a total of 60 groups of experiments were conducted. The saturated hydraulic conductivity (ksat) was obtained by flexible wall permeameter with controllable hydraulic head pressure. The results showed that the ksat of BMC increased with increasing biochar content and oxidation aging times, while decreased with adding methane-filled days. The soil-water characteristic curves (SWCCs) were obtained with soil suction measured by the filter paper method. The results indicated the water retention capacity of MBC reduced with increasing oxidation aging times but increased with adding methane-filled days. Detected by mercury intrusion porosimetry (MIP), fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM), the differences displayed the changes of pore structures and extracellular polymeric substances (EPS). The oxidation aging of biochar increased the volume of pores, resulting in the increased ksat and the decreased water retention capacity. However, the growing of methanotrophs decreased the volume of pores, resulting in the ksat decreased and the water retention capacity increased due to EPS. No matter how many times the oxidation aging process was experienced, the BMC with longer methane-filled days exhibited relatively lower ksat and better water retention capacity. This implied a more stable barrier capacity to reduce water infiltration in the long term. By combing a series of macro and micro experiments, this paper provides theoretical guidance for the application of biochar-methanotroph-clay mixture to landfill covers.

Transcriptome data from silica-preserved leaf tissue reveal gene flow patterns in a Caribbean bromeliad.

Transcriptome sequencing is a cost-effective approach that allows researchers to study a broad range of questions. However, to preserve RNA for transcriptome sequencing, tissue is often kept in special conditions, such as immediate ultracold freezing. Here, we demonstrate that RNA can be obtained from 6-month-old, field-collected samples stored in silica gel at room temperature. Using these transcriptomes, we explore the evolutionary relationships of the genus Pitcairnia (Bromeliaceae) in the Dominican Republic and infer barriers to gene flow. We extracted RNA from silica-dried leaf tissue from 19 Pitcairnia individuals collected across the Dominican Republic. We used a series of macro- and micro-evolutionary approaches to examine the relationships and patterns of gene flow among individuals. We produced high-quality transcriptomes from silica-dried material and demonstrated that evolutionary relationships on the island match geography more closely than species delimitation methods. A population genetic examination indicates that a combination of ecological and geographical features presents barriers to gene flow in Pitcairnia. Transcriptomes can be obtained from silica-preserved tissue. The genetic diversity among Pitcairnia populations does not warrant classification as separate species, but the Dominican Republic contains several barriers to gene flow, notably the Cordillera Central mountain range.

Analysis of liquid–vapor mixed migration mechanism in unsaturated soil based on the effect of temperature on soil microstructure

Moisture migration in unsaturated soils is a result of the interaction between temperature and soil microstructure. In order to reveal the mechanism of moisture increase of subgrade soils under diurnal cycle conditions, a series of macro and microscopic tests were carried out on the unsaturated silty clay and sand soil, including liquid–vapor mixed migration tests simulating a one-dimensional subgrade, environmental scanning electron microscope (ESEM), and matrix suction test. Then, the soil microstructure in microscopic images was investigated using the particle (pores) and cracks analysis system (PACS). Next, the relationship between the thermal effects of the soil–water characteristic curve (SWCC) and changes in soil microstructure was analyzed. Finally, the change mechanism of liquid–vapor mixed migration based on the change in soil microstructural under thermal effects was analyzed. The results showed under the diurnal cycle, both the silty clay and sand soil columns appeared in the phenomenon of a “diurnal cycle of water vapor migration”, which led to moisture accumulation at the top of the soil layer. In silty clay soil column, moisture was primarily driven by water vapor pressure and migrated upwards. Additionally, moisture redistribution led to changes in soil microstructure, which in turn influenced the process of moisture migration. The moisture content in the upper soil layer increased making both inter-aggregate and intra-aggregate pores decrease. The moisture content in the lower soil later decreased, leading to the water-holding capacity of the lower soil layer to increase. So, the moisture migration gradually decreased at night. In the sand soil column, moisture migration was mainly driven by gravity potential and migrated downwards. Moisture redistribution made inter-aggregate pore and matrix suction of the upper soil layer increase, leading to an increase in moisture migration at night.

