New Age and Geochemical Data from the Southern Colville and Kermadec Ridges, SW Pacific: Insights into the recent geological history and petrogenesis of the Proto-Kermadec (Vitiaz) Arc

Highlights • Age and petrogenesis of the Miocene-Pleistocene proto Kermadec arc: the Kermadec and Colville Ridge • Complex interplay between element flux from the subducting Pacific Plate and heterogenous mantle wedge • New insights into the recent tectonic history of the Kermadec arc system Abstract The intra-oceanic Kermadec arc system extends ~1300 km between New Zealand and Fiji and comprises at least 30 arc front volcanoes, the Havre Trough back-arc and the remnant Colville and Kermadec Ridges. To date, most research has focussed on the Kermadec arc front volcanoes leaving the Colville and Kermadec Ridges virtually unexplored. Here, we present seven 40Ar/39Ar ages together with a comprehensive major and trace element and Sr-, Nd-, and Pb-isotope dataset from the Colville and Kermadec Ridges to better understand the evolution, petrogenesis and splitting of the former proto-Kermadec (Vitiaz) Arc to form these two remnant arc ridges. Our 40Ar/39Ar ages range from ~7.5–2.6 Ma, which suggests that arc volcanism at the Colville Ridge occurred continuously and longer than previously thought. Recovered Colville and Kermadec Ridge lavas range from mafic picro-basalts (MgO = ~8 wt%) to dacites. The lavas have arc-type normalised incompatible element patterns and Sr and Pb isotopic compositions intermediate between Pacific MORB and subducted lithosphere (including sediments, altered oceanic crust and serpentinised uppermost mantle). Geochemically diverse lavas, including ocean island basalt-like and potassic lavas with high Ce/Yb, Th/Zr, intermediate 206Pb/204Pb and low 143Nd/144Nd ratios were recovered from the Oligocene South Fiji Basin (and Eocene Three Kings Ridge) located west of the Colville Ridge. If largely trench-perpendicular mantle flow was operating during the Miocene, this geochemical heterogeneity was likely preserved in the Colville and Kermadec sub arc mantle. The Colville and Kermadec Ridge data therefore highlight the complex interplay between pre-existing mantle heterogeneities and material fluxes from the subducting Pacific Plate. The new data allow us to present a holistic (yet simplified) picture of the tectonic evolution of the late Vitiaz Arc and northern Zealandia since the Miocene and how this tectonism influences volcanic activity along the Kermadec arc at the present

Measurement of mechanical vibrations excited in aluminium resonators by 0.6 GeV electrons

We present measurements of mechanical vibrations induced by 0.6 GeV electrons impinging on cylindrical and spherical aluminium resonators. To monitor the amplitude of the resonator's vibrational modes we used piezoelectric ceramic sensors, calibrated by standard accelerometers. Calculations using the thermo-acoustic conversion model, agree well with the experimental data, as demonstrated by the specific variation of the excitation strengths with the absorbed energy, and with the traversing particles' track positions. For the first longitudinal mode of the cylindrical resonator we measured a conversion factor of 7.4 +- 1.4 nm/J, confirming the model value of 10 nm/J. Also, for the spherical resonator, we found the model values for the L=2 and L=1 mode amplitudes to be consistent with our measurement. We thus have confirmed the applicability of the model, and we note that calculations based on the model have shown that next generation resonant mass gravitational wave detectors can only be expected to reach their intended ultra high sensitivity if they will be shielded by an appreciable amount of rock, where a veto detector can reduce the background of remaining impinging cosmic rays effectively.Comment: Tex-Article with epsfile, 34 pages including 13 figures and 5 tables. To be published in Rev. Scient. Instr., May 200

3-D focused inversion of near-seafloor magnetic data with application to the Brothers volcano hydrothermal system, Southern Pacific Ocean, New Zealand

