Essays on fractional cointegration and spurious long memory

This thesis contains four essays on fractional cointegration and spurious long memory following the introduction and related literature in the first chapter. Chapter 2 provides an analysis of fractional integration and cointegration using the high, the low, and the range stock prices instead of closing prices. We analyze the long memory trends across six Asian stock markets including Korea, Indonesia, Malaysia, Sri Lanka, India, and Pakistan. The empirical analysis provide a univariate analysis which includes the unit root tests and estimation of fractional integration in the highs, the lows, and the ranges. Range, being a linear combination of the nonstationary highs and lows, is a stationary long memory process which specifies the need to model these two extreme values and the range simultaneously in a multivariate fractional cointegration context. The fractional vector error correction model fulfills this specification while considering the short-run and long-run relationships. We also perform a forecast comparison of FVECM with alternative models. The autoregressive fractionally integrated and the Heterogeneous autoregressive models are considered to model the long memory in the ranges. Our results support the use of daily ranges as volatility estimator and FVECM to model the long-run convergence and short-run divergence in the highs and lows at the same time. In chapter 3, we analyze the true long memory or spurious long memory in the range based volatilities of spot exchange rates across 30 currencies against the USD including the developed, the developing and the emerging exchange rates. The persistence of exchange rates is of much interest for the central bank, for policymakers, and to understand the inflation dynamics in an economy. The frequency domain analysis exhibits the spurious long memory in most of the currencies due to some low-frequency contaminations, level shifts, or structural changes. We proceed with the estimation of structural points with an unknown number of breaks. Our results provide a different number of breaks across currencies which may relate to some shocks, economic crisis, and financial policies. Chapter 4 contains a detailed analysis of persistent trends in all share index and ten sectoral indices in an emerging stock market of Pakistan. There is a general consideration regarding the inefficiency of emerging markets compared to the developed markets. Our results show the existence of predictable trends across KSE100 and ten sectors. Moreover, we investigate that the existing trends are true or a result of some level shifts with a semiparametric test. According to the adaptive market hypothesis the long-range dependence is not a constant phenomenon and it varies over time corresponding to the market conditions. We analyze this time-varying long memory with a rolling window technique and observe the fluctuating trends such as persistence, antipersistence, efficiency, and inefficiency at different times. Finally, we analyze the fractional cointegration between the volatilities of the conventional index and Islamic index in chapter 5. Islamic finance attracts the attention of investors and traders regarding its different features such as zero interest rates and profit loss sharing strategies. Some researchers believe that Islamic financial markets can work as a good diversification candidate due to different performance levels during the phases of economic and political shocks. This analysis considers the conventional and Islamic indices across nine Islamic countries: Bahrain, UAE, Oman, Qatar, Malaysia, Indonesia, Egypt, Turkey, and Pakistan. Our results suggest the existence of fractional cointegration and absence of diversification opportunities between the indices in seven out of nine countries in the long-run. This implies that both types of indices follow same trends while there may exist the diversification alternatives in the other two cases

Ecocritical post-colonial studies on humans, land, and animals

Ecocritical post-colonial study is a newly emerged field in literary criticism. The theory combines the study of post-colonial environment in literary work and reveals a relationship between literature and the environment. Before the word ‘Ecocriticism’ was coined in the world of literature, from the beginning, writers were exclusively engaged presenting nature as source of inspiration and a privilege to evolve their ideas and pen them down. With the introduction of the term Ecocriticism in literary criticism by the Association of the Study of Literature and Environment (ASLE) in 1993, scholars approached the analysis of texts to highlight environmental concerns and explore the roles of literature to bring awareness to society. Post-colonialism, on the other hand, as a response to colonization, studies the cultural and economic exploitation of the colonized/marginalized-- the natives and their land. As one can see the split between the two schools of thought-- nature versus culture-- has been a trend for more than a decade. This split of thought has obliterated the fact that the environment is an integration of nature and culture, humans and nonhumans, animate and inanimate. Post-colonial ecocritical studies takes the challenge to respond to these two separate fields; post-colonial and ecocriticism, by studying the environment as a complete body composed of humans, animals, and land. It redirects critical thinking towards the relationship between humans (indigenous and foreign) and land and humans and nonhumans. My thesis, “Ecocritical Post-Colonial Studies on Humans, Animals, and Land,” focuses on the study of the following texts: Things Fall Apart by Chinua Achebe, The Hungry Tide by Amitav Ghosh, Remnants of the First Earth by Ray A. Young Bear, and Ceremony by Leslie Marmon Silko. In these multicultural texts, I examine a relationship between post-colonial land and humans and how, together, they constitute the environment. I use secondary resources on these texts to acknowledge the values, rights, and beliefs associated with nature and land in each culture and humans’ consequences of devaluing them. My study also highlights the crisis of understanding between the ancient tradition and mainstream culture, and negotiates the crisis through literary imagination. Thus, the application of Post-colonial ecocritical scholarship in my thesis has given me an opportunity to broaden my perspective on the treatment of land by post-colonial indigenous communities, and humans’ role in the environment. It has allowed me to take different approaches to peer into the texts and acknowledge the concern of a conflicting relationship between human and nonhuman within the environment, and offer a praxis to maintain harmony and equilibrium in the environment

