Changes In Mesh Size Research Articles

Effect of using time in small pelagic purse seine with two vessels (slerek) on breaking strength and mesh size change in Pengambengan Archipelago Fishing Port (PPN), Bali, Indonesia

The bunt net of a small pelagic purse seine with two vessels (slerek) serves as a place for captured fish before being loaded onto the boat. Seine nets that are operated within a certain of long time can be weathering and deterioration of the material caused by aging and environmental factors. This study aims to analyze the effect and relationship of the use time of a bunt net with Multifilament polyamide (PA) material 210 D/12 mesh size ¾ inch on breaking strength and changes in mesh size. The methods used are observation, interview, literature study and documentation to be further analyzed using descriptive analysis and MANOVA. The results showed a decrease in the breaking strength value of the net by 38% while on the contrary, a 5% increase occurred in the change in mesh size. The analysis conducted shows the influence of usage time on breaking strength by 95.9% with a very strong not unidirectional relationship level of -0.977 and the influence of usage time on changes in mesh size by 99% with a correlation coefficient value of 0.985 which means the level of relationship is very strong and unidirectional.

Bioinspired hydrogels: polymeric designs towards artificial photosynthesis.

Aquatic environments host various living organisms with active molecular systems, such as the enzymes in the thylakoid membrane that realise photosynthesis. Various challenges in achieving artificial photosynthesis, such as water splitting, have been studied using both inorganic and organic molecules. However, several problems persist, including diffusion-limited reactions and multiple redox reactions in the liquid phase. In this Feature Article, we discuss the significant challenges in using polymer networks as active mediators for photoinduced water splitting. In the creation of artificial chloroplasts, polymer networks offer various advantages, such as stable dispersions of multiple types of functional molecules and close molecular arrangements. To incorporate these features, stepwise synthesis and integration can be utilized during the hierarchical construction of polymer networks. The constituent molecules such as ruthenium complex and platinum nanoparticles in the photoinduced electron transfer circuits are closely arranged to smoothly operate forward reactions by polymer networks. The quantum efficiency of photoinduced H2 generation in gel systems is considerably higher than that of conventional solution systems. Additionally, a thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm) network of microgels can be used to integrate catalytic nanoparticles into the inside by using the electrostatic interaction and the mesh size changes. By focusing on the redox changes of copolymerised molecules that induce swelling/shrinking at a constant temperature, active electron transfer can be precisely achieved using the coil-globule transition of the PNIPAAm having viologen. This article highlights the potential of polymer networks to develop strategies for active electron transfer and energy conversion systems similar to those found in living organisms.

Developing 3D-network gels from polysaccharide gums for biomedical applications

Keeping in view the recent advancements in polysaccharide materials, gum acacia (GA) - tragacanth gum (TG) was investigated for designing polymeric network structures impregnated with cephalexin antibiotics for drug delivery (DD). Grafted product of polyvinylimidazole [poly(VIm)] and GA-TG was characterized by field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermo-gravimetric analysis (TGA) and differential scanning calorimetry (DSC). Change in mesh size (from 17.73 to 32.98 nm) and crosslinking density (between 1.64 × 10−5 to 5.06 × 10−5 mol cm−3) was found with change in poly(VIm), gum and crosslinker NNMBA content which revealed that these parameters can be tailored made as per requirement and applications. Swelling properties illustrated pH sensitivity in copolymers because of composition which is useful for colon or site-specific DD of cephalexin. FESEM and AFM demonstrated heterogeneous morphology with the rough surface topology of grafted product. XPS and FTIR confirmed the grafting of poly(VIm) onto polysaccharide chains. Drug diffusion was non-Fickian and release was fitted in Higuchi kinetic model from copolymers. The release was slow and prolonged due to drug-polymer interactions. Copolymers exhibited 31.29% scavenging ability in DPPH assay and haemolysis was less than 2% that inferred biocompatible nature. Bio-surface interactions with intestinal membrane indicated the muco-adhesive nature of copolymers. Antimicrobial properties of hydrogel were evaluated against E. coli, P. aeruginosa and S. aureus. All observations revealed that GA-TG crosslinked copolymers could be explored for colon DD of antibiotic drugs with tailored crosslinking density.

