Appetite for self-destruction: suicidal biting as a nest defense strategy in Trigona stingless bees

Self-sacrificial behavior represents an extreme and relatively uncommon form of altruism in worker insects. It can occur, however, when inclusive fitness benefits are high, such as when defending the nest. We studied nest defense behaviors in stingless bees, which live in eusocial colonies subject to predation. We introduced a target flag to nest entrances to elicit defensive responses and quantified four measures of defensivity in 12 stingless bee species in São Paulo State, Brazil. These included three Trigona species, which are locally known for their aggression. Species varied significantly in their attack probability (cross species range = 0–1, P < 0.001), attack latency (7.0–23.5 s, P = 0.002), biting duration of individual bees (3.5–508.7 s, P < 0.001), and number of attackers (1.0–10.8, P < 0.001). A “suicide” bioassay on the six most aggressive species determined the proportion of workers willing to suffer fatal damage rather than disengage from an intruder. All six species had at least some suicidal individuals (7–83 %, P < 0.001), reaching 83 % in Trigona hyalinata. Biting pain was positively correlated with an index of overall aggression (P = 0.002). Microscopic examination revealed that all three Trigona species had five sharp teeth per mandible, a possible defensive adaptation and cause of increased pain. Suicidal defense via biting is a new example of self-sacrificial altruism and has both parallels and differences with other self-sacrificial worker insects, such as the honey bee. Our results indicate that suicidal biting may be a widespread defense strategy in stingless bees, but it is not universal

Clustered engine study

Several topics are presented in viewgraph form which together encompass the preliminary assessment of nuclear thermal rocket engine clustering. The study objectives, schedule, flow, and groundrules are covered. This is followed by the NASA groundrules mission and our interpretation of the associated operational scenario. The NASA reference vehicle is illustrated, then the four propulsion system options are examined. Each propulsion system's preliminary design, fluid systems, operating characteristics, thrust structure, dimensions, and mass properties are detailed as well as the associated key propulsion system/vehicle interfaces. A brief series of systems analysis is also covered including: thrust vector control requirements, engine out possibilities, propulsion system failure modes, surviving system requirements, and technology requirements. An assessment of vehicle/propulsion system impacts due to the lessons learned are presented

Mantle to surface degassing of alkalic magmas at Erebus volcano, Antarctica

International audienceContinental intraplate volcanoes, such as Erebus volcano, Antarctica, are associated with extensional tectonics, mantle upwelling and high heat flow. Typically, erupted magmas are alkaline and rich in volatiles (especially CO2), inherited from low degrees of partial melting of mantle sources. We examine the degassing of the magmatic system at Erebus volcano using melt inclusion data and high temporal resolution open-path Fourier transform infrared (FTIR) spectroscopic measurements of gas emissions from the active lava lake. Remarkably different gas signatures are associated with passive and explosive gas emissions, representative of volatile contents and redox conditions that reveal contrasting shallow and deep degassing sources. We show that this unexpected degassing signature provides a unique probe for magma differentiation and transfer of CO2-rich oxidised fluids from the mantle to the surface, and evaluate how these processes operate in time and space. Extensive crystallisation driven by CO2 fluxing is responsible for isobaric fractionation of parental basanite magmas close to their source depth. Magma deeper than 4 kbar equilibrates under vapour-buffered conditions. At shallower depths, CO2-rich fluids accumulate and are then released either via convection-driven, open-system gas loss or as closed-system slugs that ascend and result in Strombolian eruptions in the lava lake. The open-system gases have a reduced state (below the QFM buffer) whereas the closed-system gases preserve their deep oxidised signatures (close to the NNO buffer)

The diversity and utility of amyloid fibrils formed by short amyloidogenic peptides

Amyloidogenic peptides are well known for their involvement in diseases such as type 2 diabetes and Alzheimer's disease. However, more recently, amyloid fibrils have been shown to provide scaffolding and protection as functional materials in a range of organisms from bacteria to humans. These roles highlight the incredible tensile strength of the cross-β amyloid architecture. Many amino acid sequences are able to self-assemble to form amyloid with a cross-β core. Here we describe our recent advances in understanding how sequence contributes to amyloidogenicity and structure. For example, we describe penta- and hexapeptides that assemble to form different morphologies; a 12mer peptide that forms fibrous crystals; and an eight-residue peptide originating from α-synuclein that has the ability to form nanotubes. This work provides a wide range of peptides that may be exploited as fibrous bionanomaterials. These fibrils provide a scaffold upon which functional groups may be added, or templated assembly may be performed

