bluuebunny/crossref_metadata_2025 huggingface dataset:
Statistical description of chaotic rays in a deep water acoustic waveguide
Authors: Virovlyansky A. L. , Kazarova A. Yu. , Lyubavin L. Ya.
Published: May 2007

This paper analyzes the chaotic ray dynamics at multimegater ranges in a deep water environment with internal-wave-induced fluctuations of the sound speed. The behavior of acoustic ray paths is investigated using the Hamiltonian formalism expressed in terms of action-angle variables. It is shown that the range dependence of the action variable of chaotic ray can be approximated by a random Wiener process. On the basis of this result an approximate statistical description of the chaotic ray structure is derived. Distributions of coordinates, momenta (grazing angles), and actions of sound rays are evaluated. This statistical approach is used for studying ray travel times, that is, arrival times of sound pulses coming to the receiver through different ray paths. The spread of travel times for a bundle of rays with close starting parameters and the influence of sound speed fluctuations on the timefront representing ray arrivals in the time-depth plane are examined. Estimates for the widening and bias of the timefront segment caused by the fluctuations are obtained.
Acoustic cues available for ranging by humpback whales
Authors: Mercado Eduardo , Schneider Jennifer N. , Green Sean R. , Wang Chong , Rubin Rachael D. , Banks Patchouly N.
Published: May 2007

Field measurements of sound propagation in a humpback whale habitat were collected to identify cues that a humpback whale might use to estimate its distance from sound sources. The data show that spectral cues are sufficient for estimating the relative distance a sound has traveled in such environments, and that several other cues may also provide useful information. It is suggested that listening humpback whales may use multiple cues in parallel to determine the range to singing whales.
Single-crystal lead magnesium niobate-lead titanate (PMN/PT) as a broadband high power transduction material
Authors: Moffett Mark B. , Robinson Harold C. , Powers James M. , Baird P. David
Published: May 2007

Two experimental underwater acoustic projectors, a tonpilz array, and a cylindrical line array, were built with single crystal, lead magnesium niobate/lead titanate, a piezoelectric transduction material possessing a large electromechanical coupling factor (k33=0.9). The mechanical quality factor, Qm, and the effective coupling factor, keff, determine the frequency band over which high power can be transmitted; keff cannot be greater than the piezoelectric material value, and so a high material coupling factor is a requisite for broadband operation. Stansfield’s bandwidth criteria are used to calculate the optimum Qm value, Qopt∼1.2 (1−keff2)1∕2∕keff. The results for the tonpilz projector exhibited keff=0.730, Qm=1.17 (very near optimal), and a fractional bandwidth of 0.93. For the cylindrical transducer array, keff=0.867, Qm=0.91 (larger than the optimum value, 0.7), and the bandwidth was 1.16. Although the measured bandwidths were less than optimal, they were accurately predicted by the theory, despite the highly simplified nature of the Van Dyke equivalent circuit, on which the theory is based.
Noise in contemporary neonatal intensive care
Authors: Williams Amber L. , van Drongelen Wim , Lasky Robert E.
Published: May 2007

Weekly sound surveys (n=63) were collected, using 5s sampling intervals, for two modern neonatal intensive care units (NICUs). Median weekly equivalent sound pressure levels (LEQ) for NICU A ranged from 61 to 63dB (A weighted), depending on the level of care. NICU B LEQ measurements ranged from 55 to 60dB (A weighted). NICU B was recently built with a focus on sound abatement, explaining much of the difference between the two NICUs. Sound levels exceeded 45dB (A weighted), recommended by the American Academy of Pediatrics, more than 70% of the time for all levels of care. Hourly LEQs below 50dB (A weighted) and hourly L10s below 55dB (A weighted), recommended by the Sound Study Group (SSG) of the National Resource Center, were also exceeded in more than 70% of recorded samples. A third SSG recommendation, that the 1s LMAX, should not exceed 70dB (A weighted), was exceeded relatively infrequently (<11% of the time). Peak impulse measurements exceeded 90dB for 6.3% of 5s samples recorded from NICU A and 2.8% of NICU B samples. Twenty-four h periodicities in sound levels as a function of regular staff activities were apparent, but short term variability was considerable.
Basilar membrane mechanics in the 6–9kHz region of sensitive chinchilla cochleae
Authors: Rhode William S.
Published: May 2007

The vibration of the basilar membrane in the 6–9kHz region in the chinchilla cochlea has been studied using a displacement sensitive interferometer. Displacements of 0.7–1.4nm at 0dB sound pressure level have been obtained. At the characteristic frequency (CF), rate-of-growth (ROG) functions computed as the slope of input-output (IO) functions can be as low as 0.1dB∕dB. IO functions for frequencies >CF have ROGs near 0dB∕dB and can have notches characterized by both negative slopes and expansive ROGs, i.e., >1dB∕dB. For frequencies <0.6*CF, ROGs>1.2dB∕dB were found. Cochlear gain is shown to be greater than 60dB in sensitive preparations with a single cochlea having nearly 80dB gain. The compressive nature of the cochlea remains at all levels though it is masked at frequencies >CF when the amplitude of a compression wave exceeds that of the traveling wave. The compression wave produces the plateau region of the mechanical response at high intensities and has a nearly constant phase versus frequency function implying a high velocity. The summation of the traveling and compression waves explains the occurrence of the notches in both the IO and iso-intensity functions. Vibration of the osseous spiral limbus may alter the drive to inner hair cells.
Mutual suppression in the 6kHz region of sensitive chinchilla cochleae
Authors: Rhode William S.
Published: May 2007

