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  • 1
    Electronic Resource
    Electronic Resource
    Approximate molecular orbital theory for positrons and positronium atoms bound to molecules (1976)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 80 (1976), S. 2507-2518 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100563a016
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  • 2
    Electronic Resource
    Electronic Resource
    Magnetic effects on positronium formation and annihilation in organic liquids (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 289-295 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: It was recently found that an external magnetic field markedly enhances the orthopositronium annihilation rate in certain organic solutions above and beyond that expected for the Zeeman effect. Several solutions have been studied, but the effect has been found only for nitrobenzene in n-hexane. A mechanism for this is proposed and tested numerically with a kinetics scheme modified to include nonhomogeneous spur effects. The mechanism features the quenching of orthopositronium by a short-lived triplet solute species, the concentration of which is moderated by the applied magnetic field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460396
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  • 3
    Electronic Resource
    Electronic Resource
    Temperature effects in positronium formation and lifetime in solutions of nonpolar organic solvents (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 7801-7809 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The temperature dependence of the positron annihilation lifetime (PAL) spectra of several solutions are examined. Four solvents are investigated: n-hexane, cyclohexane, squalane, and an equivolume mixture of n-hexane and squalane. Solutes in the study are nitrobenzene, nitrocyclohexane, and hexafluorobenzene. Arrhenius plots of lifetimes are made from 10 °C to 50 °C. The temperature dependence of the PAL spectra of nitrobenzene solutions in a magnetic field varying up to 15 kG are also presented. Anomalous behavior is observed for the solvents n-hexane and squalane, both neat and with nitrobenzene as a solute. In addition, it is found that the behavior of neat and nitrobenzene solutions of the n-hexane–squalane mixture is not intermediate between those involving n-hexane and squalane separately. We conclude that there is a change in the mechanism for positronium formation from n-hexane to squalane which is not accounted for by changes in free volume. Nitrocyclohexane is found to enhance positronium formation in squalane. This is the first example of antiinhibition by an aliphatic solute known to the authors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460166
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  • 4
    Electronic Resource
    Electronic Resource
    Binding energies of positronium fluoride and positronium bromide by the model potential quantum Monte Carlo method (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 7185-7190 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A method previously used by the authors in an accurate calculation of the binding energy of positronium chloride [Phys. Rev. Lett. 68, 3281 (1992)] is applied to positronium fluoride and positronium bromide. The binding energies obtained with this method are PsF, 1.98±0.17 eV; PsCl, 1.91±0.16 eV; PsBr, 1.14±0.11 eV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.464710
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  • 5
    Electronic Resource
    Electronic Resource
    Comment on "Ab initio calculation of [OH−; e+] system with consideration of electron correlation effect'' [J. Chem. Phys. 101, 5925 (1994)] (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 3147-3147 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A calculation of the positronium affinity of the hydroxyl radical (equivalently, the binding energy of positronium hydroxide, PsOH), recently reported by Tachikawa et al., is in error because an incorrect value of the electron affinity of OH was combined with their calculated positron affinity of the hydroxide anion. When the correct value of the electron affinity of OH is used, the calculated binding energy of PsOH changes sign, and PsOH is predicted to be unstable to dissociation. Thus, the conclusion reported by Tachikawa et al., namely, that PsOH is stable, is not supported by their calculations. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.471080
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  • 6
    Electronic Resource
    Electronic Resource
    Diffusion quantum Monte Carlo calculation of the binding energy and annihilation rate of positronium hydride, PsH (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 9430-9433 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Using the diffusion quantum Monte Carlo (DMC) method with importance sampling, we calculate the binding energy and annihilation rate of positronium hydride, PsH. We get 1.0661±0.0014 eV for the binding energy, and 2.463±0.020 ns−1 for the annihilation rate. The binding energy is in agreement with the results of the best Ritz variational calculations and the best DMC calculation reported to date, and the annihilation rate agrees with the results of the Ritz variational calculations but not that of the only other DMC result known to us. A new method for correcting expectation values calculated from mixed estimators is proposed and demonstrated. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477604
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  • 7
    Electronic Resource
    Electronic Resource
    Momentum distribution in benzene: A comparison of compton scattering and positron annihilation (1974)
