Residual Hydrogen Research Articles

On the cost of zero residual CO2 emission hydrogen: A techno-economic analysis of steam methane reforming with carbon capture and storage

On the cost of zero residual CO2 emission hydrogen: A techno-economic analysis of steam methane reforming with carbon capture and storage

A dynamic sample augmentation Kriging metamodeling method for industrial residue hydrogenation process

AbstractResidue hydrogenation process (RHP) plays an important role in efficient utilization of heavy oil resources. The high‐fidelity model of RHP is so complex that its optimization cost is expensive and even intractable. Furthermore, in the actual industrial processes, due to the low sampling frequencies of some sensors, only a few sampling points can be obtained with some missing values. The insufficient samples can directly affect the performance of the final model. Therefore, a new adaptive dynamic sampling (ADS) method for Kriging metamodeling is proposed. Based on a small number of valid industrial sample points, the proposed method adaptively obtains key information sampling points and selectively adds key information sampling points to update the model. First, the difference maximization strategy and the outlier distance strategy are proposed to obtain new sampling points with both global and regionalized information. Then, the new key points are used to iteratively update the Kriging predictor to obtain satisfactory accuracy. Finally, the calculation result of benchmark cases and two actual experiments validate the effectiveness of the proposed method for constructing surrogate models of complex industrial processes.

Susceptibility of carbon pipeline steels operated in natural gas distribution network to hydrogen-induced cracking

The existing network of both transit and distribution gas pipelines has recently been proposed to be used for the transportation of hydrogen as an energy fuel in the multifaceted structure of the development of renewable energy sources. From this point of view, the paper considers the sensitivity of a long-term operated steel of distribution gas pipeline to hydrogen assisted cracking as a result of preliminary electrolytic hydrogenation of flat tensile specimens, followed by determination of strength and plasticity characteristics. The research methodology has two features: (i) the specimens are cut out from the pipe in the transverse direction to the pipe axis; in this case the fracture plane is parallel to the rolling direction of metal sheet from which the pipes were made; (ii) specimen thickness is 1.2 mm maximally providing through hydrogenation. The study additionally includes determination of hydrogen concentration in the steel, and fractographic analysis. It is shown that the low-carbon steel of the 52-year-old gas pipeline with high residual hydrogen content especially sensitive to hydrogen assisted cracking, indicated by signs of low-energy fracture at the micro scale.

Estimation of Residual Hydrogen in Laser Weld by Two-dimensional Differential Calculation

It has been reported that hydrogen dissolves in the weld bead in laser welding. If the hydrogen concentration in the weld bead is high, there is concern that the weld bead may fracture during press forming of tailored blanks. Therefore, assuming that 1ppm of hydrogen is dissolved in the weld bead at welding, the change in hydrogen concentration over time is estimated by a two-dimensional difference calculation. In the calculations, hydrogen is assumed to follow the Fick’s diffusion equation, and the diffusion coefficient at room temperatures is the value determined by the authors for a 980MPa steel laser welds in the past. The diffusion coefficients at high temperatures were determined from several references. As a result, it was estimated that about 30% of the hydrogen had effused from the surface by the time the weld bead cooled to room temperature. The mechanical properties of the weld bead are considered to be governed by the maximum hydrogen concentration at the center of the weld bead cross-section, but this value cannot be measured directly. Therefore, assuming that all the hydrogen contained in the entire model is in the weld bead and considering the average hydrogen concentration in the weld bead, the ratio of the maximum hydrogen concentration to the average hydrogen concentration is around 1 up to 6h after welding, indicating that the average hydrogen concentration is a good indicator of the maximum hydrogen concentration. It was also confirmed that the logarithm of the average hydrogen concentration is proportional to time as time passes after welding and that the hydrogen concentration distribution in the thickness direction behaves as a solution of a one-dimensional diffusion equation. These results suggest that the hydrogen concentration in the laser weld bead can be considered as an analytical solution of the one-dimensional diffusion equation.

