bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal oxidative stability and effect of water on gas transport and mechanical properties in PA6‐EVOH films
Authors: Cerruti Pierfrancesco , Laurienzo Paola , Malinconico Mario , Carfagna Cosimo
Published: February 2007

The thermal oxidative stability and the effect of water on gas transport and mechanical properties of blends of polyamide 6 (PA6) with ethylene‐co‐vinyl alcohol (EVOH) and EVOH modified with carboxyl groups (EVOH‐COOH) have been investigated. The presence of EVOH reduces water vapor and oxygen gas permeability of polyamide, as well as small amounts of EVOH‐COOH further improve barrier properties, especially to oxygen. This has been explained in terms of improved interactions of the blend constituents in the amorphous phase, due to ionic linkages between the polyamide amino groups and the carboxyls of modified EVOH. The permeation to gases was found to increase with the amount of sorbed water. The morphology of the samples was found to have an effect on barrier properties, as the presence of EVOH causes the PA6 α crystalline form to increase, lowering the permeability to oxygen and water vapor. Mechanical properties are strongly affected by water sorption, as tensile modulus and strength decrease with increasing water content. Chemiluminescence (CL), infrared spectroscopy (FTIR), and tensile test were employed in order to assess the correlation between chemical composition and the thermal oxidative stability of the films aged at 110 °C in air. CL experiments suggest that the presence of EVOH and EVOH‐COOH efficiently inhibits the formation of peroxidized species during the processing, and increases the thermal oxidative stability of the films. Infrared spectroscopy showed a build‐up of carbonyl absorption in the range 1700–1780 cm−1, due to the formation of oxidation products, which is greater in the case of the pure polymer. Tensile tests on films revealed a reduction in ductility as a result of ageing for neat PA6, whereas in comparison the blends exhibit a far better long‐term stability. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 840–849, 2007
Characterization, solution properties, and morphologies of a hydrophobically associating cationic terpolymer
Authors: Zhong Chuanrong , Luo Pingya
Published: February 2007

The acrylamide‐based terpolymers (PADB) with 4‐butylstyrene (BST) as the hydrophobic monomer and dimethyldiallyammonium chloride (DMDAAC) were synthesized by the micellar free radical technique. The polymer was determined by UV, FT‐IR and 1HNMR, and the hydrophobic microblock structure of PADB was characterized successfully by the conventional DSC measurement. The use of DMDAAC improves the water solubility and intermolecular association of terpolymers. The feed amount of BST affects greatly the apparent viscosity of PADB solution. The polymer exhibits good viscosification property, salt resistance, temperature‐thickening, thixotropy, pseudoplastic behavior and shear‐thickening at low shear rate. The apparent viscosities of PADB solution remarkably increase by the addition of a small amount of surfactant. AFM measurements show that hydrophobic aggregates have been formed in 0.1 g dL−1 PADB aqueous solution, indicative of strong associations of hydrophobic groups, which are reinforced with increasing PADB concentration. The microstructures of PADB are disrupted by the addition of small amounts of salt, resulting in the decrease in solution viscosity. However, with increasing NaCl concentration, the tree‐like associating structures are formed, leading to the increase in the solution viscosity of PADB. The AFM results reveal that the solution properties of PADB are due to the associating structures in the aqueous solution and brine solution. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 826–839, 2007
Voltage‐induced resistivity relaxation in a high‐density polyethylene/graphite nanosheet composite
Authors: Lu Wei , Lin Hongfei , Chen Guohua
Published: February 2007

The resistivity relaxation behavior under applied voltages in a high‐density polyethylene/graphite nanosheet composite was investigated. The influence of applied voltages on the resistivity relaxation was measured by the collection of the electric current passing through the sample and the increasing temperature of the sample. With increments in the voltage, three distinguishable relaxation curves corresponding to different dominating mechanisms were observed. The sawed curve, corresponding to the application of a high voltage, could be attributed to the reorganization of conductive particles induced by the electric field and the destruction of the conductive network due to the thermal expansion of the high‐density polyethylene matrix. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 860–863, 2007
Dynamics of active‐layer detachment failures, Fosheim Peninsula, Ellesmere Island, Nunavut, Canada
Authors: Lewkowicz Antoni G.
Published: February 2007

Dozens of fresh active‐layer detachments were observed on the Fosheim Peninsula in late‐summer 2005 following one week of high air temperatures and nearly continuous bright sunshine. One of these shallow translational landslides started as a minor movement on an upper, steeper slope segment but over several days its front propagated 250 m downslope at velocities of 2–9 m h−1. A second, smaller active‐layer detachment developed within less than 2 hours and subsequent movement was limited. Effective stress analyses can explain the initiation of these landslides on moderate gradients. Movements across extremely low‐angled slope segments, however, likely require both dynamic loading from the moving mass and very low basal undrained shear strengths produced by high porewater pressures. The lengthy development of the large active‐layer detachment helps explain stratigraphic and morphologic features previously observed in these slope failures. Copyright © 2007 John Wiley & Sons, Ltd.
The effect of transient conditions on an equilibrium permafrost‐climate model
Authors: Riseborough Dan
Published: February 2007

