Exact low temperature results for transport properties of the interacting resonant level model

Using conformal field theory and integrability ideas, we give a full characterization of the low temperature regime of the anisotropic interacting resonant level (IRLM) model. We determine the low temperature corrections to the linear conductance exactly up to the 6th order. We show that the structure displays 'Coulomb deblocking' at resonance, i.e., a strong impurity-wire capacitive coupling enhances the conductance at low temperature.Comment: 4 pages, 2 figure

A simple method to determine evaporation and compensate for liquid losses in small-scale cell culture systems

Objectives: Establish a method to indirectly measure evaporation in microwell-based cell culture systems and show that the proposed method allows compensating for liquid losses in fed-batch processes. Results: A correlation between evaporation and the concentration of Na + was found (R 2 = 0.95) when using the 24-well-based miniature bioreactor system (micro-Matrix) for a batch culture with GS-CHO. Based on these results, a method was developed to counteract evaporation with periodic water additions based on measurements of the Na + concentration. Implementation of this method resulted in a reduction of the relative liquid loss after 15 days of a fed-batch cultivation from 36.7 ± 6.7% without volume corrections to 6.9 ± 6.5% with volume corrections. Conclusion: A procedure was established to indirectly measure evaporation through a correlation with the level of Na + ions in solution and deriving a simple formula to account for liquid losses

Using a Parallel Micro-Cultivation System (Micro-Matrix) as a Process Development Tool for Cell Culture Applications

Micro-bioreactors appear frequently in today's biotechnology industry as screening and process development tools for cell culture applications. The micro-bioreactor's small volume allows for a high throughput, and when compared to other small-scale systems, such as microtiter plates, its measurement and control capabilities offer a much better insight into the bioprocess. Applikon's micro-Matrix is one of the micro-bioreactors that are commercially available today. The micro-Matrix system consists of shaken disposable 24 deep square well plates in which each well is controlled individually for pH, dissolved oxygen (DO), and temperature. Additionally, a feeding module supports automated additions of liquid to each well. This chapter describes how the micro-Matrix can be used for fed-batch cultivations of Chinese Hamster Ovary (CHO) cells

Quasi-exactly solvable problems and the dual (q-)Hahn polynomials

A second-order differential (q-difference) eigenvalue equation is constructed whose solutions are generating functions of the dual (q-)Hahn polynomials. The fact is noticed that these generating functions are reduced to the (little q-)Jacobi polynomials, and implications of this for quasi-exactly solvable problems are studied. A connection with the Azbel-Hofstadter problem is indicated.Comment: 15 pages, LaTex; final version, presentation improved, title changed, to appear in J.Math.Phy

Raman Scattering and Anomalous Current Algebra: Observation of Chiral Bound State in Mott Insulators

Recent experiments on inelastic light scattering in a number of insulating cuprates [1] revealed a new excitation appearing in the case of crossed polarizations just below the optical absorption threshold. This observation suggests that there exists a local exciton-like state with an odd parity with respect to a spatial reflection. We present the theory of high energy large shift Raman scattering in Mott insulators and interpret the experiment [1] as an evidence of a chiral bound state of a hole and a doubly occupied site with a topological magnetic excitation. A formation of these composites is a crucial feature of various topological mechanisms of superconductivity. We show that inelastic light scattering provides an instrument for direct measurements of a local chirality and anomalous terms in the electronic current algebra.Comment: 18 pages, TeX, C Version 3.

Equal mixing time enables scale-down and optimization of a CHO cell culture process using a shaken microbioreactor system

The advancement of microbioreactor technology in recent years has transformed early- and mid-stage process development. The monitoring and control capabilities of microbioreactors not only promote the quick accumulation of process knowledge but has also led to an increased scalability when compared to traditionally used systems such as shake flasks and microtitre plates. This study seeks to establish a framework for the micro-Matrix microbioreactor (Applikon-Biotechnology BV) as process development tool. Using the Dual Indicator System for Mixing Time, the system was initially characterized for mixing properties at varying operating conditions, which was found to yield mixing times between 0.9 and 41.8 s. A matched mixing time was proposed as scale-down criterion for an IgG4 producing GS-CHO fed-batch process between a 5 L stirred tank reactor (STR) and the micro-Matrix microbioreactor. Growth trends, maximum viable cell concentrations, final titre, and glycoprofiles were nearly identical at both scales. The scale-down model was then employed to optimize a bolus feeding regime using response surface methodology, which led to a 25.4% increase of the space-time yield and a 25% increase of the final titre. The optimized feeding strategy was validated at the small-scale and successfully scaled up to the 5 L STR. This work for the first time provides a framework of how the micro-Matrix microbioreactor can be implemented in a bioprocess development workflow and demonstrates scalability of growth and production kinetics as well as IgG4 glycosylation between the micro-Matrix and a benchtop-scale STR system. Graphical Abstract and Lay Summary: (Figure presented.) Microbioreactor technology has become an essential part of early- and mid-stage bioprocess development. This study provides a framework of how the shaken micro-Matrix system can be used for cell culture process development of a mammalian CHO cell line producing a monoclonal antibody. Following scale-down from a 5 L stirred tank bioreactor, the micro-Matrix was employed for the optimisation of a feeding strategy and the optimised protocol was successfully scaled up

Towards the development of automated fed-batch cell culture processes at microscale

AIM: To investigate the impact of various feeding strategies on the growth and productivity of a GS-CHO cell line. METHODS: Feed additions were conducted at fixed volumes or linked to a marker such as cell growth or metabolism and added as bolus or near-continuously using the automated feeding module of the micro-Matrix (Applikon). RESULTS: The selected feeding regimens supported maximum viable cell densities of up to 1.9 × 107 cells ml−1 and final titers of up to 1.13 g l−1. Differences in growth and titer between feeding strategies were insignificant, with the exception of one feeding strategy. CONCLUSION: As the more complex feeding strategies did not create an advantage, the selection of a simple feeding strategy such as bolus or continuous addition of feed medium is preferred. METHOD SUMMARY Fed-batch is an easy and popular way to intensify cell cultivations. The time of addition and the volume that is added can be decisive in achieving optimal product titers. A micro-bioreactor has been used to investigate the effect of several feeding strategies on the growth and production kinetics of a GS-CHO cell line