Does sub-cluster merging accelerate mass segregation in local star formation?

The nearest site of massive star formation in Orion is dominated by the Trapezium subsystem, with its four OB stars and numerous companions. The question of how these stars came to be in such close proximity has implications for our understanding of massive star formation and early cluster evolution. A promising route toward rapid mass segregation was proposed by McMillan et al. (2007), who showed that the merger product of faster-evolving sub clusters can inherit their apparent dynamical age from their progenitors. In this paper we briefly consider this process at a size and time scale more suited for local and perhaps more typical star formation, with stellar numbers from the hundreds to thousands. We find that for reasonable ages and cluster sizes, the merger of sub-clusters can indeed lead to compact configurations of the most massive stars, a signal seen both in Nature and in large-scale hydrodynamic simulations of star formation from collapsing molecular clouds, and that sub-virial initial conditions can make an un-merged cluster display a similar type of mass segregation. Additionally, we discuss a variation of the minimum spanning tree mass-segregation technique introduced by Allison et al. (2009).Comment: 9 pages, submitted to MNRA

Best Practices for Social Media Branding

Social media is a fast growing marketplace for businesses to advertise themselves to established and potential consumers. Each platform has different algorithms, demographics, and ways for users to interact and connect. Even with a constantly growing research field and course options around the subject, understanding the behaviors of viewers on each app can still be a tough guessing game. Therefore, I have used both research studies and online courses, to present a strategy with which to efficiently and effectively market one’s business for Facebook, Instagram, and TikTok. I then present ways to understand the success of this and personal marketing strategies. Using social media can improve your business, using a strategy specific for your brand can drastically improve your business

Radiative association and inverse predissociation of oxygen atoms

The formation of \mbox{O}_2 by radiative association and by inverse predissociation of ground state oxygen atoms is studied using quantum-mechanical methods. Cross sections, emission spectra, and rate coefficients are presented and compared with prior experimental and theoretical results. At temperatures below 1000~K radiative association occurs by approach along the $1\,{}^3\Pi_u$ state of \mbox{O}_2 and above 1000~K inverse predissociation through the \mbox{B}\,{}^3\Sigma_u^- state is the dominant mechanism. This conclusion is supported by a quantitative comparison between the calculations and data obtained from hot oxygen plasma spectroscopy.Comment: submitted to Phys. Rev. A (Sept. 7., 1994), 19 pages, 4 figures, latex (revtex3.0 and epsf.sty

Solution characterization and fabrication of hydrogel microstructures on an optical fiber

Sociomicrobiology has recently come to the forefront of bioanalytical research, primarily due to its physiological impact in the medical field. The interaction of bacterial cells in small, dense populations can reveal emergent properties of microbial communities, such as increased virulence and pathogenicity, as well as create a more accurate model for bacterial behavior in natural environments. Such systems are particularly relevant in mono- and polymicrobial communities, which exhibit social behaviors as well as the potential for symbiotic and/or adversarial interactions between species. The standard techniques for culturing bacteria lack the tools to provide adequate control over polymicrobial organization on a microscopic scale or to evaluate the spatiotemporal dynamics of bacterial interactions. Using our previously developed micro-3D printing platform, we can arrange cells in biocompatible, pico-liter sized containers, allowing us to overcome these prior spatial limitations. However, key questions still exist regarding the dynamics of interactions between distinct cellular populations. This dissertation focuses on the development of a modified micro-3D printing platform that enables us to fabricate protein-based structures around bacteria on the tip of a moveable substrate. Fabricating structures on moveable substrates such as a glass rod or optical fiber allows us to precisely tune where bacterial clusters are located in relation to varying stimuli and enables delivery of fabricated structures to remote environments such as chronic wounds. However, several challenges were faced in the development of this technique, such as optimization of fabrication solutions, successful layering of hydrogels of varying composition on glass rods, and creation of a custom-built fabrication setup for fabrication on optical fiber tips. Development of these techniques enables us to better appreciate the intricacies of sociomicrobial behavior and interactions, allowing for a better understanding of microbial responses leading to antibiotic resistance, and directing a better approach towards the treatment of various microbial infections.Chemistr

Body Size Shifts in Philippine Reef Fishes: Interfamilial Variation in Responses to Protection

