Structure–property relationships in polymer-polyols-based polyurethane elastomers

Polyurethanes are a class of materials which can be regarded as filling the gap between rubbery elastomers and rigid plastics and metals. They can exhibit both high elongation and resilience, while retaining high modulus which make them unique for a wide variety of applications in which both stiffness and extensibility is needed. It is now widely accepted that the diverse properties of these copolymers are attributed to the existence of a two phase microstructure. One phase is regarded as a glassy or hard segment, whereas the other phase is considered to be rubbery and to give soft segments. These different segments are known to have glass transition temperatures above roan temperature for the hard segments and below roan temperature for the soft segments. [Continues.

The Social Family Factors and Its Influence upon The Son's Academic Excellence A field research for students of the Elites' School in Lattakia

The goal beyond this research is to highlight the influence of the social family factors on the academic excellence of sons. This research sample was on (240) of (408) male and female students who are in the first, second and the third secondary stages for the school year 2016-2017. For reaching the intended goals of this research, a questionnaire was adopted as a tool for collecting both the preliminary data and the data related to the variables of this research. The results of the research assured that the number of the family members does not have that clear effect on the academic excellence and most of the students do not get negatively affected by the parental divorce or even by the absence of one of the parents so this factor does not affect the sons' academic excellence. Also, the birth order in any student's family does not affect positively or negatively the student's academic excellence. The good and healthy relationship between the father and the sons has a clear effect on their academic excellence but, on the other hand, the relationship between the mother and the sons does not have that clear effect on their academic excellence. Moreover, this research stated that there is a positive link between the parents' moderate control and treatment practiced inside the family towards the sons and the sons' academic excellence. On the other side, this research stated that there is no link between the parents' dominating control and treatment towards the sons and the sons' academic excellence

A novel route to organonitrites by Pd-catalyzed cross-coupling of sodium nitrite and potassium organotrifluoroborates

Microwave irradiated palladium-catalyzed cross-coupling reaction of potassium styryltrifluoroborates and sodium nitrite gives the corresponding styryl nitrites in high yields. Potassium aryltrifluoroborates also furnish aryl nitrites under same reaction condition. This unprecedented cross-coupling is an interesting development and has the potential to lead to new nitration protocols

BENAICHA ZIANI, Naima. La trilogía de Abdelkader Alloula, treinta años después. Granada: Editorial Universidad de Granada, 2020, 303 páginas.

En esta reseña aborda la originalidad del teatro de Alloula, así como la aportación que realiza la autora N. Benaicha con la publicación de esta obra.&nbsp

Conservation Biological Control Practices

Natural enemies are subjected to continuous deterioration in populations especially in modern agricultural systems characterized by complete removal of plants after harvesting as well as by insecticide applications. This complete removal of plants gives rise to disappearance of natural enemies after each crop season. Conservation biological control is the protection of NEs against adverse effects of pesticides and incompatible cultural practices and improving their efficiency via providing food sources. During non-crop periods, natural enemies may need of benefit from pollen and nectar. Preservation of natural enemies can be achieved by providing habitat and resources for NEs. This chapter aimed at discussing a suggested strategy for more efficient conservation biological control comprising collection, preservation and releasing the preserved natural enemies on target crops. The collection is mainly conducted before crop harvest and during winter from fruit orchards. Preservation greenhouses are dedicated for natural enemies rather than commercial production of crops. Natural enemies taken from preservation greenhouses are released in target crops during growing season. Different techniques used in collection, preservation and release of natural enemies are reviewed. Such a conservation biological control strategy might contribute to preserve the natural bio-diversity in the agricultural environment and provide natural alternatives to pesticides

Experiential Behavioral Economics Courses: Practical lessons learned from the Middle East

