bluuebunny/crossref_metadata_2025_split huggingface dataset:
Using a cloud‐resolving model to study the effects of subgrid‐scale variations in relative humidity on direct sulphate‐aerosol forcing
Authors: Petch J. C. 
Published: February 2007

AbstractCloud‐resolving model simulations over a tropical ocean and a mid‐latitude continental region have been used to investigate the influence of subgrid‐scale variations of relative humidity on the direct radiative forcing of sulphate aerosols. Offline radiation calculations based on output from a cloud‐resolving model, with and without sulphate aerosol included, are used to calculate the direct radiative forcing of the aerosol. This forcing is compared with results from single‐column radiation calculations typical of those produced by a climate model.The results from this idealized study show that a typical climate model can underestimate the direct radiative forcing of aerosols by up to 80%. The errors in a climate‐model calculation are largest when the mean relative humidity is high or there are moist regions within a drier domain; this is usually reflected in a larger standard deviation of the relative humidity. Over the more humid tropical ocean, a climate model may underestimate the direct radiative forcing of sulphate aerosols by 43%, on average (ranging between 30% and 80%). Over the drier continental mid‐latitude region the average error is only 10%, but instantaneous values can exceed 50% during times when both the mean relative humidity and its standard deviation are large; this is typically close to convective events.
Modification of the wind speed profile caused by snowdrift: Results from observations
Authors: Bintanja Richard 
Published: February 2007

AbstractThis paper investigates how snowdrift influences the wind speed profile on the basis of meteorological and snowdrift data collected over an Antarctic snow surface during the austral summer. The friction associated with saltating snowdrift is found to significantly affect the wind speed profile by enhancing the apparent surface roughness. Several aspects of the wind speed data suggest the existence of the particle buoyancy effect associated with suspended snow particles. This effect has been theoretically predicted for snowdrift and experimentally verified for other two‐phase flows (e.g. suspended sediment in water). The observed impact of snowdrift saltation and suspension on the wind speed gradient, the total buoyancy and turbulent production rate are compared with theoretical/empirical estimates of the impact of saltation effects and particle buoyancy in suspension. It is shown that the particle buoyancy effect in snowdrift is very probably real and non‐negligible, but winds were not strong enough to demonstrate this conclusively.
An adaptive buddy check for observational quality control
Authors: Dee Dick P. , Rukhovets Leonid , Todling Ricardo , da Silva Arlindo M. , Larson Jay W. 
Published: February 2007

AbstractAn adaptive buddy‐check algorithm is presented that adjusts tolerances for suspect observations, based on the variability of surrounding data. The algorithm derives from a statistical hypothesis test combined with maximum‐likelihood covariance estimation. Its stability is shown to depend on the initial identification of outliers by a simple background check. The adaptive feature ensures that the final quality‐control decisions are not very sensitive to prescribed statistics of first‐guess and observation errors, nor on other approximations introduced into the algorithm.The implementation of the algorithm in a global atmospheric data assimilation is described. Its performance is contrasted with that of a non‐adaptive buddy check, for the surface analysis of an extreme storm that took place over Europe on 27 December 1999. The adaptive algorithm allowed the inclusion of many important observations that differed greatly from the first guess and that would have been excluded on the basis of prescribed statistics. The analysis of the storm development was much improved as a result of these additional observations.
Radar observations of precipitation and airflow on the Mediterranean side of the Alps: Autumn 1998 and 1999
Authors: Houze Robert A. , James Curtis N. , Medina Socorro 
Published: February 2007

