Artificial Barrier Research Articles

Sentinel-2 Reveals Abrupt Increment of Total Suspended Matter While Ever Given Ship Blocked the Suez Canal

The blockage of the Suez Canal, one of the world’s key trade routes, by a giant container ship in March 2021 was in the spotlight of news media worldwide, mainly because of its economic impacts. In this study, we look at this event from an environmental perspective by analyzing the impact of the artificial barrier made by the ship over the channel and of operations like dredging on the concentration of total suspended matter (TSM). In this context, multitemporal Sentinel-2 images are used to study short-term variations of TSM within a time window spanning before, during, and after the blockage event. A well-established neural network-based processor called Case 2 Regional CoastColour (C2RCC) is employed to derive remote sensing reflectance (Rrs) and then TSM concentrations from Sentinel-2 imagery. The results indicate that the stuck ship acted as an artificial barrier leading to very different TSM conditions north and south of the canal. Furthermore, the blockage of the Suez Canal and subsequent dredging caused an abrupt increment (+400%) in the concentration of TSM moving north from the ship’s location. We also identified a very high contrast between the TSM concentration in the north and south of the vessel during the blockage event.

A mechanically induced artificial potential barrier and its tuning mechanism on performance of piezoelectric PN junctions

A mechanically induced artificial potential barrier (MIAPB) is set up in the paper by a pair of tensile/compressive stresses acted on a piezoelectric PN junction. The action mechanism of MIAPB on the electric characteristics is investigated via a full-coupled model between multi-physical fields and charge carriers. A MIAPB tuning methodology is put forward and the interaction between MIAPB and the interface potential barrier is analyzed in depth. Influences of loading locations of MIAPB on barrier configuration, carrier concentrations and recombination rate are carefully illustrated and the improved I-V characteristics of a ZnO PN junction subjected to MIAPB are obtained. It is found that the tensile-stress mode of MIAPB improves performance of PN junctions by reconstructing the interface potential barrier and the compressive-stress mode by stimulating strong interaction with the interface barrier. Thus, a tensile-stress MIAPB should be applied inside the interface barrier region and a compressive-stress one outside the interface region. Numerical results show that the maximal output current can be increased by 7.16 times via a tensile-stress MIAPB and 5.18 times via a compressive-stress one, compared to the one without MIAPB, when the doping concentrations are set as 1 × 1021 m-3 with the loading spacing same as the width of the depletion-layer. Obviously, our study possesses referential significance to the mechanical tuning on the performance of piezoelectric PN junctions and piezotronic devices.

Swelling deformation of compacted bentonite considering the effects of Na cations and OH anions

Compacted bentonite has become a viable candidate as suitable artificial barrier material for restricting the movement of high-level radionuclides released from the canister in the deep geological repository. However, this material itself is fragile mainly because it is sensitive to the complex chemical environment especially alkaline components. Based on the interaction mechanism of cations and anions, this paper is mainly focused on the analysis of swelling deformation characteristics of compacted bentonite. Laboratory test results are shown that the elevated Na cations concentration can inhibit both the primary and secondary expansion process in compacted bentonite. The elevated OH anions concentration can inhibit the primary expansion process of compacted bentonite and will promote the secondary expansion process. The effects of NaOH solution with different concentrations on the swelling strain present the interaction of Na cations and OH anions. The swelling deformation of compacted bentonite is not only affected by the concentration of solution but also may be related to ionic compositions.

Preliminary comparison of contact angle and wetting resistance of water-repellent treated cotton woven fabric

Filtration capability of textile media or the resistance towards the fluid penetration through different fabrics is depending on their surface repellence. The emission of condensed exhaled air on the outer layer of the half facemask from the FFP2 (EN 149) category indicates the termination of its protective properties. The overcoming by the fluid of the textile environment of the mask in its role of an artificial barrier goes through two stages. Initially, the aerosols in the exhaled air condense and meet the repulsion from the inner fabric. Later, due to the hydrodynamic pressure, the condensed droplets pass through the textile medium, overcoming the friction among the fibrous layers. Finally, the droplets irrigate the outer, front layer of the mask and are released into the environment with all the consequences. Closest to this physiological process is the hydrostatic pressure test method. The test of resistance to fluid penetration gives a final assessment of the property of the textile environment without clarifying the elements of the process. Experimental studies have shown similarities in the results of the penetration of the fluid through the textile medium and the initial repulsion of aerosols from the surface of the fibrous layer. The repulsion of water droplets is of predominant importance in relation to the general barrier capacity of the textile media. The main indicator of water repellence is the contact angle of the free drop on the fabric. The subject of this article is the comparison between the contact angle of wetting and the penetration of the fluid by means of standard test methods. The aim of the work is to explain and model the process of fluid penetration through protective masks, as well as to optimize the properties of repulsion and resistance.