Basilar membrane (BM) vibration was measured using a displacement measuring interferometer for single-tone and two-tone suppression (2TS) paradigms in the 6–9kHz region of sensitive chinchilla cochleae that had gains near or better than 60dB. Based on prior studies of basilar membrane vibration, three significant differences remain between BM and auditory nerve (AN) 2TS responses: (1) suppression thresholds in the tail of tuning curves were much higher in BM than the auditory nerve (AN); (2) rates of suppression were significantly higher in AN than BM; and (3) the amplitude of vibration with low-frequency suppressors was always greater than the single-tone displacement rendering it impossible to explain 2TS rate suppression in the AN. The first two differences are eliminated by the results of the present study while the third remains. Suppression amplitudes greater than 40dB and rates of suppression larger than 2.5dB∕dB were found for low-frequency suppressors. A correlation between both the gain and nonlinearity of the cochlea and 2TS properties indicates that when sensitive cochleae are studied. The third difference between BM and AN behavior could be strictly a function of the high-pass filter characteristic of the inner hair cells.
Fast automatic inharmonicity estimation algorithm
Authors: Rauhala Jukka , Lehtonen Heidi-Maria , Välimäki Vesa
Published: May 2007

A new algorithm is presented for estimating the inharmonicity coefficient of slightly inharmonic stringed instrument sounds. In the proposed partial frequencies deviation method, the inharmonicity is estimated in an intuitive way by minimizing the deviation of the expected partial frequencies compared to the frequencies of the high amplitude peaks in the spectrum. This is done in an iterative process, where the algorithm converges towards the target estimation value. The algorithm is tested using both synthetic and recorded piano tones. The results show that the new algorithm produces accurate results with a small computation cost compared to other methods.
An exact point source starting field for the Fourier parabolic equation in outdoor sound propagation
Authors: Gilbert Kenneth E. , Di Xiao
Published: May 2007

A method for exactly representing a point source starting field in a Fourier parabolic equation calculation is presented. The formulation is based on an exact, analytic expression for the field in vertical wave number space (k space). The field in vertical coordinate space (z space) is obtained via a Fourier transform of the k-space field. Thus, one can directly control the Fourier components of the starting field, so that nonpropagating components are excluded. The relation of the exact starting field to the standard Gaussian starting field is demonstrated analytically. Examples of the numerical implementation of the exact starting field are given.
Grating Lobe Reduction in Transducer Arrays Through Structural Filtering of Supercritical Plates
Authors: Anderson Brian E.
Published: May 2007

The effect of placing a structural acoustic filter between water and the transducer elements of an array is investigated to help reduce undesirable grating lobes. A plate is mounted to transducer elements with a thin decoupling polyurethane layer between the transducer and the plate. The plate acts as a radiation/incidence angle filter to pass energy at angles near normal incidence, but suppress energy at large incidence angles. Grating lobe reduction is achieved at the expense of limiting the available steering of the main lobe. Within this steer angle limitation, the main lobe can be steered as normal while the grating lobe level is reduced by the plate’s angular filtering. The insertion of a plate structural filter provides an inexpensive and easily implemented approach to extend usable frequency bandwidth with reduced level grating lobes, without increasing the number of array elements. Even though some data matches theory well, a practical material has yet to be found that possesses optimal material properties. To the author’s knowledge, this work represents the first attempt to advantageously utilize a plate to provide angular dependent sound transmission filtering above the plate’s critical frequency (the supercritical frequency region). [Work sponsored by ONR Code 333, Dr. David Drumheller.]
Microstructure and Acoustical Macro-Behavior: Approach by Reconstruction of a Representative Elementary Cell
Authors: Perrot Camille
Published: May 2007

The fundamental issue of determining acoustic properties of porous media from their local geometry is examined in this Ph.D. dissertation thesis, thanks to a sample of open-cell aluminium foam analyzed by axial computed microtomography. Various geometric properties are measured to characterize the experimental sample at the cell size level. This is done in order to reconstruct a porous medium by means of idealized three- and two-dimensional unit cells. The frequency dependent thermal and velocity fields governing the propagation and dissipation of acoustic waves through rigid porous media are computed by Brownian motion simulation and the finite element method, respectively. Macroscopic behavior is derived by spatial averaging of the local fields. Our results are compared to experimental data obtained from impedance tube measurements. First, this approach leads to the identification of the macroscopic parameters involved in Pride and Lafarge semiphenomenological models. Second, it yields a direct access to thermal and viscous dynamic permeabilities. However, the bidimensional model underestimates the static viscous permeability as well as the viscous characteristic length; what thus require a three-dimensional implementation.
Destabilization of velocity feedback controllers with stroke limited inertial actuators
Authors: Baumann Oliver Nicholas , Elliott Stephen John
Published: May 2007

It has been observed when using inertial actuators for the active reduction of structural vibration, that velocity feedback controllers are liable to become unstable if the actuator is subject to stroke saturation. This article presents a simple nonlinear, time domain model of an inertial actuator mounted on a single degree of freedom system. At low amplitudes the actuator, when used in a velocity feedback control loop, increases the effective damping of the structure. At higher amplitudes the system is shown to become unstable, however, and generates limit cycle oscillations having a predictable frequency.
How Synaptotagmin Promotes Membrane Fusion
Authors: Martens Sascha , Kozlov Michael M. , McMahon Harvey T.
Published: May 2007

