Formation of centromeric heterochromatin in fission yeast requires the combined action of chromatin modifying enzymes and small RNAs derived from centromeric transcripts. Positive feedback mechanisms that link the RNAi pathway and the Clr4/Suv39h1 histone H3K9 methyltransferase complex (Clr-C) result in requirements for H3K9 methylation for full siRNA production and for siRNA production to achieve full histone methylation. Nonetheless, it has been proposed that the Argonaute protein, Ago1, is the key initial trigger for heterochromatin assembly via its association with Dicer-independent “priRNAs.” The RITS complex physically links Ago1 and the H3-K9me binding protein Chp1. Here we exploit an assay for heterochromatin assembly in which loss of silencing by deletion of RNAi or Clr-C components can be reversed by re-introduction of the deleted gene. We showed previously that a mutant version of the RITS complex (Tas3WG) that biochemically separates Ago1 from Chp1 and Tas3 proteins permits maintenance of heterochromatin, but prevents its formation when Clr4 is removed and re-introduced. Here we show that the block occurs with mutants in Clr-C, but not mutants in the RNAi pathway. Thus, Clr-C components, but not RNAi factors, play a more critical role in assembly when the integrity of RITS is disrupted. Consistent with previous reports, cells lacking Clr-C components completely lack H3K9me2 on centromeric DNA repeats, whereas RNAi pathway mutants accumulate low levels of H3K9me2. Further supporting the existence of RNAi–independent mechanisms for establishment of centromeric heterochromatin, overexpression of clr4+ in clr4Δago1Δ cells results in some de novo H3K9me2 accumulation at centromeres. These findings and our observation that ago1Δ and dcr1Δ mutants display indistinguishable low levels of H3K9me2 (in contrast to a previous report) challenge the model that priRNAs trigger heterochromatin formation. Instead, our results indicate that RNAi cooperates with RNAi–independent factors in the assembly of heterochromatin.

The modern paving industry requires the production of high-performance pavement using more sustainable approaches. Semi-flexible pavement (SFP), prepared by filling an open-graded asphalt skeleton with cement-based grouting material, has been shown to offer high performance for heavily loaded highway and airport pavement applications. The major aim of this study was therefore to evaluate SFP durability based on more sustainable preparation techniques and materials. In this research, a half warm bitumen emulsion semi-flexible mixture (HWBESFM) was designed using local materials and low energy heating technique; the contribution of various sustainable cementitious grout materials on the durability properties of the mix was then evaluated. The developed grouts were prepared using paper sludge ash (PSA) and silica fume (SF) as supplementary cementitious materials (SCM), and the durability of the HWBESFM was assessed with regard to ageing and water sensitivity. The results showed improvements in water sensitivity of HWBESFM containing OPC+PSA and OPC+SF to 66.62% and 65.73%, respectively, compared with the control mix, which demonstrated sensitivity of roughly 55%. Additionally, slight improvements were noticed in ageing resistance on incorporating SCM, those these results remained uncompetitive to traditional SFP mixtures. Overall, this initial investigation of a sustainable approach could, with some improvement, encourage further development and studies in this area.

No abstract

Grout is a substance with a cement which is characterized by a high strength and it is a high workability, so it can be injected in places of small cracks or places of water leakage. Generally, it is used to repair cracks or defects of concrete, also it can be used to fill the voids under the metal bases or digging anchors. Moreover, grout is used efficiently in the process of production the semi-flexible pavement mixtures. The purpose of this study is to design a sustainable grout using waste and by-products materials, to end as flowable grout for semiflexible pavement mixtures. The mixture of the grout was prepared using Ordinary Portland Cement (OPC), silica fume (SF), paper sludge ash (PSA), superplasticizer (SP), and water. Different proportions of mentioned materials were used to characterizing the developed grout through flowability, compressive strength, and flexural strength tests. Results showed that the flow time increases with increase in the surface area of cementitious materials. Also, the compression strength of the grouts comprised OPC+PSA, revels that there is an optimal dosage: i.e., 15% PSA. Whereas SF generally leads to increase the compression strength. On other side, flexural strength test confirmed the upgrading of developed grouts. As a conclusion, a sustainable grout can be produced with acceptable characteristics when grout constitutes are optimized.

The success of any pavement system is depending on the strength of the subgrade layer that represents a foundation on which unbound and surface course layers are placed. The strength of the subgrade layer is often defined in terms of a subgrade reaction modulus (Ks) which is typically obtained from the static plate load test (PLT). The PLT test is known to be laborious, time-consuming and relatively expensive, therefore several alternative methodologies for predicting (Ks) are required. The objective of this research is developing a 3D-finite element model using Plaxis 3D software to simulate the plate load tests, and comparing the finite element results with those obtained from experimental tests. Twenty-seven plate load tests were carried out on three different types of subgrade soils. The soils collected from different sites in Kerbala city and tested under static load under three degrees of compaction. The experimental results were verified numerically using the finite element method. In the numerical simulation, the Mohr-Coulomb model was used to represent the behavior of soil. The numerical and experimental results were analyzed and compared. The results showed a good agreement with experimental work, also showed the possibility of using Plaxis 3D in the simulation of the static plate load test.