Spontaneous Lorentz and Diffeomorphism Violation, Massive Modes, and Gravity

Theories with spontaneous local Lorentz and diffeomorphism violation contain massless Nambu-Goldstone modes, which arise as field excitations in the minimum of the symmetry-breaking potential. If the shape of the potential also allows excitations above the minimum, then an alternative gravitational Higgs mechanism can occur in which massive modes involving the metric appear. The origin and basic properties of the massive modes are addressed in the general context involving an arbitrary tensor vacuum value. Special attention is given to the case of bumblebee models, which are gravitationally coupled vector theories with spontaneous local Lorentz and diffeomorphism violation. Mode expansions are presented in both local and spacetime frames, revealing the Nambu-Goldstone and massive modes via decomposition of the metric and bumblebee fields, and the associated symmetry properties and gauge fixing are discussed. The class of bumblebee models with kinetic terms of the Maxwell form is used as a focus for more detailed study. The nature of the associated conservation laws and the interpretation as a candidate alternative to Einstein-Maxwell theory are investigated. Explicit examples involving smooth and Lagrange-multiplier potentials are studied to illustrate features of the massive modes, including their origin, nature, dispersion laws, and effects on gravitational interactions. In the weak static limit, the massive mode and Lagrange-multiplier fields are found to modify the Newton and Coulomb potentials. The nature and implications of these modifications are examined.Comment: 27 pages two-column REVTeX, accepted in Physical Review

Bis[1,3(η3)-all­yl][μ-2(η4)-1,3-bis­(di­phenyl­phosphino)-2,4-diphenyl­cyclo­buta-1,3-diene-1:3κ2 P:P′]dichlorido-1κCl,3κCl-[2(η5)-isopropyl­cyclo­penta­dien­yl]-2-cobalt(I)-1,3-dipalladium(II) dichloro­methane solvate

In the title complex, [CoPd2(C3H5)2(C8H11)Cl2(C40H30P2)]·CH2Cl2, the CoI atom is sandwiched between the cyclo­penta­dienyl and cyclo­butadiene rings. The two diphenyl­phosphine substituents of the cyclo­butadiene ring are situated opposite to each other and bind two PdII atoms, which are additionally coordinated by a chloride ion and the three C atoms of an allyl ligand, forming a distorted planar coordination environment. The Cl atoms of the dichloro­methane solvent mol­ecule (equal occupancies) and one C atom and its attached H atom of each of the allyl ligands (occupancies 0.55:0.45) are disordered

{μ-2-[(Benzothia­zol-2-yl-2κN)hydrazonomethyl-2κN]-6-methoxy­phenolato-1:2κ3 O 1,O 6:O 1}{2-[(benzo­thia­zol-2-yl-1κN)hydrazonomethyl-1κN]-6-methoxy­phenolato-1κO 1}(methanol-2κO)(nitrato-2κO)dicopper(II) nitrate

The title complex, [Cu2(C15H12N3O2S)2(NO3)(CH3OH)]NO3, has two CuII centres coordinated by two deprotonated 2-[(benzothia­zol-2-yl)hydrazonometh­yl]-6-methoxy­phenol ligands, a methanol mol­ecule and a nitrate ion. Both CuII centres are penta­coordinated in a distorted square-pyramidal fashion. The crystal structure is stabilized by N—H⋯O and O—H⋯O hydrogen bonds

KINEMATICS ANALYSIS OF SNOWSHOE RUNNING GAIT ON SAND

The purpose of this study was to ,identify the kinematics characteristics of snowshoeing on sand under different running velocity in elite Hong Kong mentally handicapped athletes. Four athletes were asked to perform the snowshoe running on sand. Kinematics parameters included single leg support time, flight time, stride frequency, velocity of center of gravity (CG), vertical displacement of CG, cycle length, str'ide length, thigh and 'knee angle under different running velocities were measured. The repeated t-test was employed to examine the differences of above kinematics parameters in different velocities of snowshoeing. The results showed that there were significant differences in stride frequency, vertical displacement of CG, cycle length, and stride length between different velocities in snowshoeing on sand

Lessons Learned from the Pandemic: The Need for Further Development of Information and Communication Technology Enhanced Mental Health Services in Hong Kong

The COVID-19 pandemic not only leads to more mental health problems because of its stressful nature but it also increases the challenges of providing services for people with mental health needs in the community This paper discusses the limitations of conventional mental health services and the potential use of information and communication technology ICT to increase service accessibility in the context of Hong Kong We review some of the local studies and services and explain why ICT-enhanced services should play a more important role in the local service system especially when there is a lack of resources and a need for social physical distancing Some future development directions have been highlighted We argue that it is necessary to further discuss the use of ICT in mental health services and develop more evidence-based web-based resources that can be incorporated into the local service syste

Coordinated Management of COVID-19 Response: Lessons From Whole-of-Society and Whole-of-Health Strategies in Wuhan, China.

Background: The outbreak of novel coronavirus disease 2019 (COVID-19) has been challenging globally following the scarcity of medical resources after a surge in demand. As the pandemic continues, the question remains on how to accomplish more with the existing resources and improve the efficiency of existing health care delivery systems worldwide. In this study, we reviewed the experience from Wuhan - the first city to experience a COVID-19 outbreak - that has presently shown evidence for efficient and effective local control of the epidemic. Material and Methods: We performed a retrospective qualitative study based on the document analysis of COVID-19-related materials and interviews with first-line people in Wuhan. Results: We extracted two themes (the evolution of Wuhan's prevention and control strategies on COVID-19 and corresponding effectiveness) and four sub-themes (routine prevention and control period, exploration period of targeted prevention and control strategies, mature period of prevention and control strategies, and recovery period). How Wuhan combatted COVID-19 through multi-tiered and multi-sectoral collaboration, overcoming its fragmented, hospital-centered, and treatment-dominated healthcare system, was illustrated and summarized. Conclusion: Four lessons for COVID-19 prevention and control were summarized: (a) Engage the communities and primary care not only in supporting but also in screening and controlling, and retain community and primary care as among the first line of COVID-19 defense; (b) Extend and stratify the existing health care delivery system; (c) Integrate person-centered integrated care into the whole coordination; and (d) Delink the revenue relationship between doctors and patients and safeguard the free-will of physicians when treating patients

COMPARISON OF SNOWSHOEING KNIEMATICS ON GRASSLAND AND SAND COURSE – PILOT STUDY

The purpose of this study was to compare the kinematics characteristics of snowshoeing on grassland and sand course in elite Hong Kong mentally handicapped athletes. Two athletes were asked to perform the snowshoeing on grassland and sand course with their maximal speed. Kinematics parameters included single leg support time, flight time, stride frequency, velocity of center of gravity (CG), vertical displacement of CG, cycle length, thigh and knee angle were measured. The results of low extremity kinematics supported that there were differences in movement pattern of snowshoeing between grassland and sand course

Tell me, show me, involve me: Supercharging Collaborative Diagnosis with Augmented Reality

Augmented reality has been broadly employed to help remote individuals communicate and coordinate. In this study, we develop and test a model that explains how augmented reality can facilitate collaborative diagnosis on an unexpected technical breakdown involving two complete strangers. Drawing on the affordance theory, we integrate the dual-task interference literature to reveal frustration valence and arousal as the underlying mechanisms. We tested our hypothesis in a laboratory experiment involving a custom-built augmented reality environment and physiological measurements. Overall, this study contributes to information system literature, human-computer interaction literature, and dual-task interference research by unearthing the effects of augmented reality characteristics on enhancing collaborative diagnosis performance