Publications by authors named "Miroslav Vaculík"

5 Publications

  • Page 1 of 1

Effects of braking conditions on nanoparticle emissions from passenger car friction brakes.

Sci Total Environ 2021 Sep 15;788:147779. Epub 2021 May 15.

University of Chemistry and Technology Prague, Technicka 5, 166 28 Prague 6, Czech Republic.

Automobile friction brakes generate, in addition to coarse particles generated by mechanical processes, highly variable amount of nanoparticles from high temperature processes. The effects of braking conditions - speed, deceleration rate, brake rotor temperatures - on nanoparticle production were investigated here, aiming to provide practical guidance for reducing emissions through driving style and traffic management. Typical brake pads and a rotor from a common passenger car were subjected, on a brake dynamometer, to three runs of the WLTP brake cycle developed for brake wear particle measurements. Additionally, four sets of common brake pads were subjected to those parts of standardized brake performance tests believed to be reasonably realistic for common driving. Particle size distributions (5.6-560 nm electric mobility diameter, without removal of volatiles) show a dominant peak at 10 nm commensurate to the severity of braking and a non-linear increase of the total particle number at higher braking powers and higher total energy dissipated. The average emissions for three runs of the WLTP brake cycle were 3.3 × 10 particles/km, while the harshest deceleration, 175-100 km/h at 5.28 m·s, has produced 8.4 to 38 × 10 particles, corresponding to 2.5-11.5 thousands of km of WLTP-like driving. While previous studies have correlated higher PN production with higher average brake rotor temperature, a more complex relationship between nanoparticle emissions and a combination of initial rotor temperature, total energy dissipated and braking power has been observed here. From a driver behavior and regulatory perspective, it appears limiting harsh braking and braking from high speeds, possibly through improved driving practices, road design and traffic management, may potentially reduce brake wear nanoparticles. From the measurement perspective, it appears that "off-cycle" braking, even if relatively infrequent, may be associated with exponentially higher emissions and non-negligible share of the total emissions, and therefore should not be neglected.
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http://dx.doi.org/10.1016/j.scitotenv.2021.147779DOI Listing
September 2021

Evolution of pediatric epilepsy surgery program over 2000-2017: Improvement of care?

Eur J Paediatr Neurol 2019 May 15;23(3):456-465. Epub 2019 Apr 15.

Department of Pediatric Neurology, Charles University, 2nd Faculty of Medicine and Motol University Hospital, V Uvalu 84, 15006, Prague, Czech Republic. Electronic address:

Purpose: We assessed trends in spectrum of candidates, diagnostic algorithm, therapeutic approach and outcome of a pediatric epilepsy surgery program between 2000 and 2017.

Methods: All pediatric patients who underwent curative epilepsy surgery in Motol Epilepsy Center during selected period (n = 233) were included in the study and divided into two groups according to time of the surgery (developing program 2000-2010: n = 86, established program 2011-2017: n = 147). Differences in presurgical, surgical and outcome variables between the groups were statistically analyzed.

Results: A total of 264 resections or hemispheric disconnections were performed (including 31 reoperations). In the later epoch median age of candidates decreased. Median duration of disease shortened in patients with temporal lobe epilepsy. Number of patients with non-localizing MRI findings (subtle or multiple lesions) rose, as well as those with epileptogenic zone adjacent to eloquent cortex. There was a trend towards one-step procedures guided by multimodal neuroimaging and intraoperative electrophysiology; long-term invasive EEG was performed in fewer patients. Subdural electrodes for long-term invasive monitoring were almost completely replaced by stereo-EEG. The number of focal resections and hemispherotomies rose over time. Surgeries were more often regarded complete. Histopathological findings of resected tissue documented developing spectrum of candidates. 82.0% of all children were seizure-free two years after surgery; major complications occurred in 4.6% procedures; both groups did not significantly differ in these parameters.

Conclusion: In the established pediatric epilepsy surgery program, our patients underwent epilepsy surgery at younger age and suffered from more complex structural pathology. Outcomes and including complication rate remained stable.
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http://dx.doi.org/10.1016/j.ejpn.2019.04.002DOI Listing
May 2019

Determination of Oxidative Potential Caused by Brake Wear Debris in Non-Cellular Systems.

J Nanosci Nanotechnol 2019 05;19(5):2869-2875

Nanotechnology Centre, VŠB-Technical University of Ostrava, 17. listopadu 15/2172, 708 33 Ostrava-Poruba, Czech Republic.

