Initial Plastic Research Articles

Self-Aggregating Tau Fragments Recapitulate Pathologic Phenotypes and Neurotoxicity of Alzheimer's Disease in Mice.

In tauopathy conditions, such as Alzheimer's disease (AD), highly soluble and natively unfolded tau polymerizes into an insoluble filament; however, the mechanistic details of this process remain unclear. In the brains of AD patients, only a minor segment of tau forms β-helix-stacked protofilaments, while its flanking regions form disordered fuzzy coats. Here, it is demonstrated that the tau AD nucleation core (tau-AC) sufficiently induced self-aggregation and recruited full-length tau to filaments. Unexpectedly, phospho-mimetic forms of tau-AC (at Ser324 or Ser356) show markedly reduced oligomerization and seeding propensities. Biophysical analysis reveal that the N-terminus of tau-AC facilitates the fibrillization kinetics as a nucleation motif, which becomes sterically shielded through phosphorylation-induced conformational changes in tau-AC. Tau-AC oligomers are efficiently internalized into cells via endocytosis and induced endogenous tau aggregation. In primary hippocampal neurons, tau-AC impaired axon initial segment plasticity upon chronic depolarization and is mislocalized to the somatodendritic compartments. Furthermore, it is observed significantly impaired memory retrieval in mice intrahippocampally injected with tau-AC fibrils, which corresponds to the neuropathological staining and neuronal loss in the brain. These findings identify tau-AC species as a key neuropathological driver in AD, suggesting novel strategies for therapeutic intervention.

Creep and strength characteristics of cemented gangue backfill under coupling effect of load and acid corrosion.

Cemented gangue backfill technology is beneficial to the reuse of solid waste and sustainable economic development. However, mine water has a great impact on the strength and deformation of cemented gangue backfill (CGB). In this study, the CGB specimens under load were placed in simulated acid mine water (H2SO4 solution). The changes in deformation, resistivity, and ultrasonic pulse velocity (UPV) of CGB were monitored. On the 360th day, the stress-strain curve and acoustic emission (AE) energy of the specimen during loading were recorded. The degradation mechanism of CGB was discussed by scanning electron microscope (SEM) and X-ray diffraction (XRD). The results showed that the deformation of CGB increased with time. The effect of H2SO4 solution concentration on the deformation was different in the early and late stages. Applying an 80% stress-strength ratio (SSR) reduced the strength and increased the deformation. The UPV and resistivity had different characteristics at different corrosion ages, which could be used for long-term stability monitoring of CGB. The CGB showed the strongest AE energy characteristics near the peak stress. The AE energy decreased with the increase of pH value in the pore compaction stage, and the AE activity of the CGB under 80% SSR was much greater than that of the CGB under 40% SSR. The erosion of the H2SO4 solution on the CGB was inhibited by applying a small load. Excessive load aggravated the erosion deterioration of CGB due to initial plastic damage. The research results can provide a reference for the durability design of CGB.

Dislocation detection of gas turbine materials using a nonlinear ultrasound modulation technique

Industrial gas turbines are used for generating electricity or driving other turbomachinery with the continuous development goal of further increasing machine efficiency. This is primarily achieved by raising the pressure ratio generated in the compressor and by increasing the turbine inlet temperature. Consequently, the hot gas components in gas turbines are subjected to extreme loads and the need for non-destructive testing and structural health monitoring techniques is becoming increasingly important to maintain these components. An important indicator for assessing the structural integrity is the determination of the initial plastic deformation.In this paper, a new method for the detection of plasticity was developed, which is based on a nonlinear ultrasonic two-frequency excitation. The one-dimensional wave equation was solved with a two-frequency excitation and combined with the expanded dislocation theory. As a result, various nonlinearity parameters were defined, showing a clear increasing or a decreasing behaviour with increasing plastic strain. This was experimentally proven with flat tensile specimen made of stainless steel and Inconel 718 (metal plates and additively manufactured). The new indicators allow the possibility to efficiently detect the initial plastic deformation in gas turbine components.

