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At least 127 records · Page 7Linked to original sources
PubMed2006

Caustic activation of rain showers.

We show quantitatively how the collision rate of droplets of visible moisture in turbulent air increases very abruptly as the intensity of the turbulence passes a threshold, due to the formation of fold caustics in their velocity field. The formation of caustics is an activated process, in which a measure of the intensity of the turbulence, termed the Stokes number St, is analogous to temperature in a chemical reaction: the rate of collision contains a factor exp(-C/St). Our results are relevant to the long-standing problem of explaining the rapid onset of rainfall from convecting clouds. Our theory does not involve spatial clustering of particles.

Causality↗
PubMed1990

[Studies on the crystallization tendency of calcium oxalate in urine--a study of experimental and computer-assisted determination of the risk of urinary calculi formation].

In this study a method o the semiquantitative determination of the crystallization tendency for calcium oxalate in urine is described. It is based on the addition of a well-defined amount of ammonium oxalate (31.3 nmol) to a urine sample (30 ml). The so caused clouding of the urine is measured by a photometer 20 min later. The method guarantees an acceptable reproducibility and is simple to be performed in each clinical laboratory. The results of mathematical correlation and discriminant analysis show that the calcium concentration influences the crystallization of calcium oxalate as most of all urinary constituents. Furthermore, evidence of a high specificity of the method is given by a reclassification rate of about 80% in the discriminant analytical computation.

Adolescent↗
PubMed2002

Universal behavior of entrainment due to coherent structures in turbulent shear flow.

A solution is suggested for a persistent mystery in the physics of turbulent flows: cumulus clouds rise to towering heights, practically without entraining the ambient medium, while apparently similar turbulent jets quickly lose their identity through entrainment and mixing. Dynamical system computations on a model vortical flow show that entrainment due to coherent structures depends sensitively on relative speeds of fluid parcels. Local heating, for example, can alter drastically the sizes of Kolmogorov-Arnol'd-Moser tori and chaotic mixing regions. The entrainment rate and, hence, the lifetime of a turbulent shear flow show a universal, nonmonotone dependence on the heating.

Journal Article↗
PubMed2002

Clinical proteomics for cancer biomarker discovery and therapeutic targeting.

As we emerge into the post-genome era, proteomics finds itself as the driving force field as we translate the nucleic acid information archive into understanding how the cell actually works and how disease processes operate. Even so, the traditionally held view of proteomics as simply cataloging and developing lists of the cellular protein repertoire of a cell are now changing, especially in the sub-discipline of clinical proteomics. The most relevant information archive to clinical applications and drug development involves the elucidation of the information flow of the cell; the "software" of protein pathway networks and circuitry. The deranged circuitry of the cell as the drug target itself as well as the effect of the drug on not just the target, but also the entire network, is what we now are striving towards. Clinical proteomics, as a new and most exciting sub-discipline of proteomics, involves the bench-to-bedside clinical application of proteomic tools. Unlike the genome, there are potentially thousands of proteomes: each cell type has its own unique proteome. Moreover, each cell type can alter its proteome depending on the unique tissue microenvironment in which it resides, giving rise to multiple permutations of a single proteome. Since there is no polymerase chain reaction equivalent to proteomics- identifying and discovering the "wiring diagram" of a human diseased cell in a biopsy specimen remains a daunting challenge. New micro-proteomic technologies are being and still need to be developed to drill down into the proteomes of clinically relevant material. Cancer, as a model disease, provides a fertile environment to study the application of proteomics at the bedside. The promise of clinical proteomics and the new technologies that are developed is that we will detect cancer earlier through discovery of biomarkers, we will discover the next generation of targets and imaging biomarkers, and we can then apply this knowledge to patient-tailored therapy.

Algorithms↗
PubMed2006

Anomalous sea surface reverberation scale model experiments.

