982 research outputs found

    Characterisation of Low Symmetry Liquid Crystal Structures

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    Noninvasive estimation of peak pulmonary artery pressure by M-mode echocardiography

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    In an attempt to predict peak pulmonary artery pressure from routine M-mode echocardiographic tracings, 95 infants and children with congenital heart disease were examined. Following the Burstin method for prediction of peak pulmonary artery pressure, which was originally based on the phonocardiogram and jugular phlebogram, M-mode echocardiography was used to measure the interval from pulmonary valve closure to tricuspid valve opening, namely, the period of isovolumic diastole. The measured interval was plotted on a modified table relating the interval, heart rate and predicted peak pulmonary artery pressure.The peak pulmonary artery pressure predicted by echocardiography was compared with that measured at cardiac catheterization. The correlation between predieted and actual peak pulmonary artery pressure was good (r = 0.86) for routine studies with the patient in the nonsedated state. All patients with a predicted peak pressure less than 40 mm Hg were found at catheterization to have a pressure less than 40 mm Hg. The correlation was better (r = 0.96) when comparing predictions made from the echocardiogram obtained while the patient was sedated for catheterization. Prediction of the magnitude of elevation of peak pressure was especially good when prediction and measurement were nearly simultaneous. Predictions were less accurate in the presence of tachycardia at rates of more than 155 beats/min. The method for estimating peak pulmonary artery pressure from M-mode echocardiographic tracings is reliable, relatively simple and clinically useful

    PhD Research in an Entrepreneurial Environment: The Innovation Realization Lab

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    This paper describes a new graduate education initiative entitled the Innovation Realization Laboratory that is funded by the National Science Foundation through the Integrative Graduate Education and Research Training (IGERT) program. The overall objective of the initiative is to have management students and Ph.D. students in science and engineering team to explore issues related to the commercialization of the Ph.D. students\u27 research results. This provides the MBA students with a real world opportunity to apply their business education in a high technology entrepreneurial situation, while providing the Ph.D. students an exposure to all of the complex issues associated with moving research findings to the marketplace. It represents an experiment to determine whether a significant enhancement of the educational experience can be acquired without placing an undue burden on either member of such a student team (or on the major professors). This program has been in operation for two years and has proven quite successful. The paper will describe the program structure, relate some of the lessons learned, and present an assessment of the program based on faculty observations and student feedback

    Macroscopic chirality of twist-bend nematic phase in bent dimers confirmed by circular dichroism

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    Many achiral bent molecules and some polymers with such repeat units exhibit a liquid crystal phase transition between a conventional nematic (N), and a second nematic (Nx) with periodically modulated orientation. Theory predicts several possible structures for the Nx phase, some of which are chiral (helical), and others achiral (e.g. zigzag). Experimentally distinguishing which modulation type is present is non-trivial and the structure is often assumed to be helical despite the other possibilities. Here we use circular dichroism (CD) spectroscopy to directly and unambiguously identify chirality in the Nx phase of two different dimer series, “DTC5Cn” and “CBCnCB”, which vary in (CH2)n spacer length (n=5, 7, 9). In doing so we have determined that the modulation type is helical in all samples. The temperature dependence of the CD signal was also investigated, suggesting that the helical structure progressively unwinds on approach to the high temperature N phas

    The TIGA technique for detecting gravitational waves with a spherical antenna

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    We report the results of a theoretical and experimental study of a spherical gravitational wave antenna. We show that it is possible to understand the data from a spherical antenna with 6 radial resonant transducers attached to the surface in the truncated icosahedral arrangement. We find that the errors associated with small deviations from the ideal case are small compared to other sources of error, such as a finite signal-to-noise ratio. An in situ measurement technique is developed along with a general algorithm that describes a procedure for determining the direction of an external force acting on the antenna, including the force from a gravitational wave, using a combination of the transducer responses. The practicality of these techniques was verified on a room-temperature prototype antenna.Comment: 15 pages, 14 figures, submitted to Physical Review

    In it together? The case for endocannabinoid–noradrenergic interactions in fear extinction

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    Anxiety and trauma-related disorders, such as post-traumatic stress disorder (PTSD), are debilitating mental illnesses with great personal and socioeconomic costs. Examining memory formation and relevant behavioural responding associated with aversive stimuli may improve our understanding of the neurobiology underlying fear memory processing and PTSD treatment. The neurocircuitry underpinning learned fear and its inhibition through extinction is complex, involving synergistic interactions between different neurotransmitter systems in inter-connected brain areas. Endocannabinoid and noradrenergic transmission have both been implicated separately in fear memory processing and PTSD, but potential interactions between these systems in relation to fear extinction have received little attention to date. Their receptors are expressed together in brain areas crucial for fear extinction, which is enhanced by both cannabinoid and noradrenergic receptor activation in these areas. Moreover, cannabinoid signalling modulates the activity of locus coeruleus noradrenaline (NA) neurons and the release of NA in the medial prefrontal cortex, a brain area that is crucial for fear extinction. Interestingly, endocannabinoid–noradrenergic system interactions have been shown to regulate the encoding and retrieval of fear memory. Thus, noradrenergic regulation of fear extinction may also be driven indirectly in part via cannabinoid receptor signalling. In this perspective paper, we collate the available relevant literature and propose a synergistic role for the endocannabinoid and noradrenergic systems in regulating fear extinction, the study of which may further our understanding of the neurobiological substrates of PTSD and its treatment

