375 research outputs found
Subharmonic bifurcation cascade of pattern oscillations caused by winding number increasing entrainment
Convection structures in binary fluid mixtures are investigated for positive
Soret coupling in the driving regime where solutal and thermal contributions to
the buoyancy forces compete. Bifurcation properties of stable and unstable
stationary square, roll, and crossroll (CR) structures and the oscillatory
competition between rolls and squares are determined numerically as a function
of fluid parameters. A novel type of subharmonic bifurcation cascade (SC) where
the oscillation period grows in integer steps as is found
and elucidated to be an entrainment process.Comment: 7 pages, 4 figure
Alginate microspheres containing temperature sensitive liposomes (TSL) for MR-guided embolization and triggered release of doxorubicin
Objective
The objective of this study was to develop and characterize alginate microspheres suitable for embolization with on-demand triggered doxorubicin (DOX) release and whereby the microspheres as well as the drug releasing process can be visualized in vivo using MRI.
Methods and Findings
For this purpose, barium crosslinked alginate microspheres were loaded with temperature sensitive liposomes (TSL/TSL-Ba-ms), which release their payload upon mild hyperthermia. These TSL contained DOX and [Gd(HPDO3A)(H2O)], a T1 MRI contrast agent, for real time visualization of the release. Empty alginate microspheres crosslinked with holmium ions (T2* MRI contrast agent, Ho-ms) were mixed with TSL-Ba-ms to allow microsphere visualization. TSL-Ba-ms and Ho-ms were prepared with a homemade spray device and sized by sieving. Encapsulation of TSL in barium crosslinked microspheres changed the triggered release properties only slightly: 95% of the loaded DOX was released from free TSL vs. 86% release for TSL-Ba-ms within 30 seconds in 50% FBS at 42°C. TSL-Ba-ms (76 ± 41 μm) and Ho-ms (64 ± 29 μm) had a comparable size, which most likely will result in a similar in vivo tissue distribution after an i.v. co-injection and therefore Ho-ms can be used as tracer for the TSL-Ba-ms. MR imaging of a TSL-Ba-ms and Ho-ms mixture (ratio 95:5) before and after hyperthermia allowed in vitro and in vivo visualization of microsphere deposition (T2*-weighted images) as well as temperature-triggered release (T1-weighted images). The [Gd(HPDO3A)(H2O)] release and clusters of microspheres containing holmium ions were visualized in a VX2 tumor model in a rabbit using MRI.
Conclusions
In conclusion, these TSL-Ba-ms and Ho-ms are promising systems for real-time, MR-guided embolization and triggered release of drugs in vivo
Community care workers, poor referral networks and consumption of personal resources in rural South Africa
Although home-based care (HBC) programs are widely implemented throughout Africa, their success depends on the
existence of an enabling environment, including a referral system and supply of essential commodities. The objective of this
study was to explore the current state of client referral patterns and practices by community care workers (CCWs), in an
evolving environment of one rural South African sub-district. Using a participant triangulation approach, in-depth
qualitative interviews were conducted with 17 CCWs, 32 HBC clients and 32 primary caregivers (PCGs). An open-ended
interview guide was used for data collection. Participants were selected from comprehensive lists of CCWs and their clients,
using a diversified criterion-based sampling method. Three independent researchers coded three sets of data – CCWs,
Clients and PCGs, for referral patterns and practices of CCWs. Referrals from clinics and hospitals to HBC occurred
infrequently, as only eight (25%) of the 32 clients interviewed were formally referred. Community care workers showed high
levels of commitment and personal investment in supporting their clients to use the formal health care system. They went
to the extent of using their own personal resources. Seven CCWs used their own money to ensure client access to clinics,
and eight gave their own food to ensure treatment adherence. Community care workers are essential in linking clients to
clinics and hospitals and to promote the appropriate use of medical services, although this effort frequently necessitated
consumption of their own personal resources. Therefore, risk protection strategies are urgently needed so as to ensure
sustainability of the current work performed by HBC organizations and the CCW volunteers.The South Africa Netherlands research Programme on Alternatives in Development (SANPAD) and AVERT, Averting HIV and AIDS (http://www.avert.org/).http://www.plosone.orgam201
Convection in Binary Fluid Mixtures. II. Localized Traveling Waves. (Physical Review E, in press)
Nonlinear, spatially localized structures of traveling convection rolls are
investigated in quantitative detail as a function of Rayleigh number for two
different Soret coupling strengths (separation ratios) with Lewis and Prandtl
numbers characterizing ethanol-water mixtures. A finite-difference method was
used to solve the full hydrodynamic field equations numerically. Structure and
dynamics of these localized traveling waves (LTW) are dominated by the
concentration field. Like in the spatially extended convective states ( cf.
