bluuebunny/crossref_metadata_2025_split huggingface dataset:
Propagation of a ground‐penetrating radar (GPR) pulse in a thin‐surface waveguide
Authors: Arcone Steven A. , Peapples Paige R. , Liu Lanbo 
Published: November 2003

Field observations are tested against modal propagation theory to find the practical limitations upon derivation of layer permittivities and signal attenuation rates from a radar moveout profile over two‐layer ground. A 65‐MHz GPR pulse was transmitted into a 30‐60‐cm‐thick surface waveguide of wet, organic silty to gravelly soil overlying a drier refracting layer of sand and gravel. Reflection profiles, trench stratigraphy, resistivity measurements, and sediment analysis were used to quantify the propagation medium and possible attenuation mechanisms. Highly dispersive modal propagation occurred within the waveguide through 35 m of observation. The fastest phase velocity occurred at the waveguide cutoff frequency of 30 MHz, which was well received by 100‐MHz antennas. This speed provides the refractive index of the lower layer, so the near‐cutoff frequencies must match a lower layer refraction. A slower, lower frequency phase of the dispersed pulse occurred at about 60–70 MHz, with an average attenuation rate of about 0.4 dB/m. Similar events appear to have reflected back and forth along the waveguide. Modal theory for the average layer thickness shows all primary events to be different aspects of a TE1 mode, predicts the correct 30–70‐MHz phase speeds and low‐frequency cutoff phenomenon, but also predicts that the 60–70‐MHz group speed should be slightly lower than observed. An Airy phase was apparently out of the bandwidth. Two‐dimensional finite‐difference time‐domain modeling qualitatively simulates the main field results. After accounting for an inverse dependency of amplitude on the square of the range, the high resistivity of the surface layer accounts for the 0.4‐dB/m attenuation rate for the 60–70‐MHz phase of the pulse. However, erratic amplitudes, interface roughness, and the reflected packets indicate scattering. We conclude that permittivities can be well estimated from dispersive moveout profiles given an average surface layer thickness, and the wide bandwidth of GPR antennas allows the full dispersion to be seen. Attenuation rates appear to be derivable from the higher frequency part of our dispersive event, for which attenuation might be least affected by the waveguide dispersion.
Differential reduction of magnetic anomalies to the pole on a massively parallel computer
Authors: Lu Richard S. , Mariano John , Willen Dennis E. 
Published: November 2003

A finite‐impulse‐response filter was implemented on a computer with massively parallel processors to reduce a magnetic anomaly map to the magnetic pole, allowing each grid node to have a different inclination and declination (differential reduction to the pole, DRTP). The dramatic speed improvement of such an implementation for the filter design and application via space‐domain convolution makes DRTP a practical tool for hydrocarbon and mineral exploration. Application of this tool to magnetic anomalies in east China reveals that the northward shift in position of the anomaly maximum generated by DRTP is 6 km for anomalies with dominant wavelengths of approximately 25 km in the northernmost part of the study area. The shift increases as the anomaly wavelength increases. Shifts for all anomaly wavelengths are even larger in the southern part of the study area, where the magnetic inclination is lower. The shift in position of the anomaly maximum for anomalies of wavelengths 25 km in the northernmost area produced by DRTP is 2 km less than that produced by a conventional reduction to the pole using the inclination and declination at the central location of the study area. Once again, such differences in shifts are larger for anomalies of longer wavelengths. The farther away from the central location, the greater is the absolute value of the difference.
Analysis of image gathers in factorized VTI media
Authors: Sarkar Debashish , Tsvankin Ilya 
Published: November 2003

