bluuebunny/crossref_metadata_2025 huggingface dataset:
A dose–response test via closed‐form solutions for constrained MLEs in survival/sacrifice experiments
Authors: Kim Wonkuk , Ahn Hongshik , Moon Hojin
Published: April 2006

In most survival–sacrifice experiments in animal carcinogenicity studies, the onset of the tumour of interest is not clinically observable. Due to the complexity of constraints for a biological justification, recently developed methods for estimating the tumour onset function and tumour‐specific survival function employ computer‐intensive numerical solutions. In this paper, closed‐form solutions for nonparametric maximum likelihood estimators are derived under explicit and implicit inequality constraints obtained from the monotonicity of the survival functions. Our methods do not require cause‐of‐death information. The proposed methods can be used to estimate the tumour onset function and the survival function of the tumour of interest. We use the proposed estimators for the development of our new dose–response trend test. A modification of the Poly‐k test is made by replacing the time‐ at‐risk weight to a function of the tumour onset survival function. The weighted least square regression method is applied to the estimated survival functions in order to construct a dose–response trend test. A simulation study is conducted to evaluate the performance of the proposed test and compare it with existing trend tests. A real example is used to illustrate the methods. Copyright © 2006 John Wiley & Sons, Ltd.
Integrated development and maintenance for the release, delivery, deployment, and customization of product software: a case study in mass‐market ERP software
Authors: Jansen Slinger , Ballintijn Gerco , Brinkkemper Sjaak , van Nieuwland Arco
Published: April 2006

The maintenance of enterprise application software at a customer site is a complex task for software vendors. This complexity results in a significant amount of work and risk. This article presents a case study of a product software vendor that tries to reduce this complexity by integrating product data management (PDM), software configuration management (SCM), and customer relationship management (CRM) into one system. The case study shows that by combining these management areas in a single software knowledge base, software maintenance processes can be automated and improved, thereby enabling a software vendor of enterprise resource planning software to serve a large number of customers with many different product configurations. Copyright © 2006 John Wiley & Sons, Ltd.
Learning from the Great Council of Revision Debate
Authors: Anderson Jeffrey H.
Published: April 2006

Should judges play a prominent policymaking role through their exercise of judicial review, or should judicial review be exercised to strike down only those acts that clearly violate the Constitution's text or historical context? Prevailing scholarship maintains that the Constitutional Convention debates provide little relevant guidance with which to answer this question. The truth is essentially the opposite: the Convention delegates extensively considered the role that judges should play in policymaking, particularly during their debate over a proposed council of revision. This essay revisits the council of revision debate. It argues that beneath the delegates' clear disagreements lies an apparent consensus, one heretofore largely unrecognized: that whether or not judges should have been invited to play the policymaking role they would have played as members of a council of revision, they should not play a policymaking role while serving on the judicial bench.
Friendship and Community in Plato's Lysis
Authors: Nichols Mary P.
Published: April 2006

Plato's Lysis addresses the problem of Plato's Republic—the tension between individual and communal good—by exploring the question of what or who is the friend. Friends, I argue, experience another as their own, and themselves as not wholly their own. Unlike the guardians of Plato's Republic, friends say both mine and not mine of one another. Grounded in both self-awareness and belonging, friendship serves as a model for philosophy, and demonstrates the possibility of associations that support our complex identity as human beings and citizens.
The Compassion of Zarathustra: Nietzsche on Sympathy and Strength
Authors: Frazer Michael L.
Published: April 2006

Contemporary theorists critical of the current vogue for compassion might like to turn to Friedrich Nietzsche as an obvious ally in their opposition to the sentiment. Yet this essay argues that Nietzsche's critique of compassion is not entirely critical, and that the endorsement of one's sympathetic feelings is actually a natural outgrowth of Nietzsche's immoralist ethics. Nietzsche understands the tendency to share in the suffering of their inferiors as a distinctive vulnerability of the spiritually strong and healthy. Their compassion, however, is an essential element of the imaginative creativity that Nietzsche holds to be the goal of human existence. Although shared suffering may prove debilitating for some, great individuals must come to affirm their compassion as necessary in achieving accurate knowledge of the human condition.
The Lawyer and the Layman: Two Perspectives on the Rule of Law
Authors: Murphy James Bernard
Published: April 2006

Philosophers and lawyers have long argued about the relation of law to politics: “does the king make law” or “does law make the king”? This persistent debate stems from two different perspectives on the nature of law. Professors of law have long noted that laypersons tend to speak of “a law” and the “laws” while lawyers tend to speak more holistically of “the law.” After discussing how rival perspectives in legal theory can be compared and evaluated, several dimensions of this contrast between the lay and the lawyerly conceptions of law: the individuation of laws, the sources of law, the ethical and imperative aspects of law, and the nature of the rule of law are analyzed. The distinction between a lawyerly and a lay perspective on law is reflected in the traditional linguistic and conceptual distinction between ius and lex. Many of the classic philosophers of law, from Plato to Hobbes, are rank laymen when it comes to their descriptions of law since the lawyerly understanding of law has only very recently achieved philosophical articulation.
Explanation Through Network Visualization
Authors: Brandes Ulrik , Kenis Patrick , Raab Jörg
Published: April 2006

