1,528 research outputs found
Fluorescent visualization of a spreading surfactant
The spreading of surfactants on thin films is an industrially and medically
important phenomenon, but the dynamics are highly nonlinear and visualization
of the surfactant dynamics has been a long-standing experimental challenge. We
perform the first quantitative, spatiotemporally-resolved measurements of the
spreading of an insoluble surfactant on a thin fluid layer. During the
spreading process, we directly observe both the radial height profile of the
spreading droplet and the spatial distribution of the fluorescently-tagged
surfactant. We find that the leading edge of spreading circular layer of
surfactant forms a Marangoni ridge in the underlying fluid, with a trough
trailing the ridge as expected. However, several novel features are observed
using the fluorescence technique, including a peak in the surfactant
concentration which trails the leading edge, and a flat, monolayer-scale
spreading film which differs from concentration profiles predicted by current
models. Both the Marangoni ridge and surfactant leading edge can be described
to spread as . We find spreading exponents, and for the ridge peak and
surfactant leading edge, respectively, which are in good agreement with
theoretical predictions of . In addition, we observe that the
surfactant leading edge initially leads the peak of the Marangoni ridge, with
the peak later catching up to the leading edge
In High Gear: A Case Study of the Hees-Edper Corporate Group
This study compares firms in the Hees-Edper Group with a number of other independent firms of similar size and in the same industries over a four-year period from 1988 to 1992, just prior to the first release of news that the Hees-Edper group was in financial trouble. During that period, HeesEdper firms recorded profitability levels comparable to (or below) those of the matched firms. The Hees-Edper firms were also shown to have been much higher risk investments well before the group\u27s financial position began to deteriorate. They were more highly levered, but even after risk levels are adjusted for this, the risk levels of Hees-Edper firms remain much higher.
Our study shows that the extreme incentive-based compensation schemes used by Hees-Edper firms encouraged managers to adopt high-risk strategies, and that the intercorporate co-insurance (allowed by the interlocking ownership structure of the firms) made this possible by increasing the group\u27s apparent debt capacity. Since this higher risk did not improve overall performance, it was arguably at an economically inefficient higher level. The higher leverage of Hees-Edper companies should have produced a sizable tax advantage because of the deductibility of interest at the corporate level. The mediocre performance of the companies thus raises the possibility that abnormally poor performance was masked by tax breaks
The Analysis of Composite Slabs with Profiled Sheeting Using a Computer Based Semi-empirical Partial Interaction Approach
Resonance energy transfer: The unified theory revisited
Resonanceenergy transfer (RET) is the principal mechanism for the intermolecular or intramolecular redistribution of electronic energy following molecular excitation. In terms of fundamental quantum interactions, the process is properly described in terms of a virtual photon transit between the pre-excited donor and a lower energy (usually ground-state) acceptor. The detailed quantum amplitude for RET is calculated by molecular quantum electrodynamical techniques with the observable, the transfer rate, derived via application of the Fermi golden rule. In the treatment reported here, recently devised state-sequence techniques and a novel calculational protocol is applied to RET and shown to circumvent problems associated with the usual method. The second-rank tensor describing virtual photon behavior evolves from a Greenâs function solution to the Helmholtz equation, and special functions are employed to realize the coupling tensor. The method is used to derive a new result for energy transfer systems sensitive to both magnetic- and electric-dipole transitions. The ensuing result is compared to that of pure electric-dipoleâelectric-dipole coupling and is analyzed with regard to acceptable transfer separations. Systems are proposed where the electric-dipoleâmagnetic-dipole term is the leading contribution to the overall rate
Treatment Strategies in Diffuse Midline Gliomas With the H3K27M Mutation: The Role of Convection-Enhanced Delivery in Overcoming Anatomic Challenges
