Perfect coupling of light to surface plasmons with ultra-narrow linewidths

We examine the coupling of electromagnetic waves incident normal to a thin silver film that forms an oscillatory grating embedded between two otherwise uniform, semi-infinite half spaces. Two grating structures are considered, in one of which the mid point of the Ag film remains fixed whereas the thickness varies sinusoidally, while in the other the mid point oscillates sinusoidally whereas the film thicknesses remains fixed. On reducing the light wavelength from the long wavelength limit, we encounter signatures in the transmission, T, and reflection, R, coefficients associated with: i) the short-range surface plasmon mode, ii) the long-range surface plasmon mode, and iii) electromagnetic diffraction tangent to the grating. The first two features can be regarded as generalized (plasmon) Wood's anomalies whereas the third is the first-order conventional (electromagnetic) Wood's anomaly. The energy density at the film surface is enhanced for wavelengths corresponding to these three anomalies, particularly for the long range plasmon mode in thin films. When exciting the silver film with a pair of waves incident from opposite directions, we find that by adjusting the grating oscillation amplitude and fixing the relative phase of the incoming waves to be even or odd, T+R can be made to vanish for one or the other of the plasmon modes; this corresponds to perfect coupling (impedance matching in the language of electrical engineering) between the incoming light and these modes.Comment: 13 pages, 5 figures. accepted J. Chem. Phy

Factors associated with severity of hepatic fibrosis in people with chronic hepatitis C infection

The document attached has been archived with permission from the editor of the Medical Journal of Australia. An external link to the publisher’s copy is included.OBJECTIVE: To determine factors associated with hepatic fibrosis development in people with chronic hepatitis C virus (HCV) infection. METHODS: As a requirement for access to interferon therapy through the S100 scheme in Australia, individual pretreatment demographic and clinical information was collected on 2986 patients from 61 hospital-based liver clinics from 1 October 1994 through 31 December 1996. Patients with both a hepatic fibrosis score and an estimated duration of HCV infection (910) were divided into 540 with no or minimal hepatic fibrosis (stage 0–1) and 370 with moderate to severe hepatic fibrosis (stage 2–3). Seven factors were examined: age at HCV infection, sex, ethnicity, source of infection, duration of infection, alcohol intake, and mean ALT level. A further analysis was performed for all 1135 patients with a hepatic fibrosis score disregarding age at and duration of HCV infection. RESULTS: In multivariate analysis, four factors were significantly associated with moderate to severe hepatic fibrosis: age at infection (OR, 2.33 for age 31–40 years, 5.27 for age > 40 years, and 0.20 for age 30 years, compared with 3 times, compared with 1.5–2 times the upper limit of normal). In the analysis disregarding age at HCV infection and duration of HCV infection, older age was strongly associated with moderate to severe hepatic fibrosis (OR, 2.32 for age 36–40 years, 2.46 for age 41–50 years, 7.87 for age 51–60 years, and 7.15 for age > 60 years, compared with 16–30 years). There was no association in either analysis with sex or source of HCV infection. CONCLUSION: These factors may assist in targeting patients for both liver biopsy-based investigation and therapeutic intervention.Mark Danta, Gregory J Dore, Lisa Hennessy, Yueming Li, Chris R Vickers, Hugh Harley, Meng Ngu, William Reed, Paul V Desmond, William Sievert, Geoff C Farrell, John M Kaldor and Robert G Bate

Transcriptomic analysis of field-droughted sorghum from seedling to maturity reveals biotic and metabolic responses.

Drought is the most important environmental stress limiting crop yields. The C4 cereal sorghum [Sorghum bicolor (L.) Moench] is a critical food, forage, and emerging bioenergy crop that is notably drought-tolerant. We conducted a large-scale field experiment, imposing preflowering and postflowering drought stress on 2 genotypes of sorghum across a tightly resolved time series, from plant emergence to postanthesis, resulting in a dataset of nearly 400 transcriptomes. We observed a fast and global transcriptomic response in leaf and root tissues with clear temporal patterns, including modulation of well-known drought pathways. We also identified genotypic differences in core photosynthesis and reactive oxygen species scavenging pathways, highlighting possible mechanisms of drought tolerance and of the delayed senescence, characteristic of the stay-green phenotype. Finally, we discovered a large-scale depletion in the expression of genes critical to arbuscular mycorrhizal (AM) symbiosis, with a corresponding drop in AM fungal mass in the plants' roots

Three-dimensional effects on extended states in disordered models of polymers

We study electronic transport properties of disordered polymers in the presence of both uncorrelated and short-range correlated impurities. In our procedure, the actual physical potential acting upon the electrons is replaced by a set of nonlocal separable potentials, leading to a Schr\"odinger equation that is exactly solvable in the momentum representation. We then show that the reflection coefficient of a pair of impurities placed at neighboring sites (dimer defect) vanishes for a particular resonant energy. When there is a finite number of such defects randomly distributed over the whole lattice, we find that the transmission coefficient is almost unity for states close to the resonant energy, and that those states present a very large localization length. Multifractal analysis techniques applied to very long systems demonstrate that these states are truly extended in the thermodynamic limit. These results reinforce the possibility to verify experimentally theoretical predictions about absence of localization in quasi-one-dimensional disordered systems.Comment: 16 pages, REVTeX 3.0, 5 figures on request from FDA ([email protected]). Submitted to Phys. Rev. B. MA/UC3M/09/9

