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1421984 results in Open Access

Page 1309 of 71100

  • Elasto-inertial dissipation in particle-laden viscoelastic Taylor–Couette flow

  • Charles Carré, Masoud Moazzen, Tom Lacassagne, S. Amir Bahrani
  • Journal:
    Journal of Fluid Mechanics / Volume 997 / 25 October 2024
    Published online by Cambridge University Press:
    10 October 2024, A19

  • Many natural and industrial processes involve the flow of fluids made of solid particles suspended in non-Newtonian liquid matrices, which are challenging to control due to the fluid's nonlinear rheology. In the present work, a Taylor–Couette canonical system is used to investigate the flow of dilute to semi-dilute suspensions of neutrally buoyant spherical particles in highly elastic base polymer solutions. Friction measurement synchronized with direct flow visualization are combined to characterize the critical conditions for the onset of elasto-inertial instabilities, expected here as a direct transition to elasto-inertial turbulence (EIT). Adding a low particle volume fraction (${\leq }2\,\%$, dilute regime) does not affect the nature of the primary transition and reduces the critical Weissenberg number for the onset of EIT, despite a significant decrease in the apparent fluid elasticity. However, for particle volume fractions ${\geq }6\,\%$ (semi-dilute regime), EIT is no longer observed in the explored Reynolds range, suggesting an apparent relaminarization with yet not further decrease in fluid elasticity. Instead, a new regime, termed here elasto-inertial dissipative (EID), was uncovered. It originates from particle–particle interactions altering particle–polymer interactions and occurring under elasto-inertial conditions comparable to those of EIT. Increasing particle volume fraction in the semi-dilute regime and, in so, the particle contribution to the overall viscosity, delays the onset of EID similarly to what was observed previously for EIT in lower elasticity fluids. After this onset, a decrease in the pseudo-Nusselt number observed with increasing inertia and particle-to-polymer concentration ratio confirms a particle-induced alteration of energy transfer in the flow.

  • ROB volume 42 issue 7 Cover and Front matter

  • Journal:
    Robotica / Volume 42 / Issue 7 / July 2024
    Published online by Cambridge University Press:
    10 October 2024, pp. f1-f2
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  • Up and to the Right: The Development, Diffusion, and Impact of the Casey Life Cycle Model on Venture Capital Policy and Practice

  • M.R. Sauter
  • Journal:
    Enterprise & Society / Volume 26 / Issue 2 / June 2025
    Published online by Cambridge University Press:
    10 October 2024, pp. 457-484
    Print publication:
    June 2025
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  • This article contributes an account of a key moment in the development of venture capital. I argue the US Small Business Administration’s Task Force on Venture and Equity Capital for Small Business, established in 1976 and headed by William J. Casey, had an outsized impact on the development of modern venture capital and its close associations with the high technology sector. The Task Force’s 1977 report was influential in establishing both the figure of the venture capitalist and the business model of institutionally supported, limited partnership venture capital in the minds of policymakers, businesspeople, and the general public. This article traces the influence of one part of the Report: a prominently featured schematic model, entitled “Life Cycle of a New Enterprise: Model of a Growing and Successful Company, 1975-1976 Financial Market Conditions.” I trace the influence of the LCM as it spread through the developing high technology sector, as shown by its appearances in business publications, governmental reports, and congressional testimonies offered by industry leaders. The LCM was genericized away from its original authors and intentions, becoming part of the economic imaginary of the technology and innovation sector.

