Increased Solubility of Mg at Ca Site in Cu<Subscript>0.5</Subscript>Tl<Subscript>0.5</Subscript>Ba<Subscript>2</Subscript>Ca<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript>10−<Emphasis Type="Italic">δ</Emphasis></Subscript> Superconductor

The Cu_0.5Tl_0.5Ba₂Ca_2?y Mg _y Cu₃O_10?δ (y=0, 0.05, 0.1, 0.2, 0.4, 0.6, 0.8, 1.0, 1.5, 2.0) superconductor has been synthesized at the atmospheric pressure by the solid-state reaction method. The zero resistivity critical temperature is found to increase to 98 K with Mg concentration of y=0.6, but saturates to 97 K with further enhancement of Mg to y=0.8, 1.0, and 1.5. The Mg doped material grows in tetragonal structure and follows P4/mmm symmetry with a &; c-axes lengths of 3.894 Å &; 15.091 Å for y=1.5. The axes lengths were decreased with the increase of Mg content in the unit cell, which shows that anisotropy of the material decreases. The critical current density and the quantity of diamagnetism in the samples with Mg contents are higher than in the samples without Mg. In order to realize the effects of decreased axes lengths on the phonon modes of Cu_0.5Tl_0.5Ba₂Ca_2?y Mg _y Cu₃O_10?δ , we have carried out FTIR absorption measurements.     

X-ray structure determination and analysis of hydrogen interactions in 3, 3′-dimethoxybiphenyl

The crystal structure of 3, 3′-dimethoxybiphenyl has been determined by X-ray diffraction methods with an aim of describing the hydrogen interaction in biphenyl derivatives. The title compound crystallizes in monoclinic space groupP2₁/c with unit cell dimensions,a = 7.706(1),b = 11.745(2),c = 12.721(2) Å, β = 92.31(1)°,Z = 4 and its structure has been refined up to the reliability index of 3.8%. The average torsion angle about the inter-ring C-C bond is 37.5°. The O1 and Ol′ atoms of the methoxy group are deviated by 0.046(1) Å and 0.234(1) Å from the mean planes of respective rings. The crystal cohesion is pronounced due to three-inter-molecular C-H...O hydrogen bonds.     

Supramolecular structure of S-(+)-marmesin—a linear dihydrofuranocoumarin

The title compound, C₁₄H₁₄O₄, a linear dihydrofuranocoumarin, was isolated from the bark ofAegle marmelos, a plant widely used in Ayurvedic system of medicine for the treatment of various ailments. The crystal structure was determined from X-ray diffraction data using direct methods. The compound crystallizes into monoclinic space group P2₁ with unit cell parameters:a] = 5.721(1) Å, b= 13.810(1) Å, c= 7.864(2) Å, β = 100.39(1)°, Z = 2. The structure was refined by full-matrix least-squares to a finalR value of 0.0523 for 1184 observed reflections. The benzopyran moiety is perfectly planar. The dihedral angle between the pyrone and benzene rings is 0.3(1)°. The furan ring has a 2α-envelope conformation. The molecules are linked by O-H…O hydrogen bonds into chains and these chains are linked into sheets by C-H…O hydrogen bonds. Further, the π-π stacking and C-H…π (arene) interactions link all of the sheets into a supramolecular structure.     

On VLSI interconnect optimization and linear ordering problem

Some well-known VLSI interconnect optimizations problems for timing, power and cross-coupling noise immunity share a property that enables mapping them into a specialized Linear Ordering Problem (LOP). Unlike the general LOP problem which is NP-complete, this paper proves that the specialized one has a closed-form solution. Let f(x,y):?²→? be symmetric, non-negative, defined for x≥0 and y≥0, and let f(x,y) be twice differentiable, satisfying ? ² f(x,y)/?x?y<0. Let π be a permutation of {1,…,n}. The specialized LOP comprises n objects, each associated with a real value parameter r _i , 1≤i≤n, and a cost f(r _i ,r _j ) associated to any two objects if |π(i)?π(j)|=1,1≤i,j≤n, and f(r _i ,r _j )=0 otherwise. We show that the permutation π which minimizes \(\sum_{i= 1}^{n - 1} f( r_{\pi^{ - 1}( i )},r_{\pi^{ - 1}( i + 1 )} )\), called “symmetric hill”, is determined upfront by the relations between the parameter values r _i .     

