Renewable beta-elemene based cyclic carbonates for the preparation of oligo(hydroxyurethane)s

Conversion of β-elemene into new β-elemene dicarbonates through epoxidation and halide salt-catalyzed CO2 cycloaddition reactions is reported. Step-growth polyaddition of this dicarbonate to five different, commercial diamines was investigated under neat conditions at 150 °C yielding non-isocyanate-based low molecular weight oligo(hydroxyurethane)s with 1.3≤Mn≤6.3 kDa and 1.3≤Ð≤2.1, and with glass transition temperatures ranging from −59 to 84 °C. The preparation of one selected polyhydroxyurethane material, obtained in the presence of Jeffamine® D-2010 was scaled-up to 43 g. The latter, when combined in a formulation using Irgacure® 2100 and Laromer® LR 9000 allowed the preparation of coatings that were analyzed with several techniques showing the potential of these biobased oligourethanes towards the preparation of commercially relevant materials

Magnetic and electronic quantum criticality in YbRh2Si2

The unconventional nature of the quantum criticality in YbRh 2Si 2 is highlighted on the basis of magnetoresistivity and susceptibility measurements. Results obtained under chemical pressure realized by isoelectronic substitution on the rhodium site are presented. These results illustrate the position of the T*-line associated with a breakdown of the Kondo effect near the antiferromagnetic instability in the low-temperature phase diagram. Whereas at zero temperature the Kondo breakdown and the antiferromagnetic quantum critical point coincide in the proximity of the stoichiometric compound, they are seen to be detached under chemical pressure: For positive chemical pressure the magnetically ordered phase extends beyond the T*(B)-line. For sufficiently high negative pressure the T*(B)-line is separated from the magnetically ordered phase. From our detailed analysis we infer that the coincidence is retained at small iridium concentrations, i.e., at small negative chemical pressure. We outline further measurements which may help to clarify the detailed behavior of the two instabilities. © 2010 Springer Science+Business Media, LLC

Shubnikov-de Haas measurements on LuRh2Si2

We present Shubnikov-de Haas measurements on LuRh2Si2, the non-magnetic reference compound to the prototypical heavy-fermion system YbRh2Si2. We find an extensive set of orbits with clear angular dependences. Surprisingly, the agreement with non-correlated band structure calculations is limited. This may be related to an uncertainty in the calculations arising from a lack of knowledge about the exact Si atom position in the unit cell. The data on LuRh2Si2 provide an extensive basis for the interpretation of measurements on YbRh2Si2 indicative of discrepancies between the high-field Fermi surface of YbRh2Si2 and the "small" Fermi surface configuration.Comment: 5 page

Hall effect measurements on YbRh2Si2 and relatives in the light of electronic structure calculations

We report experimental and theoretical investigations of the Hall effect in YbRh2Si2 and its reference compounds LuRh2Si2 and YbIr2Si2. Based on band-structure calculations we identify two bands dominating the Hall coefficient in all these compounds. For the case of LuRh2Si2 - the non-magnetic reference compound of YbRh2Si2 - the temperature dependence of the Hall coefficient is described quantitatively to arise from two hole-like bands. For YbIr2Si2 and YbRh2Si2, renormalized band calculations yield two bands of opposite character. In YbRh2Si2 these two bands almost compensate each other. We present strong indications that the sample dependences of the low-temperature Hall coefficient observed for YbRh2Si2 arise from slight variations of the relative scattering rates of the two bands. Minute changes of the composition appear to be the origin.Comment: 12 pages, 8 figure

SOCIAL DESIRABILITY AND CYNICISM: BRIDGING THE ATTITUDE-BEHAVIOR GAP IN CSR SURVEYS

Many consumer-focused corporate social responsibility (CSR) studies suggest a positive link between the responsibility demonstrated by a company and consumers’ intention to favor the company in their purchases. Yet an analogous causal effect between corporate social and financial performances is not evident. This chapter conceptualizes how social desirability and cynicism contribute to the discrepancy between consumers’ attitudes and their actual purchase behavior, and analyzes why consumer choices indicated in surveys do not consistently convert into actions

Magnetic field dependence and bottlenecklike behavior of the ESR spectra in YbRh2Si2

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Electron spin resonance (ESR) experiments at different fields or frequencies (4.1 <=nu <= 34.4 GHz) in the Kondo lattice (T-K similar or equal to 25 K) YbRh2Si2 single-crystal compounds confirmed the observation of a single anisotropic Dysonian resonance with g(perpendicular to c)congruent to 3.55 and no hyperfine components for 4.2 less than or similar to T less than or similar to 20 K. However, our studies differently reveal that (i) the ESR spectra for H-perpendicular to c show strong-field-dependent spin-lattice relaxation, (ii) a weak-field and temperature-dependent effective g value, (iii) a dramatic suppression of the ESR intensity beyond 15% of Lu doping, and (iv) a strong sample and Lu-doping (<= 15%) dependence of the ESR data. These results suggest a different scenario where the ESR signal may be associated to a coupled Yb3+-conduction electron resonant collective mode with a strong bottleneck and dynamiclike behavior.793Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)NSF (USA)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Photocatalytic Synthesis of Substituted Cyclic Carbonate Monomers for Ring-Opening Polymerization

An operationally mild, ruthenium-based photocatalytic protocol has been developed for the conversion of gamma-mono- and gamma,gamma-disubstituted allyl carbonates in the presence of Umemoto's reagent to afford substituted six-membered cyclic carbonates. Variation and diversification of the carbonate ring substitution provides access to new monomers useful in ring-opening polymerization leading to polycarbonates with potentially tailored properties, as illustrated by comparative experiments using monomers with different pi-stacking capabilities

Band-structure and anomalous contributions to the Hall effect of YbRh2Si2

We report on Hall effect measurements on YbRh2Si2 single crystals with different residual resistivity and on LuRh2Si2 single crystal. The temperature dependence of the linear-response Hall coefficient of YbRh2Si2 is described by the anomalous Hall effect and the normal contribution incorporating multi-band effects. Sample dependencies at low T are found and explained by slight changes in the charge-carrier concentrations. © 2007 Elsevier B.V. All rights reserved

Hall effect measurements and electronic structure calculations on YbRh 2 Si2 and its reference compounds LuRh2 Si 2 and YbIr2 Si2

We report experimental and theoretical investigations of the Hall effect in YbRh2 Si2 and its reference compounds LuRh2 Si2 and YbIr2 Si2. Based on band-structure calculations we identify two bands dominating the Hall coefficient in all these compounds. For the case of LuRh2 Si2 -the nonmagnetic reference compound of YbRh2 Si2 -the temperature dependence of the Hall coefficient is described quantitatively to arise from two holelike bands. For YbIr2 Si2 and YbRh2 Si2, renormalized band calculations yield two bands of opposite character. In YbRh2 Si2 these two bands almost compensate each other. We present strong indications that sample dependences of the low-temperature Hall coefficient observed for YbRh2 Si2 arise from slight variations in the relative scattering rates of the two bands. Minute changes in the composition appear to be the origin. The results of our band-structure calculations reveal that a transition of the 4f electrons from localized to itinerant leads to a decrease in the Hall coefficient. © 2010 The American Physical Society