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Article

Rainfall over Africa varies across timescales of a few days to several weeks due to several tropical and extratropical modes of variability. Excessive rains or prolonged drought regularly result in natural disasters and have thus a severe impact on the local economy, agriculture, spread of diseases, and entire ecosystems. The dynamical nature of the atmosphere allows the existence of planetary balanced modes, which are called Rossby waves, and smaller-scale unbalanced inertio-gravity (IG) waves. The former, which are more rotational, arise from the horizontal pressure gradient force, while for the latter gravity acts as the restoring force, making their flow pattern more divergent. The main source of variability in the extratropics stems from Rossby waves. At the equator, further types of convectively coupled equatorial waves (CCEWs) exist, namely Kelvin and mixed Rossby-gravity (MRG) waves. As the slowest intraseasonal tropical mode, the Madden–Julian Oscillation (MJO), which is related to Kelvin and Rossby waves, acts on a timescale of 30 to 90 days. Although it is primarily a planetary mode, the MJO has a specific “flavor” over the African continent. On the short intraseasonal timescale of 10 to 25 days, equatorial Rossby (ER) waves and the internal modes of the West African monsoon, the quasi-biweekly zonal dipole (QBZD) and the Sahel mode, modulate rainfall. On the synoptic timescale of a few days to a week, African easterly waves (AEWs) are a dominant mode over West Africa, whereas Kelvin waves predominantly modulate rainfall over equatorial Africa. Extratropical influences on northern and southern Africa manifest themselves in Rossby wave trains, which modulate synoptic to intraseasonal rainfall through tropical rainfall plumes, cold air surges, and upper-tropospheric dry air intrusions. Furthermore, the Saharan heat low (SHL) acts as a link between the northern hemispheric extratropics and tropics. Finally, the Indian monsoon, the Atlantic, Indian, and the Pacific Oceans can remotely affect the intraseasonal variability of African rainfall. Forecasting synoptic to intraseasonal rainfall variability is an integral part of seamless prediction between the weather and climate regimes. In the early 21st century, numerical weather prediction (NWP) systems can forecast larger intraseasonal signals such as the MJO several weeks into the future, but they still struggle to forecast shorter scale features reliably. Besides NWP, statistical models can successfully forecast intraseasonal variability of rainfall. Due to the relevance of synoptic to intraseasonal rainfall variability for African societies, early warning systems (EWSs) have been developed to mitigate impacts.

Article

Global terror began in the 1880s, but it took a century before a few scholars began to understand its peculiar dynamic. One reason for the difficulty was that many scholars and government officials had “historical amnesia.” When they saw it disappear, they assumed it had become part of history and no longer had contemporary relevance. But global terror disappears and then reappears. Another reason they failed to understand the pattern is that the concept of generation was rarely used to describe politics, a concept that requires one to recognize the importance of life cycles. Modern global terror comes in the form of waves precipitated by major political events that have important global significance. A wave consists of a variety of groups with similar tactics and purposes that alter the domestic and international scenes. Four very different waves have materialized: the Anarchist, the Anti-Colonial, the New Left, and the Religious. The first three have been completed and lasted around 40 years; the fourth is now in its third decade, and if it follows the rhythm of its predecessors, it should be over in the mid-2020s, but a fifth wave may emerge thereafter.

Article

V.M. Nakariakov

Magnetohydrodynamic (MHD) waves represent one of the macroscopic processes responsible for the transfer of the energy and information in plasmas. The existence of MHD waves is due to the elastic and compressible nature of the plasma, and by the effect of the frozen-in magnetic field. Basic properties of MHD waves are examined in the ideal MHD approximation, including effects of plasma nonuniformity and nonlinearity. In a uniform medium, there are four types of MHD wave or mode: the incompressive Alfvén wave, compressive fast and slow magnetoacoustic waves, and non-propagating entropy waves. MHD waves are essentially anisotropic, with the properties highly dependent on the direction of the wave vector with respect to the equilibrium magnetic field. All of these waves are dispersionless. A nonuniformity of the plasma may act as an MHD waveguide, which is exemplified by a field-aligned plasma cylinder that has a number of dispersive MHD modes with different properties. In addition, a smooth nonuniformity of the Alfvén speed across the field leads to mode coupling, the appearance of the Alfvén continuum, and Alfvén wave phase mixing. Interaction and self-interaction of weakly nonlinear MHD waves are discussed in terms of evolutionary equations. Applications of MHD wave theory are illustrated by kink and longitudinal waves in the corona of the Sun.

