Sterile neutrino production via active-sterile oscillations: the quantum Zeno effect

We study several aspects of the kinetic approach to sterile neutrino production via active-sterile mixing. We obtain the neutrino propagator in the medium including self-energy corrections up to $\mathcal{O}(G^2_F)$, from which we extract the dispersion relations and damping rates of the propagating modes. The dispersion relations are the usual ones in terms of the index of refraction in the medium, and the damping rates are $\Gamma_1(k) = \Gamma_{aa}(k) \cos^2\theta_m(k); \Gamma_2(k) = \Gamma_{aa}(k) \sin^2\theta_m(k)$ where $\Gamma_{aa}(k)\propto G^2_F k T^4$ is the active neutrino scattering rate and $\theta_m(k)$ is the mixing angle in the medium. We provide a generalization of the transition probability in the \emph{medium from expectation values in the density matrix}: $P_{a\to s}(t) = \frac{\sin^22\theta_m}{4}[e^{-\Gamma_1t} + e^{-\Gamma_2 t}-2e^{-{1/2}(\Gamma_1+\Gamma_2)t} \cos\big(\Delta E t\big)]$ and study the conditions for its quantum Zeno suppression directly in real time. We find the general conditions for quantum Zeno suppression, which for $m_s\sim \textrm{keV}$ sterile neutrinos with $\sin2\theta \lesssim 10^{-3}$ \emph{may only be} fulfilled near an MSW resonance. We discuss the implications for sterile neutrino production and argue that in the early Universe the wide separation of relaxation scales far away from MSW resonances suggests the breakdown of the current kinetic approach.Comment: version to appear in JHE

Viral coinfections in hospitalized coronavirus disease 2019 patients recruited to the international severe acute respiratory and emerging infections consortium WHO clinical characterisation protocol UK study

Background We conducted this study to assess the prevalence of viral coinfection in a well characterized cohort of hospitalized coronavirus disease 2019 (COVID-19) patients and to investigate the impact of coinfection on disease severity. Methods Multiplex real-time polymerase chain reaction testing for endemic respiratory viruses was performed on upper respiratory tract samples from 1002 patients with COVID-19, aged <1 year to 102 years old, recruited to the International Severe Acute Respiratory and Emerging Infections Consortium WHO Clinical Characterisation Protocol UK study. Comprehensive demographic, clinical, and outcome data were collected prospectively up to 28 days post discharge. Results A coinfecting virus was detected in 20 (2.0%) participants. Multivariable analysis revealed no significant risk factors for coinfection, although this may be due to rarity of coinfection. Likewise, ordinal logistic regression analysis did not demonstrate a significant association between coinfection and increased disease severity. Conclusions Viral coinfection was rare among hospitalized COVID-19 patients in the United Kingdom during the first 18 months of the pandemic. With unbiased prospective sampling, we found no evidence of an association between viral coinfection and disease severity. Public health interventions disrupted normal seasonal transmission of respiratory viruses; relaxation of these measures mean it will be important to monitor the prevalence and impact of respiratory viral coinfections going forward

Delayed mucosal anti-viral responses despite robust peripheral inflammation in fatal COVID-19

Background While inflammatory and immune responses to SARS-CoV-2 infection in peripheral blood are extensively described, responses at the upper respiratory mucosal site of initial infection are relatively poorly defined. We sought to identify mucosal cytokine/chemokine signatures that distinguished COVID-19 severity categories, and relate these to disease progression and peripheral inflammation. Methods We measured 35 cytokines and chemokines in nasal samples from 274 patients hospitalised with COVID-19. Analysis considered the timing of sampling during disease, as either the early (0-5 days post-symptom onset) or late (6-20 days post-symptom onset). Results Patients that survived severe COVID-19 showed IFN-dominated mucosal immune responses (IFN-γ, CXCL10 and CXCL13) early in infection. These early mucosal responses were absent in patients that would progress to fatal disease despite equivalent SARS-CoV-2 viral load. Mucosal inflammation in later disease was dominated by IL-2, IL-10, IFN-γ, and IL-12p70, which scaled with severity but did not differentiate patients who would survive or succumb to disease. Cytokines and chemokines in the mucosa showed distinctions from responses evident in the peripheral blood, particularly during fatal disease. Conclusions Defective early mucosal anti-viral responses anticipate fatal COVID-19 but are not associated with viral load. Early mucosal immune responses may define the trajectory of severe COVID-19

