Experimental and numerical analysis of conventional and ultrasonically-assisted cutting of bone

Bone cutting is widely used in orthopaedic, dental and neuro surgeries and is a technically demanding surgical procedure. Novel surgical methods are continually introduced in orthopaedic, neuro and dental surgeries and are aimed at minimising the invasiveness of the operation and allowing more precise cuts. One such method that utilises cutting with superimposed ultrasonic vibration is known as ultrasonically- assisted cutting (UAC). The main concern in bone cutting is the mechanical and thermal damage to the bone tissue induced by high-speed power tools. Recent technological improvements are concerned with the efforts to decrease the force required by the surgeon when cutting the bone as well as increases in surgery speed. A programme of experiments was conducted to characterise properties of a bone and get a basic understanding of the mechanics of bone cutting. The experiments included: (a) nanonindentation and tension tests to obtain the properties for the finite element (FE) bone cutting model, (b) high-speed filming to observe the chip formation process, which influences thermomechanics of the cutting process in conventional drilling (CD) and ultrasonically-assisted drilling (UAD) and, (c) plane cutting and drilling experiments to measure the levels of force and temperature rise in the bone tissue. Novel two-dimensional finite element (FE) models of cortical bone cutting were developed for conventional and ultrasonically-assisted modes with the MSC.MARC general FE code that provided thorough numerical analysis of thermomechanics of the cutting process. Mechanical properties such as the elastic modulus and strain-rate sensitivity of the bone material were determined experimentally and incorporated into the FE models. The influence of cutting parameters on the levels of stress, penetration force and temperature in the bone material was studied using conventional cutting (CC) and ultrasonically-assisted cutting (UAC). The temperature rise in the bone material near the cutting edge was calculated and the effect of cutting parameters on the level of thermal necrosis was analysed. The necrosis depth in bone was calculated as a distance from the cut surface to the point where the thermal threshold level was attained. Comparative studies were performed for the developed FE models of CC and UAC of bone and the results validated by conducting experiments and using data from scientific publications. The main outcome of the thesis is an in-depth understanding of the bone cutting process, and of its possible application in orthopaedics. Recommendations on further research developments are also suggested

Impacts of ocean acidification and other (global change) stressors on marine invertebrates