Author Posting. © American Geophysical Union, 2012. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 117 (2012): B10102, doi:10.1029/2012JB009349.We describe and apply a new inversion method for 3-D modeling of magnetic anomalies designed for general application but which is particularly useful for the interpretation of near-seafloor magnetic anomalies. The crust subsurface is modeled by a set of prismatic cells, each with uniform magnetization, that together reproduce the observed magnetic field. This problem is linear with respect to the magnetization, and the number of cells is normally greater than the amount of available data. Thus, the solution is obtained by solving an under-determined linear problem. A focused solution, exhibiting sharp boundaries between different magnetization domains, is obtained by allowing the amplitudes of magnetization to vary between a pre-determined range and by minimizing the region of the 3-D space where the source shows large variations, i.e., large gradients. A regularization functional based on a depth-weighting function is also introduced in order to counter-act the natural decay of the magnetic field intensity with depth. The inversion method has been used to explore the characteristics of the submarine hydrothermal system of Brothers volcano in the Kermadec arc, by inverting near-bottom magnetic data acquired by Autonomous Underwater Vehicles (AUVs). Different surface expressions of the hydrothermal vent fields show specific vertical structures in their underlying demagnetization regions that we interpret to represent hydrothermal upflow zones. For example, at focused vent sites the demagnetized conduits are vertical, pipe-like structures extending to depths of ~1000 m below the seafloor, whereas at diffuse vent sites the demagnetization regions are characterized by thin and inclined conduits.This contribution was made possible through funding by the New Zealand Foundation for Research, Science and Technology (FRST contract C05X0406) and by the Royal Society of New Zealand by the Marsden Fund (grant GNS1003).2013-04-1

Detailed Morphology and Structure of an Active Submarine Arc Caldera: Brothers Volcano, Kermadec Arc

A survey of the Brothers caldera volcano (Kermadec arc) with the autonomous underwater vehicle ABE has revealed new details of the morphology and structure of this submarine frontal arc caldera and the geologic setting of its hydrothermal activity. Brothers volcano has formed between major SW-NE–trending faults within the extensional field of the Havre Trough. Brothers may be unique among known submarine calderas in that it has four active hydrothermal systems, two high-temperature sulfide-depositing sites associated with faulting on the northwestern and western walls (i.e., the NW caldera and W caldera hydrothermal sites, respectively), and gas-rich sites on the summits of the constructional cones that fill most of the southern part of the caldera (i.e., the Upper and Lower cone sites). The 3.0- × 3.4-km caldera is well defined by a topographic rim encompassing ∼320° of its circumference and which lies between the bounds of two outer half-graben–shaped faults in the northwest and southeast sectors. There is not a morphologically well defined continuous ring fault (at the map resolution), although near-vertical scarps are present discontinuously at the base of sections of the wall. The width of the wall varies from <200 m at its southwest portion to ∼750 m on its northern section. The widest part of the wall is its northwest sector, which also has the largest documented area of hydrothermal alteration and where sea-floor magnetization is lowest. In addition to primary northwest-southeast elongation and southwest-northeast structures caused by faulting within the regional back-arc strain field, there are also less well developed west-southwest–north-northeast regional structures intersecting the volcano that is apparent on the ABE bathymetry and at outcrop scale from submersible observations. Asymmetrical trap-door–style caldera collapse is considered a possible mechanism for the formation of the Brothers caldera

An addressable quantum dot qubit with fault-tolerant control fidelity

Exciting progress towards spin-based quantum computing has recently been made with qubits realized using nitrogen-vacancy (N-V) centers in diamond and phosphorus atoms in silicon, including the demonstration of long coherence times made possible by the presence of spin-free isotopes of carbon and silicon. However, despite promising single-atom nanotechnologies, there remain substantial challenges in coupling such qubits and addressing them individually. Conversely, lithographically defined quantum dots have an exchange coupling that can be precisely engineered, but strong coupling to noise has severely limited their dephasing times and control fidelities. Here we combine the best aspects of both spin qubit schemes and demonstrate a gate-addressable quantum dot qubit in isotopically engineered silicon with a control fidelity of 99.6%, obtained via Clifford based randomized benchmarking and consistent with that required for fault-tolerant quantum computing. This qubit has orders of magnitude improved coherence times compared with other quantum dot qubits, with T_2* = 120 mus and T_2 = 28 ms. By gate-voltage tuning of the electron g*-factor, we can Stark shift the electron spin resonance (ESR) frequency by more than 3000 times the 2.4 kHz ESR linewidth, providing a direct path to large-scale arrays of addressable high-fidelity qubits that are compatible with existing manufacturing technologies