Efficacy of virtual plastic surgery encounters in establishment of care and surgical conversion

The efficacy of virtual visits in converting new patients into established patients undergoing surgical treatment has not been demonstrated. The aim of this study was to evaluate patient retention and surgical conversion rate after an initial virtual plastic surgery consultation. An IRB-approved retrospective review of all new plastic surgery patients seen between May and August 2020 at a single institution was conducted. The initial encounter type, chief complaint, demographics, treatment recommendation, insurance approval rate, number and modality of pre- and postoperative visits, time to procedure, follow up, and complications were recorded. Patient retention and surgery conversion rate were calculated. Statistical analysis was performed with Chi-squared test, Fisher's exact test, and unpaired t-test. In total, the records of 1889 new patients were reviewed (1635 in-person, 254 virtual). Virtual patients were younger (44.5 ± 19.0 versus 49.5 ± 20.7 years, p < 0.001), and nearly half resided greater than 50 miles away (42% versus 16%, p < 0.001). Virtual patients more frequently presented for cosmetic surgery (14% versus 7%, p < 0.001), lymphedema (15% versus 3%, p < 0.001), and gender dysphoria (11% versus 2%, p < 0.001). In-person patients presented more often for trauma (18% versus 5%, p < 0.001), elective hand complaints (16% versus 3%, p < 0.001), and breast reconstruction (9% versus 4%, p < 0.01). There were no differences in patient retention (p = 0.45) and procedure conversion rate (p = 0.21) between the groups. Telemedicine provides an opportunity to increase the practice catchment area and is as effective as in-person first encounters for establishing care and transition to surgery.

Failure mechanisms of diamond like carbon coatings characterised by in situ SEM scratch testing

In situ SEM scratch testing of DLC and Si-doped DLC deposited on Si < 100> wafers has been conducted using sharp 1 and 5 μm radii diamond asperities, enabling the stages of deformation and wear of DLC coatings to be evaluated in real time. With increasing load, initial plastic deformation and tensile cracking in the scratch track progresses to the propagation of radial and lateral cracks, and full coating spallation. In situ SEM imaging reveals nucleation of radial cracks in the DLC coating around the front and side of the moving asperity, followed by lateral crack propagation both ahead of, and behind, the asperity contact zone. Post-mortem FIB cross sectioning reveals microcracking and lateral cracks in the silicon substrate below DLC coatings prior to coating spallation. The DLC failure mechanisms are influenced by asperity geometry, with notable DLC coating lift up/delamination events occurring during the smaller 1 μm radius asperity scratch tests. The sharper 1 μm radius asperity required ∼20% of the applied load, and higher contact pressure, to initiate spallation during scratching compared the larger 5 μm asperity, indicating that smaller radii asperities are significantly more likely to cause DLC coating spallation, although the spallations they generate were observed to be, on average, smaller.

Utilization of Aloe Vera Extract as A Natural Coagulant and its Effect on The Characteristics of IRR 118 Clone Rubber

Rubber is one of the plantation products as a foreign exchange earner for the country. The process of processing rubber requires coagulants to accelerate coagulation. Aloe vera is a plant that contains compounds of organic acids, is expected to be able to accelerate the coagulation process. The purpose of this study was to determine the effect of the use of natural coagulants of aloe vera extract on the characteristics of IRR 118 clone rubber. The variations of the extracts used are natural coagulant extracts of aloe centrifugation and no centrifugation and the chemical coagulant format acid 3% as a comparison. Centrifugation of natural coagulant extract of aloe vera is carried out at a speed of 3000 rpm for 1 hour. The characterization of rubber analyzed was DRC (Dry Rubber Content), Po (Initial Plasticity), PRI (Plasticity Retention Index), ash content, evaporating substance content, mooney viscosity, dirt content, and nitrogen content. From the results of the study, it was obtained that the percentage of DRC, Po, PRI, and Mooney Viscosity was highest in AV natural coagulants without centrifugation, namely 28%, 36%, 80%, and 80%. The lowest percentage of ash, dirt and nitrogen content in natural coagulants of AV centrifugation was 0.38%, 0.014%, and 0.36%. Aloe vera natural coagulants without centrifugation and centrifuged ones can be used as coagulants for the latex coagulation process because they have met all the requirements of SNI SIR 20 and can be used as natural coagulants.

