bluuebunny/crossref_metadata_2025 huggingface dataset:
Reconsideration of the physical and empirical origins of Z–R relations in radar meteorology
Authors: Jameson A. R. , Kostinski A. B.
Published: February 2007

The rainfall rate, R, and the radar reflectivity factor, Z, are represented by a sum over a finite number of raindrops. It is shown here and in past work that these variables should be linearly related. Yet observations show that correlations between R and Z are often more appropriately described by nonlinear power laws. In the absence of measurement effects, why should this be so?

In order to justify this observation, there have been many attempts to create physical ‘explanations’ for power laws. However, the present work argues that, because correlations do not prove causation (an accepted fact in the statistical sciences), such explanations are suspect, particularly since the parametric fits are not unique and because they exhibit fundamental physical inconsistencies. So why, then, do so many correlations fit power laws when physical arguments show that Z and R should be related linearly?

It is shown in the present work that physically based, linear, relations between Z and R apply in statistically homogeneous rain. (Note that statistical homogeneity does not mean that the rain is spatially uniform.) In contrast, nonlinear power laws are empirical fits to correlated, but statistically inhomogeneous data. This conclusion is proven theoretically after developing a ‘generalized’ Z–R relation based upon physical consideration of R and Z as random variables. This relation explicitly incorporates details of the drop microphysics as well as the variability in measurements of Z and R. In statistically homogeneous rain, this generalized expression shows that the coefficient relating Z and R is a constant resulting in a linear Z–R relation. In statistically inhomogeneous rain, however, the coefficient varies in an unknown fashion so that one must resort to statistical fits, often power laws, in order to relate the two quantities empirically over widely varying conditions. This conclusion is independently verified using Monte Carlo simulations of rain from earlier work and is also corroborated using disdrometer observations. Thus, the justification for nonlinear power‐law Z–R relations is not physical, but rather statistical, in that they provide convenient parametric fits for estimating mean R from measured mean Z in statistically inhomogeneous rain.

Finally, examples based upon disdrometer data suggest that such generalized relations between two variables defined by such sums are potentially useful over a wide range of remote‐sensing problems and over a wide range of scales. The examples also offer hope that data collected over disparate sampling‐volumes and sampling‐frequencies can still be combined to yield meaningful estimates. Although additional testing is required, this allows us to write programs which combine estimates of R using remote‐sensing techniques with sparse but direct rainfall observations.
Influence of the assimilation scheme on the efficiency of adaptive observations
Authors: Bergot Thierry
Published: February 2007

The influence of assimilation schemes on the efficiency of adaptive observations is investigated, with three‐and four‐dimensional variational data assimilation (3D‐Var and 4D‐Var) systems, for 20 cases of cyclogenesis during the Fronts and Atlantic Storm‐Track Experiment (FASTEX). During FASTEX, adaptive observations were made in such a way that the forecast of synoptic‐scale systems characterized by a weak predictability was improved.

This study shows that, on average, adaptive observations significantly influence the forecast for both assimilation schemes. However, with 3D‐Var, the inclusion of adaptive observations leads to a blending of improvements and worsenings, resulting in a very weak mean improvement. In contrast, with 4D‐Var the forecasts are, on average, significantly improved at the verification time (a mean improvement of about 10% and a maximum improvement of more than 50%) without producing large variability at medium‐range.

Results confirm that the positive impact of 4D‐Var primarily occurs as a result of a change in the initial conditions in the most unstable directions. This positive impact is particularly obvious when adaptive observations are mainly located at the border of the sensitive area. In such cases, the known deficiencies of 3D‐Var may be detrimental. This study also demonstrates that the impact of sampling of the sensitive area depends on the assimilation scheme.
The diurnal cycle and African easterly waves: A land surface perspective
Authors: Taylor Christopher M. , Clark Douglas B.
Published: February 2007

Fluxes from the land surface into the atmosphere exhibit strong variability on diurnal and daily time‐scales during the Sahelian wet season. The influence of this variability on the atmosphere is examined here using a general circulation model. A land‐surface scheme with an improved description of the sparse vegetation which characterizes the Sahel is introduced, and compared with simulations using existing parameters. With smaller evaporation rates, the sparse vegetation results in a warmer and deeper planetary boundary layer (PBL) in better agreement with observations. The diurnal cycle in simulated rainfall is much weaker, due to less frequent triggering of daytime convection. The damping of diurnal variability is accompanied by enhanced daily variability, with a deep moist PBL developing over several days. Above the sparsely vegetated surface, there is also greater African easterly wave (AEW) activity, and more long‐lived rain events associated with it.

