PdTe2 Transition‐Metal Dichalcogenide: Chemical Reactivity,Thermal Stability,and Device Implementation

Palladium ditelluride (PdTe₂) is a novel transition‐metal dichalcogenide exhibiting type‐II Dirac fermions and topological superconductivity. To assess its potential in technology, its chemical and thermal stability is investigated by means of surface‐science techniques, complemented by density functional theory, with successive implementation in electronics, specifically in a millimeter‐wave receiver. While water adsorption is energetically unfavorable at room temperature, due to a differential Gibbs free energy of ≈+12 kJ mol^?1, the presence of Te vacancies makes PdTe₂ surfaces unstable toward surface oxidation with the emergence of a TeO₂ skin, whose thickness remains sub‐nanometric even after one year in air. Correspondingly, the measured photocurrent of PdTe₂‐based optoelectronic devices shows negligible changes (below 4%) in a timescale of one month, thus excluding the need of encapsulation in the nanofabrication process. Remarkably, the responsivity of a PdTe₂‐based millimeter‐wave receiver is 13 and 21 times higher than similar devices based on black phosphorus and graphene in the same operational conditions, respectively. It is also discovered that pristine PdTe₂ is thermally stable in a temperature range extending even above 500 K, thus paving the way toward PdTe₂‐based high‐temperature electronics. Finally, it is shown that the TeO₂ skin, formed upon air exposure, can be removed by thermal reduction via heating in vacuum.     

Synthesis, biological evaluation, and molecular modeling studies of rebeccamycin analogues modified in the carbohydrate moiety

A new series of indolocarbazole glycosides containing disaccharides were synthesized and their in vitro antiproliferative activity was evaluated against three human cancer cell lines (A2780, H460, and GLC4). Cytotoxicity appeared to be remarkably affected by the regio- and stereochemical features of the disaccharide moiety. In vivo antitumor activity of the compounds studied, two of which having IC(50)<100 nm, was determined using ovarian cancer cell line A2780 xenografted on nude mice. One compound showed an efficacy similar to that of the reference compound edotecarin, though with a lower long-lasting activity. The topoisomerase I inhibitory properties of some compounds were also examined. Molecular dynamics simulations of the ternary topoisomerase I-DNA-ligand complexes were performed to analyze the structural features of topoisomerase I poisoning with this class of indolocarbazoles. A plausible explanation of their biological behavior was provided. These theoretical results were compared with the recently published crystal structure of an indolocarbazole monosaccharide bound to the covalent human topoisomerase I-DNA complex.     

Insights into the Role of the Microbiota and of Short-Chain Fatty Acids in Rubinstein–Taybi Syndrome

The short-chain fatty acid butyrate, produced by the gut microbiota, acts as a potent histone deacetylase (HDAC) inhibitor. We assessed possible ameliorative effects of butyrate, relative to other HDAC inhibitors, in in vitro and in vivo models of Rubinstein–Taybi syndrome (RSTS), a severe neurodevelopmental disorder caused by variants in the genes encoding the histone acetyltransferases CBP and p300. In RSTS cell lines, butyrate led to the patient-specific rescue of acetylation defects at subtoxic concentrations. Remarkably, we observed that the commensal gut microbiota composition in a cohort of RSTS patients is significantly depleted in butyrate-producing bacteria compared to healthy siblings. We demonstrate that the effects of butyrate and the differences in microbiota composition are conserved in a Drosophila melanogaster mutant for CBP, enabling future dissection of the gut–host interactions in an in vivo RSTS model. This study sheds light on microbiota composition in a chromatinopathy, paving the way for novel therapeutic interventions.     

Assessment of weld reduction factors through experimental reference curves

The 2¼Cr1Mo (P22) is present in most of structural high-temperature applications, as results from a review on materials employed for the construction of both power and chemical plants. So, it fits well for an experimental activity in the laboratory as reference material. ISPESL, the Italian Certification Agency, carried out a low-budget program of creep and low-cycle fatigue (LCF) tests at 550 °C; the specimens (twelve plus two spare) of as-fabricated material came from a thick-wall pipe with a certified circumferential weld. They were base metal and cross-weld fusion-line centered ones. Comparison of the resistance curves obtained from LCF tests with those from codes (ASME and ISPESL) showed for the base metal good correspondence; therefore, showed the reliability of the test proceeding. For the weld it showed instead conservatism reduction at high-strain levels for the ASME design curve; moreover, it revealed an insufficient conservatism of the reduction factor proposed, which is 1/2, for the lower bound ISPESL curve. Comparison of the resistance curves obtained from creep tests with those from codes showed this: for both the base metal and weld there are a good correspondence and acceptable (low) conservatism of the strength reduction factor (SRF) proposed; for the load and temperature levels considered in the tests, it equals one. Still, the creep tests duration was within thirty hundred hours each; therefore the levels of the applied load (150.2-100 MPa) were not as low as those in typical operation conditions. For these cases, the code (ASME) proposes a lower-than-unity SRF: thus, longer tests (lower levels of the applied load) would be useful, also extending the activity to other materials.     