Phases of Mass Transfer from Hot Subdwarfs to White Dwarf Companions and Their Photometric Properties

Abstract Binary systems of a hot subdwarf B (sdB) star + a white dwarf (WD) with orbital periods less than 2–3 hr can come into contact due to gravitational waves and transfer mass from the sdB star to the WD before the sdB star ceases nuclear burning and contracts to become a WD. Motivated by the growing class of observed systems in this category, we study the phases of mass transfer in these systems. We find that because the residual outer hydrogen envelope accounts for a large fraction of an sdB star’s radius, sdB stars can spend a significant amount of time (∼tens of megayears) transferring this small amount of material at low rates (∼10−10–10−9 M ⊙ yr−1) before transitioning to a phase where the bulk of their He transfers at much faster rates ( ≳10−8 M ⊙ yr−1). These systems therefore spend a surprising amount of time with Roche-filling sdB donors at orbital periods longer than the range associated with He star models without an envelope. We predict that the envelope transfer phase should be detectable by searching for ellipsoidal modulation of Roche-filling objects with P orb = 30–100 minutes and T eff = 20,000–30,000 K, and that many (≥10) such systems may be found in the Galactic plane after accounting for reddening. We also argue that many of these systems may go through a phase of He transfer that matches the signatures of AM CVn systems, and that some AM CVn systems associated with young stellar populations likely descend from this channel.

Effect of Co substitution on hydrogenation behavior of GdNi3-xCox (x = 0, 0.2, 1.0) and crystal structure of its hydride phases

The effect of substituting Co for Ni in GdNi3 on the hydrogenation properties and phase transformation during the hydrogen absorption–desorption process of GdNi3-xCox (x = 0, 0.2, 1.0) was investigated using P–C isotherms and X-ray diffraction analysis (XRD). GdNi3 showed a residual hydrogen content of 0.6 H/M after the first desorption process. The maximum hydrogen capacity of GdNi3 was 1.0 H/M, while the reversible hydrogen capacity decreased to 0.4 H/M because of the residual hydrogen. The reversible hydrogen capacity was improved to 1.0 H/M in GdNi2.0Co1.0, and two plateaus were observed in the absorption–desorption process. The crystal structures of the full hydride phases GdNi3H3.8 and GdNi2.8Co0.2H3.8 could not be determined because of the heavy peak broadening in the XRD pattern, while the PuNi3-type structure of the original alloy was retained in the full hydride phase GdNi2.0Co1.0H3.6. The retention rates of GdNi3 and GdNi2.0Co1.0 at 100 cycles were 75% and 92%, respectively. The cyclic properties of GdNi2.0Co1.0, up to 100 cycles, favorably compared with those of LaNi5, which was found to be related to the small lattice strain formed during the first hydrogen absorption process.

Hydrogen Absorption and Desorption Behavior on Aluminum-Coated Hot-Stamped Boron Steel during Hot Press Forming and Automotive Manufacturing Processes.

Our study mainly focused on diffusible hydrogen in aluminum–silicon-coated hot-stamped boron steel during a hot press forming process and in pre-treatment sequential lines of the automotive manufacturing process using a thermal desorption spectroscopy (TDS) technique. First, in the hot stamping procedure, as the soaking time increased in the heating furnace at a specific dew point when austenitizing, a high concentration of diffusible hydrogen was absorbed into the hot-stamped boron steel. Based on the TDS analysis of hydrogen absorbed from hot stamping, the activation energy value of hydrogen trapping in 1.8 GPa grade steel is lower than that of 1.5 GPa grade steel. This means that diffusible hydrogen can be more easily diffused into defective sites of the microstructure at a higher level of the tensile strength grade. Second, in sequential pre-treatment lines of the automotive manufacturing process, additional hydrogen did not flow into the surface, and an electro-deposition process, including a baking procedure, was effective in removing diffusible hydrogen, which was similar to the residual hydrogen of the as-received state (i.e., initial cold rolled blank). Based on these results, the hydrogen absorption was facilitated during hot press forming, but the hydrogen was sequentially desorbed during automotive sequential lines on aluminum-coated hot-stamped steel parts.

