To save content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about saving content to .
To save content items to your Kindle, first ensure no-reply@cambridge.org
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Direct numerical simulations in a low-curvature viscoelastic turbulent Taylor vortex flow, with Reynolds numbers ranging from 1500 to 8000 and maximum chain extensibility ($L$) from 50 to 200, reveal a maximum drag reduction (MDR) asymptote. Compared with the classical MDR observed in planar wall-bounded shear flows, that is, drag reduction (DR) is $\sim -80\, \%$, this MDR state achieves only moderate levels of DR ($\sim -60\,\%$). This is due to the existence of large-scale structures (LSSs). A careful examination of the flow structures reveals that the polymer–turbulence interaction suppresses small-scale vortices and stabilizes the LSSs. These structural changes in turn lead to a reduction of Reynolds stress, and consequently to a DR flow state. Although Reynolds stress does not vanish as observed in classical MDR states, the small-scale vortices that heavily populate the near-wall region are also almost completely eliminated in this flow state. Concurrently, significant polymer stresses develop as a consequence of the interaction between polymer chains and LSSs that partially offset the magnitude of DR, leading to MDR asymptotes with moderate levels of DR. Moreover, we demonstrate that polymer deformation, i.e. deviation from the equilibrium state, is directly correlated with the LSSs dynamics, while the polymer deformation fluctuation displays a universal property in the MDR state. Hence, it is not surprising that the extent of DR exhibits a non-monotonic dependence on the maximum chain extensibility. Specifically, the variation in $L$ alters the incoherent and coherent angular momentum transport by small- and large-scale flow structures, respectively. To that end, the most DR flow state occurs at a moderate value $L=100$. Overall, this study further supports the universal property of polymer-induced asymptotic states in wall-bounded turbulence and paves the way for mechanistic understanding of drag modification that arises from the interaction of polymers with small- and large-scale flow structures.
This article explores the subjective experiences of transition to employment in the outsourced/offshored business service sector in Romania. Based on 138 interviews with junior and senior graduates, it maps how different ‘tidal economic waves’ associated with Romania’s economic transition have intersected working biographies since the 1990s. The paper argues that the sector generates many middle-class employment opportunities, legitimising consensus around the idea that ‘this is the best time to be young.’ Yet, informed by elements of political economy, it challenges the conventional repertoires of optimism. In doing so, it tentatively questions the long-term occupational prospects of those who take up entry-level positions in (arguably) automatable, on-the-move, and standardised jobs with lesser high-end value. The paper communicates using the structure of opportunity theory by highlighting how, alongside location, the concept of time (personal, historical, and company time) is woven into the work biographies of members of an under-researched group.
A subfossil robber fly (Diptera: Asilidae) from the genus Lasiopogon Loew is reported from a Beringian rodent, Arctic ground squirrel, Urocitellus parryii Richardson (Rodentia: Sciuridae), midden in the Yukon Territory, Canada, dated to about 16 500 years old. This is the first asilid reported from Quaternary-aged material and represents the first (sub)fossil for this genus and for the subfamily Stichopogoninae.
This article extends the validity of the conditional likelihood ratio (CLR) test developed by Moreira (2003, Econometrica 71(4), 1027-–1048) to instrumental variable regression models with unknown homoskedastic error variance and many weak instruments. We argue that the conventional CLR test with estimated error variance loses exact similarity and is asymptotically invalid in this setting. We propose a modified critical value function for the likelihood ratio (LR) statistic with estimated error variance, and prove that our modified test achieves asymptotic validity under many weak instruments asymptotics. Our critical value function is constructed by representing the LR using four statistics, instead of two as in Moreira (2003, Econometrica 71(4), 1027-–1048). A simulation study illustrates the desirable finite sample properties of our test.
