1,958 research outputs found
The future of information systems-using social systems to create protocols for the virtual environment (systems analysis through social analysis)
Information is the medium for communication, power-play, politics, and the building block for knowledge systems. It is associated with social interaction, and can be mediated by technology use. The paper argues that the key to understanding the impact of future technologies lies in the interaction between the social and technical environment. It suggests that future technologies such as virtual reality make necessary a move away from traditional methods of systems analysis and design. The interactive nature of such technology requires a validation in the social environment. The paper proposes the creation of protocols (a set of universally applicable standards) for the virtual environment. It suggests that information systems are split into three protocols: physical, learning, and cultural protocols. Finally it illustrates that their influence over each other can be understood by applying structuration theor
Systematic Survey of the Role of IGF in the Link Between Diabetes and Cancer
Epidemiological studies have proposed a link between type II diabetes and cancer via the IGF/insulin signaling pathway, which includes insulin-like peptides (IGF1, IGF2, and insulin), insulin receptors (IR-A, IR-B, IGF1R, and hybrids), and insulin substrate proteins (IRS1-6). In this study, up- and down-regulation of various components in the IGF/insulin signaling pathway are compared to clinical outcomes for cancer patients; the components include diagnosis age, overall survival, tumor invasion and vascularization, and body mass index. It was found that the up-regulation of insulin growth Factor (IGF)/insulin components was associated with overall survival and tumor invasion and vascularization, while the down-regulation of equivalent components was not associated with clinical outcomes assessed in this study. Particularly, the up-regulation of DOK5, IGF2, and IRS2 in colorectal cancer and IGF1R in liver cancer is associated with significantly decreased overall survival. Functional aberrations in either of the two proteins in co-expression pairs were identified for each cancer and correlated with overall survival and diagnosis age. Specific biomarkers proposed in this study will be further analyzed to fine-tune consistent associations that can be translated to reliable prognostic standards for the roles of IGF/insulin signaling pathway modulations that promote cancer
A mathematical model of the maximum power density attainable in an alkaline hydrogen/oxygen fuel cell
A mathematical model of a hydrogen/oxygen alkaline fuel cell is presented that can be used to predict the polarization behavior under various power loads. The major limitations to achieving high power densities are indicated and methods to increase the maximum attainable power density are suggested. The alkaline fuel cell model describes the phenomena occurring in the solid, liquid, and gaseous phases of the anode, separator, and cathode regions based on porous electrode theory applied to three phases. Fundamental equations of chemical engineering that describe conservation of mass and charge, species transport, and kinetic phenomena are used to develop the model by treating all phases as a homogeneous continuum
Evaluation of heating effects on atoms trapped in an optical trap
We solve a stochastic master equation based on the theory of Savard et al. [T. A. Savard. K. M. O'Hara, and J. E. Thomas, Phys, Rev. A 56, R1095 (1997)] for heating arising from fluctuations in the trapping laser intensity. We compare with recent experiments of Ye et al. [J. Ye, D. W. Vernooy, and H. J. Kimble, Phys. Rev. Lett. 83, 4987 (1999)], and find good agreement with the experimental measurements of the distribution of trap occupancy times. The major cause of trap loss arises from the broadening of the energy distribution of the trapped atom, rather than the mean heating rate, which is a very much smaller effect
A review of factors affecting the success of membrane protein crystallization using bicelles
Author's manuscript made available in accordance with the publisher's policy.Several reports have been published detailing various platforms for obtaining crystals of membrane proteins to determine their structure including those that use disk shaped bilayers called bicelles. While these crystals have been readily grown and used for x-ray diffraction, the general understanding as to why bicelles are adequate for such a procedure or how to rationally choose conditions remains unknown. This review intends to discuss issues of protein stabilization and precipitation in the presence of lipids that may influence crystal formation
Temporal Dynamics of Photon Pairs Generated by an Atomic Ensemble
The time dependence of nonclassical correlations is investigated for two
fields (1,2) generated by an ensemble of cold Cesium atoms via the protocol of
Duan et al. [Nature Vol. 414, p. 413 (2001)]. The correlation function R(t1,t2)
for the ratio of cross to auto-correlations for the (1,2) fields at times
(t1,t2) is found to have a maximum value Rmax=292(+-)57, which significantly
violates the Cauchy-Schwarz inequality R<=1 for classical fields. Decoherence
of quantum correlations is observed over 175 ns, and is described by our model,
as is a new scheme to mitigate this effect.Comment: 5 pages, 5 figure
Loss-resistant state teleportation and entanglement swapping using a quantum-dot spin in an optical microcavity
We present a scheme for efficient state teleportation and entanglement
swapping using a single quantum-dot spin in an optical microcavity based on
giant circular birefringence. State teleportation or entanglement swapping is
heralded by the sequential detection of two photons, and is finished after the
spin measurement. The spin-cavity unit works as a complete Bell-state analyzer
with a built-in spin memory allowing loss-resistant repeater operation. This
device can work in both the weak coupling and the strong coupling regime, but
high efficiencies and high fidelities are only achievable when the side leakage
and cavity loss is low. We assess the feasibility of this device, and show it
can be implemented with current technology. We also propose a spin manipulation
method using single photons, which could be used to preserve the spin coherence
via spin echo techniques.Comment: The manuscript is extended, including BSA fidelity, efficiency, and a
compatible scheme for spin manipulations and spin echoes to prolong the spin
coherenc
Quantum Spin Dynamics with Pairwise-Tunable, Long-Range Interactions
We present a platform for the simulation of quantum magnetism with full
control of interactions between pairs of spins at arbitrary distances in one-
and two-dimensional lattices. In our scheme, two internal atomic states
represent a pseudo-spin for atoms trapped within a photonic crystal waveguide
(PCW). With the atomic transition frequency aligned inside a band gap of the
PCW, virtual photons mediate coherent spin-spin interactions between lattice
sites. To obtain full control of interaction coefficients at arbitrary
atom-atom separations, ground-state energy shifts are introduced as a function
of distance across the PCW. In conjunction with auxiliary pump fields,
spin-exchange versus atom-atom separation can be engineered with arbitrary
magnitude and phase, and arranged to introduce non-trivial Berry phases in the
spin lattice, thus opening new avenues for realizing novel topological spin
models. We illustrate the broad applicability of our scheme by explicit
construction for several well known spin models.Comment: 18 pages, 10 figure
Quantum state transfer between motion and light
We describe schemes for transferring quantum states between light fields and
the motion of a trapped atom. Coupling between the motion and the light is
achieved via Raman transitions driven by a laser field and the quantized field
of a high-finesse microscopic cavity mode. By cascading two such systems and
tailoring laser field pulses, we show that it is possible to transfer an
arbitrary motional state of one atom to a second atom at a spatially distant
site.Comment: 10 pages, RevTex, 6 figures, to appear in Journal of Optics B:
Quantum and Semiclassical Optic
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