bluuebunny/crossref_metadata_2025 huggingface dataset:
Daytime convective development over land: A model intercomparison based on LBA observations
Authors: Grabowski W. W. , Bechtold P. , Cheng A. , Forbes R. , Halliwell C. , Khairoutdinov M. , Lang S. , Nasuno T. , Petch J. , Tao W.‐K. , Wong R. , Wu X. , Xu K.‐M.
Published: March 2006

This paper investigates daytime convective development over land and its representation in single‐column models (SCMs) and cloud‐resolving models (CRMs). A model intercomparison case is developed based on observations of the diurnal cycle and convection during the rainy season in Amazonia. The focus is on the 6 h period between sunrise and early afternoon which was identified in previous studies as critical for the diurnal cycle over summertime continents in numerical weather prediction and climate models. This period is characterized by the formation and growth of a well‐mixed convective boundary layer from the early morning temperature and moisture profiles as the surface sensible‐ and latent‐heat fluxes increase after sunrise. It proceeds with the formation of shallow convective clouds as the convective boundary layer deepens, and leads to the eventual transition from shallow to deep precipitating convection around local noon. To provide a benchmark for other models, a custom‐designed set of simulations, applying increasing in time computational domain and decreasing spatial resolution, was executed. The SCMs reproduced the previously identified problem with premature development of deep convection, less than two hours after sunrise. The benchmark simulations suggest a possible route to improve SCMs by considering a time‐evolving cumulus entrainment rate as convection evolves from shallow to deep and the cloud width increases up to an order of magnitude. The CRMs featuring horizontal grid length around 500 m are capable of capturing the qualitative aspects of the benchmark simulations, but there are significant differences among the models. Two‐dimensional CRMs tend to simulate too rapid a transition from shallow to deep convection and too high a cloud cover. Copyright © 2006 Royal Meteorological Society
A new look at the midlatitude–MJO teleconnection in the northern hemisphere winter
Authors: Kim Baek‐Min , Lim Gyu‐Ho , Kim Kwang‐Yul
Published: March 2006

The midlatitude to Madden–Julian (MJO) teleconnection in the northern hemisphere wintertime was investigated using twenty years of outgoing long‐wave radiation and National Center for Atmospheric Research/National Centers for Environmental Prediction re‐analysis data. It is revealed through empirical orthogonal functions and regression analyses that the tropical upper‐level divergence (convergence) associated with enhanced (reduced) tropical convection has a subtropical counterpart of upper‐level convergence (divergence). As the convective region of MJO moves eastward from the Indian Ocean to the western Pacific, the divergent circulation connecting the Tropics and subtropics moves eastward. From an analysis of vertical motion diagnosed by the generalized omega equation, it was revealed that the position of the subtropical Rossby gyres of the MJO with respect to the Asian‐Pacific jet was the most important factor affecting the existence of the localized divergence (convergence) and associated lower‐level vertical motion in the subtropics. As the subtropical Rossby gyres pass by the longitudinal position of the Asian‐Pacific jet, vertical motion occurs to meet the balance required by quasi‐geostrophic theory. Since this anomalous vertical motion is large enough to cause convection at that region, the diabatic heating process reinforces the vertical motion. Furthermore, other dynamical processes neglected in quasi‐geostrophic theory are activated and contribute to the vertical motion balancing the diabatic heating. As a result of the vertical motion near the jet entrance region in the subtropics, the vorticity advection by vertical wind and the tilting of vorticity become important. Since these two terms are similar in shape and magnitude, they reinforce each other during the development phase of the midlatitude–MJO teleconnection. Combining these two terms, we define the baroclinic jet source (BJS). In order to evaluate the BJS as a source for the midlatitude–MJO teleconnection, a numerical experiment is carried out. The linear barotropic model is forced by only two terms, yet the model captured clearly the main feature of the midlatitude–MJO teleconnection. Copyright © 2006 Royal Meteorological Society
Comparison of the Met Office's surface exchange scheme, MOSES, against field observations
Authors: Rooney G. G. , Claxton B. M.
Published: March 2006

Results are presented from a comparison of the Met Office Surface Exchange Scheme (MOSES) with observational data. A stand‐alone version of MOSES is used which can be forced directly with observations rather than model output. The forcing data consist of near‐surface measurements of incident radiation, wind speed, temperature, pressure, humidity and precipitation, and the model output is compared with measured surface fluxes of sensible and latent heat and with soil moisture at several levels below the surface. The dataset spans four years and comes from a grassland site with a shallow water table, the Met Office Research Unit at Cardington in Bedfordshire, UK.

