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The mean and variability of the Atlantic meridional overturning circulation (AMOC), as represented in six ocean reanalysis products, are analyzed over the period 1960–2007. Particular focus is on multi-decadal trends and interannual variability at 26.5°N and 45°N. For four of the six reanalysis products, corresponding reference simulations obtained from the same models and forcing datasets but without the imposition of subsurface data constraints are included for comparison. An emphasis is placed on identifying general characteristics of the reanalysis representation of AMOC relative to their reference simulations without subsurface data constraints. The AMOC as simulated in these two sets are presented in the context of results from the Coordinated Ocean-ice Reference Experiments phase II (CORE-II) effort, wherein a common interannually varying atmospheric forcing data set was used to force a large and diverse set of global ocean-ice models. Relative to the reference simulations and CORE-II forced model simulations it is shown that (1) the reanalysis products tend to have greater AMOC mean strength and enhanced variance and (2) the reanalysis products are less consistent in their year-to-year AMOC changes. We also find that relative to the reference simulations (but not the CORE-II forced model simulations) the reanalysis products tend to have enhanced multi-decadal trends (from 1975–1995 to 1995–2007) in the mid to high latitudes of the northern hemisphere.

The function of DNA during oxidative stress 1 and its suitability as a potential building block for molecular devices 2 , 3 , 4 depend on long-distance transfer of electrons and holes through the molecule, yet many conflicting measurements of the efficiency of this process have been reported 5 , 6 . It is accepted that charges are transported over long distances through a multistep hopping reaction 7 , 8 , 9 , 10 , 11 ; this ‘G-hopping’ 8 involves positive charges moving between guanines (Gs), the DNA bases with the lowest ionization potential. But the mechanism fails to explain the persistence of efficient charge transfer when the guanine sites are distant 7 , 12 , where transfer rates do not, as expected, decrease rapidly with transfer distance. Here we show experimentally that the rate of charge transfer between two guanine bases decreases with increasing separation only if the guanines are separated by no more than three base pairs; if more bridging base pairs are present, the transfer rates exhibit only a weak distance dependence. We attribute this distinct change in the distance dependence of the rate of charge transfer through DNA to a shift from coherent superexchange charge transfer (tunnelling) at short distances to a process mediated by thermally induced hopping of charges between adenine bases (A-hopping) at long distances. Our results confirm theoretical predictions of this behaviour 13 , 14 , 15 , 16 , 17 , emphasizing that seemingly contradictory observations of a strong 8 , 9 as well as a weak 7 , 12 influence of distance on DNA charge transfer are readily explained by a change in the transfer mechanism.

Images acquired of Saturn's rings and small moons by the Cassini Imaging Science Subsystem (ISS) during the first 9 months of Cassini operations at Saturn have produced many new findings. These include new saturnian moons; refined orbits of new and previously known moons; narrow diffuse rings in the F-ring region and embedded in gaps within the main rings; exceptionally fine-scale ring structure in moderate- to high-optical depth regions; new estimates for the masses of ring-region moons, as well as ring particle properties in the Cassini division, derived from the analysis of linear density waves; ring particle albedos in select ring regions; and never-before-seen phenomena within the rings.

The Cassini Imaging Science Subsystem acquired high-resolution imaging data on the outer Saturnian moon, Phoebe, during Cassini's close flyby on 11 June 2004 and on Iapetus during a flyby on 31 December 2004. Phoebe has a heavily cratered and ancient surface, shows evidence of ice near the surface, has distinct layering of different materials, and has a mean density that is indicative of an ice-rock mixture. Iapetus's dark leading side (Cassini Regio) is ancient, heavily cratered terrain bisected by an equatorial ridge system that reaches 20 kilometers relief. Local albedo variations within and bordering Cassini Regio suggest mass wasting of ballistically deposited material, the origin of which remains unknown.

After a potential biological incident the sampling strategy and sample analysis are crucial for the outcome of the investigation and identification. In this study, we have developed a simple sandwich ELISA based on commercial components to quantify BSA (used as a surrogate for ricin) with a detection range of 1.32-80 ng/mL. We used the ELISA to evaluate different protein swabbing procedures (swabbing techniques and after-swabbing treatments) for two swab types: a cotton gauze swab and a flocked nylon swab. The optimal swabbing procedure for each swab type was used to obtain recovery efficiencies from different surface materials. The surface recoveries using the optimal swabbing procedure ranged from 0-60% and were significantly higher from nonporous surfaces compared to porous surfaces. In conclusion, this study presents a swabbing procedure evaluation and a simple BSA ELISA based on commercial components, which are easy to perform in a laboratory with basic facilities. The data indicate that different swabbing procedures were optimal for each of the tested swab types, and the particular swab preference depends on the surface material to be swabbed.

This paper describes the Simple Ocean Data Assimilation (SODA) reanalysis of ocean climate variability. In the assimilation, a model forecast produced by an ocean general circulation model with an average resolution of 0.25° × 0.4° × 40 levels is continuously corrected by contemporaneous observations with corrections estimated every 10 days. The basic reanalysis, SODA 1.4.2, spans the 44-yr period from 1958 to 2001, which complements the span of the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) atmospheric reanalysis (ERA-40). The observation set for this experiment includes the historical archive of hydrographic profiles supplemented by ship intake measurements, moored hydrographic observations, and remotely sensed SST. A parallel run, SODA 1.4.0, is forced with identical surface boundary conditions, but without data assimilation. The new reanalysis represents a significant improvement over a previously published version of the SODA algorithm. In particular, eddy kinetic energy and sea level variability are much larger than in previous versions and are more similar to estimates from independent observations. One issue addressed in this paper is the relative importance of the model forecast versus the observations for the analysis. The results show that at near-annual frequencies the forecast model has a strong influence, whereas at decadal frequencies the observations become increasingly dominant in the analysis. As a consequence, interannual variability in SODA 1.4.2 closely resembles interannual variability in SODA 1.4.0. However, decadal anomalies of the 0–700-m heat content from SODA 1.4.2 more closely resemble heat content anomalies based on observations.