  • Diverse Disconnectedness: Homophily, Social Capital Inequality, and Student Experiences in Law School

  • Anthony Paik, Swethaa Ballakrishnen, Carole Silver, Steven Boutcher, Tanya Rouleau Whitworth
  • Journal:
    Law & Social Inquiry / Volume 50 / Issue 1 / February 2025
    Published online by Cambridge University Press:
    10 October 2024, pp. 90-128
    Print publication:
    February 2025
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  • Law school students are encouraged frequently to “network.” However, depending on demographic categories, they may have access to differently resourced social networks in law school. In this article, we draw from our mixed-methods research to explore this diversity of experience, its limitations of access, and the possible network inequalities that may limit the value of legal education to diverse students across different institutional contexts. Using survey and network data (N = 744), collected during the fall of 2019 from three law schools, as well as supplementary interview data (N = 55), we examined students’ social networks, the structures of these relationships, and their associations with law school satisfaction. We find that, while students tended to cluster based on shared characteristics (that is, race, gender, sexual identity, political orientation, religion, and age) and contexts (that is, type of program, section assignments), these emergent clusters produced disparities in satisfaction across racial categories. Homophilous networks were tied to satisfaction for Black and White students, but the same embeddedness was associated with lower satisfaction with law school for Asian and Latinx students. These results provide grounds for rethinking how diversity matters in law school and its implications for marginalized students’ experience and success.

  • Remembering Paulin Hountondji: The Zairian Interlude

  • Elisabeth Mudimbe-Boyi
  • Journal:
    African Studies Review / Volume 67 / Issue 2 / June 2024
    Published online by Cambridge University Press:
    10 October 2024, pp. 464-466
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  • Role of BT shunt in tetralogy of Fallot

  • Faiz Rasool, Amna Zafer Qureshi, Asim Khan, Tehmina Kazmi, Salman Ahmad Shah
  • Journal:
    Cardiology in the Young / Volume 34 / Issue 11 / November 2024
    Published online by Cambridge University Press:
    10 October 2024, pp. 2445-2448
  • Introduction:

    Modified Blalock-Taussig shunt (BT shunt) is a palliative operation used for cyanotic heart diseases with decreased pulmonary blood supply. The definitive management of tetralogy of Fallot (TOF) is total corrective surgery, but these patients can be palliated with BT shunt. In the modern world, the BT shunt is getting out of favour in patients with TOF. In this article, we will share our 5-year experience at our institute, which also shows a decreasing trend.

    Patients and methods:

    It is a retrospective study. Files of all the patients admitted in our department from January 2019 to December 2023 were reviewed. Age, weight, hospital stay, inotropic support duration, mechanical ventilation duration, and outcomes were studied.

    Results:

    From January 2019 to December 2023, 173 patients underwent BT shunt for TOF. The mean age was 31 months, and the mean weight was 9.3 kg. The overall mortality for BT shunt was 15% after BT shunt. Hypercyanotic spell not controlled by medical management was the most common indication for BT shunt in our setup. Most of the patients with hypercyanotic spells were also candidates for total correction but due to the emergency, BT shunt was performed.

    Conclusion:

    The role of BT shunt in patients with TOF is decreasing due to PDA/RVOT stenting, it is likely that the BT shunt in TOF will become a thing of the past in the future even in developing countries like ours.

  • Recurrent acute kidney injury is associated with delayed language development in infants with Congenital Heart Disease

  • Chetna K. Pande, Ayse Akcan-Arikan, Sonia Monteiro, Danielle Guffey, Faridis Serrano, Natasha Afonso, Kriti Puri, Barbara-Jo Achuff, Lara Shekerdemian, Lisa Noll
  • Journal:
    Cardiology in the Young / Volume 34 / Issue 11 / November 2024
    Published online by Cambridge University Press:
    10 October 2024, pp. 2377-2381
  • Objective:

    Neurodevelopmental delay is common in children who undergo surgery for Congenital Heart Disease (CHD) in infancy. Cardiac surgery associated acute kidney injury (CS-AKI) occurs frequently in the paediatric cardiac Intensive care unit (ICU). Cardiac surgery associated acute kidney injury (CS-AKI) is associated with worse neurodevelopmental scores and delay in cognitive, language, and motor domains in children with CHD. No known data exist regarding the association of CS-AKI and motor and language subscales. In this study, we explored the relationship between CS-AKI and receptive and expressive language, as well as gross and fine motor delay.

    Methods:

    This was a single centre retrospective observational cohort study. Children who underwent surgery for CHD and developed recurrent CS-AKI in the first year of life who had follow-up neurodevelopmental testing using the Bayley Scale of Infant Development Version III were included. Neurodevelopmental delay subscales assessed included: receptive and expressive language, fine and motor skills.

