Rb Systems Research Articles

Strong atom capture ability and pinning effect by doping an element with large electronegativity difference in Sb2Te3 phase change material

The ultimate goal of memory researchers and developers is to devise a universal memory to replace all memories in complex hierarchies of memory systems. Phase change memory is considered by the International Semiconductor Industry Association as the most likely emerging storage technology to achieve this ambitious goal due to its excellent performance. However, the relatively slow operation speed and poor cycle endurance are stumbling blocks for this purpose. Here, we propose a new doping strategy to construct stable bonding by introducing atoms with large electronegativity differences from the matrix Te atoms enhancing the capture ability and the pinning effect to Te atoms, which facilitates fast nucleation and suppresses migration of Te atoms to achieve significant performance improvement. Using ab initio molecular dynamics simulations, we explore and compare the atomic structures, chemical bonding, and dynamics properties of Hf doped Sb2Te3 (HfST), La doped Sb2Te3 (LaST), Rb doped Sb2Te3 (RbST) and Sr doped Sb2Te3 (SrST). In the XST (X refers to Hf, Rb, La and Sr atoms) systems, the increase of the more stable ring structure fluctuation and the stronger atom capture capability of rings enable more and faster formation of nuclei during crystallization. Higher Peierls-like distortions suggest better thermal stability. The motility of Te atoms is suppressed due to the pinning effect. High coordination of atoms and the concentration reduction of the lone-pair electron and void enable small density difference. Our results show that fast universal memory with good endurance can be achieved by the construction of strong bonding by doping atoms with large electronegativity differences, providing an important guidance for experiments and industries.

Efficiency of the new reciprocating and rotary systems with or without ultrasonics in removing root-canals filling with calcium silicate-based sealer (MTA)

BackgroundTo compare the efficiency of endodontic rotary and reciprocating systems in removing calcium silicate-sealer based fillings and to investigate the impact of passive ultrasonic irrigation (PUI) on their efficiency.Materials and methods160 root-canals were instrumented, filled with gutta-percha and calcium silicate based-sealer and divided into 10 equal groups. Five groups in which the reciprocating systems (WaveOne-Gold, Reciproc-Blue and R-Motion) and rotary systems (Fanta-AF-One and Tango-Endo) were used to remove root-canals’ fillings. In the other five groups the fillings were removed by the same systems then additionally with PUI. The times to complete retreatments procedures were recorded. Micro-computed tomography’s analysis of the root-canals fillings’ volume before and after retreatments was used to determine the remaining filling materials (RFMs) volumes.ResultsThe RFMs after using rotary systems (10.1%) was greater than after using reciprocating systems (3.8%) (P < 0.001). The RFMs after using WOG (2%) and RB systems (2.6%) were less than those in the RM (6.8%), TE (9.5%) and FAFO (10.7%) systems [P < 0.05]. The times required to remove the filling materials using the TE (3.7 min), FAFO (4.1 min) and RM (4.1 min) systems were shorter than those required by the RB (5.4 min) and WOG (4.9 min) systems [P < 0.05]. Using PUI resulted in less RFMs (1.44%) when compared to using only rotary or reciprocating systems (6.27%) [P < 0.001].ConclusionsEndodontic reciprocation systems were more effective, but needed longer times than rotary systems in removing calcium silicate based- sealers fillings. The PUI significantly improved removal of the root-canals’ filling materials.Clinical relevance: Reciprocating systems and PUI are recommended whenever root-canals retreatment is considered regardless of using calcium silicate-based sealers.