Lyman-α transmission properties of the intergalactic medium in the CoDaII simulation

ABSTRACT The decline in abundance of Lyman-α (Lyα) emitting galaxies at z ≳ 6 is a powerful and commonly used probe to constrain the progress of cosmic reionization. We use the CoDaII simulation, which is a radiation hydrodynamic simulation featuring a box of ∼94 comoving Mpc side length, to compute the Lyα transmission properties of the intergalactic medium (IGM) at z ∼ 5.8 to 7. Our results mainly confirm previous studies, i.e. we find a declining Lyα transmission with redshift and a large sightline-to-sightline variation. However, motivated by the recent discovery of blue Lyα peaks at high redshift, we also analyse the IGM transmission on the blue side, which shows a rapid decline at z ≳ 6 of the blue transmission. This low transmission can be attributed not only to the presence of neutral regions but also to the residual neutral hydrogen within ionized regions, for which a density even as low as $n_{\rm HI}\sim 10^{-9}\, \mathrm{cm}^{-3}$ (sometimes combined with kinematic effects) leads to a significantly reduced visibility. Still, we find that $\sim 1{{\ \rm per\ cent}}$ of sightlines towards M1600AB ∼ −21 galaxies at z ∼ 7 are transparent enough to allow a transmission of a blue Lyα peak. We discuss our results in the context of the interpretation of observations.

Nanometer-Thick SiN Films as Gas Barrier Coatings Densified by Vacuum UV Irradiation

Gas barrier films are widely used in electronic and packaging applications. They are also critical components of flexible organic light-emitting diodes (FOLEDs) that require high gas barrier performance. Among the various film manufacturing techniques, solution-processed thin-film encapsulation (TFE) represents a low-cost FOLED fabrication method. The nanometer-thick SiN films produced following the vacuum ultraviolet (VUV)-induced densification of solution-processed perhydropolysilazane (PHPS) films in a N2 atmosphere can potentially serve as TFE barrier films. However, the nanometer-thick PHPS densification process has not been examined in sufficient detail. We investigated and discussed the effects of the Si–N bond number, PHPS film composition, and free volume (present in the produced Si–N network) on the VUV-induced PHPS densification process. It was found that VUV irradiation caused rapid hydrogen release and film densification through the formation of Si–N bonds. The results obtained using the X-ray photoelectron spectroscopy and dynamic secondary ion mass spectrometry techniques, and the calculated residual hydrogen ratios, revealed that the film composition was strongly related to the number of residual hydrogen atoms and Si–N bonds. Notably, nanometer-thick PHPS film densification was a relatively slow process, in which the free volume in the Si–N network was considerably reduced by the atomic rearrangement induced by the simultaneous cleavage of several Si–N bonds during VUV irradiation. We believe that the results presented herein can potentially serve as a guideline for developing solution-processed nanometer-thick SiN films with relatively high density and excellent gas barrier performance (that is comparable to that exhibited by vacuum-processed barrier films).

Protein-Protein Interactions: Insight from Molecular Dynamics Simulations and Nanoparticle Tracking Analysis.

Protein-protein interaction plays an essential role in almost all cellular processes and biological functions. Coupling molecular dynamics (MD) simulations and nanoparticle tracking analysis (NTA) assay offered a simple, rapid, and direct approach in monitoring the protein-protein binding process and predicting the binding affinity. Our case study of designed ankyrin repeats proteins (DARPins)—AnkGAG1D4 and the single point mutated AnkGAG1D4-Y56A for HIV-1 capsid protein (CA) were investigated. As reported, AnkGAG1D4 bound with CA for inhibitory activity; however, it lost its inhibitory strength when tyrosine at residue 56 AnkGAG1D4, the most key residue was replaced by alanine (AnkGAG1D4-Y56A). Through NTA, the binding of DARPins and CA was measured by monitoring the increment of the hydrodynamic radius of the AnkGAG1D4-gold conjugated nanoparticles (AnkGAG1D4-GNP) and AnkGAG1D4-Y56A-GNP upon interaction with CA in buffer solution. The size of the AnkGAG1D4-GNP increased when it interacted with CA but not AnkGAG1D4-Y56A-GNP. In addition, a much higher binding free energy (∆GB) of AnkGAG1D4-Y56A (−31 kcal/mol) obtained from MD further suggested affinity for CA completely reduced compared to AnkGAG1D4 (−60 kcal/mol). The possible mechanism of the protein-protein binding was explored in detail by decomposing the binding free energy for crucial residues identification and hydrogen bond analysis.

