Shear and dielectric responses of propylene carbonate, tripropylene glycol, and a mixture of two secondary amides

Propylene carbonate and a mixture of two secondary amides, N-methylformamide and N-ethylacetamide, are investigated by means of broadband dielectric and mechanical shear spectroscopy. The similarities between the rheological and the dielectric responses of these liquids and of the previously investigated tripropylene glycol are discussed within a simple approach that employs an electrical circuit for describing the frequency-dependent behavior of viscous materials. The circuit is equivalent to the Gemant-DiMarzio-Bishop model, but allows for a negative capacitive element. The circuit can be used to calculate the dielectric from the mechanical response and vice versa. Using a single parameter for a given system, good agreement between model calculations and experimental data is achieved for the entire relaxation spectra, including secondary relaxations and the Debye-like dielectric peak in the secondary amides. In addition, the predictions of the shoving model are confirmed for the investigated liquids.     

Communication: Identical temperature dependence of the time scales of several linear-response functions of two glass-forming liquids

The frequency-dependent dielectric constant, shear and adiabatic bulk moduli, longitudinal thermal expansion coefficient, and longitudinal specific heat have been measured for two van der Waals glass-forming liquids, tetramethyl-tetraphenyl-trisiloxane (DC704) and 5-polyphenyl-4-ether. Within the experimental uncertainties the loss-peak frequencies of the measured response functions have identical temperature dependence over a range of temperatures, for which the Maxwell relaxation time varies more than nine orders of magnitude. The time scales are ordered from fastest to slowest as follows: Shear modulus, adiabatic bulk modulus, dielectric constant, longitudinal thermal expansion coefficient, and longitudinal specific heat. The ordering is discussed in light of the recent conjecture that van der Waals liquids are strongly correlating, i.e., approximate single-parameter liquids.     

On second order degree of graphs

Given a vertex v of a graph G the second order degree of v denoted as d 2(v) is defined as the number of vertices at distance 2 from v.In this paper we address the following question:What are the sufficient conditions for a graph to have a vertex v such that d2(v) ≥ d(v),where d(v) denotes the degree of v? Among other results,every graph of minimum degree exactly 2,except four graphs,is shown to have a vertex of second order degree as large as its own degree.Moreover,every K-4-free graph or every maximal planar graph is shown to have a vertex v such that d2(v) ≥ d(v).Other sufficient conditions on graphs for guaranteeing this property are also proved.     

Transverse energy distributions in Si-nucleus collisions at 10 GeV/nucleon

Transverse energy distributions have been measured for collisions of 10 GeV/nucleon Si with targets of Al, Cu and Pb using a combination of a NaI wall and a uranium based sampling calorimeter. The measured cross sectionsdσ/dE _T anddE _T /dη are consistent with full stopping and an increase, with increasing values ofE _T , of energy flow into large angles.     

A new family of noncommutative 2-spheres

We give new examples of noncommutative manifolds. In particular we construct a “strong” deformation of C(S²), consisting of a family of noncommutative 2-spheres, and study their analytic and topological properties.     

Differentiation between major species of the Actinobacillus--Haemophilus--Pasteurella group by gas chromatography of trifluoroacetic acid anhydride derivatives from whole-cell methanolysates

A method based on whole-cell methanolysis and trifluoroacetic acid anhydride derivatization was developed for routine laboratory differentiation between isolates from the Actinobacillus--Haemophilus--Pasteurella group. All species, except Haemophilus aphrophilus, contained D-glycero-D-mannoheptose, although in varying concentrations. The distribution of this sugar could be used to distinguish H. aphrophilus from Actinobacillus actinomycetemcomitans, H. paraphrophilus, H. influenzae type b, Pasteurella haemolytica, P. multocida and P. ureae, and also H. influenzae type b from Pasteurellae. The pattern of major sugars in P. ureae and P. haemolytica resembled that of A. actinomycetemcomitans. Major fatty acids of the whole-cell methanolysates provided no basis of interspecies differentiation.     

Influence of the gel-liquid phase transition on hematoporphyrin triplet deactivation in liposomes

The deactivation of the triplet state of hematoporphyrin and its dimethyl ester in unilamellar liposomes of dipalmitoyl phosphatidylcholine was studied by nanosecond laser flash photolysis. It was found that the rate of deactivation increases abruptly on raising the temperature in the region of the gel-liquid phase transition of the lipid bilayer (41 degrees C). The rate of change has its maximum at 38.4 +/- 0.5 degree C for both porphyrins. This variation is due to the high lateral mobility of the porphyrins in the liquid-crystal bilayer, which enhances the rates of concentration triplet quenching and triplet-triplet annihilation.     

Anomalies in the surface impedance penetration depth in ferromagnetic superconductors

We have investigated the surface impedance penetration depth, Λ, of ErRh₄B₄ and Er_0.5Ho_0.5Rh₄B₄ both experimentally and theoretically. For ErRh₄B₄, owing to the critical spin fluctuations just above T_s ( > T_c2), the critical temperature at which surface ferromagnetism appears, Λ^?1 decreases smoothly as T decreases toward T_s. For Er_0.5Ho_0.5Rh₄B₄, the decrease in Λ^?1 owing to spin fluctuations for T ? T_c2 is very small, and Λ^?1 decreases abruptly at T_c2. Theoretical values of Λ^?1 are in good agreement with the data.