bluuebunny/crossref_metadata_2025 huggingface dataset:
Generating unlabeled connected cubic planar graphs uniformly at random
Authors: Bodirsky Manuel , Gröpl Clemens , Kang Mihyun
Published: January 2008

We present an expected polynomial time algorithm to generate an unlabeled connected cubic planar graph uniformly at random. We first consider rooted connected cubic planar graphs, i.e., we count connected cubic planar graphs up to isomorphisms that fix a certain directed edge. Based on decompositions along the connectivity structure, we derive recurrence formulas for the exact number of rooted cubic planar graphs. This leads to rooted 3‐connected cubic planar graphs, which have a unique embedding on the sphere. Special care has to be taken for rooted graphs that have a sense‐reversing automorphism. Therefore we introduce the concept of colored networks, which stand in bijective correspondence to rooted 3‐connected cubic planar graphs with given symmetries. Colored networks can again be decomposed along the connectivity structure. For rooted 3‐connected cubic planar graphs embedded in the plane, we switch to the dual and count rooted triangulations. Since all these numbers can be evaluated in polynomial time using dynamic programming, rooted connected cubic planar graphs can be generated uniformly at random in polynomial time by inverting the decomposition along the connectivity structure. To generate connected cubic planar graphs without a root uniformly at random, we apply rejection sampling and obtain an expected polynomial time algorithm. © 2008 Wiley Periodicals, Inc. Random Struct. Alg., 2008
Harmonium Models for Video Classification
Authors: Yang Jun , Yan Rong , Liu Yan , Xing Eric P.
Published: January 2008

Accurate and efficient video classification demands the fusion of multimodal information and the use of intermediate representations. Combining the two ideas into one framework, we propose a series of probabilistic models for video representation and classification using intermediate semantic representations derived from multimodal features of video. On the basis of a class of bipartite undirected graphical models named harmonium, we propose dual‐wing harmonium (DWH) model that represents video shots as latent semantic topics derived by jointly modeling the transcript keywords and color‐histogram features of the data. Our family‐of‐harmonium (FoH) and hierarchical harmonium (HH) model extends DWH by introducing variables representing category labels of data, which allows data representation and classification to be performed in the same model. Our models are among the few attempts of using undirected graphical models for representing and classifying video data. Experiments on a benchmark video collection show different semantic interpretations of video data under our models, as well as superior classification performance in comparison with several directed models. Copyright © 2008 Wiley Periodicals, Inc., A Wiley Company Statistical Analy Data Mining 1: 000‐000, 2008
Energy loss spectra of iron
Authors: Novák M. , Bereczky R. J. , Zhang Z. M. , Ding Z. J. , Tóth J. , Varga D. , Tökési K.
Published: January 2008

We present experimental and theoretical studies of the spectra of electrons backscattered from iron. The single surface and bulk excitation ratio in the energy range between 500 and 4000 eV are calculated. The contribution of single inelastically scattered electrons is derived from a dielectric response theory and from the experimental reflected electron energy spectra using different algorithms. We present surface excitation parameters in comparison with previous results as a function of the primary energy. Moreover, we show that our Monte Carlo simulations, using the corrected surface excitation parameters obtained experimentally, describe the reflected electron energy loss spectra in the investigated energy range reasonably well. Copyright © 2008 John Wiley & Sons, Ltd.
Sample size calculation for the weighted rank statistics with paired survival data
Authors: Jung Sin‐Ho
Published: January 2008

This paper introduces a sample size calculation method for the weighted rank test statistics with paired two‐sample survival data. Our sample size formula requires specification of joint survival and censoring distributions. For modelling the distribution of paired survival variables, we may use a paired exponential survival distribution that is specified by the marginal hazard rates and a measure of dependency. Also, in most trials randomizing paired subjects, the subjects of each pair are accrued and censored at the same time over an accrual period and an additional follow‐up period, so that the paired subjects have a common censoring time. Under these practical settings, the design parameters include type I and type II error probabilities, marginal hazard rates under the alternative hypothesis, correlation coefficient, accrual period (or accrual rate) and follow‐up period. If pilot data are available, we may estimate the survival distributions from them, but we specify the censoring distribution based on the specified accrual trend and the follow‐up period planned for the new study. Through simulations, the formula is shown to provide accurate sample sizes under practical settings. Real studies are taken to demonstrate the proposed method. Copyright © 2008 John Wiley & Sons, Ltd.
Signatures of Clustering in Superparamagnetic Colloidal Nanocomposites of an Inorganic and Hybrid Nature
Authors: Rebolledo Aldo F. , Fuertes Antonio B. , Gonzalez‐Carreño Teresita , Sevilla Marta , Valdes‐Solis Teresa , Tartaj Pedro
Published: January 2008

