Steady-state Flux Research Articles

Ecmtool: fast and memory-efficient enumeration of elementary conversion modes.

Characterizing all steady-state flux distributions in metabolic models remains limited to small models due to the explosion of possibilities. Often it is sufficient to look only at all possible overall conversions a cell can catalyze ignoring the details of intracellular metabolism. Such a characterization is achieved by elementary conversion modes (ECMs), which can be conveniently computed with ecmtool. However, currently, ecmtool is memory intensive, and it cannot be aided appreciably by parallelization. We integrate mplrs-a scalable parallel vertex enumeration method-into ecmtool. This speeds up computation, drastically reduces memory requirements and enables ecmtool's use in standard and high-performance computing environments. We show the new capabilities by enumerating all feasible ECMs of the near-complete metabolic model of the minimal cell JCVI-syn3.0. Despite the cell's minimal character, the model gives rise to 4.2×109 ECMs and still contains several redundant sub-networks. ecmtool is available at https://github.com/SystemsBioinformatics/ecmtool. Supplementary data are available at Bioinformatics online.

Residence Time Distribution Analysis of Drip-Irrigated Beds—The Effect of Material and Fluid Properties with Implications for Heap Leaching Practice

The quantitative effect of particle shape, porosity, wettability, particle size, and solution viscosity on the residence time distribution (RTD) profiles of non-reactive, steady-state, drip-irrigated ore beds characteristic of heap leaching systems is presented. Results were obtained using step-up tracer tests and allowed for the analysis of preferential flow behaviour within the systems. The key findings were as follows. Increased particle sphericity enhanced channelling in beds of smaller particles, but not for larger particle sizes. Higher particle wettability caused greater liquid dispersion during both initial wetting studies and at steady-state fluid flux. Higher porosity levels and the inclusion of fines in mixed sized beds resulted in longer average solute residence times, higher liquid hold-up, longer solution and tracer breakthrough times, and increases in drain-down moisture percentages. Increasing the irrigation fluid’s viscosity, reflective of the increase in ionic concentrations in leach solutions, reduced both the solution and tracer breakthrough times and increased dispersion with signs of more discontinuous or isolated fluid volumes at steady-state. These results highlighted the importance of the inclusion of fines in agglomerated beds to improve uniform wetting especially those with low to moderate particle porosities (<2.5 m2/g specific surface area). The viscosity results suggest that there may be changes in preferential flow extent, due to variations in viscosity owing to the increasing sulphate concentration within the liquid phase in heaps and with time.

Automated reactor physics analysis framework of High Flux Isotope Reactor low-enriched uranium silicide dispersion fuel designs

The High Flux Isotope Reactor (HFIR) is a versatile research reactor that provides one of the highest steady-state neutron fluxes of any reactor in the world. The HFIR reactor physics team investigated the conversion of the current 93 wt% highly enriched uranium U3O8-Al dispersion fuel to a 19.75% low-enriched uranium (LEU) U3Si2-Al dispersion fuel. The team continuously develops a Python module to streamline the analysis steps required for an LEU core design to ensure reproducible and agile design iteration. The Python module automates the data processing between analysis steps and automates the input perturbation for branch calculations and design changes. The automated framework has proven to significantly increase the efficiency and reproducibility of the reactor physics team to design High Flux Isotope Reactor (HFIR) LEU cores and thoroughly analyze performance metrics, safety metrics, and thermal safety margins. Consequently, the team can now respond rapidly to fuel fabrication engineer and thermal-hydraulic-structural analyst requests.Numerous combinations of LEU fuel designs are explored, of which two LEU fuel designs are presented in this paper: a low density silicide design, and a high-density silicide design. Results show that both designs meet or exceed safety and performance metrics with exception for minor differences caused by the hardened spectrum from LEU.