Because events in image gathers generated after prestack depth migration are sensitive to the velocity field, they are often used in migration velocity analysis for isotropic media. Here, we present an analytic and numerical study of P‐wave image gathers in transversely isotropic media with a vertical symmetry axis (VTI) and establish the conditions for flattening such events and positioning them at the true reflector depth. Application of the weak‐anisotropy approximation leads to concise expressions for reflections in image gathers from homogeneous and factorized v(z) media in terms of the VTI parameters and the vertical velocity gradient kz. Flattening events in image gathers for any reflector dip requires accurate values of the zero‐dip NMO velocity at the surface [Vnmo (z = 0)], the gradient kz, and the anellipticity coefficient η. For a fixed error in Vnmo and kz, the magnitude of residual moveout of events in image gathers decreases with dip, while the moveout caused by an error in η initially increases for moderate dips but then decreases as dips approach 90°. Flat events in image gathers in VTI media, however, do not guarantee the correct depth scale of the model because reflector depth depends on the vertical migration velocity. For factorized v(x, z) media with a linear velocity variation in both the x‐ and z‐directions, the moveout on image gathers is controlled by Vnmo (x = z = 0), kz, η, and a combination of the horizontal velocity gradient kx and the Thomsen parameter δ (specifically, kx[Formula: see text]). If too large a value of any of these four quantities is used in migration, reflections in the image gathers curve downward (i.e., they are undercorrected; the inferred depth increases with offset), while a negative error results in overcorrection. Lateral heterogeneity tends to increase the sensitivity of moveout of events in image gathers to the parameter η, and errors in η may lead to measurable residual moveout of horizontal events in v(x, z) media even for offset‐to‐depth ratios close to unity. These results provide a basis for extending to VTI media conventional velocity analysis methods operating with image gathers. Although P‐wave traveltimes alone cannot be used to separate anisotropy from lateral heterogeneity (i.e., kx is coupled to δ), moveout of events in image gathers does constrain the vertical gradient kz. Hence, it may be possible to build VTI velocity models in depth by supplementing reflection data with minimal a priori information, such as the vertical velocity at the top of the factorized VTI layer.
Geometrical spreading in a layered transversely isotropic medium with vertical symmetry axis
Authors: Ursin Bjørn , Hokstad Ketil 
Published: November 2003

Compensation for geometrical spreading is important in prestack Kirchhoff migration and in amplitude versus offset/amplitude versus angle (AVO/AVA) analysis of seismic data. We present equations for the relative geometrical spreading of reflected and transmitted P‐ and S‐wave in horizontally layered transversely isotropic media with vertical symmetry axis (VTI). We show that relatively simple expressions are obtained when the geometrical spreading is expressed in terms of group velocities. In weakly anisotropic media, we obtain simple expressions also in terms of phase velocities. Also, we derive analytical equations for geometrical spreading based on the nonhyperbolic traveltime formula of Tsvankin and Thomsen, such that the geometrical spreading can be expressed in terms of the parameters used in time processing of seismic data. Comparison with numerical ray tracing demonstrates that the weak anisotropy approximation to geometrical spreading is accurate for P‐waves. It is less accurate for SV‐waves, but has qualitatively the correct form. For P waves, the nonhyperbolic equation for geometrical spreading compares favorably with ray‐tracing results for offset‐depth ratios less than five. For SV‐waves, the analytical approximation is accurate only at small offsets, and breaks down at offset‐depth ratios less than unity. The numerical results are in agreement with the range of validity for the nonhyperbolic traveltime equations.
A general reconstruction scheme for dominant azimuth 3D seismic data
Authors: Schonewille M. A. , Romijn R. , Duijndam A. J. W. , Ongkiehong L. 
Published: November 2003

Seismic data are usually irregularly and sparsely sampled along the spatial coordinates, which yields suboptimal imaging results. For time‐lapse data, differences in the spatial sampling of base and monitor surveys lead to undesired differences between the images of the surveys that are not due to differences in the subsurface. In this paper, an efficient two‐step reconstruction method is proposed for irregularly and sparsely sampled 3D seismic data recorded with a dominant azimuth for large offsets. The first step is reconstruction along the receiver lines such that the midpoints are exactly on crosslines. The second step is a 2D reconstruction in the crossline midpoint‐offset domain using a least‐squares estimation of Fourier components. Sparse sampling can be handled by optimizing the parameterization of the least‐squares estimation of the Fourier coefficients, and consequently it is possible to reconstruct data that would be aliased when considering single common‐midpoint gathers. The method can be used to do a geometry transformation of the data to any desired spatial grid. Since the method yields consistent results independent of the actual sampling, it is very well suited for 4D processing.
Photoperiodic effects on body mass, energy balance and hypothalamic gene expression in the bank vole
Authors: Peacock W. L. , Król E. , Moar K. M. , McLaren J. S. , Mercer J. G. , Speakman J. R. 
Published: November 2003

