Local Obstruction Research Articles

Ingestion — Associated adverse events necessitating pediatric ICU admissions

To review the pattern of food-associated pediatric intensive care unit (PICU) admissions. A retrospective chart review was conducted to analyse the pattern of food-associated PICU admissions at a teaching hospital between January 2004 and May 2007. Ten cases (7 boys and 3 girls, aged 9 month to 11.7 year) were identified. One girl developed progressive generalized urticarial rash and anaphylactic shock following consumption of bird nest drink. A boy presented with the classic triads of acute onset altered mental state, respiratory depression and small pupils following consumption of a bottle of presumed "green tea", which was subsequently found to contain methadone. In the remaining 8 cases, dried mango, peanut, peanut-shell, fishmeat ball, pork chop, bread and bone were the culprits, impacting in the airway or oesophagus. All but one patient had short ICU stay (<or=3 days). Ingestion-associated adverse events can be protean and may necessitate PICU admissions. All age groups can be affected. Solids are usually associated with symptoms from local obstruction or suffocation, while fluids may be associated with systemic manifestations. Presentations were generally acute, dramatic and unmistaken. The majority of patients made prompt and uneventful recovery and had short PICU stay.

Effect of urban-site and vegetation on channel capacity in higher altitude platform communication system

Communication services using higher altitude platforms have highlighted a need for estimating the effect of local obstructions on radio wave link. Vegetation and buildings are the major factors responsible for attenuation. The authors have calculated the radio wave attenuation because of vegetation and buildings. Here, the authors have used the fitted radio international telecommunication union model to calculate the vegetation attenuation. The attenuation because of buildings is calculated for an urban-site (residential area of Netaji Subhas Institute of Technology, NSIT, New Delhi, India) using geometrical optics and a uniform theory of diffraction. Further, channel capacity is calculated for vegetation and urban-site environment using Shannon's channel capacity theorem.

Coronary structure and perfusion in health and disease

Blood flow is distributed through the heart muscle via a system of vessels forming the coronary circulation. The perfusion of the myocardium can be hampered by atherosclerosis creating localized obstructions in the epicardial vessels or by microvascular disease. In early stages of the disease, these impediments to blood flow are offset by dilation of the resistance vessels, which normally compensates for a decrease in perfusion pressure or increased metabolism. However, this dilatory reserve can become exhausted, which in general occurs first at the deeper layers of the heart wall where intramural vessels are subjected to compressive forces related to heart contraction. In the catheterization laboratory, guide wires of 0.33 mm diameter are available that are equipped with a pressure and flow velocity sensor at the tip, which can be positioned distal to the stenosis. These signals provide information about the impediment of the stenosis on coronary flow and allow for the evaluation of the status of the microcirculation. However, the interpretation of these signals is strongly model-dependent and therefore it is of paramount importance to develop realistic models reflecting the anatomy and unique physiology of the coronary circulation.

The evolution of the mixing rate of a simple random walk on the giant component of a random graph

AbstractIn this article we present a study of the mixing time of a random walk on the largest component of a supercritical random graph, also known as the giant component. We identify local obstructions that slow down the random walk, when the average degree d is at most O($ \sqrt{\ln n} $), proving that the mixing time in this case is Θ((n/d)2) asymptotically almost surely. As the average degree grows these become negligible and it is the diameter of the largest component that takes over, yielding mixing time Θ(n/d) a.a.s.. We proved these results during the 2003–04 academic year. Similar results but for constant d were later proved independently by Benjamini et al. in 3. © 2008 Wiley Periodicals, Inc. Random Struct. Alg., 2008

Microvascular Transfer of a “Lymphatic-Bearing” Flap in the Treatment of Obstructive Lymphedema

