Effects Of Changes In Composition Research Articles

Synthesis and characterization of chromium aluminum carbide MAX phases (CrxAlCx-1) for potential biomedical applications

MAX phases, characterized as nanolaminates of ternary carbides/nitrides structure, possess a unique combination of ceramic and metallic properties, rendering them pivotal in materials research. In this study, chromium aluminum carbide ternary compounds, Cr2AlC (211), Cr3AlC2 (312), and Cr4AlC3 (413) were successfully synthesized with high purity using a facile and cost-effective sol-gel method. Structural, morphological, and chemical characterization of the synthesized phases was conducted to understand the effects of composition changes and explore potential applications. Comprehensive characterization techniques including XRD for crystalline structure elucidations, SEM for morphological analysis, EDX for chemical composition, Raman spectroscopy for elucidation of vibrational modes, XPS to analyze elemental composition and surface chemistry, and FTIR spectroscopy to ensure the functional groups analysis, were performed. X-ray diffraction analysis indicated the high purity of the synthesized Cr2AlC phase as well as other ternary compounds Cr3AlC2 and Cr4AlC3, suggesting its suitability as a precursor for MXenes production. Additionally, the antimicrobial activity against Candida albicans and biocompatibility assessments against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and HepG2 cell line were investigated. The results demonstrated significant antifungal activity of the synthesized phases against Candida albicans and negligible impact on the viability of E. coli and S. aureus. Interestingly, lower concentrations of Cr2AlC MAX phase induced cytotoxicity in HepG2 cells by triggering intercellular oxidative stress, while Cr3AlC2 and Cr4AlC3 exhibited lower cytotoxicity compared to Cr2AlC, highlighting their potential in biomedical applications.

Physicochemical Stability of Hospital Parenteral Nutrition Solutions: Effect of Changes in Composition and Storage Protocol.

(1) Background: Parenteral nutrition (PN) is a technique used for the administration of nutrients to patients for whom traditional routes cannot be used. It is performed using solutions with extremely complex compositions, which can give rise to a large number of interactions. These interactions can impact their stability and put the patient's life at risk. The aim of this study is to determine how changes in composition and storage protocol affect the stability of NP solutions. (2) Methods: Twenty-three samples were prepared according to routine clinical practice, with modifications to the concentration of some components. The samples were stored at room temperature (RT) and refrigerated (4 °C). Measurements of the droplet diameter, pH, density and viscosity were performed for both storage protocols on days 1, 3, 10 and 14. (3) Results: The samples with the lowest concentration of lipids (PN13-17) and proteins (PN18-22) showed a larger droplet diameter than the rest of the samples throughout the experiments. The USP limits were exceeded for some of the measurements of these sample groups. The pH density and viscosity remained relatively constant under the conditions studied. (4) Conclusions: The PN samples were considered stable and safe for administration under real-world conditions, but the samples with the lowest concentrations of lipids and proteins showed a tendency towards emulsion instability.

A reactive electrochemomechanical theory for growth and remodeling of polyelectrolyte hydrogels and application to dynamic polymerization of DNA hydrogels

This study develops a framework for growth and remodeling of active polyelectrolyte hydrogels that accounts for effects of compositional changes on the mechanical response. By developing a reactive electrochemomechanical theory, thermodynamical constraints upon reactive and remodeling processes are elucidated within a general framework that allows any number of chemical reactions to evolve the response of the gel and transfer mass and charge between constituents. Fully coupled, nonlinear constitutive relations are adopted for molar fluxes, allowing exploration of effects including cross-diffusion, electrophoresis, and electro-osmosis. A robust finite element implementation is developed in the open source FEBio software (febio.org) by exploiting an equivalence between electrochemomechanics and mixture theory. The implementation is verified against analytical solutions for free swelling, and a proper reduction to a prior chemomechanical theory is demonstrated for neutral gels swollen only by a solvent with no solutes. The theory and implementation are then applied to model the tunable large swelling achieved through dynamic polymerization of DNA crosslinkers seen in our recently developed experimental hydrogel system (Cangialosi et al., 2017). A novel constitutive model for reaction-driven evolution of the locking stretch λL in a non-Gaussian mechanical free energy was developed, where the increasing concentration of DNA crosslinkers makes further swelling energetically favorable. With a single free parameter, excellent agreement was found between measured and predicted equilibrium swelling ratios. This study demonstrated the ability to extend the electrochemomechanical framework to include chemical reactions and composition-aware constitutive models, and showed that development of reactive models allows simulation of complex dynamic polymerization phenomena not treated before. The theoretical frame here can be further expanded in scope to incorporate additional non-ideal and nonlinear phenomena.

