During solvent extraction, amphiphilic extractants assist the transport of metal ions across the liquid-liquid interface between an aqueous ionic solution and an organic solvent. Investigations of the role of the interface in ion transport challenge our ability to probe fast molecular processes at liquid-liquid interfaces on nanometer-length scales. Recent development of a thermal switch for solvent extraction has addressed this challenge, which has led to the characterization by X-ray surface scattering of interfacial intermediate states in the extraction process. Here, we review and extend these earlier results. We find that trivalent rare earth ions, Y(III) and Er(III), combine with bis(hexadecyl) phosphoric acid (DHDP) extractants to form inverted bilayer structures at the interface; these appear to be condensed phases of small ion-extractant complexes. The stability of this unconventional interfacial structure is verified by molecular dynamics simulations. The ion-extractant complexes at the interface are an intermediate state in the extraction process, characterizing the moment at which ions have been transported across the aqueous-organic interface, but have not yet been dispersed in the organic phase. In contrast, divalent Sr(II) forms an ion-extractant complex with DHDP that leaves it exposed to the water phase; this result implies that a second process that transports Sr(II) across the interface has yet to be observed. Calculations demonstrate that the budding of reverse micelles formed from interfacial Sr(II) ion-extractant complexes could transport Sr(II) across the interface. Our results suggest a connection between the observed interfacial structures and the extraction mechanism, which ultimately affects the extraction selectivity and kinetics.

Atomic clocks based on laser-cooled atoms are widely used as primary frequency standards. Deploying such cold atom clocks (CACs) in space is foreseen to have many applications. Here we present tests of a CAC operating in space. In orbital microgravity, the atoms are cooled, trapped, launched, and finally detected after being interrogated by a microwave field using the Ramsey method. Perturbing influences from the orbital environment on the atoms such as varying magnetic fields and the passage of the spacecraft through Earth’s radiation belt are also controlled and mitigated. With appropriate parameters settings, closed-loop locking of the CAC is realized in orbit and an estimated short-term frequency stability close to 3.0 × 10−13τ−1/2 has been attained. The demonstration of the long-term operation of cold atom clock in orbit opens possibility on the applications of space-based cold atom sensors.

Solvent extraction is used widely for chemical separations and environmental remediation. Although the kinetics and efficiency of this process rely upon the formation of ion–extractant complexes, it has proven challenging to identify the location of ion–extractant complexation within the solution and its impact on the separation. Here, we use tensiometry and X-ray scattering to characterize the surface of aqueous solutions of lanthanide chlorides and the water-soluble extractant bis­(2-ethylhexyl) phosphoric acid (HDEHP), in the absence of a coexisting organic solvent. These studies restrict ion–extractant interactions to the aqueous phase and its liquid–vapor interface, allowing us to explore the consequences that one or the other is the location of ion–extractant complexation. Unexpectedly, we find that light lanthanides preferentially occupy the liquid–vapor interface. This contradicts our expectation that heavy lanthanides should have a higher interfacial density since they are preferentially extracted by HDEHP in solvent extraction processes. These results reveal the antagonistic role played by ion–extractant complexation within the aqueous phase and clarify the advantages of complexation at the interface. Extractants in common use are often soluble in water, in addition to their organic phase solubility, and similar effects to those described here are expected to be relevant to a variety of separations processes.

Articles you may be interested inNote: High-efficiency energy harvester using double-clamped piezoelectric beams Rev. Sci. Instrum. 85, 026101 (2014); 10.1063/1.4862820Frequency up-converted wide bandwidth piezoelectric energy harvester using mechanical impact Bi-stable piezoelectric energy harvester has been found as a promising structure for vibration energy harvesting. This paper presents a high performance and simple structure bi-stable piezoelectric energy harvester based on simply supported piezoelectric buckled beam. The potential energy function is established theoretically, and electrical properties of the device under different axial compressive displacements, excitation frequencies, and accelerations are investigated systematically. Experimental results demonstrate that the output properties and bandwidth of the bi-stable nonlinear energy harvester under harmonic mechanical excitation are improved dramatically compared with the traditional linear energy harvester. The device demonstrates the potential in energy harvesting application to low-power portable electronics and wireless sensor nodes. V C 2013 AIP Publishing LLC. [http://dx.