The results of researching of Algay site in the Lower Volga region in 2022

Excavations of the Algay multi-layered site in 2022 confirmed the presence of a stratigraphic sequence of occurrence of the Neolithic and Eneolithic layers. The finds are represented by fragments of ceramics, quartzite and flint tools and production waste, animal bones and bone tools. The upper cultural layer is identified as the Khvalynskaya, middle as the Cis-Caspian layer, lower as the Orlovsky Neolithic layer. Stone inventory differs in raw materials, flint and quartzite tools were found. Scrapers of different types, points and geometric microliths were found. As for the ceramic inventory, a fragment of a wall ornamented with a jagged stamp was found in the Khvalynskaya cultural layer. However, this specimen can be attributed to both the Khvalynskaya and Altatinskaya cultures. The results of the technical and technological analysis of ceramics showed the presence of only two technological subgroups of vessels made from silty and natural clays. Vessels made of silt have not been recorded, but the results of previous years of excavations revealed the use of three types of raw materials at the Algay site. The Neolithic layer is represented by pottery with prickly incised ornaments made using the technique of pricking, retreating, and less often incising. The revealed features of the making of the dishes are close to the pottery technology of the Orlovskaya culture of the Lower Volga region, the population of the Varfolomeevskaya site (Saratov Region). The specificity of this sample is the absence of ceramics made in accordance with more archaic methods (the use of silt as the initial plastic raw material), which is known for the Algay site from previous excavations.

Pengaruh Penambahan Ekstrak Jeruk Purut (Cytrus hitrix D.C) Sebagai Koagulan Alami Terhadap Karakteristik Karet

Natural rubber is a plantation commodity that has a significant role in the country's economy. This study aims to determine the effect of the natural coagulant extract of kaffir lime with centrifugation and non-centrifugation treatment on the coagulation process, pH and coagulation time, characteristics of rubber clone IRR 118 and comparison of the quality of rubber with 2% formic acid chemical coagulant. The volume of coagulant used was 75 mL mixed with 150 mL of latex, so that coagulation occurred and produced coagulum. Then the resulting coagulum is analyzed for the characteristics of the rubber to determine the quality of the rubber. Characteristic analysis carried out was Dry Rubber Content (DRC), Initial Plasticity (Po), Plasticity Retention Index (PRI), Mooney Viscosity, ash content, impurities content, volatile matter content, and nitrogen content. The results showed that the natural coagulant extract of kaffir lime could coagulate latex, lowering the pH of latex thereby speeding up coagulation time. From the rubber characteristic test using kaffir lime natural coagulant it complies with SNI 06-1903-2017 SIR 20. The quality of rubber produced from using kaffir lime natural coagulant extract as a coagulant can equate the quality of rubber produced by using 2% formic acid chemical coagulant, but coagulant The natural ingredients used have drawbacks, namely the availability of seasonal fruit, and the need for treatment before being used as a coagulant.