Diffuse midline gliomas harboring the H3 K27M mutationâincluding the previously named diffuse intrinsic pontine glioma (DIPG)âare lethal high-grade pediatric brain tumors that are inoperable and without cure. Despite numerous clinical trials, the prognosis remains poor, with a median survival of ~1 year from diagnosis. Systemic administration of chemotherapeutic agents is often hindered by the blood brain barrier (BBB), and even drugs that successfully cross the barrier may suffer from unpredictable distributions. The challenge in treating this deadly disease relies on effective delivery of a therapeutic agent to the bulk tumor as well as infiltrating cells. Therefore, methods that can enhance drug delivery to the brain are of great interest. Convection-enhanced delivery (CED) is a strategy that bypasses the BBB entirely and enhances drug distribution by applying hydraulic pressure to deliver agents directly and evenly into a target region. This technique reliably distributes infusate homogenously through the interstitial space of the target region and achieves high local drug concentrations in the brain. Moreover, recent studies have also shown that continuous delivery of drug over an extended period of time is safe, feasible, and more efficacious than standard single session CED. Therefore, CED represents a promising technique for treating midline tumors with the H3K27M mutation
Vancomycin minimum inhibitory concentration is not a substitute for clinical judgment: Response to healthcare-associated ventriculitis and meningitis
To the EditorâWe read with interest
the new clinical practice guideline for
healthcare-associated ventriculitis and
meningitis published in Clinical Infectious
Diseases [1]. The guideline recommends
consideration of alternative therapies for
the treatment of methicillin-resistant
Staphylococcus aureus (MRSA) meningitis
and ventriculitis for isolates with a
vancomycin minimum in-hibitory
concentration (MIC) â„1ÎŒg/mL. We believe
this recommendation places inappropriate
emphasis on a single determinant of
antimicrobial therapy that has uncertain
clinical relevance and variable accuracy depending on the antimicrobial
susceptibility testing (AST) method
used. This may lead clinicians to use less
well-evidenced strategies in cases likely
to respond to vancomycin
Cloaked Facebook pages: Exploring fake Islamist propaganda in social media
This research analyses cloaked Facebook pages that are created to spread political propaganda by cloaking a user profile and imitating the identity of a political opponent in order to spark hateful and aggressive reactions. This inquiry is pursued through a multi-sited online ethnographic case study of Danish Facebook pages disguised as radical Islamist pages, which provoked racist and anti-Muslim reactions as well as negative sentiments towards refugees and immigrants in Denmark in general. Drawing on Jessie Danielsâ critical insights into cloaked websites, this research furthermore analyses the epistemological, methodological and conceptual challenges of online propaganda. It enhances our understanding of disinformation and propaganda in an increasingly interactive social media environment and contributes to a critical inquiry into social media and subversive politics
Population genetic structure in European lobsters: implications for connectivity, diversity and hatchery stocking
The European lobster Homarus gammarus is a marine crustacean prized for seafood, but populations across its range are threatened by fishery overexploitation. The speciesâ larval stages are planktonic, suggesting considerable dispersal among populations. The potential threats of overexploitation and erosion of population structure due to hatchery releases or inadvertent introductions make it important to understand the genetic structuring of populations across multiple geographic scales. Here we assess lobster population structure at a fine scale in Cornwall, southwestern UK, where a hatchery-stocking operation introduces cultured individuals into the wild stock, and at a broader European level, in order to compare the spatial scale of hatchery releases with that of population connectivity. Microsatellite genotypes of 24 individuals from each of 13 locations in Cornwall showed no fine-scale population structure across distances of up to ~230 km. Significant differentiation and isolation by distance were detected at a broader scale, using 300 additional individuals comprising a further 15 European samples. Signals of genetic heterogeneity were evident between an Atlantic cluster and samples from Sweden. Connectivity within the Atlantic and Swedish clusters was high, although evidence for isolation by distance and a transitional zone within the eastern North Sea suggested that direct gene exchange between these stocks is limited and fits a stepping-stone model. We conclude that hatchery-reared lobsters should not be released where broodstock are distantly sourced but, using Cornwall as a case study, microsatellites revealed no evidence that the normal release of hatchery stock exceeds the geographic scale of natural connectivity.European Social FundWorshipful Company of FishmongersBBSRCThis research was supported by Lobster
Grower 2, a 3 yr project funded by Innovate-UK (TS/
N006097/1) and BBSRC (BB/N013891/1) under an AgriTech
Catalyst Industrial Stage Award. We are also greatly
appreciative of the studentship funding provided by the
European Social Fund and of the grant awarded by the Fishmongerâs
Company, UK, both of which made the work possible
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