bluuebunny/crossref_metadata_2025 huggingface dataset:
Frequency dependencies of phase velocity and attenuation coefficient in a water-saturated sandy sediment from 0.3to1.0MHz
Authors: Lee Kang Il , Humphrey Victor F. , Kim Byoung-Nam , Yoon Suk Wang
Published: May 2007

The frequency-dependent phase velocity and attenuation coefficient for the fast longitudinal wave in a water-saturated sandy sediment were measured over the frequency range from 0.3to1.0MHz. The experimental data of phase velocity exhibited the significant negative dispersion, with the mean rate of decline of 120±20m∕s∕MHz. The Biot model predicted the approximately nondispersive phase velocity and the grain-shearing (GS) model exhibited the slightly positive dispersion. In contrast, the predictions of the multiple scattering models for the negative dispersion in the glass-grain composite were in general agreement with the experimental data for the water-saturated sandy sediment measured here. The experimental data of attenuation coefficient was found to increase nonlinearly with frequency from 0.3to1.0MHz. However, both the Biot and the GS models yielded the attenuation coefficient increasing almost linearly with frequency. The total attenuation coefficient given by the algebraic sum of absorption and scattering components showed a reasonable agreement with the experimental data for overall frequencies. This study suggests that the scattering is the principal mechanism responsible for the variations of phase velocity and attenuation coefficient with frequency in water-saturated sandy sediments at high frequencies.
Acoustic monitoring of the tide height and slope-water intrusion at the New Jersey Shelf in winter conditions
Authors: Turgut Altan , Orr Marshall , Pasewark Bruce
Published: May 2007

Waveguide invariant theory is used to describe the frequency shifts of constant acoustic intensity level curves in broadband signal spectrograms measured at the New Jersey Shelf during the winter of 2003. The broadband signals (270–330Hz) were transmitted from a fixed source and received at three fixed receivers, located at 10, 20, and 30km range along a cross-shelf propagation track. The constant acoustic intensity level curves of the received signals indicate regular frequency shifts that can be well predicted by the change in water depth observed through tens of tidal cycles. A second pattern of frequency shifts is observed at only 30km range where significant variability of slope-water intrusion was measured. An excellent agreement between observed frequency shifts of the constant acoustic intensity levels and those predicted by the change in tide height and slope water elevations suggests the capability of long-term acoustic monitoring of tide and slope water intrusions in winter conditions.
Measurement of focused ultrasonic fields using a scanning laser vibrometer
Authors: Wang Yuebing , Tyrer John , Zhihong Ping , Shiquan Wang
Published: May 2007

With the development of optical techniques, scanning laser vibrometers have been applied successfully in measuring particle velocities and distributions in ultrasonic fields. In this paper, to develop the optical interferometry in measuring focused fields with small amplitude, the “effective” refractive index used for plane waves and extended for spherical waves is presented, the piezo-optic effect as a function of the incident angle of the laser beam is simulated, and the ultrasonic field produced by a concave spherical transducer is calculated numerically around its focal region. To verify the feasibility of the optical method in detecting focused ultrasonic fields, a measurement system was set up that utilized both a scanning laser vibrometer and a membrane hydrophone. Measurements were made in different zones of a focusing transducer, and good results were acquired from the optical interferometry in regions where acoustic waves travel in plane form or spherical form. The data obtained from the optical method are used to reconstruct acoustic fields, and it is found that the focal plane, the maximum pressure, and the beamwidth of the transducer can be forecasted accurately.
Effects of aging on word intelligibility and listening difficulty in various reverberant fields
Authors: Sato Hayato , Sato Hiroshi , Morimoto Masayuki
Published: May 2007

Listening difficulty ratings is a new measure to evaluate speech transmission performance in public spaces. The advantage is that it can evaluate sound fields with higher speech transmission performance more accurately and sensitively than intelligibility scores. The effect of aging, or hearing level on listening difficulty ratings has not been clarified yet. In this paper, the results of the listening tests demonstrated that hearing levels above 2kHz significantly affect both word intelligibility scores and listening difficulty ratings for the aged. For the aged, both of them can be estimated from the results for the young plus the average of hearing levels at 2 and 4kHz. The equations for estimating the word intelligibility scores and the listening difficulty ratings for the aged are obtained from the multiple linear regression analyses. The estimated scores and ratings generally coincide with the measured scores and ratings, and the averaged difference between them is 5.2% for the word intelligibility scores and 3.8% for the listening difficulty ratings, in the range of listening tests performed in this paper.
The allocation of energy to echolocation pulses produced by soprano pipistrelles (Pipistrellus pygmaeus) during the wingbeat cycle
Authors: Waters Dean A. , Wong Josephine G.
Published: May 2007

