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Zr-based metallic glasses are prepared by quenching supercooled liquid under pressure. These glasses are stable in ambient conditions after decompression. The High Pressure Quenched glasses have a distinct structure and properties. The pair distribution function shows redistribution of the Zr-Zr interatomic distances and their shift towards smaller values. These glasses exhibit higher density, hardness, elastic modulus, and yield stress. Upon heating at ambient pressure, they show volume expansion and distinct relaxation behavior, reaching an equilibrated state above the glass transition. These experimental results are consistent with an idea of pressure-induced low to high density liquid transition in the supercooled melt. [ABSTRACT FROM AUTHOR]

High-entropy alloys are multicomponent solid solutions in which various elements with different chemistries and sizes occupy the same crystallographic lattice sites. Thus, none of the atoms perfectly fit the lattice site, giving rise to considerable local lattice distortions and atomic-level stresses. These characteristics can be beneficial for performance under radiation and in a high-temperature environment, making them attractive candidates as nuclear materials. We discuss electronic origin of the atomic-level stresses based upon first-principles calculations using a density functional theory approach. [ABSTRACT FROM AUTHOR]

High-entropy alloys (HEAs) are characterized not only by high values of entropy but also by high atomic-level stresses originating from mixing of elements with different atomic sizes. Particle irradiation on solids produces atomic displacements and thermal spikes. The high atomic-level stresses in HEAs facilitate amorphization upon particle irradiation, followed by local melting and re-crystallization due to thermal spikes. We speculate that this process will leave much less defects in HEAs than in conventional alloys. For this reason, they may be excellent candidates as new nuclear materials. We discuss initial results of computer simulation on model binary alloys and an electron microscopy study on Zr-Hf-Nb alloys, which demonstrate extremely high irradiation resistance of these alloys against electron damage to support this speculation. [ABSTRACT FROM AUTHOR]

Adenovirus-mediated gene therapy shows remarkable promise as a new strategy for advanced pancreatic cancer, but satisfactory clinical results have not yet been obtained. To improve this gene therapy, we investigated the effects of gemcitabine (GEM) on transgene expression by adenoviral vectors and their biological effects. We used Ad-lacZ and adenoviral vector-expressing NK4 (Ad-NK4) as representative adenoviral vectors. These vectors express β-galactosidase (β-gal) and NK4 (which inhibits the invasion of cancer cells), respectively, under the control of the CMV promoter. Cells were infected with the individual adenoviruses and then treated with GEM. GEM increased β-gal mRNA expression and β-gal activity, and increased NK4 expression in both culture media and within infected cells, in dose-dependent manners. The increased expression of NK4 delivered by Ad-NK4 had biological effects by inhibiting the invasion of cancer cells. GEM also enhanced NK4 expression in SUIT-2 cells transfected with an NK4-expressing plasmid, suggesting that GEM enhanced CMV promoter activity. In in vivo experiments, NK4 expression within subcutaneously implanted tumors was increased in GEM-treated mice compared with control mice. These results suggest that adenovirus-mediated gene therapy with GEM may be a promising approach for treating pancreatic cancer, and that this combination therapy may decrease the risks of side effects. [ABSTRACT FROM AUTHOR]

It is difficult to formulate the statistical mechanical theory of liquids and glasses, because phonons, which are the basis for the statistical mechanics of lattice dynamics in crystals, are strongly scattered and have a very short lifetime in liquids and glasses. Instead computer simulation and the “free-volume” theory are most frequently used in explaining experimental results on metallic glasses. However, both of them suffer from serious problems, as discussed in this article. We propose an alternative approach based upon the dynamics of the atomic level stresses. We review recent progress with this approach and show that it is possible to calculate thermodynamic quantities, including the glass transition temperature and the kinetics of structural relaxation, by this approach. [ABSTRACT FROM AUTHOR]

Liquids and glasses have been well known to human kind for millennia. And yet major mysteries remain in the behavior of glasses and liquids at the atomic level, and identifying the microscopic mechanisms that control the properties of glasses is one of the most challenging unsolved problems in physical sciences. For this reason, applying simplistic approaches to explain the behavior of metallic glasses can lead to serious errors. On the other hand because metallic glasses are atomic glasses with relatively simple structure, they may offer better opportunities to advance our fundamental understanding on the nature of the glass. The difficulties inherent to the problem and some recent advances are reviewed here. [ABSTRACT FROM AUTHOR]

The effect of geometrical frustration in the atomic structure on the formability of bulk metallic glasses is discussed from a general point of view. It is pointed out that there are two distinct and complementing pathways to easy glass formation: stabilizing the glass itself and destabilizing the corresponding crystalline state. While the discussions in the field tend to focus on the first one, the second in fact is a more effective approach. Examples of both will be discussed using soft-sphere, rather than hard-sphere, packing concepts. [ABSTRACT FROM AUTHOR]

