The effects of common solvents on different types of flexographic printing plates

A dynamic development which has sparked flexography is the introduction and use of photopolymer plates. These plates have simplified flexographic printing by reducing the amount of time and effort needed to prepare plates for press and makeready. An experiment was conducted to determine the effect of commonly used solvent mixtures on flexographic plates. The plates tested include those using natural rubber, Buna N, and various photopolymers. The experiment specifically studied change in hardness of these plate materials due to immersion in different solvent mixtures over time. Noticeable differances in the degree of softening of plates was observed after 24 hours of immersion. Differences in the degree of softening were found in the plates after soaking in different percents of solvents. It was also discovered what percents of different lactol spirits and normal propyl acetate added to alcohol would affect the plates the most. Further, these differences were detectable at different periods of time. Most plates softened with time. One plate softened to such a degree with the solvent of this experiment that it was difficult to determine which solvents had a significant effect. This, of course, is due to the fact that solvents compatible with this plate were not used in this experiment. All photopolymer plates performed poorly in acetates, but it would be possible to use acetates with these plates over short periods of time on small press runs. When using flexographic plates of the composition tested in this experiment it is recommended that the practitioner use less than five percent of lactol or ten percent normal propyl acetate for a minimum affect on these plates over a short period of time

Quantifying the Effect of Plasma Processes on the Global Stability of Solar Prominences

Solar prominences are structures formed of cool, chromospheric plasma magneti- cally suspended in the solar corona for up to several solar rotations. Prominences are observed to migrate through quasi-equilibria until their host magnetic field loses equilibrium with its surroundings. It has traditionally been assumed that this ob- served plasma evolution is a consequence of evolution in the magnetic field alone. However, recent results indicate that this interpretation is incomplete. This thesis uses a combination of observations and modelling to quantify the different contri- butions of plasma and magnetic field to the stability of solar prominences. Firstly, the effect of prominence plasma on its host magnetic field was deter- mined using an observational case study. The optical thickness of the prominence was used to estimate column density and mass in the lead up to its eruption. An estimate of the ratio of plasma and magnetic forces indicates plasma processes can heavily influence the equilibrium. The study of mass was then expanded to a more general study using an ana- lytical model. The full equilibrium governing a general prominence was quantified and used to show that the effect of plasma on the structure is two-fold. Firstly, in- cluding plasma in the equilibrium stabilises the prominence, when comparing with the massless case, additional magnetic forces are therefore required to overcome the modified equilibrium. Secondly, removing plasma from a prominence in equi- librium can enable the magnetic field to become unstable and cause an eruption of the prominence. Finally, the fine-scale evolution of plasma within a prominence was studied using a combination of high-resolution observations and state-of-the-art models. The results suggest that the force-balance varies over the length of the prominence, hence these structures cannot be considered solely magnetically dominated. This work suggests that the relationship between prominence plasma and mag- netic field on both global- and fine-scales contributes more to the stability of promi- nences than previously believed

3D coupled tearing-thermal evolution in solar current sheets

Combined tearing-thermal evolution plays an important role in the disruption of current sheets, and formation of cool condensations within the solar atmosphere. However, this has received limited attention to date. We numerically explore a combined tearing and thermal instability that causes the break up of an idealized current sheet in the solar atmosphere. The thermal component leads to the formation of localized, cool condensations within an otherwise 3D reconnecting magnetic topology. We construct a 3D resistive magnetohydrodynamic simulation of a force-free current sheet under solar atmospheric conditions that incorporate the non-adiabatic influence of background heating, optically thin radiative energy loss, and magnetic field aligned thermal conduction with the open source code MPI-AMRVAC. Multiple levels of adaptive mesh refinement reveal the self-consistent development of finer-scale condensation structures within the evolving system. The instability in the current sheet is triggered by magnetic field perturbations concentrated around the current sheet plane, and subsequent tearing modes develop. This in turn drives thermal runaway associated with the thermal instability of the system. We find subsequent, localized cool plasma condensations that form under the prevailing low plasma-$\beta$ conditions, and demonstrate that the density and temperature of these condensed structures are similar to more quiescent coronal condensations. Synthetic counterparts at Extreme-UltraViolet (EUV) and optical wavelengths show the formation of plasmoids (in EUV), and coronal condensations similar to prominences and coronal rain blobs in the vicinity of the reconnecting sheet. Our simulations imply that 3D reconnection in solar current sheets may well present an almost unavoidable multi-thermal aspect, that forms during their coupled tearing-thermal evolution.Comment: Accepted for publication in Astronomy and Astrophysics journa

Chiral invariant renormalization of the pion--nucleon interaction

The leading divergences of the generating functional for Green functions of quark currents between one--nucleon states are calculated with heat kernel techniques. The results allow for a chiral invariant renormalization of all two--nucleon Green functions of the pion--nucleon system to $O(p^3)$ in the low--energy expansion.Comment: 13 pages, LaTex, 2 figures in appended postscript file, Univ. Wien preprint UWThPh-1994-

Quantifying the relationship between Moreton-Ramsey waves and "EIT waves" using observations of 4 homologous wave events

