Southern Ocean laminated diatom ooze: mat deposits and potential for palaeo-flux studies, ODP leg 177, Site 1093

International audienceLaminated diatom ooze samples collected during ODP Leg 177 were analysed using scanning electron microscope (SEM) and optical microscopy to test their potential as high-resolution records of Polar Front hydrography, surface production, and export. SEM analysis from two intervals, marine isotope stage (MIS) 29 and 12/11, respectively, recovered from 50°S in the Atlantic Ocean (ODP Site 1093, Hole A, sections 13H-4 0–18 cm and 23H-4 0–22 cm), show abundant and well-preserved Thalassiothrix antarctica mats, thought to be indicative of rapid export from the surface and deposition in the sediment. A preliminary analysis of laminae succession points to a possible annual couplet/triplet succession of laminae, and suggests exceptionally high local sedimentation rates of 57 and 80 cm kyr−1 for MIS 12/11 and 29, respectively. Such high accumulation rates imply that local export from the surface layer and sequestration of biogenic silica and organic matter to the sediments may have been much higher than previously suggested

LDRD final report on new homogeneous and supported oligomerization catalysts (LDRD 42461).

The overall purpose of this LDRD is multifold. First, we are interested in preparing new homogeneous catalysts that can be used in the oligomerization of ethylene and in understanding commercially important systems better. Second, we are interested in attempting to support these new homogeneous catalysts in the pores of nano- or mesoporous materials in order to force new and unusual distributions of a-olefins to be formed during the oligomerization. Thus the overall purpose is to try to prepare new catalytic species and to possibly control the active site architecture in order to yield certain desired products during a catalytic reaction, much like nature does with enzymes. In order to rationally synthesize catalysts it is imperative to comprehend the function of the various components of the catalyst. In heterogeneous systems, it is of utmost importance to know how a support interacts with the active site of the catalyst. In fact, in the catalysis world this lack of fundamental understanding of the relationship between active site and support is the single largest reason catalysis is considered an 'empirical' or 'black box' science rather than a well-understood one. In this work we will be preparing novel ethylene oligomerization catalysts, which are normally P-O chelated homogeneous complexes, with new ligands that replace P with a stable carbene. We will also examine a commercially catalyst system and investigate the active site in it via X-ray crystallography. We will also attempt to support these materials inside the pores of nano- and mesoporous materials. Essentially, we will be tailoring the size and scale of the catalyst active site and its surrounding environment to match the size of the molecular product(s) we wish to make. The overall purpose of the study will be to prepare new homogeneous catalysts, and if successful in supporting them to examine the effects that steric constraints and pore structures can have on growing oligomer chains

Photovoltaic self-assembly.

This late-start LDRD was focused on the application of chemical principles of self-assembly on the ordering and placement of photovoltaic cells in a module. The drive for this chemical-based self-assembly stems from the escalating prices in the 'pick-and-place' technology currently used in the MEMS industries as the size of chips decreases. The chemical self-assembly principles are well-known on a molecular scale in other material science systems but to date had not been applied to the assembly of cells in a photovoltaic array or module. We explored several types of chemical-based self-assembly techniques, including gold-thiol interactions, liquid polymer binding, and hydrophobic-hydrophilic interactions designed to array both Si and GaAs PV chips onto a substrate. Additional research was focused on the modification of PV cells in an effort to gain control over the facial directionality of the cells in a solvent-based environment. Despite being a small footprint research project worked on for only a short time, the technical results and scientific accomplishments were significant and could prove to be enabling technology in the disruptive advancement of the microelectronic photovoltaics industry

The future of marine fisheries management and conservation in the United Kingdom: Lessons learnt from over 100 years of biased policy

