Scanning electron microanalysis and analytical challenges of mapping elements in urban atmospheric particles

Elemental mapping with energy-dispersive X-ray spectroscopy (EDX) associated with scanning electron microscopy is highly useful for studying internally mixed atmospheric particles. Presented is a study of individual particles from urban airsheds and the analytical challenges in qualitatively determining the composition and origin of heterogeneous urban-air particles from high-resolution elemental maps. Coarse-mode particles were taken from samples collected in three U.S. cities: Atlanta, Los Angeles, and Seattle. Elemental maps distinguished particles with heterogeneously mixed phases from those with homogeneously mixed phases that also contained inclusions or surface adducts. Elemental mapping at low and high beam energies, along with imaging at an oblique angle helped to classify particles by origin. The impact of particle shape on X-ray microanalysis was demonstrated by having the beam enter the particle at ≥ 52° from normal. Potential misinterpretations of particle composition due to artifacts in the elemental maps were minimized by tilt imaging to reveal particle surface roughness and depth, mapping at low beam energies, noting the position of the EDX detector in the map field, and assessing differences in the mass absorption coefficients of the particle's major elements to anticipate X-ray self-absorption.     

Self‐Healing Fibre Reinforced Composites via a Bioinspired Vasculature

This paper demonstrates the first steps towards self‐healing composites that exploit a design philosophy inspired by the damage tolerance and self‐repair functions of bone. Cracking in either fibre reinforced polymers (FRP) or bone, if left unattended, can grow under subsequent cyclic stresses eventually leading to catastrophic failure of the structure. On detection of cracks, an FRP component must be repaired or completely replaced, whereas bone utilises a series of complex processes to repair such damage. Under normal circumstances, these processes allow the skeleton to continually perform over the lifespan of the organism, a highly desirable aspiration for engineering materials. A simple vasculature design incorporated into a FRP via a “lost wax” process was found to facilitate a self‐healing function which resulted in an outstanding recovery (≥96%) in post‐impact compression strength. The process involved infusion of a healing resin through the vascule channels. Resin egress from the backface damage, ultrasonic C‐scan testing, and microscopic evaluation all provide evidence that sufficient vascule–damage connectivity exists to confer a reliable and efficient self‐healing function.     

Optical properties of undoped n-AlGaN/GaN superlattices as affected by built-in and external-electric field and by ar-implantation-induced partial disordering

High-resolution x-ray diffraction patterns and 90 K microcathodoluminescence (MCL) spectra were taken for undoped, symmetric AlGaN/GaN superlattices (SLs) with GaN quantum-well (QW) widths of 35 Å and 80 Å. The short-period SL spectra were blue shifted by about 60 meV compared to the GaN substrate, and the magnitude of the blue shift was increased by about 20 meV by application of a reverse bias of ?3 V (electric field of about 4 · 10⁵ V/cm) to a Schottky diode prepared on this SL. A small red shift of about 40 meV compared to GaN was observed for the long-period SL. The two latter observations were interpreted as manifestations of the presence of a strong built-in piezoelectric field, giving rise to the quantum-confined Stark effect (QCSE). Partial disordering of the short-period SL was observed after Ar ion implantation (energy 150 keV, dose 8·10¹³ cm^?2 and 80 keV, 2·10¹³ cm^?2) and subsequent annealing at 1000°C for 3 h under the protective layer of Si₃N₄. However, it was observed that this partial disordering was accompanied by strain relaxation via formation of misfit dislocations or cracks.     

Performance limitation of fiber optic methane sensors due tointerference effects

We model interference effects in fiber optic methane sensors and predict the influence on the sensitivity. System sensitivity in terms of minimum detectable methane concentration is expressed as a function of birefringence, spectral transmission characteristics and polarization dependent loss of the fiber system, and the polarization and coherence characteristics of the light source. The sensitivity is calculated for various system arrangements and compared with existing experimental data. The model predicts that the interference effects may be minimized by using a depolarized broadband source (say, 30-50 nm) with a Gaussian spectral lineshape, together with a birefringence balanced sensor configuration     

A naturalistic study of the impact of acute physical activity on feeling states and affect in women.

This field study used experience sampling procedures to examine the relationship of feeling states and affect to acute bouts of physical activity in women. Participants (N?=?86) completed brief affect and feeling state measures (a) in response to random stratified pager tones and (b) before and after acute bouts of vigorous physical activity for 6 weeks. Analysis of averaged difference scores revealed that acute vigorous physical activity was associated with significant improvements in affect and feeling states, particularly in feelings of revitalization. Moreover, within-subject analyses indicated that the effects were moderated by preactivity scores, with the greatest improvements seen when women felt worst before activity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Preparation of glycol derivatives of partially hydrogenated soybean oil fatty acids and their potential as lubricants

The online version of the original article can be found at     

Effectiveness of the Woodruff School Doctoral Teaching Intern Program

This article discusses a unique teaching internship program that has been in place in the Woodruff School of Mechanical Engineering at Georgia Institute of Technology since 1990. The objective of the program is to provide doctoral students who are considering an academic career an opportunity to gain teaching experience under the tutelage of a faculty member. This article summarizes the major findings from student evaluations and from surveys of former student and faculty participants and discusses the apparent need and benefit of such a doctoral teaching intern program. Benefits and drawbacks of participation are discussed from the intern, faculty mentor, and student points of view. Conclusions are drawn about the overall effectiveness of the program and recommendations are made for implementing a successful teaching internship program.     

Predictors of hemorrhagic transformation occurring spontaneously and on anticoagulants in patients with acute ischemic stroke

We describe a case of microscopic polyangiitis involving skin and joints after influenza vaccination. Titers of antiinfluenza A antibody were markedly elevated in synovial fluid (SF) relative to those in serum. Antiinfluenza B antibodies were not present in SF but were present in serum, suggesting a reaction specifically involving antiinfluenza A antibodies localized to the affected joint. A review identified 16 other cases of vasculitis after influenza vaccination. The cases reclassified according to the Chapel Hill diagnostic criteria identified multiple forms of vasculitis including 7 other cases of microscopic polyangiitis. Three patients had similar illnesses after previous influenza vaccination or influenza-like illness. As in our case 11 cases resolved without recurrence. While this does not provide conclusive evidence that the vaccination caused the vasculitis, together with the serologic data we present it supports this hypothesis.     

Retroactive Effects of Irrelevant Speech on Serial Recall From Short-Term Memory.

The authors report 5 serial-recall experiments. In 4 of the 5 experiments, they show that irrelevant sound (IS) has a retroactive effect on material already in memory. In Experiment 1, IS presented during a filled retention interval had a reliable effect on list recall. Four further experiments, 3 of which used retroactive IS, showed that IS continued to-have an effect on recall following a long, filled retention interval. Articulatory suppression during visual input was found to abolish the long-lasting, retroactive effect of IS, supporting the idea that IS affects the phonological-loop component of short-term memory. IS also, therefore, seems to affect a longer term memory system with which the loop interacts. (PsycINFO Database Record (c) 2010 APA, all rights reserved)