VULNERABILITY OF LOW-ARSENIC AQUIFERS TO MUNICIPAL PUMPING IN BANGLADESH

Sandy aquifers deposited >12,000 years ago, some as shallow as 30 m, have provided a reliable supply of low-arsenic (As) drinking water in rural Bangladesh. This study concerns the potential risk of contaminating these aquifers in areas surrounding the city of Dhaka where hydraulic heads in aquifers >150 m deep have dropped by 70 m in a few decades due to municipal pumping. Water levels measured continuously from 2012 to 2014 in 12 deep (>150m), 3 intermediate (90-150 m) and 6 shallow (<90 m) community wells, 1 shallow private well, and 1 river piezometer show that the resulting drawdown cone extends 15-35 km east of Dhaka. Water levels in 4 low-As community wells within the 62-147 m depth range closest to Dhaka were inaccessible by suction for up to a third of the year. Lateral hydraulic gradients in the deep aquifer system ranged from 1.7×10^-4 to 3.7×10^-4 indicating flow towards Dhaka throughout 2012-2014. Vertical recharge on the edge of the drawdown cone was estimated at 0.21±0.06 m/yr. The data suggest that continued municipal pumping in Dhaka could eventually contaminate some relatively shallow community wells.

Direct mass measurements of short-lived A=2Z-1 nuclides (63)Ge, (65)As, (67)Se, and (71)Kr and their impact on nucleosynthesis in the rp process

Mass excesses of short-lived A=2Z-1 nuclei (63)Ge, (65)As, (67)Se, and (71)Kr have been directly measured to be -46,921(37), -46,937(85), -46,580(67), and -46,320(141)  keV, respectively. The deduced proton separation energy of -90(85)  keV for (65)As shows that this nucleus is only slightly proton unbound. X-ray burst model calculations with the new mass excess of (65)As suggest that the majority of the reaction flow passes through (64)Ge via proton capture, indicating that (64)Ge is not a significant rp-process waiting point.

Preparation, structure and up-conversion luminescence properties of novel cryolite K3YF6:Er3+, Yb3

Cryolite is a suitable host for up-conversion luminescent materials due to its low phonon energy and good optical transparency. In this work, a novel up-conversion material K3YF6:Yb3+, Er3+ with a cryolite structure was prepared successfully by a solid state method. The crystal structure, morphology, composition and up-conversion luminescence properties of the as-prepared sample were characterized by X-ray diffractometry (XRD), field emission scanning electron microscopy (SEM) and fluorescence spectrometer in detail. K3YF6:Er3+, Yb3+ has a cryolite structure. Under 980 nm excitation, the as-prepared sample can generate slight green emission at 524 and 546 nm (attributed to 2H11/2 → 4I15/2 transition, 4S3/2→4I15/2 transition of Er3+) and strong red emission at 661 and 672 nm (corresponding to 4F9/2 → 4I15/2 transition, 4I9/2 → 4I15/2 transition of Er3+). All the green and red up-conversion emission of K3YF6:Er3+, Yb3+ transfer and electronic transition process of the red and green light the sample emitted, the possible luminescence mechanism is discussed in this paper.

Mass measurements of the neutron-deficient 41Ti, 45Cr, 49Fe, and 53Ni nuclides: first test of the isobaric multiplet mass equation in f p-shell nuclei

Isochronous mass spectrometry has been applied to neutron-deficient 58Ni projectile fragments at the HIRFL-CSR facility in Lanzhou, China. Masses of a series of short-lived T(z)=-3/2 nuclides including 41Ti, 45Cr, 49Fe, and 53Ni have been measured with a precision of 20-40 keV. The new data enable us to test for the first time the isobaric multiplet mass equation (IMME) in fp-shell nuclei. We observe that the IMME is inconsistent with the generally accepted quadratic form for the A=53, T=3/2 quartet. We perform full space shell model calculations and compare them with the new experimental results.

