The existence of a phase transition in classical antiferromagnetic models

For a wide class of antiferromagnetic models we prove the existence of a phase transition using an extended Peierls argument, taking into account a result of Dobrushin [R. L. Dobrushin,Funct. Anal. Appl. 2:44 (1968); in English,2:302 (1968)] for an antiferromagnetic Ising model and the results of Malyshev [V. Malyshev,Comm. Math. Phys. 40:75–82 (1975)] for ferromagnetic models (such as the anisotropic rotator). In particular we review a result of Fröhlich, Israel, Lieb, and Simon [J. Fröhlichet al., J. Stat. Phys. 22(3):297–347 (198)] obtained when reflection positivity holds.     

Synchronization between optically injected semiconductor lasers on undamped relaxation oscillations

Seeding light from a laser into the cavity of a second one is a simple experiment largely encountered in optical domain (Stover, H.L., Steier, W.H.: Appl. Phys. Lett. 8, 91–93 (1966); Lang, R.: IEEE J. Quant. Elect. 18(6), 976–983 (1982)). With an unidirectional coupling, optical injection is a basic tool to study synchronization process between oscillators. The dynamics induced in this experiment have been extensively described, theoretically and experimentally (Simpson, T.B. et al.: Quant. Semiclassical Opt. 9(5), 765–784 (1997); Wieczorek S.: Opt. Commun. 172, 279–295 (1999); Blin, S.: Comptes Rendus de la Phys. 4(6), 687–699 (2003)) but mainly when the seeded light is a continuous wave (CW). In this paper, we describe the synchronization on an undamped relaxation regime. In order to study the degree of correlation between the two synchronized lasers (TL and RL), we use a cascade of two optical injections (Guignard, C.: Conference on Lasers and Electro Optics—the Europeen Quant. Electronics Conference (CLEO-EQEC), Munich (Germany), EC1M (2003)) thus three lasers: Master-transmitter laser (TL)-receiver laser (RL). The seeding by a field showing undamped relaxations can be directly compared with the optical injection by a CW signal, especially when the injected power and the detuning between the TL and RL frequencies are varied. Synchronization on undamped relaxation are shown to occur at values of the optical injected power and detuning, for which the RL is in the locked or wave-mixing regime when it is seeded by a CW. However, additional tongues of synchronization also exist at detuning equal to the relaxation oscillation frequency (ROF).     

A Novel Series Colorimetric and Off–On Fluorescent Chemosensors for Fe3+ Based on Rhodamine B Derivative

A novel series colorimetric and off–on fluorescent chemosensors (2a, 2b, 2c) were designed and synthesized, which showed reversible and highly selective and sensitive recognition toward Fe³⁺ over other examined metal ions. Upon addition of Fe³⁺, sensors (2a, 2b) exhibit remarkably and 2c exhibits moderate enhanced absorbance intensity and color change from colorless to pink in CH₃OH–H₂O(1:1, v/v). The three compounds (2a, 2b, 2c) may therefore be applicable as rhodamine-based turn-on type fluorescent chemosensors.     

Processing of heteronuclear NMR relaxation data with the new software DASHA

The new program DASHA is an efficient implementation of common data processing steps for the protein internal dynamic analysis. The “model-free” parameters and their uncertainties (Lipari G., Szabo A.: J. Am. Chem. Soc.104, 4546–4559 (1982) can be calculated from an arbitrary combination of experimental data sets (i.e. heteronuclear¹H?¹⁵N or¹H?¹³C relaxation times and NOE values at different spectrometer frequencies). Anisotropy of the molecular rotational diffusion could be also taken into account without introduction of the new adjustable parameters into the spectral density functionJ(ω), provided the structure of the molecule is known. Parameters of chemical (conformational) exchange can be estimated from the CPMG spin-lock frequency dependences (Bloomet al.: J. Chem. Phys.42, 1615–1624 (1965); Orekhovet al.: Eur. J. Biochem.219, 887–896 (1994). The program can be used both in the interactive and batch modes. It has sophisticated PostScript plotting facilities.     

