The influence of the flow of the reacting gas on the conditions for a thermal explosion

The classical problem of thermal explosion is modified so that the chemically active gas is not at rest but is flowing in a long cylindrical pipe. Up to a certain section the heat-conducting walls of the pipe are held at low temperature so that the reaction rate is small and there is no heat release; at that section the ambient temperature is increased and an exothermic reaction begins. The question is whether a slow reaction regime will be established or a thermal explosion will occur. The mathematical formulation of the problem is presented. It is shown that when the pipe radius is larger than a critical value, the solution of the new problem exists only up to a certain distance along the axis. The critical radius is determined by conditions in a problem with a uniform axial temperature. The loss of existence is interpreted as a thermal explosion; the critical distance is the safe reactor's length. Both laminar and developed turbulent flow regimes are considered. In a computational experiment the loss of the existence appears as a divergence of a numerical procedure; numerical calculations reveal asymptotic scaling laws with simple powers for the critical distance.     

Demonstration of a new analytical grading system for the determination of pheochromocytoma within the scope of hypertension control

The problems of the phaeochromocytoma are in its rareness, its appearance--every patient with hypertension can be a carrier of a phaeochromocytoma--, its localisation--10% are situated outside the adrenal glands--, its operability with following permanent normalisation of the pressure. As hypertension is very frequent and the diagnostics is very expensive the finding of carriers of phaeochromocytomas is possible only by means of screening methods. Thus cases with an urgent suspicion are found. Such a method is described, the basis of which is a semiquantitative determination of the vanillic amygdalic acid. Instead of the usually used diazocolour-reagent in connection with a non-optimal buffer a complete nitrophenylantiazotate with a buffer of high ionic strength is taken. The pH-value 10 of the urine which is to be demanded for the colour reaction is thus reached in every case. In order to avoid falsely normal results with every urinary test a preparation with added vanillic amygdalic acid is performed and thus the presence of colour inhibitors is recognized. If the result is pathological a quantitative determination is necessary.     

Relapsing pleural exudate complicating chronic pancreatitis

Chronic pancreatitis, often with a pseudocyst, is a rare cause of a pleural exudate. A pancreatic pleural fistula is created, leading to a relapsing massive haemorrhagic pleural exudate with a very high amylase content. The diagnosis is confirmed by means of endoscopic retrograde pancreatography. Treatment is primarily conservative; surgical drainage is sometimes necessary. The prognosis is generally favourable. The case history of a young woman with this condition is presented.     

Autoimmune pancreatitis and IgG-positive sclerosing cholangitis

Sclerosing cholangitis is a heterogenous disease. Sclerosing cholangitis with an unknown cause is abbreviated PSC. PSC affects extra- as well as intra-hepatic bile ducts and since this is a permanently progressing fibrous condition, it leads to liver cirrhosis. The disease is often associated with a development of cholangocarcinoma and idiopathic intestinal inflammation. Causal therapy does not exist; liver transplantation is indicated. IgG4 cholangitis differs from PSC in a number of features. This form is, unlike PSC, linked to autoimmune pancreatitis (AIP) as well as other IgG4 sclerosing diseases. Anatomically, distal region of ductus choledochus is most frequently involved. Icterus is, unlike in PSC, a frequent symptom of AIP. There also is a distinctive histological picture--significant lymphoplasmatic infiltration of the bile duct wall with abundance of IgG4 has been described, lymphoplasmatic infiltration with fibrosis in the periportal area and the presence of obliterating phlebitis is also typical. However, intact biliary epithelium is a typical feature. IgG4 can be diagnosed even without concurrent presence of AIP. IgG4 sclerosing cholangitis is a condition sensitive to steroid therapy. At present, there is no doubt that IgG4 sclerosing cholangitis is a completely different condition to primary sclerosing cholangitis. From the clinical perspective, these diseases should be differentiated in every clinician's mind as (a) AIP is treated with corticosteroids and not with an unnecessary surgery, (b) IgG4 sclerosing cholangitis is mostly successfully treated with corticosteroids and the disease is not, unlike PSC, a risk factor for the development of cholangiocarcinoma.     

