Search

This paper studies the explicit calculation of the set of superhedging (and underhedging) portfolios where one asset is used to superhedge another in a discrete time setting. A general operational framework is proposed and trajectory models are defined based on a class of investors characterized by how they operate on financial data leading to potential portfolio rebalances. Trajectory market models will be specified by a trajectory set and a set of portfolios. Beginning with observing charts in an operationally prescribed manner, our trajectory sets will be constructed by moving forward recursively, while our superhedging portfolios are computed through a backwards recursion process involving a convex hull algorithm. The models proposed in this thesis allow for an arbitrary number of stocks and arbitrary choice of numeraire. Although price bounds, V 0 (X0, X2 ,M) ≤ V 0(X0, X2 ,M), will never yield a market misprice, our models will allow an investor to determine the amount of risk associated with an initial investment v.

Validation of predictive risk models for prolonged air leak (PAL) is essential to understand if they can help to reduce its incidence and complications. This study aimed to evaluate both the clinical and statistical performances of 4 existing models. We selected 4 predictive PAL risk models based on their scientific relevance. We referred to these models as Chicago, Bordeaux, Leeds and Pittsburgh model, respectively, according to the affiliation place of the first author. These predicting risk models were retrospectively applied to patients recorded on the second edition of the Italian Video-Assisted Thoracoscopic Surgery Group registry. Predictions for each patient were calculated based on the logistic regression coefficient values provided in the original manuscripts. All models were tested for their overall performance, discrimination, and calibration. We recalibrated the original models with the re-estimation of the model intercept and slope. We used curve decision analysis to describe and compare the clinical effects of the studied risk models. Better statistical metrics characterize the models developed on larger populations (Chicago and Bordeaux models). However, no model has a valid benefit for threshold probability greater than 0.30. The Net benefit of the most performing model (Bordeaux model) at the threshold probability of 0.11 is 23 of 1000 patients, burdened by 333 false positive cases. One of 1000 is the Net benefit at the threshold probability of 0.3. The use of PAL scores based on preoperative predictive factors cannot be currently used in a clinical setting because of a high false positive rate and low positive predictive value.

Brooker's merocyanine and its derivatives are well-studied molecules due to their very interesting optical properties. Merocyanine dyes exhibit different colors in solution depending on the solvent's polarity, pH, aggregation and intermolecular interactions. The synthesis of 1-methyl-4-[(oxocyclohexadienylidene)ethylidene]-1,4-dihydropyridine (MOED) dye yielded a particularly interesting solid state structure where in one crystal lattice, MOED and its protonated form are bound by hydrogen bonding interactions.

The title organic salt, C7H10N+·I−, was synthesized from a mixture of 4-methylpyridine and iodomethane in 2-propanol. It crystallized with three independent 1,4-dimethylpyridinium cations and three independent iodide anions in the asymmetric unit. In the crystal, there are no significant intermolecular interactions present.

Genetic causes can be directly responsible for various clinical conditions of male infertility and spermatogenic impairment. With the increased use of assisted reproduction technologies our understanding of genetic basis of male infertility has large implications not only for understanding the causes of infertility but also in determining the prognosis and management of such couples. For these reasons, the genetic investigations represent today an essential and useful tool in the treatment of male infertility. Several evidences are available for the clinical practice regarding the diagnosis; however, there are less information relative to the treatment of the genetic causes of male infertility. Focus of this review is to discuss the main and more common genetic causes of male infertility to better direct the genetics investigation in the treatment of spermatogenic impairment.

A procedure to construct Liapunov functionals for discrete Volterra equations is proposed. Using this procedure stability conditions are derived for general Volterra difference equations. Some applications of the proposed procedure for obtaining stability conditions for linear multistep methods for Volterra integro-differential equations are presented.

The discrete-time relaxation methods based on Volterra-Runge-Kutta methods for solving large system of second-kind Volterra integral equations are proposed. Convergence of the discrete-time iteration process with particular attention to parallel methods is investigated.

Investigation of the boundedness of the solutions of Volterra equations with discrete time by means of the direct Liapunov method and comparison theorems is performed. Boundedness conditions of solutions of some particular classes of equations are derived. Using such conditions, stability of Direct Quadrature methods for second kind Volterra equations is analyzed.

