Sound Spectroscopy of the Superfluid Phases of 3He in Aerogel in Zero Magnetic Field

Low-frequency sound is used to study phase transitions of ³He confined in 98% open aerogel. Superfluidity is manifested by the onset of the low frequency (slow) mode whose velocity (as a function of pressure and temperature) was used to map out the phase diagram of the B-phase and the metastable A-phase of ³He in aerogel. Analysis of the slow mode's evolution with temperature allows the development of the superfluid fraction in the A and B phases to be determined. The metastable A-phase and the equilibrium B-phase can co-exist in a properly prepared sample. Both the superfluid transition and the A→B transition exhibit a finite width of ～20–25 µK.     

Non-covalent stabilization and functionalization of boron nitride nanosheets (BNNSs) by organic polymers: formation of complex BNNSs-containing structures

The straightforward non-covalent functionalization and solubilization of hexagonal boron nitride nanosheets (BNNSs) has been achieved by reacting either polythiophene or polyvinylpyrrolidone polymers with exfoliated BNNSs. The BNNSs apparently form strong π–π stacking interactions with the polymers to yield stable derivatized nanosheets with modified properties. A number of polythiophene polymers functionalized with carboxylic acid groups that are connected to the thiophene subunit by varying numbers of CH₂-hydrocarbon linker units have also been tethered to the exfoliated BNNSs. These BNNS–polythiophene–(CH₂)_n–COOH structures have been further coordinated to pre-formed TiO₂ nanoparticles to form more complex BNNS–polythiophene–(CH₂)_n–COO–TiO₂ hybrid nanomaterials through covalent binding between the TiO₂ nanoparticle surface and the carboxylic acid functional group of the BNNS–polythiophene unit. These novel structures have been characterized by SEM, TEM, FTIR, UV–Vis, and other spectroscopic data.     

The use of mesoporous silica in the removal of Cu(I) from the cyanidation process

This research proposed the use of a mesoporous silica material (SiO₂) as a Cu(I) adsorbent in a pre-treatment of cyanide effluents employed in gold and silver extraction. Two copper sources were employed: a [Cu(CN) _X ]^?(X+1) standard solution, and a cyanide solution obtained from an ore of Peña de Bernal, Chihuahua, México, which was named Cu(I)–CN–PB. Mesoporous silica removes around 90 % of the Cu(I)–CN at 30 min in Cu(I)–CN solutions with 50 ppm of the metals; while, in a solution with a high concentration of copper (311 ppm), around 52 % was removed. The adsorption dates were adjusted following the Langmuir model; obtained a maximum adsorption capacity (Q ₀) of 8.01 mg g^?1 and a separation factor (R _L) lower than one, which indicates a favorable thermodynamic adsorption process of Cu(I)–CN by SiO₂. However, a similar copper removal capability and low selectivity was observed when Cu(I)–CN–PB was employed as the copper source. Therefore, a modification on the silica’s surface with phenyl groups was performed, in order to enhance the metallic ion selectivity. IR spectroscopy and TGA/DTA analysis confirmed the coupling of organic groups; on the other hand, nitrogen adsorption indicated a decrease on the BET surface area of the silica at 76 %, a modification of the silica structure was observed with the formation of two pore diameter (3.6 and 5.37 nm); ¹³C CP-MAS NMR indicated two different chemical shifts that corresponded to the phenyl groups on the two different pores observed. Phenyl groups enhance the selectivity for copper in the cyanide effluent, increasing the removal to 99 %.     

Three-Dimensional Network Polymeric Structure of (2-Amino-5 Ammoniopyridinium)[CuCl4]: Crystal Supramolecularity and Magnetic Properties

A single crystal structure determination of the complex (C₅H₉N₃)CuCl₄ [henceforth I] has been carried out. It crystallizes in the orthorhombic space group Cmca, with the cell parameters a=6.7053(5) Å, b=22.4171(19) Å, c=13.4173(9) Å, V=2016.8(3) Å³, and Z=8. In the complex, the anion is comprised of infinite zigzag chains of monochloro-bridged $\mathrm{CuCl}_{4}^{2-}$ units ?–CuCl₃–μ–Cl–CuCl₃–μ–Cl–CuCl₃–? surrounded by the pyridinium-ammonium cations. The Cu ions are five-coordinate to chloride ions in a distorted square-pyramidal geometry with the zigzag chains formed by corner-sharing polyhedra. The Cu ion is located 0.151 Å above the basal plane. In the crystal, there are four intermolecular hydrogen bonding interactions, linking the CuCl chains to the cations to form a 2D-network. The resulting 2D-networks are further linked by aryl?aryl (π?π) interactions within the cationic chains leading to a 3D-network. Variable temperature magnetic susceptibility data were fit to a one-dimensional S=1/2 antiferromagnetic chain model yielding C=0.44(1) emu-K/mol-Oe and J=?37(1) K.     