Synaptic vesicles loaded with neurotransmitters are exocytosed in a soluble
N
-ethylmaleimide–sensitive factor attachment protein receptor (SNARE)–dependent manner after presynaptic depolarization induces calcium ion (Ca
2+
) influx. The Ca
2+
sensor required for fast fusion is synaptotagmin-1. The activation energy of bilayer-bilayer fusion is very high (≈40
k
B
T
). We found that, in response to Ca
2+
binding, synaptotagmin-1 could promote SNARE-mediated fusion by lowering this activation barrier by inducing high positive curvature in target membranes on C2-domain membrane insertion. Thus, synaptotagmin-1 triggers the fusion of docked vesicles by local Ca
2+
-dependent buckling of the plasma membrane together with the zippering of SNAREs. This mechanism may be widely used in membrane fusion.
A Common Variant on Chromosome 9p21 Affects the Risk of Myocardial Infarction
Authors: Helgadottir Anna , Thorleifsson Gudmar , Manolescu Andrei , Gretarsdottir Solveig , Blondal Thorarinn , Jonasdottir Aslaug , Jonasdottir Adalbjorg , Sigurdsson Asgeir , Baker Adam , Palsson Arnar , Masson Gisli , Gudbjartsson Daniel F. , Magnusson Kristinn P. , Andersen Karl , Levey Allan I. , Backman Valgerdur M. , Matthiasdottir Sigurborg , Jonsdottir Thorbjorg , Palsson Stefan , Einarsdottir Helga , Gunnarsdottir Steinunn , Gylfason Arnaldur , Vaccarino Viola , Hooper W. Craig , Reilly Muredach P. , Granger Christopher B. , Austin Harland , Rader Daniel J. , Shah Svati H. , Quyyumi Arshed A. , Gulcher Jeffrey R. , Thorgeirsson Gudmundur , Thorsteinsdottir Unnur , Kong Augustine , Stefansson Kari
Published: May 2007

The global endemic of cardiovascular diseases calls for improved risk assessment and treatment. Here, we describe an association between myocardial infarction (MI) and a common sequence variant on chromosome 9p21. This study included a total of 4587 cases and 12,767 controls. The identified variant, adjacent to the tumor suppressor genes
CDKN2A
and
CDKN2B
, was associated with the disease with high significance. Approximately 21% of individuals in the population are homozygous for this variant, and their estimated risk of suffering myocardial infarction is 1.64 times as great as that of noncarriers. The corresponding risk is 2.02 times as great for early-onset cases. The population attributable risk is 21% for MI in general and 31% for early-onset cases.
Shift work, confounding and death from ischaemic heart disease
Authors: Yadegarfar G , McNamee R
Published: May 2007

Objective:

To investigate the relation between shift work and death from ischaemic heart disease (IHD) and evidence for confounding by social class and healthy shift worker effects.

Methods:

A case-referent study nested within an industrial cohort was used. Cases (n = 635) were cohort members who died of ischaemic heart disease (ICD 410–414) during 1950–98 aged 75 or under. Referents were matched on age and year of starting work at the site and were alive at time of case’s death. Shift work status was determined from historical personnel records and pre-employment weight, height, blood pressure and smoking from medical records. Social class at first employment was inferred from job titles. To overcome potential bias due to a healthy shift worker hire effect, odds ratios were calculated from survivors 10 years after hire. To control for any healthy shift worker survivor effect, they were adjusted for duration of employment and time since termination of employment. Conditional logistic regression analysis was used to estimate ORs.

Results:

55% of subjects had worked as shift workers. Shift workers were more likely than day workers to belong to social class IV or V. The OR for shift workers compared with day workers, after adjustment for pre-employment risk factors, duration of employment and restricted to those who survived 10 years after hire was 1.11 (90% CI 0.90 to 1.37). This reduced to 1.04 (90% CI 0.83 to 1.30) after inclusion of social class. No dose-response relation was found.

Conclusion:

No excess risk of death from IHD for shift workers was found. The potential for confounding by social class in this relatively homogeneous cohort underlines the need to consider such confounding in more heterogeneous populations.
A mid-Archaean island arc complex in the eastern Akia terrane, Godthåbsfjord, southern West Greenland
Authors: GARDE ADAM A.
Published: May 2007

A relict oceanic island arc complex in the eastern Akia terrane, Godthåbsfjord, southern West Greenland, constitutes a magmatic and geotectonic link between
c
. 3.05–3.0 Ga tonalitic orthogneiss and enclaves of older supracrustal amphibolite. The relict arc forms isoclinally folded panels of volcaniclastic meta-andesite with major and trace element island arc signatures, intercalated with volcano-sedimentary schist, tholeiitic amphibolite and opx-rich cumulate rocks. A zircon U–Pb age of 3071 ± 1 Ma obtained from a volcano-sedimentary schist is marginally older than the main orthogneisses and is the first depositional age reported from a supracrustal rock within Akia terrane. Granite sheets were emplaced at
c
. 3005–2980 Ma synkinematically with the isoclinal folding, and were followed by peak metamorphism at 2990–2970 Ma with substantial recrystallization of volcanic zircon and mobility of large-ion lithophile elements. The identification of the arc complex provides new insight into mid-Archaean continental crustal accretion in West Greenland, and substantiates previous ideas that the orthogneisses are products of slab melting in convergent plate-tectonic settings. The presence of the arc complex also implies that Archaean high-grade orthogneiss–amphibolite associations may not represent plate-tectonic environments distinct from granite–greenstone associations, but expose deeper sections of the same convergent systems.
Understanding basin sedimentary provenance: evidence from allied phytogeographic and heavy mineral analysis of the Palaeocene of the NE Atlantic
Authors: Jolley David W. , Morton Andrew C.
Published: May 2007

