ALBERT

Description: Author(s): C. Stock, S. R. Dunsiger, R. A. Mole, X. Li, and H. Luo A neutron scattering investigation of the magnetoelectric coupling in PbFe 1/2 Nb 1/2 O 3 has been undertaken. Ferroelectric order occurs below 400 K, as evidenced by the softening with temperature and subsequent recovery of the zone center transverse optic phonon mode energy ( ℏ Ω 0 ). Over the same tempera... [Phys. Rev. B 88, 094105] Published Fri Sep 13, 2013

Description: ABSTRACT A series of radiocarbon dates from two Epipalaeolithic sites – Kharaneh IV and Ayn Qasiyya – in the Azraq Basin of eastern Jordan provide a new perspective on the chronology and settlement patterns of this part of southwest Asia during the Late Pleistocene. We discuss the implications to our understanding of the chronology of Late Pleistocene lithic industries, particularly in regard to current hypotheses for the abandonment of eastern Jordan's ‘mega-sites’, Kharaneh IV and Jilat 6. Modelling a series of accelerator mass spectrometry dates from Kharaneh IV indicates a much shorter span of occupation for the site than previously assumed by the size and density of its deposits. Given the high density of material accumulated over a relatively short time span, we show that Kharaneh IV was an aggregation site occupied intensively by a significant number of people, providing new perspectives on the east Jordanian phenomenon of Epipalaeolithic ‘mega-sites’.

Description: Apatite incorporates variable and significant amounts of halogens (mainly F and Cl) in its crystal structure which can be used to determine the initial F and Cl concentrations of magmas. The amount of chlorine in the apatite lattice also exerts an important compositional control on the degree of fission track annealing. Chlorine measurements in apatite have conventionally required electron probe microanalysis (EPMA). Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) is increasingly used in apatite fission-track dating to determine U concentrations and also in simultaneous U-Pb dating and trace element measurements of apatite. Apatite Cl measurements by ICP-MS would remove the need for EPMA but the high (12.97 eV) first ionisation potential makes analysis challenging. Apatite Cl data were acquired using two analytical set-ups: a Resonetics M-50 193 nm ArF Excimer laser coupled to an Agilent 7700x quadrupole ICP-MS (using a 26 μm spot with an 8 Hz repetition rate) and a Photon Machines Analyte Excite 193 nm ArF Excimer laser coupled to a Thermo Scientific iCAP Qc (using a 30 μm spot with a 4 Hz repetition rate). Chlorine concentrations were determined by LA-ICP-MS (1140 analyses in total) for nineteen apatite occurrences, and there is a comprehensive EPMA Cl and F dataset for thirteen of the apatite samples. The apatite sample suite includes different compositions representative of the range likely to be encountered in natural apatites, along with extreme variants including two end-member chlorapatites. Between twenty-six and thirty-nine isotopes were determined in each apatite sample corresponding to a typical analytical protocol for integrated apatite fission track (U and Cl contents) and U-Pb dating, along with REE and trace element measurements. 35 Cl backgrounds (present mainly in the argon gas) were ~ 45–65 kcps in the first set-up and ~ 4 kcps in the second set-up. 35 Cl background-corrected signals ranged from ~ 0 cps in end-member fluorapatite to up to ~ 90 kcps in end-member chlorapatite. Use of a collision cell in both analytical set-ups decreased the low mass sensitivity by approximately an order of magnitude without improving the 35 Cl signal to background ratio. A minor Ca isotope was used as the internal standard to correct for drift in instrument sensitivity and variations in ablation volume during sessions. The 35 Cl/ 43 Ca values for each apatite (10–20 analyses each) when plotted against the EPMA Cl concentrations yield excellently constrained calibration relationships, demonstrating the suitability of the analytical protocol and that routine apatite Cl measurements by ICP-MS are achievable. This article is protected by copyright. All rights reserved.

Description: A new copper(II) phosphonatobenzenesulfonate incorporating 4,4′-bipyridine (4,4′- bipy ) as auxiliary ligand has been discovered through systematic high-throughput (HT) screening of the system Cu(NO 3 ) 2 ·3H 2 O/H 2 O 3 PC 6 H 4 SO 3 H/4,4′- bipy using different solvents. The hydrothermal synthesis of [Cu(HO 3 PC 6 H 4 SO 3 )(C 10 H 8 N 2 )]·H 2 O ( 1 ) was further optimized by screening various copper(II) salts. The crystal structure of 1 was determined by single-crystal X-ray diffraction and unveiled the presence of isolated sixfold coordinated Jahn–Teller-distorted Cu 2+ ions. The isolated CuN 2 O 4 octahedra are interconnected by phosphonate and sulfonate groups to form chains along the c- axis. The organic groups, namely phenyl rings and 4,4′- bipy molecules cross-link the chains into a three-dimensional framework. Water molecules are found in the narrow voids in the structure which are held by weak hydrogen bonds. Upon dehydration, the structure of 1 undergoes a phase transition, which was confirmed by TG measurements and temperature dependent X-ray powder diffraction. The new structure of 1-h was refined with Rietveld methods. Detailed inspection of the structure revealed the directional switching of the Jahn–Teller distortion upon de/rehydration. Weak ferro-/ferrimagnetic interactions were observed by magnetic investigations of 1 , which switch to antiferromagnetic below 3.5 K. Compounds 1 and 1-h are further characterized by thermogravimetric and elemental analysis as well as IR spectroscopy.

