Rb System Research Articles

The influence of spin-spin interaction on high partial wave Feshbach resonance in ultracold 23Na -87Rb system.

In this paper, we investigate the Feshbach resonances of high partial waves and the influence of spin-spin (S-S) interaction on ultracold scattering processes. Taking the Na23- Rb87 system as an example, we plot the variations of weakly bound state energy and elastic scattering cross section with magnetic field and with collision energy. We find that the number of splittings in high partial wave Feshbach resonances does not strictly conform to the expected l + 1 (l is rotational angular momentum), and the deviation is attributed to the influence of bound states in other channels coupled by S-S interaction. For different ml (the projection of l on the external magnetic field direction), the effects of S-S interaction lead to different scattering patterns in the incident channels. These results reveal the complex features of ultracold scattering processes in high partial waves caused by S-S interaction.

Silico antimonate nanocomposite material: I- preparation, characterization and its application for separation of strontium and rubidium from aqueous solutions

ABSTRACT Sorption of Sr(II) and/or Rb(I) onto synthesised silico antimonate (SiSb) nanocomposite was investigated in this work, using batch equilibrium and column techniques. SiSb was fabricated by precipitation technique and characterised by various analytical tools. The adsorption of Sr(II) and/or Rb(I) includes the influence of shaking time, distribution coefficient, kinetics, capacity, and column separation. The data prove that SiSb has a quick equilibrium time (40 min), the distribution coefficients (Kd) as a function of pH have maximum separation factors ( α R b S r ) equal to 162.1 at pH 6, reaction kinetics follow a pseudo-second-order model, sorption capacity for Sr(II) and Rb(I) is 48.5 and 13.8 mg/g, respectively. Column data reveal that Sr(II) can be loaded and separated from Sr(II)-Rb(I) as a simulation model for Sr(II) recovery from its Sr(II)-Rb(I) system using different concentrations of HNO3 as eluent.

Comparison of shaping ability of the Reciproc Blue and One Curve with or without glide path in simulated S-shaped root canals.

This study aimed to assess the impact of a glide-path on the shaping ability of 2 single-file instruments and to compare the centering ability, maintenance of original canal curvatures and area of instrumentation in simulated S-shaped root canals. Forty simulated S-shaped root canals were used and were prepared with One Curve (group OC), One G and OC (group GOC), Reciproc Blue (group RB) and R-Pilot and RB (group PRB) and scanned before and after instrumentation. The images were analyzed using AutoCAD. After superimposing the samples, 4 levels (D1, D2, D3, and D4) and 2 angles (Δ1 and Δ2) were established to evaluate the centering ability and modification of the canal curvatures. Then, the area of instrumentation (ΔA) was measured. The data were analyzed using 2-way analysis of variance and Tukey's test for multiple comparisons (p < 0.05). Regarding the centering ability in the apical part (D3, D4), the use of the glide-path yielded better results than the single-file groups. Among the groups at D4, OC showed the worst results (p < 0.05). The OC system removed less material (ΔA) than the RB system, and for Δ1, OC yielded a worse result than RB (p < 0.05). The glide-path improved the centering ability in the apical part of the simulated S-shaped canals. The RB system showed a better centering ability in the apical part and major respect of the canal curvatures compared with OC system.

Secondary Root Canal Treatment with Reciproc Blue and K-File: Radiographic and ESEM-EDX Analysis of Dentin and Root Canal Filling Remnants.

Secondary root canal treatment requires the complete removal of filling materials with different chemical-physical properties. A newly developed single-use NiTi instrument (Reciproc Blue, RB) may be more effective in root canal retreatment. The aim of the present study was to evaluate morphology and composition of remnants after retreatment with RB compared to traditional K-File technique, in canals obturated with Thermafil/AH Plus. Twenty-four single-rooted human teeth were shaped with NiTi obturated with AH-Plus/Thermafil and retreated using RB NiTi instruments or manual K-Files. Radiographs were taken to evaluate endodontic space and radiopacity of residual filling-material before/after procedures. After retreatment, samples were longitudinally split and observed by environmental scanning electron microscopy connected to energy dispersive X-Ray spectroscopy (ESEM-EDX) to analyze the debris/remnant position, microchemistry, and dentinal surface morphology. Time for retreatments was recorded and compared using one-way ANOVA (p-value = 0.05). Radiopaque filling residuals were found in both groups. RB system resulted statistically faster than manual K-File in retreatment procedure (p < 0.001). Root canal space radiographic appearance obtained after retreatment with RB was wider than K-File (p < 0.05). ESEM-EDX revealed 4 different morphological dentin area. Area-1: debris-free with typical Ca, P, and N composition of dentin and detected in 70% of the surface. Area-2: presence of deproteinized smear layer free from N and debris in 15% of the surface. Area-3: a thick packed smear layer N-free and with fine debris consisting of trace elements from sealer in 10% of the surface. Area-4: packed with debris and trace elements. No difference was observed between both instruments regarding root canal space appearance and ESEM-EDX analysis. Both systems were able to remove filling material but created a dentine morphology composed of packed debris and filling materials embedded into the smear layer. Dentin surface composition resulted in collagen depleted by irrigation procedures. The reciprocating system required less time to complete retreatment.

