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Photobiological Safety of luminaires and Light Sources
Štěpánek, Jaroslav ; Bendová,, Zdeňka (referee) ; Vik,, Michal (referee) ; Škoda, Jan (advisor)
This doctoral thesis called “Photobiological safety of luminaires and light sources” has focused on an optical radiation and its relation to human body. The thesis describes possible consequences on living tissue during excessive exposure to optical radiation. Among others the work deals with the light source, lamp and optical devices evaluation in dependence of photobiological safety. There is created a method of light source evaluation procedure for photobiological safety in accordance with ČSN EN 62471. The meaning of this procedure is based on its hazard calculation from measured values of irradiation to different photometric distances. Validity of procedure is verified by light source measuring, in which visual angle and photometric distance have been changed. There we can also find an application of this procedure in the UV source evaluation, which helps to determine a safe distance away from UV sources not to create any danger. The evaluated UV sources include a UVA luminaire with a dominant wavelength of 365 nm or an arc of an electric welder. The thesis also describes a method of evaluating light sources for blue light hazard for an aphakic and pseudophakic eye. This method can also help to determine the hazard for the eye without lens or with some implanted lens. Furthermore, there was developed the method of the blue light hazard assessment depending on the age of an exposed person. In terms of the work there was also created a computer programme evaluating photobiological safety resulting from the spectral data having been stored in the library programme or from spectroradiometric measurement data. The work also marginally deals with the topic of circadian rhythms, which are closely related to photobiological manifestation in an human body. Above all the work compares light sources for which equivalent illuminances are calculated, consequently light sources have the same effect on suppressing the melatonin hormone production.
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Design of the morning sun simulator
Suský, Stanislav ; Krbal, Michal (referee) ; Štěpánek, Jaroslav (advisor)
This work deals with the introduction of the influence of electromagnetic radiation on circadian rhythms and their influence on the organism. The work describes circadian rhythms and their influence on the organism, the location and description of functions of important organs and the influence of electromagnetic radiation on these organs. There are described light sources and their influence on circadian rhythms.
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Lighting with Tunable Spectral Distribution and Its Influence on Human Physiological Functions
Hanák, Petr ; Bendová,, Zdeňka (referee) ; Baxant, Petr (advisor)
In this diplomat theses are considered the effects of light on human beings, especially on physical performance. The goal of this work was to design a suitable method for evaluation of the effects of light on physical performance. Furthermore, to verify designed methods in laboratory environment and the assessment of collected data. After creating this method several people were tested under different light conditions and collected date evaluated. The results are suggesting that high intensity lighting with low wave lengths leads to an increase of physiological activity in organism and therefore to a potential decreasing physical performance.
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Phototherapy
Joklík, Vojtěch ; Škoda, Jan (referee) ; Štěpánek, Jaroslav (advisor)
This thesis describes relationship between human body and light. It is focused on perception of light with human eye, skin and their reaction to incident light and its intensity. Then it contains short description of Icterus Neonatorum (yellow-gum), Constitutional Dermatitis, Lepriasis and their treatment. It is followed by description of various sources of light, their use in medicine and reaction of body to them. This work includes measurements and evaluation of five sources of light.
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Circadian rhythms in human life - elaboration of the topic with elements of the flipped classroom teaching method
Křivohlavá, Tereza ; Mourek, Jan (advisor) ; Manková, Denisa (referee)
The thesis deals with an alternative teaching method called the flipped classroom, which was applied in the practical part to the topic of the biology of circadian rhythms. In the flipped classroom method, the phases of teaching are switched. Study material is created for the students and presented to them for home study before the class. In the actual teaching, there is then more time for clarifying ambiguities or consolidating material, which is the main advantage of the flipped classroom. Circadian rhythms are biorhythms repeating with a period of approximately 24 hours. The circadian system is controlled by the central circadian clock in the suprachiasmatic nuclei of the hypothalamus. These circadian clocks are synchronized by environmental stimuli, predominantly light. In the case of irregular artificial lighting, the body's circadian clock desynchronizes and disturbances in mood, cognitive performance, or physical health can occur. In the frame of the practical part of the thesis, a video was created to introduce students to the topic of circadian rhythms. In addition, worksheet assignments were created to practice and deepen students' knowledge of biological rhythms, as well as the design of an entire teaching unit with flipped classroom elements. Everything was tested on 4 groups of the...
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Circadian system in adolescents and the use of light therapy
Kučerová, Jana ; Červená, Kateřina (advisor) ; Pačesová, Dominika (referee)
Circadian rhythms, as regularly recurring events in living organisms with a period of approximately 24 hours, are an important part of life on Earth. To keep the period of the internal circadian clock of an organism in line with the cycle of the Earth Day, synchronization of this clock is necessary. The most important factor in synchronizing the circadian clock is light, which provides the brain with information about the phase of the Earth Day. The individual setting of the circadian clock, which is manifested in the form of a chronotype, has a profound effect on the life of the individual. Chronotypes change throughout life, and the most significant changes occur during adolescence, when the overall chronotype shifts. This results in adolescents going to bed later even though they have to get up early for school. This is also why they are more likely to suffer from sleep deprivation, be inattentive at school or fall asleep during lessons. Consequently, they experience, often with significant, social jet lag, which is a health risk. Light therapy offers a solution. This paper presents its general use, as well as specific examples of its use with delayed adolescents. However, there are also other ways to improve the situation of adolescents, e.g., delaying the start time of school in the morning,...
