•Corona virus,•Reported and unreported cases,•Isolation, quarantine, public closings;•Epidemic mathematical model
We model the COVID-19 coronavirus epidemics in China, South Korea, Italy, France, ...Germany and the United Kingdom. We identify the early phase of the epidemics, when the number of cases grows exponentially, before government implementation of major control measures. We identify the next phase of the epidemics, when these social measures result in a time-dependent exponentially decreasing number of cases. We use reported case data, both asymptomatic and symptomatic, to model the transmission dynamics. We also incorporate into the transmission dynamics unreported cases. We construct our models with comprehensive consideration of the identification of model parameters. A key feature of our model is the evaluation of the timing and magnitude of implementation of major public policies restricting social movement. We project forward in time the development of the epidemics in these countries based on our model analysis.
At the beginning of a COVID-19 infection, there is a period of time known as the exposed or latency period, before an infected person is capable of transmitting the infection to another person. We ...develop two differential equations models to account for this period. The first is a model that incorporates infected persons in the exposed class, before transmission is possible. The second is a model that incorporates a time delay in infected persons, before transmission is possible. We apply both models to the COVID-19 epidemic in China. We estimate the epidemiological parameters in the models, such as the transmission rate and the basic reproductive number, using data of reported cases. We thus evaluate the role of the exposed or latency period in the dynamics of a COVID-19 epidemic.
Low‐field MRI: An MR physics perspective Marques, José P.; Simonis, Frank F.J.; Webb, Andrew G.
Journal of magnetic resonance imaging,
June 2019, Letnik:
49, Številka:
6
Journal Article
Recenzirano
Odprti dostop
Historically, clinical MRI started with main magnetic field strengths in the ∼0.05–0.35T range. In the past 40 years there have been considerable developments in MRI hardware, with one of the primary ...ones being the trend to higher magnetic fields. While resulting in large improvements in data quality and diagnostic value, such developments have meant that conventional systems at 1.5 and 3T remain relatively expensive pieces of medical imaging equipment, and are out of the financial reach for much of the world. In this review we describe the current state‐of‐the‐art of low‐field systems (defined as 0.25–1T), both with respect to its low cost, low foot‐print, and subject accessibility. Furthermore, we discuss how low field could potentially benefit from many of the developments that have occurred in higher‐field MRI.
In the first section, the signal‐to‐noise ratio (SNR) dependence on the static magnetic field and its impact on the achievable contrast, resolution, and acquisition times are discussed from a theoretical perspective. In the second section, developments in hardware (eg, magnet, gradient, and RF coils) used both in experimental low‐field scanners and also those that are currently in the market are reviewed. In the final section the potential roles of new acquisition readouts, motion tracking, and image reconstruction strategies, currently being developed primarily at higher fields, are presented.
Level of Evidence: 5
Technical Efficacy Stage: 1
J. Magn. Reson. Imaging 2019.
Numerous problems in space physics and astrophysics require a detailed understanding of the transport and dissipation of low-frequency turbulence in an expanding magnetized flow. We employ a ...scale-separated decomposition of the incompressible MHD equations (based on an Elssasser description) and develop a moment hierarchy to describe the transport of the total energy density in fluctuations, the cross-helicity, the energy difference, and correlation lengths corresponding to forward- and backward-propagating modes and to the energy difference. The dissipation terms for the various transport equations are derived. One-point closure schemes are utilized. The technical elements of this work that distinguish it from previous studies are (1) the inclusion of the large-scale background inhomogeneous Alfvenic velocity VA at a level of detail greater than before, (2) the introduction of a tractable slow timescale closure to eliminate high-frequency interference terms that is likely to prove a useful approximation for practical problems related to the transport of turbulence in an inhomogeneous flow such as the solar wind or solar corona, and finally, (3) we develop a simplified phenomenology for the energy difference or equivalently residual energy that may be useful for practical applications. This yields a coupled system of six equations that describes the transport of turbulence in inhomogeneous sub-Alfvenic and super-Alfvenic flows. The turbulence transport equations are quasi-linear in their spatial evolution operators and nonlinear in the dissipation terms, making the model equations relatively tractable to analysis.
The past decade has provided critical information about the cytoplasmic innate immune sensing pathway of cyclic GMP-AMP synthase (cGAS) and stimulator of interferon genes (STING). These discoveries ...have broadened our understanding of the interconnectedness of the cGAS-STING pathway with autophagy, programmed cell death, Rig-I-like receptor (RLR) signaling, DNA independent interferon induction, and how this pathway responds to RNA virus infection. These advances highlight how multiple families of RNA viruses are restricted by and in turn have mechanisms to inhibit cGAS-STING dependent type-I interferon (IFN-I) induction. Here we review recent discoveries of how and why the cGAS-STING pathway responds to infection with RNA viruses, novel findings of RNA viral antagonism of the cGAS-STING innate immune sensing pathway, and attempt to provide context for a shift in thinking as to how critical this DNA sensing pathway is for the restriction of a wide range of RNA viruses.
Figure 3 in this Journal of Medical Entomology article is central to the authors' warning about an exploding white-tailed deer population but conflicts in important aspects with the relevant deer ...research. Among other problems, it shows a 60% increase in the white-tailed deer density from 1500 to 2020 when the research consensus is that the population is about the same. It shows an exploding population from 2000 to 2020 without supporting data when the population peaked around the year 2000 according to evidence-based research.
Abstract
Aims
The Valve Academic Research Consortium (VARC), founded in 2010, was intended to (i) identify appropriate clinical endpoints and (ii) standardize definitions of these endpoints for ...transcatheter and surgical aortic valve clinical trials. Rapid evolution of the field, including the emergence of new complications, expanding clinical indications, and novel therapy strategies have mandated further refinement and expansion of these definitions to ensure clinical relevance. This document provides an update of the most appropriate clinical endpoint definitions to be used in the conduct of transcatheter and surgical aortic valve clinical research.
