Total synthesis of (-)-tetrazomine and biochemical studies

2001 Summer.Includes bibliographical references.The total synthesis of (-)-tetrazomine is presented in which the relative and absolute stereochemistry of the natural product has been determined. The synthesis features a unique iminium cyclization followed by a 1,3-dipolar cylcoaddition. The stereochemistry of advance intermediates were determined by extensive 2D NMR techniques. The asymmetric synthesis of all four stereoisomers of β-hydroxy pipecolic acid has also been described. These stereoisomers were compared to the amino acid isolated from the hydrolysis of tetrazomine to determine the absolute stereochemistry of the amino acid moiety on the natural product. The route used to complete the total synthesis allowed for pipecolic acid analogs to be synthesized in order to study the effect of structure on the biochemical characteristics of these compounds. Along with oxazolidine ring containing analogs, ring opened amino nitrile analogs were also studied

Intrinsic Universality in Self-Assembly

We show that the Tile Assembly Model exhibits a strong notion of universality where the goal is to give a single tile assembly system that simulates the behavior of any other tile assembly system. We give a tile assembly system that is capable of simulating a very wide class of tile systems, including itself. Specifically, we give a tile set that simulates the assembly of any tile assembly system in a class of systems that we call \emph{locally consistent}: each tile binds with exactly the strength needed to stay attached, and that there are no glue mismatches between tiles in any produced assembly. Our construction is reminiscent of the studies of \emph{intrinsic universality} of cellular automata by Ollinger and others, in the sense that our simulation of a tile system $T$ by a tile system $U$ represents each tile in an assembly produced by $T$ by a $c \times c$ block of tiles in $U$, where $c$ is a constant depending on $T$ but not on the size of the assembly $T$ produces (which may in fact be infinite). Also, our construction improves on earlier simulations of tile assembly systems by other tile assembly systems (in particular, those of Soloveichik and Winfree, and of Demaine et al.) in that we simulate the actual process of self-assembly, not just the end result, as in Soloveichik and Winfree's construction, and we do not discriminate against infinite structures. Both previous results simulate only temperature 1 systems, whereas our construction simulates tile assembly systems operating at temperature 2

Utilizing synthetic training data for the supervised classification of rat ultrasonic vocalizations

Murine rodents generate ultrasonic vocalizations (USVs) with frequencies that extend to around 120kHz. These calls are important in social behaviour, and so their analysis can provide insights into the function of vocal communication, and its dysfunction. The manual identification of USVs, and subsequent classification into different subcategories is time consuming. Although machine learning approaches for identification and classification can lead to enormous efficiency gains, the time and effort required to generate training data can be high, and the accuracy of current approaches can be problematic. Here we compare the detection and classification performance of a trained human against two convolutional neural networks (CNNs), DeepSqueak and VocalMat, on audio containing rat USVs. Furthermore, we test the effect of inserting synthetic USVs into the training data of the VocalMat CNN as a means of reducing the workload associated with generating a training set. Our results indicate that VocalMat outperformed the DeepSqueak CNN on measures of call identification, and classification. Additionally, we found that the augmentation of training data with synthetic images resulted in a further improvement in accuracy, such that it was sufficiently close to human performance to allow for the use of this software in laboratory conditions.Comment: 25 pages, 5 main figures, 2 table

From appfest to entrepreneurs: using a hackathon event to seed a university student-led enterprise

