WorldWideScience

Sample records for biologically interesting interstellar

  1. Organic chemistry and biology of the interstellar medium

    Science.gov (United States)

    Sagan, C.

    1973-01-01

    Interstellar organic chemistry is discussed as the field of study emerging from the discovery of microwave lines of formaldehyde and of hydrogen cyanide in the interstellar medium. The reliability of molecular identifications and comparisons of interstellar and cometary compounds are considered, along with the degradational origin of simple organics. It is pointed out that the contribution of interstellar organic chemistry to problems in biology is not substantive but analogical. The interstellar medium reveals the operation of chemical processes which, on earth and perhaps on vast numbers of planets throughout the universe, led to the origin of life, but the actual molecules of the interstellar medium are unlikely to play any significant biological role.

  2. On the Cultivation of Students' Interests in Biology Teaching

    Science.gov (United States)

    Li, Yan

    2011-01-01

    This paper introduces the importance of middle school students' interests in learning biology. Considering the psychological characteristics of middle school students, this paper suggests several practical ways for inspiring students' interests in learning biology.

  3. Positive feelings in learning and interest development in biology education

    DEFF Research Database (Denmark)

    Petersen, Morten Rask; Dohn, Niels Bonderup

    2015-01-01

    support our initial hypothesis that learning can be a facilitator for interest development. This is an argument for focusing more on didactical approaches and learning environments if the goal is to have interested students. As stated by Dewey: “If we can discover a child’s urgent needs and powers...... as an optimal state that combines positive affective qualities (e.g., feelings of immediate enjoyment, good moods etc.) and positive cognitive qualities (e.g. striving for meaningful goals, relevance etc., cf. Rathunde & Csikszentmihalyi, 1993). In the literature interest is typically described as a facilitator...... for learning (e.g. Krapp, 2002). Here we turn the interplay and see learning as a facilitator for interest development. This interplay was studied in upper secondary biology education. Student’s conducted an exercise on modelling natural selection with LEGO® bricks (Christensen-Dalsgaard & Kanneworf, 2009...

  4. Positive feelings in learning and interest development in biology education

    DEFF Research Database (Denmark)

    Petersen, Morten Rask; Dohn, Niels Bonderup

    2015-01-01

    as an optimal state that combines positive affective qualities (e.g., feelings of immediate enjoyment, good moods etc.) and positive cognitive qualities (e.g. striving for meaningful goals, relevance etc., cf. Rathunde & Csikszentmihalyi, 1993). In the literature interest is typically described as a....... Findings show that students who changed conceptual understanding in the tests also experienced deeper learning and understanding of natural selection and evolution. These students also experience positive feelings towards learning and learning can enhance their interest in evolution and biology in general...

  5. RESEARCH ON INCREASING INTEREST FOR BIOLOGY BY USING WORKSHEETS

    Directory of Open Access Journals (Sweden)

    Liliana Hildegarde MUNTEAN

    2012-01-01

    Full Text Available The school's responsibility is to promote the goals of society.Today the educators must look at teaching and learning in a different context because increases the need for innovative ways to incorporate an experiential approach into management courses. Most people tend to use one of their senses more than the others. In this study, the visual learning style is the most common. By using the worksheet in the teaching-learning-assessment increased students' interest for Biology. Differentiated support granted by the teacher gave better results than with traditional lessons.

  6. On cloning: advocating history of biology in the public interest.

    Science.gov (United States)

    Maienschein, J

    2001-01-01

    Cloning - the process of creating a cell, tissue line or even a complete organism from a single cell - or the strands that led to the cloning of a mammal, Dolly, are not new. Yet the media coverage of Dolly's inception raised a range of reactions from fear or moral repulsion, to cautious optimism. The implications for controlling human reproduction were clearly in the forefront, though many issues about animals emerged as well. On topics of public interest such as cloning, historians of biology have the opportunity to make a unique contribution. Such debates are often aired as if they have no precedents, either in biology or in the ethical, moral, and social concerns arising in the public arena. The technology leading to Dolly draws on strands of research going back to the 1890s, and the cycle of the public response has been repeated often in the past century. What can we learn from examining these events historically, and how can we - or should we even try - to inform public opinion? I think we should try and will outline briefly some of the ways that can work.

  7. Activation Analysis of Biological Samples of Forensic Interest

    International Nuclear Information System (INIS)

    In forensic (crime investigation) studies, samples of a biological origin are frequently used as evidence. Often it is necessary to compare one sample (associated with a victim or the scene of a crime) with another sample of the same general type (associated with a suspect in some way). The purpose of such comparisons is to establish, if possible, that - to a high degree of probability - the two samples have a common origin. Typically, all available relevant methods of comparison are utilized in such cases by the criminalist: microscopic examination; X-ray diffraction; infra-red, visible, and ultra-violet spectrometry; and various methods of elemental analysis. The forensic applications of high-flux thermal-neutron activation analysis (NAA) have shown great promise and are attracting considerable attention. The authors' laboratory has been engaged in such forensic NAA research and development studies for the past five years. (It also operates a non-profit Forensic Activation Analysis Service, available to all law enforcement agencies, for the NAA comparison of evidence samples involved in actual criminal cases. Samples from many actual cases have been thus examined.) In the United States, NAA results have now been successfully presented in court in some 20 actual cases. Some of the evidence-type materials of interest are non-biological; others are biological. Only the latter will be discussed in this paper. The principal evidence-type materials of a biological nature that have been examined in this laboratory by high-flux thermal-NAA to date are the following: hair, blood, faeces, urine, fingernails, skin, wood, tobacco, whisky, green plants, and marijuana. (In addition, a number of these evidence-type materials have also been studied in this laboratory by high-flux photonuclear activation analysis (PNAA); attention in this paper will be largely devoted to the thermal-NAA forensic studies.) The main topics to be reported upon in this paper are: (1) limits of

  8. Complex systems of biological interest stability under ionising radiations

    International Nuclear Information System (INIS)

    This PhD work presents the study of stability of molecular systems of biological interest in the gas phase after interaction with ionising radiations. The use of ionising radiation can probe the physical chemistry of complex systems at the molecular scale and thus consider their intrinsic properties. Beyond the fundamental aspect, this work is part of the overall understanding of radiation effects on living organisms and in particular the use of ionizing radiation in radiotherapy. Specifically, this study focused on the use of low-energy multiply charged ions (tens of keV) provided by the GANIL (Caen), which includes most of the experiments presented. In addition, experiments using VUV photons were also conducted at synchrotron ELETTRA (Trieste, Italy). The bio-molecular systems studied are amino acids and nucleic acid constituents. Using an experimental crossed beams device allows interaction between biomolecules and ionising radiation leads mainly to the ionization and fragmentation of the system. The study of its relaxation dynamics is by time-of-flight mass spectrometry coupled to a coincidences measurements method. It is shown that an approach combining experiment and theory allows a detailed study of the fragmentation dynamics of complex systems. The results indicate that fragmentation is generally governed by the Coulomb repulsion but the intramolecular rearrangements involve specific relaxation mechanisms. (author)

  9. Interstellar organic chemistry.

    Science.gov (United States)

    Sagan, C.

    1972-01-01

    Most of the interstellar organic molecules have been found in the large radio source Sagittarius B2 toward the galactic center, and in such regions as W51 and the IR source in the Orion nebula. Questions of the reliability of molecular identifications are discussed together with aspects of organic synthesis in condensing clouds, degradational origin, synthesis on grains, UV natural selection, interstellar biology, and contributions to planetary biology.

  10. Synthesis of Heterocylic Compounds of Biological Interest from Carbohydrate Derivatives

    OpenAIRE

    M. F. Martinez Esperón; Fascio, M. L.; N. B. D’Accorso

    2000-01-01

    The synthesis of some isoxazolic compounds from carbohydrate derivatives is described. These products are obtained by 1,3-dipolar cycloaddition reaction and their functionalization leads to derivatives with potential biological activities.

  11. Is interstellar archeology possible?

    Science.gov (United States)

    Carrigan, Richard A.

    2012-09-01

    Searching for signatures of cosmic-scale archeological artifacts such as Dyson spheres is an interesting alternative to conventional radio SETI. Uncovering such an artifact does not require the intentional transmission of a signal on the part of the original civilization. This type of search is called interstellar archeology or sometimes cosmic archeology. A variety of interstellar archeology signatures is discussed including non-natural planetary atmospheric constituents, stellar doping, Dyson spheres, as well as signatures of stellar, and galactic-scale engineering. The concept of a Fermi bubble due to interstellar migration is reviewed in the discussion of galactic signatures. These potential interstellar archeological signatures are classified using the Kardashev scale. A modified Drake equation is introduced. With few exceptions interstellar archeological signatures are clouded and beyond current technological capabilities. However SETI for so-called cultural transmissions and planetary atmosphere signatures are within reach.

  12. Menarche and Interest in Infants: Biological and Social Influences.

    Science.gov (United States)

    Goldberg, Susan; And Others

    1982-01-01

    Reports two studies in which 12- to 13-year-old girls, half of whom were premenarcheal and half postmenarcheal, responded to pictures of infants. Concurrent assessments of interest in motherhood, cognitive sophistication about the relationship between menarche and childbearing, attitudes toward menarche, and sex-role self-image did not…

  13. The Generalizability of Students' Interests in Biology Across Gender, Country and Religion

    Science.gov (United States)

    Hagay, G.; Baram-Tsabari, A.; Ametller, J.; Cakmakci, G.; Lopes, B.; Moreira, A.; Pedrosa-de-Jesus, H.

    2013-06-01

    In order to bridge the existing gap between biology curricula and students' interests in biology, a strategy for identifying students' interest based on their questions and integrating them into the curriculum was developed. To characterize the level of generalizability of students' science interests over 600 high school students from Portugal, Turkey, England and Israel, who chose biology as an advanced subject, their interest level was ranked in 36 questions that were originally raised by Israeli students. Results indicate that students from four different countries show interest in similar science questions. The most intriguing questions were the ones that dealt with human health and new developments in reproduction and genetics. Religious affiliation had the strongest effect on students' interest level, followed by national affiliation and gender. The findings suggest that students' interest in one context is relevant to the development of interest-based learning materials in a different context. However, despite these similarities, cultural and sociological differences need to be taken into account.

  14. Interests of 5th through 10th Grade Students toward Human Biology

    Science.gov (United States)

    Erten, Sinan

    2008-01-01

    This study investigated the middle and high school students' interests towards the subjects of human biology, specifically, "Human Health and Nutrition" and "Human Body and Organs." The study also investigated sources of their interests and factors that impact their interests, namely people that they interact and courses that they take about…

  15. Interstellar Hydrides

    CERN Document Server

    Gerin, Maryvonne; Goicoechea, Javier R

    2016-01-01

    Interstellar hydrides -- that is, molecules containing a single heavy element atom with one or more hydrogen atoms -- were among the first molecules detected outside the solar system. They lie at the root of interstellar chemistry, being among the first species to form in initially-atomic gas, along with molecular hydrogen and its associated ions. Because the chemical pathways leading to the formation of interstellar hydrides are relatively simple, the analysis of the observed abundances is relatively straightforward and provides key information about the environments where hydrides are found. Recent years have seen rapid progress in our understanding of interstellar hydrides, thanks largely to far-IR and submillimeter observations performed with the Herschel Space Observatory. In this review, we will discuss observations of interstellar hydrides, along with the advanced modeling approaches that have been used to interpret them, and the unique information that has thereby been obtained.

  16. A Shadow Curriculum: Incorporating Students' Interests into the Formal Biology Curriculum

    Science.gov (United States)

    Hagay, Galit; Baram-Tsabari, Ayelet

    2011-01-01

    Students have been largely ignored in discussions about how best to teach science, and many students feel the curriculum is detached from their lives and interests. This article presents a strategy for incorporating students' interests into the formal Biology curriculum, by drawing on the political meaning of "shadow government" as alternative…

  17. Interstellar Grains

    OpenAIRE

    Draine, B. T.

    2000-01-01

    Our current understanding of interstellar dust is summarized at an introductory level. Submicron-sized interstellar dust grains absorb and scatter light, and reradiate the absorbed energy in the infrared. The grain population spans a range of sizes, from molecules containing only tens of atoms, to particles containing 10^{10} atoms. Most of the grain mass appears to be due to two types of solid, in approximately equal amounts: amorphous silicate mineral, and carbonaceous material. Approximate...

  18. The Local Interstellar Medium

    CERN Document Server

    Redfield, S

    2006-01-01

    The Local Interstellar Medium (LISM) is a unique environment that presents an opportunity to study general interstellar phenomena in great detail and in three dimensions. In particular, high resolution optical and ultraviolet spectroscopy have proven to be powerful tools for addressing fundamental questions concerning the physical conditions and three-dimensional (3D) morphology of this local material. After reviewing our current understanding of the structure of gas in the solar neighborhood, I will discuss the influence that the LISM can have on stellar and planetary systems, including LISM dust deposition onto planetary atmospheres and the modulation of galactic cosmic rays through the astrosphere - the balancing interface between the outward pressure of the magnetized stellar wind and the inward pressure of the surrounding interstellar medium. On Earth, galactic cosmic rays may play a role as contributors to ozone layer chemistry, planetary electrical discharge frequency, biological mutation rates, and cl...

  19. Nitrogen Substituted Polycyclic Aromatic Hydrocarbon As Capable Interstellar Infrared Spectrum Source Considering Astronomical Chemical Evolution Step To Biological Organic Purine And Adenine

    CERN Document Server

    Ota, Norio

    2016-01-01

    In order to find out capable chemical evolution step from astronomically created organic in interstellar space to biological organic on the earth, infrared spectrum of nitrogen substituted carbon pentagon-hexagon coupled polycyclic aromatic hydrocarbon was analyzed by the density functional theory. Ionization was modeled from neutral to tri-cation. Among one nitrogen and two nitrogen substituted NPAH, we could find good examples showing similar IR behavior with astronomically well observed one as like C8H6N1, C7H5N2, and C7H5N2. We can imagine that such ionized NPAH may be created in interstellar space by attacks of high energy nitrogen and photon. Whereas, in case of three and four nitrogen substituted cases as like C6H4N3 and C5H3N4, there were no candidate showing similar behavior with observed one. Also, IR of typical biological organic with four and five nitrogen substituted one as like purine and adenine resulted no good similarity with observed one. By such theoretical comparison, one capable story of ...

  20. A Shadow Curriculum: Incorporating Students' Interests into the Formal Biology Curriculum

    Science.gov (United States)

    Hagay, Galit; Baram-Tsabari, Ayelet

    2011-11-01

    Students have been largely ignored in discussions about how best to teach science, and many students feel the curriculum is detached from their lives and interests. This article presents a strategy for incorporating students' interests into the formal Biology curriculum, by drawing on the political meaning of "shadow government" as alternative policies developed by parties not in office. A "shadow curriculum" thus reflects the interests and information needs of those who have no voice in deciding what the formal curriculum should include, although they are the ones who are most influenced by it. High school students' interests in three Biology topics were identified ( n = 343) and retested on another student sample ( n = 375), based on their solicited questions as indicators for interests. The results of this exploratory case study showed that half of the questions asked by students in the areas of genetics, the cardiovascular system and the reproductive system are not addressed by the national curriculum. Students' questions were then expressed in the curricular language of principles, phenomena and concepts in order to create a shadow curriculum. A procedure that could be used by other researchers and practitioners to guide the development of a curriculum that is more aligned with student interests is suggested.

  1. Interstellar holography

    NARCIS (Netherlands)

    Walker, M. A.; Koopmans, L. V. E.; Stinebring, D. R.; van Straten, W.

    2008-01-01

    The dynamic spectrum of a radio pulsar is an in-line digital hologram of the ionized interstellar medium. It has previously been demonstrated that such holograms permit image reconstruction, in the sense that one can determine an approximation to the complex electric field values as a function of Do

  2. Interstellar deuteroammonia

    NARCIS (Netherlands)

    Lis, D. C.; Gerin, M.; Roueff, E.; Phillips, T. G.; Poelman, D. R.

    2008-01-01

    Close to 30 deuterated molecules have now been detected in the ISM, including doubly-deuterated species D2H+, ND2H, D2CO, CHD2OH, D2S, and D2CS, as well as triply-deuterated ammonia and methanol. We review the current understanding of depletion and deuteration processes in cold, dense interstellar m

  3. Interstellar Holography

    OpenAIRE

    Walker, Mark; Koopmans, Leon,; Stinebring, Dan; van Straten, Willem

    2008-01-01

    The dynamic spectrum of a radio pulsar is an in-line digital hologram of the ionised interstellar medium. It has previously been demonstrated that such holograms permit image reconstruction, in the sense that one can determine an approximation to the complex electric field values as a function of Doppler-shift and delay, but to date the quality of the reconstructions has been poor. Here we report a substantial improvement in the method which we have achieved by simultaneous optimisation of th...

  4. Interstellar Holography

    CERN Document Server

    Walker, Mark; Stinebring, Dan; van Straten, Willem

    2008-01-01

    The dynamic spectrum of a radio pulsar is an in-line digital hologram of the ionised interstellar medium. It has previously been demonstrated that such holograms permit image reconstruction, in the sense that one can determine an approximation to the complex electric field values as a function of Doppler-shift and delay, but to date the quality of the reconstructions has been poor. Here we report a substantial improvement in the method which we have achieved by simultaneous optimisation of the thousands of coefficients that describe the electric field. For our test spectrum of PSR B0834+06 we find that the model provides an accurate representation of the data over the full 63 dB dynamic range of the observations: residual differences between model and data are noise-like. The advent of interstellar holography enables detailed quantitative investigation of the interstellar radio-wave propagation paths for a given pulsar at each epoch of observation; we illustrate this using our test data which show the scatter...

  5. Theoretical study of the molecular bases that control photochemical processes with biological and nanotechnological interest

    OpenAIRE

    Saurí Peris, Vicenta

    2013-01-01

    El trabajo desarrollado en la tesis doctoral que lleva por título "Theoretical study of the molecular bases that control photochemical processes with biological and nanotechnological interest" se enmarca en las líneas de investigación del grupo QCEXVAL (Quantum Chemistry of the Excited State University of Valencia), que nació en el seno del departamento de Química Física de la Universitat de València en 1993. Se han abordado temas de interés metodológico, biológico y nanotecnológico. La prime...

  6. Phallometric comparison of pedophilic interest in nonadmitting sexual offenders against stepdaughters, biological daughters, other biologically related girls, and unrelated girls.

    Science.gov (United States)

    Blanchard, Ray; Kuban, Michael E; Blak, Thomas; Cantor, James M; Klassen, Philip; Dickey, Robert

    2006-01-01

    This study compared the mean levels of sexual response to children produced by four groups of men with sexual offences against prepubescent girls and two comparison groups with other offences or no offences. All groups (N = 291) consisted of patients referred for clinical assessment of their sexual behavior or interests. Group assignment was determined by the victim's age and her relation to the patient: biological daughter; stepdaughter; other biologically related girl (e.g., sister, niece, granddaughter); unrelated girl; adult woman; and no known victim. The men with sexual offences had precisely one known victim each. The patients with offences may or may not have denied the act of which they were accused, but all patients denied an erotic preference for children. Sexual response to children was assessed by means of phallometric testing, a psychophysiological technique in which the individual's penile blood volume is monitored while he is presented with a standardized set of laboratory stimuli depicting male and female children and adults. The results indicated that the mean level of pedophilic response in men with offences against daughters or stepdaughters is intermediate between that in men with offences against otherwise-related or unrelated girls and that in men with no offences against girls at all. PMID:16598663

  7. INTERSTELLAR TURBULENCE

    Directory of Open Access Journals (Sweden)

    D. Falceta-Gonçalves

    2011-01-01

    Full Text Available The Interstellar Medium (ISM is a complex, multi-phase system, where the history of the stars occurs. The processes of birth and death of stars are strongly coupled to the dynamics of the ISM. The observed chaotic and diffusive motions of the gas characterize its turbulent nature. Understanding turbulence is crucial for understanding the star-formation process and the energy-mass feedback from evolved stars. Magnetic fields, threading the ISM, are also observed, making this effort even more difficult. In this work, I briefly review the main observations and the characterization of turbulence from these observable quantities. Following on, I provide a review of the physics of magnetized turbulence. Finally, I will show the main results from theoretical and numerical simulations, which can be used to reconstruct observable quantities, and compare these predictions to the observations.

  8. Faculty of 1000: a way of identifying what are currently considered the most interesting research articles in biology

    OpenAIRE

    Velterop, Johannes JM; Weedon, David

    2002-01-01

    Faculty of 1000 is a new reviewing, evaluation and rating system of primary scientific papers in the area of biology, produced by Biology Reports Limited and published by BioMed Central Limited (www.biomedcentral.com). Both companies are part of The Current Science Group. The service will identify the current most interesting and most important research papers in biology, picked by a group of over 1000 leading international researchers from any journal, and provide reasons why these articles ...

  9. Study of radionuclides speciation with biological molecules of interest by spectrometric techniques

    International Nuclear Information System (INIS)

    Mechanisms of complexation and accumulation of the radionuclides at the cellular and molecular level are complex and poorly known because the studies on these subjects are scarce. Within the framework of this thesis, we studied the interactions of europium (analogue of trivalent actinides) and uranium (VI) (actinide) with biological molecules of interest: phyto-chelatins. Their role is to protect cells against intrusions from nonessential heavy metals (thus toxic). These proteins are likely to be implied in the mechanisms of sequestration of radionuclides in living organisms. However, their structure is complex, this is why, in order to better understand their reactivity, we extended our studies to lower entities which constitute them (amino acids and glutathione). We determined solution speciation (stoichiometry, structure) as well as the complexing constants associated with the formation of these species. These studies were undertaken by Time Resolved Laser induced Fluorescence (TRLIF), Electro-Spray Mass Spectrometry (ES-MS), Nuclear Magnetic Resonance (NMR), Fourier Transform Infra-Rouge spectroscopy (FTIR) and Extended X-ray Absorption Fine Structure Spectroscopy (EXAFS). The determination of the complexation constants enabled us to conclude that the complexing capacity of these molecules with respect to radionuclides was moderate (log10K1 < 3, pH 3 or 6), the formed species are mononuclear with only one ligand molecule (1:1). The interaction is performed via oxygenated (hard) groups. The direct complexation of europium with phyto-chelatins at acidic pH was studied jointly by TRLIF and ES-MS. The complexing capacity of these molecules is much higher than that of GSH from which they result. In addition to studies undertaken on synthetic solutions reproducing the 'biological' conditions (pH close to neutrality, ionic strength 0.1 mol/L, etc), tests of cellular contamination were realized. The quantification of integrated europium showed that those are able to

  10. Study of radionuclides speciation with biological molecules of interest by spectrometric techniques

    International Nuclear Information System (INIS)

    Mechanisms of complexation and accumulation of the radionuclides at the cellular and molecular level are complex and poorly known because the studies on these subjects are scarce. Within the framework of this thesis, we studied the interactions of these cations with biological molecules of interest. We chose to focus on an actinide: uranium (VI) as well as europium as an analogue of trivalent actinides. The selected biological molecules are the phyto-chelatins: their role is to protect cells against intrusions from nonessential heavy metals (thus toxic). These proteins are likely to be implied in the mechanisms of sequestration of radionuclides in living organisms. However, their structure is complex, this is why, in order to better include/understand their reactivity, we extended our studies to lower entities which constitute them (amino acid: glycine, glutamic acid and cysteine; polypeptides: glutathione reduced and oxidized forms). In particular, we determined solution speciation (stoichiometry, structure) as well as the complexing constants associated with the formation with these species. These studies were undertaken by Time Resolved Laser induced Fluorescence (TRLIF), Electro-Spray-Mass Spectrometry (ES-MS), Nuclear Magnetic Resonance (NMR), Fourier Transform Infra-Rouge spectroscopy (FTIR) and Extended X-ray Absorption Fine Structure Spectroscopy (EXAFS).The determination of the complexation constants enabled us to conclude that the complexing capacity of these molecules with respect to radionuclides was moderate (log10K1 ≤ 3, pH 3 or 6), the formed species are mononuclear with only one ligand molecule (1:1). The interaction is performed via oxygenated (hard) groups. The direct complexation of europium with phyto-chelatins at acidic pH was studied jointly by TRLIF and ES-MS. The complexing capacity of these molecules is much higher than that of GSH from which they result. The interaction of europium with metallothioneins is, on the contrary, lower than

  11. Stardust Interstellar Preliminary Examination

    Science.gov (United States)

    Westphal, A.; Stardust Interstellar Preliminary Examation Team: http://www. ssl. berkeley. edu/~westphal/ISPE/

    2011-12-01

    A. J. Westphal, C. Allen, A. Ansari, S. Bajt, R. S. Bastien, H. A. Bechtel, J. Borg, F. E. Brenker, J. Bridges, D. E. Brownlee, M. Burchell, M. Burghammer, A. L. Butterworth, A. M. Davis, P. Cloetens, C. Floss, G. Flynn, D. Frank, Z. Gainsforth, E. Grün, P. R. Heck, J. K. Hillier, P. Hoppe, G. Huss, J. Huth, B. Hvide, A. Kearsley, A. J. King, B. Lai, J. Leitner, L. Lemelle, H. Leroux, R. Lettieri, W. Marchant, L. R. Nittler, R. Ogliore, F. Postberg, M. C. Price, S. A. Sandford, J.-A. Sans Tresseras, T. Schoonjans, S. Schmitz, G. Silversmit, A. Simionovici, V. A. Solé, R. Srama, T. Stephan, V. Sterken, J. Stodolna, R. M. Stroud, S. Sutton, M. Trieloff, P. Tsou, A. Tsuchiyama, T. Tyliszczak, B. Vekemans, L. Vincze, D. Zevin, M. E. Zolensky, >29,000 Stardust@home dusters ISPE author affiliations are at http://www.ssl.berkeley.edu/~westphal/ISPE/. In 2000 and 2002, a ~0.1m2 array of aerogel tiles and alumi-num foils onboard the Stardust spacecraft was exposed to the interstellar dust (ISD) stream for an integrated time of 200 days. The exposure took place in interplanetary space, beyond the orbit of Mars, and thus was free of the ubiquitous orbital debris in low-earth orbit that precludes effective searches for interstellar dust there. Despite the long exposure of the Stardust collector, <<100 ISD particles are expected to have been captured. The particles are thought to be ~1μm or less in size, and the total ISD collection is probably <10-6 by mass of the collection of cometary dust parti-cles captured in the Stardust cometary dust collector from the coma of the Jupiter-family comet Wild 2. Thus, although the first solid sample from the local interstellar medium is clearly of high interest, the diminutive size of the particles and the low numbers of particles present daunting challenges. Nevertheless, six recent developments have made a Preliminary Examination (PE) of this sample practical: (1) rapid automated digital optical scanning microscopy for three

  12. Interstellar Grains: 50 Years On

    CERN Document Server

    Wickramasinghe, N Chandra

    2011-01-01

    Our understanding of the nature of interstellar grains has evolved considerably over the past half century with the present author and Fred Hoyle being intimately involved at several key stages of progress. The currently fashionable graphite-silicate-organic grain model has all its essential aspects unequivocally traceable to original peer-reviewed publications by the author and/or Fred Hoyle. The prevailing reluctance to accept these clear-cut priorities may be linked to our further work that argued for interstellar grains and organics to have a biological provenance - a position perceived as heretical. The biological model, however, continues to provide a powerful unifying hypothesis for a vast amount of otherwise disconnected and disparate astronomical data.

  13. Self-Expression Assignment as a Teaching Approach to Enhance the Interest of Kuwaiti Women in Biological Sciences

    Science.gov (United States)

    El-Sabban, Farouk

    2008-01-01

    Stimulating the interest of students in biological sciences necessitates the use of new teaching methods and motivating approaches. The idea of the self-expression assignment (SEA) has evolved from the prevalent environment at the College for Women of Kuwait University (Safat, State of Kuwait), a newly established college where the number of…

  14. Interstellar Fullerene Compounds and Diffuse Interstellar Bands

    CERN Document Server

    Omont, Alain

    2015-01-01

    Recently, the presence of fullerenes in the interstellar medium (ISM) has been confirmed, especially with the first confirmed identification of two strong diffuse interstellar bands (DIBs) with C60+. This justifies reassesing the importance of interstellar fullerenes of various sizes with endohedral or exohedral inclusions and heterofullerenes (EEHFs). The phenomenology of fullerenes is complex. In addition to formation in shock shattering, fully dehydrogenated PAHs in diffuse interstellar (IS) clouds could perhaps efficiently transform into fullerenes including EEHFs. But it is extremely difficult to assess their expected abundance, composition and size distribution, except for C60+. As often suggested, EEHFs share many properties with C60, as regards stability, formation/destruction, chemical processes and many basic spectral features. We address the importance of various EEHFs as possible DIB carriers. Specifically, we discuss IS properties and the contributions of fullerenes of various sizes and charge su...

  15. Private and collective interests; conflicts and solutions: the central theme of current thinking in evolutionary biology.

    Science.gov (United States)

    Wieser, W

    2001-01-01

    The statement made by the population geneticist Theodosius Dobzhansky (1973): "Nothing in Biology Makes Sense Except in the Light of Evolution", is often quoted as a crucially important generalization on the nature of biology. I am inclined to consider as equally important the statement: "Nothing in Evolutionary Biology Makes Sense Except in the Light of Conflicts between Parts and Systems." This generalization takes account of the dynamic nature of biological phenomena, but also of the fact that the study of transitions from autonomous units to cooperative systems has become one of the most exciting and scientifically rewarding enterprises in all of organismic biology. The problems encountered and the speculations generated in the course of this enterprise will be either of the more unit-centered or of the more system-centered type, most biologists tending to lean towards one or the other. This explains why evolutionary biology is fraught with so many antagonistic attitudes and polarizing points of view. In this essay I want specifically to draw attention to and discuss the following issues which in recent years have polarized biologists: the dual nature of genes; the logic of Hamilton's rule; the relationship between kin selection, signalling networks and systemic manipulation; the semantic problem of progress in evolution; and the evolutionary consequences of the vastly differing time scales over which genotypic and phenotypic information processing occurs in higher animals.

  16. Some chemical synthesis of 14C labelled compounds of pharmaceutical or biological interest

    International Nuclear Information System (INIS)

    The recent discovery of the tuberculostatic properties of the hydrazide of isonicotinic acid (so-called 'Isoniazide', 'Rimifon') has raised considerably its interest, as for metabolic studies which it is more interesting to have it labelled with 14C. We describe in this report the chemical synthesis of 14C carboxyl labelled isoniazide which were done in the pyridine ring to highlight his metabolic function on the Koch's bacillus. (M.B.)

  17. Some chemical synthesis of {sup 14}C labelled compounds of pharmaceutical or biological interest

    Energy Technology Data Exchange (ETDEWEB)

    Pichat, I.; Baret, C.; Audinot, M.; Herbert, M.; Lambin, J. [Commissariat a l' Energie Atomique, Lab. du Fort de Chatillon, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1955-07-01

    The recent discovery of the tuberculostatic properties of the hydrazide of isonicotinic acid (so-called 'Isoniazide', 'Rimifon') has raised considerably its interest, as for metabolic studies which it is more interesting to have it labelled with {sup 14}C. We describe in this report the chemical synthesis of {sup 14}C carboxyl labelled isoniazide which were done in the pyridine ring to highlight his metabolic function on the Koch's bacillus. (M.B.)

  18. Degradative Enzymes from the Pharmacy or Health Food Store: Interesting Examples for Introductory Biology Laboratories

    Science.gov (United States)

    Deutch, Charles E.

    2007-01-01

    Degradative enzymes in over-the-counter products from pharmacies and health food stores provide good examples of biological catalysis. These include [beta]-galactosidase in Lactaid[TM], [alpha]-galactosidase in Beano[R], [alpha]-amylase and proteases in digestive aids, and proteases in contact lens cleaners. These enzymes can be studied…

  19. Representing culture in interstellar messages

    Science.gov (United States)

    Vakoch, Douglas A.

    2008-09-01

    As scholars involved with the Search for Extraterrestrial Intelligence (SETI) have contemplated how we might portray humankind in any messages sent to civilizations beyond Earth, one of the challenges they face is adequately representing the diversity of human cultures. For example, in a 2003 workshop in Paris sponsored by the SETI Institute, the International Academy of Astronautics (IAA) SETI Permanent Study Group, the International Society for the Arts, Sciences and Technology (ISAST), and the John Templeton Foundation, a varied group of artists, scientists, and scholars from the humanities considered how to encode notions of altruism in interstellar messages . Though the group represented 10 countries, most were from Europe and North America, leading to the group's recommendation that subsequent discussions on the topic should include more globally representative perspectives. As a result, the IAA Study Group on Interstellar Message Construction and the SETI Institute sponsored a follow-up workshop in Santa Fe, New Mexico, USA in February 2005. The Santa Fe workshop brought together scholars from a range of disciplines including anthropology, archaeology, chemistry, communication science, philosophy, and psychology. Participants included scholars familiar with interstellar message design as well as specialists in cross-cultural research who had participated in the Symposium on Altruism in Cross-cultural Perspective, held just prior to the workshop during the annual conference of the Society for Cross-cultural Research . The workshop included discussion of how cultural understandings of altruism can complement and critique the more biologically based models of altruism proposed for interstellar messages at the 2003 Paris workshop. This paper, written by the chair of both the Paris and Santa Fe workshops, will explore the challenges of communicating concepts of altruism that draw on both biological and cultural models.

  20. Tethered bilayer lipid membranes (tBLMs): interest and applications for biological membrane investigations.

    Science.gov (United States)

    Rebaud, Samuel; Maniti, Ofelia; Girard-Egrot, Agnès P

    2014-12-01

    Biological membranes play a central role in the biology of the cell. They are not only the hydrophobic barrier allowing separation between two water soluble compartments but also a supra-molecular entity that has vital structural functions. Notably, they are involved in many exchange processes between the outside and inside cellular spaces. Accounting for the complexity of cell membranes, reliable models are needed to acquire current knowledge of the molecular processes occurring in membranes. To simplify the investigation of lipid/protein interactions, the use of biomimetic membranes is an approach that allows manipulation of the lipid composition of specific domains and/or the protein composition, and the evaluation of the reciprocal effects. Since the middle of the 80's, lipid bilayer membranes have been constantly developed as models of biological membranes with the ultimate goal to reincorporate membrane proteins for their functional investigation. In this review, after a brief description of the planar lipid bilayers as biomimetic membrane models, we will focus on the construction of the tethered Bilayer Lipid Membranes, the most promising model for efficient membrane protein reconstitution and investigation of molecular processes occurring in cell membranes.

  1. Sulfur-centered reactive intermediates derived from the oxidation of sulfur compounds of biological interest

    Energy Technology Data Exchange (ETDEWEB)

    Abedinzadeh, Z. [Lab. de Chimie Physique, UMR, Univ. Rene Descartes, Paris (France)

    2001-02-01

    Sulphur compounds play a central role in the structure and activity of many vital systems. In the living cell, sulfur constitutes an essential part of the defense against oxidative damage and is transformed into a variety of sulfur free radical species. Many studies of the chemistry of sulfur-centered radicals using pulse radiolysis and photolysis techniques to detect and measure the kinetics of these radicals have been published and reviewed. This paper discusses the present state of research on the formation and reactivity of certain sulfur-centered radicals [RS{sup .}, RSS{sup .}, RS{sup .+}, (RSSR){sup .+}] and their implications for biological systems. (author)

  2. Prospective of Photon Propulsion for Interstellar Flight

    Science.gov (United States)

    Bae, Young K.

    Mastering photon propulsion is proposed to be the key to overcoming the limit of the current propulsion technology based on conventional rocketry and potentially opening a new space era. A perspective on photon propulsion is presented here to elucidate that interstellar manned roundtrip flight could be achievable in a century within a frame of exiting scientific principles, once the required existing technologies are further developed. It is shown that the developmental pathway towards the interstellar flight demands not only technological breakthroughs, but consistent long-term world-scale economic interest and investment. Such interest and investment will result from positive financial returns from routine interstellar commutes that can transport highly valuable commodities in a profitable manner. The Photonic Railway, a permanent energy-efficient transportation structure based on the Beamed-Laser Propulsion (BLP) by Forward and the Photonic Laser Thruster (PLT) by the author, is proposed to enable such routine interstellar commutes via Spacetrains. A four-phased evolutionary developmental pathway towards the Interstellar Photonic Railway is proposed. Each phase poses evolutionary, yet daunting, technological and financial challenges that need to be overcome within each time frame of 20 _ 30 years, and is projected to generate multitudes of applications that would lead to sustainable reinvestment into its development. If successfully developed, the Photonic Railway would bring about a quantum leap in the human economic and social interests in space from explorations to terraforming, mining, colonization, and permanent habitation in exoplanets.

  3. Modification of chitosan derivatives of environmental and biological interest: a green chemistry approach.

    Science.gov (United States)

    Abdelaal, Magdy Y; Sobahi, Tariq R; Al-Shareef, Hossa F

    2013-04-01

    Chitosan is a non-toxic polyaminosaccharide that is available in a variety of useful forms, and its chemical and biological properties make it a very attractive biomaterial that could be used in a wide variety of medicinal applications. This work focuses on the preparation of different chitosan derivatives by treatment with ethyl cellulose, cellulose triacetate and different carbohydrates in both neutral and slightly acidic media. It also addresses modification with glycidyltrimethyl ammonium chloride, phthalic anhydride and succinic acid derivatives. The obtained derivatives were crosslinked with glutaraldehyde. Thermo-gravimetric (TGA) and FT-IR spectroscopic analyses and electron scanning microscopy (SEM) were used to characterize the obtained products and demonstrate the success of the chitosan-modification process. The obtained products were tested for their ability to uptake transition metal ions from aqueous solutions, and their ion-uptake efficiency was determined with the aid of the ICP-AES technique. The bioactivity of some selected products was tested to study the effect of their concentrations on selected microorganisms. Burkholderia cepaci, Aspergillus niger, and Candida albicans were selected as representative examples of bacteria, yeasts and fungi, respectively.

  4. Modification of chitosan derivatives of environmental and biological interest: a green chemistry approach.

    Science.gov (United States)

    Abdelaal, Magdy Y; Sobahi, Tariq R; Al-Shareef, Hossa F

    2013-04-01

    Chitosan is a non-toxic polyaminosaccharide that is available in a variety of useful forms, and its chemical and biological properties make it a very attractive biomaterial that could be used in a wide variety of medicinal applications. This work focuses on the preparation of different chitosan derivatives by treatment with ethyl cellulose, cellulose triacetate and different carbohydrates in both neutral and slightly acidic media. It also addresses modification with glycidyltrimethyl ammonium chloride, phthalic anhydride and succinic acid derivatives. The obtained derivatives were crosslinked with glutaraldehyde. Thermo-gravimetric (TGA) and FT-IR spectroscopic analyses and electron scanning microscopy (SEM) were used to characterize the obtained products and demonstrate the success of the chitosan-modification process. The obtained products were tested for their ability to uptake transition metal ions from aqueous solutions, and their ion-uptake efficiency was determined with the aid of the ICP-AES technique. The bioactivity of some selected products was tested to study the effect of their concentrations on selected microorganisms. Burkholderia cepaci, Aspergillus niger, and Candida albicans were selected as representative examples of bacteria, yeasts and fungi, respectively. PMID:23376358

  5. Interstellar fullerene compounds and diffuse interstellar bands

    Science.gov (United States)

    Omont, Alain

    2016-05-01

    Recently, the presence of fullerenes in the interstellar medium (ISM) has been confirmed and new findings suggest that these fullerenes may possibly form from polycyclic aromatic hydrocarbons (PAHs) in the ISM. Moreover, the first confirmed identification of two strong diffuse interstellar bands (DIBs) with the fullerene, C60+, connects the long standing suggestion that various fullerenes could be DIB carriers. These new discoveries justify reassessing the overall importance of interstellar fullerene compounds, including fullerenes of various sizes with endohedral or exohedral inclusions and heterofullerenes (EEHFs). The phenomenology of fullerene compounds is complex. In addition to fullerene formation in grain shattering, fullerene formation from fully dehydrogenated PAHs in diffuse interstellar clouds could perhaps transform a significant percentage of the tail of low-mass PAH distribution into fullerenes including EEHFs. But many uncertain processes make it extremely difficult to assess their expected abundance, composition and size distribution, except for the substantial abundance measured for C60+. EEHFs share many properties with pure fullerenes, such as C60, as regards stability, formation/destruction and chemical processes, as well as many basic spectral features. Because DIBs are ubiquitous in all lines of sight in the ISM, we address several questions about the interstellar importance of various EEHFs, especially as possible carriers of diffuse interstellar bands. Specifically, we discuss basic interstellar properties and the likely contributions of fullerenes of various sizes and their charged counterparts such as C60+, and then in turn: 1) metallofullerenes; 2) heterofullerenes; 3) fulleranes; 4) fullerene-PAH compounds; 5) H2@C60. From this reassessment of the literature and from combining it with known DIB line identifications, we conclude that the general landscape of interstellar fullerene compounds is probably much richer than heretofore realized

  6. Diffuse interstellar absorption bands

    Institute of Scientific and Technical Information of China (English)

    XIANG FuYuan; LIANG ShunLin; LI AiGen

    2009-01-01

    The diffuse interstellar bands (DIBs) are a large number of absorption bands that are superposed on the interstellar extinction curve and are of interstellar origin. Since the discovery of the first two DIBs in the 1920s, the exact nature of DIBs still remains unclear. This article reviews the history of the detec-tions of DIBs in the Milky Way and external galaxies, the major observational characteristics of DIBs, the correlations or anti-correlations among DIBs or between DIBs and other interstellar features (e.g. the prominent 2175 Angstrom extinction bump and the far-ultraviolet extinction rise), and the proposed candidate carriers. Whether they are also present in circumstellar environments is also discussed.

  7. Diffuse interstellar absorption bands

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The diffuse interstellar bands(DIBs) are a large number of absorption bands that are superposed on the interstellar extinction curve and are of interstellar origin. Since the discovery of the first two DIBs in the 1920s,the exact nature of DIBs still remains unclear. This article reviews the history of the detections of DIBs in the Milky Way and external galaxies,the major observational characteristics of DIBs,the correlations or anti-correlations among DIBs or between DIBs and other interstellar features(e.g. the prominent 2175 Angstrom extinction bump and the far-ultraviolet extinction rise),and the proposed candidate carriers. Whether they are also present in circumstellar environments is also discussed.

  8. The galactic interstellar medium

    CERN Document Server

    Burton, WB; Genzel, R

    1992-01-01

    This volume contains the papers of three extended lectures addressing advanced topics in astronomy and astrophysics. The topics discussed include the most recent observational data on interstellar matter outside our galaxy and the physics and chemistry of molecular clouds.

  9. Interstellar and circumstellar fullerenes

    OpenAIRE

    Bernard-Salas, J.; Cami, J.; Jones, A. P.; E. Peeters; Micelotta, E. R.; Otsuka, M; Sloan, G. C.; Kemper, F.; Groenewegen, M.

    2014-01-01

    Fullerenes are a particularly stable class of carbon molecules in the shape of a hollow sphere or ellipsoid that might be formed in the outflows of carbon stars. Once injected into the interstellar medium (ISM), these stable species survive and are thus likely to be widespread in the Galaxy where they contribute to interstellar extinction, heating processes, and complex chemical reactions. In recent years, the fullerene species C60 (and to a lesser extent C70) have been detected in a wide var...

  10. Anticipation of Personal Genomics Data Enhances Interest and Learning Environment in Genomics and Molecular Biology Undergraduate Courses.

    Science.gov (United States)

    Weber, K Scott; Jensen, Jamie L; Johnson, Steven M

    2015-01-01

    An important discussion at colleges is centered on determining more effective models for teaching undergraduates. As personalized genomics has become more common, we hypothesized it could be a valuable tool to make science education more hands on, personal, and engaging for college undergraduates. We hypothesized that providing students with personal genome testing kits would enhance the learning experience of students in two undergraduate courses at Brigham Young University: Advanced Molecular Biology and Genomics. These courses have an emphasis on personal genomics the last two weeks of the semester. Students taking these courses were given the option to receive personal genomics kits in 2014, whereas in 2015 they were not. Students sent their personal genomics samples in on their own and received the data after the course ended. We surveyed students in these courses before and after the two-week emphasis on personal genomics to collect data on whether anticipation of obtaining their own personal genomic data impacted undergraduate student learning. We also tested to see if specific personal genomic assignments improved the learning experience by analyzing the data from the undergraduate students who completed both the pre- and post-course surveys. Anticipation of personal genomic data significantly enhanced student interest and the learning environment based on the time students spent researching personal genomic material and their self-reported attitudes compared to those who did not anticipate getting their own data. Personal genomics homework assignments significantly enhanced the undergraduate student interest and learning based on the same criteria and a personal genomics quiz. We found that for the undergraduate students in both molecular biology and genomics courses, incorporation of personal genomic testing can be an effective educational tool in undergraduate science education. PMID:26241308

  11. Interstellar and circumstellar fullerenes

    CERN Document Server

    Bernard-Salas, J; Jones, A P; Peeters, E; Micelotta, E R; Otsuka, M; Sloan, G C; Kemper, F; Groenewegen, M

    2014-01-01

    Fullerenes are a particularly stable class of carbon molecules in the shape of a hollow sphere or ellipsoid that might be formed in the outflows of carbon stars. Once injected into the interstellar medium (ISM), these stable species survive and are thus likely to be widespread in the Galaxy where they contribute to interstellar extinction, heating processes, and complex chemical reactions. In recent years, the fullerene species C60 (and to a lesser extent C70) have been detected in a wide variety of circumstellar and interstellar environments showing that when conditions are favourable, fullerenes are formed efficiently. Fullerenes are the first and only large aromatics firmly identified in space. The detection of fullerenes is thus crucial to provide clues as to the key chemical pathways leading to the formation of large complex organic molecules in space, and offers a great diagnostic tool to describe the environment in which they reside. Since fullerenes share many physical properties with PAHs, understand...

  12. Interest, Attitudes and Self-Efficacy Beliefs Explaining Upper-Secondary School Students' Orientation Towards Biology-Related Careers

    Science.gov (United States)

    Uitto, Anna

    2014-01-01

    The aim of the study was to discover the contribution of students' interest in school biology, as well as their self-efficacy and attitudes towards different science subjects and mathematics when explaining students' orientation towards biology-related careers at upper-secondary school. The data of 321 K-11 students (49% women) were…

  13. SOME METHODOLOGICAL TECHNIQUES OF ACTIVATION OF THE COGNITIVE INTEREST IN BIOLOGY CLASSES OF STUDENTS OF THE MEDICAL TECHNICAL PROFILE

    Directory of Open Access Journals (Sweden)

    V. N. Baranov

    2014-01-01

    Full Text Available Research objective. Identification of possibility of the modern pedagogical receptions in development of cognitive interest in students of a medico-technical profile at biology lessons.Research techniques. The theoretical: the analysis of psychology and pedagogical and methodical literature on a research problem, the teoretiko-methodical analysis of a studied problem, development of methodical bases of its realization in biology training; approach to carrying out a lecture and practical training in biology with bionics elements. The empirical – supervision, conversation, questioning, manufacture of multimedia presentations for carrying out an interactive lecture and practical training and the analysis of results of work with them.Material and methods. Students of the 1st course being trained in the direction of preparation 201000.62 – “Biotechnical systems and technologies” (bachelor degree.Results. It is possible to carry the following to the positive moments: within interactive lecture there is a tendency to motivation change to educational activity with external on the internal; the pedagogical receptions based on interactivity, allow to keep attention of audience easier; using problem situations, it was possible to involve pupils in educational activity selectively; when using considered approach process of communication with audience gains more natural character, approaching developing relationship in teacher student system to cooperation.It is possible to carry the next moments to the negative: process of teaching becomes more intense, deman­ding from the teacher of larger concentration on a training material, and constant readiness and ability to conduct discussion; the interactive format of giving of a training material sometimes possesses smaller informational characteristics; students are not always ready to such format of educational activity that is often shown in inability to carry on the free dialogue, inability to

  14. Overview of the interstellar medium

    International Nuclear Information System (INIS)

    Establishing that the interstellar pressure is higher than usually realized and that the magnetic component is probably dominant, the author proposes a drastic revision for understanding the interstellar landscape

  15. Prebiotic molecules and interstellar grain clumps

    International Nuclear Information System (INIS)

    It is stated that interstellar molecules detected by radioastronomical techniques in galactic clouds cover a wide range of types and complexities. Amongst the heaviest recently discovered is cyanodiacetylene. There have also been earlier detections of precursors to the simplest amino-acid, glycine and probably detections of polyoxymethylene polymers and co-polymers. A possible identification of organic molecules of even greater complexity is here discussed, together with implications for the commencement of biological activity. The large departures from thermodynamic equilibrium in the interstellar medium and the co-existence of solid grains, molecules, radicals, ions, and uv photons provide conditions that are ideal for production of 'exotic' molecular species. The effect of clumping of dust grains is discussed. The possible spectral identification of highly complex organic species in the interstellar medium is also discussed and reference is made to a property common to a wide class of such molecules, that is, an absorption band centered at 2,200 A. It is tempting to identify this feature with the well-known 2,200 A band of the interstellar extinction curve. It is thought that it may be tentatively concluded that the data so far obtained could be interpreted as independent new chemical evidence of the existence of composite grain clumps in the interstellar medium and in carbonaceous chondrites, and that these grain clumps probably include a significant mass fraction of highly complex organic pre-biotic molecules that could have led to the start and dispersal of biological activity on the Earth and elsewhere in the Galaxy. Processes of natural selection probably also played an important part, particularly in the production of self-replicable peptide chains. The problem of protection of pre-biotic material against external disruptive agencies, such as u/v light, is also discussed. (U.K.)

  16. Prostate radiation in non-metastatic castrate refractory prostate cancer provides an interesting insight into biology of prostate cancer

    Directory of Open Access Journals (Sweden)

    Pascoe Abigail C

    2012-03-01

    Full Text Available Abstract Background The natural history of non-metastatic castrate refractory prostate cancer is unknown and treatment options are limited. We present a retrospective review of 13 patients with locally advanced or high risk prostate cancer, initially treated with hormone monotherapy and then treated with prostate radiation after becoming castration refractory. Findings Median PSA response following prostate radiation was 67.4%. Median time to biochemical progression following radiotherapy was 15 months and to detection of metastatic disease was 18.5 months. Median survival from castration resistance (to date of death or November 2011 was 60 months, with median survival from RT 42 months. Conclusion Prostate radiation appears to be beneficial even in patients with potential micrometastatic disease, which supports the hypothesis that the primary tumour is important in the progression of prostate cancer. These results are an interesting addition to the literature on the biology of prostate cancer especially as this data is unlikely to be available in the future due to combined prostate radiation and androgen deprivation therapy now being the standard of care.

  17. Interstellar Carbon Chains: Is Thermodynamics the Key?

    Science.gov (United States)

    Etim, Emmanuel; Chakrabarti, Sandip Kumar; Das, Ankan; Gorai, Prasanta; Arunan, Elangannan

    2016-07-01

    In an effort to further our interest in understanding basic chemistry of interstellar molecules, we carry out here an extensive investigation of the stabilities of interstellar carbon chains; C_n, H_2C_n, HC_nN and C_nX (X=N, O, Si, S, H, P, H^-, N^-). These sets of molecules account for about 20% of all the known interstellar and circumstellar molecules. Their high abundances therefore demand a serious attention. High level ab initio quantum chemical simulations are employed to accurately estimate enthalpy of formation, chemical reactivity indices; global hardness and softness; and other chemical parameters of these molecules. Chemical modeling of the abundances of these molecular species has also been performed. Of the 89 molecules considered from these groups, 47 have been astronomically observed, these observed molecules are found to be more stable with respect to other members of the group. Of the 47 observed molecules, 60% are odd number carbon chains. The reason for the high abundance of odd numbered carbon chains can easily be seen from the fact that they are more stable than the corresponding even number carbon chains. This further confirms the dominance of thermodynamics in interstellar formation processes as described in the Energy, Stability and Abundance (ESA) relationship. The next possible carbon chain molecule for astronomical observation in each group is proposed. The effect of kinetics in the formation processes of these carbon chains is shown to be largely dominated by thermodynamics.

  18. Visualizing Interstellar's Wormhole

    OpenAIRE

    James, Oliver; von Tunzelmann, Eugenie; Franklin, Paul; Thorne, Kip S.

    2015-01-01

    Christopher Nolan's science fiction movie Interstellar offers a variety of opportunities for students in elementary courses on general relativity theory. This paper describes such opportunities, including: (i) At the motivational level, the manner in which elementary relativity concepts underlie the wormhole visualizations seen in the movie. (ii) At the briefest computational level, instructive calculations with simple but intriguing wormhole metrics, including, e.g., constructing embedding d...

  19. The Ingenious Theory of Interstellar Trade

    Science.gov (United States)

    Radhakrishnan, Arun; Ganapathy, Rohan M.

    This paper extends interplanetary trade theory to an interstellar setting. It is chiefly concerned with the following question: How should interest charges on goods in transit be computed when the goods travel at speeds close to the actual speed of light? This is a problem because the time taken in transit will appear less to an observer travelling with the goods than to a stationary observer. An innovative and ingenious solution is derived from the economic theory, and two useless but TRUE theorems are proved. The interstellar trade would happen in such a way that two time frames must be considered namely that of the stationary observer whose time runs faster compared to the time frame of the observer in transit The interest in a given trade is purely based on the time taken for the debtor to pay the amount, once the goods have been delivered by the seller. But, in case of interstellar trade, the interest to be calculated in between two time frames would lead to the question of which time frame to be considered and moreover, the time taken for the goods to reach the destination is signicantly prolonged compared to the interplanetary trade, which means, even the slightest variations in the interest rate would be magnied. Apart from this, various new factors arise while calculating the interest. The factors include the time value of money, and the risk of variation in demand for goods, the risk of interspace accidents causing loss of the goods and the rate of perish-ability in case of organic goods. The first two factors considered, for which the time frame of the stationary observer is considered and the factors such as the risk of accidents and the rate of perish-ability of the goods are considered based on the time frame of the observer in transit's point of view. The reasons for such considerations and various assumptions on these concepts are dealt in this paper. The theorems that are formulated in this paper would provide the interstellar traders a basic

  20. Starry Messages: Searching for Signatures of Interstellar Archaeology

    CERN Document Server

    Carrigan, Richard A

    2010-01-01

    Searching for signatures of cosmic-scale archaeological artifacts such as Dyson spheres or Kardashev civilizations is an interesting alternative to conventional SETI. Uncovering such an artifact does not require the intentional transmission of a signal on the part of the original civilization. This type of search is called interstellar archaeology or sometimes cosmic archaeology. The detection of intelligence elsewhere in the Universe with interstellar archaeology or SETI would have broad implications for science. For example, the constraints of the anthropic principle would have to be loosened if a different type of intelligence was discovered elsewhere. A variety of interstellar archaeology signatures are discussed including non-natural planetary atmospheric constituents, stellar doping with isotopes of nuclear wastes, Dyson spheres, as well as signatures of stellar and galactic-scale engineering. The concept of a Fermi bubble due to interstellar migration is introduced in the discussion of galactic signatu...

  1. Galactic civilizations: Population dynamics and interstellar diffusion

    Science.gov (United States)

    Newman, W. I.; Sagan, C.

    1978-01-01

    The interstellar diffusion of galactic civilizations is reexamined by potential theory; both numerical and analytical solutions are derived for the nonlinear partial differential equations which specify a range of relevant models, drawn from blast wave physics, soil science, and, especially, population biology. An essential feature of these models is that, for all civilizations, population growth must be limited by the carrying capacity of the environment. Dispersal is fundamentally a diffusion process; a density-dependent diffusivity describes interstellar emigration. Two models are considered: the first describing zero population growth (ZPG), and the second which also includes local growth and saturation of a planetary population, and for which an asymptotic traveling wave solution is found.

  2. Interstellar C60+

    CERN Document Server

    Berne, Olivier; Joblin, Christine

    2012-01-01

    Buckminsterfullerene (C60) was recently detected through its infrared emission bands in the interstellar medium (ISM), including in the proximity of massive stars, where physical conditions could favor the formation of the cationic form, C60+. In addition, C60+ was proposed as the carrier of two diffuse interstellar bands in the near-IR, although a firm identification still awaits for gas-phase spectroscopic data. We examined in details the Spitzer IRS spectra of the NGC 7023 reflection nebula, at a position close (7.5") to the illuminating B star HD 200775, and found four previously unreported bands at 6.4, 7.1, 8.2 and 10.5 \\mu m in addition to the classical bands attributed to Polycylic Aromatic Hydrocarbons (PAHs) and neutral C60. These 4 bands are observed only in this region of the nebula, while C60 emission is still present slightly further away from the star, and PAH emission even further away. Based on this observation, on theoretical calculations we perform, and on laboratory studies, we attribute t...

  3. Visualizing Interstellar's Wormhole

    Science.gov (United States)

    James, Oliver; von Tunzelmann, Eugénie; Franklin, Paul; Thorne, Kip S.

    2015-06-01

    Christopher Nolan's science fiction movie Interstellar offers a variety of opportunities for students in elementary courses on general relativity theory. This paper describes such opportunities, including: (i) At the motivational level, the manner in which elementary relativity concepts underlie the wormhole visualizations seen in the movie; (ii) At the briefest computational level, instructive calculations with simple but intriguing wormhole metrics, including, e.g., constructing embedding diagrams for the three-parameter wormhole that was used by our visual effects team and Christopher Nolan in scoping out possible wormhole geometries for the movie; (iii) Combining the proper reference frame of a camera with solutions of the geodesic equation, to construct a light-ray-tracing map backward in time from a camera's local sky to a wormhole's two celestial spheres; (iv) Implementing this map, for example, in Mathematica, Maple or Matlab, and using that implementation to construct images of what a camera sees when near or inside a wormhole; (v) With the student's implementation, exploring how the wormhole's three parameters influence what the camera sees—which is precisely how Christopher Nolan, using our implementation, chose the parameters for Interstellar's wormhole; (vi) Using the student's implementation, exploring the wormhole's Einstein ring and particularly the peculiar motions of star images near the ring, and exploring what it looks like to travel through a wormhole.

  4. Hot interstellar medium

    International Nuclear Information System (INIS)

    In view of that the diffuse component of soft X-rays is emitted mainly by extended supernova remnants and the hot interstellar medium produced thereby, the following three points are discussed. (1.) In the early stage of supernova remnants expanding in low density media, neither the equipartition of energy between electrons and ions nor the ionization equilibrium holds. The shock structure is modified by the pressure of hot plasma. X-ray features of the North Polar Spur are interpreted by taking these points into account. (2.) Several compilations of X-ray line emission are compared. Those by Kato and by Raymond and Smith are different in the equilibrium ion abundances and the collisional excitation rates for some important lines. The origins of differences are shown for some examples. It is demonstrated how the difference affects astrophysical interpretations. (3.) The solar system is surrounded by a hot, tenuous interstellar medium extended in the direction of 1 -- 1500 in the northern hemisphere. In other directions X-rays emitted farther than absorbing clouds are appreciable. (author)

  5. Interstellar Atomic Abundances

    CERN Document Server

    Jenkins, E B

    2003-01-01

    A broad array of interstellar absorption features that appear in the ultraviolet spectra of bright sources allows us to measure the abundances and ionization states of many important heavy elements that exist as free atoms in the interstellar medium. By comparing these abundances with reference values in the Sun, we find that some elements have abundances relative to hydrogen that are approximately consistent with their respective solar values, while others are depleted by factors that range from a few up to around 1000. These depletions are caused by the atoms condensing into solid form onto dust grains. Their strengths are governed by the volatility of compounds that are produced, together with the densities and velocities of the gas clouds. We may characterize the depletion trends in terms of a limited set of parameters; ones derived here are based on measurements of 15 elements toward 144 stars with known values of N(H I) and N(H2). In turn, these parameters may be applied to studies of the production, de...

  6. Starry messages: Searching for signatures of interstellar archaeology

    International Nuclear Information System (INIS)

    Searching for signatures of cosmic-scale archaeological artifacts such as Dyson spheres or Kardashev civilizations is an interesting alternative to conventional SETI. Uncovering such an artifact does not require the intentional transmission of a signal on the part of the original civilization. This type of search is called interstellar archaeology or sometimes cosmic archaeology. The detection of intelligence elsewhere in the Universe with interstellar archaeology or SETI would have broad implications for science. For example, the constraints of the anthropic principle would have to be loosened if a different type of intelligence was discovered elsewhere. A variety of interstellar archaeology signatures are discussed including non-natural planetary atmospheric constituents, stellar doping with isotopes of nuclear wastes, Dyson spheres, as well as signatures of stellar and galactic-scale engineering. The concept of a Fermi bubble due to interstellar migration is introduced in the discussion of galactic signatures. These potential interstellar archaeological signatures are classified using the Kardashev scale. A modified Drake equation is used to evaluate the relative challenges of finding various sources. With few exceptions interstellar archaeological signatures are clouded and beyond current technological capabilities. However SETI for so-called cultural transmissions and planetary atmosphere signatures are within reach.

  7. Starry messages: Searching for signatures of interstellar archaeology

    Energy Technology Data Exchange (ETDEWEB)

    Carrigan, Richard A., Jr.; /Fermilab

    2009-12-01

    Searching for signatures of cosmic-scale archaeological artifacts such as Dyson spheres or Kardashev civilizations is an interesting alternative to conventional SETI. Uncovering such an artifact does not require the intentional transmission of a signal on the part of the original civilization. This type of search is called interstellar archaeology or sometimes cosmic archaeology. The detection of intelligence elsewhere in the Universe with interstellar archaeology or SETI would have broad implications for science. For example, the constraints of the anthropic principle would have to be loosened if a different type of intelligence was discovered elsewhere. A variety of interstellar archaeology signatures are discussed including non-natural planetary atmospheric constituents, stellar doping with isotopes of nuclear wastes, Dyson spheres, as well as signatures of stellar and galactic-scale engineering. The concept of a Fermi bubble due to interstellar migration is introduced in the discussion of galactic signatures. These potential interstellar archaeological signatures are classified using the Kardashev scale. A modified Drake equation is used to evaluate the relative challenges of finding various sources. With few exceptions interstellar archaeological signatures are clouded and beyond current technological capabilities. However SETI for so-called cultural transmissions and planetary atmosphere signatures are within reach.

  8. Raising Levels of Student Interest in Less Popular Areas of the Biology Curriculum: Can Teacher CPD Help?

    Science.gov (United States)

    Goodger, Bev

    2013-01-01

    An opportunity for teachers to join 80 outstanding biological sciences undergraduates in a series of practical sessions and lectures at the 2010 Gatsby Plant Science Summer School has inspired the development of teaching and learning resources for use in schools. Plant scientists have a crucial role to play in society and it is hoped that the…

  9. 学生生物学习兴趣的激发之我见%Personal View on the Motivation of Students' Biology Learning Interest

    Institute of Scientific and Technical Information of China (English)

    孔令斌

    2011-01-01

    This paper discusses how to motivate students' learning interest in biology teaching starting off from "people are not the grass and trees, who can be merciless?"%本文从“人非草木,孰能无情”引入,对生物教学中如何激发学生的学习兴趣进行了探讨。

  10. Visualizing Interstellar's Wormhole

    CERN Document Server

    James, Oliver; Franklin, Paul; Thorne, Kip S

    2015-01-01

    Christopher Nolan's science fiction movie Interstellar offers a variety of opportunities for students in elementary courses on general relativity theory. This paper describes such opportunities, including: (i) At the motivational level, the manner in which elementary relativity concepts underlie the wormhole visualizations seen in the movie. (ii) At the briefest computational level, instructive calculations with simple but intriguing wormhole metrics, including, e.g., constructing embedding diagrams for the three-parameter wormhole that was used by our visual effects team and Christopher Nolan in scoping out possible wormhole geometries for the movie. (iii) Combining the proper reference frame of a camera with solutions of the geodesic equation, to construct a light-ray-tracing map backward in time from a camera's local sky to a wormhole's two celestial spheres. (iv) Implementing this map, for example in Mathematica, Maple or Matlab, and using that implementation to construct images of what a camera sees when...

  11. Enantiospecific C(sp3)-H activation catalyzed by ruthenium nanoparticles : application to isotopic labeling of molecules of biological interest.

    OpenAIRE

    Taglang, Céline

    2015-01-01

    Isotopic labeling with deuterium and tritium is extensively used in chemistry, biology and pharmaceutical research.Numerous methods of labeling by isotopic exchange allow high isotopic enrichments but generally require harsh conditions (high temperatures, acidity). As a consequence, a general, regioselective and smooth labeling method that might be applicable to a wide diversity of substrates remains to develop. In the first part of this thesis, we demonstrated that the use of ruthenium nanop...

  12. Four Interstellar Dust Candidates from the Stardust Interstellar Dust Collector

    Science.gov (United States)

    Westphal, A. J.; Allen, C.; Bajt, S.; Bechtel, H. A.; Borg, J.; Brenker, F.; Bridges, J.; Brownlee, D. E.; Burchell, M.; Burghammer, M.; Butterworth, A. L.; Cloetens, P.; Davis, A. M.; Floss, C.; Flynn, G. J.; Fougeray, P.; Frank, D.; Gainsforth, Z.; Grun, E.; Heck, P. R.; Jillier, J. K.; Hoppe, P.; Howard, L.; Hudson, B.; Huss, G. R.