The hypervariable nearshore marine ecosystem is home to intrinsic stressors for marine organisms. Global climate change and human activity are already affecting this aquatic environment and are expected to intensify over the next decades. These diverse changes include a rise in global temperature and a decrease in ocean pH. More carbon dioxide dissolves in the sea, lowers the pH, and makes the ocean more acidic. Now the main scientific challenge is to understand and predict the response of marine life to the predicted environmental change in the ecosystem. These challenges include a better understanding of the marine life’s response to changes in distribution and tribute to evolutionary changes or extinction. Species can respond to global change in a variety of ways. They can move from the environment of tolerance zone to newly available zones, can extend tolerance by summarizing and/or modifying their physiology or behaviour, and can demonstrate that the range shrinks when the environment of certain variable environmental factors is exceeded. Most marine species can respond to transformations, including behavioural or generational genetic selections that can improve perception, individual morphology, physiology, and/or performance in changing environmental conditions when undergoing periodic and rapid changes in the environment. Familiarity and adaptability to a changing environment is a type of environmental reaction due to the plasticity of an organism. In this doctoral dissertation, studies have been carried out to understand the potential physiological or biochemical effects of some global change stressors on five important marine and estuarine invertebrates: the anthuroid isopod Cyathura carinata (Krøyer, 1847), the benthic ragworm Hediste diversicolor (O.F. Müller, 1776), the sea snail Tritia neritea (Linnaeus, 1758), the most versatile amphipod Ampelisca brevicornis (Costa, 1853), and the pseudodiaptomid copepod Calanipeda aquaedulcis (Kritschagin, 1873) from the Iberian Peninsula (SW of Spain), because all of these invertebrates have been abundantly occupying and performing dynamic roles in the estuarine food chain for a long time, they have served as a viable food source for avifauna and ichthyofauna in those areas. In Chapter 3 we investigated the physiological or biochemical plasticity of OA in isopod C. carinata, and in Chapter 4 we describe how OA and ocean warming can alter the physiological and biological changes in a ragworm H. diversicolor. The effects of temperature rises and contamination of emerging pollutants such as lithium on the sea snail are discussed in Chapter 5. To determine whether OA includes propagating effects in the ecotoxicological study, the amphipod A. brevicornis is described in Chapter, 6 and finally, whether intragenerational plasticity can offset the negative effects that OA had on the life cycle of the copepod C. aquaedulcis is described in Chapter 7. To determine the tolerance and pH threshold that C. carinata could tolerate in future acidification scenarios, estuarine isopod was exposed to four pH treatments (control: 7.9; 7.5, 7.0, 6.5). Seawater acidification had a significant impact on the longevity of C. carinata, where the population density decreased significantly when treated at the lowest pH. The longevity, survival, and swimming activity of these isopods decreased with decreasing pH. Also, the swimming activity, Na+/K+-ATPase activity, and the RNA:DNA ratio of two populations of C. carinata, one in a stable environment (pH 7.5-8.0) and the other in a variable pCO2 regime (pH 3.3-8.5), were measured to assess the probable metabolic adaptability of this species. Populations in environments with a high pCO2 regime not only showed tolerance to pH 6.5 but had higher life spans and metabolic plasticity compared to habitat populations with little pCO2 conditions. These results indicate that C. carinata populations in stable environments may be susceptible to ocean acidification and can have a detrimental effect on survival and growth. Nevertheless, ocean acidification has limited effects on the energy budget and survival of C. carinata populations in highly variable habitats, indicating that they can cope with the elevated energy demand. Differences between the indicated populations probably indicate genetic differences in resistance to ocean acidification, possibly related to local adaptation, which may provide the raw materials needed to adapt to future conditions. In addition, our results indicate that population changes and metabolic responses should be considered when evaluating the response of marine crustaceans to changes in the global environment. Ragworm H. diversicolor was exposed in the laboratory to multi-stressors effects of elevated temperature and carbon dioxide levels mimicking the future OA and GC and we assess the physiological, behavioral, and biochemical changes in this species. The temperature rise exacerbated the negative effects of OA on the survival of the ragworm, delayed the excavation, and amplified the negative effects of lowering the pH on the feeding behavior of this polychaete. This is the first time this species has been shown to reduce its feeding capacity through the acidification of seawater. Wound healing and blastemal formation were slowed by these two climatic factors, which interfere with the regeneration process of the ragworm. Current results also show that even if polychaetes' metabolic capacity increases under stress conditions, organisms can still increase or maintain their energy reserves. Our results are of great importance for the environment, given that predictive conditions for climate change will affect the life, ecological and physiological capabilities of the species. This can lead to a decrease not only at the individual and population level but also at the diversity of microbes and endofauna, waste disposal in the estuary, and biochemical cycles at the ecosystem level. Therefore, the conservation of the H. diversicolor population is very important for the normal functioning of the estuary ecosystem. Sea snail Tritia neritea was exposed to lithium (Li, 0.08 mM) contamination and the rising seawater temperature (21 °C). We investigated the survival and trophic interactions (foraging behavior, success, search time, carrion preference, feeding time, and tissue consumption) of this intertidal scavenger. Trophic interactions were assessed using a Ymaze design using the same amount of two carrion species (Solen marginatus and Mytilus galloprovincialis) given simultaneously to all snails. Lithium pollution and synergistic warming reduce the survival rate of T. neritea, triggering a scenario for potential global change. Lithium contamination changes foraging behavior and increases the time it takes for snails to reach their carrion. Although T. neritea did not show a preference for the proposed carrion species in the control group, it shifted its foraging behavior to a more energetic carrion when contaminated with Li, which may represent a strategy that compensates for the high energy use required for survival. Results showing changes in the foraging activity of coastal mollusks in a global change scenario indicate potential changes in complex nutritional interactions between marine food pathways. Estuarine amphipod A. brevicornis was examined to study the physiological behavior and biochemical effects of the amphipod under OA. Wild harvested ovigerous females were reared in the laboratory and we started the experiment with 7 days old juveniles in a simulated OA scenario with four different levels of pH for a life cycle. Amphipods were incubated for up to 22 weeks to go through F1 production, successful reproduction, and hatching, and the length of F1 progeny compared to F0. The data obtained show that as the pH value of seawater decreases, mortality increases. The fertility rate reduced to 66.1% at pH 7.5 compared to the control group. The survival rate was higher in F1 juveniles than in F0 juveniles, but growth showed the opposite tendency to F1. These physiological parameters may be related to oxidative stress caused by climate-changing conditions as free radical generation interferes with cellular function, affecting the biochemical and physiological properties of the species, including burrowing, locomotory and ventilatory behaviours. This study is critical to assessing the impact of OA and providing baseline data that can be used as a guide for developing long-term strategies for delivering manageable and sustainable solutions. Copepods are an integral part of the marine food network due to their high biomass production and nutrient turnover compared to other zooplanktons in the marine ecosystem. Despite its enormous ecological role in the oceans, little is known about the effects of OA from increasing planetary carbon dioxide emissions in the future. Little information is available on the impact of OA on European copepod C. aquaedulcis. The purpose of this study was to investigate the impact of OA across multiple generations (F1 and F2) on survival, maturity, and fertility (hatching success, nauplii formation, and total adult population). C. aquaedulcis were exposed to three different pH gradients to simulate future seawater acidification scenarios. The survival rate of the copepod from nauplius to adult was significantly reduced in pH reduction and across generations. Results have also shown to have a marked effect on fertility, represented by a much smaller number of eggs per female in each generation. Similarly, hatching success showed a downward trend towards lower pH, and F1 females had significantly lower hatching success rates than F0 females. The results presented here appear to be ecologically important as the decline in the fertility of these animals can negatively affect marine feeding pathways. This is because the nutrition and growth of ichthyofauna are highly dependent on this component in the food web

