Influence of grid resolution of large-eddy simulations on foehn-cold pool interaction.

Numerical simulations are performed to assess the influence of horizontal and vertical model resolution on the turbulent erosion of a cold-air pool (CAP) by foehn winds in an Alpine valley near Innsbruck, Austria. Strong wind shear in the transition zone from the CAP to the overlying foehn generates turbulence by shear-flow instability and contributes to the CAP erosion. The sensitivity of this process to grid resolution in the "grey zone" of turbulence is studied with the Weather Research and Forecasting model in large-eddy simulation (LES) mode with a horizontal grid spacing of 200, 40, and 13.33 m and in mesoscale mode with a grid spacing of 1 km. Moreover, two different vertical resolutions are tested. The mesoscale simulation exhibits deficiencies in the CAP development and is neither able to resolve nor parametrize the effect of Kelvin-Helmholtz (K-H) instability. In contrast, the LES with the coarsest horizontal grid spacing begins to explicitly permit K-H instability, albeit individual K-H waves are not completely resolved, and thereby greatly improves the stability and wind profile of the foehn. Refining the LES grid spacing leads to a more explicit and realistic representation of turbulence, but surprisingly has little impact on mean quantities. An increase in the vertical resolution shows the greatest benefit in the turbulent upper part of the foehn jet, whereas an increase in the horizontal resolution improves the turbulence characteristics, especially at the foehn-CAP interface. However, spectral analysis indicates that even a horizontal grid spacing of 40 m does not fully capture the energy cascade in the inertial subrange. Eddies remain too large and foehn-CAP interaction is too vigorous compared with the simulation with 13.33 m grid spacing. Nevertheless, results illustrate the potential benefit of an 𝒪(100 m) model resolution for improving numerical weather predictions in complex terrain.

Large-eddy simulation of foehn-cold pool interactions in the Inn Valley during PIANO IOP 2.

Processes of cold-air pool (CAP) erosion in an Alpine valley during south foehn are investigated based on a real-case large-eddy simulation (LES). The event occurred during the second Intensive Observation Period (IOP 2) of the PIANO field experiment in the Inn Valley, Austria, near the city of Innsbruck. The goal is to clarify the role of advective versus turbulent heating, the latter often being misrepresented in mesoscale models. It was found that the LES of the first day of IOP 2 outperforms a mesoscale simulation, is not yet perfect, but is able to reproduce the CAP evolution and structure observed on the second day of IOP 2. The CAP exhibits strong heterogeneity in the along-valley direction. It is weaker in the east than in the west of the city with a local depression above the city. This heterogeneity results from different relative contributions and magnitudes of turbulent and advective heating/cooling, which mostly act against each other. Turbulent heating is important for faster CAP erosion in the east and advective cooling is important for CAP maintenance to the west of Innsbruck. The spatial heterogeneity in turbulent erosion is linked to splitting of the foehn into two branches at the mountain range north of the city, with a stronger eastward deflected branch. Intensification of the western branch at a later stage leads to complete CAP erosion also to the west of Innsbruck. Above the city centre, turbulent heating is strongest, and so is advective cooling by enhanced pre-foehn westerlies. These local winds are the result of CAP heterogeneity and gravity-wave asymmetry. This study emphasizes the importance of shear-flow instability for CAP erosion. It also highlights the large magnitudes of advective and turbulent heating compared to their net effect, which is even more pronounced for individual spatial components.

Foehn-cold pool interactions in the Inn Valley during PIANO IOP2.

A case-study is presented of a south foehn emanating from the Wipp Valley, Austria, which encountered a cold-air pool (CAP) in the Inn Valley near the city of Innsbruck. The analysis is based on data collected during the second Intensive Observation Period of the Penetration and Interruption of Alpine Foehn (PIANO) field experiment. Foehn was initiated on 3 November 2017 by an eastward moving trough and terminated in the afternoon of 5 November 2017 by a cold front passage. On two occasions, reversed foehn flow deflected at the mountain ridge north of Innsbruck penetrated to the bottom of the Inn Valley. The first breakthrough occurred in the afternoon of 4 November 2017. It was transient and locally limited to the northwest of the city. The second (final) breakthrough occurred in the morning of 5 November 2017 and was recorded by all surface stations in the vicinity of Innsbruck. It started with a foehn air intrusion to the northeast of Innsbruck and continued with the westward propagation of the foehn-CAP boundary along the valley. Subsequently observed northerly winds above the city were caused by an atmospheric rotor. A few hours later and prior to the cold front passage, the CAP pushed back and lifted the foehn air from the ground. During both nights, shear flow instabilities formed at the foehn-CAP interface, which resulted in turbulent heating of the CAP and cooling of the foehn. However, this turbulent heating/cooling was partly compensated by other mechanisms. Especially in the presence of strong spatial CAP heterogeneity during the second night, heating in the CAP was most likely overcompensated by negative horizontal temperature advection.