Assessments of configurations, dynamics, and cause and effect are at the heart of our thinking and explanation. Although numerous methods for such assessments have been developed and are being used in daily scientific practice, visualization is usually not considered to be one of them. In this article we first argue that this is due to the common practice of visualizing data rather than the information contained in it; second, we address a number of principles for effective visualization; and third, we assess visualizations generated by the software tool visone in order to explain network outcomes using these principles.
Positional Estimation Within a Latent Space Model for Networks
Authors: Shortreed Susan , Handcock Mark S. , Hoff Peter
Published: April 2006

Recent advances in latent space and related random effects models hold much promise for representing network data. The inherent dependency between ties in a network makes modeling data of this type difficult. In this article we consider a recently developed latent space model that is particularly appropriate for the visualization of networks. We suggest a new estimator of the latent positions and perform two network analyses, comparing four alternative estimators. We demonstrate a method of checking the validity of the positional estimates. These estimators are implemented via a package in the freeware statistical language R. The package allows researchers to efficiently fit the latent space model to data and to visualize the results.
The Multilevel p2 Model
Authors: Zijlstra Bonne J. H. , van Duijn Marijtje A. J. , Snijders Tom A. B.
Published: April 2006

The p2model is a random effects model with covariates for the analysis of binary directed social network data coming from a single observation of a social network. Here, a multilevel variant of the p2model is proposed for the case of multiple observations of social networks, for example, in a sample of schools. The multilevel p2model defines an identical p2model for each independent observation of the social network, where parameters are allowed to vary across the multiple networks. The multilevel p2model is estimated with a Bayesian Markov Chain Monte Carlo (MCMC) algorithm that was implemented in free software for the statistical analysis of complete social network data, called StOCNET. The new model is illustrated with a study on the received practical support by Dutch high school pupils of different ethnic backgrounds.
Interplate coupling beneath NE Japan inferred from three‐dimensional displacement field
Authors: Suwa Yoko , Miura Satoshi , Hasegawa Akira , Sato Toshiya , Tachibana Kenji
Published: April 2006

The northeastern Japan arc is located in a typical subduction zone and is a seismically active region where large interplate earthquakes have occurred repeatedly. The nationwide GPS network has made it possible to investigate the crustal deformation in unprecedented detail; however, vertical displacements are less accurate than the horizontal ones and have not been used to constrain interplate coupling models. In this study, GPS carrier phase data are analyzed in order to estimate three components of site displacements. The result indicates uplift along the Japan Sea coast and subsidence along the Pacific Ocean coast. Using the vertical site velocities together with the horizontal ones as the data for a geodetic inversion method, a new model of interplate coupling is constructed to explain both the horizontal and vertical velocities for the interseismic period from 1997 to 2001. The model demonstrates strong coupling in the area off Miyagi and in the area off Aomori through the area off Tokachi, including the areas of asperities. The downdip limit of the locked fault zone on the plate boundary has been estimated seismologically to be at a depth of 50–60 km in northeastern Japan, and the distribution of slip deficits derived in this study indicates that the transition zone extends down to a depth of about 100 km.
Hydrogeologic responses to three‐dimensional temperature variability, Costa Rica subduction margin
Authors: Spinelli Glenn A. , Saffer Demian M. , Underwood Michael B.
Published: April 2006

Seaward of the subduction zone off Nicoya Peninsula, Costa Rica, differences in the thermal state of the ocean crust occur across a transition between crust generated at the Cocos‐Nazca Spreading Center and crust formed at the East Pacific Rise. This change in the thermal state of the subducting plate results in along‐strike differences in subduction zone temperature. These temperature variations are significant because they modulate diagenetic reaction progress and hydraulic conductivity. A numerical simulation of fluid production from opal‐to‐quartz and smectite‐to‐illite diagenesis displays an offset along strike due to the different temperatures of subduction inputs. Additionally, fluid viscosity is lower on the warm side of the margin than on the cool side. As a result, for the same permeability, hydraulic conductivity within the first 30 km from the trench is 1.25–2.0 times greater on the warm side of the margin than on the cool side. Spatial differences in hydraulic conductivity and sources of fluid likely combine to drive some flow along strike. A coupled model of fluid flow and solute transport indicates that for margin‐wedge permeability <10−19 m2, décollement permeability must be ≥10−14 m2 in order to drain fluid sources and maintain fluid pressures below lithostatic. A steady‐state model of chloride concentrations within the frontal décollement results in values higher (more saline) than those measured at Ocean Drilling Program Site 1040. One way to explain this discrepancy is for transient fluid flow to occur in a system with temporary enhancement of décollement permeability, thereby allowing transport to Site 1040 from deep zones of dehydration reactions. The onset of microseismicity on the plate boundary coincides with locations where modeled fluid overpressures dissipate in the décollement.
Daily, seasonal, and annual relationships between air and subsurface temperatures
Authors: Smerdon Jason E. , Pollack Henry N. , Cermak Vladimir , Enz John W. , Kresl Milan , Safanda Jan , Wehmiller John F.
Published: April 2006

