Chinese hamster ovary (CHO) cells were cultivated in a compact loop bioreactor using MEM-alpha medium supplemented with 10% fetal calf serum. Effects of physical and chemical environments, i.e., pH ...in the medium, stirring speed of impellers, temperature and partial pressure of oxygen (pO2) upon growth of suspended cells in the bioreactor were determined in batch cultures. Growth behavior was characterized by specific rates of growth (mu), glucose consumption (qG) and lactate production (qL), and the yield coefficients (cell yield from glucose, YX/G, and lactate yield from glucose, YL/G). An effect of medium osmolality was also evaluated with T-flask monolayer cultivation. The best growth was observed at pH 7.6, 37 degrees C, 400 rpm, 50-100% saturation with oxygen and 320 mOsmol kg-1. Corresponding to the previous work with a human melanoma cell line, the sophisticated cultivation and process control systems have been improved for CHO cells.
Knowledge of the neutron light-yield response is crucial to the understanding of scintillator-based neutron detectors. In this work, neutrons from 2--6 MeV have been used to study the scintillation ...light-yield response of the liquid scintillators NE 213A, EJ 305, EJ 331 and EJ 321P using event-by-event waveform digitization. Energy calibration was performed using a GEANT model to locate the edge positions of the Compton distributions produced by gamma-ray sources. The simulated light yield for neutrons from a PuBe source was compared to measured recoil proton distributions, where neutron energy was selected by time-of-flight. This resulted in an energy-dependent Birks parametrization to characterize the non-linear response to the lower energy neutrons. The NE 213A and EJ 305 results agree very well with existing data and are reproduced nicely by the simulation. New results for EJ 331 and EJ 321P, where the simulation also reproduces the data well, are presented.
The growth-factor prototrophic Chinese hamster ovary (CHO) SSF3 cell line was previously adapted for growth in serum-free media. Here we present a newly designed medium which allows these cells to ...grow in the absence of any exogenously added growth factors. To investigate the capacity of CHO SSF3 cells for the efficient production of recombinant proteins in protein-free media, expression plasmids containing either a human single chain urokinase-type plasminogen activator (uPA)-encoding cDNA or a humanized immunoglobulin G (IgG) kappa light chain cDNA were introduced by transfection. The tryptophan synthase (trpB) gene of Escherichia coli was used as a dominantly acting selection marker allowing the cells to survive in a medium containing indole in place of tryptophan. Some of the clones obtained exhibited a stable uPA expression over a period of several months under selective conditions and the yields were up to 74 mg of uPA/l in a bioreactor and the productivity was around 40 mg/day per 10(9) cells. The yields of IgG light chains were up to 118 mg/l and the productivity was in the order of 56 mg/day per 10(9) cells in a bioreactor. These results demonstrate the potential of CHO SSF3 cells for the efficient production of recombinant proteins under protein-free conditions.
Four sublines of Chinese hamster ovary (CHO) cells were selected or cloned on a 10% fetal calf serum supplemented MEM-alpha medium. Three of them were monolayer cultures and could proliferate by 2000 ...times a week (mu = 1.1 d 1) in T-flasks. The other subline, S1, could grow in suspension even in static T-flask cultures. The stability in chromosome number of these cell lines was investigated. By evaluating the kinetic growth parameters, i.e. the specific rates of growth, glucose consumption and lactic acid production, and the yields of cells and lactic acid from glucose, the S1 cells were considered to be the most suitable subline for the bioreactor suspension culture. The S1 cells reached the greatest maximum of cell concentration among all cell lines tested because of their efficient glucose utilization. Observed nutrient limitations in the S1 cell culture was overcome by modification of the medium composition, that is addition of 10 mg l-1 hypoxanthine, 1 mg l-1 FeSO4.7H2O, and 0.1 mg l-1 sodium putrescine, elimination of glutamine, supplementation of 6 mM asparagine and double amount of isoleucine, leucine, methionine and vitamins other than ascorbic acid, cyanocobalamin and biotin, increase of NaHCO3 concentration from 26 to 40 mM, and finally decrease of NaCl concentration from 122 to 100 mM. With this modified medium, 7.2 X 10(6) ml-1 of the maximum cell concentration was observed in a glucose fed-batch culture, the cell concentration which was twice as much as in batch cultures with the original medium.
Fast-neutron/gamma-ray pulse-shape discrimination has been performed for the organic liquid scintillators NE 213A and EJ 305 using a time-of-flight based neutron-tagging technique and waveform ...digitization on an event-by-event basis. Gamma-ray sources and a Geant4-based simulation were used to calibrate the scintillation-light yield. The difference in pulse shape for the neutron and gamma-ray events was analysed by integrating selected portions of the digitized waveform to produce a figure-of-merit for neutron/gamma-ray separation. This figure-of-merit has been mapped as a function of detector threshold and also of neutron energy determined from time-of-flight. It shows clearly that the well-established pulse-shape discrimination capabilities of NE 213A are superior to those of EJ 305. The extra information provided by the neutron-tagging technique has resulted in a far more detailed assessment of the pulse-shape discrimination capabilities of these organic scintillators.