Enhancement of optical and radiation shielding properties in calcium–magnesium silicate bioactive glasses through Na2O and P2O5 additives

The present study investigates the influence of Na2O/MgO and P2O5/SiO2 substitutions on the structure and protective properties of bioactive glasses composed of 32CaO–19MgO–0.5P2O5–0.5CaF2–48SiO2 (mole %). The glass samples are prepared using the conventional melt-quenching method. Optical analyses, including refractive index (n), molar refraction (Rm), and cationic polarizability (αm), are calculated and discussed to examine structural modifications. Raman spectroscopy is employed for detailed structural analysis. The effects of compositional changes on the protective parameters are thoroughly investigated by theoretically determining mass attenuation using the newly developed Phy-X/PSD software and XCOM programs, which are then experimentally confirmed at three selected radioactive isotope energies. Experimental measurements of mass attenuation coefficient follow the sequence: MACG1 > MACG2 > MACG3 > MACG4. Raman spectroscopy results indicate that the glass network primarily consists of silicate and phosphate species as the main structural units. An increase in the molar ratio of Na2O and P2O5 improves the radiation shielding effectiveness of the samples. Among them, sample G5, with the lowest SiO2 and MgO content, exhibits the best shielding characteristics due to its high density and molar fraction of Na2O and P2O5. A correlation between microhardness and protective effectiveness is also established. The obtained results support the potential use of these glasses as dual agents for both radiation shielding and medical devices simultaneously.

The Effects of a Small Geomagnetic Storm on Earth's Thermosphere and Ionosphere: ICON Observations of the 25 January 2021 Disturbance

AbstractIsolated geomagnetic storms during solar minimum offer the opportunity to observe the effects of solar wind on Earth's atmosphere without interference from other background changes in the ionosphere‐thermosphere system. Here, we observe the effects of a minor storm on the ionosphere at middle and low latitudes, where disturbances in thermospheric winds and composition can produce storm‐time changes in ionospheric densities. Using data from the NASA Ionospheric Connection Explorer (ICON), we investigate the competing effects of composition changes and neutral wind disturbances in modifying the ionosphere during the 25 January 2021 storm. Large enhancements in plasma densities are seen across the dayside late on 25 January, associated with large changes in meridional winds and significant high‐latitude electric current enhancements as measured by the auroral electrojet index. At the same time, we find evidence of rapid transport of heated air from the southern auroral zone to the equator in the East‐Asian sector with the appearance of deeply reduced O/N2 in the morning sector and storm‐time northward winds prior to its appearance. We observe significant, rapid erosion of the high plasma densities in the sector where thermospheric disturbance appears over 5 hr of observation. The noon‐time plasma density enhancements are short‐lived and we observe no westward perturbation in the low‐middle latitude, dayside zonal winds over a 5‐day period including the storm. Thus, we attribute the ionospheric changes to prompt penetration and meridional wind forcing, while ruling out the presence of a storm‐time disturbance dynamo and its related ionospheric effects.

Electronics with stainless steel: The work functions

The work functions of different stainless steels were investigated and found to be in the range of 4.08–4.19 eV. They characterize the passive layer, an oxide layer on top of the stainless steel bulk material. This layer makes the steels corrosion-resistant, and it also controls the possible electronic and electrochemical applications of such materials. Structured samples were measured that are especially important for applications of these materials, e.g., in solar cells or fuel cells. The effects of composition changes of the stainless steel on the work function are unexpectedly small, which is likely related to a similar number of d electrons responsible for the electronic band structure.