The performance of the model is assessed in response to the variation of some key parameters and parametric functions. The model calculation of atmospheric fluxes is found to be robust to variations in the soil thermal properties, and it is shown that there is little overall improvement in model performance as the vegetation height and ratio of scalar to momentum roughness lengths are varied over a range of possible values. The calculation of atmospheric moisture flux and soil‐moisture profile is assessed using two constant subsurface profiles of saturated hydraulic conductivity and one profile which decreases with depth. It is found that the last of these can produce a more physically accurate profile of soil moisture, but with current model tuning this produces less accurate values of atmospheric moisture flux. The model results compare favourably with those of a force–restore model. Copyright © 2006 Crown copyright
On the nonlinear interaction between global teleconnection patterns
Authors: Khokhlov V. N. , Glushkov A. V. , Loboda N. S.
Published: March 2006

Processes of nonlinear interaction between teleconnection patterns are addressed. Evidence of chaotic behaviour for the relationship between the Arctic Oscillation (AO), the Southern Oscillation (SO), and the Antarctic Oscillation (AAO) is examined using cross‐redundancy and Granger causality. The analysis is carried out for three epochs of the twentieth century, during which different trends of global temperature were observed. To study the influence of low‐frequency variations, a wavelet decomposition is applied. Presented results display many well‐known features of feedbacks between climate change and observed trends in the indices of teleconnection patterns. By using wavelet detail components, some behaviour is revealed as being particularly pure. At the same time, some findings require considerable further work, especially the apparent nonlinear interaction between the AO and the AAO. Our results are encouraging for the prospects of a useful model describing climate changes at the decadal and centurial time‐scales. Copyright © 2006 Royal Meteorological Society
Comment on ‘The local isotropy hypothesis and the turbulent kinetic energy dissipation rate in the atmospheric surface layer’ by M. Chamecki and N. L. Dias (October B, 2004, 130, 2733–2752)
Authors: Smalley R. J. , Antonia R. A.
Published: March 2006

The velocity–velocity‐increment correlation is shown to be an incorrect method for determining the interaction between the energy‐containing and inertial‐range scales of a turbulent flow. As a consequence, the correlation cannot be used as a means for testing the local isotropy hypothesis. Copyright © 2006 Royal Meteorological Society
Reply to a comment by R. J. Smalley and R. A. Antonia on ‘The local isotropy hypothesis and the turbulent kinetic energy dissipation rate in the atmospheric surface layer’ (October B, 2004, 130, 2733–2752)
Authors: Chamecki M. , Dias N. L.
Published: March 2006

In response to Smalley and Antonia's comment, we agree that our statement that closer‐to‐zero velocity–velocity‐increment correlation for larger turbulence intensity values cannot be taken as a measure of homogeneity. We also explain that, although not aware that the velocity–velocity‐increment correlation cannot be zero at finite r1, we concentrated most of our analysis on its tendency towards zero with decreasing r1, since this limit is well known for homogeneous turbulence. Copyright © 2006 Royal Meteorological Society
Life cycles of North Atlantic teleconnections under strong and weak polar vortex conditions
Authors: Walter Katrin , Graf Hans‐F
Published: March 2006

This paper investigates the role of the strength of the polar stratospheric winter vortex in the dynamics of the life cycles of North Atlantic teleconnections. A new set of teleconnection patterns was produced from low‐pass‐filtered daily 300 hPa height data of NCEP (National Centers for Environmental Prediction) reanalysis data 1958–1998. All teleconnections are meridional dipoles, which to a certain degree resemble the North Atlantic Oscillation based on surface pressure data. There are two distinct teleconnections (one over the eastern and one over the western North Atlantic) during episodes of weak polar vortex, and only one, over the central North Atlantic, during strong polar vortex episodes. The teleconnections have periods of about two weeks. Stream function tendency analysis of the life cycles shows that the relatively simple resulting teleconnections evolve from very complex structures. During the growth phase of the teleconnection indices there are strong and systematic differences between the two polar vortex regimes. While in the weak vortex regime the anomaly growth is mainly driven by transient eddy vorticity fluxes from the low‐frequency domain, in the strong vortex regime there is also low‐frequency advection of relative vorticity resulting from the interaction of low‐frequency eddies with stationary eddies. Copyright © 2006 Royal Meteorological Society
Simulation of shallow cumuli and their transition to deep convective clouds by cloud‐resolving models with different third‐order turbulence closures
Authors: Cheng Anning , Xu Kuan‐Man
Published: March 2006

The abilities of a cloud‐resolving model (CRM) with double‐Gaussian based and quasi‐Gaussian based third‐order closures (TOCs) to simulate shallow cumuli and their transition to deep convective clouds are compared in this study. The quasi‐Gaussian based TOC is fully prognostic (FP), while the double‐Gaussian based TOC is intermediately prognostic (IP). The latter only predicts three important third‐order moments while the former predicts all the third‐order moments. A shallow cumulus case is simulated by single‐column versions of the FP and IP TOC models and a large‐eddy simulation (LES). The IP TOC improves the simulation of shallow cumulus greatly over the FP TOC by producing more realistic cloud structures, when both are compared to LES. Large differences of the second‐ and third‐order moments between the FP and IP TOC simulations appear in the cloud layer, because the cloud top height is underestimated by the FP TOC simulation. Sensitivity experiments and analysis of probability density functions (pdfs) used in the TOCs show that both the turbulence‐scale condensation and higher‐order moments are important to realistic simulations of the boundary‐layer shallow cumuli.