While recent aDNA and other scientific analysis has served to underline the recurrent role of migration in the process of Neolithisation right across Europe, there remains plenty of scope for better integration of archaeogenetic and archaeological interpretations and for detailed narratives of local and regional trajectories. This paper focuses on relations between Britain and Ireland in the early Neolithic, in the first part of the 4th millennium cal BC. I argue that direct connections between Britain and Ireland have been overlooked and underplayed — hidden in plain sight — in the search for perceived common sources in continental Europe. I advance four propositions for debate: that the first Neolithic people in Ireland came mainly from Britain, perhaps from several parts of western Britain; that subsequent connections, long described but curiously not much further interpreted, constitute an intense set of interactions; that such links were probably spread over time through the early Neolithic, coming thick and fast near the beginning and perhaps even intensifying with time; and that such relations were maintained and intensified because of the concentrated circumstances of beginnings. The latter arguably contrast with those of the relationship between the Continent and southern Britain. The maintenance of connections was political, because a remembered past was actively used; lineage founders, concentrated lineages and other emergent social groupings may have developed through time as part of such a process.
To enhance radiological and nuclear emergency preparedness of hospitals while responding to the refugee crisis, the Government of the Republic of Moldova implemented an innovative approach supported by the World Health Organization (WHO). This initiative featured a comprehensive package that integrated health system assessment, analysis of existing plans and procedures, and novel medical training component. The training, based on relevant WHO and International Atomic Energy Agency (IAEA) guidance, combined theory with contemporary adult learning solutions, such as practical skill stations, case reviews, and clinical simulation exercises.
This method allowed participants to identify and address gaps in their emergency response capacities, enhancing their ability to ensure medical management of radiological and nuclear events. This course is both innovative and adaptable, offering a potential model for other countries seeking to strengthen radiological and nuclear emergency response capabilities of the acute care clinical providers.
Seasonal variation in maternal exposure to sunlight during pregnancy, which relates to variation in vitamin D and other micronutrient availability for a fetus, is a prevalent explanation for the variation of offspring traits with birth season. However, little consensus exists about the pregnancy period during which the fetus is most sensitive to maternal UV exposure and which offspring traits are most sensitive. We examined the association between 11 anthropometric traits and birth season/month among 18,459–23,876 Estonian children born in 1937–62. Nine traits showed seasonal patterns, which were generally weak, compared to the effects of family socioeconomic position (SEP). Most prominent nonlinear associations between offspring traits and birth month emerged among children of mothers in unskilled manual professions. A possible explanation is that the growth of children in high-SEP families is more strongly buffered against any external exposures (including possible shortage of maternally synthesised vitamin D and essential micronutrient availability) than in low-SEP settings. For most traits, children born in spring/summer were larger than those born in autumn/winter. Hip width, trunk length and weight showed the most distinct seasonal patterns. If these birth-season-related patterns are related to maternal sunlight exposure, our results support the view that UV exposure benefits offspring growth towards the end of pregnancy. It is also possible that children born in spring and summer benefitted from the seasonally increasing nutrient availability during the first post-natal months.
We propose a hybrid numerical model for the collective motion of fish groups, which integrates an agent-based model with a computational fluid dynamics (CFD)-based model. In the agent-based model, the fish group is represented by self-propelled particles (SPPs), incorporating social forces with local interactive rules. The CFD-based model treats the fish body with an undulated filament that responds to the hydrodynamic forces imposed by the surrounding fluid flow. These two models are coupled using a central pattern generator controller. We test this hybrid model with groups of 30–50 individuals. The results show that the group exhibits various collective behaviours, including tight schooling, sparse schooling and milling patterns, by adjusting the coefficients in the SPP model. Due to the hydrodynamic interactions, particularly with the obstacle avoidance model, both the individuals’ and the group’s mean speed fluctuate, differentiating it from traditional SPP models that typically consider volumeless particles. More interestingly, our findings indicate that fish benefit from collective motion in terms of energetic consumption in both schooling and milling patterns. It is important to note that the swimming fish are actuated using a very simple mechanism without any optimisation strategy. An additional study investigates the effects of the Reynolds number, demonstrating the capability of the current hybrid model to account for fish groups of varying body lengths or swimming speeds. Future applications of this model are promising, offering potential insights into the energetic advantages of collective motion in large-scale fish groups.
