Jan Slegr

• Professor
• Lecturer at University of Hradec Králové

Debunking conspiracy theories is a never-ending battle. These theories often suggest that the condensation trails left by jet aircraft are, in fact, chemical or biological agents intentionally dispersed for various purposes. Although any discussion with supporters of conspiracy theories is pointless, this paper outlines several potential strategies...

An ordinary ice hockey stick is nowadays a sophisticated product made of composite material. In this article, we describe a simple measurement of the mechanical properties of hockey sticks using the three-point flexural test. This experiment can be used to support teaching about elasticity. We show how the properties of a hockey stick change after...

In recent years, the world has been facing extreme heat waves, breaking all previous records. Therefore, it is essential to emphasize teaching at least the basic knowledge of psychrometry and its impact on human health and well-being. In this paper, we explain several key concepts from the field of psychometrics as well as instructions on how to as...

Osteoarthritis is the most common type of degenerative joint disease and affects millions of people. In this paper, we propose a non-obtrusive and straightforward method to assess the progression of osteoarthritis. In standard medicine praxis, osteoarthritis is observed with X-rays. In this study, we use widely available wearable sensors with gyros...

Although the inaccurate explanation of lift based solely on the Bernoulli equation can still be found in textbooks, there are many places where interested readers can gain a correct understanding. However, it is complex and involves several physical phenomena. In this paper, we describe a simple device that can be used in teaching to support the un...

Undergraduate physics laboratory exercises are very important in shaping students’ attitude to science, especially for future teachers. Recently, it is necessary to look for ways to easily create large quantities of experimental sets, not only for institutional use, but also for sets that can be produced in large quantities and distributed for use...

Background and Objectives Automatic detection of breathing disorders plays an important role in the early signalization of respiratory diseases. Measuring methods can be based on electrocardiogram (ECG), sound, oximetry, or respiratory analysis. However, these approaches require devices placed on the human body or they are prone to disturbance by e...

Background and Objectives: The mechanism of the relationship between glycemia and lipid metabolism has not been completely clarified, and slight differences may be found between authors and the kinds of evaluated parameters. Therefore, this study focused on possible changes of lipoprotein profile with regards to HOMA IR (Homeostatic Model Assessmen...

This paper describes the possibilities of supporting the teaching of neural tissue biology and biophysics through experiments with a simple, commonly available electroencephalography headset. Data are transmitted over a Bluetooth virtual serial port and can be analyzed in several ways by students or used solely as a potential motivational factor fo...

Although global warming is an irrefutable scientific fact, many people, including those who often call themselves skeptics and critical thinkers, are doubtful about this unambiguous fact. An extensive longitudinal survey amongst the students showed that even future teachers are not resistant to these misconceptions, even if they are presented with...

Although global warming is an irrefutable scientific fact, many people, including those who often call themselves skeptics and critical thinkers, are doubtful about this unambiguous fact. An extensive longitudinal survey amongst the students showed that even future teachers are not resistant to these misconceptions, even if they are presented with...

Sleep-related breathing disorders are diseases related to pharyngeal airway collapse. It can lead to several health problems such as somnolence, poorer daytime cognitive performance, and cardiovascular morbidity and mortality. However, computer-aided diagnostic (CAD) tools play a very important role in the detection of breathing disorders. It is po...

In this paper, we discuss the theory of the operation and some practical considerations for the construction of an air ionization chamber, which can be used as a very simple detector of alpha particles. These detectors have several benefits compared to spinthariscopes and spark detectors. Classical experiments with ionization chamber detectors are...

This paper describes the design of a low-cost radon detector that can easily be fabricated in large quantities for the purposes of earthquake prediction. The described detector can also be used for monitoring radon levels in houses because high radon levels pose a great health risk. A very simple air-ionization chamber for alpha particles was used,...

Seismo-ionospheric coupling is a field of great interest and is currently subject to rigorous study; using both ground and satellite data and many phenomenological features, the ionospheric precursors of earthquakes were identified. In this work, we present methods to study the stochastic properties of the lower ionosphere, derived from the data ob...

In this paper we present a critical analysis of some of the arguments of flat Earth theory, and we also try to show that this analysis and refutation of these false claims can be a useful exercise in critical thinking that is so much needed today. This article can also make it easier for teachers who are exposed to some of the arguments of flat Ear...

This article describes the construction of a simple microwave radiometer that can be used for demonstration purposes, not only in the teaching of astrophysics but also to efficiently support the interpretation of the radiation of a black body. The described device uses commonly available satellite TV components that can be purchased very cheaply an...

This paper describes the application of modern semiconductor detectors of γ and β radiation, which can be used in undergraduate laboratory experiments and lecture demonstrations as a replacement for Geiger-Müller (GM) tubes. Unlike GM tubes, semiconductor detectors do not require a high voltage power source or shaping circuits. The principle of ope...

There are only a few experiments in astrophysics that can be done in the high school environment. Some astronomical observations leading to the estimate of determining the values of various astronomical parameters (radius of the Earth, the Earth–Moon distance, and others) can be done, but the astrophysical measurements usually require specialised e...

This contribution describes principles and applications of the modern semiconductors of beta and gamma radiation. These semiconductor detectors have some beneficial characteristics compared to the still-used Geiger-Muller tubes: there is no need for high voltage for power or output pulse shaping circuits because the output of the available semicond...

This paper describes theoretical calculation of the terminal velocity of falling cat, taking the air drag into account. The results show that a fall from the seventh floor is critical for the cat so we introduce a new quantity called the 'coefficient of the cat's fear' during free fall. A subsequent experiment with a model of a cat carrying the acc...

Lower portion of the ionosphere known as the D-layer has properties of Gaussian random plane affecting very low frequency waves. This is manifested by stochastic properties of reflected VLF waves as their auto-correlation function (ACF) in time is the Bessel function of the first kind and zero order. In this paper, we show that the properties of th...

In everyday praxis, we often need demonstration measuring devices (thermometers, pH meters, etc.), with large enough displays to be easily readable from every point in the classroom. Here, we present some of the capabilities of the Arduino platform for the school environment. This microprocessor board can be used for inexpensive construction of mea...

In everyday praxis we often need to demonstrate measuring devices—such as thermometers, manometers and voltmeters— with large enough displays that they can easily be read from anywhere in the classroom. In some cases, computers with a measurement interface can be used as a substitute, but often this is not possible (for example in the lab or in an...

In this work we present the method for estimation of Wait's parameters H′H′ and β directly from measured electrical intensities of distant VLF transmitters. A very simple approach using Earth-ionosphere waveguide with highly conductive walls is used.

The authors from Faculty of Science University of Hradec Králové prepared worksheets for teaching topic “The rainbow formation” in subject physics at high school through laboratory work, which combines classical experiment and computer model. Classical experiment can be done with tools commonly available in the school science lab. A computer model...

SpaceShipTwo is a private spaceplane project which is intended for space tourism. Very few details about its construction and flight characteristics are available for the public, but with proper numerical methods some interesting results can be obtained using secondary school mathematics. An exercise about SpaceShipTwo can be used as a motivational...

We have studied the emission spectra for a single LH2 complex. The observed spectral fluctuations reflect degree of exciton delocalization and different strength of exciton-phonon coupling. We compare the measured spectra with calculated ones obtained using the model of the B850 ring with two types of uncorrelated static disorder. The positions and...