Article

Michael Wehner, Federico Castillo, and Dáithí Stone

Extremely high air temperatures are uncomfortable for everyone. For some segments of the population, they can be deadly. Both the physical and societal aspects of intense heat waves in a changing climate warrant close study. The large-scale meteorological patterns leading to such events lay the framework for understanding their underlying causal mechanisms, while several methods of quantifying the combination of heat and humidity can be used to determine when these patterns result in stressful conditions. We examine four historic heat waves as case studies to illustrate differences in the structure of heat waves and the variety of effects of extreme heat on humans, which are characterized in terms of demographic, geographic, and socioeconomic impacts, including mortality and economic ramifications. Weather station data and climate model projections for the future point to an increase in the frequency and intensity of extreme heat waves as the overall climate gets warmer. Changes in the radiative energy balance of the planet are the principal culprit behind this increase. Quantifying changes in the statistics of extreme heat waves allows for examination of changes in their potential contribution to human health risk. Large-scale mortality during heat waves always occurs within a context of other factors, including public health policy, rural and urban management and planning, and cultural practices. Consequently, the impacts of heat waves can be reduced, and may in many places be manageable into the future, through implementation of such measures as public health warning systems, effective land management, penetration of air conditioning, and increased monitoring of vulnerable or exposed individuals. Given the potential for severe impacts of the more intense heat waves that are virtually certain to occur in the warmer future, it is critical that both the physical and social sciences be considered together to enable society to adapt to these conditions.

Article

Carl Wunsch

Oceanic mixing is one of the major determinants of the ocean circulation and its climatological influences. Existing distributions of mixing properties determine the rates of storage and redistribution within the climate system of fundamental scalar tracers including heat, fresh water, oxygen, carbon, and others. Observations have overturned earlier concepts that mixing rates might be approximately uniform throughout the ocean volume, with profound implications for determining the circulation and its properties. Inferences about past and potential future oceanic circulations and the resulting climate influence require determination of changed energy inputs and the expected consequent adjustment of mixing processes and their influence.

Article

Boris Ivanov

Impacts of small celestial bodies, in terms of energy density, occupy the range between ordinary chemical high explosives and nuclear explosions. The high initial energy density of impact gives them some features of an explosion (shock waves, melting and vaporization, mechanical disruption of target rocks). A near-surface burst creates an explosion crater, and an impact often results in the creation of an impact crater. The chain of processes connected to an impact crater’s formation is named “impact cratering” or simply “cratering.” The initial kinetic energy and momenta of the impacting body (“projectile”) generates shock waves (decaying with propagation to seismic waves), heats the material (at high impact velocities, to melt or to boil target rocks). A part of the kinetic energy is converted to target material motion, creating the crater cavity. The final crater geometry depends on the scale of event—while small craters are simple bowl-shaped cavities, large enough crater transient cavities collapse in the gravity field. If collapse takes place, the final crater has a complex geometry with central peaks and concentric inner rings. The boundary crater diameter, dividing simple and complex craters, varies with target body gravity and rock strength. Comparison of a crater’s morphology on remote planets and asteroids allows us to make some estimates about their mechanical parameters (e.g., strength and friction) even before future sample return missions. On many planets large impact craters can be seen, preserved much better than on the geologically active Earth. These observations help researchers to interpret the geological and geophysical data obtained for the relatively few and heavily modified large impact craters found on continents and (rarely) at the sea bottom.

