Binocular mirror-symmetric microsaccadic sampling enables Drosophila hyperacute 3D vision.

SignificanceTo move efficiently, animals must continuously work out their x,y,z positions with respect to real-world objects, and many animals have a pair of eyes to achieve this. How photoreceptors actively sample the eyes' optical image disparity is not understood because this fundamental information-limiting step has not been investigated in vivo over the eyes' whole sampling matrix. This integrative multiscale study will advance our current understanding of stereopsis from static image disparity comparison to a morphodynamic active sampling theory. It shows how photomechanical photoreceptor microsaccades enable Drosophila superresolution three-dimensional vision and proposes neural computations for accurately predicting these flies' depth-perception dynamics, limits, and visual behaviors.

Protonation of Surface Carboxyls on Rice Straw Cellulose Nanofibrils: Effect on the Aerogel Structure, Modulus, Strength, and Wet Resiliency.

Rice straw cellulose nanofibrils from the optimal 2,2,6,6-tetramethylpiperidine-1-oxyl oxidation/blending process carrying 1.17 mmol/g surface carboxyls were protonated to varying charged (COO-Na+) and uncharged (COOH) surfaces. Reducing the electrostatic repulsion of surface charges by protonation with hydrochloric acid from 11 to 45 and 100% surface carboxylic acid most prominently reduced the aerogel densities from 8.0 to 6.6 and 5.2 mg/cm3 while increasing the mostly open cell pore volumes from 125 to 152 and 196 mL/g. Irrespective of charge levels, all aerogels were amphiphilic, super-absorptive, stable at pH 2 for up to 30 days, and resilient for up to 10 repetitive squeezing-absorption cycles. While these aerogels exhibited density-dependent dry [11.3 to 1.5 kPa/(mg/cm3)] and reduced wet [3.3 to 1.4 kPa/(mg/cm3)] moduli, the absorption of organic liquids stiffened the saturated aerogels. These data support protonation as a critical yet simple approach toward precise control of aerogels' dry and wet properties.

Microbial metabolism and adaptations in Atribacteria-dominated methane hydrate sediments.

Gas hydrates harbour gigatons of natural gas, yet their microbiomes remain understudied. We bioprospected 16S rRNA amplicons, metagenomes, and metaproteomes from methane hydrate-bearing sediments under Hydrate Ridge (offshore Oregon, USA, ODP Site 1244, 2-69 mbsf) for novel microbial metabolic and biosynthetic potential. Atribacteria sequences generally increased in relative sequence abundance with increasing sediment depth. Most Atribacteria ASVs belonged to JS-1-Genus 1 and clustered with other sequences from gas hydrate-bearing sediments. We recovered 21 metagenome-assembled genomic bins spanning three geochemical zones in the sediment core: the sulfate-methane transition zone, the metal (iron/manganese) reduction zone, and the gas hydrate stability zone. We found evidence for bacterial fermentation as a source of acetate for aceticlastic methanogenesis and as a driver of iron reduction in the metal reduction zone. In multiple zones, we identified a Ni-Fe hydrogenase-Na+ /H+ antiporter supercomplex (Hun) in Atribacteria and Firmicutes bins and in other deep subsurface bacteria and cultured hyperthermophiles from the Thermotogae phylum. Atribacteria expressed tripartite ATP-independent transporters downstream from a novel regulator (AtiR). Atribacteria also possessed adaptations to survive extreme conditions (e.g. high salt brines, high pressure and cold temperatures) including the ability to synthesize the osmolyte di-myo-inositol-phosphate as well as expression of K+ -stimulated pyrophosphatase and capsule proteins.

Sparse Neural Representation of Odor Predicts Learning.

The way in which neurons encode information remains a hotly debated topic in neuroscience. Lin and colleagues in a 2014 article in the journal Nature Neuroscience demonstrate how sparse coding in the olfactory learning and memory center of Drosophila can influence learning behavior. Coding sparsity is the idea that only a small number of neurons in a network represent any given stimulus. Using neurogenetics, computational neuroscience, and cognitive approaches, they outline the discovery of an inhibitory feedback circuit responsible for differentiating the neuronal response to different odors. Manipulating this feedback circuit, they demonstrate how the sparseness in neural networks (how easily neurons are activated) can correspond to the ability to learn a sensory discrimination more easily. From a research perspective, this paper was important as it was the first causal demonstration of the role of sparseness in learning. From a teaching point of view, this paper is valuable because it is a simple but effective introduction to artificial neural network theory, where both the abstract theory and the importance of its application is apparent to those without a mathematical or computational background.