Study of the damage and cracking of heterogeneous rocks based on the FFT method - A comparison of computer generation and image reconstruction models

Studying the influence of microstructure on the damage and cracking process of rocks is of great practical engineering importance for evaluating the mechanical properties of surrounding rocks in complex geological engineering environments. To incorporate rock microstructures into numerical models, two main methods, i.e. computer generation methods (e.g. molecular dynamics, MD) and image reconstruction methods (e.g. digital image processing, DIP), are frequently adopted. However, the strengths and weaknesses, the differences and applicability regarding the two major methods have not been systematically discussed and analyzed in simulating the damage and cracking in heterogeneous rocks. In this study, the MD model was firstly optimized based on the previous work, and the “Realistic grain size based microstructure model generation program” was developed by the observed mineral grain sizes from microscopic images. The DIP model was developed by directly using digital images of rock materials via the image reconstruction methods. On this basis, the damage and cracking process of rocks was investigated and compared with the above two models using a technique based on the Fast Fourier transforms (FFT). To this end, a series of macro and micro experiments were conducted to obtain the basic mechanical properties of the Dingziwan Granite (DG) and several examples are generated by the MD and DIP model with calibrated macro and micro parameters by the laboratory data. The two models combined with the FFT method are applied to predict the macro and micro mechanical behavior of the DG under different confining pressures and their differences and applicability are quantitatively analyzed and compared. The results indicate that, in general, the two models are both capable of predicting the macro and micro mechanical behaviors of the heterogeneous rocks, but each has its own strength. The improved MD model can efficiently study the influence of the rock heterogeneity on its macroscopic behavior, while the DIP model can highly reproduce the microcracking process such as intragranular, transgranular and grain boundary cracking.

Macroscopic mechanical behavior and microstructural evolution of compacted loess in the Chinese Loess Plateau

Understanding the mechanical behavior of compacted loess is of great significance to engineering construction on the Loess Plateau. To gain an in-depth knowledge of the variations in compressibility, shear strength and microstructure of compacted loess at different dry densities and water contents, a series of macro and microscopic tests were carried out on the loess samples, including oedometer compression tests, direct shear tests and scanning electron microscope imaging. The pore properties of loess in microscopic images were investigated using the particle (pores) and cracks analysis system. The relationship between pore microscopic indicators and mechanical parameters was explored by multivariate statistical analysis. The results show that the compression coefficient of compacted loess decreases with increasing dry density, of which trend is more significant at high water content. Both cohesion and internal friction angle decrease with increasing water content, but the former is more sensitive to changes in soil moisture. Besides, the evolution sequence of compacted loess structure is basically overhead-mosaic-flocculation with the increase of compactness and saturation. The difference is that with the compaction, the pores in the loess sample change from macropores into mesopores and then to small pores, and the directional distribution and morphological complexity of the pores weakens; while with the humidification of the loess sample, small pores and macropores transform into mesopores, and the pores are more oriented and more complex in shape. During this process, the micropore content changes are weak. Moreover, mesopores content and pore fractal dimension have a positive effect on compressibility, while micropores content and orientation probability entropy have a positive effect on shear strength.

Enhanced post freeze-thaw stability of Zn/Pb co-contaminated soil through MgO-activated steel slag and fiber treatment

This study assessed the applicability of a novel stabilization/solidification (S/S) method to control re-release potential of heavy metal (HM) in remediated HMs-polluted soils experiencing freeze-thaw cycles (F-T). In so doing, MgO-activated basic oxygen furnace (M-BOF) slag alone and its combination with polypropylene fiber were added to a soil containing a wide range of Zn and Pb. The composites were then subjected to a series of macro and micro scale tests. It was found that, unlike treatment conditions with the same dosage of cement, in the samples with low levels of HMs, the application of 15% M-BOF could satisfy the S/S regulation limits even under the destroying impacts of acid leaching and F-T. In fact, as the results of XRD and SEM tests revealed, M-BOF would be much more influential than cement in the reactions which solidify the soil mass and improve its compactness, causing a notable reduction in the HMs-remobilization risks. However, the high levels of metals might negatively affect the binder performance, and thus the soil geo-mechanical characteristics particularly during the F-T scenario. The study showed that the incorporation of fiber in the S/S system would increase its efficiency in refining the pores network, wrapping the matrix against the structure defects upon the harsh conditions. As a result, the reinforced samples display a lower degree of strength damage and a marked decrease in the loss of HMs retention abilities with the progressing F-T. Overall, the findings indicate that the M-BOF/fiber mixture can effectively be used as a multi-functional S/S agent which, over time, can keep the toxic ions in a less mobile form.