Testing equality of scale parameters of two Weibull distributions in the presence of unequal shape parameters

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CONTROLLING INFORMATION LOAD THROUGH PRE-LECTURE ASSIGNMENTS AND STUDENTS’ ACHIEVEMENT IN MATHEMATICS AT SECONDARY LEVEL

Various studies in the past explored a positive correlation between information load and students’ understanding difficulties. In topics where the thought steps exceeded the working memory limit the performance collapsed quite spectacularly. The capacity of this part of the brain is determined genetically fixed. However, the room for efficient use of this part is open largely through experience. In this study pre-learning strategy was practiced to minimize the load on working memory in order to improve students’ understanding in mathematics. To follow the strategy, twenty pre-lectures were developed from year 9 and 10 mathematics textbooks followed by twenty post-tests. A sample of 212 students was taken from two FG schools in Peshawar Cantt. The outcome was focused in terms of understanding rather memorization. No changes were made in the curriculum content, time allocation and the teachers. The results depicted significant improvement in students’ performance in the stipulated topics. The results are consistent with previous studies in very different contexts, which highlighted significant importance of pre-learning practice

Hetroglossia, Language and Identity in Twilight in Delhi

For colonized subjects, the arrival of the colonizer is fraught with socio cultural anxieties. Under the yoke a new regime, the indigenous cultural values and norms are redefined. The new cultural episteme that emerges under the dictates of colonization not only subverts the existing power structures but also redefines the practice of everyday life. In historical terms, it could be seen as dialectical struggle between the colonizer and the colonized. Mikhail Bakhtin, a Russian Formalist critic defines it as a dialogue between the two cultural discourses. In this paper, I have borrowed the theoretical framework from Bakhtin to investigate how Mir Nihal, the protagonist in Twilight in Delhi deals with the introduction of colonial episteme in the public and private spaces of his life in particular and of Indian Muslims in general. It also traces the cultural marginalization at the hands of the colonizer. I call it cultural hetroglossia to pin down the changes that are taking place in the Indian civilizational landscape because of the introduction of English language and manners. Urdu, the cherished language of the Muslim civilization in India is under threat. Mir Nihal tries to protect it at least in the private sphere of life. Dejected in the public sphere, he withdraws to the private. But the cultural onslaught is all encompassing, leaving Mir Niahl marginalized and frustrated. &nbsp

Agent Based Expert System for Online Assessment in Distributed Database Environment with Agent Cloning: A Modification

This paper introduces an alternate architectural framework of an agent based Extended Expert System for Online Assessment (EESOA) in distributed environment for the learners of ODL (Open and Distance Learning) System. The main modification is done in the question collection process by the mobile agent for student assessment form the different interconnected question database servers. Instead of Itinerary Design Pattern (in earlier framework), the Branching Design Pattern is used in this modified framework of EESOA. This necessarily uses the agent cloning process to perform the load balancing while retrieving the question set in the distributed question database environment

