185 research outputs found
Quantum Kolmogorov Complexity and Quantum Key Distribution
We discuss the Bennett-Brassard 1984 (BB84) quantum key distribution protocol
in the light of quantum algorithmic information. While Shannon's information
theory needs a probability to define a notion of information, algorithmic
information theory does not need it and can assign a notion of information to
an individual object. The program length necessary to describe an object,
Kolmogorov complexity, plays the most fundamental role in the theory. In the
context of algorithmic information theory, we formulate a security criterion
for the quantum key distribution by using the quantum Kolmogorov complexity
that was recently defined by Vit\'anyi. We show that a simple BB84 protocol
indeed distribute a binary sequence between Alice and Bob that looks almost
random for Eve with a probability exponentially close to 1.Comment: typos correcte
Strongly Incompatible Quantum Devices
The fact that there are quantum observables without a simultaneous
measurement is one of the fundamental characteristics of quantum mechanics. In
this work we expand the concept of joint measurability to all kinds of possible
measurement devices, and we call this relation compatibility. Two devices are
incompatible if they cannot be implemented as parts of a single measurement
setup. We introduce also a more stringent notion of incompatibility, strong
incompatibility. Both incompatibility and strong incompatibility are rigorously
characterized and their difference is demonstrated by examples.Comment: 27 pages (AMSart), 6 figure
Direct activation of NADPH oxidase 2 by 2-deoxyribose-1-phosphate triggers nuclear factor kappa B-dependent angiogenesis.
AbstractAims: Deoxyribose-1-phosphate (dRP) is a proangiogenic paracrine stimulus released by cancer cells, platelets, and macrophages and acting on endothelial cells. The objective of this study was to clarify how dRP stimulates angiogenic responses in human endothelial cells.Results: Live cell imaging, electron paramagnetic resonance, pull-down of dRP-interacting proteins, followed by immunoblotting, gene silencing of different NADPH oxidases (NOXs), and their regulatory cosubunits by small interfering RNA (siRNA) transfection, and experiments with inhibitors of the sugar transporter glucose transporter 1 (GLUT1) were utilized to demonstrate that dRP acts intracellularly by directly activating the endothelial NOX2 complex, but not NOX4. Increased reactive oxygen species generation in response to NOX2 activity leads to redox-dependent activation of the transcription factor nuclear factor kappa B (NF-κB), which, in turn, induces vascular endothelial growth factor receptor 2 (VEGFR2) upregulation. Using endothelial tube formation assays, gene silencing by siRNA, and antibody-based receptor inhibition, we demonstrate that the activation of NF-κB and VEGFR2 is necessary for the angiogenic responses elicited by dRP. The upregulation of VEGFR2 and NOX2-dependent stimulation of angiogenesis by dRP were confirmed in excisional wound and Matrigel plug vascularization assays in vivo using NOX2−/− mice.Innovation: For the first time, we demonstrate that dRP acts intracellularly and stimulates superoxide anion generation by direct binding and activation of the NOX2 enzymatic complex.Conclusions: This study describes a novel molecular mechanism underlying the proangiogenic activity of dRP, which involves the sequential activation of NOX2 and NF-κB and upregulation of VEGFR2. Antioxid. Redox Signal. 28, 110–130
Animal modelling for inherited central vision loss.
Disease-causing variants of a large number of genes trigger inherited retinal degeneration leading to photoreceptor loss. Because cones are essential for daylight and central vision such as reading, mobility, and face recognition, this review focuses on a variety of animal models for cone diseases. The pertinence of using these models to reveal genotype/phenotype correlations and to evaluate new therapeutic strategies is discussed. Interestingly, several large animal models recapitulate human diseases and can serve as a strong base from which to study the biology of disease and to assess the scale-up of new therapies. Examples of innovative approaches will be presented such as lentiviral-based transgenesis in pigs and adeno-associated virus (AAV)-gene transfer into the monkey eye to investigate the neural circuitry plasticity of the visual system. The models reported herein permit the exploration of common mechanisms that exist between different species and the identification and highlighting of pathways that may be specific to primates, including humans
Dynamical aspects of quantum entanglement for weakly coupled kicked tops
We investigate how the dynamical production of quantum entanglement for
weakly coupled, composite quantum systems is influenced by the chaotic dynamics
of the corresponding classical system, using coupled kicked tops. The linear
entropy for the subsystem (a kicked top) is employed as a measure of
entanglement. A perturbative formula for the entanglement production rate is
derived. The formula contains a correlation function that can be evaluated only
from the information of uncoupled tops. Using this expression and the
assumption that the correlation function decays exponentially which is
plausible for chaotic tops, it is shown that {\it the increment of the strength
of chaos does not enhance the production rate of entanglement} when the
coupling is weak enough and the subsystems (kicked tops) are strongly chaotic.