Long Memory, Spurious Memory: Persistence in Range-Based Volatility of Exchange Rates

This study considers the long memory and fractional integration in the range-based volatilities across 30 currencies against USD. Graphical analysis of the autocorrelation function at long lags and pole near zero frequencies in the periodogram suggests the existence of fractional integration. We apply semi-parametric methods to measure long-range dependence. We find a decrease in the memory estimates with an increase in the bandwidth, which indicates the presence of spurious memory rather true long memory. The hypothesis of long memory against the alternative of spurious memory is also tested by applying the different semi-parametric methods. Empirical results confirm the presence of spurious memory that may be a result of some shocks to the volatility estimator. Furthermore, the reduced memory estimates obtained by utilising an estimator accounting for level shifts also explains the inconsistency of the Local Whittle estimator. We also estimate the number of breaks for each series

The Role of Magnetic Resonance Venography in Headache Due to Suspected Cerebral Venous Sinus Thrombosis in the Presence of Normal T1 and T2 Dural Sinus Signal

OBJECTIVES Cerebral venous sinus thrombosis (CVST) is an important but uncommon aetiology of stroke.  The presentation of CVST is extremely variable clinically, moreover its onset can be either acute or subacute, and less frequently, chronic. Headache is the most common symptom of CVST.  The headache is typically diffuse and progressing in severity over days to weeks.  MRI and MRV have very high sensitivity and specificity and have become the modality of choice to confirm the diagnosis of CVST.  The aim of this study was to weigh the benefits of added MRV in patients with headache, after a negative MRI for CVST.  METHODOLOGY The total number of patients included was 207, with chief complaints of headache and suspicion of CVST. The MRV sequence used was dynamic coronal by using the time-of-flight technique. The diagnosis of CVST was made by the loss of normal signal void both on T1WI and T2WI as well as on non-visualization on MRV.RESULTSOut of these 207 patients, CVST was present in 52 patients.  Superior sagittal sinus was involved in 8 cases, right transverse sinus in 2 cases, left transverse sinus in 7 cases, left sigmoid sinus in 3 cases, and multiple sinuses in 32 cases. 34 cases out of 52 had infarction which was mostly haemorrhagic i.e. 27.  A total of 97 cases (46%) had aplastic/hypoplastic transverse segments which were mostly the left one (87, 42%) and 10 cases (4.8 %) on the right side. In none of the patients, CVST was picked by MRV alone after a negative T1 and T2 MRI. CONCLUSION In patients presenting with headache and suspected CVST additional MRV is only required if the routine MR sequences are not able to pick up the thrombus and the suspicion of CVST is very high

Newcastle disease virus induces testicular damage and disrupts steroidogenesis in specific pathogen free roosters