Biliary tract obstruction in chronic pancreatitis

Bile duct strictures are a common complication in patients with advanced chronic pancreatitis and have a variable clinical presentation ranging from an incidental finding to overt jaundice and cholangitis. The diagnosis is mostly made during investigations for abdominal pain but jaundice may be the initial clinical presentation. The jaundice is typically transient but may be recurrent with a small risk of secondary biliary cirrhosis in longstanding cases. The management of a bile duct stricture is conservative in patients in whom it is an incidental finding as the risk of secondary biliary cirrhosis is negligible. Initial conservative treatment is advised in patients who present with jaundice as most will resolve once the acute on chronic attack has subsided. A surgical biliary drainage is indicated when there is persistent jaundice for more than one month or if complicated by secondary gallstones or cholangitis. The biliary drainage procedure of choice is a choledocho-jejunostomy which may be combined with a pancreaticojejunostomy in patients who have associated pain. Since many patients with chronic pancreatitis have an inflammatory mass in the head of the pancreas, a Frey procedure is indicated but a resection should be performed when there is concern about a malignancy. Temporary endoscopic stenting is reserved for cholangitis while an expandable metal stent may be indicated in patients with severe co-morbid disease.     

Routine ultrasound-guided liver biopsy: a time whose idea has come?

Percutaneous liver biopsy is a commonly performed procedure in modern hepatology. Although it is a safe procedure and performed in most cases on an outpatient basis, complications including mortality have been reported. It is widely perceived that the use of ultrasound guiding for the biopsy produces a decrease in complications and is safer. There is now a trend for more centers to adopt a policy of ultrasound-guided biopsies only. There are, however, no official guidelines that recommend such a policy. This trend for ultrasound guidance of invasive procedures is also becoming apparent in other areas such as the insertion of a central venous line in children. The literature in support of such a position is far from conclusive. Because there are medicolegal and economic implications for the policy of routine ultrasound guiding of biopsies, we suggest that there is a need for the major professional organizations to make a clear declaration on this issue.     

Glucose regulation and oxidative stress in healthy centenarians

Aging, oxidative stress and insulin resistance are strongly correlated. There is a growing body of evidence showing that aging is associated with a significant rise in oxidative stress mainly due to a decline in anti-oxidant activity and a rise in pro-oxidant factors such as glucose and insulin concentrations. Furthermore, aging is also associated with a progressive rise in insulin resistance which is due to a complex network of environmental, anthropometric and neuro-hormonal factors. It is noteworthy that extreme longevity, e.g. centenarians, is associated with a low degree of oxidative stress and insulin resistance. The causes for such differences between aged subjects and centenarians is not fully understood. It is likely that a specific genetic background might play a role. However, the insulin gene does not seem to be involved for explaining such age-related differences.     

Benign ulceration of the gecum presenting with massive hemorrhage

Massive gastrointestinal hemorrhage secondary to benign cecal ulceration is a rare occurrence. The diagnosis of bleeding from this benign condition is rerely entertained and is often a finding on a pathologic examination. A case of massive hemorrhage from a cecal ulcer is presented, and the literature is reviewed. The role of angiographic demonstration of the lesion, if angiography is readily available, is emphasized, but surgery is the definitive therapy.     

Damage Detection at a Reinforced Concrete Specimen with Coda Wave Interferometry

Reinforced concrete is a widely used construction material in the building industry. With the increasing age of structures and higher loads there is an immense demand for structural health monitoring of built infrastructure. Coda wave interferometry is a possible candidate for damage detection in concrete whose applicability is demonstrated in this study. The technology is based on a correlation evaluation of two ultrasonic signals. In this study, two ways of processing the correlation data for damage detection are compared. The coda wave measurement data are obtained from a four-point bending test at a reinforced concrete specimen that is also instrumented with fibre optic strain measurements. The used ultrasonic signals have a central frequency of 60 kHz which is a significant difference to previous studies. The experiment shows that the coda wave interferometry has a high sensitivity for developing cracks and by solving an inverse problem even multiple cracks can be distinguished. A further specialty of this study is the use of finite elements for solving a diffusion problem which is needed to state the previously mentioned inverse problem for damage localization.     