Microstructure and mechanical properties of the laminated heterostructured material with 316L stainless steel/18Ni300 maraging steel fabricated by WAAM

Heterostructured materials (HMs) have attracted extensive interest due to their excellent properties, and additive manufacturing presents great potential in fabricating HMs. A laminated HM (LHM) was prepared by wire and arc additive manufacturing with alternating deposition of 316L stainless steel (SS) and 18Ni300 maraging steel (MS). The microstructure, chemical composition, texture and mechanical properties of the LHM thin walls were investigated and compared with those of the corresponding single-material thin walls. Remelting and mixing of the previously deposited layer caused deviations in the chemical composition in both regions. The 18Ni300 MS region microstructure was composed of austenite and martensite phases with the K-S orientation relationship, and the 316L SS region microstructure consisted of the austenite phase. All samples exhibited obvious austenite phase epitaxial growth, causing grains with the same orientation to pass through multiple deposited layers. The cubic texture in the as-fabricated 316L SS sample disappeared in the 316L SS region of the LHM samples. The Goss texture intensity in the 18Ni300 MS region decreased compared with that in the 18Ni300 MS thin walls, from 20.6 to 6.36. The 18Ni300 MS region microhardness of the LHM samples of 263 HV was lower than that of the 18Ni300 MS sample due to the lower-hardness austenite phase. The ultimate tensile strength of the LHM samples was 635.25 ± 31.1 MPa, which was between those of 316L SS and 18Ni300 MS. The uniform and total elongations of the LHM samples were 19.85 ± 3.6% and 29.2 ± 2.3%, which were higher than the mixing law-calculated values. The plasticity improvement was attributed to transformation-induced plasticity and stress state variation. In the initial plastic deformation stage, the 18Ni300 MS region underwent more plastic strain with a high dislocation density, causing the strain-induced martensitic transformation. The 316L SS region was strengthened with high strain, and its necking caused stress state conversion from uniaxial to multiaxial stress.

Numerical studies of self-organization of shear bands in one and two dimensions

In the present manuscript we perform a numerical analysis of the self-organization processes of adiabatic shear bands formation in depleted uranium, aluminum alloy, and high-strength steel in one- and two-dimensional cases. Since the processes of shear bands formation are strongly nonlinear, three materials with significantly different parameters considered allow us to generalize obtained dependencies. For all materials, we investigate the evolution of stress, temperature and velocity fields from initial to final stage of localization. It is well known that localization processes occur during the high shear rate loads in the presence of initial microstructural defects in metallic materials. Starting with a random distribution of initial stress, which models microstructural defects, we obtained new dependencies for such significant parameters of the problem considered such as localization time and spacing between shear bands. The influence of initial plastic strain rate on these parameters was also studied. We obtain the linear dependence of localization time on initial strain rate and show that spatial dimension significantly influences on its value. Also, we introduce the method of shear bands selection during computations and present new statistical distributions for band spacing. We show that the interaction between shear bands significant influences on the spacing between them.

Uncertainties in and recommendations to small punch tensile and creep tests for ductile materials

The objective of this paper is to clarify the complex nature which involves the interaction of several non-linear deformation mechanisms experienced in small punch tensile and small punch creep tests, and as a consequence, the associated difficulties in data interpretation. The paper starts with a highlight of some specific features experienced during small punch deformation, e.g., large deformation, high local plasticity, contact, the effect of initial plasticity, possible early cracking etc. and the consequences of them in data interpretation. Although several test standards have been available, uncertainties in data interpretation still exist and a universally accepted conversion method has not been available. On this basis, for the first time, critical comments on the uncertainties and applicability of the test methods in determining the tensile and creep properties and in high-temperature structural integrity assessment are addressed. Finally, recommendations on future developments are provided.

Bioinspired Platelet-Anchored Electrospun Meshes for Tight Inflammation Manipulation and Chronic Diabetic Wound Healing.