    2011-01-01

    In January 2006, the Stardust sample return capsule returned to Earth bearing the first solid samples from a primitive solar system body, Comet 81P/Wild2, and a collector dedicated to the capture and return of contemporary interstellar dust. Both collectors were approx. 0.1 sq m in area and were composed of aerogel tiles (85% of the collecting area) and aluminum foils. The Stardust Interstellar Dust Collector (SIDC) was exposed to the interstellar dust stream for a total exposure factor of 20 sq m/day. The Stardust Interstellar Preliminary Examination (ISPE) is a consortium-based project to characterize the collection using nondestructive techniques. The goals and restrictions of the ISPE are described . A summary of analytical techniques is described.

  13. Quantification of ultraviolet photon emission from interaction of charged particles in materials of interest in radiation biology research

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Syed Bilal, E-mail: ahmadsb@mcmaster.ca [Department of Medical Physics and Applied Radiation Sciences, University of McMaster, Hamilton, ON (Canada); Department of Physics and Applied Mathematics, Pakistan Institute of Engineering and Applied Sciences, Islamabad (Pakistan); McNeill, Fiona E., E-mail: fmcneill@mcmaster.ca [Department of Medical Physics and Applied Radiation Sciences, University of McMaster, Hamilton, ON (Canada); Prestwich, William V., E-mail: prestwic@mcmaster.ca [Department of Medical Physics and Applied Radiation Sciences, University of McMaster, Hamilton, ON (Canada); Byun, Soo Hyun, E-mail: soohyun@mcmaster.ca [Department of Medical Physics and Applied Radiation Sciences, University of McMaster, Hamilton, ON (Canada); Seymour, Colin, E-mail: seymouc@mcmaster.ca [Department of Medical Physics and Applied Radiation Sciences, University of McMaster, Hamilton, ON (Canada); Mothersill, Carmel E., E-mail: mothers@mcmaster.ca [Department of Medical Physics and Applied Radiation Sciences, University of McMaster, Hamilton, ON (Canada)

    2014-01-15

    In radiation biology experiments often cells are irradiated using charged particles with the intention that only a specified number of cells are hit by the primary ion track. However, in doing so several other materials such as the cell container and the growth media etc. are also irradiated, and UV radiation emitted from these materials can potentially interact with the cells. We have hypothesized that some “bystander effects” that are thought to be chemically mediated, may be, in fact, a physical effect, where UV is interacting with non-targeted cells. Based upon our hypothesis we quantified the emission of UV from Polypropylene, Mylar, Teflon, and Cellophane which are all commonly used materials in radiation biology experiments. Additionally we measured the NIST standard materials of Oyster tissue and Citrus leaves as these powdered materials are derived from living cells. Protons accelerated up to an energy of 2.2 MeV, in a 3 MV Van de Graff accelerator, were used for irradiation. Beam current was kept to 10 nA, which corresponds to a proton fluence rate of 2.7 × 10{sup 10} protons mm{sup −2} s{sup −1}. All the materials were found to emit light at UV frequencies and intensities that were significant enough to conduct a further investigation for their biological consequences. Mylar and polypropylene are commonly used in radiation induced bystander effect studies and are considered to be non-fluorescent. However our study showed that this is not the case. Significant luminescence observed from the irradiated NIST standard reference materials for Oyster tissue and Citrus leaves verified that the luminescence emission is not restricted only to the polymeric materials that are used to contain cells. It can also occur from ion interactions within the cells as well.

  14. Neocryptolepine: A Promising Indoloisoquinoline Alkaloid with Interesting Biological Activity. Evaluation of the Drug and its Most Relevant Analogs.

    Science.gov (United States)

    Larghi, Enrique L; Bracca, Andrea B J; Arroyo Aguilar, Abel A; Heredia, Daniel A; Pergomet, Jorgelina L; Simonetti, Sebastian O; Kaufman, Teodoro S

    2015-01-01

    Plants are one of the most important resources for the discovery of new drugs. The potential of natural compounds as new drug leads is clearly illustrated by the discovery and development of many modern medicines. This is an encouraging factor that drives natural products research in the vegetable kingdom. Neocryptolepine is a tetracyclic nitrogen heterocycle isolated from the African climber Cryptolepis sanguinolenta, which is widely used in traditional African medicine in many countries of Central and West Africa. The natural product is one of the representative examples of the small family of indolo[2,3-b]quinoline alkaloids, being endowed of multiple biological activities, including DNA-binding and inhibition of the enzyme topoisomerase II. It is also cytotoxic, antibacterial, antifungal and molluscicidal, also displaying antiprotozoal activity, particularly as antitrypanosomal, antileishmanial, antischistosomal and antiplasmodial. Some of these activities have been related to the product's ability to bind to DNA and to inhibit topoisomerase II; however, the exact mechanisms behind all of the observed bioactivities have not been comprehensively clarified. Major research activities regarding neocryptolepine have been focused into two seemingly opposite fields, related to its cytotoxic and antimalarial properties. Optimization of the natural product as a cytotoxic agent implied improvements in its bioavailability and activity, while the need of non-cytotoxic compounds guided the design and optimization of antimalarial agents. Therefore, the aim of the present article is to systematically review the current knowledge about the diversity of the biological activities related to neocryptolepine, its analogs and derivatives. PMID:25915612

  15. The human heart and the circulatory system as an interesting interdisciplinary topic in lessons of physics and biology

    Science.gov (United States)

    Volná, M.; Látal, F.; Kubínek, R.; Richterek, L.

    2014-01-01

    Many topics which are closely related can be found in the national curriculum of the Czech Republic for physics and biology. One of them is the heart and the circulatory system in the human body. This topic was examined cross curriculum, a teaching module was created and the topic was chosen for our research. The task was to determine if the students of bachelor study are aware of connections between physics and biology within this topic and whether we can help them effectively to describe the corresponding physics phenomena in the human body connected, for example, with a heart attack or with the measurement of blood pressure. In this paper, the heart and the circulatory system are presented as suitable topics for an interdisciplinary teaching module which includes both theoretical and experimental parts. The module was evaluated by a group of first-year undergraduate students of physics at the Faculty of Science, Palacký University. The acquired knowledge was compared with another control group through a test. The highest efficiency of the module was evaluated on the basis of questions that covered the calculation problems.

  16. Turbulence in the Interstellar Medium

    CERN Document Server

    Falceta-Goncalves, D; Falgarone, E; Chian, A C -L

    2014-01-01

    Turbulence is ubiquitous in the insterstellar medium and plays a major role in several processes such as the formation of dense structures and stars, the stability of molecular clouds, the amplification of magnetic fields, and the re-acceleration and diffusion of cosmic rays. Despite its importance, interstellar turbulence, alike turbulence in general, is far from being fully understood. In this review we present the basics of turbulence physics, focusing on the statistics of its structure and energy cascade. We explore the physics of compressible and incompressible turbulent flows, as well as magnetized cases. The most relevant observational techniques that provide quantitative insights of interstellar turbulence are also presented. We also discuss the main difficulties in developing a three-dimensional view of interstellar turbulence from these observations. Finally, we briefly present what could be the the main sources of turbulence in the interstellar medium.

  17. Searches for interstellar molecules of potential prebiotic importance

    NARCIS (Netherlands)

    Y.-J. Kuan; S.B. Charnley; H.-C. Huang; Z. Kisiel; P. Ehrenfreund; W.-L. Tseng; C.-H. Yan

    2004-01-01

    Interstellar chemistry leads to the formation of many prebiologically important molecules and is therefore of the fundamental interest to Astrobiology. Many organics can be produced in the gas phase where they can be detected. Molecules formed by reactions on the surfaces of dust grains are also bes

  18. The Interstellar Conspiracy

    Science.gov (United States)

    Johnson, Les; Matloff, Gregory L.

    2005-01-01

    If we were designing a human-carrying starship that could be launched in the not-too-distant future, it would almost certainly not use a warp drive to instantaneously bounce around the universe, as is done in Isaac Asimov's classic Foundation series or in episodes of Star Trek or Star Wars. Sadly, those starships that seem to be within technological reach could not even travel at high relativistic speeds, as does the interstellar ramjet in Poul Anderson's Tau Zero. Warp-speeds seem to be well outside the realm of currently understood physical law; proton-fusing ramjets may never be technologically feasible. Perhaps fortunately in our terrorist-plagued world, the economics of antimatter may never be attractive for large-scale starship propulsion. But interstellar travel will be possible within a few centuries, although it will certainly not be as fast as we might prefer. If humans learn how to hibernate, perhaps we will sleep our way to the stars, as do the crew in A. E. van Vogt's Far Centaurus. However, as discussed in a landmark paper in The Journal of the British Interplanetary Society, the most feasible approach to transporting a small human population to the planets (if any) of Alpha Centauri is the worldship. Such craft have often been featured in science fiction. See for example Arthur C. Clarke's Rendezvous with Rama, and Robert A. Heinlein's Orphans of the Sky. Worldships are essentially mobile versions of the O Neill free-space habitats. Constructed mostly from lunar and/or asteroidal materials, these solar-powered, multi-kilometer-dimension structures could house 10,000 to 100,000 humans in Earth-approximating environments. Artificial gravity would be provided by habitat rotation, and cosmic ray shielding would be provided by passive methods, such as habitat atmosphere and mass shielding, or magnetic fields. A late 21st century space-habitat venture might support itself economically by constructing large solar-powered satellites to beam energy back to

  19. Interstellar molecular clouds

    Science.gov (United States)

    Bally, J.

    1986-04-01

    The physical properties of the molecular phase of the interstellar medium are studied with regard to star formation and the structure of the Galaxy. Most observations of molecular clouds are made with single-dish, high-surface precision radio telescopes, with the best resolution attainable at 0.2 to 1 arcmin; the smallest structures that can be resolved are of order 10 to the 17th cm in diameter. It is now believed that: (1) most of the mass of the Galaxy is in the form of giant molecular clouds; (2) the largest clouds and those responsible for most massive star formation are concentrated in spiral arms; (3) the molecular clouds are the sites of perpetual star formation, and are significant in the chemical evolution of the Galaxy; (4) giant molecular clouds determine the evolution of the kinematic properties of galactic disk stars; (5) the total gas content is diminishing with time; and (6) most clouds have supersonic internal motions and do not form stars on a free-fall time scale. It is concluded that though progress has been made, more advanced instruments are needed to inspect the processes operating within stellar nurseries and to study the distribution of the molecular clouds in more distant galaxies. Instruments presently under construction which are designed to meet these ends are presented.

  20. Self-consistent QM/MM methodologies for structural refinement of photosystem II and other macromolecules of biological interest

    Energy Technology Data Exchange (ETDEWEB)

    Batista, Enrique R [Los Alamos National Laboratory; Sproviero, Eduardo M [YALE UNIV; Newcomer, Michael [YALE UNIV; Gascon, Jose A [YALE UNIV; Batista, Victor S [YALE UNIV

    2008-01-01

    The combination of quantum mechanics and molecular mechanics (QM/MM) is one of the most promising approaches to study the structure, function, and properties of proteins and nucleic acids. However, there some instances in which the limitations of either the MM (lack of a proper electronic description) or QM (limited to a few number of atoms) methods prevent a proper description of the system. To address this issue, we review here our approach to fine-tune the structure of biological systems using post-QM/MM refinements. These protocols are based on spectroscopy data, and/or partitioning of the system to extend the QM description to a larger region of a protein. We illustrate these methodologies through applications to several biomolecules, which were pre-optimized at the QM/MM level and then further refined using postQM/MM refinement methodologies: mod(QM/MM), which refines the atomic charges of the residues included in the MM region accounting for polarization effects; mod(QM/MM)-opt that partition the MM region in smaller parts and optimizes each part in an iterative. self-consistent way, and the Polarized-Extended X-Ray Absorption Fine Structure (P-EXAFS) fitting procedure, which fine-tune the atomic coordinates to reproduce experimental polarized EXAFS spectra. The first two techniques were applied to the guanine quadruplex. while the P-EXAFS refinement was applied to the oxygen evolving complex of photosystem II.

  1. PASTORSHIP AND THE ROMANIANS’ ETNOGENESIS - VALACHIAN CORKSCREW HORNS SHEEP BREED (“RATSCA” - AN INTERESTING BIOLOGICAL AND HISTORICAL DOCUMENT

    Directory of Open Access Journals (Sweden)

    Condrea DRAGANESCU

    2013-12-01

    Full Text Available The Corkscrew horns Valachian sheep it is a breed from the Early Egyptian (Ovis paleoegiptica phileic group, located in Serbia, Montenegro, Panonia, and Romanian border with Serbia. The tribe was named by Buffon (1780, Darwin (1865 Valachian, by Serbs Corkscrew Horns Valachian (Valaska vitorogta, by Hungarian Racka (=Serbian, by Linnaeus O.a.strpsiceros. The translation of strepsiceros into German=Zackel (Nathusius 1890, produced a confusion with the Valachian philetic group descending from the Thrakian philetic group. To avoid confusion, we proposed (1994 to use for this philetic group the Serbian name Valachian Corkscrew Horns. It is a sedentary sheep, not adapted to transhumance and to big flocks, not adapted to support wintering in open field, even to stay in the rain. Have a smaller weight of fine fibbers in the mixed wool, it seem black colour recessive, inverse than in Valachia (Tsurcana breeds. It is economically not competitive with others local and improved breed and it is in danger of extinction in Serbia and even Romania and well conserved in Hungary. It was considered as an historical document (Dunka 1984 and perhaps it is. Document the former existence of a Valachian tribe in this area, implicit the Valachian contribution to the ethno genesis of nations from this area. As an interesting genetic resource, but also for the aesthetic aspect of his horns and for some cultural reasons it deserves to have a good genetic conservation program.

  2. Photochemistry and astrochemistry: photochemical pathways to interstellar complex organic molecules

    CERN Document Server

    Oberg, Karin I

    2016-01-01

    The interstellar medium is characterized by a rich and diverse chemistry. Many of its complex organic molecules are proposed to form through radical chemistry in icy grain mantles. Radicals form readily when interstellar ices (composed of water and other volatiles) are exposed to UV photons and other sources of dissociative radiation, and, if sufficiently mobile, the radicals can react to form larger, more complex molecules. The resulting complex organic molecules (COMs) accompany star and planet formation, and may eventually seed the origins of life on nascent planets. Experiments of increasing sophistication have demonstrated that known interstellar COMs as well as the prebiotically interesting amino acids can form through ice photochemistry. We review these experiments and discuss the qualitative and quantitative kinetic and mechanistic constraints they have provided. We finally compare the effects of UV radiation with those of three other potential sources of radical production and chemistry in interstell...

  3. How to design an interesting and efficient biology classroom%如何打造趣味高效的生物课堂

    Institute of Scientific and Technical Information of China (English)

    沈长远

    2013-01-01

    本文从生物课堂的趣味性和高效性分析了课堂氛围的重要性,之后从将引用故事、角色扮演、身体语言、语言艺术四个方面分析了如何打造趣味高效的生物课堂。%This paper first analyzed the importance of the learning atmosphere in the classroom from the interesting and efficiency. Then, Analyze how to design an interesting and efficient biology classroom from four respects consist of citing stories, role-play, body language and linguistic art.

  4. Interstellar Sweat Equity

    Science.gov (United States)

    Cohen, M. H.; Becker, R. E.; O'Donnell, D. J.; Brody, A. R.

    So, you have just launched aboard the Starship, headed to an exoplanet light years from Earth. You will spend the rest of your natural life on this journey in the expectation and hope that your grandchildren will arrive safely, land, and build a new settlement. You will need to govern the community onboard the Starship. This system of governance must meet unique requirements for participation, representation, and decision-making. On a spaceship that can fly and operate by itself, what will the crewmembers do for their generations in transit? Certainly, they will train and train again to practice the skills they will need upon arrival at a new world. However, this vicarious practice neither suffices to prepare the future pioneers for their destiny at a new star nor will it provide them with the satisfaction in their own work. To hone the crewmembers' inventive and technical skills, to challenge and prepare them for pioneering, the crew would build and expand the interstellar ship in transit. This transstellar ``sweat equity'' gives a stake in the enterprise to all the people, providing meaningful and useful activity to the new generations of crewmembers. They build all the new segments of the vessel from raw materials - including atmosphere - stored on board. Construction of new pressure shell modules would be one option, but they also reconstruct or fill-in existing pressurized volumes. The crew makes new life support system components and develops new agricultural modules in anticipation of their future needs. Upon arrival at the new star or planet, the crew shall apply these robustly developed skills and self-sufficient spirit to their new home.

  5. How to arouse the interests of students in learning plant biology%如何激发学生学习植物生物学的兴趣

    Institute of Scientific and Technical Information of China (English)

    郑敏; 葛继稳; 侯新东

    2012-01-01

    植物生物学是生物科学的主要专业基础课之一,内容繁多,学生容易感到枯燥乏味.从灵活运用教学方法和网络资源、丰富实践教学形式、用成功的体验激发学生等方面出发,针对如何激发学生学习兴趣进行了植物生物学教学的初步改革和探讨.%Plant biology is one of the main basic courses of biological science, but students are easy to feel boring because of its various content. This article preliminarily proposes some teaching reforms to the question that how to stimulate students' interest in studying plant biology, such as flexible using of the teaching methods and network resources, diversified teaching practice, inspiring students through the successful experience and so on.

  6. Silicon chemistry in interstellar clouds

    Energy Technology Data Exchange (ETDEWEB)

    Langer, W.D.; Glassgold, A.E. (AT T Bell Laboratories, Murray Hill, NJ (USA) New York Univ., NY (USA))

    1990-03-01

    A new model of interstellar silicon chemistry is presented that explains the lack of SiO detections in cold clouds and contains an exponential temperature dependence for the SiO abundance. A key aspect of the model is the sensitivity of SiO production by neutral silicon reactions to density and temperature, which arises from the dependence of the rate coefficients on the population of the excited fine-structure levels of the silicon atom. As part of the explanation of the lack of SiO detections at low temperatures and densities, the model also emphasizes the small efficiencies of the production routes and the correspondingly long times needed to reach equilibrium. Measurements of the abundance of SiO, in conjunction with theory, can provide information on the physical properties of interstellar clouds such as the abundance of oxygen bearing molecules and the depletion of interstellar silicon. 38 refs.

  7. Interstellar Isotopes: Prospects with ALMA

    Science.gov (United States)

    Charnley Steven B.

    2010-01-01

    Cold molecular clouds are natural environments for the enrichment of interstellar molecules in the heavy isotopes of H, C, N and O. Anomalously fractionated isotopic material is found in many primitive Solar System objects, such as meteorites and comets, that may trace interstellar matter that was incorporated into the Solar Nebula without undergoing significant processing. Models of the fractionation chemistry of H, C, N and O in dense molecular clouds, particularly in cores where substantial freeze-out of molecules on to dust has occurred, make several predictions that can be tested in the near future by molecular line observations. The range of fractionation ratios expected in different interstellar molecules will be discussed and the capabilities of ALMA for testing these models (e.g. in observing doubly-substituted isotopologues) will be outlined.

  8. Comet Halley and interstellar chemistry

    International Nuclear Information System (INIS)

    How complex is the chemistry of the interstellar medium? How far does it evolve and how has it interacted with the chemistry of the solar system? Are the galactic chemical processes destroyed, preserved, or even enhanced in comets? Are biogenic molecules formed in space and have the formation mechanisms interacted in any way with prebiotic organic chemical processes on the early earth? Radio molecular studies of comets are important for probing deep into the coma and nuclear region and thus may help answer these questions. Comets are believed to be pristine samples of the debris left from the formation of the solar system and may have been the carrier between interstellar and terrestrial prebiotic chemistries. Recent observations of Comet Halley and subsequent comets have given the author an excellent opportunity to study the relationship between interstellar molecular chemistry and cometary chemistry

  9. Theory of interstellar medium diagnostics

    Science.gov (United States)

    Fahr, H. J.

    1983-01-01

    The theoretical interpretation of observed interplanetary resonance luminescence patterns is used as one of the must promising methods to determine the state of the local interstellar medium (LISM). However, these methods lead to discrepant results that would be hard to understand in the framework of any physical LISM scenario. Assuming that the observational data are reliable, two possibilities which could help to resolve these discrepancies are discussed: (1) the current modeling of resonance luminescence patterns is unsatisfactory and has to be improved, and (2) the extrapolated interstellar parameters are not indicative of the unperturbed LISM state, but rather designate an intermediate state attained in the outer regions of the solar system. It is shown that a quantitative treatment of the neutral gas-plasma interaction effects in the interface between the heliospheric and the interstellar plasmas is of major importance for the correct understanding of the whole complex.

  10. The Warped Science of Interstellar

    CERN Document Server

    Luminet, Jean-Pierre

    2015-01-01

    The science fiction film, Interstellar, tells the story of a team of astronauts searching a distant galaxy for habitable planets to colonize. Interstellar's story draws heavily from contemporary science. The film makes reference to a range of topics, from established concepts such as fast-spinning black holes, accretion disks, tidal effects, and time dilation, to far more speculative ideas such as wormholes, time travel, additional space dimensions, and the theory of everything. The aim of this article is to decipher some of the scientific notions which support the framework of the movie.

  11. Interstellar Initiative Web Page Design

    Science.gov (United States)

    Mehta, Alkesh

    1999-01-01

    This summer at NASA/MSFC, I have contributed to two projects: Interstellar Initiative Web Page Design and Lenz's Law Relative Motion Demonstration. In the Web Design Project, I worked on an Outline. The Web Design Outline was developed to provide a foundation for a Hierarchy Tree Structure. The Outline would help design a Website information base for future and near-term missions. The Website would give in-depth information on Propulsion Systems and Interstellar Travel. The Lenz's Law Relative Motion Demonstrator is discussed in this volume by Russell Lee.

  12. Experimental interstellar organic chemistry - Preliminary findings

    Science.gov (United States)

    Khare, B. N.; Sagan, C.

    1973-01-01

    Review of the results of some explicit experimental simulation of interstellar organic chemistry consisting in low-temperature high-vacuum UV irradiation of condensed simple gases known or suspected to be present in the interstellar medium. The results include the finding that acetonitrile may be present in the interstellar medium. The implication of this and other findings are discussed.

  13. Where Did You Come From? Where Will You Go? Human Evolutionary Biology Education and American Students' Academic Interests and Achievements, Professional Goals, and Socioscientific Decision-making

    Science.gov (United States)

    Schrein, Caitlin M.

    In the United States, there is a national agenda to increase the number of qualified science, technology, engineering, and maths (STEM) professionals and a movement to promote science literacy among the general public. This project explores the association between formal human evolutionary biology education (HEB) and high school science class enrollment, academic achievement, interest in a STEM degree program, motivation to pursue a STEM career, and socioscientific decision-making for a sample of students enrolled full-time at Arizona State University. Given a lack of a priori knowledge of these relationships, the Grounded Theory Method was used and was the foundation for a mixed-methods analysis involving qualitative and quantitative data from one-on-one interviews, focus groups, questionnaires, and an online survey. Theory development and hypothesis generation were based on data from 44 students. The survey instrument, developed to test the hypotheses, was completed by 486 undergraduates, age 18--22, who graduated from U.S. public high schools. The results showed that higher exposure to HEB was correlated with greater high school science class enrollment, particularly for advanced biological science classes, and that, for some students, HEB exposure may have influenced their enrollment, because the students found the content interesting and relevant. The results also suggested that students with higher K--12 HEB exposure felt more prepared for undergraduate science coursework. There was a positive correlation between HEB exposure and interest in a STEM degree and an indirect relationship between higher HEB exposure and motivation to pursue a STEM career. Regarding a number of socioscientific issues, including but not limited to climate change, homosexuality, and stem cell research, students' behaviors and decision-making more closely reflected a scientific viewpoint---or less-closely aligned to a religion-based perspective---when students had greater HEB exposure

  14. Formation of Amino Acid Precursors by Bombardment of Interstellar Ice Analogs with High Energy Heavy Ions

    Science.gov (United States)

    Kobayashi, Kensei; Mita, Hajime; Yoshida, Satoshi; Shibata, Hiromi; Enomoto, Shingo; Matsuda, Tomoyuki; Fukuda, Hitoshi; Kondo, Kotaro; Oguri, Yoshiyuki; Kebukawa, Yoko

    2016-07-01

    experiment, the energy of heavy ions was quite high and passed through the target mixtures. Therefore only small part of energy was deposited to the target, as is the case of the actual cosmic ray particles in interstellar ices. It is safe to say that amino acid precursors can be formed in water-rich ice mantles of interstellar dust particles (ISDs) by the action of cosmic rays. In order to compare the roles of CO and CH4 in organic formation in interstellar environments, we irradiated gaseous mixtures of CO, CH4, NH3 and/or H2O. A mixture of CO (and/or CH4) and NH3 (total 700 Torr) with liquid water was sealed in a glass tube, and the gas mixture was irradiated with 2.5 MeV protons from a Tandem accelerator (Tokyo Tech, Japan). Amino acids were determined after hydrolysis. When CO was the sole carbon source, G-value of glycine was as high as 0.3, but it was drastically decreased when CH4 was the sole carbon source. In both cases, glycine was predominant amino acids, and the other amino acids yielded much less than glycine. However, when both CO and CH4 were used as carbon sources, a wide variety of amino acids were yielded. Thus it is suggested that CH4 is an important source to give various side chains of amino acid precursors if it is present in interstellar media together with CO. Interstellar ices are actually quite complex mixtures of H2O, CO, CH3OH, CO2, CH4, NH3, and HCHO etc. It is probable that a wide variety of complex molecules including precursors of many kinds of amino acids, together with other organic compounds of biological interest, were formed in interstellar ices by cosmic rays, and such interstellar organic would be important sources of orgnics in small bodies in the solar system. [1] K. A. Kvenvolden et al., Nature, 228, 923-926 (1970). [2] J. M. Greenberg and A. Li, Biol. Sci. Space, 12, 96-101 (1998). [3] K. Kobayashi et al., Adv. Space Res., 16, 21-26 (1995). [4] T. Kasamatsu et al., Bull. Chem. Soc. Jpn., [5] M. Bernstein et al., Nature, 416, 401

  15. Herschel observations of interstellar chloronium

    NARCIS (Netherlands)

    Neufeld, David A.; Roueff, Evelyne; Snell, Ronald L.; Lis, Dariusz; Benz, Arnold O.; Bruderer, Simon; Black, John H.; De Luca, Massimo; Gerin, Maryvonne; Goldsmith, Paul F.; Gupta, Harshal; Indriolo, Nick; Le Bourlot, Jacques; Le Petit, Franck; Larsson, Bengt; Melnick, Gary J.; Menten, Karl M.; Monje, Raquel; Nagy, Zsofia; Phillips, Thomas G.; Sandqvist, Aage; Sonnentrucker, Paule; van der Tak, Floris; Wolfire, Mark G.

    2012-01-01

    Using the Herschel Space Observatory's Heterodyne Instrument for the Far-Infrared, we have observed parachloronium (H2Cl+) toward six sources in the Galaxy. We detected interstellar chloronium absorption in foreground molecular clouds along the sight lines to the bright submillimeter continuum sourc

  16. Stardust Interstellar Preliminary Examination (ISPE)

    Science.gov (United States)

    Westphal, A. J.; Allen, C.; Bajt, S.; Basset, R.; Bastien, R.; Bechtel, H.; Bleuet, P.; Borg, J.; Brenker F.; Bridges, J.

    2009-01-01

    In January 2006 the Stardust sample return capsule returned to Earth bearing the first solid samples from a primitive solar system body, C omet 81P/Wild2, and a collector dedicated to the capture and return o f contemporary interstellar dust. Both collectors were approximately 0.1m(exp 2) in area and were composed of aerogel tiles (85% of the co llecting area) and aluminum foils. The Stardust Interstellar Dust Col lector (SIDC) was exposed to the interstellar dust stream for a total exposure factor of 20 m(exp 2-) day during two periods before the co metary encounter. The Stardust Interstellar Preliminary Examination ( ISPE) is a three-year effort to characterize the collection using no ndestructive techniques. The ISPE consists of six interdependent proj ects: (1) Candidate identification through automated digital microsco py and a massively distributed, calibrated search (2) Candidate extr action and photodocumentation (3) Characterization of candidates thro ugh synchrotronbased FourierTranform Infrared Spectroscopy (FTIR), S canning XRay Fluoresence Microscopy (SXRF), and Scanning Transmission Xray Microscopy (STXM) (4) Search for and analysis of craters in f oils through FESEM scanning, Auger Spectroscopy and synchrotronbased Photoemission Electron Microscopy (PEEM) (5) Modeling of interstell ar dust transport in the solar system (6) Laboratory simulations of h ypervelocity dust impacts into the collecting media

  17. Isotopic Fractionation in Interstellar Chemistry

    Science.gov (United States)

    Charnley, Steven

    2009-01-01

    Isotopically fractionated material is found in many solar system objects, including meteorites and comets. It is thought, in some cases, to trace interstellar material that was incorporated into the solar sys tem without undergoing significant processing. In this poster, we sho w the results of several models of the nitrogen, oxygen, and carbon f ractionation in proto-stellar cores.

  18. Current topics in red cell biology: report on the Red Cell Special Interest Group meeting held at NHS Blood and Transplant Bristol on 30 October 2015.

    Science.gov (United States)

    Bullock, T; Bruce, L J; Ridgwell, K

    2016-08-01

    The Red Cell Special Interest Group (SIG) meeting, hosted by the British Blood Transfusion Society, provides an annual forum for the presentation of UK- and European-based red cell research. The 2015 meeting was held on Friday 30 October at the National Health Service Blood & Transplant (NHSBT) facility in Filton, Bristol and provided an exciting and varied programme on the themes of erythropoiesis, malaria biology and pathophysiology and red cells properties in stress and disease. Ten speakers presented on these topics over the course of one day. The meeting was well attended by over 90 delegates. Posters were presented during the lunch break, and abstracts from the posters are published at the end of this issue.

  19. PAHs in Translucent Interstellar Clouds

    Science.gov (United States)

    Salama, Farid; Galazutdinov, G.; Krelowski, J.; Biennier, L.; Beletsky, Y.; Song, I.

    2011-05-01

    We discuss the proposal of relating the origin of some of the diffuse interstellar bands (DIBs) to neutral polycyclic aromatic hydrocarbons (PAHs) present in translucent interstellar clouds. The spectra of several cold, isolated gas-phase PAHs have been measured in the laboratory under experimental conditions that mimic the interstellar conditions and are compared with an extensive set of astronomical spectra of reddened, early type stars. This comparison provides - for the first time - accurate upper limits for the abundances of specific PAH molecules along specific lines-of-sight. Something that is not attainable from IR observations alone. The comparison of these unique laboratory data with high resolution, high S/N ratio astronomical observations leads to two major findings: (1) a finding specific to the individual molecules that were probed in this study and, which leads to the clear and unambiguous conclusion that the abundance of these specific neutral PAHs must be very low in the individual translucent interstellar clouds that were probed in this survey (PAH features remain below the level of detection) and, (2) a general finding that neutral PAHs exhibit intrinsic band profiles that are similar to the profile of the narrow DIBs indicating that the carriers of the narrow DIBs must have close molecular structure and characteristics. This study is the first quantitative survey of neutral PAHs in the optical range and it opens the way for unambiguous quantitative searches of PAHs in a variety of interstellar and circumstellar environments. // Reference: F. Salama et al. (2011) ApJ. 728 (1), 154 // Acknowledgements: F.S. acknowledges the support of the NASA's Space Mission Directorate APRA Program. J.K. acknowledges the financial support of the Polish State (grant N203 012 32/1550). The authors are deeply grateful to the ESO archive as well as to the ESO staff members for their active support.

  20. The Sun's dusty interstellar environment

    Science.gov (United States)

    Sterken, Veerle

    2016-07-01

    The Sun's dusty interstellar environment Interstellar dust from our immediate interstellar neighborhood travels through the solar system at speeds of ca. 26 km/s: the relative speed of the solar system with respect to the local interstellar cloud. On its way, its trajectories are altered by several forces like the solar radiation pressure force and Lorentz force. The latter is due to the charged dust particles that fly through the interplanetary magnetic field. These trajectories differ per particle type and size and lead to varying fluxes and directions of the flow inside of the solar system that depend on location but also on phase in the solar cycle. Hence, these fluxes and directions depend strongly on the configuration of the inner regions and outer regions of the heliosphere. Several missions have measured this dust in the solar system directly. The Ulysses dust detector data encompasses 16 years of intestellar dust fluxes and approximate directions, Stardust captured returned to Earth a few of these particles sucessfully, and finally the Cassini dust detector allowed for compositional information to be obtained from the impacts on the instrument. In this talk, we give an overview of the current status of interstellar dust research through the measurements made inside of the solar system, and we put them in perspective to the knowledge obtained from more classical astronomical means. In special, we focus on the interaction of the dust with the interplanetary magnetic field, and on what we learn about the dust (and the fields) by comparing the available dust data to computer simulations of dust trajectories. Finally, we synthesize the different methods of observation, their results, and give a preview on new research opportunities in the coming year(s).

  1. Systematic Theoretical Study on the Interstellar Carbon Chain Molecules

    CERN Document Server

    Etim, Emmanuel E; Das, Ankan; Chakrabarti, Sandip K; Arunan, Elangannan

    2016-01-01

    In an effort to further our interest in understanding basic chemistry of interstellar molecules, we carry out here an extensive investigation of the stabilities of interstellar carbon chains; Cn, H2Cn, HCnN and CnX (X=N, O, Si, S, H, P, H-, N-). These sets of molecules accounts for about 20% of all the known interstellar and circumstellar molecules, their high abundances therefore demand a serious attention. High level ab initio quantum chemical calculations are employed to accurately estimate enthalpy of formation, chemical reactivity indices; global hardness and softness; and other chemical parameters of these molecules. Chemical modeling of the abundances of these molecular species has also been performed. Of the 89 molecules considered from these groups, 47 have been astronomically observed, these observed molecules are found to be more stable with respect to other members of the group. Of the 47 observed molecules, 60% are odd number carbon chains. Interstellar chemistry is not actually driven by the the...

  2. CO$_2$ Infrared Phonon Modes in Interstellar Ice Mixtures

    CERN Document Server

    Cooke, Ilsa R; Öberg, Karin I

    2016-01-01

    CO$_2$ ice is an important reservoir of carbon and oxygen in star and planet forming regions. Together with water and CO, CO$_2$ sets the physical and chemical characteristics of interstellar icy grain mantles, including desorption and diffusion energies for other ice constituents. A detailed understanding of CO$_2$ ice spectroscopy is a prerequisite to characterize CO$_2$ interactions with other volatiles both in interstellar ices and in laboratory experiments of interstellar ice analogs. We report laboratory spectra of the CO$_2$ longitudinal optical (LO) phonon mode in pure CO$_2$ ice and in CO$_2$ ice mixtures with H$_2$O, CO, O$_2$ components. We show that the LO phonon mode position is sensitive to the mixing ratio of various ice components of astronomical interest. In the era of JWST, this characteristic could be used to constrain interstellar ice compositions and morphologies. More immediately, LO phonon mode spectroscopy provides a sensitive probe of ice mixing in the laboratory and should thus enabl...

  3. Plasma Diagnostics of the Interstellar Medium with Radio Astronomy

    OpenAIRE

    Haverkorn, M.; Spangler, S.

    2013-01-01

    We discuss the degree to which radio propagation measurements diagnose conditions in the ionized gas of the interstellar medium (ISM). The "signal generators" of the radio waves of interest are extragalactic radio sources (quasars and radio galaxies), as well as Galactic sources, primarily pulsars. The polarized synchrotron radiation of the Galactic non-thermal radiation also serves to probe the ISM, including space between the emitting regions and the solar system. Radio propagation measurem...

  4. Interstellar dust. Evidence for interstellar origin of seven dust particles collected by the Stardust spacecraft.

    Science.gov (United States)

    Westphal, Andrew J; Stroud, Rhonda M; Bechtel, Hans A; Brenker, Frank E; Butterworth, Anna L; Flynn, George J; Frank, David R; Gainsforth, Zack; Hillier, Jon K; Postberg, Frank; Simionovici, Alexandre S; Sterken, Veerle J; Nittler, Larry R; Allen, Carlton; Anderson, David; Ansari, Asna; Bajt, Saša; Bastien, Ron K; Bassim, Nabil; Bridges, John; Brownlee, Donald E; Burchell, Mark; Burghammer, Manfred; Changela, Hitesh; Cloetens, Peter; Davis, Andrew M; Doll, Ryan; Floss, Christine; Grün, Eberhard; Heck, Philipp R; Hoppe, Peter; Hudson, Bruce; Huth, Joachim; Kearsley, Anton; King, Ashley J; Lai, Barry; Leitner, Jan; Lemelle, Laurence; Leonard, Ariel; Leroux, Hugues; Lettieri, Robert; Marchant, William; Ogliore, Ryan; Ong, Wei Jia; Price, Mark C; Sandford, Scott A; Sans Tresseras, Juan-Angel; Schmitz, Sylvia; Schoonjans, Tom; Schreiber, Kate; Silversmit, Geert; Solé, Vicente A; Srama, Ralf; Stadermann, Frank; Stephan, Thomas; Stodolna, Julien; Sutton, Stephen; Trieloff, Mario; Tsou, Peter; Tyliszczak, Tolek; Vekemans, Bart; Vincze, Laszlo; Von Korff, Joshua; Wordsworth, Naomi; Zevin, Daniel; Zolensky, Michael E

    2014-08-15

    Seven particles captured by the Stardust Interstellar Dust Collector and returned to Earth for laboratory analysis have features consistent with an origin in the contemporary interstellar dust stream. More than 50 spacecraft debris particles were also identified. The interstellar dust candidates are readily distinguished from debris impacts on the basis of elemental composition and/or impact trajectory. The seven candidate interstellar particles are diverse in elemental composition, crystal structure, and size. The presence of crystalline grains and multiple iron-bearing phases, including sulfide, in some particles indicates that individual interstellar particles diverge from any one representative model of interstellar dust inferred from astronomical observations and theory.

  5. A search for interstellar scandium

    Science.gov (United States)

    Snow, T. P., Jr.; Dodgen, S. L.

    1980-01-01

    The resonance line of Sc II at 3642.785 A has been sought in the interstellar spectrum of Zeta Oph, resulting in an upper limit N(Sc II) not greater than 8.6 billion/sq cm and a depletion of this element at least by a factor of 200, if Sc III contributes a negligible column density. The present upper limit may be somewhat below the level expected under the grain-formation model for interstellar depletions, and is consistent with the abundance expected if the depletions are due to gas-grain collisions. The new limit on this element helps to support the hypothesis that species within a specific range of ionization potential are preferentially depleted.

  6. Interstellar organic matter in meteorites

    Science.gov (United States)

    Yang, J.; Epstein, S.

    1983-01-01

    Deuterium-enriched hydrogen is present in organic matter in such meteorites as noncarbonaceous chondrites. The majority of the unequilibrated primitive meteorites contain hydrogen whose D/H ratios are greater than 0.0003, requiring enrichment (relative to cosmic hydrogen) by isotope exchange reactions taking place below 150 K. The D/H values presented are the lower limits for the organic compounds derived from interstellar molecules, since all processes subsequent to their formation, including terrestrial contamination, decrease their D/H ratios. In contrast, the D/H ratios of hydrogen associated with hydrated silicates are relatively uniform for the meteorites analyzed. The C-13/C-12 ratios of organic matter, irrespective of D/H ratio, lie well within those observed for the earth. Present findings suggest that other interstellar material, in addition to organic matter, is preserved and is present in high D/H ratio meteorites.

  7. One Kilogram Interstellar Colony Mission

    Science.gov (United States)

    Mole, A.

    Small interstellar colony probes based on nanotechnology will become possible long before giant multi-generation ships become affordable. A beam generator and magnetic sail can accelerate a one kg probe to .1 c, braking via the interstellar field can decelerate it, and the field in a distant solar system can allow it to maneuver to an extrasolar planet. A heat shield is used for landing and nanobots emerge to build ever-larger robots and construct colony infrastructure. Humans can then be generated from genomes stored as data in computer memory. Technology is evolving towards these capabilities and should reach the required level in fifty years. The plan appears to be affordable, with the principal cost being the beam generator, estimated at $17 billion.

  8. Physical properties of interstellar filaments

    OpenAIRE

    Fischera, Joerg; Martin, Peter G.

    2012-01-01

    We analyze the physical parameters of interstellar filaments that we describe by an idealized model of isothermal self-gravitating infinite cylinder in pressure equilibrium with the ambient medium. Their gravitational state is characterized by the ratio f_cyl of their mass line density to the maximum possible value for a cylinder in a vacuum. Equilibrium solutions exist only for f_cyl < 1. This ratio is used in providing analytical expressions for the central density, the radius, the profile ...

  9. Cost considerations for interstellar missions

    Science.gov (United States)

    Andrews, Dana G.

    This paper examines the technical and economic feasibility of interstellar exploration. Three candidate interstellar propulsion systems are evaluated with respect to technical viability and compared on an estimated cost basis. Two of the systems, the laser-propelled lightsail (LPL) and the particle-beam propelled magsail (PBPM), appear to be technically feasible and capable supporting one-way probes to nearby star systems within the lifetime of the principal investigators, if enough energy is available. The third propulsion system, the antimatter rocket, requires additional proof of concept demonstrations before its feasibility can be evaluated. Computer simulations of the acceleration and deceleration interactions of LPL and PBPM were completed and spacecraft configurations optimized for minimum energy usage are noted. The optimum LPL transfers about ten percent of the laser beam energy into kinetic energy of the spacecraft while the optimum PBPM transfers about thirty percent. Since particle beam generators are roughly twice as energy efficient as large lasers, the PBPM propulsion system requires roughly one-sixth the busbar electrical energy a LPL system would require to launch an identical payload. The total beam energy requirement for an interstellar probe mission is roughly 10 20 joules, which would require the complete fissioning of one thousand tons of Uranium assuming thirty-five percent powerplant efficiency. This is roughly equivalent to a recurring cost per flight of 3.0 Billion dollars in reactor grade enriched uranium using today's prices. Therefore, interstellar flight is an expensive proposition, but not unaffordable, if the nonrecurring costs of building the powerplant can be minimized.

  10. Photodissociation of interstellar N2

    CERN Document Server

    Li, Xiaohu; Visser, Ruud; Ubachs, Wim; Lewis, Brenton R; Gibson, Stephen T; van Dishoeck, Ewine F

    2013-01-01

    Molecular nitrogen is one of the key species in the chemistry of interstellar clouds and protoplanetary disks and the partitioning of nitrogen between N and N2 controls the formation of more complex prebiotic nitrogen-containing species. The aim of this work is to gain a better understanding of the interstellar N2 photodissociation processes based on recent detailed theoretical and experimental work and to provide accurate rates for use in chemical models. We simulated the full high-resolution line-by-line absorption + dissociation spectrum of N2 over the relevant 912-1000 \\AA\\ wavelength range, by using a quantum-mechanical model which solves the coupled-channels Schr\\"odinger equation. The simulated N2 spectra were compared with the absorption spectra of H2, H, CO, and dust to compute photodissociation rates in various radiation fields and shielding functions. The effects of the new rates in interstellar cloud models were illustrated for diffuse and translucent clouds, a dense photon dominated region and a ...

  11. Complex Chemistry on Interstellar Grains

    Science.gov (United States)

    Widicus Weaver, Susanna L.; Kelley, Matthew J.; Blake, Geoffrey A.

    Early interstellar chemical models considered complex molecule formation on grains [Allen & Robinson (1977)], but current models assume that simple molecules form on grains and subsequent gas phase ion-molecule reactions produce the more complex species [Ruffle & Herbst (2001), Charnley (2001)]. It has been shown, however, that gas phase ion-molecule reactions are insufficient for the production of such complex organic species as ethanol (CH3CH2OH) and methyl formate (CH3OCHO) [Horn et al. (2004)]. Organics such as acetaldehyde (CH3CHO), ethanol, methyl formate, acetic acid (CH3COOH), and glycolaldehyde (CH2OHCHO) have also been detected in high abundance in regions of grain mantle disruption or evaporation, indicating that these species are formed on grain surfaces [see Chengalur & Kanekar (2003), Bottinelli et al. (2004), Hollis et al. (2001)]. The mechanisms for complex molecule production on grains are clearly much more important, and much more complex, than has been recognized. Recent observational studies of these types of species have offered insight into the mechanisms for their possible grain surface synthesis. The relative hot core abundances of the 2C structural isomers methyl formate, acetic acid, and glycolaldehyde (52:2:1, respectively [Hollis et al. (2001)]) indicate that if they form on grains it is not from kinetically-controlled single-atom addition reactions. Likewise, the 3C aldose sugar, glyceraldehyde (CH2OHCHOHCHO), was not detected in Sgr B2(N-LMH) [Hollis et al. (2004)] while the 3C ketose sugar, dihydroxyacetone (CO(CH2OH)2) was detected in this source [Widicus Weaver & Blake (2005)]. Chemical pathways favoring the more stable carbonates over acids and aldehydes are required to explain these results. Interestingly, all of these species can be formed from reactions involving the abundant grain mantle constituents CO, HCOOH, and CH3OH and their radical precursors. A model has been developed to investigate this type of chemical network, and

  12. Physics of the interstellar and intergalactic medium

    CERN Document Server

    Draine, Bruce T

    2010-01-01

    This is a comprehensive and richly illustrated textbook on the astrophysics of the interstellar and intergalactic medium--the gas and dust, as well as the electromagnetic radiation, cosmic rays, and magnetic and gravitational fields, present between the stars in a galaxy and also between galaxies themselves. Topics include radiative processes across the electromagnetic spectrum; radiative transfer; ionization; heating and cooling; astrochemistry; interstellar dust; fluid dynamics, including ionization fronts and shock waves; cosmic rays; distribution and evolution of the interstellar medium

  13. Molecular collisions in the interstellar medium.

    OpenAIRE

    Flower, D

    2007-01-01

    In the interstellar medium - the space between the stars in galaxies - new stars are born from material that is replenished by the debris ejected by stars when they die. This book is a comprehensive manual for studying the collisional and radiative processes observed in the interstellar medium. This second edition has been thoroughly updated and extended to cover related topics in radiation theory. It considers the chemistry of the interstellar medium both at the present epoch and in the earl...

  14. Biologic

    CERN Document Server

    Kauffman, L H

    2002-01-01

    In this paper we explore the boundary between biology and the study of formal systems (logic). In the end, we arrive at a summary formalism, a chapter in "boundary mathematics" where there are not only containers but also extainers ><, entities open to interaction and distinguishing the space that they are not. The boundary algebra of containers and extainers is to biologic what boolean algebra is to classical logic. We show how this formalism encompasses significant parts of the logic of DNA replication, the Dirac formalism for quantum mechanics, formalisms for protein folding and the basic structure of the Temperley Lieb algebra at the foundations of topological invariants of knots and links.

  15. Upper Secondary Students' Situational Interest: A Case Study of the Role of a Zoo Visit in a Biology Class

    Science.gov (United States)

    Dohn, Niels Bonderup

    2013-01-01

    This paper comprises a presentation of the findings of a case study that investigated how situational factors triggered 12th grade students' interest during a field trip to a zoo. The purpose was to identify sources of interest and to investigate the attributes that make them interesting. Students' interest was investigated by a…

  16. Chemical Evolution in the Interstellar Medium: From Astrochemistry to Astrobiology

    Science.gov (United States)

    Allamandola, Louis J.

    2009-01-01

    Great strides have been made in our understanding of interstellar material thanks to advances in infrared astronomy and laboratory astrophysics. Ionized polycyclic aromatic hydrocarbons (PAHs), shockingly large molecules by earlier astrochemical standards, are widespread and very abundant throughout much of the Universe. In cold molecular clouds, the birthplace of planets and stars, interstellar molecules freeze onto dust and ice particles forming mixed molecular ices dominated by simple species such as water, methanol, ammonia, and carbon monoxide. Within these clouds, and especially in the vicinity of star and planet forming regions, these ices and PAHs are processed by ultraviolet light and cosmic rays forming hundreds of far more complex species, some of biogenic interest. Eventually, these are delivered to primordial planets by comets and meteorites. Astrochemical evolution, highlights of this field from a chemist's perspective, and the astronomer's infrared toolbox will be reviewed.

  17. Deuterium enrichment of interstellar dusts

    Science.gov (United States)

    Das, Ankan; Chakrabarti, Sandip Kumar; Majumdar, Liton; Sahu, Dipen

    2016-07-01

    High abundance of some abundant and simple interstellar species could be explained by considering the chemistry that occurs on interstellar dusts. Because of its simplicity, the rate equation method is widely used to study the surface chemistry. However, because the recombination efficiency for the formation of any surface species is highly dependent on various physical and chemical parameters, the Monte Carlo method is best suited for addressing the randomness of the processes. We carry out Monte-Carlo simulation to study deuterium enrichment of interstellar grain mantle under various physical conditions. Based on the physical properties, various types of clouds are considered. We find that in diffuse cloud regions, very strong radiation fields persists and hardly a few layers of surface species are formed. In translucent cloud regions with a moderate radiation field, significant number of layers would be produced and surface coverage is mainly dominated by photo-dissociation products such as, C, CH_3, CH_2D, OH and OD. In the intermediate dense cloud regions (having number density of total hydrogen nuclei in all forms ˜2 × 10^4 cm^{-3}), water and methanol along with their deuterated derivatives are efficiently formed. For much higher density regions (˜10^6 cm^{-3}), water and methanol productions are suppressed but surface coverage of CO, CO_2, O_2, O_3 are dramatically increased. We find a very high degree of fractionation of water and methanol. Observational results support a high fractionation of methanol but surprisingly water fractionation is found to be low. This is in contradiction with our model results indicating alternative routes for de-fractionation of water.

  18. HERSCHEL OBSERVATIONS OF INTERSTELLAR CHLORONIUM

    Energy Technology Data Exchange (ETDEWEB)

    Neufeld, David A.; Indriolo, Nick [Department of Physics and Astronomy, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218 (United States); Roueff, Evelyne; Le Bourlot, Jacques; Le Petit, Franck [Observatoire de Paris-Meudon, LUTH UMR 8102, 5 Pl. Jules Janssen, F-92195 Meudon Cedex (France); Snell, Ronald L. [Astronomy Department, University of Massachusetts at Amherst, Amherst, MA 01003 (United States); Lis, Dariusz; Monje, Raquel; Phillips, Thomas G. [Astronomy Department, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Benz, Arnold O. [Institute of Astronomy, ETH Zurich, 8092 Zurich (Switzerland); Bruderer, Simon [Max Planck Institut fuer Extraterrestrische Physik, Giessenbachstrasse 1, D-85748, Garching (Germany); Black, John H.; Larsson, Bengt [Department of Earth and Space Sciences, Chalmers University of Technology, Onsala (Sweden); De Luca, Massimo; Gerin, Maryvonne [LERMA, UMR 8112 du CNRS, Observatoire de Paris, Ecole Normale Superieure, UPMC and UCP (France); Goldsmith, Paul F.; Gupta, Harshal [JPL, California Institute of Technology, Pasadena, CA (United States); Melnick, Gary J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States); Menten, Karl M. [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, D-53121 Bonn (Germany); Nagy, Zsofia [Kapteyn Astronomical Institute University of Groningen, Groningen (Netherlands); and others

    2012-03-20

    Using the Herschel Space Observatory's Heterodyne Instrument for the Far-Infrared, we have observed para-chloronium (H{sub 2}Cl{sup +}) toward six sources in the Galaxy. We detected interstellar chloronium absorption in foreground molecular clouds along the sight lines to the bright submillimeter continuum sources Sgr A (+50 km s{sup -1} cloud) and W31C. Both the para-H{sup 35}{sub 2}Cl{sup +} and para-H{sup 37}{sub 2}Cl{sup +} isotopologues were detected, through observations of their 1{sub 11}-0{sub 00} transitions at rest frequencies of 485.42 and 484.23 GHz, respectively. For an assumed ortho-to-para ratio (OPR) of 3, the observed optical depths imply that chloronium accounts for {approx}4%-12% of chlorine nuclei in the gas phase. We detected interstellar chloronium emission from two sources in the Orion Molecular Cloud 1: the Orion Bar photodissociation region and the Orion South condensation. For an assumed OPR of 3 for chloronium, the observed emission line fluxes imply total beam-averaged column densities of {approx}2 Multiplication-Sign 10{sup 13} cm{sup -2} and {approx}1.2 Multiplication-Sign 10{sup 13} cm{sup -2}, respectively, for chloronium in these two sources. We obtained upper limits on the para-H{sup 35}{sub 2}Cl{sup +} line strengths toward H{sub 2} Peak 1 in the Orion Molecular cloud and toward the massive young star AFGL 2591. The chloronium abundances inferred in this study are typically at least a factor {approx}10 larger than the predictions of steady-state theoretical models for the chemistry of interstellar molecules containing chlorine. Several explanations for this discrepancy were investigated, but none has proven satisfactory, and thus the large observed abundances of chloronium remain puzzling.

  19. A Search for Interstellar Pyrimidine

    CERN Document Server

    Kuan, Y J; Charnley, S B; Kisiel, Z; Ehrenfreund, P; Huang, H C; Kuan, Yi-Jehng; Yan, Chi-Hung; Charnley, Steven B.; Kisiel, Zbigniew; Ehrenfreund, Pascale; Huang, Hui-Chun

    2003-01-01

    We have searched three hot molecular cores for submillimeter emission from the nucleic acid building-block pyrimidine. We obtain upper limits to the total pyrimidine (beam-averaged) column densities towards Sgr B2(N), Orion KL and W51 e1/e2 of 1.7E+14 cm^{-2}, 2.4E+14 cm^{-2} and 3.4E+14 cm^{-2}, respectively. The associated upper limits to the pyrimidine fractional abundances lie in the range (0.3-3)E-10. Implications of this result for interstellar organic chemistry, and for the prospects of detecting nitrogen heterocycles in general, are briefly discussed.

  20. Discovery of Interstellar Heavy Water

    OpenAIRE

    Butner, H. M.; Charnley, S. B.; Ceccarelli, C.; Rodgers, S.D.; Pardo Carrión, Juan Ramón; Parise, B.; Cernicharo, José; Davis, G. R.

    2007-01-01

    We report the discovery of doubly deuterated water (D2O, heavy water) in the interstellar medium. Using the James Clerk Maxwell Telescope and the Caltech Submillimeter Observatory 10 m telescope, we detected the 1_10–1_01 transition of para-D2O at 316.7998 GHz in both absorption and emission toward the protostellar binary system IRAS 16293-2422. Assuming that the D2O exists primarily in the warm regions where water ices have been evaporated (i.e., in a "hot corino" environment), we determi...

  1. VAPID: Voigt Absorption-Profile [Interstellar] Dabbler

    Science.gov (United States)

    Howarth, Ian D.

    2015-06-01

    VAPID (Voigt Absorption Profile [Interstellar] Dabbler) models interstellar absorption lines. It predicts profiles and optimizes model parameters by least-squares fitting to observed spectra. VAPID allows cloud parameters to be optimized with respect to several different data set simultaneously; those data sets may include observations of different transitions of a given species, and may have different S/N ratios and resolutions.

  2. Herschel observations of interstellar chloronium

    CERN Document Server

    Neufeld, David A; Snell, Ronald L; Lis, Dariusz; Benz, Arnold O; Bruderer, Simon; Black, John H; De Luca, Massimo; Gerin, Maryvonne; Goldsmith, Paul F; Gupta, Harshal; Indriolo, Nick; Bourlot, Jacques Le; Petit, Franck Le; Larsson, Bengt; Melnick, Gary J; Menten, Karl M; Monje, Raquel; Nagy, Zsofia; Phillips, Thomas G; Sandqvist, Aage; Sonnentrucker, Paule; van der Tak, Floris; Wolfire, Mark G

    2012-01-01

    Using the Herschel Space Observatory's Heterodyne Instrument for the Far-Infrared (HIFI), we have observed para-chloronium (H2Cl+) toward six sources in the Galaxy. We detected interstellar chloronium absorption in foreground molecular clouds along the sight-lines to the bright submillimeter continuum sources Sgr A (+50 km/s cloud) and W31C. Both the para-H2-35Cl+ and para-H2-37Cl+ isotopologues were detected, through observations of their 1(11)-0(00) transitions at rest frequencies of 485.42 and 484.23 GHz, respectively. For an assumed ortho-to-para ratio of 3, the observed optical depths imply that chloronium accounts for ~ 4 - 12% of chlorine nuclei in the gas phase. We detected interstellar chloronium emission from two sources in the Orion Molecular Cloud 1: the Orion Bar photodissociation region and the Orion South condensation. For an assumed ortho-to-para ratio of 3 for chloronium, the observed emission line fluxes imply total beam-averaged column densities of ~ 2.0E+13 cm-2 and ~ 1.2E+13 cm-2, respect...

  3. Detection of interstellar hydrogen peroxide

    CERN Document Server

    Bergman, P; Liseau, R; Larsson, B; Olofsson, H; Menten, K M; Güsten, R

    2011-01-01

    The molecular species hydrogen peroxide, HOOH, is likely to be a key ingredient in the oxygen and water chemistry in the interstellar medium. Our aim with this investigation is to determine how abundant HOOH is in the cloud core {\\rho} Oph A. By observing several transitions of HOOH in the (sub)millimeter regime we seek to identify the molecule and also to determine the excitation conditions through a multilevel excitation analysis. We have detected three spectral lines toward the SM1 position of {\\rho} Oph A at velocity-corrected frequencies that coincide very closely with those measured from laboratory spectroscopy of HOOH. A fourth line was detected at the 4{\\sigma} level. We also found through mapping observations that the HOOH emission extends (about 0.05 pc) over the densest part of the {\\rho} Oph A cloud core. We derive an abundance of HOOH relative to that of H_2 in the SM1 core of about 1\\times10^(-10). To our knowledge, this is the first reported detection of HOOH in the interstellar medium.

  4. Realistic Detectability of Close Interstellar Comets

    CERN Document Server

    Cook, Nathaniel V; Granvik, Mikael; Stephens, Denise C

    2016-01-01

    During the planet formation process, billions of comets are created and ejected into interstellar space. The detection and characterization of such interstellar comets (also known as extra-solar planetesimals or extra-solar comets) would give us in situ information about the efficiency and properties of planet formation throughout the galaxy. However, no interstellar comets have ever been detected, despite the fact that their hyperbolic orbits would make them readily identifiable as unrelated to the solar system. Moro-Mart\\'in et al. 2009 have made a detailed and reasonable estimate of the properties of the interstellar comet population. We extend their estimates of detectability with a numerical model that allows us to consider "close" interstellar comets, e.g., those that come within the orbit of Jupiter. We include several constraints on a "detectable" object that allow for realistic estimates of the frequency of detections expected from the Large Synoptic Survey Telescope (LSST) and other surveys. The inf...

  5. The Exobiological Role of Interstellar Polycyclic Aromatic Hydrocarbons and Ices

    Science.gov (United States)

    Hudgins, Douglas M.; DeVincenzi, Donald (Technical Monitor)

    2002-01-01

    Tremendous strides have been made in our understanding of interstellar material over the past twenty years thanks to significant, parallel developments in observational astronomy and laboratory astrophysics. Before this time, the composition of interstellar dust was largely guessed-at, the presence of ices in interstellar clouds ignored, and the notion that large, gas phase, carbon rich molecules might be abundant and widespread throughout the interstellar medium (ISM) considered impossible. Today, the composition of dust in the ISM is reasonably well constrained to micron-sized cold refractory materials comprised of amorphous and crystalline silicates mixed with an amorphous carbonaceous material containing aromatic structural units and short, branched aliphatic chains. Shrouded within the protective confines of cold, opaque molecular clouds--the birthplace of stars and planets--these cold dust particles secrete mantles of mixed molecular ices whose compositions are also well constrained. Finally, amidst the molecular inventory of these ice mantles are likely to be found polycyclic aromatic hydrocarbons (PAHs), shockingly large molecules by the standards of interstellar chemistry, the telltale infrared spectral signature of which is now recognized throughout the Universe. In the first part of this talk, we will review the spectroscopic evidence that forms the basis for the currently accepted abundance and ubiquity of PANs in the ISM. We will then look at a few specific examples which illustrate how experimental and theoretical data can be applied to interpret the interstellar spectra and track how the PAN population evolves as it passes from its formation site in the circumstellar outflows of dying stars, through the various phases of the ISM, and into forniing planetary systems. Nevertheless, despite the fact that PANs likely represent the single largest molecular reservoir of organic carbon in evolving planetary systems, they are not what would be considered

  6. Enantio-specific C(sp3)-H activation catalyzed by ruthenium nanoparticles: application to isotopic labeling of molecules of biological interest

    International Nuclear Information System (INIS)

    Isotopic labeling with deuterium and tritium is extensively used in chemistry, biology and pharmaceutical research. Numerous methods of labeling by isotopic exchange allow high isotopic enrichments but generally require harsh conditions (high temperatures, acidity). As a consequence, a general, regioselective and smooth labeling method that might be applicable to a wide diversity of substrates remains to develop. In the first part of this thesis, we demonstrated that the use of ruthenium nanoparticles, synthesized by Pr. Bruno Chaudret's team (INSA Toulouse), allowed the mild (2 bar of deuterium gas at 55 C), effective and selective H/D exchange reaction of a large variety of nitrogen-containing compounds, such as pyridines, indoles and primary, secondary and tertiary alkyl amines. The usefulness and the efficiency of this novel methodology was demonstrated by the deuteration of eight nitrogen-containing molecules of biological interest without altering their chemical and stereochemical properties. However, the conservation of the original stereochemistry of an activated chiral C-H center remains a major issue. We studied the reactivity of RuNP(at)PVP on different categories of nitrogen-containing substrates (amines, aminoacids and peptides) in water or in organic solvents. Our results showed that C-H activation of chiral carbons C(sp3) took place efficiently, selectively and, in all cases, with total retention of configuration. The wide range of applications of this procedure was demonstrated by the labeling of three chiral amines, fourteen aminoacids, three aromatic amino esters and four peptides. Moreover, our collaboration with Pr. Romuald Poteau's team (INSA Toulouse) led to the identification of two mechanisms by ab initio simulation in agreement with our experimental results: the σ-bond metathesis mechanism and the oxidative addition mechanism. These two mechanisms imply two vicinal ruthenium atoms leading to the formation an original

  7. The Identification of Complex Organic Molecules in the Interstellar Medium: Using Lasers and Matrix Isolation Spectroscopy to Simulate the Interstellar Environment

    Science.gov (United States)

    Stone, Bradley M.

    1998-01-01

    The Astrochemistry Group at NASA Ames Research Center is interested in the identification of large organic molecules in the interstellar medium Many smaller organic species (e.g. hydrocarbons, alcohols, etc.) have been previously identified by their radiofrequency signature due to molecular rotations. However, this becomes increasingly difficult to observe as the size of the molecule increases. Our group in interested in the identification of the carriers of the Diffuse Interstellar Bands (absorption features observed throughout the visible and near-infrared in the spectra of stars, due to species in the interstellar medium). Polycyclic Aromatic Hydrocarbons (PAHs) and related molecules are thought to be good candidates for these carriers. Laboratory experiments am performed at Ames to simulate the interstellar environment, and to compare spectra obtained from molecules in the laboratory to those derived astronomically. We are also interested in PAHs with respect to their possible connection to the UIR (Unidentified infrared) and ERE (Extended Red Emission) bands - emission features found to emanate from particular regions of our galaxy (e.g. Orion nebula, Red Rectangle, etc.). An old, "tried and proven spectroscopic technique, matrix isolation spectroscopy creates molecular conditions ideal for performing laboratory astrophysics.

  8. 试论中学生物教师如何提高学生的学习兴趣%On High School Biology Teachers How to Improve Students' Interest in Learning

    Institute of Scientific and Technical Information of China (English)

    孙丽欢

    2014-01-01

    为了应付各种考试,目前中学生的生物兴趣很淡,初中生物的学习主要目的还仅仅是为了升学考试,学习方法还是停留在死记硬背层面。这样兴趣的淡薄导致了初中生物教师教学的吃力,另一方面又造成了学生初中生物学习的效率低下。目前有部分初中生物教师意识到学习兴趣培养的重要性,但是由于受到教学水平的影响,也难以达到预设目标。本文从中学生物教学中存在的问题入手,着重分析如何提高中学生生物学习的兴趣。%In order to cope with the exam, the current high school students interested in a very short bio, biology junior primary purpose of learning is just for the entrance examination, or stay in rote learning levels. Such interest has led to strenuous weak teaching junior high school biology teacher, on the other hand has also caused inefficiencies junior high school biology students to learn. There are currently part of the junior high school biology teachers realized the impor-tance of learning interest in training, but due to the impact of the teaching level, it is difficult to achieve preset goals. This article from the existing high school biology teaching problems, we focus on how to improve high school students' interest in biology learning.

  9. Speckles in interstellar radio-wave scattering

    Science.gov (United States)

    Desai, K. M.; Gwinn, C. R.; Reynolds, J.; King, E. A.; Jauncey, D.; Nicholson, G.; Flanagan, C.; Preston, R. A.; Jones, D. L.