Equilibrium permafrost models assume a stationary temperature and snow‐cover climate. With a variable or changing climate, short‐term energy imbalances between the active layer and permafrost result in transient departures from the equilibrium condition. This study examines the effects of such variability on an equilibrium permafrost‐climate model, the temperature at the top of permafrost (TTOP) model. Comparisons between numerical results and temperatures predicted by the TTOP‐model suggest that stationary inter‐annual variability introduces an error in the top‐of‐permafrost temperature obtained with the equilibrium model that is higher where permafrost temperature is close to 0°C, although multi‐year averaging reduces the error to 0.1°C or less. In the presence of a warming trend, the equilibrium model prediction tracked the changing top‐of‐permafrost temperature until permafrost temperatures reached 0°C, after which the equilibrium model produced significant errors. Errors up to 1°C were due to the temperature gradient through the developing talik, and depended on the warming rate, and the thickness of the talik. For all warming rates, the error was largest when the permafrost table was about 4 m below the surface, with the error declining as the permafrost table fell. Copyright © 2007 John Wiley & Sons, Ltd.
Revisiting of a silane explosion in a photovoltaic fabrication plant
Authors: Chang Yo‐Yu , Peng Deng‐Jr , Wu Hong‐Chun , Tsaur Charng‐Cheng , Shen Chun‐Cheng , Tsai Hsiao‐Yun , Chen Jenq‐Renn
Published: February 2007

A second possible cause of a previously described silane explosion is proposed based on a more detailed examination of the physical evidence. The explosion and fire occurred in a silane gas room in a photovoltaic fabrication plant. This investigation recommends more research to investigate the characteristics of a silane release and the resulting fires and explosions. Suggestions are also made for a better silane cylinder valve design and cabinet design. Silane leaks are difficult to detect; therefore the recommendations include the need for a silane gas detector to warn the operator when there are leaks. © 2007 American Institute of Chemical Engineers Process Saf Prog, 2007.
Cross‐resistance profile of mesosulfuron‐methyl‐resistant Italian ryegrass in the southern United States
Authors: Kuk Yong In , Bugos Nilda R
Published: February 2007

Diclofop‐resistant Lolium species (ryegrass) is a major weed problem in wheat production worldwide. This study was conducted to determine the resistance pattern of diclofop‐resistant ryegrass accessions from the southern United States to mesosulfuron‐methyl, a recently commercialized herbicide for ryegrass control in wheat; to determine the cross‐resistance pattern of a Lolium multiflorum Lam. (Italian ryegrass) accession, 03‐1, to acetolactate synthase (ALS) and acetyl‐CoA carboxylase (ACCase) inhibitors; and to determine the resistance mechanism of Italian ryegrass to mesosulfuron‐methyl. Seventeen ryegrass accessions from Arkansas and Louisiana, including standard resistant and susceptible accessions, were used in this experiment. Fourteen of the 17 accessions were more resistant (four‐ to > 308‐fold) to diclofop than the standard susceptible biotype. One accession, 03‐1, was resistant to mesosulfuron‐methyl as well as to other ALS inhibitor herbicides such as chlorsulfuron, imazamox and sulfometuron. Accession 03‐1, however, did not show multiple resistance to the ACCase inhibitor herbicides diclofop, fluazifop, clethodim, sethoxydim and pinoxaden, nor to glyphosate. The in vivo ALS activity of the 03‐1 biotype was less affected by mesosulfuron‐methyl than the susceptible biotype. This indicates that the resistance mechanism of Italian ryegrass to mesosulfuron‐methyl is partly due to an alteration in the target enzyme, ALS. It is concluded that diclofop‐resistant ryegrass in the southern United States can be generally controlled by mesosulfuron‐methyl. However, mesosulfuron‐methyl must be used with caution because not all ryegrass populations are susceptible to it. There is a need for more thorough profiling of ryegrass resistance to herbicides. Copyright © 2007 Society of Chemical Industry
Toxicity and feeding deterrence of crude toxin extracts of Lecanicillium (Verticillium) lecanii (Hyphomycetes) against sweet potato whitefly, Bemisia tabaci (Homoptera: Aleyrodidae)
Authors: Wang Liande , Huang Jian , You Minsheng , Guan Xiong , Liu Bo
Published: February 2007

Crude toxins [toxinV3450 and toxinVp28, extracted from Lecanicillium (Verticillium) lecanii (Zimmermann) Gams & Zare strain V3450 and Vp28 respectively] were tested for contact toxicity, feeding deterrence and repellent activity against the sweet potato whitefly, Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae). Both toxins showed ovicidal activity to eggs, with LC50 values of 447 and 629 mg L−1 respectively. Nymphs of B. tabaci were the most susceptible stages (LC50 values were calculated at 111 mg L−1 for toxinV3450 and 216 mg L−1 for toxinVp28), and adults were the second most susceptible stages (48 h LC50 values were calculated at 178 mg L−1 for toxinV3450 and 438 mg L−1 for toxinVp28). Applied to seedlings at a concentration of 400 mg L−1, the toxins significantly (P < 0.001) reduced the hatching of whitefly eggs and the subsequent survival rate of the nymphs, and the emergence and fecundity of the progeny adults. Both toxins exhibited repellent activity at low concentration (100 mg L−1), with repellency index (RI) values of 0.645 for toxinV3450 and 0.642 for toxinVp28, and antifeedant activity at high concentration (1000 mg L−1) to adults, with antifeedant index (AFI) values of 0.713 for toxinV3450 and 0.749 for toxinVp28. The results of the present study demonstrate the toxicity, repellence and antifeedant properties of the fungi metabolite toxins on B. tabaci, which might develop as environmentally friendly plant protectant(s). Copyright © 2007 Society of Chemical Industry
On the robustness of changes in extreme precipitation over Europe from two high resolution climate change simulations
Authors: Buonomo E. , Jones R. , Huntingford C. , Hannaford J.
Published: February 2007

