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Biomedical subjects

Yu-Cheng Lin

Publications and source records attributed to Yu-Cheng Lin.

27 records · Page 2Linked to original sources
PubMed2004

Intra-retroperitoneal duplication cyst.

Duplication cyst occupying the retro- and intra-peritoneal space is a rare condition. We describe a case of duplication cyst in a 13-year-old girl who presented with abdominal pain, vomiting, and a lower abdominal mass. Plain abdominal X-ray films revealed local ileus over the lower abdomen. Ultrasonography revealed 2 double-layered cystic masses over the lower abdomen with a suspicious communicating tract. Mild hydropelvis of the right kidney was also noted. Abdominal computed tomography revealed 2 cystic lesions. One was located at the pelvic cavity just above the urinary bladder and the other was in the left retroperitoneal space. Laparotomy revealed a dumbbell-shaped intra-retroperitoneal duplication cyst with a small communicating tract. The cyst was excised without disturbing bowel continuity and the vascular supply. The patient was doing well at 1-year follow-up.

Adolescent↗
PubMed2003

Design of passive mixers utilizing microfluidic self-circulation in the mixing chamber.

This paper proposes the design of a passive micromixer that utilizes the self-circulation of the fluid in the mixing chamber for applications in the Micro Total Analysis Systems (microTAS). The micromixer with a total volume of about 20 microL and consisting of an inlet port, a circular mixing chamber and an outlet port was designed. The device was actuated by a pneumatic pump to induce self-circulation of the fluid. The self-circulation phenomenon in the micromixer was predicted by the computational simulation of the microfluidic dynamics. Flow visualization with fluorescence tracer was used to verify the numerical simulations and indicated that the simulated and the experimental results were in good agreement. Besides, an index for quantifying the mixing performance was employed to compare different situations and to demonstrate the advantages of the self-circulation mixer. The mixing efficiencies in the mixer under different Reynolds numbers (Re) were evaluated numerically. The numerical results revealed that the mixing efficiency of the mixer with self-circulation was 1.7 to 2 times higher than that of the straight channel without a mixing chamber at Re= 150. When Re was as low as 50, the mixing efficiency of the mixer with self-circulation in the mixing chamber was improved approximately 30% higher than that in the straight channel. The results indicated that the self-circulation in the mixer could enhance the mixing even at low Re. The features of simple mixing method and fabrication process make this micromixer ideally suitable for microTAS applications.

Journal Article↗
PubMed2003

Microfluidic chip for fast nucleic acid hybridization.

The design and experimental verification of a fast nucleic acid hybridization microchip using the fluidic velocity and strain rate effects was conducted. This hybridization chip was able to increase the hybridization signal 6-fold, reduce non-specific target-probe binding and background noise within 30 min, as compared to conventional hybridization methods, which may take from 4 h to overnight. Excellent correlation between experimental results and simulation analysis was obtained in this study. A detailed study of a newly designed microfluidic chip for enhancing hybridization was conducted. Three different designs of devices were fabricated and tested. Two different lengths of targets, 25-mer oligonucleotide and 1.4 kb ssDNA, were tested in this study. The hybridization efficiency can be improved by introducing velocity and extensional strain rate to the sample. This study demonstrates that the signal in the proposed method exhibits intensities 6-fold higher than those in static conditions. The necessary time for the hybridization process can be reduced from overnight to 30 min using the methods developed in this study. Experimental results also show that the strain rate provides stronger effect on hybridization than that of velocity. Combining hybridization with microfluidic concepts of velocity and strain rate effects may provide additional specificity and efficiency in nucleic acid detection and genomic study. This microfluidic hybridization chip can provide potential application in genomic study.

Algorithms↗
PubMed2003

Design of a recursively-structured valveless device for microfluidic manipulation.

A recursively-structured apparatus based on a pneumatic pumping structure has been investigated numerically and experimentally in the present study. For the T-connected channels, this apparatus demonstrated the ability to manipulate the liquid drop from a first channel to a second channel, while simultaneously preventing flow into the third channel. The microTAS research aimed at biochemical analysis miniaturization and integration has recently made explosive progress. However, there is still a considerable technical challenge in integrating these procedures into a multiple-step system. An important issue for this integration is microfluid management techniques. The microTAS method must be designed considering special transport mechanisms to move samples and reagents through the microchannels. The structure of this apparatus was simple and easily fabricated. Moreover, because there is a continuous airflow at the "outlet" during fluid manipulation, it is possible to avoid contamination of the air source similar to the "laminar flow hook" in biological experiments. Utilizing the concept of a recursive structure, one can easily design a device wherein more than three channels are included in the flow network, either intersecting in a single junction or in multiple junctions.