The drilling of hydrocarbon exploration wells in the Faroe–Shetland Basin has provided an expanding sample resource that provides material for testing recently developed palynology-based sediment transport analysis. This technique has been verified by comparison with heavy mineral analysis; both approaches have been used to identify sediment sources and input points along the strike of the Palaeocene West Shetland Platform. Integration of heavy mineral and palynological data has provided a basis for understanding arenaceous and argillaceous sediment distribution and sourcing. In addition to a source from the western, Greenland side of the basin, four argillaceous and four arenaceous sedimentary sources have been identified along the strike of the West Shetland Platform. These vary in temporal and spatial distribution, and thus provide a history of sediment source evolution. This analysis supports a persistent difference in source between the Corona Basin and the Flett and Judd Sub-basins. Although source variation and overlap between basins is evident, transfer zones represent both conduits for and barriers to effective sediment transport. Both palynological and heavy mineral evidence identifies the former presence of Late Namurian–Westphalian strata on the West Shetland Platform, which were removed by subsequent erosion.
Sedimentology and high-resolution sequence stratigraphy of the late middle to late Miocene Angostura Formation (western Borbón Basin, northwestern Ecuador)
Authors: Cantalamessa Gino , Di Celma Claudio , Ragaini Luca , Valleri Gigliola , Landini Walter
Published: May 2007

An integrated analysis of facies and palaeontological content of the middle to late Miocene (
c
. 12.4–9.1 Ma) Angostura Formation led to the identification of facies associations indicative of shoreface and inner-shelf settings. The Angostura Formation comprises eight high-frequency sequences that are stacked to form a tectonically driven lowstand sequence set. The most complete examples of sequences are bounded by transgressively modified unconformities and exhibit a threefold subdivision: (1) a basal suite of deepening-upward shoreface sediments (transgressive systems tract), including a base-of-cycle shell concentration; (2) a mid-cycle shell bed, consisting of molluscan shells dispersed in a matrix of inner-shelf muddy fine-grained sandstones; (3) a shallowing-upward unit of inner-shelf to lower shoreface sediments almost barren of mollusc fossils (highstand systems tract). Biostratigraphic constraints allowed a reasonable correlation between sequence bounding unconformities and the late middle to late Miocene high-frequency glacio-eustatic changes derived from recent δ
18
O studies. This correlation has far-reaching implications and leads to the following conclusions: (1) glacio-eustasy in tune with oxygen isotope changes at fourth-order frequency (200 ka–1 Ma duration) may have been the principal factor regulating stratigraphic packaging in the Angostura Formation; (2) these sequences provide an excellent shallow-marine outcrop record of late middle to late Miocene Antarctic glaciations.
Carbon-isotope stratigraphy of Cenomanian–Turonian platform carbonates from the southern Apennines (Italy): a chemostratigraphic approach to the problem of correlation between shallow-water and deep-water successions
Authors: Parente Mariano , Frijia Gianluca , Di Lucia Matteo
Published: May 2007

The carbon-isotope record of three sections of shallow-water carbonates from the Upper Cretaceous sequences of the southern Apennines (Italy) shows a pronounced positive excursion of about 4–5‰. Using the upper Cenomanian
Cisalveolina fraasi
level as a biostratigraphic tie-point we correlate this excursion to the OAE-2 isotopic event. Comparison with the standard reference δ
13
C curve of Eastbourne (England) shows that the overall character of the excursion is clearly reproduced in the shallow-water curves. Chemostratigraphic correlation allows definition of the age of some important shallow-water biostratigraphic events to the precision of an ammonite zone, using the well-established bio-chronostratigraphic framework defined in the Eastbourne section. The onset of the Cenomanian–Turonian isotopic excursion coincides with a transgressive trend, recorded by the occurrence of more open-marine facies and culminating with an incipient drowning in one of the sections studied. Our data suggest that the open-ocean isotopic signal is most faithfully recorded and preserved in shallow-water platform carbonates during transgressive periods, when the effects of meteoric diagenesis and seawater ageing are less severe.
An Oligocene extrusion wedge of blueschist-facies nappes on Evia, Aegean Sea, Greece: implications for the early exhumation of high-pressure rocks
Authors: Ring Uwe , Glodny Johannes , Will Thomas , Thomson Stuart
Published: May 2007