Influence of the Number of Pecking Motions at Working Length on the Shaping Ability of Single-file Systems in Long Oval-shaped Curved Canals

IntroductionThe present study compared the effect of the number of pecking motions at the working length (WL) on the shaping ability of single-file systems in long oval-shaped curved root canals. MethodsSingle-rooted mandibular premolars with long oval-shaped curved canals (25°–35°) were prescanned using micro–computed tomographic imaging, anatomically paired, and randomly divided into 3 groups (n = 15): XP-endo Shaper (XPS; FKG Dentaire, La Chaux-de-Fonds, Switzerland), Reciproc Blue (RB; VDW, Munich, Germany), and WaveOne Gold (WOG; Dentsply Sirona, Ballaigues, Switzerland). After preparation to the WL, each specimen underwent 1, 2, 4, 10, or 20 pecking motions to the WL and was rescanned. Morphologic parameters were measured and analyzed using a 2-factor repeated measures analysis of variance and the Scheirer-Ray-Hare test. ResultsThe minor apical diameter and percentage increase in canal volume increased with the number of pecking motions, whereas the percentage of unprepared canal surface area decreased (P < .05). The mean minor diameters (in mm) at D0 varied between 0.29 and 0.35 after 4 pecking motions with the RB and WOG systems and between 0.35 and 0.36 after 10 pecking motions with the XPS system. No significant differences in canal transportation or centering ratio were observed among the groups at the levels of canal curvature and canal thirds (P > .05). ConclusionsIncreasing the number of pecking motions improves the cutting efficacy of single-file systems without adversely altering the anatomic characteristics of oval-shaped curved canals. No more than 4 pecking motions for the RB and WOG systems and 10 pecking motions for the XPS system appear to be acceptable for the shaping of these difficult to clean root canals.

Isotope-Geochemical Features of Apoultrabasic Metasomatites of the Sayan–Baikal Folded Area

Abstract —The paper is concerned with a geochemical study of apoultrabasic metasomatites of the Ospa–Kitoi, Parama, and Ust’-Kelyana ophiolite massifs located in the southern folded framing of the Siberian craton. The isotope (O, C, H, Sr, and Rb) systems of dunites, serpentinites, nephrites, listvenites, and talc–carbonate rocks are studied. The isotopic composition of oxygen in olivines from dunites is characterized by δ18O = 4.6–5.5‰. The δ18O values of serpentinites (4.67–7.35‰) point to the mantle genesis of fluids and might have been inherited from ultrabasic rocks. Nephrites are slightly enriched in heavy oxygen isotope (δ18O = 6.13–9.54‰). This indicates that their fluid phase was transported from serpentinites and captured a small portion of the crustal component. The widest variations in δ18O values, from 8.12 to 17.46‰, are observed in minerals from listvenites. Carbonates from these rocks show a highly heterogeneous isotopic composition of oxygen (δ18O = 12.9–18.8‰) and carbon δ13C = –2.8 to +2.8‰). These rocks formed with the contribution of metamorphogenic fluids. According to the isotopic composition of hydrogen, the examined serpentinites are divided into two groups: with δD values specific to “magmatic water” (δD = –73.50 to –85.00‰) and those typical of meteoric fluids (δD = –151.90 to –167.20‰). The listvenites are characterized by low Rb and high Sr contents. Their 87Sr/86Sr values (0.70702–0.70971) indicate the contribution of a crustal source. The study of fluid inclusions in minerals from listvenites has shown that the rocks formed under relatively low-temperature conditions. The homogenization temperatures of fluid inclusions in quartz and magnesite from listvenites of the Ospa–Kitoi massif are 184–290 ºC and 122–182 ºC, respectively. In the Parama massif, the homogenization temperature of fluid inclusions in quartz is 130–170 ºC. The solutions that formed listvenites of the Ospa–Kitoi massif were slightly saline (TDS = 2.9–8.4 wt.% NaCl eq.), with NaCl and Na2CO3 being the main salt components.

Quasiclassical method for calculating the density of states of ultracold collision complexes

We derive a quasiclassical expression for the density of states (DOS) of an arbitrary, ultracold, $N$-atom collision complex, for a general potential energy surface (PES). We establish the accuracy of our quasiclassical method by comparing to exact quantum results for the K$_2$-Rb and NaK-NaK systems, with isotropic model PESs. Next, we calculate the DOS for an accurate NaK-NaK PES to be 0.124~$\mu$K$^{-1}$, with an associated Rice-Ramsperger-Kassel-Marcus (RRKM) sticking time of 6.0~$\mu$s. We extrapolate the DOS and sticking times to all other polar bialkali-bialkali collision complexes by scaling with atomic masses, equilibrium bond lengths, dissociation energies, and dispersion coefficients. The sticking times calculated here are two to three orders of magnitude shorter than those reported by Mayle et al. [Phys. Rev. A 85, 062712 (2012)]. We estimate dispersion coefficients and collision rates between molecules and complexes. We find that the sticking-amplified three-body loss mechanism is not likely the cause of the losses observed in the experiments.

