Spectroscopic fingerprints of iron-coordinated cobalt and iron porphyrin layers on graphene

Achieving design capabilities of monolayer 2D functional catalysts represents a challenging perspective. Coordinated single metal atom sites can offer tailored electronic configuration, ligation geometries, chemical activity and selectivity, together with stability. We report spectroscopic evidence of the formation of a 2D metal-organic framework supported by a single graphene sheet in which coordination among Tetra-Pyridyl-Porphyrins (TPyPs) is spontaneously obtained by exploiting single iron atoms. The spectroscopic characterization, together with ab initio methods, reveals that metal inter-molecular coordination occurs via the terminal nitrogen atoms contained in the pyridinic residues of adjacent TPyPs. Interestingly, the peripheral coordination of metal atoms is found to affect the electronic configuration of the porphyrins core. Due to the chemical stability of the supporting graphene layer, its weak interaction with the metal-organic framework, and the known electrochemical activity of the latter, this system represents an optimal candidate for the design and engineering of prototype 2D electrocatalytic materials

Sex-Related Disparities in Cardiac Masses: Clinical Features and Outcomes

Background. Cardiac masses (CM) represent a heterogeneous clinical scenario, and sex-related differences of these patients remain to be established. Purpose: To evaluate sex-related disparities in CMs regarding clinical presentation and outcomes. Material and Methods. The study cohort included 321 consecutive patients with CM enrolled in our Centre between 2004 and 2022. A definitive diagnosis was achieved by histological examination or, in the case of cardiac thrombi, with radiological evidence of thrombus resolution after anticoagulant treatment. All-cause mortality at follow-up was evaluated. Multivariable regression analysis assessed the potential prognostic disparities between men and women. Results. Out of 321 patients with CM, 172 (54%) were female. Women were more frequently younger (p = 0.02) than men. Regarding CM histotypes, females were affected by benign masses more frequently (with cardiac myxoma above all), while metastatic tumours were more common in men (p < 0.001). At presentation, peripheral embolism occurred predominantly in women (p = 0.03). Echocardiographic features such as greater dimension, irregular margin, infiltration, sessile mass and immobility were far more common in men. Despite a better overall survival in women, no sex-related differences were observed in the prognosis of benign or malignant masses. In fact, in multivariate analyses, sex was not independently associated with all-cause death. Conversely, age, smoking habit, malignant tumours and peripheral embolism were independent predictors of mortality. Conclusions. In a large cohort of cardiac masses, a significant sex-related difference in histotype prevalence was found: Benign CMs affected female patients more frequently, while malignant tumours affected predominantly men. Despite better overall survival in women, sex did not influence prognosis in benign and malignant masses

Alone on a wide wide sea. The origin of SECCO 1, an isolated star-forming gas cloud in the Virgo cluster

SECCO 1 is an extremely dark, low-mass (M* ≃ 105 M⊙), star-forming stellar system lying in the low-velocity cloud (LVC) substructure of the Virgo cluster of galaxies, and hosting several HII regions. Here, we review our knowledge of this remarkable system, and present the results of (a) additional analysis of our panoramic spectroscopic observations with MUSE, (b) the combined analysis of Hubble Space Telescope and MUSE data, and (c) new narrowband observations obtained with OSIRIS@GTC to search for additional HII regions in the surroundings of the system. We provide new evidence supporting an age as young as ≲4Myr for the stars that are currently ionizing the gas in SECCO 1. We identify only one new promising candidate HII region possibly associated with SECCO 1, thus confirming the extreme isolation of the system.We also identify three additional candidate pressure-supported dark clouds in Virgo among the targets of the SECCO survey. Various possible hypotheses for the nature and origin of SECCO 1 are considered and discussed, also with the help of dedicated hydrodynamical simulations showing that a hydrogen cloud with the characteristics of SECCO 1 can likely survive for ≳1 Gyr while travelling within the LVC Intra Cluster Medium.GB gratefully acknowledges the financial support by the Spanish Ministry of Economy and Competitiveness under the Ramon y Cajal Programme (RYC-2012-11537) and the grant AYA2014-56795-P. FC acknowledges funding from the INAF PRIN-SKA 2017 1.05.01.88.04

Performance of Prognostic Scoring Systems in MINOCA: A Comparison among GRACE, TIMI, HEART, and ACEF Scores

Background: the prognosis of patients with myocardial infarction with non-obstructive coronary arteries (MINOCA) is not benign; thus, prompting the need to validate prognostic scoring systems for this population. Aim: to evaluate and compare the prognostic performance of GRACE, TIMI, HEART, and ACEF scores in MINOCA patients. Methods: A total of 250 MINOCA patients from January 2017 to September 2021 were included. For each patient, the four scores at admission were retrospectively calculated. The primary outcome was a composite of all-cause death and acute myocardial infarction (AMI) at 1-year follow-up. The ability to predict 1-year all-cause death was also tested. Results: Overall, the tested scores presented a sub-optimal performance in predicting the composite major adverse event in MINOCA patients, showing an AUC ranging between 0.7 and 0.8. Among them, the GRACE score appeared to be the best in predicting all-cause death, reaching high specificity with low sensitivity. The best cut-off identified for the GRACE score was 171, higher compared to the cut-off of 140 generally applied to identify high-risk patients with obstructive AMI. When the scores were tested for prediction of 1-year all-cause death, the GRACE and the ACEF score showed very good accuracy (AUC = 0.932 and 0.828, respectively). Conclusion: the prognostic scoring tools, validated in AMI cohorts, could be useful even in MINOCA patients, although their performance appeared sub-optimal, prompting the need for risk assessment tools specific to MINOCA patients

