John P. Hughes

Identification and characterization of the familial adenomatous polyposis coli gene

DNA from 61 unrelated patients with adenomatous polyposis coli (APC) was examined for mutations in three genes (DP1, SRP19, and DP2.5) located within a 100 kb region deleted in two of the patients. The intron-exon boundary sequences were defined for each of these genes, and single-strand conformation polymorphism analysis of exons from DP2.5 identified four mutations specific to APC patients. Each of two aberrant alleles contained a base substitution changing an amino acid to a stop codon in the predicted peptide; the other mutations were small deletions leading to frameshifts. Analysis of DNA from parents of one of these patients showed that his 2 bp deletion is a new mutation; furthermore, the mutation was transmitted to two of his children. These data have established that DP2.5 is the APC gene.

Identification of deletion mutations and three new genes at the familial polyposis locus

Small (100-260 kb), nested deletions were characterized in DNA from two unrelated patients with familial adenomatous polyposis coli (APC). Three candidate genes located within the deleted region were ascertained and a previous candidate gene, MCC, was shown to be located outside the deleted region. One of the new genes contained sequence identical to SRP19, the gene coding for the 19 kd component of the ribosomal signal recognition particle. The second, provisionally designated DP1 (deleted in polyposis 1), was found to be transcribed in the same orientation as MCC. Two other cDNAs, DP2 and DP3, were found to overlap, forming a single gene, DP2.5, that is transcribed in the same orientation as SRP19.

BVRI Light Curves for 22 Type 1a Supernovae

We present 1210 Johnson/Cousins B, V, R, and I photometric observations of 22 recent Type Ia supernovae (SNe Ia): SNe 1993ac, 1993ae, 1994M, 1994S, 1994T, 1994Q, 1994ae, 1995D, 1995E, 1995al, 1995ac, 1995ak, 1995bd, 1996C, 1996X, 1996Z, 1996ab, 1996ai, 1996bk, 1996bl, 1996bo, and 1996bv. Most of the photometry was obtained at the Fred Lawrence Whipple Observatory of the Harvard-Smithsonian Center for Astrophysics in a cooperative observing plan aimed at improving the database for SNe Ia. The redshifts of the sample range from cz = 1200 to 37,000 km s-1 with a mean of cz = 7000 km s-1.

Genetic Analysis of an Inherited Predisposition to Colon Cancer in a Family with a Variable Number of Adenomatous Polyps

We studied a large kindred with a history of colorectal cancer of early onset. Proctosigmoidoscopic examination of 51 family members identified only 2 with familial polyposis coli, which strongly predisposes those who have it to colorectal cancer and which is defined as the presence of more than 100 polyps in the colon. However, eight family members had 2 to 40 colonic polyps. We suspected that in this family, colorectal cancer was the result of a mutation in the gene on chromosome 5 that is responsible for familial polyposis coli. To test our hypothesis, we obtained genotypic information on 81 family members with respect to seven polymorphic DNA markers previously shown to be linked to the locus for familial polyposis coli. Multilocus analysis of the data demonstrated genetic linkage (lod score, 5.58) between these markers and the locus responsible for the defined syndrome of colonic polyps or colorectal cancer in this kindred. These findings constitute evidence that the genetic defect in this family is a mutation in the gene that causes familial polyposis coli. We conclude that mutations at the genetic locus for familial polyposis coli may be the cause of other, more subtle syndromes involving an inherited susceptibility to colonic adenomatous polyps and colorectal cancer.

