9,130 research outputs found
Red blood cells and other non-spherical capsules in shear flow: oscillatory dynamics and the tank-treading-to-tumbling transition
We consider the motion of red blood cells and other non-spherical
microcapsules dilutely suspended in a simple shear flow. Our analysis indicates
that depending on the viscosity, membrane elasticity, geometry and shear rate,
the particle exhibits either tumbling, tank-treading of the membrane about the
viscous interior with periodic oscillations of the orientation angle, or
intermittent behavior in which the two modes occur alternately. For red blood
cells, we compute the complete phase diagram and identify a novel
tank-treading-to-tumbling transition at low shear rates. Observations of such
motions coupled with our theoretical framework may provide a sensitive means of
assessing capsule properties.Comment: 11 pages, 4 figure
Magnetic nanowires as permanent magnet materials
We present the fabrication of metallic magnetic nanowires using a low
temperature chemical process. We show that pressed powders and magnetically
oriented samples exhibit a very high coercivity (6.5 kOe at 140 K and 4.8 kOe
at 300 K). We discuss the magnetic properties of these metamaterials and show
that they have the suitable properties to realize "high temperature magnets"
competitive with AlNiCo or SmCo permanent magnets. They could also be used as
recording media for high density magnetic recording.Comment: 5 pages, 5 figure
Control methods for Dermanyssus gallinae in systems for laying hens: results of an international seminar
This paper reports the results of a seminar on poultry red mite (PRM), Dermanyssus gallinae. Eighteen researchers from eight European countries discussed life cycle issues of the mite, effects of mites on hens and egg production, and monitoring and control methods for PRM in poultry facilities. It was determined that PRM probably causes more damage than envisaged, with the cost in The Netherlands alone reaching 11 million euro per annum. However a great deal is still unknown about PRM (e.g. reproduction, survival methods, etc.) and that PRM monitoring is an important instrument in recognising and admitting the problem and in taking timely measures. Currently, the most promising control method combines heating the hen house in combination with chemical treatments. Future areas of development which show promise include the use of entomopathogenic fungi, vaccination and predatory mites. The final aim is to solve the problem of D. gallinae in housing systems for laying hens
Homothetic Wyman Spacetimes
The time-dependent, spherically symmetric, Wyman sector of the Unified Field
Theory is shown to be equivalent to a self-gravitating scalar field with a
positive-definite, repulsive self-interaction potential. A homothetic symmetry
is imposed on the fundamental tensor, and the resulting autonomous system is
numerically integrated. Near the critical point (between the collapsing and
non-collapsing spacetimes) the system displays an approximately periodic
alternation between collapsing and dispersive epochs.Comment: 15 pages with 6 figures; requires amsart, amssymb, amsmath, graphicx;
formatted for publication in Int. J. Mod. Phys.
Optical determination and identification of organic shells around nanoparticles: application to silver nanoparticles
We present a simple method to prove the presence of an organic shell around
silver nanoparticles. This method is based on the comparison between optical
extinction measurements of isolated nanoparticles and Mie calculations
predicting the expected wavelength of the Localized Surface Plasmon Resonance
of the nanoparticles with and without the presence of an organic layer. This
method was applied to silver nanoparticles which seemed to be well protected
from oxidation. Further experimental characterization via Surface Enhanced
Raman Spectroscopy (SERS) measurements allowed to identify this protective
shell as ethylene glycol. Combining LSPR and SERS measurements could thus give
proof of both presence and identification for other plasmonic nanoparticles
surrounded by organic shells
Mental health interventions for university students: A critical review of literature
Being a student, the high intensity of events within a university setting creates significant levels of stress, which may also be associated with mental health conditions such as depression and anxiety. This review aims to examine the impact of mental health interventions on mental health challenges among university students. A comprehensive literature search in Google Scholar, Academic Search Complete, PsycINFO, and APA. Thirty-two articles were included in the review from the database searched according to the PRISMA criteria. Eligible articles were appraised using Critical Appraisal Skills Programme (CASP) tools. In total, 14 randomised controlled trials and 19 cross-sectional studies with the intervention were included. Only eleven studies reported racial/ethnic characteristics of participants, and most of the studies (60%) involved female participants. Evidence indicates that cognitive-behavioural therapy applied in different modalities is a major effective therapy to reduce depression, anxiety, and suicidal symptoms and increase well-being. This review identified the effectiveness of mental health interventions on depression and anxiety among university students. The review highlighted the disparity of ethnic minority representation in mental health intervention studies; hence it is suggested that future research should incorporate elements of ethnic minorities in mental health interventions
Dealing with Harrassment in All of Its Forms
Workplace harassment in its many forms presents an increasingly serious challenge for employers, in terms of legal liability and its potential negative effect on employee behavior. This article reviews workplace harassment with attention to the affirmative defense that the Supreme Court has authorized and the factors the courts have considered in deciding whether the defense has been established. That analysis in turn is applied to a discussion of specific actions organizations might take to prevent harassment and create a more positive and effective organizational environment
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