    1991-01-01

    Observations of speckles in the scattering disk of the Vela pulsar are presented and speckle techniques for studying and circumventing scattering of radio waves by the turbulent interstellar plasma are discussed. The speckle pattern contains, in a hologrammatic fashion, complete information on the structure of the radio source as well as the distribution of the scattering material. Speckle observations of interstellar scattering of radio waves are difficult because of their characteristically short timescales and narrow bandwidths. Here, first observations are presented, taken at 13 cm wavelength with elements of the SHEVE VLBI network, of speckles in interstellar scattering.

  10. Searches for new interstellar molecules, including a tentative detection of aziridine and a possible detection of propenal

    Science.gov (United States)

    Dickens, J. E.; Irvine, W. M.; Nummelin, A.; Mollendal, H.; Saito, S.; Thorwirth, S.; Hjalmarson, A.; Ohishi, M.

    2001-01-01

    Rotational spectroscopy at millimeter wavelengths is a powerful means of investigating the chemistry of dense interstellar clouds. These regions can exhibit an interesting complement of gas phase molecules, including relatively complex organics. Here we report the tentative first astronomical detection of aziridine (ethylenimine), the possible detection of propenal (acrolein), and upper limits on the abundances of cyclopropenone, furan, hydroxyethanal (glycolaldehyde), thiohydroxylamine (NH2SH), and ethenol (vinyl alcohol) in various interstellar clouds.

  11. Silicate Composition of the Interstellar Medium

    CERN Document Server

    Fogerty, Shane; Watson, Dan M; Sargent, Benjamin A; Koch, Ingrid

    2016-01-01

    The composition of silicate dust in the diffuse interstellar medium and in protoplanetary disks around young stars informs our understanding of the processing and evolution of the dust grains leading up to planet formation. Analysis of the well-known 9.7{\\mu}m feature indicates that small amorphous silicate grains represent a significant fraction of interstellar dust and are also major components of protoplanetary disks. However, this feature is typically modelled assuming amorphous silicate dust of olivine and pyroxene stoichiometries. Here, we analyze interstellar dust with models of silicate dust that include non-stoichiometric amorphous silicate grains. Modelling the optical depth along lines of sight toward the extinguished objects Cyg OB2 No. 12 and {\\zeta} Ophiuchi, we find evidence for interstellar amorphous silicate dust with stoichiometry intermediate between olivine and pyroxene, which we simply refer to as "polivene." Finally, we compare these results to models of silicate emission from the Trapez...

  12. Physical Processes in the Interstellar Medium

    CERN Document Server

    Klessen, Ralf S

    2014-01-01

    Interstellar space is filled with a dilute mixture of charged particles, atoms, molecules and dust grains, called the interstellar medium (ISM). Understanding its physical properties and dynamical behavior is of pivotal importance to many areas of astronomy and astrophysics. Galaxy formation and evolution, the formation of stars, cosmic nucleosynthesis, the origin of large complex, prebiotic molecules and the abundance, structure and growth of dust grains which constitute the fundamental building blocks of planets, all these processes are intimately coupled to the physics of the interstellar medium. However, despite its importance, its structure and evolution is still not fully understood. Observations reveal that the interstellar medium is highly turbulent, consists of different chemical phases, and is characterized by complex structure on all resolvable spatial and temporal scales. Our current numerical and theoretical models describe it as a strongly coupled system that is far from equilibrium and where th...

  13. Cosmocultural Evolution: Cosmic Motivation for Interstellar Travel?

    Science.gov (United States)

    Lupisella, M.

    Motivations for interstellar travel can vary widely from practical survival motivations to wider-ranging moral obligations to future generations. But it may also be fruitful to explore what, if any, "cosmic" relevance there may be regarding interstellar travel. Cosmocultural evolution can be defined as the coevolution of cosmos and culture, with cultural evolution playing an important and perhaps critical role in the overall evolution of the universe. Strong versions of cosmocultural evolution might suggest that cultural evolution may have unlimited potential as a cosmic force. In such a worldview, the advancement of cultural beings throughout the universe could have significant cosmic relevance, perhaps providing additional motivation for interstellar travel. This paper will explore some potential philosophical and policy implications for interstellar travel of a cosmocultural evolutionary perspective and other related concepts, including some from a recent NASA book, Cosmos and Culture: Cultural Evolution in a Cosmic Context.

  14. Abundances in the diffuse interstellar medium

    International Nuclear Information System (INIS)

    The wealth of interstellar absorption line data obtained with the Copernicus and IUE satellites has opened up a new era in studies of the interstellar gas. It is now well established that certain elements, generally those with high condensation temperatures, are substantially under-abundant in the gas-phase relative to total solar or cosmic abundances. This depletion of elements is due to the existence of solid material in the form of dust grains in the interstellar medium. Surprisingly, however, recent surveys indicate that even volatile elements such as Zn and S are significantly depleted in many sight lines. Developments in this field which have been made possible by the large base of UV interstellar absorption line data built up over recent years are reviewed and the implications of the results for our understanding of the physical processes governing depletion are discussed. (author)

  15. Scouting the spectrum for interstellar travellers

    CERN Document Server

    Garcia-Escartin, Juan Carlos

    2012-01-01

    Advanced civilizations capable of interstellar travel, if they exist, are likely to have advanced propulsion methods. Spaceships moving at high speeds would leave a particular signature which could be detected from Earth. We propose a search based on the properties of light reflecting from objects travelling at relativistic speeds. Based on the same principles, we also propose a simple interstellar beacon with a solar sail.

  16. The Interstellar Medium of our Galaxy

    OpenAIRE

    Frisch, Priscilla C.

    2001-01-01

    The development of our understanding of the gaseous component of the interstellar medium is reviewed. During the 20th century our picture of diffuse material in space has grown from a simple model of isolated clouds in thermal equilibrium with stellar radiation fields to one of a richly varied composite of materials with a wide range of physical properties and morphologies. The solar system interacts with this dynamical interstellar medium, which dominates the properties of the interplanetary...

  17. Interstellar grain chemistry and organic molecules

    Science.gov (United States)

    Allamandola, L. J.; Sandford, S. A.

    1990-01-01

    The detection of prominant infrared absorption bands at 3250, 2170, 2138, 1670 and 1470 cm(-1) (3.08, 4.61, 4.677, 5.99 and 6.80 micron m) associated with molecular clouds show that mixed molecular (icy) grain mantles are an important component of the interstellar dust in the dense interstellar medium. These ices, which contain many organic molecules, may also be the production site of the more complex organic grain mantles detected in the diffuse interstellar medium. Theoretical calculations employing gas phase as well as grain surface reactions predict that the ices should be dominated only by the simple molecules H2O, H2CO, N2, CO, O2, NH3, CH4, possibly CH3OH, and their deuterated counterparts. However, spectroscopic observations in the 2500 to 1250 cm(-1)(4 to 8 micron m) range show substantial variation from source reactions alone. By comparing these astronomical spectra with the spectra of laboratory-produced analogs of interstellar ices, one can determine the composition and abundance of the materials frozen on the grains in dense clouds. Experiments are described in which the chemical evolution of an interstellar ice analog is determined during irradiation and subsequent warm-up. Particular attention is paid to the types of moderately complex organic materials produced during these experiments which are likely to be present in interstellar grains and cometary ices.

  18. A Manual of Mosquito Control Projects and Committee Assignments for 4-H and Scouts Biology Class Projects, Organized Community Service Programs, and Individuals Interested in Environmental Management.

    Science.gov (United States)

    Hart, Richard A.

    The mosquito control projects presented in this manual were prepared from an educational viewpoint and are intended for use by students in 4-H and Scouts and as a supplement to high school and college biology course work. The major emphasis of the projects is on integrated pest management, an approach utilizing cost-effective control methods which…

  19. Physical Processes of Interstellar Turbulence

    CERN Document Server

    Vazquez-Semadeni, Enrique

    2012-01-01

    I discuss the role of self-gravity and radiative heating and cooling in shaping the nature of the turbulence in the interstellar medium (ISM) of our galaxy. The heating and cooling cause it to be highly compressible, and, in some regimes of density and temperature, to become thermally unstable, tending to spontaneously segregate into warm/diffuse and cold/dense phases. On the other hand, turbulence is an inherently mixing process, tending to replenish the density and temperature ranges that would be forbidden under thermal processes alone. The turbulence in the ionized ISM appears to be transonic (i.e, with Mach numbers $\\Ms \\sim 1$), and thus to behave essentially incompressibly. However, in the neutral medium, thermal instability causes the sound speed of the gas to fluctuate by up to factors of $\\sim 30$, and thus the flow can be highly supersonic with respect to the dense/cold gas, although numerical simulations suggest that this behavior corresponds more to the ensemble of cold clumps than to the clumps'...

  20. Rotational spectroscopy of interstellar PAHs

    CERN Document Server

    Ali-Haïmoud, Yacine

    2013-01-01

    Polycyclic aromatic hydrocarbons (PAHs) have long been part of the standard model of the interstellar medium, and are believed to play important roles in its physics and chemistry. Yet, up to now it has not been possible to identify any specific molecule among them. In this paper, a new observational avenue is suggested to detect individual PAHs, using their rotational line emission at radio frequencies. Previous PAH searches based on rotational spectroscopy have only targeted the bowl-shaped corannulene molecule, with the underlying assumption that other polar PAHs are triaxial and as a consequence their rotational emission is diluted over a very large number of lines and unusable for detection purposes. In this paper the rotational spectrum of quasi-symmetric PAHs is computed analytically, as a function of the level of triaxiality. It is shown that the asymmetry of planar, nitrogen-substituted symmetric PAHs is small enough that their rotational spectrum, when observed with a resolution of about a MHz, has ...

  1. The interstellar medium in galaxies

    CERN Document Server

    1997-01-01

    It has been more than five decades ago that Henk van de Hulst predicted the observability of the 21-cm line of neutral hydrogen (HI ). Since then use of the 21-cm line has greatly improved our knowledge in many fields and has been used for galactic structure studies, studies of the interstellar medium (ISM) in the Milky Way and other galaxies, studies of the mass distribution of the Milky Way and other galaxies, studies of spiral struc­ ture, studies of high velocity gas in the Milky Way and other galaxies, for measuring distances using the Tully-Fisher relation etc. Regarding studies of the ISM, there have been a number of instrumen­ tal developments over the past decade: large CCD's became available on optical telescopes, radio synthesis offered sensitive imaging capabilities, not only in the classical 21-cm HI line but also in the mm-transitions of CO and other molecules, and X-ray imaging capabilities became available to measure the hot component of the ISM. These developments meant that Milky Way was n...

  2. Episodic Explosions in Interstellar Ices

    CERN Document Server

    Rawlings, J M C; Viti, S; Cecchi-Pestellini, C

    2013-01-01

    We present a model for the formation of large organic molecules in dark clouds. The molecules are produced in the high density gas-phase that exists immediately after ice mantles are explosively sublimated. The explosions are initiated by the catastrophic recombination of trapped atomic hydrogen. We propose that, in molecular clouds, the processes of freeze-out onto ice mantles, accumulation of radicals, explosion and then rapid (three-body) gas-phase chemistry occurs in a cyclic fashion. This can lead to a cumulative molecular enrichment of the interstellar medium. A model of the time-dependent chemistries, based on this hypothesis, shows that significant abundances of large molecular species can be formed, although the complexity of the species is limited by the short expansion timescale in the gas, immediately following mantle explosion. We find that this mechanism may be an important source of smaller organic species, such as methanol and formaldehyde, as well as precursors to bio-molecule formation. Most...

  3. Discovery of Interstellar Hydrogen Fluoride

    CERN Document Server

    Neufeld, D A; Schilke, P; Phillips, T G; Neufeld, David A.; Zmuidzinas, Jonas; Schilke, Peter; Phillips, Thomas G.

    1997-01-01

    We report the first detection of interstellar hydrogen fluoride. Using the Long Wavelength Spectrometer (LWS) of the Infrared Space Observatory (ISO), we have detected the 121.6973 micron J = 2 - 1 line of HF in absorption toward the far-infrared continuum source Sagittarius B2. The detection is statistically significant at the 13 sigma level. On the basis of our model for the excitation of HF in Sgr B2, the observed line equivalent width of 1.0 nm implies a hydrogen fluoride abundance of 3E-10 relative to H2. If the elemental abundance of fluorine in Sgr B2 is the same as that in the solar system, then HF accounts for ~ 2% of the total number of fluorine nuclei. We expect hydrogen fluoride to be the dominant reservoir of gas-phase fluorine in Sgr B2, because it is formed rapidly in exothermic reactions of atomic fluorine with either water or molecular hydrogen; thus the measured HF abundance suggests a substantial depletion of fluorine onto dust grains. Similar conclusions regarding depletion have previously...

  4. Stimulating Students' Interest,Activating Biology Class Teaching%激发兴趣,活跃生物课堂教学

    Institute of Scientific and Technical Information of China (English)

    闻功超

    2012-01-01

    Curiosity is juveniles' psychological feature,and it is also the cause of students' self-learning interest.Einstein has once said,"Interest is the best teacher."From this we can see that interest is the source motivation of students' active learning.In class teaching,teachers should use various means to stimulate students' learning interest,improve students' enthusiasm,so as to improve teaching quality.%好奇心、好胜心是青少年的心理特征,而好奇心又往往是触发学生自学兴趣的导火线,爱因斯坦说:"兴趣是最好的老师。"由此可见,兴趣是引起学习动机的原动力,是引发学生主动积极学习的主要因素之一。在课堂教学中,教师要运用多种教学手段、方法激发学生的学习兴趣,提高学生的学习热情,增强学习的主动性、积极性,提高教学质量。

  5. Structure analysis of interstellar clouds - II. Applying the Delta-variance method to interstellar turbulence

    NARCIS (Netherlands)

    Ossenkopf, V.; Krips, M.; Stutzki, J.

    2008-01-01

    Context. The Delta-variance analysis is an efficient tool for measuring the structural scaling behaviour of interstellar turbulence in astronomical maps. It has been applied both to simulations of interstellar turbulence and to observed molecular cloud maps. In Paper I we proposed essential improvem

  6. Some O I oscillator strengths and the interstellar abundance of oxygen

    Science.gov (United States)

    Zeippen, C. J.; Seaton, M. J.; Morton, D. C.

    1977-01-01

    Calculated and experimental oscillator strengths for the O I intersystem line at 1356 A and for other O I lines of interest in interstellar absorption-line studies are discussed. Attention is given to experimental f-values for the lines at 1302, 1305, and 1306 A, previous work on the f-values for the lines at 1356 and 1359 A, wave-function expansion, and calculations for permitted as well as intercombination lines. Copernicus observations of several interstellar absorption lines due to O I, C II, P II, and Ni II toward Zeta Oph are reported, equivalent widths are determined, and a curve-of-growth analysis is performed for the O I absorption lines. Oscillator strengths are recommended for the far-UV resonance lines of O I, and it is concluded that the oxygen in the interstellar H I regions toward Zeta Oph is depleted by 45% to 69%.

  7. The Interstellar Vision: Principles and Practice

    Science.gov (United States)

    Gilster, P. A.

    The ambitious title of the 100 Year Starship study will resonate with the public, a fact that requires the recipient of the DARPA grant to use communicators who can follow a careful strategy as they bring this vision to the Internet and other outlets. It will be necessary to spur public engagement and sustain the `buzz' that will help the organization develop its ideas. This paper examines these issues in the context of the author's long involvement with Centauri Dreams, a Web site devoted to presenting interstellar flight to a broad, general audience. Central to the presentation of the starship idea is the advocacy of long-term thinking and the value of spin-off research by placing the goal of a starship in the context of other human activities that have transcended the lifetime of individual participants. Teaching cross-generational responsibility will invoke issues of history, economics and philosophy in addition to the technology issues raised by a journey of this magnitude. The best communicators for this role will be generalists who can connect such widely dispersed disciplines. Key to the study is the development of a Web presence that uses the Internet with caution. Certain Internet myths including `the wisdom of crowds' and resistance to top-down editing will compromise the project. The benefits and drawbacks of social networking will be discussed in this context. A strong editorial voice willing to cull public responses to maintain high standards in the resulting discussions is essential. Furthermore, a high standard of reporting demands the presentation of research without associated hype and a level of discourse that educates but does not patronize its audience. Careful citation of relevant research and a willingness to set the bar of discussion high will result in feedback from researchers and the public that, with the help of strenuous moderation, will build a database of thirdparty ideas that will engage interest and add materially to the value of

  8. The Interstellar Medium Surrounding the Sun

    Science.gov (United States)

    Frisch, Priscilla C.; Redfield, Seth; Slavin, Jonathan D.

    2011-09-01

    The Solar System is embedded in a flow of low-density, warm, and partially ionized interstellar material that has been sampled directly by in situ measurements of interstellar neutral gas and dust in the heliosphere. Absorption line data reveal that this interstellar gas is part of a larger cluster of local interstellar clouds, which is spatially and kinematically divided into additional small-scale structures indicating ongoing interactions. An origin for the clouds that is related to star formation in the Scorpius-Centaurus OB association is suggested by the dynamic characteristics of the flow. Variable depletions observed within the local interstellar medium (ISM) suggest an inhomogeneous Galactic environment, with shocks that destroy grains in some regions. Although photoionization models of the circumheliospheric ISM do an excellent job of reproducing the observed properties of the surrounding ISM, the unknown characteristics of the very low-density hot plasma filling the Local Bubble introduces uncertainty about the source of ionization and nature of cloud boundaries. Recent observations of small cold clouds provide new insight into the processes affecting the local ISM. A fuller understanding of the local ISM can provide insights into the past and future Galactic environment of the Sun, and deeper knowledge of the astrospheres of nearby stars.

  9. Photodissociation and excitation of interstellar molecules

    International Nuclear Information System (INIS)

    Apart from a rather long introduction containing some elementary astrophysics, quantum chemistry and spectroscopy and an incomplete, historical review of molecular observations, this thesis is divided into three sections. In part A, a rigorous quantum chemical and dynamical study is made of the photodissociation processes in the OH and HCl molecules. In part B, the cross sections obtained in part A are used in various astrophysical problems such as the study of the abundances of the OH and HCl molecules in interstellar clouds, the use of the OH abundance as a measure of the cosmic ray ionization rate, the lifetime of the OH radical in comets and the abundance of OH in the solar photosphere. Part C discusses the excitation of the C2 molecule under interstellar conditions, its use as a diagnostic probe of the temperature, density and strength of the radiation field in interstellar clouds. Quadrupole moments and oscillator strengths are analyzed. (Auth.)

  10. Long-Term Perspectives on Interstellar Flight

    Science.gov (United States)

    Michaud, M. A. G.

    Realizing interstellar travel by machines or living beings will require not only scientific and technological progress, but also a shared secular belief among a determined minority that this enterprise is important for the human future. Their efforts may have to extend beyond individual human lifetimes. Historical perspectives, on both the past and the future, are proposed. Interstellar probes could be a more thorough way of searching for alien forms of life and intelligence in nearby systems, particularly if there were intelligent beings there who did not employ technologies our astronomical observing devices can detect from here. Perspectives on the ethical, policy, and design issues of such close encounters with alien life and intelligence are presented. Ways of accelerating the coming of interstellar probes are suggested.

  11. Interstellar water chemistry: from laboratory to observations

    CERN Document Server

    van Dishoeck, Ewine F; Neufeld, David A

    2013-01-01

    Water is observed throughout the universe, from diffuse interstellar clouds to protoplanetary disks around young stars, and from comets in our own solar system and exoplanetary atmospheres to galaxies at high redshifts. This review summarizes the spectroscopy and excitation of water in interstellar space as well as the basic chemical processes that form and destroy water under interstellar conditions. Three major routes to water formation are identified: low temperature ion-molecule chemistry, high-temperature neutral-neutral chemistry and gas-ice chemistry. The rate coefficients of several important processes entering the networks are discussed in detail; several of them have been determined only in the last decade through laboratory experiments and theoretical calculations. Astronomical examples of each of the different chemical routes are presented using data from powerful new telescopes, in particular the Herschel Space Observatory. Basic chemical physics studies remain critically important to analyze ast...

  12. 如何培养七年级学生学习生物的兴趣%How to cultivate the interest to learn biology of seven grade students

    Institute of Scientific and Technical Information of China (English)

    刘乐凤

    2013-01-01

      对某项知识的兴趣是驱动学生学习的最根本动力。对不同年龄阶段的学生培养兴趣的方法也不同。文章结合自身的教学经验以及教学成果,从生物学的新颖性、直观性、趣闻性三方面入手,通过培养学生的动手能力,营造轻松、自然、和谐的课堂气氛,以及联系实际案例三种方式,提出了培养七年级学生学习生物学兴趣的方法。%The interest is the basic power driving students to learn. The training of different ages of students’ interest have different methods. This article unifies own teaching experience and teaching achievements, from the novelty, intuitive, anecdotes of biology three respects proceed with, through the cultivation of the practical ability of students, to create relaxed, natural and harmonious atmosphere in the classroom, as well as with a real case three ways, to put forward the method to raise interest of biology learning of seven grades students.

  13. ON THE FORMATION OF DIPEPTIDES IN INTERSTELLAR MODEL ICES

    Energy Technology Data Exchange (ETDEWEB)

    Kaiser, R. I.; Kim, Y. S. [Department of Chemistry, University of Hawaii at Manoa, Honolulu, HI 96822 (United States); Stockton, A. M.; Jensen, E. C.; Mathies, R. A. [Department of Chemistry, University of California, Berkeley, CA 94720 (United States)

    2013-03-10

    The hypothesis of an exogenous origin and delivery of biologically important molecules to early Earth presents an alternative route to their terrestrial in situ formation. Dipeptides like Gly-Gly detected in the Murchison meteorite are considered as key molecules in prebiotic chemistry because biofunctional dipeptides present the vital link in the evolutionary transition from prebiotic amino acids to early proteins. However, the processes that could lead to the exogenous abiotic synthesis of dipeptides are unknown. Here, we report the identification of two proteinogenic dipeptides-Gly-Gly and Leu-Ala-formed via electron-irradiation of interstellar model ices followed by annealing the irradiated samples to 300 K. Our results indicate that the radiation-induced, non-enzymatic formation of proteinogenic dipeptides in interstellar ice analogs is facile. Once synthesized and incorporated into the ''building material'' of solar systems, biomolecules at least as complex as dipeptides could have been delivered to habitable planets such as early Earth by meteorites and comets, thus seeding the beginning of life as we know it.

  14. ON THE FORMATION OF DIPEPTIDES IN INTERSTELLAR MODEL ICES

    International Nuclear Information System (INIS)

    The hypothesis of an exogenous origin and delivery of biologically important molecules to early Earth presents an alternative route to their terrestrial in situ formation. Dipeptides like Gly-Gly detected in the Murchison meteorite are considered as key molecules in prebiotic chemistry because biofunctional dipeptides present the vital link in the evolutionary transition from prebiotic amino acids to early proteins. However, the processes that could lead to the exogenous abiotic synthesis of dipeptides are unknown. Here, we report the identification of two proteinogenic dipeptides—Gly-Gly and Leu-Ala—formed via electron-irradiation of interstellar model ices followed by annealing the irradiated samples to 300 K. Our results indicate that the radiation-induced, non-enzymatic formation of proteinogenic dipeptides in interstellar ice analogs is facile. Once synthesized and incorporated into the ''building material'' of solar systems, biomolecules at least as complex as dipeptides could have been delivered to habitable planets such as early Earth by meteorites and comets, thus seeding the beginning of life as we know it.

  15. On the Formation of Dipeptides in Interstellar Model Ices

    Science.gov (United States)

    Kaiser, R. I.; Stockton, A. M.; Kim, Y. S.; Jensen, E. C.; Mathies, R. A.

    2013-03-01

    The hypothesis of an exogenous origin and delivery of biologically important molecules to early Earth presents an alternative route to their terrestrial in situ formation. Dipeptides like Gly-Gly detected in the Murchison meteorite are considered as key molecules in prebiotic chemistry because biofunctional dipeptides present the vital link in the evolutionary transition from prebiotic amino acids to early proteins. However, the processes that could lead to the exogenous abiotic synthesis of dipeptides are unknown. Here, we report the identification of two proteinogenic dipeptides—Gly-Gly and Leu-Ala—formed via electron-irradiation of interstellar model ices followed by annealing the irradiated samples to 300 K. Our results indicate that the radiation-induced, non-enzymatic formation of proteinogenic dipeptides in interstellar ice analogs is facile. Once synthesized and incorporated into the ''building material'' of solar systems, biomolecules at least as complex as dipeptides could have been delivered to habitable planets such as early Earth by meteorites and comets, thus seeding the beginning of life as we know it.

  16. Interstellar dust particles and chemical species

    Science.gov (United States)

    Krelowski, Jacek

    Absorption spectra of translucent interstellar clouds contain known molecular bands: of CN, CH+, CH, OH, OH+, NH, C2 and C3. Moreover, one can observe more than 400 unidentified absorption features known as diffuse interstellar bands (DIBs) commonly believed to be carried by some complex, carbon bearing molecules (chain species based on a carbon scheleton, polycyclic aromatic hydrocarbons, fullerenes). DIBs are optical features observed in absorption in starlight crossing tarnslucent interstellar clouds. Despite many laboratory based studies of possible DIB carriers, it has not been possible to unambiguously link these bands to specific species. This is unfortunate, as an identification of DIBs would substantially contribute to our understanding of chemical processes in the diffuse interstellar medium. The presence of substructures inside DIB profiles, discovered by Sarre et al. (1995) and Kerr et al. (1998), indicate that DIBs are likely molecular features of gas phase species. Sofar only three DIBs have been linked to specific molecules but none of these links was confirmed beyond a doubt. Extinction is likely caused by interstellar dust particles of various sizes and shapes. The recent surveys of the extinction law demonstrate a great variety of the observed curves which proves that grains differ from cloud to cloud. A majority of distant OB stars is observed through several clouds and thus we observe usually an ill-defined average which does not differ substantially from one distant object to another. The most popularly observed CH molecule does correlate with the extinction but it is a poor correlation. The abundance of CN molecule is completely uncorrelated with the colour excess. Seemingly an exceptionally high abundance of CN is observed together with high far-UV extinction and very low intensity of diffuse interstellar bands. Interstellar molecules can be formed either in the gas phase or on grain surfaces. Small grains, responsible for the far

  17. Water in the interstellar media of galaxies

    CERN Document Server

    van der Tak, Floris

    2015-01-01

    This paper reviews recent observations of water in Galactic interstellar clouds and nearby galactic nuclei. Two results are highlighted: (1) Multi-line H$_2$O mapping of the Orion Bar shows that the water chemistry in PDRs is driven by photodissociation and -desorption, unlike in star-forming regions. (2) High-resolution spectra of H$_2$O and its ions toward 5 starburst / AGN systems reveal low ionization rates, unlike as found from higher-excitation lines. We conclude that the chemistry of water strongly depends on radiation environment, and that the ionization rates of interstellar clouds decrease by at least 10 between galactic nuclei and disks.

  18. A Rigorous Attempt to Verify Interstellar Glycine

    OpenAIRE

    Snyder, L. E.; Lovas, F. J.; Hollis, J. M.; Friedel, D. N.; Jewell, P.R.; Remijan, A.; Ilyushin, V. V.; Alekseev, E. A.; Dyubko, S. F.

    2004-01-01

    In 2003, Kuan, Charnley, and co-workers reported the detection of interstellar glycine (NH2CH2COOH) based on observations of 27 lines in 19 different spectral bands in one or more of the sources Sgr B2(N-LMH), Orion KL, and W51 e1/e2. They supported their detection report with rotational temperature diagrams for all three sources. In this paper, we present essential criteria which can be used in a straightforward analysis technique to confirm the identity of an interstellar asymmetric rotor s...

  19. The Astronomical, Astrobiological and Planetary Science Case for Interstellar Spaceflight

    OpenAIRE

    Crawford, Ian A.

    2010-01-01

    A review is presented of the scientific benefits of rapid (v >= 0.1c) interstellar spaceflight. Significant benefits are identified in the fields of interstellar medium studies, stellar astrophysics, planetary science and astrobiology. In the latter three areas the benefits would be considerably enhanced if the interstellar vehicle is able to decelerate from its interstellar cruise velocity to rest relative to the target system. Although this will greatly complicate the mission architecture, ...

  20. Electron density power spectrum in the local interstellar medium

    Science.gov (United States)

    Armstrong, J. W.; Rickett, B. J.; Spangler, S. R.

    1995-01-01

    Interstellar scintillation (ISS), fluctuations in the amplitude and phase of radio waves caused by scattering in the interstellar medium, is important as a diagnostic of interstellar plasma turbulence. ISS is also of interest because it is noise for other radio astronomical observations. The unifying concern is the power spectrum of the interstellar electron density. Here we use ISS observations through the nearby (less than or approximately =1 kpc) (ISM) to estimate the spectrum. From measurements of angular broadening of pulsars and extragalactic sources, decorrelation bandwidth of pulsars, refractive steering of features in pulsar dynamic spectra, dispersion measured fluctuations of pulsars, and refractive scintillation index measurements, we construct a composite structure function that is approximately power law over 2 x 10(exp 6) m less than scale less than 10(exp 13) m. The data are consistent with the structure function having a logarithmic slope versus baseline less than 2; thus there is a meaningful connection between scales in the radiowave fluctuation field and the scales in the electron density field causing the scattering. The data give an upper limit to the inner scale, l(sub o) less than or approximately 10(exp 8) m and are consistent with much smaller values. We construct a composite electron density spectrum that is approximately power law over at least the approximately = 5 decade wavenumber range 10(exp -13)/m less than wavenumber less than 10(exp -8)/m and that may extend to higher wavenumbers. The average spectral index of electron density over this wavenumber range is approximately = 3.7, very close to the value expected for a Kolmogorov process. The outer scale size, L(sub o), must be greater than or approximately = 10(exp 13) m (determined from dispersion measure fluctuations). When the ISS data are combined with measurements of differential Faraday rotation angle, and gradients in the average electron density, constraints can be put on the

  1. Origins of interstellar and solar system: Carbonaceous materials

    Science.gov (United States)

    Feigelson, Eric D.

    1994-10-01

    Carbon is a crucial atom in cosmochemistry. It is well-established that carbon is synthesized in stellar interiors after the main sequence, is ejected by red giants as small carbonaceous grains during their 'carbon star' phase, resides in the interstellar medium, and was later incorporated into the solar system. The mechanisms of carbon grain formation and later chemical processing are complex because, with only small thermodynamic differences, carbon can take on a bewildering variety of forms: diamond; oxides; carbides; graphite; aliphatic hydrocarbons; polycyclic aromatic hydrocarbons (PAH's); fullerenes; amorphous carbon; and other compounds. These are evidence for many of the forms of carbon found in astronomical observations. We seek to understand the possible astrophysical sites and conditions of the origins of different forms of carbon by combining state-of-the-art capabilities of carbon chemistry with astrophysical modeling. The work is a collaboration between Prof. Frenklach, a leading carbon materials scientist with both laboratory and computer modeling expertise and Prof. Feigelson, an astrophysicist with interests in star formation. The largest effort under this grant was devoted to developing this concept into a comprehensive quantitative model. In addition to explaining the astronomical properties of red giants producing carbonaceous grains, our model also can incorporate recent meteoritic findings. Finally, our induced nucleation grain formation model provides a natural explanation for the widespread presence of PAH emission bands in the Galactic interstellar medium. A brief synopsis of other activities sponsored under this grant and a list of publications from this grant is included.

  2. Stardust Interstellar Preliminary Examination II: Curating the Interstellar Dust Collector, Picokeystones, and Sources of Impact Tracks

    Science.gov (United States)

    Frank, David R.; Westphal, Andrew J.; Zolensky, Michael E.; Gainsforth, Zack; Butterworth, Anna L.; Bastien, Ronald K.; Allen, Carlton; Anderson, David; Bechtel, Hans A.; Sandford, Scott A.

    2013-01-01

    We discuss the inherent difficulties that arise during "ground truth" characterization of the Stardust interstellar dust collector. The challenge of identifying contemporary interstellar dust impact tracks in aerogel is described within the context of background spacecraft secondaries and possible interplanetary dust particles and beta-meteoroids. In addition, the extraction of microscopic dust embedded in aerogel is technically challenging. Specifically, we provide a detailed description of the sample preparation techniques developed to address the unique goals and restrictions of the Interstellar Preliminary Exam. These sample preparation requirements and the scarcity of candidate interstellar impact tracks exacerbate the difficulties. We also illustrate the role of initial optical imaging with critically important examples, and summarize the overall processing of the collection to date.

  3. Far-infrared spectroscopy of interstellar dust

    NARCIS (Netherlands)

    Tielens, AGGM; Wilson, A

    2005-01-01

    The composition of interstellar dust is best studied using mid-infrared spectroscopy. Nevertheless, the far-infrared can make some unique contributions to this field. This includes studies on the Mg/Fe ratio and the temperature of crystalline silicates, the presence of carbonates, and the precense o

  4. The Interstellar Boundary Explorer Science Operations Center

    Science.gov (United States)

    Schwadron, N. A.; Crew, G.; Vanderspek, R.; Allegrini, F.; Bzowski, M.; Demagistre, R.; Dunn, G.; Funsten, H.; Fuselier, S. A.; Goodrich, K.; Gruntman, M.; Hanley, J.; Heerikhuisen, J.; Heirtlzer, D.; Janzen, P.; Kucharek, H.; Loeffler, C.; Mashburn, K.; Maynard, K.; McComas, D. J.; Moebius, E.; Prested, C.; Randol, B.; Reisenfeld, D.; Reno, M.; Roelof, E.; Wu, P.

    2009-08-01

    The Interstellar Boundary Explorer (IBEX) Science Operations Center is responsible for supporting analysis of IBEX data, generating special payload command procedures, delivering the IBEX data products, and building the global heliospheric maps of energetic neutral atoms (ENAs) in collaboration with the IBEX team. We describe here the data products and flow, the sensor responses to ENA fluxes, the heliospheric transmission of ENAs (from 100 AU to 1 AU), and the process of building global maps of the heliosphere. The vast majority of IBEX Science Operations Center (ISOC) tools are complete, and the ISOC is in a remarkable state of readiness due to extensive reviews, tests, rehearsals, long hours, and support from the payload teams. The software has been designed specifically to support considerable flexibility in the process of building global flux maps. Therefore, as we discover the fundamental properties of the interstellar interaction, the ISOC will iteratively improve its pipeline software, and, subsequently, the heliospheric flux maps that will provide a keystone for our global understanding of the solar wind’s interaction with the interstellar medium. The ISOC looks forward to the next chapter of the IBEX mission, as the tools we have developed will be used in partnership with the IBEX team and the scientific community over the coming years to define our global understanding of the solar wind’s interaction with the local interstellar medium.

  5. Physics and chemistry of interstellar ice

    NARCIS (Netherlands)

    Guss (née Isokoski), Karoliina Marja-Riita

    2013-01-01

    The importance of ice in the interstellar medium is indisputable. Gas phase reactions relying on three-body collisions are exceedingly rare in the sparse medium between the stars. On solid surfaces, atoms and molecules can reside and rove the surface until a reaction takes place. Upon reaction, the

  6. The composition of circumstellar and interstellar dust

    NARCIS (Netherlands)

    Tielens, AGGM; Woodward, CE; Biscay, MD; Shull, JM

    2001-01-01

    A large number of solid dust components have been identified through analysis of stardust recovered from meteorites, and analysis of IR observations of circumstellar shells and the interstellar medium. These include graphite, hydrogenated amorphous carbon, diamond, PAHs, silicon-, iron-, and titanin

  7. Plasma Physics Processes of the Interstellar Medium

    CERN Document Server

    Spangler, Steven; Intrator, Thomas; Kulsrud, Russell; Lazarian, Alex; Redfield, Seth; Zweibel, Ellen

    2009-01-01

    We discuss the outstanding issues of the interstellar medium which will depend on the application of knowledge from plasma physics. We particularly advocate attention to recent developments in experimental plasma physics, and urge that the astronomical community consider support of these experiments in the next decade.

  8. Revisiting Ulysses Observations of Interstellar Helium

    Science.gov (United States)

    Wood, Brian E.; Müller, Hans-Reinhard; Witte, Manfred

    2015-03-01

    We report the results of a comprehensive reanalysis of Ulysses observations of interstellar He atoms flowing through the solar system, the goal being to reassess the interstellar He flow vector and to search for evidence of variability in this vector. We find no evidence that the He beam seen by Ulysses changes at all from 1994-2007. The direction of flow changes by no more than ~0.°3 and the speed by no more than ~0.3 km s-1. A global fit to all acceptable He beam maps from 1994-2007 yields the following He flow parameters: V ISM = 26.08 ± 0.21 km s-1, λ = 75.54 ± 0.°19, β = -5.44 ± 0.°24, and T = 7260 ± 270 K where λ and β are the ecliptic longitude and latitude direction in J2000 coordinates. The flow vector is consistent with the original analysis of the Ulysses team, but our temperature is significantly higher. The higher temperature somewhat mitigates a discrepancy that exists in the He flow parameters measured by Ulysses and the Interstellar Boundary Explorer, but does not resolve it entirely. Using a novel technique to infer photoionization loss rates directly from Ulysses data, we estimate a density of n He = 0.0196 ± 0.0033 cm-3 in the interstellar medium.

  9. Fluorescent excitation of interstellar H2

    NARCIS (Netherlands)

    Black, J.H.; Dishoeck, van E.F.

    1987-01-01

    The infrared emission spectrum of H2 excited by ultraviolet absorption, followed by fluorescence, was investigated using comprehensive models of interstellar clouds for computing the spectrum and to assess the effects on the intensity to various cloud properties, such as density, size, temperature,

  10. A Rigorous Attempt to Verify Interstellar Glycine

    Science.gov (United States)

    Snyder, L. E.; Lovas, F. J.; Hollis, J. M.; Friedel, D. N.; Jewell, P. R.; Remijan, A.; Ilyushin, V. V.; Alekseev, E. A.; Dyubko, S. F.

    2004-01-01

    In 2003, Kuan, Charnley, and co-workers reported the detection of interstellar glycine (NH2CH2COOH) based on observations of 27 lines in 19 different spectral bands in one or more of the sources Sgr BP(N-LMH), Orion KL, and W51 e1/e2. They supported their detection report with rotational temperature diagrams for all three sources. In this paper, we present essential criteria which can be used in a straightforward analysis technique to confirm the identity of an interstellar asymmetric rotor such as glycine. We use new laboratory measurements of glycine as a basis for applying this analysis technique, both to our previously unpublished 12 m telescope data and to the previously published SEST data of Nummelin and colleagues. We conclude that key lines necessary for an interstellar glycine identification have not yet been found. We identify several common molecular candidates that should be examined further as more likely carriers of the lines reported as glycine. Finally, we illustrate that rotational temperature diagrams used without the support of correct spectroscopic assignments are not a reliable tool for the identification of interstellar molecules. Subject headings: ISM: abundances - ISM: clouds - ISM: individual (Sagittarius B2[N-

  11. Unresolved velocity structure in diffuse interstellar clouds

    NARCIS (Netherlands)

    Black, J.H.; Dishoeck, van E.F.

    1988-01-01

    Recent high-resolution observations of interstellar absorption lines of CH and CN toward Zeta Oph obtained by Crane et al. (1986), and Palazzi et al. (1988), exhibit line widths that suggest thermal line broadening at high temperature, T about 1200 K. Observations of CO line emission at 2.6 mm towar

  12. Diffuse interstellar bands in RAVE survey spectra

    NARCIS (Netherlands)

    Munari, U.; Tomasella, L.; Fiorucci, M.; Bienayme, O.; Binney, J.; Bland-Hawthorn, J.; Boeche, C.; Campbell, R.; Freeman, K. C.; Gibson, B.; Gilmore, G.; Grebel, E. K.; Helmi, A.; Navarro, J. F.; Parker, Q. A.; Seabroke, G. M.; Siebert, A.; Siviero, A.; Steinmetz, M.; Watson, F. G.; Williams, M.; Wyse, R. F. G.; Zwitter, T.

    2008-01-01

    We have used spectra of hot stars from the RAVE Survey in order to investigate the visibility and properties of five diffuse interstellar bands previously reported in the literature. The RAVE spectroscopic survey for Galactic structure and kinematics records CCD spectra covering the 8400-8800 angstr

  13. TRIANGULATION OF THE INTERSTELLAR MAGNETIC FIELD

    Energy Technology Data Exchange (ETDEWEB)

    Schwadron, N. A.; Moebius, E. [University of New Hampshire, Durham, NH 03824 (United States); Richardson, J. D. [Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Burlaga, L. F. [Goddard Space Flight Center, Greenbelt, MD 20771 (United States); McComas, D. J. [Southwest Research Institute, San Antonio, TX 78228 (United States)

    2015-11-01

    Determining the direction of the local interstellar magnetic field (LISMF) is important for understanding the heliosphere’s global structure, the properties of the interstellar medium, and the propagation of cosmic rays in the local galactic medium. Measurements of interstellar neutral atoms by Ulysses for He and by SOHO/SWAN for H provided some of the first observational insights into the LISMF direction. Because secondary neutral H is partially deflected by the interstellar flow in the outer heliosheath and this deflection is influenced by the LISMF, the relative deflection of H versus He provides a plane—the so-called B–V plane in which the LISMF direction should lie. Interstellar Boundary Explorer (IBEX) subsequently discovered a ribbon, the center of which is conjectured to be the LISMF direction. The most recent He velocity measurements from IBEX and those from Ulysses yield a B–V plane with uncertainty limits that contain the centers of the IBEX ribbon at 0.7–2.7 keV. The possibility that Voyager 1 has moved into the outer heliosheath now suggests that Voyager 1's direct observations provide another independent determination of the LISMF. We show that LISMF direction measured by Voyager 1 is >40° off from the IBEX ribbon center and the B–V plane. Taking into account the temporal gradient of the field direction measured by Voyager 1, we extrapolate to a field direction that passes directly through the IBEX ribbon center (0.7–2.7 keV) and the B–V plane, allowing us to triangulate the LISMF direction and estimate the gradient scale size of the magnetic field.

  14. Plasma Diagnostics of the Interstellar Medium with Radio Astronomy

    CERN Document Server

    Haverkorn, Marijke

    2013-01-01

    We discuss the degree to which radio propagation measurements diagnose conditions in the ionized gas of the interstellar medium (ISM). The "signal generators" of the radio waves of interest are extragalactic radio sources (quasars and radio galaxies), as well as Galactic sources, primarily pulsars. The polarized synchrotron radiation of the Galactic non-thermal radiation also serves to probe the ISM, including space between the emitting regions and the solar system. Radio propagation measurements provide unique information on turbulence in the ISM as well as the mean plasma properties such as density and magnetic field strength. Radio propagation observations can provide input to the major contemporary questions on the nature of ISM turbulence, such as its dissipation mechanisms and the processes responsible for generating the turbulence on large spatial scales. Measurements of the large scale Galactic magnetic field via Faraday rotation provide unique observational input to theories of the generation of the ...

  15. Organic Chemistry: From the Interstellar Medium to the Solar System

    Science.gov (United States)

    Sandford, Scott; Witteborn, Fred C. (Technical Monitor)

    1997-01-01

    This talk will review the various types of organic materials observed in different environments in the interstellar medium, discuss the processes by which these materials may have formed and been modified, and present the evidence supporting the contention that at least a fraction of this material survived incorporation, substantially unaltered, into our Solar System during its formation. The nature of this organic material is of direct interest to issues associated with the origin of life, both because this material represents a large fraction of the Solar System inventory of the biogenically-important elements, and because many of the compounds in this inventory have biogenic implications. Several specific examples of such molecules will be briefly discussed.

  16. Simple parametrization of photon mass energy absorption coefficients of H-, C-, N- and O-based samples of biological interest in the energy range 200–1500 keV

    Indian Academy of Sciences (India)

    V Manjunathaguru; T K Umesh

    2009-02-01

    In this paper, we provide polynomial coefficients and a semi-empirical relation using which one can derive photon mass energy absorption coefficient of any H-, C-, N-, O-based sample of biological interest containing any other elements in the atomic number range 2–40 and energy range 200–1500 keV. More interestingly, it has been observed in the present work that in this energy range, both the mass attenuation coefficients and the mass energy absorption coefficients for such samples vary only with respect to energy. Hence it was possible to represent the photon interaction properties of such samples by a mean value of these coefficients. By an independent study of the variation of the mean mass attenuation coefficient as well as mass energy absorption coefficient with energy, two simple semi-empirical relations for the photon mass energy absorption coefficients and one relation for the mass attenuation coefficient have been obtained in the energy range 200–1500 keV. It is felt that these semi-empirical relations can be very handy and convenient in biomedical and other applications. One possible significant conclusion based on the results of the present work is that in the energy region 200–1500 keV, the photon interaction characteristics of any H-, C-, N-, O-based sample of biological interest which may or may not contain any other elements in the atomic number range 2–40 can be represented by a sample-independent (single) but energy-dependent mass attenuation coefficient and mass energy absorption coefficient.

  17. Interstellar Probe: The Next Step To Flight

    Science.gov (United States)

    McNutt, Ralph; Zurbuchen, Thomas H.

    2016-07-01

    In the years following the discovery of the solar wind, the term "heliosphere" was coined and defined as "the region of interplanetary space where the solar wind is flowing supersonically." In June 1971, with the development of the Pioneer probes to Jupiter and beyond well underway, a session of the American Astronautical Society meeting considered scientific exploration reaching beyond the solar system and into the interstellar medium. Despite many discussions, studies, and meetings since, the most recent held under the auspices of the Keck Institute for Space Studies (8-11 September 2014 and 13-15 January 2015), such missions have been relegated to the '"future" due to the large distances and solar system escape speeds contemplated for their execution. In the meantime, the Voyager Interstellar Mission (VIM), consisting of the twin Voyager spacecraft almost 40 years since their respective launches, are making inroads into this region beyond the termination shock of the solar wind, a new region of the solid bodies of the solar system has been opened by the New Horizons flyby of the Pluto system, and the Cassini Ion and Neutral CAmera (INCA) and Interstellar Boundary Explorer (IBEX) have remotely sensed neutral atoms that have provided significant clues to the global structure of the interaction of the solar wind and interstellar medium. It is now time for a dedicated mission to the regime beyond the solar system to explore our galactic environment. A first, near-term implementation can be carried out with the near-current flight system technology. What is also clear is that the high speeds required will limit the spacecraft to a relatively small mass of no more than ~500 kg, regardless of the propulsion details. The recent success of the New Horizons mission at the Pluto system illustrates that with modern technologies, such spacecraft sizes can still accommodate the means to produce paradigm-shifting science, providing for a compelling scientific mission. The

  18. Searches for new interstellar molecules, including a tentative detection of aziridine and a possible detection of propenal

    OpenAIRE

    DICKENS, J.E; IRVINE, W.M; Nummelin, A.; MØLLENDAL, H; Saito, S.; Thorwirth, S.; Hjalmarson, Å.; OhiShi, M

    2001-01-01

    Rotational spectroscopy at millimeter wavelengths is a powerful means of investigating the chemistry of dense interstellar clouds. These regions can exhibit an interesting complement of gas phase molecules, including relatively complex organics. Here we report the tentative first astronomical detection of aziridine (ethylenimine), the possible detection of propenal (acrolein), and upper limits on the abundances of cyclopropenone, furan, hydroxyethanal (glycolaldehyde), thiohydroxylamine (NH2S...

  19. Organic Synthesis in Simulated Interstellar Ice Analogs

    Science.gov (United States)

    Dworkin, Jason P.; Bernstein, Max P.; Sandford, Scott A.; Allamandola, Louis J.; Deamer, David W.; Elsila, Jamie; Zare, Richard N.

    2001-01-01

    Comets and carbonaceous micrometeorites may have been significant sources of organic compounds on the early Earth. Ices on grains in interstellar dense molecular clouds contain a variety of simple molecules as well as aromatic molecules of various sizes. While in these clouds the icy grains are processed by ultraviolet light and cosmic radiation which produces more complex organic molecules. We have run laboratory simulations to identify the types of molecules which could have been generated photolytically in pre-cometary ices. Experiments were conducted by forming various realistic interstellar mixed-molecular ices with and without polycyclic aromatic hydrocarbons (PAHs) at approx. 10 K under high vacuum irradiated with UV light from a hydrogen plasma lamp. The residue that remained after warming to room temperature was analyzed by HPLC, and by laser desorption mass spectrometry. The residue contains several classes of compounds which may be of prebiotic significance.

  20. Interstellar Turbulence II: Implications and Effects

    CERN Document Server

    Scalo, J

    2004-01-01

    Interstellar turbulence has implications for the dispersal and mixing of the elements, cloud chemistry, cosmic ray scattering, and radio wave propagation through the ionized medium. This review discusses the observations and theory of these effects. Metallicity fluctuations are summarized, and the theory of turbulent transport of passive tracers is reviewed. Modeling methods, turbulent concentration of dust grains, and the turbulent washout of radial abundance gradients are discussed. Interstellar chemistry is affected by turbulent transport of various species between environments with different physical properties and by turbulent heating in shocks, vortical dissipation regions, and local regions of enhanced ambipolar diffusion. Cosmic rays are scattered and accelerated in turbulent magnetic waves and shocks, and they generate turbulence on the scale of their gyroradii. Radio wave scintillation is an important diagnostic for small scale turbulence in the ionized medium, giving information about the power spe...

  1. Structural Evolution of Interstellar Polycyclic Aromatic Hydrocarbons

    Science.gov (United States)

    Hammonds, Mark; Candian, Alessandra; Mori, Tamami; Usui, Fumihiko; Onaka, Takashi

    2015-08-01

    Polycyclic Aromatic Hydrocarbons (PAHs) are an important reservoir for molecular carbon in the interstellar medium (ISM), and investigations into their chemistry and behaviour may be important to the understanding of how carbon is processed from simple forms into complex prebiotic molecules such as those detected in chondritic meteorites. In this study, infrared astronomical data from AKARI and other observatories are used together with laboratory and theoretical data to study variations in the structure of emitting PAHs in interstellar environments using spectroscopic decomposition techniques and bands arising from carbon-hydrogen bond vibrations at wavelengths from 3 - 14 microns. Results and inferences are discussed in terms of the processing of large carbonaceous molecules in astrophysical environments.

  2. Interstellar Gas and a Dark Disk

    CERN Document Server

    Kramer, Eric David

    2016-01-01

    We introduce a potentially powerful method for constraining or discovering a thin dark matter disk in the Milky Way. The method relies on the relationship between the midplane densities and scale heights of interstellar gas being determined by the gravitational potential, which is sensitive to the presence of a dark disk. We show how to use the interstellar gas parameters to set a bound on a dark disk and discuss the constraints suggested by the current data. However, current measurements for these parameters are discordant, with the uncertainty in the constraint being dominated by the molecular hydrogen midplane density measurement, as well as by the atomic hydrogen velocity dispersion measurement. Magnetic fields and cosmic ray pressure, which are expected to play a role, are uncertain as well. Although a small dark disk is slightly favored, the current data is inadequate to establish its existence

  3. Interstellar Gas and a Dark Disk

    Science.gov (United States)

    Kramer, Eric David; Randall, Lisa

    2016-10-01

    We introduce a potentially powerful method for constraining or discovering a thin dark matter disk in the Milky Way. The method relies on the relationship between the midplane densities and scale heights of interstellar gas being determined by the gravitational potential, which is sensitive to the presence of a dark disk. We show how to use the interstellar gas parameters to set a bound on a dark disk and discuss the constraints suggested by the current data. However, current measurements for these parameters are discordant, with the uncertainty in the constraint being dominated by the molecular hydrogen midplane density measurement, as well as by the atomic hydrogen velocity dispersion measurement. Magnetic fields and cosmic ray pressure, which are expected to play a role, are uncertain as well. The current models and data are inadequate to determine the disk's existence, but taken at face value, may favor its existence depending on the gas parameters used.

  4. Isotope Fractionation in the Interstellar Medium

    Science.gov (United States)

    Charnley, Steven

    2011-01-01

    Anomalously fractionated isotopic material is found in many primitive Solar System objects, such as meteorites and comets. It is thought, in some cases, to trace interstellar matter that was incorporated into the Solar Nebula without undergoing significant processing. We will present the results of models of the nitrogen, oxygen, and carbon fractionation chemistry in dense molecular clouds, particularly in cores where substantial freeze-out of molecules on to dust has occurred. The range of fractionation ratios expected in different interstellar molecules will be discussed and compared to the ratios measured in molecular clouds, comets and meteoritic material. These models make several predictions that can be tested in the near future by molecular line observations, particularly with ALMA.

  5. Local Interstellar Magnetic Field Determined from the Interstellar Boundary Explorer Ribbon

    Science.gov (United States)

    Zirnstein, E. J.; Heerikhuisen, J.; Funsten, H. O.; Livadiotis, G.; McComas, D. J.; Pogorelov, N. V.

    2016-02-01

    The solar wind emanating from the Sun interacts with the local interstellar medium (LISM), forming the heliosphere. Hydrogen energetic neutral atoms (ENAs) produced by the solar-interstellar interaction carry important information about plasma properties from the boundaries of the heliosphere, and are currently being measured by NASA's Interstellar Boundary Explorer (IBEX). IBEX observations show the existence of a “ribbon” of intense ENA emission projecting a circle on the celestial sphere that is centered near the local interstellar magnetic field (ISMF) vector. Here we show that the source of the IBEX ribbon as a function of ENA energy outside the heliosphere, uniquely coupled to the draping of the ISMF around the heliopause, can be used to precisely determine the magnitude (2.93 ± 0.08 μG) and direction (227.°28 ± 0.°69, 34.°62 ± 0.°45 in ecliptic longitude and latitude) of the pristine ISMF far (∼1000 AU) from the Sun. We find that the ISMF vector is offset from the ribbon center by ∼8.°3 toward the direction of motion of the heliosphere through the LISM, and their vectors form a plane that is consistent with the direction of deflected interstellar neutral hydrogen, thought to be controlled by the ISMF. Our results yield draped ISMF properties close to that observed by Voyager 1, the only spacecraft to directly measure the ISMF close to the heliosphere, and give predictions of the pristine ISMF that Voyager 1 has yet to sample.

  6. Interstellar Communication: The Case for Spread Spectrum

    OpenAIRE

    Messerschmitt, David G

    2011-01-01

    Spread spectrum, widely employed in modern digital wireless terrestrial radio systems, chooses a signal with a noise-like character and much higher bandwidth than necessary. This paper advocates spread spectrum modulation for interstellar communication, motivated by robust immunity to radio-frequency interference (RFI) of technological origin in the vicinity of the receiver while preserving full detection sensitivity in the presence of natural sources of noise. Receiver design for noise immun...

  7. Prolactin: estimation and interest in clinical biology

    International Nuclear Information System (INIS)

    The recent development of radio-immunoassay of prolactin has permitted, in recent years, better understanding of its role in hormone regulation. In man, the secretion of prolactin is submitted to physiological variations dependent on sex, age and also environment. It is also modified by numerous drugs. Certain of them are used during stimulation tests and inhibition tests of the pituitary gland. The determination of basic prolactinemia and during dynamic tests is now a factor in basis diagnosis for the clinician who now has available efficacious chemotherapy (derived from rye ergot) in the treatment of hyperprolactinemia

  8. Diffuse interstellar bands in M33

    CERN Document Server

    Smith, Keith T; Evans, Christopher J; Cox, Nick L J; Sarre, Peter J

    2013-01-01

    We present the first sample of diffuse interstellar bands (DIBs) in the nearby galaxy M33. Studying DIBs in other galaxies allows the behaviour of the carriers to be examined under interstellar conditions which can be quite different from those of the Milky Way, and to determine which DIB properties can be used as reliable probes of extragalactic interstellar media. Multi-object spectroscopy of 43 stars in M33 has been performed using Keck/DEIMOS. The stellar spectral types were determined and combined with literature photometry to determine the M33 reddenings E(B-V)_M33. Equivalent widths or upper limits have been measured for the {\\lambda}5780 DIB towards each star. DIBs were detected towards 20 stars, demonstrating that their carriers are abundant in M33. The relationship with reddening is found to be at the upper end of the range observed in the Milky Way. The line of sight towards one star has an unusually strong ratio of DIB equivalent width to E(B-V)_M33, and a total of seven DIBs were detected towards...

  9. H2 recombination on interstellar grains

    International Nuclear Information System (INIS)

    From a consideration of relevant theoretical and experimental data it is concluded that H atoms (but not H2 molecules) will be chemisorbed on interstellar graphite grains, with H2 formation proceeding efficiently for graphite grain temperatures less than 70 K. It is argued that graphite grains will act as the principle sites for H2 formation, with a formation rate of Rapprox. =4 x 10/sup -17/ cm3 s/sup -1/. Heating by H2 molecules formed by surface recombination is analyzed in the context of the available experimental data, and a heating rate is derived and compared with other suggested cloud heating mechanisms. We conclude that H2 recombination will provide the largest heat source in diffuse clouds if the albedo of interstellar dust in the 912--1200 A region is high (approx.0.9), whereas if the albedo in this wavelength region is lower (approx.0.5), photoelectron ejection from grains will tend to predominate, and can explain observed cloud temperatures with a carbon depletion factor of approximately 2, a factor attributable to a normal interstellar abundance of graphite grains

  10. Rangifer and human interests

    Directory of Open Access Journals (Sweden)

    David G. Anderson

    2000-03-01

    Full Text Available This article reviews biological and anthropological literatute on wild and tame Rangifer to demonstrate the powerful effect that this species has had on the imaginations of biologists, social scientists and local hunters. Through identifying a general 'human interest' in Rangifer, the author argues that there is great potential for these three communities to work together. To demonstrate this idea, the paper reviews several examples of successful and unsuccessful 'alliances' between local peoples and both natural and social scientists which have had a fundamental impact upon the history of these sciences. The paper examines recent theorerical models which suggest that human action is a major factor in the behaviour and ecology of the animals. The paper also analyses the ideas of many indigenous people for whom there is no categorical difference between semi-domesticated, semi-sedentary and migratory Rangifer through comparison with many 'anomalous' texts in English and Russian language wildlife biology. By reviewing the history of scholarly interest in Rangifer, the author argues that contemporary models of Rangifer behaviour and identity could be 'revitalised' and 'recalibrated' through the establishment of that dialogue between scientists and local peoples which so characterised the 19th century. Such a dialogue, it is argued, would help mediate many of the political conflicts now appearing in those districts where Rangifer migrate.

  11. Interstellar propulsion using a pellet stream for momentum transfer

    International Nuclear Information System (INIS)

    A pellet-stream concept for interstellar propulsion is described. Small pellets are accelerated in the solar system and accurately guided to an interstellar probe where they are intercepted and transfer momentum. This propulsion system appears to offer orders-of-magnitude improvements in terms of engineering simplicity and power requirements over any other known feasible system for transport over interstellar distance in a time comparable to a human lifespan

  12. Implications of Interstellar Dust and Magnetic Field at the Heliosphere

    OpenAIRE

    Frisch, P. C.

    2007-01-01

    Tiny interstellar dust grains causing the polarization of light from the nearest stars are deflected sideways in the outer heliosheath regions, along with the interstellar magnetic field. Observations of optical polarization of stars beyond the heliosphere nose, suggest the direction of the upwind interstellar magnetic field is relatively constant. The polarizations of nearby stars and offset angle between HeI and HeI flowing into the heliosphere have position angles in galactic coordinates o...

  13. The Astronomical, Astrobiological and Planetary Science Case for Interstellar Spaceflight

    CERN Document Server

    Crawford, Ian A

    2010-01-01

    A review is presented of the scientific benefits of rapid (v >= 0.1c) interstellar spaceflight. Significant benefits are identified in the fields of interstellar medium studies, stellar astrophysics, planetary science and astrobiology. In the latter three areas the benefits would be considerably enhanced if the interstellar vehicle is able to decelerate from its interstellar cruise velocity to rest relative to the target system. Although this will greatly complicate the mission architecture, and extend the overall travel time, the scientific benefits are such that this option should be considered seriously in future studies.

  14. Analysis of "Midnight" Tracks in the Stardust Interstellar Dust Collector: Possible Discovery of a Contemporary Interstellar Dust Grain

    Science.gov (United States)

    Westphal, A. J.; Allen, C.; Bajit, S.; Bastien, R.; Bechtel, H.; Bleuet, P.; Borg, J.; Brenker, F.; Bridges, J.; Brownlee, D. E.; Burchell, M.; Burghammer, M.; Butterworth, A. L.; Cloetens, P.; Cody, G.; Ferrior, T.; Floss, C.; Flynn, G. J.; Frank, D.; Gainsforth, Z.; Grun, E.; Hoppe, P.; Hudson, B.; Kearsley, A.; Lai, B.

    2010-01-01

    In January 2006, the Stardust sample return capsule returned to Earth bearing the first solid samples from a primitive solar system body, Comet 81P/Wild2, and a collector dedicated to the capture and return of contemporary interstellar dust. Both collectors were approximately 0.1m(exp 2) in area and were composed of aerogel tiles (85% of the collecting area) and aluminum foils. The Stardust Interstellar Dust Collector (SIDC) was exposed to the interstellar dust stream for a total exposure factor of 20 m(exp 2) day. The Stardust Interstellar Preliminary Examination (ISPE) is a three-year effort to characterize the collection using nondestructive techniques.

  15. A New Interstellar Cyclic Molecule, Ethylene Oxide

    Science.gov (United States)

    Dickens, J. E.; Irvine, W. M.; Ohishi, M.; Ikeda, M.; Ishikawa, S.; Nummelin, A.; Hjalmarson, A.

    1997-12-01

    Ethylene oxide (c-C2H4O) is only the fourth known ring molecule identified in the interstellar medium, detected in the Galactic Center cloud SgrB2(N) by Dickens et al. (1997). It is the higher energy isomer of both the more familiar interstellar species acetaldehyde (CH3CHO) and the as yet undetected molecule vinyl alcohol (CH2CHOH). Dickens et al. (1997) reported a c-C2H4O molecular column density about an order of magnitude less than that reported for CH3CHO in SgrB2(N). This is a factor of 200 larger than the predictions of the new standard gas phase chemistry model of Lee, Bettens, and Herbst (1996), suggesting that the formation of c-C2H4O may be related to molecular formation on interstellar grains. We present observations of the c-C2H4O to CH3CHO abundance ratio in 5 additional molecular clouds. The data were taken in October 1997 with the Swedish-European Submillimeter Telescope in Chile. The confirmation of ethylene oxide in molecular clouds provides an appealing scenario for the first link in the chain of reactions leading to the origin of life, since it has been suggested as a possible pathway to the formation of the related cyclic molecule oxiranecarbonitrile (c-C3H3NO; cf., Dickens et al. 1996), a precursor to the synthesis of sugar phosphates which comprise the backbone of our molecular genetic structure. References: Dickens, J.E., Irvine, W.M., Ohishi, M., Ikeda, M., Ishikawa, S., Nummelin, A., and Hjalmarson, A. 1997, Astrophys. J., 489 (in press). Dickens, J.E. et al. 1996, Orig. Life Evol. Biosphere, 26, 97. Lee, H.-H., Bettens, R.P.A., and Herbst, E. 1996, Astron. Astrophys. Supp., 119, 111.

  16. Interstellar communication: The case for spread spectrum

    Science.gov (United States)

    Messerschmitt, David G.

    2012-12-01

    Spread spectrum, widely employed in modern digital wireless terrestrial radio systems, chooses a signal with a noise-like character and much higher bandwidth than necessary. This paper advocates spread spectrum modulation for interstellar communication, motivated by robust immunity to radio-frequency interference (RFI) of technological origin in the vicinity of the receiver while preserving full detection sensitivity in the presence of natural sources of noise. Receiver design for noise immunity alone provides no basis for choosing a signal with any specific character, therefore failing to reduce ambiguity. By adding RFI to noise immunity as a design objective, the conjunction of choice of signal (by the transmitter) together with optimum detection for noise immunity (in the receiver) leads through simple probabilistic argument to the conclusion that the signal should possess the statistical properties of a burst of white noise, and also have a large time-bandwidth product. Thus spread spectrum also provides an implicit coordination between transmitter and receiver by reducing the ambiguity as to the signal character. This strategy requires the receiver to guess the specific noise-like signal, and it is contended that this is feasible if an appropriate pseudorandom signal is generated algorithmically. For example, conceptually simple algorithms like the binary expansion of common irrational numbers like π are shown to be suitable. Due to its deliberately wider bandwidth, spread spectrum is more susceptible to dispersion and distortion in propagation through the interstellar medium, desirably reducing ambiguity in parameters like bandwidth and carrier frequency. This suggests a promising new direction in interstellar communication using spread spectrum modulation techniques.