Further SAR studies on natural template based neuroprotective molecules for the treatment of Alzheimer’s disease

In our earlier paper, we described ferulic acid (FA) template based novel series of multifunctional cholinesterase (ChE) inhibitors for the management of AD. This report has further extended the structure–activity relationship (SAR) studies of this series of molecules in a calibrated manner to improve upon the ChEs inhibition and antioxidant property to identify the novel potent multifunctional molecules. To investigate the effect of replacement of phenylpiperazine ring with benzylpiperazine, increase in the linker length between FA and substituted phenyl ring, and replacement of indole moiety with tryptamine on this molecular template, three series of novel molecules were developed. All synthesized compounds were tested for their acetyl and butyryl cholinestrases (AChE and BChE) inhibitory properties. Enzyme inhibition and PAS binding studies identified compound 13b as a lead molecule with potent inhibitor property towards AChE/BChE (AChE IC50 = 0.96 ± 0.14 µM, BChE IC50 = 1.23 ± 0.23 µM) compared to earlier identified lead molecule EJMC-G (AChE IC50 = 5.74 ± 0.13 μM, BChE IC50 = 14.05 ± 0.10 μM, respectively). Molecular docking and dynamics studies revealed that 13b fits well into the active sites of AChE and BChE, forming stable and strong interactions with key residues Trp86, Ser125, Glu202, Trp 286, Phe295, Tyr 337 in AChE, and with Trp 82, Gly115, Tyr128, and Ser287 in BChE. The compound, 13b was found to be three times more potent antioxidant in a DPPH assay (IC50 = 20.25 ± 0.26 µM) over the earlier identified EJMC-B (IC50 = 61.98 ± 0.30 µM) and it also was able to chelate iron. Co-treatment of 13b with H2O2, significantly attenuated and reversed H2O2-induced toxicity in the SH-SY5Y cells. The parallel artificial membrane permeability assay-blood brain barrier (PAMPA-BBB) revealed that 13b could cross BBB efficiently. Finally, the in-vivo efficacy of 13b at dose of 10 mg/kg in scopolamine AD model has been demonstrated. The present study strongly suggests that the naturally inspired multifunctional molecule 13b may behave as a potential novel therapeutic agent for AD management.

What ecological and functional changes follow the positioning of an artificial barrier? Answers from a 4-year investigation on soft bottom benthic communities

What ecological and functional changes follow the positioning of an artificial barrier? Answers from a 4-year investigation on soft bottom benthic communities

Numerical Analysis of Soil Water Dynamics during Spinach Cultivation in a Soil Column with an Artificial Capillary Barrier under Different Irrigation Managements

Artificial capillary barriers (CBs) are used to improve root zone conditions as they can keep water and nutrients in the root zone by limiting downward percolation. Numerical analysis is one of the promising tools for evaluating CB systems’ performance during the cultivation of leafy vegetables. This study aims to investigate the effects of the CB system on soil water dynamics during spinach cultivation in a soil column under different irrigation scenarios using HYDRUS (2D/3D) by comparing uniform (UNI), line-source (LSI), and plant-targeted (PTI) irrigations combined with alternative irrigation schedules. Simulation results of volumetric soil water contents were generally corresponding to measured data. Simulation results with various hypothetical irrigation scenarios exhibited that the CB was an effective system to diminish percolation losses and improve the root zone’s soil water storage capacity. On the other hand, evaporation loss can be increased as more water is maintained near the surface. While this loss can be significantly minimized by reducing the water application area, the irrigation amount must be carefully defined because applying water in a smaller area may accelerate downward water movement so that the water content at the CB interface can reach close to saturation. In addition to the malfunction of the CB layer, it may also cause a reduction of plant root water uptake (RWU) because the root zone is too wet. Among evaluated irrigation scenarios, irrigating every two days with PTI was the best scenario for the spinach as water use efficiency was greatly improved.

