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2007

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Articles 5311 - 5340 of 6758

Full-Text Articles in Physical Sciences and Mathematics

E-Government Service Delivery Capabilities: An Analysis Of The Arab Countries In Africa & The Middle East, Akemi T. Chatfield, Omar Alhujran Jan 2007

E-Government Service Delivery Capabilities: An Analysis Of The Arab Countries In Africa & The Middle East, Akemi T. Chatfield, Omar Alhujran

Faculty of Informatics - Papers (Archive)

Much of the existing empirical research focused on e-govemments in developed countries in the Western world. In consequence, very little is known about egovemment development efforts and current progress in the Arab countries. This research attempts to bridge the knowledge gap by conducting a qualitative analysis of the current practices of leading e-govemment Arab countries vis-a-vis those who lag behind them in their e-govemment maturity. The analysis results show a wide digital divide within the sixteen Arab e-govemment developments in terms of e-govemment service delivery capabilities.

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Editorial Board & Iowa Academy Of Science Officers And Directors Jan 2007

Editorial Board & Iowa Academy Of Science Officers And Directors

Journal of the Iowa Academy of Science: JIAS

No abstract provided.

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Back Cover Jan 2007

Back Cover

Journal of the Iowa Academy of Science: JIAS

No abstract provided.

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Cover - Table Of Contents Jan 2007

Cover - Table Of Contents

Journal of the Iowa Academy of Science: JIAS

No abstract provided.

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An Inventory Of The Vascular Flora Of Hamilton County, Iowa (2001-2004), Jimmie D. Thompson Jan 2007

An Inventory Of The Vascular Flora Of Hamilton County, Iowa (2001-2004), Jimmie D. Thompson

Journal of the Iowa Academy of Science: JIAS

A botanical survey of the vascular flora of Hamilton County, Iowa was conducted from 2001 to 2004. During this survey 973 taxa (761 native) were encountered. A search of the literature and a survey of Iowa State University's Ada Hayden Herbarium for additional documented specimens added 28 taxa to the flora. This total of 1001 taxa places Hamilton County fourth in vascular plant richness among inventories conducted in Iowa since 1950. A checklist including common names of most taxa, habitat and abundance data for all taxa encountered during the current survey is presented. Information on earlier collections includes source and …

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Front Matter Jan 2007

Front Matter

Journal of the Iowa Academy of Science: JIAS

No abstract provided.

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Narrow Sense Heritability And Additive Genetic Correlations In Alfalfa Subsp. Falcata, Heathcliffe Riday, E. Charles Brummer Jan 2007

Narrow Sense Heritability And Additive Genetic Correlations In Alfalfa Subsp. Falcata, Heathcliffe Riday, E. Charles Brummer

Journal of the Iowa Academy of Science: JIAS

The complex genetics of autotetraploid alfalfa (Medicago sativa L.) make additive genetic variance component estimation difficult. Halfsib family variances often are used to estimate additive genetic variances and, by extension, narrow sense heritabilities and additive genetic correlations. These estimates contain a portion of the dominance variance. Using such calculations, in conjunction with parent-offspring covariance estimates, the dominance component can be separated from the additive genetic component. This is rarely done. This study reports average estimates across 30 populations, of both additive and dominance variance component estimates based on between halfsib family variance and parent-offspring covariance for biomass yield, plant height, …

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Fall And Winter Food Habits Of Bobcats (Lynx Rufus) In Iowa, Kelcey J. Brockmeyer, William R. Clark Jan 2007

Fall And Winter Food Habits Of Bobcats (Lynx Rufus) In Iowa, Kelcey J. Brockmeyer, William R. Clark

Journal of the Iowa Academy of Science: JIAS

The bobcat (Lynx rufus) is a widely distributed native felid of North America but nearly disappeared from Iowa due to habitat loss and unregulated harvest that occurred during the century after European settlement. Bobcats are repopulating the state and are now relatively common in southern Iowa. This study was part of a research project to understand the ecology of the species in Iowa's landscape so that conservation plans could be established. We determined food habits by the examination of stomach contents from 100 bobcat carcasses that were accidentally killed in traps, killed by automobiles, or radio-marked individuals found dead during …

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Dynamics Of Starvation In Humans, Baojun Song, Diana M. Thomas Jan 2007

Dynamics Of Starvation In Humans, Baojun Song, Diana M. Thomas

Department of Applied Mathematics and Statistics Faculty Scholarship and Creative Works

A differential equation model describing the dynamics of stored energy in the form of fat mass, lean body mass and ketone body mass during prolonged starvation is developed. The parameters of the model are estimated using available data for 7 days into starvation. A simulation of energy stores for a normal individual with body mass index between 19 and 24 and an obese individual with body mass index over 30 are calculated. The length of time the obese subject can survive during prolonged starvation is estimated using the model.