  17. Solar lens mission concept for interstellar exploration

    Science.gov (United States)

    Brashears, Travis; Lubin, Philip; Turyshev, Slava; Shao, Michael; Zhang, Qicheng

    2015-09-01

    The long standing approach to space travel has been to incorporate massive on-board electronics, probes and propellants to achieve space exploration. This approach has led to many great achievements in science, but will never help to explore the interstellar medium. Fortunately, a paradigm shift is upon us in how a spacecraft is constructed and propelled. This paper describes a mission concept to get to our Sun's Gravity Lens at 550AU in less than 10 years. It will be done by using DE-STAR, a scalable solar-powered phased-array laser in Earth Orbit, as a directed energy photon drive of low-mass wafersats. [1] [2] [3] [4] [5] With recent technologies a complete mission can be placed on a wafer including, power from an embedded radio nuclear thermal generator (RTG), PV, laser communications, imaging, photon thrusters for attitude control and other sensors. As one example, a futuristic 200 MW laser array consisting of 1 - 10 kw meter scale sub elements with a 100m baseline can propel a 10 gram wafer scale spacecraft with a 3m laser sail to 60AU/Year. Directed energy propulsion of low-mass spacecraft gives us an opportunity to capture images of Alpha Centauri and its planets, detailed imaging of the cosmic microwave background, set up interstellar communications by using gravity lenses around nearby stars to boost signals from interstellar probes, and much more. This system offers a very large range of missions allowing hundreds of wafer scale payload launches per day to reach this cosmological data reservoir. Directed Energy Propulsion is the only current technology that can provide a near-term path to utilize our Sun's Gravity Lens.

  18. Interstellar colonization and the zoo hypothesis

    International Nuclear Information System (INIS)

    Michael Hart and others have pointed out that current estimates of the number of technological civilizations arisen in the Galaxy since its formation is in fundamental conflict with the expectation that such a civilization could colonize and utilize the entire Galaxy in 10 to 20 million years. This dilemma can be called Hart's paradox. Resolution of the paradox requires that one or more of the following are true: we are the Galaxy's first technical civilization; interstellar travel is immensely impractical or simply impossible; technological civilizations are very short-lived; or we inhabit a wildnerness preserve. The latter is the zoo hypothesis

  19. The 2014 KIDA network for interstellar chemistry

    CERN Document Server

    Wakelam, V; Herbst, E; Pavone, B; Bergeat, A; Béroff, K; Chabot, M; Faure, A; Galli, D; Geppert, W D; Gerlich, D; Gratier, P; Harada, N; Hickson, K M; Honvault, P; Klippenstein, S J; Picard, S D Le; Nyman, G; Ruaud, M; Schlemmer, S; Sims, I R; Talbi, D; Tennyson, J; Wester, R

    2015-01-01

    Chemical models used to study the chemical composition of the gas and the ices in the interstellar medium are based on a network of chemical reactions and associated rate coefficients. These reactions and rate coefficients are partially compiled from data in the literature, when available. We present in this paper kida.uva.2014, a new updated version of the kida.uva public gas-phase network first released in 2012. In addition to a description of the many specific updates, we illustrate changes in the predicted abundances of molecules for cold dense cloud conditions as compared with the results of the previous version of our network, kida.uva.2011.

  20. Composition, structure, and chemistry of interstellar dust

    Science.gov (United States)

    Tielens, A. G. G. M.; Allamandola, L. J.

    1987-01-01

    Different dust components present in the interstellar medium (IM) such as amorphous carbon, polycyclic aromatic hydrocarbons, and those IM components which are organic refractory grains and icy grain mantles are discussed as well as their relative importance. The physical properties of grain surface chemistry are discussed with attention given to the surface structure of materials, the adsorption energy and residence time of species on a grain surface, and the sticking probability. Consideration is also given to the contribution of grains to the gas-phase composition of molecular clouds.

  1. A COMPILATION OF INTERSTELLAR COLUMN DENSITIES

    Energy Technology Data Exchange (ETDEWEB)

    Gudennavar, S. B.; Bubbly, S. G.; Preethi, K. [Department of Physics, Christ University, Hosur Road, Bangalore 560 029, Karnataka (India); Murthy, Jayant, E-mail: shivappa.b.gudennavar@christuniversity.in, E-mail: jmurthy@yahoo.com [Indian Institute of Astrophysics, II Block, Koramangala, Bangalore 560 034, Karnataka (India)

    2012-03-01

    We have collated absorption line data toward 3008 stars in order to create a unified database of interstellar column densities. These data have been taken from a number of different published sources and include many different species and ionizations. The preliminary results from our analysis show a tight relation [N(H)/E(B - V) = 6.12 Multiplication-Sign 10{sup 21}] between N(H) and E(B - V). Similar plots have been obtained with many different species, and their correlations along with the correlation coefficients are presented.

  2. A COMPILATION OF INTERSTELLAR COLUMN DENSITIES

    International Nuclear Information System (INIS)

    We have collated absorption line data toward 3008 stars in order to create a unified database of interstellar column densities. These data have been taken from a number of different published sources and include many different species and ionizations. The preliminary results from our analysis show a tight relation [N(H)/E(B – V) = 6.12 × 1021] between N(H) and E(B – V). Similar plots have been obtained with many different species, and their correlations along with the correlation coefficients are presented.

  3. Interstellar nomads: The problem of detecting comets

    Science.gov (United States)

    Jones, Eric M.; Newman, William I.; Campbell, Donald B.

    1993-01-01

    This paper shows that, using only a modest extrapolation of current phased-array radar and massively parallel processor computer technologies, radar transmitter in the outer solar system or in interstellar space could be used to detect comets passing within 1 or 2 AU of the transmitter. It discusses how this potential development could be instrumental to the colonisation of the outer solar system and beyond. This development is germane to contemporary investigations of the population of the Oort cloud as well as to the Search for Extraterrestrial Intelligence (SETI) question.

  4. Ambient Interstellar Pressure and Superbubble Evolution

    CERN Document Server

    Oey, M S

    2004-01-01

    High ambient interstellar pressure is suggested as a possible factor to explain the ubiquitous observed growth-rate discrepancy for supernova-driven superbubbles and stellar wind bubbles. Pressures of P/k ~ 1e5 cm-3 K are plausible for regions with high star formation rates, and these values are intermediate between the estimated Galactic mid-plane pressure and those observed in starburst galaxies. High-pressure components also are commonly seen in Galactic ISM localizations. We demonstrate the sensitivity of shell growth to the ambient pressure, and suggest that superbubbles ultimately might serve as ISM barometers.

  5. LOCAL INTERSTELLAR MAGNETIC FIELD DETERMINED FROM THE INTERSTELLAR BOUNDARY EXPLORER RIBBON

    Energy Technology Data Exchange (ETDEWEB)

    Zirnstein, E. J.; Livadiotis, G.; McComas, D. J. [Southwest Research Institute, San Antonio, TX 78228 (United States); Heerikhuisen, J.; Pogorelov, N. V. [Department of Space Science, University of Alabama in Huntsville, Huntsville, AL 35899 (United States); Funsten, H. O., E-mail: ezirnstein@swri.edu [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

    2016-02-10

    The solar wind emanating from the Sun interacts with the local interstellar medium (LISM), forming the heliosphere. Hydrogen energetic neutral atoms (ENAs) produced by the solar-interstellar interaction carry important information about plasma properties from the boundaries of the heliosphere, and are currently being measured by NASA's Interstellar Boundary Explorer (IBEX). IBEX observations show the existence of a “ribbon” of intense ENA emission projecting a circle on the celestial sphere that is centered near the local interstellar magnetic field (ISMF) vector. Here we show that the source of the IBEX ribbon as a function of ENA energy outside the heliosphere, uniquely coupled to the draping of the ISMF around the heliopause, can be used to precisely determine the magnitude (2.93 ± 0.08 μG) and direction (227.°28 ± 0.°69, 34.°62 ± 0.°45 in ecliptic longitude and latitude) of the pristine ISMF far (∼1000 AU) from the Sun. We find that the ISMF vector is offset from the ribbon center by ∼8.°3 toward the direction of motion of the heliosphere through the LISM, and their vectors form a plane that is consistent with the direction of deflected interstellar neutral hydrogen, thought to be controlled by the ISMF. Our results yield draped ISMF properties close to that observed by Voyager 1, the only spacecraft to directly measure the ISMF close to the heliosphere, and give predictions of the pristine ISMF that Voyager 1 has yet to sample.

  6. Determination of Interstellar O Parameters Using the First Two Years of Data From the Interstellar Boundary Explorer

    Science.gov (United States)

    Schwadron, N. A.; Möbius, E.; McComas, D. J.; Bochsler, P.; Bzowski, M.; Fuselier, S. A.; Livadiotis, G.; Frisch, P.; Müller, H.-R.; Heirtzler, D.; Kucharek, H.; Lee, M. A.

    2016-09-01

    The direct measurements of interstellar matter by the Interstellar Boundary Explorer (IBEX) mission have opened a new and important chapter in our study of the interactions that control the boundaries of our heliosphere. Here we derive for the quantitative information about interstellar O flow parameters from IBEX low-energy neutral atom data for the first time. Specifically, we derive a relatively narrow four-dimensional parameter tube along which interstellar O flow parameters must lie. Along the parameter tube, we find a large uncertainty in interstellar O flow longitude, 76.°0 ± 3.°4 from χ 2 analysis and 76.°5 ± 6.°2 from a maximum likelihood fit, which is statistically consistent with the flow longitude derived for interstellar He, 75.°6 ± 1.°4. The best-fit O and He temperatures are almost identical at a reference flow longitude of 76°, which provides a strong indication that the local interstellar plasma near the Sun is relatively unaffected by turbulent heating. However, key differences include an oxygen parameter tube for the interstellar speed (relation between speed and longitude) that has higher speeds than those in the corresponding parameter tube for He, and an upstream flow latitude for oxygen that is southward of the upstream flow latitude for helium. Both of these differences are likely the result of enhanced filtration of interstellar oxygen due to its charge-exchange ionization rate, which is higher than that for helium. Furthermore, we derive an interstellar O density near the termination shock of {5.8}-0.8+0.9× {10}-5 cm‑3 that, within uncertainties, is consistent with previous estimates. Thus, we use IBEX data to probe the interstellar properties of oxygen.

  7. Photodissociation regions in the interstellar medium of galaxies

    NARCIS (Netherlands)

    Hollenbach, DJ; Tielens, AGGM

    1999-01-01

    The interstellar medium of galaxies is the reservoir out of which stars are born and into which stars inject newly created elements as they age. The physical properties of the interstellar medium are governed in part by the radiation emitted by these stars. Far-ultraviolet (6 eV

  8. Fulleranes and Carbon Nanostructures in the Interstellar Medium

    Science.gov (United States)

    Iglesias-Groth, Susana; Cataldo, Franco

    We review the potential contribution of single fullerenes and buckyonions to interstellar extinction. Photoabsorption spectra of these molecules are compared with some of the most relevant features of interstellar extinction, the UV bump, the far UV rise and the diffuse interstellar bands. According to semiempirical models, photoabsorption by fullerenes (single and multishell) could explain the shape, width and peak energy of the most prominent feature of the interstellar absorption, the UV bump at 2,175 Å. Other weaker transitions are predicted in the optical and near-infrared providing a potential explanation for diffuse interstellar bands. In particular, several fullerenes could contribute to the well known strong DIB at 4,430 Å comparing cross sections and available data for this DIB and the UV bump we estimate a density of fullerenes in the diffuse interstellar medium of 0.1-0.2 ppm. These molecules could then be a major reservoir for interstellar carbon. We give an estimation of the carbon fraction locked in these molecules. We discuss the rotation rates and electric dipole emission of hydrogenated icosahedral fullerenes in various phases of the interstellar medium. These molecules could be the carriers of the anomalous microwave emission detected by Watson et al. (Astrophys. J. 624:L89, 2005) in the Perseus molecular complex and Cassasus et al. (2006) in the dark cloud LDN 1622. Hydrogenated forms of fullerenes may account for the dust-correlated microwave emission detected in our Galaxy by Cosmic Microwave Background experiments.

  9. Study of radionuclides speciation with biological molecules of interest by spectrometric techniques; Etude de la speciation des radionucleides avec les molecules d'interet biologique par approche spectrometrique

    Energy Technology Data Exchange (ETDEWEB)

    Lourenco, V

    2007-07-15

    Mechanisms of complexation and accumulation of the radionuclides at the cellular and molecular level are complex and poorly known because the studies on these subjects are scarce. Within the framework of this thesis, we studied the interactions of these cations with biological molecules of interest. We chose to focus on an actinide: uranium (VI) as well as europium as an analogue of trivalent actinides. The selected biological molecules are the phyto-chelatins: their role is to protect cells against intrusions from nonessential heavy metals (thus toxic). These proteins are likely to be implied in the mechanisms of sequestration of radionuclides in living organisms. However, their structure is complex, this is why, in order to better include/understand their reactivity, we extended our studies to lower entities which constitute them (amino acid: glycine, glutamic acid and cysteine; polypeptides: glutathione reduced and oxidized forms). In particular, we determined solution speciation (stoichiometry, structure) as well as the complexing constants associated with the formation with these species. These studies were undertaken by Time Resolved Laser induced Fluorescence (TRLIF), Electro-Spray-Mass Spectrometry (ES-MS), Nuclear Magnetic Resonance (NMR), Fourier Transform Infra-Rouge spectroscopy (FTIR) and Extended X-ray Absorption Fine Structure Spectroscopy (EXAFS).The determination of the complexation constants enabled us to conclude that the complexing capacity of these molecules with respect to radionuclides was moderate (log{sub 10}K{sub 1} {<=} 3, pH 3 or 6), the formed species are mononuclear with only one ligand molecule (1:1). The interaction is performed via oxygenated (hard) groups. The direct complexation of europium with phyto-chelatins at acidic pH was studied jointly by TRLIF and ES-MS. The complexing capacity of these molecules is much higher than that of GSH from which they result. The interaction of europium with metallothioneins is, on the contrary

  10. Searching for Cost Optimized Interstellar Beacons

    CERN Document Server

    Benford, Gregory; Benford, Dominic

    2009-01-01

    What would SETI Beacon transmitters be like if built by civilizations with a variety of motivations, but who cared about cost? We studied in a companion paper how, for fixed power density in the far field, we could build a cost-optimum interstellar Beacon system. Here we consider, if someone like us were to produce a Beacon, how should we look for it? High-power transmitters might be built for wide variety of motives other than twoway communication; Beacons built to be seen over thousands of light years are such. Altruistic Beacon builders will have to contend with other altruistic causes, just as humans do, so may select for economy of effort. Cost, spectral lines near 1 GHz and interstellar scintillation favor radiating frequencies substantially above the classic water hole. Therefore the transmission strategy for a distant, cost-conscious Beacon will be a rapid scan of the galactic plane, to cover the angular space. Such pulses will be infrequent events for the receiver. Such Beacons built by distant advan...

  11. Galactic civilizations - Population dynamics and interstellar diffusion

    Science.gov (United States)

    Newman, W. I.; Sagan, C.

    1981-01-01

    A model is developed of the interstellar diffusion of galactic civilizations which takes into account the population dynamics of such civilizations. The problem is formulated in terms of potential theory, with a family of nonlinear partial differential and difference equations specifying population growth and diffusion for an organism with advantageous genes that undergoes random dispersal while increasing in population locally, and a population at zero population growth. In the case of nonlinear diffusion with growth and saturation, it is found that the colonization wavefront from the nearest independently arisen galactic civilization can have reached the earth only if its lifetime exceeds 2.6 million years, or 20 million years if discretization can be neglected. For zero population growth, the corresponding lifetime is 13 billion years. It is concluded that the earth is uncolonized not because interstellar spacefaring civilizations are rare, but because there are too many worlds to be colonized in the plausible colonization lifetime of nearby civilizations, and that there exist no very old galactic civilizations with a consistent policy of the conquest of inhabited worlds.

  12. Formation of Benzene in the Interstellar Medium

    Science.gov (United States)

    Jones, Brant M.; Zhang, Fangtong; Kaiser, Ralf I.; Jamal, Adeel; Mebel, Alexander M.; Cordiner, Martin A.; Charnley, Steven B.; Crim, F. Fleming (Editor)

    2010-01-01

    Polycyclic aromatic hydrocarbons and related species have been suggested to play a key role in the astrochemical evolution of the interstellar medium, but the formation mechanism of even their simplest building block-the aromatic benzene molecule-has remained elusive for decades. Here we demonstrate in crossed molecular beam experiments combined with electronic structure and statistical calculations that benzene (C6H6) can be synthesized via the barrierless, exoergic reaction of the ethynyl radical and 1,3- butadiene, C2H + H2CCHCHCH2 --> C6H6, + H, under single collision conditions. This reaction portrays the simplest representative of a reaction class in which aromatic molecules with a benzene core can be formed from acyclic precursors via barrierless reactions of ethynyl radicals with substituted 1,3-butadlene molecules. Unique gas-grain astrochemical models imply that this low-temperature route controls the synthesis of the very first aromatic ring from acyclic precursors in cold molecular clouds, such as in the Taurus Molecular Cloud. Rapid, subsequent barrierless reactions of benzene with ethynyl radicals can lead to naphthalene-like structures thus effectively propagating the ethynyl-radical mediated formation of aromatic molecules in the interstellar medium.

  13. Interstellar sulfur isotopes and stellar oxygen burning

    CERN Document Server

    Chin, Y N; Whiteoak, J B; Langer, N; Churchwell, E B; Chin, Y N

    1995-01-01

    A 12C32S, 13C32S, 12C34S, and 12C33S J = 2 - 1 line survey has been made to study interstellar 32S/34S and 34S/33S ratios from the galactic disk. The four CS isotopomers were detected in 20 star forming regions with galactocentric distances between 3 and 9 kpc. From a comparison of line velocities, the C33S J = 2 - 1 rest frequency is about 250 kHz below the value given in the Lovas (1992) catalog. Taking 12C/13C ratios from Wilson & Rood (1994) and assuming equal 12C32S and 13C32S excitation temperatures and beam filling factors, 12C32S opacities are in the range 3 to 15; average 32S/34S and 34S/33S isotope ratios are 24.4 +/- 5.0 and 6.27 +/- 1.01, respectively. While no systematic variation in the 34S/33S isotope ratio is found, the 32S/34S ratio increases with galactocentric distance when accounting for the 12C/13C gradient of the galactic disk. A fit to the unweighted data yields 32S/34S = 3.3 +/- 0.5 (dGC/kpc) + 4.1 +/- 3.1 with a correlation coefficient of 0.84. Since the interstellar sulfur (S) is...

  14. Precursors to Interstellar Shocks of Solar Origin

    Science.gov (United States)

    Gurnett, D. A.; Kurth, W. S.; Stone, E. C.; Cummings, A. C.; Krimigis, S. M.; Decker, R. B.; Ness, N. F.; Burlaga, L. F.

    2015-12-01

    On or about 2012 August 25, the Voyager 1 spacecraft crossed the heliopause into the nearby interstellar plasma. In the nearly three years that the spacecraft has been in interstellar space, three notable particle and field disturbances have been observed, each apparently associated with a shock wave propagating outward from the Sun. Here, we present a detailed analysis of the third and most impressive of these disturbances, with brief comparisons to the two previous events, both of which have been previously reported. The shock responsible for the third event was first detected on 2014 February 17 by the onset of narrowband radio emissions from the approaching shock, followed on 2014 May 13 by the abrupt appearance of intense electron plasma oscillations generated by electrons streaming outward ahead of the shock. Finally, the shock arrived on 2014 August 25, as indicated by a jump in the magnetic field strength and the plasma density. Various disturbances in the intensity and anisotropy of galactic cosmic rays were also observed ahead of the shock, some of which are believed to be caused by the reflection and acceleration of cosmic rays by the magnetic field jump at the shock, and/or by interactions with upstream plasma waves. Comparisons to the two previous weaker events show somewhat similar precursor effects, although differing in certain details. Many of these effects are very similar to those observed in the region called the "foreshock" that occurs upstream of planetary bow shocks, only on a vastly larger spatial scale.

  15. Ion-Neutral Collisions in the Interstellar Medium: Wave Damping and Elimination of Collisionless Processes

    CERN Document Server

    Spangler, Steven R; Redfield, Seth

    2010-01-01

    Most phases of the interstellar medium contain neutral atoms in addition to ions and electrons. This introduces differences in plasma physics processes in those media relative to the solar corona and the solar wind at a heliocentric distance of 1 astronomical unit. In this paper, we consider two well-diagnosed, partially-ionized interstellar plasmas. The first is the Diffuse Ionized Gas (DIG) which is probably the extensive phase in terms of volume. The second is the gas that makes up the Local Clouds of the Very Local Interstellar Medium (VLISM). Ion-neutral interactions seem to be important in both media. In the DIG, ion-neutral collisions are relatively rare, but sufficiently frequent to damp magnetohydrodynamic (MHD) waves (as well as propagating MHD eddies) within less than a parsec of the site of generation. This result raises interesting questions about the sources of turbulence in the DIG. In the case of the VLISM, the ion-neutral collision frequency is higher than that in the DIG, because the hydroge...

  16. Ion-Neutral Collisions in the Interstellar Medium: Wave Damping and Elimination of Collisionless Processes

    Science.gov (United States)

    Spangler, Steven R.; Savage, Allison H.; Redfield, Seth

    2011-09-01

    Most phases of the interstellar medium contain neutral atoms in addition to ions and electrons. This introduces differences in plasma physics processes in those media relative to the solar corona and the solar wind at a heliocentric distance of 1 astronomical unit. In this paper, we consider two well-diagnosed, partially-ionized interstellar plasmas. The first is the Warm Ionized Medium (WIM) which is probably the most extensive phase in terms of volume. The second is the gas of the Local Clouds of the Very Local Interstellar Medium (VLISM). Ion-neutral interactions seem to be important in both media. In the WIM, ion-neutral collisions are relatively rare, but sufficiently frequent to damp magnetohydrodynamic (MHD) waves (as well as propagating MHD eddies) within less than a parsec of the site of generation. This result raises interesting questions about the sources of turbulence in the WIM. In the case of the VLISM, the ion-neutral collision frequency is higher than that in the WIM, because the hydrogen is partially neutral rather than fully ionized. We present results showing that prominent features of coronal and solar wind turbulence seem to be absent in VLISM turbulence. For example, ion temperature does not depend on ion mass. This difference may be due to ion-neutral collisions, which distribute power from more effectively heated massive ions such as iron to other ion species and neutral atoms.

  17. Photochirogenesis: Photochemical models on the absolute asymmetric formation of amino acids in interstellar space

    Science.gov (United States)

    Meinert, Cornelia; de Marcellus, Pierre; Le Sergeant D'Hendecourt, Louis; Nahon, Laurent; Jones, Nykola C.; Hoffmann, Søren V.; Bredehöft, Jan Hendrik; Meierhenrich, Uwe J.

    2011-10-01

    Proteins of all living organisms including plants, animals, and humans are made up of amino acid monomers that show identical stereochemical L-configuration. Hypotheses for the origin of this symmetry breaking in biomolecules include the absolute asymmetric photochemistry model by which interstellar ultraviolet (UV) circularly polarized light (CPL) induces an enantiomeric excess in chiral organic molecules in the interstellar/circumstellar media. This scenario is supported by a) the detection of amino acids in the organic residues of UV-photo-processed interstellar ice analogues, b) the occurrence of L-enantiomer-enriched amino acids in carbonaceous meteorites, and c) the observation of CPL of the same helicity over large distance scales in the massive star-forming region of Orion. These topics are of high importance in topical biophysical research and will be discussed in this review. Further evidence that amino acids and other molecules of prebiotic interest are asymmetrically formed in space comes from studies on the enantioselective photolysis of amino acids by UV-CPL. Also, experiments have been performed on the absolute asymmetric photochemical synthesis of enantiomer-enriched amino acids from mixtures of astrophysically relevant achiral precursor molecules using UV-circularly polarized photons. Both approaches are based on circular dichroic transitions of amino acids that will be highlighted here as well. These results have strong implications on our current understanding of how life's precursor molecules were possibly built and how life selected the left-handed form of proteinogenic amino acids.

  18. Chemical Simulations of Prebiotic Molecules: Interstellar Ethanimine Isomers

    Science.gov (United States)

    Quan, Donghui; Herbst, Eric; Corby, Joanna F.; Durr, Allison; Hassel, George

    2016-06-01

    The E- and Z-isomers of ethanimine (CH3CHNH) were recently detected toward the star-forming region Sagittarius (Sgr) B2(N) using the Green Bank Telescope PRIMOS cm-wave spectral data, and imaged by the Australia Telescope Compact Array. Ethanimine is not reported in the hot cores of Sgr B2, but only in gas that absorbs at +64 and +82 km s-1 in the foreground of continuum emission generated by H ii regions. The ethanimine isomers can serve as precursors of the amino acid alanine and may play important roles in forming biological molecules in the interstellar medium. Here we present a study of the chemistry of ethanimine using a gas-grain simulation based on rate equations, with both isothermal and warm-up conditions. In addition, the density, kinetic temperature, and cosmic ray ionization rate have been varied. For a variety of physical conditions in the warm-up models for Sgr B2(N) and environs, the simulations show reasonable agreement with observationally obtained abundances. Isothermal models of translucent clouds along the same line of sight yield much lower abundances, so that ethanimine would be much more difficult to detect in these sources despite the fact that other complex molecules have been detected there.

  19. Chemical Simulations of Prebiotic Molecules: Interstellar Ethanimine Isomers

    Science.gov (United States)

    Quan, Donghui; Herbst, Eric; Corby, Joanna F.; Durr, Allison; Hassel, George

    2016-06-01

    The E- and Z-isomers of ethanimine (CH3CHNH) were recently detected toward the star-forming region Sagittarius (Sgr) B2(N) using the Green Bank Telescope PRIMOS cm-wave spectral data, and imaged by the Australia Telescope Compact Array. Ethanimine is not reported in the hot cores of Sgr B2, but only in gas that absorbs at +64 and +82 km s‑1 in the foreground of continuum emission generated by H ii regions. The ethanimine isomers can serve as precursors of the amino acid alanine and may play important roles in forming biological molecules in the interstellar medium. Here we present a study of the chemistry of ethanimine using a gas-grain simulation based on rate equations, with both isothermal and warm-up conditions. In addition, the density, kinetic temperature, and cosmic ray ionization rate have been varied. For a variety of physical conditions in the warm-up models for Sgr B2(N) and environs, the simulations show reasonable agreement with observationally obtained abundances. Isothermal models of translucent clouds along the same line of sight yield much lower abundances, so that ethanimine would be much more difficult to detect in these sources despite the fact that other complex molecules have been detected there.

  20. Diffuse interstellar bands as probes of small-scale interstellar structure

    CERN Document Server

    Smith, Keith T; Sarre, Peter J

    2013-01-01

    We present observations which probe the small-scale structure of the interstellar medium using diffuse interstellar bands (DIBs). Towards HD 168075/6 in the Eagle Nebula, significant differences in DIB absorption are found between the two lines of sight, which are separated by 0.25 pc, and {\\lambda}5797 exhibits a velocity shift. Similar data are presented for four stars in the {\\mu} Sgr system. We also present a search for variations in DIB absorption towards {\\kappa} Vel, where the atomic lines are known to vary on scales of ~10 AU. Observations separated by ~9 yr yielded no evidence for changes in DIB absorption strength over this scale, but do reveal an unusual DIB spectrum.

  1. Comparisons of the Interstellar Magnetic Field Directions obtained from the IBEX Ribbon and Interstellar Polarizations

    CERN Document Server

    Frisch, Priscilla C; Berdyugin, Andrei; Funsten, Herbert O; Magalhaes, Mario; McComas, David J; Piirola, Vilppu; Schwadron, Nathan A; Slavin, Jonathan D; Wiktorowicz, Sloane J

    2010-01-01

    Variations in the spatial configuration of the interstellar magnetic field (ISMF) near the Sun can be constrained by comparing the ISMF direction at the heliosphere found from the Interstellar Boundary Explorer spacecraft (IBEX) observations of a 'Ribbon' of energetic neutral atoms (ENAs), with the ISMF direction derived from optical polarization data for stars within ~40 pc. Using interstellar polarization observations towards ~30 nearby stars within 90 deg of the heliosphere nose, we find that the best fits to the polarization position angles are obtained for a magnetic pole directed towards ecliptic coordinates of lambda, beta 263 deg, 37 deg (or galactic coordinates of L,B 38 deg, 23deg), with uncertainties of +/- 35 deg, based on the broad minimum of the best fits and the range of data quality. This magnetic pole is 33 deg from the magnetic pole that is defined by the center of the arc of the ENA Ribbon. The IBEX ENA ribbon is seen in sightlines that are perpendicular to the ISMF as it drapes over the he...

  2. The interstellar dust reservoir: SPICA's view on dust production and the interstellar medium in galaxies

    CERN Document Server

    Kemper, F; Jones, O C; Srinivasan, S

    2016-01-01

    Typical galaxies emit about one third of their energy in the infrared. The origin of this emission reprocessed starlight absorbed by interstellar dust grains and reradiated as thermal emission in the infrared. In particularly dusty galaxies, such as starburst galaxies, the fraction of energy emitted in the infrared can be as high as 90%. Dust emission is found to be an excellent tracer of the beginning and end stages of a star's life, where dust is being produced by post-main-sequence stars, subsequently added to the interstellar dust reservoir, and eventually being consumed by star and planet formation. This work reviews the current understanding of the size and properties of this interstellar dust reservoir, by using the Large Magellanic Cloud as an example, and what can be learned about the dust properties and star formation in galaxies from this dust reservoir, using SPICA, building on previous work performed with the Herschel and Spitzer Space Telescopes, as well as the Infrared Space Observatory.

  3. Thermal instability in the interstellar medium

    Directory of Open Access Journals (Sweden)

    J. Ghanbari

    2000-06-01

    Full Text Available   This study demonstrates how thermal structures in the interstellar medium can emerge as a result of thermal instability. For a two-dimensional case, the steady state thermal structures was investigeted and it was shown that a large class of solutions exist. For a one –dimensional case the conductivity was found to be negligible. The effects of to cal cooling on the thermal instability were explored in some depth. In this case analytical results for time-dependent cooling function were presented, too. We studied nonlinear wave phenomena in thermal fluid systems, with a particular emphasis on presenting analytical results. When conductivity is proportional to temperature, the beliavior of thermal waves is soliton like. For slow thermal waves, approximate analytical results were presented. Extensions of this work are discussed briefly, together with possible astrophysical applications.

  4. A speckle hologram of the interstellar plasma

    Science.gov (United States)

    Desai, K. M.; Gwinn, C. R.; Reynolds, J.; King, E. A.; Jauncey, D.; Flanagan, C.; Nicolson, G.; Preston, R. A.; Jones, D. L.

    1992-01-01

    Observations of a speckle hologram of scattering material along the line of sight to the Vela pulsar indicate that this material is concentrated in the Vela supernova remnant, deep within the Gum Nebula. The speckle hologram is observed through the amplitude and phase variations of the interferometric cross-power spectrum with time and frequency. These variations describe the density fluctuations of the interstellar plasma, in a holographic fashion. The decorrelation due to the phase variations of the speckles yields the angular size of the scattering disk; comparison with the bandwidth of their amplitude variations yields a characteristic distance from earth to the scattering material of 0.81 +/- 0.03 of the distance from earth to the pulsar. This result is consistent with theories of irregularities associated with particle acceleration in shocks in supernova remnants.

  5. AN ULTRAVIOLET SEARCH FOR INTERSTELLAR CS

    International Nuclear Information System (INIS)

    High- and medium-resolution ultraviolet spectra from the Space Telescope Imaging Spectrograph (STIS) and the Goddard High Resolution Spectrograph (GHRS) were used to study the diatomic molecule CS through the C-X(0,0) band at 1401 A. The band was modeled to verify profile shape. The rest wavelength of the C-X band is refined to a value of 1400.88 A and a 3σ lower limit is set on the oscillator strength at 0.14 based on equivalent width upper limits of the A-X(0,0) CS Band at 2577 A. The strength of the 1401 A band is compared to other interstellar parameters and implications for CS formation and destruction are briefly discussed.

  6. Atom addition reactions in interstellar ice analogues

    CERN Document Server

    Linnartz, Harold; Fedoseev, Gleb

    2015-01-01

    This review paper summarizes the state-of-the-art in laboratory based interstellar ice chemistry. The focus is on atom addition reactions, illustrating how water, carbon dioxide and methanol can form in the solid state at astronomically relevant temperatures, and also the formation of more complex species such as hydroxylamine, an important prebiotic molecule, and glycolaldehyde, the smallest sugar, is discussed. These reactions are particularly relevant during the dark ages of star and planet formation, i.e., when the role of UV light is restricted. A quantitative characterization of such processes is only possible through dedicated laboratory studies, i.e., under full control of a large set of parameters such as temperature, atom-flux, and ice morphology. The resulting numbers, physical and chemical constants, e.g., barrier heights, reaction rates and branching ratios, provide information on the molecular processes at work and are needed as input for astrochemical models, in order to bridge the timescales t...

  7. Interstellar Communication: The Case for Spread Spectrum

    CERN Document Server

    Messerschmitt, David G

    2012-01-01

    Spread spectrum, widely employed in modern digital wireless terrestrial radio systems, chooses a signal with a noise-like character and much higher bandwidth than necessary. This paper advocates spread spectrum modulation for interstellar communication, motivated by robust immunity to radio-frequency interference (RFI) of technological origin in the vicinity of the receiver while preserving full detection sensitivity in the presence of natural sources of noise. Receiver design for noise immunity alone provides no basis for choosing a signal with any specific character, therefore failing to reduce ambiguity. By adding RFI to noise immunity as a design objective, the conjunction of choice of signal (by the transmitter) together with optimum detection for noise immunity (in the receiver) leads through simple probabilistic argument to the conclusion that the signal should possess the statistical properties of a burst of white noise. Thus spread spectrum also provides an implicit coordination between transmitter a...

  8. Supernova Feedback in an Inhomogeneous Interstellar Medium

    CERN Document Server

    Martizzi, Davide; Quataert, Eliot

    2014-01-01

    Supernova (SN) feedback is one of the key processes shaping the interstellar medium (ISM) of galaxies. SNe contribute to (and in some cases may dominate) driving turbulence in the ISM and accelerating galactic winds. Modern cosmological simulations have sufficient resolution to capture the main structures in the ISM of galaxies, but are typically still not capable of explicitly resolving all of the small-scale stellar feedback processes, including the expansion of supernova remnants (SNRs). We perform a series of controlled three-dimensional hydrodynamic (adaptive mesh refinement, AMR) simulations of single SNRs expanding in an inhomogeneous density field with statistics motivated by those of the turbulent ISM. We use these to quantify the momentum and thermal energy injection from SNe as a function of spatial scale and the density, metallicity, and structure of the ambient medium. Using these results, we develop an analytic sub-resolution model for SN feedback for use in galaxy formation simulations. We then...

  9. Sending and Searching for Interstellar Messages

    CERN Document Server

    Zaitsev, Alexander

    2007-01-01

    There is a close interrelation between Searching for Extraterrestrial Intelligence (SETI) and Messaging to Extraterrestrial Intelligence (METI). For example, the answers to the questions "Where to search" and "Where to send" are equivalent, in that both require an identical selection from the same target star lists. Similar considerations lead to a strategy of time synchronization between sending and searching. Both SETI and METI use large reflectors. The concept of "magic frequencies" may be applicable to both SETI and METI. Efforts to understand an alien civilization's Interstellar Messages (IMs), and efforts to compose our own IMs so they will be easily understood by unfamiliar Extraterrestrials, are mutually complementary. Furthermore, the METI-question: "How can we benefit from sending IMs, if a response may come only thousands of years later?" begs an equivalent SETI-question: "How can we benefit from searching, if it is impossible now to perceive the motivations and feelings of those who may have sent ...

  10. Molecular hydrogen formation in the interstellar medium

    CERN Document Server

    Cazaux, S

    2002-01-01

    We have developed a model for molecular hydrogen formation under astrophysically relevant conditions. This model takes fully into account the presence of both physisorbed and chemisorbed sites on the surface, allows quantum mechanical diffusion as well as thermal hopping for absorbed H-atoms, and has been benchmarked versus recent laboratory experiments on H2 formation on silicate surfaces. The results show that H2 formation on grain surface is efficient in the interstellar medium up to some 300K. At low temperatures (<100K), H2 formation is governed by the reaction of a physisorbed H with a chemisorbed H. At higher temperatures, H2 formation proceeds through reaction between two chemisorbed H atoms. We present simple analytical expressions for H2 formation which can be adopted to a wide variety of surfaces once their surfaces characteristics have been determined experimentally.

  11. Interstellar grains in elliptical galaxies grain evolution

    CERN Document Server

    Tsai, J C; Tsai, John C; Mathews, William G

    1995-01-01

    We consider the lifecycle of dust introduced into the hot interstellar medium in isolated elliptical galaxies. Dust grains are ejected into galactic-scale cooling flows in large ellipticals by normal mass loss from evolving red giants. Newly introduced dust rapidly enters the hot gas environment and is sputtered away by thermal collisions with ions. Before the grains are completely sputtered away, they emit prodigious amounts of infrared radiation which may contribute to the large far infrared luminosities observed in ellipticals. In order to study the global properties of grains in ellipticals we construct a new series of King-type galactic models which are consistent with the fundamental plane, galactic mass to light ratios and other relevant observational correlations. We describe a new ``continuity'' procedure to construct simple time-dependent gas dynamic models for cooling flows. In all galaxy models, although grains can flow a considerable distance from their radius of origin before being sputtered awa...

  12. Formation of Cyanoformaldehyde in the interstellar space

    CERN Document Server

    Das, Ankan; Chakrabarti, Sandip K; Saha, Rajdeep; Chakrabarti, Sonali

    2013-01-01

    Cyanoformaldehyde (HCOCN) molecule has recently been suspected towards the Sagittarius B2(N) by the Green Bank telescope, though a confirmation of this observation has not yet been made. In and around a star forming region, this molecule could be formed by the exothermic reaction between two abundant interstellar species, H$_2$CO and CN. Till date, the reaction rate coefficient for the formation of this molecule is unknown. Educated guesses were used to explain the abundance of this molecule by chemical modeling. In this paper, we carried out quantum chemical calculations to find out empirical rate coefficients for the formation of HCOCN and different chemical properties during the formation of HCOCN molecules. Though HCOCN is stable against unimolecular decomposition, this gas phase molecule could be destroyed by many other means, like: ion-molecular reactions or by the effect of cosmic rays. Ion-molecular reaction rates are computed by using the capture theories. We have also included the obtained rate coef...

  13. Template matching method for the analysis of interstellar cloud structure

    CERN Document Server

    Juvela, M

    2016-01-01

    The structure of interstellar medium can be characterised at large scales in terms of its global statistics (e.g. power spectra) and at small scales by the properties of individual cores. Interest has been increasing in structures at intermediate scales, resulting in a number of methods being developed for the analysis of filamentary structures. We describe the application of the generic template-matching (TM) method to the analysis of maps. Our aim is to show that it provides a fast and still relatively robust way to identify elongated structures or other image features. We present the implementation of a TM algorithm for map analysis. The results are compared against rolling Hough transform (RHT), one of the methods previously used to identify filamentary structures. We illustrate the method by applying it to Herschel surface brightness data. The performance of the TM method is found to be comparable to that of RHT but TM appears to be more robust regarding the input parameters, for example, those related t...

  14. Reanalysis of the interstellar CH abundance

    International Nuclear Information System (INIS)

    A detailed investigation of the term structure of the X2II, A2Δ, B2Σ-, and C2Σ+ systems of CH is presented, as well as a discussion of a number of errors that have been found with respect to the historical analysis of the interstellar CH abundance. The primary cause for these errors is the neglect of the Λ doubling of the ground state. The effects of including this splitting are the following: (1) the oscillator strength doubles for each line arising from the ground state of the B-X and C-X electronic systems; (2) the 4300, 3886, and 3143 A lines each consist of a blend of two lines separated by 1.43, 1.28, and 2.17 km s-1, respectively; (3) the line at 3886 A arises solely from the upper half of the Λ doublet, and the lines at 3890 and 3878 A arise from the lower half of the Λ doublet; (4) the line at 3143 A arises solely from the lower half of the Λ doublet, and the lines at 3146 and 3137 A arise from the upper half of the Λ doublet; (5) the excitation temperature (a measure of the relative level population) of the ground-state Λ doublet has been calculated for the interstellar CH along the line of sight toward four stars (zeta Per, zeta Oph, X Per, and chi Oph) using published equivalent withs. The excitation temperature appears to be less than zero toward X Per and zeta Per, indicating that the population of the ground-state Λ doublet is inverted. The level populations along other lines of sight are known to be inverted from observations of the radio CH lines; this is the first detection of a radio maser by optical methods

  15. The Search for Interstellar Sulfide Grains

    Science.gov (United States)

    Keller, Lindsay P.; Messenger, Scott

    2010-01-01

    The lifecycle of sulfur in the galaxy is poorly understood. Fe-sulfide grains are abundant in early solar system materials (e.g. meteorites and comets) and S is highly depleted from the gas phase in cold, dense molecular cloud environments. In stark contrast, sulfur is essentially undepleted from the gas phase in the diffuse interstellar medium, indicating that little sulfur is incorporated into solid grains in this environment. It is widely believed that sulfur is not a component of interstellar dust grains. This is a rather puzzling observation unless Fe-sulfides are not produced in significant quantities in stellar outflows, or their lifetime in the ISM is very short due to rapid destruction. Fe sulfide grains are ubiquitous in cometary samples where they are the dominant host of sulfur. The Fe-sulfides (primarily pyrrhotite; Fe(1-x)S) are common, both as discrete 0.5-10 micron-sized grains and as fine (5-10 nm) nanophase inclusions within amorphous silicate grains. Cometary dust particles contain high abundances of well-preserved presolar silicates and organic matter and we have suggested that they should contain presolar sulfides as well. This hypothesis is supported by the observation of abundant Fe-sulfides grains in dust around pre- and post-main sequence stars inferred from astronomical spectra showing a broad 23 micron IR feature due to FeS. Fe-sulfide grains also occur as inclusions in bona fide circumstellar amorphous silicate grains and as inclusions within deuterium-rich organic matter in cometary dust samples. Our irradiation experiments show that FeS is far more resistant to radiation damage than silicates. Consequently, we expect that Fe sulfide stardust should be as abundant as silicate stardust in solar system materials.

  16. Searching for Cost-Optimized Interstellar Beacons

    Science.gov (United States)

    Benford, Gregory; Benford, James; Benford, Dominic

    2010-01-01

    What would SETI beacon transmitters be like if built by civilizations that had a variety of motives but cared about cost? In a companion paper, we presented how, for fixed power density in the far field, a cost-optimum interstellar beacon system could be built. Here, we consider how we should search for a beacon if it were produced by a civilization similar to ours. High-power transmitters could be built for a wide variety of motives other than the need for two-way communication, this would include beacons built to be seen over thousands of light-years. Extraterrestrial beacon builders would likely have to contend with economic pressures just as their terrestrial counterparts do. Cost, spectral lines near 1GHz, and interstellar scintillation favor radiating frequencies substantially above the classic "water hole." Therefore, the transmission strategy for a distant, cost-conscious beacon would be a rapid scan of the galactic plane with the intent to cover the angular space. Such pulses would be infrequent events for the receiver. Such beacons built by distant, advanced, wealthy societies would have very different characteristics from what SETI researchers seek. Future searches should pay special attention to areas along the galactic disk where SETI searches have seen coherent signals that have not recurred on the limited listening time intervals we have used. We will need to wait for recurring events that may arrive in intermittent bursts. Several new SETI search strategies have emerged from these ideas. We propose a new test for beacons that is based on the Life Plane hypotheses.

  17. From Interstellar PAHs and Ices to the Origin of Life

    Science.gov (United States)

    Allamandola, Louis J.; DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    Tremendous strides have been made in our understanding of interstellar material over the past twenty years thanks to significant, parallel developments in observational astronomy and laboratory astrophysics. Twenty years ago the composition of interstellar dust was largely guessed at, the concept of ices in dense molecular clouds ignored, and the notion of large, abundant, gas phase, carbon rich molecules widespread throughout the interstellar medium (ISM) considered impossible. Today the composition of dust in the diffuse ISM is reasonably well constrained to micron-sized cold refractory materials comprised of amorphous and crystalline silicates mixed with an amorphous carbonaceous material containing aromatic structural units and short, branched aliphatic chains. In dense molecular clouds, the birthplace of stars and planets, these cold dust particles are coated with mixed molecular ices whose composition is very well constrained. Lastly, the signature of carbon-rich polycyclic aromatic hydrocarbons (PAHs), shockingly large molecules by earlier interstellar chemistry standards, is widespread throughout the Universe. The first part of this lecture will describe how infrared studies of interstellar space, combined with laboratory simulations, have revealed the composition of interstellar ices (the building blocks of comets) and the high abundance and nature of interstellar PAHs. The laboratory database has now enabled us to gain insight into the identities, concentrations, and physical state of many interstellar materials. Within a dense molecular cloud, and especially in the solar nebula during the star and planet formation stage, the materials frozen into interstellar/precometary ices are photoprocessed by ultraviolet light, producing more complex molecules. The remainder of the presentation will focus on the photochemical evolution of these materials and the possible role of these compounds on the early Earth. As these materials are thought to be the building

  18. Some Open Questions in the Physics of Interstellar Dust

    Science.gov (United States)

    Draine, Bruce T.

    2014-06-01

    Our efforts to understand interstellar dust proceed by trying to develop models that are consistent with the laws of physics as well as with the many observational constraints provided by astronomical observations, the meteoritic record, and observations of interstellar dust grains entering the solar system today.I will review some open questions in physics and surface chemistry that are important for current modeling of dust.Nature has provided us with hundreds of spectroscopic clues -- the diffuse interstellar bands -- and it is an embarrasment that we haven't yet been able to decipher them.Interstellar grains contain iron, which could be in ferromagnetic or ferrimagnetic materials. If so, does magnetic dissipation contribute significantly to emission from dust at microwave and submm frequencies? This can be addressed in the laboratory.We do know that interstellar grains are not spherical, but we don't know whether they are compact, or whether they are have extended "fluffy" structures. To find out, we will have to compare observed optical properties of interstellar dust with theoretical models. How can we calculate the optical properties of fluffy grains at wavelengths ranging from X-rays to far-infrared? Theoretical methods will be described.It seems very likely that interstellar grains are often destroyed in the ISM; if so, then the observed abundance of grains requires that new grain material be formed in interstellar space. How can grain materials "grow" in the ISM? In particular, is it possible to grow amorphous silicates in cold interstellar clouds? What about carbonaceous material, in particular the nanoparticles that are thought to be responsible for the strong "PAH" emission bands? The possibilities and limitations of laboratory studies will be discussed.

  19. Searching for Naphthalene Cation Absorption in the Interstellar Medium

    Science.gov (United States)

    Searles, Justin M.; Destree, Joshua D.; Snow, Theodore P.; Salama, Farid; York, Donald G.; Dahlstrom, Julie

    2011-05-01

    Interstellar naphthalene cations (C10H+ 8) have been proposed by a study to be the carriers of a small number of diffuse interstellar bands (DIBs). Using an archive of high signal-to-noise spectra obtained at the Apache Point Observatory, we used two methods to test the hypothesis. Both methods failed to detect significant absorption at lab wavelengths of interstellar spectra with laboratory spectra. We thereby conclude that C10H+ 8 is not a DIB carrier in typical reddened sight lines.

  20. SEARCHING FOR NAPHTHALENE CATION ABSORPTION IN THE INTERSTELLAR MEDIUM

    International Nuclear Information System (INIS)

    Interstellar naphthalene cations (C10H+8) have been proposed by a study to be the carriers of a small number of diffuse interstellar bands (DIBs). Using an archive of high signal-to-noise spectra obtained at the Apache Point Observatory, we used two methods to test the hypothesis. Both methods failed to detect significant absorption at lab wavelengths of interstellar spectra with laboratory spectra. We thereby conclude that C10H+8 is not a DIB carrier in typical reddened sight lines.

  1. A Matter of Interest

    Science.gov (United States)

    Scott, Paul

    2009-01-01

    In these days of financial turmoil, there is greater interest in depositing one's money in the bank--at least one might hope for greater interest. Banks and various trusts pay compound interest at regular intervals: this means that interest is paid not only on the original sum deposited, but also on previous interest payments. This article…

  2. Modelling interstellar organics: relevance for the identification of unidentified interstellar features

    Science.gov (United States)

    Malloci, Giuliano

    2003-02-01

    This thesis is part of the research activity of the Astrochemistry Group of the Cagliari Astronomical Observatory and the Physics Department at the University of Cagliari. The subjects of this work are two specific astrophysical problems concerning the Interstellar Medium (ISM) analysis: 1) the identification of Diffuse Interstellar Bands (DIBs) - Unidentified Infrared Bands (UIBs); 2) the identification of the Extended Red Emission (ERE). A new theoretical approach to the spectroscopic identification of these specific Unidentified Interstellar Features is presented.Concerning the DIBs-UIBs, this work is an extension of a computational Monte-Carlo model developed in the past few years by our group (Mulas G. A&A 1998,338,243) with the aim to integrate quantum-chemical ab initio tecnhiques in it and thus produce a self-contained molecular simulator. Concerning ERE, a general recipe is developed in order to extrapolate the expected photoluminescence of small particles starting from available laboratory results obtained on bulk samples. All the numerical results were obtained for interstellar carbonaceous compounds, hence the title ``Modelling interstellar organics'' given to the thesis. In particular, a specific molecule belonging to the class of polycyclic aromatic hydrocarbons (PAHs) is chosen as a test case to discuss the PAHs-DIBs-UIBs proposal, while the optical properties of laboratory samples of hydrogenated amorphous carbon (HAC) are used to obtain numerical results to be compared with luminescence phenomena such as ERE originating from some solid component of the ISM. The introductive chapter is intended to introduce the unfamiliar reader to the specific topic under study, and a short overview of the scientific scenario involved is given. Then, Part I and II discuss separately the two models above and represent the body of the work; each chapter follows a standard article format: introduction, theoretical method, numerical results, discussion and

  3. Aluminum Foils of the Stardust Interstellar Collector: The Challenge of Recognizing Micrometer-sized Impact Craters made by Interstellar Grains

    Science.gov (United States)

    Kearsley, A. T.; Westphal, A. J.; Burchell, M. J.; Zolensky, Michael E.

    2008-01-01

    Preliminary Examination (PE) of the Stardust cometary collector revealed material embedded in aerogel and on aluminium (Al) foil. Large numbers of sub-micrometer impact craters gave size, structural and compositional information. With experience of finding and analyzing the picogram to nanogram mass remains of cometary particles, are we now ready for PE of the Interstellar (IS) collector? Possible interstellar particle (ISP) tracks in the aerogel are being identified by the stardust@home team. We are now assessing challenges facing PE of Al foils from the interstellar collector.

  4. Multiphase turbulent interstellar medium: some recent results from radio astronomy

    CERN Document Server

    Roy, Nirupam

    2015-01-01

    The radio frequency 1.4 GHz transition of the atomic hydrogen is one of the important tracers of the diffuse neutral interstellar medium. Radio astronomical observations of this transition, using either a single dish telescope or an array interferometer, reveal different properties of the interstellar medium. Such observations are particularly useful to study the multiphase nature and turbulence in the interstellar gas. Observations with multiple radio telescopes have recently been used to study these two closely related aspects in greater detail. Using various observational techniques, the density and the velocity fluctuations in the Galactic interstellar medium was found to have a Kolmogorov-like power law power spectra. The observed power law scaling of the turbulent velocity dispersion with the length scale can be used to derive the true temperature distribution of the medium. Observations from a large ongoing atomic hydrogen absorption line survey have also been used to study the distribution of gas at d...

  5. The interstellar absorption-line spectrum of Mu Ophiuchi

    Science.gov (United States)

    Cardelli, J.; Boehm-Vitense, E.

    1982-01-01

    UV interstellar lines have been measured on high-resolution, long- and short-wavelength IUE spectra of the B8 V star Mu Oph. Column densities for the observed atoms and ions have been determined as well as turbulent velocities. The interstellar spectrum of Mu Oph is similar to the ones for Rho Oph and Zeta Oph. The ionization equilibria of several elements give consistent limits for the electron density. The C I line arising from different fine-structure levels are studied to yield estimates on the physical conditions in the cloud. Relative depletion of elements in the cloud seen in the interstellar spectrum of Mu Oph follows the same pattern as seen in the interstellar spectra of Zeta Oph and six other stars in the Rho Oph cloud complex.

  6. Design for minimum energy in starship and interstellar communication

    CERN Document Server

    Messerschmitt, David G

    2014-01-01

    The design of an interstellar digital communication system at radio wavelengths and interstellar distances is considered, with application to communication with starships and extraterrestrial civilizations. The distances involved are large, resulting in a need for large transmitted power and/or large antennas. In light of a fundamental tradeoff between wider signal bandwidth and lower signal energy per bit delivered to the receiver, the design uses unconstrained bandwidth and thus minimizes delivered energy. One major challenge for communication with civilizations is the initially uncoordinated design and, if the distances are greater, new impairments introduced by the interstellar medium. Unconstrained bandwidth results in a simpler design, helping overcome the absence of coordination. An implicit coordination strategy is proposed based on approaching the fundamental limit on energy delivered to the receiver in the face of jointly observable impairments due to the interstellar medium (dispersion, scattering,...

  7. Combining Magnetic and Electric Sails for Interstellar Deceleration

    CERN Document Server

    Perakis, Nikolaos

    2016-01-01

    The main benefit of an interstellar mission is to carry out in-situ measurements within a target star system. To allow for extended in-situ measurements, the spacecraft needs to be decelerated. One of the currently most promising technologies for deceleration is the magnetic sail which uses the deflection of interstellar matter via a magnetic field to decelerate the spacecraft. However, while the magnetic sail is very efficient at high velocities, its performance decreases with lower speeds. This leads to deceleration durations of several decades depending on the spacecraft mass. Within the context of Project Dragonfly, initiated by the Initiative of Interstellar Studies (i4is), this paper proposes a novel concept for decelerating a spacecraft on an interstellar mission by combining a magnetic sail with an electric sail. Combining the sails compensates for each technologys shortcomings: A magnetic sail is more effective at higher velocities than the electric sail and vice versa. It is demonstrated that using ...

  8. Refractive Interstellar Scintillation for Flux Density Variations of Two Pulsars

    Institute of Scientific and Technical Information of China (English)

    周爱芝; 吴鑫基; 艾力·伊沙木丁

    2003-01-01

    The flux density structure functions of PSRs B0525+21 and B2111+46 are calculated with the refractive interstellar scintillation (RISS) theory. The theoretical curves are in good agreement with observations [Astrophys.J. 539 (2000) 300] (hereafter S2000). The spectra of the electron density fluctuations both are of Kolmogorov spectra. We suggest that the flux density variations observed for these two pulsars are attributed to refractive interstellar scintillation, not to intrinsic variability.

  9. Interstellar medium structure and content and gamma ray astronomy

    International Nuclear Information System (INIS)

    A general description of gamma-ray astronomy is presented with special emphasis on the study of diffuse gamma-ray emission. This is followed by a collection of reflections and observations on the structure and the gas and dust content of the local interstellar medium. Results of gamma-ray observations on the local interstellar medium are given. The last part is devoted to the whole of the galactic gamma-ray emission and its interpretation

  10. Atomic and Molecular Phases of the Interstellar Medium

    CERN Document Server

    Mac Low, Mordecai-Mark

    2016-01-01

    This review covers four current questions in the behavior of the atomic and molecular interstellar medium. These include whether the atomic gas originates primarily in cold streams or hot flows onto galaxies; what the filling factor of cold gas actually is in galactic regions observationally determined to be completely molecular; whether molecular hydrogen determines or merely traces star formation; and whether gravity or turbulence drives the dynamical motions observed in interstellar clouds, with implications on their star formation properties.

  11. Radiation-pressure-driven dust waves inside bursting interstellar bubbles

    OpenAIRE

    Ochsendorf, B. B.; Verdolini, S.; Cox, N.L.J.; Berné, O.; Kaper, L.; Tielens, A. G. G. M.

    2014-01-01

    Massive stars drive the evolution of the interstellar medium through their radiative and mechanical energy input. After their birth, they form "bubbles" of hot gas surrounded by a dense shell. Traditionally, the formation of bubbles is explained through the input of a powerful stellar wind, even though direct evidence supporting this scenario is lacking. Here we explore the possibility that interstellar bubbles seen by the Spitzer- and Herschel space telescopes, blown by stars with log (L/L⊙)...

  12. Adsorption on interstellar analog surfaces : from atoms to organic molecules

    OpenAIRE

    Doronin, Mikhail

    2015-01-01

    Gas-grain interaction plays an important role in the chemistry of the cold interstellar medium and protoplanetary disks. A key parameter for modeling the exchange between grain surfaces and gas phase is adsorption energy, Ea. This work aims to develop a reliable and systematic experimental/theoretical approach to determine the adsorption energies of relevant atoms and molecules on models of interstellar grain surfaces. Employed experimental technique is the Temperature Programmed Desorption. ...

  13. Filtering of interstellar dust in the heliosphere

    Science.gov (United States)

    Sterken, V. J.

    2012-08-01

    The space between the stars is filled with gas and interstellar dust (ISD). The dust grains cause extinction of the starlight that we observe and they play an important role in the evolution of galaxies and in the formation of stellar and planetary systems. The ISD has been long observed by astronomical methods, the grains were measured by in-situ measurements of spacecraft in the solar system and even samples of interstellar material have been brought back to Earth by the Stardust mission in 2006. Many questions on the composition, morphology and size distribution of ISD still exist today which require more and improved measurements. Modeling and understanding the ISD flow through the solar system is needed to interpret these observations and to fully extract the information on ISD grains carried by these measurements. Also, the modelling is necessary for designing and optimizing future ISD missions. The modeling in this thesis follows this flow of ISD through the solar system taking into account three main forces: solar gravity, solar radiation pressure force and Lorentz forces resulting from the motion of the charged grains through the interplanetary magnetic field (IMF). Simulations of dust trajectories over a large range of grain parameters β and Q/m were performed. β is the ratio of solar radiation pressure force to gravity and depends on the grain size, morphology and material. Q/m is the charge to mass ratio. The influence of solar radiation pressure force and Lorentz forces on the trajectories, densities and fluxes were systematically studied. Radiation pressure reduces gravitational attraction and can become even dominant (β > 1) for particles of about 0.2 μm radius, leading to a void region downstream from the Sun: the β -cone. The ISD flow under the influence of solar radiation pressure and gravity only is axi-symmetric, stationary and can even be calculated analytically. Lorentz force becomes stronger for smaller grains having higher Q=m and

  14. Interstellar Mapping and Acceleration Probe (IMAP)

    Science.gov (United States)

    Schwadron, Nathan

    2016-04-01

    Our piece of cosmic real-estate, the heliosphere, is the domain of all human existence - an astrophysical case-history of the successful evolution of life in a habitable system. By exploring our global heliosphere and its myriad interactions, we develop key physical knowledge of the interstellar interactions that influence exoplanetary habitability as well as the distant history and destiny of our solar system and world. IBEX was the first mission to explore the global heliosphere and in concert with Voyager 1 and Voyager 2 is discovering a fundamentally new and uncharted physical domain of the outer heliosphere. In parallel, Cassini/INCA maps the global heliosphere at energies (~5-55 KeV) above those measured by IBEX. The enigmatic IBEX ribbon and the INCA belt were unanticipated discoveries demonstrating that much of what we know or think we understand about the outer heliosphere needs to be revised. The next quantum leap enabled by IMAP will open new windows on the frontier of Heliophysics at a time when the space environment is rapidly evolving. IMAP with 100 times the combined resolution and sensitivity of IBEX and INCA will discover the substructure of the IBEX ribbon and will reveal in unprecedented resolution global maps of our heliosphere. The remarkable synergy between IMAP, Voyager 1 and Voyager 2 will remain for at least the next decade as Voyager 1 pushes further into the interstellar domain and Voyager 2 moves through the heliosheath. The "A" in IMAP refers to acceleration of energetic particles. With its combination of highly sensitive pickup and suprathermal ion sensors, IMAP will provide the species and spectral coverage as well as unprecedented temporal resolution to associate emerging suprathermal tails with interplanetary structures and discover underlying physical acceleration processes. These key measurements will provide what has been a critical missing piece of suprathermal seed particles in our understanding of particle acceleration to high

  15. Matrix isolation as a tool for studying interstellar chemical reactions

    Science.gov (United States)

    Ball, David W.; Ortman, Bryan J.; Hauge, Robert H.; Margrave, John L.

    1989-01-01

    Since the identification of the OH radical as an interstellar species, over 50 molecular species were identified as interstellar denizens. While identification of new species appears straightforward, an explanation for their mechanisms of formation is not. Most astronomers concede that large bodies like interstellar dust grains are necessary for adsorption of molecules and their energies of reactions, but many of the mechanistic steps are unknown and speculative. It is proposed that data from matrix isolation experiments involving the reactions of refractory materials (especially C, Si, and Fe atoms and clusters) with small molecules (mainly H2, H2O, CO, CO2) are particularly applicable to explaining mechanistic details of likely interstellar chemical reactions. In many cases, matrix isolation techniques are the sole method of studying such reactions; also in many cases, complexations and bond rearrangements yield molecules never before observed. The study of these reactions thus provides a logical basis for the mechanisms of interstellar reactions. A list of reactions is presented that would simulate interstellar chemical reactions. These reactions were studied using FTIR-matrix isolation techniques.

  16. VUV spectroscopy of carbon dust analogs: contribution to interstellar extinction

    Science.gov (United States)

    Gavilan, L.; Alata, I.; Le, K. C.; Pino, T.; Giuliani, A.; Dartois, E.

    2016-02-01

    Context. A full spectral characterization of carbonaceous dust analogs is necessary to understand their potential as carriers of observed astronomical spectral signatures such as the ubiquitous UV bump at 217.5 nm and the far-ultraviolet (FUV) rise common to interstellar extinction curves. Aims: Our goal is to study the spectral properties of carbonaceous dust analogs from the FUV to the mid-infrared (MIR) domain. We seek in particular to understand the spectra of these materials in the FUV range, for which laboratory studies are scarce. Methods: We produced analogs to carbonaceous interstellar dust encountered in various phases of the interstellar medium: amorphous hydrogenated carbons (a-C:H), for carbonaceous dust observed in the diffuse interstellar medium, and soot particles, for the polyaromatic component. Analogs to a-C:H dust were produced using a radio-frequency plasma reactor at low pressures, and soot nanoparticles films were produced in an ethylene (C2H4) flame. We measured transmission spectra of these thin films (thickness Kronig inversion. We used these constants for comparison to existing interstellar extinction curves. Conclusions: We extend the spectral measurements of these types of carbonaceous analogs into the VUV and link the spectral features in this range to the 3.4 μm band. We suggest that these two materials might contribute to different classes of interstellar extinction curves.

  17. The hydrogen coverage of interstellar PAHs [Polycyclic Aromatic Hydrocarbons

    International Nuclear Information System (INIS)

    The rate at which the CH bond in interstellar Polycyclic Aromatic Hydrocarbons (PAHs) rupture due to the absorption of a uv photon has been calculated. The results show that small PAHs (less than or equal to 25 carbon atoms) are expected to be partially dehydrogenated in regions with intense uv fields, while large PAHs (greater than or equal to 25 atoms) are expected to be completely hydrogenated in those regions. Because estimate of the carbon content of interstellar PAHs lie in the range of 20 to 25 carbon atoms, dehydrogenation is probably not very important. Because of the absence of other emission features besides the 11.3 micrometer feature in ground-based 8 to 13 micrometer spectra, it has been suggested that interstellar PAHs are partially dehydrogenated. However, IRAS 8 to 22 micrometer spectra of most sources that show strong 7.7 and 11.2 micrometer emission features also show a plateau of emission extending from about 11.3 to 14 micrometer. Like the 11.3 micrometer feature, this new feature is attributed to the CH out of plane bending mode in PAHs. This new feature shows that interstellar PAHs are not as dehydrogenated as estimated from ground-based 8 to 13 micrometer spectra. It also constrains the molecular structure of interstellar PAHs. In particular, it seems that very condensed PAHs, such as coronene and circumcoronene, dominate the interstellar PAH mixture as expected from stability arguments

  18. Interest rate derivatives

    DEFF Research Database (Denmark)

    Svenstrup, Mikkel

    This Ph.D. thesis consists of four self-contained essays on valuation of interest rate derivatives. In particular derivatives related to management of interest rate risk care are considered.......This Ph.D. thesis consists of four self-contained essays on valuation of interest rate derivatives. In particular derivatives related to management of interest rate risk care are considered....

  19. Spatial distribution of interstellar dust in the Sun's vicinity. Comparison with neutral sodium-bearing gas

    Science.gov (United States)

    Vergely, J.-L.; Valette, B.; Lallement, R.; Raimond, S.