Low frequency sea surface sound backscattering from approximately 100 Hz to a few kHz observed from the 1960s broadband measurements using explosive charges to the Critical Sea Test measurements conducted in the 1990 s is substantially higher than explained by rough sea surface scattering theory. Alternative theories for explaining this difference range from scattering by bubble plumes/clouds formed by breaking waves to stochastic scattering from fluctuating bubble layers near the sea surface. In each case, theories focus on reverberation in the absence of the large-scale surface wave height fluctuations that are characteristic of a sea that produces bubble clouds and plumes. At shallow grazing angles, shadowing of bubble plumes and clouds caused by surface wave height fluctuations may induce first order changes in the backscattered signal strength. To understand the magnitude of shadowing effects under controlled and repeatable conditions, scale model experiments were performed in a 3 m x 1.5 m x 1.5 m tank at the Technical University of Denmark. The experiments used a 1 MHz transducer as the source and receiver, a computer controlled data acquisition system, a scale model target, and a surface wave generator. The scattered signal strength fluctuations observed at shallow angles are characteristic of the predicted ocean environment. These experiments demonstrate that shadowing has a first order impact on bubble plume and cloud scattering strength and emphasize the usefulness of model scale experiments for studying underwater acoustic events under controlled conditions.

Journal Article↗
PubMedDate not supplied

Complex partial status epilepticus provoked by ingestion of alcohol: a case report.

A 27-year-old man had a 5-year history of a peculiar state characterized by clouded consciousness provoked by ingestion of alcohol. The episode was identified electroclinically as nonconvulsive status epilepticus and was activated by ingestion of alcohol. Single-photon emission computed tomography (SPECT) examination during the nonconvulsive status epilepticus showed increased regional cerebral perfusion in the right frontal region. This finding, along with the EEG expressions, supports a cortical origin of the nonconvulsive status epilepticus and a diagnosis of complex partial status epilepticus (CPSE). To our knowledge, this is the first report of a documented case of CPSE during intoxication provoked by alcohol ingestion and also of a SPECT examination during CPSE.

Adult↗
PubMed2006

[Design of geometric models of the removable partial denture framework].

PURPOSE: The aim of this study was to introduce a method on computer aided design (CAD) of removable partial denture(RPD) framework based on domestic CAD/CAM software system, which contributes to the further research to develop the domestic software system applied in restorative dentistry. METHODS: Point cloud data of a partially edentulous cast, a mandibular Kennedy Class II modification 2 arch, was captured by an optical scanning system with projective grating and high-resolution digital camera. Using domestic CAD/CAM software system, the above point cloud data was reduced, digital surveying line and inserting path were determined. In terms of the principle of clinical design, the tissue surfaces and polishing surfaces of every component of RPD were built such as clasp, rest, lingual bar, and mesh construction, et al. As well as the characteristic structures of the framework, including the half-pear shaped cross section of lingual bar, the internal and external finish lines, the tissue stop at the tissue surface of mesh construction and so on, were fabricated on the base of reduced data model. 3-D surface model of the RPD framework was created. RESULTS: Geometric model of the RPD framework was fabricated successfully, which took on good fitting, high visibility and editing conveniently. And the data converted to STL file format that could be read by any other CAD/CAM software system and was in preparation for subsequent computer aided manufacture (CAM) of RPD framework. CONCLUSIONS: It is suggested that this method based on domestic software in CAD of RPD framework be feasible.

Computer-Aided Design↗
PubMed2000

Simple box model for dense-gas dispersion in a straight sloping channel.

A box model for instantaneous release and subsequent one-dimensional spreading of isothermal dense gases on sloping surfaces is presented. A numerical solution and an approximate analytical solution of the model equations are compared to the experimental data obtained in a sloping heavy-gas channel of the Institute of Fluid Dynamics at ETH-Zürich. The influence of the rear wall of the containment from where the cloud is released is analysed. Different entrainment assumptions, in particular the scaling of the entrainment parameters, are discussed. The numerical values of the entrainment parameters are tuned by computer optimization in order to obtain best agreement of the theoretical results with experimental data.

Chemical Industry↗
PubMed1986

Time domain formulation of pulse-Doppler ultrasound and blood velocity estimation by cross correlation.

The Doppler effect is usually described as a frequency shift of the backscattered signals from moving targets with respect to the frequency transmitted. Recently, real-time blood flow imaging has become possible thanks to the development of a new velocity estimator based on phase-shift measurements of successive echoes. However, this method suffers from the well-known limitations of pulse-Doppler instruments. A new formulation is presented which describes the pulse-Doppler effect on the successive echoes from a cloud of moving targets as a progressive translation in time due to the displacement of the scatterers between two excitations. This approach allows us to generate efficiently computer-simulated data in order to evaluate accurately the various processing techniques. Furthermore, it leads to a novel class of velocity estimators in the time domain which measure the time shifts which are proportional to the local blood velocity. Among them, the cross correlation of the received rf signals turns out to be well suited. A local cross-correlation function is first calculated from a consecutive pair of range-gated echoes and the time shift is then determined by searching for the time position with the maximum correlation. The time-correlation technique is shown to provide accurate velocity profiles with broadband transducers. Moreover, the classical velocity limitation of pulse-Doppler is overcome because there is no ambiguity in measuring a time shift instead of a phase shift. These major advantages should make quantitative flow mapping possible and more reliable.

