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Granular flows appear frequently in the natural world and in civil engineering applications. These flows can exhibit features which are surprising and counter-intuitive and are often used to test the limits of the classical continuum approximation for modelling of fluid flows. An important sub-class of the granular flows are the gravity-driven granular flows, which include the granular column collapse and the flow of granular material down through a vertical pipe. In this article, quantitative analysis is performed of the flow using video analysis software. The utility and relevance of the experiment for development of experimental skills in physics students and modelling of unexpected phenomena is discussed.

We use a tensile testing machine to create stress-strain plots and determine Young's modulus for some ductile and plastic materials. Supplementary videos are also provided.

The Crookes radiometer (also known as a light mill) is a fascinating sunlight-powered device, in which a set of vanes is placed inside a glass bulb within which a partial vacuum has been pulled. The vanes then rotate when sunlight shines on the bulb. The reason for the turning of the vanes was subject to intense debate and many students still have an incorrect understanding of the device. We analyse the forces involved in a much less well-known radiometer (called the Hettner radiometer) and show that this can help us to understand the forces involved in the Crookes radiometer in a more unified way.

We outline the basic theory behind white light interferometry and the workings of a typical light interferometer microscope. We study WLI images obtained for rough and smooth chrome steel spheres to illustrate the principle that curved rough surfaces can be imaged with such a device as long as the surface roughness is kept within certain limits.

In this article, we construct a very simple double pendulum (the concept of a pendulum should be familiar to all beginning students of classical mechanics). Since a double pendulum has two degrees of freedom, we suggest that this pendulum can be used in the classroom environment to illustrate the concept of normal modes, and we use video software to show that it is possible to observe a normal mode in action. The pendulum as we describe it should be constructable by all students and is much simpler than the similar experimental setups described in the literature.

It is well known that Newton's work on mechanics depended in a crucial way on the previous observations of Galileo. The key insight of Galileo was that one can analyze the motion of bodies using experiments and mathematical equations. One experimental observation that roughly emerges from this work in modern terms is that two objects of different mass that are simultaneously released from rest and allowed to fall under the influence of gravity through a vacuum should hit the ground at the same time (this is essentially what is called the equivalence principle in general relativity). In popular legend, it is said that Galileo tested this by dropping two balls of different masses from the Leaning Tower of Pisa and showing that they hit the ground at the same time, but the historical evidence suggests that this is unlikely as he seems to have experimented mostly with balls rolling down inclined slopes.

We outline the physics involved in the use of scanning electron microscopy (SEM) and modernise the usual textbook treatment by explaining how one can now obtain high-quality images with non-conductive specimens. As a concrete example of an application in biology, we provide several magnification series of a flea obtained using SEM.

The notion of a boundary condition is typically considered to be somewhat advanced and not suitable to be introduced in high school level physics. In this article, we give a simple visual demonstration of the difference between Dirichlet and Neumann boundary conditions for a string which oscillates according to the one-dimensional wave equation. The classical Dirichlet problem for a vibrating string in the plane is mathematically deep, but we will avoid the mathematical issues here and only focus on some key physical points which are relevant for understanding how waves propagate along strings.

The physical problem of a body of water in a tank that drains through a hole in the base is a classical problem that has been studied since at least the time of Torricelli. To fixate this in a student's mind, one could ask them to visualize a bathtub that is being drained through the plughole or a bottle being drained through a tap. This problem is an ideal one to propose at the secondary school level, since it provides a nice example of a physically relevant elementary ODE that can be studied by students with some calculus skills, and it also provides an opportunity to start introducing some concepts from fluid dynamics, as well as general mathematical modelling skills. Like the brachistochrone, the draining vessel and variants of it have been studied many times in the literature. We will focus on a simple pedagogical example, but there are many other possibilities. For example, Castro de Oliveira et al. performed experiments to measure the speed of water flowing through a pinhole at the bottom of a cylindrical bottle as a function of time and the level of water. In the process, they made an empirical correction to Torricelli's law. Cross studied three different arrangements whereby air and water can flow into or out of two small holes in the side of a water bottle. Hong studied the unsteady draining problem for an incompressible, non-viscous fluid to obtain an exact solution of the unsteady Bernoulli equation, showing that once again Torricelli's law must be modified in this situation. In a more mathematically involved treatment, Digilov showed that one can obtain an analytic solution for time evolution of a liquid column draining under gravity through a capillary tube in terms of a special function called the Lambert W function. More recently, Durbin studied vessel drainage of fluids of different viscosities through tubes of varying lengths.

