Journal articles on the topic 'Irregular air gap'

The air gap response of a specific semi-submersible platform subjected to irregular waves is considered. Detailed model tests for this structure are studied in depth. Using time-histories of both motions and air gap, statistical analyses both for the absolute near-structure wave elevation (with respect to a fixed observer), and the relative wave elevation (with respect to the moving structure) are performed. Statistics of wave crest amplification, due to diffraction, are established. Corresponding amplification factors are derived from linear diffraction theory, and the results of theory and observations are critically compared.

Solidification of a pure metal against a flat mold surface is examined using a nonuniform thermohypoelastic beam. Heat is removed with a spatially periodic heat flux superimposed onto uniform cooling, which leads to irregular growth of the casting. The associated nonuniform temperature field also produces nonuniform deformation in the casting which in time may lead to air gap nucleation along the mold/casting interface. Air gap nucleation is defined as the circumstance where the local mold/casting interface pressure falls to zero. Unstable growth occurs when such air gaps nucleate beneath thickness minima, thus further reducing heat transfer at these positions, and dramatically amplifying the existing thickness nonuniformity. The time to onset of instability depends upon material properties such as density, latent heat, thermal conductivity, elastic constants, and coefficient of thermal expansion as well as upon process parameters such as cooling rate, fluid pressure, and wavelength of the periodic heat flux.

A similarity reduction of the Navier–Stokes equations for the motion of an infinite rotating disk above an air-bearing table yields a coupled pair of ordinary differential equations governed by a Reynolds number $Re=Wh/{\it\nu}$ and a rotation parameter $S=\sqrt{2}h{\it\Omega}/W$, where $h$ is the float height, $W$ is the air levitation velocity, ${\it\Omega}$ is the disk rotation rate, and ${\it\nu}$ is the kinematic viscosity of air. After deriving the small- and large-Reynolds-number behaviour of solutions, the equations are numerically integrated over a wide range of $Re{-}S$ parameter space. Zero-lift boundaries are computed as well as the boundaries separating pure outward flow from counter-flow in the gap. The theory is used to model the steady float height of a finite-radius air hockey disk under the assumption that the float height is small relative to the diameter of the disk and the flow is everywhere laminar. The steady results are tested against direct numerical simulation (DNS) of the unsteady axisymmetric Navier–Stokes equations for the cases where the disk rotates at constant angular velocity but is either at a fixed height or free to move axially. While a constant shift in the gap pressure conforms closely to that found using steady theory, the interaction of the radial jet emanating from the gap with a vertical transpiration field produces vortex rings which themselves propagate around to interact with the jet. Although these structures diffuse as they propagate up and away from the gap, they induce a departure from the steady-flow assumption of atmospheric pressure at the gap exit, thus inducing small irregular axial oscillations of the floating disk.

The analysis phase of the Wave Crest Sensor Intercomparison Study (WACSIS) focussed on the interpretation of the wave data collected by the project during the winter of 1997–98. Many aspects of wave statistics have been studied, but the main emphasis has been on crest height distributions, and recommendations for crest heights to be used in air gap calculations. In this paper, we first describe comparisons of the crest height distributions derived from the sensors (radars, wave staffs, laser) and from simulations based on 3-D second-order irregular wave models. These comparisons permit us to make conclusions on the quality of these models and to qualify the ability of some sensors to measure the crest heights accurately. In the second part, two new parametric models of the crest height distributions are discussed and their superiority to standard parametric models is demonstrated.

This article describes a series of model tests conducted to examine extreme wave events associated with tropical cyclonic conditions and their impacts on an offshore deck structure. Extreme waves of a representative cyclonic sea state were examined in a towing tank within long-crested irregular wave trains. Experimental results presented include global forces and localised slamming pressures acting on a rigidly mounted box-shaped deck, which represents a simplified topside structure of a tension leg platform. The effect of static set-down on the still-water air gap was investigated by applying an equivalent reduction for the deck clearance. It was found that a small reduction of 20 mm (2.5 m full scale) in the original deck clearance can lead to a doubling of the magnitude of the horizontal force and the vertical upward-directed force components, as well as significantly increased slamming pressures in many locations on the deck underside.

