Development of a Portland Cement-Based Material with Agave salmiana Leaves Bioaggregate

Depending on the morphology of the natural fibers, they can be used as reinforcement to improve flexural strength in cement-based composites or as aggregates to improve thermal conductivity properties. In this last aspect, hemp, coconut, flax, sunflower, and corn fibers have been used extensively, and further study is expected into different bioaggregates that allow diversifying of the raw materials. The objective of the research was to develop plant-based concretes with a matrix based on Portland cement and an aggregate of Agave salmiana (AS) leaves, obtained from the residues of the tequila industry that have no current purpose, as a total replacement for the calcareous aggregates commonly used in the manufacturing of mortars and whose extraction is associated with high levels of pollution, to improve their thermal properties and reduce the energy demand for air conditioning in homes. Characterization tests were carried out on the raw materials and the vegetal aggregate was processed to improve its compatibility with the cement paste through four different treatments: (a) freezing (T/C), (b) hornification (T/H), (c) sodium hydroxide (T/NaOH), and (d) solid paraffin (T/P). The effect of the treatments on the physical properties of the resulting composite was evaluated by studying the vegetal concrete under thermal conductivity, bulk density, and compressive strength tests with a volumetric ratio between the vegetal aggregate and the cement paste of 0.36 and a water/cement ratio of 0.35. The hornification treatment showed a 15.2% decrease in the water absorption capacity of the aggregate, resulting in a composite with a thermal conductivity of 0.49 W/mK and a compressive strength of 8.66 MPa, which allows its utilization as a construction material to produce prefabricated blocks.     

Dynamic Ranges of Retinal Nerve Fiber and Optic Nerve Head Parameters Measured Using Optical Coherence Tomography in Glaucoma: A Longitudinal Study

PurposeTo evaluate the dynamic range of retinal nerve fiber layer (RNFL) and optic nerve head (ONH) parameters measured using optical coherence tomography (OCT) in conditions ranging from nonglaucomatous status to advanced glaucoma by longitudinal observation.MethodsA total of 15 eyes from 12 participants with glaucoma progression from a nonglaucomatous status to advanced glaucoma were included. The RNFL and ONH parameters were compared between the nonglaucomatous and advanced stages within the same eye. The absolute and relative changes in OCT parameters were analyzed.ResultsThe median highest intraocular pressure was 42.5 mmHg (interquartile range, 37.5 to 54.5 mmHg), and the final mean deviation of the visual field test was −24.68 dB (interquartile range, −23.93 to −31.13 dB). The median relative changes in RNFL thickness were −40.6% in the overall area, and −51.9%, −21.4%, −51.1%, and −41.8% in the superior, nasal, inferior, and temporal quadrants, respectively (all p < 0.05). Relative changes in the rim area, disc area, average cup to disc ratio, vertical cup to disc ratio, and cup volume were −56.64%, 0.59%, 62.10%, 66.0%, and 337.90%, respectively (all p < 0.05, except for disc area with a p-value of 0.753).ConclusionsThe dynamic range of the RNFL thickness ranged from 40.6% to 51.9%, and the dynamic range of the ONH parameters ranged from 56.64% to 337.90%. During the course of glaucoma progression, the cup volume showed the widest dynamic range. However, the disc area did not show significant changes.     

Bond Properties of Magnesium Phosphate Cement-Based Engineered Cementitious Composite with Ordinary Concrete

A magnesium phosphate cement-based engineered cementitious composite (MPC-ECC) was developed using polyvinyl alcohol (PVA) fibers and fly ash. In this study, the bond behavior of MPC-ECC with ordinary concrete was evaluated through single and double shear bond strength tests. The effects of the water to solid mass ratio (W/S), the sand to binder mass ratio (S/B), the molar ratio of MgO to KH2PO4 (M/P), the fly ash content (F), the borax dosage (B), the volume fraction of PVA fibers (Vf), and curing age on the bond behavior of MPC-ECC with ordinary concrete were examined. The results showed that as the W/S increased, the single and double shear bond strengths were gradually reduced. As the S/B increased, the double shear bond strength increased; the single shear bond strength first decreased up to an S/B of 0.1 and then increased. With the increase of M/P, the single and double shear bond strengths increased. With the increase of F, the single shear bond strength first increased up to an F of 30% and then decreased; the double shear bond strength decreased. With the increase of B, the single and double shear bond strengths increased first and then decreased, and their strength reached its maximum at a B of 6%. The increase of Vf improved the single and double shear bond strengths. The research results can provide some technical guidance for repairing concrete structures with MPC-ECC.     

A Review on Synthetic Fibers for Polymer Matrix Composites: Performance,Failure Modes and Applications

In the last decade, synthetic fiber, as a reinforcing specialist, has been mainly used in polymer matrix composites (PMC’s) to provide lightweight materials with improved stiffness, modulus, and strength. The significant feature of PMC’s is their reinforcement. The main role of the reinforcement is to withstand the load applied to the composite. However, in order to fulfill its purpose, the reinforcements must meet some basic criteria such as: being compatible with the matrix, making chemical or adhesion bonds with the matrix, having properties superior to the matrix, presenting the optimal orientation in composite and, also, having a suitable shape. The current review reveals a detailed study of the current progress of synthetic fibers in a variety of reinforced composites. The main properties, failure modes, and applications of composites based on synthetic fibers are detailed both according to the mentioned criteria and according to their types (organic or inorganic fibers). In addition, the choice of classifications, applications, and properties of synthetic fibers is largely based on their physical and mechanical characteristics, as well as on the synthesis process. Finally, some future research directions and challenges are highlighted.     