Dynamics of mass transfer caused by the photoinduced spatially inhomogeneous modulation of mobility in a multicomponent medium

The reasons behind the three-dimensional mass transfer of the inert components of a mixture in which photoinduced spatially inhomogeneous polymerization takes place are discussed. Such a mass transfer is responsible for the laser-induced formation of controllable diffraction gratings in polymer composites containing liquid crystals [R. L. Sutherland, V. P. Tondiglia, L. V. Natarajan, and T. J. Bunning, Chem. Mater. 5, 1533 (1993); R. L. Sutherland, V. P. Tondiglia, and L. V. Natarajan, Appl. Phys. Lett. 64, 1074 (1994); R. L. Sutherland, V. P. Tondiglia, L. V. Natarajan, et al., J. Nonlinear Opt. Phys. Mater. 5, 89 (1996); R. Caputo, A. V. Sukhov, and C. Umeton, Mol. Mater. 12, 192 (1999)]. The semiphenomenological model proposed in this work is based on the assumption that mass transfer results from conventional Fickian diffusion which, however, does not occur over the entire volume of the sample, but only in regions free from clusters of long polymer chains. It is shown that such a “restriction of the active volume” is responsible for the conventional diffusion of inert components of liquid crystals as well as reagents and low-molecular products (short chains), in spite of the initial spatial homogeneity of concentrations in the sample. The qualitative predictions of the model coincide with the experimental results [R. Caputo, A. V. Sukhov, and C. Umeton, Mol. Mater. 12, 192 (1999)].     

EPR,the X-ray Structure and DFT Calculations of the Nitroxide Biradical with One Acetylene Group in the Bridge

Two short nitroxide biradicals of similar composition, R6′–R6′ (B0) and R6′–(C ≡ C)–R6′ (B1), where R6′ is 1-oxyl-2,2,6,6-tetramethyl-3,4-ene-nitroxide ring, have been investigated by electron paramagnetic resonance spectroscopy and X-ray structural analysis. Quantum chemical calculations at UDFT/B3LYP/cc-pVDZ level were also performed and compared with the X-ray structural data. Zero-field splitting parameters D for B0 and B1 were found to be equal ?0.0048 and ?0.0022 cm^?1, respectively, in good agreement with quantum chemical prediction. Potential energy surface scans corresponding to pathways of the conformational rearrangements were calculated; rotation barriers for B0 and B1 were found to be 19.2 and 4.0 kJ/mol, respectively; and structural rigidity and probable differences in biradicals behavior are discussed. Calculations of spin density distribution in biradicals B0 and B1 were also carried out.     

Basic kinetic wealth-exchange models: common features and open problems

We review the basic kinetic wealth-exchange models of Angle [J. Angle, Social Forces 65, 293 (1986); J. Math. Sociol. 26, 217 (2002)], Bennati [E. Bennati, Rivista Internazionale di Scienze Economiche e Commerciali 35, 735 (1988)], Chakraborti and Chakrabarti [A. Chakraborti, B. K. Chakrabarti, Eur. Phys. J. B 17, 167 (2000)], and of Dragulescu and Yakovenko [A. Dragulescu, V.M. Yakovenko, Eur. Phys. J. B 17, 723 (2000)]. Analytical fitting forms for the equilibrium wealth distributions are proposed. The influence of heterogeneity is investigated, the appearance of the fat tail in the wealth distribution and the relaxation to equilibrium are discussed. A unified reformulation of the models considered is suggested.     

