Evaluation of toughness in AISI 4340 alloy steel austenitized at low and high temperatures

It has been reported for as-quenched AISI 4340 steel that high temperature austenitizing treatments at 1200°C, instead of conventional heat-treatment at 870°C, result in a two-foldincrease in fracture toughness,K _Ic, but adecrease in Charpy impact energy. This paper seeks to find an explanation for this discrepancy in Charpy and fracture toughness data in terms of the difference betweenK _Ic and impact tests. It is shown that the observed behavior is independent of shear lip energy and strain rate effects, but can be rationalized in terms of the differing response of the structure produced by each austenitizing treatment to the influence of notch root radius on toughness. The microstructural factors which affect this behavior are discussed. Based on these and other observations, it is considered that the use of high temperature austenitizing be questioned as a practical heat-treatment procedure for ultrahigh strength, low alloy steels. Finally, it is suggested that evaluation of material toughness should not be based solely onK _Ic or Charpy impact energy values alone; both sharp crack fracture toughness and rounded notch impact energy tests are required. formerly with Effects Technology, Inc., Santa Barbara, CA     

Effect of surface properties of different food contact materials on the efficiency of quaternary ammonium compounds residue recovery and persistence

Residues of quaternary ammonium compounds (QACs) remaining after sanitising were evaluated for a number of materials used in food plants. The residues were collected by swabs and measured using a spectrophotometric method. Surface topography and energy affected the QACs recovery. Highest percentage of QACs recovery was achieved for the tile material (102.2%) which had the most hydrophilic properties and least irregularities in surface topology, followed by stainless steel (82.1%). Meanwhile, the lowest recovery occurred in PVC (42.1%) and resin (44.3%) that exhibited hydrophobic characteristics and abrupt changes in height profile in a given surface area. Monitoring of QACs residues deposited on the surfaces after 7 days showed that the recovery of QACs in PVC and resin reduced significantly (P < 0.05), supposing that QACs might be degraded or interacted with the materials. However, no significant changes in residue recovery were observed for tiles and stainless steel surfaces after 7 days.     

Genetic analysis of geraniol metabolism during fermentation

Geraniol produced by grape is the main precursor of terpenols which play a key role in the floral aroma of white wines. We investigated the fate of geraniol during wine fermentation by Saccharomyces cerevisiae. The volatile compounds produced during fermentation of a medium enriched with geraniol were extracted by Stir-bar sorptive extraction and analysed by GC–MS. We were able to detect and quantify geranyl acetate but also citronellyl- and neryl-acetate. The presence of these compounds partly explains the disparition of geraniol. The amounts of terpenyl esters are strain dependant. We demonstrated both by gene overexpression and gene-deletion the involvement of ATF1 enzyme but not ATF2 in the acetylation of terpenols. The affinity of ATF1 enzyme for several terpenols and for isoamyl alcohol was compared. We also demonstrated that OYE2 is the enzyme involved in geraniol to citronellol reduction. Fermenting strain deleted from OYE2 gene produces far less citronellol than wild type strain. Moreover lab strain over-expressing OYE2 allows 87% geraniol to citronellol reduction in bioconversion experiment compared to about 50% conversion with control strain.     

Effects of the indigenous microflora of minimally processed lettuce on the survival and growth of Listeria innocua

Interactions between the natural background microflora of shredded lettuce and Listeria innocua (in lieu of Listeria monocytogenes ) were studied. The effect of increasing the initial size of indigenous populations (from 10³ to 10⁶–10⁷ CFU g⁻¹) was tested for its ability to reduce L. innocua growth on shredded lettuce. Co-culture experiments were performed in model media, where bacterial isolates from the indigenous microflora were tested for possible inhibitory effects. Varying the size of the indigenous populations had no effect on L. innocua survival or growth. However, interactions with individual species and mixed populations from lettuce did affect the survival and growth of L. innocua in model media. In general, mixed populations diminished L. innocua growth. In the undiluted lettuce medium, the various species tested individually either reduced or did not affect the growth of L. innocua . However, when the medium was diluted, some species extended the survival of L. innocua . Competition between the indigenous microflora and L. innocua resided mostly with the Enterobacter spp. and not with the pseudomonads. Enterobacter cloacae was particularly effective in reducing L. innocua growth. Lactic acid bacteria also reduced L. innocua growth in undiluted media. It is concluded that interactions with the natural background microflora may play an important role in determining the dynamics of Listeria populations on shredded lettuce.     