Intranasal Administration of Dolutegravir-Loaded Nanoemulsion-Based In Situ Gel for Enhanced Bioavailability and Direct Brain Targeting

Dolutegravir's therapeutic effectiveness in the management of neuroAIDS is mainly limited by its failure to cross the blood-brain barrier. However, lipid-based nanovesicles such as nanoemulsions have demonstrated their potential for the brain targeting of various drugs by intranasal delivery. Thus, the purpose of this study was to develop a Dolutegravir-loaded nanoemulsion-based in situ gel and evaluate its prospective for brain targeting by intranasal delivery. Dolutegravir-loaded nanoemulsions were prepared using dill oil, Tween® 80, and Transcutol® P. Optimization of the nanoemulsion particle size and drug release was carried out using a simplex lattice design. Formulations (F1-F7 and B1-B6) were assessed for various pharmaceutical characteristics. Ex vivo permeation and ciliotoxicity studies of selected in situ gels (B1) were conducted using sheep nasal mucosa. Drug targeting to the brain was assessed in vivo in rats following the nasal delivery of B1. The composition of oil, surfactant, and cosurfactant significantly (p < 0.05) influenced the dependent variables (particle size and % of drug release in 8 h). Formulation B1 exhibits pharmaceutical characteristics that are ideal for intranasal delivery. The mucosal steady-state flux noticed with BI was significantly greater (p < 0.005) than for the control gel. A histopathology of nasal mucosa treated with BI showed no signs of toxicity or cellular damage. Intranasal administration of B1 resulted in greater Cmax (~six-fold, p < 0.0001) and AUC0-α (~five-fold, p < 0.0001), and decreased Tmax (1 h) values in the brain, compared to intravenous administration. Meantime, the drug level in the plasma was relatively low, suggesting less systemic exposure to Dolutegravir through intranasal delivery. In summary, the promising data observed here signifies the prospective of B1 to enhance the brain targeting of Dolutegravir by intranasal delivery and it could be used as a feasible and practicable strategy for the management of neuroAIDS.

Computational studies of molecular permeation through large-pore channels.

Connexin hemichannels are a family of highly regulated non-beta-barrel large-pore channels permeable to diverse small molecules. Despite their critical roles in mediating biological signaling, the molecular basis of selective permeation through these pores remains unclear. To bridge the knowledge gap between the structure and function of these large-pore channels, we use two complementary molecular dynamics (MD) simulation techniques, rare-event sampling and non-equilibrium steady-state flux, to compute the free energies and kinetics of molecular permeation through connexins. The link between these macroscopic properties and atomistic details of the permeation process provides valuable information for understanding the selectivity of large-pore channels and how human connexin mutations cause diseases.

Lateral Transport During Membrane Permeation in Diffusion Cell: In Silico Study on Edge Effect and Membrane Blocking

Membrane transport in diffusion cell studies is not one-dimensional from the donor to the receptor. Lateral diffusion within the membrane into the surrounding clamped region can lead to edge effect. Lateral diffusion can also affect the impact of an object blocking the membrane in a diffusion cell. The effects of lateral transport on permeation across a two-layer membrane in diffusion cells were investigated in this study under edge effect and membrane blocking conditions that could be encountered in previous gingiva and hypothetical skin permeation studies. Model simulations of time-dependent and steady-state transport were performed using COMSOL Multiphysics. The simulations indicated edge effect could increase the steady-state flux across the membrane up to 35% with a relatively thick membrane and small diffusion cell opening (e.g., gingiva study). The edge effect decreased when the relative thickness and permeability of the major barrier (top layer in the two-layer membrane) decreased. When the membrane was partially blocked by an object, lateral diffusion within the membrane could mitigate its impact: e.g., when the object was in the receptor, the impact caused by membrane blocking was reduced more than half. Therefore, membrane lateral transport should be considered under certain circumstances in permeation studies using diffusion cells.