Blood Flow Velocity↗
PubMed2005

Isoprene forms secondary organic aerosol through cloud processing: model simulations.

Isoprene accounts for more than half of non-methane volatile organics globally. Despite extensive experimentation, homogeneous formation of secondary organic aerosol (SOA) from isoprene remains unproven. Herein, an incloud process is identified in which isoprene produces SOA. Interstitial oxidation of isoprene produces water-soluble aldehydes that react in cloud droplets to form organic acids. Upon cloud evaporation new organic particulate matter is formed. Cloud processing of isoprene contributes at least 1.6 Tg yr(-1) to a global biogenic SOA production of 8-40 Tg yr(-1). We conclude that cloud processing of isoprene is an important contributor to SOA production, altering the global distribution of hygroscopic organic aerosol and cloud condensation nuclei.

Aerosols↗
PubMedDate not supplied

A second generation apparatus for time-resolved electron cryo-microscopy using stepper motors and electrospray.

We describe here a second generation apparatus for studying transient reaction conformations in macromolecules and their complexes by electron cryo-microscopy. Reactions are trapped by rapid freezing in times ranging from a few milliseconds to tens of seconds after initiation. Blotting of the electron microscope grid and freezing it in liquid ethane uses computer controlled microstepping motors. For the fastest time resolution, a blotted grid containing a thin film of one reactant is sprayed with small droplets containing a second reactant just before freezing. The spray is produced electrically (electrospray), which gives a dense cloud of droplets <1 microm in diameter from the 1-2 microl of solution required per grid. A second method in which two solutions are first mixed by turbulent flow and then blotted prior to freezing is used for reactions with time courses >1s.

Biophysical Phenomena↗
PubMedDate not supplied

Daily duration of vitamin D synthesis in human skin with relation to latitude, total ozone, altitude, ground cover, aerosols and cloud thickness.

Vitamin D production in human skin occurs only when incident UV radiation exceeds a certain threshold. From simulations of UV irradiances worldwide and throughout the year, we have studied the dependency of the extent and duration of cutaneous vitamin D production in terms of latitude, time, total ozone, clouds, aerosols, surface reflectivity and altitude. For clear atmospheric conditions, no cutaneous vitamin D production occurs at 51 degrees latitude and higher during some periods of the year. At 70 degrees latitude, vitamin D synthesis can be absent for 5 months. Clouds, aerosols and thick ozone events reduce the duration of vitamin D synthesis considerably, and can suppress vitamin D synthesis completely even at the equator. A web page allowing the computation of the duration of cutaneous vitamin D production worldwide throughout the year, for various atmospheric and surface conditions, is available on the Internet at http://zardoz.nilu.no/~olaeng/fastrt/VitD.html and http://zardoz.nilu.no/~olaeng/fastrt/VitD-ez.html. The computational methodology is outlined here.

Aerosols↗
PubMed1990

Psychology of the scientist: LXIII. Perceiving scattergrams: is visual line fitting related to estimation of the correlation coefficient?

Visual line fitting and direct estimation of the correlation coefficient were carried out by 50 subjects using computer-generated scattergrams as stimuli. In visual line fitting, slopes of visual lines were generally greater than the corresponding regression slopes, in agreement with the hypothesis that visual lines are placed so as to bisect the cloud of displayed points at the cloud's major axis rather than to approximate a regression line. Subjects tended to underestimate the correlation coefficient, scaling their judgments of linear structure somewhat more as if they were judging the coefficient of determination. With the actual degree of linear structure partialed out, there were no strong relationships between measures of visual line fitting and measures of estimation. While both of these tasks offer quickly-obtained correlates of linear structure in scattergrams, users should be aware of their biases. We suggest that visual lines do not approximate regression lines very well and estimates of correlation do not approximate the correlation coefficient very well, because the perceptual processes involved perform operations other than regression and correlation. In the present data, these operations appeared to be independent of each other.

