Superfici di suddivisione: teoria, algoritmi ed applicazioni

Le superfici di suddivisione sono un ottimo ed importante strumento utilizzato principalmente nell’ambito dell’animazione 3D poichè consentono di definire superfici di forma arbitraria. Questa tecnologia estende il concetto di B-spline e permette di avere un’estrema libertà dei vincoli topologici. Per definire superfici di forma arbitraria esistono anche le Non-Uniform Rational B-Splines (NURBS) ma non lasciano abbastanza libertà per la costruzione di forme libere. Infatti, a differenza delle superfici di suddivisione, hanno bisogno di unire vari pezzi della superficie (trimming). La tecnologia NURBS quindi viene utilizzata prevalentemente negli ambienti CAD mentre nell’ambito della Computer Graphics si è diffuso ormai da più di 30 anni, l’utilizzo delle superfici di suddivisione. Lo scopo di questa tesi è quello di riassumere, quindi, i concetti riguardo questa tecnologia, di analizzare alcuni degli schemi di suddivisione più utilizzati e parlare brevemente di come questi schemi ed algoritmi vengono utilizzati nella realt`a per l’animazione 3D.

Fluctuation properties in random walks on networks and simple integrate and fire models

In questa tesi si è studiato l’insorgere di eventi critici in un semplice modello neurale del tipo Integrate and Fire, basato su processi dinamici stocastici markoviani definiti su una rete. Il segnale neurale elettrico è stato modellato da un flusso di particelle. Si è concentrata l’attenzione sulla fase transiente del sistema, cercando di identificare fenomeni simili alla sincronizzazione neurale, la quale può essere considerata un evento critico. Sono state studiate reti particolarmente semplici, trovando che il modello proposto ha la capacità di produrre effetti "a cascata" nell’attività neurale, dovuti a Self Organized Criticality (auto organizzazione del sistema in stati instabili); questi effetti non vengono invece osservati in Random Walks sulle stesse reti. Si è visto che un piccolo stimolo random è capace di generare nell’attività della rete delle fluttuazioni notevoli, in particolar modo se il sistema si trova in una fase al limite dell’equilibrio. I picchi di attività così rilevati sono stati interpretati come valanghe di segnale neurale, fenomeno riconducibile alla sincronizzazione.

Sperimentazione di algoritmi di localizzazione per sorgenti acustiche

L'obiettivo di questo elaborato è quello di realizzare un sistema di acquisizione real-time e low cost, in grado di stimare la posizione di una sorgente sonora. Per acquisizione real-time si intende un sistema in grado di seguire gli spostamenti della sorgente audio nell'ambiente, limitando il più possibile i tempi di latenza fra un'acquisizione e l'altra. A tal fine si sfrutteranno due coppie di microfoni, che concorrereranno in maniera sequenziale alla stima dell'angolo di arrivo del suono (e quindi della retta su cui giace il punto di provenienza del suono). Combinando i dati raccolti dai quattro microfoni sarà dunque possibile risalire alla posizione di provenienza della sorgente sonora. Il software (implementato in MATLAB) verrà ampiamente discusso nei seguenti capitoli, il suo scopo sarà quello di gestire l'acquisizione dati, garantire il funzionamento real-time e fornire una stima di posizione della sorgente sonora, mostrando il relativo errore commesso durante la misura, nel caso in cui si conosca a priori la posizione della sorgente.

Algoritmi per la correzione di distorsioni in immagini

Studio, analisi ed implementazione di algoritmi esistenti per la correzione di distorsioni in immagini, con introduzione delle semplificazioni necessarie per la sua realizzazione in dispositivi embedded. Introduzione di nuovi metodi di semplificazione. Calibrazione di una telecamera o un sistema di telecamere stereo con lenti wide angle o fisheye tramite opencv.

Disseminazioni in reti peer-to-peer attraverso algoritmi di gossip a due fasi

Gli algoritmi di gossip sono utilizzati per la disseminazione di messaggi in una rete peer-to-peer. La tesi tratta lo sviluppo, l'implementazione e l'analisi di quattro nuovi algoritmi di gossip "a due fasi". Gli algoritmi sono stati sviluppati e testati con il simulatore LUNES per poi essere analizzati in vari confronti con gli algoritmi classici dell'ambito, ovvero Fixed Probability e Conditional Broadcast. Le prove sono state effettuate su varie tipologie di grafi, ovvero Random, Scale-free, Small-world e K-Regular.

Fecal calprotectin correlates more closely with the Simple Endoscopic Score for Crohn's disease (SES-CD) than CRP, blood leukocytes, and the CDAI

Studies evaluating the correlation between the widely used Simple Endoscopic Score for Crohn's disease (SES-CD) and noninvasive markers are scarce. The aim of this study was to evaluate the correlation between the SES-CD and fecal calprotectin, C-reactive protein (CRP), blood leukocytes, and the Crohn's disease activity index (CDAI).