A shallow to deep convective cloud transition case is also simulated by the two‐dimensional (2‐D) version of the CRM with FP and IP TOCs. Both simulations can capture the transition from the shallow cumuli to deep convective clouds. The IP simulations produce more and deeper shallow cumuli than the FP simulations, but the FP simulations produce larger and wider convective clouds than the IP simulations. The temporal evolutions of cloud and precipitation are closely related to the turbulent transport, the cold pool and the cloud‐scale circulation. The large amount of turbulent mixing associated with the shallow cumuli slows down the increase of the convective available potential energy and inhibits the early transition to deep convective clouds in the IP simulation. When the deep convective clouds fully develop and the precipitation is produced, the cold pools produced by the evaporation of the precipitation are not favourable to the formation of shallow cumuli. As a whole, the IP simulations are able to more realistically capture the transition processes than the FP simulations, when both are compared to an LES‐resolution 3‐D simulation of the same case. Copyright © 2006 Royal Meteorological Society
A low‐ozone episode during the European heatwave of August 2003
Authors: Orsolini Yvan J. , Nikulin Grigory
Published: March 2006

An intense low‐ozone episode (LOE) was observed over Scandinavia and the North Sea in the middle of August 2003. The LOE occurred under exceptional meteorological conditions, associated with a severe heatwave over Europe. The column ozone minimum for summer (June, July and August) 2003 was reached during the event.

Using meteorological analyses, satellite ozone observations from the Total Ozone Mapping Spectrometer and the Michelson Interferometer for Passive Atmospheric Sounding aboard the Environment Satellite, we demonstrate that the LOE results from the conjunction of a deep tropospheric blocking over Europe, and a displaced Arctic pool of low‐ozone air in the stratosphere, above the anticyclone. The anticyclonic anomaly is part of a Rossby wave train that is apparent throughout the troposphere, and whose influence is felt up to 50 hPa. In the mid‐stratosphere (e.g. 30 hPa) long‐period westward propagating planetary waves dominate, with a ridge extending over northern Europe in mid‐August.

We band‐pass filtered the geopotential field to isolate sub‐monthly fluctuations, and calculated three‐dimensional wave activity fluxes for quasi‐stationary, quasi‐geostrophic disturbances embedded in a zonally asymmetric basic state. Results clearly indicate that upward wave fluxes in the lower stratosphere originate from the Atlantic sector, upstream of the maturing blocking. Copyright © 2006 Royal Meteorological Society
Impact study of the 2003 North Atlantic THORPEX Regional Campaign
Authors: Fourrié Nadia , Marchal David , Rabier Florence , Chapnik Bernard , Desroziers Gerald
Published: March 2006

An experiment took place during autumn 2003 with the aim of testing the feasibility of an operational targeting of observations over the North Atlantic Ocean in the context of the international programme THORPEX. The purpose of this paper is to evaluate the impact of these additional observations in the French operational model ARPEGE during the last three weeks of the campaign. Results are shown for large regions over and around the North Atlantic Ocean and for specific verification areas. Over Europe, the addition of observations is slightly beneficial for the forecast, mostly in the low troposphere over wide areas and above 100 hPa. However, the impact of extra data is more significant but also more mixed for the dedicated verification areas: they are case, forecast‐range and level dependent. In addition, the information content is studied with the Degrees of Freedom for Signal (DFS) for the evaluation of the observation impact on the analysis of one case of December 2003. Firstly, the variations of the DFS have been illustrated in a simplified data assimilation system. It has been found for that case that satellite data have the most important global contribution to the overall analysis, especially the humidity sensitive infrared radiances. For the conventional data, the wind measurements of the aircraft and from the geostationary satellites are the most informative. For the targeted area, the data from aircraft and the dropsondes have the largest DFS. It has been noted that the DFS of the dropsondes located in the sensitivity maximum is larger than the other one even if there is no link between the DFS and the forecast. However, the impact of the dropsondes grows with respect to the forecast range and leads to an improvement of the forecast for this case. Copyright © 2006 Royal Meteorological Society
Laboratory investigation of positive streamer discharges from simulated ice hydrometeors
Authors: Petersen Danyal , Bailey Matthew , Hallett John , Beasley William H.
Published: March 2006

Positive streamer discharges have been observed from ice crystals grown from the vapour under controlled temperature and air pressure corresponding to the standard atmosphere and also constant air pressure of 850 hPa. Crystals of size comparable to larger precipitation crystals were grown in a vapour diffusion chamber at various temperatures and pressures, and were subject to electric fields using an in situ electrode assembly. Results show that individual positive streamer discharges can occur at temperatures from near freezing down to at least −38°C when subject to electric fields on the order of 500kV m−1, in contrast to previous reports of continuous positive streamer discharges occurring only at temperatures warmer than −18°C for pure ice crystals. These results suggest that positive streamer discharges can occur on frozen precipitation particles at high altitudes in thunderclouds, given a sufficiently strong electric field. Such discharges may be a necessary element of the lightning‐initiation process. Copyright © 2006 Royal Meteorological Society
Vertically integrated sensible‐heat budgets for stable nocturnal boundary layers
Authors: Nakamura Reina , Mahrt L.
Published: March 2006

The stable nocturnal boundary layer is commonly viewed or modelled as a balance between the temperature tendency (cooling) and vertical heat‐flux divergence. Sometimes the radiative‐flux divergence is also included. This perspective has dictated the design of field experiments for investigating stable nocturnal boundary layers.