Sir: A number of operations have been advocated for the management of obstructive lymphedema. The reestablishment of lymphatic pathways following free tissue transfer has also been documented with lymphoscintigraphic studies in patients who have undergone free flap reconstruction.1–3 We present a new approach to treating obstructive lymphedema using a posterior tibial artery “lymphatic-bearing” free flap, with not only a vascular pedicle but also a lymphatic pedicle to bridge the lymphatic obstruction site. A 23-year-old man presented with lymphedema in his right lower extremity following an extirpative operation for removal of a mass in the right groin 4 years earlier. He was referred to our department with complaints of a recurrent bout of lymphangioitis and increased swelling of his right lower extremity. Preoperative lymphoscintigraphy demonstrated the blockade of lymphatic drainage in the right groin (Fig. 1).Fig. 1.: Preoperative lymphoscintigram shows obstruction of lymphatic drainage in the right groin at 60 minutes after injection.A 7 × 9-cm defect was created after scar excision in the right groin. We then designed an 8 ×10-cm posterior tibial artery “lymphatic” flap in the left lower leg. Before the flap was harvested, 2 ml of patent blue dye was injected into the web space of left foot to visualize the superficial lymphatics of the right leg (Fig. 2). The proximal posterior tibial artery and its accompanying venae comitantes were used as the vascular pedicle of the flap, while one large lymphatic acted as a bridge for direct reconstruction of the lymphatic pathway. The flap was transferred as the standard procedure, but the proximal lymphatic of the flap was anastomosed with a lymphatic collector below the right inguinal ligament, a distal lymphatic of the flap with a lymphatic collector in the middle of medial thigh.Fig. 2.: Intraoperative visualization of the superficial lymphatics by staining with patent blue dye (note the big lymphatic marked by a suture).The flap survived completely, and the patient has not had an episode of lymphangioitis with the obvious lymphedema reduction in the affected leg since the reconstructive procedure. A postoperative follow-up lymphoscintigram at 6 months showed marked improvement of lymphatic drainage by demonstration of the lymphatic pathway along the microsurgically reconstructed lymphatic route (Fig. 3).Fig. 3.: Six-month postoperative lymphoscintigram demonstrating the lymphatic pathway across the reconstructed right groin.The early replacement of resected lymph collectors is the most logical surgical approach to overcome a localized obstruction of lymph flow. Bridging of localized obstruction of lymph drainage by transplantation of lymph collectors was developed by Baumeister et al. in 1981.4 In this patient, we transplanted the lymphatics, which were carried by a free flap with both rich blood and lymph supply, to reconstruct the lymphatic pathway in the obstructive lymphedema. There are two advantages to the lymphatic-bearing flap: first, it can improve the tissue coverage for the lymphatic blockade site; and second, the lymphatic vessels included in a free flap can act as a lymphatic “bridge” to restore the lymphatic outflow by additional microvascular anastomoses with lymphatic vessels in the recipient site. A lymphoscintigram taken at 6 months after operation demonstrated lymph flow across the previous obstruction site along the reconstructed route, which may result from both the reconstructed lymphatic pathway and the flap transplantation. This preliminary report suggests that this operative intervention might be a viable option in the treatment of obstructive lymphedema. Shengli Li, M.D. Weigang Cao, M.D. Kaixiang Cheng, M.D. Ti-Sheng Chang, M.D. Department of Plastic and Reconstructive Surgery Ninth People's Hospital Medical School of Shanghai Jiao Tong University Shanghai, P. R. China

L’obstruction d’Euler locale d’une application

Our objective is to present a generalization for the local Euler obstruction of a holomorphic function singular at the origin to the case of a holomorphic map f:(V,0)→(ℂ k ,0), where (V, 0) is a germ of complex analytic variety, equidimensional of dimension n≥k. The principal result (Theorem 6.1) is a formula which computes the local Euler obstruction, defined for k-frames by Brasselet, Seade, Suwa, in terms of the local Euler obstruction of f.

Conidiobolomicose em ovinos no Estado de Mato Grosso

Relatam-se os achados epidemiológicos, clínicos, patológicos e micológicos de conidiobolomicose em ovinos no Estado de Mato Grosso. A doença ocorreu em uma propriedade no município de Nobres, em um rebanho com 40 ovelhas adultas, entre os meses de janeiro a junho de 2007. Aproximadamente 30% dos ovinos da propriedade adoeceram e todos os doentes morreram em curso clínico de 2-5 semanas. O quadro clínico foi caracterizado por apatia, emagrecimento, dificuldade respiratória com dispnéia, respiração ruidosa e oral, secreção nasal mucosa ou sero-sanguinolenta, exoftalmia unilateral, por vezes com cegueira, e morte. Havia desaparecimento de etmoturbinados com substituição por tecido bran-cacento, finamente granular, multilobulado e friável infil-trando-se na lâmina cribiforme, no septo nasal e nas coa-nas em todos os ovinos necropsiados. Lesões similares foram encontradas em linfonodos regionais (2 casos), pulmões (3), encéfalo (2) e em linfonodos do abomaso (1). Microscopicamente havia inflamação granulomatosa da região rinocerebral, caracterizada por necrose, proliferação de tecido conjuntivo, infiltrado de neutrófilos, eosinófilos, células epitelióides e células gigantes multinucleadas freqüentemente circundando material Splendori-Hoeppli, onde havia imagens negativas de hifas. Na impregnação pela Prata-Metenamina, as hifas tinham septos e ramificações escassas e irregulares, com dilatação balonosa terminal e com forte demarcação de contornos. Iso-lou-se de tecido nasal de quatro ovinos Conidiobolus sp.

