4,726 research outputs found
Money, Inflation, and Relative Prices: Implications for U.S. Agriculture
In a recent study, Starleaf, Meyers, and Womack (S-M-W, 1985) analyzed the behavior of annual time series data in the United States on various farm and nonfarm price indices over the 1929-1983 period and three subperiods in order to examine the proposition that changes in the general rate of inflation have Nonneutral effects on the farm sector. They found that short-run increases (decreases) in the rate of inflation of farm input and nonfarm output prices have typically been accompanied by even larger short-run increases (decreases) in the rate of inflation of farm output prices. While S-M-W did not explicitly account for the effects of unanticipated inflation on these relative prices in their empirical analysis, they concluded that these regularities indicate that an unanticipated increase (decrease) in general inflation rate tends to enhance (diminish) the well-being of farmers. This conclusion is consistent with macroeconomic theory that unanticipated aggregate demand shocks will affect relative prices in favor of producers of nondurable goods traded in flex-price markets. It is however, surprising to the believers of the conventional wisdom, who content that farmers suffer from inflation. Tweeten, for example, has presented evidence in several studies that he says support the view that farmers hare harmed by higher rates of general price inflation
Book Reviews
Reviews of the following books: Chansonetta: The Life and Photographs of Chansonetta Stanley Emmons, 1859-1937 by Marius B. Peladeau; Raymond Then and Now by Ernest H. Knight; The Jesuit Heritage of New England by Vincent A. Lapomarda; The Landing: A Remembrance of Her People and Shipyards by Thomas W. Murphy; A History of the Town of Hancock, 1828-1979 prepared by the Sesquicentennial Committee of the Town of Hancoc
An Empirical Evaluation of Statistical Matching Methodologies
Using known data, the methodologies available for microdata file merging are compared. Results indicate that various techniques work or do not work in specific circumstances. An optimal-constrined merge model with an absolute difference distance function provide the best results
Book Reviews
Reviews of the following books: History of Belfast in the 20th Century: by Jay David and Tim Hughes, with Megan Pinette; At Home With The General: A Visit to the Joshua L. Chamberlain Museum by Allan M. Levinsky; âDo Your Job!â An Illustrated Bicentennial History of the Portsmouth Naval Shipyard, 1800-2000 by Richard E. Winslow, III; Super U: The History and Politics of the University of Maine System by James Libb
Mermithid Nematodes: SEM Observations Comparing Hexamethyldisilazane and Critical Point Drying Methods
Morphological features of mermithid nematodes (Mermithidae) were studied with scanning electron microscopy, using hexamethyldisilazane-air drying in comparison with critical point drying via liquid carbon dioxide. Although general morphologic preservation of both HMDS-dried and CP-dried specimens was similar, structural features of the complex cuticle and internal organization were more easily resolved at higher magnifications in the HMDS-dried nematodes. These features include the superficial cuticular annulations, the fibrillar inner cuticle and peg-like microtrabeculae. The previously undescribed microtrabeculae are of special interest since they may facilitate an interaction of the mermithid (and perhaps nameatodes in general) musculature with its body wall that, at least in part, may account for the unique thrashing locomotion so characteristic of these organisms
The impact of oxidation on spore and pollen chemistry
Sporomorphs (pollen and spores) have an outer wall composed of sporopollenin. Sporopollenin chemistry contains both a signature of ambient ultraviolet-B flux and taxonomic information, but it is currently unknown how sensitive this is to standard palynological processing techniques. Oxidation in particular is known to cause physical degradation to sporomorphs, and it is expected that this should have a concordant impact on sporopollenin chemistry. Here, we test this by experimentally oxidizing Lycopodium (clubmoss) spores using two common oxidation techniques: acetolysis and nitric acid. We also carry out acetolysis on eight angiosperm (flowering plant) taxa to test the generality of our results. Using Fourier Transform infrared (FTIR) spectroscopy, we find that acetolysis removes labile, non-fossilizable components of sporomorphs, but has a limited impact upon the chemistry of sporopollenin under normal processing durations. Nitric acid is more aggressive and does break down sporopollenin and reorganize its chemical structure, but when limited to short treatments (i.e. â€10 min) at room temperature sporomorphs still contain most of the original chemical signal. These findings suggest that when used carefully oxidation does not adversely affect sporopollenin chemistry, and that palaeoclimatic and taxonomic signatures contained within the sporomorph wall are recoverable from standard palynological preparations
Noble gases in deepwater oils of the U.S. Gulf of Mexico