Methods and results
Several years after the publication of the VARC-2 manuscript, an in-person meeting was held involving over 50 independent clinical experts representing several professional societies, academic research organizations, the US Food and Drug Administration (FDA), and industry representatives to (i) evaluate utilization of VARC endpoint definitions in clinical research, (ii) discuss the scope of this focused update, and (iii) review and revise specific clinical endpoint definitions. A writing committee of independent experts was convened and subsequently met to further address outstanding issues. There were ongoing discussions with FDA and many experts to develop a new classification schema for bioprosthetic valve dysfunction and failure. Overall, this multi-disciplinary process has resulted in important recommendations for data reporting, clinical research methods, and updated endpoint definitions. New definitions or modifications of existing definitions are being proposed for repeat hospitalizations, access site-related complications, bleeding events, conduction disturbances, cardiac structural complications, and bioprosthetic valve dysfunction and failure (including valve leaflet thickening and thrombosis). A more granular 5-class grading scheme for paravalvular regurgitation (PVR) is being proposed to help refine the assessment of PVR. Finally, more specific recommendations on quality-of-life assessments have been included, which have been targeted to specific clinical study designs.
Conclusions
Acknowledging the dynamic and evolving nature of less-invasive aortic valve therapies, further refinements of clinical research processes are required. The adoption of these updated and newly proposed VARC-3 endpoints and definitions will ensure homogenous event reporting, accurate adjudication, and appropriate comparisons of clinical research studies involving devices and new therapeutic strategies.
Graphical Abstract
Voyager 1 observed Kolmogorov-like (k−5/3) compressible turbulence just upwind of the heliopause. Subsequent measurements by Voyager 1 further from the heliopause revealed that the observed ...fluctuations were now fully incompressible, with a k−5/3 spectrum that was essentially identical to that of the earlier compressible spectrum. Zank et al. showed that only compressible fast magnetosonic modes could be transmitted from the inner heliosheath into the very local interstellar medium (VLISM), and could exhibit a k−5/3 spectrum. We show here that the small plasma beta VLISM admits three-wave interactions between a fast magnetosonic mode, a zero-frequency mode, and an Alfvén wave. The fast magnetosonic mode is converted to an incompressible Alfvén (or zero-frequency) mode with wavenumber almost identical to that of the initial compressible fast mode. The initial compressible and generated incompressible spectra are essentially identical. For the wavelength range observed by Voyager 1, we estimate that compressible fast modes are fully mode-converted to incompressible fluctuations within ∼10 au of the heliopause. We suggest that the VLISM magnetic field spectrum is a superposition of a higher amplitude ∼k−5/3 spectrum of heliospheric origin with an estimated correlation length ∼30 au, having a minimum wavenumber ∼(100)−1 (au)−1, and a lower amplitude (possibly local) ISM k−5/3 spectrum, the latter possessing an outer scale ≥2 pc. We suggest that the transmission of compressible turbulence from an inner asterosheath into the local circumstellar interstellar medium surrounding a star, and the subsequent mode conversion to incompressible turbulence, may be a general mechanism by which stars drive turbulence in the interstellar medium.
Surgical aortic valve replacement (SAVR) has long been the mainstay of therapy for severe aortic stenosis. However, transcatheter aortic valve replacement (TAVR) is now generally accepted as the new ...standard of care for patients with symptomatic aortic stenosis who are not candidates for open surgery. Arguably TAVR may also be a preferred alternative to SAVR in carefully selected high-risk, but still operable, patients in whom morbidity and mortality may be reduced. Although TAVR outcomes continue to improve, concerns remain with respect to vascular injury, stroke, paravalvular regurgitation, and valve durability. However, it seems likely that with ongoing refinement of transcatheter valve systems, techniques, and patient selection TAVR is becoming an increasingly appealing option for a much broader range of patients. Randomized trials and ongoing surveillance will play an important role as we enter a new era of rigorous clinical evaluation for minimally invasive therapies for structural heart disease.
Abstract Primary biliary cirrhosis (PBC), primary sclerosing cholangitis (PSC) and autoimmune hepatitis (AIH) represent the three major hepatic autoimmune conditions. Patient morbidity and mortality ...remain high across these three diseases, and an unmet need for rational therapy exists. Disease understanding has focused on combining clinical and laboratory based science to provide better insights into the joint host and environmental factors necessary for the initiation, and perpetuation, of hepato-biliary inflammation. Twin studies, family studies, population studies and an inter-relationship with other autoimmune phenomena suggest a genetic component to risk for each disease. Until recently, understanding of this genetic risk has been limited to HLA haplotypes. Associations with risk-conferring and protective HLA haplotypes are present in all three diseases. Over the last few years, genome-wide association studies (GWAS), and related genetic association studies, have greatly increased understanding of the genetic risk signature of these three diseases and autoimmunity in general. Here we consider the rationale for GWAS in general and with specific reference to hepatic autoimmunity. We consider the process of GWAS, and highlight major findings to date. Potential functional implications of key findings are discussed including the IL-12/STAT4 pathway in PBC and the CD28/IL-2 pathway in PSC. We describe the marked pleiotropy demonstrated by PBC and PSC, which is consistent with other autoimmune diseases. Further, we focus on specific gene associations including SH2B3 , which is common to all three diseases, and FUT2 in PSC, which represents a link between environment and genetics. We review attempts to translate GWAS findings into basic laboratory models including in vivo systems and highlight where clinical observations relate to genetics. Finally we describe deficiencies in GWAS to date and consider future study of genetics in hepatic autoimmunity.
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