Frequency spectrum of Cherenkov radiation and radioastronomical method for measuring the flux of ultrahigh-energy cosmic particles

The frequency spectrum of a radio pulse generated by a cascade shower in the Moon’s regolith has been calculated with the inclusion of the transverse sizes of the shower and the inhomogeneous distribution of excess electrons over the disc radius. The character of the spectrum differs significantly from the previous results that were obtained by E. Zas et al., Phys. Rev. D 45, 362 (1992), and J. Alvarez-Muñis et al., astro-ph/0003315, and were more recently used by T. H. Hankins et al., Mon. Not. R. Astron. Soc. 283, 1027 (1996); P. W. Gorham et al., astro-ph/9906504; and P. W. Gorham et al., astro-ph/0310232. The maximum-intensity region lies in a range of 500–600 MHz. In a frequency range of 1.5–2 GHz, the radiation intensity decreases by several orders of magnitude. This seems to be one of the causes of the absence of events in experimental works of T. H. Hankins et al., Mon. Not. R. Astron. Soc. 283, 1027 (1996); P. W. Gorham et al., astro-ph/9906504; and P. W. Gorham et al., astro-ph/0310232, which closed Z-burst models.     

Theg-tensor anisotropy of the triplet state of the primary electron donor in the photosynthetic bacteriumRhodobacter sphaeroides by high-field (95 GHz) EPR

The anisotropy of theg-tensor of the light-induced triplet state of the primary electron donor (D) of the photosynthetic bacteriumRhodobacter sphaeroides is determined by electron-spin-echo-detected electron paramagnetic resonance at 95 GHz. Measurements on frozen solutions of quinone-depleted reaction centers yield g-values along the principal directions of the zero-field splitting tensor (Norris J.R., Budil D.E., Gast P., Chang C.H., ElKabbani O., Schiffer M.: Proc. Natl. Acad. Sci. USA86, 4335–4339, 1989).g-Values determined are: 2.00308, 2.00238, and 2.00138. The deviation from axial symmetry and thez-component of the g-tensor are smaller than observed in the cation radical of D.     

An Alternative Approach to Understanding the Observed Positron Fraction

Space-based observations by PAMELA (Adriani et al., Nature 458, 607, 2009), Fermi-LAT (Ackerman et al., Phys. Rev. Lett. 105, 01103, 2012), and AMS (Aguilar et al., Phys. Rev. Lett. 110, 141102, 2013) have demonstrated that the positron fraction (e+/total-e) increases with increasing energy above about 10 GeV. According to the propagation model for Galactic cosmic rays in widespread use (Moskalenko & Strong, Astrophys. J. 493, 693, 1998), the production of secondary positrons from interaction of cosmic-ray protons and heavier nuclei with the interstellar medium gives a generally falling positron fraction between 10 and 100 GeV, with secondary positrons accounting for only ～20 % of the observed positron fraction at 100 GeV; so some other physical phenomena have been proposed to explain the data. An alternative approach to interpreting the positron observations is to consider these data as presenting an opportunity for re-examining models of Galactic cosmic-ray propagation. Following release of the PAMELA data, three groups published propagation models (Shaviv, et al., Phys. Rev. Lett. 103, 111302, 2009, Cowsik and Burch, Phys. Rev. D. 82, 023009, 2010, Katz et al., Mon. Not. R. Aston. Soc. 405, 1458 2010) in which the observed positron fraction is explained entirely by secondary positrons produced in the interstellar medium. In May of this year, stimulated by the AMS extension of the positron data to higher energy with excellent statistics, two of those groups presented further development of their calculations (Cowsik et al. 2013, Blum et al. 2013), again concluding that the observed positrons can be understood as secondaries. None of the authors of these five papers was registered for the 33rd International Cosmic Ray Conference (ICRC). Although I am not an author of any of these papers, I have some close familiarity with one of these recent papers, so the conference organizers invited me to bring this alternative approach to the attention of the conference. The present paper is a summary of the material I presented, along with a brief comment about reaction at the conference to this approach.     

Volume reflection and volume refraction of relativistic particles in a uniformly bent crystal

The scattering of fast charged particles in a bent crystal has been analyzed in the framework of relativistic classical mechanics. The expressions obtained for the deflection function are in satisfactory agreement with the experimental data for the volume reflection of relativistic protons obtained by Yu. M. Ivanov et al., Phys. Rev. Lett. 97, 144801 (2006); Yu. M. Ivanov et al., Pis’ma Zh. Eksp. Teor. Fiz. 84, 445 (2006) [JETP Lett. 84, 372 (2006)]; and W. Scandale et al., Phys. Rev. Lett. 98, 154801 (2007). The features of the scattering of the particles on ring potentials are considered in a wide range of impact parameters.     