Effective field theories which describe the coupling between gravity and matter fields have recently been extended to include terms with operators of non-minimal mass dimension. These terms preserve the usual gauge symmetries but may violate local Lorentz and diffeomorphism invariance. The number of possible terms in the field theory explodes once one allows for non-minimal operators, with no criterion to choose between them. We suggest as such a criterion to focus on terms which violate Lorentz invariance via a (pseudo)vector background field, leaving a number of possible terms in the Higgs, gauge, and gravitational sectors. Further study of these terms is motivated by the proposed correspondence between the general effective theory for Lorentz violation and emergent Lorentz symmetry in condensed-matter systems, which is mostly unexplored for higher mass dimension operators and couplings to gauge fields and gravity. We suggest bounds in the Higgs sector and we show that some of the coefficients in the gauge sector vanish at one loop, whereas others have bounds which are comparable with those suggested by Kostelecký and Li for coefficients in Lorentz-violating QCD and QED coupled to quarks. We also find new bounds in the gravitational sector by considering the Robertson--Walker model. Finally, we discuss the special case where only diffeomorphism invariance is spontaneously broken and explain why it does not allow for non-trivial Nambu--Goldstone modes. [ABSTRACT FROM AUTHOR]

This article provides an analysis of the physics behind the shattering of glass and ceramic objects when they are dropped or impacted. The study utilizes video analysis to examine the process of fracture propagation and the phenomenon of bouncing before breaking into pieces. The article emphasizes the significance of understanding the resilience of ceramic and glass materials to impacts, particularly in applications such as vehicle and aircraft armor and orthopedic surgery. The experimental setup and results are presented, highlighting the necessity of high-speed cameras to capture crack propagation on a precise timescale. The article also discusses an experiment involving the impact and breakage of ceramic mugs and a wine glass, focusing on the physics of breakage and the conservation of energy. The experiment demonstrates that the speed of crack propagation is limited and that each individual piece of the broken object possesses less kinetic energy than the original object. The article suggests that this experiment can serve as an educational tool for students to comprehend materials and load bearing. Further investigations can be conducted to examine the properties of the materials and the exact failure mechanism during load bearing. [Extracted from the article]

A key concept in current fluid dynamics and its applications to biology and technology is a phenomenon known as wetting. Wetting is familiar from everyday life and is simply the ability of a liquid to stay in contact with a solid surface. The wettability depends on the properties of the liquid and the solid and can be characterized by the static equilibrium contact angle ? (the angle at which the liquid--gas interface meets the liquid--solid interface). A contact angle below 90° indicates favorable wetting such that a drop of the liquid would spread over a large amount of the flat solid surface, whereas a high contact angle indicates that very little of the solid is wetted (this can be seen in Fig. 1, which shows various stages of surface wetting in terms of the equilibrium contact angle). Nevertheless, this theory generally sounds quite dry or difficult to visualize when explained to students for the first time. The theory of the contact angle also contains some controversies and has undergone some recent developments. We propose a simple classroom demonstration with superhydrophobic sand that gives a concrete visualization of "superhydrophobicity" and outline how the phenomenon can be explained macroscopically with wetting theory. There are several interesting physical effects that are due to superhydrophobicity: experimental studies have found, for example, that superhydrophobic spheres always splash when they impact a body of liquid. In terms of applications, there are various possibilities for water storage with superhydrophobic sand outlined in the chemistry literature.

Research was conducted to examine the hypothesis that the activation state of p38 mitogen-activated protein kinase determines the efficiency of ATP competition for pyridinylimidazole inhibitor binding. Human p38 was expressed in Drosophila S2 cells and preparations of mixed unphosphorylated and homogeneously diphosphorylated forms of the enzyme were characterized. Results indicate that pyridinylimidazoles may block the biological activity of p38 kinase by binding to the inactive form of p38 and reducing its rate of activation.

Human polymorphonuclear leukocyte elastase (PMNE) damages tissue, and an oral dosage of L-680,833 inhibits PMNE ,thus having a therapeutic value. L-680,833 is a low-molecular weight synthetic inhibitor. It restricts the damage caused by the intratracheal induction of human PNE in hamster lungs. The release of enzymes following the transfer of enzymes into the pleural cavity of mice is also inhibited.