SUMMARY
We examined the effect of increasing photoperiod, at a constant low temperature, on the body mass and energy budget of the bank vole Clethrionomys glareolus. Simultaneously, we determined the hypothalamic gene expression of neuropeptides and receptors known to be involved in short-term energy balance. Despite an increase in body mass(approximately 10% of initial mass), we found no significant changes in any energetic parameters (food intake, energy assimilation rate, resting metabolic rate and total daily energy expenditure by doubly-labelled water). Apparent energy assimilation efficiency was higher in voles exposed to long-days (LD)compared to short-days (SD). Surprisingly, gene expression of corticotrophin releasing factor (CRF; in the paraventricular nucleus), and the melanocortin-3 receptor (in the arcuate nucleus), both known to be involved in appetite suppression and elevation of energy expenditure in short-term energy balance,were higher in voles kept in LD compared to SD. CRF expression was also elevated in females compared to males. These paradoxical data suggest an alternative mechanism for the control of seasonal body mass changes compared to short-term body mass changes, and between male and female voles. Furthermore, they highlight the need for studies to perform simultaneous measurements at both the molecular and whole animal levels.
The low-affinity glucocorticoid receptor regulates feeding and lipid breakdown in the migratory Gambel's white-crowned sparrowZonotrichia leucophrys gambelii
Authors: Landys Mėta M. , Ramenofsky Marilyn , Guglielmo Christopher G. , Wingfield John C. 
Published: November 2003

SUMMARYPlasma corticosterone increases during spring migration in a variety of bird species, including the Gambel's white-crowned sparrow Zonotrichia leucophrys gambelii. Corticosterone is elevated specifically in association with migratory flight, suggesting that corticosterone may promote processes such as energy mobilization and/or migratory activity. General effects of glucocorticoids support such a prediction. Because glucocorticoids exert permissive effects on food intake, corticosterone may also participate in the regulation of migratory hyperphagia. To examine the role of corticosterone during migration, we induced Gambel's white-crowned sparrows to enter the migratory condition and compared food intake and locomotor activity between controls and birds injected with RU486 - an antagonist to the low-affinity glucocorticoid receptor (GR). In addition, we investigated effects of RU486 in birds that were subjected to a short-term fast. Results indicate that RU486 did not affect locomotor activity. However, consistent with its effects in mammals, RU486 suppressed food intake. Thus, hyperphagia and migratory restlessness, the two behaviors that characterize migration, may be regulated by different mechanisms. Lastly, RU486 antagonized fasting-induced lipid mobilization, as evidenced by decreased plasma free fatty acids. Thus, data on spring migrants suggest that endogenous corticosterone levels act through the GR to support hyperphagia and that the GR promotes availability of lipid fuel substrates in association with periods of energetic demand, e.g. during migratory flight.
Parameteridentifikation für ereignisdiskrete Systeme (Parameter Identification for Discrete Event Systems)
Authors: Schullerus G. , Krebs V. 
Published: November 2003

Abstract
Der vorliegende Beitrag befasst sich mit der experimentellen Modellbildung für zeitbewertete ereignisdiskrete Systeme und stellt ein Verfahren zur Identifikation solcher Systeme vor. Ausgangspunkt ist die Darstellung der Dynamik der Ereigniszeitpunkte eines Synchronisationsgraphen mit Hilfe der Max-Plus-Algebra in einer der Zustandsraumdarstellung zeitdiskreter Systeme strukturell ähnlichen Form. Auf der Grundlage dieser Struktur erfolgt eine Schätzung der Zeitbewertungen, so dass ein Gleichungsfehler minimiert wird. Der Beitrag befasst sich zudem mit dem Entwurf geeigneter Anregungssignale, die eine exakte Bestimmung der Systemparameter ermöglichen.
DFG-Schwerpunktprogramm "Sicherheit in der Informations- und Kommunikationstechnik" (Priority Program "Security in the Information and Communication Technology")
Authors: Wohlgemuth S. , Gerd tom Markotten Daniela , Jendricke Uwe , Müller Gordon 
Published: November 2003