OBJECTIVE: To investigate the anatomy and function of the velopharyngeal mechanism in musicians who experience symptoms of stress velopharyngeal insufficiency (VPI) compared to musicians who do not. METHODS: The velopharyngeal mechanism of 13 musicians, 8 with reported symptoms of stress VPI and 5 without, were evaluated using video nasendoscopy before and after 30 minutes of playing. All nasendoscopic recordings were rated by an external speech-language pathologist and ear, nose and throat surgeon for maintenance of velopharyngeal closure, type of velopharyngeal closure pattern, and velopharyngeal gap. RESULTS: Six out of 8 cases with stress VPI had nasal air leak during the assessment, 2 of whom had fatigue-related increased symptoms. Three controls had mild nasal air leak without affecting the consistency of soft palate seal nor quality of playing, suggesting that evidence of nasal air leak is not always symptomatic of stress VPI. All cases had unusual anatomical characteristics, such as the soft palate closing against an irregular surface on the posterior nasopharyngeal wall, which may cause insufficient velopharyngeal closure. Typically the soft palate contacted the nasopharyngeal wall higher when playing a wind instrument compared to during speech. CONCLUSION: Specific anatomical features and factors such as fatigue and stress may affect maintenance of velopharyngeal closure in persons with stress VPI. It is important that musicians with stress VPI are evaluated while playing their instrument. Future studies into stress VPI would benefit by including objective assessment components and some degree of quantifiable measurements.

In radiation therapy, a bolus is used to improve dose distribution in superficial tumors; however, commercial boluses lack conformity to patient surface leading to the formation of an air gap between the bolus and patient surface and suboptimal tumor control. The aim of this study was to explore 3D-printing technology for the development of patient-specific conformal 3D-printed devices, which can be used for the radiation treatment of superficial head and neck cancer (HNC). Two 3D boluses (0.5 and 1.0 cm thick) for surface dose build-up and patient-specific 3D phantom were printed based on reconstruction of computed tomography (CT) images of a patient with HNC. The 3D-printed patient-specific phantom indicated good tissue equivalency (HU = −32) and geometric accuracy (DSC = 0.957). Both boluses indicated high conformity to the irregular skin surface with minimal air gaps (0.4–2.1 mm for 0.5 cm bolus and 0.6–2.2 mm for 1.0 cm bolus). The performed dose assessment showed that boluses of both thicknesses have comparable effectiveness, increasing the dose that covers 99% of the target volume by 52% and 26% for single field and intensity modulated fields, respectively, when compared with no bolus case. The performed investigation showed the potential of 3D printing in development of cost effective, patient specific and patient friendly conformal devices for dose verification in radiotherapy.

In order to analyze the dynamic response of medium-speed maglev train in the speed range of 0–200 km/h, the suspension performance, suspended energy consumption, and riding comfort of the train stimulated by random track irregularities are discussed in this paper. Firstly, the model of medium-speed maglev train including car body, air spring vibration isolation system, and the suspension system is established. Then, a controller based on flux inner feedback loop and PID outer feedback loop is designed for the suspension system. The established model is stimulated by the actual track power spectrum in full speed range. The simulation results show that the fluctuation of suspension gap is less than ±4 mm. Furthermore, thanks to the adding of permanent magnet, the power consumption is significantly reduced, which is of benefit to the electromagnet heating problem and on-board levitation power supply system. The riding comfort of the train moving on the irregular track using Sperling index is assessed. The experimental results validate the effectiveness of the proposed analytical calculation model of medium-speed maglev train. It is shown that medium-speed maglev train achieved good performance, significant power reduction, and satisfactory riding comfort.