Correlated Gaussian approach to anisotropic resonantly interacting few-body systems

Quantum mechanical few-body systems in reduced dimensionalities can exhibit many interesting properties such as scale-invariance and universality. Analytical descriptions are often available for integer dimensionality, however, numerical approaches are necessary for addressing dimensional transitions. The Fully-Correlated Gaussian method provides a variational description of the few-body real-space wavefunction. By placing the particles in a harmonic trap, the system can be described at various degrees of anisotropy by squeezing the confinement. Through this approach, configurations of two and three identical bosons as well as heteronuclear (Cs–Cs–Li and K–K–Rb) systems are described during a continuous deformation from three to one dimension. We find that the changes in binding energies between integer dimensional cases exhibit a universal behavior akin to that seen in avoided crossings or Zeldovich rearrangement.

Evaluation of several instrumentation techniques and irrigation methods on the percentage of untouched canal wall and accumulated dentine debris in C-shaped canals.

To evaluate the effect of instrumentation using Reciproc Blue (RB; VDW, Munich, Germany) and XP-endo Shaper (XP-S; FKG Dentaire, La Chaux-deFonds, Switzerland) systems on the area of untouched canal wall (AUCW), accumulated hard-tissue debris (AHTD) and the efficacy of three irrigation protocols on percentage reductions (red%) of AHTD within C-shaped canals of mandibular molars. Seventy mandibular molars with C-shaped canals were scanned, matched and assigned to two shaping groups (n=35): RB and XP-S. Following instrumentation, specimens were triple-matched with respect to the amount of remaining debris and assigned to three irrigation subgroups (n=10): syringe-and-needle irrigation (SNI), XP-endo Finisher (XP-F; FKG Dentaire) and passive ultrasonic irrigation (PUI). The AUCW% and AHTD% after instrumentation and the red% of AHTD after irrigation were calculated from micro-computed tomography. Data were analysed using comparisons for two groups (RB vs. XP-S) or multiple subgroups followed by pairwise comparison procedures (SNI vs. XP-F vs. PUI) at α=0.05. For RB and XP-S, 33.04% and 30.45%, respectively, of the canal wall remained untouched (P>0.05). For both groups, the apical third had larger AUCW% than the coronal third (P<0.05). Instrumentation with RB left more debris (2.8%) than XP-S (1.1%) (P<0.05). The PUI and XP-F subgroups had higher mean red% of AHTD than the SNI subgroup; the difference was significant for RB (P<0.05) but not for XP-S. Both RB and XP-S systems were associated with similar AUCW after instrumenting C-shaped canals. RB left significantly greater levels of AHTD compared with XP-S. PUI and XP-F irrigation removed more debris than SNI when using the RB system.

Magnetic Resonance Frequency Shifts of Spin-Polarized Cesium Atoms in a Cs–Rb Mixture

The interaction of spin-polarized cesium atoms with cesium and rubidium atoms under conditions of optical orientation of atoms is considered. On the basis of data on spin-exchange complex cross sections in the Cs–Cs and Cs–Rb systems, a calculation of a magnetic resonance frequency shift of cesium atoms in a Cs–Rb mixture, as well as comparison of the calculated values of the frequency shift with experimental data, is performed.

Magnetic-resonance-frequency shifts in spin-exchange collisions of Rb and Cs alkali-metal atoms

On the basis of data on spin-exchange complex cross sections in the Rb–Rb and Cs–Rb systems, the magnetic-resonance-frequency shifts of rubidium atoms upon collisions in a mixture of Cs–Rb alkalimetal atoms are calculated. The results obtained are compared with the experimental data and the previous theoretical data.