Effect of alkali activators on diffusivity of metakaolin-based geopolymers

A basic investigation into whether a geopolymer can be utilized as a part of an artificial barrier during radioactive waste disposal was conducted in this study. Geopolymers are comprised primarily alumina and silica, and they exhibit negligible leaching owing to the absence of calcium. Studies on geopolymers are limited compared to those on other cementitious materials because the physical characteristics of geopolymers vary with the production conditions. In this work, metakaolin based geopolymers were prepared, and their diffusion performance was analyzed. The results indicate that the diffusivity of cesium in a geopolymer is affected by the type of alkali activator. Sodium-activated geopolymers had higher cesium adsorption capacity than potassium-activated geopolymers. The cesium adsorption capacity also had a significant effect on the diffusivity of cesium in the geopolymers. It was shown that, in addition to the pore structure and surface area, the mobility of water affects the diffusion performance of the geopolymer.

Development of swelling pressure for pellet mixture and compacted block of GMZ bentonite

Bentonite pellet mixture is considered as a candidate buffer/backfill material for construction of artificial barrier in high-level radioactive waste (HLW) repository. Compared to that of a compacted bentonite block, one of the most obvious features of this material is its initially discrete pellets and significant structural heterogeneity, leading to a distinctive swelling behaviour. In this paper, a comparative study concerning development of swelling pressure on hydration was conducted on pellet mixture and compacted block of Gaomiaozi (GMZ) bentonite specimens with an identical dimensions (50 mm in diameter and 35 mm in height) and dry density (1.45 Mg/m3). Results show that, within the initial 72 h, the swelling pressure of pellet mixture increases at a lower rate and achieves a lower peak value than those of the compacted bentonite block. Then, the swelling pressure of the pellet mixture varies slightly while that of the compacted bentonite block decreases significantly before increasing again. Eventually, the swelling pressure for the two specimens approaches to an almost similar final stable value, 0.939 MPa and 0.947 MPa, respectively. Based on an insight into the mechanism of swelling pressure development, a new theory on competition between the accumulated and dissipated wedging pressures (AWP and DWP) within the specimen was proposed for interpreting the different developments of swelling pressure between the two specimens. As water infiltrates, the AWP continuously increases, while the DWP firstly increases and then decreases. At a given infiltration time, the AWP of pellet mixture is smaller than that of compacted bentonite block due to accommodation of the pellets swelling deformation by inter-pellet voids. While within the initial hundreds hours of infiltration, the DWP within pellet mixture could be larger than that in compacted bentonite block due to the deformation (swelling or compression), damage (cracking or collapse) and displacement (rotation or dislocation) of the pellets. For both specimens, the macro and micro void ratios decrease while the meso void ratio increases with infiltration, leading to a gradually homogenized pore structure. Taking the pore size distribution curve of the middle layer of compacted bentonite block specimen after 720 h hydration as a reference, a porosity homogenization index (PHI) was defined to reflect the degree of pore structure homogenization. Generally, the PHIs of the upper, middle and lower part of the two specimens decrease with infiltration time. At a given time, the PHIs of pellet mixture are higher than those of compacted bentonite block but the difference between them decreases, leading to corresponding decrease of the swelling pressure difference. Considering the low swelling pressure (<1.0 MPa) of the current pellet mixture, it is necessary to improve its swelling capacity either by denser compaction or property modification for the safety of long-term operation of a HLW repository.

Apexification Using Mineral Trioxide Aggregate and Modified Internal Matrix: A Case Report

When pulpal necrosis occurs in immature teeth, one of the treatment alternatives is the creation of an artificial apical barrier through the placement of an apical plug. However, controlling the mineral trioxide aggregate (MTA) during placement has proven difficult. Several studies evaluated the use of resorbable barriers to act as an internal matrix to prevent accidental extrusion of MTA. The aim of this case report was to document the effectiveness of Surgicel as a modified internal matrix for proper placement of MTA during management of immature teeth with necrotic pulp using the apical plug technique. A 12-year-old female patient reported with the chief complaint of a badly mutilated lower right second premolar. The tooth suffered enamel hypoplasia and had a defective coronal structure. It was asymptomatic except for slight tenderness to percussion. Based on the clinical and radiographic findings, a diagnosis of pulpal necrosis with symptomatic apical periodontitis was made. The 3- and 6-month followup showed radiographic evidence of continued root and hard tissue formation. Based on these findings, we infer that Surgicel can be used as a modified internal matrix to prevent extrusion of the MTA into the periapical area and allow for proper MTA placement. Keywords: Apexification; Apical plug; Mineral trioxide aggregate; Calcium hydroxide; Surgicel; Modified internal matrix

Use of Mineral Trioxide Aggregate with or without a Collagen Sponge as an Apical Plug in Teeth with Immature Apices.

