Thallium as a tracer of fluid–rock interaction in the shallow Mariana forearc

Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Earth and Planetary Science Letters 430 (2015): 416-426, doi:10.1016/j.epsl.2015.09.001.Fluids driven off the subducting Pacific plate infiltrate the shallow Mariana 26 forearc and lead to extensive serpentinization of mantle peridotite. However, the sources, pathways, and chemical modifications of ascending, slab-derived fluids remain poorly constrained and controversial. In this study, we use thallium (Tl) concentrations and isotopic ratios of serpentinized peridotite and rodingitized diabase from the South Chamorro and Conical Seamounts to discriminate between potential fluid sources with distinct Tl isotope compositions. Serpentinite samples from the Mariana forearc all display ε205Tl > - 0.5 (where ε205Tl = 10,000 x (205Tl/203Tlsample-205Tl/203TlSRM 997)/(205Tl/203TlSRM 997)), which is significantly enriched in 205Tl compared to the normal mantle (ε205Tl = -2). Given that high temperature hydrothermal processes do not impart significant Tl isotope fractionation, the isotope compositions of the serpentinites must reflect that of the serpentinizing fluid. Pelagic sediments are the only known slab component that consistently display ε205Tl > -0.5 and, therefore, we interpret the heavy Tl isotope signatures as signifying that the serpentinizing fluids were derived from subducting pelagic sediments. A rodingitized diabase from Conical Seamount was found to have an ε205Tl of 0.8, suggesting that sediment-sourced serpentinization fluids could also affect diabase and other mafic lithologies in the shallow Mariana forearc. Forearc rodingitization of diabase led to a strong depletion in Tl content and a virtually complete loss of K, Na and Rb. The chemical composition of hybrid fluids resulting from serpentinization of harzburgite with concomitant rodingitization of diabase can be highly alkaline, depleted in Si, yet enriched in Ca, Na, K, and Rb, which is consistent with the composition of fluids emanating from mud volcanoes in the Mariana forearc. Our study suggests that fluid-rock interactions between sedimentary, mafic, and ultramafic lithologies are strongly interconnected even in the shallowest parts of subduction zones. We conclude that transfer of fluids and dissolved elements at temperatures and pressures below 400°C and 1GPa, respectively, must be taken into account when elemental budgets and mass transfer between the subducting plate, the forearc, the deep mantle and the ocean are evaluated.This study was funded by NSF grants EAR-1119373 and -1427310 to SGN, NSF grant OCE-1059534 to FK and a grant from the WHOI Deep Ocean Exploration Institute to FK and SGN

School Connectedness: An Analysis of Students\u27 Relationship with Their School

This paper will review the research on school connectedness. More specifically how can school counselors increase their students’ connection to school? What have school counselors done to improve this connection, and have they been successful? As positive change agents who work for the entire student population, school counselors are in an ideal position to improve the students’ lives. It is the goal of this paper to educate readers about school counselors and school connectedness

A two-week clinical evaluation of the safety of Systane® Ultra in contact lens-wearing patients

David KadingSpecialty Eyecare Group, Kirkland, WA, USAObjective: To evaluate the safety of Systane® Ultra Lubricant Eye Drops (test solution) in contact lens wearers. A currently marketed contact lens rewetting drop was the control solution.Participants: This investigator- and patient-masked, single-site, randomized, and prospective study involved 45 successful contact lens wearers.Methods: Eligible subjects’ baseline biomicroscopy findings, visual acuity, and corneal staining score were recorded. Subjects received either the test or control solution with masked labeling. Subjects were instructed to instill their assigned solution in both eyes: 15 minutes prior to lens insertion, at least one drop during lens wear and another drop immediately following lens removal. After 14 days, biomicroscopy results, visual acuity, and corneal staining score were recorded.Results: No adverse events were documented for either the test or the control solution. For subjects using Systane® Ultra, no statistically significant change was detected in visual acuity (= 0.7667) or corneal staining score (P = 1.000). For subjects using the control solution, the change in visual acuity (P = 0.0011, mean difference = 1.70 ± 3.22 standard deviation) was not clinically relevant and there was no significant change in corneal staining score (P = 0.5413).Conclusions: This clinical study provided evidence of safety and compatibility of Systane® Ultra Lubricant Eye Drops in contact lens wearers.Keywords: lubricant eye drop, contact lens, safety, dry ey

An Optical Readout TPC (O-TPC) for Studies in Nuclear Astrophysics With Gamma-Ray Beams at HIgS

