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The work is devoted to luminescent properties of trivalent lanthanide complexes dispersed in thermoplastic host matrices. Polyethylene films and polypropylene-rods, both doped with these complexes, were manufactured using an extrusion technique. Two kinds of dopants were used: Eu(III)-thenoyltrifluoroacetone-1,10-phenanthroline complex (1) and Eu(III)-La(III)-1,10-phenanthroline complex (2). Absorption, excitation, emission spectra and lifetime of luminescence were studied. The impact of the polymer matrix on the emission spectra was investigated. Emission spectra of the films were studied at room and helium temperatures. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) surface mapping showed that in the Eu(III)-La(III) complex europium forms islands (clusters) with a dimension of 1 mm, whereas lanthanum was dispersed more uniformly in the polymer matrix. Dependence of emission intensity on the excitation was determined.

C lassroom experiments on atmospheric pressure focus largely on demonstrating its existence, often in a most impressive way. A series of amusing physics demonstrations is widely known and practiced by educators teaching the topic. However, measuring the value of atmospheric pressure (P atm ) is generally done in a rather mundane way, simply by reading some commercially produced meter. Even though students building a 35-ft high water barometer 1,2 is definitely instructive, as is the measurement of P atm with much smaller gas-filled devices, 3,4 there exist hardly any physics lab exercises focused on the measurement of atmospheric pressure. This paper describes a modification of a well-known physics demonstration into an experiment that allows one to estimate atmospheric pressure quite accurately. Our simple and inexpensive apparatus can be used in lecture demonstrations or as a tool in an educational laboratory setting. The Classic DemonstrationThe demonstration upon which our method is based is the well-known one in which a drinking glass nearly full of water is covered with a piece of cardboard and then inverted while holding the cardboard in place. When the cardboard is released, no water spills out. The explanation is straightforward. Forced by gravity to slip downward slightly, the column of water acts like a piston, reducing the air pressure P inside the glass until equilibrium is a)Fig. 1. Schematic representation of the experiment: (a) initial position, the cover is pressed by hand against the opening of the partially filled, inverted bottle; (b) water is gradually released from the bottle; (c) equilibrium is achieved. 493achieved. The slip distance ∆s is small (less than a millimeter) and so the cardboard is displaced only very slightly from the glass. The surface tension of the water is sufficient to prevent it from seeping out through the tiny gap. The demonstration works reliably with a short cylindrical container but can often fail when using a tall cylinder or partly filled bottle. 5,6 It turns out in these cases that the slip distance depends strongly on the amount of water in the container. Weltin 7 has derived a formula for determining ∆s for a column of liquid in an inverted cylindrical container. The slip distance is always very small if the container is nearly full or almost empty. However, it's possible for ∆s to be rather large-6 mm for a half-full cylinder 50-cm high. And even larger values of ∆s occur if the container has a narrow opening as in the case of a glass bottle. Such a large displacement of the water column results in the cardboard being pushed completely away from the container opening and the water spilling out. Our MethodWe start with a glass bottle that is nearly full of water and hold a small piece of cardboard firmly against the top as we invert the bottle [Fig 1(a)]. If the cardboard were now simply released, the column of water would slip so far downward that it would push the cardboard away from the opening and all the water would spill out. Instead, we hold the cardboar...

Rotating and rolling rigid bodies exemplify a fascinating theorem of topology, jokingly called the “hairy ball” theorem, which demands that any continuous tangent vector field on the sphere has at least one point where the field is zero. We demonstrate via a gedanken experiment how drilling through a rotating ball, thereby converting it into a torus, leads to the elimination of zero-velocity points on the ball surface. Using the same reasoning, zero-velocity points can be removed from the surface of a drilled spinning top. We discuss the location of zero-velocity points on the surfaces of rigid bodies rolling with no slip and with slip. Observations made from different reference frames identify various zero-velocity points. Illustrative experiments visualizing zero-velocity points are presented.

Pure and doped antiferromagnetic CsMnC13 2H20 (CMC) crystals have been studied in the temperature range 4.2-300 K. With an increase in temperature the luminescence time and intensity of doped CMC crystals (1% and 0.1% Cu'+) decrease. The exciton-emission quenching is associated with exciton migration and trapping. The emission decay kinetics is approximated by the calculated curves obtained using the Kenkre and Onipko, Malysheva, and Zozulenko theories. The exciton hopping ( $V) and trapping ( U) rates have been defined. Exciton trapping by the Cu + traps in CMC is ineScient. The dependences 8'(T) and U(T) are given for two dopant concentrations in CMC obtained in the temperature range 77-237 K.