Distortions to Agricultural Incentives in Sri Lanka

Distorted incentives, agricultural and trade policy reforms, national agricultural development, Agricultural and Food Policy, International Relations/Trade, F13, F14, Q17, Q18,

Dynamic behaviour of fibre composite multilayer sandwich plates with delaminations

Composites are continuing to gain prominence for structural as well as non-structural applications all over the world. A structural composite multilayer slab can be manufactured by gluing several of the composite sandwiches together to form a laminated composite slab. Delamination between layers is one of the major failure modes which threaten the reliability of composite structures. Delamination can also cause changes to dynamic behaviour. Dynamic analysis of three dimensional models of structures enables more realistic assessment of their free vibration behaviour. The dynamic behaviour of fibre composite multilayer sandwich plates with different configurations of delamination is presented in this paper. A parametric investigation is carried out to assess the influence of parameters including length, width and location of delamination, size and support conditions of the plates on the free vibration behaviour, using three dimensional modelling with Strand7 finite element software package. Plate elements for skins and brick elements for core of each sandwich layer are used in the model development for plates representing their actual behaviour. It is revealed that the decrease in natural frequency with the increase in the extent of debonding is greatly dependent on the boundary conditions, location of the debond and also on the mode number

A preliminary study of mecA gene expression and methicillin resistance in staphylococci isolated from the human oral cavity

Introduction: Staphylococci are common human commensals that acquire methicillin resistance via the mecA gene. Methicillin resistance in staphylococci from various clinical sources has been assessed using cefoxitin disc diffusion test (CDDT) and PCR detection of the mecA gene. However, oral staphylococci have been studied less frequently compared with other clinical sources. There are no previous studies on methicillin resistance in oral staphylococci in Sri Lanka.Objective: This study aimed to demonstrate methicillin resistance in staphylococci isolated from the human oral cavity using CDDT and PCR detection of mecA gene.Materials and methods: Twenty-five oral isolates of staphylococci were selected after confirming their identity using colony morphology, Gram stain, catalase test, and the coagulase test. Further authentication of identity was obtained using amplification of the 16S rRNA gene. Methicillin resistance was demonstrated using CDDT and PCR detection of the mecA gene.Results: There were 7 (28%) isolates of coagulase positive (presumed S. aureus) and 18 (72%) of coagulase negative staphylococci (CoNS). All the coagulase positive isolates were methicillin sensitive. Within the 18 CoNS, 2 (11%) were methicillin resistant and were found to carry the mecA gene using PCR. Conclusion: Coagulase positive and negative staphylococci with or without methicillin resistance may colonize the human oral cavity. Coagulase negative staphylococci were the majority in this limited study. Further studies are warranted to determine the incidence of staphylococci in the oral cavity and their antimicrobial sensitivity.</p

