1,721,015 research outputs found
Rilievo 3D della Tensa Capitolina mediante metodologia laser scanning
No full textNell’ambito del rilievo tridimensionale di oggetti di interesse archeologico, artistico, architettonico ed ingegneristico, è sempre più frequente l’utilizzo di metodologie laser scanning e fotogrammetriche terrestri1. Tali metodologie consentono di acquisire elevate quantità di dati in tempi brevi, ad alta risoluzione e con precisioni elevate; le informazioni ottenute sono utilizzate per la ricostruzione virtuale della geometria e della morfologia delle superfici degli oggetti di interesse, per scopi di archivio e conservazione, analisi strutturale, studi dettagliati, navigazione e fruizione virtuale ecc...2.
La metodologia laser scanning si avvale di strumenti hardware dotati di una sorgente laser, il cosiddetto “mezzo attivo”. Gli strumenti che vengono utilizzati possono essere suddivisi in tre differenti classi: laser scanner a tempo di volo, a differenza di fase e a triangolazione. Nel primo caso, i punti vengono acquisiti misurando il “tempo di volo” (Time Of Flight – TOF) di un impulso laser che percorre la distanza strumento-oggetto in andata e in ritorno; in quelli a differenza di fase vengono confrontate le fasi di un determinato segnale in partenza ed in arrivo, in quelli a triangolazione vengono misurati gli angoli in uscita ed in entrata tra il raggio laser e lo strumento.
In ogni caso, vengono utilizzati specchi rotanti che, mediante piccole rotazioni, permettono di direzionare il raggio laser verso le superfici dell’oggetto e orientarlo nello spazio con micro spostamenti per acquisire grandi quantità di punti ad alta densità. Questi strumenti sono detti a scansione in quanto proiettano sulla superficie esposta dell’oggetto un segnale laser puntuale o a striscia, orizzontale o verticale.
Il passaggio del segnale sulla superficie dell’oggetto definisce una griglia regolare con un passo di campionamento scelto in funzione dello scopo del rilievo e che corrisponde alla risoluzione della misura; questa griglia risulta strettamente dipendente dal tipo di laser scanner, dall’ottica utilizzata e dalla distanza strumento-oggetto, i cui nodi rappresentano i punti che vengono poi acquisiti sulla superficie dell’oggetto. Di ognuno di questi vengono calcolate le coordinate X, Y, Z rispetto ad un sistema di riferimento la cui origine è posta all’interno dello strumento, in corrispondenza del centro di emissione del raggio laser: l’insieme dei punti acquisiti viene definito “nuvola di punti”.
Generalmente risulta però più semplice poter lavorare con superfici continue: le nuvole di punti nella fase di post-processamento vengono convertite in superfici dette mesh. L’operazione di meshing, infatti, realizzata con strumenti software dedicati, costruisce tali superfici a partire dall’interconnessione tra i punti acquisiti creando così una rete di poligoni irregolari, normalmente triangoli, da cui l’acronimo TIN (Triangulated Irregular Net). In questo modo è possibile procedere con le successive fasi di costruzione di un modello virtuale dell’oggetto rilevato ed ottenere il Modello Digitale delle Superfici (Digital Surface Model – DSM
"Small Objects" and "Micro-DEM": Surface Analysis by point and Stripe laser Scanners.
No full textWorkshop on: "3D Digital Imaging and Modelling: Applications of Heritage, Industry, Medicine and Land
3D laser scanning surveys in the modelling of cultural heritage.
No full text3D high resolution survey is now performed mainly with photogrammetry and laser scanning methodologies providing very dense and accurate point clouds. Alignment of all acquired points in a defined reference system generates a metrically correct 3D model of the objects. Photographic information can be associated to the model too. Terrestrial applications have recently demonstrated the potentialities of the techniques, which are useful in different fields.
