Stepwise substitution of oxo-centered,trinuclear chromium(III) carboxylates with Schiff base

Oxo-centered, trinuclear, mixed-ligand complexes of chromium(III) have been synthesized by stepwise substitutions of acetate ions of [Cr₃O(OOCMe)₄(OOCR)₃] · 3MeOH (1) and the isolated products of the type [Cr₃O(OOCMe)₂ (SB)(OOCR)₃]PF₆ · 3MeOH (2), [Cr₃O(OOCMe)(SB)₂(OOCR)₃]PF₆ · 3MeOH (3) and [Cr₃O(SB)₃(OOCR)₃]PF₆ · 3MeOH (4) [where R = C₁₃H₂₇ and HSB = C₆H₄(OH)CHNC₆H₄Cl] have been characterized by a full battery of complementary physico–chemical methods including spectral (infrared, electronic, FAB mass and powder XRD) studies, elemental and thermogravimetric analyses, molar conductance and magnetic susceptibility measurements. The infrared spectra suggest the bridging nature of both carboxylate and Schiff base anions along with ν _asym(Cr₃O) vibrations in the complexes. The trinuclear nature of the complexes has been assessed from FAB mass data. Electronic spectra and magnetic moment values were consistent with chromium(III) ion present in an octahedral environment which was supported by their powder X-ray diffraction data. Cyclic voltammetric data of complex (4) indicate a reversible oxidation wave and an irreversible reduction wave in the range − 1.2–0.6 V. The decomposition pathway of all the complexes has been discussed on the basis of thermogravimetric analysis data. Conductance data indicate the monocationic nature of the complexes and their plausible structure has been established on the basis of above physico–chemical studies.     

Synthesis, Characterization and Phosphodiester Bond Cleavage Studies of the Dinuclear, Thioacetatocobalt(II) of 3-methylsulfanylpropionic Acid Complex

A new dinuclear cobalt(II) complex containing monothioacetate and 3-methylsulfanylpropionate ligands was synthesized and fully characterized by spectral, magnetic moment, electrochemical, elemental, thermal and FAB mass analyses data. In order to explore the role of labile metal complexes in promoting phosphodiester hydrolysis, kinetic and mechanistic studies were performed. The hydrolyses of ethyl 4-nitrophenylphosphate (ENPP) and the bis(4-nitrophenyl)phosphate (BNPP) complex are catalytic, as determined by the observations of both rate enhancement and turnover. The pH versus rate profile indicates that deprotonation of the metal-coordinated water occurs to form the active catalyst.     

Substitution reactions of thorium(IV) acetate to synthesize nano-sized carboxylate complexes

Some mixed-ligand thorium(IV) complexes with the general formula [Th(OOCCH₃)_4?nL_n] (L = anions of myristic, palmitic or stearic acid and n = 1–4) have been synthesized by the stepwise substitution of acetate ions of thorium(IV) acetate with straight chain carboxylic acids in toluene under reflux. The complexes were characterized by elemental analyses, spectral (electronic, infrared, NMR and powder XRD) studies, electrical conductance and magnetic susceptibility measurements. Doubly and triply bridged coordination modes of the ligands were established by their infrared spectra and nano-size of the complexes by powder XRD. Room temperature magnetic susceptibility measurements revealed diamagnetic nature of the complexes. Electronic absorption spectra of the complexes showed π → π*, n → π* and charge transfer transitions. Molar conductance values indicated the complex to be non-electrolytes. These are a new type of mixed-ligand thorium(IV) complexes for which a nano-sized, oxygen bridged polymeric structure has been established on the basis of physico-chemical studies.     

On sample path properties of semistable processes

This paper contains three main results: In the first result a correspondence principle between semistable measures on L_p, 1 ≤ p < ∞, and Banach space valued semistable processes is established. In the second result it is shown that the paths of a Banach space valued semistable process belong to L_p with probability zero or one, and necessary and sufficient conditions for the two alternatives to hold are given. In the third result necessary and sufficient conditions are given for almost sure path absolute continuity for certain Banach space valued semistable processes.     