Anorectal manometry with and without ketamine for evaluation of defecation disorders in children.

INTRODUCTION: Anorectal manometry (ARCM) provides valuable information in children with chronic constipation and fecal incontinence but may not be tolerated in the awake child. This study aimed to evaluate the effect of ketamine anesthesia on the assessment of anorectal function by manometry and to evaluate defecation dynamics and anal sphincter resting pressure in the context of pathophysiology of chronic functional (idiopathic) constipation and soiling in children. METHODS: This was a prospective study of children who were investigated for symptoms of chronic constipation and soiling between April 2001 and April 2004. We studied 52 consecutive children who had awake ARCM, biofeedback training and endosonography (awake group) and 64 children who had ketamine anesthesia for ARCM and endosonography (ketamine group). We age matched 31 children who had awake anorectal studies with 27 who had ketamine anesthesia. RESULTS: The children in awake and ketamine groups were comparable for age, duration of bowel symptoms and duration of laxative treatments. ARCM profile was comparable between the awake and the ketamine groups with regard to anal sphincter resting pressure, rectal capacity, amplitude of rectal contractions, frequency of rectal and IAS contractions and functional length of anal canal. Of 52 children who had awake ARCM, dyssynergia of the EAS muscles was observed in 22 (42%) and median squeeze pressure was 87mm Hg (range 25-134). The anal sphincter resting pressure was non-obstructive and comparable to healthy normal children. Rectoanal inhibitory reflex was seen in all children excluding diagnosis of Hirschsprung disease. CONCLUSIONS: Ketamine anesthesia does not affect quantitative or qualitative measurements of autonomic anorectal function and can be used reliably in children who will not tolerate the manometry while awake. Paradoxical contraction of the EAS can only be evaluated in the awake children and should be investigated further as the underlying cause of obstructive defecation in patients with chronic functional constipation and soiling.

Effects of urban density on carbon dioxide exchanges: Observations of dense urban, suburban and woodland areas of southern England.

Anthropogenic and biogenic controls on the surface-atmosphere exchange of CO2 are explored for three different environments. Similarities are seen between suburban and woodland sites during summer, when photosynthesis and respiration determine the diurnal pattern of the CO2 flux. In winter, emissions from human activities dominate urban and suburban fluxes; building emissions increase during cold weather, while traffic is a major component of CO2 emissions all year round. Observed CO2 fluxes reflect diurnal traffic patterns (busy throughout the day (urban); rush-hour peaks (suburban)) and vary between working days and non-working days, except at the woodland site. Suburban vegetation offsets some anthropogenic emissions, but 24-h CO2 fluxes are usually positive even during summer. Observations are compared to estimated emissions from simple models and inventories. Annual CO2 exchanges are significantly different between sites, demonstrating the impacts of increasing urban density (and decreasing vegetation fraction) on the CO2 flux to the atmosphere.

Clinical and psychosocial functioning in adolescents and young adults with anorectal malformations and chronic idiopathic constipation.

BACKGROUND: Faecal incontinence (FI) and constipation occur following corrective surgery for anorectal malformations (ARMs) and in children or adults with chronic constipation without a structural birth anomaly (chronic idiopathic constipation, CIC). Such symptoms may have profound effects on quality of life (QoL). This study systematically determined the burden of FI and constipation in these patients in adolescence and early adulthood, and their effect on QoL and psychosocial functioning in comparison with controls. METHODS: Patients with ARMs or CIC were compared with age- and sex-matched controls who had undergone appendicectomy more than 1 year previously and had no ongoing gastrointestinal symptoms. Constipation and FI were evaluated using validated Knowles-Eccersley-Scott Symptom (KESS) and Vaizey scores respectively. Standardized QoL and psychometric tests were performed in all groups. RESULTS: The study included 49 patients with ARMs (30 male, aged 11-28 years), 45 with CIC (32 male, aged 11-30 years) and 39 controls (21 male, aged 11-30 years). The frequency of severe constipation among patients with ARMs was approximately half that seen in the CIC group (19 of 49 versus 31 of 45); however, frequencies of incontinence were similar (22 of 49 versus 21 of 45) (P < 0·001 versus controls for both symptoms). Physical and mental well-being were significantly reduced in both ARM and CIC groups compared with controls (P = 0·001 and P = 0·015 respectively), with generally worse scores among patients with CIC. Both were predicted by gastrointestinal symptom burden (P < 0·001). There were no statistically significant differences in state or trait psychiatric morbidity between groups. CONCLUSION: FI and constipation are major determinants of poor QoL in adolescents and young adults with ARMs and in those with CIC.

