Analysis of Wavelength-Routed Optical Burst-Switched Network Performance

This paper studies a novel scalable network architecture combining optical burst switching (OBS) with dynamic wavelength allocation to guarantee quality of service (QoS), forming a wavelength-routed optical burst-switched network. All processing and buffering functions are concentrated at the network edge and bursts are assigned to fast tuneable lasers and routed over a bufferless optical transport core using dynamic wavelength assignment. Different burst aggregation mechanisms are evaluated for a range of traffic statistics in terms of delay and packet loss rate. New network performance parameters in an analytical model quantify the advantages of dynamic wavelength allocation. The results define the operational gain achievable with dynamic wavelength assignment compared to quasi-static wavelength routed optical networks.     

The Role of Single-Nucleotide Variants of NOS1, NOS2, and NOS3 Genes in the Comorbidity of Arterial Hypertension and Tension-Type Headache

Patients with tension-type headache (TTH) have an increased risk of developing arterial hypertension (AH), while hypertensive subjects do seem to have an increased risk of TTH. We searched for full-text English publications in databases using keywords and combined word searches over the past 15 years. In addition, earlier publications of historical interest were included in the review. In our review, we summed up the single nucleotide variants (SNVs) of Nitric Oxide Synthases (NOSs) genes involved in the development of essential AH and TTH. The results of studies we discussed in this review are contradictory. This might be due to different designs of the studies, small sample sizes in some of them, as well as different social and geographical characteristics. However, the contribution of genetic and environmental factors remains understudied. This makes the issue interesting for researchers, as understanding these mechanisms can contribute to a search for new approaches to pathogenetic and disease-modifying treatment of the AH and TTH phenotype. New drugs against AH and TTH can be based on inhibition of nitric oxide (NO) production, blockade of steps in the NO-cGMP pathway, or NO scavenging. Indeed, selective neuronal NOS (n-NOS) and inducible NOS (i-NOS) inhibitors are already in early clinical development.     

Human Lanosterol 14-Alpha Demethylase (CYP51A1) Is a Putative Target for Natural Flavonoid Luteolin 7,3′-Disulfate

Widespread pathologies such as atherosclerosis, metabolic syndrome and cancer are associated with dysregulation of sterol biosynthesis and metabolism. Cholesterol modulates the signaling pathways of neoplastic transformation and tumor progression. Lanosterol 14-alpha demethylase (cytochrome P450(51), CYP51A1) catalyzes one of the key steps in cholesterol biosynthesis. The fairly low somatic mutation frequency of CYP51A1, its druggability, as well as the possibility of interfering with cholesterol metabolism in cancer cells collectively suggest the clinical importance of CYP51A1. Here, we show that the natural flavonoid, luteolin 7,3′-disulfate, inhibits CYP51A1 activity. We also screened baicalein and luteolin, known to have antitumor activities and low toxicity, for their ability to interact with CYP51A1. The K_d values were estimated using both a surface plasmon resonance optical biosensor and spectral titration assays. Unexpectedly, in the enzymatic activity assays, only the water-soluble form of luteolin—luteolin 7,3′-disulfate—showed the ability to potently inhibit CYP51A1. Based on molecular docking, luteolin 7,3′-disulfate binding suggests blocking of the substrate access channel. However, an alternative site on the proximal surface where the redox partner binds cannot be excluded. Overall, flavonoids have the potential to inhibit the activity of human CYP51A1 and should be further explored for their cholesterol-lowering and anti-cancer activity.     

Essential oil of Nepeta x faassenii Bergmans ex Stearn (N. mussinii Spreng. x N. nepetella L.): a comparison study

