Riemannian Gaussian distributions on the space of positive-definite quaternion matrices

Recently, Riemannian Gaussian distributions were defined on spaces of positive-definite real and complex matrices. The present paper extends this definition to the space of positive-definite quaternion matrices. In order to do so, it develops the Riemannian geometry of the space of positive-definite quaternion matrices, which is shown to be a Riemannian symmetric space of non-positive curvature. The paper gives original formulae for the Riemannian metric of this space, its geodesics, and distance function. Then, it develops the theory of Riemannian Gaussian distributions, including the exact expression of their probability density, their sampling algorithm and statistical inference.Comment: 8 pages, submitted to GSI 201

Guidelines for the establishment of a search and rescue service

The main reason for embarking on this topic is the urgent necessity for establishing a Search and Rescue Service in the Kingdom of Saudi Arabia. Many disasters have been caused by a minor accident such as electrical spark , or a match stick, hesitation in taking actions to avoid collisions, which result in loss of lives and property. To minimize such losses one must have a responsive Search and Rescue Service, which unfortunately is not properly established in the Kingdom. The area is congested with traffic without any search and rescue coverage by the Kingdom or even neighbouring countries, which should be available in all coastal states to render such services. This is part of the coastal states international obligation as stated in :- 1) The International Convention for the Safety of Life at Sea, 1974 (SOLAS \u2774), Regulation 15 - Chapter V. 2) The UN Convention on the High Seas, 1958 - Article 12(2). 3) The UN Convention on the Law of the Sea, 1978\u27 (UNCLOS III). Article 98 (2) refers to: Duty to render assistance. As I have discovered, carrying out research in this field was hard but my educational background and speciality as a technical person (Marine Engineer) have assisted greatly whilst conducting such a task. However, because of the importance and necessity of this topic for the Kingdom which oversees two strategic maritime zones (the Red Sea and the Arabian Gulf) each as important as the other, and since the Kingdom is the leading country in the region in many aspects, she must obviously and automatically play the leading role and take the necessary steps to establish such a valuable and active service in the field of Search and Rescue . She should take into consideration her ability to conduct such a service after careful study and well established research nationally, regionally, and internationally. Therefore this study has chiefly been derived from information provided by states which have had considerable experience in the field of Search and Rescue, e.g. Federal Republic of Germany, Sweden, United Kingdom, United States, and Canada. The study and research was not limited to reading their publications. Field visits were made to most of them mainly: United States of America, the Federal Republic of Germany, as well as the host country of the World Maritime University - Sweden. Even though the Kingdom of Saudi Arabia has the means to establish a Search and Rescue Service with the latest techniques available, my study was based on providing practical and economical Search and Rescue coverage of the area

A review of social cohesion initiatives and challenges with a focus on Jordan and education

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Leadership style, organisational culture and disputes in public construction

The increasing occurrence of construction disputes has compounded the fragmentation, complexity and adversarial nature of the construction industry. Disputes are associated with high cost, delays, low quality and even the destruction of important relationships among project parties that have taken long years to build and disputes have become ‘the rule rather than the exception’. Despite considerable attempts in literature towards dispute minimization in construction projects, very few studies have addressed the roots behind the occurrence of disputes. Leadership and organisational culture are key influential factors in the construction industry. Effective project leaders should, not only achieve the goals and objectives of the organisations they lead, but also, minimize conflicts and disputes. Also by instilling strong organisational culture, construction organisations can control dispute to minimum levels. Therefore, this study aims to draw research attention toward the core of disputes by providing theoretical insight and empirical investigation concerning the roots of this problem. A framework is presented to minimize disputes in public organisations of construction. The mixed methodology adopted includes a survey conducted to investigate the current practice and semi-structured interviews to explore best practice that combined to form a foundation for the framework that assess leaders and organisations to minimize construction disputes. The findings revealed that among the most significant dispute causes are: delay by the contractor, lack of team spirit, slow contractor response, poor communication, unrealistic tendering, inadequate contractor selection, unforeseen site conditions and inadequate site supervision. Significant correlations were noted between transformational leadership and the most significant dispute causes. Also significant association was indicated between clan culture and disputes. Emerging from the study is that transformational leadership and clan culture appear to be the most suitable leadership style and organisational culture, respectively, in public construction organisations (owner organisations) that help minimize disputes with contractors