Wind observations above an urban river using a new lidar technique, scintillometry and anemometry.

Airflow along rivers might provide a key mechanism for ventilation in cities: important for air quality and thermal comfort. Airflow varies in space and time in the vicinity of rivers. Consequently, there is limited utility in point measurements. Ground-based remote sensing offers the opportunity to study 3D airflow in locations which are difficult to observe with conventional approaches. For three months in the winter and spring of 2011, the airflow above the River Thames in central London was observed using a scanning Doppler lidar, a scintillometer and sonic anemometers. First, an inter-comparison showed that lidar-derived mean wind-speed estimates compare almost as well to sonic anemometers (root-mean-square error (rmse) 0.65-0.68 ms(-1)) as comparisons between sonic anemometers (0.35-0.73 ms(-1)). Second, the lidar duo-beam operating strategy provided horizontal transects of wind vectors (comparison with scintillometer rmse 1.12-1.63 ms(-1)) which revealed mean and turbulent airflow across the river and surrounds; in particular, channelled airflow along the river and changes in turbulence quantities consistent with the roughness changes between built and river environments. The results have important consequences for air quality and dispersion around urban rivers, especially given that many cities have high traffic rates on roads located on riverbanks.

Combined vertical reduction rectoplasty and sacral nerve stimulation for rectal evacuatory dysfunction and faecal incontinence associated with previous anorectal malformation.

Functional outcomes following surgery for anorectal malformation are variable, with many children experiencing persisting anorectal dysfunction. We describe a 34-year-old female with previous vestibular fistula who experienced lifelong rectal evacuatory dysfunction and faecal incontinence; she was treated in a two stage process producing efficient defecation and almost total continence.

Importance of extrasphincteric mechanisms in the pathophysiology of faecal incontinence in adults with a history of anorectal anomaly.

BACKGROUND: Although surgery for congenital anorectal anomalies (ARAs) aims to preserve anorectal function, faecal incontinence and constipation often result. Apart from the anal sphincters, continence is dependent on multiple anatomical and physiological factors. The aim of this study was to evaluate adults with a history of ARA to determine the role of such factors in functional outcome. METHODS: The study included 20 consecutive adult patients with faecal incontinence who had undergone anorectal surgery as infants. Comprehensive testing included anal manometry, endoanal ultrasonography, tests of pudendal nerve function and rectal sensory function, evacuation proctography and colonic transit studies. RESULTS: Anal resting tone and squeeze increments were both attenuated in 15 of 19 patients. Integrity of the internal and external anal sphincters was compromised in 16 and 15 of 18 patients respectively. Eleven of 13 had evidence of pudendal neuropathy. Rectal sensation was abnormal in 14 of 18 patients, of whom ten were hypersensitive and four hyposensitive. Rectal evacuation was abnormal in nine of 14. Colonic transit was delayed in five of eight patients with constipation. CONCLUSION: Faecal incontinence in adult patients with ARA is related to various pathophysiologies. Structural integrity of the anal sphincters is a major factor, but extrasphincteric mechanisms, notably rectal sensory function, may be as important.

Evaluation of outcome of anorectal anomaly in childhood: the role of anorectal manometry and endosonography.

The aim of this study was to evaluate role of anorectal manometry (ARM) and anal endosonography (ES) in assessment of the internal anal sphincter (IAS) quality on continence outcome following repair of anorectal anomalies (ARA). We devised a scoring system to evaluate the quality of the IAS based on ARM and ES and correlated the scores with clinical outcome, using a modified Wingfield score (MWS) for faecal continence. We also assessed the implication of megarectum and neuropathy on faecal continence. Of 54 children studied, 34 had high ARA and 20 had low ARA. Children with high ARA had poor sphincters on ES and ARM, and also poor faecal continence compared to those with low ARA. The presence of megarectum and neuropathy was associated with uniformly poor outcome irrespective of the IAS quality. The correlations between MWS on one hand, and ES and ARM scores for IAS on the other hand were weak in the whole study group, ES r = 0.27, P < 0.04, and ARM r = 0.39, P < 0.004. However, the correlations were strong in those who had isolated ARA without megarectum or neuropathy, ES r = 0.51, P < 0.02 and ARM r = 0.55, P < 0.01, respectively. In conclusion, the ARM and ES are valuable in evaluation of continence outcome in children after surgery for ARA and those with good quality IAS had better faecal continence. The IAS is a vital component in functional outcome in absence of neuropathy and megarectum.

