6,763 research outputs found
Evaluation of thermal insulation materials
Data was obtained on silicone-bonded fiberglass, isocyanurate foam, and two dozen other insulators. Materials were selected to withstand heat sterilization, outer space, and the Martian atmosphere. Significant environmental parameters were vibration, landing shock, and launch venting
Relativistic ionization-rescattering with tailored laser pulses
The interaction of relativistically strong tailored laser pulses with an
atomic system is considered. Due to a special tailoring of the laser pulse, the
suppression of the relativistic drift of the ionized electron and a dramatic
enhancement of the rescattering probability is shown to be achievable. The high
harmonic generation rate in the relativistic regime is calculated and shown to
be increased by several orders of magnitude compared to the case of
conventional laser pulses. The energies of the revisiting electron at the
atomic core can approach the MeV domain, thus rendering hard x-ray harmonics
and nuclear reactions with single atoms feasible
Light scattering and phase behavior of Lysozyme-PEG mixtures
Measurements of liquid-liquid phase transition temperatures (cloud points) of
mixtures of a protein (lysozyme) and a polymer, poly(ethylene glycol) (PEG)
show that the addition of low molecular weight PEG stabilizes the mixture
whereas high molecular weight PEG was destabilizing. We demonstrate that this
behavior is inconsistent with an entropic depletion interaction between
lysozyme and PEG and suggest that an energetic attraction between lysozyme and
PEG is responsible. In order to independently characterize the lysozyme/PEG
interactions, light scattering experiments on the same mixtures were performed
to measure second and third virial coefficients. These measurements indicate
that PEG induces repulsion between lysozyme molecules, contrary to the
depletion prediction. Furthermore, it is shown that third virial terms must be
included in the mixture's free energy in order to qualitatively capture our
cloud point and light scattering data. The light scattering results were
consistent with the cloud point measurements and indicate that attractions do
exist between lysozyme and PEG.Comment: 5 pages, 2 figures, 1 tabl
Effect of transient pinning on stability of drops sitting on an inclined plane
We report on new instabilities of the quasi-static equilibrium of water drops
pinned by a hydrophobic inclined substrate. The contact line of a statically
pinned drop exhibits three transitions of partial depinning: depinning of the
advancing and receding parts of the contact line and depinning of the entire
contact line leading to the drop's translational motion. We find a region of
parameters where the classical Macdougall-Ockrent-Frenkel approach fails to
estimate the critical volume of the statically pinned inclined drop
Visualisation of alternating shielding gas flow in GTAW
The alternating shielding gas technique is a method of achieving transient arc characteristics during arc welding; however the complex flow that occurs through its use has not been investigated previously. A schlieren system was used to image density gradients that arise when alternating argon and helium shield gases, under varying flow parameters, with gas tungsten arc welding (GTAW). A theoretical analysis was carried out to determine the conditions under which the technique facilitates arc pulsing, in particular to avoid mixing the shield gases in the delivery pipe prior to the welding nozzle. At appropriate pulsing frequency and flow rates, a stable horizontal region of helium was obseved in the weld region, maintained in position by the denser argon from the preceding pulse. This higher than average mass fraction of helium when applying the shielding gases alternately, compare to a premixed gas with the same volume of argon and helium, increased the weld penetration by 13% on average, suggesting a modest improvement in heat transfer
How Polarized Have We Become? A Multimodal Classification of Trump Followers and Clinton Followers
Polarization in American politics has been extensively documented and
analyzed for decades, and the phenomenon became all the more apparent during
the 2016 presidential election, where Trump and Clinton depicted two radically
different pictures of America. Inspired by this gaping polarization and the
extensive utilization of Twitter during the 2016 presidential campaign, in this
paper we take the first step in measuring polarization in social media and we
attempt to predict individuals' Twitter following behavior through analyzing
ones' everyday tweets, profile images and posted pictures. As such, we treat
polarization as a classification problem and study to what extent Trump
followers and Clinton followers on Twitter can be distinguished, which in turn
serves as a metric of polarization in general. We apply LSTM to processing
tweet features and we extract visual features using the VGG neural network.
