Deep far infrared ISOPHOT survey in "Selected Area 57", I. Observations and source counts

We present here the results of a deep survey in a 0.4 sq.deg. blank field in Selected Area 57 conducted with the ISOPHOT instrument aboard ESAs Infrared Space Observatory (ISO) at both 60 um and 90 um. The resulting sky maps have a spatial resolution of 15 x 23 sq.arcsec. per pixel which is much higher than the 90 x 90 sq.arcsec. pixels of the IRAS All Sky Survey. We describe the main instrumental effects encountered in our data, outline our data reduction and analysis scheme and present astrometry and photometry of the detected point sources. With a formal signal to noise ratio of 6.75 we have source detection limits of 90 mJy at 60 um and 50 mJy at 90 um. To these limits we find cumulated number densities of 5+-3.5 per sq.deg. at 60 um and 14.8+-5.0 per sq.deg.at 90 um. These number densities of sources are found to be lower than previously reported results from ISO but the data do not allow us to discriminate between no-evolution scenarios and various evolutionary models.Comment: 15 pages, 11 figures, accepted by Astronomy & Astrophysic

Hyper-Ramsey Spectroscopy of Optical Clock Transitions

We present non-standard optical Ramsey schemes that use pulses individually tailored in duration, phase, and frequency to cancel spurious frequency shifts related to the excitation itself. In particular, the field shifts and their uncertainties of Ramsey fringes can be radically suppressed (by 2-4 orders of magnitude) in comparison with the usual Ramsey method (using two equal pulses) as well as with single-pulse Rabi spectroscopy. Atom interferometers and optical clocks based on two-photon transitions, heavily forbidden transitions, or magnetically induced spectroscopy could significantly benefit from this method. In the latter case these frequency shifts can be suppressed considerably below a fractional level of 10^{-17}. Moreover, our approach opens the door for the high-precision optical clocks based on direct frequency comb spectroscopy.Comment: 5 pages, 4 figure

A Direct Reduction from k-Player to 2-Player Approximate Nash Equilibrium

We present a direct reduction from k-player games to 2-player games that preserves approximate Nash equilibrium. Previously, the computational equivalence of computing approximate Nash equilibrium in k-player and 2-player games was established via an indirect reduction. This included a sequence of works defining the complexity class PPAD, identifying complete problems for this class, showing that computing approximate Nash equilibrium for k-player games is in PPAD, and reducing a PPAD-complete problem to computing approximate Nash equilibrium for 2-player games. Our direct reduction makes no use of the concept of PPAD, thus eliminating some of the difficulties involved in following the known indirect reduction.Comment: 21 page

Process optimization for semi-continuous virus production at high cell densities

Background. Unlike production of recombinant proteins, continuous production of viral vaccines at high cell densities (HCD) is still constrained by host cell lysis during virus propagation and limited virus recovery from culture broth. Nevertheless, advanced fed-batch [1] and perfusion strategies can be applied to achieve a high-yield virus production processes. In this study, the development of a high-yield semi-continuous process for the production and purification of the modified vaccinia Ankara virus isolate MVA-CR19 and influenza A/PR/8 in HCD cultivations of the suspension cell line AGE1.CR.pIX (ProBioGen AG, Berlin) is presented. Methods. Depending on the required scale, high cell concentrations (~ 50×106 cell mL-1) were achieved either through medium renewal by periodic centrifugation (semi-perfusion) in 50 mL cultivations or using an alternating tangential flow (ATF) perfusion system for 1 L bioreactors. Process development and optimization comprised three phases: 1) assessment of different fed-batch and medium exchange strategies for the propagation of MVA-CR19 or influenza A/PR/8 viruses in 50 mL cultivations; 2) scale-up and process optimization of the high-yield process strategy to a 1 L bioreactor with the ATF system, and 3) integration of a purification process step using magnetic sulfated cellulose particles (MSCP). For both viruses, conventional batch cultivation (no addition/medium exchange after infection) was compared with processes applying fed-batch, periodic medium exchange and the combination of both during virus propagation. Results. Perfusion and semi-perfusion at a feeding rate of 0.05 nL/cell×d was suitable to propagate AGE1.CR.pIX cells above 60×106 cells/mL with neither limitation nor overload of nutrients. For infections in 50 mL, the application of a combined strategy comprising an initial fed-batch phase followed by a periodic virus harvest phase resulted in the highest product yield with a more than 10-fold increase, compared to the conventional batch processes at 4 to 8×106 cell/mL [2]. Additionally, a 3-fold increase in both cell-specific yield (virus/cell) and volumetric productivity (virus/L×d) could be obtained. Although product harvesting was suboptimal when up-scaling to a 1 L bioreactor with ATF-system, comparable increases in virus yields and productivity with respect to the conventional batch process were observed. In all cases, cell-specific yields and volumetric productivities reached their peak values at the peak virus concentrations, indicating that the process should be stopped at that time point. Eventually, selection of the optimal pore size of the membrane of the ATF-system allowed semi-continuous harvesting of the produced viruses and its purification with MSCPs with a recovery of about 50%. Conclusion. Compared to conventional batch processes, the developed HCD process offers significantly higher productivities including the option to integrate a purification step in a semi-continuous mode. Overall, the results show that there is a great potential for semi-continuous HCD processes for the production of viral vaccines in larger scales, which could intensify the discussion towards the establishment of true continuous production process

A Sample Sifter for the Proposed Icebreaker Mars Mission

The Icebreaker mission proposes to land at the site where the Phoenix mission discovered an environment that is habitable for life in recent times [1], and search for biomarkers of life. The subsurface ice is expected at shallow depth (<10 cm below the surface)[2]. By drilling up to 1 m depth into the icy material, Icebreaker plans to sample ice that was warm during past high obliquity periods. Samples are analyzed for organics and biomolecules

Broad-line radio galaxies: old and feeble?

Far-infrared photometry of broad-line radio galaxies shows this class of AGN to consist of many hot and some cool infrared emitters, with peaks in their spectral energy distributions around 25 micron or longward of 60 micron, respectively. Quantitative analysis indicates that this distribution relates to a substantial dispersion in the strength of the cool dust component: broad-line radio galaxies are relatively poor in large-scale dust. Possibly they have undergone a different merger evolution, or are relatively old AGN.Comment: Accepted for publication in A&A Letter

Abundance analysis of Am binaries and search for tidally driven abundance anomalies - III. HD116657, HD138213, HD155375, HD159560, HD196544 and HD204188

We continue here the systematic abundance analysis of a sample of Am binaries in order to search for possible abundance anomalies driven by tidal interaction in these binary systems. New CCD observations in two spectral regions (6400-6500, 6660-6760 AA) of HD116657, HD138213, HD155375, HD159560, HD196544 and HD204188 were obtained. Synthetic spectrum analysis was carried out and basic stellar properties, effective temperatures, gravities, projected rotational velocities, masses, ages and abundances of several elements were determined. We conclude that all six stars are Am stars. These stars were put into the context of other Am binaries with 10 < Porb < 200 days and their abundance anomalies discussed in the context of possible tidal effects. There is clear anti-correlation of the Am peculiarities with v sin i. However, there seems to be also a correlation with the eccentricity and may be with the orbital period. The dependence on the temperature, age, mass, and microturbulence was studied as well. The projected rotational velocities obtained by us were compared to those of Royer et al. (2002) and Abt & Morrell (1995).Comment: 11 pages, 3 tables, 12 figures. Accepted for publication in Monthly Notices of the Royal Astronomical Societ