The nucleus of the Jupiter-family comet 19P/Borrelly was closely observed by the Miniature Integrated Camera and Spectrometer aboard the Deep Space 1 spacecraft on 22 September 2001. The 8-kilometer-long body is highly variegated on a scale of 200 meters, exhibiting large albedo variations (0.01 to 0.03) and complex geologic relationships. Short-wavelength infrared spectra (1.3 to 2.6 micrometers) show a slope toward the red and a hot, dry surface (≤345 kelvin, with no trace of water ice or hydrated minerals), consistent with ∼10% or less of the surface actively sublimating. Borrelly's coma exhibits two types of dust features: fans and highly collimated jets. At encounter, the near-nucleus coma was dominated by a prominent dust jet that resolved into at least three smaller jets emanating from a broad basin in the middle of the nucleus. Because the major dust jet remained fixed in orientation, it is evidently aligned near the rotation axis of the nucleus.

A subsurface low oxygen zone is located in the eastern tropical North Atlantic Ocean (ETNA) in the upper ocean with the core of the hypoxic (O2 ≦60 µmol kg−1) oxygen minimum zone (OMZ) at 400 to 500 m depth. The subsurface circulation in the OMZ region is derived from observations and data assimilation results. Measurements in the ETNA of velocity, oxygen and of a tracer (CF3SF5) that was released in April 2008 at  ∼  8° N, 23° W (at  ∼  330 m depth) in November–December 2008, in November–December 2009 and October–November 2010 show the circulation in the upper part of the OMZ with spreading to the east in the North Equatorial Countercurrent (NECC) region and northwestward around the Guinea Dome. Three floats equipped with oxygen sensors deployed at  ∼  8° N, 23° W with parking depths at 330, 350 and 400 m depths were used to estimate velocity along the float trajectory at the surface and at the parking depth. At the 350 m park depth north of 9° N a cyclonic northwestward flow across the OMZ was observed. The northward drift of a float into the upper OMZ and a stronger cyclonic flow around the Guinea Dome seem to be connected to a strong Atlantic Meridional Mode (AMM) event in 2009. A near-surface cyclonic circulation cell east of the Cape Verde Islands reaches down into the OMZ layer. The circulation of the upper OMZ mirrors the near-surface circulation. Oxygen measurements from the cruises used here, as well as from other recent cruises up to the year 2014, confirm the continuous deoxygenation trend in the upper OMZ since the 1960s near the Guinea Dome. The three floats deployed with the tracer show spreading paths consistent with the overall observed tracer spreading. Oxygen sensors on the floats remained well calibrated for more than 20 months, and so the oxygen profiles can be used to investigate mesoscale eddy signatures. Mesoscale eddies may modify the oxygen distribution in OMZs. However, in general eddies are less energetic in the ETNA south of the Cape Verde Islands compared to similar latitudes in the eastern tropical South Pacific.

False-positive serological reactions (FPSR) due to infections with Yersinia enterocolitica serotype O[ratio ]9 (YeO[ratio ]9) are a problem in tests for brucellosis. In the present study, FPSR in classical and novel tests for brucellosis following experimental infections of pigs with YeO[ratio ]9 were compared with responses of B. suis biovar 2-inoculated pigs. FPSR were limited to 2–9 weeks post-YeO[ratio ]9 inoculation, while B. suis-infected pigs were test-positive throughout the 21-week period of investigation. Although YeO[ratio ]9-inoculated pigs exhibited FPSR in Brucella tests for a limited period of time, the serological responses in a YeO[ratio ]9-purified O-antigen indirect ELISA did not decrease accordingly. Analysis of available cross-sectional serum samples from pig herds naturally infected with YeO[ratio ]9 or B. suis biovar 2 confirmed that the observed difference in the duration of the serological responses between the two infections could be used to discriminate between herds infected with B. suis biovar 2 and YeO[ratio ]9.

The Simple Ocean Data Assimilation (SODA) reanalysis (1958–2001) is used to investigate the decadal variability in the equatorial thermocline in the Pacific. Whereas the thermocline depth exhibits weak variation at decadal time scales, the temperature change in the vicinity of the thermocline in the western Pacific is significant and has a vertical scale of ∼150 m. Based on a modal decomposition of the model variability, it is shown that such temperature change can be interpreted to a large extent as vertical displacements of the isotherms associated with the Kelvin and first meridional Rossby waves of the first three baroclinic modes. This indicates that decadal change at the subsurface in the warm pool region may be forced by the winds, consistent with the results of a multimode linear model simulation. The decadal mode of vertical temperature can be described by the first two dominant statistical modes (EOFs): the first mode is associated with changes in the slope of the thermocline (swallowing in the western-central Pacific and deepening in the eastern Pacific), representative of the 1976/77 climate shift and ahead of the ENSO modulation; and the second mode corresponds to a basinwide uplift of the thermocline and behind the ENSO modulation. It is further shown that the subsurface temperature in the warm pool region is negatively skewed, which results from the ENSO asymmetry. The results are consistent with the hypothesis of change in mean state resulting from the residual effect of the asymmetric ENSO variability.