Amsterdam, Netherlands
Amsterdam, Netherlands

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Anielski D.,Max Planck Advanced Study Group at CFEL | Anielski D.,Max Planck Institute for Nuclear Physics | Boll R.,Max Planck Advanced Study Group at CFEL | Boll R.,Max Planck Institute for Nuclear Physics | And 52 more authors.
Optics InfoBase Conference Papers | Year: 2012

We present static and time-resolved photoelectron angular distributions of laser-aligned p-fluorophenylacetylene and OCS molecules photoionized by fs-FEL pulses. The results are a proof-of-principle for recording dynamic structural changes of a molecule during Coulomb explosion. © 2012 OSA.

Anielski D.,Max Planck Advanced Study Group at CFEL | Anielski D.,Max Planck Institute for Nuclear Physics | Anielski D.,PNSensor GmbH | Boll R.,Max Planck Advanced Study Group at CFEL | And 116 more authors.
International Conference on Ultrafast Structural Dynamics, ICUSD 2012 | Year: 2012

We present static and time-resolved photoelectron angular distributions of laser-aligned p-fluorophenylacetylene and OCS molecules photoionized by fs-FEL pulses. The results are a proof-of-principle for recording dynamic structural changes of a molecule during Coulomb explosion. © 2012 OSA.

Gademann G.,FOM AMOLF | Ple F.,Amplitude | Paul P.-M.,Amplitude | Vrakking M.J.J.,FOM AMOLF | Vrakking M.J.J.,Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy
Optics Express | Year: 2011

We demonstrate the first carrier-envelope phase (CEP)-stabilized chirped pulse amplification system with pulse peak-powers in the terawatt regime. The system, which eventually is intended to be used in the generation of isolated attosecond pulses, consists of two consecutive multipass amplification stages. The first amplification stage is a commercial CEP-stable kHz system including a single 13-pass amplifier reaching a pulse energy of 2.3 mJ. Pulses are picked after the first stage at a repetition rate of 50 Hz and are further amplified in a 5-pass power-amplifier to pulse energies that reach up to 80 mJ before compression. After compression the pulse energy is 35mJ at a pulse duration of 32 fs, signifying a peak power of 1.1 terawatt. Peak-powers exceeding 1.5 TW should easily be achievable by improving the efficiency of the grating compressor. The CEP-stability of the terawatt system is demonstrated by single shot measurements of the residual CEP jitter at the full repetition rate and show an excellent root-mean-square value of 315 mrad. © 2011 Optical Society of America.

Bot M.,Leiden University | De Jager S.C.A.,Leiden University | MacAleese L.,FOM AMOLF | Lagraauw H.M.,Leiden University | And 8 more authors.
Journal of Lipid Research | Year: 2013

Lysophosphatidic acid (LPA), a bioactive lysophospholipid, accumulates in the atherosclerotic plaque. It has the capacity to activate mast cells, which potentially exacerbates plaque progression. In this study, we thus aimed to investigate whether LPA contributes to plaque destabilization by modulating mast cell function. We here show by an imaging mass spectrometry approach that several LPA species are present in atherosclerotic plaques. Subsequently, we demonstrate that LPA is a potent mast cell activator which, unlike other triggers, favors release of tryptase. Local perivascular administration of LPA to an atherosclerotic carotid artery segment increases the activation status of perivascular mast cells and promotes intraplaque hemorrhage and macrophage recruitment without impacting plaque cell apoptosis. The mast cell stabilizer cromolyn could prevent intraplaque hemorrhage elicited by LPAmediated mast cell activation. Finally, the involvement of mast cells in these events was further emphasized by the lack of effect of perivascular LPA administration in mast cell deficient animals. We demonstrate that increased accumulation of LPA in plaques induces perivascular mast cell activation and in this way contributes to plaque destabilization in vivo. This study points to local LPA availability as an important factor in atherosclerotic plaque stability. Copyright © 2013 by the American Society for Biochemistry and Molecular Biology, Inc.

Fornai L.,University of Padua | Angelini A.,University of Padua | Klinkert I.,FOM AMOLF | Giskes F.,FOM AMOLF | And 11 more authors.
Analytical and Bioanalytical Chemistry | Year: 2012

Cardiovascular diseases are the world's number one cause of death, accounting for 17.1 million deaths a year. New high-resolution molecular and structural imaging strategies are needed to understand underlying pathophysiological mechanism. The aim of our study is (1) to provide a molecular basis of the heart animal model through the local identification of biomolecules by mass spectrometry imaging (MSI) (three-dimensional (3D) molecular reconstruction), (2) to perform a cross-species validation of secondary ion mass spectrometry (SIMS)- based cardiovascular molecular imaging, and (3) to demonstrate potential clinical relevance by the application of this innovative methodology to human heart specimens. We investigated a MSI approach using SIMS on the major areas of a rat and mouse heart: the pericardium, the myocardium, the endocardium, valves, and the great vessels. While several structures of the heart can be observed in individual two-dimensional sections analyzed by metal-assisted SIMS imaging, a full view of these structures in the total heart volume can be achieved only through the construction of the 3D heart model. The images of 3D reconstruction of the rat heart show a highly complementary localization between Na+, K+, and two ions at m/z 145 and 667. Principal component analysis of the MSI data clearly identified different morphology of the heart by their distinct correlated molecular signatures. The results reported here represent the first 3D molecular reconstruction of rat heart by SIMS imaging.© Springer-Verlag Berlin Heidelberg 2012.

Gerber F.,University of Zürich | Marty F.,University of Zürich | Eijkel G.B.,FOM AMOLF | Basler K.,University of Zürich | And 3 more authors.
Analytical Chemistry | Year: 2013

Time-of-flight secondary ion mass spectrometry imaging is a rapidly evolving technology. Its main application is the study of the distribution of small molecules on biological tissues. The sequential image acquisition process remains susceptible to measurement distortions that can render imaging data less analytically useful. Most of these artifacts show a repetitive nature from tile to tile. Here we statistically describe these distortions and derive two different algorithms to correct them. Both a generalized linear model approach and the linear discriminant analysis approach are able to increase image quality for negative and positive ion mode data sets. Additionally, performing simulation studies with repetitive and nonrepetitive tiling error we show that both algorithms are only removing repetitive distortions. It is further shown that the spectral component of the data set is not altered by the use of these correction methods. Both algorithms presented in this work greatly increase the image quality and improve the analytical usefulness of distorted images dramatically. © 2013 American Chemical Society.

Hanselmann M.,The Interdisciplinary Center | Roder J.,The Interdisciplinary Center | Roder J.,Robert Bosch GmbH | Kothe U.,The Interdisciplinary Center | And 3 more authors.
Analytical Chemistry | Year: 2013

Digital staining for the automated annotation of mass spectrometry imaging (MSI) data has previously been achieved using state-of-the-art classifiers such as random forests or support vector machines (SVMs). However, the training of such classifiers requires an expert to label exemplary data in advance. This process is time-consuming and hence costly, especially if the tissue is heterogeneous. In theory, it may be sufficient to only label a few highly representative pixels of an MS image, but it is not known a priori which pixels to select. This motivates active learning strategies in which the algorithm itself queries the expert by automatically suggesting promising candidate pixels of an MS image for labeling. Given a suitable querying strategy, the number of required training labels can be significantly reduced while maintaining classification accuracy. In this work, we propose active learning for convenient annotation of MSI data. We generalize a recently proposed active learning method to the multiclass case and combine it with the random forest classifier. Its superior performance over random sampling is demonstrated on secondary ion mass spectrometry data, making it an interesting approach for the classification of MS images. © 2012 American Chemical Society.

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