During the dawn of chemistry
, when the temperature of the young Universe had fallen below some 4,000 kelvin, the ions of the light elements produced in Big Bang nucleosynthesis recombined in reverse ...order of their ionization potential. With their higher ionization potentials, the helium ions He
and He
were the first to combine with free electrons, forming the first neutral atoms; the recombination of hydrogen followed. In this metal-free and low-density environment, neutral helium atoms formed the Universe's first molecular bond in the helium hydride ion HeH
through radiative association with protons. As recombination progressed, the destruction of HeH
created a path to the formation of molecular hydrogen. Despite its unquestioned importance in the evolution of the early Universe, the HeH
ion has so far eluded unequivocal detection in interstellar space. In the laboratory the ion was discovered
as long ago as 1925, but only in the late 1970s was the possibility that HeH
might exist in local astrophysical plasmas discussed
. In particular, the conditions in planetary nebulae were shown to be suitable for producing potentially detectable column densities of HeH
. Here we report observations, based on advances in terahertz spectroscopy
and a high-altitude observatory
, of the rotational ground-state transition of HeH
at a wavelength of 149.1 micrometres in the planetary nebula NGC 7027. This confirmation of the existence of HeH
in nearby interstellar space constrains our understanding of the chemical networks that control the formation of this molecular ion, in particular the rates of radiative association and dissociative recombination.
In recent years, a plethora of observations with high spectral resolution of sub-millimetre and far-infrared transitions of methylidene (CH), conducted with Herschel and SOFIA, have demonstrated this ...radical to be a valuable proxy for molecular hydrogen that can be used for characterising molecular gas within the interstellar medium on a Galactic scale, including the CO-dark component. We report the discovery of the 13CH isotopologue in the interstellar medium using the upGREAT receiver on board SOFIA. We have detected the three hyperfine structure components of the ≈2 THz frequency transition from its X2Π1∕2 ground-state towards the high-mass star-forming regions Sgr B2(M), G34.26+0.15, W49(N), and W51E and determined 13CH column densities. The ubiquity of molecules containing carbon in the interstellar medium has turned the determination of the ratio between the abundances of the two stable isotopes of carbon, 12C/13C, into a cornerstone for Galactic chemical evolution studies. Whilst displaying a rising gradient with galactocentric distance, this ratio, when measured using observations of different molecules (CO, H2CO, and others), shows systematic variations depending on the tracer used. These observed inconsistencies may arise from optical depth effects, chemical fractionation, or isotope-selective photo-dissociation. Formed from C+ either through UV-driven or turbulence-driven chemistry, CH reflects the fractionation of C+, and does not show any significant fractionation effects, unlike other molecules that were previously used to determine the 12C/13C isotopic ratio. This makes it an ideal tracer for the 12C/13C ratio throughout the Galaxy. By comparing the derived column densities of 13CH with previously obtained SOFIA data of the corresponding transitions of the main isotopologue 12CH, we therefore derive 12C/13C isotopic ratios toward Sgr B2(M), G34.26+0.15, W49(N) and W51E. Adding our values derived from 12∕13CH to previous calculations of the Galactic isotopic gradient, we derive a revised value of 12C/13C = 5.87(0.45)RGC + 13.25(2.94).
Abstract
Atomic oxygen is a key species in the mesosphere and thermosphere of Venus. It peaks in the transition region between the two dominant atmospheric circulation patterns, the retrograde ...super-rotating zonal flow below 70 km and the subsolar to antisolar flow above 120 km altitude. However, past and current detection methods are indirect and based on measurements of other molecules in combination with photochemical models. Here, we show direct detection of atomic oxygen on the dayside as well as on the nightside of Venus by measuring its ground-state transition at 4.74 THz (63.2 µm). The atomic oxygen is concentrated at altitudes around 100 km with a maximum column density on the dayside where it is generated by photolysis of carbon dioxide and carbon monoxide. This method enables detailed investigations of the Venusian atmosphere in the region between the two atmospheric circulation patterns in support of future space missions to Venus.