BSACI guidelines for the management of rhinosinusitis and nasal polyposis

This guidance for the management of patients with rhinosinusitis and nasal polyposis has been prepared by the Standards of Care Committee (SOCC) of the British Society for Allergy and Clinical Immunology (BSACI). The recommendations are based on evidence and expert opinion and are evidence graded. These guidelines are for the benefit of both adult physicians and paediatricians treating allergic conditions. Rhinosinusitis implies inflammation of the nose and sinuses which may or may not have an infective component and includes nasal polyposis. Acute rhinosinusitis lasts up to 12 weeks and resolves completely. Chronic rhinosinusitis persists over 12 weeks and may involve acute exacerbations. Rhinosinusitis is common, affecting around 15% of the population and causes significant reduction in quality of life. The diagnosis is based largely on symptoms with confirmation by nasendoscopy. Computerized tomography scans and magnetic resonance imaging are abnormal in approximately one third of the population so are not recommended for routine diagnosis but should be reserved for those with acute complications, diagnostic uncertainty or failed medical therapy. Underlying conditions such as immune deficiency, Wegener's granulomatosis, Churg-Strauss syndrome, aspirin hypersensitivity and allergic fungal sinusitis may present as rhinosinusitis. There are few good quality trials in this area but the available evidence suggests that treatment is primarily medical, involving douching, corticosteroids, antibiotics, anti-leukotrienes, and anti-histamines. Endoscopic sinus surgery should be considered for complications, anatomical variations causing local obstruction, allergic fungal disease or patients who remain very symptomatic despite medical treatment. Further well conducted trials in clearly defined patient groups are needed to improve management.

Lymphoplasmacytic sclerosing pancreatitis forming a localized mass: a variant form of autoimmune pancreatitis

To elucidate the correlation of autoimmune pancreatitis (AIP) and mass-forming pancreatitis, in which a localized mass is formed in the pancreas. Nine cases of mass-forming pancreatitis were divided into two groups, one consisting of cases that met the histological diagnostic criteria for AIP by the Japan Pancreas Society (JPS) and the other consisting of cases which did not. Histological findings, immunohistological findings, and pancreatograms were compared between these groups. Six cases met the histological criteria of JPS (group A) and the other three did not (group B). In the mass-forming portion in group A, the wall of the pancreatic duct showed marked thickening. However, the epithelium was well preserved, and dilatation of the branch ducts or protein plugs were rarely observed. All cases showed marked obliterative phlebitis. The IgG4 labeling index (LI) was 25% or more in all but one case. In the portion other than the mass, the lobular structure was well preserved and the IgG4 LI was less than 10%. The pancreatogram showed localized stenosis or obstruction at the site of the mass associated with a normal-appearing main pancreatic duct in the remaining portion. In group B, histological findings typical of chronic pancreatitis with dilated branch ducts and protein plugs were observed. Obliterative phlebitis was not confirmed. The IgG4 LI in the mass-forming portion was low (2.3%-11.1%). There exists a subgroup of AIP showing localized mass formation and stenosis or obstruction of the main pancreatic duct with prominent obliterative phlebitis associated with a normal ductal segment.

Geometric Theory of Columnar Phases on Curved Substrates

We study thin self-assembled columns constrained to lie on a curved, rigid substrate. The curvature presents no local obstruction to equally spaced columns in contrast with curved crystals for which the crystalline bonds are frustrated. Instead, the vanishing compressional strain of the columns implies that their normals lie on geodesics which converge (diverge) in regions of positive (negative) Gaussian curvature, in analogy to the focusing of light rays by a lens. We show that the out of plane bending of the cylinders acts as an effective ordering field.

Simulation of the effect of local obstructions and blockage on airflow and aerosol deposition in central human airways

Investigation of the effect of sidewall and carinal tumours, airway constrictions and airway blockage on the inspiratory airflow and particle deposition in the large central human airways was the primary objective of this study. A computational fluid and particle dynamics model was implemented, validated and applied in order to simulate the air and particle transport and to quantify the aerosol deposition in double airway bifurcation models. Our investigations revealed that surface abnormalities and tubular constrictions can significantly alter the airstreams and the related local aerosol deposition distributions. Sidewall tumours have lead to an enhanced deposition of large particles and caused lower deposition efficiency values of nano-particles compared to the deposition efficiency in healthy airways. Central tumours multiplied the deposition efficiency of large particles but hardly affected the deposition efficiency of nano-particles. Airway blockage caused a significant redistribution of particle deposition sites. The deposition efficiency of the inhaled aerosols in constricted airways was much higher than the same deposition efficiency in healthy airways. Current results might help in the understanding of the adverse health effects of the inhaled air-pollutants in patients with lung disease and might be integrated into future aerosol therapy protocols.

