State and parameter estimation approach to monitoring AGR nuclear core

This work concerns with the problem of monitoring an Advanced Gas-cooled Nuclear Reactor (AGR) core. This plant (figure 1) makes use of the heat given by the nuclear efficient reaction to produce electricity by means of steam turbines. These are driven by steam, which is heated, from the AGR gas using a heat exchanger. One of the advantages of a gas cooled reactor is the high temperature that the gas can achieve so that when it is used in conjunction with the heat exchanger and steamed turbine the thermal efficiency is very high

Condition monitoring of an advanced gas-cooled nuclear reactor core

A critical component of an advanced gas-cooled reactor station is the graphite core. As a station ages, the graphite bricks that comprise the core can distort and may eventually crack. Since the core cannot be replaced, the core integrity ultimately determines the station life. Monitoring these distortions is usually restricted to the routine outages, which occur every few years, as this is the only time that the reactor core can be accessed by external sensing equipment. This paper presents a monitoring module based on model-based techniques using measurements obtained during the refuelling process. A fault detection and isolation filter based on unknown input observer techniques is developed. The role of this filter is to estimate the friction force produced by the interaction between the wall of the fuel channel and the fuel assembly supporting brushes. This allows an estimate to be made of the shape of the graphite bricks that comprise the core and, therefore, to monitor any distortion on them

Merging C-C σ-bond activation of cyclobutanones with CO2 fixation via Ni-catalysis

A carboxylative Ni-catalyzed tandem C-C σ-bond activation of cyclobutanones followed by CO2-electrophilic trapping is documented as a direct route to synthetically valuable 3-indanone-1-acetic acids. The protocol shows an adequate functional group tolerance and useful chemical outcomes (yield up to 76%) when AlCl3 is adopted as an additive. Manipulations of the targeted cyclic scaffolds and a mechanistic proposal based on experimental evidence complete the investigation

C-N coupling between µ-aminocarbyne and nitrile ligands promoted by tolylacetylide addition to [Fe2CN(Me)(Xyl)}(CO)(CO)(NCCMe3)(Cp)2][SO3CF3]: formation of a novel bridging allene-diaminocarbene ligand

The reaction of the mu-aminocarbyne complex [Fe-2{mu-CN(Me)(Xyl)}(mu-CO)(CO)(NCCMe3)(CP)(2)][SO3CF3] (2) (Xyl = 2,6-Me2C6H3) with tolylacetylide, followed by treatment with HSO3CF3 affords the complex [Fe-2{mu-eta(1):eta(3)C(Tol)double bondCdouble bondC(CMe3)N(H)CN(Me)(Xyl)}(mu-CO)(CO)(Cp-2)][SO3CF3] (3) (Tol = 4-MeC6H4). The X-ray molecular structure of 3 reveals the peculiar character of the bridging ligand, which exhibits both eta(1):eta(2) allene and aminocarbene nature. The formation of 3 proceeds through several intermediate species, which have been detected by IR spectroscopy. Addition of HSO3CF3 at an early stage of the reaction between 2 and LiCdropCTol leads to the formation of the imine complex [Fe-2{mu-CN(Me)Xyl}(mu-CO)(CO){NHC(CdropCTol)CMe3}(Cp)(2)][SO3CF3] (6) indicating that the first step of the reaction consists in the acetylide addition at the coordinated NCCMe3. The molecular structure of 6 has been elucidated by an X-ray diffraction study

Stereochemistry of the insertion of disubstituted alkynes into the metal aminocarbyne bond in diiron complexes