We report on the construction, tests, calibrations and commissioning of an Optical Readout Time Projection Chamber (O-TPC) detector operating with a CO2(80%) + N2(20%) gas mixture at 100 and 150 Torr. It was designed to measure the cross sections of several key nuclear reactions involved in stellar evolution. In particular, a study of the rate of formation of oxygen and carbon during the process of helium burning will be performed by exposing the chamber gas to intense nearly mono-energetic gamma-ray beams at the High Intensity Gamma Source (HIgS) facility. The O-TPC has a sensitive target-drift volume of 30x30x21 cm^3. Ionization electrons drift towards a double parallel grid avalanche multiplier, yielding charge multiplication and light emission. Avalanche induced photons from N2 emission are collected, intensified and recorded with a Charge Coupled Device (CCD) camera, providing two-dimensional track images. The event's time projection (third coordinate) and the deposited energy are recorded by photomultipliers and by the TPC charge-signal, respectively. A dedicated VME-based data acquisition system and associated data analysis tools were developed to record and analyze these data. The O-TPC has been tested and calibrated with 3.183 MeV alpha-particles emitted by a 148Gd source placed within its volume with a measured energy resolution of 3.0%. Tracks of alpha and 12C particles from the dissociation of 16O and of three alpha-particles from the dissociation of 12C have been measured during initial in-beam test experiments performed at the HIgS facility at Duke University. The full detection system and its performance are described and the results of the preliminary in-beam test experiments are reported.Comment: Supported by the Richard F. Goodman Yale-Weizmann Exchange Program, ACWIS, NY, and USDOE grant Numbers: DE-FG02-94ER40870 and DE-FG02-97ER4103

Piezo-Electrochemical Transducer Effect (PECT) Intercalated Graphite Micro-Electromechanical Actuators

The purpose of this research is to investigate the Piezo-Electrochemical Transducer (PECT) effect in intercalated graphite as a possible mechanism of actuation for micro-electromechanical systems (MEMS). This dissertation presents the results of research into the PECT effect in H2SO4-intercalated graphitized carbon fibers, including both electrical and mechanical characteristics of this effect. PECT fibers achieve up to 1.7% strain at 1.4 V of applied potential. In contrast, the piezoelectric material polyvinylidene difluoride (PVDF) generates only 0.01% strain and polysilicon thermal expansion between 0.02 and 0.06% strain depending on the thermal conductivity of the particular polysilicon that the actuators are fabricated in. This work concludes that PECT carbon fiber actuators achieve two orders of magnitude better strain than PVDF piezoelectric actuators and polysilicon thermal expansion in the same voltage range of operation. In addition to this highly improved strain, the devices, after an initial peak power consumption of 227 micronW, a PECT device uses only 260 nW to hold actuation. Although slow operation and unpractical intercalants are serious drawbacks to PECT actuators, the characteristics of strain and power consumption presented in this dissertation prove that PECT actuators, given some minor modifications, prove to be a competitive alternative to current MEMS actuators

Micro-Electromechanical Switches for Micro-Satellite Power Transfer

In the past few years, microelectromechanical systems (MEMS) have emerged as a promising new technology with tremendous application potential. One of the possible implementations of MEMS technology is in the development of micro-satellites. It should be possible to mass-produce micro-satellites at a fraction of the cost of one conventional satellite. In order for satellites to be robust, a method of transferring power to systems must be addressed. As micro-satellites are made with conventional integrated circuit technologies at a very small scale, a means of transferring power on a similar scale will be investigated. This research addresses the issue of the design, fabrication, and testing of a MEMS switch for space based micro-satellites. Devices are designed and submitted to the Microelectronics Corporation of North Carolina for fabrication. Several different design approaches are attempted, including those using electrostatic and thermal properties for actuation. Fabricated devices are tested using a microprobe station for power usage, power transfer, and frequency characteristics. Devices produce a wide range of results, the best of which transfer large amounts of power in a wide range of frequencies including DC. Recommendations are made to the sponsor agency including the most appropriate designs for use in micro-satellite applications

Calibration of CR-39 Nuclear Track Detectors with Alpha-Particles and Protons for a Measurement of Neutron Interactions with 7Be and the Primordial 7Li Problem

The Primordial Lithium problem of Big Bang Nucleosynthesis (BBN), a prediction of 7Li abundance which is considerably larger than observed, has important implications for the standard model of cosmology. Since 7Li is produced by the later decay of 7Be it is important to study the destruction of 7Be during the epoch of BBN, in order to examine possible reduction of the predicted abundance of 7Li, in particular the destruction of 7Be with neutrons. The high flux of 50 keV epithermal neutrons (1010 n/sec/cm2) produced by a Liquid Lithium (LiLiT) target at the Soreq Applied Research Accelerator Facility (SARAF) in Yavne, Israel offers opportunities for research at BBN energy. Due to the high intensity of the neutron flux at SARAF, background can be overwhelming for spectroscopic detectors. The plastic polymer CR-39 (poly allyl diglycol carbonate - PADC, C12H18O7) was chosen as a detector that can withstand the high neutron and associated gamma-ray flux. CR-39 Nuclear Track Detectors (NTD) have been calibrated for detection of alpha-particles and protons in a high neutron flux environment. These detectors can be used to detect damage caused by ionizing radiation on the plastic through a process of chemical etching. Charged particles leave behind a trademark path of chemical bonds broken by incoming ionized radiation. After chemical etching, the broken bonds are visible under a microscope in the form of circular pits. A segmentation algorithm was developed using ImageJ/FIJI to analyze the pits and calibrate the detectors for use in the 7Be and neutron experiment at SARAF

Documenting Macrophytes and Thier Habitat Preferences in Southeastern South Dakota