Integrating these two sets of features boosts the overall performance. We are
able to achieve an accuracy of 69%, suggesting that the high degree of
polarization recorded in the literature has started to manifest itself in
social media as well.Comment: 16 pages, SocInfo 2017, 9th International Conference on Social
Informatic
Regulations & exemptions during the COVID-19 pandemic for new medical technology, health services & data
The rapid evolution of the COVID-19 pandemic has sparked a large unmet need for new or additional medical technology and healthcare services to be made available urgently. Healthcare, Academic, Government and Industry organizations and individuals have risen to this challenge by designing, developing, manufacturing or implementing innovation. However, both they and healthcare stakeholders are hampered as it is unclear how to introduce and deploy the products of this innovation quickly and legally within the healthcare system. Our paper outlines the key regulations and processes innovators need to comply with, and how these change during a public health emergency via dedicated exemptions. Our work includes references to the formal documents regarding UK healthcare regulation and governance, and is meant to serve as a guide for those who wish to act quickly but are uncertain of the legal and regulatory pathways that allow new a device or service to be fast-tracked
Bronchial Artery Embolisation for Massive Haemoptysis: Immediate and Long-Term Outcomes-A Retrospective Study.
INTRODUCTION: Bronchial artery embolisation (BAE) is an established treatment method for massive haemoptysis. The aim of this study is to evaluate the impact of BAE on in-hospital outcomes and long-term survival in patients with massive haemoptysis. METHODS: Retrospective review of all cases of acute massive haemoptysis treated by BAE between April 2000 and April 2012 with at least a 5 year follow up of each patient. Targeted BAE was performed in cases with lateralising symptoms, bronchoscopic sites of bleeding or angiographic unilateral abnormal vasculature. In the absence of lateralising symptoms or signs, bilateral BAE was performed. RESULTS: 96 BAEs were performed in 68 patients. The majority (64 cases, 67%) underwent unilateral procedures. 83 (86.5%) procedures resulted in immediate/short term control of haemoptysis which lasted for longer than a month. The mean duration of haemoptysis free period after embolisation was 96 months. There were three major complications (cardio-pulmonary arrest, paraparesis and stroke). 38 (56%) patients were still alive at least 5 years following their BAE. Benign causes were associated with significantly longer haemoptysis free periods, mean survival 108 months compared to 32 months in patients with an underlying malignant cause (p = 0.005). An episode of haemoptysis within a month of the initial embolisation was associated reduced overall survival (p = 0.033). CONCLUSION: BAE is effective in controlling massive haemoptysis. Long-term survival depends on the underlying pulmonary pathology. Strategies are required to avoid incomplete initial embolisation, which is associated with ongoing haemoptysis and high mortality despite further BAE
Dissimilar friction stir welding of duplex stainless steel to low alloy structural steel
In the present study, 6 mm nominal thickness dissimilar steel plates were joined using friction stir welding. The materials used were duplex stainless steel and low alloy structural steel. The weld was assessed by metallographic examination and mechanical testing (transverse tensile and fatigue). Microstructural examination identified four distinct weld zones and a substantially hard region within the stir zone at the base of the weld tool pin. Fatigue specimens demonstrated high level fatigue life and identified four distinct fracture modes
Tenodesis Grasp Emulator: Kinematic Assessment of Wrist-Driven Orthotic Control
Wrist-driven orthotics have been designed to assist people with C6-7 spinal
cord injury, however, the kinematic constraint imposed by such a control
strategy can impede mobility and lead to abnormal body motion. This study
characterizes body compensation using the novel Tenodesis Grasp Emulator, an
adaptor orthotic that allows for the investigation of tenodesis grasping in
subjects with unimpaired hand function. Subjects perform a series of
grasp-and-release tasks in order to compare normal (test control) and
constrained wrist-driven modes, showing significant compensation as a result of
the constraint. A motor-augmented mode is also compared against traditional
wrist-driven operation, to explore the potential role of hybrid human-robot
control. We find that both the passive wrist-driven and motor-augmented modes
fulfill different roles throughout various tasks tested. Thus, we conclude that
a flexible control scheme that can alter intervention based on the task at hand
holds the potential to reduce compensation in future work.Comment: 7 pages, 11 figures, submitted to International Conference on
Robotics and Automation (ICRA) 2022. Video Supplement:
https://youtu.be/NIgKg5R3Ro
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