Reconstruction of the lipid metabolism for the microalga Monoraphidium neglectum from its genome sequence reveals characteristics suitable for biofuel production

Bogen C, Al-Dilaimi A, Albersmeier A, et al. Reconstruction of the lipid metabolism for the microalga Monoraphidium neglectum from its genome sequence reveals characteristics suitable for biofuel production. BMC Genomics. 2013;14(1): 926.BACKGROUND: Microalgae are gaining importance as sustainable production hosts in the fields of biotechnology and bioenergy. A robust biomass accumulating strainof the genus Monoraphidium (SAG 48.87) was investigated in this work as apotential feedstock for biofuel production. The genome was sequenced, annotated, and key enzymes for triacylglycerol formation were elucidated. RESULTS: Monoraphidium neglectum was identified as an oleaginous species with favourable growth characteristics as well as a high potential for crude oil production, based on neutral lipid contents of approximately 21% (dry weight) under nitrogen starvation, composed of predominantly C18:1 and C16:0 fatty acids. Further characterization revealed growth in a relatively wide pH range and salt concentrations of up to 1.0% NaCl, in which the cells exhibited larger structures. This first full genome sequencing of a member of the Selenastraceae revealed a diploid, approximately 68 Mbp genome with a G + C content of 64.7%. The circular chloroplast genome was assembled to a 135,362 bp single contig, containing 67 protein-coding genes. The assembly of the mitochondrial genome resulted in two contigs with an approximate total size of 94 kb, the largest known mitochondrial genome within algae. 16,761 protein-coding genes were assigned to the nuclear genome. Comparison of gene sets with respect to functional categories revealed a higher gene number assigned to the category "carbohydrate metabolic process" and in "fatty acid biosynthetic process" in M. neglectum when compared to Chlamydomonas reinhardtii and Nannochloropsis gaditana, indicating a higher metabolic diversity for applications in carbohydrate conversions of biotechnological relevance. CONCLUSIONS: The genome of M. neglectum, as well as the metabolic reconstruction of crucial lipid pathways, provides new insights into the diversity of the lipid metabolism in microalgae. The results of this work provide a platform to encourage the development of this strain for biotechnological applications and production concepts

Quality versus quantity: foraging decisions in the honeybee (Apis mellifera scutellata) feeding on wildflower nectar and fruit juice

Foraging animals must often decide among resources which vary in quality and quantity. Nectar is a resource that exists along a continuum of quality in terms of sugar concentration and is the primary energy source for bees. Alternative sugar sources exist, including fruit juice, which generally has lower energetic value than nectar. We observed many honeybees (Apis mellifera scutellata) foraging on juice from fallen guava (Psidium guajava) fruit near others foraging on nectar. To investigate whether fruit and nectar offered contrasting benefits of quality and quantity, we compared honeybee foraging performance on P. guajava fruit versus two wildflowers growing within 50 m, Richardia brasiliensis and Tridax procumbens. Bees gained weight significantly faster on fruit, 2.72 mg/min, than on either flower (0.17 and 0.12 mg/min, respectively). However, the crop sugar concentration of fruit foragers was significantly lower than for either flower (12.4% vs. 37.0% and 22.7%, respectively). Fruit foragers also spent the most time handling and the least time flying, suggesting that fruit juice was energetically inexpensive to collect. We interpret honeybee foraging decisions in the context of existing foraging models and consider how nest-patch distance may be a key factor for central place foragers choosing between resources of contrasting quality and quantity. We also discuss how dilute solutions, such as fruit juice, can help maintain colony sugar–water balance. These results show the benefits of feeding on resources with contrasting quality and quantity and that even low-quality resources have value

Study protocol: developing a decision system for inclusive housing: applying a systematic, mixed-method quasi-experimental design

