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[en] In orthodontic science, diagnosis of facial skeletal type (class I, II, and III) is essential to make the correct treatment plan that is usually expensive and complicated. Sometimes results from analysis of lateral cephalometry radiographies are not enough to discriminate facial skeletal types. In this situation, knowledge about the relationship between the shape and size of the sella turcica and the type of facial skeletal class can help to make a more definitive decision for treatment plan. The present study was designed to investigate this relationship in patients referred to a dental school in Iran. In this descriptive-analytical study, cephalometric radiographies of 90 candidates for orthodontic treatment (44 females and 46 males) with an age range of 14 - 26 years and equal distribution in terms of class I, class II, and class III facial skeletal classification were selected. The shape, length, diameter, and depth of the sella turcica were determined on the radiographs. Linear dimensions were assessed by one-way analysis of variance while the correlation between the dimensions and age was investigated using Pearson’s correlation coefficient. Sella turcica had normal morphology in 24.4% of the patients while irregularity (notching) in the posterior part of the dorsum sella was observed in 15.6%, double contour of sellar floor in 5.6%, sella turcica bridge in 23.3%, oblique anterior wall in 20% and pyramidal shape of the dorsum sella in 11.1% of the subjects. In total, 46.7% of class I patients had a normal shape of sella turcica, 23.3% of class II patients had an oblique anterior wall and a pyramidal shape of the dorsum sella, and 43.3% of class III individuals had sella turcica bridge (the greatest values). Sella turcica length was significantly greater in class III patients compared to class II and class I (P < 0.0001). However, depth and diameter of sella turcica were similar in class I, class II, and class III patients. Furthermore, age was significantly correlated to the diameter of sella turcica as greater diameters were observed in older ages (P < 0.04). A significant relationship exists between the type of facial skeletal classification and the shape of the sella turcica; as in class III patients, sella turcica bridge was reported with a higher frequency. Also, sella turcica had a significantly higher length in these patients than in those with class I and class II facial skeletal types
[en] The dynamic behavior of bridges under the effect of moving loads simulating the vehicle moving along the bridge structure idealized by an Euler beam is analyzed. We will present the dynamic behavior of beams under the stress of moving loads (or masses) by the analytical and semi-analytical approaches. When the mass of the bridge structure is comparable to that of the vehicle, the mobile source requesting the bridge is simulated by a mass. In most practical cases, the mobile force used is due to the effects of the gravitational moving masses: . When the moving mass is small compared to the beam mass, the obtained solution under the effect of moving force is approximately correct for the solution obtained with the moving mass. Otherwise, the problem of the moving mass is imperative. To do this, we wrote a program in Matlab language which reflects the dynamic behavior of beams under the effect of moving charges, which gives the following results The frequencies and modes of vibration, the dynamics deflection of the beam requested by moving force, the dynamic response (DAF: dynamic amplification factor) of the beam requested by a moving force, over the whole length of the beam, for all times and for different speeds. The numerical example that we look to see for study the dynamic behavior of this type of bridge under moving loads is that of a thin beam unamortised on simple support and length of 50m, under the solicitation of moving force and mass at a constant speed and varies from 0 to 100 m / s (M. A. Foda, 1997), depending on the relationship between the vehicle mass and the mass of the bridge that will allow us to see the contribution of the choice of modelling type on the total response and then the vibration of bridge, also we will study the effect of type of simulation of the load by moving force or mass on the dynamic amplification factor and comparing our results with those from the literature. (author)
[en] Clad steel possesses benefits of the both component metals in terms of mechanical performance, corrosion resistance, sustainability and lower full lifecycle cost, etc. As a result, it has been more and more widely used in the petroleum, chemical, marine, shipbuilding and metallurgical industries, including stainless-clad steel and titanium clad steel. Such clad steel has also great potential for application in building and bridge structures. For better understanding material properties of such clad steel, a review of research progress available in the literature is conducted herein, as well as recent research undertaken by the authors’ group at Tsinghua University. It can be found that very limited research reported in the literature mainly concerns static material properties of the clad steel, and primary relations between clad ratio and strength are suggested. The authors carried out material tests on both titanium and stainless-clad steel plates, with different clad ratios being incorporated. For the stainless-clad steel tests, both material and butt welded connections are tested, and various elevated temperatures are considered. In addition, tension coupon tests under cyclic loadings are also briefly introduced herein. Primary constitutive relations developed by the authors are reviewed in this paper. All the research findings and proposed formulae may provide an essential basis for future structural analysis, and may promote its application in structural engineering. (Author)
[en] Currently most railway bridges in Australia require the replacement of the timber transoms that reside in the railway system. Composite steel and precast reinforced concrete transoms have been proposed as the replacement for the current timber counterparts. This paper outlines the structural benefits of composite steel-concrete transoms for ballastless tracks when retrofitted to existing railway steel bridges. However, in existing studies, it is found that there is little investigation into the effect of derailment loading on reinforced concrete transoms. Therefore, this paper provides an investigation of derailment impact loading on precast reinforced concrete transoms. The paper herein investigates the derailment impact loading of a train through experimental testing and numerical analysis of conventional reinforced concrete transoms. The paper also evaluates the potential use of 3 different shear connectors; welded shear studs, Lindapter bolts and Ajax bolts. The results of the experimental tests and finite element models are used to determine whether each transom is a viable option for the replacement of the current timber transoms on the existing bridges in Australia and whether they provide a stronger and longer lasting solution to the current transom problem. (Author)
[en] We have considered an effect of atomic electrons on the nuclear 229mTh-229gTh transition in 229Th3+ due to the electronic bridge process. Based on a recent experimental result we assumed the energy difference between the isomeric and the ground nuclear states to be equal to 7.6 eV. We have calculated the ratios of the electronic bridge process probability (ΓEB) to the probability of the nuclear radiative transition (ΓN) for the electronic 5f5/2→6d3/2,6d5/2,7s and the 7s→7p1/2,7p3/2 transitions and found ΓEB/ΓN∼0.01-0.1 for the former and ΓEB/ΓN∼20 for the latter.
