Nano-protrusions in intercalated graphite: understanding the structural and electronic effects through DFT.

Complex phenomena characterize the intercalation of ions inside stratified crystals. Their comprehension is crucial in view of exploiting the intercalation mechanism to change the transport properties of the crystal or obtaining a fine control of crystal delamination. In particular, the relationship between the concentration and nature of intercalated ions and surface structural modifications of the host stratified crystal is still under debate. Here, we discuss a theoretical effort to provide a rationale for some structural changes observed on the highly oriented pyrolytic graphite (HOPG) surface after electrochemical treatment in perchloric and sulphuric acid solutions. The formation of the so-called nano-protrusions on the basal plane of intercalated graphite was previously observed with scanning tunneling microscopy (STM). In this work, we employed both STM and density functional theory (DFT) simulations to elucidate the physical and chemical mechanisms driving the emergence of these nano-protrusions. The DFT results show that, in a bilayer graphene system, the presence of a single ion can generate a nano-protrusion with 2.49 Å height and 21.27 Å width. In the deformed area, the C-C bond length is stretched by about 2.5% more than the normal graphene bond. These values are of the same dimensional scale as those reported in previous STM experimental results.25 However, the simulated STM images obtained by increasing the amount of intercalated ions per area suggest that the presence of more than one ion is needed for the deformation of the uppermost graphite layer during the early stages of intercalation. In contrast, in a multilayer graphene system, no significant surface deformation is detected when ions are intercalated between the third and fourth layers. Charge analysis indicates an altered distribution of the charges as a consequence of the intercalation. The charge transfer from graphene layers to the intercalated ions results in a surface layer more prone to oxidation.

ADA_ETA_BIO2021: real-world evaluation of adherence, persistence, and cost-effectiveness of originator and biosimilar biologic drugs in the treatment of rheumatoid arthritis: a multicenter study in Italy.

OBJECTIVES: The objective was to assess the adherence, persistence, and costs of bDMARDs through a multicentre study of nine Italian hospital pharmacies. METHODS: The drugs analysed were Abatacept, Adalimumab, Certolizumab, Etanercept, Golimumab and Tocilizumab.Adult subjects with Rheumatoid Arthritis were considered in the analysis.In this study, we calculated the following metrics: Adherence to treatment was evaluated as dose-intensity, which is the ratio between the amount of medication received and probably taken by the patient at home (Received Daily Dose, RDD) and the amount prescribed by the clinician (Prescribed Daily Dose, PDD). Persistence was calculated as the number of days between the first and last dispensing of the same drug. Lastly, costs were assessed based on persistence to treatment and normalized for adherence. RESULTS: Adherence to treatment was found to be above 0.8 for all drugs studied. The median persistence for a 5-year treatment period was 1.4 years for Abatacept, 1.7 years for Adalimumab, 1.8 years for Certolizumab, 1.4 years for Etanercept, 1.3 years for Golimumab, and 1.6 years for Tocilizumab. CONCLUSIONS: This multicentre retrospective observational study of bDMARDs used in the treatment of RA showed that, for all the drugs studied, there was no problem with adherence to treatment but rather a difficulty in maintaining treatment with the same drug over time.

Driving Organic Nanocrystals Dissolution Through Electrochemistry.

We have recently discussed how organic nanocrystal dissolution appears in different morphologies and the role of the solution pH in the crystal detriment process. We also highlighted the role of the local molecular chemistry in porphyrin nanocrystals having comparable structures: in water-based acid solutions, protonation of free-base porphyrin molecules is the driving force for crystal dissolution, whereas metal (ZnII ) porphyrin nanocrystals remain unperturbed. However, all porphyrin types, having an electron rich π-structure, can be electrochemically oxidized. In this scenario, a key question is: does electrochemistry represent a viable strategy to drive the dissolution of both free-base and metal porphyrin nanocrystals? In this work, by exploiting electrochemical atomic force microscopy (EC-AFM), we monitor in situ and in real time the dissolution of both free-base and metal porphyrin nanocrystals, as soon as molecules reach the oxidation potential, showing different regimes according to the applied EC potential.

Cysteine-Modified Self-Assembling Peptides on Gold: The Role of the Head and Tail.

Molecular self-assembly consists of the spontaneous aggregation of molecules into a well-defined structure guided by noncovalent bonds. The self-assembly strategy is ubiquitous in nature and recently has been proposed as a nature-mimetic strategy in polymer science and biomaterial engineering. In this context, we aim at designing and testing innovative but simple chemical strategies to efficiently modify surfaces by exploiting minor modifications in the bioactive molecule functionalities, for example, introducing cysteine (Cys) as a terminal residue in self-assembling peptides (SAPs). In this work, we report the attenuated total reflection-Fourier transform infrared spectroscopy, synchrotron radiation-induced X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure spectroscopy, and time-of-flight secondary ion mass spectrometry investigation of self-assembled layers of oligopeptides anchored onto gold surfaces through cysteine residues, opportunely inserted in an SAP (EAK16-II) main chain in three different positions: at the amine end group, at the carboxyl end group, and at both terminal groups (i.e., a bidentate SAP). This study, which allowed us to individuate in the bidentate SAP the best candidate for the controlled production of ordered SAP layers on the gold substrate surface, is envisaged to open wide perspectives for efficient chemical modification of surfaces with biomolecules, leading to obtaining innovative bioactive materials for applications in the field of tissue engineering.

Optical Conductivity of Two-Dimensional Silicon: Evidence of Dirac Electrodynamics.

The exotic electrodynamics properties of graphene come from the linearly dispersive electronic bands that host massless Dirac electrons. A similar behavior was predicted to manifest in freestanding silicene, the silicon counterpart of graphene, thereby envisaging a new route for silicon photonics. However, the access to silicene exploitation in photonics was hindered so far by the use of optically inappropriate substrates in experimentally realized silicene. Here we report on the optical conductivity of silicon nanosheets epitaxially grown on optically transparent Al2O3(0001) from a thickness of a few tens of nanometers down to the extreme two-dimensional (2D) limit. When a 2D regime is approached, a Dirac-like electrodynamics can be deduced from the observation of a low-energy optical conductivity feature owing to a silicene-based interfacing to the substrate.

[Hospital consumption of antibiotics at the Policlinico Hospital of the Second University of Naples: results of retrospective data collection]. / Monitoraggio delle prescrizioni di antibiotici nei reparti dell'A.O.U. Policlinico Seconda Università di Napoli attraverso l'analisi retrospettiva dei consumi.

In the therapeutic field, analysis of antibiotics consumption and use is of great importance: it is considered a necessary prerequisite for initiating measures to rationalize the use of antibiotics, but also to limit bacterial resistance. In this light, we conducted an observational study on antibiotics consumption at the Policlinico University Hospital in Naples to evaluate the prescription of antibiotics in the hospital's four main divisions. We used the Defined Daily Dose (DDD) as a measure of antibiotics consumption, and collected data retrospectively from 2006 to 2007. Our findings clearly show a 23.3% increase in antibiotics consumption in 2007 vs 2006. The classes of antibiotics experiencing the greatest percentage increases were penicillins and other beta-lactams, quinolones and glycopeptides. In particular, among other beta-lactams (J01D) in 2007 was the consumption of third-generation cephalosporins and carbapenems. The surgical division showed the largest increase in use of antibiotics, while in intensive care we found a reduction. Our data suggest consumption data should be compared with information on prescriptions and costs so as to monitor more closely the consumption of antibiotics and thus rationalize their use with a view to reducing the phenomenon of bacterial resistance. Finally, it would be useful to launch a training program for the proper use of antibiotics in our University Hospital.