Analysis of the Hybrid of Mudar/Snake Grass Fiber-Reinforced Epoxy with Nano-Silica Filler Composite for Structural Application

Natural fiber composite materials are competent materials that may replace conventional synthetic materials where the strength to weight ratio is essential. In this paper, the mechanical characteristics of composites made up of randomly oriented natural fibers (mudar fiber and snake grass fiber) with nano-silica filler are detailed for the first time. From the various literature surveys, the critical length of mudar and snake grass fiber is chosen as 40 mm and 30 mm, respectively. The test samples were prepared with a fiber content of 10%, 20%, 30%, and 40% with an equal amount of mudar and snake grass fiber. The percentage of nano-filler is maintained as constant as 3% with all the compositions. The composites showed that the highest mechanical properties were found at 30% fiber volume. The maximum tensile strength is 45 MPa, and the flexural strength is 51 MPa. The maximum impact strength is 4.5 J. Sample ID 3 provided the best results compared to other proportions. The fiber/matrix adhesion was investigated using a scanning electron microscope (SEM). These predominant mechanical properties make it easier for the implementation of the prepared composite material in structural and automotive applications.

Epigenetic Deregulation of Telomere-Related Genes in Newly Diagnosed Multiple Myeloma Patients

High-risk Multiple Myeloma (MM) patients were found to maintain telomere length (TL), below the margin of short critical length, consistent with proactive overexpression of telomerase. Previously, DNA methylation has been shown as a determinant of telomere-related gene (TRG) expression and TL to assess risk in different types of cancer. We mapped genome-wide DNA methylation in a cohort of newly diagnosed MM (NDMM; n = 53) patients of major molecular subgroups, compared to age-matched healthy donors (n = 4). Differential methylation and expression at TRG-loci were analyzed in combination with overlapping chromatin marks and underlying DNA-sequences. We observed a strong correlation (R2 ≥ 0.5) between DNA methylation and expression amongst selective TRGs, such that demethylation at the promoters of DDX1 and TERF1 were associated to their oncogenic upregulation, while demethylation at the bodies of two key tumor suppressors ZNF208 and RAP1A led to downregulation of the genes. We demonstrated that TRG expression may be controlled by DNA methylation alone or in cooperation with chromatin modifications or CCCTC-binding factor at the regulatory regions. Additionally, we showed that hypomethylated DMRs of TRGs in NDMM are stabilized with G-quadruplex forming sequences, suggesting a crucial role of these epigenetically vulnerable loci in MM pathogenesis. We have identified a panel of five TRGs, which are epigenetically deregulated in NDMM patients and may serve as early detection biomarkers or therapeutic targets in the disease.

Improve urban traffic efficiency with prohibiting left-turn policy

Enhancing traffic flow plays an important role in the traffic management of urban arterial networks. The policy of prohibiting left-turn (PLT) at selected highly demanded intersections has been adopted as an attempt to increase the efficiency at these intersections. In this paper, we study the impact of PLT by mathematical analysis and simulations based on the cellular automaton model. Using the flow-density relation, three system performance indexes are examined: the average trip completion rate, the average traffic flow, and the average velocity of vehicles. Different route guidance strategies, including the shortest path and the quickest path, are investigated. We show that when left turn is prohibited, vehicles are distributed more homogeneously in the road network, and the system performs better and reaches a higher capacity. We also derive a critical length of link, above which the benefit of PLT will decrease.

Local buckling of thin-walled circular hollow section under uniform bending

This article presents a semi-analytical finite strip method based on Marguerre’s shallow shell theory and Kirchhoff’s assumption. The formulated finite strip is used to study the buckling behavior of thin-walled circular hollow sections (CHS) subjected to uniform bending. The shallow finite strip program of the present study is compared to the plate strip implemented in CUFSM4.05 program for demonstrating the accuracy and better convergence of the former. By varying the length of the CHS, the signature curve relating buckling stresses to half-wave lengths is established. The minimum local buckling point with critical stress and corresponding critical length can be found from the curve. Parametric studies are performed to propose approximative expressions for calculating the local critical stress and local critical length of steel and aluminum CHS.

Economic and mathematical model of selecting a gas supply system based on biomethane and natural gas

