the dilemma in Pd-catalyzed polyketone synthesis

A series of Pd-complexes containing nonsymmetrical bis(aryl-imino)acenaphthene (Ar-BIAN) ligands, characterized by substituents on the meta positions of the aryl rings, have been synthesized, characterized and applied in CO/vinyl arene copolymerization reactions. Crystal structures of two neutral Pd-complexes have been solved allowing comparison of the bonding properties of the ligand. Kinetic and mechanistic investigations on these complexes have been performed. The kinetic investigations indicate that in general ligands with electron- withdrawing substituents give more active, but less stable, catalytic systems, although steric effects also play a role. The good performance observed with nonsymmetrical ligands is at least in part due to a compromise between catalyst activity and lifetime, leading to a higher overall productivity with respect to catalysts based on their symmetrical counterparts. Additionally, careful analysis of the reaction profiles provided information on the catalyst deactivation pathway. The latter begins with the reduction of a Pd(II) Ar-BIAN complex to the corresponding Pd(0) species, a reaction that can be reverted by the action of benzoquinone. Then the ligand is lost, a process that appears to be facilitated by the contemporary coordination of an olefin or a CO molecule. The so formed Pd(0) complex immediately reacts with another molecule of the initial Pd(II) complex to give a Pd(I) dimeric species that irreversibly evolves to metallic palladium. Mechanistic investigations performed on the complex with a nonsymmetrical Ar-BIAN probe evidence that the detected intermediates are characterized by the Pd–C bond trans to the Pd–N bond of the aryl ring bearing electron-withdrawing substituents. In addition, the intermediate resulting from the insertion of 4-methylstyrene into the Pd–acyl bond is a five-member palladacycle and not the open-chain η3-allylic species observed for complexes with Ar-BIANs substituted in ortho position

Cognitive appraisals and team performance under stress: a simulation study

Objectives The present study explored how challenge and threat responses to stress relate to performance, anxiety, confidence, team identity and team characteristics (time spent in training and postgraduate experience) in a medical simulation‐based team competition. Methods The study was conducted during a national simulation‐based training event for residents, the SIMCUP Italia 2018. The SIMCUP is a simulation competition in which teams of four compete in simulated medical emergency scenarios. Cross‐sectional data were collected prior to the 3 days of the competition. Subjects included 95 participants on 24 teams. Before the competition on each day, participants completed brief self‐report measures that assessed demands and resources (which underpin challenge and threat responses to stress), cognitive and somatic anxiety, self‐confidence and team identification. Participants also reported time (hours) spent practising as a team and years of postgraduate experience. A team of referees judged each scenario for performance and assigned a score. A linear mixed model using demands and resources was built to model performance. Results The data showed that both demands and resources have positive effects on performance (31 [11‐50.3] [P < .01] and 54 [25‐83.3] [P < .01] percentage points increase for unitary increases in demands and resources, respectively); however, this is balanced by a negative interaction between the two (demands * resources interaction coefficient = −10 [−16 to −4.2]). A high level of resources is associated with better performance until demands become very high. Cognitive and somatic anxieties were found to be correlated with demands (Pearson's r = .51 [P < .01] and Pearson's r = .48 [P < .01], respectively). Time spent training was associated with greater perceptions of resources (Pearson's r = .36 [P < .01]). Conclusions We describe a model of challenge and threat that allows for the estimation of performance according to perceived demands and resources, and the interaction between the two. Higher levels of resources and lower demands were associated with better performance

a case study on the selection of promising functional starter strains from grape yeasts a report by student of food science and technology degree university of foggia southern italy

The main aim of this research, performed by some students in Food Science and Technology of Foggia University, is to show how perform the selection of a functional starter through a step-by-step procedure. Fifteen yeast strains were studied in order to assess their biotechnological traits, e.g. catalase, urease, B-glucosidase, pectolytic and xylanolytic activities, production of H2S, resistance to copper, SO2 and acetic acid, growth at different temperatures, alkaline pH, in presence of different amounts of ethanol and glucose, and some probiotic properties. After studying these abilities, yeasts were identified through the miniaturized system API 20 C AUX and two kinds of multivariate analyses (Cluster Analysis and Principal Component Analysis) were performed to highlight the best strains.</p

Use of backboards in cardiopulmonary resuscitation: a systematic review and meta-analysis

To achieve optimal chest compression depth, victims of cardiac arrest should be placed on a firm surface. Backboards are usually placed between the mattress and the back of a patient in the attempt to increase cardiopulmonary resuscitation (CPR) quality, but their effectiveness remains controversial. A systematic search was performed to include studies on humans and simulation manikins assessing CPR quality with or without backboards. The primary outcome of the meta-analysis was the difference in chest compression depth between these two conditions. Out of 557 records, 16 studies were included in the review and all were performed on manikins. The meta-analysis, performed on 15 articles, showed that the use of backboards during CPR increases chest compression depth by 1.46 mm in manikins. Despite statistically significant, this increase could have a limited clinical impact on CPR, due to the substantial heterogeneity of experimental conditions and the scarcity of other CPR quality indicators

THE LAYER PEROVSKITES AS THERMAL-ENERGY STORAGE-SYSTEMS

A series of compounds of the general formula (n-CnH2n+1NH3)2MCl4 (where M is a divalent metal atom and 8 ≤ n ≤ 18) undergoing high enthalpy reversible solid-solid phase transitions is considered. Although their transition enthalpy values are lower than those of the corresponding normal paraffins, the advantage of remaining solid after the phase change, together with other properties, makes these compounds of potential interest in the field of thermal energy storage systems