Inversions of borehole temperature profiles that reconstruct past ground surface temperature (GST) changes have been used to estimate historical changes in surface air temperature (SAT). Paleoclimatic interpretations of GST reconstructions are based on the assumption that GST and SAT changes are closely coupled over decades, centuries, and longer. This assumption has been the subject of some debate because of known differences between GST and SAT at timescales of hours, days, seasons, and years. We investigate GST and SAT relationships on daily, seasonal, and annual timescales to identify and characterize the principal meteorological changes that lead to short‐term differences between GST and SAT and consider the effects of those differences on coupling between the two temperatures over much longer time periods. We use observational SAT and subsurface data from Fargo, North Dakota; Prague, Czech Republic; Cape Henlopen State Park, Delaware; and Cape Hatteras National Seashore, North Carolina. These records comprise intradaily observations that span parts of one or two decades. We compare subsurface temperature observations to calculations from a conductive subsurface model driven with daily SAT as the surface boundary condition and show that daily differences exist between observed and modeled subsurface temperatures. We also analyze year‐to‐year spectral decompositions of daily SAT and subsurface temperature time series and show that dissimilarities between mean annual GST and SAT are attributable to differences in annual amplitudes of the two temperature signals. The seasonal partitioning of these amplitude differences varies from year to year and from site to site, responding to variable evapotranspiration and cryogenic effects. Variable year‐to‐year differences between mean annual GST and SAT are closely estimated using results from a multivariate regression model that associates the partial influences of seasonal meteorological conditions with the attenuation of annual GST amplitudes.
Rain rate and attenuation statistics along paths in a tropical coastal area from radar data
Authors: Nzeukou Armand , Sauvageot Henri , Féral Laurent
Published: April 2006

A data set on rain rate distribution was collected by radar from a coastal site located at tropical latitude in West Africa where the rain field is strongly heterogeneous. It is used to compute rain rate (R) and microwave attenuation (A) statistics integrated along four paths located onshore, offshore, and perpendicularly to the coast, that is, north and south of the radar. These statistics are analyzed in order to see if coastal effects on rain fields induce significant differences between the conditions of microwave propagation along the four paths. R and A averaged along the paths are found to be mixed lognormal distributions with parameters μ and σ (mean and standard deviation, respectively) almost constant for the four paths, which shows that locally, the rain field is approximately ergodic. The probability of rain occurrence is found to be lower for the paths located offshore and north with respect to onshore and south. These differences are linked to the presence of positive gradients of rainfall occurrences between sea and land areas and between north and south areas. The magnitude of these differences is about 100%. The statistical variation coefficient, that is, CV = μ/σ, is found to be close to 2.24, a value observed in many other sites. For the attenuation, CV is found to be dependent on the exponential coefficient of the relation between the specific attenuation and the rain rate. For attenuation, the parameters of the probability density function are given for nine frequencies between 3 and 94 GHz.
Trends in aerosol nutrient solubility along a west–east transect of the Saharan dust plume
Authors: Baker A. R. , French M. , Linge K. L.
Published: April 2006

Simple leaching protocols have been used to examine trends in the solubility of aerosol nutrients (Fe, P and Si) along a west – east transect through the Saharan dust plume (German SOLAS cruise M55) and between Saharan and southern hemisphere‐origin aerosols. Solubilities were in the range 0.5–7.9% for Fe, 2.3–67% for P and 0.02–1.1% for Si, with lower values corresponding to samples of Saharan origin. Previous laboratory studies have suggested that aerosol Fe solubility might be enhanced by acid‐ and/or photo‐chemistry during transport through the atmosphere, but only the solubility of P was observed to be higher at the western end of the transect than the eastern. This implies that if (photo)chemical processing of aerosol Fe occurs in the atmosphere, significant enhancement of Fe solubility requires longer than the 5–10 days associated with transport of Saharan dust across the tropical Atlantic Ocean.
Changing electrical nature of Saturn's rings: Implications for spoke formation
Authors: Farrell W. M. , Desch M. D. , Kaiser M. L. , Kurth W. S. , Gurnett D. A.
Published: April 2006

During Cassini's orbit insertion at Saturn, the trajectory took the spacecraft overtop the planet's famed ring system. At this time, the Cassini Radio and Plasma Wave Science (RPWS) instrument obtained unprecedented observations of electron density in the vicinity of the rings. Using this information and a model of photoemission anticipated from the rings, we demonstrate that the ring surface potential undergoes a seasonal change in electrical configuration, being primarily unipolar (of one charge polarity/potential) during the Voyager era and now bipolar (two separate polarities/potentials) during the Cassini era. We calculate the approximate ring/sun opening angle required for the transition from unipolar to bipolar configuration. Using electron density profiles, we explicitly examine the conditions for current balance on the B ring and show which regions are most likely to charge to positive potentials and those that may remain negative as a function of ring opening angle relative to the sun. Finally, we demonstrate that the current body of observations of Saturn ring spokes is consistent with their formation only on negatively‐charged surfaces, and suggest future times and locations to look for spoke activity based upon the model.
Impact of increasing greenhouse gas concentrations in seasonal ensemble forecasts
Authors: Doblas‐Reyes F. J. , Hagedorn R. , Palmer T. N. , Morcrette J.‐J.
Published: April 2006