Problem-oriented documentation: design and widespread adoption of a novel toolkit in a commercial electronic health record.

Problem-oriented documentation is an accepted method of note construction which facilitates clinical thought processes. However, problem-oriented documentation is challenging to put into practice using commercially available electronic health record (EHR) systems. Our goal was to create, iterate, and distribute a problem-oriented documentation toolkit within a commercial EHR that maximally supported clinicians' thinking, was intuitive to use, and produced clear documentation. We used an iterative design process that stressed visual simplicity, data integration, a predictable interface, data reuse, and clinician efficiency. Creation of the problem-oriented documentation toolkit required the use of EHR-provided tools and custom programming. We developed a problem-oriented documentation interface with a 3-column view showing (1) a list of visit diagnoses, (2) the current overview and assessment and plan for a selected diagnosis, and (3) a list of medications, labs, data, and orders relevant to that diagnosis. We also created a series of macros to bring information collected through the interface into clinicians' notes. This toolkit was put into a live environment in February 2019. Over the first 9 months, the custom problem-oriented documentation toolkit was used in a total of 8385 discrete visits by 28 clinicians in 13 ambulatory departments. After 9 months, the go-live education and EHR optimization teams in our health system began promoting the toolkit to new and existing users of our EHR resulting in a significantly increased uptake by outpatient clinicians. In April 2022 alone, the toolkit was used in more than 92000 ambulatory visits by 894 users in 271 departments across our health system. As a health-system client of a commercial EHR, we developed and deployed a revised problem-oriented documentation toolkit that is used by clinicians more than 92000 times a month. Key success elements include an emphasis on usability and an effective training effort.

Effect of Moisture on the Macro Failure Characteristics of Weakly Consolidated Mudstone: Mesomechanism

Mudstone, whose significant characteristic is water-weakening, widely exists in all kinds of geotechnical engineering, which brings great security risks to engineering safety. In this paper, through a series of macro and meso test methods, the macro and meso action mechanism of water on the weakly consolidated plane of mudstone was studied. In the uniaxial compressive strength test, the mudstone cementation plane was the main part of the fracture derived. Under the moist state, the strength of mudstone would decrease significantly, which was inversely correlated with relative moisture content. In the case of flooding, mudstone cracking occurred only along the cementation plane. Through ESEM+mapping test, results showed the humidification curing caused obvious damage to the cemented plane, where sodium and calcium were lost without a certain cause. The cemented plane was rich in kinds of clay minerals in mesoscale and presented an inhomogeneous state. The surface hardness data obtained from nanoindentation were discrete and difficult to quantitatively evaluate the mesomechanical properties. However, compared with the dry state, the data set of the moist state had a significant decline, showing a weakening effect. The mudstone is prone to fail along these weakly consolidated planes. Moisture intrudes into the bedding plane further deteriorating their consolidation.

