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Biomedical subjects

H W Chiu

Publications and source records attributed to H W Chiu.

8 recordsLinked to original sources
PubMed2006

Developing an NLP and IR-based algorithm for analyzing gene-disease relationships.

OBJECTIVES: High-throughput techniques such as cDNA microarray, oligonucleotide arrays, and serial analysis of gene expression (SAGE) have been developed and used to automatically screen huge amounts of gene expression data. However, researchers usually spend lots of time and money on discovering gene-disease relationships by utilizing these techniques. We prototypically implemented an algorithm that can provide some kind of predicted results for biological researchers before they proceed with experiments, and it is very helpful for them to discover gene-disease relationships more efficiently. METHODS: Due to the fast development of computer technology, many information retrieval techniques have been applied to analyze huge digital biomedical databases available worldwide. Therefore we highly expect that we can apply information retrieval (IR) technique to extract useful information for the relationship of specific diseases and genes from MEDLINE articles. Furthermore, we also applied natural language processing (NLP) methods to do the semantic analysis for the relevant articles to discover the relationships between genes and diseases. RESULTS: We have extracted gene symbols from our literature collection according to disease MeSH classifications. We have also built an IR-based retrieval system, "Biomedical Literature Retrieval System (BLRS)" and applied the N-gram model to extract the relationship features which can reveal the relationship between genes and diseases. Finally, a relationship network of a specific disease has been built to represent the gene-disease relationships. CONCLUSIONS: A relationship feature is a functional word that can reveal the relationship between one single gene and a disease. By incorporating many modern IR techniques, we found that BLRS is a very powerful information discovery tool for literature searching. A relationship network which contains the information on gene symbol, relationship feature, and disease MeSH term can provide an integrated view to discover gene-disease relationships.

Algorithms↗
PubMed2001

Theoretical simulation of holographic polymer-dispersed liquid-crystal films via pattern photopolymerization-induced phase separation.

A theoretical simulation has been performed to elucidate the emergence of nematic domains during pattern photopolymerization-induced phase separation in holographic polymer-dispersed liquid crystals. We consider a reference system consisting of a single-component nematic, namely, 4-n-heptyl-4(')-cyanobiphenyl (T(NI)=42 degrees C), and a polymer network made from multifunctional monomers. To mimic pattern photopolymerization, the reaction rate was varied periodically in space through wave mixing. In the theoretical development, the photopolymerization kinetics was coupled with the time-dependent Ginzburg-Landau model C equations by incorporating the local free energy densities pertaining to isotropic liquid-liquid mixing, nematic ordering, and network elasticity. The simulated morphological patterns in the concentration and orientation order parameter fields show discrete layers of liquid-crystal droplets alternating periodically with polymer-network-rich layers. The Fourier transforms of these patterns show sharp diffraction spots arising from the periodic layers. As the layer thickness is reduced, the liquid-crystal molecules are confined in the narrow stripes. The liquid-crystal domains appear uniform along the stripes, which in turn gives rise to sharper diffraction spots in Fourier space. Of particular interest is that our simulated stratified patterns are in qualitative agreement with reported experimental observations.

Journal Article↗
PubMed2000

The relationship of late potentials to assessment of heart rate variability in post-infarction patients.

In order to investigate the relationship of late potential (LP) to assessment of heart rate variability (HRV) after acute myocardial infarction (AMI), we studied 101 Chinese patients with AMI (10+/-2.4 days) in Taiwan by collecting 24-h ECG from a Holter tape recorder and signal-averaged ECG from a high-resolution ECG cart. Of the 101 patients, 36 patients had LP (LP group) and 65 patients did not (NLP group). The mean heart rate was significantly lower in the LP group than in the NLP group (P<0.05). The LP group had a significantly increased high-frequency (HF) spectral component of HRV compared with the NLP group (P<0.005), but their low-frequency (LF) to HF ratio (LF/HF) was lower (P<0.05). Analysis of the circadian variation of HRV revealed significant difference of morning SDRR (standard deviation of normal RR intervals) compared with noon SDRR (P<0.05 in the LP group, P<0.005 in the NLP group) and evening SDRR (P<0.05 in the LP group, P<0.005 in the NLP group). In the NLP group, morning HF (normalized unit, nu) was 0.258+/-0.098 compared with noon HF (nu) of 0.219+/-0.83 (P<0.05) and evening HF (nu) of 0. 225+/-0.085 (P<0.05). Nine patients died during follow-up from cardiac causes, three (8.3%) in the LP group and six (9.2%) in the NLP group. In post-MI patients, there was higher vagal tone in patients with late potentials compared to those without late potentials. NLP patients had more circadian change in vagal tone compared with LP patients.