Zusammenfassung
Das Schwerpunktprogramm "Sicherheit in der Informations- und Kommunikationstechnik" wird seit Ende 1999 für die Dauer von sechs Jahren von der Deutschen Forschungsgemeinschaft gefördert. In diesem Schwerpunktprogramm forschen zwölf Universitäten und Forschungseinrichtungen an der Konzeption und der praktischen Entwicklung von Sicherheitsmechanismen und deren Integration zu einem sicheren Gesamtsystem für heutige und zukünftige Szenarien. Dieser Artikel stellt das Referenzszenario, die Projekte sowie ihren Beitrag zum sicheren Gesamtsystem des Schwerpunktprogramms vor.
Extended bond-valence model as a tool for designing topology of inorganic crystal structures
Authors: Urusov Vadim S. 
Published: November 2003

Abstract
The simple rules, based on the bond-valence matching and coordination numbers balance, are extended to minimum-size polyhedral cluster in order to describe all probable bonding topologies for a given inorganic substance. This approach, referred to as the Extended Bond-Valence Model (EBVM), allows one to construct the corresponding connectivity matrices and then to calculate predicted bond valences and bond lengths. The subsequent estimates of individual and average bond distortion indices make it possible to select most probable bonding geometry and compare it with experimental data, whenever feasible. The EBVM approach is applied to predict the bonding topologies of Al2SiO5 polymorphs and hypothetical structures for all allowable coordination environments of cations and anions.
Domain structure and refinement of the triclinic superstructure of 1T-TaSe2 by single crystal X-ray diffraction
Authors: Wiegers G. A. , de Boer J. L. , Meetsma A. , van Smaalen S. 
Published: November 2003

Abstract
The 131/2
a
0 x 131/2
a
0 superstructure of 1T-TaSe2 at room temperature has been studied by singel-crystal X-ray diffraction. The basic structure has symmetry P3̅m1 with a
0 = 3.4733 Å and c
0 = 6.2715 Å. The superstructure has a pseudo hexagonal lattice, but it is triclinic with a 169-fold, 131/2
a
0 x 131/2
a
0 x 13c
0 hexagonal supercell with 13 centering vectors. Structure refinements have been performed using space group P1̅ and the primitive unit cell with a basal plane 131/2
a
0 x 131/2
a
0 supercell, and with C = 2a
0 + c
0. Refinements converged to R
F = 0.086 for 2327 observed reflections. Hexagram shaped clusters of 13 Ta atoms are the principle feature of this 13-fold superstructure, in accordance with the study of Brouwer and Jellinek (Physica B 99 (1980) 51). In the present refinement, significant deviations are found from local 6/m symmetry as it was assumed by Brouwer and Jellinek. The relative phase of the superstructure on neighbouring layers represents the most favourable packing of the buckled planes of Se atoms, and elastic coupling between Se atoms of consecutive layers is identified as the driving force for the observed inter-layer shift vector 2a
0. The small deviations from trigonal symmetry of the clusters are responsible for the observation of an ordered superstructure, as it is opposed to a stacking of layers according a random selection of shift vectors (2a
0, 2a
0 + b
0, and -a
0 - 3b
0) that are equivalent by the trigonal symmetry of the basic structure.
Adsorption of 1,10-Phenanthroline and Sodium Naphthalene 2-Sulfonate onto Activated Charcoal from Mixed Solutions
Authors: de Bussetti Silvia G. , Ferreiro Eladio A. 
Published: November 2003

Abstract
The adsorption (pH = 10) of single solution and binary mixtures of 1,10-phenanthroline (OP) and sodium naphthalene 2-sulfonate (SNS) on activated charcoal was studied. The maximum values for single solution adsorption were 1.811 mmol/g and 0.611 mmol/g for OP and SNS, respectively. Taking into account the total surface area of each molecule and the total maximum area of coverage on the charcoal, a specific area of 899.7 m2/g was determined for OP and 231.8 m2/g for SNS, indicating that orthophenanthroline molecules have a higher affinity for charcoal and that SNS adsorption occurs at specific sites. The results with binary mixtures show that OP hinders SNS adsorption, probably due to a steric impediment, and that adsorption of OP itself is independent of SNS, reaching comparable levels to the single solution. Using a competitive adsorption model it was shown that the two molecules do not compete for charcoal surface area. Application of the Langmuir two-surface adsorption model to the single solutions and binary mixtures indicates the existence of specific sites on charcoal with affinity for OP and SNS, respectively. In the case of the binary mixtures it was shown that the sum of the individual maximum quantities of adsorbed molecules lies within the same order of magnitude as the value determined by applying the Langmuir equation to each one individually.
The influence of soil heterogeneity on exploratory tunnelling by the subterranean termite Coptotermes frenchi (Isoptera: Rhinotermitidae)
Authors: Evans T.A. 
Published: November 2003

