Anatomic-electrophysiological correlations concerning the pathways for atrioventricular conduction.

The remarkable success of radiofrequency ablation in recent decades in curing atrioventricular nodal reentrant tachycardias has intensified efforts to provide a solid theoretical basis for understanding the mechanisms of atrioventricular transmission. These efforts, which were made by both anatomists and electrophysiologists, frequently resulted in seemingly controversial observations. Quantitatively and qualitatively, our understanding of the mysteries of propagation through the inhomogeneous and extremely complex atrioventricular conduction axis is much deeper than it was at the beginning of the past century. We must go back to the initial sources, nonetheless, in an attempt to provide a common ground for evaluating the morphological and electrophysiological principles of junctional arrhythmias. In this review, we provide an account of the initial descriptions, which still provide an appropriate foundation for interpreting recent electrophysiological findings

Twisted atrioventricular connections in double inlet right ventricle: evaluation by magnetic resonance imaging

Twisted atrioventricular connections occur almost exclusively in the hearts with biventricular atrioventricular connections. Only one example of double inlet left ventricle has been illustrated in which the axes of the two atrioventricular valves crossed each other. We describe herein three patients, and one autopsied specimen, with double inlet right ventricle in which magnetic resonance imaging clearly demonstrated twisted atrioventricular connections

Transthoracic three-dimensional echocardiography for the assessment of straddling tricuspid or mitral valves

Background The advent of 3D echocardiography has provided a technique which, potentially, could afford significant additional information over conventional cross-sectional echocardiography in the assessment of patients with straddling atrioventricular valves prior to surgical correction. Methods Eight patients, aged from 1 month to 9˙2 years, were examined with 3D echocardiography. All but three had discordant ventriculoarterial connections or double outlet right ventricle. Data suitable for reconstruction was acquired with transthoracic scanning. Right and left ventricular volumes were calculated in the 3D dataset. Results 3D echocardiography proved capable of defining the exact degree of straddling by imaging theproportion of tension apparatus attached to either side of the ventricular septum. It was able also to display the atrioventricular junction “en face”, thus permitting identification of the precise site of insertion of the muscular ventricular septum relative to the atrioventricular junction. This made it possiblefirst, to calculate the degree of valvar override, and second, to predict the location of the penetrating atrioventricular bundle. End-diastolic volume of the right ventricle in those with straddling tricuspid valves was 73 (61–83)% of normal, and, of the left ventricle in those with mitral valvar straddling 71 (40‐97)% of normal. Conclusions 3D echocardiography can aid in planning the optimal surgical procedure in patients with straddling or overrriding atrioventricular valves, as it provides diagnostic information superiorto standard crosssectional techniques. It also allows for exact measurement of the volumes of the respective ventricles

Using Dramatic Monologue for Teaching Social Sciences

During the welcoming session at the start of every academic year, teachers in Vanier College’s Psychology Department put on a skit to introduce incoming “psychology major” students, in a concise and entertaining manner, to the three different theoretical approaches currently prevailing in the discipline. In the skit, a teacher plays the role of a client who consults a psychotherapist (played by another teacher) for help with a marital problem. Seeking a solution to his problem, the “client” appears on stage three different times and receives treatment from three psychotherapists (played by another teacher) of different theoretical orientations: B.F. Skinner, Sigmund Freud, and “Dr. Phil”, the famous American talk-show host (who respectively represent behaviorism, psychoanalysis, and cognitive psychology). Generally speaking, this skit is the first real exposure to psychological theories for the new cohort of students. Based on the feedback received afterwards, it seems to have made a powerful impression on them. Which explains why we keep putting on the same skit year after year! One reason for the impressive success of this simple skit is quite clear: complex ideas can be effectively conveyed to even the most uninitiated in a concise and easily understood manner through dramatic techniques, because drama is engaging, entertaining, and thought-provoking.published_or_final_versio

Toward integration of reading and service learning through an interdisciplinary program

This study examined the effect of an interdisciplinary program of reading and service learning on the cognitive and affective development of university students in Hong Kong. As Nussbaum (1997) stated, literature plays a vital role in educating citizens of the world through its narrative imagination and its power of promoting understanding and empathy toward the life of others. Halstead and Pike (2006) also emphasized that art can foster reflection upon action and bring about change in behavior as a result of perspective change. In this study, 24 freshmen read literary works under the theme of children's welfare and explored issues related to the welfare of children worldwide. Their reflections on these materials were expressed in writing and in a presentation. In the following semester, the students participated in voluntary services within and outside Hong Kong. All students completed a questionnaire on their humanistic concerns and sense of global citizenship at the beginning and the end of the project. Results showed that students were conscious of their changes after joining the program and stated their growth in values and knowledge. The pre-post-t-test analysis suggested that students had made significant improvement in the following areas: (1) their attitude toward serving others, especially in their personal and social values; (2) their engagement in reading literary and nonfiction works which reflect social and moral issues of the world; (3) their attention to world affairs; (4) their concern for the underprivileged; and (5) awareness of their potential in helping the poor. © 2011 The Author(s).published_or_final_versionSpringer Open Choice, 21 Feb 201