A mechanism is proposed to explain the increased frequency of AEWs above sparser vegetation, based on wave composites in the model. Surface heating of the lower atmosphere is modulated strongly by AEWs. This occurs via a surface‐convection‐radiation feedback. Estimates of the boundary‐layer heat budget indicate that variations in surface heating can, to a large extent, account for the low‐level temperature signal characteristic of AEWs. By reinforcing the low‐level temperature anomalies, the surface may influence the meridional wind signature of the wave above the PBL. Further evidence of the close coupling between the land surface and atmosphere is found by examining the modulation of precipitation by AEWs. Surface heat and moisture fluxes influence the build‐up of convective available potential energy ahead of the wave trough. In this way, the properties of the surface can affect the timing and intensity of rainfall associated with, an AEW.
Surface fluxes under shear‐free convection
Authors: Akylas E. , Tombrou M. , Lalas D. , Zilitinkevich S. S.
Published: February 2007

In this study, theoretical models of Schumann, Sykeset al., Beljaars, and Zilitinkevichet al.are examined, compared with data, and evaluated with regard to the calculation of the minimum friction velocity and the heat transfer coefficient. All data employed in earlier papers, namely those from meteorological campaigns SCOPE, TOGA COARE and BOREX‐95, and the Schmidt and Schumann and Sykes and Henn large‐eddy simulations (LESs), are considered. To achieve objective comparison between different formulae, empirical coefficients are recalculated by fitting theoretical curves separately for field data and for data from LESs. Despite essential differences in the shapes of the vertical profiles and the surface‐layer height formulations applied in different models, practically all of them perform rather similarly and in fairly good correspondence with the chosen data set. However, a remarkable systematic difference is observed between data from measurements, on the one hand, and LES data, on the other. It is argued that this difference results from a contribution from uncounted mean‐wind shear to the friction velocity in the field experiments. By this expedient, applicability of LESs to the resistance and heat‐mass transfer problem is confirmed, and empirical coefficients in the resistance and heat transfer formulations are refined.
Relationship between singular vectors and transient features in the background flow
Authors: Reynolds C. A. , Gelaro R. , Doyle J. D.
Published: February 2007

The relationships between singular vectors (SVs) and transient features in the background flow are examined through both composite techniques and case‐studies. The SVs are derived using the NOGAPS forward and adjoint tangent models based on 48‐hour forecasts during the NORPEX period. Composite results and case‐studies both reveal significant spatial relationships between the SVs and transient features in the background flow. The SV perturbations often occur below distinctive high potential‐vorticity (PV) features in the middle‐to‐upper troposphere. Case‐studies reveal that the SVs propagate upward rapidly and have an impact on these PV features through the end of the optimization interval. In order to investigate how these small, initial perturbations have such a large impact on future development, the relationship between SVs and the quasi‐geostrophic forcing is examined through the use of Q‐vectors. The SV perturbations, while scaled to have a very small impact on the temperature and wind fields, have a very large impact on the mid‐tropospheric Q‐vectors. In contrast, the impact of the SV on the Q‐vectors is negligible when added to an analysis field for which it is not optimal (e.g. the analysis field from another day). These findings establish a significant relationship between the SV perturbations and dynamically active regions in the middle troposphere, and point toward an integral link between SVs and upper‐level PV precursors in synoptic development.
Ensembles using multiple models and analyses
Authors: Richardson D. S.
Published: February 2007

The performance of the European Centre for Medium‐Range Weather Forecasts (ECMWF) Ensemble Prediction System (EC EPS) is compared with that of a number of alternative configurations which incorporate information from additional analyses or an additional model or both. Each configuration is approximately equivalent in size, resolution and computational cost and could therefore in principle provide an alternative operational EPS. A multi‐centre ensemble system (MC EPS) is constructed by replacing half of the EC EPS with integrations of the Met Office (UKMO) model perturbed about the UKMO analysis. Two additional configurations are constructed using the ECMWF model only, but adding information available from four other operational analyses. A ‘consensus’ ensemble (CONS EPS) is generated by adding the operational EC EPS perturbations to the mean of the available analyses (the consensus analysis); a multi‐analysis ensemble (MA EPS) is generated by combining smaller ensembles of ECMWF‐model integrations perturbed about each of the available operational analyses. The different systems are compared over a large sample of 60 cases covering the period October 1998 to July 1999.

All the alternative configurations are found to improve over the EC EPS in terms of ensemble‐mean skill, ensemble spread, and probabilistic evaluation. For 500 hPa height, the MC EPS is consistently the most skilful configuration, but for 850 hPa temperature the MC and MA systems are equivalent. The CONS EPS is generally less skilful than the other two alternatives. The benefit of the MC EPS over the MA EPS for 500 hPa height can be attributed to the combination of different models within the MC EPS. However, it is shown that application of a simple bias correction to the ensemble members removes the advantage of the MC EPS. It is also noted that, by construction, the MC and MA systems have larger initial spread than the EC and CONS configurations. It is demonstrated that increasing the amplitude of the initial perturbations of the CONS EPS improves the performance of this configuration to be comparable with the MC and MA systems. It is concluded that the benefit of the MC EPS can be realized using the single‐model EC EPS incorporating information from additional operational analyses (provided that the issue of model bias is addressed), thus avoiding the technical difficulties of maintaining more than one model in an operational EPS.
A strategy for high‐resolution ensemble prediction. I: Definition of representative members and global‐model experiments
Authors: Molteni F. , Buizza R. , Marsigli C. , Montani A. , Nerozzi F. , Paccagnella T.
Published: February 2007