We show that the Styra Nappe of the Cycladic Blueschist Unit on Evia constitutes a wedge of high-pressure rocks extruded during early stages of orogeny. The nappe pile on Evia was assembled during D
2
top-to-the-SSW-directed thrusting (in restored Oligocene coordinates), which emplaced the Styra and Ochi nappes of the Cycladic Blueschist Unit above the Almyropotamos Nappe between
c
. 33 and 21 Ma. Peak metamorphism of the Almyropotamos Nappe at
c
. 23 Ma occurred at lower metamorphic pressure, showing exhumation of the Styra Nappe during underthrusting and burial of the Almyropotamos Nappe. This exhumation was largely accomplished by the D
2
top-to-the-NNE-displacing Mt. Ochi normal-sense shear zone. Normal shearing commenced at
c
. 33 Ma under peak high-pressure metamorphism in the Styra and Ochi nappes. Fission-track dating indicates slow cooling after D
2
in the Styra Nappe. Subsequently, the former thrust contact between the Almyropotamos Nappe and the Styra Nappe was reactivated as a D
3
top-to-the-ESE extensional shear zone and this extensional phase led to the formation of a number of Middle to Late Miocene graben. Our main conclusion is that there is strong evidence for an Oligocene extrusion wedge accomplishing the early exhumation of the Styra Nappe, which demonstrates the importance of extrusion wedges for the initial exhumation of the Cycladic Blueschist Unit.
The Formation of the Solar System
Authors: Russell Sara S.
Published: May 2007

The study of the origin and evolution of the Solar System is based on laboratory analysis of meteorites and other extraterrestrial materials, and on astronomical observations of star-forming regions today. A virtual consensus holds that the Solar System formed from the collapse of interstellar cloud material under its own gravity about 4.56 Ga ago. This process led initially to a dusty disc forming around the newly formed Sun. The material in the disc accreted into small planetary bodies, called planetesimals, which in turn made up the building blocks of planets. Some planetesimals survived as asteroids. Fragments of these bodies make up the majority of meteorites that fall to Earth. The most common type of meteorite are chondrites. These formed from accretion of material from the dusty disc. Most chondrites were heated, probably by radioactive decay, and became metamorphosed. Other meteorite types include those made from basalts and iron metal alloys; these testify to extensive heating to produce melting on some planetesimals. Impacts of large (>100 km bodies) were responsible for forming much of the diversity seen among planets. Indeed, impact of a Mars-sized body into the early Earth is believed to have caused the formation of the terrestrial Moon.
Pluton shapes in the Cornubian Batholith: new perspectives from gravity modelling
Authors: Taylor Graeme K.
Published: May 2007

Gravity modelling of the Dartmoor, Bodmin, St. Austell and Carnmenellis plutons of the Cornubian Batholith of SW England strongly supports a tabular form for the exposed granites. Modelled thicknesses for the individual bodies, with the exception of Dartmoor, are consistent with those derived from empirical relationships for plutons and laccoliths. In the case of the Dartmoor, Bodmin and St. Austell plutons the deepest parts are located near their southern margins, suggesting a steep conduit with northerly and outward direct flows. Modelling of the Carnmenellis granite suggests a more centrally located feeder. In the case of Dartmoor, at least, the granite appears to have exploited the Devonian–Carboniferous interface during its emplacement.
Public Policy Analysis: Ideas and Impacts
Authors: Gormley William T.
Published: May 2007

▪ Abstract  Both economists and political scientists have made important contributions to the field of public policy analysis. Economists have stressed the roles of competition, natural monopolies, information asymmetries, externalities, incentives, and federalism in promoting or undermining efficiency. Political scientists, in contrast, have focused more on the mechanics of agenda change, the likelihood of nonincremental policy change, and how the policy-making process varies across issue areas. Economists have influenced government decisions that led to the creation of public utility commissions, emissions trading, revenue sharing, and health maintenance organizations. Political scientists have influenced government decisions on the design of political institutions (environmental impact statements, legislative redistricting) and on the choice of public policies (criminal justice strategies, welfare reform). In general, the presence of a scholarly consensus facilitates the use of policy analysis. However, interest group politics and electoral incentives also play an important role.
Political Finance in Comparative Perspective
Authors: Scarrow Susan E.
Published: May 2007

▪ Abstract  This article reviews efforts to study the impact of money in politics in democracies outside of the United States. In recent years, democracies around the world have begun to publish increasing amounts of data on candidate and party finance. Although much of this information is partial, and some of it is even deliberately misleading, it has nevertheless opened up many new opportunities for researchers to systematically examine the role of money in politics. The development of theories about the origins and impact of political finance regimes and regulations has not kept pace with the newly emerging data. As a result, the field offers increasing scope for researchers to make policy-relevant contributions. Much of the recent research in this area asks how much, and in what ways, the amounts and sources of funding matter. Do either or both of these influence elections or other political outcomes? This article begins by reviewing attempts to answer these questions, then considers some of the promising new areas of investigation in this field.
Political Places and Institutional Spaces: The Intersection of Political Science and Political Geography
Authors: Ethington Philip J. , McDaniel Jason A.
Published: May 2007

▪ Abstract  Political geography is one of the most exciting subdisciplines to emerge from the “spatial turn” in the social sciences. Arising largely within the discipline of geography, political geography has deep implications for political science, and yet these implications have not yet been widely recognized among political scientists. Conversely, political geographers have not yet profited enough from the rich field of political science. Political geography has the potential to dramatically transform many areas of established political science research. We focus on two: (a) the study of “contextual effects” on political behavior and (b) the study of governance by applying the “new institutionalism.” By spatializing the basic premises of these political science subfields, researchers can find new ways of looking at old questions. We conclude that political scientists should move beyond territorial questions of geography and begin thinking about the intrinsic spatiality of all political action, events, and institutions.
How Domestic Is Domestic Politics? Globalization and Elections
Authors: Kayser Mark Andreas
Published: May 2007

