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حكاية غريق
تدور الرواية حول حكاية غريق أمضى عشرة أيام عائما على متن زورق دون طعام أو شراب. ونصب بطلا قوميا، ثم تهاوت عليه قبلات ملكات الجمال ؛ فأصبح ثريا بفضل ما قام بتصويره من إعلانات. وعقب نشر تفاصيل الحكاية تفجرت الفضيحة ؛ حيث كان الفوز والتكريم والثروة من نصيب الغريق، أما الصحفي الذي أخذ على عاتقه جمع أطراف الحكاية، فقد كان مصيره النفي والتشريد.
BOOK
Ice breaking by a high-speed water jet impact
Ice breaking has become one of the main problems faced by ships and other equipment operating in an ice-covered water region. New methods are always being pursued and studied to improve ice-breaking capabilities and efficiencies. Based on the strong damage capability, a high-speed water jet impact is proposed to be used to break an ice plate in contact with water. A series of experiments of water jet impacting ice were performed in a transparent water tank, where the water jets at tens of metres per second were generated by a home-made device and circular ice plates of various thicknesses and scales were produced in a cold room. The entire evolution of the water jet and ice was recorded by two high-speed cameras from the top and front views simultaneously. The focus was the responses of the ice plate, such as crack development and breakup, under the high-speed water jet loads, which involved compressible pressure ${P_1}$ and incompressible pressure ${P_2}$. According to the main cause and crack development sequence, it was found that the damage of the ice could be roughly divided into five patterns. On this basis, the effects of water jet strength, ice thickness, ice plate size and boundary conditions were also investigated. Experiments validated the ice-breaking capability of the high-speed water jet, which could be a new auxiliary ice-breaking method in the future.
Journal Article
Impulsive impact of a twin hull
An impulsively starting motion of two cylindrical bodies floating on a free liquid surface is considered. The shape of the cross-section of each body and the distance between them are arbitrary. The integral hodograph method is advanced to derive the complex velocity potential defined in a rectangular parameter region in terms of the elliptic quasi-doubly periodic Jacobi theta functions. A system of singular integral equations in the velocity magnitude on the free surface and in the slope of the wetted part of each body is derived using the kinematic boundary condition, which is then solved numerically. The velocity field, the pressure impulse on the bodies and the added mass coefficients of each body immediately after the impact are determined in a wide range of distances between the bodies and for cross-sectional shapes such as the flat plate and half-circle.
Journal Article
Depression and post-traumatic stress during major social unrest in Hong Kong: a 10-year prospective cohort study
Hong Kong has been embroiled in increasingly violent social unrest since June, 2019. We examined the associated population mental health burden, risk factors, and health-care needs.
In a population-based prospective cohort, adult participants aged 18 years or older were assessed at nine timepoints from 2009. Probable depression was measured using the Patient Health Questionnaire-9 (score ≥10) and suspected post-traumatic stress disorder (PTSD) by the PTSD Checklist—Civilian Version (score ≥14), plus direct exposure to traumatic events related to the ongoing social unrest. We used multivariable logistic regression to identify factors associated with both outcomes, adjusting for doctor-diagnosed depression or anxiety disorders before the unrest. On the basis of routine service statistics and respondents' intention to seek professional care, we projected the number of additional ambulatory specialist psychiatric visits required.
After the two baseline surveys, we followed up random subsets of 1213–1736 adults at each timepoint. Probable depression was reported by 11·2% (95% CI 9·8–12·7) of participants in 2019, compared with 1·9% (1·6–2·1) during 2009–14 and 6·5% (5·3–7·6) in 2017 after the Occupy Central Movement and before the current unrest. Prevalence of suspected PTSD in 2019 was estimated to be 12·8% (11·2–14·4). Age, sex, educational attainment, or household income were not associated with either outcome, whereas heavy social media use (≥2 h per day) was associated with both. Political attitude or protest participation was not associated with probable depression, but neutrality towards the extradition bill approximately halved the risk of suspected PTSD. Family support mitigated against probable depression. We estimated that the mental health burden identified would translate into roughly an excess 12% service requirement to the public sector queue or equivalent.
We have identified a major mental health burden during the social unrest in Hong Kong, which will require substantial increases in service surge capacity. Health-care and social care professionals should be vigilant in recognising possible mental health sequelae. In a world of increasing unrest, our findings might have implications for service planning to better protect population mental health globally.
Research Grants Council, University Grants Committee of Hong Kong, Hong Kong Jockey Club Charities Trust.
