Search Results - (Author, Cooperation:M. Helmer)

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  1. 1
    R. Daw ; J. Finkelstein ; M. Helmer
    Nature Publishing Group (NPG)
    Published 2012
    Staff View
    Publication Date:
    2012-08-17
    Publisher:
    Nature Publishing Group (NPG)
    Print ISSN:
    0028-0836
    Electronic ISSN:
    1476-4687
    Topics:
    Biology
    Chemistry and Pharmacology
    Medicine
    Natural Sciences in General
    Physics
    Keywords:
    Climate Change ; Communicable Diseases/epidemiology ; Conservation of Energy Resources/*methods/*trends ; Floods ; Food Supply ; Fossil Fuels/utilization ; *Renewable Energy/statistics & numerical data ; Water Supply
    Published by:
    Latest Papers from Table of Contents or Articles in Press
  2. 2
    Helmer, M. ; Plane, J. M. C.

    College Park, Md. : American Institute of Physics (AIP)
    Published 1993
    Staff View
    ISSN:
    1089-7690
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Chemistry and Pharmacology
    Notes:
    The reaction K+HCl→KCl+H was studied by the pulsed photodissociation at 193.3 nm of KCl vapor to produce K atoms in an excess of HCl and He bath gas, followed by time-resolved laser induced fluorescence spectroscopy of atomic K at 766.5 nm [K(4 2P3/2–4 1S1/2)]. The HCl concentration was monitored by absorption spectroscopy at 184.9 nm. This reaction exhibits non-Arrhenius behavior, with the rate coefficient being given by k(252 K〈T〈780 K)=(1.69±0.52)×10−10 exp[−(15.21±2.00) kJ mol−1/RT]+(1.51±0.12)×10−11 exp[−(4.94±1.72) kJ mol−1/RT] cm3 molecule−1 s−1. The quoted uncertainties are 2σ. This result is in very good accord with several molecular beam studies, whose relative reaction cross sections can now be put onto an absolute basis. Ab initio calculations were then employed to determine the saddle points on the reaction potential energy hypersurface as a function of the K–Cl–H angle. There is a marked steric effect, with the reaction proceeding through a linear transition state or one that is strongly bent (θKClH=49.1°). The reaction is also characterized by a late barrier, in accord with the observed enhancement of the reaction cross section by vibrational excitation of the HCl. Transition state theory calculations with the linear transition state are shown to be in excellent accord with the experimental results, and indicate that the non-Arrhenius behavior of the reaction is caused by a very loose transition state, rather than a significant contribution to the reaction from vibrationally excited HCl at higher temperatures. Finally, the influence of the reverse reaction on the chemistry of meteor-ablated potassium in the upper atmosphere is discussed.
    Type of Medium:
    Electronic Resource
    URL:
    Articles: DFG German National Licenses
  3. 3
    Denk, W. ; Helmer, M. ; Missliwetz, J.
    Springer
    Published 1990
    Staff View
    ISSN:
    1437-1596
    Keywords:
    Choke holds ; Obstruction of neck arteries in the ultrasonic continous-wave doppler ; Unterarmwürgen ; Obstruktion der arteriellen Halsgefäße im CW-Doppler
    Source:
    Springer Online Journal Archives 1860-2000
    Topics:
    Medicine
    Law
    Description / Table of Contents:
    Zusammenfassung Mittels Dopplersonographie wird der Einfluβ zweier Unterarmwürgetechniken auf die Durchblutung der Carotiden and Vertebralarterien untersucht. Hierbei ergibt sich fur Würgegriffe, bei denen der Arm dem Hals schräg anliegt eine bis zum Perfusionsstop reichende Durchblutungsminderung beider Gefäβe, die in ihrem Ausmaβ durch die Richtung der Kraftausübung zu beeinflussen ist. Als weitere relevante Faktoren werden Anspannung der Halsmuskulatur des Gewürgten sowie andere Abwehrmaβ-nahmen diskutiert. In der schnittbildsonographischen Darstellung zeigt sich die Vertebralarterie zwischen ihrem Abgang aus der Subclavia and dem Eintritt in die Foramina transversaria der Halswirbelquerfortsätze ungeschiitzt und komprimierbar.
    Notes:
    Summary By means of continous wave doppler the effect of two choke holds (Carotid sleeper, Nami-juji-jime) on the carotid and vertebral arteries was investigated. For both choke holds, which are characterized by pressure on lateral parts of the neck, we found an obstruction up to a complete stop of flow. The degree of obstruction depended on the direction of force. The vertebral artery can be compressed between the subclavian artery and the foramina transversaria, therefore it was most effective to press on the lower neck. Tensing the neck muscles can reduce the effect of choking.
    Type of Medium:
    Electronic Resource
    URL:
    Articles: DFG German National Licenses
  4. 4
    Denk, W. ; Helmer, M. ; Missliwetz, J.
    Springer
    Published 1990
    Staff View
    ISSN:
    1437-1596
    Keywords:
    Choke holds ; Obstruction of neck arteries in the ultrasonic continous-wave doppler ; Unterarmwürgen ; Obstruktion der arteriellen Halsgefäßeim CW-Doppler
    Source:
    Springer Online Journal Archives 1860-2000
    Topics:
    Medicine
    Law
    Description / Table of Contents:
    Zusammenfassung Mittels Dopplersonographie wird der Einfluß zweier Unterarmwürgetechniken auf die Durchblutung der Carotiden und Vertebralarterien untersucht. Hierbei ergibt sich für Würgegriffe, bei denen der Arm dem Hals schräg anliegt eine bis zum Perfusionsstop reichende Durchblutungsminderung beider Gefäße, die in ihrem Ausmaß durch die Richtung der Kraftausübung zu beeinflussen ist. Als weitere relevante Faktoren werden Anspannung der Halsmuskulatur des Gewürgten sowie andere Abwehrmaßnahmen diskutiert. In der schnittbildsonographischen Darstellung zeigt sich die Vertebralarterie zwischen ihrem Abgang aus der Subclavia und dem Eintritt in die Foramina transversaria der Halswirbelquerfortsätze ungeschützt und komprimierbar.
    Notes:
    Summary By means of continous wave doppler the effect of two choke holds (Carotid sleeper, Nami-juji-jime) on the carotid and vertebral arteries was investigated. For both choke holds, which are characterized by pressure on lateral parts of the neck, we found an obstruction up to a complete stop of flow. The degree of obstruction depended on the direction of force. The vertebral artery can be compressed between the subclavian artery and the foramina transversaria, therefore it was most effective to press on the lower neck. Tensing the neck muscles can reduce the effect of choking.
    Type of Medium:
    Electronic Resource
    URL:
    Articles: DFG German National Licenses
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    Helmer, M[arie]

    Madrid : Periodicals Archive Online (PAO)
    Published 1952
    Staff View
    ISSN:
    0034-8341
    Topics:
    Ethnic Sciences
    Description / Table of Contents:
    RESEÑAS DE LIBROS
    Notes:
    Sección bibliográfica
    URL:
    Articles: DFG German National Licenses
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  10. 10
    Helmer, M[arie]

    Madrid : Periodicals Archive Online (PAO)
    Published 1952
    Staff View
    ISSN:
    0034-8341
    Topics:
    Ethnic Sciences
    Description / Table of Contents:
    RESEÑAS DE LIBROS
    Notes:
    Sección bibliográfica
    URL:
    Articles: DFG German National Licenses
  11. 11
    HELMER, M[ARIE]

    Madrid : Periodicals Archive Online (PAO)
    Published 1952
    Articles: DFG German National Licenses