Oxygen content of the fixative is important in the interpretation of the ultrastructure of ischaemic myocardium

Isolated rat hearts were subjected to 15, 45, or 60 minutes of global ischaemia and then fixed by perfusion at 37°C with glutaraldehyde containing various amounts of oxygen. This either had been bubbled with 100% oxygen (PO₂ 620 mm Hg) or with 100% nitrogen (PO₂ 40 mm Hg) immediately before use, or it had been routinely prepared and stored exposed to atmospheric oxygen (PO₂ 245 mm Hg). The ultrastructure of myocytes and endothelial cells subjected to 15 minutes of ischaemia was not affected by the treatment of the fixative. However, when the tissue subjected to longer periods of ischaemia was fixed with routinely prepared or oxygen-bubbled glutaraldehyde, ultrastructural changes characteristic of reoxygenation damage were uniformly evident in both the microvasculature and myocytes. These qualitatively distinct changes included mitochondrial swelling, cell swelling, endothelial bleb formation, and narrowing of capillary lumina. These abnormalities were not observed in tissue fixed with nitrogen-bubbled glutaraldehyde. These findings indicate that deliberate steps should be taken to reduce or eliminate dissolved oxygen from the fixatives used to study ischaemic tissues. Otherwise artefactual reoxygenation damage in vitro may occur and make valid ultrastructural interpretation difficult or impossible.     

Self-Irradiation Cascade Simulations in Plutonium Metal: Model Behavior at High Energy

The Modified Embedded Atom Method model for Pu metal is revised so that it more accurately captures the behavior of the Ziegler-Biersack-Littmark model of ion-ion interactions. Two revision are tested with somewhat different stiffnesses in the 2-1000 eV range. The revised models show higher damage levels at 20 KeV than an earlier model, suggesting that the behavior of the models above 100 eV is dominating damage production, at least in the earlier stages of the cascade. Work was performed at Los Alamos National Laboratory under the auspices of the US Department of Energy, under contract DE-AC52-06NA25396.     

Pool boiling on a superhydrophilic surface

Titanium Dioxide, TiO₂, is a photocatalyst with a unique characteristic. A surface coated with TiO₂ exhibits an extremely high affinity for water when exposed to UV light and the contact angle decreases nearly to zero. Inversely, the contact angle increases when the surface is shielded from UV. This superhydrophilic nature gives a self-cleaning effect to the coated surface and has already been applied to some construction materials, car coatings and so on. We applied this property to the enhancement of boiling heat transfer. An experiment involving the pool boiling of pure water has been performed to make clear the effect of high wettability on heat transfer characteristics. The heat transfer surface is a vertical copper cylinder of 17 mm in diameter and the measurement has been done at saturated temperature and in a steady state. Both TiO₂-coated and non-coated surfaces were used for comparison. In the case of the TiO₂-coated surface, it is exposed to UV light for a few hours before experiment and it is found that the maximum heat flux (CHF) is about two times larger than that of the uncoated surface. The temperature at minimum heat flux (MHF) for the superhydrophilic surface is higher by 100 K than that for the normal one. The superhydrophilic surface can be an ideal heat transfer surface. Copyright © 2002 John Wiley & Sons, Ltd.     

Measurement of specimen charging in scanning electron microscopy with a kelvin probe

A vibrating Kelvin probe in form of a platinum wire loop is used to measure the surface potential U_s on electron-irradiated free-floating metal and insulator specimens as a function of electron energy E. This allows an accurate measurement of the critical electron energy E₂ for no charging. At energies below E₂, the positive charging increases with decreasing energy to U_s=2–5 eV at E=0.5 keV and switching off the collector bias of the Everhart-Thornley detector. A two-to threefold increase of U_s is observed when the bias is switched on. For E > E₂, the strong increase of a negative surface potential can be measured. Insulating films free-supported on a conductive substrate show a steep decrease to small positive and negative U_s when the film thickness becomes lower than the electron range at a critical energy E₃ > E₂. At insulating specimen the temporal decrease of charging can be measured when the electron beam is switched off.     

HCMOS器件γ辐射损伤电路分析

本文对最基本的HCMOS器件(反相器和与非门)作了γ辐射损伤实验。通过器件性能变化,分析了γ辐射对电路的作用。     

Prediction of High-Temperature Long-Term Strength for Damaged Structures

A method is proposed for analytical estimation of the high-temperature long-term strength of structures with material discontinuities, which are stress raisers. We consider the processes involving the formation of diffusion pores. Diffusion processes in metals are strongly enhanced with increasing temperature and stresses.     

快重离子在石墨中引起表面及体径迹的STM研究

用多种快重离子辐照高定向石墨（HOPG），借助扫描隧道显微镜（STM）系统地研究了表面及体内缺陷，结果表明，离子在表面及解理面上都形成了小丘状的缺陷，且在表面较容易形成，可以用非连续损伤径迹结构来对其进行解释。     

含预制分层损伤复合材料层合板在压缩载荷下破坏过程和剩余强度的模拟

本文运用一种具有较高精度的高阶位移模式,结合特定的损伤判据和刚度折减方法,建立了一种含损伤有限元模型,并利用其对多个含预制分层损伤的复合材料层合板在压缩载荷下的破坏过程进行了数值模拟,并最终得到这些层合板的剩余强度。与实验结果的对比表明,该数值模拟方法具有较高的精度和有效性。     

Ion irradiation—induced structure damage to botanic samples using the ion transmission energy spectrum

1 INTRODUCTIONThe new aPplications of low energy heavy ion beam in irradi4ted botanical materialswere studied in recellt yeaxs. The beaminduced mutation effect on crop seeds has causedthe attention of physicist and biologists.[1l:] FOr examPle, 1ow energy ions can induceremarkable mutation to rice seeds.[3] There are many special phenomena when heavyions bombard botanic sW1e due to its special structure. Some studies showed that tllepenetration depths of some ions were far larger than t…