Tight manipulation of the initial leukocytes infiltration and macrophages plasticity towards the M2 phenotype remain a challenge for diabetic wound healing. Inspired by the platelet function and platelet-macrophage interaction, a platelet-anchored polylactic acid-b- polyethylene glycol-b-polylactic acid (PLA-PEG-PLA) electrospun dressing was developed for inflammatory modulation and diabetic wounds healing acceleration. PLA-PEG-PLA electrospun meshes encapsulated with thymosin β4 (Tβ4) and CaCl2 was fabricated with electrospinning, followed by immersion of electrospun mesh in platelet-rich plasma to firmly anchor the platelets. We demonstrated that the anchored platelets on electrospun mesh could enhance the initial macrophage recruitment and control the Tβ4 release from electrospun meshes to facilitate the macrophages polarization to the M2 phenotype. The inflammatory regulation promoted the expression of vascular endothelial growth factor (VEGF) and the migration of vascular endothelial cells for angiogenesis, resulting in accelerated diabetic wounds healing. Therefore, our work paved a new way to design platelet-inspired electrospun meshes for inflammation manipulation and diabetic wound healing. This article is protected by copyright. All rights reserved.

Evolution mechanism for a surface gradient nanostructure in GH4169 superalloy induced by an ultrasonic surface rolling process

In this study, the evolution mechanism of surface gradient nanostructure induced by the ultrasonic surface rolling process (USRP) in GH4169 superalloy was investigated. The gradient nanostructure, which was characterized using transmission electron microscopy, revealed that the repeated impacts induced by USRP produced a gradient nanostructure with a thickness of ∼330 μm at the surface of the material. Equiaxed nanograins with an average grain size of ∼30 nm were observed on the topmost surface, and the grain size gradually increased with depth. In the nanocrystallization mechanism, dislocations first formed as a result of the initial plastic strain introduced by USRP. Next, dislocation tangles and dislocation walls were formed and gave rise to the formation of low-angle and high-angle grain boundaries, which resulted in grain refinement. As plastic strain accumulated, nanoscale deformation twins were formed. The interaction between dislocations and deformation twins further refined the parent grains to produce equiaxed nanograins with high-angle grain boundaries. In addition, stacking faults were generated when the interaction between dislocations and deformation twins was initiated. A 9R structure was observed inside the nanograins at the topmost surface that significantly improved the work-hardening capacity of the superalloy by acting both as dislocation blockers and dislocation storage sites. The microhardness of the nanostructured GH4169 superalloy was improved by 67% as compared to the untreated material.

Bet-hedging via dispersal aids the evolution of plastic responses to unreliable cues.

Adaptive plasticity is expected to evolve when informative cues predict environmental variation. However, plastic responses can be maladaptive even when those cues are informative, if prediction mistakes are shared across members of a generation. These fitness costs can constrain the evolution of plasticity when initial plastic mutants use of cues of only moderate reliability. Here, we model the barriers to the evolution of plasticity produced by these constraints and show that dispersal across a metapopulation can overcome them. Constraints are also lessened, though not eliminated, when plastic responses are free to evolve gradually and in concert with increased reliability. Each of these factors be viewed as a form of bet-hedging: by lessening correlations in the fates of relatives, dispersal acts as diversifying bet-hedging, while producing submaximal responses to a cue can be understood as a conservative bet-hedging strategy. While poor information may constrain the evolution of plasticity, the opportunity for bet-hedging may predict when that constraint can be overcome.

Identifying strain-dependent structural defects in granular materials from the hidden structure-plasticity relationship

When subjected to mechanical loads, granular materials exhibit heterogeneous local plastic responses. Although there is a general consensus that such plastic heterogeneity is closely correlated to the structure configuration, the extent and manner in which the initial particle structure determines the plastic dynamics remain ill-understood due to the complex local environment of granular materials. In this study, we present an investigation of the structural origin of shear-induced plastic heterogeneity through a series of numerical triaxial shear tests. A machine learning (ML) framework is employed to address the hidden relationship between the initial structure configuration and plasticity at different loading stages. It is confirmed that there are some pre-existing structural defects independent of loading protocol which is the origin of small strain plastic rearrangements and can be identified with outstanding accuracy by our trained ML models. We then show that the dominant structural features determining plasticity depend on strain, wherein the plastic activity at small strains is governed by contact number but becomes dominated by local packing fraction at large strains. By exploring the temporal correlation of the two structural features, we finally prove this transition results from the differences in their memory effects.

