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The stability of free jets is one of the fundamental problems that has driven the development of new theoretical and numerical methods in fluid mechanics. Extensive research has focused on the convective instabilities that characterise their elusive dynamics. However, in real-world configurations, free jets are often confined by solid walls which may exhibit different degrees of flexibility. The present paper presents, for the first time, evidence that even slightly flexible nozzles can lead to global instabilities. To show it, we adopted the classical tools of linear stability analysis, solving the fluid–structure interaction (FSI) problem by an arbitrary Lagrangian–Eulerian method, formulating a monolithic three-field problem. The investigation of the base flow properties reveals the effect of the Reynolds number, based on the bulk velocity and channel height, in the range $[50,200]$ and of the plate stiffness on the nozzle deformation and on the jet flow development. Exploiting an idea first proposed by Luchini and Charru, we develop an ad hoc quasi-one-dimensional model capable of predicting the displacement of elastic boundaries even for large displacements. The stability and sensitivity analysis shows that the interaction of the flow with the flexible structure leads to two categories of globally unstable modes: sinuous (in-phase) modes and varicose (out-of-phase) modes. All the results presented have been cross-checked with direct numerical simulations of the nonlinear FSI system, revealing that the instabilities correspond to supercritical bifurcations. This work has significant implications for many natural and industrial phenomena where a jet is produced by a compliant nozzle.
In 1934 C.V. Raman, Nobel Prize laureate in physics, founded the Indian Academy of Sciences in an attempt to create a single unified national scientific society for India. Instead, due to actions of Raman, the Royal Society and other British and Indian scientists, three distinct Indian science academies emerged and have persisted to the present day. Taking place against a background of British imperialism, Indian nationalism and scientific internationalism, Raman’s actions provide a fascinating case study of scientific production and the shaping of scientific networks in (British) India. This paper scrutinizes this hitherto unexplored late imperial stage of the Indian scientific landscape and highlights the versatile role of British imperialism in influencing the founding and functioning of the Indian Academy of Sciences under Raman. The latter’s national and international career and leadership testify to a complex relationship where the personal and the political became intertwined with science in (British) India.
We develop a representation theory of categories as a means to explore characteristic structures in algebra. Characteristic structures play a critical role in isomorphism testing of groups and algebras, and their construction and description often rely on specific knowledge of the parent object and its automorphisms. In many cases, questions of reproducibility and comparison arise. Here we present a categorical framework that addresses these questions. We prove that every characteristic structure is the image of a functor equipped with a natural transformation. This shifts the local description in the parent object to a global one in the ambient category. Through constructions in representation theory, such as tensor products, we can combine characteristic structure across multiple categories. Our results are constructive and stated in the language of a constructive type theory which facilitates their implementation in proof checkers.
The dynamics of information diffusion on social media platforms vary significantly between individual communities and the broader population. This study explores and compares the differences between community-based interventions and population-wide approaches in adjusting the spread of information. We first examine the temporal dynamics of social media groups, assessing their behavior through metrics such as time-dependent posts and retweets. Using functional data analysis, we investigate Twitter activities related to incidents such as the Skripal/Novichok case. We present three ways to quantify disparities between communities and uncover the strategies used by each group to promote specific narratives. We then compare the impact of targeted, community-based interventions with that of broader, population-wide responses in shaping the diffusion of information. Through this analysis, we identify key differences in how communities engage with and amplify information, revealing distinct patterns in the diffusion process. Our findings provide a comparative framework for understanding the relative consequences of different intervention strategies, offering insights into how targeted and broad approaches influence public discourse across social media platforms.
What explains China’s decision to sign an alliance treaty with North Korea in 1961? The treaty was redundant to deter the United States and South Korea because China had credibly established its resolve and capability to defend North Korea after the outbreak of the Korean War in June 1950. The treaty even increased the risk of China’s entrapment in a Korean conflict. This article develops a triangular theory of alliance formation to show that China’s signing of the treaty was intended to drive a wedge between North Korea and the Soviet Union, not to deter South Korea and the United States. China was thus willing to incur more risk to neutralize North Korea from a pro-Soviet position. This article tests the theory by process tracing events in the China–North Korea–Soviet Union triangle from 1948 to 1961 with a plausibility probe of the China–North Vietnam–Soviet Union triangle from 1954 to 1965. The article concludes with implications for the contemporary China–North Korea–Russia bloc and the study of alliance politics in the Asian context.