In the last few years, tens of alternative weather forecasts have been made available to forecasters by operational ensemble prediction systems. In many forecasting applications, it is useful to identify (possibly in an objective way) a few representative ensemble members, deemed to represent the most interesting weather scenarios. In this paper, a strategy to select representative members (RMs hereafter) from an ensemble prediction is developed, and applied to four cases of medium‐range ensemble forecasts performed with the European Centre for Medium‐Range Weather Forecasts (ECMWF) Ensemble Prediction System (EPS). The four case‐studies correspond to events of very intense rainfall (leading to localized floods) in the Alpine region, selected as benchmarks for numerical simulations in the Mesoscale Alpine Programme. The RM selection procedure uses a cluster analysis of the ensemble forecasts as its first step. For each cluster, an RM is defined to be the member with the smallest ratio between its average distance from the members of its own cluster and its average distance from the members of the other clusters. Distances are computed either using an L2‐norm applied to 700 hPa geopotential height fields or an L1‐norm to precipitation fields.

RMs are compared with cluster centroids in the four case‐studies of extreme rainfall. By definition, RMs are characterized by a synoptic‐scale atmospheric flow similar to the flow of the corresponding cluster centroid, but they contain more small‐scale features, especially in the prediction of weather parameters such as precipitation.

RM initial conditions can be used to initiate higher‐resolution global forecasts; alternatively, RMs may be used to define initial and boundary conditions for nested high‐resolution forecasts with limited‐area models. Integrations of RMs with the ECMWF global model at T1 319 horizontal resolution (compared with the T1 159 resolution used in the EPS) were performed. Results indicate that each higher‐resolution forecast, started from RM initial conditions, remains closer to the low‐resolution RM than to other ensemble members, but provides a more detailed forecast of weather parameters, especially in regions of complex topography. Experiments with a nested limited‐area model, started from the same set of RMs, are described in a companion paper.
Microphysical properties of continental clouds from in situ measurements
Authors: Korolev A. V. , Isaac G. A. , Mazin I. P. , Barker H. W.
Published: February 2007

It is important to gain knowledge about the microphysical characteristics of continental clouds in order to properly understand their formation, their radiative properties and their ability to produce precipitation. Satellites to remotely sense cloud properties, and cloud interactions with aircraft that fly through them require knowledge of cloud microphysics. Moreover, numerical simulations of global climate are sensitive to small systematic changes in cloud optical properties, but very few large datasets are available that document the characteristics of continental clouds. This paper summarizes 9 x 104 km of in‐cloud measurements made by the Central Aerological Observatory over the former USSR during 1977‐84. Statistical characteristics of total water content (W), extinction coefficient (β), effective diameter (Deff) and effective concentration (Neff) are summarized as functions of temperature and cloud type, for measurements archived at 700 m horizontal resolution. The effect of threshold sensitivity, or cloud definition, on the statistical distributions is discussed. Decreases of W, β and Neff with colder temperatures are consistent with our general knowledge of cloud formation. For all temperature intervals and cloud types, correlations between pairs of W, β and Deff are too small thereby barring any hope of simple linear parametrizations. Differences in W, β, Deff and Neff for the various cloud types indicate changes in cloud formation mechanisms. These data can assist in verification studies of cloud parametrization schemes in general‐circulation models, numerical weather‐prediction models, and cloud‐resolving models. The problems of cloud type, scale averaging, variability over a model grid cell, distribution of water between the liquid and ice phase, and the lumping together of precipitating and non‐precipitating clouds must be considered in these studies.
FASTEX IOP 18: A very deep tropopause fold. I: Synoptic description and modelling
Authors: Donnadille Jérǒme , Cammas Jean‐Pierre , Mascart Patrick , Lambert Dominique , Gall Robert
Published: February 2007

The life cycle of a very deep tropopause fold (820 hPa) is documented with aircraft and ship observations during the Intensive Observing Period 18 of the Fronts and Atlantic Storm‐Track EXperiment (FASTEX). The initial setting involves a coherent tropopause disturbance and an associated Arctic tropopause fold. The confluence episode that results from the phasing up of the tropopause disturbance and a southern ridge, ends in the formation of an intense jet streak, the dynamics of which are associated with the development of a polar tropopause fold. A diagnostic analysis suggests that the final dramatic stratospheric intrusion is the consequence of the vertical superposition of the Arctic and polar tropopause folds. The Mesoscale Non‐Hydrostatic (Meso‐NH) model is used to discuss this hypothesis. Mixing of the passive stratospheric tracer within the marine boundary layer is investigated with sensitivity tests which unplug, in turn, the model physical parametrizations. Finally, upper‐level forcings associated with the development of the tropopause fold are investigated in detail in a companion paper.
Stacked slantwise convective circulations
Authors: Browning K. A. , Chapman D. , Dixon R. S.
Published: February 2007

It is well known that classical (ana) cold fronts tend to be characterized by mesoscale circulations in which upright line convection feeds a layer of concentrated rearward slantwise ascent. Occasionally, however, as in the case‐study presented in this paper, two and sometimes more of these mesoscale circulations coexist within the same cold‐frontal zone. The two slantwise circulations described were observed to be stacked one above the other with a vertical wavelength of less than 2 km. Although it is often suspected that the circulations at ana‐cold fronts are enhanced by mesoscale processes such as conditional symmetric instability (CSI) or ΔM‐adjustment, it is notoriously difficult to discriminate between these circulations and the larger‐scale transverse circulation within which they are embedded. The occurrence in this study of multiple circulations with small vertical scale helps to distinguish them from the large‐scale circulation, and this has motivated the detailed examination of this case.

