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Ever more agricultural economics departments are offering appointments for nine rather than twelve months but little if any analysis of the impact of this change has been done. Our research shows that converting to nine-month contracts is an effective way to raise salaries without an initial outlay of new funds and thus meets the retention criterion. Lower ranks do not suffer significantly lower salaries (without supplements) and professors earn more. Because the nine-month alternative costs more, justification for converting all twelve-month faculty members must rest on other factors, such as enhanced grants or comparability.
Despite the absence of artificial light pollution at Antarctic plateau sites such as Dome A, other factors such as airglow, aurorae and extended periods of twilight have the potential to adversely affect optical observations. We present a statistical analysis of the airglow and aurorae at Dome A using spectroscopic data from Nigel, an optical/near-IR spectrometer operating in the 300–850 nm range. The median auroral contribution to the B, V and R photometric bands is found to be 22.9, 23.4 and 23.0 mag arcsec−2 respectively. We are also able to quantify the amount of annual dark time available as a function of wavelength; on average twilight ends when the Sun reaches a zenith distance of 102.6°.
We show a low temperature gas-phase synthesis route to produce faceted aluminum crystals in the aerosol phase. Use of triisobutylaluminum whose decomposition temperature is below the melting point of elemental aluminum enabled us to grow nanocrystals from its vapor. Combustion tests show an increase in energy release compared to commercial nanoaluminum. Production of aluminum in an oxygen free environment resulted in a bare aluminum surface that was passivated in separate experiments with nickel and iron by decomposition of their carbonyl precursors.
The low vapor pressure of many energetic materials presents a challenge for detection by non-contact methods. We address this limitation by illuminating energetic materials including TNT and RDX with infrared lasers tuned to strong molecular absorption bands to efficiently heat trace amounts present on substrates. This substantially increases their vapor signatures for direct detection, obviating the need to swab surfaces for solid particles or to collect headspace vapors for extended time periods. The instantaneously generated vapor produced by Laser Trace Vaporization (LTV) can be detected by any number of techniques which can accommodate vapor sampling or spectroscopic analysis. Currently the testbed for LTV incorporates a tunable quantum cascade laser (QCL) to illuminate the sample and an ion mobility spectrometer (IMS) to validate the signal enhancement. The LTV technique works well with all tested substrates, though the thermal and spectroscopic properties of the substrate can influence the efficiency of the vaporization. Computational results from laser heating along with experimental thermal kinetic measurements were used to optimize LTV laser irradiation parameters. In addition to a range of LTV results for different explosives and substrates, we explore the effects of wavelength-dependent heating on the sample and substrate.
Following the generic strategy of creating core-shell structured nanoparticles reported by our group previously  and exploring its applications, an aerosol route combined with iron carbonyl decomposition was developed to encapsulate strong oxidizer within mild oxidizer particles. This modified method enables the application of hygroscopic nano-energetic materials by stabilizing them within a water-insoluble shell. Fe2O3/I2O5 composite oxidizers have been created. Some of the results obtained from combustion tests show that the composite system significantly outperforms the single metal oxide (Fe2O3) system in both pressurization rate and peak pressure. The time-resolved mass spectrometry shows that a significant amount of O2 and I2 are released from the composite oxidizers. These preliminary results suggest a supplement to the previous strategy of obtaining the core-shell structured composite oxidizers and the method still needs to be further optimized.
A T-Jump/Time-of-Flight Mass Spectrometer (T-Jump/TOFMS) is used to probe the decomposition of several aminotetrazole containing energetic materials under very high heating rates of 105-106 K/s. Subtle differences between materials in functional group placement and anion composition allow for further understanding of the decomposition pathway of the tetrazole structure and various anions. Two decomposition pathways for the tetrazole ring are observed, which result in the primary formation of HN3 or N2. Further analysis is performed using a rapid-heating μ-DSC device, which revealed lower activation energies than previously reported.
RED is a technique we have developed for stand-off detection of trace explosives using infrared (IR) photo-thermal imaging [1,2,3]. RED incorporates compact IR quantum cascade lasers tuned to strong characteristic absorption bands and may be used to illuminate explosives present as particles on a surface. An IR focal plane array is used to image the surface and detect any small increase in the thermal emission upon laser illumination. We have previously demonstrated the technique at several meters to 10’s of meters of stand-off distance indoors and in field tests [4,5], while operating the lasers below the eye-safe intensity limit (100 mWcm2) . Sensitivity to traces of explosives as small as a nanogram has been demonstrated. By varying the incident wavelength slightly, we can readily show selectivity between individual explosives such as TNT and RDX. Using a sequence of lasers at different wavelengths, we increase both sensitivity and selectivity. A complete detection protocol can be performed in a sub-second time domain. More recently, RED has been used to emphasize measurements with cooled detectors in addition to examining the utility of filtering the collected thermal emission signal which is rich in analyte-specific spectroscopic information. A next generation RED system and detection algorithm is being developed to take advantage of these more powerful features. This manuscript will include an overview of the approach and recent experimental results.
Dye-sensitized solar cells composed of an n-doped ZnO nanowire array and a p-doped polymer layer appears to be a promising candidate for low-cost production of environment-friendly solar cells. In this work, we investigate hybrid devices consisting of a transparent conducting oxide (TCO) substrate, ZnO-nanowires (ZnO-NW) or a sol-gel prepared ZnO layer, a ruthenium dye (N719) and a PEDOT:PSS or P3HT layer. The dense polycrystalline ZnO layer is able to prevent short circuits, which have a strong effect on the performance of the solar cells. This is demonstrated by the use of only the ZnO layer which improves the open circuit voltage by a factor of 2 and the efficiency by a factor of 1.7 compared to cells with nanowires. That indicates that the system combined with a thin but dense ZnO layer and NW grown on it will show further improvement. Furthermore three different TCO substrates were investigated. Impedance spectroscopy (IS) reveals at least one additional Schottky barrier formed with ZnO:Al substrates. Spectral photovoltage measurements clearly show distinct absorption features correlated with the ZnO and N719 dye.
