State of Florida Division of Administrative Hearings: Petitioner\u27s First Interrogatories to University of North Florida

Legal documents related to a dispute between the Sawmill Slough Conservation Club vs. the University of North Floridahttps://digitalcommons.unf.edu/sawmill_history/1011/thumbnail.jp

State of Florida Division of Administrative Hearings: Petitioner\u27s First Interrogatories to St. Johns River Water Management District

Legal documents related to a dispute between the Sawmill Slough Conservation Club vs. the University of North Floridahttps://digitalcommons.unf.edu/sawmill_history/1009/thumbnail.jp

State of Florida Division of Administrative Hearings: Motion to Dismiss

Legal documents related to a dispute between the Sawmill Slough Conservation Club vs. the University of North Floridahttps://digitalcommons.unf.edu/sawmill_history/1012/thumbnail.jp

Fight On! A Thirty Year History of the Sawmill Slough Conservation Club

A history of the Sawmill Slough Conservation Club from it\u27s beginnings to 2003https://digitalcommons.unf.edu/conservation_club/1000/thumbnail.jp

Prediction of the Crystal Structures of Perovskites Using the Software Program SPuDS

The software program SPuDS has been developed to predict the crystal structures of perovskites, including those distorted by tilting of the octahedra. The user inputs the composition and SPuDS calculates the optimal structure in ten different Glazer tilt systems. This is performed by distorting the structure to minimize the global instability index, while maintaining rigid octahedra. The location of the A-site cation is chosen so as to maximize the symmetry of its coordination environment. In its current form SPuDS can handle up to four different A-site cations in the same structure, but only one octahedral ion. Structures predicted by SPuDS are compared with a number of previously determined structures to illustrate the accuracy of this approach. SPuDS is also used to examine the prospects for synthesizing new compounds in tilt systems with multiple A-site coordination geometries (a+a+a+, a0b+b+, a0b-c+)

Jahn-Teller Distortions, Cation Ordering and Octahedral Tilting in Perovskites

In transition metal oxides, preferential occupation of specific d orbitals on the transition metal ion can lead to the development of a long-range ordered pattern of occupied orbitals. This phenomenon, referred to as orbital ordering, is usually observed indirectly from the cooperative Jahn-Teller distortions (CJTDs) that result as a consequence of the orbital ordering. This paper examines the interplay between orbital ordering, octahedral tilting and cation ordering in perovskites. Both ternary AMX3 perovskites containing an active Jahn-Teller (J-T) ion on the octahedral site and quaternary A2MM\u27X6 perovskites containing a J-T ion on one-half of the octahedral sites have been examined. In AMX3 perovskites, the tendency is for the occupied 3d3x2-r2 and 3d3z2-r2 orbitals to order in the ac plane, as exemplified by the crystal structures of LaMnO3 and KCuF3. This arrangement maintains a favorable coordination environment for the anion sites. In AMX3 perovskites, octahedral tilting tends to enhance the magnitude of the J-T distortions. In A2MM\u27X6 perovskites, the tendency is for the occupied 3d3z2-r2 orbitals to align parallel to the c axis. This pattern maintains a favorable coordination environment about the symmetric M\u27-cation site. The orbital ordering found in rock-salt ordered A2MM\u27X6 perovskites is compatible with octahedral rotations about the c axis (Glazer tilt system a0a0c-) but appears to be incompatible with GdFeO3-type octahedral tilting (tilt system a-b+a-)

Testing of the LSST's photometric calibration strategy at the CTIO 0.9 meter telescope