Mesoscale circulations of the kind described are difficult to detect: numerical weather prediction (NWP) models, even high‐resolution models, do not usually represent them, and conventional observations do not show them clearly. This study takes advantage of observations from a high‐resolution microwave Doppler radar plus a high‐resolution analysis of ultra‐high‐frequency wind‐profiler radar data, analysed in the context of output from an operational mesoscale NWP model. The study defines the mesoscale structure of the event sufficiently carefully to provide a basis for future idealized modelling studies to investigate the possible roles of CSI and ΔM‐adjustment, both of which appear to play a part in the maintenance of the circulations.
Lightning initiation–conventional and runaway‐breakdown hypotheses
Authors: Solomon R. , Schroeder V. , Baker M. B.
Published: February 2007

We evaluate two candidate mechanisms for the onset of lightning in the relatively low electric fields measured inside thunderstorms. The first is conventional dielectric breakdown due to local enhancement of the electric field in the vicinity of hydrometeors. The second is runaway breakdown, due to extended acceleration of high‐energy electrons (from cosmic rays or terrestrial sources of ionizing radiation) by the in‐cloud electric field. We compare the electric fields required for lightning onset by each mechanism with those observed inside lightning‐producing clouds, and we examine the sensitivity of the computed results to input parameters and assumptions. The conclusion of our analysis is that the conventional breakdown mechanism alone cannot trigger lightning while the runaway breakdown mechanism appears a more likely candidate. We identify the parameters on which each mechanism depends and emphasize the impact of observational uncertainties on our conclusions.
Large wood debris recruitment on differing riparian landforms along a Gulf Coastal Plain (USA) stream: a comparison of large floods and average flows
Authors: Golladay Stephen W. , Battle Juliann M. , Palik Brian J.
Published: February 2007

In southeastern Coastal Plain streams, wood debris can be very abundant and is recruited from extensive forested floodplains. Despite importance of wood debris, there have been few opportunities to examine recruitment and redistribution of wood in an undisturbed setting, particularly in the southeastern Coastal Plain. Following extensive flooding in 1994, measurements of individual downed trees (species, dbh, orientation, distance from base‐flow channel and condition) were made across replicated riparian landforms in a Gulf Coastal Plain 5th‐order stream. Annually, the fate of these trees was determined and newly recruited trees were noted. More than 300 downed trees have been recorded. Recruitment varied across landforms with more constrained reaches having greatest mortality. Total tree mortality varied substantially across years. Generally, tree recruitment was greatest in years with substantial floods (1994 and 1998). For each riparian landform type, tree mortality was correlated with the maximum daily flow during the period preceding annual debris surveys. This relationship was particularly strong for sand ridges (r2 = 0.942) and low terraces (r2 = 0.915), but was significant for floodplains (r2 = 0.413). Greatest rates of debris recruitment per maximum daily flow were observed for sand ridges followed by low terraces. Flood characteristics also influenced debris recruitment. The 1994 flood was caused by a tropical storm and resulted in a rapid rise in streamflow. Much of the debris recruited during this flood was from toppled trees and was oriented parallel to the stream channel. In contrast, the 1998 flood was preceded by a wetter than average winter with more gradually rising flows and there was no relationship between riparian landform and debris characteristics. These results indicate that wood recruitment dynamics in Coastal Plain streams are complex. Wood recruitment rates are controlled by cyclical variations in climate interacting with riparian geomorphology. Infrequent high flows appear critical in the maintenance of the instream debris pool. Copyright © 2007 John Wiley & Sons, Ltd.
On learning thresholds of parities and unions of rectangles in random walk models
Authors: Roch Sébastien
Published: February 2007

In a recent breakthrough, [Bshouty et al., J Comput Syst Sci 71 (2005), 250–265] obtained the first passive‐learning algorithm for DNFs under the uniform distribution. They showed that DNFs are learnable in the Random Walk and Noise Sensitivity models. We extend their results in several directions. We first show that thresholds of parities, a natural class encompassing DNFs, cannot be learned efficiently in the Noise Sensitivity model using only statistical queries. In contrast, we show that a cyclic version of the Random Walk model allows to learn efficiently polynomially weighted thresholds of parities. We also extend the algorithm of Bshouty et al. to the case of Unions of Rectangles, a natural generalization of DNFs to {0,…,b − 1}n. © 2007 Wiley Periodicals, Inc. Random Struct. Alg., 2007
Anatomy of a group model‐building intervention: building dynamic theory from case study research
Authors: Luna‐Reyes Luis Felipe , Martinez‐Moyano Ignacio J. , Pardo Theresa A. , Cresswell Anthony M. , Andersen David F. , Richardson George P.
Published: February 2007