Article

Stefano Tibaldi and Franco Molteni

The atmospheric circulation in the mid-latitudes of both hemispheres is usually dominated by westerly winds and by planetary-scale and shorter-scale synoptic waves, moving mostly from west to east. A remarkable and frequent exception to this “usual” behavior is atmospheric blocking. Blocking occurs when the usual zonal flow is hindered by the establishment of a large-amplitude, quasi-stationary, high-pressure meridional circulation structure which “blocks” the flow of the westerlies and the progression of the atmospheric waves and disturbances embedded in them. Such blocking structures can have lifetimes varying from a few days to several weeks in the most extreme cases. Their presence can strongly affect the weather of large portions of the mid-latitudes, leading to the establishment of anomalous meteorological conditions. These can take the form of strong precipitation episodes or persistent anticyclonic regimes, leading in turn to floods, extreme cold spells, heat waves, or short-lived droughts. Even air quality can be strongly influenced by the establishment of atmospheric blocking, with episodes of high concentrations of low-level ozone in summer and of particulate matter and other air pollutants in winter, particularly in highly populated urban areas. Atmospheric blocking has the tendency to occur more often in winter and in certain longitudinal quadrants, notably the Euro-Atlantic and the Pacific sectors of the Northern Hemisphere. In the Southern Hemisphere, blocking episodes are generally less frequent, and the longitudinal localization is less pronounced than in the Northern Hemisphere. Blocking has aroused the interest of atmospheric scientists since the middle of the last century, with the pioneering observational works of Berggren, Bolin, Rossby, and Rex, and has become the subject of innumerable observational and theoretical studies. The purpose of such studies was originally to find a commonly accepted structural and phenomenological definition of atmospheric blocking. The investigations went on to study blocking climatology in terms of the geographical distribution of its frequency of occurrence and the associated seasonal and inter-annual variability. Well into the second half of the 20th century, a large number of theoretical dynamic works on blocking formation and maintenance started appearing in the literature. Such theoretical studies explored a wide range of possible dynamic mechanisms, including large-amplitude planetary-scale wave dynamics, including Rossby wave breaking, multiple equilibria circulation regimes, large-scale forcing of anticyclones by synoptic-scale eddies, finite-amplitude non-linear instability theory, and influence of sea surface temperature anomalies, to name but a few. However, to date no unique theoretical model of atmospheric blocking has been formulated that can account for all of its observational characteristics. When numerical, global short- and medium-range weather predictions started being produced operationally, and with the establishment, in the late 1970s and early 1980s, of the European Centre for Medium-Range Weather Forecasts, it quickly became of relevance to assess the capability of numerical models to predict blocking with the correct space-time characteristics (e.g., location, time of onset, life span, and decay). Early studies showed that models had difficulties in correctly representing blocking as well as in connection with their large systematic (mean) errors. Despite enormous improvements in the ability of numerical models to represent atmospheric dynamics, blocking remains a challenge for global weather prediction and climate simulation models. Such modeling deficiencies have negative consequences not only for our ability to represent the observed climate but also for the possibility of producing high-quality seasonal-to-decadal predictions. For such predictions, representing the correct space-time statistics of blocking occurrence is, especially for certain geographical areas, extremely important.

Article

Claudia J. Dewane

Clinical social work is a derivative profession, drawing its knowledge and practice base from several theoretical schools. The four primary theoretical schools contributing to social-work philosophy are psychodynamic, humanist, cognitive–behavioral, and postmodern. Acceptance and commitment therapy (ACT), although considered one of the third-wave behavioral approaches, draws from all four theoretical schools of clinical intervention. This entry gives an overview of ACT development, its essential features, empirical base, tenets and techniques, and relevance to the social-work profession.

Article

The historical role of landed elites as obstacles to democratic consolidation in Latin America has been widely studied. Four decades after the onset of the third wave, however, the issue of how these elites have adapted to the new democratic context remains unexplored. The question of why these elites who supported military coups each time a government threatened their interests have mostly played by the democratic rulebook during the past four decades still needs to be answered. Important structural and political transformations took place in Latin America during the last half of the 20th and the first decade of the 21st century that affected agrarian elites’ incentives and capacity to organize politically. The first change was urbanization, which undermined agrarian elites’ capacity to mobilize the votes of the rural poor in favor of their political representatives. The second was an increase in the importance of agricultural exports as a source of foreign exchange and revenue for Latin American countries thanks to the commodity boom of the 2000s. The third change was the arrival to power of left-wing parties with redistributive agendas, threatening agrarian elites’ interests in the region with the highest land inequality in the world. However, the fact that these governments relied on revenues from agriculture to fund their policy agendas created tension between the leftists’ ideological preferences for a more equal distribution of land and their fiscal needs. Dominant theories in political science suggest that democratization should lead to redistribution from the rich to the poor, as democracies represent the preferences of a wider spectrum of citizens than nondemocracies. Landowners, given the fixed nature of their assets, should be easy targets for increased taxation or expropriation. However, these theories understate landowners’ capacity to organize politically and use democratic institutions to their advantage. In fact, if we look at contemporary Latin America, we see that four decades of democracy have not changed the region’s extremely high land inequality. Agrarian elites in Latin America have deployed a variety of political influence strategies to protect themselves from redistribution. In some cases, such as Chile and El Salvador, they have built conservative parties to represent their interests in Congress. In others, like Brazil, they have invested in multiparty representation through a congressional caucus. Lastly, in other countries such as Argentina and Bolivia, agrarian elites have not been able to organize their electoral representation and instead have protected their interests from outside the policymaking arena through protests.