Collective action in apartment building management in Hong Kong

With the expansion of the world\u27s population, apartment buildings have become popular, especially in metropolitan areas all over the world. Although apartment buildings could economize on the use of land, they may generate collective action problems among owners in the building management process, resulting in a “tragedy of the commons” in the urban environment. However, in the literature, there has been a lack of research that has investigated collective action problems in building management. In order to fill the gap, this study surveys collective action in apartment building management and proposes to utilize the institutional analysis and development (IAD) framework to analyze their problems. Making references to the literature on collective action and drawing from studies of common-pool resource management in particular, this paper classifies collective management actions into four categories, namely: 1) rules design, 2) rules enforcement, 3) maintenance decision making, and 4) performance monitoring. It further illustrates the application of the IAD model by empirically investigating a specific collective action—the appointment of a property management company (PMC). By using the logistic regression model for 2989 single block residential apartment buildings in 18 districts in Hong Kong, this paper will show that building condition, building location, the number of owners, and the presence of an owners\u27 organization each have a different impact on a property\u27s likelihood of appointing a PMC. The results of this paper should shed light on both collective action theory and building management

The effects of building management practices on residential property prices in Hong Kong

Building management and maintenance has gained its importance after a series of disastrous building-related incidents in Hong Kong. To facilitate the management of an apartment building, homeowners usually form an owners’ association among themselves and/or appoint an external property management agent (PMA) to manage the building on their behalf. Empirical studies found that the involvement of these bodies was conducive to a better-performing built environment, and that premium was added to better-performing properties. Yet, these studies often took the formation of owners’ association and engagement of external PMA in a building as dichotomous variables in exploratory models, and thus ignored the variations in the adopted building management practices in different buildings even with the same building management setting. Making use of the data collected from two previous research projects, a hedonic price analysis was carried out to study whether specific building management practices added value to the properties concerned. The analysis results indicated that properties in buildings with good documentations (eg keeping of as-built architectural drawings and incident records), thoughtful emergency planning (eg presence of emergency plan and regular fire drills) and property-all-risk insurance coverage were sold at a premium, ceteris paribus. Policy and practical implications then follow

Rapport and its managerial implications in FM service outsourcing relationships

In Hong Kong, client companies tend not to renew contracts with relationship partners and may change facilities management (FM) service providers on a frequent basis. This phenomenon is common in the FM industry. Inspired by the phenomenon of changing service providers, this study sheds light on a social relations perspective in outsourcing relationships and aims to investigate the factors that affect FM service outsourcing relationships. Open interviews with 20 FM managers were conducted, and the interview results were analysed with content analysis and coding methods. The empirical findings were interpreted on two levels. First, FM managers believe that rapport is an influential factor that affects FM service outsourcing relationships. Second, the courses in which the interviewees explain the manifestation of rapport and its significance reveal that common goals, shared values, trust, openness, and coordination are the factors that not only nurture the formation of rapport, but also have significant influences on social relations in the process of outsourcing. A framework has been developed to describe the conceptual relationships found in the empirical findings from the interviews. Eight guidelines have been outlined to indicate the managerial implications of this study

《專業樓宇檢查指引》第一冊: 1980年前落成住宅及商住大廈 Professional guide to building inspections: volume 1: pre-1980 residential & composite buildings in Hong Kong

本指引 - 並非單為強制驗樓計劃而設; • 屋宇署就該計劃已出版作業備考2012 - 而是涵蓋一般專業驗樓須知 - 第一冊配合該計劃，提供以下4+1項的檢查指引: • 外牆 • 結構 • 走火與防火結構 • 排水系統 及 • 僭建物 This Guide –Is not just for MBIS; •MBIS CoP 2012 is provided by BD (2012) –But for general building inspections; –Volume 1 is particularly drafted for the following 4+1 aspects： •External Elements & Others Physical Elements •Structural Elements •Fire Safety Elements •Drainage System and •UB

Open building implementation in high-rise residential buildings in Hong Kong

Aging of building stock is emerging. Open Building as a sustainable approach to deal with the problems associated with the aging housing stock is seldom applied in high-rise, densely populated built environment. With aims to identify the constraints and seek rooms for Open Building implementation in aforementioned context, a survey of 495 building layout plans from ten major housing estates in Hong Kong is conducted. The floor plans are analysed against the Open Building characteristics and criteria laid down by Tiuri (1998). Facts and obstacles of achieving Open Building in the territory are unearthed, and opportunities for implementation are then discussed. The layout and structure of the surveyed private residential buildings in Hong Kong are very much alike. They are in fact closed buildings without the capacity to adapt, so any change in user requirements cannot be accommodated easily. Implementing Open Building using flexible and green fittings remains a viable option that enables transformation in existing housing stock

Planning buildings for a high-rise environment in Hong Kong: a review of building appeal decisions (1st ed.)

This book examines 40 cases decided by the Building Appeal Board with reference to the overlapping jurisdictions of the Buildings, Lands and Planning authorities in controlling building development