Ga^+ beam lithography for nanoscale silicon reactive ion etching

By using a dry etch chemistry which relies on the highly preferential etching of silicon, over that of gallium (Ga), we show resist-free fabrication of precision, high aspect ratio nanostructures and microstructures in silicon using a focused ion beam (FIB) and an inductively coupled plasma reactive ion etcher (ICP-RIE). Silicon etch masks are patterned via Ga^+ ion implantation in a FIB and then anisotropically etched in an ICP-RIE using fluorinated etch chemistries. We determine the critical areal density of the implanted Ga layer in silicon required to achieve a desired etch depth for both a Pseudo Bosch (SF_6/C_4F_8) and cryogenic fluorine (SF_6/O_2) silicon etching. High fidelity nanoscale structures down to 30 nm and high aspect ratio structures of 17:1 are demonstrated. Since etch masks may be patterned on uneven surfaces, we utilize this lithography to create multilayer structures in silicon. The linear selectivity versus implanted Ga density enables grayscale lithography. Limits on the ultimate resolution and selectivity of Ga lithography are also discussed

Participatory Mapping of Mid-Holocene Anthropogenic Landscapes in Guyana with Kite Aerial Photography

The nature and degree of human modifications of humid tropical forests in Amazonia have been widely debated over the past two decades Many regions provide significant evidence of late Holocene anthropogenic influence by settled populations but the antiquity of human interventions is still poorly understood due to a lack of earlier archaeological sites across the broad region particularly pertaining to the mid-Holocene Here we report on Amerindian occupations spanning the period from ca 6000-3000 BP along the middle Berbice River Guyana including early evidence in Amazonia of cultural practices widely considered indicative of settled villages notably terra preta or black earth soils mound construction and ceramic technology These more settled occupations of the mid-Holocene initiated a trajectory of landscape domestication extending into historical times including larger-scale late Holocene social formations Collaborative research with local indigenous communities including archaeological excavations landscape mapping using kite based aerial photography and three-dimensional photogrammetry was designed to promote the decolonization of archaeological knowledge production and encourage indigenous ownership of Amerindian history and cultural heritage in Guyan

How to identify sex chromosomes and their turnover

Although sex is a fundamental component of eukaryotic reproduction, the genetic systems that control sex determination are highly variable. In many organisms the presence of sex chromosomes is associated with female or male development. Although certain groups possess stable and conserved sex chromosomes, others exhibit rapid sex chromosome evolution including transitions between male and female heterogamety, and turnover in the chromosome pair recruited to determine sex. These turnover events have important consequences for multiple facets of evolution, as sex chromosomes are predicted to play a central role in adaptation, sexual dimorphism, and speciation. However, our understanding of the processes driving the formation and turnover of new sex chromosome systems is limited, in part because we lack a complete understanding of inter‐specific variation in the mechanisms by which sex is determined. New bioinformatic methods are making it possible to identify and characterize sex chromosomes in a diverse array of non‐model species, rapidly filling in the numerous gaps in our knowledge of sex chromosome systems across the tree of life. In turn, this growing dataset is facilitating and fueling efforts to address many of the unanswered questions in sex chromosome evolution. Here, we synthesize the available bioinformatic approaches to produce a guide for characterizing sex chromosome system and identity simultaneously across clades of organisms. Furthermore, we survey our current understanding of the processes driving sex chromosome turnover, and highlight important avenues for future research

An RF-powered micro-reactor for the detection of astrobiological target molecules on planetary bodies

We describe a sample-processing micro-reactor that utilizes 60 GHz RF radiation with approximately 730 mW of output power. The instrument design and performance characterization are described and then illustrated with modeling and experimental studies. The micro-reactor's efficiency on affecting hydrolysis of chemical bonds similar to those within large complex molecules was demonstrated: a disaccharide—sucrose—was hydrolyzed completely under micro-reactor conditions. The products of the micro-reactor-facilitated hydrolysis were analyzed using mass spectroscopy and proton nuclear magnetic resonance analytical techniques

Castleberry v. Branscum: A Divided Texas Supreme Court Increases Shareholder Liability for Corporate Contractual Obligations.

Abstract Forthcoming

Optimising planned medical education strategies to develop learners' person-centredness: a realist review

Context: Person-centeredness is a stated aim for medical education; however, studies suggest this is not being achieved. There is a gap in our understanding of how, why and in what circumstances medical education interventions that aim to develop person-centredness are successful. Methods: A realist review was conducted with a search of Medline, Embase, HMIC and ERIC databases and the grey literature using the terms ‘medical education’ and ‘person-centred’ and related synonyms. Studies that involved a planned educational intervention in medical education with data on outcomes related to person-centredness were included. The analysis focused on how and why different educational strategies interact with biomedical learner perspectives to trigger mechanisms that may or may not lead to a change in perspective towards person-centredness. Results: Sixty-one papers representing fifty-three interventions were included in the final synthesis. Nine context–intervention–mechanism–outcome configuration (CIMOc) statements generated from the data synthesis make up our refined programme theory. Where educational interventions focused on communication skills learning or experiences without person-centred theory, learners experienced dissonance with their biomedical perspective which they resolved by minimising the importance of the learning, resulting in perspective endurance. Where educational interventions applied person-centred theory to meaningful experiences and included support for sense making, learners understood the relevance of person-centeredness and felt able to process their responses to learning, resulting in perspective transformation towards person-centredness. Conclusion: Our findings offer explanations as to why communication skills-based interventions may be insufficient to develop learners' person-centredness. Integrating experiential person-centred learning with theory on why person-centredness matters to clinical practice and enabling learners to make sense of their responses to learning, may support perspective transformation towards person-centredness. Our findings offer programme and policymakers testable theory to inform the development of medical education strategies that aim to support person-centredness

Role of Nutrition in Alcoholic Liver Disease: Summary of the Symposium at the ESBRA 2017 Congress.

The symposium, "Role of Nutrition in Alcoholic Liver Disease", was held at the European Society for Biomedical Research on Alcoholism Congress on 9 October 2017 in Crete, Greece. The goal of the symposium was to highlight recent advances and developments in the field of alcohol and nutrition. The symposium was focused on experimental and clinical aspects in relation to the role of different types of dietary nutrients and malnutrition in the pathogenesis of alcoholic liver disease (ALD). The following is a summary of key research presented at this session. The speakers discussed the role of dietary fats and carbohydrates in the development and progression of alcohol-induced multi-organ pathology in animal models of ALD, analyzed novel nutrition-related therapeutics (specifically, betaine and zinc) in the treatment of ALD, and addressed clinical relevance of malnutrition and nutrition support in ALD. This summary of the symposium will benefit junior and senior faculty currently investigating alcohol-induced organ pathology as well as undergraduate, graduate, and post-graduate students and fellows

Castleberry v. Branscum: A Divided Texas Supreme Court Increases Shareholder Liability for Corporate Contractual Obligations.

Abstract Forthcoming