The wasp petiole (waist) is a self-assembled, multifunctional, hierarchically structured tube, which in some species has a simple, near-cylindrical shape that simplifies mechanical property characterization. We describe studies performed by scanning electron microscopy and transmission electron microscopy that reveal several details about the hierarchical structure of mud dauber wasp petiole, including: the number and thickness of the concentric layers of cuticle comprising the wall; the similarity (and differences) between the wall structure and the structure of multi-layer corrugated cardboard; and the different anisotropies of the dorsal and ventral internal surfaces. We also describe a simple experiment in which a petiole is used as a cantilever to determine its stiffness in bending; the result (1.5 GPa) demonstrates a material efficiency in bending similar to that of GFRP and aluminum.
We have measured the transient events of the α-β martensitic transformation in nanocrystalline Ti films via single shot electron diffraction patterns with 1.5 ns temporal resolution. This was accomplished with a newly constructed dynamic transmission electron microscope (DTEM), which combines pulsed laser systems and pump-probe techniques with a conventional TEM. The DTEM thereby enables studies of transformations that are (1) far too fast to be captured by conventional bulk techniques, and (2) difficult to study with current ultrafast electron diffraction (UED) instruments (which typically require an accumulation of multiple shots for each diffraction pattern). Martensitic transformations in nanocrystalline materials meet both criteria, with their rapid nucleation, characteristic interface velocities ∼1 km/s, and significant irreversible microstructural changes. Free-standing 40-nm-thick Ti films were laser-heated at a rate of ∼1010 K/s to a temperature above the 1155 K transition point, then probed at various time intervals with a 1.5-ns-long intense electron pulse. Diffraction patterns show an almost complete transition to the β phase within 500 ns. Post-mortem analysis (after the sample is allowed to cool) shows a reversion to the α phase coupled with substantial grain growth, lath formation, and texture modification. The cooled material also shows a complete lack of apparent dislocations, suggesting the possible importance of a "massive" short-range diffusion mechanism.
This paper outlines a simple method to fabricate a bilayer membrane consisting of a thin nanoporous gold layer infused with uncured polydimethylsiloxane. The fabrication technique offers excellent adhesion due to mechanical interlocking between porous layer and elastomer, and excellent electrical conductivity up to 25% strain, despite a very low effective elastic modulus (∼1.35 MPa) due to cracks in the embedded gold layer. Initially freestanding circular membranes displayed significant out of plane buckling, and created difficulties in extraction of membrane mechanical properties. The underlying mechanisms of compressive stress accumulation that lead to membrane buckling and remedies to prevent it are discussed.
This study examined healthcare utilization in the past year by subjects who screened positive for bipolar versus unipolar depression.
A self-administered survey was completed in 2002 by a United States population-based sample. Respondents were categorized into one of three subgroups: bipolar depressed screen positive (BP DEP+, n=394); unipolar depressed screen positive (UP DEP+, n=794); and control subjects (n=1,612).
For depressive symptoms in the past year, BP DEP+ respondents were significantly more likely than UP DEP+ respondents to report a healthcare visit to a number of diverse care providers. In analyses controlled for demographics and depression severity, the differences in psychiatric hospitalization, psychologist/counselor outpatient visit, substance abuse/social services visit, and number of emergency room visits remained significant between BP DEP+ and UP DEP+ respondents.
Subjects with self-reported bipolar depression sought care more often from a number of diverse healthcare resources than subjects with self-reported unipolar depression. These findings underscore the morbidity associated with bipolar depression.
This study tested the hypothesis that the hippocampus has a
relatively specific role in retaining information over delays.
Thirty-seven subjects with probable Alzheimer's disease were
evaluated with a verbal memory task and structural MRI. Cortical gray
matter but not hippocampal volume predicted immediate free recall. In
contrast, hippocampal volume was the best predictor of how well
information was retained over a delay, even after controlling for
levels of immediate recall. Results suggest that the role of the
hippocampus is relatively specific to the consolidation of new
memories. (JINS, 2004, 10, 639–643.)
A residual demand model for beef exports to Japan is specified and estimated. The objective is to estimate the extent of market power. It is assumed that each exporting country faces a downward-sloping residual demand curve, which reflects the market demand minus the supplies of competitors, and that exporters maximize profit through their output decisions. The analysis is disaggregated by beef cut and form to capture the variation by beef market segments. The results indicate that the highest markup of price over marginal cost belongs to U.S. frozen ribs, the only indication of market power by U.S. exporters. Canada is found to have limited market power, whereas Australia and New Zealand enjoy some market power, including five chilled beef categories.
This article examines the impacts of monetary policy on agricultural prices in four Asian economies using time series analysis and graph theory. The estimations clearly show that agricultural prices overshoot their long-run equilibrium values for Korea, Philippines, and Thailand, and the overshooting for agricultural prices is larger than for manufactured prices. Impulse-response functions and variance-decomposition analysis based on directed graphs and causal structures highlight the complex interplay among the variables in the model and how those relationships differ by country. Money supply changes clearly affect real variables and relative prices for all countries either through overshooting or non-neutrality of money.