The adaptive da/dN method: a solution to the problem of processing crack growth data

The standard fatigue data‐processing procedure, published in ASTM E647, is not adapted to the use of modern crack length measurement techniques. Because the use of this standard is usually required by journals, the raw data are often reduced to only a few data points. This way valuable information is simply thrown away and mathematical errors are unintentionally made. More importantly, the fact that no satisfactory reduction method exists, has led to destandardization of the processing procedure. Therefore, a new standard processing method is desired. In this paper a new data‐processing method, referred to as the ‘adaptive da/dN method’, is proposed and discussed. This method is suitable for both optical and modern (electrical or automated) measurement techniques as well as modern (computer‐assisted or ‐controlled) processing techniques. The adaptive da/dN method is validated both by data generated with a certain amount of scatter as well as actual experimental data. It shows a more accurate behaviour than the ASTM standards for all data types.     

Effect of Curing Conditions on the Capillary Porosity of Hardened Portland Cement Pastes

The capillary pore structure of hardened portland cement pastes cured by high-pressure steam, chemical acceleration, high-pressure steam with reactive SiO₂, water immersion, water immersion and high-pressure steam, and hot-pressing was measured using mercury porosimetry to 50,000 psi. Differences of > 2 orders of magnitude exist in the average capillary pore diameters of the cement pastes studied. The largest pores (∼1 to 3 μm in diameter) are associated with high-pressure steam-cured pastes. The smallest average capillaries observed were 0.02 μm for pastes steam-cured with reactive SiO₂. Hot-pressed pastes had essentially no porosity accessible to mercury. The application of pore size control to problems of polymer-impregnated concrete is discussed.     

ENERGY COMSUMPTION IN STEAM BLANCHERS1

The energy consumption of several steam blanchers was monitored to identify design characteristics which are most energy conserving. Hydrostatically sealing the units to prevent escape of steam was shown to be significant in reducing energy usage. Results are compared with estimates of energy efficiency found in the literature and are shown to be in agreement.     

BREAKDOWN OF XYLAN BY ENZYMES FROM HUMAN COLONIC BACTERIA

Xylan from Larchwood was utilized as a carbon source by three species of Bacteroides from the human colon: Bacteroides ovatus, Bacteroides eggerthii and Bacteroides fragilis subsp. a. Xylan-degrading enzymes of all three species were cell-associated rather than extracellular, i.e. xylanase activity was detected in sonically disrupted bacteria but not in the extracellular fluid. The state of hydration of the xylan was an important factor in determining the extent to which the xylan was hydrolyzed by the bacterial enzymes. When xylan which had been partially hydrated by autoclaving was subjected to centrifugation at 17,000 xg for 20 min at 4⁰C, a portion of the xylan was pelleted. This portion, which was presumably less well hydrated than the xylan which remained in solution, was not digested at all by the bacterial enzymes. By contrast, xylan which remained soluble after centrifugation (soluble xylan) was degraded by bacterial xylanases. Xylose was the main product of digestion, although traces of arabinose, glucose and higher oligomers of xylose were also detected. Even after exhaustive hydrolysis, less than 60% of the soluble xylan was hydrolyzed. Removal of most of the arabinose branches did not increase the extent of hydrolysis. Moreover, the carbohydrate composition of the portion of the soluble xylan which resisted hydrolysis was the same as the composition of the xylan which was hydrolyzed. Thus it is likely that hydrolysis was limited by aggregate formation rather than by structural features such as arabinose branches.     

ROLLING THE DICE? CASINOS,TAX REVENUES,AND THE SOCIAL COSTS OF GAMING

ABSTRACT: Advocates for casino gambling in urban centers point to the benefits from increased taxes and job opportunities. While there is evidence to sustain those claims, those who oppose legalized gambling point to the personal and social costs that result from increased numbers of addicted gamblers and believe those negative outcomes exceed the fiscal gains. Each time voters and public officials are asked to vote for or against expanded gambling centers to produce more tax revenue, advocates for the opposing positions point to different studies— some illustrating increased social and personal costs, while others extol the fiscal returns to urban areas. Using trend line and regression analyses of outcomes in three states with casinos—Michigan, Indiana, and West Virginia—as well as Ohio that borders these states, this study attempts to provide a new perspective. The work reported here finds no significant negative changes in unemployment, bankruptcy, or crime rates after casinos opened. Further, while in some regression models small increments in personal bankruptcy filings were noted, the most stringent model found no significant increases in personal bankruptcies related to a casino's presence. While one study of three social problems will not close the gap between casino advocates and opponents, these results provide voters and public officials with important information from which to weigh the fiscal gains from casinos to determine if the benefits are attractive enough to warrant what is found to be a small risk of very modest (or no) increments in some selected social problems.     

表面贴技术选择的问题探讨

表面贴连接器的设计优点更胜以往，但更为重要的是了解其关键功能的细节以配合与满足不同性能的要求。     

DEGRADATION OF GUAR GUM BY ENZYMES PRODUCED BY A BACTERIUM FROM THE HUMAN COLON

A strain of Bacteroides ovatus from the human colon was grown on guar gum, a highly-branched galactomannan which is widely used as a food additive. Growth on guar gum induced production o f extracellular enzymes which partially degraded and/or deaggregated guar gum. The enzymes rapidly reduced the viscosity of guar gum solutions, while breaking only a limited number of glycosidic bonds. The molecular weight (versus dextran standards) of the guar gum decreased sharply as the viscosity decreased. No mono-, di- or trisaccharides were produced during enzyme action, although small quantities of higher oligomers were present after longer (5–8 h) incubations. The enzyme had a sharp temperature optimum at 37°C for an incubation time of 60 min, but was stable for only a few hours at this temperature. These results demonstrate how enzymes produced and elaborated by human colon bacteria can markedly alter the physical properties of a dietary component which reaches the colon. Further studies of both substrate and enzymes will be required to establish the mechanism of this alteration and to establish how B. ovatus is able to utilize guar gum for growth.