Pn Reaction Research Articles

Fluorescent cholesteric liquid crystal polymers with dual properties: design, synthesis and characterisation

ABSTRACT In this study, we have synthesised fluorescent liquid crystal polymers with good fluorescence and optical properties through effective molecular design. Firstly, two series of cholesteric liquid crystal polymers (PN and PS series) were prepared by graft copolymerisation of cholesteric monomer(N1), monomer containing cyanobiphenyls with different length of carbon-chain (N2 and N3) and monomer containing bromine (6-Br) with polymethylhydrosiloxane chain as the polymer backbone. Secondly, we obtained fluorescent polymers RPN and RPS series by etherification reaction of PN and PS series with fluorescent monomer (F). The molecular structures and mesomorphic behaviour of monomers and polymers were characterised by usual ways. All the polymers are confirmed to consist with molecular design. The fluorescence of the polymers was investigated by fluorescence spectroscopy and fluorescent images. The fluorescence intensity of polymers is highly dependent on temperature. Fluorescent cholesteric liquid crystal polymers emitted different intensity fluorescence under ultraviolet irradiation and some regularities were summarised. RPN series with short carbon-chain meets our expectations for performance with dual effects of fluorescence and selective reflection, which were well verified. The effect of monomers with different chain lengths on the properties of fluorescent polymers has been described.

Synthesis, characterization and band gap energy of new water soluble fluorescent diethanolamine-boron-subphthalocyanine dye using B nanoparticles and SiB6 microparticles

In the present work, the novel synthesis methods were developed for the preparation of a new water soluble and fluorescent diethanolamine-boron-subphthalocyanine (Dea-B-SubPc) dye. The boron nanoparticles and SiB6 were utilized as the boron sources for the Dea-B-SubPc synthesis. In order to obtain the boron nanoparticles, the powder mixture of boron microparticles, phthalonitrile (Pn) and KCl was encapsulated into a Cu pipe and then mechanically roll-milled at room-temperature. The Dea-B-SubPc dye was synthesized via the reaction of the roll-milled boron nanoparticles and Pn in 50 % Dea-toluene solution at 120 °C. The Dea-B-SubPc was also synthesized by the reaction of Pn and SiB6 microparticles using similar experimental conditions. The prepared Dea-B-SubPc was characterized by using the SEM, FT-IR, NMR, HR-ESI-MS, cyclic voltammetry (CV), UV–vis. absorption and fluorescence (FL) emission spectroscopy. The Dea-B-SubPc is soluble in H2O, DMSO, MeOH and EtOH solvents. The optical band gap energy of the Dea-B-SubPc was found as 2.15 eV in MeOH and H2O, and 2.10 eV in DMSO. The Dea-B-SubPc solutions exhibited FL emissions at 592.2 nm in DMSO, 575.2 nm in MeOH and 577.8 nm in H2O with the excitation at 450 nm. The EHOMO and ELUMO energy levels of the Dea-B-SubPc were calculated as −5.82 eV and −4.08 eV, respectively and then the electrochemical band gap energy was found as 1.74 eV using the CV measurements. In summary, both the B nanoparticles and SiB6 microparticles were used successfully for the synthesis of the Dea-B-SubPc as a new fluorescent and low band gap energy dye material.

A new pattern of the partial nitrification and Anammox immobilized gel beads: core-shell embedded carrier

Single-stage partial nitrification and Anammox (PN/A) is an efficient and energy-saving denitrification process for wastewater. However, its application is limited by the growth conditions of microorganisms. Therefore, we improved the PN/A by developing a novel core−shell embedded carrier. With Anammox gel as the core and Ammonia-oxidizing bacteria gel as the shell, these beads can achieve dissolved oxygen partitioning and provide a suitable environment for the growth of different bacteria. On this basis, the influence of the shape of core−shell embedded gel on nitrogen removal performance was systematically studied, and the internal morphology and pore size of gel beads were characterized. The results showed that the nitrogen removal efficiency of spherical and square gels was increased by 33.70% and 13.47%, respectively, in the batch test. Fluorescence in situ hybridization confirmed the stratified growth of ammonia-oxidizing bacteria and Anammox in carriers, and the relative abundance value of the two bacteria were 1.25:1 and 1.43:1, respectively. Although the mechanical strength of square gel beads is slightly higher than that of spherical, spherical gel is considered the most suitable gel shape due to its small pore size and poor pore connectivity, which ensures the matching of internal Anammox and external PN reaction. In the long-term experiment, the core−shell embedded beads still had the design characteristics, and the TN removal efficiency was increased by 36.25% despite occasional oxygen excess.

