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.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

Treatment of Helicobacter pylori infection

Helicobacter pylori is a serious, chronic, progressive, and transmissible infection associated with a significant morbidity and mortality, which alone emphasizes the priority of developing adequate prophylactic or therapeutic measures. What was previously termed "asymptomatic H. pylori infection" is now recognized as a latent infection, and it is now accepted that the presence of an H. pylori infection is an indication for eradication therapy. Successful cure of H. pylori infection requires 2 or more antibiotics. Antibiotic resistance is the major impediment of cure. The ideal duration of therapy is unknown, but in general, 1 week therapy is less effective than longer durations. Compliance is important for the success of treatment; therefore, the favored regimen should have the least side effects. At present, a proton pump inhibitor (or ranitidine bismuth citrate)-clarithromycin triple therapy with either amoxicillin or metronidazole, for at least 10 days is considered first-line therapy. The alternative is quadruple therapy containing a proton pump inhibitor, bismuth, tetracycline, and a higher dose of metronidazole. Quadruple therapy is the best choice after failure of proton pump inhibitor-clarithromycin triple therapy. Confirmation of successful therapy with a urea breath test or a stool antigen test is now the standard of practice.     

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.     

Electrocardiography of the hypertensive patient: correlations with hemodynamic parameters]

A comparative study between electrocardiographic signs of left ventricular hypertrophy and haemodynamic parameters is performed in 184 permanent hypertensive patients. They are divided into 3 groups taking into account the level of electrocardiographic changes. Patients with a normal electrocardiogram have a slight increase in arterial pressure, an increase in cardiac index (P is less than 0.01) and total peripheral resistances (P is less than 0.001) and a reduction of plasma volume (P is less than 0.001). Patients with a moderate change in their electrocardiogram have normal cardiac output, high peripheral resistances (P is less than 0.001) and a slight decrease in plasma volume (P is less than 0.05). Patients with a left major ventricular hypertrophy have a reduced cardiac output (P is less than 0.01), increased peripheral resistances (P is less than 0.001) and a normal plasma volume. The significance of such facts, especially concerning the hemodynamic response in upright position, is discussed.     

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.     

Bacterial toxins and diarrhoea

Bacteria and their toxins are responsible for an enormous burden of diarrhoeal disease. Knowledge about the toxins and their mechanisms of action is limited. Thus, although considerable information is available about the mechanism of action of cholera toxin and a small number of heat-stable enterotoxins, information on the role and action of many others is incomplete. The demonstration of a toxic effect in a test system does not necessarily imply that that activity is relevant to the pathogenesis of the diarrhoea. On the other hand, the absence of a toxic effect in experimental systems does not eliminate the possibility that a toxin is responsible for a particular organism's clinical effects. This is a field of active research and much more work is clearly required.     

Reflex syncope : diagnosis and therapy

Reflex-mediated syncope is a common cause for syncope. The first step in evaluating the cause of syncope is to assess the risk of a life-threatening cause for syncope, e.g., ventricular arrhythmias. Reflex-mediated syncope has to be differentiated from orthostatic syncope. In orthostatic syncope, there is an insufficient autonomic response. In contrast to a reflex-mediated syncope, in which the autonomic nervous system acts inappropriately, reflex-mediated syncope is classified into the classical vasovagal form, the situational form, or due to carotid sinus hypersensitivity. In the elderly, often a mixed form is present. Treatment is difficult. Most important is educating the patient and avoiding precipitating factors. Physical maneuvers, e.g., counter pressure maneuvers, are more effective than drug treatment. Permanent pacing is rarely needed. However, before indicating a pacemaker, a correlation between bradycardia and syncope should be documented. This is often only possible by implanting a monitoring device at an early stage.     

Adult growth hormone deficiency in patients with fibromyalgia

Adult growth hormone (GH) deficiency is a welldescribed clinical syndrome with many features reminiscent of fibromyalgia. There is evidence that GH deficiency as defined in terms of a low insulin-like growth factor-1 (IGF-1) level occurs in approximately 30% of patients with fibromyalgia and is probably the cause of some morbidity. It seems most likely that impaired GH secretion in fibromyalgia is related to a physiologic dysregulation of the hypothalamic-pituitary-adrenal axis (HPA) with a resulting increase in hypothalamic somatostatin tone. It is postulated that impaired GH secretion is secondary to chronic physical and psychological stressors. It appears that impaired GH secretion is more common than clinically significant GH deficiency with low IGF-1 levels. The severe GH deficiency that occurs in a subset of patients with fibromyalgia is of clinical relevance because it is a treatable disorder with demonstrated benefits to patients.