The individual and co‐operative properties of inorganic and hybrid superparamagnetic colloidal nanocomposites that satisfy all the requirements of magnetic carriers in the biosciences and/or catalysis fields are been studied. Essential to the success of this study is the selection of suitable synthetic routes (aerosol and nanocasting) that allow the preparation of materials with different matrix characteristics (carbon, silica, and polymers with controlled porosity). These materials present magnetic properties that depend on the average particle size and the degree of polydispersity. Finally, the analysis of the co‐operative behavior of samples allows for the detection of signatures of clustering, which are closely related to the textural characteristics of samples and the methodology used to produce the magnetic carriers.
Carbon Nanotubes with High Bone‐Tissue Compatibility and Bone‐Formation Acceleration Effects
Authors: Usui Yuki , Aoki Kaoru , Narita Nobuyo , Murakami Narumichi , Nakamura Isao , Nakamura Koichi , Ishigaki Norio , Yamazaki Hiroshi , Horiuchi Hiroshi , Kato Hiroyuki , Taruta Seiichi , Kim Yoong Ahm , Endo Morinobu , Saito Naoto
Published: January 2008

Carbon nanotubes (CNTs) have been used in various fields as composites with other substances or alone to develop highly functional materials. CNTs hold great interest with respect to biomaterials, particularly those to be positioned in contact with bone such as prostheses for arthroplasty, plates or screws for fracture fixation, drug delivery systems, and scaffolding for bone regeneration. Accordingly, bone‐tissue compatibility of CNTs and CNT influence on bone formation are important issues, but the effects of CNTs on bone have not been delineated. Here, it is found that multi‐walled CNTs adjoining bone induce little local inflammatory reaction, show high bone‐tissue compatibility, permit bone repair, become integrated into new bone, and accelerate bone formation stimulated by recombinant human bone morphogenetic protein‐2 (rhBMP‐2). This study provides an initial investigational basis for CNTs in biomaterials that are used adjacent to bone, including uses to promote bone regeneration. These findings should encourage development of clinical treatment modalities involving CNTs.
Linking Proteins with Anionic Nanoparticles via Protamine: Ultrasmall Protein‐Coupled Probes for Magnetic Resonance Imaging of Apoptosis
Authors: Schellenberger Eyk , Schnorr Jörg , Reutelingsperger Chris , Ungethüm Liset , Meyer Wolfdietrich , Taupitz Matthias , Hamm Bernd
Published: January 2008

Magnetic resonance imaging (MRI) of a target in vivo depends on the surface, size, and particle relaxivity of the target‐specific nanoparticles for MRI. Here a new method for decorating very small iron oxide particles (VSOPs) with target‐specific ligands is described. The method is based on the electrostatic attraction of the strongly positively charged peptide protamine to the anionic citrate shell of the electrostatically stabilized VSOPs. The protamine coat allows linkage chemistry and chimera technology to functionalize VSOPs or other negative charged surfaces with biologics. Annexin A5 (anxA5)–VSOP utilizing thiol chemistry was generated to couple biologically active anxA5 to VSOPs for in vivo MRI of apoptosis. Annexin A5–VSOP comprises five anxA5 molecules per iron oxide nanoparticle with a high R2 particle relaxivity of 180 000 mM−1 s−1 yet small hydrodynamic diameter of only 14.7±2.9 nm beneficial for in vivo MRI of extravascular targets.
Emergency Surgery of the Abdominal Aorta in a Porcine Model: Two Sequential Experiments
Authors: Lozano Francisco S. , Rodríguez José M. , García‐Criado Francisco J. , Gonzalez‐Porras Jose R. , Sanchez‐Guijo Fermin M. , Sanchez‐Conde Pilar , García‐Sanchez Jose E.
Published: January 2008

The aim of this study was to design an aggressive nonlethal animal model that would simulate surgical treatment of the abdominal aorta with a view to studying the systemic inflammatory response. Fourteen pigs were subjected to two sequential experiments. Experiment A was performed to determine the response to two degrees of hemorrhage: (A1) 40% bleeding; and (A2) 60% bleeding over 15 minutes followed by midline laparotomy and aortic dissection. Experiment B included two methods of aortic repair: (B1) aortic resection and replacement with a prosthesis; and (B2) aortic bypass without aortic resection. In the latter two groups, suprarenal aortic cross‐clamping was placed for 30 minutes after a 40% hemorrhage. We analyzed various inflammatory markers and mortality. The 40% bleeding (vs. 60%) elicited a smaller decrease in mean arterial pressure (110 ± 6 vs. 89 ± 9 mmHg) but did not cause irreversible shock or mortality. After the 40% hemorrhage, the B1 aortic repair caused two cases of paraplegia. We have developed a model to study the combined effect of bleeding and aortic cross‐clamping.
Long‐term Outcome of Treatment of Early Carcinoma of the Lip with Nd:YAG Laser
Authors: Tewari Mallika , Rai Pramod , Kumar Mohan , Shukla Hari S.
Published: January 2008

Background

The aim of this study was to assess the efficacy of the Nd:YAG laser for treating stage I squamous cell carcinoma (SCC) of the lip. The retrospective study was performed in a tertiary care referral hospital in northern India.

Methods

In January 2007 the records of patients treated by Nd:YAG laser ablation of the lip between January 1997 and January 2000 were reviewed. Patients with a minimum follow‐up of 5 years were included. The postoperative integrity of facial nerve, cosmetic and functional results, and disease (recurrence)‐free survival (DFS) were assessed.

Results

Of the 46 patients included, 42 were disease‐free at the end of the first year and 38 after 5 years. Six patients required repeat lasering for a residual or recurrent lesion. Two patients developed regional lymph node metastasis with no infield recurrence and underwent modified radical neck dissection. The 5‐year DFS rate was 82.6%. Site of lip involvement (upper or lower), history of tobacco use, or grade of the tumor had no influence on DFS. Cosmetic results were excellent and without any significant complication.