    2010-07-01

    Aims: 3D tomography of the interstellar dust and gas may be useful in many respects, from the physical and chemical evolution of the interstellar medium itself to foreground decontamination of the cosmic microwave background, or various studies of the environments of specific objects. However, while spectral data cubes of the galactic emission become increasingly precise, the information on the distance to the emitting regions has not progressed as well and relies essentially on the galactic rotation curve. Our goal here is to bring more precise information on the distance to nearby interstellar dust and gas clouds within 250 pc. Methods: We apply the best available calibration methods to a carefully screened set of stellar Strömgren photometry data for targets possessing a Hipparcos parallax and spectral type classification. We combine the derived interstellar extinctions and the parallax distances for about 6000 stars to build a 3D tomography of the local dust. We use an inversion method based on a regularized Bayesian approach and a least squares criterion, optimized for this specific data set. We apply the same inversion technique to a totally independent set of neutral sodium absorption data available for about 1700 target stars. Results: We obtain 3D maps of the opacity and the distance to the main dust-bearing clouds within 250 pc and identify in those maps well-known dark clouds and high galactic more diffuse entities. We calculate the integrated extinction between the Sun and the cube boundary and compare this with the total galactic extinction derived from infrared 2D maps. The two quantities reach similar values at high latitudes, as expected if the local dust content is satisfyingly reproduced and the dust is closer than 250 pc. Those maps show a larger high latitude dust opacity in the North compared to the South, reinforcing earlier evidences. Interestingly the gas maps do not show the same asymmetry, suggesting a polar asymmetry of the dust to gas

  20. The Interstellar Boundary Explorer (IBEX): Tracing the Interaction between the Heliosphere and Surrounding Interstellar Material with Energetic Neutral Atoms

    CERN Document Server

    Frisch, Priscilla C

    2010-01-01

    The Interstellar Boundary Explorer (IBEX) mission is exploring the frontiers of the heliosphere where energetic neutral atoms (ENAs) are formed from charge exchange between interstellar neutral hydrogen atoms and solar wind ions and pickup ions. The geography of this frontier is dominated by an unexpected nearly complete arc of ENA emission, now known as the IBEX 'Ribbon'. While there is no consensus agreement on the Ribbon formation mechanism, it seems certain this feature is seen for sightlines that are perpendicular to the interstellar magnetic field as it drapes over the heliosphere. At the lowest energies, IBEX also measures the flow of interstellar H, He, and O atoms through the inner heliosphere. The asymmetric helium profile suggests that a secondary flow of helium is present, such as would be expected if some fraction of helium is lost through charge exchange in the heliosheath regions. The detailed spectra characterized by the ENAs provide time-tagged samples of the energy distributions of the under...

  1. A local interstellar spectrum for galactic electrons

    CERN Document Server

    Potgieter, M S

    2013-01-01

    We present a heliopause spectrum at 120 AU from the Sun for galactic electrons over an energy range from 1 MeV to 50 GeV that can be considered the lowest possible local interstellar spectrum (LIS). The primary focus of this work is on the spectral shape of the LIS below ~1.0 GeV. This is done by using a comprehensive numerical model for solar modulation in comparison with Voyager 1 observations at 110 AU from the Sun and PAMELA data at Earth. Below ~1.0 GeV this LIS exhibits a power law with E^-1.5, where E is the kinetic energy of these electrons. However, reproducing the PAMELA electron spectrum for 2009, requires a LIS with a different power law of the form E^-3.15 above ~5 GeV. Combining the two power laws with a smooth transition from low to high energies yields a LIS over the full energy range that is relevant and applicable to the modulation of cosmic ray electrons in the heliosphere. The power-law form of this LIS below ~1.0 GeV produces a challenge to the origin of these low energy galactic electron...

  2. The dynamics of interstellar cloud complexes

    International Nuclear Information System (INIS)

    This paper describes the numerical simulation of the evolution of a large cloud complex of 1.5 x 105 solar masses consisting initially of 48 clouds of equal mass moving with random supersonic velocities. We allow for arbitrary three-dimensional motion with self-gravity and with heating and cooling mechanisms which are appropriate to the interstellar medium. Sequences with initial chaotic motion and with associated kinetic energies which are near the virial energy have been examined. The results show that, provided the energy in chaotic motion is below the virial value, a large fraction of the matter will form clumps. Many of the clumps are rotating rapidly and form extended disc system. The number of clumps formed is small (the largest number, about eight, formed in the sequence with least kinetic energy) and the free-fall time of the clumps is much less than that of the complex. We therefore expect star formation to occur before the initial clumps collide. (author)

  3. Interstellar Bubbles in Two Young HII Regions

    CERN Document Server

    Naze, Y; Points, S D; Danforth, C W; Rosado, M; Chen, C H R; Naze, Yael; Chu, You-Hua; Points, Sean D.; Danforth, Charles W.; Rosado, Margarita

    2001-01-01

    Massive stars are expected to produce wind-blown bubbles in the interstellar medium; however, ring nebulae, suggesting the existence of bubbles, are rarely seen around main-sequence O stars. To search for wind-blown bubbles around main-sequence O stars, we have obtained high-resolution Hubble Space Telescope WFPC2 images and high-dispersion echelle spectra of two pristine HII regions, N11B and N180B, in the Large Magellanic Cloud. These HII regions are ionized by OB associations that still contain O3 stars, suggesting that the HII regions are young and have not hosted any supernova explosions. Our observations show that wind-blown bubbles in these HII regions can be detected kinematically but not morphologically because their expansion velocities are comparable to or only slightly higher than the isothermal sound velocity in the HII regions. Bubbles are detected around concentrations of massive stars, individual O stars, and even an evolved red supergiant (a fossil bubble). Comparisons between the observed bu...

  4. Deuterium enrichment of the interstellar grain mantle

    Science.gov (United States)

    Das, Ankan; Sahu, Dipen; Majumdar, Liton; Chakrabarti, Sandip K.

    2016-01-01

    We carry out Monte Carlo simulation to study deuterium enrichments of interstellar grain mantles under various physical conditions. Based on the physical properties, various types of clouds are considered. We find that in diffuse cloud regions, very strong radiation fields persists and hardly a few layers of surface species are formed. In translucent cloud regions with a moderate radiation field, significant number of layers would be produced and surface coverage is mainly dominated by photo-dissociation products such as, C, CH3, CH2D, OH and OD. In the intermediate dense cloud regions (having number density of total hydrogen nuclei in all forms ˜2 × 104 cm-3), water and methanol along with their deuterated derivatives are efficiently formed. For much higher density regions (˜106 cm-3), water and methanol productions are suppressed but surface coverages of CO, CO2, O2 and O3 are dramatically increased. We find a very high degree of fractionation of water and methanol. Observational results support a high fractionation of methanol but surprisingly water fractionation is found to be low. This is in contradiction with our model results indicating alternative routes for de-fractionation of water. Effects of various types of energy barriers are also studied. Moreover, we allow grain mantles to interact with various charged particles (such as H+, Fe+, S+ and C+) to study the stopping power and projected range of these charged particles on various target ices.

  5. Electron Irradiation of Interstellar Ice Analogues

    Science.gov (United States)

    Nair, B. G.; Mason, N. J.

    2011-05-01

    Molecular synthesis in the Universe primarily occurs in the icy mantles on dust grains in dense interstellar dust clouds. The interaction of photons, electrons and cosmic rays with these ice mantles triggers complex chemical synthesis leading to the formation of complex molecules. Such molecular reactions can only be understood by systematic laboratory studies. In our experiments astrophysical environments are recreated in the laboratory using an ultra high vacuum chamber (UHV) capable of reaching pressures of the order of 10 -10 mBar containing a liquid helium cryostat capable of attaining a temperature of 20 K. Ice films are deposited on a ZnSe substrate (cooled by cryostat) by background deposition and irradiated with electrons of 1KeV energy. Chemical changes induced by electron irradiation were monitored by an infrared spectrometer. By varying the temperature, we also investigate the temperature dependence on the kinetics of the reactions. In this poster we will present the first results of electron irradiation of simple organic molecules like formamide (HCONH2) and allyl alcohol (CH2CHCH2OH).

  6. Interstellar chemical differentiation across grain sizes

    Science.gov (United States)

    Ge, J. X.; He, J. H.; Li, Aigen

    2016-07-01

    In this work, we investigate the effects of ion accretion and size-dependent dust temperatures on the abundances of both gas-phase and grain-surface species. While past work has assumed a constant areal density for icy species, we show that this assumption is invalid and the chemical differentiation over grain sizes is significant. We use a gas-grain chemical code to demonstrate this numerically for two typical interstellar conditions: a dark cloud (DC) and a cold neutral medium (CNM). It is shown that, although the grain-size distribution variation (but with the total grain surface area unchanged) has little effect on the gas-phase abundances, it can alter the abundances of some surface species by up to ∼2-4 orders of magnitude. The areal densities of ice species are larger on smaller grains in the DC model as a consequence of ion accretion. However, the surface areal density evolution tracks are more complex in the CNM model due to the combined effects of ion accretion and dust temperature variation. The surface areal density differences between the smallest ( ∼ 0.01 μm) and the biggest ( ∼ 0.2 μm) grains can reach ∼1 and ∼5 orders of magnitude in the DC and CNM models, respectively.

  7. Deuterium enrichment of the interstellar grain mantle

    CERN Document Server

    Das, Ankan; Chakrabarti, Sandip K

    2015-01-01

    We carry out Monte-Carlo simulation to study deuterium enrichment of interstellar grain mantles under various physical conditions. Based on the physical properties, various types of clouds are considered. We find that in diffuse cloud regions, very strong radiation fields persists and hardly a few layers of surface species are formed. In translucent cloud regions with a moderate radiation field, significant number of layers would be produced and surface coverage is mainly dominated by photo-dissociation products such as, C,CH_3,CH_2D,OH and OD. In the intermediate dense cloud regions (having number density of total hydrogen nuclei in all forms ~ 2 x 10^4 cm^-3), water and methanol along with their deuterated derivatives are efficiently formed. For much higher density regions (~ 10^6 cm^-3), water and methanol productions are suppressed but surface coverage of CO,CO_2,O_2,O_3 are dramatically increased. We find a very high degree of fractionation of water and methanol. Observational results support a high frac...

  8. Interstellar chemical differentiation across grain sizes

    CERN Document Server

    Ge, Jixing; Li, Aigen

    2016-01-01

    In this work we investigate the effects of ion accretion and size-dependent dust temperatures on the abundances of both gas-phase and grain-surface species. While past work has assumed a constant areal density for icy species, we show that this assumption is invalid and the chemical differentiation over grain sizes are significant. We use a gas-grain chemical code to numerically demonstrate this in two typical interstellar conditions: dark cloud (DC) and cold neutral medium (CNM). It is shown that, although the grain size distribution variation (but with the total grain surface area unchanged) has little effect on the gas-phase abundances, it can alter the abundances of some surface species by factors up to $\\sim2-4$ orders of magnitude. The areal densities of ice species are larger on smaller grains in the DC model as the consequence of ion accretion. However, the surface areal density evolution tracks are more complex in the CNM model due to the combined effects of ion accretion and dust temperature variati...

  9. Interstellar Medium Absorption Profile Spectrograph (IMAPS)

    Science.gov (United States)

    Jenkins, E. B.

    1985-08-01

    The design and fabrication of an objective-grating echelle spectrograph to fly on sounding rockets and record spectra of stars from approximately 920 to 1120A with a resolving power lambda/delta lambda = 200,000 is discussed. The scientific purpose of the program is to observe, with ten times better velocity resolution than before, the plentiful absorption lines in this spectral region produced by atoms, ions and molecules in the interstellar medium. In addition, an important technical goal is to develop and flight-quality a new ultraviolet, photon-counting image sensor which has a windowless, opaque photocathode and a CCD bombarded directly by the accelerated photoelectrons. Except for some initial difficulties with the performance of CCDs, the development of the payload instrument is relatively straightforward and our overall design goals are satisfied. The first flight occurred in late 1984, but no data were obtained because of an inrush of air degraded the instrument's vacuum and caused the detector's high voltage to arc. A second flight in early 1985 was a complete success and obtained a spectrum of pi Sco. Data from this mission are currently being reduced; quick-look versions of the spectra indicate that excellent results will be obtained. Currently, the payload is being reconfigured to fly on a Spartan mission in 1988.

  10. Dynamic spectral mapping of interstellar plasma lenses

    CERN Document Server

    Tuntsov, Artem V; Koopmans, Leon V E; Bannister, Keith W; Stevens, Jamie; Johnston, Simon; Reynolds, Cormac; Bignall, Hayley E

    2015-01-01

    Compact radio sources sometimes exhibit intervals of large, rapid changes in their flux-density, due to lensing by interstellar plasma crossing the line-of-sight. A novel survey program has made it possible to discover these "Extreme Scattering Events" (ESEs) in real time, resulting in a high-quality dynamic spectrum of an ESE observed in PKS 1939-315. Here we present a method for determining the column-density profile of a plasma lens, given only the dynamic radio spectrum of the lensed source, under the assumption that the lens is either axisymmetric or totally anisotropic. Our technique relies on the known, strong frequency dependence of the plasma refractive index in order to determine how points in the dynamic spectrum map to positions on the lens. We apply our method to high-frequency (4.2-10.8 GHz) data from the Australia Telescope Compact Array of the PKS 1939-315 ESE. The derived electron column-density profiles are very similar for the two geometries we consider, and both yield a good visual match t...

  11. Hydrogenation reactions in interstellar CO ice analogues

    CERN Document Server

    Fuchs, G W; Ioppolo, S; Romanzin, C; Bisschop, S E; Andersson, S; Van Dishoeck, E F; Linnartz, H

    2009-01-01

    Hydrogenation reactions of CO in inter- and circumstellar ices are regarded as an important starting point in the formation of more complex species. Previous laboratory measurements by two groups on the hydrogenation of CO ices resulted in controversial results on the formation rate of methanol. Our aim is to resolve this controversy by an independent investigation of the reaction scheme for a range of H-atom fluxes and different ice temperatures and thicknesses. Reaction rates are determined by using a state-of-the-art ultra high vacuum experimental setup to bombard an interstellar CO ice analog with room temperature H atoms. The reaction of CO + H into H2CO and subsequently CH3OH is monitored by a Fourier transform infrared spectrometer in a reflection absorption mode. In addition, after each completed measurement a temperature programmed desorption experiment is performed to identify the produced species. Different H-atom fluxes, morphologies, and ice thicknesses are tested. The formation of both formaldeh...

  12. Identification of more interstellar C60+ bands

    CERN Document Server

    Walker, Gordon; Maier, John; Campbell, Ewen

    2015-01-01

    Based on gas-phase laboratory spectra at 6 K, Campbell et al. (2015) confirmed that the diffuse interstellar bands (DIBs) at 9632.7 and 9577.5A are due to absorption by the fullerene ion C60+. They also reported the detection of two other, weaker bands at 9428.5 and 9365.9A. These lie in spectral regions heavily contaminated by telluric water vapour lines. We acquired CFHT ESPaDOnS spectra of HD183143 close to the zenith and chopped with a nearby standard to correct for the telluric line absorption which enabled us to detect a DIB at 9365.9A of relative width and strength comparable to the laboratory absorption. There is a DIB of similar strength and FWHM at 9362.5A. A stellar emission feature at 9429A prevented detection of the 9428.5A band. However, a CFHT archival spectrum of HD169454, where emission is absent at 9429A, clearly shows the 9428.5A DIB with the expected strength and width. These results further confirm C60+ as a DIB carrier.

  13. Three-Dimensional Messages for Interstellar Communication

    Science.gov (United States)

    Vakoch, Douglas A.

    One of the challenges facing independently evolved civilizations separated by interstellar distances is to communicate information unique to one civilization. One commonly proposed solution is to begin with two-dimensional pictorial representations of mathematical concepts and physical objects, in the hope that this will provide a foundation for overcoming linguistic barriers. However, significant aspects of such representations are highly conventional, and may not be readily intelligible to a civilization with different conventions. The process of teaching conventions of representation may be facilitated by the use of three-dimensional representations redundantly encoded in multiple formats (e.g., as both vectors and as rasters). After having illustrated specific conventions for representing mathematical objects in a three-dimensional space, this method can be used to describe a physical environment shared by transmitter and receiver: a three-dimensional space defined by the transmitter--receiver axis, and containing stars within that space. This method can be extended to show three-dimensional representations varying over time. Having clarified conventions for representing objects potentially familiar to both sender and receiver, novel objects can subsequently be depicted. This is illustrated through sequences showing interactions between human beings, which provide information about human behavior and personality. Extensions of this method may allow the communication of such culture-specific features as aesthetic judgments and religious beliefs. Limitations of this approach will be noted, with specific reference to ETI who are not primarily visual.

  14. Supernovae Driven Turbulence In The Interstellar Medium

    CERN Document Server

    Gent, Frederick

    2014-01-01

    I model the multi-phase interstellar medium (ISM) randomly heated and shocked by supernovae, with gravity, differential rotation and other parameters we understand to be typical of the solar neighbourhood. The simulations are 3D extending horizontally 1 x 1 kpc squared and vertically 2 kpc, symmetric about the galactic mid-plane. They routinely span gas number densities 1/10000 to 100 per cubic cm, temperatures 100 to 100 MK, speeds up to 10000 km/s and Mach number up to 25. Radiative cooling is applied from two widely adopted parameterizations, and compared directly to assess the sensitivity of the results to cooling. There is strong evidence to describe the ISM as comprising well defined cold, warm and hot regions, which are statistically close to thermal and total pressure equilibrium. This result is not sensitive to the choice of parameters considered here. The distribution of the gas density within each can be robustly modelled as lognormal. Appropriate distinction is required between the properties of t...

  15. Interstellar HOCN in the Galactic center region

    CERN Document Server

    Bruenken, S; Martin, S; Verheyen, L; Menten, K M

    2010-01-01

    Aims. Our aim is to confirm the interstellar detection of cyanic acid, HOCN, in the Galactic center clouds. It has previously been tentatively detected only in Sgr B2(OH). Methods. We used a complete line survey of the hot cores Sgr B2(N) and (M) in the 3 mm range, complemented by additional observations carried out with the IRAM 30 m telescope at selected frequencies in the 2 mm band and towards four additional positions in the Sgr B2 cloud complex in the 2 and 3 mm bands. The spectral survey was analysed in the local thermodynamical equilibrium approximation (LTE) by modeling the emission of all identified molecules simultaneously. This allowed us to distinguish weak features of HOCN from the rich line spectrum observed in Sgr B2(N) and (M). Lines of the more stable (by 1.1 eV) isomer isocyanic acid, HNCO, in these sources, as well as those of HOCN and HNCO towards the other positions, were analysed in the LTE approximation as well. Results. Four transitions of HOCN were detected in a quiescent molecular cl...

  16. Interstellar Contact - A Thousand-Year Perspective

    Science.gov (United States)

    Tough, A.

    Rapid progress is already being made in space exploration and the scientific search for intelligent life. By the year 3000, humankind will likely be sending extraordinarily smart probes and even staffed spaceships to explore nearby stars and planetary systems. Because any other civilizations in our galaxy are likely much older than humankind, their technology likely became capable long ago of exploring their galactic neighbourhood. Their motivation to do so is probably very strong, according to three sets of disciplined speculation: some role-playing exercises; a set of four universal values shared by all civilizations; and Vulpetti's Conscious-Life Expansion Principle. If other civilizations (or their intelligent probes) are already traveling throughout the galaxy, and if we do the same by the year 3000, it seems highly probable that contact will be made one way or another. Indeed, during the next 1000 years, we may experience contact in various ways (telescopes, probes, or staffed spacecraft) and with various civilizations. Of all the positive events that humanity will experience over the next 1000 years, interstellar contact will likely have the highest impact. Humanity's major benefits will likely include practical information, answers to major questions, changes in our view of ourselves, and cooperation in joint galactic projects.

  17. Identification of More Interstellar C60+ Bands

    Science.gov (United States)

    Walker, G. A. H.; Bohlender, D. A.; Maier, J. P.; Campbell, E. K.

    2015-10-01

    Based on gas-phase laboratory spectra at 6 K, Campbell et al. confirmed that the diffuse interstellar bands (DIBs) at 9632.7 and 9577.5 Å are due to absorption by the fullerene ion {{{C}}}60+. They also reported the detection of two other, weaker bands at 9428.5 and 9365.9 Å. These lie in spectral regions heavily contaminated by telluric water vapor lines. We acquired CFHT ESPaDOnS spectra of HD 183143 close to the zenith and chopped with a nearby standard to correct for the telluric line absorption which enabled us to detect a DIB at 9365.9 Å of relative width and strength comparable to the laboratory absorption. There is a DIB of similar strength and FWHM at 9362.5 Å. A stellar emission feature at 9429 Å prevented detection of the 9428.5 Å band. However, a CFHT archival spectrum of HD 169454, where emission is absent at 9429 Å, clearly shows the 9428.5 Å DIB with the expected strength and width. These results further confirm {{{C}}}60+ as a DIB carrier. Based on observations obtained at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council of Canada, the Institut National des Sciences de l’Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii.

  18. Constraining the Properties of Cold Interstellar Clouds

    Science.gov (United States)

    Spraggs, Mary Elizabeth; Gibson, Steven J.

    2016-01-01

    Since the interstellar medium (ISM) plays an integral role in star formation and galactic structure, it is important to understand the evolution of clouds over time, including the processes of cooling and condensation that lead to the formation of new stars. This work aims to constrain and better understand the physical properties of the cold ISM by utilizing large surveys of neutral atomic hydrogen (HI) 21cm spectral line emission and absorption, carbon monoxide (CO) 2.6mm line emission, and multi-band infrared dust thermal continuum emission. We identify areas where the gas may be cooling and forming molecules using HI self-absorption (HISA), in which cold foreground HI absorbs radiation from warmer background HI emission.We are developing an algorithm that uses total gas column densities inferred from Planck and other FIR/sub-mm data in parallel with CO and HISA spectral line data to determine the gas temperature, density, molecular abundance, and other properties as functions of position. We can then map these properties to study their variation throughout an individual cloud as well as any dependencies on location or environment within the Galaxy.Funding for this work was provided by the National Science Foundation, the NASA Kentucky Space Grant Consortium, the WKU Ogden College of Science and Engineering, and the Carol Martin Gatton Academy for Mathematics and Science in Kentucky.

  19. Status of the Stardust ISPE and the Origin of Four Interstellar Dust Candidates

    Science.gov (United States)

    Westphal, A. J.; Allen, C.; Ansari, A.; Bajt, S.; Bastien, R. S.; Bassim, N.; Bechtel, H. A.; Borg, J.; Brenker, F. E.; Bridges, J.; Brownlee, D. E.; Burchell, M.; Burghammer, M.; Butterworth, A. L.; Changela, H.; Cloetens, P.; Davis, A. M.; Floss, C.; Flynn, G.; Fougeray, P.; Frank, D.; Gainsforth, Z.; Gruen, E.; Sandford, S. A.; Zolensky, M. E.

    2012-01-01

    Some bulk properties of interstellar dust are known through infrared and X-ray observations of the interstellar medium. However, the properties of individual interstellar dust particles are largely unconstrained, so it is not known whether individual interstellar dust particles can be definitively distinguished from interplanetary dust particles in the Stardust Interstellar Dust Collector (SIDC) based only on chemical, mineralogical or isotopic analyses. It was therefore understood from the beginning of the Stardust Interstellar Preliminary Examination (ISPE) that identification of interstellar dust candidates would rest on three criteria - broad consistency with known extraterrestrial materials, inconsistency with an origin as secondary ejecta from impacts on the spacecraft, and consistency, in a statistical sense, of observed dynamical properties - that is, trajectory and capture speed - with an origin in the interstellar dust stream. Here we quantitatively test four interstellar dust candidates, reported previously [1], against these criteria.

  20. Composition and evolution of Interstellar Grain mantle under the effects of photo-dissociation

    CERN Document Server

    Das, Ankan

    2011-01-01

    We study the chemical evolution of interstellar grain mantle by varying the physical parameters of the interstellar medium (ISM). To mimic the exact interstellar condition, gas grain interactions via accretion from the gas phase and desorption (thermal evaporation and photo-evaporation) from the grain surface are considered. We find that the chemical composition of the interstellar grain mantle is highly dependent on the physical parameters associated with a molecular cloud. Interstellar photons are seen to play an important role towards the growth and the structure of the interstellar grain mantle. We consider the effects of interstellar photons (photo-dissociation and photo-evaporation) in our simulation under various interstellar conditions. We notice that the effects of interstellar photons dominate around the region of lower visual extinction. These photons contribute significantly in the formation of the grain mantle. Energy of the incoming photon is attenuated by the absorption and scattering by the in...

  1. Formation of HI Clouds in Shock-compressed Interstellar Medium: Physical Origin of Angular Correlation Between Filamentary Structure and Magnetic Field

    CERN Document Server

    Inoue, Tsuyoshi

    2016-01-01

    Recent observations of neutral Galactic interstellar medium showed that filamentary structures of HI clouds are aligned with the interstellar magnetic field. Many interesting applications are proposed based on the alignment such as measurement of magnetic field strength through the Chandrasekhar-Fermi method and removal of polarized foreground dust emissions for the detection of inflationary polarized emission in the cosmic microwave background radiation. However, the physical origin of the alignment remains to be explained. To understand the alignment mechanism, we examine formation of HI clouds triggered by shock compression of diffuse warm neutral medium using three-dimensional magnetohydrodynamic simulations with the effects of optically thin cooling and heating. We show that the shock-compressed diffuse interstellar medium of density n~1 cm^-3 evolves into HI clouds with typical density n~50 cm^-3 via thermal instability driven by cooling, which is consistent with previous studies. We apply a machine vis...

  2. Small-scale structure in the interstellar medium: time-varying interstellar absorption towards {\\kappa} Velorum

    CERN Document Server

    Smith, Keith T; Cordiner, Martin A; Sarre, Peter J; Smith, Arfon M; Bell, Tom A; Viti, Serena

    2012-01-01

    Ultra-high spectral resolution observations of time-varying interstellar absorption towards {\\kappa} Vel are reported, using the Ultra-High Resolution Facility on the Anglo-Australian Telescope. Detections of interstellar Ca I, Ca II, K I, Na I and CH are obtained, whilst an upper limit on the column density is reported for C_2. The results show continued increases in column densities of K I and Ca I since observations ~ 4 yr earlier, as the transverse motion of the star carried it ~ 10 AU perpendicular to the line of sight. Line profile models are fitted to the spectra and two main narrow components (A & B) are identified for all species except CH. The column density N(K I) is found to have increased by 82 +10-9 % between 1994 and 2006, whilst N(Ca I) is found to have increased by 32 +- 5 % over the shorter period of 2002-2006. The line widths are used to constrain the kinetic temperature to T_k,A 7 * 10^3 cm^-3 and n_B > 2 * 10^4 cm^-3. Calcium depletions are estimated from the Ca I / K I ratio. Compar...

  3. Points of Interest: What Determines Interest Rates?

    Science.gov (United States)

    Schilling, Tim

    Interest rates can significantly influence people's behavior. When rates decline, homeowners rush to buy new homes and refinance old mortgages; automobile buyers scramble to buy new cars; the stock market soars, and people tend to feel more optimistic about the future. But even though individuals respond to changes in rates, they may not fully…

  4. The Size Distribution of Arecibo Interstellar Particles and Its Implications

    Science.gov (United States)

    Meisel, David D.; Janches, Diego; Mathews, John D.

    2002-11-01

    Size histograms of all Arecibo ultra-high-frequency radar micrometeors detected in 1997-1998 whose radii were measured by atmospheric drag are presented. Most can be fitted with either a lognormal function or, alternatively, one or more power-law functions. Either form is indicative of significant fragmentation. The interplanetary dust particle (IDP) histogram results are discussed and compared with those considered to be extrasolar particles, including a subset of those deemed to be true interstellar particles (ISPs). The Arecibo IDP power-law results are shown to agree well with those derived from IRAS dust bands and Long-Duration Exposure Facility cratering, thus confirming the applicability of the sample to the derivation of mass estimates. A dichotomy between size histograms of particles with preperihelion Earth encounters and those with postperihelion encounters is evidence that significant size histogram change occurs when the smallest particles, including all ISPs, pass close to the Sun, even if only once. A small sample of previously undetected Arecibo postperihelion ISPs coming from the direction of the known Ulysses gas and dust flow are shown to have a size distribution and solar system dynamical properties similar to other Arecibo ISPs and therefore can be combined with previous ISP results to obtain a more robust sample. Derived mass flux points for the Arecibo ISPs agree well (over 5 orders of magnitude of mass) with a previously derived mass flux distribution function for Ulysses/Galileo spacecraft dust. This combined spacecraft and ground-based mass flux function is then used to infer a number of interesting mass-related solar system and astrophysical quantities.

  5. Biological Oceanography

    Science.gov (United States)

    Abbott, M. R.

    1984-01-01

    Within the framework of global biogeochemical cycles and ocean productivity, there are two areas that will be of particular interest to biological oceanography in the 1990s. The first is the mapping in space time of the biomass and productivity of phytoplankton in the world ocean. The second area is the coupling of biological and physical processes as it affects the distribution and growth rate of phytoplankton biomass. Certainly other areas will be of interest to biological oceanographers, but these two areas are amenable to observations from satellites. Temporal and spatial variability is a regular feature of marine ecosystems. The temporal and spatial variability of phytoplankton biomass and productivity which is ubiquitous at all time and space scales in the ocean must be characterized. Remote sensing from satellites addresses these problems with global observations of mesocale (2 to 20 days, 10 to 200 km) features over a long period of time.

  6. Organic Compounds in Circumstellar and Interstellar Environments

    Science.gov (United States)

    Kwok, Sun

    2015-06-01

    Recent research has discovered that complex organic matter is prevalent throughout the Universe. In the Solar System, it is found in meteorites, comets, interplanetary dust particles, and planetary satellites. Spectroscopic signatures of organics with aromatic/aliphatic structures are also found in stellar ejecta, diffuse interstellar medium, and external galaxies. From space infrared spectroscopic observations, we have found that complex organics can be synthesized in the late stages of stellar evolution. Shortly after the nuclear synthesis of the element carbon, organic gas-phase molecules are formed in the stellar winds, which later condense into solid organic particles. This organic synthesis occurs over very short time scales of about a thousand years. In order to determine the chemical structures of these stellar organics, comparisons are made with particles produced in the laboratory. Using the technique of chemical vapor deposition, artificial organic particles have been created by injecting energy into gas-phase hydrocarbon molecules. These comparisons led us to believe that the stellar organics are best described as amorphous carbonaceous nanoparticles with mixed aromatic and aliphatic components. The chemical structures of the stellar organics show strong similarity to the insoluble organic matter found in meteorites. Isotopic analysis of meteorites and interplanetary dust collected in the upper atmospheres have revealed the presence of pre-solar grains similar to those formed in old stars. This provides a direct link between star dust and the Solar System and raises the possibility that the early Solar System was chemically enriched by stellar ejecta with the potential of influencing the origin of life on Earth.

  7. Isotopic composition of carbonaceous-chondrite kerogen Evidence for an interstellar origin of organic matter in meteorites

    Science.gov (United States)

    Kerridge, J. F.

    1983-01-01

    Stepwise combustion has revealed systematic patterns of isotopic heterogeneity for C, H and N in the insoluble organic fraction (m-kerogen) from the Orgueil and Murray carbonaceous chondrites. Those patterns are essentially identical for both meteorites, indicating a common source of m-kerogen. The data cannot be reconciled with a single mass-fractionation process acting upon a single precursor composition. This indicates either a multi-path history of mass-dependent processing or a significant nucleogenetic contribution, or both. If mass-fractionation were the dominant process, the magnitude of the observed isotopic variability strongly suggests that ion-molecule reactions at very low temperatures, probably in interstellar clouds, were responsible. In any case, an interstellar, rather than solar nebular, origin for at least some of the meteoritic organic matter is indicated. This has interesting implications for the origin of prebiotic molecules, temperatures in the early solar system, and the isotopic compositions of volatiles accreted by the terrestrial planets.

  8. Detection of diffuse interstellar bands in M31

    CERN Document Server

    Cordiner, M A; Trundle, C; Evans, C J; Hunter, I; Przybilla, N; Bresolin, F; Salama, F

    2008-01-01

    We investigate the diffuse interstellar band (DIB) spectrum in the interstellar medium of M31. The DEIMOS spectrograph of the W. M. Keck observatory was used to make optical spectroscopic observations of two supergiant stars, MAG 63885 and MAG 70817, in the vicinity of the OB78 association in M31 where the metallicity is approximately equal to solar. The 5780, 5797, 6203, 6283 and 6613 DIBs are detected in both sightlines at velocities matching the M31 interstellar Na I absorption. The spectra are classified and interstellar reddenings are derived for both stars. Diffuse interstellar band (DIB) equivalent widths and radial velocities are presented. The spectrum of DIBs observed in M31 towards MAG 63885 is found to be similar to that observed in the Milky Way. Towards MAG 70817 the DIB equivalent widths per unit reddening are about three times the Galactic average. Compared to observations elsewhere in the Universe, relative to reddening the M31 ISM in the vicinity of OB78 is apparently a highly favourable env...

  9. The Local Interstellar Magnetic Field Determined from the IBEX Ribbon

    Science.gov (United States)

    Zirnstein, E.; Funsten, H. O.; Heerikhuisen, J.; Livadiotis, G.; McComas, D. J.; Pogorelov, N. V.

    2015-12-01

    As the solar wind plasma flows away from the Sun, it eventually collides with the local interstellar medium, creating the heliosphere. Neutral atoms from interstellar space travel inside the heliosphere and charge-exchange with the solar wind plasma, creating energetic neutral atoms (ENAs). Some of these ENAs travel outside the heliosphere, undergo two charge-exchange events, and travel back inside the heliosphere towards Earth, with the strongest intensity in directions perpendicular to the interstellar magnetic field (IMF). It is widely believed that this process generates the "ribbon" of enhanced ENA intensity observed by the Interstellar Boundary Explorer (IBEX), and has been shown to explain many key features of the observations. IBEX observations of the ribbon are composed of a complex, line-of-sight integration of ENAs that come from different distances beyond the heliopause, and thus the ENAs detected by IBEX over a wide range of energies are uniquely coupled to the IMF draped around the heliosphere. We present a detailed analysis of the IBEX ribbon measurements using 3D simulations of the heliosphere and computations of the ribbon flux at Earth based on IBEX capabilities, and derive the magnitude and direction of the IMF required to reproduce the position of the IBEX ribbon in the sky. These results have potentially large implications for our understanding of the solar-interstellar environment.

  10. Potential formation of three pyrimidine bases in interstellar regions

    CERN Document Server

    Majumdar, Liton; Das, Ankan; Chakrabarti, Sandip K

    2015-01-01

    Work on the chemical evolution of pre-biotic molecules remains incomplete since the major obstacle is the lack of adequate knowledge of rate coefficients of various reactions which take place in interstellar conditions. In this work, we study the possibility of forming three pyrimidine bases, namely, cytosine, uracil and thymine in interstellar regions. Our study reveals that the synthesis of uracil from cytosine and water is quite impossible under interstellar circumstances. For the synthesis of thymine, reaction between uracil and :CH2 is investigated. Since no other relevant pathways for the formation of uracil and thymine were available in the literature, we consider a large gas-grain chemical network to study the chemical evolution of cytosine in gas and ice phases. Our modeling result shows that cytosine would be produced in cold, dense interstellar conditions. However, presence of cytosine is yet to be established. We propose that a new molecule, namely, C4N3OH5 could be observable in the interstellar ...

  11. Understanding Interest Rate Volatility

    DEFF Research Database (Denmark)

    Volker, Desi

    This thesis is the result of my Ph.D. studies at the Department of Finance of the Copenhagen Business School. It consists of three essays covering topics related to the term structure of interest rates, monetary policy and interest rate volatility. The rst essay, \\Monetary Policy Uncertainty...... and Interest Rates", examines the role of monetary policy uncertainty on the term structure of interest rates. The second essay, \\A Regime-Switching A ne Term Structure Model with Stochastic Volatility" (co-authored with Sebastian Fux), investigates the ability of the class of regime switching models...... with and without stochastic volatility to capture the main stylized features of U.S. interest rates. The third essay, \\Variance Risk Premia in the Interest Rate Swap Market", investigates the time-series and cross-sectional properties of the compensation demanded for holding interest rate variance risk. The essays...

  12. Status of Solar Sail Propulsion Within NASA - Moving Toward Interstellar Travel

    Science.gov (United States)

    Johnson, Les

    2015-01-01

    NASA is developing solar sail propulsion for two near-term missions and laying the groundwork for their future use in deep space and interstellar precursor missions. Solar sails use sunlight to propel vehicles through space by reflecting solar photons from a large, mirror-like sail made of a lightweight, highly reflective material. This continuous photon pressure provides propellantless thrust, allowing for very high (Delta)V maneuvers on long-duration, deep space exploration. Since reflected light produces thrust, solar sails require no onboard propellant. The Near Earth Asteroid (NEA) Scout mission, managed by MSFC, will use the sail as primary propulsion allowing it to survey and image one or more NEA's of interest for possible future human exploration. Lunar Flashlight, managed by JPL, will search for and map volatiles in permanently shadowed Lunar craters using a solar sail as a gigantic mirror to steer sunlight into the shaded craters. The Lunar Flashlight spacecraft will also use the propulsive solar sail to maneuver into a lunar polar orbit. Both missions use a 6U cubesat architecture, a common an 85 sq m solar sail, and will weigh less than 12 kilograms. Both missions will be launched on the first flight of the Space Launch System in 2018. NEA Scout and Lunar Flashlight will serve as important milestones in the development of solar sail propulsion technology for future, more ambitious missions including the Interstellar Probe - a mission long desired by the space science community which would send a robotic probe beyond the edge of the solar system to a distance of 250 Astronomical Units or more. This paper will summarize the development status of NEA Scout and Lunar Flashlight and describe the next steps required to enable an interstellar solar sail capability.

  13. Interstellar Pickup Ion Production in the Global Heliosphere and Heliosheath

    CERN Document Server

    Wu, Yihong; Guo, Xiaocheng

    2016-01-01

    Interstellar Pickup ions (PUIs) play a significant part in mediating the solar wind (SW) interaction with the interstellar medium. In this paper, we examine the details of spatial variation of the PUI velocity distribution function (VDF) in the SW by solving the PUI transport equation. We assume the PUI distribution is isotropic resulting from strong pitch-angle scattering by wave-particle interaction. A three-dimensional model combining the MHD treatment of the background SW and neutrals with a kinetic treatment of PUIs throughout the heliosphere and the surrounding local interstellar medium (LISM) has been developed. The model generates PUI power law tails via second-order Fermi process. We analyze how PUIs transform across the heliospheric termination shock (TS) and obtain the PUI phase space distribution in the inner heliosheath including continuing velocity diffusion. Our simulated PUI spectra are compared with observations made by New Horizons, Ulysses, Voyager 1, 2 and Cassini, and a satisfactory agree...

  14. A scenario for interstellar exploration and its financing

    CERN Document Server

    Bignami, Giovanni F

    2013-01-01

    This book develops a credible scenario for interstellar exploration and colonization. In so doing, it examines: • the present situation and prospects for interstellar exploration technologies; • where to go: the search for habitable planets; • the motivations for space travel and colonization; • the financial mechanisms required to fund such enterprises. The final section of the book analyzes the uncertainties surrounding the presented scenario. The purpose of building a scenario is not only to pinpoint future events but also to highlight the uncertainties that may propel the future in different directions. Interstellar travel and colonization requires a civilization in which human beings see themselves as inhabitants of a single planet and in which global governance of these processes is conducted on a cooperative basis. The key question is, then, whether our present civilization is ready for such an endeavor, reflecting the fact that the critical uncertainties are political and cultural in nature. I...

  15. Interstellar Refractive Scintillation and Intraday Polarization Angle Swings

    Institute of Scientific and Technical Information of China (English)

    Shan-Jie Qian; Xi-Zhen Zhang; A. Kraus

    2005-01-01

    Intraday polarization angle swings of ~180° observed in two sources (QSO 0917+624 and QSO 1150+812) are discussed in the framework of refractive interstellar scintillation by a continuous interstellar medium. Model-fits to the I-,Q- and U- light curves were made for both sources. It is shown that for the case of 0917+624 both the intraday intensity variations and the polarization angle swing of ~180° could be explained consistently in terms of a four-component model, which comprises one steady and two scintillating polarized components and one further non-polarized scintillating component. The polarization angle swing of ~180° observed in 1150+812, which occurred when the polarized flux density was almost constant, could not be explained in terms of refractive scintillation by a continuous medium and might be due to other mechanisms (e.g., scintillation by interstellar clouds).

  16. Experimental evidence of water formation on interstellar dust grains

    CERN Document Server

    Dulieu, F; Fillion, J-H; Matar, E; Momeni, A; Pirronello, V; Lemaire, J L

    2009-01-01

    The synthesis of water is one necessary step in the origin and development of life. It is believed that pristine water is formed and grows on the surface of icy dust grains in dark interstellar clouds. Until now, there has been no experimental evidence whether this scenario is feasible or not. We present here the first experimental evidence of water synthesis under interstellar conditions. After D and O deposition on a water ice substrate (HO) held at 10 K, we observe production of HDO and DO. The water substrate itself has an active role in water formation, which appears to be more complicated than previously thought. Amorphous water ice layers are the matrices where complex organic prebiotic species may be synthesized. This experiment opens up the field of a little explored complex chemistry that could occur on interstellar dust grains, believed to be the site of key processes leading to the molecular diversity and complexity observed in our universe.

  17. Carbon and oxygen isotope fractionation in dense interstellar clouds

    Science.gov (United States)

    Langer, W. D.; Graedel, T. E.; Frerking, M. A.; Armentrout, P. B.

    1984-01-01

    It is pointed out that isotope fractionation as a result of chemical reactions is due to the small zero-point energy differences between reactants and products of isotopically distinct species. Only at temperatures near absolute zero does this energy difference become significant. Favorable conditions for isotope fractionation on the considered basis exist in space within dense interstellar clouds. Temperatures of approximately 10 K may occur in these clouds. Under such conditions, ion-molecule reactions have the potential to distribute isotopes of hydrogen, carbon, oxygen unequally among the interstellar molecules. The present investigation makes use of a detailed model of the time-dependent chemistry of dense interstellar clouds to study cosmological isotope fractionation. Attention is given to fractionation chemistry and the calculation of rate parameters, the isotope fractionation results, and a comparison of theoretical results with observational data.

  18. Radiative torques on interstellar grains; 1, superthermal spinup

    CERN Document Server

    Draine, B T; Weingartner, Joseph C

    1996-01-01

    Irregular dust grains are subject to radiative torques when irradiated by interstellar starlight. It is shown how these radiative torques may be calculated using the discrete dipole approximation. Calculations are carried out for one irregular grain geometry, and three different grain sizes. It is shown that radiative torques can play an important dynamical role in spinup of interstellar dust grains, resulting in rotation rates which may exceed even those expected from H_2 formation on the grain surface. Because the radiative torque on an interstellar grain is determined by the overall grain geometry rather than merely the state of the grain surface, the resulting superthermal rotation is expected to be long-lived. By itself, long-lived superthermal rotation would permit grain alignment by normal paramagnetic dissipation on the "Davis-Greenstein" timescale. However, radiative torques arising from anisotropy of the starlight background can act directly to alter the grain alignment on much shorter timescales, a...

  19. Mapping the interstellar medium in galaxies with Herschel/SPIRE

    CERN Document Server

    Eales, S A; Wilson, C D; Bendo, G J; Cortese, L; Pohlen, M; Boselli, A; Gomez, H L; Auld, R; Baes, M; Barlow, M J; Bock, J J; Bradford, M; Buat, V; Castro-Rodriguez, N; Chanial, P; Charlot, S; Ciesla, L; Clements, D L; Cooray, A; Cormier, D; Davies, J I; Dwek, E; Elbaz, D; Galametz, M; Galliano, F; Gear, W K; Glenn, J; Griffin, M; Hony, S; Isaak, K G; Levenson, L R; Lu, N; Madden, S; O'Halloran, B; Okumura, K; Oliver, S; Page, M J; Panuzzo, P; Papageorgiou, A; Parkin, T J; Perez-Fournon, I; Rangwala, N; Rigby, E E; Roussel, H; Rykala, A; Sacchi, N; Sauvage, M; Schulz, B; Schirm, M R P; Spinoglio, L; Srinivasan, S; Stevens, J A; Symeonidis, M; Trichas, M; Vaccari, M; Vigroux, L; Wozniak, H; Wright, G S; Zeilinger, W W

    2010-01-01

    The standard method of mapping the interstellar medium in a galaxy, by observing the molecular gas in the CO 1-0 line and the atomic gas in the 21-cm line, is largely limited with current telescopes to galaxies in the nearby universe. In this letter, we use SPIRE observations of the galaxies M99 and M100 to explore the alternative approach of mapping the interstellar medium using the continuum emission from the dust. We have compared the methods by measuring the relationship between the star-formation rate and the surface density of gas in the galaxies. We find the two methods give relationships with a similar dispersion, confirming that observing the continuum emission from the dust is a promising method of mapping the interstellar medium in galaxies.

  20. Reaction Networks For Interstellar Chemical Modelling: Improvements and Challenges

    CERN Document Server

    Wakelam, V; Herbst, E; Troe, J; Geppert, W; Linnartz, H; Oberg, K; Roueff, E; Agundez, M; Pernot, P; Cuppen, H M; Loison, J C; Talbi, D

    2010-01-01

    We survey the current situation regarding chemical modelling of the synthesis of molecules in the interstellar medium. The present state of knowledge concerning the rate coefficients and their uncertainties for the major gas-phase processes -- ion-neutral reactions, neutral-neutral reactions, radiative association, and dissociative recombination -- is reviewed. Emphasis is placed on those reactions that have been identified, by sensitivity analyses, as 'crucial' in determining the predicted abundances of the species observed in the interstellar medium. These sensitivity analyses have been carried out for gas-phase models of three representative, molecule-rich, astronomical sources: the cold dense molecular clouds TMC-1 and L134N, and the expanding circumstellar envelope IRC +10216. Our review has led to the proposal of new values and uncertainties for the rate coefficients of many of the key reactions. The impact of these new data on the predicted abundances in TMC-1 and L134N is reported. Interstellar dust p...

  1. Structure analysis of interstellar clouds: II. Applying the Delta-variance method to interstellar turbulence

    CERN Document Server

    Ossenkopf, V; Stutzki, J

    2008-01-01

    The Delta-variance analysis is an efficient tool for measuring the structural scaling behaviour of interstellar turbulence in astronomical maps. In paper I we proposed essential improvements to the Delta-variance analysis. In this paper we apply the improved Delta-variance analysis to i) a hydrodynamic turbulence simulation with prominent density and velocity structures, ii) an observed intensity map of rho Oph with irregular boundaries and variable uncertainties of the different data points, and iii) a map of the turbulent velocity structure in the Polaris Flare affected by the intensity dependence on the centroid velocity determination. The tests confirm the extended capabilities of the improved Delta-variance analysis. Prominent spatial scales were accurately identified and artifacts from a variable reliability of the data were removed. The analysis of the hydrodynamic simulations showed that the injection of a turbulent velocity structure creates the most prominent density structures are produced on a sca...

  2. First Global Observations of the Interstellar Interaction from the Interstellar Boundary Explorer (Invited)

    Science.gov (United States)

    McComas, D. J.

    2009-12-01

    The Sun moves through the local interstellar medium, continuously emitting ionized, supersonic solar wind plasma and carving out a cavity in interstellar space, called the heliosphere. The Interstellar Boundary Explorer (IBEX) spacecraft has just completed the first all-sky maps of the interstellar interaction at the edge of the heliosphere, by imaging energetic neutral atoms (ENAs) emanating from this region. IBEX all-sky maps and energy spectra provide detailed information about the interaction. Our observations show globally distributed fluxes ordered by the solar wind structure, which are superposed by another, unexpected feature, which is neither seen by the Voyager spacecraft nor predicted by any current model or theory. This talk summarizes the IBEX observations, shares our unexpected results, and discusses some of the possible ideas for what may be missing in our current understanding of the heliosphere’s global interaction. IBEX Science Team: D.J. McComas1,2, F. Allegrini1,2, P. Bochsler3, M. Bzowski4, E.R. Christian5, G.B. Crew6, R. DeMajistre7, H. Fahr8, H. Fichtner9, P.C. Frisch10, H.O. Funsten11, S. A. Fuselier12, G. Gloeckler13, M. Gruntman14, J. Heerikhuisen15, V. Izmodenov16, P. Janzen17, P. Knappenberger18, S. Krimigis7,19, H. Kucharek20, M. Lee20, G. Livadiotis1, S. Livi1,2, R.J. MacDowall5, D. Mitchell7, E. Möbius20, T. Moore5, N.V. Pogorelov15, D. Reisenfeld17, E. Roelof7, L. Saul3, N.A. Schwadron21, P.W. Valek1,2, R. Vanderspek6, P. Wurz3, G.P. Zank15 (1)Southwest Research Institute, San Antonio, TX, USA (2) University of Texas at San Antonio, San Antonio, TX, USA (3)University of Bern, Physikalisches Institut, CH-3012 Bern, Switzerland (4)Space Research Centre of the Polish Academy of Sciences, Warsaw, Poland (5)NASA Goddard Space Flight Center, Greenbelt, MD, USA (6)Massachusetts Institute of Technology, Cambridge, MA, USA (7)Applied Physics Laboratory, Johns Hopkins University, Laurel, MD, USA (8)University of Bonn, Bonn, Germany (9)Ruhr

  3. Connecting The Interstellar Gas And Dust Properties Of Distant Galaxies

    Science.gov (United States)

    Kulkarni, Varsha

    The properties of interstellar gas and dust in distant galaxies are fundamental parameters in constraining galaxy evolution models. Quasar absorption systems (QASs), which trace intervening galaxies along the sightlines to luminous background quasars, provide invaluable tools to directly study gas and dust in distant normal galaxies. Recent studies of QASs have found interesting trends in both gas and dust properties, such as correlations in metallicity with redshift and dust depletions. Our Spitzer spectroscopic studies also indicate that silicate dust grains are present in QASs, and in fact, at a level higher than expected for diffuse gas in the Milky Way. Moreover, the silicate dust grains in these distant galaxies may be substantially more crystalline than those in the Milky Way interstellar medium. We now propose a comprehensive study of the gas and dust properties of all QASs with strong Ly-alpha and/or metal absorption lines that have adequate archival IR data to probe the study of dust. Our analysis will include data primarily from the NASA-supported Spitzer, Herschel, HST, and Keck Observatory archives, along with a small amount of VLT/SDSS archival data. Our specific goals are as follows: (1) We will measure a large range of metal absorption lines in high-resolution quasar spectra from Keck, HST, and VLT archives to uniformly determine the metallicity, dust depletions, ionization, and star formation rates in the foreground QASs. In particular, we will study the variations in these quantities with gas velocity, using Voigt profile fitting techniques to determine the velocity structure. This analysis will also allow us to quantify the kinematics of the absorbing gas. (2) We will use archival Spitzer IRS quasar spectra to search for and measure the strengths of the 10 and 18 micron silicate dust absorption features for a much larger sample of QASs than previously studied. (3) We will fit the observed silicate absorption features in the Spitzer archival

  4. Stardust Interstellar Preliminary Examination V: XRF analyses of interstellar dust candidates at ESRF ID13

    Science.gov (United States)

    Brenker, Frank E.; Westphal, Andrew J.; Vincze, Laszlo; Burghammer, Manfred; Schmitz, Sylvia; Schoonjans, Tom; Silversmit, Geert; Vekemans, Bart; Allen, Carlton; Anderson, David; Ansari, Asna; Bajt, SašA.; Bastien, Ron K.; Bassim, Nabil; Bechtel, Hans A.; Borg, Janet; Bridges, John; Brownlee, Donald E.; Burchell, Mark; Butterworth, Anna L.; Changela, Hitesh; Cloetens, Peter; Davis, Andrew M.; Doll, Ryan; Floss, Christine; Flynn, George; Fougeray, Patrick; Frank, David R.; Gainsforth, Zack; Grün, Eberhard; Heck, Philipp R.; Hillier, Jon K.; Hoppe, Peter; Hudson, Bruce; Huth, Joachim; Hvide, Brit; Kearsley, Anton; King, Ashley J.; Lai, Barry; Leitner, Jan; Lemelle, Laurence; Leroux, Hugues; Leonard, Ariel; Lettieri, Robert; Marchant, William; Nittler, Larry R.; Ogliore, Ryan; Ong, Wei Ja; Postberg, Frank; Price, Mark C.; Sandford, Scott A.; Tresseras, Juan-Angel Sans; Simionovici, Alexandre S.; Solé, Vicente A.; Srama, Ralf; Stadermann, Frank; Stephan, Thomas; Sterken, Veerle J.; Stodolna, Julien; Stroud, Rhonda M.; Sutton, Steven; Trieloff, Mario; Tsou, Peter; Tsuchiyama, Akira; Tyliszczak, Tolek; Korff, Joshua; Wordsworth, Naomi; Zevin, Daniel; Zolensky, Michael E.

    2014-09-01

    Here, we report analyses by synchrotron X-ray fluorescence microscopy of the elemental composition of eight candidate impact features extracted from the Stardust Interstellar Dust Collector (SIDC). Six of the features were unambiguous tracks, and two were crater-like features. Five of the tracks are so-called "midnight" tracks—that is, they had trajectories consistent with an origin either in the interstellar dust stream or as secondaries from impacts on the Sample Return Capsule (SRC). In a companion paper reporting synchrotron X-ray diffraction analyses of ISPE candidates, we show that two of these particles contain natural crystalline materials: the terminal particle of track 30 contains olivine and spinel, and the terminal particle of track 34 contains olivine. Here, we show that the terminal particle of track 30, Orion, shows elemental abundances, normalized to Fe, that are close to CI values, and a complex, fine-grained structure. The terminal particle of track 34, Hylabrook, shows abundances that deviate strongly from CI, but shows little fine structure and is nearly homogenous. The terminal particles of other midnight tracks, 29 and 37, had heavy element abundances below detection threshold. A third, track 28, showed a composition inconsistent with an extraterrestrial origin, but also inconsistent with known spacecraft materials. A sixth track, with a trajectory consistent with secondary ejecta from an impact on one of the spacecraft solar panels, contains abundant Ce and Zn. This is consistent with the known composition of the glass covering the solar panel. Neither crater-like feature is likely to be associated with extraterrestrial materials. We also analyzed blank aerogel samples to characterize background and variability between aerogel tiles. We found significant differences in contamination levels and compositions, emphasizing the need for local background subtraction for accurate quantification.

  5. Interest Rates and Inflation

    OpenAIRE

    Coopersmith, Michael; Gambardella, Pascal J.

    2016-01-01

    This article is an extension of the work of one of us (Coopersmith, 2011) in deriving the relationship between certain interest rates and the inflation rate of a two component economic system. We use the well-known Fisher relation between the difference of the nominal interest rate and its inflation adjusted value to eliminate the inflation rate and obtain a delay differential equation. We provide computer simulated solutions for this equation over regimes of interest. This paper could be of ...

  6. Interstellar Propulsion Research: Realistic Possibilities and Idealistic Dreams

    Science.gov (United States)

    Johnson, Les

    2009-01-01

    Though physically possible, interstellar travel will be exceedingly difficult. Both the known laws of physics and the limits of our current understanding of engineering place extreme limits on what may actually be possible. Our remote ancestors looked at the night sky and assumed those tiny points of light were campfires around which other tribes were gathered -- and they dreamed of someday making the trip to visit them. In our modern era, we've grown accustomed to humans regularly traveling into space and our robots voyaging ever-deeper into the outer edges of our solar system. Traveling to those distant campfires (stars) has been made to look easy by the likes of Captains Kirk and Picard as well as Han Solo and Commander Adama. Our understanding of physics and engineering has not kept up with our imaginations and many are becoming frustrated with the current pace at which we are exploring the universe. Fortunately, there are ideas that may one day lead to new physical theories about how the universe works and thus potentially make rapid interstellar travel possible -- but many of these are just ideas and are not even close to being considered a scientific theory or hypothesis. Absent any scientific breakthroughs, we should not give up hope. Nature does allow for interstellar travel, albeit slowly and requiring an engineering capability far beyond what we now possess. Antimatter, fusion and photon sail propulsion are all candidates for relatively near-term interstellar missions. The plenary lecture will discuss the dreams and challenges of interstellar travel, our current understanding of what may be possible and some of the "out of the box" ideas that may allow us to become an interstellar species someday in the future.

  7. Interstellar Matter and the Boundary Conditions of the Heliosphere

    Science.gov (United States)

    Frisch, Priscilla C.

    1998-07-01

    The interstellar cloud surrounding the solar system regulates the galactic environment of the Sun, and determines the boundary conditions of the heliosphere. Both the Sun and interstellar clouds move through space, so these boundary conditions change with time. Data and theoretical models now support densities in the cloud surrounding the solar system of n(H0)=0.22±0.06 cm-3, and n(e-)˜0.1 cm-3, with larger values allowed for n(H0) by radiative transfer considerations. Ulysses and Extreme Ultraviolet Explorer satellite He0 data yield a cloud temperature of 6400 K. Nearby interstellar gas appears to be structured and inhomogeneous. The interstellar gas in the Local Fluff cloud complex exhibits elemental abundance patterns in which refractory elements are enhanced over the depleted abundances found in cold disk gas. Within a few parsecs of the Sun, inconclusive evidence for factors of 2-5 variation in Mg+ and Fe+ gas phase abundances is found, providing evidence for variable grain destruction. In principle, photoionization calculations for the surrounding cloud can be compared with elemental abundances found in the pickup ion and anomalous cosmic-ray populations to model cloud properties, including ionization, reference abundances, and radiation field. Observations of the hydrogen pile up at the nose of the heliosphere are consistent with a barely subsonic motion of the heliosphere with respect to the surrounding interstellar cloud. Uncertainties on the velocity vector of the cloud that surrounds the solar system indicate that it is uncertain as to whether the Sun and α Cen are or are not immersed in the same interstellar cloud.

  8. Interstellar organic globules in meteorites and comets

    Science.gov (United States)

    Messenger, Scott; Nakamura-Messenger, Keiko; Keller, Lindsay

    Organic matter in primitive meteorites and interplanetary dust particles (IDPs) is often enriched in D/H and 15N/14N relative to terrestrial values [1-3] due to preservation of interstellar cold molecular cloud material [1]. Some meteorites and IDPs contain micrometer-size inclusions with extreme H and N isotopic anomalies [2-4], possibly due to preserved primordial organic grains. In the Tagish Lake meteorite the main carriers of these anomalies are sub-micrometer, hollow organic globules [5]. Similar objects have been observed in extracts of other chondritic meteorites, but little is known about their N and H isotopic compositions [6-8]. We have measured the H, C, and N isotopic compositions of organic globules in the Bells CM2 carbonaceous chondrite meteorite, NASA Stardust (comet Wild-2) mission samples, and in ‘cometary' IDPs. High-resolution TEM imaging and EELS show that the globules consist of structurally amorphous carbon lacking long range order or development of graphite-like domains. In almost all cases the organic globules have strong enrichments in D/H and 15N/14N. These isotopic anomalies likely resulted from low temperature ( 10 K) chemical reactions in a cold molecular cloud or at the outer regions of the protosolar nebula. These results show that microscopic organic grains were widespread constituents of the protoplanetary disk. Microscopic organic globules may thus have been a common form of prebiotic organic matter delivered to the early Earth by comets and meteorites. References: [1] Messenger S. and Walker R.M. in Astrophysical Implications of the Laboratory Study of Presolar Materials (1997), p.545. [2] Messenger S. (2000) Nature 404, 968. [3] Busemann H. et al. (2006), Science 312, 727. [4] Floss C. et al. (2004) Science 303, 1355. [5] Nakamura-Messenger K. et al. (2006) Science, 314, 1439. [6] Claus G. and Nagy B., (1961) Nature 192, 594 [7] Aoki T., Akai J., Makino K. (2003) Int Symp.Evol. of Solar System Materials 5 [8] Garvie L

  9. The interstellar medium and the soft X-ray background

    Science.gov (United States)

    Snowden, S. L.

    1996-01-01

    The soft X-ray background (SXRB) surface brightness provides data to study the approximately 10(exp 6) K plasma of the local interstellar medium of our Galaxy. Various studies were carried out in order to search for negative correlation, or shadowing, of the SXRB, and were coupled with interstellar medium absorption line studies. The purpose was to determine whether the distances to the shadowing material will lead to a three dimensional mapping of the X-ray emitting, and X-ray absorbing components.

  10. Interstellar abundance and depletion studies along Galactic sightlines

    Science.gov (United States)

    Haris, U.; Murthy, Jayant; Sofia, Ulysses

    2016-07-01

    The Far Ultraviolet Spectroscopic Explorer (FUSE) and Hubble Space Telescope (HST) has enhanced our understanding many aspects of interstellar medium of our galaxy. The wavelength coverage of FUSE and HST is of great astrophysical importance. We use FUSE and HST data for interstellar abundances studies of some important atomic species, such as sulphur and silicon. We report the newly derived column densities by measuring the equivalent widths of several ultraviolet absorption lines. Comparisons of observed depletions and grain properties with existing dust models will be discussed.

  11. Interest rates mapping

    CERN Document Server

    Kanevski, M; Pozdnoukhov, A; Timonin, V

    2007-01-01

    The present study deals with the analysis and mapping of Swiss franc interest rates. Interest rates depend on time and maturity, defining term structure of the interest rate curves (IRC). In the present study IRC are considered in a two-dimensional feature space - time and maturity. Geostatistical models and machine learning algorithms (multilayer perceptron and Support Vector Machines) were applied to produce interest rate maps. IR maps can be used for the visualisation and patterns perception purposes, to develop and to explore economical hypotheses, to produce dynamic asses-liability simulations and for the financial risk assessments. The feasibility of an application of interest rates mapping approach for the IRC forecasting is considered as well.

  12. Interstellar X-Ray Absorption Spectroscopy of the Crab Pulsar with the LETGS

    Science.gov (United States)

    Paerels, Frits; Weisskopf, Martin C.; Tennant, Allyn F.; ODell, Stephen L.; Swartz, Douglas A.; Kahn, Steven M.; Behar, Ehud; Becker, Werner; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    We study the interstellar X-ray absorption along the line of sight to the Crab Pulsar. The Crab was observed with the Low Energy Transmission Grating Spectrometer on the Chandra X-ray Observatory, and the pulsar, a point source, produces a full resolution spectrum. The continuum spectrum appears smooth, and we compare its parameters with other measurements of the pulsar spectrum. The spectrum clearly shows absorption edges due to interstellar Ne, Fe, and O. The O edge shows spectral structure that is probably due to O bound in molecules or dust. We search for near-edge structure (EXAFS) in the O absorption spectrum. The Fe L absorption spectrum is largely due to a set of unresolved discrete n=2-3 transitions in neutral or near-neutral Fe, and we analyze it using a new set of dedicated atomic structure calculations, which provide absolute cross sections. In addition to being interesting in its own right, the ISM absorption needs to be understood in quantitative detail in order to derive spectroscopic constraints on possible soft thermal radiation from the pulsar.

  13. MECHANISTICAL STUDIES ON THE PRODUCTION OF FORMAMIDE (H2NCHO) WITHIN INTERSTELLAR ICE ANALOGS

    International Nuclear Information System (INIS)

    Formamide, H2NCHO, represents the simplest molecule containing the peptide bond. Consequently, the formamide molecule is of high interest as it is considered an important precursor in the abiotic synthesis of amino acids, and thus significant to further prebiotic chemistry, in more suitable environments. Previous experiments have demonstrated that formamide is formed under extreme conditions similar throughout the interstellar medium via photolysis and the energetic processing of ultracold interstellar and solar system ices with high-energy protons; however, no clear reaction mechanism has been identified. Utilizing a laboratory apparatus capable of simulating the effects of galactic cosmic radiation on ultralow temperature ice mixtures, we have examined the formation of formamide starting from a variety of carbon monoxide (CO) to ammonia (NH3) ices of varying composition. Our results suggest that the primary reaction step leading to the production of formamide in low-temperature ices involves the cleavage of the nitrogen-hydrogen bond of ammonia forming the amino radical (NH2) and atomic hydrogen (H), the latter of which containing excess kinetic energy. These suprathermal hydrogen atoms can then add to the carbon-oxygen triple bond of the carbon monoxide (CO) molecule, overcoming the entrance barrier, and ultimately producing the formyl radical (HCO). From here, the formyl radical may combine without an entrance barrier with the neighboring amino radical if the proper geometry for these two species exists within the matrix cage.

  14. A New View on Interstellar Dust - High Fidelity Studies of Interstellar Dust Analogue Tracks in Stardust Flight Spare Aerogel

    Science.gov (United States)

    Zolensky, Michael E.; Postberg F.; Allen, C.; Bajt, S.; Bechtel, H. A.; Borg, J.; Brenker, F.; Bridges, J.; Brownlee, D. E.; Bugiel, S.; Burchell, M.; Burghammer, M.; Butterworth, A. L.; Cloetens, P.; Davis, A. M.; Floss, C.; Flynn, G. J.; Frank, D.; Gainsforth, Z.

    2011-01-01

    In 2000 and 2002 the Stardust Mission exposed aerogel collector panels for a total of about 200 days to the stream of interstellar grains sweeping through the solar system. The material was brought back to Earth in 2006. The goal of this work is the laboratory calibration of the collection process by shooting high speed [5 - 30km/s] interstellar dust (ISD) analogues onto Stardust aerogel flight spares. This enables an investigation into both the morphology of impact tracks as well as any structural and chemical modification of projectile and collector material. First results indicate a different ISD flux than previously assumed for the Stardust collection period.