Article

Grit Kirstin Koeltzsch

The cultural movement known as Hallyu (or Korean Wave) and the transnational popularity of K-pop music and dance have long been established as an important phenomenon in the global world, including in Latin America. This form of South Korean contemporary popular culture has had a major impact in Argentina, especially among the young population. Despite the cultural and geographical distance, young Argentines incorporate aspects of K-pop culture in their daily lives, including music, dance, K-drama, and food, and some of them even try to learn the Korean language. Thanks to technology, they perceive, almost in real time, what happens on the Asian continent and connect with fans and fandoms, not only in Korea but also in other parts of the world. This shows that globalization is not a process of homogenization; these young Latin American people also take the Korean Wave as motivation to learn about transpacific history and cultures. Furthermore, K-pop is a visual phenomenon, and dance plays an important role. The dance routines or choreographies are complex, and emphasize the music. Dance definitely transcends language barriers. Thus, young Argentines explore new aspects of corporality through dance performances. In their spare time, they organize dance contests and activities, and so generate spaces for their own articulation. It is particularly interesting to draw attention to gender role performance and the way in which local youth react to the influence of a transgressive gender identity performed by Koreans, in the context of a strongly patriarchal and heteronormative Argentine society. It shows that body/ dance articulation is not just a tool for creativity but also for disputing gender norms and stereotypical gender images in our society.

Article

Sayaka Aritake-Okada and Sunao Uchida

Research indicates that both acute and chronic physical activity improve sleep. Effects on sleep include prolongation of total sleep time, slow wave sleep increase, rapid eye movement sleep decrease, wake after sleep onset reduction, and shortened sleep latency. However, detailed biological mechanisms of these effects have not been well elucidated. Past studies strongly suggest that the sleep-promoting effect of exercise could be multifactorial. Increase of slow wave sleep, which has been repeatedly reported, strongly suggests physical activity effects on central nervous system function. Physical activity also elevates body temperature, alters glucose, and impacts other metabolic regulations. Habitual exercise also alters autonomic nervous system predominance measured by heart rate variability.

Article

K-pop is a form of South Korean popular music directed at a global audience that fuses Korean and foreign musical elements. While “idols” (performers who sing, dance, and engage in extra-musical activity) are the most visible, K-pop encompasses a wide variety of genres. Emerging in the wake of a major financial crisis that prompted a restructuring of the Korean economy, K-pop benefits from increased freedom in cultural expression, support by the Korean government, and a global cultural movement that reaches East Asia and beyond. The first K-pop groups appeared in the early 1990s, drawing on hip-hop and rhythm and blues popular in the United States. The use of rap and b-boying/breakdance style, along with emotional vocals of R&B, became staples for first-generation “idol” groups. Initially presenting an approachable image, they later took on more mature concepts before they disbanded in the late 1990s. Several continue to influence the K-pop music scene, even as subsequent generations of K-pop artists emerge. These idol groups have diversified their images as well as their musical styles. Several solo artists have emerged, and hip-hop groups continue to participate. All of this musical activity is governed by Korean agencies, the largest of which are responsible for the creation and management of “idols,” while others encourage indie artists and still others are led by K-pop artists themselves. In addition to the promotional strategies of agencies, media, both professional and fan-driven, play a large role in the global spread of K-pop. The fans themselves are also active participants, acting as both audience members and content producers.

