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The solar magnesium II core-to-wing ratio has been a well-studied proxy for chromospheric activity since 1978. Daily measurements at high spectral (0.1 nm) resolution began with the launch of the Solar Radiation and Climate Experiment (SORCE) in 2003. The next generation of measurements from the Extreme Ultraviolet Sensor (EUVS) on the Geostationary Operational Environmental Satellite 16 (GOES-16) will add high time cadence (every 30 seconds) to the observational Mg II irradiance record. We present a comparison of the two measurements during the period of overlap.
Ultraviolet (UV) Solar spectral Irradiance (SSI) has been measured from orbit on a regular basis since the beginning of the space age. These observations span four Solar Cycles, and they are crucial for our understanding of the Sun-Earth connection and space weather. SSI at these wavelengths are the main drivers for the upper atmosphere including the production and destruction of ozone in the stratosphere. The instruments that measure UV SSI not only require good preflight calibration, but also need a robust method to maintain that calibration on orbit. We will give an overview of the catalog of current and former UV SSI measurements along with the calibration philosophy of each instrument and an estimation of the uncertainties in the published irradiances.
We present the first results of a dedicated search for Diffuse Interstellar Bands that have profiles with FWHM > 6 Å. Broad DIBs have been noticed in past surveys using averages of multiple sight lines (e.g. Jenniskens & Désert, 1994), but careful detection, measurement, and cataloguing for individual sight lines has not been done since the pioneering work of Herbig (1995). We have initiated an observing campaign using the Apache Point Observatory in order to obtain low-resolution spectra to search for such broad DIBs and monitor their behaviour from star to star. A first sample of 21 stars with 0.3 < E(B-V) < 3.3 mag, along with 15 matched low-reddening stars, were observed with the APO/DIS B400 (R ~ 450) and R300 (R ~ 1000) gratings to obtain spectra having S/N > 500.
Anomalously broad diffuse interstellar bands (DIBs) at 5780.5, 5797.1, 6196.0, and 6613.6 Å are found in absorption along the line of sight to Herschel 36, an O star system next to the bright Hourglass nebula of the Hii region Messier 8. Excited lines of CH and CH+ are seen as well. We show that the region is very compact and itemize other anomalies of the gas. An infrared-bright star within 400 AU is noted. The combination of these effects produces anomalous DIBs, interpreted by Oka et al. (2013, see also this volume) as being caused predominantly by infrared pumping of rotational levels of relatively small molecules.
Optical limiting, degenerate four-wave mixing and transient absorption experiments have been performed on a neat liquid lead substituted phthalocyanine. The photophysical mechanisms responsible for the good optical limiting observed in other phthalocyanine solutions are maintained in this pure liquid despite its different peripheral substitution pattern. The liquid is shown to have excited state absorption cross sections that exceed those of the ground state through much of the visible spectrum. Hybrid absorptive/refractive nonlinear response is demonstrated to contribute to both the four-wave mixing and optical limiting response. The mechanism and states responsible are discussed.
Researchers at the Pacific Northwest National Laboratory (PNNL) investigated the effects of gadolinium oxide concentration on the air oxidization of gadolinium oxide-doped uranium dioxide using thermogravimetry and differential scanning calorimetry to determine if such doping could improve uraniumdioxide's stability as a nuclear fuel during potential accident scenarios in a nuclear reactor or during long-term disposal. We undertook this study to determine whether the resistance of the uranium dioxide to oxidation to the orthorhombic U3O8 with its attendant crystal expansion could be prevented by addition of gadolinium oxide. Our studies found that gadolinium has little effect on the thermal initiation of the first step of the reported two-step air oxidation of UO2; however, increasing gadolinium oxide content does stabilize the initial tetragonal or cubic product allowing significant oxidation before the second expansive step to U3O8 begins.
This research examines the processes which native Spanish-speaking learners of English and English-only students engage in when inferring meaning for unknown English words that have Spanish cognates. Conducted within the context of a large-scale vocabulary intervention that taught word inferencing strategies, including a cognate strategy, this qualitative study describes cognate strategy use among a small sample of participants. The data suggest that explicit instruction, students' metalinguistic and metacognitive skills, and the structural characteristics of cognate pairs are associated with cognate recognition.