Failure Modes of Platinized pn+-GaInP Photocathodes for Solar-Driven H2 Evolution.

The long-term stability for the hydrogen-evolution reaction (HER) of homojunction pn+-Ga0.52In0.48P photocathodes (band gap = 1.8 eV) with an electrodeposited Pt catalyst (pn+-GaInP/Pt) has been systematically evaluated in both acidic and alkaline electrolytes. Electrode dissolution during chronoamperometry was correlated with changes over time in the current density-potential (J-E) behavior to reveal the underlying failure mechanism. Pristine pn+-GaInP/Pt photocathodes yielded an open-circuit photopotential (Eoc) as positive as >1.0 V vs the potential of the reversible hydrogen electrode (RHE) and a light-limited current density (Jph) of >12 mA cm-2 (1-sun illumination). However, Eoc and Jph gradually degraded at either pH 0 or pH 14. The performance degradation was attributed to three different failure modes: (1) gradual thinning of the n+-emitter layer due to GaInP dissolution in acid; (2) active corrosion of the underlying GaAs substrate at positive potentials causing delamination of the upper GaInP epilayers; and (3) direct GaAs/electrolyte contact compromising the operational stability of the device. This work reveals the importance of both substrate stability and structural integrity of integrated photoelectrodes toward stable solar fuel generation.

Linking structure and dynamics with two-neutron halos

We present a theoretical description of (p, pn) reactions induced by two-neutron halo nuclei at intermediate energies. For this purpose, we use a reaction framework that incorporates a full three-body model for the projectile, and we focus on the cases of 11Li and 14Be. Our results provide a direct link between the structure properties of these nuclei and different reaction observables, such as relative-energy spectra or momentum distributions. We discuss also on the link between dineutron correlations and opening-angle distributions.

Reaction of two pion production pd → pdππ in the resonance region

The ANKE@COSY data on the reaction of two-pion production in the GeV region are analyzed within the theoretical model by Platonova and Kukulin. The model includes excitation of the dibaryon resonance DIJ = D03(2380) with the spin J = 3 and isospin I = 0 observed by the WASA@COSY in the reaction pn → dπ0π0, and its decay D03 → D12 + π → d + π + π, where D12(2150) is another dibaryon resonance. Distributions on the invariant masses of the final dππ and ππ systems are calculated.

Improvement of electrochemical detection of transthyretin synthetic peptide and its amino acids on carbon electrodes: Glassy carbon versus amorphous carbon nitride a-CNx

Amorphous carbon nitride a-CN0.26 thin films were elaborated on transparent and conductive glass/indium-tin oxide (ITO) wafers to improve the electroanalytical detection of transthyretin peptide (PN) and specific amino acids (AA) from its sequence, which constitutes a great challenge for the diagnosis of transthyretin-related familial amyloïd polyneuropathy (ATTR). The naphthalene-2,3-dicarboxyaldehyde (NDA) label was used for the derivatization reaction of PN and AAs to form N-2-substituted-1-cyanobenz-[f]-isoindole derivatives (CBI) which are both fluorescent and electroactive. The results obtained on a-CN0.26 were compared with those observed on glassy carbon (GC) as a reference material. It was shown that a soft anodic pre-treatment protocol on glass/ITO/a-CN0.26 electrode in a KCl aqueous solution drastically improved the performances of the CBI-PN and CBI-AA oxidation peak. The oxidation peak potential for all CBI derivatives varied in the same range than those measured on GC and pre-treated glass/ITO/a-CN0.26, while no discrimination could be obtained on as-grown glass/ITO/a-CN0.26 electrodes. For almost all the tested CBI derivatives, peak areas, full-widths at peak mid-height, peak current density and their standard deviation (SD) values were improved on a pre-treated a-CN0.26 electrode in comparison with GC.

