Distribution and abundance of western gray whales during a seismic survey near Sakhalin Island, Russia.

Exxon Neftegas Limited, operator of the Sakhalin-1 consortium, is developing oil and gas reserves on the continental shelf off northeast Sakhalin Island, Russia. DalMorNefteGeofizika (DMNG), on behalf of the Sakhalin-1 consortium, conducted a 3-D seismic survey of the Odoptu license area during 17 August-9 September 2001. A portion of the primary known feeding area of the endangered western gray whale (Eschrichtius robustus) is located adjacent to the seismic block. The data presented here were collected as part of daily monitoring to determine if there was any measurable effect of the seismic survey on the distribution and abundance of western gray whales. Mitigation and monitoring program included aerial surveys conducted between 19 July and 19 November using the methodology outlined by the Southern California High Energy Seismic Survey team (HESS). These surveys provided documentation of the distribution, abundance and bottom feeding activity of western gray whales in relation to seismic survey sounds. From an operations perspective, the aerial surveys provided near real-time data on the location of whales in and outside the feeding area, and documented whether whales were displaced out of an area normally used as feeding habitat. The objectives of this study were to assess (a) temporal changes in the distribution and abundance of gray whales in relation to seismic survey, and (b) the influence of seismic survey, environmental factors, and other variables on the distribution and abundance of gray whales within their preferred feeding area adjacent to Piltun Bay. Multiple regression analysis revealed a limited redistribution of gray whales southward within the Piltun feeding area when the seismic survey was fully operational. A total of five environmental and other variables unrelated to seismic survey (date and proxies of depth, sea state and visibility) and one seismic survey-related variable (seg3d, i.e., received sound energy accumulated over 3 days) had statistically significant effects on the distribution and abundance of gray whales. The distribution of two to four gray whales observed on the surface (i.e., about five to ten whales in total) has likely been affected by the seismic survey. However, the total number of gray whales observed within the Piltun feeding area remained stable during the seismic survey.

Bis[aminoguanidinium(1+)] hexafluorozirconate(IV): redeterminations and normal probability analysis.

The crystal structure of bis[aminoguanidinium(1+)] hexafluorozirconate(IV), (CH(7)N(4))(2)[ZrF(6)], originally reported by Bukvetskii, Gerasimenko & Davidovich [Koord. Khim. (1990), 16, 1479-1484], has been redetermined independently using two different samples. Normal probability analysis confirms the reliability of all refined parameter standard uncertainties in the new determinations, whereas systematic error detectable in the earlier work leads to a maximum difference of 0.069 (6) A in atomic positions between the previously reported and present values of an F-atom y coordinate. Radiation-induced structural damage in aminoguanidinium polyfluorozirconates may result from minor displacements of H atoms in weak N-H...F bonds to new potential minima and subsequent anionic realignment.

Aminoguanidinium(1+) pentafluorozirconate: multiple redetermination and comparisons.

The structure of CN(4)H(7)ZrF(5) reported by Bukvetskii et al. [Koord. Khim. (1992). 18, 576-579] has been independently redetermined on the basis of measurements on three different crystals. Assuming all four resulting structures are drawn from a normal distribution, normal probability analysis of the atomic coordinates taken in pairs reveals joint standard uncertainties that are underestimated by factors as large as 16.5 for the x(Zr) coordinate. Unit-cell parameters in the four crystals similarly have joint uncertainties, under the same assumption, that are underestimated by factors as large as 83.0 for the b axis. The variations in axial lengths from crystal to crystal and the declines in standard reflection intensities by 13-15% in at least two of the crystals measured are consistent with the inference that the distribution is not normal. Rather, the differences observed may be assumed to be caused by small but highly significant radiation-induced structural changes. The large underestimations hence reflect physical differences among the four irradiated crystals. The determinations show that the CN(4)H(7)(+1) cation is exactly planar except for the two H atoms bonded to the terminal N atom; the plane of this NH(2) group is normal to that of the cation. The average length of the three independent C-N bonds is 1.318 (11) A; the N-N bond length is 1.397 (3) A. Distorted ZrF(7) pentagonal bipyramids share edges, forming chains linked by N-H...F bonds to the CN(4)H(7)(+1) ions.

Anhydrous ammonioguanidinium(2+) and dihydrated bis[aminoguanidinium(1+)] hexafluorosilicates: new co-products of preparing ferroelectric ammonioguanidinium(2+) hexafluorozirconate.

Ammonioguanidinium hexafluorosilicate, CH8N4(2+).SiF6(2-), and bis(aminoguanidinium) hexafluorosilicate dihydrate, 2CH7N4+.SiF6(2-).2H2O, are new materials formed as by-products in course of preparing ferroelectric CH8N4ZrF6 in the presence of glassware. Their structures were determined for comparison with the corresponding hexafluorozirconates. All atoms including the eight H atoms in the CH8N4(2+) cation and the seven H atoms in the CH7N4+ cation have been located and refined with wR(F2) = 0.0653, R = 0.0255, S = 1.146 and wR(F2) = 0.0745, R = 0.0301, S = 1.065, respectively. The N2C-N-N backbone of the 2+ cation is close to planarity, while that of the 1+ cation does not differ significantly from planarity. The SiF6(2-) octahedron is nearly ideally regular in both materials, with < Si-F > = 1.684 (unbiassed estimator of standard uncertainty = 0.016) A in the anhydrous hexafluorosilicate and 1.6801 (unbiassed estimator of standard uncertainty = 0.0006) A in the dihydrate. The combination of coulombic and NH...F interactions in CH8N4SiF6 results in a relatively dense variant of the NaCl structure. In addition to similar forces, the dihydrate is also characterized by the role of the water molecule with its strong NH...O interactions; its packing efficiency is, however, appreciably less than that of the anhydrous hexafluorosilicate with an approximately 8% increase in void space. Cleaved crystals of the dihydrate are frequently twinned across the (001) composition plane, with a twofold rotation about the b axis as the twin operation.