Spectroscopic factor and proton formation probability for the d3/2 proton emitter 151mLu

The quenching of the experimental spectroscopic factor for proton emission from the short-lived d3/2 isomeric state in 151mLu was a long-standing problem. In the present work, proton emission from this isomer has been reinvestigated in an experiment at the Accelerator Laboratory of the University of Jyväskylä. The proton-decay energy and half-life of this isomer were measured to be 1295(5) keV and 15.4(8) μs, respectively, in agreement with another recent study. These new experimental data can resolve the discrepancy in the spectroscopic factor calculated using the spherical WKB approximation. Using the R-matrix approach it is found that the proton formation probability indicates no significant hindrance for the proton decay of 151mLu

Evidence for octupole collectivity in Pt-172

Excited states in the extremely neutron-deficient nucleus Pt-172 were populated via Ru-96(Kr-78, 2p) and Mo-92(Kr-83, 3n) reactions. The level scheme has been extended up to an excitation energy of approximate to 5MeV and tentative spin-parity assignments up to I-pi = 18(+). Linear polarization and angular distribution measurements were used to determine the electromagnetic E1 character of the dipole transitions connecting the positive-parity ground-state band with an excited side-band, firmly establishing it as a negativeparity band. The lowestmember of this negative-parity structure was firmly assigned spin-parity 3(-). In addition, we observed an E3 transition from this 3(-) state to the ground state, providing direct evidence for octupole collectivity in Pt-172. Large-scale shell model (LSSM) and total Routhian surface (TRS) calculations have been performed, supporting the interpretation of the 3(-) state as a collective octupole-vibrational state.Peer reviewe

Identification of excited states in 107Te

Excited states in the extremely neutron-deficient nucleus 107Te have been identified from two separate experiments using the recoil-decay tagging technique. Two connected structures were observed on the basis of γγ-coincidence relations and tentatively assigned as built on the mixed-parentage νg7/2d5/2 and νh11/2 intruder configurations. The observed structures were compared with large-scale shell-model calculations and total Routhian surface calculations. Collective behavior was discovered to persist in the νh11/2 band of 107Te which highlights the shape-polarizing effect of a single valence neutron occupying the h11/2 intruder orbit as the N=50 shell closure is approached.peerReviewe

Fabrication and characterization of novel forward osmosis membranes based on layer-by-layer assembly

In the study of synthesizing LbL FO membranes, the membrane substrate was firstly tailored (high porosity, finger-like pores, thin thickness, and high hydrophilicity) to achieve a small structural parameter of 0.5 mm. Secondly, the polyelectrolyte layers were deposited on the support membrane top surface for a number of times by soaking repeatedly in poly(allylamine hydrochloride) (PAH) and poly(sodium 4-styrene-sulfonate) (PSS) in an alternative sequence. Increasing the number of polyelectrolyte layers improved the selectivity of the LbL membranes while reducing their water permeability. The more selective membrane 6#LbL (with 6 polyelectrolyte layers) had much lower reverse solute transport compared to 3#LbL and 1#LbL. The FO water flux was found to be strongly affected by both membrane water permeability and reverse solute transportation. Severe solute reverse transport was observed for the active-layer-facing-draw-solution (AL-DS) membrane orientation, which is likely due to the suppression of Donnan exclusion by the high ionic strength of the draw solution. In contrast, the active-layer-facing-feed-solution (AL-FS) orientation showed remarkable FO performance (15, 20, and 28 L/m2.h at 0.1, 0.5, and 1.0 M MgCl2, respectively, for membrane 3#LbL using distilled water as feed solution).Doctor of Philosoph