Effects of fish oil-derived fatty acids on suboptimal cardiovascular health: A multicenter, randomized, double-blind, placebo-controlled trial

BACKGROUND AND AIMS

Suboptimal health and metabolic disorders are common in the general population. Both are related to cardiovascular disease. Suboptimal cardiovascular health is defined by the presence of both suboptimal health and metabolic disorders. The aim of the study was to investigate the potential benefit of n-3 long-chain polyunsaturated fatty acids (LCPUFA) in participants with suboptimal cardiovascular health.

METHODS AND RESULTS

A total of 422 participants with suboptimal cardiovascular health, from two clinics in China, were enrolled from September 2014 to April 2015. All the enrolled participants were randomly assigned to receive 4 g/d of fish oil or placebo for three months. Suboptimal health was defined using an accepted questionnaire. Metabolic disorders were defined as one or more abnormalities in blood pressure, fasting plasma glucose, blood lipids, and body mass index (BMI). After treatment, the mean BMI fell significantly more in the n-3 LCPUFA group than in the placebo group (-0.29 ± 0.06 kg/m² vs. -0.02 ± 0.06 kg/m², P = 0.003). Similar results were found in the changes of suboptimal health status and suboptimal cardiovascular health status (P < 0.05 for all). In a multivariate analysis, the n-3 LCPUFA group was 5.44 (1.15, 25.67) times more likely to have optimal cardiovascular health status after treatment.

CONCLUSIONS

n-3 LCPUFA intake improved suboptimal cardiovascular health in this placebo-controlled, randomized, double-blind trial.

TRIAL REGISTRATION

This study is registered at www.clinicaltrials.govNCT02103517.

Identification of the Lowest T=2, J^{π}=0^{+} Isobaric Analog State in ^{52}Co and Its Impact on the Understanding of β-Decay Properties of ^{52}Ni

Masses of ^{52g,52m}Co were measured for the first time with an accuracy of ∼10  keV, an unprecedented precision reached for short-lived nuclei in the isochronous mass spectrometry. Combining our results with the previous β-γ measurements of ^{52}Ni, the T=2, J^{π}=0^{+} isobaric analog state (IAS) in ^{52}Co was newly assigned, questioning the conventional identification of IASs from the β-delayed proton emissions. Using our energy of the IAS in ^{52}Co, the masses of the T=2 multiplet fit well into the isobaric multiplet mass equation. We find that the IAS in ^{52}Co decays predominantly via γ transitions while the proton emission is negligibly small. According to our large-scale shell model calculations, this phenomenon has been interpreted to be due to very low isospin mixing in the IAS.

Controllable crystal form transformation and luminescence properties of up-conversion luminescent material K3Sc0.5Lu0.5F6: Er3+, Yb3+ with cryolite structure

In this paper, a novel cryolite-type up-conversion luminescent material K3Sc0.5Lu0.5F6: Er3+, Yb3+ with controllable crystal form was synthesized by a high temperature solid state method. K3Sc0.5Lu0.5F6: Er3+, Yb3+ can crystallize in monoclinic or cubic form at different temperatures. The composition, structure and up-conversion luminescence (UCL) properties of K3Sc0.5Lu0.5F6: Er3+, Yb3+ samples with different crystal form were investigated in detail. It is impressive that both monoclinic and cubic forms of K3Sc0.5Lu0.5F6: Er3+, Yb3+ show green emission (2H11/2/4S3/2→4I15/2). The luminescence intensity of cubic K3Sc0.5Lu0.5F6 is much higher than that of the monoclinic form, and the reasons are also discussed in detail. The results show that the luminescence intensity of up-conversion materials can be effectively tuned by controlling the crystal form. According to the power dependent UCL intensity, the UCL mechanism and electronic transition process were discussed. In addition, the fluorescence decay curves were characterized and the thermal coupling levels (TCLs) of Er3+ (2H11/2/4S3/2 → 4I15/2) in the range of 304-574 k were used to study the optical temperature sensing characteristics. All the results show that K3Sc0.5Lu0.5F6: Er3+, Yb3+ can be used in electronic components and have potential application value in temperature sensing fields.