Nanoscale transient polarization gratings

We present the generation of transient polarization gratings at the nanoscale, achieved using a tailored accelerator configuration of the FERMI free electron laser. We demonstrate the capabilities of such a transient polarization grating by comparing its induced dynamics with the ones triggered by a more conventional intensity grating on a thin film ferrimagnetic alloy. While the signal of the intensity grating is dominated by the thermoelastic response of the system, such a contribution is suppressed in the case of the polarization grating. This exposes helicity-dependent magnetization dynamics that have so-far remained hidden under the large thermally driven response. We anticipate nanoscale transient polarization gratings to become useful for the study of any physical, chemical and biological systems possessing chiral symmetry

Characterization of Mars rotational dynamics from Doppler tracking of the InSight lander

In the last decades the evolution of radio science has made it possible to infer the atmosphere composition, the surface and the internal structure of the planets. Since the arrival of the first landers on Mars it was possible to make accurate measurements of the dynamics of this planet; in this thesis we will focus on InSight, considering the data disclosed by the JPL relative to the period from November 26th, 2018 to August 15th, 2021. In particular, the Doppler and Range measurements conducted by the RISE (Rotation and Interior Structure Experiment) will be analyzed. Since the accuracy of these measurements was improved significantly the effects due to the atmosphere of Mars might be measured so it should thus be possible to obtain a better estimate of the parameters characterizing the rotational dynamic of Mars. A large part of this study will therefore be dedicated to the study, modeling, implementation and analysis of the atmosphere of Mars, in both its components: troposphere and ionosphere. Once the complete model of Mars had been built, i.e. including the atmosphere, it was then possible to analyze the residuals, obtained between the data of the measurements carried out and the values predicted by the developed model, in order to obtain an estimate of the rotational dynamic of Mars

Monolayer mono- e bi-metallici di tetra-pyridyl porfirine dall’UHV a pressione quasi-ambiente

I materiali bidimensionali costituiti da atomi metallici incorporati in una struttura organica (2D-MOF) stanno guadagnando sempre più interesse nel panorama della scienza delle superfici. La loro dimensionalità consente in maniera naturale di sfruttare le tante tecniche sperimentali con sensitività superficiale, che consentono di studiare in dettaglio la loro geometria, struttura elettronica e reattività chimica. L’ambiente chimico locale dei siti attivi li rende infatti catalizzatori a singolo atomo ideali per lo studio della catalisi eterogenea. In questa tesi, ci si è concentrati sulla crescita e caratterizzazione in Ultra Alto Vuoto (UHV) e sull’investigazione della reattività da UHV a pressione quasi ambiente di M1TPyPM2 2D-MOF (con M1,2 = Fe, Co) auto-assemblati su Grafene/Ir(111). Nella prima parte, alcuni monolayer sono stati selezionati ed investigati in UHV con una combinazione di tecniche vibrazionali (IR-Vis SFG), di microscopia e spettroscopia elettronica (STM/STS, NEXAFS, XPS), confrontando i risultati con la letteratura e simulazioni DFT ab initio. Nella seconda parte, si è esposto un monolayer di CoTPyP/Gr/Ir(111) ad una atmosfera di acqua e ossigeno gassosi (fino a frazioni di millibar). Una intensa risonanza una intensa risonanza vibrazionale è apparsa a 1712 cm-1 negli spettri di Spettroscopia a Frequenza Somma acquisiti in situ, associata alla molecola di idroperossile, un importante intermedio di reazione per la Reazione di Riduzione dell’Ossigeno (ORR). Misure NAP-XPS hanno confermato la nostra tesi grazie all’analisi dei livelli di core di ossigeno e cobalto, mentre un esperimento SFG time-resolved ci ha consentito di ispezionare il legame tra l’idroperossile e le molecole di acqua che lo circondano. Nell’ultima parte, il monossido di carbonio è stato sfruttato come una sonda per investigare la struttura elettronica e la coordinazione locale dei siti attivi in un monolayer di CoTPyPCo/Gr/Ir(111). Gli spettri IR-Vis SFG misurati in situ hanno evidenziato la presenza di interazioni a lungo raggio promosse dal MOF stesso, includendo l’anti-cooperatività del processo stesso di adsorbimento del CO, a patto che i siti attivi siano sufficientemente vicini. L’esperimento si è rivelato essere un potente strumento per investigare deboli effetti legati all'affinità chimica del layer, potenzialmente responsabili del notevole incremento delle prestazioni elettrochimiche di questi materiali, uno degli aspetti scientifici alla base di questo lavori di tesi.Bi-dimensional metal-organic frameworks (2D-MOF) are a relatively new class of materials that are gaining particular interest in surface science. Their dimensionality naturally allows the exploitation of many surface-sensitive techniques, beneficial to study with great detail their geometry, electronic structure, and chemical reactivity. On the other hand, the well-defined chemical environment of the active sites makes them ideal single-atom catalysts for heterogeneous catalysis. In this thesis, we focus on the Ultra High Vacuum (UHV) growth and characterization, and on the investigation of the reactivity from UHV to Near Ambient Pressure (NAP) of M1TPyPM2 2D Metal-organic Frameworks (MOFs, with M1,2 = Fe, Co) self-assembled on almost free-standing Graphene/Ir(111). In the first part, some selected monolayers have been investigated in UHV with a combination of vibrational- (IR-Vis SFG), real-space imaging and spectroscopy (STM/STS), and electronic- (NEXAFS, XPS) sensitive techniques, and the results compared with the literature and ab initio DFT. In the second part, we exposed a CoTPyP/Gr/Ir(111) monolayer to a mixture of water and oxygen gases (up to fractions of mbar), and an intense bending mode appeared at 1712 cm-1 in Sum Frequency Generation spectra collected in situ: this is associated with the hydroperoxyl molecule, an important reaction intermediate for the Oxygen Reduction Reaction. NAP-XPS measurements confirmed our thesis through O 1s and Co 2p core levels analysis, while pump-probe SFG allowed us to directly inspect the coupling between the hydroperoxyl and the surrounding water molecules representing the solvent. In the last part, carbon monoxide has been exploited as a probe to investigate the CoTPyPCo/Gr/Ir(111) local sites' electronic structure and coordination. The IR-Vis SFG spectra collected in situ showed evidence of both long-range MOF-driven interactions, including the anti-cooperativity of the CO adsorption process, provided that active sites are sufficiently close to each other. This experiment has been revealed to be an effective approach to investigate subtle effects in the MOF chemical affinity, possibly responsible for the remarkable non-linear increase of the electrocatalytic performances of such M1TPyPM2 compounds, which is one of the scientific interests at the basis of this thesis

