bluuebunny/crossref_metadata_2025 huggingface dataset:
A simple mathematical model to analyse a fluidyne heat machine
Authors: Özdemir M , Özgüç A. F.
Published: February 2003

In this study, the hydrodynamics and thermodynamics of a fluidyne heat machine having three columns are analysed systematically. The mathematical model of the system is considered in three parts, that is liquid, vapour, and interfacial regions. The liquid and vapour phases are separated by an interfacial surface where evaporation and condensation occur. It is assumed that heat input and output only take place at the interfaces so that the liquid and vapour phases can be considered as lumped open systems. While the major and minor losses are considered in the liquid phase, the state of the vapour phase changes isentropically. The proposed mathematical formulation of the system is solved by a Runga—Kutta method and compared with the experimental data of a previous study. The results of the solution are in good agreement with the experimental data. It is shown that work will not be produced by the system considered in this study, and that the system only overcomes the major and minor losses.
Reduction in NOx emission of diesel engines by in-cylinder catalysis
Authors: Bannikov M. G. , Draper P. H. , Chattha J. A. , Vasilev I. P. , Gavrilenko P. N.
Published: February 2003

In-cylinder catalysis as a method for reducing the nitrogen oxides emission of diesel engines has been investigated experimentally. Desirable effects could be achieved only when intensive interaction of combustion products with the catalyst-coated surface was provided. It was found that a design based on a combustion chamber of variable geometry could give useful results, particularly for non-turbocharged engines.
Optimization of the power output from ducted turbines
Authors: Lawn C. J.
Published: February 2003

For many years there has been interest in the possibility of enhancing the performance of wind turbines by encasing them in a duct or ‘shroud’, but practical considerations have prevented commercial realization. While this possibility is not ruled out, more beneficial schemes for shrouding may well arise for water turbines in tidal streams. In this paper, the performance of a shrouded turbine has been analysed using one-dimensional theory by treating the ducts upstream and downstream of the turbine as contractions or expansions having specified diffusion efficiencies. It is shown that, for given diffuser efficiencies, there is an optimum turbine resistance for generating maximum power, because the swallowing capacity of the duct is increased as the resistance decreases. Simple experiments with static resistance elements in the duct have confirmed this theory for the swallowing capacity and shown that there is little to be gained by controlled diffusion at inlet. However, efficient controlled diffusion at outlet can lead to power enhancements of more than 30 per cent over an optimized turbine of the same area in the freestream. To achieve this, a more lightly loaded turbine must be utilized. Claims in the literature of much greater enhancements than this are sometimes made in relation to non-optimized conditions for the freestream case. The alternative requirement, that maximum power should be extracted from a given inlet area, is also analysed and shown to require a highly loaded turbine.
On the accuracy of retrieved wind information from Doppler lidar observations
Authors: Davies F. , Collier C. G. , Bozier K. E. , Pearson G. N.
Published: February 2003

A single pulsed Doppler lidar was successfully deployed to measure air flow and turbulence over the Malvern hills, Worcester, UK. The DERA Malvern lidar used was a $\hbox{CO}_{2} \ 10.6\ \mu \hbox{m}$ pulsed Doppler lidar. The lidar pulse repetition rate was 120 Hz and had a pulse duration of $0.6\ \mu \hbox{s}$. The system was set up to have 41 range gates with range resolution of 112 m. This gave a theoretical maximum range of approximately 4.6 km. The lidar site was 2 km east of the Malvern hill ridge which runs in a north–south direction and is approximately 6 km long. The maximum height of the ridge is 430 m. Two elevation scans (Range–Height Indicators) were carried out parallel and perpendicular to the mean surface flow. Since the surface wind was primarily westerly the scans were carried out perpendicular and parallel to the ridge of the Malvern hills.

The data were analysed and horizontal winds, vertical winds and turbulent fluxes were calculated for profiles throughout the boundary layer. As an aid to evaluating the errors associated with the derivation of velocity and turbulence profiles, data from a simple idealized profile was also analysed using the same method. The error analysis shows that wind velocity profiles can be derived to an accuracy of 0.24 m s−1 in the horizontal and 0.3 m s−1 in the vertical up to a height of 2500 m. The potential for lidars to make turbulence measurements, over a wide area, through the whole depth of the planetary boundary layer and over durations from seconds to hours is discussed. Copyright © 2003 Royal Meteorological Society
Inferring instantaneous, multivariate and nonlinear sensitivities for the analysis of feedback processes in a dynamical system: Lorenz model case‐study
Authors: Aires Filipe , Rossow William B.
Published: February 2003

As an alternative to classical linear feedback analysis, we present a nonlinear approach for the determination of the sensitivities of a dynamical system from observations of its variations. The new methodology consists of statistical estimates of all the pair‐wise relationships among the system state variables based on a neural‐network modelling of the system dynamics (its time evolution). The model can then be used to estimate the instantaneous, multivariate, nonlinear sensitivities. Classical feedback analysis is re‐examined in terms of these sensitivities, which are shown to be more fundamental in the analysis of feedback processes than estimates of feedback factors and to provide a more appropriate representation of the system's behaviour. The method is described and tested on synthetic observations of the time variations of the Lorenz low‐order atmospheric model where the correct sensitivities can be evaluated analytically. Copyright © 2003 Royal Meteorological Society
Phase transformation of mixed‐phase clouds
Authors: Korolev Alexei , Isaac George
Published: February 2003