The Results of CHD7 Analysis in Clinically Well-Characterized Patients with Kallmann Syndrome

Item does not contain fulltextCONTEXT: Kallmann syndrome (KS) and CHARGE syndrome are rare heritable disorders in which anosmia and hypogonadotropic hypogonadism co-occur. KS is genetically heterogeneous, and there are at least eight genes involved in its pathogenesis, whereas CHARGE syndrome is caused by autosomal dominant mutations in only one gene, the CHD7 gene. Two independent studies showed that CHD7 mutations can also be found in a minority of KS patients. OBJECTIVE: We aimed to investigate whether CHD7 mutations can give rise to isolated KS or whether additional features of CHARGE syndrome always occur. DESIGN: We performed CHD7 analysis in a cohort of 36 clinically well-characterized Dutch patients with KS but without mutations in KAL1 and with known status for the KS genes with incomplete penetrance, FGFR1, PROK2, PROKR2, and FGF8. RESULTS: We identified three heterozygous CHD7 mutations. The CHD7-positive patients were carefully reexamined and were all found to have additional features of CHARGE syndrome. CONCLUSION: The yield of CHD7 analysis in patients with isolated KS seems very low but increases when additional CHARGE features are present. Therefore, we recommend performing CHD7 analysis in KS patients who have at least two additional CHARGE features or semicircular canal anomalies. Identifying a CHD7 mutation has important clinical implications for the surveillance and genetic counseling of patients

Stochastic pump effect and geometric phases in dissipative and stochastic systems

The success of Berry phases in quantum mechanics stimulated the study of similar phenomena in other areas of physics, including the theory of living cell locomotion and motion of patterns in nonlinear media. More recently, geometric phases have been applied to systems operating in a strongly stochastic environment, such as molecular motors. We discuss such geometric effects in purely classical dissipative stochastic systems and their role in the theory of the stochastic pump effect (SPE).Comment: Review. 35 pages. J. Phys. A: Math, Theor. (in press

Platelets in Patients with Premature Coronary Artery Disease Exhibit Upregulation of miRNA340* and miRNA624*

Coronary artery disease (CAD) is the leading cause of human morbidity and mortality worldwide, underscoring the need to improve diagnostic strategies. Platelets play a major role, not only in the process of acute thrombosis during plaque rupture, but also in the formation of atherosclerosis itself. MicroRNAs are endogenous small non-coding RNAs that control gene expression and are expressed in a tissue and disease-specific manner. Therefore they have been proposed to be useful biomarkers. It remains unknown whether differences in miRNA expression levels in platelets can be found between patients with premature CAD and healthy controls. In this case-control study we measured relative expression levels of platelet miRNAs using microarrays from 12 patients with premature CAD and 12 age- and sex-matched healthy controls. Six platelet microRNAs were significantly upregulated (miR340*, miR451, miR454*, miR545:9.1. miR615-5p and miR624*) and one miRNA (miR1280) was significantly downregulated in patients with CAD as compared to healthy controls. To validate these results, we measured the expression levels of these candidate miRNAs by qRT-PCR in platelets of individuals from two independent cohorts; validation cohort I consisted of 40 patients with premature CAD and 40 healthy controls and validation cohort II consisted of 27 patients with artery disease and 40 healthy relatives. MiR340* and miR624* were confirmed to be upregulated in patients with CAD as compared to healthy controls in both validation cohorts. Two miRNAs in platelets are significantly upregulated in patients with CAD as compared to healthy controls. Whether the two identified miRNAs can be used as biomarkers and whether they are cause or consequence of the disease remains to be elucidated in a larger prospective stud