Die globalisierte Fertigung beruht auf einer eindeutigen Produktbeschreibung. Fertigungsunterlagen müssen überall gelesen und gleich interpretiert werden. Das Normenwerk hat hierzu das Konzept der ...Geometrischen Produktspezifizierung (GPS) geschaffen. Die GPS-Regeln geben vor, wie Bauteile dimensionell, geometrisch und oberflächentechnologisch zu beschreiben sind. Hierzu wurden eine Vielzahl von Normen und Kurzzeichen geschaffen, die ein Konstrukteur als spezielles Wissen beherrschen und als Beschreibungssprache erlernen muss. Dieses Buch stellt das Tolerierungssystem im Zusammenhang dar, leistet Hilfestellung bei der Interpretation wesentlicher Normen und der Nutzung von Tolerierungsprinzipien und zeigt die Anwendung anhand von konkreten Beispiele, so dass die gewünschte Bauteilfunktionalität letztlich auch gewährleistet ist. Durch die Darlegung des DIN-ISO- und des ASME-Konzeptes auch in der CAD- Konstruktion ist das Buch inhaltlich hoch aktuell.
Der Leitgedanke von TRIZ ist es, Problemstellungen zu strukturieren und dadurch Lösungszeiten zu verkürzen. TRIZ steht für "Theorie des erfinderischen Problemlösens". Die Methode wurde von dem ...russischen Wissenschaftler und Erfinder G. S. Altschuller konzipiert. TRIZ basiert auf der Analyse von ca. 2 Millionen Patenten und ist ein systematischer Ansatz zur Entwicklung neuer Produkte. TRIZ bietet eine breite Palette an Werkzeugen zur strategischen Produktplanung. Die Werkzeuge unterstützen Konstrukteure und Entwickler, neue Produktideen umzusetzen und neue, patentfähige Konzepte zu realisieren. TRIZ trägt dazu bei, daß Denkbarrieren überwunden und die Ergebnisse anderer Fachgebiete genutzt werden - und TRIZ hilft Führungskräften und Entscheidungsträgern aller Sparten, die Produktivität und Wirtschaftlichkeit ihrer Bereiche zu steigern. Ob die Methode konventionell oder softwareunterstützt betrieben wird, hängt ganz von der individuellen Entscheidung des Anwenders ab. Mittlerweile wird TRIZ in zahlreichen Unternehmen und in allen Branchen erfolgreich als Instrument eingesetzt. Das vorliegende Buch wendet sich an Ingenieure, in deren Verantwortung die Findung und Einführung neuer Produkte liegt, und an Studenten der Konstruktionstechnik, die TRIZ in ihrem Berufsleben erfolgreich einsetzen wollen.
Haben die Konstrukteure früher mit Worten auf der Zeichnung vermerkt, was zur Herstellung relevant war, so müssen heute Fertigungsanmerkungen weltweit verständlich sein. Die Inhalte der hierfür ...geschaffenen DIN EN ISO-Normen zu vermitteln ist Ziel dieses Buches.
High-latitude intermediate-velocity clouds (IVCs) are part of the Milky Way’s H I halo and originate from either a galactic fountain process or extragalactic gas infall. They are partly molecular and ...can most of the time be identified in CO. Some of these regions also exhibit high-velocity cloud gas, which is mostly atomic, and gas at local velocities (LVCs), which is partly atomic and partly molecular. We conducted a study on the IVCs Draco and Spider, both were exposed to a very weak UV field, using the spectroscopic receiver upGREAT on the Stratospheric Observatory for Infrared Astronomy (SOFIA). The 158 µm fine-structure line of ionized carbon (C II ) was observed, and the results are as follows: In Draco, the C II line was detected at intermediate velocities (but not at local or high velocities) in four out of five positions. No C II emission was found at any velocity in the two observed positions in Spider. To understand the excitation conditions of the gas in Draco, we analyzed complementary CO and H I data as well as dust column density and temperature maps from Herschel . The observed C II intensities suggest the presence of shocks in Draco that heat the gas and subsequently emit in the C II cooling line. These shocks are likely caused by the fast cloud’s motion toward the Galactic plane that is accompanied by collisions between H I clouds. The nondetection of C II in the Spider IVC and LVC as well as in other low-density clouds at local velocities that we present in this paper (Polaris and Musca) supports the idea that highly dynamic processes are necessary for C II excitation in UV-faint low-density regions.
