3,832 research outputs found
Wavelength-scale stationary-wave integrated Fourier-transform spectrometry
Spectrometry is a general physical-analysis approach for investigating
light-matter interactions. However, the complex designs of existing
spectrometers render them resistant to simplification and miniaturization, both
of which are vital for applications in micro- and nanotechnology and which are
now undergoing intensive research. Stationary-wave integrated Fourier-transform
spectrometry (SWIFTS)-an approach based on direct intensity detection of a
standing wave resulting from either reflection (as in the principle of colour
photography by Gabriel Lippmann) or counterpropagative interference
phenomenon-is expected to be able to overcome this drawback. Here, we present a
SWIFTS-based spectrometer relying on an original optical near-field detection
method in which optical nanoprobes are used to sample directly the evanescent
standing wave in the waveguide. Combined with integrated optics, we report a
way of reducing the volume of the spectrometer to a few hundreds of cubic
wavelengths. This is the first attempt, using SWIFTS, to produce a very small
integrated one-dimensional spectrometer suitable for applications where
microspectrometers are essential
Ray-optical refraction with confocal lenslet arrays
Two parallel lenslet arrays with focal lengths f1 and f2 that share a common focal plane (that is, which are separated by a distance f1+f2) can refract transmitted light rays according to Snell's law, but with the 'sin's replaced with 'tan's. This is the case for a limited range of input angles and other conditions. Such confocal lenslet arrays can therefore simulate the interface between optical media with different refractive indices, n1 and n2, whereby the ratio η=-f2/f1 plays the role of the refractive-index ratio n2/n1. Suitable choices of focal lengths enable positive and negative refraction. In contrast to Snell's law, which leads to nontrivial geometric imaging by a planar refractive-index interface only for the special case of n1=±n2, the modified refraction law leads to geometric imaging by planar confocal lenslet arrays for any value of η. We illustrate some of the properties of confocal lenslet arrays with images rendered using ray-tracing software
A microscopic view on contact angle selection
We discuss the equilibrium condition for a liquid that partially wets a solid
on the level of intermolecular forces. Using a mean field continuum
description, we generalize the capillary pressure from variation of the free
energy and show at what length scale the equilibrium contact angle is selected.
After recovering Young's law for homogeneous substrates, it is shown how
hysteresis of the contact angle can be incorporated in a self-consistent
fashion. In all cases the liquid-vapor interface takes a nontrivial shape,
which is compared to models using a disjoining pressure.Comment: 12 pages, 6 figure
Fire analysis of steel frames with the use of artificial neural networks
The paper presents an alternative approach to the modelling of the mechanical behaviour of steel frame material when exposed to the high temperatures expected in fires. Based on a series of stress-strain curves obtained experimentally for various temperature levels, an artificial neural network (ANN) is employed in the material modelling of steel. Geometrically and materially, a non-linear analysis of plane frame structures subjected to fire is performed by FEM. The numerical results of a simply supported beam are compared with our measurements, and show a good agreement, although the temperature-displacement curves exhibit rather irregular shapes. It can be concluded that ANN is an efficient tool for modelling the material properties of steel frames in fire engineering design studies. (c) 2007 Elsevier Ltd. All rights reserved
The Impact of the COVID-19 Pandemic on Avoidance of Health Care, Symptom Severity, and Mental Well-Being in Patients With Coronary Artery Disease
The COVID-19 pandemic affected regular health care for patients with chronic diseases.