In this chapter 3D survey methodologies are explained, discussed and applied. These techniques have been used in different domains: in engineering field, as a geometrical support to structural analysis and in the monitoring of small variations by comparison of different surveys, co-registered in the same reference system. In architectural field, photogrammetry and laser scanning techniques are widely used for documentation and as support for restoration of buildings, while in territory survey are used for cartographic map production and in the monitoring of deformation areas (volcanoes, glaciers and landslides areas, shorelines) comparing the surveys at different time. In archaeology and in the study of cultural heritage, they allow for virtual reconstruction of buildings and objects. Moreover, in medicine, a metric survey helps quantitative evaluation of prosthesis and pre- and post- surgical interventions conditions by comparison of different models. In the sequel, some applications are described, showing different aspects concerning the 3D survey in the framework of cultural heritage. The “Cavallo ligneo” of the “Palazzo della Ragione” in Padua (a wooden horse from a middle age economical and political building), allows focusing on reconstruction of lacunas in the data generated by operative limitations. The “Arche Scaligere” in Verona, is used for discussing the integration between laser scanning and digital photogrammetric data, thus evaluating the accuracy of the methodologies. The work on the “San Prosdocimo” Chapel, which is located in “Santa Giustina” Basilica in Padua, is focused on different procedures for texture mapping of digital images on the 3D models distinguishing between point cloud models and surface model
Analysis of 2,5-dimethoxy-amphetamines and 2,5-dimethoxy-phenethylamines aiming their determination in biological matrices: a review
Full text linkPurpose: The present review aims to provide an overview of methods for the quantification of 2,5-dimethoxy-amphetamines and -phenethylamines in different biological matrices, both traditional and alternative ones. Methods: A complete literature search was carried out with PubMed, Scopus and the World Wide Web using relevant keywords, e.g., designer drugs, amphetamines, phenethylamines, and biological matrices. Results: Synthetic phenethylamines represent one of the largest classes of “designer drugs”, obtained through chemical structure modifications of psychoactive substances to increase their pharmacological activities. This practice is also favored by the fact that every new synthetic compound is not considered illegal by existing legislation. Generally, in a toxicological laboratory, the first monitoring of drugs of abuse is made by rapid screening tests that sometimes can occur in false positive or false negative results. To reduce evaluation errors, it is mandatory to submit the positive samples to confirmatory methods, such as gas chromatography or liquid chromatography combined to mass spectrometry, for a more specific qualitative and quantitative analysis. Conclusions: This review highlights the great need for updated comprehensive analytical methods, particularly when analyzing biological matrices, both traditional and alternative ones, for the search of newly emerging designer drugs
Hexanol-Based Supramolecular Solvents Tool for the Determination of 11 Illicit Phenethylamines in Oral Fluid by LC-MS/MS
No full textMonitoring of new phenethylamine designer drugs in oral fluid (OF) is a crucial aim in workplace testing and driving under the influence of drug programs. In this study a simple and very quick method for the quantification of 11 illicit drugs in OF, which gave negative results to immunoassay tests, is proposed. Sample treatment and extraction of analytes were simultaneously achieved by applying supramolecular solvents (SUPRAS) tool. Chromatographic separation and compounds quantification were carried out by liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. Efficacy of cleaning-up/extraction of this SUPRAS approach was fully confirmed by recovery and matrix effect results. The entire analytical procedure was validated following the international guidelines. The SUPRAS extraction coupled with LC-MS/MS resulted in powerful tool for the control of phenethylamines abuse, with rapid run time and minimal sample preparation. The use of this methodology could be easily extended to monitoring of other drugs of abuse
Integrazione di metodologie di rilievo terrestre ad alta risoluzione per il rilievo di fossili
No full textNell’ambito del restauro di piccoli oggetti o di caratteristiche minute (come, ad esempio, fessurazioni) di elementi di dimensioni medio-grandi, è necessario utilizzare sistemi di rilievo 3D ad alta risoluzione per la corretta definizione delle caratteristiche geometriche.
