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Willi Stahlhofen

Bio: Willi Stahlhofen is an academic researcher. The author has contributed to research in topics: Aerosol & Particle size. The author has an hindex of 28, co-authored 61 publications receiving 3097 citations.


Papers
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Journal ArticleDOI
TL;DR: In this paper, the authors presented experimentally determined total and regional deposition data for breathing monodisperse aerosols of a wide particle size range at different patterns through the mouth and nose.

1,002 citations

Journal ArticleDOI
TL;DR: The retention of the radioactive particles present in the body after aerosol administration is measured with a body counter designed and constructed for these experiments, and the elimination of material from the chest is found to be much slower for the material deposited in the alveolar region than for the amount deposit in the tracheobronchial tree.
Abstract: The experimental techniques and the results of inhalation studies with radioaerosols on normal non-smokers for mouth-breathing are described and discussed. Monodisperse iron oxide particles tagged with198Au are produced with a spinning top generator in the aerodynamic size range between 1 to 10 µm. An aerosol inhalation apparatus enables the subjects to breathe under standardized conditions with respect to tidal volume and breathing frequency. The calculation of total deposition is based upon measurements of the number of in- and exhaled particles per breath by means of photometric methods and pneumotachography. The retention of the radioactive particles present in the body after aerosol administration is measured with a body counter designed and constructed for these experiments. Retention measurements as functions of time after inhalation are carried out in extrathoracic-, chest- and stomach-position. The body counter consists of four shielded NaF(TI)-detectors. The geometrical arrangement, the collimat...

404 citations

Journal ArticleDOI
TL;DR: Whenever the mean residence time of the particles in the respiratory tract was short deposition for mouth-breathing was found to be almost independent of particle size in the diameter range below 1 μm revealing the significance of mixing.

155 citations

Journal ArticleDOI
TL;DR: The data demonstrate that mucociliary clearance does not remove all particles deposited in the airways and that a significant fraction undergoes long-term retention mechanisms, the origin of which is still under discussion.
Abstract: Spherical monodisperse ferromagnetic iron oxide particles of 1.9-microm geometric and 4.2-microm aerodynamic diameter were inhaled by 13 healthy nonsmoking subjects using the shallow bolus technique. The bolus width was 100 ml, and the penetration front depth was 150 +/- 27 ml. The mean flow rate during inhalation and exhalation was 250 ml/s. The Fowler dead space and the phase 1 dead space of the airways were 282 +/- 49 and 164 +/- 34 ml, respectively. Deposition was below 20% without breath holding and 51 +/- 8% after an 8-s breath-holding time. We attempted to confine the bolus deposition to the bronchial airways by limiting the bolus front depth to the phase 1 dead space volume. Particle retention was measured by the magnetopneumographic method over a period of 9 mo. Particle clearance from the airways showed a fast and a slow phase; 49 +/- 9% followed the fast phase with a mean half-time of 3.0 +/- 1.6 h and characterized the mucociliary clearance. The remaining fraction was cleared slowly with a half-time of 109 +/- 78 days. The slow clearance phase was comparable to clearance measurements from the lung periphery of healthy nonsmokers, which allowed macrophage-dependent clearance mechanisms of the slow cleared fraction to be taken into account. Despite the fact that part of the slowly cleared particles may originate from peripheral deposition, the data demonstrate that mucociliary clearance does not remove all particles deposited in the airways and that a significant fraction undergoes long-term retention mechanisms, the origin of which is still under discussion.

148 citations

Journal ArticleDOI
TL;DR: A great intersubject variability of extrathoracic, tracheobronchial and alveolar deposition was found and the highest one was observed for particle deposition in the extrath oracic airways.
Abstract: Regional deposition of inhaled particles was studied experimentally for 9 health subjects breathing the same aerosol under the same breathing conditions in order to evaluate intersubject variability of regional deposition. A great intersubject variability of extrathoracic, tracheobronchial and alveolar deposition was found. The highest one was observed for particle deposition in the extrathoracic airways. This biological variability of regional deposition has to be taken into account for considerations of health related aspects of aerosol inhalation.