Site-Dependent Oxidation States of Single Cobalt Atoms in a Porphyrin-Based Monolayer on Graphene

We investigate a layer of cobalt tetrapyridyl porphyrins (CoTPyPs) self-assembled on an almost freestanding graphene (GR) sheet supported by Ir(111) with complementary experimental techniques and density functional theory (DFT) ab initio simulations. Beside the metal atoms enclosed within the porphyrin macrocycles, additional Co atoms can be accommodated at the molecular network’s interstice via physical vapor deposition and can bind up to four adjacent molecules. Therefore, such a system presents two metallic sites, both tetra-coordinated to nitrogen atoms. At the same time, a rearrangement of the network occurs depending on the coverage of such additional atoms. The bare CoTPyPs arrange themselves on GR in an almost hexagonal close-packed pattern with alternating orientations. The addition of extra Co atoms causes a dramatic transformation in the network. At full peripheral metal coverage (i.e., one additional Co per CoTPyP), the network drastically changes becoming almost square. Intermediate coverages display different peculiar patterns characterized by unique chiral structures. Importantly, our DFT calculations reveal a remarkable effect on the system’s work function attributed to the presence of these additional metal atoms, despite their extremely small amount even at full coverage (less than 2% of a monolayer with respect to the number of carbon atoms in the GR sheet). Furthermore, we report a different behavior of the two Co sites showing different oxidation states and molecular orbital occupations

Site-Dependent Oxidation States of Single Cobalt Atoms in a Porphyrin-Based Monolayer on Graphene

We investigate a layer of cobalt tetrapyridyl porphyrins (CoTPyPs) self-assembled on an almost freestanding graphene (GR) sheet supported by Ir(111) with complementary experimental techniques and density functional theory (DFT) ab initio simulations. Beside the metal atoms enclosed within the porphyrin macrocycles, additional Co atoms can be accommodated at the molecular network’s interstice via physical vapor deposition and can bind up to four adjacent molecules. Therefore, such a system presents two metallic sites, both tetra-coordinated to nitrogen atoms. At the same time, a rearrangement of the network occurs depending on the coverage of such additional atoms. The bare CoTPyPs arrange themselves on GR in an almost hexagonal close-packed pattern with alternating orientations. The addition of extra Co atoms causes a dramatic transformation in the network. At full peripheral metal coverage (i.e., one additional Co per CoTPyP), the network drastically changes becoming almost square. Intermediate coverages display different peculiar patterns characterized by unique chiral structures. Importantly, our DFT calculations reveal a remarkable effect on the system’s work function attributed to the presence of these additional metal atoms, despite their extremely small amount even at full coverage (less than 2% of a monolayer with respect to the number of carbon atoms in the GR sheet). Furthermore, we report a different behavior of the two Co sites showing different oxidation states and molecular orbital occupations