Contention-Free Complete Exchange Algorithms on Clusters

To construct a large commodity clustec a hierarchical network is generally adopted for connecting the host muchines, where a Gigabit backbone switch connects a few commodity switches with uplinks to achieve scaled bisectional bandwidth. This type of interconnection usually results in link contention and has congestion developed at the uplink ports. Moreover, the non-detenninistic delays on scheduling communication events in clusters accelerate the building up of congestion amongst these uplink ports, which lead to severe packets drop and hinder the overall performance. In this paper, we focus on the practical design of high-speed complete exchange algorithm on a commodity cluster interconnected by a hierarchical Ethemet-based network. By exploiting some architectural characteristics of the interconnection in optimizing the performunce of a complete exchange algorithm, we introduce a congestion control mechanism - global windowing that monitors and regulates the trafic load, together with a permutation scheme - reorder scheme that effectively alleviates the congestion problem. We evaluate our algorithm and compare its performance with other algorithms in a PC cluster connected by various types of switches, including Gigabit Ethernet, input-buffered and shared-memory Fast Ethernet switches.published_or_final_versio

Robot-assisted versus standard laparoscopic partial nephrectomy: comparison of perioperative outcomes from a single institution

OBJECTIVE: To evaluate the perioperative outcomes of robot-assisted laparoscopic partial nephrectomy and standard laparoscopic partial nephrectomy in a teaching hospital. DESIGN: Retrospective study. SETTING: Division of Urology, Department of Surgery, Queen Mary and Tung Wah hospitals, Hong Kong. PATIENTS: The first 10 consecutive patients who had robot-assisted laparoscopic partial nephrectomy for renal tumours between January 2008 and September 2009 with prospective data collection were evaluated. Their outcomes were compared with the last 10 consecutive patients in our database, who had standard laparoscopic partial nephrectomy between November 2004 and October 2007. MAIN OUTCOME MEASURES: Demographics, tumour characteristics, perioperative outcomes, renal function, and pathological outcomes. RESULTS: There were no differences between the groups with regard to age (63 vs 56 years; P=0.313) and tumour size (2.7 vs 2.8 cm; P=0.895). No significant difference was found between the two groups with respect to the operating room time (376 vs 361 min; P=0.722), estimated blood loss (329 vs 328 mL; P=0.994), and length of hospital stay (7 vs 14 days; P=0.213). A statistically significant shorter mean warm ischaemic time for the robot-assisted group was noted (31 vs 40 minutes; P=0.032). Respective renal functional outcomes as shown by the difference between day 0 and day 60 serum creatinine levels were comparable (+10 vs +7 mmol/L; P=0.605). In both groups, there were no intra-operative complications or instances of surgical margin tumour involvement. Three patients endured postoperative complications in the standard laparoscopic group (a perinephric haematoma, urine leakage, and lymph leakage) compared with one in the robot-assisted group (a perinephric haematoma). These complications all resolved with conservative treatment. CONCLUSIONS: Robot-assisted laparoscopic partial nephrectomy is a technically feasible alternative to standard laparoscopic partial nephrectomy, and provides comparable results. Robot-assisted laparoscopic partial nephrectomy appears to offer the advantage of decreased warm ischaemic time. Longer follow-up is required to assess renal function and oncological outcomes. Further experience and randomised trials are necessary to compare robot-assisted with standard laparoscopic partial nephrectomy.published_or_final_versio

Wilson's disease: A patient undiagnosed for 18 years

Wilson's disease, an autosomal recessive disorder of copper metabolism, is the most common inherited hepatic disease in Hong Kong. Diagnosis is based on the presence of Kayser-Fleischer rings, typical neurological symptoms, and/or a low serum ceruloplasmin concentration (<0.20 g/L). Early detection and treatment protect patients and their presymptomatic siblings from devastating organ damage. The diagnosis of Wilson's disease may nonetheless be overlooked if only established clinical and laboratory tests are used as diagnostic criteria. We report diagnosis of the disorder using genetic analysis of ATP7B in a presymptomatic sibling who escaped diagnosis during family screening 18 years previously. The patient was 11 months old when family screening was performed following diagnosis of Wilson's disease in an elder sister. The boy was considered to be unaffected on the basis of laboratory results in the expected range: serum copper level, 4.6 μmol/L; serum ceruloplasmin level, 0.16 g/L; and 24-hour urinary copper excretion, 0.14 μmol/day. Molecular analysis of ATP7B was performed; it revealed that the two siblings shared the same compound heterozygous mutations (G943D and 2299delC). We recommend that molecular diagnosis is the only definitive means of diagnosing Wilson's disease in children younger than 1 year.published_or_final_versio