The calibration hardware system of the Large Synoptic Survey Telescope (LSST) is designed to measure two quantities: a telescope's instrumental response and atmospheric transmission, both as a function of wavelength. First of all, a "collimated beam projector" is designed to measure the instrumental response function by projecting monochromatic light through a mask and a collimating optic onto the telescope. During the measurement, the light level is monitored with a NIST-traceable photodiode. This method does not suffer from stray light effects or the reflections (known as ghosting) present when using a flat-field screen illumination, which has a systematic source of uncertainty from uncontrolled reflections. It allows for an independent measurement of the throughput of the telescope's optical train as well as each filter's transmission as a function of position on the primary mirror. Second, CALSPEC stars can be used as calibrated light sources to illuminate the atmosphere and measure its transmission. To measure the atmosphere's transfer function, we use the telescope's imager with a Ronchi grating in place of a filter to configure it as a low resolution slitless spectrograph. In this paper, we describe this calibration strategy, focusing on results from a prototype system at the Cerro Tololo Inter-American Observatory (CTIO) 0.9 meter telescope. We compare the instrumental throughput measurements to nominal values measured using a laboratory spectrophotometer, and we describe measurements of the atmosphere made via CALSPEC standard stars during the same run

Structure Prediction of Ordered and Disordered Multiple Octahedral Cation Perovskites using SPuDS

The software package SPuDS has previously been shown to accurately predict crystal structures of AMX3 and A1 - xA\u27xMX3 perovskites that have undergone octahedral tilting distortions. This paper describes the extension of this technique and its accuracy for A2MM\u27X6 ordered double perovskites with the aristotype Fm3̄m cubic structure, as well as those that have undergone octahedral tilting distortions. A survey of the literature shows that roughly 70% of all ordered double perovskites undergo octahedral tilting distortions. Of the 11 distinct types of octahedral tilting that can occur in ordered perovskites, five tilt systems account for ~97% of the reported structures. SPuDS can calculate structures for the five dominant tilt systems, Fm3̄m (a0a0a0), I4/m (a0a0c-), R3̄ (a-a-a-), I2/m (a0b-b-) and P21/n (a-a-b+), as well as two additional tilt systems, Pn3̄ (a+a+a+) and P4/mnc (a0a0c+). Comparison with reported crystal structures shows that SPuDS is quite accurate at predicting distortions driven by octahedral tilting. The favored modes of octahedral tilting in ordered double perovskites are compared and contrasted with those in AMX3 perovskites. Unit-cell pseudosymmetry in Sr- and Ca-containing double perovskites is also examined. Experimentally, Sr2MM\u27O6 compounds show a much stronger tendency toward pseudosymmetry than do Ca2MM\u27O6 compounds with similar tolerance factors

Structure Determination of A2M3+TaO6 and A2M3+NbO6 Ordered Perovskites: Octahedral Tilting and Pseudosymmetry

The room-temperature crystal structures of six A2M3+M5+O6 ordered perovskites have been determined from neutron and X-ray powder diffraction data. Ba2YNbO6 adopts the aristotype high-symmetry cubic structure (space group Fm3̄m, Z = 4). The symmetries of the remaining five compounds were lowered by octahedral tilting distortions. Out-of-phase rotations of the octahedra about the c axis were observed in Sr2CrTaO6 and Sr2GaTaO6, which lowers the symmetry to tetragonal (space group = I4/m, Z = 2, Glazer tilt system = a0a0c-). Octahedral tilting analogous to that seen in GdFeO3 occurs in Sr2ScNbO6, Ca2AlNbO6 and Ca2CrTaO6, which lowers the symmetry to monoclinic (space group P21/n, Z = 2, Glazer tilt system = a-a-c+). The Sr2MTaO6 (M = Cr, Ga, Sc) compounds have unit-cell dimensions that are highly pseudo-cubic. Ca2AlNbO6 and Ca2CrTaO6 have unit-cell dimensions that are strongly pseudo-orthorhombic. This high degree of pseudosymmetry complicates the space-group assignment and structure determination. The space-group symmetries, unit-cell dimensions and cation ordering characteristics of an additional 13 compositions, as determined from X-ray powder diffraction data, are also reported. An analysis of the crystal structures of 32 A2MTaO6 and A2MNbO6 perovskites shows that in general the octahedral tilt system strongly correlates with the tolerance factor