86 citations


Cited by
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01 Jan 2000
TL;DR: This annex is aimed at providing a sound basis for conclusions regarding the number of significant radiation accidents that have occurred, the corresponding levels of radiation exposures and numbers of deaths and injuries, and the general trends for various practices, in the context of the Committee's overall evaluations of the levels and effects of exposure to ionizing radiation.
Abstract: NOTE The report of the Committee without its annexes appears as Official Records of the General Assembly, Sixty-third Session, Supplement No. 46. The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Secretariat of the United Nations concerning the legal status of any country, territory, city or area, or of its authorities, or concerning the delimitation of its frontiers or boundaries. The country names used in this document are, in most cases, those that were in use at the time the data were collected or the text prepared. In other cases, however, the names have been updated, where this was possible and appropriate, to reflect political changes. Scientific Annexes Annex A. Medical radiation exposures Annex B. Exposures of the public and workers from various sources of radiation INTROdUCTION 1. In the course of the research and development for and the application of atomic energy and nuclear technologies, a number of radiation accidents have occurred. Some of these accidents have resulted in significant health effects and occasionally in fatal outcomes. The application of technologies that make use of radiation is increasingly widespread around the world. Millions of people have occupations related to the use of radiation, and hundreds of millions of individuals benefit from these uses. Facilities using intense radiation sources for energy production and for purposes such as radiotherapy, sterilization of products, preservation of foodstuffs and gamma radiography require special care in the design and operation of equipment to avoid radiation injury to workers or to the public. Experience has shown that such technology is generally used safely, but on occasion controls have been circumvented and serious radiation accidents have ensued. 2. Reviews of radiation exposures from accidents have been presented in previous UNSCEAR reports. The last report containing an exclusive chapter on exposures from accidents was the UNSCEAR 1993 Report [U6]. 3. This annex is aimed at providing a sound basis for conclusions regarding the number of significant radiation accidents that have occurred, the corresponding levels of radiation exposures and numbers of deaths and injuries, and the general trends for various practices. Its conclusions are to be seen in the context of the Committee's overall evaluations of the levels and effects of exposure to ionizing radiation. 4. The Committee's evaluations of public, occupational and medical diagnostic exposures are mostly concerned with chronic exposures of …

3,924 citations

Journal ArticleDOI
TL;DR: The working group report presents a broad data gathering strategy applicable to this early stage in the development of a risk assessment process for nanomaterials, and there is a strong likelihood that biological activity of nanoparticles will depend on physicochemical parameters not routinely considered in toxicity screening studies.
Abstract: The rapid proliferation of many different engineered nanomaterials (defined as materials designed and produced to have structural features with at least one dimension of 100 nanometers or less) presents a dilemma to regulators regarding hazard identification. The International Life Sciences Institute Research Foundation/Risk Science Institute convened an expert working group to develop a screening strategy for the hazard identification of engineered nanomaterials. The working group report presents the elements of a screening strategy rather than a detailed testing protocol. Based on an evaluation of the limited data currently available, the report presents a broad data gathering strategy applicable to this early stage in the development of a risk assessment process for

2,015 citations

Journal ArticleDOI
TL;DR: This review briefly covers aggregation theory focusing on Derjaguin-Landau-Verwey-Overbeak (DLVO)-based models most commonly used to describe the thermodynamic interactions between two particles in a suspension.
Abstract: Unique forms of manufactured nanomaterials, nanoparticles, and their suspensions are rapidly being created by manipulating properties such as shape, size, structure, and chemical composition and through incorporation of surface coatings. Although these properties make nanomaterial development interesting for new applications, they also challenge the ability of colloid science to understand nanoparticle aggregation in the environment and the subsequent effects on nanomaterial transport and reactivity. This review briefly covers aggregation theory focusing on Derjaguin-Landau-Verwey-Overbeak (DLVO)-based models most commonly used to describe the thermodynamic interactions between two particles in a suspension. A discussion of the challenges to DLVO posed by the properties of nanomaterials follows, along with examples from the literature. Examples from the literature highlighting the importance of aggregation effects on transport and reactivity and risk of nanoparticles in the environment are discussed.

1,014 citations

Journal ArticleDOI
TL;DR: In this article, the authors present the major issues concerned with biomass combustion with special reference to the small scale fluidized bed systems (small to pilot scale). Problems have been identified, mechanisms explained and solutions have been indicated.

1,012 citations

Journal ArticleDOI
TL;DR: In this paper, the authors presented experimentally determined total and regional deposition data for breathing monodisperse aerosols of a wide particle size range at different patterns through the mouth and nose.

1,002 citations