Background Identifying the housing preferences of people with complex disabilities is a much needed, but under-developed area of practice and scholarship. Despite the recognition that housing is a social determinant of health and quality of life, there is an absence of empirical methodologies that can practically and systematically involve consumers in this complex service delivery and housing design market. A rigorous process for making effective and consistent development decisions is needed to ensure resources are used effectively and the needs of consumers with complex disability are properly met. Methods/Design This 3-year project aims to identify how the public and private housing market in Australia can better respond to the needs of people with complex disabilities whilst simultaneously achieving key corporate objectives. First, using the Customer Relationship Management framework, qualitative (Nominal Group Technique) and quantitative (Discrete Choice Experiment) methods will be used to quantify the housing preferences of consumers and their carers. A systematic mixed-method, quasi-experimental design will then be used to quantify the development priorities of other key stakeholders (e.g., architects, developers, Government housing services etc.) in relation to inclusive housing for people with complex disabilities. Stakeholders randomly assigned to Group 1 (experimental group) will participate in a series of focus groups employing Analytical Hierarchical Process (AHP) methodology. Stakeholders randomly assigned to Group 2 (control group) will participate in focus groups employing existing decision making processes to inclusive housing development (e.g., Risk, Opportunity, Cost, Benefit considerations). Using comparative stakeholder analysis, this research design will enable the AHP methodology (a proposed tool to guide inclusive housing development decisions) to be tested. Discussion It is anticipated that the findings of this study will enable stakeholders to incorporate consumer housing preferences into commercial decisions. Housing designers and developers will benefit from the creation of a parsimonious set of consumer-led housing preferences by which to make informed investments in future housing and contribute to future housing policy. The research design has not been applied in the Australian research context or elsewhere, and will provide a much needed blueprint for market investment to develop viable, consumer directed inclusive housing options for people with complex disability

A central role for dityrosine crosslinking of Amyloid-β in Alzheimer’s disease

Background Alzheimer’s disease (AD) is characterized by the deposition of insoluble amyloid plaques in the neuropil composed of highly stable, self-assembled Amyloid-beta (Aβ) fibrils. Copper has been implicated to play a role in Alzheimer’s disease. Dimers of Aβ have been isolated from AD brain and have been shown to be neurotoxic. Results We have investigated the formation of dityrosine cross-links in Aβ42 formed by covalent ortho-ortho coupling of two tyrosine residues under conditions of oxidative stress with elevated copper and shown that dityrosine can be formed in vitro in Aβ oligomers and fibrils and that these links further stabilize the fibrils. Dityrosine crosslinking was present in internalized Aβ in cell cultures treated with oligomeric Aβ42 using a specific antibody for dityrosine by immunogold labeling transmission electron microscopy. Results also revealed the prevalence of dityrosine crosslinks in amyloid plaques in brain tissue and in cerebrospinal fluid from AD patients. Conclusions Aβ dimers may be stabilized by dityrosine crosslinking. These results indicate that dityrosine cross-links may play an important role in the pathogenesis of Alzheimer’s disease and can be generated by reactive oxygen species catalyzed by Cu2+ ions. The observation of increased Aβ and dityrosine in CSF from AD patients suggests that this could be used as a potential biomarker of oxidative stress in AD

Medium modification of jet fragmentation in Au+Au collisions at sqrt(s_NN)=200 GeV measured in direct photon-hadron correlations

The jet fragmentation function is measured with direct photon-hadron correlations in p+p and Au+Au collisions at sqrt(s_NN)=200 GeV. The p_T of the photon is an excellent approximation to the initial p_T of the jet and the ratio z_T=p_T^h/p_T^\gamma is used as a proxy for the jet fragmentation function. A statistical subtraction is used to extract the direct photon-hadron yields in Au+Au collisions while a photon isolation cut is applied in p+p. I_ AA, the ratio of jet fragment yield in Au+Au to that in p+p, indicates modification of the jet fragmentation function. Suppression, most likely due to energy loss in the medium, is seen at high z_T. The fragment yield at low z_T is enhanced at large angles. Such a trend is expected from redistribution of the lost energy into increased production of low-momentum particles.Comment: 562 authors, 70 insitutions, 8 pages, and 3 figures. Submitted to Phys. Rev. Lett. v2 has minor changes to improve clarity. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm