Effects of posts on dentin stress distribution in pulpless teeth.

A finite element analysis was carried out to study the roles of posts in reducing dentin stress in pulpless teeth. Two-dimensional plane strain models of the midlabiolingual section of a human maxillary central incisor were first analyzed. The results showed that the gold alloy post reduced maximal dentin stress by as much as 30%. However, the integrity of the dentin was compromised and the effects of the post were likely to be exaggerated in such models. In an effort to correct for these problems, plane stress models with side plates and axisymmetric models were analyzed. Posts were found to reduce maximal dentin stress by only 3% to 8% when the teeth were subjected to masticatory and traumatic loadings in these latter models. Although posts reduced maximal dentin stress by as much as 20% when the teeth were loaded vertically, teeth such as incisors and canines normally are not subjected to vertical loadings. Thus the reinforcement effects of posts seem to be doubtful in these teeth.     

Trend analysis of social and economic indicators of mammography use in Hawaii.

We examine the relationship between ethnicity and income as determinants of mammography use over a span of four years as a means of assessing community intervention impacts. The sample consisted of 1,447 women older than 34 years, living in Hawaii, who participated in the Behavioral Risk Factor Surveillance System (BRFSS). The percentage of women in the sample reporting a screening mammogram within the past two years was 31.4% in 1987, 54.1% in 1989, and 51.6% in 1990. Women of Hawaiian ancestry had the lowest percentage of mammogram use in the past two years (38.7%), while Japanese women had the highest percentage (49.8%). Results of logistic regression analysis indicate a significant increase in mammography use from 1987 to 1989 and no difference from 1989 to 1990. Findings also showed an association between age, income, and ethnicity with use in the past two years. Greater age, higher income, and Japanese origin, compared to Hawaiian, were all independently associated with increased odds of having had a mammogram in the past two years. We discuss results in terms of program evaluation and future research implications for community health surveys.     

Numbers and proportions of unmyelinated axons at cervical levels in the fasciculus gracilis of monkey and cat.

The present study is a quantitative analysis of the unmyelinated fiber population in the fasciculus gracilis of the second cervical segment of cat and monkey. We find that unmyelinated fibers represent 13.7% of the total fiber population in this pathway in the cat and 18.9% in the monkey (Macaca fascicularis). The existence of such large numbers of these axons suggests that there may be a sizeable ascending fine primary afferent pathway in the fasciculus gracilis in cat and monkey whose destination is presumably the dorsal column nuclei. These findings are of interest in regard to classic ideas that the afferent fibers in the dorsal columns are large myelinated fibers that convey fine discriminative information to the dorsal column nuclei.     

The epidemiology of urinary dysfunction in Chinese women

The epidemiology of urinary dysfunction in a Chinese population living in Hong Kong was investigated. Fifteen hundred ethnic Chinese women answered a telephone questionnaire including symptoms of urinary dysfunction, anthropometric measurements, obstetric history and place of birth. The relative predictive value of these factors was analyzed using logistic regression. The prevalence of urinary dysfunction was 13%. Ten percent reported stress incontinence, and 4% had urgency or urge incontinence. The strongest predictor was place of birth, with women born in mainland China having the highest prevalence of pure stress incontinence (OR 1.33, CI 1.1–1.6). For the symptoms of detrusor instability age was the strongest predictor, with women over 50 years being at greater risk (OR 2.8, CI 1.6–5.0). Contrary to earlier beliefs, urinary dysfunction in Chinese women is as common as in Caucasian women. Place of birth is the strongest predictor for pure stress incontinence, with women born in mainland China being at greater risk. This suggests that environmental factors in early life have a differential effect on the development of urinary incontinence. EDITORIAL COMMENT: Taiwan Chinese women have a comparable prevalence of urinary dysfunction with Hong Kong Chinese women. A survey representing a multistage sample of 82 678 women aged 18 years or older was conducted in the Taipei area from January to June 1993. A total of 818 cases were interviewed by trained students. One hundred and eighty-nine (23.1%) of the respondents reported having had some degree of incontinence in the preceding 12 months, 28 (3.4%) reporting regular incontinence. Most presented with stress urinary incontinence, whereas urge incontinence and mixed incontinence were more commonly seen in the elderly group (aged 60 years or older). The risk factors for urinary incontinence included age, number of vaginal deliveries (>3), number of abortions (>2) and maternal history of incontinence. Voiding symptoms (irritative or obstructive) and constipation were significantly more prevalent among respondents with incontinence than those without (P<0.001). This evidence also indicates that the long-held belief that Chinese women have a much lower prevalence of urinary dysfunction than western women has all but ended.     

