Carbon Nanodots from an In Silico Perspective

Carbon nanodots (CNDs) are the latest and most shining rising stars among photoluminescent (PL) nanomaterials. These carbon-based surface-passivated nanostructures compete with other related PL materials, including traditional semiconductor quantum dots and organic dyes, with a long list of benefits and emerging applications. Advantages of CNDs include tunable inherent optical properties and high photostability, rich possibilities for surface functionalization and doping, dispersibility, low toxicity, and viable synthesis (top-down and bottom-up) from organic materials. CNDs can be applied to biomedicine including imaging and sensing, drug-delivery, photodynamic therapy, photocatalysis but also to energy harvesting in solar cells and as LEDs. More applications are reported continuously, making this already a research field of its own. Understanding of the properties of CNDs requires one to go to the levels of electrons, atoms, molecules, and nanostructures at different scales using modern molecular modeling and to correlate it tightly with experiments. This review highlights different in silico techniques and studies, from quantum chemistry to the mesoscale, with particular reference to carbon nanodots, carbonaceous nanoparticles whose structural and photophysical properties are not fully elucidated. The role of experimental investigation is also presented. Hereby, we hope to encourage the reader to investigate CNDs and to apply virtual chemistry to obtain further insights needed to customize these amazing systems for novel prospective applications

Selecting molecular or surface centers in carbon dots-silica hybrids to tune the optical emission: A photo-physics study down to the atomistic level

In this work, we unveil the fluorescence features of citric acid and urea-based Carbon Dots (CDs) through a photo-physical characterization of nanoparticles synthesized, under solvent-free and open-air condi-tions, within silica-ordered mesoporous silica, as a potential host for solid-state emitting hybrids. Compared to CDs synthesized without silica matrices and dispersed in water, silica-CD hybrids display a broader emission in the green range whose contribution can be increased by UV and blue laser irradi-ation. The analysis of hybrids synthesized within different silica (MCM-48 and SBA-15) calls for an active role of the matrix in directing the synthesis toward the formation of CDs with a larger content of graphitic N and imidic groups at the expense of N-pyridinic molecules. As a result, CDs tuned in size and with a larger green emission are obtained in the hybrids and are retained once extracted from the silica matrix and dispersed in water. The kinetics of the photo-physics under UV and blue irradiation of hybrid samples show a photo-assisted formation process leading to a further increase of the relative contribution of the green emission, not observed in the water-dispersed reference samples, suggesting that the porous matrix is involved also in the photo-activated process. Finally, we carried out DFT and TD-DFT calcula-tions on the interaction of silica with selected models of CD emitting centers, like surface functional groups (OH and COOH), dopants (graphitic N), and citric acid-based molecules. The combined experimen-tal and theoretical results clearly indicate the presence of molecular species and surface centers both emitting in the blue and green spectral range, whose relative contribution is tuned by the interaction with the surrounding media

Occurrence and traceability of Salmonella spp. in five Sardinian fermented sausage facilities

The aims of the present study were to evaluate the presence of Salmonella in five fermented sausage processing plants and their products during the production process, and to trace the possible sources of contamination. A total of 270 samples were collected: mixture of ground pork meat and fat, products at the end of acidification, sausages at the end of ripening and, during production stages, surfaces in contact with meat and surfaces not in contact with meat. For samples of ground meat, product at the end of acidification and sausages at the end of ripening, the pH and water activity (aw), were determined. All the samples were tested for the presence of Salmonella. Thirtytwo Salmonella isolates were obtained, subjected to serotyping and PFGE. The sausages at the end of ripening pH and aw mean values were 5.39±0.24 and 0.91±0.03, respectively. Salmonella was detected in three processing plants with an overall prevalence of 16.7% in food samples and 5.8% in environmental samples. Salmonella prevalence was 24% in ground meat and products at the end of acidification and was also detected in a sample of sausage at the end of ripening (2%). In environmental samples, Salmonella was detected in 6.6% of surfaces in contact with meat and 5% of surfaces not in contact with meat. Five serotypes were identified among 32 isolates: S. Derby (37.5%), S. Typhimurium and S. Rissen (both 25%), S. Give and monophasic S. Typhimurium (both 6.25%). Six different pulsotypes were obtained with PFGE. The serotypes and the PFGE pattern of the strains were specific for each facility with no overlapping between different processing plants. The same observation can be pointed out considering different sampling days for the same processing plants, thus presumably indicating the raw material (ground pork meat and fat) as the source of contamination. The detection of Salmonella in a sample of sausage at the end of ripening highlights the ability of the pathogen to survive during manufacturing process

A review of the main genetic factors influencing the course of COVID-19 in Sardinia: the role of human leukocyte antigen-G

