bluuebunny/crossref_metadata_2025 huggingface dataset:
Flow over a hill covered with a plant canopy
Authors: Finnigan J. J. , Belcher S. E.
Published: February 2004

We develop an analytical model for atmospheric boundary‐layer flow over a hill that is covered with a vegetation canopy. The slope of the hill is assumed to be small enough that the flow above the canopy can be treated within the linear framework of Hunt. Perturbations to the flow within the canopy are driven by the pressure gradient associated with the flow over the hill. In the upper canopy this pressure gradient is balanced by downwards turbulent transport of momentum and the canopy drag. The flow there can be calculated from linearized dynamics, which show that the maximum streamwise winds are where the perturbation pressure is at a minimum, i.e. near the crest of the hill. Deep within the canopy the pressure gradient associated with the flow over the hill is balanced by the canopy drag, here the nonlinear canopy drag. This nonlinear balance shows how the streamwise winds are largest where the perturbation pressure gradient is largest, i.e. on the upwind slope of the hill. In the lee of the hill this nonlinear solution shows how the pressure gradient decelerates the wind deep within the canopy, leading to separation with a region of reversed flow when the canopy is sufficiently deep. Coupling between the out‐of‐phase flows within and above the canopy means that the maximum velocity is further upwind of the hill crest than in flow over a rough hill, while the extra turbulent mixing caused by the canopy significantly reduces the magnitude of the velocity speed‐up over the hill. Finally, we find that there is no formal limit process where the solutions with a canopy yield the well‐known solutions for flow over a rough hill. This finding calls into question the very use of a roughness length in accelerating or decelerating turbulent boundary layers. Copyright © 2004 Royal Meteorological Society
An improved general fast radiative transfer model for the assimilation of radiance observations
Authors: Matricardi Marco , Chevallier Frederic , Kelly Graeme , Thépaut Jean‐Noel
Published: February 2004

An improved version of the RTTOV (Radiative Transfer for the Television Infrared Observation Satellite (TIROS) Operational Vertical Sounder) fast radiative transfer model used operationally at the European Centre for Medium‐Range Weather Forecasts (ECMWF) for the assimilation of Advanced TIROS Operational Vertical Sounder (ATOVS) radiances has been developed. This new model computes radiances for the Atmospheric Infrared Sounder and reproduces line‐by‐line radiances and Jacobians for the surface‐sensing, water vapour and ozone channels of the ATOVS with significantly improved accuracy. The profile‐dependent predictors used by the improved model to parametrize the atmospheric optical depths are based on the approach followed by the ECMWF fast radiative transfer model for the Infrared Atmospheric Sounding Interferometer (RTIASI). To improve the accuracy of the fast model in reproducing line‐by‐line radiances for the Infrared Atmospheric Sounder, modifications have been made to the predictors used in RTIASI by introducing a revised set of predictors for ozone and adding new predictors to model the water vapour continuum type absorption. To eliminate discontinuities in the water vapour Jacobians observed in RTIASI, data are now weighted prior to performing the regression. Copyright © 2004 Royal Meteorological Society
The counter‐propagating Rossby‐wave perspective on baroclinic instability. II: Application to the Charney model
Authors: Heifetz E. , Methven J. , Hoskins B. J. , Bishop C. H.
Published: February 2004

The constant‐density Charney model describes the simplest unstable basic state with a planetary‐vorticity gradient, which is uniform and positive, and baroclinicity that is manifest as a negative contribution to the potential‐vorticity (PV) gradient at the ground and positive vertical wind shear. Together, these ingredients satisfy the necessary conditions for baroclinic instability. In Part I it was shown how baroclinic growth on a general zonal basic state can be viewed as the interaction of pairs of ‘counter‐propagating Rossby waves’ (CRWs) that can be constructed from a growing normal mode and its decaying complex conjugate. In this paper the normal‐mode solutions for the Charney model are studied from the CRW perspective.

Clear parallels can be drawn between the most unstable modes of the Charney model and the Eady model, in which the CRWs can be derived independently of the normal modes. However, the dispersion curves for the two models are very different; the Eady model has a short‐wave cut‐off, while the Charney model is unstable at short wavelengths. Beyond its maximum growth rate the Charney model has a neutral point at finite wavelength (r=1). Thereafter follows a succession of unstable branches, each with weaker growth than the last, separated by neutral points at integer r—the so‐called ‘Green branches’. A separate branch of westward‐propagating neutral modes also originates from each neutral point. By approximating the lower CRW as a Rossby edge wave and the upper CRW structure as a single PV peak with a spread proportional to the Rossby scale height, the main features of the ‘Charney branch’ (0<r<1) can be deduced without prior calculation of the normal modes. Furthermore, CRWs from this branch are seen to make a smooth transition into the boundary and interior PV structure of the neutral modes appearing at r=1. The behaviour of the other branches and neutral points is essentially the same when viewed from the CRW perspective, but with cancelling interior PV structures reducing the self and mutual interaction of the CRWs. The underlying dynamics determining the nature of all the solutions is the difference in the scale‐dependence of PV inversion for boundary and interior PV anomalies, the Rossby‐wave propagation mechanism and the CRW interaction. The behaviour of the Charney modes and the first neutral branch, which rely on tropospheric PV gradients, are arguably more applicable to the atmosphere than modes of the Eady model where the positive PV gradient exists only at the tropopause. Copyright © 2004 Royal Meteorological Society
A probabilistic approach for SeaWinds data assimilation
Authors: Portabella M. , Stoffelen A.
Published: February 2004