In Situ Evolution of Pores in Lithium Hydride at Elevated Temperatures Characterized by X-ray Computed Tomography

The evolution of defects such as pores at elevated temperatures is crucial for revealing the thermal stability of lithium hydride ceramic. The in situ evolution of pores in sintered lithium hydride ceramic from 25 °C to 500 °C, such as the statistics of pores and the 3D structure of pores, was investigated by X-ray computed tomography. Based on the statistics of pores, the porosity significantly increased from 25 °C to 200 °C and decreased after 200 °C, due to the significant change in the number and total volume of the round-shaped pores and the branched crack-like pores with an increasing temperature. According to the 3D structure of pores, the positions of pores did not change, and the sizes of pores went up in the range of 25–200 °C and went down after 200 °C. Some small round-shaped pores with an Equivalent Diameter of less than 9 μm appeared at 200 °C and disappeared at elevated temperatures. Some adjacent pores of all types connected at 200 °C, and some branched crack-like pores gradually disconnected with an increasing temperature. The expansion of pores at 200 °C caused by the release of residual hydrogen and the contraction of pores after 200 °C because of the migration and diffusion of some hydrogen in pores might be the reason for the evolution of pores with an increasing temperature.

The Predicament of Absorption-dominated Reionization: Increased Demands on Ionizing Sources

Abstract The reionization epoch concludes when ionizing photons reach every corner of the universe. Reionization has generally been assumed to be limited primarily by the rate at which galaxies produce ionizing photons, but the recent measurement of a surprisingly short ionizing photon mean free path of 0.75 − 0.45 + 0.65 proper Mpc at z = 6 by Becker et al. suggests that absorption by residual neutral hydrogen in the otherwise ionized intergalactic medium may play a much larger role than previously expected. Here we show that consistency between this short mean free path and the coeval dark pixel fraction in the Lyα forest requires a cumulative output of 6.1 − 2.4 + 11 ionizing photons per baryon by reionization’s end, well above the typically required ∼1–3. This represents a dramatic increase in the ionizing photon budget over previous estimates, greatly exacerbating the tension with measurements of the ionizing output from galaxies at later times. Translating this constraint into the instantaneous ionizing production from galaxies in our model, we find log 10 f esc ξ ion / ( erg / Hz ) − 1 = 25.02 − 0.21 + 0.45 at z ∼ 6. Even with optimistic assumptions about the ionizing production efficiency of early stellar populations, and assuming the galaxy luminosity function extends to extremely faint sources (M UV ≤ − 11), complete reionization requires the escape fraction of ionizing photons to exceed 20% across the galaxy population. This is far larger than observed in any galaxy population at lower redshifts, requiring rapid evolution in galaxy properties after the first billion years of cosmic time. This tension cannot be completely relieved within existing observational constraints on the hydrogen neutral fraction and mean free path.

Drug repurposing approach against Mycobacterium tuberculosis Enoyl-[acyl-carrier-protein] reductase: insight from molecular dynamics simulations

ABSTRACT Enoyl-[acyl-carrier-protein] reductase (InhA) is one of the major targets for the inhibition of Mycobacterium tuberculosis (Mtb). Herein, we introduce a drug repurposing approach against Mtb-InhA: Insight from molecular dynamic simulations. The approach was found hopeful to identify in silico hits with better binding affinities as compared to isoniazid. Four drug hits displayed higher total binding energies (ΔG tot) in relation to isoniazid with DB04007 exhibiting the highest ΔG tot of −41.11 kcal/mol as compared to the −7.89 kcal/mol from isoniazid. Herein, the results revealed that the isoniazid is less stable compared to DB04007. Hence, this pattern was reiterated by the lower RoG of DB04007. Both DB04007 and isoniazid exhibited a structural evolution denoted to common flexibility changes. A distinct increase in fluctuation was seen in the RMSF of DB04007 which could be attributed to Ser92 forming 2 hydrogen bonds with the inhibitor, the distal amino acids affecting stability and the evolution of residues 195-210 from a primary to a secondary structure. DB04007 exhibited a higher total binding free energy due to the residual van der Waals and hydrogen bonding interactions as compared to the isoniazid. This approach can potentially serve as a platform for the development and discovery of novel drugs.