Statistical analysis of the effect of machining parameters on fatigue life of aerospace grade aluminum alloy (AL 6082T6)

In this research work, aerospace grade aluminium alloy (Al 6082-T6) was analysed for the effect of cutting parameters on the fatigue life of the machined samples and optimization of cutting parameters for response factor. Different combinations of machining parameters were selected according to the ISO 3685 for sample preparation. Fatigue life of the samples was the response variable under investigation. Specimens for the rotating bending fatigue test were prepared according to the BS ISO 1143:2010 standards. The cutting inserts were selected from Sandvik Coromant catalogue recommended for machining of Al 6082-T6 alloy. A Designed of Experiment (DoE) with full factorial design was employed and a total of 81 experiments were performed for combination of cutting parameters. Fatigue life of the samples was observed to decreases with increasing feed rate, which is attributed to the compressive residual stresses at the surface of the samples. However, fatigue life increased with higher cutting speed and Depth of Cut (DoC)

Evaluation Of Dengue Fever Knowledge Among The General Population And Its Prevalence, Clinical Features In Penang General Hospital

Dengue is one of the most important global public health problem, particularly in South East Asian countries. Despite the presence of the disease in Penang since 1902, no documented evidence existed on the knowledge of dengue among the general population. The current resurgence of the disease necessitates an evaluation of public knowledge, prevalence, clinical features and fluid management of dengue in Penang. In cross-sectional study data were collected from the general population to asses the knowledge. A total of 862 respondents of the population were participated in the study.Majority (97.2%) of the population were familiar with the disease dengue

Urinary tract infection

Over two years, 9892 mid-stream urine samples from patients attending the Aga Khan University Hospital, Karachi were cultured. Significant bacterial growth was seen in 23.5% samples. Further iden­tification of these organisms Eevealed 40% of E.coli, 16% Pseudomonas aeruginosa, 11% Klebsiella aerogenes, 5.0% Enterobacter sp., 13% Protdus sp., 4.0% Serratia liquifaciens, 1.0% Acinetobacter sp., 3.0% Citrobacter sp., 4.0% Enterococci, 0.5% Staphylococcus aureus. Results of sensitivity tests performed with antibiotics Ampicillin, Cotrimoxa.zole, Nitrofurantoin, Nalidixic acid, Gentamicin, Amikacin, Pipemedic acid, Cefotaxime, Azactain and Carbenicillin did not reveal any distinct patter

Behrens-Fisher Analogs for Discrete and Survival Data

Discrete data often exhibit variation greater or smaller than predicted by a simple model. Negative binomial distribution and beta-binomial distribution are popular and widely used to accommodate the extra-Poisson and extra-binomial variations respectively in analyzing discrete data. Weibull distribution is one of the most popular distributions in survival data analysis. Often both discrete and survival data appear in groups and it may be of interest to compare certain characteristics of two groups of such data. The purpose of this dissertation is to deal with Behrens-Fisher analogs for data that follow negative binomial, beta-binomial and Weibull distributions. We first develop six test procedures, namely, LR, LR ( bc ), T 2 , T 2 ( bc ), T 1 and T N , for testing the equality of two negative binomial means assuming unequal dispersion parameters. A simulation study is conducted to compare the performance of the test procedures. Two sets of data are analyzed. For small to moderate sample sizes, the statistic T 1 shows best overall performance. For large sample sizes, all six statistics perform well and are found similar in terms of maintaining size and power. We, then, develop eight test procedures, namely, LR, C ml , C kmm , C qb , C qs , C eq , C rs and C ars , for testing the equality of proportions in two beta-binomial distributions where the dispersion parameters are assumed unknown and unequal. These test procedures are compared through simulation studies and data analysis. The LR test is observed to maintain the nominal level reasonably well accompanied with the best power performance. The next best is the performance of the statistic C eq in terms of nominal level and power. Last but not least, we develop four test procedures, namely, LR, C ml , C cr and C tg , for testing the equality of scale parameters of two Weibull distributions where the shape parameters are unequal and compare these statistics through simulation studies and data analysis. For small sample sizes, the statistics LR and C ml hold nominal level most effectively. The statistic C cr shows highest power although its level is also higher (liberal). For moderate and large sample sizes the overall performance of the statistic LR is found to be superior to others