4 research outputs found
Adaptation of Staphylococcus xylosus to nutrients and osmotic stress in a salted meat model
Staphylococcus xylosus is commonly used as starter culture for meat fermentation. Its technological properties are mainly characterized in vitro, but the molecular mechanisms for its adaptation to meat remain unknown. A global transcriptomic approach was used to determine these mechanisms. S. xylosus modulated the expression of about 40% to 50% of the total genes during its growth and survival in the meat model. The expression of many genes involved in DNA machinery and cell division, but also in cell lysis, was up-regulated. Considering that the S. xylosus population remained almost stable between 24 and 72 h of incubation, our results suggest a balance between cell division and cell lysis in the meat model. The expression of many genes encoding enzymes involved in glucose and lactate catabolism was up-regulated and revealed that glucose and lactate were used simultaneously. S. xylosus seemed to adapt to anaerobic conditions as revealed by the overexpression of two regulatory systems and several genes encoding cofactors required for respiration. In parallel, genes encoding transport of peptides and peptidases that could furnish amino acids were up-regulated and thus concomitantly a lot of genes involved in amino acid synthesis were down-regulated. Several genes involved in glutamate homeostasis were up-regulated. Finally, S. xylosus responded to the osmotic stress generated by salt added to the meat model by overexpressing genes involved in transport and synthesis of osmoprotectants, and Na+ and H+ extrusion
Absolute multilateration between spheres
Environmental effects typically limit the accuracy of large scale coordinate measurements in
applications such as aircraft production and particle accelerator alignment. This paper presents
an initial design for a novel measurement technique with analysis and simulation showing that
that it could overcome the environmental limitations to provide a step change in large scale
coordinate measurement accuracy. Referred to as absolute multilateration between spheres
(AMS), it involves using absolute distance interferometry to directly measure the distances
between pairs of plain steel spheres. A large portion of each sphere remains accessible as
a reference datum, while the laser path can be shielded from environmental disturbances.
As a single scale bar this can provide accurate scale information to be used for instrument
verification or network measurement scaling. Since spheres can be simultaneously measured
from multiple directions, it also allows highly accurate multilateration-based coordinate
measurements to act as a large scale datum structure for localized measurements, or to be
integrated within assembly tooling, coordinate measurement machines or robotic machinery.
Analysis and simulation show that AMS can be self-aligned to achieve a theoretical combined
standard uncertainty for the independent uncertainties of an individual 1 m scale bar of
approximately 0.49 µm. It is also shown that combined with a 1 µm m−1
standard uncertainty
in the central reference system this could result in coordinate standard uncertainty magnitudes
of 42 µm over a slender 1 m by 20 m network. This would be a sufficient step change in
accuracy to enable next generation aerospace structures with natural laminar flow and part-topart
interchangeability