High sensitivity refractive index sensor based on simple diffraction from phase grating

We present a technique for refractive index sensing using a phase grating structure. A grating under normal incidence can be designed such that the 1st order diffracted light travels at a diffraction angle of 90o with respect to the 0th order. The diffracted light which is along the direction of periodicity can further get diffracted from the grating and interfere with the 0th order light. Under this condition, the π phase difference that arises between the two interfering beams results in a transmission dip. We can tune this dip wavelength for senor applications, based on the grating equation. Both simulation and experimental data are presented in the paper which shows good agreement with each other

Leaching of metals and metalloids from highway marking glass beads and the potential environmental impact

Glass beads are embedded in pavement markings to obtain retroreflectivity which plays a crucial role in the lighting-up effect needed for safe driving. Elevated metal and metalloid concentrations of As, Sb, and Pb have recently been observed in imported glass beads. The main objective of this research was to assess the environmental impact associated with applying these imported glass beads in highway markings. To achieve this objective, total metal concentrations were measured using two techniques: hydrofluoric acid digestion followed by inductively coupled plasma mass spectroscopy (HF/ICP-MS), and field portable x-ray fluorescence (FP-XRF) spectroscopy. A number of leaching studies were conducted and included two standard United States Environmental Protection Agency (U.S. EPA) methods: the toxicity characteristic leaching procedure (TCLP) and the synthetic precipitation leaching procedure (SPLP). In addition, a factorial study was conducted to determine the impact of environmentally relevant factors such as pH, chemicals applied on roadways, particle size, and time on metal and metalloid leaching. To compare results among the three types of studies (TCLP, SPLP, and factorial study), a select batch of glass beads with elevated concentrations was used. FP-XRF was observed to be as reliable a tool for measuring total metal and metalloid concentrations and is recommended over the use of HF/ICP-MS. Results demonstrated that the most important factors affecting leaching were pH and time. For anions such as HAsO42- and SbO3-, leaching increased with increasing pH, while for cations including Pb2+, it increased as pH decreased. Sequential extraction was conducted as well to better understand the form of metals and metalloids associated with the glass beads. While 3% were extracted in the exchangeable (As, Mn, and Ba) and the oxidizable forms (Pb), greater than 97% of metals and metalloids were associated with the glass matrix. Further studies to assess leaching as a function of total concentration in the imported batch were conducted for 30 days. Non-parametric statistics were applied to test concentrations that resulted in excess of the groundwater quality criteria. Results demonstrated that the New Jersey Default Leachate Groundwater limits for As were exceeded for 98% of the samples tested. In case of Pb, these limits were exceeded for 58% of the samples and with Sb 15%. These results suggest a potential environmental impact to groundwater used as a drinking water source when either storing glass beads in bulk or disposing of the roadway marking material in bulk

Exploring the Influence of Functional Status on Older Adults\u27 Social Relationships in Assisted Living Communities

Social relationships can have considerable influence on physical and mental well-being. AL research suggests that other residents are among the most available social contacts and that co-resident relationships can affect life satisfaction, quality of life, and well-being. Although functional status influences social relationships, research has yet to provide an in-depth understanding of how cognitive and physical function affects co-resident relationships in AL. In this thesis, I present an analysis of qualitative data collected over a one-year period in two diverse settings. The thesis addressed: 1) How does functional status influence co-resident relationships? ; and 2) What factors shape its influence? Analysis was guided by principles of Grounded Theory Method. Coming together and pulling apart signifies the key finding that functional status is multi-directional, fluid, and operates in different ways in various situations and across time. Facility and resident –level factors further affect the influence of functional status on co-resident relationships

Complexes of Organic Arsonic Acids: Part VIII - Complexes of VO2+ & Cu2+ with Arylarsonic Acids

988-99

Pairing correlations in N~Z pf-shell nuclei

We perform Shell Model Monte Carlo calculations to study pair correlations in the ground states of $N=Z$ nuclei with masses A=48-60. We find that $T=1$, $J^{\pi}=0^+$ proton-neutron correlations play an important, and even dominant role, in the ground states of odd-odd $N=Z$ nuclei, in agreement with experiment. By studying pairing in the ground states of $^{52-58}$Fe, we observe that the isovector proton-neutron correlations decrease rapidly with increasing neutron excess. In contrast, both the proton, and trivially the neutron correlations increase as neutrons are added. We also study the thermal properties and the temperature dependence of pair correlations for $^{50}$Mn and $^{52}$Fe as exemplars of odd-odd and even-even $N=Z$ nuclei. While for $^{52}$Fe results are similar to those obtained for other even-even nuclei in this mass range, the properties of $^{50}$Mn at low temperatures are strongly influenced by isovector neutron-proton pairing. In coexistence with these isovector pair correlations, our calculations also indicate an excess of isoscalar proton-neutron pairing over the mean-field values. The isovector neutron-proton correlations rapidly decrease with temperatures and vanish for temperatures above $T=700$ keV, while the isovector correlations among like nucleons persist to higher temperatures. Related to the quenching of the isovector proton-neutron correlations, the average isospin decreases from 1, appropriate for the ground state, to 0 as the temperature increases

Subgap Two-Photon States in Polycyclic Aromatic Hydrocarbons: Evidence for Strong Electron Correlations

Strong electron correlation effects in the photophysics of quasi-one-dimensional $\pi$-conjugated organic systems such as polyenes, polyacetylenes, polydiacetylenes, etc., have been extensively studied. Far less is known on correlation effects in two-dimensional $\pi$-conjugated systems. Here we present theoretical and experimental evidence for moderate repulsive electron-electron interactions in a number of finite polycyclic aromatic hydrocarbon molecules with $D_{6h}$ symmetry. We show that the excited state orderings in these molecules are reversed relative to that expected within one-electron and mean-field theories. Our results reflect similarities as well as differences in the role and magnitude of electron correlation effects in these two-dimensional molecules compared to those in polyenes.Comment: 11 pages, 5 figures, 2 table