Microwave-assisted extract of rhodomyrtone from rhodomyrtus tomentosa leaf: Anti-inflammatory, antibacterial, antioxidant, and safety assessment of topical rhodomyrtone formulation

ABSTRACT Series of works on the biological properties of rhodomyrtone, a major active component of Rhodomyrtus tomentosa leaf has been reported. In this study, rhodomyrtone-rich microwave-assisted extract from R. tomentosa leaf (RT-MAE) before formulation was profiled for phytochemical composition using gas chromatography-mass spectrometry (GC-MS) and targeted for anti-inflammatory activity with topical application. The formulation was assessed for bioactivity, biocompatibility, and safety on human volunteers. The GC-MS spectra indicated a rich content of phytosterols, sesquiterpenes, and acylphloroglucinols. At concentrations 50–600 ng/mL, RT-MAE before formulation treated macrophages showed >86% cell viability. Nitric oxide production significantly decreased by 19.26–88.36% following the treatment with 50–600 ng/mL RT-MAE before formulation (p < 0.001). Moreover, a significant (p < 0.01) concentration-dependent downregulation of lipopolysaccharide-induced IL-6, IL-1β, iNOS, and COX-2 mRNA was observed in RT-MAE before formulation treated macrophages. The extract demonstrated minimum inhibitory (MIC) and minimum bactericidal concentration (MBC) at 0.25–4 and 1–16 μg/mL, respectively. The antioxidant activity of RT-MAE before formulation indicated IC50 of 0.16 and 0.06 ug/mL for DPPH and ABTS assays, respectively. Ex-vivo diffusion of rhodomyrtone from formulation showed steady-state flux 64.935 ng/cm2 h, with >80% viability on HaCaT cells. Safety assessment of formulation containing RT-MAE after formulation was conducted on healthy volunteers. Hematological and biochemical analysis showed no significant difference between test and baseline (p < 0.05). The results suggested that the formulation can be effectively employed as a topical inflammatory agent.

Flux in Tilted Potential Systems: Negative Resistance and Persistence

Many real-world systems are well-modeled by Brownian particles subject to gradient dynamics plus noise arising, e.g., from the thermal fluctuations of a heat bath. Of central importance to many applications in physics and biology (e.g., molecular motors) is the net steady-state particle current or “flux” enabled by the noise and an additional driving force. However, this flux cannot usually be calculated analytically. Motivated by this, we investigate the steady-state flux generated by a nondegenerate diffusion process on a general compact manifold; such fluxes are essentially equivalent to the stochastic intersection numbers of Manabe (Osaka Math J 19(2):429–457, 1982). In the case that noise is small and the drift is “gradient-like” in an appropriate sense, we derive a graph-theoretic formula for the small-noise asymptotics of the flux using Freidlin–Wentzell theory. When additionally the drift is a local gradient sufficiently close to a generic global gradient, there is a natural flux equivalent to the entropy production rate—in this case our graph-theoretic formula becomes Morse-theoretic, and the result admits a description in terms of persistent homology. As an application, we provide a mathematically rigorous explanation of the paradoxical “negative resistance” phenomenon in Brownian transport discovered by Cecchi and Magnasco (Phys Rev Lett 76(11):1968, 1996).

Compatibility of large ELM control and stable partial detachment with neon/argon seeding in EAST

It is necessary to achieve simultaneous exhaust of excessive transient and steady-state heat fluxes on the divertor target for the divertor protection in the future fusion reactors. The sustained large ELM control and stable partial detachment have been achieved concurrently with argon (Ar) or neon (Ne) seeding in EAST. With Ne seeding, the large ELMs with frequency f ELM ∼ 100 Hz disappear and a stable ELM-free state with H 98,y2 > 1 is maintained. Meanwhile, the electron temperature T et around the lower outer strike point decreases from more than 70 eV during the large ELM burst to less than 5 eV in the stable ELM-free phase. In addition, a slight improvement of plasma confinement is observed in the partially detached state, mainly attributed to the increased electron density n e and ion temperature T i in the core region. In the pedestal region, the density gradient and the electron temperature show subtle variation. The effective charge number Z eff increases significantly after Ne seeding, leading to a decrease in the edge bootstrap current and the pedestal pressure gradient, and thus the stabilization of ELMs. With Ar seeding, the large ELMs are also suppressed at first, but soon transit to type-III ELMs with a high f ELM ∼ 1 kHz, highly correlated with the energy confinement degradation. The steady-state and transient heat fluxes on the divertor can be both well reduced with Ar/Ne seeding in EAST.