Risk assessment in the first fifteen minutes: a prospective cohort study of a simple physiological scoring system in the emergency department

Introduction The survival of patients admitted to an emergency department is determined by the severity of acute illness and the quality of care provided. The high number and the wide spectrum of severity of illness of admitted patients make an immediate assessment of all patients unrealistic. The aim of this study is to evaluate a scoring system based on readily available physiological parameters immediately after admission to an emergency department (ED) for the purpose of identification of at-risk patients. Methods This prospective observational cohort study includes 4,388 consecutive adult patients admitted via the ED of a 960-bed tertiary referral hospital over a period of six months. Occurrence of each of seven potential vital sign abnormalities (threat to airway, abnormal respiratory rate, oxygen saturation, systolic blood pressure, heart rate, low Glasgow Coma Scale and seizures) was collected and added up to generate the vital sign score (VSS). VSSinitial was defined as the VSS in the first 15 minutes after admission, VSSmax as the maximum VSS throughout the stay in ED. Occurrence of single vital sign abnormalities in the first 15 minutes and VSSinitial and VSSmax were evaluated as potential predictors of hospital mortality. Results Logistic regression analysis identified all evaluated single vital sign abnormalities except seizures and abnormal respiratory rate to be independent predictors of hospital mortality. Increasing VSSinitial and VSSmax were significantly correlated to hospital mortality (odds ratio (OR) 2.80, 95% confidence interval (CI) 2.50 to 3.14, P < 0.0001 for VSSinitial; OR 2.36, 95% CI 2.15 to 2.60, P < 0.0001 for VSSmax). The predictive power of VSS was highest if collected in the first 15 minutes after ED admission (log rank Chi-square 468.1, P < 0.0001 for VSSinitial;,log rank Chi square 361.5, P < 0.0001 for VSSmax). Conclusions Vital sign abnormalities and VSS collected in the first minutes after ED admission can identify patients at risk of an unfavourable outcome.

Simple and objective method for routine detection of the macular pigment xanthophyll

A new simple method for two-dimensional determination of optical density of macular pigment xanthophyll (ODx) in clinical routine is based on a single blue-reflection fundus image. Individual different vignetting is corrected by a shading function. For its construction, nodes are automatically found in structureless image regions. The influence of stray light in elderly crystalline lenses is compensated by a correction function that depends on age. The reproducibility of parameters in a one-wavelength reflection method determined for three subjects (47, 61, and 78 years old) was: maxODx = 6.3%, meanODx = 4.6%, volume = 6%, and area = 6% already before stray-light correction. ODx was comparable in pseudophakic and in an eye with a crystalline lens of the same 11 subjects after stray-light correction. Significant correlation in ODx was found between the one-wavelength reflection method and the two-wavelength autofluorescence method for pseudophakic and cataract eyes of 19 patients suffering from dry age-related macular degeneration (AMD) (R(2) = 0.855). In pseudophakic eyes, maxODx was significantly lower for dry AMD (n = 45) (ODx = 0.491±0.102 ODU) than in eyes with healthy fundus (n = 22) (ODx = 0.615±0.103 ODU) (p = 0.000033). Also in eyes with crystalline lens, maxODx was lower in AMD (n = 125) (ODx = 0.610±0.093 ODU) than in healthy subjects (n = 45) (ODx = 0.674±0.098 ODU) (p = 0.00019). No dependence on age was found in the pseudophakic eyes both of healthy subjects and AMD patients.

Three-dimensional portable document format: a simple way to present 3-dimensional data in an electronic publication

Three-dimensional (3D) models of teeth and soft and hard tissues are tessellated surfaces used for diagnosis, treatment planning, appliance fabrication, outcome evaluation, and research. In scientific publications or communications with colleagues, these 3D data are often reduced to 2-dimensional pictures or need special software for visualization. The portable document format (PDF) offers a simple way to interactively display 3D surface data without additional software other than a recent version of Adobe Reader (Adobe, San Jose, Calif). The purposes of this article were to give an example of how 3D data and their analyses can be interactively displayed in 3 dimensions in electronic publications, and to show how they can be exported from any software for diagnostic reports and communications among colleagues.

A simple tool for stereological assessment of digital images: the STEPanizer

STEPanizer is an easy-to-use computer-based software tool for the stereological assessment of digitally captured images from all kinds of microscopical (LM, TEM, LSM) and macroscopical (radiology, tomography) imaging modalities. The program design focuses on providing the user a defined workflow adapted to most basic stereological tasks. The software is compact, that is user friendly without being bulky. STEPanizer comprises the creation of test systems, the appropriate display of digital images with superimposed test systems, a scaling facility, a counting module and an export function for the transfer of results to spreadsheet programs. Here we describe the major workflow of the tool illustrating the application on two examples from transmission electron microscopy and light microscopy, respectively.

A simple, economical, and effective portable paediatric mock circulatory system

Ventricular assist devices (VADs) and total artificial hearts have been in development for the last 50 years. Since their inception, simulators of the circulation with different degrees of complexity have been produced to test these devices in vitro. Currently, a new path has been taken with the extensive efforts to develop paediatric VADs, which require totally different design constraints. This paper presents the manufacturing details of an economical simulator of the systemic paediatric circulation. This simulator allows the insertion of a paediatric VAD, includes a pumping ventricle, and is adjustable within the paediatric range. Rather than focusing on complexity and physiological simulation, this simulator is designed to be simple and practical for rapid device testing. The simulator was instrumented with medical sensors and data were acquired under different conditions with and without the new PediaFlowTM paediatric VAD. The VAD was run at different impeller speeds while simulator settings such as vascular resistance and stroke volume were varied. The hydraulic performance of the VAD under pulsatile conditions could be characterized and the magnetic suspension could be tested via manipulations such as cannula clamping. This compact mock loop has proven to be valuable throughout the PediaFlow development process and has the advantage that it is uncomplicated and can be manufactured cheaply. It can be produced by several research groups and the results of different VADs can then be compared easily.