Quantum interference in the presence of a resonant medium.

Interaction of light with media often occurs with a femtosecond response time. Its measurement by conventional techniques requires the use of femtosecond lasers and sophisticated time-gated optical detection. Here we demonstrate that by exploiting quantum interference of entangled photons it is possible to measure the dephasing time of a resonant media on the femtosecond time scale (down to 100 fs) using accessible continuous wave laser and single-photon counting.

Thermally Induced Self-Assembly and Cyclization of l-Leucyl-l-Leucine in Solid State.

Thermal treatment of oligopeptides is one of the methods for synthesis of organic nanostructures. However, heating may lead not only to self-assembly of the initial molecules, but also to chemical reactions resulting in the formation of new unexpected nanostructures or change in the properties of the existing ones. In the present work, the reaction of cyclization of dipeptide l-leucyl-l-leucine in solid state under heating was studied.

Molecular Bases of Brain Preconditioning.

Preconditioning of the brain induces tolerance to the damaging effects of ischemia and prevents cell death in ischemic penumbra. The development of this phenomenon is mediated by mitochondrial adenosine triphosphate-sensitive potassium ([Formula: see text]) channels and nitric oxide signaling (NO). The aim of this study was to investigate the dynamics of molecular changes in mitochondria after ischemic preconditioning (IP) and the effect of pharmacological preconditioning (PhP) with the [Formula: see text]-channels opener diazoxide on NO levels after ischemic stroke in rats.

Signatures of a magnetic field-induced unconventional nematic liquid in the frustrated and anisotropic spin-chain cuprate LiCuSbO.

Modern theories of quantum magnetism predict exotic multipolar states in weakly interacting strongly frustrated spin-1/2 Heisenberg chains with ferromagnetic nearest neighbor (NN) inchain exchange in high magnetic fields. Experimentally these states remained elusive so far. Here we report strong indications of a magnetic field-induced nematic liquid arising above a field of ~13 T in the edge-sharing chain cuprate LiSbCuO ≡ LiCuSbO.

Tuning the spin coherence time of Cu(II)-(bis)oxamato and Cu(II)-(bis)oxamidato complexes by advanced ESR pulse protocols.

We have investigated with the pulsed ESR technique at X- and Q-band frequencies the coherence and relaxation of Cu spins = 1/2 in single crystals of diamagnetically diluted mononuclear [-BuN][Cu(opba)] (1%) in the host lattice of [-BuN][Ni(opba)] (99%, opba = -phenylenebis(oxamato)) and of diamagnetically diluted mononuclear [-BuN][Cu(opbo-Pr)] (1%) in the host lattice of [-BuN][Ni(opbo-Pr)] (99%, opbo-Pr = -phenylenebis((propyl)oxamidato)). For that we have measured the electron spin dephasing time at different temperatures with the two-pulse primary echo and with the special Carr-Purcell-Meiboom-Gill (CPMG) multiple microwave pulse sequence. Application of the CPMG protocol has led to a substantial increase of the spin coherence lifetime in both complexes as compared to the primary echo results.

Non-zeolitic properties of the dipeptide l-leucyl-l-leucine as a result of the specific nanostructure formation.

The non-zeolitic behavior of l-leucyl-l-leucine and its self-organization in solid state and from solutions with the formation of different nanostructures are reported. This dipeptide forms porous crystals, but does not exhibit molecular sieve effects typical of classical zeolites and biozeolites. The specific sorption properties of l-leucyl-l-leucine result from a change in its crystal packing from channel-type to layered-type, when binding strong proton acceptors or proton donors of molecular size greater than 18-20 cm mol.

A study of the formation of magnetically active solid dispersions of phenacetin using atomic and magnetic force microscopy.

A lot of pharmaceutical substances have a poor solubility that limits their absorption and distribution to the targeted sites to elicit the desired action without causing untoward effects on healthy cells or tissues. For such drugs, new modes of delivery have to be developed for efficient and effective delivery of the drug to the target site. Formation of magnetically active solid dispersion of such drugs could be a useful approach to addressing this problem because they combine targeted delivery and good solubility.

Separation of enzymatic functions and variation of spin state of rice allene oxide synthase-1 by mutation of Phe-92 and Pro-430.

