Small Residence Time Research Articles

Prediction of Threonine-Tyrosine Kinase Receptor-Ligand Unbinding Kinetics with Multiscale Milestoning and Metadynamics.

Accurately describing protein-ligand binding and unbinding kinetics remains challenging. Computational calculations are difficult and costly, while experimental measurements often lack molecular detail and can be unobtainable. Here, we extend our multiscale milestoning method, Simulation-Enabled Estimation of Kinetics Rates (SEEKR), with metadynamics molecular dynamics simulations to yield accurate small molecule drug residence times. Using the pharmaceutically relevant threonine-tyrosine kinase (TTK) and eight long-residence-time (tens of seconds to hours) inhibitors, we demonstrate accurate prediction of absolute and rank-ordered ligand residence times and free energies of binding.

Impact of heteroaggregation between microplastics and algae on particle vertical transport

Understanding the impacts of microplastics (MPs) on aqueous environments requires understanding their transport dynamics and how their presence affects other natural processes and cycles. In this context, one aspect to consider is how MPs interact with freshwater snow (FWS), a mixture of algae and natural particles. FWS is one of the primary drivers of the flux of organic matter from the water surface to the bottom sediment, where zooplankton, diurnal migration, fish faecal pellets settling and turbulent mixing can also play prominent roles. Understanding how MPs and FWS heteroaggregation affects their respective settling velocities is important to assess not only MPs fate and transport but also their ecological impacts by altering FWS deposition and thereby nutrient cycling. In this present study, we obtained a mechanistic understanding of the processes controlling MPs settling dynamics and heteroaggregation with FWS and the subsequent impacts on the settling rates of both MPs and ballasted FWS. Here we used a plexiglass column equipped with a stereoscopic camera system to track the settling velocities of (1) MPs of various compositions, densities and morphologies, (2) FWS flocs and (3) MP–FWS agglomerates. For each experimental set, thousands of particles were tracked over a series of image sequences. We found that agglomerates with high-density MPs settled at least twofold faster than FWS alone, implying a much smaller residence time in the water column, except for cases with MP fibres or low-density plastics. These findings will help to refine MP fate models and, while contingent on MPs number, may impact biogeochemical cycles by changing the flux of nutrients contained in FWS to the sediment.

Determination of the bioavailability and biodistribution of a single dose of oral cholecalciferol/Calcirol® soft gelatin capsule by pharmacoscintigraphy- CalSci study

Background: It is required to study the bioavailability and biodistribution of specific cholecalciferol formulation before prescribing. Pharmacoscintigraphy is an established radiological-imaging technique that is used to map various drug formulations as they traverses the human body (biodistribution) in real-time. We evaluated the bioavailability and biodistribution pattern, transit time, and gastrointestinal clearance of a single dose of Calcirol® soft gelatin capsule 60,000 IU [an oral cholecalciferol (vitamin D) formulation] using pharmacoscintigraphy. Methods: Six male healthy adult volunteers were administered a single oral dose of Calcirol® soft gelatin capsule labelled with technetium-99m. Post-dosing, serial venous blood samples were collected till day 27 for the estimation of the plasma levels of 25-hydroxycholecalciferol and 1,25-dihydroxycholecalciferol levels. Different pharmacokinetic parameters were calculated. Sequential static gamma imaging was performed to evaluate the biodistribution of Calcirol® soft gelatin capsule. Descriptive statistics was used. Various pharmacokinetic parameters were calculated from the concentration-time curves. Statistical analysis was carried out using Student’s t-test. Suitable multivariate analysis was performed based on the distribution of data. All statistical analyses were performed using SAS® Software (v 9.4). Results: The overall absorption of Calcirol® soft gelatin capsule was 93.23%, which was fully from the small intestine. It led to achieving a sufficient level of 25-hydroxycholecalciferol (>60 ng/ml) within 6 hours of oral intake. The levels of plasma 25-hydroxycholecalciferol and 1,25-dihydroxycholecalciferol increased (maximum around 6 and 18 days, respectively). The small intestinal residence time was around 16 hours. No adverse event was noted. Conclusions: This was the first pharmacoscintigraphy study in the world which demonstrated the favourable bio-distribution of the Calcirol softgels supporting its role in vitamin D supplementation.