The aim of this study is to provide an experimental properties evaluation of a standard filter material (cellulose) and materials with fiber layer addition with small diameters (nanofibers). Filter media, including cellulose, used in the internal combustion engine inlet air filtration are made of high diameter fibres, approx. 15 µm. Significantly higher separation and filtration efficiency performance are obtained for materials with lower fibre diameters (nanofibres), however, at the expense of a significantly higher pressure drop, affecting the engine performance. Filter media manufacturers mainly specify the structure parameters (pore size, air permeability and thickness), without giving any information on the dust filtration performance and rate. The literature includes test results for models of different filter media structures. Filtration process modelling using polydisperse dust with particles of different shape and density and irregular filter media structure is possible using advanced computer techniques, however, the process is complex and requires many simplifications. Test results can be applied directly in the automotive industry. The data can be obtained by experimental tests on filter medium specimens, complete filter elements or air filters which are costly and time-consuming tests, however, those test methods are the most reliable. Conditions and testing methodology for intake air filter materials used in internal combustion engines were developed. Filtration and flow resistance efficiency and accuracy were done depending on test dust mass stopped per unit area. Tested materials filtration efficiency was assessed by a filtration quality factor, which includes experimentally determined efficiency and accuracy as well as flow resistance values. Much higher efficiency and filtration accuracy of dust grains below 5 µm in filtration materials with nanofibers addition compared to standard filtration material (filter paper) were demonstrated. For the same flow resistance values, filter materials with nanofibers addition accumulate smaller dust mass than standard filter paper. Usage of materials with nanofibers addition used in motor vehicles intake air filtration ensures their high efficiency and accuracy. It minimises its components wear, but at the expense of faster flow resistance increase, which shortens filter life and increases filter replacement frequency. Results obtained during the experimental research partly fill the gap when it comes to the basic material properties used in internal combustion engines intake air filter partitions production.

The pressure-regulating valve can realize the rapid adjustment and precise controlling of operating pressure and Mach number, to stabilize the flow field and avoid the test interference such as the air source loss or the unstable flow. This paper takes the design and optimization of pressure-regulating valve in trisonic intermittent wind tunnel as the research object to investigate its special pressure-regulating characteristic and performance in the wind tunnel. According to the requirement of the wind tunnel, the annular-gap type pressure-regulating valve is selected to match its wide adjustment range of operating parameter, high regulation accuracy, and low running resistance. The design and optimization of the pressure-regulating valve are carried out, including aerodynamic and structural design, analysis on pressure regulation characteristics, kinematics analysis, flow field analysis, vibration analysis, and structure optimization. The design and selection of some important components are carried out based on the pneumatic design and performance requirements. The pressure regulation characteristics of the pressure regulating valve are discussed and the affecting factors of the irregular flow are analyzed and evaluated by numerical simulation. The final structure of the pressure-regulating valve is determined and the test results perform well with prediction of characteristic curve.

Although Mediterranean wetlands are characterized by extreme natural water level fluctuations in response to irregular precipitation patterns, global climate change is expected to amplify this pattern by shortening precipitation seasons and increasing the incidence of summer droughts in this area. As a consequence, a part of the lake sediment will be exposed to air-drying in dry years when the water table becomes low. This periodic sediment exposure to dry/wet cycles will likely affect biogeochemical processes. Unexpectedly, to date, few studies are focused on assessing the effects of water level fluctuations on the biogeochemistry of these ecosystems. In this review, we investigate the potential impacts of water level fluctuations on phosphorus dynamics and on greenhouse gases emissions in Mediterranean wetlands. Major drivers of global change, and specially water level fluctuations, will lead to the degradation of water quality in Mediterranean wetlands by increasing the availability of phosphorus concentration in the water column upon rewetting of dry sediment. CO2 fluxes are likely to be enhanced during desiccation, while inundation is likely to decrease cumulative CO2 emissions, as well as N2O emissions, although increasing CH4 emissions. However, there exists a complete gap of knowledge about the net effect of water level fluctuations induced by global change on greenhouse gases emission. Accordingly, further research is needed to assess whether the periodic exposure to dry–wet cycles, considering the extent and frequency of the cycles, will amplify the role of these especial ecosystems as a source of these gases and thereby act as a feedback mechanism for global warming. To conclude, it is pertinent to consider that a better understanding about the effect of water level fluctuations on the biogeochemistry of Mediterranean wetlands will help to predict how other freshwater ecosystems will respond.