Two Regional Climate Model (RCM) projections of changes in extreme precipitation over Europe are assessed and compared. This provides insight into the importance of RCM formulation in representing changes in climate extremes at high spatial resolution. The models concerned are two recent Hadley Centre RCMs, HadRM2 and HadRM3, and are applied at a horizontal resolution of approximately 50 km over Europe, nested within the Hadley Centre coupled Atmosphere Ocean General Circulation Model (AOGCM), HadCM2. The simulation periods are thirty years with fixed concentrations of greenhouse gases representing the climate of 1961–1990 and twenty years representing transient climate change for 2080–2100. The use of common boundary conditions to drive the two RCMs allows us to determine whether their different formulations significantly alter the downscaled projections.

The RCM simulations of precipitation extremes are compared with observations from a dense rain‐gauge network over Great Britain, aggregated to the grid used by the RCMs. Both RCMs simulate realistically extreme precipitation occurring over timescales of one to thirty days and for return periods of two to twenty years. In particular, relative errors in the magnitude of extreme precipitation are generally no larger than those in the mean. The two regional models show different patterns of errors for daily precipitation extremes, with the main difference in the western and upland areas of Great Britain where they are underestimated in HadRM2 and overestimated in HadRM3. Change in extremes over all land areas in the domain show increases in intensity everywhere (except for the Iberian peninsula and Mediterranean coast) with most of these significant at the 5% level. Projected increases are greatest for those extremes which are the rarest and shortest duration (i.e. the most intense), both in relative and thus absolute terms. The large‐scale patterns of these changes are very similar in the two RCMs implying they are generally robust to the RCM formulation changes. Given the demonstrated quality of the models this enhances our confidence in the projected changes and suggests that they are mainly conditioned by the large‐scale response in the driving GCM. Copyright Crown Copyright 2007. Reproduced with the permission of the Controller of HMSO. Published by John Wiley & Sons, Ltd
Impact of airborne Doppler lidar observations on ECMWF forecasts
Authors: Weissmann Martin , Cardinali Carla
Published: February 2007

During the Atlantic THORPEX Regional Campaign (A‐TReC) in autumn 2003, the airborne Doppler lidar of the Deutsches Zentrum für Luft‐ und Raumfahrt (DLR) was used to observe wind in predicted sensitive regions. In eight flights, the system measured a total of 1600 wind profiles that were experimentally assimilated in the global assimilation system at the European Centre for Medium‐Range Weather Forecasts (ECMWF). The present study assesses the impact of these Doppler lidar measurements in Numerical Weather Prediction (NWP). It is shown that lidar observations have a significant impact on the analyses as well as on forecasts owing to high accuracy and spatial resolution. The measurements reduce the errors of the 1–4 day forecasts of geopotential height, wind, and humidity over Europe throughout the troposphere. On average, Doppler lidar measurements reduce the 2–4 day forecast error of geopotential height over Europe by 3%. This is a promising result, considering that observations have been gathered from only 28.5 flight hours. Dropsondes released in the same area as the Doppler lidar was operating show good agreement for measured winds, but smaller analysis impact and less reduction of the forecast error. Copyright © 2007 Royal Meteorological Society
Including Coriolis effects in the Prandtl model for katabatic flow
Authors: Stiperski Ivana , Kavčič Iva , Grisogono Branko , Durran Dale R.
Published: February 2007

Katabatic flow down long glaciers in high latitudes experiences deflection due to the Coriolis force. If the Coriolis force is added to the classic Prandtl model for katabatic flow, the cross‐slope wind component does not approach a true steady state, but rather diffuses upwards in time. On the other hand, the down‐slope component and the potential temperature perturbations do reach stationarity on the same time‐scale as in the classic Prandtl model. Numerical and approximate analytic solutions are presented describing this spatio‐temporal behaviour. Both solutions are in accordance with physical intuition. The analytic approximate solution can be useful in boundary‐layer parameterizations and data analysis. Copyright © 2007 Royal Meteorological Society
Using numerical weather prediction to assess climate models
Authors: Rodwell M. J. , Palmer T. N.
Published: February 2007

