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The federal government asserted a role in fighting narcotics abuse since the early 20^th century, but it was not until the Richard Nixon administration starting in 1969 that a federal “war on drugs” became high profile. Nixon stressed drives against smuggling heroin from counties like Turkey and Mexico. His administration's efforts were marred by raids on erroneous locations by a new federal Office of Drug Law Enforcement. A successor agency called the ‘Drug Enforcement Administration’ jockeyed with the FBI for supremacy in the drug enforcement field. Drug treatment generally had lower priority when it came to funding. A scourge of “crack” cocaine spread in the mid‐1980s, causing Congress to increase penalties for drug abuse in such a way that black people who primarily used crack were punished much more severely than whites who tended to use cocaine's powder form. An effort to coordinate federal antidrug resources better resulted in the establishment of a White House director of drug control policy (“drug czar”) in 1989; the first to hold the position was former education secretary William Bennett. Drug abuse declined in the 1990s, but there was disagreement over the primary cause. Advocates credited a combination of more‐intense law enforcement, better treatment, and establishment of more than 500 “drug courts” that could ride herd on offenders. The numbers of drug abusers were creeping back up by 1999.

This chapter considers the three theorized causes of crime declines in increasing order of novelty—first police, then the rise and fall of crack cocaine, and finally the impact of increased access to abortion that, advocates claim, caused a shift in the crime-risk profile of birth cohorts in the 1970s. After an introductory discussion of the definition and special problems of theories that were inspired by the 1990s' decline, unequal attention is given to the three explanations covered. Over half of the chapter addresses the thesis that crime declines in the 1990s were caused by the coming-of-age of population cohorts that were altered by the impact of elective abortion in the United States in the 1970s.

Although dissolution reactions involving water can etch and decompose oxides, truly catastrophic failures of oxide structures usually involve fractures and mechanical failures. Geologists and geochemists have long recognized that water and ice both play key roles in promoting the fracture and crumbling of rock (see Chapter 17). Freezing and thawing create stresses that amplify the rate at which water attacks metal–oxygen bonds at the crack tip. The interplay between water and stressed oxides also leads to common failures in man-made objects, ranging from the growth of cracks from flaws in windshields to the rupture of optical fibers in communication systems. In this chapter, we outline how mechanical deformations change the reactivity of metal–oxygen bonds with respect to water and other chemicals, and how reactions on strained model compounds have been used to predict time to failure as a function of applied stress. The basic phenomenon of stress corrosion cracking is illustrated in Figure 16.1. Cracks can propagate through oxide materials at extremely fast rates, as anyone who has dropped a wine glass on the floor can attest. High-speed photography reveals that when glass shatters, cracks can spread at speeds of hundreds of meters per second, or half the speed of sound in the glass. At the other end of the spectrum, cracks in glass can grow from preexisting flaws so slowly that only a few chemical bonds are broken at the crack tip per hour. Because mechanical failures are associated with cracking, it is critical for design engineers to understand the factors that control crack growth rates for this enormous range of crack velocities (a factor of 1012). In addition, because it is difficult to measure crack velocities slower than 10−8 m/second, it is often necessary to make major extrapolations from measured data to predict the long-term reliability of glass and ceramic objects. Will an optical fiber under stress fail in 1 year or 10 years? Answering this question can require accurate extrapolations down to crack growth rates as low as 10−10 m/second.

This chapter begins with a discussion of the causes of the roughening and grooving of solid surfaces. It then discusses Asaro-Tiller surface instability, phase field models, surface patterns caused by energetic photons and ions, surface stress during rapid heating, stress corrosion cracking, and numerical methods.

Loaded slit cracks are modelled as continuous distributions of dislocations with infinitesimal Burgers vectors. Cauchy-type singular integral equations for the density of Burgers vector in these distributions are solved using the theory of Chebyshev polynomials. The elastic fields of mode I elastic slit cracks are derived and the stress intensity factor is defined. Other defects may interact with cracks such as dislocations. This leads to the concepts of shielding and anti-shielding of cracks by dislocations. The Dugdale–Bilby–Cottrell–Swinden model of a mode I crack completely shielded by a plastic zone is derived. By introducing a dislocation free zone between the plastic zone and the crack tip the crack tip is only partially shielded, enabling more brittle tendencies to be described. Griffith’s energy criterion for the growth of an existing crack is seen as necessary but not sufficient. The Barenblatt crack introduces the influence of interatomic forces at the crack tip.

Surface cracks and boundaries give contrast in acoustic microscopy even when they are so fine that by conventional resolution criteria they would be expected to be scarcely visible. The contrast arises from the scattering of Rayleigh waves, and the evidence for this is the tell‐tale presence of fringes parallel to cracks, with spacing equal to half a Rayleigh wavelength. Contrast theory based on separating the specular and Rayleigh components of the signal give a good account of the fringes which are observed. Time‐resolved measurements can be made of crack‐tip diffracted signals. The remarkable contrast from cracks is useful in the study of indentation and fracture of low‐ductility materials.

