7,320 research outputs found
Polar magneto-optical Kerr effect in antiferromagnetic MAs (M=Cr, Mn, Fe) under an external magnetic field
Antiferromagnetic metals attract tremendous interest for memory applications
due to their expected fast response dynamics in the terahertz frequency regime.
Reading from and writing information into these materials is not easily
achievable using magnetic fields, due to weak high-order magneto-optical
signals and robustness of the magnetic structure against external magnetic
fields. Polarized electromagnetic radiation is a promising alternative for
probing their response, however, when ideal antiferromagnetic symmetry is
present, this response vanishes. Hence, in this work we combine
first-principles simulations with measurements of the polar magneto-optical
Kerr effect under external magnetic fields, to study magneto-optical response
of antiferromagnetic MAs (M=Cr, Mn, and Fe). We devise a computational
scheme to compute the magnetic susceptibility from total-energy changes using
constraints on magnetic-moment tilting. Our predictions of the spectral
dependence of polar magneto-optical Kerr rotation and ellipticity allow us to
attribute these effects to breaking of the magnetic symmetry. We show that
tilting affects the exchange interaction, while the spin-orbit interaction
remains unaffected as the tilting angle changes. Our work provides
understanding of the polar magneto-optical Kerr effect on a band structure
level and underscores the importance of the magnetic susceptibility when
searching for materials with large magneto-optical response.Comment: 9 pages, 9 figure
Higgs Boson Bounds in Three and Four Generation Scenarios
In light of recent experimental results, we present updated bounds on the
lightest Higgs boson mass in the Standard Model (SM) and in the Minimal
Supersymmetric extension of the Standard Model (MSSM). The vacuum stability
lower bound on the pure SM Higgs boson mass when the SM is taken to be valid up
to the Planck scale lies above the MSSM lightest Higgs boson mass upper bound
for a large amount of SUSY parameter space. If the lightest Higgs boson is
detected with a mass M_{H} < 134 GeV (150 GeV) for a top quark mass M_{top} =
172 GeV (179 GeV), it may indicate the existence of a fourth generation of
fermions. The region of inconsistency is removed and the MSSM is salvagable for
such values of M_{H} if one postulates the existence of a fourth generation of
leptons and quarks with isodoublet degenerate masses M_{L} and M_{Q} such that
60 GeV 170 GeV.Comment: 7 pages, 4 figures. To be published in Physical Review
Embodiment design of soft continuum robots
This article presents the results of a multidisciplinary project where mechatronic engineers worked alongside biologists to develop a soft robotic arm that captures key features of octopus anatomy and neurophysiology. The concept of embodiment (the dynamic coupling between sensory-motor control, anatomy, materials and environment that allows for the animal to achieve adaptive behaviours) is used as a starting point for the design process but tempered by current engineering technologies and approaches. In this article, the embodied design requirements are first discussed from a robotic viewpoint by taking into account real-life engineering limitations; then, the motor control schemes inspired by octopus nervous system are investigated. Finally, the mechanical and control design of a prototype is presented that appropriately blends bio-inspiration and engineering limitations. Simulated and experimental results show that the developed continuum robotic arm is able to reproduce octopus-like motions for bending, reaching and grasping
Community prevalence of antibodies to human immunodeficiency virus in Rural and Urban Vellore, Tamil Nadu
Background: Human immunodeficiency virus (HIV) infection and acquired immunodeficiency syndrome (AIDS) are becoming increasingly common in India. Currently, antenatal prevalence is a surrogate marker for HIV prevalence in the community. The association between antenatal and community prevalence of HIV needs to be validated so that estimates can be verified or adjusted appropriately Methods: A probability proportional to size cluster survey was conducted in the Kaniyambadi block of Vellore district and in the urban wards of Vellore town to estimate the prevalence of antibodies to rubella from August 1999 to February 2000. All personal identifier data from the serum samples were removed to yield a collection for which only the age and sex were known. Estimation of antibodies to HIV in sera from individuals between 15 and 40 years of age, was carried out by one screening ELISA and the reactive sera were further subjected to a supplementary test. Results: We tested 1512 serum samples from subjects residing in rural areas and 1358 samples from those residing in urban areas. The seropositivity among rural samples was 0.66% and among urban samples 1.4%. The prevalence was almost equal among men and women and the youngest infected individual was 15 years old. Conclusion: The prevalence of HIV during the period of study was similar to the national surveillance data for Tamil Nadu based on antenatal women. HIV prevalence differs in urban and rural Tamil Nadu, with urban areas having a higher burden of the disease
Review of recently reported Ricin detection techniques focusing on combined immunoassay detection with abrin and saxitoxin in human plasma
Increasing non-traditional threats from biological or chemical weapons, the Organisation for the Prohibition of Chemical Weapons (OPCW) have tried to perform the preliminary analysis of biotoxin sample to standardize analysis methods and strengthen analytical capabilities among OPCW member countries. With the changes of new analysis, ROK CBRN Defense Research Institute (CDRI) established enzyme-linked immunosorbent assay (ELISA) and cytotoxicity analysis methods for ricin, abrin, and saxitoxin through the OPCW exercise on Biotoxin sample analysis. Thus, this study aims to established analytical methods (ELISA and cytotoxicity analysis) for the biological toxins called ricin, abrin and saxitoxin according to recent OPCW Biotoxin detection exercise. In particular, to refine practical and effective methods of biological analysis, we reviewed recent research on scientific analysis of ricin as a potential bioterror weapon, letter with ricin sent in White House, and suggested future agendas for preparedness testing
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