Soprano pipistrelles exhibit considerable plasticity in both the structure and rate of echolocation call production. In search phase in the laboratory, calls are produced either as a single pulse per wingbeat cycle, or as double pulses. The amplitude of double pulses is reduced compared to the preceding single pulse. The energy flux density of either pulse of a double pulse per wingbeat was lower than a single pulse per wingbeat, and is achieved by a combination of reduction in both duration and amplitude. The combined energy of the double pulses is not significantly greater than the single pulse which precedes it. The decision to produce a double pulse may be an indication of the bat requiring additional information from the target. The production of double pulses per wingbeat may serve to achieve a higher rate of information flow for no significant increase in energetic expenditure when a possible target is detected. The proposal that echolocation during flight comes for free as a by-product of the intimate coupling among wingbeat, respiration, and echolocation is discussed.
Multiaspect target detection via the infinite hidden Markov model
Authors: Ni Kai , Qi Yuting , Carin Lawrence
Published: May 2007

A new multiaspect target detection method is presented based on the infinite hidden Markov model (iHMM). The scattering of waves from a target is modeled as an iHMM with the number of underlying states treated as infinite, from which a full posterior distribution on the number of states associated with the targets is inferred and the target-dependent states are learned collectively. A set of Dirichlet processes (DPs) are used to define the rows of the HMM transition matrix and these DPs are linked and shared via a hierarchical Dirichlet process. Learning and inference for the iHMM are based on a Gibbs sampler. The basic framework is applied to a detailed analysis of measured acoustic scattering data.
Blind identification of aggregated microphones in time domain
Authors: Matsumoto Mitsuharu , Hashimoto Shuji
Published: May 2007

This paper introduces an algorithm for blind identification of aggregated microphones in time domain. The features of our approach are summarized as follows: (1) The proposed method treats the blind identification problem of anechoic mixtures in the time domain. (2) The proposed method can identify the gain of each microphone for the directions of sounds whose number is more than the number of the microphones. (3) The proposed method does not utilize the statistical independence of the sounds. The sounds may be not only statistically independent but may also be statistically dependent. (4) The proposed method treats the partially disjoint sounds in the time domain. The sounds may overlap in the frequency domain unlike the sparseness approach. (5) The proposed method does not need to estimate the intervals where sounds are disjoint. First, it is shown that the problem of blind identification and blind source separation can be described not as a convolutive model, but as an instantaneous model in the case of the anechoic mixing when aggregated microphones are assumed. The necessary conditions and the algorithm with experimental results are also described.
Noise in the operating rooms of Johns Hopkins Hospital
Authors: Kracht Jonathan M. , Busch-Vishniac Ilene J. , West James E.
Published: May 2007

Very little reliable information exists on the sound levels present in an operating room environment. To remedy this situation, sound pressure levels of the operating rooms in Johns Hopkins Hospital were monitored before, during, and after operations. The data were analyzed to determine background sound levels, average equivalent sound levels Leq, frequency distribution, and peak sound pressure levels Lpeak. Each surgery was matched to the period of noise it produced permitting the association of sound levels with particular types of surgeries and the determination of various sound measures for classes of surgery (e.g., orthopedic, neurological, etc.). Averaging over many surgeries, orthopedic surgery was found to have the highest Leq at approximately 66dB(A). Neurosurgery, urology, cardiology, and gastrointestinal surgery followed closely, ranging from 62 to 65dB(A). By considering the Lpeak along with the Leq values, a pattern emerges for the various surgical divisions. Gastrointestinal and thoracic surgery are relatively quiet among the surgical divisions. Neurosurgery and orthopedics have sustained high sound levels. Cardiology surgery has a more moderate average sound level but includes brief periods of extremely high peak sound levels. For neurosurgery and orthopedic surgery, peak levels exceeded 100dB over 40% of the time. The highest peak levels routinely seen during surgery were well in excess of 120dB.
Acoustic modes propagating along the free surface of granular media
Authors: Aleshin V. , Gusev V. , Tournat V.
Published: May 2007

In unconsolidated granular materials under gravity there exist acoustical waves propagating along the surface with anomalously low sound velocity. The presented theory describes these guided surface acoustic modes (GSAM) confined between the surface of the granular materials and in-depth layers with increasing rigidity. The analysis is based on the obtained original analytical solution of the Helmholtz equation that has never been used both in classical and quantum mechanics. This solution is valid for a particular rigidity profile, whereas the general case of grains with or without adhesion has been analyzed numerically. In contrast to the Rayleigh wave polarized in the sagittal (vertical) plane, which is the unique localized mode in a homogeneous solid, an infinite number of modes with sagittal polarization as well as an infinite number of shear horizontal modes have been found. The difference in physical mechanisms of localization is discussed, and the transformation of the GSAMs into the Rayleigh wave at the increasing adhesion is demonstrated: The first sagittal mode transforms into the Rayleigh one, while the others delocalize. The theory explains the experimentally observed magnitude of velocity for the acoustic waves in sand elliptically polarized in the sagittal plane.
Bayesian focalization: Quantifying source localization with environmental uncertainty
Authors: Dosso Stan E. , Wilmut Michael J.
Published: May 2007