As a consequence of intense fishing pressure, fished populations experience reduced population sizes and shifts in body size toward the predominance of smaller and early maturing individuals. Small, early-maturing fish exhibit significantly reduced reproductive output and, ultimately, reduced fitness. As part of resource management and biodiversity conservation programs worldwide, no-take marine protected areas (MPAs) are expected to ameliorate the adverse effects of fishing pressure. In an attempt to advance our understanding of how coral reef MPAs meet their long-term goals, this study used visual census data from 23 MPAs and fished reefs in the Philippines to address three questions: (1) Do MPAs promote shifts in fish body size frequency distribution towards larger body sizes when compared to fished reefs? (2) Do MPA size and (3) age contribute to the efficacy of MPAs in promoting such shifts? This study revealed that across all MPAs surveyed, the distribution of fishes between MPAs and fished reefs were similar; however, large-bodied fish were more abundant within MPAs, along with small, young-of-the-year individuals. Additionally, there was a significant shift in body size frequency distribution towards larger body sizes in 12 of 23 individual reef sites surveyed. Of 22 fish families, eleven demonstrated significantly different body size frequency distributions between MPAs and fished reefs, indicating that shifts in the size spectrum of fishes in response to protection are family-specific. Family-level shifts demonstrated a significant, positive correlation with MPA age, indicating that MPAs become more effective at increasing the density of large-bodied fish within their boundaries over time

A Leptin-regulated Circuit Controls Glucose Mobilization During Noxious Stimuli

Adipocytes secrete the hormone leptin to signal the sufficiency of energy stores. Reductions in circulating leptin concentrations reflect a negative energy balance, which augments sympathetic nervous system (SNS) activation in response to metabolically demanding emergencies. This process ensures adequate glucose mobilization despite low energy stores. We report that leptin receptor–expressing neurons (LepRb neurons) in the periaqueductal gray (PAG), the largest population of LepRb neurons in the brain stem, mediate this process. Application of noxious stimuli, which often signal the need to mobilize glucose to support an appropriate response, activated PAG LepRb neurons, which project to and activate parabrachial nucleus (PBN) neurons that control SNS activation and glucose mobilization. Furthermore, activating PAG LepRb neurons increased SNS activity and blood glucose concentrations, while ablating LepRb in PAG neurons augmented glucose mobilization in response to noxious stimuli. Thus, decreased leptin action on PAG LepRb neurons augments the autonomic response to noxious stimuli, ensuring sufficient glucose mobilization during periods of acute demand in the face of diminished energy stores

Anomalous Microwave Emission from the HII region RCW175

We present evidence for anomalous microwave emission in the RCW175 \hii region. Motivated by 33 GHz 13\arcmin resolution data from the Very Small Array (VSA), we observed RCW175 at 31 GHz with the Cosmic Background Imager (CBI) at a resolution of 4\arcmin. The region consists of two distinct components, G29.0-0.6 and G29.1-0.7, which are detected at high signal-to-noise ratio. The integrated flux density is $5.97\pm0.30$ Jy at 31 GHz, in good agreement with the VSA. The 31 GHz flux density is $3.28\pm0.38$ Jy ($8.6\sigma$) above the expected value from optically thin free-free emission based on lower frequency radio data and thermal dust constrained by IRAS and WMAP data. Conventional emission mechanisms such as optically thick emission from ultracompact \hii regions cannot easily account for this excess. We interpret the excess as evidence for electric dipole emission from small spinning dust grains, which does provide an adequate fit to the data.Comment: 5 pages, 2 figures, submmited to ApJ Letter

Specific Subpopulations of Hypothalamic Leptin Receptor-Expressing Neurons Mediate the Effects of Early Developmental Leptin Receptor Deletion on Energy Balance

ACKNOWLEDGEMENTS We thank MedImmune, Inc. and James Trevaskis, PhD and Christopher Rhodes, PhD for the gift of leptin. We thank members of the Myers and Olson labs for helpful discussions. Research support was provided by the Michigan Diabetes Research Center (NIH P3 0 DK020572, including the Molecular Genetics, Animal Phenotyping, and Clinical Cores), the American Diabetes Association (MGM), the Marilyn H. Vincent Foundation (MGM), the NIH (MGM: D K05673 1; ACR:DK071212; MBA: DK097861), the BBSRC (LKH: BB/NO17838/1) and WellcomeTrust (LKH: 098012).Peer reviewedPublisher PD

The efficacy of unsupervised home-based exercise regimens in comparison to supervised lab-based exercise training upon cardio-respiratory health facets

Supervised high-intensity interval training (HIIT) can rapidly improve cardiorespiratory fitness (CRF). However, the effectiveness of time-efficient unsupervised home-based interventions is unknown. Eighteen volunteers completed either: laboratory-HIIT (L HIIT); home-HIIT (H-HIIT) or home-isometric hand-grip training (H-IHGT). CRF improved significantly in L-HIIT and H-HIIT groups, with blood pressure improvements in the H-IHGT group only. H-HIIT offers a practical, time-efficient exercise mode to improve CRF, away from the laboratory environment. H-IHGT potentially provides a viable alternative to modify blood pressure in those unable to participate in whole-body exercise