Filter feeders are key to small microplastic residence times in stratified lakes: A virtual experiment

Microplastic (MP) is potentially harmful to lake ecosystems, with its uptake into the food web largely controlled by its residence time in the lake water column. Here we combine laboratory and virtual experiments to quantify residence times of small MP (<15 μm) in two contrasting model lakes; Lake Constance (large lake) and Esthwaite Water (a small lake). We compare MP residence times in a purely physical system with MP transport controlled by sinking and mixing to a model where, in addition to physical processes, zooplankton package MP into faecal pellets that are then egested into the water column. The laboratory experiments showed that MP settling velocities increased from ~5 × 10−6–10−3 mm s−1 for pristine MP to ~1 mm s−1 for MP embedded faeces. Modeled lake residence times for the 0.5 and 5 μm particles were >15 years in the abiotic models, while in the biotic simulations they were reduced to ~1 year. There was little difference between abiotic and biotic simulations for the 15 μm particles. The ratio of the MP zooplankton uptake velocity to the sinking velocity (v_up/vs_epi) was used to classify biological vs. physical transport pathways. For the 0.5 and 5 μm particles v_up/vs_epi was ≫1 in all cases for both lakes, while for the 15 μm MP there was a transition between biological and physical processes dominating residence times depending on zooplankton numbers. Our results suggest that packaging of small MP in faecal pellets by zooplankton will control its residence time in lakes. Moreover, the majority of small MP will cycle through organisms before reaching the sediment, increasing the likelihood of negative ecological effects and transfer in the food web.

Seasonal variations in residence time and water age in the Mundaú-Manguaba Estuarine Lagoon System, AL (Brazil)

The Characteristic Hydraulic Times (CHT), called Residence Time (RT) and Water Age (WA), were analyzed in the Mundaú-Manguaba Estuarine Lagoon System (MMELS – AL, Brazil), using the SisBaHiA® – Environmental Hydrodynamics Base System, for two scenarios: wet season, from May to July 2018; and dry season, from October to December 2018. The hydrodynamic modelings appropriately represented water level variations measured in the lagoons. The analysis of residual currents revealed how hydrodynamic circulation was affected by seasonal variations, and provided essential information to understand the results of the RT and WA simulations. This study deepened the knowledge regarding the RT of the water masses inside the lagoons, and reinforced how river discharges significantly influence their export, which resulted, considering the spatial scope, in much smaller RT in the wet season compared to the dry season. The WA analysis added new and significant knowledge about water renewal, from a different perspective, and as yet little-explored in the study region. Among the results obtained, the most relevant refer to the dry season, in which it was found that the “oldest” waters in the Mundaú L. occurred near the southeast region, while in the Manguaba L., in the vicinity of the central region. Both regions were confirmed as the places that present the most critical trophic state index in each lagoon, showing that WA is a CHT that indicates the regions most conducive to more critical trophic states.&#x0D; Keywords: Mundaú-Manguaba lagoons, residence time, water age.

Micromixing and Co-Precipitation in Continuous Microreactors with Swirled Flows and Microreactors with Impinging Swirled Flows

One of the promising methods for process intensification for micromixing, co-precipitation, and crystallization in continuous reactors is the use of vigorous vortices. A combination of the high intensity of the kinetic energy input with the small volume of the micromixing volume allows to concentrate the energy dissipation rate up to 104 W/kg and more. As the embodiment of such an idea, four new types of microreactors with intensively swirled flows were created and studied as a tool for continuous co-precipitation and crystallization. A correlation between residence time and segregation index was found: the smaller residence time, the higher energy dissipation rate and better quality of micromixing. A method for the synthesis of oxides of a number of transition metals in microreactors with intensively swirled flows with subsequent thermal treatment of co-precipitation products has been developed. This method was used to obtain ensembles of nanosized particles of zirconium oxides, as well as calcium and strontium fluorides. In comparison with the currently widely used hydro- and solvothermal methods, the proposed method has high productivity (around 10 m3/day for lab scale device), can significantly reduce the duration of the process, provides low energy consumption, does not require a large number of labor-intensive operations, is technologically advanced and easily scalable.