The effect of composition changes on the structure and electronic properties of jamesonite: a DFT study.

Models of jamesonite with different compositions were built by different amounts of Sb or Pb substitution at Fe sites, and their structures and electronic properties were studied using the DFT method. The structure and properties of jamesonite significantly changed after Sb or Pb substitution. The lengths of the Sb-S and Pb-S bonds are larger than those of the corresponding Fe-S bonds of pure jamesonite, and the polarization of iron atoms adjacent to substitute atoms is weakened. After one Sb atom substitution, the S atoms bonded to Sb (substitution atom) gain more charges than those before Sb substitution. The Sb atom has more positive charges than the corresponding Fe atom before Sb substitution. For one Pb substitution system, the electrons transfer from the substituted Pb to adjacent S atoms, and the larger negative charge of the S atoms causes a slightly stronger Pb-S bond. With increasing Sb or Pb content, the electronic structural changes of the adjacent atoms are similar to those of one Sb or Pb substitution. However, the increase of 4-coordination Sb or 4-coordination Pb with the decrease of Fe atom changes the electronic structure of jamesonite, which will change its flotation performance.

Прогнозування теплофізичних властивостей хромовмісних феросплавів

The purpose of the work is to develop predictive models of thermophysical properties of chromium-containing ferroalloys. The Institute of Ferrous Metallurgy of the National Academy of Sciences of Ukraine conducts systematic studies of the physicochemical and thermophysical properties of ferroalloys with their modeling. With the use of the created "Ferrosplav" database, the article presents predictive models of thermophysical properties of chromium-containing ferroalloys for modeling the processes of interaction of ferroalloys with liquid steel. The physicochemical model of metal melt structuring is based on the use of interatomic interaction parameters. The metal melt is considered as a chemically unified system, and factor analysis with the generation of models of the optimal structure. Predictive models of thermophysical properties of chromium-containing ferroalloys were developed with an interval of 0.027–8.5% С and 29.2–72.7% Cr: Tsolidus, Tliquidus, ρ = f (d, ZY). The analysis of experimental data on the thermophysical properties of chromium-containing ferroalloys showed a close relationship with the parameters of interatomic interaction. The developed models make it possible to predict the effect of composition changes, expressed through integral parameters of interatomic interaction, on the properties of chromium-containing ferroalloys with an interval of 0.027-8.5% C and 29.2 – 72.7% Cr. They can be used to assess the properties of both a single grade and the entire range of chromium-containing ferroalloys.

Sensitivity Analysis of Reinforced Aluminum Based Metal Matrix Composites

Metal matrix composites (MMCs) have wide applications due to being lightweight, their high strength, and immense resistance to wear. To explore new generation materials like aluminum-based metal matrix composites (AMCs) for wide engineering applications, the present work aimed at investigating the effect of changes in composition, sintering time, and temperature on the hardness and surface roughness of AMCs containing SiC and ZrSiO4 in wt % of 5, 20, 30, and 40 binary and hybrid sample pallets. The samples have been prepared by powder metallurgy (PM) method under 1000 psi pressure. After compaction, the above pallets sintered at different temperatures ranging from 500 °C to 1100 °C with an increment of 200 °C and 15 min intervals for four levels of temperature and time, respectively. Afterwards, sensitivity analysis has been done by investigating the effect of chemical composition, sintering time, and sintering temperature of the binary and hybrid composites on hardness and surface roughness. Morphological studies on the composites were carried out using field emission scanning electron microscope (FESEM) with energy dispersive spectroscopy (EDS). It has been observed that hardness is increased by increasing the sintering temperature in the case of SiC, whereas surface roughness did not change much by changing the composition. Additionally, a rise in temperature lead to liquid-state sintering. SEM images obtained during the elemental analysis showed that porosity is generated within the samples after sintering due to the higher melting point of reinforcements compared to a base metal, i.e., aluminum. Mathematical equations have also been developed via regression analysis using Minitab and excel for the confirmation and validation of experimental data. Analysis of Variance (ANOVA) has also been done, and its tables are shown and discussed in the paper. Hence, the most optimized findings relating the changes in the composition of reinforcements, sintering temperature, and sintering time (input variables) with porosity, hardness, and surface roughness have been presented in the current study.