Rice allene oxide synthase-1 mutants carrying F92L, P430A or F92L/P430A amino acid substitution mutations were constructed, recombinant mutant and wild type proteins were purified and their substrate preference, UV-vis spectra and heme iron spin state were characterized. The results show that the hydroperoxide lyase activities of F92L and F92L/P430A mutants prefer 13-hydroperoxy substrate to other hydroperoxydienoic acids or hydroperoxytrienoic acids. The Soret maximum was completely red-shifted in P430A and F92L/P430A mutants, but it was partially shifted in the F92L mutant.

Measurement of J-couplings between chemically equivalent nuclei using off-resonance decoupling.

The method of measuring J-couplings between chemically equivalent nuclei in isotopically/magnetically non-equivalent environment, based on off-resonance decoupling, is described. The approach uses intensities, rather than frequencies of the spectral peaks and, therefore, the accuracy of measurement is not limited by spectral resolution.

Modulation of defensive reflex conditioning in snails by serotonin.

Highlights Daily injection of serotonin before a training session accelerated defensive reflex conditioning in snails.Daily injection of 5-hydroxytryptophan before a training session in snails with a deficiency of serotonin induced by the "neurotoxic" analog of serotonin 5,7-dihydroxytryptamine, restored the ability of snails to learn.After injection of the "neurotoxic" analogs of serotonin 5,6- and 5,7-dihydroxytryptamine as well as serotonin, depolarization of the membrane and decrease of the threshold potential of premotor interneurons was observed.

Influence of structural anisotropy on mesogenity of Eu(III) adducts and optical properties of vitrified films formed on their base.

A new series of europium adducts with the general formula Eu(CPDk3-CnH2n+1)3Phen, where CPDk3-CnH2n+1 denotes β-diketones and Phen is 1,10-phenanthroline, was synthesized. The obtained mesogenic complexes were heated to the temperatures of the isotropic liquid state and then cooled. The complexes having short CH3 and C2H5 substituents crystallized upon cooling, and the complexes with longer substituents from C3H7 to C6H13 underwent a glass transition with the formation of optically transparent amorphous films.

Electron Spin Density on the N-Donor Atoms of Cu(II)-(Bis)oxamidato Complexes As Probed by a Pulse ELDOR Detected NMR.

We have applied the pulse ELDOR detected NMR (EDNMR) technique to determine the tensors of the transferred Cu (S = 1/2) - (14)N (I = 1) hyperfine (HF) interaction in single crystals of diamagnetically diluted mononuclear o-phenylenebis(N(R)-oxamide) complexes of [(n)Bu4N]2[Cu(opboR2)] (R = Et 1, (n)Pr 2) (1%) in a host lattice of [(n)Bu4N]2[Ni(opboR2)] (R = Et 3, (n)Pr 4) (99%) (1@3 and 2@4)). To facilitate the analysis of our EDNMR data and to analyze possible manifestations of the nuclear quadrupole interaction in the EDNMR spectra, we have treated a model electron-nuclear system of the coupled S = 1/2 and I = 1 spins using the spin density matrix formalism. It appears that this interaction yields a peculiar asymmetry of the EDMR spectra that manifests not only in the shift of the positions of the EDNMR lines that correspond to the forbidden EPR transitions, as expected, but also in the intensities of the EDNMR lines.

Membrane-Sugar Interactions Probed by Pulsed Electron Paramagnetic Resonance of Spin Labels.

Sugars can stabilize biological systems under extreme desiccation and freezing conditions. Hypothetical molecular mechanisms suggest that the stabilization effect may be determined either by specific interactions of sugars with biological molecules or by the influence of sugars on the solvating shell of the biomolecule. To explore membrane-sugar interactions, we applied electron spin echo envelope modulation (ESEEM) spectroscopy, a pulsed version of electron paramagnetic resonance (EPR), to phospholipid bilayers with spin-labeled lipids added and solvated by aqueous deuterated sucrose and trehalose solutions.

Random strain effects in optical and EPR spectra of electron-nuclear excitations in CaWO4:Ho(3+) single crystals.

We study paramagnetic Ho(3+) centers in CaWO4, a promising material for applications in quantum electronics and quantum information devices. Oriented single crystals with nominal holmium concentrations 0.05, 0.

Low-temperature molecular motions in lipid bilayers in the presence of sugars: insights into cryoprotective mechanisms.

