3,129 research outputs found
Fundamental noise limitations to supercontinuum generation in microstructure fiber
Broadband noise on supercontinuum spectra generated in microstructure fiber
is shown to lead to amplitude fluctuations as large as 50 % for certain input
laser pulse parameters. We study this noise using both experimental
measurements and numerical simulations with a generalized stochastic nonlinear
Schroedinger equation, finding good quantitative agreement over a range of
input pulse energies and chirp values. This noise is shown to arise from
nonlinear amplification of two quantum noise inputs: the input pulse shot noise
and the spontaneous Raman scattering down the fiber.Comment: 16 pages with 6 figure
Nonlinear optical interactions in silicon waveguides
The strong nonlinear response of silicon photonic nanowire waveguides allows for the integration of nonlinear optical functions on a chip. However, the detrimental nonlinear optical absorption in silicon at telecom wavelengths limits the efficiency of many such experiments. In this review, several approaches are proposed and demonstrated to overcome this fundamental issue. By using the proposed methods, we demonstrate amongst others supercontinuum generation, frequency comb generation, a parametric optical amplifier, and a parametric optical oscillator
Economic Interests and the European Union: A Catalyst for European Integration or a Hindrance?
The influence of economic interest groups on national policy-making on European Union-level policy and European integration seems to be case specific and circumstantial. Certain economic interests (for example, pension funds) are so influential that some of them become almost inseparable from the state. However, economic interests are less likely to become influential when broad institutional questions are
negotiated, rather than specific rules with a clear cost-benefit balance. And it is especially when they feel challenged by the state that they turn their efforts to
EU-level lobbying. The record of economic interest groups in EU policy-making appears also to be mixed. They are influential when they enjoy privileged institutionalised
interactions with a policy-making node, such as European Parliament (EP) committees. However, access to the EP has recently become less privileged and institutional advocacy has become more contested, to the disadvantage of interest groups. Many economic interest groups actually obstruct the legislative process with seemingly inconsistent behaviour: they are in favour of European integration in general, but end up lobbying against concrete pieces of legislation if they are costly to them
Unraveling the Effects of Acute Inflammation on Pharmacokinetics: A Model-Based Analysis Focusing on Renal Glomerular Filtration Rate and Cytochrome P450 3A4-Mediated Metabolism
Background and Objectives
Acute inflammation caused by infections or sepsis can impact pharmacokinetics. We used a model-based analysis to evaluate the effect of acute inflammation as represented by interleukin-6 (IL-6) levels on drug clearance, focusing on renal glomerular filtration rate (GFR) and cytochrome P450 3A4 (CYP3A4)-mediated metabolism.
Methods
A physiologically based model incorporating renal and hepatic drug clearance was implemented. Functions correlating IL-6 levels with GFR and in vitro CYP3A4 activity were derived and incorporated into the modeling framework. We then simulated treatment scenarios for hypothetical drugs by varying the IL-6 levels, the contribution of renal and hepatic drug clearance, and protein binding. The relative change in observed area under the concentration-time curve (AUC) was computed for these scenarios.
Results
Inflammation showed opposite effects on drug exposure for drugs eliminated via the liver and kidney, with the effect of inflammation being inversely proportional to the extraction ratio (ER). For renally cleared drugs, the relative decrease in AUC was close to 30% during severe inflammation. For CYP3A4 substrates, the relative increase in AUC could exceed 50% for low-ER drugs. Finally, the impact of inflammation-induced changes in drug clearance is smaller for drugs with a larger unbound fraction.
Conclusion
This analysis demonstrates differences in the impact of inflammation on drug clearance for different drug types. The effects of inflammation status on pharmacokinetics may explain the inter-individual variability in pharmacokinetics in critically ill patients. The proposed model-based analysis may be used to further evaluate the effect of inflammation, i.e., by incorporating the effect of inflammation on other drug-metabolizing enzymes or physiological processes
Is there still a place for the concept of therapeutic regression in psychoanalysis?