Scatterometer sea surface wind observations are being successfully assimilated into numerical weather prediction models. The quality of the winds retrieved from the new SeaWinds scatterometer (onboard the QuikSCAT satellite) depends on the subsatellite cross‐track location. In particular, the poor azimuth separation or diversity between views in the nadir region results in poor quality winds. In the QuikSCAT nadir region, where the local cost‐function minima are broad, the use of the standard procedure results in arbitrary and inaccurate winds. A new scheme, which accounts for broad cost‐function minima by allowing more ambiguous wind solutions, i.e. a multiple solution scheme (MSS), is proposed as an alternative to the standard procedure. The probability of every ambiguous solution being the ‘true’ wind is empirically derived, and used in the ambiguity‐removal procedure to make the scheme flexible enough to accept many wind solutions.

A comparison between the standard wind retrieval and the MSS procedures at 100 km resolution is then performed, using independent model winds for validation. The MSS turns out to be more in agreement with the model reference than the standard procedure, especially at nadir. Moreover, it shows more spatially consistent and realistic winds by more effectively exploiting the information content of the observations. Copyright © 2004 Royal Meteorological Society
A new procedure for estimating observation errors in AMSU data and its application to retrieval
Authors: Chou Chien‐Ben , Huang Huei‐Ping
Published: February 2004

An accurate estimate of observation errors is crucial to the retrieval of atmospheric profiles from satellite data using a variational method. In practice, observation errors, both systematic and random, are often estimated from the difference between satellite observations and simulated satellite observations obtained from a radiative‐transfer operator with a 12 h forecast as its input. Observation errors estimated by this approach may be contaminated by errors in the 12 h forecast. This work describes a practical way to eliminate the 12 h forecast error and improve the estimate of the observation error in the Advanced Microwave Sounding Unit (AMSU) data. Following the philosophy of the National Meteorological Center (NMC) method (that derives the statistics of forecast error from the differences between pairs of forecasts at disparate ranges valid at the same time), in this study the pairs of forecasts at different ranges in the NMC method are first converted to brightness temperatures in the AMSU channels by a radiative‐transfer operator. The 12 h forecast errors are then determined from the representations of these forecasts in radiance space spanned by the AMSU channels. Since most AMSU channels have beam position‐dependent systematic observation errors, the procedure further takes into account this dependence by performing the statistics separately for sub‐groups of data in each AMSU channel with different beam positions. In a case‐study, after eliminating the 12 h forecast error obtained by this procedure from the total estimated observation error, the remaining random error of the satellite observation is shown to be smaller than the background error (provided by 12 h forecasts of a numerical weather‐prediction model) in most of the AMSU temperature sounding channels. Using the error‐corrected AMSU data in these channels, a retrieval experiment using a one‐dimensional variational scheme shows an improvement of 0.2–0.4 K over the background error in the retrieved temperature profiles above 780 hPa. Copyright © 2004 Royal Meteorological Society
The dynamics of a midlatitude cyclone with very strong latent‐heat release
Authors: Ahmadi‐Givi F. , Graig G. C. , Plant R. S.
Published: February 2004

The role of latent‐heat release in an explosively developing cyclone from the Fronts and Atlantic Storm‐Track Experiment is examined within the potential vorticity (PV) framework. Using conventional synoptic analysis, piecewise PV inversion and numerical simulations, the development is described in terms of an upper‐level PV (UPV) anomaly, a surface potential‐temperature anomaly and diabatically generated PV anomalies in the lower and upper troposphere. The relative contributions of each anomaly to the cyclogenesis are investigated, along with the interactions between anomalies.

In contrast to previous case‐studies, the results of PV inversion and sensitivity tests reveal that the contribution from the surface thermal anomaly is much weaker than those associated with the upper‐level and diabatically generated PV anomalies. A low‐level PV (LPV) anomaly is generated rapidly in response to the UPV anomaly, and dominates the intensification of the system, but its associated circulation has only a modest feedback effect on the upper levels. However, diabatic reduction of PV in the upper troposphere is found to have important effects on the UPV anomaly. In particular, latent heating tends to destroy the UPV anomaly by inhibiting its downward penetration and reducing its horizontal extent. Copyright © 2004 Royal Meteorological Society
An axisymmetric model of a mature tropical cyclone incorporating azimuthal vorticity
Authors: Pearce Robert P.
Published: February 2004

The inner core of an axisymmetric mature hurricane‐type vortex is first constructed using the gradient‐wind‐balance condition by specifying the tangential wind, v, and the mean temperature excess of the eye, which is assumed to be at rest. These parameters are used to define the configuration of the eye wall. A relation is then obtained relating the eye radius to a parameter α in the relation rαv=constant, defining the inflow tangential wind at radius r, a parameter Γ involving v(=vR) at a radius R of order 100 km, and the eye temperature. This relation is shown to be readily adaptable to a model with an eye in solid rotation.