Lactobezoar with perforation in a premature infant.

An unusual case of neonatal gastric perforation secondary to a large milk curd bezoar (lactobezoar) in a premature infant is reported. Following surgical treatment the infant made a full and uncomplicated recovery. Aetiological factors associated with the development of lactobezoars and their diagnosis and treatment are discussed.

Investigations for incontinence and constipation after surgery for Hirschsprung's disease in children.

Surgery for Hirschsprung's disease is associated with high rate of morbidity, in the form of either constipation or incontinence or a combination of the two. This study investigates the mechanisms responsible for incontinence and/or constipation following the pull-through operation for Hirschsprung's disease. There were 19 children (15 boys and 4 girls), who at the time of study; 16 had undergone Duhamel, 1 Rehbein, and 2 Soave operation. We classified patients according to their symptoms into 3 groups: Group A was incontinent of faeces; Group B was constipated and incontinent of faeces, and Group C was constipated only. The median age at referral was 6 years, and the median period after operation was 5 years. All patients were investigated by intestinal transit study, endoanal sonography and anorectal manometry. Group A had normal or rapid transit study, as opposed to Groups B and C, who had delayed-transit study. On endoanal sonography, all children had an intact internal and an external anal sphincter, below the level of pull-through operation. The anorectal manometry showed a significantly lower resting anal pressure in the incontinent Group A as compared to the constipated children with or without incontinence in Group B or C (38 mmHg versus 57 or 66 mmHg respectively). The rectal pressure was also significantly higher in children in Group A as compared to those in Group B or C (71 mmHg versus 42 or 36 mmHg). The ratio of rectal/anal pressure was higher in incontinent children in Group A, as compared to constipated children in Group B or C. Therefore, constipation can be caused by high anal resting pressure and a weak rectal peristalsis, while faecal incontinence can be secondary to poor compliance and elevated rectal pressure in the presence of normal or low anal sphincter resting pressure. Aperients are the mainstay of treatment of constipation, however, children with incontinence are more difficult to treat. We did not attempt to define the pattern of nerve plexus because of poor results of revision operation for residual hypoganglionic segment and intestinal neuronal dysplasia. Treatment of these children can become more rational, if furnished with detailed functional studies. We advocate investigation of the anorectal function at an early stage in symptomatic children after surgery for Hirschsprung's disease, and less invasive treatment should be considered before embarking on major surgery.

Evaluation of dysfunction following reconstruction of an anorectal anomaly.

To evaluate the utility of anorectal manometry (ARM) and magnetic resonance imaging (MRI) with an endocoil in the assessment of dysfunction in children with repaired anorectal anomalies (ARA), 15 patients aged 1 to 15 years with repaired ARAs and chronic faecal incontinence or constipation were prospectively recruited. They underwent clinical assessment using a modified Wingfield score (MWS). ARM and MRI with an endocoil and conventional external coil were carried out. The results of ARM alone, MRI alone, and a combination of ARM and MRI were correlated with the MWS. Manometric internal anal sphincter (IAS) scores determined from sphincter length and activity correlated with MWS (r = 0.56, P = 0.02); manometric scores of rectal peristaltic activity did not. Overall manometric score (IAS and rectal scores combined) showed a correlation with MWS (r = 0.55, P = 0.02). Endoanal MRI sphincter scores did not correlate with MWS, but the presence of a megarectum on MRI did (r = 0.44, P = 0.05). Overall MRI score did not correlate with MWS. Minor neurosacral anomalies were shown on MRI in 3 children who had poor functional scores. Combined manometric and MRI scores showed a correlation with MWS (r = 0.58, P = 0.01). ARM and MRI are potentially useful in the assessment of dysfunction of children with repaired ARAs. Both modalities require refinement and further assessment in the context of directing management.

Duodenal perforation: a diagnostic pitfall in non-accidental injury.

Duodenal perforation is a rare, life threatening injury associated with non-accidental blunt abdominal trauma. Diagnostic delay is common, as the true history is concealed and signs may be minimal. Double contrast computed tomography is the most sensitive investigation to confirm clinical suspicion. We report three cases, all with other features typical of non-accidental injury.

Transanal MR imaging after repair of anorectal anomalies in children: appearances in pull-through versus posterior sagittal reconstructions.