This paper presents the development and implementation of experiential behavioral economics course in three Middle East universities. Experiential learning has proven to have many benefits for students because of putting them at the center of the learning process and allowing them to learn by doing. More specifically, as part of the practical sessions, students were tasked to design, implement and report on one field experiment conducted in collaboration with a nudge unit. We believe that this approach whereby students apply their knowledge through experimentation to address issues relevant to their communities and environment can be more effective and impactful than traditional teaching or relying only on classroom-based experiments. In this paper, we share the lessons learned from the journey of delivering several experiential behavioral economics courses

Mitral valve annuloplasty with a homemade single-sized polytetrafluoroethylene band in degenerative mitral regurgitation

Background: Although mitral annuloplasty is an essential component of mitral repair, there remains little agreement on the ideal device to be used or the ideal sizing method.Objectives: The purpose of this study was to report the early clinical and echocardiographic outcomes of patients undergoing repair for degenerative mitral regurgitation using a homemade single-sized (65 mm) Polytetrafluoroethylene band, and comparing it to the use of commercially available complete rigid rings.Patients and methods: This is a retrospective study including 106 patients, who underwent mitral repair for degenerative mitral regurgitation at Cairo University Hospitals between February 2013 and July 2019. These patients were divided into 2 groups. Group (A) included 69 patients who underwent repair with a single-sized band, and group (B) included 37 patients whose repair included the use of a commercial rigid ring. The primary endpoint was freedom from significant mitral regurgitation at one-year follow-up. Secondary endpoints included mean mitral valve gradient measured postoperatively, and freedom from reoperation at one year.Results: There was no statistically significant difference between both groups in any of the above-mentioned endpoints being examined.Conclusion: The use of a single-sized Polytetrafluoroethylene band for annuloplasty in degenerative mitral disease showed satisfactory results comparable to the commercial rigid rings. Further studies with longer follow-up are needed to confirm the durability of mitral repair using this technique

Design, fabrication and flight testing of a surveillance UAV

Unmanned Aerial Vehicle (UAV) is becoming increasingly popular because it can perform variety of functions. These functions include surveillance, reconnaissance, monitoring, data collection and rescue operation. The purpose of this work is to design, fabricate and fly a low weight, low cost, small size UAV for a surveillance mission. The design is carried out based on Advanced Aircraft Analysis (AAA) software. The design process starts with the design specifications for a typical surveillance mission. Aircraft weight, wing loading and power loading were estimated in performance sizing process. Geometry was estimated using preliminary sizing. Aerodynamics of the aircraft was determined, which enabled the performance and stability to be analysed. If the desired performance is not achieved, the sizing is readjusted until a final design is reached. The aircraft was manufactured using foam, carbon rods, and fibreglass. The aircraft successfully flew at the first trial flight. This was followed by a successful flight with aerial photograph

Tricuspid valve repair by DeVega technique versus ring annuloplasty in patients with functional severe tricuspid regurge

AbstractBackgroundRepairing the tricuspid valve in patients undergoing left heart valve surgery is still controversial. Severe Tricuspid regurge is repaired by most surgeons, while moderate regurge is frequently unaddressed. Another controversy is the technique of repair. DeVega technique is widely used; still, the longevity of this repair is still questioned. The risk of its early failure and subsequent recurrence of significant regurge requiring redo surgery has led many surgeons to adopt the use of annuloplasty rings. The aim of our study was to assess the short term results (1 year) of tricuspid repair with or without ring annuloplasty.Patients and methods80 patients who had tricuspid repair concomitantly with mitral valve surgery at Cairo University Hospitals over 5 years were studied by echocardiography at discharge and at 1 year after surgery.Results62 patients had repair using the DeVega annuloplasty (group A) while 18 had ring annuloplasty (group B). The mean age was 33 ± 6 years and 37 ± 8 years for group A and B respectively. The cardiopulmonary bypass (CPB) time was relatively longer in group B. There was only one mortality in group A. Echocardiography done for all patients of both groups at discharge and at 1 year postoperatively showed no significant difference between both groups.ConclusionTricuspid repair using ring annuloplasty has good results but with no significant benefits over DeVega annuloplasty at one year