Evaluation of the Bond Stress Transfer Mechanism in CFSTs

This paper studies the non-linear distribution of bond–slip behavior in the steel concrete interface of a Concrete Filled Steel Tube (CFST). Specifically, it concerns the regions of geometric discontinuity occurring in composite beams of CFST column-frame connection points. The study was conducted through an analytical model that represented the bond stress transfer mechanism within these areas. The resulting deductions were drawn up on the basis of the elasticity theory and the non-linear bond–slip relationship between the steel jacket and the confined concrete. This paper highlights how the model proposed here was able to obtain, not only the closed-form analytical expression of the transferring length involved in the bond stress transfer mechanism in CFSTs but also the expressions of concrete and steel jacket stresses and strains. In addition, the procedure also obtained the bond stress and slip trend in the above-mentioned length for rectangular and circular concrete filled steel tubes. The use of this model also resulted in an analytical expression for the calculation of the ultimate load in CFSTs. In this paper, the ultimate load predictions were compared with the experimental results obtained from 97 tests carried out on circular concrete filled tubes (CCFTs) and 35 tests on rectangular concrete filled tubes (RCFTs). The predictions drawn up with this model have been found to be the most accurate and uniform in comparison with those obtained from models proposed by other authors and Eurocode. With reference to the experimental-to-analytical load value ratio, the AVG and COV values obtained from the model proposed here are 0.86 and 0.42, and 1.06 and 0.57 for CCFT and RCFT analyses, respectively

An explicitly solvable model of the spontaneous PT-symmetry breaking

We contemplate the pair of the purely imaginary delta-function potentials on a finite interval with Dirichlet boundary conditions. The two parameter model exhibits nicely the expected quantitative features of the unavoided level crossing and of a "phase-transition" complexification of the energies. Combining analytic and numerical techniques we investigate strength- and position-dependence of its spectrum.Comment: presented in the int. conference "Pseudo-Hermitian Hamiltonians in Quantum Physics III" (Instanbul, Koc University, June 20 - 22, 2005). accepted in Czechoslovak J. Phy

Magnonic Charge Pumping via Spin-Orbit Coupling

The interplay between spin, charge, and orbital degrees of freedom has led to the development of spintronic devices like spin-torque oscillators, spin-logic devices, and spin-transfer torque magnetic random-access memories. In this development spin pumping, the process where pure spin-currents are generated from magnetisation precession, has proved to be a powerful method for probing spin physics and magnetisation dynamics. The effect originates from direct conversion of low energy quantised spin-waves in the magnet, known as magnons, into a flow of spins from the precessing magnet to adjacent normal metal leads. The spin-pumping phenomenon represents a convenient way to electrically detect magnetisation dynamics, however, precessing magnets have been limited so far to pump pure spin currents, which require a secondary spin-charge conversion element such as heavy metals with large spin Hall angle or multi-layer layouts to be detectable. Here, we report the experimental observation of charge pumping in which a precessing ferromagnet pumps a charge current, demonstrating direct conversion of magnons into high-frequency currents via the relativistic spin-orbit interaction. The generated electric current, differently from spin currents generated by spin-pumping, can be directly detected without the need of any additional spin to charge conversion mechanism and amplitude and phase information about the relativistic current-driven magnetisation dynamics. The charge-pumping phenomenon is generic and gives a deeper understanding of the recently observed spin-orbit torques, of which it is the reciprocal effect and which currently attract interest for their potential in manipulating magnetic information. Furthermore, charge pumping provides a novel link between magnetism and electricity and may find application in sourcing alternating electric currents.Comment: 3 figure

Morphological and ophthalmoscopic features of epiretinal membranes after intravitreal injection of various doses of aflibercept in patients with proliferative diabetic retinopathy

Background: Although methods are available to treat proliferative diabetic retinopathy (PDR), 30% of cases progress, which is an indication for vitrectomy. Purpose: To investigate the ophthalmoscopic and morphological features of epiretinal membranes (ERMs) in patients with PDR depending on the dose of preoperative intravitreal aflibercept (PIA). Material and Methods: Seventy-five patients (75 eyes) with PDR and the presence of fibrovascular ERM with a marked proliferative component were involved in the study. Patients were divided into three groups: eyes of group 1 or control group (31 eyes) received vitrectomy without PIA; group 2 (17 eyes), PIA 1.0 mg; and group 3 (27 eyes), PIA 2.0 mg. We performed a histological study on specimens of fibrovascular ERMs surgically obtained from patients to determine the microscopic features of these membranes. Results: There was ophthalmoscopic and microscopic evidence that aflibercept pretreatment in vitrectomy for PDR resulted in fibrosis of the ERM. The extent of fibrosis of the ERM and obliteration of newly formed blood vessels in the ERM depended on the dose of PIA. Complete obliteration of newly formed blood vessels in the ERM was observed as early as day 3 after 2.0-mg intravitreal aflibercept injection compared to day 5 after 1.0-mg intravitreal aflibercept injection. Pretreatment with 1.0-mg intravitreal aflibercept in vitrectomy for PDR reduced the probability of complications associated with ERM contraction, worsening of the tractional component and the development of a retinal break

Bio-mining of Lanthanides from Red Mud by Green Microalgae

Red mud is a by-product of alumina production containing lanthanides. Growth of green microalgae on red mud and the intracellular accumulation of lanthanides was tested. The best growing species was Desmodesmus quadricauda (2.71 cell number doublings/day), which accumulated lanthanides to the highest level (27.3 mg/kg/day), if compared with Chlamydomonas reinhardtii and Parachlorella kessleri (2.50, 2.37 cell number doublings and 24.5, 12.5 mg/kg per day, respectively). With increasing concentrations of red mud, the growth rate decreased (2.71, 2.62, 2.43 cell number doublings/day) due to increased shadowing of cells by undissolved red mud particles. The accumulated lanthanide content, however, increased in the most efficient alga Desmodesmus quadricauda within 2 days from zero in red-mud free culture to 12.4, 39.0, 54.5 mg/kg of dry mass at red mud concentrations of 0.03, 0.05 and 0.1%, respectively. Red mud alleviated the metal starvation caused by cultivation in incomplete nutrient medium without added microelements. Moreover, the proportion of lanthanides in algae grown in red mud were about 250, 138, 117% higher than in culture grown in complete nutrient medium at red mud concentrations of 0.03, 0.05, 0.1%. Thus, green algae are prospective vehicles for bio-mining or bio-leaching of lanthanides from red mud

A survey of xerophilic Aspergillus from indoor environment, including descriptions of two new section Aspergillus species producing eurotium-like sexual states

Volume: 19Start Page: 1End Page: 3

Work incentive and other effects of social assistance and unemployment benefit policy in the Czech Republic

In this paper we provide an account of most of the passive labor market policies (unemployment compensation, social assistance, state social support and the pension system) in the Czech Republic during the 1990–1996 period. The eligibility requirements and benefit levels are described in great detail. Using Labor Force Survey data, we compare the characteristics of unemployed people receiving unemployment benefits with those receiving social assistance and those not receiving any benefits and we find significant differences in their characteristics. Finally, we provide an analysis of the work disincentive effects of the unemployment and social assistance benefits by comparing these benefits to market wages and by analyzing the effect of being in the system on the duration of unemployment of two cohorts of unemployed in 1994 and 1995. We find that social assistance benefits are fairly generous for low income families with more children, individuals with these characteristics have a higher probability of receiving social assistance and they tend to stay unemployed longer than those people with relatively fewer dependants. We conclude that the social assistance scheme seems to be having some disincentive effects for at least one group in the population.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45833/1/181_2005_Article_BF01205681.pd