Congenital Morgagni’s hernia in infants and children: a national review

Background: Congenital Morgagni’s hernia (CMH) is rare and has unique features in terms of clinical presentation, high incidence of bilaterality, and associated anomalies. This is a review of all CMH cases reported from Saudi Arabia, highlighting clinical features, associated anomalies, aspects of diagnosis, and management.Patients and methods: A Medline search was made for all manuscripts published from Saudi Arabia on CMH. The total number of patients, their age at diagnosis, sex, clinical features, associated anomalies, site of hernia, and methods of treatment were recorded.Results: From 1991 to 2014, 19 manuscripts were published from Saudi Arabia. The total number of patients reported was 106 (72 male and 31 female). In three patients, the sex was not reported. Their mean age was 23.8 months (1 month–9 years). Recurrent chest infection was the most common presentation [56 (54.4%)]. In seven (6.8%) patients, the hernia was discovered incidentally and 19 (18.4%) presented acutely. Associated anomalies were seen in 66 (64%) of 103 patients. Down’s syndrome (30%) and congenital heart disease (23%) were the most common. Sixty-four (60.4%) underwent repair through an abdominal approach, 36 (34%) underwent laparoscopicassisted repair, and in five (4.7%) patients the hernia was repaired laparoscopically. In 94 patients, the site of the hernia was specified [45 (47.9%) right, 22 (23.4%) left, and 27 (28.7%) bilateral]. Four (3.8%) developed recurrences and three had an incisional hernia. One developed midgut volvulus 3 years postoperatively.Conclusion: CMH is rare and the presentation is nonspecific and variable but the majority present with repeated attacks of chest infection. Physicians caring for these patients should be aware of this, and infants and children with repeated attacks of chest infection should be investigated. It is also important to evaluate these patients for possible associated anomalies, including an echocardiogram. Once the diagnosis of CMH is confirmed, they should be repaired surgically regardless of whether symptomatic or asymptomatic. The laparoscopic-assisted approach is a simple, safe, and sound technique, and leaving the hernia sac intact has no adverse effects.Keywords: associated anomalies, congenital diaphragmatic hernia congenital Morgagni’s hernia, treatmen

Congenital Paraesophageal Hernia with Intrathoracic Gastric Volvolus in Two Sisters

Congenital paraesophageal hernia is rare in infants and children. This paper describes our experience with seven infants and children with congenital paraesophageal hernia with emphasis on two sisters who presented with unusually large paraesophageal hernias and herniation of most of the stomach resulting in intrathoracic gastric volvolus. The literature on the subject is also reviewed

Megacystis microcolon intestinal hypoperistalsis syndrome: a report of a variant

Megacystis microcolon intestinal hypoperistalsis syndrome is a very rare cause of functional intestinal obstruction in newborns. It is associated with nonobstructed distended urinary bladder, microcolon, and decreased or absent intestinal peristalsis. The prognosis is poor and most patients die early because of sepsis or total parental nutrition-related complications. This report describes a new case of megacystis microcolon intestinal hypoperistalsis syndrome associated with meconium ileus, dilated stomach, and megaesophagus.Keywords: intestinal hypoperistalsis syndrome, megacystis, microcolo

Splenic Complications of Sickle Cell Anemia and the Role of Splenectomy

Sickle cell disease is one of the common hemoglobinopathies in the world. It can affect any part of the body and one of the most common and an early organ to be affected in SCA is the spleen. It is commonly enlarged during the first decade of life but then undergoes progressive atrophy leading to autosplenectomy. This however is not the case always and sometimes splenomegaly persist necessitating splenectomy for a variety of reasons including acute splenic sequestration crisis, hypersplenism, massive splenic infarction and splenic abscess. Splenic complications of SCA are known to be associated with an increased morbidity and in some it may lead to mortality. To obviate this, splenectomy becomes an essential part of their management. This review is based on our experience in the management of 173 children with various splenic complications of SCA necessitating splenectomy