Terminal alkynes (HCdropCR') (R'=COOMe, CH2OH) insert into the metal-carbyne bond of the diiron complexes [Fe-2{mu-CN(Me)(R)} (mu-CO)(CO)(NCMe)(Cp)(2)][SO3CF3] (R=Xyl, 1a; CH2Ph, 1b; Me, 1c; Xyl=2,6-Me2C6H3), affording the corresponding mu-vinyliminium complexes [Fe-2{mu-sigma:eta(3)-C(R')=CHC=N(Me)(R)}(mu-CO)(CO)(Cp)(2)][SO3CF3] (R=Xyl, R'=COOMe, 2; R=CH2Ph, R'=COOMe, 3; R=Me, R'=COOMe, 4; R=Xyl, R'=CH2OH, 5; R=Me, R'=CH2OH, 6). The insertion is regiospecific and C-C bond formation selectively occurs between the carbyne carbon and the CH moiety of the alkyne. Disubstituted alkynes (R'CdropCR') also insert into the metal-carbyne bond leading to the formation of [Fe-2{mu-sigma:eta(3)- C(R')=C(R')C=N(Me)(R)}(mu-CO)(CO)(Cp)(2)][SO3CF3] (R'=Me, R=Xyl, 8; R'=Et, R=Xyl, 9; R'=COOMe, R=Xyl, 10; R'=COOMe, R=CH2Ph, 11; R'= COOMe, R=Me, 12). Complexes 2, 3, 5, 8, 9 and 11, in which the iminium nitrogen is unsymmetrically substituted, give rise to E and/or Z isomers. When iminium substituents are Me and Xyl, the NMR and structural investigations (X-ray structure analysis of 2 and 8) indicate that complexes obtained from terminal alkynes preferentially adopt the E configuration, whereas those derived from internal alkynes are exclusively Z. In complexes 8 and 9, trans and cis isomers have been observed, by NMR spectroscopy, and the structures of trans-8 and cis-8 have been determined by X-ray diffraction studies. Trans to cis isomerization occurs upon heating in THF at reflux temperature. In contrast to the case of HCdropCR', the insertion of 2-hexyne is not regiospecific: both [Fe-2{mu-sigma:eta(3)-C(CH2CH2CH3)=C(Me)C=N(Me)(R)} (mu-CO)(CO)(Cp)(2)][SO3CF3] (R=Xyl, 13; R=Me, 15) and [Fe-2{mu-sigma:eta(3)-C(Me)=C(CH2CH2CH3)C=N(Me)(R)}(mu-CO)(CO)(Cp)(2)][SO3CF3] (R=Xyl, 14, R=Me, 16) are obtained and these compounds are present in solution as a mixture of cis and trans isomers, with predominance of the former

Hydride addition at m-vinyliminium ligand obtained from disubstituted alkynes

New μ-vinylalkylidene complexes cis-[Fe2{μ-η1:η3-Cγ(R′)Cβ(R″)CαHN(Me)(R)}(μ-CO)(CO)(Cp)2] (R = Me, R′ = R″ = Me, 3a; R = Me, R′ = R″ = Et, 3b; R = Me, R′ = R″ = Ph, 3c; R = CH2Ph, R′ = R″ = Me, 3d; R = CH2Ph, R′ = R″ = COOMe, 3e; R = CH2 Ph, R′ = SiMe3, R″ = Me, 3f) have been obtained b yreacting the corresponding vinyliminium complexes [Fe2{μ-η1:η3-Cγ(R′)Cβ(R″)CαN(Me)(R)}(μ-CO)(CO)(Cp)2][SO3CF3] (2a–f) with NaBH4. The formation of 3a–f occurs via selective hydride addition at the iminium carbon (Cα) of the precursors 2a–f. By contrast, the vinyliminiumcis-[Fe2{μ-η1:η3-Cγ (R′) = Cβ(R″)Cα = N(Me)(Xyl)}(μ-CO)(CO)(Cp)2][SO3CF3] (R′ = R″ = COOMe, 4a; R′ = R″ = Me, 4b; R′ = Prn, R″ = Me, 4c; Prn = CH2CH2CH3, Xyl = 2,6-Me2C6H3) undergo H− addition at the adjacent Cβ, affording the bis-alkylidene complexes cis-[Fe2{μ-η1:η2-C(R′)C(H)(R″)CN(Me)(Xyl)}(μ-CO)(CO)(Cp)2], (5a–c). The cis and trans isomers of [Fe2{μ-η1:η3-Cγ(Et)Cβ(Et)CαN(Me)(Xyl)}(μ-CO)(CO)(Cp)2][SO3CF3] (4d) react differently with NaBH4: the former reacts at Cα yielding cis-[Fe2{μ-η1:η3-Cγ(Et)Cβ(Et)CαHN(Me)(Xyl)}(μ-CO)(CO)(Cp)2], 6a, whereas the hydride attack occurs at Cβ of the latter, leading to the formation of the bis alkylidene trans-[Fe2{μ-η1:η2-C(Et)C(H)(Et)CN(Me)(Xyl)}(μ-CO)(CO)(Cp)2] (5d). The structure of 5d has been determined by an X-ray diffraction study. Other μ-vinylalkylidene complexes cis-[Fe2{μ-η1:η3-Cγ(R′)Cβ(R″)CαHN(Me)(Xyl)}(μ-CO)(CO)(Cp)2], (R′ = R″ = Ph, 6b; R′ = R″ = Me, 6c) have been prepared, and the structure of 6c has been determined by X-ray diffraction. Compound 6b results from treatment of cis-[Fe2{μ-η1:η3-Cγ(Ph)Cβ(Ph)CαN(Me)(Xyl)}(μ-CO)(CO)(Cp)2][SO3CF3] (4e) with NaBH4, whereas 6c has been obtained by reacting 4b with LiHBEt3. Both cis-4d and trans-4d react with LiHBEt3 affording cis-6a