Estimates of climate change remain uncertain—hampering strategic decision making in many sectors. In large part this uncertainty arises from uncertainty in the computational representation of known physical processes. This model component of climate change uncertainty is increasingly being assessed using perturbed model experiments. Some such model perturbations have, for example, led to headline global warming estimates of as much as 12 °C. These experiments consider many differently perturbed versions of a given base model and assess the likelihood of each perturbed model's climate prediction based on how well it simulates present‐day climate. In these experiments, the computational cost of the model assessment is extremely high unless one assumes that the climate anomalies associated with different model perturbations can be combined linearly. Here we demonstrate a different method, which harnesses the power of the data assimilation system to assess directly the perturbed physics of a model. Data assimilation involves the incorporation of daily observations to produce initial conditions (analyses) for numerical weather prediction (NWP). The method used here quantifies systematic initial tendencies in the first few time steps of a model forecast. After suitable temporal averaging, these initial tendencies imply systematic imbalances in the physical processes associated with model error. We show how these tendencies can be used to produce probability weightings for each model that could be used in the construction of probability distribution functions of climate change. The approach typically costs 5% of the cost of a 100‐year coupled model simulation that might otherwise be used to assess the simulation of present‐day climate. Importantly, since the approach is amenable to linear analysis, it could further reduce the cost of model assessment by several orders of magnitude: making the exercise computationally feasible. The initial tendency approach can only assess ‘fast physics’ perturbations, i.e. perturbations that have an impact on weather forecasts as well as climate. However, recent publications suggest that most of the present model parameter uncertainty is associated with fast physics. If such a test were adopted, assessment of the ability to simulate present‐day climate would then only be required for models that ‘pass’ the fast physics test. The study highlights the advantages of a more seamless approach to forecasting that combines NWP, climate forecasting, and all scales in‐between. Copyright © 2007 Royal Meteorological Society
Comments on deriving the equilibrium height of the stable boundary layer
Authors: Steeneveld G. J. , van de Wiel B. J. H. , Holtslag A. A. M.
Published: February 2007

Recently, the equilibrium height of the stable boundary layer received much attention in a series of papers by Zilitinkevich and co‐workers. In these studies the stable boundary‐layer height is derived in terms of inverse interpolation of different boundary‐layer height scales, each representing a prototype boundary layer. As an alternative we propose an inverse interpolation of the eddy diffusivities for each prototype before applying the definition of the Ekman layer depth. The new equation for the stable boundary‐layer height improves performance in a comparison against four observational datasets. Copyright © 2007 Royal Meteorological Society
Further comments on the equilibrium height of neutral and stable planetary boundary layers
Authors: Zilitinkevich Sergej , Esau Igor , Baklanov Alexander
Published: February 2007

The height of the neutrally and stably stratified turbulent planetary boundary layers (PBLs) in the atmosphere and hydrosphere is controlled by numerous factors of different natures. The PBL deepening is facilitated by turbulent mixing caused, first of all, by the velocity shear at the surface, and prevented by the Earth's rotation and the negative buoyancy forces caused by the flow–surface interaction and the stable static stability in the free atmosphere above the PBL. The balance between these factors is often complicated by the baroclinic shears and large‐scale vertical motions (usually disregarded in field experiments), not to mention temporal and horizontal variability of natural PBL flow. It is not surprising that until now many alternative (sometimes contradictory) formulations for the stable PBL height have been proposed and no consensus achieved. To the authors' opinion, the most natural way to investigate this complex problem is to consider step by step the PBL height in comparatively simple, basic equilibrium regimes (controlled by limited factors), to develop and to validate theoretical models for these regimes, and only afterwards to switch to general diagnostic (equilibrium) and prognostic (non‐steady) equations. In the present paper, we briefly summarize recent investigations following the above strategy, and present new data supporting our earlier theoretical conclusions and recommendations. We would not recommend using PBL height equations inconsistent with firmly established basic‐regime formulations. Copyright © 2007 Royal Meteorological Society
Flash flood forecasting: What are the limits of predictability?
Authors: Collier C. G.
Published: February 2007

Flash floods may occur suddenly and be accompanied by other hazards such as landslides, mud flows, damage to infrastructure and even death. In the UK such events are comparatively rare occurring on average only once or twice per year. Warning systems must depend upon the accurate real‐time provision of rainfall information, high‐resolution numerical weather forecasts and the operation of hydrological model systems in addition to forecast delivery procedures not discussed in this paper. In this paper we review how flash floods are forecast considering the limitations and uncertainty involved in both the meteorological and hydrological aspects of forecasting systems. Data assimilation and the use of ensembles are both key elements across disciplines. Assessing the susceptibility of river catchments to extreme flooding is considered, and statistical methods of estimating the likelihood of extreme rainfall and floods within a changing climate are examined. Ways of constraining flash flood forecasts are noted as one way to improve forecast performance in the future. Copyright © 2007 Royal Meteorological Society
The role of the ocean in the Madden–Julian Oscillation: Implications for MJO prediction
Authors: Woolnough S. J. , Vitart F. , Balmaseda M. A.
Published: February 2007

The role of coupled processes in the Madden–Julian Oscillation (MJO) is investigated in the European Centre for Medium‐Range Weather Forecasts Monthly Forecasting System.

A series of forecasts initialized daily for 47 days during the Tropical Ocean Global Atmosphere Coupled Ocean Atmosphere Response Experiment (TOGA‐COARE) period are performed with sea surface temperatures (SSTs) provided by persistence of initial conditions, and coupling to either a full dynamical ocean model with vertical resolution in the upper ocean typical of coupled models (10 m), or, a 1D mixed layer ocean model with high (∼1 m) vertical resolution in the upper ocean.