The glaciation time of a mixed‐phase cloud due to the Wegener–Bergeron–Findeisen mechanism is calculated using an adiabatic one‐dimensional numerical model for the cases of zero, ascending, descending and oscillating vertical velocities. The characteristic values of the glaciation time are obtained for different concentrations of ice particles and liquid‐water content. Steady state is not possible for the ice‐water content/total water content ratio in a uniformly vertically moving mixed‐phase parcel. The vertical oscillation of a cloud parcel may result in a periodic evaporation and activation of liquid droplets in the presence of ice particles during infinite time. After a certain time, the average ice‐water content and liquid‐water content reach a steady state. This phenomenon may explain the existence of long‐lived mixed‐phase stratiform layers. The obtained results are important for understanding the mechanisms of formation and life cycle of mixed‐phase clouds. Copyright © 2003 Royal Meteorological Society
Microphysical characterization of mixed‐phase clouds
Authors: Korolev Alexei V. , Isaac George A. , Cober Stewart G. , Strapp J. Walter , Hallett John
Published: February 2003

A detailed study of mixed‐phase clouds associated with frontal systems obtained from a large dataset collected by the Convair 580 aircraft of the National Research Council (NRC) of Canada is presented. The total length of analysed in‐cloud legs having total‐water content (TWC) >0.01g m−3 was about 44×103km. The ice–water fraction (µ3=ice−water content/TWC) had a minimum in the range 0.1<µ3<0.9, and two maxima for liquid clouds (µ3<0.1) and ice clouds (µ3>0.9). The concentration of particles in glaciated clouds was found to be nearly constant at 2 – 5 cm −3 for temperatures −35°C<T<0°C. The concentration of droplets in liquid clouds decreased with decreasing temperature. The mean volume diameter of particles in ice clouds varied between 20 μm and 35 μm, and in liquid clouds between 10 μm and 12 μm. Both ice‐ and liquid‐water content decreased with decreasing temperature. The results of this study may be used for validation of remote‐sensing retrievals, and for weather‐ and climate‐models. Copyright © 2007 Royal Meteorological Society
The formation mechanism of the Bonin high in August
Authors: Enomoto Takeshi , Hoskins Brian J. , Matsuda Yoshihisa
Published: February 2003

The Bonin high is a subtropical anticyclone that is predominant near Japan in the summer. This anticyclone is associated with an equivalent‐barotropic structure, often extending throughout the entire troposphere. Although the equivalent‐barotropic structure of the Bonin high has been known for years among synopticians because of its importance to the summer climate in east Asia, there are few dynamical explanations for such a structure. The present paper attempts to provide a formation mechanism for the deep ridge near Japan. We propose a new hypothesis that this equivalent‐barotropic ridge near Japan is formed as a result of the propagation of stationary Rossby waves along the Asian jet in the upper troposphere (‘the Silk Road pattern’). First, the monthly mean climatology is examined in order to demonstrate this hypothesis. It is shown that the enhanced Asian jet in August is favourable for the propagation of stationary Rossby waves and that the regions of descent over the eastern Mediterranean Sea and the Aral Sea act as two major wave sources. Second, a primitive‐equation model is used to simulate the climatology of August. The model successfully simulates the Bonin high with an equivalent‐barotropic structure. The upper‐tropospheric ridge is found to be enhanced by a height anomaly of more than 80 m at 200 hPa, when a wave packet arrives. Sensitivity experiments are conducted to show that the removal of the diabatic cooling over the Asian jet suppresses the Silk Road pattern and formation of an equivalent‐barotropic ridge near Japan, while the removal of the diabatic heating in the western Pacific does not. Copyright © 2003 Royal Meteorological Society
Impact of ice microphysics on multiscale organization of tropical convection in two‐dimensional cloud‐resolving simulations
Authors: Grabowski Wojciech W.
Published: February 2003

This paper documents the impact of ice microphysics on the multiscale organization of tropical convection as simulated in two‐dimensional cloud‐resolving model simulations. Results from simulations which apply warm‐rain microphysics are compared with results from a simulation which includes ice processes presented previously in this journal. In these simulations, moist convection and large‐scale dynamics interact on an unprecedented range of spatial and temporal scales, albeit within a limited two‐dimensional dynamical framework. In general, the large‐scale organization of convection is similar in all simulations, although the scale and propagation speed of convectively‐coup led gravity waves are different between the warm‐rain and ice simulations. The most striking differences are on the mesoscale. The warm‐rain simulations feature mesoscale convective systems with a reduced stratiform component and shorter life cycle than mesoscale systems in the simulation with ice microphysics. These impacts are consistent with previous modelling studies of the impact of ice microphysics on organized convection. It is hypothesized that the shorter life cycle of mesoscale convective systems in warm‐rain simulations influences scale selection of the large‐scale convectively‐coup led gravity waves. Moreover, the vertical transport of horizontal momentum is affected as well. To the author's knowledge this is the first time the impact of cloud microphysics on mesoscale convective systems is shown to affect the coupling between deep convection and large‐scale perturbations in the tropics. Copyright © 2003 Royal Meteorological Society
The predictability of extratropical cyclones: Nonlinear sensitivity to localized potential‐vorticity perturbations
Authors: Beare R. J. , Thorpe A. J. , White A. A.
Published: February 2003