In this paper the waveform methods for solving systems of second kind Volterra integral equations are introduced. The convergence properties of continuous-time waveform methods on finite length and infinite length time intervals are investigated, with particular regard to parallel waveform relaxation methods.

This paper concerns parallel frontal predictor-corrector methods. Order and stability of these methods are investigated, when the corrector is solved both by the fixed point iteration method and by the Newton method.

Management of solitary pulmonary nodule (SPN) and micronodule (SPMN) is still debated. The use of 18F-FDG PET/CT or CT multislice screening for early lung cancer detection, have increased the frequency of displaying indeterminate single lung nodule with diameter between 0.1 cm and 2 cm. The first choice is to wait and do radiological follow-up, since the evaluation of temporal changes in a small mass may contribute to differentiate a malign from benign pathology. In case of unchanged images not capable of orientating the diagnostician or no possible preoperative diagnosis by bronchoscopy and percutaneous needle biopsy, surgical treatment is necessary allowing the histological characterization of lesion and a good prognosis of disease. Video-assisted thoracoscopic surgery and muscle-sparing minithoracotomy have become routine, each of these furnishing precise indications. The purpose of the study was to establish the main investigative method for indeterminate lung nodules, considering the continuous evolution of endoscopic and radiological techniques.

Fully parallel Runge-Kutta-Nystrom methods are introduced and their properties of accuracy, stability, and dispersion are investigated. Fully parallel Runge-Kutta-Nystrom methods with two and three stages are constructed.

We report a case of 68-year-old patient underwent a magnetic resonance imaging (MRI) of the skull and a computed tomography (CT) of the thorax for rhinorrhea and dyspnea. The MRI showed an irregular ethmoidal lesion and the CT of the thorax underlined a solid nodular neoformation in the upper right pulmonary lobe. The patient underwent rhinoscopy with biopsies that showed an ethmoidal adenocarcinoma; excision of the tumour was carried out via trans-sphenoid. After one month the patient underwent wedge-resections in video-thoracoscopy (VATS). Perioperative histologic examination revealed a lung metastases due to an adenocarcinoma of the ethmoid. The patient was treated with chemotherapy and did not show relapses after 12 months from VATS.

We investigate the stability of the numerical solutions resulting from applying very general classes of Runge-Kutta methods to Volterra integral and integro-differential equations with degenerate kernels. The results are generalizations of previous results obtained by the authors for exact collocation methods for these equations.

Objective To examine the diagnostic and therapeutic role of fiber-optic and rigid bronchoscopy in pediatric patients with foreign body inhalations. Methods From January 1986 to December 2004, we observed 128 young patients with suspicion of foreign body aspiration. Patients were divided into 3 groups: group I, patients with negative chest X-ray; group II, patients with radiological direct signs; group III, patients with radiological indirect signs. Results Removal of the foreign body was effected in 105 patients by rigid bronchoscopy and in 13 patients by fiber-optic bronchoscopy. In 3 group II patients a thoracotomy with a bronchotomy was necessary. Conclusions Fiber-optic bronchoscopy showed a diagnostic accuracy rate of 100 % but played a poor therapeutic role with a case resolution of 10.7 %. Rigid bronchoscopy was the main technique, permitting the removal of the tracheobronchial foreign body in 97.2 % of patients.

We described a rare case of pulmonary and parotid cyst for echinococcus granulosus in an eighty-one-year-old patient. Lesion was discovered in the lung owing to a clinical presentation. A swelling was the only sign in the parotid gland. Time between lung and parotid excision was 14 days. Time of hospitalizations was 4+/-1 day.

Surgical tracheostomy morbidity led the authors to investigate new election techniques. The aim of this retrospective study was to assess the translaryngeal tracheostomy (TLT), complications and cost.From January 1998 to January 2001, 104 patients were treated with TLT modified: 69 males (66.3%) and 35 females (33.7%), average age 52.6 +/- 9.5 years. The original pathologies were: traumatical (36), neurological (37), surgical (9), heart (4), respiratory (18). The average time between intubation and execution of TLT was 4.2 +/- 1.3 days.Fifty four patients died (52%) and 50 patients lived (48%). Two complications (1.9%) occurred in those who survived: a breaking of the guidewire in traction. Extraction of the tracheostomy tube by clamp, a haemorrhage in 2nd post-operative day due to a thyroid vessel lesion. The haemostasis was performed by classical tracheostomy. The average number of days to decannulation was 25 +/- 1 days.TLT reduces trauma or trachea and neighbouring structures. This technique is safe and easy. TLT is an effective method, in non-urgent situations, in children and adults, as well as in brachytypes and the obese.

