Considered to be representative of a generic bridge deck geometry and characterised by a highly unsteady flow field, the 5:1 rectangular cylinder has been the main case study in a number of studies ...including the “Benchmark on the Aerodynamics of a Rectangular 5:1 Cylinder” (BARC). There are still a number of limitations in the knowledge of (i) the mechanism of the vortex-induced vibration (VIV) and (ii) of the turbulence-induced effect for this particular geometry. Extended computational and wind tunnel studies were therefore conducted by the authors to address these issues. This paper primarily describes wind tunnel and computational studies using a sectional model in an attempt to bring more insight into Point (i). By analysing the distribution and correlation of the surface pressure around an elastically mounted 5:1 rectangular cylinders in smooth and turbulent flow, it revealed that the VIV was triggered by the motion-induced leading-edge vortex; a strongly correlated flow feature close to the trailing edge was then responsible for an increase in the structural response.
•Vortex-induced vibration (VIV) for a 5:1 rectangular cylinder was studied.•CFD and wind tunnel testing displayed similar traits.•VIV was triggered by the motion-induced leading edge vortex.•Vortices impinged on the trailing edge, increasing the structural response.
A new design of coaxial rotary joint (RJ) made compact by applying "folded" choke quarter-wave impedance transformer is proposed for very high-frequency surveillance radar. The final prototype, which ...measures L <inline-formula> <tex-math notation="LaTeX">388\,\,\text {mm} \times \text {D}\,\,106 </tex-math></inline-formula> mm, demonstrated 0.04-dB insertion loss and 28-dB return loss within the operating frequency range of 150-170 MHz. The RJ is able to handle peak power of 15 kW during experiments. By avoiding reliability issues inherent in contacting RJ, the lifetime and stability of the whole radar system would be remarkably enhanced.
Three‐dimensional structures of I86A and C295A mutant secondary alcohol dehydrogenase (SADH) from Thermoanaerobacter pseudoethanolicus were determined by x‐ray crystallography. The tetrameric ...structure of C295A‐SADH soaked with NADP+ and dimethyl sulfoxide (DMSO) was determined to 1.85 Å with an Rfree of 0.225. DMSO is bound to the tetrahedral zinc in each subunit, with ligands from SG of Cys‐37, NE2 of His‐59, and OD2 of Asp‐150. The nicotinamide ring of NADP is hydrogen‐bonded to the N of Ala‐295 and the O of Val‐265 and Gly‐293. The O of DMSO is connected to a network of hydrogen bonds with OG of Ser‐39, the 3′‐OH of NADP, and ND1 of His‐42. The structure of I86A‐SADH soaked with 2‐pentanol and NADP+ contains (R)‐2‐pentanol bound in each subunit, ligated to the tetrahedral zinc, and connected to the proton relay network. The structure of I86A‐SADH soaked with 3‐methylcyclohexanol and NADP+ has alcohol bound in three subunits. Two of the sites have the alcohol ligated to the zinc in an axial position, with OE2 of Glu‐60 in the other axial position of a trigonal bipyramidal complex. One site has 3‐methylcyclohexanol bound noncovalently, with the zinc in an inverted tetrahedral geometry with Glu‐60. The fourth site also has the zinc in a trigonal bipyramidal complex with axial Glu‐60 and water ligands. These structures demonstrate that ligand exchange of SADH involves pentacoordinate and inverted zinc complexes with Glu‐60. Furthermore, we see a network of hydrogen bonds connecting the substrate oxygen to the external solvent that is likely to play a role in the mechanism of SADH.
The GeoSHM project feasibility study for monitoring the Forth Road Bridge is briefly introduced and the instrumentation summarised. The events of January 9th, 2015 are described, when the bridge was ...struck by storm Elon, which caused widespread damage across Scotland and led to the temporary closure of the bridge when a van was blown over. During this storm an anomalous large amplitude response was observed.