Osteoporosis and related fragility fractures represent a serious and global public health problem.To evaluate whether the modified eighth section of Eight-section Brocade (MESE) exercise could improve the symptom and indexes associated with osteoporosis in postmenopausal women.Guangzhou and Liuzhou hospital of traditional Chinese medicine in China.Women (n = 198) aged 50 to 75 years were randomized into Control, Ca, MESE, and MESE + Ca.Subjects in Ca and MESE groups were separately asked to consume thrice daily Calcium Carbonate Chewable D3 tablet and to perform thrice daily MESE exercise by 7 repetitions per time for 12 months. Subjects in MESE + Ca group performed such the combined treatment project for 12 months. Body height and Hospital for Special Surgery (HSS) scores of both knees, chronic back pain visual analogue scale scores (VAS), bone mineral density (BMD) at L2 to L4 and the left femoral neck, 3-feet Up and Go Test (3′) and one-leg Stance (OLS).In our study, the improvement in chronic back pain of the patients in Ca, MESE, and MESE + Ca group was better than that in control group. There was 1.9% and 1.7%, 2.3%, and 2.1% net profit in left femoral neck and lumbar BMD after the treatment for 12 months in MESE and MESE + Ca groups. For the balance capacity, the subjects in MESE and MESE + Ca groups secured much better performance than those in Ca and control group after the treatment for 12 months (P < 0.001, P < 0.001).The treatment of MESE exercise is the most effective for the improvement of the symptom and indexes in postmenopausal women. Importantly, the low attrition and the high exercise compliance indicate that MESE exercise is safe, feasible, and well tolerated by postmenopausal women.

Structural evolution of Li(3−3x)M4xNb(1−x)O4 (M=Mg,Zn; 0≤x≤0.9) and microwave dielectric properties of Li(3−3x)Mg4xNb(1−x)O4 have been studied by X‐ray diffraction, scanning electron microscopy, Raman spectra, infrared reflectivity (IR) fitting, and microwave resonant measurement in this work. The crystal symmetry changed from the ordered cubic Li3NbO4 (I‐43m, x=0) into disordered cubic phase (Fm3m) when 0.01≤x<1/3 for the Mg‐doped samples. An intermediate compound of Li3Mg2NbO6 (SG:Fddd) with orthorhombic structure formed at x=1/3 composition. MgO secondary phase appeared in addition to Li3Mg2NbO6 phase in the x>1/3 compositions, and its content increased with the further increase of x. Short‐range cation ordering was confirmed to be present in the cubic phase by Raman analysis. Mixture of Li3NbO4 and ZnO phases was observed in the whole composition range for the ZnO‐added samples. For the Mg‐doped samples, the dielectric constant increased slightly with x increasing up to x=1/3 and decreased with the further increase of x. The Q×f value increased greatly with the increasing x and saturated within the composition range of 0.1≤x<1/3. Further increasing x resulted in a decrease in Q×f value. All samples exhibited negative τf value. Minimum τf value of −22 ppm/°C was obtained at x=1/3. The IR reflection spectra of the x=0, 0.2, and 1/3 samples were analyzed by Kramers–Kroning analysis and classical oscillator model simulation. The dielectric properties were extrapolated down to the microwave range using the classical oscillator model for fitting the dielectric function. The calculated dielectric constants were in agreement with the experimental ones, whereas, the calculated Q×f values showed a reverse varying trend compared with the experimental data.

No abstract

During solvent extraction of rare earth ions, an aqueous electrolyte solution is placed in contact with an immiscible organic solution of extractants to enable extractant-facilitated transport of ions into the organic solvent. Although ex-perimental methodologies such as x-ray and neutron scattering have been applied to characterize ion-extractant complexes, identifying the site of ion-extractant complexation has proven challenging. Here, we use tensiometry and surface-sensitive x-ray scattering to study the surface of aqueous solutions of lanthanide chlorides and the water-soluble extractant bis(2-ethylhexyl) phosphate (HDEHP), in the absence of a coexisting organic solvent. These studies restrict interactions of HDEHP with trivalent lanthanide ions to the aqueous phase and the liquid-vapor interface, allowing us to explore the consequences that one or the other is the site of ion-extractant complexation. Unexpectedly, we find that light lanthanides preferentially occupy the liquid-vapor interface, with an overwhelming preference for a light lanthanide, Nd, when present in a mixture with a heavy lanthanide, Er. This contradicts our expectation that heavy lanthanides should have a higher interfacial density since they are preferentially extracted by HDEHP in the presence of an organic phase. These results reveal the antagonistic role played by ion-extractant complexation within the aqueous phase and clarify the potential advantages of water-insoluble extractants that interact with ions primarily at the interface during the process of solvent extraction.