Can market frictions really explain the price impact asymmetry of block trades? Evidence from the Saudi stock market

We empirically examine the price impact of block trades, in the Saudi Stock Market over the time period of 2005-2008. Using a unique dataset of intraday data consisting of 2.3 million block buys and 1.9 million block sales, we find an asymmetry in the price impact of block purchases and sales. The asymmetry persists even when we account for the bidask bias in block trades, which is contrary to the previous literature. Overall, our findings suggest that in an emerging market where institutional trading is relatively scarce, market microstructure cannot explain the asymmetry in the price impact of large trades

What happens around earning announcements? An investigation of information asymmetry and trading activity in the Saudi market

This paper examines stock returns and trading activities around earnings announcements for listed companies in the Saudi stock market (SSM). Specifically, we examine the levels of stock liquidity, trading activity, volatility, bid-ask spread, asymmetric information and investor trading behaviour around earnings announcements for all firms in the market for the period 2002-2009. Abnormal price and volume reactions around earnings announcements suggest that these announcements produce highly informative contents. The magnitude of the cumulative abnormal returns around earnings announcement is induced by trading activity in the two weeks before the release date. We also show evidence of an increased adverse selection cost around earnings announcement, which is then gradually reduced in the post-announcement period, indicating that earnings announcements reduce uncertainty in the market. We also examine trading behaviour among small and large investors in the market through constructing order imbalance measures. In general, large investors are more sophisticated and show higher informed trading before earnings announcements whereas smaller investors show stronger reaction to news. Moreover, small investors show a buying pattern which is consistent with times-series based earnings surprise. They are net-buyers for good news and net-sellers for bad news portfolios

The Effects of Marriage before College Graduation on the Educational Attainments and Personal Fulfillment of Saudi Women

This research explored the effects of marriage before college graduation on the educational attainments and personal fulfillment of Saudi women. The purpose of this study was to gather and analyze data from women who were married before completing a college degree and women who were married after completing a college degree in order to measure how marriage has affected their lives in different ways. The data was gathered by surveying 215 Saudi women. According to the findings of the study, marriage before college graduation did limit educational attainment to some extent. The survey results suggested that a significant percentage of the total participants did not complete their education after marriage. A substantial percentage of the total participants believed that getting married limited their educational prospects or reduced the likelihood of continuing their education. Moreover, according to the findings of the study in regard to the personal fulfilment, marriage before college graduation did impact the personal fulfillment in some areas of the participants’ lives, yet not for other areas of their lives. Career satisfaction and achievements were the most impacted areas as the survey results suggested that the majority of the women who were married before college graduation were unemployed. Also, survey results suggested that a significant percentage of the total participants believed that getting married limited their career achievement prospects or reduced the likelihood of pursuing a career

Comparison of Albuterol Delivery between High Frequency Oscillatory Ventilation and Conventional Mechanical Ventilation in a Simulated Adult Lung Model using Different Compliance Levels

