Structural integrity and healing efficiency study of micro-capsule based composite materials via 1H NMR relaxometry.

In this work we present a novel approach utilizing nuclear magnetic resonance (NMR) relaxometry to assess the structural stability of microcapsules employed as self-healing agents in advanced aerospace composites both in ambient and harsh environmental conditions. We successfully correlate the amount of the encapsulated self-healing agent with the signal intensity and confirm non-destructively the quantity of the encapsulated self-healing agent mass for the first time in the literature using 1H NMR spin-spin relaxation techniques on urea-formaldehyde (UF) microcapsules of different diameters containing an epoxy healing agent. The amount of self-healing agent is shown to increase by reducing the capsule diameter; however, the reduced shell mass renders the capsules more fragile and prone to failure. Most notably, via NMR experiments conducted during thermal cycling simulating flight conditions, we demonstrate that the microcapsule integrity under thermal fatigue varies according to their size. Especially we experimentally verify that the microcapsules with the most sensitive shells are the 147 nm and 133 nm diameter microcapsules, which are the most commonly used in self-healing systems. Finally, we were able to retrieve the same results using a portable NMR spectrometer developed in-house for in situ microcapsule testing, thus demonstrating the potential of NMR relaxometry as a powerful non-destructive evaluation tool for the microcapsule production line.

Effects of air exposure on desiccation and photosynthetic performance of Cymodocea nodosa with and without epiphytes and Ulva rigida in comparison, under laboratory conditions.

The seagrass Cymodocea nodosa and the chlorophyte Ulva rigida growing in the upper sublittoral zones of the Mediterranean Sea are exposed to air during low tides. We compared the desiccation coefficient (k), and the photosynthetic performance (ΔF/Fm') of C. nodosa leaves with and without epiphytes to that of U. rigida. The recovery ability of these two species was assessed by ΔF/Fm', after re-immersion. The desiccation coefficient (k) significantly (p < 0.01) varied among the three macrophyte materials, while the lowest k values were measured both in C. nodosa leaves with epiphytes and U. rigida. ΔF/Fm' significantly declined with decreasing RWC for all materials, while significant differences in the physiological response were observed between U. rigida and the other two materials. Thallus pieces of U. rigida showed higher desiccation tolerance compared to C. nodosa leaves, with its ΔF/Fm' under 75% degree of dehydration reaching to its initial values thirty (30) minutes after re-immersion, when C. nodosa only reached the 50%. This study provides valuable information on possible changes in the two species distribution under different desiccation scenarios.

Identification of the abiotic stress-related transcription in little Neptune grass Cymodocea nodosa with RNA-seq.

Seagrasses exhibit vital ecological roles in the marine environment. Nevertheless, the genomic resources available for seagrasses are still scarce. In the present study, the transcriptome of Cymodocea nodosa was sequenced with a view to study the molecular mechanisms underlying abiotic stress responses. The sequenced transcriptome for the species was near-complete and a high percentage of the transcripts was computationally annotated. An experimental simulation of marine plant exposure to extreme temperature (34°C), salinity (50psu) and their combination was conducted. A dynamic transcriptome 24h response (short-term) from stress initialization was recorded. The most noteworthy alteration in gene expression was observed in heat-stressed plants. Transcripts associated with development, photosynthesis, osmotic balance and stress-response were differentially expressed, under the set experimental conditions. Results indicate a potential negative interaction of heat and osmotic stress on seagrasses transcriptome.

Effects of high temperature on the ultrastructure and microtubule organization of interphase and dividing cells of the seagrass Cymodocea nodosa.

Short-time temperature effects (34-40 °C) on microtubule (MT) organization and on cell structure of young epidermal leaf cells of the seagrass Cymodocea nodosa were investigated under laboratory conditions using transmission electron microscopy (TEM) and tubulin immunofluorescence. The interphase MT network was affected by the increased temperature, the effect being time dependent and expressed in both the form and the orientation of the MT bundles. After 1 h at 38 °C, there was also a severe disturbance in dividing cells with thick and short MTs in the mitotic spindle and atypically organized phragmoplasts, while after 2 h at 38 °C the mitotic index was tenfold reduced compared with the control material. After 6 h at 38 °C, a large number of telophase cells were observed, meaning that cytokinesis was blocked. TEM observation revealed cells with uncompleted cell plates consisting of swollen vesicles and branched cisternae, with no phragmoplast MTs. These cells bear a nucleolus with segregated fibrillar and granular zones, an increased number of swollen mitochondria, and numerous parallel arrays of endoplasmic reticulum cisternae in the cortical cytoplasm. The possible relationship of these changes in C. nodosa with a response mechanism in order to face elevated temperature effects of climate change is discussed.

The use of Ender nails in tibial shaft fractures.

The results of 31 fractures of the tibial shaft treated with closed Ender nailing and early weight-bearing are reported. Twenty-five of these fractures were closed and six open. All fractures united between 6 and 16 weeks after operation. No case of deep wound infection was encountered. Comminuted fractures of the proximal and distal third were prone to angular deformities and needed cast protection post-operatively. Nail reinsertion became necessary in two patients. Delay of operation renders closed reduction very difficult. The advantages of this method are: 1) normal knee and ankle movements are possible during healing and 2) there is relatively rapid restoration of bone continuity.