Insertion of a biliary endoprosthesis using a balloon dilatation catheter

Adequate function of a percutaneous biliary endoprosthesis is accomplished by its successful positioning through the site of obstruction. Stent insertion is greatly facilitated when a peripheral bile duct is entered parallel to its long axis or the stent angled in a caudal direction. When the biliary system is entered in a cephalad direction, insertion may be laborious and a mature tract is often required. We describe the technique for such a positioning of a large-bore, long endoprosthesis using a vascular balloon dilatation catheter.     

Zufallsbefund Proteinurie

A positive signal when testing urine for proteinuria is a frequent finding, either in the context of a routine medical check-up or when searching for a specific renal disorder. This brief overview aims to provide assistance in the classification of proteinuria and to provide guidance to the next diagnostic and therapeutic steps. The normal urine protein loss of a healthy adult is less then 150 mg/day. Higher rates of proteinuria should be confirmed as this is often a sign of glomerular or tubular damage. In addition, proteinuria is a strong prognostic factor for cardiovascular and total mortality. Principally, proteinuria is 1) a symptom of renal diseases, 2) a progression factor for renal diseases and 3) a risk factor for cardiovascular diseases and total mortality. In this article proteinuria is defined, the correlation to various renal diseases is described and the relevance for progression of renal diseases and total mortality is shown. Finally, diagnostic procedures are described and a perspective on therapeutic measures is provided.     

Mediastinal myelolipoma

Myelolipoma is a rare tumor, and a mediastinal location is extremely unusual. The main pathologic feature is the coexistence of mature adipose tissue and bone marrow cells; the presence of megakaryocytes is essential for diagnosis. The successful removal of a mediastinal myelolipoma in a 59-year-old man is described.     

Solution of the embedding problem and decomposition of symmetric matrices.

A solution of the problem of calculating cartesian coordinates from a matrix of interpoint distances (the embedding problem) is reported. An efficient and numerically stable algorithm for the transformation of distances to coordinates is then obtained. It is shown that the embedding problem is intimately related to the theory of symmetric matrices, since every symmetric matrix is related to a general distance matrix by a one-to-one transformation. Embedding of a distance matrix yields a decomposition of the associated symmetric matrix in the form of a sum over outer products of a linear independent system of coordinate vectors. It is shown that such a decomposition exists for every symmetric matrix and that it is numerically stable. From this decomposition, the rank and the numbers of positive, negative, and zero eigenvalues of the symmetric matrix are obtained directly.     

Intradural extramedullary tuberculoma of the spinal cord: a review of reported cases

Intradural extramedullary tuberculoma of the spinal cord (IETSC) is a rare modality of tuberculosis, with only a few cases described so far. Here we review 22 reports of the disease found in the literature of the last 25 years. IETSC is closely associated with tuberculous meningitis (TM). Both conditions may occur simultaneously, but more frequently IETSC is preceded by TM. IETSC has been described in a predominantly young population of both genders. The pathogenesis is unknown, although a paradoxical reaction to antituberculous medication is a reasonable possibility. The disease presents insidiously with paraparesis, hypoesthesia with a sensory level, and bladder dysfunction, due to cord involvement or compression by the inflammatory process. Permanent paraparesis is a common sequela. MRI is the diagnostic technique of choice in IETSC. Prompt surgical excision of the tuberculoma is the cornerstone of therapy. Antituberculous treatment is also indicated; unless resistance is present, conventional chemotherapy is probably enough. Corticosteroids are also generally recommended. In conclusion, IETSC is a rare complication of TM, which presents insidiously, despite adequate antituberculous treatment. To avoid the permanent disability that this condition may provoke, an early diagnosis and prompt treatment is critical.     

