Shape-induced force fields in optical trapping

Advances in optical tweezers, coupled with the proliferation of two-photon polymerization systems, mean that it is now becoming routine to fabricate and trap non-spherical particles. The shaping of both light beams and particles allows fine control over the flow of momentum from the optical to mechanical regimes. However, understanding and predicting the behaviour of such systems is highly complex in comparison with the traditional optically trapped microsphere. In this Article, we present a conceptually new and simple approach based on the nature of the optical force density. We illustrate the method through the design and fabrication of a shaped particle capable of acting as a passive force clamp, and we demonstrate its use as an optically trapped probe for imaging surface topography. Further applications of the design rules highlighted here may lead to new sensors for probing biomolecule mechanics, as well as to the development of optically actuated micromachines

A community-based intervention to reduce antibiotic use for upper respiratory tract infections in regional South Australia

The document attached has been archived with permission from the editor of the Medical Journal of Australia. An external link to the publisher’s copy is included.Objective: To evaluate the effectiveness of a community-based and GP-based intervention in reducing unnecessary antibiotic prescribing for upper respiratory tract infections (URTIs) including sore throats, sinusitis and otitis media. Design: Analysis of pharmacy dispensing data in June to October before (2000) and after (2001) the intervention, which commenced on 25 June 2001. Setting and participants: Local consumers, health professionals, the Adelaide Southern Division of General Practice, the South Australian Government, and the local media in a rural region of South Australia, covering about 2000 square kilometres, with a population of over 20 000. Intervention: Community dissemination of consumer information on antibiotic use for URTIs (including a local media campaign) and education of health professionals (including sessions with general practitioners at the four practices in the study area) on current Australian therapeutic guidelines for antibiotics, and a validated clinical scoring system for decision making in managing sore throat. Main outcome measures: Total dispensing data from local pharmacies for the months of June to October in 2000 and 2001, covering the six antibiotics considered most likely to be used for URTIs (amoxycillin, amoxycillin/clavulanic acid, cefaclor, doxycycline, erythromycin and roxithromycin). Results: The dispensing of the six antibiotics reduced by 32% overall, from 77.1 to 52.9 defined daily doses per 1000 population per day, with statistically significant reductions in the range of 31%–70% for individual antibiotics; there was no reduction for amoxycillin with or without clavulanic acid. Conclusion: The intervention was associated with reduced dispensing of unnecessary antibiotics for URTIs.William B Dollman, Vanessa T LeBlanc, Lynette Stevens, Peter J O’Connor and John D Turnidg

Temporal perception deficits in schizophrenia: integration is the problem, not deployment of attentions

Patients with schizophrenia are known to have impairments in sensory processing. In order to understand the specific temporal perception deficits of schizophrenia, we investigated and determined to what extent impairments in temporal integration can be dissociated from attention deployment using Attentional Blink (AB). Our findings showed that there was no evident deficit in the deployment of attention in patients with schizophrenia. However, patients showed an increased temporal integration deficit within a hundred-millisecond timescale. The degree of such integration dysfunction was correlated with the clinical manifestations of schizophrenia. There was no difference between individuals with/without schizotypal personality disorder in temporal integration. Differently from previous studies using the AB, we did not find a significant impairment in deployment of attention in schizophrenia. Instead, we used both theoretical and empirical approaches to show that previous findings (using the suppression ratio to correct for the baseline difference) produced a systematic exaggeration of the attention deficits. Instead, we modulated the perceptual difficulty of the task to bring the baseline levels of target detection between the groups into closer alignment. We found that the integration dysfunction rather than deployment of attention is clinically relevant, and thus should be an additional focus of research in schizophrenia

Structure, chemistry, and charge transfer resistance of the interface between Li7La3Zr2O12 electrolyte and LiCoO2 cathode