The effect of composition change and allocation in raw material on the carbonaceous structural evolution during calcination process

To investigate the effect of calcination process on the characteristics of different carbonaceous structures, decant oil (DO) and low-temperature coal tar (LCT) were selected as materials to refine and blend to prepare the green cokes with different microstructures, and the influence of calcination on the structural evolution of green cokes with different orientation and planarity was studied. It is concluded that the nitrogen content of calcined needle coke decreased to a relatively low value at the calcination temperature of 1300℃ and the removal of QI decreased the sulfur content in calcined cokes. Calcination process would further promote the accumulation of aromatic lamellae on the original basis. The abundant QI in LCT led to the formation of mosaic structures in green coke stage and calcination aggravated the poor planarity of aromatic sheets of mosaic texture. The refining process and blend of raw materials significantly enhanced the proportion of key components and calcination improved the extendability and planarity of graphitic aromatic sheets with the increase of Tri-Ar and Tetra-Ar. In addition, calcination further optimized the aromatic lamellae of acicular domain texture with good planarity and structural orientation, and DO-CNC obtained the highest stacking parameters (Lc = 3.55 nm; N = 11.30; d002 = 3.445 Å).

Effects of composition changes of coal treated with hydrochloric acid on pore structure and fractal characteristics

In order to investigate the influence of coal compositions on the pore structure, low temperature gas adsorption (LTGA) method was used to analyze the pore evolution of coal samples treated with hydrochloric acid. The results demonstrate that hydrochloric acid treatment significantly reduced the content of minerals and volatile matter in coal, which could increase the porosity and the pore connectivity of coal. The removal of volatile matter has an obvious reaming effect on supermicropores, but ultramicropores remained unchanged. The role of minerals in pores of different pore widths is different, which are the fillers in macropores, the skeletons of some large mesopores and the blockage in some small mesopores. With the decrease of minerals, the macropore volume increased, and the large mesopore volume first decreased and then increased. In addition, the opening of many closed small mesopores increased the fractal dimension D2 of pore structure complexity, and provides an increase in specific surface area, but it has no significant relationship with the fractal dimension D1 of pore surface roughness.

Effect of Copper Cobalt Oxide Composition on Oxygen Evolution Electrocatalysts for Anion Exchange Membrane Water Electrolysis.

Copper cobalt oxide nanoparticles (CCO NPs) were synthesized as an oxygen evolution electrocatalyst via a simple co-precipitation method, with the composition being controlled by altering the precursor ratio to 1:1, 1:2, and 1:3 (Cu:Co) to investigate the effects of composition changes. The effect of the ratio of Cu2+/Co3+ and the degree of oxidation during the co-precipitation and annealing steps on the crystal structure, morphology, and electrocatalytic properties of the produced CCO NPs were studied. The CCO1:2 electrode exhibited an outstanding performance and high stability owing to the suitable electrochemical kinetics, which was provided by the presence of sufficient Co3+ as active sites for oxygen evolution and the uniform sizes of the NPs in the half cell. Furthermore, single cell tests were performed to confirm the possibility of using the synthesized electrocatalyst in a practical water splitting system. The CCO1:2 electrocatalyst was used as an anode to develop an anion exchange membrane water electrolyzer (AEMWE) cell. The full cell showed stable hydrogen production for 100 h with an energetic efficiency of >71%. In addition, it was possible to mass produce the uniform, highly active electrocatalyst for such applications through the co-precipitation method.