Fate and transport of testosterone in agricultural soils

Hormones excreted in animal waste have been measured in surface and groundwater associated with manure that is applied to the land surface. Limited studies have been done on the fate and transport of androgenic hormones in soils. In this study, batch and column experiments were used to identify the fate and transport of radiolabeled [14C] testosterone in agricultural soils. The batch results indicated that aqueous-phase concentrations decreased for the first 5 h and then appeared to increase through time. The first-order sorption kinetics ranged from 0.08 to 0.640 h(-1) for the first 5 h. Beyond 5 h the increase in aqueous 14C could have been caused by desorption of testosterone back into the aqueous phase. However, metabolites were also produced beyond 5 h and would have likely resulted in the increase in aqueous 14C by sorption site competition and/or by lower sorption affinity. There were weak correlations of sorption with soil particle size, organic matter, and specific surface area. Testosterone was the dominant compound present in the soil column effluents, and a fully kinetic-sorption, chemical nonequilibrium model was used to describe the data. Column experiment sorption estimates were lower than the batch, which resulted from rate-limiting sorption due to the advective transport. The column degradation coefficients (0.404-0.600 h(-1)) were generally higher than values reported in the literature for 17beta-estradiol. Although it was found that testosterone degraded more readily than 17beta-estradiol, it appeared to have a greater potential to migrate in the soil because it was not as strongly sorbed. This study underlined the importance of the simultaneous transformation and sorption processes in the transport of hormones through soils.     

The effect of multiple yeasts co-inoculations on Sauvignon Blanc wine aroma composition,sensory properties and consumer preference

Consumer acceptance testing has been only recently applied in wine research, to assess wine sensory attributes that affect hedonic liking. The aim of this study was to investigate the effect of Saccharomyces yeast co-inoculations on wine volatile composition and sensory profiles, and to determine if differences were sufficient enough to affect consumer acceptance. Fermentations were conducted using two- and three-yeast co-inoculations, and single strains. Yeast inocula differed substantially in volatile thiols and other flavour compounds, and in their sensory properties. Wines from four yeast inocula which showed large sensory differences were subjected to consumer testing by 120 consumers, with differences in overall liking found. Four clusters of consumers were identified, with one group strongly preferring the two-yeast co-inoculated wine with an intermediate sensory profile, while another group favoured the wine made using the three-yeast co-inoculation. This study has demonstrated that the yeast inoculum used to conduct fermentation affects consumer acceptance.     

Fiber yield for fully bleached kraft pulps from black locust (Robinia pseudoacacia) and silver maple (Acer saccharinum)

Robinia pseudoacacia ) and silver maple (Acer saccharinum) with emphasis being placed on fiber yield. Black locust had longer fibers, a higher Seifert cellulose content, and a lower lignin content compared to the maple. The results were higher strength and bleached pulp yield for the black locust. The final yields were 49.5% for black locust and 47.7% for maple. These values are significantly higher than the 40–42% that is normally obtained for bleached softwood kraft pulps.

---

     

Analysis of ultracentrifugation interference patterns with image digitizer: Application to molecular weight determination of SRM 1478 polystyrene

A new method for the analysis of ultracentrifugation interference patterns with the use of a commercial image digitizer is given. The application of the method to the sedimentation equilibrium data for SRM 1478 polystyrene leads to a weight-average molecular weight of 37 400 g mol⁻¹ having a sample standard deviation of 0.7% and an expected systematic error limit of 2%.     

Effect of water deficit on yield and protein content in pearl millet grains

Seventy-two pearl millet genotypes were water stressed at panicle development and grain filling stages. Neither grain yields, yield components, protein percent nor total protein per unit area were affected by water deficit during panicle development but protein content per grain was increased. When plants were water stressed during grain filling, grain yield, grains per unit area and 1000 grain weight were reduced, but grain protein percentage increased. Total protein per unit area was reduced primarily due to lower grain yield. The protein content per grain was unaffected by stress, suggesting that the apparent increase in protein percentage is due to reduced carbohydrate accumulation under stress.