Nonthermal X-Ray Emission from the Shell-Type Supernova Remnant G347.3-0.5

Recent ASCA observations of G347.3-0.5, an SNR discovered in the ROSAT All-Sky Survey, reveal nonthermal emission from a region along the northwestern shell (Koyama et al. 1997). Here we report on new pointed ASCA observations of G347.3-.5 which confirm this result for all the bright shell regions and also reveal similar emission, although with slightly different spectral properties, from the remainder of the SNR. Curiously, no thermal X-ray emission is detected anywhere in the remnant. We derive limits on the amount of thermal emitting material present in G347.3-0.5 and present new radio continuum, CO and infrared results which indicate that the remnant is distant and of moderate age. We show that our observations are broadly consistent with a scenario that has most of the supernova remnant shock wave still within the stellar wind bubble of its progenitor star, while part of it appears to be interacting with denser material. A point source at the center of the remnant has spectral properties similar to those expected for a neutron star and may represent the compact relic of the supernova progenitor.Recent ASCA observations of G347.3-0.5, a supernova remnant (SNR) discovered in the ROSAT All-Sky Survey, reveal nonthermal emission from a region along the northwestern shell. Here we report on new pointed ASCA observations of G347.3-0.5 that confirm this result for all the bright shell regions and also reveal similar emission, although with slightly different spectral properties, from the remainder of the SNR. Curiously, no thermal X-ray emission is detected anywhere in the remnant. We derive limits on the amount of thermal emitting material present in G347.3-0.5 and present new radio continuum, CO, and infrared results that indicate that the remnant is distant and of moderate age. We show that our observations are broadly consistent with a scenario that has most of the supernova remnant shock wave still within the stellar wind bubble of its progenitor star, while part of it appears to be interacting with denser material. A point source at the center of the remnant has spectral properties similar to those expected for a neutron star and may represent the compact relic of the supernova progenitor.

RX J0852.0–4622: Another Nonthermal Shell-Type Supernova Remnant (G266.2–1.2)

The newly discovered supernova remnant G266.2-1.2 (RX J0852.0-4622), along the line of sight to the Vela supernova remnant (SNR), was observed with ASCA for 120 ks. We find that the X-ray spectrum is featureless and well described by a power law, extending to three of the class of shell-type SNRs dominated by nonthermal X-ray emission. Like G347.3-0.5, this low-latitude remnant displays discrete regions of enhanced emission along the rim as well as faint nonthermal emission from the interior. We derive limits on the thermal content of the remnant emission, although the presence of the Vela SNR compromises our ability to seriously constrain a low-temperature component. Limits placed on the amount of Sc-K emission are compared with the expected flux based on the reported 44Ti emission from G266.2-1.2. We also report on an unresolved X-ray source surrounded by diffuse emission near the center of the remnant. The properties of the source are not well determined but appear consistent with the interpretation that the source is a neutron star surrounded by a synchrotron nebula. Alternatively, the source may be associated with one of two stars located within the positional error circle, but this appears somewhat unlikely.

Detection of the power spectrum of cosmic microwave background lensing by the Atacama Cosmology Telescope.

We report the first detection of the gravitational lensing of the cosmic microwave background through a measurement of the four-point correlation function in the temperature maps made by the Atacama Cosmology Telescope. We verify our detection by calculating the levels of potential contaminants and performing a number of null tests. The resulting convergence power spectrum at 2° angular scales measures the amplitude of matter density fluctuations on comoving length scales of around 100 Mpc at redshifts around 0.5 to 3. The measured amplitude of the signal agrees with Lambda cold dark matter cosmology predictions. Since the amplitude of the convergence power spectrum scales as the square of the amplitude of the density fluctuations, the 4σ detection of the lensing signal measures the amplitude of density fluctuations to 12%.

The Atacama Cosmology Telescope: a measurement of the cosmic microwave background power spectrum at 148 and 218 GHz from the 2008 southern survey

We present measurements of the cosmic microwave background (CMB) power spectrum made by the Atacama Cosmology Telescope at 148 GHz and 218 GHz, as well as the cross-frequency spectrum between the two channels. Our results clearly show the second through the seventh acoustic peaks in the CMB power spectrum. The measurements of these higher-order peaks provide an additional test of the ΛCDM cosmological model. At l>3000, we detect power in excess of the primary anisotropy spectrum of the CMB. At lower multipoles 500 < l < 3000, we find evidence for gravitational lensing of the CMB in the power spectrum at the 2.8σ level. We also detect a low level of Galactic dust in our maps, which demonstrates that we can recover known faint, diffuse signals.

A MILLION-SECOND CHANDRA VIEW OF CASSIOPEIA A

We introduce a million second observation of the supernova remnant Cassiopeia A with the Chandra X-Ray Observatory. The bipolar structure of the Si-rich ejecta (northeast jet and southwest counterpart) is clearly evident in the new images, and their chemical similarity is confirmed by their spectra. These are most likely due to jets of ejecta as opposed to cavities in the circumstellar medium, since we can reject simple models for the latter. The properties of these jets and the Fe-rich ejecta will provide clues to the explosion of Cas A.