Earth tomography with atmospheric neutrino oscillations

The study of the flux of atmospheric neutrino crossing the Earth can provide useful information not only on the matter density of the different layers that make up the planet but also on their chemical composition. The key phenomenon that makes this possible is flavor oscillations and their dependence on the electron density along the neutrino baseline. To extract the relevant information, we simulate the energy and azimuth angle distribution of events produced in a generic neutrino telescope by atmospheric neutrinos passing through the deepest parts of the Earth. Changes in the densities of the outer core and the mantle are implemented by varying the location of the boundary between these layers so that the restrictions on the mass of and the moment of inertia of the Earth are both satisfied. This allows us to examine the effect of simultaneous changes in composition and density of the outer core, unlikely other works on the subject, where only one of these quantities was varied.

Enhanced current collection of CdTe solar cells in the long wavelength region by co-evaporation deposition CdSexTe1-x films

Using a gradient band gap absorption layer to ensure high short-circuit current density is one of the key factors to prepare high-efficiency CdTe solar cells. CdSexTe1-x films with different selenium compositions were prepared by vacuum co-evaporation deposition technology. The effects of composition changes on the structure, morphology and properties of the films were studied. CdSexTe1-x films were incorporated into the CdTe solar cells with the structure of Glass/SnO2:F/CdS/CdSexTe1-x/CdTe/ZnTe:Cu/Au. The results show that the structure of CdSexTe1-x films is cubic when x is 0, 0.23 or 0.41, and while x is 0.61, 0.78 or 1 the structure is hexagonal. The minimum optical band gap is 1.40 eV with x = 0.41. It is found that in the long wavelength region, the cut-off edge of quantum efficiency curve depends on not only the thickness of CdSexTe1-x film with specific Se composition, but also the whole preparation process of solar cells. After using a 70 nm CdSe0.41Te0.59 film and 70 nm ZnTe:Cu back contact buffer layer, the cut-off edge of the long wavelength region can be reduced to 1.40 eV and the short-circuit current density of the device without antireflection layer reaches up to 28.8 mA/cm2.

Effect of compositional changes on the structural properties of borophosphate glasses: ATR-FTIR and Raman spectroscopy

In the present work, two sets of glass compositions: (79.5-x) B2O3 + x P2O5 + 10 Na2O + 10 PbO + 0.5AgO and 54.5 B2O3 + (25-x) P2O5 + (10+x) Na2O + 10 PbO + 0.5AgO (x = 0, 5, 10, 15, 20, 25 mol%), were prepared and investigated by means of their density, molar volume, UV-Vis optical absorption, IR absorption and Raman spectroscopic methods. Both density and molar volume properties with x mol% of P2O5 and Na2O in glasses were discussed. The effects of P2O5, B2O3 and Na2O in the optical energy gap (Eopt) are also presented and discussed. In Raman analysis, an increase of P2O5 resulted in a clear conversion of B Ø3 to B Ø4 units with four non-bridging oxygens bonded to phosphate groups (POB linkages, pyro- and ortho-phosphates) identified in all the spectra. With increasing Na2O, the metaphosphate network gets extensively depolymerized, resulting in the conversion of Q1 to Q° structural units. In IR absorption analysis, the addition of P2O5 at the expense of B2O3 resulted in the decrease of BO bonds with enhancements of P-O- and P=O bonds in PO2- groups. An increase of Na2O at the expense of P2O5, evinced a tendency of B Ø4 tetrahedra/BØ3 trigonal to create diborate/pyroborate groups to accommodate excess amount of Na cations into the BO network.

The Effect of Compositional Changes Due to Seasonal Variation on Milk Density and the Determination of Season-Based Density Conversion Factors for Use in the Dairy Industry.

