Simplified Models to Capture the Effects of Restraints in Glass Balustrades under Quasi-Static Lateral Load or Soft-Body Impact

Structural glass balustrades are usually composed of simple glass panels which are designed under various restraint solutions to minimize large out-of-plane deflections and prematurely high tensile/compressive stress peaks under lateral loads due to crowd. Linear supports, point-fixing systems, and others can be used to create geometrical schemes based on the repetition of simple modular units. Among others, linear restraints that are introduced at the base of glass panels are mechanically described in the form of ideal linear clamps for glass, in which the actual geometrical and mechanical details of real fixing components are reduced to rigid nodal boundaries. This means that, from a modelling point of view, strong simplifications are introduced for design. In real systems, however, these multiple components are used to ensure appropriate local flexibility and adequately minimize the risk of premature stress peaks in glass. The present study draws attention to one of these linear restraint solutions working as a clamp at the base of glass panels in bending. The accuracy and potential of simplified mechanical models in characterizing the effective translational and rotational stiffness contributions of its components are addressed, with the support of efficient and accurate Finite Element (FE) numerical models and experimental data from the literature for balustrades under double twin-tyre impact. Intrinsic limits are also emphasized based on parametric calculations in quasi-static and dynamic regimes

Reaction of Glycerol with Trimethyl Orthoformate: Towards the Synthesis of New Glycerol Derivatives

The reactivity of glycerol with trimethyl orthoformate is here described with an emphasis on developing a reliable synthetic approach for glycerol valorization. The glycerol based orthoester 4-(dimethoxymethoxy)methyl)-2-methoxy-1,3-dioxolane (3) was synthesized, under catalytic as well as catalyst-free conditions, by taking advantage of the thermodynamically controlled equilibrium between intermediates. Both Brønsted and Lewis acid catalysts accelerated the attainment of such an equilibrium, particularly Brønsted acidic ionic liquids BSMImHSO4 and BSMImBr were the most effective compounds for this reaction. The kinetic profiles allowed the proposal of a mechanism that accounts for the selectivity of the reaction

Lessons learned during the development of LEDSAT from the students of the S5Lab

The LEDSAT 1U Cubesat, a satellite roughly 10x10x11cm, was developed between late 2016 and 2021 by students of Sapienza University of Rome. The project was conceived with the help of the University of Michigan and started being developed by space engineering master students of Sapienza in a class context. The team of the S5Lab (Sapienza Space System and Space Surveillance Laboratory) continued the project and applied for the Fly Your Satellite! Programme of ESA Education, which has followed the development of the CubeSat, providing important expert support and periodic reviews. The approach brought to the students an invaluable educational experience as they participated actively in the development of a spacecraft with the typical milestones of satellite projects. The mission objectives of LEDSAT include the use of onboard LEDs for improved orbit determination, experimental attitude determination and backup light communication. Each of the six sides of the CubeSat houses an LED board of a different color (red, green, and blue) with opposite sides with paired color. The LEDs can flash a pattern predefined by radio telecommand and the light is observed using ground telescopes. The design of the spacecraft started in late 2016 and was presented at the selection workshop of the Fly Your Satellite! Programme in May 2017. Final assembly took place in mid-2020 after which the team performed functional and environmental testing between October and December 2020, with the objective of ensuring the survivability of the spacecraft in the space environment and characterization of its behavior. After successful testing, the spacecraft was integrated inside the deployer in July 2021 in Brno, Czech Republic and was launched from Kourou, French Guiana on August 17th, 2021, aboard the Vega VV19 launcher. The spacecraft is now in orbit and operating nominally, with the LED flashes having been observed several times. The development of the spacecraft was not without difficulty, with preventable issues arising through testing that imposed design changes and further analysis - the paper will walk through the project since its conception, throughout the development, the functional and environmental testing of the payload and at system level, emphasizing the lessons learned by the students

A pyridyl-triazole ligand for ruthenium and iridium catalyzed C=C and C=O hydrogenations in water/organic solvent biphasic systems

