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In vivo experimental analysis of human brain tissue poses substantial challenges and ethical concerns. To address this problem, we developed a computational method called the Brain Gene Expression and Network-Imputation Engine (BrainGENIE) that leverages peripheral-blood transcriptomes to predict brain tissue-specific gene-expression levels. Paired blood-brain transcriptomic data collected by the Genotype-Tissue Expression (GTEx) Project was used to train BrainGENIE models to predict gene-expression levels in ten distinct brain regions using whole-blood gene-expression profiles. The performance of BrainGENIE was compared to PrediXcan, a popular method for imputing gene expression levels from genotypes. BrainGENIE significantly predicted brain tissue-specific expression levels for 2947-11,816 genes (false-discovery rate-adjusted p < 0.05), including many transcripts that cannot be predicted significantly by a transcriptome-imputation method such as PrediXcan. BrainGENIE recapitulated measured diagnosis-related gene-expression changes in the brain for autism, bipolar disorder, and schizophrenia better than direct correlations from blood and predictions from PrediXcan. We developed a convenient software toolset for deploying BrainGENIE, and provide recommendations for how best to implement models. BrainGENIE complements and, in some ways, outperforms existing transcriptome-imputation tools, providing biologically meaningful predictions and opening new research avenues.

Galaxy clusters, the most massive collapsed structures, have been routinely used to determine cosmological parameters. When using clusters for cosmology, the crucial assumption is that they are relaxed. However, subarcminute resolution Sunyaev-Zel'dovich (SZ) effect images compared with high resolution X-ray images of some clusters show significant offsets between the two peaks. We have carried out self-consistent N-body/hydrodynamical simulations of merging galaxy clusters using FLASH to study these offsets quantitatively. We have found that significant displacements result between the SZ and X-ray peaks for large relative velocities for all masses used in our simulations as long as the impact parameters were about 100-250 kpc. Our results suggest that the SZ peak coincides with the peak in the pressure times the line-of-sight characteristic length and not the pressure maximum (as it would for clusters in equilibrium). The peak in the X-ray emission, as expected, coincides with the density maximum of the main cluster. As a consequence, the morphology of the SZ signal and therefore the offset between the SZ and X-ray peaks change with viewing angle. As an application, we compare the morphologies of our simulated images to observed SZ and X-ray images and mass surface densities derived from weak lensing observations of the merging galaxy cluster CL0152-1357. We find that a large relative velocity of 4800 km/s is necessary to explain these observations. We conclude that an analysis of the morphologies of multi-frequency observations of merging clusters can be used to put meaningful constraints on the initial parameters of the progenitors., Comment: 10 pages, 10 Figures and 1 Table, accepted for publication in the Astrophysical Journal

Galaxy clusters, the most massive collapsed structures, have been routinely used to determine cosmological parameters. When using clusters for cosmology, the crucial assumption is that they are relaxed. However, subarcminute resolution Sunyaev-Zel'dovich (SZ) effect images compared with high-resolution X-ray images of some clusters show significant offsets between the two peaks. We have carried out self-consistent N-body/hydrodynamical simulations of merging galaxy clusters using FLASH to study these offsets quantitatively. We have found that significant displacements result between the SZ and X-ray peaks for large relative velocities for all masses used in our simulations as long as the impact parameters were about 100-250 kpc. Our results suggest that the SZ peak coincides with the peak in the pressure times the line-of-sight characteristic length and not the pressure maximum (as it would for clusters in equilibrium). The peak in the X-ray emission, as expected, coincides with the density maximum of the main cluster. As a consequence, the morphology of the SZ signal, and therefore the offset between the SZ and X-ray peaks, change with viewing angle. As an application, we compare the morphologies of our simulated images to observed SZ and X-ray images and mass surface densities derived from weak-lensing observations of the merging galaxy cluster CL0152-1357, we find that a large relative velocity of 4800 km s-1 is necessary to explain the observations. We conclude that an analysis of the morphologies of multi-frequency observations of merging clusters can be used to put meaningful constraints on the initial parameters of the progenitors.

Asteroids can be eclipsed by other bodies in the Solar System, but no direct observation of an asteroid eclipse has been reported to date. We describe a statistical method to predict an eclipse for an asteroid based on the analysis of the orbital elements covariance matrix. By propagating a set of Virtual Asteroids to an epoch correspondent to a close approach with a Solar System planet or natural satellite, it is possible to estimate the probability of a partial or total eclipse. The direct observation of an eclipse can provide data useful to improve the asteroid orbit, especially for dim asteroids typically observed only for a few days. We propose two different methods: the first, based on the inclusion of the apparent magnitude residuals into the orbit's least squares minimization process, capable of improving the asteroid's nominal orbit and the related covariance matrix; the second, based on weighting different Virtual Asteroids in relation to their apparent magnitude during the eclipse, useful for recovery purposes. As an application, we have numerically investigated the possibility of a Near Earth Asteroid eclipsed by the Moon or the Earth in the 1990-2050 period. A total of 74 distinct eclipses have been found, involving 59 asteroids. In particular, the asteroid (99942) Apophis has a probability of about 74% to enter the Moon's penumbra cone and a probability of about 6% to enter the umbra cone on April 14, 2029, less than six hours after a very close approach to Earth., Comment: 14 pages, 2 tables, 8 figures, submitted to ICARUS

