PCDD/F Emissions from Light-Duty Diesel Vehicles Operated under Highway Conditions and a Diesel-Engine Based Power Generator

PCDD/F emissions from three light-duty diesel vehicles–two vans and a passenger car–have been measured in on-road conditions. We propose a new methodology for small vehicles: a sample of exhaust gas is collected by means of equipment based on United States Environmental Protection Agency (U.S. EPA) method 23A for stationary stack emissions. The concentrations of O2, CO, CO2, NO, NO2 and SO2 have also been measured. Six tests were carried out at 90-100 km/h on a route 100 km long. Two additional tests were done during the first 10 minutes and the following 60 minutes of the run to assess the effect of the engine temperature on PCDD/F emissions. The emission factors obtained for the vans varied from 1800 to 8400 pg I-TEQ/Nm3 for a 2004 model year van and 490-580 pg I-TEQ/Nm3 for a 2006 model year van. Regarding the passenger car, one run was done in the presence of a catalyst and another without, obtaining emission factors (330-880 pg I-TEQ/Nm3) comparable to those of the modern van. Two other tests were carried out on a power generator leading to emission factors ranging from 31 to 78 pg I-TEQ/Nm3. All the results are discussed and compared with literature.

The influence of the sample introduction system on signals of different tin compounds in inductively coupled plasma-based techniques

The influence of the sample introduction system on the signals obtained with different tin compounds in inductively coupled plasma (ICP) based techniques, i.e., ICP atomic emission spectrometry (ICP–AES) and ICP mass spectrometry (ICP–MS) has been studied. Signals for test solutions prepared from four different tin compounds (i.e., tin tetrachloride, monobutyltin, dibutyltin and di-tert-butyltin) in different solvents (methanol 0.8% (w/w), i-propanol 0.8% (w/w) and various acid matrices) have been measured by ICP–AES and ICP–MS. The results demonstrate a noticeable influence of the volatility of the tin compounds on their signals measured with both techniques. Thus, in agreement with the compound volatility, the highest signals are obtained for tin tetrachloride followed by di-tert-butyltin/monobutyltin and dibutyltin. The sample introduction system exerts an important effect on the amount of solution loading the plasma and, hence, on the relative signals afforded by the tin compounds in ICP–based techniques. Thus, when working with a pneumatic concentric nebulizer, the use of spray chambers affording high solvent transport efficiency to the plasma (such as cyclonic and single pass) or high spray chamber temperatures is recommended to minimize the influence of the tin chemical compound. Nevertheless, even when using the conventional pneumatic nebulizer coupled to the best spray chamber design (i.e., a single pass spray chamber), signals obtained for di-tert-butyltin/monobutyltin and dibutyltin are still around 10% and 30% lower than the corresponding signal for tin tetrachloride, respectively. When operating with a pneumatic microconcentric nebulizer coupled to a 50 °C-thermostated cinnabar spray chamber, all studied organotin compounds provided similar emission signals although about 60% lower than those obtained for tin tetrachloride. The use of an ultrasonic nebulizer coupled to a desolvation device provides the largest differences in the emission signals, among all tested systems.

Modelling of the surface emission of the low magnetic field magnetar SGR 0418+5729

We perform a detailed modelling of the post-outburst surface emission of the low magnetic field magnetar SGR 0418+5729. The dipolar magnetic field of this source, B=6×1012G estimated from its spin-down rate, is in the observed range of magnetic fields for normal pulsars. The source is further characterized by a high pulse fraction and a single-peak profile. Using synthetic temperature distribution profiles, and fully accounting for the general-relativistic effects of light deflection and gravitational redshift, we generate synthetic X-ray spectra and pulse profiles that we fit to the observations. We find that asymmetric and symmetric surface temperature distributions can reproduce equally well the observed pulse profiles and spectra of SGR 0418. None the less, the modelling allows us to place constraints on the system geometry (i.e. the angles ψ and ξ that the rotation axis makes with the line of sight and the dipolar axis, respectively), as well as on the spot size and temperature contrast on the neutron star surface. After performing an analysis iterating between the pulse profile and spectra, as done in similar previous works, we further employed, for the first time in this context, a Markov-Chain Monte Carlo approach to extract constraints on the model parameters from the pulse profiles and spectra, simultaneously. We find that, to reproduce the observed spectrum and flux modulation: (a) the angles must be restricted to 65° ≲ ψ + ξ ≲ 125° or 235° ≲ ψ + ξ ≲ 295°; (b) the temperature contrast between the poles and the equator must be at least a factor of ∼6, and (c) the size of the hottest region ranges between 0.2 and 0.7 km (including uncertainties on the source distance). Lastly, we interpret our findings within the context of internal and external heating models.