OBJECTIVE: Our objective was to use transanal MR imaging to compare the anatomic appearance of the components of the anal sphincter and the pattern of scarring after a pull-through perineoplasty versus a posterior sagittal anorectoplasty. SUBJECTS AND METHODS: Sixteen children ranging in age from 10 months to 15 years (mean, 10 years) were imaged using transanal receiver coils appropriate to the size of the child. Five had low, four intermediate, and seven high anomalies. Seven had undergone a transanal pull-through procedure, and nine had undergone posterior sagittal reconstruction. The integrity of the muscles was assessed on T1-weighted and short inversion time inversion recovery transverse and coronal images using a qualitative MR imaging score. The pattern of scarring was also assessed. RESULTS: In the transanal pull-through group, four of seven patients showed external sphincter deficiency. A circumferential low-signal-intensity band was seen inferior to the sphincter in six patients. All posterior sagittal reconstructions had a long posterior midline scar. Five of nine patients showed external sphincter deficiency, whereas a further two had internal sphincter deficiency. No differences were seen in MR imaging scores for each operative procedure for all grades of severity of anorectal anomaly. However, a comparison between high and intermediate anomalies showed a small improvement in MR imaging score using the transanal pull-through procedure (Mann-Whitney U test = 3, p < .03). Manometric pressures obtained in 13 patients were poor. CONCLUSION: Transanal MR imaging identifies focal defects and patterns of scarring of the anal sphincter complex in infants and children and provides valuable information about individual muscle components.

High-resolution MR imaging of the anal sphincter in children: a pilot study using endoanal receiver coils.

OBJECTIVE: The purpose of this study was to obtain high-resolution MR images of the various components of the anal sphincter complex in children who have anorectal disorders. We therefore used dedicated endoanal receiver coils for MR imaging. CONCLUSION: Our pilot study suggested that MR imaging that uses a dedicated endoanal coil may have considerable diagnostic potential in children who have anorectal disorders.

Bladder and kidney function after cure of pelvic rhabdomyosarcoma in childhood.

Eleven survivors of pelvic rhabdomyosarcoma underwent bladder function studies and upper urinary tract evaluation at a mean of 6.6 years after completion of therapy, which included a conservative, bladder-sparing surgical policy. Primary tumour sites were: bladder base/prostate, 6; bladder dome, 1; vagina, 2; and pelvic side wall, 2. Seven children (five bladder base/prostate, one vagina and one pelvic side wall tumours) had received irradiation to the pelvis with external beam alone, brachytherapy or both. All seven of these patients had markedly reduced functional bladder capacity (11-48% of mean expected value for age) and abnormal voiding patterns, though bladder compliance was not reduced and bladder emptying was almost complete in five cases. Four of these children also had upper tract dilatation and two required reconstructive bladder surgery because of severe bilateral hydronephrosis. By contrast, each of four children treated without radiotherapy had a normal functional bladder capacity and a normal voiding pattern. all survivors of pelvic rhabdomyosarcoma, especially those who have received radiotherapy, should be carefully monitored for dysfunction of both lower and upper urinary tracts. The frequency-volume voiding chart is a sensitive and easily accomplished method of assessing bladder function in these patients.

Conservative surgery in multimodal therapy for pelvic rhabdomyosarcoma in children.

Twenty-six previously untreated children, median age 3.4 years, with pelvic rhabdomyosarcoma (RMS) were seen between 1983 and 1988. Fourteen were girls. The planned strategy was to conserve pelvic organs, especially the bladder, by using primary chemotherapy, conservative surgery and, in most cases, radiotherapy. With a median follow-up of 71 months (range 34-103 months) overall survival was 73%, with no treatment-related death. The bladder salvage rate of 88% in survivors with bladder base/prostate primaries was much higher than that reported by the United States Intergroup Rhabdomyosarcoma Studies (IRS), though many of the preserved bladders did not function normally. We identified problems with both radiological and histological off-treatment monitoring. The overall accuracy of computerised tomographic (CT) scanning for prediction of tumour recurrence was only 81%, and endoscopic biopsies proved misleading in four of the ten bladder base/prostate patients monitored by serial cystoscopy. We conclude that a higher cure rate can be achieved by using intensive chemotherapy/radiotherapy and conservative surgery to treat children with pelvic RMS. Factors that might contribute to our favourable bladder salvage results, compared with those of the IRS, include (a) the fact that one of two specialist surgeons monitored and operated on all these patients and (b) our increasing awareness, during the study, that post-chemotherapy/radiotherapy histopathology and pelvic CT scan appearances may be misleading. Referral to paediatric centres with special experience of pelvic RMS may help raise the rate of bladder salvage in these children.