<p class="judulabstrakindo">ABSTRAK</p><p class="abstrakindo">Perairan Teluk Benoa merupakan kawasan semi tertutup dengan mulut sempit yang memisahkan antara Pulau Serangan dan Tanjung Benoa. Arus laut perairan Teluk Benoa, yang dekat pantai berperan penting dalam proses transpor sedimen di daerah pantai yang merupakan daerah gelombang mulai pecah hingga ke arah garis pantai. Tujuan penelitian adalah mengetahui karakteristik arus laut yang terjadi, analisis dari penyajian secara <em>scatter plot</em> dan <em>stic plot</em>, sehingga diketahui faktor dominan pembangkit arus tersebut. Data arus laut diperoleh dari hasil pengukuran pihak swasta menggunakan alat ukur ADCP. Analisis arus laut dengan <em>scatter</em> dan <em>stic plot</em><em> </em>untuk melihat arah dominan arus, serta melihat hubungan kejadian arus dengan pasang surut air laut, selain itu juga dengan perhitungan kisaran kecepatan arus yang terjadi selama pengukuran. Hasil yang diperoleh adalah arus laut di perairan Teluk Benoa berkisar antara 0,001 - 1,715 m/s (pengamatan bulan Juni - Juli 2015). Kecepatan arus pada mulut teluk lebih besar (maksimal sebesar 1,715 m/s), sedangkan di dalam teluk kecepatan arus lebih rendah (maksimal sebesar 0,883 m/s). Pada saat air pasang, arah arus dominan ke arah dalam teluk dan saat air laut surut arah dominan arus ke arah luar teluk. Kesimpulan yang diperoleh adalah kejadian arus laut di perairan Teluk Benoa lebih dominan berupa arus pasang surut. Saat kondisi bulan purnama kecepatan arus lebih tinggi dari pada saat posisi bulan separuh (kuarter pertama atau ketiga). Pada umumnya, pada mulut teluk memiliki arus yang cukup tinggi sebagai akibat celah sempit, dengan pola yang tidak beraturan akibat pengaruh perlintasan kapal dan aktivitas keluar masuk teluk.</p><p><strong>Kata kunci</strong>: arus laut, karakteristik arus laut, arus pasang surut, Teluk Benoa</p><p class="judulabstraking">ABSTRACT</p><p class="abstraking">Benoa Bay waters is a semi-enclosed area with quite a narrow mouth that separates the Serangan Island and Tanjung Benoa. Ocean currents in Benoa Bay, which is close to the beach plays an important role in the process of sediment transport in the beach area where is the waves began to break up towards the shoreline. The research objective was to know the characteristics of ocean currents that occur, from the analysis of the scatter and stic plot, so it’s known that the dominant factor of the current generator. The data of ocean currents obtained from the measurement of private parties using ADCP measuring instrument. Analysis of ocean currents with scatter and stic plot to see the dominant direction of current, and to see the relationship of current occurrence with the tide, besides also with calculation of current velocity. The results obtained are ocean currents in the Benoa Bay waters ranged from 0,001 to 1,715 m/s (observations in June-July 2015). Flow velocity at the mouth of the bay is greater (maximum of 1,715 m/s), while in the lower bay flow speed (maximum of 0,883 m/s). At high tide, the dominant current direction towards the bay and vice versa during low tide predominant direction of flow towards the outside of the bay. The conclusion is the incidence of ocean currents in the Benoa Bay waters is predominantly influenced by the tidal current. When the full moon conditions the current velocity is higher than at half month position. In general, at the mouth of the bay has a current high enough as a result of the narrow gap, with irregular pattern due to the influence and activities of ship crossings in and out of the bay.</p><p><strong>Keywords</strong>: <em>ocean current, characteristics of ocean current, tidal current, Benoa Bay</em></p>

Analysis of the negative moment near re-entrant corner in different thickness of different gap plates under the vertical distribution load. Discovered that reduced the thickness of this irregular slab also to be possible to satisfy the supporting capacity and the normal operation requirements.

