Prethermal Stability of Eigenstates under High Frequency Floquet Driving.

Systems subject to high-frequency driving exhibit Floquet prethermalization, that is, they heat exponentially slowly on a timescale that is large in the drive frequency, τ_{h}∼exp(ω). Nonetheless, local observables can decay much faster via energy conserving processes, which are expected to cause a rapid decay in the fidelity of an initial state. Here we show instead that the fidelities of eigenstates of the time-averaged Hamiltonian, H_{0}, display an exponentially long lifetime over a wide range of frequencies-even as generic initial states decay rapidly. When H_{0} has quantum scars, or highly excited eigenstates of low entanglement, this leads to long-lived nonthermal behavior of local observables in certain initial states. We present a two-channel theory describing the fidelity decay time τ_{f}: the interzone channel causes fidelity decay through energy absorption, i.e., coupling across Floquet zones, and ties τ_{f} to the slow heating timescale, while the intrazone channel causes hybridization between states in the same Floquet zone. Our work informs the robustness of experimental approaches for using Floquet engineering to generate interesting many-body Hamiltonians, with and without scars.

How Does a Locally Constrained Quantum System Localize?

At low energy, the dynamics of excitations of many physical systems are locally constrained. Examples include frustrated antiferromagnets, fractional quantum Hall fluids, and Rydberg atoms in the blockaded regime. Can such locally constrained systems be fully many-body localized? In this Letter, we answer this question affirmatively and elucidate the structure of the accompanying quasilocal integrals of motion. By studying disordered spin chains subject to a projection constraint in the z direction, we show that full many-body localization (MBL) is stable at strong z-field disorder and identify a new mechanism of localization through resonance at strong transverse disorder. However, MBL is not guaranteed; the constraints can "frustrate" the tendency of the spins to align with the transverse fields and lead to full thermalization or criticality. We further provide evidence that the transition is discontinuous in local observables with large sample-to-sample variations. Our dynamical phase diagram is accessible in current Rydberg atomic experiments which realize programmable constrained Ising Hamiltonians.

Review article: quality of follow-up care for anaphylaxis in the emergency department.

The prevalence of allergic disorders is rising, with a corresponding increase in patients presenting to an ED with anaphylaxis. Appropriate follow up is required for patients with anaphylaxis. We reviewed two potential performance indicators for the quality of post-discharge care: (i) the rate of self-injectable adrenaline prescription; and (ii) the referral rate for follow-up care with allergy specialists. A search of Cochrane Library, PubMed and Google Scholar was performed using the following initial search string: anaphylaxis and 'emergency department'. We considered any (interventional or observational design) study assessing post-discharge care in anaphylaxis, measured by either adrenaline self-injection prescription or allergist referral. Subjects were patients with (suspected) anaphylaxis or severe allergic reaction, with no age limit. This review summarises findings from 16 relevant papers, all retrospective analyses of post-discharge care for anaphylaxis. Weighted arithmetic means were calculated for rates of prescription of adrenaline auto-injector and referral to an allergist following admission to an ED in patients with (suspected) anaphylaxis or severe allergic reaction. Prescription rates for self-injected adrenaline at the time of discharge following anaphylaxis varied from 0% to 68%, with a mean of 44%. Allergist referral rates ranged from 0% to 84%, with a mean of 33%. This review demonstrates that there is room for improvement in post-discharge care for patients who present to the ED with an anaphylactic reaction.

Little evidence of human infection with equine influenza during the 2007 epizootic, Queensland, Australia.

