橡胶等静压成型纳米ZrO2(3Y)粉素坯

对像等静压成型（Rubber isostatic pressing,RIP)制备纳米Y－TZP陶瓷作了初步研究。研究结果表明，通过RIP成型，可以获得相对密度较高、体积较大的ZrO2(3Y)素坯，并在较低温度下无压烧结得到纳米Y－TZP陶瓷。在1100℃下烧结2h所得的Y－TZP陶瓷的相对密度可达97％，晶粒仅为70nm左右，相对密度较高，平均孔径小是RIP成型素坯烧结温度低的主要原因。     

Programmed cell death in the development of the mouse external auditory canal

Programmed cell death (PCD) is an essential event for development. The purpose of this work was to ascertain how PCD, in vivo designated apoptosis, is involved in the development of the external auditory canal. We performed a time sequence study of the distribution of apoptosis during the development of external auditory canal (EAC) of the mouse. ICR mice ranging in age from embryonic day 11.5 (E11.5) to 12 days after birth (DAB) were used in the present study. A part of each head including both ears was removed and was processed according to its purpose. Light and electron microscopy for morphological studies and TUNEL method (Gavrieli et al. [1992] J Cell Biol., 119:493-501) for histochemical studies were used. On E11.5, distinct TUNEL-positive staining occurred in the branchial arch. Between E15.5 and 1DAB, TUNEL-positive cells were observed throughout the EAC and the number of these cells decreased with age. On E15.5 and E16.5, numerous TUNEL-positive cells were observed in a cavity remained in the epithelial plate. Transmission electron microscopy revealed that these cells had the features of apoptosis. From 3-12 DAB, no apoptosis was observed in the EAC except for the terminal differentiation of the skin of the EAC. Apoptosis was not observed during recanalization of the EAC, but occurred during the formation of the epithelial plate. The investigation established that PCD is involved in the formation of the epithelial plate, whereas only cornification of the epithelium of the EAC is associated with recanalization.     

Thermal hydraulic study on a high-temperature gas–gas heat exchanger with helically coiled tube bundles

An experimental study was carried out to investigate flow-induced vibration, heat transfer and pressure drop of helically coiled tubes of an intermediate heat exchanger (IHX) for the HTTR, using a full-size partial model and air as the fluid. The test model has 54 helically coiled tubes separated into three layer bundles, surrounding the center pipe. The vibration of the tube bundles was mainly at the center pipe, and the individual vibrations of the tube bundles were not significant under the operation conditions of the IHX. The heat transfer of the tube outside, due to forced convection, was obtained as a function of Re^0.51Pr^0.3, and the friction factor, depending on the tube arrangement, was proportional to Re^−0.14.     

Simple and Patlak models for myocardial blood flow measurements with nitrogen-13-ammonia and PET in humans

The Simple and Patlak models for estimating myocardial blood flow with 13N-ammonia have become attractive for clinical applications with PET because of their simplicity and ease of implementation. However, these models are sensitive to factors such as the data acquisition times and data integration times, which can cause errors in the estimation of myocardial blood flow, as demonstrated in this study. Limiting the application of these models to specific conditions can minimize the errors. METHODS: Dynamic PET images of the uptake of 13N-ammonia in the heart were obtained in seven humans under rest and dipyridamole stress. Myocardial blood flow was estimated using the Simple and Patlak models for different data acquisition times and data integration times. Blood flow values were compared to flow values computed with the two-compartment model as a reference. RESULTS: Blood flow values calculated with the Simple and Patlak models during the first 2 min of data acquisition were closely correlated to the two-compartment model values. Longer acquisition times resulted in significant underestimation of blood flow for the Simple model. Long integration times of greater than 60 sec also resulted in significant underestimation of blood flow for both models. CONCLUSION: The Simple and Patlak models produce estimates of myocardial blood flow that are well correlated with the two-compartment model estimated blood flows for the integration time of 60 sec from 60 to 120 sec postinjection. Because of the errors associated with longer data acquisition times and longer integration times, use of these models should be limited to a well-documented data acquisition paradigm.     

Prostate specific antigen (PSA) value adjusted for transition zone volume and free PSA (gamma-seminoprotein)/PSA ratio in the diagnosis of prostate cancer in patients with intermediate PSA levels

OBJECTIVE: To identify binding proteins of leptin in human plasma. METHODS: Binding was evaluated by electrophoresis, size exclusion chromatography (SEC), Western blotting, and radioisotope labeling. Quantification of leptin and the different forms of alpha2-macroglobulin (alpha2-M) was performed by ELISA. RESULTS: Leptin interacts with the proteinase inhibitor, alpha2-M. 125I-labeled leptin specifically binds to the transformed inhibitor, which arises by reaction with proteinases or with reactive primary amines. No leptin binding was observed to the native alpha2-M, which abundantly occurs in plasma. The complex formation between leptin and alpha2-M was found to proceed within minutes and was stable, as it resisted separation by SEC and electrophoresis. The Kd of the complex was 2.14 +/- 0.78 micromol/l. Complex formation with transformed alpha2-M did not interfere with the immunological determination of leptin in plasma. The leptin-alpha2-M complex was found to be recognized by the alpha2-M receptor/low density lipoprotein receptor-related protein. By computer analysis, a simple model is presented showing that the degree of transformation of alpha2-M may significantly influence the leptin concentration in blood. CONCLUSIONS: The proteinase inhibitor, alpha2-M, may act as a leptin-binding protein in human plasma. Binding of leptin to transformed alpha2-M and its rapid clearance by the alpha2-M receptor may significantly influence the bioavailability of leptin in human plasma.     

Cerebral cytochrome oxidase monitoring by near infrared spectroscopy during selective cerebral perfusion

To evaluate selective cerebral perfusion (SCP) for brain protection, the redox state of cytochrome oxidase (Cyt. aa3) in brain tissue were studied in 27 patients with thoracic aortic repair. The redox state of Cyt. aa3 was monitored by near infrared spectroscopy (NIRS) (OM-110, Shimazu). There were no significant changes in the Cyt. aa3 redox state in 13 (Group I), the oxidation state of Cyt. aa3 decreased then recovered to control levels in 12 (Group II), and the oxidation state decreased but did not recover in 2 patients (Group III). Postoperative cerebral damage was observed in 5 patients; blindness occurred in one patient in Group I (8.3%), 2 patients developed hemiplegia in Group II (15.4%), and the 2 patients in Group III failed to reawaken (100%). The incidence of cerebral damage was significantly higher in Group III than in Groups I and II (p < 0.05). We conclude that monitoring the redox state of Cyt. aa3 using NIRS is useful in predicting postoperative cerebral damage. However, it is necessary to increase the number of measurement sites since NIRS can reflect the state in only a small area of the brain.     

Ionization and scintillation produced by relativistic Au, He and H ions in liquid argon

We have measured ionization and scintillation produced by relativistic ions of Au, He and H in liquid argon. The sum of ionization signal and scintillation signal per unit energy deposition is the same for He and H ions, which is also the same as that for relativistic Ne, Fe and La ions previously measured. We have found that quenching occurs when liquid argon is irradiated by relativistic Au ions and that the sum per unit energy deposition for the Au ions is 70–76% of that for the other ions mentioned above.     

DNA labeling reagent containing carbodiimide

We have synthesized a number of fluorescent compounds having a carbodiimide function and tested if it can be used to label DNA. They all reacted well with DNA in a very short time. Some of them showed different fluorescent characteristics when they bound to DNA such as band shift or change in fluorescent intensity.