Instability of composite beams in hogging bending

This work is concerned with local buckling and lateral distortional buckling, two aspects of instability that govern the design of composite beams in hogging regions. Local buckling in hogging regions of a continuous composite beam was modelled by moment curvature characteristics of a cantilever, modified by two curvature ratios, K1 and K2. Test based expressions for K1 and K2, in terms of a combined slenderness λc, were developed, and subsequently used in numerical analyses of 50 two-span composite beams to assess moment redistribution allowed for Class 2 beams by draft Eurocode 4. The analyses include effects of non-linear material properties, residual stresses and local buckling. The parametrical studies include adverse values, in relation to practice, of relative length of adjacent spans, span-to-depth ratio, and ratio of hogging to sagging moment of resistances. It is concluded that the redistribution of elastic bending moments allowed by the draft Eurocode 4 is safe and economical. Distortional lateral buckling of composite beams with both continuous and discrete U-frame actions was studied experimentally. Distortional lateral buckling was found in the tests of two composite beams with inverted U-frame actions. Web distortion was effectively reduced by vertical web stiffeners, which form a part of discrete U-frames together with the slab and the connection of U-frame. The work provides background to assess lateral buckling strength for composite beams with both continuous and discrete U-frame actions. A further theoretical approach on the topic of discrete inverted U-frame action was presented. Strength and stiffness of discrete U-frame connections were also studied. The strength of a discrete U-frame connection was found to be influenced by both the shear failure of concrete, and the yielding of steel top flange in the connection. A simple rule to assure strength of U-frame connections is proposed by checking these two failures separately. The prediction of shear failure of a U-frame connection is based on a truss model, and the prediction of failure in the steel top flange is based on a rigid plastic mechanism. A semi-empirical formula for flexibility of a U-frame connection was derived. They were all checked against test results. Interactive U-frame force and U-frame stiffness were also studied. A tentative design method for discrete U-frame composite beams was proposed

Disease-causing mutations in genes encoding transcription factors critical for photoreceptor development

Photoreceptor development of the vertebrate visual system is controlled by a complex transcription regulatory network. OTX2 is expressed in the mitotic retinal progenitor cells (RPCs) and controls photoreceptor genesis. CRX that is activated by OTX2 is expressed in photoreceptor precursors after cell cycle exit. NEUROD1 is also present in photoreceptor precursors that are ready to specify into rod and cone photoreceptor subtypes. NRL is required for the rod fate and regulates downstream rod-specific genes including the orphan nuclear receptor NR2E3 which further activates rod-specific genes and simultaneously represses cone-specific genes. Cone subtype specification is also regulated by the interplay of several transcription factors such as THRB and RXRG. Mutations in these key transcription factors are responsible for ocular defects at birth such as microphthalmia and inherited photoreceptor diseases such as Leber congenital amaurosis (LCA), retinitis pigmentosa (RP) and allied dystrophies. In particular, many mutations are inherited in an autosomal dominant fashion, including the majority of missense mutations i

Dispersion Characteristics of Elastic Waves in Saturated Soils

Based on the wave equations established by the authors, the dispersion characteristics of elastic waves in saturated soils are analyzed and verified by laboratory test and seismic survey in the field. The results can be used for determination of physical and mechanical parameters of saturated soils, such as, Poisson\u27s ratio, depth for first appearance of full saturation, porosity and unit weight by measurement of wave velocities

Transcriptional precision in photoreceptor development and diseases – Lessons from 25 years of CRX research

The vertebrate retina is made up of six specialized neuronal cell types and one glia that are generated from a common retinal progenitor. The development of these distinct cell types is programmed by transcription factors that regulate the expression of specific genes essential for cell fate specification and differentiation. Because of the complex nature of transcriptional regulation, understanding transcription factor functions in development and disease is challenging. Research on the Cone-rod homeobox transcription factor CRX provides an excellent model to address these challenges. In this review, we reflect on 25 years of mammalian CRX research and discuss recent progress in elucidating the distinct pathogenic mechanisms of four CRX coding variant classes. We highlight how in vitro biochemical studies of CRX protein functions facilitate understanding CRX regulatory principles in animal models. We conclude with a brief discussion of the emerging systems biology approaches that could accelerate precision medicine for CRX-linked diseases and beyond

Dynamics modeling and experimental modal analysis of bolt loosening for lightning rod

Lightning rods are effective to prevent lightning damage in power systems. However, under the influence of severe weather conditions, they often face failure problems, mainly manifested as tilt and fracture caused by bolt loosening which can result in significant economic losses. Therefore, it is very meaningful to detect the loosening of the lightning rod. The vibration-based method is an effective method for bolt loosening detection and is suitable for use on large lightning rods. This paper built a finite element model of the lightning rod Flange-Bolt Structure Unit (FBSU) based on the virtual material method, designed an effective acquisition test of the vibration signal under different loosening conditions of the lightning rod FBSU. The experimental results showed that it was effective to establish the dynamic model of the lightning rod FBSU by using the virtual material method. According to the measured vibration signal, the frequency response function was obtained by TIME MDOF method, and the preliminary judgment of bolt loosening can be realized. This study lays the foundation for the precise positioning and the extent of loosening detection of lightning rod bolt loosening, and also provides a guideline for the vibration test design of large bolted structures similar to lightning rods

Disease-causing mutations in genes encoding transcription factors critical for photoreceptor development

Photoreceptor development of the vertebrate visual system is controlled by a complex transcription regulatory network. OTX2 is expressed in the mitotic retinal progenitor cells (RPCs) and controls photoreceptor genesis. CRX that is activated by OTX2 is expressed in photoreceptor precursors after cell cycle exit. NEUROD1 is also present in photoreceptor precursors that are ready to specify into rod and cone photoreceptor subtypes. NRL is required for the rod fate and regulates downstream rod-specific genes including the orphan nuclear receptor NR2E3 which further activates rod-specific genes and simultaneously represses cone-specific genes. Cone subtype specification is also regulated by the interplay of several transcription factors such as THRB and RXRG. Mutations in these key transcription factors are responsible for ocular defects at birth such as microphthalmia and inherited photoreceptor diseases such as Leber congenital amaurosis (LCA), retinitis pigmentosa (RP) and allied dystrophies. In particular, many mutations are inherited in an autosomal dominant fashion, including the majority of missense mutations in CRX and NRL. In this review, we describe the spectrum of photoreceptor defects that are associated with mutations in the above-mentioned transcription factors, and summarize the current knowledge of molecular mechanisms underlying the pathogenic mutations. At last, we deliberate the outstanding gaps in our understanding of the genotype–phenotype correlations and outline avenues for future research of the treatment strategies

Analysis of Pile-Soil Dynamic Interaction by Combination of BEM and FEM

A hybrid method, in which soil media is modeled by 3-D boundary elements and the pile by 1-D finite elements, for an analysis of dynamic pile-soil interaction is investigated. A new series of equations and an efficient method to deal with singularity of integrals are presented. Several effects including pile length, stiffness of the pile and surrounding soil on dynamic response are studied. Finally, the characteristics of impaired and intact piles are investigated and compared; and some case studies are presented