AbstractThe exploration of sand-filled arenas by workers of an entire colony of the Australian, subterranean foraging, tree-nesting termite, Coptotermes frenchi Hill was investigated under laboratory conditions. The first experiment tested whether termite exploration of sand was influenced by the presence of gaps or objects in the sand. Gaps and objects were chosen to represent soil heterogeneity in the urban environment: gaps to represent tunnels dug by other animals, perspex strips to represent cables and pipes, and wood strips to represent roots. Termites always chose to explore gaps thoroughly before they began tunnelling in the sand. Significantly more and longer tunnels were excavated from the end of gaps at the far end of the arenas, and relatively little tunnelling occurred around and along objects. Termite density was significantly greater around and along wood compared with perspex blocks. The second experiment tested whether termite exploratory tunnelling was influenced by soil moisture. The termites tunnelled slowly in dry sand, but after discovering a patch of wet sand, increased tunnelling five-fold until it was completely explored, after which activity declined. Energy and water conservation may be behind these patterns of exploratory tunnelling as well as those seen in large field studies, but caution is urged when interpreting small scale laboratory experiments to explain large scale field data.
Termite colony ontogeny: a long-term assessment of reproductive lifespan, caste ratios and colony size in Reticulitermes flavipes (Isoptera: Rhinotermitidae)
Authors: Long C.E. , Thorne B.L. , Breisch N.L. 
Published: November 2003

AbstractThirty Reticulitermes flavipes (Kollar) colonies established by alates collected from two separate field sites were raised in the laboratory for eight years. Twenty-one of the colonies were founded by alates from one field source and nine from another, providing demographic data from two unrelated parental lineages. Colony totals ranged from 3620 to 11641 individuals, with no significant difference in size between lineages. Soldier caste proportion of the colony total and mean wet weights for workers, soldiers and kings were significantly different between the two lineages. This suggests that at least a portion of the variability observed in caste ratios and body size may be heritable. One founding reproductive had died in five of the colonies (17%); none lost both parents. The queenless colonies contained exclusively female replacement reproductives (neotenics); the kingless colony contained a female-skewed mixture of male and female neotenics. All the nests that lost a founding parent contained significantly more pre-alate nymphs than the nests with both a king and a queen. Comparisons with published reports of ontogenetic patterns in other termites and social insects are discussed.
Naltrexone in the treatment of male alcoholics—an effectiveness study in Singapore
Authors: LEE ARTHUR , TAN SHAWN , LIM DOMINIC , WINSLOW R. M. , WONG K. E. , ALLEN JOHN , HALL WAYNE , PARKER GORDON 
Published: November 2003

AbstractNaltrexone has been demonstrated in western studies to be a useful pharmacological adjunct within treatment programmes for alcoholic patients. We report the first study of its efficacy and usefulness in an Asian region. This project was designed to allow naltrexone's performance to be assessed under routine clinical conditions but with patients selected on the basis of their being likely to comply. Following in‐patient detoxification, 53 male alcohol‐dependent patients admitted to the Alcohol Treatment Centre at Woodbridge Hospital, Singapore, were enrolled in a 12‐week, placebo‐controlled trial of naltrexone hydrochloride (50 mg/day). Subjects were randomized on a 2:1 basis, with 35 receiving naltrexone and 18 receiving placebo. Analyses identified that a higher percentage of naltrexone patients completed the study (40% vs. 22%). In the study non‐completers, the dropout rate due to drinking relapse was also lower in the naltrexone group (9% vs. 43%). Of the 39 patients for whom drinking status over the trial could be ascertained, fewer naltrexone‐treated patients drank (33% vs. 53%). Alcohol craving scores also showed a selective and distinct reduction in the naltrexone‐treated group. Results suggest that naltrexone may be an effective and safe aid to treatment of alcohol dependent patients in Asian patients, for whom the aims are to reduce alcohol craving and drinking reinstatement, but where compliance is likely to be low.