There is a range of phenomena which, if misrepresented in a numerical weather prediction model, could cause localized finite‐amplitude errors in the potential vorticity (PV). Examples are: convective systems, the tropopause PV trough, and orographic PV perturbations. Motivated by this, the sensitivity of short‐range cyclone forecasts (up to two days) to localized finite‐amplitude initial PV anomalies is investigated using a method termed ‘PV‐sensitivity mapping’. An initial PV‐anomaly perturbation is applied at each grid point in turn and the corresponding impact in a nonlinear cyclone development is computed. In contrast to the adjoint method, there is no linear approximation. The PV‐sensitivity map depicts the forecast time impacts (in energy and pressure) for each initial spatial location of PV perturbation. A nonlinear three‐dimensional quasi‐geostrophic model is used because it has PV as a prognostic variable, is numerically efficient, and simulates the essence of cyclogenesis.

The sensitivity maps are calculated for a dry and a moist cyclone scenario, and for a synoptic‐scale and mesoscale initial PV perturbation. The degree of nonlinearity in error growth is significant for the moist case. The most sensitive regions for both cases are in the region of the steering level and the incipient cold and warm fronts. A physical interpretation using PV thinking is given. © Royal Meteorological Society, 2003. A. A. White's contribution is Crown copyright
Feature calibration and alignment to represent model forecast errors: Empirical regularization
Authors: Nehrkorn Thomas , Hoffman Ross N. , Grassotti Christopher , Louis Jean‐François
Published: February 2003

A method for characterizing errors for weather forecasts and analyses, called feature calibration and alignment (FCA), decomposes model forecast error into phase error, amplitude error and residual error. Phase and amplitude errors are represented by large‐scale displacements and biases of a field. In this study FCA is used to represent errors in realistic univariate two‐dimensional analysis and forecast fields. In previous work FCA was tuned subjectively. Here, a methodology to determine an empirical constraint that regularizes the FCA solutions is developed. This version of FCA still has some tunable parameters, but the new method greatly reduces the subjective nature of FCA. The data used are European Centre for Medium‐Range Weather Forecasts analyses and one‐ to ten‐day forecasts of 500 hPa geopotential height. A stepwise procedure is used to derive the statistics of the error components for ideally chosen spectral truncations. The stepwise FCA statistics are then used to define a constraint that controls the size of the spectral coefficients of the FCA representation of the phase and amplitude errors. A large fraction (∼90%) of the 500 hPa geopotential‐height forecast‐error variance is explained by FCA, demonstrating that a large part of the forecast error can be described as large‐scale phase and bias errors. The fraction of variance explained increases with forecast length, and is slightly larger in winter than in summer. The constrained FCA solutions are more efficient and exhibit less of a tendency for multiple solutions when compared to the unconstrained FCA solutions. Copyright © 2003 Royal Meteorological Society
Comparison of model‐derived and radar‐observed freezing‐level heights: Implications for vertical reflectivity profile‐correction schemes
Authors: Mittermaier Marion P. , Illingworth Anthony J.
Published: February 2003

In the current operational Met Office scheme for deriving rainfall rates from radar, the height of the enhanced radar return associated with melting snow, the bright band, is determined using the height of the $0\ ^{\circ}\hbox{C}$ isotherm obtained from the Met Office Unified Mesoscale Model (UM) forecast. In this paper the potential errors of using model forecast heights as input to the bright‐band correction scheme are investigated. The UM and European Centre for Medium‐Range Weather Forecasts (ECMWF) model forecasts of wet‐bulb $0\ ^{\circ}\hbox{C}$ isotherm heights (WBZ) are compared with the height of the ‘step’ increase in reflectivity in the vertical profiles recorded by the vertically pointing 94 GHz Galileo cloud radar at Chilbolton. High‐frequency radars do not measure an enhanced ‘bright band’ at the melting layer, rather a sudden increase of reflectivity as the ice particles become coated in water. This sudden step can be used to locate accurately the height of the WBZ.

Results show that the UM predicts the WBZ height with a root‐mean‐square error of 147 m and a bias of 15 m. This is within the worst‐case tolerance of 200 m of the operational bright‐band correction scheme. Factors that may influence the accuracy are the presence of deep isothermal layers and timing errors concerning the passage of fronts, but these are found not to be serious. An investigation into the deterioration of the UM 36‐hour forecast shows that half the error is introduced at the initialization time, highlighting the fact that further improvements can be achieved through a better definition of the initial state of the atmosphere. The ECMWF forecast is for a longer lead time, but comparison for the same lead‐time errors as the UM shows that the performance of the two models is comparable.