The experiment with the full dynamical model shows improved skill compared with the persisted SST experiment, indicating a role for coupled processes in the MJO. The experiment with the mixed layer model shows a further improvement in skill over the full dynamical ocean, particularly for the phases of the MJO where the convection is active over the Indian Ocean or West Pacific. This further improvement comes about from an enhanced sensitivity of the SST to the surface flux anomalies associated with the MJO.

Additional sensitivity experiments reveal that the improved representation of the diurnal cycle which results from the increased vertical resolution is a significant factor in the improved skill of the experiments with the mixed layer model. Copyright © 2007 Royal Meteorological Society
Critical re‐evaluation of the bulk transfer coefficient for sensible heat over the ocean during unstable and neutral conditions
Authors: Ann‐Sofi Smedman , Ulf Sahlée , Erik Högström , Cecilia Johansson
Published: February 2007

A new analysis of the neutral heat transfer coefficient CHN on data from Östergarnsholm is presented, which is primarily based on a limited set of measurements with the very accurate MIUU (Meteorological Institute of the University of Uppsala) instrument, but with additional information from an extensive set of measurements with Solent sonic R2. Sonic data are, however, used with great caution, since for wind speed U above 10 m s−1, a strongly wind‐speed‐dependent correction is shown to be required. This error is roughly proportional to (U − 10) for sea–air temperature differences less than 4–5 K. For a larger temperature difference, no correction appears to be necessary in the wind speed range 10–15 m s−1.

We infer from our data that for conditions when unstable and near‐neutral conditions prevail, measurements of the sea surface—air temperature difference are accurate to within 0.1 K at our site. This means that data for a range of relatively small temperature differences (0.5–1.5 K) which were often rejected in previous studies could be retained. It is observed that a rapid increase of CH and CHN occurs in that range.

For wind speed above 10 m s−1, CHN is observed to increase rapidly with U10. During those conditions, the wave field at the site is known to have characteristics very similar to those in deep‐sea conditions. In a previous analysis of data from Östergarnsholm, it was speculated that observed high CHN values could be due to spray. Calculations with a spray model showed, however, conclusively that for wind speeds less than 14 m s−1, the spray effect on the sensible heat flux is expected to be small. The high CHN values must instead be due to dynamic effects.

It is demonstrated that when the Obukhov length L is less than about − 150 m a regime with very specific characteristics ensues. This regime is dominated by surface‐layer scale eddies, which cause Monin–Obukhov relations for the exchange of sensible heat to break down. The characteristics of this surface‐layer regime are treated in detail in the companion paper.

The rise of CHN with wind speed is shown to be closely related to a corresponding increase of z0T with roughness Reynolds number for winds above 10 m s−1. This means that during those conditions, traditional surface renewal theory for heat is no longer valid. It is suggested that this, in turn, is a result of increasing importance of wave‐breaking with increasing wind and with a possible link to processes in near‐surface atmospheric layers in the regime with −L > 150 m. Copyright © 2007 Royal Meteorological Society
Heat/mass transfer in the slightly unstable atmospheric surface layer
Authors: Smedman Ann‐Sofi , Högström Ulf , Hunt J.C.R. , Sahlée Erik
Published: February 2007

In very slightly unstable conditions, when the Obukhov length is much greater than the surface layer depth, it is observed that the structure of the surface layer turbulence does not accord with standard similarity theory. In particular the efficiency of the turbulent exchange of sensible and latent heat is observed to be more strongly enhanced than is consistent with the standard model. Also the profiles of dissipation of turbulent kinetic energy and temperature fluctuation variance are found to depend on the structure of the whole boundary layer (i.e. are non‐local), indicating that a large‐scale transport process is at work. At the same time, co‐spectral analysis shows how the large‐scale eddy motions that determine the heat transport process near the surface are typically 1/5 of the surface layer depth. All these features are found to be similar in measurements at a marine site and at a flat land site, indicating that they are determined by the dynamics of the whole boundary layer rather than being simply dependent on the surface boundary conditions.

We hypothesize that in slightly unstable conditions there is a bifurcation in the structure of the large‐scale eddy motions. This is a transition from quasi‐steady longitudinal roll structures to detached eddies. In the particular regime identified here, the unsteady component dominates the heat transport at the surface. The observed enhancement in the surface layer of the eddy diffusivity of heat is observed to be significantly greater than for momentum. This is shown to be consistent with observations and with a model calculation of the interaction between the surface layer and the descending detached eddies. Copyright © 2007 Royal Meteorological Society
Thermodynamic functions of conformational changes, part IV: Functional analysis of conformational entropy of substituted ethane and methanol
Authors: Viskolcz Béla , Szori Milan , Izsak Robert , Fejer Szilard N. , Csizmadia Imre G.
Published: February 2007