A meridional circulation is constructed by specifying its azimuthal vorticity, η, and then calculating the temperature field required to maintain a steady state; the full azimuthal vorticity equation rather than the gradient‐wind‐balance approximation is used for this purpose. The main additional terms are those arising from vorticity advection by the meridional flow and a vorticity source related to the temperature lapse rate. The latter is the dominant additional term and implies model tangential winds which are about 5% supergradient near the eye wall.

The role of the meridional circulation in both exporting the heat and importing the angular momentum required by the surface transfers is examined. The observed restriction of α to a narrow band between 0.5 and 0.6 is shown to be consistent with its being determined by the ratio given by the strength of the surface heating divided by the mean temperature excess in the eye. (=ΔTE), which must itself be restricted within a narrow band and can be regarded as determining α. It is inferred that the model's maximum wind is effectively determined solely by ΔTE. On the other hand, the eye radii of similar systems are roughly proportional to R, i.e. larger systems of similar intensities have larger eyes.

Finally a conceptual model of the intensification phase is presented. After first demonstrating that a ring of deep convection must contract, it is shown that the intensification process can be characterized as a downwards and inwards penetration of the eye wall from the convective ring outflow near the tropopause, limiting the contraction. Copyright © 2004 Royal Meteorological Society
Specification and prediction of monthly and seasonal rainfall over the south‐west peninsula of England
Authors: McGregor Glenn R. , Phillips Ian D.
Published: February 2004

An assessment of the extent to which atmospheric variables add to the specification and predictability of rainfall over the south‐west peninsula of England (SWPE), as provided by North Atlantic sea surface temperatures (SSTs), is undertaken. To this end multivariate specification and prediction models are developed, describing rainfall variations over the SWPE at monthly and seasonal time‐scales. Results reveal that synchronous variations in atmospheric circulation characteristics are the main specifiers of monthly and seasonal rainfall variability, chiefly mean monthly sea‐level pressure, vorticity and atmospheric water vapour flux. In contrast, the predictability of rainfall for one‐ and two‐months, and one‐ and two‐seasons ahead is more dependent on SST than atmospheric circulation variability. Both the tropical Atlantic and the Greenland–Iceland (Norwegian Sea) regions of the North Atlantic appear important as centres of action in terms of SST–SWPE rainfall links. Although SSTs account for the majority of variance in monthly and seasonal rainfall, a moderate improvement of rainfall prediction is achieved with the inclusion of atmospheric water vapour flux in prediction models for one‐month to two‐seasons ahead, as it acts as an atmospheric bridge between the ocean and land in terms of precipitation delivery. The empirical relationships revealed between SWPE rainfall, and atmospheric and SST variability are discussed in terms of the main components of the North Atlantic climate system. Copyright © 2004 Royal Meteorological Society
Variational data assimilation in the tropics: The impact of a background‐error constraint
Authors: Žagar Nedjeljka , Gustafsson Nils , Källén Erland
Published: February 2004

Geostrophic adjustment theory predicts that wind information is a primary information source in the tropics. We ask whether this is true when variational data assimilation including a background‐error constraint is applied. The question is investigated by carrying out three‐ and four‐dimensional variational (4D‐Var) data assimilation experiments with nonlinear shallow‐water equations and idealized waves. The contribution to the analysis from mass and wind field observations is contrasted to that of spectral characteristics and multivariate relationships of equatorial waves built into a background‐error covariance matrix. A background‐error term for the analysis is built by using the tropical eigenmodes and the observed variability is used to determine the relative weights for different modes.

Single observation sensitivity experiments illustrate an important impact of Kelvin and mixed Rossby–gravity waves in reducing the coupling between the mass and wind fields, found when only equatorial Rossby waves are utilized in the background‐error constraint.

The assimilation experiments demonstrate two main features. First, the wind field information is of greater value than the mass field information, in spite of the known error statistics. A second intriguing feature is that the assimilation of wind observations better resolves smaller‐scale features of the height field than the assimilation of height data. When height data are used, a somewhat different analysis response is obtained for the zonal and meridional wind components, due to the strong projection onto the Kelvin wave structure for height observations. Finally, a comparison of different time windows for 4D‐Var illuminates the sensitivity of height field assimilation to the length of the assimilation window. Copyright © 2004 Royal Meteorological Society
Instability in a class of explicit two‐time‐level semi‐Lagrangian schemes
Authors: Durran Dale R. , Reinecke P. Alexander
Published: February 2004

Recently Gospodinov and collaborators derived a family of second‐order two‐time‐level semi‐Lagrangian schemes that contain an undetermined parameter α. It is shown that, when using one of these schemes to approximate the forcing terms in partial differential equations in a semi‐Lagrangian coordinate frame, the choice of α has a critical influence on the absolute stability of the method. Optimal stability properties are obtained by choosing α = ¼ which corresponds to the SETTLS scheme proposed by Hortal. Copyright © 2004 Royal Meteorological Society
Physically based two‐moment bulkwater parametrization for warm‐cloud microphysics
Authors: Chen Jen‐Ping , Liu Sen‐Tsong
Published: February 2004

A two‐moment bulkwater parametrization scheme for warm‐cloud microphysics is developed via statistical analyses of results from a detailed parcel model. This computationally efficient scheme is quite accurate and produces bulkwater properties which resemble the results from a fully explicit microphysical model. It responds sensitively to the effect of aerosol types on the cloud drop number concentration and the timing of rain initiation. Diagnostic formulae are also provided for the group fall velocity, number and mass sedimentation fluxes, the radar reflectivity factor, and the effective radii of cloud drops and raindrops. This physically sound and easy to use parametrization scheme could be useful in improving the microphysical representation in regional‐ and cloud‐scale models. Copyright © 2004 Royal Meteorological Society
Contour‐advective semi‐Lagrangian algorithms for many‐layer primitive‐equation models
Authors: Mohebalhojeh A. R. , Dritschel D. G.
Published: February 2004

For an f‐plane many‐layer primitive‐equation isopycnal model, three ‘contour‐advective semi‐Lagrangian’ (CASL) algorithms and a standard pseudo‐spectral (PS) algorithm are compared as regards their representation of balance and imbalance during the evolution of a highly complex vortical flow with substantial activity in small horizontal and vertical scales. The three CASL algorithms employ (q,h,δ), (q,δ,γ), and (q,γ,Ξ) as their prognostic variables, where q is the Rossby potential vorticity, h is layer thickness, δ is horizontal divergence, γ and Ξ represent departures of vorticity from, respectively, geostrophic and Bolin–Charney balance. It is demonstrated that the CASL algorithm with (q,δ,γ) improves on the algorithm with (q,h,δ) across nearly the whole range of applicability of the algorithms, i.e. practically up to the limit where overturning and diabatic effects may dominate. Unlike in the PS algorithm, the improvement is achieved without sacrificing the accuracy of the vortical part of the flow by excessive damping. Copyright © 2004 Royal Meteorological Society
Climate response to tropospheric absorbing aerosols in an intermediate general‐circulation model
Authors: Cook J. , Highwood E. J.
Published: February 2004

This study uses idealized aerosol distributions with the Reading Intermediate General‐Circulation Model (IGCM) to assess and explain the climate response in that model to absorbing tropospheric aerosol. We find that the sign of the direct aerosol radiative forcing is not a good indication of the sign of the resulting global and annual mean surface temperature change. The climate sensitivity parameter for aerosols which absorb some solar radiation is much larger than that for CO2or solar experiments with the same model.

Reasons for the enhanced surface temperature response in the presence of aerosol are examined. Significant changes in cloud amount occur, some of which appear most influenced by the change in surface temperature and may be generic to any mechanism that warms the surface. A reduction in low cloud amount occurs when the aerosol single‐scattering albedo is less than 0.95; the so‐called ‘semi‐direct’ effect of aerosols is clearly evident in this model. We suggest that this aerosol–cloud feedback is present in all GCMs which include absorbing tropospheric aerosol but remains largely undiagnosed. Comparisons with a previous study and further sensitivity tests suggest that the magnitude of this effect and the mechanisms behind it are strongly dependent on the cloud scheme employed. Copyright © 2004 Royal Meteorological Society
Effects of shear sheltering in a stable atmospheric boundary layer with strong shear
Authors: Smedman Ann‐Sofi , Högström Ulf , Hunt J. C. R.
Published: February 2004

Data from two marine field experiments in the Baltic Sea with stable stratification have been analysed. The purpose was to test the concept of the ‘detached’ or ‘top‐down’ eddies and the ‘shear‐sheltering’ mechanism in the presence of a low‐level wind speed maximum in the atmosphere. Data used include turbulence and profile measurements on two 30 m towers and concurrent wind profiles throughout the boundary layer obtained from pilot‐balloon soundings.

Measurements show that large eddies are being suppressed when there is a low‐level wind speed maximum present somewhere in the layer 40–300 m above the water surface and when the stratification is slightly stable. The effect is seen both in normalized standard deviations of the velocity components and in corresponding component spectra. In previous work it was argued that the relatively large eddies, which dominate the low wave number spectra in measurements in the surface layer, are detached or top‐down eddies generated higher up in the boundary layer, that interact with the surface layer. The low‐level wind maximum introduces a distinct layer with strong vorticity which, according to the shear‐sheltering hypothesis, prevents these eddies from penetrating downwards.