The system dynamics group at the Rockefeller College of the University at Albany has been developing techniques to create system dynamic models with groups of managers during the last 25 years. Building upon their tradition in decision conferencing, the group has developed a particular style that involves a facilitation team in which people play different roles. Throughout these years of experience, the group has also developed several “scripts” to elicit knowledge from experts based on small‐groups research, and well‐established practices in the development of system dynamics models. This paper constitutes a detailed documentation of a relatively small‐scale modeling effort that took place in early 2001, offering a “soup to nuts” description of group model building at Albany. The paper describes in detail nine of the scripts that the group has developed, offering some reflections about their advantages and limitations. Copyright © 2006 John Wiley & Sons, Ltd.
Psychological well‐being and psychosocial work environment characteristics among emergency medical and nursing staff
Authors: Escribà‐Agüir Vicenta , Pérez‐Hoyos Santiago
Published: February 2007

The aim of this study was to determine if the effect of psychosocial work environment on psychological well‐being was different for doctors and nurses who work in emergency departments in Spain. A cross‐sectional survey was carried out among 945 emergency doctors and nurses staff from Spain. The outcome variable was the psychological well‐being measured by two dimensions of SF‐36 Health Survey (SF‐36) (mental health, vitality) and one dimension of Maslach's Burnout Inventory (emotional exhaustion). The explanatory variable was the psychosocial work environment evaluated according to Karasek and Johnson's demand‐control model that includes the dimensions of psychological demands, job control, supervisor social support and co‐workers' social support. The adjusted odds ratios and their 95 per cent confidence intervals were calculated by logistic regression. The prevalence of low vitality, bad mental health and high emotional exhaustion was higher among doctors than nurses. Exposure to high psychological demands increased the probability of low vitality, bad mental health and high emotional exhaustion among doctors and nurses. Low job control and low co‐workers' social support at work were associated with poor psychological well‐being only among doctors. Low job supervisors' social support increased the risk of bad mental health among doctors and of high emotional exhaustion among nurses. There is a different effect of psychosocial work environment on psychological well‐being between doctors and nurses. Copyright © 2007 John Wiley & Sons, Ltd.
Fabrication of CuO nanoparticle interlinked microsphere cages by solution method
Authors: Qi Jian Quan , Tian Hu Yong , Li Long Tu , Chan Helen Lai Wah
Published: February 2007

Here we report a very simple method to convert conventional CuO powders to nanoparticle interlinked microsphere cages by solution method. CuO is dissolved into aqueous ammonia, and the solution is diluted by alcohol and dip coating onto a glass substrate. Drying at 80 °C, the nanostructures with bunchy nanoparticles of Cu(OH)2can be formed. After the substrate immerges into the solution and we vaporize the solution, hollow microspheres can be formed onto the substrate. There are three phases in the as-prepared samples, monoclinic tenorite CuO, orthorhombic Cu(OH)2, and monoclinic carbonatodiamminecopper(II) (Cu(NH3)2CO3). After annealing at 150 °C, the products convert to CuO completely. At annealing temperature above 350 °C, the hollow microspheres became nanoparticle interlinked cages.
Formulation of ultralow interfacial tension systems using extended surfactants
Authors: Witthayapanyanon A. , Acosta E. J. , Harwell J. H. , Sabatini D. A.
Published: February 2007

Inspired by the concept of lipophilic and hydrophilic linkers, extended surfactants have been proposed as highly desirable candidates for the formulation of microemulsions with high solubilization capacity and ultralow interfacial tension (IFT), especially for triglyceride oils. The defining characteristic of an extended surfactant is the presence of one or more intermediate‐polarity groups between the hydrophilic head and the hydrophobic tail. Currently only limited information exists on extended surfactants; such knowledge is especially relevant for cleaning and separation applications where the cost of the surfactant and environmental regulations prohibit the use of concentrated surfactant solutions. In this work, we examine surfactant formulations for a wide range of oils using dilute solutions of the extended surfactant classes sodium alkyl polypropyleneoxide sulfate (R‐(PO)x−SO4Na), and sodium alkyl polypropyleneoxide‐polyethyleneoxide sulfate (R‐(PO)y‐(EO)z−SO4Na). The IFT of these systems was measured as a function of electrolyte and surfactant concentration for polar and nonpolar oils. The results show that these extended surfactant systems have low critical micelle concentrations (CMC) and critical microemulsion concentrations (CμC) compared with other surfactants. We also found that the unique structure of these extended surfactants allows them to achieve ultralow IFT with a wide range of oils, including highly hydrophobic oils (e.g., hexadecane), triolein, and vegetable oils, using only ppm levels of these extended surfactants. It was also found that the introduction of additional PO and EO groups in the extended surfactant yielded lower IFT and lower optimum salinity, both of which are desirable in most formulations. Based on the optimum formulation conditions, it was found that the triolein sample used in these experiments behaved as a very polar oil, and all other vegetable oils displayed very hydrophobic behavior. This unexpected triolein behavior is suspected to be due to uncharacterized impurities in the triolein sample, and will be further evaluated in future research.
Solubility in and affinity for the bile salt micelle of plant sterols are important determinants of their intestinal absorption in rats
Authors: Hamada Tadateru , Goto Hitomi , Yamahira Takashi , Sugawara Takashi , Imaizumi Katsumi , Ikeda Ikuo
Published: February 2007

