Contributions from changes in various solar indices in cycles 20–23 and 24 to the modulation of cosmic rays

The modulation of cosmic rays (CRs) observed at neutron monitors during the minimum, growth, maximum, and beginning of the decay of solar activity (SA) of cycle 24 (2008–2015) is compared to the modulation of CRs in the same periods of SA of cycles 20–23. After a prolonged minimum of SA between cycles 23 and 24 in 2007–2009 and the maximum of CRs at the end of 2009, when CR intensity exceeded the previous four CR maxima, the SA growth phase displayed weaker modulation of CRs than in the corresponding periods of the previous cycles. The shorter variations in CRs (oscillations with variable periods and activity spikes) were clearer against the background of the reduction in the 11-year variation during SA growth in 2011–2014. The current SA cycle (24) saw a scenario with two SA maxima, and the CRs showed one minimum at the end of 2014 that differed from the maximum of 2009 by ≈12% for particles with a rigidity of 10 GV. CR modulation in the last cycle was the weakest since neutron monitors began operating. At the beginning of 2015, the CRs started to recover. Possible reasons for the unusually weak CR modulation are considered. Quantitative estimates are made of the contribution from different characteristics of the solar magnetic field to CR modulation in the period of cycle 24 under study and in the corresponding periods of solar cycles 20–23, and the estimates are compared.     

Synthesis of lactic acid–Zr(IV) phosphate nanocomposite ion exchanger for green remediation

Lactic acid–Zr(IV) phosphate nanocomposite (LA/ZPNC) ion exchanger was synthesised by sol-gel method. The nanocomposite ion exchanger was characterized by different techniques such as Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy X-ray diffraction (XRD) and thermogravimetric analysis (TGA/DTA/DSC). LA/ZPNC was employed for different physicochemical properties such as ion exchange capacity, elution behaviour, effect of eluent concentration, pH titration and thermal stability. The ion exchange capacity of LA/ZPNC was higher as compared to their inorganic counterpart. pH results indicate the bifunctional nature of nanocomposite. A degradation efficiency of 89.47 % was attained in 4 h of illumination. The distribution coefficient (K _d) studies of LA/ZPNC ion exchanger were investigated for eight different metal ions and found more selective for Al³⁺ with higher K _d value. It was explored for photocatalytic study of methylene blue under solar illumination.     

Anomalous Hall effect in (Co41Fe39B20) x (Al-O)100 − x nanocomposites

The concentration dependence of the coefficient R _s characterizing the anomalous Hall effect (AHE) has been studied by measuring the electrical resistivity ρ, magnetoresistance, and the magnetic field dependence of magnetization and Hall resistivity of (Co₄₁Fe₃₉B₂₀) _x (Al-O)_{100 ? x} nanocomposite thin films. It has been demonstrated that the AHE coefficient increases by more than an order of magnitude with a decrease in the percentage x of the amorphous ferromagnetic metal from 60 to 30 and its behavior is described by the relation R _s ～ ρ ^m , where m = 0.46 ± 0.1. At the same time, the coefficient characterizing the normal Hall effect grows by a factor of less than 10. The mechanisms underlying the giant Hall effect in nanocomposites have been discussed.     

Structural and property changes in poly (vinylidene fluoride–trifluoroethylene) 70/30 mol % copolymer induced by proton irradiation

Poly(vinylidene fluoride–trifluoroethylene) 70/30 mol% copolymer has been irradiated with 3 MeV protons at doses ranging from 43 to 200 Mrad. The effects of irradiation on the polarization hysteresis, dielectric properties, lattice spacing, phase transition behavior and electric-field-induced strain have been studied. The irradiated copolymer exhibits the characteristic behavior of a relaxor ferroelectric, including frequency dispersion of the dielectric constant, which follows the Vogel–Fulcher rule. These results indicate that the proton irradiation breaks up the coherent polarization domains in the copolymer into nano-sized regions, thereby converting the copolymer to a relaxor ferroelectric. X-ray diffraction measurements show that the nano-sized regions are in the non-polar phase. Since the lattice spacing of the non-polar phase is substantially different from that of the polar phase, the local phase transformation between these two phases induced by an external electric field gives rise to a large lattice strain and hence a giant electrostrictive response. PACS 77     

Structural feature of calf thymus deoxyribonucleic acid–ruthenium(III) interaction in aqueous solution by difference Fourier transformed infrared spectroscopy

Here is the report on the interaction of ruthenium(III) species with DNA in aqueous solution at pH 7.42 by Fourier transformed infrared difference spectroscopy. Under the physiological pH and molar ratio [Ruthenium]/[DNA]?=?1/80–1/20 direct binding to guanine-N7, adenine-N7, and surprising binding to exocyclic thymine-O2 was found. At low metal concentration no significant shift of the absorption bands was observed, only nonspecific electrostatic binding of ruthenium(III) with negatively charged phosphate groups occurred. The increase of ruthenium(III) concentration caused DNA double helix destabilization and direct binding of the metal cation to guanine-N7 and thymine-O2. At higher ruthenium(III) concentrations denaturation of the DNA helix is evident with no apparent binding of ruthenium(III) to adenine and cytosine. Helix opening allows migration of ruthenium(III) ions from phosphate to available nucleobases (guanine and thymine). No alteration of the sugar phosphate geometry was observed thus confirming that DNA remains in B conformation.     