Approaches to Preceramic Polymer Fiber Fabrication and On-Demand Applications

The demand for lightweight, high-modulus, and temperature-resistant materials for aerospace and other high-temperature applications has contributed to the development of ceramic fibers that exhibit most of the favorable properties of monolithic ceramics. This review demonstrates preceramic-based polymer fiber spinning and fiber classifications. We discuss different types of fiber spinning and the advantages of each. Tuning the preceramic polymer chemical properties, molar mass, functional chemistry influences, and incorporation with fillers are thoroughly investigated. Further, we present the applications of preceramic-based polymer fibers in different fields including aerospace, biomedical, and sensor applications. This concise review summarizes recent developments in preceramic fiber chemistry and essential applications.     

Estimating Low- and High-Cyclic Fatigue of Polyimide-CF-PTFE Composite through Variation of Mechanical Hysteresis Loops

The fatigue properties of neat polyimide and the “polyimide + 10 wt.% milled carbon fibers + 10 wt.% polytetrafluoroethylene” composite were investigated under various cyclic loading conditions. In contrast to most of the reported studies, constructing of hysteresis loops was performed through the strain assessment using the non-contact 2D Digital Image Correlation method. The accumulation of cyclic damage was analyzed by calculating parameters of mechanical hysteresis loops. They were: (i) the energy losses (hysteresis loop area), (ii) the dynamic modulus (proportional to the compliance/stiffness of the material) and (iii) the damping capacity (calculated through the dissipated and total mechanical energies). On average, the reduction in energy losses reached 10–18% at the onset of fracture, whereas the modulus variation did not exceed 2.5% of the nominal value. The energy losses decreased from 20 down to 18 J/m³ (10%) for the composite, whereas they reduced from 30 down to 25 J/m³ (17%) for neat PI in the low-cycle fatigue mode. For high-cycle fatigue, energy losses decreased from 10 to 9 J/m³ (10%) and from 17 to 14 J/m³ (18%) for neat PI and composite, respectively. For this reason, the changes of the energy losses due to hysteresis are of prospects for the characterization of both neat PI and the reinforced PI-based composites.     

正常与炎症牙髓中降钙素基因相关肽免疫反应神经纤维的研究

目的观察人正常与炎症牙髓中降钙素基因相关肽免疫反应神经纤维（CGRP－IRF）的分布，为深入探讨神经系统如何参与牙髓的各种生理，病理改变的调节作用提供新的资料。方法采用ABC免疫组化法观察人正常牙髓中CGRP－IRF的分布及龋源性炎症牙髓中CGRP－IRF的改变。结果牙髓中CGRP－IRF为许多串珠状棕褐色点状连成的线条，含明显的膨体。正常牙髓中，CGRP－IRF多沿血管走行并分布在血管周围，一些单根CGRP－IRF远离血管，主要分布在造牙本质细胞下神经丛。髓角处，偶尔可见CGRP-IRF突入造牙本质细胞层。炎症牙髓中，在病损下方和血管周围CGRP－IRF明显增多。结论CGRP－IRF广泛分布于人牙髓中，在牙髓炎症中起重要作用。     

近视眼视网膜神经纤维层厚度与中央角膜厚度相关性研究

Objective To explore the relationship between retinal nerve fiber layer (RNFL) thickness and central corneal thickness (CCT) in myopia eyes.Methods 91 cases (91eyes) were selected from ophthalmological outpatients including 28cases with low myopia ( spherical equivalence [ SE ] ＞ -3.0D), 33 cases with moderate myopia (SE -0.3D ～ -6.0D) and 30 cases with high myopia (SE ＜ -6.0D).All patients received ocular standard examination including intraocular pressure, refraction, slitlamp biomicroscopy and fundus examination.Other ocular diseases except refractive error were excluded.RNFL thickness and CCT were measured by RTVue Fourior-OCT ( Optovue Inc, USA).Refraction diopter was shown as SE.Results The mean RNFL thickness and CCT was ( 108.5 ± 10.1 ) μm, (524.7 ±36.8)μm respectively.These were no significantly different among low, moderate and high myopia ( P ＞ 0.05 ).Temporal RNFL thickness( tl1 ,tu1 ) was significantly positive related with CCT( r =0.281,0.093 of tl1, r= 0.352,0.167 of tu1 respectively in single and multiple variable analysis; P ＜ 0.05 ), nasal ( nl2, nu2)and inferior nasal RNFL thickness( in2,in1 )was significantly positive related with SE( P ＜0.05), inferior temporal RNFL thickness( it2)was significantly negative related with SE( P ＜0.05), and RNFL thickness in other regions were not significant related with CCT and SE ( P ＞ 0.05 ) in single and multiple variable regressive analysis.Conclusion Relationship between RNFL thickness of local paradisc region and CCT in myopia eyes suggested that CCT should be correlative with some sensible structural parameters in glaucomatous neuropathy and might be important in the diagnosis and therapy of glaucoma.     

Ultra-High-Performance Concrete (UHPC): A State-of-the-Art Review

The interest of researchers in UHPC has increased over the past decade. It is crucial to understand the structural behavior of reinforced UHPC (R/UHPC) components under various loading conditions before they can be used as a replacement for conventional concrete. Although several studies on ultra-high-performance concrete (UHPC) have been conducted, the knowledge is scattered, and no one can easily judge the performance and methodology of UPHC. Therefore, the purpose of this study was to review the research studies already carried out on UHPC. The review focuses on the materials’ physical and chemical composition, mechanical and durability characteristics, fire resistance, and environmental benefits of UHPC. Design considerations for effectively utilizing UHPC in structural elements are also presented. The best UHPFRC mixture is obtainable with a steel fiber content of 2–3% and a water-to-cement ratio of 0.2–0.3. The review also discusses the essentials recommendation for future research on UHPC.