Highly efficient of nitrogen removal from mature landfill leachate using a combined DN-PN-Anammox process with a dual recycling system

An efficient and stable combined denitrification-partial nitrification-Anammox process with a dual recycling system was used to remove nitrogen from mature landfill leachate. After 155 d of operation, the NO3− as the PN-Anammox byproduct was almost treated with biodegradable organic carbon in raw wastewater in a pre-denitrification reactor by external recycling system. When raw landfill leachate with NH4+-N concentration of 1900 mg/L was treated, an integrated reactor with airlift recycling was combined with the PN and Anammox reactions to efficiently remove NH4+ from the inflow. The total nitrogen concentration of effluent stabilized at 20 mg/L and total nitrogen removal efficiency was 99%. The maximum NO2− production rate in the aerobic zone was 2.2 kg/(m3·d) and the maximum nitrogen removal rate in the anaerobic zone was 21.4 kg/(m3·d). The most common phyla among the nitrification and the Anammox functional bacteria were Nitrosomonas, Candidatus Kuenenia, and Candidatus Brocadia after landfill leachate treatment.

Phenomenological study of the pp→π+pn reaction

Fully constrained bubble chamber data on the pp -> pi+ pn and pp -> pi+ d reactions are used to investigate the ratio of the counting rates for the two processes as function of the pn excitation energy Q. Though it is important to include effects associated with the p-wave nature of pion production, the data are insufficient to establish unambiguously the dependence on Q. The angular distributions show the presence of higher partial waves which seem to be anomalously large at small Q. The dispersion relation method to determine scattering lengths is extended to encompass cases where, as for the pp -> pi+ pn reaction, there is a bound state and, in a test example, it is shown that the values deduced for the low energy neutron-proton scattering parameters are significantly influenced by the pion p-wave behavior.

Phenomenology of spin observables in the reactions of meson production with the 1 S 0 Diproton pN → {pp} s X

Formalism for spin observables for production of pseudoscalar, scalar, and vectormesons in pN collision with formation of the 1S0 diproton {pp}s in the final state is considered in model-independent way assuming parity and angular momentum conservation. Production of the pseudoscalar mesons (Jπ = 0−) is described by two spin amplitudes and both of them can be completely determined by measurement of unpolarized cross section dσ0, vector analyzing power Ay, and spin-correlation coefficients Cx,x = −Cz,z> and Cx,z. Similar result is obtained for production of scalar mesons (Jπ = 0+). It is shown that measurement of the tensor polarization t20 of the vector meson V (Jπ = 1−) in the reaction pN → {pp}sV in collinear kinematics gives the same information as measurement of the spin-correlation coefficients Cz,z or Cy,y.

A new neutron detector with a high position resolution for the study of the (p,pn) reaction on rare isotopes

We are developing a neutron detector with a position resolution better than 3 mm to study the single particle properties of nuclei by the knockout ( p , pn ) reaction at intermediate energies. We constructed a prototype detector consisting of scintillating fibers and multi-anode photomultiplier tubes (PMTs). A test experiment using 70-MeV proton and 68- and 50-MeV neutron was performed for characterizing its performance. In preliminary results, a position resolution of about 3 mm, is realized, as designed. The resulting separation-energy resolution would be 1 MeV, when using this system at a distance of 2 m from the target for measuring the ( p , pn ) reaction.

New Interpretation of the ABC Effect in Two-Pion Production in NN Collisions

We investigate the basic 2π-fusion reaction pn → d + (ππ)0 in the energy region Tp = 1–1.4GeV within the framework of a model based on a D03-dibaryon production and its subsequent decay via two interfering routes: through an intermediate σ meson and through an isovector dibaryon D12. We demonstrate that the constructive interference of the above two mechanisms gives a strong near-threshold enhancement in the ππ invariant-mass spectrum, i.e., the so-called ABC effect. It is shown that the σ-meson emission from the D03 dibaryon plays a crucial role in reproducing the shape and position of the ABC enhancement and is tightly related to the idea of chiral symmetry restoration in dense and excited hadronic systems, such as the D03 state.