Synthesis and Stability of New Nitrophenol Complexes of <Superscript>99<Emphasis Type="Italic">m</Emphasis></Superscript>Tc as Possible Hypoxia Imaging Radiopharmaceuticals

Seven new nitrophenol derivatives were synthesized; their ^99mTc complexes (N₂OS chelates), which are possible hypoxia tumor imaging agents, were prepared by the reaction with [^99mTc]NaTcO₄ in the presence of SnCl₂ at pH 10. The in vitro biostabilty of the complexes was evaluated. The purity and stability (in human and rat serum) of the complexes were evaluated by chromatographic methods (TLC, HPLC). The most stable (for more than 6 h) is the complex of ^99mTc with 3-[3′-N-(2″-hydroxy-5″-nitrobenzylamino)-2′-hydroxypropyl]-1-methylthiourea.     

Spin Dynamics in the Bi-Directional Charge Density Wave State of High-<Emphasis Type="Italic">T</Emphasis><Subscript><Emphasis Type="Italic">c</Emphasis></Subscript> Superconductors

In this paper, we investigate the dynamical spin susceptibility in the bi-directional charge density wave (BCDW) state by adopting a random-phase approximation. In the BCDW state, we find that no spin resonance exists and only a broad commensurate peak appears for the frequency dependence of the dynamical spin susceptibility at Q = (π,π), though a low-energy spin gap feature can also be found as in the superconducting state. While the “hourglass” type of the dispersion for the BCDW state bears some similarities with that in the superconducting state, the momentum distribution of Im χ ^+?(Q,ω) is just the opposite with the incommensurate peaks lying along the diagonal direction for the energy below ω _c and along the axial direction above ω _c . In the coexistence of SC and BCDW, the frequency dependence of the dynamical spin susceptibility at Q = (π,π) generally shows the two-peak structure, reflecting two energy scales of the spin excitations. These unique features may serve as signatures to verify whether or not the BCDW state is responsible for the formation of the Fermi arcs.     

Band Modification Effect on the Normal and Superconducting State Properties of Bulk MgB<Subscript>2</Subscript>

Modification of σ and π bands was studied in MgB₂ by doping 3, 6 and 9 wt% of C and Fe, respectively. The samples synthesized by a solid-state route were characterized by XRD, and magnetization (M) and resistivity (ρ) measurements were in the temperature range (T) 4.2–300 K and magnetic field range (B) 0–12 T, respectively. The decrease (increase) of the lattice parameter a with C (Fe) doping, consistent with B (Mg) site substitution, confirms the expected changes in σ (π) bands. This is supported by the fact that normal-state ρ(T) of all the samples can be fitted by a two-band model and the scattering rates in both the bands are found to be dependent on the dopant. The influence of C and Fe doping on various superconducting properties of the host MgB₂ is also found to be significantly different. For instance, in the presence of magnetic field, Fe doping shows a much larger broadening of the superconducting transition when compared to C doping. The critical current density (J _C(B)) at 4.2 K vanishes for C (Fe) doping at around T～12 (～3). It is shown that the band modification and the superconducting properties are correlated.     

The size and impact of the elite set of publications in scientometric assessments

Several scientometric impact indicators [total citations, h, g, and π-index, percentage rank position (PRP), weighted citation share (WCS)] of 190 elite papers of 15 members of the Hungarian Academy of Sciences active in three different fields were calculated. From the indices the PRP indicator proved to be independent of the citation practices in the fields. The PRP index of a journal paper can be calculated in per cent as unity minus (the rank number of the paper by citation frequency within the publishing journal minus one divided with the total number of papers in the journal) times hundred. The sum of the PRP index of the elite papers of a scientist may characterize his or her total publication performance. The size of the elite set of journal papers within the total was calculated by different methods. The h-index and g-index corresponds to the size of the elite, i.e. number of the elite papers according to the h-statistics and g-statistics, respectively. The number of papers in the π-set is equal to the square root of total papers. The π-index equals to one hundredth of citations to the π-set papers. In the present paper the size of the elite set is determined as the number of papers in the h-set, g-set, or π-set, and as 10 % of total papers, or number of papers cited 2, 3, or 5 times the mean citation rate (MCR) of the publishing journal. The π-citation threshold model is presented for demonstrating how MCR and the distribution of citations over the papers may influence the size of the elite set and the corresponding π-index. It was found that the scientific performances concluded from the π-index obtained from elite sets of different size are in good agreement.     