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Effects Of Sorbate Speciation On Sorption Of Selected Sulfonamides In Three Loamy Soils, Sudarshan Kurwadkar, Craig Adams, Michael Meyer, Dana Kolpin Jan 2007

Effects Of Sorbate Speciation On Sorption Of Selected Sulfonamides In Three Loamy Soils, Sudarshan Kurwadkar, Craig Adams, Michael Meyer, Dana Kolpin

United States Geological Survey: Staff Publications

Sorption of sulfamethazine (SMN) and sulfathiazole (STZ) was investigated in three soils, a North Carolina loamy sand, an Iowa sandy loam, and a Missouri loam, under various pH conditions. A significant increase in the sorption coefficient (KD) was observed in all three soils, as the sulfonamides converted from an anionic form at higher pH to a neutral/cationic form at lower pH. Above pH 7.5, sulfonamides exist primarily in anionic form and have higher aqueous solubility and no cationic character, thereby consequently leading to lower sorption to soils. The effect of speciation on sorption is not the same …

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Development Of The California Current During The Past 12,000 Yr Based On Diatoms And Silicoflagellates, John A. Barron, David Bukry Jan 2007

Development Of The California Current During The Past 12,000 Yr Based On Diatoms And Silicoflagellates, John A. Barron, David Bukry

United States Geological Survey: Staff Publications

Detailed diatom and silicoflagellates records in three cores from the offshore region of southern Oregon to central California reveal the evolution of the northern part of the California Current during the past 12,000 yr. The early Holocene, prior to ∼9 ka, was characterized by relatively warm sea surface temperatures (SST), owing to enhanced northerly flow of the subtropical waters comparable to the modern Davidson Current. Progressive strengthening of the North Pacific High lead to intensification of the southward flow of the California Current at ∼8 ka, resulting in increased coastal upwelling and relatively cooler SST which persisted until ∼5 ka. …

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Solar Forcing Of Gulf Of California Climate During The Past 2000 Yr Suggested By Diatoms And Silicoflagellates, John A. Barron, David Bukry Jan 2007

Solar Forcing Of Gulf Of California Climate During The Past 2000 Yr Suggested By Diatoms And Silicoflagellates, John A. Barron, David Bukry

United States Geological Survey: Staff Publications

High-resolution records of the past 2000 yr are compared in a north–south transect (28° N to 24° N) of three cores from the eastern slopes of the Guaymas, Carmen, and Pescadero Basins of the Gulf of California (hereafter referred to as the “Gulf”). Evenly-spaced samples from the varved sediments in each core allow sample resolution ranging from ∼ 16 to ∼ 37 yr.

Diatoms and silicoflagellates capture the seasonal variation between a late fall to early spring period of high biosiliceous productivity, that is driven by northwest winds, and a summer period of warmer, more stratified waters during which these …

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Integrating Laboratory Creep Compaction Data With Numerical Fault Models: A Bayesian Framework, Delphine D. Fitzenz, André Jalobeanu, Stephen H. Hickman Jan 2007

Integrating Laboratory Creep Compaction Data With Numerical Fault Models: A Bayesian Framework, Delphine D. Fitzenz, André Jalobeanu, Stephen H. Hickman

United States Geological Survey: Staff Publications

We developed a robust Bayesian inversion scheme to plan and analyze laboratory creep compaction experiments. We chose a simple creep law that features the main parameters of interest when trying to identify rate-controlling mechanisms from experimental data. By integrating the chosen creep law or an approximation thereof, one can use all the data, either simultaneously or in overlapping subsets, thus making more complete use of the experiment data and propagating statistical variations in the data through to the final rate constants. Despite the nonlinearity of the problem, with this technique one can retrieve accurate estimates of both the stress exponent …