The water soluble pyridyl-triazole ligand sodium 2-(1-((pyridin-2-yl)methyl)-1H-1,2,3-triazol-4-yl) ethyl sulfate (Nal) has been successfully employed in combination with ruthenium and iridium for catalytic hydrogenation of C=C and C=O double bonds in water/toluene biphasic systems. Reaction of the ligand with [RuCl2(eta(6)-p-cymene)](2) affords the new water soluble complex [RuCl(eta(6)-p-cymene)(1)] (2) which has been found to be catalytically active in the water/organic solvent biphasic hydrogenation using styrene and 2-cyclohexen-1-one as model substrates. Very conveniently, the iridium based catalytic system is prepared by simply stirring in water [Ir(eta(4)-COD)C1]2 with Nal (Ir:Nal molar ratio-1:4), the resulting solution is catalytically active and appears more efficient than 2. With both the Ru- and Ir-based systems the catalytically active aqueous phases can be used at least three times without loss of activity. (C) 2014 Elsevier B.V. All rights reserved

Terpolymerisation of 1-olefin and ethene with CO catalysed by the [PdCl2(dppp)] complex in methanol as a solvent [dppp = 1,3-bis(diphenylphosphino)propane]

The catalytic activity of the [PdCl2(dppp)] complex in the 1-olefin/ethene (E)/CO terpolymerisation has been studied in MeOH (containing 1000 ppm of H2O) as a solvent. The 1-olefins tested were propene (P), 1-hexene (Hex), 1-decene (D) and styrene (S). At 90 °C and 45 atm (E/CO = 1/1), the system [PdCl2(dppp)]/TsOH (p-toluenesulfonic acid) = 1/8 catalyses efficiently the reactions leading to 5000 g PECO/(g Pd h), 5600 g HexECO/(g Pd h), 5650 g DECO/(g Pd h) and 4100 g SECO/(g Pd h). In particular, it has been studied deeper the effect of Hex and S concentrations on productivities, average molecular weights and melting temperatures of HexECO and SECO, respectively. A mechanism of reaction has been also proposed and discussed, supported by IR, and NMR characterizations

Appendectomy during the COVID-19 pandemic in Italy: a multicenter ambispective cohort study by the Italian Society of Endoscopic Surgery and new technologies (the CRAC study)

Major surgical societies advised using non-operative management of appendicitis and suggested against laparoscopy during the COVID-19 pandemic. The hypothesis is that a significant reduction in the number of emergent appendectomies was observed during the pandemic, restricted to complex cases. The study aimed to analyse emergent surgical appendectomies during pandemic on a national basis and compare it to the same period of the previous year. This is a multicentre, retrospective, observational study investigating the outcomes of patients undergoing emergent appendectomy in March-April 2019 vs March-April 2020. The primary outcome was the number of appendectomies performed, classified according to the American Association for the Surgery of Trauma (AAST) score. Secondary outcomes were the type of surgical technique employed (laparoscopic vs open) and the complication rates. One thousand five hundred forty one patients with acute appendicitis underwent surgery during the two study periods. 1337 (86.8%) patients met the inclusion criteria: 546 (40.8%) patients underwent surgery for acute appendicitis in 2020 and 791 (59.2%) in 2019. According to AAST, patients with complicated appendicitis operated in 2019 were 30.3% vs 39.9% in 2020 (p = 0.001). We observed an increase in the number of post-operative complications in 2020 (15.9%) compared to 2019 (9.6%) (p < 0.001). The following determinants increased the likelihood of complication occurrence: undergoing surgery during 2020 (+ 67%), the increase of a unit in the AAST score (+ 26%), surgery performed > 24 h after admission (+ 58%), open surgery (+ 112%) and conversion to open surgery (+ 166%). In Italian hospitals, in March and April 2020, the number of appendectomies has drastically dropped. During the first pandemic wave, patients undergoing surgery were more frequently affected by more severe appendicitis than the previous year's timeframe and experienced a higher number of complications. Trial registration number and date: Research Registry ID 5789, May 7th, 202

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements