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Search Results: 1 - 10 of 480007 matches for " S. L. Lui "
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The Choice of Peritoneal Dialysis Catheter Implantation Technique by Nephrologists
T. Yip,S. L. Lui,W. K. Lo
International Journal of Nephrology , 2013, DOI: 10.1155/2013/940106
The Choice of Peritoneal Dialysis Catheter Implantation Technique by Nephrologists
T. Yip,S. L. Lui,W. K. Lo
International Journal of Nephrology , 2013, DOI: 10.1155/2013/940106
Abstract: Peritoneal dialysis catheter (PDC) is the lifeline of peritoneal dialysis (PD) patients. One of the critical issues for successful PD is a well-functioning PDC which is timely inserted. It is the implantation technique rather than the catheter design that determines the outcome of the catheter. Dedication in acquiring the appropriate technique is vital to the success of a PD program. In this paper, we discuss the pros and cons of various techniques used for PDC implantation. A detailed description of PDC implantation by using the minilaparotomy method is presented. We strongly recommend mini-laparotomy as the method of choice for PDC implantation by nephrologists. Peritoneal dialysis (PD) is a well-established technique of renal replacement therapy in patients with end-stage renal disease (ESRD). The advantages of PD include preservation of residual renal function, better patient survival in the first few years, better quality of life and cost-effectiveness over hemodialysis [1–4]. Thus, PD is well suited to act as a first-line renal replacement therapy in an integrated approach to end-stage renal failure care. In Hong Kong, “PD-first” policy has been adopted since mid-1980s. Currently, up to 80% of ESRD patients on maintenance dialysis are on PD. It has provided a successful model for the PD first policy. For a PD program to succeed, access to peritoneal dialysis catheter (PDC) implantation must be timely and the procedure must be performed by an experienced operator with low catheter failure rates and complications. PDC can be implanted percutaneously or by open surgery (Table 1). The standard percutaneous placement includes the “trocar and cannula” method and the Seldinger technique, with variations like fluoroscopy-assisted or peritoneoscopy-assisted placement. Open surgical approach includes minilaparotomy and laparoscopic placement. Table 1: Comparison of different methods of peritoneal dialysis catheter implantation. In many centers, PDC is implanted by surgeons, either by minilaparotomy or laparoscopic approach. However, referral to surgeons usually causes delay in initiating PD therapy, for both the waiting time to see a surgeon and the time required to arrange the operation afterwards. The date of implantation is often not under the control of nephrologists and this may make timely implantation of a PDC an impossible dream. Some patients may be forced to remain on hemodialysis with a central venous catheter, which is associated with an accelerated decrease in residual renal function and high rates of bacteremia and mortality. Survival data
An Exact Formulation of the Time-Ordered Exponential using Path-Sums
P. -L. Giscard,K. Lui,S. J. Thwaite,D. Jaksch
Mathematics , 2014, DOI: 10.1063/1.4920925
Abstract: We present the path-sum formulation for $\mathsf{OE}[\mathsf{H}](t',t)=\mathcal{T}\,\text{exp}\big(\int_{t}^{t'}\!\mathsf{H}(\tau)\,d\tau\big)$, the time-ordered exponential of a time-dependent matrix $\mathsf{H}(t)$. The path-sum formulation gives $\mathsf{OE}[\mathsf{H}]$ as a branched continued fraction of finite depth and breadth. The terms of the path-sum have an elementary interpretation as self-avoiding walks and self-avoiding polygons on a graph. Our result is based on a representation of the time-ordered exponential as the inverse of an operator, the mapping of this inverse to sums of walks on graphs and the algebraic structure of sets of walks. We give examples demonstrating our approach. We establish a super-exponential decay bound for the magnitude of the entries of the time-ordered exponential of sparse matrices. We give explicit results for matrices with commonly encountered sparse structures.