Sulfate resistance of eco-friendly and sulfate-resistant concrete using seawater sea-sand and high-ferrite Portland cement

The resource shortage of freshwater and river sand promotes the development of seawater sea-sand concrete (SWSSC). However, most of the previous studies of SWSSC focused on plain ordinary Portland cement (OPC) systems, the poor sulfate resistance of which is detrimental to the durability and sustainability development of SWSSC. High ferrite Portland cement (HFPC) has higher sulfate resistance, higher abrasion resistance, and low energy consumption and CO2 emission in comparison with OPC, thus providing a great alternative for SWSSC. Here, we investigate the sulfate resistance of SWSSC using OPC and HFPC. The deterioration process, the sulfate attack products, and the microstructure changes were analyzed by a series of macro and micro analysis. The results show that OPC concrete is seriously damaged with an 83.9% loss of strength. Seawater sea-sand can improve the sulfate resistance, which is mainly due to the refinement of pore structure and the consumption of erodible components. Moreover, compared with SWSSC using OPC, SWSSC using HFPC shows much better sulfate resistance, and the important role of Fe in increasing the stability of hydration products is revealed. Such findings contribute to an in-depth understanding of the deterioration mechanism and the improvement of sulfate resistance of SWSSC.

Trends and cycles in macro series: The case of US real GDP

AbstractThis paper proposes a new modeling framework capturing both the long‐run and the cyclical components of a time series. As an illustration, we apply it to four US macro series, namely, annual and quarterly real gross domestic product (GDP) and GDP per capita. The results indicate that the behavior of US GDP can be captured accurately by a model incorporating both stochastic trends and stochastic cycles that allows for some degree of persistence in the data. Both appear to be mean reverting, although the stochastic trend is nonstationary, while the cyclical component is stationary, with cycles repeating themselves every 6–10 years.

Estimating robustness

I estimate and evaluate a model with a representative agent who is concerned that the persistence properties of her baseline model of consumption and inflation are misspecified. Coping with model uncertainty, she discovers a pessimistically biased worst-case model that dictates her behavior. I combine interest rates and aggregate macro series with cross-equation restrictions implied by robust control theory to estimate this worst-case distribution and show that (1) the model's predictions about key features of the yield curve are in line with the data, and (2) the degree of pessimism underlying these findings is plausible. Interpreting the worst-case as the agent's subjective belief, I derive model implied interest rate forecasts and compare them with analogous survey expectations. I find that the model can replicate the dynamics and average level of bias found in the survey.

Experimental Study on Engineering Properties and Microstructure of Expansive Soils Treated by Lime Containing Silica Nanoparticles Under Various Temperatures

In this study, improvement rate of engineering properties of expansive soils caused by the effect of varying curing temperature together with the addition of Silica Nanoparticles on lime was evaluated utilizing a series of macro and micro-structural tests. Based on the results, as the temperature decreases (especially temperatures below 20 °C with storage duration shorter than 28 days), pozzolanic activities as well as growth process of cementitious mixtures (e.g. CSH and CAH Nanostructures), is disrupted and after the addition of lime, the improvement process will be majorly affected by short-term reactions (Cation-exchange capacity and increase in Osmotic pressure). Under such circumstances, it was found that an increase in the content of the mentioned additives can just control the expandability and the other geotechnical characteristics such as bearing capacity and settlement potential are negligibly improved. On the other hand, the results indicate that when the mixture of lime-silica nanoparticles (LNS) is added, undesirable effect of temperature loss on the engineering parameters is leveled down and unlike the limitations of lime performance, the compressive strength of improved specimens follows an increasing trend in proportion to the rate of increase in the additives content. Based on the X-ray diffractions as well as SEM images, the reason behind less susceptibility of specimens containing LNS to temperature and storage duration and consequently, a better behavior in comparison with those including just lime, arose from a greater number and faster process of pozzolanic reactions and compaction of the mixture’s structure. Conclusively, application of LNS (especially in cold weather and short curing duration) intensifies the lime’s effect and in addition, reduces the consumption of additives by 50%.