Hydrogen isotope dissolution and release behavior in Y‐doped BaCeO3

AbstractOxides having a perovskite structure are known to exhibit good proton conductivity in a high‐temperature region, which makes them potential candidates in the tritium recovery and purification system of the electrochemical devices of fusion reactors such as hydrogen pumps, hydrogen sensors, and tritium monitoring systems. But the dissolution of hydrogen into the proton conductor and its release behavior is not well known yet. In this study, the dissolution and release behavior of hydrogen was investigated in BaCe0.9Y0.1O3−α proton conductor by exposing deuterium gas (D2) and heavy water vapor (D2O) at 600 or 700°C for 5 h. The dissolved deuterium amount in the sample was measured using a temperature‐programmed desorption analysis (TDS) method. The relationship between the amount of deuterium dissolved in the sample with the exposure pressure was also investigated. At room temperature (RT), the diffusivity of hydrogen (e.g., deuterium) was calculated from the change of the amount of residual hydrogen in the exposed sample due to the change of storage time. The Tritium Migration Analysis Program, Version 4 (TMAP4) simulation code was used to simulate and compare the experimental value of the obtained diffusivity. Although diffusivity at RT has not been reported in the past, the diffusivity is close to the extrapolation value of the literature data. From the comparison of this research results with literature, it may consider that the dominant diffusion mechanism does not change regardless of the temperature range.

Recovering Density Fields inside Quasar Proximity Zones at z ∼ 6

Abstract The matter density field at z ∼ 6 is very challenging to probe. One of the traditional probes of the low density intergalactic medium that works successfully at lower redshifts is the Lyα forest in quasar spectra. However, at the end of reionization, the residual neutral hydrogen usually creates saturated absorption, thus much of the information about the gas density is lost. Luckily, in a quasar proximity zone, the ionizing radiation is exceptionally intense, thus creating a large region with nonzero transmitted flux. In this study we use the synthetic spectra from simulations to investigate how to recover the density fluctuations inside the quasar proximity zones. We show that, under ideal conditions, the density can be recovered accurately with a small scatter. We also discuss how systematics such as the quasar continuum fitting and reionization models affect the results. This study shows that by analyzing the absorption features inside quasar proximity zones we can potentially constrain quasar properties and the environments they reside in.

Study of bleaching of old newsprint recycled paper: reproduction of newspaper material

With the utilization of used newspaper into the paper making industry, bleaching has been an area of concern to obtain a balance between desired brightness and the amount of treatment it requires. Motivation of this study was to optimize bleaching of recycled newsprint fibers in terms of five variables namely hydrogen peroxide charge, amount of sodium hydroxide employed, pulp consistency, bleaching temperature, and bleaching time. Experimental work was conducted in the laboratory to simulate bleaching plant and it was found that higher peroxide charge is better for improvement in brightness, but it is uneconomical to increase peroxide charge indefinitely. The amount of hydrogen peroxide is added so that the residual peroxide at the end of the reaction is not less than 10% of the initially added peroxide. Sodium hydroxide provides alkalinity which is very important for making the fibers flexible and softening of ink particles but it also contributes to pulp yellowing if residual hydrogen peroxide contents are lesser than the minimum required value. So, for 16 kg t−1 of hydrogen peroxide, 6 kg t−1 of sodium hydroxide prevented the brightness reversion in this study. Higher pulp consistency is better but unavailability of very high consistency pulp mixer in the industry is a limiting factor for higher than 30% pulp consistency. Temperature and time are quite interrelated and, with the given bleaching conditions, a temperature of 95 °C with 10 min residence time was found to be optimum for this study. It was also observed that multiple pre-washings increase brightness and save bleaching chemicals.