Tower‐based micrometeorological data from three field campaigns are analysed to evaluate the vertically integrated sensible‐heat budget for nocturnal stable conditions. Our analysis indicates frequent occurrence of large imbalance between the temperature tendency and vertical heat‐flux divergence terms. The values of the radiative‐flux divergence are generally too small and sometimes of the wrong sign to explain the residual. An analysis of random flux errors and uncertainties in the tendency term indicate that such errors cannot explain large imbalances, suggesting the importance of advection of temperature or possibly the divergence of mesoscale fluxes. The implied role of advection is consistent with circumstantial evidence. Even weak surface heterogeneity can create significant horizontal gradients in stable boundary layers. However, it is shown that existing field data and observational strategy do not allow adequate evaluation of advection and mesoscale flux divergence terms. Copyright © 2006 Royal Meteorological Society
Seasonal forecasting of tropical storm frequency using a multi‐model ensemble
Authors: Vitart Fr'ed'eric
Published: March 2006

The skill of seven coupled ocean–atmosphere models to predict the frequency of tropical storms from 1987 to 2001 has been assessed using a procedure for tracking model tropical storms. The tropical storm tracker takes account of the difference of atmospheric horizontal resolution between the different models. Results indicate that the models display some skill in predicting the interannual variability of tropical storms over the Atlantic, the eastern North Pacific, the western North Pacific, the Australian basin and the South Pacific. A simple multi‐model forecast has been built by adding all the seven ensemble forecasts together after calibration. The skill of the simple multi‐model system is overall better than the skill of any individual model. Over a specific basin, combining several models leads to better forecasts than the best individual model. This indicates that the multi‐model approach could benefit the dynamical seasonal forecast of tropical storms.

This conclusion is also valid for a longer time period (1959–2001). However, the individual models and the simple multi‐model display less skill in predicting the interannual variability of tropical storms in the earlier decades. Copyright © 2006 Royal Meteorological Society
Impact of flow‐dependent analysis‐error covariance norms on extratropical singular vectors
Authors: Buehner Mark , Zadra Ayrton
Published: March 2006

Flow‐dependent analysis‐error covariances are estimated from the 128 member analysis ensembles of a pre‐operational implementation of the ensemble Kalman filter. Singular vectors are then computed with the initial‐time norm defined using the inverse of these error covariances and the final‐time norm defined by the total energy over North America. An optimization time interval of either 24 or 48 hours is used and the horizontal resolution of the singular vectors is 3°. Provided that the analysis‐error covariance estimates are accurate, these singular vectors should optimally explain the forecast error at the final time. To reduce the sampling error due to the small ensemble size, the analysis‐error covariances are spatially localized. The impact of using the analysis‐error covariance norm, with or without spatial localization, on the 20 leading singular vectors is measured relative to using the total‐energy norm. In addition, the singular vectors are also compared with sets of 20 randomly selected members of the analysis ensembles.

The results are generally consistent with those of previous studies with the maximum impact from the initial‐time norm seen at the initial time. The growth is significantly reduced by using the analysis‐error covariance norm instead of total energy and the smallest growth is obtained when no covariance localization is applied. The total‐energy singular vectors are slightly more effective at explaining forecast error for most lead times than the analysis‐error covariance singular vectors. This may point to errors in the covariance estimates, the importance of model error in affecting forecast‐error evolution, or shortcomings with the tangent linear model used to compute the singular vectors. The use of a random selection of members from the analysis ensembles shows an even larger impact. In contrast with the singular vectors that continuously grow over the 72 h period examined, the total energy of the ensemble members initially decays during tangent linear model integrations. Also, the amount of forecast error explained by the ensemble members is significantly less than for all types of singular vectors. This suggests that, with respect to predicting forecast uncertainty over North America, the current approach of randomly selecting analysis ensemble members to initialize the ensemble prediction system may be improved. Copyright © 2006 Crown copyright
Subseasonal‐to‐interdecadal variability of the Australian monsoon over North Queensland
Authors: Robertson Andrew W. , Kirshner Sergey , Smyth Padhraic , Charles Stephen P. , Bates Bryson C.
Published: March 2006

Daily rainfall occurrence and amount at 11 stations over North Queensland are examined for summers 1958–1998, using a Hidden Markov Model (HMM). Daily rainfall variability is described in terms of the occurrence of five discrete ‘weather states’, identified by the HMM. Three states are characterized respectively by very wet, moderately wet, and dry conditions at most stations; two states have enhanced rainfall along the coast and dry conditions inland. Each HMM rainfall state is associated with a distinct atmospheric circulation regime. The two wet states are accompanied by monsoonal circulation patterns with large‐scale ascent, low‐level inflow from the north‐west, and a phase reversal with height; the dry state is characterized by circulation anomalies of the opposite sense. Two of the states show significant associations with midlatitude synoptic waves.