Ice is a material that exhibits both ductile flow, as in the flow of a glacier, and also brittle fracture, as in the crushing of ice under impact from an icebreaker. This chapter considers laboratory-scale experiments on the deformation of single crystals and of polycrystalline ice and their interpretation. Creep of single crystals occurs by the glide and multiplication of dislocations on the basal plane and is thus highly anisotropic. In polycrystalline specimens deformed under constant load the creep accelerates, reaches a steady state and finally accelerates again. The deformation of individual grains is confined by those around them, and large stresses build up which may be relieved by diffusion or by cracking. The theory of fracture involves both the nucleation of cracks and their propagation.

This book is about recent mathematical, numerical and statistical approaches for elasticity imaging of inclusions and cracks with waves at zero, single or multiple non-zero frequencies. It considers important developments in asymptotic imaging, stochastic modeling, and analysis of both deterministic and stochastic elastic wave propagation phenomena and puts them together in a coherent way. It gives emphasis on deriving the best possible imaging functionals for small inclusions and cracks in the sense of stability and resolution. For imaging extended elastic inclusions, the book develops accurate optimal control methodologies and examines the effect of uncertainties of the geometric or physical parameters on their stability and resolution properties. It also presents an asymptotic framework for vibration testing and a method for identifying, locating, and estimating inclusions and cracks in elastic structures by measuring their modal characteristics.

This chapter examines rap's unique expressive position in relation to the primary contradictions of crack cocaine's punishment structure as well as recent arguments condemning this structure, including those from the U.S. Supreme Court and the U.S. Sentencing Commission. After discussing the contradictory policy contexts out of which crack's lethal logic of work eventually emerged, the chapter considers the “punitive turn” in U.S. crime-control policy and the “scholarly near misses” that have influenced analyses of the rap–crack connection. It suggests ways of rethinking the rap–crack connection in order to move beyond reductionist accounts in which rap and inner-city communities are taken as mere reflections of each other.

This chapter examines the cultural resonance between rap and crack cocaine by focusing on the complicated sociolegal logics that paved the way for the drug's lethal effects, and out of which its symbolic power developed. It first considers the law and policy on crack, including the bill signed by President Barack Obama in August 2010 repealing the mandatory minimum for the simple possession of crack and reducing the sentencing disparity between crack trafficking and powder trafficking from 100-to-1 to 18-to-1. It then traces the history of the paradoxical punishment of crack cocaine, arguing that the 100-to-1 sentencing disparity between powder and crack was deliberately and intentionally created. It also discusses the link between the 100-to-1 sentencing disparity and the so-called “Kingpin Strategy,” along with the violence that came to be associated with crack's low-level distribution system. Finally, the chapter explores the broad consensus among researchers that the lethal violence of the crack era was a product of the systemic features of crack markets themselves.

The chapter gives the etymology of the word “avalanche”. It defines the various types of snow avalanches, as slab, full-depth or loose snow, dense or airborne-powder, spontaneous or artificial ones. It also mentions the fact that other materials, such as sand, rock-falls, and landslides, may behave in a similar way, as developed in chapter 4. It also aims at making clear a number of idioms often used in this field. The content of each of the book chapters is also summarized.

This introductory chapter explains that the book explores the ways in which rap expresses one of the most powerful symbols of America's paradoxical crime policy: the 100-to-1 sentencing disparity between crack cocaine and powder whereby someone convicted of “simply” possessing five grams of crack had been required by law to serve no less than five years in prison. Drawing on the author's personal experiences with rap and crack, the book examines the degree to which crack cocaine emerged as a primary symbolic referent through the development of an important reflexive lyrical stance that many rap artists in the 1990s took toward their own commercialization. It discusses the cultural consequences of crack's paradoxical punishment, focusing on a reflexive lyrical stance that emerged in 1990s New York rap, which critiqued the music industry for being corrupt, unjust, and criminal. The book also considers how rappers began drawing parallels between the “rap game” and the “crack game,” juxtaposing their own exploits in street crime with the machinations of industry executives.

This chapter explains that from the site of Mons Claudianus, which lies 50 kilometers south of Gebel Dokhan, the Romans hewed the enormous columns of speckled, white granite which were to grace some of the most splendid buildings of Roman antiquity, among them Trajan's Forum and the Pantheon itself. There are approximately 130 quarries in the hills surrounding Mons Claudianus, many of which contain examples of the variety of objects the Romans fashioned from the fine stone but discarded because of cracks or other defects. Recent discoveries indicate that at some point during its occupation, as many as 920 people lived at Mons Claudianus. Scholars do not know exactly when or why quarrying ceased there. The archaeological research at Mons Claudianus itself is becoming increasingly difficult because the site is threatened by modern quarrying, which every year destroys valuable inscriptions in the surrounding area.