185 research outputs found
TRACING SULFUR SOURCES IN AN ARCHEAN HYDROTHERMAL SYSTEM USING SULFUR MULTIPLE ISOTOPES - A CASE STUDY FROM THE KIDD CREEK VOLCANOGENIC MASSIVE SULFIDE DEPOSIT
Mass-independent fractionation of sulfur isotopes in the Archean atmosphere resulted in surface sulfur reservoirs with distinct isotopic signatures. These signatures are used to trace the movement of sulfur through an Archean seafloor hydrothermal system associated with the Kidd Creek volcanogenic massive sulfide (VMS) deposit. Isotopic measurements of sulfides from the 2.7 Ga Kidd Creek VMS deposit reflect two separate sulfur sources for ore precipitation. Subseafloor ore has a predominantly juvenile sulfur source. with a small (~3%) component of seawater sulfate, which was transported through the hydrothermal system to the site of precipitation. Surface sulfides contain a significant proportion of sulfur that was stripped from coeval seawater sulfate or native sulfur at the site of precipitation. Mass-independent isotopic signatures are also used in a sulfur multiple-isotope framework to evaluate isotopic disequilibrium and to assess the suitability of mineral pairs for paleothermometric calculations in the Kidd Creek VMS deposit
Boiling-induced formation of colloidal gold in black smoker hydrothermal fluids
Gold colloids occur in black smoker fluids from the Niua South
hydrothermal vent field, Lau Basin (South Pacific Ocean), confirming
the long-standing hypothesis that gold may undergo colloidal
transport in hydrothermal fluids. Six black smoker vents, varying
in temperature from 250 °C to 325 °C, were sampled; the 325 °C
vent was boiling at the time of sampling and the 250 °C fluids were
diffusely venting. Native gold particles ranging from <50 nm to 2
ÎĽm were identified in 4 of the fluid samples and were also observed
to precipitate on the sampler during collection from the boiling vent.
Total gold concentrations (dissolved and particulate) in the fluid samples
range from 1.6 to 5.4 nM in the high-temperature, focused flow
vents. Although the gold concentrations in the focused flow fluids are
relatively high, they are lower than potential solubilities prior to boiling
and indicate that precipitation was boiling induced, with sulfide
lost upon boiling to exsolution and metal sulfide formation. Gold
concentrations reach 26.7 nM in the 250 °C diffuse flow sample, and
abundant native gold particles were also found in the fluids and associated
sulfide chimney and are interpreted to be a product of colloid
accumulation and growth following initial precipitation upon boiling.
These results indicate that colloid-driven precipitation as a result of
boiling, the persistence of colloids after boiling, and the accumulation
of colloids in diffuse flow fluids are important mechanisms for the
enrichment of gold in seafloor hydrothermal systems
Hydrothermal Chimney Distribution on the Endeavour Segment, Juan de Fuca Ridge
The Endeavour Segment of the Juan de Fuca Ridge is well known for its abundance of hydrothermal vents and chimneys. One-meter scale multibeam mapping data collected by an autonomous undersea vehicle revealed 572 chimneys along the central 14 km of the segment, although only 47 are named and known to be active. Hydrothermal deposits are restricted to the axial graben and the near-rims of the graben above a seismically mapped axial magma lens. The sparse eruptive activity on the segment during the last 4,300 years has not buried inactive chimneys, as occurs at more magmatically robust mid-ocean ridges
At Sea Test 2 deployment cruise : cruise 475 on board R/V Oceanus September 22 – 26, 2011 Woods Hole –Woods Hole, MA
The R/V Oceanus, on Cruise 475, carried out the deployment of three moorings for the
Coastal and Global Scale Nodes (CGSN) Implementing Organization of the NSF Ocean
Observatories Initiative. These three moorings are prototypes of the moorings to be used
by CGSN at the Pioneer, Endurance, and Global Arrays. Oceanus departed from Woods
Hole, Massachusetts on September 22, 2011 and steamed south to the location of the
mooring deployments on the shelf break. Over three days, September 23-25, Oceanus
surveyed the bottom at the planned mooring sites, deployed the moorings, and carried out
on site verification of the functioning of the moorings and moored hardware. Oceanus
returned to Woods Hole on September 26, 2011.Funding was provided by the National Science Foundation
through the Consortium for Ocean Leadershi
Self-Affirmation Improves Problem-Solving under Stress