Article

Jennifer Clegg and Richard Lansdall-Welfare

Neoliberalism is a transatlantic free market ideology based on individual liberty and limited government, developed by Hayek and von Mises. In its third wave (1980–2008), commitment to deregulation, privatization, and individual freedom moved beyond the economy into politics and culture. The citizen was recast as a consumer, and public servants became required to satisfy consumer choice. This addressed 1970s social turmoil and improved economies, but the increased wealth went to elites while resources declined for the poor. Hayek had argued for social welfare safety nets initially, but these were rejected by peers in the Mont Pelerin Society. Business-funded transatlantic think tanks promulgated the neoliberal tenets that markets are wiser than any government and state interference makes things worse. Yet, despite these rhetorical claims, neoliberalism has actually been imposed, driven, and underwritten by governments that claim their policy is nonintervention. Neoliberalism soon influenced the political economies of most countries in the developed world, but the degree of separation engendered between rich and poor is a political choice: most extreme in the United States, with the United Kingdom a close second. Establishing neoliberal values like autonomy and choice as taken for granted occurred by “hollowing out” organizations and communities in ways that block dissent and drastically narrow the scope for debate. Psychology is both an academic and applied discipline, with applied psychologists significantly outnumbering academics throughout the 20th century. Expansion was particularly marked during third-wave neoliberalism (1980–2008) in the United Kingdom, when the British Psychological Society grew more than fivefold to over 40,000 members. Two special editions of journals in 2018 and 2019 raised concerns about the relationship between psychology and neoliberalism. In sum, they argued that applied psychology’s self-presentation as a discipline that can solve the problems experienced by individuals glosses over the social origin of most human difficulties, and that modern psychology’s alienated and individualist epistemology makes it a potent neoliberal institution rather than a discipline that can generate alternatives.

Article

Venus is a slowly rotating planet with a thick atmosphere (~9.2 MPa at the surface). Ground- and satellite-based observations have shown atmospheric superrotation (atmospheric rotation much faster than solid surface rotation), global-scale cloud patterns (e.g., Y-shaped and bow-shaped structures), and polar vortices (polar hot dipole and fine structures). The Venusian atmospheric circulation, controlled by the planet’s radiative forcing and astronomical parameters, is quite different from the earth’s. As the meteorological data have been stored, understanding of the atmospheric circulation has been gradually enriched with the help of theories of geophysical fluid dynamics and meteorology. In the cloud layer far from the surface (49–70 km altitude), superrotational flows (east-to-west zonal winds) exceeding 100 m/s and meridional (equator-to-pole) flows have been observed along with planetary-scale brightness variations unique to Venus. The fully developed superrotation, which is ~60 times faster than the planetary rotation, is maintained by meridional circulation and waves. For the planetary-scale variations, slow-traveling waves with stationary and solar-locked structures and fast-traveling waves with phase velocities of around the superroational wind speeds are dominant in the cloud layer. Thermal tides, Rossby waves, Kelvin waves, and gravity waves play important roles in mechanisms for maintaining fast atmospheric rotation. In the lower atmosphere below the cloud layer, the atmospheric circulation is still unknown because of the lack of global observations. In addition to the limited observations, the atmospheric modeling contributes to deep understanding of the atmospheric circulation system. Recent general circulation models have well simulated the dynamical and thermal structures of Venus’s atmosphere, though there remain outstanding issues.

Article

Hundreds of planets are already known to have orbits only a few times wider than the stars that host them. The tidal interaction between a planet and its host star is one of the main agents shaping the observed distributions of properties of these systems. Tidal dissipation in the planet tends make the orbit circular, as well as synchronizing and aligning the planet’s spin with the orbit, and can significantly heat the planet, potentially affecting its size and structure. Dissipation in the star typically leads to inward orbital migration of the planet, accelerating the star’s rotation, and in some cases destroying the planet. Some essential features of tidal evolution can be understood from the basic principles that angular momentum and energy are exchanged between spin and orbit by means of a gravitational field and that energy is dissipated. For example, most short-period exoplanetary systems have too little angular momentum to reach a tidal equilibrium state. Theoretical studies aim to explain tidal dissipation quantitatively by solving the equations of fluid and solid mechanics in stars and planets undergoing periodic tidal forcing. The equilibrium tide is a nearly hydrostatic bulge that is carried around the body by a large-scale flow, which can be damped by convection or hydrodynamic instability, or by viscoelastic dissipation in solid regions of planets. The dynamical tide is an additional component that generally takes the form of internal waves restored by Coriolis and buoyancy forces in a rotating and stratified fluid body. It can lead to significant dissipation if the waves are amplified by resonance, are efficiently damped when they attain a very short wavelength, or break because they exceed a critical amplitude. Thermal tides are excited in a planetary atmosphere by the variable heating by the star’s radiation. They can oppose gravitational tides and prevent tidal locking, with consequences for the climate and habitability of the planet. Ongoing observations of transiting exoplanets provide information on the orbital periods and eccentricities as well as the obliquity (spin–orbit misalignment) of the star and the size of the planet. These data reveal several tidal processes at work and provide constraints on the efficiency of tidal dissipation in a variety of stars and planets.