An alternative approach is to derive the bright‐band height from volumetric radar scans at different elevations. This study suggests that, at least in the UK, operational model predictions of the freezing‐level height are within the specified 200 m error, but that the use of volumetric scans, even under idealized conditions, cannot achieve this accuracy. Copyright © 2003 Royal Meteorological Society
Numerical simulations of stably stratified flow through a mountain pass
Authors: Ross A. N. , Vosper S. B.
Published: February 2003

The effect of boundary‐layer friction in stably stratified flow through a mountain pass is examined through a series of idealized numerical simulations. Both two‐dimensional (2‐D) simulations of flow through a valley which is infinitely long in the direction of the flow and three‐dimensional (3‐D) simulations of flow through a pass in a 2‐D ridge are conducted. For the 2‐D simulations the secondary flow induced by the flow turning in the boundary layer is investigated and the behaviour categorized depending on the location of any flow separation on the valley side. The separation (diagnosed using surface stresses) is found to depend primarily on a Froude number based on the valley depth. The generation of potential vorticity (PV) in the boundary layer adjacent to the valley sides is examined in the 2‐D simulations, and numerical results are found to agree well with simple scaling analysis.

In the 3‐D case PV is still generated in the boundary layer adjacent to the sides of the pass, and this PV is advected out of the pass by the flow across the mountain. When the upstream flow is sufficiently strongly stratified (Froude number based on the mountain height less than unity) a hydraulic jump occurs on the lee side of the mountain ridge, enabling advection of the PV out of the boundary layer and into the interior of the flow. Examination of the PV structure on isentropic surfaces downwind of the mountain ridge reveals the presence of PV banners which originate from the sides of the pass. In these simulations frictional processes within the boundary layer appear to dominate the production of the PV banners, and gravity‐wave breaking plays a relatively minor role. © Royal Meteorological Society, 2003. S. B. Vosper's contribution is Crown copyright.
On the cloud processing of aerosol particles: An entraining air‐parcel model with two‐dimensional spectral cloud microphysics and a new formulation of the collection kernel
Authors: Kerkweg Astrid , Wurzler Sabine , Reisin Tamir , Bott Andreas
Published: February 2003

A study has been made of the modification of marine aerosol particles due to cloud processes and the impact of the modified aerosols on the microphysical structure of future clouds. For this purpose, an entraining air‐parcel model with two‐dimensional spectral cloud microphysics was used. In order to treat collision/coalescence processes in the two‐dimensional microphysical module, a new realistic and continuous formulation of the collection kernel was developed. Based on experimental and theoretical data, the kernel covers the entire investigated size range of aerosols, cloud and rain drops, that is the kernel combines all important collision/coalescence processes such as the collision of cloud drops as well as the impaction scavenging of small aerosols by big raindrops. Since chemical reactions in the gas phase and in cloud drops have an important impact on the physico‐chemical properties of aerosol particles, the parcel model has been extended by a chemical module describing gas‐phase and aqueous‐phase chemical reactions. However, it is shown that in the numerical case‐studies presented in this paper the modification of aerosols by chemical reactions has a minor influence on the microphysical structure of future clouds. The production of large aerosol particles by collision/coalescence processes is mainly responsible for an enhanced formation of rain in a second cloud event. Copyright © 2003 Royal Meteorological Society
Variational assimilation of radar reflectivities in a cirrus model. I: Model description and adjoint sensitivity studies
Authors: Benedetti Angela , Stephens Graeme L. , Vukićević Tomislava
Published: February 2003

This paper presents an ice microphysics model to be used in variational assimilation of cloud‐radar data. The model predicts the vertical and temporal evolution of the parameters of a modified gamma size distribution describing an ice‐cloud crystal population, given an initial atmospheric state. Microphysical variables are mapped onto radar reflectivities using an explicit radar forward model. Evolution equations take into account microphysical processes relevant to ice‐crystal growth, such as vapour‐diffusion growth, aggregation, and gravitational sedimentation. The thermodynamic and dynamic state is specified from a numerical forecast or a radiosonde sounding and is assumed constant over the model integration time. Due to this assumption, the model provides no feedback to the environmental state and thus cannot be used for long‐term cloud forecasts. However, when the model is integrated over a short time interval, and the atmospheric conditions are close to water saturation at cloud levels, the model is shown to compare well with observations. An adjoint of a linearized version of the cloud model is derived and applied to investigate model sensitivities to input variables and model parameters. Results show a large sensitivity of model outputs to temperature and selected parameters related to the crystal fall‐velocity parametrization. Copyright © 2003 Royal Meteorological Society
Conditional probability seasonal predictions of precipitation
Authors: Clark Robin , Déque Michel
Published: February 2003

Underlying, slowly evolving sea surface temperatures (SSTs) can influence atmospheric processes on seasonal time‐scales raising hopes of producing successful seasonal forecasts using computer models. Unfortunately internal atmospheric instability and nonlinear dynamics of the atmosphere limit their skill even with perfect (ob‐served) SSTs. An approach using analogues in an ensemble environment is shown to increase the skill of seasonal forecasts by using raw model ensemble forecasts to generate enlarged analogue ensembles consisting entirely of observations from other years. These new ensembles are a cheap and effective way of producing larger ensembles, which use readily available historical information about the real atmosphere which raw models do not. Conditional probability predictions from these new ensembles are shown to have higher skill than raw model forecasts in all seasons, in all parts of the world. They are also shown to be more skilful than climatology in certain seasons, also in all regions of the world. They can also be used to aid skill prediction. Copyright © 2003 Royal Meteorological Society
The impact of upstream blocking, drainage flow and the geostrophic pressure gradient on the persistence of cold‐air pools
Authors: ZÄngl G.
Published: February 2003

Idealized numerical simulations are performed to investigate dynamical mechanisms affecting the persistence of cold‐air pools in basins and valleys. The first orography type considered is a shallow elongated basin located upstream of a mountain ridge. For sensitivity tests, the mountain ridge is removed. The second type is a basin embedded in a plateau‐like mountain ridge. In part of the simulations, this basin has an outflow towards the lee‐side plain so as to assess the impact of the drainage flow. The large‐scale flow is taken to be in geostrophic balance. In the standard setting, it is perpendicular to the basin and the ridge.