Fabrication of aquaporin-based biomimetic membrane for seawater desalination

This study focuses on enhancing the mechanical strength of aquaporin (AQP)-based biomimetic membranes for seawater desalination. AQP incorporated vesicles were embedded into the selective layer of an optimized thin film composite (TFC) membrane. The resultant membrane, denoted as ASW, exhibited a stable water flux around 20 L·m−2·h−1 and 99% NaCl rejection at a constant pressure of 55 bar using 32,000 mg·L−1 NaCl solution as feed in reverse osmosis (RO) measurement. The robustness of the ASW membranes were evaluated. The water flux of ASW membrane was almost 100% enhanced compared with that of AQP-free control TFC membranes. The filtration performance of the ASW membrane was further evaluated by a seven-day desalination test using a real seawater secondary effluent collected from a desalination plant in Singapore as feed. To our best knowledge, our study is the first report on the AQP-incorporated RO membrane applied for seawater desalination. A commercial SW30HR membrane was tested in parallel for comparison. The robust ASW membrane exhibited a nearly 80% higher water flux in comparison to the SW30HR membrane with a comparable overall solute rejection, suggesting the advantage and feasibility of Aquaporin based biomimetic membranes for seawater desalination.Economic Development Board (EDB)National Research Foundation (NRF)Public Utilities Board (PUB)Accepted versionThe research is conducted under the IAF-PP project supported by the Singapore National Research Foundation and PUB, Singapore's National Water Agency. Funding support from the Singapore Economic Development Board to the Singapore Membrane Technology Centre is also gratefully acknowledged

Highly efficient forward osmosis based on porous membranes : applications and implications

For the first time, forward osmosis (FO) was performed using a porous membrane with an ultrafiltration (UF)-like rejection layer and its feasibility for high performance FO filtration was demonstrated. Compared to traditional FO membranes with dense rejection layers, the UF-like FO membrane was 2 orders of magnitude more permeable. This gave rise to respectable FO water flux even at ultralow osmotic driving force, for example, 7.6 L/m2.h at an osmotic pressure of merely 0.11 bar (achieved by using a 0.1% poly(sodium 4-styrene-sulfonate) draw solution). The membrane was applied to oil/water separation, and a highly stable FO water flux was achieved. The adoption of porous FO membranes opens a door to many new opportunities, with potential applications ranging from wastewater treatment, valuable product recovery, and biomedical applications. The potential applications and implications of porous FO membranes are addressed in this paper.MOE (Min. of Education, S’pore)Accepted versio

Polymersomes-based high-performance reverse osmosis membrane for desalination

Polymersomes-based reverse osmosis (RO) membrane (PBM) for desalination was reported for the first time. An amphiphilic tri-block copolymer, PMOXA6-PDMS35-PMOXA6 (ABA), was self-assembled to form polymersomes with spherical nanostructure. The polymersomes were then immobilized into a polyamide network via an interfacial polymerization reaction on top of polysulfone membrane substrate. Under a moderate salinity condition, the PBM presented almost doubled water permeability and higher salt rejection than the control membrane without polymersomes in the polyamide network. Based on the results of a series of characterization the better water permeation of the PBM is believed to result from larger globular features containing highly water permeable polymersomes, which created a higher void fraction in the selective layer, whereas the highly cross-linked polyamide selective layer as well as the polymersome bilayer’s impermeability to NaCl may led to the enhanced salt rejection. Surprisingly, at an elevated NaCl concentration up to 32,000 ppm, the PBM exhibited ~ 60% water flux enhancement and even better NaCl rejection as compared with commercial seawater RO membranes. In general, the PBM presented a water flux similar to the RO membranes with loose polyamide matrix (BW30), but a rejection behavior close to the dense RO membranes (SW30). This study provides a paradigm shift in developing new-generation RO membranes for energy and cost-effective desalination process.NRF (Natl Research Foundation, S’pore)EDB (Economic Devt. Board, S’pore)Accepted versio

'Are there good and bad divorces?' The impact of the divorce process on the well-being of ex-partners after separation

Silica gel (SG)–polyacrylonitrile (PAN) composite forward osmosis (FO) membranes have been synthesized and characterized in the present work. The incorporation of SG particles into the PAN support layer significantly changed its water permeability and salt rejection rate. In the range of 0.25–1.0 wt.% SG loading, water permeability of membranes were enhanced after the embedment of SG, most likely due to the both porous nature of SG and the enhanced substrate porosity. However, a reduction in both water permeability and salt rejection was observed if further increase in SG loading (2.0 wt.%), possibly as a result of the agglomeration of SG. The most permeable SG–PAN FO membrane (M1.00, with 1.0 wt.% SG loading) had a significantly higher water permeability compared to the control pure PAN FO membrane (M0.00). This membrane achieved high FO water fluxes of >100 L/m2 h was achieved by using the 1 M MgCl2 as the draw solution (DS) and 0–10 mM NaCl as the feed solution (FS). To the best knowledge of the authors, this is the first study reporting the development and application of SG–PAN mixed matrix FO membranes (MMMs) based on layer-by-layer assembly