Comparative Experimental and Density Functional Theory (<Emphasis Type="Italic">DFT</Emphasis>) Study of the Physical Properties of MgB<Subscript>2</Subscript> and AlB<Subscript>2</Subscript>

In the present study, we report an intercomparison of various physical and electronic properties of MgB₂ and AlB₂. In particular, the results of phase formation, resistivity ρ(T), thermoelectric power S(T), magnetization M(T), heat capacity (C _P ), and electronic band structure are reported. The original stretched hexagonal lattice with a=3.083 Å, and c=3.524 Å of MgB₂ shrinks in c-direction for AlB₂ with a=3.006 Å, and c=3.254 Å. The resistivity ρ(T), thermoelectric power S(T) and magnetization M(T) measurements exhibited superconductivity at 39 K for MgB₂. Superconductivity is not observed for AlB₂. Interestingly, the sign of S(T) is +ve for MgB₂ the same is ?ve for AlB₂. This is consistent with our band structure plots. We fitted the experimental specific heat of MgB₂ to Debye–Einstein model and estimated the value of Debye temperature (Θ _D) and Sommerfeld constant (γ) for electronic specific heat. Further, from γ, the electronic density of states (DOS) at Fermi level N(E _F) is calculated. From the ratio of experimental N(E _F) and the one being calculated from DFT, we obtained value of λ to be 1.84, thus placing MgB₂ in the strong coupling BCS category. The electronic specific heat of MgB₂ is also fitted below T _c using α-model and found that it is a two gap superconductor. The calculated values of two gaps are in good agreement with earlier reports. Our results clearly demonstrate that the superconductivity of MgB₂ is due to very large phonon contribution from its stretched lattice. The same two effects are obviously missing in AlB₂, and hence it is not superconducting. DFT calculations demonstrated that for MgB₂, the majority of states come from σ and π 2p states of boron on the other hand σ band at Fermi level for AlB₂ is absent. This leads to a weak electron phonon coupling and also to hole deficiency as π bands are known to be of electron type, and hence obviously the AlB₂ is not superconducting. The DFT calculations are consistent with the measured physical properties of the studied borides, i.e., MgB₂ and AlB₂.     

Conductivity in Cuprates Arises from Two Different Sources: One-Electron Exchange and Disproportionation

Simulation of the resistivity in the normal state of doped La_2?x Sr _x CuO₄ has been performed using a hopping model based on Marcus theory. The results are in substantial agreement with experimental results. At oxidative doping, Cu(III) sites are formed and electron mobility possible due to hopping: Cu(III)Cu(II) → Cu(II)Cu(III) (one-electron exchange). In the underdoped, non-metallic region, the resistivity (ρ) decreases from almost insulation at T = 0 to a minimum at about T = 100 K. ρ then increases more than linearly with T (～T ^3/2) in the region 100 < T < 500 K. A photo-induced metal-metal (MM) charge transfer transition at 2 eV 2Cu(II) + h ν→ Cu(I) + Cu(III) is responsible for the strong absorption in the visible spectrum of La₂CuO₄. The down-shift of spectral density with doping (x) in La_2?x Sr _x CuO₄ depends on the appearance of Cu(III) sites which makes optical as well as thermal one-electron exchange transitions possible with lower energy. Disproportionation occurs spontaneously for x > 0.06, opening up for electron pair formation. Configuration interaction between two-electron states of low chemical potential, but strong vibrational coupling, gives rise to the superconductor and pseudogaps. Data from photo-induced conductivity and absorption spectra are used in the simulation, which gives results in good agreement with experiments. Possible explanations for Raman and MIR absorption suggest themselves.     

Structural investigation of V<Subscript>2</Subscript>O<Subscript>5</Subscript>–P<Subscript>2</Subscript>O<Subscript>5</Subscript>–K<Subscript>2</Subscript>O glass system with antibacterial potential

The xV₂O(1?x)[0.8 P₂O₅ ? 0.2 K₂O] glass system with 0 ≤ x ≤ 50 mol% was prepared and the structural changes induced in these glasses by increasing the vanadium oxide content were investigated by IR and ESR spectroscopies. The dual behaviour role of V₂O₅ oxide, as network modifier (for x ≤ 10 mol%) and the network former (x ≥ 20 mol%), as a consequence of phosphate network depolymerization and P–O–V and V–O–V linkages appearance was also highlighted. The antibacterial effect of the glasses with x ≤ 20 mol% V₂O₅ content was tested by optical density (OD) measurements. A linear correlation between the amount of vanadium and the antibacterial effect was evidenced.     

