16,045 research outputs found
Effect of hypoosmotic pressure on cell growth and antibody production in recombinant Chinese hamster ovary cell culture
No full textTo determine the response of recombinant Chinese hamster ovary (rCHO) cells subjected to hypoosmotic pressure, rCHO cells (CS13*-1.0) producing a chimeric antibody were cultivated in the hypoosmolar medium resulting from NaCl subtraction. At hypoosmotic pressure, CS13*-1.0 cells displayed decreased specific growth rate (μ) and increased specific antibody productivity (qAb). When the medium osmolality was decreased from 300 mOsm kg (physiological osmolality) to 150 mOsm kg, μ was decreased by 68% and qAb was increased by 128%. To understand the mechanism of enhanced qAb resulting from hypoosmotic pressure, cellular responses of cells in the exponential phase of growth were observed at the transcription level. Total cytoplasmic RNA content per cell at 150 mOsm kg was increased by 140%, compared with that at 300 mOsm kg. On a per μg RNA basis, immunoglobulin (Ig) mRNA levels at 150 mOsm kg were comparable to those at 300 mOsm kg, indicating that hypoosmotic pressure did not lead to the preferential transcription of Ig mRNAs. Taken together, the data obtained here suggest that the increase in total RNA pool is primarily responsible for the enhanced qAb of CS 13*1.0 cells subjected to hypoosmotic pressure
Radiation-hardening of low noise readout integrated circuit for infrared focal plane arrays
No full textResource-efficient wireless relaying protocols
No full textRelay-aided communication is considered one of the key techniques to achieve high throughput at low cost in future wireless systems. However, when transmitting signals via a relay, additional time slots, antennas, or frequency slots are required, which may erode the potential gain of relay-aided systems. In this article various approaches to creating relay-aided systems are reviewed. The advantages and disadvantages of various relaying schemes are compared in terms of their slot efficiency, error rate performance, and feasibility. Our detailed comparisons and the numerical results indicate that the specific family of network coding aided relaying protocols constitutes one of the most promising solutions. We conclude this article by listing a number of open problems
DESIGN AND FABRICATION OF HIGH TRANSCONDUCTANCE MODULATION-DOPED (Al,Ga)As/GaAs FETS.
No full textModulation-doped FETS grown by MBE exhibit very high currents and transconductances per unit gate width. In short gate FETs the high transconductances are a result of large electron velocities; typically 2 multiplied by 10**7 cm/s at 77 K. Since the low field mobility does not strongly affect device performance, improvements were obtained by adjusting the parameters of the heterostructure to maximize charge transfer across the heterojunction. An improved calculation of the maximum charge transfer is used to derive closed expressions for the maximum current and transconductance. Predictions of increasing current and transconductance as the undoped (Al,Ga)As spacer layer thickness is decreased have been verified by experimental results.The work at the University of Illinois is funded by the Air Force Office of Scientific Research and the Joint Services Electronics Program. The work at the University of Minnesota is partially funded by the Army Research Office and the Microelectronic and Information Sciences Center at the University of Minnesota. The authors would like to express their thanks to Dr.E.Hall and Dr.H.Goronkin and Mr.T.Miers of Motorola for providing the FET masks. The technical assistance of J.Klem and D.Arnold is greatly appreciated
A new distortion measure for spectral quantization based on the LSF intermodel interlacing property
No full textThe line spectral frequencies (LSFs) extracted from successive analysis orders are interlaced with each other. This intermodel interlacing property gives a new relationship between the closeness of LSFs and their spectral sensitivities, which motivates a new weighting function for LSF distortion measurement. By applying this new weighting function to LSF quantization, we have achieved a significantly better performance than the conventional heuristic weighting functions in both clean and noise environments. In addition, the proposed weighting function gives better performance than the weighting function based on a high-rate approximation (Gardner weighting (GW)) [W.R. Gardner, B.D. Rao, IEEE Trans. Speech Audio Processing 3 (5) (1995) 367] in noise environments while their performances are comparable in clean environments. Moreover, the complexity of the proposed weighting function is much lower than that of the GW function. (C) 2001 Elsevier Science B.V. All rights reserved.
Effects of cloned gene dosage on the response of recombinant CHO cells to hyperosmotic pressure in regard to cell growth and antibody production
No full textThe effect of cloned gene dosage on growth and product formation under hyperosmotic conditions has been studied using recombinant Chinese hamster ovary (rCHO) cell lines producing chimeric antibody. Batch cultures of four rCHO cell lines carrying different numbers of antibody gene copies were carried out using the hyperosmolar medium. Depending on cloned gene dosage, hyperosmotic pressure decreased specific growth rate (μ) and increased specific antibody productivity (q Ab) to a different degree. The cell line with lower cloned gene dosage displayed more significant enhancement in q Ab and less reduction in μ at hyperosmolalities. However, the cell line with higher cloned gene dosage still yielded higher maximum antibody concentration at hyperosmolality up to 469 mOsm/kg. Northern blot analysis showed a positive relationship between immunoglobulin mRNA level per cell and q Ab, indicating that transcriptional regulation was involved in the response of rCHO cells to hyperosmotic pressure. Cell cycle analysis showed that hyperosmotic pressure induced G 1-phase arrest, suggesting that the increase of cell population in G 1-phase may contribute in part to enhanced q Ab at hyperosmolality. Taken together, although the cell line with lower cloned gene dosage displayed more significant enhancement in q Ab at hyperosmolality, the factor that determined the maximum antibody concentration in hyperosmotic rCHO cell cultures was almost exclusively the gene dosage
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