Conclusion

Our results support the use of the Nd:YAG laser for treatment of stage I SCC of the lip with minimal morbidity and good DFS.
Reliability and Validity of Self-Efficacy for Learning Form (SELF) Scores of College Students
Authors: Zimmerman Barry , Kitsantas Anastasia
Published: January 2008

Abstract. We studied psychometric properties of the SELF with 223 college students. The SELF assesses students' self-efficacy beliefs regarding their use of specific self-regulatory processes in various areas of academic functioning. To determine the validity of SELF scores, the following outcome measures were studied: perceived responsibility, homework quantity, and homework quality. In addition, students' grades, standardized test scores (SAT), and instructor ratings of students' self-regulated skills were investigated. Students' scores on both the original SELF and an abridged form of the scale (SELF-A) were found to have a unitary factor structure and high level of internal reliability. Interestingly, the SELF-A was superior in its prediction of all validity measures except the SAT, which was comparable for the two forms.
New Insights into the Self-Regulation of Writing Skills in Secondary Vocational Education
Authors: Boekaerts Monique , Rozendaal Jeroen S.
Published: January 2008

Abstract. The purpose of this study was to investigate predictors of metacognitive self-regulation for students in secondary vocational education. Drawing on research and theory characterizing writing as a complex skill, we analyzed students' reported metacognitive strategy use in relation to three writing genres: writing an email, term paper, and application letter. The participants were 967 vocational students enrolled in six education programs. Multiple regression analyses with metacognitive strategy use as criterion variable and as a predictor set: capacity beliefs, context beliefs, gender, and perceived instrumentality of writing for the attainment of personal goals, revealed that capacity and context beliefs significantly predicted metacognitive strategy use for the three genres but genre-specific effects were found for perceived instrumentality of writing for the attainment of personal goals. Metacognitive strategy use had no relation with career goals, a positive relation with mastery goals, and a negative relation with well-being goals. The results illustrate the complexity of predicting metacognitive strategy use and signal the importance of insight into students' personal goals.
Response of the Strickland and Fly River confluence to postglacial sea level rise
Authors: Lauer J. Wesley , Parker Gary , Dietrich William E.
Published: January 2008

The sand bed portion of the Fly River system in Papua New Guinea was influenced significantly by postglacial sea level rise, but this response differed along the three main low‐gradient branches of the system: the main stem lower Fly River and its two tributary reaches, the middle Fly River and the Strickland River. A numerical model for valley development over ∼1000 to ∼10,000 year timescales is presented that can account for the coupled morphodynamic evolution of the main stem and its two tributaries. It is shown that the underlying theory includes both advective and diffusive terms for morphodynamic evolution, in contrast to other purely diffusive models for valley development. The advective terms arise due to the inclusion of backwater in the theory. The model is applied to the Fly River system over the 20,000 years since glacial low stand of sea level. Results imply that the relatively low sediment supply to the middle Fly River compared with that to the Strickland probably prevented the middle Fly from keeping pace with aggradation along the downstream lower Fly River. The middle Fly may still be responding to this forcing. It appears unlikely that the middle Fly River was incised more than ∼10 m prior to the onset of base level rise. This implies that the low‐stand lower Fly River passed through a zone characterized by channel slopes much steeper than the present slope somewhere between the junction with the Strickland River and the low‐stand delta.
Oligocene deep water export from the North Atlantic and the development of the Antarctic Circumpolar Current examined with neodymium isotopes
Authors: Scher Howie D. , Martin Ellen E.
Published: January 2008

Neodymium (Nd) isotopes were measured on 181 samples of fossil fish teeth recovered from Oligocene to Miocene sections at Ocean Drilling Program Site 1090 (3700 m water depth) on Agulhas Ridge in the Atlantic sector of the Southern Ocean. A long‐term decreasing trend toward less radiogenic Nd isotope compositions dominates the record. This trend is interrupted by shifts toward more radiogenic compositions near the early/late Oligocene boundary and the Oligocene/Miocene boundary. Overall, ɛNd values at Agulhas Ridge are more radiogenic than at other Atlantic locations, and are similar to those at Indian Ocean locations. The pattern of variability is remarkably similar to Nd isotope results from Walvis Ridge (South Atlantic) and Ninetyeast Ridge (Indian Ocean). In contrast, Agulhas Ridge and Maud Rise Nd isotope records do not show similar patterns over this interval. Results from this study indicate that deep water in the Atlantic flowed predominantly from north to south during the Oligocene and Miocene, and that export of Northern Component Water (NCW) to the Southern Ocean increased in the late Oligocene. There is also evidence for efficient exchange of deep waters between the Atlantic sector of the Southern Ocean and the Indian Ocean, although the direction of deep water flow is not entirely clear from these data. The shifts to more radiogenic Nd isotopic compositions most likely represent increases in the flux of Pacific waters through Drake Passage, and the timing of these events reflect development of a mature Antarctic Circumpolar Current (ACC). The relative timing of increased NCW export and ACC maturation support hypotheses that link deep water formation in the North Atlantic to the opening of Drake Passage.
Regional application of the PnET‐BGC model to assess historical acidification of Adirondack lakes
Authors: Zhai Jing , Driscoll Charles T. , Sullivan Timothy J. , Cosby Bernard J.
Published: January 2008