Marine wild-capture fisheries depend on the capacity of the ocean to provide a flow of harvestable resources to sustain the industry. Paradoxically, conventional fishing often undermines these resources by degrading the environment and overexploiting fish stocks. Many UK fisheries have declined for over a century due to a biased focus on their social-economic value and lack of recognition that they are social-ecological systems and need to be managed as such. With the UK’s recent transition to an independent coastal state, the Fisheries Act (2020) and associated Joint Fisheries Statement provide an opportunity to correct this. Focusing on the ecological foundations, a more sustainable future for UK fisheries may be achieved by: (1) implementing a conservative quota setting system based on Maximum Sustainable Yield (MSY), defined as that which would occur when the biomass of a population of the target species is at 50% of that estimated at carrying capacity, to set catch limits rather than targets. The biomass of fish stocks should be allowed to regenerate to a minimum of 120% of that which will achieve MSY to provide a buffer against the uncertainty in ecological response to climate change. (2) Fishing capacity should be reduced while redistributing a greater share of the quota to sectors of the fleet that are demonstrably more sustainable; recognising that short term compensation may be required by some to mitigate the impacts of displaced activity until the benefits of stock recovery are realised. (3) Greater restrictions should be applied to ensure the most damaging fishing techniques (e.g. bottom trawling and dredging) are prohibited as appropriate in the network of marine protected areas. Protection should be enforced to promote the regeneration of degraded habitats and restoration of fish populations to help achieve the objectives as set out in the Ac

Evaluation of an Impedance Threshold Device as a VIIP Countermeasure

Visual Impairment/Intracranial Pressure (VIIP) is a top human spaceflight risk for which NASA does not currently have a proven mitigation strategy. Thigh cuffs (Braslets) and lower body negative pressure (LBNP; Chibis) devices have been or are currently being evaluated as a means to reduce VIIP signs and symptoms, but these methods alone may not provide sufficient relief of cephalic venous congestion and VIIP symptoms. Additionally, current LBNP devices are too large and cumbersome for their systematic use as a countermeasure. Therefore, a novel approach is needed that is easy to implement and provides specific relief of symptoms. This investigation will evaluate an impedance threshold device (ITD) as a VIIP countermeasure. The ITD works by providing up to 7 cm H2O (approximately 5 mmHg) resistance to inspiratory air flow, effectively turning the thorax into a vacuum pump upon each inhalation which lowers the intrathoracic pressure (ITP) and facilitates venous return to the heart. The ITD is FDA-approved and was developed to augment venous return to the central circulation and increase cardiac output during cardiopulmonary resuscitation (CPR) and in patients with hypotension. While the effect of ITD on CPR survival outcomes is controversial, the ITD's ability to lower ITP with a concomitant decrease in intracranial pressure (ICP) is well documented. A similar concept that creates negative ITP during exhalation (intrathoracic pressure regulator; ITPR) decreased ICP in 16 of 20 patients with elevated ICP in a hospital pilot study. ITP and central venous pressure (CVP) have been shown to decrease in microgravity however ITP drops more than CVP, indicating an increased transmural CVP. This could explain the paradoxical distention of jugular veins (JV) in microgravity despite lower absolute CVP and also suggests that JV transmural pressure is not dramatically elevated. Use of an ITD may lower JV pressure enough to remove or relieve cephalic venous congestion. During spaceflight experiments with Braslet thigh cuffs and modified (open-glottis) Mueller maneuvers, Braslets alone reduced cardiac preload but only reduced the internal JV (IJV) cross sectional area by 23%. The addition of Mueller maneuvers resulted in an IJV area reduction of 48%. This project will test if ITD essentially applies a Mueller maneuver with added negative ITP in every respiratory cycle, acting to: 1) reduce venous congestion in the neck and 2) potentially lower ICP. The expected mechanism of action is that in microgravity (or an analog) blood is relocated toward the heart from vasculature in the head and neck. Once validated, the ITD would be an exceptionally easy countermeasure to deploy and test on the ISS. Dosage could be altered though 1) duration of application and 2) inspiratory resistance set point. Effects could be additionally enhanced through co-application with other countermeasures such as thigh cuffs or LBNP

Transmission potential of Rift Valley fever virus over the course of the 2010 epidemic in South Africa.