Optimization of Graphene Layers Grown on Pt/Ti/SiO2 by Hot Filament Chemical Vapor Deposition

Large area single and bilayer graphene are grown on Pt/Ti/SiO₂ substrates by hot filament chemical vapor deposition (HFCVD) with and without the assistance of Cu foil. The quality and number of graphene layers deposited on the substrate are assessed by Raman Spectroscopy. Atomic Force Microscopy (AFM) is used for assessing the surface topography of the graphene films grown on the Pt/Ti/SiO₂ substrates. The microstructure and elemental analyses are performed by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The results show that bilayer graphene growth is facilitated by a copper foil placed nearby Pt/Ti/SiO2 substrate and by a high filament temperature in the HFCVD reactor. Monolayer graphene grows only when no copper foil is placed near the Pt/Ti/SiO₂ substrate at a low filament temperature. The approach paves a novel pathway towards the layer-controlled growth of graphene on Pt/Ti/SiO₂ substrates by HFCVD for frontier applications.     

Semistable laws on topological vector spaces

Summary In this paper we discuss three types of results: Firstly, we present two Lévy-Hinin type representations of Poisson type infinitely divisible (i.d.) laws on certain topological vector (TV) spaces; one of these complements a known representation due to Dettweiler. Secondly, we define and characterize r-semistable laws on locally convex TV spaces and also obtain good representation of their characteristic functions. Finally, we discuss the existence and the continuity of the semigroup { _tt>0} of i.d. laws on locally convex TV spaces. These complement similar known results of Siebert.The research of this author is partially supported by the Office of Naval Research under contract No. N0014-78-C-0468     

Supports of semi-stable probability measures on locally convex spaces

LetE be a locally convex space. Let be an absolutely convexly tight Radom semi-stable probability measure onE with index 1<2 and Lévy measureM. The main result of this paper shows that the closed semigroup generated by the support ofM and the negative of the barycenter ofM restricted to a suitable compact subset ofE is a (closed) linear space ofE, and that the support of is a suitable translate of this linear space. This result complements a few known results concerning the supports of stable and semi-stable probability measures. In particular, it extends an analogous result proved recently for the support of -stable probability measures 1<2 (Ref. 4). Related results concerning the support of Radon semi-stable probability measures onE of index 0<<1 are also discussed.The research of this author was partially supported by AFSOR Grant No. 90-0168The research of this author was supported by KBN Grant, and the University of Tennessee Science Alliance, a State of Tennessee Center of Excellence.     

Positions of the magnetoroton minima in the fractional quantum Hall effect

The multitude of excitations of the fractional quantum Hall state are very accurately understood, microscopically, as excitations of composite fermions across their Landau-like Λ levels. In particular, the dispersion of the composite fermion exciton, which is the lowest energy spin conserving neutral excitation, displays filling-factor-specific minima called “magnetoroton” minima. Simon and Halperin employed the Chern-Simons field theory of composite fermions [Phys. Rev. B 48, 17368 (1993)] to predict the magnetoroton minima positions. Recently, Golkar et al. [Phys. Rev. Lett. 117, 216403 (2016)] have modeled the neutral excitations as deformations of the composite fermion Fermi sea, which results in a prediction for the positions of the magnetoroton minima. Using methods of the microscopic composite fermion theory we calculate the positions of the roton minima for filling factors up to 5/11 along the sequence s/ (2s + 1) and find them to be in reasonably good agreement with both the Chern-Simons field theory of composite fermions and Golkar et al.’s theory. We also find that the positions of the roton minima are insensitive to the microscopic interaction in agreement with Golkar et al.’s theory. As a byproduct of our calculations, we obtain the charge and neutral gaps for the fully spin polarized states along the sequence s/ (2s ± 1) in the lowest Landau level and the n = 1 Landau level of graphene.