However, the impact of the pandemic on primary care for patients with coronary artery
disease (CAD) who are enrolled in a structured disease management program (DMP) in
Germany is not clear. We investigated whether the pandemic affected primary care and
health outcomes of DMP-CAD patients (n = 750) by using a questionnaire assessing
patients’ utilization of medical care, CAD symptoms, as well as health behavior and
mental health since March 2020. We found that out of concern about getting infected
with COVID-19, 9.1% of the patients did not consult a medical practitioner despite
having CAD symptoms. Perceived own influence on infection risk was lower and anxiety
was higher in these patients compared to symptomatic CAD patients who consulted
a physician. Among the patients who reported chest pain lasting longer than 30 min,
one third did not consult a medical practitioner subsequently. These patients were
generally more worried about COVID-19. Patients with at least one worsening CAD
symptom (chest pain, dyspnea, perspiration, or nausea without apparent reason) since
the pandemic showed more depressive symptoms, higher anxiety scores, and were less
likely to consult a doctor despite having CAD symptoms out of fear of infection. Our
results provide evidence that the majority of patients received sufficient medical care
during the COVID-19 pandemic in Germany. However, one in ten patients could be
considered particularly at risk for medical undersupply and adverse health outcomes.
The perceived infection risk with COVID-19 might have facilitated the decision not to
consult a medical doctor
The roles of motivation and ability in controlling the consequences of stereotype suppression
Two experiments investigated the conditions under which previously suppressed stereotypes are applied in impression formation. In Experiment 1, the extent to which a previously suppressed racial stereotype influenced subsequent impressions depended on the race of the target who was subsequently encountered. Whereas impressions of race-unspecified targets were assimilated to the stereotype following its suppression, no such effects were observed when the target belonged to the racial group whose stereotype had been initially suppressed. These results demonstrate that when perceivers are motivated to avoid stereo-typing individuals, the influence of a stereotype that has been previously activated through suppression is minimized. Experiment 2 demonstrated that these processing goals effectively reduce the impact of suppression-activated stereotypes only when perceivers have sufficient capacity to enact the goals. These results suggest that both sufficient motivation and capacity are necessary to prevent heightened stereotyping following stereotype suppression
Effects of 1,3-Butadiene, Isoprene, and Their Photochemical Degradation Products on Human Lung Cells
Because of potential exposure both in the workplace and from ambient air, the known carcinogen 1,3-butadiene (BD) is considered a priority hazardous air pollutant. BD and its 2-methyl analog, isoprene (ISO), are chemically similar but have very different toxicities, with ISO showing no significant carcinogenesis. Once released into the atmosphere, reactions with species induced by sunlight and nitrogen oxides convert BD and ISO into several photochemical reaction products. In this study, we determined the relative toxicity and inflammatory gene expression induced by exposure of A549 cells to BD, ISO, and their photochemical degradation products in the presence of nitric oxide. Gas chromatography and mass spectrometry analyses indicate the initial and major photochemical products produced during these experiments for BD are acrolein, acetaldehyde, and formaldehyde, and products for ISO are methacrolein, methyl vinyl ketone, and formaldehyde; both formed < 200 ppb of ozone. After exposure the cells were examined for cytotoxicity and interleukin-8 (IL-8) gene expression, as a marker for inflammation. These results indicate that although BD and ISO alone caused similar cytotoxicity and IL-8 responses compared with the air control, their photochemical products significantly enhanced cytotoxicity and IL-8 gene expression. This suggests that once ISO and BD are released into the environment, reactions occurring in the atmosphere transform these hydrocarbons into products that induce potentially greater adverse health effects than the emitted hydrocarbons by themselves. In addition, the data suggest that based on the carbon concentration or per carbon basis, biogenic ISO transforms into products with proinflammatory potential similar to that of BD products
Effectiveness evaluation of data mining based IDS
Proceeding of: 6th Industrial Conference on Data Mining, ICDM 2006, Leipzig, Germany, July 14-15, 2006.Data mining has been widely applied to the problem of Intrusion Detection in computer networks. However, the misconception of the underlying problem has led to out of context results. This paper shows that factors such as the probability of intrusion and the costs of responding to detected intrusions must be taken into account in order to compare the effectiveness of machine learning algorithms over the intrusion detection domain. Furthermore, we show the advantages of combining different detection techniques. Results regarding the well known 1999 KDD dataset are shown.Publicad
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