A Rift Valley fever (RVF) epidemic affecting animals on domestic livestock farms was reported in South Africa during January-August 2010. The first cases occurred after heavy rainfall, and the virus subsequently spread countrywide. To determine the possible effect of environmental conditions and vaccination on RVF virus transmissibility, we estimated the effective reproduction number (Re) for the virus over the course of the epidemic by extending the Wallinga and Teunis algorithm with spatial information. Re reached its highest value in mid-February and fell below unity around mid-March, when vaccination coverage was 7.5%-45.7% and vector-suitable environmental conditions were maintained. The epidemic fade-out likely resulted first from the immunization of animals following natural infection or vaccination. The decline in vector-suitable environmental conditions from April onwards and further vaccination helped maintain Re below unity. Increased availability of vaccine use data would enable evaluation of the effect of RVF vaccination campaigns

Chiral multichromic single crystals for optical devices (LDRD 99406).

This report summarizes our findings during the study of a novel system that yields multi-colored materials as products. This system is quite unusual as it leads to multi-chromic behavior in single crystals, where one would expect that only a single color would exist. We have speculated that these novel solids might play a role in materials applications such as non-linear optics, liquid crystal displays, piezoelectric devices, and other similar applications. The system examined consisted of a main-group alkyl compound (a p block element such as gallium or aluminum) complexed with various organic di-imines. The di-imines had substituents of two types--either alkyl or aromatic groups attached to the nitrogen atoms. We observed that single crystals, characterized by X-ray crystallography, were obtained in most cases. Our research during January-July, 2006, was geared towards understanding the factors leading to the multi-chromic nature of the complexes. The main possibilities put forth initially considered (a) the chiral nature of the main group metal, (b) possible reduction of the metal to a lower-valent, radical state, (c) the nature of the ligand(s) attached to the main group metal, and (d) possible degradation products of the ligand leading to highly-colored products. The work carried out indicates that the most likely explanation considered involves degradation of the aromatic ligands (a combination of (c) and (d)), as the experiments performed can clearly rule out (a) and (b)

A new Holocene record of geomagnetic secular variation from Windermere, UK

Paleomagnetic secular variation (PSV) records serve as valuable independent stratigraphic correlation and dating tools for marine and terrestrial sediment sequences, and enhance knowledge of geomagnetic field dynamics. We present a new radiocarbon-dated record (WINPSV-12K) of Holocene geomagnetic secular variation from Windermere, updating the existing 1981 UK master PSV curve. Our analyses used continuous U-channel samples taken from the center of four sediment cores retrieved from Windermere in 2012. The natural remanent magnetization (NRM) of each U-channel was measured before and after stepwise alternating field (AF) demagnetization on a superconducting rock magnetometer at intervals of 0.5-cm or 1-cm. The NRM data reveal a stable and well-defined primary magnetization. Component declinations and inclinations estimated using Principal Component Analysis (PCA) of NRM data from the four Windermere cores correlate well on their independent radiocarbon age models. The four records were stacked using a sliding window bootstrap method, resulting in a composite Holocene PSV record (WINPSV-12K). On millennial timescales WINPSV-12K correlates well with other records from Western Europe and the northern North Atlantic to a resolution of ∼ 1 kyr, given age uncertainties and spatial variability between records. WINPSV-12K also compares well to the CALS10k.2 and pfm9k.1a model predictions for Windermere. Key regionally-significant PSV inclination features of WINPSV-12K which correlate with other North Atlantic records include peaks at 5–6, 8.5, and 10 cal ka BP, and a trough at 7calkaBP. Key PSV declination features include the eastward swing from 5.5–2.3 cal ka BP followed by a major westward excursion at 2.3 cal ka BP, peaks at 1.1 and 7calkaBP, and troughs at 5.4 and 8.2 cal ka BP, with the caveat that an estimated magnetic lock-in delay of at least 100–200 yr is present. PSV variations on 1–3 kyr timescales are interpreted to represent strengthening and weakening of the North American versus the Siberian and European–Mediterranean high-latitude flux lobes, based on the close similarities between the North Atlantic regional records and the antiphase existing in the East Asian Stack record and the North East Pacific inclination stack. WINPSV-12K provides a regionally-important new PSV reference curve whose prominent features may serve as stratigraphic markers for North Atlantic paleo-records

