436 research outputs found
Role of insulin-like growth factor binding protein-3 in 1, 25-dihydroxyvitamin-d 3 -induced breast cancer cell apoptosis.
Insulin-like growth factor I (IGF-I) is implicated in breast cancer development and 1, 25-dihydroxyvitamin D3 (1, 25-D3) has been shown to attenuate prosurvival effects of IGF-I on breast cancer cells. In this study the role of IGF binding protein-3 (IGFBP-3) in 1, 25-D3-induced apoptosis was investigated using parental MCF-7 breast cancer cells and MCF-7/VD(R) cells, which are resistant to the growth inhibitory effects of 1, 25-D3. Treatment with 1, 25-D3 increased IGFBP-3 mRNA expression in both cell lines but increases in intracellular IGFBP-3 protein and its secretion were observed only in MCF-7. 1, 25-D3-induced apoptosis was not associated with activation of any caspase but PARP-1 cleavage was detected in parental cells. IGFBP-3 treatment alone produced cleavage of caspases 7, 8, and 9 and PARP-1 in MCF-7 cells. IGFBP-3 failed to activate caspases in MCF-7/VD(R) cells; however PARP-1 cleavage was detected. 1, 25-D3 treatment inhibited IGF-I/Akt survival signalling in MCF-7 but not in MCF-7/VD(R) cells. In contrast, IGFBP-3 treatment was effective in inhibiting IGF-I/Akt pathways in both breast cancer lines. These results suggest a role for IGFBP-3 in 1, 25-D3 apoptotic signalling and that impaired secretion of IGFBP-3 may be involved in acquired resistance to vitamin D in breast cancer
First-principles calculations for the adsorption of water molecules on the Cu(100) surface
First-principles density-functional theory and supercell models are employed
to calculate the adsorption of water molecules on the Cu(100) surface. In
agreement with the experimental observations, the calculations show that a H2O
molecule prefers to bond at a one-fold on-top (T1) surface site with a tilted
geometry. At low temperatures, rotational diffusion of the molecular axis of
the water molecules around the surface normal is predicted to occur at much
higher rates than lateral diffusion of the molecules. In addition, the
calculated binding energy of an adsorbed water molecule on the surfaces is
significantly smaller than the water sublimation energy, indicating a tendency
for the formation of water clusters on the Cu(100) surface.Comment: 5 pages, 3 figures, submitted to Phys. Rev.
HRM inside UK e-commerce firms : innovations in the ‘new’ economy and continuities with the ‘old’
The e-commerce approach to people management (i.e. HRM) is popularly believed to be radically new and an innovative rewriting of the ‘old’ rules of employment. Yet little is known about which HR practices are used by such companies, and what might explain these companies’ policy selections in the realm of HR. Exploratory survey data based on a sample of 30 small-medium UK e-commerce firms reports use of employee involvement in decision-making, internal communication, financial participation and reward schemes, performance evaluation, training and provision for employment security. Insights from interviews with five senior managers from the sample augment the survey data with qualitative evidence on e-commerce firms’ approach to HR. The findings suggest that this approach falls somewhere between radical ‘new’ innovations and enduring continuities with ‘old’ people management techniques, and that this has parallels with the experience of small-medium enterprises generally
Assessing the Polarization of a Quantum Field from Stokes Fluctuation
We propose an operational degree of polarization in terms of the variance of
the projected Stokes vector minimized over all the directions of the Poincar\'e
sphere. We examine the properties of this degree and show that some problems
associated with the standard definition are avoided. The new degree of
polarization is experimentally determined using two examples: a bright squeezed
state and a quadrature squeezed vacuum.Comment: 4 pages, 2 figures. Comments welcome
Maximally polarized states for quantum light fields
The degree of polarization of a quantum state can be defined as its
Hilbert-Schmidt distance to the set of unpolarized states. We demonstrate that
the states optimizing this degree for a fixed average number of photons
present a fairly symmetric, parabolic photon statistics, with a
variance scaling as . Although no standard optical process yields
such a statistics, we show that, to an excellent approximation, a highly
squeezed vacuum can be considered as maximally polarized.Comment: 4 pages, 3 eps-color figure
"Which-path information" and partial polarization in single-photon interference experiments
It is shown that the degree of polarization of light, generated by
superposition in a single-photon interference experiment, may depend on the
indistinguishability of the photon-paths.Comment: 9 page
An insight into polarization states of solid-state organic lasers
The polarization states of lasers are crucial issues both for practical
applications and fundamental research. In general, they depend in a combined
manner on the properties of the gain material and on the structure of the
electromagnetic modes. In this paper, we address this issue in the case of
solid-state organic lasers, a technology which enables to vary independently
gain and mode properties. Different kinds of resonators are investigated:
in-plane micro-resonators with Fabry-Perot, square, pentagon, stadium, disk,
and kite shapes, and external vertical resonators. The degree of polarization P
is measured in each case. It is shown that although TE modes prevail generally
(P>0), kite-shaped micro-laser generates negative values for P, i.e. a flip of
the dominant polarization which becomes mostly TM polarized. We at last
investigated two degrees of freedom that are available to tailor the
polarization of organic lasers, in addition to the pump polarization and the
resonator geometry: upon using resonant energy transfer (RET) or upon pumping
the laser dye to an higher excited state. We then demonstrate that
significantly lower P factors can be obtained.Comment: 12 pages, 12 figure
A study of random resistor-capacitor-diode networks to assess the electromagnetic properties of carbon nanotube filled polymers
We determined the frequency dependent effective permittivity of a large
ternary network of randomly positioned resistors, capacitors, and diodes. A
linear circuit analysis of such systems is shown to match the experimental
dielectric response of single-walled carbon nanotube (SWCNT) filled polymers.
This modeling method is able to reproduce the two most important features of
SWCNT filled composites, i.e. the low frequency dispersion and dipolar
relaxation. As a result of the modeling important physical conclusion proved by
the experimental data was done: the low frequency behavior of SWCNT-filled
polymer composites is mostly caused by the fraction of semiconducting SWCNTs
- …