Adult↗
PubMed2000

Developments in vapour cloud explosion blast modeling.

TNT Equivalency methods are widely used for vapour cloud explosion blast modeling. Presently, however, other types of models are available which do not have the fundamental objections TNT Equivalency models have. TNO Multi-Energy method is increasingly accepted as a more reasonable alternative to be used as a simple and practical method. Computer codes based on computational fluid dynamics (CFD) like AutoReaGas, developed by TNO and Century Dynamics, could be used also in case a more rigorous analysis is required. Application of the Multi-Energy method requires knowledge of two parameters describing the explosion: a charge size and a charge strength. During the last years, research has led to an improved determination of the charge strength (i.e., the class number or source overpressure) to be chosen to apply the blast charts. A correlation has been derived relating the charge strength to a set of parameters describing the boundary conditions of the flammable cloud and the fuel in the cloud. A simple approach may not be satisfactory in all situations. The overpressure distribution inside a vapour cloud explosion is generally not homogeneous and the presence of obstructions causes directional blast propagation in the near field. A CFD approach, in which the actual situation is modeled, supplies case-specific results. An overview of the key aspects relevant to the application of the Multi-Energy method and CFD modeling is provided. Then the application of the two methods is demonstrated for an example problem involving the calculation of the explosion blast load on a structure at some distance from the explosion in an offshore platform complex.

Air Pollution↗
PubMed1996

An operational perspective on measuring aerosol cloud dynamics.

Three areas are discussed in this paper: 1) U.S. Air Force Reserve/USDA bioassays to determine the effective swath width of ultra-low volume (ULV) aerial applications conducted with the C-130 Modular Aerial Spray System (MASS), 2) the use of aerial spray computer models to predict spray offset distance and their use as a substitute for field testing, and 3) a demonstration on an aerial spray expert system called ASPEX being developed at the U.S. Air Force Reserve Aerial Spray Branch.

Animals↗
PubMed2026

Practicing Data Science in Interactive Notebooks.

The Jupyter Notebook is a platform for interactive computing that displays code and results in the same browser, making it valuable for teaching, prototyping, data analysis, and collaboration. Its explicit&#xa0;and transparent structure greatly reproducibility&#xa0;while&#xa0;its backend server supports flexible deployment. In the past few years, Jupyter notebooks and similar tools have become increasingly popular. In this chapter, we will review key aspects of data analysis in a cloud environment and demonstrate common tasks for analyzing metabolomics data using template notebooks. This is an accompaniment to the basic bioinformatics tools and essential data science toolkit introduced in the first edition.

Software↗
PubMed1994

Why two eyes are better than one for judgements of heading.

Are two eyes needed for judging direction of self-motion? Traditional analyses stress that the pattern of optic flow in one eye is sufficient. The main difficulty is how to deal with the eye or head rotation. Extraretinal signals help, but humans can also discount the effect of rotation purely on the basis of monocular flow provided the scene contains depth. Depth differences give rise to changing binocular disparities when the observer moves. These disparities are ignored in monocular theories of judgements of heading. Using computer generated displays, we investigated whether stereoscopic presentation improves heading judgements for conditions that pose problems to the monocular observer. We found that adding disparities to simulated ego-motion through a cloud of dots made heading judgements up to four times more tolerant to motion noise. The same improvement was found when the disparities specify the initial distances throughout the motion sequence. We conclude that binocular disparities improve judgements of heading by imposing a depth order on the elements of the scene, not because they provide additional information on the elements' motion in depth.

Depth Perception↗
PubMed1989

[Brain abscess. Prognostic factors].

Thirty-eight cases of cerebral abscess were analysed retrospectively for any factors that might influence outcome. Using the "Glasgow outcome score", age, history, level of consciousness, as well as various computed tomography findings (cisternal swelling, compression of the ventricular system, degree of oedema and size of abscess) were considered for their prognostic value. It was found that age over 40 years and clouded consciousness exerted a statistically significant unfavourable effect (P less than 0.05). Outcome was also unfavourable in half the patients with multiple abscesses, but the number of cases (six) was too small to be statistically significant. All other variables had no statistically significant influence on prognosis.

Adolescent↗