There\u27s A Garden In Hawaii

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Phase Transformations in Binary Colloidal Monolayers

Phase transformations can be difficult to characterize at the microscopic level due to the inability to directly observe individual atomic motions. Model colloidal systems, by contrast, permit the direct observation of individual particle dynamics and of collective rearrangements, which allows for real-space characterization of phase transitions. Here, we study a quasi-two-dimensional, binary colloidal alloy that exhibits liquid-solid and solid-solid phase transitions, focusing on the kinetics of a diffusionless transformation between two crystal phases. Experiments are conducted on a monolayer of magnetic and nonmagnetic spheres suspended in a thin layer of ferrofluid and exposed to a tunable magnetic field. A theoretical model of hard spheres with point dipoles at their centers is used to guide the choice of experimental parameters and characterize the underlying materials physics. When the applied field is normal to the fluid layer, a checkerboard crystal forms; when the angle between the field and the normal is sufficiently large, a striped crystal assembles. As the field is slowly tilted away from the normal, we find that the transformation pathway between the two phases depends strongly on crystal orientation, field strength, and degree of confinement of the monolayer. In some cases, the pathway occurs by smooth magnetostrictive shear, while in others it involves the sudden formation of martensitic plates.Comment: 13 pages, 7 figures. Soft Matter Latex template was used. Published online in Soft Matter, 201

Sources, mechanisms, and timescales of sediment delivery to a New England salt marsh

© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Baranes, H., Woodruff, J., Geyer, W., Yellen, B., Richardson, J. & Griswold, F. Sources, mechanisms, and timescales of sediment delivery to a New England salt marsh. Journal of Geophysical Research: Earth Surface, 127, (2022): e2021JF006478, https://doi.org/10.1029/2021jf006478.he availability and delivery of an external clastic sediment source is a key factor in determining salt marsh resilience to future sea level rise. However, information on sources, mechanisms, and timescales of sediment delivery are lacking, particularly for wave-protected mesotidal estuaries. Here we show that marine sediment mobilized and delivered during coastal storms is a primary source to the North and South Rivers, a mesotidal bar-built estuary in a small river system impacted by frequent, moderate-intensity storms that is typical to New England (United States). On the marsh platform, deposition rates, clastic content, and dilution of fluvially-sourced contaminated sediment by marine material all increase down-estuary toward the inlet, consistent with a predominantly marine-derived sediment source. Marsh clastic deposition rates are also highest in the storm season. We observe that periods of elevated turbidity in channels and over the marsh are concurrent with storm surge and high wave activity offshore, rather than with high river discharge. Flood tide turbidity also exceeds ebb tide turbidity during storm events. Timescales of storm-driven marine sediment delivery range from 2.5 days to 2 weeks, depending on location within the estuary; therefore the phasing of storm surge and waves with the spring-neap cycle determines how effectively post-event suspended sediment is delivered to the marsh platform. This study reveals that sediment supply and the associated resilience of New England mesotidal salt marshes involves the interplay of coastal and estuarine processes, underscoring the importance of looking both up- and downstream to identify key drivers of environmental change.The project described in this publication was in part supported by Grant or Cooperative Agreement No. G20AC00071 from the U.S. Geological Survey and a Department of Interior Northeast Climate Adaptation Science Center graduate fellowship awarded to H.E.B (G12AC00001)

The Effects of Policy Guidance on Perceptions of the Fed's Reaction Function

In the past few years, the Federal Open Market Committee (FOMC) has been using forward guidance about the federal funds rate in a more explicit way than ever before. This paper explores the market reaction to the forward guidance, with particular focus on the use of calendar dates and economic thresholds in the FOMC statement. The results show that market participants interpreted the FOMC's policy guidance as conveying important information about the Committee's policy reaction function. In particular, market participants came to expect the FOMC to wait for lower levels of unemployment for a given level of inflation before beginning to raise the target federal funds rate, thereby shifting to a more accommodative policy approach aimed at supporting the economic recovery

