8,488 research outputs found
The influence of bovine serum albumin on β-lactoglobulin denaturation, aggregation and gelation
peer-reviewedThe effect of bovine serum albumin (BSA) on the heat-induced denaturation, aggregation and subsequent acid-induced gelation of β-lactoglobulin (β-lg) was investigated in this work. Changes in the denaturation kinetics of β-lg during heating at 78 °C were determined by monitoring the disappearance of the native protein by reverse-phase chromatography. Replacing β-lg with increasing amounts of BSA, while keeping the total protein concentration constant at 5% (w/w), significantly increased the denaturation rate of β-lg from 2.57Âą0.30Ă10â3(g Lâ1)(1ân)sâ1 to 5.07Âą0.72Ă10â3(g Lâ1)(1ân)sâ1 (β-lg: BSA ratio of 3:1 w/w). The reaction order for β-lg was 1.40Âą0.09. Partial replacement of β-lg with BSA (β-lg: BSA ratio of 3:1 w/w) significantly increased the reaction order to 1.67Âą0.13. Heat-induced aggregates between β-lg and BSA were studied by dynamic light scattering, two-dimensional electrophoresis and size exclusion chromatography. The partial replacement of β-lg with BSA significantly changed the gelling properties of the acid-induced gels. A rapid rate of acidification resulted in a significant decrease, while a slow acidification rate resulted in a significant increase in gel strength. Size exclusion chromatography demonstrated that intermolecular disulphide bond formation occurred during both heat-induced denaturation/aggregation and subsequent acid-induced gelation. Results clearly indicate that BSA contributed to the formation of these disulphide bonds.This work was funded under the Food Institutional Research Measure (FIRM) of the National Development Plan 2000-2006. J. Kehoe is funded by the Teagasc Walsh Fellowship schem
Broughton Archipelago Clam Terrace Survey : final report
During a 1995 aerial video survey of the coastline
of Johnstone Strait, an unusual shoreline feature
was noted and termed âclam terracesâ (inset)
because of the terrace-type morphology and the
apparent association with high clam productivity
on the sandflats. Typical alongshore lengths of the
terrace ridges are 20-50m, and across-shore widths
are typically 20-40m.
An area with an especially high density of clam
terraces was noted in the Broughton Archipelago,
between Broughton and Gilford Islands of
southeastern Queen Charlotte Strait. Clam terraces
in this area were inventoried from the aerial video
imagery to quantify their distribution. The terraces accounted for over 14 km of shoreline and
365 clam terraces were documented.
A three-day field survey by a coastal geomorphologist, archeologist and marine biologist was
conducted to document the features and determine their origin. Nine clam terraces were
surveyed. The field observations confirmed that: the ridges are comprised of boulder/cobblesized
material, ridge crests are typically in the range of 1-1.5m above chart datum, sandflats are
comprised almost entirely of shell fragments (barnacles and clams) and sandflats have very high
shellfish production. There are an abundance of shell middens in the area (over 175) suggesting
that the shellfish associated with the terraces were an important food source of aboriginal
peoples.
The origin of the ridges is unknown; they appear to be a relict feature in that they are not actively
being modified by present-day processes. The ridges may be a relict sea-ice feature, although the
mechanics of ridge formation is uncertain. Sand accumulates behind the ridge because the supply
rate of the shell fragments exceeds the dispersal rate in these low energy environments.
The high density areas of clam terraces correspond to high density areas of shell middens, and it
is probable that the clam terraces were subjected to some degree of modification by aboriginal
shellfish gatherers over the thousands of years of occupation in the region. (Document contains 39 pages
Fatigue testing a plurality of test specimens and method
Described is a fatigue testing apparatus for simultaneously subjecting a plurality of material test specimens to cyclical tension loading to determine the fatigue strength of the material. The fatigue testing apparatus includes a pulling head having cylinders defined therein which carry reciprocating pistons. The reciprocation of the pistons is determined by cyclical supplies of pressurized fluid to the cylinders. Piston rods extend from the pistons through the pulling head and are attachable to one end of the test specimens, the other end of the test specimens being attachable to a fixed base, causing test specimens attached between the piston rods and the base to be subjected to cyclical tension loading. Because all the cylinders share a common pressurized fluid supply, the breaking of a test specimen does not substantially affect the pressure of the fluid supplied to the other cylinders nor the tension applied to the other test specimens
Microcrack Initiation and Growth
A Monte Carlo simulation technique to predict the mean and scatter in fatigue lifetime of certain 2000 and 7000 series aluminum alloys is described. The method is based upon models of surface microcrack nucleation and early growth, which comprise the initiation phase of the fatigue failure process. The experimental basis for the models is discussed, and examples of predicted numbers and lengths of microcracks developed during fatigue of Al 2219-T851 are compared with experiments. Scatter in lifetime and mean lifetime predictions are also discussed. These are obtained from repeated running of the fatigue simulation, for which scatter in lifetime results from the effect of local microscopic variations in alloy microstructure on the time of crack initiation. The association of the method with a retirement for cause philosophy is noted
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