  15. The VLT-FLAMES Tarantula Survey. IX. The interstellar medium seen through Diffuse Interstellar Bands and neutral sodium

    OpenAIRE

    Loon, van, J.J.W.A.; Bailey, M.; Tatton, B. L.; Maíz Apellániz, J; Crowther, P. A.; Koter, de, A.; Evans, C J; Hénault-Brunet, V.; Howarth, I. D.; Richter, P.; Sana, H.; Simón-Díaz, S.; Taylor, W.; N. R. Walborn

    2012-01-01

    Context. The Tarantula Nebula (a.k.a. 30 Dor) is a spectacular star-forming region in the Large Magellanic Cloud (LMC), seen through gas in the Galactic disc and halo. Diffuse interstellar bands (DIBs) offer a unique probe of the diffuse, cool-warm gas in these regions. Aims. The aim is to use DIBs as diagnostics of the local interstellar conditions, whilst at the same time deriving properties of the yet-unknown carriers of these enigmatic spectral features. Methods. Spectra of over 800 early...

  16. Gravitational lensing by spinning black holes in astrophysics, and in the movie Interstellar

    International Nuclear Information System (INIS)

    Interstellar is the first Hollywood movie to attempt depicting a black hole as it would actually be seen by somebody nearby. For this, our team at Double Negative Visual Effects, in collaboration with physicist Kip Thorne, developed a code called Double Negative Gravitational Renderer (DNGR) to solve the equations for ray-bundle (light-beam) propagation through the curved spacetime of a spinning (Kerr) black hole, and to render IMAX-quality, rapidly changing images. Our ray-bundle techniques were crucial for achieving IMAX-quality smoothness without flickering; and they differ from physicists’ image-generation techniques (which generally rely on individual light rays rather than ray bundles), and also differ from techniques previously used in the film industry’s CGI community. This paper has four purposes: (i) to describe DNGR for physicists and CGI practitioners, who may find interesting and useful some of our unconventional techniques. (ii) To present the equations we use, when the camera is in arbitrary motion at an arbitrary location near a Kerr black hole, for mapping light sources to camera images via elliptical ray bundles. (iii) To describe new insights, from DNGR, into gravitational lensing when the camera is near the spinning black hole, rather than far away as in almost all prior studies; we focus on the shapes, sizes and influence of caustics and critical curves, the creation and annihilation of stellar images, the pattern of multiple images, and the influence of almost-trapped light rays, and we find similar results to the more familiar case of a camera far from the hole. (iv) To describe how the images of the black hole Gargantua and its accretion disk, in the movie Interstellar, were generated with DNGR—including, especially, the influences of (a) colour changes due to doppler and gravitational frequency shifts, (b) intensity changes due to the frequency shifts, (c) simulated camera lens flare, and (d) decisions that the film makers made about

  17. The Interstellar Magnetic Field Close to the Sun II

    CERN Document Server

    Frisch, P C; Berdyugin, A; Piirola, V; DeMajistre, R; Funsten, H O; Magalhaes, A M; Seriacopi, D B; McComas, D J; Schwadron, N A; Slavin, J D; Wiktorowicz, S J

    2012-01-01

    The magnetic field in the local interstellar medium (ISM) provides a key indicator of the galactic environment of the Sun and influences the shape of the heliosphere. The direction of the interstellar magnetic field (ISMF) near the Sun is studied using polarized starlight. The local ISMF direction is found from matching the polarization position angles for interstellar data towards nearby stars using weighted fits. New polarization observations are presented and used in the analysis. The local field is close to the ISMF direction found from the center of the Ribbon of energetic neutral atoms discovered by the Interstellar Boundary Explorer mission. Both the magnetic field and kinematics of the local ISM are consistent with a scenario where the local ISM is a fragment of the Loop I superbubble. An ordered component of the local ISMF is found in a region where PlanetPol data show that polarization increases with distance. It extends to within 8 parsecs of the Sun and implies a weak curvature in the nearby ISMF....

  18. Three-Component Dust Models for Interstellar Extinction

    Indian Academy of Sciences (India)

    C. Muthumariappan

    2010-03-01

    Interstellar extinction curves obtained from the ‘extinction without standard’ method were used to constrain the dust characteristics in the mean ISM (V = 3.1), along the lines of sight through a high latitude diffuse molecular cloud towards HD 210121 (V = 2.1) and in a dense interstellar environment towards the cluster NGC 1977 (V = 6.42). We have used three-component dust models comprising silicate, graphite and very small carbonaceous grains (polycyclic aromatic hydrocarbons) following the grain size distributions introduced by Li & Draine in 2001. It is shown that oxygen, carbon and silicon abundances derived from our models are closer with the available elemental abundances for the dust grains in the ISM if F & G type stars atmospheric abundances are taken for the ISM than the solar. The importance of very small grains in modelling the variation of interstellar extinction curves has been investigated. Grain size distributions and elemental abundances locked up in dust are studied and compared at different interstellar environments using these three extinction curves. We present the albedo and the scattering asymmetry parameter evaluated from optical to extreme-UV wavelengths for the proposed dust models.

  19. The interstellar medium towards the Ara OB1 region

    CERN Document Server

    Henderson, Christopher D; Hearnshaw, John B

    2008-01-01

    We present high resolution (R ~ 4 km/s) absorption measurements of the interstellar NaI and CaII lines measured towards 14 early-type stars of distance 123 pc - 1650 pc, located in the direction of the Ara OB1 stellar cluster. The line profiles can broadly be split into four distinct groupings of absorption component velocity, and we have attempted to identify an origin and distance to each of these interstellar features. For gas with absorption covering the velocity range -10 km/s < V_helio < +10 km/s, we can identify the absorbing medium with local gas belonging to the Lupus-Norma interstellar cavity located between 100 and 485 pc in this galactic direction. Gas with velocities spanning the range -20 km/s < V_helio < +20 km/s is detected towards stars with distances of 570-800 pc. We identify a wide-spread interstellar feature at V_helio ~ -15 km/s with the expanding HI shell called GSH 337+00-05, which is now placed at a distance of ~530 pc.

  20. The shape and composition of interstellar silicate grains

    CERN Document Server

    Min, M; De Koter, A; Hovenier, J W; Keller, L P; Markwick-Kemper, F

    2006-01-01

    We investigate the composition and shape distribution of silicate dust grains in the interstellar medium. The effect of the amount of magnesium in the silicate lattice is studied. We fit the spectral shape of the interstellar 10 mu extinction feature as observed towards the galactic center. We use very irregularly shaped coated and non-coated porous Gaussian Random Field particles as well as a statistical approach to model shape effects. For the dust materials we use amorphous and crystalline silicates with various composition and SiC. The results of our analysis of the 10 mu feature are used to compute the shape of the 20 mu silicate feature and to compare this with observations. By using realistic particle shapes we are, for the first time, able to derive the magnesium fraction in interstellar silicates. We find that the interstellar silicates are highly magnesium rich (Mg/(Fe+Mg)>0.9) and that the stoichiometry lies between pyroxene and olivine type silicates. This composition is not consistent with that o...

  1. Radiation-pressure-driven dust waves inside bursting interstellar bubbles

    NARCIS (Netherlands)

    B.B. Ochsendorf; S. Verdolini; N.L.J. Cox; O. Berné; L. Kaper; A.G.G.M. Tielens

    2014-01-01

    Massive stars drive the evolution of the interstellar medium through their radiative and mechanical energy input. After their birth, they form "bubbles" of hot gas surrounded by a dense shell. Traditionally, the formation of bubbles is explained through the input of a powerful stellar wind, even tho

  2. VUV spectroscopy of carbon dust analogs: contribution to interstellar extinction

    CERN Document Server

    Gavilan, L; Le, K C; Pino, T; Giuliani, A; Dartois, E

    2016-01-01

    A full spectral characterization of carbonaceous dust analogs is necessary to understand their potential as carriers of observed astronomical spectral signatures such as the ubiquitous UV bump at 217.5 nm and the far-ultraviolet (FUV) rise common to interstellar extinction curves. Our goal is to study the spectral properties of carbonaceous dust analogs from the FUV to the mid-infrared (MIR) domain. We seek in particular to understand the spectra of these materials in the FUV range, for which laboratory studies are scarce. We produced analogs to carbonaceous interstellar dust encountered in various phases of the interstellar medium: amorphous hydrogenated carbons (a-C:H), for carbonaceous dust observed in the diffuse interstellar medium, and soot particles, for the polyaromatic component. Analogs to a-C:H dust were produced using a radio-frequency plasma reactor at low pressures, and soot nanoparticles films were produced in an ethylene (C$_2$H$_4$) flame. We measured transmission spectra of these thin films ...

  3. Interstellar Matter and the Boundary Conditions of the Heliosphere

    CERN Document Server

    Frisch, P C

    1998-01-01

    The interstellar cloud surrounding the solar system regulates the galactic environment of the Sun, and determines the boundary conditions of the heliosphere. Both the Sun and interstellar clouds move through space, so these boundary conditions change with time. Data and theoretical models now support densities in the cloud surrounding the solar system of n(HI)=0.22+/-0.06 cm^-3, and n(e-)~0.1 cm-3, with larger values allowed for n(HI) by radiative transfer considerations. Ulysses and Extreme Ultraviolet Explorer satellite HeI data yield a cloud temperature of 6,400 K. Nearby interstellar gas appears to be structured and inhomogeneous. The interstellar gas in the Local Fluff cloud complex exhibits elemental abundance patterns in which refractory elements are enhanced over the depleted abundances found in cold disk gas. Within a few parsecs of the Sun, inconclusive evidence for factors of 2--5 variation in MgII and FeII gas phase abundances is found, providing evidence for variable grain destruction. Observatio...

  4. Debenture Interest Rates

    Data.gov (United States)

    Department of Housing and Urban Development — Interest rates to be paid on debentures issued with respect to a loan or mortgage insured by the Federal Housing Commissioner under the provisions of the National...

  5. Interest rates and inflation

    OpenAIRE

    Michael Coopersmith

    1981-01-01

    A relation between interest rates and inflation is presented using a two component economic model and a simple general principle. Preliminary results indicate a remarkable similarity to classical economic theories, in particular that of Wicksell.

  6. FWS Interest Simplified

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — These boundaries are simplified from the U.S. Fish and Wildlife Service Real Estate Interest data layer containing polygons representing tracts of land (parcels) in...

  7. MAPPING THE INTERSTELLAR MEDIUM WITH NEAR-INFRARED DIFFUSE INTERSTELLAR BANDS

    Energy Technology Data Exchange (ETDEWEB)

    Zasowski, G.; Ménard, B. [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Bizyaev, D. [Apache Point Observatory, Sunspot, NM 88349 (United States); García-Hernández, D. A. [Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife (Spain); Pérez, A. E. García; Majewski, S. R. [Department of Astronomy, University of Virginia, Charlottesville, VA 22904 (United States); Hayden, M. R.; Holtzman, J.; Kinemuchi, K. [Department of Astronomy, New Mexico State University, Las Cruces, NM 88003 (United States); Johnson, J. A.; Wilson, J. C. [Department of Astronomy, The Ohio State University, Columbus, OH 43210 (United States); Nidever, D. L. [Department of Astronomy, University of Michigan, Ann Arbor, MI 48104 (United States); Shetrone, M., E-mail: gail.zasowski@gmail.com [The University of Texas at Austin, McDonald Observatory, McDonald Observatory, TX 79734 (United States)

    2015-01-01

    We map the distribution and properties of the Milky Way's interstellar medium as traced by diffuse interstellar bands (DIBs) detected in near-infrared stellar spectra from the SDSS-III/APOGEE survey. Focusing exclusively on the strongest DIB in the H band, at λ ∼ 1.527 μm, we present a projected map of the DIB absorption field in the Galactic plane, using a set of about 60,000 sightlines that reach up to 15 kpc from the Sun and probe up to 30 mag of visual extinction. The strength of this DIB is linearly correlated with dust reddening over three orders of magnitude in both DIB equivalent width (W {sub DIB}) and extinction, with a power law index of 1.01 ± 0.01, a mean relationship of W {sub DIB}/A{sub V} = 0.1 Å mag{sup –1} and a dispersion of ∼0.05 Å mag{sup –1} at extinctions characteristic of the Galactic midplane. These properties establish this DIB as a powerful, independent probe of dust extinction over a wide range of A{sub V} values. The subset of about 14,000 robustly detected DIB features have a W {sub DIB} distribution that follows an exponential trend. We empirically determine the intrinsic rest wavelength of this transition to be λ{sub 0} = 15 272.42 Å  and use it to calculate absolute radial velocities of the carrier, which display the kinematical signature of the rotating Galactic disk. We probe the DIB carrier distribution in three dimensions and show that it can be characterized by an exponential disk model with a scale height of about 100 pc and a scale length of about 5 kpc. Finally, we show that the DIB distribution also traces large-scale Galactic structures, including the Galactic long bar and the warp of the outer disk.

  8. Gaps in Political Interest

    DEFF Research Database (Denmark)

    Robison, Joshua

    2015-01-01

    Political interest fundamentally influences political behavior, knowledge, and persuasion (Brady, Verba, & Schlozman, 1995; Delli Carpini & Keeter, 1996; Luskin, 1990; Zukin, Andolina, Keeter, Jenkins, & Delli Carpini, 2006). Since the early 1960s, the American National Election Studies (ANES) ha...... participation questions or feeling thermometer items before this measure significantly influences reports of mass interest. Ultimately, the results reported here serve as further caution on the use of this measure....

  9. Interest Rate Risk Management

    OpenAIRE

    Gottvald, Jan

    2013-01-01

    The topic of this Thesis deals with interest rate risk measurement and management in a bank. After the introduction, risks are defined separately in competence of ALM and risk management department, followed by objectives of ALM unit including historical development. Described methods of measuring and managing risk are partly basis for a case study in which the repricing gap model and consequently band BPV have been used. The main aim of the study is to compare the open interest position with...

  10. Ribose and related sugars from ultraviolet irradiation of interstellar ice analogs

    Science.gov (United States)

    Meinert, Cornelia; Myrgorodska, Iuliia; de Marcellus, Pierre; Buhse, Thomas; Nahon, Laurent; Hoffmann, Søren V.; d'Hendecourt, Louis Le Sergeant; Meierhenrich, Uwe J.

    2016-04-01

    Ribose is the central molecular subunit in RNA, but the prebiotic origin of ribose remains unknown. We observed the formation of substantial quantities of ribose and a diversity of structurally related sugar molecules such as arabinose, xylose, and lyxose in the room-temperature organic residues of photo-processed interstellar ice analogs initially composed of H2O, CH3OH, and NH3. Our results suggest that the generation of numerous sugar molecules, including the aldopentose ribose, may be possible from photochemical and thermal treatment of cosmic ices in the late stages of the solar nebula. Our detection of ribose provides plausible insights into the chemical processes that could lead to formation of biologically relevant molecules in suitable planetary environments.

  11. Combining Magnetic and Electric Sails for Interstellar Deceleration

    Science.gov (United States)

    Perakis, Nikolaos; Hein, Andreas M.

    2016-07-01

    The main benefit of an interstellar mission is to carry out in-situ measurements within a target star system. To allow for extended in-situ measurements, the spacecraft needs to be decelerated. One of the currently most promising technologies for deceleration is the magnetic sail which uses the deflection of interstellar matter via a magnetic field to decelerate the spacecraft. However, while the magnetic sail is very efficient at high velocities, its performance decreases with lower speeds. This leads to deceleration durations of several decades depending on the spacecraft mass. Within the context of Project Dragonfly, initiated by the Initiative of Interstellar Studies (i4is), this paper proposes a novel concept for decelerating a spacecraft on an interstellar mission by combining a magnetic sail with an electric sail. Combining the sails compensates for each technologys shortcomings: A magnetic sail is more effective at higher velocities than the electric sail and vice versa. It is demonstrated that using both sails sequentially outperforms using only the magnetic or electric sail for various mission scenarios and velocity ranges, at a constant total spacecraft mass. For example, for decelerating from 5% c, to interplanetary velocities, a spacecraft with both sails needs about 29 years, whereas the electric sail alone would take 35 years and the magnetic sail about 40 years with a total spacecraft mass of 8250 kg. Furthermore, it is assessed how the combined deceleration system affects the optimal overall mission architecture for different spacecraft masses and cruising speeds. Future work would investigate how operating both systems in parallel instead of sequentially would affect its performance. Moreover, uncertainties in the density of interstellar matter and sail properties need to be explored.

  12. POLYCYCLIC AROMATIC HYDROCARBONS AND THE DIFFUSE INTERSTELLAR BANDS: A SURVEY

    International Nuclear Information System (INIS)

    We discuss the proposal of relating the origin of some of the diffuse interstellar absorption bands (DIBs) to neutral polycyclic aromatic hydrocarbons (PAHs) present in translucent interstellar clouds. An assessment of ionized PAHs will be examined in a future report. The spectra of several cold, isolated gas-phase PAHs have been measured in the laboratory under experimental conditions that mimic the interstellar conditions and are compared with an extensive set of astronomical spectra of reddened, early-type stars. This comparison provides-for the first time-accurate upper limits for the abundances of specific PAH molecules along specific lines of sight, something not attainable from IR observations alone. The comparison of these unique laboratory data with high-resolution, high signal-to-noise ratio spectra leads to two major findings: (1) a finding specific to the individual molecules that were probed in this study and, which leads to the clear and unambiguous conclusion that the abundance of these specific neutral PAHs must be very low in the individual translucent interstellar clouds that were probed in this survey (PAH features remain below the level of detection) and, (2) a general finding that neutral PAHs exhibit intrinsic band profiles that are similar to the profile of the narrow DIBs indicating that the carriers of the narrow DIBs must have close molecular structure and characteristics. This study is the first quantitative survey of neutral PAHs in the optical range and it opens the way for unambiguous quantitative searches of PAHs in a variety of interstellar and circumstellar environments.

  13. The chemistry of cold, dark interstellar clouds

    Science.gov (United States)

    Irvine, W. M.

    1987-01-01

    In recent years the nearby cold, dark clouds have been shown to possess a rich chemistry, with interesting differences with respect to warmer massive-star-forming regions and also among the cold clouds themselves. Thirty-nine molecular species are now known in these regions. Recent molecular detections and upper limits in dark clouds are discussed, with particular emphasis on the tricarbon species C3O, C3H, and C3H2.

  14. The VLT-FLAMES Tarantula Survey. IX. The interstellar medium seen through diffuse interstellar bands and neutral sodium

    NARCIS (Netherlands)

    J.Th. van Loon; M. Bailey; B.L. Tatton; J. Maíz Apellániz; P.A. Crowther; A. de Koter; C.J. Evans; V. Hénault-Brunet; I.D. Howarth; P. Richter; H. Sana; S. Simón-Díaz; W. Taylor; N.R. Walborn

    2013-01-01

    Context. The Tarantula Nebula (a.k.a. 30 Dor) is a spectacular star-forming region in the Large Magellanic Cloud (LMC), seen through gas in the Galactic disc and halo. Diffuse interstellar bands (DIBs) offer a unique probe of the diffuse, cool-warm gas in these regions. Aims. The aim is to use DIBs

  15. Stardust Interstellar Preliminary Examination VIII: Identification of crystalline material in two interstellar candidates

    Science.gov (United States)

    Gainsforth, Zack; Brenker, Frank E.; Simionovici, Alexandre S.; Schmitz, Sylvia; Burghammer, Manfred; Butterworth, Anna L.; Cloetens, Peter; Lemelle, Laurence; Tresserras, Juan-Angel Sans; Schoonjans, Tom; Silversmit, Geert; Solé, Vicente A.; Vekemans, Bart; Vincze, Laszlo; Westphal, Andrew J.; Allen, Carlton; Anderson, David; Ansari, Asna; Bajt, SašA.; Bastien, Ron K.; Bassim, Nabil; Bechtel, Hans A.; Borg, Janet; Bridges, John; Brownlee, Donald E.; Burchell, Mark; Changela, Hitesh; Davis, Andrew M.; Doll, Ryan; Floss, Christine; Flynn, George; Fougeray, Patrick; Frank, David; Grün, Eberhard; Heck, Philipp R.; Hillier, Jon K.; Hoppe, Peter; Hudson, Bruce; Huth, Joachim; Hvide, Brit; Kearsley, Anton; King, Ashley J.; Lai, Barry; Leitner, Jan; Leroux, Hugues; Leonard, Ariel; Lettieri, Robert; Marchant, William; Nittler, Larry R.; Ogliore, Ryan; Ong, Wei Ja; Postberg, Frank; Price, Mark C.; Sandford, Scott A.; Srama, Ralf; Stephan, Thomas; Sterken, Veerle; Stodolna, Julien; Stroud, Rhonda M.; Sutton, Steven; Trieloff, Mario; Tsou, Peter; Tsuchiyama, Akira; Tyliszczak, Tolek; von Korff, Joshua; Zevin, Daniel; Zolensky, Michael E.

    2014-09-01

    Using synchrotron-based X-ray diffraction measurements, we identified crystalline material in two particles of extraterrestrial origin extracted from the Stardust Interstellar Dust Collector. The first particle, I1047,1,34 (Hylabrook), consisted of a mosaiced olivine grain approximately 1 µm in size with internal strain fields up to 0.3%. The unit cell dimensions were a = 4.85 ± 0.08 Å, b = 10.34 ± 0.16 Å, c = 6.08 ± 0.13 Å (2σ). The second particle, I1043,1,30 (Orion), contained an olivine grain ≈ 2 µm in length and >500 nm in width. It was polycrystalline with both mosaiced domains varying over ≈ 20° and additional unoriented domains, and contained internal strain fields Fo65 (2σ). Orion also contained abundant spinel nanocrystals of unknown composition, but unit cell dimension a = 8.06 ± 0.08 Å (2σ). Two additional crystalline phases were present and remained unidentified. An amorphous component appeared to be present in both these particles based on STXM and XRF results reported elsewhere.

  16. The interstellar medium in Andromeda's dwarf spheroidal galaxies: I. Content and origin of the interstellar dust

    CERN Document Server

    De Looze, Ilse; Bendo, George J; Fritz, Jacopo; Boquien, Mederic; Cormier, Diane; Gentile, Gianfranco; Kennicutt, Robert C; Madden, Suzanne C; Smith, Matthew W L; Young, Lisa

    2016-01-01

    Dwarf spheroidal galaxies are among the most numerous galaxy population in the Universe, but their main formation and evolution channels are still not well understood. The three dwarf spheroidal satellites (NGC147, NGC185, and NGC205) of the Andromeda galaxy are characterised by very different interstellar medium (ISM) properties, which might suggest them being at different galaxy evolutionary stages. While the dust content of NGC205 has been studied in detail by De Looze et al. (2012), we present new Herschel dust continuum observations of NGC147 and NGC185. The non-detection of NGC147 in Herschel SPIRE maps puts a strong constraint on its dust mass (< 128 Msun). For NGC185, we derive a total dust mass M_d = 5.1 x 10^3 Msun, which is a factor of ~2-3 higher than that derived from ISO and Spitzer observations and confirms the need for longer wavelength observations to trace more massive cold dust reservoirs. We, furthermore, estimate the dust production by asymptotic giant branch (AGB) stars and supernovae...

  17. Discovery of Interstellar Propylene (CH_2CHCH_3): Missing Links in Interstellar Gas-Phase Chemistry

    CERN Document Server

    Marcelino, N; Agundez, M; Roueff, E; Gerin, M; Martín-Pintado, J; Mauersberger, R; Thum, C

    2007-01-01

    We report the discovery of propylene (also called propene, CH_2CHCH_3) with the IRAM 30-m radio telescope toward the dark cloud TMC-1. Propylene is the most saturated hydrocarbon ever detected in space through radio astronomical techniques. In spite of its weak dipole moment, 6 doublets (A and E species) plus another line from the A species have been observed with main beam temperatures above 20 mK. The derived total column density of propylene is 4 10^13 cm^-2, which corresponds to an abundance relative to H_2 of 4 10^-9, i.e., comparable to that of other well known and abundant hydrocarbons in this cloud, such as c-C_3H_2. Although this isomer of C_3H_6 could play an important role in interstellar chemistry, it has been ignored by previous chemical models of dark clouds as there seems to be no obvious formation pathway in gas phase. The discovery of this species in a dark cloud indicates that a thorough analysis of the completeness of gas phase chemistry has to be done.

  18. Ideal Biological Characteristics for Long-Duration Manned Space Travel

    Science.gov (United States)

    Cardion, A. L.

    As we consider the technical challenges we will overcome to launch our first interstellar mission, it is natural that we envision our own view from the deck of that starship. However, the cold reality of the vast distances of interstellar space, in keeping with the history of space flight, clearly indicates that our first forays into such missions will likely be unmanned probes. Indeed, it is the limitations of our own biology and psychology, primarily in their fragility and brevity, that anchor us to the terrestrial environment upon which we depend. But by considering the diversity of biological adaptation documented on Earth, in combination with the promise of an advanced bioengineering program, we can begin to imagine how evolution or design could adapt the intrepid travellers to long-duration stresses inherent to interstellar flight.

  19. Interstellar medium and star formation studies with the Square Kilometre Array

    CERN Document Server

    Manoj, P; Mahewar, G; Kamath, U S; Tej, A

    2016-01-01

    Stars and planetary systems are formed out of molecular clouds in the interstellar medium. Although the sequence of steps involved in star formation are generally known, a comprehensive theory which describes the details of the processes that drive formation of stars is still missing. The Square Kilometre Array (SKA), with its unprecedented sensitivity and angular resolution, will play a major role in filling these gaps in our understanding. In this article, we present a few science cases that the Indian star formation community is interested in pursuing with SKA, which include investigation of AU-sized structures in the neutral ISM, the origin of thermal and non-thermal radio jets from protostars and the accretion history of protostars, and formation of massive stars and their effect on the surrounding medium.

  20. Gravitational lens of the sun - Its potential for observations and communications over interstellar distances

    Science.gov (United States)

    Eshleman, V. R.

    1979-01-01

    The gravitational field of the sun acts as a spherical lens to magnify the intensity of radiation from a distant source along a semi-infinite focal line. A spacecraft anywhere on that line in principle could observe, eavesdrop, and communicate over interstellar distances, using equipment comparable in size and power with what is now used for interplanetary distances. If one neglects coronal effects, the maximum magnification factor for coherent radiation is inversely proportional to the wavelength, being 100 million at 1 millimeter. The principal difficulties are that the nearest point on the focal half-line is about 550 times the sun-earth distance, separate spacecraft would be needed to work with each stellar system of interest, and the solar corona would severely limit the intensity of coherent radiation while also restricting operations to relatively short wavelengths.

  1. Interest rates factor model

    Science.gov (United States)

    Lee, Sangwook; Kim, Min Jae; Kim, Soo Yong

    2011-07-01

    Interdependence of the interest rates of the US, the UK, and Japan is analyzed in this work by means of spectral analysis and network methods. A predominant effective factor in the interest rate market is which country floats a bond issue, and a minor effective factor is time to maturity of bonds. Power-law cross-correlation among different countries is analyzed by the detrended cross-correlation analysis method. Long-range cross-correlation is found between the first factors of interest rate, while there is no cross-correlation between some of the second factors. The tail dependency is indicated by tail indices from Archimedean copulas, including an empirical copula. In contrast to other pairs, the US-UK first factor pair has tail dependencies in both the upper-tail and lower-tail. Dynamic properties of interest rate are modeled by a stochastic volatility model. The properties of mean reverting and volatility clustering are observed and reflected in this model. The proposed simulation method combines the dependence structures and the factor dynamics model; it simultaneously describes the interest rates of different countries.

  2. Fullerenes, Organics and the Diffuse Interstellar Bands

    Science.gov (United States)

    Foing, Bernard H.

    2016-07-01

    The status of DIB research has strongly advanced since 20 years [1], as well as the quest for fullerenes, PAHs and large organics in space. In 1994 we reported the discovery of two near IR diffuse bands coincident with C60+, confirmed in subsequent years [2-6] and now by latest laboratory experiments. A number of DIB observational studies have been published, dealing with: DIB surveys [1,7-10]; measurements of DIB families, correlations and environment dependences [11-14]; extragalactic DIBs [15, 16]. Resolved substructures were detected [17,18] and compared to predicted rotational contours by large molecules [19]. Polarisation studies provided upper limits constraints [20, 21]. DIBs carriers have been linked with organic molecules observed in the interstellar medium [22-25] such as IR bands (assigned to PAHs), Extended Red Emission or recently detected Anomalous Microwave Emission (AME, assigned to spinning dust) and with spectroscopic IR emission bands measured with ISO or Spitzer. Fullerenes and PAHs have been proposed to explain some DIBs and specific molecules were searched in DIB spectra [eg 2-6, 26-31]. These could be present in various dehydrogenation and ionisation conditions [32,33]. Experiments in the laboratory and in space [eg 34-36] allow to measure the survival and by-products of these molecules. We review DIB observational results and their interpretation, and discuss the presence of large organics, fullerenes, PAHs, graphenes in space. References [1] Herbig, G. 1995 ARA&A33, 19; [2] Foing, B. & Ehrenfreund, P. 1994 Natur 369, 296; [3] Foing, B. & Ehrenfreund, P. 1997 A&A317, L59; [4] Foing, B. & Ehrenfreund, P. 1995 ASSL202, 65; [5] Ehrenfreund, P., Foing, B. H. 1997 AdSpR19, 1033; [6] Galazutdinov, G. A. et al. 2000 MNRAS317, 750; [7] Jenniskens, P., Desert, F.-X. 1994 A&AS106, 39; [8] Ehrenfreund, P. et al. 1997 A&A318, L28; [9] Tuairisg, S. Ó. et al. 2000 A&AS142, 225; [10] Cox, N. et al. 2005 A&A438, 187; [11] Cami, J. et al. 1997A&A.326, 822

  3. Observations of Carbon Isotopic Fractionation in Interstellar Formaldehyde

    Science.gov (United States)

    Wirstrom, E. S.; Charnley, S. B.; Geppert, W. D.; Persson, C. M.

    2012-01-01

    Primitive Solar System materials (e.g. chondrites. IDPs, the Stardust sample) show large variations in isotopic composition of the major volatiles (H, C, N, and O ) even within samples, witnessing to various degrees of processing in the protosolar nebula. For ex ample. the very pronounced D enhancements observed in IDPs [I] . are only generated in the cold. dense component of the interstellar medium (ISM), or protoplanetary disks, through ion-molecule reactions in the presence of interstellar dust. If this isotopic anomaly has an interstellar origin, this leaves open the possibility for preservation of other isotopic signatures throughout the form ation of the Solar System. The most common form of carbon in the ISM is CO molecules, and there are two potential sources of C-13 fractionation in this reservoir: low temperature chemistry and selective photodissociation. While gas-phase chemistry in cold interstellar clouds preferentially incorporates C-13 into CO [2], the effect of self-shielding in the presence of UV radiation instead leads to a relative enhancement of the more abundant isotopologue, 12CO. Solar System organic material exhibit rather small fluctuations in delta C-13 as compared to delta N-15 and delta D [3][1], the reason for which is still unclear. However, the fact that both C-13 depleted and enhanced material exists could indicate an interstellar origin where the two fractionation processes have both played a part. Formaldehyde (H2CO) is observed in the gas-phase in a wide range of interstellar environments, as well as in cometary comae. It is proposed as an important reactant in the formation of more complex organic molecules in the heated environments around young stars, and formaldehyde polymers have been suggested as the common origin of chondritic insoluable organic matter (IOM) and cometary refractory organic solids [4]. The relatively high gas-phase abundance of H2CO observed in molecular clouds (10(exp- 9) - 10(exp- 8) relative to H2) makes

  4. Pronounced Practice & Learners’ Interest

    Institute of Scientific and Technical Information of China (English)

    陈作棋

    2009-01-01

    <正>The present s tudy presents a detailed report of the project implemented to solve the problem that most of my students don’t like doing the oral practice I assign them to do after class. It is hypothesized that learners’ interest in pronunciation after class will be increased by a better organization in this

  5. Spousal Conflicts of Interest

    Science.gov (United States)

    Lewis, Shana R.

    2005-01-01

    Romantic relationships bud and sometimes bloom in the school district workplace. When those relationships involve a sitting member of a school board or an administrator with responsibility for managing other employees, questions about a conflict of interest will be raised. Most states have laws prohibiting a public official from taking official…

  6. The interstellar medium in Andromeda's dwarf spheroidal galaxies - I. Content and origin of the interstellar dust

    Science.gov (United States)

    De Looze, Ilse; Baes, Maarten; Bendo, George J.; Fritz, Jacopo; Boquien, Médéric; Cormier, Diane; Gentile, Gianfranco; Kennicutt, Robert C.; Madden, Suzanne C.; Smith, Matthew W. L.; Young, Lisa

    2016-07-01

    Dwarf spheroidal galaxies are among the most numerous galaxy population in the Universe, but their main formation and evolution channels are still not well understood. The three dwarf spheroidal satellites (NGC 147, NGC 185, and NGC 205) of the Andromeda galaxy are characterized by very different interstellar medium properties, which might suggest them being at different galaxy evolutionary stages. While the dust content of NGC 205 has been studied in detail in an earlier work, we present new Herschel dust continuum observations of NGC 147 and NGC 185. The non-detection of NGC 147 in Herschel SPIRE maps puts a strong constraint on its dust mass (≤128^{+124}_{-68} M⊙). For NGC 185, we derive a total dust mass Md = 5.1±1.0 × 103 M⊙, which is a factor of ˜2-3 higher than that derived from ISO and Spitzer observations and confirms the need for longer wavelength observations to trace more massive cold dust reservoirs. We, furthermore, estimate the dust production by asymptotic giant branch (AGB) stars and supernovae (SNe). For NGC 147, the upper limit on the dust mass is consistent with expectations of the material injected by the evolved stellar population. In NGC 185 and NGC 205, the observed dust content is one order of magnitude higher compared to the estimated dust production by AGBs and SNe. Efficient grain growth, and potentially longer dust survival times (3-6 Gyr) are required to account for their current dust content. Our study confirms the importance of grain growth in the gas phase to account for the current dust reservoir in galaxies.

  7. Trans-cis molecular photoswitching in interstellar Space

    CERN Document Server

    Cuadrado, S; Roncero, O; Aguado, A; Tercero, B; Cernicharo, J

    2016-01-01

    As many organic molecules, formic acid (HCOOH) has two conformers (trans and cis). The energy barrier to internal conversion from trans to cis is much higher than the thermal energy available in molecular clouds. Thus, only the most stable conformer (trans) is expected to exist in detectable amounts. We report the first interstellar detection of cis-HCOOH. Its presence in ultraviolet (UV) irradiated gas exclusively (the Orion Bar photodissociation region), with a low trans-to-cis abundance ratio of 2.8+-1.0, supports a photoswitching mechanism: a given conformer absorbs a stellar photon that radiatively excites the molecule to electronic states above the interconversion barrier. Subsequent fluorescent decay leaves the molecule in a different conformer form. This mechanism, which we specifically study with ab initio quantum calculations, was not considered in Space before but likely induces structural changes of a variety of interstellar molecules submitted to UV radiation.

  8. The Origin of Radio Scintillation In the Local Interstellar Medium

    CERN Document Server

    Linsky, Jeffrey L; Redfield, Seth

    2007-01-01

    We study three quasar radio sources (B1257-326, B1519-273, and J1819+385) that show large amplitude intraday and annual scintillation variability produced by the Earth's motion relative to turbulent-scattering screens located within a few parsecs of the Sun. We find that the lines of sight to these sources pass through the edges of partially ionized warm interstellar clouds where two or more clouds may interact. From the gas flow vectors of these clouds, we find that the relative radial and transverse velocities of these clouds are large and could generate the turbulence that is responsible for the observed scintillation. For all three sight lines the flow velocities of nearby warm local interstellar clouds are consistent with the fits to the transverse flows of the radio scintillation signals.

  9. Antimatter Assisted Inertial Confinement Fusion Propulsion Systems for Interstellar Missions

    Science.gov (United States)

    Halyard, R. J.

    Current developments such as the Ion Compressed Antimatter Nuclear (ICAN-II) propulsion system proposed by the Pennsylvania State University Center for Space Propulsion Engineering open the way to the possible use of available supplies of antiprotons to power antimatter assisted inertial confinement fusion (AAICF) propulsion systems for interstellar missions. Analysis indicates that light weight AAICF propulsion systems with specific impulses in excess of seven hundred thousand seconds may be feasible within the next 30 years. AAICF should prove to be the optimum propulsion system since it possesses high thrust, low weight and high exhaust velocity. The purpose of this paper is to evaluate the potential of AAICF propulsion for interstellar missions such as NASA Administrator Dan Goldin's Alpha Centauri Flyby and a Barnard's Star Orbital Mission, and to compare these projections with previous performance estimates for ICF Laser Beam propulsion systems.

  10. Scattering by Interstellar Dust Grains. II. X-Rays

    CERN Document Server

    Draine, B T

    2003-01-01

    Scattering and absorption of X-rays by interstellar dust is calculated for a model consisting of carbonaceous grains and amorphous silicate grains. The calculations employ realistic dielectric functions with structure near X-ray absorption edges, with resulting features in absorption, scattering, and extinction. Differential scattering cross sections are calculated for energies between 0.3 and 10 keV. The median scattering angle is given as a function of energy, and simple but accurate approximations are found for the X-ray scattering properties of the dust mixture, as well as for the angular distribution of the scattered X-ray halo for dust with simple spatial distributions. Observational estimates of the X-ray scattering optical depth are compared to model predictions. Observations of X-ray halos to test interstellar dust grain models are best carried out using extragalactic point sources.

  11. Supernova Feedback on the Interstellar Medium and Star Formation

    CERN Document Server

    Hensler, Gerhard

    2010-01-01

    Supernovae are the most energetic stellar events and influence the interstellar medium by their gasdynamics and energetics. By this, both also affect the star formation positively and negatively. In this paper, we review the development of the complexity of investigations aiming at understanding the interchange between supernovae and their released hot gas with the star-forming molecular clouds. Commencing from analytical studies the paper advances to numerical models of supernova feedback from superbubble scales to galaxy structure. We also discuss parametrizations of star-formation and supernova-energy transfer efficiencies. Since evolutionary models from the interstellar medium to galaxies are numerous and apply multiple recipes of these parameters, only a representative selection of studies can be discussed here.

  12. X-Ray Absorption and Scattering by Interstellar Grains

    CERN Document Server

    Hoffman, John A

    2015-01-01

    Interstellar abundance determinations from fits to X-ray absorption edges often rely on the following false assumptions: (1) the grains are "optically thin" at the observed X-ray wavelengths, and (2) scattering is insignificant and can be ignored. We show instead that scattering contributes significantly to the attenuation of X-rays for realistic dust grain size distributions and substantially modifies the spectrum near absorption edges of elements present in grains. The dust attenuation modules used in major X-ray spectral fitting programs do not take this into account. We show that the consequences of neglecting scattering on the determination of interstellar elemental abundances are modest; however, scattering (along with uncertainties in the grain size distribution) must be taken into account when near-edge extinction fine structure is used to infer dust mineralogy. We advertise the benefits and accuracy of anomalous diffraction theory for both X-ray halo analysis and near edge absorption studies. An open...

  13. The nature of interstellar dust as revealed by light scattering

    Directory of Open Access Journals (Sweden)

    D. A. Williams

    2011-09-01

    Full Text Available Interstellar dust was first identified through the extinction that it causes of optical starlight. Initially, observational and theoretical studies of extinction were made to identify simple ways of removing the effect of extinction. Over the last few decades it has become clear that dust has a number of very important roles in interstellar physics and chemistry, and that through these roles dust affects quite fundamentally the evolution of the Milky Way and other galaxies. However, our detailed knowledge of the actual material of dust remains relatively poor. The use of accurate models for the interaction of electromagnetic radiation with particles of arbitrary shape and composition remains vital, if our description of dust is to improve.

  14. The Gaia-ESO Survey: Tracing interstellar extinction

    CERN Document Server

    Schultheis, M; Recio-Blanco, A; de Laverny, P; Hill, V; Gilmore, G; Alfaro, E J; Costado, M T; Bensby, T; Damiani, F; Feltzing, S; Flaccomio, E; Lardo, C; Jofre, P; Prisinzano, L; Zaggia, S; Jimenez-Esteban, F; Morbidelli, L; Lanzafame, A C; Hourihane, A; Worley, C; Francois, P

    2015-01-01

    Large spectroscopic surveys have enabled in the recent years the computation of three-dimensional interstellar extinction maps thanks to accurate stellar atmospheric parameters and line-of-sight distances. Such maps are complementary to 3D maps extracted from photometry, allowing a more thorough study of the dust properties. Our goal is to use the high-resolution spectroscopic survey Gaia-ESO in order to obtain with a good distance resolution the interstellar extinction and its dependency as a function of the environment and the Galactocentric position. We use the stellar atmospheric parameters of more than 5000 stars, obtained from the Gaia-ESO survey second internal data release, and combine them with optical (SDSS) and near-infrared (VISTA) photometry as well as different sets of theoretical stellar isochrones, in order to calculate line-of-sight extinction and distances. The extinction coefficients are then compared with the literature to discuss their dependancy on the stellar parameters and position in ...

  15. Tholins - Organic chemistry of interstellar grains and gas

    Science.gov (United States)

    Sagan, C.; Khare, B. N.

    1979-01-01

    The paper discusses tholins, defined as complex organic solids formed by the interaction of energy - for example, UV light or spark discharge - with various mixtures of cosmically abundant gases - CH4, C2H6, NH3, H2O, HCHO, and H2S. It is suggested that tholins occur in the interstellar medium and are responsible for some of the properties of the interstellar grains and gas. Additional occurrences of tholins are considered. Tholins have been produced experimentally; 50 or so pyrolytic fragments of the brown, sometimes sticky substances have been identified by gas chromatography-mass spectrometry, and the incidence of these fragments in tholins produced by different procedures is reported.

  16. Interstellar ^{60}Fe on the Surface of the Moon.

    Science.gov (United States)

    Fimiani, L; Cook, D L; Faestermann, T; Gómez-Guzmán, J M; Hain, K; Herzog, G; Knie, K; Korschinek, G; Ludwig, P; Park, J; Reedy, R C; Rugel, G

    2016-04-15

    A dying massive star ends in a supernova explosion ejecting a large fraction of its mass into the interstellar medium. If this happens nearby, part of the ejecta might end on Solar System bodies and, in fact, radioactive ^{60}Fe has been detected on the Pacific ocean floor in about 2 Ma old layers. Here, we report on the detection of this isotope also in lunar samples, originating presumably from the same event. The concentration of the cosmic ray produced isotope ^{53}Mn, measured in the same samples, proves the supernova origin of the ^{60}Fe. From the ^{60}Fe concentrations found we deduce a reliable value for the local interstellar fluence in the range of 1×10^{8}  at/cm^{2}. Thus, we obtain constraints on the recent and nearby supernova(e). PMID:27127953

  17. Determining the Fractal Dimension of the Interstellar Medium

    CERN Document Server

    Sanchez, Nestor; Perez, Enrique

    2008-01-01

    The Interstellar Medium seems to have an underlying fractal structure, which can be characterized through its fractal dimension (Df). However, several factors may affect the determination of Df, such as distortions due to projection, low image resolution, opacity of the cloud, and low signal-to-noise ratio. Here we use both simulated clouds and real molecular cloud maps to study these effects in order to estimate Df in a reliable way. Our results indicate in a self-consistent way that the fractal dimension of the Interstellar Medium is in the range 2.6 < Df < 2.8, which is significantly higher than the value Df = 2.3 usually assumed in the literature.

  18. Redshifted Diffuse Interstellar Bands in Orion OB1 association

    CERN Document Server

    Krełowski, J; Mulas, G; Maszewska, M; Cecchi-Pestellini, C

    2015-01-01

    The wavelength displacement of the Diffuse Interstellar Bands at 4502, 5705, 5780, 6284, and 7224 \\AA\\ with respect to the well known, narrow atomic/molecular interstellar lines (of Ca{\\sc ii} and Na{\\sc i}) have been measured in the spectra of the 2 Orion Trapezium stars HD 37022 and HD 37020, using the HARPS\\textendash N spectrograph, fed with the 3.5 m Telescopio Nazionale Galileo, and the BOES spectrograph, fed with the 1.8m Korean telescope. The red shift is $\\sim$25 km/s for all these DIBs. We discuss the various possible origins of this very peculiar wavelength shift in the light of the particular physical conditions in the Orion Trapezium. The above mentioned shift is seemingly absent in the DIBs at 6196 and 6993 \\AA.

  19. The effect of selective desorption mechanisms during interstellar ice formation

    CERN Document Server

    Kalvans, Juris

    2015-01-01

    Major components of ices on interstellar grains in molecular clouds - water and carbon oxides - occur at various optical depths. This implies that selective desorption mechanisms are at work. An astrochemical model of a contracting low-mass molecular cloud core is presented. Ice was treated as consisting of the surface and three subsurface layers (sublayers). Photodesorption, reactive desorption, and indirect reactive desorption were investigated. The latter manifests itself through desorption from H+H reaction on grains. Desorption of shallow subsurface species was included. Modeling results suggest the existence of a "photon-dominated ice" during the early phases of core contraction. Subsurface ice is chemically processed by interstellar photons, which produces complex organic molecules. Desorption from the subsurface layer results in high COM gas-phase abundances at Av = 2.4...10mag. This may contribute towards an explanation for COM observations in dark cores. It was found that photodesorption mostly gove...

  20. $H_{2}$ Formation on Interstellar Grains in Different Physical Regimes

    CERN Document Server

    Biham, O; Katz, N; Pirronello, V; Vidali, G

    1998-01-01

    An analysis of the kinetics of H2 formation on interstellar dust grains is presented using rate equations. It is shown that semi-empirical expressions that appeared in the literature represent two different physical regimes. In particular, it is shown that the expression given by Hollenbach, Werner and Salpeter [ApJ, 163, 165 (1971)] applies when high flux, or high mobility, of H atoms on the surface of a grain, makes it very unlikely that H atoms evaporate before they meet each other and recombine. The expression of Pirronello et al.\\ [ApJ, 483, L131 (1997)] -- deduced on the basis of accurate measurements on realistic dust analogue -- applies to the opposite regime (low coverage and low mobility). The implications of this analysis for the understanding of the processes dominating in the Interstellar Medium are discussed.

  1. Isotopic Fractionation in Comets: Quantifying the Contribution of Interstellar Chemistry

    Science.gov (United States)

    Charnley, Steven

    2010-01-01

    Anomalously fractionated isotopic material is found in many primitive Solar System objects, such as meteorites and comets. It is thought, in some cases, to trace interstellar matter that was incorporated into the Solar Nebula without undergoing significant processing. We will present the results of models of the nitrogen, oxygen, and carbon fractionation chemistry in dense molecular clouds, particularly in cares where substantial freeze-taut of molecules on to dust has occurred. The range of fractionation ratios expected in different interstellar molecules will be discussed and compared to the ratios measured in molecular clouds, comets and meteoritic material. These models make several predictions that can be tested in the near future by molecular line observations, particularly with the GBT.

  2. Interstellar HI Shells Identified in the SETHI Survey

    CERN Document Server

    Sallmen, Shauna M; Bellehumeur, Brooke; Tennyson, Elizabeth M; Grunwald, Kurt; Lo, Cheuk Man

    2015-01-01

    Galactic HI (neutral hydrogen) shells are central to our understanding of the interstellar medium (ISM), which plays a key role in the development and evolution of galaxies, including our own. Several models involving supernovae and stellar winds have contributed to our broad understanding, but a complete, detailed picture remains elusive. To extend existing Galactic shell catalogs, we visually examined the SETHI (Search for Extraterrestrial HI) database to identify shell-like structures. This high-sensitivity 21-cm radio survey covering the Arecibo sky uniquely provides high-resolution data on shells at a wide range of Galactic latitudes. We present basic information (location, radial velocity, angular size, shape) for 74 previously unidentified HI shells. Due to limitations of coverage and data quality, and the biases inherent in search techniques, our catalog is not a complete sample of Galactic shells. We discuss the catalog completeness, and comment on the new shells' relationship with known interstellar...

  3. Hydrocarbon anions in interstellar clouds and circumstellar envelopes

    CERN Document Server

    Millar, T J; Cordiner, M A; Herbst, Eric; Walsh, C

    2007-01-01

    The recent detection of the hydrocarbon anion C6H- in the interstellar medium has led us to investigate the synthesis of hydrocarbon anions in a variety of interstellar and circumstellar environments. We find that the anion/neutral abundance ratio can be quite large, on the order of at least a few percent, once the neutral has more than five carbon atoms. Detailed modeling shows that the column densities of C6H- observed in IRC+10216 and TMC-1 can be reproduced. Our calculations also predict that other hydrocarbon anions, such as C4H- and C8H-, are viable candidates for detection in IRC+10216, TMC-1 and photon-dominated regions such as the Horsehead Nebula.

  4. The interstellar chemistry of H2C3O isomers

    Science.gov (United States)

    Loison, Jean-Christophe; Agúndez, Marcelino; Marcelino, Núria; Wakelam, Valentine; Hickson, Kevin M.; Cernicharo, José; Gerin, Maryvonne; Roueff, Evelyne; Guélin, Michel

    2016-01-01

    We present the detection of two H2C3O isomers, propynal and cyclopropenone, toward various starless cores and molecular clouds, together with upper limits for the third isomer propadienone. We review the processes controlling the abundances of H2C3O isomers in interstellar media showing that the reactions involved are gas-phase ones. We show that the abundances of these species are controlled by kinetic rather than thermodynamic effects. PMID:27013768

  5. The Diffuse Interstellar Bands: A Major Problem in Astronomical Spectroscopy

    CERN Document Server

    Sarre, P J

    2006-01-01

    A critical review of the very long-standing problem of the diffuse interstellar bands is presented with emphasis on spectroscopic aspects of observational, modelling and laboratory-based research. Some research themes and ideas that could be explored theoretically and experimentally are discussed. The article is based on the Journal of Molecular Spectroscopy Review Lecture presented at the 60th Ohio State University International Symposium on Molecular Spectroscopy, June 2005.

  6. Dust Plasma Analogue for Interstellar 217.5 nm Extinction

    Directory of Open Access Journals (Sweden)

    Stefanović, I.

    2008-12-01

    Full Text Available The new ultraviolet (UV extinction measurements of carbonaceous nanoparticles in the range from 140 nm to 260 nm are presented. The plasma polymerized hydrocarbon nanoparticles were already proposed as a new astro analogue, which describe the infrared (IR extinction spectra in an excellent way. We use the same particles to find the possible carrier of the "mysterious" UV 217.5 nm extinction "bump" of interstellar media (ISM.

  7. Numerical study of rotating interstellar clouds: equilibrium and collapse

    International Nuclear Information System (INIS)

    Equilibrium and collapse of rotating, axisymmetric, idealized interstellar gas clouds is calculated with a 2D hydrodynamics code. The hydrodynamics features an improved angular momentum advection algorithm. Angular momentum is advected consistently with mass by deriving angular momentum fluxes from mass fluxes and the local distribution of specific angular momentum. Local conservation is checked by a graph of mass versus specific angular momentum for the cloud as a whole

  8. On the relationship between Red Rectangle and diffuse interstellar bands

    CERN Document Server

    Zagury, Frederic

    2009-01-01

    A careful examination of Red Rectangle bands which have been considered as diffuse interstellar bands (DIBs) in emission shows that a few are likely to be artifacts in the spectrum. Some others result from atmospheric extinction. Consequences for the Red Rectangle band/DIB associations are examined. I will also comment a striking resemblance between the DIB spectrum and the spectrum of NO2 in the 6150-6250A region. This suggests that some DIBs could be provoked by atmospheric molecules.

  9. The interstellar chemistry of H2C3O isomers

    OpenAIRE

    Loison, Jean-Christophe; Agúndez, Marcelino; Marcelino, Núria; Wakelam, Valentine; Hickson, Kevin M.; Cernicharo, José; Gerin, Maryvonne; Roueff, Evelyne; Guélin, Michel

    2016-01-01

    We present the detection of two H2C3O isomers, propynal and cyclopropenone, toward various starless cores and molecular clouds, together with upper limits for the third isomer propadienone. We review the processes controlling the abundances of H2C3O isomers in interstellar media showing that the reactions involved are gas-phase ones. We show that the abundances of these species are controlled by kinetic rather than thermodynamic effects.

  10. Dark matter properties implied by gamma ray interstellar emission models

    OpenAIRE

    Balázs, Csaba; Li, Tong

    2016-01-01

    We infer dark matter properties from gamma ray residuals extracted using eight different interstellar emission scenarios proposed by the Fermi-LAT Collaboration to explain the Galactic Center gamma ray excess. Adopting the most plausible simplified ansatz, we assume that the dark matter particle is a Majorana fermion interacting with standard fermions via a scalar mediator. Using this theoretical hypothesis and the Fermi residuals we calculate Bayesian evidences, including Fermi-LAT exclusion...

  11. Numerical study of rotating interstellar clouds: equilibrium and collapse

    Energy Technology Data Exchange (ETDEWEB)

    Norman, M.L.

    1980-06-01

    Equilibrium and collapse of rotating, axisymmetric, idealized interstellar gas clouds is calculated with a 2D hydrodynamics code. The hydrodynamics features an improved angular momentum advection algorithm. Angular momentum is advected consistently with mass by deriving angular momentum fluxes from mass fluxes and the local distribution of specific angular momentum. Local conservation is checked by a graph of mass versus specific angular momentum for the cloud as a whole.

  12. Energy Budget and the Virial Theorem in Interstellar Clouds

    OpenAIRE

    Vazquez-Semadeni, Enrique

    1997-01-01

    The Virial Thoerem is a mathematical expression obtained from the equation of motion for a fluid, which describes the energy budget of particular regions within the flow. This course reviews the basic theory leading to the Virial Theorem, discusses its applicability and limitations, and then summarizes observational results concerning the physical and statistical properties of interstellar clouds which are normally understood in terms of the Virial Theorem, in particular the so-called ``Larso...

  13. The interstellar chemistry of H2C3O isomers

    CERN Document Server

    Loison, Jean-Christophe; Marcelino, Núria; Wakelam, Valentine; Hickson, Kevin M; Cernicharo, José; Gerin, Maryvonne; Roueff, Evelyne; Guélin, Michel

    2015-01-01

    We present the detection of two H2C3O isomers, propynal and cyclopropenone, toward various starless cores and molecular clouds, together with upper limits for the third isomer propadienone. We review the processes controlling the abundances of H2C3O isomers in interstellar media showing that the reactions involved are gas-phase ones. We show that the abundances of these species are controlled by kinetic rather than thermodynamic effects.

  14. Interstellar Extinction and Polarization by Graphite-Silicate Clusters

    Science.gov (United States)

    Johnson, E. T.; Draine, B. T.

    2004-12-01

    The geometry of interstellar dust continues to be uncertain. In some models, intertellar grains are assumed to homogeneous spheres, with a suitable mixture of sizes and compositions in order to reproduce observations of of absorption and scattering (e.g., Weingartner & Draine 2001, or Zubko et al. 2004). However, it is often thought that the larger interstellar grains may be formed by agglomeration of smaller particles, with the resulting ``cluster'' being of nonuniform composition and having a ``fluffy'' geometry. The optical properties of such ``fluffy'' grains have sometimes been estimated using ``effective medium theory'' or other approximations, but it is now possible to directly calculate scattering and absorption using the discrete dipole approximation (Draine & Flatau 1994). We construct candidate clusters by random ballistic agglomeration of small graphite and silicate spheres, and calculate their scattering and absorption cross sections using the discrete dipole approximation code DDSCAT 6.x (Draine & Flatau 2004). We consider a model for interstellar dust consisting of very small grains plus clusters built by ballistic agglomeration with a suitable size distribution, and we test the model by trying to reproduce the observed wavelength dependence of interstellar extinction and polarization. This research was supported in part by NSF grants AST-0216105 and AST-0406883. References: Draine, B.T., & Flatau, P.J. 1994, JOSA, A11, 1491l Draine, B.T., & Flatau, P.J. 2004, http://arxiv.org/abs/astro-ph/0409262l Weingartner, J.C., & Draine, B.T. 2001, ApJ, 548, 296l Zubko, V., Dwek, E., & Arendt, R.G. 2004, ApJS, 152, 211l

  15. SMM detection of interstellar Al-26 gamma radiation

    Science.gov (United States)

    Share, G. H.; Kinzer, R. L.; Chupp, E. L.; Forrest, D. J.; Rieger, E.

    1985-01-01

    The gamma ray spectrometer on the Solar Maximum Mission Satellite has detected the interstellar Al-26 line when the Galactic center traversed its aperture. The center of the emission is consistent with the location of the Galactic center, but the spatial distribution is presently not well defined. The total flux in the direction of the Galactic center is 4.3 + or - 0.4) x .0001 gamma/sq cm-s-rad for an assumed population I distribution.

  16. Innovation and social interests

    Directory of Open Access Journals (Sweden)

    Vratuša-Žunjić Vera

    2010-01-01

    Full Text Available The paper focuses on socially and historically structured circumstances surrounding and moral problems involved in the pragmatic definition of innovation as 'novelty proven useful by its users'. Contending conceptions and strategies of innovation of the organization of social relations in dialectical social systems are compared and socially and historically contextualized in the so-called 'transition countries' on the new Eastern border of the European Union. The conclusion is that the cited pragmatic definition of innovation may be misused for an apology of morally dubious new ends and means in the narrow interest of particular groups of users, often at the expense and against the interest of a majority of other individuals and social groups.

  17. Corporate Conflicts of Interest

    OpenAIRE

    Joel S. Demski

    2003-01-01

    This paper surveys conflicts of interest in the corporate governance arena, with emphasis on auditors, boards of directors, analysts and investment bankers, regulators, management, attorneys and investors. Enron provides a host of examples as well. I stress the multifaceted nature of these conflicts, and the fact most research looks at some conflicts, such as auditor independence, absent the larger setting and potential interactions among various players. I further speculate herding behavior ...

  18. Microanalysis of Hypervelocity Impact Residues of Possible Interstellar Origin

    Science.gov (United States)

    Stroud, Rhonda M.; Achilles, Cheri; Allen, Carlton; Anasari, Asna; Bajt, Sasa; Bassim, Nabil; Bastien, Ron S.; Bechtel, H. A.; Borg, Janet; Brenker, Frank E.; Bridges, John; Brownlee, Donald E.; Burchell, Mark; Burghammer, Manfred; Butterworth, Anna L.; Changela, Hitesh; Cloetens, Peter; Davis, Andrew M.; Doll, Ryan; Floss, Christine; Flynn, George; Fougeray, Patrick; Frank, David; Sandford, Scott A.; Zolensky, Michael E.

    2012-01-01

    The NASA Stardust spacecraft deployed two collector trays, one dedicated to the collection of dust from Comet Wild 2, and the other for the capture of interstellar dust (ISD). The samples were returned successfully to Earth in 2006, and now provide an unprecedented opportunity for laboratory-based microanalysis of materials from the outer solar system and beyond. Results from the cometary sample studies have demonstrated that Wild 2 contains much more refractory condensate material and much less pristine extra-solar material than expected, which further indicates that there was significant transport of inner solar system materials to the Kuiper Belt in the early solar system [1]. The analysis of the interstellar samples is still in the preliminary examination (PE) phase, due to the level of difficulty in the definitive identification of the ISD features, the overall low abundance, and its irreplaceable nature, which necessitates minimally invasive measurements [2]. We present here coordinated microanalysis of the impact features on the Al foils, which have led to the identification of four impacts that are possibly attributable to interstellar dust. Results from the study of four ISD candidates captured in aerogel are presented elsewhere [2].

  19. Evolution of interstellar dust and stardust in the solar neighbourhood

    CERN Document Server

    Zhukovska, Svitlana; Trieloff, Mario

    2007-01-01

    The abundance evolution of interstellar dust species originating from stellar sources and from condensation in molecular clouds in the local interstellar medium of the Milky Way is studied and the input of dust material to the Solar System is determined. A one-zone chemical evolution model of the Milky Way for the elemental composition of the disk combined with an evolution model for its interstellar dust component similar to that of Dwek (1998) is developed. The dust model considers dust-mass return from AGB stars as calculated from synthetic AGB models combined with models for dust condensation in stellar outflows. Supernova dust formation is included in a simple parameterized form which is gauged by observed abundances of presolar dust grains with supernova origin. For dust growth in the ISM a simple method is developed for coupling this with disk and dust evolution models. The time evolution of the abundance of the following dust species is followed in the model: silicate, carbon, silicon carbide, and iro...

  20. Project Icarus: A Review of Interstellar Starship Designs

    Science.gov (United States)

    Obousy, R. K.

    Interstellar missions have been proposed as a priority for research into (1) the interstellar medium and any number of astrophysical studies which could be performed en-route, (2) astrophysical studies of a target star, or stars, if a multiple system is selected, (3) planetary science studies of any planets in the target system, including moons and large asteroids, and (4) astrobiological and exobiological studies of any habitable planets which may be found in a target system.The primary challenges associated with any interstellar mission relate to the distances involved, and missions conducted on timescales of a human lifetime are not possible using conventional chemical propulsion. Numerous unique solutions have been proposed including; beamed energy propulsion, fission/fusion propulsion, antimatter propulsion, and more exotic ideas like wormholes and warp drives. In this talk a broad overview of the state-of-the-art in starship design is presented. In addition a discussion the merits and limitations of these proposals is included. Finally an examination of the technological maturity of these concepts and the possibility of their realization within a century is presented.

  1. (Biological dosimetry)

    Energy Technology Data Exchange (ETDEWEB)

    Preston, R.J.

    1990-12-17

    The traveler attended the 1st International Conference on Biological Dosimetry in Madrid, Spain. This conference was organized to provide information to a general audience of biologists, physicists, radiotherapists, industrial hygiene personnel and individuals from related fields on the current ability of cytogenetic analysis to provide estimates of radiation dose in cases of occupational or environmental exposure. There is a growing interest in Spain in biological dosimetry because of the increased use of radiation sources for medical and occupational uses, and with this the anticipated and actual increase in numbers of overexposure. The traveler delivered the introductory lecture on Biological Dosimetry: Mechanistic Concepts'' that was intended to provide a framework by which the more applied lectures could be interpreted in a mechanistic way. A second component of the trip was to provide advice with regard to several recent cases of overexposure that had been or were being assessed by the Radiopathology and Radiotherapy Department of the Hospital General Gregorio Maranon'' in Madrid. The traveler had provided information on several of these, and had analyzed cells from some exposed or purportedly exposed individuals. The members of the biological dosimetry group were referred to individuals at REACTS at Oak Ridge Associated Universities for advice on follow-up treatment.

  2. How Do Interest in Sciences Vary with Gender?

    Science.gov (United States)

    Gafoor, K. Abdul

    2011-01-01

    This study explores interest in physics, chemistry and biology among school students in Kerala. It used a sample of 3236 (1659 boys, 1577 girls) students studying in upper primary to higher secondary classes. Three separate versions of scale of interest in science were used to quantify interest in science of upper primary, secondary and higher…

  3. The Secondary Stream of Interstellar Neutral Hydrogen Flow

    Science.gov (United States)

    Nakagawa, H.; Fukunishi, H.; Watanabe, S.; Takahashi, Y.; Taguchi, M.; Yamazaki, A.

    2005-12-01

    The solar system is located in a low-density interstellar cloud. Neutral hydrogen and helium atoms of the interstellar medium can penetrate deep into the heliosphere without being completely interrupted by the solar wind plasma. Consequently, there is a uniform flow of interplanetary hydrogen and helium in the solar system. This neutral hydrogen and helium flow is called `interstellar wind'. Spacecraft data demonstrated that the upstream direction of the interplanetary neutral helium flow is (254.7°+-0.4°, 5.2°+-0.2°) in the ecliptic coordinate system [Witte, 2004; Vallerga et al., 2004; Gloeckler et al., 2004], while it is (252.5°+-0.5°, 8.8°+-0.5°) for the interplanetary neutral hydrogen [Lallement, et al., 2005; Quemerais et al., 1999]. The presence of this well-established primary stream leads the hydrogen and helium glows to symmetry with respect to the 74° / 254° ecliptic longitude axis. Meanwhile, the existence of a secondary stream of the neutral wind inside the heliosphere arriving from a direction between about 260° and 290° ecliptic longitude, about 10° - 40° different from the upstream primary interstellar neutral flow direction, has been proposed recently by a synthetic analysis of a wide variety of spacecraft observations [M. R. Collier, private communication]. In this study, we have performed a detailed analysis of the interstellar hydrogen resonance glow data obtained from ultraviolet imaging spectrometer (UVS) measurements onboard Nozomi spacecraft. Although the UVS instrument instantaneously points a certain direction with the field-of-view which is perpendicular to the spin axis controlled toward the Earth, spatial distributions of emissions are measured by using the spin and orbital motion of the Nozomi spacecraft. One year observations enable us to derive the full sky image of Lyman alpha emission. We plotted the data obtained in the ecliptic plane from 2000 to 2001 and compared them with the model calculations in cases of the

  4. Flux and composition of interstellar dust at Saturn from Cassini's Cosmic Dust Analyzer.

    Science.gov (United States)

    Altobelli, N; Postberg, F; Fiege, K; Trieloff, M; Kimura, H; Sterken, V J; Hsu, H-W; Hillier, J; Khawaja, N; Moragas-Klostermeyer, G; Blum, J; Burton, M; Srama, R; Kempf, S; Gruen, E

    2016-04-15

    Interstellar dust (ISD) is the condensed phase of the interstellar medium. In situ data from the Cosmic Dust Analyzer on board the Cassini spacecraft reveal that the Saturnian system is passed by ISD grains from our immediate interstellar neighborhood, the local interstellar cloud. We determine the mass distribution of 36 interstellar grains, their elemental composition, and a lower limit for the ISD flux at Saturn. Mass spectra and grain dynamics suggest the presence of magnesium-rich grains of silicate and oxide composition, partly with iron inclusions. Major rock-forming elements (magnesium, silicon, iron, and calcium) are present in cosmic abundances, with only small grain-to-grain variations, but sulfur and carbon are depleted. The ISD grains in the solar neighborhood appear to be homogenized, likely by repeated processing in the interstellar medium. PMID:27081064

  5. Flux and composition of interstellar dust at Saturn from Cassini’s Cosmic Dust Analyzer

    Science.gov (United States)

    Altobelli, N.; Postberg, F.; Fiege, K.; Trieloff, M.; Kimura, H.; Sterken, V. J.; Hsu, H.-W.; Hillier, J.; Khawaja, N.; Moragas-Klostermeyer, G.; Blum, J.; Burton, M.; Srama, R.; Kempf, S.; Gruen, E.