The author uses his own failure to find a place for the idea of therapeutic regression in his clinical thinking or practice as the basis for an investigation into its meaning and usefulness. He makes a distinction between three ways the term ‘regression’ is used in psychoanalytic discourse: as a way of evoking a primitive level of experience; as a reminder in some clinical situations of the value of non-intervention on the part of the analyst; and as a description of a phase of an analytic treatment with some patients where the analyst needs to put aside normal analytic technique in order to foster a regression in the patient. It is this third meaning, which the author terms “therapeutic regression” that this paper examines, principally by means of an extended discussion of two clinical examples of a patient making a so-called therapeutic regression, one given by Winnicott and the other by Masud Khan. The author argues that in these examples the introduction of the concept of therapeutic regression obscures rather than clarifies the clinical process. He concludes that, as a substantial clinical concept, the idea of therapeutic regression has outlived its usefulness. However he also notes that many psychoanalytic writers continue to find a use for the more generic concept of regression, and that the very engagement with the more particular idea of therapeutic regression has value in provoking questions as to what is truly therapeutic in psychoanalytic treatment
An Algebraic Approach to Linear-Optical Schemes for Deterministic Quantum Computing
Linear-Optical Passive (LOP) devices and photon counters are sufficient to
implement universal quantum computation with single photons, and particular
schemes have already been proposed. In this paper we discuss the link between
the algebraic structure of LOP transformations and quantum computing. We first
show how to decompose the Fock space of N optical modes in finite-dimensional
subspaces that are suitable for encoding strings of qubits and invariant under
LOP transformations (these subspaces are related to the spaces of irreducible
unitary representations of U(N)). Next we show how to design in algorithmic
fashion
LOP circuits which implement any quantum circuit deterministically. We also
present some simple examples, such as the circuits implementing a CNOT gate and
a Bell-State Generator/Analyzer.Comment: new version with minor modification
Efficient Mild Organosolv Lignin Extraction in a Flow-Through Setup Yielding Lignin with High beta-O-4 Content
Current lignin fractionation methods use harsh conditions that alter the native lignin structure, resulting in a recalcitrant material which is undesired for downstream processing. Milder fractionation processes allow for the isolation of lignins that are high in beta-aryl ether (beta-O-4) content, however, at reduced extraction efficiency. The development of improved lignin extraction methods using mild conditions is therefore desired. For this reason, a flow-through setup for mild ethanosolv extraction (120 degrees C) was developed. The influence of acid concentration, ethanol/water ratio, and the use of other linear alcohol co-solvents on the delignification efficiency and the beta-O-4 content were evaluated. With walnut shells as model feedstock, extraction efficiencies of over 55% were achieved, yielding lignin with a good structural quality in terms of beta-O-4 linking motifs (typically over 60 per 100 aromatic units). For example, lignin containing 66 beta-O-4 linking motifs was obtained with an 80:20 n-propanol/water ratio, 0.18 M H2SO4 with overall a good extraction efficiency of 57% after 5 h. The majority of the lignin was extracted in the first 2 hours and this lignin showed the best structural quality. Compared to batch extractions, both higher lignin extraction efficiency and higher beta-O-4 content were obtained using the flow setup
Real-Time Data Driven Wildland Fire Modeling
We are developing a wildland fire model based on semi-empirical relations
that estimate the rate of spread of a surface fire and post-frontal heat
release, coupled with WRF, the Weather Research and Forecasting atmospheric
model. A level set method identifies the fire front. Data are assimilated using
both amplitude and position corrections using a morphing ensemble Kalman
filter. We will use thermal images of a fire for observations that will be
compared to synthetic image based on the model state.Comment: 8 pages, 4 figures. ICCS 0
Talk like an expert: The construction of expertise in news comments concerning climate change
This article explores how readers of UK newspapers construct expertise around climate change. It draws on 300 online readers’ comments on news items in The Guardian, Daily Mail and The Telegraph, concerning the release of the International Panel on Climate Change report calling for immediate action on climate change. Comments were analysed using discursive psychology. We identified a series of discursive strategies that commenters adopted to present themselves as experts in their commentary. The (mostly indirect) use of category entitlements (implicitly claiming themselves as expert) and the presentation of one’s argument as factual (based on direct or indirect technical knowledge or common sense) emerged as common ways in which readers made claims to expertise, both among the supporters and among the sceptics of climate change science. Our findings indicate that expertise is a fluid concept, constructed in diverse ways, with important implications for public engagement with climate change science
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