Bullous pneumopathy is considered a surgical disease, although her treatment is still discussed. The initial attempts of surgical treatment were founded on erroneous physiopathological concepts and date back to early years of 1900. These surgical treatments intended to external drainage of giant bullae, their marsupialized or to reduction of extension of bullae by pneumoperitonaeum, section of phrenic nerve or thoracoplasty. The definition of emphysematous bullae has been much improved with the development of computed tomography. A precise study of their size, of their position and of condition of residual pulmonary parenchyma may be considered important to decide the surgical treatment: this must determine the removal of bulla and the reexpansion of compressed pulmonary parenchyma. The Authors report a case of giant bulla, initially wrong interpreted as pneumothorax, of exceptional observation for her malformative origin, diagnoses and surgical treated on an eleven years old child.

The aim of this work was to evaluate the different surgical repair procedures and to discuss their technical applications according to the indications. From april 1989 to november 1999 we observed 18 patients, 12 males (66.7%) and 6 females (33.3%) presenting tumors of the chest wall. All patients were submitted preoperatively to a general respiratory check-up, and to an assessment of loco-regional and metastatic lesions. In 13 patients (72.2%), on the basis of topographical and morphological characteristics of the mass, we performed a transthoracic needle biopsy under scanner monitoring. The exeresis, in 6 patients (33.3%), implied a large resection of osteo-muscular structures. In 10 patients (55.6%), the benign nature of lesion, required extirpation solely of the tumor. In 2 patients (11.1%), owing to the extensive infiltration of the primary neoplasm, solely complementary treatment was carried out. Reconstruction of the thoracic wall was performed using associated myoplasty in all cases. In 3 subjects a prosthesis was installed; in 1 case a costal transposition association is necessary. Histological observation of the excised material revealed 16 primary tumors, 12 benign (75%) and 4 malignant (25%). Transthoracic needle biopsy under scanner monitoring confirmed the diagnosis in 100% of the cases operated. Fourteen patients (87.5%) are alive 73 +/- 35 months after intervention, without resumption of the disease. Two patients died (12.5%) VIII and VI months following the operation. Two patients not operated, died after VI and V months. Appropriate choice of techniques and of repair materials allowed valid oncological, aesthetical and functional results independently from the extent of the parietal defect.

Between January 1980 and December 1997 twenty-one patients with a mass in the posterior mediastinum came under our observation. All of the patients underwent chest radiography, bronchoscopy, respiratory function tests, perfusional and ventilatory radionuclide scans, a computed tomography (CT) of the chest and blood gas analysis. In cases involving neurogenic tumours magnetic resonance imaging (MRI) was used. Ten patients underwent CT guided transthoracic needle biopsy. The excision was performed by means of a thoracotomy in 12 cases (57.1%) and by video assisted thoracoscopy surgery (VATS) in the other 9 (42.9%); no deaths were recorded. Eleven neurilemmomas, two bronchogenic cysts, two paragangliomas, two neuroepitheliomas, one neurogenic sarcoma and three esophageal duplications were found. The authors believe an accurate pre-operative assessment of the lesion can be obtained using CT and MRI. The video assisted thoracoscopy (VAT) is a useful method of diagnosis and treatment as it can be converted into VATS if the lesion is benign or cystic. Thoracotomy is necessary when the mass is malignant or when there is adhesion to or invasion of surrounding tissues.

Stability conditions for Volterra equations with discrete time are obtained using the direct Lyapunov method, without the usual assumption of the summability of the series of the coefficients. Using such conditions, the stability of some numerical methods for second kind Volterra integral equations is analyzed.

