Rubberised bitumen manufacturing assisted by rheological measurements

This paper investigates the effect of processing temperature and time on the rheological properties of recycled tyre rubber-modified bitumens (RTR-MBs) produced using two different base binders and an ambient ground crumb rubber modifier (CRM). The production of the RTR-MBs was accomplished by means of a standard Brookfield rotational viscometer together with a modified impeller, dual helical impeller, to allow mixing as well as real-time viscosity measurements of the produced RTR-MBs. The rheological properties of the final RTR-MBs were determined by means of standard dynamic mechanical analysis oscillatory and multiple stress creep recovery testing using a dynamic shear rheometer. The results indicate that the low processing conditions (160°C and 60 min) are not appropriate for developing RTR-MBs with enhanced physical and rheological properties. However, allowing the crumb rubber to interact with the base binder for longer mixing times (140 min) led to the development of an enhanced rubber (polymer) network structure within the blend (i.e. swelling of the CRM particles) and superior rheological properties. At the other extreme, using high-processing conditions (200°C and 140 min) led to RTR-MBs in which the rubber network had been subjected to devulcanisation and depolymerisation with a subsequent reduction in modification

Knitting for heart valve tissue engineering.

Knitting is a versatile technology which offers a large portfolio of products and solutions of interest in heart valve (HV) tissue engineering (TE). One of the main advantages of knitting is its ability to construct complex shapes and structures by precisely assembling the yarns in the desired position. With this in mind, knitting could be employed to construct a HV scaffold that closely resembles the authentic valve. This has the potential to reproduce the anisotropic structure that is characteristic of the heart valve with the yarns, in particular the 3-layered architecture of the leaflets. These yarns can provide oriented growth of cells lengthwise and consequently enable the deposition of extracellular matrix (ECM) proteins in an oriented manner. This technique, therefore, has a potential to provide a functional knitted scaffold, but to achieve that textile engineers need to gain a basic understanding of structural and mechanical aspects of the heart valve and in addition, tissue engineers must acquire the knowledge of tools and capacities that are essential in knitting technology. The aim of this review is to provide a platform to consolidate these two fields as well as to enable an efficient communication and cooperation among these two research areas

First report of early blight caused by Alternaria protenta on potato in Algeria

Potato (Solanum tuberosum L.) is one of the most important vegetable crop grown in Algeria. Although less studied than late blight, early blight caused by large-spored Alternaria species including A. solani, and A. grandis is an important foliar disease on these crops under Algerian climatic conditions. Over the past few years, this disease became a major constraint on potato production in Algeria and high incidences of early blight (up to 80 %) were recorded in the north-western parts of Algeria (Bessadat et al., 2016). During years 2012-2014, surveys were carried out and sampling was performed in 12 potato growing regions from East to West and from North to South of Algeria. Two hundred and forty-seven samples with typical early blight symptoms (dark, elongated or circular lesions with concentric rings surrounded by a yellow halo) were collected. Two to three lesions perleaf were excised, surface disinfested for 2 min in 0.1% (v/v) sodium hypochlorite solution and plated on potato dextrose agar medium at 22°C. Twenty-two pure cultures were induced to sporulate by plating on V8 medium and incubating for two weeks under alternating 12 h darkness and 12 h near UV light. Cultural and morphological characteristics of the isolates [color and pigmentation of the culture, shape and size of the conidia (conidial length and width, beak length)] compared with those in the literature (Simmons, 2007) did not clearly differentiate between the large-spored Alternaria species currently reported on potato crops. For identification at the species level, partial regions of the calmodulin (cal) and RNA polymerase second largest subunit (rpb2) genes were amplified using published primer sets (Gannibal et al., 2014; Woudenberg et al., 2014) and sequenced. Maximum likelihood cluster analyses of the resulting nucleotide sequences revealed two isolates (AD82 and AD86 isolated from potato samples collected in the El Oued region) with sequences at the two loci [GenBank accession Nos. KX870505 and KX870506 (cal locus), KX870507 and KX870508 (rpb2 locus)] that shared 100% sequence homology to A. protenta isolate CBS 116696 (KJ718394, JQ646236) and were thus assigned to this species. A. protenta was previously known in Africa only on Helianthus annuus (Simmons, 1986) but isolates from S. tuberosum and S. lycopersicum collected in New Zealand and USA and formerly recognized as A. solani, were recently moved to A. protenta based on phylogeny (Woudenberg et al., 2014). To confirm pathogenicity of the two A. protenta isolates, leaves of susceptible 3-week-old potato plants were inoculated with two 10 µL drops of a 104 conidia/ml suspension. All leaves inoculated with A. protenta showed extending lesions that may reach up 50% of the leaf area at 21 dpi. To our knowledge, we report the first occurrence of A. protenta as pathogen on potato in Algeria.

Total Knee Arthroplasty for Post-Traumatic Proximal Tibial Bone Defect: Three Cases Report

Bone stock deficiency in primary as well as in revision total knee arthroplasty (TKA) represents a difficult problem to surgeon with regard to maintaining proper alignment of the implant components and in establishing a stable bone-implant interface. Different surgical procedures are available in these situations, for instances the use of bone cement, prosthetic augments, custom implant, and wire mesh with morsellized bone grafting and structural bone allograft. Structural allograft offers a numerous advantages as easy remodeling and felling cavitary or segmental defects, excellent biocompatibility, bone stock restoration and potential for ligamentous reattachment. In this article we report a short term result of three cases affected by severe segmental medial post/traumatic tibial plateau defect in arthritic knee, for which massive structural allograft reconstruction and primary total knee replacement were carried. The heights of the bone defect were between 27-33 mm and with moderate medio-lateral knee instability. Pre-operative AKS score in three cases was 30, 34 and 51 points consecutively and improved at the last follow-up to 83, 78 and 85 consecutively. No acute or chronic complication was observed. Last radiological exam referred no signs of prosthetic loosening, no secondary resorption of bone graft and well integrated graft to host bone. These results achieved in our similar three cases have confirmed that the structural bone allograft is a successful biological material to restore hemi-condylar segmental tibial bone defect when total knee replacement is indicated

Ice-lens formation and geometrical supercooling in soils and other colloidal materials

We present a new, physically-intuitive model of ice-lens formation and growth during the freezing of soils and other dense, particulate suspensions. Motivated by experimental evidence, we consider the growth of an ice-filled crack in a freezing soil. At low temperatures, ice in the crack exerts large pressures on the crack walls that will eventually cause the crack to split open. We show that the crack will then propagate across the soil to form a new lens. The process is controlled by two factors: the cohesion of the soil, and the geometrical supercooling of the water in the soil; a new concept introduced to measure the energy available to form a new ice lens. When the supercooling exceeds a critical amount (proportional to the cohesive strength of the soil) a new ice lens forms. This condition for ice-lens formation and growth does not appeal to any ad hoc, empirical assumptions, and explains how periodic ice lenses can form with or without the presence of a frozen fringe. The proposed mechanism is in good agreement with experiments, in particular explaining ice-lens pattern formation, and surges in heave rate associated with the growth of new lenses. Importantly for systems with no frozen fringe, ice-lens formation and frost heave can be predicted given only the unfrozen properties of the soil. We use our theory to estimate ice-lens growth temperatures obtaining quantitative agreement with the limited experimental data that is currently available. Finally we suggest experiments that might be performed in order to verify this theory in more detail. The theory is generalizable to complex natural-soil scenarios, and should therefore be useful in the prediction of macroscopic frost heave rates.Comment: Submitted to PR