Intestinal absorption of various plant sterols was investigated in thoracic duct‐cannulated normal rats. Lymphatic recovery was the highest in campesterol, intermediate in brassicasterol and sitosterol, and the lowest in stigmasterol and sitostanol. Higher solubility in the bile salt micelle was observed in sitosterol, campesterol, and sitostanol than in brassicasterol and stigmasterol. The solubility of the latter two sterols was extremely low. When the affinity of plant sterols for the bile salt micelle was compared in an in vitro model system, which assessed sterol transfer from the micellar to the oil phase, the transfer rate was the highest in brassicasterol, intermediate in campesterol and stigmasterol, and lowest in sitosterol and sitostanol. Although no significant correlations between lymphatic recovery of plant sterols and their micellar solubility or transfer rate from the bile salt micelle were observed, highly positive correlation was obtained between the lymphatic recovery and the multiplication value of the micellar solubility and the transfer rate. These observations strongly suggest that both solubility in and affinity for the bile salt micelle of plant sterols are important determinants of their intestinal absorption in rats.
Diacylglycerol acyltransferases from Vernonia and Stokesia prefer substrates with vernolic acid
Authors: Yu Keshun , McCracken Charles T. , Li Runzhi , Hildebrand David F.
Published: February 2007

Genetic engineering of common oil crops for industrially valuable epoxy FA production by expressing epoxygenase genes alone had limited success. Identifying other key genes responsible for the selective incorporation of epoxy FA into seed oil in natural high accumulators appears to be an important next step. We investigated the substrate preferences of acyl CoA: diacylglycerol acyltransferases (DGAT) of two natural high accumulators of vernolic acid, Vernonia galamensis and Stokesia laevis, as compared with a common oilseed crop soybean. Developing seed microsomes were fed with either [14C]oleoyl CoA or [14C]vernoloyl CoA in combinations with no exogenous DAG or with 1,2‐dioleoyl‐sn‐glycerol, 1‐palmitoyl‐2‐vernoloyl‐sn‐glycerol, 1,2‐divernoloyl‐sn‐glycerol, 1,2‐dioleoyl‐rac‐glycerol, or 1,2‐divernoloyl‐rac‐glycerol to determine their relative incorporation into TAG. The results showed that in using sn‐1,2‐DAG, the highest DGAT activity was from the substrate combination of vernoloyl CoA with 1,2‐divernoloyl‐sn‐glycerol, and the lowest was from vernoloyl CoA or oleoyl CoA with 1,2‐dioleoyl‐sn‐glycerol in both V. galamensis and S. laevis. Soybean DGAT was more active with oleoyl CoA than vernoloyl CoA, and more active with 1,2‐dioleoyl‐sn‐glycerol when oleoyl CoA was fed. DGAT assays without exogenous DAG, or with exogenous sn‐1,2‐DAG fed individually or simultaneously showed consistent results. In combinations with either oleoyl CoA or vernoloyl CoA, DGAT had much higher activity with rac‐1,2‐DAG than with their corresponding sn‐1,2‐DAG, and the substrate selectivity was diminished when rac‐1,2‐DAG were used instead of sn‐1,2‐DAG. These studies suggest that DGAT action might be an important step for selective incorporation of vernolic acid into TAG in V. galamensis and S. laevis.
HPLC method for quantification and characterization of cholesterol and its oxidation products in eggs
Authors: Mazalli Mônica R. , Sawaya Alexandra C. H. F. , Eberlin Marcos N. , Bragagnolo Neura
Published: February 2007

A new method was developed for the simultaneous determination of cholesterol and its oxidation products in eggs, using HPLC with UV and refractive index (RI) detectors, and HPLC interfaced with atmospheric pressure chemical ionization coupled to MS (HPLC‐APCI‐MS). The best conditions for direct saponification of the sample and extraction of the nonsaponifiable material were defined using complete factorial designs with central points. The method showed accuracy and precision with a detection limit between 0.002 and 0.079 μg/g. The oxides cholest‐5‐ene‐3β, 20α‐diol identified by HPLC‐UV‐RI were not confirmed by HPLC‐APCI‐MS.
Feasibility of near real‐time image‐guided sinus surgery using intraoperative fluoroscopic computed axial tomography
Authors: Brown Seth M. , Sadoughi Babak , Cuellar Hernando , von Jako Ron , Fried Marvin P.
Published: February 2007

Objective

One of the main limitations of image‐guided surgery is that navigation relies on the use of a CT scan obtained before surgery and is unable to be updated during the procedure. A software addition has been developed to allow reconstruction of CT‐like images from a series of fluoroscopic scans and integrate these into an image‐guided system (GE Healthcare Surgical Navigation, Lawrence, MA). We report our initial experience with a series of patients undergoing intraoperative fluoroscopic navigation in sinus surgery.

Study Design and Settings

After institutional review board clearance, we prospectively studied 14 consecutive patients undergoing image‐guided sinus surgery with the use of intraoperative fluoroscopy.

