NEUROTOXICOLOGICAL EFFECTS OF CHLORPYRIFOS AND DELTAMETHRIN ON DOPAMINE AND ACETYLCHOLINE SYSTEMS IN DROSOPHILA MELANOGASTER

Emerging evidence suggests a positive association between pesticide exposure and sporadic Parkinson\u27s disease (PD) development. The molecular mechanisms of PD and other neurodegenerative diseases are not fully understood, which hinders the development of therapeutic agents to cure or prevent the development of such diseases. Drosophila has been widely used as a model organism to study various neurodegenerative diseases and to screen for promising therapeutic agents. The aims of this study were: (i) investigating the toxic effect of 24 hours exposure to chlorpyrifos (CPF) and deltamethrin (DLM) on the dopaminergic system and AChE activity in Drosophila melanogaster; (ii) comparing different methodologies to test negative geotaxis behavior in D. melanogaster; and (iii) investigating the combined neuroprotective effects of ferulic acid (FA), and Thymoquinone (TQ) natural compounds on DLM induced neurotoxicity. Adult male wild-type flies were exposed to either CPF, DLM, for 24 hours, or concomitantly exposed to DLM and individual neuroprotective agents, or their mix for 72 hours in 10% sucrose on a cotton swab. CPF/DLM-treated flies climbed shorter distances in the negative geotaxis assay as well as had a higher incidence of mortality when compared to the control group. Evidently, CPF/DLM exposure caused a disturbance in the expression of DA-related genes. The DLM exposure for 72 hours caused a higher incidence of mortality and severe locomotor defects. Co-treatment with neuroprotective agents offered protection against these toxic effects of DLM after 72 hours. DLM caused significant inhibition of AChE which was ameliorated with the concomitant exposure with FA. Our results suggest that FA and TQ were effective in reducing the toxicity induced by DLM in D. melanogaster as well as confirm the utility of this model to investigate potential therapeutic strategies on movement disorders, including PD. The present study indicates that a single molecule can interact and affect multiple systems that are not related to their main mechanism of action. Data gathered in the present study may be important for the assessment of the safety of insecticides that humans are at risk of daily exposure to them. Moreover, this study presents a potential natural compound that can ameliorate and protect against the neurotoxicity that is caused by these insecticides

Effects of Deicing Salts on the Durability of Concrete Incorporating Supplementary Cementitious Materials

Structural Engineering and Materials Laboratory of the University of Kansa

Accounting regulation in Nigeria : institutionalisation, accounting quality effects and capital market effects

This study examines three different aspects of accounting regulation in Nigeria. The first empirical chapter (chapter 2) examines the process of the institutionalisation of IFRS in Nigeria and its outcome. Using data from documents, interviews and survey, the chapter finds that IFRS is substantively adopted by Nigerian listed firms, as they use it for internal reporting. Furthermore, the institutionalisation process involves three levels of social order (i.e., Social, political and economic level; organisational field; and organisational level) at which different agents reinforce one another to ensure that institutionalisation of IFRS in Nigeria is substantive. The second empirical chapter examines whether accounting regulation in the form of IFRS adoption and/or enforcement of accounting standards lead(s) to higher accounting quality. The effects of these two regulatory mechanisms were assessed on three dimensions of accounting quality using fixed-effect regressions for earnings management, binary logistic regression for timely loss recognition, and a system dynamic panel model for earnings persistence on a sample of non-financial companies listed on the Nigerian Stock Exchange. The chapter finds that IFRS adoption significantly increases earnings management and reduces earnings persistence, while institutional reform, through the setting up of the Financial Reporting Council of Nigeria (FRCN) to enforce and monitor compliance with accounting standards, reduces earnings management. The third empirical chapter examines the effect of accounting regulation in the form of IFRS adoption and enforcement on market liquidity in Nigeria. The chapter adopts a longitudinal research design and analyses hand-collected panel data sets from semi-structured archives. Three proxies of market liquidity (i.e., bid-ask spread, zero returns, and volume) were adopted for the study. Firm-quarter observations of 1,416, 1,417 and 1,418 were analysed using a random-effect model for bid-ask-spread and a fixed-effect regression for both zero returns and volume, respectively. The chapter finds that both IFRS adoption and enforcement significantly improve the Nigerian stock market liquidity.School of Social Sciences PhD scholarshi

Do information asymmetry proxies measure information asymmetry?

