692 research outputs found
Steerable filters generated with the hypercomplex dual-tree wavelet transform
The use of wavelets in the image processing domain is still in its
infancy, and largely associated with image compression. With
the advent of the dual-tree hypercomplex wavelet transform (DHWT)
and its improved shift invariance and directional selectivity,
applications in other areas of image processing are more
conceivable. This paper discusses the problems and solutions in
developing the DHWT and its inverse. It also offers a practical
implementation of the algorithms involved. The aim of this work
is to apply the DHWT in machine vision.
Tentative work on a possible new way of feature extraction is
presented. The paper shows that 2-D hypercomplex basis wavelets
can be used to generate steerable filters which allow rotation
as well as translation.</p
A machine vision extension for the Ruby programming language
Dynamically typed scripting languages have become popular in recent years. Although interpreted languages allow for substantial reduction of software development time, they are often rejected due to performance concerns.
In this paper we present an extension for the programming
language Ruby, called HornetsEye, which facilitates the development
of real-time machine vision algorithms within Ruby. Apart from providing integration of crucial libraries for input and output, HornetsEye provides fast native implementations (compiled code) for a generic set of array operators. Different array operators were compared with equivalent implementations in C++. Not only was it possible to achieve comparable real-time performance, but also to exceed the efficiency of the C++ implementation in several cases.
Implementations of several algorithms were given to demonstrate
how the array operators can be used to create concise
implementations.</p
Line-scanning microphotolysis for diffraction-limited measurements of lateral diffusion
Fluorescence microphotolysis was combined with confocal laser-scanning microscopy to yield a method, herein referred to as line-scanning microphotolysis (LINESCAMP), for the measurement of molecular transport at a lateral resolution of approximately 0.34 microns and a temporal resolution of approximately 0.5 ms. A confocal microscope was operated in the line scan mode, while the laser beam power could be switched during scanning between low monitoring and high photolysing levels in less then a microsecond. The number and location of line segments to be photolysed could be freely determined. The length of the photolysed segments could be also chosen and was only limited by diffraction. Together with instrumentation a new, completely general, theoretical framework for the evaluation of diffusion measurements was developed. Based on the numerical simulation of diffusion processes employing a modified Crank-Nicholson scheme, the theory could be applied to any photobleaching geometry and profile as the initial condition and took into account the convolution with the microscope point spread function. With small diffraction-limited areas, the method yielded accurate values for diffusion coefficients in the range between approximately 10(-4) and 1 micron2 s-1. A first application of the method to the diffusion of a fluorescently labeled tracer inside the cell nucleus showed the potential of the method for the study of complex biological systems
Virtual Campus – Trends and Perspectives in Germany
In the last few years in Germany virtual campus initiatives have been funded considerably. In our paper we will give a review of comments and recommendations of the advisory boards in higher education policy and of the various funding schemes on the level of the federal states and the federal government. An analysis of the current program „New Media in Education” indicates trends of possible developments as well as hindrances in the virtualization of higher educationIn: A.J. Kallenberg and M.J.J.M. van de Ven (Eds), 2002, The New Educational Benefits of ICT in Higher Education: Proceedings. Rotterdam: Erasmus Plus BV, OECR
ISBN 90-9016127-
Unraveling the "Pressure-Effect" in Nucleation
The influence of the pressure of a chemically inert carrier-gas on the
nucleation rate is one of the biggest puzzles in the research of gas-liquid
nucleation. Different experiments can show a positive effect, a negative
effect, or no effect at all. The same experiment may show both trends for the
same substance depending on temperature, or for different substances at the
same temperature. We show how this ambiguous effect naturally arises from the
competition of two contributions: nonisothermal effects and pressure-volume
work. Our model clarifies seemingly contradictory experimental results and
quantifies the variation of the nucleation ability of a substance in the
presence of an ambient gas. Our findings are corroborated by results from
molecular dynamics simulation and might have important implications since
nucleation in experiments, technical applications, and nature practically
always occurs in the presence of an ambient gas.Comment: 4 pages, 3 figures. v2: All citations now appear correctly. v3:
Updated one point in Fig.
IUCF High Intensity Polarized Ion Source
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
Control over phase separation and nucleation using a laser-tweezing potential
Control over the nucleation of new phases is highly desirable but elusive. Even though there is a long history of crystallization engineering by varying physicochemical parameters, controlling which polymorph crystallizes or whether a molecule crystallizes or forms an amorphous precipitate is still a poorly understood practice. Although there are now numerous examples of control using laser-induced nucleation, the absence of physical understanding is preventing progress. Here we show that the proximity of a liquid–liquid critical point or the corresponding binodal line can be used by a laser-tweezing potential to induce concentration gradients. A simple theoretical model shows that the stored electromagnetic energy of the laser beam produces a free-energy potential that forces phase separation or triggers the nucleation of a new phase. Experiments in a liquid mixture using a low-power laser diode confirm the effect. Phase separation and nucleation using a laser-tweezing potential explains the physics behind non-photochemical laser-induced nucleation and suggests new ways of manipulating matter
PARP inhibition sensitizes childhood high grade glioma, medulloblastoma and ependymoma to radiation
Poly ADP-ribose polymerase (PARP) is a protein involved in single strand break repair. Recently, PARP inhibitors have shown considerable promise in the treatment of several cancers, both in monotherapy and in combination with cytotoxic agents. Synthetic lethal action of PARP inhibitors has been observed in tumors with mutations in double strand break repair pathways. In addition, PARP inhibition potentially enhances sensitivity of tumor cells to DNA damaging agents, including radiotherapy. Aim of this study is to determine the radiosensitizing properties of the PARP inhibitor Olaparib in childhood medulloblastoma, ependymoma and high grade glioma (HGG). Increased PARP1 expression was observed in medulloblastoma, ependymoma and HGG, as compared to non-neoplastic brain tissue. Pediatric high grade glioma, medulloblastoma and ependymoma gene expression profiling revealed that high PARP1 expression is associated with poor prognosis. Cell growth inhibition assays with Olaparib resulted in differential sensitivity, with IC50 values ranging from 1.4 to 8.4 μM, irrespective of tumor type and PARP1 protein expression. Sensitization to radiation was observed in medulloblastoma, ependymoma and HGG cell lines with subcytotoxic concentrations of Olaparib, which coincided with persistence of double strand breaks. Combining PARP inhibitors with radiotherapy in clinical studies in childhood high grade brain tumors may improve therapeutic outcome
Pathogen-induced hatching and population-specific life-history response to water-borne cues in brown trout (Salmo trutta)
Hatching is an important niche shift, and embryos in a wide range of taxa can either accelerate or delay this life-history switch in order to avoid stage-specific risks. Such behavior can occur in response to stress itself and to chemical cues that allow anticipation of stress. We studied the genetic organization of this phenotypic plasticity and tested whether there are differences among populations and across environments in order to learn more about the evolutionary potential of stress-induced hatching. As a study species, we chose the brown trout (Salmo trutta; Salmonidae). Gametes were collected from five natural populations (within one river network) and used for full-factorial in vitro fertilizations. The resulting embryos were either directly infected with Pseudomonas fluorescens or were exposed to waterborne cues from P. fluorescens-infected conspecifics. We found that direct inoculation with P. fluorescens increased embryonic mortality and induced hatching in all host populations. Exposure to waterborne cues revealed population-specific responses. We found significant additive genetic variation for hatching time, and genetic variation in trait plasticity. In conclusion, hatching is induced in response to infection and can be affected by waterborne cues of infection, but populations and families differ in their reaction to the latter
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