AbstractThis study constructs and analyses composite three‐dimensional fields of Doppler‐radar observed radial velocity and reflectivity for all precipitation events occurring in the Lago Maggiore region on the Mediterranean side of the Alps during autumn 1998 and 1999. Mean patterns for the two years are in close agreement with each other. The radar data are consistent with previous rain‐gauge studies in showing that the rain was heaviest over the lower windward slopes, and decreased toward higher terrain. The three‐dimensional reflectivity fields show that precipitation growth occurred mainly at low altitudes. The composite radar data show that the precipitation was most intense when the mean flow around the 2 km level was southerly or south‐easterly, i.e. when the mean flow was most perpendicular to the Alpine barrier.Sounding data from Milan indicated the Froude number of the flow upstream of the Lago Maggiore region. When the Froude number was high, the flow proceeded directly up and over the terrain of the lower Alpine slopes. Under these unblocked conditions, the low‐level flow (including the layer from the surface to 2 km above mean sea level) rose directly up and over the terrain, and the precipitation was greatly enhanced over the lower windward slopes and over the portions of the Po Valley just upstream of the mountains. Under unblocked conditions, the precipitation enhancement only extended a short distance (a few tens of kilometres) upstream of the Alps. When the upstream Froude number computed from the Milan sounding was low (blocked conditions), the Doppler radial velocities indicated that the low‐level flow (in the layer below 2 km above mean sea level) turned cyclonically as it approached the Alpine barrier, instead of rising over the terrain. The composite radar reflectivity data showed less precipitation enhancement directly over the windward slope, but in contrast to the unblocked case showed that the precipitation was enhanced 140 km or more upstream of the terrain. Evidently, the low‐level flow began rising far in advance of the barrier in blocked conditions.The 1998 and 1999 autumn data sample further indicates the relative roles of wind speed and stability, which are combined in the Froude number. When the wind speed upstream was strong (>8 m s−1), significant precipitation enhancement occurred on the windward slope of the Alps in the Lago Maggiore region, regardless of the static stability. However, the enhancement was far greater under unstable conditions. When the wind speed was weak (<8 m s−1), the precipitation was generally near or below average, except when the stability was low and some patchy enhancement occurred over the Po Valley just upwind of the Alps. A diurnal precipitation maximum occurred in the early morning hours (0700–1000 LST), possibly where down‐valley flow converged with synoptic‐scale up‐valley flow.
Modelling the generation of gravity waves by a maritime continent thunderstorm
Authors: Lane Todd P. , Reeder Michael J. 
Published: February 2007

AbstractObserved wind and temperature profiles are used to initialize a model calculation of a maritime continent thunderstorm, and the numerical solution is used to explore the effect of tropospheric shear on the gravity‐wave generation. The resultant convective system is qualitatively similar to that observed. The modelled gravity waves propagate away from the cloud with wave‐fronts that are approximately circular, implying that the convective clouds do not generate waves which propagate in a preferred direction.The gravity‐wave generation is related to the oscillation of the convective updraughts about their level of neutral buoyancy. While the general features of the gravity waves are similar in most respects to a previous study which used an idealized wind profile, the frequency of the gravity waves is Doppler‐shifted by the tropospheric wind shear. The result is a much broader power spectrum in comparison to the idealized cases.
Can an ensemble transform Kalman filter predict the reduction in forecast‐error variance produced by targeted observations?
Authors: Majumdar S. J. , Bishop C. H. , Etherton B. J. , Szunyogh I. , Toth Z. 
Published: February 2007

AbstractThe ensemble transform Kalman filter (ET KF) is currently used at the National Centers for Environmental Prediction (NCEP) to identify deployments of aircraft‐borne dropwindsondes that are likely to significantly improve 1‐3 day forecasts of winter storms over the continental United States. It is unique among existing targeted observing strategies in that it attempts to predict the reduction in forecast‐error variance associated with each deployment of targeted observations. To achieve this, the ET KF predicts the variance of ‘signals’ for each feasible deployment, where a signal represents the difference between two forecasts, initialized with and without the targeted observations. For linear forecast‐error evolution, the signal variance is equal to the reduction in forecast‐error variance, provided that observation‐ and background‐error covariances are accurately specified and identical to those produced by the operational data‐assimilation scheme. However, background‐error covariances assumed by the ET KF are both imperfect and different from the imperfect error covariances used in NCEP's 3D‐Var data‐assimilation scheme, and hence their signal statistics are likely to differ.In spite of these differences, a linear relationship of positive gradient is found to exist between the ET KF signal variance and the sample variance of NCEP signal realizations at both the targeted analysis and forecast verification times, for 30 forecasts from the 2000 Winter Storm Reconnaissance Program. This relationship enables the NCEP signal variance to be predicted by the ET KF, via a statistical rescaling that corrects the ET KF's current over‐prediction of signal variance magnitude. A monotonically increasing relationship is also found to exist between the NCEP signal variance and the reduction in NCEP forecast‐error variance. The ET KF signal variance predictions can be used to make quantitative estimates of the forecast‐error‐variance reducing effect of targeted observations. Potential benefits include (i) making rapid decisions on when and where to deploy targeted observations, (ii) warning operational data quality‐control schemes against the rejection of observational data if the signal variance is large, and (iii) estimating the likelihood of economic benefit due to any future deployment of observations.
Flood frequency and routing processes at a confluence of the middle Yellow River in China
Authors: He Hongming , Zhou Jie , Yu Qian , Tian Yong Q. , Chen Robert F. 
Published: February 2007