In the limit of the wind maximum occurring at a very low height (less than about 100 m), usual turbulence statistics characteristic of the ‘canonical’ boundary layer are found. Combining all the statistics, it is demonstrated that the wavelength of maximum spectral energy is locally related to a turbulence length‐scale, which shows that for values of the Richardson number of unity or less the effect of the local wind gradient is greater than that of static stability. The reduction of length‐scale with the strength of a low‐level wind maximum, explains the observed reduction (by a factor of two) of the turbulent flux of sensible heat at the surface. This result indicates that the shear‐sheltering mechanism is likely to play an important role in the turbulent exchange process at the surface in sea areas where low‐level wind maxima are a frequently occurring phenomenon, such as the Baltic and other large water bodies surrounded by landmasses. Copyright © 2004 Royal Meteorological Society
Positional relationship between the facial nerve and other structures of the temporal bone
Authors: Dai Peidong , Zhang Tianyu , Wang Keqiang , Song Jichang , Qian Wen , Wang Zhengmin
Published: February 2004

The quantitative relationships between the position of the mastoid segment of the facial nerve, mastoid pneumatization and the positions of neighbouring structures are undetermined. Using high resolution computed tomography (HRCT), the positions of these structureswere measured in 66 normal temporal bones. A new method for measuring the volume of pneumatization in the temporal bone based on the serial digital images of CT was designed. The method of partial correlation analysis was used to find the real relationship of the two variables. The results suggest that the factors that influence the position of the mastoid segment of the facialnerve are complicated and multiple. The development of the cranium including the temporal bone,the temporal bone pneumatization and the variable position of the jugular bulb are considered to be important factors.
Bone conduction auditory brainstem responses in infants
Authors: Campbell P. E. , Harris C. M. , Hendricks S. , Sirimanna T.
Published: February 2004

The contribution of air conduction auditory brainstem response (AC-ABR) testing in the paediatric population is widely accepted in clinical audiology. However, this does not allow for differentiation between conductive and sensorineural hearing loss. The purpose ofthis paper is to review the role of bone conduction auditory brainstem responses (BC-ABR). It is argued that despite such technical difficulties as a narrow dynamic range, masking dilemmas, stimulus artifact and low frequency underestimation of hearing loss, considerable evidence exists to suggest that BC-ABR testing provides an important contribution in the accurate assessmentof hearing loss in infants. Modification of the BC-ABR protocol is discussed and the technical difficulties that may arise are addressed, permitting BC-ABR to be used as a tool in the differential diagnosis between conductive and sensorineural hearing. Two relevant case studies are presented to highlight the growing importance of appropriate management in early identification of hearing loss. It can be concluded that BC-ABR should be adopted as a routine clinical diagnostic tool.
Principles of septal correction
Authors: Marshall A. H. , Johnston M. N. , Jones N. S.
Published: February 2004

The operation of septoplasty is often given to junior surgeons to perform and dismissed as a simple procedure. This can lead to unsatisfactory results with unnecessary morbidity for the patient and disillusionment for the surgeon. Trainee surgeons feel that the operation of septoplasty is poorly taught. Some common problems encountered during septal surgery are described and a variety of surgical solutions are offered.
Portable method for the determination of snoring site by sound analysis
Authors: Bieger-Farhan A. K. , Chadha N. K. , Camilleri A. E. , Stone P. , McGuinness K.
Published: February 2004

It has been shown that computerized sound frequency analysis can be used todistinguish between different snoring sites. The aim of this study was to investigate whether aportable recording method using audiotapes and digital minidisc formats could produce waveformssimilar to a computer recording.

The snores of 12 subjects in their natural sleep were recorded onto audiotape, minidisc and directly onto a computer. For each snorer and recording method 30 snore samples were analysed and their power ratio was calculated indicating the relative amount of sound below and above a set frequency. It was found that the power ratios from audiotape recordings were significantly different to those from computer recordings for all snoring sites (p = 0.0007), whereasthere was no significant difference between minidisc and computer recordings (p = 0.41).

These results indicate that it would be possible to base a portable snore analysis system for site determination on minidisc, but not on audiotape recordings.
Non-recurrent inferior laryngeal nerve in thyroid surgery: report of three cases and review of the literature
Authors: Abboud Bassam , Aouad Rony
Published: February 2004

The non-recurrent inferior laryngeal nerve (NRILN) is a nerve anomaly that can be associated with an increased risk of vocal fold paralysis. The purpose of this study wasto report three new cases of this anomaly, underline the necessity of recognizing its possibility for the prevention of intra-operative nerve damage and a review of the literature.

Three cases of thyroid surgery associated with right NRILN are reported.

Two patients underwent bilateral thyroidectomy for a multinodular goitre and for a toxic multinodular goitre respectively. The third patient had a right lobectomy and isthmectomy for a thyroid nodule. All patients had identification of the recurrent laryngeal nerve on the left sideand NRILN on the right side. The diagnosis of the NRILN was made per-operatively on all cases. A post-operative computed tomography (CT) scan in two patients, showed a retrooesophageal aberrant right subclavian artery. Post-operatively, all patients had normal vocal fold function on laryngoscopy.