We summarize the results of numerical simulations of colliding gas-rich disk galaxies in which the impact velocity is set parallel to the spin axes of the two galaxies. The effects of varying the impact speed are studied with particular attention to the resulting gaseous structures and shockwave patterns, and the time needed to produce these structures. The simulations employ an N-body treatment of the stars and dark matter, together with an SPH treatment of the gas, in which all components of the models are gravitationally active. The results indicate that for such impact geometries, collisions can lead to the very rapid formation of a central, rapidly rotating, dense gas disk, and that in all cases extensive star formation is predicted by the very high gas densities and prevalence of shocks, both in the nucleus and out in the galactic disks. As the dense nucleus is forming, gas and stars are dispersed over very large volumes, and only fall back towards the nucleus over long times. In the case of low impact velocities, this takes an order of magnitude more time than that needed for the formation of a dense nucleus., Comment: To be published in Proceedings of 'The Evolution of Galaxies III- From simple approaches to self-consistent models,' held in Kiel, Germany, July 2002, Astrophysics and Space Science (Kluwer), vol. 284, p. 479, 2003

We resolve the extended X-ray emission from the prototypical ultraluminous infrared galaxy Arp 220. Extended, faint edge-brightened, soft X-ray lobes outside the optical galaxy are observed to a distance of 10 to 15 kpc on each side of the nuclear region. Bright plumes inside the optical isophotes coincide with the optical line emission and extend 11 kpc from end to end across the nucleus. The data for the plumes cannot be fit by a single temperature plasma, and display a range of temperatures from 0.2 to 1 keV. The plumes emerge from bright, diffuse circumnuclear emission in the inner 3 kpc centered on the Halpha peak, which is displaced from the radio nuclei. There is a close morphological correspondence between the Halpha and soft X-ray emission on all spatial scales. We interpret the plumes as a starburst-driven superwind, and discuss two interpretations of the emission from the lobes in the context of simulations of the merger dynamics of Arp 220., Comment: Accepted for publication in ApJ; see also astro-ph/0208477 (Paper 1)

We present a brief overview of some recent observations of colliding galaxies and relevant numerical simulations. These are compared, and details of the locations and history of collision induced star formation are explored, with possible application to star formation at earlier epochs., Comment: 6 pages, uses newpasp.sty, to be published in the proceedings of III "Guillermo Haro" Astrophysics Conference on Cosmic Evolution and Galaxy Formation: Structure, Interactions, and Feedback, held in Puebla, Mexico, November 15 - 19, 1999

Colliding galaxies are excellent laboratories for studying galactic evolution and global star formation. Computer simulations of galaxy collisions, in which at least one galaxy has a significant gaseous component, show the production of density enhancements and shock waves in the interstellar medium. These high-density regions coincide with the locations of recent, large-scale star formation in observations of some real colliding galaxies. Thus, combined n-body/hydrodynamic computer simulations can be used to explore the history and conditions of star forming regions in colliding galaxies. The galaxy system Arp 119 (CPG 29) contains a southern member, Arp 119S (Mrk 984), that has an extremely disturbed appearance, and a northern member, Arp 119N, a gas-poor elliptical. The morphology of both members can be fit well by a simulation in which a gas-rich disk galaxy has been impacted by an equal mass elliptical that had a trajectory approximately perpendicular to the plane of the disk and passed through the disk slightly off-center. We compare multi-wavelength observations of the Arp 119 system with a combined n-body/SPH simulation of colliding galaxies. We find that the progression of recent, large-scale star formation in this galaxy can be accounted for by a single, outwardly propagating collision-induced density wave in the gas., Comment: Submitted to The Astrophysical Journal; for related simulation material, see http://www.astro.uiuc.edu/collide/video.html