The data for January 9th, 2015 are analysed to show that the extreme response and the corresponding wind are non-stationary and non-Gaussian. Further analysis of the rainfall radar data for the same time shows a line of intense rainfall extending for over 100 km, which passes the site of the bridge at exactly the time of the peak response. The rainfall intensity was high enough to indicate that this feature was caused by convective activity and this observation was corroborated by records of lightning strikes. It is concluded that non-stationary wind events can give rise to large response of long span bridge structures and that this response can exceed that observed from the stationary wind field. Furthermore, historical data confirm that energetic squall lines are not uncommon in the UK. Therefore, the assumption of stationarity in predicting the wind induced response of long span bridges may be non-conservative and the climatology of large convective systems, such as squall lines, should be considered in assessing the wind hazard for these structures.
•Presents evidence from field monitoring of the non-stationary response of a long span bridge to wind loading.•Presents evidence associating intense rainfall radar data with observed non-stationary large amplitude response.•Demonstrates the added value of using GNSS sensors to monitor the deflection of large structures under wind load.
During mammalian neocortical development, neural precursor cells generate neurons first and astrocytes later. The cell fate switch from neurons to astrocytes is a key process generating proper ...numbers of neurons and astrocytes. Although the intracellular mechanisms regulating this cell fate switch have been well characterized, extracellular regulators are still largely unknown. Here, we uncovered that fibroblast growth factor (FGF) regulates the cell fate switch from neurons to astrocytes in the developing cerebral cortex using mice of both sexes. We found that the FGF signaling pathway is activated in radial glial cells of the ventricular zone at time points corresponding to the switch in cell fate. Our loss- and gain-of-function studies using
electroporation indicate that activation of FGF signaling is necessary and sufficient to change cell fates from neurons to astrocytes. We further found that the FGF-induced neuron-astrocyte cell fate switch is mediated by the MAPK pathway. These results indicate that FGF is a critical extracellular regulator of the cell fate switch from neurons to astrocytes in the mammalian cerebral cortex.
Although the intracellular mechanisms regulating the neuron-astrocyte cell fate switch in the mammalian cerebral cortex during development have been well studied, their upstream extracellular regulators remain unknown. By using
electroporation, our study provides
data showing that activation of FGF signaling is necessary and sufficient for changing cell fates from neurons to astrocytes. Manipulation of FGF signaling activity led to drastic changes in the numbers of neurons and astrocytes. These results indicate that FGF is a key extracellular regulator determining the numbers of neurons and astrocytes in the mammalian cerebral cortex, and is indispensable for the establishment of appropriate neural circuitry.
Because folding of the cerebral cortex in the mammalian brain is believed to be crucial for higher brain functions, the mechanisms underlying its formation during development and evolution are of ...great interest. Although it has been proposed that increased neural progenitors in the subventricular zone (SVZ) are responsible for making cortical folds, their roles in cortical folding are still largely unclear, mainly because genetic methods for gyrencephalic mammals had been poorly available. Here, by taking an advantage of our newly developed in utero electroporation technique for the gyrencephalic brain of ferrets, we investigated the role of SVZ progenitors in cortical folding. We found regional differences in the abundance of SVZ progenitors in the developing ferret brain even before cortical folds began to be formed. When Tbr2 transcription factor was inhibited, intermediate progenitor cells were markedly reduced in the ferret cerebral cortex. Interestingly, outer radial glial cells were also reduced by inhibiting Tbr2. We uncovered that reduced numbers of SVZ progenitors resulted in impaired cortical folding. When Tbr2 was inhibited, upper cortical layers were preferentially reduced in gyri compared to those in sulci. Our findings indicate the biological importance of SVZ progenitors in cortical folding in the gyrencephalic brain.
The paper presents a generalization of the conventional analytical approach where the quasi-steady theory is utilised to evaluate the across-wind aerodynamic damping of slender single beam ...structures. This generalized theory considers the variation of structural and aerodynamic parameters along the structural height, together with the nature of the vertical wind profile and mode shapes. Closed-form solutions for typical uniform and tapered tall buildings are given. A numerical application on a prototype tall building shows that the conventional method may be oversimplified, which results in incorrect predictions of the aerodynamic damping.