Author Posting. © American Geophysical Union, 2018. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 19(11), (2018): 4218-4235. doi: 10.1029/2018GC007654Hydrocarbon migration and emplacement processes remain underconstrained despite the vast potential economic value associated with oil and gas. Noble gases provide information about hydrocarbon generation, fluid migration pathways, reservoir conditions, and the relative volumes of oil versus water in the subsurface. Produced gas HeâNeâArâKrâXe data from two distinct oil fields in the Gulf of Mexico (Genesis and HooverâDiana) are used to calibrate a model that takes into account both waterâoil solubility exchange and subsequent gas cap formation. Reconstructed noble gas signatures in oils reflect simple (twoâphase) oilâwater exchange imparted during migration from the source rock to the trap, which are subsequently modified by gas cap formation at current reservoir conditions. Calculated, oil to water volume ratios ( urn:x-wiley:15252027:media:ggge21714:ggge21714-math-0001) in Tertiaryâsourced oils from the HooverâDiana system are 2â3 times greater on average than those in the Jurassic sourced oils from the Genesis reservoirs. Higher urn:x-wiley:15252027:media:ggge21714:ggge21714-math-0002 in HooverâDiana versus Genesis can be interpreted in two ways: either (1) the Hoover reservoir interval has 2â3 times more oil than any of the individual Genesis reservoirs, which is consistent with independent estimates of oil in place for the respective reservoirs, or (2) Genesis oils have experienced longer migration pathways than HooverâDiana oils and thus have interacted with more water. The ability to determine a robust urn:x-wiley:15252027:media:ggge21714:ggge21714-math-0003, despite gas cap formation and possible gas cap loss, is extremely powerful. For example, when volumetric hydrocarbon ratios are combined with independent estimates of hydrocarbon migration distance and/or formation fluid volumes, this technique has the potential to differentiate between large and small oil accumulations.We thank ExxonMobil for funding and providing the samples. In addition, we thank James Scott and two anonymous reviewers for their comprehensive and constructive reviews, as well as Janne BlichertâToft for editorial handling.2019-04-1
Impact experiments into multiple-mesh targets: Concept development of a lightweight collisional bumper
The utility of multiple-mesh targets as potential lightweight shields to protect spacecraft in low-Earth orbit against collisional damage is explored. Earlier studies revealed that single meshes comminute hypervelocity impactors with efficiencies comparable to contiguous targets. Multiple interaction of projectile fragments with any number of meshes should lead to increased comminution, deceleration, and dispersion of the projectile, such that all debris exiting the mesh stack possesses low specific energies (ergs/sq cm) that would readily be tolerated by many flight systems. The study is conceptually exploring the sensitivity of major variables such as impact velocity, the specific areal mass (g/sq cm) of the total mesh stack (SM), and the separation distance (S) between individual meshes. Most experiments employed five or ten meshes with total SM typically less than 0.5 the specific mass of the impactor, and silicate glass impactors rather than metal projectiles. While projectile comminution increases with increasing impact velocity due to progressively higher shock stresses, encounters with multiple-meshes at low velocity (1-2 km/s) already lead to significant disruption of the glass impactors, with the resulting fragments being additionally decelerated and dispersed by subsequent meshes, and, unlike most contiguous single-plate bumpers, leading to respectable performance at low velocity. Total specific bumper mass must be the subject of careful trade-off studies; relatively massive bumpers will generate too much debris being dislodged from the bumper itself, while exceptionally lightweight designs will not cause sufficient comminution, deceleration, or dispersion of the impactor. Separation distance was found to be a crucial design parameter, as it controls the dispersion of the fragment cloud. Substantial mass savings could result if maximum separation distances were employed. The total mass of debris dislodged by multiple-mesh stacks is modestly smaller than that of single, contiguous-membrane shields. The cumulative surface area of all penetration holes in multiple mesh stacks is an order of magnitude smaller than that in analog multiple-foil shields, suggesting good long-term performance of the mesh designs. Due to different experimental conditions, direct and quantitative comparison with other lightweight shields is not possible at present
Biomechanical Tolerance of Whole Lumbar Spines in Straightened Posture Subjected to Axial Acceleration
Quantification of biomechanical tolerance is necessary for injury prediction and protection of vehicular occupants. This study experimentally quantified lumbar spine axial tolerance during accelerative environments simulating a variety of military and civilian scenarios. Intact human lumbar spines (T12âL5) were dynamically loaded using a customâbuilt drop tower. Twentyâthree specimens were tested at subâfailure and failure levels consisting of peak axial forces between 2.6 and 7.9âkN and corresponding peak accelerations between 7 and 57âg. Military aircraft ejection and helicopter crashes fall within these high axial acceleration ranges. Testing was stopped following injury detection. Both peak force and acceleration were significant (pâ\u3câ0.0001) injury predictors. Injury probability curves using parametric survival analysis were created for peak acceleration and peak force. Fiftyâpercent probability of injury (95%CI) for force and acceleration were 4.5 (3.9â5.2âkN), and 16 (13â19âg). A majority of injuries affected the L1 spinal level. Peak axial forces and accelerations were greater for specimens that sustained multiple injuries or injuries at L2âL5 spinal levels. In general, forceâbased tolerance was consistent with previous shorterâsegment lumbar spine testing (3â5 vertebrae), although studies incorporating isolated vertebral bodies reported higher tolerance attributable to a different injury mechanism involving structural failure of the cortical shell. This study identified novel outcomes with regard to injury patterns, wherein more violent exposures produced more injuries in the caudal lumbar spine. This caudal migration was likely attributable to increased injury tolerance at lower lumbar spinal levels and a faster inertial mass recruitment process for high rate load application. Published 2017. This article is a U.S. Government work and is in the public domain in the USA
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