Stabilization of Auto-Igniting Flames Within a Gas Turbine Sequential Combustor, Through the Control of Static Temperature Variation—Detailed Numerical Investigation

Abstract Axially staged combustion systems offer both enhanced operability and fuel flexibility for gas turbines, allowing stable operation and low emissions across a wide range of engine loads. The sequential combustion concept, where the first combustion stage is supported by a standard lean premixed flame and the second stage relies on an auto-ignition-dominated flame, forms the focus of the present contribution. Within the present state of the art, the still-oxygen-rich exhaust gases from the first stage are mixed with second stage fuel within a sequential burner. Within the presently investigated concept, the flame is anchored by establishing a positive static temperature gradient within the burner. The advantage of such a concept is that it potentially allows for very small combustor residence times and can be easily incorporated into an integrated combustor–nozzle guide vane. The concept does however present significant challenges, which are investigated within then present contribution. A critical challenge is that, in order to setup the static temperature gradient, the flow has to be accelerated to a relatively high Mach number, ca. 0.7, and then decelerated in a diffusing section where the flame is located. Achieving fuel/air premixing and combustion, while achieving acceptable pressure drops is not trivial at the high velocities. Additionally, the dynamic stability of the concept is not clear and needs to be investigated. Within the present work, compressible computational fluid dynamics (CFD) is used to investigate the pressure drop characteristics within the system. It is demonstrated that for the system a total pressure drop of less than 6% can be achieved. To realize this, the premixing section includes multipoint fuel injection coupled with mixing devices. The arrangement is designed to both limit excessive pressure losses by focusing losses within regions of the flow where they contribute effectively to fuel/air mixing as well as locating the flame where Rayleigh losses are acceptable. The dynamic behavior of the system is studied by way of two-dimensional (2D) fully premixed CFD. Investigation of the flame response to harmonic perturbations in inlet temperature shows that the flame transfer function (FTF) is characterized by amplitude growing, in line with the concept of auto-ignition at low Mach number, linearly with frequency. The rate of growth with frequency of the FTF amplitude is rather high reaching up to 60 times the imposed relative fluctuation of inlet temperature at a frequency of 600 Hz. This rapid growth is in line with the behavior of auto-ignition at low Mach number. A substantial difference with the low Mach number concept is given by upstream traveling acoustic waves generated by the flame that going through high Mach number locations, can affect, in respect of the conservation of entropy transported by convection, the upstream temperature distribution and therefore auto-ignition itself.

S1061 A Scintigraphic Study to Evaluate the Localization and Delivery Function of a Drug Delivery System (DDS) Device in Patients With Active Ulcerative Colitis (UC) in a Fasted State

Introduction: The clinical remission in moderate to severe ulcerative colitis (UC) and Crohn’s has plateaued at ∼15-20% even with the approval of multiple biologics/drugs. Altas study clearly demonstrated that the lack of adequate amount of drug at the diseased site is responsible for limited clinical benefit. The Drug Delivery System (DDS) is an ingestible electronic targeted delivery device containing a localization system to identify colon entry based on the gastrointestinal (GI) anatomy and deliver a bolus dose of a therapeutic compound to the colon mucosa to improve efficacy and reduce systemic toxicity. DDS was shown to be well-tolerated and functioned as intended in identifying and releasing radiotracer in the colon of normal healthy volunteers (NHV). Here, we aim to evaluate the safety and functionality of DDS in active UC patients in a fasted state. Methods: Patients with endoscopy and histology confirmed UC and active UC status defined as having Mayo score ≥ 2 or elevated Fecal Calprotectin Protein or high sensitivity C-reactive protein within one month of the screening visit were eligible for the study. Each patient was fasted overnight and dosed with a single DDS capsule prior to resuming a normal diet. Each capsule was filled with radioactive marker 111In-DTPA to independently identify DDS localization and to visualize payload release; water radiolabeled with 99mTc-DTPA was co-administered with the DDS to delineate GI landmarks by gamma scintigraphy. The GI transit of DDS and delivery location of the radiotracer were confirmed by serial gamma scintigraphy imaging. Results: This is a preliminary analysis of an ongoing study of active UC patients with Mayo scores between 3-8 enrolled and dosed in the study. GI transit metrics of DDS were consistent with the variable GI motility and the frequent bowel movements observed among active UC patients. DDS device demonstrated correct localization identification of colon entry and release of radiotracer in the colon regardless of variable GI motility, the level of inflammation, or blood in the colon of UC patients compared to NHV (Table), confirmed by gamma scintigraphy image analysis. The dispersion of the radiotracer adequately covered the colon from the site of release throughout the remainder of the colon. Conclusion: This result demonstrated that DDS functioned as intended in identifying and releasing the payload in the colon regardless of GI motility or disease status. Table 1. - GI transits, Residence Time, and Radiotracer (111In-DTPA) Delivery Location of DDS Device post-dose in Active UC patients (PM-602) and Normal Healthy Volunteers (NHV) (PM-601) Subject Mayo score Gastric emptying time (min) Small intestine Residence time (min) Arrival Time at Cecum (min) 1st Capsule release In-111 (min) Capsule location at the time of 1st capsule release Capsule Recovery Time (hrs) No. of Bowel Movements required to recover Capsule 602-116-001 6 104 169 273 324 Cecum 47.67 3 602-116-002 3 23 122 145 190 Cecum 26.50 3 602-116-003 8 38 292 330 354 Cecum 32.83 5 601-NHV (N = 11)* Median N/A 29 228 270 368 Cecum/Asc Colon/Splenic Flexure 23.99 1 (n=6)2 (n=4)3 (n=1) *Excluded one subject due to anomalous transit of the DDS device from the stomach to the duodenum and then back into the stomach.

