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  • 1
    Electronic Resource
    Electronic Resource
    Crossed-beam reaction of carbon atoms with hydrocarbon molecules. IV. Chemical dynamics of methylpropargyl radical formation, C4H5, from reaction of C(3Pj) with propylene, C3H6 (X 1A) (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 4945-4953 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The reaction between ground state carbon atoms and propylene, C3H6, was studied at average collision energies of 23.3 and 45.0 kJ mol−1 using the crossed molecular beam technique. Product angular distributions and time-of-flight spectra of C4H5 at m/e=53 were recorded. Forward-convolution fitting of the data yields a maximum energy release as well as angular distributions consistent with the formation of methylpropargyl radicals. Reaction dynamics inferred from the experimental results suggest that the reaction proceeds on the lowest 3A surface via an initial addition of the carbon atom to the π-orbital to form a triplet methylcyclopropylidene collision complex followed by ring opening to triplet 1,2-butadiene. Within 0.3–0.6 ps, 1,2-butadiene decomposes through carbon–hydrogen bond rupture to atomic hydrogen and methylpropargyl radicals. The explicit identification of C4H5 under single collision conditions represents a further example of a carbon–hydrogen exchange in reactions of ground state carbon with unsaturated hydrocarbons. This versatile machine represents an alternative pathway to build up unsaturated hydrocarbon chains in combustion processes, chemical vapor deposition, and in the interstellar medium. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473543
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  • 2
    Electronic Resource
    Electronic Resource
    Crossed beam reaction of atomic carbon C(3Pj) with hydrogen sulfide, H2S(X1A1): Observation of the thioformyl radical, HCS(X2A′) (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 5288-5291 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: One of the simplest organosulfur reactions, that between ground state carbon atoms, C(3Pj), and hydrogen sulfide, H2S(X1A1), was studied at an average collision energy of 21.0 kJ mol−1 using the crossed molecular beams technique. The product angular distribution and time-of-flight spectra of m/e=45 (HC32S) were monitored. Forward-convolution fitting of our data yields an almost isotropic center-of-mass angular flux-distribution, whereas the center-of-mass translational energy flux distribution peaks at about 50 kJ mol−1, indicating a tight exit transition state from the decomposing thiohydroxycarbene HCSH complex to the reaction products. The high energy cut-off of the translational energy flux distribution is consistent with the formation of the thioformyl radical HCS in its X2A electronic ground state. The first experimental verification of an existing thiohydroxycarbene intermediate and the rigorous assignment of the HCS radical product under single collision conditions explicitly suggest inclusion of the title reaction in chemical reaction networks of molecular clouds TMC-1 and OMC-1, the outflow of the carbon star IRC+10216, Shoemaker/Levy 9 impact-induced nonequilibrium sulfur chemistry in the Jovian atmosphere, as well as combustion of sulfur containing coal.© 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473561
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  • 3
    Electronic Resource
    Electronic Resource
    Crossed-beam reaction of carbon atoms with hydrocarbon molecules. III: Chemical dynamics of propynylidyne (l-C3H;X 2Πj) and cyclopropynylidyne (c-C3H;X 2B2) formation from reaction of C(3Pj) with acetylene, C2H2(X 1Σg+) (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 1729-1741 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The reaction between ground state carbon atoms, C(3Pj), and acetylene, C2H2(X 1Σg+), is studied at three collision energies between 8.8 and 45.0 kJ mol−1 using the crossed molecular beams technique. Product angular distributions and time-of-flight spectra of C3H at m/e=37 are recorded. Forward-convolution fitting of the data yields weakly polarized center-of-mass angular flux distributions decreasingly forward scattered with respect to the carbon beam as the collision energy rises from 8.8 to 28.0 kJ mol−1, and isotropic at 45.0 kJ mol−1. Reaction dynamics inferred from the experimental data and ab initio calculations on the triplet C3H2 and doublet C3H potential energy surface suggest two microchannels initiated by addition of C(3Pj) either to one acetylenic carbon to form s-trans propenediylidene or to two carbon atoms to yield triplet cyclopropenylidene via loose transition states located at their centrifugal barriers. Propenediylidene rotates around its B/C axis and undergoes [2,3]-H-migration to propargylene, followed by C–H bond cleavage via a symmetric exit transition state to l-C3H(X 2Πj) and H. Direct stripping dynamics contribute to the forward-scattered second microchannel to form c-C3H(X 2B2) and H. This contribution is quenched with rising collision energy. The explicit identification of l-C3H(X 2Πj) and c-C3H(X 2B2) under single collision conditions represents a one-encounter mechanism to build up hydrocarbon radicals in the interstellar medium and resembles a more realistic synthetic route to interstellar C3H isomers than hitherto postulated ion–molecule reactions. Relative reaction cross sections to the linear versus cyclic isomer correlate with actual astronomical observations and explain a higher [c-C3H]/[l-C3H] ratio in the molecular cloud TMC-1 ((approximate)1) as compared to the circumstellar envelope surrounding the carbon star IRC+10216 ((approximate)0.2) via the atom-neutral reaction C(3Pj)+C2H2(X 1Σg+). © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474092
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  • 4
    Electronic Resource
    Electronic Resource
    Crossed beam reaction of atomic carbon, C(3Pj), with the propargyl radical, C3H3(X 2B2): Observation of diacetylene, C4H2(X 1Σg+) (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 8713-8716 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The reaction of ground-state carbon, C(3Pj), with the propargyl radical, C3H3(X 2B2), is investigated at an average collision energy of 42.0 kJmol−1 employing the crossed molecular beams technique and a universal mass spectrometric detector. The laboratory angular distribution and time-of-flight spectra of the C4H2 product are recorded at m/e=50. Forward-convolution fitting of our data reveals the formation of diacetylene, HCCCCH, in its X1Σg+ electronic ground state. The reaction dynamics are governed by an initial attack of C(3Pj) to the π-electron density at the acetylenic carbon atom of the propargyl radical, followed by a [1,2]-hydrogen migration to the n-C4H3 isomer. A final carbon–hydrogen bond rupture yields atomic hydrogen and diacetylene through a tight exit transition state located 30–60 kJmol−1 above the products. This first successful crossed molecular beams study of a reaction between an atom and a free radical marks the beginning of the next generation of crossed beams experiments elucidating the formation of molecular species in combustion processes, chemical vapor deposition, in the interstellar medium, outflows of carbon stars, and hydrocarbon-rich planetary atmospheres via radical–radical reactions. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475025
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  • 5
    Electronic Resource
    Electronic Resource
    Vaskulitische Verlaufsform einer Neuroborreliose mit Thalamusinfarkt (1997)
    Springer
    Der Nervenarzt 68 (1997), S. 339-341 
    Details
    ISSN: 1433-0407
    Keywords: Schlüsselwörter Neuroborreliose ; Zerebrale Vaskulitis ; Thalamusinfarkt ; Key words Neuroborreliosis ; Cerebral vasculitis ; Thalamic infarction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary A 20-year-old man without vascular risk factors presented with paraesthesia of the left side of the body with acute onset. Cerebral magnetic resonance imaging showed an infarction in the right thalamus. Intra-arterial digital subtraction angiography revealed stenosis of the right thalamic vessels. Recent infection by Borrelia burgdorferi was demonstrated by typical findings in the cerebrospinal fluid: lymphocytic pleocytosis and intrathecal synthesis of borrelial-specific antibodies. The diagnosis of a borrelial-induced vasculitis with secondary thalamic infarction was made from these findings. After antibiotic treatment with cefrtriaxone, the patient was discharged without residual complaints.