Multi-Element Analysis of Spanish Date Palm (Phoenix dactylifera L.) by Inductively Coupled Plasma-Based Techniques. Discrimination Using Multivariate Statistical Analysis

The elemental analysis of Spanish palm dates by inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry is reported for the first time. To complete the information about the mineral composition of the samples, C, H, and N are determined by elemental analysis. Dates from Israel, Tunisia, Saudi Arabia, Algeria and Iran have also been analyzed. The elemental composition have been used in multivariate statistical analysis to discriminate the dates according to its geographical origin. A total of 23 elements (As, Ba, C, Ca, Cd, Co, Cr, Cu, Fe, H, In, K, Li, Mg, Mn, N, Na, Ni, Pb, Se, Sr, V, and Zn) at concentrations from major to ultra-trace levels have been determined in 13 date samples (flesh and seeds). A careful inspection of the results indicate that Spanish samples show higher concentrations of Cd, Co, Cr, and Ni than the remaining ones. Multivariate statistical analysis of the obtained results, both in flesh and seed, indicate that the proposed approach can be successfully applied to discriminate the Spanish date samples from the rest of the samples tested.

Tight-Binding Approximations in 1D and 2D Coupled-Cavity Photonic Crystal Structures

Light confinement and controlling an optical field has numerous applications in the field of telecommunications for optical signals processing. When the wavelength of the electromagnetic field is on the order of the period of a photonic microstructure, the field undergoes reflection, refraction, and coherent scattering. This produces photonic bandgaps, forbidden frequency regions or spectral stop bands where light cannot exist. Dielectric perturbations that break the perfect periodicity of these structures produce what is analogous to an impurity state in the bandgap of a semiconductor. The defect modes that exist at discrete frequencies within the photonic bandgap are spatially localized about the cavity-defects in the photonic crystal. In this thesis the properties of two tight-binding approximations (TBAs) are investigated in one-dimensional and two-dimensional coupled-cavity photonic crystal structures We require an efficient and simple approach that ensures the continuity of the electromagnetic field across dielectric interfaces in complex structures. In this thesis we develop \textrm{E} -- and \textrm{D} --TBAs to calculate the modes in finite 1D and 2D two-defect coupled-cavity photonic crystal structures. In the \textrm{E} -- and \textrm{D} --TBAs we expand the coupled-cavity \overrightarrow{E} --modes in terms of the individual \overrightarrow{E} -- and \overrightarrow{D} --modes, respectively. We investigate the dependence of the defect modes, their frequencies and quality factors on the relative placement of the defects in the photonic crystal structures. We then elucidate the differences between the two TBA formulations, and describe the conditions under which these formulations may be more robust when encountering a dielectric perturbation. Our 1D analysis showed that the 1D modes were sensitive to the structure geometry. The antisymmetric \textrm{D} mode amplitudes show that the \textrm{D} --TBA did not capture the correct (tangential \overrightarrow{E} --field) boundary conditions. However, the \textrm{D} --TBA did not yield significantly poorer results compared to the \textrm{E} --TBA. Our 2D analysis reveals that the \textrm{E} -- and \textrm{D} --TBAs produced nearly identical mode profiles for every structure. Plots of the relative difference between the \textrm{E} and \textrm{D} mode amplitudes show that the \textrm{D} --TBA did capture the correct (normal \overrightarrow{E} --field) boundary conditions. We found that the 2D TBA CC mode calculations were 125-150 times faster than an FDTD calculation for the same two-defect PCS. Notwithstanding this efficiency, the appropriateness of either TBA was found to depend on the geometry of the structure and the mode(s), i.e. whether or not the mode has a large normal or tangential component.

