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A van den Bos

Publications and source records attributed to A van den Bos.

13 recordsLinked to original sources
PubMed2005

Maximum likelihood estimation of structure parameters from high resolution electron microscopy images. Part I: a theoretical framework.

This paper is the first part of a two-part paper on maximum likelihood (ML) estimation of structure parameters from electron microscopy images. In principle, electron microscopy allows structure determination with a precision that is orders of magnitude better than the resolution of the microscope. This requires, however, a quantitative, model-based method. In our opinion, the ML method is the most appropriate one since it has optimal statistical properties. This paper aims to provide microscopists with the necessary tools to apply this method so as to determine structure parameters as precisely as possible. It reviews the theoretical framework, including model assessment, the derivation of the ML estimator of the parameters, the limits to precision and the construction of confidence regions and intervals for ML parameter estimates. In a companion paper [Van Aert et al., Ultramicroscopy, this issue, 2005], a practical example will be worked out.

Journal Article↗
PubMed2005

Maximum likelihood estimation of structure parameters from high resolution electron microscopy images. Part II: a practical example.

This paper is the second part of a two-part paper on maximum likelihood (ML) estimation of structure parameters from electron microscopy images. In order to show the practical applicability of the theoretical methods described in the first part of this two-part paper, an experimental study of an aluminium crystal is presented. In this study, structure parameters, atom column distances in particular, are estimated from high-resolution transmission electron microscopy (HRTEM) images using the ML method. The necessary steps to be made in the application of this method will be worked out one by one, including model assessment, the computation of the ML parameter estimates, and the construction of confidence intervals for these parameter estimates.

Journal Article↗
PubMed2003

Is atomic resolution transmission electron microscopy able to resolve and refine amorphous structures?

Atomic resolution transmission electron microscopy, even with an aberration free microscope, is only able to resolve and refine amorphous structures at the atomic level for very small foil thicknesses. Then, a precision of the order of 0.01 A is possible, but this may require long recording times, especially for light atoms. For larger thicknesses, amorphous structures can in principle only be resolved and refined using electron tomography.

Journal Article↗
PubMed2003

Feasibility of a new in vitro approach to evaluate cellular damage following co-infusion of red blood cell concentrates and intravenous drug solutions.

INTRODUCTION: Transfusion guidelines may result in unwanted delay in infusion schemes, as simultaneous infusion of blood components and drug solutions is universally prohibited. The aim of this study was to measure possible damage to red cells by drug solutions, as manifested by haemolysis, using a dynamic model that resembles the clinical setting. METHODS: Stored filtered and irradiated RBC concentrates and drug solutions were co-infused in an in vitro dynamic model. Also, incubation in a static model was performed. The haemolytic potency of the drug solutions was measured by determining free haemoglobin (fHb) levels. RESULTS AND DISCUSSION: Neither in the dynamic tests nor in the static tests did fHb levels exceed the maximally acceptable standard for filtered RBC concentrates according to Dutch specification guidelines. In the static test model, fHb levels were slightly elevated compared with those of control samples, as well as those in the dynamic test model. CONCLUSION: A novel in vitro dynamic infusion system appears to represent a useful technique to calculate possible damage to RBCs resulting from co-infused drug solutions. Co-infusion of the drug solutions tested with filtered and irradiated RBC concentrates did not produce fHb levels above the levels accepted by the Dutch national guidelines. Apart from haemolysis, other parameters reflecting RBC damage should be investigated in future studies.

Drug-Related Side Effects and Adverse Reactions↗
PubMed2002

Optimal experimental design of STEM measurement of atom column positions.

A quantitative measure is proposed to evaluate and optimize the design of a high-resolution scanning transmission electron microscopy (STEM) experiment. The proposed measure is related to the measurement of atom column positions. Specifically, it is based on the statistical precision with which the positions of atom columns can be estimated. The optimal design, that is, the combination of tunable microscope parameters for which the precision is highest. is derived for different types of atom columns. The proposed measure is also used to find out if an annular detector is preferable to an axial one and if a C(s)-corrector pays off in quantitative STEM experiments. In addition, the optimal settings of the STEM are compared to the Scherzer conditions for incoherent imaging and their dependence on the type of object is investigated.

Journal Article↗
PubMed2001

Does a monochromator improve the precision in quantitative HRTEM?