A set of 44‐year seasonal ensemble coupled model forecasts performed with annually updated greenhouse gas concentrations is compared to a standard seasonal ensemble forecast experiment performed with fixed concentrations. The former shows more realistic temperature variability and better forecast quality. The improvement in model variability is due to a better simulation of climate trends and suggests that realistic initial conditions are not enough to reproduce this long‐term variability. The better probabilistic forecast quality is mostly due to the increased ability to reliably discriminate the occurrence of events and non‐events. These results are relevant for the improvement of operational seasonal forecasts and provide new evidence of the effects of anthropogenic changes in atmospheric composition.
Wet phases in tropical southern Africa during the last glacial period
Authors: Garcin Yannick , Vincens Annie , Williamson David , Guiot Joël , Buchet Guillaume
Published: April 2006

A 45,000‐year high‐resolution sedimentary record from Lake Masoko in Tanzania shows the climate in this part of East Africa to have been characterized by a short and less severe dry season during the Last Glacial Maximum. Moisture and lake‐level proxies, pollen assemblages and magnetic susceptibility, indicate that rainfall in the Masoko area was strongly controlled by low‐latitude insolation (i.e., precessional forcing). Such observations contrast with the climatic patterns previously reconstructed in East Africa for the last glacial. Indeed, widespread dry conditions are generally observed and are attributed to the predominant control of high latitude glacial forcing over insolation forcing on the tropical hydrology. However, during the Younger Dryas cold event, out of phase with regional insolation behaviour, wetter conditions prevailed in this area, suggesting that the rainfall belt over Africa was probably shifted to the South, bringing moisture to the southernmost tropics.
Global Mapping Function (GMF): A new empirical mapping function based on numerical weather model data
Authors: Boehm J. , Niell A. , Tregoning P. , Schuh H.
Published: April 2006

Troposphere mapping functions are used in the analyses of Global Positioning System and Very Long Baseline Interferometry observations to map a priori zenith hydrostatic and wet delays to any elevation angle. Most analysts use the Niell Mapping Function (NMF) whose coefficients are determined from site coordinates and the day of year. Here we present the Global Mapping Function (GMF), based on data from the global ECMWF numerical weather model. The coefficients of the GMF were obtained from an expansion of the Vienna Mapping Function (VMF1) parameters into spherical harmonics on a global grid. Similar to NMF, the values of the coefficients require only the station coordinates and the day of year as input parameters. Compared to the 6‐hourly values of the VMF1 a slight degradation in short‐term precision occurs using the empirical GMF. However, the regional height biases and annual errors of NMF are significantly reduced with GMF.
Destruction of the tertiary ozone maximum during a solar proton event
Authors: Seppälä A. , Verronen P. T. , Sofieva V. F. , Tamminen J. , Kyrölä E. , Rodger C. J. , Clilverd M. A.
Published: April 2006

Ozone observations from the GOMOS instrument together with a coupled ion and neutral chemistry model are used to study the effects of the January 2005 solar storms on the polar winter middle atmosphere. The model results indicate strong HOx and NOx enhancements in the mesosphere, and simultaneous ozone depletion maximizing between 70–80 km. During strong proton forcing GOMOS measurements show the destruction of the tertiary ozone maximum, observed at polar latitudes near 72 km before the events. This altitude is concurrent with the largest HOx enhancements in the model results. We observe for the first time the disappearance of the tertiary ozone maximum, and determine the underlying cause. With subsiding proton forcing GOMOS measurements show the reappearance of the tertiary ozone maximum, returning to normal values by January 24. Our results indicate that even moderate solar events (>10 MeV proton flux of >5000 pfu) can cause significant ozone depletion (>70%) in the middle atmosphere.
Analyses of unusual long‐period earthquakes with extended coda recorded at Katmai National Park, Alaska, USA
Authors: De Angelis Silvio
Published: April 2006

A swarm of six long‐period (LP) events with slowly decaying coda wave amplitudes and durations up to 120 s, was recorded by seismic stations located in the proximity of Mt. Griggs, a fumarolically active volcano in the Katmai National Park, Alaska, during December 8–21, 2004. Spectral analyses reveal the quasi‐monochromatic character of the waveforms, dominated by a 2.5 Hz mode frequently accompanied by a weaker high‐frequency onset (6.0–9.0 Hz). Particle motion azimuths and inclination angles show a dominant WNW‐ESE direction of polarization for all the signals, and suggest that seismic energy is radiated by a stable source at shallow depth. Damping coefficients between 0.0014 and 0.0063 are estimated by fitting an exponential decay model to the signal's coda; corresponding quality factors range from 78 to 351. The source of the waveforms is modelled as a resonant cavity filled with a fluid/gas mixture.
Effects of threshold retrievals on estimates of the aerosol indirect radiative forcing
Authors: Matheson Mark A. , Coakley James A. , Tahnk William R.
Published: April 2006

