Spin squeezing and quantum correlations

We discuss the notion of spin squeezing considering two mutually exclusive classes of spin-s states, namely, oriented and non-oriented states. Our analysis shows that the oriented states are not squeezed while non-oriented states exhibit squeezing. We also present a new scheme for construction of spin-s states using 2s spinors oriented along different axes. Taking the case of s=1, we show that the ‘non-oriented’ nature and hence squeezing arise from the intrinsic quantum correlations that exist among the spinors in the coupled state.     

Ruthenium(II), rhodium(III) and iridium(III) based effective catalysts for hydrogenation under aerobic conditions

The new cationic mononuclear complexes [(η⁶-arene)Ru(Ph-BIAN)Cl]BF₄ [η⁶-arene = benzene (1), p-cymene (2)], [(η⁵-C₅H₅)Ru(Ph-BIAN)PPh₃]BF₄ (3) and [(η⁵-C₅Me₅)M(Ph-BIAN)Cl]BF₄ [M = Rh (4), Ir (5)] incorporating 1,2-bis(phenylimino)acenaphthene (Ph-BIAN) are reported. The complexes have been fully characterized by analytical and spectral (IR, NMR, FAB-MS, electronic and emission) studies. The molecular structure of the representative iridium complex [(η⁵-C₅Me₅)Ir(Ph-BIAN)Cl]BF₄ has been determined crystallographically. Complexes 1–5 effectively catalyze the reduction of terephthaldehyde in the presence of HCOOH/CH₃COONa in water under aerobic conditions and, among these complexes the rhodium complex [(η⁵-C₅Me₅)Rh(Ph-BIAN)Cl]BF₄ (4) displays the most effective catalytic activity.     

New modelling approach for damped mutilayed composites

The aim of this paper is to get a good approximation of damping properties of viscoelastic damped sandwich structures. Firstly we will compare the classical models based on the kinematics of Kirchhoff-Love, Mindlin, Reddy or Touratier. In the second stage these models are used to establish the zig-zag models which describe a piecewise continuous displacement field. These models are compared in the static and the dynamic fields. In all cases the Finite-Element-based solution is considered as reference. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Design and synthesis of fluorescent 6-aryl[1,2-c]quinazolines serving as selective and sensitive ‘on-off’ chemosensor for Hg in aqueous media

Three fluorescent quinazolines thiophen-2-yl-5,6-dihydrobenzo-[4,5]imidazo[1,2-c]quinazoline (1), pyridin-3-yl-5,6-dihydrobenzo-[4,5]imidazo-[1,2-c]quinazoline (2) and phenyl-5,5′,6,6′-dihydrobenzo-[4,4′,5,5′]imidazo-[1.1′,2-c,2′-c]quinazoline (3) have been synthesized. Structures of 1 and 3 have been authenticated crystallographically. Quinazolines 1-3 exhibit highly selective ‘on-off’ switching for Hg²⁺ ions. The fluorescence intensity displayed a linear relationship with respect to Hg²⁺ concentration (0.1-1.0 μM; R² = 0.99) with detection limit of 2.0 × 10⁻⁷ M.     

Well-posedness of a model of strain gradient plasticity for plastically irrotational materials

The initial boundary value problem corresponding to a model of strain gradient plasticity due to [Gurtin, M., Anand, L., 2005. A theory of strain gradient plasticity for isotropic, plastically irrotational materials. Part I: Small deformations. J. Mech. Phys. Solids 53, 1624–1649] is formulated as a variational inequality, and analysed. The formulation is a primal one, in that the unknown variables are the displacement, plastic strain, and the hardening parameter. The focus of the analysis is on those properties of the problem that would ensure existence of a unique solution. It is shown that this is the case when hardening takes place. A similar property does not hold for the case of softening. The model is therefore extended by adding to it terms involving the divergence of plastic strain. For this extended model the desired property of coercivity holds, albeit only on the boundary of the set of admissible functions.     

Theory of sheath in a collisional multi-component plasma

The aim of this brief report is to study the behaviour of sheath structure in a multi-component plasma with dust-neutral collisions. The plasma consists of electrons, ions, micron size negatively charged dust particles and neutrals. The sheath-edge potential and sheath width are calculated for collisionally dominated sheath. Comparison of collisionless and collisionally dominated sheath are made.     