Limits and CO2equilibration of near-coast alkalinity enhancement

Abstract. Ocean alkalinity enhancement (OAE) has recently gained attention as a potential method for carbon dioxide removal (CDR) at gigatonne (Gt) scale, with near-coast OAE operations being economically favorable due to proximity to mineral and energy sources. In this paper we study critical questions which determine the scale and viability of OAE. Which coastal locations are able to sustain a large flux of alkalinity at minimal pH and ΩArag (aragonite saturation) changes? What is the interference distance between adjacent OAE projects? How much CO2 is absorbed per unit of alkalinity added? How quickly does the induced CO2 deficiency equilibrate with the atmosphere? Choosing relatively conservative constraints on ΔpH or ΔOmega, we examine the limits of OAE using the ECCO LLC270 (0.3∘) global circulation model. We find that the sustainable OAE rate varies over 1–2 orders of magnitude between different coasts and exhibits complex patterns and non-local dependencies which vary from region to region. In general, OAE in areas of strong coastal currents enables the largest fluxes and depending on the direction of these currents, neighboring OAE sites can exhibit dependencies as far as 400 km or more. At these steady state fluxes most regional stretches of coastline are able to accommodate on the order of 10s to 100s of megatonnes of negative emissions within 300 km of the coast. We conclude that near-coastal OAE has the potential to scale globally to several Gt CO2 yr−1 of drawdown with conservative pH constraints, if the effort is spread over the majority of available coastlines. Depending on the location, we find a diverse set of equilibration kinetics, determined by the interplay of gas exchange and surface residence time. Most locations reach an uptake efficiency plateau of 0.6–0.8 mol CO2 per mol of alkalinity after 3–4 years, after which there is only slow additional CO2 uptake. Regions of significant downwelling (e.g., around Iceland) should be avoided by OAE deployments, as in such locations up to half of the CDR potential of OAE can be lost to bottom waters. The most ideal locations, reaching a molar uptake ratio of around 0.8, include North Madagascar, California, Brazil, Peru and locations close to the Southern Ocean such as Tasmania, Kerguelen and Patagonia, where the gas exchange appears to occur faster than the surface residence time. However, some locations (e.g., Hawaii) take significantly longer to equilibrate (up to 8–10 years) but can still eventually achieve high uptake ratios.

Biodegradable Polymeric Pharmaceutical Nanoemulgel Coloaded with Eucalyptol‐Lornoxicam: Fabrication and Characterizations for Possible Better Pain Management

Nanoemulgels are considered as potential and ideal drug delivery systems for the transdermal administration of poorly soluble drugs like lornoxicam. Their intrinsic characteristics, such as small globule size as well as excipient type, make transdermal passage of the drug easier. The current study was aimed at developing nanoemulgel based formulation of lornoxicam coloaded with eucalyptol to enhance drug skin permeation and bioavailability in order to promote therapeutic outcome in appropriate time. High shear homogenization technique was utilized to develop optimized lornoxicam encapsulated nanoemulsion followed by its conversion into nanoemulgel formulation by the addition of 1% Carbopol 940 as gelling agent. Different characterization tests were performed on optimized formulation such as surface charge, particle size and size distribution, viscosity, spreadability, pH, drug content determination, drug entrapment efficiency, in vitro drug release, and drug permeation analysis. The optimized formulation had globule size of 143.7 ± 2.18 nm. The results of drug entrapment efficiency, in vitro drug release, and skin penetration experiments were found satisfactory. Based on the formulation type, permeability parameters such as permeability constant (Kp), enhancement ratio (Er), and steady state flux (Jss) revealed greater values and satisfactory outcomes. When compared to other formulations (LRX nanoemulgel and EU nanoemulgel), the LRX‐EU nanoemulgel formulation produced improved skin permeation profile (flux, 189.63 ± 7.68 μg/cm2/h; permeability coefficient, 2.09 ± 0.067 cm/h; and ER, 4.274). This work clearly proved that lornoxicam coloaded with eucalyptol nanoemulgel formulations could be developed to generate stable drug delivery systems. Thus, LRX‐EU NEG formulation seems promising in terms of physicochemical properties, enhanced bioavailability, and high skin penetration profile as compared to LRX NEG formulation.