▪ Abstract  Studies of how economic globalization influences domestic politics have disproportionately focused on questions of policy rather than politics. Recently, however, a number of studies have examined how economic globalization influences politics—specifically electoral politics. This article surveys these new studies, which have often appeared in disparate research areas, and argues that they constitute considerable evidence that international economic integration influences seemingly domestic political processes.
What Have We Learned About the Causes of Corruption from Ten Years of Cross-National Empirical Research?
Authors: Treisman Daniel
Published: May 2007

▪ Abstract  I review recent efforts by political scientists and economists to explain cross-national variation in corruption using subjective ratings, and examine the robustness of reported findings. Quite strong evidence suggests that highly developed, long-established liberal democracies, with a free and widely read press, a high share of women in government, and a history of openness to trade, are perceived as less corrupt. Countries that depend on fuel exports or have intrusive business regulations and unpredictable inflation are judged more corrupt. Although the causal direction is usually unclear, instrumenting with income as of 1700 suggests higher development does cause lower perceived corruption. However, controlling for income, most factors that predict perceived corruption do not correlate with recently available measures of actual corruption experiences (based on surveys of business people and citizens that ask whether they have been expected to pay bribes recently). Reported corruption experiences correlate with lower development, and possibly with dependence on fuel exports, lower trade openness, and more intrusive regulations. The subjective data may reflect opinion rather than experience, and future research could usefully focus on experience-based indicators.
The U.S. DOE Fuel Cell Sub-Program
Authors: Epping Kathi , Kopasz John P. , Benjamin Thomas , Podolski Walter
Published: May 2007

This paper provides an overview and shows the most recent results of the Department of Energy's (DOE) Polymer electrolyte membrane (PEM) fuel cell research and development effort. The goal of this sub-program is to develop and demonstrate fuel cell power systems technologies for transportation, stationary, and portable applications. The program emphasizes fuel replacement for light duty vehicles, to reduce U.S. dependence on imported petroleum. PEM fuel cells are the focus for light duty vehicles because they have fast-start capability, high efficiency and operate at low temperatures. The fuel cell sub- program supports the overarching goal of the President's Hydrogen Fuel Initiative, to enable industry commercialization decisions by 2015. This paper summarizes progress and trends seen in fiscal year 2006. The paper also details how the current cost, performance, and durability of fuel cell systems, stacks, and components compare with DOE targets for the year 2015.
Acid-doped Polyimide Electrolyte Membranes with Pendant Benzimidazole Groups for Fuel Cell Applications
Authors: Jang Wonbong , Choi Seunghyck , Lee Seokkyu , Park Sunah , Seo Jongchul , Shul Yonggun , Han Haksoo
Published: May 2007

A benzimidazole pendant diamine, 5-(1H-benzoimidazol-2-yl)- benzene-1-3-diamine, was synthesized from 2-(3,5-dinitro- phenyl)-1H-benzoimidazole. Here the dinitro compound was prepared from 3,5-dinitrobenzoyl chloride and 1,2-phenylene diamine. The benzimidazole pendant diamine was used to synthesis polyimide with pendant benzimidazole groups. These pendant benzimidazole groups present in polyimide main chain were used to dope phosphoric acid and phosphomolibdic acid thereby proton conducting polyelectrolyte membranes were prepared from them. The effect of changing concentration of phosphoric acid and phosphomolibdic acid on the properties of the membranes was studied. It was found that doping of phosphoric acid increased the conductivity at 30% R.H. and further addition of phosphomolibdic acid further increased the conductivity, which can be a promising applicable candidate for the high temperature operation and low humidity required fuel cell.
Self-assembled PEMs for Direct Formic Acid Fuel Cells
Authors: Tang Haolin , Pan Mu , Wan Zhaohui , Yuan Runzhang
Published: May 2007

Direct liquid fuel cells have attracted intensive research because of the promised application in portable fuel cell systems. Liquid fuel such as formic acid crossover through the proton exchange membranes (PEMs, e.g. NafionTM membrane) is one of the major obstacles that currently prevent the widespread commercial applications of direct liquid fuel cell. In this paper, PEMs constructed by self-assembling metal nanoparticles on NafionTM membranes were prepared to probe the direct formic crossover behaviors. The results show that the fuel crossover has a remarkable decrease comparing with the original PEMs. This satisfactory performance gives the self- assembled PEMs a promised prospect in direct liquid fuel cells.
Electric Field Effect for Pt Particle on Carbon Particle
Authors: Suzuki Hitoshi , Shingu Hiroshi , Morikawa Shigeru , Ohyagi Shinsuke , Kimura Yuki , Shintaku Masayuki , Kumamoto Akihito , Kaito Chihiro
Published: May 2007