Results

All patients had preoperative and postoperative fluoroscopic images reconstructed into CT‐like images. By the conclusion of the study, images were adequate in quality and accurate navigation was achieved.

Conclusion

Real‐time image‐guided sinus surgery using fluoroscopy is feasible. Future studies will need to focus on defining the procedures that could benefit, such as tumor resection, to enhance patient safety during these operations.
Efficacy of once‐daily esomeprazole treatment in patients with laryngopharyngeal reflux evaluated by 24‐hour pH monitoring
Authors: Reichel Oliver , Jeanette Keller , Rasp Gerd , Hagedorn Hjalmar , Berghaus Alexander
Published: February 2007

Objective

Laryngopharyngeal reflux (LPR) is generally treated with twice‐daily proton‐pump inhibitor (PPI) therapy. In this study, the efficacy of esomeprazole 40 mg once‐daily together with lifestyle modifications was determined by repeated 24‐hour pH monitoring.

Study Design and Setting

A prospective study. Fortynine patients with suspected LPR underwent 24‐hour pH monitoring. Twenty‐seven of 49 patients with measurable abnormal proximal reflux reflected by a reflux area index (RAI) >6.3 were treated with esomeprazole 40 mg every day, and a second pH study was performed.

Results

In 22 of 27 patients, everyday PPI treatment reduced the RAI. Four of 5 patients with no RAI reduction reported on symptomatic relief.

Conclusion

In a considerable number of patients with suspected LPR, pH monitoring reveals no abnormal proximal reflux. Esomeprazole 40 mg every day together with lifestyle modifications could reach adequate acid suppression in a large number of patients. Symptom improvement is also reported by patients without measurable effects of therapy.
Total laryngectomy and T3‐T4 laryngeal cancer without other adverse histopathology
Authors: Ampil Federico L. , Nathan Cherie Ann O. , Lian Timothy S. , Caldito Gloria , Milligan Edward
Published: February 2007

Objective

We sought to determine the postoperative management, incidence of tumor recurrence in the neck, and outcome in laryngeal cancer patients whose risk for tumor relapse is not clear.

Study Design and Setting

Thirty patients (27 of whom had transglottic tumors) met the study criteria (resected T3‐T4 laryngeal cancer, histologically negative cervical nodes, and no other adverse histopathology). A group of 12 patients who underwent surgery alone was compared with a second group of 18 patients with similar characteristics but who received postoperative radiotherapy.

Results

Overall survival at five years was 50% in the surgery alone group and 61% in the combined therapy group (P = 0.63). Among the 28 evaluable patients with a median follow‐up of 44 months, the relapse rate in the neck was 25% in the surgery alone group and was 0% in the postoperatively irradiated group (P = 0.07). Recurrences in the neck remained uncontrolled in two of the three patients at the time of death.

Conclusion and Significance

Postoperative radiotherapy deserves consideration in selected cases of T3‐T4 laryngeal cancer without adverse histopathology.
Quantifying the source area of macroscopic charcoal with a particle dispersal model
Authors: Peters Matthew Edward , Higuera Philip Edward
Published: February 2007

To aid interpreting the source area of charcoal in lake-sediment records, we compare charcoal deposition from an experimental fire to predictions from a particle dispersal model. This provides both a theoretical framework for understanding how lake sediments reflect fire history and a foundation for simulating sediment-charcoal records. The dispersal model captures the two-dimensional patterns in the empirical data (predicted vs. observed r2 = 0.67, p < 0.001). We further develop the model to calculate the potential charcoal source area (PCSA) for several classes of fires. Results suggest that (1) variations in airborne charcoal deposition can be explained largely by the size of PCSAs relative to fire sizes and (2) macroscopic charcoal travels many kilometers, longer than suggested by dispersal data from experimental fires but consistent with dispersal data from uncontrolled fires.
Regulations and procedures in parasite vaccine development
Authors: SCHETTERS TH. P. M. , GRAVENDYCK M.
Published: February 2007

Although immunisation protocols for a wide variety of parasitic diseases have been developed, it is often questioned why these do not always reach the market. In this review information about the regulations and procedures that apply to licensing the production and marketing of medicinal preparations, especially parasite vaccines, is presented. These general regulations specify issues on product (quality, safety, efficacy and potency) and production (facilities and consistency). Vaccine developers and manufacturers have to comply with these regulations, which may involve years of research and development. Moreover, where the manufacturer claims specific features of the product, these claims have to be corroborated by (experimental) data. A series of principles has been used to develop vaccines against parasite infections varying from the use of (attenuated) live vaccines to killed vaccines and subunit vaccines. The implications of some specific regulatory issues associated with these approaches are discussed.
Evolution of a shoaling internal solitary wavetrain
Authors: Bourgault D. , Blokhina M. D. , Mirshak R. , Kelley D. E.
Published: February 2007

Field observations of an internal solitary wavetrain impacting a shoaling bottom are presented. Measurements of the spatio‐temporal characteristics of the shoaling waves are given, as well as estimations of the mixing they may have caused upon impact. The observations are discussed in the context of numerical simulations, laboratory experiments, and hypotheses recently raised on the origin and evolution of internal solitary waves in coastal environments.
Renewed ground uplift at Campi Flegrei caldera (Italy): New insight on magmatic processes and forecast
Authors: Troise C. , De Natale G. , Pingue F. , Obrizzo F. , De Martino P. , Tammaro U. , Boschi E.
Published: February 2007