Numerical simulation of erosion of misaligned W/Cu monoblocks caused by ITER-like type-Iedge localized modes

The thermal performance of the divertor W/Cu monoblock tiles under the ITER-like transient events has been one of the main concerns for ITER plasma facing components. Owing to the assembly tolerances during installation, the leading edge caused by misalignment between toroidal neighboring tiles will receive the extremely high cumulative heat flux and be damaged. In this work, we develop a two-dimensional heat conductivity model, including evaporation, radiation, melting process, and coupling cooling water condition, to investigate the thermal erosion of two shapes of tiles of W/Cu monoblock (unshaped and beveled tiles) with misalignment in a range from 0 to 0.3 mm, within the allowable maximum misalignment for ITER. To reflect the geometrical effects of castellated divertor tiles on the properties of its adjacent plasma, the energy flux density distribution arriving at the castellated divertor tile surface is evaluated first by using a two-dimension-in-space and three-dimension-in-velocity particle-in-cell plus Monte Carlo collisions code, and the obtained energy flux distribution is then used as input for the heat conduction model. The simulation results show that the maximum temperature of the unshaped tile with no misalignment is lower than that of the beveled tile under the steady-state inter-ELM heat flux, which increases more quickly than that of the beveled tile with misalignment increasing and will be larger than that of the beveled tile when misalignment is not less than 0.105 mm. Two shapes of the divertor tiles would melt and vaporize under typical heat flux density of a transient event of type-I edge localized modes (ELMs) for ITER, deposition energy of 1 MJ·m&lt;sup&gt;–2&lt;/sup&gt; in a duration of 600 μs. The highest temperature, the maximum melting thickness, the maximum vaporization thickness of the unshaped tile with no misalignment are higher than those of the beveled tile except the melting volume ratio. The thermal erosion of the unshaped tile increases more remarkably than that of the beveled tile with misalignment increasing, and the melting volume ratio of the unshaped tile will exceed that of the beveled tile at a misalignment of 0.17 mm. In comparison with the unshaped tile, the beveled tile is more resistant to such a high heat flux of an ELM and misalignment.

Ionic current driven by a viscosity gradient.

Gradients of voltage, pressure, temperature, and salinity can transport objects in micro- and nanofluidic systems by well-known mechanisms. This paper explores the dynamics of particles in a viscosity gradient with numerical simulations. The different stochastic rules used to integrate the random motion of Brownian particles affect the steady-state distribution of particles in a diffusivity gradient. Importantly, the simulations illuminate the important role that the boundary conditions play, disallowing a steady-state flux when the boundary conditions mimic those of a closed container, but allowing flux when they mimic electrodes. These results provide an interpretation for measurements of a steady ionic current flowing between electrodes separated by a nanofluidic channel with a liquid viscosity gradient.

Oral Bioavailability Enhancement of Vancomycin Hydrochloride with Cationic Nanocarrier (Leciplex): Optimization, In Vitro, Ex Vivo, and In Vivo Studies

To explore the performance of the cationic nanocarrier leciplex (LPX) in escalating the oral bioavailability of vancomycin hydrochloride (VAN) by promoting its intestinal permeability. With the aid of a D-optimal design, the effect of numerous factors, including lipid molar ratio, cationic surfactant molar ratio, cationic surfactant type, and lipid type, on LPX characteristics, including entrapment efficacy (EE%), particle size (P.S.), polydispersity index (P.I.), zeta potential value (Z.P.), and steady-state flux (Jss) were assessed. The optimized formula was further evaluated in terms of morphology, ex vivo permeation, stability, cytotoxicity, and in vivo pharmacokinetic study. The optimized formula was spherical-shaped with an E.E. of 85.2 ± 0.95%, a P.S. of 52.74 ± 0.91 nm, a P.I. of 0.21 ± 0.02, a Z.P. of + 60.8 ± 1.75 mV, and a Jss of 175.03 ± 1.68 µg/cm2/h. Furthermore, the formula increased the intestinal permeability of VAN by 2.3-fold compared to the drug solution. Additionally, the formula was stable, revealed good mucoadhesive properties, and was well tolerated for oral administration. The in vivo pharmacokinetic study demonstrated that the VAN Cmax increased by 2.99-folds and AUC0-12 by 3.41-folds compared to the drug solution. These outcomes proved the potentiality of LPX in increasing the oral bioavailability of poorly absorbed drugs.