Ru(0) and Ru(II) Nitrosyl Pincer Complexes: Structure, Reactivity, and Catalytic Activity

Despite considerable interest in ruthenium carbonyl pincer complexes and their substantial catalytic activity, there has been relatively little study of the isoelectronic ruthenium nitrosyl complexes. Here we describe the synthesis and reactivity of several complexes of this type as well as the catalytic activity of complex 6. Reaction of the PNP ligand (PNP = 2,6-bis((t)Bu2PCH2)pyridine) with RuCl3(NO)(PPh3)2 yielded the Ru(II) complex 3. Chloride displacement by BAr(F-) (BAr(F-) = tetrakis(3,5-bis(trifluoromethyl)phenyl)borate) gave the crystallographicaly characterized, linear NO Ru(II) complex 4, which upon treatment with NaBEt3H yielded the Ru(0) complexes 5. The crystallographically characterized Ru(0) square planar complex 5·BF4 bears a linear NO ligand located trans to the pyridilic nitrogen. Further treatment of 5·BF4 with excess LiOH gave the crystallographicaly characterized Ru(0) square planar, linear NO complex 6. Complex 6 catalyzes the dehydrogenative coupling of alcohols to esters, reaching full conversion under air or under argon. Reaction of the PNN ligand (PNN = 2-((t)Bu2PCH2)-6-(Et2NCH2)pyridine) with RuCl3(NO)(H2O)2 in ethanol gave an equilibrium mixture of isomers 7a and 7b. Further treatment of 7a + 7b with 2 equivalent of sodium isopropoxide gave the crystallographicaly characterized, bent-nitrosyl, square pyramidal Ru(II) complex 8. Complex 8 was also synthesized by reaction of PNN with RuCl3(NO)(H2O)2 and Et3N in ethanol. Reaction of the "long arm" PN(2)N ligand (PN(2)N = 2-((t)Bu2PCH2-)-6-(Et2NCH2CH2)pyridine) with RuCl3(NO)(H2O)2 in ethanol gave complex 9, which upon treatment with 2 equiv of sodium isopropoxide gave complex 10. Complex 10 was also synthesized directly by reaction of PN(2)N with RuCl3(NO)(H2O)2 and a base in ethanol. A noteworthy aspect of these nitrosyl complexes is their preference for the Ru(0) oxidization state over Ru(II). This preference is observed with both aromatized and dearomatized pincer ligands, in contrast to the Ru(II) oxidation state which is preferred by the analogous carbonyl complexes.

Isospin decomposition of the basic double-pionic fusion in the region of the ABC effect

Exclusive and kinematically complete high-statistics measurements of the basic double-pionic fusion reactions pn→dπ0π0, pn→dπ+π− and pp→dπ+π0 have been carried out simultaneously over the energy region of the ABC effect using the WASA detector setup at COSY. Whereas the isoscalar reaction part given by the dπ0π0 channel exhibits the ABC effect, i.e. a low-mass enhancement in the ππ-invariant mass distribution, as well as the associated resonance structure in the total cross section, the isovector part given by the dπ+π0 channel shows a smooth behavior consistent with the conventional t-channel ΔΔ process. The dπ+π− data are very well reproduced by combining the data for isovector and isoscalar contributions, if the kinematical consequences of the isospin violation due to different masses for charged and neutral pions are taken into account.

