Nano-scale analysis of titanium dioxide fingerprint-development powders

Titanium dioxide based powders are regularly used in the development of latent fingerprints on dark surfaces. For analysis of prints on adhesive tapes, the titanium dioxide is suspended in a surfactant and used in the form of a small particle reagent (SPR). Analysis of commercially available products shows varying levels of effectiveness of print development, with some powders adhering to the background as well as the print. Scanning electron microscopy (SEM) images of prints developed with different powders show a range of levels of aggregation of particles. Analytical transmission electron microscopy (TEM) of the fingerprint powder shows TiO2 particles with a surrounding coating, tens of nanometres thick, consisting of Al and Si rich material. X ray photoelectron spectroscopy (XPS) is used to determine the composition and chemical state of the surface of the powders; with a penetration depth of approximately 10nm, this technique demonstrates differing Ti: Al: Si ratios and oxidation states between the surfaces of different powders. Levels of titanium detected with this technique demonstrate variation in the integrity of the surface coating. The thickness, integrity and composition of the Al/Si-based coating is related to the level of aggregation of TiO2 particles and efficacy of print development

Demystifying our Grandparent's De Bruijn Sequences with Concatenation Trees

Some of the most interesting de Bruijn sequences can be constructed in seemingly unrelated ways. In particular, the "Granddaddy" and "Grandmama" can be understood by joining necklace cycles into a tree using simple parent rules, or by concatenating smaller strings (e.g., Lyndon words) in lexicographic orders. These constructions are elegant, but their equivalences seem to come out of thin air, and the community has had limited success in finding others of the same ilk. We aim to demystify the connection between cycle-joining trees and concatenation schemes by introducing "concatenation trees". These structures combine binary trees and ordered trees, and traversals yield concatenation schemes for their sequences. In this work, we focus on the four simplest cycle-joining trees using the pure cycling register (PCR): "Granddaddy" (PCR1), "Grandmama" (PCR2), "Granny" (PCR3), and "Grandpa" (PCR4). In particular, we formally prove a previously observed correspondence for PCR3 and we unravel the mystery behind PCR4. More broadly, this work lays the foundation for translating cycle-joining trees to known concatenation constructions for a variety of underlying feedback functions including the complementing cycling register (CCR), pure summing register (PSR), complementing summing register (CSR), and pure run-length register (PRR)

Incoherent dynamics in neutron-matter interaction

Coherent and incoherent neutron-matter interaction is studied inside a recently introduced approach to subdynamics of a macrosystem. The equation describing the interaction is of the Lindblad type and using the Fermi pseudopotential we show that the commutator term is an optical potential leading to well-known relations in neutron optics. The other terms, usually ignored in optical descriptions and linked to the dynamic structure function of the medium, give an incoherent contribution to the dynamics, which keeps diffuse scattering and attenuation of the coherent beam into account, thus warranting fulfilment of the optical theorem. The relevance of this analysis to experiments in neutron interferometry is briefly discussed.Comment: 15 pages, revtex, no figures, to appear in Phys. Rev.

Direct evidence for the magnetic ordering of Nd ions in NdFeAsO by high resolution inelastic neutron scattering

We investigated the low energy excitations in the parent compound NdFeAsO of the Fe-pnictide superconductor in the $\mu$eV range by a back scattering neutron spectrometer. The energy scans on a powder NdFeAsO sample revealed inelastic peaks at E = 1.600 $\pm 0.003 \mu$eV at T = 0.055 K on both energy gain and energy loss sides. The inelastic peaks move gradually towards lower energy with increasing temperature and finally merge with the elastic peak at about 6 K. We interpret the inelastic peaks to be due to the transition between hyperfine-split nuclear level of the $^{143}$Nd and $^{145}$Nd isotopes with spin $I = 7/2$. The hyperfine field is produced by the ordering of the electronic magnetic moment of Nd at low temperature and thus the present investigation gives direct evidence of the ordering of the Nd magnetic sublattice of NdFeAsO at low temperature

Effects of Process Variables and Size Scale on Solidification Microstructure in Laser-Based Solid Freeform Fabrication of Ti-6Al-4V

Mechanical Engineerin

ACE Data from the ACE Science Center

The purpose of the ACE Science Center (ASC) is to perform level 1 processing of data from the nine science instruments aboard the Advanced Composition Explorer (ACE) spacecraft and to facilitate access to all ACE data by both the instrument investigators and the space physics community. We describe the ACE data products available from the ASC and the methods by which users may access the data

Observer with a constant proper acceleration

Relying on the equivalence principle, a first approach of the general theory of relativity is presented using the spacetime metric of an observer with a constant proper acceleration. Within this non inertial frame, the equation of motion of a freely moving object is studied and the equation of motion of a second accelerated observer with the same proper acceleration is examined. A comparison of the metric of the accelerated observer with the metric due to a gravitational field is also performed.Comment: 5 figure

Nuclear Incompressibility in Asymmetric Systems at Finite Temperature and Entropy

The nuclear incompressibility $\kappa$ is investigated in asymmetric systems in a mean field model. The calculations are done at zero and finite temperatures and include surface, Coulomb and symmetry energy terms for several equations of state. Also considered is the behavior of the incompressibility at constant entropy $kappa_Q$ which is shown to have a very different behavior than the isothermal $kappa$. Namely, $kappa_Q$ decreases with increasing entropy while the isothermal $kappa$ increases with increasing $T$. A duality is found between the adiabatic $kappa_Q$ and the T=0 isothermal $kappa$. Analytic and also simple approximate expressions for $kappa$ are given.Comment: 11 page