Reparable key distribution protocols for Internet environments

A new concept of reparable key distribution protocol is introduced in this paper. The merit of a reparable protocol is in that once all compromised keys have been replaced by secure keys, the protocol is secure. We show that the key distribution protocol of Lu et al. (1989), for Internet is not reparable. A reparable one is proposed instead     

Polymorphic ventricular tachycardias induced by D-sotalol and phenylephrine in canine preparations of atrioventricular block: initiation in the conduction system followed by spatially unstable re-entry

OBJECTIVE: Polymorphic ventricular tachycardias (PVT) occur spontaneously in canine hearts under the combination of D-sotalol (S), bradycardia and phenylephrine (PE). We investigated the hypotheses that: (1) the activation patterns of the initial PVT beats would be consistent with an origin in the ventricular conduction system; and (2) the inhomogeneous prolongation of repolarisation intervals can provide refractory barriers for re-entrant activity. METHODS: Unipolar electrograms were recorded from 127 epicardial (EPI) sites with a sock electrode array as well as from intramural and endocardial sites during PVTs. Electrograms were analysed to generate isochronal maps and measure the spatial distribution of activation-recovery intervals (ARI). RESULTS: Under S (9.9-14.5 mg.l-1), spontaneously terminating PVTs (cycle length of 270 +/- 43 ms, n = 45) (mean +/- s.d.) occurred when a PE bolus (10-50 micrograms.kg-1) was injected. The first beat of the PVTs occurred with a coupling interval of several hundred ms to the preceding idioventricular beat (IDV) without any bridging activity and its earliest EPI breakthrough occurred in areas overlying the terminations of the right or left bundle branch. ARI values measured in IDV (295 +/- 47 ms) were significantly prolonged prior to PVT (462 +/- 92 ms). Prolongation was greater in apical than in basal epicardial areas, and at endocardial than epicardial sites (to > 500 ms). Maximum delays > 200 ms developed in the regions of marked ARI prolongation and, in later beats, circus movement re-entry occurred around refractory barriers, shifting between various regions of the ventricles. CONCLUSION: Thus, PVTs occurring spontaneously under conditions of delayed repolarisation originate from shifting sites in the ventricular conduction system and re-entrant activity shifting between various regions of the ventricle may occur in later beats of the more sustained arrhythmias.     

A novel erase scheme to suppress overerasure in a scaled 2-bit nitride storage flash memory cell

The cause of over-erasure in a two-bit nitride storage flash memory cell is investigated. Extra positive charges accumulated above the n/sup +/ junction and channel-shortening enhanced drain-induced barrier lowering effect are found to be responsible for threshold voltage (V/sub t/) lowering in an over-erased cell. A modified erase scheme is proposed to resolve this issue. By applying a source voltage during erase, the erase speed can be well controlled for cells with different channel lengths and a wide range of program-state V/sub t/ distribution, which will reduce overerasure significantly.     

Buried selectively oxidized AlGaAs structures grown on nonplanar substrates

We demonstrate a novel buried oxide-grating structure formed by selectively oxidized Al/sub x/Ga/sub 1-x/As grown on nonplanar substrates using low-pressure metal-organic chemical vapor deposition (MOCVD) for the first time. Localized aluminum content variation in AlGaAs is obtained with MOCVD growth on nonplanar substrate. Buried aluminum oxide/semiconductor-distributed-feedback structure is achieved with selective oxidation of these AlGaAs layers. We fabricated a resonant-cavity-enhanced photodetector with the imbedded buried-oxide structure and measured the photodetector responsivity spectrum.     

The five cysteine residues located in the active site region of bovine aspartyl (asparaginyl) beta-hydroxylase are not essential for catalysis

In previous chemical modification studies on bovine aspartyl (asparaginyl) beta-hydroxylase, cysteines were implicated as critical catalytic residues. Using site-directed mutagenesis, the five cysteine residues located in a highly conserved region of the enzyme identified as the active site were individually mutated to alanine. Substitutions at cysteine 637, 644, 656, 681, and 696 resulted in active mutant enzymes indicating that these residues are not required for catalysis.     

Synthesis and photoconductive characteristics of biphenylporphyrin‐containing poly(amic acid)s and polyimides

Three series of biphenylporphyrin (BPP)‐containing poly(amic acid)s (PAAs) were synthesized and converted into heat‐treated polyimides (HPIs) and chemically treated polyimides (CPIs). Viscosity measurements, UV–vis and IR spectroscopies, as well as thermogravimetric analysis (TGA), were used to characterize the structures of the polymers. UV–vis spectra revealed that the BPP units formed aggregates in PAA and CPI films, rather than in HPI films. Photoinduced discharge was used to characterize the photoconductive properties of these polymer films. It was found that the photosensitivity was greatly enhanced by introducing BPP units into the polymer chains. For these three series of polymers, the photosensitivity increased in the order PAA < HPI < CPI according to the content of BPP in the polymers. The photoconductive characteristics were interpreted by the intrinsic π—π* process of BPP aggregation and the extrinsic process of charge‐transfer complex formation. The best photoconductive performances of the CPIs were attributed to the existence of two charge‐carrier‐generation processes. Copyright © 2004 Society of Chemical Industry     

Giant nodular goiter

The paper presents own experience in surgical treatment of nodular goitre with mass exceeding 1000 g. In the analysed material of 1180 strumectomies, three such cases were found. Preparation for surgery included administration of Lugol solution, and possibly anxiolytics. The operation of removal of giant nodular goitre caused no significant technical difficulties. The postoperative course was uncomplicated, and cosmetic effect in remote examination was satisfactory.     

Study of the factors influencing colour yield of an ink-jet printed cotton fabric

In this study, the factors influencing the final colour yield of an ink-jet printed cotton fabric were investigated. The factors included the content of the pretreatment paste (the amounts of sodium alginate, sodium bicarbonate and urea) and the steaming time. Four different inks – cyan, magenta, yellow and black – were used in this study and the influences of these factors on the four different colours were studied through experimental design. The results showed that apart from the influence of individual factors, the final colour yield also depended on the interaction effect of the factors.     

光纤监控电视系统的中心监控装置

本文以一个四十八台摄象机和四台监视器的系统为例,介绍一种由MCS-51系列单片机组成的光纤监控电视系统中心监控装置部件的设计考虑。