10,022 research outputs found
The solar dynamic radiator with a historical perspective
A historical perspective on pumped-fluid loop space radiators provides a basis for the design of the Space Station Solar Dynamic (SD) power module radiator. SD power modules, capable of generating 25 kW (electrical) each, are planned for growth in Station power requirements. The Brayton cycle SD module configuration incorporates a pumped-fluid loop radiator that must reject up to 99 kW (thermal). The thermal/hydraulic design conditions in combination with required radiator orientation and packaging envelope form a unique set of constraints as compared to previous pumped-fluid loop radiator systems. Nevertheless, past program successes have demonstrated a technology base that can be applied to the SD radiator development program to ensure a low risk, low cost system
Improving the clinical value and utility of CGM systems: issues and recommendations: a joint statement of the European Association for the Study of Diabetes and the American Diabetes Association Diabetes Technology Working Group
The first systems for continuous glucose monitoring (CGM) became available over 15 years ago. Many then believed CGM would revolutionize the use of intensive insulin therapy in diabetes; however, progress toward that vision has been gradual. Although increasing, the proportion of individuals using CGM rather than conventional systems for self-monitoring of blood glucose on a daily basis is still low in most parts of the world. Barriers to uptake include cost, measurement reliability (particularly with earlier-generation systems), human factors issues, lack of a standardized format for displaying results, and uncertainty on how best to use CGM data to make therapeutic decisions. This Scientific Statement makes recommendations for systemic improvements in clinical use and regulatory (pre- and postmarketing) handling of CGM devices. The aim is to improve safety and efficacy in order to support the advancement of the technology in achieving its potential to improve quality of life and health outcomes for more people with diabetes
Improving the clinical value and utility of CGM systems: issues and recommendations : a joint statement of the European Association for the Study of Diabetes and the American Diabetes Association Diabetes Technology Working Group
The first systems for continuous glucose monitoring (CGM) became available over 15Â years ago. Many then believed CGM would revolutionise the use of intensive insulin therapy in diabetes; however, progress towards that vision has been gradual. Although increasing, the proportion of individuals using CGM rather than conventional systems for self-monitoring of blood glucose on a daily basis is still low in most parts of the world. Barriers to uptake include cost, measurement reliability (particularly with earlier-generation systems), human factors issues, lack of a standardised format for displaying results and uncertainty on how best to use CGM data to make therapeutic decisions. This scientific statement makes recommendations for systemic improvements in clinical use and regulatory (pre- and postmarketing) handling of CGM devices. The aim is to improve safety and efficacy in order to support the advancement of the technology in achieving its potential to improve quality of life and health outcomes for more people with diabetes
Non-Markovian Dynamics and Entanglement of Two-level Atoms in a Common Field
We derive the stochastic equations and consider the non-Markovian dynamics of
a system of multiple two-level atoms in a common quantum field. We make only
the dipole approximation for the atoms and assume weak atom-field interactions.
From these assumptions we use a combination of non-secular open- and
closed-system perturbation theory, and we abstain from any additional
approximation schemes. These more accurate solutions are necessary to explore
several regimes: in particular, near-resonance dynamics and low-temperature
behavior. In detuned atomic systems, small variations in the system energy
levels engender timescales which, in general, cannot be safely ignored, as
would be the case in the rotating-wave approximation (RWA). More problematic
are the second-order solutions, which, as has been recently pointed out, cannot
be accurately calculated using any second-order perturbative master equation,
whether RWA, Born-Markov, Redfield, etc.. This latter problem, which applies to
all perturbative open-system master equations, has a profound effect upon
calculation of entanglement at low temperatures. We find that even at zero
temperature all initial states will undergo finite-time disentanglement
(sometimes termed "sudden death"), in contrast to previous work. We also use
our solution, without invoking RWA, to characterize the necessary conditions
for Dickie subradiance at finite temperature. We find that the subradiant
states fall into two categories at finite temperature: one that is temperature
independent and one that acquires temperature dependence. With the RWA there is
no temperature dependence in any case.Comment: 17 pages, 13 figures, v2 updated references, v3 clarified results and
corrected renormalization, v4 further clarified results and new Fig. 8-1
Particle dynamics inside shocks in Hamilton-Jacobi equations
Characteristics of a Hamilton-Jacobi equation can be seen as action
minimizing trajectories of fluid particles. For nonsmooth "viscosity"
solutions, which give rise to discontinuous velocity fields, this description
is usually pursued only up to the moment when trajectories hit a shock and
cease to minimize the Lagrangian action. In this paper we show that for any
convex Hamiltonian there exists a uniquely defined canonical global nonsmooth
coalescing flow that extends particle trajectories and determines dynamics
inside the shocks. We also provide a variational description of the
corresponding effective velocity field inside shocks, and discuss relation to
the "dissipative anomaly" in the limit of vanishing viscosity.Comment: 15 pages, no figures; to appear in Philos. Trans. R. Soc. series
SU(4) lattice gauge theory with decuplet fermions: Schr\"odinger functional analysis
We complete a program of study of SU(N) gauge theories coupled to two flavors
of fermions in the two-index symmetric representation by performing numerical
simulations in SU(4). The beta function, defined and calculated via the
Schr\"odinger functional, runs more slowly than the two-loop perturbative
result. The mass anomalous dimension levels off in strong coupling at a value
of about 0.45, rendering this theory unsuitable for walking technicolor. A
large-N comparison of this data with results from SU(2) and SU(3) reveals
striking regularities.Comment: 15 pages, 15 figure
The [4+2]âCycloaddition of αâNitrosoalkenes with Thiochalcones as a Prototype of Periselective HeteroâDielsâAlder ReactionsâExperimental and Computational Studies
The [4+2]âcycloadditions of αânitrosoalkenes with thiochalcones occur with high selectivity at the thioketone moiety of the dienophile providing styrylâsubstituted 4Hâ1,5,2âoxathiazines in moderate to good yields. Of the eight conceivable heteroâDielsâAlder adducts only this isomer was observed, thus a prototype of a highly periselective and regioselective cycloaddition has been identified. Analysis of crude product mixtures revealed that the αânitrosoalkene also adds competitively to the thioketone moiety of the thiochalcone dimer affording bisâheterocyclic [4+2]âcycloadducts. The experiments are supported by highâlevel DFT calculations that were also extended to related heteroâDielsâAlder reactions of other nitroso compounds and thioketones. These calculations reveal that the title cycloadditions are kinetically controlled processes confirming the role of thioketones as superdienophiles. The computational study was also applied to the experimentally studied thiochalcone dimerization, and showed that the 1,2âdithiin and 2Hâthiopyran isomers are in equilibrium with the monomer. Again, the DFT calculations indicate kinetic control of this process
Path integrals and symmetry breaking for optimal control theory
This paper considers linear-quadratic control of a non-linear dynamical
system subject to arbitrary cost. I show that for this class of stochastic
control problems the non-linear Hamilton-Jacobi-Bellman equation can be
transformed into a linear equation. The transformation is similar to the
transformation used to relate the classical Hamilton-Jacobi equation to the
Schr\"odinger equation. As a result of the linearity, the usual backward
computation can be replaced by a forward diffusion process, that can be
computed by stochastic integration or by the evaluation of a path integral. It
is shown, how in the deterministic limit the PMP formalism is recovered. The
significance of the path integral approach is that it forms the basis for a
number of efficient computational methods, such as MC sampling, the Laplace
approximation and the variational approximation. We show the effectiveness of
the first two methods in number of examples. Examples are given that show the
qualitative difference between stochastic and deterministic control and the
occurrence of symmetry breaking as a function of the noise.Comment: 21 pages, 6 figures, submitted to JSTA
The Problems of Biobanking and the Law of Gifts
The practice of biobanking is of major importance to biomedical research in modern Western economies. However, biobanking is troubled by a number of ethical and legal concerns including issues of consent, control and privacy. Recent developments in the networking of biobanks and the sharing of samples and data have exacerbated these issues. This paper outlines these problems and then examines how they can be understood through the law of gifts. Much of the debate on how tissue is donated to biobanks has occurred without reference to the law of gifts. This is most probably due to the res nullius rule, which, until recently, has prevented unprocessed human tissue from being considered an object of property. But recent changes to the common lawâs approach to human tissue now invite a reconsideration of the role that gifts law can play in tissue banking (and tissue donation more generally). This paper will proceed on the assumption that tissue which has not been subject to work and skill may nevertheless be held as property and that the decision to donate to a tissue bank can be treated as an example of a legally recognised gift. The paper begins with an example of tissue banking and the legal and ethical issues which it raises. Most prominent amongst these difficulties is the focus on tissue banking on informed consent, a doctrine originally designed to deal with negligence advice and bodily interferences in medical treatment and research. While understandable, the focus on informed consent has created a number of problems particularly in areas of unspecified research, unanticipated findings and privacy. The chapter then moves to reviewing the basic law of gifts by examining the elements of gifts in both law and equity and the requirements for conveying them. The chapter also explains the lawâs capacity to recognise different conditions in gifts that limit the also creates the possibility of conditional dispositions which allow for donors to maintain some rights over the tissue, with the possibility of a form of interest which would enable the donor to regain possession and control of their tissue if here was a breach. This paper argues that an application of the law of gifts is a flexible and useful way of reconceptualising the ethical and legal difficulties of biobanking.NHMRC Project Grant 102992
Outbreak of acute hepatitis C following the use of anti-hepatitis C virus--screened intravenous immunoglobulin therapy
BACKGROUND and AIMS: Hepatitis C virus (HCV) infection has been associated with intravenous (IV) immunoglobulin (Ig), and plasma donations used to prepare IV Ig are now screened to prevent transmission. Thirty-six patients from the United Kingdom received infusions from a batch of anti-HCV antibody-screened intravenous Ig (Gammagard; Baxter Healthcare Ltd., Thetford, Norfolk, England) that was associated with reports of acute hepatitis C outbreak in Europe. The aim of this study was to document the epidemiology of this outbreak. METHODS: Forty-six patients from the United Kingdom treated with Gammagard (34 exposed and 12 unexposed to the batch) returned epidemiological questionnaires. RESULTS: Eighty-two percent of the exposed patients (28 of 34) became positive for HCV RNA. Eighteen percent of the patients (6 of 34) who had infusions with this batch tested negative for HCV RNA, but 2 of the patients had abnormal liver function and subsequently seroconverted to anti-HCV antibody positive. Twenty-seven percent of the patients (9 of 34) developed jaundice, and 79% (27 of 34) had abnormal liver transferase levels. Virus isolates (n=21), including an isolate from the implicated batch, were genotype 1a and virtually identical by sequence analysis of the NS5 region, consistent with transmission from a single source. CONCLUSIONS: Hepatitis C infection can be transmitted by anti-HCV-screened IV Ig. Careful documentation of IV Ig batch numbers and regular biochemical monitoring is recommended for all IV Ig recipients
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