The CO2 growth rate is one of the key geophysical quantities reflecting the dynamics of climate change as atmospheric CO2 growth is the primary driver of global warming. As recent studies have shown that TCCON (Total Carbon Column Observing Network) measurement footprints embrace quasi-global coverage, we examined the sensitivity of TCCON to the global CO2 growth. To this end, we used the aggregated TCCON observations (2006-2019) to retrieve Annual Growth Rate of CO2 (AGR) at global scales. The global AGR estimates from TCCON (AGRTCCON) are robust and independent, from (a) the station-wise seasonality, from (b) the differences in time series across the TCCON stations, and from (c) the type of TCCON stations used in the calculation (“background” or “contaminated” by neighboring CO2 sources). The AGRTCCON potential error, due to the irregular data sampling is relatively low (2.4–17.9%). In 2006–2019, global AGRTCCON ranged from the minimum of 1.59 ± 2.27 ppm (2009) to the maximum of 3.27 ± 0.82 ppm (2016), whereas the uncertainties express sub-annual variability and the data gap effects. The global AGRTCCON magnitude is similar to the reference AGR from satellite data (AGRSAT = 1.57–2.94 ppm) and the surface-based estimates of Global Carbon Budget (AGRGCB = 1.57–2.85). The highest global CO2 growth rate (2015/2016), caused by the record El Niño, was nearly perfectly reproduced by the TCCON (AGRTCCON = 3.27 ± 0.82 ppm vs. AGRSAT = 3.23 ± 0.50 ppm). The overall agreement between global AGRTCCON with the AGR references was yet weakened (r = 0.37 for TCCON vs. SAT; r = 0.50 for TCCON vs. GCB) due to two years (2008, 2015). We identified the drivers of this disagreement; in 2008, when only few stations were available worldwide, the AGRTCCON uncertainties were excessively high (AGRTCCON = 2.64 ppm with 3.92 ppm or 148% uncertainty). Moreover, in 2008 and 2015, the ENSO-driven bias between global AGRTCCON and the AGR references were detected. TCCON-to-reference agreement is dramatically increased if the years with ENSO-related biases (2008, 2015) are forfeited (r = 0.67 for TCCON vs. SAT, r = 0.82 for TCCON vs. GCB). To conclude, this is the first study that showed promising ability of aggregated TCCON signal to capture global CO2 growth. As the TCCON coverage is expanding, and new versions of TCCON data are being published, multiple data sampling strategies, dynamically changing TCCON global measurement footprint, and the irregular sensitivity of AGRTCCON to strong ENSO events; all should be analyzed to transform the current efforts into a first operational algorithm for retrieving global CO2 growth from TCCON data.

Hydro-turbine generator unit turning test is a key step to check the installation quality of the shafting system. The unit turning data is very important for bearing clearance adjustment. The traditional unit turning test and bearing clearance adjustment are based on a condition of that the spindle turning orbit is an approximate circle. It is simple to be used in the field operation and applicable to the most units. The trajectory of the turning orbit shows irregular shape when the spindle has a certain part of the flaw. If the traditional method is used for the unit turning and adjusting the bearing clearance, this may cause the eccentricity of three guide bearing bushes and uneven of the bearing clearance. The unit may appear a high temperature or large swing phenomenon after its commission. Seriously the unit may be burned and permanent damage. To solve this problem, this paper proposed a new method to calculate a minimum rotation space of the shaft in the bearing for each guide bearing clearance according to a geometric algorithm. Using the new method, according to the minimum circumscribed circle of the turning axis locus and final position of the turning spindle after unit turning, the bearing clearances corresponding to each turning number on the shaft can be calculated precisely. And then the bearing radial position is distributed properly so that the bearing is in the centre of rotation to the centre of the concentric circle. Therefore, the specific value of each bearing clearance adjustment is obtained. Site testing results show that using the new method the high temperature and large adjustment gap caused by using the traditional method can be avoided. Thus, the hydro-turbine generator unit operating stability is improved.

