The thickness of shock layers in liquid chromatography

At high concentrations, one boundary (the front if the isotherm is convex upward) of the elution band of a single component becomes very steep. Similarly, in frontal analysis, the same boundary is self-sharpening. These steep boundaries are called shock layers. They result from the steady-state equilibrium between a nonlinear thermodynamics of phase equilibrium on the one hand, which tends to create a concentration discontinuity, and axial dispersion and a finite rate of mass transfer on the other hand, which tend to relax the concentration gradient. We show that the width of experimental breakthrough curves recorded in frontal analysis agrees well with the prediction of the shock layer theory of Rhee and Amundson in the high concentration range. It is a function of the coefficients of the column HETP equation and the height of the concentration step and is independent of the column length, after the steady state is achieved. In the low concentration range, a discrepancy is observed when the column length is short and the migration distance is insufficient to achieve constant pattern behavior.

Further studies on the plasma-sprayed amorphous phase in hydroxyapatite coatings and its deamorphization

Plasma-sprayed hydroxyapatite coatings contain a quite large amount of amorphous phase. Infrared analysis shows that the plasma-sprayed amorphous phase is an oxyapatite and the coating predetermined as a hydroxyapatite is proved to be an oxyhydroxyapatite with a small quantity of hydroxyapatite. Heat treatment promotes the transformation of amorphous oxyapatite into a crystalline hydroxyapatite structure and reduces the dissolution rate of the coatings. Further studies focus on the properties of the amorphous phase, showing that amorphous oxyapatite is more soluble in 0.15 M lactic acid at 25 degrees C and that water molecules can accelerate the amorphous/crystalline transformation of the hydroxyapatite structure during the plasma-spraying process.

Amorphous phase and morphological structure of hydroxyapatite plasma coatings

It is shown that under standard conditions of plasma spraying hydroxyapatite powder reaches the substrate in the form of molten drops. On striking the surface, the molten drop splatters, cools rapidly and solidifies. Consequently, a pancake particle surrounded by tiny spherical or differently shaped particles is formed on the substrate. The solidified particles are partly crystallized. Besides the crystalline hydroxyapatite, they contain some supercooled molten hydroxyapatite, i.e. amorphous hydroxyapatite. Build-up of these particles during coating gives a porous pancake-globular structure. During a brief vacuum heating at 630 degrees C, the amorphous phase is crystallized and completely crystalline hydroxyapatite coatings are obtained.

Field molecular epidemiology. Feasibility of monitoring for the malignant bladder cell phenotype in a benzidine-exposed occupational cohort

Modern molecular and cellular biology have provided powerful new approaches to study cancer in the research laboratory, but these techniques have not been used extensively in field studies or in screening of high-risk occupational cohorts. The primary objective of this study was to demonstrate the use of cellular and molecular methods in combination with medical and epidemiologic methods to identify cancer cases, risk factors, and markers in a previously identified and defined cohort of Chinese workers exposed to benzidine. The screening of exposed workers included occupational, medical, and smoking histories to identify exogenous risk factors, a limited physical examination, Papanicolaou (PAP) urinary cytology, measurement of urine pH, quantitative fluorescence image analysis (QFIA) cytology to detect DNA hyperploidy, and quantitative fluorescence to detect expression of a low-grade bladder tumor-associated antigen (p300) by exfoliated urothelial cells and elevated expression of the neu oncogene product (p185). Detailed analysis of the accuracy of epidemiologic data and the adequacy of samples and accuracy of molecular techniques was carried out. Three groups were included in this study: group 1 included 23 bladder cancer cases who had previously been exposed to benzidine and served as two surrogates for late-emerging disease; group 2 consisted of 20 subjects with previous exposure history but not previously diagnosed with bladder cancer; and group 0 was the nonexposure and nonbladder cancer controls. The results showed that accurate questionnaire data and urine samples can be obtained at remote sites. Among the 20 group 2 subjects, two displayed abnormal findings by both QFIA cytology and p300 expression and were later confirmed to have bladder cancer.(ABSTRACT TRUNCATED AT 250 WORDS)

The AMP-binding domain on adenylate kinase. Evidence for a conformational change during binary-to-ternary complex formation via photoaffinity labeling analyses