BACKGROUND: Equine influenza virus (EIV) is considered enzootic in Europe (except Iceland), Asia, North Africa, and North and South America. When EIV outbreaks occur they may severely impact the equine and tourist industries. Australia faced its first EIV outbreak beginning in August of 2007. The outbreak was concentrated in New South Wales and Queensland, with more than 1400 confirmed EIV infections in horses during the first month. Rapid response from the equine industry and the federal government was successful and Australia was declared free from EIV by the end of 2007. OBJECTIVES: This cross-sectional study was designed to examine associations between exposure to EIV-infected horses and evidence of EIV infection in humans. STUDY DESIGN: Employing informed consent, between October 2007 and April 2008, 100 subjects (89 with horse exposures and 11 non-exposed) were enrolled during equine events and at the University of the Sunshine Coast. All subjects provided a blood sample and were asked to complete an online questionnaire including health history, animal exposure and demographic information. Sera samples were tested for the presence of antibodies against two H3N8 EIV strains using microneutralization, hemagglutination inhibition, and enzyme-linked lectin assays. RESULTS: Evidence for H3N8 infection was sparse, with only 9 study participants having any indication of H3N8 infection and the seroreactivity seen was low and easily explained by cross-reactions against human influenza strains or vaccines. CONCLUSIONS: These data provide little evidence to support the premise that EIV infections occurred among humans exposed to EIV-infected horses during the 2007 Australian epizootic.

The impact of a short-term iyengar yoga program on the health and well-being of physically inactive older adults.

BACKGROUND: With the current challenge of rapidly aging populations, practices such as yoga may help older adults stay physically active, healthy, and fulfilled. METHODS: The impact of an 8-week Iyengar yoga program on the holistic health and well-being of physically inactive people aged 55 years and over was assessed. Thirty-eight older adults (mean age 73.21±8.38 years; 19 intervention, 19 control) engaged in either twice-weekly yoga classes or continued their usual daily routines. Physical health measures were muscle strength, active range of motion, respiratory function (FEV1), resting blood pressure, and immune function (salivary IgA and lysozyme). Self-perceived general, physical, mental, spiritual, and social health and well-being were assessed with the Life's Odyssey Questionnaire and the SF12v2™ Health Survey. RESULTS: Muscle strength, active range of motion, physical well-being, and aspects of mental well-being (emotional well-being and self-care) improved significantly in the yoga group (p<.05). Median changes in most of these variables were also significantly different from those in the control group. CONCLUSIONS: Participation in Iyengar yoga programs by older people is beneficial for health and well-being, and greater availability of such programs could improve quality of life.

Blood monocytes, myeloid dendritic cells and the cytokines interleukin (IL)-7 and IL-15 maintain human CD4+ T memory cells with mixed helper/regulatory function.

The number and function of human T cells in the periphery are regulated by homeostatic signals received from antigen-presenting cells (APCs) and the common gamma chain (gammac) cytokines interleukin (IL)-7 and IL-15. We found that, in the absence of introduced antigen, blood monocytes or myeloid dendritic cells (MDCs) in the presence of IL-7 and IL-15 (IL-7/IL-15) can regulate CD4(+) T memory (Tm) cell numbers by polyclonal cell proliferation. The dynamics of CD4(+) Tm cell proliferation, in the presence of IL-7/IL-15, was dependent on contact with MDCs and to a lesser extent on contact with monocytes. IL-7/IL-15 either alone or combined with monocytes or MDCs enhanced the proportion of CD4(+) Tm cells with activated and effector phenotype and diminished the helper function of CD4(+) Tm cells. These CD4(+) Tm cells, preconditioned with IL-7/IL-15 alone or with monocytes or MDCs and IL-7/IL-15, reduced T cell-dependent immunoglobulin M (IgM) and IgG responses. This appeared to be a contact-dependent effect involving a reduction in antibody-producing CD27(+) B memory cells, but contact-independent suppression by soluble factors also contributed to the antibody-producing capacity of CD27(+) B memory cells. These results indicate that blood monocytes, MDCs and the cytokines IL-7/IL-15 contribute to homeostasis of CD4(+) Tm cells by regulating their number, activation state and helper/suppressor (regulatory) function. In healthy individuals, this mode of regulating CD4(+) Tm cell homeostasis may provide a basis for the control of autoimmune responses.