Some sufficient conditions for global exponential stability of delayed Hopfield neural networks.

In this paper, we have derived some sufficient conditions for existence and uniqueness of equilibrium and global exponential stability in delayed Hopfield neural networks by using a different approach from the usually used one where the existence, uniqueness of equilibrium and stability are proved in two separate steps, rather we first prove global exponential convergence to 0 of the difference between any two solutions of the original neural networks, the existence and uniqueness of equilibrium is the direct results of this procedure. We obtain the conditions by suitable construction of Lyapunov functionals and estimation of derivates of the Lyapunov functionals by the well-known Young's inequality and Holder's inequality. The proposed conditions are related to p-norms of vector or matrix, p in [1, infinity] and thus unify and generalize some results in the literature.     

Solitary Small Hepatic Angiosarcoma: Initial and Follow-up Imaging Findings

We report an uncommon case of solitary, small hepatic angiosarcoma that was initially considered as a hemangioma. We present the imaging findings, with an emphasis on the initial and follow-up CT and MR findings, as well as report on the more suggestive findings of angiosarcoma than those of a hemangioma.     

Isolation of a renal function-facilitating constituent from the Oriental drug, salviae miltiorrhizae radix

An attempt was made to isolate the active component which exhibits an improving effect on renal function from Salviae Miltiorrhazae Radix (Chinese crude drug). Systematic isolation from aqueous extract of Salviae Miltiorrhizae Radix was carried out, and Compound 1 was found to be more effective than any of the other constituents in improving renal functional parameters; that is, a marked reduction of glomerular filtration rate following adenine ingestion was improved by administration of this substance. The renal plasma flow and renal blood flow were also increased in renal failure rats. On the basis of chemical and spectroscopic data, Compound 1 was shown to be identical with magnesium lithospermate B.     

Pinhole collimator scintigraphy in differential diagnosis of metastasis, fracture, and infections of the spine

The informational gains obtained by the use of pinhole collimator scintigraphy (PCS) have been well documented. The present study has been undertaken to prospectively investigate its efficacy in diagnosing several commonly occurring spinal diseases. Patient material consisted of metastatic cancer (39 vertebrae), compression fractures (33 vertebrae), tuberculous spondylitis (17 vertebrae), and pyogenic spondylitis (six vertebrae). PCS findings were characterized in terms of localization, appearance, and homogeneity of abnormal radionuclide accumulation. Thus, metastatic cancer manifested as diffusely or focally homogeneous accumulation within the vertebral body or as a typical short-segmental accumulation along the end-plate, whereas compression fracture manifested as characteristic board-like accumulation along the entire length of end-plates. Tuberculous spondylitis, on the other hand, revealed homogeneous accumulation throughout the vertebral body, and pyogenic spondylitis revealed accumulation at the end-zone of opposing vertebral bodies giving sandwich-like appearance. The disk space at the affected level was not narrowed in the former two diseases but it was narrowed in the latter two. It was concluded that PCS may be useful in differentiating metastatic cancer, compression fracture, tuberculous spondylitis, and pyogenic spondylitis.     

Calculation of Hydrolytic Rate Constants of Poly(ortho ester)s from Molecular Weights Determined by Gel Permeation Chromatography

Purpose. To obtained rate constants from weight-averaged (M_w) or z-averaged (M_z) molecular weights for polymers of Schule-Flory distribution and undergoing random scission. These constants were compared with those obtained by parallel ¹HNMR studies. Methods. The hydrolysis of two poly(ortho ester)s were followed by ¹HNMR and gel permeation chromatography (GPC). Results. Equations to convert number-averaged (M_n), M_w and M_z into fraction of backbone remaining (f_c) were derived. First-order hydrolytic rate constants of two poly(ortho ester)s; DETOSU-HD and DETOSU-CDM were calculated using these relationships. The rate constants calculated from ¹HNMR, M_z and M_w were 0.215, 0.218 and 0.182 hr^–1, respectively, for DETOSU-CDM and 0.152, 0.086 and 0.038 hr^–l for DETOSU-HD. The large discrepancy in the rates determined by ¹HNMR and GPC in the latter case was attributed to that the detector response (refractive index) of the monomers was lower than that of the high molecular weight polymer. The difference is small in the case of DETOSU-CDM, and the rates calculated from GPC data were comparable or nearly identical to that obtained from ¹HNMR data. Conclusions. Although GPC can yield rapid and valuable kinetic data for the degradation of biodegradable polymers, the system, however, must be carefully calibrated to account for the variations in Mark-Houwink coefficients and in the response of the mass detector between the high and low MW polymers.