Extrapolation of high-voltage stress measurements to low-voltageoperation for thin silicon-oxide films

Breakdown and wearout in MOS capacitors fabricated with 10 nm-thick silicon oxide films on p-type silicon are discussed. They have been stressed at high voltages. The high-voltage-stress-induced changes in the oxide properties are extrapolated to low operating voltages. The stress voltages ranged from -7.5 V to -14.5 V. The fluence during the stress was systematically varied front 2×10^-5 C/cm² to 6 C/cm² by varying the stress time at each voltage. The number of interface traps generated by the stress increased as the stress voltage and fluence increased. However, the interface trap generation rate decreased as the fluence increased. The trap generation rate at low operating voltages was very high, but because the current through the oxide was small, the total number of traps generated was low. The trap generation rate was proportional to the inverse square root of the fluence with a voltage dependence that decreased as the fluence increased. Extrapolation of the high-voltage-stress measurements to 5 V shows that easily detectable changes in the oxide properties would only occur after several years of 5 V operation. Extrapolation of charge-to-breakdown and time-to-breakdown data to 5 V operation indicates that breakdown would occur after hundreds of years of device operation     

Block acknowledgment: redesigning the window protocol

A window protocol based on the block acknowledgment method, in which acknowledgment message has two numbers, m and n, to acknowledge the reception of all data messages with sequence numbers ranging from m to n, is discussed. In the window protocol, message sequence numbers are taken from a finite domain and both message disorder and loss can be tolerated. An initial version of the protocol that uses a simplified timeout action and unbounded sequence numbers is presented, the simplified timeout action in the protocol is replaced by a sophisticated one without disturbing the protocol's correctness, and the unbounded sequence numbers are replaced by bounded ones while preserving the protocol's correctness. Remarks concerning other variations of the protocol are also presented     

Suprasellar tension pneumocyst after transsphenoidal surgery. Case report

Tension pneumocephalus is an uncommon occurrence after transsphenoidal surgery. The author presents an unusual case of postoperative visual deterioration related to expanding air within a suprasellar tumor cavity.     

Dissolution kinetics of Widmanstätten γ-Ag2AI precipitates

A combination of scanning electron microscope and electron probe studies has been conducted on the dissolution of Widmanstätten γ-Ag₂Al plates in Al-15.3 wt pct Ag alloys between the temperatures of 466 °C and 494 °C. Individual rather than averaged kinetic events have been monitored in all cases. The kinetics at the tip were observed to be linear with time and at the broadface to be parabolic with time. The broadface kinetics were slower than expected for volume diffusion control. Electron probe measurements round the dissolving precipitate gave similar diffusion profiles at the tip and the broadface. These indicated a slower dissolution rate at the tip than observed experimentally and a faster rate at the broadface than observed experimentally. A mechanism to explain the discrepancy between the kinetic and probe results is suggested.     

Measurement of the fracture toughness of polymer-non-polymer interfaces

One of the primary factors limiting the development of a better understanding of polymer-non-polymer adhesion is the lack of a good testing method for the measurement of the strength of the interface. In this paper polymer-non-polymer adhesion is evaluated in terms of the fracture toughness of the interface using an asymmetric double cantilever beam testing geometry. The test is applied to the measurement of polystyrene (PS)-glass and PS-silicon (native oxide) interfaces modified by PS-poly(2 vinylpyridine) (PVP) and PS-poly methyl methacrylate (PMMA) diblock copolymers. The importance of mixed mode crack propagation is demonstrated and it is shown that through an appropriate choice of sample geometry, the crack-tip trajectory can be controlled so that the crack is forced to propagate along the interface. The PS-glass test, in particular, is shown to overcome many of the traditional problems of adhesion measurements, such as failure, away from the interface and effects of far-field deformation in the polymer. The interfacial fracture toughness of the PS-glass and PS-silicon interfaces without copolymer modification are approximately the same and weak with values of 1 J m^–2. The addition of the block copolymers results in significant (>40-fold) increases in the interfacial fracture energies. The increase in fracture toughness is dependent on the quantity and degree of organization of the block copolymer at the interface.     

Lipopolysaccharide stimulates both nuclear localization of the nuclear factor kappa B 50-kDa subunit and loss of the 105-kDa precursor in RAW264 macrophage-like cells

Nuclear factor kappa B (NF-kappa B) is an important regulator of gene expression in cells of the immune system. One such gene, tumor necrosis factor, is induced by bacterial lipopolysaccharide (LPS) in macrophages, and this induction has been shown to be mediated in part by NF-kappa B activation in murine macrophages. In this study, immunochemical analysis was used to follow LPS activation of the NF-kappa B 50-kDa subunit in the RAW264 macrophage-like cell line. The recombinant NF-kappa B 50-kDa subunit was used as an immunogen to produce a rabbit antiserum, which was then affinity-purified using a portion of the NF-kappa B 50-kDa subunit that does not have homology to other members of the c-rel gene family. Untreated macrophages had little NF-kappa B in the nucleus as detected by Western immunoblotting. The protein was predominantly localized in the cytoplasmic fraction. Interestingly, NF-kappa B was found as the 50-kDa mature protein and 105-kDa precursor. After LPS treatment, there was a rapid nuclear translocation of NF-kappa B as detected by immunoblot analysis. There was also a rapid decrease in the amount of the cytoplasmic 105-kDa protein. This may indicate that the 105-kDa protein is a reservoir for the 50-kDa protein and that one of the actions of LPS is to increase the rate of 105-kDa precursor processing.     

Effect of environmental conditions on smoke propagation

This paper examines the influence of oxygen and environmental temperature on the generation of smoke from burning polystyrene sheet. The experimentation was performed using a Stanton Redcroft HFTA linked to a Stanton Redcroft FTB Smoke Box. The results showed that different forms of smoke were formed depending upon the environmental conditions. For example, in oxygen-enriched atmospheres and at elevated environmental temperatures, as in spacecraft fires, large smoke particles were formed with a lower level of obscuration. This phenomenon was accompanied by higher rates of burn and high fire temperatures. At lower oxygen contents, as in real-life fire conditions, close to the Critical Oxygen Index, finer smoke particles were formed which gave a higher level of obscuration. The time to maximum obscuration was comparatively long.