Reconstructing the Evolutionary History of Chromosomal Races on Islands: A Genome-Wide Analysis of Natural House Mouse Populations.

Chromosomal evolution is widely considered to be an important driver of speciation, as karyotypic reorganization can bring about the establishment of reproductive barriers between incipient species. One textbook example for genetic mechanisms of speciation are large-scale chromosomal rearrangements such as Robertsonian (Rb) fusions, a common class of structural variants that can drastically change the recombination landscape by suppressing crossing-over and influence gene expression by altering regulatory networks. Here, we explore the population structure and demographic patterns of a well-known house mouse Rb system in the Aeolian archipelago in Southern Italy using genome-wide data. By analyzing chromosomal regions characterized by different levels of recombination, we trace the evolutionary history of a set of Rb chromosomes occurring in different geographical locations and test whether chromosomal fusions have a single shared origin or occurred multiple times. Using a combination of phylogenetic and population genetic approaches, we find support for multiple, independent origins of three focal Rb chromosomes. The elucidation of the demographic patterns of the mouse populations within the Aeolian archipelago shows that an interplay between fixation of newly formed Rb chromosomes and hybridization events has contributed to shaping their current karyotypic distribution. Overall, our results illustrate that chromosome structure is much more dynamic than anticipated and emphasize the importance of large-scale chromosomal translocations in speciation.

ANN Based Improved Regenerative Braking System on PV/Battery Powered Electric Vehicles with Single Stage Interaction Converter

Hybrid features batteriesand photovoltaic (PV) module located on the roof of electric Vehicles (EV) can be effectively used by a single stage interaction converter (SSIC). SSIC is introduced for directing the energy flow amid the PV panel, battery and BLDC machine.In this paper a novel braking system is used for charing electrical vehicles using solar battery system (PV) integrated with BLDC motor. It is called as RBS (Regenerative Braking System). During the RB process, generator function is provided by BLDC motor. In order to boost the BLDC-Back-EMF, a suitable switching algorithm is used. By boosting the inverter and SSIC converter the DC-Link voltage reference is reduced to charge the battery. It increases the efficiency of the RB system. In this paper Aritifical Neural Network is used to provide a smooth and reliable brake with distributed force. This proposed BLDC-Back-EMF is experimented in MATLAB Simulink software and the results are verified. Speed, Breaking-Force, torque and front-RB force, rearmeachnical-RB force and other voltage, power are verified.

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.

Observability of the Efimov spectrum in an electron-atom-atom system

The bound states of a system consisting of two heavy identical atoms and one light electron interacting through the finite-range pairwise potentials are explored, focusing on their dependence on the electron-atom scattering length. In the case of an exact resonance in the electron-atom interaction, the binding energy of an electron yields an effective $1/r^{2}$ potential for the relative motion of the atoms; One major finding is a universal potential that depends on the polarization length which goes beyond the Efimov region. An analytic expression for that potential is extracted from numerical calculations. The spectrum of the e+Rb+Rb system produced by the electron-atom polarization interaction exhibits three main sections, a non-universal transition region, a quasi-Efimov region, and a densely packed Efimov region.

Effect of No-Till and Raised-Bed Planting on Soil Moisture Conservation and Productivity of Summer Maize (Zea mays) in Eastern Himalayas

Productivity of summer maize (Zea mays) is relatively low in hill ecosystem of north-eastern region (NER) of India due to scanty rainfall, lack of irrigation and low residual soil moisture. Conservation tillage along with suitable land management system can improve the soil moisture regime and performance of maize. Field experiment was conducted for 2 years (2012 and 2013) with six combinations of tillage and land configuration practices, viz. CT–FB: conventional tillage (CT) with flatbed planting (FB), CT–RF: CT with ridge and furrow planting (RF), CT–RB: CT with raised-bed planting (RB), NT–FB: no-till (NT) with FB, NT–RF: NT with RF and NT–RB: NT with RB. Results revealed that significantly higher soil moisture content (22.8–23.4% and 21.0–25.3%) was found in NT–RB system as compared those under CT–FB (19.0–19.4% and 17.0–21.2%) at 0–60 cm soil depth in both years 2012 and 2013, respectively, at all the period of moisture estimation. The NT–RB system being on a par with NT–RF recorded significantly higher root length, rooting density, leaf area index and biomass accumulation as compared to other treatments. The average (2 years) maximum number of cobs ha−1 (63,518 cobs per plant), cob weight (272 g per cob), green cob (11.2 M ha−1) and fodder yield (50.5 Mg ha−1) were also recorded under NT–RB system. So, it is recommended to grow summer maize under NT–RB system for higher soil moisture conservation, improved plant growth and subsequently good fodder and green cob yield in the hills of NER.

