Bond between glulam and NSM CFRP laminates

With the aim of evaluating the bond behaviour between glulam and carbon fibre reinforced polymer laminates strips, an experimental program using pull-out tests was carried, when the near-surface strengthening technique is applied. Two main variables were studied: the bond length and the type of pull-out test configuration. The instrumentation included the loaded and free-end slips, as well as the pull-out force. Based on the obtained experimental results, and applying an analytical-numerical strategy, the local bond stress-slip relationship was determined. In this work the tests are described, the obtained results are presented and analysed, and the applicability of an inverse analysis to obtain the local bond law is demonstrated.This work is supported by FEDER funds through the Operational Programme for Competitiveness Factors - COMPETE and National Funds through FCT - Portuguese Foundation for Science and Technology under the project PTDC/ECM/74337/2006. The authors also like to thank all the companies that have been involved supporting and contributing for the development of this study, mainly: S&P Clever Reinforcement Iberica Lda., Portilame, MAPEI and Rothoblaas

Bond behavior between glulam and GFRP's by pullout tests

To evaluate the bond behavior between glulam and GFRP rods, applied according to the near-surface mounted strengthening technique, an experimental program composed of beam and direct pullout tests was carried. In this experimental program three main variables were analyzed: the GFRP type, the GFRP location into the groove, and the bond length. From the monitoring system it was registered the loaded and free end slips, and the pullout force. Based on these experimental results, and applying an analytical-numerical strategy, the local bond stress-slip relationship was calculated. In this work the tests are described, the obtained results are presented and discussed, and the applicability of the inverse analysis to obtain the local bond law is demonstrated.This work is supported by FEDER funds through the Operational Programme for Competitiveness Factors - COMPETE and National Funds through FCT – Portuguese Foundation for Science and Technology under the project PTDC/ECM/74337/2006. The authors also like to thank all the companies that have been involved supporting and contributing for the development of this study, mainly: INEGI, S&P Clever Reinforcement Ibérica Lda., Portilame, MAPEI and Rothoblaas

Creep behavior of concrete elements strengthened with NSM CFRP laminate strips under different environmental conditions

The present work intends to contribute for the knowledge on the long-term deformational performance of concrete structures strengthened with the near-surface mounted (NSM) technique. For that purpose a wide experimental program has been initiated using beam pullout and slab specimens submitted to sustained loads under the following environmental conditions: (i) 20ºC temperature and 55% relative humidity; (ii) immersed in water tank at 20ºC with 0% of chlorides; (iii) immersed in water tank at 20ºC with 2.5% of chlorides; (iv) submitted to wet/dry cycles at 20ºC with 2.5% of chlorides. The slabs are continuously monitored in terms of mid-span vertical deflection and strains (in concrete, CFRP laminate strip and steel reinforcements), whereas for the case of the beam pullout specimens monitoring includes the free and loaded end slips and strain in CFRP laminate strip. The present paper summarizes the preliminary results

CTU Depth Decision Algorithms for HEVC: A Survey

High-Efficiency Video Coding (HEVC) surpasses its predecessors in encoding efficiency by introducing new coding tools at the cost of an increased encoding time-complexity. The Coding Tree Unit (CTU) is the main building block used in HEVC. In the HEVC standard, frames are divided into CTUs with the predetermined size of up to 64x64 pixels. Each CTU is then divided recursively into a number of equally sized square areas, known as Coding Units (CUs). Although this diversity of frame partitioning increases encoding efficiency, it also causes an increase in the time complexity due to the increased number of ways to find the optimal partitioning. To address this complexity, numerous algorithms have been proposed to eliminate unnecessary searches during partitioning CTUs by exploiting the correlation in the video. In this paper, existing CTU depth decision algorithms for HEVC are surveyed. These algorithms are categorized into two groups, namely statistics and machine learning approaches. Statistics approaches are further subdivided into neighboring and inherent approaches. Neighboring approaches exploit the similarity between adjacent CTUs to limit the depth range of the current CTU, while inherent approaches use only the available information within the current CTU. Machine learning approaches try to extract and exploit similarities implicitly. Traditional methods like support vector machines or random forests use manually selected features, while recently proposed deep learning methods extract features during training. Finally, this paper discusses extending these methods to more recent video coding formats such as Versatile Video Coding (VVC) and AOMedia Video 1(AV1)

On the Effectiveness of Video Recolouring as an Uplink-model Video Coding Technique