This paper applies a Bayesian formulation to study ocean acoustic source localization as a function of uncertainty in environmental properties (water column and seabed) and of data information content [signal-to-noise ratio (SNR) and number of frequencies]. The approach follows that of the optimum uncertain field processor [A. M. Richardson and L. W. Nolte, J. Acoust. Soc. Am. 89, 2280–2284 (1991)], in that localization uncertainty is quantified by joint marginal probability distributions for source range and depth integrated over uncertain environmental properties. The integration is carried out here using Metropolis Gibbs’ sampling for environmental parameters and heat-bath Gibbs’ sampling for source location to provide efficient sampling over complicated parameter spaces. The approach is applied to acoustic data from a shallow-water site in the Mediterranean Sea where previous geoacoustic studies have been carried out. It is found that reliable localization requires a sufficient combination of prior (environmental) information and data information. For example, sources can be localized reliably for single-frequency data at low SNR (−3dB) only with small environmental uncertainties, whereas successful localization with large environmental uncertainties requires higher SNR and/or multifrequency data.
Contributions of individual components to the overall loudness of a multitone complex
Authors: Leibold Lori J. , Tan Hongyang , Khaddam Samar , Jesteadt Walt
Published: May 2007

The contributions of individual components to the overall loudness of a multitone complex were examined in a two-interval, loudness judgment task. Stimuli were five-tone complexes centered on 1000Hz, with six different logarithmic frequency spacings, corresponding to bandwidths from 46 to 2119Hz. Stimuli were presented for 300ms (10ms rise/fall). The overall level of the standard complex was fixed at 60dB SPL (53dB∕component). Levels of the individual components of the comparison complex were selected at random from a rectangular distribution with a range of 20dB. Perceptual weights were computed by calculating the point-biserial correlation between the difference in the level of each component across the two intervals and the subject’s response. When all components fell within the same critical band, weights varied little across components. In contrast, the range of weights increased with increasing frequency separation, with more weight given to the lowest and highest frequency components. A relation between component weight and masked threshold was observed for all but the widest spacing condition. Perceptual weights and masked thresholds were largely in agreement with the loudness model [Moore et al., J. Audio. Eng. Soc. 45, 224–237 (1997)], except at the widest bandwidth.
Effects of simultaneous perturbations of voice pitch and loudness feedback on voice F and amplitude control
Authors: Larson Charles R. , Sun Jean , Hain Timothy C.
Published: May 2007

Perturbations in either voice pitch or loudness feedback lead to changes in a speaker’s voice fundamental frequency (F0) or amplitude. Voice pitch or loudness perturbations were presented individually (either pitch or loudness shift stimuli) or simultaneously (pitch combined with loudness shift stimuli) to subjects sustaining a vowel to test the hypothesis that the mechanisms for these two response types are independent. For simultaneous perturbations, pitch and loudness both changed in the same direction or in opposite directions. Results showed that subjects responded with voice F0 or amplitude responses that opposed the direction of the respective pitch- or loudness shift stimuli. Thus, depending on the stimulus direction, both responses could either change in the same direction or in the opposite direction to each other. F0 response magnitudes were greatest with pitch-shift only stimuli (18 cents), smallest for loudness shift stimuli (10 cents) and intermediate with pitch combined with loudness shift stimuli (13 and 16 cents). Amplitude responses were largest with +3dB stimuli (0.96dB) and smallest with −3dB stimuli (0.49dB) but were not affected by the addition of pitch-shift stimuli. Results suggest the F0 and amplitude response mechanisms may be independent but interact in some conditions.
Vibrotactile transduction and transducers
Authors: Mortimer Bruce J. P. , Zets Gary A. , Cholewiak Roger W.
Published: May 2007

The body’s sense of touch is potentially a versatile channel for the conveyance of directional, spatial, command, and timing information. Most practical implementations of vibrotactile systems require compact, light-weight actuators that can be mounted against the body. Eccentric mass motors are widely used for this application, yet their output is limited and the effects of loading on the transducers due to the skin and mounting arrangement have been largely ignored. Conventional linear actuators are well suited as vibrotactile transducers and can provide high output, but are typically limited to laboratory research due to their large size and cost. The effect of loading on various practical vibrotactile transducers is investigated using a skin impedance phantom and measuring the transducer displacement with respect to additional mass loading. Depending on the transducer design, loading can dramatically reduce the vibratory displacement and, in the case of eccentric mass motors, also increase the operating frequency. In contrast, a new linear actuator design can be designed to be almost independent of skin loading, by considering the mechanical impedance of the load and optimizing the transducer contact area.
Forward and reverse waves in nonclassical models of the cochlea
Authors: de Boer Egbert
Published: May 2007

