Studio conformazionale di un derivato dendrimerico dell'acido L-glutammico tramite spettroscopia NMR e IR

Con questo lavoro si vuole proporre un modello conformazionale di una molecola dendrimerica tramite studi di spettroscopia NMR e FT-IR. Prima di inoltrarci nel fitto bosco di picchi spettroscopici introduciamo brevemente questa classe di composti [1a,b,c]. Le specie dendrimeriche sono dette tali in quanto strutturate da un corpo centrale (monomero di pochi u.m.a. ad esempio un amminoacido o un anello aromatico polifunzionalizzato) da cui si diramano vari bracci a loro volta ramificati. Se la molecola è molto grossa il risultato finale prende la forma di un granulo che presenta la superficie esterna ricca dei gruppi funzionali propri dei monomeri costituenti. L'utilizzo principale di questi composti comporta l'attivazione della loro superficie, ottenuta legando ai gruppi funzionali determinate molecole. È così possibile, per esempio, il veicolamento di farmaci a specifici siti attivi. Inoltre, sfruttando la formazione di legami non covalenti, alcuni dendrimeri sono utilizzati come fasi stazionarie in tecniche cromatografiche GC, HPLC, e scambio ionico. La possibilità di costruire dendrimeri con monomeri chirali ha portato queste molecole ad essere delle ottime candidate per lo studio degli effetti macroscopici della chiralità molecolare. In questo campo ci sono studi sulla chiralità del “core”, dei bracci dendrimerici o solo della superficie [2]. I gruppi funzionali superficiali possono essere di vario tipo e alcuni possono essere in grado di legarsi tra loro (ad esempio gruppi amminici e carbonilici con legami ad idrogeno). I legami possono avvenire sia tra due rami dendrimerici della stessa molecola (legami intramolecolari), sia tra gruppi funzionali di altre molecole (legami intermolecolari). Nel caso di legami ad idrogeno intermolecolari, quello che accade è l'aggregamento di due o più molecole dendrimeriche. Questo fenomeno genera lunghe catene di dendrimeri dette fibrille, le cui soluzioni assumono macroscopicamente l'aspetto di gel [3]. I gel dendrimerici ad una certa temperatura (o meglio in un intervallo di temperature) subiscono una transizione di fase, si rompono i legami ad idrogeno e le fibrille si scindono in dendrimeri liberi; questo processo non è sempre reversibile. Molto comuni sono i composti dendrimerici costruiti usando amminoacidi come monomeri, alcuni dei quali, ad esempio l'acido glutammico e la lisina, avendo più di un gruppo amminico o più di un gruppo carbossilico, sono in grado di legare, tramite legami ammidici, più molecole contemporaneamente. Questo fa si che alcuni dendrimeri vengano studiati dal punto di vista conformazionale per fare meglio luce sul tema del folding delle proteine [4]. Il dendrimero studiato in questa tesi, un trimero dell'acido glutammico, è troppo piccolo per essere considerato come un frammento significativo di una proteina; il nostro lavoro è comunque finalizzato allo studio conformazionale di questa molecola. Questo compito è stato affrontato utilizzando comuni tecniche di indagine spettroscopica NMR sia monodimensionali che bidimensionali, integrandole anche con alcuni spettri all'infrarosso che come vedremo sono stati cruciali per il fine del lavoro. I risultati verranno presentati grossomodo nell'ordine in cui sono stati registrati; i parametri sperimentali di ogni esperimento sono riportati in un capitolo a parte. In fine verrà formulata un'ipotesi conformazionale compatibile con i dati raccolti

Machine Learning for Understanding Focal Epilepsy

The study of neural dysfunctions requires strong prior knowledge on brain physiology combined with expertise on data analysis, signal processing, and machine learning. One of the unsolved issues regarding epilepsy consists in the localization of pathological brain areas causing seizures. Nowadays the analysis of neural activity conducted with this goal still relies on visual inspection by clinicians and is therefore subjected to human error, possibly leading to negative surgical outcome. In absence of any evidence from standard clinical tests, medical experts resort to invasive electrophysiological recordings, such as stereoelectroencephalography to assess the pathological areas. This data is high dimensional, it could suffer from spatial and temporal correlation, as well as be affected by high variability across the population. These aspects make the automatization attempt extremely challenging. In this context, this thesis tackles the problem of characterizing drug resistant focal epilepsy. This work proposes methods to analyze the intracranial electrophysiological recordings during the interictal state, leveraging on the presurgical assessment of the pathological areas. The first contribution of the thesis consists in the design of a support tool for the identification of epileptic zones. This method relies on the multi-decomposition of the signal and similarity metrics. We built personalized models which share common usage of features across patients. The second main contribution aims at understanding if there are particular frequency bands related to the epileptic areas and if it is worthy to focus on shorter periods of time. Here we leverage on the post-surgical outcome deriving from the Engel classification. The last contribution focuses on the characterization of short patterns of activity at specific frequencies. We argue that this effort could be helpful in the clinical routine and at the same time provides useful insight for the understanding of focal epilepsy

