4,080 research outputs found
Total and Differential Phylloquinone (Vitamin K1) Intakes of Preterm Infants from All Sources during the Neonatal Period.
All newborns require phylloquinone after birth to prevent vitamin K deficiency bleeding. Babies born prematurely may be at particular risk of deficiency without adequate supplementation during infancy. The main sources of phylloquinone in preterm babies during the neonatal period are the prophylactic dose of phylloquinone given at birth, and that derived from parenteral and/or enteral feeding. This observational study formed part of a prospective, multicentre, randomised, controlled trial that examined the vitamin K status of preterm infants after random allocation to one of three phylloquinone prophylactic regimens at birth (0.5 or 0.2 mg intramuscularly or 0.2 mg intravenously). In this nutritional sub-study we quantified the proportional and total phylloquinone intakes of preterm infants within the neonatal period from all sources. Almost all infants had average daily phylloquinone intakes that were in excess of the currently recommended amounts. In infants who did not receive parenteral nutrition, the bolus dose of phylloquinone given at birth was the major source of phylloquinone intake, whereas in infants who received parenteral nutrition, the intake from the parenteral preparation exceeded that from the bolus dose by a ratio of approximately 3:1. Our study supports the concern of others that preterm infants who receive current parenteral nutrition formulations may be receiving excessive vitamin K
Multiplicity in Early Stellar Evolution
Observations from optical to centimeter wavelengths have demonstrated that
multiple systems of two or more bodies is the norm at all stellar evolutionary
stages. Multiple systems are widely agreed to result from the collapse and
fragmentation of cloud cores, despite the inhibiting influence of magnetic
fields. Surveys of Class 0 protostars with mm interferometers have revealed a
very high multiplicity frequency of about 2/3, even though there are
observational difficulties in resolving close protobinaries, thus supporting
the possibility that all stars could be born in multiple systems. Near-infrared
adaptive optics observations of Class I protostars show a lower binary
frequency relative to the Class 0 phase, a declining trend that continues
through the Class II/III stages to the field population. This loss of
companions is a natural consequence of dynamical interplay in small multiple
systems, leading to ejection of members. We discuss observational consequences
of this dynamical evolution, and its influence on circumstellar disks, and we
review the evolution of circumbinary disks and their role in defining binary
mass ratios. Special attention is paid to eclipsing PMS binaries, which allow
for observational tests of evolutionary models of early stellar evolution. Many
stars are born in clusters and small groups, and we discuss how interactions in
dense stellar environments can significantly alter the distribution of binary
separations through dissolution of wider binaries. The binaries and multiples
we find in the field are the survivors of these internal and external
destructive processes, and we provide a detailed overview of the multiplicity
statistics of the field, which form a boundary condition for all models of
binary evolution. Finally we discuss various formation mechanisms for massive
binaries, and the properties of massive trapezia.Comment: Accepted for publication as a chapter in Protostars and Planets VI,
University of Arizona Press (2014), eds. H. Beuther, R. Klessen, C.
Dullemond, Th. Hennin
System-performance analysis of optimized gain-switched pulse source employed in 40-and 80-Gb/s OTDM systems
The development of ultrashort optical pulse sources, exhibiting excellent temporal and spectral profiles, will play a crucial role in the performance of future optical time division multiplexed (OTDM) systems. In this paper, we demonstrate the difference in performance in 40- and 80-Gb/s OTDM systems between optical pulse sources based on a gain-switched laser whose pulses are compressed by a nonlinearly and linearly chirped fiber Bragg grating. The results achieved show that nonlinear chirp in the wings of the pulse leads to temporal pedestals formed on either side of the pulse when using the linearly chirped grating, whereas with the nonlinearly chirped grating, pedestals are essentially eliminated. In an OTDM system, these pedestals cause coherent interaction between neighboring channels, resulting in intensity fluctuations that lead to a power penalty of 1.5 dB (40 Gb/s) and 3.5 dB (80 Gb/s) in comparison to the case where the nonlinearly chirped grating is used. Simulations carried out with the aid of Virtual Photonics Inc. verify the results achieved
FROG characterisation of SOA-based wavelength conversion using XPM in conjunction with shifted filtering up to line rates of 80 GHz
The work we present here builds on recent work where we obtained 80 Gb/s error free performance using cross phase modulation (XPM) in an SOA in conjunction with a blue shifted bandpass filter. Here we present a detailed characterisation of this wavelength conversion scheme using a Frequency Resolved Optical Gating (FROG) measurement scheme for both red and blue shifted filtering. This type of characterisation has not been provided before to the best of our knowledge and is an important analysis firstly to achieve a full understanding of the gain and phase dynamics exploited by the wavelength conversion scheme presented and secondly to design a filter so that an optimum performance can be obtaine
Analysis of bit rate dependence up to 80 Gbit/s of a simple wavelength converter based on XPM in a SOA and a shifted filtering
This paper provides the analysis of wavelength converted pulses obtained with a simple semiconductor
optical amplifier (SOA)-based wavelength conversion scheme, which exploits cross phase modulation
(XPM) in an SOA in conjunction with shifted filtering. The analysis includes experimental measurements
of the back-to-back system performances as well as frequency-resolved optical gating (FROG) characterisations
of the wavelength converted pulses. These measurements are implemented at different bit rates
up to 80 Gbit/s and for both red and blue-shifted filtering, particularly showing different patterning effect
dependencies of red and blue-shifting techniques. This analysis is developed by the addition of a numerical
study which corroborates the experimental results. A further understanding of the different performances