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Stress Orientations Of Taiwan Chelungpu-Fault Drilling Project (Tcdp) Hole-A As Observed From Geophysical Logs, Hung-Yu Wu, Kuo-Fong Ma, Mark Zoback, Naomi Boness, Hisao Ito, Jih-Hao Hung, U.S. Geological Survey Jan 2007

Stress Orientations Of Taiwan Chelungpu-Fault Drilling Project (Tcdp) Hole-A As Observed From Geophysical Logs, Hung-Yu Wu, Kuo-Fong Ma, Mark Zoback, Naomi Boness, Hisao Ito, Jih-Hao Hung, U.S. Geological Survey

United States Geological Survey: Staff Publications

The Taiwan Chelungpu-fault Drilling Project (TCDP) drilled a 2-km-deep research borehole to investigate the structure and mechanics of the Chelungpu Fault that ruptured in the 1999 Mw 7.6 Chi-Chi earthquake. Geophysical logs of the TCDP were carried out over depths of 500–1900 m, including Dipole Sonic Imager (DSI) logs and Formation Micro Imager (FMI) logs in order to identify bedding planes, fractures and shear zones. From the continuous core obtained from the borehole, a shear zone at a depth of 1110 meters is interpreted to be the Chelungpu fault, located within the Chinshui Shale, which extends from 1013 to …

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Microsatellite Loci For Distinguishing Spotted Owls (Strix Occidentalis), Barred Owls (Strix Varia), And Their Hybrids, W. Chris Funk, Thomas D. Mullins, Eric D. Forsman, Susan M. Haig Jan 2007

Microsatellite Loci For Distinguishing Spotted Owls (Strix Occidentalis), Barred Owls (Strix Varia), And Their Hybrids, W. Chris Funk, Thomas D. Mullins, Eric D. Forsman, Susan M. Haig

United States Geological Survey: Staff Publications

We identified four diagnostic microsatellite loci that distinguish spotted owls (Strix occidentalis), barred owls (Strix varia), F1 hybrids and backcrosses. Thirty-four out of 52 loci tested (65.4%) successfully amplified, and four of these loci (11.8%) had allele sizes that did not overlap between spotted and barred owls. The probability of correctly identifying a backcross with these four loci is 0.875. Genotyping potential hybrid owls with these markers revealed that field identifications were often wrong. Given the difficulty of identifying hybrids in the field, these markers will be useful for hybrid identification, law enforcement and spotted …

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Possible Impacts Of Early-11th-, Middle-12th-, And Late-13th-Century Droughts On Western Native Americans And The Mississippian Cahokians, Larry V. Benson, Michael S. Berry, Edward A. Jolie, Jerry D. Spangler, David W. Stahle, Eugene M. Hattori Jan 2007

Possible Impacts Of Early-11th-, Middle-12th-, And Late-13th-Century Droughts On Western Native Americans And The Mississippian Cahokians, Larry V. Benson, Michael S. Berry, Edward A. Jolie, Jerry D. Spangler, David W. Stahle, Eugene M. Hattori

United States Geological Survey: Staff Publications

One or more of three intense and persistent droughts impacted some Native American cultures in the early-11th, middle-12th and late- 13th centuries, including the Anasazi, Fremont, Lovelock, and Mississippian (Cahokian) prehistorical cultures. Tree-ring-based reconstructions of precipitation and temperature indicate that warm drought periods occurred between AD 990 and 1060, AD 1135 and 1170, and AD 1276 and 1297. These droughts occurred during minima in the Pacific Decadal Oscillation and may have been associated with positive values of the Atlantic Multidecadal Oscillation. Each of the Native American cultures was supported, to a greater or lesser degree, by precipitation-dependent resources. Both the …

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Hydrologic Connectivity And The Contribution Of Stream Headwaters To Ecological Integrity At Regional Scales1, Mary C. Freeman, Catherine M. Pringle, C. Rhett Jackson Jan 2007

Hydrologic Connectivity And The Contribution Of Stream Headwaters To Ecological Integrity At Regional Scales1, Mary C. Freeman, Catherine M. Pringle, C. Rhett Jackson