The NRILN is a rare anomaly but overlooking its possibility may lead to severe operative morbidity. This is an additional argument in favour of systematic dissection of the recurrent inferior laryngeal nerve during thyroid surgery.
Unusual complication of surgical voice restoration
Authors: Counter P. , Slack L. , Athey G. , Robson A.
Published: February 2004

A case of oesophageal obstruction following the removal of a tracheoesophageal valve by division is presented. The obstruction was caused by impaction of a portion of thevalve at a previously undiscovered benign oesophageal stricture. The obstruction was resolved by interventional radiology with no long-term sequelae. To the best of our knowledge this complication has not been described previously.
Jugulotympanic paraganglioma (glomus tumour) presenting with recurrent epistaxis
Authors: Effat Kamal G. , Karam Mohammed
Published: February 2004

A case is presented where a left jugulotympanic paraganglioma (JTP) extended to the nasopharynx and the patient presented with recurrent epistaxis. Although initial biopsy of an aural polyp had been suggestive of the diagnosis several years previously, the diagnosis was not confirmed until the patient presented with recurrent epistaxis and severe anaemia. Tothe best of our knowledge, this is the first case reported of such a presentation of JTP.
Submandibular neurilemmoma; a diagnostic dilemma
Authors: Almeyda Robert , Kothari Prasad , Chau Ha , Cumberworth Vincent
Published: February 2004

Neurilemmomas are slow growing, benign neoplasms of neural crest Schwann cell origin. They arise from any peripheral, spinal or cranial nerve except the olfactory and optic. Presentation is usually asymptomatic but focal neurological signs and symptoms may be associated with nerve compression. With approximately one third of all documented cases presenting in the head and neck region, we report a case of a submandibular neurilemmoma misdiagnosed pre-operatively. The diagnostic difficulties are discussed and the current literature reviewed. Thiscase highlights the importance of inclusion of nerve sheath tumours in differential diagnoses of soft tissue lesions in the head and neck.
Case of thymic parathyroid carcinoma in a haemodialysis patient: application of tumour chemosensitivity testing
Authors: Srouji I. A. , Resouly A. , Cree I. A.
Published: February 2004

Parathyroid carcinoma is a rare tumour, which is often difficult to diagnose. This is especially true in patients with pre-existing tertiary hyperparathyroidism of end-stage renal disease. A case is presented of parathyroid carcinoma in a haemodialysis patient withunusual thymic involvement. After demonstrating the difficulty in pre-operative diagnosis and risk of recurrence, the importance of non-surgical treatment options is discussed and the investigation of individual tumour chemosensitivity is introduced, which is new to this type of cancer.
Managing or managed? Experience of general practitioners in English Primary Care Groups and Trusts
Authors: Locock L. , Regen E. , Goodwin N.
Published: February 2004

This article presents findings from a wider UK Department of Health funded evaluation of English Primary Care Groups (PCGs) and Trusts (PCTs). It presents qualitative research into the experiences of general practitioners (GPs) in these PCG/Ts and explores the extent to which GPs manage, or are managed by, these new organizations. Using the framework of stratification theory, the paper explores whether there is any evidence to suggest PCTs will strengthen collective medical control over resource allocation whilst fending off management control of clinical decision-making. It also examines whether individual GPs not involved at board level feel a loss of control over decisions and their own clinical practice. A stratified random sample of 20 GPs was selected for in-depth interview. The in-depth interviews were designed to capture the full complexity and variety of GPs' experiences that routinely available data could not capture. GPs were anxious that clinical decisions were, or could, be overridden by other concerns such as cost control. The extent to which primary care professionals leading PCGs and PCTs could fend off managerial control was doubted. However, whilst GPs felt under threat, this was more an anticipated threat than a reality. GPs within PCG/Ts seem prepared to accept a degree of standardization if they feel that this is consistent with good clinical care. However, although there was the impression of greater central control, PCGs and PCTs and Government policies did not appear to have made an impression on clinical autonomy.
Quantifying priorities in healthcare: transparency or illusion?
Authors: Mullen Penelope M
Published: February 2004

Explicit priority setting in healthcare, which often involves multiple criteria and value judgements, has come to prominence in a number of different healthcare systems over the past decade. Drawing on the results of a survey of priority setting in practice in the UK National Health Service, this paper analyses issues associated with quantification in priority setting, focusing on techniques for eliciting and aggregating values, the criteria and form of models used and their application in priority setting. The findings reveal a clear focus on equity, a strong concern to demonstrate openness, consistency and transparency in priority setting-leading to greater use of explicit multi-criteria models-and a notable focus on the quality of 'evidence'. However, reported difficulties in weighting over-long lists of non-commensurate and overlapping criteria, the inclusion of inappropriate criteria, and attributes of the form of models employed, lead to the conclusion that the implications of the methods are not always appreciated, the resulting priority 'scores' sometimes misunderstood and, in some cases, the concern for transparency and explicitness appears to outweigh concern for methodological understanding-leading to an illusion of transparency.
Clinical priority criteria in orthopaedics: a validation study using the SF36 quality of life questionnaire
Authors: Theis J-C.
Published: February 2004

This study reports a validation trial of a clinical priority scoring tool in orthopaedic surgery based on five dimensions related to need and ability to benefit using the SF36 health related quality of life questionnaire. Seventy patients attending an orthopaedic outpatient clinic were asked to complete the questionnaire before being seen by an orthopaedic specialist. Their clinical priority for surgery was scored using a tool which assesses five dimensions of clinical need with a maximum of 100 points. Our study has shown that the clinical priority scores correlate very well with the quality of life of patients and that those who were selected for surgery had a significantly worse quality of life compared to those not qualifying for surgery due to the lack of financial resources. Although this study has limits, it should provide sufficient information to healthcare clinicians and managers that this tool will select those patients who have the highest need and ability to benefit from surgery.
Is there a problem with quality in the Greek hospital sector? Preliminary results from a patient satisfaction survey
Authors: Niakas D. , Gnardellis C. , Theodorou M.
Published: February 2004