Description: Author(s): Gesine A. Steudle, Sebastian Knauer, Ulrike Herzog, Erik Stock, Vladimir A. Haisler, Dieter Bimberg, and Oliver Benson We present an experimental implementation of optimum measurements for quantum state discrimination. Optimum maximum-confidence discrimination and optimum unambiguous discrimination of two mixed single-photon polarization states were performed. For the latter the states of rank 2 in a four-dimensiona... [Phys. Rev. A 83, 050304] Published Fri May 20, 2011

Description: The bifunctional metalloligand bis(carboxyethylgermanium)sesquioxide, (HOOCCH 2 CH 2 Ge) 2 O 3 , was employed in the systematic high-throughput (HT) investigation of the system Zn 2+ /(HOOCCH 2 CH 2 Ge) 2 O 3 /H 2 O/C 4 H 9 OH. Two new metal-organogermanates Zn[(OOCCH 2 CH 2 Ge) 2 O 3 ] ( 1 ) and Zn 2 (O 3 GeCH 2 CH 2 COO) ( 2 ) were discovered that show two new structural motifs for this class of compounds. Whereas in compound 1 a formal intercalation in the structure of (HOOCCH 2 CH 2 Ge) 2 O 3 is observed, 2 exhibits a new layered structure composed of CGeO 3 and ZnO 4 unit linked by μ 3 -oxygen atoms. Both connectivity modes lead to dense three-dimensional framework structures.

Description: Author(s): C. Stock, L. C. Chapon, A. Schneidewind, Y. Su, P. G. Radaelli, D. F. McMorrow, A. Bombardi, N. Lee, and S.-W. Cheong We have investigated spin fluctuations in the langasite compound Ba_{3} NbFe_{3} Si_{2} O_{14} both in the ordered state and as a function of temperature. The low-temperature magnetic structure is defined by a spiral phase characterized by magnetic Bragg peaks at q⃗=(0,0,τ~1/7) onset at T_{N} =27... [Phys. Rev. B 83, 104426] Published Wed Mar 30, 2011

Description: Crystal Growth & Design DOI: 10.1021/cg2012205

Description: [1]  Diel vertical migration (DVM) of zooplankton and micronekton is widespread in the ocean and forms a fundamental component of the biological pump, but is generally overlooked in global models of the Earth System. We develop a parameterization of DVM in the ocean and integrate it with a size-structured NPZD model. We assess the model's ability to recreate ecosystem and DVM patterns at three well observed Pacific sites, ALOHA, K2 and EQPAC, and use it to estimate the impact of DVM on marine ecosystems and biogeochemical dynamics. Our model includes: (1) a representation of migration dynamics in response to food availability and light intensity, (2) a representation of the digestive and metabolic processes that decouple zooplankton feeding from excretion, egestion and respiration, and (3) a light-dependent parameterization of visual predation on zooplankton. The model captures the first order patterns in plankton biomass and productivity across the biomes, including the biomass of migrating organisms. We estimate that realistic migratory populations sustain active fluxes to the mesopelagic zone equivalent to between 15 and 40 % the particle export, and contribute up to half of the total respiration within the layers affected by migration. The localized active transport has important consequences for the cycling of oxygen, nutrients and carbon. We highlight the importance of decoupling zooplankton feeding and respiration and excretion with depth for capturing the impact of migration on the redistribution of carbon and nutrients in the upper ocean.

Description: Author(s): Zhijun Xu, Jinsheng Wen, E. Mamontov, C. Stock, P. M. Gehring, and Guangyong Xu We report measurements of the neutron diffuse scattering in a single crystal of the relaxor ferroelectric material 95.5%Pb(Zn 1/3 Nb 2/3 )O 3 -4.5%PbTiO 3 (PZN-4.5%PT). We show that the diffuse scattering at high temperatures has a quasielastic component with energy width ≳0.1 meV. On cooling the total dif... [Phys. Rev. B 86, 144106] Published Fri Oct 05, 2012