United States Geological Survey: Staff Publications

Cumulatively, headwater streams contribute to maintaining hydrologic connectivity and ecosystem integrity at regional scales. Hydrologic connectivity is the water-mediated transport of matter, energy and organisms within or between elements of the hydrologic cycle. Headwater streams compose over two-thirds of total stream length in a typical river drainage and directly connect the upland and riparian landscape to the rest of the stream ecosystem. Altering headwater streams, e.g., by channelization, diversion through pipes, impoundment and burial, modifies fluxes between uplands and downstream river segments and eliminates distinctive habitats. The large-scale ecological effects of altering headwaters are amplified by land uses that alter …

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Loess Deposits, Origins And Properties, Daniel R. Muhs Jan 2007

Loess Deposits, Origins And Properties, Daniel R. Muhs

United States Geological Survey: Staff Publications

Loess is an eolian (windblown) sediment that is an important archive of Quaternary climate changes. It may provide one of the most complete terrestrial records of interglacial–glacial cycles. Loess is unusual as a record of Quaternary climate change because it is one of the few sediments that is deposited directly from the atmosphere. Thus, it is a geologic deposit that contains a record of atmospheric circulation and can be used to reconstruct synoptic-scale paleoclimatology. Loess is also unusual in that it can be dated directly using ‘trapped electron’ or luminescence methods that require only the sediment itself. Commonly, loess deposits …

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Sexual Selection Drives Speciation In An Amazonian Frog, Kathryn E. Boul, W. Chris Funk, Catherine R. Darst, David C. Cannatella, Michael J. Ryan Jan 2007

Sexual Selection Drives Speciation In An Amazonian Frog, Kathryn E. Boul, W. Chris Funk, Catherine R. Darst, David C. Cannatella, Michael J. Ryan

United States Geological Survey: Staff Publications

One proposed mechanism of speciation is divergent sexual selection, whereby divergence in female preferences and male signals results in behavioural isolation. Despite the appeal of this hypothesis, evidence for it remains inconclusive. Here, we present several lines of evidence that sexual selection is driving behavioural isolation and speciation among populations of an Amazonian frog (Physalaemus petersi). First, sexual selection has promoted divergence in male mating calls and female preferences for calls between neighbouring populations, resulting in strong behavioural isolation. Second, phylogenetic analysis indicates that populations have become fixed for alternative call types several times throughout the species’ range, …

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Ichnofacies, Ichnocoenoses, And Ichnofabrics Of Quaternary Shallow-Marine To Dunal Tropical Carbonates: A Model And Implications, H. Allen Curran Jan 2007

Ichnofacies, Ichnocoenoses, And Ichnofabrics Of Quaternary Shallow-Marine To Dunal Tropical Carbonates: A Model And Implications, H. Allen Curran

Geosciences: Faculty Publications

A model of five ichnocoenoses within the Skolithos and Psilonichnus ichnofacies characterizes the modern, Holocene, and Pleistocene coastal-carbonate depositional environments and limestones of the Bahamas, as well as the Miami Limestone of south Florida. The subtidal to intertidal ichnocosnoses of the Skolithos ichnofacies are dominated by trace-making activities and trace fossils of callianassid shrimp, which can create distinctive and maximum ichnofabrics. Fossil Upogebia vasquezi burrows found in intertidal calcarenites and burrows of the trace fossil Psilonichnus upsilon, most common in beach backshore beds, have excellent potential as stratigraphic markers and can be used as indicators of past sea-level positions. …

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The Effect Of Dextran On Subunit Exchange Of Αa-Crystallin, A. Ghahghaei, A. Rekas, W. E. Price, J. A. Carver Jan 2007

The Effect Of Dextran On Subunit Exchange Of Αa-Crystallin, A. Ghahghaei, A. Rekas, W. E. Price, J. A. Carver

Faculty of Science - Papers (Archive)

α-Crystallin, a member of small heat shock protein (sHsp) family, is comprised of αA and αB subunits and acts as a molecular chaperone by interacting with unfolding proteins to prevent their aggregation. The αA-crystallin homopolymer consists of 30-40 subunits that are undergoing dynamic exchange. α-Crystallin and αA-crystallin are poorer chaperones in the presence of the crowding agent, dextran. Using fluorescence resonance energy transfer, it is shown that the αAcrystallin subunit exchange rate strongly increased with temperature. Binding of reduced ovotransferrin to αA-crystallin markedly decreases the rate of subunit exchange, as does the presence of dextran. In addition, in the presence …