Magnetization in Nanocrystalline PLD Zinc Ferrite Thin Films Deposited on Fused Quartz Substrate

The nanocrystalline zinc ferrite (ZnFe₂ O ₄) thin films were grown on the fused quartz substrate using pulsed laser deposition. The effects of atmospheric conditions on structural, magnetic, and morphological properties have been systematically studied using X-ray diffraction, vibrating sample magnetometry, and atomic force microscopy. The films showed textured growth of zinc ferrite for the substrate temperatures at ≥ 600 °C irrespective of the ambient environment. Interestingly, thin films of zinc ferrite showed a magnetic hysteresis loop in contrast to the paramagnetic nature of their bulk counterpart. The value of saturation magnetization (4π M _s) increased from 130 to 360 G when the substrate temperature was increased from room temperature (RT) to 800 °C in the oxygen atmosphere. In the absence of oxygen pressure, the value of 4π M _s is observed to be 330 G for the film deposited at RT and found to increase to a value of 670 G when the film is deposited at 400 °C and the maximum value of 2580 G is observed for the film deposited at 700 °C. However, the value of 4π M _s of 800 °C dropped down to 2000 G.     

Investigation of ITS-90 Inconsistencies in Overlap Region of the Water-indium,Water-tin,and Water-zinc Sub-ranges

One of the significant uncertainties in Standard Platinum Resistance Thermometer (SPRT) calibration by fixed-points method is Type I non-uniqueness (sub-range inconsistencies). Sub-ranges water-tin (W ₉ ) and water-indium (W ₁₀ ) lies in the water-zinc (W ₈ ) sub-range of the International Temperature Scale of 1990. Therefore, three sub-range inconsistencies [W ₈ and W ₉ (SRI _8–9 ), W ₈ and W ₁₀ (SRI _8–10 ), and W ₉ and W ₁₀ (SRI _9–10 )] occur. This paper investigated these inconsistencies using the calibration data of 12 SPRTs from six manufacturers. The result shows that the magnitude of the inconsistency for SRI _8–9 , SRI _8–10 , and SRI _9–10 are about 2.5, 2.2 and 1.8 mK, respectively.     

Influence of the Hybrid Combination of Multiwalled Carbon Nanotubes and Graphene Oxide on Interlaminar Mechanical Properties of Carbon Fiber/Epoxy Laminates

An effective strategy to improve the mode I and mode II interlaminar fracture toughness (G _IC and G _IIC ) of unidirectional carbon fiber/epoxy (CF/E) laminates using a hybrid combination of multiwalled carbon nanotubes (MWCNTs) and graphene oxide (GO) is reported. Double cantilever beam (DCB) and end notched flexure (ENF) tests were conducted to evaluate the G _IC and G _IIC of the CF/E laminates fabricated with sprayed MWCNTs, GO and MWCNTs/GO hybrid. Scanning electron microscopy was employed to observe the fracture surfaces of tested DCB and ENF specimens. Experimental results showed the positive effect on the G _IC and G _IIC by 17% and 14% improvements on CF/E laminates with 0.25 wt.% MWCNTs/GO hybrid content compared to the neat CF/E. Also, the interlaminar shear strength value was increased for MWCNTs/GO-CF/E laminates. A synergetic effect between MWCNTs and GO resulted in improved interlaminar mechanical properties of CF/E laminates made by prepregs.     

Determination of the Alfvén Oscillation Location in the TUMAN-3M Tokamak Plasma

The Alfvén oscillations have been studied in ohmically heated deuterium discharges with LH-transition in the TUMAN-3M tokamak in order to clarify their location in a plasma column. The Alfvén oscillation location was determined by comparison of the oscillation frequency measured with magnetic probes and that calculated from local density assuming the typical dispersion relation for Alfvén waves f = (2π)^?1k_||v _A , where v _A is the Alfvén velocity and k_|| is the the parallel wave number in the direction of the magnetic field. It was found that they are localized in central part of plasma column inside r/a < 0.5 region. Candidate sets of mode numbers have been determined.     