of red and blue filtering techniques, presented in the literature, can thus be proposed. The
placement of the filter to undertake red-shifted filtering (RSF) allows us to achieve very short pulse
widths but high bit rate operation is limited by pattern effects. The blue-shifted filtering (BSF) technique
shows optimum performance as regards to patterning effects even if the wavelength converted pulses
can be larger
80-Gb/s OTDM system analysis of a vertical microcavity-based saturable absorber for the enhancement of pulse pedestal suppression
In future high-speed optical time-division-multiplexed (OTDM) systems, an important factor that needs to be considered for optical pulse generation schemes is the impact of pulse pedestals on the overall system performance. The results presented in this letter are two-fold; first, the impact due to the height of pulse pedestals in an 80-Gb/s OTDM system are established. Second, a solution is provided to overcome these high pedestal levels through the use of a vertical microcavity saturable absorber, which can significantly reduce the pulse pedestal level and give enhanced system performanc
Automatic Abstraction for Congruences
One approach to verifying bit-twiddling algorithms is to derive invariants between the bits that constitute the variables of a program. Such invariants can often be described with systems of congruences where in each equation , (unknown variable m)\vec{c}\vec{x}$ is a vector of propositional variables (bits). Because of the low-level nature of these invariants and the large number of bits that are involved, it is important that the transfer functions can be derived automatically. We address this problem, showing how an analysis for bit-level congruence relationships can be decoupled into two parts: (1) a SAT-based abstraction (compilation) step which can be automated, and (2) an interpretation step that requires no SAT-solving. We exploit triangular matrix forms to derive transfer functions efficiently, even in the presence of large numbers of bits. Finally we propose program transformations that improve the analysis results
Hurting and healing in therapeutic environments: how can we understand the role of the relational context?
It has long been recognized that relationships are key to good mental health service delivery and yet the quality of the relational context remains poorly understood. This article brings together three studies that utilize very different methodologies to explore the various ways in which a process of therapeutic change can be aided or prevented by relational factors. All three studies took place within the context of therapeutic communities. The first study uses narrative ethnography and interaction ritual theory to explain how the mechanisms of everyday encounters in two therapeutic communities transform negative feeling into a sense of belonging and positive emotions such as confidence. The second study uses grounded theory to explore how the relational setting and the altered context of the researcher in a therapeutic faith community environment induces either a positive or negative quality of relationships. The final study uses a novel autoethnographic methodology to inform understanding of the relational experience of mental health treatment by comparing and contrasting multiple perspectives of different treatment environments. The paper concludes by identifying the expression and containment of affect in a congruent environment, belonging and hope, and fluid hierarchies of relational structures as key aspects of the relational context informing change
Rich Counter-Examples for Temporal-Epistemic Logic Model Checking
Model checking verifies that a model of a system satisfies a given property,
and otherwise produces a counter-example explaining the violation. The verified
properties are formally expressed in temporal logics. Some temporal logics,
such as CTL, are branching: they allow to express facts about the whole
computation tree of the model, rather than on each single linear computation.
This branching aspect is even more critical when dealing with multi-modal
logics, i.e. logics expressing facts about systems with several transition
relations. A prominent example is CTLK, a logic that reasons about temporal and
epistemic properties of multi-agent systems. In general, model checkers produce
linear counter-examples for failed properties, composed of a single computation
path of the model. But some branching properties are only poorly and partially
explained by a linear counter-example.
This paper proposes richer counter-example structures called tree-like
annotated counter-examples (TLACEs), for properties in Action-Restricted CTL
(ARCTL), an extension of CTL quantifying paths restricted in terms of actions
labeling transitions of the model. These counter-examples have a branching
structure that supports more complete description of property violations.
Elements of these counter-examples are annotated with parts of the property to
give a better understanding of their structure. Visualization and browsing of
these richer counter-examples become a critical issue, as the number of
branches and states can grow exponentially for deeply-nested properties.
This paper formally defines the structure of TLACEs, characterizes adequate
counter-examples w.r.t. models and failed properties, and gives a generation
algorithm for ARCTL properties. It also illustrates the approach with examples
in CTLK, using a reduction of CTLK to ARCTL. The proposed approach has been
implemented, first by extending the NuSMV model checker to generate and export
branching counter-examples, secondly by providing an interactive graphical
interface to visualize and browse them.Comment: In Proceedings IWIGP 2012, arXiv:1202.422
Control via electron count of the competition between magnetism and superconductivity in cobalt and nickel doped NaFeAs
Using a combination of neutron, muon and synchrotron techniques we show how
the magnetic state in NaFeAs can be tuned into superconductivity by replacing
Fe by either Co or Ni. Electron count is the dominant factor, since Ni-doping
has double the effect of Co-doping for the same doping level. We follow the
structural, magnetic and superconducting properties as a function of doping to
show how the superconducting state evolves, concluding that the addition of 0.1
electrons per Fe atom is sufficient to traverse the superconducting domain, and
that magnetic order coexists with superconductivity at doping levels less than
0.025 electrons per Fe atom.Comment: 4 pages, 6 figure
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