    2016-04-01

    Interstellar dust (ISD) is the condensed phase of the interstellar medium. In situ data from the Cosmic Dust Analyzer on board the Cassini spacecraft reveal that the Saturnian system is passed by ISD grains from our immediate interstellar neighborhood, the local interstellar cloud. We determine the mass distribution of 36 interstellar grains, their elemental composition, and a lower limit for the ISD flux at Saturn. Mass spectra and grain dynamics suggest the presence of magnesium-rich grains of silicate and oxide composition, partly with iron inclusions. Major rock-forming elements (magnesium, silicon, iron, and calcium) are present in cosmic abundances, with only small grain-to-grain variations, but sulfur and carbon are depleted. The ISD grains in the solar neighborhood appear to be homogenized, likely by repeated processing in the interstellar medium.

  6. STRUCTURE OF THE INTERSTELLAR BOUNDARY EXPLORER RIBBON FROM SECONDARY CHARGE-EXCHANGE AT THE SOLAR–INTERSTELLAR INTERFACE

    Energy Technology Data Exchange (ETDEWEB)

    Zirnstein, E. J.; McComas, D. J. [Southwest Research Institute, San Antonio, TX 78228 (United States); Heerikhuisen, J., E-mail: ezirnstein@swri.edu, E-mail: dmccomas@swri.edu, E-mail: jacob.heerikhuisen@uah.edu [Department of Space Science and Center for Space Plasma and Aeronomic Research, University of Alabama in Huntsville, Huntsville, AL 35899 (United States)

    2015-05-01

    In 2009, the Interstellar Boundary Explorer discovered a bright “ribbon” of energetic neutral atom (ENA) flux in the energy range ≤0.4–6 keV, encircling a large portion of the sky. This observation was not previously predicted by any models or theories, and since its discovery, it has been the subject of numerous studies of its origin and properties. One of the most studied mechanisms for its creation is the “secondary ENA” process. Here, solar wind ions, neutralized by charge-exchange with interstellar atoms, propagate outside the heliopause; experience two charge-exchange events in the dense outer heliosheath; and then propagate back inside the heliosphere, preferentially in the direction perpendicular to the local interstellar magnetic field. This process has been extensively analyzed using state-of-the-art modeling and simulation techniques, but it has been difficult to visualize. In this Letter, we show the three-dimensional structure of the source of the ribbon, providing a physical picture of the spatial and energy scales over which the secondary ENA process occurs. These results help us understand how the ribbon is generated and further supports a secondary ENA process as the leading ribbon source mechanism.

  7. Serving the Public Interest

    DEFF Research Database (Denmark)

    Markussen, Thomas; Tyran, Jean-Robert

    We present a model of political selection in which voters elect a president from a set of candidates. We assume that some of the candidates are benevolent and that all voters prefer a benevolent president, i.e. a president who serves the public interest. Yet, political selection may fail in our...... system is likely to produce good governance. That is, if benevolent candidates are common, if the president has little discretionary power, and if the public sector is effective. We analyze the role of institutions like investigative media and re-election and show that they can improve or further hamper...

  8. A Comment on "The Far Future of Exoplanet Direct Characterization" - the Case for Interstellar Space Probes

    OpenAIRE

    Crawford, Ian A.

    2010-01-01

    Following on from ideas presented in a recent paper by Schneider et al. (2010) on "The Far Future of Exoplanet Direct Characterization", I argue that they have exaggerated the technical obstacles to performing such 'direct characterization' by means of fast (order 0.1c) interstellar space probes. A brief summary of rapid interstellar spaceflight concepts that may be found in the literature is presented. I argue that the presence of interstellar dust grains, while certainly something which wil...

  9. Urea, glycolic acid, and glycerol in an organic residue produced by ultraviolet irradiation of interstellar/pre-cometary ice analogs.

    Science.gov (United States)

    Nuevo, Michel; Bredehöft, Jan Hendrik; Meierhenrich, Uwe J; d'Hendecourt, Louis; Thiemann, Wolfram H-P

    2010-03-01

    More than 50 stable organic molecules have been detected in the interstellar medium (ISM), from ground-based and onboard-satellite astronomical observations, in the gas and solid phases. Some of these organics may be prebiotic compounds that were delivered to early Earth by comets and meteorites and may have triggered the first chemical reactions involved in the origin of life. Ultraviolet irradiation of ices simulating photoprocesses of cold solid matter in astrophysical environments have shown that photochemistry can lead to the formation of amino acids and related compounds. In this work, we experimentally searched for other organic molecules of prebiotic interest, namely, oxidized acid labile compounds. In a setup that simulates conditions relevant to the ISM and Solar System icy bodies such as comets, a condensed CH(3)OH:NH(3) = 1:1 ice mixture was UV irradiated at approximately 80 K. The molecular constituents of the nonvolatile organic residue that remained at room temperature were separated by capillary gas chromatography and identified by mass spectrometry. Urea, glycolic acid, and glycerol were detected in this residue, as well as hydroxyacetamide, glycerolic acid, and glycerol amide. These organics are interesting target molecules to be searched for in space. Finally, tentative mechanisms of formation for these compounds under interstellar/pre-cometary conditions are proposed.

  10. X-ray Halos and Large Grains in the Diffuse Interstellar Medium

    OpenAIRE

    Witt, Adolf N.; Smith, Randall K.; Dwek, Eli

    2001-01-01

    Recent observations with dust detectors on board the interplanetary spacecraft Ulysses and Galileo have recorded a substantial flux of large interstellar grains with radii between 0.25 and 2.0 mu entering the solar system from the local interstellar cloud. The most commonly used interstellar grain size distribution is characterized by a a^-3.5 power law in grain radii a, and extends to a maximum grain radius of 0.25 mu. The extension of the interstellar grain size distribution to such large r...

  11. Real interest parity decomposition

    Directory of Open Access Journals (Sweden)

    Alex Luiz Ferreira

    2009-09-01

    Full Text Available The aim of this paper is to investigate the general causes of real interest rate differentials (rids for a sample of emerging markets for the period of January 1996 to August 2007. To this end, two methods are applied. The first consists of breaking the variance of rids down into relative purchasing power pariety and uncovered interest rate parity and shows that inflation differentials are the main source of rids variation; while the second method breaks down the rids and nominal interest rate differentials (nids into nominal and real shocks. Bivariate autoregressive models are estimated under particular identification conditions, having been adequately treated for the identified structural breaks. Impulse response functions and error variance decomposition result in real shocks as being the likely cause of rids.O objetivo deste artigo é investigar as causas gerais dos diferenciais da taxa de juros real (rids para um conjunto de países emergentes, para o período de janeiro de 1996 a agosto de 2007. Para tanto, duas metodologias são aplicadas. A primeira consiste em decompor a variância dos rids entre a paridade do poder de compra relativa e a paridade de juros a descoberto e mostra que os diferenciais de inflação são a fonte predominante da variabilidade dos rids; a segunda decompõe os rids e os diferenciais de juros nominais (nids em choques nominais e reais. Sob certas condições de identificação, modelos autorregressivos bivariados são estimados com tratamento adequado para as quebras estruturais identificadas e as funções de resposta ao impulso e a decomposição da variância dos erros de previsão são obtidas, resultando em evidências favoráveis a que os choques reais são a causa mais provável dos rids.

  12. Heterocyclic Anions of Astrobiological Interest

    Science.gov (United States)

    Cole, Callie A.; Demarais, Nicholas J.; Yang, Zhibo; Snow, Theodore P.; Bierbaum, Veronica M.

    2013-12-01

    As more complex organic molecules are detected in the interstellar medium, the importance of heterocyclic molecules to astrobiology and the origin of life has become evident. 2-Aminothiazole and 2-aminooxazole have recently been suggested as important nucleotide precursors, highlighting azoles as potential prebiotic molecules. This study explores the gas-phase chemistry of three deprotonated azoles: oxazole, thiazole, and isothiazole. For the first time, their gas-phase acidities are experimentally determined with bracketing and H/D exchange techniques, and their reactivity is characterized with several detected interstellar neutral molecules (N2O, O2, CO, OCS, CO2, and SO2) and other reactive species (CS2, CH3Cl, (CH3)3CCl, and (CH3)3CBr). Rate constants and branching fractions for these reactions are experimentally measured using a modified commercial ion trap mass spectrometer whose kinetic data are in good accord with those of a flowing afterglow apparatus reported here. Last, we have examined the fragmentation patterns of these deprotonated azoles to elucidate their destruction mechanisms in high-energy environments. All experimental data are supported and complemented by electronic structure calculations at the B3LYP/6-311++G(d,p) and MP2(full)/aug-cc-pVDZ levels of theory.

  13. Heterocyclic anions of astrobiological interest

    Energy Technology Data Exchange (ETDEWEB)

    Cole, Callie A.; Demarais, Nicholas J.; Bierbaum, Veronica M. [Department of Chemistry and Biochemistry, 215 UCB, University of Colorado, Boulder, CO 80309 (United States); Yang, Zhibo [Department of Chemistry and Biochemistry, University of Oklahoma, Norman, OK 73019 (United States); Snow, Theodore P., E-mail: Callie.Cole@colorado.edu, E-mail: Nicholas.Demarais@colorado.edu, E-mail: Veronica.Bierbaum@colorado.edu, E-mail: Zhibo.Yang@ou.edu, E-mail: Theodore.Snow@colorado.edu [Department of Astrophysical and Planetary Sciences, 391 UCB, University of Colorado, Boulder, CO 80309 (United States)

    2013-12-20

    As more complex organic molecules are detected in the interstellar medium, the importance of heterocyclic molecules to astrobiology and the origin of life has become evident. 2-Aminothiazole and 2-aminooxazole have recently been suggested as important nucleotide precursors, highlighting azoles as potential prebiotic molecules. This study explores the gas-phase chemistry of three deprotonated azoles: oxazole, thiazole, and isothiazole. For the first time, their gas-phase acidities are experimentally determined with bracketing and H/D exchange techniques, and their reactivity is characterized with several detected interstellar neutral molecules (N{sub 2}O, O{sub 2}, CO, OCS, CO{sub 2}, and SO{sub 2}) and other reactive species (CS{sub 2}, CH{sub 3}Cl, (CH{sub 3}){sub 3}CCl, and (CH{sub 3}){sub 3}CBr). Rate constants and branching fractions for these reactions are experimentally measured using a modified commercial ion trap mass spectrometer whose kinetic data are in good accord with those of a flowing afterglow apparatus reported here. Last, we have examined the fragmentation patterns of these deprotonated azoles to elucidate their destruction mechanisms in high-energy environments. All experimental data are supported and complemented by electronic structure calculations at the B3LYP/6-311++G(d,p) and MP2(full)/aug-cc-pVDZ levels of theory.

  14. Heterocyclic anions of astrobiological interest

    International Nuclear Information System (INIS)

    As more complex organic molecules are detected in the interstellar medium, the importance of heterocyclic molecules to astrobiology and the origin of life has become evident. 2-Aminothiazole and 2-aminooxazole have recently been suggested as important nucleotide precursors, highlighting azoles as potential prebiotic molecules. This study explores the gas-phase chemistry of three deprotonated azoles: oxazole, thiazole, and isothiazole. For the first time, their gas-phase acidities are experimentally determined with bracketing and H/D exchange techniques, and their reactivity is characterized with several detected interstellar neutral molecules (N2O, O2, CO, OCS, CO2, and SO2) and other reactive species (CS2, CH3Cl, (CH3)3CCl, and (CH3)3CBr). Rate constants and branching fractions for these reactions are experimentally measured using a modified commercial ion trap mass spectrometer whose kinetic data are in good accord with those of a flowing afterglow apparatus reported here. Last, we have examined the fragmentation patterns of these deprotonated azoles to elucidate their destruction mechanisms in high-energy environments. All experimental data are supported and complemented by electronic structure calculations at the B3LYP/6-311++G(d,p) and MP2(full)/aug-cc-pVDZ levels of theory.

  15. Radio Wave Scintillations and Models of Interstellar Turbulence

    Science.gov (United States)

    Spangler, Steven R.

    1998-05-01

    There are a number of well-established observational results from radio scintillations which have implications for the nature of interstellar turbulence. Among such results are evidence for anisotropy and a Kolmogorov spectrum for the density irregularities. It is probable the galactic magnetic field organizes these irregularities so that spatial gradients along the field are much less than those perpendicular to the field. Such a behavior for turbulence is predicted by theories of magnetohydrodynamic turbulence in which the amplitude is small. The turbulence is then described by a theory termed reduced magnetohydrodynamics. A limiting case of reduced magnetohydrodynamics is two dimensional magnetohydrodynamics, in which the direction of the large scale magnetic field z defines the ignorable coordinate. Two dimensional magnetohydrodynamics consists of a pair of coupled nonlinear partial differential equations for the velocity stream function psi and the z component of the magnetic vector potential A_z. A number of observed features of interstellar turbulence can be identified with solutions to the equations of two dimensional magnetohydrodynamics. Examples are the development of Kolmogorov-like spectra for the velocity and magnetic field from a wide class (although not totally general) initial conditions, a natural explanation for the formation of intermittancy in turbulence, and the rapid development of small scale, large spatial wavenumber fluctuations, in contrast to the eddy cascade of hydrodynamic turbulence. The equations of two dimensional magnetohydrodynamics may serve as a simple but tractable model of interstellar plasma turbulence that may complement and be superior to the traditional model of an ensemble of magnetohydrodynamic waves.

  16. Effects of turbulent dust grain motion to interstellar chemistry

    Science.gov (United States)

    Ge, J. X.; He, J. H.; Yan, H. R.

    2016-02-01

    Theoretical studies have revealed that dust grains are usually moving fast through the turbulent interstellar gas, which could have significant effects upon interstellar chemistry by modifying grain accretion. This effect is investigated in this work on the basis of numerical gas-grain chemical modelling. Major features of the grain motion effect in the typical environment of dark clouds (DC) can be summarized as follows: (1) decrease of gas-phase (both neutral and ionic) abundances and increase of surface abundances by up to 2-3 orders of magnitude; (2) shifts of the existing chemical jumps to earlier evolution ages for gas-phase species and to later ages for surface species by factors of about 10; (3) a few exceptional cases in which some species turn out to be insensitive to this effect and some other species can show opposite behaviours too. These effects usually begin to emerge from a typical DC model age of about 105 yr. The grain motion in a typical cold neutral medium (CNM) can help overcome the Coulomb repulsive barrier to enable effective accretion of cations on to positively charged grains. As a result, the grain motion greatly enhances the abundances of some gas-phase and surface species by factors up to 2-6 or more orders of magnitude in the CNM model. The grain motion effect in a typical molecular cloud (MC) is intermediate between that of the DC and CNM models, but with weaker strength. The grain motion is found to be important to consider in chemical simulations of typical interstellar medium.

  17. OBSERVATIONAL CONSTRAINTS ON METHANOL PRODUCTION IN INTERSTELLAR AND PREPLANETARY ICES

    International Nuclear Information System (INIS)

    Methanol (CH3OH) is thought to be an important link in the chain of chemical evolution that leads from simple diatomic interstellar molecules to complex organic species in protoplanetary disks that may be delivered to the surfaces of Earthlike planets. Previous research has shown that CH3OH forms in the interstellar medium predominantly on the surfaces of dust grains. To enhance our understanding of the conditions that lead to its efficient production, we assemble a homogenized catalog of published detections and limiting values in interstellar and preplanetary ices for both CH3OH and the other commonly observed C- and O-bearing species, H2O, CO, and CO2. We use this catalog to investigate the abundance of ice-phase CH3OH in environments ranging from dense molecular clouds to circumstellar envelopes around newly born stars of low and high mass. Results show that CH3OH production arises during the CO freezeout phase of ice-mantle growth in the clouds, after an ice layer rich in H2O and CO2 is already in place on the dust, in agreement with current astrochemical models. The abundance of solid-phase CH3OH in this environment is sufficient to account for observed gas-phase abundances when the ices are subsequently desorbed in the vicinity of embedded stars. CH3OH concentrations in the ices toward embedded stars show order-of-magnitude object-to-object variations, even in a sample restricted to stars of low mass associated with ices lacking evidence of thermal processing. We hypothesize that the efficiency of CH3OH production in dense cores and protostellar envelopes is mediated by the degree of prior CO depletion.

  18. DISCOVERY OF INTERSTELLAR ANIONS IN CEPHEUS AND AURIGA

    International Nuclear Information System (INIS)

    We report the detection of microwave emission lines from the hydrocarbon anion C6H- and its parent neutral C6H in the star-forming region L1251A (in Cepheus), and the pre-stellar core L1512 (in Auriga). The carbon-chain-bearing species C4H, HC3N, HC5N, HC7N, and C3S are also detected in large abundances. The observations of L1251A constitute the first detections of anions and long-chain polyynes and cyanopolyynes (with more than five carbon atoms) in the Cepheus Flare star-forming region, and the first detection of anions in the vicinity of a protostar outside of the Taurus molecular cloud complex, indicating a possible wider importance for anions in the chemistry of star formation. Rotational excitation temperatures have been derived from the HC3N hyperfine structure lines and are found to be 6.2 K for L1251A and 8.7 K for L1512. The anion-to-neutral ratios are 3.6% and 4.1%, respectively, which are within the range of values previously observed in the interstellar medium, and suggest a relative uniformity in the processes governing anion abundances in different dense interstellar clouds. This research contributes toward the growing body of evidence that carbon chain anions are relatively abundant in interstellar clouds throughout the Galaxy, but especially in the regions of relatively high density and high depletion surrounding pre-stellar cores and young, embedded protostars.

  19. Consequences of the Solar System passage through dense interstellar clouds

    Directory of Open Access Journals (Sweden)

    A. G. Yeghikyan

    Full Text Available Several consequences of the passage of the solar system through dense interstellar molecular clouds are discussed. These clouds, dense (more than 100 cm-3, cold (10–50 K and extended (larger than 1 pc, are characterized by a gas-to-dust mass ratio of about 100, by a specific power grain size spectrum (grain radii usually cover the range 0.001–3 micron and by an average dust-to-gas number density ratio of about 10-12. Frequently these clouds contain small-scale (10–100 AU condensations with gas concentrations ranging up to 10 5 cm-3. At their casual passage over the solar system they exert pressures very much enhanced with respect to today’s standards. Under these conditions it will occur that the Earth is exposed directly to the interstellar flow. It is shown first that even close to the Sun, at 1 AU, the cloud’s matter is only partly ionized and should mainly interact with the solar wind by charge exchange processes. Dust particles of the cloud serve as a source of neutrals, generated by the solar UV irradiation of dust grains, causing the evaporation of icy materials. The release of neutral atoms from dust grains is then followed by strong influences on the solar wind plasma flow. The behavior of the neutral gas inflow parameters is investigated by a 2-D hydrodynamic approach to model the interaction processes. Because of a reduction of the heliospheric dimension down to 1 AU, direct influence of the cloud’s matter to the terrestrial environment and atmosphere could be envisaged.

    Key words. Interplanetary physics (heliopause and solar wind termination; interplanetary dust; interstellar gas

  20. Marine biology

    International Nuclear Information System (INIS)

    This book discusses both taxonomic and ecological topics on marine biology. Full coverage of marine organisms of all five kingdoms is provided, along with interesting and thorough discussion of all major marine habitats. Organization into six major parts allows flexibility. It also provides insight into important topics such as disposal of nuclear waste at sea, the idea that life began on the ocean floor, and how whales, krill, and people interact. A full-color photo chapter reviews questions, and exercises. The contents are: an overview marine biology: fundamental concepts/investigating life in the ocean; the physical ocean, the ocean floor, the nature of water, the nature and motion of ocean water; general ecology, conditions for life in the sea, biological productivity and energy transfer; marine organisms; monera, protista, mycota and metaphyta; the smaller marine animals, the large animals marine habitats, the intertidal zone/benthos of the continental shelf, the photic zone, the deep ocean, the ocean under stress, marine pollution, appendix a: the metric system and conversion factors/ appendix b: prefixes and suffixes/ appendix c: taxonomic classification of common marine organisms, and glossary, and index

  1. Marine biology

    Energy Technology Data Exchange (ETDEWEB)

    Thurman, H.V.; Webber, H.H.

    1984-01-01

    This book discusses both taxonomic and ecological topics on marine biology. Full coverage of marine organisms of all five kingdoms is provided, along with interesting and thorough discussion of all major marine habitats. Organization into six major parts allows flexibility. It also provides insight into important topics such as disposal of nuclear waste at sea, the idea that life began on the ocean floor, and how whales, krill, and people interact. A full-color photo chapter reviews questions, and exercises. The contents are: an overview marine biology: fundamental concepts/investigating life in the ocean; the physical ocean, the ocean floor, the nature of water, the nature and motion of ocean water; general ecology, conditions for life in the sea, biological productivity and energy transfer; marine organisms; monera, protista, mycota and metaphyta; the smaller marine animals, the large animals marine habitats, the intertidal zone/benthos of the continental shelf, the photic zone, the deep ocean, the ocean under stress, marine pollution, appendix a: the metric system and conversion factors/ appendix b: prefixes and suffixes/ appendix c: taxonomic classification of common marine organisms, and glossary, and index.

  2. Potential Variations in the Interstellar N I Abundance

    OpenAIRE

    Knauth, David C.; Andersson, B-G; McCandliss, Stephan R.; Moos, H. Warren

    2003-01-01

    We present Far Ultraviolet Spectroscopic Explorer (FUSE) and Space Telescope Imaging Spectrograph observations of the weak interstellar N I doublet at 1160 Angstroms toward 17 high-density sight lines [N(Htot)>=10^21 cm^-2]. When combined with published data, our results reveal variations in the fractional N I abundance showing a systematic deficiency at large N(Htot). At the FUSE resolution (~20 km s^-1), the effects of unresolved saturation cannot be conclusively ruled out, although O I at ...

  3. The determination of electron abundances in interstellar clouds

    Science.gov (United States)

    Wootten, A.; Snell, R.; Glassgold, A. E.

    1979-01-01

    An independent method is proposed for the determination of electron abundances in dense clouds based upon the abundance ratio of HCO(+) and CO. The method is derived from a simple application of gas phase ion molecule interstellar chemistry. It is noted that unlike the fractionation of deuterated molecules, it applies to warm as well as to cool clouds. The method is illustrated with the results of the recent abundance survey of Wooten et al. (1978). Finally, it is shown that in cases where deuterium enhancement is measured, an upper limit can be obtained for the cosmic ray ionization rate.

  4. Electron density and carriers of the diffuse interstellar bands

    OpenAIRE

    Gnacinski, P.; Sikorski, J. K.; Galazutdinov, G. A.

    2007-01-01

    We have used the ionisation equilibrium equation to derive the electron density in interstellar clouds in the direction to 13 stars. A linear relation was found, that allows the determination of the electron density from the Mg I and Mg II column densities in diffuse clouds. The comparison of normalised equivalent width of 12 DIBs with the electron density shows that the DIBs equivalent width do not change with electron density varying in the range ne=0.01-2.5 cm^-3. Therefore the DIBs carrie...

  5. Spectroscopy of the earth's atmosphere and interstellar medium

    CERN Document Server

    Rao, KN

    1992-01-01

    Spectroscopy of the Earth's Atmosphere and Interstellar Medium focuses on the characteristics of the electromagnetic spectrum of the Earth's atmosphere in the far-infrared and microwave regions. It discusses the modes of observation in field measurements and reviews the two techniques used in the spectral region. Organized into six chapters, this volume begins with an overview of the effect of water-vapor absorption, followed by a discussion on the two frequently used method for deriving atmospheric parameters from high-resolution infrared atmospheric spectra, namely, the equivalent width

  6. Physical conditions in CaFe interstellar clouds

    OpenAIRE

    Gnacinski, P.; Krogulec, M.

    2007-01-01

    Interstellar clouds that exhibit strong Ca I and Fe I lines were called CaFe clouds. The ionisation equilibrium equations were used to model the column densities of Ca II, Ca I, K I, Na I, Fe I and Ti II in CaFe clouds. The chemical composition of CaFe clouds is that of the Solar System and no depletion of elements onto dust grains is seen. The CaFe clouds have high electron densities n=1 cm^-3 that leads to high column densities of neutral Ca and Fe.

  7. Time markers in interstellar communication. [with binary star civilizations

    Science.gov (United States)

    Pace, G. W.; Walker, J. C. G.

    1975-01-01

    The chances that two civilizations establish contact with each other by means of interstellar radio communication are exceedingly small in the absence of time markers which will tell the two civilizations when to search for one another. In the case of binary stars, suitable time markers are provided by the apastron and the periastron. Single star civilization would transmit signals to binaries at the observation of apastron and periastron and the binary star civilization would scan single stars at the proper time for the reception of these signals.

  8. Capture of interplanetary and interstellar dust by the jovian magnetosphere.

    Science.gov (United States)

    Colwell, J E; Horányi, M; Grün, E

    1998-04-01

    Interplanetary and interstellar dust grains entering Jupiter's magnetosphere form a detectable diffuse faint ring of exogenic material. This ring is composed of particles in the size range of 0. 5 to 1.5 micrometers on retrograde and prograde orbits in a 4:1 ratio, with semimajor axes 3 jovian radii, eccentricities 0. 1 < e < 0.3, and inclinations i less, similar 20 degrees or i greater, similar 160 degrees. The size range and the orbital characteristics are consistent with in situ detections of micrometer-sized grains by the Galileo dust detector, and the measured rates match the number densities predicted from numerical trajectory integrations. PMID:9525863

  9. Gas-grain models for interstellar anion chemistry

    OpenAIRE

    Cordiner, M. A.; Charnley, S. B.

    2012-01-01

    Long-chain hydrocarbon anions CnH- (n=4, 6, 8) have recently been found to be abundant in a variety of interstellar clouds. In order to explain their large abundances in the denser (prestellar/protostellar) environments, new chemical models are constructed that include gas-grain interactions. Models including accretion of gas-phase species onto dust grains and cosmic-ray-induced desorption of atoms are able to reproduce the observed anion-to-neutral ratios, as well as the absolute abundances ...

  10. The UV interstellar spectrum and environment of SN 1987A

    International Nuclear Information System (INIS)

    The author discusses how the unusually strong C IV and Si IV features in the UV spectrum of SN 1987A, plus x-ray and optical data obtained prior to this explosive event suggest that SN 1987A exploded in a large low density cavity or superbubble. This cavity was carved out of the interstellar medium by the stellar winds and previous supernovae due to the large concentration of massive stars near SN 1987A. These stars, cavity, and associated nebulosity, as evidenced by extended [0 III], form an H II region complex with a diameter of approximately 1 Kpc

  11. Linear polarization structures in LOFAR observations of the interstellar medium in the 3C196 field

    CERN Document Server

    Jelić, V; Pandey, V N; Mevius, M; Haverkorn, M; Brentjens, M A; Koopmans, L V E; Zaroubi, S; Abdalla, F B; Asad, K M B; Bus, S; Chapman, E; Ciardi, B; Fernandez, E R; Ghosh, A; Harker, G; Iliev, I T; Jensen, H; Kazemi, S; Mellema, G; Offringa, A R; Patil, A H; Vedantham, H K; Yatawatta, S

    2015-01-01

    This study aims to characterise linear polarization structures in LOFAR observations of the interstellar medium (ISM) in the 3C196 field, one of the primary fields of the LOFAR-Epoch of Reionization key science project. We have used the high band antennas (HBA) of LOFAR to image this region and RM-synthesis to unravel the distribution of polarized structures in Faraday depth. The brightness temperature of the detected Galactic emission is $5-15~{\\rm K}$ in polarized intensity and covers the range from -3 to +8 ${\\rm rad~m^{-2}}$ in Faraday depth. The most interesting morphological feature is a strikingly straight filament at a Faraday depth of $+0.5~{\\rm rad~m^{-2}}$ running from north to south, right through the centre of the field and parallel to the Galactic plane. There is also an interesting system of linear depolarization canals conspicuous in an image showing the peaks of Faraday spectra. We have used the Westerbork Synthesis Radio Telescope (WSRT) at 350 MHz to image the same region. For the first tim...

  12. Inquiring Minds: Theorizing Children's Interests

    Science.gov (United States)

    Hedges, Helen; Cooper, Maria

    2016-01-01

    Children's interests are a common foundation for early childhood curricula. Yet, little research is available about the fundamental nature of children's interests and analytical ways to recognize and engage with these. Early work on children's interests adopted a psychological perspective and associated interests with activity choices. Recent work…

  13. Analytical Pharmaceutical Chemistry--Bridging Disciplines and Interests

    Science.gov (United States)

    Smith, Robert V.

    1977-01-01

    Because of their interest and expertise in the analysis of drugs in biological fluids, analytical pharmaceutical chemists can contribute significantly to interdisciplinary research and teaching efforts. Suggestions for such efforts are described. (Author/LBH)

  14. On the formation of pyridine in the interstellar medium.

    Science.gov (United States)

    Parker, Dorian S N; Kaiser, Ralf I; Kostko, Oleg; Troy, Tyler P; Ahmed, Musahid; Sun, Bing-Jian; Chen, Shih-Hua; Chang, A H H

    2015-12-21

    Nitrogen-substituted polycyclic aromatic hydrocarbons (NPAHs) have been proposed to play a key role in the astrochemical evolution of the interstellar medium, but the formation mechanism of even their simplest building block - the aromatic pyridine molecule - has remained elusive for decades. Here we reveal a potential pathway to a facile pyridine (C5H5N) synthesis via the reaction of the cyano vinyl (C2H2CN) radical with vinyl cyanide (C2H3CN) in high temperature environments simulating conditions in carbon-rich circumstellar envelopes of Asymptotic Giant Branch (AGB) stars like IRC+10216. Since this reaction is barrier-less, pyridine can also be synthesized via this bimolecular reaction in cold molecular clouds such as in TMC-1. The synchronized aromatization of precursors readily available in the interstellar medium leading to nitrogen incorporation into the aromatic rings would open up a novel route to pyridine derivatives such as vitamin B3 and pyrimidine bases as detected in carbonaceous chondrites like Murchison. PMID:26569517

  15. BENZENE FORMATION ON INTERSTELLAR ICY MANTLES CONTAINING PROPARGYL ALCOHOL

    International Nuclear Information System (INIS)

    Propargyl alcohol (CHCCH2OH) is a known stable isomer of the propenal (CH2CHCHO) molecule that was reported to be present in the interstellar medium (ISM). At astrochemical conditions in the laboratory, icy layers of propargyl alcohol grown at 85 K were irradiated by 2 keV electrons and probed by a Fourier Transform InfraRed spectrometer in the mid-infrared (IR) region, 4000-500 cm–1. Propargyl alcohol ice under astrochemical conditions was studied for the first time; therefore, IR spectra of reported amorphous (85 K) and crystalline (180 K) propargyl alcohol ices can be used to detect its presence in the ISM. Moreover, our experiments clearly show benzene (C6H6) formation to be the major product from propargyl alcohol irradiation, confirming the role of propargyl radicals (C3H3) formed from propargyl alcohol dissociation that was long expected based on theoretical modeling to effectively synthesize C6H6 in the interstellar icy mantles

  16. Hydrogen isotope exchanges between water and methanol in interstellar ices

    CERN Document Server

    Faure, A; Theulé, P; Quirico, E; Schmitt, B

    2015-01-01

    The deuterium fractionation of gas-phase molecules in hot cores is believed to reflect the composition of interstellar ices. The deuteration of methanol is a major puzzle, however, because the isotopologue ratio [CH2DOH]/[CH3OD], which is predicted to be equal to 3 by standard grain chemistry models, is much larger (~20) in low-mass hot corinos and significantly lower (~1) in high-mass hot cores. This dichotomy in methanol deuteration between low-mass and massive protostars is currently not understood. In this study, we report a simplified rate equation model of the deuterium chemistry occurring in the icy mantles of interstellar grains. We apply this model to the chemistry of hot corinos and hot cores, with IRAS 16293-2422 and the Orion~KL Compact Ridge as prototypes, respectively. The chemistry is based on a statistical initial deuteration at low temperature followed by a warm-up phase during which thermal hydrogen/deuterium (H/D) exchanges occur between water and methanol. The exchange kinetics is incorpor...

  17. Evidence for the Heating of Atomic Interstellar Gas by PAHs

    CERN Document Server

    Helou, G; Hollenbach, D J; Dale, D A; Contursi, A; Helou, George; Malhotra, Sangeeta; Hollenbach, David J.; Dale, Daniel A.; Contursi, Alessandra

    2001-01-01

    We report a strong correlation between the [CII] 158 micron cooling line and the mid-infrared flux in the 5-10 micron range in a wide variety of star-forming galaxies. The mid-infrared flux is dominated by Aromatic Feature Emission (AFE), which is thought to arise from large polycyclic aromatic hydrocarbon molecules or `PAHs' and generally associated with the smallest interstellar grains. The [CII] line is the dominant gas coolant in most regions of atomic interstellar gas, and therefore reflects the heating input to the gas. The ratio of these two quantities, [CII]/AFE, remains nearly constant with the ratio of the IRAS 60 micron band flux to the 100 micron band flux, R(60/100). This is in contrast to the drop in the [CII]/FIR ratio with increasing R(60/100), which signal higher dust temperatures and more intense radiation fields. We interpret the stable [CII]/AFE ratio as evidence that gas heating is dominated by the PAHs or small grains which are also AFE carriers over a wide range of conditions. The trend...

  18. Shell-Shocked: The Interstellar Medium Near Cygnus X-1

    CERN Document Server

    Sell, P H; Richards, E; Maccarone, T J; Russell, D M; Gallo, E; Fender, R; Markoff, S; Nowak, M

    2014-01-01

    We conduct a detailed case-study of the interstellar shell near the high-mass X-ray binary, Cygnus X-1. We present new WIYN optical spectroscopic and Chandra X-ray observations of this region, which we compare with detailed MAPPINGS III shock models, to investigate the outflow powering the shell. Our analysis places improved, physically motivated constraints on the nature of the shockwave and the interstellar medium (ISM) it is plowing through. We find that the shock is traveling at less than a few hundred km/s through a low-density ISM (< 5 cm^-3). We calculate a robust, 3 sigma upper limit to the total, time-averaged power needed to drive the shockwave and inflate the bubble, < 2 x 10^38 erg/s. We then review possible origins of the shockwave. We find that a supernova origin to the shockwave is unlikely and that the black hole jet and/or O-star wind can both be central drivers of the shockwave. We conclude that the source of the Cygnus X-1 shockwave is far from solved.

  19. Restructuring and destruction of hydrocarbon dust in the interstellar medium

    Science.gov (United States)

    Murga, M. S.; Khoperskov, S. A.; Wiebe, D. S.

    2016-02-01

    A model describing the main processes determining the evolution of hydrocarbon dust grains of arbitrary size under astrophysical conditions corresponding to regions of ionized hydrogen (HII regions) and supernova remnants is presented. The processes considered include aromatization and photodestruction, sputtering by electrons and ions, and shattering during collisions between grains. The model can be used to calculate the size distribution of the grains and the degree of aromatization during the evolution of HII regions and supernova remnants for a specified radiation field, relative velocity between the gas and dust, etc. The contribution of various processes to the evolution of hydrocarbon dust grains for parameters typical for the interstellar medium of our Galaxy is considered. Small grains (with fewer than 50 carbon atoms) should be fully aromatized in the interstellar medium. If larger grains initially have an aliphatic structure, this is preserved to a substantial extent. Variation in the size distribution of the grains due to collisions between grains depend appreciably on the adopted initial size distribution. With an initial distribution corresponding to that of Mathis et al. (1977), the mass fraction contributed by smaller grains tends to increase with time, while, with an initial distribution corresponding to that of Jones et al. (2013), in which the fraction of small grains is initially high, there is a general decrease in the number of grains of various sizes with time.

  20. The interaction of relativistic spacecrafts with the interstellar medium

    CERN Document Server

    Hoang, Thiem; Burkhart, Blakesley; Loeb, Abraham

    2016-01-01

    The Breakthrough Starshot initiative aims to launch a gram-scale spacecraft to a speed of $v\\sim 0.2$c, capable of reaching the nearest star system, $\\alpha$ Centauri, in about 20 years. However, a critical challenge for the initiative is the damage to the spacecraft by interstellar gas and dust during the journey. In this paper, we quantify the interaction of a relativistic spacecraft with gas and dust in the interstellar medium. For gas bombardment, we find that damage by track formation due to heavy elements is an important effect. We find that gas bombardment can potentially damage the surface of the spacecraft to a depth of $\\sim 0.1$ mm for quartz material after traversing a gas column of $N_{\\rm H}\\sim 2\\times 10^{18}\\rm cm^{-2}$ along the path to $\\alpha$ Centauri, whereas the effect is much weaker for graphite material. The effect of dust bombardment erodes the spacecraft surface and produces numerous craters due to explosive evaporation of surface atoms. For a spacecraft speed $v=0.2c$, we find that...

  1. THE STRUCTURE, ORIGIN, AND EVOLUTION OF INTERSTELLAR HYDROCARBON GRAINS

    Energy Technology Data Exchange (ETDEWEB)

    Chiar, J. E.; Ricca, A. [SETI Institute, Carl Sagan Center, 189 Bernardo Avenue, Mountain View, CA 94043 (United States); Tielens, A. G. G. M. [Leiden Observatory, P.O. Box 9513, NL-2300 RA Leiden (Netherlands); Adamson, A. J., E-mail: jchiar@seti.org, E-mail: Alessandra.Ricca@1.nasa.gov, E-mail: tielens@strw.leidenuniv.nl, E-mail: aadamson@gemini.edu [Gemini Observatory, Northern Operations Center, 670 North A' ohoku Place, Hilo, HI 96729 (United States)

    2013-06-10

    Many materials have been considered for the carrier of the hydrocarbon absorption bands observed in the diffuse interstellar medium (ISM). In order to refine the model for ISM hydrocarbon grains, we analyze the observed aromatic (3.28, 6.2 {mu}m) and aliphatic (3.4 {mu}m) hydrocarbon absorption features in the diffuse ISM along the line of sight toward the Galactic center Quintuplet Cluster. Observationally, sp {sup 2} bonds can be measured in astronomical spectra using the 6.2 {mu}m CC aromatic stretch feature, whereas the 3.4 {mu}m aliphatic feature can be used to quantify the fraction of sp {sup 3} bonds. The fractional abundance of these components allows us to place the Galactic diffuse ISM hydrocarbons on a ternary phase diagram. We conclude that the Galactic hydrocarbon dust has, on average, a low H/C ratio and sp {sup 3} content and is highly aromatic. We have placed the results of our analysis within the context of the evolution of carbon dust in the ISM. We argue that interstellar carbon dust consists of a large core of aromatic carbon surrounded by a thin mantle of hydrogenated amorphous carbon (a-C:H), a structure that is a natural consequence of the processing of stardust grains in the ISM.

  2. Chemistry of nitrile anions in the interstellar medium

    International Nuclear Information System (INIS)

    Despite the extreme conditions of temperature (down to 10K) and density (down to 100 molecules/cm3), the giant molecular clouds and the circumstellar envelopes present a rich and complex chemistry. To date, more than 180 molecules have been detected in the InterStellar Medium (ISM) with a large abundance of nitriles (RC≡N). In addition, several anions have been recently observed in this medium: C4H¯, C6H¯, C8H¯, CN¯, C3N¯ and C5N¯. These last species should play a key role in the molecular growth towards complexity. To explore this hypothesis, their reactivity must be studied in the laboratory. The FALP-MS and the CRESU experimental apparatuses of the Rennes University are able to measure absolute rate coefficient of various chemical reactions, including the ion – molecule reactions, in gas phase at low temperature (from 300K for the FALP-MS down to 15K for the CRESU). Therefore, these experimental tools are particularly adapted to the kinetic studies of reactions potentially involved in the Interstellar Medium. One of the difficulties encountered in experiments with anions is their generation. We describe here the formation of the CN¯ and C3N¯ anions by dissociative electron attachment on the molecular precursors BrCN and BrC3N

  3. Variations of the Interstellar Extinction Law within the Nearest Kiloparsec

    CERN Document Server

    Gontcharov, George

    2016-01-01

    Multicolor photometry from the Tycho-2 and 2MASS catalogues for 11 990 OB and 30 671 K-type red giant branch stars is used to detect systematic large-scale variations of the interstellar extinction law within the nearest kiloparsec. The characteristic of the extinction law, the total-to-selective extinction ratio $R_V$, which also characterizes the size and other properties of interstellar dust grains, has been calculated for various regions of space by the extinction law extrapolation method. The results for the two classes of stars agree: the standard deviation of the "red giants minus OB" $R_V$ differences within 500 pc of the Sun is 0.2. The detected $R_V$ variations between 2.2 and 4.4 not only manifest themselves in individual clouds but also span the entire space near the Sun, following Galactic structures. In the Local Bubble within about 100 pc of the Sun, $R_V$ has a minimum. In the inner part of the Gould Belt and at high Galactic latitudes, at a distance of about 150 pc from the Sun, $R_V$ reaches...

  4. RUSTY OLD STARS: A SOURCE OF THE MISSING INTERSTELLAR IRON?

    International Nuclear Information System (INIS)

    Iron, the universe's most abundant refractory element, is highly depleted in both circumstellar and interstellar environments, meaning it exists in solid form. The nature of this solid is unknown. In this Letter, we provide evidence that metallic iron grains are present around oxygen-rich asymptotic giant branch stars, where it is observationally manifest as a featureless mid-infrared excess. This identification is made using Spitzer Space Telescope observations of evolved globular cluster stars, where iron dust production appears ubiquitous and in some cases can be modeled as the only observed dust product. In this context, FeO is examined as the likely carrier for the 20 μm feature observed in some of these stars. Metallic iron appears to be an important part of the dust condensation sequence at low metallicity, and subsequently plays an influential role in the interstellar medium. We explore the stellar metallicities and luminosities at which iron formation is observed, and how the presence of iron affects the outflow and its chemistry. The conditions under which iron can provide sufficient opacity to drive a wind remain unclear.

  5. The Interstellar Medium in the Kepler Search Volume

    CERN Document Server

    Johnson, Marshall C; Jensen, Adam G

    2015-01-01

    The properties of the interstellar medium (ISM) surrounding a planetary system can impact planetary climate through a number of mechanisms, including changing the size of the astrosphere (one of the major shields for cosmic rays) as well as direct deposition of material into planetary atmospheres. In order to constrain the ambient ISM conditions for exoplanetary systems, we present observations of interstellar Na I and K I absorption towards seventeen early-type stars in the Kepler prime mission field of view. We identify 39 Na I and 8 K I velocity components, and attribute these to eleven ISM clouds. Six of these are detected towards more than one star, and for these clouds we put limits on the cloud properties, including distance and hydrogen number density. We identify one cloud with significant (>1.5 cm$^{-3}$) hydrogen number density located within the nominal ~100 pc boundary of the Local Bubble. We identify systems with confirmed planets within the Kepler field of view that could lie within these ISM c...

  6. Thermoluminescence of Simulated Interstellar Matter after Gamma-ray Irradiation

    CERN Document Server

    Koike, K; Koike, C; Okada, M; Chihara, H

    2002-01-01

    Interstellar matter is known to be strongly irradiated by radiation and several types of cosmic ray particles. Simulated interstellar matter, such as forsterite $\\rm Mg_{2}SiO_{4}$, enstatite $\\rm MgSiO_{3}$ and magnesite $\\rm MgCO_{3}$ has been irradiated with the $\\rm ^{60}Co$ gamma-rays in liquid nitrogen, and also irradiated with fast neutrons at 10 K and 70 K by making use of the low-temperature irradiation facility of Kyoto University Reactor (KUR-LTL. Maximum fast neutron dose is $10^{17}n_f{\\rm /cm^{2}}$). After irradiation, samples are stored in liquid nitrogen for several months to allow the decay of induced radioactivity. We measured the luminescence spectra of the gamma ray irradiated samples during warming to 370K using a spectrophotometer. For the forsterite and magnesite, the spectra exhibit a rather intense peak at about 645 -- 655 nm and 660 nm respectively, whereas luminescence scarcely appeared in olivine sample. The spectra of forsterite is very similar to the ERE of the Red Rectangle.

  7. Rusty old stars: a source of the missing interstellar iron?

    CERN Document Server

    McDonald, Iain; Zijlstra, Albert A; Matsunaga, Noriyuki; Matsuura, Mikako; Kraemer, Kathleen E; Bernard-Salas, Jeronimo; Markwick, Andrew J

    2010-01-01

    Iron, the Universe's most abundant refractory element, is highly depleted in both circumstellar and interstellar environments, meaning it exists in solid form. The nature of this solid is unknown. In this Letter, we provide evidence that metallic iron grains are present around oxygen-rich AGB stars, where it is observationally manifest as a featureless mid-infrared excess. This identification is made using Spitzer Space Telescope observations of evolved globular cluster stars, where iron dust production appears ubiquitous and in some cases can be modelled as the only observed dust product. In this context, FeO is examined as the likely carrier for the 20-micron feature observed in some of these stars. Metallic iron appears to be an important part of the dust condensation sequence at low metallicity, and subsequently plays an influential role in the interstellar medium. We explore the stellar metallicities and luminosities at which iron formation is observed, and how the presence of iron affects the outflow an...

  8. Interstellar Scintillation of the Double Pulsar J0737$-$3039

    CERN Document Server

    Rickett, B J; Nava, C F; McLaughlin, M A; Ransom, S M; Camilo, F; Ferdman, R D; Freire, P C C; Kramer, M; Lyne, A G; Stairs, I H

    2014-01-01

    We report here a series of observations of the interstellar scintillation (ISS) of the double pulsar J0737$-$3039 over the course of 18 months. As in earlier work (Coles et al., 2005) the basic phenomenon is the variation in the ISS caused by the changing transverse velocities of each pulsar, the ionized interstellar medium (IISM), and the Earth. The transverse velocity of the binary system can be determined both by VLBI and timing observations. The orbital velocity and inclination is almost completely determined from timing observations, but the direction of the orbital angular momentum is not known. Since the Earth's velocity is known, and can be compared with the orbital velocity by its effect on the timescale of the ISS, we can determine the orientation $\\Omega$ of the pulsar orbit with respect to equatorial coordinates ($\\Omega = 65\\pm2$ deg). We also resolve the ambiguity ($i= 88.7$ or $91.3$ deg) in the inclination of the orbit deduced from the measured Shapiro delay by our estimate $i=88.1\\pm0.5$ deg....

  9. Interstellar scintillation of the double pulsar J0737–3039

    Energy Technology Data Exchange (ETDEWEB)

    Rickett, B. J.; Coles, W. A.; Nava, C. F. [ECE Dept., University of California San Diego, La Jolla, CA 92093-0407 (United States); McLaughlin, M. A. [West Virginia University, Morgantown, WV 26505 (United States); Ransom, S. M. [National Radio Astronomy Observatory, Charlottesville, VA 22903 (United States); Camilo, F. [National Astronomy and Ionosphere Center, Arecibo, PR 00612-8346 (United States); Ferdman, R. D.; Kramer, M.; Lyne, A. G. [Jodrell Bank Center for Astrophysics, University of Manchester, M13 9PL (United Kingdom); Freire, P. C. C. [Dept. of Physics, McGill University, Montréal, QC H3A 2T8 (Canada); Stairs, I. H., E-mail: bjrickett@ucsd.edu [Dept. of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1 (Canada)

    2014-06-01

    We report a series of observations of the interstellar scintillation (ISS) of the double pulsar J0737–3039 over the course of 18 months. As in earlier work, the basic phenomenon is the variation in the ISS caused by the changing transverse velocities of each pulsar, the ionized interstellar medium (IISM), and the Earth. The transverse velocity of the binary system can be determined both by very long baseline interferometry and timing observations. The orbital velocity and inclination is almost completely determined from timing observations, but the direction of the orbital angular momentum is not known. Since the Earth's velocity is known, and can be compared with the orbital velocity by its effect on the timescale of the ISS, we can determine the orientation Ω of the pulsar orbit with respect to equatorial coordinates (Ω = 65 ± 2°). We also resolve the ambiguity (i = 88.°7 or 91.°3) in the inclination of the orbit deduced from the measured Shapiro delay by our estimate i = 88.°1 ± 0.°5. This relies on the analysis of the ISS over both frequency and time, and provides a model for the location, anisotropy, turbulence level, and transverse phase gradient of the IISM. We find that the IISM can be well-modeled during each observation, typically of a few orbital periods, but its turbulence level and mean velocity vary significantly over the 18 months.

  10. Colliding interstellar bubbles in the direction of l=54{\\deg}

    CERN Document Server

    Zychova, Lenka

    2016-01-01

    Interstellar bubbles are structures in the interstellar medium with diameters of a few to tens of parsecs. Their progenitors are stellar winds, intense radiation of massive stars, or supernova explosions. Star formation and young stellar objects are commonly associated with these structures. We compare IR observations of bubbles N115, N116 and N117 with atomic, molecular and ionized gas in this region. While determining the dynamical properties of the bubbles, we also look into their ambient environment to understand their formation in a wider context. For finding bubbles in HI (VLA Galactic Plane Survey) and CO data (Galactic Ring Survey), we used their images from Galactic Legacy Infrared Mid-Plane Survey. We manually constructed masks based on the appearance of the bubbles in the IR images and applied it to the HI and CO data. We determined their kinematic distance, size, expansion velocity, mass, original density of the maternal cloud, age and energy input. We identified two systems of bubbles: the first,...

  11. Herschel/HIFI discovery of interstellar chloronium (H$_2$Cl$^+$)

    CERN Document Server

    Lis, D C; Neufeld, D A; Schilke, P; Müller, H S P; Gupta, H; Bell, T A; Comito, C; Phillips, T G; Bergin, E A; Ceccarelli, C; Goldsmith, P F; Blake, G A; Bacmann, A; Baudry, A; Benedettini, M; Benz, A; Black, J; Boogert, A; Bottinelli, S; Cabrit, S; Caselli, P; Castets, A; Caux, E; Cernicharo, J; Codella, C; Coutens, A; Crimier, N; Crockett, N R; Daniel, F; Demyk, K; Dominic, C; Dubernet, M -L; Emprechtinger, M; Encrenaz, P; Falgarone, E; Fuente, A; Gerin, M; Giesen, T F; Goicoechea, J R; Helmich, F; Hennebelle, P; Henning, Th; Herbst, E; Hily-Blant, P; Hjalmarson, Å; Hollenbach, D; Jack, T; Joblin, C; Johnstone, D; Kahane, C; Kama, M; Kaufman, M; Klotz, A; Langer, W D; Larsson, B; Bourlot, J Le; Lefloch, B; Petit, F Le; Li, D; Liseau, R; Lord, S D; Lorenzani, A; Maret, S; Martin, P G; Melnick, G J; Menten, K M; Morris, P; Murphy, J A; Nagy, Z; Nisini, B; Ossenkopf, V; Pacheco, S; Pagani, L; Parise, B; Pérault, M; Plume, R; Qin, S -L; Roueff, E; Salez, M; Sandqvist, A; Saraceno, P; Schlemmer, S; Schuster, K; Snell, R; Stutzki, J; Tielens, A; Trappe, N; van der Tak, F F S; van der Wiel, M H D; van Dishoeck, E; Vastel, C; Viti, S; Wakelam, V; Walters, A; Wang, S; Wyrowski, F; Yorke, H W; Yu, S; Zmuidzinas, J; Delorme, Y; Desbat, J -P; Güsten, R; Krieg, J -M; Delforge, B

    2010-01-01

    We report the first detection of chloronium, H$_2$Cl$^+$, in the interstellar medium, using the HIFI instrument aboard the \\emph{Herschel} Space Observatory. The $2_{12}-1_{01}$ lines of ortho-H$_2^{35}$Cl$^+$ and ortho-H$_2^{37}$Cl$^+$ are detected in absorption towards NGC~6334I, and the $1_{11}-0_{00}$ transition of para-H$_2^{35}$Cl$^+$ is detected in absorption towards NGC~6334I and Sgr~B2(S). The H$_2$Cl$^+$ column densities are compared to those of the chemically-related species HCl. The derived HCl/H$_2$Cl$^+$ column density ratios, $\\sim$1--10, are within the range predicted by models of diffuse and dense Photon Dominated Regions (PDRs). However, the observed H$_2$Cl$^+$ column densities, in excess of $10^{13}$~cm$^{-2}$, are significantly higher than the model predictions. Our observations demonstrate the outstanding spectroscopic capabilities of HIFI for detecting new interstellar molecules and providing key constraints for astrochemical models.

  12. Testing New Ideas Regarding the Nature of Interstellar Extinction

    CERN Document Server

    Turner, David G; Balam, David D

    2014-01-01

    The nature of Galactic interstellar extinction is tested using reddening line parameters for several fields in conjunction with equivalent widths $W(\\lambda4430)$ for the diffuse interstellar band at $4430$ \\AA. The Cardelli et al.$\\;$relations [29] at infrared, optical, and ultraviolet wavelengths are inconsistent with the newly-derived quadratic variation of $R_V({\\rm observed})$ on reddening slope $X$. A minimum of $R_V=2.82\\pm0.06$ exists for $X=0.83\\pm0.10$, and is argued to represent true Galactic extinction described by $A(\\lambda)\\propto \\lambda^{-1.375}$. It matches expectations for a new description of extinction in the infrared, optical, and ultraviolet by Zagury [32]. Additional consequences, reddened stars with no 2175 \\AA$\\;$feature and a correlation of normalized $\\lambda4430$ absorption with $X$, are not predicted by the Cardelli et al.$\\;$relation [29]. Known variations in $X$ from 0.62 to 0.83, and corresponding variations in $R_V({\\rm observed})$ from 4.0 to 2.8, presumably result from forw...

  13. Accurate Modeling of X-ray Extinction by Interstellar Grains

    Science.gov (United States)

    Hoffman, John; Draine, B. T.

    2016-02-01

    Interstellar abundance determinations from fits to X-ray absorption edges often rely on the incorrect assumption that scattering is insignificant and can be ignored. We show instead that scattering contributes significantly to the attenuation of X-rays for realistic dust grain size distributions and substantially modifies the spectrum near absorption edges of elements present in grains. The dust attenuation modules used in major X-ray spectral fitting programs do not take this into account. We show that the consequences of neglecting scattering on the determination of interstellar elemental abundances are modest; however, scattering (along with uncertainties in the grain size distribution) must be taken into account when near-edge extinction fine structure is used to infer dust mineralogy. We advertise the benefits and accuracy of anomalous diffraction theory for both X-ray halo analysis and near edge absorption studies. We present an open source Fortran suite, General Geometry Anomalous Diffraction Theory (GGADT), that calculates X-ray absorption, scattering, and differential scattering cross sections for grains of arbitrary geometry and composition.

  14. Refractive Focusing of Interstellar Clouds and Intraday Polarization Angle Swings

    Institute of Scientific and Technical Information of China (English)

    Shan-Jie Qian; T. P. Krichbaum; Long Gao; Xi-Zhen Zhang; A. Witzel; J. A. Zensus

    2007-01-01

    Intraday variations of compact extragalactic radio sources in flux density and polarization are generally interpreted in terms of refractive scintillation from the continuous interstellar medium of our Galaxy. However, continuous polarization angle swings of ~ 180°(for example, the one observed in the QSO 0917+624) could not be interpreted in this way.Qian et al. have shown that the polarization angle swing observed in the QSO 1150+812 can be explained in terms of focusing-defocusing effect by an interstellar cloud, which occults two closely-placed polarized components. Here we further show that the polarization angle swing event observed in the QSO 0917+624 can also be explained in this way. We also found evidence for the cloud eclipsing a non-polarized (core) component during a short period outside the swing. A particular (and specific) plasma-lens model is proposed to model-fit the polarization swing event of 0917+624. Some physical parameters related to the plasma-lens and the source components are estimated. The brightness temperatures of the two lensed components are estimated to be ~ 1.6 × 1013 K. Thus bulk relativistic motion with a Lorentz factor less than ~20 may be sufficient to avoid the inverse - Compton catastrophe.

  15. Cosmic-ray induced diffusion in interstellar ices

    CERN Document Server

    Kalvans, Juris

    2014-01-01

    Cosmic rays are able to heat interstellar dust grains. This may enhance molecule mobility in icy mantles that have accumulated on the grains in dark cloud cores. A three-phase astrochemical model was used to investigate the molecule mobility in interstellar ices. Specifically, diffusion through pores in ice between the subsurface mantle and outer surface, assisted by whole-grain heating, was considered. It was found that the pores can serve as an efficient transport route for light species. The diffusion of chemical radicals from the mantle to the outer surface are most effective. These species accumulate in the mantle because of photodissociation by the cosmic-ray induced photons. The faster diffusion of hydrogen within the warm ice enhances the hydrogenation of radicals on pore surfaces. The overall result of the whole grain heating-induced radial diffusion in ice are higher abundances of the ice species whose synthesis involve light radicals. Examples of stable species synthesized this way include the comp...

  16. Scientists Toast the Discovery of Vinyl Alcohol in Interstellar Space

    Science.gov (United States)

    2001-10-01

    Astronomers using the National Science Foundation's 12 Meter Telescope at Kitt Peak, AZ, have discovered the complex organic molecule vinyl alcohol in an interstellar cloud of dust and gas near the center of the Milky Way Galaxy. The discovery of this long-sought compound could reveal tantalizing clues to the mysterious origin of complex organic molecules in space. Vinyl Alcohol and its fellow isomers "The discovery of vinyl alcohol is significant," said Barry Turner, a scientist at the National Radio Astronomy Observatory (NRAO) in Charlottesville, Va., "because it gives us an important tool for understanding the formation of complex organic compounds in interstellar space. It may also help us better understand how life might arise elsewhere in the Cosmos." Vinyl alcohol is an important intermediary in many organic chemistry reactions on Earth, and the last of the three stable members of the C2H4O group of isomers (molecules with the same atoms, but in different arrangements) to be discovered in interstellar space. Turner and his colleague A. J. Apponi of the University of Arizona's Steward Observatory in Tucson detected the vinyl alcohol in Sagittarius B -- a massive molecular cloud located some 26,000 light-years from Earth near the center of our Galaxy. The astronomers were able to detect the specific radio signature of vinyl alcohol during the observational period of May and June of 2001. Their results have been accepted for publication in the Astrophysical Journal Letters. Of the approximately 125 molecules detected in interstellar space, scientists believe that most are formed by gas-phase chemistry, in which smaller molecules (and occasionally atoms) manage to "lock horns" when they collide in space. This process, though efficient at creating simple molecules, cannot explain how vinyl alcohol and other complex chemicals are formed in detectable amounts. For many years now, scientists have been searching for the right mechanism to explain how the building

  17. MAD with Aliens? Interstellar deterrence and its implications

    CERN Document Server

    Korhonen, Janne M

    2013-01-01

    The possibility that extraterrestrial intelligences (ETIs) could be hostile to humanity has been raised as a reason to avoid even trying to contact ETIs. However, there is a distinct shortage of analytical discussion about the risks of an attack, perhaps because of an implicit premise that we cannot analyze the decision making of an alien civilization. This paper argues that we can draw some inferences from the history of the Cold War and nuclear deterrence in order to show that at least some attack scenarios are likely to be exaggerated. In particular, it would seem to be unlikely that the humanity would be attacked simply because it might, some time in the future, present a threat to the ETI. Even if communication proves to be difficult, rational decision-makers should avoid unprovoked attacks, because their success would be very difficult to assure. In general, it seems believable that interstellar conflicts between civilizations would remain rare. The findings advise caution for proposed interstellar miss...

  18. Small-Scale Interstellar Na I Structure Toward M92

    CERN Document Server

    Andrews, S M; Lauroesch, J T; Andrews, Sean M.; Meyer, David M.

    2001-01-01

    We have used integral field echelle spectroscopy with the DensePak fiber-optic array on the KPNO WIYN telescope to observe the central 27" x 43" of the globular cluster M92 in the Na I D wavelength region at a spatial resolution of 4". Two interstellar Na I absorption components are evident in the spectra at LSR velocities of 0 km/s (Cloud 1) and -19 km/s (Cloud 2). Substantial strength variations in both components are apparent down to scales limited by the fiber-to-fiber separations. The derived Na I column densities differ by a factor of 4 across the Cloud 1 absorption map and by a factor of 7 across the Cloud 2 map. Using distance upper limits of 400 and 800 pc for Cloud 1 and Cloud 2, respectively, the absorption maps indicate structure in the ISM down to scales of 1600 and 3200 AU. The fiber-to-fiber Na I column density differences toward M92 are comparable to those found in a similar study of the ISM toward the globular cluster M15. Overall, the structures in the interstellar components toward M92 have...

  19. The 1st Fermi LAT SNR Catalog: the Impact of Interstellar Emission Modeling

    CERN Document Server

    Brandt, T J; de Palma, F; Johannesson, G; Tibaldo, L

    2013-01-01

    Galactic interstellar emission contributes substantially to Fermi LAT observations in the Galactic plane, the location of the majority of supernova remnants (SNRs). To explore some systematic effects on SNRs' properties caused by interstellar emission modeling, we have developed a method comparing the official LAT interstellar emission model results to eight alternative models. We created the eight alternative Galactic interstellar models by varying a few input parameters to GALPROP, namely the height of the cosmic ray propagation halo, cosmic ray source distribution in the Galaxy, and atomic hydrogen spin temperature. We have analyzed eight representative SNRs chosen to encompass a range of Galactic locations, extensions, and spectral properties using the eight different interstellar emission models. We will present the results and method in detail and discuss the implications for studies such as the 1st Fermi LAT SNR Catalog.

  20. THE INTERSTELLAR MAGNETIC FIELD CLOSE TO THE SUN. II

    International Nuclear Information System (INIS)

    The magnetic field in the local interstellar medium (ISM) provides a key indicator of the galactic environment of the Sun and influences the shape of the heliosphere. We have studied the interstellar magnetic field (ISMF) in the solar vicinity using polarized starlight for stars within 40 pc of the Sun and 90° of the heliosphere nose. In Frisch et al. (Paper I), we developed a method for determining the local ISMF direction by finding the best match to a group of interstellar polarization position angles obtained toward nearby stars, based on the assumption that the polarization is parallel to the ISMF. In this paper, we extend the analysis by utilizing weighted fits to the position angles and by including new observations acquired for this study. We find that the local ISMF is pointed toward the galactic coordinates l, b =47° ± 20°, 25° ± 20°. This direction is close to the direction of the ISMF that shapes the heliosphere, l, b =33° ± 4°, 55° ± 4°, as traced by the center of the 'Ribbon' of energetic neutral atoms discovered by the Interstellar Boundary Explorer (IBEX) mission. Both the magnetic field direction and the kinematics of the local ISM are consistent with a scenario where the local ISM is a fragment of the Loop I superbubble. A nearby ordered component of the local ISMF has been identified in the region l ≈0° → 80° and b ≈0° → 30°, where PlanetPol data show a distance-dependent increase of polarization strength. The ordered component extends to within 8 pc of the Sun and implies a weak curvature in the nearby ISMF of ∼0.025 pc–1. This conclusion is conditioned on the small sample of stars available for defining this rotation. Variations from the ordered component suggest a turbulent component of ∼23°. The ordered component and standard relations between polarization, color excess, and Ho column density predict a reasonable increase of N(H) with distance in the local ISM. The similarity of the ISMF directions traced by

  1. In-situ Measurements of Interplanetary and Interstellar Dust

    Science.gov (United States)

    Grün, E.