Market microstructure based proxies for information asymmetry have been widely used for over two decades. However, their empirical validation is surprisingly scarce. We attempt to address this gap by empirically testing two of the more popular proxies, namely, Glosten and Harris (1988) adverse selection cost component of the bid-ask spread (lambda), and Easley, Hvidkjaer, and O’Hara (2002) probability of informed trading (PIN). We estimate these proxies across three portfolios: broad-based ETFs, sector ETFs, and common stocks. Arguably, information asymmetry about broad-based ETFs should be primarily related to market wide information asymmetry, while information asymmetry about stocks should be mostly related to firm characteristics. We find that while PIN is highest for the broad-based portfolio and lowest for the stock portfolio, lambda is highest for the stock portfolio and lowest for the broad-based portfolio. To the extent that information asymmetry about stocks should be greater than information asymmetry about systematic factors, we provide evidence in support of lambda as a measure of information asymmetry. PIN is more closely related to liquidity

Resisting institutionalized corruption: The case of public audit in Nigeria

In a highly corrupt environment such as Nigeria, accounting practices have been permeated by corruption in the wider society. As such, several studies on the relationship between accounting and corruption have unveiled a symbiotic association between accountants and corruption. Contrary to this popular viewpoint, this study shows that there are instances of resistance to corruption by accountants in such environments. This study adopts a multiple case study approach. We used two case studies to demonstrate the consistency of the Auditors-General for the Federation (AuGFs) in resisting institutionalized corruption and one case study to show that AuGFs’ resistance is not commonplace in Nigeria. Data were gathered from interviews, videos, and documents. We found that AuGFs resist corruption through the disclosure of accounting irregularities in their audit reports despite the severe consequences associated with exposing corrupt practices in Nigeria. However, they hide this resistance through a number of strategies to sustain the resistance and avert possible repercussions of corruption disclosure. Prior studies of accounting and corruption in developing countries often find accountants enabling corrupt practices through their silence or through active participation in such practices. However, this study shows how accountants also resist corruption in a highly corrupt developing country, which is rare in the literature

Design and distortion analysis of fully integrated image reject RF CMOS frontends

This thesis presents the design and experimental results of a 7.3GHz notch image reject filter, combined with a 5.8GHz low-noise amplifier (LNA), for integrated heterodyne receiver front-ends. A new image reject filter implementation is proposed. Q-enhancement circuitry for on-chip inductors are used to optimize the depth of image rejection. Experimental results show that more than 62dB of image rejection at 7.3GHz can be obtained in a standard CMOS 0.18mum technology, while operating from a 1.8V supply. The LNA exhibits a gain of 15.8dB and an IIP3 of -5.3dBm while consuming 9mW of power. With maximum image rejection, the LNA-notch combination circuit achieves a 4.1dB noise figure at 5.8GHz. The proposed notch filter alone can operate from a 1V supply voltage. It is shown analytically how circuit stability can be ensured.The implementation of new robust and stable high-Q CMOS image reject filters, which enables the realization of fully integrated heterodyne 5GHz RF receivers is also presented. A cascade of two notch filters with their image reject frequencies slightly offsetted is proposed, in order to obtain a wide image rejection bandwidth, without having to resort to the overhead of automatic tuning circuitry. Thus, power consumption, area, and complexity are significantly reduced. Experimental results show that more than 30d$ of image rejection can be obtained in a standard 0.18mum CMOS technology, over a 400MHz bandwidth centered at 7.4GHz