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Aryl Nitro Reduction With Iron Powder Or Stannous Chloride Under Ultrasonic Irradiation, A. B. Gamble, James A. Garner, Christopher Gordon, S. M. J. O'Conner, Paul A. Keller Jan 2007

Aryl Nitro Reduction With Iron Powder Or Stannous Chloride Under Ultrasonic Irradiation, A. B. Gamble, James A. Garner, Christopher Gordon, S. M. J. O'Conner, Paul A. Keller

Faculty of Science - Papers (Archive)

The selective reduction of aryl nitro compounds in the presence of sensitive functionalities, including halide, carbonyl, nitrile and ester substituents under ultrasonic irradiation at 35 kHz is reported in yields of 39-98%. Iron powder proved superior to stannous chloride with high tolerance of sensitive functional groups and high yields of the desired aryl amines in relatively short reaction times. Simple experimental procedure and purification also make the iron reduction of aryl nitro compounds advantageous over other methods of reduction.

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Coastal Systems And Low-Lying Areas, R. J. Nicholls, P. P. Wong, V. Burkett, J. Codignotto, J. Hay, R. Mclean, S. Ragoonaden, C. D. Woodroffe, P. A. O. Abuodha, J. Arblaster, B. Brown, D. Forbes, J. Hall, S. Kovats, J. Lowe, K. Mcinnes, S. Moser, S. Rupp-Armstrong, Y. Saito Jan 2007

Coastal Systems And Low-Lying Areas, R. J. Nicholls, P. P. Wong, V. Burkett, J. Codignotto, J. Hay, R. Mclean, S. Ragoonaden, C. D. Woodroffe, P. A. O. Abuodha, J. Arblaster, B. Brown, D. Forbes, J. Hall, S. Kovats, J. Lowe, K. Mcinnes, S. Moser, S. Rupp-Armstrong, Y. Saito

Faculty of Science - Papers (Archive)

Since the IPCC Third Assessment Report (TAR), our understanding of the implications of climate change for coastal systems and low-lying areas (henceforth referred to as ‘coasts’) has increased substantially and six important policy-relevant messages have emerged. Coasts are experiencing the adverse consequences of hazards related to climate and sea level (very high confidence). Coasts are highly vulnerable to extreme events, such as storms, which impose substantial costs on coastal societies [6.2.1, 6.2.2, 6.5.2]. Annually, about 120 million people are exposed to tropical cyclone hazards, which killed 250,000 people from 1980 to 2000 [6.5.2]. Through the 20th century, global rise of …

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Discontinuities In Stream Nutrient Uptake Below Lakesin Mountain Drainage Networks, Michelle A. Baker Jan 2007

Discontinuities In Stream Nutrient Uptake Below Lakesin Mountain Drainage Networks, Michelle A. Baker

Michelle A. Baker

In many watersheds, lakes and streams are hydrologically linked in spatial patterns that influence material transport and retention. We hypothesized that lakes affect stream nutrient cycling via modifications to stream hydrogeomorphology, source‐waters, and biological communities. We tested this hypothesis in a lake district of the Sawtooth Mountains, Idaho. Uptake of NO3− and PO4−3 was compared among 25 reaches representing the following landscape positions: lake inlets and outlets, reaches >1‐km downstream from lakes, and reference reaches with no nearby lakes. We quantified landscape‐scale hydrographic and reach‐scale hydrogeomorphic, source‐water, and biological variables to characterize these landscape positions and analyze relationships to nutrient …

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Demonstration Of Magnetoelectric Scanning Probe Microscopy, Jason R. Hattrick-Simpers, Liyang Dai, Manfred Wuttig, Ichiro Takeuchi, Eckhard Quandt Jan 2007

Demonstration Of Magnetoelectric Scanning Probe Microscopy, Jason R. Hattrick-Simpers, Liyang Dai, Manfred Wuttig, Ichiro Takeuchi, Eckhard Quandt

Faculty Publications

A near-field room temperature scanning magnetic probe microscope has been developed using a laminated magnetoelectric sensor. The simple trilayer longitudinal-transverse mode sensor, fabricated using Metglas as the magnetostrictive layer and polyvinylidene fluoride as the piezoelectric layer, shows an ac field sensitivity of 467±3μV∕Oe in the measured frequency range of 200Hz–8kHz. The microscope was used to image a 2mm diameter ring carrying an ac current as low as 10−5A. ac fields as small as 3×10−10T have been detected.