Adult↗
PubMed1998

Esophageal PP intervals for analysis of short-term heart rate variability in patients with atrioventricular block before and after insertion of a temporary ventricular inhibited pacemaker.

Heart rate variability (HRV) analysis is a useful method for assessment of the activities of autonomic nervous system. The RR intervals in ECG is measured for this purpose. However, RR intervals are not suitable for HRV analysis in atrioventricular block (AV) block patients with ventricular inhibited (VVI) pacemaker, as the intervals will be fixed by the ventricular pacemaker. Thus we used an esophageal lead to detect PP intervals for analysis of HRV. The aim of this study was to evaluate the short-term HRV by using an esophageal electrode to detect the atrial signal and PP intervals in AV block patients. Fifteen AV block patients before and after temporary VVI pacemaker and 15 subjects with normal AV conduction (control group) were enrolled in this study. The atrial signals from esophageal lead, ECG and intraatrial lead were recorded. The duration was 10 min. We compared correlation coefficient of PP intervals from different leads in AV block patients and the control group. We also compared the PP interval's variability parameters between the control group and AV block patients, before and after insertion of a temporary ventricular inhibited pacemaker. The esophageal PP intervals were excellently correlated with intraatrial AA intervals (r=0.98+/-0.01). The HRV using esophageal PP intervals with time domain demonstrated a significant decrease in patients with AV block (standard deviation of all PP intervals (SDNN) (s)=0.022+/-0.014; percentage difference between adjacent PP intervals that are greater than 50 ms (pNN-50) (%)=0.052+/-0.038; square root of the mean of squares of differences between duration of neighboring PP intervals (r-MSDD) (s)=0.322+/-0.082) but this returned to normal after insertion of a temporary ventricular inhibited pacemaker (SDNN (s)=0.035+/-0.009; pNN-50 (%)=2.540+/-1.682; r-MSDD (s)=0.542+/-0.190). However, the ratio of low frequency/high frequency (LF/HF) still increased (LF/HF=4.120+/-1.802). The result of this short-term HRV analysis suggested that withdrawal of vagal tone or increased sympathetic activity in AV block patients compared with the control group. This appearance was normalized after insertion of a temporary VVI pacemaker. however, abnormal sympathovagal balance still remained.

Aged↗
PubMed1997

Heart rate variability in patients with atrioventricular block.

BACKGROUND: Heart rate variability (HRV) analysis has been an established method for assessment of the activities of autonomic nervous system. Conventionally, the RR intervals from the surface electrocardiogram (ECG) are used for HRV analysis, however, analysis of the RR intervals may not be suitable in patients with atrioventricular (AV) node dysfunction, particularly in patients with certain degree of AV block. We used an esophageal electrode to detect PP intervals for HRV analysis in these patients. METHODS: Seven AV block patients and 13 subjects with normal AV conduction (control group) were enrolled in this study. The signals from esophageal lead, surface lead and intraatrial lead were recorded. Correlation coefficient of heart beat intervals from different leads was analyzed. Then we compared the HRV parameter recorded by esophageal lead between AV block patients and the control group. RESULTS: The AA intervals in intraatrial ECG and the PP intervals in surface ECG were poorly correlated (r = 0.489) in the AV block patients. However, intraatrial ECG was correlated well with esophageal ECG (r = 0.968). HRV with time domain decreased significantly in patients with AV block. The standard deviation of NN intervals (SDNN), pNN-50 and r-MSSD in the control group and the AV block patients were 0.035 +/- 0.006 vs. 0.021 +/- 0.016 seconds (p = 0.002), 3.210 +/- 3.120 vs. 0.050 +/- 0.040% (p = 0.027) and 0.577 +/- 0.181 vs. 0.318 +/- 0.084 seconds (p = 0.009), respectively. CONCLUSIONS: The esophageal lead recording is a non-invasive, easy and safe method to detect HRV of AV block patients whose vagal activity is abnormal.

Electrocardiography↗
PubMedDate not supplied

Systemic trichomoniasis in a squab operation.

Systemic trichomoniasis was responsible for severe morbidity and mortality in a commercial squab operation. Squabs of 1 to 3 weeks of age were primarily affected. Extensive caseous necrosis of the liver, heart, lung, and intestinal mesentery was observed grossly. Histologically, extensive heterophilic inflammation surrounded the necrotic areas and was observed perivascularly in areas that were uninvolved grossly. Numerous trichomonads were demonstrated in affected tissues with Bodian's silver stain.

Animals↗