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.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

Theoretical problems related to the attachment of microtubules to kinetochores.

A possible model is analyzed for the maintenance of attachment of a shortening microtubule (MT) to a kinetochore. In this model it is assumed that a MT is inserted and held in a sleeve or channel of the outer layer of a kinetochore while subunits are lost from the MT tip through the central layer of the kinetochore. A second problem considered is the elementary bioenergetics of MT growth and shortening, as associated with the presence or absence of a GTP cap on the MT ends. The free-energy source is the hydrolysis of GTP in solution. The third problem discussed is the kinetics of capture of a centrosomal MT by a target (e.g., a kinetochore).     

A case of giant cell tumor of the hipbone invading the bladder

Giant cell tumor of bone (GCTB) is a very rare neoplasm of the skeleton (about one new case per million population per year). In literature there is a great confusion about GCTB. The majority of authors think that GCTB is a benign locally aggressive tumor, others think that this is a malignant neoplasm and some authors think that GCTB is a reactive condition. This is the first case in literature of GCTB of the hipbone invading the bladder.     

The “benefits” of the mini-extracorporeal circulation in the minimal invasive cardiac surgery era

Mini-extracorporeal circulation (MECC) constitutes a novel miniaturized cardiopulmonary bypass (CPB) circuit, heparin-coated and primed with aprotinin. Its membrane oxygenation is similar to conventional cardio-pulmonary bypass (CCPB), but it is a completely closed-volume system due to the lack of the venous reservoir which has been removed. In a mini circuit, the reservoir is the patient himself. Consequently, air entering the venous cannula is avoided. Nevertheless, the capabilities of MECC have been expanded either by the inclusion of a suction device that is only activated on direct contact with liquid in some circuits or by postoperative autotransfusion of the wrecked erythrocytes by a separate suction device with a cell-saver. Although the tubing diameter is similar between the two systems, the tubing length of the MECC is around half that of the CCPB, resulting in the restriction of priming volume. As a consequence, a higher hematocrit thus a limited need for perioperative blood transfusion is achieved due to less hemodilution. In addition, the inflammatory response is also diminished as a result of less artificial surface area interacting with blood. Finally, a lower dose of heparin is required prior to MECC than prior to CCPB.     

Relapse in a child with otogenic tetanus

Otogenic tetanus is common in a developing country like India. However, adequate sedation and elimination of spasms by medical treatment is sufficient in most cases. Once treated, relapses are rare. The authors report a 2-year-old girl who relapsed twice after near complete recovery. This communiqué is intended to highlight that tetanus is still a significant health problem in third-world countries and a relapse after such a dreadful disease is terrifying.     

Lungentumor mit arteriellem Verschluss

Sarcoma of the pulmonary artery is a rare tumor with a difficult diagnosis. Typically there is an occlusion of the pulmonary artery, which is often misinterpreted as pulmonary thromboembolism. Frequently the lung is already involved at the time of diagnosis. We report on a case of such a neoplasm with a predominant pulmonary tumor mass. The consideration of this tumor entity in the differential diagnosis is important for the early diagnosis and adequate therapy and surgery planning.     

Importance of Internal Variability in Clinical Trials of Cardiovascular Disease

A well conducted randomised controlled trial (RCT) is extremely important in the field of cardiovascular medicine. At the same time, it is equally important to understand the strengths and limitations of any RCT, and internal variability is a concept in clinical trials that is poorly understood. Variability in a clinical trial may be introduced at an individual level or during measurement, sampling, or conduct of the trial. It is not the same as internal validity, which is a broader concept of accuracy; to be valid, a study should minimise variability and have sound methodology. There are various steps that may be followed to minimise the internal variability in a clinical trial. One aspect of great importance is the adjudication process, which should be done meticulously and is often a step that is overlooked. It is important to standardise each step as much as possible, to ensure consistency and reduce noise at all levels. The concepts discussed in this review may serve as a roadmap to limit the influence of internal variability and maximise internal validity of RCT results.     

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.     

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.