Clonal integration in Ochthochloa compressa under extreme environmental conditions

While multiple studies have indicated the benefit of clonal integration and its role in resisting harsh environmental conditions, many researchers have indicated the need for further studies to understand fully the role of clonal integration and what determines the optimal strategies in various environments. In this project a series of studies were carried out in an extremely arid area (Al Thumam area in the Arabian Peninsula) to contribute to the knowledge of the benefits of clonal integration and understanding the behaviour of the clonal grass Ochthochloa compressa. This study is unique because it has investigated the benefits of clonality in one of the harshest environments where clonal plants are found. Experiment 1. I aimed to understand the patterns of spread and expansion of stolons, particularly whether stolons grew in random directions or are directed to better patches by the mother ramets to establish new daughter ramets maximizing their chances of success. I measured nutrient contents (N, P and K) in patches where mother plants grew, and where daughter ramets had established. In addition, I sampled nearby unoccupied patches. Mother plants were found in patches with higher N concentrations than where the daughter ramets were found. There were no differences in concentration of P; while K was the lowest where not fully rooted daughters were found. The results suggest that daughter ramets did not establish in the best areas, indicating that the spread and expansion of stolons in the O. compressa occurs randomly. Experiment 2. I investigated the effects of the addition of fertilizer to mother and daughter ramets, including addition of nutrients to daughters disconnected from the mother ramets. Cutting the stolons caused to death of the daughter because these ramets were still dependent on the mother ramets. When connected, mothers that received nutrients affected some transference nutrients to daughter ramets. In contrast, the daughters accumulated the nutrients in above ground tissue when receiving added fertilizer, and there was no sign of transference to the mother ramet. Nutrient addition did not affect in any case the efficiency photosynthetic in both mother and daughter ramets. Experiment 3. In this experiment, I focused on the effect of the distance between mother and daughter ramets on the performance of daughter ramets. Daughters located close to the mother ramets could suffer competition by the mother if they are within the area of the root system. The results showed no significant differences between mother and daughter ramets in the concentration of nitrogen, phosphorus, and potassium nor in photosynthetic activity. This indicates that the daughters have the ability to resist competition through continued support from their mothers despite the scarcity of resources and the harsh environmental conditions in the study area. Experiment 4. In this experiment, I studied the effect of simulated grazing on both mother and daughter ramets when one of them was clipped and 50-60% of the leaves were removed, while remaining connected. Clipping did not affect the N content of mother ramets, but the concentration of phosphorus was decreased by clipping. K was lower in mother ramets connected to clipped daughters. Daughters connected to clipped mothers had higher N concentration but K and P did not change. Clipping of daughters did not have any effect on mother ramets concentration of nutrients. Photosynthetic efficiency did not record any significant differences when ramets were clipped. The results indicate that O. compressa strategy to resist grazing consists mainly in continuing to support daughter ramets. As far as I know, this is the first study of the phenomenon of clonal integration for O. compressa. This study revealed the importance of clonal integration for O. compressa to resistance of the harsh environmental conditions. Under the harsh conditions these plants live, the preferred strategy seems to be for the mother ramets to expand by producing ramets in random sites and heavily subsidize their growth with nutrient, and almost certainly water. Indeed, I documented strong evidence of transfer of nutrients through the stolons from mother ramets to daughter ramets but no evidence of transfer in the other direction even when nutrients were supplied to daughters. Further, seemingly surplus N available to the mother when clipping limited their foliar tissues was directed to daughters rather than to re-sprouting (which was probably limited by water availability). The insights obtained on the biology of O. compressa are critical as it is a native plant in a harsh environment, and it is suitable for fodder for pastoral animals, as well as having potential for restoration of degraded areas. Further, it provides new insights into the phenomenon of clonal integration in harsh habitats, and area which still needs further study and research.Thesis (Ph.D.) -- University of Adelaide, School of Biological Sciences, 201

Maritime boundary delimitation of the kingdom of Saudi Arabia a study in political geography