Views and Experience on Patient Engagement in Healthcare Professionals and Patients—How Are They Different?  [PDF]
Eliza L. Y. Wong, Siufai Lui, Annie W. L. Cheung, Carrie H. K. Yam, Nicole F. Huang, Wilson W. S. Tam, Engkiong Yeoh
Open Journal of Nursing (OJN) , 2017, DOI: 10.4236/ojn.2017.76046
Abstract: A patient-centered approach is used to build a therapeutic alliance between patients and the healthcare professionals in care process which should be supported by a good engagement of both parties. The study aimed to explore the gap between healthcare professionals and patients on patient engagement in hospital. It was a cross-sectional survey. 2774 doctors and nurses from Department of Medicine of public hospitals completed the self-administered questionnaire and 1042 patients discharged from corresponding wards completed the telephone interviews. Participants were interviewed using structural questionnaires. The Mann-Whitney test or Pearson’s chi-square test was used to analyze the agreement between health-care professionals and patients on the views and experiences of patient engagement. A difference was considered to be statistically significant when the p-value was <0.05. Although both groups valued the importance of patient engagement, there was a discrepancy on understanding, views and experiences. More healthcare professionals particularly in nursing were concerned about the possible negative impact of the engagement. The majority of healthcare professionals reported that they engaged well with patients, and perceived more difficulties than patients did. The findings highlighted the mutual understanding of patient engagement, involvement and challenges encountered by both groups in Department of Medicine, which was crucial in efforts to provide meaningful patient engagement in regards to jurisdictions, health system, specialty, discipline and background of patients. It provided insight that a collaborative strategy involving both healthcare professional and patients might be an alternative approach to improving patient engagement.
Human Nail Clippings as a Source of DNA for Genetic Studies  [PDF]
Le Truong, Hannah Lui Park, Seong Sil Chang, Argyrios Ziogas, Susan L. Neuhausen, Sophia S. Wang, Leslie Bernstein, Hoda Anton-Culver
Open Journal of Epidemiology (OJEpi) , 2015, DOI: 10.4236/ojepi.2015.51006
Abstract: Blood samples have traditionally been used as the main source of DNA for genetic analysis. How-ever, this source can be difficult in terms of collection, transportation, and long-term storage. In this study, we investigated whether human nail clippings could be used as a source of DNA for SNP genotyping, null-allele detection, and whole-genome amplification. From extracted nail DNA, we achieved amplicons up to a length of ~400 bp and >96% concordance for SNP genotyping and 100% concordance for null-allele detection compared to DNA derived from matched blood sam-ples. For whole-genome amplification, OmniPlex performed better than Multiple Displacement Amplification with a success rate of 89.3% and 76.8% for SNP genotyping and null-allele detection, respectively. Concordance was ~98% for both methods. When combined with OmniPlex whole-genome amplification, human nail clippings could potentially be used as an alternative to whole blood as a less invasive and more convenient source of DNA for genotyping studies.
Calibration of Tethered Particle Motion Experiments
L. Han,B. Lui,S. Blumberg,J. Beausang,P. Nelson,R. Phillips
Quantitative Biology , 2008,
Abstract: The Tethered Particle Motion (TPM) method has been used to observe and characterize a variety of protein-DNA interactions including DNA looping and transcription. TPM experiments exploit the Brownian motion of a DNA-tethered bead to probe biologically relevant conformational changes of the tether. In these experiments, a change in the extent of the bead's random motion is used as a reporter of the underlying macromolecular dynamics and is often deemed sufficient for TPM analysis. However, a complete understanding of how the motion depends on the physical properties of the tethered particle complex would permit more quantitative and accurate evaluation of TPM data. For instance, such understanding can help extract details about a looped complex geometry (or multiple coexisting geometries) from TPM data. To better characterize the measurement capabilities of TPM experiments involving DNA tethers, we have carried out a detailed calibration of TPM magnitude as a function of DNA length and particle size. We also explore how experimental parameters such as acquisition time and exposure time affect the apparent motion of the tethered particle. We vary the DNA length from 200bp to 2.6kbp and consider particle diameters of 200, 490 and 970nm. We also present a systematic comparison between measured particle excursions and theoretical expectations, which helps clarify both the experiments and models of DNA conformation.
Computing Quasiconformal Maps on Riemann surfaces using Discrete Curvature Flow
W. Zeng,L. M. Lui,F. Luo,J. S. Liu T. F. Chan,S. T. Yau,X. F. Gu
Mathematics , 2010,
Abstract: Surface mapping plays an important role in geometric processing. They induce both area and angular distortions. If the angular distortion is bounded, the mapping is called a {\it quasi-conformal} map. Many surface maps in our physical world are quasi-conformal. The angular distortion of a quasi-conformal map can be represented by Beltrami differentials. According to quasi-conformal Teichm\"uller theory, there is an 1-1 correspondence between the set of Beltrami differentials and the set of quasi-conformal surface maps. Therefore, every quasi-conformal surface map can be fully determined by the Beltrami differential and can be reconstructed by solving the so-called Beltrami equation. In this work, we propose an effective method to solve the Beltrami equation on general Riemann surfaces. The solution is a quasi-conformal map associated with the prescribed Beltrami differential. We firstly formulate a discrete analog of quasi-conformal maps on triangular meshes. Then, we propose an algorithm to compute discrete quasi-conformal maps. The main strategy is to define a discrete auxiliary metric of the source surface, such that the original quasi-conformal map becomes conformal under the newly defined discrete metric. The associated map can then be obtained by using the discrete Yamabe flow method. Numerically, the discrete quasi-conformal map converges to the continuous real solution as the mesh size approaches to 0. We tested our algorithm on surfaces scanned from real life with different topologies. Experimental results demonstrate the generality and accuracy of our auxiliary metric method.