For decades, conventional video compression formats have advanced via incremental improvements with each subsequent standard achieving better rate-distortion (RD) efficiency at the cost of increased encoder complexity compared to its predecessors. Design efforts have been driven by common multi-media use cases such as video-on-demand, teleconferencing, and video streaming, where the most important requirements are low bandwidth and low video playback latency. Meeting these requirements involves the use of computa- tionally expensive block-matching algorithms which produce excellent compression rates and quick decoding times. However, emerging use cases such as Wireless Video Sensor Networks, remote surveillance, and mobile video present new technical challenges in video compression. In these scenarios, the video capture and encoding devices are often power-constrained and have limited computational resources available, while the decoder devices have abundant resources and access to a dedicated power source. To address these use cases, codecs must be power-aware and offer a reasonable trade-off between video quality, bitrate, and encoder complexity. Balancing these constraints requires a complete rethinking of video compression technology. The uplink video-coding model represents a new paradigm to address these low-power use cases, providing the ability to redistribute computational complexity by offloading the motion estimation and compensation steps from encoder to decoder. Distributed Video Coding (DVC) follows this uplink model of video codec design, and maintains high quality video reconstruction through innovative channel coding techniques. The field of DVC is still early in its development, with many open problems waiting to be solved, and no defined video compression or distribution standards. Due to the experimental nature of the field, most DVC codec to date have focused on encoding and decoding the Luma plane only, which produce grayscale reconstructed videos. In this thesis, a technique called “video recolouring” is examined as an alternative to DVC. Video recolour- ing exploits the temporal redundancies between colour planes, reducing video bitrate by removing Chroma information from specific frames and then recolouring them at the decoder. A novel video recolouring algorithm called Motion-Compensated Recolouring (MCR) is proposed, which uses block motion estimation and bi-directional weighted motion-compensation to reconstruct Chroma planes at the decoder. MCR is used to enhance a conventional base-layer codec, and shown to reduce bitrate by up to 16% with only a slight decrease in objective quality. MCR also outperforms other video recolouring algorithms in terms of objective video quality, demonstrating up to 2 dB PSNR improvement in some cases