The objective of this study was to determine the effect of seasonal variation on milk composition and establish an algorithm to predict density based on milk composition to enable the calculation of season-based density conversion calculations. A total of 1035 raw whole milk samples were collected from morning and evening milking of 60 spring-calving individual cows of different genetic groups, namely Jersey, Elite HF (Holstein–Friesian) and National Average HF, once every two weeks for a period of 9 months (March–November, 2018). The average mean and standard deviation for milk compositional traits were 4.72 ± 1.30% fat, 3.85 ± 0.61% protein and 4.69 ± 0.30% lactose and density was estimated at 1.0308 ± 0.002 g/cm3. The density of the milk samples was evaluated using three methods: a portable density meter, DMA 35; a standard desktop version, DMA 4500M; and an Association of Official Agricultural Chemists (AOAC) method using 100-mL glass pycnometers. Statistical analysis using a linear mixed model showed a significant difference in density of milk samples (p < 0.05) across seasonal and compositional variations adjusted for the effects of days in milk, parity, the feeding treatment, the genetic group and the measurement technique. The mean density values and standard error of mean estimated for milk samples in each season, i.e., spring, summer and autumn were 1.0304 ± 0.00008 g/cm3, 1.0314 ± 0.00005 g/cm3 and 1.0309 ± 0.00007 g/cm3, respectively.

On Numerical Stabilization in Modeling Double-Diffusive Viscous Fingering

A firm understanding and control of viscous fingering (VF) and miscible displacement will be vital to a wide range of industrial, environmental, and pharmaceutical applications, such as geological carbon-dioxide sequestration, enhanced oil recovery, and drug delivery. We restrict our study to VF, a well-known hydrodynamic instability, in miscible fluid systems but consider double-diffusive (DD) effects---the combined effect of compositional changes because of solute transport and temperature. One often uses numerical formulations to study VF with DD effects. The primary aim of the current study is to show that popular formulations have limitations to study VF with DD effect. These limitations include exhibiting node-to-node spurious oscillations, violating physical constraints such as the non-negativity of the concentration field or mathematical principles such as the maximum principle, and suppressing physical instabilities. We will use several popular stabilized finite element formulations---the SUPG formulations and three modifications based on the SOLD approach---in our study. Using representative numerical results, we will illustrate two critical limitations. First, we document that these formulations do not respect the non-negative constraint and the maximum principle for the concentration field. We will also show the impact of these violations on how viscous fingers develop. Second, we show that these stabilized formulations, often used to suppress numerical instabilities, may also suppress physical instabilities, such as viscous fingering. Our study will be valuable to practitioners who use existing numerical formulations and to computational mathematicians who develop new formulations.

Effects of compositional changes on up-conversion photoluminescence and electrical properties of lead-free Er-doped K0.5Na0.5NbO3-SrTiO3 transparent ceramics

Er-doped K0.5Na0.5NbO3-SrTiO3 transparent ceramics were fabricated by traditional pressureless sintering. The dual effects of Er3+ and SrTiO3 contents on the microstructures, optical transparencies and optoelectronic properties of the ceramics were investigated. The introduction of Er3+ and Sr2+ results in decreasing grain size and generating cation vacancies, affecting the density and uniformity of the ceramics. The ceramics exhibit superior transmittance: T ∼55% in the visible region (760 nm) and ∼75% in the infrared region (2000 nm), which is dependent on optical band gap energy. In terms of electrical properties, the ceramics also possess relaxor-like characteristics, low dielectric loss and suitable piezoelectric constants. Due to Er3+, the ceramics exhibit composition-tunable green and red up-conversion photoluminescence emissions, whose intensities are related to the crystal symmetry. Combined with good optical and electrical properties, the ceramics open up potential applications in the electrical/optical interdisciplinary field, such as visible displays, solid-state lasers and transparent electronic devices.