All-solid-state batteries promise significant safety and energy density advantages over liquid-electrolyte batteries. The interface between the cathode and the solid electrolyte is an important contributor to charge transfer resistance. Strong bonding of solid oxide electrolytes and cathodes requires sintering at elevated temperatures. Knowledge of the temperature dependence of the composition and charge transfer properties of this interface is important for determining the ideal sintering conditions. To understand the interfacial decomposition processes and their onset temperatures, model systems of LiCoO2 (LCO) thin films deposited on cubic Al-doped Li7La3Zr2O12 (LLZO) pellets were studied as a function of temperature using interface-sensitive techniques. X-ray photoelectron spectroscopy (XPS), secondary ion mass spectroscopy (SIMS), and energy-dispersive X-ray spectroscopy (EDS) data indicated significant cation interdiffusion and structural changes starting at temperatures as low as 300°C. La2Zr2O7 and Li2CO3 were identified as decomposition products after annealing at 500°C by synchrotron X-ray diffraction (XRD). X-ray absorption spectroscopy (XAS) results indicate the presence of also LaCoO3, in addition to La2Zr2O7 and Li2CO3. Based on electrochemical impedance spectroscopy, and depth profiling of the Li distribution upon potentiostatic hold experiments on symmetric LCO|LLZO|LCO cells, the interfaces exhibited significantly increased impedance, up to 8 times that of the as-deposited samples after annealing at 500°C. Our results indicate that lower-temperature processing conditions, shorter annealing time scales, and CO2-free environments are desirable for obtaining ceramic cathode-electrolyte interfaces that enable fast Li transfer and high capacity

Flammable biomes dominated by eucalypts originated at the Cretaceous-Palaeogene boundary

Fire is a major modifier of communities, but the evolutionary origins of its prevalent role in shaping current biomes are uncertain. Australia is among the most fire-prone continents, with most of the landmass occupied by the fire-dependent sclerophyll and savanna biomes. In contrast to biomes with similar climates in other continents, Australia has a tree flora dominated by a single genus, Eucalyptus, and related Myrtaceae. A unique mechanism in Myrtaceae for enduring and recovering from fire damage likely resulted in this dominance. Here, we find a conserved phylogenetic relationship between post-fire resprouting (epicormic) anatomy and biome evolution, dating from 60 to 62 Ma, in the earliest Palaeogene. Thus, fire-dependent communities likely existed 50 million years earlier than previously thought. We predict that epicormic resprouting could make eucalypt forests and woodlands an excellent long-term carbon bank for reducing atmospheric CO2 compared with biomes with similar fire regimes in other continents

A Cretaceous origin for fire adaptations in the Cape flora

Fire has had a profound effect on the evolution of worldwide biotas. The Cape Floristic Region is one of the world's most species-rich regions, yet it is highly prone to recurrent fires and fire-adapted species contribute strongly to the overall flora. It is hypothesized that the current fire regimes in the Cape could be as old as 6-8 million years (My), while indirect evidence indicates that the onset of fire could have reached 18 million years ago (Ma). Here, we trace the origin of fire-dependent traits in two monocot families that are significant elements in the fire-prone Cape flora. Our analysis shows that fire-stimulated flowering originated in the Cape Haemodoraceae 81 Ma, while fire-stimulated germination arose in the African Restionaceae at least 70 Ma, implying that wildfires have been a significant force in the evolution of the Cape flora at least 60 My earlier than previous estimates. Our results provide strong evidence for the presence of fire adaptations in the Cape from the Cretaceous, leading to the extraordinary persistence of a fire-adapted flora in this biodiversity hotspot, and giving support to the hypothesis that Cretaceous fire was a global phenomenon that shaped the evolution of terrestrial floras

Shallow water marine sediment bacterial community shifts along a natural CO2 gradient in the Mediterranean Sea off Vulcano, Italy.

The effects of increasing atmospheric CO(2) on ocean ecosystems are a major environmental concern, as rapid shoaling of the carbonate saturation horizon is exposing vast areas of marine sediments to corrosive waters worldwide. Natural CO(2) gradients off Vulcano, Italy, have revealed profound ecosystem changes along rocky shore habitats as carbonate saturation levels decrease, but no investigations have yet been made of the sedimentary habitat. Here, we sampled the upper 2 cm of volcanic sand in three zones, ambient (median pCO(2) 419 μatm, minimum Ω(arag) 3.77), moderately CO(2)-enriched (median pCO(2) 592 μatm, minimum Ω(arag) 2.96), and highly CO(2)-enriched (median pCO(2) 1611 μatm, minimum Ω(arag) 0.35). We tested the hypothesis that increasing levels of seawater pCO(2) would cause significant shifts in sediment bacterial community composition, as shown recently in epilithic biofilms at the study site. In this study, 454 pyrosequencing of the V1 to V3 region of the 16S rRNA gene revealed a shift in community composition with increasing pCO(2). The relative abundances of most of the dominant genera were unaffected by the pCO(2) gradient, although there were significant differences for some 5 % of the genera present (viz. Georgenia, Lutibacter, Photobacterium, Acinetobacter, and Paenibacillus), and Shannon Diversity was greatest in sediments subject to long-term acidification (>100 years). Overall, this supports the view that globally increased ocean pCO(2) will be associated with changes in sediment bacterial community composition but that most of these organisms are resilient. However, further work is required to assess whether these results apply to other types of coastal sediments and whether the changes in relative abundance of bacterial taxa that we observed can significantly alter the biogeochemical functions of marine sediments