COMPARISON OF ALBUTEROL DELIVERY BETWEEN HIGH FREQUENCY OSCILLATORY VENTILATION AND CONVENTIONAL MECHANICAL VENTILATION IN A SIMULATED ADULT LUNG MODEL USING DIFFERENT COMPLIANCE LEVELS By Waleed A. Alzahrani, BSRT BACKGROUND: Delivery of aerosol by pMDI has been described with conventional mechanical ventilation (CMV) but not with high frequency oscillatory ventilation (HFOV). The purpose of this study was to compare aerosol delivery to a simulated 75 kg adult with low compliance during both CMV and HFOV. Since actuation of pMDI with inspiration is not feasible with HFOV, we investigated the impact of actuation timing only during CMV. METHOD: CMV (Respironics Esprit) and HFOV (Sensor Medics 3100B) ventilators with passover humidifiers and heated circuits were connected by 8 mm ID ETT and filter (Respirgard II, Vital Signs) to a test lung (TTL) with compliance settings of 20 and 40 ml/cm H2O in order to simulate a non compliant lung. Settings for CMV (VT 6 ml/kg, I:E 1:1, PEEP 20 cm H2O, and RR 25/min), and HFOV (RR 5 Hz, IT 33%, ∆P 80 cm H2O and mPaw 35 cm H2O) were used, with similar mPaw on CMV and HFOV. Parameters were selected based on ARDSnet protective lung strategy (Fessler and Hess, Respiratory Care 2007) Eight actuations of albuterol from pMDI (ProAir HFA, Teva Medical) with double nozzle small volume spacer (Mini Spacer, Thayer Medical) placed between the “Y” adapter and ETT at more than 15 sec intervals for each condition (n=3). During CMV, pMDI actuations were synchronized (SYNC) with the start of inspiration at more than 15 s, and nonsynchronized (NONSYNC) with actuations at 15 s intervals. Drug was eluted from the filter and analyzed by spectrophotometry (276 nm). Repeated measures ANOVA, pairwise comparisons and independent t- tests were performed at the significance level of 0.05. RESULTS: In all cases, aerosol delivery was greater with HFOV than CMV (p\u3c0.05). Synchronizing pMDI actuations with the beginning of inspiration increased aerosol deposition significantly at compliance levels 20 ml/cm H2O and 40 ml/cm H2O (p=0.011 and p=0.02, respectively). Lung compliance and aerosol delivery are directly related. Increasing lung compliance to 40 ml/cmH2O improved aerosol delivery during CMV and HFOV (p\u3c0.05). CONCLUSION: Albuterol deposition with pMDI was more than two fold greater with HFOV than CMV in this in-vitro lung model. Changing lung compliance has almost 2 fold impact on aerosol delivery during both modes of ventilation. Furthermore, synchronizing pMDI actuations during CMV improved aerosol delivery up to 4 fold

Four essays on return behaviour and market microstructures: Evidence from the Saudi stock market

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.This dissertation is divided into an introductory chapter and four essays. Chapter one discusses the importance of the study and describes the development and growth of the market as well. The first part (Chapters 2 & 3) examines stock returns behaviour and trading activity around earnings announcements. The second part (Chapters 4 & 5) examines price impact asymmetry and the price effects of block trades in the market microstructure context. Each essay addresses some aspects of market microstructure and stock returns behaviour in order to aid researchers, investors and regulators to understand a market which lacks research coverage. The research provides empirical evidence on issues such as the efficiency of the market, information asymmetry, liquidity and price impact of block trades. In first part of the thesis, event study and regression analysis were used to measure the price reaction around earnings announcements and to examine trading activity, information asymmetry and liquidity. In second part the determinants of the price impact of block trades were examined with regard to trade size, market condition and time of the day effects using transaction data. Liquidity and information asymmetry issues of block trades were also studied in this part