The main effect of a large‐scale pressure gradient is to induce a circulation within a cold‐air pool until the upper boundary of the cold pool is inclined such as to compensate for the ambient pressure gradient. The cold air accumulates where the ambient pressure is lowest. For a shallow basin, this means that part of the cold air may be lost due to advection out of the basin. The upstream influence of a mountain ridge in the lee of a shallow basin is found to be twofold. It tends to deflect the low‐level flow towards the lower pressure, leading to an additional ridge‐parallel force on the cold‐air pool. On the other hand, the absolute wind speed is reduced, diminishing the turbulent mixing near the top of the cold pool. The simulations show that the first effect prevails for ridge‐normal flow while second effect may dominate for other flow directions. Drainage flow out of a valley is found to be very important as it promotes the penetration of warm air into valleys very effectively. It may cause a cold pool in a deep valley to disappear more quickly than a cold pool in a shallow basin. Sensitivity tests show that the persistence of a cold pool depends on its depth, on its vertically integrated heat deficit, and on the maximum heat deficit at the bottom of the cold pool. Copyright © 2003 Royal Meteorological Society
Nasal polyps: Still more questions than answers
Authors: Bateman Neil D. , Fahy Colm , Woolford Timothy J.
Published: February 2003

Nasal polyps are common, affecting one to four per cent of the population. Their cause, however, remains unknown and it is possible that it is not the same in all patients. They have a clear association with asthma, aspirin sensitivity and cystic fibrosis. Histologically they demonstrate large quantities of extracellular fluid, mast cell degranulation and an infiltrate of inflammatory cells, usually eosinophils. While this appearance would suggest an allergic pathology there is little conclusive evidence to support this in most patients. There is, however, some preliminary evidence to suggest that a local allergic process could be the cause. While allergic fungal sinusitis is a well defined clinical entity with recognized diagnostic criteria the ubiquitous nature of fungal spores makes the role of fungal infection in patients with nasal polyps difficult to determine and currently this remains unclear.

Surgical treatment of nasal polyps has declined in recent years as the benefits of medical treatment have become increasingly recognized. There is good evidence to support the use of corticosteroids both as a primary and post-operative treatment in the majority of patients. Other medical treatments require further evaluation before they could be considered a viable alternative to steroids. Assessment of the literature regarding surgical intervention is difficult and there is little evidence on which to base a surgical treatment philosophy. The authors believe that an endoscopic approach using a microdebrider facilitates accurate removal of polyps with preservation of normal anatomy.
Treatment of Ménière’s disease by intratympanic gentamicin application
Authors: Assimakopoulos Dimitrios , Patrikakos George
Published: February 2003

Ménière’s disease is a vestibular disorder characterized by episodic vertigo, tinnitus, fluctuant hearing loss, and ear fullness, with vertiginous attacks being the most disabling complaint. The effectiveness of conservative treatment has been variable, while surgical techniques provide more permanent relief from vertigo, but pose possible morbidity and cochlear risk. Intratympanic administration of gentamicin has been proposed as an alternative for patients with debilitating Ménière’s disease who have failed to respond to standard medical treatment. The goal of such treatment is to control vertigo by partially or completely destroying the vestibular system, while at the same time maintaining hearing.

In this review we present the current medical literature on pathophysiology, pharmacokinetics, administration methods, dosage, treatment protocols, and problems related to intratympanic administration of gentamicin for patients with MD.

Intratympanic gentamicin administration is a simple medical modality for treatment of persistent vertigo in patients with Ménière’s disease. According to recent world research protocols, we propose the instillation of gentamicin by transtympanic injection, as a quick, easy, well-tolerated, ambulatory and cost-effective technique. Drug solution concentrations should be dependent on the frequency, intensity and duration of vertigo spells, as well as the degree of existing hearing loss, thus providing progressive vertigo relief with a low possibility of secondary deafness.
Philipp Friedrich Arnold, Ludvig Levin Jacobson and their contribution to head and neck anatomy
Authors: Lekakis G. K.
Published: February 2003

Philipp Friedrich Arnold and Ludvig Levin Jacobson were two of the greatest anatomists of the 19th century. Within this paper their backgrounds and their contribution to the development of various aspects of head and neck anatomy are considered.
External auditory canal duplication anomalies associated with congenital aural atresia
Authors: Blevins Nikolas H. , Byahatti Seema V. , Karmody Collin S.
Published: February 2003

Maldevelopment of the first branchial cleft can produce a broad spectrum of anomalies in its derivative structure, the external auditory canal (EAC). Failure of the cleft to develop normally can result in either the absence of a normally patent EAC (atresia, or stenosis) or a duplication anomaly (cyst, sinus, or fistula). Despite their common origins, the coexistence of these anatomical abnormalities is quite unusual. We present four patients with both aural atresia and duplication anomalies of the EAC. Three patients had non-syndromic unilateral aural atresia and presented with periauricular lesions originating from the first branchial cleft. The other patient had a variant of Treacher Collins syndrome and presented with draining infra-auricular fistulae.

