Design and characterisation of parallel miniature bioreactors for bioprocess optimisation and scale-up.

The establishment of a high productivity microbial fermentation process requires the experimental investigation of many interacting variables. In order to speed up this procedure a novel miniature stirred bioreactor system is described which enables parallel operation of 4-16 independently controlled fermentations. Each miniature bioreactor is of standard geometry (100 mL maximum working volume) and is fitted with a magnetically driven six-blade miniature turbine impeller (dj = 20 mm, dj/dj = 1/3) operating in the range 100 - 2000 rpm. Aeration is achieved via a sintered sparger at flow rates in the range of 0 - 2 vvm. Continuous on-line monitoring of each bioreactor is possible using miniature pH, dissolved oxygen and temperature probes, while PC-based software enables independent bioreactor control and real-time visualisation of parameters monitored on-line. Initial characterisation of the bioreactor involved quantification of the volumetric oxygen mass transfer coefficient as a function of agitation and aeration rates. The maximum kLa value obtained was 0.11 s" The reproducibility of E. coli TOP10 pQR239 and B. subtilis ATCC6633 fermentations was shown in four parallel fermentations of each organism. For E. coli (1000 rpm, 1 vvm) the maximum specific growth rate, umax, was 0.68 0.01 h"1 and the final biomass concentration obtained, Xr,nai, was 3.8 0.05 g.L"1. Similarly for B. subtilis (1500 rpm, 1 vmm) umax was 0.45 0.01 h"1 and Xrinai was 9.0 0.06 g.L"1. Biomass growth kinetics increased with increases in agitation and aeration rates and the implementation of gas blending for control of DOT levels enabled umax and Xfmai values as high as 0.93 h"1 and 8.1 g.L"1 respectively to be achieved. The value of the miniature bioreactor design for high throughput experimentation was further demonstrated when Design of Experiments (DoE) techniques were employed to assess three variables temperature, pH and inducer concentration, for the optimisation of CHMO expression in E. coli TOP 10 pQR239. The optimised regression model derived from the results of 20 fermentations concluded that only temperature and inducer concentration had a significant influence, predicting a maximum specific CHMO activity of 105.9 U.g"1 at 37.1 C and 0.11 %w/v. This was in good agreement with the experimentally determined results at these conditions. In order to enable the predictive scale-up of miniature bioreactor results, the engineering characterisation of the miniature turbine impeller predicted a Power number of 3.5 based on experimental ungassed power consumption measurements. As a result of the numerous literature correlation relating kLa, gassed power per unit volume and superficial gas velocity being designed for much larger scale bioreactors, a similar correlation has been specifically derived for the miniature bioreactor scale. Constant ki,a has been shown to be the most reliable basis for predictive scale-up of fermentation results from the miniature bioreactor to conventional laboratory scale. This was confirmed over a range of kLa values (0.04-0.11 s"1), with good agreement between final biomass concentrations and maximum specific growth rates. In addition successful scale-up of the DoE results for optimum CHMO expression in E. coli at a constant kLa value of 0.04 s"1 yielded final biomass concentrations of 4.9 g.L"1 and 5.1 g.L"1 respectively in the miniature bioreactor and the 2 L vessel, and the CHMO activity obtained was 105.9 U.g"1 and 105.2 U.g"1 respectively. Finally, alternative on-line methods for monitoring cell growth within the miniature bioreactors without the need for repeated sampling have been described. The application of a novel optical density probe for monitoring biomass growth kinetics on-line has shown that comparable results for calculated maximum specific growth rates were obtained from off-line and on-line OD measurements 0.67 and 0.68 h"1 respectively. Thermal profiling techniques were also investigated as an alternative means for monitoring cell growth based on the natural heat generated by a microbial culture. Initial results showed that the heat generated during E. coli TOP 10 pQR239 fermentations followed the same pattern as the off-line growth curve. The maximum specific growth rates calculated from off-line and on-line thermal data were also in good agreement, 0.66 0 0.04 h"1 and 0.69 0 0.05 h"1 respectively. In summary the miniature bioreactor system designed and evaluated here provides a useful tool for the rapid optimisation and scale-up of microbial fermentation processes

Current-carrying cosmic string loops 3D simulation: towards a reduction of the vorton excess problem

