Neutron activation analyses of ground samples of safe-packing insulation have shown that dust from different sources may be
differentiated by trace element content. Between 10 and 20 elements were identified in each of 54 samples, and comparison
of the activation “fingerprints” offers a good prospect for positively or negatively matching two or more samples.
After a formal explanation of Mayer's enthalpy balance method as applied to biological reaction rates, the history of its
application is traced from Rubner's dog to accounting for the energy of muscle contraction. The introduction of microcalorimetry
allowed the method generally to be used for cells in vitro and now particular emphasis can be paid to the growth of cells
for the production of therapeutically-important heterologous proteins. In these systems, enthalpy balance studies contribute
to defining catabolic processes, designing media, understanding the mechanisms of growth and controlling cultures using heat
flux as an on-line sensor of metabolic activity.
Microcalorimeters to monitor the heat dissipation of bench-scale animal cell cultures on line and in real time require a continuous
circuit between the vessel measuring heat flow rate and the bioreactor. The modifications to the transmission lines and calorimetric
heat exchanger were to: (i) reverse the usual upward direction of the cell suspension in the flow vessel to downwards; (ii)
install an in situ washing/cleaning facility; (iii) use low diffusivity PEEK material; and (iv) maintain thermal equilibration
by water-jacketing the transmission tubing. Chemical calibration showed that there was more than a 20% difference between
the physical volume and the effective thermal volume. An appropriate thermodynamic system was defined in order to permit enthalpy
Authors:C. Allen, K. O'Reilly, B. Cantor, and P. Evans
Differential scanning calorimetry (DSC) combined with an entrained droplet technique  has been successfully used on a series of melt spun alloys with deliberate impurity additions to study the nucleation related aspects of secondary phase selection during solidification of dilute Al alloys. This paper illustrates how DSC is a sensitive tool for determining the effect impurities can have on the nucleation of secondary phases, and hence material properties of these alloys. Stepped cooling/isothermal holding profile DSC has also been used in preliminary investigations of the thermodynamic range of formation of the Al—Fe eutectic phases and their nucleation and growth solidification kinetics.
Authors:A. Kidane, Y. Guan, P. Evans, M. Kaderbhai, and R. Kemp
It is claimed, though not without dispute, that genetically engineered mammalian cells grow more slowly than their progenitor
cells because the recombinant gene system causes a metabolic burden. This was found to be the case for CHO cells transfected
with expression vectors forcytochrome b5. The slower growth was associated with lower metabolic activity measured by heat flux and mitochondrial activity (rhodamine
123 fluorescence). The calorimetric-respirometric ratio was similar for all cell types, implying that the greater fluxes of
glucose and glutamine in the recombinant cells was channelled to biosynthesis. This demand probably restricted the supply
of pyruvate to the mitochondria in these cells.
Authors:P. Warwick, N. Evans, A. Hall, G. Walker, and E. Steigleder
Conditional stability constants have been determined for U(IV) and U(VI) Boom Clay humic acid (BCHA) and Aldrich humic acid
(AHA) complexes, under anaerobic and carbonate free conditions. The constants are needed for nuclear waste repository performance
assessment purposes. The U(IV) constants were obtained by developing an approach based on the solubility product of amorphous
U(OH)4. The U(VI) constants were obtained by applying the Schubert ion-exchange approach.
Authors:J. Tsai, S. Owega, G. Evans, R. Jervis, M. Fila, P. Tan, and O. Malpica
Summertime urban PM2.5 was collected on cellulose filters in downtown Toronto, using a customized air sampler (635 l/min). Mass concentrations for up to 19 trace elements/ions were measured by ICP-AES, INAA and IC. Source apportionment was performed on these results including additional carbon and total mass concentrations using positive matrix factorization (PMF). PMF factors exhibited trends that indicated soil (18%), stationary (19%), secondary (48%), and vehicle (15%) sources. Potential source contribution function (PSCF) analysis identified probable sources of the stationary and secondary PM2.5 as originating from the south and southwest of Toronto.