Coordination preference and magnetic properties of FeII assemblies with a bis-azole bearing 1,2,4-triazole and tetrazole

With a new bis-azole molecular fragment (Htt) bearing 1,2,4-triazole and tetrazole, a mononuclear complex [Fe(tt)₂(H₂O)₄]·2H₂O (1), a trinuclear complex [Fe₃(tt)₆(H₂O)₆]·2H₂O (2) and a 1D coordination polymer [Fe(tt)(Htt)₂]BF₄·2CH₃OH (3) were obtained by varying reaction conditions. Htt acts either as an anionic or neutral ligand depending upon the reaction medium and pH. Thermal variation of spin states of 1–3 were investigated in the range 77–300?K by ⁵⁷Fe M?ssbauer spectroscopy. 1 totally remains in high-spin state over the entire temperature range whereas no spin crossover was evidenced in 2. Nearly 1:1 high-spin and low-spin population ratio is found in 3, which remains constant over the entire temperature range investigated.     

Classical field theory methods in laser physics. III. Propagation of laser radiation in vacuum outside a resonator

The third Part of our work continues the analysis of the problem considered in Parts I and II [J. Russ. Laser Res.,17, 205 (1996);18, 2 (1997)]. We continue the search for the answer to the question: What is laser radiation from the viewpoint of the classical theory of wave fields? Here, we give one of the possible interpretations of propagation of laser radiation in vacuum outside a resonator from both the nonrelativistic and relativistic points of view. The relation between the metric and the radiation field structure is noted. Moreover, the third Part contains the conclusion concerning the work as a whole. It presents the main observations that may be useful for further studies of the problem.     

The Reaction of Synechocystis Catalase–Peroxidase (KatG) with Isoniazid Investigated by Multifrequency (9–285 GHz) EPR Spectroscopy

Three distinct electron paramagnetic resonance (EPR) spectra of radical intermediates formed as reactive intermediates in the catalytic cycle of Synechocystis catalase–peroxidase were identified. Multifrequency EPR spectroscopy, combined with site-directed mutagenesis and selective deuterium labeling of Trp and Tyr residues, allowed us to unequivocally assign such intermediates to an [Fe(IV) = O Por ^·+] species, the first committed intermediate in monofunctional peroxidases and two protein-based radicals, identified as Trp106 ^· and a Tyr ^· , formed subsequently to the [Fe(IV) = O Por ^·+] species by intramolecular electron transfer. Our recent characterization of the Mycobacterium tuberculosis catalase–peroxidase showed that the Trp ^· sites differ among these enzymes, and that the [Fe(IV) = O Trp ^· ] species was the reactive intermediate with the prodrug isoniazid. Accordingly, the question to address was whether the dissimilarity in the sites for the formation of the Trp ^· intermediates and in the geometry of the distal side was reflected by differences in the peroxidase-like reaction of Synechocystis and Mycobacterium tuberculosis catalase–peroxidases with the prodrug isoniazid. Our findings show that in the Synechocystis enzyme, the isoniazid substrate can get closer to the heme distal side and can react readily with the [Fe(IV) = O Por ^·+] species, at variance to the situation in the M. tuberculosis catalase–peroxidase. These results indicate that, as in the case of monofunctional peroxidases, the difference in the sites for the formation of the Trp ^· as alternative reactive intermediates to the [Fe(IV) = O Por ^·+] species is correlated to differences in substrate binding sites.     