The Relation of Environmental Conditions With Charge Structure in Central Argentina Thunderstorms

AbstractIn this study we explored the environmental conditions hypothesized to induce a dominant charge structure in thunderstorms in the province of Cordoba, Argentina, during the RELAMPAGO‐CACTI (Remote sensing of Electrification, Lightning, And Mesoscale/microscale Processes with Adaptive Ground Observations‐Clouds, Aerosols, Complex Terrain Interactions) field campaigns. Hypothesized environmental conditions are thought to be related to small warm cloud residence time and warm rain growth suppression, which lead to high cloud liquid water contents in the mixed‐phase zone, contributing to positive charging of graupel and anomalous charge structure storms. Data from radiosondes, a cloud condensation nuclei (CCN) ground‐based instrument and reanalysis were used to characterize the proximity inflow air of storms with anomalous and normal charge structures. Consistent with the initial hypothesis, anomalous storms had small warm cloud depth caused by dry low‐level humidity and low 0°C height. Anomalous storms were associated with lower CCN concentrations than normal storms, an opposite result to the initial expectation. High CAPE is not an important condition for the development of anomalous storms in Argentina, as no clear pattern could be found among the different parameters calculated for updraft proxy that would be consistent with the initial hypothesis.

Structure and propagation speed of autoignition-assisted flames of jet fuels

The flame structure and propagation speed of autoignition-assisted fuel-lean and fuel-rich flames of jet fuels are numerically and analytically investigated at elevated pressures and temperatures. The results show that while the propagation speed increases dramatically for large residence time, for fuels with strong low temperature chemistry (LTC), the propagation speed may first increase slightly at relatively small residence time. The species evolution in time shows that with the increase of propagation speed, the trajectories for autoignition-assisted flames first rapidly and then gradually converge to the autoignition trajectory. Furthermore, transport budget analysis shows that as the propagation speed increases, the balance in the high temperature reaction zone evolves from reaction-diffusion balance to reaction-convection balance, demonstrating the transition from flame propagation to autoignition. An analytical model, which only needs to calculate the corresponding 0D autoignition process, is proposed to predict the autoignition-assisted flame speed. The good qualitative agreement with the 1D simulation result indicates that the autoignition assistance on the propagation speed mainly results from the temperature rise ahead of the preheat zone. Finally, different scaling correlations for the normalized flame propagation speed Sl/Sl0 are compared, showing a universal scaling for n-heptane, n-dodecane, and Jet-A over a wide range of pressures (5–35 atm), temperatures (600–1015 K), and equivalence ratios (0.5–1.2) with the normalized maximum mole fractions of CO.

Physical and Chemical Evolution of Lunar Mare Regolith

AbstractThe lunar landscape evolves both physically and chemically over time due to impact cratering and energetic processes collectively known as space weathering. Despite returned soil samples and global remote sensing reflectance measurements, the rate of space weathering in the lunar regolith is not well understood. To address this, we developed a novel three‐dimensional landscape evolution model to simulate the physical processes that control the burial, excavation, and transport of regolith on airless bodies. Applying this model to the lunar mare, we find that over billions of years of surface evolution, material typically spends only a few million years on the surface where it is exposed to the effects of space weathering. The small surface residence times are a result of vigorous mixing by small‐scale impacts, predominantly driven by secondary crater formation. We deduce the rate of space weathering by comparing our modeled distribution of surface residence times on the lunar mare to measurements of space weathering maturity from Apollo soil samples and orbital surface reflectance datasets. These chemical constraints indicate that soil on the lunar mare reaches maturity in 7 Myr of cumulative surface exposure though due to uncertainties in the rate of small secondary crater production, this timescale could be 2–3 times higher. Weathering progresses more rapidly upon initial exposure to space but the surface residence time required to achieve maturity is realized over billions of years as regolith is repeatedly buried and exposed by small impacts.