Saudi Arabia was the first Arab country to claim offshore jurisdiction and the first Middle Eastern state to define its offshore waters. This study examines the principal geographical factors which have resulted in the present Saudi maritime boundary. The semi-enclosed sea, islands, reefs, natural resources of the continental shelf, exclusive economic zone and coastline, can all be considered principal geographical factors that have influenced Saudi territorial waters policy. Islands, for example, play an effective role in increasing the area of Saudi internal waters, increasing the breadth of the territorial sea, straight baseline and the delimitation of maritime boundary in the Red Sea and the Arabian Gulf with opposite and adjacent states. Natural resources demanded the swift implementation of unique agreements, used later as an example worldwide. The author has drawn the 1958 Saudi straight baseline and a theoretical straight baseline based on the 1982 Convention and states practice. The territorial sea which is drawn on this basis along the Red Sea and the Arabian Gulf coasts, is affected by the presence of islands and reefs. The Saudi Exclusive Fishing Zone claimed by the 1974 decree gave the Kingdom the same right as the 1982 Exclusive Economic Zone (EEZ), but the Kingdom had to adapt the latter in order to gain more control over its resources and non-mineral activities. The importance of the 1949 Saudi decree can be found in the contribution made by Saudi Arabia to the development of the law of the sea, and to safeguarding the national hydrocarbon resources (natural gas and oil) on and below its seabed. Saudi Arabia engaged in several agreements, mainly in the Gulf, in order to define its boundary. This study has highlighted these agreements as a model which can be used in different parts of the world to solve similar disputes, and can be adopted as methods of maritime delimitation between opposite and adjacent states. The importance of the economic factor has been shown, along with security, as the main factor influencing the successful conclusion of such agreements, but where there is no such importance, the boundary may become less significant and by the absence of such motivation the boundary may not be defined. Saudi waters are a rich and highly important maritime area. This is based on the facts that Saudi Arabia has 30 per cent of the world seawater desalination plants; that the sea represents food, fuel and wealth to Saudi Arabia; and that the existence of huge deserts emphasises the importance of the sea

The Bioactivity and Photocatalytic Properties of Titania Nanotube Coatings Produced with the Use of the Low-Potential Anodization of Ti6Al4V Alloy Surface

Titania nanotube (TNT) coatings were produced using low-potential anodic oxidation of Ti6Al4V substrates in the potential range 3–20 V. They were analysed by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The wettability was estimated by measuring the contact angle when applying water droplets. The bioactivity of the TNT coatings was established on the basis of the biointegration assay (L929 murine fibroblasts adhesion and proliferation) and antibacterial tests against Staphylococcus aureus (ATCC 29213). The photocatalytic efficiency of the TNT films was studied by the degradation of methylene blue under UV irradiation. Among the studied coatings, the TiO2 nanotubes obtained with the use of 5 V potential (TNT5) were found to be the most appropriate for medical applications. The TNT5 sample possessed antibiofilm properties without enriching it by additional antimicrobial agent. Furthermore, it was characterized by optimal biocompatibility, performing better than pure Ti6Al4V alloy. Moreover, the same sample was the most photocatalytically active and exhibited the potential for the sterilization of implants with the use of UV light and for other environmental applications

Corrosion inhibition of copper in chloride media by 2-mercapto-4-(p-methoxyphenyl)-6-oxo-1,6-dihydropyrimidine-5-carbonitrile: Electrochemical and theoretical study

AbstractElectrochemical frequency modulation (EFM), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization have been used to investigate the inhibition effect of a new pyrimidine heterocyclic derivative, namely 2-mercapto-4-(p-methoxyphenyl)-6-oxo-1,6-dihydropyrimidine-5-carbonitrile (MPD) on copper corrosion in 3.5% NaCl solutions at 25±1°C. The electrochemical investigations showed that MPD gives sufficient inhibition against copper corrosion in 3.5% NaCl solutions. Potentiodynamic polarization measurements have shown that the MPD inhibit both the cathodic and anodic processes and thus it classified as mixed-type inhibitor. EIS measurements indicate that the values of constant phase elements (CPEs) tend to decrease and both charge-transfer resistance and inhibition efficiency tend to increase by increasing the inhibitor concentration. Electrochemical kinetic parameters obtained using EFM methods were comparable with that calculated from traditional measurements (EIS and potentiodynamic polarization). Molecular simulation technique was used to investigate the adsorption configuration of MPD on copper surface. Number of electrons transferred from MPD to the copper surface was calculated by semi-empirical quantum chemical calculations

Effect of DLC Coating on Tribological Behavior of Cylinder Liner-piston Ring Material Combination When Lubricated with Jatropha Oil

AbstractThe expansion of modern engines would have been unfeasible without advanced lubricant chemistry and proper lubricant formulation. Introduction of diamond like carbon (DLC) coatings opens further possibilities in improving performance of engine and transmission components, which cannot longer be achieved only by lubricant design.DLC coatings show extremely good promise for a number of applications in automotive components as they exhibit excellent tribological properties. In this paper, the tribological performance of hydrogenated amorphous carbon (a-C: H)DLC coating with Jatropha oil was evaluated using a four ball Tribometer also with commercial synthetic lubrication oil (SAE 40) used as base lubricant. Experimental results demonstrated that the hydrogenated amorphous carbon (a-C: H)DLC coating exhibited better performance with Jatropha oil in terms of wear and friction under similar operating conditions compared to the uncoated stainless. Thus, usage of hydrogenated amorphous carbon (a-C: H)DLC coating with Jatropha oil in the long run may have a positive impact on engine life