    Notes: Zusammenfassung Bei einem 20jährigen Mann ohne Gefäßrisikofaktoren war es zum akuten Auftreten von Parästhesien der linken Körperhälfte gekommen. Die zerebrale Magnetresonanztomographie (MRT) zeigte einen Thalamusinfarkt rechts. Die intraarterielle digitale Subrationsangiographie (DSA) erbrachte Hinweise für eine Stenosierung thalamischer Gefäße rechts. Eine Borrelia-burgdorferi-Infektion konnte durch typische Liquorbefunde (lymphozytäre Pleozytose, intrathekale Synthese borrelienspezifischer Antikörper) nachgewiesen werden. Gestützt auf diese Befunde wurde die Diagnose einer borrelien-induzierte Vaskulitis mit sekundärem Thalamusinfarkt gestellt. Nach Durchführung einer antibiotischen Behandlung mit Ceftriaxon konnte der Patient ohne neurologische Auffälligkeiten entlassen werden.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001150050133
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  • 6
    Electronic Resource
    Electronic Resource
    Verlauf und Prognose der FSME (1997)
    Springer
    Der Nervenarzt 68 (1997), S. 324-330 
    Details
    ISSN: 1433-0407
    Keywords: Schlüsselwörter FSME ; Klinische Prognose ; Neuropsychologische Testung ; Key words Tick-borne encephalitis ; Clinical outcome ; Neuropsychological testing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Sixty-three patients with tick-borne encephalitis were studied for sequelae up to 5 years after the acute illness (median: 12 months, range: 1–44 months). Patients were examined clinically, by neuropsychological testing and by electroencephalography. The clinical presentation during the acute stage was as follows: Meningitis (M, n=12), Meningoencephalitis (Me, n=27), Meningoencephalomyelitis (My, n=15), and Meningoencephaloradiculitis (R, n=9). A total of 59 patients reported a neurasthenic syndrome after discharge, which correlated with the severity of the acute illness. Twenty patients were not able to work because of reduced stress tolerance, fatigue or an elevated emotional sensitivity, which lasted for 3 months at most. In some patients hypacusis (n=7), severe dysarthria and dysphagia (n=4) remained essentially unimproved for years following the acute illness. While in 8/9 patients with radiculitis paresis of the extremities improved well over months to years, improvement was quite limited in all patients with myelitis. In 41/55 patients, investigations by electroencephalography revealed normal findings even within months after acute illness. Persistent cognitive deficits were present only in 7/11 patients with a severe course of disease.
    Notes: Zusammenfassung Mit der Frage möglicher Folgeschäden wurden 63 Patienten, die zwischen 1990 und 1995 an einer FSME erkrankt waren, klinisch, neuropsychologisch und elektroenzephalographisch nachuntersucht (Intervall zur akuten Erkrankung: Median: 12 Monate, Spanne: 1–44 Monate). Während der akuten Erkrankungsphase lagen folgende klinische Syndrome vor: Meningitis (M, n=12), Meningoenzephalitis (Me, n=27), Meningoenzephalomyelitis (My, n=15) und Meningoenzephaloradikulitis (R, n=9). Anamnestisch bestand bei 59 Patienten nach der Entfieberung ein neurasthenisches Syndrom, welches in Ausprägung und Dauer eine Korrelation zur Schwere der akuten Erkrankung zeigte. 20 Patienten waren nach der Entlassung aus der Klinik allein aufgrund einer erheblichen subjektiven Leistungsminderung, einer vermehrten Erschöpfbarkeit und einer erhöhten emotionalen Labilität bis zu 3 Monate arbeitsunfähig. Bei der Nachuntersuchung fanden sich bei 34 Patienten (M: 1, Me: 9, My: 15, R: 9) pathologische Befunde im neurologischen Status. Persistierende Störungen der Hirnnerven äußerten sich als Hypakusis (n=7), Dysphagie und Dysarthrie (n=4). Während die Extremitätenparesen bei 8/9 Patienten mit einer Radikulitis innerhalb von wenigen Monaten bis Jahren eine fast vollständige Rückbildung zeigten, war die Besserungstendenz der Para- und Tetraparesen bei der Myelitis auch nach bis zu 3 Jahren deutlich geringer. Elektroenzephalographisch war bei 41/55 nachuntersuchten Patienten bereits nach wenigen Monaten ein Normalbefund zu erheben. Überdauernde, objektivierbare kognitive Defizite bestanden nur bei 7/11 Patienten mit schwerer Verlaufsform einer FSME.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001150050130
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  • 7