This paper addresses the question as to what extent the incorporation of a monochromator in an electron microscope can enhance the performance of high resolution transmission electron microscopy (HRTEM). The monochromator will reduce the chromatic aberration, and hence the information limit, at the expense of beam current, leading to a decrease in signal intensity and a corresponding decrease in signal-to-noise ratio (SNR). Both aspects, information limit and SNR, have been included in a quantitative evaluation based on the statistical precision with which the position of an atom column can be estimated. It is shown that the effect of a monochromator on the attainable precision depends on the microscope and monochromator parameters, as well as on the characteristics of the object.

Journal Article↗
PubMed2000

Modeling of an intelligent pressure sensor using functional link artificial neural networks.

A capacitor pressure sensor (CPS) is modeled for accurate readout of applied pressure using a novel artificial neural network (ANN). The proposed functional link ANN (FLANN) is a computationally efficient nonlinear network and is capable of complex nonlinear mapping between its input and output pattern space. The nonlinearity is introduced into the FLANN by passing the input pattern through a functional expansion unit. Three different polynomials such as, Chebyschev, Legendre and power series have been employed in the FLANN. The FLANN offers computational advantage over a multilayer perceptron (MLP) for similar performance in modeling of the CPS. The prime aim of the present paper is to develop an intelligent model of the CPS involving less computational complexity, so that its implementation can be economical and robust. It is shown that, over a wide temperature variation ranging from -50 to 150 degrees C, the maximum error of estimation of pressure remains within +/- 3%. With the help of computer simulation, the performance of the three types of FLANN models has been compared to that of an MLP based model.

Algorithms↗
PubMed2000

Aberration and the Strehl ratio.

An exact expression is derived for the Strehl ratio as a function of the minimum root-mean-square aberration value that may produce it. The result is applicable to any aperture and is shown to imply a similar expression for the Strehl ratio as a function of the minimum amplitude range of the aberration.

Models, Theoretical↗
PubMed1982

International disaster identification report. Investigative and dental aspects.

This meeting, held in October 1980 in Apeldoorn, Netherlands, was a very serious effort to begin international cooperation in a much needed area: disaster investigation and identification. Under the leadership of Col. Arie van den Bos of the Royal Police of the Netherlands, the work was accomplished with representatives and observers from many major countries represented. Efforts were made to solve the enigma of international cooperation. A plane crash of an airline of a major country in a distant country can be properly investigated only with the cooperation of the carrier and the country in which the tragedy occurred. The International Academy of Legal Medicine and Social Medicine devoted a 3-day program to the study of this problem during their last international meeting in Lyon, France, and it will be discussed further in Vienna in 1982 under the leadership of Prof. Wilhelm Holczabek. The experience of Norwegian investigators is mentioned as an example of the type of problems encountered with foreign nationals involved in a crash in the country, or a disaster involving a ship or a oil platform where foreign nationals are working, or in a tragedy such as the propylene explosion in Tarragona, Spain, which resulted in more than 200 tourists from many countries dying in the fire, many bodies burned beyond recognition.

Congresses as Topic↗
PubMed1980

Mass identification: a multidisciplinary operation. The Dutch experience.

The organization of the Disaster Unit of the National Police Force of the Netherlands is described. Several aspects of its operation are discussed, including the recovery operation, technical identification, tactical identification, and finally the details of the Dutch operation in the disaster at Tenerife. The Tenerife disaster operation included the work at the crash site and temporary morgue setup, the method of technical identification, and the supplementary investigations upon return to the Netherlands. The success of this difficult task, shown by positive identification of 82% of the bodies of the victims, is truly remarkable.

Accidents, Aviation↗
PubMedDate not supplied

High-resolution electron microscopy and electron tomography: resolution versus precision.

The performance of high-resolution electron microscopy and electron tomography is usually discussed in terms of two-point resolution, expressing the possibility of perceiving separately two image points of an object. However, the concept resolution obtains another meaning if one uses prior knowledge about the object and the imaging procedure in the form of a parametric model describing the expectations of the observations. The unknown parameters, such as the positions of the components in an object, can be measured quantitatively by fitting this model to the observations. Due to the statistical nature of the experiment, the resulting solutions for the positions of the components and therefore for the distance between the components will never be exact. An alternative to resolution is then the precision with which the distance can be measured. In the present paper, it is shown that the precision depends on the size of the components, the distance between the components, the resolution of the instrument, and the number of electron counts. For electron tomography, it also depends on the orientation of the object with respect to the rotation axis.

Image Processing, Computer-Assisted↗