This retrospective study aimed to evaluate the clinical outcomes of the apical plug performed using MTA with or without collagen sponge in immature anterior maxillary teeth with necrotic pulp. The study included apical obturation of 20 upper incisor teeth from 18 patients and outcomes of 12-month follow-up. The teeth were divided into 2 groups with 10 cases in each group according to the apexification protocol (Group 1; apical plug with MTA, Group 2; collagen sponge and apical plug with MTA). The artificial apical barrier, approximately 4-mm-thick, was created with MTA in each group. Based on clinical and radiographic criteria, the outcome was assessed using the periapical index (PAI) by 2 calibrated investigators. In this study, 3 of the 6 teeth (50%) in Group 1 and 5 of the 8 teeth (62.5%) in Group 2 healed at the 12-month follow-up. However, there was no statistically significant difference between the groups at the post-treatment follow-up times. The use of collagen as an apical matrix prior to the MTA plug can be suggested due to favorable clinical outcomes.

LOCALIZATION OF EXPLOSION PULSES IN A CLOSED SPACE IN COAL MINES

The data on the prospect of using an artificial high pressure water barrier as a method of localizing the explosion impulse in the confined space of tunnels and mines are presented. The explosion impulse and the process of its decay in interaction with water fog have been studied. In the course of field research, an explosion was simulated in the shock installation, and a method for its localization was developed using four water screens (barriers). The water screen was created using a system of ring-shaped water distribution headers with high pressure nozzles installed in a circle. Hexogen was used as an explosive. Experiments on localization of explosions were carried out on the base of the "Grigol Tsulukidze Mining Institute of Georgia" in Tbilisi, Georgia, together with the research group of the Faculty of Chemistry and Chemical Technology of al Farabi Kazakh National University and the Institute of Combustion Problems. The influence of the water barrier on the process of shock wave attenuation at 3 points of overvoltage of the section is established. The test results showed that the average values of the overpressure in the three sections were reduced by 38.8%, 26.67% and 19.2%, respectively. The action of the shock wave occurs according to an exponential function, and all other wave changes along any other trajectory on the plane of h – t change are described by a single time dependence.

Designing artificial carbon clusters using Ge2Sb2Te5/C superlattice-like structure for phase change applications

Resistance drift and heat loss are two challenges in phase change memory. In this work, superlattice-like (SLL) Ge2Sb2Te5/C film was fabricated, which was designed to suppress the resistance drift and heat loss of the device. Ab initio molecular dynamics simulations were used to evaluate the evolution of C nanofilms at the atomic scale and most C atoms were found accumulated spontaneously as nanometer-scale carbon clusters. Long-range atomic migrations were restrained because of the artificial carbon clusters, which contributed to the resistance drift suppression. The fabricated carbon nanolayers were also believed to serve as an artificial thermal barrier, and an energy-inexpensive amorphization process based on the device has been achieved. With two-dimensional finite element analysis, we found that the suppressed heat dissipation in the programming regions were related to the low interfacial thermal conductance between the C and Ge2Sb2Te5. The Ge2Sb2Te5/C SLL thin film demonstrates potential for high-performance phase change memory applications.