In “classical” models of the cochlea the mechanical properties of the cochlear partition (in which the basilar membrane plays a dominant role) depend only on the local longitudinal coordinate. Wave propagation in such models is the same for both propagation directions, towards the apex and towards the base. “Nonclassical” models contain mechanical properties that depend on variables at more than one location. In such models the properties of wave propagation may well be asymmetrical. This note presents an analysis of feed-forward and feed-backward models, with the emphasis on the properties of forward and reverse waves. In both of these classes of model, wave amplification for forward waves turns into wave attenuation for reverse waves. The slope of the phase pattern is nearly the same for the two types of waves, it is increased in feed-forward models and decreased in feed-backward models—with respect to a model without feedback.
Simulating the acquisition of lexical tones from continuous dynamic input
Authors: Gauthier Bruno , Shi Rushen , Xu Yi
Published: May 2007

Infants develop phonetic categories by simply being exposed to adult speech. It remains unclear, however, how they handle the extensive variability inherent to speech, and how they process multiple linguistic functions that share the same acoustic parameters. Across four neural network simulations of lexical tone acquisition, self-organizing maps were trained with continuous speech input of increasing variability. Robust tonal categorization was achieved by tracking the velocity profiles of fundamental frequency contours. This result suggests that continuous speech signal carries sufficient categorical information that can be directly processed, and that dynamic acoustic information can be used for resolving the variability problem.
Loudness control in pianists as exemplified in keystroke force measurements on different touches
Authors: Kinoshita Hiroshi , Furuya Shinichi , Aoki Tomoko , Altenmüller Eckart
Published: May 2007

The relationship between the key depression force on an upright piano and the level of loudness of a generated tone was examined when pianists hit a force-sensor built-in key with “struck” or “pressed” type of touch. The vertical displacement of the key, and the radiated piano sounds were also recorded. It was found that for both types of touch, simple exponential functions could adequately describe the relation of the force amplitude with the level of the piano tone as well as that of the impulse of the force with the piano tone. The impulse of the force generated before the maximum key depression moment commonly amounted to above 80% of the total impulse produced at the tone below mezzo-forte. It, however, decreased to around 60% at fortissimo, indicating a decrease in the efficiency of the force application for sound production. The two types of touch differed in their force profiles. The struck touch was characterized by a steeper initial force increase with greater fluctuations in the subsequent period than the pressed touch. The struck touch also demonstrated lower maximum force and less impulse at fortissimo. The inter-pianist variation in the force and impulse, and the “finger-noise” are also herein examined.
Pulsed Mid-Infrared Laser Stimulation of the Auditory Nerve in the Gerbil: Implications for Cochlear Implants
Authors: Izzo Agnella D.
Published: May 2007

Light can artificially stimulate nerve activity in vivo and has the advantage of a higher spatial selectivity relative to that which can be obtained with electrical stimulation. An increased spatial selectivity of stimulation could improve the function of neuroprosthetics, such as cochlear implants, whose performance is limited by overlapping electric fields from neighboring electrodes. The studies reported here investigated optical stimulation of nerves in the gerbil auditory system. Pulsed, infrared light was used to elicit compound action potentials (CAPs) from the gerbil cochlea in vivo. Penetration depth was varied by changing the wavelength of irradiation, to select the tissue depth of stimulation. Experiments showed no immediate damage to the cochlea when optically stimulating at 400Hz for several hours. Immunohistochemical staining for the protein c-FOS revealed spatial specificity of the optically stimulated cochleae: only the spiral ganglion cells directly in the optical path revealed c-FOS staining, indicating that they were stimulated. In contrast, c-FOS staining of electrically stimulated cochleae demonstrated electric current spread. An electrophysiologic measurement of the spatial specificity of optical stimulation was conducted with tone-on-light masking experiments. Results from tone-on-light masking studies revealed tuning curves that were similar in extent to tone-on-tone tuning curves.
Tracking Solar Gravity Modes: The Dynamics of the Solar Core
Authors: García Rafael A. , Turck-Chièze Sylvaine , Jiménez-Reyes Sebastian J. , Ballot Jérôme , Pallé Pere L. , Eff-Darwich Antonio , Mathur Savita , Provost Janine
Published: May 2007

Solar gravity modes have been actively sought because they directly probe the solar core (below 0.2 solar radius), but they have not been conclusively detected in the Sun because of their small surface amplitudes. Using data from the Global Oscillation at Low Frequency instrument, we detected a periodic structure in agreement with the period separation predicted by the theory for gravity dipole modes. When studied in relation to simulations including the best physics of the Sun determined through the acoustic modes, such a structure favors a faster rotation rate in the core than in the rest of the radiative zone.
Xeno-oestrogenic activity in serum as marker of occupational pesticide exposure
Authors: Andersen Helle Raun , Nielsen Flemming , Nielsen Jesper Bo , Kjaerstad Mia Birkhoej , Baelum Jesper , Grandjean Philippe
Published: May 2007

Background:

An increasing number of currently used pesticides are reported to possess oestrogen-like properties or to disturb the endocrine system in other ways.

Objectives:

To investigate if xeno-oestrogenic activity in serum can be used as a biomarker of the combined exposure to pesticides with oestrogen-like properties in an occupational setting.