Dominance of benthic fluxes in the oceanic beryllium budget and implications for paleo-denudation records.

The ratio of atmosphere-derived 10Be to continent-derived 9Be in marine sediments has been used to probe the long-term relationship between continental denudation and climate. However, its application is complicated by uncertainty in 9Be transfer through the land-ocean interface. The riverine dissolved load alone is insufficient to close the marine 9Be budget, largely due to substantial removal of riverine 9Be to continental margin sediments. We focus on the ultimate fate of this latter Be. We present sediment pore-water Be profiles from diverse continental margin environments to quantify the diagenetic Be release to the ocean. Our results suggest that pore-water Be cycling is mainly controlled by particulate supply and Mn-Fe cycling, leading to higher benthic fluxes on shelves. Benthic fluxes may help close the 9Be budget and are at least comparable to, or higher (~2-fold) than, the riverine dissolved input. These observations demand a revised model framework, which considers the potentially dominant benthic source, to robustly interpret marine Be isotopic records.

Aerobic, anaerobic, and excess postexercise oxygen consumption energy expenditure of muscular endurance and strength: 1-set of bench press to muscular fatigue.

We use a new approach to the estimation of energy expenditure for resistance training involving nonsteady state measures of work (weight × displacement), exercise O2 uptake, blood lactate, and recovery O2 uptake; all lifts were performed to muscular failure. Our intent was to estimate and compare absolute and relative aerobic and anaerobic exercise energy expenditure and recovery energy expenditure. Single-set bench press lifts of ∼ 37, ∼ 46, and ∼ 56% (muscular endurance-type exercise) along with 70, 80, and 90% (strength-type exercise) of a 1 repetition maximum were performed. Collectively, the muscular endurance lifts resulted in larger total energy expenditure (60.2 ± 14.5 kJ) as compared with the strength lifts (43.2 ± 12.5 kJ) (p = 0.001). Overall work also was greater for muscular endurance (462 ± 131 J) as opposed to strength (253 ± 93 J) (p = 0.001); overall work and energy expenditure were related (r = 0.87, p = 0.001). Anaerobic exercise and recovery energy expenditure were significantly larger for all strength lifts as compared with aerobic exercise energy expenditure (p < 0.001). For the muscular endurance lifts, anaerobic energy expenditure was larger than recovery energy expenditure (p < 0.001) that in turn was larger than aerobic exercise energy expenditure (p < 0.001). We conclude that for a single set of resistance training to fatigue, the anaerobic and recovery energy expenditure contributions can be significantly larger than aerobic energy expenditure during the exercise. To our surprise, recovery energy expenditure was similar both within strength and muscular-endurance protocols and between protocols; moreover, recovery energy expenditure had little to no relationship with aerobic and anaerobic exercise energy expenditure or work.

Sediment Microbial Communities Influenced by Cool Hydrothermal Fluid Migration.

Cool hydrothermal systems (CHSs) are prevalent across the seafloor and discharge fluid volumes that rival oceanic input from rivers, yet the microbial ecology of these systems are poorly constrained. The Dorado Outcrop on the ridge flank of the Cocos Plate in the northeastern tropical Pacific Ocean is the first confirmed CHS, discharging minimally altered <15°C fluid from the shallow lithosphere through diffuse venting and seepage. In this paper, we characterize the resident sediment microbial communities influenced by cool hydrothermal advection, which is evident from nitrate and oxygen concentrations. 16S rRNA gene sequencing revealed that Thaumarchaea, Proteobacteria, and Planctomycetes were the most abundant phyla in all sediments across the system regardless of influence from seepage. Members of the Thaumarchaeota (Marine Group I), Alphaproteobacteria (Rhodospirillales), Nitrospirae, Nitrospina, Acidobacteria, and Gemmatimonadetes were enriched in the sediments influenced by CHS advection. Of the various geochemical parameters investigated, nitrate concentrations correlated best with microbial community structure, indicating structuring based on seepage of nitrate-rich fluids. A comparison of microbial communities from hydrothermal sediments, seafloor basalts, and local seawater at Dorado Outcrop showed differences that highlight the distinct niche space in CHS. Sediment microbial communities from Dorado Outcrop differ from those at previously characterized, warmer CHS sediment, but are similar to deep-sea sediment habitats with surficial ferromanganese nodules, such as the Clarion Clipperton Zone. We conclude that cool hydrothermal venting at seafloor outcrops can alter the local sedimentary oxidation-reduction pathways, which in turn influences the microbial communities within the fluid discharge affected sediment.

