Potential use of an irradiated natural tin target for preparation of a mixed sealed source based on 12-tungstocerate gel matrix for radiometric calibration purposes

Irradiated natural tin target and 12-tungstocerate gel matrix were used for preparing a ¹¹³Sn and ^124,125Sb sealed source. The distribution coefficients of ¹¹³Sn/^113m In and ^124,125Sb ions on 12-tungstocerate gel matrix were determined in relation to HCl concentration. 12-Tungstocerate gel matrix was loaded with ¹¹³Sn/^113m In and ^124,125Sb by equilibrating an irradiated Sn(IV) solution with 0.5 g of the matrix at pH 1 (HCl) for 24 h at 25 ± 1°C. A mixed sealed source of ¹¹³Sn/^113m In and ^124,125Sb was prepared by packing 105 mg of the loaded matrix in the cylindrical cavity of a Chinese artelone capsule. The activity of the source was in the millicurie range. The source successfully passed quality control tests.     

Condensed matter physics journals

On the basis of a citation/reference criterion, 20 core journals are selected in the field of condensed matter physics. Citation data and indicators from 1980Journal Citation Reports reveal their different characteristic features such as applied orientation, communication function and longevity. The manually obtained data for the core journals are written into a matrix in order to determine an appropriate ranking parameter. The method ofPrice is used first to reduce the diagonal elements and then, following the method ofGeller, influence weights are calculated for the core journals. Influence weights are determined also for non-core journals using only the references received from the core.     

The use of citations matrices to group journals

A method of grouping journals within a wide discipline area into clusters is proposed, based on a algorithm that attempts to re-order a citations matrix so that it is block diagonal, or block recursive. The algorithm is based on a penalty function which allows one to account for the level of citation, not just the distribution of citations between journals. A case study involving eight economics journals is presented which illustrates the principles involved, but which also highlights the computational problems associated with extending the analysis to larger numbers of journals.The permission of the Institute for Scientific Information to access data from theSocial Science Citations Index ^® is gratefully acknowledged, as are the comments of a reviewer, who brought additional literature to my attention.     

Fast Algorithms for Structured Least Squares and Total Least Squares Problems

We consider the problem of solving least squares problems involving a matrix M of small displacement rank with respect to two matrices Z₁ and Z₂. We develop formulas for the generators of the matrix M ^HM in terms of the generators of M and show that the Cholesky factorization of the matrix M ^HM can be computed quickly if Z₁ is close to unitary and Z₂ is triangular and nilpotent. These conditions are satisfied for several classes of matrices, including Toeplitz, block Toeplitz, Hankel, and block Hankel, and for matrices whose blocks have such structure. Fast Cholesky factorization enables fast solution of least squares problems, total least squares problems, and regularized total least squares problems involving these classes of matrices.     

Critical current properties of V3Ga with third element additions

Critical current densities of over 1.7 × 10⁶ Acm^?2 at 10T and 4.2K have been achieved in multifilamentary V₃Ga wire produced by a modified bronze technique. Attempts to further improve this value were made by adding a third element, either Ti or Zr, to the V-Ga alloy filaments along with Al to the Cu-Ga matrix. The effects of reaction temperature and layer thickness with the third element additions were qualitatively similar to those measured for wires without third element additions, ie lower reaction temperatures and smaller layer thickness gave higher J_c values. At low reaction temperatures, these composite wires with third element additions exhibited slower growth rates and lower J_c values than those obtained for V-Ga cores in a Cu-Ga matrix, at higher temperatures just the opposite was true. In all cases, however, the J_c values obtained were lower than the best we have been able to achieve using V + Ga filaments and Cu + Ga matrix under optimum conditions.     

Prescribed practices of authorship: review of codes of ethics from professional bodies and journal guidelines across disciplines

Guidelines on authorship requirements are common in biomedical journals but it is not known how authorship is defined by journals and scholarly professional organizations across research disciplines. Prevalence of authorship statements, their specificity and tone, and contributions required for authorship were assessed in 185 journals from Science Citation Index (SCI) and Social Science Citation Index (SSCI), 260 journals from Arts & Humanities Citation Index (A&HCI) and 651 codes of ethics from professional organizations from the online database of the Center for the Study of Ethics in the Profession, USA. In SCI, 53?% of the top-ranked journals had an authorship statement, compared with 32?% in SSCI. In a random sample of A&HCI-indexed journals, only 6?% of the journals addressed authorship. Only 71 (11?%) codes of ethics carried a statement on authorship. Almost all journals had defined authorship criteria compared with 33?% of the ethics codes ( $ \chi_{1}^{2} $ ?=?75.975; P?<?0.001). The tone of the statements in the journals was aspirational, whereas ethics codes used a normative language for defining authorship ( $ \chi_{1}^{2} $ ?=?51.709, P?<?0.001). Journals mostly required both research and writing contributions for authorship, while two-thirds of the ethics codes defined only research as a mandatory contribution. In conclusion, the lack of and variety of authorship definitions in journals and professional organizations across scientific disciplines may be confusing for the researchers and lead to poor authorship practices. All stakeholders in research need to collaborate on building the environment where ethical behaviour in authorship is a norm.     