Effect of airborne particle abrasion on microtensile bond strength of total-etch adhesives to human dentin

Aim of this study was to investigate a specific airborne particle abrasion pretreatment on dentin and its effects on microtensile bond strengths of four commercial total-etch adhesives. Midcoronal occlusal dentin of extracted human molars was used. Teeth were randomly assigned to 4 groups according to the adhesive system used: OptiBond FL (FL), OptiBond Solo Plus (SO), Prime & Bond (PB), and Riva Bond LC (RB). Specimens from each group were further divided into two subgroups: control specimens were treated with adhesive procedures; abraded specimens were pretreated with airborne particle abrasion using 50 mu m Al2O3 before adhesion. After bonding procedures, composite crowns were incrementally built up. Specimens were sectioned perpendicular to adhesive interface to producemultiple beams, which were tested under tension until failure. Data were statistically analysed. Failure mode analysis was performed. Overall comparison showed significant increase in bond strength (p < 0.001) between abraded and no-abraded specimens, independently of brand. Intrabrand comparison showed statistical increase when abraded specimens were tested compared to no-abraded ones, with the exception of PB that did not show such difference. Distribution of failure mode was relatively uniform among all subgroups. Surface treatment by airborne particle abrasion with Al2O3 particles can increase the bond strength of total-etch adhesive

Hey there's DALILA: a DictionAry LearnIng LibrAry

Dictionary Learning and Representation Learning are machine learning methods for decomposition, denoising and reconstruction of data with a wide range of applications such as text recognition, image processing and biological processes understanding. In this work we present DALILA, a scientific Python library for regularised dictionary learning and regularised representation learning that allows to impose prior knowledge, if available. DALILA, differently from the others available libraries for this purpose, is flexible and modular. DALILA is designed to be easily extended for custom needs. Moreover, it is compliant with the most widespread ML Python library and this allows for a straightforward usage and integration. We here present and discuss the theoretical aspects and discuss its strength points and implementation

Copper Carbonate Hydroxide as Precursor of Interfacial CO in CO2 Electroreduction

Copper electrodes are especially effective in catalysis of C2 and further multi-carbon products in the CO2 reduction reaction (CO2RR) and therefore of major technological interest. The reasons for the unparalleled Cu performance in CO2RR are insufficiently understood. Here, the electrode–electrolyte interface was highlighted as a dynamic physical-chemical system and determinant of catalytic events. Exploiting the intrinsic surface-enhanced Raman effect of previously characterized Cu foam electrodes, operando Raman experiments were used to interrogate structures and molecular interactions at the electrode–electrolyte interface at subcatalytic and catalytic potentials. Formation of a copper carbonate hydroxide (CuCarHyd) was detected, which resembles the mineral malachite. Its carbonate ions could be directly converted to CO at low overpotential. These and further experiments suggested a basic mode of CO2/carbonate reduction at Cu electrodes interfaces that contrasted previous mechanistic models: the starting point in carbon reduction was not CO2 but carbonate ions bound to the metallic Cu electrode in form of CuCarHyd structures. It was hypothesized that Cu oxides residues could enhance CO2RR indirectly by supporting formation of CuCarHyd motifs. The presence of CuCarHyd patches at catalytic potentials might result from alkalization in conjunction with local electrical potential gradients, enabling the formation of metastable CuCarHyd motifs over a large range of potentials

Operando Raman spectroscopy tracks oxidation-state changes in an amorphous Co oxide material for electrocatalysis of the oxygen evolution reaction