Effect of Semiconductor Parasitic Capacitances on Ground Leakage Current in Three-Phase Current Source Inverters

This paper investigates the influence of power semiconductor parasitic components on the ground leakage current in the three-phase Current Source Inverter topology, in the literature called H7 or CSI7. This topology allows reducing converter conduction losses with respect to the classic CSI, but at the same time makes the topology more susceptible to the parasitic capacitances of the semiconductors devices. In the present work, a grid-connected converter for photovoltaic power systems is considered as a case study, to investigate the equivalent circuit for ground leakage current. The same analysis can be extended to applications regarding electric drives, since the HF model of electric machines is characterized by stray capacitance between windings and the stator slots/motor frame. Simulation results proved the correctness of the proposed simplified common-mode circuit and highlighted the need of an additional common-mode inductor filter in case of resonance frequencies of the common-mode circuit close to harmonics of the power converter switching frequency. Experimental results are in agreement with the theoretical analysis

Perioperative Management Of Children With Neuromuscular Disorders Based On A Common Protocol: A Prospective, National Study In Italy

BACKGROUND: Children with neuromuscular diseases (NMDs) often display respiratory muscle weakness which increases the risk of postoperative pulmonary complications (PPCs) after general anaesthesia. Non-invasive ventilation (NIV) associated with mechanical insufflation-exsufflation (MI-E) can reduce the incidence and severity of PPCs. The aim of this study was to report our experience with a shared peri-operative protocol that consists in using NIV combined with MI-E to improve the postoperative outcome of NMD children (IT-NEUMA-Ped).METHOD: We conducted a multicenter, observational study on 167 consecutive paediatric patients with NMDs undergoing anaesthesia from December 2015 to December 2018 in a network of 13 Italian hospitals.RESULTS: We found that 89% of the 167 children (mean age 8 years old) were at high risk of PPCs, due to the presence of at least one respiratory risk factor. In particular, 51% of them had preoperative ventilatory support dependence. Only 14 (8%) patients developed PPCs and only two patients needed tracheostomy. Average hospital length of stay (LOS) was 6 [2-14] days. The study population was stratified according to preoperative respiratory devices dependency and invasiveness of the procedure. Patients with preoperative ventilatory support dependence showed significantly higher ICU admission rate and longer hospital LOS.CONCLUSION: Diseases severity seems to be more related to the outcome of this population than invasiveness of procedures. NIV combined with MI-E can help in preventing and resolve PPCs

Catalyst activity or stability: the dilemma in Pd-catalyzed polyketone synthesis

A series of Pd-complexes containing nonsymmetrical bis(aryl-imino)acenaphthene (Ar-BIAN) ligands, featured by substituents on the meta positions of the aryl rings, have been synthesized, characterized and applied in CO/vinyl arene copolymerization reactions. Crystal structures of two neutral Pd-complexes have been solved allowing comparison of the bonding properties of the ligand. Kinetic and mechanistic investigations on these complexes have been performed. The kinetic investigations indicate that in general ligands with electron-withdrawing substituents give more active, but less stable, catalytic systems, although steric effects also play a role. The good performance observed with nonsymmetrical ligands is at least in part due to a compromise between catalyst activity and lifetime, leading to a higher overall productivity with respect to catalysts based on their symmetrical counterparts. Additionally, careful analysis of the reaction profiles provided information on the catalyst deactivation pathway. The latter begins with the reduction of a Pd(II) Ar-BIAN complex to the corresponding Pd(0) species, a reaction that can be reverted by the action of benzoquinone. Then the ligand is lost, a process that appears to be facilitated by the contemporary coordination of an olefin or a CO molecule. The so formed Pd(0) complex immediately reacts with another molecule of the initial Pd(II) complex to give a Pd(I) dimeric species that irreversibly evolves to metallic palladium. Mechanistic investigations performed on the complex with a nonsymmetrical Ar-BIAN probe evidence that the detected intermediates are featured by the Pd-C bond trans to the Pd-N bond of the aryl ring bearing electron-withdrawing substituents. In addition, the intermediate resulting from the insertion of 4-methylstyrene into the Pd-acyl bond is a five-member palladacycle and not the open-chain \uf0683-allylic species observed for complexes with Ar-BIANs substituted in ortho position

Perioperative management of children with neuromuscular disorders based on a common protocol: A prospective, national study in Italy

BACKGROUND: Children with neuromuscular diseases (NMDs) often display respiratory muscle weakness which increases the risk of postoperative pulmonary complications (PPCs) after general anaesthesia. Non-invasive ventilation (NIV) associated with mechanical insufflation-exsufflation (MI-E) can reduce the incidence and severity of PPCs. The aim of this study was to report our experience with a shared peri-operative protocol that consists in using NIV combined with MI-E to improve the postoperative outcome of NMD children (IT-NEUMA-Ped).METHOD: We conducted a multicenter, observational study on 167 consecutive paediatric patients with NMDs undergoing anaesthesia from December 2015 to December 2018 in a network of 13 Italian hospitals.RESULTS: We found that 89% of the 167 children (mean age 8 years old) were at high risk of PPCs, due to the presence of at least one respiratory risk factor. In particular, 51% of them had preoperative ventilatory support dependence. Only 14 (8%) patients developed PPCs and only two patients needed tracheostomy. Average hospital length of stay (LOS) was 6 [2-14] days. The study population was stratified according to preoperative respiratory devices dependency and invasiveness of the procedure. Patients with preoperative ventilatory support dependence showed significantly higher ICU admission rate and longer hospital LOS.CONCLUSION: Diseases severity seems to be more related to the outcome of this population than invasiveness of procedures. NIV combined with MI-E can help in preventing and resolve PPCs