Microstructural characterization of terbium-doped ceria

The microstructures of Ce_1−xTb_xO_2−δ (0.10 ≤ x ≤ 0.50) sintered samples were studied systematically using transmission electron microscopy. The sintered samples consist of not only fluorite-structured matrix but also nano-sized precipitates. Correspondingly, diffuse scattering and extra reflections related to the precipitates were observed in the selected area diffraction patterns. The composition of the precipitates was studied quantitatively by electron energy-loss spectroscopy, indicating that the precipitates have higher Tb concentration than that of the matrix. Furthermore, Tb³⁺ and Ce³⁺ cations were observed to segregate in the precipitates.     

Transport characteristics of ZrO2 dispersed mixed (BaCl2)1−x-(KCl)x solid electrolytes

Composite solid electrolytes in the system [(BaCl₂)_1−x:(KCl)_x]_1−y:(ZrO₂)_y were prepared following the conventional ceramic powder processing route. In the mixed matrix system prepared by melt quench technique, a nominal increase in conductivity (σ) was found in (BaCl₂)_0.9:(KCl)_0.1. On ZrO₂ particle dispersion in this mixed matrix, the maximum conductivity (∼90 times that of base matrix value) was found to occur with 50 m/o of ZrO₂. Conductivity increases monotonically over the temperature range from 100 to 300 °C studied and attains the value of 10 × 10⁻⁶ S cm⁻¹ at 300 °C. The mobility (μ) of the charge carriers at room temperature was found to be 18.5 × 10⁻² cm² V⁻¹ s⁻¹ and the increase in μ with temperature was not very significant. The transference ionic number determination showed that the electrical conductivity of the electrolyte is predominantly due to ions. This study indicates that the conductivity is governed by mobile ion concentration.     

Optical properties of nanocrystalline Ga1−xInxSb/SiO2 films

Ga_1−xIn_xSb (x=0.19, 0.38, 0.63) nanoparticles embedded in a SiO₂ matrix were grown on the glass substrates by radio-frequency magnetron co-sputtering. X-ray diffraction patterns strongly support the existence of nanocrystalline Ga_1−xIn_xSb in the SiO₂ matrix. The changes in binding energies with Ga_1−xIn_xSb nanocrystals deposition have been directly observed by X-ray photoemission spectroscopy, and these show the existence of Ga_1−xIn_xSb nanocrystals in the SiO₂ matrix. Room-temperature Raman spectra show that the Raman peaks of the Ga_1−xIn_xSb-SiO₂ composite film have a larger red-shift of about 95.3 cm⁻¹ (longitudinal-optical mode) and 120.1 cm⁻¹ (transverse-optical mode) than that of bulk GaSb, suggesting the existence of phonon confinement and tensile stress effects. Additionally, the room-temperature optical transmission data exhibit a large blue-shift with respect to that of the bulk semiconductor due to the strong quantum confinement effect.     

Exchange Bias, Memory and Freezing Effects in NiFe2O4 Nanoparticles

Single-phase NiFe₂O₄ nanoparticles embedded in SiO₂ matrix have been synthesized by sol-gel method. Average particle size lies in the range 8?C12 nm. Magnetic measurements are taken by SQUID-magnetometer with a maximum applied field of ??7 T and temperature down to 4.2 K. An exchange bias effect in nanoparticles is due to the existence of strong core-shell interactions and it vanishes as the particle size decreases (<4?nm). Spin disorder and frustration appear at the core-shell interface due to broken bonds on the surface. We have observed the exchange bias effect via hysteresis loop shift, when the sample is cooled in an applied field of 5?T. In both AC and DC fields, our system exhibit memory effects at the halted temperatures. Furthermore, a sharp increase of coercivity at low temperatures (<50 K) is observed, which is attributed to increased surface anisotropy at low temperatures. For saturation magnetization vs. temperature data, Bloch??s T ^3/2 law (M(T)=M(0)?(1?BT ^b )) is fitted well and yields: B=4??10^?05 K^?3/2 and b=1.53. All these measurements prove the presence of exchange bias (core-shell interactions), memory effects, validation of Bloch??s T ^3/2 law and freezing effects in nickel ferrite nanoparticles dispersed in SiO₂ matrix.     

