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We examine the mechanisms responsible for the onset of the three-dimensional mode B instability in the wake behind a circular cylinder. We show that it is possible to explicitly account for the stabilising effect of spanwise viscous diffusion and then demonstrate that the remaining mechanisms involved in this short-wavelength instability are preserved in the limit of zero wavelength. Using the resulting simplified equations, we show that perturbations in different fluid particles interact only through the in-plane viscous diffusion which turns out to have a destabilising effect. We also show that in the presence of viscous diffusion, the closed trajectories which had been conjectured to play a crucial role in the onset of the mode B instability are not actually a prerequisite for the growth of mode B type perturbations. We combine these observations to identify the three essential ingredients for the development of the mode B instability: (i) the amplification of perturbations in the braid regions due to the stretching mechanism; and the spreading of perturbations through (ii) viscous diffusion, and (iii) cross-flow advection which transports fluid between the two braid regions on either side of the cylinder. Finally, we develop a simple criterion that allows the prediction of the regions where three-dimensional short-wavelength perturbations are amplified by the stretching mechanism. The approach used in our study is general and has the potential to give insights into the onset of three-dimensionality via short-wavelength instabilities in other flows.
We conducted a systematic review of the medical, nursing, forensic, and social science literature describing events and processes associated with what happens after a traumatic death in the socio-cultural context of largely Western and high-income societies. These include death notification, why survivors choose to view or not view the body, forensic practices affecting viewing the body, alternatives to viewing, and social and cultural practices following the death. We also describe how elements of these processes may act to increase or lessen some of the negative cognitive and emotional consequences for both survivors and providers. The information presented is applicable to those who may be faced with traumatic deaths, including those who work in medicine, nursing, and law enforcement, as well as first responders, forensic investigators, funeral directors, and the families of the deceased.
Maintaining object grasp stability represents a pivotal challenge within the domain of robotic manipulation and upper-limb prosthetics. Perturbations originating from external sources frequently disrupt the stability of grasps, resulting in slippage occurrences. Also, if the grasping forces are not optimal while controlling the slip, it may result in the deformation of the objects. This study investigates the robustification of a reinforcement learning (RL) policy for implementing intelligent bionic reflex control, i.e., slip and deformation prevention of the grasped objects. RL-derived policies are vulnerable to failures in environments characterized by dynamic variability. To mitigate this vulnerability, we propose a methodology involving the incorporation of an adaptive sliding mode controller into a pre-trained RL policy. By exploiting the inherent invariance property of the sliding mode algorithm in the presence of uncertainties, our approach strengthens the robustness of the RL policies against diverse and dynamic variations. Numerical simulations substantiate the efficacy of our approach in robustifying RL policies trained within simulated environments.
The new mineral popugaevaite Ca3[B5O6(OH)6]FCl2·8H2O was found at the Internatsional’nyi diamond mine, Internatsional’naya kimberlite pipe, Sakha (Yakutia) Republic, Russia. It belongs to the low-temperature hydrothermal mineral assemblage formed in the contact zone between kimberlite and a boron-bearing halite rock. Popugaevaite occurs as veinlets in massive aggregates of ekaterinite and crusts (up to 0.7 mm thick and up to 1 cm × 4 cm in area) on ekaterinite nodules embedded in halite. Other associated minerals are Fe-rich szaibélyite, serpentine, dolomite, pyrrhotite and chalcopyrite. Crude prismatic crystals of popugaevaite are up to 0.3 × 1 mm. The mineral is transparent, colourless, with vitreous lustre and perfect {010} cleavage. It is optically biaxial (–), α 1.502(2), β 1.523(2), γ 1.530(2) and 2Vmeas = 50(10)°. The chemical composition (wt.%, electron-microprobe, boron by ICP-MS, H2O calculated by stoichiometry) is: CaO 28.54, B2O3 28.62, F 3.19, Cl 11.50, H2O 32.83, O = (F,Cl) –3.94, total 100.74. The empirical formula, calculated based on 23 O+F+Cl and 22 H atoms per formula unit, is Ca3.07B4.96O6.03(OH)6F1.01Cl1.96·8H2O. Popugaevaite is monoclinic, space group Pn, a = 8.7055(11), b = 8.1025(11), c = 14.812(2) Å, β = 91.367(7)°, V = 1044.5(2) Å3 and Z = 2. The strongest reflections of the powder X-ray diffraction pattern [d,Å(I,%)(hkl)] are: 8.12(100)(010), 4.058(27)(020), 3.577(15)($\bar 1$21), 2.936(10)(123), 2.834(16)(301, $\bar 1$05) and 2.283(10)(133). The crystal structure was solved based on single-crystal XRD data and refined on powder data by the Rietveld method, Rwp = 0.0058, Rp = 0.0043 and Robs = 0.0241. Popugaevaite is an isostructural analogue of brianroulstonite Ca3[B5O6(OH)6](OH)Cl2·8H2O with F– instead of the OH– group non-bound with boron. The structure is based upon the layers of twelve-membered rings of alternating BO3 triangles and BO2(OH)2 tetrahedra. The mineral is named in honour of the Russian geologist Larisa Anatol’evna Popugaeva (1923–1977), one of the principal discoverers of diamondiferous kimberlite pipes in Yakutia.
