198 research outputs found
Modelling and experiments of self-reflectivity under femtosecond ablation conditions
We present a numerical model which describes the propagation of a single
femtosecond laser pulse in a medium of which the optical properties dynamically
change within the duration of the pulse. We use a Finite Difference Time Domain
(FDTD) method to solve the Maxwell's equations coupled to equations describing
the changes in the material properties. We use the model to simulate the
self-reflectivity of strongly focused femtosecond laser pulses on silicon and
gold under laser ablation condition. We compare the simulations to experimental
results and find excellent agreement.Comment: 11 pages, 8 figure
Coherent vibrations of submicron spherical gold shells in a photonic crystal
Coherent acoustic radial oscillations of thin spherical gold shells of
submicron diameter excited by an ultrashort optical pulse are observed in the
form of pronounced modulations of the transient reflectivity on a subnanosecond
time scale. Strong acousto-optical coupling in a photonic crystal enhances the
modulation of the transient reflectivity up to 4%. The frequency of these
oscillations is demonstrated to be in good agreement with Lamb theory of free
gold shells.Comment: Error in Eqs.2 and 3 corrected; Tabl. I corrected; Fig.1 revised; a
model that explains the dependence of the oscillation amplitude of the
transient reflectivity with wavelength adde
A highly efficient titanium-based olefin polymerisation catalyst with a monoanionic iminoimidazolidide pi-donor ancillary ligand
The titanium complex Cp[1,3-(2',6' Me2C6H3) (2)(CH2N)(2)C=N] Ti(CH2Ph)(2), with a monoanionic eta(1)-iminoimidazolidide ancillary ligand, is shown to be a highly efficient catalyst for olefin polymerisation when activated with the Lewis acid B(C6F5)(3)
Investigating the current knowledge and needs concerning a follow-up for long-term cardiovascular risks in Dutch women with a preeclampsia history:a qualitative study
Background There is increasing evidence that a history of preeclampsia is an important risk factor for future cardiovascular events. Awareness of this risk could provide opportunities for identification of women at risk, with opportunities for prevention and / or early intervention. A standardized follow-up has not yet been implemented in the north of the Netherlands. The objective of this qualitative study was to explore the opinions and wishes among women and physicians about the follow-up for women with a history of preeclampsia. Methods Semi-structured interviews with 15 women and 14 physicians (5 obstetricians, 4 general practitioners, 3 vascular medicine specialists and 2 cardiologists) were performed and addressed topics about knowledge on CVR, current - and future follow-up. Women were approached through the HELLP foundation and their physicians. Physicians were approached by email. The interviews were recorded, typed and coded using ATLAS.ti software. A theoretical-driven thematic analysis was performed. Results Women had some knowledge about the association between preeclampsia and the increased CVR, but missed information from their health care providers. Specialists were aware of the association, but the information and advice they provided to their patients was minimal and inconsistent according to themselves. Whereas some general practitioners regarded their own knowledge as limited. There was a clear desire among women for a more extensive follow-up with specific attention to both emotional and physical consequences of preeclampsia. Physicians indicated that they preferred to see a follow up program concerning the CVR at the general practitioner as part of the already existent cardiovascular risk management (CVRM) program. Conclusion Women and medical specialists consider it important to improve aftercare for women after a pregnancy complicated by preeclampsia. Introducing these women into the CVRM program at the general practitioner is regarded as a preferred first step. Further research is warranted to establish an evidence-based guideline for the follow-up of these women
Correlated terahertz acoustic and electromagnetic emission in dynamically screened InGaN/GaN quantum wells
We investigate acoustic and electromagnetic emission from optically excited strained piezoelectric In0.2Ga0.8N/GaN multiple quantum wells (MQWs), using optical pump-probe spectroscopy, time-resolved Brillouin scattering, and THz emission spectroscopy. A direct comparison of detected acoustic signals and THz electromagnetic radiation signals demonstrates that transient strain generation in InGaN/GaN MQWs is correlated with electromagnetic THz generation, and both types of emission find their origin in ultrafast dynamical screening of the built-in piezoelectric field in the MQWs. The measured spectral intensity of the detected Brillouin signal corresponds to a maximum strain amplitude of generated acoustic pulses of 2%. This value coincides with the static lattice-mismatch-induced strain in In0.2Ga0.8N/GaN, demonstrating the total release of static strain in MQWs via impulsive THz acoustic emission. This confirms the ultrafast dynamical screening mechanism in MQWs as a highly efficient method for impulsive strain generatio