Electronic energy levels of trivalent lanthanide ions in chalcogenide glasses: Case of Pr3+, Sm3+, and Dy3+

Praseodymium-, samarium-, and dysprosium-doped chalcogenide glasses from Ga–Ge–(Sb)–Se system were prepared. The Slater electrostatic F^k (k = 2,4,6), spin-orbit (ζ_4f), and configuration–interaction (α) parameters of Pr³⁺, Sm³⁺, and Dy³⁺ ions, calculated on the basis of transmittance spectra, were studied. The dependences of all mentioned parameters on the chemical composition of the glassy matrix are discussed.     

Influence of water-cement ratio on the properties of 2-2 cement based piezoelectric composite

Composites with 2-2 connectivity were fabricated from plates of “PMN” ceramic embedded in a sulphoaluminate cement matrix by a cut-filling process. The influences of the water-cement ratio in the matrix on the properties of the composite were analyzed. The results show that when the water-cement ratio is less than 0.4, the piezoelectric stain factor d₃₃ and piezoelectric voltage factor g₃₃ increase smoothly. When the water-cement ratio is larger than 0.4, d₃₃ and g₃₃ increase obviously with increasing the water-cement ratio. This is attributed to a more effective contact between the active and matrix phases. d₃₃ = 322 pc N^− 1 and g₃₃ = 20.9 mV mN^− 1 at a water-cement ratio of 0.45. The planar electromechanical coupling coefficient K_p of the composite is nearly independent of the water-cement ratio. With increasing the water-cement ratio, the thickness electromechanical coupling coefficient K_t of the composite increases, while the mechanical quality factor Q_m exhibits the trend of decrease.     

Spectroscopic study of Zn1−xCoxO thin films showing intrinsic ferromagnetism

Dilute magnetic semiconductors are widely studied due to their potential applications in spin-resolved electronics. We report the direct evidences of intrinsic ferromagnetism in the primarily ferromagnetic ZnO:Co thin films using near-edge X-ray absorption fine structure (NEXAFS) and soft X-ray magnetic circular dichroism (XMCD). The single phase Zn_1−xCo_xO thin films with nominal compositions (0.00 ≤ x ≤ 0.15) were synthesized by a spray pyrolysis technique, which exhibit room temperature ferromagnetism as revealed by alternating gradient force magnetometer (AGFM) measurements. The spectroscopic measurements indicate that most of Co dopants have substituted for Zn sites in ZnO matrix and they are present in divalent Co²⁺ (d⁷) state with tetrahedral symmetry according to the atomic multiplet calculations. The O 1s NEXAFS spectra suggest strong hybridization between O 2p and Co 3d electrons within ZnO matrix. The Co 2p XMCD measurements rule out the magnetism due to the presence of Co clusters, and show that Co–O–Co bonding provides localized magnetic moments leading to ferromagnetism.     

The Spectrum of Doubly Ionized Tungsten (W III)

The spectrum of doubly ionized tungsten (W III) was produced in a sliding-spark discharge and recorded photographically on the NIST 10.7-m normal-incidence vacuum spectrograph in the 600–2680 Å spectral region. The analysis has led to the establishment of 71 levels of the interacting 5d⁴, 5d³ 6s and 5d² 6s² even configurations and 164 levels of the interacting 5d³ 6p and 5d² 6s 6p odd ones. A total of 2636 lines have been classified as transitions between the 235 experimentally determined levels. Comparison between the observed levels and those calculated from matrix diagonalizations with least-squares fitted parameters shows an rms deviation of ±87 cm⁻¹ for the even configurations and ±450 cm⁻¹ for the odd ones.     

Improving SCImago Journal &; Country Rank (SJR) subject classification through reference analysis

In order to re-categorize the SCImago Journal & Country Rank (SJR) journals based on Scopus, as well as improve the SJR subject classification scheme, an iterative process built upon reference analysis of citing journals was designed. The first step entailed construction of a matrix containing citing journals and cited categories obtained through the aggregation of cited journals. Assuming that the most representative categories in each journal would be represented by the highest citation values regarding categories, the matrix vectors were reduced using a threshold to discern and discard the weakest relations. The process was refined on the basis of different parameters of a heuristic nature, including (1) the development of several tests applying different thresholds, (2) the designation of a cutoff, (3) the number of iterations to execute, and (4) a manual review operation of a certain amount of multi-categorized journals. Despite certain shortcomings related with journal classification, the method showed a solid performance in grouping journals at a level higher than categories—that is, aggregating journals into subject areas. It also enabled us to redesign the SJR classification scheme, providing for a more cohesive one that covers a good proportion of re-categorized journals.     