Extremely high values of the relative permittivity up to 107 and the magnetocapacitance up to 105% have been found in La1 − x Sr x MnO3 single crystals ( x = 0.1, 0.11). These phenomena are observed even at room temperature. The observed behavior can be a consequence of the strong interaction among charge, spin, and lattice degrees of freedom, which leads to charge and phase separation in the regime before the percolation threshold. [ABSTRACT FROM AUTHOR]

The evolution of the structure of K1− x LixTa1− y NbyO3 single crystals with x = 0.001, y = 0.026, and 1900 ppm Cu (KLTN277) and with x = 0.0014 and y = 0.024 (KLTN123), which exhibit an extremely high permittivity (up to 4 × 105 in the quasi-static regime for the KLTN277 crystal), is investigated in the range from room temperature to 20 K. It is demonstrated that, upon cooling to the lowest temperatures, both crystals retain their cubic structure, but the lattice parameters pass through a minimum at the temperature of the observed anomalies of the dielectric response (∼50 K). In the neutron diffraction pattern of the KLTN123 sample, satellites appear in the vicinity of the ( hhh) reflections at temperatures below ∼50 K. These satellites can be associated with the nucleation of the rhombohedral phase. [ABSTRACT FROM AUTHOR]

It is widely accepted that the remarkable properties of complex transition-metal oxides, such as colossal magnetoresistivity, are consequences of collaborative behaviors of many degrees of freedom, namely spin, charge, orbital moment and lattice. In stark contrast, most of the theories on the mechanism of the high-temperature superconductivity focus only on the spin degree of freedom. We suggest that the complex behaviors of the cuprates, including the electronic phase separation, involve charge as well as lattice degrees of freedom, and the interplay of the lattice and spin may be centrally important to the superconductivity of the cuprates. We speculate that an intermediate phase may appear when the Mott–Hubbard insulator is doped, and may support the two-component superconductivity involving spins and phonons. [ABSTRACT FROM AUTHOR]

For a long time the majority opinion in the field of high-temperature superconductivity (HTSC) has been that it is purely an electronic phenomenon involving spin, and could be explained by a t– J Hamiltonian. Phonons and local distortion were regarded as irrelevant or harmful to HTSC. However, various experimental results indicate strong phonon involvement and ubiquitous presence of local spin–charge–lattice inhomogeneity. We suggest that the electron–phonon (e–p) coupling in the cuprate is unconventional, and a synergetic coupling of spin, charge, and phonon could explain the HTSC phenomenon. In our view the spin–charge–lattice inhomogeneity is a signature of such a coupling and an important component of the HTSC mechanism. [ABSTRACT FROM AUTHOR]

We measured the phonon dispersions of YBa2Cu3O6.15 and YBa2Cu3O6.95 by time-of-flight inelastic neutron scattering. The in-plane bond-stretching modes in the metallic phase showed a distinct a-b plane anisotropy beyond what is expected for structural origin. Such anisotropy in the longitudinal optical modes, which is absent in the TO, suggests strong in-plane anisotropy in the underlying electronic structure. Apical oxygen bond-stretching modes showed a large frequency change between the insulating and the metallic phases. This large softening also is beyond structural origin, and suggests the effect of local electronic environment. [ABSTRACT FROM AUTHOR]

For a long time the majority view has been that phonons are irrelevant to the mechanism of high-temperature superconductivity. However, recent experimental results, including the neutron inelastic scattering measurements reviewed here, seriously challenge this view. We point out that the electron–phonon coupling in the cuprates can be substantially different from that in simple metals because of the covalency and strong electron correlation. In particular certain phonon branches induce substantial intersite charge transfer that can result in a negative electronic dielectric susceptibility. Such a strong electron–phonon coupling of certain modes could form the basis for the phonon mechanism of superconductivity in the cuprates. [ABSTRACT FROM AUTHOR]