Introduction: A large number of risk and protective factors have been identified during the SARS-CoV-2 pandemic which may influence the outcome of COVID-19. Among these, recent studies have explored the role of HLA-G molecules and their immunomodulatory effects in COVID-19, but there are very few reports exploring the genetic basis of these manifestations. The present study aims to investigate how host genetic factors, including HLA-G gene polymorphisms and sHLA-G, can affect SARS-CoV-2 infection. Materials and Methods: We compared the immune-genetic and phenotypic characteristics between COVID-19 patients (n = 381) with varying degrees of severity of the disease and 420 healthy controls from Sardinia (Italy). Results: HLA-G locus analysis showed that the extended haplotype HLA-G*01:01:01:01/UTR-1 was more prevalent in both COVID-19 patients and controls. In particular, this extended haplotype was more common among patients with mild symptoms than those with severe symptoms [22.7% vs 15.7%, OR = 0.634 (95% CI 0.440 – 0.913); P = 0.016]. Furthermore, the most significant HLA-G 3’UTR polymorphism (rs371194629) shows that the HLA-G 3’UTR Del/Del genotype frequency decreases gradually from 27.6% in paucisymptomatic patients to 15.9% in patients with severe symptoms (X2 = 7.095, P = 0.029), reaching the lowest frequency (7.0%) in ICU patients (X2 = 11.257, P = 0.004). However, no significant differences were observed for the soluble HLA-G levels in patients and controls. Finally, we showed that SARS-CoV-2 infection in the Sardinian population is also influenced by other genetic factors such as β-thalassemia trait (rs11549407C>T in the HBB gene), KIR2DS2/HLA-C C1+ group combination and the HLA-B*58:01, C*07:01, DRB1*03:01 haplotype which exert a protective effect [P = 0.005, P = 0.001 and P = 0.026 respectively]. Conversely, the Neanderthal LZTFL1 gene variant (rs35044562A>G) shows a detrimental consequence on the disease course [P = 0.001]. However, by using a logistic regression model, HLA-G 3’UTR Del/Del genotype was independent from the other significant variables [ORM = 0.4 (95% CI 0.2 – 0.7), PM = 6.5 x 10-4]. Conclusion: Our results reveal novel genetic variants which could potentially serve as biomarkers for disease prognosis and treatment, highlighting the importance of considering genetic factors in the management of COVID-19 patients

Performance and EMC Analysis of an Interleaved PFC Boost Converter Topology

An extensive experimental analysis of a two-phase Interleaved PFC Boost converter (I-PFC-B) is presented in this paper. It aims to highlight the most important features of I-PFCB operation, in terms of both performances and Electromagnetic Compatibility (EMC) issues. Therefore, several experimental tests are performed inside an anechoic RF chamber; in particular, Power Factor, Total Harmonic Distortion Factor, Current Crest Factor and energy efficiency are determined at different I-PFC-B output powers. Furthermore, appropriate Conducted and Radiated Emission tests are performed, in accordance with international standards, in order to reveal IPFC-B aptitude as a non-intentional Electromagnetic Interference (EMI) source. The results highlight poor I-PFC-B performances at light loads, as well as potential conducted EMI issues within low and medium frequency ranges

An Improved Averaged Model for Boost DC-DC Converters

An improved averaged model suitable for boost DCDC converters is presented in this paper. It is developed on the basis of the averaging technique with the aim of appropriately taking into account the effects of switching phenomena. Thus, two appropriate trapezoidal signals have been introduced in order to model the transient evolutions of voltages and currents of the DC-DC converter devices over both turn-on and turn-off of the switch. This enables the synthesis of an appropriate averaged model of boost DC-DC converters, which can be usefully employed in determining average voltage and current evolutions, as well as steady state average powers. The worth and effectiveness of the proposed modelling approach has been validated through a simulation study, which refers to the case of a traditional boost DC-DC converter

Rimonabant, a potent CB1 cannabinoid receptor antagonist, is a G alpha(i/o) protein inhibitor

Rimonabant is a potent and selective cannabinoid CB1 receptor antagonist widely used in animal and clinical studies. Besides its antagonistic properties, numerous studies have shown that, at micromolar concentrations rimonabant behaves as an inverse agonist at CB1 receptors. The mechanism underpin- ning this activity is unclear. Here we show that micromolar concentrations of rimonabant inhibited Gai/o- type G proteins, resulting in a receptor-independent block of G protein signaling. Accordingly, rimona- bant decreased basal and agonist stimulated [35S]GTPgS binding to cortical membranes of CB1- and GABAB-receptor KO mice and Chinese Hamster Ovary (CHO) cell membranes stably transfected with GABAB or D2 dopamine receptors. The structural analog of rimonabant, AM251, decreased basal and baclofen-stimulated GTPgS binding to rat cortical and CHO cell membranes expressing GABAB receptors. Rimonabant prevented G protein-mediated GABAB and D2 dopamine receptor signaling to adenylyl cyclase in Human Embryonic Kidney 293 cells and to G protein-coupled inwardly rectifying Kþ channels (GIRK) in midbrain dopamine neurons of CB1 KO mice. Rimonabant suppressed GIRK gating induced by GTPgS in CHO cells transfected with GIRK, consistent with a receptor-independent action. Biolumines- cent resonance energy transfer (BRET) measurements in living CHO cells showed that, in presence or absence of co-expressed GABAB receptors, rimonabant stabilized the heterotrimeric Gai/o-protein complex and prevented conformational rearrangements induced by GABAB receptor activation. Rimo- nabant failed to inhibit Gas-mediated signaling, supporting its specificity for Gai/o-type G proteins. The inhibition of Gai/o protein provides a new site of rimonabant action that may help to understand its pharmacological and toxicological effects occurring at high concentration