Methods:

Serum samples were obtained from two separate cohorts representing non-pregnant and pregnant female greenhouse workers in Denmark. Serum samples from 270 non-pregnant women and 173 pregnant women were analysed for xeno-oestrogenic activity. A fraction containing major xeno-oestrogens but without pharmaceutical and endogenously produced oestrogens was isolated from each serum sample by solid-phase extraction and tested for oestrogenic response in a MCF-7 cell proliferation assay. The pesticide exposure for each woman was categorised as low, medium or high based on information collected by detailed interviews of the women and the employers.

Results:

In both cohorts, an exposure-associated increase in the xeno-oestrogenic activity in serum was demonstrated. Among the pregnant women, the association between pesticide exposure and xeno-oestrogenic activity in serum was statistically significant for women who had been at work within the last week, while no association was observed for women who had not been at work during the most recent week.

Conclusions:

The study illustrates the usefulness of this biomarker for qualitative assessment of the combined exposure to mixtures of oestrogen-like pesticides. Although the individual pesticides responsible for the xeno-oestrogenic response were not identified, the study demonstrates that, even within highly-controlled greenhouse operations, occupational exposure to oestrogen-like pesticides can result in detectable impacts on hormonal activity in the blood.
Limits of longitudinal decline for the interpretation of annual changes in FEV1in individuals
Authors: Hnizdo Eva , Sircar Kanta , Yan Tieliang , Harber Philip , Fleming James , Glindmeyer Henry W
Published: May 2007

Objective:

Spirometry-based screening programmes often conduct annual assessment of longitudinal changes in forced expiratory volume in 1 second (FEV1) to identify individuals with excessive rates of decline. Both the American Thoracic Society (ATS) and the American College of Occupational and Environmental Medicine (ACOEM) recommend a reference limit value of ⩾15% for excessive annual decline. Neither the ATS nor the ACOEM adjust this limit for the precision of the existing spirometry data. The authors propose an improved method of defining the reference limit of longitudinal annual FEV1decline (LLD) based on the precision of the spirometry data.

Method:

The authors used data from four monitoring programmes and measured their data precision using a pair-wise within-person variation statistic. They then derived programme- and gender-specific absolute and relative LLD values and validated these against the 95th percentiles for observed yearly changes in FEV1.

Results:

The relative limit for annual decline was more practical than the absolute limit as it adjusted for gender differences in the magnitude of FEV1. The programme-specific relative limit values were in good agreement with 95th percentiles for year-to-year FEV1changes and ranged from 6.6% to 15.8%. For individuals with COPD and bronchial hyperreactivity the 95th percentiles for year-to-year changes were about 15% and higher.

Conclusions:

The relative longitudinal limit for annual FEV1decline based upon precision of measurements is valid and can be generalised to different gender and population groups. A relative limit of approximately 10% appears appropriate for good quality workplace monitoring programmes, whereas a limit of about 15% appears appropriate for clinical evaluation of individuals with an obstructive airway disease. Computer software based on the method described is available from the corresponding author.
The late Mesoproterozoic–early Neoproterozoic tectonostratigraphic evolution of NW Scotland: the Torridonian revisited
Authors: Kinnaird T.C. , Prave A.R. , Kirkland C.L. , Horstwood M. , Parrish R. , Batchelor R.A.
Published: May 2007

The Torridonian succession of NW Scotland comprises three groups, deposited during late Mesoproterozoic to early Neoproterozoic time, the Stoer, Sleat and Torridon. Previous workers have inferred that each was formed in a rift basin and that each is internally conformable. New fieldwork and detrital zircon age data indicate that this model is incorrect. Our main findings are as follows: (1) the facies characteristics and detrital zircon data for the Sleat Group indicate that it is genetically unrelated to the Torridon Group; (2) the Sleat and Stoer Groups contain features suggestive of deposition in extension-related basins that predate the
c
. 1.0 Ga Grenville Orogeny; (3) the base of the Applecross–Aultbea succession of the Torridon Group is an unconformity; (4) the Applecross–Aultbea succession is most objectively interpreted as a non-marine molasse. The significance of these data is that they can be used as a constraint to test and define tectonic models for the deposition of the Torridonian succession and geological evolution of the Scottish Highlands. The view that the Torridonian rocks record deposition in a suite of long-lived rifts whereas the rest of the consanguineous Laurentian margin experienced collisional and orogenic episodes becomes equivocal and in need of reassessment, if not outright abandonment.
Magneto-biostratigraphy of the Middle to Upper Triassic transition, central Spitsbergen, arctic Norway
Authors: Hounslow Mark W. , Hu Mengyu , MØrk Atle , Vigran Jorunn Os , Weitschat Wolfgang , Orchard Michael J.
Published: May 2007

