Prolactin stimulation of tyrosyl phosphorylation of Shc proteins in Nb2 lymphoma cells, but not mammary tissues

AbstractProlactin (PRL) stimulates lactogenesis in mammary cells and mitogenesis in a variety of cell types including Nb2 cells. Studies indicate that a different composite of signaling pathways is involved in the PRL stimulation of mitogenesis as compared to lactogenesis. In the present studies, PRL is shown to stimulate the tyrosyl phosphorylation of all three isoforms of Shc proteins in Nb2 cells (mitogenesis), but not in the mammary gland. Maximal phosphorylation of the Shc proteins is expressed between 10 and 15 min after a 50-ng/ml PRL treatment. In addition, there is an increased association between the Grb2 protein and Shc proteins upon PRL stimulation. However, no increased association between JAK2 and Shc proteins was observed in either the Nb2 cells or mammary tissues

Strength enhancement of aluminium honeycombs caused by entrapped air underdynamic out-of-plane compression

The out-of-plane crushing behaviour of aluminium hexagonal honeycombs containing different percentages of holes (i.e., the fraction of penetrated cells to the total) was extensively investigated over a wide range of strain rates where each test was conducted at constant compression velocity. Strength enhancement due to the increase of the strain rate and the entrapped air was studied. It is found that the strain hardening of honeycomb structures during the dynamic crush is mostly attributed to the pressure change caused by the entrapped air. The leaking rate, δ̇, was then studied and found to be dependent on the strain and strain rate, and independent of the wall thickness to edge length ratio, t/l. An empirical constitutive relation describing the plastic collapse stress in relation to the t/l ratio, the strain and strain rate is proposed, which agrees well with the experimental results. © 2012 Elsevier Ltd. All rights reserved.S. Xu, J.H. Beynon, D. Ruan, T.X. Y

Precision Measurement of the Proton Flux in Primary Cosmic Rays from Rigidity 1 GV to 1.8 TV with the Alpha Magnetic Spectrometer on the International Space Station

A precise measurement of the proton flux in primary cosmic rays with rigidity (momentum/charge) from 1 GV to 1.8 TV is presented based on 300 million events. Knowledge of the rigidity dependence of the proton flux is important in understanding the origin, acceleration, and propagation of cosmic rays. We present the detailed variation with rigidity of the flux spectral index for the first time. The spectral index progressively hardens at high rigidities.</p

Dynamic behavior of a semi-infinite elastic hardening-softening beam subjected to a pulse loading

The dynamic response of a semi-infinite elastic hardening-softening beam subjected to a suddenly applied moment and a transverse pulse loading at its tip, with the magnitude being inversely proportional to the square root of time, is analyzed. Four different deformation modes are identified. The numerical results demonstrate that in one of these modes, a finite softening region exists and propagates along the beam

Use of high-efficiency energy absorbing device to arrest progressive collapse of tall building

The World Trade Center collapse has brought attention to progressive collapse of tall buildings and the study of possible countermeasures. From the viewpoint of energy transfer, this analysis explains why the collapse could not stop by itself once began. By introducing a design parameter called collapse stability index that controls design against progressive collapse, it is found that conventional design of a tall building usually leads to an inherently unstable structure in the event of a progressive collapse. In a subsequent feasibility study in this paper, a heavy-duty metal-based honeycomb energy absorbing structure is proposed. Using a finite element analysis, it is demonstrated that the structure is capable of absorbing potential energy released in a tall building collapse. The added energy absorbing devices will only occupy a small percentage of the total floor space. By properly designing and installing such devices, a progressive collapse, should it happen in a tall building, may be arrested within a few floors, and hence, the building is inherently stable to the progressive collapse. The theory is also elaborated with the example of the World Trade Center collapse

Deformation mechanism and defect sensitivity of notched Free-free beam and cantilever beam under impact

This paper studies the dynamic behavior of pre-notched free-free beam and pre-notched cantilever beam subjected to step loading at a free end, as typical structures with defects. Special attention is paid to the deformation mechanism and the defect sensitivity in the plastic energy dissipation. By employing the rigid, perfectly plastic material idealization, complete solutions are obtained for combinations of the notch size, notch position and the magnitude of load. Apart from a one-hinge mode, two- and three-hinge modes are observed and analyzed. It is revealed that the first hinge, which is the one closest to the loading point, dissipates most of the input energy. If the first hinge forms at the notched section, the energy dissipation is highly sensitive to the notch; otherwise, it is insensitive. It is also noted that when the load increases, the defect sensitive region shrinks to a narrower region close to the loading point, indicating that under a large load, the notch may affect the energy dissipation remarkably, only if it is very close to the loading point. To reveal the interaction between the traveling hinges and the notched section, a pre-notched cantilever beam subjected to a rigid striker on its free end is analyzed. It is found that for a heavy striker, the stationary hinge either on the root or on the notched section dissipates most of energy and only when the notched section is sufficiently close to the impact point, the traveling hinge can move across the notch, indicating that the energy dissipation is insensitive to the notch. However, for a very light striker, the defect sensitivity is influenced by the traveling distance of the hinge and the deformation mechanism in the modal phase. (C) 2002 Elsevier Science Ltd. All rights reserved