Isotopic Shift of Atom-Dimer Efimov Resonances in K-Rb Mixtures: Critical Effect of Multichannel Feshbach Physics.

Multichannel Efimov physics is investigated in ultracold heteronuclear admixtures of K and Rb atoms. We observe a shift in the scattering length where the first atom-dimer resonance appears in the ^{41}K-^{87}Rb system relative to the position of the previously observed atom-dimer resonance in the ^{40}K-^{87}Rb system. This shift is well explained by our calculations with a three-body model including van der Waals interactions, and, more importantly, multichannel spinor physics. With only minor differences in the atomic masses of the admixtures, the shift in the atom-dimer resonance positions can be cleanly ascribed to the isolated and overlapping Feshbach resonances in the ^{40}K-^{87}Rb and ^{41}K-^{87}Rb systems, respectively. Our study demonstrates the role of multichannel Feshbach physics in determining Efimov resonances in heteronuclear three-body systems.

Integrating agronomic practices to reduce greenhouse gas emissions while increasing the economic return in a rice-based cropping system

The effective mitigation of greenhouse gas (GHG) emissions from crop cultivation requires an overall consideration, due to the trade-off relationship between GHGs and the mitigation measures sometimes undermining grain yields and economic returns. To explore the maximum potential of GHG mitigation without sacrificing economic returns, we investigated the GHG emissions, crop yields and economic returns over two years in three rice-cropping systems (rice–wheat, RW; rice–fava bean, RB; and rice–fallow, RF). Different N fertilization levels and straw incorporation methods were employed in each of the rice-cropping systems at the study site, in the Taihu Lake region (TLR) of China. Bean straw produced in the RB system was fermented aerobically before incorporation, while straws produced in the RW and RF systems were directly incorporated into the soils. Relative to the traditional RW system, methane emissions during the rice seasons were significantly reduced by 29–44% in the RB system; annual N inputs were reduced by 43%; annual nitrous oxide emissions for N fertilization treatments were decreased by 56–69%; and the average rice yield was increased by 5.2%. As a result, the GHG intensity (GHGI) was significantly reduced by 11–41%, and the annual net economic benefit (NEB) was increased by 22–94%. Compared with the RW system, the GHGI in the RF system was increased by 8–30% and the NEB was decreased by 3–33%. Considering the current rice/wheat production practices employed in the TLR, the GHGI could be reduced by 26% while the NEB could be improved by 23%, with an annual reduction in the N application rate (currently 525kgNha−1) by 20% and the conversion of the RW systems into RB systems that use straw fermentation. The results of this study suggest that high economic return and GHG mitigation could be simultaneously achieved by the integrated adoption of reasonable reduction in N application rates, the use of appropriate rice-cropping systems and by employing eco-friendly straw management.

Exploration of electron-vibrational interaction in the 5d states of Eu2+ ions in ABaPO4 (A=Li, Na, K and Rb) phosphors.

This work reports the theoretical analysis of the electron-vibrational interaction (EVI) in 4f-5d optical transitions of Eu2+ ions in ABaPO4 (A=Li, Na, K and Rb) systems. The EVI parameters were estimated from the recently reported room temperature photoluminescence results, by employing the spectrum-fitting method. Parameters such as the Huang-Rhys factor, effective phonon energy, Stokes shift and zero-phonon line position were estimated and are reported here. The estimated EVI parameters were validated by modeling the emission band and establishing the agreement between the experimental and modeled emission bands. Copyright © 2016 John Wiley & Sons, Ltd.

Ab initiointeraction potentials and scattering lengths for ultracold mixtures of metastable helium and alkali-metal atoms

We have obtained accurate ab initio quartet potentials for the diatomic metastable triplet helium + alkali-metal (Li, Na, K, Rb) systems, using all-electron restricted open-shell coupled cluster singles and doubles with noniterative triples corrections [CCSD(T)] calculations and accurate calculations of the long-range $C_6$ coefficients. These potentials provide accurate ab initio quartet scattering lengths, which for these many-electron systems is possible, because of the small reduced masses and shallow potentials that results in a small amount of bound states. Our results are relevant for ultracold metastable triplet helium + alkali-metal mixture experiments.

