Sequence homology between RNAs encoding rat α-fetoprotein and rat serum albumin

We have determined the sequences of the recombinant DNA inserts of three bacterial plasmid cDNA clones containing most of the rat α-fetoprotein mRNA. The resultant nucleotide sequence of α-fetoprotein was exhaustively compared to the nucleotide sequence of the mRNA encoding rat serum albumin. These two mRNAs have extensive homology (50%) throughout and the same intron locations. The amino acid sequence of rat α-fetoprotein has been deduced from the nucleotide sequence, and its comparison to rat serum albumin's amino acid sequence reveals a 34% homology. The regularly spaced positions of the cysteines found in serum albumin are conserved in rat α-fetoprotein, indicating that these two proteins may have a similar secondary folding structure. These homologies indicate that α-fetoprotein and serum albumin were derived by duplication of a common ancestral gene and constitute a gene family

Expansion and Collapse in the Cosmic Web

We study the kinematics of the gaseous cosmic web at high redshift with Lyman alpha forest absorption in multiple QSO sightlines. Using a simple analytic model and a cosmological hydrodynamic simulation we constrain the underlying three-dimensional distribution of velocities from the observed line-of-sight distribution of velocity shear across the plane of the sky. The distribution is found to be in good agreement with the intergalactic medium (IGM) undergoing large scale motions dominated by the Hubble flow. Modeling the Lyman alpha clouds analytically and with a hydrodynamics simulation, the average expansion velocity of the gaseous structures causing the Lyman alpha forest in the lower redshift (z = 2) sample appears about 20 percent lower than the local Hubble expansion velocity. We interpret this as tentative evidence for some clouds undergoing gravitational collapse. However, the distribution of velocities is highly skewed, and the majority of clouds at redshifts from 2 to 3.8 expand typically about 5 - 20 percent faster than the Hubble flow. This behavior is explained if most absorbers in the column density range typically detectable are expanding filaments that stretch and drain into more massive nodes. We find no evidence for the observed distribution of velocity shear being significantly influenced by processes other than Hubble expansion and gravitational instability, like galactic winds. To avoid overly disturbing the IGM, winds may be old and/or limp by the time we observe them in the Lyman alpha forest, or they may occupy only an insignificant volume fraction of the IGM. (abridged)Comment: 63 pages, 26 figures, AAS Latex; ApJ, in pres

Effect of Visual Media Use on School Performance: A Prospective Study

Purpose: To identify mechanisms for the impact of visual media use on adolescents\u27 school performance. Methods: We conducted a 24-month, four-wave longitudinal telephone study of a national sample of 6,486 youth aged 10 to 14 years. Exposure measures: latent construct for screen exposure time (weekday time spent viewing television/playing videogames, presence of television in bedroom) and variables for movie content (proportion of PG-13 and R movies viewed). Outcome measure: self- and parent reports of grades in school. Effects of media exposures on change in school performance between baseline and 24 months were assessed using structural equation modeling. Information about hypothesized mediators (substance use, sensation seeking, and school problem behavior) was obtained at baseline and at the 16-month follow-up. Results: Adjusted for baseline school performance, baseline levels of mediators, and a range of covariates, both screen exposure time and media content had adverse effects on change in school performance. Screen exposure had an indirect effect on poor school performance through increased sensation seeking. Viewing more PG-13 and R-rated movies had indirect effects on poor school performance mediated through increases in substance use and sensation seeking. R-rated viewing also had an indirect effect on poor school performance through increased school behavior problems. The effect sizes of exposure time and content on the intermediate variables and ultimately on school performance were similar to those for previously recognized determinants of these mediators, including household income, parenting style, and adolescents\u27 self-control. Conclusions: These aspects of visual media use adversely affect school performance by increasing sensation seeking, substance use, and school problem behavior

Are AGN Broad Emission Lines Formed by Discrete Clouds? --- Analysis of Keck High Resolution Spectroscopy of NGC 4151

We search for a direct signature of discrete ''clouds'' in the broad line region (BLR) of the Seyfert galaxy NGC 4151. For this purpose we apply cross correlation (CC) analysis to a high resolution KECK spectrum of the galaxy. No such signature is found in the data. In order for cloud models to be compatible with this result, there must be at least $\sim3\times10^7$ emitting clouds in the BLR, where the limit is based on simulation of a homogeneous cloud population. More realistic distributions increase the lower limit to above $10^8$. These numbers are an order of magnitude improvement on our previous limit from Mrk 335, where the improvement comes from higher S/N, broader lines, and refined simulations. Combined with the predicted upper limit for the number of emitting clouds in NGC 4151 ($10^6-10^7$), the derived lower limit puts a strong constraint on the cloud scenario in the BLR of this object. Similar constraints can be paled on models where the emission originates in streams and sheets. Thus, this investigation suggests that the BELs in NGC 4151, and by extension in all AGNs, are not made of an ensemble of discrete independent emitters.Comment: 18 pages, 8 figures, LaTeX aaspp style, to be published in MNRA

PCNS: A novel protocadherin required for cranial neural crest migration and somite morphogenesis in Xenopus