Many Greek politicians and media attribute high dissatisfaction with the public health services to the quality of public hospitals. Provoking this view, this study attempts to investigate the patient's opinion and provides some preliminary results for the level of services provided by three public hospitals. A patient satisfaction survey with a self-administered questionnaire of 1295 adult patients show high rates for medical and nursing services and fair rates for hotel services and facilities. The medical-nursing index (which can range from 0 to 100) shows a mean of 86.4 and the rate for the hotel services is 75.9. Statistical analysis shows different satisfaction rates by age and level of education, an outcome that is consistent with other similar satisfaction studies. Differences of patient satisfaction relating to the area of hospital need to be examined carefully by gathering more data from Greek hospitals. Our preliminary results demonstrate that the high dissatisfaction of the public cannot be attributed to the quality of hospital care.
On the Low Frequency Noise Assessment Method
Authors: Lenzuni Paolo
Published: February 2004

A new assessment method for low frequency noise annoyance is proposed. A new frequency weighting is introduced, and its robustness tested. Possible effects of impulsiveness and tonality are discussed. The method proposed explicitly includes correction factors for the former, while the latter is shown to be insignificant in this context. The method is cross-checked with existing methods based on frequency weightings, and its performance is objectively quantified using synthetic indicators.
Vibration Perception Thresholds Assessed by Two Different Methods in Healthy Subjects
Authors: Zamyslowska-Szmytke Ewa , Szymczak Wieslaw , Sliwinska-Kowalska Mariola
Published: February 2004

The values of vibration perception threshold (VPT) should be related to the equipment and methods of measurement that differ between European countries. ISO Standard 13091-1-2001 specifies the general guidelines regarding device facilities and measurement methodology. This study was designed to compare VPTs in healthy subjects by using two different methods of measurement. The first one was a standard technique applied currently in Poland and the second one was based on the principles of the International Standard ISO 13091-1-2001. The study comprised 187 healthy subjects, aged 17–57 years, not occupationally exposed to vibration. Both measurements of VPTs were performed using the same equipment (P-8, EmsonMat). The main differences in methodology between the Polish standard method and the method of ISO included:

different mode of stimuli presentation (ascending in standard vs. Bekesy in ISO method), frequency range applied (63–500 Hz vs. 4–125 Hz), probe contact force (larger in Polish method), probe diameter (12 mm vs. 5 mm) and its surface (plane vs. rough).

The results obtained found that the mean VPTs differed significantly at the overlapping frequencies depending on the method used, the differences varied from 2.2 to 6.4 dB at frequencies 125 and 250Hz, respectively. The correlation between the thresholds obtained by both methods at these frequencies was moderate (correlation coefficients about 0.6), although statistically significant. In the ISO method, the best VPTs were found at 4 and 125 Hz. There was a poor correlation between the thresholds at the extreme frequencies (i.e. 125 and 4 Hz) and rather high between adjacent frequencies (i.e. 25 and 32 Hz). Age, weight and height were significant covariates in both measurements. The model to calculate the normative values of VPTs adjusted for explanatory factors was set up in this study. It was concluded that different methods of VPT measurement are not comparable. The ISO method seems to supply more information about skin receptors and different kinds of tough sense than the Polish standard method. In order to perform international cohort studies there is a need to establish a unified standardised method of vibrotactile sense assessment.
Ground Vibration Generated by a Harmonic Load Moving in a Circular Tunnel in a Layered Ground
Authors: Sheng X , Jones C J C , Thompson D J
Published: February 2004

All modes of transport impact on e environment. Although railways are seen as environmentally advantageous in many ways, the issues of noise and vibration are often seen as their weakness. For trains running in tunnels where direct airborne noise is effectively screened, structure-borne or ‘ground-borne’ noise caused by vibration propagated through the ground is the most important concern. The vibration of interest in this case has frequency components from about 15 Hz to 200 Hz.

To understand the mechanisms of vibration propagation from tunnels, a predictive model has been developed for ground vibration generated by a stationary or moving harmonic load applied in a circular lined or unlined tunnel in a layered ground. This study is the first step towards the use of discrete wavenumber methods to model ground vibration from underground trains. Discrete wavenumber methods fall into three categories: the discrete wavenumber fictitious force method, the discrete wavenumber finite element method and the discrete wavenumber boundary element method. This study uses the discrete wavenumber fictitious force method. Based on the moving Green's functions for a layered half-space and those for a cylinder of infinite length, boundary integral equations over the tunnel-soil interface are established. Unlike the conventional boundary integral equation in elastodynamics, the method used here only requires the displacement Green's function. This is achieved by introducing the excavated part of the ground as an extra substructure. The boundary integral equations are further transformed into a set of algebraic equations by expressing each quantity involved in the boundary integral equations in terms of a Fourier series.