The thermodynamic functions ΔH and ΔS, were computed along the dihedral angle (x) of conformational change for a few selected single rotors: YCH2CH2Y and YCH2OH. The computations were carried out at the B3LYP/6–31G(d,p) level of theory, with 5° increments in x, under very tight optimization condition. The entropy function, S(x), was generated for the full range (0° to 360°) of internal rotation and was subjected to functional analysis. We found the general rule that S(x) had critical points at or near the critical points of ΔH(x); therefore, (dS/dx) vanished for all critical points (minima and transition states) of ΔH(x). However, the entropy derivative also vanished at certain characteristic conformations that were not manifested on the potential energy or enthalpy function. These geometries were classified as “latent minima” or “latent critical points.” The conformational entropy change was related to the relative information (I/I180) of the same state, where the reference state was chosen to be the anti conformation (x = 180°). According to the relationship ln(I/I180) = −ΔS/R, information accumulation was observed in the case of 1,2‐disubtituted ethane and information depletion occurred in the case of fluoromethanol and ethyl alcohol. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007
Formation of diagnostic product ions from cyanobacterial cyclic peptides by the two‐bond fission mechanism using ion trap liquid chromatography/multi‐stage mass spectrometry
Authors: Mayumi Tsuyoshi , Kato Hajime , Kawasaki Yoshito , Harada Ken‐ichi
Published: February 2007

Product ions obtained by tandem mass spectrometry (MS/MS) are quite effective for the amino acid sequencing of linear peptides. However, in the case of cyclic peptides, the fragmentation pattern is complicated because the cleavages occur randomly and product ions are generated as an, bn, cn, xn, yn and zn series ions; therefore, the authors have never obtained sufficient sequence information. In order to overcome this problem, we applied ion trap liquid chromatography/multi‐stage mass spectrometry (LC/MSn) and characterized the product ions obtained from anabaenopeptins and aeruginopeptins as the cyclic peptides. For the anabaenopeptins, MS2 analysis did not provide sufficient sequence information on the cyclic structure, and MS3 analysis was applied to sequence the constituent amino acids. Diagnostic product ions were obtained by the MS3 analysis and were quite effective for obtaining the sequence information of the constituent amino acids. MS2 analysis was, however, sufficient to obtain the sequence information of the aeruginopeptins. In both cases, the resulting product ions obtained from the cyclic structures were formed by the two‐bond fission mechanism of the precursor ion, in which an initial fission of the cyclic structure to a linear one and subsequent fission(s) at the peptide bonds are included. The fragmentations were similar for the structurally related compounds, indicating that the cleavages occurred at definite peptide bonds. In addition, the resulting product ions are generated as bn series ions and the mass difference facilitates the amino acid sequencing. Thus, ion trap LC/MSn provides sequence information, and the resulting product ions are reproducible among the structurally related compounds and reliable for the sequencing of the constituent amino acids of the cyclic structure. Copyright © 2007 John Wiley & Sons, Ltd.
Mass spectrometric analysis of the individual variability of Bothrops jararaca venom peptide fraction. Evidence for sex‐based variation among the bradykinin‐potentiating peptides
Authors: Pimenta Daniel C. , Prezoto Benedito C. , Konno Katsuhiro , Melo Robson L. , Furtado Maria F. , Camargo Antonio C. M. , Serrano Solange M. T.
Published: February 2007

Variation in the snake venom proteome is well documented and it is a ubiquitous phenomenon at all taxonomical levels. However, variation in the snake venom peptidome is so far not described. In this work we used mass spectrometry [liquid chromatography/mass spectrometry (LC/MS) and matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOFMS)] to explore sex‐based differences among the venom peptides of eighteen sibling specimens of Bothrops jararaca of a single litter born and raised in the laboratory. MALDI‐TOFMS analyses showed individual variability among the bradykinin‐potentiating peptides (BPPs), and, interestingly, four new peptides were detected only in female venoms and identified by de novo sequencing as cleaved BPPs lacking the C‐terminal Q‐I‐P‐P sequence. Similar results were obtained with venom from wild‐caught adult non‐sibling specimens of B. jararaca and in this case we were able to identify the gender of the specimen by analyzing the MALDI‐TOF profile of the peptide fraction and finding the cleaved peptides only in female venoms. Synthetic replicates of the cleaved BPPs were less potent than the full‐length BPP‐10c in potentiating the bradykinin hypotensive effect, suggesting that the C‐terminus is critical for the interaction of the BPPs with their mammalian molecular targets. This work represents a comprehensive mass spectrometric analysis of the peptide fraction of B. jararaca venom and shows for the first time sex‐based differences in the snake venom peptidome of sibling and non‐sibling snakes and suggests that the BPPs may follow distinct processing pathways in female and male individuals. Copyright © 2007 John Wiley & Sons, Ltd.
Effect of Dose, Schedule, and Rate of Administration on Radiosensitization by a High‐Concentration Perflubron Emulsion/Carbogen
Authors: Teicher Beverly A. , Herman Terence S. , Holden Sylvia A. , Liu Shide , Menon Krishna
Published: February 2007