Palaeomagnetic and biostratigraphic data were obtained for the latest Ladinian and most of the Carnian (Botneheia Formation to basal Kapp Toscana Group), from two sections in central Spitsbergen (Svalbard archipelago). Thermal and alternating field (AF) demagnetization reveals a magnetization of both normal and reversed polarities. The mean directions pass reversal and fold tests and are similar to other European Late Triassic palaeopoles. One of the sections displays 15° of vertical-axis, clockwise, tectonic rotation on a décollement in the underlying Botneheia Formation. The magnetostratigraphy is dominated by normal polarity in the uppermost Botneheia Formation and into the Tschermakfjellet and basal De Geerdalen formations. A substantial hiatus characterizes the Ladinian–Carnian boundary in central Spitsbergen, so reverse magnetozones, identified in Tethyan sections near this boundary, are absent. Magnetostratigraphic correlation, along with palynostratigraphic constraints, indicates that most of the De Geerdalen Formation is Lower Carnian. The magnetostratigraphy and palynology indicates that the Isfjorden Member (upper unit of the De Geerdalen Formation) is probably mid-Carnian in age. Change in the lithological architecture in the Isfjorden Member, compared with the underlying parts of the De Geerdalen Fm, suggests a hiatus near the base of the member, which may represent a mid-Carnian unconformity, not previously recognized on Spitsbergen.
Textural immaturity of cumulates as an indicator of magma chamber processes: infiltration and crystal accumulation in the Rum Eastern Layered Intrusion
Authors: Holness M.B.
Published: May 2007

Textural maturity describes the extent to which rocks have approached textural equilibrium. For igneous rocks, this is a function of the time-integrated thermal history in the sub-solidus which, for cumulate rocks, generally translates to the cooling history via the rate of solidification of the accumulating crystal mush. The most straightforward way to quantify the textural maturity of orthocumulates (
sensu lato
) is to measure the angle subtended at the corners of interstitial grains. Texturally mature cumulates have angle populations with median values of
c
. 120°, whereas texturally immature cumulates have lower medians, inherited by the interstitial phase, which infills either an impingement texture in the accumulating mush or a texturally equilibrated pore topology. Textural observations of allivalites from the Rum Layered Suite demonstrate that stratigraphically localized excursions towards textural immaturity are the result of either transient, relatively rapid, solidification rates (perhaps a result of the arrival of cold crystal-laden bodies of fluid on the chamber floor) or late-stage infiltration of fully solidified cumulates by evolved liquids expelled upwards by compaction of underlying horizons. These two processes have distinct textural and compositional signatures.
Dinosaurs of Great Britain and the role of the Geological Society of London in their discovery: basal Dinosauria and Saurischia
Authors: Naish Darren , Martill David M.
Published: May 2007

Beginning with Buckland's 1824 description of
Megalosaurus
, the Geological Society of London played a leading role during the 19th century discovery of dinosaurs in Britain. Here we review the society's role and assess the current knowledge of saurischian dinosaurs in the country. Of Britain's 108 dinosaur species (excluding
nomina nuda
and objective synonyms), 32% have been named in the pages of Society publications. Britain has a rich and diverse dinosaur record ranging from the Rhaetian to the Cenomanian, and includes a surprising taxonomic diversity. Alleged Lower and Middle Triassic dinosaurs from Britain are suspect or erroneous. Sauropodomorphs represent all of the major clades and several have their earliest global appearances in the British record (Diplodocoidea, Rebbachisauridae and Titanosauria), implying that this region was biogeographically important for this group. The British theropod record is diverse, and includes the earliest spinosaurids, carcharodontosaurids and coelurosaurs. Although some specimens are represented by near-complete skeletons, much material is fragmentary and indeterminate, and
c
. 54% of British dinosaur taxa are considered
nomina dubia
. In part this high number results from the genesis of dinosaur science in Britain and the corresponding obsolescence of supposedly diagnostic characters.
The effect of tilting on fault propagation and network development in sandstone–shale sequences: a case study from the Lodève Basin, southern France
Authors: Wibberley Christopher A.J. , Petit Jean-Pierre , Rives Thierry
Published: May 2007

Extensional basins often evolve both with the generation of normal faults at all scales, and with tilting in the hanging walls and footwalls of major structures. This paper examines the effect of regional tilting on the development of normal fault arrays in an anisotropic sequence, using the asymmetric Lodève Basin, France, as a case study. The orientation range of normal faults is found not to match that expected by continued symmetric generation of conjugate normal faults during tilting. Instead, continued generation of new faults preferentially occurred for faults dipping opposite to the direction of tilt, with propagation perpendicular to bedding. The presence of early bedding-perpendicular joints in the competent sandstone units aided propagation of these faults during tilting and this preferential asymmetric development. Bedding-parallel slip surfaces were activated as normal faults during the later stages of bedding tilting, showing complex interaction patterns with later faults downthrowing in the direction opposite to bedding tilting. Hence knowledge of the timing between tilting of the strata and deformation helps in evaluating the likely complexity of fault arrays at subseismic scales in extensional basins, and may also help in understanding the evolution of fault systems in tilted normal fault blocks at the reservoir scale.
Superimposed folding and oblique structures in the palaeomargin-derived units of the Central Betics (SW Spain)
Authors: Crespo-Blanc Ana
Published: May 2007