In this paper we demonstrate for the first time the connection between the spatial and temporal progression of star formation and the changing locations of the very dense regions in the gas of a massive disk galaxy (NGC 1144) in the aftermath of its collision with a massive elliptical (NGC 1143). These two galaxies form the combined object Arp 118, a collisional ring galaxy system. The results of 3D, time-dependent, numerical simulations of the behavior of the gas, stars, and dark matter of a disk galaxy and the stars and dark matter in an elliptical during a collision are compared with multiwavelength observations of Arp 118. The collision that took place approximately 22 Myr ago generated a strong, non-linear density wave in the stars and gas in the disk of NGC 1144, causing the gas to became clumped on a large scale. This wave produced a series of superstarclusters along arcs and rings that emanate from the central point of impact in the disk. The locations of these star forming regions match those of the regions of increased gas density predicted the time sequence of models. The models also predict the large velocity gradients observed across the disk of NGC 1144. These are due to the rapid radial outflow of gas coupled to large azimuthal velocities in the expanding ring, caused by the impact of the massive intruder., Comment: 12 pages in document, and 8 figures (figures are separate from the document's file); Submitted to Astrophysical Journal Letters

During the past several years, a RAND-developed "The Day After..." exercise methodology has been developed and used to explore strategic planning options, both for nuclear proliferation and counterproliferation, and, more recently, for questions involving "security in cyberspace" and "information warfare (IW)." On March 23, 1996, a "The Day After.. in Cyberspace" exercise with approximately 60 participants was conducted at RAND's Washington D.C. offices, under the sponsorship of the Defense Advanced Research Projects Agency. The purpose was to generate suggestions and options regarding research and development initiatives to enhance the security of the U.S. information infrastructure. The scenario used in this exercise involved a Mideast crisis situation, with Iran as an aggressor. We used a variation of the scenario that had been used earlier to explore other aspects of planning for cyberspace security, as documented in Molander, Riddile, and Wilson (1996). Participants in the exercise spent approximately three hours in individual groups, and another two hours in plenary sessions, discussing both short-term technical fixes to counter 1W allacks that were hypothesized to occur in the year 2000 and longer-term research strategies that could be initiated now to avoid significant vulnerabilities in the future. These discussions ranged over known problems with the current information infrastructure, and both common wisdom and some novel approaches to tightening the security of those systems on which our nation depends. We highlight below some of the observations and suggestions resulting from these discussions that appear to be relevant to DARPA's planning for R&D investments in the field of cyberspace security.

The volcanic rocks of the Bearpaw Mountains are part of the Montana high-potassium province, emplaced through Archaean rocks of the Wyoming Craton between 54 and 50 Ma ago. Extrusive rocks, dominated by minettes and latites, have a volume of Ü 825 km3. The minettes range in composition from 20 to 6% MgO. The more magnesian varieties contain the phenocryst assemblage forsterite + Cr-spinel + diopside ± phlogopite. More evolved rocks are olivine-free, with an assemblage of either salite + phlogopite + pseudoleucite or salite + phlogopite + analcime. The analcime is thought to be secondary after leucite, produced by loss of potassium from the minettes. Mineral chemistry and textures, especially of clinopyroxenes, indicate that mixing between minette magmas of varying degrees of evolution was commonplace. Compositional variation was further extended by accumulation of olivine + spinel + clinopyroxene phenocrysts, and by the preservation of mantle xenocrysts in the minettes. The primary minette magmas are inferred to have had 12–14% MgO and to have been generated at 30 kb from an olivine + diopside + phlogopite-bearing source. The primary magmas evolved dominantly by fractionation of olivine + diopside. The minettes have high contents of large ion lithophile elements (LILE) and light rare earth elements (LREE), with K2O up to 6.18%, Ba 5491 ppm, Sr 2291 ppm, and Ce 99 ppm. (87Sr/86Sr)0 ranges from 0.707 to 0.710 and £Nd varies from –10 to –16. These data, plus high LILE/HFSE (high field strength elements) values, are interpreted to show that the minettes contain at least three different mantle components. The lithosphere was initially depleted in Archaean times, but was metasomatically enriched in the Proterozoic and in the late Cretaceous and early Tertiary. The latites have many chemical features in common with the minettes, such as potassic character and high LILE/HFSE values. They formed by fractional crystallization of minette magma in combination with assimilation

NR 20140805

REDUCE is a program designed for general algebraic computations of interest to physicists and engineers. Its capabilities include: Expansion and ordering of rational functions of polynomials; symbolic differentiation; substitutions in a wide variety of forms; reduction of quotients of polynomials by cancellation of common factors; calculation of symbolic determinants; calculations of interest to high energy physicists including spin 1/2 and spin 1 algebra. The program is written completely in the language LISP 1.5 and may therefore be run with little modification on any computer possessing a LISP 1.5 compiler or interpreter. (Author), Report on Stanford Artificial Intelligence Project. Also available as Stanford Univ., Calif. Inst. of Theoretical Physics. Rept. no. ITP-292.