The result is confirmed by numerical experiments. The perturbative approach is
also applied to a weakly chaotic region, where tori and chaotic sea coexist in
the corresponding classical phase space, to reexamine a recent numerical study
that suggests an intimate relationship between the linear stability of the
corresponding classical trajectory and the entanglement production rate.Comment: 16 pages, 11 figures, submitted to Phys. Rev.
Exploration of 2-deoxy-D-ribose and 17β-Estradiol as alternatives to exogenous VEGF to promote angiogenesis in tissue-engineered constructs
Aim: In this study, we explored the angiogenic potential and proangiogenic concentration ranges of 2-deoxy-D-ribose (2dDR) and 17β-Estradiol (E2) in comparison with VEGF. The 2dDR and E2 were then loaded into tissue engineering (TE) scaffolds to investigate their proangiogenic potential when released from fibers. Materials & methods:Ex ovo chick chorioallantoic membrane (CAM) assay was used to evaluate angiogenic activity of 2dDR and E2. Both factors were then introduced into scaffolds via electrospinning to assess their angiogenic potential when released from fibers. Results: Both factors were approximately 80% as potent as VEGF and showed a dose-dependent angiogenic response. The sustained release of both agents from the scaffolds stimulated neovascularization over 7 days in the chorioallantoic membrane assay. Conclusion: We conclude that both 2dDR and E2 provide attractive alternatives to VEGF for the functionalization of tissue engineering scaffolds to promote angiogenesis in vivo
Relativity of quantum states and observables
Under the principle that quantum mechanical observables are invariant under relevant symmetry transformations, we explore how the usual, non-invariant quantities may capture measurement statistics. Using a relativisation mapping, viewed as the incorporation of a quantum reference frame, we show that the usual quantum description approximates the relative one precisely when the reference system admits an appropriate localisable quantity and a localised state. From this follows a new perspective on the nature and reality of quantum superpositions and optical coherence
Expression of the thymidine phosphorylase gene in epithelial ovarian cancer
Thymidine phosphorylase (TP) is associated with angiogenesis and the progression of solid tumours. High intracellular levels of this enzyme indicate increased chemosensitivity to pyrimidine antimetabolites. TP gene expression in 56 cases of epithelial ovarian cancer (27 of serous, 10 mucinous, 12 endometrioid, five clear cell and two undifferentiated) were analysed by polymerase chain reaction of RNA after reverse transcription. These included eight of low malignant potential. Twenty were stage I, four stage II, 27 stage III and five stage IV. The level of TP gene expression was presented by the relative yield of the TP gene to the β2-microglobulin gene. TP gene expression ranged from 0.19 to 5.38 (median 0.93). The value of TP gene expression in stage III–IV was significantly higher than that of TP gene expression in stage I–II (P = 0.0005). Histological grade significantly associated with TP gene expression (P = 0.008), but histological subtype did not (P = 0.166). A follow-up study of 34 cases after complete resection of the primary tumours by surgical operation was performed. TP gene expression of the cases with recurrence showed significantly higher levels compared to cases without recurrence (P = 0.049). Survival data were available for 47 of the 56 patients. The prognosis of the patients with high TP gene expression (equal to, or greater than, median) was to be significantly worse than patients with low TP gene expression (less than median) (P = 0.021). The TP gene expression level may play one of the key roles in the biology of ovarian epithelial cancer and define a more aggressive tumour phenotype. A new therapeutic intervention mediated by TP protein activity is anticipated. © 1999 Cancer Research Campaig
Nature versus nurture in two highly enantioselective esterases from Bacillus cereus and Thermoanaerobacter tengcongensis
There is an increasing need for the use of biocatalysis to obtain enantiopure compounds as chiral building blocks for drug synthesis such as antibiotics. The principal findings of this study are: i) the complete sequenced genomes of Bacillus cereus ATCC 14579 and Thermoanaerobacter tengcongensis MB4 contain a hitherto undescribed enantioselective and alkaliphilic esterase (BcEST and TtEST, respectively) that is specific for the production of (R)-2-benzyloxy-propionic acid ethyl ester, a key intermediate in the synthesis of levofloxacin, a potent antibiotic; and, ii) directed evolution targeted for increased thermostability of BcEST produced two improved variants, but in either case the 3 \u2013 5\ub0C increase in the apparent melting temperature (Tm) of the mutants over the native BcEST that has a Tm of 50\ub0C was outperformed by TtEST, a naturally-occurring homolog with a Tm of 65\ub0C. Protein modeling of BcEST mapped the S148C and K272R mutations at protein surface and the I88T and Q110L mutations at more buried locations. This work expands the repertoire of characterized members of the \u3b1/\u3b2 fold-hydrolase superfamily. Further, it shows that genome mining is an economical option for new biocatalyst discovery and we provide a rare example of a naturally-occurring thermostable biocatalyst that outperforms experimentally-evolved homologs that carry out the same hydrolysis.Peer reviewed: YesNRC publication: Ye
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