Hackathons were once industry-specific programming sprints to get overdue features and applications completed; today they are a worldwide phenomenon, with businesses, educators, and entrepreneurs taking an interest in the benefits they can provide. Hackathons can be a breeding ground for brainstorming, innovation, networking, and product development, and as such they can have multiple outcomes including the sparking of new businesses and entrepreneurial activity. This paper investigates the effectiveness of utilising a hackathon as the genesis for the creation of sustainable student entrepreneurial activity. In particular, it seeks to evaluate the effectiveness of using hackathon-type events to initiate a successful University student enterprise project. The paper outlines the findings from this project, and concludes with a series of recommendations from the authors, on how one should market and structure a hackathon, and whether this vehicle should be chosen as a means to initiate a student enterprise project. The key factors that led to the success of this project were: the degree of formal structure that was introduced into the timings of the principle activities, not normally a feature of this kind of event, including scheduled “diversions” to break up the weekend; keeping the goals achievable; the duration of the event, in this case 48 hours spread over three days; the involvement of representatives from local businesses in the judging process; and crucially the adoption of an over-riding ethos for the event that focussed not on providing completed problem solutions but on potential innovative solutions that may not have been fully-functional. Areas for improvement included: inviting more students from earlier study years of degree programmes, not always the target audience for University hackathon activity; inviting students from a wide range of disciplines to ensure a broad set of participant skills and to encourage the formation of multi-disciplinary groupings by enforcing a balance of skills across teams, which as a corollary means not always allowing friendship groups to remain together; employing a team sufficiently large enough to support the duration of a long event; and careful consideration of the extent of competitiveness adopted in the event ethos. The project was part of the institution’s “Student as Producer” initiative where students and staff work side-by-side on research projects. Undergraduate students were fully involved in all aspects of the project, including an independent team who contributed to the authoring of this paper

Evaluating the climate effects of mid-1800s deforestation in New England, USA, using a Weather, Research, and Forecasting (WRF) Model Multi-Physics Ensemble

The New England region of the northeastern United States has a land use history characterized by forest clearing for agriculture and other uses during European colonization and subsequent reforestation following widespread farm abandonment. Despite these broad changes, the potential influence on local and regional climate has received relatively little attention. This study investigated wintertime (December through March) climate impacts of reforestation in New England using a high-resolution (4 km) multiphysics ensemble of the Weather Research and Forecasting Model. In general, the conversion from mid-1800s cropland/grassland to forest led to warming, but results were sensitive to physics parameterizations. The 2-m maximum temperature (T2max) was most sensitive to choice of land surface model, 2-m minimum temperature (T2min) was sensitive to radiation scheme, and all ensemble members simulated precipitation poorly. Reforestation experiments suggest that conversion of mid-1800s cropland/grassland to present-day forest warmed T2max +0.5 to +3 K, with weaker warming during a warm, dry winter compared to a cold, snowy winter. Warmer T2max over forests was primarily the result of increased absorbed shortwave radiation and increased sensible heat flux compared to cropland/grassland. At night, T2min warmed +0.2 to +1.5 K where deciduous broadleaf forest replaced cropland/grassland, a result of decreased ground heat flux. By contrast, T2min of evergreen needleleaf forest cooled –0.5 to –2.1 K, primarily owing to increased ground heat flux and decreased sensible heat flux

From hackathon to student enterprise: an evaluation of creating successful and sustainable student entrepreneurial activity initiated by a university hackathon

Hackathons are a worldwide phenomenon, with both industry and educators considering the opportunities and benefits that they generate. They can provide a forum for innovation, networking, and product design and development, thereby offering multiple outcomes. This paper develops the authors’ previous work on the effectiveness of utilising a hackathon as the spark for initiating student entrepreneurial activity by considering the success of the student enterprise that was created as a result and the extent to which that success was attributable to the hackathon event. Using a case study approach, the paper seeks to evaluate the effectiveness of using hackathon-type events to initiate a successful University student enterprise project and to identify the key elements in the future organisation of such a hackathon event that might lead to a sustainable and effective student enterprise. The paper outlines the findings from this project, which focus on the team building and bonding that take place in such an event, and concludes with a series of recommendations from the authors on how one should market and structure a hackathon to best ensure the success of a subsequently formed student enterprise, based on the evaluation of the project one year after it was founded. The evaluation of the project was undertaken as part of the institution’s “Student as Producer” initiative where students and staff work side-by-side on research projects. An independent team of undergraduate students was fully involved in all aspects of the project evaluation, including the authoring of this paper

Livestock branding in Oklahoma

The Oklahoma Cooperative Extension Service periodically issues revisions to its publications. The most current edition is made available. For access to an earlier edition, if available for this title, please contact the Oklahoma State University Library Archives by email at [email protected] or by phone at 405-744-6311