ESTIMATION OF CORRECT MEASUREMENT OF THE TITANIUM RETAINED IMPLANTS AREA BY CT EXPERIMENTAL MODEL

Annotation: This article presents the results of evaluating the measurement of the area of titanium mesh implants using computed tomography (CT) data based on the use of an experimental model. Hernioplasty using mesh implants is a modern method of treating hernias of the anterior abdominal wall. The most common complication of hernia surgery is hernia recurrence. The main reason for the development of recurrence is the discrepancy between the size of the implant and the hernial defect, which may occur due to a decrease in the size of the mesh after its installation. CT can be used to assess changes in mesh size. The study showed that the dimensions obtained because of non-invasive measurement of the mesh implant by CT did not significantly differ from the dimensions of the implant obtained intraoperatively. Thus, CT is a highly effective method for assessing the size of titanium mesh implants and can be used in clinical practice.

Topology optimization for disc structures with buckling and displacement constraints

This article presents a novel topology optimization framework, which takes the key nodal displacements and the critical buckling load factor as constraints to guarantee that the designs of torsional disc structures not only satisfy the resistant capability of in-plane deformation but also do not cause out-of-plane buckling failure. The composite exponential filter functions and Taylor expansion are applied to obtain the approximate explicit functions between structural performance and topological design variables based on the results of static and buckling analyses. The dual-sequence quadratic programming algorithm is applied to solve the explicit topology optimization model. In addition, an adaptive image filter technology is developed to overcome the numerical instability problem that occurs in the finite element model of discs with significant changes in mesh size. Finally, some designs of torsional disc structures are presented to illustrate the effectiveness and feasibility of this method.

Effect of Loop Defects on the High Strain Rate Behavior of PEGDA Hydrogels: A Molecular Dynamics Study.

The high strain rate behavior of nonideal poly(ethylene glycol) diacrylate hydrogels under uniaxial tension and transient-state shear deformations is investigated using molecular dynamics (MD) simulations. This work specifically focuses on the influence of first-order loop defects, including their effect on topological evolutions. Two approaches are proposed to systematically introduce first-order loops, allowing separate and controllable investigations of effective cross-link functionality and cross-link density. MD simulations confirm that first-order loop defects are elastically inactive, but the topological disruptions caused by the presence of loop defects influence mechanical behavior. For decreasing effective cross-link functionality but constant cross-link density, a weaker tensile stress-strain response and decreasing shear-thickening behavior are observed. This is due to nonaffine translation of cross-link junction positions during deformation. Hydrogels with lower cross-link density but constant effective functionality show a stronger stress-strain response and an earlier transition between entropic and enthalpic deformation regimes. This behavior is correlated to changes in mesh size caused by the introduction of loops within an elastically active network. However, the resulting range of cross-link densities is not sufficient to cause measurable changes in shear-thickening behavior. To conclude, reductions in effective cross-link functionality are more important to high strain rate behavior than reductions in cross-link density.

Immediate Catch Reduction or Catch Increase When the Mesh Size Is Changed

Changes in mesh size are often rejected by fisheries management. Fishermen also do not like changes in mesh size. Apparently, a lower, but secure current yield and revenue counts more in the decisions than uncertain benefits in the future. A calculation method is presented that can be used to calculate the immediate changes in yield. It is shown that even large changes in mesh size do not necessarily lead to large changes in yield. Reductions or increases in catches can usually be easily compensated by immediate changes in fishing effort. In addition, it is shown how changes in mesh size affect the biomass of caught undersized fish (discards). As the results depend on the length distribution within the studied area, no general conclusions can be made. The length distribution in the area must therefore be determined in advance each time changes are planned.

