157 research outputs found
Syntheses and Antibacterial Studies of Some 1-Phenyl-3-(4-(2-ethanoloxy) phenyl)-5-aryl-1H-pyrazoles
A series of 1-phenyl-3-(4-(2-ethanoloxy) phenyl)-5-aryl-1H-pyrazoles were synthesized from chalcones, that is, 3-aryl-1-(4-hydroxyphenyl) prop-2-en-1-ones and studied for their in vitro antibacterial activity. Chalcones 1 on reaction with phenyl hydrazine in the presence of acetic acid and few drops of hydrochloric acid yielded the corresponding 1-phenyl-3-(4-hydroxyphenyl)-5-aryl-1H-pyrazoles 2 which on further reaction with 2-chloroethanol furnished the title compounds 3. ese compounds were characterized by CHN analyses, IR, mass and 1 H NMR spectral data. All the compounds were evaluated for their in vitro antibacterial activity against two Gram positive strains (Bacillus subtilis and Staphylococcus aureus) and two Gram negative strains (Escherichia coli and Pseudomonas aeruginosa), and their minimum inhibitory concentration (MIC) was determined
Geometric phase around exceptional points
A wave function picks up, in addition to the dynamic phase, the geometric
(Berry) phase when traversing adiabatically a closed cycle in parameter space.
We develop a general multidimensional theory of the geometric phase for
(double) cycles around exceptional degeneracies in non-Hermitian Hamiltonians.
We show that the geometric phase is exactly for symmetric complex
Hamiltonians of arbitrary dimension and for nonsymmetric non-Hermitian
Hamiltonians of dimension 2. For nonsymmetric non-Hermitian Hamiltonians of
higher dimension, the geometric phase tends to for small cycles and
changes as the cycle size and shape are varied. We find explicitly the leading
asymptotic term of this dependence, and describe it in terms of interaction of
different energy levels.Comment: 4 pages, 1 figure, with revisions in the introduction and conclusio
Synthesis, characterization and redox behaviour of benzoyldiazenido- and oxorhenium complexes bearing N,N- and S,S-type ligands
The reactions of [ReCl2{eta(2)-N2C(O)Ph}(PPh3)(2)](1) with 2-aminopyrimidine (H(2)Npyrm), 2,2'-bipyridine (bpy) and tetraethylthiuram disulfide (tds), in MeOH upon reflux, lead to the new eta(1)-(benzoyldiazenido)-rhenium(III) complexes [ReCl{eta(1)-N2C(O)Ph}(HNpyrm)(PPh3)(2)](2)and [ReCl2{eta(1)-N2C(O)Ph}(bpy)(PPh3)] (3), and the known oxo(diethyldithiocarbamato)dirhenium(v)complex [Re2O2(mu O){Et2NC(S)S}(4)](4), respectively. The Et2NC(S)S ligands in 4 result from S-S bond rupture of tds molecules. The obtained compounds have been characterized by IR, H-1, P-31{H-1} and C-13{H-1} NMR spectroscopies, FAB(+)-MS, elemental and single-crystal X-ray diffraction (for 2 and 4)analyses. Complex 2 represents the first structurally characterized Re compound derived from 2-aminopyrimidine. Besides, the redox behaviour of 2-4 in CH2Cl2 solution has been studied by cyclic voltammetry, and the Lever electrochemical ligand parameter (E-L)has been estimated, for the first time, for HNpyrm. The electrochemical results are discussed in terms of electronic properties of the Re centres and the ligands
1-Methyl-1-azonia-3,5-diaza-7-phosphatricyclo[3.3.1.13,7]decane tetrafluoroborate
The title compound, C7H15N3P+·BF4
− or [PTA-Me][BF4], is the N-methylated derivative of the well known water-soluble aminophosphine 1,3,5-triaza-7-phosphaadamantane (PTA). The asymmetric unit consists of a cage-like cation [PTA-Me]+ and a disordered tetrafluoroborate anion; two F atoms are disordered equally over two sites. A network of weak intermolecular C—H⋯F hydrogen bonds results in a three-dimensional supramolecular assembly
Three-dimensional hydrogen-bonded supramolecular assembly in tetrakis(1,3,5-triaza-7-phosphaadamantane)copper(I) chloride hexahydrate
The structure of the title compound, [Cu(PTA)4]Cl·6H2O (PTA is 1,3,5-triaza-7-phosphaadamantane, C6H12N3P), is composed of discrete monomeric [Cu(PTA)4]+ cations, chloride anions and uncoordinated water molecules. The CuI atom exhibits tetrahedral coordination geometry, involving four symmetry-equivalent P–bound PTA ligands. The structure is extended to a regular three-dimensional supramolecular framework via numerous equivalent O—H⋯N hydrogen bonds between all solvent water molecules (six per cation) and all PTA N atoms, thus simultaneously bridging each [Cu(PTA)4]+ cation with 12 neighbouring units in multiple directions. The study also shows that PTA can be a convenient ligand in crystal engineering for the construction of supramolecular architectures
