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The presence of a mean magnetic field aligned with the direction of the acceleration greatly modifies the development of the Rayleigh–Taylor instability (RTI). High resolution direct numerical simulations of the Boussinesq–Navier–Stokes equations under the magnetohydrodynamics approximation reveal that, after an initial damping of the perturbations at the interface between the two miscible fluids, a rapid increase of the mixing layer is observed. Structures are significantly stretched in the vertical direction because magnetic tension prevents small-scale shear instabilities. When the vertical turbulent velocity exceeds the Alfvén velocity, the flow transitions to turbulence, structures break and an enhanced mixing occurs with strong dissipation. Afterwards, the mixing zone slows down and its growth rate is decreased compared to the hydrodynamic case. For larger magnitudes of the mean magnetic field, a strong anisotropy persists, and an increased fraction of potential energy injected into the system is lost into turbulent magnetic energy: as a consequence, the mixing zone growth rate is decreased even more. This phenomenology is embedded in a general buoyancy-drag equation, derived from simplified equations that reflect the large-scale dynamics, in which the drag coefficient is increased by the presence of turbulent magnetic energy.
Little and Meng (L&M) (2023) question the prevailing narrative of widespread democratic backsliding by showing that various objective indicators of democracy are flat over time. However, because recent democratic decline is concentrated in democracies, the objective indicators can accurately test for backsliding only if they can track democratic quality within democracies. This response article shows that they cannot, for conceptual and empirical reasons. The indicators generally can distinguish democracies from autocracies but are blind to variation in quality within democracies. L&M, therefore, are showing that one form of variation in democracy is stagnant but are systematically missing the very type of variation that has most informed current warnings about backsliding.
Diagnostic stewardship seeks to improve ordering, collection, performance, and reporting of tests. Test results play an important role in reportable HAIs. The inclusion of HAIs in public reporting and pay for performance programs has highlighted the value of diagnostic stewardship as part of infection prevention initiatives. Inappropriate testing should be discouraged, and approaches that seek to alter testing solely to impact a reportable metric should be avoided. HAI definitions should be further adapted to new testing technologies, with focus on actionable and clinically relevant test results that will improve patient care.
Congress recently enacted significant reforms to the laws governing the reporting and publication of international agreements in the United States. These reforms were adopted in December 2022 and took effect in September 2023, and the State Department issued regulations implementing them in early October 2023.
The study aims to understand the interplay between sustainability strategy and the approach to sustainability reporting in small- and medium-sized enterprises (SMEs). To achieve this purpose, a case study is developed, examining four companies that exemplify different sustainability strategy types delineated by Baumgartner: introverted, extroverted, conservative, and visionary. According to the findings of the research, while it is possible to identify sustainability strategies based on the key defining elements of the adopted conceptual map, and to interpret the company’s perception and approach to sustainability reporting considering the sustainability strategy, integrating owner-manager values, stakeholder proximity, and supply chain dynamics the conceptual map becomes a more adaptable and practical tool for SMEs seeking to thrive in an increasingly sustainability-focused business landscape. The incorporation of these insights extends Baumgartner’s work, enhancing the comprehension of sustainability strategies within SMEs and providing implications for regulatory bodies, consultants, and managers.
Jetting of collapsing bubbles is a key aspect in cavitation-driven fluid–solid interactions as it shapes the bubble dynamics and additionally due to its direct interaction with the wall. We study experimentally and numerically the near-wall collapse and jetting of a single bubble seeded into the stagnation flow of a wall jet, i.e. a jet that impinges perpendicular onto a solid wall. High-speed imaging shows rich and rather distinct bubble dynamics for different wall jet flow velocities and bubble-to-wall stand-off distances. The simulations use a volume-of-fluid method that allows us to numerically determine the microscopic and transient pressures and shear stresses on the wall. It is shown that a wall jet at moderate flow velocities of a few metres per second already shapes the bubble ellipsoidally inducing a planar and convergent jet flow. The distinct bubble dynamics allow us to tailor the wall interaction. In particular, the shear stresses can be increased by orders of magnitude without increasing impact pressures the same way. Interestingly, at small seeding stand-offs, the bubble during the final collapse stage can lift off the wall and migrate against the flow direction of the wall jet such that the violent collapse occurs away from the wall.
Let T be the theory of dense cyclically ordered sets with at least two elements. We determine the classifying space of $\mathsf {Mod}(T)$ to be homotopically equivalent to $\mathbb {CP}^\infty $. In particular, $\pi _2(\lvert \mathsf {Mod}(T)\rvert )=\mathbb {Z}$, which answers a question in our previous work. The computation is based on Connes’ cycle category $\Lambda $.
Let Σ be a σ-algebra of subsets of a set Ω and $B(\Sigma)$ be the Banach space of all bounded Σ-measurable scalar functions on Ω. Let $\tau(B(\Sigma),ca(\Sigma))$ denote the natural Mackey topology on $B(\Sigma)$. It is shown that a linear operator T from $B(\Sigma)$ to a Banach space E is Bochner representable if and only if T is a nuclear operator between the locally convex space $(B(\Sigma),\tau(B(\Sigma),ca(\Sigma)))$ and the Banach space E. We derive a formula for the trace of a Bochner representable operator $T:B({\cal B} o)\rightarrow B({\cal B} o)$ generated by a function $f\in L^1({\cal B} o, C(\Omega))$, where Ω is a compact Hausdorff space.