One of the most pressing environmental problems that waterbodies currently face is eutrophication. When eutrophication occurs in lakes, phytoplankton dominance increases and macrophyte (aquatic plant) populations decrease. Macrophyte population fluctuation can be used to detect eutrophication and indicate lake health. Despite this novel use of macrophytes, the state of South Dakota has few, if any, baseline public records of its macrophyte species. In an effort to establish a record and work towards the use of macrophytes as potential eutrophication indicators in South Dakota, this study seeks to provide a better understanding of the macrophytes that occur in the southeastern portion of the state and their relationships with lake habitats. The objectives of this study were to 1) survey the macrophytes of a small sample of lakes in southeastern South Dakota, 2) evaluate the relationships between existing macrophytes and the physical characteristics of their lakes, and 3) determine if there are any predictable habitat preferences. The survey was conducted at a total of 78 sample sites among two lakes during mid-summer 2020. Macrophyte samples were taken using a weighted sampling rake and substrates were visually estimated. Overall, ten different macrophytes types, including emergent, submerged, and free-floating species and genera, were recorded among sample sites. West 81 Lake had the highest species richness, with nine species present and a significantly higher (P \u3c 0.05) average species richness than Island Lake. Additionally, West 81 Lake showed a significantly higher (P \u3c 0.05) presence frequency of silt/muck substrates than Island Lake and a significant positive (P \u3c 0.05) relationship between percent silt/muck and species richness. Both lakes demonstrated a significant negative (P \u3c 0.05) relationship between percent clay and species richness. As the results suggest, both percent silt/muck and percent clay play important roles in determining the types of macrophytes in southeastern South Dakota lakes, and silt/muck dominated habitat systems appear to be preferred by a diverse array of macrophytes

Tracking along-arc sediment inputs to the Aleutian arc using thallium isotopes.

Sediment transport from the subducted slab to the mantle wedge is an important process in understanding the chemical and physical conditions of arc magma generation. The Aleutian arc offers an excellent opportunity to study sediment transport processes because the subducted sediment flux varies systematically along strike (Kelemen et al., 2003) and many lavas exhibit unambiguous signatures of sediment addition to the sub-arc mantle (Morris et al., 1990). However, the exact sediment contribution to Aleutian lavas and how these sediments are transported from the slab to the surface are still debated. Thallium (Tl) isotope ratios have great potential to distinguish sediment fluxes in subduction zones because pelagic sediments and low-temperature altered oceanic crust are highly enriched in Tl and display heavy and light Tl isotope compositions, respectively, compared with the upper mantle and continental crust. Here, we investigate the Tl isotope composition of lavas covering almost the entire Aleutian arc a well as sediments outboard of both the eastern (DSDP Sites 178 and 183) and central (ODP Hole 886C) portions of the arc. Sediment Tl isotope compositions change systematically from lighter in the Eastern to heavier in the Central Aleutians reflecting a larger proportion of pelagic sediments when distal from the North American continent. Lavas in the Eastern and Central Aleutians mirror this systematic change to heavier Tl isotope compositions to the west, which shows that the subducted sediment composition is directly translated to the arc east of Kanaga Island. Moreover, quantitative mixing models of Tl and Pb, Sr and Nd isotopes reveal that bulk sediment transfer of ∼0.6–1.0% by weight in the Eastern Aleutians and ∼0.2–0.6% by weight in the Central Aleutians can account for all four isotope systems. Bulk mixing models, however, require that fractionation of trace element ratios like Ce/Pb, Cs/Tl, and Sr/Nd in the Central and Eastern Aleutians occurs after the sediment component was mixed with the mantle wedge. Models of Sr and Nd isotopes that involve sediment melting require either high degrees of sediment melting (>50%), in which case trace element ratios like Ce/Pb, Cs/Tl, and Sr/Nd of Aleutian lavas need to be produced after mixing with the mantle, or significant fluid additions from the underlying oceanic crust with Sr and Nd isotope compositions indistinguishable from the mantle wedge as well as high Sr/Nd ratios similar to that of low (<20%) degree sediment melts. Thallium isotope data from Western Aleutian lavas exhibit compositions slightly lighter than the upper mantle, which implies a negligible sediment flux at this location and probably involvement of low-temperature altered oceanic crust in the generation of these lavas. In general, the lightest Tl isotope compositions are observed for the highest Sr/Y ratios and most unradiogenic Sr and Pb isotope compositions, which is broadly consistent with derivation of these lavas via melting of eclogitized altered oceanic crust

Vocabulary Instruction and Student Participation and Retention

This action research investigated vocabulary retention and participation gain from integrating close reading passages into a Kindergarten and Second Grade public school classroom. The methods incorporated included turn and talk opportunities, student journals, and close reading passages. Thirty-six primary school aged students were included in the study. Sources of data collection include a teacher self-evaluation survey, vocabulary recognition task, observational checklist, and observational rubric. Students displayed an increase in vocabulary retention and participation. Because of the students’ increase in retention and participation during whole group instruction, we will continue to use close reading passages in our classrooms