Newcastle disease (ND), which is caused by Newcastle disease virus (NDV), can cause heavy economic losses to the poultry industry worldwide. It is characterised by extensive pathologies of the digestive, respiratory, and nervous systems and can cause severe damage to the reproductive system of egg-laying hens. However, it is unknown whether NDV replicates in the male reproductive system of chickens and induces any pathologies. In this study, we selected a representative strain (i.e. ZJ1) of the most common genotype (i.e. VII) of NDV to investigate whether NDV can induce histological, hormonal, and inflammatory responses in the testes of specific pathogen free (SPF) roosters. NDV infection increased the expression of toll like receptor TLR3, TLR7, MDA5, IFN-α, IFN-β, IFN-γ, IL-8, and CXCLi1 in the testes of NDV-infected roosters at 5 days post-infection (dpi). Severe histological changes, including decrease in the number of Sertoli cells and individualized, shrunken spermatogonia with pyknotic nuclei, were observed at 3 dpi. At 5 dpi, the spermatogenic columns were disorganized, and there were fewer cells, which were replaced by necrotic cells, lipid vacuoles, and proteinaceous homogenous material. A significant decrease in the plasma concentrations of testosterone and luteinizing hormone (LH) and the mRNA expression of their receptors in the testes, steroidogenic acute regulatory protein, cytochrome P450 side-chain cleavage enzyme, and 3β-hydroxysteroid dehydrogenase in the NDV-infected group was observed relative to those in the control group (P < 0.05). Collectively, these results indicate that NDV infection induces a severe inflammatory response and histological changes, which decrease the steroidogenesis. © 2020 The Author(s)

Global, regional, and national burden of meningitis and its aetiologies, 1990–2019: a systematic analysis for the Global Burden of Disease Study 2019

Background: Although meningitis is largely preventable, it still causes hundreds of thousands of deaths globally each year. WHO set ambitious goals to reduce meningitis cases by 2030, and assessing trends in the global meningitis burden can help track progress and identify gaps in achieving these goals. Using data from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019, we aimed to assess incident cases and deaths due to acute infectious meningitis by aetiology and age from 1990 to 2019, for 204 countries and territories. Methods: We modelled meningitis mortality using vital registration, verbal autopsy, sample-based vital registration, and mortality surveillance data. Meningitis morbidity was modelled with a Bayesian compartmental model, using data from the published literature identified by a systematic review, as well as surveillance data, inpatient hospital admissions, health insurance claims, and cause-specific meningitis mortality estimates. For aetiology estimation, data from multiple causes of death, vital registration, hospital discharge, microbial laboratory, and literature studies were analysed by use of a network analysis model to estimate the proportion of meningitis deaths and cases attributable to the following aetiologies: Neisseria meningitidis, Streptococcus pneumoniae, Haemophilus influenzae, group B Streptococcus, Escherichia coli, Klebsiella pneumoniae, Listeria monocytogenes, Staphylococcus aureus, viruses, and a residual other pathogen category. Findings: In 2019, there were an estimated 236 000 deaths (95% uncertainty interval [UI] 204 000–277 000) and 2·51 million (2·11–2·99) incident cases due to meningitis globally. The burden was greatest in children younger than 5 years, with 112 000 deaths (87 400–145 000) and 1·28 million incident cases (0·947–1·71) in 2019. Age-standardised mortality rates decreased from 7·5 (6·6–8·4) per 100 000 population in 1990 to 3·3 (2·8–3·9) per 100 000 population in 2019. The highest proportion of total all-age meningitis deaths in 2019 was attributable to S pneumoniae (18·1% [17·1–19·2]), followed by N meningitidis (13·6% [12·7–14·4]) and K pneumoniae (12·2% [10·2–14·3]). Between 1990 and 2019, H influenzae showed the largest reduction in the number of deaths among children younger than 5 years (76·5% [69·5–81·8]), followed by N meningitidis (72·3% [64·4–78·5]) and viruses (58·2% [47·1–67·3]). Interpretation: Substantial progress has been made in reducing meningitis mortality over the past three decades. However, more meningitis-related deaths might be prevented by quickly scaling up immunisation and expanding access to health services. Further reduction in the global meningitis burden should be possible through low-cost multivalent vaccines, increased access to accurate and rapid diagnostic assays, enhanced surveillance, and early treatment. Funding: Bill & Melinda Gates Foundation

Impact of COVID-19 on cardiovascular testing in the United States versus the rest of the world