accompanying paper), the Soret-induced concentration variations strongly
influence, via density changes, the buoyancy forces that drive convection. The
spatio-temporal properties of this feed-back mechanism, involving boundary
layers and concentration plumes, show that LTW's are strongly nonlinear states.
Light intensity distributions are determined that can be observed in side-view
shadowgraphs. Detailed analyses of all fields are made using colour-coded
isoplots, among others. In the frame comoving with their drift velocity, LTW's
display a nontrivial spatio-temporal symmetry consisting of time-translation by
half an oscillation period combined with vertical reflection through the
horizontal midplane of the layer. A time-averaged concentration current is
driven by a phase difference between the waves of concentration and vertical
velocity in the bulk of the LTW state. The associated large-scale concentration
redistribution stabilizes the LTW and controls its drift velocity into the
quiescent fluid by generating a buoyancy-reducing concentration "barrier" ahead
of the leading LTW front. The selection of the width of the LTW's is
investigated and comparisons with experiments are presented.Comment: 18 pages and 6 figures as uuencoded Postscript file (using uufiles) 1
color figure as uuencoded Postscript file, a high resolution version of the
color figure (about 10MB) can be requested from [email protected] or
[email protected].: (Barten)present address: PSI, CH-5232 Villigen
PSI, Switzerlan
Amplitude measurements of Faraday waves
A light reflection technique is used to measure quantitatively the surface
elevation of Faraday waves. The performed measurements cover a wide parameter
range of driving frequencies and sample viscosities. In the capillary wave
regime the bifurcation diagrams exhibit a frequency independent scaling
proportional to the wavelength. We also provide numerical simulations of the
full Navier-Stokes equations, which are in quantitative agreement up to
supercritical drive amplitudes of 20%. The validity of an existing perturbation
analysis is found to be limited to 2.5% overcriticaly.Comment: 7 figure
Rights, Knowledge, and Governance for Improved Health Equity in Urban Settings
All three of the interacting aspects of daily urban life (physical environment, social conditions, and the added pressure of climate change) that affect health inequities are nested within the concept of urban governance, which has the task of understanding and managing the interactions among these different factors so that all three can be improved together and coherently. Governance is defined as: “the process of collective decision making and processes by which decisions are implemented or not implemented”: it is concerned with the distribution, exercise, and consequences of power. Although there appears to be general agreement that the quality of governance is important for development, much less agreement appears to exist on what the concept really implies and how it should be used. Our review of the literature confirmed significant variation in meaning as well as in the practice of urban governance arrangements. The review found that the linkage between governance practices and health equity is under-researched and/or has been neglected. Reconnecting the fields of urban planning, social sciences, and public health are essential “not only for improving local governance, but also for understanding and addressing global political change” for enhanced urban health equity. Social mobilization, empowering governance, and improved knowledge for sustainable and equitable development in urban settings is urgently needed. A set of strategic research questions are suggested
Hybrid video quality prediction: reviewing video quality measurement for widening application scope
