4,091 research outputs found
The oncolytic activity of Newcastle disease virus in clear cell renal carcinoma cells in normoxic and hypoxic conditions: the interplay between von Hippel-Lindau and interferon-β signaling
Viral-mediated oncolysis is a promising cancer therapeutic approach offering an increased efficacy with less toxicity than the current therapies. The complexity of solid tumor microenvironments includes regions of hypoxia. In these regions, the transcription factor, hypoxia inducible factor (HIF), is active and regulates expression of many genes that contribute to aggressive malignancy, radio-, and chemo-resistance. To investigate the oncolytic efficacy of a highly virulent (velogenic) Newcastle disease virus (NDV) in the presence or absence of HIF-2α, renal cell carcinoma (RCC) cell lines with defective or reconstituted wild-type (wt) von Hippel-Lindau (VHL) activity were used. We show that these RCC cells responded to NDV by producing only interferon (IFN)-β, but not IFN-α, and are associated with increased STAT1 phosphorylation. Restoration of wt VHL expression enhanced NDV-induced IFN-β production, leading to prolonged STAT1 phosphorylation and increased cell death. Hypoxia augmented NDV oncolytic activity regardless of the cells' HIF-2α levels. These results highlight the potential of oncolytic NDV as a potent therapeutic agent in the killing of hypoxic cancer cells
Magnetic field generation in finite beam plasma system
For finite systems boundaries can introduce remarkable novel features. A well
known example is the Casimir effect [1, 2] that is observed in quantum
electrodynamic systems. In classical systems too novel effects associated with
finite boundaries have been observed, for example the surface plasmon mode [3]
that appears when the plasma has a finite extension. In this work a novel
instability associated with the finite transverse size of a beam owing through
a plasma system has been shown to exist. This instability leads to distinct
characteristic features of the associated magnetic field that gets generated.
For example, in contrast to the well known unstable Weibel mode of a beam
plasma system which generates magnetic field at the skin depth scale, this
instability generates magnetic field at the scales length of the transverse
beam dimension [4]. The existence of this new instability is demonstrated by
analytical arguments and by simulations conducted with the help of a variety of
Particle - In - Cell (PIC) codes (e.g. OSIRIS, EPOCH, PICPSI). Two fluid
simulations have also been conducted which confirm the observations.
Furthermore, laboratory experiments on laser plasma system also provides
evidence of such an instability mechanism at work
Performance Limits of Stochastic Sub-Gradient Learning, Part II: Multi-Agent Case
The analysis in Part I revealed interesting properties for subgradient
learning algorithms in the context of stochastic optimization when gradient
noise is present. These algorithms are used when the risk functions are
non-smooth and involve non-differentiable components. They have been long
recognized as being slow converging methods. However, it was revealed in Part I
that the rate of convergence becomes linear for stochastic optimization
problems, with the error iterate converging at an exponential rate
to within an neighborhood of the optimizer, for some and small step-size . The conclusion was established under weaker
assumptions than the prior literature and, moreover, several important problems
(such as LASSO, SVM, and Total Variation) were shown to satisfy these weaker
assumptions automatically (but not the previously used conditions from the
literature). These results revealed that sub-gradient learning methods have
more favorable behavior than originally thought when used to enable continuous
adaptation and learning. The results of Part I were exclusive to single-agent
adaptation. The purpose of the current Part II is to examine the implications
of these discoveries when a collection of networked agents employs subgradient
learning as their cooperative mechanism. The analysis will show that, despite
the coupled dynamics that arises in a networked scenario, the agents are still
able to attain linear convergence in the stochastic case; they are also able to
reach agreement within of the optimizer
Solar wind collisional heating
To properly describe heating in weakly collisional turbulent plasmas such as
the solar wind, inter-particle collisions should be taken into account.
Collisions can convert ordered energy into heat by means of irreversible
relaxation towards the thermal equilibrium. Recently, Pezzi et al. (Phys. Rev.
