Cardiosperminsulfate - a sulphur containing cyanogenic glucoside from cardiospermum grandiflorum

Isolation and structure elucidation of cardiospermin-5-sulfate, the first reported sulphur containing cyanogenic glycoside is described. The compound coocurs with cardiospermin in Cardiospermum grandiflorum Sw. (Sapindaceae).     

Carnot cycles in general relativity

Classical thermodynamics has been developed with the assumption that, either no gravitational fields are present in the thermodynamic systems, or that the fields act on the Newtonian mass of the systems only and not on any other kind of internal energy like heat. In order to find the exact thermodynamic relations for systems with gravitational fields, the wellknown Carnot cycles are used, taking into account the action of gravitation. The gravitation is described by general relativity. The Carnot efficiency is calculated in the case of stationary fields. Temperature for general relativistic systems can be defined with the help of Kelvin's principle analogously to classical thermodynamics, and the Carnot efficiency can then be expressed with temperatures instead of heat energies. In the case of strong gravitational fields, the Carnot efficiency can become equal to one even if the temperatures are both different from zero. Thermodynamic equilibrium can be expressed by using the Carnot efficiency, and it can be proved that for equilibrium the Tolman relation = constantholds quite generally for systems with stationary gravitational fields.Presented at the International Conference on Gravitation and Relativity, Copenhagen, July 1971.For 1969–71 on leave of absence at the Center for Relativity Theory, University of Texas at Austin, Austin, Texas, as a Faculty Associate supported by the National Science Foundation (Grant No. GU-1598).     

Tellur

Ohne Zusammenfassung     

Quantum Groups and Double Quiver Algebras

For a finite dimensional semisimple Lie algebra and a root q of unity in a field k, we associate to these data a double quiver . It is shown that a restricted version of the quantized enveloping algebras is a quotient of the double quiver algebra .*The author is partially supported by the National Science Foundation of China (Grant. 10271014) and Natural Science Foundation of Beijing City (grant. 1042001)     

Sliding-induced decoupling and charge transfer between the coexisting Q1 and Q2 charge density waves in NbSe3

Using high-resolution x-ray scattering in the presence of an applied current, we report evidence for a dynamical decoupling between the two NbSe3 charge-density waves (CDWs), Q1 (T(C1)=145 K) and Q2 (T(C2)=59 K), coexisting below T(C2). Simultaneous and oppositely directed shifts of the relevant CDW superlattice spots develop above a threshold current which we identify as the depinning threshold I(C1) for the more strongly pinned upper CDW Q1 (I(C1) approximately 10I(C2)). In contrast with shifts induced by current conversion processes, the present effect is not current polarized and is not limited to the current-contact regions. We propose a model which explains this instability through a sliding-induced charge transfer between the two electronic reservoirs corresponding to the Q1 and Q2 CDWs.     

Ultrafast optics establishes metrological standards in high-frequency electronics

A measurement system is reported that allows for the complete characterization of high-speed oscilloscopes. The measurements are based on ultrafast optical methods, which are used to generate picosecond electrical pulses with photoconductive switches as test signals. The properties of the test pulses are determined by the electro-optic sampling method, which provides traceability to the unit of length and, hence, to the unit of time. The photoconductive switches combined with the electro-optic sampling system represent a primary standard in electrical pulse metrology. With the well-characterized pulses from this standard, the complex transfer function, the impulse and step response, as well as the intrinsic risetime of high-speed oscilloscopes are determined. Risetimes of 6–7 ps can be measured with an expanded uncertainty of 1.2 ps. PACS 84.40.Ua; 84.40.Az; 84.30.Ng     

Observation of heterodyne mixing in surface x-ray photon correlation spectroscopy experiments

We report measurements of propagating capillary waves on a liquid water surface at T=5 degrees C with x-ray photon correlation spectroscopy. The experiment has been performed under grazing incidence conditions with an incoming x-ray beam below the critical angle of total external reflection. In the q region investigated the measured intensity-intensity autocorrelation functions of the liquid water surface were found to be heterodyne signals, i.e., a combination of first- and second-order correlation functions g(1)(tau) and g(2)(tau).     

Microstructure and dynamics near an attractive colloidal glass transition

The microstructure and dynamics of a colloidal system interacting via short-ranged interparticle potential is studied by ultra-small-angle x-ray scattering and x-ray photon correlation spectroscopy. A colloidal gas-liquid type transition is induced when the short-ranged attractive interactions attain sufficient magnitude. The development of liquidlike structure is preceded by a systematic transition in the particle dynamics from diffusive to constrained motion and then completely frozen behavior. This demonstrates the existence of a jamming transition induced by strong short-ranged attractive interactions even at low packing fractions.     

Free subgroups of branch groups

A procedure is described for constructing branch groups on the binary tree, which yields in particular finitely generated branch groups with non-cyclic free subgroups.