A tremendous number of objective video quality measurement algorithms have been developed during the last two decades. Most of them either measure a very limited aspect of the perceived video quality or they measure broad ranges of quality with limited prediction accuracy. This paper lists several perceptual artifacts that may be computationally measured in an isolated algorithm and some of the modeling approaches that have been proposed to predict the resulting quality from those algorithms. These algorithms usually have a very limited application scope but have been verified carefully. The paper continues with a review of some standardized and well-known video quality measurement algorithms that are meant for a wide range of applications, thus have a larger scope. Their individual artifacts prediction accuracy is usually lower but some of them were validated to perform sufficiently well for standardization. Several difficulties and shortcomings in developing a general purpose model with high prediction performance are identified such as a common objective quality scale or the behavior of individual indicators when confronted with stimuli that are out of their prediction scope. The paper concludes with a systematic framework approach to tackle the development of a hybrid video quality measurement in a joint research collaboration.Polish National Centre for Research and Development (NCRD) SP/I/1/77065/10, Swedish Governmental Agency for Innovation Systems (Vinnova
Research Priorities for Neglected Infectious Diseases in Latin America and the Caribbean Region
Dujardin, J. C. et al. 5 p.-1 tab.Global priorities for research in neglected
infectious diseases (NIDs) can be assessed
in different ways, but it is important to
realize that regional priorities may significantly
differ one from another. The region
of Latin America and the Caribbean (LAC)
is—along with Africa and Asia—more
affected by NIDs than other regions of the
world. Some of the Latin American NIDs
are common to other continents, while
others are very specific or disproportionately
affect the Latin American region [1–
3] (Table 1). Because of its huge ecological
diversity, ongoing environmental changes,
and massive migrations, LAC is also a
catalyst for the (re-)emergence and spreading
of NIDs, both inside and outside the
subcontinent. Following a colloquium on
NIDs in LAC held in Lima, Peru, between
12 and 14 November 2009, a thematic
workshop was organized with the support
of the European Commission (EC). It
involved 29 scientists (16 from the Americas,
two from the Democratic Republic of
Congo and India, respectively, and nine
from Europe) working on different NIDs
and representing several research areas
from basic to applied. This report summarizes
the consensus comments of the expert
group after oral and written consultation. It
is envisaged that this document should
stimulate a debate within the scientific
community and serve as a recommendation
for future actions by international or
regional funding agencies in the area of
NIDs in LACThis work was supported by the Directorate-General for Development Cooperation of the Belgian Government (framework agreement 03, project 95502) and the European CommissionPeer reviewe
Different Patterns of Evolution in the Centromeric and Telomeric Regions of Group A and B Haplotypes of the Human Killer Cell Ig-Like Receptor Locus
The fast evolving human KIR gene family encodes variable lymphocyte receptors specific for polymorphic HLA class I determinants. Nucleotide sequences for 24 representative human KIR haplotypes were determined. With three previously defined haplotypes, this gave a set of 12 group A and 15 group B haplotypes for assessment of KIR variation. The seven gene-content haplotypes are all combinations of four centromeric and two telomeric motifs. 2DL5, 2DS5 and 2DS3 can be present in centromeric and telomeric locations. With one exception, haplotypes having identical gene content differed in their combinations of KIR alleles. Sequence diversity varied between haplotype groups and between centromeric and telomeric halves of the KIR locus. The most variable A haplotype genes are in the telomeric half, whereas the most variable genes characterizing B haplotypes are in the centromeric half. Of the highly polymorphic genes, only the 3DL3 framework gene exhibits a similar diversity when carried by A and B haplotypes. Phylogenetic analysis and divergence time estimates, point to the centromeric gene-content motifs that distinguish A and B haplotypes having emerged ∼6 million years ago, contemporaneously with the separation of human and chimpanzee ancestors. In contrast, the telomeric motifs that distinguish A and B haplotypes emerged more recently, ∼1.7 million years ago, before the emergence of Homo sapiens. Thus the centromeric and telomeric motifs that typify A and B haplotypes have likely been present throughout human evolution. The results suggest the common ancestor of A and B haplotypes combined a B-like centromeric region with an A-like telomeric region
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