In this paper necessary and sufficient conditions for the exponential stability of discrete linear Volterra systems are proved. Sufficient conditions, expressed directly in terms of the coefficients, are derived

The aim of this study was to evaluate the benefits of total intravenous anaesthesia (TIVA), with the administration of drugs intravenously and the maintenance of pulmonary ventilation with oxygen enriched air, with respect to inhalatory anaesthesia, in thoracotomies with single lung ventilation.The study, devoloped in collaboration between the Service of Anaesthesia and Resuscitation and the Division of Thoracic Surgery of the Hospital of Teramo, was carried out in two groups of patients chosen at random; fifty patients divided into two groups of twenty-five were studied. Pre-medication and induction was similar in both groups; maintenance, however, varied: a total intravenous anaesthesia was given to patients in group A whereas patients in group B received an inhalatory anaesthesia. These parameters were considered: pressure values, heartbeat, PaO2 and PaCO2 levels, SatO2 and EtCO2.Both protocols respected anaesthetic guidelines in terms of controlling pressure values, heartbeat and levels of PaCO2 during bipulmonary ventilation. Significantly statistical differences were observed in the oxygenation during one lung ventilation: the mean values of PaO2 being significantly higher in group A.On the basis of this experience, it can be conclude that TIVA offers the following advantages: a better oxygenation during one lung ventilation, good recovery of post operative consciousness with no psychomotor disturbances, absence of pollution in the operating theatre.

The Authors carried out an retrospective analysis on 81 patients, 67 men and 14 women, suffering from non post-surgical thoracic empyema, to evaluate the different therapeutic procedures and respective indications. The unsuccessful response to the preserving approach (intercostal drainage and pleural lavage twice a day with specific antibiotics or antiseptics) in 56 cases, induced the Authors to carry out a video-thoracoscopy (VAT), that allowed them to define the infection stage and subsequent treatment (the carrying on of a pleural drainage-lavage in 32 cases, the transcurrent pleural irrigation in 10 cases, the open window thoracostomy followed by myoplasty in 6 cases with bronchopleural fistula, the decortication with associated pleural exeresis in 6 cases with bronchopleural fistula, the decortication with associated pleural exeresis in 6 cases, the streptokinase in pleural cavity in 2 cases). There were registered totally 3 deaths (3.7%). The Authors in conclusion assert that the VAT, carried out after the unsuccessful preserving treatment, allows the evaluation of the infection stage and consequently suggests therapy.

The aim of this study is to evaluate the utility of surgical treatment in patients with pectus excavatum (PE) or pectus carinatum (PC). Fifteen patients underwent surgical treatment because of their psycological and anatomical condition, more serious in 6 patients (5 with PE and 1 with PC). The degree of these chest wall deformities was evaluated as resulting from CT scan of the thorax, by the ratio between the transversal and the front/back diameters, according to Haller. The Authors recommend surgical operation in the post-puberal age up to 21 years because of good results obtained using Ravitch approach (only 1 case of partial relapse of PE), even though modified in PE cases with the application of flat steel prosthesis and in PC cases for uncutting the perichondral beds. The choice of surgical procedure derives, in our opinion, from the correction of these anatomic deformities and from the greater sense of improved cosmesis that might result.

A 56-year-old male patient came under our observation when a peripheral round mass in his right lung which he had since 1991 and which was believed to be a bronchogenic cyst, showed a volumetric enlargement of 2 cm. After performing a lobectomy of the middle lobe, the histopathological examination revealed the presence of a mucinous cystadenoma of borderline malignancy.

Clinical research on 75 cases of mediastinal masses has been carried out with the aim of evaluating the diagnostic value of Magnetic Resonance (MR). Results which have been achieved point to a remarkable potentiality of MR especially in the characterization and spatial definition of the masses and in the study of the spinal canal. These results, as well as the non-invasivity of the procedure, lead us to consider MR as an investigation of primary importance in the diagnostic assessment of mediastinal pathology.

The great interest in VATS over the last few years has extended the indications for this technique in order to avoid risks. There are additional indications (e.g. spontaneous pneumothorax), including several benign diseases of the lung, pleura, mediastinum and oesophagus. But other indications for the procedure are still controversial, for example lung resection for primary bronchial cancer. In this report the Authors, on the basis of their own experience, try to define the present and approaching perspectives for VATS.