The flow over a cambered NACA 65(1)–412 airfoil at $Re\,=\,2\times 10^4$ is described based on a high-order direct numerical simulation. Simulations are run over a range of angles of attack, $\alpha$, where a number of instabilities in the unsteady, three-dimensional flow field are identified. The balance and competing effects of these instabilities are responsible for significant and abrupt (with respect to $\alpha$) changes in flow regime, with measurable consequences in time-averaged, integrated force coefficients, and in the far-wake footprint. At low $\alpha$, the flow is strongly influenced by vortex roll-up from the pressure side at the trailing edge. The interaction of this large-scale structure with shear and three-dimensional modal instabilities in the separated shear layer and associated wake region on the suction side, explains the transitions and bifurcations of the the flow states as $\alpha$ increases. The transition from a separation at low $\alpha$ to reattachment and establishment of a laminar separation bubble at the trailing edge at critical $\alpha$ is driven by instabilities within the separated shear layer that are absent at lower angles. Instabilities of different wavelengths are then shown to pave the path to turbulence in the near wake.
Protein-losing enteropathy remains a formidable and underrecognised complication following Fontan surgery, contributing significantly to morbidity and mortality among affected patients. Despite substantial progress in managing single-ventricle CHDs, protein-losing enteropathy persists as a major clinical challenge, particularly in resource-constrained environments where specialised diagnostic modalities are scarce. This manuscript discusses the prevalence, clinical presentation, diagnostic hurdles, and management of protein-losing enteropathy in post-Fontan patients, drawing from clinical experiences in Vietnam. Among 95 post-Fontan patients reviewed, the prevalence of protein-losing enteropathy was 4.2%, with considerable morbidity necessitating invasive interventions and, in some cases, resulting in mortality. Diagnostic limitations, including restricted access to alpha-1-antitrypsin clearance testing, highlight the urgent need for heightened clinical suspicion and pragmatic diagnostic approaches. We advocate for integrating low-cost, widely accessible screening measures, such as routine serum protein monitoring, into standard post-Fontan care protocols to enhance early detection and management of protein-losing enteropathy. Furthermore, we underscore the critical importance of global collaboration and multicentre research initiatives to address the worldwide burden of protein-losing enteropathy, facilitate resource-sharing, and develop evidence-based interventions. Coordinated international efforts are essential to closing diagnostic and treatment gaps, ultimately improving survival and quality of life for patients living with the Fontan circulation.
The temporal characteristics of fully localised turbulent bands in transitional channel flow remains unclear due to the difficulty in resolving the large length and time scales involved. Here, we tackle this problem by performing statistical lifetime studies in sufficiently large computational domains. The results show signs of stochastic memoryless decay of a fully localised band, suggesting a chaotic-saddle behaviour of the entire band as a coherent entity. Although the mean lifetime of a turbulent band was reported to increase with the band length, our data suggest that it saturates at a certain length. This saturation results in a characteristic lifetime for a fully developed band with a changing length due to the intermittent chipping and decay of turbulence at the upstream end. This memoryless behaviour is observed down to Reynolds number $Re=630$ in our study and we propose that the onset of the memoryless behaviour is in the range of $Re\simeq 620{-}630$. Our data also show that the time it takes for a perturbed flow to enter the saddle, i.e. to start behaving memorylessly, can be thousands of convective time units, which is comparable to the maximum achievable observation time in existing channel set-ups and may pose difficulties for experiments.
While the traditional Japanese diet has been suggested to increase blood pressure due to its high Na content, whether the contemporary Japanese diet is associated with blood pressure remains elusive. We developed a traditional Japanese diet score (nine items: white rice, miso soup, soy products, vegetables, mushrooms, seaweeds, fish, salty food and green tea) and a modified version by substituting white rice with whole-grain rice, reverse scoring for salty food and adding fruits, raw vegetables and dairy products using data from 12 213 employees from Japanese companies. Hypertension was defined as a blood pressure of 140/90 mmHg or more or the use of antihypertensive drugs. A multi-level Poisson regression model with a robust variance estimator was used to calculate prevalence ratios (PR) and 95 % CI while adjusting for covariates. The adjusted PR (95 % CI) of hypertension for the lowest through highest quartiles of the traditional Japanese diet score were 1·00 (reference), 0·94 (0·88, 1·02), 0·98 (0·90, 1·06) and 0·96 (0·90, 1·02), respectively (P for trend = 0·29), while those for the modified Japanese diet score were 1·00 (reference), 0·96 (0·94, 0·99), 0·95 (0·85, 1·05) and 0·94 (0·87, 1·01), respectively (P for trend = 0·10). In this cross-sectional study, close adherence to the traditional Japanese diet was not associated with the prevalence of hypertension, whereas there was a suggestion of an inverse association between the modified Japanese diet and the prevalence of hypertension.