    2008-09-01

    Dust is finely dispersed solid material in interplanetary space. It derives from a number of sources: larger meteoroids, comets, asteroids, the planets, and satellites, and there is interstellar dust sweeping through the solar system. These dust particles range in size from assemblages of a few molecules to tenth millimetre-sized grains. Dust particles absorb and scatter solar radiation and emit thermal radiation giving rise to Zodiacal light at visible and thermal emission at infrared wavelengths. Astronomical observations of both emissions provide information on the average properties of very large number of particles and their spatial distribution. Information on the physical and chemical properties and the orbital motion is obtained by direct methods. Direct methods include: (1) collection of dust particles (Fig. 1) on collectors on spacecraft returned to Earth and on airplanes in the stratosphere, (2) investigations of dust impacts craters on lunar samples and manmade impact plates returned from space, and (3) insitu measurements of individual particles by instruments on board satellites and space probes. Dust particles collected in the upper atmosphere provide the morphology and chemical and mineralogical composition of extraterrestrial particles of 5 to 50 microns in diameter but no information on the source of these particles is obtained. The NASA Stardust mission was the first space mission that returned dust from a comet. The study of impact craters on man-made and lunar surface samples exposed to space is used to characterize the flux of interplanetary micrometeoroids and their size distribution. Microcraters have been found ranging from 0.02 μm to millimetres in diameter. In-situ detectors on board of satellites and spaceprobes for the measurement of interplanetary dust have been used in the ecliptic plane from inside Mercury's orbit to the Kuiper belt and in space above and below the solar poles. Penetration detectors have a detection threshold of

  2. THE INTERSTELLAR MAGNETIC FIELD CLOSE TO THE SUN. II

    Energy Technology Data Exchange (ETDEWEB)

    Frisch, P. C. [Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637 (United States); Andersson, B-G [SOFIA Science Center, Universities Space Research Association, NASA Ames Research Center, M.S. N232-12 Moffett Field, CA 94035 (United States); Berdyugin, A.; Piirola, V. [Finnish Centre for Astronomy with ESO, University of Turku (Finland); DeMajistre, R. [The Johns Hopkins University Applied Physics Laboratory, Laurel, MD (United States); Funsten, H. O. [Los Alamos National Laboratory, Los Alamos, NM (United States); Magalhaes, A. M.; Seriacopi, D. B. [Inst. de Astronomia, Geofisica e Ciencias Atmosfericas, Universidade de Sao Paulo (Brazil); McComas, D. J. [Southwest Research Institute, San Antonio, TX (United States); Schwadron, N. A. [Space Science Center, University of New Hampshire, Durham, NH (United States); Slavin, J. D. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States); Wiktorowicz, S. J. [Department of Astronomy, University of California at Santa Cruz, Santa Cruz, CA (United States)

    2012-12-01

    The magnetic field in the local interstellar medium (ISM) provides a key indicator of the galactic environment of the Sun and influences the shape of the heliosphere. We have studied the interstellar magnetic field (ISMF) in the solar vicinity using polarized starlight for stars within 40 pc of the Sun and 90 Degree-Sign of the heliosphere nose. In Frisch et al. (Paper I), we developed a method for determining the local ISMF direction by finding the best match to a group of interstellar polarization position angles obtained toward nearby stars, based on the assumption that the polarization is parallel to the ISMF. In this paper, we extend the analysis by utilizing weighted fits to the position angles and by including new observations acquired for this study. We find that the local ISMF is pointed toward the galactic coordinates l, b =47 Degree-Sign {+-} 20 Degree-Sign , 25 Degree-Sign {+-} 20 Degree-Sign . This direction is close to the direction of the ISMF that shapes the heliosphere, l, b =33 Degree-Sign {+-} 4 Degree-Sign , 55 Degree-Sign {+-} 4 Degree-Sign , as traced by the center of the 'Ribbon' of energetic neutral atoms discovered by the Interstellar Boundary Explorer (IBEX) mission. Both the magnetic field direction and the kinematics of the local ISM are consistent with a scenario where the local ISM is a fragment of the Loop I superbubble. A nearby ordered component of the local ISMF has been identified in the region l Almost-Equal-To 0 Degree-Sign {yields} 80 Degree-Sign and b Almost-Equal-To 0 Degree-Sign {yields} 30 Degree-Sign , where PlanetPol data show a distance-dependent increase of polarization strength. The ordered component extends to within 8 pc of the Sun and implies a weak curvature in the nearby ISMF of {approx}0.{sup 0}25 pc{sup -1}. This conclusion is conditioned on the small sample of stars available for defining this rotation. Variations from the ordered component suggest a turbulent component of {approx}23 Degree-Sign . The

  3. Biological Threats

    Science.gov (United States)

    ... Workplace Plans School Emergency Plans Main Content Biological Threats Biological agents are organisms or toxins that can ... for Disease Control and Prevention . Before a Biological Threat Unlike an explosion, a biological attack may or ...

  4. Radical-Molecule Reaction C3H + H2O on Amorphous Water Ice: A Promising Route for Interstellar Propynal

    Science.gov (United States)

    Xie, Hong-bin; Shao, Chang-bin; Ding, Yi-hong

    2007-11-01

    Intriguing propynal (HCCCHO) has been attracting chemist's attention since 1955. However, to date, no satisfying conclusion concerning its formation mechanism in the interstellar medium (ISM) has been reached, although a variety of gas-reaction models, including ion-molecule, radical-molecule, and molecule-molecule, have been postulated. In this paper, we consider for the first time the gas-grain interaction model that involves heterogeneous reaction at the surface of dust grain or in the icy mantles to account for the propynal's formation. Based on the detailed density functional theory (DFT) and Gaussian-3 potential energy surface studies, we found that although the gaseous process C3H+H2O-->propynal+H must surmount a considerable entrance barrier (around 10 kcal mol-1), amorphous water ice can significantly catalyze the propynal's formation to be barrierless. So, this model should be a more reasonable one for propynal's formation in the low-temperature interstellar space. This result may also represent one rare case of the water-catalyzed reaction associated with a molecular radical in space. Future experimental studies are greatly desired to probe such interesting processes.

  5. Is life the rule or the exception? The answer may be in the interstellar clouds

    Science.gov (United States)

    2002-05-01

    (PACS and SPIRE) and a very high resolution heterodyne spectrometer (HIFI) - will be housed in a superfluid helium cryostat. Herschel will be placed in a transfer trajectory towards its operational orbit around the Earth-Sun L2 point by an Ariane 5 (shared with Planck) in early 2007. Once operational FIRST will offer a minimum of 3 years of routine observations; roughly 2/3 of the available observing time is open to the general astronomical community through a standard competitive proposal procedure. This result is consistent with (although of course does not prove) the theory that the main ingredients for life came from outer space, and therefore that chemical processes leading to life are likely to have occurred elsewhere. This reinforces the interest in an already 'hot' research field, astrochemistry. ESA's forthcoming missions Rosetta and Herschel will provide a wealth of new information for this topic. Amino acids are the 'bricks' of the proteins, and proteins are a type of compound present in all living organisms. Amino acids have been found in meteorites that have landed on Earth, but never in space. In meteorites amino acids are generally thought to have been produced soon after the formation of the Solar System, by the action of aqueous fluids on comets and asteroids - objects whose fragments became today's meteorites. However, new results published recently in Nature by two independent groups show evidence that amino acids can also form in space. Between stars there are huge clouds of gas and dust, the dust consisting of tiny grains typically smaller than a millionth of a millimetre. The teams reporting the new results, led by a United States group and a European group, reproduced the physical steps leading to the formation of these grains in the interstellar clouds in their laboratories, and found that amino acids formed spontaneously in the resulting artificial grains. The researchers started with water and a variety of simple molecules that are known to

  6. Using IBEX data to constrain the heliosphere's large-scale structure: interstellar neutral gas and the Warm Breeze

    Science.gov (United States)

    Bzowski, Maciej; McComas, David; Galli, Andre; Kucharek, Harald; Wurz, Peter; Sokol, Justyna M.; Schwadron, Nathan; Heirtzler, David M.; Kubiak, M. Marzena A.; Möbius, Eberhard; Fuselier, Stephen; Swaczyna, Paweł; Leonard, Trevor; Park, Jeewoo

    2016-07-01

    The large-scale structure of the heliosphere is governed by the interaction of the partly ionized, magnetized interstellar gas and the magnetized, fully ionized solar wind, structured in heliolatitude. Determining factors of this interaction are the density and flow velocity of interstellar gas relative to the Sun, the Mach number of this flow and the strength and inclination of the interstellar magnetic field to the flow vector at the interstellar side, and the magnitude of dynamic pressure of solar wind and the strength of its embedded magnetic field at the solar side. As a result of charge exchange interactions operating in the boundary region between the heliosphere and interstellar matter, a new population of neutral atoms is created, in addition to the population of unperturbed interstellar neutral gas. Both of these populations penetrate deep inside the heliosphere, where they can be sampled by the first space probe dedicated to observations of the heliosphere and its immediate surroundings by means of neutral atoms: the Interstellar Boundary Explorer (IBEX). Due to distortion of the heliosphere from axial symmetry, the secondary population of interstellar neutrals, created via charge exchange between the plasma flowing past the heliopause and the unperturbed pristine neutral interstellar gas, appears to be coming from a different direction than the unperturbed interstellar neutral flow. These two directions should be coplanar with the plane defined by the local interstellar magnetic field and the flow direction of the unperturbed gas. IBEX provides an unprecedented opportunity to study and interpret these relations. The IBEX science team have recently accomplished important milestones in researching the primary and secondary populations of interstellar gas and their relation to the local interstellar magnetic fields. First, the temperature and velocity vector of the inflowing interstellar neutral gas has been determined with unprecedented robustness based

  7. The VLT-FLAMES Tarantula Survey. IX. The interstellar medium seen through Diffuse Interstellar Bands and neutral sodium

    CERN Document Server

    van Loon, Jacco Th; Tatton, Benjamin L; Apellaniz, Jesus Maiz; Crowther, Paul A; de Koter, Alex; Evans, Christopher J; Henault-Brunet, Vincent; Howarth, Ian D; Richter, Philipp; Sana, Hugues; Simon-Diaz, Sergio; Taylor, William; Walborn, Nolan R

    2012-01-01

    The Tarantula Nebula (30 Dor) is a spectacular star-forming region in the Large Magellanic Cloud, seen through gas in the Galactic Disc and Halo. Diffuse Interstellar Bands offer a unique probe of the diffuse, cool-warm gas in these regions. The aim is to use DIBs as diagnostics of the local interstellar conditions, whilst at the same time deriving properties of the yet-unknown carriers. Spectra of over 800 early-type stars from the VLT Flames Tarantula Survey (VFTS) were analysed. Maps were created, separately, for the Galactic and LMC absorption in the DIBs at 4428 and 6614 Ang and - in a smaller region near the central cluster R136 - neutral sodium (Na I D); we also measured the DIBs at 5780 and 5797 Ang. The maps show strong 4428 and 6614 Ang DIBs in the quiescent cloud complex to the south of 30 Dor but weak absorption in the harsher environments to the north (bubbles) and near the OB associations. The Na maps show at least five kinematic components in the LMC and a shell-like structure surrounding R136,...

  8. Diffuse Interstellar Bands vs. Known Atomic and Molecular Species in the Interstellar Medium of M82 toward SN 2014J

    CERN Document Server

    Welty, Daniel E; Dahlstrom, Julie A; York, Donald G

    2014-01-01

    We discuss the absorption due to various constituents of the interstellar medium of M82 seen in moderately high resolution, high signal-to-noise ratio optical spectra of SN 2014J. Complex absorption from M82 is seen, at velocities 45 $\\le$ $v_{\\rm LSR}$ $\\le$ 260 km s$^{-1}$, for Na I, K I, Ca I, Ca II, CH, CH$^+$, and CN; many of the diffuse interstellar bands (DIBs) are also detected. Comparisons of the column densities of the atomic and molecular species and the equivalent widths of the DIBs reveal both similarities and differences in relative abundances, compared to trends seen in the ISM of our Galaxy and the Magellanic Clouds. Of the ten relatively strong DIBs considered here, six (including $\\lambda$5780.5) have strengths within $\\pm$20% of the mean values seen in the local Galactic ISM, for comparable N(K I); two are weaker by 20--45% and two (including $\\lambda$5797.1) are stronger by 25--40%. Weaker than "expected" DIBs [relative to N(K I), N(Na I), and E(B-V)] in some Galactic sight lines and towar...

  9. Native Americans' Interest in Horticulture.

    Science.gov (United States)

    Meyer, Mary Hockenberry

    1999-01-01

    Focus groups arranged by local Native American Master Gardeners on two Minnesota reservations determined community interest in extension-horticulture programs. Topics of interest included food preservation and historical Native-American uses of plants. (SK)

  10. Atmospheric entry survival and the possibility of stratospheric collection of modern interstellar dust

    Science.gov (United States)

    Flynn, George J.

    1997-03-01

    Taylor et al. (1996) detected the ion trails of dust particles, estimated to range from 15 to 45 microns in diameter, entering the Earth's atmosphere with velocities of about 100 km/s. Since this velocity significantly exceeds the solar system escape velocity, these particles were identified as interstellar. Taylor et al. observed a seasonal peak in the detected flux, and interpreted this peak to indicate the time of year when the Earth, in its heliocentric orbit, is moving directly towards a stream of incoming interstellar dust, increasing the geocentric velocity of the particles so that particles as small as 15 to 45 microns in diameter produce micrometeors detectable by Taylor et al.'s radar system. Six months later, when the Earth's heliocentric motion is directly opposite the direction of the interstellar flux, the atmospheric entry velocity of these interstellar grains will be reduced by twice the Earth's orbital velocity, and, instead of producing ion trails, some of these interstellar grains may enter the Earth's atmosphere without melting or vaporizing. Those interstellar grains which enter the atmosphere without melting will settle into the Earth's stratosphere in the same manner as the interplanetary dust particles, which are routinely collected by NASA stratospheric sampling aircraft. Thus, interstellar dust particles in the 5-20 micron size range may be present on the NASA stratospheric collection surfaces flown during the favorable collection season.

  11. Interstellar Seeing. I. Superresolution Techniques Using Radio Scintillation

    CERN Document Server

    Cordes, J M

    2000-01-01

    Interstellar scintillation can be used to probe transverse sizes of radio sources on scales inaccessible to the nominal resolution of any terrestrial telescope, e.g. $\\lesssim 10^{-6}$ arc sec. Methodology is presented that exploits this superresolution phenomenon for both single aperture and interferometer observations. The treatment applies to the saturated (strong-scattering) regime and holds for both thin screens and extended media. A general signal model for radio sources is presented, {\\it scintillated amplitude modulated noise}, which applies to compact, incoherent synchrotron sources such as AGNs and gamma-ray burst sources and also to known, coherent sources such as masers and pulsars. The exact probability density function for measured intensities and interferometric visibilities is obtained by solving a general Fredholm problem. An approximate density function is also obtained by using the equivalent number of degrees of freedom in scintillation modulations. The scintillation modulation variance is...

  12. Cosmic ray propagation in the interstellar magnetic fields

    CERN Document Server

    Giacinti, G

    2014-01-01

    The propagation of TeV-PeV cosmic rays (CR) in our Galaxy can be described as a diffusive process. We discuss here two effects, with important observational consequences, that cannot be predicted by the diffusion approximation in its usual form. First, we present an explanation for the CR anisotropies observed at small angular scales on the sky. We show that the local magnetic field configuration within a CR mean free path from Earth naturally results in CR flux anisotropies at small and medium scales. Second, we point out that TeV-PeV CRs should be expected to diffuse strongly anisotropically in the interstellar medium on scales smaller than the maximum scale of spatial fluctuations of the field, $\\sim 100$ pc. This notably questions the usual assumptions on CR diffusion around sources.

  13. Impulsive Spot Heating and Thermal Explosion of Interstellar Grains Revisited

    CERN Document Server

    Ivlev, A V; Vasyunin, A; Caselli, P

    2015-01-01

    The problem of impulsive heating of dust grains in cold, dense interstellar clouds is revisited theoretically, with the aim to better understand leading mechanisms of the explosive desorption of icy mantles. It is rigorously shown that if the heating of a reactive medium occurs within a sufficiently localized spot (e.g., heating of mantles by cosmic rays), then the subsequent thermal evolution is characterized by a single dimensionless number $\\lambda$. This number identifies a bifurcation between two distinct regimes: When $\\lambda$ exceeds a critical value (threshold), the heat equation exhibits the explosive solution, i.e., the thermal (chemical) explosion is triggered. Otherwise, thermal diffusion causes the deposited heat to spread over the entire grain -- this regime is commonly known as the whole-grain heating. The theory allows us to find a critical combination of the physical parameters that govern the explosion of icy mantles due to impulsive spot heating. In particular, the calculations suggest tha...

  14. Radio Scintillation due to Discontinuities in the Interstellar Plasma Density

    CERN Document Server

    Lambert, H; Lambert, Hendrik; Rickett, Barney

    1999-01-01

    We develop the theory of interstellar scintillation as caused by an irregular plasma having a power-law spatial density spectrum with a spectral exponent of 4 corresponding to a medium with abrupt changes in its density. An ``outer scale'' is included in the model representing the typical scale over which the density of the medium remains uniform. Such a spectrum could be used to model plasma shock fronts in supernova remnants or other plasma discontinuities. We investigate and develop equations for the decorrelation bandwidth of diffractive scintillations and the refractive scintillation index and compare our results with pulsar measurements. We consider both a medium concentrated in a thin layer and an extended irregular medium. We conclude that the discontinuity model gives satisfactory agreement for many diffractive measurements, in particular the VLBI meaurements of the structure function exponent between 5/3 and 2. However, it gives less satisfactory agreement for the refractive scintillation index than...

  15. Estimating stellar parameters and interstellar extinction from evolutionary tracks

    Science.gov (United States)

    Sichevsky, S.; Malkov, O.

    Developing methods for analyzing and extracting information from modern sky surveys is a challenging task in astrophysical studies. We study possibilities of parameterizing stars and interstellar medium from multicolor photometry performed in three modern photometric surveys: GALEX, SDSS, and 2MASS. For this purpose, we have developed a method to estimate stellar radius from effective temperature and gravity with the help of evolutionary tracks and model stellar atmospheres. In accordance with the evolution rate at every point of the evolutionary track, star formation rate, and initial mass function, a weight is assigned to the resulting value of radius that allows us to estimate the radius more accurately. The method is verified for the most populated areas of the Hertzsprung-Russell diagram: main-sequence stars and red giants, and it was found to be rather precise (for main-sequence stars, the average relative error of radius and its standard deviation are 0.03% and 3.87%, respectively).

  16. The HCS+/CS abundance ratio in interstellar clouds

    International Nuclear Information System (INIS)

    The ion-molecule reactions and ion-electron recombination of HCS+ have been studied in a variety of laboratory experiments at room temperature. CS has a very large proton affinity so that many reactions can lead to HCS+, which is found to be unreactive with nearly all abundant interstellar molecules. In addition the dissociative recombination rate coefficient of HCS+ is the lowest the present authors have measured for a heavy polyatomic ion. New calculations of the rate coefficient for the H3+-CS reaction are also presented, and it is found that this increases by an order of magnitude as the temperature decreases from 300 to 10K. These theoretical data, together with the laboratory results are used to explain the high [HCS+]/[CS] ratio observed in TMC-1. (author)

  17. How Interstellar Chemistry (and Astrochemistry More Generally) Became Useful

    CERN Document Server

    Hartquist, T W; Falle, S A E G

    2008-01-01

    In 1986 Alex Dalgarno published a paper entitled "Is Interstellar Chemistry Useful?" By the middle 1970s, and perhaps even earlier, Alex had hoped that astronomical molecules would prove to: possess significant diagnostic utility; control many of the environments in which they exist; stimulate a wide variety of physicists and chemists who are at least as fascinated by the mechanisms forming and removing the molecules as by astronomy. His own research efforts have contributed greatly to the realization of that hope. This paper contains a few examples of: how molecules are used to diagnose large-scale dynamics in astronomical sources including star forming regions and supernovae; the ways in which molecular processes control the evolution of astronomical objects such as dense cores destined to become stars and very evolved giant stars; theoretical and laboratory investigations that elucidate the processes producing and removing astronomical molecules and allow their detection.

  18. Dust as interstellar catalyst I. Quantifying the chemical desorption process

    CERN Document Server

    Minissale, M; Cazaux, S; Hocuk, S

    2015-01-01

    Context. The presence of dust in the interstellar medium has profound consequences on the chemical composition of regions where stars are forming. Recent observations show that many species formed onto dust are populating the gas phase, especially in cold environments where UV and CR induced photons do not account for such processes. Aims. The aim of this paper is to understand and quantify the process that releases solid species into the gas phase, the so-called chemical desorption process, so that an explicit formula can be derived that can be included into astrochemical models. Methods. We present a collection of experimental results of more than 10 reactive systems. For each reaction, different substrates such as oxidized graphite and compact amorphous water ice are used. We derive a formula to reproduce the efficiencies of the chemical desorption process, which considers the equipartition of the energy of newly formed products, followed by classical bounce on the surface. In part II we extend these resul...

  19. Properties of Turbulence in the Very Local Interstellar Clouds

    CERN Document Server

    Spangler, Steven R; Redfield, Seth

    2011-01-01

    We have investigated the degree to which turbulence in the Very Local Interstellar Clouds resembles the highly-studied turbulence in the solar corona and the solar wind. The turbulence diagnostics for the Local Clouds are the absorption line widths measured along 32 lines of sight to nearby stars, yielding measurements for 53 absorption components (Redfield and Linsky 2004). We have tested whether the Local Cloud turbulence has the following properties of turbulence in the solar corona or the solar wind: (a) velocity fluctuations mainly perpendicular to the average magnetic field, (b) a temperature anisotropy in the sense that the perpendicular temperature is larger than the parallel temperature (or at least enhanced relative to expectation), and (c) an ion temperature which is dependent on the ion Larmor radius, in the sense that more massive ions have higher temperatures. Our analysis of the data does not show compelling evidence for any of these properties in Local Cloud turbulence, indicating possible dif...

  20. Detecting Pulsars with Interstellar Scintillation in Variance Images

    CERN Document Server

    Dai, S; Bell, M E; Coles, W A; Hobbs, G; Ekers, R D; Lenc, E

    2016-01-01

    Pulsars are the only cosmic radio sources known to be sufficiently compact to show diffractive interstellar scintillations. Images of the variance of radio signals in both time and frequency can be used to detect pulsars in large-scale continuum surveys using the next generation of synthesis radio telescopes. This technique allows a search over the full field of view while avoiding the need for expensive pixel-by-pixel high time resolution searches. We investigate the sensitivity of detecting pulsars in variance images. We show that variance images are most sensitive to pulsars whose scintillation time-scales and bandwidths are close to the subintegration time and channel bandwidth. Therefore, in order to maximise the detection of pulsars for a given radio continuum survey, it is essential to retain a high time and frequency resolution, allowing us to make variance images sensitive to pulsars with different scintillation properties. We demonstrate the technique with Murchision Widefield Array data and show th...

  1. Graph-based interpretation of the Molecular Interstellar Medium Segmentation

    CERN Document Server

    Colombo, Dario; Ginsburg, Adam; Duarte-Cabral, Ana; Hughes, Annie

    2015-01-01

    We present a generalization of the Giant Molecular Cloud (GMC) identification problem based on cluster analysis. The method we designed, SCIMES (Spectral Clustering for Interstellar Molecular Emission Segmentation) considers the dendrogram of emission in the broader framework of graph theory and utilizes spectral clustering to find discrete regions with similar emission properties. For Galactic molecular cloud structures, we show that the characteristic volume and/or integrated CO luminosity are useful criteria to define the clustering, yielding emission structures that closely reproduce "by-eye" identification results. SCIMES performs best on well-resolved, high-resolution data, making it complementary to other available algorithms. Using 12CO(1-0) data for the Orion-Monoceros complex, we demonstrate that SCIMES provides robust results against changes of the dendrogram-construction parameters, noise realizations and degraded resolution. By comparing SCIMES with other cloud decomposition approaches, we show t...

  2. Shielding of CO from dissociating radiation in interstellar clouds

    Science.gov (United States)

    Glassgold, A. E.; Huggins, P. J.; Langer, W. D.

    1985-01-01

    The paper investigates the photodissociation of CO in interstellar clouds in the light of recent laboratory studies which suggest that line rather than continuum processes dominate its dissociation by ultraviolet radiation. Using a simple radiative transfer model, the shielding of representative dissociating bands is estimated, including self-shielding, mutual shielding between different isotopes, and near coincidences with strong lines of H2. Each of these processes materially affects the photodestruction rates of the various isotopic species in the transition regions of molecular clouds. These results are combined with an appropriate gas phase chemical model to determine how the abundances of the CO isotopes vary with depth into the cloud. It is found that self-shielding and mutual shielding cause significant variations in isotopic ratios. In addition, fractionation enhances species containing C-13. The relationship between the column densities of CO and H2 is found to vary for the different isotopes and to be sensitive to local conditions.

  3. The formation of buckminsterfullerene (C$_{60}$) in interstellar space

    CERN Document Server

    Berné, Olivier

    2011-01-01

    Buckminsterfullerene (C$_{60}$) was recently confirmed to be the largest molecule identified in space. However, it remains unclear how, and where this molecule is formed. It is generally believed that C$_{60}$ is formed from the build up of small carbonaceous compounds, in the hot and dense envelopes of evolved stars. Analyzing infrared observations, obtained by Spitzer and Herschel, we found that C$_{60}$ is efficiently formed in the tenuous and cold environment of an interstellar cloud illuminated by strong ultraviolet (UV) radiation fields. This implies that another formation pathway, efficient at low densities, must exist. Based on recent laboratory and theoretical studies, we argue that Polycyclic Aromatic Hydrocarbons are converted into graphene, and subsequently C$_{60}$, under UV irradiation from massive stars. This shows that alternative - top-down - routes are key to understanding the organic inventory in space.

  4. Bounds on halo-particle interactions from interstellar calorimetry

    Science.gov (United States)

    Chivukula, Sekhar R.; Cohen, Andrew G.; Dimopoulos, Savas; Walker, Terry P.

    1990-01-01

    It is shown that the existence of neutral interstellar clouds constrains the interaction of any particulate dark-matter candidate with atomic hydrogen to be quite small. Even for a halo particle of mass 1 PeV (10 to the 6 GeV), it is shown that the cross section with hydrogen must be smaller than the typical atomic cross section that is expected for a positively charged particle bound to an electron. The argument presented is that if the clouds are in equilibrium, then the rate at which energy is deposited by collisions with dark-matter particles must be smaller than the rate at which the cloud can cool. This argument is used to constrain the interaction cross section of dark matter with hydrogen. Remarks are made on the general viability of charged dark matter. Comments are also made on a bound which derives from the dynamical stability of the halo.

  5. Ionization front-driven turbulence in the clumpy interstellar medium

    CERN Document Server

    Peters, Thomas; Klessen, Ralf S

    2008-01-01

    We present 3D radiation-gasdynamical simulations of an ionization front running into a dense clump. In our setup, a B0 star irradiates an overdensity which is at a distance of 10 pc and modelled as a supercritical 100 M_sol Bonnor-Ebert sphere. The radiation from the star heats up the gas and creates a shock front that expands into the interstellar medium. The shock compresses the clump material while the ionizing radiation heats it up. The outcome of this "cloud-crushing" process is a fully turbulent gas in the wake of the clump. In the end, the clump entirely dissolves. We propose that this mechanism is very efficient in creating short-living supersonic turbulence in the vicinity of massive stars.

  6. Altobiobots: A Biorobotic Interface Platform for Interstellar Travel

    Science.gov (United States)

    Altomare, A. C.

    Altobiobots (ABB) are a category of ideal nanorobots with specific capabilities which allow them to reside symbiotically within the nuclei of all nucleate cells in the human body. ABBs facilitate a biorobotic interface through genetic interaction with a host organism and wireless communication among external sources. ABBs create an intra-organism network of uniquely identifiable constituants by utilizing a recursive algorithm, AAnotation, to self-assign non-redundant alphanumerically compressed addresses. The primary context for the development of the ABB biorobotic interface platform is to facilitate interplanetary and interstellar space travel by liberating the capacity for human adaptability. Secondary goals include precise spatial and temporal control of gene expression, enhancement of cerebral brain functions, and disease intervention.

  7. Pulsar Scintillation Studies and Structure of the Local Interstellar Medium

    CERN Document Server

    Bhat, N D R; Rao, A P; Preethi, P B; Gupta, Yashwant

    1999-01-01

    Results from new observations of pulsars using the Ooty Radio Telescope (ORT) are used for investigating the structure of the Local Interstellar Medium (LISM). The observations show anomalous scintillation effects towards several nearby pulsars, and these are modeled in terms of large-scale spatial inhomogeneities in the distribution of plasma density fluctuations in the LISM. A 3-component model, where the Solar neighbourhood is surrounded by a shell of enhanced plasma turbulence, is proposed for the LISM. The inferred scattering structure is strikingly similar to the Local Bubble. Further, analysis based on recent scintillation measurements show evidence for enhanced scattering towards pulsars located in the general direction of the Loop I Superbubble. The model for the LISM has been further extended by incorporating the scattering due to turbulent plasma associated with Loop I.

  8. The Interstellar Reddening Law within 3kpc from the Sun

    CERN Document Server

    Sung, Hwankyung

    2014-01-01

    We have investigated the interstellar reddening law of young open clusters within 3kpc from the Sun using optical, near-IR 2MASS, and Spitzer IRAC data. The total-to-selective extinction ratio Rv of 162 young open clusters (log t{age} <= 7.3) listed in the open cluster database WEBDA is determined from the color excess ratios. The young open clusters in the Sgr-Car arm show a relatively higher $R_V$, those in the Per arm and in the Cygnus region of the local arm show a relatively smaller value, and those in the Mon-CMa region of the local arm show a normal value (Rv ~ 3.1).

  9. The Turbulence Power Spectrum in Optically Thick Interstellar Clouds

    CERN Document Server

    Burkhart, Blakesley; Ossenkopf, V; Stutzki, J

    2013-01-01

    The Fourier power spectrum is one of the most widely used statistical tools to analyze the nature of magnetohydrodynamic turbulence in the interstellar medium. Lazarian & Pogosyan (2004) predicted that the spectral slope should saturate to -3 for an optically thick medium and many observations exist in support of their prediction. However, there have not been any numerical studies to-date testing these results. We analyze the spatial power spectrum of MHD simulations with a wide range of sonic and Alfv\\'enic Mach numbers, which include radiative transfer effects of the $^{13}$CO transition. We confirm numerically the predictions of Lazarian & Pogosyan (2004) that the spectral slope of line intensity maps of an optically thick medium saturates to -3. Furthermore, for very optically thin supersonic CO gas, where the density or CO abundance values are too low to excite emission in all but the densest shock compressed gas, we find that the spectral slope is shallower than expected from the column density....

  10. Structure and Stability of Interstellar Molecule C3S

    Institute of Scientific and Technical Information of China (English)

    YU,Hai-Tao(于海涛); FU,Hong-Gang(傅宏刚); CHI,Yu-Juan(池玉娟); HUANG,Xu-Ri(黄旭日); LI,Ze-Sheng(李泽生); SUN,Jia-Zhong(孙家钟)

    2002-01-01

    The singlet and triplet potential energy surfaces of interstellar molecule C3S are predicted at the UB3LYP/6-311 (d) and UCCSD(T)/6-311 + G(2df) (single-point) levels. The linear singlet isomer CCCS with 1 ∑ + electronic state is found to be thermodynamically and kinetically the most stable species on the singlet surface followed by other four singiet isomers, which are unstable on the basis of calculated results. On the triplet sur face, the lowest-lying species, which lies 248.79 kJ/mol above linear singlet species CCCS, is chain CCCS connectivity with 3A' electronic state. Other four triplet isomers can be considered as unstable species by means of transition state and potential energy surface scan technologies. The structures, vibrational frequencies, dipole moments and rotational constants of all optimized species are also calculated.

  11. Photoionisation and Heating of a Supernova Driven, Turbulent, Interstellar Medium

    CERN Document Server

    Barnes, J E; Hill, Alex S; Haffner, L M

    2014-01-01

    The Diffuse Ionised Gas (DIG) in galaxies traces photoionisation feedback from massive stars. Through three dimensional photoionisation simulations, we study the propagation of ionising photons, photoionisation heating and the resulting distribution of ionised and neutral gas within snapshots of magnetohydrodynamic simulations of a supernova driven turbulent interstellar medium. We also investigate the impact of non-photoionisation heating on observed optical emission line ratios. Inclusion of a heating term which scales less steeply with electron density than photoionisation is required to produce diagnostic emission line ratios similar to those observed with the Wisconsin H{\\alpha} Mapper. Once such heating terms have been included, we are also able to produce temperatures similar to those inferred from observations of the DIG, with temperatures increasing to above 15000 K at heights |z| > 1 kpc. We find that ionising photons travel through low density regions close to the midplane of the simulations, while...

  12. Branching processes in biology

    CERN Document Server

    Kimmel, Marek

    2015-01-01

    This book provides a theoretical background of branching processes and discusses their biological applications. Branching processes are a well-developed and powerful set of tools in the field of applied probability. The range of applications considered includes molecular biology, cellular biology, human evolution and medicine. The branching processes discussed include Galton-Watson, Markov, Bellman-Harris, Multitype, and General Processes. As an aid to understanding specific examples, two introductory chapters, and two glossaries are included that provide background material in mathematics and in biology. The book will be of interest to scientists who work in quantitative modeling of biological systems, particularly probabilists, mathematical biologists, biostatisticians, cell biologists, molecular biologists, and bioinformaticians. The authors are a mathematician and cell biologist who have collaborated for more than a decade in the field of branching processes in biology for this new edition. This second ex...

  13. Synthesis of Formamide and Related Organic Species in the Interstellar Medium via Chemical Dynamics Simulations

    Science.gov (United States)

    Spezia, Riccardo; Jeanvoine, Yannick; Hase, William L.; Song, Kihyung; Largo, Antonio

    2016-08-01

    We show, by means of direct dynamics simulations, how it is possible to define possible reactants and mechanisms leading to the formation of formamide in the interstellar medium. In particular, different ion-molecule reactions in the gas phase were considered: NH3OH+, NH2OH{}2+, H2COH+, and NH4 + for the ions and NH2OH, H2CO, and NH3 for the partner neutrals. These calculations were combined with high level ab initio calculations to investigate possible further evolution of the products observed. In particular, for formamide, we propose that the NH2OH{}2+ + H2CO reaction can produce an isomer, NH2OCH{}2+, that, after dissociative recombination, can produce neutral formamide, which was observed in space. The direct dynamics do not pre-impose any reaction pathways and in other reactions, we did not observe the formation of formamide or any possible precursor. On the other hand, we obtained other interesting reactions, like the formation of NH2CH{}2+. Finally, some radiative association processes are proposed. All of the results obtained are discussed in light of the species observed in radioastronomy.

  14. The interstellar medium and star formation in nearby galaxies. Ludwig Biermann Award Lecture 2013

    Science.gov (United States)

    Bigiel, F.; Cormier, D.; Schmidt, T.

    In this overview article we present some of the key projects we pursue in our Emmy Noether group. Our work is focused on nearby galaxies, where we use multi-wavelength, state-of-the-art survey data to probe distribution, abundance and properties of gas and dust in the interstellar medium (ISM) on [Si II] kpc scales. We study the average, radial distributions of atomic (H I) and molecular hydrogen (H2) across the disks of spiral galaxies and assess local (on 1 kpc scales) correlations between H I, H2 and star formation rate (SFR) surface densities across the inner, optical disks of our sample of [Si II] 30 spiral galaxies. The short H2 depletion times ([Si II] 2 Gyr) we find raises the question of if and how star formation is refueled in galactic disks. We look for such signatures of radial gas flows in our H I data and find compelling evidence at least in one case. We extend and compare our gas-SFR studies to the outer disks of galaxies, where conditions change significantly in the ISM, e.g., low metallicity and dust abundance. We focus on star formation at low-metallicity further with detailed ISM studies in dwarf galaxies, where we combine spectroscopic observations in the infrared with detailed modelling to learn about composition and detailed physical properties of the ISM. Of particular interest is the question of what drives large scale star formation in galaxies at low metallicity.

  15. Dust emission and scattering in dense interstellar clouds

    Science.gov (United States)

    Juvela, M.

    2015-10-01

    Dust has a crucial role in the physics of interstellar medium (ISM) and it is one of the main tracers used in studies of dense clouds. Its importance has been accentuated by the large amounts of data available from the recent fleet of infrared and submillimetre satellites. These observations are providing further insights into the properties of interstellar dust grains and the changes they undergo during the star formation process. We examine some of the evidence for dust evolution coming from submillimetre dust emission and from light scattering at near-infrared and mid-infrared wavelengths. Planck and Herschel satellite observations have covered the peak of large grain emission, enabling studies of large cloud areas with unprecedented sensitivity and detail. The data are confirming results from earlier studies where changes of submillimetre dust opacity and spectral index were first reported. The changes are connected to dust evolution and growth as dust moves from diffuse ISM to molecular clouds and into pre-stellar clumps. Corroborating evidence on dust growth has been obtained recently from mid-infrared where enhanced scattering, the 'coreshine' phenomenon, is attributed to the growth of up to micron-sized dust particles. We will summarise results of previous infrared and submillimetre studies. We will describe ongoing work on Herschel data, done partly in the context of the programme Galactic Cold Cores (GCC). We will also discuss recent results from the Spitzer project Hunting coreshine, where the mid-infrared scattering is investigated in a partly related sample. We will also touch on some of the problems and modelling challenges encountered in these studies.

  16. Chemistry of nitrile anions in the interstellar medium

    Energy Technology Data Exchange (ETDEWEB)

    Carles, S.; Le Garrec, J.-L.; Biennier, L. [Institut de Physique de Rennes, Département de Physique Moléculaire, Astrophysique de Laboratoire, UMR CNRS 6251, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex (France); Guillemin, J.-C. [Institut des Sciences Chimiques de Rennes, Ecole Nationale Supérieure de Chimie de Rennes, CNRS, UMR 6226, 11 Allée de Beaulieu, CS 50837,35708 Rennes Cedex 7 (France)

    2015-12-31

    Despite the extreme conditions of temperature (down to 10K) and density (down to 100 molecules/cm{sup 3}), the giant molecular clouds and the circumstellar envelopes present a rich and complex chemistry. To date, more than 180 molecules have been detected in the InterStellar Medium (ISM) with a large abundance of nitriles (RC≡N). In addition, several anions have been recently observed in this medium: C{sub 4}H{sup ¯}, C{sub 6}H{sup ¯}, C{sub 8}H{sup ¯}, CN{sup ¯}, C{sub 3}N{sup ¯} and C{sub 5}N{sup ¯}. These last species should play a key role in the molecular growth towards complexity. To explore this hypothesis, their reactivity must be studied in the laboratory. The FALP-MS and the CRESU experimental apparatuses of the Rennes University are able to measure absolute rate coefficient of various chemical reactions, including the ion – molecule reactions, in gas phase at low temperature (from 300K for the FALP-MS down to 15K for the CRESU). Therefore, these experimental tools are particularly adapted to the kinetic studies of reactions potentially involved in the Interstellar Medium. One of the difficulties encountered in experiments with anions is their generation. We describe here the formation of the CN{sup ¯} and C{sub 3}N{sup ¯} anions by dissociative electron attachment on the molecular precursors BrCN and BrC{sub 3}N.

  17. Differential adsorption of CHON isomers at interstellar grain surfaces

    Science.gov (United States)

    Lattelais, M.; Pauzat, F.; Ellinger, Y.; Ceccarelli, C.

    2015-06-01

    Context. The CHON generic chemical formula covers different isomers such as isocyanic acid (HNCO), cyanic acid (HOCN), fulminic acid (HCNO), and isofulminic acid (HONC); the first three have been identified in a large variety of environments in the interstellar medium (ISM). Several phenomena could be at the origin of the observed abundances, such as different pathways of formation and destruction involving gas phase reactions with different possible activation barriers and/or surface processes depending on the local temperature and the nature of the support. Aims: The scope of this article is to shed some light on the interaction of the CHON isomers with interstellar grains as a function of the nature of the surface and to determine the corresponding adsorption energies in order to find whether this phenomenon could play a role in the abundances observed in the ISM. Methods: The question was addressed by means of numerical simulations using first principle periodic density functional theory (DFT) to represent the grain support as a solid of infinite dimension. Results: Regardless of the nature of the model surface (water ice, graphene, silica), two different classes of isomers were identified: weakly bound (HNCO and HCNO) and strongly bound (HOCN and HONC), with the adsorption energies of the latter group being about twice those of the former. The range of the adsorption energies is (from highest to lowest) HOCN > HONC > HNCO > HCNO. They are totally disconnected from the relative stabilities, which range from HNCO > HOCN > HCNO > HONC. Conclusions: The possibility of hydrogen bonding is the discriminating factor in the trapping of CHON species on grain surfaces. Whatever the environment, differential adsorption is effective and its contribution to the molecular abundances should not be ignored. The theoretical adsorption energies provided here could be profitably used for a more realistic modeling of molecule-surfaces interactions.

  18. Terrestrial atmospheric effects induced by counterstreaming dense interstellar cloud material

    Science.gov (United States)

    Yeghikyan, A.; Fahr, H.

    The Solar System during its life has encountered more than 10 times with dense interstellar clouds with particle concentrations about 10(8)-10(9) m(-3) and more suppressing the heliopause to dimensions smaller than 1 AU and bringing the Earth in immediate contact with the interstellar matter. For cloud's concentration greater than of 10(8) m(-3), the flow material at the Earth, completely shielded from solar wind protons would be only subject to solar photoionization processes. Previously published results were limited to consideration of processes outside of the accretion radius and have not been taken into account the photoionization. We have developed a 2D-2-fluid gasdynamical numerical code to describe the behavior of the incoming neutral matter near the Earth, taken into account both the photoionization and the gravity of the Sun. Increased neutral hydrogen fluxes ranging from 10(13) to 10(16) m(-2)s(-1) would cause an alteration of the terrestrial atmosphere. During immersion in the cloud the total incident flux of neutral hydrogen onto the terrestrial atmosphere in the steady state would be balanced by the upward escape flux of hydrogen and the downward flux of water, which is the product of hydrogen-oxygen chemistry via even-odd reaction schemes. In that case hydrogen acts as a catalyst for the destruction of oxygen atoms and causes the ozone concentration to diminish pronouncedly above 50 km from a factor of 1.5 at the stratopause to about a factor of 1000 and more at the mesopause. Thus, depending on the encounter parameters the large mixing ratio of hydrogen decreases the ozon concentration in the mesosphere and triggers an ice age of relatively long duration.

  19. From Interstellar Polycyclic Aromatic Hydrocarbons and Ice to the Origin of Life

    Science.gov (United States)

    Allamandola, Louis

    2004-01-01

    Tremendous strides have been made in our understanding of interstellar material over the past twenty years thanks to significant, parallel developments in observational astronomy and laboratory astrophysics. Twenty years ago the composition of interstellar dust was largely guessed at, the concept of ices in dense molecular clouds ignored, and the notion of large, abundant, gas phase, carbon rich molecules widespread throughout the interstellar medium (ISM) considered impossible. Today the composition of dust in the diffuse ISM is reasonably well constrained to cold refractory materials comprised of amorphous and crystalline silicates mixed with an amorphous carbonaceous material containing aromatic structural units and short, branched aliphatic chains. In the dense ISM, the birthplace of stars and planets, these cold dust particles are coated with mixed molecular ices whose composition is very well constrained. Lastly, the signature of carbon-rich polycyclic aromatic hydrocarbons (PAHs), shockingly large molecules by early interstellar chemistry standards, is widespread throughout the Universe. The first part of this talk will describe how infrared studies of interstellar space, combined with laboratory simulations, have revealed the composition of interstellar ices (the building blocks of comets) and the high abundance and nature of interstellar PAHs. The laboratory database has now enabled us to gain insight into the identities, abundances, and physical state of many interstellar materials. Within a dense molecular cloud, and especially in the presolar nebula, the materials frozen into the interstellar/precometary ices are photoprocessed by ultraviolet light and produce more complex molecules. The remainder of the presentation will focus on the photochemical evolution of these materials and the possible role of these compounds on the to the carbonaceous components of micrometeorites, they are likely to have been important sources of complex materials on the early

  20. Diffuse Interstellar Bands versus Known Atomic and Molecular Species in the Interstellar Medium of M82 toward SN 2014J

    Science.gov (United States)

    Welty, Daniel E.; Ritchey, Adam M.; Dahlstrom, Julie A.; York, Donald G.

    2014-09-01

    We discuss the absorption due to various constituents of the interstellar medium (ISM) of M82 seen in moderately high-resolution, high signal-to-noise ratio optical spectra of SN 2014J. Complex absorption from M82 is seen, at velocities 45 <~ v LSR <~ 260 km s-1, for Na I, K I, Ca I, Ca II, CH, CH+, and CN; many of the diffuse interstellar bands (DIBs) are also detected. Comparisons of the column densities of the atomic and molecular species and the equivalent widths of the DIBs reveal both similarities and differences in relative abundances, compared to trends seen in the ISM of our Galaxy and the Magellanic Clouds. Of the 10 relatively strong DIBs considered here, 6 (including λ5780.5) have strengths within ±20% of the mean values seen in the local Galactic ISM, for comparable N(K I); 2 are weaker by 20%-45% and 2 (including λ5797.1) are stronger by 25%-40%. Weaker than "expected" DIBs (relative to N(K I), N(Na I), and E(B - V)) in some Galactic sight lines and toward several other extragalactic supernovae appear to be associated with strong CN absorption and/or significant molecular fractions. While the N(CH)/N(K I) and N(CN)/N(CH) ratios seen toward SN 2014J are similar to those found in the local Galactic ISM, the combination of high N(CH+)/N(CH) and high W(5797.1)/W(5780.5) ratios has not been seen elsewhere. The centroids of many of the M82 DIBs are shifted relative to the envelope of the K I profile—likely due to component-to-component variations in W(DIB)/N(K I) that may reflect the molecular content of the individual components. We compare estimates for the host galaxy reddening E(B - V) and visual extinction A V derived from the various interstellar species with the values estimated from optical and near-IR photometry of SN 2014J.

  1. Diffuse interstellar bands versus known atomic and molecular species in the interstellar medium of M82 toward SN 2014J

    International Nuclear Information System (INIS)

    We discuss the absorption due to various constituents of the interstellar medium (ISM) of M82 seen in moderately high-resolution, high signal-to-noise ratio optical spectra of SN 2014J. Complex absorption from M82 is seen, at velocities 45 ≲ v LSR ≲ 260 km s–1, for Na I, K I, Ca I, Ca II, CH, CH+, and CN; many of the diffuse interstellar bands (DIBs) are also detected. Comparisons of the column densities of the atomic and molecular species and the equivalent widths of the DIBs reveal both similarities and differences in relative abundances, compared to trends seen in the ISM of our Galaxy and the Magellanic Clouds. Of the 10 relatively strong DIBs considered here, 6 (including λ5780.5) have strengths within ±20% of the mean values seen in the local Galactic ISM, for comparable N(K I); 2 are weaker by 20%-45% and 2 (including λ5797.1) are stronger by 25%-40%. Weaker than 'expected' DIBs (relative to N(K I), N(Na I), and E(B – V)) in some Galactic sight lines and toward several other extragalactic supernovae appear to be associated with strong CN absorption and/or significant molecular fractions. While the N(CH)/N(K I) and N(CN)/N(CH) ratios seen toward SN 2014J are similar to those found in the local Galactic ISM, the combination of high N(CH+)/N(CH) and high W(5797.1)/W(5780.5) ratios has not been seen elsewhere. The centroids of many of the M82 DIBs are shifted relative to the envelope of the K I profile—likely due to component-to-component variations in W(DIB)/N(K I) that may reflect the molecular content of the individual components. We compare estimates for the host galaxy reddening E(B – V) and visual extinction A V derived from the various interstellar species with the values estimated from optical and near-IR photometry of SN 2014J.

  2. Diffuse interstellar bands versus known atomic and molecular species in the interstellar medium of M82 toward SN 2014J

    Energy Technology Data Exchange (ETDEWEB)

    Welty, Daniel E.; York, Donald G. [Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Ritchey, Adam M. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Dahlstrom, Julie A., E-mail: dwelty@oddjob.uchicago.edu [Department of Physics and Astronomy, Carthage College, 2001 Alford Park Drive, Kenosha, WI 53140 (United States)

    2014-09-10

    We discuss the absorption due to various constituents of the interstellar medium (ISM) of M82 seen in moderately high-resolution, high signal-to-noise ratio optical spectra of SN 2014J. Complex absorption from M82 is seen, at velocities 45 ≲ v {sub LSR} ≲ 260 km s{sup –1}, for Na I, K I, Ca I, Ca II, CH, CH{sup +}, and CN; many of the diffuse interstellar bands (DIBs) are also detected. Comparisons of the column densities of the atomic and molecular species and the equivalent widths of the DIBs reveal both similarities and differences in relative abundances, compared to trends seen in the ISM of our Galaxy and the Magellanic Clouds. Of the 10 relatively strong DIBs considered here, 6 (including λ5780.5) have strengths within ±20% of the mean values seen in the local Galactic ISM, for comparable N(K I); 2 are weaker by 20%-45% and 2 (including λ5797.1) are stronger by 25%-40%. Weaker than 'expected' DIBs (relative to N(K I), N(Na I), and E(B – V)) in some Galactic sight lines and toward several other extragalactic supernovae appear to be associated with strong CN absorption and/or significant molecular fractions. While the N(CH)/N(K I) and N(CN)/N(CH) ratios seen toward SN 2014J are similar to those found in the local Galactic ISM, the combination of high N(CH{sup +})/N(CH) and high W(5797.1)/W(5780.5) ratios has not been seen elsewhere. The centroids of many of the M82 DIBs are shifted relative to the envelope of the K I profile—likely due to component-to-component variations in W(DIB)/N(K I) that may reflect the molecular content of the individual components. We compare estimates for the host galaxy reddening E(B – V) and visual extinction A {sub V} derived from the various interstellar species with the values estimated from optical and near-IR photometry of SN 2014J.

  3. Interest Organizations across Economic Sectors

    DEFF Research Database (Denmark)

    Berkhout, Joost; Carroll, Brendan; Braun, Caelesta;

    2015-01-01

    of collective action of businesses. In contrast, we do not find consistent evidence that political institutions produce ‘demand’ for interest organizations by making laws, developing public policy or spending money. This is in contrast to the extensive evidence that such factors affect lobbying practices....... The European Union interest system is (partially) shaped by economic factors, relatively independent from public policy or institutions.......The number of interest organizations (density) varies across policy domains, political issues and economic sectors. This shapes the nature and outcomes of interest representation. In this contribution, we explain the density of interest organizations per economic sector in the European Union...

  4. The influence of variations of elemental composition on the thermal properties of interstellar gas

    Science.gov (United States)

    Vasiliev, E. O.; Shchekinov, Yu. A.

    2016-10-01

    The mixing of metals and redistribution of the relative abundances of chemical elements in the interstellar medium often takes place on a timescale that exceeds the characteristic timescales for many other processes, such as ionization and the establishment of thermal equilibrium. Under these conditions, different regions of interstellar gas can have different thermal, chemical, and spectral properties. The paper considers the ionization kinetics and thermal regime of interstellar gas with variations in the relative elemental abundances. The thermal properties and observational (spectral) characteristics are most sensitive to variations of the relative abundance of carbon, oxygen, neon, and iron. The dynamic consequences of such variations are considered.

  5. IUE Observations of the Gaseous Component of the Local Interstellar Medium

    Science.gov (United States)

    Gilra, D. P.

    1984-01-01

    Discovery of interstellar Ge, Ga, and Kr is reported. Several intercombination lines of Fe 2 are detected. The depletion is most pronounced in Ca, Ti, and V. The highly ionized gas C 4 and Si 4 is not co-extensive with the Si 2 and C 2 gas nor with the O 6 gas. The molecular gas (CO) shows very small velocity dispersion (b approximately 1 km/sec). HD 149404 has the richest interstellar spectrum (except molecules) of all the stars in this study. HD 147889, the heavily obscured star in the Rho Oph cloud, has the strongest interstellar CO spectrum. Noisy nature of the spectra precludes detection of other molecules.

  6. Neutral interstellar medium phases and star formation tracers in dwarf galaxies

    Science.gov (United States)

    Cigan, Phillip Johnathan

    Dwarf galaxies present interesting observational challenges for the studies of various galaxy properties: despite their abundance and proximity to the Milky Way, they typically have very low surface brightnesses and small physical sizes. Until now, only the extreme variety of dwarfs --- those undergoing strong bouts of star formation --- have been observed in the FIR, due to observational difficulties. However, this population does not represent the majority of dwarfs, which have only moderate star formation rates and extremely low metallicity (the fraction of heavy elements to hydrogen). The advent of the Herschel Space Telescope, with its superior resolution and sensitivity over previous generations of telescopes, has made it possible to measure FIR spectral lines and broadband continuum in normal dwarf galaxies, expanding the scope of studies beyond the brighter, but more extreme, varieties. The general goal of my research was to study the conditions in the interstellar media (ISM) of typical dwarf galaxies. The LITTLE THINGS (Local Irregulars That Trace Luminosity Extremes, TheHI Nearby Galaxy Survey) project aims to unravel many mysteries of nearby dwarfs using a suite of multi-wavelength data, and the new additions from Herschel help provide insight into the physics of these systems. I reduced and analyzed FIR fine-structure spectral line data for the LITTLE THINGS sample to study the different phases of the ISM, as well as FIR photometry data to access the dust properties and infrared continuum emission in these systems. The FIR spectral lines are diagnostics for the conditions in the ISM of galaxies, telling us about heating efficiency, the fraction of gas that resides in photodissociation regions (PDRs), abundance of highly ionized gas from massive stars, and other physical descriptions. The photometric continuum observations enable the modeling of interstellar dust properties -- dust plays an important role in shielding and cooling molecular clouds which

  7. Attitude of teenagers towards biology

    OpenAIRE

    Lavtižar, Teja

    2016-01-01

    ROSE project is a comprehensive study in which students' attitudes towards Science and Technology affected by many factors have been examined. In our study, only some aspects have been focused due to a narrower field of biology which has been interested in, and the direction of the attitude between Biology to elementary school students has been checked. The purpose of the master's work has been to determine the attitude of the teenagers to Biology as science and Biology as a school subjec...

  8. Diffuse interstellar band at 8620 Å in rave: A new method for detecting the diffuse interstellar band in spectra of cool stars

    Energy Technology Data Exchange (ETDEWEB)

    Kos, J.; Zwitter, T. [Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, 1000 Ljubljana (Slovenia); Grebel, E. K. [Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstraße 12-14, D-69120 Heidelberg (Germany); Bienayme, O.; Siebert, A. [Observatorie astronomique de Strasbourg, Université de Strasbourg, 11 rue de l' Université, F-67000 Strasbourg (France); Binney, J. [Rudolf Peierls Centre for Theoretical Physics, Keble Road, Oxford OX1 3NP (United Kingdom); Bland-Hawthorn, J. [Sydney Institute for Astronomy, School of Physics A28, University of Sydney, NSW 2008 (Australia); Freeman, K. C. [Research School of Astronomy and Astrophysics, Australian National University, Canberra (Australia); Gibson, B. K. [Jeremiah Horrocks Institute, University of Central Lancashire, Preston PR1 2HE (United Kingdom); Gilmore, G.; Kordopatis, G. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Navarro, J. F. [University of Victoria, Victoria, BC V8P 5C2 (Canada); Parker, Q.; Reid, W. A. [Department of Physics and Astronomy, Macquarie University, Sydney, NSW 2109 (Australia); Seabroke, G. [Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking RH5 6NT (United Kingdom); Siviero, A.; Steinmetz, M. [Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam (Germany); Watson, F. [Australian Astronomical Observatory, P.O. Box 915, North Ryde, NSW 1670 (Australia); Wyse, R. F. G., E-mail: janez.kos@fmf.uni-lj.si [Johns Hopkins University, Homewood Campus, 3400 North Charles Street, Baltimore, MD 21218 (United States)

    2013-12-01

    Diffuse interstellar bands (DIBs) are usually observed in spectra of hot stars, where interstellar lines are rarely blended with stellar ones. The need for hot stars is a strong limitation in the number of sightlines we can observe and their distribution in the Galaxy, as hot stars are rare and concentrated in the Galactic plane. We are introducing a new method, where interstellar lines can be observed in spectra of cool stars in large spectroscopic surveys. The method is completely automated and does not require prior knowledge of the stellar parameters. The main step is a construction of the stellar spectrum, which is done by finding other observed spectra that lack interstellar features and are otherwise very similar to the spectrum in question. Such spectra are then combined into a single stellar spectrum template, matching the stellar component of the observed spectrum. We demonstrate the performance of this new method on a sample of 482,430 Radial Velocity Experiment survey spectra. However, many spectra have to be combined (48 on average) in order to achieve a signal-to-noise ratio high enough to measure the profile of the DIB at 8620 Å, hence limiting the spatial information about the interstellar medium. We compare its equivalent width with extinction maps and with Bayesian reddening, calculated for individual stars, and provide a linear relation between the equivalent width and reddening. Separately from the introduced method, we calculate equivalent widths of the DIB in spectra of hot stars with known extinction and compare all three linear relations.

  9. Upper secondary students’ situational interest:

    DEFF Research Database (Denmark)

    Dohn, Niels Bonderup

    2013-01-01

    interest was investigated by a descriptive interpretive approach, based on data from classroom and field trip observations, video recording, and interviews. The findings provided evidence that substantial situational interest can be generated during a fieldtrip to a zoo. Students’ interest was triggered......This paper comprises a presentation of the findings of a case study that investigated how situational factors triggered 12th grade students’ interest during a field trip to a zoo. The purpose was to identify sources of interest and to investigate the attributes that make them interesting. Students....... The study implies that zoo visits can provide students with affective experiences, which can be a powerful way to stimulate students’ learning motivation....

  10. Arousing Students' Interest Through Games

    Institute of Scientific and Technical Information of China (English)

    李新清

    2013-01-01

    As is well known,interest is the best teacher and it can cause motivation. "Motivation is what moves the students from boredom to interest, It's something like engine and steering wheel of an automobile . "(Spolsky. B. 1989 ) So I decided to adopt some different kinds of games in my lessons to arouse the learners' interest and motivate them , and help them keep up their English learning.

  11. Supervising interest rate risk management

    OpenAIRE

    Lopez, Jose A.

    2004-01-01

    This Economic Letter reviews the Basel Capital Accord's stated principles on interest rate risk. In brief, the principles strongly support the idea that banks' internal risk assessments should, whenever possible, form the basis for supervisory oversight of their interest rate risk profiles. The principles suggest supervisory guidelines for assessing the adequacy of interest rate risk management systems, such as focusing on banks' internal control functions and stress-testing results.

  12. Interest Rate Determination in Lebanon

    OpenAIRE

    Tushar Poddar; Mangal Goswami; Juan Sole; Victor Echévarria Icaza

    2006-01-01

    This paper seeks to understand how interest rates are formed in Lebanon, by focusing on the pass-through from benchmark rates, prevailing liquidity conditions, and the main characteristics of the Lebanese economy, notably its open capital account, fixed exchange rate, high government borrowing requirement, large public debt, and high degree of deposit dollarization. We find that international interest rates are an important element in the determination of interest rates in Lebanon. In particu...

  13. Committed to the Public Interest?

    DEFF Research Database (Denmark)

    Holm Pedersen, Lene

    2014-01-01

    While politicians are often seen as being motivated by narrow self-interest, this article offers an alternative view. The relationship between two pro-social dimensions – Commitment to the Public Interest (CPI) and User Orientation (UO) – and behavioural outcomes among local councillors is analyzed....... The raison d'être for the local councils is to define the public interest. In line with this, CPI, which is directed towards doing good for the public interest, is associated with working hours and political influence; this is much less so for UO, which is directed towards doing good for individual citizens...

  14. Cosmic Rays and MHD Turbulence Generation in Interstellar Giant Molecular Clouds

    Science.gov (United States)

    Schlickeiser, R.; Caglar, M.; Lazarian, A.

    2016-06-01

    The diffusive propagation of nonrelativistic cosmic ray (CR) protons undergoing energy losses by ionization in a dense homogeneous infinitely extended interstellar molecular cloud (MC) is investigated. The steady-state transport equation for the differential number density of nonrelativistic CR protons is solved with the boundary condition that at the edge of cloud it agrees with the interstellar CR number density. It is shown that giant interstellar MCs with column depths much greater than about 7\\cdot {10}22 cm‑2 are an efficient sink of nonrelativistic CRs. At small penetration depths the CRs lose energy by ionizing and heating the molecular gas, whereas at large penetration depths they are collectively dissipated by the streaming instability, which transfers one-half of the energy density of the incoming interstellar nonrelativistic CRs to Alfvénic magnetic field turbulence.

  15. Quantum chemical analysis for the formation of glycine in the interstellar medium

    Institute of Scientific and Technical Information of China (English)

    Amresh Singh; Shivani; Alka Misra; Poonam Tandon

    2013-01-01

    Glycine (C2H5NO2) was the first amino acid to be detected in space by the stardust space probe in Comet Wild2,and is used by living organisms to make proteins.We discuss three different reaction paths for the formation of glycine in interstellar space from some simpler molecules detected in the interstellar medium.The possibility of the formation of glycine in interstellar space is considered by radicalradical and radical-molecule interaction schemes using quantum chemical calculations with density functional theory at the B3LYP/6-31G (d,p) level.In the chemical pathways we discuss,a few reactions are found to be totally exothermic and barrierless while others are endothermic with a very small reaction barrier,thus giving rise to a high probability of forming glycine in interstellar space.

  16. Dynamical interstellar medium with Gaia and ground-based massive spectroscopic stellar surveys

    CERN Document Server

    Zwitter, Tomaž

    2015-01-01

    The ongoing Gaia mission of ESA will provide accurate spatial and kinematical information for a large fraction of stars in the Galaxy. Interstellar extinction and line absorption studies toward a large number of stars at different distances and directions can give a 3-dimensional distribution map of interstellar absorbers, and thus reach a similar spatial perfection. Under certain morphologies (e.g. geometrically thin absorption curtains) one can infer a complete velocity vector from its radial velocity component and so obtain a dynamical information comparable to stars. But observations of a large number of stars at different distances are needed to determine the location of the absorption pockets. Therefore, techniques to measure interstellar absorptions towards (abundant) cool stars are needed. A complex mix of colliding absorption clouds is found in the Galactic plane. Thus, one would wish to start with deep observations to detect the weak, but simpler interstellar absorptions at high Galactic latitudes. ...

  17. Energy and mass balance in the three-phase interstellar medium

    Science.gov (United States)

    Wang, Zhong; Cowie, Lennox L.

    1988-01-01

    Details of the energy and mass balances are considered in the context of a three-phase interstellar medium. The rates of mass exchange between the different phases are derived based on the pressure variations created by supernova remnant expansions. It is shown that the pressure-confined warm and cold gases have stable temperatures under a variety of interstellar conditions. The three-phase quasi-static configuration is found to be a natural outcome, and both warm and cold phases generally contribute about half of the total mass density to the diffuse interstellar gas. The model is also likely to be self-regulatory in the sense that variations of the input parameters do not strongly alter the general result, which is consistent with most current observations. The consequences of extreme conditions on this model are considered, and the possible implications for interstellar medium in other galaxies are briefly discussed.

  18. Two-component model of the interaction of an interstellar cloud with surrounding hot plasma

    OpenAIRE

    Provornikova, E. A.; Izmodenov, V. V.; Lallement, R.

    2011-01-01

    We present a two-component gasdynamic model of an interstellar cloud embedded in a hot plasma. It is assumed that the cloud consists of atomic hydrogen gas, interstellar plasma is quasineutral. Hydrogen atoms and plasma protons interact through a charge exchange process. Magnetic felds and radiative processes are ignored in the model. The influence of heat conduction within plasma on the interaction between a cloud and plasma is studied. We consider the extreme case and assume that hot plasma...

  19. Density Studies of MHD Interstellar Turbulence: Statistical Moments, Correlations and Bispectrum

    OpenAIRE

    Burkhart, Blakesley; Falceta-Goncalves, D.; Kowal, G.; Lazarian, A.

    2008-01-01

    We present a number of statistical tools for obtaining studying turbulence in molecular clouds and diffuse interstellar medium. For our tests we used of three-dimensional 512 cube compressible MHD isothermal simulations performed for different sonic and Alfvenic Mach numbers. We introduce the bispectrum, a new tool for statistical studies of the interstellar medium which, unlike an ordinary power spectrum of turbulence, preserves the phase information of the stochastic field. We show that the...

  20. A Fluorescent Aerogel for Capture and Identification of Interplanetary and Interstellar Dust

    CERN Document Server

    Dominguez, G; Phillips, M L F; Jones, S M; Dominguez, Gerardo; Westphal, Andrew J.; Phillips, Mark L.F.; Jones, Steven M.

    2003-01-01

    Contemporary interstellar dust has never been analyzed in the laboratory, despite its obvious astronomical importance and its potential as a probe of stellar nucleosynthesis and galactic chemical evolution. Here we report the discovery of a novel fluorescent aerogel which is capable of capturing hypervelocity dust grains and passively recording their kinetic energies. An array of these "calorimetric" aerogel collectors in low earth orbit would lead to the capture and identification of large numbers of interstellar dust grains.