Hyphal invasion of Candida albicans inhibits human beta-defensins expression

published_or_final_versio

Dynamic behaviour of composite sandwich beams and plates with debonds

Fibre Reinforced Polymer (FRP) composites are continuing to gain prominence in structural as well as non-structural applications all over the world due to their outstanding properties such as high strength to weight ratio, corrosion resistance, good thermal performance, anti-fire performance and reduction of carbon dioxide emissions both through its method of production and their effective thermal insulation qualities. The increased popularity and demand for FRP composites have spurred research efforts in both academia and civil construction industry. A composite sandwich structural element can be made-up by attaching two thin and stiff skins to a lightweight and thick core, which serves as a building block for constructing laminated structural sandwich composites for civil engineering applications. A structural composite multilayer beam or plate can be manufactured by gluing two or more composite sandwiches together to form a laminated composite. An Australian manufacturer has fabricated a new generation structural Glass Fibre Reinforced Polymer (GFRP) sandwich panel made from E-glass fibre skin and a high strength modified phenolic core for civil engineering applications, the outstanding features of the sandwich material being high strength to weight ratio, good thermal insulation and termite resistance. These features offer the composite panel a wide range of applications in Australian construction industry as structural elements such as beams, slabs, bridge decks and railway sleepers. While sandwich composite construction has some great benefits, the behaviour of sandwich structures containing damage is much more complex and one of the major factors limiting the optimum usage of the same. Although perfect bond between the skin and the core is a common assumption, an important issue that needs to be considered in using a composite beam or slab is the development of debonding between the skin and the core, which is a predominant damage mode of these sandwiches. Interlayer debonding or delamination is also a predominant form of damage phenomenon in laminated composites, which can often be pre-existing or can take place under service conditions. Debonding and delamination cause significant changes in the vibration parameters, such as natural frequencies and mode shapes of structures leading to serviceability issues related to deflection limits. During the design stages of FRP composite structures, it is vital to identify how the global response of these structures will be affected by skin-core debonding and interlayer delamination. Even though the dynamic behaviour of undamaged sandwich panels is the subject of extensive research, papers reported on the dynamic behaviour of sandwich panels with debonding are less presented in the literature. Specifically, knowledge on seismic behaviour of composites with debonds is severely limited. Further research is therefore needed into investigation of the dynamic behaviour of debonded composite structural elements to gain wider acceptance of composites by the structural composite field around the globe. Finite element method is particularly versatile and effective in the analysis of complex structural behaviour of the composite structures. The use of dynamic analysis methods helps the engineer to better understand the behaviour of a structure subjected to an earthquake. This research deals with the investigation of the influence of debonding on the dynamic characteristics of novel GFRP beams and plates by finite element based numerical simulations and analyses using STRAND7 finite element (FE) software package. The research approach is to develop a three dimensional computer model and conduct numerical simulations to assess the dynamic behaviour. The FE model developed has been validated with published experimental, analytical and numerical results for fully bonded as well as debonded beams and slabs. Dynamic seismic response investigation of structures containing GFRP slab panels with debonds subjected to a probable earthquake loading is also incorporated. The influence of various factors such as debonding size, location of debonding, boundary condition of the structural member and the effect of multiple debonding has been delineated with the aid of an extensive parametric investigation and comparative analyses. Generally it was evident from all the analyses that debonding and interlayer delamination cause reduction in magnitudes of natural frequency. Moreover, some vibration modes and accordingly the mode shapes are also noticeably changed. It is generally observed that higher natural frequencies and mode shapes are more influenced by the presence of debonding. Yet there are exceptions to this trend depending on how severely the local modes are affected by debonding. It is observed that the associated mode shapes explain the causes of these inconsistencies. Furthermore, the results show that the presence of relatively small debonding or delamination has an insignificant effect on the natural frequencies and associated mode shapes. The results also suggest that fastening the delamination region is an effective corrective measure in decreasing the natural frequency variation, hence improving its dynamic performance compared to the delaminated panel. To sum up, the results suggest that debonding and delamination predominantly leads to reduction of the natural frequencies and modifying the modes of vibrations thus altering the mode shapes as well, resulting in dramatic changes in dynamic characteristics when extents of debonding are large. The more the supports are restrained, the greater the influence on free vibration characteristics. Most importantly, the findings demonstrate the feasibility of non-destructive methods to detect debonding and delamination damage in practical composite structures. The results of the seismic study show that the seismic performance of the considered buildings is unresponsive to small percentages of debonding of the GFRP slab panels. An existence of extensive percentage of debonding causes a slight increase in the maximum vertical displacement and reduction of natural frequencies of the buildings due to loss of stiffness occurring due to debonding. The results of this study will offer engineers and designers a better understanding of the influence of debonding and delamination on the dynamic performance of FRP composites in general, in addition to its direct application to Australian composite industry. Finally, the study provides valuable insights into the seismic behaviour of composite slabs with debonding thus facilitating the actual application of these findings in worldwide composite industry