Part load operation of SOFC/GT hybrid systems: Stationary analysis

In a global energetic context characterized by the increasing demand of oil and gas, the depletion of fossil resources and the global warming, more efficient energy systems and, consequently, innovative energy conversion processes are urgently required. A possible solution can be found in the fuel cells technology coupled with classical thermodynamic cycle technologies in order to make hybrid systems able to achieve high energy/power efficiency with low environmental impact. Moreover, due to the synergistic effect of using a high temperature fuel cell such as solid oxide fuel cell (SOFC) and a recuperative gas turbine (GT), the integrated system efficiency can be significantly improved. In this paper a steady zero dimensional model of a SOFC/GT hybrid system is presented. The core of the work consists of a performance analysis focused on the influence of the GT part load functioning on the overall system efficiency maintaining the SOFC power set to the nominal one. Also the proper design and management of the heat recovery section is object of the present study, with target a global electric efficiency almost constant in part load functioning respect to nominal operation. The results of this study have been used as basis to the development of a dynamic model, presented in the following part of the study focused on the plant dynamic analysis.     

The Sleep Disturbance Scale for Children (SDSC). Construction and validation of an instrument to evaluate sleep disturbances in childhood and adolescence

To attempt a categorization of sleep disorders in children, we developed a 27 item Likert-type rating scale (Sleep Disturbance Scale for Children: SDSC) and assessed the psychometric properties was developed. The scale was distributed to the mothers of 1304 children (1157 controls, mean age 9.8 y; 147 sleep disorder subjects, mean age 9.2y, composed of four clinical groups: Insomnia 39 subjects, Hypersomnia 12 subjects, Respiratory disturbances during sleep 25 subjects and Parasomnias 71 subjects). The internal consistency was high in controls (0.79) and remained at a satisfactory level in sleep disorder subjects (0.71); the test/retest reliability was adequate for the total (r = 0.71) and single item scores. The factor analysis (variance explained 44.21%) yielded six factors which represented the most common areas of sleep disorders in childhood and adolescence. Enuresis was the only item with a factor loading lower than 0.40 and with a low inter-item correlation and was therefore eliminated, resulting in a final scale of 26 items. The re-evaluation of the sample, using the factor scores, supported the validity and the discriminating capacity of the scales between controls and the four clinical groups. The correlation between factor scores corroborated the hypothesis that childhood sleep disturbances are not independent entities nor do they cluster into different groupings related to each other. The SDSC appears to be a useful tool in evaluating the sleep disturbances of school-age children in clinical and non-clinical populations.     

An energetic–exergetic analysis of a residential CHP system based on PEM fuel cell

The use of fuel cell systems for distributed residential power generation represents an interesting alternative to traditional thermoelectric plants due to their high efficiency and the potential recovering of the heat generated by the internal electrochemical reactions. In this paper the study of a micro cogenerative (CHP) energy system based on a Proton Exchange Membrane fuel cell (PEMFC) is reported.     

Nonsymmetrical drying tests—Experimental and numerical results for free and constrained spruce samples

The paper brings new insights into nonsymmetrical convective drying, a configuration in which stresses induce a global change of the section shape of a wooden board with five insulated faces. Two experimental devices that allow to test simultaneously “twin” wooden boards have been developed: the first board is free and its curvature is collected vs. time; the second one is constrained and the force required to keep it flat is collected vs. time. Convective drying tests have been performed on radial specimens of spruce, 5 and 15?mm thick at 45 and 65°C. The results are commented and compared with simulation runs. For this purpose, a 1-D mechanical formulation is embedded in the computational code of heat and mass transfer TransPore. The objective of the comparison between numerical and experimental results is a better understanding of the coupled phenomena and the identification of some transfer and mechanical parameters.     

Local surface morphology and chemistry of SnO2 thin films deposited by rheotaxial growth and thermal oxidation method for gas sensor application

In this paper experimental results of a comparative X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS) study of the crystalline structure, the local morphology, and the surface and in-depth chemistry of SnO₂ thin films obtained by Rheotaxial Growth and Thermal Oxidation (RGTO) method are presented. XRD rules out even a minor presence of a coexisting SnO phase. AFM and SEM show a fractal like morphology of nanograins (20 nm typical size) agglomerated in clusters of crystallites with a bimodal size distribution. XPS shows that the surface of the SnO₂ crystallites is slightly under-stoichiometric as expected from the oxygen deficient termination of their facets. Noteworthy, as evidenced by XPS depth profiles, there are no significant changes of the surface chemistry of the RGTO film with argon ion sputtering.     

Study of SOFC-SOE transition on a RSOFC stack

Reversible Solid Oxide Fuel Cell (RSOFC) can perform both power production and electricity storage with high efficiency and reduced cost using the same device for both functions. Within the frame of a small scale application and distributed generation, RSOFC systems operate connected to the grid switching from electrolysis to fuel cell and vice versa depending on load and grid peculiarities. The study aims to investigate the behavior of RSOFC in the two operation modes and in the transition phase. The analysis moves from the thermal equilibrium and electrical performances data gathered during the test of a six cells SOFC short stack. In particular, the effect of gas composition was deeply investigated. A mapping of performances was realized through polarization curves. Dilution of reactants, both in SOFC and SOE brings to reduction in performances while different compositions during SOE-SOFC transition did not give any significant effect to stack voltages. The dynamic model was derived from experimental results; thermal and electrical transient response to current variation was determined under several operating conditions and related transfer functions were identified characterizing the device dynamic behavior.