The Subbetic units consist of a deformed wedge of sedimentary rocks deriving from the South Iberian palaeomargin, in the westernmost segment of the Alpine–Mediterranean orogenic belt. In the central Betics, shortening produced folding, thrusting and nappe-stacking. The structural trend is NE–SW to ENE–WSW, and the internal structure of the thrust sheets, which shows no preferred vergence, is strongly controlled by the rheology of the décollement level, a viscous layer of Triassic evaporites, and of the overlying carbonate rock sequence. The relationships of piggyback basin Miocene sediments with the main structures show that the latter developed during the Aquitanian–Burdigalian transition. Superimposed folding is described for the first time in the study area. The origin of the interference cannot be determined at present, but may be related to initially oblique structures refolded during progressive deformation. A revision of previously published palaeomagnetic data in the light of the data presented in this paper, in conjunction with a model of the structural evolution of the Subbetic units of the western Betics, permits us to establish milestones of the tectonic evolution of the external zones in the northern branch of the Gibraltar Arc.
Channel flow and the Himalayan–Tibetan orogen: a critical review
Authors: Harris Nigel
Published: May 2007

The movement of a low-viscosity crustal layer in response to topographic loading provides a potential mechanism for (1) eastward flow of the Asian lower crust causing the peripheral growth of the Tibetan Plateau and (2) southward flow of the Indian middle crust to be extruded along the Himalayan topographic front. Thermomechanical models for channel flow link such extrusion to focused orographic precipitation at the surface. Isotopic constraints on the timing of fault movement, anatexis and thermobarometric evolution of the exhumed garnet- to sillimanite-grade metasedimentary rocks support mid-crustal channel flow during the Early to Mid-Miocene. Exhumed metamorphic assemblages suggest that the dominant mechanism of the viscosity reduction that is a requirement for channel flow was melt weakening along the upper surface, defined by the South Tibetan Detachment System, and strain softening along the base, bounded by the Main Central Thrust. Neotectonic extrusion, bounded by brittle Quaternary faults south of the Main Central Thrust, is positively correlated with the spatial distribution of precipitation across a north–south transect, suggesting climate–tectonic linkage over a million-year time scale. A proposed orogen-wide eastward increase in extrusion rate over 20 Ma reflects current precipitation patterns but climate–tectonic linkage over this time scale remains equivocal.
The End of Economic Voting? Contingency Dilemmas and the Limits of Democratic Accountability
Authors: Anderson Christopher J.
Published: May 2007

▪ Abstract  The predominant normative justification for research on economic voting has been its essential role in shaping democratic accountability. A systematic examination of this literature reveals, however, that economic voting is highly contingent on two critical moderating factors: voters themselves and the political context in which they make judgments. The trend toward a better and more realistic understanding of economic voting produced by almost four decades of empirical research has created what I label “contingency dilemmas” for the field's normative foundations because economic voting does not function as envisioned by advocates of democratic accountability. This essay reviews these empirical findings and critically examines how they affect the economic voting paradigm. It argues that, when viewed from a normative perspective, contingent accountability is clearly problematic, and it calls for a reconsideration of the normative underpinnings of the economic voting paradigm in light of the current state of knowledge.
Be Careful What You Wish For: The Rise of Responsible Parties in American National Politics
Authors: Rae Nicol C.
Published: May 2007

▪ Abstract  Among advanced democracies, the United States has traditionally been unique owing to the absence of ideological mass political parties. American parties’ scholars have nevertheless traditionally viewed stronger and more ideologically distinct national parties as essential to improve the quality of the American democratic process, a view reflected in the 1950 APSA report, Toward a More Responsible Party System. In the following decades the American parties appeared to weaken still further in all aspects, but this apparent party decline in fact signified a transition to a contemporary American party system with more polarized parties similar to those envisaged by the 1950 report. It remains doubtful, however, that American democracy has been enhanced by these developments. Ironically, the advent of more ideologically coherent parties has also made party scholars more aware of the potentially unhealthy side effects that may attend such a development in a separated governing system.
Divided Politics: Bicameralism, Parties, and Policy in Democratic Legislatures
Authors: Heller William B.
Published: May 2007

▪ Abstract  This article surveys the rationales for and effects of legislative bicameralism. At heart, second chambers facilitate representation for groups or interests that otherwise might be ignored. They do so not only by making more legislative seats available to legislators elected from different districts and possibly by different rules, but more importantly by giving more legislators a voice in the legislative process. Traditional views of bicameralism hold that second chambers can matter because their members have the authority to veto or at least delay bills, so that whether they do in fact affect legislative content depends on whether and to what extent majority preferences differ across chambers. A new current of legislative research focuses on how the existence of a second chamber provides a forum for bargaining over policy and, in the process, creates a need for policy bargains within parties as well as across chamber majorities that would be unnecessary in a unicameral legislature.
Electoral Laws, Parties, and Party Systems in Latin America
Authors: Morgenstern Scott , Vázquez-D’Elía Javier
Published: May 2007