Empirical estimates of the aerosol indirect radiative forcing often rely on threshold cloud retrievals applied to multispectral satellite imagery data. In such retrievals, pixels having radiances that surpass prescribed thresholds are assumed to be overcast even if they are only partially cloud covered. This assumption leads to cloud visible optical depths that are underestimated and droplet radii that are overestimated. As regional cloud cover increases, overcast pixels become more common and the biases in cloud properties decrease. Because aerosol optical depths derived from cloud‐free pixels also increase with regional cloud cover (Loeb and Manalo‐Smith, 2005), the biases in threshold‐derived cloud properties can be mistakenly interpreted as being evidence for the effects of aerosols on clouds. Because of the biases, threshold retrievals of cloud properties are likely to lead to overestimates of the aerosol indirect forcing. A retrieval scheme that accounts for fractional cloud cover within an imager pixel is used to estimate the enhancement in the indirect radiative forcing that arises from threshold cloud retrievals. The enhancements prove to be relatively small, approximately 20%. If cloud liquid water is held fixed to estimate the forcing, the biases in threshold‐derived droplet radii and in the sensitivity of droplet radii to changes in aerosol nearly cancel so that the estimates are almost the same for threshold and partly cloudy pixel retrievals.
An unusual mesospheric bore event observed at high latitudes over Antarctica
Authors: Nielsen K. , Taylor M. J. , Stockwell R. G. , Jarvis M. J.
Published: April 2006

All‐sky CCD observations of short‐period mesospheric gravity waves have been made from Halley Station, Antarctica (76°S, 27°W). On 27 May, 2001, an unusual wave event exhibiting several features characteristic of a “bore” was observed in the OH, Na, and O2 nightglow emissions. Mesospheric bores are rare wave events that have previously been observed at mid‐ and low‐latitudes. This event was particular interesting as: (1) it initially appeared as a single, high contrast, linear front, accompanied by a sharp enhancement in intensity in all three emissions, (2) a number of trailing wave crests were observed to form with a measured growth rate of 6.6 waves/hr, and (3) the wave pattern exhibited unusual dynamics with significant variability in the observed phase speed and a reduction in the horizontal wavelength by ∼50% over a 1‐hr period. The location of Halley and the observed propagation suggests a ducted wave consistent with current bore models.
In situ observation at L = 2.3–5 by the Akebono satellite of the plasmaspheric depletion during the September 1998 magnetic storm
Authors: Kawano H. , Chi P. J. , Kumamoto A. , Morioka A.
Published: April 2006

From ground‐based observations at L = 2.07 of the field line resonance (FLR) during an intense magnetic storm on 25 September 1998, Chi et al. (2000) estimated that the equatorial plasma density at L = 2.07 dropped to 25% of the prestorm value. Such depletion very close to the Earth is unusual. Two possible interpretations of the result are: (1) the plasmapause moved inward past L = 2.07, and (2) the plasmapause remained outside L = 2.07, but the density within the plasmasphere decreased. To distinguish between these possibilities, we examine in situ observations of the electron density made by the Akebono satellite at L = 2.3–5 on four passes during the same storm. The electron density measured by Akebono at a reference L shell of L ∼2.5 changed with time in a manner consistent with the FLR‐based estimates. On three of these passes, the plasmapause was located at L > 3, and if the plasmaspheric L profile of the Akebono density data is extrapolated inward, for each pass, its value at L = 2.07 matches the FLR‐based estimates. However, on the pass at 2323–2351 UT on 25 September that corresponded to the severe density decrease detected at L = 2.07, Akebono did not detect a plasmapause in the L range (>2.3) for which the electron density data were available. For the same pass, inward extrapolation of the density measured at L > 2.3 was a factor of ∼5 smaller than the FLR‐based estimate. This implies that there was a sharp density inward gradient (the plasmapause) at 2.07 < L < 2.3, supporting the second interpretation.
A fluid model with finite Larmor radius effects for mirror mode dynamics
Authors: Passot T. , Sulem P. L.
Published: April 2006

A fluid model retaining hydrodynamic nonlinearities together with a linear approximation of the Landau damping and of the finite Larmor radius effects is constructed to describe the dynamics of quasi‐transverse low‐frequency waves in a homogeneous magnetized plasma. It accurately reproduces the kinetic theory predictions for the mirror instability, including its quenching at small transverse scales. The dispersion relation of kinetic Alfvén waves is also recovered. This model should provide an efficient tool for numerical simulations of nonlinear mirror mode dynamics, at least near threshold.
Validation of the Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR‐E) sea surface temperature in the Southern Ocean
Authors: Dong Shenfu , Gille Sarah T. , Sprintall Janet , Gentemann Chelle
Published: April 2006