[en] Highlights: • New bone formation is a key finding in spondyloarthritis. • Intradiscal high signal intensity on T1W MRI is distinctive of spondyloarthritis. • Vertebral corner bridging on MRI performs as a specific sign of spondyloarthritis. • Transdiscal ankylosis on MRI performs as a specific sign of spondyloarthritis. • Presence of syndesmophytes on MRI is not a reliable sign of spondyloarthritis. - Abstract: ObjectivesTo study the presence of high signal intensity of the intervertebral disc, syndesmophytes, vertebral corner bridging and transdiscal ankylosis on spinal T1-weighted MR images in spondyloarthritis (SpA).
[en] Direct spectroscopic evidence for a hydride bridge in the Ni–R form of [NiFe] hydrogenase has been obtained using iron-specific nuclear resonance vibrational spectroscopy. This article focuses on the long and strenuous experimental journey to search for and identify this first spectroscopic evidence for a hydride in Ni–R. Direct spectroscopic evidence for a hydride bridge in the Ni–R form of [NiFe] hydrogenase has been obtained using iron-specific nuclear resonance vibrational spectroscopy (NRVS). The Ni–H–Fe wag mode at 675 cm−1 is the first spectroscopic evidence for a bridging hydride in Ni–R as well as the first iron-hydride-related NRVS feature observed for a biological system. Although density function theory (DFT) calculation assisted the determination of the Ni–R structure, it did not predict the Ni–H–Fe wag mode at ∼675 cm−1 before NRVS. Instead, the observed Ni–H–Fe mode provided a critical reference for the DFT calculations. While the overall science about Ni–R is presented and discussed elsewhere, this article focuses on the long and strenuous experimental journey to search for and experimentally identify the Ni–H–Fe wag mode in a Ni–R sample. As a methodology, the results presented here will go beyond Ni–R and hydrogenase research and will also be of interest to other scientists who use synchrotron radiation for measuring dilute samples or weak spectroscopic features.
[en] Highway and railway bridges are exposed to cyclic stressing due to traffic loads and, therefore, have to be evaluated concerning fatigue. In most cases the fatigue evaluation is performed according to Eurocode 3 Part 1-9 on nominal stresses. To apply this nominal stress approach a detail catalogue is required classifying all relevant constructional details in terms of fatigue. Unfortunately, the existing detail catalogue of Eurocode 3 Part 1-9 reflects the state of the art of the 1990s and misses constructional details being important for today’s bridge design. As an example the derivation of a new detail, the so-called lamellae joint, is presented. Furthermore, for two new types of innovative steel bridges, where Eurocode 3 Part 1-9 does not yet specify rules able to evaluate the characteristics of these bridges, research results are shown. These are the thick-plate trough bridges and truss bridges made of thick-walled circular hollow sections (CHS). The paper starts with an overview on the recent Eurocode developments, addressing more specific the fatigue verification according to EN 1993-1-9 and the statistical analysis of fatigue test data. In the following, information is given on the outcome of some recent research projects striving to extend the application range of Eurocode 3 Part 1-9. The final conclusion, in spite of all differences, show a common tendency. (Author)
[en] Highlights: • Five 3D CoII2-xZnIIx coordination polymers have been synthesized by in situ hydrothermal reaction. • CoII compound exhibits the coexistence of antiferromagnetic ordering and slow magnetic dynamics. • The bimetallic CoII2-xZnIIx series tend to compress slow dynamics. - Abstract: Five novel isomorphous 3D CoII2-xZnIIx (0 ≤x ≤ 2) coordination frameworks formulated as [CoII2-xZnIIx(pymtz)2(N3)2(H2O)2]·2H2O, (x = 0 (1), 1 (2), 1.5 (3), 1.7 (4), 2 (5), pymtz = 5-(3-pyrimidyl)tetrazolate) were synthesized by in situ hydrothermal reaction and then structurally and magnetically characterized. In these compounds, adjacent metal ions are linked by mixed double azide and tetrazolate bridges to give 1D coordination chains, and each chain is interlinked by pymtz ligands into 3D frameworks with (3,4,6)-connected net of (3.6.8)(32.61.73)(22.214.171.124.112) topology. Magnetic studies indicate that the homometallic CoII compound (1) exhibits the coexistence of antiferromagnetic ordering and slow magnetic dynamics, while the bimetallic CoII2-xZnIIx series (2-4) show the innocent blending effect which tends to decrease the blocking temperature (TB) of the spin slow dynamics. The homometallic ZnII compound (5) exhibits strong luminescence in the solid state at room temperature while the luminescent intensity of 5 gradually decreases as ZnII is replaced by CoII.