Porewater and particulate geochemistry during Maria S. Merian cruise MSM17/4

We present sedimentary geochemical data and in situ benthic flux measurements of dissolved inorganic nitrogen (DIN: NO3-, NO2-, NH4+) and oxygen (O2) from 7 sites with variable sand content along 18°N offshore Mauritania (NW Africa). Bottom water O2 concentrations at the shallowest station were hypoxic (42 µM) and increased to 125 µM at the deepest site (1113 m). Total oxygen uptake rates were highest on the shelf (-10.3 mmol O2 /m2 d) and decreased quasi-exponentially with water depth to -3.2 mmol O2 /m2 d. Average denitrification rates estimated from a flux balance decreased with water depth from 2.2 to 0.2 mmol N /m2 d. Overall, the sediments acted as net sink for DIN. Observed increases in delta 15NNO3 and delta 18ONO3 in the benthic chamber deployed on the shelf, characterized by muddy sand, were used to calculate apparent benthic nitrate fractionation factors of 8.0 pro mille (15epsilon app) and 14.1 pro mille (18epsilon app). Measurements of delta 15NNO2 further demonstrated that the sediments acted as a source of 15N depleted NO2-. These observations were analyzed using an isotope box model that considered denitrification and nitrification of NH4+ and NO2-. The principal findings were that (i) net benthic 14N/15N fractionation (epsilon DEN) was 12.9 ± 1.7pro mille, (ii) inverse fractionation during nitrite oxidation leads to an efflux of isotopically light NO2- (-22 ± 1.9 pro mille), and (iii) direct coupling between nitrification and denitrification in the sediment is negligible. Previously reported epsilon DEN for fine-grained sediments are much lower (4-8 pro mille). We speculate that high benthic nitrate fractionation is driven by a combination of enhanced porewater-seawater exchange in permeable sediments and the hypoxic, high productivity environment. Although not without uncertainties, the results presented could have important implications for understanding the current state of the marine N cycle.

Iron isotope and chemical compositions of sediments and basalts drilled seaward of the Mariana Trench

The purpose of this work is to study the mobility and budget of Fe isotopes in the oceanic crust and in particular during low-temperature interaction of seawater with oceanic basalt. We carried out this investigation using samples from Ocean Drilling Program (ODP) Site 801C drilled during Leg 129 and Leg 185 in Jurassic Pacific oceanic crust seaward of the Mariana Trench. The site comprises approximately 450 m of sediment overlying a section of 500 m of basalt, which includes intercalated pelagic and chemical sediments in the upper basaltic units and two low-temperature (10-30°C) ocherous Si-Fe hydrothermal deposits. Fe was chemically separated from 70 selected samples, and 57Fe/54Fe ratios were measured by MC-ICP-MS Isoprobe. The isotopic ratios were measured relative to an internal standard solution and are reported relative to the international Fe-standard IRMM-14. Based on duplicate measurements of natural samples, an external precision of 0.2? (2 sigma) has been obtained. The results indicate that the deep-sea sediment section has a restricted range of d57Fe, which is close to the igneous rock value. In contrast, large variations are observed in the basaltic section with positive d57Fe values (up to 2.05?) for highly altered basalts and negative values (down to ?2.49?) for the associated alteration products and hydrothermal deposits. Secondary Fe-minerals, such as Fe-oxyhydroxides or Fe-bearing clays (celadonite and saponite), have highly variable d57Fe values that have been interpreted as resulting from the partial oxidation of Fe(2+) leached during basalt alteration and precipitated as Fe(3+)-rich minerals. In contrast, altered basalts at Site 801C, which are depleted in Fe (up to 80%), display an increase in d57Fe values relative to fresh values, which suggest a preferential leaching of light iron during alteration. The apparent fractionation factor between dissolved Fe(2+) and Fe remaining in the mineral is from 0.5? to 1.3? and may be consistent with a kinetic isotope fractionation where light Fe is stripped from the minerals. Alternatively, the formation of secondary clays minerals, such as celadonite during basalt alteration may incorporate preferentially the heavy Fe isotopes, resulting in the loss of light Fe isotopes in the fluids. Because microbial processes within the oceanic crust are of potential importance in controlling rates of chemical reactions, Fe redox state and Fe-isotope fractionation, we evaluated the possible effect of this deep biosphere on Fe-isotope signatures. The Fe-isotope systematics presented in this study suggest that, even though iron behavior during seafloor weathering may be mediated by microbes, such as iron-oxidizers, d57Fe variations of more than 4? may also be explained by abiotic processes. Further laboratory experiments are now required to distinguish between various processes of Fe-isotope fractionation during seafloor weathering.

