Experimental Investigation of the Froth Height in Columns with Sandwich Packings

Sandwich packings, consisting of alternatingly stacked conventional structured packings with different geometric surface areas, are promising for increasing capacity and efficiency of separation columns. Film flow and froth flow evolve along a stack, which requires comprehensive fluid dynamic analysis. In particular, the froth height is an essential parameter to determine the spatial extent of the flow regimes. Ultrafast X‐ray tomography and a 3D‐printed pressure drop profile measurement module were applied to independently estimate this parameter. The results are compared with existing correlations.     

Genetic parameters of forage dry matter intake and milk produced from forage in Swedish Red and Holstein dairy cows

High-yielding dairy cows are often fed high proportions of cereal grain and pulses. For several reasons, it would be desirable to replace these feed sources with forage, which is not suitable for human consumption. Feeding large amounts of forage to dairy cows could also make dairy production more publicly acceptable in the future. In this study, we estimated genetic parameters for total dry matter intake (DMI), DMI from forage (DMI_For), energy-corrected milk (ECM), and ECM produced from forage (ECM_For). A total of 1,177 lactations from 575 cows of Swedish Red (SR) and Holstein (HOL) dairy breeds were included in the study. Mixed linear animal random regression models were used, with fixed effect of calving season and lactation week nested within parity 1 and 2+, fixed effect of calving year, and random regression coefficients for breeding value (up to linear) and permanent environmental effect (up to quadratic) of the cow. Heritability for DMI and DMI_For was generally higher for HOL than for SR in all-parity data and in later parities; however, the opposite was true for first parity. Heritability for DMI and DMI_For during the first 8 wk averaged 0.11 and 0.15, respectively, in all-parity data for the 2 breeds. Corresponding values for ECM_For and ECM were 0.21 and 0.29, respectively. In first parity, values were 0.32, 0.36, 0.28, and 0.51, respectively. The genetic correlation between DMI and DMI_For was high, above 0.83, and fairly constant across the lactation. The genetic correlation between ECM_For and ECM was close to unity in the later part of lactation for both breeds, but was around 0.8 in the early lactation for both breeds; it decreased for HOL to 0.54 in wk 17. The genetic correlations between DMI and ECM_For and between DMI_For and ECM_For were low and negative for HOL (absolute value ～0.2–0.3), but changed for SR from weakly positive in early lactation to negative values and back to positive toward the end of lactation. For most traits, the correlation between wk 1 and wk 8 into the lactation was very high; the lowest value was for DMI in HOL at 0.81. The genetic correlation between parities was rather high in the first part of the lactation. During the first 8 wk, the correlation was lower for HOL than for SR, except for ECM. We found that DMI_For and ECM_For showed reasonably large heritability, and future work should explore the possibility of genomic evaluations.     

Comparison of four methods to enumerate probiotic bifidobacteria in a fermented food product

Four methods of enumeration were compared by monitoring levels of probiotic bifidobacteria in fermented oat drink during storage. Strains of Bifidobacterium longum and B. lactis were quantified by plate counts, fluorescent in situ hybridization (FISH), quantitative real-time PCR and commercial LIVE/DEAD BacLight bacterial viability kit, and the methods were further developed to suit the enumeration of bifidobacteria in fermented foods. Plate counts of both B. lactis and B. longum were lower than the PCR and FISH counts. The LIVE/DEAD counts of B. lactis were comparable to PCR and FISH counts. The plate counts of B. lactis were slightly but significantly lower than LIVE/DEAD counts, suggesting that the cells that were not able to grow on plates may have become dormant. The plate counts of B. longum were several log units lower than LIVE/DEAD counts, suggesting that a remarkable part of the cells were dormant. Real-time PCR and FISH were shown to suit the quantification of the total amount of probiotic bifidobacteria in foods. Plate counts and LIVE/DEAD counts provided conflicting information on viability especially in the case of B. longum. We conclude that the choice of enumeration method for probiotic bacteria may have significant effect on the results of the analysis. The strain-specific properties and the objects of the analysis should be taken into account when enumeration methods for different probiotic strains are chosen.     

Lactic acid bacteria in marinades used for modified atmosphere packaged broiler chicken meat products

Lactic acid bacteria (LAB) in some marinades commonly used in Finland for modified atmosphere packaged poultry meat products were enumerated and identified to determine whether the marinades contained LAB species that cause meat spoilage. The concentrations of LAB in 51 marinade samples ranged from less than 100 to 8.0 x 10(5) CFU/ml. Seventeen of the samples produced LAB growth only after enrichment, and in five samples no growth was detected either by direct culturing or enrichment. Eighty-eight randomly selected isolates, 51 from the enumerated plates and 37 from enriched samples, were identified using a database of 16S and 23S rRNA gene HindIII restriction fragment length polymorphism patterns of over 300 type and references LAB strains as operational taxonomic units in numerical analyses. The predominating LAB in the enumerated samples was Lactobacillus plantarum (25 of 51 isolates). Eleven isolates were identified as Lactobacillus paracasei subsp. paracasei, and nine were Lactobacillus parabuchneri. None of these species are considered specific spoilage LAB in marinated modified atmosphere packaged poultry meat products nor have they been reported to dominate in unspoiled late-shelf-life products. These results indicate that even though marinades may contain high numbers of LAB, they are not necessarily sources of specific meat spoilage LAB. Therefore, risks associated with meat quality are not predicted by quantitative enumeration of LAB in marinades.     

Biofuel developments in Sweden and the Netherlands: Protection and socio-technical change in a long-term perspective

This paper reviews long-term development of biofuels in Sweden and the Netherlands. In particular this paper explores the social dynamics of ‘niche protection’. The Swedish and Dutch cases are analyzed by means of the Strategic Niche Management (SNM) perspective extended with insights from political science. Our main argument is that the development of biofuels and the way this development is protected relies on a variety of actor strategies and (local and global) discourses. This case therefore suggests that policy making for biofuels is a complex and non-linear process that can only partly be managed by policy actors.     

An analysis of hydrogen production from renewable electricity sources

Three aspects of producing hydrogen via renewable electricity sources are analyzed to determine the potential for solar and wind hydrogen production pathways: a renewable hydrogen resource assessment, a cost analysis of hydrogen production via electrolysis, and the annual energy requirements of producing hydrogen for refueling. The results indicate that ample resources exist to produce transportation fuel from wind and solar power. However, hydrogen prices are highly dependent on electricity prices. For renewables to produce hydrogen at $2 kg⁻¹, using electrolyzers available in 2004, electricity prices would have to be less than $0.01 kWh⁻¹. Additionally, energy requirements for hydrogen refueling stations are in excess of 20 GWh/year. It may be challenging for dedicated renewable systems at the filling station to meet such requirements. Therefore, while plentiful resources exist to provide clean electricity for the production of hydrogen for transportation fuel, challenges remain to identify optimum economic and technical configurations to provide renewable energy to distributed hydrogen refueling stations.