ABC effect as a signal of chiral symmetry restoration in hadronic collisions

A new nonconventional mechanism for the basic 2{\pi}-fusion reaction pn --> d+({\pi}{\pi})_0 in the energy region T_p = 1.0-1.4 GeV is suggested. The mechanism is aimed at providing a consistent explanation for the comprehensive experimental studies of this reaction in exclusive setting done recently by the WASA-at-COSY Collaboration. The basic assumption of the model proposed is the production of the I(JP) = 0(3+) dibaryon resonance D03 in the pn collision. The interference of two decay channels of this resonance: D_03 --> d + {\sigma} --> d + ({\pi}{\pi})_0 and D_03 --> D_12 + {\pi} --> d + ({\pi}{\pi})_0 is shown to give a strong near-threshold enhancement in the {\pi}{\pi} invariant mass spectrum, which is well known as the ABC effect. The {\sigma}-meson parameters found to reproduce the ABC enhancement are in a general agreement with models which predict the chiral symmetry restoration at high excitation energy and/or high density of matter, although they are essentially less than those accepted for the free {\sigma} meson. So, this result might be considered as an indication of partial chiral symmetry restoration in dense and excited quark matter.

Study of Tensor Correlations in 4He via the 4He(p, dp)d and 4He(p, dp)pn Reactions

Tensor correlations in 4He were studied via the (p, dp) reaction at the incident energy of 392 MeV with a focus on spin configurations of correlated pn pairs in 4He at high relative momenta \({(P_{\rm rel}^{\rm cor})}\). The preliminary results show that the correlated pn pair at \({P_{\rm rel}^{\rm cor} = 310 {\rm MeV/c}}\) predominantly has the channel spin S = 1, which is consistent with the characteristics of tensor correlations.

ChPT Calculation for Two Pion Production in NN Collision Reaction at Threshold

We investigate the two pion production in NN collision reaction at threshold with Chiral Perturbation Theory (ChPT). The leading-order diagrams are presented and as an example we give the results of complete calculation of the reaction pn → d ππ at threshold. It is found that the leading order diagrams are of equal importance as expected by power counting. The role of initial, intermediate and final state interactions in nucleon-nucleon system is also investigated and found to be very important. The calculations also show that the non-resonant contributions near threshold in the two-pion production in NN collision reaction is sizable and important.

Experimental studies of few-body systems at MAMI

Few-body experiments at the Mainz Microtron were focused on a number of selected topics. Double-polarization experiments to determine the neutron electric form factor Gen have been performed using both deuterium and polarized helium-3 targets. The structure of 3He has been studied in the reactions 3H e e(ee,e′n) and 3H e e(ee,e′p) with large (transversal) missing momenta and in quasi-elastic electron scattering. Electromagnetically induced two-nucleon knockout has been investigated in order to study the role of correlated nucleon-nucleon motion in the nucleus. Measurements of the (e,e′pn) reaction on 3He and 16O were performed for the first time. A triple-polarization experiment of type 3H e e(ee,e′ep)d has been performed, where, in addition, the spin of the knocked out proton is analyzed. This measurement provides information on the spin-dependent momentum distribution of proton-deuteron clusters in the 3He nucleus. Hence, by tagging the outgoing deuteron spin-polarized 3He might also serve as an effective polarized proton target for electron scattering experiments. Moreover, in inclusive 3,4He(e,e′) measurements at low momentum transfer, the effect of 3-body-forces has been studied.

Separation of differential np → pn charge-exchange cross section into flip and nonflip parts at T n = 0.5–2.0 GeV

New results of the Delta-Sigma experiment on measuring the R dp ratio made it possible to separate flip and nonflip parts of the differential cross section of the np → pn reaction at zero angle using the Dean formula. Phase-shift-analysis (PSA) solutions for elastic np → np scattering are transformed into a np → pn charge-exchange representation using unitary transformations, which testifies to the good agreement of the theoretical and experimental results.

CHARGE SYMMETRY BREAKING IN pn → dπ0

We study charge symmetry breaking (CSB) in the reaction pn → dπ0. CSB manifests itself in a forward-backward asymmetry of the differential cross section measured recently at TRIUMF. A complete calculation of CSB effects at leading order in chiral perturbation theory is performed. A new leading-order operator is included. This allows us to extract the strong contribution to the neutron-proton mass difference from the analysis. The value obtained is consistent with the result of Gasser and Leutwyler based on the Cottingham sum rule and with an extraction from lattice QCD.