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\"Two children learn about four different states of matter (solid, liquid, gas, and plasma) and what happens when matter changes form.\"-- Provided by publisher.

We have observed both superluminal and ultraslow light propagation in an alexandrite crystal at room temperature. Group velocities as slow as 91 meters per second to as fast as -800 meters per second were measured and attributed to the influence of coherent population oscillations involving chromium ions in either mirror or inversion sites within the crystal lattice. Namely, ions in mirror sites are inversely saturable and cause superluminal light propagation, whereas ions in inversion sites experience conventional saturable absorption and produce slow light. This technique for producing large group indices is considerably easier than the existing methods to implement and is therefore suitable for diverse applications.

\"Many people are familiar with the states of matter called solid, liquid, and gas, but they may not have heard of the other two states, plasmas and Bose-Einstein condensates. In this notable book, readers will learn what all these states are as well as what happens to matter to trigger a change from one form to another. The comprehensible text is supported by clear and helpful images, diagrams, and fact boxes as well as vocabulary that serves to highlight key science terms.\"-- Provided by publisher.

The development of zeolite-like structures with extra-large pores (>12-membered rings, 12R) has been sporadic and is currently at 30R. In general, templating via molecules leads to crystalline frameworks, whereas the use of organized assemblies that permit much larger pores produces noncrystalline frameworks. Synthetic methods that generate crystallinity from both discrete templates and organized assemblies represent a viable design strategy for developing crystalline porous inorganic frameworks spanning the micro and meso regimes. We show that by integrating templating mechanisms for both zeolites and mesoporous silica in a single system, the channel size for gallium zincophosphites can be systematically tuned from 24R and 28R to 40R, 48R, 56R, 64R, and 72R. Although the materials have low thermal stability and retain their templating agents, single-activator doping of Mn 2+ can create white-light photoluminescence.

Children can experience scientific concepts by using materials in their everyday world to perform safe and fun experiments.

The phonon is the physical particle responsible for the transmission of sound and heat; controlling the properties of phonons in materials could trigger many advances, which are reviewed here. Prepare for the age of phononics In the emerging research area of phononics, control over the mechanical vibrations that transmit sound and heat — phonons — plays a central role. Like photons and electrons, phonons can be treated as particles for many purposes, so can be harnessed and manipulated for useful applications. The phonon spectrum covers a wide range of effects, from low- frequency acoustics, to ultrasound and to heat, so that phononic techniques could enable a wide range of applications such as in earth quake protection, acoustics and heat management. In this review, Martin Maldovan discusses several approaches to the control of phonons at different length scales, for example phononic crystals, metamaterials, thermoelectrics and optomechanical devices. Today's digital revolution is underpinned by the high degree of control that can be imposed over electrons in semiconductors; Maldovan argues that precise control over phonons could have similar surprising and exciting consequences. The phonon is the physical particle representing mechanical vibration and is responsible for the transmission of everyday sound and heat. Understanding and controlling the phononic properties of materials provides opportunities to thermally insulate buildings, reduce environmental noise, transform waste heat into electricity and develop earthquake protection. Here I review recent progress and the development of new ideas and devices that make use of phononic properties to control both sound and heat. Advances in sonic and thermal diodes, optomechanical crystals, acoustic and thermal cloaking, hypersonic phononic crystals, thermoelectrics, and thermocrystals herald the next technological revolution in phononics.

Introduction to the concept of matter, including states of matter; volume and mass; and atoms, electrons, and protons. Explains microscopic properties of matter and the periodic table of elements.

A new source of softening Conventional metals gain much of their strength through the interaction of dislocations with obstacles such as grain boundaries, whereas the geometrical constraints prevailing in nanostructured materials limit such effects. Huajian Gao and colleagues now report molecular dynamics simulations which reveal that the strength of ultrafine grained copper containing twin boundaries can be controlled by a dislocation nucleation mechanism activated below a critical twin thickness. The motion of the new dislocations leads to the migration of twin planes, and as a result the material becomes softer. The smaller the grains, the smaller the twin-boundary spacing and the higher the maximum strength of the material. The strength of conventional metals is determined by the interaction of dislocations with obstacles such as grain boundaries. Molecular dynamics simulations reveal that the strength of ultrafine-grained copper containing twin boundaries can be controlled by a dislocation nucleation mechanism activated below a critical twin thickness. Below this thickness the material becomes softer. The smaller the grains, the smaller the critical twin boundary spacing, and the higher the metal's maximum strength. In conventional metals, there is plenty of space for dislocations—line defects whose motion results in permanent material deformation—to multiply, so that the metal strengths are controlled by dislocation interactions with grain boundaries 1 , 2 and other obstacles 3 , 4 . For nanostructured materials, in contrast, dislocation multiplication is severely confined by the nanometre-scale geometries so that continued plasticity can be expected to be source-controlled. Nano-grained polycrystalline materials were found to be strong but brittle 5 , 6 , 7 , 8 , 9 , because both nucleation and motion of dislocations are effectively suppressed by the nanoscale crystallites. Here we report a dislocation-nucleation-controlled mechanism in nano-twinned metals 10 , 11 in which there are plenty of dislocation nucleation sites but dislocation motion is not confined. We show that dislocation nucleation governs the strength of such materials, resulting in their softening below a critical twin thickness. Large-scale molecular dynamics simulations and a kinetic theory of dislocation nucleation in nano-twinned metals show that there exists a transition in deformation mechanism, occurring at a critical twin-boundary spacing for which strength is maximized. At this point, the classical Hall–Petch type of strengthening due to dislocation pile-up and cutting through twin planes switches to a dislocation-nucleation-controlled softening mechanism with twin-boundary migration resulting from nucleation and motion of partial dislocations parallel to the twin planes. Most previous studies 12 , 13 did not consider a sufficient range of twin thickness and therefore missed this strength-softening regime. The simulations indicate that the critical twin-boundary spacing for the onset of softening in nano-twinned copper and the maximum strength depend on the grain size: the smaller the grain size, the smaller the critical twin-boundary spacing, and the higher the maximum strength of the material.

Discusses the properties of matter, focusing on hot and cold objects with definitions and examples to illustrate.

This book presents comprehensively the science and technology behind the formulation of disperse systems like emulsions, suspensions, foams and others. Starting with a general introduction, the book covers a broad range of topics like the role of different classes of surfactants, stability of disperse systems, formulation of different dispersions, evaluation of formulations and many more. Many examples are included, too. Written by the experienced author and editor Tharwart Tadros, this book is indispensable for every scientist working in the field.