▪ Abstract  With a focus on Latin America, this literature review considers the extent to which electoral systems affect different aspects of parties and party systems. We find that standard electoral system variables fail many empirical tests that try to tie them to any facet of parties or party systems. Still, methodological considerations regarding interactions with party strategies, party organization, and many contextual variables loom large, so we cannot reject the hypothesis that electoral systems are influential. Analyses, therefore, must go far beyond formal electoral rules generally or a simple focus on single aspects of electoral rules (such as the district magnitude) when trying to explain political behaviors.
State Repression and Political Order
Authors: Davenport Christian
Published: May 2007

▪ Abstract  State repression includes harassment, surveillance/spying, bans, arrests, torture, and mass killing by government agents and/or affiliates within their territorial jurisdiction. Over the past 40 years, the systematic study of state repression has grown considerably. The development of this work, however, has been uneven. Though unified in their focus on the problem of order (i.e., trying to ascertain how political authorities wield coercive power amid potential and actual domestic challengers), different scholars tend to emphasize distinct aspects of the topic. Consequently, a great deal of progress has been made in specific areas but others have lagged behind. In this review, I attempt to identify the dominant traditions in the repression literature, the core empirical findings, and some persisting puzzles.
Irrational Choice and Mortal Combat as Political Destiny: The Essential Carl Schmitt
Authors: McCormick John P.
Published: May 2007

▪ Abstract  The reissue of Carl Schmitt's most important works, Political Theology and The Concept of the Political, offers the opportunity for reflection on Schmitt's pervasive influence over myriad fields of political and legal studies and for re-evaluation of the basic tenets of his thought. In these works, the conservative Weimar jurist unveiled his theory of ”the exception,“ put forth his ”friend/enemy“ thesis of politics, and insisted that Enlightenment rationality had undermined the European state, leaving it vulnerable to the forces of atheism, anarchism, and socialism that were taking root in Soviet Russia. Among other issues, this article explores Schmitt's Janus-faced critique of liberalism: For Schmitt, liberals are either not worthy to be considered enemies because they deny the inevitability of mortal combat, or they are, in fact, consummate enemies because they successfully punish and destroy adversaries under the cover of universal, humanitarian principles. The article also interrogates the status of morality in Schmitt's conception of the political—specifically, whether the categories of good and evil inform the distinction between friend and enemy, or whether the political operates in a sphere completely autonomous of morality and theology.
Influences of Gas Diffusion Layer Design Parameters on the Performance of Polymer Electrolyte Fuel Cells
Authors: Kitahara Tatsumi , Konomi Toshiaki , Murata Makoto , Berg Norbert , Wilde Peter
Published: May 2007

Experiments examining the influences of gas diffusion layer (GDL) design parameters on the performance of polymer electrolyte fuel cells (PEFCs) are carried out under controlled clamp pressure conditions. The PEFC performance is strongly affected by the humidity of the supplied gas. Under moderate-humidity conditions, improved performance is obtained using an untreated GDL with high air permeability, whereas under high-humidity conditions, improved performance is obtained using a GDL treated with PTFE. The addition of a microporous layer (MPL) under humid conditions significantly reduces flooding on the electrode, thereby decreasing the concentration overpotential. The MPL is also effective for preventing the membrane electrode assembly (MEA) from drying out under low-humidity conditions.
Diagnostic Tools for In-situ and Ex-situ Investigations of Fuel Cells and Components at the German Aerospace Center
Authors: Schulze Mathias , Gülzow Erich , Friedrich K. Andreas , Metzger Patrick , Schiller Günter
Published: May 2007

The analysis of the processes in fuel cells is a main topic at the German Aerospace Center (DLR). The degradation of cell components - especially electrodes - and changes during start- up processes are of foremost interest. For this purpose physical and electrochemical methods are used individually and in combination. In this paper, studies using a combination of methods were performed on different fuel cell types. The examples in the field of low temperature fuel cells, namely alkaline fuel cells (AFC), polymer electrolyte fuel cells (PEFC), and direct methanol fuel cells (DMFC), are mainly focused on the alteration of the electrodes due to electrochemical operation; for solid oxide fuel cells (SOFC) an example for the investigation of the local operating conditions is given.
Preparation of PtRu/C Anode Electrocatalysts using NaBH4 as Reducing Agent and OH- ions as Stabilizing Agent
Authors: Spinace Estevam V. , Indelicato do Vale Luis Antonio , Oliveira Neto Almir , Linardi Marcelo
Published: May 2007

PtRu/C electrocatalysts were prepared using NaBH4 as reducing agent and OH- ions as stabilizing agent. The electrocatalysts were characterized by EDX, XRD, TEM and cyclic voltammetry. The electro-oxidation of methanol was studied by cyclic voltammetry using the thin porous coating. Active PtRu/C electrocatalysts for methanol oxidation could be prepared by a simple methodology.