The Role of Prrx1 and Snai2 as Master Regulators of Fibroblast Identity

Mammalian development involves a complex system of regulatory signals and reactions, leading to the creation of distinct tissues with specific structures and functions controlled by various gene expression profiles. Tissue-specific gene expression is by controlled specific combinations of transcription factors and cofactors that dictate cell differentiation via activation and repression of genes in mammalian cells. Whole genome microarray analyses of fibroblasts have revealed candidate genes that may serve as master regulators of fibroblast identity, such as Prrx1 and Snai2, that activate downstream genes such as Bmp3, Twist, Shox2, Cfos, Slug, Sema3A, Spp1, and Col1a1. A previous study showed that Prrx1 and Snai2 play important roles in activating expression of fibroblast identity using somatic cell hybrids as model systems. Based on these results, we sought to examine the role of Prrx1 and Snai2 in affecting the phenotyope of liver-derived cells using hepatoma cells as a model system. Expression plasmids containing Prrx1 and Snai2 expression cassettes were transfected separately into Fg14 rat hepatoma cells using a standard transfection technique, then G418-resistant clones were selected (pooled and individually) and monitored for over-expression of Prrx1 and Snai2. RNA was extracted and used to synthesize cDNA. Quantitative real-time polymerase chain reaction (qPCR) was carried out using specific primer pairs and signals normalized to GAPDH mRNA levels. In addition, we observed alteration morphology and cell migration using Scratch Assays. qPCR analysis revealed that both Prrx1 and Snai2 were successfully over-expressed in pooled Fg14 transfectants and individual clones compared to non-transfected cells. Next we monitored expression of several genes known to be important in liver and fibroblast function. Results show that Snai2 activated several genes (Twist,Cfos,Shox2,and Bmp3) in Fg14 hepatoma cells. Although several other fibroblast genes (SEMA3A and Spp1) were relatively unaffected. Prrx1 overexpression resulted in activation of (Cfos,Twist,Shox2,Bmp3,and Col1a1) expression in Fg14 hepatoma, but (SEMA3A and Spp1) were unaffected. Based on these findings we hypothesized that overexpression of fibroblast-specific transcription factor Prrx1 and Snai2 would result in loss of hepatoma phenotype. We therefore monitored expression of a panel of liver-specific genes using qPCR analysis. Results show that several liver related genes are repressed by these transcription factors, leading to partial loss of the hepatic phenotype. We observed that the cells re-acquired a spindle-shaped morphology and more significantly an enhanced migration capability, which is reminiscent of parental fibroblast cells. In conclusion, these results suggest that candidate core Prrx1 and Snai2 serve as a useful starting point for studying transcriptional control of cell identity and reprogramming of mammalian cell types

Using Artificial Intelligence and Cybersecurity in Medical and Healthcare Applications

Healthcare fields have made substantial use of cybersecurity systems to provide excellent patient safety in many healthcare situations. As dangers increase and hackers work tirelessly to elude law enforcement, cybersecurity has been a rapidly expanding field in the news over the past ten years. Although the initial motivations for conducting cyberattacks have generally remained the same over time, hackers have improved their methods. It is getting harder to identify and stop evolving threats using conventional cybersecurity tools. The development of AI methodologies offers hope for equipping cybersecurity professionals to fend against the ever-evolving threat posed by attackers. Therefore, an artificial intelligence- based Convolutional Neural Network (CNN) is introduced in this paper in which the cyberattacks are detected with more excellent performance. This paper presents unique conditions using the Ant Colony Optimization based Convolutional Neural Network (ACO-CNN) mechanism. This model has been built and supplied collaboratively with a dataset containing samples of web attacks for detecting cyberattacks in the healthcare sector. The results show that the created framework performs better than the modern techniques by detecting cyberattacks more accurately

Applying Lean to the AC-130 Maintenance Process for the Royal Saudi Air Force

The ideas expressed in this research come from the researchers experiences working in the AC-130 maintenance squadron in the Royal Saudi Air Force. The AC-130 maintenance process is not currently being used as effectively as it could be to make AC-130 fully mission capable. That can be done by improving communication, reducing distances needed to move or transport anything during the maintenance process and by efficient use of the available qualified workforces, tools and equipment. Consideration is given to applying an existing management technique to the Royal Saudi Air Forces AC-130 Maintenance Squadrons. The selected technique is the Lean management approach. The research suggests that Lean can help and improve AC-130 maintenance process in the Royal Saudi Air Force for several reasons. One of the most important reasons of using Lean is that it will get rid of waste and measure the process improvement of C-130s. If Lean is implemented, there will be reduction of (65 -96 ) on the cycle time. The bottom line benefit that the research suggests is to minimize the time required to maintain the aircraft C-130 and improve the availability rate

The impact of co-infection of influenza A virus on the severity of Middle East Respiratory Syndrome Coronavirus

This article is made available for unrestricted research re-use and secondary analysis in any form or by 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.Ho and colleagues recently drew attention to the consequences of co-infection with Influenza and HIV.1 We present four cases of combined infection with influenza and Middle East Respiratory Syndrome Coronavirus (MERS-CoV) infection. Nasopharyngeal swabs or tracheal aspirates were tested for MERS-CoV using real-time reverse-transcription polymerase chain reaction (RT-PCR).2, 3 Samples were tested for Influenza A, B and H1N1 by rapid molecular test (GenEXper for detection of flu A, B and 2009 H1N1, Cepheid)