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Rapid Structural Mapping Of Ternary Metallic Alloy Systems Using The Combinatorial Approach And Cluster Analysis, C. J. Long, Jason R. Hattrick-Simpers, M. Murakami, R. C. Srivastava, I. Takeuchi, V. L. Karen, X. Li Jan 2007

Rapid Structural Mapping Of Ternary Metallic Alloy Systems Using The Combinatorial Approach And Cluster Analysis, C. J. Long, Jason R. Hattrick-Simpers, M. Murakami, R. C. Srivastava, I. Takeuchi, V. L. Karen, X. Li

Faculty Publications

We are developing a procedure for the quick identification of structural phases in thin film composition spread experiments which map large fractions of compositional phase diagrams of ternary metallic alloy systems. An in-house scanning x-ray microdiffractometer is used to obtain x-ray spectra from 273 different compositions on a single composition spread library. A cluster analysissoftware is then used to sort the spectra into groups in order to rapidly discover the distribution of phases on the ternary diagram. The most representative pattern of each group is then compared to a database of known structures to identify known phases. Using this method, …

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Exafs Characterization Of Dendrimer‐Derived Pt/Γ‐Al2O3, A. Siani, Oleg S. Alexeev, Christopher T. Williams, Harry J. Ploehn, Michael D. Amiridis Jan 2007

Exafs Characterization Of Dendrimer‐Derived Pt/Γ‐Al2O3, A. Siani, Oleg S. Alexeev, Christopher T. Williams, Harry J. Ploehn, Michael D. Amiridis

Faculty Publications

The various steps involved in the preparation of a Pt/γ‐Al2O3 material using hydroxyl‐terminated generation four (G4OH) PAMAM dendrimers as templates were monitored by EXAFS. The results indicate that Cl ligands in the Pt precursors (H2PtCl6 and K2PtCl4) were partially replaced by aquo ligands upon hydrolysis to form [PtCl3(H2O)3]+ and [PtCl2(H2O)2] species. After interaction of such species with G4OH, Cl ligands from the first coordination shell of Pt were further replaced by nitrogen atoms from the dendrimer interior, …

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Introduction To The Integrated Guidance Concept, Center For Coastal Resources Management, Virginia Institute Of Marine Science Jan 2007

Introduction To The Integrated Guidance Concept, Center For Coastal Resources Management, Virginia Institute Of Marine Science

Reports

Rivers & Coast is a periodic publication of the Center for Coastal Resources Management, Virginia Institute of Marine Science. The goal of Rivers & Coast is to keep readers well informed of current scientific understanding behind key environmental issues related to watershed rivers and coastal ecosystems of the Chesapeake Bay.

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Unitary And Nonunitary Approaches In Quantum Field Theory, K D. Lamb, Christopher C. Gerry, Rainer Grobe Jan 2007

Unitary And Nonunitary Approaches In Quantum Field Theory, K D. Lamb, Christopher C. Gerry, Rainer Grobe

Faculty publications – Physics

We use a simplified essential state model to compare two quantum field theoretical approaches to study the creation of electron-positron pairs from the vacuum. In the unitary approach the system is characterized by a state with different numbers of particles that is described by occupation numbers and evolves with conserved norm. The nonunitary approach can predict the evolution of wave functions and density operators with a fixed number of particles but time-dependent norms. As an example to illustrate the differences between both approaches, we examine the degree of entanglement for the Klein paradox, which describes the creation of an electron-positron …

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A New Lower Bound On Guard Placement For Wireless Localization, Mirela Damian, Robin Flatland, Joseph O'Rourke, Suneeta Ramswami Jan 2007

A New Lower Bound On Guard Placement For Wireless Localization, Mirela Damian, Robin Flatland, Joseph O'Rourke, Suneeta Ramswami

Computer Science: Faculty Publications

The problem of wireless localization asks to place and orient stations in the plane, each of which broadcasts a unique key within a fixed angular range, so that each point in the plane can determine whether it is inside or outside a given polygonal region. The primary goal is to minimize the number of stations. In this paper we establish a lower bound of ⌊2n/3⌋−1 stations for polygons in general position, for the case in which the placement of stations is restricted to polygon vertices, improving upon the existing ⌈n/2⌉ lower bound.

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