We are humbled by the quantity and quality of the commentaries on our article in this special issue. Our goal was not to answer definitively how global democracy has changed in recent years but rather to provoke a debate about how we collectively can improve the scholarship on this question. The range of viewpoints raised in this special issue have made important advances on this goal.
Li, Ma and Wang have provided in [13] a partial classification of the so-called Moebius deformable hypersurfaces, that is, the umbilic-free Euclidean hypersurfaces $f\colon M^n\to \mathbb{R}^{n+1}$ that admit non-trivial deformations preserving the Moebius metric. For $n\geq 5$, the classification was completed by the authors in [12]. In this article we obtain an infinitesimal version of that classification. Namely, we introduce the notion of an infinitesimal Moebius variation of an umbilic-free immersion $f\colon M^n\to \mathbb{R}^m$ into Euclidean space as a one-parameter family of immersions $f_t\colon M^n\to \mathbb{R}^m$, with $t\in (-\epsilon, \epsilon)$ and $f_0=f$, such that the Moebius metrics determined by ft coincide up to the first order. Then we characterize isometric immersions $f\colon M^n\to \mathbb{R}^m$ of arbitrary codimension that admit a non-trivial infinitesimal Moebius variation among those that admit a non-trivial conformal infinitesimal variation, and use such characterization to classify the umbilic-free Euclidean hypersurfaces of dimension $n\geq 5$ that admit non-trivial infinitesimal Moebius variations.
In 1936 Gianni Caproni, one of the biggest aircraft producers in Italy, bought one of the biggest engineering companies in Emilia Romagna, the Officine Meccaniche Reggiane, and started manufacturing and exporting some of the topmost fighters ever produced in Italy. Based on different archival sources this paper would like to shed light on why, despite a national technological obsolescence in the field a company, which focused on the production of railway material, was able to come up with the most technologically innovative fighters (the Re. 2000 and successive models) which soon conquered the Italian and foreign markets. The author would like to indicate the original characteristics which help explain its primacy: the unique features of the Reggiane, the role of the new owner, risk-taker and forward-looking entrepreneur Gianni Caproni and in particular the importance of the transmission of knowledge, which in those autarchic years and in this particular case was reached by attracting human capital from abroad. The general argumentation of the paper would like to show the importance of deeply excavating in the company’s history, managerial choices, risk-taking attitudes, and knowledge transfer in explaining an otherwise almost inexplicable international business success in a such a competitive sector. The approach is not purely descriptive: the paper analyses the facts and figures of the Officine Meccaniche Reggiane before and after the Caproni takeover, it evaluates the company’s innovative production strategy in the new field of aircraft production and offers new interpretations on its success story in this field.
In this article, we introduce and study the notion of Goldie dimension for C*-algebras. We prove that a C*-algebra A has Goldie dimension n if and only if the dimension of the center of its local multiplier algebra is n. In this case, A has finite-dimensional center and its primitive spectrum is extremally disconnected. If moreover, A is extending, we show that it decomposes into a direct sum of n prime C*-algebras. In particular, every stably finite, exact C*-algebra with Goldie dimension, that has the projection property and a strictly full element, admits a full projection and a non-zero densely defined lower semi-continuous trace. Finally we show that certain C*-algebras with Goldie dimension (not necessarily simple, separable or nuclear) are classifiable by the Elliott invariant.
This study examined the effect of perceived ethnic marginalization, perception towards Nigerian democracy, and socioeconomic condition on support for secession among members of the Igbo ethnic group. Perceived ethnic marginalization and negative perceptions toward Nigerian democracy were found to positively correlate with support for secession. Socioeconomic condition was measured at the household and communal levels. The household measure had no effect on support for secession, but the communal measure did: socioeconomic condition at the communal level positively correlated with support for secession. Igbo ethnicity increased the likelihood of supporting secession, while belonging to the Hausa/Fulani and Yoruba ethnic groups reduced the likelihood of supporting secession.
We investigate the existence and branching patterns of wave trains in the mass-in-mass (MiM) lattice, which is a variant of the Fermi–Pasta–Ulam (FPU) lattice. In contrast to FPU lattice, we have to solve coupled advance-delay differential equations, which are reduced to a finite-dimensional bifurcation equation with an inherited Hamiltonian structure by applying a Lyapunov–Schmidt reduction and invariant theory. We establish a link between the MiM lattice and the monatomic FPU lattice. That is, the monochromatic and bichromatic wave trains persist near $\mu =0$ in the nonresonance case and in the resonance case $p:q$ where $q$ is not an integer multiple of $p$. Furthermore, we obtain the multiplicity of bichromatic wave trains in $p:q$ resonance where $q$ is an integer multiple of $p$, based on the singular theorem.
Alors que la lutte contre la corruption est généralement considérée comme une responsabilité de la Justice ou des agences anticorruptions, des recherches montrent que les institutions supérieures de contrôle des finances publiques (ISC) peuvent aussi jouer un rôle essentiel. Cependant, ce rôle n'est pas toujours clairement défini et pourrait diverger selon les contextes. L'objectif de cet article est de mieux cerner le rôle des ISC dans la lutte contre la corruption du point de vue des acteurs directement concernés, soit les membres des ISC. Treize entretiens, réalisés avec des vérificateurs au Québec et des magistrats en France et au Sénégal, démontrent une contribution effective de ces institutions dans le combat contre la corruption, bien qu'elles n'en aient pas le mandat explicite.