The role of migration barriers for dispersion of Proliferative Kidney Disease—Balance between disease emergence and habitat connectivity

Natural and uninterrupted water courses are important for biodiversity and fish population stability. Nowadays, many streams and rivers are obstructed by artificial migration barriers, often preventing the migration of fish. On the other hand, distribution of pathogens by migrating fishes is still a point of concern. Pathogen transport and transmission is a driving force in the dynamics of many infectious diseases. The aim of the study was to investigate the possible consequences of the removal of an artificial migration barrier for the upstream transport of Tetracapsuloides bryosalmonae, the causative agent of Proliferative Kidney Disease (PKD) in brown trout, by migrating fish. To test this question, a river system was selected with a migration barrier separating a PKD positive river from a PKD negative tributary. After removal of the barrier, PKD prevalence and pathology was examined during five years after elimination of the barrier. In the tributary, no PKD was recorded at any time of the survey. By means of unidirectional PIT (passive integrated transponder)-tagging, we confirmed upstream migration of adult brown trout into the tributary during the cold season, presumably for spawning. By eDNA, we confirmed presence of T. bryoalmonae and Fredericella sp., the definitive host, DNA in water from the PKD positive river stretch, but not in the PKD negative tributary. Our study illustrates the importance of the connectivity of streams for habitat maintenance. Although migration of brown trout from a PKD-positive river into a PKD-negative tributary, mainly for spawning, was confirmed, upstream spreading of PKD was not observed.

Root growth responses to mechanical impedance are regulated by a network of ROS, ethylene and auxin signalling in Arabidopsis.

Summary The growth and development of root systems is influenced by mechanical properties of the substrate in which the plants grow. Mechanical impedance, such as by compacted soil, can reduce root elongation and limit crop productivity.To understand better the mechanisms involved in plant root responses to mechanical impedance stress, we investigated changes in the root transcriptome and hormone signalling responses of Arabidopsis to artificial root barrier systems in vitro.We demonstrate that upon encountering a barrier, reduced Arabidopsis root growth and a characteristic ‘step‐like’ growth pattern is due to a reduction in cell elongation associated with changes in signalling gene expression. Data from RNA‐sequencing combined with reporter line and mutant studies identified essential roles for reactive oxygen species, ethylene and auxin signalling during the barrier response.We propose a model in which early responses to mechanical impedance include reactive oxygen signalling integrated with ethylene and auxin responses to mediate root growth changes. Inhibition of ethylene responses allows improved growth in response to root impedance, an observation that may inform future crop breeding programmes.

Prevention of Frey's Syndrome with the Use of Porcine Dermal Collagen Graft: Retrospective Analysis of 76 "Formal" Parotidectomies for Benign Pathologies.

Frey's syndrome is a well-known complication of parotid surgery; its prevention may be achieved by the use of an interpositional barrier between the overlying flaps and the exposed parenchymal bed of parotid gland. The aim of this study was to retrospectively evaluate clinical outcomes with and without the interpositional placement of a porcine dermal collagen graft (PDCG) for prevention of syndrome occurrence. We conducted a 20-year retrospective study including the patients who had undergone "formal" (superficial, total, or subtotal) parotidectomies for benign pathologies. The inclusion criteria also involved patients that were (i) regularly monitored about clinical symptoms related to syndrome, and (ii) examined with Minor starch-iodine test. The severity of the diagnosed syndrome was retrospectively evaluated according to the grading score system of Luna-Ortiz. To assess group differences in terms of the extent of dissection in operating sites, we estimated the tumor and histological specimen volumes using the available dimensions. We included 73 patients who had undergone 76 formal parotid surgeries. The surgical sites were divided into 2 groups: (1) Group A consisted of 44 sites that were reconstructed with a SMAS flap, and (2) Group B, comprised 32 sites where a PDCG was additionally applied as an artificial preventive barrier. At a mean follow-up of 26.3 months, a significantly lower incidence of clinically diagnosed Frey's syndrome was found after the use of dermal collagen interpositional barrier (P = .031). Specifically, subjective symptoms were reported at an incidence of 31.8% in Group A and 6.7% in Group B. Minor's test was positive at an incidence of 59.09% in Group A and 21.87% in Group B (P = .004, 95% CI). Severe Frey's syndrome was observed in 31.82% of the patients of Group A and in 3.12% of the patients of Group B (P = .002, 95% CI). Since there were no statistical significant differences between the volumes of the removed tumors and the excised histological specimens, the extent of dissection was not proved to influence the occurrence of Frey's syndrome in the compared groups. Porcine dermal collagen is a safe, practical, and useful means for parotid reconstruction, since it seems to contribute in prevention of Frey's syndrome when increased amount of glandular tissue has to be removed. Additional randomized controlled studies with bigger samples are required to better assess the PDCG use in parotid surgery.