Perfluorochemical emulsions are highly biocompatible materials which carry and deliver oxygen when a high oxygen content atmosphere is breathed. The concentrated perflubron emulsion Oxygent™CA (Oxygent) used in the current study is a second generation perfluorocarbon emulsion which is much more stable and much more concentrated (90% w/v perflubron) than the earlier preparations. In combination with single dose radiation, a range of Oxygent doses corresponding to perfluorochemical levels from 4 to 12 g/kg led to dose modifying factors from 1.2 to 1.9, respectively. With daily fractionated radiation and daily Oxygent administration over the same dosage range, dose modifying factors from 1.4 to 2.1 were achieved. In general, administration of Oxygent prior to each radiation fraction produced the greatest enhancement in tumor response, although the highest dose of Oxygent administered (12 g/kg) on alternate days with daily carbogen breathing produced a comparable tumor growth delay to 4 g/kg of the perfluorochemical emulsion administered daily with carbogen breathing. Rapid administration of the emulsion was necessary to achieve maximal enhancement of tumor growth delay from this therapeutic adjuvant. These results indicate that dose, schedule of administration, and rate of infusion are important variables to consider in the design of clinical trials to maximize the therapeutic benefit achievable with perfluorochemical emulsions as adjuvants to radiation therapy. © 1993 Wiley‐Liss, Inc.
Effects of Tamoxifen on the Radiosensitivity of Hormonally Responsive and Unresponsive Breast Carcinoma Cells
Authors: Wazer David E. , Joyce Melita , Chan Winnie , Gewirtz David , Lin Peck‐Sun , Solares Guido , Schmidt‐Ullrich Rupert K.
Published: February 2007

The effect of tamoxifen on the radiosensitivity of an estrogen receptor positive (ER+) and an estrogen receptor negative (ER−) breast carcinoma cell line was studied in vitro. Tamoxifen concentrations of 1 and 5 μM inhibited the proliferation of ER+ MCF‐7 cells but had little effect on the growth of ER− MDA‐MB‐231. A 48 hr incubation in tamoxifen increased the proportion of G0/G1 MCF‐7 cells, but minimally altered the cell cycle kinetics of MDA‐MB‐231 cells. Tamoxifen resulted in a small but significant increase in the mean inactivation dose of subconfluent cultures of the ER+ cells but had no effect on the ER− cells. The predominant change for MCF‐7 cells was a decrease in the linear damage coefficient, alpha. This was not associated with any enhanced capacity to recover from split radiation fractions. There was no difference in radiosensitivity comparing irradiated log‐phase to immediately plated plateau‐phase cells. However, 24 hr delayed plating of irradiated plateau‐phase cells resulted in decreased radiosensitivity of a magnitude comparable to that seen with tamoxifen. Quantitation of DNA strand fragmentation revealed no difference in the amount of single or double strand break induction nor the kinetics of strand break repair for cultures irradiated with or without tamoxifen. We conclude that tamoxifen results in a small decrease in the radiosensitivity of proliferating hormone responsive breast carcinoma cells and this effect appears to be most related to delay in cycle progression after release from tamoxifen inhibition. © 1993 Wiley‐Liss, Inc.
Radiotherapy Alone in Breast Cancer:Analysis of Tumor Parameters, Tumor and Lymph Node Doses, Lymph Node Control, Distant Metastasis, and Survival Rates—The Experience of the Gustave‐Roussy Institute and the Princess Margaret Hospital
Authors: Arriagada R. , Mouriesse H. , Sarrazin D. , Deboer G. , Bush R. S.
Published: February 2007

This retrospective analysis involved 453 breast cancer patients treated by radiotherapy alone at the Princess Margaret Hospital and at the Institut Gustave‐Roussy. These patients either had operable tumors, but were unfit for general anesthesia, or had inoperable tumors due to local contraindications to surgery. Results were analyzed according to lymph node response, lymph node recurrence rate, distant metastasis rate, survival rate, tumor size, clinical N category, age, tumor dose, axillary dose, and internal mammary chain irradiation. Multivariate analysis permitted the definition of a risk score for axillary lymph node recurrence (RSLN) according to two independent factors: tumor size and clinical N category. It was shown that the RSLNwas a good single composite prognostic factor for lymph node control. Increase in axillary dose gave a similar effect on the axillary lymph node recurrence relative risk for all the RSLNgroups. According to the slope of the axillary dose‐effect curve, it was deduced that a dose increase of 15 Gy can decrease the relative risk of lymph node recurrence 2‐fold. A similar slope was previously described for tumor dose and local control. A risk score for distant metastases (RSM) was calculated according to three independent prognostic factors: tumor size, clinical N category, and age. The RSMwas not influenced by the tumor or the axillary dose but by the treatment of the internal mammary chain. Similar results were obtained for the risk score for death (RSD). The present data emphasize the role of the lymph node radiation dose in the lymph node control of locally advanced breast cancer. © 1993 Wiley‐Liss, Inc.
Role of Tertiary Collimation for Linac‐Based Radiosurgery
Authors: Smith Vernon , Schell Michael C. , Larson David A.
Published: February 2007

For the stereotactic irradiation of intracranial lesions with a linear accelerator, the use of a tertiary collimating system can be expected to confer several benefits in comparison to the use of the standard linac collimating jaw system. Moving the collimator closer to the patient should lead to reduced penumbra and reduced susceptibility to positioning error. In addition, the use of a circular rather than a square aperture should yield a more advantageous dose distribution for irradiation techniques which follow spherical geometry. An investigation using film dosimetry with a tissue‐equivalent head phantom demonstrated that the tertiary system was superior to the standard jaw system as expected. © 1993 Wiley‐Liss, Inc.
Lumbosacral plexopathy secondary to hyperfractionated radiation therapy: A case presentation and literature review
Authors: Johnstone Peter A. S. , Wasscrmann Eric M. , O'Connell Paul G. , Delaney Thomas F.
Published: February 2007

Damage to the lumbosacral plexus is an infrequent complication of radiation therapy to pelvic or spinal lesions. Described is a case of neurologic injury presenting in a young man treated definitively for a paraspinal soft tissue sarcoma. Neurologic symptoms and signs were limited to lower motor neuron deficits without sensory or sphincter disturbances. There remains no evidence of recurrence of the primary lesion. This is the first reported case of lumbosacral plexopathy occurring after a course of hyperfractionated radiotherapy. © 1993 Wiley‐Liss, Inc

This article is a US government work and, as such, is in the public domain in the United States of America.