Small bipolarons and extended states of guest Na and Rb atoms in quasi-two-dimensional disorderedM7.8−δAl7.8Si8.2O32.0(M=Na, Rb)

The evolution of the electronic properties of guest Na and Rb atoms in a disordered deformable lattice is investigated for a series of guest-atom densities $n$. The quasi-two-dimensional host ${M}_{7.8\ensuremath{-}\ensuremath{\delta}}{\mathrm{Al}}_{7.8}{\mathrm{Si}}_{8.2}{\mathrm{O}}_{32.0}$ ($M$=Na, Rb), known as zeolite P, is used. The Na system is a stubborn bipolaronic insulator to the maximum $n$ of 1.03. In contrast, the Rb system exhibits a crossover from a bipolaronic insulator to a conducting phase analogous to a disordered metal at $n$ = 0.89. A critical region undergoing polaronic melting appears in the vicinity of the crossover on the insulating side, evidenced by a reduction in the small bipolaron absorption band and a drop in the activation energy. Transition to the conducting phase coincides with the appearance of a midinfrared band and an increase in the charge-carrier decay length, suggesting the polaronic and extended nature of the carriers. These findings constitute rare examples of electron-lattice coupling opening (or closing) a mobility gap and scaling the continuity (or discontinuity) of a conducting transition in the face of disorder.

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.

ChemInform Abstract: Discovery of a Red‐Emitting Li3RbGe8O18:Mn4+ Phosphor in the Alkali‐Germanate System: Structural Determination and Electronic Calculations.

AbstractA solid‐state combinatorial chemistry approach in the M—Ge—O (M: Li, K, Rb) system doped with Mn4+ results in the title phosphor (initial Mn levels of 0.005 M) which is prepared by firing the alkali carbonates, GeO2, and MnCO3 in air (multiple sample container, 800 °C, 4 h).

Biofilms in bioremediation and wastewater treatment: characterization of bacterial community structure and diversity during seasons in municipal wastewater treatment process.

The bacterial community structure and diversity were assessed at the scale of rotating biodisk procedure (RB) in a semi-industrial pilot plant. As well, the Salmonella community was particularly monitored, and the effects of ultraviolet (UV-C254) on the bacterial community were studied. The identification of dominant bacteria revealed the presence of beneficial and useful species that could play an important role in the process of wastewater purification. Several species as Enterobacter agglomerans, Cronobacter sakazakii, and Pantoea agglomerans known for their bioremediation activities were revealed in the majority of biofilm samples. Common detection of Salmonella community provides evidence that the RB system did not seriously affect Salmonella. Furthermore, the investigation on the (UV)-C254 inactivation of the whole bacterial community, in secondary treated wastewater, showed variable UV resistance results. No Salmonella detection was registered at a dose of around 1440mWscm-2 since a total disappearance of Salmonella was recorded.

Discovery of a Red-Emitting Li3RbGe8O18:Mn4+ Phosphor in the Alkali-Germanate System: Structural Determination and Electronic Calculations.

A solid-state combinatorial chemistry approach, which used the A-Ge-O (A = Li, K, Rb) system doped with a small amount of Mn4+ as an activator, was adopted in a search for novel red-emitting phosphors. The A site may have been composed of either a single alkali metal ion or of a combination of them. This approach led to the discovery of a novel phosphor in the above system with the chemical formula Li3RbGe8O18:Mn4+. The crystal structure of this novel phosphor was solved via direct methods, and subsequent Rietveld refinement revealed a trigonal structure in the P3̅1m space group. The discovered phosphor is believed to be novel in the sense that neither the crystal structure nor the chemical formula matches any of the prototype structures available in the crystallographic information database (ICDD or ICSD). The measured photoluminescence intensity that peaked at a wavelength of 667 nm was found to be much higher than the best intensity obtained among all the existing A2Ge4O9 (A = Li, K, Rb) compounds in the alkali-germanate system. An ab initio calculation based on density function theory (DFT) was conducted to verify the crystal structure model and compare the calculated value of the optical band gap with the experimental results. The optical band gap obtained from diffuse reflectance measurement (5.26 eV) and DFT calculation (4.64 eV) results were in very good agreement. The emission wavelength of this phosphor that exists in the deep red region of the electromagnetic spectrum may be very useful for increasing the color gamut of LED-based display devices such as ultrahigh-definition television (UHDTV) as per the ITU-R BT.2020-2 recommendations and also for down-converter phosphors that are used in solar-cell applications.