The dynamical evolution of superconducting cosmic string loops with specific equations of state describing timelike and spacelike currents is studied numerically. This analysis extends previous work in two directions: first it shows results coming from a fully three dimensional simulation (as opposed to the two dimensional case already studied), and it now includes fermionic as well as bosonic currents. We confirm that in the case of bosonic currents, shocks are formed in the magnetic regime and kinks in the electric regime. For a loop endowed with a fermionic current with zero-mode carriers, we show that only kinks form along the string worldsheet, therefore making these loops slightly more stable against charge carrier radiation, the likely outcome of either shocks or kinks. All these combined effects tend to reduce the number density of stable loops and contribute to ease the vorton excess problem. As a bonus, these effects also may provide new ways of producing high energy cosmic rays.Comment: 11 pages, RevTeX 4 format, 8 figures, submitted to PR

Measurement of the B0-anti-B0-Oscillation Frequency with Inclusive Dilepton Events

The $B^0$-$\bar B^0$ oscillation frequency has been measured with a sample of 23 million \B\bar B pairs collected with the BABAR detector at the PEP-II asymmetric B Factory at SLAC. In this sample, we select events in which both B mesons decay semileptonically and use the charge of the leptons to identify the flavor of each B meson. A simultaneous fit to the decay time difference distributions for opposite- and same-sign dilepton events gives $\Delta m_d = 0.493 \pm 0.012{(stat)}\pm 0.009{(syst)}$ ps$^{-1}$.Comment: 7 pages, 1 figure, submitted to Physical Review Letter

Search for the standard model Higgs boson decaying into two photons in pp collisions at sqrt(s)=7 TeV

A search for a Higgs boson decaying into two photons is described. The analysis is performed using a dataset recorded by the CMS experiment at the LHC from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross section of the standard model Higgs boson decaying to two photons. The expected exclusion limit at 95% confidence level is between 1.4 and 2.4 times the standard model cross section in the mass range between 110 and 150 GeV. The analysis of the data excludes, at 95% confidence level, the standard model Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The largest excess of events above the expected standard model background is observed for a Higgs boson mass hypothesis of 124 GeV with a local significance of 3.1 sigma. The global significance of observing an excess with a local significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is estimated to be 1.8 sigma. More data are required to ascertain the origin of this excess.Comment: Submitted to Physics Letters

Measurement of isolated photon production in pp and PbPb collisions at sqrt(sNN) = 2.76 TeV

Isolated photon production is measured in proton-proton and lead-lead collisions at nucleon-nucleon centre-of-mass energies of 2.76 TeV in the pseudorapidity range |eta|<1.44 and transverse energies ET between 20 and 80 GeV with the CMS detector at the LHC. The measured ET spectra are found to be in good agreement with next-to-leading-order perturbative QCD predictions. The ratio of PbPb to pp isolated photon ET-differential yields, scaled by the number of incoherent nucleon-nucleon collisions, is consistent with unity for all PbPb reaction centralities.Comment: Submitted to Physics Letters

Identification of common genetic risk variants for autism spectrum disorder

Autism spectrum disorder (ASD) is a highly heritable and heterogeneous group of neurodevelopmental phenotypes diagnosed in more than 1% of children. Common genetic variants contribute substantially to ASD susceptibility, but to date no individual variants have been robustly associated with ASD. With a marked sample-size increase from a unique Danish population resource, we report a genome-wide association meta-analysis of 18,381 individuals with ASD and 27,969 controls that identified five genome-wide-significant loci. Leveraging GWAS results from three phenotypes with significantly overlapping genetic architectures (schizophrenia, major depression, and educational attainment), we identified seven additional loci shared with other traits at equally strict significance levels. Dissecting the polygenic architecture, we found both quantitative and qualitative polygenic heterogeneity across ASD subtypes. These results highlight biological insights, particularly relating to neuronal function and corticogenesis, and establish that GWAS performed at scale will be much more productive in the near term in ASD.Peer reviewe

Measurement of the CP-Violating Asymmetry Amplitude sin2β\beta

We present results on time-dependent CP-violating asymmetries in neutral B decays to several CP eigenstates. The measurements use a data sample of about 88 million Y(4S) --> B Bbar decays collected between 1999 and 2002 with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. We study events in which one neutral B meson is fully reconstructed in a final state containing a charmonium meson and the other B meson is determined to be either a B0 or B0bar from its decay products. The amplitude of the CP-violating asymmetry, which in the Standard Model is proportional to sin2beta, is derived from the decay-time distributions in such events. We measure sin2beta = 0.741 +/- 0.067 (stat) +/- 0.033 (syst) and |lambda| = 0.948 +/- 0.051 (stat) +/- 0.017 (syst). The magnitude of lambda is consistent with unity, in agreement with the Standard Model expectation of no direct CP violation in these modes