506 research outputs found
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
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
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
Exercise for health: a randomized, controlled trial evaluating the impact of a pragmatic, translational exercise intervention on the quality of life, function and treatment-related side effects following breast cancer
Exercise for Health was a randomized, controlled trial designed to evaluate two modes of delivering (face-to-face [FtF] and over-the-telephone [Tel]) an 8-month translational exercise intervention, commencing 6-weeks post-breast cancer surgery (PS). Outcomes included quality of life (QoL), function (fitness and upper body) and treatment-related side effects (fatigue, lymphoedema, body mass index, menopausal symptoms, anxiety, depression and pain). Generalised estimating equation modelling determined time (baseline [5 weeks PS], mid-intervention [6 months PS], post-intervention [12 months PS]), group (FtF, Tel, Usual Care [UC]) and time-by-group effects. 194 women representative of the breast cancer population were randomised to the FtF (n = 67), Tel (n = 67) and UC (n = 60) groups. There were significant (p < 0.05) interaction effects on QoL, fitness and fatigue with differences being observed between the treatment groups and the UC group. Trends observed for the treatment groups were similar. The treatment groups reported improved QoL, fitness and fatigue over time and changes observed between baseline and post-intervention were clinically relevant. In contrast, the UC group experienced no change, or worsening QoL, fitness and fatigue, mid-intervention. Although improvements in the UC group occurred by 12-months post-surgery, the change did not meet the clinically relevant threshold. There were no differences in other treatment-related side effects between groups. This translational intervention trial, delivered either FtF or Tel, supports exercise as a form of adjuvant breast cancer therapy that can prevent declines in fitness and function during treatment and optimise recovery post-treatment
Lithic technological responses to Late Pleistocene glacial cycling at Pinnacle Point Site 5-6, South Africa
There are multiple hypotheses for human responses to glacial cycling in the Late Pleistocene, including changes in population size, interconnectedness, and mobility. Lithic technological analysis informs us of human responses to environmental change because lithic assemblage characteristics are a reflection of raw material transport, reduction, and discard behaviors that depend on hunter-gatherer social and economic decisions. Pinnacle Point Site 5-6 (PP5-6), Western Cape, South Africa is an ideal locality for examining the influence of glacial cycling on early modern human behaviors because it preserves a long sequence spanning marine isotope stages (MIS) 5, 4, and 3 and is associated with robust records of paleoenvironmental change. The analysis presented here addresses the question, what, if any, lithic assemblage traits at PP5-6 represent changing behavioral responses to the MIS 5-4-3 interglacial-glacial cycle? It statistically evaluates changes in 93 traits with no a priori assumptions about which traits may significantly associate with MIS. In contrast to other studies that claim that there is little relationship between broad-scale patterns of climate change and lithic technology, we identified the following characteristics that are associated with MIS 4: increased use of quartz, increased evidence for outcrop sources of quartzite and silcrete, increased evidence for earlier stages of reduction in silcrete, evidence for increased flaking efficiency in all raw material types, and changes in tool types and function for silcrete. Based on these results, we suggest that foragers responded to MIS 4 glacial environmental conditions at PP5-6 with increased population or group sizes, 'place provisioning', longer and/or more intense site occupations, and decreased residential mobility. Several other traits, including silcrete frequency, do not exhibit an association with MIS. Backed pieces, once they appear in the PP5-6 record during MIS 4, persist through MIS 3. Changing paleoenvironments explain some, but not all temporal technological variability at PP5-6.Social Science and Humanities Research Council of Canada; NORAM; American-Scandinavian Foundation; Fundacao para a Ciencia e Tecnologia [SFRH/BPD/73598/2010]; IGERT [DGE 0801634]; Hyde Family Foundations; Institute of Human Origins; National Science Foundation [BCS-9912465, BCS-0130713, BCS-0524087, BCS-1138073]; John Templeton Foundation to the Institute of Human Origins at Arizona State Universit
Unambiguous observation of blocked states reveals altered, blocker-induced, cardiac ryanodine receptor gating
The flow of ions through membrane channels is precisely regulated by gates. The architecture and function of these elements have been studied extensively, shedding light on the mechanisms underlying gating. Recent investigations have focused on ion occupancy of the channel’s selectivity filter and its ability to alter gating, with most studies involving prokaryotic K+ channels. Some studies used large quaternary ammonium blocker molecules to examine the effects of altered ionic flux on gating. However, the absence of blocking events that are visibly distinct from closing events in K+ channels makes unambiguous interpretation of data from single channel recordings difficult. In this study, the large K+ conductance of the RyR2 channel permits direct observation of blocking events as distinct subconductance states and for the first time demonstrates the differential effects of blocker molecules on channel gating. This experimental platform provides valuable insights into mechanisms of blocker-induced modulation of ion channel gating
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
Directing cell therapy to anatomic target sites in vivo with magnetic resonance targeting
Cell-based therapy exploits modified human cells to treat diseases but its targeted application
in specific tissues, particularly those lying deep in the body where direct injection is not
possible, has been problematic. Here we use a magnetic resonance imaging (MRI) system to
direct macrophages carrying an oncolytic virus, Seprehvir, into primary and metastatic tumour
sites in mice. To achieve this, we magnetically label macrophages with super-paramagnetic
iron oxide nanoparticles and apply pulsed magnetic field gradients in the direction of the
tumour sites. Magnetic resonance targeting guides macrophages from the bloodstream into
tumours, resulting in increased tumour macrophage infiltration and reduction in tumour
burden and metastasis. Our study indicates that clinical MRI scanners can not only track the
location of magnetically labelled cells but also have the potential to steer them into one or
more target tissues
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