Wear debris from automotive brake systems represents a major source of non-exhaust emissions from road traffic and its production increases with number of cars worldwide. However, impact of brake wear debris on the environment and organisms is still not clear. One of the most possible ways by which these particles may affect living organisms is oxidative stress. Production of reactive oxidative species may cause damage of basic cell components, lipids, proteins, etc. Aim of this study is to perform characterization of airborne and nonairborne fractions of brake wear debris generated during standard dynamometer tests and evaluation of its potential to induce oxidative stress via lipid peroxidation and carbonylation of proteins in non-cellular system. Elemental and phase composition were determined by scanning electron microscopy, Raman microspectroscopy, and X-ray powder diffraction analysis. Carbon in amorphous form and graphite, copper, and iron in form of oxides were identified as major components in both studied fractions. Characteristic size of studied wear particles was evaluated by dynamic light scattering. Both airborne and nonairborne samples showed ability to induce oxidative stress which results from determination of carbonylated proteins.
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http://dx.doi.org/10.1166/jnn.2019.15866DOI Listing
May 2019

Automotive airborne brake wear debris nanoparticles and cytokinesis-block micronucleus assay in peripheral blood lymphocytes: A pilot study.

Environ Res 2016 07 29;148:443-449. Epub 2016 Apr 29.

Health Effects Laboratory, Department of Environmental Chemistry, NILU-Norwegian Institute for Air Research, Instituttveien 18, 2007 Kjeller, Norway.

Motor vehicle exhaust and non-exhaust processes play a significant role in environmental pollution, as they are a source of the finest particulate matter. Emissions from non-exhaust processes include wear-products of brakes, tires, automotive hardware, road surface, and traffic signs, but still are paid little attention to. Automotive friction composites for brake pads are composite materials which may consist of potentially hazardous materials and there is a lack of information regarding the potential influence of the brake wear debris (BWD) on the environment, especially on human health. Thus, we focused our study on the genotoxicity of the airborne fraction of BWD using a brake pad model representing an average low-metallic formulation available in the EU market. BWD was generated in the laboratory by a full-scale brake dynamometer and characterized by Raman microspectroscopy, scanning electron microscopy, and transmission electron microscopy showing that it contains nano-sized crystalline metal-based particles. Genotoxicity tested in human lymphocytes in different testing conditions showed an increase in frequencies of micronucleated binucleated cells (MNBNCs) exposed for 48h to BWD nanoparticles (NPs) (with 10% of foetal calf serum in culture medium) compared with lymphocytes exposed to medium alone, statistically significant only at the concentration 3µg/cm(2) (p=0.032).
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http://dx.doi.org/10.1016/j.envres.2016.04.022DOI Listing
July 2016

Fanconi anemia with biallelic FANCD1/BRCA2 mutations - Case report of a family with three affected children.

Eur J Med Genet 2016 Mar 2;59(3):152-7. Epub 2015 Dec 2.

Department of Pediatric Hematology and Oncology, Charles University in Prague, Second Faculty of Medicine and University Hospital Motol, Prague, Czech Republic.

Fanconi anemia, complementation group D1 with bi-allelic FANCD1 (BRCA2) mutations, is a very rare genetic disorder characterized by early onset of childhood malignancies, including acute leukemia, brain cancer and nephroblastoma. Here, we present a case report of a family with 3 affected children in terms of treatment outcome, toxicity and characterization of the malignancies using comprehensive cytogenetic analysis. The first child was diagnosed with T-cell acute lymphoblastic leukemia when he was 11 months old. During chemotherapy, he suffered from repeated pancytopenia, sepsis and severe vincristine polyneuropathy, and 18 months after primary diagnosis, he succumbed to secondary acute monocytic leukemia. The second child was diagnosed with stage 2 triphasic nephroblastoma (Wilms tumor), when he was 3 years and 11 months old. During chemotherapy, he suffered from vincristine polyneuropathy. Currently, he is in complete remission, 29 months following the initial diagnosis. The third child was diagnosed with medulloblastoma with classical histology, when she was 4 years and 5 months old. After the first cycle of chemotherapy, she suffered from prolonged pancytopenia, sepsis and severe skin and mucosal toxicity. Six weeks after primary diagnosis, a first relapse in the posterior fossa was diagnosed, and at 7 and half months after primary diagnosis, a second relapse was diagnosed that led to the patient's death. Our case report underscores tumor heterogeneity, treatment toxicity and poor outcome in Fanconi anemia patients of complementation group D1.
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http://dx.doi.org/10.1016/j.ejmg.2015.11.013DOI Listing
March 2016