Antimatter was first predicted in 1931, by Dirac. Work with high-energy antiparticles is now commonplace, and anti-electrons are used regularly in the medical technique of positron emission tomography scanning. Antihydrogen, the bound state of an antiproton and a positron, has been produced at low energies at CERN (the European Organization for Nuclear Research) since 2002. Antihydrogen is of interest for use in a precision test of nature's fundamental symmetries. The charge conjugation/parity/time reversal (CPT) theorem, a crucial part of the foundation of the standard model of elementary particles and interactions, demands that hydrogen and antihydrogen have the same spectrum. Given the current experimental precision of measurements on the hydrogen atom (about two parts in 10(14) for the frequency of the 1s-to-2s transition), subjecting antihydrogen to rigorous spectroscopic examination would constitute a compelling, model-independent test of CPT. Antihydrogen could also be used to study the gravitational behaviour of antimatter. However, so far experiments have produced antihydrogen that is not confined, precluding detailed study of its structure. Here we demonstrate trapping of antihydrogen atoms. From the interaction of about 10(7) antiprotons and 7 × 10(8) positrons, we observed 38 annihilation events consistent with the controlled release of trapped antihydrogen from our magnetic trap; the measured background is 1.4 ± 1.4 events. This result opens the door to precision measurements on anti-atoms, which can soon be subjected to the same techniques as developed for hydrogen.

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The crystallization kinetics and degree of crystallinity of polycaprolactone (PCL) were studied using the technique of differential scanning calorimetry (DSC). The crystallization exotherms measured using DSC were analyzed using a modified Avrami equation. The modification limited the analysis of the data to the primary crystallization process, where the Avrami equation is applicable. Both the degree of crystallinity and primary composite rate constant were found to decrease with increasing molecular weight. The observations have been explained in terms of the unified reptation‐nucleation theory. Copyright © 2006 John Wiley & Sons, Ltd.

Bark beetle outbreaks and wildfires are principal drivers of change in western North American forests, and both have increased in severity and extent in recent years. These two agents of disturbance interact in complex ways to shape forest structure and composition. For example, mountain pine beetle, Dendroctonus ponderosae Hopkins, epidemics alter forest fuels with consequences for the frequency and intensity of wildfires and, conversely, fire injury to trees can promote bark beetle attack and increase beetle populations. Given the great influence these processes have on forest ecosystems, a better understanding of how bark beetles and fires interact is needed to better manage forests and to predict and manage wildfires. Here we review current knowledge on how fire and bark beetles interact, focusing on the mountain pine beetle. We highlight research on how fuel reduction treatments and wildfires affect bark beetles and how bark beetles can affect wildfires by modifying the moisture content, chemistry, and structure of fuels. Last, we discuss the implications these findings have for fire management and firefighter safety.

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