Characterization of CMP Slurries Using Densitometry and Refractive Index Measurements

We investigated the possibility of employing refractive index (RI) measurements for inline incoming slurry control at the point of use (POU), as an alternative to the widespread densitometry method. As such, it became necessary to determine if RI could detect smaller changes in slurry composition and, therefore, provide a tighter control. Three industrially-relevant silica-based slurries, namely, Fujimi PL-7106, Klebosol 1501-50, and CMC W7801, were characterized using both densitometry and RI measurements. Initial solutions of the three slurries were prepared and increasingly small amounts of ultrapurified water (UPW) were added to study the change in slurry properties. Results showed that both density and RI decreased linearly with the addition of water for all three slurries, with the 1501-50 being the most sensitive to water addition. A linear correlation between the two properties was found, with R2 values that exceeded 0.95 in all cases. Furthermore, the approximate limit of detection of both metrology tools was estimated based on the slope of the fitting line and resolution. When compared to densitometry, RI was found to be the far superior method for detecting smaller changes in water concentration.

The Characteristics of Growth of Bacilli Formed Fouling on Wooden Constructions

Problem of biofilm formation have a great significance for environmental microbiological research. Biospheric microorganisms can form biofilm, that provide bacteria resistance to influence of different environmental factors. Some of the most common bacteria in biosphere are bacilli, among them there are film-forming strains.Bacillus spp.ia a well-known film forming microorganisms that colonize environmental objects. The biofilm fouling of underwater elements of small wooden constructions located on the Dnieper River near the city of the Dnipro (Ukraine) was studied. It was found that biofilms from surfaces of water constructions include bacilli. It is established that the mean values of CFU in samples from running and still water were (1.81±0.52)×108and (1.83±0.53)×108CFU / ml respectively per area of wooden sample approximately 1 cm2, while during the laboratory cultivation of the film, formed by these cultures on the plate, the number of cells was (4.90±0.93)×107and (4.60±1.07)×107CFU / ml per 1 cm2of the well’s bottom, which was an approximate limit of the content of cells of theBacillus spp.film per unit of area.

Exact and approximate limit behaviour of the Yule tree’s cophenetic index

In this work we study the limit distribution of an appropriately normalized cophenetic index of the pure–birth tree conditioned onncontemporary tips. We show that this normalized phylogenetic balance index is a submartingale that converges almost surely and inL2. We link our work with studies on trees without branch lengths and show that in this case the limit distribution is a contraction–type distribution, similar to the Quicksort limit distribution. In the continuous branch case we suggest approximations to the limit distribution. We propose heuristic methods of simulating from these distributions and it may be observed that these algorithms result in reasonable tails. Therefore, we propose a way based on the quantiles of the derived distributions for hypothesis testing, whether an observed phylogenetic tree is consistent with the pure–birth process. Simulating a sample by the proposed heuristics is rapid, while exact simulation (simulating the tree and then calculating the index) is a time–consuming procedure. We conduct a power study to investigate how well the cophenetic indices detect deviations from the Yule tree and apply the methodology to empirical phylogenies.

Proposed Revision to Nuclear Piping Thermal Expansion Stress Limit

Piping thermal expansion stress limits for ASME Section III Class 2/3 piping are directly based on the original thermal expansion stress rules given in B31.1-1955. Cyclic thermal expansion stresses are limited by Equation 10 to SA where SA is a function of the expected number of full temperature cycles. The Eq. 10 limit may be exceeded, if the pressure-plus-weight stresses are below their limit. This requirement is expressed as Eq. 11. The basis for Eqs. 10 and 11 is not well understood in the industry, and has caused confusion. One typical comment is — Why have an Eq. 10 limit if it can be exceeded? The history and development of the thermal expansion stress limits are presented. The thermal expansion stress limits from B31.1 are based on relaxation considerations and prevention of yield or creep strain even though the failure mode of concern is fatigue cycling. Hence, the thermal expansion stress limit is an implied and approximate limit on fatigue. Recommendations for changes to the Section III Class 2/3 rules are provided. A direct fatigue based stress limit is proposed.