In 2003, rescue excavations at Piazzeta dell'Anfiteatro, Trento, identified an extramural funerary area dated to the 5th c. CE. The necropolis yielded 45 coins (3rd–5th c.), most of which were involuntary losses. Owing to the sound stratigraphy of the site, these coins present a reliable sample of coinage circulating in Tridentum during the 5th c. This study presents a brief synthesis of the transformations undergone by the Late Antique city, so as to understand the dynamics attested in Piazzeta dell'Anfiteatro, a description of the stratigraphic units that contained coins, and a detailed analysis of the coins from several perspectives. The aim is to improve our understanding of the Late Antique monetary history of the city and Trentino's territory.
Despite the growing interest in secondary state efforts to avoid choosing sides in great power competition, International Relations scholars have paid scant attention to the question of how great powers respond to secondary state ‘hedging’. We offer a first approximation for this important question by focusing on ‘high-value’ hedgers, i.e. secondary states whose location or capabilities afford them the potential to tip the scales in a great power war. We posit that great powers are likely to accommodate high-value hedgers and refrain from trying to manipulate their alignment choice. This is because the likelihood and costs of losing a high-value hedger are such that competing great powers would rather be safe than sorry. Concretely, we expect established and rising great powers to (re)assure high-value hedgers: the former by demonstrating their commitment to a regional balance of power, and the latter by showing they harbour no ill intent towards the hedging secondary state. To probe our argument, we examine how Great Britain and Germany responded to Dutch hedging in the early 20th century, and how the United States and China are responding to Singapore’s hedging today.
What are the legal and political criteria that distinguish between ‘correct’ and ‘unacceptable’ legal mobilisation? How does populism facilitate legal mobilisation? The questions of the workshop organizers led us back in Hungary to the democratic transition from socialism to liberal democracy in 1989, when legal mobilisation for the rule of law, democracy and human rights was led first and primarily by non-state actors (National Round Table). Participants of the democratic transition prepared the complete revision of the 1949 Constitution, which was an emblematic element in addition to the many legislative drafts of the transitory nature of the creation of the new system. In 2010, after the successful political mobilisation, the populist party coalition (lead by Viktor Orban) gained a two-thirds constitution-making majority in Parliament (in the absence of two opposition parties), and the Parliament adopted the new Fundamental Law (new constitution). This was also an emblematic element of the new legal mobilisation conducted by the two-thirds populist Government majority. This article will describe how populism – through the instrumentalisation of the law (disregarding the inherent values in/of law based on value choice) and the destruction of institutional checks and balances – facilitated new legal mobilisation. Based on this experience of the outcome of the equally strong and effective legal mobilisation in Hungary of the liberal and the illiberal (democratic and autocratic, respectively) transitions, in this article we aim to make valid theoretical propositions on how to assess ‘correct’ and ‘incorrect’ legal mobilisation and what influences the relevance of non-state actors in populism.
Folate metabolism is involved in the development and progression of various cancers. We investigated the association of single nucleotide polymorphisms (SNP) in folate-metabolising genes and their interactions with serum folate concentrations with overall survival (OS) and liver cancer-specific survival (LCSS) of newly diagnosed hepatocellular carcinoma (HCC) patients. We detected the genotypes of six SNP in three genes related to folate metabolism: methylenetetrahydrofolate reductase (MTHFR), 5-methyltetrahydrofolate-homocysteine methyltransferase reductase (MTRR) and 5-methyltetrahydrofolate-homocysteine methyltransferase (MTR). Cox proportional hazard models were used to calculate multivariable-adjusted hazard ratios (HR) and 95 % CI. This analysis included 970 HCC patients with genotypes of six SNP, and 864 of them had serum folate measurements. During a median follow-up of 722 d, 393 deaths occurred, with 360 attributed to HCC. In the fully-adjusted models, the MTRR rs1801394 polymorphism was significantly associated with OS in additive (per G allele: HR = 0·84, 95 % CI: 0·71, 0·99), co-dominant (AG v. AA: HR = 0·77; 95 % CI: 0·62, 0·96) and dominant (AG + GG v. AA: HR = 0·78; 95 % CI: 0·63, 0·96) models. Carrying increasing numbers of protective alleles was linked to better LCSS (HR10–12 v. 2–6 = 0·70; 95 % CI: 0·49, 1·00) and OS (HR10–12 v. 2–6 = 0·67; 95 % CI: 0·47, 0·95). Furthermore, we observed significant interactions on both multiplicative and additive scales between serum folate levels and MTRR rs1801394 polymorphism. Carrying the variant G allele of the MTRR rs1801394 is associated with better HCC prognosis and may enhance the favourable association between higher serum folate levels and improved survival among HCC patients.