Interference Mitigation Using Uplink Power Control in 5G Relay-Based Heterogeneous Networks

Heterogeneous network (HetNet) is an attractive solution for future cellular networks with high data rate and coverage requirements. In HetNets, small cells such as micro cells, pico cells, femto cells and relay node (RN) are added to the network of macro cells in the same region. A large number of low power RNs produces new cell edges with significant intra-cell and inter-cell interferences. In the uplink (UL) scenarios of time-division based HetNets with RN, the user equipment (UE) desired signal may be interfered by the transmissions of the co-channel UEs during the first time slot and by the transmissions of the co-channel UEs or RNs during the second time slot. The interference caused by the RNs may significantly degrade the UE signal. UL transmission power control (PC) is essential for mitigating interference and, as a result, enhancing the cell edge and overall system performance. This research proposes a PC algorithm in order to mitigate the UL interference in 5g relay-based HetNets. This research also investigates the UL performance of HetNets when PC is applied at the RNs. Simulation results indicate that UL PC at the RNs greatly reduces average interference and improves average UL signal-to-interference-plus-noise ratio (SINR) and average UL end-to-end throughput compared to the situation in which UL PC is not implemente

Incidence of COVID-19 among returning travelers in quarantine facilities: A longitudinal study and lessons learned

This article is made available for unrestricted research re-use and secondary analysis in any form or be any means with acknowledgement of the original source. These permissions are granted for the duration of the World Health Organization (WHO) declaration of COVID-19 as a global pandemic.Introduction: The emergence of the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) had resulted in an unpresented global pandemic. In the initial events, the Kingdom of Saudi Arabia implemented mandatory quarantine of returning travelers in order to contain COVID-19 cases. Materials and methods: This is a longitudinal study of the arriving travelers to Quarantine facilities and the prevalence of positive SARS-CoV-2 as detected by RT-PCR. Results: During the study period, there was a total of 1928 returning travelers with 1273 (66%) males. The age range was 28 days–69 years. Of all the travelers, 23 (1.2%) tested positive for SARS-CoV-2. Of the first swab, 14/1928 (0.7%) tested positive. The positivity rate was 0.63% and 0.92% among males and females, respectively (P = 0.57). The second swab was positive in 9 (0.5%) of the other 1914 who were initially negative with a positivity rate of 0.39% and 0.62% among males and females, respectively (P = 0.49). There was no statistical difference in the positivity rates between first and second swab (P = 0.4). Of all travelers, 40 (n = 26, 1.3%) were admitted from the quarantine facility to the hospital due to COVID-19 related positive results or development of symptoms such as fever, cough, and respiratory symptoms; and 14 (0.7%) were admitted due to non-COVID-19 related illness. Conclusion: This study showed the efforts put for facility quarantine and that such activity yielded a lower incidence of positive cases. There was a need to have a backup healthcare facility to accommodate those developing a medical need for evaluation and admission for non-COVID-19 related illnesses

Bond strength of adhesive luting agents to caries-affected dentin

Introduction: The aim of this study was to evaluate the bond strength of adhesive luting agents to caries-affected dentin (CAD). Methods: Forty human molars were sectioned to create dental slices presenting exposed occlusal dentin. Half of the samples were submitted to eight caries-induction demineralizing/mineralizing cycles. The pH-cycling model consisted of three hours in a demineralizing solution followed by 45 hours of immersion in a mineralizing solution. Dentin hardness was measured before and after the pH cycling. Resin cement cylinders were built up over the dentin surface using RelyX Unicem or RelyX ARC/Scotchbond Multipurpose Plus. The cement cylinders were submitted to shear load, and the data were analyzed using two-way analysis of variance (ANOVA) and Tukey test (p<0.05). Hardness data were also submitted to two-way ANOVA and Tukey test (p<0.05). The relationship of hardness vs bond strength was assessed via nonlinear regression analysis. Results: Sound dentin (tested and used in caries induction) showed similar values of hardness and were superior to CAD. Both resin cements showed higher bond strength to sound dentin than to CAD. Independent of substrate, RelyX ARC showed the highest values of bond strength. A positive linear relationship between dentin hardness and bond strength was observed for both cements evaluated. Conclusions: The adhesive luting agents evaluated showed lower bond strength to CAD