The role of small RNAs in susceptibility and tolerance to cassava mosaic disease

A dissertation presented by Sarah Jane Rogans to The Faculty of Science, University of the Witwatersrand, Johannesburg in fulfilment of the requirements for the degree of Doctor of Philosophy in the School of Molecular and Cell Biology. 2016Cassava (Manihot esculenta, Crantz) is considered to be an important food security crop consumed by over a billion peoples globally, many who subsist on it. Cassava mosaic disease (CMD) is one of the main biotic and economically important constraints to cassava cultivation in sub-Saharan Africa. Geminiviruses are the casual agents of CMD and cause disease to many staple food and cash crops of great economic importance worldwide. There are currently 11 species of Begomoviruses that belong to the Geminiviridae family. South African cassava mosaic virus (SACMV) is a circular ssDNA bipartite (DNA A and DNA B components) begomovirus belonging to the family Geminiviridae, and is one of the causal agents of cassava mosaic disease (CMD) endemic to southern Africa. Various strategies to control CMD are currently being investigated, one of which is cis-genics, which involves manipulation of endogenous host genes to combat viral pathogens. In order to achieve this, it is imperative to elucidate molecular mechanisms involved in host-virus interactions. Endogenous small RNAs (sRNAs), including microRNAs (miRNAs), have been found associated with gene regulatory mechanisms in response to virus infection. Amongst the non-coding host sRNAs targeting viruses are small interfering RNAs (siRNAs) associated with posttranscriptional gene silencing (PTGS) and transcriptional gene silencing (TGS), which are involved in the host RNA silencing pathway. The RNA silencing pathway is a highly conserved basal immunity pathway involved in host defence against plant viruses. The aim of this study was to identify siRNAs and miRNAs associated with gene regulatory mechanism in response to SACMV infection and to determine if they a play a role in the susceptible or recovery phenotype observed in SACMV tolerant cassava landrace TME3 or T200, respectively. Furthermore, virus-derived siRNA (vsRNA) populations targeting the DNA A and B components of SACMV were also investigated. MicroRNAs (miRNAs) are an important class of endogenous non-coding single-stranded small RNAs (21-24 nt in length), which serve as post-transcriptional negative regulators of gene expression in plants. Despite the economic importance of Manihot esculenta Crantz (cassava) only 153 putative cassava miRNAs (from multiple germplasm) are available to date in miRBase (V.21). Therefore, both conserved and novel miRNAs needed to be identified in cassava before we could determine what association they had with SACMV infection. In this part of the study, mature sequences of all known plant miRNAs were used as a query for homologous searches against cassava EST and GSS databases, and additional identification of novel and conserved miRNAs were gleaned from next generation sequencing (NGS) of two cassava landraces (T200 from southern Africa and TME3 from West Africa) at three different growth stages post explant transplantation and acclimatization. EST and GSS derived data revealed 259 and 32 conserved miRNAs in cassava, and one of the miRNA families (miR2118) from previous studies has not been reported in cassava. NGS data collectively displayed expression of 289 conserved miRNAs in leaf tissue, of which 230 had not been reported previously. Of the 289 conserved miRNAs identified in T200 and TME3, 208 were isomiRs. Thirty-nine novel cassava-specific miRNAs of low abundance, belonging to 29 families, were identified. Thirty-eight (98.6%) of the putative new miRNAs identified by NGS have not been previously reported in cassava. Several miRNA targets were identified in T200 and TME3, highlighting differential temporal miRNA expression between the two cassava landraces. This study contributes to the expanding knowledge base of the micronome of this important crop. MicroRNAs play a crucial role in stress response in plants, including biotic stress caused by viral infection. Viruses however can interfere with and exploit the silencing-based regulatory networks, causing the deregulation of miRNAs. This study aimed to understand the regulation of miRNAs in tolerant (TME3) and susceptible (T200) cassava landraces infected with SACMV. Next-generation sequencing was used for analysing small RNA libraries from infected and mock-inoculated cassava leaf tissue collected at 12, 32 and 67 dpi (days post-inoculation). The total number of differentially expressed miRNAs (normalized against mock-inoculated samples) across all three time points was 204 and 209 miRNAs, in TME3 and T200 infected plants, respectively, but the patterns of log2fold changes in miRNA families over the course of infection differed between the two landraces. A high number were significantly altered at 32 dpi when T200 and TME3 plants showed severe symptoms. Notably, in T200 69% and 28 (100%) of miRNA families were upregulated at 12 and 32 dpi, respectively. In contrast, TME3 showed an early pre-symptomatic response at 12 dpi where a high number (87%) of miRNAs showed a significant log2fold downregulation. Endogenous targets were predicted in the cassava genome for many of the identified miRNA families including transcription factors, disease resistance (R)-genes and transposable elements. Interestingly, some of the miRNA families (miR162, miR168 and miR403) that were significantly affected in both T200 and TME3 upon SACMV infection were shown to target proteins (DCL1, AGO1 and AGO2) that play important roles in the RNA silencing pathway. From results, we suggest that the early (12 dpi) miRNA response to SACMV in TME3 appears to involve PTGS-associated AGO1, DCL2 and a cohort of R genes belonging to the miR395 family which may prime the plant for tolerance and recovery downstream, while in T200, SACMV suppresses AGO1, AGO2 (at 32 and 67 dpi), and DCL2 (32 dpi) mediated RNA silencing, leading to severe persistent disease symptoms. This study provides insights into miRNA-mediated SACMV cassava interactions and may provide novel targets for control strategies aimed at developing CMD-resistance cassava varieties Endogenous small RNAs (sRNAs) associated with gene regulatory mechanisms respond to virus infection, and virus-derived small interfering RNAs (vsRNAs) have been implicated in recovery or symptom remission in some geminivirus-host interactions. Transcriptional gene silencing (TGS) (24 nt vsRNAs) and post transcriptional gene silencing (PTGS) (21-23 nt vsRNAs) have been associated with geminivirus intergenic (IR) and coding regions, respectively. In this Illumina deep sequencing study, we compared for the first time, the small RNA response to South African cassava mosaic virus (SACMV) of cassava landrace TME3 which shows a recovery and tolerant phenotype, and T200, a highly susceptible landrace. Interestingly, different patterns in the percentage of SACMV-induced normalized total endogenous sRNA reads were observed between T200 and TME3. Notably, in T200 there was a significant increase in 21 nt sRNAs during the early pre-symptomatic response (12 dpi) to SACMV compared to mock, while in TME3, the 22 nt size class increased significantly at 32 dpi. While vsRNAs of 21 to 24 nt size classes covered the entire SACMV DNA- A and DNA-B genome components in T200 and TME3, vsRNA population counts were significantly lower at 32 (symptomatic stage) and 67 dpi in tolerant TME3 compared with T200 (non-recovery). It is suggested that the high accumulation of primary vsRNAs, which correlated with high virus titres and severe symptoms in susceptible T200, may be due to failure to target SACMV-derived mRNA. In contrast, in TME3 low vsRNA counts may represent efficient PTGS of viral mRNA, leading to a depletion/sequestration of vsRNA populations, supporting a role for PTGS in tolerance/recovery in TME3. Notably, in TME3 at recovery (67 dpi) the percentage (expressed as a percentage of total vsRNA counts) of redundant and non-redundant (unique) 24 nt vsRNAs increased significantly. Since methylation of the SACMV genome was not detected by bisulfite sequencing, and vsRNA counts targeting the IR (where the promoters reside) were very low in both the tolerant or susceptible landraces, we conclude that 24 nt vsRNA-mediated RNA directed genome methylation does not play a central role in disease phenotype in these landraces, notwithstanding recognition for a possible role in histone modification in TME3. This work represents an important step toward understanding variable roles of sRNAs in different cassava genotype-geminivirus interactions. Also, by comparing the differences between a tolerant and susceptible host the aim is to achieve better understanding of the effect of pathogens on host sRNAome, an area that is deserving of me attention in plant systems. The expectation is that these findings presented in the PhD will contribute to the long-term goals of devising new methods of disease control against SACMV and understanding the complex interconnected mechanisms involved in virus-host interactome.LG201