AbstractFloods cause environmental hazards and influence on socio‐economic activities. In this study, we evaluated the historic flood frequency at a confluence in the middle Yellow River, China. A non‐parametric, multivariate, empirical, orthogonal function matrix model, which consists of time correlation coefficients of flood discharge at different gauge stations and flood events was used for the analysis of flood frequency. The model addresses the characteristics of confluent floods such as frequency and the probability in multiple tributary rivers. Flood frequency analysis is often coupled with studies of hydrological routing processes that reduce the flood capacity of the rivers. Flood routing to the confluence were simulated using kinematic wave theory. Results of this flood frequency analysis showed that flooding frequency has intensified in the past 500 years, especially during the 19th century. Flooding in streams above the confluence was more frequent than in streams below the confluence. Over the last 2000 years, concurrent flooding in multiple tributary rivers accounted for 67.5% of the total flooding in the middle Yellow River. Simulation of flood routing processes shows that the decreased flooding capacity and elevated river bed of the shrunken main channel leads to an increased flood wave propagation time (24–52.3 h) in the study area after 1995. The model indicates that human activities, such as constructions of the Sanmenxia Dam, have changed flood routing boundary conditions and have contributed to the increased flood frequency at the confluence. Copyright © 2007 John Wiley & Sons, Ltd.
Long‐term and short‐term customer reaction: a two‐stage queueing approach
Authors: Ackere Ann van , Haxholdt Christian , Larsen Erik R. 
Published: February 2007

AbstractWe analyse a simple, deterministic queueing system with feedback. We model a customer's decision to seek service as a two‐stage process: (1) deciding whether or not to use a facility (become a customer), and (2) deciding the frequency of use (daily, weekly, monthly, etc.). We consider both a constant and a deterministic, time‐dependent usage pattern. We ignore variability, and focus on three forms of feedback: (1) the service rate increases as queue length increases; (2) the frequency with which customers use the service depends on customers' perception of recent waiting times; and (3) the number of customers depends on their perception of long‐term average waiting time. Although highly stylised, this model captures the essential features of many real‐life systems whose average arrival rate varies over time. The main conclusions are that more capacity can make the system less manageable, and a stronger external cycle can be a stabilising factor. The model turns out to be remarkably robust to external disturbances. Copyright © 2006 John Wiley & Sons, Ltd.
Viruses, lipid rafts and signal transduction
Authors: Rauch Susanne , Fackler Oliver T. 
Published: February 2007

AbstractLipid rafts are defined as highly dynamic microdomains in cellular membranes that are enriched in sphingolipids, cholesterol and raft‐targeted proteins. This particular lipid and protein composition is thought to facilitate protein‐protein interactions to create microdomains with distinct biological properties. Lipid rafts have been implicated in central cellular processes such as signal transduction and protein trafficking. This review focuses on strategies used by three viral pathogens (measles virus, Epstein‐Barr virus and human immunodeficiency virus) to manipulate their target cells by altering the signal transduction properties of such cellular microdomains in the infected host.
Ranked reservoir sampling: an extension to the reservoir sampling algorithm
Authors: Kirkham C. C. 
Published: February 2007

AbstractThis paper describes a simple extension to the reservoir sampling algorithm to allow its use with ranked records. Here the fixed‐sized sample must include records in order of rank, but a fair selection must occur to choose the lowest‐ranked records included. The result is produced after a single pass through the records. Copyright © 2007 John Wiley & Sons, Ltd.
Evolution@home: observations on participant choice, work unit variation and low‐effort global computing
Authors: Loewe Laurence 
Published: February 2007