Graphic Abstract
This paper explores the development of a smart Structural Health Monitoring (SHM) platform tailored for long-span bridge monitoring, using the Forth Road Bridge (FRB) as a case study. It discusses ...the selection of smart sensors available for real-time monitoring, the formulation of an effective data strategy encompassing the collection, processing, management, analysis, and visualization of monitoring data sets to support decision-making, and the establishment of a cost-effective and intelligent sensor network aligned with the objectives set through comprehensive communication with asset owners. Due to the high data rates and dense sensor installations, conventional processing techniques are inadequate for fulfilling monitoring functionalities and ensuring security. Cloud-computing emerges as a widely adopted solution for processing and storing vast monitoring data sets. Drawing from the authors' experience in implementing long-span bridge monitoring systems in the UK and China, this paper compares the advantages and limitations of employing cloud- computing for long-span bridge monitoring. Furthermore, it explores strategies for developing a robust data strategy and leveraging artificial intelligence (AI) and digital twin (DT) technologies to extract relevant information or patterns regarding asset health conditions. This information is then visualized through the interaction between physical and virtual worlds, facilitating timely and informed decision-making in managing critical road transport infrastructure.
The presence of free-grazing ducks (FGD) has consistently been shown to be associated with highly pathogenic avian influenza virus (HPAIV) H5N1 outbreaks in South-East Asia. However, the lack of ...knowledge about the transmission pathways limits the effectiveness of control efforts. To address this gap, we developed a probabilistic transmission model of HPAIV H5N1 in the nomadic FGD production system in Viet Nam, assuming different scenarios to address parameter uncertainty. Results suggested that HPAIV H5N1 could spread within the nomadic FGD production system, with an estimated flock-level effective reproduction number (r
) ranging from 2.16 (95% confidence interval (CI): 1.39-3.49) to 6.10 (95%CI: 3.93-9.85) depending on the scenario. Indirect transmission via boats and trucks was shown to be the main transmission route in all scenarios. Results suggest that r
could be reduced below one with 95% confidence if 86% of FGD flocks were vaccinated in the best-case scenario or 95% in the worst-case scenario. If vaccination was combined with cleaning and disinfection of transport vehicles twice a week, vaccination coverage could be lowered to 60% in the best-case scenario. These findings are of particular relevance for prioritising interventions for effective control of HPAIV in nomadic free-grazing duck production systems.
Structural Health Monitoring (SHM) is a relatively new branch of civil engineering that focuses on assessing the health status of infrastructure, such as long-span bridges. Using a broad range of ...in-situ monitoring instruments, the purpose of the SHM is to help engineers understand the behaviour of structures, ensuring their structural integrity and the safety of the public. Under the Integrated Applications Promotion (IAP) scheme of the European Space Agency (ESA), a feasibility study (FS) project that used the Global Navigation Satellite Systems (GNSS) and Earth Observation (EO) for Structural Health Monitoring of Long-span Bridges (GeoSHM) was initiated in 2013. The GeoSHM FS Project was led by University of Nottingham and the Forth Road Bridge (Scotland, UK), which is a 2.5 km long suspension bridge across the Firth of Forth connecting Edinburgh and the Northern part of Scotland, was selected as the test structure for the GeoSHM FS project. Initial results have shown the significant potential of the GNSS and EO technologies. With these successes, the FS project was further extended to the demonstration stage, which is called the GeoSHM Demo project where two other long-span bridges in China were included as test structures. Led by UbiPOS UK Ltd. (Nottingham, UK), a Nottingham Hi-tech company, this stage focuses on addressing limitations identified during the feasibility study and developing an innovative data strategy to process, store, and interpret monitoring data. This paper will present an overview of the motivation and challenges of the GeoSHM Demo Project, a description of the software and hardware architecture and a discussion of some primary results that were obtained in the last three years.
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