Satellite sea surface temperature (SST) measurements from Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR‐E) are compared with in situ temperature observations from high‐resolution expendable bathythermograph and hull‐mounted thermosalinograph data along two sections (south of Australia and Drake Passage) in the Southern Ocean. To eliminate the effects of diurnal warming and low wind speed, we use only AMSR‐E data collected within 5 hours of the in situ observations, with wind speeds exceeding 6 m s−1. The AMSR‐E measurements are warmer than in situ observations during summer and are colder than in situ observations during winter. Factors that may cause the temperature difference are examined, including wind speed, columnar water vapor, columnar cloud water, geographic location, local temperature, and time of observation. Of these, wind speed and columnar water vapor are found to be the major factors contributing to the temperature difference between AMSR‐E SST and in situ SST observations. The temperature difference decreases with increasing wind speed and water vapor. AMSR‐E and in situ SST observations are also compared with simultaneous Moderate Resolution Imaging Spectroradiometer (MODIS) SST and weekly Reynolds Optimum Interpolated (OI) SST. Results suggest that the OI SSTs have a warm bias for both summer and winter; MODIS SSTs indicate a cold bias. In contrast, AMSR‐E SSTs show little bias relative to expendable bathythermographs.
Interannual variability in northeast Pacific circulation
Authors: Douglass Elizabeth , Roemmich Dean , Stammer Detlef
Published: April 2006

Interannual variability of the circulation in the northeast Pacific Ocean is explored through a joint analysis of expendable bathythermograph (XBT) and expendable conductivity‐temperature‐depth (XCTD) data, satellite altimetry, and output from a model that was constrained by ocean data. XBT temperature profiles with high spatial resolution are available in the eastern North Pacific along two repeated transects. These ship tracks, along with the coast of North America, define a closed “box” which is used to study the time‐mean circulation and its variability on interannual timescales. Geostrophic velocities from XBT data are compared with geostrophic velocities from model output as well as the full model velocity fields. Correlations in variability on interannual timescales between transport in the subpolar gyre and in the subtropical gyre are present in both model output and data. The nature of the variability, and its relation to the changes of the strength of the North Pacific Current (NPC), which supplies the water for both gyres, are explored. Interannual variability in gyre transport is found to be related to both the bifurcation of the NPC, resulting in an anticorrelation in transport between the two gyres, and to variations in NPC strength, resulting in simultaneous changes in the two gyres. The dominant signal is found to be a long‐term increase in the NPC, which results in a strengthening of the subtropical gyre. Possible connections with local‐scale wind stress changes and with the El Niño/Southern Oscillation phenomenon are also explored.
Numerical sensitivity studies on the impact of aerosol properties and drop freezing modes on the glaciation, microphysics, and dynamics of clouds
Authors: Diehl K. , Simmel M. , Wurzler S.
Published: April 2006

Numerical simulations were performed to investigate the effects of drop freezing in immersion and contact modes for a convective situation. For the description of heterogeneous drop freezing, new approaches were used considering the significantly different ice nucleating efficiencies of various ice nuclei. An air parcel model with a sectional two‐dimensional description of the cloud microphysics was employed. Sensitivity studies were undertaken by varying the insoluble particle types as well as the soluble fraction of the aerosol particles showing the effects of these parameters on drop freezing and their possible impact on the vertical cloud dynamics. The soluble fraction ɛ decides whether immersion or contact freezing will be the major process. For high ɛ values, immersion freezing is the dominant process. In such cases the freezing process is strongly temperature‐dependent, and the ice nucleation efficiency of the insoluble particle types becomes important for efficient freezing. The freezing point depression can be neglected because of the preferential freezing of large drops. Contact freezing is the major process in cases of lower ɛ values. In these cases the freezing process is less dependent on temperature and aerosol particle type. For conditions of efficient freezing, cold, high‐altitude, completely glaciated clouds could form. The presented approaches for immersion and contact freezing can be incorporated further into mesoscale and global models to estimate the effects of specific ice nuclei on ice formation.
Internal variability and pattern identification in cirrus cloud structure: The Fokker‐Planck equation approach
Authors: Ivanova K. , Shirer H. N. , Clothiaux E. E.
Published: April 2006

Using 35‐GHz millimeter wave radar observations collected at the Southern Great Plains site of the Atmospheric Radiation Measurements (ARM) program, we study physical processes in cirrus cloud layers having different stratifications. The time‐dependent probability distribution functions of the backscattering cross section within different layers in the cloud describe the dynamics of the pertinent physical processes. The time‐dependent tails of the probability distribution functions provide the signature of intermittency characterizing turbulent flows. In the framework of the Fokker‐Planck equation approach, we derive the behavior of the drift D(1) and diffusion D(2) terms that characterize the deterministic and stochastic parts, respectively, of the dynamics of the probability distribution functions directly from the time series of observed backscattering cross section. We derive the Langevin equation that governs the temporal evolution of the backscattering cross‐section signal in cloud layers having different stratification. Finally, we ascertain that the drift γ and diffusion β coefficients of the backscattering cross‐section signal in the upper well‐mixed, neutrally stratified layer of the cirrus cloud satisfy the relationship γ = 2β, which is valid for fully developed turbulence owing to the Kolmogorov −4/5 law.
Emissions from the laboratory combustion of wildland fuels: Particle morphology and size
Authors: Chakrabarty Rajan K. , Moosmüller Hans , Garro Mark A. , Arnott W. Patrick , Walker John , Susott Ronald A. , Babbitt Ronald E. , Wold Cyle E. , Lincoln Emily N. , Hao Wei Min
Published: April 2006