The Adirondack region of New York has high inputs of acidic deposition and large numbers of acidic lakes. The biogeochemical model, PnET‐BGC, was applied to 44 statistically representative Environmental Monitoring and Assessment Program (EMAP) lake watersheds in the Adirondacks. Model simulations help provide an understanding of historical effects of acidic deposition on soils and lake waters. Model simulations indicate that median annual concentrations of SO42− and NO3− in the 44 EMAP lakes were 15.9 μeq/L and 3.8 μeq/L, respectively, in 1850, compared to the median current measured values of 88.8 μeq/L and 20.0 μeq/L. Simulated median values of pH, acid‐neutralizing capacity (ANC), and soil percent base saturation were 6.63, 67.7 μeq/L, and 12.3%, respectively, in 1850, compared to the median current measured values of 5.95, 27.8 μeq/L, and 7.9%. The estimated historical surface water acidification was greatest in lakes having low ANC below values of 100 μeq/L. This pattern of historical acidification is in agreement with a previous paleolimnological investigation.
Field observations of soil moisture variability across scales
Authors: Famiglietti James S. , Ryu Dongryeol , Berg Aaron A. , Rodell Matthew , Jackson Thomas J.
Published: January 2008

In this study, over 36,000 ground‐based soil moisture measurements collected during the SGP97, SGP99, SMEX02, and SMEX03 field campaigns were analyzed to characterize the behavior of soil moisture variability across scales. The field campaigns were conducted in Oklahoma and Iowa in the central USA. The Oklahoma study region is sub‐humid with moderately rolling topography, while the Iowa study region is humid with low‐relief topography. The relationship of soil moisture standard deviation, skewness and the coefficient of variation versus mean moisture content was explored at six distinct extent scales, ranging from 2.5 m to 50 km. Results showed that variability generally increases with extent scale. The standard deviation increased from 0.036 cm3/cm3 at the 2.5‐m scale to 0.071 cm3/cm3 at the 50‐km scale. The log standard deviation of soil moisture increased linearly with the log extent scale, from 16 m to 1.6 km, indicative of fractal scaling. The soil moisture standard deviation versus mean moisture content exhibited a convex upward relationship at the 800‐m and 50‐km scales, with maximum values at mean moisture contents of roughly 0.17 cm3/cm3 and 0.19 cm3/cm3, respectively. An empirical model derived from the observed behavior of soil moisture variability was used to estimate uncertainty in the mean moisture content for a fixed number of samples at the 800‐m and 50‐km scales, as well as the number of ground‐truth samples needed to achieve 0.05 cm3/cm3 and 0.03 cm3/cm3 accuracies. The empirical relationships can also be used to parameterize surface soil moisture variations in land surface and hydrological models across a range of scales. To our knowledge, this is the first study to document the behavior of soil moisture variability over this range of extent scales using ground‐based measurements. Our results will contribute not only to efficient and reliable satellite validation, but also to better utilization of remotely sensed soil moisture products for enhanced modeling and prediction.
Response of the Gulf of Alaska 3D winter circulation to oceanic climate shifts: Ecosystem implications
Authors: Auad Guillermo
Published: January 2008

Recent measurements of zooplankton biomass and biological productivity in the Gulf of Alaska have raised a number of questions regarding possible linkages between climate and availability of renewable resources. In this article we compare 3 abrupt oceanic regime shifts in the Gulf of Alaska, the 1976–1977 warming shift, the 1998 cooling episode, and the 1998 to 1999 El Niño to La Niña transition, against concomitant changes in biological conditions reported in the literature. After the 1976–1977 warming shift, changes in the Gulf's 3D circulation, i.e., interior upwelling, onshore transport and coastal downwelling, had the same sign as their climatological means, thus providing a candidate explanation to the observed increased productivity of the upper ocean. Warming and cooling transitions have associated with them very different patterns of both horizontal and vertical circulation, where the latter is confirmed to be linked to the wind stress curl variability. Important shifts in the local biology have been reported in the literature (warming of 1976–1997 and El Niño to La Niña transition of 1998–1999) when climatological shifts in our simulated vertical velocities were large; in turn, when they were small, the ecosystem did not show significant changes and this was in part due to the resilience set by the 1976–1977 shift through the strengthening of the GOA's mean 3D circulation.
Causal link between Quaternary paleoclimatic changes and volcanic islands evolution
Authors: Quidelleur X. , Hildenbrand A. , Samper A.
Published: January 2008

Giant landslides and resulting tsunamis represent the main geologic hazards linked to volcanic island evolution. From offshore and onland studies, flank failures have been identified around numerous islands, in most geodynamic contexts. However, the triggering conditions are still poorly understood and several causes may act simultaneously to reach a critical threshold. Here we show that most large volume (>10 km3) landslides occur at glacial stages termination and we propose that a causal relationship between flank collapse of volcanic islands and global climatic changes has existed at least since 900 kyr. Moreover, ages reported here favour the hypothesis that major collapses occurred during the onset of glacial to interglacial transitions when sudden influx of melt water from polar ice caps causes rapid sea level rise. We propose that rapid sea level rise induces enhanced coastal erosion and sudden changes of pore pressure conditions within basal layers, which favour edifice failure.
Utility of thermal image sharpening for monitoring field‐scale evapotranspiration over rainfed and irrigated agricultural regions
Authors: Agam Nurit , Kustas William P. , Anderson Martha C. , Li Fuqin , Colaizzi Paul D.
Published: January 2008