Grid generated turbulence under the rigid boundary influence

An experimental investigation was carried out to study the grid generated turbulence and rigid boundary interaction for different mesh size of grid. Quadrant analysis technique was adopted here to provided information on the turbulent bursting events contributing to the Reynolds shear stress at the near rigid boundary region. It was observed that, near the rigid boundary the contribution to the total shear stress due to the ejection and sweeping events changed significantly for larger mesh size. The relative dominance of these two events were found to contribute in a cyclic manner in the near bed region, whereas such phenomenon disappeared in the main flow region. The distribution of the time interval of the ejection and sweeping events were found to change with the change in mesh size of the grid. To characterize the behaviour of eddies, several turbulence scales such as the integral scale, the Kolmogorov microscale, and the Taylor length scales were determined and compared for different mesh size of grids under rigid boundary influence. Integral and Kolmogorov length scales for larger mesh size were less compared to smaller mesh size, which implied that the smaller mesh size reduced the turbulent kinetic energy dissipation at a rate faster than the larger mesh size.

Long-term retromuscular and intraperitoneal mesh size changes within a randomized controlled trial on incisional hernia repair, including a review of the literature

Purpose Ingrowth of fibroblasts in a polypropylene mesh may cause contraction and a later recurrence. We assessed mesh contraction in intraabdominal and retromuscular implantation after incisional hernia repair.MethodsA cohort of patients within an RCT on laparoscopic (LHR) versus open hernia repair (OHR) had their mesh borders marked with metal clips. X-ray was performed on postoperative day 1 and after 1 year. Total length, width, and dislocation were measured. A tacker fixated large-pore polypropylene mesh was used in LHR, and a retromuscular small-pore heavy-weight mesh was sutured to the midline in OHR. Patient’s pain was assessed before surgery and after 1 year.ResultsFor analysis 37/47 patients remained: 20 LHR and 17 OHR. Hernia defect area was median 41 cm2 in LHR and 25 cm2 in OHR (p < 0.140). Implanted mesh size was 300 cm2 for LHR and 240 cm2 for OHR (p < 0.341). After 1 year the mesh area decreased by 4.4% and 0.5% in LHR and OHR, respectively (p < 0.063). Longitudinal distance decreased by 2.8% in LHR and by 2.6% in OHR (p < 0.269). Transverse distance decreased by 1.6% in LHR but increased by 3.1% in OHR (p < 0.005). Dislocation was seen in four LHR and one OHR. Two recurrent and one port-site hernia were diagnosed after LHR. Measurements between observers were identical in 58% and consensus was made in the remainder. Pain was not correlated to mesh area change.ConclusionsMesh contraction after 1 year is not a clinical issue for an intraperitoneal large-pore mesh or a retromuscular small-pore mesh. It is not correlated to postoperative pain.

Photo‐crosslinked poly(ethylene glycol) diacrylate (PEGDA) hydrogels from low molecular weight prepolymer: Swelling and permeation studies

ABSTRACTThe aim of this work was to assess the diffusive properties of poly(ethylene glycol) diacrylate (PEGDA)‐based hydrogels, derived from low MW prepolymers, in view of potential biomedical applications. Several hydrogels were synthesized through UV irradiation of PEGDA solutions for different exposure times. Swelling measurements in distilled water were performed to estimate the yielded crosslink density, while swelling tests at 37 °C in selected media allowed to analyze the mesh size changes induced by various pH and ionic strength (IonS) conditions. The transport of glucose and insulin through thin hydrogel membranes was finally assessed in a modified Ussing chamber at physiological values of pH and IonS (7.4 and 150 mM, respectively). Results showed that the swelling was dependent on the IonS (with swelling reductions up to 20–30% for IonS increases in the range 0–300 mM) and, to a lesser extent, on the pH of the surrounding medium (with swelling increments of about 10% for increasing pH in the range 2.5–11). All hydrogels were also permeable to glucose and insulin, which displayed comparable diffusion coefficients (in the order of 10−6 cm2/s). Specific interactions between glucose and the polymer chains were evidenced by values of the partition coefficient higher than unity. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44380.