Der Leitgedanke von TRIZ ist es, Problemstellungen zu strukturieren und dadurch Lösungszeiten zu verkürzen. TRIZ steht für "Theorie des erfinderischen Problemlösens". Die Methode wurde von dem ...russischen Wissenschaftler und Erfinder G. S. Altschuller konzipiert. TRIZ basiert auf der Analyse von ca. 2 Millionen Patenten und ist ein systematischer Ansatz zur Entwicklung neuer Produkte. TRIZ bietet eine breite Palette an Werkzeugen zur strategischen Produktplanung. Die Werkzeuge unterstützen Konstrukteure und Entwickler, neue Produktideen umzusetzen und neue, patentfähige Konzepte zu realisieren. TRIZ trägt dazu bei, daß Denkbarrieren überwunden und die Ergebnisse anderer Fachgebiete genutzt werden - und TRIZ hilft Führungskräften und Entscheidungsträgern aller Sparten, die Produktivität und Wirtschaftlichkeit ihrer Bereiche zu steigern. Ob die Methode konventionell oder softwareunterstützt betrieben wird, hängt ganz von der individuellen Entscheidung des Anwenders ab. Mittlerweile wird TRIZ in zahlreichen Unternehmen und in allen Branchen erfolgreich als Instrument eingesetzt. Das vorliegende Buch wendet sich an Ingenieure, in deren Verantwortung die Findung und Einführung neuer Produkte liegt, und an Studenten der Konstruktionstechnik, die TRIZ in ihrem Berufsleben erfolgreich einsetzen wollen.
In recent years, a plethora of observations with high spectral resolution of sub-millimetre and far-infrared transitions of methylidene (CH), conducted with
Herschel
and SOFIA, have demonstrated this ...radical to be a valuable proxy for molecular hydrogen that can be used for characterising molecular gas within the interstellar medium on a Galactic scale, including the CO-dark component. We report the discovery of the
13
CH isotopologue in the interstellar medium using the upGREAT receiver on board SOFIA. We have detected the three hyperfine structure components of the ≈2 THz frequency transition from its X
2
Π
1∕2
ground-state towards the high-mass star-forming regions Sgr B2(M), G34.26+0.15, W49(N), and W51E and determined
13
CH column densities. The ubiquity of molecules containing carbon in the interstellar medium has turned the determination of the ratio between the abundances of the two stable isotopes of carbon,
12
C/
13
C, into a cornerstone for Galactic chemical evolution studies. Whilst displaying a rising gradient with galactocentric distance, this ratio, when measured using observations of different molecules (CO, H
2
CO, and others), shows systematic variations depending on the tracer used. These observed inconsistencies may arise from optical depth effects, chemical fractionation, or isotope-selective photo-dissociation. Formed from C
+
either through UV-driven or turbulence-driven chemistry, CH reflects the fractionation of C
+
, and does not show any significant fractionation effects, unlike other molecules that were previously used to determine the
12
C/
13
C isotopic ratio. This makes it an ideal tracer for the
12
C/
13
C ratio throughout the Galaxy. By comparing the derived column densities of
13
CH with previously obtained SOFIA data of the corresponding transitions of the main isotopologue
12
CH, we therefore derive
12
C/
13
C isotopic ratios toward Sgr B2(M), G34.26+0.15, W49(N) and W51E. Adding our values derived from
12∕13
CH to previous calculations of the Galactic isotopic gradient, we derive a revised value of
12
C/
13
C = 5.87(0.45)
R
GC
+ 13.25(2.94).