Binary scientific star coauthors core size

It is examined whether the relationship J ∝ A/r ^α , and the subsequent coauthor (CA) core notion (Ausloos, Scientometrics 95(3):895–909, 2013), between the number (J) of joint publications (JPs) by a “main scientist” [leading investigator (LI)] with her/his CAs can be extended to a team-like system. This is done by considering that each CA can be so strongly tied to the LI that they are forming binary scientific star (BSS) systems with respect to their other collaborators. Moreover, publications in peer review journals and in “proceedings”, both often thought to be of “different quality”, are separately distinguished. The role of a time interval for measuring J and α is also examined. New indirect measures are also introduced. For making the point, two LI cases with numerous CAs are studied. It is found that only a few BSS need to be usefully examined. The exponent α turns out to be “second scientist” weakly dependent, but still “size” and “publication type” dependent, according to the number of CAs or JP. The CA core value is found to be (CA or JP) size and publication type dependent, but remains in an understandable range. Somewhat unexpectedly, no special qualitative difference on the BSS CA core value is found between publications in peer review journals and in proceedings. In conclusion, some remark is made on partner cooperation in BSS teams. It is suggested that such measures can serve as criteria for distinguishing the role of scientists in a team.     

Effect on the journal impact factor of the number and document type of citing records: a wide-scale study

We studied the effect on journal impact factors (JIF) of citations from documents labeled as articles and reviews (usually peer reviewed) versus citations coming from other documents. In addition, we studied the effect on JIF of the number of citing records. This number is usually different from the number of citations. We selected a set of 700 journals indexed in the SCI section of JCR that receive a low number of citations. The reason for this choice is that in these instances some citations may have a greater impact on the JIF than in more highly-cited journals. After excluding some journals for different reasons, our sample consisted of 674 journals. We obtained data on citations that contributed to the JIF for the years 1998?C2006. In general, we found that most journals obtained citations that contribute to the impact factor from documents labeled as articles and reviews. In addition, in most of journals the ratio between citations that contributed to the impact factor and citing records was greater than 80% in all years. Thus, in general, we did not find evidence that citations that contributed to the impact factor were dependent on non-peer reviewed documents or only a few citing records.     

Analysis of the Spectrum of Doubly Ionized Molybdenum (Mo III)

The spectrum of doubly ionized molybdenum (Mo III) was produced in a sliding spark discharge and recorded photographically on the NIST 10.7-m normal incidence spectrograph in the 800-3250 Å spectral region. The analysis has led to the establishment of 76 levels of the interacting 4d⁴, 4d³ 5s and 4d² 5s² even configurations, 73 levels of the interacting 4d³ 5d and 4d³ 6s even configurations, and 181 levels of the interacting 4d³ 5p and 4d² 5s5p odd configurations. Approximately 3100 lines have been classified as transitions between these experimentally determined levels. Comparison between the observed levels and those calculated from matrix diagonalizations with least-squares fitted parameters shows standard deviations of 44, 33, and 183 cm⁻¹, respectively, for the levels of the three sets of configurations.     

A simplified solution of the regenerator periodic problem: the case for air conditioning

This work presents an analytical solution for the periodic heat transfer problem of regenerators used in air conditioning, which are operating at low regeneration temperatures and mass flow rates. These types of regenerators are characterized by NTU/Cr ^?<1. The partial differential equations for hot and cold airflows as well as the regenerator matrix were solved using a successive transformation of variables. They were reduced to the ordinary Bessel differential equation of the type xf″+f′?xf=0. The conventional initial and reversal boundary conditions were used in this work. The solution gives a correlation for the prediction of the regenerator effectiveness. Besides the effectiveness, the solution facilitates the calculation of the matrix temperature distribution and exit airflow temperatures. The result is compared with the available numerical and analytical solutions from literature. The result of this analysis reveals that the consideration of a non-linear matrix temperature distribution as in some previous work for low temperature regenerators just complicates the solution procedure with no significant improvement in the accuracy within the parameter space typical for air conditioning applications.     

Fabrication of microwave exfoliated graphite oxide reinforced thermoplastic polyurethane nanocomposites: Effects of filler on morphology,mechanical, thermal and conductive properties

Different formulations of microwave-exfoliated graphite oxide (MEGO) based thermoplastic polyurethane (TPU) nanocomposites were successfully prepared via melt blending followed by injection molding. The spectroscopic study indicated that a strong interfacial interaction had developed between the MEGO and the TPU matrix. The microscopic observations showed that the MEGO layers were homogeneously dispersed throughout the TPU matrix. Thermal analysis indicated that the glass transition temperatures (T_g) of the nanocomposites increased with increasing MEGO content and their thermal stability improved in comparison with pure TPU matrix. The mechanical properties of nanocomposites improved substantially by the incorporation of MEGO into the TPU matrix. Electrical conductivity test indicated that a conductivity of 10⁻⁴ S cm⁻¹ was achieved in the nanocomposite containing only 4.0 wt.% of MEGO.