AbstractMany simulation efforts in ecology and evolutionary biology employ individual‐based models that are well suited for including many biological details. These models often pose serious computational challenges if all biologically interesting parameter combinations are to be explored. The challenges are even greater for biologists who often lack supercomputing facilities and the manpower for implementing complex global computing systems such as SETI@home. Under such limiting conditions, evolution@home started as a one‐man effort to distribute simulations of Muller's ratchet to Internet‐connected computers of participants from the general public. This paper addresses experiences in low‐effort global computing made with evolution@home over more than four years. It shows how allowing participants to choose the class of computational complexity they want to contribute to can help to deal with the bewildering variety of computational complexities that easily result from individual‐based models. Results suggest that, as a first rough approximation, participants' complexity choices are distributed surprisingly even over all reasonable classes of CPU‐time and RAM requirements. More often than not, participants tend to finish the simulations they start, if they are committed enough to submit any results at all. Potential uses of intermediate simulation results are discussed and the error of magnitude is introduced to help to deal with imprecise CPU‐time predictions. Experiences with the choices of over 300 users who have contributed more than 100 000 simulations with a total of over 80 years CPU time are reviewed. Copyright © 2007 John Wiley & Sons, Ltd.
Large calcifications in ovaries otherwise normal on ultrasound
Authors: Brown D. L. , Laing F. C. , Welch W. R. 
Published: February 2007

AbstractObjectiveTo evaluate calcifications ≥ 5 mm in length in ovaries that are otherwise normal on ultrasound, and to determine whether such large ovarian calcifications are an indicator of ovarian neoplasm.MethodsThis was a retrospective study reviewing pelvic ultrasound results at our unit between October 1994 and April 2002 to identify patients with ovarian calcifications that were ≥ 5 mm in maximum length in otherwise normal ovaries, and who also had follow‐up imaging studies. Patient medical histories were reviewed, calcification characteristics, including number, size, shape and laterality of calcifications, were recorded and follow‐up imaging studies were reviewed to assess change in size of the calcification and to see if a neoplasm had developed.ResultsThe study group consisted of 28 patients. The mean length of imaging follow‐up was 35.2 ± 30.7 months. The mean size of the calcifications was 7.4 ± 2.3 (range, 5–13) mm. The calcification remained stable in all 28 patients and no ovarian neoplasms developed in any of the patients. Histological confirmation was available in one patient and this revealed dystrophic calcification in a corpus albicans.ConclusionCalcifications ranging from 5 to 13 mm in length in otherwise normal ovaries remain stable on follow‐up imaging and are not an indicator of current or future ovarian neoplasm. Copyright © 2007 ISUOG. Published by John Wiley & Sons, Ltd.
Effect of aromatic ring in the alkyl chain on surface properties of arylalkyl surfactant solutions
Authors: Xu Zhigang , Li Pengfei , Qiao Weihong , Li Zongshi , Cheng Lubo 
Published: February 2007

AbstractSurface properties of two series of anionic arylalkyl surfactants, containing different aromatic rings in the straight aliphatic chain, sodium N‐aryloleyl‐N‐methyl‐2‐aminoethanesulfonates and sodium N‐aryloleyl p‐methoxyanili‐nesulfonates, were investigated. An increase of the aromatic ring size in the alkyl chain increases the critical micelle concentration (CMC) and surface tension at CMC. However, this also decreases the efficiency and effectiveness in reducing water surface tension. The dominant factor of the decrease of efficiency and effectiveness is attributed to the function of the hydrophilic segment and hydrophobic segment for arylalkyl surfactants, respectively. The same results are found in the standard free energy of adsorption (ΔGoads) and the standard free energy of micellization (ΔGomic) values. Moreover, with the increase of the aromatic ring size, the adsorption and micellization of arylalkyl surfactants begin to weaken. The data indicate that some parts of surface properties for arylalkyl surfactants are affected by the bulkiness of the arylalkyl chain. The results provide opportunities for further detailed examination of surface properties of arylalkyl surfactants with other branched alkyl chains.
Experimental design for optimization of peroxide formulation stability and cost
Authors: Blanco Marcel , Coello Jordi , Sánchez M. Jesús 
Published: February 2007