Non-small cell lung cancer (NSCLC) shows a complex cytogenetic heterogeneity and up to now no particular chromosomal aberration seems to characterize its malignant evolution. We therefore performed cytogenetic analyses of 20 primary NSCLC, 8 adenocarcinomas and 12 squamous cell carcinomas on direct preparations or short-term cultures. Only 1 case was analyzed after long-term culture. Results were obtained from 11 samples and clonal rearrangements were found in 3 cases, a diploid and a near-triploid clone with several aberrations such as i (9q), rob (14; 15) and rob (21; 21) in 1 case, a near-triploid clone in 1 case, and Y chromosome loss in 1 case. Other aberrations found were sporadic, but + 7 aneuploidy and translocations involving 1p were detected in 2 and 3 samples respectively. Although to date it has been very difficult to recognize primary changes in NSCLC, nevertheless a literature review and our results indicate that i(9q) and robertsonian translocations are relevant findings.

In this paper, we analyse parallel iteration of Volterra-Runge-Kutta methods (PIVRK methods) for solving second-kind Volterra integral equations on parallel computers. We focus on the determination of the region of convergence C and on the stability region Sm of the iterated method obtained after m iterations. Results are presented for the convolution test equation. It turns out that the stability region Sm does not necessarily converge to the stability region S of the corrector. However, for finite m, Sm need not to be contained in C or S and may be much larger than C.

A class of methods depending on some parameters are introduced for the numerical solution of the Abel integral equations of the second kind. Some bounds on the parameters are determined so that the corresponding methods have infinite stability intervals.

Fifty patients with bronchogenic carcinoma were prospectively studied by both CT and MR during 10 days preceding thoracotomy. Results of CT and MR were compared with the surgical and pathology findings. No statistically significant difference was found between the two imaging methods for the evaluation of node involvement (N2). MR appear to be superior to CT in the aortopulmonary and subcarinal areas.

Twenty-five patients with bronchogenic carcinoma were prospectively studied by both CT and MR during 10 days preceding thoracotomy. MR scans included contiguous axial and coronal slices. Results of CT and MR studies were compared with the surgical and pathological findings. Although no significant difference was found between the two imaging methods for the evaluation of mediastinal nodes. MR appear to be superior to CT in the aortopulmonary and subcarinal node areas.

This paper is concerned with the analysis of the stability of a class of one-step integration methods, originated by the Lanczos tau method and applicable to particular linear differential systems. It is proved that these methods are A-stable for every order.

The purpose of this paper is to analyze the stability properties of one-step collocation methods for the second kind Volterra integral equation through application to the basic test and the convolution test equation.

The tau method approximates the solution of a differential equation with a polynomial, which is the exact solution of a differential equation obtained by adding to the right hand side of the given equation a perturbation term, consisting of a suitably chosen linear combination of polynomials. Until now the Chebyshev and Legendre polynomials have been used to this purpose, but the determination of the best perturbation term is, still, an open problem. In this paper a perturbation term depending on the differential equation is chosen. For this formulation of the tau method, the existence of an infinite sequence of tau approximants and the convergence of the error to zero is proved. An estimate of the local truncation error is also given, and the stability properties are discussed. Numerical results are also reported.

The stability of the de Hoog and Weiss Runge-Kutta methods is analyzed for the Volterra integrodifferential equations with respect to the basic test equation and for Volterra integral equations with respect to the linear convolution equation. Stability regions are determined for some choices of the parameters.

Stability criteria are derived for difference equations of Volterra type with degenerate kernels. The main tool in this analysis is the use of the new representation formula which allows us to express the solution of discrete Volterra equation with degenerate kernel in terms of the fundamental matrix of the corresponding first-order system of the difference equations.

The diagnostic significance of the histological typing of lung cancer carried out on preoperative bronchoscopic biopsy samples is assessed in relation to final morphological diagnosis on operating material. In this connection 176 of 624 cases of lung cancer documented histologically from January 1980 to December 1987 in which preoperative biopsy sample was followed by removal of the lung are analysed. The 4 basic histotypes of lung cancer according to the WHO (1981) classification are considered. A positive diagnosis for cancer was encountered in 138 cases (78.4%) with histotype confirmed in 122, whereas a negative diagnosis was encountered in 38 cases (21.6%). These findings also permitted further considerations, including the possible limitations of the technique.