Music, discourse and intuitive technology

This paper proposes that intuitive technologies play a vital role in cognition and cultural reception. The case of music is considered in particular. The perceived temporality of contemporary technology is shown to be an artificial barrier to the acknowledgement of longer-term dynamics. The increased role of explanatory metaphors from technology is traced across various fields of study. Processes of sense-making—conscious or otherwise—are seen as an informal, unreflected repertory of mechanisms ranging from predictive models to instrumental metaphors. It is suggested that these derive by assimilation and induction from the technological milieu within which the subject develops and operates. The acquisition of these models and metaphors is itself an imaginative process, based on experience ranging from partial expertise to fantastical extrapolation.

Studying the influence of the carbon dioxide injection period duration on the gas recovery factor during the gas condensate fields development under water drive

Purpose. Studying the process of carbon dioxide injection at the boundary of the initial gas-water contact in order to slow down the formation water inflow into producing reservoirs and increase the final hydrocarbon recovery factors. Methods. To assess the influence on gas recovery factor of the duration of carbon dioxide injection period at the initial gas-water contact, a reservoir development is studied using the main Eclipse and Petrel hydrodynamic modeling tools of the Schlumberger company on the example of a hypothetical three-dimensional model of a gas-condensate reservoir. Findings. The dependence of the main technological indicators of reservoir development on the duration of the carbon dioxide injection period at the initial gas-water contact has been determined. It has been revealed that an increase in the duration of the non-hydrocarbon gas injection period leads to a decrease in the formation water cumulative production. It has been found that when injecting carbon dioxide, an artificial barrier is created due to which the formation water inflow into the gas-saturated intervals of the productive horizon is partially blocked. The final gas recovery factor when injecting carbon dioxide is 61.98%, and when developing the reservoir for depletion – 48.04%. The results of the research performed indicate the technological efficiency of carbon dioxide injection at the boundary of the initial gas-water contact in order to slow down the formation water inflow into producing reservoirs and increase the final hydrocarbon recovery factors for the conditions of a particular field. Originality. The optimal value of duration of the carbon dioxide injection period at the initial gas-water contact has been determined, which is 16.32 months based on the statistical processing of calculated data for the conditions of a particular field. Practical implications. The use of the results makes it possible to improve the existing technologies for the gas condensate fields development under water drive and to increase the final hydrocarbon recovery factor.

Behavior of compacted Ca-bentonite subjected to HMC loading: observations and interpretation

This study presents result of HMC experimental test and discussions of chemical effort in Cabentonite. SWCC test, swelling pressure test and unconfined compression test as hydro-mechanical-chemical (HMC) test were applied to Cabentonite-sand mixture. Na-type bentonite has been studied to predict safety and confidence for artificial barrier layer consist of bentonite that many experimental research reports are represented, and can offer technology advanced comprehensive performance due to mathematical simulation models associated to physical parameters on thermal-hydration-mechanical-chemical properties. This study proposed a significant property for calcium bentonite to relate evaluating safety in radioactive waste disposal system, which emphasised much influence of suction and salinity chloride to hydration-mechanical behaviour for Calcium bentonite.

Evaluation of the rheotaxis behavior of juveniles of the prawn Macrobrachium tenellum Smith, 1871 (Decapoda: Palaemonidae) under laboratory conditions

Understanding the upstream migration of amphidromous prawns is important to address the impact of anthropomorphic activities in natural freshwater ecosystems. The ability of Macrobrachium tenellum (Smith, 1871) juveniles to overcome an artificial barrier was evaluated, simulating an obstacle in their upstream migration, under an experimental laboratory system. The prawns were collected from a stream located in Puerto Vallarta, Mexico (N = 1000). An experimental recirculation system was used, which consisted of a tank with a capacity of 600 L, a sheet of galvanized steel that acted as an anthropogenic barrier and two submersible electric pumps with flows of 0.12 L/s and 0.40 L/s. In this system, two inclinations of the barrier were tested, 45° and 90° in combination with the two flows. The results show that there are significant differences between the treatments with different inclinations, where a higher stimulation response was observed at the 90° angle. Within this inclination, the flow of 0.40 L/s produced the highest stimulation to climb the barrier in prawns between 30 and 60 mm in length. This study demonstrates the direct relationship between the slope and the effect of water flow of the anthropogenic barriers that hinder the migration process of M. tenellum.