Judges are not the first political officials that come to mind when one considers the role of social media in modern politics. Following in the wake of some prominent judicial personalities adopting Twitter, however, a growing number of state high court judges have adopted and established more public personas on the platform. Judges use Twitter in substantively different ways than traditional elected officials (Curry and Fix 2019); however, little is understood about how the use of such social media platforms affects broader judicial networks. Recognizing that judges, like typical social media users, may aspire to expand their networks to build and appeal to broader audiences, we contend that active participation in judicial Twitterverse could yield personal and professional advantages. Here, we address a currently unexplored question: To what extent have judges formed a distinctive “judicial network,” on Twitter, and what discernible patterns present in these networks? Leveraging the unique structure of social media, we collect comprehensive network data on judging using Twitter and analyze what institutional and social factors impact greater power within the judicial network. We find that early adoption, electoral concerns, and connective links between judges all impact the strength of the judicial network, highlighting the complex motivations driving judicial Twitter engagement, and the significance of network building in judges’ social media strategies and its potential impact on career advancement.
Wave-assisted propulsion (WAP) systems directly convert wave energy into thrust using elastically mounted hydrofoils. The wave conditions as well as the design of the hydrofoil drive the fluid–structure interaction of the hydrofoil and, consequently, its performance. We employ simulations using a sharp-interface immersed boundary method to examine the effect of three key parameters on the flow physics, the fluid–structure interaction as well as thrust performance of these systems – the stiffness of the torsional spring, the location of the pitch axis and the Strouhal number. We demonstrate the utility of ‘maps’ of energy exchange between the flow and the hydrofoil system, as a way to understand and predict these characteristics. The force-partitioning method (FPM) is used to decompose the pressure forces into interpretable components and to quantify the mechanisms associated with thrust generation. Based on the results from FPM, a phenomenological model for the thrust generated by the WAP foil is presented. The parameters associated with this model are estimated based on data from over 450 distinct simulations. The predictions of the model are compared with the simulations and the use of this model for guiding WAP design is discussed.
Damage initiation hotspots around features, such as bolts and ply drops, must be investigated during the preliminary design phase of large composite structures, such as composite airframes. A global-local modelling approach is commonly employed to perform this investigation, whereby a global low-fidelity model is used to drive high-fidelity local models around the features of interest. However, this methodology is slow, repetitive and expert-dependent. In this investigation, we address these issues by applying machine learning techniques to this global-local modelling framework and demonstrate the time-saving benefit when predicting damage initiation of bolted composite joints. Feature engineering of model inputs and outputs, and appropriate customisation of machine learning methods enables damage initiation prediction. Special consideration is given to the boundary conditions that must be varied to simulate the response of the bolted composite joints. Results show over three orders of magnitude time-saving benefit and satisfactory accuracy of the proposed methodology. This indicates its potential to be developed further into a rapid design and optimisation tool.
Recently, women’s presence on top boards of directors has significantly increased, challenging the long standing of male-led corporate elites. In light of the still-developing literature, this article provides a century-long examination of women’s entry into the Spanish corporate elite, offering several original contributions. In addition to its pioneering input into the country’s historiography, the work uses a holistic model to introduce a comparative European approach. Moreover, it empirically examines the significant yet previously unexplored impact of elite training institutions on the advancement of female directors as well as their arrival through a national holding company and their presence in leading publicly traded companies. Findings showed four distinct stages in their trajectory: discriminatory exclusion, during the first third of the twentieth century; exceptional inclusion, with early positions in their family-owned firms; gradual incorporation, with increased political representation and expanded academic access in the latter decades of the last century; and promotion, supported by twenty-first-century political strategies, while still revealing the handicap of women’s delayed entry into the corporate network.
Let G be a finite group and let $\chi $ be an irreducible character of G. The number $|G:\mathrm {ker}\chi |/\chi (1)$ is called the codegree of the character $\chi $. We provide several relations between the structure of G and the codegrees of the characters in a given subset of $\mathrm {Irr}(G)$, where $\mathrm {Irr}(G)$ is the set of all complex irreducible characters of G. For example, we show that if the codegrees of all strongly monolithic characters of G are odd, then G is solvable, analogous to the well-known fact that if all irreducible character degrees of a finite group are odd, then that group is solvable.
Placental vascular anastomoses are traditionally thought to exist exclusively in monochorionic pregnancies. However, they have been reported in dichorionic twin pregnancies as well. In turn, twin to twin transfusion syndrome (TTTS) and twin anemia polycythemia sequence (TAPS) have also been noted to impact some of these gestations. Through discussion of one such case at our institution along with a review of the available literature, we review the proposed pathophysiology of placental vascular anastamoses in dichorionic twin gestations, and aim to raise awareness of the possibility of associated pathologies in dichorionic gestations. This is an emerging area of literature that will require future study to guide prenatal surveillance and mitigate morbidity.