Long-range potential fluctuations and 1/f noise in hydrogenated amorphous silicon
We present a microscopic theory of the low-frequency voltage noise (known as
"1/f" noise) in micrometer-thick films of hydrogenated amorphous silicon. This
theory traces the noise back to the long-range fluctuations of the Coulomb
potential produced by deep defects, thereby predicting the absolute noise
intensity as a function of the distribution of defect activation energies. The
predictions of this theory are in very good agreement with our own experiments
in terms of both the absolute intensity and the temperature dependence of the
noise spectra.Comment: 8 pages, 3 figures, several new parts and one new figure are added,
but no conceptual revision
IDLaS-NL – A platform for running customized studies on individual differences in Dutch language skills via the internet
We introduce the Individual Differences in Language Skills (IDLaS-NL) web platform, which enables users to run studies on individual differences in Dutch language skills via the internet. IDLaS-NL consists of 35 behavioral tests, previously validated in participants aged between 18 and 30 years. The platform provides an intuitive graphical interface for users to select the tests they wish to include in their research, to divide these tests into different sessions and to determine their order. Moreover, for standardized administration the platform provides an application (an emulated browser) wherein the tests are run. Results can be retrieved by mouse click in the graphical interface and are provided as CSV-file output via email. Similarly, the graphical interface enables researchers to modify and delete their study configurations. IDLaS-NL is intended for researchers, clinicians, educators and in general anyone conducting fundamental research into language and general cognitive skills; it is not intended for diagnostic purposes. All platform services are free of charge. Here, we provide a description of its workings as well as instructions for using the platform. The IDLaS-NL platform can be accessed at www.mpi.nl/idlas-nl
STAIRS4WORDS: A new adaptive test for assessing receptive vocabulary size in English, Dutch, and German
Semi-automatic standardized analysis method to objectively evaluate near-infrared fluorescent dyes in image-guided surgery
Significance: Near-infrared fluorescence imaging still lacks a standardized, objective method to evaluate fluorescent dye efficacy in oncological surgical applications. This results in difficulties in translation between preclinical to clinical studies with fluorescent dyes and in the reproduction of results between studies, which in turn hampers further clinical translation of novel fluorescent dyes. Aim: Our aim is to develop and evaluate a semi-automatic standardized method to objectively assess fluorescent signals in resected tissue. Approach: A standardized imaging procedure was designed and quantitative analysis methods were developed to evaluate non-targeted and tumor-targeted fluorescent dyes. The developed analysis methods included manual selection of region of interest (ROI) on white light images, automated fluorescence signal ROI selection, and automatic quantitative image analysis. The proposed analysis method was then compared with a conventional analysis method, where fluorescence signal ROIs were manually selected on fluorescence images. Dice similarity coefficients and intraclass correlation coefficients were calculated to determine the inter- and intraobserver variabilities of the ROI selections and the determined signal- and tumor-to-background ratios. Results: The proposed non-targeted fluorescent dyes analysis method showed statistically significantly improved variabilities after application on indocyanine green specimens. For specimens with the targeted dye SGM-101, the variability of the background ROI selection was statistically significantly improved by implementing the proposed method. Conclusion: Semi-automatic methods for standardized quantitative analysis of fluorescence images were successfully developed and showed promising results to further improve the reproducibility and standardization of clinical studies evaluating fluorescent dyes.</p
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