Pleuropulmonary blastoma: a case report

Pulmonary blastoma is a rare seen malignant tumor. It is generally reported in adults. The tumor including immature mesenchimal and/or epithelial structures is morphologically similar to fetal lung tissue. In this study, a male patient having been operated is presented because of the mass found in his chest X-ray. The lesion is histopathologically reported as a pleuropulmonary blastoma. The literature is reviewed because this case has a bad prognosis and is rarely seen.     

Tissue-specific hemostasis in mice

Blood coagulation is essential to maintain hemostasis in organisms with a vascular network. Formation of a fibrin-rich clot at a site of vessel injury is a highly complex process that is orchestrated by the coagulation protease cascade. This cascade is regulated by 3 major anticoagulant pathways. Removal of a clot is mediated by the fibrinolytic system. Defects in the regulation of clot formation lead to either hemorrhage or thrombosis. Tissue factor, the primary cellular initiator of blood coagulation, is a transmembrane receptor that is expressed in a tissue-specific manner. The 3 major anticoagulants are tissue factor pathway inhibitor, antithrombin, and protein C, the latter requiring a transmembrane receptor called thrombomodulin for its activation. Tissue factor pathway inhibitor and thrombomodulin are expressed by endothelial cells in a tissue-specific manner, whereas antithrombin and protein C circulate in the plasma. Fibrinolysis requires the activation of plasminogen to plasmin, which is mediated by tissue-type plasminogen activator and urokinase-type plasminogen activator. Interestingly, tissue-type plasminogen activator is expressed by a subset of endothelial cells of discrete size and location. These observations, together with the phenotypes of mice that have defects in the procoagulant, anticoagulant, and fibrinolytic pathways, indicate that hemostasis is regulated in a tissue-specific manner.     

Peanut aspiration in an adult.

We present a case history of a 34-year old adult who aspirated a peanut. Peanut inhalation is a well-recognized condition in children, but is rare in adults. Diagnosis is often difficult and requires a high index of clinical suspicion. A brief review of the literature is presented.     

Acute myocardial infarction caused by coronary artery dissection after a blunt chest trauma

Acute myocardial infarction is a life-threatening condition. Coronary dissection after blunt chest trauma is a rare event. Chest pain is a common symptom after chest trauma, which may relate to chest contusion without cardiac injury or myocardial infarction. Differentiation between minor cardiac contusion and significant cardiac injury is difficult and it is a challenge for physicians to diagnose traumatic cardiac injury early. We report a case of a 40-year-old man suffering from coronary artery dissection after a blunt chest trauma and intracranial hemorrhage after percutaneous coronary intervention.     

Supersymmetric Hilbert space

A generalization is given of the notion of a symmetric bilinear form over a vector space, which includes variables of positive and negative signature ("supersymmetric variables"). It is shown that this structure is substantially isomorphic to the exterior algebra of a vector space. A supersymmetric extension of the second fundamental theorem of invariant theory is obtained as a corollary. The main technique is a supersymmetric extension of the standard basis theorem. As a byproduct, it is shown that supersymmetric Hilbert space and supersymplectic space are in natural duality.     

Local treatment of carcinoma of the rectum

Conclusions Local treatment of carcinomain situ of the rectum is the procedure of choice. It is also preferable when there is a focal malignant change in a polyp with a pedicle that is not invaded by the cancer, and when a sessile carcinoma of low grade is less than 2 cm. in diameter. These indications may be extended in some cases when the general condition of the patient precludes a radical surgical procedure, when the patient, because of a poor mental condition, would not be able to manage the colostomy himself, and when a colostomy is refused. When a carcinoma of the rectum is inoperable, or when there is distant metastasis, local treatment may provide gratifying palliation. Read at the Canberra meeting of the Royal Australasian College of Surgeons. Canberra, Australia, November 28, 1964.