Population dynamics parameters of narrow-barred Spanish mackerel, Scomberomorus commerson (Lacèpéde, 1800), from commercial catch in the northern Persian Gulf

Population dynamics parameters of Scomberomorus commerson in Bushehr area waters of Iran were analyzed between October 2011 and September 2012. Fork length frequencies were collected from the gill net commercial catch. Von Bertalanffy growth function was used to estimate growth parameters K and L∞. Instantaneous total mortality rate (Z), instantaneous natural mortality rate (M) and the instantaneous fishing mortality rate (F) were also calculated. Resource status was evaluated by comparing estimates of the fishing mortality rate with target (Fopt) and limit (Flimit) biological reference points. FiSAT program was used to assess growth and mortality parameters. Based on the growth curve analysis, growth parameters were: K=0.5year−1 and L∞=148cm. Instantaneous total mortality was Z=0.97year−1. The estimate of M=0.56year−1 and F=0.41year−1, resulting in an exploitation rate (F/Z) of E=0.42year−1. Target and limit biological reference points were: Fopt=0.28year−1 and Flimit=0.37year−1. Size at capture at probabilities of 0.25 (L25), 0.5 (L0.5) and 0.75 (L0.75), were 46.3 cm, 55 cm and 60.2 cm respectively. Longevity (Tmax) was calculated as 3/K equal to 6 years. The exploitation rate (E) did not indicate overfishing; however, Fopt and Flimit rates were lower than fishing mortality (F), suggesting that overexploitation occurred. Growth parameters in the present study showed that the gillnet fishery catches of S. commerson that are of ages 1 or 2, which may not have reached maturity. Gillnet mesh size can be a factor why the catch is composed of mostly small, immature fish. Therefore, changes in mesh size and net size should be considered.

Photoinduced Deformation of Rigid Azobenzene-Containing Polymer Networks

Photoresponsive poly(amide acid) (PAA) gels containing multiple azobenzene units in a rigid aromatic backbone were synthesized. A centimeter-long cantilever made up of the photoresponsive PAA gel exhibited reversible bending motions upon blue (442 nm) and visible light (>490 nm) irradiation. The network structure in the PAA gels during alternating photoirradiation of blue and visible light was characterized using in situ scanning microscopic dynamic light scattering (SMILS), which revealed reversible mesh-size changes synchronized with the photoisomerization of azobenzene moieties. The photomechanical responses of the PAA gel were likely due to photoinduced contracting and stretching motions of the polymer backbone. A numerical calculation of photon absorptions revealed that photoisomerization in a very thin layer of the surface (∼40 μm) generated large macroscopic motion and large strain in the gel cantilever. The photoresponsive capability is, however, reduced or eliminated when the PAA gels are transfo...

On the role of hydrogel structure and degradation in controlling the transport of cell-secreted matrix molecules for engineered cartilage

Damage to cartilage caused by injury or disease can lead to pain and loss of mobility, diminishing one's quality of life. Because cartilage has a limited capacity for self-repair, tissue engineering strategies, such as cells encapsulated in synthetic hydrogels, are being investigated as a means to restore the damaged cartilage. However, strategies to date are suboptimal in part because designing degradable hydrogels is complicated by structural and temporal complexities of the gel and evolving tissue along multiple length scales. To address this problem, this study proposes a multi-scale mechanical model using a triphasic formulation (solid, fluid, unbound matrix molecules) based on a single chondrocyte releasing extracellular matrix molecules within a degrading hydrogel. This model describes the key players (cells, proteoglycans, collagen) of the biological system within the hydrogel encompassing different length scales. Two mechanisms are included: temporal changes of bulk properties due to hydrogel degradation, and matrix transport. Numerical results demonstrate that the temporal change of bulk properties is a decisive factor in the diffusion of unbound matrix molecules through the hydrogel. Transport of matrix molecules in the hydrogel contributes both to the development of the pericellular matrix and the extracellular matrix and is dependent on the relative size of matrix molecules and the hydrogel mesh. The numerical results also demonstrate that osmotic pressure, which leads to changes in mesh size, is a key parameter for achieving a larger diffusivity for matrix molecules in the hydrogel. The numerical model is confirmed with experimental results of matrix synthesis by chondrocytes in biodegradable poly(ethylene glycol)-based hydrogels. This model may ultimately be used to predict key hydrogel design parameters towards achieving optimal cartilage growth.

