HBsAg Production in Methanol Controlled P. pastoris GS115 MutS Bioreactor Process

When producing recombinant proteins with Pichia pastoris, cultivation parameters, such as induction temperature, dissolved oxygen level and residual methanol concentration play a crucial role in product biosynthesis and subsequent purification, therefore to maximize protein yields, the optimization of these parameters is imperative. Two different Pichia pastoris cultivation strategies for HBsAg VLP production in a 5 L stirred-tank bioreactor and the influence of different cultivation parameters on product yield were investigated. Residual methanol concentrations were controlled at low (>0.01 g/L), medium (1.5-2.0 g/L) and high (5.0-6.0 g/L) levels using a PI-based feed rate control algorithm based on the online methanol sensor signal. Product was purified using a novel and rapid purification method including steps of ammonium sulfate precipitation, size-exclusion chromatography and hydrophobic interaction chromatography. Employing an in-situ methanol sensor probe, the PI-based methanol feed rate control algorithm provided residual methanol concentration control with an average deviation of ±0.4 g/L from set-point value. Employing a cultivation protocol with an increased methanol concentration controlled at 6.0 g/L and a reduced DO level below 10 %, resulting in a final dry cell biomass concentration of 140 g/L and purified HBsAg VLPs yield of 186 mg/L. Developed purification method proved advantageous to other described methods, as it did not include time consuming extraction and centrifugation steps.

Feed rate control in robotic bone drilling process

The bone drilling process is characterised by various parameters, the most important of which are the feed rate (mm/s) and the drill speed (rpm). They highly reflect the final effects and results of the drilling process, such as mechanical and thermal damages of bone tissue and hole quality. During manual drilling, these parameters are controlled by the surgeon based on his practical skills. But automatic drilling can assure an optimal result of the manipulation where such parameters are under control. During bicortical automatic bone drilling such a process consists of several stages: searching the contact with the first cortex, cortex drilling and automatic stop; searching the contact with the second cortex, cortex drilling and automatic stop; drill bit extraction. This work presents a way to control the feed rate during different stages of the bone drilling process (an original feed rate control algorithm) using the orthopaedic drilling robot (ODRO). The feed rate control is based on a proposed algorithm created and realised by specific software. During bicortical bone drilling process the feed rate takes various values in any stage in the range 0.5–6 mm/s. These values depend on drill bit position and real time force sensor data. The novelty of this work is the synthesis of an original feed rate control algorithm to solve the main problems of bone drilling in orthopaedic surgery – minimisation the drilling time (the heat generation); eliminating of the drill bit slip at the first (near) cortex and the drill bit bending at the second (far) cortex; minimising the risk of micro cracks which causes Traumatic Osteonecrosis; improving hole quality of the drilled holes; eliminating of the drill bit slip and the drill bit bending at the second cortex; minimising the value of the second cortex drill bit penetration by bicortical bone drilling.

A Novel Two-Level Rate Control Algorithm Based on Visual Attention for 360-Degree Video for Versatile Video Coding Standard

360-degree video is providing users with an interactive experience to explore the scenes freely. But, because only a small portion of the entire video, called viewport, is watched at every point in time, transmitting the entire video is bandwidth-consuming. Since, the perceptual quality of such video mainly depends on the quality of the viewport, more bandwidth should be assigned to these important parts of the scene. Hence, understanding how people observe and explore 360-degree content is essential. In this paper, we propose a new Two-level rate control algorithm which tries to allocate more bits for encoding the viewport parts of a 360-degree video. The head and eye movements of the observers is used to investigate the visual attention of people to detect the viewports. Then, a Coding Tree Unit (CTU) level rate assignment approach is proposed to assign a proper number of bits to each CTU of the viewport and non-viewport parts. It is assumed that higher motion complexity results in higher bitrates of the encoded video. So, we propose to assign the proper number of bits to each CTU according to its motion complexity. Another novel part of our proposed approach is proposing a new metric to parameterize the motion complexity of each CTU using the high-order motion models in Versatile Video Coding (VVC) standard. Experimental results show that our proposed rate control, on average, achieves 58.27% reduction in bitrate in the Bjøntegaard-Bitrate scales, compared to the standard VCC standard. Furthermore, the proposed scheme provides a significantly better subjective viewing quality compared to the-state-of-the-art methods.