Performance Optimization of Storable Bipropellant Engines to Fully Exploit Advanced Material Technologies

This paper summarizes the work performed to dale on the NASA Cycle 3A Advanced Chemical Propulsion Technology Program. The primary goals of the program are to design, fabricate, and test high performance bipropellant engines using iridium/rhenium chamber technology to obtain 335 seconds specific impulse with nitrogen tetroxide/hydrazine propellants and 330 seconds specific impulse with nitrogen tetroxide/monomethylhydrazine propellants. Aerojet has successfully completed the Base Period of this program, wherein (1) mission and system studies have been performed to verify system performance benefits and to determine engine physical and operating parameters, (2) preliminary chamber and nozzle designs have been completed and a chamber supplier has been downselected, (3) high temperature, high pressure off-nominal hot fire testing of an existing state-of-the-art high performance bipropellant engine has been completed, and (4) thermal and performance data from the engine test have been correlated with new thermal models to enable design of the new engine injector and injector/chamber interface. In the next phase of the program, Aerojet will complete design, fabrication, and test of the nitrogen tetroxide/hydrazine engine to demonstrate 335 seconds specific impulse, and also investigate improved technologies for iridium/rhenium chamber fabrication. Achievement of the NRA goals will significantly benefit NASA interplanetary missions and other government and commercial opportunities by enabling reduced launch weight and/or increased payload. At the conclusion of the program, the objective is to have an engine ready for final design and qualification for a specific science mission or commercial application. The program also constitutes a stepping stone to future, development, such as higher pressure pump-fed in-space storable engines

The effect of exercise intensity on circulating hepatokine concentrations in healthy men [Abstract]

The effect of exercise intensity on circulating hepatokine concentrations in healthy men [Abstract

Feasibility and acceptability of a remotely delivered, home-based, pragmatic resistance ‘exercise snacking’ intervention in community-dwelling older adults: A pilot randomised controlled trial

Background: Very few older adults meet current muscle strengthening exercise guidelines, and several barriers exist to supervised, community-based resistance exercise programs. Older adults therefore require access to feasible resistance exercise modalities that may be performed remotely. This pilot study assessed the feasibility and acceptability of undertaking a four-week home-based resistance ‘exercise snacking’ intervention (performed either once, twice, or thrice daily) when delivered and monitored remotely in older adults. Methods: Thirty-eight community-dwelling older adults [mean ± SD age 69.8 ± 3.8 y, 63% female] were randomised to complete resistance ‘exercise snacks’ (9-minute sessions) either once (n = 9), twice (n = 10), or thrice (n = 9) daily, or allocated to usual-activity control (n = 10). Exercise adherence and adverse events were assessed using an exercise diary, and acceptability of the intervention was explored using an online questionnaire. Physical function [balance, 5-times sit-to-stand (STS), and 30-second STS tests] was assessed remotely at baseline and follow-up using videoconferencing. Results: The intervention was feasible and safe, with 100% participant retention, high adherence (97, 82, and 81% for once, twice, and thrice daily, respectively), and only two adverse events from a total of 1317 ‘exercise snacking’ sessions. The exercise intervention was rated as enjoyable (75% reported their enjoyment as ≥ 4 on a 5-point Likert scale), easy to perform, and most (82%) planned to continue similar exercise at home. We also found it was feasible to assess measures of physical function via videoconferencing, although effect sizes for 4-week changes in both 5-STS (d range, 0.4–1.4) and 30-STS (d range, 0.7–0.9) following the exercise intervention were similar to controls (d = 1.1 and 1.0 for 5-STS and 30-STS, respectively). Conclusions: Resistance ‘exercise snacking’ may be a feasible strategy for engaging older adults in home-based resistance exercise when delivered and monitored remotely. The findings of this pilot feasibility trial support the need for longer-term studies in larger cohorts to determine the effectiveness of resistance ‘exercise snacking’ approaches for improving physical function in older adults. Trial registration: The trial was retrospectively registered on 10/11/2021 with the Australian New Zealand Clinical Trials Registry (ANZCTR) (ACTRN12621001538831)