    Results:

    The study cohort included 203 children. Recurrent CS-AKI was significantly associated with lower scores in receptive and expressive language, as well as fine and gross motor on unadjusted analyses. On adjusted analyses, recurrent CS-AKI was significantly associated with severe receptive language delay.

    Conclusion:

    The independent association of recurrent CS-AKI with severe language delay in children who undergo surgery for CHD in infancy is novel. Our findings may contribute to the understanding of language impairment in this population. Further studies are required to better understand this relationship and any potentially modifiable factors.

  • Failure of China's COVID-19 health diplomacy in wining hearts and minds in Thailand and the Philippines: political efficacy constrained by local politics

  • Xirui Li, Zi Yang, Mingjiang Li
  • Journal:
    International Journal of Asian Studies / Volume 22 / Issue 1 / January 2025
    Published online by Cambridge University Press:
    10 October 2024, pp. 83-102
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  • Amid the COVID-19 pandemic, China extended significant medical aid to international communities, aiming to combat the virus's spread and foster global solidarity. However, despite the appreciation expressed by recipient governments for China's assistance, the general public's perception of China did not significantly improve. This prompts the question: why did China's COVID-19 health diplomacy fail to resonate with foreign audiences? This article delves into the cases of Thailand and the Philippines to argue that public perceptions of countries providing aid can be heavily influenced by domestic political dynamics, particularly when incumbent governments already face legitimacy challenges prior to aid delivery. By scrutinizing the implementation of China's aid and the state-to-state relations between China and incumbent governments, political opposition forces can exploit any shortcomings or missteps, placing blame squarely on the incumbents. Given the existing distrust toward incumbent governments, the public is more inclined to accept messages propagated by opposition groups, thereby hindering any positive shift in perception toward China. This perspective complements existing research that predominantly focuses on the diplomatic strategies of donor countries, suggesting instead that the domestic politics of host countries play a pivotal role in shaping the effectiveness of foreign nations' efforts to cultivate favorable images among foreign audiences.

  • Phase segregation of a partially miscible binary mixture subjected to an external force field

  • Chih-Che Chueh, Roberto Mauri, Antonio Bertei
  • Journal:
    Journal of Fluid Mechanics / Volume 997 / 25 October 2024
    Published online by Cambridge University Press:
    10 October 2024, A29
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  • When a partially miscible binary mixture is quenched below its critical temperature, it transitions from its single-phase to a two-phase region, undergoing phase separation. The processes of formation and coalescence of droplets are driven by diffusive and convective phenomena, taking place isotropically in the system. The application of an external force field, which exerts a different contribution on the two species, breaks the symmetry of phase separation, leading to the segregation of two equilibrated phases separated by a single interface. This study investigates the dynamics of phase segregation under an external force. The effects of various force magnitudes, captured by the Bond number, in both high- and low-viscosity mixtures, distinguished by different fluidity numbers, are quantified via numerical simulations by using the phase field model. The intricate dynamics of formation, floating and coalescence of droplets towards complete segregation are described along with the quantification of the segregation time, revealing different patterns for high and low Bond numbers. Results show that in none of the cases, formation and floating can be regarded as strictly serial processes. A universal scaling between segregation time, Bond number, fluidity number and domain size is not possible, with a power-law dependence emerging only under the diffusion-dominated regime.

  • Steady solutions of quasi-geostrophic flows in basins, gulfs and channels on a β-plane

  • Jeasson F. Gonzalez, L. Zavala Sansón, F. Graef
  • Journal:
    Journal of Fluid Mechanics / Volume 997 / 25 October 2024
    Published online by Cambridge University Press:
    10 October 2024, A24

  • Nonlinear steady solutions of the barotropic quasi-geostrophic equation in basins, gulfs and channels on a $\beta$-plane are presented. The domains are rectangular with arbitrary aspect ratios. The two-dimensional solutions assume a linear relationship between the potential vorticity $q$ and the stream function $\psi$. The sign of the slope in the linear $q\unicode{x2013}\psi$ relationship defines two broad sets of solutions. For a positive slope, the solutions in a closed basin correspond to the inertial gyres derived by Fofonoff in 1954. The negative slope solutions consist of normal modes that can be resonant. For gulfs and channels, the conditions at the open boundaries are almost arbitrary flows entering or leaving the domain. Such conditions allow a great variety of solutions in the interior, characterised mainly by arrays of vortices with alternate signs. Several examples are presented and discussed.