We investigated the effectiveness of fosfomycin combined with other antibiotics, such as piperacillin, cefepime, ceftazidime, imipenem, meropenem, aztreonam, gentamicin, or levofloxacin, against 30 Pseudomonas aeruginosa strains, including multidrug-resistant strains, isolated from clinical specimens, using the efficacy time index (ETI) assay. The assay refers to the result of pharmacokinetics obtained from adult men volunteers, and yields an ETI to evaluate the effect of a combination of antimicrobial agents. With the ETI, based on serum concentration 3 h after the administration of two antimicrobial agents, the effectiveness of antimicrobial combinations was evaluated as follows: poor, ETI < 0.5; fair, 0.5 ≤ ETI < 1; good, 1 ≤ ETI < 8; and excellent, ETI ≥ 8. The combination of fosfomycin and cefepime (efficacy rate [excellent plus good], 76.7%) and fosfomycin/aztreonam (efficacy rate, 76.7%) appeared to be the most effective, followed by fosfomycin/meropenem (efficacy rate, 76.6%), fosfomycin/imipenem (efficacy rate, 73.3%), fosfomycin/ceftazidime (efficacy rate, 70%), fosfomycin/gentamicin (efficacy rate, 70%), fosfomycin/piperacillin (efficacy rate, 66.7%), and fosfomycin/levofloxacin (efficacy rate, 66.7%). Fosfomycin/cefepime, fosfomycin/aztreonam, and fosfomycin/meropenem may be clinically useful in selected patients, particularly for P. aeruginosa. The ETI assay provided information on the minimum inhibitory concentration (MIC) of many pairs of combined antimicrobial agents simultaneously. The ETI assay may be a useful technique with which to investigate the effect of combinations of antimicrobial agents against P. aeruginosa, including multidrug-resistant strains. [ABSTRACT FROM AUTHOR]

Recent experimental results on cuprates and manganites, including those of elastic and inelastic neutron scattering measurements, suggest that charges are not homogeneously distributed even in the metallic state in these compounds. Charge inhomogeneity results from spin/lattice charge constriction. In cuprates the LO phonons strongly reflect the temperature- and composition-dependent charge inhomogeneity and may possibly be involved in causing it. Unlike the static stripes that compete against superconductivity, the charge inhomogeneity seen by the LO phonons is markedly increased in the superconducting phase. A new mechanism of high-temperature superconductivity involving lattice/spin charge constriction is proposed. [ABSTRACT FROM AUTHOR]

Colossal magnetoresistivity (CMR) is caused by a magnetic field-induced insulator-to-metal transition. It is arguably one of the most dramatic phenomena that occur in solids due to competing forces in a complex system. In the CMR oxides the electron-phonon coupling and spin correlations that favor charge localization are competing against the electron kinetic energy and lattice elasticity that prefer charge delocalization. The CMR phenomenon occurs at the crossover point of charge-localized (insulating) and charge-delocalized (metallic) states, where the system is particularly susceptible to external stimuli such as a magnetic field. The competitions among these forces are usually considered globally as volume averages. However, since the system is complex and the phenomenon is non-linear, local fluctuations dominate the behavior of the system near the critical point. Therefore the system would appear spatially inhomogeneous if the measurement is made with certain time and length scales. To characterize and understand such a system it is required to deploy local approaches in which the competing interactions are evaluated locally. Experimentally, the pulsed neutron pair-density function (PDF) analysis is one of the methods of local structural study. Using the PDF technique it is suggested that the phase transition occurs via local and percolative processes. Also through the analysis of the local structure it is shown that the ionic size effect on the CMR phenomenon is not caused by a change in the band width as is usually assumed, but is due to local structural changes that affect polaron stability. The critical ionic size determined by this approach is in excellent agreement with experimental observations. The PDF results also indicate that the local structure of layered manganites is close to that of perovskite, suggesting that they share common elements of the CMR mechanisms. [ABSTRACT FROM AUTHOR]

The reaction of ethylene on a model automotive emissions control catalyst consisting of Rh particles on an epitaxial ceria film grown on the (100) surface of an yttria stabilized zirconia single crystal was studied using TPD. The TPD results showed that ethylene undergoes dehydrogenation on the model catalyst at temperatures below 500 K depositing carbon on the Rh particles. Surface carbon formed in this manner was oxidized to CO upon heating to above 550 K using oxygen supplied by the ceria lattice. Heating to 900 K was found to induce reduction of the ceria film resulting in a marked decrease in oxidation activity. [ABSTRACT FROM AUTHOR]

The lattice effects of charge localization in manganites and cuprates arediscussed from the local structural point of view. Pulsed neutron atomicpair-density function (PDF) analysis indicates that in La1− xSr xMnO3 the realstructure deviates from the average crystal structure, and the localJahn–Teller (JT) distortion of Mn3+O6 octahedra remains even in themetallic phase. This leads to a concept of the critical ionic size factorfor the formation of JT polarons. The colossal magnetoresistance (CMR)phenomena are observed in the crossover region from localized to delocalizedcharge states. This concept also explains the asymmetry of the phase diagramwhich is difficult to understand in the current band picture. Similarconsideration may help understand the lattice effects in superconductingcuprates. [ABSTRACT FROM AUTHOR]

Local lattice distortions suggesting nonuniform charge distributions were found to be a common feature of manganites and cuprates in the metallic state by neutron scattering studies. The atomic pair-density function (PDF) determined by pulsed neutron powder diffraction showed that in La1-xSrxMnO3 doped holes form lattice polarons which persist even in the metallic state. In La1.85Sr0.15CuO4 the energy width of the LO phonons around (π,0) determined by inelastic neutron scattering reflects magnetic satellites indicative of spin charge stripe formation. The implications of such nonuniform charge distribution for metal-insulator transition and superconductivity are discussed. [ABSTRACT FROM AUTHOR]