Biological rejuvenation of iron oxides in bioturbated marine sediments.

The biogeochemical cycle of iron is intricately linked to numerous element cycles. Although biological processes that catalyze the reductive side of the iron cycle are established, little is known about microbial oxidative processes on iron cycling in sedimentary environments-resulting in the formation of iron oxides. Here we show that a potential source of sedimentary iron oxides originates from the metabolic activity of iron-oxidizing bacteria from the class Zetaproteobacteria, presumably enhanced by burrowing animals in coastal sediments. Zetaproteobacteria were estimated to be a global total of 1026 cells in coastal, bioturbated sediments, and predicted to annually produce 8 × 1015 g of Fe in sedimentary iron oxides-55 times larger than the annual flux of iron oxides deposited by rivers. These data suggest that iron-oxidizing Zetaproteobacteria are keystone organisms in marine sedimentary environments-despite their low numerical abundance-yet exert a disproportionate impact via the rejuvenation of iron oxides.

Does insecure attachment mediate the relationship between trauma and voice-hearing in psychosis?

This study extends existing research and theoretical developments by exploring the potential mediating role of insecure attachment within the relationship between trauma and voice-hearing. Fifty-five voice hearers with a psychosis-related diagnosis completed comprehensive assessments of childhood trauma, adult attachment, voice-related severity and distress, beliefs about voices and relationships with voices. Anxious attachment was significantly associated with the voice-hearing dimensions examined. More sophisticated analysis showed that anxious attachment mediated the relationship between childhood sexual and emotional abuse and voice-related severity and distress, voice-malevolence, voice-omnipotence, voice-resistance and hearer-dependence. Anxious attachment also mediated the relationship between childhood physical neglect and voice-related severity and distress and hearer-dependence. Furthermore, consistent with previous research, the relationship between anxious attachment and voice-related distress was mediated by voice-malevolence, voice-omnipotence and voice-resistance. We propose a model whereby anxious attachment mediates the well-established relationship between trauma and voice-hearing. In turn, negative beliefs about voices may mediate the association between anxious attachment and voice-related distress. Findings presented here highlight the need to assess and formulate the impact of attachment patterns upon the voice-hearing experience in psychosis and the potential to alleviate voice-related distress by fostering secure attachments to therapists or significant others.

Microbial community dynamics based on 16S rRNA gene profiles in a Pacific Northwest estuary and its tributaries.

We analyzed bacterioplankton community structure in Tillamook Bay, Oregon and its tributaries to evaluate phylogenetic variability and its relation to changes in environmental conditions along an estuarine gradient. Using eubacterial primers, we amplified 16S rRNA genes from environmental DNA and analyzed the PCR products by length heterogeneity polymerase chain reaction (LH-PCR), which discriminates products based on naturally occurring length differences. Analysis of LH-PCR profiles by multivariate ordination methods revealed differences in community composition along the estuarine gradient that were correlated with changes in environmental variables. Microbial community differences were also detected among different rivers. Using partial 16S rRNA sequences, we identified members of dominant or unique gene fragment size classes distributed along the estuarine gradient. Gammaproteobacteria and Betaproteobacteria and members of the Bacteroidetes dominated in freshwater samples, while Alphaproteobacteria, Cyanobacteria and chloroplast genes dominated in marine samples. Changes in the microbial communities correlated most strongly with salinity and dissolved silicon, but were also strongly correlated with precipitation. We also identified specific gene fragments that were correlated with inorganic nutrients. Our data suggest that there is a significant and predictable change in microbial species composition along an estuarine gradient, shifting from a more complex community structure in freshwater habitats to a community more typical of open ocean samples in the marine-influenced sites. We also demonstrate the resolution and power of LH-PCR and multivariate analyses to provide a rapid assessment of major community shifts, and show how these shifts correlate with environmental variables.