    Springer
    Applied physics 4 (1974), S. 249-256 
    Details
    ISSN: 1432-0630
    Keywords: Momentum distribution ; Benzene ; Compton scattering ; Positron annihilation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Probabilities in momentum space for the benzene molecule are calculated for two cases: An ordinary benzene molecule, and benzene with a bound positron which is coalesced with one of the electrons. The former probability is related to the Compton scattering profile; the latter, to angular correlation measurements made in positron annihilation experiments. In this work we make two comparisons on the basis of quantum mechanical calculations; a) between Compton scattering and positron annihilation results, and b) among the several possible positron annihilation results associated with different symmetries for the positronic molecular orbital (PMO). The Compton scattering results are found to be similar to the positron annihilation results for the more symmetrical PMOs; and all these are quite different from the positron annihilation results for the less symmetrical PMOs. A suggestion for a crucial experiment is made.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00884236
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  • 8
    Electronic Resource
    Electronic Resource
    An improved wave function for positronium hydride: Preliminary report (1974)
    Springer
    Applied physics 3 (1974), S. 159-160 
    Details
    ISSN: 1432-0630
    Keywords: Positronium ; Positronium hydride
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract An improved wave function for positronium hydride is reported. The new wave function, which is of the same form as previously reported [Lebeda, C. F., Schrader, D. M.: Phys. Rev.178, 24 (1969)] yields a total energy of −0.7792 a.u., the lowest and hence most accurate value yet reported. This total energy indicates that positronium hydride is more stable than separated positronium and hydrogen atoms by 0.794 eV. The calculated annihilation rate, 2.22 nsec−1, is compared with available experimental evidence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00884415
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  • 9
    Electronic Resource
    Electronic Resource
    Selective removal of hypersecreting pituitary adenomas? (1976)
    Springer
    Acta neurochirurgica 35 (1976), S. 27-42 
    Details
    ISSN: 0942-0940
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The aim of this study of 101 pre- and postoperatively controlled hypersecreting pituitary adenomas (80 acromegalies, 15 Cushing's diseases, 6 Nelson's syndromes) was to establish in what cases a selective adenoma extirpation by the transnasal route is possible and advisable. In primary operations on acromegalics with small and medium size tumours 92% were postoperatively GH normal. Eighty five per cent of these had intact pituitary function. The results with larger tumours were worse (72%). During a control period of 1.5–5.5 years a renewed elevation of GH levels was observed in three cases, all in the first year, but never after clearly selective adenomectomy. These results, and the anterior lobe biopsies, which showed no GH cell hyperplasia, favour selective adenoma extirpation. In contrast to acromegaly, nodular ACTH cell hyperplasia in the anterior lobe was found in most cases of Cushing's disease, and therefore complete hypophysectomy was performed. The cortisol levels became either normal or, in most cases, lower than normal. A selective operation was performed on 6 Nelson tumours. The ACTH values became normal in about 50% of the patients but there was a tendency towards recurrence. Our experiences with Cushing's disease and Nelson's syndrome lead us to recommend total hypophysectomy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01405930
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  • 10
    Electronic Resource
    Electronic Resource
    Plasma-ACTH und Nelson-Tumoren bei bilateral adrenalektomierten Cushing-Patienten (1975)
    Springer
    Journal of molecular medicine 53 (1975), S. 923-926 
    Details
    ISSN: 1432-1440
    Keywords: Cushing's syndrome ; bilateral adrenalectomy ; plasma-ACTH ; Nelson's syndrome ; Cushing-Syndrom ; bilaterale Adrenalektomie ; Plasma-ACTH ; Nelson-Syndrom
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Von 18 Patienten, die wegen eines Cushing-Syndroms bilateral adrenalektomiert worden waren, zeigten 16 einen übernormalen, 6 davon einen stark erhöhten Plasma-ACTH-Spiegel. 5 von diesen hatten außerdem eine vergrößerte Sella und eine verstärkte Hautpigmentierung. Bei 4 dieser Patienten wurde ein mucoidzelliges Hypophysenadenom selektiv entfernt. Postoperativ waren die ACTH-Werte normalisiert, ohne daß endokrine Ausfälle von seiten der Hypophyse feststellbar waren. Eine ACTH-Langzeitkontrolle ergab ähnliche Werte wie für die bilateral adrenalektomierten Cushing-Patienten ohne Sellaexkavation und Pigmentierung.
    Notes: Summary Bilaterally adrenalectomized patients (18) because of Cushing's syndrome were studied. 16 of these 18 persons exhibited fairly high plasma ACTH levels. Distinctly elevated plasma ACTH levels were observed in 6 of them. 5 patients of this group showed an enlarged sella and deep pigmentation of the skin. 4 of the latter group had a mucoid cell adenoma which was removed selectively. After the surgery the ACTH values were found to be within normal range without any significant endocrine dysfunction of the pituitary. A long-term ACTH survey revealed that the ACTH levels remained within the ranges of bilaterally adrenalectomized Cushing patients without concomitant enlargement of the sella or pigmentation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01468985
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