The utility of a thermal image sharpening algorithm (TsHARP) in providing fine resolution land surface temperature data to a Two‐Source‐Model for mapping evapotranspiration (ET) was examined over two agricultural regions in the U.S. One site is in a rainfed corn and soybean production region in central Iowa. The other lies within the Texas High Plains, an irrigated agricultural area. It is concluded that in the absence of fine (sub‐field scale) resolution thermal data, TsHARP provides an important tool for monitoring ET over rainfed agricultural areas. In contrast, over irrigated regions, TsHARP applied to kilometer‐resolution thermal imagery is unable to provide accurate fine resolution land surface temperature due to significant sub‐pixel moisture variations that are not captured in the sharpening procedure. Consequently, reliable estimation of ET and crop stress requires thermal imagery acquired at high spatial resolution, resolving the dominant length‐scales of moisture variability present within the landscape.
Cassini encounters with hot flow anomaly‐like phenomena at Saturn's bow shock
Authors: Masters A. , Arridge C. S. , Dougherty M. K. , Bertucci C. , Billingham L. , Schwartz S. J. , Jackman C. M. , Bebesi Z. , Coates A. J. , Thomsen M. F.
Published: January 2008

The first observations of the kronian equivalent of hot flow anomalies (HFAs) are presented. Using magnetic field and plasma data we discuss two events that were observed upstream of Saturn's bow shock during the first two orbits of the Cassini spacecraft. We suggest that these events result from the interaction between interplanetary current sheets and the shock surface. This same interaction is responsible for HFAs at the terrestrial bow shock. Calculations of electron temperature reveal an increase by a factor of approximately two for the first event, which is less than for terrestrial HFAs where the increase is by approximately an order of magnitude. In contrast to terrestrial HFAs we find that these events are associated with density enhancement rather than reduction. Estimates of the total pressure for the first event imply that the central region is expanding.
Response of submarine hydrologic monitoring instruments to formation pressure changes: Theory and application to Nankai advanced CORKs
Authors: Sawyer Audrey Hucks , Flemings Peter , Elsworth Derek , Kinoshita Masataka
Published: January 2008

We describe the response of a compressible submarine hydrologic monitoring instrument to formation pressure changes in low‐diffusivity rock. The measured pressure depends on the frequency of the pressure signal, the hydraulic diffusivity, and the wellbore storage. The Nankai advanced circulation obviation retrofit kits (ACORKs) (offshore Japan) record tide‐induced formation pressure changes with small amplitudes (<10% of seafloor amplitudes) and large phase shifts (>25°). The pressure measurements occur in thick, homogeneous, compressible, low‐permeability sediment, where in situ tidal pressure responses should approximate the seafloor tidal signal. A wellbore storage of 2 × 10−8 m3 Pa−1 can explain many of the observed tidal responses, given the hydraulic diffusivities of the monitored intervals. A reduced permeability around the wellbore of 1000‐fold and a wellbore storage of 10−11 m3 Pa−1 can also reconcile the data. Our analysis suggests that ACORK screens in the Lower Shikoku Basin facies have a critical frequency on the order of 5 × 10−8 Hz (equivalent to a period of 250 days); higher‐frequency formation pressure signals will be distorted in the pressure record. Within the Lower Shikoku Basin facies the time for this monitoring system to record 90% of an instantaneous pressure change is on the order of 10 d. We suggest that the ACORK instrument compliance contributes to, but does not fully explain, the small tidal amplitudes and large phase shifts recorded at the least permeable monitoring intervals.
Effects of uncertainty magnitude and accuracy on assimilation of multiscale measurements for snowpack characterization
Authors: Durand Michael , Margulis Steven A.
Published: January 2008

Hydrologists regularly utilize data assimilation (DA) techniques to merge remote sensing measurements with physical models in order to characterize hydrologic reservoirs. DA methods generally require an estimate of the uncertainty of the various inputs to the models; in practice, however, the uncertainty of these quantities is often unknown. This paper explores the effects of the unknown uncertainty on the efficiency of a multifrequency, multiscale hydrologic DA scheme for snowpack characterization. Synthetic passive microwave (PM) measurements at 25 km and near‐infrared (NIR) measurements at 1 km were assimilated, and both snow water equivalent (SWE) and grain size were estimated at 1 km resolution. It is found that the uncertainty magnitude had a significant effect on the efficiency of both SWE and grain size estimation, but that the uncertainty magnitude had very different effects on these two variables because of the different PM and NIR measurement scales. Secondly, it was found that the uncertainty accuracy had a very important role in this DA scheme and that the filter may degrade the estimate of SWE and grain size if key model inputs are misspecified. Finally, four metrics were used to assess the difference between the PM and NIR measurement innovations and their expected values. It was shown that these metrics could potentially be used in an adaptive filtering scheme to correct misspecified uncertainty. More investigation will be required before the feasibility of such an adaptive filtering scheme is established. These findings have important ramifications for snowpack estimation since it implies that in the context of DA schemes, better use will be made of remote sensing products when better physical characterization of the uncertainty of modeled estimates of snow states is available.
Seasonal gravity wave activity observed with the Equatorial Atmosphere Radar and its relation to rainfall information from the Tropical Rainfall Measuring Mission
Authors: Alexander S. P. , Tsuda T. , Shibagaki Y. , Kozu T.
Published: January 2008

