Linearly Dichroic Plasmonic Lens and Hetero-Chiral Structures

We present theoretical and experimental study of plasmonic Hetero-Chiral structures, comprised of constituents with opposite chirality. We devise, simulate and experimentally demonstrate different schemes featuring selective surface plasmon polariton focusing of orthogonal polarization states and standing plasmonic vortex fields.Comment: 9 pages, 6 figure

Gap plasmon polariton structure for very efficient micro to nano scale interfacing

The seamless transition between micro-scale photonics and nano-scale plasmonics requires the mitigation between different waveguiding mechanisms as well as between few orders of magnitude in the field lateral size, down to a small fraction of a wavelength. By exploiting gap plasmon polariton waves both at the micro and nano scale, very high power transfer efficiency (>60%) can be achieved using an ultrashort (few microns) non adiabatic tapered gap plasmon waveguide. Same mechanism may be used to harvest impinging light waves and direct them into a nano hole or slit, to exhibit an anomalous transmission - without the conventional periodic structures. The special interplay of plasmonic and oscillating modes is analyzed.Comment: Submitted to PRL. Part of the work was presented at IPRA-2005 conference, paper JWA

How to improve influenza vaccine coverage of healthcare personnel

Abstract Influenza causes substantial morbidity and mortality worldwide each year. Healthcare-associated influenza is a frequent event. Health care personnel (HCP) may be the source for infecting patients and may propagate nosocomial outbreaks. All HCP should receive a dose of influenza vaccine each year to protect themselves and others. This commentary will discuss the study recently published in the IJHPR by Nutman and Yoeli which assessed the beliefs and attitudes of HCP in an Israel hospital regarding influenza and the influenza vaccine. Unfortunately, as noted by Nutman and Yoeli in this issue many HCP in Israel choose not to receive influenza immunization and many harbor misconceptions regarding their risk for influenza as well as the benefits of influenza vaccine. We also discuss proven methods to increase acceptance by HCP for receiving an annual influenza vaccine

Emergence of the persistent spin helix in semiconductor quantum wells

According to Noethers theorem, for every symmetry in nature there is a corresponding conservation law. For example, invariance with respect to spatial translation corresponds to conservation of momentum. In another well-known example, invariance with respect to rotation of the electrons spin, or SU(2) symmetry, leads to conservation of spin polarization. For electrons in a solid, this symmetry is ordinarily broken by spin-orbit coupling, allowing spin angular momentum to flow to orbital angular momentum. However, it has recently been predicted that SU(2) can be achieved in a two-dimensional electron gas, despite the presence of spin-orbit coupling. The corresponding conserved quantities include the amplitude and phase of a helical spin density wave termed the persistent spin helix. SU(2) is realized, in principle, when the strength of two dominant spin-orbit interactions, the Rashba (strength parameterized by \alpha) and linear Dresselhaus (\beta_1), are equal. This symmetry is predicted to be robust against all forms of spin-independent scattering, including electron-electron interactions, but is broken by the cubic Dresselhaus term (\beta_3) and spin-dependent scattering. When these terms are negligible, the distance over which spin information can propagate is predicted to diverge as \alpha approaches \beta_1. Here we observe experimentally the emergence of the persistent spin helix in GaAs quantum wells by independently tuning \alpha and \beta_1. Using transient spin-grating spectroscopy, we find a spin-lifetime enhancement of two orders of magnitude near the symmetry point.........Comment: Will be published in Nature on April 2, 200

Prenatal Organochlorine and Methylmercury Exposure and Memory and Learning in School-Age Children in Communities Near the New Bedford Harbor Superfund Site, Massachusetts

Background: Polychlorinated biphenyls (PCBs), organochlorine pesticides, and methylmercury (MeHg) are environmentally persistent with adverse effects on neurodevelopment. However, especially among populations with commonly experienced low levels of exposure, research on neurodevelopmental effects of these toxicants has produced conflicting results. Objectives: We assessed the association of low-level prenatal exposure to these contaminants with memory and learning. Methods: We studied 393 children, born between 1993 and 1998 to mothers residing near a PCB-contaminated harbor in New Bedford, Massachusetts. Cord serum PCB, DDE (dichlorodiphenyldichloroethylene), and maternal peripartum hair mercury (Hg) levels were measured to estimate prenatal exposure. Memory and learning were assessed at 8 years of age (range, 7–11 years) using the Wide Range Assessment of Memory and Learning (WRAML), age-standardized to a mean ± SD of 100 ± 15. Associations with each WRAML index—Visual Memory, Verbal Memory, and Learning—were examined with multivariable linear regression, controlling for potential confounders. Results: Although cord serum PCB levels were low (sum of four PCBs: mean, 0.3 ng/g serum; range, 0.01–4.4), hair Hg levels were typical of the U.S. fish-eating population (mean, 0.6 μg/g; range, 0.3–5.1). In multivariable models, each microgram per gram increase in hair Hg was associated with, on average, decrements of –2.8 on Visual Memory (95% CI: –5.0, –0.6, p = 0.01), –2.2 on Learning (95% CI: –4.6, 0.2, p = 0.08), and –1.7 on Verbal Memory (95% CI: –3.9, 0.6, p = 0.14). There were no significant adverse associations of PCBs or DDE with WRAML indices. Conclusions: These results support an adverse relationship between low-level prenatal MeHg exposure and childhood memory and learning, particularly visual memory. Citation: Orenstein ST, Thurston SW, Bellinger DC, Schwartz JD, Amarasiriwardena CJ, Altshul LM, Korrick SA. 2014. Prenatal organochlorine and methylmercury exposure and memory and learning in school-age children in communities near the New Bedford Harbor Superfund Site, Massachusetts. Environ Health Perspect 122:1253–1259; http://dx.doi.org/10.1289/ehp.130780

Effects of Space Charge, Dopants, and Strain Fields on Surfaces and Grain Boundaries in YBCO Compounds

Statistical thermodynamical and kinetically-limited models are applied to study the origin and evolution of space charges and band-bending effects at low angle [001] tilt grain boundaries in YBa$_2$Cu$_3$O$_7$ and the effects of Ca doping upon them. Atomistic simulations, using shell models of interatomic forces, are used to calculate the energetics of various relevant point defects. The intrinsic space charge profiles at ideal surfaces are calculated for two limits of oxygen contents, i.e. YBa$_2$Cu$_3$O$_6$ and YBa$_2$Cu$_3$O$_7$. At one limit, O$_6$, the system is an insulator, while at O$_7$, a metal. This is analogous to the intrinsic and doping cases of semiconductors. The site selections for doping calcium and creating holes are also investigated by calculating the heat of solution. In a continuum treatment, the volume of formation of doping calcium at Y-sites is computed. It is then applied to study the segregation of calcium ions to grain boundaries in the Y-123 compound. The influences of the segregation of calcium ions on space charge profiles are finally studied to provide one guide for understanding the improvement of transport properties by doping calcium at grain boundaries in Y-123 compound.Comment: 13 pages, 5 figure

Music Education, Aesthetics, and the Measure of Academic Achievement

Grades and test scores are the traditional measurement of academic achievement. Quantitative improvements on standardized scores in Math/Science/Language are highly-coveted outcomes for meeting accreditation standards required for institutional program funding. Music and the Fine Arts, difficult to assess by traditional academic achievement measurement, and often devalued as so-called “luxury” subjects, struggle for necessary funding. Showing measureable collateral value to other academic subjects—such as math—in order to justify music program funding is dubious. To objectify the purpose of music education in terms of its influence on other subjects is to overlook aesthetic value. The scholarly literature recognizes an historical tendency to correlate music activities and aptitude to other subjects (and to intelligence in general), but quantitative causeeffect claims are not supported scientifically. Music participation from childhood helps build productive, well-socialized, excellent people, but to quantitatively trace the cause to music itself remains unproven. To recognize the benefits of music and the arts by aesthetic merit involves practical, holistic views of education not based on quantifiable test scoring

Non-diffusive spin dynamics in a two-dimensional electrongas

We describe measurements of spin dynamics in thetwo-dimensional electron gas in GaAs/GaAlAs quantum wells. Opticaltechniques, including transient spin-grating spectroscopy, are used toprobe the relaxation rates of spin polarization waves in the wavevectorrange from zero to 6E4 cm-1. We find that the spin polarization lifetimeis maximal at nonzero wavevector, in contrast with expectation based onordinary spin diffusion, but in quantitative agreement with recenttheories that treat diffusion in the presence of spin-orbitcoupling