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Investigations into mechanisms of the interaction between platinum complexes and irradiation at low (∼2 Gy) doses in hypoxic cells: I. Role of single‐strand breaks
Authors: Walter P. , Korbelik M. , Spadinger I. , Skov K.
Published: February 2007

There is a need for radiosensitizers, to be used in conjunction with fractionated radiotherapy (∼2 Gy), because of the resistance of the hypoxic portions of tumors. A marked selective interaction between cisplatin (cis‐diamminedichloroplatinum (II)) and low doses of radiations was reported in hypoxic cells [Korbelik and Skov: Radiat Res 119:145–156, 1989]. A first hypothesis might be the interference with repair of radiationinduced DNA breaks by cisplatin, or vice versa. In order to study these possible mechanisms of interaction, the effects of changing the delivery time of cisplatin before and after low‐dose X‐irradiation of hypoxic cells were investigated. Survival after low doses of X‐rays of both Chinese hamster ovary (CHO) and V79 cells growing exponentially was assessed using the Cell Analyzer for location of individual cells. In cells exposed to cisplatin (2.5 μM for 1 hr) and low doses of X‐rays in hypoxia, the pronounced enhancement ratio (ER; 1.7 in CHO, 1.8 in V79) did not decrease regardless of scheduling (up to 8 hr after or 3 hr before irradiation). Since the repair of single‐strand breaks (SSB) is rapid, it appears that interference with their repair is not a major contribution to the interaction. The longer‐term damage (or misrepair) was examined indirectly by looking at 1) colony size: CHO cells which were irradiated with low doses of X‐rays (1 Gy, hypoxia) or treated with cisplatin (2.5 μM) produced smaller colonies than controls; the data for the combined treatments are presented, and 2) chromosome aberrations in hypoxic CHO cells: the ER for exchanges agrees with the survival data. © 1993 Wiley‐Liss, Inc.
Accelerated repopulation during radiotherapy: Quantitative evidence for delayed onset
Authors: Brenner David J.
Published: February 2007

The time of onset of accelerated tumor‐clonogen repopulation produced by radiotherapy is an important, but unresolved question. The suggestion by Withers et al. [Acta Oncol 27:131–146, 1988] and colleagues [Maciejewski and Majewski: Radiother Oncol 21:163–170, 1991] that onset is delayed has been questioned due to the variety of data sources and the methodology used to reach this conclusion. We describe an analysis of a single clinical data set, which allows a more credible estimate of the time of onset of accelerated repopulation. We analyze a recent report of tumor control of T2 and T3 laryngeal cancer as a function of dose and overall time. By virtue of their broad dynamic range, these results allow an estimate to be made of the time of onset of accelerated repopulation based on a single self‐consistent data set. The analyses suggest that rapid proliferation in these tumors is delayed by an estimated 32 days (95% confidence limits of 21–36 days). For these laryngeal tumors, and within the framework of the linear‐quadratic model, the hypothesis that accelerated repopulation begins at the start of radiotherapy can be rejected in favor of the suggestion that accelerated repopulation begins after 3–5 weeks. This conclusion, if generally true, would have significant ramifications for the design of optimized radiotherapeutic protocols. © 1993 Wiley‐Liss, Inc.
Long‐term results of combined modality therapy for esophageal cancer
Authors: Kavanagh Brian D. , Montana Gustavo S. , Crawford Jeffrey , Wolfe Walter G. , Anscher Mitchell S.
Published: February 2007

Published local control and survival rates strongly suggest the superiority of concurrent chemotherapy (CT) and radiotherapy (RT) over RT alone in the management of esophageal cancer, at least in the first 2–3 years after treatment. It is not yet known, however, if these promising early results will be sustained at 5 years and beyond. The present report updates a series that includes 103 patients with clinical stages I—III esophageal cancer treated with combined RT (44–64 Gy) and CT (5‐fluorouracil or etoposide plus cisplatin or carboplatin) either as definite therapy (n = 45) or as pre‐esophagectomy treatment (n = 58). Five year actuarial local control was 53% in the surgery group and 39% in the group without surgery (P < 0.01). Overall survival of both groups was 14% at 5 years. Late local failures and deaths beyond 3 years occurred in both groups. These results, combined with the few other series documenting 5 year outcomes, are not substantially different from 5 year results reported after RT alone. We conclude that extended follow‐up of 5 years or more is necessary before any combined modality regimen can be considered to be superior to single modality therapy for esophageal cancer. © 1993 Wiley‐Liss, Inc.