In questo lavoro sono state utilizzate metodologie integrate laser scanning, fotogrammetriche digitali terrestri e topografiche classiche per il rilievo tridimensionale di fossili vegetali e animali con lo scopo del restauro conservativo: le nuvole di punti estratte dalle diverse metodiche sono state confrontate per valutare precisioni e limiti di applicabilità delle stesse. I prodotti ottenuti sono stati successivamente utilizzati nella fase di restaur
Enantiomeric separation by HPLC of 1,4-dihydropyridines with vancomycin as chiral sector
No full textAnalysis on the deterioration of road pavements through laser scanning technology
No full textThe need to organise and rationalise maintenance interventions on road pavements, through management systems that are cost-effective and functional, has led to the setting up of Pavement Management Systems (PMS).
These systems consider the objectives of transportation-related policies, as well as budget limitations of road infrastructure Management Authorities. They also provide for the arrangement of urgent maintenance works, when the paving deterioration is particularly harsh. In addition, there is a need to set up a PMS according to the actual situations and to plan outlay, times and feasibility. This paper presents a methodological approach to survey the deterioration state of road paving and to manage the maintenance intervention through a non-destructive system based on terrestrial laser scanner surveys. The images related to the deterioration state have been acquired by different resolution sensors; segmentation, extraction and classification operations have also been done. The images have been compressed at different levels, in order to extract the deterioration state information, through edge extraction, smoothing and quality enhancement operators. The deteriorated road surface is acquired as a dense point cloud, for producing metrically correct 3-D models. The geometric three-dimensional information, acquired by the laser scanner sensor, is integrated with the real radiometric information of the object in order to obtain truly photorealistic digital 3-D objects.
It is therefore possible to extract metric information relative to the deteriorated state from a quantitative point of view, defining the deterioration severity level. The data, related metadata, images and 3-D global models can be managed by a Relational DataBase Management System (RDBMS), which allows both technicians and managers to evaluate the deterioration evolution over time and to plan the most suitable maintenance for the pavement restoration
LC-MS/MS analysis of acetaminophen and caffeine in amniotic fluid
No full textThe intake of several substances by pregnant women could be
hazardous to the fetus and mother's health: many substances can
cross the placenta and reach the fetal compartment, causing adverse
outcomes. Consequently, to accurately measure the presence of
xenobiotics in fetal matrices, sensitive and specific bioanalytical
methods are necessary: this would allow the assessment of fetal
exposure to substanceswhich, although licit, can be dangerous for the
fetal and child's growth. The aim of this study was to develop and
validate a liquid chromatography tandem mass spectrometry method
for the simultaneous determination and quantitation of caffeine and
acetaminophen in amniotic fluid. Amniotic fluid is a quite complex
biological matrix and, as such, it requires a purification step prior to
analysis. The extraction method has been optimized by comparing
three different commercially available SPE cartridges (SupelTM Select
HLB, Phenomenex Strata C18-E, and Agilent ABS Elut-NEXUS), and a
liquid/liquid extraction with acetonitrile. A reverse-phase HPLC with a
C18 column and gradient elution programwas used. MS detectionwas
carried out in MRM mode. Quantitation was performed using the
internal standard method. Validation parameters were very satisfactory.
The high selectivity and sensitivity of the method (LOQ < 9.5 ng
mL1, and LOD < 3.3 ngmL1) allowed us to determine target analytes
even in small amounts. Precision, matrix effect, and stability were also
evaluated. The whole validated method has finally been applied to the
analysis of 194 real samples of human amniotic fluid obtained from
pregnant women (15–21 weeks of gestation) in order to monitor the
effective intake of target analytes: 96% of the examined women
consumed caffeine during pregnancy while a lower percentage (20%)
showed acetaminophen intake. The whole procedure is simple and
easy to perform with minimal sample preparation and short analysis
time
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