In this study, we tackle the challenge of inferring the initial conditions of a Rayleigh–Taylor mixing zone for modelling purposes by analysing zero-dimensional (0-D) turbulent quantities measured at an unspecified time. This approach assesses the extent to which 0-D observations retain the memory of the flow, evaluating their effectiveness in determining initial conditions and, consequently, in predicting the flow’s evolution. To this end, we generated a comprehensive dataset of direct numerical simulations, focusing on miscible fluids with low density contrasts. The initial interface deformations in these simulations are characterised by an annular spectrum parametrised by four non-dimensional numbers. To study the sensitivity of 0-D turbulent quantities to initial perturbation distributions, we developed a surrogate model using a physics-informed neural network (PINN). This model enables computation of the Sobol indices for the turbulent quantities, disentangling the effects of the initial parameters on the growth of the mixing layer. Within a Bayesian framework, we employ a Markov chain Monte Carlo (MCMC) method to determine the posterior distributions of initial conditions and time, given various state variables. This analysis sheds light on inertial and diffusive trajectories, as well as the progressive loss of initial conditions memory during the transition to turbulence. Furthermore, it identifies which turbulent quantities serve as better predictors of Rayleigh–Taylor mixing zone dynamics by more effectively retaining the memory of the flow. By inferring initial conditions and forward propagating the maximum a posteriori (MAP) estimate, we propose a strategy for modelling the Rayleigh–Taylor transition to turbulence.
This article examines whether artificial intelligence (AI)-driven harm can be classified as moral or natural evil, or whether a new category – artificial evil – is needed. Should AI’s harm be seen as a product of human design, thus maintaining moral responsibility for its creators, or whether AI’s autonomous actions resemble natural evil, where harm arises unintentionally? The concept of artificial evil, combining elements of both moral and natural evil, is presented to better address this dilemma. Just as AI is still a form of intelligence (albeit non-biological), artificial evil would still be evil in the sense that it results in real harm or suffering – it is just that this harm is produced by AI systems rather than by nature or human moral agents directly. The discussion further extends into the realm of defence or theodicy, drawing parallels with the Free Will Defence, questioning if AI autonomy may be justified even if it results in harm, much like human free will. Ultimately, the article calls for a re-evaluation of our ethical frameworks and glossary of terms to address the emerging challenges of AI autonomy and its moral implications.
In England, the Civil Contingencies Act (Contingency Planning) Regulations 2005 require National Health Service (NHS) Trusts which provide hospital accommodation and services in relation to accidents or emergencies to conduct Emergency Preparedness, Resilience and Response (EPRR) exercises. The NHS England EPRR Framework specifies the minimum frequencies of these exercises. This review assessed the number of Trusts conducting exercises in accordance with these frequencies one year after the national NHS COVID-19 response was stepped down.
Methods
The outcome of interest was the number of Trusts having a record of conducting their most recent exercises in accordance with the minimum frequencies required by the NHS England EPRR Framework.
Results
Of the applicable 122 Trusts, 95 had a record of conducting a communication systems exercise, 115 had a record of conducting a table-top exercise, 106 had a record of conducting a live play exercise and 90 had a record of conducting a command post exercise in accordance with the minimum frequencies.
Conclusion
Over one fifth of Trusts did not have a record of conducting an EPRR communications systems exercise as required. This review may also be of interest to other state-level bodies which specify high level EPRR requirements to healthcare providers.
The goniadid polychaete Goniadella gracilis (Verrill, 1873), currently considered as a non-indigenous species in European waters, is reported for the first time in Italian waters of the Tyrrhenian and Ionian Seas. A detailed description of individuals of this species from the Mediterranean Sea is provided, including the pigmentation pattern of the specimens, which to our knowledge has never been reported before in literature. In addition, new molecular data, 18S and COI sequences, from Mediterranean specimens are presented and compared with data from the North-Eastern Atlantic. On the basis of the available evidence, the status of G. gracilis in the Mediterranean basin is discussed, and the species is here proposed to be considered as a questionable species in the area.