Journal Article
pLARmEB: integration of least angle regression with empirical Bayes for multilocus genome-wide association studies
Multilocus genome-wide association studies (GWAS) have become the state-of-the-art procedure to identify quantitative trait nucleotides (QTNs) associated with complex traits. However, implementation of multilocus model in GWAS is still difficult. In this study, we integrated least angle regression with empirical Bayes to perform multilocus GWAS under polygenic background control. We used an algorithm of model transformation that whitened the covariance matrix of the polygenic matrix K and environmental noise. Markers on one chromosome were included simultaneously in a multilocus model and least angle regression was used to select the most potentially associated single-nucleotide polymorphisms (SNPs), whereas the markers on the other chromosomes were used to calculate kinship matrix as polygenic background control. The selected SNPs in multilocus model were further detected for their association with the trait by empirical Bayes and likelihood ratio test. We herein refer to this method as the pLARmEB (polygenic-background-control-based least angle regression plus empirical Bayes). Results from simulation studies showed that pLARmEB was more powerful in QTN detection and more accurate in QTN effect estimation, had less false positive rate and required less computing time than Bayesian hierarchical generalized linear model, efficient mixed model association (EMMA) and least angle regression plus empirical Bayes. pLARmEB, multilocus random-SNP-effect mixed linear model and fast multilocus random-SNP-effect EMMA methods had almost equal power of QTN detection in simulation experiments. However, only pLARmEB identified 48 previously reported genes for 7 flowering time-related traits in Arabidopsis thaliana.
Journal Article
Effect of closure of live poultry markets on poultry-to-person transmission of avian influenza A H7N9 virus: an ecological study
Transmission of the novel avian influenza A H7N9 virus seems to be predominantly between poultry and people. In the major Chinese cities of Shanghai, Hangzhou, Huzhou, and Nanjing—where most human cases of infection have occurred—live poultry markets (LPMs) were closed in April, 2013, soon after the initial outbreak, as a precautionary public health measure. Our objective was to quantify the effect of LPM closure in these cities on poultry-to-person transmission of avian influenza A H7N9 virus.
We obtained information about every laboratory-confirmed human case of avian influenza A H7N9 virus infection reported in the four cities by June 7, 2013, from a database built by the Chinese Center for Disease Control and Prevention. We used data for age, sex, location, residence type (rural or urban area), and dates of illness onset. We obtained information about LPMs from official sources. We constructed a statistical model to explain the patterns in incidence of cases reported in each city on the basis of the assumption of a constant force of infection before LPM closure, and a different constant force of infection after closure. We fitted the model with Markov chain Monte Carlo methods.
85 human cases of avian influenza A H7N9 virus infection were reported in Shanghai, Hangzhou, Huzhou, and Nanjing by June 7, 2013, of which 60 were included in our main analysis. Closure of LPMs reduced the mean daily number of infections by 99% (95% credibility interval 93–100%) in Shanghai, by 99% (92–100%) in Hangzhou, by 97% (68–100%) in Huzhou, and by 97% (81–100%) in Nanjing. Because LPMs were the predominant source of exposure to avian influenza A H7N9 virus for confirmed cases in these cities, we estimated that the mean incubation period was 3·3 days (1·4–5·7).
LPM closures were effective in the control of human risk of avian influenza A H7N9 virus infection in the spring of 2013. In the short term, LPM closure should be rapidly implemented in areas where the virus is identified in live poultry or people. In the long term, evidence-based discussions and deliberations about the role of market rest days and central slaughtering of all live poultry should be renewed.
Ministry of Science and Technology, China; Research Fund for the Control of Infectious Disease; Hong Kong University Grants Committee; China–US Collaborative Program on Emerging and Re-emerging Infectious Diseases; Harvard Center for Communicable Disease Dynamics; and the US National Institutes of Health.
Journal Article
Network interventions for managing the COVID-19 pandemic and sustaining economy
Sustaining economic activities while curbing the number of new coronavirus disease 2019 (COVID-19) cases until effective vaccines or treatments become available is a major public health and policy challenge. In this paper, we use agent-based simulations of a network-based susceptible−exposed−infectious−recovered (SEIR) model to investigate two network intervention strategies for mitigating the spread of transmission while maintaining economic activities. In the simulations, we assume that people engage in group activities in multiple sectors (e.g., going to work, going to a local grocery store), where they interact with others in the same group and potentially become infected. In the first strategy, each group is divided into two subgroups (e.g., a group of customers can only go to the grocery store in the morning, while another separate group of customers can only go in the afternoon). In the second strategy, we balance the number of group members across different groups within the same sector (e.g., every grocery store has the same number of customers). The simulation results show that the dividing groups strategy substantially reduces transmission, and the joint implementation of the two strategies could effectively bring the spread of transmission under control (i.e., effective reproduction number ≈ 1.0).