The classification and management of first branchial cleft anomalies is reviewed in light of these cases. An understanding of the embryogenesis of the external ear is necessary to successfully recognize and treat this spectrum of deformities. A classification system is presented that encompasses the full spectrum of first cleft anomalies.
Nasal septal perforation repair using open septoplasty and unilateral bipedicled flaps
Authors: Newton J. R. , White P. S. , Lee M. S. W.
Published: February 2003

The aim of this study was to assess the success of the technique of open septoplasty with bipedicled flaps in achieving long-term closure and control of symptoms. Between 1993 and 2000, 32 patients underwent surgery for nasal septum perforation. Twenty patients with large perforations underwent posterior edge repair only. The remaining 12 patients (five female, and seven male) with perforations less than 20 mm in diameter underwent open septoplasty and a unilateral bipedicled flap closure. A retrospective review involving a symptom scores assessment and follow-up examination was conducted. One patient died of unrelated illness, and was excluded. Results showed 10 of the remaining 11 patients achieved closure after a mean follow up of 10 months. The symptoms of crusting (p < 0.0001), epistaxis (p < 0.02), discharge (p < 0.012), whistling (p < 0.011), and overall discomfort (p < 0.02), were all significantly improved. We conclude that by using this technique on patients with small perforations less than 20 mm, it is possible to achieve up to a 90 per cent perforation closure rate, and a significant improvement in patients’ symptoms.
Voice rehabilitation after laryngectomy with the Provox® voice prosthesis in South Africa
Authors: Cornu Anne-Sophie , Vlantis Alexander C. , Elliott Haley , Gregor R. Theo
Published: February 2003

A study was undertaken to determine whether the Provox® voice prosthesis provides good voice rehabilitation following a total laryngectomy in the urban, suburbanand rural populations served by a tertiary referral hospital in South Africa.

Between 1995 and 1999, a cohort of 128 patients at Tygerberg Hospital was rehabilitated with the Provox™ voice prosthesis after laryngectomy. In 104 patients primary placement of the prosthesis was done at the time of the laryngectomy. Mean device life and adverse events were determined. Voice quality was assessed subjectively in 104 patients and objectively in 26 patients.

The mean device life was 303 days and adverse events occurred in 16 patients. Subjectively, 77 of 104 patients had a good voice, and objectively 22 of 26 patients had good voice intelligibility. The Provox® voice prosthesis provides good voice rehabilitation following total laryngectomy, with minimal complications, in the population served by Tygerberg Hospital.
The use of the KTP laser in the management of hypertrophic tracheal mucosa and granulation tissue around Provox® valve protheses
Authors: Smith W. K. , Pfleiderer A. G.
Published: February 2003

The development of hypertrophic mucosa and granulation tissue around a tracheo-oesophageal fistula voice prosthesis is a commonly encountered problem occurring in 15–20 per cent of patients. Upsizing of the voice prosthesis as well as cautery (silver nitrate and electocautery) are used to counteract this problem to a varying degree of success. The use of the CO2 laser has been mentioned by some authors but details of the method and results have not been published. We report the successful use of the KTP laser for removing such granulations whilst retaining the valve and discuss the reasons why this method should be considered.
Management of N0 neck in laryngeal carcinoma. Impact on patient’s survival
Authors: Pinilla M. , González F. M. , López-Cortijo C. , Arellano B. , Herrero J. , Trinidad A. , Vergara J.
Published: February 2003

Management of patients with carcinoma of the larynx should systematically include an appropriate treatment of lymph nodes according to the TNM stage. One of the most controversial points of the treatment in these patients is the management of the clinically negative neck (N0). A retrospective study of 295 patients with laryngeal carcinoma and N0 neck undergoing treatment in our centre between 1983 and 1993 is presented. We observed a significant decrease in the survival of clinically N0 patients with histologically affected lymphnodes. Lymphadenopathy was more frequently detected in patients with supraglottic tumours (38 per cent) when compared to glottic tumours (16 per cent). In our experience, routine bilateral and unilateral dissection of N0 necks in all supraglottic tumours and in T3–T4 glottic tumours, respectively, is the most beneficial approach for patients in terms of survival.
Simple, painless, cosmetic closure of endaural incisions
Authors: Bhalla R. K. , Lesser T. H. J.
Published: February 2003

Endaural incisions provide a cosmetic approach to the middle-ear cleft, tympanic membrane for myringoplasty, and attic and antrum for small cavity mastoidectomy. These wounds have traditionally been closed with sutures, but platelet or fibrin adhesives provide an alternative. However, discomfort at the time of suture removal, particularly in children, and the risk of transmission of blood-borne infections in gels are limitations to these wound closure techniques. This paper describes our experience with Histoacryl® glue (butyl-2-cyanoacrylate) in closing endaural incisions.
Necrotizing fasciitis: a rare occurrence in the external auditory meatus
Authors: Umapathy N. , Su A. P.
Published: February 2003