Oceanography. Centennial changes in North Pacific anoxia linked to tropical trade winds.

Climate warming is expected to reduce oxygen (O2) supply to the ocean and expand its oxygen minimum zones (OMZs). We reconstructed variations in the extent of North Pacific anoxia since 1850 using a geochemical proxy for denitrification (δ(15)N) from multiple sediment cores. Increasing δ(15)N since ~1990 records an expansion of anoxia, consistent with observed O2 trends. However, this was preceded by a longer declining δ(15)N trend that implies that the anoxic zone was shrinking for most of the 20th century. Both periods can be explained by changes in winds over the tropical Pacific that drive upwelling, biological productivity, and O2 demand within the OMZ. If equatorial Pacific winds resume their predicted weakening trend, the ocean's largest anoxic zone will contract despite a global O2 decline.

Patient and environmental service employee satisfaction of using germicidal bleach wipes for patient room cleaning.

More healthcare institutions are using bleach products which are sporicidal to reduce Clostridium difficile infection (CDI). There may be patient and employee concerns about the appearance of bleach residue left on surfaces, odors, and respiratory tract irritation. The intervention used bleach wipes for daily and terminal patient room cleaning to reduce transmission of CDI and was implemented on patient care units with a relatively high incidence of CDI. Both patients and Environmental Services (ES) staff were surveyed to assess their satisfaction of the bleach wipe product used during room cleaning. Patients (n = 94) (91%) continued to be very satisfied with how well their rooms were cleaned every day. Bleach wipes were well tolerated by patients (n = 44) (100%) surveyed on the medical units and less tolerated by patients (n = 50) (22%) on the hematology-oncology units. ES staff (6) reported less satisfaction and more respiratory irritation from using the bleach wipes; however, later their satisfaction improved.

Dissolution of fluoride complexes following microwave-assisted hydrofluoric acid digestion of marine sediments.

Microwave-assisted, hydrofluoric acid digestion is an increasingly common tool for the preparation of marine sediment samples for analysis by a variety of spectrometric techniques. Here we report that analysis of terrigenous-dominated sediment samples occasionally results in anomalously low values for several elements, including Al, Ba, Ca, Mg, and Sr. Measured concentrations of these elements increased with time between sample preparation and sample analysis, reaching stable values after 8-29 days. This lag is explained by the formation and subsequent dissolution of poorly soluble fluoride phases during digestion. Other elements, such as Fe, Mn, and Ti, showed little or no lag and were quickly measurable at a stable value. Full re-dissolution of the least soluble fluorides, which incorporate Al and Mg, requires up to four weeks at room temperature, and this duration can vary among sedimentary matrices. This waiting time can be reduced to 6 days (or shorter) if the samples are heated to ≈ 60°C for 24h.

The synthesis of organo-soluble anatase nanocrystals from amorphous titania.

Highly soluble anatase nanocrystals of 4 nm diameter have been prepared by the reaction of amorphous titania with trifluoroacetic acid. The solubility of the nanocrystals is a result of surface bound carboxylate groups, and enables the organic-inorganic hybrid material to be processed from solution to yield high quality coatings and thin-films.

A targeted strategy to wipe out Clostridium difficile.

This study evaluated daily cleaning with germicidal bleach wipes on wards with a high incidence of hospital-acquired Clostridium difficile infection (CDI). The intervention reduced hospital-acquired CDI incidence by 85%, from 24.2 to 3.6 cases per 10,000 patient-days, and prolonged the median time between hospital-acquired CDI cases from 8 to 80 days.

A high-resolution paleoclimate record spanning the past 25,000 years in southern East Africa.

High-resolution profiles of the mass accumulation rate of biogenic silica and other geochemical proxies in two piston cores from northern Lake Malawi provide a climate signal for this part of tropical Africa spanning the past 25,000 years. The biogenic silica mass accumulation rate was low during the relatively dry late Pleistocene, when the river flux of silica to the lake was suppressed. Millennial-scale fluctuations, due to upwelling intensity, in the late Pleistocene climate of the Lake Malawi basin appear to have been closely linked to the Northern Hemisphere climate until 11 thousand years ago. Relatively cold conditions in the Northern Hemisphere coincided with more frequent north winds over the Malawi basin, perhaps resulting from a more southward migration of the Intertropical Convergence Zone.