Effect of Distributed Particle Magnetic Moments on the Magnetization of NiO Nanoparticles

Magnetization of nanoparticles of NiO are measured and analyzed taking into account a distribution in particle magnetic moment. We find that disregarding this distribution in the analysis is the reason for the many anomalous observations reported on this system in the literature.Comment: 4 pages, 2 figure

Exact Study of the Effect of Level Statistics in Ultrasmall Superconducting Grains

The reduced BCS model that is commonly used for ultrasmall superconducting grains has an exact solution worked out long ago by Richardson in the context of nuclear physics. We use it to check the quality of previous treatments of this model, and to investigate the effect of level statistics on pairing correlations. We find that the ground state energies are on average somewhat lower for systems with non-uniform than uniform level spacings, but both have an equally smooth crossover from the bulk to the few-electron regime. In the latter, statistical fluctuations in ground state energies strongly depend on the grain's electron number parity.Comment: 4 pages, 3 eps figs, RevTe

Superconducting correlations in metallic nanoparticles: exact solution of the BCS model by the algebraic Bethe ansatz

Superconducting pairing of electrons in nanoscale metallic particles with discrete energy levels and a fixed number of electrons is described by the reduced BCS model Hamiltonian. We show that this model is integrable by the algebraic Bethe ansatz. The eigenstates, spectrum, conserved operators, integrals of motion, and norms of wave functions are obtained. Furthermore, the quantum inverse problem is solved, meaning that form factors and correlation functions can be explicitly evaluated. Closed form expressions are given for the form factors that describe superconducting pairing.Comment: revised version, 5 pages, revtex, no figure

Multivariate analysis of biologging data reveals the environmental determinants of diving behaviour in a marine reptile

Diving behaviour of ‘surfacers' such as sea snakes, cetaceans and turtles is complex and multi-dimensional, thus may be better captured by multi-sensor biologging data. However, analysing these large multi-faceted datasets remains challenging, though a high priority. We used high-resolution multi-sensor biologging data to provide the first detailed description of the environmental influences on flatback turtle (Natator depressus) diving behaviour, during its foraging life-history stage. We developed an analytical method to investigate seasonal, diel and tidal effects on diving behaviour for 24 adult flatback turtles tagged with biologgers. We extracted 16 dive variables associated with three-dimensional and kinematic characteristics for 4128 dives. K-means and hierarchical cluster analyses failed to identify distinct dive types. Instead, principal component analysis objectively condensed the dive variables, removing collinearity and highlighting the main features of diving behaviour. Generalized additive mixed models of the main principal components identified significant seasonal, diel and tidal effects on flatback turtle diving behaviour. Flatback turtles altered their diving behaviour in response to extreme tidal and water temperature ranges, displaying thermoregulation and predator avoidance strategies while likely optimizing foraging in this challenging environment. This study demonstrates an alternative statistical technique for objectively interpreting diving behaviour from multivariate collinear data derived from biologgers

Lean-Burn Stationary Natural Gas Reciprocating Engine Operation with a Prototype Miniature Diode Side Pumped Passively Q-switched Laser Spark Plug

To meet the ignition system needs of large bore lean burn stationary natural gas engines a laser diode side pumped passively Q-switched laser igniter was developed and used to ignite lean mixtures in a single cylinder research engine. The laser design was produced from previous work. The in-cylinder conditions and exhaust emissions produced by the miniaturized laser were compared to that produced by a laboratory scale commercial laser system used in prior engine testing. The miniaturized laser design as well as the combustion and emissions data for both laser systems was compared and discussed. It was determined that the two laser systems produced virtually identical combustion and emissions data

Modified differentials and basic cohomology for Riemannian foliations

We define a new version of the exterior derivative on the basic forms of a Riemannian foliation to obtain a new form of basic cohomology that satisfies Poincar\'e duality in the transversally orientable case. We use this twisted basic cohomology to show relationships between curvature, tautness, and vanishing of the basic Euler characteristic and basic signature.Comment: 20 pages, references added, minor corrections mad

Interplay between pairing and exchange in small metallic dots

We study the effects of the mesoscopic fluctuations on the competition between exchange and pairing interactions in ultrasmall metallic dots when the mean level spacing is comparable or larger than the BCS pairing energy. Due to mesoscopic fluctuations, the probability to have a non-zero spin ground state may be non-vanishing and shows universal features related to both level statistics and interaction. Sample to sample fluctuations of the renormalized pairing are enlightened.Comment: 10 pages, 5 figure

Conformal mapping methods for interfacial dynamics

The article provides a pedagogical review aimed at graduate students in materials science, physics, and applied mathematics, focusing on recent developments in the subject. Following a brief summary of concepts from complex analysis, the article begins with an overview of continuous conformal-map dynamics. This includes problems of interfacial motion driven by harmonic fields (such as viscous fingering and void electromigration), bi-harmonic fields (such as viscous sintering and elastic pore evolution), and non-harmonic, conformally invariant fields (such as growth by advection-diffusion and electro-deposition). The second part of the article is devoted to iterated conformal maps for analogous problems in stochastic interfacial dynamics (such as diffusion-limited aggregation, dielectric breakdown, brittle fracture, and advection-diffusion-limited aggregation). The third part notes that all of these models can be extended to curved surfaces by an auxilliary conformal mapping from the complex plane, such as stereographic projection to a sphere. The article concludes with an outlook for further research.Comment: 37 pages, 12 (mostly color) figure

(47171) 1999 TC36, A Transneptunian Triple

We present new analysis of HST images of (47171) 1999 TC36 that confirm it as a triple system. Fits to the point-spread function consistently show that the apparent primary is itself composed of two similar-sized components. The two central components, A1 and A2, can be consistently identified in each of nine epochs spread over seven years of time. In each instance the component separation, ranging from 0.023+/-0.002 to 0.031+/-0.003 arcsec, is roughly one half of the Hubble Space Telescope's diffraction limit at 606 nm. The orbit of the central pair has a semi-major axis of a~867 km with a period of P~1.9 days. These orbital parameters yield a system mass that is consistent with Msys = 12.75+/-0.06 10^18 kg derived from the orbit of the more distant secondary, component B. The diameters of the three components are dA1= 286(+45,-38) km, dA2= 265(+41,-35 km and dB= 139(+22,-18) km. The relative sizes of these components are more similar than in any other known multiple in the solar system. Taken together, the diameters and system mass yield a bulk density of p=542(+317,-211) kg m^-3. HST Photometry shows that component B is variable with an amplitude of >=0.17+/-0.05 magnitudes. Components A1 and A2 do not show variability larger than 0.08+/-0.03 magnitudes approximately consistent with the orientation of the mutual orbit plane and tidally-distorted equilibrium shapes. The system has high specific angular momentum of J/J'=0.93, comparable to most of the known Transneptunian binaries.Comment: 16 pages, 8 figures, 6 tables. Accepted to Icaru