Using the characteristics of rootless cone deposits to estimate the energetics of explosive lava–water interactions

During volcanic eruptions, the interaction of magma and groundwater can produce thermohydraulic explosions capable of significantly increasing the eruption energy. The most well-known mechanism by which explosive magma–water interactions occur, molten fuel–coolant interaction (MFCI), is a complex series of macro- and microscale processes which have been simulated using laboratory-scale experiments. As a natural analog for MFCI experiments, we utilize rootless cone beds formed by lava–water explosions to estimate explosion energy. The specific mechanical energy of the lava–water explosions studied here occurs over a broader range (4 to 178 kJ/kg) than MFCI experiments and includes estimates for the highest-energy lava–water explosions studied to date. Explosion energy is partitioned similarly over the two systems, with kinetic transport and fragmentation energy making up 25–40% and 42–80% of the mechanical energy, respectively, which overlap the ranges estimated for MFCI experiments. Our study of lava–water explosions therefore provides a field-scale analog of MFCI laboratory experiments for understanding the energetics, and therefore hazards, of MFCI in natural systems.

Application of novel Persian gum hydrocolloid in soil stabilization

Persian gum as a newly introduced source of carbohydrate polymers obtained from the trunk and branches of wild almond trees of Zagros forests in Iran, has found wide applications in food and pharmaceutical industry owing to its unique structure. However, its behavior in soil environment is still unknown. This paper proposes application of Persian gum to stabilization process of a low plasticity clayey soil. A series of macro and micro scale tests including unconfined compression strength, direct shear test, scanning electron microscopy imaging, Stereo zoom microscopy, Brunauer, Emmett and Teller tests, thermal gravimetric analysis and Particle size analysis were conducted on soil stabilized with different amounts of Persian gum. All defined tests were also conducted on previously studied soil additives, xanthan and guar gums. The results confirm the successful performance of Persian gum in binding soil particles, pore filling, thermal stability, soil fluctuation and formation of large particles in comparison to common hydrocolloids.

Experimental and Numerical Sizing of Delamination Defects in Layered Composite Materials

A methodical approach to the estimation of the localization zone and geometric parameters of delamination defects in layered composite materials is discussed. It is based on mathematical processing of the experimental results of deformation measurements obtained with a grid of fiber-optic sensors. The results of methodological developments related to the determination of the optimal topology of the grid of sensors are shown to ensure the detection of defects of a given size with the necessary accuracy and determination of their parameters. Methods for computational analysis and simulation of the strain-stress state in the defect zone based on the algorithm used for modeling the problems of strain-stress analysis in the defect zone using 2D finite elements instead of 3D ones are reported. These procedures allow one to use models of lower dimensionality while retaining all the features of the strain-stress state. The results of methodological developments related to the determination of the defect parameters from the results of strain measurements using the methodology of solving the inverse problem are shown. This methodology is based on solving the problem of minimizing the discrepancy between the vector of deformation response and the vector of initial parameters. The technique is implemented as software consisting of a series of macros for ANSYS and programs for MATLAB. The results of cyclic testing of a sample made of a multilayer composite material with a delamination type of defects are presented. The increment in the defect size upon loading is estimated by the mathematical processing of data recorded by fiber-optic strain sensors glued on one of the sample surfaces based on the solution of the inverse problem. Comparison of the results of calculations of geometric parameters of the defects with the measurement data obtained by the method of ultrasonic flaw detection shows good agreement between them.

Bone detritus in sediments of Tethis ocean

The comparative study of the Oligocene bone breccia geochemistry in the lower part of the Oligocene deposits (Mangishlak, Oligocene Miocene) has been studied along with the recent uranium deposits. Studies of the Namibian shelf samples where the series of macro- and microelements have been analized, including major and minor elements, which showes their similarity of major elements and miner elements in the both deposits old and Recent samples. From the other side the similarity between uranium mineralization has been found in the uranium mineralization in Maikop and recent bones on the Namibian shelve. The paleogeographic data of the Maikop Basin showed that the ore deposits have been formed in the productive shallow sea where mass mortality of the fish happened often as well as in present Ocean. The high values of metal concentration is the older bones in the Tethis are related to evaporation and saturation of marine water.

Use of ROOT to build a software optimized for parameter estimation and simulations with Distributed Delay Model

ROOT is a software package developed by a CERN project started in 1994 by René Brun for statistical analysis in high-energy physics. This software package can also be used in the field of protecting plants against pest insects. Indeed, for a long time there has been a significant use of the Distributed-Delay Model, but there is no specific software available to date that is useful for following the research from the first step to simulations and field validations.This work, through ROOT's libraries, builds a series of macros that consent to do non-linear fits with functions such as Erlang PDF, linear-rate, Logan, Briére, Sharpe and De Michele, thereby giving support to the parameters-estimate step in laboratory sessions and then numerically solving the Distributed-Delay Model equations. This study supplies results both graphically and numerically.

