531 research outputs found
Emile Borel's difficult days in 1941
The German forces occupying Paris arrested Emile Borel and three other
members of the Acad\'emie des Sciences in October 1941 and released them about
five weeks later. Why? We examine some relevant German and French archives and
other sources and propose some hypotheses. In the process, we review how the
Occupation was structured and how it dealt with French higher education and
some French mathematicians
A high signal to noise ratio map of the Sunyaev-Zel'dovich increment at 1.1 mm wavelength in Abell 1835
We present an analysis of an 8 arcminute diameter map of the area around the
galaxy cluster Abell 1835 from jiggle map observations at a wavelength of 1.1
mm using the Bolometric Camera (Bolocam) mounted on the Caltech Submillimeter
Observatory (CSO). The data is well described by a model including an extended
Sunyaev-Zel'dovich (SZ) signal from the cluster gas plus emission from two
bright background submm galaxies magnified by the gravitational lensing of the
cluster. The best-fit values for the central Compton value for the cluster and
the fluxes of the two main point sources in the field: SMM J140104+0252, and
SMM J14009+0252 are found to be ,
6.5 mJy and 11.3 mJy, where the first error
represents the statistical measurement error and the second error represents
the estimated systematic error in the result. This measurement assumes the
presence of dust emission from the cluster's central cD galaxy of
mJy, based on higher frequency observations of Abell 1835. The cluster image
represents one of the highest-significance SZ detections of a cluster in the
positive region of the thermal SZ spectrum to date. The inferred central
intensity is compared to other SZ measurements of Abell 1835 and this
collection of results is used to obtain values for and the cluster peculiar velocity km/s.Comment: 9 pages, 5 figure
The Game of Pure Strategy is solved!
We solve the classical "Game of Pure Strategy" using linear programming. We
notice an intricate even-odd behavior in the results of our computations, that
seems to encourage odd or maximal bids
Characterisation of Herschel-SPIRE flight model optical performances
The Spectral and Photometric Imaging Receiver (SPIRE) is one of three scientific instruments on ESA's Herschel Space Observatory. This long wavelength instrument covers 200 to 670μm with a three band photometric camera and a two band imaging Fourier Transform Spectrometer (IFTS). Following first results reported in a previous paper, we discuss the in-band optical performances of the flight model as measured extensively during several dedicated test campaigns. Complementary to the experimentally probed spectral characteristics of the instrument detailed in an accompanying paper (see L.D. Spencer et al., in these proceedings), attention is focused here on a set of standard but key tests aimed at measuring the spatial response of the Photometer and Spectrometer end-to-end optical chain, including detector. Effects of defocus as well as source size extent, in-band wavelength, and polarization are also investigated over respective Photometer and Spectrometer field-of-views. Comparison with optical modelling, based on instrument design knowledge and some of the internal component measured characteristics, is performed. Beyond the specific characterisation of each effect, this allows estimating in each band where optical behaviour and detector behaviour respectively dominates and also reconstructing some of the contributors to the instrument throughput. Based on this analysis, retrieved optical performances are finally assessed against the related science-driven instrument requirements
Transformation of Olfactory Representations in the Drosophila Antennal Lobe
Molecular genetics has revealed a precise stereotypy in the projection of primary olfactory sensory neurons onto secondary neurons. A major challenge is to understand how this mapping translates into odor responses in these second-order neurons. We investigated this question in Drosophila using whole-cell recordings in vivo. We observe that monomolecular odors generally elicit responses in large ensembles of antennal lobe neurons. Comparison of odor-evoked activity from afferents and postsynaptic neurons in the same glomerulus revealed that second-order neurons display broader tuning and more complex responses than their primary afferents. This indicates a major transformation of odor representations, implicating lateral interactions within the antennal lobe
Bolocam Survey for 1.1 mm Dust Continuum Emission in the c2d Legacy Clouds. II. Ophiuchus
We present a large-scale millimeter continuum map of the Ophiuchus molecular
cloud. Nearly 11 square degrees, including all of the area in the cloud with
visual extinction more than 3 magnitudes, was mapped at 1.1 mm with Bolocam on
the Caltech Submillimeter Observatory (CSO). By design, the map also covers the
region mapped in the infrared with the Spitzer Space Telescope. We detect 44
definite sources, and a few likely sources are also seen along a filament in
the eastern streamer. The map indicates that dense cores in Ophiuchus are very
clustered and often found in filaments within the cloud. Most sources are
round, as measured at the half power point, but elongated when measured at
lower contour levels, suggesting spherical sources lying within filaments. The
masses, for an assumed dust temperature of 10 K, range from 0.24 to 3.9 solar
masses, with a mean value of 0.96 solar masses. The total mass in distinct