Objectives: This study sought to quantify and compare the decline in volumes of cardiovascular procedures between the United States and non-US institutions during the early phase of the coronavirus disease-2019 (COVID-19) pandemic. Background: The COVID-19 pandemic has disrupted the care of many non-COVID-19 illnesses. Reductions in diagnostic cardiovascular testing around the world have led to concerns over the implications of reduced testing for cardiovascular disease (CVD) morbidity and mortality. Methods: Data were submitted to the INCAPS-COVID (International Atomic Energy Agency Non-Invasive Cardiology Protocols Study of COVID-19), a multinational registry comprising 909 institutions in 108 countries (including 155 facilities in 40 U.S. states), assessing the impact of the COVID-19 pandemic on volumes of diagnostic cardiovascular procedures. Data were obtained for April 2020 and compared with volumes of baseline procedures from March 2019. We compared laboratory characteristics, practices, and procedure volumes between U.S. and non-U.S. facilities and between U.S. geographic regions and identified factors associated with volume reduction in the United States. Results: Reductions in the volumes of procedures in the United States were similar to those in non-U.S. facilities (68% vs. 63%, respectively; p = 0.237), although U.S. facilities reported greater reductions in invasive coronary angiography (69% vs. 53%, respectively; p < 0.001). Significantly more U.S. facilities reported increased use of telehealth and patient screening measures than non-U.S. facilities, such as temperature checks, symptom screenings, and COVID-19 testing. Reductions in volumes of procedures differed between U.S. regions, with larger declines observed in the Northeast (76%) and Midwest (74%) than in the South (62%) and West (44%). Prevalence of COVID-19, staff redeployments, outpatient centers, and urban centers were associated with greater reductions in volume in U.S. facilities in a multivariable analysis. Conclusions: We observed marked reductions in U.S. cardiovascular testing in the early phase of the pandemic and significant variability between U.S. regions. The association between reductions of volumes and COVID-19 prevalence in the United States highlighted the need for proactive efforts to maintain access to cardiovascular testing in areas most affected by outbreaks of COVID-19 infection

Adding 6 months of androgen deprivation therapy to postoperative radiotherapy for prostate cancer: a comparison of short-course versus no androgen deprivation therapy in the RADICALS-HD randomised controlled trial

Background Previous evidence indicates that adjuvant, short-course androgen deprivation therapy (ADT) improves metastasis-free survival when given with primary radiotherapy for intermediate-risk and high-risk localised prostate cancer. However, the value of ADT with postoperative radiotherapy after radical prostatectomy is unclear. Methods RADICALS-HD was an international randomised controlled trial to test the efficacy of ADT used in combination with postoperative radiotherapy for prostate cancer. Key eligibility criteria were indication for radiotherapy after radical prostatectomy for prostate cancer, prostate-specific antigen less than 5 ng/mL, absence of metastatic disease, and written consent. Participants were randomly assigned (1:1) to radiotherapy alone (no ADT) or radiotherapy with 6 months of ADT (short-course ADT), using monthly subcutaneous gonadotropin-releasing hormone analogue injections, daily oral bicalutamide monotherapy 150 mg, or monthly subcutaneous degarelix. Randomisation was done centrally through minimisation with a random element, stratified by Gleason score, positive margins, radiotherapy timing, planned radiotherapy schedule, and planned type of ADT, in a computerised system. The allocated treatment was not masked. The primary outcome measure was metastasis-free survival, defined as distant metastasis arising from prostate cancer or death from any cause. Standard survival analysis methods were used, accounting for randomisation stratification factors. The trial had 80% power with two-sided α of 5% to detect an absolute increase in 10-year metastasis-free survival from 80% to 86% (hazard ratio [HR] 0·67). Analyses followed the intention-to-treat principle. The trial is registered with the ISRCTN registry, ISRCTN40814031, and ClinicalTrials.gov, NCT00541047. Findings Between Nov 22, 2007, and June 29, 2015, 1480 patients (median age 66 years [IQR 61–69]) were randomly assigned to receive no ADT (n=737) or short-course ADT (n=743) in addition to postoperative radiotherapy at 121 centres in Canada, Denmark, Ireland, and the UK. With a median follow-up of 9·0 years (IQR 7·1–10·1), metastasis-free survival events were reported for 268 participants (142 in the no ADT group and 126 in the short-course ADT group; HR 0·886 [95% CI 0·688–1·140], p=0·35). 10-year metastasis-free survival was 79·2% (95% CI 75·4–82·5) in the no ADT group and 80·4% (76·6–83·6) in the short-course ADT group. Toxicity of grade 3 or higher was reported for 121 (17%) of 737 participants in the no ADT group and 100 (14%) of 743 in the short-course ADT group (p=0·15), with no treatment-related deaths. Interpretation Metastatic disease is uncommon following postoperative bed radiotherapy after radical prostatectomy. Adding 6 months of ADT to this radiotherapy did not improve metastasis-free survival compared with no ADT. These findings do not support the use of short-course ADT with postoperative radiotherapy in this patient population