Mechanistic Model Describes Wettability Change in Sandstones and Carbonates

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 190236, “Modeling Wettability Change in Sandstones and Carbonates Using a Surface-Complexation-Based Method,” by Aboulghasem K.N. Korrani, SPE, and Gary R. Jerauld, SPE, BP, prepared for the 2018 SPE Improved Oil Recovery Conference, Tulsa, 14–18 April. The paper has not been peer reviewed. Previously proposed models of wettability change have not been tied to the chemistry that controls wettability but instead were driven by simplistic criteria such as salinity level or concentration of an adsorbed species. In this paper, after testing proposed models in the literature on sandstones and carbonates, the authors propose a mechanistic surface-complexation-based model that describes observations quantitatively for ionically treated waterfloods. To the best of the authors’ knowledge, this is the first surface-complexation-based model that describes fully ionic compositional dependence observed in ionically treated waterfloods in both sandstones and carbonates. Introduction While some debate remains about the underlying mechanisms of ionically tuned waterflooding, the geochemical reactions that control the wetting of crude oil on the rock surface are likely to be central to a detailed description of the process. Models of wettability change often have been simplistic and not tied to the chemistry that controls wettability, instead driven by a simplistic criterion such as salinity level or concentration of an adsorbed species. Such models are inadequate for modeling the effect of compositional changes in brine, which is key to optimizing ionic design. One problem has been the lack of reservoir models that included geochemistry. The oilfield reactive-transport simulators are simplistic; in these, either aqueous reactions are assumed to be ideal (i.e., with aqueous activity coefficients of unity) or they lack important geochemical features such as kinetics or surface-complexation reactions. In a previous work, the authors assumed that decrease in the total ionic strength is the driving mechanism for wettability change during low-salinity waterflooding. The reason was that the total ionic strength is the controlling parameter for the double-layer expansion. Double-layer thickness increases as the brine total ionic strength decreases. The thickness of the double layer is an inverse function of the square root of the total ionic strength. However, the proposed model was too simple and was unable to predict many low-salinity or modified-salinity waterflooding observations, such as the detrimental effect of divalents on oil recovery in sandstones, the positive effect of sulfate in chalks, the positive effect of high pH in sand-stones, and the detrimental effect of sodium chloride in chalks. In this study, the authors identified and tested an alternative approach based on a stability analysis of thin water film, which yields a dimensionless group, a ratio of electrostatic-to-Van der Waals (VdW) forces called the stability number. The stability number can be used as a measure of wettability. The authors use simulation software to model surface reactions that can estimate surface charge and potential from surface-complexation models, demonstrating that this process can be used in a model to match a wide variety of data in sandstones and carbonates found in models in the literature. The complete paper provides details of these comparisons.

Implications of crop model ensemble size and composition for estimates of adaptation effects and agreement of recommendations

Climate change is expected to severely affect cropping systems and food production in many parts of the world unless local adaptation can ameliorate these impacts. Ensembles of crop simulation models can be useful tools for assessing if proposed adaptation options are capable of achieving target yields, whilst also quantifying the share of uncertainty in the simulated crop impact resulting from the crop models themselves. Although some studies have analysed the influence of ensemble size on model outcomes, the effect of ensemble composition has not yet been properly appraised. Moreover, results and derived recommendations typically rely on averaged ensemble simulation results without accounting sufficiently for the spread of model outcomes. Therefore, we developed an Ensemble Outcome Agreement (EOA) index, which analyses the effect of changes in composition and size of a multi-model ensemble (MME) to evaluate the level of agreement between MME outcomes with respect to a given hypothesis (e.g. that adaptation measures result in positive crop responses). We analysed the recommendations of a previous study performed with an ensemble of 17 crop models and testing 54 adaptation options for rainfed winter wheat (Triticum aestivum L.) at Lleida (NE Spain) under perturbed conditions of temperature, precipitation and atmospheric CO2 concentration. Our results confirmed that most adaptations recommended in the previous study have a positive effect. However, we also showed that some options did not remain recommendable in specific conditions if different ensembles were considered. Using EOA, we were able to identify the adaptation options for which there is high confidence in their effectiveness at enhancing yields, even under severe climate perturbations. These include substituting spring wheat for winter wheat combined with earlier sowing dates and standard or longer duration cultivars, or introducing supplementary irrigation, the latter increasing EOA values in all cases. There is low confidence in recovering yields to baseline levels, although this target could be attained for some adaptation options under moderate climate perturbations. Recommendations derived from such robust results may provide crucial information for stakeholders seeking to implement adaptation measures.