ANK2 loss-of-function variants are associated with epilepsy, and lead to impaired axon initial segment plasticity and hyperactive network activity in hiPSC-derived neuronal networks.

To characterize a novel neurodevelopmental syndrome due to loss-of-function (LoF) variants in Ankyrin 2 (ANK2), and to explore the effects on neuronal network dynamics and homeostatic plasticity in human induced pluripotent stem cell-derived neurons. We collected clinical and molecular data of twelve individuals with heterozygous de novo LoF variants in ANK2. We generated a heterozygous LoF allele of ANK2 using CRISPR/Cas9 in human induced pluripotent stem cells (hiPSCs). HiPSCs were differentiated towards excitatory neurons of which we measured spontaneous electrophysiological responses using micro-electrode arrays (MEAs), characterized somatodendritic morphology and axon initial segment (AIS) structure and plasticity. We found a broad neurodevelopmental disorder, comprising intellectual disability, autism spectrum disorders, and early onset epilepsy. Using MEAs, we found that hiPSC-derived neurons with heterozygous LoF of ANK2 show a hyperactive and desynchronized neuronal network. ANK2 deficient neurons also showed increased somatodendritic structures and altered AIS structure of which its plasticity is impaired upon activity-dependent modulation. Phenotypic characterization of patients with de novo ANK2 LoF variants define a novel NDD with early onset epilepsy. Our functional in vitro data of ANK2-deficient human neurons show a specific neuronal phenotype in which reduced ANKB expression leads to hyperactive and desynchronized neuronal network activity, increased somatodendritic complexity and AIS structure and impaired activity-dependent plasticity of the AIS.

Initial postoperative plasticity as a predictor of mid-term stereoacuity outcome after surgery for intermittent exotropia

BackgroundIntermittent exotropia (IXT) would cause different degrees of damage to stereopsis. We aimed to introduce a visual perception plasticity score (VPPS) that reflects initial postoperative plasticity and evaluate its effectiveness in predicting the mid-term surgical outcome in IXT patients.MethodsA total of 149 patients with intermittent exotropia who underwent surgery in November 2018 and October 2019 were recruited. All subjects underwent detailed ocular examinations before and after surgery. VPPS were calculated based on visual perception examination system at one week postoperatively. Demographic, angle of deviation and stereopsis were collected and analyzed with regard to the VPPSs preoperatively and at one week, one month, three months, six months postoperatively. Predictive performances of VPPS were assessed using receiver operating characteristic (ROC) curves, the area under the curve (AUC) and cut-offs were obtained.ResultsOf the 149 patients, the average deviation was 43Δ at distance and 46Δ at near. The average rate of normal stereopsis before surgery was 22.81% at distance and 29.53% at near. Higher VPPS was associated with preoperative better near stereoacuity (r = 0.362, p = 0.000), less angle of deviation at distance (r=-0.164, p = 0.046), and better near (r = 0.400, p = 0.000) and distant stereoacuity (r = 0.321, p = 0.000) during the early postoperative period (1 week). The areas under the curves suggested that VPPS could be an effective predictor of sensory outcome(AUC>0.6). Cut-off values of 50 and 80 were calculated for VPPS using ROC curve analysis.ConclusionHigher VPPSs were associated with a greater possibility of stereopsis improvement in patients with IXT. VPPS is a potentially promising indicator to predict the mid-term surgical outcome of intermittent exotropia.