Variability of the monsoon on time‐scales from subseasonal to interdecadal is interpreted in terms of changes in the frequency of occurrence of the five HMM rainfall states. Large subseasonal variability is identified in terms of active and break phases, and a highly variable monsoon onset date. The occurrence of the very wet and dry states is somewhat modulated by the Madden–Julian oscillation. On interannual time‐scales, there are clear relationships with the El Niño–Southern Oscillation and Indian Ocean sea surface temperatures (SSTs). Interdecadal monsoonal variability is characterized by stronger monsoons during the 1970s, and weaker monsoons plus an increased prevalence of drier states in the later part of the record.

Stochastic simulations of daily rainfall occurrence and amount at the 11 stations are generated by introducing predictors based on large‐scale precipitation from (a) reanalysis data, (b) an atmospheric general circulation model (GCM) run with observed SST forcing and (c) antecedent June–August Pacific SST anomalies. The reanalysis large‐scale precipitation yields relatively accurate station‐level simulations of the interannual variability of daily rainfall amount and occurrence, with rainfall intensity less well simulated. At some stations, interannual variations in 10‐day dry‐spell frequency are also simulated reasonably well. The interannual quality of the simulations is markedly degraded when the GCM simulations are used as inputs, while antecedent Pacific SST inputs yield an anomaly correlation skill comparable to that of the GCM. Copyright © 2006 Royal Meteorological Society
Resonant and Non-Resonant Sound Transmission through a Finite Panel
Authors: Trevathan Jeremy W. , Pearse John R.
Published: March 2006

The contributions of resonant and non-resonant components to the overall sound transmission through a finite panel have been studied numerically. It was seen that the fundamental mode makes a significant contribution to the non-resonant sound transmission through a finite panel. Therefore, the non-resonant sound transmission loss of a finite panel can be determined, when using a coupled finite element/boundary element analysis, by constructing a structural model with only the fundamental mode in the modal database. The sound transmission loss obtained using this method represents the non-resonant transmission loss of the panel at all frequencies apart from those in the vicinity of the natural frequency of the fundamental mode. The analysis of panels containing higher order modes showed that these modes only contribute to the overall sound transmission loss of a panel at frequencies close to their natural frequencies. The resonant contribution of these higher order modes is reduced by the presence of damping.
Effects of Air-Layer Subdivision: A New Method of Improving Sound Insulation
Authors: Toyoda Masahiro , Tanaka Mikito , Takahashi Daiji
Published: March 2006

In the impact of floors, sound transmission through walls, and structure-borne sound transmission in buildings, there is a possibility of improving the insulation by restricting the air particle motion at the interface of the vibrating surface and the air. One of the practical ways for realizing this condition is by subdividing the air layer at the interface in the direction parallel to the radiating surface. This novel method for noise control has an attractive simplicity and a real practical benefit. In this paper, the mechanism, causing this effect, is discussed using analytical models of acoustic radiation and sound transmission. As a result of this investigation, it is seen that the effect of this method is characterized by reduction of acoustic radiation at low frequencies near and below the critical frequency of coincidence. The method is validated experimentally.
Sound Flanking Transmission: Assessment by a Slit Method
Authors: Martína M.A. , Tarrero A.I. , Aparicio A. , González J. , Machimbarrena M.
Published: March 2006

The aim of this study is to understand the effect of flanking transmissions on room sound transmission. For this purpose, three tests have been carried out in-situ in three rooms with similar layout. The assessment method consisted of cutting one or two slits on the source room walls and measuring before and after cutting. Measurements of air-borne sound insulation, impact sound isolation (with impact on the source room lateral walls) and acceleration measured on the receiving room lateral walls, were made.

The slit prevent transmission of wall vibration, originated by sound excitation, and thus allows us to quantify the associated flanking transmission. It is also shown that, if the slit is sealed with silicone, there is almost no change in the results, and it can be concluded that it is the difference in impedance, which prevents transmission.
Measurement of the Sound Reduction Index as a Function of the Incidence Angle by Two Different Methods
Authors: Brutel-Vuilmet Claire , Guigou-Carter Catherine , Villot Michel , Jean Philippe
Published: March 2006

Generally sound reduction index R is measured for an incident diffuse field, and does not take into account the angular dependency. However, the variation of reduction index with direction of incoming wave can be significant, and it may be necessary to consider the angular influence in acoustical transmission problems, especially when considering directional noise sources. This paper presents two experimental methods, developed to measure the sound reduction index as a function of the incidence angle. Two set-ups, implemented in standard acoustical transmission laboratories, have been tested. In the first system, the vibrating wall is excited by a sound source which simulates a plane wave, with a given incidence angle. This incident field is generated by an acoustical horn. The reduction index R(θ) is obtained sequentially, for different angular positions of the source, from both the measurement of the outside wall pressure level and the transmitted pressure level. In the second system, the studied structure is excited by a diffuse field, and a wave by wave decomposition of the radiated intensity yields the reduction index as a function of the angle of incidence. The decomposition of the radiated intensity is based on the use of an acoustical holography technique, NAH-Phonoscopy. The mathematical formulation of the two methods is detailed. Experimental results are presented and compared to theoretical data. Then, the advantages and limits of each system are discussed.
Empirical Prediction of Workshop Fitting Densities for Noise Prediction by Ray Tracing
Authors: Hodgson Murray , Scherebnyj Katrina
Published: March 2006