Five years of tropospheric data below 12 km from the Equatorial Atmosphere Radar (EAR) are examined for seasonal and interannual gravity wave activity. Results are compared with data from the Tropical Rainfall Measuring Mission (TRMM) satellite. A semiannual cycle of vertical wind variances inside and above convection is found. Maxima occur at the equinoxes and minima at the solstices. This semiannual cycle is also observed in the TRMM storm height and surface rainfall. Half of the vertical wind variance above convection is due to waves with periods of less than 2 h, with the rest coming from waves with periods of less than 24 h. On average, 78% of the total horizontal wind variance above convection is due to waves with periods of less than 24 h. The TRMM rainfall at 2 km altitude is greater than the EAR surface rainfall, suggesting that the EAR site is not representative of regional rainfall conditions. Momentum fluxes are calculated and shown to be dominated by multiday processes, although standard deviations are greater than the mean values.
A numerical study on the response of wave number spectra of atmospheric gravity waves to lower atmospheric forcing
Authors: Zhang Shao Dong , Yi Fan
Published: January 2008

Starting from a set of nonrotating, fully nonlinear basic atmospheric kinetic equations, we numerically study the response of wave number spectra for atmospheric gravity wavefields to different excitation sources. The simulation results show that only when excited by a localized random momentum source do the horizontal and vertical wave number spectra of the gravity wavefields exhibit a “quasi‐universal” spectral structure, indicating that the random characteristic of the source may play an important role in forming a “universal” spectrum. By adjusting several tunable parameters in our model, we numerically study the influences of the source properties and background winds on the wave number spectra. Our simulations suggest that the intermittency and asymmetry of wave sources and a sheared background wind will lead to shallower wave number spectra. Apart from these differences, vertical wave number spectra arising from different sources and background conditions exhibit some conformities. For instance, generally, the spectral slopes for the vertical wind fluctuations are larger (in magnitude) than those for the horizontal wind and temperature fluctuations, and the slopes for the horizontal wind fluctuations are usually slightly smaller than those for the temperature fluctuations.
Factorial method as a tool for estimating the relative contribution to precipitation of cloud microphysical processes and environmental conditions: Method and application
Authors: Teller A. , Levin Z.
Published: January 2008

The factorial experiment method is presented as a tool for evaluating the sensitivity of precipitation to changes in atmospheric thermodynamic conditions and cloud microphysical characteristics in mixed phase convective clouds. As an example, the method is adopted here for analysis of the sensitivity of precipitation to changes in various parameters using simulations with the Tel Aviv University 2D (TAU 2D) cloud model. The cloud model was run in 80 scenarios in order to determine the relative sensitivity of precipitation in eastern Mediterranean winter mixed phase convective clouds to changes in cloud condensation nuclei (CCN) concentration, parameterization of ice formation mechanisms and initial atmospheric thermodynamic conditions. When these parameters act synergistically to suppress precipitation (by increasing the concentration of CCN and of small ice crystals and reducing the water vapor mixing ratio), for the cases simulated here, a decrease of about 2°C in the entire profile of the ambient temperature while keeping the relative humidity constant has the same contribution to precipitation suppression as an increase of about 400 cm−3 in the CCN concentration. It is shown that under the warmest and most humid atmospheric thermodynamic conditions simulated here, the suppression of precipitation is affected more by the increased CCN than by the ice generation processes, whereas in colder atmospheric conditions the reverse is true. For a given atmospheric sounding the time of rain initiation strongly depends on the CCN concentrations. The role of ice generation begins to affect precipitation at a later stage when the cloud is more mature.
Understanding biases in shortwave cloud radiative forcing in the National Center for Atmospheric Research Community Atmosphere Model (CAM3) during El Niño
Authors: Li Gang , Zhang Guang Jun
Published: January 2008

This study aims to understand the weak response of shortwave cloud radiative forcing (SWCF) to El Niño in the NCAR CAM3. Observations from ERBE and CERES show strong negative SWCF in the central and eastern equatorial Pacific during El Niño. The standard CAM3 simulation at T42 resolution severely underestimates this response, with even wrong sign in the eastern Pacific. However, an experimental simulation at the same resolution, but with a modified convection parameterization scheme, simulates the cloud shortwave response to El Niño well, although the improvement in the eastern Pacific is not as significant as in the western and central Pacific. To unravel the mechanistic differences in SWCF response to El Niño between the two simulations, the authors analyze the cloud amount, cloud liquid water path (LWP), cloud ice water path (IWP), and convective and large‐scale precipitation. It is shown that positive LWP anomalies are mainly responsible for the improved SWCF response to El Niño in the experimental simulation. Interaction among deep convection, shallow convection and low‐level clouds is explored to explain this result. Negative LWP anomalies, largely due to reduced cloud water content and amount of low clouds during El Niño in the standard CAM3, weaken the SWCF response. Comparison with a higher‐resolution simulation of CAM3 at T85 shows that the T85 simulation produces realistic SWCF response through greatly increased cloud water and ice content in the middle and upper troposphere, while reduced low‐level cloud water content remains a problem.
Uncertainty evaluation of ozone production and its sensitivity to emission changes over the Ile‐de‐France region during summer periods
Authors: Deguillaume L. , Beekmann M. , Derognat C.
Published: January 2008