Mass Measurement of Upper fp-Shell N=Z-2 and N=Z-1 Nuclei and the Importance of Three-Nucleon Force along the N=Z Line

Using a novel method of isochronous mass spectrometry, the masses of ^{62}Ge, ^{64}As, ^{66}Se, and ^{70}Kr are measured for the first time, and the masses of ^{58}Zn, ^{61}Ga, ^{63}Ge, ^{65}As, ^{67}Se, ^{71}Kr, and ^{75}Sr are redetermined with improved accuracy. The new masses allow us to derive residual proton-neutron interactions (δV_{pn}) in the N=Z nuclei, which are found to decrease (increase) with increasing mass A for even-even (odd-odd) nuclei beyond Z=28. This bifurcation of δV_{pn} cannot be reproduced by the available mass models, nor is it consistent with expectations of a pseudo-SU(4) symmetry restoration in the fp shell. We performed ab initio calculations with a chiral three-nucleon force (3NF) included, which indicate the enhancement of the T=1 pn pairing over the T=0 pn pairing in this mass region, leading to the opposite evolving trends of δV_{pn} in even-even and odd-odd nuclei.

Controlling the Fluorescence Behavior of Hydrophobic Pigments by Supramolecular Self-Assembling on Organic Layered Silicate Minerals

This research focused on the supramolecular self-assembly of organic fluorescent molecules on organically modified layered silicate minerals to design and prepare layered nanocomposites with excellent fluorescence properties. Aromatic hydrocarbons are hydrophobic and poorly loaded on the hydrophilic surface of layered silicate minerals, but they are easily captured by an organically modified mineral surface. Montmorillonite (MMT) and saponite (SAP), typical 2:1 type layered silicate minerals with different octahedral cations, were modified with the cationic surfactant octadecyl trimethylammonium chloride (OTAC) and loaded with pyrene (an aromatic hydrocarbon dye) with different molar ratios to the cationic surfactant by supramolecular self-assembling to construct fluorescent nanocomposites. The effect of pyrene concentration and the octahedral cation of the 2:1 type layered silicate minerals on photoluminescence properties was investigated. The fluorescence spectra of the nanocomposites prepared under low pyrene concentrations showed two bands at around 400 and 470 nm, corresponding to the monomer and excimer emissions; the band intensity of the excimer shoots up with the increase of pyrene concentration, reflecting different contributions from monomer and dimer species and the formation of radical aggregates. The excellent heat resistance of the layered silicate structure can effectively protect pyrene molecules from external environmental influences.

Nuclear Structure of Dripline Nuclei Elucidated through Precision Mass Measurements of ^{23}Si, ^{26}P, ^{27,28}S, and ^{31}Ar

Using the Bρ-defined isochronous mass spectrometry technique, we report the first determination of the ^{23}Si, ^{26}P, ^{27}S, and ^{31}Ar masses and improve the precision of the ^{28}S mass by a factor of 11. Our measurements confirm that these isotopes are bound and fix the location of the proton dripline in P, S, and Ar. We find that the mirror energy differences of the mirror-nuclei pairs ^{26}P-^{26}Na, ^{27}P-^{27}Mg, ^{27}S-^{27}Na, ^{28}S-^{28}Mg, and ^{31}Ar-^{31}Al deviate significantly from the values predicted assuming mirror symmetry. In addition, we observe similar anomalies in the excited states, but not in the ground states, of the mirror-nuclei pairs ^{22}Al-^{22}F and ^{23}Al-^{23}Ne. Using ab initio VS-IMSRG and mean field calculations, we show that such a mirror-symmetry breaking phenomenon can be explained by the extended charge distributions of weakly bound, proton-rich nuclei. When observed, this phenomenon serves as a unique signature that can be valuable for identifying proton-halo candidates.