Temperature dependence of the electric quadrupole interaction in PbHfO3

The temperature dependence of the Electric Field Gradient (EFG) in PbHfO₃ was studied in the temperature range 25–225°C by the Differential Perturbed Angular Correlation method. In the two anti-ferroelectric phases below 215°C, not too close to either transition temperature, the EFG decreases as the temperature increases toward T_c. Just above T_c an abrupt rise of EFG was observed indicating a critically behaving contribution to EFG. The results are interpreted in terms of a model based on the local static as well as time-dependent changes of the electric environment, at a lattice site. In accord with the predictions of this model the results exhibit qualitatively the P²_s temperature dependence of EFG far from T_c, where P_s is the sub-lattice polarization, while in close proximity to T_c the dominant contribution to EFG is due to the susceptibility X_q connected with the soft-mode fluctuations. The derived critical exponents are in agreement with previous experimental results on related compounds and with theoretical predictions. A hitherto unobserved additional component of V_zz was established, behaving critically at the antiferro-paraelectric transition at 215°C. This new component is interpreted to originate in local fluctuations connected with the central mode.     

Cross section determination for the reaction K+p → K+pπ+π−π0 and K+π+π+π−n at 8.2 and 16 GeV/c

The cross sections for the reactions: (a) K⁺p → K⁺pπ⁺π^?π⁺ and (b) K⁺p → K⁺π⁺π⁺π^?n have been determined at 8.2 and 16 GeV/c with the following results:at 8.2 GeV/c: (a) 0.99 ± 0.07 mb, (b) 0.41 ± 0.04 mb;at 16 GeV/c: (a) 0.72 ± 0.05 mb, (b) 0.28 ± 0.05 mb.Using the available data at other energies, the cross-section dependence of these reactions on the incident momentum is discussed.     

Ueber conjugirte binäre Formen und deren geometrische Construction

Ohne ZusammenfassungDie vorliegende Untersuchung ist im Jahre 1881 in Folge einer freundlichen Anregung von Seiten meines verehrten Lehrers, Herrn Prof. Rosanes, begonnen worden, dem ich auch für manmgfachen Rath bei Fortführung derselben zu lebhaftem Danke verpflichtet bin. Im Februar 1882 war ich in der Lage, Herr Prof. Rosanes von dem wesentlichen Inhalt der hier wiedergegebenen Arbeit Mittheilung zu machen. Nachdem ich sie alsdann Mai 1882 zum Zweck meiner Promotion der philosophischen Facultät der Universität Breslau überreicht und im October desselben Jahres als Dissertation hatte drucken lassen, war es zunächst meine Absicht, die erlangten Resultate noch eingehender zu verfolgen und später in erweiterter Fassung einem grösseren Leserkreise zuzuführen. Inzwischen hat Herr W. F. Meyer in Tübingen ein Buch Ueber Apolarität und rationale Curven (März 1883) herausgegeben, welches neben Anderem einige Sätze darbietet, die auch in einem Theil meiner Arbeit (nämlich den §§ 1, 2 und 8) enthalten sind^*). Diese Publication lässt es mir wünschenswerth erscheinen, einerseits, auf den abweichenden Gesichtspunkt binzuweisen, der mich auf die von Herrn Meyer entwickelten Sätze geführt hat, andrerseits die übrigen Resultate meiner Abhandlung zu veröffentlichen, welche zur Lösung eines constructiven Problems hinführen und überdies jene ersterwähnten Sätze in neuem Lichte erscheinen lassen.     

Glycine position permutations and peptide length alterations change the aggregation state and efficacy of ion-conducting, pore-forming amphiphiles

Changes in the peptide chain of amphiphilic heptapeptides known to form ion-conducting pores in bilayers dramatically alter transport efficacy and the aggregation number of pore formation.     

A remark on the motivic Galois group and the quantum coadjoint action

It has been suggested that the Grothendieck–Teichmüller group GT should act on the Duflo isomorphism of su(2), but the corresponding realization of GT turned out to be trivial. We show that a solvable quotient of the motivic Galois group – which is supposed to agree with GT – is closely related to the quantum coadjoint action on for q a root of unity, i.e. in the quantum group case one has a nontrivial realization of a quotient of the motivic Galois group. From a discussion of the algebraic properties of this realization we conclude that in more general cases than it should be related to a quantum version of the motivic Galois group. Finally, we discuss the relation of our construction to quantum field and string theory and explain what we believe to be the ‘physical reason’ behind this relation between the motivic Galois group and the quantum coadjoint action. This might be a starting point for the generalization of our construction to more involved examples.     

Soft manifold dynamics behind negative thermal expansion

Minimal models are developed to examine the origin of large negative thermal expansion in underconstrained systems. The dynamics of these models reveals how underconstraint can organize a thermodynamically extensive manifold of low-energy modes which not only drives negative thermal expansion but extends across the Brillioun zone. Mixing of twist and translation in the eigenvectors of these modes, for which in ZrW2O8 there is evidence from infrared and neutron scattering measurements, emerges naturally in our model as a signature of the dynamics of underconstraint.     

Kondo scaling in the optical response of YbIn1-xAgxCu4

Theoretical work on Kondo systems predicts universality in the scaling of observable quantities with the Kondo temperature, T(K). Here we report infrared-frequency optical response measurements of the correlated system YbIn(1-x)AgxCu4. We observe that x-dependent variations in the frequency and strength of a low-energy excitation are related to the x-dependent Kondo temperature. Comparison of the inferred trends with existing theory and a model calculation provides a framework in which to view these experimental results as scaling phenomena arising from local-moment/conduction electron hybridization.