Introduction. A promising direction in the development of gas supply systems, which is widely used in the developed countries of the world, is the use of an alternative energy source — biomethane. The effective use of biomethane requires the development of scientific provisions and recommendations for the use of biomethane gas supply systems, taking into account technical and economic factors. Therefore, it is urgent to develop an economic and mathematical model for choosing a gasification method and determining the area of rational use of gas supply systems with biomethane. Materials and methods. To develop an economic and mathematical model for choosing a method for gasification of settlements, methods of mathematical modeling and parametric optimization were used. The implementation of the economic and mathematical model was carried out in the Mathcad software package. Mathematical and graphic processing of the results obtained was carried out. Results. An economic and mathematical model was developed for determining the rational area of application of biome­thane for gas supply to settlements. The model is based on the technical and economic calculation of the reduced costs for gas supply systems with network natural gas and biomethane. Using the developed model, the technical parameters of the biomethane gas supply system were determined: the critical length of the gas pipeline branch, the radius of the biomethane plant, the biomethane consumption, the length of the gas pipeline for the biomethane supply, and the reduced costs to the gas supply system. A graph of the dependence of the critical length of the gas pipeline branch on the population size has been obtained, which makes it possible to determine the area of rational use of biomethane for gas supply to settlements. It was found that for a rural settlement with a population of 5,000 people, the critical length of the gas pipeline branch is 24.820–28.044 km, for an urban-type settlement with a population of 15,000 people, the length of the gas pipeline branch is 50.923–64.677 km, and for a city with a population of 30,000 people — 89.617–127.279 km. Conclusions. The results obtained can be used for the development and design of gas supply systems based on biomethane for the gasification of settlements remote from the main gas pipelines. The use of biomethane makes it possible to gasify settlements in developed agricultural regions and to increase the efficiency of the gas transportation system of the Russian Federation.

Colony-like Protocell Superstructures

We report the formation, growth, and dynamics of model protocell superstructures on solid surfaces, resembling single cell colonies. These structures, consisting of several layers of lipidic compartments enveloped in a dome-shaped outer lipid bilayer, emerged as a result of spontaneous shape transformation of lipid agglomerates deposited on thin film aluminum surfaces. Collective protocell structures were observed to be mechanically more stable compared to isolated spherical compartments. We show that the model colonies encapsulate DNA and accommodate non-enzymatic, strand displacement DNA reactions. The membrane envelope is able to disassemble and expose individual daughter protocells, which can migrate and attach via nano-tethers to distant surface locations, while maintaining their encapsulated contents. Some colonies feature ‘exo-compartments’, which spontaneously extend out of the enveloping bilayer, internalize DNA, and merge again with the superstructure. A continuum elastohydrodynamic theory that we developed reveals that the subcompartment formation must be governed by attractive van der Waals (vdW) interactions between the membrane and surface. The balance between membrane bending and vdW interactions yields a critical length scale of 273 nm, above which the membrane invaginations can form subcompartments. The findings support our hypotheses that in extension of the ‘lipid world hypothesis’, protocells may have existed in the form of colonies, potentially benefiting from the increased mechanical stability provided by a superstructure.

Optimization of the critical overlap length of hudraulic distributors regarding cavitation inception

The present paper is focused on the optimization of the overlap length in various types of distributors in hydraulic systems. It has been shown that this length has a strong influence on cavitation in rotating distributors, so its optimization would be beneficial to reduce the detrimental effects of cavitation, such as noise, vibrations, and instabilities. The objective of the present study is to generalize the modelling of the overlap length to different types of distributors and to determine the critical length at cavitation inception. The results show that the pressure losses in rotating distributors and in other types of distributors are similar, including the slide-valves that are the vast majority of distributors in hydraulic systems. It is confirmed that the overlap length has a stronger influence on the cavitation development than the distributor rotation speed. A critical overlap length of 0.071 mm is obtained, below which no significant development of cavitation is obtained, at all rotation speeds. Article Highlights The pressure losses in a rotating distributor and in a slide-valve can be expressed similarly. The overlap length has a large influence on the cavitation development, much larger than the rotation speed. A critical overlap length of 0.071 mm was obtained, below which there is almost no cavitation, for any rotation speed.

Optimization of the Ultimate Bearing Capacity of Reinforced Soft Soils through the Concept of the Critical Length of Stone Columns

The objective of this paper is to develop an analytical equation based on the concept of the critical-length of columns in order to optimize the ultimate bearing-capacity of soft soils, supporting a strip footing and reinforced by a group of floating stone columns. Optimization procedure was performed on three-dimensional numerical models simulated on the Flac3D computer code, for various soft-soils with different undrained-cohesions (Cu=15–35kPa), reinforced by columns of varying lengths (L) and area replacement ratio (As=10-40%), considering different footing widths B. Obtained results indicate that the optimal bearing-capacity ratio (Ultimate bearing-capacity of reinforced soil/unreinforced soil) is reached for the column critical-length ratio (Lc/B) and increase with increase of the later ratio, depending on As and Cu. Analysis of results also showed that the optimal values of the bearing-capacity ratio in the reinforced soils remain bounded between the lower and higher values (1.28-2.32), respectively for minimal and maximal values of the critical-length ratio (1.1) and (4.4). Based on these results, a useful analytical equation is proposed by the authors, for the expression of the critical-length; thus ensuring an optimal pre-dimensioning of the stone columns. The proposed equation was compared with the data available in the literature and showed good agreement. Doi: 10.28991/cej-2021-03091737 Full Text: PDF