Performance Evaluation on Several Exchange-correlation Functional Ap-proximations in Calculations of Alkali-metals and IB Group Metals Pair Potentials

In the present paper, inter-atomic pair potentials in alkali-metals and IB group metals, in crystal state and dia- tomic system, respectively, are systematically calculated by means of electronic density functional theory with several ex- change-correlation (EC) functional approximations. In the absence of experimental potential function information, exper- imentally available bonding length and binding energy of crystal lattice structure, and equilibrium separation and potential minimum of diatomic systems, are used for the first time in the context of potential energy as a function of atom separa- tion, to evaluate the performance of the EC approximations considered in calculating the main properties of neutral atom potential energy curve. Comparison between the experiment measures and first-principle calculations indicates that (i) all EC functional approximations show great changes in their performances for different systems, and the performances of a given EC functional approximation are variable even for the same element but different structures. (ii) The EC functional approximations considered show relatively stronger adaptability in calculations for the crystal lattice structures of both al- kali-metals and IB metals, but the performances for the IB metals Cu, Ag, Au diatomic systems degrade somewhat; more than that, the alkali-metal Li, Na, K, Rb, and Cs diatomic systems are inexorably the most difficult to be dealt with by all EC approximations considered. (iii) Although the calculated inter-atomic pair potentials in the diatomic system comprised of the IB metals and alkali-metals, respectively, display unmistakable deviations from the experimental measures, they still constitute specific empirical materials on which effective inter-atomic pair potentials are constructed to take into ac- count the three-body interactions in the statistical mechanics theory considering only two-body interactions.

Density Functional Theory of MH–MOH Solid Solubility (M = Alkali) and Experiments in NaH–NaOH

We present first-principles solubility calculations of H–/[OH]− mixing in binary alkali metal hydrides MH and their corresponding hydroxides MOH, for M ={Li, Na, K, Rb, Cs}. Solid solubility in the MH–MOH system may play an important role in solid-phase reactions involving the MH system, including for example many aluminum-based complex hydrides of the alkali metals, such as NaAlH4 and LiAlH4. Our results indicate that the available cell volume for H– and OH– groups correlates strongly with mixing, and MOH is soluble in MH for M ={Na, K, and Rb} where available volumes for H– and OH– anions differ by less than about 15%, very similar to a Hume–Rothery type rule for intermetallics. The predicted mixing temperatures for the K and Rb systems are lower than for the Na system, in part because of the similarity in MH and MOH primitive cell volumes. Critical temperature diagrams for the formation of solid solution MH–MOH mixtures as a function of MOH concentration are calculated using a free energy minimization in the grand canonical ensemble. Differential scanning calorimetry and in situ X-ray diffraction measurements of the NaH1–x(OH)x system are presented for a range of compositions (0.3 ≤ x ≤ 1.0). As the temperature is raised, the polymorphic phase transitions present in NaOH occur concomitantly with H–/OH– mixing, eventually forming a single-phase cubic structure; the behavior is fully reversible on cooling. Finally, the formation of solid solution MH/MOH reduces the decomposition temperature of NaH1–x(OH)x to lower temperatures than pure NaH while increasing the stability in the KH and RbH systems.

Thermodynamic assessment of the Bi-alkali metal (Li, Na, K, Rb) systems using the modified quasichemical model for the liquid phase

Bi-alkali metal (Li, Na, K, Rb) binary systems have been systematically assessed based on the available phase diagrams and thermodynamic data. The modified quasichemical model, which takes short-range ordering into account, is used to describe the liquid phase. All intermetallic phases are treated as stoichiometric compounds. A set of self-consistent model parameters is obtained and the experimental data are reproduced well within experimental error limits. The enthalpy of mixing, entropy of mixing, and activity of element are calculated, showing the liquid phase exhibits maximum short-range ordering at 75at% X (X=Li, Na, K, Rb). Some systematic variations and regularities are presented, indicating the enthalpy and entropy of mixing for the liquid phase at the maximum short-range ordering along with the enthalpy of formation and melting temperature of intermediate compound BiX3 change with the atomic radius of alkali metals regularly.