High levels of acute and chronic stress are known to impair problem-solving and creativity on a broad range of tasks. Despite this evidence, we know little about protective factors for mitigating the deleterious effects of stress on problem-solving. Building on previous research showing that self-affirmation can buffer stress, we tested whether an experimental manipulation of self-affirmation improves problem-solving performance in chronically stressed participants. Eighty undergraduates indicated their perceived chronic stress over the previous month and were randomly assigned to either a self-affirmation or control condition. They then completed 30 difficult remote associate problem-solving items under time pressure in front of an evaluator. Results showed that self-affirmation improved problem-solving performance in underperforming chronically stressed individuals. This research suggests a novel means for boosting problem-solving under stress and may have important implications for understanding how self-affirmation boosts academic achievement in school settings. © 2013 Creswell et al
Index
Seafloor massive sulfide deposits form in remote environments, and the assessment of deposit size and composition through drilling is technically challenging and expensive. To aid the evaluation of the resource potential of seafloor massive sulfide deposits, three-dimensional inverse modelling of geophysical potential field data (magnetic and gravity) collected near the seafloor can be carried out to further enhance geologic models interpolated from sparse drilling. Here, we present inverse modelling results of magnetic and gravity data collected from the active mound at the Trans-Atlantic Geotraverse hydrothermal vent field, located at 26o08'N on the Mid-Atlantic Ridge, using autonomous underwater vehicle (AUV) and submersible surveying. Both minimum-structure and surface geometry inverse modelling methods were utilized. Through deposit-scale magnetic modelling, the outer extent of a chloritized alteration zone within the basalt host rock below the mound was resolved, providing an indication of the angle of the rising hydrothermal fluid and the depth and volume of seawater/hydrothermal mixing zone. The thickness of the massive sulfide mound was determined by modelling the gravity data, enabling the tonnage of the mound to be estimated at 2.17 +/- 0.44 Mt through this geophysics-based, non-invasive approach
Ampullary cancers harbor ELF3 tumor suppressor gene mutations and exhibit frequent WNT dysregulation
The ampulla of Vater is a complex cellular environment from which adenocarcinomas arise to form a group of histopathologically heterogenous tumors. To evaluate the molecular features of these tumors, 98 ampullary adenocarcinomas were evaluated and compared to 44 distal bile duct and 18 duodenal adenocarcinomas. Genomic analyses revealed mutations in the WNT signaling pathway among half of the patients and in all three adenocarcinomas irrespective of their origin and histological morphology. These tumors were characterized by a high frequency of inactivating mutations of ELF3, a high rate of microsatellite instability, and common focal deletions and amplifications, suggesting common attributes in the molecular pathogenesis are at play in these tumors. The high frequency of WNT pathway activating mutation, coupled with small-molecule inhibitors of β-catenin in clinical trials, suggests future treatment decisions for these patients may be guided by genomic analysis
Working in the Public Interest Law Conference
Entirely student organized, WIPI seeks to bring together eminent practitioners in their respective fields, students, and faculty to discuss practical approaches to lawyering which can best serve the poor. Practical methods of challenging poverty are often not covered in traditional law school courses. This conference seeks to remedy that and provide dynamic, creative ways to combat poverty through the vehicle of the law
Genomic and molecular analyses identify molecular subtypes of pancreatic cancer recurrence
Pancreatic cancer (PC) remains a highly lethal malignancy, and most patients with localized disease that undergo surgical resection still succumb to recurrent disease. Pattern of recurrence after pancreatectomy is heterogenous, with some studies illustrating that site of recurrence can be associated with prognosis.1 Another study suggested that tumors that develop local and distant recurrence can be regarded as a homogenous disease with similar outcomes.2 Here we investigate novel molecular determinants of recurrence pattern after pancreatectomy for PC
NEWS AND NOTES 1988, VOL.19, NO.3
https://digitalcommons.rockefeller.edu/news_and_notes_1988/1001/thumbnail.jp
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