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Hormonal synchronization of fetal circadian clocks in suprachiasmatic nuclei
Kapsdorferová, Viktória ; Sumová, Alena (advisor) ; Sehadová, Hana (referee)
Rhythmic non-light maternal signals, such as various behavioral, neurohumoral or metabolic factors, may play a key role in synchronization of the fetal circadian clock. This diploma thesis focuses more closely on the possible role of leptin and dopamine in the hormonal synchronization of the fetal central clock resides in the suprachiasmatic nuclei of the hypothalamus. A transgenic mouse fetus, which has luciferase fused to the clock gene Period 2, was used as an experimental model. This allowed us to monitor the operation of the fetal central clock in real time by recording the bioluminescence of tissue explants. Exogenous administration of dopamine during the decline in bioluminescence at normalized circadian time 15 induces larger phase delays compared to vehicle. Leptin, on the other hand, can participate in the development of spontaneous rhythms by stabilizing the integrity of the circadian rhythm, manifested by slowing down the rhythm dampening. At the level of individual cellular oscillators, significant regional differences in amplitude and period were not observed using bioluminescence microscopy. However, a slight dispersion of cell phases was observed after administration of dopamine during decreasing bioluminescence. In the case of leptin, there was a prolongation of period of the cell...
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Development of the circadian system after systemic potentiation of GABAergic transmission in early ontogenesis
Dušek, Jakub ; Bendová, Zdeňka (advisor) ; Mareš, Pavel (referee)
The circadian system is the evolutionary response of organisms to repetitive geophysical conditions and allows organisms to devote their energy to solving sudden changes. Although the circadian system developed to help organisms survive and thrive in dynamic conditions, system itself is sensitive to external changes. During critical developmental period of the mammalian CNS, the neonatal period, the circadian systém is significantly vulnerable. Benzodiazepines, pharmaceuticals widely prescribed for half a century, interfere with GABAergic transmission, which is critical type of signaling for the functioning of the circadian systém. The purpose of this thesis is to determine whether and how the development and functioning of the circadian system is altered after administration of a drug from the benzodiazepine class, clonazepam, during the critical developmental period. This thesis examines changes in the expression profile of selected genes in the hippocampus, olfactory bulb and frontal cortex of two ontogenetic stages of rats. Results of this work suggest that benzodiazepines administred in the neonatal period disrupt the development of the circadian system and that these changes, particularly in the hippocampus, persist for certain time. Key words: circadian system; circadian rhythms;...
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Circadian rhythms in adipocytes and impact of their disruption
Zavřelová, Michaela ; Sumová, Alena (advisor) ; Spišská, Veronika (referee)
This bachelor thesis deals with circadian rhythms in adipocytes and the consequences of their disruption. The thesis summarizes current scientific knowledge and explores the mechanism of rhythm control at the molecular level, which is formed by transcriptional translational feedback loops. Adipocytes control lipid metabolism through the production of adipokines, adipogenesis, lipogenesis, and lipolysis. The research focuses on how clock genes are involved in these processes. All of these events, which are characteristic of adipocytes, are highly regulated and the genes that are involved in them are transcriptionally activated by clock gene proteins. Circadian rhythms are an integral part of our lives, and desynchronization of rhythms between the main oscillator, which is the suprachiasmatic nuclei, and peripheral adipocytes can lead to metabolic disorders, which in turn can lead to obesity, insulin resistance, or type 2 diabetes. Obesity is one of the biggest problems of modern society, and disrupted circadian rhythms due to today's lifestyle are one of the causes of its development. Key words: circadian rhythms, clock genes, adipocytes, obesity, PPARγ, adipogenesis, lipogenesis, lipolysis, leptin, adiponectin
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Influence of binaural beats on ideomotoric coordination
Pavlovič, Ondřej ; Pánek, David (advisor) ; Pavlů, Dagmar (referee)
Name: The effects of binaural beats on sleep quality: a systematic review Aims of the study: The main objective of this study is to present the possibilities of influencing stress and sleep, to determine the effect of binaural beats (BB) stimulation on sleep quality and parameters, and to determine the specifics of effective BB therapy based on the available data. Materials and methods: This systematic review includes scientific articles and clinical studies published in relevant and/or peer-reviewed journals and conference proceedings. Three electronic databases (Web of Science, Scopus, PubMed) were searched for all available sources published from 2000 to January 2023 in English language. The search was conducted using relevant keywords and their combinations. The screening and subsequent process of elimination was based on set of eligibility and inclusion criteria. Results: Total of fourteen studies met the eligibility criteria. BB stimulation increased subjectively perceived sleep quality and reduced mental tension. Objectively, it reduces time of falling asleep, accelerates the onset of deeper sleep stages (N2 and N3) and increases their duration, as well as the total sleep time. The parameters optimal for effective BB stimulation can be laid out as follows: BB in the frequency range of 2 to 4...
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