Microstructure, crystallography and stable isotope composition of Crassostrea gigas

Many marine molluscs produce complex shells of calcium carbonate. These shells are formed under strict biological control to provide a range of functions to ensure the survival of the living organism. These inspiring biomineral structures can also provide an archive of environmental change via proxies such as δ18O and δ13C within the shell carbonate. However, the intimate relationship between the biological and environmental controls influencing biomineral production can often obscure the environmental signal, making it difficult to interpret environmental information from shell proxies. Understanding the design of biomineral structures will further our knowledge of biomineralisation as a whole, while understanding the controls that influence shell production will ensure that shell proxies applied to palaeoenvironmental studies are accurate. Oysters are sessile bivalve molluscs that have evolved since the Triassic and expanded to occupy a range of habitats with almost global distribution, providing an example of a highly successful biomineral system. This study investigates the ultrastructure, crystallography and stable isotope composition of the Pacific oyster, Crassostrea gigas from estuarine and marine environments. The method by which oysters adhere to hard substrates is also investigated. Both valves of the oyster shell are composed predominantly of low Mg calcite in three forms; an outer prismatic region, an inner foliated structure and chalk lenses which appear sporadically throughout the valves. Aragonite is restricted to the myostracum and parts of the hinge structure. Crystallographic analysis shows that, despite variations in structural morphology, the superimposed layers of the oyster shell maintain a single crystallographic orientation with the crystallographic c-axis orientated perpendicular to the outer shell surface. Varying crystal morphology, while maintaining crystallographic unity, may be a deliberate design to provide the oyster shell with both strength and flexibility. In general, there is no difference in the overall ultrastructure or microstructural arrangement of estuarine and marine oysters. Estuarine oysters contain significantly more chalk than marine equivalents suggesting that the appearance of chalk lenses is, to some degree, triggered by an external environmental stimulus. Stable carbon and oxygen isotope analysis of folia and chalk provides further insights into the appearance of chalk in the oyster shell structure. There is no significant difference in the isotope composition of folia or chalky layers, although patterns of δ13C and δ18O of folia and chalk reveal key differences between the two structures. Folia display a narrower range of δ18O values compared with chalk and exhibit significant interspecimen variation with respect to δ13C. Interspecimen variation, with respect to either δ18O or δ13C is absent in chalk samples. These patterns suggest that secretion of folia requires a more specific environmental stimulus and a greater input of metabolic carbon than chalk. Chalk is apparently secreted across a greater range of environmental conditions, with less metabolic regulation. Deviation from optimal environmental conditions, for example during periods of reduced salinity and/or cold or warm temperatures, may reduce metabolism causing the oyster to deliberately default from folia to chalk secretion. In general, folia and chalk in both estuarine and marine oysters is secreted in oxygen isotope equilibrium with the ambient environment. Another aspect of the oyster biomineral system is their ability to adhere tightly, and usually permanently, to a range of hard substrates by cementation of the left valve. Investigation of the contact zone between oyster shells and biological (other oyster shells) and inorganic (rock) substrates reveals the influence of both biogenic and non-biogenic processes in oyster cementation. Original adhesion is brought about by secretion of an organic adhesive which acts as a nucleating surface onto which crystals precipitate which have random orientation and are composed of high Mg calcite. The lack of orientation and elevated Mg content suggests that these crystals are nucleating outwith the biological control experienced by the shell biomineralisation process and are formed from inorganic precipitation from seawater. It is proposed that oysters do not control, or secrete, the crystalline cement but instead they secrete an organic film onto which crystals precipitate from seawater. Oysters thus provide excellent examples of both biologically induced and biologically controlled mineralisation