The electric field effect on Pt cluster-carbon particle nanosystem for the polymer electrolyte fuel (PEFC) cell has been directly demonstrated by two experimental methods. The Pt- C catalyst was flown to the plus plate about 830 V/cm2 electric field due to the electrostatic tension for the nanosystem. The Pt particle surface was covered with graphene layers. In order to make clear the electric field effect, the Pt-C system was put in the 1 volt field and the alteration of the system was directly observed by transmission electron microscopy. The alteration of Pt surface and structure of carbon particles have been discussed as the intense electric field action of the order of 1000 volt on the nanosystem.
Chemical Treatment of Aluminum Bipolar Plates for PEM Fuel Cells
Authors: Nasrallah Magdi M. , Adel Mohamed M.
Published: May 2007

A major component in PEM cell stack design and performance is the bipolar plates connecting the cells. Although many lightweight bipolar plates have been suggested yet cost and performance remain unresolved. Chemically treated Al was used. The Al substrate is pretreated in Zinc solution before dipping in different concentrations of nickel alloy solutions, mainly Ni-W-P, Ni-Co-P, and Ni-Co-W-P. A series of the coated samples was electroplated using Ni-P solution after electroless coating. The coated samples, where characterized and tested using, SEM, EDAX, Electrical Conductivity, and Electrochemical Corrosion techniques. The effect of changing alloy composition and deposition time on the electrical conductivity and corrosion resistance are reported. The most promising sample was that coated with Ni-Co-P before electroplating, this sample was machined for cross flow gas design and used as a bipolar plate in a PEM cell configuration. I-V performance test was conducted at room temperature and 23.7mA and 640mV with varying resistance. A duration test carried out for a period of 100 hours, showed constant voltage and current throughout the duration period of the test. The interrelations between properties, microstructure, composition, and performance are discussed.
Bilirubin Oxidase Biocathodes for Ethanol Biofuel Cells
Authors: Duma Rodica , Minteer Shelley D.
Published: May 2007

A biological fuel cell is a device that converts biochemical energy into electrical energy using a biocatalyst. The basic principle is that the process of fuel (substrate) oxidation by microorganisms or enzymes in the fuel cells offers electrons and protons for electricity production. This paper details the development of bilirubin oxidase biocathodes for ethanol/oxygen biofuel cells. In the described configuration, both the anode and the cathode electrodes in the biofuel cell employ biological catalysts (enzymes) instead of traditional metallic fuel cell catalysts. This enzymatic biofuel cell employs alcohol dehydrogenase to oxidize ethanol at the anode and bilirubin oxidase to reduce oxygen at the cathode. This ethanol/oxygen biofuel cell has an active lifetime of about 20 days and shows power densities of up to 1.67mW/cm2. The biocathode described in this paper is unique in that bilirubin oxidase is immobilized within a modified Nafion DE520 polymer that acts both to entrap and stabilize the enzyme. The biocathode is fuel tolerant at low fuel concentrations (1mM), which leads to a fuel cell that employs both renewable catalysts and fuel, but does not require a separator membrane to separate anolyte from catholyte.
Impedance Analysis and Electrochemical Measurements of A Direct Borohydride Fuel Cell Constructed with Ag Anode
Authors: Sanli Elif , Celikkan Huseyin , Uysal Bekir Z. , Aksu Mehmet L.
Published: May 2007

The catalytic activity of the silver metal as regards to the oxidation of borohydride for fuel cell applications was investigated by cyclic voltammetry (CV), open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS). It was observed that the oxidized Ag electrode leads to the six-electron oxidation of borohydride. According the CV results, the oxides formed upon the Ag surface have catalytic effect on the oxidation of borohydride. A DBFC was constructed using Ag powder as anode and Ni powder as cathode having Nafion-117 membrane producing a voltage of 0.52 V and a power density of 45 mW /cm2 at room temperature in a %10 NaBH4 in 6 M NaOH medium as anolyte and %3.5 H2O2 solution as an oxidant. The complex plane plots of the electrochemical impedance of Ag electrodes show an apparent inductive semicircle, indicating the presence of the reaction intermediate Ag(HO)2- . Decrease of charge transfer resistances (Rct) observed in Nyquist plots was due to fast kinetics of the Ag2O/Ag couple that Ag2O reduces Ag with NaBH4.
Investigation of Aligned Carbon Nanotubes as a Novel Catalytic Electrodes for PEM Fuel Cells
Authors: Liu Di-Jia , Yang Junbing , Gosztola David J.
Published: May 2007

Recent progress in synthesizing and characterizing aligned carbon nanotubes (ACNT) as the electrode catalyst material for proton exchange membrane fuel cells (PEMFC) is reported. Catalytically functionalized ACNT active towards the electrocatalytic reduction of oxygen were prepared by a chemical vapor deposition method. The electrocatalytic activities and the nanostructures of the ACNT layers were investigated by cyclic voltammetry and scanning electron microscopy. To understand the nature of the transition metal as the catalytically active site in the ACNT, we also conducted an in situ X-ray absorption spectroscopic investigation at the Advanced Photon Source at Argonne National Laboratory. The oxidation state and coordination structure of the transition metals embedded inside the nanotubes were monitored by examining the EXAFS spectra collected under different polarization potentials. We clearly observed the change in the electronic and coordinational structures during the oxygen reduction reaction.
Electrically Conductive Polymer-based Blends for Proton Exchange Membrane Fuel Cell Gas Diffusion Layers
Authors: Deyrail Yves , Mighri Frej , Bousmina Mosto , Yakisir Dincer
Published: May 2007

