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Molekulové simulace nukleace ledu
Pluhařová, Eva ; Kolafa, Jiří (referee) ; Jungwirth, Pavel (advisor)
Title: Molecular simulations of ice nucleation Author: Eva Pluhařová Department: Department of Physical and Macromolecular Chemistry Faculty of Science UK Advisor: doc. Mgr. Pavel Jungwirth, DSc., IOCB AS CR, v.v.i. Advisor's e-mail address: pavel.jungwirth@uochb.cas.cz Abstract: By means of molecular dynamics simulations we have systematically investigated homogeneous ice nucleation in neat and surface contaminated water. As models of the adsorbates we have assumed pentanol and pentanoic acid. In neat water nucleation preferentially starts in the subsurface region, which accommodates better than the bulk the volume increase associated with freezing. Homogeneous ice nucleation is affected more by alcohol than by acid. Water slabs covered by a disordered layer of pentanol exhibit negligible preference for subsurface nucleation and longer nucleation times in comparison with neat water, while nucleation times are almost unaffected by the presence of pentanoic acid and the subsurface preference is only slightly decreased. We tried to rationalize the differences between the effects of different compounds by their ability to orient water molecules and to change their mobility. The fact that adsorbates differ in the influence on homogeneous ice nucleation has important implications for the microphysics of...
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Molecular Simulations of Surfaces of Aqueous Solutions
Vácha, Robert ; Jungwirth, Pavel (advisor) ; Kolafa, Jiří (referee) ; Barvík, Ivan (referee)
This thesis consists of 18 papers, in which we investigated the behavior of molecules and ions at aqueous interfaces by means of molecular dynamics (MD) simulations. We started our simulations with the surface of neat water, where we investigated the behavior of hydronium and hydroxide ions, i.e., the products of autolysis of water that are of 10�7M concentration in pure water. The results, ranging from ab initio high level calculations on water clusters and ab initio dynamics on small systems to statistically converged classical molecular dynamics simulations are mutually consistent47,48,50. The observed surface adsorption of hydronium is also consistent with the surface selective spectroscopy experiments (VSFG, SHG, PES)45,51,55{59, surface tension measurements60, and with _-potential measurements of acidic solutions62,63. The spectroscopy and surface tension experiments are also in agreement with the weak surface repulsion/non-accumulation of hydroxide observed in our simulations. However, there are macroscopic measurements, such as higher pH electrophoretic mobility measurements, titration of oil emulsions, and thin _lm stability experiments that indicate a negative charge on air/water and oil/water interfaces 61{71. Even though these experiments do not directly reveal the chemical nature or...
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Specifications of marketing research conducted with underage respondents
Čepek, Michal ; Průša, Přemysl (advisor) ; Kolafa, Jan (referee)
This diploma thesis deals with the ethics of marketing research conducted with underage respondents. Child security is a very hot topic these days; therefore the field of market research should use only methods tolerated by parents. Global as well as local market research associations regularly publish codes of conduct and guidelines dealing with the ethics in market research. However, they define only basic rules and regulations and do not reflect the specificity of each method and technique. The goal of this diploma thesis is to identify methods used in market research that are not perceived as ethical by parents. Results should motivate research agencies to eliminate using such methods or at least modify them to decrease the level of controversy among general public. In order to identify unethically perceived market research methods, the author of the thesis conducted a quantitative research among the needed target group: parents of school kids. The survey found 5 methods that are considered ethical and thus do not pose any significant threat to the industry of market research: taste test, observation, product test, eye-tracking and communication test. Two methods were labeled as unethical by the respondents: field experiment and online discussion groups. Those methods can be used without any major changes provided that agencies communicate openly with parents all details regarding the research. They have to make sure that parents understand the methodology and are sure to let their children participate in such a project. Finally, three methods were recognized as highly unethical or even illegal: neuromarketing, netnography and geolocation (geomarketing). These methods carry a high probability of damaging the positive image of market research industry among general public. Less than one quarter of respondents consider these methods as suitable for use with kids and at the same time more than 25 % of parents think that those methods are illegal. In case of neuromarketing, it is recommended to firstly explain the used methodology in detail and, if possible, demonstrate its 100 % safety in presence of a doctor. Netnography was evaluated as highly unethical. On the other hand, it is a type of observation; therefore, its use in reality is unlikely to be registered by public. As a result, there does not have to be any severe steps taken to regulate this method. Geolocation scored as the most unethical market research method in the survey. This method is therefore not recommended for use as it carries an enormous risk of damaging the whole market research industry.
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