Groundwater–Stream Connectivity Mediates Metal(loid) Geochemistry in the Hyporheic Zone of Streams Impacted by Historic Mining and Acid Rock Drainage

High concentrations of trace metal(loid)s exported from abandoned mine wastes and acid rock drainage pose a risk to the health of aquatic ecosystems. To determine if and when the hyporheic zone mediates metal(loid) export, we investigated the relationship between streamflow, groundwater–stream connectivity, and subsurface metal(loid) concentrations in two ~1-km stream reaches within the Bonita Peak Mining District, a US Environmental Protection Agency Superfund site located near Silverton, Colorado, USA. The hyporheic zones of reaches in two streams—Mineral Creek and Cement Creek—were characterized using a combination of salt-tracer injection tests, transient-storage modeling, and geochemical sampling of the shallow streambed (&amp;lt;0.7 m). Based on these data, we present two conceptual models for subsurface metal(loid) behavior in the hyporheic zones, including (1) well-connected systems characterized by strong hyporheic mixing of infiltrating stream water and upwelling groundwater and (2) poorly connected systems delineated by physical barriers that limit hyporheic mixing. The comparatively large hyporheic zone and high hydraulic conductivities of Mineral Creek created a connected stream–groundwater system, where mixing of oxygen-rich stream water and metal-rich groundwater facilitated the precipitation of metal colloids in the shallow subsurface. In Cement Creek, the precipitation of iron oxides at depth (~0.4 m) created a low-hydraulic-conductivity barrier between surface water and groundwater. Cemented iron oxides were an important regulator of metal(loid) concentrations in this poorly connected stream–groundwater system due to the formation of strong redox gradients induced by a relatively small hyporheic zone and high fluid residence times. A comparison of conceptual models to stream concentration–discharge relationships exhibited a clear link between geochemical processes occurring within the hyporheic zone of the well-connected system and export of particulate Al, Cu, Fe, and Mn, while the poorly connected system did not have a notable influence on metal concentration–discharge trends. Mineral Creek is an example of a hyporheic system that serves as a natural dissolved metal(loid) sink, whereas poorly connected systems such as Cement Creek may require a combination of subsurface remediation of sediments and mitigation of upstream, iron-rich mine drainages to reduce metal export.

Experimental investigation of the residence time behavior of a wiped film evaporator

Wiped film evaporators (WFEs) are characterized by small hold-up and short residence times, making them well suited for the separation of thermally sensitive substances and for fast chemical reactions. Since fluid dynamics and heat transfer in WFEs are highly interdependent, the effects of different wiper geometries, operating parameters and physical properties on the residence time behavior are manifold and poorly understood. In this work, the influence of liquid load, wiper speed and liquid viscosity on the residence time distribution (RTD) of a wiped liquid film was investigated. Tracer experiments were conducted without evaporation in a stainless steel WFE alternatively equipped with a spring-loaded comb wiper and a roller wiper. A detailed comparison of both wipers demonstrated that at a high liquid load and an increased viscosity, shorter residence times were achieved with the roller wiper, which could be explained by a strongly pronounced bow wave with an increased vertical flow velocity. Using a comb wiper, an increase in dispersion with rising liquid load at higher viscosity was demonstrated.

Using expansion units to improve CO2 absorption for natural gas purification - A study on the hydrodynamics and mass transfer

Abstract The usage of capillary tubes for CO2 absorption suffers from small residence time, which leads to reduced performance for large throughput. This work presents a method of connecting expansion units to capillary tubes to serve as a residence time delayer. The effect of the expansion unit on gas–liquid hydrodynamics, pressure drop and mass transfer coefficient (kLa) are investigated under various operating pressures up to 4.0 MPa, for both physical and chemical absorption. A novel periodic jetting flow is found in the expansion unit, which can intensify the CO2 absorption. Experimental results show that the strategy can significantly decrease the pressure drop while maintaining the absorption performance to a large extent. The overall kLa for physical and chemical absorption are correlated to pressure drop, respectively. Besides, CO2 loading in rich absorbents increases dramatically compared to literature studies with only micromixers or capillary tubes, which is beneficial to regenerate solvent. The study verifies the concept that pre-treatment with water can largely reduce the usage of amines, and can also provide a guide for process design in natural gas purification such as biogas recovery.