Luminescent piano-stool complexes incorporating 1-(4-cyanophenyl)imidazole: synthesis, spectral, and structural studies

Three novel luminescent piano-stool arene ruthenium complexes of general formula [(eta(6)-arene)RuCl(2)(CPI)] (eta(6)-arene = benzene, 1, p-cymene, 2, and hexamethylbenzene, 3; CPI=1-(4-cyanophenyl)imidazole were prepared. The molecular structures of 2 and 3 were determined crystallographically. Reaction of 1-3 with EPh(3) (E = P, As, or Sb) and N-N donor bases such as 2,2'-bipyridine and 1,10-phenanthroline afforded cationic mononuclear complexes of general formula [(eta(6)-arene)RuCl(CPI)(EPh(3))](+) (eta(6)-arene = C(6)H(6), E = P (1a), E = As (1b), E = Sb(1c); eta(6)-arene = C(10)H(14), E = P (2a), E = As (2b), E = Sb (2c); eta(6)-arene = C(6)Me(6), E = P (3a), E = As (3b), E = Sb (3c)) and [(eta(6)-arene)Ru(N-N)(CPI)](2+) (eta(6)-arene = C(6)H(6), N-N = bipy (1d), N-N = phen (1e); eta(6)-arene = C(10)H(14), N-N = bipy (2d), N-N = phen (2e); eta(6)-arene = C(6)Me(6), N-N = bipy (3d), N-N = phen (3e)). Molecular structures of 1a and 2a were also confirmed by X-ray crystallography. Structural studies of the complexes 2, 3, 1a, and 2a supported coordination of CPI through the imidazole nitrogen and the presence of a pendant nitrile group. Structural data also revealed stabilization of crystal packing in the complexes 2, 3, and 2a by C-H...X (X = Cl, F) type inter- and intramolecular interactions and in complex 1a by pi-pi stacking. Moreover, neutral homonuclear bimetallic complexes 2f,g were prepared by using complex 2 as a metallo-ligand, where CPI acts as a bridge between two metal centers. Emission spectra of the mononuclear complexes [(eta(6)-arene)RuCl(2)(CPI)] and its derivatives exhibited intense luminescence when excited in the metal to ligand charge-transfer band.     

Analysis of a shielded TE011 mode composite dielectric resonator for stable frequency reference

Analysis of a TE₀₁₁ mode composite sapphire-rutile dielectric resonator has been carried out to study the temperature variation of resonance frequency, close to the Cs atomic clock hyperfine frequency of 9.192 GHz. The complementary behavior of dielectric permittivity with temperature of the composite has been exploited to obtain the desired turning point in the resonant frequency. The frequency of the composite structure is found to be independent of the shield diameter beyond four times the puck diameter.     

Exquisite 1D Assemblies Arising from Rationally Designed Asymmetric Donor–Acceptor Architectures Exhibiting Aggregation‐Induced Emission as a Function of Auxiliary Acceptor Strength

One‐dimensional nanostructures with aggregation‐induced emission (AIE) properties have been fabricated to keep the pace with growing demand from optoelectronics applications. The compounds 2‐[4‐(4‐methylpiperazin‐1‐yl)benzylidene]malononitrile ( PM1 ), 2‐{4‐[4‐(pyridin‐2‐yl)piperazin‐1‐yl]‐benzylidene}malononitrile ( PM2 ), and 2‐{4‐[4‐(pyrimidin‐2‐yl)piperazin‐1‐yl]benzylidene}malononitrile ( PM3 ) have been designed and synthesized by melding piperazine and dicyanovinylene to investigate AIE in an asymmetric donor–acceptor (D–A) construct of A′–D–π–A‐ topology. The synthetic route has been simplified by using phenylpiperazine as a weak donor (D), dicyanovinylene as an acceptor (A), and pyridyl/pyrimidyl groups ( PM2/PM3 ) as auxiliary acceptors (A′). It has been established that A′ plays a vital role in triggering AIE in these compounds because the same D–A construct led to aggregation‐caused quenching upon replacing A′ with an electron‐donating ethyl group ( PM1 ). Moreover, the effect of restricted intramolecular rotation and twisted intramolecular charge transfer on the mechanism of AIE has also been investigated. Furthermore, it has been clearly shown that the optical disparities of these A′–D–π–A architectures are a direct consequence of comparative A′ strength. Single‐crystal X‐ray analyses provided justification for role of intermolecular interactions in aggregate morphology. Electrochemical and theoretical studies affirmed the effect of the A′ strength on the overall properties of the A′–D–π–A system.