N-heterocyclic germylenes: structural characterisation of some heavy analogues of the ubiquitous N-heterocyclic carbenes

The X-ray crystal structures of three N-heterocyclic germylenes (NHGes) have been elucidated including the previously unknown 1,3-bis(2,6-dimethylphenyl)diazagermol-2-ylidene (1). In addition, the X-ray crystal structures of the previously synthesised 1,3-bis(2,4,6-trimethylphenyl)diazagermol-2-ylidene (2) and 1,3-bis(2,6-diisopropylphenyl)diazagermol-2-ylidene (3) are also reported. The discrete molecular structures of compounds 1 to 3 are comparable, with Ge-N bond lengths in the range 1.835-1.875 Å, while the N-Ge-N bond angles range between 83.6 and 85.2°. Compound 2 was compared to the analogous N-heterocyclic carbene species, 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes). The major geometrical difference observed, as expected, was the bond angle around the divalent group 14 atom. The N-Ge-N bond angle was 83.6° for compound 2 versus the N-C-N bond angle of 101.4° for IMes. The Sn equivalent of (1), 1,3-bis(2,6-dimethylphenyl)diazastannol-2-ylidene (4), has also been synthesised and its crystal structure is reported here. In order to test their suitability as ligands, compounds 1 to 3 were reacted with a wide range of transition metal complexes. No NHGes containing metal complexes were observed. In all cases the NHGe either degraded or gave no reaction

Shuttle orbiter Ku-band radar/communications system design evaluation: High gain antenna/widebeam horn

The physical characteristics of the high gain antenna reflector and feed elements are described. Deficiencies in the sum feed are discussed, and lack of atmospheric venting is posed as a potential problem area. The measured RF performance of the high gain antenna is examined and the high sidelobe levels measured are related to the physical characteristics of the antenna. An examination of the attributes of the feed which might be influenced by temperature extremes shows that the antenna should be insensitive to temperature variations. Because the feed support bipod structure is considered a significant contributor to the high sidelobe levels measured in the azimuth plane, pod relocation, material changes, and shaping are suggested as improvements. Alternate feed designs are presented to further improve system performance. The widebeam horn and potential temperature effects due to the polarizer are discussed as well as in the effects of linear polarization on TDRS acquisition, and the effects of circular polarization on radar sidelobe avoidance. The radar detection probability is analyzed as a function of scan overlap and target range

Standing Swells Surveyed Showing Surprisingly Stable Solutions for the Lorenz '96 Model

The Lorenz '96 model is an adjustable dimension system of ODEs exhibiting chaotic behavior representative of dynamics observed in the Earth's atmosphere. In the present study, we characterize statistical properties of the chaotic dynamics while varying the degrees of freedom and the forcing. Tuning the dimensionality of the system, we find regions of parameter space with surprising stability in the form of standing waves traveling amongst the slow oscillators. The boundaries of these stable regions fluctuate regularly with the number of slow oscillators. These results demonstrate hidden order in the Lorenz '96 system, strengthening the evidence for its role as a hallmark representative of nonlinear dynamical behavior.Comment: 10 pages, 8 figure

Engineering evaluations and studies. Report for Ku-band studies, exhibit A

System performance aspects of the Ku band radar communication hardware and investigations into the Ku band/payload interfaces are discussed. The communications track problem caused by the excessive signal dynamic range at the servo input was investigated. The management/handover logic is discussed and a simplified description of the transmitter enable logic function is presented. Output noise produced by a voltage-controlled oscillator chip used in the SPA return-link channel 3 mid-bit detector is discussed. The deployed assembly (DA) and EA-2 critical design review data are evaluated. Cross coupling effects on antenna servo stability were examined. A series of meetings on the acceptance test specification for the deployed assembly is summarized

Hydrogeological report on water well monitoring in Aboriginal lands to May 2002

Water well monitoring data from wells on Aboriginal lands (Pitjantjatjara, Yalata, Nepabunna and Oak Valley) are summarised for the period April 2001 to May 2002. This report also shows plots and analysis of all data for each well since monitoring began. In the Pitjantjatjara lands aquifers at all communities except Kalka, Mimili and Fregon showed significant recharge and water levels have recovered to, or are above, the levels recorded at the time of drilling. The three exceptions are probably extensive aquifers that have generally been free from signs of depletion. The only community for which there is any short term (5-10 years) concern is Indulkana. Whilst there was recharge to the older wells, the community now relies on the Indulkana Range wells for a larger portion of its water supply. The aquifer in which these wells is completed was not recharged and water levels are declining. At Nepabunna supplies are still marginal and the heavy pumping regime has made monitoring insensitive to small but possibly significant changes. Modification of the monitoring is required, preferably with separate monitoring wells. The Yalata aquifer is unaffected by pumping, but the groundwater level appears to be declining by natural drainage. No recharge is observed. Oak Valley supplies have held up remarkably well, but are still regarded as fragile. Stringent water management is essential if the additional costs of importing water are to be avoided.repor