Desmoid tumours in patients with familial adenomatous polyposis and desmoid region adenomatous polyposis coli mutations

:The aim of this study was to determine the proportion of patients with familial adenomatous polyposis (FAP) who had mutations in the desmoid region of the adenomatous polyposis coli (APC) gene that phenotypically expresses desmoid disease, and to determine the role for surgery in these patients. Data from the North West Region FAP database and case notes were analysed retrospectively. Of 363 patients with FAP, 47 from ten families had APC mutations in the desmoid region 3' to codon 1399. Of 22 patients undergoing surgery, 16 developed desmoids, and of these 12 had mesenteric desmoid disease. Complications from mesenteric desmoids were death (two patients), enterectomy (three), local resection (three), fistula (one), cholangitis and local resection (one), bowel obstruction (one) and bowel and ureteric obstruction (one). Preoperative polyp burden ranged from 0 to 100 in eight patients (median age 24.5 (range 16-39) years) and more than 100 in seven (median age 39 (range 31-64) years). One patient had no record of polyp burden. In individuals with 3' APC mutations, abdominal surgery is associated with a 65 per cent risk of developing mesenteric desmoids. An alternative strategy might be to attempt to manage the polyps endoscopically.

Squamoid Cyst of Pancreatic Ducts: A Distinct Type of Cystic Lesion in the Pancreas

The clinicopathologic features of a hitherto unrecognized cystic tumor of the pancreas are documented, and its possible relationship to a more common incidental microscopic lesion is analyzed. Six patients (3 men and 3 women) had undergone resection specifically for this cyst type. The mean age of the patients was 63 years (range 52 to 79 y) and the mean size of the tumors was 2.6 cm (median 1.5, range 0.8 to 9 cm). The cysts had variable lining ranging from attenuated, flat squamoid cells to transitional, to stratified squamous without keratinization (no granular layer). The cells forming the basal/parabasal region expressed p63 (transitional/squamous cell marker, not detected in any normal pancreas or nonsquamous neoplasia) and the surface cells were positive for MUC 1 and MUC 6 (markers present in intercalated duct cells), and negative for GLUT-1 (consistent marker of serous adenomas). The lesions appeared to be unilocular cystic dilatation of the ducts that typically contained distinctive muco-proteinaceous acidophilic acinar secretions forming concretions, confirming their communication with the acinar system, and suggesting a localized obstruction in their pathogenesis (a form of "retention" cyst). A thin fibrous wall devoid of any lymphoid tissue separated the cysts from unremarkable parenchyma. There was no evidence of pancreatitis (fibrosis or inflammation). Separately, 110 pancreata resected for various reasons were analyzed, and what seems to be microscopic/incidental version of this process was identified in 10 examples (8%). These microcysts were found lying within compact acinar tissue, and appeared to be transforming from intercalated ducts, some focally connected to acinar elements, and they had abortive (nonbridging) septae with pseudo-loculated appearance, irregular contours and often showed tightly packed clusters of ducts with similar morphology described in the cases underwent resection specifically for this cyst type. In conclusion, the distinctive morphologic, immunophenotypic, and clinical characteristics of this cystic lesion warrant its classification as a separate entity. We propose to refer to it as squamoid cyst of pancreatic ducts. It seems to be a metaplastic cystic transformation beginning in the intercalated ducts. Although obstructive etiology is suspected, a specific factor or surrogate evidence of obstruction such as chronic pancreatitis is typically lacking.

Déformations formelles de revêtements: un principe local-global

LetC be a generically smooth, locally complete intersection curve defined over an algebraically closed fieldk of characteristicp≥0. LetG⊃ AutkC be a finite group of automorphisms ofC. We develop a theory ofG-equivariant deformations of the Galois coverC→C/G. We give a thorough study of the local obstructions, those localized at singular or widely ramified points, to deform equivariantly a cover. As an application, we discuss the case ofG-equivariant deformations of semistable curves.

Local syzygies of multiplier ideals

In recent years, multiplier ideals have found many applications in local and global algebraic geometry. Because of their importance, there has been some interest in the question of which ideals on a smooth complex variety can be realized as multiplier ideals. Other than integral closure no local obstructions have been known up to now, and in dimension two it was established by Favre-Jonsson and Lipman-Watanabe that any integrally closed ideal is locally a multiplier ideal. We prove the somewhat unexpected result that multiplier ideals in fact satisfy some rather strong algebraic properties involving higher syzygies. It follows that in dimensions three and higher, multiplier ideals are very special among all integrally closed ideals.