Two electrically conductive polymer-based blends were carefully formulated, using twin-screw extrusion process, in order to develop porous gas diffusion layers (GDLs) for proton exchange membrane fuel cells (PEMFCs). Two low-viscosity polymers, polyamide 11 (PA11) and Polyethylene terephtalate (PET), were selected as the matrix phase. Blend electrical conductivity was ensured by using a mixture of high specific surface area carbon black and synthetic flake graphite. Final GDL porosity was generated by melt blending the PA11 or the PET matrix with polystyrene (PS) followed by PS extraction with tetrahydrofuran, THF, solvent. Blends processability and final GDL conductivity and porosity were compared with those recently obtained by Yakisir et al. (1, 2). PA-11 was found to be the most suitable polymer for this study since it led to best GDL porosity and through-plane conductivity.
Ion Conductivity of Semi-Interpenetrating Polymer Network Membranes based Sulfonated co-Polyimide
Authors: Lee Seokkyu , Jang Wonbong , Choi Seunghyuk , Han Haksoo
Published: May 2007

Novel sulfonated co-polyimide and poly ethylene glycol diacrylate based semi-interpenetrating polymer network membranes have been prepared for the fuel cell applications. These membranes were characterized by determining, ion exchange capacity, water uptake and proton conductivity. The proton conductivity of the membranes was in the order of 10- 1Scm-1 at 90 {degree sign}C and generally increased with increasing poly ethylene glycol diacrylate content.
Compatibility and Durability of Fuel Cell Materials
Authors: Guo Qunhui , Pollard Richard , Ruby James
Published: May 2007

In fuel-cell systems, components such as plates, gaskets, and hoses can impact stack durability by releasing species in a manner that adversely affects the mechanical- and chemical properties of the membrane electrode assembly (MEA) or those of the components themselves. Contamination may originate from the main constituents of the components, from incomplete processing of the materials, or from small quantities of additives used to facilitate processing. Cell tests and autopsies reveal some of the complex interactions that can lead to failure and show that periods of dormancy can exacerbate the impact of the contaminants. Compatibility tests have been performed to help identify materials that meet practical durability, cost, and performance targets.
400 W High Temperature PEM Fuel Cell Stack Test
Authors: Andreasen So̸ren J. , Kær So̸ren K.
Published: May 2007

This work demonstrates the operation of a 30 cell high temperature PEM (HTPEM) fuel cell stack. This prototype stack has been developed at the Institute of Energy Technology, Aalborg University, as a proof-of-concept for a low pressure cathode air cooled HTPEM stack. The membranes used are Celtec P- 1000 series MEAs by Pemeas, with an active area of 45cm2. The low pressure gas channels enable the use of low power blowers instead of a compressor which increases the overall system efficiency. This initial system was made to test the bipolar plate design, and there is no need for humidification of the species as in a LTPEM fuel cell system. The use of the HTPEM fuel cell makes it possible to use reformed gas at high CO concentrations, still with a stable efficient performance.
Numerical Simulation of Coolant Electrolysis in Composite Plate Polymer Electrolyte Membrane Fuel Cell Stacks
Authors: Peterson Amy M. , Im Kyoung-Su , Lai Ming-Chia
Published: May 2007

Two- and three- dimensional numerical models of a PEM fuel cell have been developed to investigate the effects of shunt current within the coolant channel. The model accounts for the electrostatic equation solved for a ten cell fuel stack for idealized and realistic coolant channels including varying conductivities of the solution. The electrostatic equation was solved in the coolant channel for the fully insulated, non- insulated, and incremental lengths of insulation on the channels. The model results found that the length of the insulation on the coolant channel plays an important role in shunt current reduction and fuel cell performance. The case of insulating the coolant channels was found to show that current density propagated further into the channels as increased lengths of insulation were used. However, the strength of the current density from the ending point of the insulation was found to decrease with increasing insulation lengths. Furthermore, a simple experiment was conducted idealizing the fuel cell as batteries connected in series and then submerged in a low conductivity solution. A camera was used to capture the current potential in the different stacks and to validate the numerical model.
Method for Measuring the Distribution of Crossover Current During Operation
Authors: Nishikawa Hisao , Sasou Hidetoshi , Hariyama Suguru
Published: May 2007

Low humidity operation is desired for automobile use due to lower cost and simplified system. However in low humidity condition,H2 crossover occurs in a short time. A study was conducted to establish a method for measuring the distribution of crossover current during operation of the cell.This measurement method can contribute to understanding the cell degaradation mechanism.
Analysis of Flow Errors and Resulting Stoichiometry Uncertainties while Using a Fuel Cell Stack Test Station for Reactant Delivery and Control.
Authors: Lewinski Krzysztof A. , Jaworski Andrzej P.
Published: May 2007

This paper communicates our work on the analysis of difficulties with and limitations of proper delivery of reactants to a fuel cell system that are the result of statistical uncertainties of settings of individual control and measurement devices in the control system. We attempt to set a statistics based groundwork for estimating uncertainties in actual fluid flow in fuel cell stack relative to desired flow set points, stoichiometries and size. Although only the fuel side of the test station that is particularly poorly matched to its test subject is analyzed in the presented example, the method is equally applicable to any control systems and to other pertinent fluids. Similar analysis can and should be performed during design stages of any control scheme for fuel cell systems. This work is most pertinent for (and was a direct response to challenges associated with) stack operation under extremely low stoichiometry conditions.