Article

Time gaps existed in the first three waves between precipitating political events and the development of terrorist activity. But now the time gap has disappeared because the precipitating events were directly associated with terrorism. All of those events occurred in the Islamic world where religion was employed to justify terror. Jewish, Sikh, and Christian terror groups emerged very quickly afterwards, but Islamic groups were larger, more durable, and had a more significant global impact. The international world changed; Iran’s religious revolution made it a major player; and the Soviet Union’s collapse intensified Islamic opposition to the United States. Sikh, Jewish, and Christian terrorists came from a national base, but Islamic ones often emerged from many countries to join a particular group; and two critical groups, al-Qaeda and ISIS, aimed to re-establish a caliphate embracing the Islamic world. Diasporas provided financial support as they had in other waves, but some Islamic immigrants, like first wave anarchists, employed terror in their new homes and often left those homes to seek targets elsewhere. “Suicide bombing” or “self-martyrdom,” the wave’s distinguishing tactic, made it the most destructive wave. The only religious groups to embrace this tactic were Islamic, though ironically, the secular Tamil Tigers used it and did so more often than any Islamic group did. Islamic groups initiated social services for their societies, a program not seen earlier, and the Tamil Tigers adopted social services for their communities as well. Al-Qaeda, born in the resistance to the Soviet Afghan invasion, became the wave’s most important group. After difficulties in helping uprisings outside Afghanistan in the Islamic world, it decided to strike the United States, and its 9/11 attacks, the wave’s high point, are the most destructive terrorist acts ever. The United States then invaded Afghanistan forcing al-Qaeda to leave that country. Instead of completing the job, however, the United States decided to invade Iraq to prevent Iraq from giving al-Qaeda weapons of mass destruction, weapons Iraq did not have. This over-reaction inflamed Muslims everywhere, enabling al-Qaeda to get more recruits and develop Iraqi resistance. One crucial focus of al-Qaeda in Iraq was its gruesome atrocities towards the Shia population, which produced violence between Sunni and Shia throughout the Islamic world. The United States ultimately eliminated al-Qaeda in Iraq, and al-Qaeda Central was unable to get another ground base. Al-Qaeda Central then adopted two methods to revitalize itself. The lone wolf strategy, developed first by U.S. Christian terrorists, did not produce many significant results. At the same time, many franchises were created but each focused on local activities and did not strengthen al-Qaeda’s global capacities. A new situation developed with the “Arab Spring” in 2011, when peaceful secular demonstrations for equality and democracy were transformed into violent conflicts between Shia and Sunni sects. Syria, the bloodiest scene, attracted support from Shia and Sunni elements everywhere and encouraged Russia and the United States to get engaged. ISIS (Islamic State), the remnant of al-Qaeda in Iraq, was reborn and grew immensely there as it captured much territory in Iraq and Syria and became the wave’s most important group. Al-Qaeda Central also became involved and eventually turned against ISIS. In a short time ISIS lost most of the territory gained, and its European strikes to get the West more deeply involved in the conflict by sending troops to Syria and Iraq failed. Al-Qaeda and ISIS franchises continue to fight each other, a conflict that may end the wave.