Effects of lattice distortion and chemical short-range ordering on the incipient behavior of Ti-based multi-principal element alloys: MD simulations and DFT calculations

One of key factors in designing high-performance alloys is to understand their incipient behavior. To get detailed real-time atomic scale evolutions of multi-principal element alloys (MPEAs) during nanoindentation incipient yielding, molecular dynamics (MD) simulations were carried out. Emphases are given to the effects of lattice distortion (LD) and chemical short-range ordering (CSRO) on the initiation of plasticity in body-centered cubic (BCC) MPEAs. The initial plastic mechanism is embryo nucleation assisted and the incipient behavior is strongly affected by LD and CSRO. Specifically, the embryo nucleation load Pe is reduced by LD and CSRO and the incipient drop P0 is lowered by LDI that only comes from atomic size difference and further declined by CSRO. This is because LD and CSRO could boost embryo nucleation, which can act as precursors for dislocation nucleation. This is consistent with the free-end nudged elastic band observations. Although Pe is weakened by LDII generated by introducing extra elements, P0 is intensified because severe LD could dominate the following process. The dislocation starvation mechanism is found in an average-atom (AA) model. However, it is replaced by dislocation interactions due to LD and CSRO. Density functional theory (DFT) calculations suggest that charge density distribution and the amount of directional Al-Al bonding would play a critical role in the onset of plastic deformation. When a larger indenter radius was used in MD simulations, the dislocation starvation mechanism is absent in AA model due to the reduced maximum shear stress. Instead, the dislocation propagation prevails. With respect to the orientation effect, three investigated orientations demonstrate a distinct yielding behavior.

Twin thickness-dependent tensile deformation mechanism on strengthening-softening of Si nanowires

Twin thickness-dependent deformation and the transition from strengthening to softening in twinned silicon nanowires are investigated using molecular dynamics simulations with cylindrical and hexagonal cross sections. The results show that the transition from strengthening to softening occurs at critical twin thicknesses of 8.1 nm (11.0 TB s) with cylindrical cross section and 11.0 nm (8 TBs) with hexagonal cross section with decreasing twin thickness, and that the strongest twin thickness originates from a transition in the initial plasticity mechanism from full dislocation nucleation and interaction with the TBs to partial dislocation nucleation and gliding parallel to the TBs. Moreover, it is found that the relationship between peak stress and twin thickness can be divided into two regions. Several full and partial dislocations are formed in the regions with strengthening twin thickness range. The accumulation and pile-up of these dislocations and their interaction with the TBs at high density cause the Hall-Petch strengthening behavior. In contrast, few full and partial dislocations are formed with softening twin thickness range. These dislocations are nucleated and propagate parallel to the TBs, resulting in TB migration that causes inverse Hall-Petch softening behavior. Our simulation results provide sufficient insight into the mechanical behavior of twinned silicon nanowires with cylindrical and hexagonal cross sections. The study will be helpful to the further understanding of CTB-related mechanical behaviors of non-metallic materials and non-metallic system.

A computational investigation of cis-gene regulation in evolution

In biological processes involving gene networks, genes regulate other genes that determine the phenotypic traits. Gene regulation plays an important role in evolutionary dynamics. In a genetic algorithm, a trans-gene regulatory mechanism was shown to speed up adaptation and evolution. Here, we examine the effect of cis-gene regulation on an adaptive system. The model is haploid. A chromosome is partitioned into regulatory loci and structural loci. The regulatory genes regulate the expression and functioning of structural genes via the cis-elements in a probabilistic manner. In the simulation, the change in the allele frequency, the mean population fitness and the efficiency of phenotypic selection are monitored. Cis-gene regulation increases adaption and accelerates the evolutionary process in comparison with the case involving absence of gene regulation. Some special features of the simulation results are as follows. A low ratio of regulatory loci and structural loci gives higher adaptation for fixed total number of loci. Plasticity is advantageous beyond a threshold value. Adaptation is better for large number of total loci when the ratio of regulatory loci to structural loci is one. However, it reaches a saturation beyond which the increase in the total loci is not advantageous. Efficiency of the phenotypic selection is higher for larger value of the initial plasticity.