The diagnosis and management of a patient with a sloughing otitis externa thought to be necrotizing fasciitis is described. The clinical characteristics of this condition, diagnostic difficulties faced and a brief literature review are presented.
Gunshot injuries to the temporal bone
Authors: Moore P. L. , Selby G. , Irving R. M.
Published: February 2003

The current incidence of missile injury to the temporal bone (MITB) is very low in the United Kingdom. However, the increasing frequency of firearm violence in Britain suggestsa greater risk of occurrence. This, along with the devastating potential sequelae of MITB (facial palsy, dead ear, intracranial damage, major vascular injury and cosmetic disfigurement), requires otolaryngologists to be conversant with all aspects of their management. The risk of major complications is much higher with MITB than with temporal bone injury following blunt trauma, and surgical management is, therefore, much more common. We present one such case, and review the literature outlining the pathogenesis, clinical features, and recommended management.
Epithelioid haemangioendothelioma arising in the nasal cavity
Authors: Girolamo Alberto Di , Giacomini Pier Giorgio , Coli Antonella , Castri Federica , de Padova Alessandro , Bigotti Giulio
Published: February 2003

We report here the case of an epithelioid haemangioendothelioma (EHE) arising in the nasal cavity which is, to the best of our knowledge, the first ever described example in the world literature in that particular site.

The patient is a 23-year-old male who presented with repeated episodes of epistaxis from the nasal cavity and with a 1.5 cm reddish, polypoid, smooth, spontaneously bleeding nodule in the rightmiddle meatus. This lesion was histologically diagnosed as epithelioid haemangioendothelioma. Immunohistochemically the neoplasm displayed striking positivity for CD31, CD34 and vimentin. A surgical approach was performed by ’facial degloving’, removing the right inferior turbinate, the anterior two-thirds of the middle turbinate and the medial wall of the ethmoid bone. After 12 months follow-up the patient is disease-free, without any local or distant recurrence.
Use of a nitinol stent to treat dysphagia post-laryngopharyngectomy
Authors: Sheahan Patrick , Walsh Michael A.
Published: February 2003

Permanent dysphagia occurring after laryngectomy or laryngopharyngectomy is uncommon, and when it does occur, can usually be treated by periodic dilatation under general anaesthesia. Occasionally, however, conservative treatment is insufficient, and patients require long-term feeding via a gastrostomy or jejunostomy tube. We describe the case of a man with an anastamotic stricture post-pharyngectomy who underwent insertion of a nitinol stent across the stricture for treatment of dysphagia. The patient’s swallowing was significantly improved in the short-term, however, ultimately, florid granulation tissue formation led to obstruction of the stent and a disappointing long-term result. This, to our knowledge, is the first documentation of the use of a stent to treat dysphagia in a patient post-laryngectomy or pharyngolaryngectomy.
Tissue augmentation using Bioplastique® as a treatment of leakage around a Provox® 2 voice prosthesis
Authors: Rokade A. V. , Mathews J. , Reddy K. T .V.
Published: February 2003

Rehabilitation of voice and speech after laryngectomy with valve prosthesis has become a well-established practice in recent years. The formation of tracheo-oesophageal fistula (TOF) and the subsequent management of the patient with a voice prosthesis can be associated with a number of problems and complications.

We report a new technique of the use of injectable Bioplastique® in the treatment of persistent leakage around Provox® 2 voice prosthesis. Our experience in two cases has shown that it is a relatively simple and effective procedure in stopping the leak around the valve immediately and is without any short-term complications.
An unusual metastatic site of laryngeal carcinoma: scapular muscles
Authors: Yucel Emre A. , Demirel Tayfun , Demiryont Misten , Egeli Unal , Deger Kemal
Published: February 2003

It is well known that in advanced cervical metastatic disease of head and neck squamous cell carcinoma, the incidence of distant metastasis is high. A case of distant metastasis to the scapular muscles from an uncontrolled cervical metastasis of laryngeal carcinoma is presented. Other unusual metastatic sites are reviewed and the possible mechanism of the spread is discussed.
Two reactions of Haloferax volcanii RNA splicing enzymes: Joining of exons and circularization of introns
Authors: SALGIA SHILPA R. , SINGH SANJAY K. , GURHA PRIYATANSH , GUPTA RAMESH
Published: February 2003

Archaeal RNA splicing involves at least two protein enzymes, a specific endonuclease and a specific ligase. The endonuclease recognizes and cleaves within a characteristic bulge-helix-bulge (BHB) structure formed by pairing of the regions near the two exon–intron junctions, producing 2‘,3′-cyclic phosphate and 5′-hydroxyl termini. The ligase joins the exons and converts the cyclic phosphate into junction phosphate. The ligated product contains a seven-base hairpin loop, in which the splice junction is in between the two 3′ terminal residues of the loop. Archaeal splicing endonucleases are also involved in rRNA processing, cutting within the BHB structures formed by pairing of the 5′ and 3′ flanking regions of the rRNAs. Large free introns derived from pre-rRNAs have been observed as stable and abundant circular RNAs in certain Crenarchaeota, a kingdom in the domain Archaea. In the present study, we show that the cells of Haloferax volcanii, a Euryarchaeote, contain circular RNAs formed by 3′,5′-phosphodiester linkage between the two termini of the introns derived from their pre-tRNAs. H. volcanii ligase, in vitro, can also circularize both endonuclease-cleaved introns, and non-endonuclease-produced substrates. Exon joining and intron circularization are mechanistically similar ligation reactions that can occur independently. The size of the ligated hairpin loop and position of the splice junction within this loop can be changed in in vitro ligation reactions. Overall, archaeal RNA splicing seems to involve two sets of two symmetric transesterification reactions each.
Common and distinctive features of GNRA tetraloops based on a GUAA tetraloop structure at 1.4 Å resolution
Authors: CORRELL CARL C. , SWINGER KERREN
Published: February 2003