Abstract Abstract 1013 We report a novel haemoglobin (Hb) variant at position [β42 Phe → Cys] found in a Caucasian male infant with severe chronic haemolytic anaemia. He presented at 5 weeks of age with fever and vomiting and was found to have apparent oxygen saturations of 82% in air by pulse oximetry and Hb 6.7 g/dl. Absolute reticulocyte count 353 × 109/l, LDH 872 u/L, bilirubin 23 mmol/L, direct antiglobulin test (DAT) negative. Blood film showed marked anisopoikilocytosis, keratocytes, irregularly contracted cells, basophilic stippling, nucleated red blood cells, and increased polychromasia consistent with haemolysis and oxidative damage. Echocardiogram, electrocardiogram and chest radiograph were normal. Arterial blood gas revealed normal PaO2. Haptoglobins were absent. Required regular blood transfusions until 6 months of age when he achieved a 3 months period without transfusion and could be further investigated. Hb electrophoresis showed a normal pattern. No evidence of glucose 6 phosphate deficiency, pyruvate kinase or 5' pyrimindine nucleotide deficiency. Heinz preparation was positive, with positive heat stability and isopropanol test suggesting the presence of variant haemoglobin. Snap frozen mass spectrometry was performed which demonstrated a low abundance (4%) of a variant haemoglobin. This was further characterised by DNA sequencing of the beta-globin gene which revealed the presence of a novel heterozygous mutation of the beta chain. A single amino acid substitution at the 42 amnio acid of the beta chain was identified resulting in Phenylalanine being replaced by cysteine [β42 Phe → Cys]. Both parents were studied for the mutation and were found to be negative. At 2 years of age the level of variant haemoglobin was 12% and oxygen dissociation curve showed oxygen P50 of 29.5 mmHg (reference range: 29.5 – 32.0) indicating no evidence of altered oxygen affinity. He continues with severe chronic haemolytic anaemia exacerbated by infections and requires a monthly regular transfusion regime. Phenylalanine in position 42 (the first position of the region between the C and D helices - CD1) of the β chain participates in the contacts with haem. It is a critical amino acid in the haem pocket, maintaining solubility and stability. Substitution of this phenylalanine by cysteine removes a contact with haem leaving a gap at the surface of the haem pocket and results in instability. There are three other Hb variants resulting from substitutions in position 42: Hb Hammersmith, Hb Louisville and Hb Sendagi, substitutions for serine, leucine and valine respectively. Hb Hammersmith being more severe and leading to transfusion dependence in some of the cases, whilst the others are mild to moderate, only requiring transfusions for infective episodes. There are over 800 variant Hb are described with the majority not being clinically significant. Of those which are significant, greater then 95% are due to single amino acid substitutions (as in our case) which changes the structure of the Hb. The clinical abnormalities are attributable to the changes in Hb solubility, stability and capacity to carry and deliver oxygen. Disclosures: No relevant conflicts of interest to declare.