EFFECTS OF DEICING SALTS ON THE DURABILITY OF CONCRETE INCORPORATING SUPPLEMENTARY CEMENTITIOUS MATERIALS

The durability of concrete mixtures incorporating one of two supplementary cementitious materials (SCMs), slag cement or Class C fly ash, exposed to sodium chloride (NaCl), calcium chloride (CaCl2), or magnesium chloride (MgCl2) is evaluated based on damage due to wetting and drying and scaling, with the goal of determining appropriate replacement levels of portland cement using these SCMs. The mixtures had water-to-cementitious material ratios of 0.38 and 0.44 and SCM percentage replacements of portland cement of 0%, 20%, 35%, and 50% by volume. Fourteen concrete mixtures (204 specimens) were cast to evaluate the damage to concrete subjected to 300 cycles of wetting and drying while exposed to solutions of one of the three deicing salts or deionized water in which the temperature of the specimens ranged from 39.2 ºF (4 ºC) during the wetting cycle to 73 ± 3 ºF (23 ± 2 ºC) during the drying cycle. Of special interest were the effects of CaCl2 and MgCl2, which result in the formation of calcium oxychloride. Durability was evaluated based on the average relative dynamic modulus of elasticity and the nature of physical damage, if any. Mixtures subjected to CaCl2 or MgCl2 that exhibit no spalling at test completion are considered to be durable. Ten concrete mixtures (156 specimens) were cast with curing periods of 14 or 28 days to investigate scaling over 56 cycles in accordance with Quebec test BNQ NQ 2621-900 using NaCl or CaCl2. Mixtures are considered durable if the average cumulative mass losses are less than the BNQ NQ 2621-900 failure limit of 0.10 lb/ft2. The results show that wetting and drying with deionized water or an NaCl solution does not cause deterioration of concrete. Exposure to CaCl2 and MgCl2, however, both of which result in the formation of calcium oxychloride, causes physical damage and a reduction in the dynamic modulus of concrete with portland cement as the only binder, with CaCl2 being the more deleterious of the two. A partial replacement of portland cement with either slag cement or Class C fly ash is effective in producing durable concrete exposed to CaCl2 or MgCl2. Using a 20% replacement of portland cement with an SCM, however, is not sufficient to produce durable concrete under conditions that result in the formation of calcium oxychloride, while replacing 35% or 50% of the portland cement with one of the SCMs used in this study is. The results, also, show that using slag cement or Class C fly ash as a replacement of portland cement results in an increase in scaling compared to concrete with portland cement as the only binder. For mixtures with portland cement as the only binder and with a 20% slag cement replacement of portland cement, CaCl2 causes somewhat more scaling than NaCl. For mixtures with a replacement percentage using either SCM of 35%, NaCl causes more scaling than CaCl2. In all cases, however, the scaling mass losses for mixtures with 35% SCM replacements of portland cement were below the BNQ NQ 2621-900 failure limit. At 50% volume replacements, the increase in scaling is noticeably higher than with 20% and 35% replacements, especially for mixtures exposed to NaCl. The mass losses for mixtures with a 50% SCM replacement of portland cement exposed to NaCl exceeded the BNQ NQ 2621-900 failure limit. Extending the curing period from 14 to 28 days has no measurable effect on the scaling for most concrete mixtures in the study. Based on the findings of the wetting and drying and scaling tests, a partial replacement of portland cement with either slag cement or Class C fly ash is essential to produce durable concrete that will be subjected to the deicing salts CaCl2 or MgCl2 that cause the formation of calcium oxychloride. Using a 20% volume replacement of portland cement is not adequate, while a 35% volume replacement is. Replacement percentages above 35%, however, are not recommended when the deicing salt NaCl may be used because of increasingly poor scaling resistance with increasing slag cement and Class C fly ash replacement levels

Cyclic Instability Behaviour of Sand-Silt Mixture Under Partial Cyclic Reversal Loading

Flow liquefaction is one of the most catastrophic failure phenomena in geotechnical engineering. It is a form of instability and can be observed during monotonic loading or cyclic loading. It is referred to as static instability/liquefaction for monotonic loading and cyclic instability for cyclic loading. To investigate the link between these behaviours, a number of stress controlled cyclic triaxial tests were carried out on loose sand-silt mixture under cyclic ‘reversal’ and ‘non-reversal’ loading condition. Cyclic reversal loading was partial reversal. Its peak-trough magnitudes were chosen in such a way that cyclic instability was triggered in compression side of the stress space. Thus it gives an opportunity to compare cyclic instability (both for partial ‘reversal’ and ‘non-reversal’) with static instability observed in monotonic loading condition. The test condition covers a range of initial mean effective confining stresses and void ratio. The equivalent granular state parameter was used to synthesize the test results irrespective of fines contents. Test results showed that cyclic instability was governed by the stress ratio at static instability for the same equivalent granular state parameter irrespective of fines contents. Thus, equivalent granular state parameter can be used as a predictor of cyclic instability for cyclic ‘reversal’ and ‘non-reversal’ loading if cyclic instability is triggered in compression side of the stress space