Article

Ray Surette

The term “copycat crime” implies that the root of a crime can be found in exposure to a live model or media content concerning a prior crime. The four basic components of a copycat crime are a “generator crime” (a media portrayal of a crime or a real-world crime that is the precursor of a subsequent crime), “criminogenic models” (media content or real-world offenders that portray a subsequently copied crime), “copycat criminal” (an individual who commits a crime after being influenced by criminogenic media content, live models, or a combination of the two), and “copycat crime” (a crime whose occurrence or form is influenced by prior exposure to media content and/or live criminal models). The linked crimes are seen as sharing a unique criminogenic dynamic with the first crime serving as a generator for later copycat crimes with substantial elements of the first crime present in the second. The premise of copycat crime is that exposure to a generator crime is the linking mechanism and that the removal of the exposure would eliminate the occurrence or form of the subsequent copycat crime. There is no theory of copycat crime, but there are four theoretical perspectives that are pertinent. Under the first perspective, imitation has been examined as a general human behavior within biology and psychology. The second perspective, social contagion, studies imitation in collective groups with a focus on the life cycle of crime waves. The third perspective is the study of the diffusion of social innovations and focuses on the factors that encourage adoption of a new, socially accepted and advocated behavior. In diffusion research, criminal behaviors have not been a major consideration. The final theoretical perspective is social learning theory, which focuses on how humans learn new behaviors in social settings. Despite the attention of these four research streams, research on copycat crime has not been extensive. One reason for the deficiency is the difficulty in identifying copycat crimes. Whereas other crimes are relatively straightforward to quantify and are routinely tallied in official law enforcement statistics, copycat crimes are not counted in any systematic way. Copycat crime has traditionally been conceived within an emphasis on direct exposure to live person-to-person models. The media as a source of crime models has historically been downplayed. As the media evolved in the 20th century the study of mediated copycat crime models ascended so that the dominant contemporary view of copycat crime is that of media-sourced transmissions. Copycat crimes are today linked to literature, movies, television shows, music, video games, and print and television news, but despite concern and a large number of studies of violent media’s relationship to social aggression, the rigorous study of copycat crime has lagged. At this time, copycat effects are felt to be relatively rare and are most likely to appear in at-risk individuals predisposed to crime and in preexisting criminal populations. The effect of the media is thought to be more qualitative (affecting criminal behavior) than quantitative (affecting the number of criminals). Whether copycat crime effects influence any particular individual depends on the interaction of the content of a particular media product (its characterizations of crime and criminals), the individual’s predispositions toward crime (personal criminal history, family, and environmental factors), and the media’s social context (preexisting cultural norms toward crime, crime opportunities, and nature of the mass media). The most likely individual to be a copycat offender is hypothesized to be a socially isolated but criminally confident offender who is exposed to multiple live criminal models and has immersed themselves in criminogenic media.

Article

Ralf Weisse and Birgit Hünicke

A multitude of geophysical processes contribute to and determine variations and changes in the height of the Baltic Sea water surface. These processes act on a broad range of characteristic spatial and timescales ranging from a few seconds to millennia. On very long timescales, the northern parts of the Baltic are uplifting due to the still ongoing visco-elastic response of the Earth to the last deglaciation, and mean sea level is decreasing in these regions. Over centuries, the Baltic Sea responds to changes in global and North Atlantic mean sea level. Processes affecting global mean sea level, such as warming of the world ocean or melting of glaciers and of polar ice sheets, do have an imprint on Baltic Sea levels. Over decades, variations and changes in atmospheric circulation affect transport through the Danish Straits connecting the Baltic and North seas. As a result, the amount of water in the Baltic Sea and the height of the sea level vary. Similarly, atmospheric variability on shorter timescales down to a few days cause shorter period variations of transport through the Danish Straits and Baltic Sea level. On even shorter timescales, the Danish Straits act as a low pass filter, and high frequency variations of the water surface within the Baltic Sea such as storm surges, wind waves, or seiches are solely caused internally. All such processes have undergone considerable variations and changes in the past. Similarly, they are expected to show variations and changes in the future and across a broad range of scales, leaving their imprint on observed and potential future Baltic Sea level and its variability.