AbstractProtocadherins (Pcdhs), a major subfamily of cadherins, play an important role in specific intercellular interactions in development. These molecules are characterized by their unique extracellular domain (EC) with more than 5 cadherin-like repeats, a transmembrane domain (TM) and a variable cytoplasmic domain. PCNS (Protocadherin in Neural crest and Somites), a novel Pcdh in Xenopus, is initially expressed in the mesoderm during gastrulation, followed by expression in the cranial neural crest (CNC) and somites. PCNS has 65% amino acid identity to Xenopus paraxial protocadherin (PAPC) and 42–49% amino acid identity to Pcdh 8 in human, mouse, and zebrafish genomes. Overexpression of PCNS resulted in gastrulation failure but conferred little if any specific adhesion on ectodermal cells. Loss of function accomplished independently with two non-overlapping antisense morpholino oligonucleotides resulted in failure of CNC migration, leading to severe defects in the craniofacial skeleton. Somites and axial muscles also failed to undergo normal morphogenesis in these embryos. Thus, PCNS has essential functions in these two important developmental processes in Xenopus

Identifying Primordial Substructure in NGC 2264

We present new Spitzer Space Telescope observations of the young cluster NGC2264. Observations at 24 micron with the Multiband Imaging Photometer has enabled us to identify the most highly embedded and youngest objects in NGC2264. This letter reports on one particular region of NGC2264 where bright 24 micron sources are spatially configured in curious linear structures with quasi-uniform separations. The majority of these sources (~60% are found to be protostellar in nature with Class I spectral energy distributions. Comparison of their spatial distribution with sub-millimeter data from Wolf-Chase (2003) and millimeter data from Peretto et al. (2005) shows a close correlation between the dust filaments and the linear spatial configurations of the protostars, indicating that star formation is occurring primarily within dense dusty filaments. Finally, the quasi-uniform separations of the protostars are found to be comparable in magnitude to the expected Jeans length suggesting thermal fragmentation of the dense filamentary material.Comment: Accepted for publication in ApJL, 5 pages, 4 figures. Color version available from the following webpages: http://cfa-www.harvard.edu/~pteixeir/ and http://cfa-www.harvard.edu/~clada

Comparing media and family predictors of alcohol use: a cohort study of US adolescents

Objective: To compare media/marketing exposures and family factors in predicting adolescent alcohol use. Design: Cohort study. Setting: Confidential telephone survey of adolescents in their homes. Participants: Representative sample of 6522 US adolescents, aged 10–14 years at baseline and surveyed four times over 2 years. Primary: outcome measure Time to alcohol onset and progression to binge drinking were assessed with two survival models. Predictors were movie alcohol exposure (MAE), ownership of alcohol-branded merchandise and characteristics of the family (parental alcohol use, home availability of alcohol and parenting). Covariates included sociodemographics, peer drinking and personality factors. Results: Over the study period, the prevalence of adolescent ever use and binge drinking increased from 11% to 25% and from 4% to 13%, respectively. At baseline, the median estimated MAE from a population of 532 movies was 4.5 h and 11% owned alcohol-branded merchandise at time 2. Parental alcohol use (greater than or equal to weekly) was reported by 23% and 29% of adolescents could obtain alcohol from home. Peer drinking, MAE, alcohol-branded merchandise, age and rebelliousness were associated with both alcohol onset and progression to binge drinking. The adjusted hazard ratios for alcohol onset and binge drinking transition for high versus low MAE exposure were 2.13 (95% CI 1.76 to 2.57) and 1.63 (1.20 to 2.21), respectively, and MAE accounted for 28% and 20% of these transitions, respectively. Characteristics of the family were associated with alcohol onset but not with progression. Conclusion: The results suggest that family focused interventions would have a larger impact on alcohol onset while limiting media and marketing exposure could help prevent both onset and progression

Manifestation of classical wave delays in a fully quantized model of the scattering of a single photon

We consider a fully quantized model of spontaneous emission, scattering, and absorption, and study propagation of a single photon from an emitting atom to a detector atom both with and without an intervening scatterer. We find an exact quantum analog to the classical complex analytic signal of an electromagnetic wave scattered by a medium of charged oscillators. This quantum signal exhibits classical phase delays. We define a time of detection which, in the appropriate limits, exactly matches the predictions of a classically defined delay for light propagating through a medium of charged oscillators. The fully quantized model provides a simple, unambiguous, and causal interpretation of delays that seemingly imply speeds greater than c in the region of anomalous dispersion.Comment: 18 pages, 4 figures, revised for clarity, typos corrrecte

The nuclear AC-Stark shift in super-intense laser fields

The direct interaction of super-intense laser fields in the optical frequency domain with nuclei is studied. As main observable, we consider the nuclear AC-Stark shift of low-lying nuclear states due to the off-resonant excitation by the laser field. We include the case of accelerated nuclei to be able to control the frequency and the intensity of the laser field in the nuclear rest frame over a wide range of parameters. We find that AC-Stark shifts of the same order as in typical quantum optical systems relative to the respective transition frequencies are feasible with state-of-the-art or near-future laser field intensities and moderate acceleration of the target nuclei. Along with this shift, we find laser-induced modifications to the proton root-mean-square radii and to the proton density distribution. We thus expect direct laser-nucleus interaction to become of relevance together with other super-intense light-matter interaction processes such as pair creation.Comment: 10 pages, 2 eps figure