SN 2020bqj: A Type Ibn supernova with a long-lasting peak plateau

Context. Type Ibn supernovae (SNe Ibn) are a rare class of stripped envelope supernovae interacting with a helium-rich circumstellar medium (CSM). The majority of the SNe Ibn reported in the literature display a surprising homogeneity in their fast-evolving lightcurves and are typically found in actively starforming spiral galaxies. Aims. We present the discovery and the study of SN 2020bqj (ZTF20aalrqbu), a SN Ibn with a long-duration peak plateau lasting 40 days and hosted by a faint low-mass galaxy. We aim to explain its peculiar properties using an extensive photometric and spectroscopic data set. Methods. We compare the photometric and spectral evolution of SN 2020bqj with regular SNe Ibn from the literature, as well as with other outliers in the SN Ibn subclass. We fit the bolometric and multi-band lightcurves with powering mechanism models such as radioactive decay and CSM interaction. We also model the host galaxy of SN 2020bqj. Results. The risetime, peak magnitude and spectral features of SN 2020bqj are consistent with those of most SNe Ibn, but the SN is a clear outlier in the subclass based on its bright, long-lasting peak plateau and the low mass of its faint host galaxy. We show through modeling that the lightcurve of SN 2020bqj can be powered predominantly by shock heating from the interaction of the SN ejecta and a dense CSM, combined with radioactive decay. The peculiar Type Ibn SN 2011hw is a close analog to SN 2020bqj in terms of lightcurve and spectral evolution, suggesting a similar progenitor and CSM scenario. In this scenario a very massive progenitor star in the transitional phase between a luminous blue variable and a compact Wolf-Rayet star undergoes core-collapse, embedded in a dense helium-rich CSM with an elevated opacity compared to normal SNe Ibn, due to the presence of residual hydrogen. This scenario is consistent with the observed properties of SN 2020bqj and the modeling results. Conclusions. SN 2020bqj is a compelling example of a transitional SN Ibn/IIn based on not only its spectral features, but also its lightcurve, host galaxy properties and the inferred progenitor properties. The strong similarity with SN 2011hw suggests this subclass may be the result of a progenitor in a stellar evolution phase that is distinct from those of progenitors of regular SNe Ibn.

Implications of COD analysis use in the peracetic acid-based wastewater treatment.

Peracetic acid (PAA) stands out as a safe and environmental-friendly oxidant and disinfectant which has been effectively used in wastewater treatment. Chemical oxygen demand (COD) is a very popular analysis in wastewater treatment; however, the interference of residual PAA on the COD measurement is still unknown. In this context, this study investigated the implications of applying the COD analysis in PAA-based treatment. Each 1 mg·L-1 of PAA increased the COD concentration around 13.5 mg O2·L-1. Residual PAA and hydrogen peroxide (H2O2) were efficiently neutralized by sodium metabisulfite (SMBS) at the optimal SMBS/PAA ratio of 10.2:1 in a wide pH range (5 to 9). The effect of PAA addition on the COD concentration was evaluated in different water matrices (potassium hydrogen phthalate and wastewater solutions). The COD results with the SMBS addition at optimal SMBS/PAA ratio were lower than the ones without it. It may happen due to the neutralization of residual H2O2/PAA and the complexity of the water matrices which can interfere in the COD results. This study discussed the impact of the residual H2O2/PAA neutralization before the COD analysis, and this investigation can be used as a practical guideline for the correct COD measurement in PAA-based treatment.

Ultrasonic nanocrystal surface modification for strength improvement and suppression of hydrogen permeation in multi-layered steel

Hydrogen embrittlement of multi-layered steel (MLS) is significantly affected by a degree of hydrogen permeation from surface layers to interfaces. Here, the surface microstructure of multi-layered steel was modified for the first time using ultrasonic nanocrystal surface modification (UNSM), and the roles of UNSM-treated surface layers in strength and hydrogen permeation behavior were investigated by examining microstructural evolutions of the surface layer. Since the UNSM induced the compressive residual stress, grain refinement, and deformation twin formation at the specimen surface, the yield strength greatly improved via synergetic contributions of the grain refinement effect and dislocation strengthening. In addition, the UNSM-affected zone of 150–210 µm along depth direction effectively suppressed the hydrogen permeation by supplying compressive residual stresses and hydrogen trapping sites including grain boundaries, dislocations, and twin boundaries.

When treatment increases the contaminant's ecotoxicity: A study of the Fenton process in the degradation of methylene blue

The degradation of dyes can generate harmful by-products, thereby requiring the need to evaluate the toxicity to aquatic organisms. This study aims to evaluate the chronic ecotoxicity of methylene blue dye degraded by the Fenton process using the non-target planarian Girardia tigrina as a sensitive bioindicator of environmental contamination. The bioassays evaluated the lethality of several concentrations of the untreated and degraded dye methylene blue (MB), as well as, their sub-lethal effects on locomotion, feeding, regeneration, and reproduction. In both acute and chronic tests, the degraded dye had a stronger toxic effect when compared to the untreated dye. This negative effect after treatment was mainly associated with the presence of residual hydrogen peroxide and iron (and consequently the hydroxyl radical formed). We conclude that the utilization of the Fenton process using less oxidizing agents should be considered as important alternatives for the protection of aquatic ecosystems, without compromising the efficient removal of MB.