    Evaluating Puget Sound Marine Protected Areas to Improve MPA Policy and Implementation

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    In 2009, an inventory concluded there were 127 MPAs across the State of Washington. Despite this large number, relatively little is known about how well the MPAs are managed or how to improve their effectiveness, particularly in the Puget Sound. To understand how Puget Sound MPAs function from a social-ecological perspective, we will investigate the following key research questions: (1) What conditions and processes lead to successful MPA implementation?; (2) What are the opportunities for Puget Sound MPA planning processes to improve MPA management effectiveness and declare new, successful MPAs?; and (3) Should MPAs be used to increase social-ecological resilience in response to rockfish recovery needs, habitat loss, changing use patterns of Puget Sound resources, ocean acidification, and concomitant climate stresses? We will investigate these questions using literature reviews, key informant interviews, survey instruments, semi-structured interviews, and reviews of ecological monitoring data. Additionally, we will perform a scenario-planning workshop to improve MPA management, help resolve long-standing disagreements between various constituency groups, and possibly identify new MPA sites. We will also investigate whether impacts from climate change could serve as a potential “common ground” between disparate stakeholders for designing and evaluating spatial conservation strategies in a changing environment. Treaty tribes, who have unique rights and authorities as resource co-managers, are explicitly included in our research and scenario planning exercise. The objective of our presentation is to share our preliminary project design and solicit feedback to potentially improve it

    Interferometric mapping of the 3.3-mm continuum emission of comet 17P/Holmes after its 2007 outburst

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    Comet 17P/Holmes underwent a dramatic outburst in October 2007, caused by the sudden fragmentation of its nucleus and the production of a large quantity of grains scattering sunlight. We report on 90 GHz continuum observations carried out with the IRAM Plateau de Bure interferometer on 27.1 and 28.2 October 2007 UT, i.e., 4-5 days after the outburst. These observations probed the thermal radiation of large dust particles, and therefore provide the best constraints on the mass in the ejecta debris. The thermal emission of the debris was modelled and coupled to a time-dependent description of their expansion after the outburst. The analysis was performed in the Fourier plane. Visibilities were computed for the two observing dates and compared to the data to measure their velocity and mass. Optical data and 250-GHz continuum measurements published in the literature were used to further constrain the dust kinematics and size distribution. Two distinct dust components in terms of kinematic properties are identified in the data. The large-velocity component, with typical velocities V0 of 50-100 m/s for 1 mm particles, displays a steep size distribution with a size index estimated to q = -3.7 (\pm0.1), assuming a minimum grain size of 0.1 \mum. It corresponds to the fast expanding shell observed in optical images. The slowly-moving "core" component (V0 = 7-9 m/s) detected near the nucleus has a size index |q| < 3.4 and contains a higher proportion of large particles than the shell. The dust mass in the core is in the range 0.1-1 that of the shell. Using optical constants pertaining to porous grains (50% porosity) made of astronomical silicates mixed with water ice (48% in mass), the total dust mass Mdust injected by the outburst is estimated to 4-14 x 10**11 kg, corresponding to 3-9% the nucleus mass.Comment: 15 pages with 11 figures and 7 tables. Accepted for publication in Astronomy & Astrophysic

    Cannabidiol Prevents Spontaneous Fear Recovery after Extinction and Ameliorates Stress-Induced Extinction Resistance

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    Cannabidiol, the main non-psychotropic constituent of cannabis, has potential as a treatment for anxiety-related disorders since it reduces learned fear expression and enhances fear extinction. The return of fear over time after successful extinction and stress-induced extinction resistance are potential barriers to the treatment of these disorders with extinction-based psychological therapy. In two experiments using rats subjected to auditory fear conditioning, we determined the effects of systemic cannabidiol treatment on (1) delayed extinction and later spontaneous fear recovery, and (2) extinction resistance caused by immediate extinction (the immediate extinction deficit (IED)). In Experiment 1, cannabidiol was given before delayed extinction occurring 24 h after conditioning, with extinction recall and spontaneous fear recovery tested drug-free 1 and 21 days after extinction, respectively. We found that cannabidiol had no effect on extinction recall but it prevented spontaneous fear recovery. In Experiment 2, the IED procedure was first validated, with immediate extinction occurring 30 min after conditioning. We confirmed that immediate extinction impaired extinction recall, compared to delayed extinction. Next, cannabidiol was given before immediate or no extinction, with extinction recall tested drug-free the next day. We found that cannabidiol rescued the IED, which did not involve effects on fear memory consolidation. In summary, cannabidiol prevented spontaneous fear recovery after delayed extinction and ameliorated extinction resistance caused by immediate extinction. Although the pharmacological mechanisms underlying these effects remain to be determined, our results add to evidence indicating that cannabidiol might prove useful as an adjunct for potentiating the psychological treatment of anxiety-related disorders
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