Empirical models were developed for predicting frequency-varying fitting densities in industrial workshops for use in the prediction of noise levels by a ray-tracing model. Eleven typical workshops with varying dimensions, types, quantities and distributions of fittings, in which octave-band sound-propagation curves and the fitting dimensions had been measured, were involved. The workshops were modeled and sound-propagation curves were predicted for a range of fitting densities. The predicted curves were compared with the measured curves to determine the ‘best-fit’ fitting density. Linear-regression analysis was then used to find empirical models for predicting the best-fit fitting densities from physical parameters calculated from the fitting and workshop dimensions. The average fitting-to-workshop height ratio, the fitting-to-workshop volume ratio and the number of fittings were the parameters that predicted the fitting density best. Preliminary validation work, involving the comparison of sound-propagation curves predicted with the empirically-predicted fitting densities by ray tracing and the curves measured in four other workshops, suggests that the empirical models are inherently valid.
Industrial Noise in Nigeria: Measurements, Analysis, Dose and Effects
Authors: Onuu Michael U. , Akpan Aniefiok O.
Published: March 2006

Industrial noise pollution has been assessed in 27 industries in south-eastern Nigeria. A total of 750 workers were contacted with working schedules of 6–12h/day, over 5 working days and with exposure times that varied between 0 second and 37.5 minutes were contacted. Noise exposure ratings of greater than unity were found in over 20 of the industries. Although almost all the workers contacted wanted occupational noise pollution controlled because of its various effects on them, a few still responded that they liked occupational noise. This gives credence to the assertion that ignorance of the irreversible nature of the far-reaching and wide-ranging effects of environmental noise pollution could yet be one reason for the “willing” exposure of the industrial plant workers to occupational noise.
Yeast initiator tRNA identity elements cooperate to influence multiple steps of translation initiation
Authors: Kapp Lee D. , Kolitz Sarah E. , Lorsch Jon R.
Published: March 2006

All three kingdoms of life employ two methionine tRNAs, one for translation initiation and the other for insertion of methionines at internal positions within growing polypeptide chains. We have used a reconstituted yeast translation initiation system to explore the interactions of the initiator tRNA with the translation initiation machinery. Our data indicate that in addition to its previously characterized role in binding of the initiator tRNA to eukaryotic initiation factor 2 (eIF2), the initiator-specific A1:U72 base pair at the top of the acceptor stem is important for the binding of the eIF2•GTP•Met-tRNAi ternary complex to the 40S ribosomal subunit. We have also shown that the initiator-specific G:C base pairs in the anticodon stem of the initiator tRNA are required for the strong thermodynamic coupling between binding of the ternary complex and mRNA to the ribosome. This coupling reflects interactions that occur within the complex upon recognition of the start codon, suggesting that these initiator-specific G:C pairs influence this step. The effect of these anticodon stem identity elements is influenced by bases in the T loop of the tRNA, suggesting that conformational coupling between the D-loop–T-loop substructure and the anticodon stem of the initiator tRNA may occur during AUG codon selection in the ribosomal P-site, similar to the conformational coupling that occurs in A-site tRNAs engaged in mRNA decoding during the elongation phase of protein synthesis.
Bone remodelling around a cemented polyethylene cup
Authors: Shetty N. R. , Hamer A. J. , Kerry R. M. , Stockley I. , Eastell R. , Wilkinson J. M.
Published: March 2006

The aims of this study were to examine the repeatability of measurements of bone mineral density (BMD) around a cemented polyethylene Charnley acetabular component using dual-energy x-ray absorptiometry and to determine the longitudinal pattern of change in BMD during the first 24 months after surgery.

The precision of measurements of BMD in 19 subjects ranged from 7.7% to 10.8% between regions, using a four-region-of-interest model. A longitudinal study of 27 patients demonstrated a transient decrease in net pelvic BMD during the first 12 months, which recovered to baseline at 24 months. The BMD in the region medial to the dome of the component reduced by between 7% and 10% during the first three months, but recovered to approximately baseline values by two years.

Changes in BMD in the pelvis around cemented acetabular components may be measured using dual-energy x-ray absorptiometry. Bone loss after insertion of a cemented Charnley acetabular component is small, transient and occurs mainly at the medial wall of the acetabulum. After two years, bone mass returns to baseline values, with a pattern suggesting a uniform transmission of load to the acetabulum.
Interpersonal sensitivities: Their links to mood, anger and gender
Authors: Gilbert P. , Irons C. , Olsen K. , Gilbert J. , McEwan K.
Published: March 2006