The morphology of particles emitted by wildland fires contributes to their physical and chemical properties but is rarely determined. As part of a study at the USFS Fire Sciences Laboratory (FSL) investigating properties of particulate matter emitted by fires, we studied the size, morphology, and microstructure of particles emitted from the combustion of eight different wildland fuels (i.e., sagebrush, poplar wood, ponderosa pine wood, ponderosa pine needles, white pine needles, tundra cores, and two grasses) by scanning electron microscopy. Six of these fuels were dry, while two fuels, namely the tundra cores and one of the grasses, had high fuel moisture content. The particle images were analyzed for their density and textural fractal dimensions, their monomer and agglomerate number size distributions, and three different shape descriptors, namely aspect ratio, root form factor, and roundness. The particles were also probed with energy dispersive X‐ray spectroscopy confirming their carbonaceous nature. The density fractal dimension of the agglomerates was determined using two different techniques, one taking into account the three‐dimensional nature of the particles, yielding values between 1.67 and 1.83, the other taking into account only the two‐dimensional orientation, yielding values between 1.68 and 1.74. The textural fractal dimension that describes the roughness of the boundary of the two‐dimensional projection of the particle was between 1.10 and 1.19. The maximum length of agglomerates was proportional to a power a of their diameter and the proportionality constant and the three shape descriptors were parameterized as function of the exponent a.
Structure and dynamics of the summertime atmospheric boundary layer over the Antarctic Plateau: 2. Heat, moisture, and momentum budgets
Authors: van As Dirk , van den Broeke Michiel R.
Published: April 2006

This paper presents the summertime budgets of heat, moisture and momentum in the atmospheric boundary layer at Kohnen base (75°00′S, 0°04′E, 2892 m above sea level), located in the interior of East Antarctica. For this purpose we performed a model simulation for clear‐sky conditions and constant large‐scale forcing, using a high‐resolution one‐dimensional atmospheric model which has been validated by observations (see van As et al., 2006). Turbulent exchange is the dominant component in the heat budget, heating the daytime well‐mixed layer by a maximum of 1.0 K h−1. Radiative heating and cooling are important, and are largest near the surface and just above and below the large temperature and humidity gradients of the nighttime stable layer. Vertical heat advection, which is introduced by the wind speed component along the slope, is the smallest heat‐budget component in the atmospheric boundary layer, but becomes significant above it. The same is valid for vertical advection in the moisture budget, which is again dominated by turbulent exchange in the atmospheric boundary layer. The model generates solid precipitation (diamond dust) in the nighttime stable boundary layer. In the stable layer the temperature deficit with respect to the free atmosphere can be larger than 10 K, forcing a relatively large katabatic acceleration (up to 2.7 m s−1 h−1). Katabatic forcing is chiefly opposed by turbulent momentum transfer (friction). The katabatic forcing decreases with height but is nonzero above the atmospheric boundary layer. In the nighttime stable layer we find a jet which is chiefly forced by katabatics, and in the residual layer above it we find alternating wind maxima and minima as a result of an inertial oscillation.
Analysis of HF signal power observations on two North American circuits
Authors: McNamara Leo F. , Barton Richard J. , Bullett Terence W.
Published: April 2006

Observations of HF signal powers on two circuits in North America have been compared with the values predicted by two HF propagation programs, Voice of America Coverage Analysis Program (VOACAP) and Advanced Stand Alone Prediction System (ASAPS). Neither program consistently provided the more reliable predicted signal powers. For the longer circuit considered (2820 km WWV Fort Collins to Hanscom Air Force Base), ASAPS was found to be the more accurate program for the lower frequencies (at night), while VOACAP was the more accurate for the higher frequencies (during the day). The RMS errors ranged from a few decibels to 15 dB. For daytime 7.335 MHz propagation on the 490 km CHU Ottawa to Hanscom Air Force Base circuit, the VOACAP RMS errors (∼4 dB) were less than the ASAPS RMS errors (∼8 dB). The errors for the two programs were very similar for 3.330 MHz propagation, peaking at ∼9 dB just after sunrise and just before sunset and ∼3 dB during the night.
Exhumation of basement‐cored uplifts: Example of the Kyrgyz Range quantified with apatite fission track thermochronology
Authors: Sobel Edward R. , Oskin Michael , Burbank Douglas , Mikolaichuk Alexander
Published: April 2006

The Kyrgyz Range, the northernmost portion of the Kyrgyzstan Tien Shan, displays topographic evidence for lateral propagation of surface uplift and exhumation. The highest, most deeply dissected segment lies in the center of the range. To the east, topography and relief decrease, and preserved remnants of a Cretaceous regional erosion surface imply minimal amounts of bedrock exhumation. The timing of exhumation of range segments defines the lateral propagation rate of the range‐bounding reverse fault and quantifies the time and erosion depth needed to transform a mountain range from a juvenile to a mature morphology. New multicompositional apatite fission track (AFT) data from three transects from the eastern Kyrgyz Range, combined with published AFT data, demonstrate that the range has propagated over 110 km eastward over the last ∼7–11 Myr. On the basis of the thermal and topographic evolutionary history, we present a model for a time‐varying exhumation rate driven by rock uplift and changes in erodability and the timescale of geomorphic adjustment to surface uplift. Easily eroded, Cenozoic sedimentary rocks overlying resistant basement control early, rapid exhumation and exhibit slow surface uplift rates. As increasing amounts of resistant basement are exposed, exhumation rates decrease while surface uplift rates are sustained or increase, thereby growing topography. As the range becomes high enough to cause ice accumulation and to develop steep river valleys, fluvial and glacial erosion becomes more powerful, and exhumation rates once again increase. Independently determined range‐normal shortening rates also varied over time, suggesting a feedback between erosional efficiency and shortening rate.
Changes in MOC and gyre‐induced Atlantic Ocean heat transport
Authors: Drijfhout S. S. , Hazeleger W.
Published: April 2006

