The effects of human activities on natural radiation exposure: Health and regulatory implications

A decade ago, interest in “enhanced” natural radiation was focused primarily on localized industrial activities, e.g., uranium, radium, thorium and phosphate production. Recognition that all human activities influence natural radiation exposure, and that indoor radon exposure is particularly sensitive to such activities (building construction practice, occupant life-styles) has added a new dimension to the problem. Public health assessments must address the problem of high individual risks of lung cancer as well as substantial population risks that are only minimally ameliorated by reduction of high exposures. In the United States, Federal, State, and local government agencies are collaborating with the private sector in developing the information needed for public guidance. Voluntary standards relating to building construction practices are likely to be developed.     

Using formalized temporal message-flow diagrams

Temporal message-flow diagrams (TMFDs), alternatively called sequence charts, interaction diagrams, event traces, or actor diagrams, are illustrations of a system's global message-passing activity over time, and a pictorial aid to understanding the system's behavior. They are widely used for requirements and documentation for network protocols and object-oriented applications. We present a general formalism for TMFDs, describe a suite of tools we have designed that employs this formalism, and present our experiences with these tools. The formalism and tools described serve to support and broaden the use of TMFDs in developing communicating systems.     

Good-bye key escrow,hello key recovery

On 2 October 1996, IBM announced the formation of a new business alliance which will develop a different approach to law enforcement — accessible encryption that will not face government export controls or require the ‘escrowing’ of keys with either escrow ‘quote agents’ or trusted third parties. The day before, the White House announced a new government plan that would permit companies that promise to participate in a ‘key recovery’ system to receive a six-month license to export up to 56-bit DES encryption. When they fulfill their obligations and the government is satisfied that it can get access to the decryption keys, the 56-bit limit will be lifted. If, by the end of the two-year grace period, companies have not fulfilled their obligations to implement a key-recovery scheme, the 56-bit limit will be reduced to the current 40-bit export limit.     

Reaction of Iradium with Metal Carbides in the Temperature Range of 1923 to 2400 K

The reactions of titanium carbide and hafnium carbide with iridium have been studied in thin film couples fabricated by vapor deposition processes. The reaction product layers after exposure in the temperature range of 1923 to 2400 K are dependent on the stoichiometry of the metal carbide layers and range from simple solid solutions to MIr_x compounds. The observed microstructures are predictable from available thermochemical data. The morphology of residual carbon in the reacted metal carbide-iridium product layer varies from interfacial deposits to uniform carbon dispersion and depends upon exposure temperature and metal carbide stoichiometry.     

Formation of Azobenzenes and Azoxybenzenes from the Aqueous Reactions of Anilines and Ozone

Azobenzenes and azoxybenzenes are two of the products identified from the aqueous reaction of anilines with ozone. Aniline concentration and functional groups on the benzene ring of aniline affected the amount of azobenzenes and azoxybenzenes formed; (1) decreasing the aniline concentration significantly increased azobenzene formation, and (2) electron-withdrawing groups increased the formation of its related azobenzene and azoxybenzene, whereas electron-donating groups had the opposite effect.     

远逝的清代不朽的艺术

1911年，清朝衰落。自此有关中国陶瓷艺术学术方面的论述将所有历经朝代直到清代的物品载入了史册。美国西雅图艺术博物馆最近的瓷器展出一“瓷器的故事”便是一个很好的例证。景德镇作为中国具有千年历史的瓷都，在这次展览目录中包括该博物馆馆长Mimi Gardner Gates所作的附录中得以频繁地提及，正表明了：当今虽然陶瓷作品在景德镇仍然继续，但也许除了清代成就的余音之外，鲜有艺术上的意义，这一点显然是可以理解的，因为并没有重要文献会告诉我们一个截然不同的故事。“瓷器的故事”目录对于Robert Tichane于1983年发表的《景德镇》一书，一本令人大开眼界的书作出了脚注，并将其推崇为中国景德镇之行的“当代报道”。当然，这里的“当代”是从艺术历史的标准而言，而不是从时间上的最近而言，任何人必须大胆深入挖掘这样一个问题，即自从清代结束以来，中国的陶瓷艺术究竟发生了什么？     

A MECHANISTICALLY BASED MATHEMATICAL MODEL OF SULFUR DIOXIDE ABSORPTION INTO A CALCIUM HYDROXIDE SLURRY IN A SPRAY DRYER

A mathematical model has been developed to predict So₂ absorption and removal during the constant rate drying period of a spray dryer. The model, based on film theory, treats the atomized slurry droplets as spheres containing discrete sorbent particles of slaked lime with the fluid uniformly distributed around the individual particles. The model includes gas and liquid phase mass transfer coefficients as well as resistance to Ca(OH)₂ dissolution. A sensitivity analysis has been conducted and a comparison was made between pilot-scale experimental data and model-predicted values of S0₂ removal efficiency.     

ON GENERALIZED FRACTIONAL PROCESSES

Abstract. A class of stationary long-memory processes is proposed which is an extension of the fractional autoregressive moving-average (FARMA) model. The FARMA model is limited by the fact that it does not allow data with persistent cyclic (or seasonal) behavior to be considered. Our extension, which includes the FARMA model as a special case, makes use of the properties of the generating function of the Gegenbauer polynomials, and we refer to these models as Gegenbauer autoregressive moving-average (GARMA) models. While the FARMA model has a peak in the spectrum at f = 0, the GARMA process can model long-term periodic behavior for any frequency 0 f 0.5. Properties of the GARMA process are examined and techniques for generation of realizations, model identification and parameter estimation are proposed. The use of the GARMA model is illustrated through simulated examples as well as with classical sunspot data.     

A second-generation system for unbiased reading frame selection

Reading frame selection of nucleic acids has important implications for protein engineering and genomics. Current methods are limited because selection of the gene of interest inevitably depends on the solubility of its translated product. Here we report the construction of the pInSALect vector, which provides strict reading frame selection without concomitant selection for protein solubility or folding. This plasmid incorporates the cis-splicing VMA intein sequence from Saccharomyces cerevisiae to facilitate the post-translational self-excision of the protein of interest, thereby eliminating potential aggregation problems. Results from two libraries of chimeric glycinamide ribonucleotide formyltransferases confirm the superior performance of pInSALect over existing reading frame selection systems.