Fast iterative solver for convection‐diffusion systems with spectral elements

AbstractWe introduce a solver and preconditioning technique based on Domain Decomposition and the Fast Diagonalization Method that can be applied to tensor product based discretizations of the steady convection–diffusion equation. The method is based on a Robin–Robin interface preconditioner coupled to a fast diagonalization solver which is used to efficiently eliminate the interior degrees of freedom and perform subsidiary subdomain solves. Using a spectral element discretization, we first apply our technique to constant wind problems, and then propose a means for applying the technique as a preconditioner for variable wind problems. We demonstrate that iteration counts are mildly dependent on changes in mesh size and convection strength. © 2009 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2011

Effect of Hang‐in Percentage on Catch Rates of Flounder in the North Carolina Inshore Gill‐Net Fishery

AbstractThe effects of hang‐in percentage (degree of tautness) on the catch efficiency of gill nets for paralichthine flounders in North Carolina were examined using monofilament gill nets with 5.75‐in stretched mesh. Nets with hang‐in percentages of 33% and 60% were fished in pairs and were separated by a single monofilament gill net of 5.50‐in stretched mesh. Catches of the paired test nets were significantly different, with the catches obtained by the looser nets (60% hang‐in) exceeding the catches in the more tightly hung nets (33% hang‐in) by 37% in number of fish and 46% in estimated weight. Length‐frequency distributions of the catch were not significantly different between the paired nets with different hang‐in percentages. Length‐frequency distributions of legal‐sized fish taken in 5.50‐ and 5.75‐in stretched‐mesh nets were significantly different, with the smaller mesh size resulting in a smaller (left‐shifted) length‐frequency distribution. Thus, hang‐in percentage can be manipulated to alter flounder harvest rates per unit of net, and small changes in mesh size can alter the size distribution of the catch.

Modeling the Selectivity of the Cod-end of a Trawl Using Chaotic Fish Behavior and Neural Networks

Using empirical data of fish performance and physiological limits as well as physical stimuli and environmental data, a cod-end selectivity model based on a chaotic behavior model using the psycho-hydraulic wheel and neural-network approach was established to predict fish escape or herding responses in trawl and cod-end designs. Fish responses in the cod-end were categorized as escape or herding reactions based on their relative positions and reactions to the net wall. Fish movements were regulated by three factors: escape time, a visual looming effect, and an index of body girth-mesh size. The model was applied to haddock in a North Sea bottom trawl including frequencies of movement components, swimming speed, angular velocity, distance to net wall, and the caught-fish ratio; simulation results were similar to field observations. The ratio of retained fish in the cod-end was limited to 37-95% by optomotor coefficient values of 0.3-1.0 and to 13-67% by looming coefficient values of 0.1-1.0. The selectivity curves generated by this model were sensitive to changes in mesh size, towing speed, mesh type, and mesh shape.

Use of (weighted) essentially non-oscillatory advection schemes in a mesoscale model