The topological location of the nucleotide substrate binding environments on adenylate kinase has been explored with the fluorescent molecule [4-benzoyl]benzoyl-1-amidofluorescein (BzAF) and the nucleotide analog 3'-O-[4-benzoyl]benzoyl-ATP (BzATP), which are site-directed photoaffinity probes that bind covalently at the individual nucleotide sites. The MgBzATP substituted for MgATP as a substrate for this enzyme, whereas BzAF, which is neither a substrate nor a nucleotide, behaved as a competitive inhibitor for each nucleotide site independently. BzAF could be directed specifically to either of the nucleotide sites by near saturation of the second site with its natural nucleotide substrate. Using this second site blocking approach, each nucleotide site, in turn, could be protected competitively from BzAF-induced photoinhibition by the presence of its natural substrate. This strategy showed that under photolysis, the Kd(BzAF) of 0.1 mM (for the MgATP site) and 0.2 mM (for the AMP site) were nearly identical with the Km(app) values determined for MgATP and AMP, respectively. Pseudo first-order photolysis kinetics with [3H]BzAF revealed covalent binding stoichiometries for full inhibition of 1 mol of probe/mol of enzyme at either site. Thus, we prepared the binary complex ([3H]BzAF-enzyme) by photo-labeling the MgATP site-blocked enzyme with [3H]BzAf to 1:1 molar stoichiometry. Tryptic digestion followed by partial sequencing of the [3H]BzAF-labeled enzyme disclosed that BzAF was bound specifically within the peptide span Gly64-->Arg77. This amino acid domain therefore probably constitutes the neighborhood identifiable with AMP binding. Furthermore, we also achieved double photocovalent labeling of adenylate kinase with both photoprobes, by first cross-linking with approximately 1 mol of MgBzATP, followed by approximately 0.9 mol of [3H]BzAF, thus generating a ternary covalent complex. Comparison of the fluorescence of the binary species and the ternary (BzATP-enzyme-[3H]BzAF) complex revealed altered fluorescence emission profiles, which could indicate that a conformational change occurs during formation of the ternary (or transition state) complex.

Divalent cation-dependent stimulation of ligand binding to the 46-kDa mannose 6-phosphate receptor correlates with divalent cation-dependent tetramerization

The quaternary structure and binding activity of the murine 46-kDa mannose 6-phosphate receptor (46MPR) were studied in semi-intact murine cells that overexpress the murine receptor. Chemical cross-linking studies showed that the murine 46MPR exists in monomer, dimer, and tetramer forms in membranes of overexpressing murine cells. Treatment of permeabilized cells with Mn2+ increased the tetramer form of 46MPR, and this tetramerization was reversed by removal of Mn2+. Thus, the divalent cations affected the distribution of receptor among the three forms, favoring tetramerization at the expense of dimer and monomer. Low temperature (4 degrees C) also increases the fraction present as tetramer. The binding assay results show that Mn2+ is required for the 46MPR to achieve and retain the ability to bind ligand at 37 degrees C but not at 4 degrees C. Preincubation with Mn2+ produced a 3-fold increase in Man-6-P-specific binding of beta-glucuronidase which paralleled the 3-fold increase in tetramer seen during preincubation with Mn2+. The similarity of the effects of addition and removal of Mn2+ on enzyme binding to the effects of Mn2+ on favoring tetramer formation suggests that divalent cation-dependent tetramerization of the 46MPR contributes to the stimulation of ligand binding to the 46MPR by divalent cations.

Experimental study of high-frequency two-way jet ventilation

BACKGROUND AND METHODS

A new mode of jet ventilation, high-frequency two-way jet ventilation, was devised and introduced to increase CO2 elimination. High-frequency two-way jet ventilation was achieved by adding reverse jet pulses inside the trachea through an intratracheal reverse jet system to the expiratory phase of common high-frequency jet ventilation. The ventilatory efficiency and features of high-frequency two-way jet ventilation were investigated and compared with those features of high-frequency jet ventilation in ten dogs in the same experimental condition. Random sample selection and randomized crossover trial were used for comparison between high-frequency two-way jet ventilation and high-frequency jet ventilation. Peak inspiratory pressure, end-expiratory pressure, and the arterial blood gas variables (PaO2, PaCO2, and pH) were measured during the study.

RESULTS

PaCO2 with high-frequency two-way jet ventilation was about 35% lower than that with high-frequency jet ventilation (from 45 to 29 torr [6.0 to 3.9 kPa], p less than .01). Simultaneously, peak inspiratory pressure and end-expiratory pressure during high-frequency two-way jet ventilation were significantly lower than those same variables measured during high-frequency jet ventilation. End-expiratory pressure of high-frequency two-way jet ventilation was a negative pressure (-2.45 +/- 0.45 cm H2O). The pH of high-frequency two-way jet ventilation was significantly higher than that of high-frequency jet ventilation.

CONCLUSIONS

Compared with high-frequency jet ventilation, high-frequency two-way jet ventilation demonstrated a ventilatory feature of increasing CO2 elimination and simultaneously decreasing airway pressure.

Personal characteristics of Chinese children and their discrepancies: a report on children's development in Anhui (I)

The authors report on a 1990 survey on the characteristics of children in China which included 1,000 primary school pupils in Anhui Province. The focus is on differences between only children and those with brothers or sisters. The results suggest that "the development of temperaments, moral character, behavior and basic ability of primary school pupils in Anhui is generally healthy despite certain discrepancies among different types of children."

The threshold of survival for system of two species in a polluted environment

The effects of toxicants on naturally stable two-species communities are studied. Persistence-extinction thresholds are given for populations in the toxicant stressed Lotka-Volterra model of two interacting species. The threshold results are expressed in terms of relationships involving the population intrinsic growth rates, dose-response parameters, and interaction rates.