Relapsing Polychondritis is an autoimmune disease that can present with a variety of non-specific symptoms involving the ears, nose, throat, head and neck. Although uncommon, we should be aware of this disease entity, and should include it as a differential diagnosis in patients who complain of difficulty breathing. It is also prudent that we never forget to look at the larger picture beyond specific symptoms to understand and explain a patient’s condition. CASE An 18 year old female was admitted at the Pediatric emergency room (PER) due to recurrent, non-productive cough associated with occasional difficulty of breathing. One year prior to this admission, the patient complained of on and off cough, with no other associated symptoms. There was no improvement with antibiotics she was given at a local clinic, and the cough spontaneously resolved only to recur. Along with the recurrent cough, she eventually experienced difficulty of breathing and found herself in and out of the hospital, treated for bronchial asthma or pulmonary tuberculosis. Due to the symptoms’ recurring and worsening nature, the family consulted at our institution, where she was referred to the ORL service for further evaluation. On examination, she exhibited hoarseness, occasional stridor and difficulty of breathing. She also had a characteristic saddle nose deformity. Flexible nasolaryngotracheoscopy revealed a smooth extraluminal bulge extending from the area of the subglottis up to the second tracheal ring, at the 4 to 7 o’clock position of the neck. A neck soft tissue lateral (STL) film showed widening of the prevertebral soft tissue spaces with irregular calcifications at the level of C4 to C6 pushing the trachea anteriorly, causing narrowing of the tracheal air column (Fig. 1). CT scans revealed a homogenous, ill-defined mass, posterolateral to the trachea, pushing the trachea anteriorly (Fig. 2). A CT-guided aspiration biopsy (CT-GAB) was deferred by the radiologist who opined that the biopsy would be technically difficult since the mass was small and adjacent to the vessels. Prophylactic tracheostomy and open biopsy were recommended, but no consent was given by the family, and they opted to go home. 4 months after, the patient returned to the PER with difficulty of breathing. She was also noted to have bilateral auricular perichondritis and ocular redness which were described by the mother as usually associated with her episodes of dyspnea. An emergent tracheostomy and suspension laryngoscopy were performed, revealing marked enlargement of the cricoid and arytenoid cartilages. Both appeared to be heavily calcified. The thyroid cartilage was thinned out and was laterally splayed. On tracheoscopy, a smooth, mucosal swelling and smooth tracheal rings with concentric narrowing were seen. An open biopsy revealed an extraluminal hard, gritty mass adherent to the thyroid cartilage, posteriorly extending from the thyroid notch to the first tracheal ring. Biopsy specimens measuring approximately 1.5 x 1.5 cm aggregate diameter were sent for histopathology which revealed fragments of mature hyaline cartilage and lamellar bone with fragments of fibrocartilaginous tissue of chronic non-specific inflammation. With the history of recurrent cough and dyspnea; saddle-nose deformity; binaural perichondritis; ocular redness/inflammation, and histologic finding of cartilage inflammation, an assessment of relapsing polychondritis was made. She was referred to the Rheumatology service for further evaluation. and started on steroids, with note of improvement of her symptoms. DISCUSSION Relapsing polychondritis is a rare, autoimmune condition. It is characterized by recurrent inflammation leading to destruction of cartilage and other connective tissues. The ear, nose and tracheobronchial cartilage are most commonly affected.1 Males and females are affected equally with an average age at diagnosis of 51 years old. Only a few cases of relapsing polychondritis have been reported in children.2 It is believed that autoantibodies to cartilage components, specifically to collagen type II, cause inflammatory infiltration and cellular mechanisms involving lysosomal enzyme release and eventually result in the destruction of the cartilage due to the following mechanisms: excessive release of proteolytic enzymes by chondrocytes, down-regulation of collagen synthesis, and autoimmune reactions against cartilage intercellular matrix components.3 Histopathologic studies reveal cartilage destruction with loss of basophilic staining and islands of lymphocytic infiltration. Subsequently, fragmentation of cartilage occurs with replacement by fibrous tissue. 4 Relapsing polychondritis most often manifests as swelling and erythema of the ear (88%) and arthralgias (81%). Repeated auricular inflammation, scarring and retraction may cause the appearance of “cauliflower ears.” Ocular inflammation manifests in almost 60% of patients.5,2 Relapsing polychondritis may also result in dermatologic, cardiac, renal and neurologic manifestations. Respiratory involvement is the most common cause of death.6 Chondritis may affect the external nares, nasal septal turbinates, eustachian tubes, epiglottis, larynx, thyroid, cricoid, arytenoid, trachea, and bronchi. Nasal chondritis involves the distal part of the nasal septum and may lead to a saddle nose deformity. Laryngotracheal involvement may initially manifest as recurrent cough. Hoarseness, dyspnea, anterior neck pain, stridor, and wheezing may also be observed. The obstruction is due to edema, vocal cord palsy, and fixed subglottic or bronchial stenoses. This may suddenly exacerbate to dynamic airway collapse necessitating the need for tracheostomy.1,5 Life-threatening respiratory involvement is more common in females with a 2.6:1 ratio.4 Due to the wide-spectrum of signs and symptoms and their non-specificity, a diagnosis of relapsing polychondritis is often only attained a few years after the first manifestation of the disease and after repeated consults with various specialists. The time from onset of initial symptoms to diagnosis varies from 8 months to 13 years.4 McAdam, et al,7 proposed diagnostic criteria based on the most common clinical features of relapsing polychondritis. This was further modified by Damiani and Levine8 (See Table 1). Our patient presented with five of McAdam’s signs namely: recurrent chondritis of both ears, chondritis of nasal cartilages, chondritis of the laryngotracheal cartilage, and ocular inflammation. Hence, a diagnosis of relapsing polychondritis was established. There is no specific laboratory exam for relapsing polychondritis. However, normocytic, normochromic anemia, mild leukocytosis, thrombocytosis, hypergammaglobulinemia and elevated ESR are often observed.6,9 Our patient manifested with normocytic, hypochromic anemia, mild leukocytosis and with thrombocytosis. Bronchoscopy is an indispensable tool in establishing the exact site, nature and severity of airway involvement. It may show an inflammation of the tracheobronchial tree with narrowing or collapse of the airways. Bronchoscopy must be done with caution as it may cause dyspnea, airway collapse, hypoxia, asphyxia and death.4 Bronchoscopy in this patient revealed an inflamed and edematous epiglottis with progressive concentric narrowing of the tracheal space. A computed tomography (CT) scan can show deformity or circumferential thickening of the cricoid or tracheal cartilage, edema, and fibrosis or ossification of the soft tissues.6 The course of relapsing polychondritis may vary from immediate death to a relatively benign and painless course for several years. The prognosis is based on the degree of respiratory and cardiovascular involvement.2 Corticosteroids are the mainstay of treatment in relapsing polychondritis. This is due to their anti-inflammatory and anti-chondrolytic properties. Non-steroidal anti-inflammatory drugs, dapsone and colchicines may be used for mild cases. Immunosuppressive therapy in the form of cyclophosphamide, azathioprine and cyclosporine is used for severe cases.2,5 Our patient was initially treated with hydrocortisone 100 mg IV every 12 hours and was later shifted to prednisone 40 mg per day. Her disease was sufficiently controlled with this medication. Tracheostomy, as was performed in our patient, may be necessary when there is respiratory distress and subglottic involvement. Other possible adjuncts to medical therapy include continuous positive airway pressure for symptomatic relief, and metallic stent placement.5,10