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.

The genesis of metal zonation in the Weilasituo and Bairendaba Ag–Zn–Pb–Cu–(Sn–W) deposits in the shallow part of a porphyry Sn–W–Rb system, Inner Mongolia, China

The Weilasituo and Bairendaba Zn–Pb–Ag–Cu–(Sn–W) sulphide deposits are located in the southern part of Great Xing'an Range of Inner Mongolia in China. The deposits are located at shallow depths in the newly discovered Weilasituo porphyry hosting Sn–W–Rb mineralization. The mineralization at Weilasituo and Bairendaba consist of zoned massive sulphide veins within fractures cutting the Xilinhot Metamorphic Complex and quartz diorite. The Weilasituo deposit gradually zones from the Cu-rich Zn–Cu sulphide mineralization in the west to Zn-rich Zn–Cu sulphide mineralization in the east. The Bairendaba deposit has a Cu-bearing and Zn-rich core through a transitional zone devoid of copper to an outer zone of Zn–Pb–Ag mineralization. Three main veins contain more than 50wt.% of the contained metal in the two deposits with their metal ratios displaying a systematic and gradual increase in Zn/Cu, Pb/Zn and Ag/Zn ratios from the western part of Weilasituo to the eastern part of Bairendaba.Three stages of vein-type mineralization are recognized. Early, sub-economic mineralization consists of a variable proportion of euhedral arsenopyrite, pyrite, quartz, and rare wolframite, scheelite, cassiterite, magnetite and cobaltite. This was succeeded by main stage mineralization with economic concentration of zoned Cu, Zn, Pb and Ag sulphide minerals along strike within the veins. The zones consist of the assemblages: (1) pyrrhotite–Fe-rich sphalerite–chalcopyrite(–quartz–fluorite) at west Weilasituo; (2) pyrrhotite–Fe-rich sphalerite–chalcopyrite(–galena–tetrahedrite–quartz–fluorite) at east Weilasituo; (3) pyrrhotite–Fe-rich sphalerite–chalcopyrite(–galena–tetrahedrite–quartz–fluorite) in the centre of Bairendaba; (4) pyrrhotite–Fe-rich sphalerite–galena(–chalcopyrite–tetrahedrite–quartz–fluorite) in the transition zone of Bairendaba; and (5) pyrrhotite–Fe-rich sphalerite–galena–tetrahedrite(–chalcopyrite–falkmanite–argentite–pyrargyrite–quartz–fluorite) in the outer zone at Bairendaba. Post-main ore stage is devoid of sulphides and characterized overprinting of fluorite, sericite, chlorite, illite, kaolinite and calcite.Zircon SHRIMP U–Pb dating, Zircon LA–ICP–MS U–Pb dating, molybdenite Re–Os isochron dating, and muscovite Ar–Ar dating indicate the Beidashan granitic batholith was intruded at 140±3Ma (MSWD=3.3), the porphyritic monzogranite from marginal facies of the Beidashan batholith was intruded at 139±2Ma (MSWD=0.75), the mineralized quartz porphyry was intruded at 135±2Ma (MSWD=0.91), the greisen mineralization occurred at 135±11Ma (MSWD=7.2), and the post-main ore stage muscovite deposited at 129.5±0.9Ma. The new geochronology data show the porphyry Sn–W–Rb and vein-type sulphide mineralization are contemporaneous with granitic magmatism in the region.The metal zonation at the Weilasituo and Bairendaba deposits is a result of progressive metal deposition. This was during the evolution of a metal-bearing fluid along the strike of the veins and during the main stage of ore formation at the upper part of the deep-seated porphyry Sn–W–Rb system. This progressive zonation indicates that the deposits represent end-numbers formed from one ore-forming fluid, which moved from west to east from the porphyry. The metal zonation patterns of the major veins are consistent with metal-bearing fluid entering the system with the precipitation of chalcopyrite proximally and sphalerite, galena and Ag-bearing minerals more distally. We show that the mechanism of metal deposition is therefore controlled by thermodynamic conditions resulting in the progressive separation of sulphides from the metal-bearing fluid. The temperature gradient between the inflow zone and the outflow zone appears to be one of the key parameters controlling the formation of the metal zonation pattern. The sulphide precipitation sequence is consistent with a low fS2 and low fO2 state of the acidic metal-bearing fluid. The metal zonation pattern provides helpful clues from which it is possible to establish the nature of fluid migration and metal deposition models to locate a possible porphyry mineralization at depth in the Great Xing'an Range, which is consistent with the geology of the newly discovered porphyry Sn–W–Rb system.