Plain and weighted essentially non-oscillatory advection schemes (ENO and WENO) are implemented in the atmospheric model METRAS to solve the advective terms in the momentum equations. They are an alternative to the currently used centred differences that are stabilized by a Shapiro filter. For the (W)ENO schemes, two approaches are tested for reconstructing the advective fluxes on an Arakawa-C grid. The resulting four second-order (one filtered and three unfiltered) and two (unfiltered) third-order numerical schemes are tested for three different types of test case, i.e. one type consisting of three idealized density current cases, one case with stationary mountain waves and one case with land–sea breeze combined with mountain–valley wind circulations (LSBM). The results are compared to each other and to results of METRAS with centred differences (CDF). When using uniform grids, one of the (W)ENO schemes is ruled out as it turns out to be unstable. The (W)ENO results as well as the CDF result are altogether plausible. They are very similar for stationary and non-convective situations. For convective situations (case LSBM) the results are spread leading to a multi-numerics ensemble. By comparison of the results of the filtered and unfiltered second-order ENO scheme, it is shown that one reason for the spread is the Shapiro filter. As the filter is only meant to stabilize the solution, it must be assumed that the changes caused by the filter are artificial. A grid with step-wise changes in mesh size tested for the density current identifies some shortcomings in the numerical schemes. On this grid the CDF solution contains a large amount of non-physical oscillation while the (W)ENO schemes show reasonable results. When using the second-order (W)ENO schemes, the total CPU time is not much larger than for the CDF scheme. Therefore, two second-order (W)ENO schemes are recommended for step-wise changes in mesh size. The use of the third-order (W)ENO schemes is not justifiable as they do not provide considerably better results and may need more total CPU time. Copyright © 2006 Royal Meteorological Society

One-sided Post-processing for the Discontinuous Galerkin Method Using ENO Type Stencil Choosing and the Local Edge Detection Method

In a previous paper by Ryan and Shu [Ryan, J. K., and Shu, C.-W. (2003). \hboxMethods Appl. Anal. 10(2), 295---307], a one-sided post-processing technique for the discontinuous Galerkin method was introduced for reconstructing solutions near computational boundaries and discontinuities in the boundaries, as well as for changes in mesh size. This technique requires prior knowledge of the discontinuity location in order to determine whether to use centered, partially one-sided, or one-sided post-processing. We now present two alternative stencil choosing schemes to automate the choice of post-processing stencil. The first is an ENO type stencil choosing procedure, which is designed to choose centered post-processing in smooth regions and one-sided or partially one-sided post-processing near a discontinuity, and the second method is based on the edge detection method designed by Archibald, Gelb, and Yoon [Archibald, R., Gelb, A., and Yoon, J. (2005). SIAM J. Numeric. Anal. 43, 259---279; Archibald, R., Gelb, A., and Yoon, J. (2006). Appl. Numeric. Math. (submitted)]. We compare these stencil choosing techniques and analyze their respective strengths and weaknesses. Finally, the automated stencil choices are applied in conjunction with the appropriate post-processing procedures and it is determine that the resulting numerical solutions are of the correct order.

Impacts of mesh-size regulation of gillnets on the pikeperch fisheries in the Archipelago Sea, Finland

In the Archipelago Sea, one of the most valuable species in the professional and recreational fisheries is the pikeperch ( Sander lucioperca), mainly caught with gillnets. Currently, the minimum mesh size (bar length) for pikeperch gillnet fishing in the Archipelago Sea is 43–45 mm. Enlarging the mesh size has been suggested to ensure the biological sustainability of pikeperch fishing. The impacts of enlarging the minimum allowable mesh size to 50 mm were analysed using a bio-economic simulation model and data based on pikeperch samples from professional catches from 1978 to 1997, and catch statistics. The effect of uncertainty in the variable values was examined by specifying probability distribution functions for the main variables and using Monte Carlo simulation. According to the results, the yield would be reduced by 50% in the first year, but after some years it would stabilise at about 20% higher level than before the shift. The biomass of the spawning stock would be doubled as a result of the larger mesh size, which would reduce the risk of low recruitment and benefit the fisheries in the long term. However, the short-term impacts on the profitability of commercial fishing would be negative, because it would take 3 years before the expected present value of the catch exceeded the value prior to the change in mesh size, and 8 years before the expected net present value of the catch would be positive. The challenge for fisheries management is to find a solution that would be both biologically and economically reasonable.

Discards from Deep-water Bottom Trawling in the Eastern-Central Mediterranean Sea and Effects of Mesh Size Changes

Discards from Deep-water Bottom Trawling in the Eastern-Central Mediterranean Sea and Effects of Mesh Size Changes