  • Social Capital, Social Health Insurance, and Health-related Quality of Life among People with Chronic Disease: Cultural and Ideational Perspectives

  • Padmore Adusei Amoah, Samuel Ampadu Oteng
  • Journal:
    Social Policy and Society , First View
    Published online by Cambridge University Press:
    10 October 2024, pp. 1-18
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  • This study extends debates on implications of informal welfare for population health and well-being. It examines whether cultural and ideational precepts such as social capital, affect enrolment in National Health Insurance Scheme (NHIS) among people living with chronic disease(s) in Ghana. It also explores how NHIS enrolment explains the association between social capital and health-related quality of life (HRQoL) using empirical data from five regions in Ghana. Results indicate that bonding social capital was associated with HRQoL. Bridging and linking social capital were positively and negatively associated with enrolment in NHIS, respectively. Enrolment in the NHIS explained the relationships of trust in neighbours, bridging and linking social capital with HRQoL. Thus, while social capital can improve HRQoL of people living with chronic disease(s), it does so by, among others, influencing their participation in formal health protective services. Culturally driven informal welfare resources are critical to making formal programmes meaningful to people.

  • Toward ab initio molecular simulation of reacting air: Mach 15 air flow over a blunt wedge

  • Paolo Valentini, Maninder S. Grover, Nicholas J. Bisek
  • Journal:
    Journal of Fluid Mechanics / Volume 997 / 25 October 2024
    Published online by Cambridge University Press:
    10 October 2024, A27

  • We present a Mach 15 air flow over a blunt two-dimensional wedge simulated using the direct molecular simulation method. As electronically excited states are not modelled, the resulting air mixture around the wedge contains the electronic ground states only, namely ${\rm N}_2(\text {X}^1 \varSigma _g^{+})$, ${\rm O}_2(\text {X}^3 \varSigma _g^{-})$, ${\rm NO}(\text {X}^2\varPi _r)$, ${\rm N}(^4{\rm S})$ and ${\rm O}(^3{\rm P})$. All the potential energy surfaces (PESs) that are used to model the various interactions between air particles are ab initio, with two notable exceptions, namely ${\rm N}_2+{\rm NO}$ and ${\rm O}_2+{\rm NO}$. At the selected free-stream conditions, strong vibrational non-equilibrium is observed in the shock layer. The flow is characterized by significant chemical activity, with near-complete oxygen dissociation, considerable formation of NO and minimal molecular nitrogen dissociation. Complex mass diffusion kinetics, driven by composition, temperature and pressure gradients, are identified in the shock layer. All these physical phenomena are directly coupled to, and responsible for, the mechanics of the gas flow and are all solely traceable to the PESs’ inputs, without the need for any thermochemical models, mixing rules or constitutive laws for transport properties. Because the flow is entirely at near-continuum conditions, it is a gas-phase thermophysics benchmark that is useful to enhance the fidelity of continuum models used in computational fluid dynamics of hypersonic flows.

  • Longitudinal echocardiographic parameters for evaluation of pulmonary hypertension in preterm infants with very low birth weight

  • Kwannapas Saengsin, Varangthip Khuwuthayakorn, Yupada Prongprot, Rekwan Sittiwangkul, Phichayut Phinyo, Krittai Tanasombatkul, Munranee Langu
  • Journal:
    Cardiology in the Young / Volume 34 / Issue 11 / November 2024
    Published online by Cambridge University Press:
    10 October 2024, pp. 2388-2397
  • Background:

    Echocardiography is essential for the evaluation of pulmonary hypertension. We determined the feasible quantitative parameter for screening and monitoring pulmonary hypertension in preterm infants.

