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"Hill, A S"
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Structure in the Magnetic Field of the Milky Way Disk and Halo Traced by Faraday Rotation
Magnetic fields in the ionized medium of the disk and halo of the Milky Way impose Faraday rotation on linearly polarized radio emission. We compare two surveys mapping the Galactic Faraday rotation, one showing the rotation measures of extragalactic sources seen through the Galaxy, and one showing Faraday depth of the diffuse Galactic synchrotron emission from the Global Magneto-Ionic Medium Survey. Comparing the two data sets in 5° × 10° bins shows good agreement at intermediate latitudes, 10° < ∣b∣ < 50°, and little correlation between them at lower and higher latitudes. Where they agree, both tracers show clear patterns as a function of Galactic longitude, ℓ; in the northern hemisphere a strong sin(2ℓ) pattern; and in the southern hemisphere a sin(ℓ+π) pattern. Pulsars with height above or below the plane ∣z∣ > 300 pc show similar ℓ dependence in their rotation measures. Nearby nonthermal structures show rotation measure shadows as does the Orion–Eridanus superbubble. We describe families of dynamo models that could explain the observed patterns in the two hemispheres. We suggest that a field reversal, known to cross the plane a few hundred parsecs inside the solar circle, could shift to positive z with increasing Galactic radius to explain the sin(2ℓ) pattern in the northern hemisphere. Correlation shows that rotation measures from extragalactic sources are one to two times the corresponding rotation measure of the diffuse emission, implying Faraday complexity along some lines of sight, especially in the southern hemisphere.
Journal Article
Conservation of waterlogged wood—past, present and future perspectives
This paper reviews the degradation, preservation and conservation of waterlogged archaeological wood. Degradation due to bacteria in anoxic and soft-rot fungi and bacteria in oxic waterlogged conditions is discussed with consideration of the effect on the chemical composition of wood, as well as the deposition of sulphur and iron within the structure. The effects on physical properties are also considered. The paper then discusses the role of consolidants in preserving waterlogged archaeological wood after it is excavated as well as issues to be considered when reburial is used as a means of preservation. The use of alum and polyethylene glycol (PEG) as consolidants is presented along with various case studies with particular emphasis on marine artefacts. The properties of consolidated wood are examined, especially with respect to the degradation of the wood post-conservation. Different consolidants are reviewed along with their use and properties. The merits and risks of reburial and in situ preservation are considered as an alternative to conservation.
Journal Article
The Diffuse Ionized Gas Halo of the Large Magellanic Cloud
The Large Magellanic Cloud (LMC) has an extensive Hα emission halo that traces an extended, warm ionized component of its interstellar medium. Using the Wisconsin Hα Mapper telescope, we present the first kinematic Hα survey of an extensive region around the LMC, from (ℓ, b) = (264.°5, − 45.°5) to (295.°5, − 19.°5), covering +150 ≤ v LSR ≤ + 390 km s−1. We find that ionized hydrogen exists throughout the galaxy and extends several degrees beyond detected neutral hydrogen emission (logNHI/cm−2≈18.3) as traced by 21 cm in current surveys. Using the column density structure of the neutral gas and stellar line-of-sight depths as a guide, we estimate the upper limit mass of the ionized component of the LMC to be roughly M ionized ≈ (0.6–1.8) × 109 M ☉, which is comparable to the total neutral atomic gas mass in the same region (M neutral ≈ 0.76–0.85 × 109 M ☉). Considering only the atomic phases, we find M ionized/M ionized+neutral, to be 46%–68% throughout the LMC and its extended halo. Additionally, we find an ionized gas cloud that extends off of the LMC at (ℓ, b) ≈ (285°, − 28°) into a region previously identified as the Leading Arm complex. This gas is moving at a similar line-of-sight velocity as the LMC and has M ionized/M ionized+neutral = 13%–51%. This study, combined with previous studies of the SMC and extended structures of the Magellanic Clouds, continues to suggest that warm, ionized gas is as massive and dynamically important as the neutral gas in the Magellanic System.
Journal Article
What is the role of the accessibility of wood hydroxyl groups in controlling moisture content?
It has often been claimed that the equilibrium moisture content (EMC) of wood is controlled by the available hydroxyl group content and their accessibility, but this has not been proven. In the present study, the accessibility of the hydroxyl groups were analysed by deuterium exchange in a dynamic vapour sorption apparatus, and generally poor correlation with the EMC and hydroxyl group accessibility was found. Therefore, the role of the accessibility of wood hydroxyl groups in relation to exerting sole influence on the EMC is disputable. It is concluded that there has to be an additional mechanism to exercise control over the EMC in addition to hydroxyl group accessibility.
Journal Article
A critical discussion of the physics of wood–water interactions
This paper reviews recent findings on wood–water interaction and puts them into context of established knowledge in the field. Several new findings challenge prevalent theories and are critically discussed in an attempt to advance current knowledge and highlight gaps. The focus of this review is put on water in the broadest concept of wood products, that is, the living tree is not considered. Moreover, the review covers the basic wood–water relation, states and transitions. Secondary effects such as the ability of water to alter physical properties of wood are only discussed in cases where there is an influence on state and/or transition.
Journal Article
What do Patients Want?
What do Patients Want? provides readers with an insight into patients' psychoanalytic experiences \"from the couch\".Outcome studies have usually privileged the practitioner or researcher's voice, whilst underutilizing the rich published accounts of patients' own stories. Thus very little is understood or valued as to what actually takes place between patient and analyst, from the patient's perspective. This book sets out to tell the stories of eighteen ex-patients who, in interviews, reflected upon their experiences and described the factors which they believed were helpful - or not - in their analytic treatment. Free associating to an open question about how they understood and gave meaning to their personal journeys, these patients provided very vivid accounts of their analyses, demonstrated with clinical material. Their stories generally indicate a sophisticated understanding of the analytic process. Significant findings are discussed in each chapter, and then key conceptual issues are brought together at the end. The book is written in a journey format with each chapter related to a specific theme.
eBook
Sorption behaviour of torrefied wood and charcoal determined by dynamic vapour sorption
The most important variable of biomass-based fuels is moisture, because it affects the entire logistic chain by creating problems related to transport, handling, storage, and combustion. Recently, there has been a growing interest in thermal pre-treatment of biomass-based fuels by torrefaction. Torrefaction is intended to overcome the moisture-related problems by significantly reducing hygroscopicity and thus the logistics of solid biofuels could be improved. In order to gain a deeper insight on the changes induced by torrefaction, the sorption properties of Finnish birch and spruce wood were investigated. The sorption isotherms, hysteresis, accessibility, and surface area were investigated with dynamic vapour sorption. Also the particle size distributions and the clustering behaviour of water molecules were examined. As a result of the thermal pre-treatment, accessibility, adsorption of water vapour, and hysteresis were reduced. Particle size distribution was shifted towards smaller particles and the surface area measured with the BET method was reduced. Hysteresis was also reduced, which may be linked to the overall reduction in material’s hygroscopicity, as well as changes in porosity. The particle size affects sorption by increasing the surface area, but has a dual effect on accessibility, as it also blocks access to pores through agglomeration. In practice, the most important result is the increased hydrophobicity, but also the increased porosity and reduced particle size are to be considered as they can affect the handling and storage properties of torrefied and charred material negatively.
Journal Article