In an attempt to both prepare nanocrystalline bismuth and understand the fundamental chemistry behind the formation of this potentially interesting material, we have examined the reduction of BiCl3 in the presence of strongly coordinating solvents and ligands. These studies have resulted in the formation of bismuth powders with approximate average particle sizes of between 20 and 40 nm which exhibit large size distributions. The simultaneous reduction of both gold and bismuth precursors, done in an attempt to better control the final particle size, instead produces Au2Bi of comparable dimensions. There is no evidence that the ligands utilized in either of these systems remain bound to the final product. These nanocrystalline powders have been characterized through XRD and TEM, and full details of the synthesis are presented.
The wavelength dependence of the nonlinear absorption for lead tetrakis (cumyl-phenoxy) phthalocyanine (PbPc(CP)4) and lead octa (α-pentoxy) napthalocyanine (PbNc(α-PO)8) are reported. The ground state absorption and the reverse saturable absorption are substantially red shifted in PbNc (α-PO)8 as expected. Such control over the reverse saturable absorption is crucial to design optical limiting materials for specific wavelength ranges.
To explore the use of phthalocyanine materials as a solid-state component in an optical limiter, the issues of morphology, film processing and optical limiter activity/stability are investigated. Metal-free and lead phthalocyanine films with glassy morphologies are obtained by chemically functionalizing the ring periphery with an amine-epoxy substitution. Uniform films were obtained by a shearing technique. Comparative optical measurements are made on the amine-epoxy lead phthalocyanine compound as a concentrated solution and as a glassy thin film. Both the solution and film are reverse saturable absorbers at 590 nm. The concentrated solution is a very effective optical limiter. The glassy thin film is susceptible to damage (cavitation caused by the incident beam) and performs comparably only at low incident energies. A liquid matrix may have the benefit of self-healing such damage.
Systematic studies of the nonlinear optical properties of metallo-organic materials have led to the development of promising new phthalocyanine materials for optical limiting. Several heavy metal substituted phthalocyanines exhibit a strong nonlinear absorption that is useful for optical limiters in the visible. In fast optical systems, other mechanisms, such as the thermal refraction, contribute to the limiting. The spectral window for limiting can by modified by altering the molecular structure.
An AFM-based nanolithography process is described. We employ the local electric field of a metal-coated AFM tip which is operated in air to selectively oxidize regions of a H-passivated Si surface. The resulting oxide, ∼ 3 nm thick, is used as a mask for selective etching of the unoxidized regions of Si. This AFM-based fabrication process is fast, reliable, simple to perform and is well suited for device fabrication. We apply this technique to the fabrication of Si and GaAs nanostructures, as well as to the fabrication of a nanometer-scale Si side-gated transistor. In addition, we discuss the ultimate resolution limits of the technique.
Using gel electrophoresis we demonstrate the attachment of short ssDNAs to a new type of water-soluble gold nanocluster that is encapsulated with ethylene oxide ligands. Initial experiments indicate that these DNA/nanocluster conjugates can subsequently be hybridized to a longer DNA template suggesting a pathway for nanofabrication of multi-cluster assemblies.
Zeta Tau (HD 37202) is a well known Be/shell star of spectral type B1 IVe and vsin(i) = 220 km/sec (Slettebak 1982). Its visual and UV variability have been studied extensively (Heap 1975; Hubert-Delplace and van der Hucht 1978; Hubert-Delplace et al. 1983; Dawanas and Hirata 1984; Harmanec 1984). Zeta Tau has also been found to be a binary with an orbital period of 132.97 days (Harmanec 1984). Irregular light variations have been observed (Hoffleit 1982) and long term variations not associated with the 132.97 day period have also been seen (Hubert-Delplace et al. 1983).
The acquisition of the morphological rules for plural, agentive, and diminutive suffixes in Dutch was studied. Subjects included 7- and 12-year-old native speakers, and second-language learners in three age groups (5–10 years, 12–18 years, and adult). The first- and second-language learners showed very similar orders of acquisition for the rule systems governing plural and diminutive, but the second-language learners showed a subtle form of interference from their first language in acquiring the agentive. The findings suggest that morphological acquisition proceeds piecemeal, with the learning of specific word ending + allomorph sequences, and that generalizations at the level of morphological rules may not be made even after several years of correct performance with the allomorph in question.
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