Microsatellite instability and mismatch repair gene mutations are common in young colorectal cancer patients in Hong Kong

Conference Theme: Challenges to Specialists in the 21st centurypublished_or_final_versio

Generalized self-driven AC-DC synchronous rectification techniques for single- and multiphase systems

This paper extends the single-phase self-driven synchronous rectification (SDSR) technique to multiphase ac-dc systems. Power MOSFETs with either voltage- or current-sensing self-driven gate drives are used to replace the diodes in the rectifier circuits. The generalized methodology allows multiphase SDSRs to be designed to replace the multiphase diode rectifiers. Unlike the traditional SR that is designed for high-frequency power converters, the SDSR proposed here can be a direct replacement of the power diode bridges for both low- and high-frequency operations. The SDSR utilizes its output dc voltage to supply power to its control circuit. No start-up control is needed because the body diodes of the power MOSFETs provide the diode rectifier for the initial start-up stage. The generalized method is demonstrated in 2-kW one-phase and three-phase SDSRs for inductive, capacitive, and resistive loads. Power loss reduction in the range of 50%-69% has been achieved for the resistive load. © 2009 IEEE.published_or_final_versio

Using self-driven AC-DC synchronous rectifier as a direct replacement for traditional power diode rectifier

Synchronous rectification has previously been adopted in switched-mode circuits for reducing the conduction losses particularly in high-frequency, low-voltage, and high-current applications. This paper presents a generalized self-driven ac-dc synchronous rectification technique that can be used even at mains frequency to develop an ac-dc synchronous rectifier that behaves like a diode bridge but with much reduced conduction losses and without control integrated circuits. This generalized concept can be extended from single-phase to multiphase systems. Experiments based on 1- and 2-kW single-phase systems have been successfully conducted for capacitive, inductive, and resistive loads. Very significant power loss reduction (over 50%) has been achieved in the rectification stage at both 110- and 220-V ac mains operations. This patent-pending circuit can be regarded as a direct replacement of a general-purpose diode rectifier. Due to the reduction of power loss, further reduction in the size and cost of the heat sink or thermal management for the power circuit becomes possible. © 2011 IEEE.published_or_final_versio

Effects of chelators (desferal, deferiprone & deferaairox) on the growth of klebsiella and aeromonas isolated from transfusion dependent thalassemia patients

Poster Presentation (Doctor’s Session)Infection is among the leading causes of death for thalassemia major patients. The known predisposing factors of infection include prior splenectomy, iron overload and use of iron chelator such as desferal (desferrioxamine). While encapsulated organisms frequently found in splenectomized patients were readily controlled by prophylactic vaccination and vigilant antibiotic treatment, ferrophilic organisms such as Yersinia and Klebsiella remains common among Thalassemic patients. The inductive iron overloaded environment favours the growth of these organisms but their growth is also affected by the environment temperature. For example, Yersinia infection is more prevalent in temperate regions and Klebsiella infection is commonly found in subtropical areas. Furthermore, the use of iron chelator in the form of desferal further aggravates the risk of Yersinia infection. It is because the iron membrane transport protein siderophore found in desferal can be adopted by the bacteria for iron acquisition. However, oral chelators such as deferiprone do not enhance growth of Yersinia in vitro or in vivo. In order to find out whether such observation can be extended to Klebsiella and Aeromona infection, in vitro culture assay using Klebsiella pneumoniae and Aeromonas hydrophila obtained directly from our transfusion dependent thalassaemic patients were performed. The growth rates of the bacteria under iron rich, iron poor with or without different chelators were assessed. The growth rates were analyzed by both: (1) optic density of bacterial broth; and (2) colony count by bacterial agar plate. We found that the growth of Klebsiella was marginally enhanced by desferal in vitro when compared to Yersinia. Such unfavourable effect was not found in either deferiprone or deferasirox in vitro. On the other hand, the growth of Aeromonas was not affected by the presence of any of the 3 chelators. Therefore, we suggested that factors other than desferal may account for the increase prevalence of Klebsiella and Aeromonas infection among Asian thalassemic patients. It also suggests that oral chelators are safe for thalassemic patients during febrile illness. Unlike desferal, withholding iron chelator during infectious period may not be mandatory. But care has to be exercised especially for patients on deferiprone, since neutropenia has to be ruled out during febrile illness. This project was supported by the Children's Thalassaemia Foundationspublished_or_final_versio