Metal-organic and supramolecular lead(II) networks assembled from isomeric nicotinoylhydrazone blocks : the effects of ligand geometry and counter-ion on topology and supramolecular assembly
A new series of six structurally diverse lead(II) coordination compounds was assembled from two isomeric nicotinoylhydrazones as neutral ligands and three Pb(II) salts with different monoanions (chloride, nitrate and thiocyanate) as starting materials. The products were isolated in good yields and were fully characterized, including by single-crystal Xray diffraction and theoretical methods. Within the six compounds, three feature 2D metal-organic networks, two are 1D coordination polymers, and another one comprises discrete 0D dimeric units. The structures of the latter low dimensional compounds are extendable into 2D supramolecular networks. The topology of the coordination or supramolecular networks is primarily dictated by the geometry of the nicotinoylhydrazone used as a main building block. In contrast, supramolecular interactions are greatly influenced by the choice of the anion in the starting lead(II) salt, which is demonstrated by Hirshfeld surface analysis. In fact, the topological analysis and classification of metal-organic or supramolecular underlying networks in the obtained compounds was performed, disclosing the hcb, 2C1, gek1, SP 1-periodic net (4,4)(0,2) and 3,4L83 topological types; the latter topology was docummented for three compounds, including both coordination and supramolecular networks. In two compounds containing thiocyanate moieties there are supramolecular contacts between thiocyanate anions and lead centres. These were shown by DFT calculations to be strong tetrel bonds (–15.3 and –16.7 kcal/mol) between the σ-hole of the lead atom and the π-system of the thiocyanate S–C bond
R-MAE: Regions Meet Masked Autoencoders
In this work, we explore regions as a potential visual analogue of words for
self-supervised image representation learning. Inspired by Masked Autoencoding
(MAE), a generative pre-training baseline, we propose masked region
autoencoding to learn from groups of pixels or regions. Specifically, we design
an architecture which efficiently addresses the one-to-many mapping between
images and regions, while being highly effective especially with high-quality
regions. When integrated with MAE, our approach (R-MAE) demonstrates consistent
improvements across various pre-training datasets and downstream detection and
segmentation benchmarks, with negligible computational overheads. Beyond the
quantitative evaluation, our analysis indicates the models pre-trained with
masked region autoencoding unlock the potential for interactive segmentation.
The code is provided at https://github.com/facebookresearch/r-mae
Aminoalcoholate-driven tetracopper(II) cores as inhibitors of aggregation of β-amyloid
Fourth WG Meeting CA15135 : Final status of WG activities within MuTaLig COST Action, 5-6 March 2020, Izmir, Turkiye [http://www.mutalig.eu/wp-content/uploads/2020/03/Book_of_abstracts_WG_Izmir.pdf
Separation of variables for the quantum SL(2,R) spin chain
We construct representation of the Separated Variables (SoV) for the quantum
SL(2,R) Heisenberg closed spin chain and obtain the integral representation for
the eigenfunctions of the model. We calculate explicitly the Sklyanin measure
defining the scalar product in the SoV representation and demonstrate that the
language of Feynman diagrams is extremely useful in establishing various
properties of the model. The kernel of the unitary transformation to the SoV
representation is described by the same "pyramid diagram" as appeared before in
the SoV representation for the SL(2,C) spin magnet. We argue that this kernel
is given by the product of the Baxter Q-operators projected onto a special
reference state.Comment: 26 pages, Latex style, 9 figures. References corrected, minor
stylistic changes, version to be publishe
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