Surface fluorinated Ce-doped TiO2 nanostructure photocatalyst: A trap and remove strategy to enhance the VOC removal from indoor air environment

A series of cerium-doped TiO2 anatase-brookite polymorphs with different low Ce contents (0.2–1.5 atomic %) were synthesized by a facile hydrothermal method as efficient visible-light-driven photocatalysts. Then, the surface fluorination of the Ce-TiO2 photocatalyst with optimum Ce content (0.5%Ce-TiO2) was studied further to increase its efficiency, particularly in high humid conditions. After coating of the synthesized photocatalysts on nickel foam, their photocatalytic performance was investigated in a continuous-flow reactor with small residence time through methyl ethyl ketone (MEK) degradation. Based on the characterization results, using an appropriate amount of Ce dopant and surface fluorination can significantly inhibit the charge carrier recombination. A significant improvement (about 4 times) in visible-driven photocatalytic activity has been demonstrated for F-0.5%Ce-TiO2 compared to P25. Specifically, the surface fluorination promoted the 0.5%Ce-TiO2 photoactivity in high humid conditions (e.g., 40% and 60%). After surface fluorination, removal efficiency of 0.5%Ce-TiO2 at RH = 60% improved from 52% to 60% under UV and from 47% to 54% under visible light irradiation. The MEK removal efficiency for one-layer and three-layer of 0.5%Ce-TiO2 photocatalyst are respectively 62% and 79% under UV, and 56% and 75% under visible light irradiation. Notably, the by-product generation was considerably decreased and reached the lowest amount for the three-layer F-0.5%Ce-TiO2 photocatalyst.

Carbon-doped TiO2 film to enhance visible and UV light photocatalytic degradation of indoor environment volatile organic compounds

Abstract Carbon-doped P25, a visible-light-driven photocatalyst, was prepared to remove methyl ethyl ketone (MEK) from the indoor air environment. The effect of key parameters such as carbon content, relative humidity and light type on the photocatalyst efficiency, reaction rate and by-products generation rate were evaluated. C-doped P25 photocatalysts coated on nickel foam enhanced photocatalytic degradation and the reaction rate of gas-phase MEK under visible and UV light, compared with a commercial P25 coated on the same substrate material. The results indicate that the photocatalytic degradation efficiency and the reaction rate of all examined photocatalysts under UV light are higher than visible light. All the experiments were carried out in two continuous reactors with a small residence time (0.025 s), 2.95 mg/m3 (1000 ppb) inlet contaminant concentration and at four different relative humidity levels (0, 20, 40 and 60 %). As a result, the optimum relative humidity was 20 % and 40 % for visible-PCO and UV-PCO of C-doped P25, respectively. Moreover, C-P25-0.1 % showed the highest MEK degradation under all tested conditions. The removal efficiency was enhanced from 77 % to 94 %, when three layers C-P25-0.1 % photocatalyst, was under UV light, and increased from 50 % to 67 % under visible light. Moreover, the by-product generation was considerably decreased for three-layer C-P25-0.1 % photocatalyst.

Smart Oral Administration of Polydopamine-Coated Nanodrugs for Efficient Attenuation of Radiation-Induced Gastrointestinal Syndrome.

High-dose ionizing radiation can lead to death from the unrecoverable damage of the gastrointestinal tract, especially the small intestine. Until now, the lack of predilection for the small intestine and rapid clearance by digestive fluids limit the effects of conventional radioprotective formulations. Herein, an innovative radioprotective strategy is developed for attenuating gastrointestinal syndrome by smart oral administration nanodrugs. The nanodrug is first engineered by encapsulating thalidomide into chitosan-based nanoparticles, and then coated with polydopamine. The behaviors of gastric acid-resistance, and pH-switchable controlled release in the small intestine enhance the oral bioavailability of the pyroptosis inhibitor thalidomide. In a mouse model, nanodrugs demonstrate prolonged small intestinal residence time and accessibility to the crypt region deep in the mucus. Furthermore, the nanodrugs ameliorate survival rates of C57BL/6J mice irradiated by 14Gy of subtotal body irradiation and also maintain their epithelial integrity. This work may provide a promising new approach for efficiently attenuating lethal radiation-induced gastrointestinal syndrome and add insights into developing nanodrug-based therapies with improved efficacy and minimum side effects.

