Effectiveness of Surface Treatment Techniques for Composite Bonding with Different Contamination Levels

Various surface treatment techniques have been developed to promote adhesive bond performance for composite structural components in aerospace applications. The condition of the pre-bond surface is critical to achieving desirable bond quality. Contamination on bonding surfaces is well recognized as a major threat to ultimate bond performance. Variation in contamination level has brought additional challenges into manufacturing process control. High fidelity surface treatment techniques are required for effective removal of contaminants over a wide range of contamination levels. In this study, a common contaminant, i.e. silicone mold release, was introduced to pre-bond composite surfaces with different concentrations. Plasma and laser surface treatment techniques were performed and their effectiveness in restoring and enhancing desirable bond quality was investigated. Surface characterization techniques, including water contact angle goniometry, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, were conducted to assess the condition of contaminated surfaces and the improvement induced by plasma and laser surface treatments. Failure modes from a customized double cantilever beam test were investigated before and after surface treatments. Fundamental mechanisms of plasma and laser surface treatments on the composite bonding surfaces were also investigated

Insights Into the Deglacial Variability of Phytoplankton Community Structure in the Eastern Equatorial Pacific Ocean Using [\u3csup\u3e231\u3c/sup\u3ePa/\u3csup\u3e230\u3c/sup\u3eTh]xs and Opal-Carbonate Fluxes

Fully and accurately reconstructing changes in oceanic productivity and carbon export and their controls is critical to determining the efficiency of the biological pump and its role in the global carbon cycle through time, particularly in modern CO2 source regions like the eastern equatorial Pacific (EEP). Here we present new high-resolution records of sedimentary 230Th-normalized opal and nannofossil carbonate fluxes and [231Pa/230Th]xs ratios from site MV1014-02-17JC in the Panama Basin. We find that, across the last deglaciation, phytoplankton community structure is driven by changing patterns of nutrient (nitrate, iron, and silica) availability which, in turn, are caused by variability in the position of the Intertropical Convergence Zone (ITCZ) and associated changes in biogeochemical cycling and circulation in the Southern Ocean. Our multi-proxy work suggests greater scrutiny is required in the interpretation of common geochemical proxies of productivity and carbon export in the EEP

The Sediment Green-Blue Color Ratio as a Proxy for Biogenic Silica Productivity Along the Chilean Margin

Sediment cores recently collected from the Chilean Margin during D/V JOIDES Resolution Expedition 379T (JR100) document variability in shipboard-generated records of the green/blue (G/B) ratio. These changes show a strong coherence with benthic foraminiferal δ18O, Antarctic ice core records, and sediment lithology (e.g., higher diatom abundances in greener sediment intervals), suggesting a climate-related control on the G/B. Here, we test the utility of G/B as a proxy for diatom productivity at Sites J1002 and J1007 by calibrating G/B to measured biogenic opal. Strong exponential correlations between measured opal% and the G/B were found at both sites. We use the empirical regressions to generate high-resolution records of opal contents (opal%) on the Chilean Margin. Higher productivity tends to result in more reducing sedimentary conditions. Redox-sensitive sedimentary U/Th generally co-varies with the reconstructed opal% at both sites, supporting the association between sediment color, sedimentary U/Th, and productivity. Lastly, we calculated opal mass accumulation rate (MAR) at Site J1007 over the last ∼150,000 years. The G/B-derived opal MAR record from Site J1007 largely tracks existing records derived from traditional wet-alkaline digestion from the south and eastern equatorial Pacific (EEP) Ocean, with a common opal flux peak at ∼50 ka suggesting that increased diatom productivity in the EEP was likely driven by enhanced nutrient supply from the Southern Ocean rather than dust inputs as previously suggested. Collectively, our results identify the G/B ratio as a useful tool with the potential to generate reliable, high-resolution paleoceanographic records that circumvent the traditionally laborious methodology.publishedVersio

Deep submarine infiltration of altered geothermal groundwater on the south Chilean Margin

Submarine groundwater discharge is increasingly recognized as an important component of the oceanic geochemical budget, but knowledge of the distribution of this phenomenon is limited. To date, reports of meteoric inputs to marine sediments are typically limited to shallow shelf and coastal environments, whereas contributions of freshwater along deeper sections of tectonically active margins have generally been attributed to silicate diagenesis, mineral dehydration, or methane hydrate dissociation. Here, using geochemical fingerprinting of pore water data from Site J1003 recovered from the Chilean Margin during D/V JOIDES Resolution Expedition 379 T, we show that substantial offshore freshening reflects deep and focused contributions of meteorically modified geothermal groundwater, which is likely sourced from a reservoir ~2.8 km deep in the Aysén region of Patagonia and infiltrated marine sediments during or shortly after the last glacial period. Emplacement of fossil groundwaters reflects an apparently ubiquitous phenomenon in margin sediments globally, but our results now identify an unappreciated locus of deep submarine groundwater discharge along active margins with potential implications for coastal biogeochemical processes and tectonic instability.publishedVersio

Methods of phenotypic identification of non-tuberculous mycobacteria

Non-tuberculous mycobacteria (NTM) are composed of mycobacterial species other than the Mycobacterium tuberculosis complex. Initially thought to be mere contaminants when isolated from clinical specimens, literature is increasing by the day showing NTM as proven pathogens. Due to the difference in antimicrobial susceptibility of different species, it becomes imperative for the microbiology laboratory to identify them to the species level. Molecular methods are available for rapid and accurate identification, but in a resource limited nation, phenotypic methods, albeit time consuming, are of paramount importance. By means of this article, the authors intend provide a concise summary of the basic biochemical reactions which can be done to identify most commonly isolated NTM. Keywords: Biochemical reactions, Non tuberculous mycobacteria, Phenotypic identificatio

