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61.
62.
Summary The application of quantitative DSC to the determination of the thermodynamic stability over a range of temperatures is demonstrated with the four polymorphs (I–IV) of pyrithlydione. At first sight, the enthalpy of transition between I and II, calculated by means of van't Hoff isobars and the respective solubilities in n-heptane, differs from the DSC-results by a factor of 2. This is due to association of the solute, and can be established by examining the nature of different solutions of pyrithyldione by means of infrared spectroscopy. The measured densities (1.13 and 1.17 g/cm3) of I (m. p. 96.5° C) and II (m. p. 92° C) are in agreement with the enantiotropism of both forms. The very low heat of fusion (3.7 kJ/ mole) of IV (m. p. 63.5° C) suggests that this unstable form is in the plastic crystalline state. III (m. p. 87° C) can be obtained only from IV. The stability of the polymorphic phases of pyrithyldione is represented in a semi-schematic energy/temperature diagram.
A part of this work was reported at the 8th International Microchemical Symposium, Graz, August 25–30, 1980. 相似文献
Thermodynamik und IR-Spektroskopie von vier Pyrithyldion-Modifikationen
Zusammenfassung Die Anwendung der quantitativen Differentialkalorimetrie für die Bestimmung der thermodynamischen Stabilität im gesamten Temperaturbereich wird an den vier Modifikationen (I–IV) von Pyrithyldion gezeigt. Auf den ersten Blick unterscheidet sich die Umwandlungsenthalpie zwischen Mod. I und II, welche aufgrund der van't Hoffschen Reaktionsisobare und der entsprechenden Löslichkeiten in n-Heptan berechnet wurde, von den kalorimetrischen Werten um den Faktor 2. Dieser Umstand ist auf die Assoziation des Gelösten im Lösungsmittel zurückzuführen, was sich durch die IR-Spektroskopie verschiedener Lösungen von Pyrithyldion bestätigen ließ. Die gemessenen Dichten (1,13 und 1,17 g/cm3) von Mod. I (Fp. 96,5° C) und Mod. II (Fp. 92° C) entsprechen dem enantiotropen Verhalten dieser beiden Formen. Die äußerst geringe Schmelzwärme (3,7 kJ/mol) von Mod. IV (Fp. 63,5° C) weist darauf hin, daß sich diese unstabile Form im plastisch-kristallinen Zustand befindet. Mod. III (Fp. 87° C) wird nur über Mod. IV erhalten. Die thermodynamische Stabilität der vier Pyrithyldion-Modifikationen wurde in einem halbschematischen Energie/Temperatur-Diagramm dargestellt.
A part of this work was reported at the 8th International Microchemical Symposium, Graz, August 25–30, 1980. 相似文献
63.
When prior partial information about a state to be cloned is available, it can be cloned with a fidelity higher than that of universal quantum cloning. We experimentally verify this intriguing relationship between the cloning fidelity and the prior information by reporting the first experimental optimal quantum state-dependent cloner, using nuclear magnetic resonance techniques. Our experiments may further cast important implications into many quantum information processing protocols. 相似文献
64.
We report on a matter wave interferometer realized with entangled pairs of trapped 87Rb atoms. Each pair of atoms is confined at a single site of an optical lattice potential. The interferometer is realized by first creating a coherent spin superposition of the two atoms and then tuning the interstate scattering length via a Feshbach resonance. The selective change of the interstate scattering length leads to an entanglement dynamics of the two-particle state that can be detected in a Ramsey interference experiment. This entanglement dynamics is employed for a precision measurement of atomic interaction parameters. Furthermore, the interferometer allows us to separate lattice sites with one or two atoms in a nondestructive way. 相似文献
65.
We consider a category of effect algebras and formulate an abstract-hidden variables problem for an object of this category. A notion of indeterministic object is introduced as of an object which induces a Kochen–Specker-type contradiction. A sufficient condition for an object to be indeterministic is derived. An abstract algebraic point of view on a no-hidden variables example constructed by Mermin is given. The notion of a passage to the semiclassical limit is analyzed and refined. 相似文献
66.
Transfer of data in linear quantum registers can be significantly simplified with preengineered but not dynamically controlled interqubit couplings. We show how to implement a mirror inversion of the state of the register in each excitation subspace with respect to the center of the register. Our construction is especially appealing as it requires no dynamical control over individual interqubit interactions. If, however, individual control of the interactions is available then the mirror inversion operation can be performed on any substring of qubits in the register. In this case, a sequence of mirror inversions can generate any permutation of a quantum state of the involved qubits. 相似文献
67.
68.
We demonstrate the controlled coherent transport and splitting of atomic wave packets in spin-dependent optical lattice potentials. Such experiments open intriguing possibilities for quantum state engineering of many body states. After first preparing localized atomic wave functions in an optical lattice through a Mott insulating phase, we place each atom in a superposition of two internal spin states. Then state selective optical potentials are used to split the wave function of a single atom and transport the corresponding wave packets in two opposite directions. Coherence between the wave packets of an atom delocalized over up to seven lattice sites is demonstrated. 相似文献
69.
Du J Zou P Shi M Kwek LC Pan JW Oh CH Ekert A Oi DK Ericsson M 《Physical review letters》2003,91(10):100403
Examples of geometric phases abound in many areas of physics. They offer both fundamental insights into many physical phenomena and lead to interesting practical implementations. One of them, as indicated recently, might be an inherently fault-tolerant quantum computation. This, however, requires one to deal with geometric phases in the presence of noise and interactions between different physical subsystems. Despite the wealth of literature on the subject of geometric phases very little is known about this very important case. Here we report the first experimental study of geometric phases for mixed quantum states. We show how different they are from the well-understood, noiseless, pure-state case. 相似文献
70.
GSH and L-His are abundant biomolecules and likely biological ligands for Zn(II) under certain conditions. Potentiometric titrations provide evidence of formation of ternary Zn(II) complexes with GSH and L-His or D-His with slight stereoselectivity in favour of L-His (ca. 1 log unit of stability constant). The solution structure of the ZnH(GSH)(L-His)(H2O) complex at pH 6.8, determined by NMR, includes tridentate L-His, monodentate (sulfur) GSH, and weak interligand interactions. Calculations of competitivity of this complex for Zn(II) binding at pH 7.4 indicate that it is likely to be formed in vivo under conditions of GSH depletion. Otherwise, GSH alone emerges as a likely Zn(II) carrier. 相似文献