Synergistic effect of particle size, shear rate and driving-force during microfiltration of fruit juices: Toward a relevant choice of pretreatments and filtration conditions

With an objective to recommend relevant operating conditions for fruit juice microfiltration, the combined effect of particle size, shear rate and driving-force on fouling was studied. The filterability of three orange juices with different granulometry was estimated at pilot scale under different shear rates and driving forces (flux or TMP, in immersed and side-stream membrane configuration respectively). In flux-driven filtrations, fluxes to avoid an intense fouling were identified (below 5–10 L.h−1.m−2 for studied juices) and the role of juice granulometry on fouling highlighted. In TMP-driven filtrations, whatever the juice granulometry, steady-state fluxes were TMP-independent but shear rate dependent (around 10 and 30 L.h−1.m−2, for 4500 s−1 and 15500 s-1 respectively). The results demonstrated that, whatever their granulometry, juice filterability was higher in low shear rate flux-driven filtrations, than in high shear rate TMP-driven ones, which relativizes the relevance of crossflow filtration.

Antifouling and antibacterial performance evaluation of polyethersulfone membranes modified with AZ63 alloy.

Antibacterial membranes have attracted researchers' interest in recent years as a possible approach for dealing with biofouling on the membrane surface. This research aims to see if blending AZ63 Mg alloy into a polyethersulphone (PES) membrane can improve antifouling and separation properties. The composite membranes' pure water flux continued to increase from pristine PES to PES/AZ63 2.00 wt%. The results showed that PES/AZ63 2.00 wt% membrane supplied the highest permeate flux of E. coli. The steady-state fluxes of AZ63 composite membranes were 113.24, 104.38 and 44.79 L/m2h for PES/AZ63 2.00 wt%, 1.00 wt%, and 0.50 wt%, respectively. The enhanced biological activity of AZ63 was studied based on antioxidant activity, DNA cleavage, antimicrobial, anti-biofilm, bacterial viability inhibition and photodynamic antimicrobial therapy studies. The maximum DPPH scavenging activity was determined as 81.25% with AZ63. AZ63 indicated good chemical nuclease activity and also showed moderate antimicrobial activity against studied strains. The highest biofilm inhibition of AZ63 was 83.25% and 71.63% towards P. aeruginosa and S. aureus, respectively. The cell viability inhibition activity of AZ63 was found as 96.34% against E. coli. The photodynamic antimicrobial therapy results displayed that AZ63 demonstrated 100% bacterial inhibition when using E. coli.

A Multivector-Based Model Predictive Current Control of PMSM Drive With Enhanced Torque and Flux Response

Model predictive current control (MPCC) is a modern current control technique with the provision to include multivariable objectives and nonlinearities. In this article, a multivector-based MPCC is proposed for the speed control of a two-level voltage source inverter (VSI) fed permanent magnet synchronous motor (PMSM) drive, to improve the steady-state (SS) torque and flux response. The multivector operation is obtained using an extended control set (ECS) that utilizes two adjacent-active voltage-space vectors (VSVs) with an appropriate distribution coefficient. However, the augmentation of the control set (CS) catalyzes an undesirable increase in the computational burden. To address this limitation, a lookup table-based VSV preselection scheme based on stator current error is employed. The VSV grouping is based on the gradient of stator current error and effectively replicates the control scheme with all ECS-VSVs. Subsequently, the amplitude of the selected optimum ECS-VSV is optimized using an average error minimization technique. The optimum duration of the ECS-VSV is determined without employing space vector modulation (SVM). Hence, the complexity of the proposed scheme is minimized, and the SS torque and flux performance are enhanced without compromising the dynamic performance of the drive. The effectiveness of the proposed scheme is verified by conducting comprehensive comparisons with conventional MPCC and recently published literature.