Transition metal oxides are of high interest in both energy storage (batteries) and production of non-fossil fuels by (photo)electrocatalysis. Their functionally crucial charge (oxidation state) changes and electrocatalytic properties are best investigated under electrochemical operation conditions. We established operando Raman spectroscopy for investigation of the atomic structure and oxidation state of a non-crystalline, hydrated, and phosphate-containing Co oxide material (CoCat), which is an electrocatalyst for the oxygen evolution reaction (OER) at neutral pH and is structurally similar to LiCoO2 of batteries. Raman spectra were collected at various sub-catalytic and catalytic electric potentials. 2H labeling suggests Co oxidation coupled to Co—OH deprotonation at catalytic potentials. 18O labeling supports O—O bond formation starting from terminally coordinated oxygen species. Two broad bands around 877 cm−1 and 1077 cm−1 are assigned to CoCat-internal H2PO4-. Raman peaks corresponding to terminal oxide (Co=O) or reactive oxygen species were not detectable; 1000–1200 cm−1 bands were instead assigned to two-phonon Raman scattering. At an increasingly positive potential, the intensity of the Raman bands decreased, which is unexpected and explained by self-absorption relating to CoCat electrochromism. A red-shift of the Co—O Raman bands with increasing potentials was described by four Gaussian bands of potential-dependent amplitudes. By linear combination of Raman band amplitudes, we can follow individually the Co(2+/3+) and Co(3+/4+) redox transitions, whereas previously published x-ray absorption spectroscopy analysis could determine only the averaged Co oxidation state. Our results show how electrochemical operando Raman spectroscopy can be employed as a potent analytical tool in mechanistic investigations on OER catalysis

A longitudinal study of intonation in an a cappella singing quintet

Objective The skill to control pitch accurately is an important feature of performance in singing ensembles as it boosts musical excellence. Previous studies analyzing single performance sessions provide inconclusive and contrasting results on whether singers in ensembles tend to use a tuning system which deviates from equal temperament for their intonation. The present study observes the evolution of intonation in a newly formed student singing quintet during their first term of study. Methods/Design A semiprofessional singing quintet was recorded using head-worn microphones and electrolaryngograph electrodes to allow fundamental frequency (fo) evaluation of the individual voices. In addition, a camcorder was used to record verbal interactions between singers. The ensemble rehearsed a homophonic piece arranged for the study during five rehearsal sessions over four months. Singers practiced the piece for 10 minutes in each rehearsal, and performed three repetitions of the same pieces pre-rehearsal and post-rehearsal. Audio and electrolaryngograph data of the repeated performances, and video recordings of the rehearsals were analyzed. Aspects of intonation were then measured by extracting the fo values from the electrolaryngograph and acoustic signal, and compared within rehearsals (pre and post) and between rehearsals (rehearsals 1 to 5), and across repetitions (take 1 to 3). Time-stamped transcriptions of rehearsal discussions were used to identify verbal interactions related to tuning, the tuning strategies adopted, and their location (bar or chord) within the piece. Results/Discussion Tuning of each singer was closer to equal temperament than just intonation, but the size of major thirds was slightly closer to just intonation, and minor thirds closer to equal temperament. These findings were consistent within and between rehearsals, and across repetitions. Tuning was highlighted as an important feature of rehearsal during the study term, and a range of strategies were adopted to solve tuning related issues. This study provides a novel holistic assessment of tuning strategies within a singing ensemble, furthering understanding of performance practices as well as revealing the complex approach needed for future research in this area. These findings are particularly important for directors and singers to tailor rehearsal strategies that address tuning in singing ensembles, showing that approaches need to be context driven rather than based on theoretical ideal

Classification of Epileptic Activity Through Temporal and Spatial Characterization of Intracranial Recordings

Focal epilepsy is a chronic condition characterized by hyper-activity and abnormal synchronization of a specific brain region. For pharmacoresistant patients, the surgical resection of the critical area is considered a valid clinical solution, therefore, an accurate localization is crucial to minimize neurological damage. In current clinical routine the characterization of the Epileptogenic Zone (EZ) is performed using invasive methods, such as Stereo-ElectroEncephaloGraphy (SEEG). Medical experts perform the tag of neural electrophysiological recordings by visually inspecting the acquired data, a highly time consuming and subjective procedure. Here we show the results of an automatic multi-modal classification method for the evaluation of critical areas in focal epileptic patients. The proposed method represents an attempt in the characterization of brain areas which integrates the anatomical information on neural tissue, inferred using Magnetic Resonance Imaging (MRI) in combination with spectral features extracted from SEEG recordings

Prevention of coronary microvascular obstruction by addressing ischemia reperfusion injury-part a

Most recently, substantial research efforts were directed to the treatment and prevention of coronary microvascular obstruction (CMVO) by targeting various mechanisms involved in its multifactorial pathophysiology. Among other strategies, antiplatelets and vasodilators were tested in order to reduce thrombus burden and coronary vasospasm potentially resulting in enhanced myocardial perfusion. Furthermore, the impact of intensified statin therapy was evaluated in numerous investigations. Although most of these studies failed to convincingly prove beneficial effects regarding CMVO, especially antiplatelets and statins are indispensable cornerstones of post-infarction medical therapy. This chapter discusses the scientific evidence and guideline recommendations for the use of antiplatelets, statins, and vasodilators in patients with myocardial infarction with a particular focus on their efficacy to treat or prevent CMVO