This research examines occupants’ ability to detect lighting differences as a function of proximity to the illuminated area. By understanding how proximity influences light difference detection, energy-saving lighting design techniques can be developed that do not negatively impact the appearance of architectural interiors. The experiment examined vertical surface illumination, hypothesizing that vertical illuminance difference detection thresholds would increase with greater spatial separation from the observer, regardless of gaze conditions. Illuminance was selected as the accepted metric for assessing lighting, aligning with commonly used standards, such as the European Standard and the Australian/New Zealand Standard. Eighty participants viewed a 10.0 m × 2.4 m vertical wall with five sections using a five-alternative forced choice method to identify the dimmer section. Eight experimental conditions manipulated participant position and gaze, with each subject completing 10 trials for 20 lighting conditions. Participants’ ability to detect lighting differences was very poor for wall end portions, regardless of position or gaze. Results suggest vertical illuminance in temporarily unoccupied areas can be reduced by at least 10% without affecting perceived illumination quality. Greater reductions of 25% can be achieved in room corners. These findings provide a foundation for future research into illuminance optimization across all surfaces within architectural spaces.
As data are becoming increasingly important resources for municipal administrations in the context of urban development, formalization of urban data governance (DG) is considered a prerequisite to systematic municipal data practice for the common good. Unlike for larger cities, it is unclear how common such formalized DG is in rural districts and small towns. We therefore mapped the current status quo in small municipalities in Germany as a case exemplifying the broader phenomenon. We systematically searched online for policy documents on DG in all metropolitan regions, all rural districts, and a quota sample of nearly a sixth of all German small towns. We then performed content analysis of the identified documents along predefined categories of urban development. Results show that hardly any small towns dispose of relevant policy documents. Rural districts are somewhat more active in formally defining DG. Identified policy documents tend to address mostly economic activities, social infrastructure, and demography, whereas Housing and Urban design and public space are among the least mentioned categories of urban development.
Received scholarship by H.T. Huang and others has argued that the high incidence of lactose intolerance in East Asians discouraged the Chinese from adopting dairy on health grounds before the twentieth century. However, such wisdom overlooks Chinese medical literature that prescribes fresh dairy to treat chronic diarrhea. This essay considers what famed healer Sun Simiao (581–682) had to say about the uses of dairy products in treating digestive ailments. Towards this end, we consider the Essential Formulas Worth a Thousand Pieces of Gold for Emergencies (Beiji qianjin yaofang 備急千金要方) and the Supplemental Formulas Worth a Thousand Pieces of Gold (Qianjin yifang 千金翼方). We then compare the uses of dairy in the Sun corpus to both contemporary and earlier texts. Our analysis shows that Tang-dynasty (618–907) healers regarded milk products as generally good for the gut, and, in some cases, recommended using fresh dairy for cases of flux.
Mental health conditions among youths are increasing rapidly, taking into consideration their biological, psychological and social development in the time of technological advancement with its associated challenges. Therefore, this study examined the psychometric properties of eight mental health scales among Ghanaian youth. A total of 708 youths (62.1% females; 10–29 years) from junior high schools, senior high schools and a university were recruited to respond to measures on depression, anxiety, somatic symptoms, obsessive–compulsive symptoms, insomnia, smartphone application-based addiction, internet addiction, life satisfaction, stress and cognitive fatigue. Confirmatory factor analysis (CFA) and Pearson’s r were used to analyse the data. The findings indicated acceptable CFA fit for all scales (comparative fit index [CFI] >0.9, Tucker–Lewis index [TLI] >0.9, root mean square error of approximation [RMSEA] <0.08 and standardized root mean square residual [SRMR] <0.08), and internal reliability was satisfactory (Cronbach’s α = 0.774–0.868 and McDonald’s ω = 0.775–0.870). Correlation analyses showed significant relationships between all the measures except for life satisfaction and internet addiction, and stress and life satisfaction. Both the CFA indices and correlation analyses indicate that all the mental health measures demonstrate acceptable initial evidence of reliability and construct validity.
Depression is underrecognized in primary care, which is a barrier to treatment. For the last decade, Zimbabwe has invested in increasing access to depression treatment within primary healthcare. This study describes depression recognition by nurses and referral to treatment in four primary care clinics in Zimbabwe. Research staff screened 200 patients after they attended a primary care visit at a study clinic. They assessed depression using the PHQ-9 and assessed depression and/or anxiety using the Shona Symptoms Questionnaire (SSQ-14). Medical records were examined for depression and/or anxiety diagnoses. Positive depression and anxiety screens were compared with nurse documentation. 69.5% of participants were women and 56.5% were living with HIV. 6.0% had a PHQ-9 score ≥11, indicative of depression, and 22.0% had an SSQ score ≥9, indicative of depression and/or anxiety. None of the patients who screened positive for probable depression and/or anxiety were recognized by nurses. Nurses who saw the patients in the sample were surveyed. Most had not received formal training on mental health in primary care (mhGAP) prior to patient data collection. Despite efforts to expand depression treatment in Zimbabwe, individuals with probable depression were unrecognized by nurses, though nurses offered some care for other mental health conditions.