Campi Flegrei caldera, including the extremely urbanised city of Naples, is the most risky volcanic area in the World. The last eruption in the area (1538) occurred at the end of some decades of ground uplift, superimposed to secular subsidence. During the last four decades, it experienced a huge uplift phase, reaching about 3.5 m in 1985, when a subsidence phase started. Recent geodetic data demonstrate that such a subsidence phase has terminated, and a new uplift episode started in November 2004, with a low but increasing rate leading to about 0.04 m of uplift till the end of October 2006. A new indicator, based on the monitoring of maximum horizontal to vertical displacement ratio with continuous GPS, indicates that this uplift is likely to be associated with input of magmatic fluids from a shallow magma chamber. The method is promising to monitor magma intrusion processes, at this and other volcanoes.
New Tertiary paleomagnetic poles from Mongolia and Siberia at 40, 30, 20, and 13 Ma: Clues on the inclination shallowing problem in central Asia
Authors: Hankard Fatim , Cogné Jean‐Pascal , Kravchinsky Vadim A. , Carporzen Laurent , Bayasgalan Amgalan , Lkhagvadorj Purevdorj
Published: February 2007

We report results of a paleomagnetic study of 490 cores from 59 sites, corresponding to 52 distinct basaltic flows from Mongolia and Siberia: Khaton Sudal (39.4 Ma, 44.5°N/101.4°E), Taatsyn Gol (1, 31.5 Ma, 45.4°N/101.3°E; 2, 28.0 Ma, 45.5°N/101.1°E), Ust Bokson (19.9 Ma, 52.1°N/100.3°E), and Taatsyn Gol (3, 12.7 Ma, 45.5°N/101.0°E). Stepwise thermal and alternating field demagnetizations isolated a stable high‐temperature component (HTC) of magnetization in most specimens, which we interpret as the primary magnetization of these basaltic lava flows. The four corresponding paleopoles appear consistent with coeval paleopoles from other Asian effusive formations. However, except for the 12.7 Ma paleopole, the paleopoles are systematically far‐sided from the European apparent polar wander path (APWP) with respect to site locations, corresponding to anomalously shallow inclinations in Tertiary Asian effusive formations. In the hypothesis of a dipolar magnetic field in the Tertiary, this indicates a ∼1000–1500 km position of the Siberia craton and Amuria block farther south than expected at 40 and 30 Ma. Tectonically, this interpretation implies decoupling and relative rotations between the western and eastern parts of Eurasia between the Cretaceous and Present. We show that if Siberia were located more to the south, the ∼15°–20° paleolatitude anomaly generally observed in sedimentary formations from central Asia reduces to a more reasonable average value of ∼7°, which could result from the superimposition of shallowing mechanisms due to sedimentary processes and northward motion of Asian blocks under the effect of ongoing penetration of India into Eurasia in the Tertiary.
The 18.6‐year lunar nodal cycle and surface temperature variability in the northeast Pacific
Authors: McKinnell Stewart M. , Crawford William R.
Published: February 2007

The 18.6‐year lunar nodal cycle (LNC) is a significant feature of winter (January) air and sea temperatures along the North American west coast over a 400‐year period. Yet much of the recent temperature variation can also be explained by wind patterns associated with the PNA teleconnection. At Sitka, Alaska, (57°N) and nearby stations in northern British Columbia, the January PNA index accounts for over 70% of average January air temperatures in lengthy meteorological records. It appears that the LNC signal in January air temperatures in this region is not independent of the PNA, but is a component of it. The Sitka air temperature record, along with SSTs along the British Columbia coast and the PNA index have significant cross‐correlations with the LNC that appear at a 2‐year lag, LNC leading. The influence of the PNA pattern declines in winter with decreasing latitude but the LNC component does not. It appears as a significant feature of long‐term SST variation at Scripps Pier and the California Current System. The LNC also appears over centennial‐scales in proxy temperatures along western North America. The linkage of LNC‐moderated surface temperatures to processes involving basin‐scale teleconnections expands the possibility that the proximate mechanism may be located remotely from its expression in the northeast Pacific. Some of the largest potential sources of a diurnal tidal signal in the atmosphere are located in the western Pacific; the Sea of Okhotsk and the Indonesian archipelago.
A Visualization Testbed for Analyzing the Performance of Computational Linguistics Algorithms
Authors: Eick Stephen G. , Mauger Justin , Ratner Alan
Published: February 2007

We have built an AJAX-enabled browser-based testbed for evaluating the performance of computational linguistics algorithms. Our testbed consists of a visualization system and analysis portal. Our focus is on algorithms that classify and cluster documents by assigning weights to words and scoring each document against high-dimensional reference concept vectors. The testbed visualization and algorithm analysis techniques include Confusion Matrices, ROC Curves, Document Visualizations showing word importance, and Interactive Reports. A unique aspect of our testbed is document visualizations built using Scalable Vector Graphics that show why documents are assigned to particular concepts and categories.