Study of the kinetics and mechanism of rapid self-assembly in block copolymer thin films during solvo-microwave annealing

Microwave annealing is an emerging technique for achieving ordered patterns of block copolymer films on substrates. Little is understood about the mechanisms of microphase separation during the microwave annealing process and how it promotes the microphase separation of the blocks. Here, we use controlled power microwave irradiation in the presence of tetrahydrofuran (THF) solvent, to achieve lateral microphase separation in high- lamellar-forming poly(styrene-b-lactic acid) PS-b-PLA. A highly ordered line pattern was formed within seconds on silicon, germanium and silicon on insulator (SOI) substrates. In-situ temperature measurement of the silicon substrate coupled to condition changes during "solvo-microwave" annealing allowed understanding of the processes to be attained. Our results suggest that the substrate has little effect on the ordering process and is essentially microwave transparent but rather, it is direct heating of the polar THF molecules that causes microphase separation. It is postulated that the rapid interaction of THF with microwaves and the resultant temperature increase to 55 degrees C within seconds causes an increase of the vapor pressure of the solvent from 19.8 to 70 kPa. This enriched vapor environment increases the plasticity of both PS and PLA chains and leads to the fast self-assembly kinetics. Comparing the patterns formed on silicon, germanium and silicon on insulator (SOI) and also an in situ temperature measurement of silicon in the oven confirms the significance of the solvent over the role of substrate heating during "solvo-microwave" annealing. Besides the short annealing time which has technological importance, the coherence length is on a micron scale and dewetting is not observed after annealing. The etched pattern (PLA was removed by an Ar/O-2 reactive ion etch) was transferred to the underlying silicon substrate fabricating sub-20 nm silicon nanowires over large areas demonstrating that the morphology is consistent both across and through the film.

Processes of social flourishing and their liminal collapse: elements to a genealogy of globalization

This article aims at exploring a long-term historical perspective on which contemporary globalization can be more meaningfully situated. A central problem with established approaches to globalization is that they are even more presentist than the literature on modernization was. Presentism not only means the ignoring of history, but also the unreflective application to history of concepts taken from the study of the modern world. In contrast, it is argued that contemporary globalization is not a unique development, but rather is a concrete case of a historical type. Taking as its point of departure the spirit, rather than the word, of Max Weber, this article extends the scope of sociological investigation into archaeological evidence. Having a genealogical design and introducing the concept of ‘liminality’, the article approaches the modern process of globalization through reconstructing the internal dynamics of another type of historical change called ‘social flourishing’. Taking up the Weberian approach continued by Eisenstadt in his writings on ‘axial age’, it moves away from situations of crisis as reference point, shifting attention to periods of revival by introducing the term ‘epiphany’. Through the case of early Mesopotamia, it shows how social flourishing can be transmogrified into globalizing growth, gaining a new perspective concerning the kind of ‘animating spirit’ that might have driven the shift from Renaissance to Reformation, the rise of modern colonialism, or contemporary globalization. More generally, it will retrieve the long-term historical background of the axial age and demonstrate the usefulness and importance of archaeological evidence for sociology.

Microscopic processes in global relativistic jets containing helical magnetic fields

In the study of relativistic jets one of the key open questions is their interaction with the environment on the microscopic level. Here, we study the initial evolution of both electron–proton (e−–p+) and electron–positron (e±) relativistic jets containing helical magnetic fields, focusing on their interaction with an ambient plasma. We have performed simulations of “global” jets containing helical magnetic fields in order to examine how helical magnetic fields affect kinetic instabilities such as the Weibel instability, the kinetic Kelvin-Helmholtz instability (kKHI) and the Mushroom instability (MI). In our initial simulation study these kinetic instabilities are suppressed and new types of instabilities can grow. In the e−–p+ jet simulation a recollimation-like instability occurs and jet electrons are strongly perturbed. In the e± jet simulation a recollimation-like instability occurs at early times followed by a kinetic instability and the general structure is similar to a simulation without helical magnetic field. Simulations using much larger systems are required in order to thoroughly follow the evolution of global jets containing helical magnetic fields.

Risk of repeated self-harm and associated factors in children, adolescents and young adults

Background: Repeated self-harm represents the single strongest risk factor for suicide. To date no study with full national coverage has examined the pattern of hospital repeated presentations due to self-harm among young people. Methods: Data on consecutive self-harm presentations were obtained from the National Self-Harm Registry Ireland. Socio-demographic and behavioural characteristics of individuals aged 10–29 years who presented with self-harm to emergency departments in Ireland (2007–2014) were analysed. Risk of long-term repetition was assessed using survival analysis and time differences between the order of presentations using generalised estimating equation analysis. Results: The total sample comprised 28,700 individuals involving 42,642 presentations. Intentional drug overdose was the most prevalent method (57.9%). Repetition of self-harm occurred in 19.2% of individuals during the first year following a first presentation, of whom the majority (62.7%) engaged in one repeated act. Overall, the risk of repeated self-harm was similar between males and females. However, in the 20–24-year-old age group males were at higher risk than females. Those who used self-cutting were at higher risk for repetition than those who used intentional drug overdose, particularly among females. Age was associated with repetition only among females, in particular adolescents (15–19 years old) were at higher risk than young emerging adults (20–24 years old). Repeated self-harm risk increased significantly with the number of previous self-harm episodes. Time differences between first self-harm presentations were detected. Time between second and third presentation increased compared to time between first and second presentation among low frequency repeaters (patients with 3 presentations only within 1 year following a first presentation). The same time period decreased among high frequency repeaters (patients with at least 4 to more than 30 presentations). Conclusion: Young people with the highest risk for repeated self-harm were 15–19-year-old females and 20–24-year-old males. Self-cutting was the method associated with the highest risk of self-harm repetition. Time between first self-harm presentations represents an indicator of subsequent repetition. To prevent risk of repeated self-harm in young people, all individuals presenting at emergency departments due to self-harm should be provided with a risk assessment including psychosocial characteristics, history of self-harm and time between first presentations.