Article

Arms control is a strategy by governments to overcome the security dilemma with institutionalized cooperation. It comes in three versions, arms control proper, with stability as the main objective; non-proliferation as a sub-category of arms control, so understood with the main objective being to preserve the distributive status quo concerning certain weapon types; and disarmament, with the objective to eliminate a specific weapon type. Confidence building is a crosscutting functional concept lumping together many different measures that can serve all three versions. Arms control does not reject self-help as a basis of national security, but entrusts a significant piece of it to cooperation with potential enemies. Hence, arms control—with the exception of unilateral, hegemonic arms control imposed on others, and of non-proliferation for preserving an existing oligopoly—is a difficult subject for realism and neorealism, but also for post-modernism. It presents a solvable puzzle for rationalists and no problem at all for constructivists who, to the contrary, can dig into norms, discourses, and identities. Concerning stability and change, arms control can be looked at from two opposite perspectives. Since it aims at stability, critical security approaches have labeled it as a conservative, status quo orientated strategy. But there is also a transformational perspective: arms control as a vehicle to induce and reinforce a fundamental redefinition of the relationship between states. Naturally, the concept of disarmament shows the greatest affinity to the transformational perspective. A related issue is whether arms control is a result of political circumstances, a dependent variable without a political impact of its own, or whether it has causal effect on interstate relations. Constructivism proposes a dialectical relationship in which arms control and broader policy influence each other. From this reflection, the question of the conditions of success and failure flows naturally. Conducive interstate relations (or extrinsic shocks), technology, domestic structures, learning, leadership, perception, and ideology have been candidates for the independent master variable. Three models tackle the relationship of arms control and historical time: the enlightenment intuition of steady progress; a series of waves, each of which leaves the world in a more cooperative state than the previous one; and the circle—arms control ebbs and flows alternatively, but achievements are fully lost in each ebb period. We can distinguish four arms control discourses: arms control as the maiden of deterrence; arms control subordinated to defense needs; arms control under the imperative of disarmament; and arms control as the instrument of human security, the survival and well-being of human individuals, notably civilians. As with all politics, arms control involves justice issues: the distribution of values (security/power), access to participation in decision making, and the granting of recognition as legitimate actor. Arms control negotiations are ripe with justice claims, and failure through incompatible justice demands happens frequently. Also, emotions play a key role: frustration and ensuing resentment, anger, and existential fear can prevent success. Finally, compassion, empathy, and trust are ingredients in successful arms control processes.

Article

Paulina Junni and Satu Teerikangas

There are many types of mergers and acquisitions (M&A), be they a minority acquisition to explore a potential high growth emerging market, a takeover of a financially distressed firm with the aim of turning it around, or a private equity firm seeking short- to medium-term returns. The terms “merger” and “acquisition” are often used interchangeably, even though they have distinct denotations: In an acquisition, the acquirer purchases the majority of the shares (over 50%) of another company (the “target”) or parts of it (e.g., a business unit or a division). In a merger, a new company is formed in which the merging parties share broadly equal ownership. The term “merger” is often used strategically by acquirers to alleviate fears and send out a message of friendly combination to employees. In terms of transaction numbers, the majority of M&A transactions are acquisitions, whereas mega-merger deals gain media attention owing to transaction size. While M&A motives, acquirer types, and dynamics differ, most M&A share the aim of generating value from the transaction in some form. Yet a prevalent dilemma in the M&A practice and literature is that M&A often fail to deliver the envisioned benefits. Reasons for negative acquirer performance stem from overestimating potential synergies and paying high premiums for targets pre-deal. Another problem lies in securing post-deal value creation. Post-deal challenges relate to optimal integration speed, the degree of integration, change, or integration management, communication, resource and knowledge sharing, employee motivation and turnover, and cultural integration. Researchers are calling for more research on how pre-deal processes such as target evaluation and negotiations influence M&A performance. A closer look at this literature, though, highlights several controversies. First, the literature often lacks precision when it comes to defining M&A. We call for future research to be explicit concerning the type of merger or acquisition transaction, and the organizational contexts of the acquiring and target firms. Second, we are still lacking robust and unified frameworks that explain M&A occurrence and performance. One of the reasons for this is that the literature on M&A has developed in different disciplines, focusing on either pre- or post-deal aspects. This has resulted in a “silo” effect with a limited understanding about the combined effects of financial, strategic, organizational, and cultural factors in the pre- and post-deal phases on M&A performance. Third, M&A studies have failed to critically scrutinize the M&A phenomenon, including aspects such as power, politics, and managerial drivers. Fourth, scholars have tended to focus on single, isolated M&A. We call for future research on M&A programs and M&A as part of broader corporate strategies. Finally, the study of M&A has suffered from a managerial bias, with insufficient attention paid to the rank and file, such as engineers, or marketing or administrative employees. We therefore call for future research that takes a broader view on actors involved in M&A, placing a greater emphasis on individuals’ roles and practices.