The LHCb muon control system the DAQ domain Bocci, V.; Cadeddu, S.; Carletti, M. ...
2007 IEEE Nuclear Science Symposium Conference Record,
2007-Oct., Letnik:
3
Conference Proceeding
Odprti dostop
The LHCb Muon system consists of 122000 front-end channels, distributed on about 8000 front-end boards (on detector). 152 off detector boards (each containing 192 channels) gather information from ...front-end and send it to the DAQ and trigger systems. The Muon system is highly configurable and is conceived to allow a deep control of the behavior of the whole system during data taking. This results in a large number of configuration and status registers to be handled. The Muon control system, part of the LHCb experiment control system, is based on a PVSS II framework and is managed by a hierarchical finite state machine. We illustrate the control system architecture and the characteristics of its components, control units and device units. We also illustrate system performance in data communication, between the OPC servers and system electronics, obtained through a suitable design of dedicated firmware.
In the last few years many detector technologies for thermal neutron detection have been developed in order to face the shortage of 3He, which is now much less available and more expensive. Moreover ...the 3He-based detectors can not fulfil the requirements in performance, e.g. the spatial resolution and the counting rate capability needed for the new instruments. The Boron-10-based gaseous detectors have been proposed as a suitable choice. This and other alternatives technologies are being developed at ESS. Higher intensities mean higher signals but higher background as well. The signal-to-background ratio is an important feature to study, in particular the gamma-ray and the fast neutron contributions. This paper investigates, for the first time, the fast neutrons sensitivity of 10B-based thermal neutron detector. It presents the study of the detector response as a function of energy threshold and the underlying physical mechanisms. The latter are explained with the help of theoretical considerations and simulations.
The LHCb experiment, presently under construction at CERN (European Center for Nuclear Research) Large Hadron Collider (LHC), aims at the study of CP violation in the B meson sector. Its key elements ...will be a muon detector which allows triggering and muon identification from inclusive b decays. The electronic system of the whole detector is very complex and its muon detector experiment control system (ECS) allows monitoring and control of a number of front-end (FE) boards in excess of 7000. The services board (SB) system is in charge of controlling muon detector FE electronics. It consists of 10 crates of equipment (6U height); each crate contains two kinds of modules: a pulse distribution module (PDM) and up to 20 SBs connected via a custom backplane. The PDM is used to generate and distribute a low jitter synchronous test pulse in a chosen phase relation with the LHC machine clock, for timing alignment of the detector FE, a 40 MHz clock signal synchronous with LHC operation , and it allows distribution of 4 CANbus branches as well as routing of special messages to each SB using a custom data bus available on its backplane. A SB makes possible monitoring and control of FE circuitry, as well as communication between FE electronics and the external world. Four embedded local monitor board (ELMB) modules, based on an 8-bit microcontroller (Atmel ATMegal28), running customized firmware are hosted by one SB; they allow communication via twelve serial links with FE cards and are able to communicate with each other using their on-board links. Each SB controls 96 FE boards or, in other words, 1536 channels. One SB crate contains up to 80 microcontrollers, which can adjust and monitor operation of up to 30720 FE channels. This work depicts the hardware architecture of each module, up to a complete system overview, also covering in detail those aspects of electronics design of equipment functioning in a radiation environment.
A light-yield calibration of an NE 213A organic liquid scintillator detector has been performed using both monoenergetic and polyenergetic gamma-ray sources. Scintillation light was detected in a ...photomultiplier tube, and the corresponding pulses were subjected to waveform digitization on an event-by-event basis. The resulting Compton edges have been analyzed using a Geant4 simulation of the detector which models both the interactions of the ionizing radiation as well as the transport of scintillation photons. The simulation is calibrated and also compared to well-established prescriptions used to determine the Compton edges, resulting ultimately in light-yield calibration functions. In the process, the simulation-based method produced information on the gain and intrinsic pulse-height resolution of the detector. It also facilitated a previously inaccessible understanding of the systematic uncertainties associated with the calibration of the scintillation-light yield. The simulation-based method was also compared to well-established numerical prescriptions for locating the Compton edges. Ultimately, the simulation predicted as much as 17% lower light-yield calibrations than the prescriptions. These calibrations indicate that approximately 35% of the scintillation light associated with a given gamma-ray reaches the photocathode. It is remarkable how well two 50 year old prescriptions for calibrating scintillation-light yield in organic scintillators have stood the test of time.
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