Realistic communication model for parallel computing on cluster

We present a model for parallel computation on commodity cluster. Our cluster model is targeted as a tool for performance analysis and algorithm design. We abstract the communication event by means of local and remote data movements, and explicitly expose the contention problems by capturing them in our parameters. To validate our model, we compare the prediction accuracy of our model with the Postal model for the popular tree-based broadcast algorithm. Our model provides good prediction accuracy and answers to some performance issues that are missing in existing models. We examine the gather collective operation, in which contention delay dominates its overall execution time. Based on the model, we design a communication schedule for the gather operation that is based on the upper and lower bounds, in which the congestion behavior could be under our control and achieve optimal results by avoiding data loss.published_or_final_versio

Step-changed long-period fiber gratings

Author name used in this publication: Chung-Loong ChoyAuthor name used in this publication: A-Ping ZhangAuthor name used in this publication: Muhtesem Süleyman DemokanAuthor name used in this publication: Xiao-Ming Tao2001-2002 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Exploring the Intrabinary Shock from the Redback Millisecond Pulsar PSR J2129-0429

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Ten-year experience with liver transplantation at Queen Mary Hospital: retrospective study.

OBJECTIVE: To report the experience with liver transplantation at the Queen Mary Hospital from 1991 to 2000. DESIGN: Retrospective study. SETTING: Liver transplant centre of a University teaching hospital, Hong Kong. PATIENTS: One hundred and forty-eight patients (127 adults and 21 children) who underwent a total of 155 liver transplants using 75 cadaver grafts (full-size, 67; reduced-size, 5; split, 3) and 80 living donor grafts (left lateral segment, 15; left lobe, 6; right lobe, 59) from October 1991 to December 2000 were reviewed. MAIN OUTCOME MEASURES: Graft and patient survival rate. RESULTS: The most common disease indications for liver transplantation were chronic hepatitis B-related liver disease (n=74) in adults and biliary atresia (n=14) in children. Eighteen patients had hepatocellular carcinoma. Forty-eight (31%) liver transplants (three ABO-incompatible) were performed in high-urgency situations for patients requiring intensive care. The proportion of living donor liver transplants was 47.7% in adults and 73.9% in children. The overall 1-year and 5-year patient survival rates were 82% and 77%, respectively. The survival of high-risk recipients, such as those with fulminant hepatic failure (80%), chronic hepatitis B (81%), or hepatocellular carcinoma (94%), was not inferior to that of other patients. CONCLUSION: Over the last decade, the promotion of (cadaver) organ donation through public education coupled with innovative techniques in living donor liver transplantation have enabled a liver transplantation programme to be established in Hong Kong with gratifying results.published_or_final_versio

Discovery Of An Ultracompact Gamma-ray Millisecond Pulsar Binary Candidate

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Role of polymorphisms of the inflammatory response genes and DC-SIGNR in genetic susceptibility to SARS and other infections.

Research Fund for the Control of Infectious Diseases: Research Dissemination Reports (Series 2)1. A genetic risk-association study involving more than 1200 subjects showed individuals homozygous for L-SIGN tandem repeats are less susceptible to SARS infection. 2. This was supported by in vitro binding studies that demonstrated homozygous L-SIGN, compared to heterozygous, had higher binding capacity for SARS coronavirus (SARS-CoV), with higher proteasome-dependent viral degradation. In contrast, homozygous L-SIGN demonstrated lower binding capacity for HIV1-gp120.3. Genetic-association studies for single nucleotide polymorphisms of the inflammatory response genes, namely TNF-alpha, INF-alpha, INF-beta, INF-gamma, IL1-alpha, IL1-beta, IL-4, IL-6 and iNOS, failed to show a significant association with SARS clinical outcomes or susceptibility.published_or_final_versio

Refractive-index sensing with ultra-thin plasmonic nanotubes

We study the refractive-index sensing properties of plasmonic nanotubes with a dielectric core and ultra-thin metal shell. The few-nm thin metal shell is described by both the usual Drude model and the nonlocal hydrodynamic model to investigate the effects of nonlocality. We derive an analytical expression for the extinction cross section and show how sensing of the refractive index of the surrounding medium and the figure-of-merit are affected by the shape and size of the nanotubes. Comparison with other localized surface plasmon resonance sensors reveals that the nanotube exhibits superior sensitivity and comparable figure-of-merit