16,883 research outputs found
Goos-H\"anchen and Imbert-Fedorov beam shifts: An overview
We consider reflection and transmission of polarized paraxial light beams at
a plane dielectric interface. The field transformations taking into account a
finite beam width are described based on the plane-wave representation and
geometric rotations. Using geometrical-optics coordinate frames accompanying
the beams, we construct an effective Jones matrix characterizing
spatial-dispersion properties of the interface. This results in a unified
self-consistent description of the Goos-H\"anchen and Imbert-Fedorov shifts
(the latter being also known as spin-Hall effect of light). Our description
reveals intimate relation of the transverse Imbert-Fedorov shift to the
geometric phases between constituent waves in the beam spectrum and to the
angular momentum conservation for the whole beam. Both spatial and angular
shifts are considered as well as their analogues for the higher-order vortex
beams carrying intrinsic orbital angular momentum. We also give a brief
overview of various extensions and generalizations of the basic beam-shift
phenomena and related effects.Comment: 24 pages, 6 figure, to appear in J. Opt. (special issue "Beam
shifts"
Stable skyrmions from extra dimensions
We show that skyrmions arising from compact five dimensional models have
stable sizes. We numerically obtain the skyrmion configurations and calculate
their size and energy. Although their size strongly depends on the magnitude of
localized kinetic-terms, their energy is quite model-independent ranging
between 50-65 times F_pi^2/m_rho, where F_pi is the Goldstone decay constant
and m_rho the lowest Kaluza-Klein mass. These skyrmion configurations
interpolate between small 4D YM instantons and 4D skyrmions made of Goldstones
and a massive vector boson. Contrary to the original 4D skyrmion and previous
5D extensions, these configurations have sizes larger than the inverse of the
cut-off scale and therefore they are trustable within our effective 5D
approach. Such solitonic particles can have interesting phenomenological
consequences as they carry a conserved topological charge analogous to baryon
number.Comment: 20 pages, 3 figure
Out-of-equilibrium tricritical point in a system with long-range interactions
Systems with long-range interactions display a short-time relaxation towards
Quasi Stationary States (QSSs) whose lifetime increases with system size. With
reference to the Hamiltonian Mean Field (HMF) model, we here show that a
maximum entropy principle, based on Lynden-Bell's pioneering idea of "violent
relaxation", predicts the presence of out-of-equilibrium phase transitions
separating the relaxation towards homogeneous (zero magnetization) or
inhomogeneous (non zero magnetization) QSSs. When varying the initial condition
within a family of "water-bags" with different initial magnetization and
energy, first and second order phase transition lines are found that merge at
an out--of--equilibrium tricritical point. Metastability is theoretically
predicted and numerically checked around the first-order phase transition line.Comment: Physical Review Letters (2007
Theoretical evidence for efficient p-type doping of GaN using beryllium
Ab initio calculations predict that Be is a shallow acceptor in GaN. Its
thermal ionization energy is 0.06 eV in wurtzite GaN; the level is valence
resonant in the zincblende phase. Be incorporation is severely limited by the
formation of Be_3N_2. We show however that co-incorporation with reactive
species can enhance the solubility. H-assisted incorporation should lead to
high doping levels in MOCVD growth after post-growth annealing at about 850 K.
Be-O co-incorporation produces high Be and O concentrations at MBE growth
temperatures.Comment: revised Feb 24 199
Public Hazard, Personal Peril: The Impact of Non-Governmental Organizations in the Environmental Justice Movement
This article argues that the local emphasis of what I call micromovements that form the larger Environmental Justice Movement could gain more traction from relationships with Non-Governmental Organizations. Such partnerships are emerging on a national level; however, since the localized movements communicate with, but are not partners with, national organizations such as the National Black Environmental Network, it is unclear how such partnerships add value to the activities of local groups. Moreover, some partnerships are forged for the organization of a specific event such as a conference or working group study Part II of this article discusses an overview of the history of the Environmental Justice Movement and legal remedies available for environmental justice claims. Part III addresses the partnerships between nongovernmental organizations and grassroots movements focusing specifically on one community\u27s struggle with Velsicol Chemical Corporation. Finally, Part VI discusses the obstacles grassroots movement leaders face in trying to change policy and protect their community and how NGOs can be helpful to these efforts
Are Artificial Tans the New Cigarette? How Plaintiffs Can Use the Lessons of Tobacco Litigation in Bringing Claims Against the Indoor Tanning Industry
Indoor tanning salons have grown significantly in popularity during recent years. Scientific research has revealed a strong link between skin cancer and ultraviolet light exposure from indoor tanning lamps. Despite such dangers, federal regulations place minimal restrictions on the labeling of indoor tanning lamps. Indoor tanning salons work vigorously to dispel notions of a link to skin cancer, often falsely promoting various health benefits of indoor tanning. The first lawsuit for injuries resulting from indoor tanning was recently filed against an indoor tanning salon, and other such litigation is poised to follow. This Note examines three potential tort claims against indoor tanning manufacturers and salons, and suggests ways to formulate compelling arguments in each instance. In doing so it draws on cases finding liability in the context of cigarettes, identifying similarities between the indoor tanning and cigarette industries
Public Hazard, Personal Peril: The Impact of Non-Governmental Organizations in the Environmental Justice Movement
This article argues that the local emphasis of what I call micromovements that form the larger Environmental Justice Movement could gain more traction from relationships with Non-Governmental Organizations. Such partnerships are emerging on a national level; however, since the localized movements communicate with, but are not partners with, national organizations such as the National Black Environmental Network, it is unclear how such partnerships add value to the activities of local groups. Moreover, some partnerships are forged for the organization of a specific event such as a conference or working group study Part II of this article discusses an overview of the history of the Environmental Justice Movement and legal remedies available for environmental justice claims. Part III addresses the partnerships between nongovernmental organizations and grassroots movements focusing specifically on one community\u27s struggle with Velsicol Chemical Corporation. Finally, Part VI discusses the obstacles grassroots movement leaders face in trying to change policy and protect their community and how NGOs can be helpful to these efforts
Metagenomic-based Surveillance of Pacific Coast tick Dermacentor occidentalis Identifies Two Novel Bunyaviruses and an Emerging Human Ricksettsial Pathogen.
An increasing number of emerging tick-borne diseases has been reported in the United States since the 1970s. Using metagenomic next generation sequencing, we detected nucleic acid sequences from 2 novel viruses in the family Bunyaviridae and an emerging human rickettsial pathogen, Rickettsia philipii, in a population of the Pacific Coast tick, Dermacentor occidentalis in Mendocino County sampled annually from 2011 to 2014. A total of 250 adults of this human-biting, generalist tick were collected from contiguous chaparral and grassland habitats, and RNA from each individually extracted tick was deep sequenced to an average depth of 7.3 million reads. We detected a Francisella endosymbiont in 174 ticks (70%), and Rickettsia spp. in 19 ticks (8%); Rickettsia-infected ticks contained R. rhipicephali (16 of 250, 6.4%) or R. philipii (3 of 250,1.2%), the agent of eschar-associated febrile illness in humans. The genomes of 2 novel bunyaviruses (>99% complete) in the genera Nairovirus and Phlebovirus were also identified and found to be present in 20-91% of ticks, depending on the year of collection. The high prevalence of these bunyaviruses in sampled Dermacentor ticks suggests that they may be viral endosymbionts, although further studies are needed to determine whether they are infectious for vertebrate hosts, especially humans, and their potential role in tick ecology
- …