GNRA tetraloops (N is A, C, G, or U; R is A or G) are basic building blocks of RNA structure that often interact with proteins or other RNA structural elements. Understanding sequence-dependent structural variation among different GNRA tetraloops is an important step toward elucidating the molecular basis of specific GNRA tetraloop recognition by proteins and RNAs. Details of the geometry and hydration of this motif have been based on high-resolution crystallographic structures of the GRRA subset of tetraloops; less is known about the GYRA subset (Y is C or U). We report here the structure of a GUAA tetraloop determined to 1.4 Å resolution to better define these details and any distinctive features of GYRA tetraloops. The tetraloop is part of a 27-nt structure that mimics the universal sarcin/ricin loop from Escherichia coli 23S ribosomal RNA in which a GUAA tetraloop replaces the conserved GAGA tetraloop. The adenosines of the GUAA tetraloop form an intermolecular contact that is a commonplace RNA tertiary interaction called an A-minor motif. This is the first structure to reveal in great detail the geometry and hydration of a GUAA tetraloop and an A-minor motif. Comparison of tetraloop structures shows a common backbone geometry for each of the eight possible tetraloop sequences and suggests a common hydration. After backbone atom superposition, equivalent bases from different tetraloops unexpectedly depart from coplanarity by as much as 48°. This variation displaces the functional groups of tetraloops implicated in protein and RNA binding, providing a recognition feature.
Absence of transitive and systemic pathways allows cell-specific and isoform-specific RNAi in Drosophila
Authors: ROIGNANT JEAN-YVES , CARRÉ CLÉMENT , MUGAT BRUNO , SZYMCZAK DIMITRI , LEPESANT JEAN-ANTOINE , ANTONIEWSKI CHRISTOPHE
Published: February 2003

RNA interference (RNAi) designates the multistep process by which double-stranded RNA induces the silencing of homologous endogenous genes. Some aspects of RNAi appear to be conserved throughout evolution, including the processing of trigger dsRNAs into small 21–23-bp siRNAs and their use to guide the degradation of complementary mRNAs. Two remarkable features of RNAi were uncovered in plants and Caenorhabditid elegans. First, RNA-dependent RNA polymerase activities allow the synthesis of siRNA complementary to sequences upstream of or downstream from the initial trigger region in the target mRNA, leading to a transitive RNAi with sequences that had not been initially targeted. Secondly, systemic RNAi may cause the targeting of gene silencing in one tissue to spread to other tissues. Using transgenes expressing dsRNA, we investigated whether transitive and systemic RNAi occur in Drosophila. DsRNA-producing transgenes targeted RNAi to specific regions of alternative mRNA species of one gene without transitive effect directed to sequences downstream from or upstream of the initial trigger region. Moreover, specific expression of a dsRNA, using either cell-specific GAL4 drivers or random clonal activation of a GAL4 driver, mediated a cell-autonomous RNAi. Together, our results provide evidence that transitive and systemic aspects of RNAi are not conserved in Drosophila and demonstrate that dsRNA-producing transgenes allow powerful reverse genetic approaches to be conducted in this model organism, by knocking down gene functions at the resolution of a single-cell type and of a single isoform.
Viroid RNA systemic spread may depend on the interaction of a 71-nucleotide bulged hairpin with the host protein VirP1
Authors: MANIATAKI ELSA , TABLER MARTIN , TSAGRIS MINA
Published: February 2003

Viroids are noncoding circular single-stranded RNAs that are propagated systemically in plants. VirP1 is a protein from tomato, which is an excellent host for potato spindle tuber viroid (PSTVd), and it has been isolated by virtue of its specific in vitro binding to PSTVd RNA. We report on the specific in vivo interaction of VirP1 with full-length viroid RNA as well as with subfragments in the three-hybrid system. The terminal right domain (TR) of PSTVd was identified as a strong interacting partner for VirP1. A weaker partner is provided by a right-hand subfragment of hop stunt viroid (HSVd), a viroid that infects tomato poorly. We present a sequence and structural motif of the VirP1-interacting subfragments. The motif is disturbed in the replicative but nonspreading R+ mutant of the TR. According to our in vivo and in vitro binding assays, the interaction of this mutant with VirP1 is compromised. We propose that the AGG/CCUUC motif bolsters recognition of the TR by VirP1 to achieve access of the viroid to pathways that propagate endogenous RNA systemic signals in plants. Systemic trafficking has been suggested for miRNA precursors, of which the TR, as a stable bulged hairpin 71 nt long, is quite reminiscent.