The Phonon Modes with Strong Electron–Phonon Interactions in p- and n-Type High T c Superconductors

The phonon modes with strong electron–phonon interactions were investigated by two-phonon Raman scattering in p- and n-type high T _c superconductors. In p-type superconductors, the strong electron–phonon interaction mode changes from the breathing mode at (π, π) to the half breathing mode at (π, 0) as carrier density increases across the optimum doping in LSCO or the 60 K phase in YBCO. It is in good accordance with the change of the superconducting coherent peak position in k-space. In n-type superconductors, the strong electron–phonon interaction modes change from (0.4π, 0.4π) to (0.4π, 0) at the insulator–superconductor transition. Electron–phonon interactions play an important role in superconductivity.     

Young's modulus of Fe-, Co-, Pd- and Pt-based amorphous wires produced by the in-rotating-water spinning method

This paper presents the Young's modulus of Fe_100?x?y Si _x B _y , Fe_100?x?y P _x C _y , Co_100?x?y Si _x B _y , Pd_77.5Cu₆Si_16.5, Pd₄₈Ni₃₂P₂₀ and Pt₆₀Ni₁₅P₂₅ amorphous wires determined from the Young's modulus sound velocity measurement. With increasing metalloid content, the Young's modulus increases from 1.58×10¹¹ to 1.87×10¹¹ N m^?2 for Fe-Si-B, from 1.40×10¹¹ to 1.52×10¹¹ N m^?2 for Fe-P-C and from 1.73×10¹¹ to 1.75×10¹¹ N m^?2 for Co-Si-B systems. The increase in Young's modulus with the amount of metalloid elements is the largest for B, followed by Si, C and then P. The Young's modulus of Fe- and Co-Si-B amorphous wires increases significantly with the replacement of iron or cobalt by IV–VII group transition metals. It was recognized that there existed a strong correlation between Young's modulus (E) and tensile fracture strength (σ _f); the ratio of σ _f to E is approximated to be 0.02 for all the amorphous wires investigated. These results imply that the Young's modulus is dominated mainly by the structural and compositional short-range orderings due to the strong interaction between metal and metalloid atoms which hinders the internal displacements. The existence of a constant ratio for σ _f/E was interpreted to originate from a common mechanism for plastic flow of the amorphous wires. Further, it was noted that the Young's modulus of the Fe- and Co-based amorphous wires with diameters of ? 100 to 120 Μm was slightly lower than that of the amorphous ribbons with thicknesses of ? 20 to 25 Μm. This difference was attributed to the difference in structural ordering due to the differences in the solidification processes.     

Production of muons for fusion catalysis using a migma configuration

Muon-catalyzed fusion requires a very efficient means of producing muons. We describe a muon-producing magnetic-mirror scheme with triton migma that may be more energy efficient than any heretofore proposed. If one could catalyze 200 fusions per muon and employ a uranium blanket that would multiply the neutron energy by a factor of 10, one might produce electricity with an overall plant efficiency (ratio of electric energy produced to nuclear energy released) approaching 30%.The self-colliding arrangement of triton orbits will result in many π⁻'s being produced near the axis of the magnetic mirror. The pions quickly decay into muons, which are transported into a small (few cm diameter) reactor chamber producing approximately 1 MW/m² neutron flux on the chamber walls.     

Magnetic properties of sputtered multilayers of Mo/Ni

We have studied the d.c. magnetization of Mo/Ni artificial superlattices in the temperature range 5–300 K and in magnetic fields of up to 10⁷/4πAm^-1 (10kG). The saturation magnetization and the Curie temperature behavior are consistent with expectations based on thin film effects. However, there are indications of ferromagnetic coupling across the normal metal and the coercive field shows an unexpected peak at a layer thickness of 25 Å.     