Macrofossil evidence for a rapid and severe Cretaceous–Paleogene mass extinction in Antarctica

Debate continues about the nature of the Cretaceous–Paleogene (K–Pg) mass extinction event. An abrupt crisis triggered by a bolide impact contrasts with ideas of a more gradual extinction involving flood volcanism or climatic changes. Evidence from high latitudes has also been used to suggest that the severity of the extinction decreased from low latitudes towards the poles. Here we present a record of the K–Pg extinction based on extensive assemblages of marine macrofossils (primarily new data from benthic molluscs) from a highly expanded Cretaceous–Paleogene succession: the López de Bertodano Formation of Seymour Island, Antarctica. We show that the extinction was rapid and severe in Antarctica, with no significant biotic decline during the latest Cretaceous, contrary to previous studies. These data are consistent with a catastrophic driver for the extinction, such as bolide impact, rather than a significant contribution from Deccan Traps volcanism during the late Maastrichtian

Microcolony Imaging of Aspergillus fumigatus Treated with Echinocandins Reveals Both Fungistatic and Fungicidal Activities

Background: The echinocandins are lipopeptides that can be employed as antifungal drugs that inhibit the synthesis of 1,3b-glucans within the fungal cell wall. Anidulafungin and caspofungin are echinocandins used in the treatment of Candida infections and have activity against other fungi including Aspergillus fumigatus. The echinocandins are generally considered fungistatic against Aspergillus species. Methods: Culture of A. fumigatus from conidia to microcolonies on a support of porous aluminium oxide (PAO), combined with fluorescence microscopy and scanning electron microscopy, was used to investigate the effects of anidulafungin and caspofungin. The PAO was an effective matrix for conidial germination and microcolony growth. Additionally, PAO supports could be moved between agar plates containing different concentrations of echinocandins to change dosage and to investigate the recovery of fungal microcolonies from these drugs. Culture on PAO combined with microscopy and image analysis permits quantitative studies on microcolony growth with the flexibility of adding or removing antifungal agents, dyes, fixatives or osmotic stresses during growth with minimal disturbance of fungal microcolonies. Significance: Anidulafungin and caspofungin reduced but did not halt growth at the microcony level; additionally both drugs killed individual cells, particularly at concentrations around the MIC. Intact but not lysed cells showed rapid recovery when the drugs were removed. The classification of these drugs as either fungistatic or fungicidal is simplistic. Microcolon

Fire History from Life-History: Determining the Fire Regime that a Plant Community Is Adapted Using Life-Histories

Wildfire is a fundamental disturbance process in many ecological communities, and is critical in maintaining the structure of some plant communities. In the past century, changes in global land use practices have led to changes in fire regimes that have radically altered the composition of many plant communities. As the severe biodiversity impacts of inappropriate fire management regimes are recognized, attempts are being made to manage fires within a more ‘natural’ regime. In this aim, the focus has typically been on determining the fire regime to which the community has adapted. Here we take a subtly different approach and focus on the probability of a patch being burnt. We hypothesize that competing sympatric taxa from different plant functional groups are able to coexist due to the stochasticity of the fire regime, which creates opportunities in both time and space that are exploited differentially by each group. We exploit this situation to find the fire probability at which three sympatric grasses, from different functional groups, are able to co-exist. We do this by parameterizing a spatio-temporal simulation model with the life-history strategies of the three species and then search for the fire frequency and scale at which they are able to coexist when in competition. The simulation gives a clear result that these species only coexist across a very narrow range of fire probabilities centred at 0.2. Conversely, fire scale was found only to be important at very large scales. Our work demonstrates the efficacy of using competing sympatric species with different regeneration niches to determine the probability of fire in any given patch. Estimating this probability allows us to construct an expected historical distribution of fire return intervals for the community; a critical resource for managing fire-driven biodiversity in the face of a growing carbon economy and ongoing climate change