Rheology Behavior of Hydrophobically Modified Poly(acrylic acid) with Twin-Tailed Pendant in Water—Ethylene Glycol Mixture

A hydrophobically modified poly(acrylic acid) (HMPA) with twin-tailed hydrophobic pendant side groups was prepared by precipitation polymerization. The rheology behavior of HMPA was examined in mixtures of water and ethylene glycol (EG) of different proportions. It was shown that the solvent had a direct impact on both the steady and dynamic rheology behaviors of the HMPA solutions. The change of hydrophobic interactions in the EG-rich mixtures may be attributed to the observed decrease in polymer coil dimension together with a lower tendency of the hydrophobes to form junctions. As the temperature decreased, the viscosities and numbers of active junctions of HMPA in water–EG mixtures increased.     

Induction and repair of DNA double-strand breaks in rat cerebellar cortex exposed to <Superscript>60</Superscript>Co γ-rays

The induction and repair of DNA double-strand breaks are studied using the immunohistochemical staining procedure of paraffin-embedded rat cerebellum tissues after exposure to γ-rays of ⁶⁰Co. The dose dependence of radiation-induced colocalized γH2AX/53BP1 foci is studied and its linear character is established. It is shown that these foci are efficiently eliminated 24 h after irradiation.     

High-temperature background of internal friction in (Co45Fe45Zr10) x (Al2O3)100 − x , Co x (CaF2)100 − x , and Co x (PZT)100 − x nanocomposites

The elastic (G) and inelastic (Q ^?1) properties of (Co₄₅Fe₄₅Zr₁₀) _x (Al₂O₃)_{100 ? x} , Co _x (CaF₂)_{100 ? x} , and Co _x (PZT)_{100 ? x} (x = 23–76 at %) nanocomposites obtained by ion-beam sputtering are studied in the temperature range 300–900 K. A significant rise in the Q Q ^?1 (T) curve is observed at temperatures above 650 K, which is attributed to thermally activated migration of point defects under the conditions of confined geometry.     

Preparation and Characterization of Inorganic–Organic Composites with Highly Dense CdS Nanoparticles Using Poly(2-acetamidoacrylic acid) Hydrogels

We report the template-based synthesis of inorganic CdS nanoparticles (NPs) in the interior of a poly(2-acetamidoacrylic acid) (PAAA) hydrogel as a novel type of nanocomposite by ion exchange in an aqueous system. Transmission electron microscopy (TEM) confirmed that the semiconductor CdS NPs was dispersed homogeneously in the hydrogel without particle aggregation. The average crystallite sizes calculated from the X-ray powder diffraction (XRD) pattern using the Scherrer equation, the absorption threshold from the ultraviolet-visible (UV-Vis) spectra and TEM were 3.02, 5.16 and 5.2 nm, respectively. In contrast to the uncapped CdS NPs, which had precipitated from the solution immediately after the reaction, the CdS NPs capped by the PAAA hydrogels did not show any observable changes, even after 6 months. This was confirmed by the lack of a red-shift in the absorption edge of the PAAA-capped CdS NPs and by TEM. Thermogravimetric analysis (TGA) showed that the CdS-embedded PAAA gel had superior thermal stability to the pure PAAA gel. In addition, the CdS NPs content in the dry composite gel was more than 70 wt%, indicating that the PAAA hydrogels have a large holding capacity for CdS NPs.     

Compatibilizing Action of a Poly(styrene–butadiene) Triblock Co-polymer in ABS/PET-G Blends

The morphology of blends of poly(acrylonitrile-co-butadiene-co-styrene) (ABS) and poly(ethylene terephthalate glycol) (PET-G) has been investigated with special reference to the effect of blend ratio and compatibilization. Scanning electron microscopy (SEM) examination revealed different morphologies such as dispersed, cocontinuous and phase inverted depending on the composition, which indicates that the binary blends are immiscible and form a two-phase structure. Tensile properties decreased with increase in the ABS content while the impact strength reached an optimum at ca. 70% ABS. Influence of a triblock co-polymer based on styrene and butadiene (SBS) on morphology, mechanical measurements and failure topography was used as criterion of the compatibilization effect. The compatiblizing action of SBS was evidenced by the sharp decrease in domain size of the dispersed phase followed by an increase at higher concentrations. The conformation of the compatibilizer at the interface was further analyzed based on the area occupied by the compatibilizer at the blend interface. The results were in agreement with the theoretical predictions of Noolandi and Hong. The extent of interface adhesion in these blends was analyzed by examination of the fracture-surface morphology. Addition of SBS also improved notched impact, elongation-at-break, tensile strength and modulus of elasticity. These results confirm that SBS is an effective compatibilizer for ABS/PET-G blends.     