The SPOrt Project: Cosmological and Astrophysical Goals

We present the cosmological and astrophysical objectives of the SPOrt mission, which is scheduled for flying on the International Space Station (ISS) in the year 2002 with the purpose of measuring the diffuse sky polarized radiation in the microwave region. We discuss the problem of disentangling the cosmic background polarized signal from the Galactic foregrounds.Comment: 10 pages; 5 PS figures; requires aipproc2.cls, aipproc2.sty, epsfc.tex; to appear in Proc. of ``3K Cosmology'', Rome 5-10 Oct. 199

Resolving a guanine-quadruplex structure in the SARS-CoV-2 genome through circular dichroism and multiscale molecular modeling

The genome of SARS-CoV-2 coronavirus is made up of a single-stranded RNA fragment that can assume a specific secondary structure, whose stability can influence the virus's ability to reproduce. Recent studies have identified putative guanine quadruplex sequences in SARS-CoV-2 genome fragments that are involved in coding for both structural and non-structural proteins. In this contribution, we focus on a specific G-rich sequence referred to as RG-2, which codes for the non-structural protein 10 (Nsp10) and assumes a guanine-quadruplex (G4) arrangement. We provide the secondary structure of RG-2 G4 at atomistic resolution by molecular modeling and simulation, validated by the superposition of experimental and calculated electronic circular dichroism spectra. Through both experimental and simulation approaches, we have demonstrated that pyridostatin (PDS), a widely recognized G4 binder, can bind to and stabilize RG-2 G4 more strongly than RG-1, another G4 forming sequence that was previously proposed as a potential target for antiviral drug candidates. Overall, this study highlights RG-2 as a valuable target to inhibit the translation and replication of SARS-CoV-2, paving the way towards original therapeutic approaches against emerging RNA viruses.Parallel or hybrid? A combination of multiscale molecular modeling and circular dichroism is used to predict a G-quadruplex structure at atomistic resolution in the SARS-CoV-2 genome

Sequence randomness and polymer collapse transitions

Contrary to expectations based on Harris' criterion, chain disorder with frustration can modify the universality class of scaling at the theta transition of heteropolymers. This is shown for a model with random two-body potentials in 2D on the basis of exact enumeration and accurate Monte Carlo results. When frustration grows beyond a certain finite threshold, the temperature below which disorder becomes relevant coincides with the theta one and scaling exponents definitely start deviating from those valid for homopolymers.Comment: 4 pages, 4 eps figure

Virological and Immunological Monitoring of Human Cytomegalovirus Infection in Heart and Small Bowel/Multivisceral Transplantation

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