On the origin of Robertsonian fusions in nature: evidence of telomere shortening in wild house mice.

The role of telomere shortening to explain the occurrence of Robertsonian (Rb) fusions, as well as the importance of the average telomere length vs. the proportion of short telomeres, especially in nature populations, is largely unexplored. In this study, we have analysed telomere shortening in nine wild house mice from the Barcelona Rb system with diploid numbers ranging from 29 to 40 chromosomes. We also included two standard (2n=40) laboratory mice for comparison. Our data showed that the average telomere length (considering all chromosomal arms) is influenced by both the diploid number and the origin of the mice (wild vs. laboratory). In detail, we detected that wild mice from the Rb Barcelona system (fused and standard) present shorter telomeres than standard laboratory mice. However, only wild mice with Rb fusions showed a high proportion of short telomeres (only in p-arms), thus revealing the importance of telomere shortening in the origin of the Rb fusions in the Barcelona system. Overall, our study confirms that the number of critically short telomeres, and not a simple reduction in the average telomere length, is more likely to lead to the origin of Rb fusions in the Barcelona system and ultimately in nature.

Genetic recombination variation in wild Robertsonian mice: on the role of chromosomal fusions and Prdm9 allelic background.

Despite the existence of formal models to explain how chromosomal rearrangements can be fixed in a population in the presence of gene flow, few empirical data are available regarding the mechanisms by which genome shuffling contributes to speciation, especially in mammals. In order to shed light on this intriguing evolutionary process, here we present a detailed empirical study that shows how Robertsonian (Rb) fusions alter the chromosomal distribution of recombination events during the formation of the germline in a Rb system of the western house mouse (Mus musculus domesticus). Our results indicate that both the total number of meiotic crossovers and the chromosomal distribution of recombination events are reduced in mice with Rb fusions and that this can be related to alterations in epigenetic signatures for heterochromatinization. Furthermore, we detected novel house mouse Prdm9 allelic variants in the Rb system. Remarkably, mean recombination rates were positively correlated with a decrease in the number of ZnF domains in the Prdm9 gene. The suggestion that recombination can be modulated by both chromosomal reorganizations and genetic determinants that control the formation of double-stranded breaks during meiosis opens new avenues for understanding the role of recombination in chromosomal speciation.

First-principles study of the binary intermetallics in theAu–Rbsystem

First-principles calculations within density functional theory (DFT) with the projector augmented wave (PAW) technique were used to investigate the stabilities of intermetallics in the Au – Rb system at 0 K. Four intermetallics: Au7Rb3, Au3Rb2, Au5Rb and AuRb were investigated in their observed experimental structures. The Au2Rb compound, reported in the Au – Rb phase diagrams without specifying explicitly its structure, was also investigated by inspecting several hypothetical structures. A suspect compound ( AuRb2) was also investigated. Results show that: (i) The Au3Rb2and Au7Rb3compounds, which were never reported in any Au – Rb phase diagram, are stable at 0 K. (ii) The Au2Rb compound is not a ground state for all the tested structures. (iii) Stability of the Au5Rb and AuRb compounds was confirmed. (iv) The new compound AuRb2, not yet reported experimentally, is found mechanically stable at 0 K.

Light-assisted cold chemical reactions of barium ions with rubidium atoms

Light-assisted reactive collisions between laser-cooled Ba+ ions and Rb atoms were studied in an ion–atom hybrid trap. The reaction rate was found to strongly depend on the electronic state of the reaction partners with the largest rate constant [7(2) × 10−11 cm3 s−1] obtained for the excited Ba+(6s)+Rb(5p) reaction channel. Similar to the previously studied Ca++Rb system, charge transfer and radiative association were found to be the dominant reactive processes. The generation of molecular ions by radiative association could directly be observed by their sympathetic cooling into a Coulomb crystal. Potential energy curves up to the Ba+(6s)+Rb(5p) asymptote and reactive-scattering cross sections for the radiative processes were calculated. The theoretical rate constant obtained for the lowest reaction channel Ba+(6s)+Rb(5s) is compatible with the experimental estimates obtained thus far.