Traumatic deep vein thrombosis in a soccer player: A case study

A 42 year-old male former semi-professional soccer player sustained a right lower extremity popliteal contusion during a soccer game. He was clinically diagnosed with a possible traumatic deep vein thrombosis (DVT), and sent for confirmatory tests. A duplex doppler ultrasound was positive for DVT, and the patient was admitted to hospital for anticoagulation (unfractionated heparin, warfarin). Upon discharge from hospital the patient continued oral warfarin anticoagulation (six months), and the use of compression stockings (nine months). He followed up with his family doctor at regular intervals for serial coagulation measurements, and ultrasound examinations. The patient's only identified major thrombotic risk factor was the traumatic injury. One year after the initial deep vein thrombosis (DVT) the patient returned to contact sport, however he continued to have intermittent symptoms of right lower leg pain and right knee effusion. Athletes can develop vascular injuries in a variety of contact and non-contact sports. Trauma is one of the most common causes of lower extremity deep vein thrombosis (DVT), however athletic injuries involving lower extremity traumatic DVT are seldom reported. This diagnosis and the associated risk factors must be considered during the initial physical examination. The primary method of radiological diagnosis of lower extremity DVT is a complete bilateral duplex sonography, which can be augmented by other methods such as evidence-based risk factor analysis. Antithrombotic medication is the current standard of treatment for DVT. Acute thrombolytic treatment has demonstrated an improved therapeutic efficacy, and a decrease in post-DVT symptoms. There is a lack of scientific literature concerning the return to sport protocol following a DVT event. Athletic individuals who desire to return to sport after a DVT need to be fully informed about their treatment and risk of reoccurrence, so that appropriate decisions can be made

The role of secreted aspartyl proteinases in Candida tropicalis invasion and damage of oral mucosa

Candida virulence attributes include the ability to colonize and invade host tissues, and the secretion of hydrolytic enzymes. Although Candida albicans is regarded as the principal fungi causing infections in humans, other species, particularly Candida tropicalis, are increasingly being recognized as human pathogens. Relatively little is known, however, about the virulence attributes associated with C. tropicalis. The present study aimed to investigate epithelial infection by C. tropicalis using a reconstituted human oral epithelium (RHOE) together with confocal laser scanning microscopy and real-time PCR. A comparison of clinical strains was made in terms of tissue colonization, invasion and C. tropicalis secreted aspartyl proteinase (SAPT) gene expression. All C. tropicalis strains were able to colonize RHOE in a strain-dependent manner. After 12 h of infection, C. tropicalis was found to be highly invasive, with extensive tissue damage occurring after 24 h. Real-time PCR of C. tropicalis SAPT1-4 genes showed that expression was strain-dependent, with SAPT2-4 transcripts being frequently detected and SAPT1 rarely detected. Tissue invasion and damage was not inhibited by the presence of pepstatin A. Accordingly, and given that an increase in infection time was not accompanied with an increase in SAPT gene expression, it can be suggested that the proteinases are not involved in invasion and damage of RHOE by C. tropicalis. In summary, C. tropicalis can be considered as highly invasive with the ability to induce significant tissue damage. These features, however, do not appear to be related to specific SAPT gene expression.We would like to thank Mrs Kath Allsopp for processing and sectioning the tissue samples. This work was supported by grant SFRH/BD/28341/2006 from 'Fundacao para a Ciencia e Tecnologia' (FCT), Portugal

Impact of brief exposure to antifungal agents on the post-antifungal effect and hemolysin activity of oral Candida albicans

AbstractPost-antifungal effect (PAFE) of Candida and its production of hemolysin are determinants of candidal pathogenicity. Candida albicans is the foremost aetiological agent of oral candidosis, which can be treated with polyene, azole, and echinocandin antifungals. However, once administered, the intraoral concentrations of these drugs tend to be subtherapeutic and transient due to the diluent effect of saliva and cleansing effect of the oral musculature. Hence, intra-orally, Candidamay undergo a brief exposure to antifungal drugs.Objective Therefore, the PAFE and hemolysin production of oral C. albicans isolates following brief exposure to sublethal concentrations of the foregoing antifungals were evaluated.Material and Methods A total of 50 C. albicans oral isolates obtained from smokers, diabetics, asthmatics using steroid inhalers, partial denture wearers and healthy individuals were exposed to sublethal concentrations of nystatin, amphotericin B, caspofungin, ketoconazole and fluconazole for 60 min. Thereafter, the drugs were removed and the PAFE and hemolysin production were determined by previously described turbidometric and plate assays, respectively.Results Nystatin, amphotericin B, caspofungin and ketoconazole induced mean PAFE (hours) of 2.2, 2.18, 2.2 and 0.62, respectively. Fluconazole failed to produce a PAFE. Hemolysin production of these isolates was suppressed with a percentage reduction of 12.27, 13.47, 13.33, 8.53 and 4.93 following exposure to nystatin, amphotericin B, caspofungin, ketoconazole and fluconazole, respectively.Conclusions Brief exposure to sublethal concentrations of antifungal drugs appears to exert an antifungal effect by interfering with the growth as well as hemolysin production of C. albicans