[Observation on the epidemiologic efficacy for 9 years on epidemic meningococcal polysaccharide vaccine of group A by district immunization method]

According to previous studies, there might be a peak of epidemic meningitis in Baoding City in 1984. For preventing the epidemic, we carried out vaccination with meningococcal polysaccharide vaccine by district immunization method during the 1980-1984 and then vaccination only to the children aged 12-24 months every year. The vaccination rate was 80.01% in 1980-1984 and was 97.15% in 1985-1988. During the 9 years, 833,377 children of vaccination group were observed, 4 of whom developed this disease, with an incidence of 0.48/100,000; and 304,085 children in the control group were observed, 25 of whom contracted this illness, with an incidence of 8.22/100,000. The protective rate of vaccine was 94.16% and the efficacy index was 1:17.12. This result showed that peak year of epidemic meningitis predicted in 1984 was prevented by vaccine immunization and the incidence of this disease was continuously kept less than 1/100,000 for 9 years.

A Chinese female postnuptial leaving home model--a procedure for analyzing main parameters alpha and beta in the setting up, testing and estimation of the model

"The first section of this article...sets up a model for leaving home after marriage that is suited to China's situation. The second section performs a statistical test and verification of the formulated model for leaving home after marriage. The third section...proposes a method for analyzing the main parameters...in the model...." The model is set up along the lines of the Brass-Gompertz relational fertility model.

Intestinal metaplasia and gastric carcinoma. A histochemical and immunohistochemical study

This article sums up the histochemical and immunohistochemical study of 55 cases of gastric carcinoma and 21 controls with benign gastric lesions. The results showed most of the adjacent mucosa of gastric carcinoma developed incomplete type intestinal metaplasia (IM). The percentage of Type IIb (ie, secreting sulphomucin) reached 72.5%. In most cases, high iron diamine (HID) rose in cancerous tissue and concomitantly in the IM epithelium of the adjacent gastric carcinoma. The phenomena of separation condition of HID+ in cancerous tissue, HID- in IM epithelium surrounding carcinoma, or HID- in cancerous cell but HID+ in IM of the surrounding epithelium of carcinoma, were much fewer. The two kinds of mucin antigen distribution were observed simultaneously. In the control and gastric carcinoma groups, neither large intestinal mucin antigen (LIMA) nor small intestinal mucin antigen (SIMA) could be detected in the normal epithelium of gastric mucosa. SIMA was mainly found in the goblet cells of IM and the mucous cells of columnar epithelium, while LIMA was mainly present in the columnar cells, in luminal border and/or in goblet cells. LIMA in the carcinoma group is apparently higher than that in the controls. The percentage of LIMA+ in the IM epithelium of adjacent gastric carcinoma and that in carcinoma cells were also raised in most cases. All these demonstrated a close relationship between IM and gastric carcinoma. Our results also showed that not only HID+, but also LIMA+ may represent a precancerous lesion in gastric carcinoma.

[Investigation on resources of the Chinese drug beimu in Gansu Province]

Based on a resources investigation and taxonomic research on the medicinal plants of Fritillaria from Gansu Province. Nine species one variety and one cultivation variety have been reported. Records and distribution of the species, together with a key for the species and a key for the powdered drug have been furnished as well.

Persistence and extinction of a population in a polluted environment

Models of the persistence and extinction of a population or community in a polluted environment have been investigated in several papers. But all of those papers have a basic assumption that the capacity of the environment is so large that the change of toxicants in the environment that comes from uptake and egestion by the organisms can be neglected. This assumption is not made in this article. Some sufficient conditions on persistence or extinction of a population have been obtained, and the threshold between the two has also been obtained for most situations.

[Acute toxicity of flesh oil of Hippophae rhamnoides L. and its protection against experimental hepatic injury]

Protection by flesh oil of Hippophae rhamnoides against hepatotoxicity induced by CCl4 and acetaminophen (AAP) is reported in this paper. It was found that the oil markedly inhibited MDA formation of liver induced by CCl4 and AAP, decreased sGPT levels induced by CCl4 and blocked depletion of GSH damaged liver induced by AAP.LD50 greater than 45.0 g/kg.

[Short-term curative effect of cultured Cordyceps sinensis (Berk.) Sacc. Mycelia in chronic hepatitis B]

33 cases of chronic hepatitis B. patients treated with cultured Cordyceps sinensis mycelia have shown that the drug improves the liver function, promotes negative transfer HBsAg, and markedly helps to raise plasma albumin, resist high gamma globulin and to adjust body immunocompetence. It is therefore suggested that cultured Cordyceps sinensis mycelia may be used as a medicine for chronic hepatitis B. patients in adjusting protein metabolism and correcting inversion of albumin and globulin.

Long-pulsewidth pulsed Nd:YAG laser

A several millisecond pulsewidth pulsed Nd:YAG laser with output power of 200 W average and 5000 W peak is developed, and its performance is investigated. The experimental results are taken as a guide to designing and constructing a long-pulsewidth pulsed laser with high average output power.