High Pressure Calorimetry. Comparison of two systems (differential vs. single cell). Application to the phase change of water under pressure

In high pressure calorimetry the pressure change is used to obtain the desired phenomenon (i.e. phase change) at constant temperature. Two high pressure calorimeters have been developed to measure the latent heat of fusion of pure water (hexagonal ice-type I) at subzero temperature. Both calorimeters used a constant pressurisation rate produced with a high pressure pump driven by a step motor. The first calorimeter was a single cell calorimeter where mercury acted as the pressurisation fluid, while the second one was differential (two cells) and was pressurised with pentane. Both calorimeters gave high accuracy data of latent heat of fusion of pure water, which were determined taking into account that either the fluid used to pressurise or the pressurisation rate affected the calorimetric signal. This revised version was published online in July 2006 with corrections to the Cover Date.     

Low temperature phase transition in cubic elpasolithe crystal Cs2NaBiCl6

The structural properties of the cubic compound Cs₂NaBiCl₆ have been investigated. X-ray diffraction patterns were observed from 300 to 7 K. On lowering the temperature, this compound undergoes a structural transformation starting at 90 K. This structural evolution was monitored by the thermal behavior of the 400 and 440 reflections. The crystallographic data was completed by Raman scattering measurements on an oriented sample. The phase transformation involves only the external mode corresponding to the Cs⁺ translation. The lattice instability of Cs₂NaBiCl₆ appears to be related to the size of the cesium ion site. Comparison with results obtained for isomorphous compounds strongly supports our interpretations.     

Orthosymmetric ortholattices and Rickart*-rings

Orthosymmetric ortholattices (OSOLs) have been introduced in order to approximate ortholattices of closed subspaces of a Hilbert space. In this paper, some new properties of OSOLs are proved and the main result states that lattices of projections of Rickart^*-rings, satisfying 2x=0 impliesx=0, carry a natural structure of OSOL.     

Orthosymmetries and Jordan Triples

Orthosymmetric ortholattices (OSOLs) have beenintroduced in order to approximate Hilbertian lattices(ortholattices of closed subspaces of a Hilbert space).Axioms of OSOLs are selected properties of usual orthogonal symmetries on a Hilbertian latticeand many posets defined by means of associative orJordan algebras possess a set of automorphismssatisfying these axioms. In this paper, we describe andillustrate a method using Jordan triples and whichprovides a common setting for the study oforthosymmetries in associative algebras and Jordanalgebras.     

Compositions of Sasaki projections

In an orthomodular lattice (abbreviated OML) L, a Sasaki projection is a mappinga _x(a)=x(x va) fromL toL, wherexL. We study compositions of finite numbers of Sasaki projections and of the same Sasaki projections composed in inverse order. By using the Baer-semigroup of all finite compositions of Sasaki projections, we establish a new characterization of kernels of congruences in OMLs and a generalization of the parallelogram law for dimension OMLs. Our results are also related to quantum measurements via Pool's definition of the change of the support of a state after a measurement.     

Late‐Stage Isotopic Carbon Labeling of Pharmaceutically Relevant Cyclic Ureas Directly from CO2

A robust, click‐chemistry‐inspired procedure for radiolabeling of cyclic ureas was developed. This protocol, suitable for all carbon isotopes (¹¹C, ¹³C, ¹⁴C), is based on the direct functionalization of carbon dioxide: the universal building block for carbon radiolabeling. The strategy is operationally simple and reproducible in different radiochemistry centers, exhibits remarkably wide substrate scope with short reaction times, and demonstrates superior reactivity as compared to previously reported systems. With this procedure, a variety of pharmaceuticals and an unprotected peptide were labeled with high radiochemical efficiency.     

Dispelling myths on superposition attacks: formal security model and attack analyses

Designs, Codes and Cryptography - With the emergence of quantum communication, it is of folkloric belief that the security of classical cryptographic protocols is automatically broken if the...