This paper describes in outline the structure and use of REDUCE, a program designed for large-scale algebraic computations of interest to applied mathematicians, physicists and engineers. The capabilities of the system include: expansion, ordering and reduction of rational functions of polynomials, symbolic differentiation, substitutions for variables and expressions appearing in other expressions, simplification of symbolic determinants and matrix expressions, tensor and non-commutative algebraic calculations of interest to high energy physicists. (Modified author abstract), Also available as Stanford Univ., Calif. Inst. of Theoretical Physics. Rept. no. ITP-282. Report on Stanford Artificial Intelligence Project.

The paper describes a system of programs in the language LISP 1.5 which handles all stages of calculation from the specification of an elementary-particle process in terms of a Hamiltonian of interaction or Feynman diagrams to the derivation of an absolute square of the matrix element for the process. Examples of significant parts of the programs are presented in the text. (Author), Report on Stanford Artificial Intelligence Project. Prepared in cooperation with Stanford Univ., Calif., Inst. of Theoretical Physics, Rept. no. ITP-333 and Texas Univ., Austin. Center for Particle Theory, Rept. no. CPT-4.

When it was first formulated in 1960, the programming language LISP was a truly machine independent language. However, even the earliest computer implementation encountered problems in input-output control and the handling of free variables which were not considered in the original paper. Successive implementations of LISP on more sophisticated machines have solved such problems by independent methods and introduced extensions of the language peculiar to those machines. The paper is an attempt to provide a uniform subset of LISP 1.5 and its variants as it exists today. The version of LISP described, which we call Standard LISP, is sufficiently restricted in form so that programs written in it can run under any LISP system upwardly compatible with LISP 1.5. As function names vary from system to system and input-output control is different, some modification of the code of course necessary before function definitions can be successfully compiled in any given system. However, this modification is performed automatically by a preprocessor, which is custom built for a particular system., Report on Stanford Artificial Intelligence Project.

The real part of the virtual Compton amplitude can be directly determined from measurements of electron (or muon) bremsstrahlung or pair photoproduction. In general, the interference of the Compton amplitude with the Bethe-Heitler amplitude for pair production or bremsstrahlung yields a contribution to the cross section which is antisymmetric when the leptons are interchanged. This interference contribution thus produces different cross sections for electron and positron bremsstrahlung at a given scattering energy and angle. Also, the counting rate for pair production will depend on which lepton has the greater momentum. The determination of the real part of the Compton amplitude would supply information on the isobar resonance shape, test the dispersion relation for the forward amplitude, and resolve uncertainties in the determination of the nucleon resonances. A simple estimate for the lepton asymmetry of the pair production cross sections due to the forward Compton amplitude is given in addition to a complete calculation of the effect of the first nucleon resonance using the isobar model. The results are also discussed for nuclear targets. For the latter case, a broadening of the isobar decay width due to absorption in the nuclear medium must be taken into account. (Author), Prepared in cooperation with Stanford Univ., Calif., Inst. of Theoretical Physics, Rept. no. ITP-336 and Texas Univ., Austin, Center for Particle Theory, Rept. no. CPT-10.

One of the most significant features of programs designed for non-numeric calculation is that the size of expressions manipulated, and hence the amount of storage necessary, changes continually during the execution of the program. It is therefore usually not possible for the user to know ahead of time just how much output his program will produce, or whether the calculation will in fact fail because of lack of available computer memory. The key to keeping both the size of intermediate expressions and output under control often lies in the manner in which substitutions for variables and expressions declared by the programmer are implemented by the system. In this paper various methods which have been developed to perform these substitutions in the author's own system REDUCE are discussed. A brief discription of the REDUCE system is also given. (Author), Presented at IBM Summer Institute on Symbolic Mathematics by Computer, Boston, Mass., Jul-Aug 68.

Pion photoproduction from nucleons has proved a useful tool in the study of the pion-nucleon interaction because of the dominance of the strong final-state interaction between emitted pion and recoil nucleon. There has remained, however, a noticeable lack of data at high momentum transfer in the region of the second pion-nucleon resonance. In particular, the zero angle measurement provides an important test of the hypothesis that the direct photo-electric term is responsible for the difference in position of this resonance in pi o and pi = photoproduction. The present experiment was designed to study this region using the Stanford Mark III linear accelerator. The results of the experiment establish that the discrepancy in resonance positions is not due to the photo-electric term, and also establish the possibility of a high momentum transfer enhancement of pi o photoproduction caused by crossed nucleon and nucleon isobar exchanges. The paper is divided into into five parts. In Section II, the experimental equipment and techniques are described. Section III contains an account of the data reduction, and the results are then interpreted in Section IV. Finally, in Section V, general conclusions are drawn. (Author), In cooperation with Institute of Theoretical Physics, Stanford Univ., Calif. Contract AF49 638 1389.

$7000 pressed brick house begun

A lecture given at the Infantry and Cavalry School (now the Command and General Staff College).

This lecture was given at the School for Infantry and Cavalry (now the Command and General Staff College) The lectures was given by Captain Clint C. Hearn.