ASCA X-Ray Spectroscopy of Large Magellanic Cloud Supernova Remnants and the Metal Abundances of the Large Magellanic Cloud

We present the results of X-ray spectroscopy of a flux-limited sample of seven middle-aged supernova remnants (SNRs) in the Large Magellanic Cloud (LMC): N23, N49, N63A, DEM 71, N132D, 0453-68.5, and N49B. We constructed self-consistent nonequilibrium ionization SNR models assuming a Sedov solution for the dynamical evolution, and then applied the resulting spectral models to the data obtained by the Solid State Imaging Spectrometer on board the Advanced Satellite for Cosmology and Astrophysics. All the remnants were reasonably well described by the model, which allowed us to derive accurate values for their physical parameters, i.e., ages, densities, initial explosion energies, and metal abundances. The derived explosion energies vary from 5 × 1050 to 6 × 1051 ergs. A restricted subset of the sample exists for which the ionization and Sedov dynamical ages agree quite well under the assumption that the electron and ion temperatures are not fully equilibrated at the shock front; for these four SNRs, the mean value of the initial explosion energy is (1.1 ± 0.5) × 1051 ergs. We show that it is likely that the other three remnants, all of which have inferred explosion energies 3 × 1051 ergs, exploded within preexisting cavities in the interstellar medium. The limits on high-energy X-ray emission (3 keV) that we present indicate that these SNRs do not contain very luminous pulsar-powered synchrotron nebulae, in general agreement with our picture of them as evolved, middle-aged remnants. We find statistical evidence for enrichment by supernova ejecta in the sense that smaller remnants show a somewhat higher mean metallicity than the larger ones. In the case of DEM 71, the putative remnant of a Type Ia supernova, the derived abundance of iron is about a factor of 2 larger than the other remnants in the sample. These things being said, however, the derived abundances are in general dominated by swept-up interstellar material, and so we use the SNR sample to estimate the mean LMC gas-phase abundances. We find that the astrophysically common elements from oxygen to iron are less abundant than the solar values by factors of 2-4. Overall, these results are consistent with previous ones based on optical and UV data but do not show the anomalous overabundance of magnesium and silicon seen by others.We present the results of X-ray spectroscopy of a flux-limited sample of seven middle-aged supernova remnants (SNRs) in the Large Magellanic Cloud (LMC): N23, N49, N63A, DEM71, N132D, 0453−68.5, and N49B. We constructed self-consistent nonequilibrium ionization SNR models assuming a Sedov solution for the dynamical evolution, and then applied the resulting spectral models to the data obtained by the Solid-state Imaging Spectrometer onboard the Advanced Satellite for Cosmology and Astrophysics. All the remnants were reasonably well described by the model, allowing us to derive accurate values for their physical parameters, i.e., ages, densities, initial explosion energies, and metal abundances. The derived explosion energies vary from 5 × 10 50 erg to 6 × 10 51 erg. A restricted subset of the sample exists for which the ionization and Sedov dynamical ages agree quite well under the assumption that the electron and ion temperatures are not fully equilibrated at the shock front; for these four SNRs the mean value of the initial explosion energy is (1.1 ± 0.5) × 10 51 erg. We show that it is likely that the other three remnants exploded within preexisting cavities in the interstellar medium. The limits on high energy X-ray emission (> ∼ 3 keV) that we present indicate that these SNRs do not contain very luminous pulsar-powered synchrotron nebulae, in general agreement with our picture of them as evolved, middle-aged remnants. We find statistical evidence for enrichment by supernova ejecta in the sense that smaller remnants show a somewhat higher mean metallicity than the larger ones. In the case of DEM71, the putative remnant of a Type Ia supernova, the derived abundance of iron is about a factor of two larger than the other remnants in the sample. These things being said, however, the derived abundances are in general dominated by swept-up interstellar material and so we use the SNR sample to estimate the mean LMC gas-phase abundances. We find that the astrophysically common elements from oxygen to iron are less abundant than the solar values by factors of – 2 – 2–4. Overall these results are consistent with previous ones based on optical and UV data, but do not show the anomalous overabundance of magnesium and silicon seen by others.