Results presented in this paper illustrate the effect of a tunnel on vibration propagation at the ground surface and the difference between a lined tunnel and an unlined tunnel.
Modified LQG/LTR Control Methodology in Active Structural Control
Authors: Sheng Yan , Wang Chao , Pan Ying , Zhang Xinhua
Published: February 2004

This paper presents a new active structural control design methodology comparing the conventional linear-quadratic-Gaussian synthesis with a loop-transfer-recovery (LQG/LTR) control approach for structures subjected to ground excitations. It results in an open-loop stable controller. Also the closed-loop stability can be guaranteed. More importantly, the value of the controller's gain required for a given degree of LTR is orders of magnitude less than what is required in the conventional LQG/LTR approach. Additionally, for the same value of gain, the proposed controller achieves a much better degree of recovery than the LQG/LTR-based controller. Once this controller is obtained, the problems of control force saturation are either eliminated or at least dampened, and the controller band-width is reduced and consequently the control signal to noise ratio at the input point of the dynamic system is increased. Finally, numerical examples illustrate the above advantages.
Acid-Activated Carbons from Peanut Shells: Synthesis, Characterization and Uptake of Organic Compounds from Aqueous Solutions
Authors: Romero Luis C. , Bonomo Antonio , Gonzo Elio E.
Published: February 2004

Activated carbon with a high adsorption capacity for the removal of organic compounds from aqueous solutions was made from phosphoric acid-activated peanut shells. Adsorption isotherms for the uptake of phenol, iodine, Methylene Blue and tannic acid were obtained at 22°C. Freundlich, Langmuir and previously developed equation models all explained the experimental data satisfactorily. Further analysis using the Dubinin–Radushkevich equation showed that the maximum micropore volume accessible to the adsorbate decreased as the molecular size increased, suggesting a molecular sieve or gate effect. A comparison was made with the micropore volume as determined by nitrogen adsorption at −196°C. The results presented indicate that peanut shell residues provide a suitable option for the preparation of activated carbon with good surface properties and the ability to remove organic compounds from aqueous solutions.
Surface and Catalytic Properties of the Co3O4/MgO System Doped with Ag2O and MoO3
Authors: Ghozza A.M.
Published: February 2004

The effects on their surface and catalytic properties of doping 0.2Co3O4/MgO solids with Ag2O or MoO3 (0.2–1.0 wt%) were investigated using nitrogen adsorption at −196°C, the oxidation of CO by O2 at 200–250°C and the decomposition of H2O2 at 30–50°C. The results revealed that doping the investigated system followed by calcination at 500–900°C brought about a progressive increase in the specific surface area to an extent proportional to the amount of dopants added. This led to an increase in the catalytic activities of the doped solids towards H2O2 decomposition, especially for solids calcined at 700°C and 900°C. However, this increase was more pronounced with MoO3 doping. On the other hand, the catalytic activity of the investigated system in CO oxidation by O2 expressed as the reaction rate constant per unit surface area (k̅) was found to decrease on increasing the amount of Ag2O and MoO3 added. Calcination of the investigated system at 900°C led to the effective dissolution of most of the cobalt oxide added into the MgO lattice to yield a CoO-MgO solid solution. Doping 0.2Co3O4/MgO solid followed by heating at 500, 700 and 900°C did not alter the mechanism of the catalytic reaction but increased the concentration of Co3+-Co2+ ion pairs acting as active sites in the process.
Removal of Heavy Metal Ions Using the Fungus Penicillium Canescens
Authors: Say Ridvan , Yilmaz Nalan , Denizli Adil
Published: February 2004

The potential use of the fungus Penicillium canescens for the removal of cadmium, lead, mercury and arsenic ions from aqueous solutions was evaluated in this study. Equilibrium biosorption of the heavy metal ions was attained in 4 h. The binding of heavy metal ions to P. canescens was clearly pH-dependent. Under acidic conditions, the heavy metal ion loading capacity increased with increasing pH, presumably as a result of heavy metal speciation and competition with hydrogen ions for the same binding sites. The adsorption of heavy metal ions attained a plateau value at ca. pH 5.0. The maximum adsorption capacities of the heavy metal ions studied onto the fungal biomass under non-competitive conditions were 26.4 mg/g for As(III), 54.8 mg/g for Hg(II), 102.7 mg/g for Cd(II) and 213.2 mg/g for Pb(II), respectively. The competitive adsorption capacities of the heavy metal ions were 2.0 mg/g for As(III), 5.8 mg/g for Hg(II), 11.7 mg/g for Cd(II) and 32.1 mg/g for Pb(II), respectively, at a 50-mg/l initial concentration of the metal ions. The same affinity order was observed under non-competitive and competitive adsorption conditions, i.e. Pb(II) > Cd(II) > Hg(II) > As(III). The equilibrium loading capacity of Pb(II) was greater than that of other metal ions, the fungal biomass showing preference towards the binding of Pb(II) over Cd(II), Hg(II) and As(III). Elution of heavy metal ions was performed using 0.5 M HCl. The fungus Penicillium canescens could be used for biosorption over six cycles.