The approach of Bayesian Monte Carlo analysis has been used for evaluating model uncertainty in ozone production and its sensitivity to emission changes. This approach has been applied to the ozone fields calculated by the CHIMERE regional model in the Ile‐de‐France area during the 1998 and 1999 summer seasons. The AIRPARIF network measurements of urban NO and O3 concentrations and rural O3 over the Ile‐de‐France region have been used for constraining the Monte Carlo simulations. Our results yield the following major conclusions: (1) The simulated formation of O3 plumes are mainly located in southwestern to southeastern directions downwind the Paris area. (2) Uncertainties on simulated ozone concentrations and several derived quantities are evaluated and reduced using the BMC approach; simulated urban and plume ozone concentrations are enhanced through the observational constraint as compared to those obtained from the unconstrained model. (3) The chemical regime over the urban area of Paris and within plumes is clearly VOC sensitive on the average over two summers. This statement is robust with respect to the BMC uncertainty analysis.
Temporal variations in physical and chemical features of cryoconite holes on Canada Glacier, McMurdo Dry Valleys, Antarctica
Authors: Fountain Andrew G. , Nylen Thomas H. , Tranter Martyn , Bagshaw Elizabeth
Published: January 2008

Cryoconite holes in the McMurdo Dry Valleys are ice‐lidded, thus isolating the pools of water from the atmosphere and from potential surface melt. Hourly measurements of ice and water temperature and water electrical conductivity (EC) were recorded to broadly characterize the physical and chemical changes on daily to seasonal timescales. Overall, subsurface ice/water temperatures were typically several degrees warmer than air temperatures, underscoring the importance of subsurface solar heating. At no time was surface melt observed and the holes melted from within. Detailed differences in the timing and magnitude of both temperature and EC variations during melt‐out and freezeup existed between holes despite short separation distances (<1 m). We attribute these differences to small‐scale changes in the optical characteristics of the ice and perhaps different efficiencies in hydrologic connections between holes. The holes melt‐deepened quickly in the first half of the summer before slowing to a rate equal to the rate of surface ablation that kept hole depth constant for the remainder of the season. The relatively constant EC of the hole waters during midsummer indicates that these holes were connected to a subsurface water system that flushed the holes with fresher meltwater. The early and late season ECs are dominated by freeze‐thaw effects that concentrate/dilute the solutes. We speculate that high solute concentrations imply high nutrient concentrations in early summer that may help alleviate potential stresses caused by the production of new biomass after the winter freeze.
A need to improve reconstructions of the fluctuations in the calcite compensation depth over the course of the Cenozoic
Authors: Broecker Wallace S.
Published: January 2008

Reconstructions based on back‐tracked depths of the transition between CaCO3‐bearing and CaCO3‐depleted sediment suggest that over the last 65 million years the ocean's CaCO3 compensation depth (CCD) has remained within the range 4.0 ± 0.6 km. Taken at face value, these results indicate that depth of the calcite saturation horizon and hence also the product of the Ca++ and CO3= concentrations have remained nearly constant. In turn, this suggests that the ratio of calcite production to ingredient supply has not undergone large changes. In this paper, the method used to reconstruct the temporal fluctuations and interocean differences in the depth of the calcite saturation horizon is scrutinized. The basis for my concern is that offset between the depth of the calcite saturation horizon and the depth where dissolution reduces the CaCO3 content to 20% (i.e., the CCD) can vary by a half kilometer or so depending on the rain rates of CaCO3 and non CaCO3. When observations on modern ocean sediments are used to test the reliability of these reconstructions, the result is that when averaged over a full glacial cycle, the depth of the CCDs in the Pacific and Indian oceans fall within the long‐term range. Reliable documentation of fluctuations around this long‐term average requires that additional measurements, such as extent of fragmentation, be used to supplement those of CaCO3 content.
Particle‐in‐cell simulation of the incoherent scatter radar spectrum
Authors: Diaz M. A. , Semeter J. L. , Oppenheim M. , Zettergren M.
Published: January 2008

A particle‐in‐cell (PIC) approach is presented and utilized to simulate incoherent scatter radar (ISR) spectra. In particular, a two‐dimensional simulation is performed of a small, unmagnetized, F region plasma volume in thermodynamic equilibrium. The simulation results are compared to the analytical ISR spectra obtained for a plasma in thermodynamic equilibrium, and they are shown to be in agreement. Even though some plasma parameters have to be modified to limit the computational cost, the physical conclusions obtained by simulation can remain unaltered. The PIC approach can be extended to study distorted ISR spectra to obtain insights into the underlying physical phenomena. This simulation also provides a means for studying the time evolution of spectral distortions, which could enable the development of procedures for estimating plasma parameters from distorted spectra.
Combining a spatial model with geochemical tracers and river station data to construct a catchment sediment budget
Authors: Rustomji Paul , Caitcheon Gary , Hairsine Peter
Published: January 2008