cores is 42 solar masses, 0.5 to 2% of the total cloud mass, and the total mass
above 4 sigma is about 80 solar masses. The mean densities in the cores are
quite high, with an average of 1.6 x 10^6 per cc, suggesting short free-fall
times. The core mass distribution can be fitted with a power law with slope of
2.1 plus or minus 0.3 for M>0.5 solar masses, similar to that found in other
regions, but slightly shallower than that of some determinations of the local
IMF. In agreement with previous studies, our survey shows that dense cores
account for a very small fraction of the cloud volume and total mass. They are
nearly all confined to regions with visual extinction at least 9 mag, a lower
threshold than found previously.Comment: 47 pages, 16 figures, accepted for Ap
A Mathematical Analysis of the Dynamics of Prion Proliferation
How do the normal prion protein (PrP(C)) and infectious prion protein (PrP(Sc)) populations interact in an infected host? To answer this question, we analyse the behavior of the two populations by studying a system of differential equations. The system is constructed under the assumption that PrP(Sc) proliferates using the mechanism of nucleated polymerization. We prove that with parameter input consistent with experimentally determined values, we obtain the persistence of PrP(Sc). We also prove local stability results for the disease steady state, and a global stability result for the disease free steady state. Finally, we give numerical simulations, which are confirmed by experimental data
The Bolocam 1.1 mm Lockman Hole Galaxy Survey: SHARC II 350 micron Photometry and Implications for Spectral Models, Dust Temperatures, and Redshift Estimation
We present 350 micron photometry of all 17 galaxy candidates in the Lockman
Hole detected in a 1.1 mm Bolocam survey. Several of the galaxies were
previously detected at 850 microns, at 1.2 mm, in the infrared by Spitzer, and
in the radio. Nine of the Bolocam galaxy candidates were detected at 350
microns and two new candidates were serendipitously detected at 350 microns
(bringing the total in the literature detected in this way to three). Five of
the galaxies have published spectroscopic redshifts, enabling investigation of
the implied temperature ranges and a comparison of photometric redshift
techniques.
Lambda = 350 microns lies near the spectral energy distribution peak for z =
2.5 thermally emitting galaxies. Thus, luminosities can be measured without
extrapolating to the peak from detection wavelengths of lambda > 850 microns.
Characteristically, the galaxy luminosities lie in the range 1.0 - 1.2 x 10^13
L_solar, with dust temperatures in the range of 40 K to 70 K, depending on the
choice of spectral index and wavelength of unit optical depth. The implied dust
masses are 3 - 5 x 10^8 M_solar. We find that the far-infrared to radio
relation for star-forming ULIRGs systematically overpredicts the radio
luminosities and overestimates redshifts on the order of Delta z ~ 1, whereas
redshifts based on either on submillimeter data alone or the 1.6 micron stellar
bump and PAH features are more accurate.Comment: In Press (to appear in Astrophysical Journal, ApJ 20 May 2006 v643 1)
47 pages, 10 figures, 4 table
POLOCAM: a millimeter wavelength cryogenic polarimeter prototype for MUSIC-POL
As a proof-of-concept, we have constructed and tested a cryogenic polarimeter in the laboratory as a prototype for the MUSIC instrument (Multiwavelength Sub/millimeter Kinetic Inductance Camera). The POLOCAM instrument consists of a rotating cryogenic polarization modulator (sapphire half-waveplate) and polarization analyzer (lithographed copper polarizers deposited on a thin film) placed into the optical path at the Lyot stop (4K cold pupil stop) in a cryogenic dewar. We present an overview of the project, design and performance results of the POLOCAM instrument (including polarization efficiencies and instrumental polarization), as well as future application to the MUSIC-POL instrument
Archival Legacy Investigations of Circumstellar Environments: Overview and First Results
We are currently conducting a comprehensive and consistent re-processing of
archival HST-NICMOS coronagraphic surveys using advanced PSF subtraction
methods, entitled the Archival Legacy Investigations of Circumstellar
Environments program (ALICE, HST/AR 12652). This virtual campaign of about 400
targets has already produced numerous new detections of previously unidentified
point sources and circumstellar structures. We present five newly spatially
resolved debris disks revealed in scattered light by our analysis of the
archival data. These images provide new views of material around young
solar-type stars at ages corresponding to the period of terrestrial planet
formation in our solar system. We have also detected several new candidate
substellar companions, for which there are ongoing followup campaigns (HST/WFC3
and VLT/SINFONI in ADI mode). Since the methods developed as part of ALICE are
directly applicable to future missions (JWST, AFTA coronagraph) we emphasize
the importance of devising optimal PSF subtraction methods for upcoming
coronagraphic imaging missions. We describe efforts in defining direct imaging
high-level science products (HLSP) standards that can be applicable to other
coronagraphic campaigns, including ground-based (e.g., Gemini Planet Imager),
and future space instruments (e.g., JWST). ALICE will deliver a first release
of HLSPs to the community through the MAST archive at STScI in 2014.Comment: Proceedings of the SPIE, 9143-199. 17 pages, 11 figure
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