Analysis (GC and GC/MS) of an essential oil sample obtained from dry leaves of Nepeta x faassenii Bergmans ex Steam, a hybrid species produced by crossbreeding N. mussinii Spreng. with N. nepetella L., led to the identification of 109 constituents that represented 95.9% of the oil. The major constituents were 4aalpha,7alpha,7aalpha-nepetalactone (67.8%), 1,8-cineole (6.6%), germacrene D (4.8%), beta-pinene (2.7%), (E)-beta-ocimene (2.6%), 4aalpha,7beta,7aalpha-nepetalactone (2.3%) and (E)-beta-farnesene (1.0%). Chemical composition of the oil was compared, using multivariate statistical analyses (MVA) with those of the oils of other Nepeta taxa, in particular N. mussinii and N. nepetella. This was done in order to explore the mode of inheritance of the monoterpene biosynthetic apparatus of N. faassenii. Chemical composition of the volatiles of a Nepeta taxon (different populations) can be subject to variation due to environmental and geographical factors. To accommodate this fact in the MVAs, along side with N. faassenii essential oil, additional 6 oils (3 different populations of N. nuda L. and N. cataria L. from Serbia) were included in this study (isolated and analyzed (chemically and statistically)). The MVA analyses recognized N. faassenii as being closely related to both N. mussinii and N. nepetella. If the relative content of oil constituents per plant and not per chromatogram were used as variables in the MVA (this was done by simple multiplication of the yields and relative percentages of components) a higher degree of mutual similarity (in respect to the monoterpene biosynthesis) of N. faassenii to N. mussinii, than to the other parent species, was observed.     

Phenyl α-bromovinyl sulfone in cycloadditions with azomethine ylides: an unexpected facile aromatization of the cycloadducts into pyrroles

Phenyl α-bromovinyl sulfone reacts with glycine ester Schiff bases regioselectively in the presence of catalytic amounts of AgOAc and DBU yielding polysubstituted pyrrolidine cycloadducts. Utilization of excess DBU induces subsequent facile aromatization of the cycloadducts and affords 5-arylpyrrole-2-carboxylic acid esters in 39-85% yields in a single step.     

Interval optimal control problem in a Hilbert space

An optimal control problem for a system involving an interval parameter is considered. The concepts of a universal optimal state and a universal optimal control are introduced. The existence and uniqueness of a universal solution to the interval optimal control problem is proved, and an algorithm for its determination is presented. The interval optimal control problem for a system described by the boundary value problem for a second-order ordinary differential equation is solved as an example.     

Role of ambient gas in heating of metal samples by femtosecond pulses of laser radiation

In this work we consider an experimentally observed effect of significant increasing of the residual heat in metal targets at their irradiation with femtosecond laser pulses in an ambient gas in respect to the vacuum conditions. Numerical modelling of heating of a platinum target by femtosecond laser pulses in argon under normal conditions has been performed taking into account gas breakdown in the focussing region of the laser beam in front of the target. The applied model is based on a combination of a thermal model describing heating and phase transitions in irradiated samples and a hydrodynamic model to describe motion of the ambient gas perturbed by laser irradiation as a result of multiphoton ionization. The hot ambient gas is shown to heat efficiently the irradiated sample. The hydrodynamic processes in the ambient gas play an important role in heating. This work was financially supported by the Russian Foundation for Basic Research (Project 08-01-00264-a) and the INTAS/SB RAS Program (Project 06-1000013-8949).     

Direct formylation of 2-pyridone core of 3-N-methylcytisine via Duff reaction; synthesis of 9-enyl, 9-ynyl and 9-imino derivatives

The first direct synthesis of 3-N-methyl-9-formylcytisine via electrophylic formylation is described. It is established, that Vilsmeier-Haack and Gatterman variants of this reaction are unsuccessful in the case with 3-substituted (-)-cytisine derivatives, but Duff procedure (with hexamethylenetetramine in trifluoroacetic acid) gives a possibility to obtain the target pseudo aromatic aldehyde with the 69% yield. Convenient precursors for [4 + 2]- or [3 + 2]-cycloaddition reactions are obtained by means of condensation of synthesized 3-N-methyl-9-formylcytisine with acetone, nitromethane and phosphorous ylides with yields from 70 to 87%. Alternative aprroach to alkenyl products and to 9-alkynyl-3-methylcytisine is realized using the Heck and Sonogashira cross-coupling reactions of methyl vinyl ketone, cyclohexenone or trimethylsilylacetylene with 9-bromo-3-methylcytisine (55, 70 and 60% accordingly). It is shown, that interaction of 3-N-methyl-9-formylcytisine with hydroxylamines leads to corresponding nitrone (93%) and oxime (70%). All individual compounds are isolated by column chromatography and completely characterized on the basis of NMR spectroscopy data.