Upon doping the Mott-Hubbard insulator, an intermediate phase may be formed before the system reaches the Fermi-liquid phase. The pseudogap state and the spin/charge stripe phase are the possible examples of such a phase. We propose a new intermediate phase that has the form of the superlattice with $2\sqrt{2}a\times 2\sqrt{2}b$ in the CuO plane, and allows the coexistence of the Mott-Hubbard insulator and the Fermi-liquid. This hypothesis is supported by neutron diffraction data, the phonon dispersion determined by neutron scattering and the recent ARPES data. The implications of such a phase on the mechanism of high-temperature superconductivity are discussed. [ABSTRACT FROM AUTHOR]

We present the results of a structural study of metallic alloy liquids from high temperature through the glass transition. We use high energy X-ray scattering and electro-static levitation in combination with molecular dynamics simulation and show that the height of the first peak of the structure function, S(Q) − 1, follows the Curie-Weiss law. The structural coherence length is proportional to the height of the first peak, and we suggest that its increase with cooling may be related to the rapid increase in viscosity. The Curie temperature is negative, implying an analogy with spin-glass. The Curie-Weiss behavior provides a pathway to an ideal glass state, a state with long-range correlation without lattice periodicity, which is characterized by highly diverse local structures, reminiscent of spin-glass. [ABSTRACT FROM AUTHOR]

Lattice polarons play an important role in the mechanism of colossal magnetoresistance in the (La/Sr) n+1Mn nO3 n+1 manganites. Local lattice distortions were characterized by the pulsed neutron pair density function (PDF) analysis. The result shows that the doped holes form polarons related to the Jahn–Teller (JT) effect, both in the two-dimensional layered crystals ( n=2) and in the perovskites ( n=∞). The temperature effects are also similar in both systems suggesting that lattice polarons are largely independent of the crystal symmetry. [ABSTRACT FROM AUTHOR]

Liquid 4He becomes superfluid and flows without resistance below temperature 2.17 K. Superfluidity has been a subject of intense studies and notable advances were made in elucidating the phenomenon by experiment and theory. Nevertheless, details of the microscopic state, including dynamic atom-atom correlations in the superfluid state, are not fully understood. Here using a technique of neutron dynamic pair-density function (DPDF) analysis we show that 4He atoms in the Bose-Einstein condensate have environment significantly different from uncondensed atoms, with the interatomic distance larger than the average by about 10%, whereas the average structure changes little through the superfluid transition. DPDF peak not seen in the snap-shot pair-density function is found at 2.3 Å, and is interpreted in terms of atomic tunnelling. The real space picture of dynamic atom-atom correlations presented here reveal characteristics of atomic dynamics not recognized so far, compelling yet another look at the phenomenon. [ABSTRACT FROM AUTHOR]

The range of magnitude of the liquid viscosity, η, as a function of temperature is one of the most impressive of any physical property, changing by approximately 17 orders of magnitude from its extrapolated value at infinite temperature (ηo) to that at the glass transition temperature, Tg. We present experimental measurements of containerlessly processed metallic liquids that suggest that log(η/ηo) as a function of TA/T is a potentially universal scaled curve. In stark contrast to previous approaches, the scaling requires only two fitting parameters, which are on average predictable. The temperature TA corresponds to the onset of cooperative motion and is strongly correlated with Tg, suggesting that the processes underlying the glass transition first appear in the high temperature liquid. [ABSTRACT FROM AUTHOR]

The neutron powder diffractometer NPD at the Manuel Lujan Neutron Scattering Center (MLNSC) at Los Alamos National Laboratory is the neutron powder diffractometer with the highest resolution in the United States. We are currently upgrading NPD by adding a large number of position-sensitive detectors in the backscattering position. The upgraded instrument will make it possible to collect data from a powder sample over a wide range in Q with high Q resolution at high data rates. This design will optimize the instrument for total scattering measurements, including Bragg as well as diffuse scattering, allowing us to determine the crystallographic average structure as well as the local structure, often responsible for the properties of complex materials. [ABSTRACT FROM AUTHOR]

We present the results of inelastic neutron-scattering measurements of a twinned crystal of YBa[sub 2]Cu[sub 3]O[sub 6.95] using the MAPS spectrometer of the ISIS facility of the RutherfordAppleton Laboratory as well as the HFIR of the Oak Ridge National Laboratory. The dispersion of the Cu-O bondstretching modes indicates a strong dielectric anisotropy within the plane and associated electronic anisotropy, supporting the dynamic stripe model. The results suggest a possibility that phonons play a major role in the mechanism of high-temperature superconductivity. [ABSTRACT FROM AUTHOR]