Exploring the Impact of Nitrogen Doping on the Optical Properties of Carbon Dots Synthesized from Citric Acid

The differences between bare carbon dots (CDs) and nitrogen-doped CDs synthesized from citric acid as a precursor are investigated, aiming at understanding the mechanisms of emission and the role of the doping atoms in shaping the optical properties. Despite their appealing emissive features, the origin of the peculiar excitation-dependent luminescence in doped CDs is still debated and intensively being examined. This study focuses on the identification of intrinsic and extrinsic emissive centers by using a multi-technique experimental approach and computational chemistry simulations. As compared to bare CDs, nitrogen doping causes the decrease in the relative content of O-containing functional groups and the formation of both N-related molecular and surface centers that enhance the quantum yield of the material. The optical analysis suggests that the main emission in undoped nanoparticles comes from low-efficient blue centers bonded to the carbogenic core, eventually with surface-attached carbonyl groups, the contribution in the green range being possibly related to larger aromatic domains. On the other hand, the emission features of N-doped CDs are mainly due to the presence of N-related molecules, with the computed absorption transitions calling for imidic rings fused to the carbogenic core as the potential structures for the emission in the green range

Evolution of the microbiological profile of vacuum-packed ricotta salata cheese during shelf-life

Ricotta salata cheese is a salted variety of ricotta traditionally made in Sardinia (Italy) from the whey remaining after the production of Pecorino Romano protected designation of origin or other sheep milk cheeses. Ricotta salata cheese is very critical for the possible growth of pathogenic and spoilage microorganisms. Sporadic cases of listeriosis associated with ricotta salata cheese have been reported over recent years. The objective of the present study was to assess the evolution of spoilage and pathogen microorganism of vacuum-packed ricotta salata cheese during the entire product shelf-life. The durability study was conducted on 18 vacuum-packed ricotta salata cheese samples analysed at the beginning of the shelf-life and after 60 and 90 days of refrigerated storage. Pathogens as Listeria monocytogenes and Bacillus cereus were never detected. During shelf-life total bacterial counts ranged between 7.90±0.64 and 9.19±0.58 CFU g-1 on the rind and between 2.95±0.68 and 4.27±1.10 CFU g-1 in the inner paste, while Enterobacteriaceae ranged between 4.22±0.66 and 5.30±0.73 CFU g-1 on the rind and 3.13±1.80 and 2.80±0.88 CFU g-1 in the inner paste. By considering the technology used, the intrinsic properties and the almost total absence of competing microflora, ricotta salata cheese can support the growth of spoilage and pathogen microorganisms originating from the processing environment. The high level of total bacterial counts and Enterobacteriaceae observed both on the rind and in the inner paste suggests contamination of the product from the processing environment. Therefore, a strict implementation of hygiene during processing is essential in order to reduce the load of environmental contaminants that may grow during refrigerated storage

Clinical and epidemiological features of ulcerative colitis patients in Sardinia, Italy: Results from a multicenter study

BACKGROUND There are little data on the epidemiological and clinical features of adult patients with ulcerative colitis (UC) in the different Italian regions, mainly derived from the absence of a national registry. This prevents correct interpretation of the disease burden. AIM To assess the main clinical and epidemiological features of adult patients diagnosed with UC in Sardinia, Italy. METHODS We performed a multicenter, observational, cross-sectional study that included adult patients with UC enrolled in seven gastroenterology unit centers in Sardinia. Data were obtained from the patients' medical records and from a questionnaire administered at the inclusion visit. RESULTS Four hundred and forty-two patients with UC were included. The median age at diagnosis was 39 years (interquartile range 28-48). After a median disease duration of 10 years, 53 patients experienced proximal extension of proctitis or left-sided colitis. Seventy-five patients developed extraintestinal manifestations. Nineteen patients (4.3%) developed cancer: two with colorectal cancer and seventeen with extracolonic cancers. Mesalazine (5-ASA) remains the mainstay of treatment for UC. Overall, 95 patients (21.5%) were treated with one or more biologic agents, whereas 15 patients (3.4%) underwent surgery, mostly colectomy. CONCLUSION Our results provide important insights into the clinical and epidemiological features of patients with UC, and while waiting for a national Italian registry, present eligible data on the UC population in Sardinia