Information about diffuse pollutant sources in river catchments and the processes responsible for their generation is often obtained using geochemical tracing, in‐stream monitoring, or process based modeling. Yet these methods are rarely combined. In this study, we combine these three methods to produce a catchment sediment budget for the Lake Burragorang catchment in Australia. The physically based process model SedNet was modified using local catchment data to constrain predicted hillslope erosion rates in forested areas, the rate and texture of sediment supply from gully erosion, and the predicted floodplain deposition rates. The model's capacity to match the geochemical tracer (both spatial source and erosion process) data and gauging station load data improved markedly. Hillslope erosion, primarily in the steeper, mainly forested areas near the reservoir, is identified by the model as the main source of sediment delivered to Lake Burragorang. The contribution from gully and river bank erosion is comparatively small, though gully erosion can be locally dominant. This result is consistent with the tracer data. Utilizing multiple independent data sets allows for a more rigorous evaluation of model performance and, it is argued, increases the likelihood that the model is correctly representing the main components of the catchment's sediment budget. The identification of diffuse sediment sources in other catchments can clearly benefit from combining a range of observational data with a structured model evaluation process.
On the space‐time evolution of a cholera epidemic
Authors: Bertuzzo E. , Azaele S. , Maritan A. , Gatto M. , Rodriguez‐Iturbe I. , Rinaldo A.
Published: January 2008

We study how river networks, acting as environmental corridors for pathogens, affect the spreading of cholera epidemics. Specifically, we compare epidemiological data from the real world with the space‐time evolution of infected individuals predicted by a theoretical scheme based on reactive transport of infective agents through a biased network portraying actual river pathways. The data pertain to a cholera outbreak in South Africa which started in 2000 and affected in particular the KwaZulu‐Natal province. The epidemic lasted for 2 years and involved about 140,000 confirmed cholera cases. Hydrological and demographic data have also been carefully considered. The theoretical tools relate to recent advances in hydrochory, migration fronts, and infection spreading and are novel in that nodal reactions describe the dynamics of cholera. Transport through network links provides the coupling of the nodal dynamics of infected people, who are assumed to reside at the nodes. This proves a realistic scheme. We argue that the theoretical scheme is remarkably capable of predicting actual outbreaks and, indeed, that network structures play a controlling role in the actual, rather anisotropic propagation of infections, in analogy to spreading of species or to migration processes that also use rivers as ecological corridors.
Conformational switch of angiotensin II type 1 receptor underlying mechanical stress‐induced activation
Authors: Yasuda Noritaka , Miura Shin‐ichiro , Akazawa Hiroshi , Tanaka Toshimasa , Qin Yingjie , Kiya Yoshihiro , Imaizumi Satoshi , Fujino Masahiro , Ito Kaoru , Zou Yunzeng , Fukuhara Shigetomo , Kunimoto Satoshi , Fukuzaki Koichi , Sato Toshiaki , Ge Junbo , Mochizuki Naoki , Nakaya Haruaki , Saku Keijiro , Komuro Issei
Published: January 2008

The angiotensin II type 1 (AT1) receptor is a G protein‐coupled receptor that has a crucial role in the development of load‐induced cardiac hypertrophy. Here, we show that cell stretch leads to activation of the AT1 receptor, which undergoes an anticlockwise rotation and a shift of transmembrane (TM) 7 into the ligand‐binding pocket. As an inverse agonist, candesartan suppressed the stretch‐induced helical movement of TM7 through the bindings of the carboxyl group of candesartan to the specific residues of the receptor. A molecular model proposes that the tight binding of candesartan to the AT1 receptor stabilizes the receptor in the inactive conformation, preventing its shift to the active conformation. Our results show that the AT1 receptor undergoes a conformational switch that couples mechanical stress‐induced activation and inverse agonist‐induced inactivation.
DNA‐damage response control of E2F7 and E2F8
Authors: Panagiotis Zalmas L , Zhao Xiujie , Graham Anne L , Fisher Rebecca , Reilly Carmel , Coutts Amanda S , La Thangue Nicholas B
Published: January 2008

Here, we report that the two recently identified E2F subunits, E2F7 and E2F8, are induced in cells treated with DNA‐damaging agents where they have an important role in dictating the outcome of the DNA‐damage response. The DNA‐damage‐dependent induction coincides with the binding of E2F7 and E2F8 to the promoters of certain E2F‐responsive genes, most notably that of the E2F1 gene, in which E2F7 and E2F8 coexist in a DNA‐binding complex. As a consequence, E2F7 and E2F8 repress E2F target genes, such as E2F1, and reducing the level of each subunit results in an increase in E2F1 expression and activity. Importantly, depletion of either E2F7 or E2F8 prevents the cell‐cycle effects that occur in response to DNA damage. Thus, E2F7 and E2F8 act upstream of E2F1, and influence the ability of cells to undergo a DNA‐damage response. E2F7 and E2F8, therefore, underpin the DNA‐damage response.