AbstractCleaning formulations typically contain, in addition to surfactant, a bleaching agent that is usually hydrogen peroxide. This active agent has the disadvantage that it becomes unstable with time, which necessitates the use of various additives in the formulation to ensure its stability. In this work, a study of the different types of surfactants, chelating agents, radical scavengers, stabilizers, and solvents commonly used in the bleaching industry, was made to identify the mixture that better stabilizes an aqueous solution of hydrogen peroxide.The strategy used starts with a screening step based on a hyper‐Greco‐Latin square design. In subsequent steps, a Box‐Wilson design is used to construct a response surface model to identify the composition ensuring the highest possible stability in the formulation. A desirability function is then obtained that allows the stability of the formulation to be maximized and its cost simultaneously minimized. Such a function is optimized using the Nelder‐Mead algorithm.The stability study was made by heating the mixtures at 60°C for variable periods of time. A mixture containing four of these additives was found to provide the best stability, and the solvent did not have any effect on the stabilization. However, this mixture exceeded the expectations in terms of cost, so the composition was adjusted to obtain the best compromise between stability and cost. As the stabilizer is the more expensive additive, in this optimization step its composition was reduced. In the final formulation, the stabilizer concentration can be reduced by up to 23% with respect to that obtained in the previous step without detracting from stability, thereby saving 18.8%.
Identification and production of n−8 odd‐numbered polyunsaturated fatty acids by a Δ12 desaturation‐defective mutant of Mortierella alpina 1S‐4
Authors: Zhang Shuo , Sakuradani Eiji , Shimizu Sakayu 
Published: February 2007

AbstractA mutant of Mortierella alpina, JT‐180, which is defective in its Δ12 desaturase activity but exhibits enhanced activities of Δ5 and Δ6 desaturases, produced a high proportion (up to 80%) of odd‐chain FA when grown on 3% n‐heptadecane. Following growth of the mutant on n‐heptadecane, three unusual odd‐chain fatty acyl residues were identified as 6,9‐heptadecadienoic acid (17∶2), 8,11‐nonadecadienoic acid (19∶2), and 5,8,11‐nonadecatrienoic acid (19∶3) by means of GC‐MS, MS‐MS, and NMR analysed. The mycelial contents of these FA reached 20.3, 3.6, and 5.8 ⧎/g dry mycelia, respectively, when it was cultivated in medium comprising 4% (vol/vol) n‐heptadecane and 1% (wt/vol) yeast extract, pH 6.0, at 28°C for 7 d. The biosynthetic route (n−8 route) to 19∶3 was presumed to mimic the n−9 route to Mead acid (20∶3 n−9) in mammals: 17∶0→9–17∶1→6,9–17∶2→8,11–19∶2→5,8,11–19∶3.
Pediatric retropharyngeal lymphadenitis: Differentiation from retropharyngeal abscess and treatment implications
Authors: Shefelbine Sarah E. , Mancuso Anthony A. , Gajewski Byron J. , Ojiri Hiroya , Stringer Scott , Sedwick Jack D. 
Published: February 2007

ObjectivesOur objectives were to review the retropharyngeal anatomy, define retropharyngeal adenitis and abscess, and determine if CT may guide the clinician in treatment planning for pediatric retropharyngeal infections.Study Design and SettingA retrospective chart review and CT scan review of 30 children with retropharyngeal infections.ResultsAll patients had retropharyngeal adenitis. Average volume of the low‐attenuation focus in the medical treatment group was 1.2 cm3. Average volume in the surgical group was 4 cm3. Surgery patients with no purulent findings were then grouped with the medical treatment group; the average volume of the low‐attenuation focus in this group was 2.2 cm3. Average volume in the group in which purulence was identified was 4.4 cm3.ConclusionCT can identify patients with retropharyngeal infections who have a high likelihood of being successfully treated with antibiotics alone.SignificanceCT imaging may assist in avoiding unnecessary surgical exploration.