Search PubMed⌕ Search

Biomedical subjects

C N Chen

Publications and source records attributed to C N Chen.

84 records · Page 5Linked to original sources
PubMedDate not supplied

An iterative phase correction program for nuclear magnetic resonance (NMR) spectra.

An iterative algorithm is given to correct for the zeroth and first order phase errors in NMR spectroscopy. A FORTRAN computer program is listed and two sample runs exemplified. No a priori knowledge of the existing phase errors is required. The parameters are optimised iteratively under the assumption that when the spectrum is correctly phased the ratio of the area above the spectrum to that below it is a maximum.

Algorithms↗
PubMedDate not supplied

An in vitro study on restoring bond strength of a GIC to saliva contaminated enamel under unrinse condition.

OBJECTIVES: This study attempted to find a method of restoring the tensile bond strength of glass ionomer cement (GIC) to saliva contaminated enamel under unrinse condition. METHODS: One hundred and thirty human non-carious permanent teeth were divided into two major groups. Either treatment with air drying, acetone, polyacrylic acid, maleic acid, tartaric acid, Scotchbond primer or no treatment at all was applied to both clean and saliva contaminated enamel surfaces prior to GIC placement. Samples were debonded in tension after 7 days of storage in water using a universal testing machine. Statistical analysis was performed using one-way ANOVA, Tukey's studentized range test and Wilcoxon's rank sums test to determine the significance of the difference of tensile bond strengths within and between the two major groups. RESULTS: Bond strength of GIC to clean enamel was 2.46+/-0.79 MPa while the bond strength of GIC to wet contaminated enamel was significantly reduced to 1.28+/-0.32 MPa (p<0.01). However, the bond strengths were restored when the contaminated enamel surfaces were air-dried (2.19+/-0.38 MPa) or applied with either maleic acid (2.80+/-0.63 MPa) or Scotchbond primer (2.13+/-0.65 MPa) before placing GIC over the enamels. CONCLUSIONS: Air drying, or application of maleic acid or Scotchbond primer to the contaminated enamel without rinsing prior to GIC placement can restore the tensile bond strength to a level similar to that of non-contaminated control.

Acetone↗
PubMedDate not supplied

Selective population inversion in NMR.

Population inversion of a selected region of a spectrum is a concept which has wide application in both NMR spectroscopy and imaging. While inversion of population at any one frequency is a trivial matter, ensuring an accurate inversion over a specified bandwidth, with negligible perturbation of the magnetization outside that bandwidth, is a major problem. However, by using as a driving function a complex radiofrequency (r.f.) pulse with an envelope of the form (sech beta t)1+5i where 1/beta is the temporal width and t is time, we have found that above a critical r.f. power threshold, magnetization is accurately inverted over a very sharply defined bandwidth, while outside that region, magnetization is returned to its initial position, and population is unaffected. Within the broad limits imposed by our equipment, we have also discovered that the phenomenon is independent of the incident r.f. power.

Magnetic Resonance Spectroscopy↗
PubMedDate not supplied

At least two genes reside within a large intron of the dunce gene of Drosophila.

The dunce locus of Drosophila melanogaster is considered to house a gene involved in memory, because flies carrying lesions at the locus have shortened memory of several different conditioned behaviours. Our recent partial characterization of the gene at the molecular level, along with prior genetic and biochemical evidence, recently provides compelling evidence that the gene codes for the enzyme cAMP phosphodiesterase. The observation that the gene encodes at least six overlapping poly(A)+ RNA molecules ranging in size from 4.2 to 9.5 kilobases (kb) (ref. 8), suggests that the gene is extraordinarily complex. Here we provide the sequence of a dunce complementary DNA clone and the corresponding genomic coding regions which show that the organization of the gene is elaborate. The cDNA clone defines dunce exons which are separated by a large intron of 79 kb. More importantly, at least two other genes are shown to reside within the large intron, including the well-defined glue protein gene, Sgs-4. The location of dunce exons relative to the molecular breakpoints of chromosomal aberrations with defined cytological positions indicates that the dunce gene extends over more than five polytene chromosome bands.

Animals↗
PubMedDate not supplied

Misdiagnoses in a Chinese narcoleptic patient with delayed onset of cataplexy.

Narcolepsy is a chronic condition that usually afflicts the patient for decades. It is more common than is generally appreciated. However, it is likely to be misdiagnosed because doctors are unfamiliar with some of the symptoms. Its significant socioeconomic impact on the patient's quality of life warrants prompt medical attention.

Anxiety↗
PubMedDate not supplied

Gastric cancer in the young.

BACKGROUND/AIMS: Gastric cancer in the young is relatively uncommon, but it carries important clinical significance. This study was designed to determine the clinicopathological characteristics of young patients who underwent a gastrectomy for gastric cancer in order to improve clinical management. METHODOLOGY: From January 1977 to December 1994, 997 patients underwent surgical treatment for gastric cancer in the Department of Surgery of the National Taiwan University Hospital. All of these patients were classified into 6 groups based on their age at the time of surgery. Of these, 52 patients (5.2%) were 35 years of age or younger. The clinicopathological data of these patients were reviewed and compared to the data of the other age groups. RESULTS: There was a female predominance, with a male:female ratio of 1:1.36. In the majority of patients, the time period from the onset of symptoms to the time of diagnosis was less than one year (76.9%). Epigastralgia was the most common complaint (65.4%). Six patients (11%) were diagnosed as having a benign peptic ulcer during the first endoscopy. Histologically, there were more diffuse (65.4%) and scirrhous types of gastric cancer in the young group. Half of the patients (49.9%) were at TNM stage III or IV at the time of surgery. Curative resections were performed on 49 patients. The cumulative 5-year survival rate was 36.1% among the young patients, which was no different from the survival rates of the other age groups. While the 5-year survival rate of patients with stage I gastric cancer was 90% in the young age group, of the 26 patients with stage III or IV, only one survived more than 5 years. Four female patients (13.3%) were found to have metastases to the ovaries during follow-up. CONCLUSION: The clinicopathological characteristics of young patients with gastric cancer are as follows: 1) female dominance; 2) more diffuse and scirrhous types of gastric carcinoma; 3) the prognosis after surgery depends on the stage rather than the age; 4) free use of endoscopy and clinical alertness are important for the early diagnosis of malignancy in young patients.

Adult↗
PubMedDate not supplied

Synchronous hepatocellular carcinoma or metastatic hepatic tumor with primary gastric cancer.

BACKGROUND/AIMS: When a solitary hepatic tumor occurs synchronously with gastric cancer, it is usually presumed to be metastatic. However, this may not be true in a place like Taiwan, where hepatocellular carcinoma (HCC) is prevalent. This study was conducted to examine the clinicopathological factors of both conditions. METHODOLOGY: A retrospective analysis of 14 patients who underwent a synchronous hepatectomy in combination with radical gastrectomy over the past 15 years was performed. RESULTS: Seven patients had metastatic gastric cancer, and seven had concomitant gastric and hepatic cancer. Serosal invasion and lymph node metastasis were the major features in the patients with metastatic gastric cancer. Early gastric cancer was found in three of the patients with the coexisting primary cancers. No patient with solitary metastatic cancer survived more than one year, but long-term survival of more than two years was achieved in two patients with the two forms of cancer. CONCLUSIONS: Double cancer of the stomach and liver should be kept in mind in patients with gastric cancer concomitant with a solitary hepatic tumor, in order to provide optimal treatment.

Aged↗