Anthropogenic change of the Atlantic meridional ocean heat transport (AOHT) is diagnosed from a large ensemble of climate simulations over the period 1940–2080, as well as its relation to changes in the Meridional Overturning Circulation (MOC) and the gyre circulation in the Atlantic. Internal variability in AOHT is closely associated with MOC variability. The anthropogenic change in AOHT, however, does not follow the forced decrease in the MOC. Thermohaline changes in the intermediate and deep water masses that are formed in the subpolar gyre cause the vertical temperature gradient near the western boundary to increase. As a result, the heat transport by the baroclinic gyre component largely compensates the decreased heat transport by the MOC.
Soft sticky dipole-quadrupole-octupole potential energy function for liquid water: An approximate moment expansion
Authors: Ichiye Toshiko , Tan Ming-Liang
Published: April 2006

A new, efficient potential energy function for liquid water is presented here. The new model, which is referred here as the soft sticky dipole-quadrupole-octupole (SSDQO) model, describes a water molecule as a Lennard-Jones sphere with point dipole, quadrupole, and octupole moments. It is a single-point model and resembles the hard-sphere sticky dipole potential model for water by Bratko et al. [J. Chem. Phys. 83, 6367 (1985)] and the soft sticky dipole model by Ichiye and Liu [J. Phys. Chem. 100, 2723 (1996)] except now the sticky potential consists of an approximate moment expansion for the dimer interaction potential, which is much faster than the true moment expansion. The object here is to demonstrate that the SSDQO potential energy function can accurately mimic the potential energy function of a multipoint model using the moments of that model. First, the SSDQO potential energy function using the dipole, quadruple, and octupole moments from SPC/E, TIP3P, or TIP5P is shown to reproduce the dimer potential energy functions of the respective multipoint model. In addition, in Monte Carlo simulations of the pure liquid at room temperature, SSDQO reproduces radial distribution functions of the respective model. However, the Monte Carlo simulations using the SSDQO model are about three times faster than those using the three-point models and the long-range interactions decay faster for SSDQO (1∕r3 and faster) than for multipoint models (1∕r). Moreover, the contribution of each moment to the energetics and other properties can be determined. Overall, the simplicity, efficiency, and accuracy of the SSDQO potential energy function make it potentially very useful for studies of aqueous solvation by computer simulations.
Surface-enhanced resonance Raman scattering and background light emission coupled with plasmon of single Ag nanoaggregates
Authors: Itoh Tamitake , Biju Vasudevanpillai , Ishikawa Mitsuru , Kikkawa Yasuo , Hashimoto Kazuhiro , Ikehata Akifumi , Ozaki Yukihiro
Published: April 2006

We investigated the optical properties of isolated single aggregates of Ag nanoparticles (Ag nanoaggregates) on which rhodamine 6G molecules were adsorbed to reveal experimentally a correlation among plasmon resonance Rayleigh scattering, surface-enhanced resonance Raman scattering (SERRS), and its background light emission. From the lack of excitation-laser energy dependence of background emission maxima we concluded that the background emission is luminescence, not Raman scattering. The polarization dependence of both SERRS and background emission was the same as that of the lowest-energy plasmon resonance maxima, which is associated with a longitudinal plasmon. From the common polarization dependence, we identified that the lowest-energy plasmon is coupled with both SERRS and background emission. In addition, we revealed that the lowest-energy plasmon with a higher quality factor (Q factor) yields larger SERRS and background emission intensity. Also, we identified that the Q factor dependence of the SERRS intensity was similar to that of the background emission intensity. This similarity directly supported us to demonstrate an enhancement of both SERRS and background emission by coupling with a common plasmon radiative mode.
Facilitated diffusion of DNA-binding proteins: Efficient simulation with the method of excess collisions
Authors: Merlitz Holger , Klenin Konstantin V. , Wu Chen-Xu , Langowski Jörg
Published: April 2006

In this paper, a new method to efficiently simulate diffusion controlled second order chemical reactions is derived and applied to site-specific DNA-binding proteins. The protein enters a spherical cell and propagates via two competing modes, a free diffusion and a DNA-sliding mode, to search for its specific binding site in the center of the cell. There is no need for a straightforward simulation of this process. Instead, an alternative and exact approach is shown to be essentially faster than explicit random walk simulations. The speed-up of this novel simulation technique is rapidly growing with system size.