Lett., vol. 116, 2016, p. 145001) showed that the plasma collisionality is
enhanced by the presence of fine structures in velocity space. Here, the
analysis is extended by directly comparing the effects of the fully nonlinear
Landau operator and a linearized Landau operator. By focusing on the relaxation
towards the equilibrium of an out of equilibrium distribution function in a
homogeneous force-free plasma, here it is pointed out that it is significant to
retain nonlinearities in the collisional operator to quantify the importance of
collisional effects. Although the presence of several characteristic times
associated with the dissipation of different phase space structures is
recovered in both the cases of the nonlinear and the linearized operators, the
influence of these times is different in the two cases. In the linearized
operator case, the recovered characteristic times are systematically larger
than in the fully nonlinear operator case, this suggesting that fine velocity
structures are dissipated slower if nonlinearities are neglected in the
collisional operator
Locus model for space-time fabric and quantum indeterminacies
A simple locus model for the space-time fabric is presented and is compared
with quantum foam and random walk models. The induced indeterminacies in
momentum are calculated and it is shown that these space-time fabric
indeterminacies are, in most cases, negligible compared with the quantum
mechanical indeterminacies. This result restricts the possibilities of an
experimental observation of the space-time fabric
Some Remarks about the Complexity of Epidemics Management
Recent outbreaks of Ebola, H1N1 and other infectious diseases have shown that
the assumptions underlying the established theory of epidemics management are
too idealistic. For an improvement of procedures and organizations involved in
fighting epidemics, extended models of epidemics management are required. The
necessary extensions consist in a representation of the management loop and the
potential frictions influencing the loop. The effects of the non-deterministic
frictions can be taken into account by including the measures of robustness and
risk in the assessment of management options. Thus, besides of the increased
structural complexity resulting from the model extensions, the computational
complexity of the task of epidemics management - interpreted as an optimization
problem - is increased as well. This is a serious obstacle for analyzing the
model and may require an additional pre-processing enabling a simplification of
the analysis process. The paper closes with an outlook discussing some
forthcoming problems
Ferromagnetic and insulating behavior of LaCoO3 films grown on a (001) SrTiO3 substrate. A simple ionic picture explained ab initio
This paper shows that the oxygen vacancies observed experimentally in thin
films of LaCoO3 subject to tensile strain are thermodynamically stable
according to ab initio calculations. By using DFT calculations, we show that
oxygen vacancies on the order of 6 % forming chains perpendicular to the (001)
direction are more stable than the stoichiometric solution. These lead to
magnetic Co2+ ions surrounding the vacancies that couple ferromagnetically. The
remaining Co3+ cations in an octahedral environment are non magnetic. The gap
leading to a ferromagnetic insulating phase occurs naturally and we provide a
simple ionic picture to explain the resulting electronic structure.Comment: 7 pages, 7 figure
Wave-like Decoding of Tail-biting Spatially Coupled LDPC Codes Through Iterative Demapping
For finite coupling lengths, terminated spatially coupled low-density
parity-check (SC-LDPC) codes show a non-negligible rate-loss. In this paper, we
investigate if this rate loss can be mitigated by tail-biting SC-LDPC codes in
conjunction with iterative demapping of higher order modulation formats.
Therefore, we examine the BP threshold of different coupled and uncoupled
ensembles. A comparison between the decoding thresholds approximated by EXIT
charts and the density evolution results of the coupled and uncoupled ensemble
is given. We investigate the effect and potential of different labelings for
such a set-up using per-bit EXIT curves, and exemplify the method for a 16-QAM
system, e.g., using set partitioning labelings. A hybrid mapping is proposed,
where different sub-blocks use different labelings in order to further optimize
the decoding thresholds of tail-biting codes, while the computational
complexity overhead through iterative demapping remains small.Comment: presentat at the International Symposium on Turbo Codes & Iterative
Information Processing (ISTC), Brest, Sept. 201
Simulation Theorems via Pseudorandom Properties
We generalize the deterministic simulation theorem of Raz and McKenzie
[RM99], to any gadget which satisfies certain hitting property. We prove that
inner-product and gap-Hamming satisfy this property, and as a corollary we
obtain deterministic simulation theorem for these gadgets, where the gadget's
input-size is logarithmic in the input-size of the outer function. This answers
an open question posed by G\"{o}\"{o}s, Pitassi and Watson [GPW15]. Our result
also implies the previous results for the Indexing gadget, with better
parameters than was previously known. A preliminary version of the results
obtained in this work appeared in [CKL+17]
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