A new varve sequence from Windermere, UK, records rapid ice retreat prior to the Lateglacial Interstadial (GI-1)

Annually laminated sediments (varves) provide excellent temporal resolution to study rapid environmental change, but are rare in the early part of the Last Termination (∼19–∼11.7 ka BP). We present a new >400 varve year (vyr) varve sequence in two floating parts from Windermere, a lake at the southern margin of the mountains of northwest England. This sequence records the final retreat of the Windermere glacier at the southern edge of the Lake District Ice Cap during the transition from Heinrich Stadial 1 (∼18–∼14.7 ka BP) into the Lateglacial Interstadial (∼14.7–∼12.9 ka BP). Laminated sediments from four lake cores from Windermere's northern and southern basins were investigated and shown to be varved. These sequences are integrated with seismic reflection evidence to reconstruct south-to-north deglaciation. Seismic and sedimentological evidence is consistent with gradual stepped ice retreat along the entire southern basin and into the northern basin between 255 and 700 vyr prior to the appearance of significant biota in the sediment that heralded the Lateglacial Interstadial, and had retreated past a recessional moraine (RM8) in the northern basin by 121 vyr prior to the interstadial. The Lateglacial Interstadial age of this biota-bearing unit was confirmed by 14C-dating, including one date from the northernmost core of ∼13.5 cal ka BP. A change in mineralogy in all four cores as the glacier retreated north of the Dent Group (the northernmost source of calcareous bedrock) and a decrease in coarse grains in the varves shows that the ice had retreated along the entire North Basin at ∼70 vyr prior to the Lateglacial Interstadial. The estimated retreat rate is 70–114 m yr−1 although buried De Geer moraines, if annual, may indicate retreat of 120 m yr−1 with a ≥3 year stillstand at a recessional moraine halfway along the basin. The glacier then retreated north of the lake basin, becoming land-terminating and retreating at 92.5–49 m yr−1. The northernmost core has a varve sequence ending at least 111 vyr after the other core chronologies, due to the increased proximity to remnant ice in the catchment uplands into the early Lateglacial Interstadial. We show that almost all of the glacier retreat in the Windermere catchment occurred before the abrupt warming at the onset of the Lateglacial Interstadial, in keeping with similar findings from around the Irish Sea Basin, and suggesting a similar retreat timescale for other radial valley glaciers of the Lake District Ice Cap. The seismic and core evidence also show the potential for a much longer varve chronology extending at least 400 and potentially over 1000 vyr further back into Heinrich Stadial 1 (18–14.7 ka BP), suggesting that glacier retreat in the Windermere valley initiated at least before 15.5 ka BP and perhaps 16 ka BP

LDRD final report on "fundamentals of synthetic conversion of CO2 to simple hydrocarbon fuels" (LDRD 113486).

Energy production is inextricably linked to national security and poses the danger of altering the environment in potentially catastrophic ways. There is no greater problem than sustainable energy production. Our purpose was to attack this problem by examining processes, technology, and science needed for recycling CO{sub 2} back into transportation fuels. This approach can be thought of as 'bio-inspired' as nature employs the same basic inputs, CO{sub 2}/energy/water, to produce biomass. We addressed two key deficiencies apparent in current efforts. First, a detailed process analysis comparing the potential for chemical and conventional engineering methods to provide a route for the conversion of CO{sub 2} and water to fuel has been completed. No apparent 'showstoppers' are apparent in the synthetic route. Opportunities to improve current processes have also been identified and examined. Second, we have also specifically addressed the fundamental science of the direct production of methanol from CO{sub 2} using H{sub 2} as a reductant