Computer Simulation↗
PubMed2003

Design and simulation of the micromixer with chaotic advection in twisted microchannels.

Chaotic mixers with twisted microchannels were designed and simulated numerically in the present study. The phenomenon whereby a simple Eulerian velocity field may generate a chaotic response in the distribution of a Lagrangian marker is termed chaotic advection. Dynamic system theory indicates that chaotic particle motion can occur when a velocity field is either two-dimensional and time-dependent, or three-dimensional. In the present study, micromixers with three-dimensional structures of the twisted microchannel were designed in order to induce chaotic mixing. In addition to the basic T-mixer, three types of micromixers with inclined, oblique and wavelike microchannels were investigated. In the design of each twisted microchannel, the angle of the channels' bottoms alternates in each subsection. When the fluids enter the twisted microchannels, the flow sways around the varying structures within the microchannels. The designs of the twisted microchannels provide a third degree of freedom to the flow field in the microchannel. Therefore, chaotic regimes that lead to chaotic mixing may arise. The numerical results indicate that mixing occurs in the main channel and progressively larger mixing lengths are required as the Peclet number increased. The swaying of the flow in the twisted microchannel causes chaotic advection. Among the four micromixer designs, the micromixer with the inclined channel most improved mixing. Furthermore, using the inclined mixer with six subsections yielded optimum performance, decreasing the mixing length by up to 31% from that of the basic T-mixer.

Computer Simulation↗
PubMed2002

Long-term immunogenicity and efficacy of universal hepatitis B virus vaccination in Taiwan.

The long-term immunogenicity of universal hepatitis B virus (HBV) vaccine is seldom studied in large-scale prospective community-based populations, especially in adolescents. This study enrolled 1200 children aged 7 years with complete HBV immunization in infancy and determined HBV surface antigen (HBsAg), its antibody (anti-HBs), and HBV core antibody (anti-HBc) annually until the children were aged 14 years. Eleven children had new HBV infections with anti-HBc positivity as the only marker. None became positive for HBsAg or had detectable HBV DNA by polymerase chain reaction. The percentage of protective anti-HBs in 951 children without booster vaccination gradually decreased from 71.1% at age 7 years to 37.4% at age 12 years. Only 1 of the 200 children in the booster group and 2 of the 258 children in the nonbooster group developed new anti-HBc positivity. The results suggest that routine booster vaccination may not be required to provide protection against chronic HBV infection before age 15 years.

Adolescent↗
PubMed2002

Mechanism of hydrodynamic separation of biological objects in microchannel devices.

In this study, the separation mechanism employed in hydrodynamic chromatography in microchannel devices is analyzed. The main purpose of this work is to provide a methodology to develop a predictive model for hydrodynamic chromatography for biological macromolecules in microchannels and to assess the importance of various phenomenological coefficients. A theoretical model for the hydrodynamic chromatography of particles in a microchannel is investigated herein. A fully developed concentration profile for non-reactive particles in a microchannel was obtained to elucidate the hydrodynamic chromatography of these particles. The external forces acting on the particles considered in this model include the van der Waals attractive force, double-layer force as well as the gravitational force. The surface forces, such as van der Waals attractive force as well as the double-layer repulsive force, can either enhance or hinder the average velocity of the macromolecular particles. The average velocity of the particles decreases with the molecular radius because the van der Waals attractive force increases the concentration of the particles near the channel surface, which is the low-velocity region. The transport velocity of the particles is dominated by the gravity and the higher density enlarges the effect caused by gravity.

Chromatography, Liquid↗
PubMedDate not supplied

Traumatic intramural hematoma of the duodenum: report of one case.

Traumatic intramural hematoma of the duodenum is a rare entity in children. A high clinical index of suspicion is necessary for early and accurate diagnosis. We report a 10-year-old girl presenting with a sudden onset of epigastralgia after impact on the epigastrium by the edge of a wooden bed while playing on it. Symptoms of high gastrointestinal obstruction were severe, with bilious and large amounts of nasogastric effluent. Image studies revealed a large hematoma extending from the second to the third portion of the duodenum. Her condition was managed successfully by conservative treatments with nasogastric decompression and total parenteral nutrition. Her hospital course was uneventful. This report serves as a reminder to clinicians to consider intramural hematoma of the duodenum in the differential diagnosis of blunt abdominal trauma.

Abdomen, Acute↗