Micro-Reactor Device For Dbsa-catalyzed Biodiesel Synthesis from Microalgae Chlorella Sp.

The micro-reactor device was fabricated from Teflon and tested as a tool for biodiesel synthesis process from micro algae using Dodecylbenzenesulfonic acid catalyst. The variables influenceing on the biodiesel yield were optimized. The maximum yield of biodiesel of 99% was obtained at the reaction conditions of (temperature: 373.15 K, residence time: 20 min, methanol/oil ratio: 20, co-solvent amount: 30 wt% and catalyst amount: 11wt%). The influence of water content also investigated and recommended to be less than 0.5 wt %. The acid value also reduced to a value of less than 0.5 % at the optimum reaction condition. DBSA was found highly active catalyst for the esterification and transesterification reaction in the micro – reactor device. Biodiesel was produced in microreactor device at a small residence time (20 min) compared to the very long time consumed by the conventional batch process. Isopropanol was used as a co-solvent in the process and showed highly active in the biodiesel production.

Performance of surface fluorinated P25-TiO2 on the photocatalytic degradation of volatile organic compounds in indoor environment

Volatile organic compounds (VOCs) are considered as a major group of indoor air contaminants with several adverse health effects. Photocatalytic oxidation process (PCO) has been applied for the removal of indoor VOCs. In the PCO process, the adsorption extent of water molecules on the surface of photocatalysts is a decisive factor for PCO efficiency. Water molecules contribute in PCO process either as; a) the main hydroxyl radical’s source and enhance the removal efficiency, or b) compete with VOCs to adsorb on the super-hydrophilic surface of P25 and reduce the photodegradation efficiency. In this study, the effects of surface fluorination on the photoactivity and surface hydrophilicity of commercial P25 were investigated. The fluorinated P25 (F-P25) nanoparticles were synthesized to remove methyl ethyl ketone (MEK) from the indoor environment. Surface fluorination formed the surface ≡ Ti – F by an exchange reaction between the surface hydroxyl groups (OH) and fluoride ions (F−) and decreased the water vapor adsorption on the photocatalyst’s surface. Herein, the photocatalytic efficiency of F-P25 was compared to P25 under a continuous-flow condition with a small residence time (0.026 sec) at four different relative humidity levels (0, 20, 40, and 60%). Furthermore, the performances of F-P25 and P25 on the generation of by-products, including formaldehyde and acetaldehyde were also evaluated. The results revealed that the F-P25 enhanced the photodegradation of MEK compared to bare-P25 in all tested relative humidity levels; however, the generation of the by-products increased as relative humidity increased.

Isotope pool dilution reveals rapid turnover of small quaternary ammonium compounds

Studies of how nitrogen (N) becomes available have tended to focus on depolymerisation of proteins and subsequent uptake of amino acids, yet amino acids and their polymers are not the only organic N compounds in soil. For example, concentrations of small quaternary ammonium compounds in the extracellular fraction of soil are often comparable to those of amino acids. We know that there is rapid turnover of amino acids in the extracellular fraction of soil, but there are no comparable data for small quaternary ammonium compounds. The most common function of small quaternary ammonium compounds is as intracellular osmolytes, which leads to the hypothesis that at constant osmolarity microbes would neither efflux nor take up osmolytes and thus there would be negligible flux of quaternary ammonium compounds through the extracellular fraction of soil. To test this hypothesis isotope pool dilution was used to compare gross fluxes of three quaternary ammonium compounds (betaine, carnitine and hercynine) with gross fluxes of two amino acids (glycine, alanine) in three different soils. Contrary to our hypothesis extracellular pools of betaine, carnitine and hercynine were highly dynamic and turned over rapidly. For example, in one soil the mean residence times of all quaternary ammonium compounds varied between 6 and 14 min such that pools would have turned over 100 to 240 times per day. Mean residence times of quaternary ammonium compounds were notably longer in soils from two other sites, yet remained shorter than 60 min such that pools would turnover many tens of time per day. Gross fluxes of betaine, carnitine and hercynine through the extracellular pool were 3–75 times slower than for the amino acid alanine, and thus fluxes of small quaternary ammonium compounds likely account for only a small fraction of the bio-available N that is produced and consumed. The combination of small concentrations and short residence times suggest there is intense microbial competition and active uptake of betaine, carnitine and hercynine from the extracellular fraction of soil.