Search

When magnetic order is suppressed by frustrated interactions, spins form a highly correlated fluctuating 'spin liquid' state down to low temperatures. The magnetic order of local moments can also be suppressed when they are fully screened by conduction electrons through the Kondo effect. Thus, the combination of strong geometrical frustration and Kondo screening may lead to novel types of quantum phase transition. We report low-temperature thermodynamic measurements on the frustrated Kondo lattice Pr2Ir2O7, which exhibits a chiral spin liquid state below 1.5 K as a result of the frustrated interaction between Ising 4f local moments and their interplay with Ir conduction electrons. Our results provide a first clear example of zero-field quantum critical scaling that emerges in a spin liquid state of a highly frustrated metal. [ABSTRACT FROM AUTHOR]

any pressure sensitive quantum critical point (QCP) the thermal expansion is more singular than the specific heat leading to a divergence of the Grüneisen parameter. For a magnetic field sensitive QCP, the complementary property is the magnetic Grüneisen ratio which equals the magnetocaloric effect. Here we use both properties to investigate magnetic QCPs in different heavy fermion (HF) metals starting from CeNiGe. The influence of dimensionality on quantum criticality is addressed by the comparison of cubic CeInSn with layered CeMInSn (M = Co, Rh) systems, in which Sn doping both acts as tuning parameter and introduces slight disorder. Near the field-tuned QCP in undoped CeCoIn a crossover scale T is discovered which separates 2D (at T> T) from 3D (at T< T) quantum criticality. Disorder, introduced by Sn-doping, is found to increase T, stabilizing 3D behavior. We also compare the magnetic Grüneisen ratio in the approach of the field-tuned QCP in YbRhSi with zero-field Grüneisen parameter data on YbRh(SiGe) ( x=0, x=0.05). Both properties indicate quantum criticality incompatible with the predictions of the itinerant theory. [ABSTRACT FROM AUTHOR]

A novel tyrosinase inhibitor, an arbutin derivative having undecylenic acid at the 6-position of its glucose moiety, was enzymatically synthesized. Its inhibitory activity was studied in vitro by using catechol and phenol as substrates. The IC50 value of the arbutin ester on tyrosinase using catechol (4 × 10−4 M) was 1% of that when arbutin (4 × 10−2 M) was used. Using phenol, IC50 of the arbutin ester (3 × 10−4 M) as substrate was 10% of that of arbutin (3 × 10−3 M). These results suggest that the arbutin ester inhibits the latter part of the tyrosinase reaction, which consists of hydroxylation and oxidation. [ABSTRACT FROM AUTHOR]

The point at absolute zero where matter becomes unstable to new forms of order is called a quantum critical point (QCP). The quantum fluctuations between order and disorder[SUP1-5] that develop at this point induce profound transformations in the finite temperature electronic properties of the material. Magnetic fields are ideal for tuning a material as close as possible to a QCP, where the most intense effects of criticality can be studied. A previous study[SUP6] on the heavy-electron material YbRh[SUB2]Si[SUB2] found that near a field-induced QCP electrons move ever more slowly and scatter off one another with ever increasing probability, as indicated by a divergence to infinity of the electron effective mass and scattering cross-section. But these studies could not shed light on whether these properties were an artefact of the applied field[SUP7,8], or a more general feature of field-free QCPs. Here we report that, when germanium-doped YbRh[SUB2]Si[SUB2] is tuned away from a chemically induced QCP by magnetic fields, there is a universal behaviour in the temperature dependence of the specific heat and resistivity: the characteristic kinetic energy of electrons is directly proportional to the strength of the applied field. We infer that all ballistic motion of electrons vanishes at a QCP, forming a new class of conductor in which individual electrons decay into collective current-carrying motions of the electron fluid. [ABSTRACT FROM AUTHOR]

We have determined the distribution of the 5f-quadrupoles and detected the 5f-quadrupole order in the uranium intermetallics, uranium dipnictides and UPd3, with 238U Mössbauer spectroscopy. We have declared that the distribution of the 5f-qaudrupoles depends on the magnetic sequence in uranium dipnictides. The distribution of the 5f-quadrupole is spherical in UBi2, while those are oblate within c-plane in UP2, UAs2 and USb2. We have observed the sudden drop of the recoil-free fraction above the transition temperature of the quadrupole order in UPd3. The present result suggests the change of the phonon states due to the quadrupole order in this compound. [ABSTRACT FROM AUTHOR]