Kinetics of gas-phase conversion of U<Subscript>3</Subscript>O<Subscript>8</Subscript> into water-soluble compounds in nitrating atmosphere at 25–30°С

The kinetics of the gas-phase conversion of U₃O₈ in NO_x–H₂O (vapor)–air and HNO₃ (vapor)–H₂O (vapor)–air atmospheres was fitted by the Kazeev–Kolmogorov–Erofeev equation. The following parameters n and K were obtained: for experiments in NO_x–H₂O (vapor)–air atmosphere, n = 0.2 ± 0.1 and K = 0.2 ± 0.2 h^–1; for experiments in HNO₃ (vapor)–H₂O (vapor)–air atmosphere, n = 0.3 ± 0.2 and K = 0.03 ± 0.02 h^–1 (confidence probability p = 0.95). For the U₃O₈ conversion in both media, n < 0.5, which suggests the diffusion control of the U₃O₈ conversion under the action of both HNO₃ and NO_x.     

Dehydration-induced structural transformations of the microporous zirconosilicate elpidite

The structural transformations accompanying the thermal dehydration of natural elpidite, Na₂ZrSi₆O₁₅ · 3H₂O, have been studied by X-ray powder diffraction and IR spectroscopy. The crystal structures of both elpidite (a = 7.1136(1), b = 14.6764(2), c = 14.5977(2) Å; sp. Gr. Pbcm) and the dehydration product Na₂ZrSi₆O₁₅ (a = 14.0899(1), b = 14.4983(1), c = 14.3490(1)Å; sp. gr. Cmce = Cmca) are based on a heteropolyhedral Si-Zr-O framework. The Na cations and (in hydrous elpidite) H₂O molecules reside in extra-framework sites. The dehydration-induced distortion of the framework leads to a doubling of the a cell parameter, and the water loss is accompanied by a considerable decrease in molar volume.     

Numerical simulation of IR absorption,reflection, and scattering in dispersed water-oxygen media

The method of molecular dynamics along with the flexible model of molecules are used to study the spectral characteristics of systems of clusters of (H₂O) _n , (O₂) _m (H₂O) _n , and (O) _i (H₂O) _n , m ≤ 2, i ≤ 4, 10 ≤ n ≤ 50. It is demonstrated that the integral intensity of absorption of IR radiation decays after water clusters adsorb oxygen. In addition, the adsorption of oxygen causes a significant decrease in the reflection coefficient R of monochromatic IR radiation. In so doing, the R(ω) spectrum splits into bands and exhibits seven peaks in the frequency region of 0 ≤ ω ≤ 3500 cm^?1. The dissociation of oxygen molecules captured by clusters makes the peaks of R(ω) spectrum more resolved. The attachment of molecular oxygen by clusters leads to decay of the power of their IR radiation, while the capture of atomic oxygen, on the contrary, is accompanied by an increase in the rate of dissipation of energy accumulated by water aggregates.     

Space charge limited conduction in CdSe thin films

The current (I)-voltage (V) characteristics of thermally evaporated CdSe thin films having thickness in the range 850–3000 Å and deposited within the substrate temperature of 303–573 K show nearly linear dependence at low voltage and afterwards a non-linear behaviour at higher voltage range. A detailed study ofI-V curves in dark and under illumination clearly reveals the mechanism as ohmic at low voltage and that of trap limited space charge limited conduction (SCLC) at higher voltage. The transition voltage (V_t) from ohmic to SCLC is found to be quite independent of ambient temperature as well as intensity of illumination. SCLC is explained on the basis of the exponential trap distribution in CdSe films. Trap depths estimated from the lnI vs 10³/T plots are found to be within 0.60-0.37 eV. Using the relevant SCLC theory, the carrier concentration, n₀, total trap concentration, N_t, and the ratio of free charge to trapped charge, θ, have been calculated and correlated with ambient temperature and intensity of illumination.     

Influence of anodic passivation on electrical characteristics of Al/<Emphasis Type="Italic">p</Emphasis>-Si/Al and Al/V<Subscript>2</Subscript>O<Subscript>5</Subscript>/<Emphasis Type="Italic">p</Emphasis>-Si/Al diodes

In this paper, the V₂O₅ thin film has been grown on the both p-type semiconductor and glass substrate by the spray pyrolysis method. For optical and structural properties of thin film, the optical absorption, SEM, AFM and XRD measurements have been done. It is observed that films exhibit polycrystalline behavior. The effects of anodic passivation on the characteristic parameters of diodes have been investigated using current–voltage (I–V) characteristics. The I–V measurements of the diodes have been performed at the room temperature in the dark. The main electrical parameters such as ideality factor (n) and barrier height (Φ _b ) of diodes have been calculated from the forward bias I–V characteristics. Likewise, the values of series resistance (R _s ) of diodes have been obtained from Norde method. It is observed that while the ideality factor decreases with anodic passivation, the barrier height increases.