Magnetoresistance and magnetic breakdown in the quasi-two-dimensional conductors (BEDT-TTF)2_2MHg(SCN)4_4[M=K,Rb,Tl]

The magnetic field dependence of the resistance of (BEDT-TTF)$_2$MHg(SCN)$_4$[M=K,Rb,Tl] in the density-wave phase is explained in terms of a simple model involving magnetic breakdown and a reconstructed Fermi surface. The theory is compared to measurements in pulsed magnetic fields up to 51 T. The value implied for the scattering time is consistent with independent determinations. The energy gap associated with the density-wave phase is deduced from the magnetic breakdown field. Our results have important implications for the phase diagram.Comment: 5 pages, RevTeX + epsf, 3 figures. To appear in Physical Review B, Rapid Communications, September 15, 199

Versagenssimulation dynamisch belasteter Proben mit unterschiedlichen Mehrachsigkeitszuständen unter Verwendung des Johnson-Cook-Versagensmodells für eine Nickelbasislegierung

Das Versagensverhalten verschiedener prismatischer Scherproben wurde in einer Split-Hopkinson-Pressure-Bar-Anlage und das verschiedener gekerbter Rundzugproben in einer Schnellzerreißmaschine bei hohen Dehnraten untersucht. In Finite-Elemente-Simulationen mit ausschließlich einem viskoplastischen Deformationsmodell (Johnson-Cook), das thermische Entfestigung berücksichtigt, werden die experimentellen Kraft-Zeit-Verläufe weder bezüglich des Zeitpunktes des Einsetzens des Versagens noch bezüglich des dann auftretenden starken Kraftabfalls richtig wiedergegeben. Erst bei zusätzlicher Verwendung eines Schädigungs- bzw. Versagensmodells ist eine zufriedenstellende Übereinstimmung von Experiment und Simulation zu erzielen. Bei den vorgestellten Untersuchungen wurde das Johnson-Cook -Versagensmodell verwendet, das auch den Einfluss der Mehrachsigkeit berücksichtigt. Das Materialverhalten kann in Versuchen, die einen breiten Bereich von Mehrachsigkeiten aufweisen, mit nur einem Satz von Materialparametern simuliert werden

Convergence of Density Functional Iterative Procedures with a Newton-Raphson Algorithm

INTRODUCTION State of the art first-principles calculations of electronic structures aim at finding the ground state electronic density distribution. The performance of such methodologies is determined by the effectiveness of the iterative solution of the nonlinear density functional equation. We present a novel approach based on the appropriate density mapping. We start with the simplest density functional model, i.e., the atomic Thomas-Fermi model. Traditional mixing methods may not be appropriate for the larger complex systems of current technological interest. Mixing employs successive approximation iterates of a fixed point mapping. Such iterates are often found to converge very slowly or not at all. Attempting to resolve this, we have designed a quadratically convergent operator version of the Newton-Raphson method. From the minimization of the Thomas-Fermi functional, one obtains by variational methods a nonlinear integral mapping for which the ground state density function is a fixed point. THOMAS-FERMI MODEL After the functional minimization, we obtain, for the atomic number Z, the following mapping for the nonnegative density ρ in SI units: where κ = 3 5/3 π 4/3h2 /(10m). Here, the usual Lagrange multiplier μ, which fixes the number of electrons, has been set to zero, as appropriate for the neutral atom where and where N is the number of electrons. OPERATOR NEWTON-RAPHSON METHOD To apply the Newton-Raphson method, we introduce the mapping Y = I − R • P . In terms of this mapping, the iterates are given by Q new = Q old + δQ, where δQ is determined by the implicit relatio

Simulation der Spansegmentierung beim Hochgeschwindigkeits- Zerspanen unter Berücksichtigung duktiler Schädigung

Die für das Hochgeschwindigkeitsspanen charakteristische Segmentierung der Späne wird durch eine starke Lokalisierung der Deformation in der primären Scherzone verursacht. Für die untersuchte Nickelbasislegierung IN718 wurden lokal in den Scherbändern eines segmentierten Spans ausgeprägte Gefügeänderungen in Form sehr starker Kornstreckungen sowie teilweise Trennungen der Abgleitufer festgestellt. Ein viskoplastisches Modell, welches nur Dehnungsverfestigung und thermische Entfestigung berücksichtigt, ist nicht ausreichend, um das Versagen durch Scherbandbildung und die in einem Scherband bei seiner Entstehung gemessenen Temperaturen zutreffend wiederzugeben.Im Rahmen einer makroskopischen Betrachtung des Werkstoffverhaltens wird ein einfaches Modell für duktile Schädigung bei hohen Verformungsgeschwindigkeiten und großen Deformationen untersucht. Der Einfluss der Spannungs-Mehrachsigkeit auf die duktile Schädigung wird anhand von Hochgeschwindigkeits-Zugversuchen an gekerbten Proben sowie anhand von Doppel-Scherversuchen im Split-Hopkinson-Pressure-Bar-Aufbau simuliert. Durch die Berücksichtigung duktiler Schädigung gelingt sowohl die Darstellung der segmentierten Spanform bei gleichzeitiger Wiedergabe der in einem entstehenden Scherband gemessenen Temperaturen bei einer FESimulation des Orthogonal-Spanprozesses als auch die Simulation der Geschwindigkeitsabhängigkeit der Spansegmentierung