Microlocal study of topological Radon transforms and real projective duality

Various topological properties of projective duality between real projective varieties and their duals are obtained by making use of the microlocal theory of (subanalytically) constructible sheaves developed by Kashiwara [M. Kashiwara, Index theorem for constructible sheaves, Astérisque 130 (1985) 193–209] and Kashiwara–Schapira [M. Kashiwara, P. Schapira, Sheaves on Manifolds, Grundlehren Math. Wiss., vol. 292, Springer, Berlin–Heidelberg–New York, 1990]. In particular, we prove in the real setting some results similar to the ones proved by Ernström in the complex case [L. Ernström, Topological Radon transforms and the local Euler obstruction, Duke Math. J. 76 (1994) 1–21]. For this purpose, we describe the characteristic cycles of topological Radon transforms of constructible functions in terms of curvatures of strata in real projective spaces.

EULER OBSTRUCTION, POLAR MULTIPLICITIES AND EQUISINGULARITY OF MAP GERMS IN $\mathcal{O}(n,p), n &lt; p$

There are two main goals in this article, one of them is to minimize the number of invariants needed to obtain Whitney equisingular one parameter families of finitely determined holomorphic map germs ft:(ℂn,0) → (ℂp,0), with n &lt; p. The other is to show how to compute the local Euler obstruction of the stable types which appear in a finitely determined map germ in these dimensions. The polar multiplicities of all stable types and the 0-stable singularities are the invariants that guarantee the Whitney equisingularity of such families and the polar multiplicities are the numbers that also allow us to compute the local Euler obstruction. Therefore our first step is to describe all stable types which appear when n &lt; p and show the relationship between the polar multiplicities in each stable type. Using the fact that these polar multiplicities are upper semi-continuous we minimize the number of invariants that guarantee Whitney equisingularity of such a family. We also apply the relationship between the polar multiplicities in each stable type and a result of Lê and Teissier to show how to compute the local Euler obstruction of the stable types which appear in these dimensions.

Bronchial Typical Carcinoid Tumors

The current WHO classification of lung tumors recognizes bronchial typical carcinoid as low-grade neuroendocrine tumors. These tumors grow slowly but can metastasize to regional nodes (4 to 20%) and more rarely to extrathoracic sites. Symptoms are usually related to local compression and obstruction of the bronchial tree. Paraneoplastic syndrome can be present (carcinoid syndrome, Cushing's syndrome, acromegaly). Preoperative diagnosis is usually obtained with bronchoscopic biopsy. Computed tomography and somatostatin receptor scintigraphy are useful in the preoperative staging. Only selected cases can be treated endoscopically with laser resection. The complete surgical resection remains the only therapy with curative intent in the majority of patients. Parenchyma-sparing resections are indicated whenever possible. Overall survival after surgery is excellent (5-year rate, 87 to 100%) with low recurrence rate (2 to 11%). N-status and type of resection seem not to affect prognosis. Local relapse can be treated successfully with surgery, whereas distant metastases have a poor prognosis even after chemotherapy.

Counting conifolds and Dijkgraaf–Vafa matrix models for three matrices

We study superpotential perturbations of q deformed N = 4 Yang–Mills for q a root of unity. This is a special case whose geometry is associated to an orbifold with three lines of codimension two singularities meeting at the origin. We perform field theory perturbations that leave only co-dimension three singularities of conifold type in the geometry. We show that there are two “fractional brane” solutions of the F-term equations for each singularity in the deformed geometry, and that the number of complex deformations of that geometry also matches the number of singularities. This proves that for this case there are no local or non-local obstructions to deformation. We also show that the associated Dijkgraaf–Vafa matrix model has a solvable sector, and that the loop equations in this sector encode the full deformed geometry of the theory.

Geometric structures as deformed infinitesimal symmetries

A general model for geometric structures on differentiable manifolds is obtained by deforming infinitesimal symmetries. Specifically, this model consists of a Lie algebroid, equipped with an affine connection compatible with the Lie algebroid structure. The curvature of this connection vanishes precisely when the structure is locally symmetric. This model generalizes Cartan geometries, a substantial class, to the intransitive case. Simple examples are surveyed and corresponding local obstructions to symmetry are identified. These examples include foliations, Riemannian structures, infinitesimalGG-structures, symplectic and Poisson structures.