Freely-propagating global waves in the solar atmosphere are commonly observed using Extreme UltraViolet passbands (EUV or "EIT waves"), and less regularly in H-alpha (Moreton-Ramsey waves). Despite decades of research, joint observations of EUV and Moreton-Ramsey waves remain rare, complicating efforts to quantify the connection between these phenomena. We present observations of four homologous global waves originating from the same active region between 28-30 March 2014 and observed using both EUV and H-alpha data. Each global EUV wave was observed by the Solar Dynamics Observatory, with the associated Moreton-Ramsey waves identified using the Global Oscillations Network Group (GONG) network. All of the global waves exhibit high initial velocity (e.g., 842-1388 km s$^{-1}$ in the 193A passband) and strong deceleration (e.g., -1437 - -782 m s$^{-2}$ in the 193A passband) in each of the EUV passbands studied, with the EUV wave kinematics exceeding those of the Moreton-Ramsey wave. The density compression ratio of each global wave was estimated using both differential emission measure and intensity variation techniques, with both indicating that the observed waves were weakly shocked with a fast magnetosonic Mach number slightly greater than one. This suggests that, according to current models, the global coronal waves were not strong enough to produce Moreton-Ramsey waves, indicating an alternative explanation for these observations. Instead, we conclude that the evolution of the global waves was restricted by the surrounding coronal magnetic field, in each case producing a downward-angled wavefront propagating towards the north solar pole which perturbed the chromosphere and was observed as a Moreton-Ramsey wave.Comment: 12 pages, 5 figures, accepted for publication in The Astrophysical Journa

Artificial light at night reverses monthly foraging pattern under simulated moonlight

Mounting evidence shows that artificial light at night (ALAN) alters biological processes across levels of organization, from cells to communities. Yet, the combined impacts of ALAN and natural sources of night-time illumination remain little explored. This is in part due the lack of accurate simulations of the complex changes moonlight intensity, timing and spectra throughout a single night and lunar cycles in laboratory experiments. We custom-built a novel system to simulate natural patterns of moonlight to test how different ALAN intensities affect predator–prey relationships over the full lunar cycle. Exposure to high intensity ALAN (10 and 50 lx) reversed the natural lunar-guided foraging pattern by the gastropod mesopredator Nucella lapillus on its prey Semibalanus balanoides. Foraging decreased during brighter moonlight in naturally lit conditions. When exposed to high intensity ALAN, foraging increased with brighter moonlight. Low intensity ALAN (0.1 and 0.5 lx) had no impact on foraging. Our results show that ALAN alters the foraging pattern guided by changes in moonlight brightness. ALAN impacts on ecosystems can depend on lunar light cycles. Accurate simulations of night-time light cycle will warrant more realistic insights into ALAN impacts and also facilitate advances in fundamental night-time ecology and chronobiology

TESTING VARIANCE COMPONENTS BY TWO JACKKNIFE METHODS

The jackknife method, a resampling technique, has been widely used for statistical tests for years. The pseudo value based jackknife method (defined as pseudo jackknife method) is commonly used to reduce the bias for an estimate; however, sometimes it could result in large variation for an estimate and thus reduce the power for parameters of interest. In this study, a non-pseudo value based jackknife method (defined as non-pseudo jackknife method) was used for testing variance components under mixed linear models. We compared this non-pseudo value based jackknife method and the pseudo value based method by simulation regarding their biases, Type I errors, and powers. Our simulated results showed that biases obtained by the two jackknife methods are very similar; however, the non-pseudo value based method had higher testing powers than the pseudo value based method while the non-pseudo value based method had lower Type I error rates than the preset nomial probability values. Thus, we concluded that the non-pseudo value based jackknife method is superior to the pseudo value based method for testing variance components under a general mixed linear model

Human-animal entanglements in bushmeat trading in Sierra Leone: An ethnographic assessment of a potential zoonotic interface

‘Bushmeat’ markets are often portrayed as chaotic spaces where exotic wild animals are sold. They are hypothesized to be important sites for zoonotic disease transmission, given the prolonged and intense nature of the cross-species encounters that occur within them. Whilst such markets have received some attention from researchers, rich qualitative descriptions of everyday practices in these markets are rare. Depictions of wild animal markets as sites for potential viral amplification often rely on exoticizing assumptions and narratives rather than actual evidence, and in some cases are based more on ideology than on science. We provide an in-depth ethnographic account of two bushmeat markets in Bo, Sierra Leone. Our analysis goes beyond common assumptions that zoonotic risk is located solely in the knowledge and behaviours of traders. Our account sheds light on the modes of touch, closeness and contact that shape this hypothesised zoonotic interface, outlining the possible risks to different people who use and spend time in the market. We found that inadequate infrastructure and sanitation facilities created risks of zoonotic disease transmission for diverse actors including traders, customers, children, and the wider public. Butchering and trading practices frequently resulted in people directly and indirectly encountering animal fluids. We also discuss how public health management of these markets focused on individual behaviours rather than on improving conditions. Urgent sanitary reform and infrastructure upgrades in these sites that support the economic needs of traders could encourage voluntary compliance with biosafety measures amongst traders seeking to balance responsibilities to family and public health. Our study reveals the value of moving beyond exoticized narratives about bushmeat markets to yield situated insights for reducing risk at this interface