The account in Odyssey Book 9 of Odysseus’ safe arrival by ship on ‘Goat Island’ off the coast of the land of the Cyclopes, the elaborate description of the geography of the island itself, and even the specific detail of Odysseus and his shipmates slaughtering with bows and spears 108 + 1 wild goats all work together to serve as an ‘anticipatory doublet’ of the account in the second half of the epic of Odysseus’ safe arrival by ship on the island of Ithaca, the elaborate description of the geography of the island itself, and even the specific detail of Odysseus and his comrades slaughtering with bow and spears the 108 arrogant suitors + 1 treacherous goatherd.
Anxiety and depression are common among patients with wounds, impairing healing and quality of life. This study estimated their prevalence and associated factors across community-and referral care facilities in Taabo, Côte d’Ivoire.
Method
An exploratory cross-sectional study included 157 patients aged ≥16 years with wounds, recruited consecutively between October and December 2023. Anxiety and depression were assessed using the Hospital Anxiety and Depression Scale (HADS). Demographic and wound characteristics were collected. Associations were examined using Chi-square or Fisher’s exact tests, and multivariate logistic regression adjusted for age and gender identified independent factors.
Results
Anxiety and depression scores were lowest at household level (6.0 and 5.4) compared to health centre (7.4 and 6.9) and general hospital (9.1 and 9.8). Prevalence was 25.4% and 18.5% at the household level, 49.0% and 55.1% at health centre and 77.4% and 84.9% at the general hospital. Anxiety was independently associated with older age and female gender, while depression was associated to female gender, larger wound size (≥5 cm) and referral-level care.
Conclusion
Early household-based wound care by CHWs was associated with lower prevalence of anxiety and depression. Integrating psychosocial support into wound management, particularly at referral facilities, may reduce the mental health burden.
Seed banking is the preferred strategy for the ex situ conservation of Seed Plants, due to its effectiveness in preserving whole organisms and genetic diversity at relatively low cost. However, not all seeds are suitable for long-term storage, particularly those classified as recalcitrant or desiccation-sensitive, which limits the applicability of seed banking for certain species. In Chile, the proportion and identification of recalcitrant species remain largely unknown. In this study, we investigated the storage behaviour of potentially recalcitrant species and evaluated two predictive models of seed recalcitrance based on morphological, ecological and taxonomic variables. One of these models was subsequently employed to estimate the incidence of recalcitrance among Chilean tree species. Most of the species assessed exhibited clear sensitivity to desiccation. The Seed Coat Ratio–Seed Mass model showed the highest precision and recall. Nevertheless, models incorporating ecological and taxonomic variables also performed well at the genus level. Using a Boosted Regression Tree model refined through experimental data and literature review, we estimate that 19% (n = 11) of Chilean tree species possess recalcitrant seeds. Among the tree and shrub species confirmed as recalcitrant in this study (n = 17), 71% are endemic to Chile (n = 12), and 53% are categorized as threatened (n = 9). These findings provide a stronger basis for prioritizing alternative ex situ conservation strategies beyond seed banking for species with recalcitrant seeds.
Surety supervision is one of the most onerous bail conditions imposed on legally innocent people pretrial. Sureties are generally family or friends who promise a sum of money and agree to supervise the accused, enforcing conditions and reporting non-compliance. Drawing on data from 32 in-depth interviews with individuals who have acted as sureties, this paper examines the complex, contradictory, and damaging implications of exploiting personal relationships for the state’s surveillance and monitoring interests. We argue that by placing sureties in such a role, the court stresses the accused’s social relationships by transforming the accused’s support network into an apparatus of state control. Sureties describe exploited relational bonds and ruptured relationships, insisting they will never act as a surety again. We conclude by outlining directions for reform, including changing the nature of surety supervision, decriminalization and developing bail supervision programs.
In recent decades, support for the far right has surged in many countries. One common explanation for this is that far-right support is a backlash against left-wing governments and their policies. We investigate the causal effect of the partisan make-up of governments on the electoral results of far-right parties. Evidence from over-time comparative data and a quasi-experimental analysis based on a regression discontinuity design in Spain indicates that far-right parties benefit electorally when the current government is on the left. In further analyses, we employ a novel regression discontinuity design (RDD)-based sampling strategy to examine original individual-level survey data from Spanish municipalities close to the discontinuity cutoff. These data show that the likely mechanism underlying the backlash effect is an ideological shift to the right among the electorate when left-wing parties govern. Overall, the far right benefits more when the mainstream left governs than when the mainstream right does.