Enrichment containing large numbers of slow-growing bacteria was developed by repeated batch culture under high biomass concentrations (more than 10 000 mg biomass/l). The characteristics of slow-growing bacterial populations were elucidated by application of colony-forming-curve (CFC) analysis. The CFC were obtained by counting the number of visible colonies on agar plates at successive intervals. The enrichment consisted of several groups with different colony-forming rates and the slow-growing bacteria appeared on cell extract/agar plates after 7 days of incubation. It was found that large numbers of slow-growing bacteria survived under starvation conditions. One of the slow colony-forming bacteria, strain TI-X7, was tentatively identified as being of the genus Micrococcus. The enrichment contained a large amount of Micrococcus-like tetrad cells. The dialysate fractions in excess cell extract, permeable through dialysis tubing, were extremely effective for growth of strain TI-X7. [ABSTRACT FROM AUTHOR]

This paper examined the biodegradability of a new aliphatic polyester, polyethylene succinate (PES), at a high incubation temperature of 50°C. The distribution and population of total colonies and of PES degrading micro organisms on polymer-emulsified agar plates were determined using the plate count and clear zone methods. The PES-decomposers were present in six of 10 soil samples and the total number ranged from 2.0×104 to 2.2×106 c.f.u./g of samples. Degrading microorganisms constituted between 20 and 80% of the total colonies on PES–agar plates. A single PES-degrading strain, TT96, was isolated and tested for its biodegrading capacity on PES powder and on other aliphatic polyesters: poly(beta-hydroxybutyrate) (PHB), polycaprolactone (PCL), poly(butylene succinate) (PBS), and poly(L-lactide) (PLA). Degraded films of PES and PBS were presented and compared using scanning electron microscopy. Strain TT96 was able to create clear zones on all the polymers used, except on PHB-agar plates. Liquid culture test after 2 weeks showed that TT96 completely degraded PCL powder but had very little activity on other samples. Scanning electron micrograph confirmed the microbial attack of TT96 on PES and PBS films. PES film surfaces were degraded more uniformly compared to PBS films which were decomposed only in some parts. [ABSTRACT FROM AUTHOR]

CeCoIn5 undergoes a phase transition within the superconducting (SC) state. A new superconducting state occupies a high field–low temperature (HFLT) corner of the SC state in the H– T plane, and is a strong candidate for realization of the spatially inhomogeneous Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) superconducting state predicted theoretically in 1960s. We present specific heat data on Cd- and Hg-doped CeCoIn5 that shows that the HFLT phase is suppressed by minute amount of impurities, few hundred parts per million. At this concentration, the average distance between impurities is close to twice the superconducting coherence length ξ, suggesting that ξ is the characteristic length of the HFLT state. We conclude that our investigations support the superconducting, posibly FFLO, origin of the HFLT state. [ABSTRACT FROM AUTHOR]

Superconductivity without phonons has been proposed for strongly correlated electron materials that are tuned close to a zero-temperature magnetic instability of itinerant charge carriers. Near this boundary, quantum fluctuations of magnetic degrees of freedom assume the role of phonons in conventional superconductors, creating an attractive interaction that ‘glues’ electrons into superconducting pairs. Here we show that superconductivity can arise from a very different spectrum of fluctuations associated with a local (or Kondo-breakdown) quantum critical point that is revealed in isotropic scattering of charge carriers and a sublinear, temperature-dependent electrical resistivity. At this critical point, accessed by applying pressure to the strongly correlated, local-moment antiferromagnet CeRhIn5, magnetic and charge fluctuations coexist and produce electronic scattering that is maximal at the optimal pressure for superconductivity. This previously unanticipated source of pairing glue opens possibilities for understanding and discovering new unconventional forms of superconductivity. [ABSTRACT FROM AUTHOR]

A strip of tread compound cut from a truck tire was degraded only slightly when it was used as the sole growth substrate for a strain of Nocardia. On the contrary, its degradation was markedly enhanced by addition of a strip cut from a latex glove which the organism readily utilized as a growth substrate. When a glove strip was added, the biomass concentration in the experimental flask became more than 10-foldhigher than the control without a glove strip and the colonization of the tire strip was significantly enhanced. After 8 weeks' cultivation, about 28% of the tire strip was disintegrated into very small black particles (mostly less than 30 gm in diameter) and the weight of the remaining unchanged portion of the strip was about 49% of the initial weight. Four kinds of truck tire treads were attacked in differing degrees by the organism under-the same conditions. The treads containing more than 70 phr (parts per hundred of rubber) of natural rubber were considerably attacked, while those with a natural rubber content of less than 55 phr were attacked only slightly. The microbial activity against the rubber in the side wall of a truck tire was relatively high, but the inner liner was hardly attacked and the bead rubbernot at all. [ABSTRACT FROM AUTHOR]