Purification of pectin by ultrafiltration in combination with sodium citrate

Ultrafiltration is an effective method to improve the purity of pectin, but membrane fouling is an urgent problem to overcome. In this work, trisodium citrate, sodium caseinate and calcium caseinate were combined with ultrafiltration to separate and purify pectin extract. The molecular weight cutoff (MWCO) of the ultrafiltration membrane and the sodium citrate concentration were optimized using the color and clarity of the pectin extract as indices, and the influence of sodium citrate on the pectin particle size and zeta potential was further studied. Finally, the pectin extraction yield, some physicochemical indices, including galacturonic acid (Gal A) content, esterification degree, and ash content, and the surface morphology of the pectin particles were measured. The results showed that the ultrafiltration membrane fouling was effectively controlled and that the steady-state flux increased by 2-fold when the pectin extract was treated with a polyether sulfone (PES) UF membrane (100 kDa) in combination with sodium citrate at a concentration of 0.25 mg/ml. The pectin extraction yield increased to 16.4%, and the resulting pectin was a higher-ester refined pectin with a Gal A content of 89.7%, DE content of 77.42%, and ash content of 0.63%. The combination of sodium citrate and ultrafiltration was beneficial not only for improving the permeability and separation performance of the ultrafiltration process but also for providing an example of a monovalent salt as a precipitation agent.

Assessing Thermal Response of Redox Conduction for Anti-Arrhenius Kinetics in a Microbial Cytochrome Nanowire.

A micrometers-long helical homopolymer of the outer-membrane cytochrome type S (OmcS) from Geobacter sulfurreducens is proposed to transport electrons to extracellular acceptors in an ancient respiratory strategy of biogeochemical and technological significance. OmcS surprisingly exhibits higher conductivity upon cooling (anti-Arrhenius kinetics), an effect previously attributed to H-bond restructuring and heme redox potential shifts. Herein, the temperature sensitivity of redox conductivity is more thoroughly examined with conventional and constant-redox and -pH molecular dynamics and quantum mechanics/molecular mechanics. A 30 K drop in temperature constituted a weak perturbation to electron transfer energetics, changing electronic couplings (⟨Hmn⟩), reaction free energies (ΔGmn), reorganization energies (λmn), and activation energies (Ea) by at most |0.002|, |0.050|, |0.120|, and |0.045| eV, respectively. Changes in ΔGmn reflected -0.07 ± 0.03 V shifts in redox potentials that were caused in roughly equal measure by altered electrostatic interactions with the solvent and protein. Changes in intraprotein H-bonding reproduced the earlier observations. Single-particle diffusion and multiparticle steady-state flux models, parametrized with Marcus theory rates, showed that biologically relevant incoherent hopping cannot qualitatively or quantitatively describe electrical conductivity measured by atomic force microscopy in filamentous OmcS. The discrepancy is attributed to differences between solution-phase simulations and solid-state measurements and the need to model intra- and intermolecular vibrations explicitly.

Purification of bioactive compounds from blackberry pomace: Investigation of techniques to reduce fouling during flat membrane ultrafiltration process

Here we evaluated the use of static turbulence promoters of different pin diameters and ultrasound during the ultrafiltration of the blackberry pomace extract. The steady state fluxes during ultrafiltration of blackberry extract pomace through a polymeric 10 kDa membrane under ultrasound irradiation and with turbulence promoters with pins of 2.5 and 3.5 of diameters were 3.12 ± 0.08, 6.00 ± 0.14 and 4.02 ± 0.36 L h−1 m−2, respectively. The steady state flux under conventional ultrafiltration was 2.22 ± 0.12 L h−1 m−2. Cake formation was more effectively mitigated with the turbulence promoters than with ultrasound, since turbulence promoters provided the formation of effective secondary flows, while the ultrasound waves were not able to effectively remove the compressed cake layer. The permeate flux was greater with the turbulence promoter of pins with diameters of 2.5 mm than of 3.5 mm at the same specific energy consumption. The ultrafiltration process retained almost 80% of the bioactive compounds from the blackberry pomace extract and the applied devices did not significantly change the characteristics of the permeate extract. Thus, the use of turbulence promoters with pins of small diameters is recommended to improve the permeate flux during ultrafiltration process.