Search results for "perch"
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Structure and properties of 2-cyanopyridinium perchlorate [2-CNPyH][ClO4]
2006
The crystal structure of 2-cyanopyridinium perchlorate, [2-CNPyH][ClO4], has been determined at 100 (phase II) and 293 K (phase I). It is monoclinic P 21 at 100 K and orthorhombic P 212121 at 293 K. The dynamic properties of the crystal were studied by differential scanning calorimetry, dilatometry, pyroelectric, dielectric, proton (1H NMR), chlorine (35Cl NMR) magnetic resonance spectroscopies and the infrared method. The crystal undergoes a structural phase transition () at 170 K characterized by a complex mechanism involving both 'order–disorder' and 'displacive' contributions. It reveals pyroelectric properties below 170 K. The dielectric relaxation existing over phase I is due to the m…
Static and MAS 35CI NMR and Molecular Motions of ClO −4 Ions in the Various Phases of Multimethylammonium Perchlorates
1986
Static and MAS*) 35CI NMR data of CIO−4 ions in the low-, intermediate- and high-temperature phases of trimethylammonium, dimethylammonium and monomethylammonium perchlorates are reported. The observed solid-solid phase transitions are interrelated with the motional state of the perchlorate ions. In the low-temperature phase III of trimethylammonium perchlorate there is an anisotropic motion of the ClO−4 ions with a constant quadrupole frequency of 185 kHz and an increasing value of the asymmetry parameter when approaching phase transition III-II. The activation energy for this motion is found to be 44.3 kj/mol. At the transition III-II the ClO−4 ions gain orientational degrees of freedom m…
Calix[4]arenes as Selective Extracting Agents. An NMR Dynamic and Conformational Investigation of the Lanthanide(III) and Thorium(IV) Complexes
2000
The lanthanide and Th4+ complexes with calix[4]arene ligands substituted either on the narrow or at the wide rim by four coordinating groups behave totally differently as shown by an NMR investigation of the dia- and paramagnetic complexes. Solutions of complexes were prepared by reacting anhydrous metal perchlorate salts with the ligands in dry acetonitrile (CAUTION). Relaxation time T1 titrations of acetonitrile solutions of Gd3+ by calixarenes indicate that ligands subsituted on the narrow rim form stable 1:1 complexes whether they feature four amide groups (1) or four phosphine oxide functions. In contrast, a ligand substituted by four (carbamoylmethyl)-diphenylphosphine oxide moieties …
Electrochemical and Spectroelectrochemical Studies of Diphosphorylated Metalloporphyrins. Generation of a Phlorin Anion Product
2015
Two series of diphosphoryl-substituted porphyrins were synthesized and characterized by electrochemistry and spectroelectrochemistry in nonaqueous media containing 0.1 M tetra-n-butylammonium perchlorate (TBAP). The investigated compounds are 5,15-bis(diethoxyphosphoryl)-10,20-diphenylporphyrins (Ph)2(P(O)(OEt)2)2PorM and 5,15-bis(diethoxyphosphoryl)-10,20-di(para-carbomethoxyphenyl)porphyrins (PhCOOMe)2(P(O)(OEt)2)2PorM where M = 2H, Co(II), Ni(II), Cu(II), Zn(II), Cd(II), or Pd(II). The free-base and five metalated porphyrins with nonredox active centers undergo two ring-centered oxidations and two ring-centered reductions, the latter of which is followed by a chemical reaction of the por…
Electrochemical Growth and Physico-Chemical Characterization in Organic Medium of Nb2O5 Thin Films
2008
Investigations about the energetics and the electrical properties of niobium thin film, electrochemically grown, were performed in an organic solution of acetonitrile and lithium perchlorate. The study of the energetics of the Nb2O5/organic solution interface was performed by means of a non-destructive optical technique, photocurrent spectroscopy. By means of this technique, it was possible estimating the value of the flat band potential and locating conduction and valence band. A more cathodic value of flat band potential in respect with acidic solution was found in organic medium. From impedance spectra, the electrical circuit that gives best fitting values is constituted by two resistanc…
Vacuum Topology of the Two Higgs Doublet Model
2011
We perform a systematic study of generic accidental Higgs-family and CP symmetries that could occur in the two-Higgs-doublet-model potential, based on a Majorana scalar-field formalism which realizes a subgroup of GL(8,C). We derive the general conditions of convexity and stability of the scalar potential and present analytical solutions for two non-zero neutral vacuum expectation values of the Higgs doublets for a typical set of six symmetries, in terms of the gauge-invariant parameters of the theory. By means of a homotopy-group analysis, we identify the topological defects associated with the spontaneous symmetry breaking of each symmetry, as well as the massless Goldstone bosons emergin…
Collider signals of the Mirror Twin Higgs boson through the hypercharge portal
2019
We consider the collider signals arising from kinetic mixing between the hypercharge gauge boson of the Standard Model and its twin counterpart in the Mirror Twin Higgs model, in the framework in which the twin photon is massive. Through the mixing, the Standard Model fermions acquire charges under the mirror photon and the mirror Z boson. We determine the current experimental bounds on this scenario, and show that the mixing can be large enough to discover both the twin photon and the twin Z at the LHC, or at a future 100 TeV hadron collider, with dilepton resonances being a particularly conspicuous signal. We show that, in simple models, measuring the masses of both the mirror photon and …
Group-Theoretic analysis of the mixing angle in the electroweak gauge group
1996
In this paper the authors provide strong mathematical support for the idea that the experimentally measured magnitude 1 - M{sub W}{sup 2}/M{sub Z}{sup 2} associated with sin{sup 2}{theta}{sub w} in the standard model of electroweak interactions cannot be simultaneously identified with the squared quotient of the electric charge by the SU(2) charge, e{sup 2}/g{sup 2}. In fact, the natural, mathematical requirement that the Weinberg rotation between the gauge fields associated with the third component of the {open_quotes}weak isospin{close_quotes} (T{sub 3}) and the hypercharge (Y) proceeds from a global Lie-group homomorphism of the SU(2) {circle_times} U(1){sub y} gauge group in some locall…
Weakly interacting dark matter particle of a minimal technicolor theory
2007
We consider the possibility that a massive fourth family neutrino, predicted by a recently proposed minimal technicolor theory, could be the source of the dark matter in the Universe. The model has two techniflavors in the adjoint representation of a SU(2) techicolor gauge group and its consistency requires the existence of a fourth family of leptons. By a suitable hypercharge assignment the techniquarks together with the new leptons look like a conventional fourth standard model family. We show that the new (Majorana) neutrino N can be the dark matter particle if m{sub N}{approx}100-500 GeV and the expansion rate of the Universe at early times is dominated by an energy component scaling as…
SU(6) Extension of the Weinberg-Tomozawa Meson-Baryon Lagrangian
2005
A consistent SU(6) extension of the Weinberg-Tomozawa meson-baryon chiral Lagrangian is constructed which incorporates vector meson and baryon decuplet degrees of freedom. The corresponding Bethe-Salpeter approximation predicts the existence of an isoscalar spin-parity ${3/2}^-$ $K^*N$ bound state (strangeness +1) with a mass around 1.7--1.8$ $GeV. It is the highest hypercharge state of an antidecuplet SU(3) representation and it is unstable through $K^*$ decay. The estimated width of this state (neglecting d-wave $KN$ decay) turns out to be small ($\Gamma \le 15 $MeV). Clear signals of this resonance would be found in reactions like $\gamma p \to {\bar K}^0 p K^+ \pi^-$ by looking at the t…