This paper explores two interpersonal sensitivities (to rejection and to social put‐down) in a group of 54 depressed men and 50 depressed women. Measures of anhedonia, anxiety, anger, social comparison, and submissive behaviour were also obtained. We found no differences in rejection sensitivity, anger, anhedonia, or anxiety between the sample of depressed men and women. Depressed women rated themselves as more submissive and more inferior than depressed men, and blamed themselves more for being criticized and put‐down by other people. Principal components analysis (PCA) revealed three underlying factors: mood (including anxiety and depression), internalization (related to self‐blame and feelings of low rank), and externalization (related to anger and blaming others for criticism). For both men and women internalization was significantly correlated with depression. However, externalization was negatively related to depression in women, but positively related to depression in men.
Prediction of Source Rock Origin by Chemometric Analysis of Fourier Transform Infrared—Attenuated Total Reflectance Spectra of Oil Petroleum: Evaluation of Aliphatic and Aromatic Fractions by Self-Modeling Mixture Analysis
Authors: Abbas Ouissam , Dupuy Nathalie , Rebufa Catherine , Vrielynck Laurence , Kister Jacky , Permanyer Albert
Published: March 2006

This study describes a new methodology for the interpretation of Fourier transform infrared (FT-IR) attenuated total reflectance (ATR) spectra of Algerian, Brazilian, and Venezuelan crude oils. It is based on a comparative study between a chemometric treatment and the classical one, which refers to indices calculation. In fact, the combined use of FT-IR indices and principal component analysis (PCA) has led to the classification of the studied samples in terms of geographic distribution. Quantitative analysis has been successfully realized by the supervised method partial least squares (PLS), which has permitted the prediction of the locations of oils. We have also applied another mathematical processing method, simple-to-use interactive self-modeling mixture analysis (SIMPLISMA), to evaluate the aromatic and aliphatic composition of the oils by extracting pure spectra representative of the different fractions.
Second-Order Calibration of Excitation—Emission Matrix Fluorescence Spectra for the Determination of N-Phenylanthranilic Acid Derivatives
Authors: de la Peña A. Muñoz , Mansilla A. Espinosa , Díez N. Mora , Gil D. Bohoyo , Olivieri A. C. , Escandar G. M.
Published: March 2006

A spectrofluorimetric method has been developed for the quantitative determination of mefenamic, flufenamic, and meclofenamic acids in urine samples. The method is based on second-order data multivariate calibration (unfolded partial least squares (unfolded-PLS), multi-way PLS (N-PLS), parallel factor analysis (PARAFAC), self-weighted alternating trilinear decomposition (SWATLD), and bilinear least squares (BLLS)). The analytes were extracted from the urine samples in chloroform prior to the determination. The chloroform extraction was optimized for each analyte, studying the agitation time and the extraction pH, and the optimum values were 10 minutes and pH 3.5, respectively. The concentration ranges in chloroform solution of each of the analytes, used to construct the calibration matrix, were selected in the ranges from 0.15 to 0.8 μg mL−1 for flufenamic and meclofenamic acids and from 0.25 to 3.0 μg mL−1 for mefenamic acid. The combination of chloroform extraction and second-order calibration methods, using the excitation–emission matrices (EEMs) of the three analytes as analytical signals, allowed their simultaneous determination in human urine samples, in the range of approximately 80 mg L−1 to 250 mg L−1, with satisfactory results for all the assayed methods. Improved results over unfolded-PLS and N-PLS were found with PARAFAC, SWATLD, and BLLS, methods that exploit the second-order advantage.
A Vapor–Liquid–Solid Mechanism for Growing 3C‐SiC Single‐Domain Layers on 6H‐SiC(0001)
Authors: Soueidan M. , Ferro G.
Published: March 2006

Growing device‐quality 3C‐SiC monocrystalline material is still an issue despite two decades of work dedicated to the subject. Using silicon as the substrate generates too many defects in the layers, owing to lattice mismatch, while it is very difficult to control the initial nucleation on an α‐SiC substrate so that 60° rotated domains are randomly formed. Herein, the elaboration of mono‐orientated 3C‐SiC layers on a 6H‐SiC(0001) on‐axis, Si face substrate using a vapor–liquid–solid mechanism is reported. This non‐conventional approach for growing monocrystalline layers involves feeding a Ge–Si melt by a propane flux at a temperature ranging from 1250 to 1550 °C. We show that, by using this technique, the 3C‐SiC material is almost always obtained on an hexagonal substrate, even if the crystal seed is oriented 8° off‐axis. Using on‐axis 6H‐SiC seeds and optimal growth conditions results in the reproducible deposition of single‐domain 3C‐SiC layers. A mechanism is proposed to clarify some aspects of this process.
Heterogeneous–homogeneous interactions in catalytic microchannel reactors
Authors: Chattopadhyay S. , Veser G.
Published: March 2006

Micromachining of chemical reactors enables the manufacture of microchannel reactors with unsually large surface‐to‐volume ratios. This can strongly affect the coupling between heterogeneous (wall) reactions and homogeneous (gas‐phase) reactions, ultimately leading to a complete quenching of homogeneous reactions. Using a 2D boundary‐layer model coupled with detailed reaction kinetics for surface and gas‐phase reactions, we investigate the ignition behavior of hydrogen/air mixtures in a Pt‐coated microchannel. The influence of temperature, pressure, reactor diameter, and fuel‐to‐air ratio is studied. We find that a purely kinetic radical scavenging by the catalytic surface can indeed result in a complete suppression of gas‐phase reactions. However, the attainability of “intrinsic safety” in microchannel reactors is strongly dependent on a fine interplay between homogeneous and heterogeneous reaction pathways in the individual reaction system. In particular, the strong dependency of homogeneous reactions on pressure leads to a breakdown of intrinsic reactor safety at sufficiently high reactor pressure. A generalized equation for the boundary of safe reactor operation is derived for the current reaction system. © 2006 American Institute of Chemical Engineers AIChE J, 2006
Observations of recirculation in the bore fluid during hollow fiber spinning
Authors: Su Y. , Lipscomb G. G. , Balasubramanian H. , Lloyd D. R.
Published: March 2006