    Methods:

    This secondary analysis of a prospective cohort single-centre study was conducted between August 2019 and September 2020. Serial echocardiography was performed 7 and 28 days after birth and at 36 weeks postmenstrual age. The data of infants who developed pulmonary hypertension at 36 weeks postmenstrual age were compared with those without pulmonary hypertension. We also modelled the parameters’ trend and performed an interaction test using multi-level Gaussian regression.

    Results:

    Out of 30 infants enrolled in the study, 79 echocardiograms were analysed. Left ventricular eccentric index was obtainable in all infants, while tricuspid jet velocity was measurable in 44.1%. Left ventricular eccentric index correlated well with tricuspid regurgitation jet velocity (r = 0.77, P < 0.001). Six infants were diagnosed with newly developed or persistent pulmonary hypertension at 36 weeks postmenstrual age. Serial left ventricular eccentric index showed a significantly different increasing trend in the pulmonary hypertension group (change per day: +0.004; P = 0.090) from the decreasing trend among a non-pulmonary hypertension group (change per day: –0.001; P = 0.041) (P for interaction = 0.007). Right ventricular systolic function and right ventricular isovolumic systolic velocity revealed a reducing trend in the pulmonary hypertension group, which was different from the improving trend in non-pulmonary hypertension infants. Infants with low current weight, low postmenstrual age, and requiring high-flow oxygen therapy at day 28 of life trended to increase the risk of late pulmonary hypertension.

    Conclusion:

    Left ventricular eccentric index and right ventricular isovolumic systolic velocity were feasible for assessing pulmonary hypertension and should be incorporated into pulmonary hypertension evaluation. Serial left ventricular eccentric index and right ventricular isovolumic systolic velocity may help predict late pulmonary hypertension and early detection of right ventricular dysfunction.

  • Global longitudinal strain is a surrogate marker for time constant of isovolumic relaxation in post-Fontan operation patients with single right ventricle and preserved ejection fraction

  • Kota Suzuki, Masaki Nii, Takehiro Tanabe, Mizuhiko Ishigaki, Keisuke Sato, Jun Yoshimoto, Sung-Hae Kim, Norie Mitsushita, Yasuhiko Tanaka
  • Journal:
    Cardiology in the Young / Volume 34 / Issue 12 / December 2024
    Published online by Cambridge University Press:
    10 October 2024, pp. 2587-2595
  • Background:

    The time constant of isovolumic relaxation is an established index of ventricular relaxation, a major component of diastolic function, even in a single right ventricle. However, the specific echocardiographic parameters for estimating diastolic dysfunction are insufficient for a single right ventricle. This study aimed to investigate the echocardiographic indices associated with time constant of isovolumic relaxation in post-Fontan operation patients with a single right ventricle.

    Methods:

    We included 39 patients with hypoplastic left heart syndrome after Fontan operation with an ejection fraction ≥45% and preserved valve function. First, the correlation between echocardiographic parameters and time constant of isovolumic relaxation was examined, and partial correlation coefficients were calculated using age and heart rate as covariates. Next, univariate regression analysis was performed using time constant of isovolumic relaxation as the objective variable and echocardiographic parameters as independent variables, followed by multivariate regression analysis incorporating parameters with p < 0.10.

    Results:

    Among the echocardiographic parameters, global longitudinal strain correlated most strongly with time constant of isovolumic relaxation (r = 0.778, p < 0.001). This was consistent with the partial correlation coefficients (r = 0.707, p < 0.001). Using stepwise multivariate regression analysis, only global longitudinal strain was found to be an independent predictor of time constant of isovolumic relaxation (adjusted R2 = 0.551).

    Conclusions:

    Global longitudinal strain could be used as a surrogate marker of time constant of isovolumic relaxation, an invasive indicator of relaxation impairment, in post-Fontan operation patients with a single right ventricle, preserved ejection fraction, and valve function.

Page 1309 of 71100