Duration of androgen deprivation therapy with postoperative radiotherapy for prostate cancer: a comparison of long-course versus short-course androgen deprivation therapy in the RADICALS-HD randomised trial

Background Previous evidence supports androgen deprivation therapy (ADT) with primary radiotherapy as initial treatment for intermediate-risk and high-risk localised prostate cancer. However, the use and optimal duration of ADT with postoperative radiotherapy after radical prostatectomy remains uncertain. Methods RADICALS-HD was a randomised controlled trial of ADT duration within the RADICALS protocol. Here, we report on the comparison of short-course versus long-course ADT. Key eligibility criteria were indication for radiotherapy after previous radical prostatectomy for prostate cancer, prostate-specific antigen less than 5 ng/mL, absence of metastatic disease, and written consent. Participants were randomly assigned (1:1) to add 6 months of ADT (short-course ADT) or 24 months of ADT (long-course ADT) to radiotherapy, using subcutaneous gonadotrophin-releasing hormone analogue (monthly in the short-course ADT group and 3-monthly in the long-course ADT group), daily oral bicalutamide monotherapy 150 mg, or monthly subcutaneous degarelix. Randomisation was done centrally through minimisation with a random element, stratified by Gleason score, positive margins, radiotherapy timing, planned radiotherapy schedule, and planned type of ADT, in a computerised system. The allocated treatment was not masked. The primary outcome measure was metastasis-free survival, defined as metastasis arising from prostate cancer or death from any cause. The comparison had more than 80% power with two-sided α of 5% to detect an absolute increase in 10-year metastasis-free survival from 75% to 81% (hazard ratio [HR] 0·72). Standard time-to-event analyses were used. Analyses followed intention-to-treat principle. The trial is registered with the ISRCTN registry, ISRCTN40814031, and ClinicalTrials.gov , NCT00541047 . Findings Between Jan 30, 2008, and July 7, 2015, 1523 patients (median age 65 years, IQR 60–69) were randomly assigned to receive short-course ADT (n=761) or long-course ADT (n=762) in addition to postoperative radiotherapy at 138 centres in Canada, Denmark, Ireland, and the UK. With a median follow-up of 8·9 years (7·0–10·0), 313 metastasis-free survival events were reported overall (174 in the short-course ADT group and 139 in the long-course ADT group; HR 0·773 [95% CI 0·612–0·975]; p=0·029). 10-year metastasis-free survival was 71·9% (95% CI 67·6–75·7) in the short-course ADT group and 78·1% (74·2–81·5) in the long-course ADT group. Toxicity of grade 3 or higher was reported for 105 (14%) of 753 participants in the short-course ADT group and 142 (19%) of 757 participants in the long-course ADT group (p=0·025), with no treatment-related deaths. Interpretation Compared with adding 6 months of ADT, adding 24 months of ADT improved metastasis-free survival in people receiving postoperative radiotherapy. For individuals who can accept the additional duration of adverse effects, long-course ADT should be offered with postoperative radiotherapy. Funding Cancer Research UK, UK Research and Innovation (formerly Medical Research Council), and Canadian Cancer Society

Ecocritical and Postcolonial Study of Humans, Land, and Space

Modern environmental study has emerged as a broad genre. It studies humans and their place in nature. In literature, the complex relationship between humans and nature, pastoral imagery, land and its ownership, scientific intrusion into natural world, have been the subjects of literary and cultural analysis. postcolonial ecocritics, like environmental historian Alfred Crosby, inaugurate the understanding of ecology as a part of imperial practice in their studies. Postcolonial criticism provides the platform to understand the imperial embedded in ecological practices. In this project, I study ecocriticism and postcolonialism by examining colonial impact on humans, land, and space