The ponding problem on flat steel roof grids

Due to several reasons, a flat steel roof grid of industrial or commercial single-story buildings may be very flexible in the vertical direction. Due to its flexibility, a ponding effect can take place. The rainwater fills the space created by vertical deflection of the roof grid and this space increases under the gradually accumulated rainwater until equilibrium is reached.Ponding may be full or partial, and it is a self exciting phenomenon that can lead to grid instability. The problem is strongly non-linear, since the rainwater distribution on the roof grid in not known a priori.A closed form response to particular ponding cases and a simple grid geometry is achieved. Moreover, a non-linear finite element technique is presented in order to study the small/large deflection solution to the ponding problem of a complex flat steel roof grid.Finally, several steel roof grids are examined in order to illustrate the effect of precambering, grid dimensions and vertical flexibility on the ponding effect. The practical significance of a large deflection analysis for practical situations is also elucidated.     

Linear MMSE estimation of time-frequency variant channels for MIMO-OFDM systems

This paper proposes two low-complexity two-dimensional channel estimators for MIMO-OFDM systems derived from a joint time-frequency channel estimator. The estimators exploit both time and frequency correlations of the wireless channel via use of Slepian-basis expansions. The computational saving comes from replacing a two-dimensional Slepian-basis expansion with two serially concatenated one-dimensional Slepian-basis expansions. Performance in terms of normalized mean square error (NMSE) vs. signal-to-noise ratio (SNR) is analyzed via numerical simulations and compared with the original estimator. The analysis of the performance takes into account the impact of both system and channel parameters. The estimators are finally tested when used within the loop of an iterative receiver for MIMO-OFDM systems.     

Fatigue behaviour of tensile steel/CFRP joints

In this paper the fatigue performance of tensile steel/CFRP (Carbon Fibre Reinforced Polymer) double shear lap joints is discussed. Joints were realized with two steel plates and two CFRP strips bonded using epoxy adhesive. Fatigue tests were performed on 16 specimens under constant stress range loading cycles. Two stress ratios (R = 0.1 and R = 0.4) were considered to investigate their influence on the fatigue lifetime. Debonding was observed to occur at stress concentration zones and propagate along the CFRP/adhesive interfaces. The stiffness degradation of the steel joint due to progressive debonding of the adhesive represents an index for the subsequent and progressive global failure. S–N curves are defined and compared to the fatigue resistance of welded detail categories of the Eurocode 3. The tests showed that the stress ratio, R, has a marginal influence on the fatigue lifetime of the steel/CFRP double shear lap joints. Finally, a fatigue limit corresponding to a stress range in the steel plate equal to 75 MPa was conservatively estimated during the tests. The fatigue limit seems to be insensitive to the stress ratio R.     

No Time to Die: How Kidney Cancer Evades Cell Death

The understanding of the pathogenesis of renal cell carcinoma led to the development of targeted therapies, which dramatically changed the overall survival rate. Nonetheless, despite innovative lines of therapy accessible to patients, the prognosis remains severe in most cases. Kidney cancer rarely shows mutations in the genes coding for proteins involved in programmed cell death, including p53. In this paper, we show that the molecular machinery responsible for different forms of cell death, such as apoptosis, ferroptosis, pyroptosis, and necroptosis, which are somehow impaired in kidney cancer to allow cancer cell growth and development, was reactivated by targeted pharmacological intervention. The aim of the present review was to summarize the modality of programmed cell death in the pathogenesis of renal cell carcinoma, showing in vitro and in vivo evidence of their potential role in controlling kidney cancer growth, and highlighting their possible therapeutic value.     

Understanding the Behaviour of Human Cell Types under Simulated Microgravity Conditions: The Case of Erythrocytes

Erythrocytes are highly specialized cells in human body, and their main function is to ensure the gas exchanges, O₂ and CO₂, within the body. The exposure to microgravity environment leads to several health risks such as those affecting red blood cells. In this work, we investigated the changes that occur in the structure and function of red blood cells under simulated microgravity, compared to terrestrial conditions, at different time points using biochemical and biophysical techniques. Erythrocytes exposed to simulated microgravity showed morphological changes, a constant increase in reactive oxygen species (ROS), a significant reduction in total antioxidant capacity (TAC), a remarkable and constant decrease in total glutathione (GSH) concentration, and an augmentation in malondialdehyde (MDA) at increasing times. Moreover, experiments were performed to evaluate the lipid profile of erythrocyte membranes which showed an upregulation in the following membrane phosphocholines (PC): PC16:0_16:0, PC 33:5, PC18:2_18:2, PC 15:1_20:4 and SM d42:1. Thus, remarkable changes in erythrocyte cytoskeletal architecture and membrane stiffness due to oxidative damage have been found under microgravity conditions, in addition to factors that contribute to the plasticity of the red blood cells (RBCs) including shape, size, cell viscosity and membrane rigidity. This study represents our first investigation into the effects of microgravity on erythrocytes and will be followed by other experiments towards understanding the behaviour of different human cell types in microgravity.     

A Hybrid Magneto-Optic Capacitive Memory with Picosecond Writing Time

The long-term future of information storage requires the use of sustainable nanomaterials in architectures operating at high frequencies. Interfaces can play a key role in this pursuit via emergent functionalities that break out from conventional operation methods. Here, spin-filtering effects and photocurrents are combined at metal-molecular-oxide junctions in a hybrid magneto-capacitive memory. Light exposure of metal-fullerene-metal oxide devices results in spin-polarized charge trapping and the formation of a magnetic interface. Because the magnetism is generated by a photocurrent, the writing time is determined by exciton formation and splitting, electron hopping, and spin-dependent trapping. Transient absorption spectroscopy measurements show changes in the electronic states as a function of the magnetic history of the device within picoseconds of the optical pumping. The stored information is read using time-resolved scanning magneto optic Kerr effect measurements during microwave irradiation. The emergence of a magnetic interface in the picosecond timescale opens new paths of research to design hybrid magneto-optic structures operating at high frequencies for sensing, computing, and information storage.