Photon recycling in Fabry-Perot micro-cavities based on Si$_3$N$_4$ waveguides
F. Riboli,A. Recati,N. Daldosso,L. Pavesi,G. Pucker,A. Lui,S. Cabrini,E. Di Fabrizio
Physics , 2005, DOI: 10.1016/j.photonics.2005.12.001
Abstract: We present a numerical analysis and preliminary experimental results on one-dimensional Fabry-Perot micro-cavities in Si$_3$N$_4$ waveguides. The Fabry-Perot micro-cavities are formed by two distributed Bragg reflectors separated by a straight portion of waveguide. The Bragg reflectors are composed by a few air slits produced within the Si$_3$N$_4$ waveguides. In order to increase the quality factor of the micro-cavities, we have minimized, with a multiparametric optimization tool, the insertion loss of the reflectors by varying the length of their first periods (those facing the cavity). To explain the simulation results the coupling of the fundamental waveguide mode with radiative modes in the Fabry-Perot micro-cavities is needed. This effect is described as a recycling of radiative modes in the waveguide. To support the modelling, preliminary experimental results of micro-cavities in Si$_3$N$_4$ waveguides realized with Focused Ion Beam technique are reported.
Optimization of Surface Registrations using Beltrami Holomorphic Flow
L. M. Lui,T. W. Wong,W. Zeng,X. F. Gu,P. M. Thompson,T. F. Chan,S. T. Yau
Mathematics , 2010,
Abstract: In shape analysis, finding an optimal 1-1 correspondence between surfaces within a large class of admissible bijective mappings is of great importance. Such process is called surface registration. The difficulty lies in the fact that the space of all surface diffeomorphisms is a complicated functional space, making exhaustive search for the best mapping challenging. To tackle this problem, we propose a simple representation of bijective surface maps using Beltrami coefficients (BCs), which are complex-valued functions defined on surfaces with supreme norm less than 1. Fixing any 3 points on a pair of surfaces, there is a 1-1 correspondence between the set of surface diffeomorphisms between them and the set of BCs. Hence, every bijective surface map can be represented by a unique BC. Conversely, given a BC, we can reconstruct the unique surface map associated to it using the Beltrami Holomorphic flow (BHF) method. Using BCs to represent surface maps is advantageous because it is a much simpler functional space, which captures many essential features of a surface map. By adjusting BCs, we equivalently adjust surface diffeomorphisms to obtain the optimal map with desired properties. More specifically, BHF gives us the variation of the associated map under the variation of BC. Using this, a variational problem over the space of surface diffeomorphisms can be easily reformulated into a variational problem over the space of BCs. This makes the minimization procedure much easier. More importantly, the diffeomorphic property is always preserved. We test our method on synthetic examples and real medical applications. Experimental results demonstrate the effectiveness of our proposed algorithm for surface registration.
Cluster observation of plasma flow reversal in the magnetotail during a substorm
A. T. Y. Lui, Y. Zheng, Y. Zhang, S. Livi, H. Rème, M. W. Dunlop, G. Gustafsson, S. B. Mende, C. Mouikis,L. M. Kistler
Annales Geophysicae (ANGEO) , 2006,
Abstract: We investigate in detail a reversal of plasma flow from tailward to earthward detected by Cluster at the downstream distance of ~19 RE in the midnight sector of the magnetotail on 22 August 2001. This flow reversal was accompanied by a sign reversal of the Bz component and occurred during the late substorm expansion phase as revealed by simultaneous global view of auroral activity from IMAGE. We examine the associated Hall current system signature, current density, electric field, Lorentz force, and current dissipation/dynamo term, the last two parameters being new features that have not been studied previously for plasma flow reversals. It is found that (1) there was no clear quadrupole Hall current system signature organized by the flow reversal time, (2) the x-component of the Lorentz force did not change sign while the other two did, (3) the timing sequence of flow reversal from the Cluster configuration did not match tailward motion of a single plasma flow source, (4) the electric field was occasionally dawnward, producing a dynamo effect, and (5) the electric field was occasionally larger at the high-latitude plasma sheet than near the neutral sheet. These observations are consistent with the current disruption model for substorms in which these disturbances are due to shifting dominance of multiple current disruption sites and turbulence at the observing location.
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