Sugars and sugar alcohols can stabilize biological systems under extreme conditions of desiccation and freezing. Phospholipid bilayers solvated by aqueous solutions of sucrose, trehalose, and sorbitol at concentrations of 0.2 and 1 M and containing incorporated spin-labeled stearic acids were studied by electron spin echo (ESE) spectroscopy, a pulsed version of electron paramagnetic resonance (EPR).

Communication: Long-lived states of nuclear spins in solids.

We report an observation of extremely long-lived spin states in systems of dipolar-coupled nuclear spins in solids. The "suspended echo" experiment uses a simple stimulated echo pulse sequence and creates non-equilibrium states which live many orders of magnitude longer than the characteristic time of spin-spin dynamics T2. Large amounts of information can be encoded in such long-lived states and subsequently retrieved by an application of a single "reading" pulse.

Evidence for triplet superconductivity in a superconductor-ferromagnet spin valve.

We have studied the dependence of the superconducting (SC) transition temperature on the mutual orientation of magnetizations of Fe1 and Fe2 layers in the spin valve system CoO(x)/Fe1/Cu/Fe2/Pb. We find that this dependence is nonmonotonic when passing from the parallel to the antiparallel case and reveals a distinct minimum near the orthogonal configuration. The analysis of the data in the framework of the SC triplet spin valve theory gives direct evidence for the long-range triplet superconductivity arising due to noncollinearity of the two magnetizations.

Manifestation of new interference effects in a superconductor-ferromagnet spin valve.

Superconductor-ferromagnet (S/F) spin valve effect theories based on the S/F proximity phenomenon assume that the superconducting transition temperature Tc of F1/F2/S or F1/S/F2 trilayers for parallel magnetizations of the F1 and F2 layers (T(c)(P)) are smaller than for the antiparallel orientations (T(c)(AP)). Here, we report for CoOx/Fe1/Cu/Fe2/In multilayers with varying Fe2-layer thickness the sign-changing oscillating behavior of the spin valve effect ΔT(c) = T(c)(AP) - T(c)(P). We observe the full direct effect with T(c)(AP) > T(c)(P) for Fe2-layer thickness d(Fe2) < 1 nm and the full inverse (T(c)(AP) < T(c((P)) effect for d(Fe2) ≥ 1 nm.

Experimental observation of the spin screening effect in superconductor/ferromagnet thin film heterostructures.

We have studied the nuclear magnetic resonance (NMR) of 51V nuclei in the superconductor/ferromagnet thin film heterostructures Pd_{1-x}Fe_{x}/V/Pd_{1-x}Fe_{x} and Ni/V/Ni in the normal and superconducting state. Whereas the position and shape of the NMR line in the normal state for the trilayers is identical to that observed in a single V layer, in the superconducting state the line shape definitely changes, developing a systematic distortion of the high-field wing of the resonance line. We consider this as the first experimental evidence for the penetration of ferromagnetism into the superconducting layer, a phenomenon which has been theoretically predicted recently and dubbed the spin screening effect.

Ultrahigh interference spatial compression of light inside the subwavelength aperture of a near-field optical probe.

Spatial effects of interference and interaction of light modes in the subwavelength part of the near-field optical microscopy probe have been theoretically studied. It was found that the mode interference can lead to higher spatial compression of light (wavelength is equal to 500 nm in free space) within the transverse size of 25 nm inside the probe output aperture of 100 nm in diameter. The results predict a principal possibility of higher spatial resolution in the near-field optical microscopy technique.

Peculiar manifestation of the dipole-dipole interaction between non-Kramers paramagnetic centers as studied by tunable high-frequency EPR spectroscopy.

EPR spectral shape of non-Kramers paramagnetic centers (PCs) is theoretically analyzed under conditions of saturation. The analysis is performed in a model that includes the spectral diffusion process induced by a random modulation of the dipole-dipole interaction of the paramagnetic centers, by reorientations of magnetic moments. It is shown that around zero magnetic field, a 'hole' might appear in the EPR spectrum.

Complete reconstruction of the quantum state of a single-photon wave packet absorbed by a Doppler-broadened transition.

An idea for how to reconstruct the quantum state of a nonstationary single-photon wave packet absorbed in a macroscopic medium with inhomogeneously broadened lines is presented. An analytical treatment of the problem is performed and the requirements on the proposed scheme for complete recovery of the recorded nonstationary quantum state with a probability close to unity is described. The physical nature of the present scheme is also discussed.