Synthesis and Study the Effect of Donor-Acceptor Substituent on Fluorescence Behavior of Thieno[3, 2-c]pyridine Derivatives

4-Hetero-1-yl-2-bromothieno[3,2-c]pyridines 3(a–d) were synthesized by the reaction of 2-bromo-4-chlorothieno[3,2-c]pyridine (1) and cyclic amine 2(a–d), which on Suzuki coupling with substituted boronic acids 4(a–f) exclusively converted to corresponding 4-hetero -1-yl-2-arylthieno[3,2-c]pyridine 5(a–x) in good yields. The effect of donor-acceptor substituent on absorption emission properties and fluorescent quantum yield of new thienopyridine derivatives 5(a-x) were studied.     

Localization in the ground state of a disordered array of quantum rotators

We consider the zero-temperature behavior of a disordered array of quantum rotators given by the finite-volume Hamiltonian: $$H_\Lambda = - \mathop \Sigma \limits_{x \in \Lambda } \frac{{h(x)}}{2}\frac{{\partial ^2 }}{{\partial \varphi (x)^2 }} - J\mathop \Sigma \limits_{\left\langle {x,y} \right\rangle \in \Lambda } \cos (\varphi (x) - \varphi (y))$$ , wherex,y∈Z ^d , 〈,〉 denotes nearest neighbors inZ ^d ;J>0 andh={h(x)>0,x∈Z ^d } are independent identically distributed random variables with common distributiondμ(h), satisfying ∫h ^?δ dμ(h)<∞ for some δ>0. We prove that for anym>0 it is possible to chooseJ(m) sufficiently small such that, if 0<J<J(m), for almost every choice ofh and everyx∈Z ^d the ground state correlation function satisfies $$\left\langle {\cos (\varphi (x) - \varphi (y))} \right\rangle \leqq C_{x,h,J} e^{ - m\left| {x - y} \right|} $$ for ally∈Z ^d withC _x,h,J <∞.     

Contiguity and Entire Separability of States on von Neumann Algebras

We introduce the notions of the contiguity and entirely separability for two sequences of states on von Neumann algebras. The ultraproducts technique allows us to reduce the study of the contiguity to investigation of the equivalence for two states. Here we apply the Ocneanu ultraproduct and the Groh–Raynaud ultraproduct (see Ocneanu (1985), Groh (J. Operator Theory, 11, 2, 395–404 1984), Raynaud (J. Operator Theory, 48, 1, 41–68, 2002), Ando and Haagerup (J. Funct. Anal., 266, 12, 6842–6913, 2014)), as well as the technique developed in Mushtari and Haliullin (Lobachevskii J. Math., 35, 2, 138–146, 2014).     

Aging effect in CaLaBa{Cu1???xFex}3O7???�� with 0 �� x �� 0.07 studied by M?ssbauer spectroscopy

In this work, we study the long-term aging effect caused by Fe atoms in the superconductor CaLaBa{Cu_1???xFe_x}₃O_7????? with 0 ?? x ?? 0.07. XRD confirms that this system has a YBCO-like structure. The critical temperature (T_c) is strongly affected by aging and depends on the amount of Fe in the structure. Room temperature Mössbauer spectroscopy reveals the presence of the typical species A, B?CB ??, C and new species E ?? and F. Interestingly; A, which corresponds to the Fe^3?+? atom located in the Cu(1) of the chains with spin S _z = 3/2, shows a drastic reduction which means migration to the species B, B ?? and C. Species B and B ?? correspond to the Fe^3?+? in the Cu(2) site forming planar quasi-octahedral and planar square pyramidal, while the C specie is a square pyramidal with O(5) respectively (spin S_z = 3/2 in all these cases). Aging causes loss of superconductivity in the samples with 5 and 7% of iron content.     

Indole-based Fluorescent Sensors for Selective Detection of Hg2+

A series of indole-based fluorescent chemosensors 1–4 were prepared and investigated characteristick features with transition metal ions. Sensors 1 and 2 were selective for Hg²⁺ ion among a series of metal ions in H₂O–DMSO with association constants of 4.60×10⁴ and 5.90×10⁴?M^?1 and detection limits of 140 and 101.6 μM, respectively.