Kinetics of Heterogeneous Isotopic Exchange of 60Co/Co3Co(CN)6 2 · 12 H2O in Aqueous Solution

The heterogeneous exchange reaction between cobalt ions in solution and Co₃Co(CN)_{6 2} · 12 H₂O has been studied. It is found that the exchange rate increases as the concentration of Co²⁺ ions in solution decreases. The results show that the exchange rate is controlled by the surface reaction at the solid-liquid interface. The activation parameters E_a, ΔH^#, ΔS^#, and ΔG^# are calculated.     

Temperature-dependent critical resolved shear stress model for (Cu–Au)–Co alloys in pure shear mode

Based on a limited energy storage viewpoint proposed by our team, it is assumed that there is a maximum constant value for the maximum storage of energy per unit volume when dislocation slip starts in a metal. A temperature-dependent critical resolved shear stress (CRSS) model without any fitting parameters is developed for metals in a pure shear mode. The CRSSs of Cu, Cu–Au, Cu–Co and Cu–Au–Co in the pure shear mode are predicted, and are in excellent agreement with the experimental results. This work offers an approach to predict the temperature-dependent CRSS for metals in the pure shear mode.     

Hydrogen induced changes of the interlayer coupling in Fe(3)/V(x) superlattices (x=11–16)

The effect of hydrogen on the magnetic exchange coupling between iron layers through vanadium spacer layers has been studied with magneto-optical Kerr effect experiments in Fe₍₃₎/V_(x) superlattices. Here x refers to the number of V monolayers varying from 11 to 16 and the Fe layer thickness is fixed at three monolayers. Without hydrogen the superlattice is antiferromagnetic (AFM) for x between 12 and 14 and ferromagnetic (FM) in all other cases. With hydrogen loading the coupling can be switched from AFM to FM and vice versa. As previously observed with neutron reflectivity measurements (Hjörvarsson et al., Phys. Rev. Lett. 79 (1997) 901) the change of the interlayer coupling upon hydrogen uptake is not simply due to the expansion of the non-magnetic vanadium spacer layer but more likely to the distortion of the Fermi surface. Bilinear and biquadratic exchange couplings can be recognized by the magnetic hysteresis loops and their coupling energies have been extracted by fits to the curves. For all samples the easy axis of the magnetization is in the plane without any preferred in-plane direction. Hydrogen loading does not affect the magnetic anisotropy of these samples.     

The Application of Infrared Spectra to Structural Problems in Copper(II) Complexes of 2,2′-Bipyridine

The infrared spectra of the complexes [Cu(bipy)₃] (C10₄)^2′ [Cu(bipy)₂] (C10₄)₂, [Cu(bipy)₂I]I, [cu(bipy)₂I] C10₄ and [Cu(bipy)(C10₄)₂] (bipy - 2,2′-bipyridine) are discussed in relation to their known or probable structures. Evidence for tetragonal distortion of [Cu(bipy)₃]₂₊ but not [Cu(phen)₃]₂₊ (phen = 1, 10-phenanthroline) is adduced.     

Using X-PEEM to study biomaterials: Protein and peptide adsorption to a polystyrene–poly(methyl methacrylate)-b-polyacrylic acid blend

Recent synchrotron-based soft X-ray photoemission electron microscopy (X-PEEM) studies of protein and peptide interaction with phase segregated and patterned polymer surfaces in the context of optimization of candidate biomaterials are reviewed and a study of a new system is reported. X-PEEM and atomic force microscopy (AFM) were used to investigate the morphology of a phase-segregated thin film of a polystyrene/poly(methyl methacrylate)-b-polyacrylic acid (PS/PMMA-PAA) blend, and its interactions with negatively charged human serum albumin (HSA) and positively charged SUB-6 (a cationic antimicrobial peptide, RWWKIWVIRWWR-NH₂) at several pHs. At neutral pH, where the polymer surface is partially negatively charged, HSA and SUB-6 peptide showed contrasting adsorption behavior which is interpreted in terms of differences in their electrostatic interactions with the polymer surface.