Abstract: A method of controlling additive delivery during a bioreaction in a bioreactor comprises running a bioreaction in a bioreactor including adding additive into the bioreactor during spaced-apart feed events, where contents of the bioreactor equilibrate during a stabilisation period after a feed event; making in situ measurements of a bulk physical property of the bioreactor contents during the bioreaction to obtain process trend data; calculating a derivative of process trend data obtained over a measurement period beginning after a stabilisation period, the derivative being a metabolic rate index (MRI); and using the MRI to determine a time for starting a next feed event. A controller for a bioreactor and a bioreactor system are configured to operate according to the method.

Abstract: Apparatus (2) comprising a cylindrical substrate (4), and an integrated optical circuit which is provided on the cylindrical substrate and which comprises at least one optical waveguide (6). A process for producing the apparatus (2) is also disclosed.

Abstract: A method of simultaneously defining a waveguide and grating in a sample of photosensitive material comprises providing a sample of material (24) having a region which is photosensitive to light of a specific wavelength, generating a spot of light (22) at the specific wavelength, the spot having a periodic intensity pattern of high and low intensity fringes, and a width which is related to the width of the channel, positioning the spot within the photosensitive region and causing relative movement between the sample and the light spot along the desired path of the waveguide/grating define a channel of altered refractive index by exposing parts of the photosensitive region to the light spot. Modulation of the light spot to produce multiple exposures produces a grating, while continuous exposure results in a uniform waveguide. These structures can be written in straight lines or around curves, and can be accurately overwritten, so that complex optical devices can be produced in a single fabrication step.