Origin of multiplexing capabilities of multifrequency magnetic ratchets

Through a combination of theory, numerical simulation, and experiment, we investigate the motion of magnetic beads on the surface of a magnetic ratchet driven by multifrequency fields. Here, we focus on the influence of static forcing terms, which were not included in previous models, and we derive analytical models that show why the static forcing terms are responsible for inducing beads of two different sizes to move in opposite directions on the same ratchet potential. We begin our analysis with the simplest possible forcing model, and we show that the main effect of the static forcing terms is to delay the phase of flux reversal. From there, we move onto the full analysis and theoretically derive the phase range for which opposite motion among two different bead types is achieved. Based on these theoretical results, we conduct experimental investigations that explore the effects of bead size and static forcing coefficient on the direction of bead motion, which confirm most of the expected trends. These results shed light both on past experimental work both by ourselves and others, as well as elucidate the more general multiplexing capabilities of ratchets

Magnetophoretic circuits for digital control of single particles and cells.

The ability to manipulate small fluid droplets, colloidal particles and single cells with the precision and parallelization of modern-day computer hardware has profound applications for biochemical detection, gene sequencing, chemical synthesis and highly parallel analysis of single cells. Drawing inspiration from general circuit theory and magnetic bubble technology, here we demonstrate a class of integrated circuits for executing sequential and parallel, timed operations on an ensemble of single particles and cells. The integrated circuits are constructed from lithographically defined, overlaid patterns of magnetic film and current lines. The magnetic patterns passively control particles similar to electrical conductors, diodes and capacitors. The current lines actively switch particles between different tracks similar to gated electrical transistors. When combined into arrays and driven by a rotating magnetic field clock, these integrated circuits have general multiplexing properties and enable the precise control of magnetizable objects

Validation of high gradient magnetic field based drug delivery to magnetizable implants under flow

IEEE Transactions on Biomedical Engineering, 55(2): pp. 643-649.The drug-eluting stent’s increasingly frequent occurrence late stage thrombosis have created a need for new strategies for intervention in coronary artery disease. This paper demonstrates further development of our minimally invasive, targeted drug delivery system that uses induced magnetism to administer repeatable and patient specific dosages of therapeutic agents to specific sites in the human body. Our first aim is the use of magnetizable stents for the prevention and treatment of coronary restenosis; however, future applications include the targeting of tumors, vascular defects, and other localized pathologies. Future doses can be administered to the same site by intravenous injection. This implant-based drug delivery system functions by placement of a weakly magnetizable stent or implant at precise locations in the cardiovascular system, followed by the delivery of magnetically susceptible drug carriers. The stents are capable of applying high local magnetic field gradients within the body, while only exposing the body to a modest external field. The local gradients created within the blood vessel create the forces needed to attract and hold drug-containing magnetic nanoparticles at the implant site. Once these particles are captured, they are capable of delivering therapeutic agents such as antineoplastics, radioactivity, or biological cells

Older adults' attitudes about continuing cancer screening later in life: a pilot study interviewing residents of two continuing care communities

BACKGROUND: Individualized decision making has been recommended for cancer screening decisions in older adults. Because older adults' preferences are central to individualized decisions, we assessed older adults' perspectives about continuing cancer screening later in life. METHODS: Face to face interviews with 116 residents age 70 or over from two long-term care retirement communities. Interview content included questions about whether participants had discussed cancer screening with their physicians since turning age 70, their attitudes about information important for individualized decisions, and their attitudes about continuing cancer screening later in life. RESULTS: Forty-nine percent of participants reported that they had an opportunity to discuss cancer screening with their physician since turning age 70; 89% would have preferred to have had these discussions. Sixty-two percent believed their own life expectancy was not important for decision making, and 48% preferred not to discuss life expectancy. Attitudes about continuing cancer screening were favorable. Most participants reported that they would continue screening throughout their lives and 43% would consider getting screened even if their doctors recommended against it. Only 13% thought that they would not live long enough to benefit from cancer screening tests. Factors important to consider stopping include: age, deteriorating or poor health, concerns about the effectiveness of the tests, and doctors recommendations. CONCLUSION: This select group of older adults held positive attitudes about continuing cancer screening later in life, and many may have had unrealistic expectations. Individualized decision making could help clarify how life expectancy affects the potential survival benefits of cancer screening. Future research is needed to determine whether educating older adults about the importance of longevity in screening decisions would be acceptable, affect older adults' attitudes about screening, or change their screening behavior