On the relationship between citations of publication output and Hirsch index h of authors: conceptualization of tapered Hirsch index h T, circular citation area radius R and citation acceleration a

The nature of the empirical proportionality constant A in the relation L = Ah ² between total number of citations L of the publication output of an author and his/her Hirsch index h is analyzed using data of the publication output and citations for six scientists elected to the membership of the Royal Society in 2006 and 199 professors working in different institutions in Poland. The main problem with the h index of different authors calculated by using the above relation is that it underestimates the ranking of scientists publishing papers receiving very high citations and results in high values of A. It was found that the value of the Hirsch constant A for different scientists is associated with the discreteness of h and is related to the tapered Hirsch index h _T by A ^1/2 ≈ 1.21h _T. To overcome the drawback of a wide range of A associated with the discreteness of h for different authors, a simple index, the radius R of circular citation area, defined as R = (L/π)^1/2 ≈ h, is suggested. This circular citation area radius R is easy to calculate and improves the ranking of scientists publishing high-impact papers. Finally, after introducing the concept of citation acceleration a = L/t ² = π(R/t)² (t is publication duration of a scientist), some general features of citations of publication output of Polish professors are described in terms of their citability. Analysis of the data of Polish professors in terms of citation acceleration a shows that: (1) the citability of the papers of a majority of physics and chemistry professors is much higher than that of technical sciences professors, and (2) increasing fraction of conference papers as well as non-English papers and engagement in administrative functions of professors result in decreasing citability of their overall publication output.     

Experimenting with the partnership ability φ-index on a million computer scientists

Schubert introduced the partnership ability φ-index relying on a researcher’s number of co-authors and collaboration rate. As a Hirsch-type index, φ was expected to be consistent with Schubert–Glänzel’s model of h-index. Schubert demonstrated this relationship with the 34 awardees of the Hevesy medal in the field of nuclear and radiochemistry (r ² = 0.8484). In this paper, we upscale this study by testing the φ-index on a million researchers in computer science. We found that the Schubert–Glänzel’s model correlates with the million empirical φ values (r ² = 0.8695). In addition, machine learning through symbolic regression produces models whose accuracy does not exceed a 6.1 % gain (r ² = 0.9227). These results suggest that the Schubert–Glänzel’s model of φ-index is accurate and robust on the domain-wide bibliographic dataset of computer science.     

High rate calorimetry with missing energy trigger

In this contribution we describe the behaviour of the WA78 uranium-scintillator calorimeter used like a live-dump in high intensity (6×10⁶π/burst, burst = 2.4 s) beam. The use of this calorimeter in the trigger is also described.     

Synthesis and characterization of phosphorescent platinum complexes containing phenylpyridazine

Synthesis and characterization of a series of square planar Pt(II)-phenylpyridazine complexes are reported. The complexes have the general structure of (C–N)Pt(O–O), where HC–N is 3-phenyl-pyridazine (ppdz), 3-(3′-trifluoromethylphenyl)pyridazine (3′tfmppdz), 3-(3′-methoxyphenyl)-pyridazine (3′meoppdz), 3-(4′-methoxyphenyl)pyridazine (4′meoppdz), or 3-phenyl-6-chloro-pyridazine (6Clppdz) and HO–O is acetylacetone (Hacac). Reaction of K₂PtCl₄ with a HC–N ligand forms the dimer, (C–N)Pt(μ-Cl)₂Pt(C–N), which is cleaved with Hacac to give the corresponding monomer, (C–N)Pt(O–O). The emission characteristics of these complexes are governed by the substituents of the cyclometalating ligands, showing emission λ_max values from 508 to 610 nm. Strong spin-orbit coupling of the platinum atom allows for the formally forbidden mixing of the ¹MLCT with the ³MCLT and ³(π–π*) states.     

Evidence of Tl+ mobility in the pyrochlore phase TlxNbO2+xF1−x

The mobility of Tl⁺ ions in the cubic pyrochlore phase Tl_xNbO_2+xF_1?x is investigated by means of dielectric relaxation studies and conductivity measurements. The conductivity increases rapidly with x : σ300°C = 7.0 10^?6 (πcm)^?1 for x = 0.50, and 6.0 10^?3 (πcm)^?1 for x = 0.55. Conductivity data, dielectric losses peaks and 205 Tl NMR measurements are consistent with a Tl⁺ motion with ΔE = 0.23 eV, explained in terms of crystal structure and related to the Tl⁺ polarizability.     