Double salts Cs1 − xMxH2PO4 (M = Na, K, Rb) as proton conductors

Structural, transport and thermal properties of the Cs1−xMxH2PO4 (M = Na, K, Rb) systems were studied in a wide range of compositions (x=0–0.9). The solid solutions are formed in all Cs1−xMxH2PO4 systems. The cell parameters in double salts decrease compared to CsH2PO4. The range of existence of Cs1−xMxH2PO4 solid solutions significantly differs for different cations, x=0–0.9 for M = Rb+, x=0–0.3 for K+ and Na+. Proton conductivity of low-temperature phase of double salts increases by 1–3 orders of magnitude depending significantly on the composition and size of introduced metal ions, whereas proton conductivity of high-temperature phase decreases no more than 1.5–2 times. The temperature of superionic phase transition increases for the Cs1−xRbxH2PO4 systems (about ≤20°C) and decreases for Cs1−xKxH2PO4.

Thermodynamic assessments of six binary systems of alkali metals

Among the phase diagrams of six binary systems composed of alkali metals, Sodium (Na), Potassium (K), Rubidium (Rb) and Cesium (Cs), three of them, those of the Cs–K, Cs–Rb and K–Rb systems, indicate a complete range of solid solubility, and the other three, those of the Cs–Na, K–Na and Na–Rb systems, have the eutectic type characteristic. The computational thermodynamic descriptions of the six binary systems were modeled by the CALPHAD technique. The solution phases, liquid and body-centered cubic, were described using a substitution model, with the excess Gibbs energies formulated by the Redlich–Kister expression. The intermediate phases with no solubility ranges, KNa 2 and CsNa 2, were treated as stoichiometric compounds. The thermodynamic properties and the phase diagrams of the six binary systems were predicted. The consistency between the calculated results and the reported experimental measurements for the phase equilibria and the thermochemical properties has been obtained for all of the six binary systems.

Substitution Effect on Metal–Insulator Transition of K2V8O16

The effect of the substitution of various ions on the metal–insulator (MI) transition at 170 K in K 2 V 8 O 16 has been investigated. Both Rb and Ti form complete solid solution systems: K 2- x Rb x V 8 O 16 and K 2 V 8- y Ti y O 16 , respectively. The substitution of Rb for K or of Ti for V splits the transition into two transitions: the high-temperature transition is a first-order MI transition from a tetragonal structure to a tetragonal structure, and the low-temperature transition is a second-order transition to a monoclinic structure. In K 2- x Rb x V 8 O 16 , the former terminates to an MI transition at around 220 K in Rb 2 V 8 O 16 , while the latter disappears at x > 0.6. In K 2 V 8- y Ti y O 16 , both transitions disappear at y > 0.5. The substitution of Cr for V also results in a similar splitting of the transition and the rapid disappearance of both transitions. The substitution of Na or Ba for K suppresses the MI transition without any splitting of the transition, although the solubility of bo...

Possible involvement of whole-arm reciprocal translocations (WARTs) in the evolution of a Mus musculus domesticus Robertsonian system from Greece

The evolution of the Robertsonian (Rb) system of the house mouse (Mus musculus domesticus) located in Peloponnisos (Greece) is examined, under the possibility of whole arm reciprocal translocation (WART) involvement in the formation process of two of its Rb races with 2n = 24 and 2n = 28, respectively, characterized by monobrachial homology. Our contribution reinforces the opinion that WARTs may have been more actively involved in the formation of Rb races in this subspecies than previously thought. Moreover, the consideration of WARTs, when studying complex Rb systems permits the suggestion of more sensible and parsimonial pathways for their phylogenetic history than when WARTs are excluded.