    Electronic Resource
    Electronic Resource
    Discovery of utmost inner time precision in chromatography (1997)
    Springer
    Fresenius' journal of analytical chemistry 359 (1997), S. 208-212 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An up to now unknown high “inner time precision” in isocratic gas chromatography (GC) and high pressure column liquid chromatography (HPLC) has been realized using quartz clock driven A/D converters and special statistically evaluating integration software. This millisecond level inner time precision is detectable by two very linear data correlations: a) the log of adjusted retention times (log(t R′)) versus the molecular weight of separated members of homologues and b) the peak width at half height versus correct k-values of the homologues. The inner time precision at the millisecond level is not lost by slight errors (up to seconds) in the starting times of GC or HPLC determinations. The correlation coefficient of the two linear data correlations allows a thorough analysis of instrument quality. The highly linear correlation of peak width and k in a wide range of mobile phase speeds is in disagreement with theoretical models of chromatography. Especially the rule of variance additivity is not valid in isocratic elution chromatography.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160050562
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  • 8
    Electronic Resource
    Electronic Resource
    Vergleich von Valsalva-Manöver und distaler Dekompression zur Refluxprüfung der V. saphena magna (1997)
    Springer
    Gefässchirurgie 2 (1997), S. 204-207 
    Details
    ISSN: 1434-3932
    Keywords: Key words Superior saphenous vein ; Reflux-assessment ; Duplex sonography ; Phlebography ; Schlüsselwörter V. saphena magna ; Refluxprüfung ; Duplexsonographie ; Phlebographie
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Fragestellung: Eine differenzierte Indikation der verschiedenen Manöver zur Prüfung des Refluxes der V. saphena magna wird in der Literatur nicht angegeben, könnte aber klinisch relevant sein. Material und Methoden: Im Screening haben wir bei 19 Patienten eine Diskrepanz zwischen Valsalva-Manöver und distaler Dekompression gefunden. 7 dieser Patienten zeigten eine CVI Grad 2 oder 3. In der Untersuchung haben wir die Refluxdauer duplex-sonographisch bei Anwendung von Valsalva-Manöver, distaler Dekompression manuell und mittels Blutdruckmanschette sowie durch Aktivierung der Wadenmuskelsprunggelenkspumpe verglichen. Ergebnisse: Der Refluxmittelwert zeigte beim Valsalva-Manöver eine „early incompetence“ unter 1 s, bei den 3 distalen Manövern durchgehend pathologische Refluxe. Eine aszendierende Phlebographie war in einem Fall nicht beurteilbar, zeigte bei 8 Phlebogrammen keinen Reflux, bei 2 Beinen einen Reflux. Schlußfolgerung: Das Valsalva-Manöver, sei es duplexsonographisch, sei es phlebographisch dokumentiert, erfaßt einen Teil der klinisch relevanten Refluxe der V. saphena magna nicht. Die distalen Manöver erscheinen sensitiver zum Erfassen einer klinisch relevanten Insuffizienz der V. saphena magna.
    Notes: Abstract A differentiated indication for different maneuvers for assessment of reflux of the superior saphenous vein is not mentioned in medical publications, although this might be clinically important. In a screening examination 19 patients were found to show a discrepancy between results using Valsalva maneuver and distal decompression. Of these patients 7 had chronic venous insufficiency grade II or III. Our study analyzed the time of reflux following Valsalva maneuver, pneumatic and manual distal decompression of the calf and calf muscle activation. Mean values of reflux following Valsalva maneuver were less than 1 s. The three distal maneuvers showed comparable pathologic lengths of reflux. In one ascending phlebography reflux of the superior saphenous vein could not be assessed; 8 phlebographies showed no reflux, and 2 did. We conclude that Valsalva maneuver, whether documented sonographically or by phlebography, misses reflux of the superior saphenous vein in some clinically relevant cases. Distal maneuvers seem to be more sensitive in determining clinically important reflux of the superior saphenous vein.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007720050037
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