Abstract Introduction: Bolus material is frequently used on patient’s skin during radiation therapy to reduce or remove build-up effect for high-energy beams. However, the air-gaps formed between the bolus and the skin’s irregular surface reduce the accuracy of treatment planning. To achieve a good treatment outcome using bolus, experimental investigations are required to choose its thickness and to quantify the air-gap effect. Material and methods: Measurements for a 6 MV photon beam with a fixed source surface distance were carried out using the 31021 Semiflex 3D chamber into the water phantom. Firstly, the depth of maximum dose (R100) and the dose value at surface (Ds) were evaluated as a function of bolus thickness for some square fields. Secondly, to test the effect of the air-gaps ranged from 5 to 30 mm with a step of 5 mm between the bolus and the phantom surface, a water-equivalent RW3 (Goettingen White Water) slab form of 10 mm thickness was considered as a bolus. Results: We observed that the linear behaviour of R100 in terms of the bolus thickness makes the choice of this parameter more convenient depending on field size. In addition, increasing the air-gaps widens the penumbra and created electrons that have a greater probability to quit the radiation field borders before reaching the surface. The dose spread of the off-field area could have a significant influence on the patient treatment. Conclusion: Based on dose distribution comparisons between the measurements with and without air-gaps for the field size of 100 mm × 100 mm, it has been demonstrated that a maximum air-gap value lower than 5 mm would be desirable for an efficient use of the bolus technique.

Abstract The commercial flat bolus cannot form perfect contact with the irregular surface of the patient’s skin, resulting in an air gap. The purpose of this study was to evaluate the feasibility of using a 3D customized bolus from silicone rubber. The silicone rubber boluses were studied in basic characteristics. The 3D customized bolus was fabricated at the nose, cheek and neck regions. The point dose and planar dose differences were evaluated by comparing with virtual bolus. The hardness, thickness, density, Hounsfield unit (HU) and dose attenuation of the customized bolus were quite similar to a commercial bolus. When a 3D customized bolus was placed on the RANDO phantom, it can significantly increase buildup region doses and perfectly fit against the irregular surface shape. The average point dose differences of 3D customized bolus were −1.1%, while the commercial bolus plans showed −1.7%. The average gamma results for planar dose differences comparison of 3D customized bolus were 93.9%, while the commercial bolus plans were reduced to 91.9%. Overall, A silicone rubber bolus produced the feasible dosimetric properties and could save cost compared to a commercial bolus. The 3D printed customized bolus is a good buildup material and could potentially replace and improve treatment efficiency.