Expedition 379T Proceedings, Digging Deeper with the JR100: Extending high resolution paleoclimate records from the Chilean Margin to the Eemian

<p>Expedition 379T of the D/V JOIDES Resolution was the first in the new NSF funded JR100 program, intended to provide the US paleoceanographic community a new way for recovering long sediment records (up to 100 meters below seafloor) outside of the IODP program. As such, it bridges between the conventional coring capability on UNOLS ships and the deep sea drilling program. The primary objective of the expedition was to investigate links between oceanographic changes at the northern margin of the Antarctic Circumpolar Current and climate variability on the South American continent over the past few glacial-interglacial cycles, with a special emphasis on obtaining high-resolution records of the Eemian interval and the last two glacial terminations. Given very high sedimentation rates along the Chilean margins, the new cores will enable reconstruction of surface and intermediate water variability at centennial-to-millennial resolution, which will extend available records from previous coring expeditions (ODP Expedition 202), thus permitting comparison of Southern Hemisphere records of the Holocene and last interglacial (LIG- Eemian), terminations I and II, and the MIS 5e-5d glacial inception. </p><p>Eight sites were cored during Expedition 379T, recovering a total of 2232 m of sediment cores in 670–3055 m water depth with an average recovery of 101.8% during 14.62 days of on-site operations (Table T1). Despite delayed departure at Punta Arenas and several bad weather days that prevented us from coring some of the planned sites, we have achieved almost all the expedition objectives. The eight sites extend over a wide latitudinal distance (46-36°S) covering the modern transition from the Antarctic subpolar to the subtropical zones (Figure F1) as well as spanning water depths intersecting the Antarctic Intermediate Water (AAIW), Pacific Deep Water (PDW) and Circumpolar deep water (CPDW) water masses (Figure F2).  Six of the sites are located on the Chilean margins at intermediate water depths (670-1534 mbsl) and the other two sites are situated in deep water off the shelf (2032 and 3055 mbsl).  Three holes were APC cored in all but one site (J1003 has only two holes) allowing for compositing complete splices for paleoceanographic reconstructions (Figure F3). Shipboard analyses of the sediment cores included determining properties including magnetic susceptibility (MS), gamma ray attenuation (GRA), natural gamma radiation (NGR), visual description and imaging, paleomagnetic measurements, and micropaleontology (foraminifers, nannofossil and diatoms).  Low-resolution (1 per core) interstitial water samples were collected for shipboard elemental analysis at each site.  In addition, high-resolution interstitial water samples (1 per section) were collected at each site for further shore-based isotopic and elemental investigations totaling 472 IW samples.</p><p>Of the 30 science-party members we had 15 graduate students and 7 postdocs, assisted by 6 senior scientists. All members of the science-party were trained in and carried out the shipboard analyses, and contributed to the interpretations and report writing. We adopted the report format used on IODP expeditions to ensure future users of the cores have all the necessary information to interpret the wealth of data collected onboard; we recommend that this be done on future JR100 expeditions. Finally, two undergraduate students were trained by the technical staff, and two Chilean observers both fully participated in the shipboard analyses.  It is our opinion that the educational component is another important strength of the JR100 program.</p&gt

Microbial cell distribution in the Guaymas Basin subseafloor biosphere, a young marginal rift basin with rich organics and steep temperature gradient

<p>Guaymas Basin is a young marginal rift basin in the Gulf of California characterized by active seafloor spreading and rapid sediment deposition, including organic-rich sediments derived from highly productive overlying waters and terrigenous sediments from nearby continental margins. The combination of active seafloor spreading and rapid sedimentation within a narrow basin results in a dynamic environment where linked physical, chemical, and biological processes regulate the cycling of sedimentary carbon and other elements. This continuum of interrelating processes from magma to microbe motivated International Ocean Discovery Program Expedition 385 and is reflected in its title, “Guaymas Basin Tectonics and Biosphere.”</p><p>During IODP Expedition 385, organic-rich sediments with sill intrusions on the flanking regions and in the northern axial graben of Guaymas Basin (in eight sites) were drilled and core samples were recovered. Those cored samples were examined for their microbial cell abundance in a highly sensitive manner by density-gradient cell separation at the super clean room of Kochi Core Center, Japan, followed by direct counting on fluorescence microscopy. Cell abundance in surficial seafloor sediment (~10<sup>9</sup> cells/cm<sup>3</sup>) was roughly 1000 times higher than the bottom seawater (~10<sup>6</sup> cells/cm<sup>3</sup>) and gradually decreased with increasing depth and temperature. In contrast to the cell abundance profile observed at Nankai Trough (IODP Exp. 370), the gradual decrease of cell abundance was observed up to around 75ºC, and we detected microbial cells even at hot horizons above 100ºC.</p><p>We will present the overview of the microbial cell distribution in the Guaymas Basin and discuss its relation to the current and past environmental conditions, e.g., temperature and sill-intrusion, etc.</p&gt

Heat flow and thermal regime in the Guaymas Basin, Gulf of California: Estimates of conductive and advective heat transport

International audienc

Heat flow and thermal regime in the Guaymas Basin, Gulf of California: Estimates of conductive and advective heat transport

International audienc