Hollow fiber membranes are used widely in membrane separation processes because of their high surface area to volume ratio. Several models have been developed for the hollow fiber spinning process. However, many details of the process are not well understood. In this work, the conservation of mass and momentum equations are solved for isothermal, axisymmetric hollow fiber spinning. In contrast to past work, the conservation equations are solved for both the bore and clad fluids. The two sets of equations are linked by continuity of velocity and stress across the bore–clad interface. Simulation results show an unexpected recirculation region in the bore fluid under certain operating conditions. For a given die geometry, the presence/absence and size of the recirculation region is dependent on the bore‐to‐clad flow rate ratio and bore‐to‐clad viscosity ratio. The appearance of the recirculation region leads to a more rapid decrease of both fiber outer and inner radii after die swell. The predicted changes in fiber radii are in better agreement with experimental observations than predictions from the one‐dimensional thin filament analysis. © 2006 American Institute of Chemical Engineers AIChE J, 2006
Influence of premade and in situ compatibilizers in polypropylene/ethylene–propylene–diene terpolymer thermoplastic elastomeric olefins and thermoplastic vulcanizates
Authors: Naskar K. , Noordermeer J. W. M.
Published: March 2006

During dynamic vulcanization of polypropylene (PP)/ethylene–propylene–diene terpolymer (EPDM) blends with dicumyl peroxide/triallyl cyanurate, there is a possibility of the generation of in situ graft links at the interface. Three potential compatibilizers (PP‐grafted EPDM, styrene–ethylenebutylene–styrene, and trans‐polyoctenamer) for PP/EPDM blends were first investigated as references to obtain a quantified insight into the effects to be expected from in situ graft links. Only the first compatibilizer showed some compatibilizing action in straight, unvulcanized blends, as evidenced by a slight increase in the tensile strength of the blend and a somewhat smaller EPDM particle size within the PP matrix. Also, dynamic mechanical testing, in particular, the glass‐transition temperatures of the PP and EPDM components, showed some signs of compatibilization. The PP‐grafted EPDM resembled most closely the structures of PP and EPDM. In the spectra obtained with high temperature, solid‐state NMR, there was an indication that PP–EPDM graft links were generated during the dynamic vulcanization process that still remained after the extraction of the free PP phase from the thermoplastic vulcanizate film. NMR relaxation experiments gave further evidence for the graft links formed in situ. In all cases, only qualitative indications could be achieved because of the extremely low number of graft links formed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3877–3888, 2006
Preparation and XPS surface chemical analysis of PS/PU nanocomposites
Authors: Zhu Yan , Zhang Lian‐Meng , Zheng Hua , Sun Duo‐Xian
Published: March 2006

Aqueous emulsions of anionic polyurethane ionomers, based on polypropylene glycol as soft segment, isophorone diisocyanate as diisocyanate, dimethylolpropionic acid as chain extender and potential ionic center, and triethylamine as neutralizer, were synthesized. They were mixed with styrene monomers to prepare polystyrene–polyurethane (PS/PU) nanocomposites by an evocator. The sizes and distributions of the particles were measured by dynamic light scattering, and the microstructure of the nanocomposites was observed by transmission electron microscope. X‐ray photoelectron spectroscopy (XPS) was used to study the surface characterization of anionic PU and PS/PU nanocomposites. It could be found that the nanoparticles of PU could encapsulate the styrene monomers effectively and the leakage type of every element in PU was not affected by the introduction of Ps. There were more hard segments on the surface of crosslinking PS/PU nanocomposites because of the formation of crosslinking structure and interpenetrating polymer network between PU and PS. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3889–3894, 2006
Relationship between the network morphology and properties of commercial vinyl ester resins
Authors: Rodriguez Exequiel , Larrañaga Maider , Mondragón Iñaki , Vázquez Analía
Published: March 2006

Two commercial vinyl ester resins, Derakane 411‐350 (resin D) and Derakane 411‐350 Momentum (resin M), were characterized. Despite the large quantity of publications in the literature about vinyl ester resins, few experimental results have been reported for resin M. The effect of the styrene content on the mechanical properties and morphological structure was studied. An increase in the styrene content produced a network with a low storage modulus in the rubber state and a glass‐transition temperature. The apparent average molecular weight between crosslink points and glass‐transition temperature were slightly higher for resin D than for resin M. The Fourier transform infrared spectra and molecular weight distributions were similar. However, resin M was tougher than resin D, and this may have been due to the closer structure in the fully cured state. Atomic force microscopy was performed for each cured resin and confirmed the difference in the nanostructures. The main reason for the differences in the developed structures was the use of an accelerator, which influenced the final morphology. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3895–3903, 2006