Journal Article
Impulsive impact of a body fully submerged in an open container
An impulsively starting motion of a cylindrical body submerged below a calm water surface in an open container of arbitrary shape is considered. This work generalizes the case of an infinite-depth liquid studied by Semenov et al. (J. Fluid Mech., vol. 919, 2021, R4). Particular attention is paid to the interaction between the body, the free surface and the container. The integral hodograph method is employed to derive the complex velocity potential in a parameter plane. The boundary-value problem is reduced to a system of integral equations, which is solved numerically. The velocity field, the pressure impulse on the body and the container wall and the added mass just after the impact are determined for a wide range of depths of submergence and container geometries and for various cross-sectional shapes of the body, such as a flat plate, a circle and a rectangle.
Journal Article
Nonlinear ice sheet/liquid interaction in a channel with an obstruction
The interaction between the flow in a channel with an obstruction on the bottom and an elastic sheet representing the ice covering the liquid is considered for the case of steady flow. The mathematical model based on the velocity potential theory and the theory of thin elastic shells fully accounts for the nonlinear boundary conditions at the elastic sheet/liquid interface and on the bottom of the channel. The integral hodograph method is employed to derive the complex velocity potential of the flow, which contains the velocity magnitude at the interface in explicit form. This allows one to formulate the coupled ice/liquid interaction problem and reduce it to a system of nonlinear equations in the unknown magnitude of the velocity at the interface. Case studies are carried out for a semi-circular obstruction on the bottom of the channel. Three flow regimes are studied: a subcritical regime, for which the interface deflection decays upstream and downstream; an ice supercritical and channel subcritical regime, for which two waves of different lengths may exist; and a channel supercritical regime, for which the elastic wave is found to extend downstream to infinity. All these regimes are in full agreement with the dispersion equation. The obtained results demonstrate a strongly nonlinear interaction between the elastic and the gravity wave near the first critical Froude number where their lengths approach each other. The interface shape, the bending moment and the pressure along the interface are presented for wide ranges of the Froude number and the obstruction height.
Journal Article
Mental Health, Risk Factors, and Social Media Use During the COVID-19 Epidemic and Cordon Sanitaire Among the Community and Health Professionals in Wuhan, China: Cross-Sectional Survey
The mental health consequences of the coronavirus disease (COVID-19) pandemic, community-wide interventions, and social media use during a pandemic are unclear. The first and most draconian interventions have been implemented in Wuhan, China, and these countermeasures have been increasingly deployed by countries around the world.
The aim of this study was to examine risk factors, including the use of social media, for probable anxiety and depression in the community and among health professionals in the epicenter, Wuhan, China.
We conducted an online survey via WeChat, the most widely used social media platform in China, which was administered to 1577 community-based adults and 214 health professionals in Wuhan. Probable anxiety and probable depression were assessed by the validated Generalized Anxiety Disorder-2 (cutoff ≥3) and Patient Health Questionnaire-2 (cutoff ≥3), respectively. A multivariable logistic regression analysis was used to examine factors associated with probable anxiety and probable depression.
Of the 1577 community-based adults, about one-fifth of respondents reported probable anxiety (n=376, 23.84%, 95% CI 21.8-26.0) and probable depression (n=303, 19.21%, 95% CI 17.3-21.2). Similarly, of the 214 health professionals, about one-fifth of surveyed health professionals reported probable anxiety (n=47, 22.0%, 95% CI 16.6-28.1) or probable depression (n=41, 19.2%, 95% CI 14.1-25.1). Around one-third of community-based adults and health professionals spent ≥2 hours daily on COVID-19 news via social media. Close contact with individuals with COVID-19 and spending ≥2 hours daily on COVID-19 news via social media were associated with probable anxiety and depression in community-based adults. Social support was associated with less probable anxiety and depression in both health professionals and community-based adults.
The internet could be harnessed for telemedicine and restoring daily routines, yet caution is warranted toward spending excessive time searching for COVID-19 news on social media given the infodemic and emotional contagion through online social networks. Online platforms may be used to monitor the toll of the pandemic on mental health.
Journal Article