Mechanical and thermal properties of hot pressed neodymium-substituted britholite Ca9Nd(PO4)5(SiO4)F2

Neodymium-substituted britholite, a phosphate–silicate apatite Ca₉Nd(PO₄)₅(SiO₄)F₂, is considered as a potential host matrix for specific immobilization of radionuclides. Complementary investigations have been carried out to complete the database concerning this compound. The aim was to establish mechanical and thermal properties of dense britholite. Hot pressing was used to nearly fully densify the material. Low values of mechanical properties were found: 0.75 MPa m^1/2 for the fracture toughness and 95 MPa for the flexural strength. The Young's modulus and the Poisson's ratio were 108 GPa and 0.30, respectively. The specific and the thermal conductivity at 298 K were Cp=0.75 J g⁻¹ K⁻¹ and λ=1.15 W m⁻¹ K⁻¹. The average coefficient of thermal expansion in the 20–1000 °C temperature range was α=21×10⁻⁶ K⁻¹.     

Laser Interferometer for Space Gravitational Waves Detection and Earth Gravity Mapping

The idea of using space laser interferometer to measure the relative displacement change between two satellites has been considered for space gravitational waves detection and Earth gravity filed mapping in recent years. Some investigations on the key issues of laser interferometer in our working team have been presented in this paper. An on-ground laser interferometer prototype used for the demonstration of satellite-to-satellite ranging has been constructed, which is equipped with phasemeter, laser pointing modulation and laser phase-locking control. The experimental results show that path-length measurement sensitivity of the laser interferometer reaches 200 pm/√ Hz, and phase measurement precision achieves 2π × 10^??5 rad/√ Hz, and laser pointing modulation precision is better than 80 nrad/√ Hz, and laser phase-locking control precision attains 2π × 10^??4 rad/√ Hz within the frequency regime of 1 mHz–1 Hz. All of these demonstrate that the proposed laser interferometer has very promising feasibility to meet the requirement of the Taiji, TianQin and Space Advanced Gravity Measurement (SAGM) missions which are put forward by Chinese scientists.     

Novel D-π-A dye sensitizers of polymeric metal complexes with phenylethyl or carbazole derivatives as donors for dye-sensitized solar cells: synthesis,characterization, and photovoltaic application

Four novel polymeric metal complexes containing D-π-A type structures were synthesized, characterized and applied as dye sensitizers in dye-sensitized solar cells (DSSCs). The alkoxy benzene or carbazole (CZ) derivative acts as an electron donor (D), C=C acts as π-bridge (π) and the 8-hydroxyquinoline derivative complex acts as electron acceptor. Bipyridine derivative was ancillary ligand as well as providing anchoring group. FT-IR, gel permeation chromatography, thermogravimetric analyses, differential scanning calorimetry, UV–Vis absorption spectroscopy, Elemental analysis, cyclic voltammetry, J-V curves and input photon to converted current efficiency plots were introduced to investigate the four dyes. These dyes exhibit good thermal stability with 5 % weight loss at temperatures (T_d) of around 300 °C. For the DSSCs devices using dyes with CZ derivatives as electron D (P2, P4) exhibited higher power conversion efficiency (PCE) than that with alkoxy benzene (P1, P3). The DSSC based on P4 exhibited the highest PCE value of 2.42 % (J _sc  = 4.93 mA/cm², V _oc  = 0.73 V, FF = 67.2 %) under AM 1.5G solar irradiation. This indicates a new way to design dye sensitizers for DSSCs.     

Measurement of magnetic properties of single crystal YIG by non-resonant method

A non-resonant microwave technique has been employed for the determination of saturation magnetisation (4πM _s ) andg-factor of pure and Gd-doped single crystal YIG spheres yielding accurate values. It was found that 4πM _s =1720–1751 g for undoped and 1595 g for 10% Gd-doped YIG spheres whileg _eff=2·00–2·0039. The advantages of this method are simplicity and complete absence of propagation corrections necessary in cavity resonance experiments.     