Formation of a nonanuclear copper(II) cluster with 3,5-dimethylpyrazolate starting from an NHC complex of copper(I) chloride

The complete nonanuclear cluster in bis[1,3-bis(2,6-dimethylphenyl)imidazolium] di--chlorido-tetrachloridooctakis(-3,5-dimethylpyrazolato)hexa-3- hydroxido-nonacopper(II) chloroform disolvate, [HIXy]2[Cu9(-pz*)8(3- OH)6(2-Cl)2Cl4]2CHCl3 or (C19H21N2)2[Cu9(C5H7N2)8Cl6(OH)6]2CHCl3, where pz* is the 3,5-dimethylpyrazolyl anion, C5H7N2 , and HIXy is the 1,3- bis(2,6-dimethylphenyl)imidazolium cation, C19H21N2 +, is generated by a crystallographic centre of symmetry with a square-planar CuII ion bound to four 3-OH ions lying on the inversion centre. Of the four remaining unique CuII atoms, three adopt CuN2O2Cl square-pyramidal coordination geometries with the chloride ion in the apical position and one has a distorted CuN2OCl tetrahedral geometry. The dianionic nonanuclear core can be described as a 24-membered [CuNN]8 ring that contains a Cu9O6Cl6 core. The cluster features three intramolecular O—H Cl hydrogen bonds. In the crystal, weak C— H N and C—H Cl interactions link the components. Polynuclear paramagnetic clusters of this type are of considerable interest due to their relevance to both the bioinorganic and single-molecule magnets research fields

Assessing Accommodation Suppliers' Perceptions of Climate Change Adaptation Actions on Koh Phi Phi Island, Thailand

Koh Phi Phi Don is among the most visited island tourism destinations in Thailand. Due to the island’s topography and development patterns, most accommodation suppliers on the island are likely to be exposed to a range of climate change impacts, particularly sea-level rise, which can pose a severe risk to the local tourism operations. This study aimed to explore perceptions of climate change adaptation actions in response to impacts typically associated with climate change. This study, furthermore, investigated possible obstacles, barriers, and incentives influencing decision-making processes of accommodation owner-managers (the private sector) to adapt to climate change. The investigation builds on 81 surveys and 12 in-depth interviews. The findings provide evidence that most of the sampled businesses already implemented (consciously or not) climate change adaptation measures, such as insurance coverage, water treatment appliances, and staff training on emergency responses. Through a concentration of power on the island, their action is hindered, which creates a barrier to a sustainable and climate risk-informed development pathway

What does the Iowa farmer want from radio market news?

Most of the results in this report are based on a personal interview survey of Iowa open-country farmers. Ninety-six percent (178,000) of the operators of Iowa open-country farms sold one or more of Iowa\u27s six top cash farm income products in 1948. About 92 percent of the open-country zone farm operators listened to day-to-day broadcasts of market reports* before making their last sales of butcher hogs, cattle, corn, soybeans, cream or whole milk and eggs

An Inverse Compton Scattering Origin of X-ray Flares from Sgr A*

The X-ray and near-IR emission from Sgr A* is dominated by flaring, while a quiescent component dominates the emission at radio and sub-mm wavelengths. The spectral energy distribution of the quiescent emission from Sgr A* peaks at sub-mm wavelengths and is modeled as synchrotron radiation from a thermal population of electrons in the accretion flow, with electron temperatures ranging up to $\sim 5-20$\,MeV. Here we investigate the mechanism by which X-ray flare emission is produced through the interaction of the quiescent and flaring components of Sgr A*. The X-ray flare emission has been interpreted as inverse Compton, self-synchrotron-Compton, or synchrotron emission. We present results of simultaneous X-ray and near-IR observations and show evidence that X-ray peak flare emission lags behind near-IR flare emission with a time delay ranging from a few to tens of minutes. Our Inverse Compton scattering modeling places constraints on the electron density and temperature distributions of the accretion flow and on the locations where flares are produced. In the context of this model, the strong X-ray counterparts to near-IR flares arising from the inner disk should show no significant time delay, whereas near-IR flares in the outer disk should show a broadened and delayed X-ray flare.Comment: 22 pages, 6 figures, 2 tables, AJ (in press

Shuttle orbiter Ku-band radar/communications system design evaluation

Tasks performed in an examination and critique of a Ku-band radar communications system for the shuttle orbiter are reported. Topics cover: (1) Ku-band high gain antenna/widebeam horn design evaluation; (2) evaluation of the Ku-band SPA and EA-1 LRU software; (3) system test evaluation; (4) critical design review and development test evaluation; (5) Ku-band bent pipe channel performance evaluation; (6) Ku-band LRU interchangeability analysis; and (7) deliverable test equipment evaluation. Where discrepancies were found, modifications and improvements to the Ku-band system and the associated test procedures are suggested