Numerical investigation of the external sulfate attack induced expansion response of cement paste by using crystallization pressure

A series of macro- and microscopic models have been proposed to numerically investigate the expansion response in hardened cement paste (HCP) caused by external sulfate attack (ESA). In the models, a HCP cylindrical specimen and a representative volume element (RVE) are respectively chosen as macroscopic and microscopic objects. Numerical simulation on the expansion response in the HCP specimen immersed into Na2SO4 solution is performed. The results show that the macroscopic and microscopic expansion responses in HCP induced by crystallization pressure are different. At the macroscale, the stress state (the radial, hoop and axial stresses) of HCP in the surface layer of the specimen transforms from a triaxial tension to tension–compression–tension state, and further becomes tension–compression–compression. But, the HCP is always in a triaxial tension state in the interior of the specimen without ESA. At the microscale, the hoop tensile stress in RVE increases rapidly with immersion time and is responsible for the initiation of microcracks in the cement paste of RVE. By comparing the macroscopic and microscopic expansion responses, the microscopic stress is larger than the macroscopic stress in the sulfate corrosion zone of the specimen. It indicates that, the analysis on the ESA-induced damage of HCP needs to consider both the macroscopic and microscopic expansive stresses.

Effects of curvature-related DEM contact model on the macro- and micro-mechanical behaviours of granular soils

A comprehensive comparison between the Hertz–Mindlin model and the linear spring model in true triaxial shear simulations of granular soils was conducted using the discrete-element method (DEM). The no-slip Hertz–Mindlin model for general elastic non-spherical particles with smooth surfaces was revisited and implemented for superellipsoidal particles in an in-house DEM code. Three groups of specimens with a grain size distribution of Ottawa 20–30 sands, consisting of spheres, ellipsoids and superellipsoids, respectively, were subjected to triaxial shear DEM simulations with the Hertz–Mindlin model and the linear spring model. The corresponding mechanical behaviours were examined in terms of a series of macro- and micro-parameters. It was found that the linear spring model was able to resemble the Hertz–Mindlin model in aspects of both microscopic and macroscopic mechanical behaviours of granular media with spherical and/or non-spherical particles. This finding suggests that the linear spring model can be used to investigate micro-mechanical behaviours of granular soils, even with complex particle shapes.

Experimental and numerical sizing of a delamination defect in layered composite materials

A methodical approach to the estimation of the localization zone and geometric parameters of a delamination defect in layered composite materials is presented on the basis of mathematical processing of the experimental results of deformation measurements obtained with a grid of fiber-optic sensors. The results of methodological developments related to the determination of the optimal topology of the grid of sensors to ensure the detection of defects of a given size with the necessary accuracy and determination of their parameters are presented. We present methods for computational analysis and simulation of the strain-stress state in the defect zone, based on the algorithm used for modeling the problems of strain-stress analysis in the defect zone using 2D finite elements, instead of 3D ones, thus allowing the use a model of lower dimensionality and retain all the features of the stress-strain state. The results of methodological developments related to the determination of the defect parameters from the results of strain measurements using the methodology of solving the inverse problem, based on solving the problem of minimizing the discrepancy between the vector of deformation response and the vector of initial parameters are presented. The technique is implemented as a software consisting of a series of macros for ANSYS and programs for MATLAB. The results of cyclic testing of a sample from a multilayer CM with a delamination type of defect are presented. Estimation of the increment in the defect size upon loading is performed by mathematical processing of data recorded by fiber-optic strain sensors glued on one of the sample surfaces, based on the solution of the inverse problem. Comparison of the results of calculations of geometric parameters of the defects with the measurement data obtained by the method of ultrasonic flaw detection showed good agreement between them.