Iron(III) and Cobalt(III) Complexes with Oxalate and Phenanthroline: Synthesis,Crystal Structure,Spectroscopy Properties and Magnetic Properties

We report herein the synthesis and physicochemical characterization of two mixed-ligand complexes of the following stoichiometric formulae: [Fe(phen)₂(ox)](NO₃)?2H₂O (1) and [Co(phen)₂(ox)](NO₃)?4H₂O (2) (as phen: 1,10-orthophenanthroline; ox: oxalate dianion). Both compounds have been prepared by slow evaporation at room temperature and characterized by single-crystal X-ray diffraction. They have been characterized by IR and UV–Vis spectra and thermoanalysis (TG and DTA) The structures of these compounds are highly symmetric. Indeed, the two compounds are isomorphous and crystallize in the orthorhombic space group Ibca. In each material, the M^III ion has a slightly distorted square bipyramidal environment, coordinated by one oxalate ion and two 1,10-orthophenanthroline ligands. Structural cohesion is established essentially by π–π interactions between the rings of phen groups and intermolecular O–H…O hydrogen bonds connecting the ionic entities and uncoordinated water molecules. Magnetic susceptibility measurements of (1) in the range 5–300 K exhibit paramagnetic behavior at high temperature. However, at low temperature, the magnetic data show the occurrence of weak antiferromagnetic intermolecular interactions between the local spins.     

Magnetic and structural properties of NdFeB thin film prepared by step annealing

The crystallization of the amorphous phase into the tetragonal Nd₂Fe₁₄B (Φ) phase and the corresponding changes in magnetic properties have been examined by step annealing experiment using a 2 μm thick NdFeB film sample. Microstructural and magnetic analysis indicate that the film was magnetically soft as deposited with the coercivity H_ci⊥ <16 kA m⁻¹ and the remnant magnetization 4πM_r⊥ <0.02 T. Annealing at a temperature of 550 °C, a coercivity value around 784 kA m⁻¹ was developed and diffraction analysis showed evidence of Φ phase 002l peaks being aligned perpendicular to the film plane. At an optimum annealing temperature of 575 °C, the remnant magnetization of this anisotropic thin film is around 0.60 T with intrinsic coercivity of ∼1340 kA m⁻¹. Annealing the film sample at 200 °C≤T_ann≤750 °C showed variations in magnetic properties that were mostly due to the change in the perpendicular anisotropy. Based on 4πM_s⊥ values plotted against T_ann, a dip in 4πM_s⊥ values was observed as T_ann increased in the soft-to-hard magnetic characteristics transition region and rose as the hard crystalline phase started to form. The results show that the magnetic properties of the NdFeB film were slightly influenced by the presence of NdO, film surface roughening and the small increase in crystal size as a consequence of repeated heat treatment. At T_ann ∼300 °C, the nominal saturation magnetization indicated a certain degree of weak perpendicular magnetic anisotropy in the film sample considered to be essential in the enhancement of coercivity in crystallized films.     

Monolayer studies of sugar- and nucleoside-terminated dendrimers at the air–water interface

Sugar- and adenosine-terminated dendrimers, [1,2-o-Isopropylideneribosyl-(G₁-12acid), -(G₂-36acid)] and [Adenosyl-(G₁-12acid), -(G₂-36acid)], were synthesized using Newkome's dendrimer synthetic method. Langmuir and Langmuir–Blodgett (LB) monolayers of these dendrimers have been constructed and characterized at the air–water interface and on solid substrates by measuring surface pressure–molecular area (Π–A) isotherms, atomic force microscopy (AFM), ellipsometry and contact angle measurement. Π–A isotherms and AFM images showed that these dendrimers formed stable and homogeneous monolayers without aggregation on pure water surface. The first and second generation of sugar-terminated dendrimers show molecular areas of 647 and 1359 Ų, respectively. Ellipsometry measurement indicates that the thickness of both the first and the second generation of sugar-terminated dendrimers were about 10 Å. This reflects a flat orientation of both molecules at the air–water interface. On the other hand, the first generation of adenosine-terminated dendrimer shows an area of 105.6 Ų per molecule with a thickness of 16 Å, and for the second generation, the area was 738.4 Ų with a thickness of 27 Å. These results suggested that adenosine-terminated dendrimers maintain a spherical form at the air–water interface. It was found that small difference in the structure of thymine and uracil in the subphase critically affects the interaction of the molecules and conformation of the dendrimers at the interface.