Optics and Optoelectronics of Two-dimensional Semiconducting Monolayers and Heterostructures

Thesis (Ph.D.)--University of Washington, 2016-06

Modeling of optical detection of spin-polarized carrier injection into light-emitting devices

We investigate the emission of multimodal polarized light from light emitting devices due to spin-aligned carrier injection. The results are derived through operator Langevin equations, which include thermal and carrier-injection fluctuations, as well as nonradiative recombination and electronic g-factor temperature dependence. We study the dynamics of the optoelectronic processes and show how the temperature-dependent g factor and magnetic field affect the degree of polarization of the emitted light. In addition, at high temperatures, thermal fluctuation reduces the efficiency of the optoelectronic detection method for measuring the degree of spin polarization of carrier injection into nonmagnetic semicondutors.

Entanglement and the Einstein-Podolsky-Rosen paradox with coupled intracavity optical down-converters

We show that two evanescently coupled χ((2)) parametric down-converters inside a Fabry-Perot cavity provide a tunable source of quadrature squeezed light, Einstein-Podolsky-Rosen (EPR) correlations and quantum entanglement. Analyzing the operation in the below threshold regime, we show how these properties can be controlled by adjusting the coupling strengths and the cavity detunings. As this can be implemented with integrated optics, it provides a possible route to rugged and stable EPR sources.

Statistics of single-electron signals in electron-multiplying charge-coupled devices

Electron-multiplying charge coupled devices promise to revolutionize ultrasensitive optical imaging. The authors present a simple methodology allowing reliable measurement of camera characteristics and statistics of single-electron events, compare the measurements to a simple theoretical model, and report camera performance in a truly photon-counting regime that eliminates the excess noise related to fluctuations of the multiplication gain.

Bright entanglement and the Einstein-Podolsky-Rosen paradox with coupled parametric oscillators

We show that two evanescently coupled chi((2)) parametric oscillators provide a tunable bright source of quadrature squeezed light, Einstein-Podolsky-Rosen correlations and quantum entanglement. Analysing the system in the above threshold regime, we demonstrate that these properties can be controlled by adjusting the coupling strengths and the cavity detunings. As this can be implemented with integrated optics, it provides a possible route to rugged and stable EPR sources. (C) 2005 Elsevier B.V. All rights reserved.

Gain switching of an external cavity grating-coupled surface emitting laser with wide tunability

The gain-switched, single frequency operation of an external cavity grating-coupled surface emitting laser with a wavelength tuning range of 100 nm was presented. The light in the grating section was coupled out of the laser at a specific angle to the surface of the device. Analysis showed that within the driving current range, lasing in the device only occurred when the external cavity was properly aligned.

Dual-peak long-period fiber gratings with enhanced refractive index sensitivity by finely tailored mode dispersion that uses the light cladding etching technique

We have experimentally investigated the mode dispersion property and refractive index sensitivity of dual-peak long-period fiber gratings (LPGs) that were sensitized by hydrofluoric acid (HF) etching. The nature of the coupled cladding modes close to the dispersion turning point makes the dual-peak LPGs ultrasensitive to cladding property, permitting a fine tailoring of the mode dispersion and index sensitivity by the light cladding etching method using HF acid of only 1% concentration. As an implementation of an optical biosensor, the etched device was used to detect the concentration of hemoglobin protein in a sugar solution, showing a sensitivity as high as 20 nm/1%.

Multispectral imaging of the ocular fundus using light emitting diode illumination

We present an imaging system based on light emitting diode (LED) illumination that produces multispectral optical images of the human ocular fundus. It uses a conventional fundus camera equipped with a high power LED light source and a highly sensitive electron-multiplying charge coupled device camera. It is able to take pictures at a series of wavelengths in rapid succession at short exposure times, thereby eliminating the image shift introduced by natural eye movements (saccades). In contrast with snapshot systems the images retain full spatial resolution. The system is not suitable for applications where the full spectral resolution is required as it uses discrete wavebands for illumination. This is not a problem in retinal imaging where the use of selected wavelengths is common. The modular nature of the light source allows new wavelengths to be introduced easily and at low cost. The use of wavelength-specific LEDs as a source is preferable to white light illumination and subsequent filtering of the remitted light as it minimizes the total light exposure of the subject. The system is controlled via a graphical user interface that enables flexible control of intensity, duration, and sequencing of sources in synchrony with the camera. Our initial experiments indicate that the system can acquire multispectral image sequences of the human retina at exposure times of 0.05 s in the range of 500-620 nm with mean signal to noise ratio of 17 dB (min 11, std 4.5), making it suitable for quantitative analysis with application to the diagnosis and screening of eye diseases such as diabetic retinopathy and age-related macular degeneration.